Characterization of low range GaAs

We present the results of a study of GaAs material grown at substrate temperatures below 250°C (low range GaAs) by molecular beam epitaxy. This material is amorphous and highly resistive and can be converted to single crystal through annealing process. The crystallization process is investigated by transmission electron microscopy, reflection high-energy electron diffraction, and double-crystal x-ray diffraction techniques.     

A cellular neural network methodology for deformable object simulation.

This paper presents a new methodology to simulate soft object deformation by drawing an analogy between a cellular neural network (CNN) and elastic deformation. The potential energy stored in an elastic body as a result of a deformation caused by an external force is propagated among mass points by a nonlinear CNN. The novelty of the methodology is that: 1) CNN techniques are established to describe the potential energy distribution of the deformation for extrapolating internal forces and 2) nonlinear materials are modeled with nonlinear CNNs rather than geometric nonlinearity. Integration with a haptic device has been achieved for deformable object simulation with force feedback. The proposed methodology not only predicts the typical behaviors of living tissues, but it also accommodates isotropic, anisotropic, and inhomogeneous materials, as well as local and large-range deformation.     

Image-adaptive watermarking using 2D chirps

Linear chirps, a special case of polynomial phase exponentials, have recently been proposed for digital watermarking. In this work, we propose a known-host-state methodology for designing image watermarks that are robust to compression. We use a two-dimensional frequency-modulated chirp as a spreading function in a block-based spatial watermarking scheme. In each block, the chirp is used to embed binary phase information. Chirp parameters allow for spectral shaping of the watermark to match host content. Since host state is known to the embedder, it is possible to tune the chirp for optimum performance, particularly against compression. In contrast to existing chirp watermarking where only a single watermark is generally embedded, the proposed block chirp watermarking allows for a much higher payload. Detection is done using chirp transform subject to key exchange for security. We show that the proposed method significantly outperforms non-adaptive watermarking across all compression factors under variety of attacks.     

Investigation on Crystallization and Optical Properties of Ca1−xLaxF2+x Glass‐Ceramics

Transparent oxyfluoride glass‐ceramics containing Er³⁺, Yb³⁺:Ca_1?xLa_xF_2+x nanocrystals, which may have potential applications in the fields of solid‐state laser and luminescence, were prepared. Crystallization of Ca_1?xLa_xF_2+x and behavior of Yb³⁺ and Er³⁺ during the heat treatment was investigated. Results showed that alumina content had a significant effect on crystallization of Ca_1?xLa_xF_2+x in the SiO₂–Al₂O₃–CaF₂–LaF₃ system. Due to the size of phase‐separated areas, the size of the crystals during the heat treatment did not change significantly. After crystallization of Ca_1?xLa_xF_2+x in the glass, the majority of Er³⁺ ions incorporated into the Ca_1?xLa_xF_2+x crystals during the heat‐treatment process. Time‐resolved luminescence of Er³⁺ ions in the samples around 842 nm showed that the solubility of Er³⁺ ions in Ca_1?xLa_xF₃ crystals is higher than pure CaF₂ crystals. The glass undergoes an enormous phase separation, which keeps the Yb³⁺ ions within the other separated phase. Therefore, only at high temperatures (790°C) or with a long heat‐treatment time (72 h), there is a possibility for Yb³⁺ ions to be incorporated into the fluorine phase.     

Intuitionistic (<Emphasis Type="Italic">S</Emphasis>, <Emphasis Type="Italic">T</Emphasis>)-fuzzy hyperquasigroups

The concept of intuitionistic fuzzy subhyperquasigroups in a hyperquasigroup with respect to an s-norm and a t-norm on intuitionistic fuzzy sets is introduced and their properties of such hyperquasigroups are studied. Intuitionistic (S, T)-fuzzy relations on a hyperquasigroup G are discussed. In particular, we investigate connections hyperquasigroups with binary quasigroups.     

Analysis of Quality of Services in LTE and Mobile WiMAX

Third Generation Partnership Project Long Term Evolution (3GPP LTE) and Worldwide Interoperability for Microwave Access (WiMAX) face challenges in providing Quality of Services (QoS). In this Paper, the Quality of Services of Mobile WiMAX and 3GPP LTE are analyzed and compared. We analyze the LTE and WiMAX performances in downlink employing an analytical approach for estimating the Quality of Services based on its parameters including delay and bit error rate (BER). Our proposed approach consists of two steps. The physical layer is simulated using the finite state Markov channel (FSMC) model to calculate the bit error rate. Then, the data link layer is simulated employing the effective bandwidth model for both constant and variable rate traffics. Our analysis demonstrates that WiMAX provides better QoS in low average signal to noise ratio (SNR). However, by increasing the average signal to noise ratio, both technologies provide almost the same QoS.     

Numerical simulation of sliding wear for a polymer–polymer sliding contact in an automotive application

Injection moulded polymer-based components are important for cost effective and fast production/assembly of auxiliary mechanisms in automotive industry. Wear is one of the critical factors, which influences the reliability and useful life in such mechanical components. Experimental determination of life parameters in terms of wear has both a cost and time impact. Therefore, the ability to predict wear at the development stage enables the designers to come up with a better design, longer useful life and more reliable products. This paper presents a numerical simulation of wear for a polymer–polymer sliding surface contact in dry conditions. Finite element analysis (FEA) is used as a tool to calculate nodal pressures at the contact area for small sliding steps. These pressures are then inputted to a customized wear calculating routine. The routine uses averaged wear coefficients (wear rates) obtained from custom designed experiments. The FE contact geometry is modified after each sliding step to account for the contact height decay thus determining wear volume loss over usage time and predicting the worn geometry.     

Using transient plane source sensor for determination of thermal properties of vacuum insulation panels

The energy use in buildings has to be decreased to reach the targets and regulations in the European Union. One way of reducing the energy demand is to use vacuum insulation panels (VIP) in the building envelope. To make sure the declared thermal properties of the VIP are valid for the mounted panels, in situ measurements are needed. The transient plane source (TPS) method allows fast measurement of the thermal properties of a variety of materials. However, the large anisotropy of the VIP makes it hard to interpret the temperature increase in the TPS sensor. This paper presents a comparison between an analytical solution, numerical simulations and TPS measurements of polystyrene and polystyrene with aluminum film. Polystyrene and aluminum were used instead of VIP to increase the number of setups. The numerical simulation model was validated by comparing the simulated temperature increase with an analytical solution for the polystyrene sample. The simulated temperature increase in the polystyrene sample after 40 s was 7.8% higher than the TPS measurements. For the case with polystyrene with aluminum film, the deviation was 5.7%. Losses in the wires of the TPS sensor, uncertainties regarding the material parameters and surface resistances could explain the deviations.