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Width of cluster plasmon resonances: Bulk dielectric functions and chemical interface damping
(1993)
The damping of collective electron resonances in clusters which develop into plasmon polaritons at larger sizes is investigated for free, supported, and embedded neutral metal clusters. Embedding of free 2 nm Ag clusters of 2-nm diameter into a SiO2 matrix leads to an increase of the width of the resonances by more than a factor of 3. The optical spectra are compared with the Mie theory using size-effect-modified dielectric functions of the solid state. The results corroborate the assumption that the widths of the resonances strongly depend on chemical interface effects. The results are briefly discussed with regard to limited-mean-free-path and quantum-size-effect theories and a recent approach by Persson. It is demonstrated that the widths of the spectra of supported and embedded clusters have to be interpreted with care since true intrinsic size effects of the clusters appear to be less effective than previously believed and can be obscured by the chemical interface damping.
© 1993 The American Physical Society
White matter abnormalities and brain activation in schizophrenia: a combined DTI and fMRI study
(2007)
Visible and invisible mirages: comparing inferior mirages in the visible and thermal infrared
(2015)
Abstract
Visible (VIS)-light and thermal infrared (IR) inferior mirages in the 8–14 μm waveband have been observed simultaneously for the takeoff and landing of various airplanes at distances of several kilometers. Similarities as well as differences between the VIS and IR mirages are discussed.
© 2014 Optical Society of America
Two stationary plane free boundary value problems for the Navier-Stokes equations are studied. The first problem models the viscous two-fluid flow down a perturbed or slightly distorted inclined plane. The second one describes the viscous two-fluid flow in a perturbed or slightly distorted channel. For sufficiently small data and under certain conditions on parameters the solvability and uniqueness results are proved for both problems. The asymptotic behaviour of the solutions is investigated. For the second problem an example of nonuniqueness is constructed. Computational results of flow problems that are very close to the above problems are presented. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Vertebral Pneumatization
(2011)
In this study, we have investigated the form of velocity and pressure functions of a fluid oscillating between two parallel glass sheets that form a circular Hele-Shaw cell. The flow has been considered to be radial, incompressible and laminar. The time-dependent Navier-Stokes equation has been solved in cylindrical coordinates using Fourier transform, and the oscillating flow velocity across the thickness of the cell has been obtained at different times. The flow velocity function in the unsteady state is related to the vertical component of the coordinates in the form of parabolic functions and also to the inverse of the radial component. The time dependence appears as a simple harmonic with a frequency equal to the oscillation frequency. The velocity of the flow is maximum at the middle of the cell along its height and gradually decreases from the middle towards the top or bottom plane and reaches zero. Pressure does not depend on the height and changes logarithmically with the radius. The dependence of pressure on time is also a simple harmonic with the external frequency, but it has a phase shift with respect to the velocity.
Universality of correlationships among pulse parameters for different MIG Welding Power Sources
(2001)
There are two aims for the second part of this paper: verifying the theory presented in the first part through parameter variation and comparison between simulation and experiment, and to study the effect of the belt structure on the cornering properties of radial tyres. Research has been carried out with a passenger car radial tyre and two different kinds of truck or bus radial tyres using both simulation and experiment. This second part of the paper shows that belt structure plays an important role in the generation of tyre forces and moments in addition to the effects of the tread stiffness and friction coefficients. The theory and method presented in this paper opens a new robust way to predict the tyre forces and moments from the tyre design and provides a reliable model for a generation mechanism.
Tyre rolling kinematics and prediction of tyre forces and moments: part I - theory and method
(2012)
A new method to describe tyre rolling kinematics and how to calculate tyre forces and moments is presented. The Lagrange–Euler method is used to calculate the velocity and contact deformation of a tyre structure under large deformation. The calculation of structure deformation is based on the Lagrange method, while the Euler method is used to analyse the deformation and forces in the contact area. The method to predict tyre forces and moments is built using kinematic theory and nonlinear finite element analysis. A detailed analysis of the tyre tangential contact velocity and the relationships between contact forces, contact areas, lateral forces, and yaw and camber angles has been performed for specific tyres. Research on the parametric sensitivity of tyre lateral forces and self-aligning torque on tread stiffness and friction coefficients is carried out in the second part of this paper.
Twice in a blue moon
(2009)
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.
Topodiagnostic value of blink reflex R1 changes: a digital postprocessing MRI correlation study
(2001)
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.
Three-dimensional vibration of a ring with a noncircular cross-section on an elastic foundation
(2018)
This research paper examines the potential consequences of AI technology on democratic systems. The study focuses on two main areas: the weakening of the media and the emergence of "smart dictatorship." The paper examines the ways in which AI can be used to supervise, manipulate, and frustrate the media, thereby weakening its role as a check on government and corporate power. The study also explores how AI technology can be used to create an "omnidirectional monitoring" society, where individuals are constantly monitored and controlled through the use of "panopticon" techniques and "social bots". This can lead to the emergence of a "postdemocratic" society, characterized by growing inequality, dehumanization, and the
manipulation of information on online media platforms. The research methodology adopted in the study is qualitative, using expert interviews with three experts who
discussed the overall use of AI and its disruptive effects on democracy, such as the creation of fake news, filter bubbles, and algorithm bias. In conclusion, this research highlights the need for increased awareness and regulation of AI technology to ensure its responsible use and to protect democratic values.
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.
The surface to volume ratio in thermal physics: from cheese cube physics to animal metabolism
(2008)
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 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.
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.
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 Great Shutdown
(2023)
This research aims to examine the potential impact of a military escalation of the China-Taiwan conflict on global economies, with a particular focus on the microchip production industry in Taiwan. The academic paper will analyze the current economic ties between Taiwan and other countries, as well as the potential consequences of a disruption in trade and production caused by a military conflict. The research will also examine the role of Taiwan's microchip industry in the global supply chain and its potential vulnerability to a disruption in the event of a military escalation. Additionally, this scientific paper will explore the possible economic responses of other countries and the international community to a military escalation of the China-Taiwan conflict. The research will use a combination of the systematic literature review and the scenario technique to demonstrate potential impact of a military escalation of the China-Taiwan conflict on global economies, with a specific focus on the microchip production industry in Taiwan.
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.
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.
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
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.
We present a method for the arbitrage-free interpolation of plain-vanilla option prices and implied volatilities, which is based on a system of integral equations that relates terminal density and option prices. Using a discretization of the terminal density, we write these integral equations as a system of linear equations. We show that the kernel matrix of this system is, in general, ill-conditioned, so that it cannot be solved for the discretized density using a naive approach. Instead, we construct a sparse model for the kernel matrix using singular value decomposition (SVD), which allows us not only to systematically improve the condition number of the kernel matrix, but also determines the computational effort and accuracy of our method. In order to allow for the treatment of realistic inputs that may contain arbitrage, we reformulate the system of linear equations as an optimization problem, in which the SVD-transformed density minimizes the error between the input prices and the arbitrage-free prices generated by our method. To further stabilize the method in the presence of noisy input prices or arbitrage, we apply an 𝐿1-regularization to the SVD-transformed density. Our approach, which is inspired by recent progress in theoretical physics, offers a flexible and efficient framework for the arbitrage-free interpolation of plain-vanilla option prices and implied volatilities, without the need to explicitly specify a stochastic process, expansion basis functions or any other kind of model. We demonstrate the capabilities of our method in a number of artificial and realistic test cases.
Deutsche Telekom, one of the world's leading integrated telecommunications companies, has recently shifted its focus in event marketing to prioritize more personal co-creational communication on regional occasions, rather than largescale events. This paper outlines the three-part LAW-principle that Deutsche Telekom follows in its brand communication in Germany, providing examples for each of the three pillars. The co-creation resulting from brand communication is changing the role of marketing and brand practitioners. They are now required to negotiate with various stakeholders.
Smectic films in a collapsing catenoid develop spontaneous wrinkling patterns like solid sheets.
Smectic freely-suspended films can wrinkle like solid sheets. This has been demonstrated earlier with shape-fluctuating smectic bubbles. Here, we exploit the collapse of smectic catenoid films with a central equatorial film to expose the latter to rapid lateral compression. Wrinkle formation is observed in the planar film and the thickness dependence of the undulation wavelength is measured. In addition to the central film, its border undergoes an undulation instability as well.
Irradiance during total lunar eclipses is simulated using a pinhole model. The Moon is illuminated by direct sunlight that is refracted into the Earth’s shadow as it passes through the atmosphere at the terminator but is depleted by scattering by molecules, extinction by aerosol particles, absorption by ozone, and obstruction by clouds and elevated land. On a spherical, sea-level Earth, and a cloudless, molecular atmosphere with no ozone, the eclipsed Moon appears red and calculated irradiance at the center of the umbra is reduced by a factor of about 2400 from direct moonlight. Selective absorption mainly of light around 600 nm by stratospheric ozone turns the periphery of the umbra pale blue. Typical distributions of aerosol particles, ozone, mountains, and clouds around the terminator reduce irradiance by an additional factor of the order of 100.
© 2008 Optical Society of America
Irradiance and color during the total lunar eclipses of 2007 and 2008 are simulated using a ray tracing model that includes refraction, scattering by molecules, and observed or climatological distributions of aerosols, ozone, clouds, and topography around the terminator. Central portions of the umbra appear deep red for almost all eclipses due to preferential removal of short wavelengths in the spectrum of sunlight by scattering in the lower troposphere. The fringe of the umbra appears turquoise or blue due to selective removal of wavelengths around 600 nm by the Chappuis absorption bands of ozone in the stratosphere. Asymmetric distributions of clouds and aerosols, particularly for the 2008 eclipse, produce minimum calculated irradiance up to 17 arc min from the umbra center, while high ozone content over the arctic makes the northern edge of the umbra deepest blue.
© 2008 Optical Society of America
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.