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Institute
Sensing is nowadays an accepted application of phononic crystals with chemical and biosensors for liquid analytes being the perhaps most promising ones. A liquid-filled defect is introduced that turns into a resonant cavity. Similar to the well-known resonant sensors sensitivity can be increased with higher operating frequencies. We introduce a Sandwiched Phononic Crystal (SPC), which applies a resonant cavity located between two stacked layers on top of a SAW device. Key challenges are coupling of surface acoustic wave into the liquid cavities and avoiding scattering of the guided waves into the bulk of the sensor chip.
Lässt man einen Körper fallen, so beschleunigt dieser auf Meereshöhe in unseren Breiten bekanntermaßen mit etwa 9,8 m/s2. Ist es dennoch möglich, dass unter diesen Bedingungen ein Körper schneller fallen kann? Was auf den ersten Blick paradox erscheint, ist durchaus möglich, wie sich mit Hochgeschwindigkeitsvideos eindrucksvoll belegen lässt.
Wohl jeder, der schon einmal mit Physik zu tun hatte, kennt die meist grünlichen Leuchtspuren von Oszillographen. Sie ermöglichen es, zeitabhängige Signale zu visualisieren und quantitativ auszumessen, insbesondere auch dann, wenn die Phänomene sehr schnell ablaufen. Die Reaktionsdynamik der leuchtenden Phosphore auf den Bildschirmen wird mit Hochgeschwindigkeits-Videos deutlich sichtbar.
SMath Studio is mathematical notebook software similar to Mathcad. Its outstanding and intuitive support for scientific units makes it an invaluable asset in higher engineering education. SMath Studio has been used for more than ten years in various courses at Brandenburg University of Applied Sciences, Germany (Technische Hochschule Brandenburg, THB). To enhance the usability of the software, substantial contributions have been made. One of them is the Maxima plugin for access to the free and open-source computer algebra system Maxima. This plugin combines the flexible notebook format of SMath Studio with powerful symbolic functions like integrals and solvers for algebraic and differential equations. Additionally, the plugin adds interactive 3D graphics to SMath. The paper discusses the basic design, features, and limitations, and showcases some applications.
SMath Studio mit Maxima
(2020)
SMath with Maxima
(2023)
So weit das Auge trägt
(2023)
Sichtweiten in der Atmosphäre reichen von wenigen Metern im Nebel bis zu einigen hundert Kilometern bei extrem guten Fernsichtbedingungen. Die zugrundeliegende Physik geht vom Wahrnehmungskontrast aus. Dieser ändert sich mit der Entfernung entlang der Sichtlinie zwischen Objekt und Auge aufgrund von Lichtstreuung und Absorption an den Bestandteilen der Atmosphäre. Dazu kommt bei der Fernsicht die Refraktion, die es erlaubt, auch über den durch die Kugelform der Erde geometrisch bedingten Horizont hinaus zu sehen.
Solar load and reflection effects and respective time constants in outdoor building inspections
(2009)
Eisenbahnschienen können unter Betriebsbedingungen brechen. Mit Hilfe der Bruchmechanik lassen sich das Risswachstums- und Bruchverhalten der Schienen untersuchen. Um dieses Verhalten z.B. im Hinblick auf die zerstörungsfreie Prüfung der Schienen im Gleis analysieren zu können, müssen die folgenden Einzelheiten bekannt sein:
Betriebs- und Bruchbedingungen (Schienentyp, Radkräfte, Biegemomente, Temperaturen, Normalkräfte und Eigenspannungen),
die bruchmechanischen Eigenschaften des Schienenstahls unter Betriebsbedingungen,
die Form der Risse und die entsprechenden Spannungsintensitätsfaktoren.
Für Schienen des Typs R65 sind die Spannungsintensitätsfaktoren für Querrisse, die von der Fahrfläche ausgehen, mit dem FEM-Programm ANSYS berechnet worden für die radkraftbedingte Biegung, für Temperatur-Normalkräfte sowie für die Längseigenspannungen.
Springende Hüpfgummis
(2015)
Karl-Otto Edel: Stationen auf dem Weg unseres Absolventen Thomas Schnitzer: Beruf – Abitur – Studium – Diplom – Promotion – Professur. Dargelegt werden die Stationen der beruflichen Entwicklung des Absolventen der Fachhochschule Brandenburg, der als erster nach der Promotion zum Dr.-Ing. zum Professor berufen wurde.
Abstract
Stehaufkreisel sind faszinierende physikalische Spielzeuge, die scheinbar die Schwerkraft auszutricksen vermögen: Nach anfänglicher Rotation drehen sie sich so um, dass sie schließlich auf der früheren Spitze rotieren. Hochgeschwindigkeits-Videos ermöglichen es, die komplizierten mathematischen Lösungen ihrer Bewegung experimentell zu überprüfen.
Strahlungsgesetz und Augenempfindlichkeit: Bemerkungen zu einer klassischen Fehlinterpretation
(2001)
Single dielectric microspheres can manipulate light focusing and collection to enhance optical interaction with surfaces. To demonstrate this principle, we experimentally investigate the enhancement of the Raman signal collected by a single dielectric microsphere, with a radius much larger than the exciting laser spot size, residing on the sample surface. The absolute microsphere-assisted Raman signal from a single graphene layer measured in air is more than a factor of two higher than that obtained with a high numerical aperture objective. Results from Mie’s theory are used to benchmark numerical simulations and an analytical model to describe the isolated microsphere focusing properties. The analytical model and the numerical simulations justify the Raman signal enhancement measured in the microsphere-assisted Raman spectroscopy experiments.
Despite the increasing number of accidents in process industry caused by human error, there are still too few efforts devoted to this area. This is mainly caused by people's tendency to overestimate human's capability in interacting with their working environment and moreover by the unavailability of reliable analysis methods.
Because of the current lack of adequate methods, human factors (HF) analysis is not widely performed in process industry. Some HF techniques developed in the process industry were examined regarding their practical applicability and were unfortunately proved to be unsuitable for an elaborate HF analysis. Therefore, a new approach was developed, which provides a systematic way in performing a qualitative HF analysis to achieve a safer operation and decrease the number of human failure events.
HF consideration during the design of a process plant is the key to minimize accidents caused by human error in process industry. Thus, an approach to incorporate HF into design phase is described in this article, which can help achieving a safer operation as early as possible with minimized costs. © 2009 American Institute of Chemical Engineers Process Saf Prog 2009
In this study we have examined the potential of excess wind use in Germany. Excess wind constitutes roughly 40% of unused capacities of installed wind power in Germany. Using LP modelling and representative annual load profiles on an hourly resolution, we investigate the impact of the price level for wind peak power supply of residential quarters with heat, cold and electricity in Germany in combination with different power ratios of wind supply and demand. As we show, an application of wind peak tariff is technically and economically feasible and allows using green leftover energy without going in competition with e.g., green fuels or green H2 production.
Freezing of lakes is described using a simplified one-dimensional model, which gives ice thickness, ice growth rates, and ice surface temperature as a function of time. Model data for a specific lake with known meteorological conditions are compared to estimated ice thickness using a simple optical method. Finally, more advanced potential students projects are briefly discussed and results of a numerical solution are compared to the simplified model.
abstract
A large part of photonics research and development, as well as commercial applications such as optical data transmission or infrared thermal imaging, occurs in the infrared spectral range between 0.8 μm and 15 μm. However, relatively little material is so far available for experimentally teaching the physics and optics of this spectral range. We report a respective new approach in the near infrared (NIR) range between 0.8 μm and 1.7 μm that allows visualization of a number of fascinating physics phenomena. First, we use the near-infrared sensitivity of silicon-based detectors in rather inexpensive video cameras and digital single-lens reflex cameras by removing the infrared-blocking filter and replacing it with a visible-radiation blocking filter. Second, we utilize modern NIR cameras based on InGaAs detectors. With both camera types we illustrate and explain a number of physics concepts that are especially suitable for curricula in optics and photonics. Examples include the strangely bright appearance of vegetation, contrast enhancement between clouds and sky, the initially surprising differences of optical material properties between the VIS and NIR range, the possibilities of visualizing buried hidden structures and texts, and recent medical applications to locate blood vessels below the skin. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
The Patellostabilometer: A New Device for Quantification of Mediolateral Patella Displacement
(2023)
Mediolateral patella displacement is of interest for diagnostics and clinically relevant
research questions. Apart from manual testing, no standardized method is currently available. Proper
quantification of patella mobility is necessary to better understand pathologies at the patellofemoral
joint. Patella mobility was assessed in 25 healthy individuals using a Patellostabilometer, a new
prototype instrument for quantification of the mediolateral patella displacement. The participants
underwent measurements of the mediolateral displacement three times using the Patellostabilome-
ter. A maximal force of 10 N was applied for patella movement. Additionally, leg length and
circumference of the knee, upper- and lower-leg were measured. Lateral patella displacement of
18.27 ± 3.76 mm (range 15.85–20.64 mm, interquartile range (IQR) of 4.79) was measured. The medial
patella displacement showed 24.47 ± 6.59 mm (range 19.29–29.76 mm, IQR of 10.47). The test–retest
measurement error was 2.32 ± 1.76 mm (IQR of 2.38 mm), with five outliers. There was greater
test–retest variability between the measurements of the medial displacement compared to the lateral
one. The test–retest variability reached 7% of the patella displacement. Other parameters provided no
significant correlations. Based on the natural patellofemoral mobility, a precise and clinically relevant
quantification of patella mobility is allowed.
The physics behind the sometimes strange effects and 'unnatural' appearance of near-infrared (NIR) photographs is discussed in terms of reflection, absorption and transmission of NIR radiation with the respective objects. Besides discussing how NIR cameras work, several visible and NIR photograph pairs are presented, which include vegetation, natural water, clouds, the sky, and humans. In addition, some physics-oriented experimental NIR images are presented which clearly demonstrate some of the basic physics behind some of these awesome sights.
Disclinations or disclination clusters in smectic C freely suspended films with topological charges larger than one are unstable. They disintegrate, preferably in a spatially symmetric fashion, into single defects with individual charges of +1, which is the smallest positive topological charge allowed in polar vector fields. While the opposite process of defect annihilation is well-defined by the initial defect positions, disintegration starts from a singular state and the following scenario including the emerging regular defect patterns must be selected by specific mechanisms. We analyze experimental data and compare them with a simple model where the defect clusters adiabatically pass quasi-equilibrium solutions in one-constant approximation. It is found that the defects arrange in geometrical patterns that correspond very closely to superimposed singular defect solutions, without additional director distortions. The patterns expand by affine transformations where all distances between individual defects scale with the same time-dependent scaling factor proportional to the square-root of time.
The surface to volume ratio in thermal physics: from cheese cube physics to animal metabolism
(2008)
Abstract
A very old and well-known magical trick is the so-called tablecloth pull. A table is covered with a tablecloth, on top of which are certain objects. The task is to remove the tablecloth while the objects—which must not be touched—stay on top of the table. This article describes the physics behind the experiment, and presents examples recorded with high-speed cameras.
Thermography of Microsystems
(2004)
Three-dimensional vibration of a ring with a noncircular cross-section on an elastic foundation
(2018)
Among load cases concerning vehicle suspension strength and durability, the misuse case is very special because of large obstacles. In this paper, an extension of the flexible belt model RMOD-K 7 concerning misuse situations is discussed. In normal rolling conditions, contact occurs between tire and road surface. To handle misuse deformations, the contact between the inner surface of the tire and the rim has to be dealt with. Results of the validation process are shown, leading to normal forces up to 70 [kN]. The model can be used together with mbs full vehicle models. One example is the determination of the critical test velocity, which generates the maximum of suspension stresses and can be found using RMOD-K 7.
Context awareness is critical for the successful execution of processes. In the abundance of business process management (BPM) research, frameworks exclusively devoted to extracting context from textual process data are scarce. With the deluge of textual data and its increasing value for organizations, it becomes essential to employ relevant text analytics techniques to increase the awareness of process workers, which is important for process execution. The present paper addresses this demand by developing a framework for context awareness based on process executions-related textual data using a well-established layered BPM context model. This framework combines and maps various text analytics techniques to the layers of the context model, aiming to increase the context awareness of process workers and facilitate informed decision-making. The framework is applied in an IT ticket processing case study. The findings show that contextual information obtained using our framework enriches the awareness of process workers regarding the process instance urgency, complexity, and upcoming tasks and assists in making decisions in terms of these aspects.
Large three-dimensional metallic parts can be printed layer-by-layer using gas metal arc directed energy deposition (GMA-DED) process at a high deposition rate and with little or no material wastage. Fast responsive real-time monitoring of GMA-DED process signatures and their transient variations is required for printing of dimensionally accurate and structurally sound parts. A systematic experimental investigation is presented here on multi-layer GMA-DED with two different scanning strategies using a high strength low alloy (HSLA) filler wire. The dynamic metal transfer, melt pool temperature field and its longitudinal cross-section, and arc voltage and current are monitored synchronously. The transient arc heat input and the melt pool solidification cooling rate are estimated from the monitored signals. The layer-wise variations of the melt pool dimension, surface temperature profile, thermal cycles, and solidification cooling rate are examined for different scanning strategies. It is comprehended that the part defects can be minimized, and the mass production of zero-defect parts can be achieved in GMA-DED process with synchronized monitoring and assessment of the real-time process signatures.
Tropfen auf dem kalten Wein
(2012)
Viele kennen die leidvolle Erfahrung: Beim Frühstückstisch gießt man einen Schuss Milch in den Kaffee, und prompt spritzt eine kleine Fontäne aus der Tasse, und ein Tropfen landet – hier gilt Murphys Gesetz fast immer – auf dem frisch angezogenen Hemd oder mit etwas Glück nur auf der Tischdecke. Man kann dieses Phänomen unter kontrollierten Bedingungen mit Hochgeschwindigkeits-Kameras analysieren und interessante Physik hinter den Spritzern aufspüren.