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Sustainable software architecture is crucial for the success of an evolving system that is affected by its context and environment. However, deviations between software design and implementation are often uncontrolled and induce architectural erosion. The literature describes several symptoms and observes this phenomenon in open source software. Prominent reasons for the occurrence of architectural erosion include a rushed evolution, recurring changes, a lack of developers' awareness, time pressures, and the accumulation of design decisions. Architectural erosion is also prevalent in academic projects, but it still needs to be researched in-depth in a real-life setting.
In this work, a single case study investigates the symptoms and reasons for architectural erosion in open source software originating from academia by employing a mixed-methods approach. Architectural metrics from a static code analysis using ARCADE Core are contrasted with developers' perspectives sourced from semistructured interviews. The investigated project is JackTrip, a cross-platform application for realtime networked music performances and Internet reverberation research.
The first research question aims at assessing the trend of structural symptoms for architectural erosion in JackTrip. The results show a significant increase in link overload smells in the course of the evolution, which reached 11 as of version 1.6.2. This supports the developers' perception of a rushed evolution corresponding to the second research question, which asks to what extent prominent causes for architectural erosion apply. Additionally, the interview data evince time constraints related to tight research funding and the commercialization of the project. Research question 3 investigates how the academic environment and the problem domain relate to the symptoms and reasons for architecture erosion. It has been found that these influences shape the development approach and impact contributor selection.
In relation to a certain inexperience and lack of commitment of open source developers as a reason for architectural erosion, the results suggest further studies and opt for ending the discussion regarding skills. Currently, the role of an architect or dedicated architectural work does not seem to be present in the JackTrip project. However, structural issues described in this work should not be considered as categorical statements about its software architecture as they would need to be confirmed on a code level.
This study aims to optimize the power generation of a conventional Manzanares solar chimney (SC) plant through strategic modifications to the collector inlet height, chimney diameter, and chimney divergence. Employing a finite volume-based solver for numerical analysis, we systematically scrutinize influential geometric parameters, including collector height (hi = 1.85 to 0.1 m), chimney inlet diameter (dch = 10.16 to 55.88 m), and chimney outlet diameter (do = 10.16 to 30.48 m). Our findings demonstrate that reducing the collector inlet height consistently leads to increased power output. The optimal collector inlet height of hi = 0.2 m results in a significant power increase from 51 to 117.42 kW (~ 2.3 times) without additional installation costs, accompanied by an efficiency of 0.25%. Conversely, enlarging the chimney diameter decreases the chimney base velocity and suction pressure. However, as turbine-driven power generation rises, the flow becomes stagnant beyond a chimney diameter of 45.72 m. At this point, power generation reaches 209 kW, nearly four times greater than the Manzanares plant, with an efficiency of 0.44%. Nevertheless, the cost of expanding the chimney diameter is substantial. Furthermore, the impact of chimney divergence is evident, with power generation, collector efficiency, overall efficiency, and collector inlet velocity all peaking at an outer chimney diameter of 15.24 m (corresponding to an area ratio of 2.25). At this configuration, power generation increases to 75.91 kW, approximately 1.5 times more than the initial design. Remarkably, at a low collector inlet height of 0.2 m, combining it with a chimney diameter of 4.5 times the chimney inlet diameter (4.5dch) results in an impressive power output of 635.02 kW, signifying a substantial 12.45-fold increase. To model the performance under these diverse conditions, an artificial neural network (ANN) is effectively utilized.
Assessing the effects of the energy transition and liberalization of energy markets on resource adequacy is an increasingly important and demanding task. The rising complexity in energy systems requires adequate methods for energy system modeling leading to increased computational requirements. Furthermore, with complexity, uncertainty increases likewise calling for probabilistic assessments and scenario analyses. To adequately and efficiently address these various requirements, new methods from the field of data science are needed to accelerate current methods. With our systematic literature review, we want to close the gap between the three disciplines (1) assessment of security of electricity supply, (2) artificial intelligence, and (3) design of experiments. For this, we conduct a large-scale quantitative review on selected fields of application and methods and make a synthesis that relates the different disciplines to each other. Among other findings, we identify metamodeling of complex security of electricity supply models using AI methods and applications of AI-based methods for forecasts of storage dispatch and (non-)availabilities as promising fields of application that have not sufficiently been covered, yet. We end with deriving a new methodological pipeline for adequately and efficiently addressing the present and upcoming challenges in the assessment of security of electricity supply.
Knowledge is our most valuable asset! Due to the increasing fluctuation caused by demographic change, the change in society and the industry, companies are increasingly confronted with knowledge management. Therefore, companies have problems with carrying out projects effectively. There are several models, methods and tools to develop an effective concept for knowledge management. Can the process capability of projects be ensured despite high fluctuation? What appropriate methods and tools are available to manage knowledge? These and more questions are clarified in the course of this work and presented in a conceptual proposal.
Product placement on YouTube: An explorative study on YouTube creators’ experiences with advertisers
(2017)
During its process of diffusion, YouTube has become increasingly attractive for advertisers, not only in terms of classical commercials (like pre-roll ads) but also in terms of product placement opportunities. This article aims to explore the processes between YouTube creators and advertisers concerning product placement enquiries. For this purpose, YouTube creators from Germany ( n = 57) answered an online survey about their experiences with advertisers. The creators covered a wide range of YouTube channel genres (beauty, fashion, comedy, gaming, cooking) and differed in number of subscribers. Some creators who took part in the survey had less than 20,000 subscribers, others had between 20,000 and 500,000 subscribers and still others had more than 500,000 subscribers. How often do YouTube creators use product placement? Is paid-for placement an important source of finance for them? How professional are the relations and processes between YouTube creators and advertisers? Before presenting and discussing the results of the empirical survey of the current use of product placement, a brief history of how YouTube has become a marketing space for advertisers is provided.
Rotary mowers are ofen used for forage harvesting in agriculture, as this technology can achieve a high throughput. These knives are therefore exposed to high levels of wear and tear, and will also be ofen changed because of loss of material by bad cutting quality. That
is why it is interesting to save costs during manufacturing in spite of a correspondingly long service life. This research records the current manufacturing quality of the mower blades and examines how they behave in comparison. Based on the obtained results, further decisions on the methods, procedures and ways of extending the life of the disc mower blades should be proposed. For the investigations, a test bench based on a wear pot was used. The wear that occurs on the blade is determined using several parameters and compared accordingly. The parameters of the test setup determined as a result of the test can be used for further studies of wear resistance.
In the intersection of technology and music listening, understanding user experiences is paramount. This research employed the Experience Sampling Method via the smartphone app MuPsych to continuously capture real-time data on individuals' music listening behaviors and related emotional responses. Over a span of two weeks, participants from Germany were prompted to report on various factors as they engaged in music listening, resulting in a rich dataset. Results indicate that Spotify Premium was the most frequently used music application, with personal playlists being the preferred listening format. To unravel the intricacies of these responses and their determinants, linear mixed-effects model analysis was utilized. Among the critical findings, the Perceived Usefulness and Perceived Ease of Use, two of the central constructs of the Technology Acceptance Model, emerged as significant predictors for the valence and enjoyment of the music experienced by users during the onset of music listening sessions. This highlights the imperative role of user-friendly interfaces in enhancing positive emotional states even before fully engaging with the music, underscoring the need for designers and developers of music-related apps to prioritise usability and useful functions.
Well-trained professionals, like social workers, are essential for effective prevention of child sexual abuse (CSA). The present study assesses knowledge and knowledge acquisition regarding CSA in social work undergraduate students in a cross-sectional design. Three options for acquisition were assumed: 1) professional education, 2) media consumption, or 3) own experiences of CSA. Results indicated no improvement of knowledge through any of the prior mentioned sources and a high variability in knowledge. In contrast to expectations, personal experiences of CSA were associated with a higher threshold in recognition of CSA incidents. The meaning of the results for prevention and intervention are discussed by highlighting the role of taboos in professional education and the effects of media coverage.
Introduction. Music streaming services have changed how music is played and perceived, but also how it is managed by individuals. Voice interfaces to such services are becoming increasingly com-mon, for example through voice assistants on mobile and smart devices, and have the poten-tial to further change personal music management by introducing new beneficial features and new challenges.
Method. To explore the implications of voice assistants for personal music listening and management we surveyed 248 participants online and in a lab setting to investigate (a) in which situa-tions people use voice assistants to play music, (b) how the situations compare to established activities common during non-voice assistant music listening, and (c) what kinds of com-mands they use.
Analysis. We categorised 653 situations of voice assistant use, which reflect differences to non-voice assistant music listening, and established 11 command types, which mostly reflect finding or refinding activities but also indicate keeping and organisation activities.
Results. Voice assistants have some benefits for music listening and personal music management, but also a notable lack of support for traditional personal information management activities, like browsing, that are common when managing music.
Conclusion. Having characterised the use of voice assistants to play music, we consider their role in per-sonal music management and make suggestions for improved design and future research.
Artificial intelligence and design of experiments for resource adequacy assessment in power systems
(2024)
A two-component system for control and monitoring of solar power towers with molten salt receivers is proposed. The control component consists of a model predictive control applica-tion (MPC) with a flexible objective function and on-line tunable weights, which runs on a In-dustrial PC and uses a reduced order dynamic model of the receiver’s thermal and flow dy-namics. The second component consists of a service-life monitoring unit, which estimates the service-life consumption of the absorber tubes depending on the current mode of operation based on thermal stresses and creep fatigue in the high temperature regime. The calculation of stresses is done based on a detailed finite element study, in which a digital twin of the re-ceiver was developed. By parallelising the model solver, the estimation of service-life con-sumption became capable of real-time operation. The system has been implemented at a test facility in Jülich, Germany, and awaits field experiments. In this paper, the modeling and archi-tecture are presented along simulation results, which were validated on a hardware-in-the-loop test bench. The MPC showed good disturbance rejection while respecting process variable constraints during the simulation studies.
Magnetic Resonance (MR) elastography is a method for measuring tissue elasticity via phase images acquired with an MR scanner. The propagation of periodic mechanical waves through the tissue can be captured by means of a modified phase contrast sequence. These waves are generated with a mechanical oscillator (actuator) and coupled into the tissue through the skin. The actuator must be capable of generating a sinusoidal excitation with excellent phase and amplitude stability, while not disturbing the MR imaging process. In this work, an actuator based on a piezoelectric principle was developed. Based on the imaging evaluation of several material samples, the housing for the piezoelectric ceramic was constructed of aluminum. Smaller parts of the housing were manufactured from brass and titanium to fulfill the mechanical constraints. A lever was used to transfer the oscillation generated by the piezoelectric ceramic to the point of excitation. The lever amplifies the piezoelectric motion, allowing for a more compact design. Three different lever designs were characterized by an acceleration sensor both outside and inside the magnet. It was shown that the rigidity of the lever, as determined by its material and form, was decisive in determining the resonant frequency of the system and therefore the maximum practical frequency of operation. It was also shown that the motion of the oscillator is unaffected by the electromagnetic fields of the MR imager. The final design can be placed directly in the magnet bore within a few centimeters of the tissue volume to be imaged without generating significant artifacts. An amplitude range of 0–1 mm in the frequency range from 0 to over 300 Hz was achieved, sufficient for performing most MR elastography applications. © 2002 Wiley Periodicals, Inc. Concepts in Magnetic Resonance (Magn Reson Engineering) 15: 239–254, 2002
Men afflicted with hypogonadism have reduced fat-free mass and in some cases a loss in muscle strength. We hypothesize that muscle elasticity of the lower extremities differs between patients with hypogonadism and healthy controls. The shear modulus of the soleus muscle was measured non-invasively using MR elastography (MRE) at 0%, 5%, 10%, 15%, and 20% of the subject’s maximum applied force. The results from this study showed statistical differences between the patients and controls, even though there were no statistical differences in applied force.
Men afflicted with chronic obstructive pulmonary disease (COPD) show signs of muscle dysfunction, such as increased muscle fatigue and acidosis during exercise. We hypothesize that muscle elasticity of the lower extremities differs between patients with COPD and age-related controls. The shear modulus of the soleus muscle was measured non-invasively using MR elastography (MRE) at 0%, 5%, 10%, 15%, and 20% of the subject’s maximum applied force. The results from this study showed statistical differences between the patients and controls, even though there were no statistical differences in the maximum applied force.
The Chylla–Haase polymerization reactor is widely accepted as a benchmark process for the evaluation of control strategies for batch reactors. In this contribution a control concept based on Exact I/O-Linearization is proposed and compared to a conventional cascade control structure. In order to adapt the exact linearization control strategy to various polymerization products and batch conditions, an advanced probabilistic inference algorithm (Sigma-Point Kalman Filter) is applied and investigated. Sigma-Point Kalman Filters have the major improvement of simplified implementation compared to local linearization methods (i.e. Extended Kalman Filter) because no analytical Jacobians are required. Stochastic simulation studies are introduced and show the effectiveness, accuracy and benefit of the control concept. Within several scenarios a satisfying robustness against structural errors in the underlying model equations for the nonlinear control law and the inference algorithm is demonstrated. Furthermore it is pointed out, that with little effort in reassembling the plant design, control performance can be improved significantly.
This article deals with the cost optimal commitment of power systems. System stability is often only considered after solving the commitment problem. We show by example that a cost optimization may result in a mode of operation that, while economically optimal, is unstable or has otherwise unacceptable dynamics. As a remedy, we propose to use the so-called normal vector method, which has been developed for the optimization of nonlinear dynamical systems with stability boundaries and uncertain parameters. We apply the method to a small sample power grid, where the optimization goal is to minimize the energy production costs for a given power consumption.
Stability and cost optimality of power generation and supply systems must not be considered independently from one another. Simple examples show that optimizing cost without considering stability may result in modes of operation that, while economically optimal, are unstable. We demonstrate that stability, robustness, and optimality can be considered systematically and simultaneously by combining bifurcation theory and nonlinear optimization. Essentially, the proposed method enforces a backoff distance between the optimal point of operation and operational or stability boundaries in the space of the optimization variables, where bifurcation theory is used to describe nonlinear stability boundaries.