@inproceedings{SteglichMaiStolareketal.2016, author = {Steglich, Patrick and Mai, Christian and Stolarek, David and Lischke, Stefan and Kupijai, Sebastian and Villringer, Claus and Pulwer, Silvio and Heinrich, Friedhelm and Bauer, Joachim and Meister, Stefan and Knoll, Dieter and Casalboni, Mauro and Schrader, Sigurd}, title = {Partially slotted silicon ring resonator covered with electro-optical polymer}, series = {Proceedings of SPIE}, booktitle = {Proceedings of SPIE}, issn = {1996-756X}, doi = {10.1117/12.2217725}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13771}, year = {2016}, abstract = {In this work, we present for the first time a partially slotted silicon ring resonator (PSRR) covered with an electro-optical polymer (Poly[(methyl methacrylate)-co-(Disperse Red 1 acrylate)]). The PSRR takes advantage of both a highly efficient vertical slot waveguide based phase shifter and a low loss strip waveguide in a single ring. The device is realized on 200 mm silicon-on-insulator wafers using 248 nm DUV lithography and covered with the electro-optic polymer in a post process. This silicon-organic hybrid ring resonator has a small footprint, high optical quality factor, and high DC device tunability. A quality factor of up to 105 and a DC device tunability of about 700 pm/V is experimentally demonstrated in the wavelength range of 1540 nm to 1590 nm. Further, we compare our results with state-of-the-art silicon-organic hybrid devices by determining the poling efficiency. It is demonstrated that the active PSRR is a promising candidate for efficient optical switches and tunable filters.}, language = {en} } @article{GerhardLetienCressentetal.2020, author = {Gerhard, Christoph and Letien, Emilie and Cressent, Thomas and Hofmann, Mandy}, title = {Inline monitoring of hydrogenous plasma-induced defect formation within fused silica via plasma emission spectroscopy}, series = {Applied Physics A: Materials Science and Processing}, volume = {126}, journal = {Applied Physics A: Materials Science and Processing}, issn = {1432-0630}, doi = {10.1007/s00339-020-3347-5}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13118}, year = {2020}, abstract = {In this paper, the indirect monitoring of plasma-induced defect formation within fused silica via plasma emission spectroscopy is presented. It is shown that low-pressure plasma treatment with hydrogen as process gas leads to a decrease in UV transmission of fused silica. This decrease can be directly attributed to oxygen vacancy-related defects and the presence of hydrogen within the silicon dioxide glass network. By the analysis of the plasma composition, it was observed that the amount of oxygen within the plasma increases with increasing treatment duration. Hence, oxygen was continuously released from glass network in the course of the plasma treatment. It was further observed that this release is strongly dependent on the applied plasma power where the lowest process efficiency occurs at the highest plasma power. It is shown that an increase in plasma power leads to a remarkable increase in light emission from the working gas, hydrogen. This observation indicates that the higher the degree of excitation and ionisation of the plasma, the lower the efficiency of plasma-induced formation of oxygen deficiency-related defects. This finding is of mentionable relevance for a better understanding of plasma-induced surface modification and coating processes.}, language = {en} } @inproceedings{N’TsoukpoeKoFalcozetal.2020, author = {N'Tsoukpoe, Kokouvi Edem and Ko, Ga{\"e}lle Kafira and Falcoz, Quentin and Coulibaly, Y{\´e}zouma}, title = {Design, construction and experimental investigation of a linear Fresnel concentrator for sustainable energy services in Sub-Saharan Africa}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SI-1a}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13194}, pages = {7 -- 16}, year = {2020}, abstract = {Concentrating solar power (CSP) is considered as one of the promising ways for future sustainable electricity generation, especially in the Sahel region, which is characterized by high direct solar irradiation, but also severe and acute energy poverty. In this paper, we focus on the linear Fresnel system, which it is probably the simplest CSP technology and presents the lowest investment costs. However, it is the less investigated CSP technology and several authors expect significant cost reduction of this technology. Therefore, deeper knowledge on the technology is required. We aim at investigating the coupling of a linear Fresnel system with various energy processes in order to bring out its interests for the Sahel region and, hence, provide sustainable energy services such as electricity generation for rural areas, cooling and refrigeration via sorption cold production, hot water or steam supply for semi-industrial or industrial processes. We have built a linear Fresnel collector of 7.5 m2. The receiver has been designed as a trapezoidal receiver with multi-tubular absorber; it has been experimentally investigated in order to determine its thermal performance, especially the heat loss coefficients. Jatropha curcas oil, a locally produced non-edible vegetable oil is used as heat transfer fluid. The concentrator has been characterised in order to find its optical, thermal and global efficiencies. Paths for the prototype performance improvement have been identified and examined.}, language = {en} } @inproceedings{ReiffStephan2020, author = {Reiff-Stephan, J{\"o}rg}, title = {Implementation approaches for distributed energy management systems in production}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SIV-1b}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13220}, pages = {116 -- 124}, year = {2020}, abstract = {The energy management of manufacturing facilities must be taken increasing account for an efficient operation within a production process. Future efforts and solutions will focus on improvement of the process stability and on cost reduction to meet the needs of successfully compete in local and global markets especially for SME. The paper describes an approach for manufacturing facilities using an example for thermoprocessing equipment. For this purpose, the TPS-principle Jidōka is used, the mechanism of self-adapting limit setting as well as an implementation is presented prototypically.}, language = {en} } @inproceedings{ReiffStephan2020, author = {Reiff-Stephan, J{\"o}rg}, title = {Solar power in product development}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SII-1b}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13206}, pages = {55 -- 65}, year = {2020}, abstract = {The availability of electrical energy is one of the essential basic elements for economic growth and humanitarian living conditions. In one of the poorest regions of Western Africa - in the savannah region of northern Togo - the central expansion of electricity grids has not taken place. Decentralized solutions based on renewable energy systems can help here and promote the region's development. In the presented paper, the various renewable energy carrier systems were examined with regard to their use in the savannah region of Western Africa. The solar energy carrier system could be used as a power supplier in the secondary conversion process to mechanical power. Subsequently, a prototype for a clay brick production machine was designed and a digital mock-up was developed. Together with the partners in Togo, the prototype is built and tested in the field. Experiences are being gathered in cooperation with Bonita-Haus and will be incorporated into the educational content in Togo as well as at the Technical University of Wildau. This will make a significant contribution to the utilization of the technology at the site and to improving the living conditions in Western Africa.}, language = {en} } @inproceedings{GieseFuerkus2020, author = {Giese, Lutz B. and F{\"u}rkus, Stefan}, title = {A Short Approximation Method to Pre-estimate the Electric Yield of Wind Farms}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SI-2b}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13256}, pages = {34 -- 40}, year = {2020}, abstract = {Amongst the Renewable Energy Sources (RES) contributing to the worldwide electricity production, wind energy became very important. Germany and several other countries own significant wind potentials. 2\% of a country's area can be used for wind farms, thus Germany could produce easily up to 200 TWhel yearly just onshore. However, often legal and especially financial aspects decide about the speed of development. Careful project preparation guaranteed by professional management is obligatory. Beside factors such as (i) rights to the property and (ii) electric grid connection, (iii) the sufficiency of the wind and peripheral conditions need to be known. A proper wind forecast and yield prognoses are important items. To solve these tasks, professional programs are sold on the markets. To offer a convenient alternative, authors will present software based on Excel named as WindCalc 1.5, which is still under development.}, language = {en} } @inproceedings{Giese2020, author = {Giese, Lutz B.}, title = {Turnaround in Energy Policy - Measures to Reduce the Carbon Dioxide Emission from the Private Sector}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SIII-1a}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13248}, pages = {81 -- 86}, year = {2020}, abstract = {The greenhouse gases (GHG) carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) are considered mainly to be responsible for the additional anthropogenic greenhouse effect, the so-called "global warming". In the private sector, the "Rational Use of Energy" can be a very effective tool (i) to reduce the greenhouse gas emissions, (ii) to decrease the annual energy costs and furthermore (iii) it prepares the integration of Renewable Energy Sources by saving conventional, mostly fossil energy. Aim of this paper is (i) to show that by applying energy saving measures, the primary energy demand and thus the individual (direct) carbon dioxide emission can be reduced in a relevant scale. (ii) It is to give laterally information about (ii.i) the energy market structure and (ii.ii) the legal backgrounds in the EU.}, language = {en} } @inproceedings{AfenyivehAdanleteAdjanohDouti2020, author = {Afenyiveh, Serge Dzo Mawuefa and Adanlete Adjanoh, Assiongbon and Douti, Dam-Be Lardja}, title = {Optical simulation of a parabolic solar concentrator}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SII-2a}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13238}, pages = {66 -- 72}, year = {2020}, abstract = {This work presents a 3D ray tracing approach for the optical simulation of a parabolic solar concentrator for a thermo-magnetic (Curie motor) experiment. An approach based on Snell's law of reflection (geometrical optics) in vector form is used in this study. We consider the solid angle of the sun through a rotation of the concentrator around an axis. This paper aims to set up a digital technical tool as flexible as possible for applications in the field of renewable energy.Mathematical modelling as well as numerical simulation in Python environment are presented. The aim of the proposed algorithm is to be used for the concentration of light rays on any optical system, symmetrical or not. Better yet, offers a solar tracking model.}, language = {en} } @inproceedings{SteglichPaulMaietal.2021, author = {Steglich, Patrick and Paul, Martin and Mai, Christian and B{\"o}hme, Andrea and Bondarenko, Siegfried and Weller, Michael G. and Mai, Andreas}, title = {A monolithically integrated micro fluidic channel in a silicon-based photonic-integrated-circuit technology for biochemical sensing}, series = {Proc. SPIE 11772, Optical Sensors 2021}, booktitle = {Proc. SPIE 11772, Optical Sensors 2021}, doi = {10.1117/12.2588791}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13925}, year = {2021}, abstract = {In this work, a cost-effective optofluidic system is propossed and preliminary experimental results are presented. A microfluidic channel monolithically integrated into a photonic integrated circuit technology is used in conjunc- tion with a cyclo-olefin copolymer (COC) substrate to provide fluidic in- and output ports. We report on initial experimental results as well as on the simple and cost-effective fabrication of this optofluidic system by means of micro-milling.}, language = {en} } @inproceedings{OPUS4-1342, title = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, editor = {Amouzou, Kou 'santa and Adanlete Adjanoh, Assiongbon and Reiff-Stephan, J{\"o}rg}, isbn = {978-3-9819225-5-4}, doi = {10.15771/978-3-9819225-5-4}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13424}, year = {2020}, abstract = {Conference Proceedings of the 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes. 1st July 2020 - Kara, Togo.}, language = {en} } @inproceedings{N’GobiDonnouAgbazoetal.2020, author = {N'Gobi, Gabin Koto and Donnou, Hagninou E. V. and Agbazo, M{\´e}dard and Akpo, Aristide. B. and Kounouhewa, Basile B.}, title = {Estimation of the Global Solar Radiation Received on the Soil in Nalohou and Natitingou (Northern Benin)}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SII-1a}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13376}, pages = {41 -- 54}, year = {2020}, abstract = {The design of solar energy systems requires knowledge of the global solar radiation received by solar panels on the ground. However, for many developing countries such as the Benin Republic, there is a serious lack of radiometric stations everywhere in the country. The unavailability of these data, therefore, limits knowledge regarding the optimal functioning of solar installations. To cope with these difficulties, a method for estimating the global irradiation is developed at Nalohou AMMA CATCH station and Natintingou synoptic station, two sites in North-West Benin. This model depends on meteorological and astronomical parameters. Meteorological data such as sunshine duration, relative humidity, and air temperature have been collected on the synoptic station of Natitingou, and observed data of irradiation are collected from Nalohou. They are used to validate the model. The results show that the estimation of the mean square deviation value is around 10 -2 . Overall solar radiation is significant in this region and its annual average value varies between 9.80 kWh/m2 and 10.50 kWh/m2. This model can, therefore, be used by solar system operators to optimize energy production in the region.}, language = {en} } @inproceedings{vandeSandCorasanitiReiffStephan2020, author = {van de Sand, Ron and Corasaniti, Sandra and Reiff-Stephan, J{\"o}rg}, title = {Review of Condition Based Maintenance approaches for vapor compression refrigeration systems}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SI-2a}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13369}, pages = {24 -- 33}, year = {2020}, abstract = {Vapor compression refrigeration systems are subject to performance degradation over time due to the presence of faults. However, latest work in the field of condition-based maintenance shows promising results in the automatic early detection of anomalous behaviour as well as in accurate machine diagnostics and can, therefore, increase the overall system reliability by simultaneously preventing machine downtimes. In this paper, the latest research works carried out within the last decade are reviewed and the approaches are classified regarding their working principles. Furthermore, the work at hand depicts the current research trend in this field and outlines current obstacles.}, language = {en} } @inproceedings{SmajicDuspara2020, author = {Smajic, H. and Duspara, T.}, title = {Design and manufacturing of an unmanned aerial vehicle with air quality control system}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SIII-1b}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13396}, pages = {87 -- 93}, year = {2020}, abstract = {Within the scope of this project, a fully functional model of an unmanned aerial vehicle with an air control system was developed and implemented as a prototype. By using the mobile measuring stations, it is feasible to measure the air quality in any part of the city, independent of the measuring altitude.}, language = {en} } @inproceedings{Dable2020, author = {Dable, Etienne}, title = {Construction of PV Systems for Elementary Schools in the Savannah of Togo}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SIV-1a}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13415}, pages = {111 -- 115}, year = {2020}, abstract = {The savannah region in northern Togo borders on Ghana, Burkina Faso and Benin (Figure 1). It covers 8,596 km2, which is 15\% of the total area of Togo. The regional capital Dapaong has about 100,000 inhabitants. The savannah region consists of 5 prefectures, 70 cantons, 1,073 villages and 451 hamlets. The number of inhabitants is growing rapidly. The population figures were 828,224 in 2010 and 890,403 in 2013, a growth rate of 8.2\% in only 3 years. With 105 inhabitants per km2 the savannah region is more densely populated than German Mecklenburg-Vorpommern (69 inhabitants per km2). The savannah region is the poorest region in the country. In the villages, subsistence farming prevails. Surpluses are sold at village markets or nearby city markets with little profit, since raw products are rarely processed and certainly not processed and the purchasing power in the region is low. The sensitive savannah floors are overused. During the long dry season (October to May) there is a lack of artificial irrigation. The climate change affects the savannah region through shorter and irregular rainy seasons. Deforestation leads to further drying out of the soil. The population is increasing, becoming poorer and poorer and uses almost exclusively wood for cooking in the villages. This leads to further deterioration of the arable land. Harvest yields are falling because improved seeds and fertilisers are also lacking. The infrastructure in the region is at an extremely low level. There are no industrial enterprises in the savannah region. There is an almost complete lack of companies that process and refine agricultural products. There is a lack of storage facilities and cold chains for agricultural products. Only for wood and charcoal there are transport routes from the international highway to regions with better purchasing power. A major obstacle to the establishment of small businesses is the lack of electricity.}, language = {en} } @inproceedings{KrouBabaSegbeayaetal.2020, author = {Krou, Nitale M'Balikine and Baba, Gnon and Segbeaya, Kwamivi N. and Akpaki, Ogouvid{\´e}}, title = {Energy recovery from sewage sludge and fermentable fractions of solid waste from the city of Sokode by co-digestion}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SIII-2a}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13262}, pages = {94 -- 101}, year = {2020}, abstract = {One of the consequences of the improvement of the living conditions of the populations is the strong demand in thermal energy for the households whereas in the developing countries, the cost of living is a brake with all the social layers to reach supply of butane gas for their energy needs. This study takes place in the context of energy, environmental and sanitation challenges in the city of Sokod{\´e}. Indeed, we are witnessing more and more growing needs for butane gas, firewood or charcoal for cooking or lighting in the city of Sokod{\´e} as everywhere in other cities of the same size. Thus by the production of energy in situ, the condition of the populations will be able to improve significantly thanks to the recovery of sludge and fermentable fractions of solid waste into biogas. The objective of this work is to produce and recover methane from fermentable waste produced in the city of Sokod{\´e}. The methane or biogas recovered will be used as fuel to fuel kitchens in households. The resulting digestate will serve as an organic amendment to agricultural soils in the commune of Sokod{\´e}. Laboratory scale tests have been carried out to validate the value of co-digestion of sewage sludge with fermentable solid waste. The results obtained have shown that the methanogenic potential of sewage sludge is low compared to that of fermentable solid waste. The co-digestion of the two products allows a greater production of methane representing an energy gain compared to the methanisation of the sewage sludge alone. This study shows that waste (sludge from public septic tanks, waste from markets, hotels and fermentable households) can be considered an appreciable energy resource. Their Co-treatment would, while reducing the nuisance associated with this waste, produce valuable energy.}, language = {en} } @inproceedings{LiskerNowitzkiHellwigetal.2020, author = {Lisker, Roberto and Nowitzki, Mario and Hellwig, Udo and Wildenauer, Franz-Xaver}, title = {Comparable numerical study on different working fluids for micro scale power cycle integrated into a pellet fired boiler}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SII-2b}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13383}, pages = {73 -- 80}, year = {2020}, abstract = {A cost-effective power cycle shall be developed to supply heat and electricity (co-generation). The aim of this study is to find an appropriate power cycle and working fluid for a friction turbine application. Due to its low production costs, better scalability and low-maintenance requirements, a friction turbine, also known as Tesla turbine, shall be used. In order to find a proper working fluid and estimate the efficiency and power output,a numerical study was performed on five promising working fluids namely Xenon, Argon, Helium, Air and superheated Steam. The simulation model consists of three disks with a diameter of 0,25 m and an outlet diameter of 0,12 mm rotating at constant 10.000 rpm.It is tried to keep the Gap Reynolds number at a constant 73, to ensure a laminar flow regime between the disks. The outcome of the numerical study showed that all working fluids are suitable. The highest efficiency (shaft power / technical power) has been achieved with steam (96\%) and a power output of 126 W/gap. The least efficiency with 89\% has been realized with air and a Power output of 118 W/gap. The noble gases are in between these fluids. By comparing the simulation data and taken into account numerical and estimation errors,all five working fluids are at par. Thus, the choice of the working fluid and the power cycle is an economical. While a hot gas air turbine is not as efficient as the steam turbine, the invest and maintenance costs are lower due to less heat exchangers and necessaries like water reconditioningand a phase separator.}, language = {en} } @inproceedings{OPUS4-1409, title = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021) : 6th April 2021 - Kara, Togo : Conference Proceedings}, editor = {Reiff-Stephan, J{\"o}rg and Amouzou, Kou 'santa and Adanlete Adjanoh, Assiongbon}, publisher = {TIB Open Publishing}, address = {Hannover}, issn = {2748-8829}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14093}, year = {2021}, abstract = {Renewable energy sources are more important today than ever before, as they represent a key factor in reducing greenhouse emissions and fossil fuel consumption. Avoiding excessive burdens on future generations has now become the declared challenge of this century and justifies the efforts we must undertake to reduce global warming. This can only be achieved by conceiving new technical approaches, exploiting alternative resources and by raising people's awareness of the sustainable use of their own livelihoods. However, this change in awareness is a process that needs to be driven forward, especially in the field of research and education, and is therefore the declared aim of the Joint German-West African Conference on Sustainable, Renewable Energy Systems - SusRES. This annual conference provides a platform for exchange between scientists, students and many other interested parties, with technological progress at the forefront of the event. The SusRES conference is known as an accelerator for an ever-growing international network, not limited to the circumstances of a single country or even continent, which strives to take on and meet the global challenges of the present and future. This year's guiding theme of the event -Decentralized systems as a key factor in clean energy production for locations with limited infrastructure- of the event is primarily based on the consideration of how the energy supply of the future is to be designed. For some years now, a paradigm shift towards decentralised energy supply has been observed, which opens up new possibilities especially in areas with weak infrastructural supply. This is not just about providing energy from renewable resources, but also about exploiting this energy we have today efficiently and sustainably, whereby intelligent and interconnected systems play an ever-increasing role. The reader is provided with exciting insights into these topics within this conference proceedings elaborated by stakeholders from twelve time zones and four continents. In their contributions, the authors address important findings, especially from research but also from teaching, which represent an important milestone in their activities and thus make a significant contribution to our declared goals.}, language = {en} } @article{LukoseLiskerAkhtaretal.2021, author = {Lukose, R. and Lisker, Marco and Akhtar, Fatima and Fraschke, Mirko and Grabolla, T. and Mai, Andreas and Lukosius, Mindaugas}, title = {Influence of plasma treatment on SiO2/Si and Si3N4/Si substrates for large-scale transfer of graphene}, series = {Scientific Reports}, volume = {11}, journal = {Scientific Reports}, issn = {2045-2322}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14179}, year = {2021}, abstract = {One of the limiting factors of graphene integration into electronic, photonic, or sensing devices is the unavailability of large-scale graphene directly grown on the isolators. Therefore, it is necessary to transfer graphene from the donor growth wafers onto the isolating target wafers. In the present research, graphene was transferred from the chemical vapor deposited 200 mm Germanium/Silicon (Ge/Si) wafers onto isolating (SiO2/Si and Si3N4/Si) wafers by electrochemical delamination procedure, employing poly(methylmethacrylate) as an intermediate support layer. In order to influence the adhesion properties of graphene, the wettability properties of the target substrates were investigated in this study. To increase the adhesion of the graphene on the isolating surfaces, they were pre-treated with oxygen plasma prior the transfer process of graphene. The wetting contact angle measurements revealed the increase of the hydrophilicity after surface interaction with oxygen plasma, leading to improved adhesion of the graphene on 200 mm target wafers and possible proof-of-concept development of graphene-based devices in standard Si technologies.}, language = {en} } @article{SteglichBondarenkoMaietal.2020, author = {Steglich, Patrick and Bondarenko, Siegfried and Mai, Christian and Paul, Martin and Weller, Michael G. and Mai, Andreas}, title = {CMOS-Compatible Silicon Photonic Sensor for Refractive Index Sensing Using Local Back-Side Release}, series = {IEEE Photonics Technology Letters}, volume = {32}, journal = {IEEE Photonics Technology Letters}, number = {19}, issn = {1941-0174}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13649}, pages = {1241 -- 1244}, year = {2020}, abstract = {Silicon photonic sensors are promising candidates for lab-on-a-chip solutions with versatile applications and scalable production prospects using complementary metal-oxide semiconductor (CMOS) fabrication methods. However, the widespread use has been hindered because the sensing area adjoins optical and electrical components making packaging and sensor handling challenging. In this work, a local back-side release of the photonic sensor is employed, enabling a separation of the sensing area from the rest of the chip. This approach allows preserving the compatibility of photonic integrated circuits in the front-end of line and metal interconnects in the back-end of line. The sensor is based on a micro-ring resonator and is fabricated on wafer-level using a CMOS technology. We revealed a ring resonator sensitivity for homogeneous sensing of 106 nm/RIU.}, language = {en} } @book{OPUS4-1806, title = {Electromagnetic Propagation and Waveguides in Photonics and Microwave Engineering}, editor = {Steglich, Patrick}, publisher = {IntechOpen}, address = {London}, isbn = {978-1-83968-190-5}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-18063}, publisher = {Technische Hochschule Wildau}, pages = {192}, year = {2020}, abstract = {Optical and microwave waveguides have attracted much research interest in both science and industry. The number of potential applications for their use is growing rapidly. This book examines recent advances in the broad field of waveguide technology. It covers current progress and latest breakthroughs in emergent applications in photonics and microwave engineering. The book includes ten contributions on recent developments in waveguide technologies including theory, simulation, and fabrication of novel waveguide concepts as well as reviews on recent advances.}, subject = {Wellenleiter}, language = {en} } @article{SopinskyyGrytsenkoVillringeretal.2023, author = {Sopinskyy, Mykola and Grytsenko, Kostyantyn and Villringer, Claus and Kolomzarov, Yurii and Schrader, Sigurd}, title = {Determination of scattering and Urbach absorption contributions to the light extinction in PTFE films by using graphical representation technique and numerical solution of the inverse problem}, series = {Semiconductor Physics, Quantum Electronics \& Optoelectronics}, volume = {26}, journal = {Semiconductor Physics, Quantum Electronics \& Optoelectronics}, number = {3}, publisher = {National Academy of Sciences of Ukraine. Institute for Semiconductor Physics}, address = {Kyiv}, issn = {1605-6582}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-18035}, pages = {303 -- 314}, year = {2023}, abstract = {Ellipsometrically obtained spectral dependences of ordinary αxy and extra-ordinary αz extinction/attenuation coefficients within the spectral range λ = 300…980 nm of uniaxially anisotropic polytetrafluoroethylene (PTFE) films were analyzed. We considered the capabilities and specific features of the graphical representation technique for determining the contribution of Rayleigh scattering and Urbach absorption to light attenuation in the spectral range beyond fundamental absorption. It has been shown that the graphical approach enables to estimate these contributions qualitatively, semi-quantitatively or quantitatively, depending on the situation. The conclusions made using the analysis of graphical representation are confirmed by numerical solution of the inverse problem via simulation of the αxy (λ), αz (λ) experimental dependences within the framework of a best-fit procedure. Being based on both of these approaches, we have ascertained that, in the as-prepared PTFE films, the so-called anomalous light scattering (ALS) with the spectral dependence of scattering coefficient αs ≈ as λ-p (p > 4) takes place. Transformation of scattering from ALS to the Rayleigh one with p ≈ 4 due to annealing is accompanied by an increase of Urbach (subband) absorption. Both of these factors cause narrowing the dynamic range of extinction coefficient values. Both scattering and absorption coefficients are higher for the component of light polarized along the normal to the substrate as compared to the component polarized in parallel to it. The relationship between observed behavior of the scattering and absorption coefficients and the film structure has been discussed.}, language = {en} } @article{RoosHoqueKlimešovaetal.2023, author = {Roos, Andreas Hult and Hoque, Ziaul and Klimešov{\´a}, Eva and Ben Ltaief, Ltaief and Medina, Cristian and Jurkovič, Matej and Albrecht, Martin and Finke, Ondřej and Hort, Ondřej and Nejdl, Jaroslav and Mudrich, Marcel and Andreasson, Jakob and Krikunova, Maria}, title = {Electron correlation dynamics in atomic Kr excited by XUV pulses and controlled by NIR laser pulses of variable intensity}, series = {New Journal of Physics}, volume = {25}, journal = {New Journal of Physics}, publisher = {Institute of Physics Publishing (IOP)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-16987}, year = {2023}, abstract = {We have investigated the possibility to track and control correlation dynamics of valence electrons in krypton (Kr) initiated by the absorption of one extreme ultraviolet (XUV) photon. In this investigation, pump-probe experiments have been performed where monochromatized single high-harmonics at photon energies 29.6, 32.8, and 35.9 eV have been used as pump to populate different intermediate excited states. A temporally delayed near-infrared (NIR) pulse probes the population of various decay channels via the detection of Kr²⁺ ion yields and its transient profiles. We observe that by varying the NIR pulse intensity within a range from 0.3 x 10¹³ to 2.6 x 10¹³ W cm⁻², the shape of the Kr²+ transient profile changes significantly. We show that by varying the intensity of the NIR pulse, it is possible—(i) to control the ratio between sequential and non-sequential double ionization of Kr; (ii) to selectively probe quantum beating oscillations between Kr+* satellite states that are coherently excited within the bandwidth of the XUV pulse; and (iii) to specifically probe the relaxation dynamics of doubly excited (Kr**) decay channels. Our studies show that the contribution of different ionization and decay channels (i)-(iii) can be altered by the NIR pulse intensity, thus demonstrating an efficient way to control the ionization dynamics in rare gas atoms.}, language = {en} } @inproceedings{SteglichMai2021, author = {Steglich, Patrick and Mai, Andreas}, title = {Analysis of BTO-on-Si-waveguides for energy-efficient electro-optical modulators}, series = {Proc. SPIE 11775, Integrated Optics: Design, Devices, Systems and Applications VI}, booktitle = {Proc. SPIE 11775, Integrated Optics: Design, Devices, Systems and Applications VI}, doi = {10.1117/12.2592501}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13934}, year = {2021}, abstract = {In this work, we analyze a horizontal slot waveguide configuration, which evaluates the potential for an integration of barium titanate (BTO) based modulators into a photonic integrated circuit (PIC) technology based on siliconon- insulator (SOI) wafer. The waveguide configuration consists of a doped crystal silicon layer, a Ba0:7Sr0:3TiO3 (BST) template layer, a barium titanate (BTO) layer and a doped poly-silicon layer on top. In contrast to current approaches, we analyze the performance of this waveguide-structure by using a vertical electrode configuration that is formed by the doped silicon layer. In this way, the electric field strength is dramatically increased compared to current horizontal electrode configuration.}, language = {en} } @article{YeshchenkoDmitrukGrytsenkoetal.2009, author = {Yeshchenko, Oleg A. and Dmitruk, Igor M. and Grytsenko, Kostyantyn and Prokopets, Vadym M. and Kotko, Andriy V. and Schrader, Sigurd}, title = {Influence of interparticle interaction on melting of gold nanoparticles in Au/polytetrafluoroethylene nanocomposites}, series = {Journal of Applied Physics}, volume = {105}, journal = {Journal of Applied Physics}, number = {9}, issn = {1089-7550}, doi = {10.1063/1.3125274}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-9759}, year = {2009}, abstract = {The temperature dependence of the surface plasmon resonance energy and width in 5 nm spherical gold nanoparticles embedded in a polymer polytetrafluoroethylene matrix has been studied using absorption spectroscopy. The jumplike features have been observed in these dependences indicating the melting of gold nanoparticles at temperatures considerably lower than the bulk melting point. The interaction between gold nanoparticles sufficiently affects the melting of nanoparticles. The increase in the filling factor of the particles leads to a decrease in the melting temperature of gold nanoparticles.}, language = {en} } @book{OPUS4-1809, title = {Fiber Optics - From Fundamentals to Industrial Applications}, editor = {Steglich, Patrick and De Matteis, Fabio}, publisher = {IntechOpen}, address = {London}, isbn = {978-1-83881-157-0}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-18093}, publisher = {Technische Hochschule Wildau}, pages = {102}, year = {2019}, abstract = {Optical fibers in metrology, telecommunications, sensors, manufacturing, and health science have gained massive research interest. The number of applications is increasing at a fast pace. This book aims to present a collection of recent advances in fiber optics, addressing both fundamental and industrial applications. It covers the current progress and latest breakthroughs in emergent applications of fiber optics. The book includes five chapters on recent developments in optical fiber communications and fiber sensors, as well as the design, simulation, and fabrication of novel fiber concepts.}, language = {en} } @book{OPUS4-1808, title = {Plasmonic Nanostructures - Basic Concepts, Optimization and Applications}, editor = {Steglich, Patrick}, publisher = {IntechOpen}, address = {London}, isbn = {978-1-80356-004-5}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-18084}, publisher = {Technische Hochschule Wildau}, pages = {126}, year = {2023}, abstract = {Plasmonics includes the fundamentals of surface plasmon polaritons in metals, and its rapidly increasing applications in biochemistry, nanotechnology, optical communication, sensing, and medicine. Surface plasmon polaritons have become popular because of their ultrasensitive optical measurement capabilities, and in recent years they have also been employed for ultra-high-speed data transfer. This book presents recent advances in the broad field of plasmonics, covering not only current progress and the latest breakthroughs in emergent applications but also geometry optimizations and the fundamentals of physical interactions.}, subject = {Plasmonik}, language = {en} } @article{BauerGutkeHeinrichetal.2020, author = {Bauer, Joachim and Gutke, Marko and Heinrich, Friedhelm and Edling, Matthias and Stoycheva, Vesela and Kaltenbach, Alexander and Burkhardt, Martin and Gruenefeld, Martin and Gamp, Matthias and Gerhard, Christoph and Steglich, Patrick and Steffen, Sebastian and Herzog, Michael and Dreyer, Christian and Schrader, Sigurd}, title = {Novel UV-transparent 2-component polyurethane resin for chip-on-board LED micro lenses}, series = {Optical Materials Express}, volume = {10}, journal = {Optical Materials Express}, number = {9}, issn = {2159-3930}, doi = {10.1364/OME.393844}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13472}, pages = {2085 -- 2099}, year = {2020}, abstract = {In this work we present a novel optical polymer system based on polyurethane elastomer components, which combines excellent UV transparency with high thermal stability, good hardness, high surface tension and long pot life. The material looks very promising for encapsulation and microlensing applications for chip-on-board (CoB) light-emitting diodes (LED). The extinction coefficient k, refractive index n, and bandgap parameters were derived from transmission and reflection measurements in a wavelength range of 200-890 nm. Thermogravimetry and differential scanning calorimetry were used to provide glass transition and degradation temperatures. The surface tension was determined by means of contact angle measurements. As proof of concept, a commercial InGaN-CoB-LED is used to demonstrate the suitability of the new material for the production of microlenses.}, language = {en} } @article{GoldenbergKoehlerKahleetal.2020, author = {Goldenberg, Leonid and K{\"o}hler, Mathias and Kahle, Olaf and Dreyer, Christian}, title = {Impact of inorganic nanoparticles on optical properties of low refractive index waveguiding polymers}, series = {Optical Materials Express}, volume = {10}, journal = {Optical Materials Express}, number = {11}, issn = {2159-3930}, doi = {10.1364/OME.405700}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13521}, pages = {2987 -- 2997}, year = {2020}, abstract = {The objective of this work is to improve the optical properties of low refractive index polymers used for waveguide by introduction of inorganic nanoparticles. Copolymers of fluorinated monomers and glycidyl methacrylate are used. Introduction of SiO2 nanoparticles into polymer matrix is performed by direct mixing; copolymerization with SiO2 nanoparticles modified by monomer, and in situ sol-gel formation of SiO2 during photochemical cross-linking and annealing catalyzed by photoacid generator. It is demonstrated that nanoparticles are able to decrease thermo-optic coefficient. It is also possible to fabricate waveguiding layers by direct introduction of nanoparticles without compromising of optical propagation losses.}, language = {en} } @article{FelkeGrothHempeletal.2024, author = {Felke, Florens and Groth, Anne and Hempel, Martin and Czerny, Bernhard and Khatibi, Golta and D{\"o}hler, Torsten and Geißler, Ute}, title = {Effect of the loop forming process on the lifetime of aluminum heavy wire bonds under accelerated mechanical testing}, series = {Microelectronics Reliability}, volume = {154}, journal = {Microelectronics Reliability}, publisher = {Elsevier}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-18631}, year = {2024}, abstract = {Heavy wire bonding is one of the most common interconnection technologies in manufacturing of high-power electronics. For industrial applications, the long-term reliability of these connections is crucial. Besides the selection of the wire material and the loop geometry itself, the loop forming process parameters also have an influence on the reliability of the wire bond. In this work, the influence of the backward bond head movement during wire bonding process on the quality of wire bond connections was systematically investigated and qualified by cyclic mechanical lifetime tests, surface roughness measurements of the heel area by laser confocal microscopy and static pull tests. The wire bond loops were fabricated with 300 μm aluminum H11 and H14CR wires with different hardness values. The lifetime at low frequency cycle and high frequency cycle regime was determined by means of two different mechanical cyclic test methods operating at 5 Hz and at 60 kHz respectively. The results have shown, that the surface topology of the heel region caused by the initial plastic deformation during the loop forming process has a significant effect on the wire bond failure due to heel cracking. The number of loading cycles to failure shows an inverse correlation with the degree of surface roughness in a so called wrinkling analysis in the low and high frequency cycle regime. The soft wire exhibits different lifetimes compared to the hard ones depending on the testing conditions, while a significant decrease of the lifetime is observed with >30 \% reverse movement during bonding in all cases.}, language = {en} } @inproceedings{SieversVillringerLebeketal.2023, author = {Sievers, Jan and Villringer, Claus and Lebek, Werner and Gilani, Taravat Saeb and Laufer, Jan}, title = {Photoacoustic tomography using a Fabry-Perot sensor with homogeneous optical thickness and wide-field camera-based detection}, series = {Opto-Acoustic Methods and Applications in Biophotonics VI}, booktitle = {Opto-Acoustic Methods and Applications in Biophotonics VI}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-17850}, year = {2023}, abstract = {Fabry-Perot (FP) sensors are typically read out using a raster scan to acquire tomographic Photoacoustic (PA) images. To speed up the recording time, wide-field illumination of the sensor in combination with a camera as detector can be used. In this study, an sCMOS camera and wavelengths around 517 nm are used to interrogate a FP sensor with a homogeneous optical thickness over a 4 cm2 aperture. The recorded time series show PA signals are acquired over the entire area of the interrogation beam. The performance of the system, such as the noise equivalent pressure, is evaluated.}, language = {en} } @article{DubrovinskaiaDubrovinskyCrichtonetal.2005, author = {Dubrovinskaia, Natalia and Dubrovinsky, Leonid and Crichton, Wilson and Langenhorst, Falko and Richter, Asta}, title = {Aggregated diamond nanorods, the densest and least compressible form of carbon}, series = {Applied Physics Letters}, volume = {87}, journal = {Applied Physics Letters}, number = {8}, issn = {0003-6951}, doi = {10.1063/1.2034101}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-5646}, year = {2005}, abstract = {We report the synthesis of aggregated diamondnanorods (ADNRs) from fullerene C60C60 at 20(1) GPa and 2200  °C using a multianvil apparatus. Individual diamond nanoroads are of 5-20 nm in diameter and longer than 1μm1μm. The x-ray and measured density of ADNRs is ∼0.2\%-0.4\%∼0.2\%-0.4\% higher than that of usual diamond. The extremely high isothermal bulk modulusKT=491(3)GPaKT=491(3)GPa [compare to KT=442(4)GPaKT=442(4)GPa of diamond] was obtained by in situx-ray diffraction study. Thus, ADNRs is the densest among all carbonmaterials and it has the lowest so far experimentally determined compressibility.}, language = {en} } @misc{BraeskeKlohsMirre2016, author = {Br{\"a}ske, J{\"o}rn and Klohs, Steffen and Mirre, Thomas}, title = {Untersuchung zum Ausfall der Strangf{\"u}hrungsrollen in der horizontalen Zone einer Brammenstranggussanlage}, series = {Wissenschaftliche Beitr{\"a}ge 2016}, volume = {20}, journal = {Wissenschaftliche Beitr{\"a}ge 2016}, issn = {0949-8214}, doi = {10.15771/0949-8214_2016_1_7}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-5346}, pages = {49 -- 58}, year = {2016}, abstract = {Es besteht ein Problem durch den h{\"a}ufigen Ausfall der Strangf{\"u}hrungsrollen und die resultierenden erheblichen Verluste durch den Produktionsausfall, welcher beim Ersetzen der Rolleneinheiten entsteht. Um die Ursachen zu ergr{\"u}nden wurden, zun{\"a}chst die Randbedingungen und das Schadensbild analysiert. Daraus entstand die Hypothese, dass allgemein eine zu hohe Temperaturbelastung f{\"u}r die Sch{\"a}digung der Lagerkomponenten verantwortlich ist und dies die grundlegende Ursache f{\"u}r die weitere Zerst{\"o}rung darstellt. Folglich musste eine Messeinrichtung installiert werden, um genauere Erkenntnisse {\"u}ber den {\"U}berhitzungsvorgang zu erlangen. Zu diesem Zweck wurden mehrere Verfahren zur Temperaturmessung miteinander verglichen, woraufhin eine Auswahl anhand einer Nutzwertanalyse erfolgte. Die Auswertung der gewonnenen Messdaten zeigte, dass die Charakteristik der aufgezeichneten {\"U}berhitzungen sehr variabel ist. Weiterhin konnte keine Abh{\"a}ngigkeit von einem Prozessparameter ermittelt werden. Die genauer betrachteten Vorg{\"a}nge konnten nicht oder nur eingeschr{\"a}nkt als Ursache f{\"u}r die {\"U}berhitzung nachgewiesen werden. Wenngleich somit weitere Untersuchungen erforderlich sind, wurden m{\"o}gliche Maßnahmen zur L{\"o}sung des Problems vorgeschlagen.}, language = {de} } @article{OuAnwandKoegleretal.2014, author = {Ou, Xin and Anwand, Wolfgang and K{\"o}gler, Reinhard and Zhou, Hong-Bo and Richter, Asta}, title = {The role of helium implantation induced vacancy defect on hardening of tungsten}, series = {Journal of Applied Physics}, volume = {115}, journal = {Journal of Applied Physics}, number = {12}, issn = {1089-7550}, doi = {10.1063/1.4870234}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-5623}, year = {2014}, abstract = {Vacancy-type defects created by helium implantation in tungsten and their impact on the nano-hardness characteristics were investigated by correlating the results from the positron annihilation spectroscopy and the nano-indentation technique. Helium implantation was performed at room temperature (RT) and at an elevated temperate of 600 °C. Also, the effect of post-annealing of the RT implanted sample was studied. The S parameter characterizing the open volume in the material was found to increase after helium irradiation and is significantly enhanced for the samples thermally treated at 600 °C either by irradiation at high temperature or by post-annealing. Two types of helium-vacancy defects were detected after helium irradiation; small defects with high helium-to-vacancy ratio (low S parameter) for RT irradiation and large defects with low helium-to-vacancy ratio (high S parameter) for thermally treated tungsten. The hardness of the heat treated tungsten coincides with the S parameter, and hence is controlled by the large helium-vacancy defects. The hardness of tungsten irradiated at RT without thermal treatment is dominated by manufacturing related defects such as dislocation loops and impurity clusters and additionally by trapped He atoms from irradiation effects, which enhance hardness. He-stabilized dislocation loops mainly cause the very high hardness values in RT irradiated samples without post-annealing.}, language = {en} } @article{RoggeZinnProspositoetal.2017, author = {Rogge, Christian and Zinn, Steffen and Prosposito, Paolo and Francini, Roberto and Foitzik, Andreas}, title = {Transmitted light pH optode for small sample volumes}, series = {Journal of Sensors and Sensor Systems}, volume = {6}, journal = {Journal of Sensors and Sensor Systems}, number = {2}, issn = {2194-878X}, doi = {10.5194/jsss-6-351-2017}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-10093}, pages = {351 -- 359}, year = {2017}, abstract = {An innovative concept of a low-cost pH optode with working volumes of less than 150 µL is presented. The pH monitoring is based on the color changing effect of pH indicators. The optode includes an RGB color sensor patch TCS34725 from Adafruit, a controllable LED and reactor slides and is addressed by a self-written LabVIEW© software. Utilizing the hue value of the HSV color model, it is possible to analyze the color change of the indicator and estimate the pH value of the analyzed samples by exploiting sigmoidal fit models. Measurements carried out with phenol red and DMEM (Dulbecco's Modified Eagle's Medium) reported a standard error of calibration in the physiologic pH range (6.5-7.5) of ±0.04 pH units.}, language = {en} } @article{MaierClausiusRichteretal.2021, author = {Maier, Petra and Clausius, Benjamin and Richter, Asta and Bittner, Benjamin and Hort, Norbert and Menze, Roman}, title = {Crack Propagation in As-Extruded and Heat-Treated Mg-Dy-Nd-Zn-Zr Alloy Explained by the Effect of LPSO Structures and Their Micro- and Nanohardness}, series = {Materials}, volume = {14}, journal = {Materials}, number = {13}, publisher = {MDPI}, issn = {1996-1944}, doi = {10.3390/ma14133686}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14194}, year = {2021}, abstract = {The investigation of the crack propagation in as-extruded and heat-treated Mg-Dy-Nd-Zn-Zr alloy with a focus on the interaction of long-period stacking-ordered (LPSO) structures is the aim of this study. Solution heat treatment on a hot extruded Mg-Dy-Nd-Zn-Zr (RESOLOY®) was done to change the initial fine-grained microstructure, consisting of grain boundary blocky LPSO and lamellar LPSO structures within the matrix, into coarser grains of less lamellar and blocky LPSO phases. C-ring compression tests in Ringer solution were used to cause a fracture. Crack initiation and propagation is influenced by twin boundaries and LPSO lamellae. The blocky LPSO phases also clearly hinder crack growth, by increasing the energy to pass either through the phase or along its interface. The microstructural features were characterized by micro- and nanohardness as well as the amount and location of LPSO phases in dependence on the heat treatment condition. By applying nanoindentation, blocky LPSO phases show a higher hardness than the grains with or without lamellar LPSO phases and their hardness decreases with heat treatment time. On the other hand, the matrix increases in hardness by solid solution strengthening. The microstructure consisting of a good balance of grain size, matrix and blocky LPSO phases and twins shows the highest fracture energy.}, language = {en} } @article{SmithChristopherKennyetal.2003, author = {Smith, Roger and Christopher, D. and Kenny, S. D. and Richter, Asta and Wolf, Bodo}, title = {Defect generation and pileup of atoms during nanoindentation of Fe single crystals}, series = {Physical Review B}, volume = {67}, journal = {Physical Review B}, number = {24}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14855}, year = {2003}, abstract = {Complementary large scale molecular-dynamics simulations and experiments have been carried out to determine the atomistic mechanisms of the nanoindentation process in single crystal Fe {110}, {100}, and {111}. The defect formation and motion causes the complex mechanisms of plastic and elastic deformation which is reflected in the pileup patterns. The experimental results show distinct patterns of pileup material which are dependent on the individual crystal faces and the superposition of the stress field of the indenter. The highest pileup around the indenter hole occurs on the {100} surface and the shallowest on {111}. The least symmetric surface is {110} which produces an experimental pileup pattern displaying only twofold symmetry with the axially symmetric indenter. The pyramidal indenter produces an asymmetric pattern which changes as the crystal is rotated with respect to the tip but repeats with threefold rotational symmetry. Material displacement occurs primarily in planes of the {110} family. Pileup is formed by cross slip between planes of the same family which intersect in ⟨111⟩ directions. For the {110} surface, dislocation loops propagate in the four in-plane ⟨111⟩ directions and the two inclined ⟨111⟩ directions. The loops that propagate in the in-plane directions are terminated by edge dislocations at the surface. These transport material away from the tip but cannot produce pileup. The loops that propagate in the inclined direction cross slip and cause the observed pileup. The {100} surface has fourfold rotational symmetry and all the ⟨111⟩ directions are inclined. The dislocation loops propagate in these directions and cross slip readily occurs, leading to a large pileup. The {111} face shows the least pileup which is more spread out over the surface. In this case the dislocation loops propagate in shallow slip planes and do not readily cross slip. Experimentally determined force-depth curves show distinct "pop-ins" which correspond to the formation of dislocations. The contact pressure (nanohardness) is not a constant and increases with decreasing indentation depth. It also changes with crystal face. Calculated force-depth curves match the experimental trend but give estimates of the nanohardness and Young's modulus higher than those values experimentally determined.}, language = {en} } @article{GerhardDobis2021, author = {Gerhard, Christoph and Dobis, Alexander}, title = {Manufacturing-induced surface contaminations}, series = {Vakuum in Forschung und Praxis}, volume = {33}, journal = {Vakuum in Forschung und Praxis}, number = {1}, publisher = {Wiley}, doi = {https://doi.org/10.1002/vipr.202100752}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15656}, pages = {33 -- 37}, year = {2021}, abstract = {Summary In the course of classical optics manufacturing glass components are in permanent direct contact with aqueous operating materials. Such contact leads to a certain absorption of water and hydrogenous compounds that may induce severe glass defects. In this contribution, absorption of hydrogen and other contaminants during grinding of glass was observed and qualitatively detected via laser-induced breakdown spectroscopy. It is shown that hydrogen, calcium, magnesium, and carbon are implanted into the glass surface where the contaminant concentration increases over grinding time or contact time of the glass surface with water and the grinding tool, respectively. The contaminants hydrogen, calcium, and magnesium can be attributed to the water used as lubricant. In contrast, carbon most likely originates from wear debris of the used silicon carbide grinding pads. Several possible mechanisms that lead to such surface contamination of glasses during grinding - diffusion, accumulation in micro cracks as well as the formation of hydrated silica - are finally introduced.}, language = {en} } @article{TarabrinBushunovTeslenkoetal.2021, author = {Tarabrin, Mikhail K. and Bushunov, Andrey A. and Teslenko, Andrei A. and Sakharova, Tatiana and Hinkel, Jonas and Usenov, Iskander and D{\"o}hler, Torsten and Geißler, Ute and Artyushenko, Viacheslav and Lazarev, Vladimir A.}, title = {Fabrication of an antireflection microstructure on AgClBr polycrystalline fiber by single pulse femtosecond laser ablation}, series = {Optical Materials Express}, volume = {11}, journal = {Optical Materials Express}, number = {2}, publisher = {Optical Society of America}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15384}, pages = {487 -- 496}, year = {2021}, abstract = {Polycrystalline infrared (PIR) fibers are used for numerous applications, one of those being power delivery for CO2 lasers. However, the fiber tip surface's transmittance cannot be increased with conventional antireflection coatings due to the surface unevenness. Antireflection microstructures (ARMs) offer an alternative way of increasing transmittance. In this work, ARMs were fabricated on the fiber tip surface of an AgClBr fiber by single-pulse femtosecond laser ablation. A single-surface transmittance of 92.8\% at 10.6 μm, a CO2 laser operation wavelength, was achieved. The proposed method can help significantly improve the systems' efficiency, where power delivery for CO2 lasers or sources operating in the wide wavelength range is required.}, language = {en} } @inproceedings{DietrichvandeSandReiffStephan2021, author = {Dietrich, Alexander and van de Sand, Ron and Reiff-Stephan, J{\"o}rg}, title = {Implementation of a Machine Tool Retrofit System}, series = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, booktitle = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, publisher = {TIB Open Publishing}, address = {Hannover}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15004}, pages = {239 -- 247}, year = {2021}, abstract = {Small and medium-sized companies increasingly turning their attention towards the fourth industrial revolution. In order to increase their own long-term competitiveness, there is a growing desire to make production smarter, more efficient, safer and more sustainable through new technologies. Often, however, existing plants cannot be easily replaced by modern equipment. The reasons for this can be high investment costs, excessive downtimes or the unavailability of an equivalent machine. An alternative solution to the purchase of new equipment is the modernisation or expansion of existing systems, also called retrofitting. Thus, this paper deals with the retrofit process of a machine tool, whereby the software architecture of the control unit is the primary concern of this work.}, language = {en} } @inproceedings{GieseReiffStephan2021, author = {Giese, Lutz B. and Reiff-Stephan, J{\"o}rg}, title = {Hydrogen and Usability of Hydrogen Storage Technologies}, series = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, booktitle = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, publisher = {TIB Open Publishing}, address = {Hannover}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14937}, pages = {97 -- 106}, year = {2021}, abstract = {Science, technology and politics agree: hydrogen will be the energy carrier of the future. It will replace fossil fuels based on a sufficient supply from sustainable energy. Since the possibilities of storing and transporting hydrogen play a decisive role here, the so-called LOHC (Liquid Organic Hydrogen Carriers) can be used as carrier materials. LOHC carrier materials can reversibly absorb hydrogen, store it without loss and release it again when needed. Since little or no pressure is required, normal containers or tanks can be used. The volume or mass-related energy densities can reach around a quarter of liquid fossil fuels. This paper is to give an introduction to the field of hydrogen storage and usage of those LOHC, in particular. The developments of the last ten years have been related to the storage and transport of hydrogen with LOHC. These are crucial to meet the future demand for energy carriers e.g. for mobile applications. For this purpose, all transport systems are under consideration as well as the decentralized supply of rural areas with low technological penetration, e.g. regions of Western Africa which are often characterized by a lack of energy supply. Hydrogen bound in LOHC can provide a hazard-free alternative for distribution. The paper provides an overview of the conversion forms as well as the chemical carrier materials. Dibenzyltoluene as well as N-ethylcarbazole - as examples for LOHC - are discussed as well as chemical hydrogen storage materials like ammonia boranes as alternatives to LOHC.}, language = {en} } @inproceedings{vandeSandCorasanitiReiffStephan2021, author = {van de Sand, Ron and Corasaniti, Sandra and Reiff-Stephan, J{\"o}rg}, title = {Positive-Unlabelled Learning based Novelty Detection for Industrial Chillers}, series = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, volume = {1}, booktitle = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, publisher = {TIB Open Publishing}, address = {Hannover}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14965}, pages = {155 -- 164}, year = {2021}, abstract = {Chiller systems are used in many different applications in both the industrial and the commercial sector. They are considered major energy consumers and thus contribute a non-negligible factor to environmental pollution as well as to the overall operating cost. In addition, chillers, especially in industrial applications, are often associated with high reliability requirements, as unplanned system downtimes are usually costly. As many studies over the past decades have shown, the presence of faults can lead to significant performance degradation and thus higher energy consumption of these systems. Thus, data-driven fault detection plays an ever-increasing role in terms of energy efficient control strategies. However, labelled data to train associated algorithms are often only available to a limited extent, which consequently inhibits the broad application of such technologies. Therefore, this paper presents an approach that exploits only a small amount of labelled and large amounts of unlabelled data in the training phase in order to detect fault related anomalies. For this, the model utilizes the residual space of the data transformed through principal component analyses in conjunction with a biased support vector machine, which can be ascribed to the concept of semi-supervised learning, or more specifically, positive-unlabelled learning.}, language = {en} } @inproceedings{FalkvandeSandCorasanitietal.2021, author = {Falk, Constantin and van de Sand, Ron and Corasaniti, Sandra and Reiff-Stephan, J{\"o}rg}, title = {A Comparison Study of Data-Driven Anomaly Detection Approaches for Industrial Chillers}, series = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, booktitle = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, publisher = {TIB Open Publishing}, address = {Hannover}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14970}, pages = {165 -- 174}, year = {2021}, abstract = {Faults in industrial chiller systems can lead to higher energy consumption, increasing wear of system components and shorten equipment life. While they gradually cause anomalous system operating conditions, modern automatic fault detection models aim to detect them at low severity by using real-time sensor data. Many scientific contributions addressed this topic in the past and presented data-driven approaches to detect faulty system states. Although many promising results were presented to date, there is lack of suitable comparison studies that show the effectiveness of the proposed models by use of data stemming from different chiller systems. Therefore this study aims at detecting a suitable data-driven approach to detect faults reliable in different domains of industrial chillers. Thus, a unified procedure is developed, to train all algorithms in an identical way with same data-basis. Since most of the reviewed papers used only one dataset for training and testing, the selected approaches are trained and validated on two different datasets from real refrigeration systems. The data-driven approaches are evaluated based on their accuracy and true negative rate, from which the most suitable approach is derived as a conclusion.}, language = {en} } @unpublished{SteglichRabusSadaetal.2021, author = {Steglich, Patrick and Rabus, Dominik G. and Sada, Cinzia and Paul, Martin and Weller, Michael G. and Mai, Christian and Mai, Andreas}, title = {Silicon Photonic Micro-Ring Resonators for Chemical and Biological Sensing: A Tutorial}, series = {TechRxiv}, journal = {TechRxiv}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-16840}, year = {2021}, abstract = {Silicon photonic micro-ring resonators (MRR) developed on the silicon-on-insulator (SOI) platform, owing to their high sensitivity and small footprint, show great potential for many chemical and biological sensing applications such as label-free detection in environmental monitoring, biomedical engineering, and food analysis. In this tutorial, we provide the theoretical background and give design guidelines for SOI-based MRR as well as examples of surface functionalization procedures for label-free detection of molecules. After introducing the advantages and perspectives of MRR, fundamentals of MRR are described in detail, followed by an introduction to the fabrication methods, which are based on a complementary metal-oxide semiconductor (CMOS) technology. Optimization of MRR for chemical and biological sensing is provided, with special emphasis on the optimization of waveguide geometry. At this point, the difference between chemical bulk sensing and label-free surface sensing is explained, and definitions like waveguide sensitivity, ring sensitivity, overall sensitivity as well as the limit of detection (LoD) of MRR are introduced. Further, we show and explain chemical bulk sensing of sodium chloride (NaCl) in water and provide a recipe for label-free surface sensing.}, language = {en} } @article{AlberAssfalgNayerietal.2022, author = {Alber, J and Assfalg, L and Nayeri, C N and Paschereit, C O and Lahr, Markus and Semmler, L and Twele, J and Fortmann, J and Fischer, J and Latoufis, K and Dorn, I}, title = {3D printed rotor blades for a research wind turbine: Aerodynamic and structural design and testing}, series = {Journal of Physics: Conference Series}, volume = {2265}, journal = {Journal of Physics: Conference Series}, publisher = {Institute of Physics Publishing (IOP)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-16314}, year = {2022}, abstract = {This study combines the design, the 3D printing and the testing of a small 3-bladed wind turbine rotor for research and teaching purposes. The objective is the additive manufacturing of a rotor with a radius of one meter, as an alternative to subtractive methods, such as computerized milling. The blade design is developed using freely available software packages. The aerodynamic considerations include the airfoil selection, the calculation of the blade geometry and the simulation of the ultimate load cases. The structural considerations are focussed on the printable materials, the infill structures and the retrofit of a load-carrying spar. The rotor blades are 3D printed with the BigRep One at the maker space of the TH Wildau. The structural integrity of the prototype blade is tested in terms of the ultimate root bending moments and the centrifugal forces at the HTW Berlin. The aerodynamic run-up tests are performed at the large wind tunnel of the TU Berlin measuring the power curves. The successful prototype paves the way for follow-up projects, such as open field tests and the 3D printing of larger rotor blades.}, language = {en} } @article{HermannGrojoAxenteetal.2017, author = {Hermann, J{\"o}rg and Grojo, David and Axente, Emanuel and Gerhard, Christoph and Burger, Miloš and Craciun, Valentin}, title = {Ideal radiation source for plasma spectroscopy generated by laser ablation}, series = {Physical Review E}, volume = {96}, journal = {Physical Review E}, number = {5}, publisher = {American Physical Society (APS)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-16132}, year = {2017}, abstract = {Laboratory plasmas inherently exhibit temperature and density gradients leading to complex investigations. We show that plasmas generated by laser ablation can constitute a robust exception to this. Supported by emission features not observed with other sources, we achieve plasmas of various compositions which are both uniform and in local thermodynamic equilibrium. These properties characterize an ideal radiation source opening multiple perspectives in plasma spectroscopy. The finding also constitutes a breakthrough in the analytical field as fast analyses of complex materials become possible.}, language = {en} } @misc{GerhardLetienCressentetal.2019, author = {Gerhard, Christoph and Letien, Emilie and Cressent, Thomas and Hofmann, Mandy}, title = {Impact of the plasma power on plasma-induced increase in absorption of fused silica}, series = {Wissenschaftliche Beitr{\"a}ge 2019}, volume = {23}, journal = {Wissenschaftliche Beitr{\"a}ge 2019}, issn = {0949-8214}, doi = {10.15771/0949-8214_2019_5}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-10802}, pages = {33 -- 37}, year = {2019}, abstract = {In the last decades, laser machining of fused silica has gained in importance where the main challenge is to overcome the high transmission of this medium in order to achieve surface absorption. One approach is plasma treatment using hydrogenous process gases. In doing so, a near-surface glass layer is chemically modified by a removal of oxygen and an implantation of hydrogen, resulting in the formation of optically active defects and an increase in absorption. Against this background, the impact of the plasma power on plasma-induced increase in absorption of fused silica was investigated in the present work. Here, the highest efficiency of the plasma treatment process was found at the lowest applied plasma power whereas for higher plasma powers, a notably lower increase in absorption was observed. This effect is attributed to the decomposition of plasma species required for initiating the formation of optically active defects within the glass. Such decomposition increases with rising power due to the corresponding increase in electric field strength within the plasma. This finding is of substantial interest for an extensive understanding of plasma-glass interactions.}, language = {en} } @inproceedings{PrelipceanuCojocariuGrauretal.2015, author = {Prelipceanu, Marius and Cojocariu, Lucian and Graur, Adrian and Schrader, Sigurd}, title = {Analysis of thermally stimulated processes in new phenanthroline derivatives suitable for optoelectronic devices}, series = {Journal of Physics: Conference Series (JPCONF)}, volume = {585}, booktitle = {Journal of Physics: Conference Series (JPCONF)}, issn = {1742-6596}, doi = {10.1088/1742-6596/585/1/012011}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-12050}, year = {2015}, abstract = {Thermally stimulated processes have been studied in thin films of phenanthroline derives to describe the states that had been localized. Ultraviolet Photoelectron Spectroscopy had checked out before thin films of new pyrrolo[l,2-a][l,10] phenanthroline derivatives [1], in order to further applications in optoelectronic devices. The investigated compounds have an electronic band structure which is due to the substituent (R=NO2, Cl) induced transformations of molecular orbitals. Thermally stimulated discharge currents (TSDC) attested dipolar and charge transport mechanisms. Each TSDC peak has been assigned to elementary processes that are different utilizing in addition dielectric spectroscopy (DES), and the mean trap depths have been approximated from thermally stimulated luminescence (TSL) curves.}, language = {en} } @article{KsianzouVelagapudiGrimmetal.2006, author = {Ksianzou, Viachaslau and Velagapudi, R. K. and Grimm, Bernd and Schrader, Sigurd}, title = {Polarization-dependent optical characterization of poly(phenylquinoxaline) thin films}, series = {Journal of Applied Physics}, volume = {100}, journal = {Journal of Applied Physics}, number = {6}, issn = {1089-7550}, doi = {10.1063/1.2349471}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-9761}, year = {2006}, abstract = {Linear optical properties of two types of poly(phenylquinoxaline) (PPQ) are studied by multiwavelength prism coupling technique and optical absorption spectroscopy. Surface roughness measurements are done using atomic force microscopy. PPQs form smooth films of high optical quality having refractive indices above 1.7 in the visible and near infrared spectral ranges. Enhanced birefringence of Δn∼0.04Δn∼0.04 has been observed in both PPQ films prepared by spin coating. Sellmeier coefficients are derived for the wavelength range starting from 0.532to1.064μm0.532to1.064μm for both TE and TM polarizations. Quantum chemical calculations both on the semiempirical and on the ab initio level are carried out in order to calculate the first-order molecular polarizability tensors of the polymer repeat units. From the obtained tensor elements, theoretical values for both the average refractive indices and the maximum expectable birefringence are calculated. Based on these values a more detailed interpretation of the experimental findings is carried out. The dispersion of refractive index is quantified by the value of Abbe's constant (νd)(νd). In our case the value νd≈11νd≈11 indicates high dispersion in the visible spectral range. The imaginary part kk of the complex refractive index n∗=n-ikn*=n-ik reaches values of k⩽10-3k⩽10-3 in the wavelength range from 0.5to1μm0.5to1μm.}, language = {en} } @article{MinaevJanssonAgrenetal.2006, author = {Minaev, Boris and Jansson, Emil and {\AA}gren, Hans and Schrader, Sigurd}, title = {Theoretical study of phosphorescence in dye doped light emitting diodes}, series = {The Journal of Chemical Physics}, volume = {125}, journal = {The Journal of Chemical Physics}, number = {23}, issn = {1089-7690}, doi = {10.1063/1.2388263}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-9775}, year = {2006}, abstract = {Phosphorescence of platinum(II) octaethyl porphyrin (PtOEP), which has been used in organic light emitting diodes to overcome the efficiency limit imposed by the formation of triplet excitons, is studied by time-dependent (TD) density functional theory (DFT).}, language = {en} } @article{GerhardGimpelTascheetal.2018, author = {Gerhard, Christoph and Gimpel, Thomas and Tasche, Daniel and Koch, Jennifer and Br{\"u}ckner, Stephan and Flachenecker, G{\"u}nter and Wieneke, Stephan and Schade, Wolfgang and Vi{\"o}l, Wolfgang}, title = {Atmospheric pressure plasma-assisted femtosecond laser engraving of aluminium}, series = {Journal of Physics D: Applied Physics}, volume = {51}, journal = {Journal of Physics D: Applied Physics}, issn = {1361-6463}, doi = {10.1088/1361-6463/aab6e6}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-10521}, pages = {1 -- 7}, year = {2018}, abstract = {In this contribution, we report on the impact of direct dielectric barrier discharge argon plasma at atmospheric pressure on femtosecond laser engraving of aluminium. It is shown that the assisting plasma strongly affects the surface geometry and formation of spikes of both laser-engraved single lines and patterns of adjacent lines with an appropriate overlap. Further, it was observed that the overall ablation depth is significantly increased in case of large-scale patterning whereas no notable differences in ablation depth are found for single lines. Several possible mechanisms and underlying effects of this behaviour are suggested. The increase in ablation depth is supposed to be due to a plasma-induced removal of debris particles from the cutting point via charging and oxidation as supported by EDX analysis of the re-solidified debris. Furthermore, the impact of a higher degree of surface wrinkling as well as direct interactions of plasma species with the aluminium surface on the ablation process are discussed.}, language = {en} }