Free vibration analysis of solar functionally graded plates with temperature-dependent material properties using second order shear deformation theory

Second-order shear deformation theory (SSDT) is employed to analyze vibration of temperature-dependent solar functionally graded plates (SFGP’s). Power law material properties and linear steady-state thermal loads are assumed to be graded along the thickness. Two different types of SFGP’s such as ZrO₂/Ti-6Al-4V and Si₃N₄/SUS304 are considered. Uniform, linear, nonlinear, heat-flux and sinusoidal thermal conditions are imposed at the upper and lower surface for simply supported SFGPs. The energy method is applied to derive equilibrium equations, and solution is based on Fourier series that satisfy the boundary conditions (Navier’s method). Non-dimensional results are compared for temperature-dependent and temperature-independent SFGP’s and validated with known results in the literature. Numerical results indicate the effect of material composition, plate geometry, and temperature fields on the vibration characteristics and mode shapes. The results obtained using the SSDT are very close to results from other shear deformation theories.     

A shock tube with a high-repetition-rate time-of-flight mass spectrometer for investigations of complex reaction systems

A conventional membrane-type stainless steel shock tube has been coupled to a high-repetition-rate time-of-flight mass spectrometer (HRR-TOF-MS) to be used to study complex reaction systems such as the formation of pollutants in combustion processes or formation of nanoparticles from metal containing organic compounds. Opposed to other TOF-MS shock tubes, our instrument is equipped with a modular sampling unit that allows to sample with or without a skimmer. The skimmer unit can be mounted or removed in less than 10 min. Thus, it is possible to adjust the sampling procedure, namely, the mass flux into the ionization chamber of the HRR-TOF-MS, to the experimental situation imposed by species-specific ionization cross sections and vapor pressures. The whole sampling section was optimized with respect to a minimal distance between the nozzle tip inside the shock tube and the ion source inside the TOF-MS. The design of the apparatus is presented and the influence of the skimmer on the measured spectra is demonstrated by comparing data from both operation modes for conditions typical for chemical kinetics experiments. The well-studied thermal decomposition of acetylene has been used as a test system to validate the new setup against kinetics mechanisms reported in literature.     

Analysis of photocurrent in the i-layer of GaAs-based n–i–p solar cell

A numerical investigation of the intrinsic layer effect on the improvement of GaAs n–i–p solar cell performances is presented. Solution of Poisson's equation together with continuity equations for electrons and holes allows the determination of carrier's density, electric field and recombination profiles within the i-layer. The analysis examines the effect of i-layer thickness on the electric field, recombination rate and collection efficiency. It is found that increasing the i-layer thickness increases the absorption while it reduces the electric field and increases the recombination rate. The three competing parameters have to be monitored simultaneously so as to obtain an optimal thickness. To achieve this, the variation of the total photocurrent is used as indicator. The photocurrent shows a sharp increase in the domain of very thin i-layers (<0.5 μm) then a saturation is reached for thicker layers (>1 μm), the simulation is performed for thicknesses up to 2 μm.     

RF Testing on a Mixed Signal Tester

In this paper, testing of radio frequency (RF) devices with mixed-signal testers is discussed. General purpose automatic test equipment (ATE) will be used. In this paper, a more universal test structure utilizing RF building blocks is proposed. A global positioning system (GPS) device is used as an example to illustrate how to develop the RF test plan with this usage. The test plan developed includes fast, cost-effective and dedicated circuitry.

Pilot contamination mitigation based on antenna subset transmission for mmWave massive MIMO

This paper tackles the problem of pilot contamination (PC) in mmWave Massive MIMO cellular systems. We propose an analog precoder based on antenna subset transmission technique to mitigate the PC. This technique ensures the interfering signal to become noise‐like signal thus helping a more efficient estimation of channel coefficients. Also, this strategy is low cost and introduces no complexity load. The result shows the effectiveness of the proposed precoder to mitigate PC issue.     

Reducing Test Time in the High-Volume Production of Analog Circuits using Efficient Test-Vector Generation and Interpolation Techniques

Test cost is one of the main factors determining the profit margin of a device in production. Current test strategies require hundreds of measurements to determine the specifications of a parameter. In this paper, we present an automatic test-vector generation technique that is based on transfer function manipulation and requires only one circuit simulation. The proposed method consists of generating the first set of vectors by applying a derivation technique to the golden transfer function of the circuit under test (CUT). An interpolation technique allows a new transfer function to be constructed based on the first set of test vectors. The difference between the reconstructed transfer function and the golden transfer function is used to select the second set of test vectors. These new test vectors are selected to achieve the best possible fit. Our technique reduces the test vector size to values that at present can be achieved only by using powerful and time-consuming fault simulation tools. As an example, we apply the method to state variable and Chebyshev filters. We also compute the fault coverage in order to demonstrate the effectiveness of this new technique.     

Effects of spatial cuing on luminance detectability: Psychophysical and electrophysiological evidence for early selection.

Three experiments were conducted to determine whether attention-related changes in luminance detectability reflect a modulation of early sensory processing. Exps 1 and 2 used peripheral cues to direct attention and found substantial effects of cue validity on target detectability; these effects were consistent with a sensory-level locus of selection but not with certain memory- or decision-level mechanisms. In Exp 3, event-related brain potentials were recorded in a similar paradigm using central cues, and attention was found to produce changes in sensory-evoked brain activity beginning within the 1st 1 msec of stimulus processing. These changes included both an enhancement of sensory responses to attended stimuli and a suppression of sensory responses to unattended stimuli; the enhancement and suppression effects were isolated to different neural responses, indicating that they may arise from independent attentional mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)