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There are potential applications for high operating temperature (HOT) Hg1-xCdxTe (MCT) infrared (IR) devices for both defense and commercial applications. MCT absorption can be raised either by increasing the absorber thickness or by lowering the operating temperature. However, if we can increase MCT absorption by using plasmonic materials, it will help in both HOT operation and increasing signal to noise ratio. We studied three Gold (Au) plasmonic structures for the absorption enhancement of MCT materials in the wavelength band of 3-7 μm. By using RF module in COMSOL multiphysics software, we found a large increase (1.85X) of MCT absorption when the optimized Au plasmonic structure is used. The increase in absorption at 4.5-6 μm is higher than that at 3-4 μm. The increased absorption due to plasmonic structure allows absorber thickness to decrease which leads to decrease in dark current and HOT devices. We report here record 90% increase in absorption of MCT material at room temperature at peak wavelength around 3.4 μm by using optimized plasmonic structure. [ABSTRACT FROM AUTHOR]

Accurately predicting the reliability of a physical system under aleatory uncertainty requires a very large number of physical output testing. Alternatively, a simulation-based method can be used, but it would involve epistemic uncertainties due to imperfections in input distribution models, simulation models, and surrogate models, as well as a limited number of output testing due to cost. Thus, the estimated output distributions and their corresponding reliabilities would become uncertain. One way to treat epistemic uncertainty is to use a hierarchical Bayesian approach; however, this could result in an overly conservative reliability by integrating possible candidates of input distribution. In this paper, a new confidence-based reliability assessment method that reduces unnecessary conservativeness is developed. The epistemic uncertainty induced by a limited number of input data is treated by approximating an input distribution model using a bootstrap method. Two engineering examples and one mathematical example are used to demonstrate that the proposed method (1) provides less conservative reliability than the hierarchical Bayesian analysis, yet (2) predicts the reliability of a physical system that satisfies the user-specified target confidence level, and (3) shows convergence behavior of reliability estimation as numbers of input and output test data increase. [ABSTRACT FROM AUTHOR]

Presents a theoretical calculation on the peak position of the absorption wavelength for a wide range of detector parameters. Photoconductive gain of the detectors with respect to the energies of the final state of the optical transition and the satellite valleys of the detector material; Additional corrections related to the effective mass of the electrons besides the correction due to many-body effects; Photon energy of the absorption peak.

Presents a study which examined the influence of the nonuniform photogeneration on the electric-field distribution of quantum well photoconductors under drift velocity saturation. Photoconductive gain; Main source of noise current and noise gain factor; Conclusion.

Analyzes photocurrent and excess current noise in a quantum well infrared photodetector (QWIP) using a drift-diffusion model of charge carrier transport. Information on QWIP; Influence of the nonuniform light absorption on photoconductive and noise gain; Details of the equations for photocurrent.

Provides information on a study wherein a long-wavelength infrared hot-electron transistor with low dark current is demonstrated. Methods; Results; Conclusion.

Bias dependent magnetoresistance of morphologically different [La.sub.1-x][Sr.sub.x][MnO.sub.3](LSMO) films, i.e., epitaxial and polycrystalline films, are investigated, 1-V curves exhibit nonlinear behavior indicative of electron tunneling between neighboring grains. Furthermore, two clear minima are observed in the bias dependent magnetoresistance of the polycrystalline film on sapphire substrate in spite of no anomalous behavior in the epitaxial film. The minima appear at the voltages where the I-V curve deviates from the ohmic character. The bias dependent magnetoresistance also increases with increasing voltage. The novel aspects of the bias dependent magnetoresistance are discussed in connection with spin polarized tunneling. Index Terms--colossal magnetoresistance (CMR), manganite, tunneling

In reliability-based design optimization (RBDO), dependent input random variables and varying standard deviation (STD) should be considered to correctly describe input distribution model. The input dependency and varying STD significantly affect sensitivity for the most probable target point (MPTP) search and design sensitivity of probabilistic constraint in sensitivity-based RBDO. Hence, accurate sensitivities are necessary for efficient and effective process of MPTP search and RBDO. In this paper, it is assumed that dependency of input random variable is limited to the bivariate statistical correlation, and the correlation is considered using bivariate copulas. In addition, the varying STD is considered as a function of input mean value. The transformation between physical X-space and independent standard normal U-space for correlated input variable is presented using bivariate copula and marginal probability distribution. Using the transformation and the varying STD function, the sensitivity for the MPTP search and design sensitivity of probabilistic constraint are derived analytically. Using a mathematical example, the accuracy and efficiency of the developed sensitivities are verified. The RBDO result for the mathematical example indicates that the developed methods provide accurate sensitivities in the optimization process. In addition, a 14D engineering example is tested to verify the practicality and scalability of the developed sensitivity methods. [ABSTRACT FROM AUTHOR]

In this study, the fatigue crack propagation in composite material is investigated by experimental result. When another material exists at fatigue crack propagation in case of composite, the durability against fatigue crack is smaller or greater than in case of matrix without another material. As another material is composite material, it refers to steel or material. Another material influences the crack propagation. As the experimental results can be agreed with simulation data, all experimental data in this study are verified. These experimental and analysis results can be applied into real field effectively. The estimation of safety design and life will be of great value industrially. [ABSTRACT FROM AUTHOR]

The conventional reliability-based design optimization (RBDO) methods assume that a simulation model is able to represent the real physics accurately. However, this assumption may not always hold as the simulation model could be biased. Accordingly, designed product based on the conventional RBDO optimum may either not satisfy the target reliability or be overly conservative design. Therefore, simulation model validation using output experimental data, which corrects model bias, should be integrated in the RBDO process. With particular focus on RBDO, the model validation needs to account for the uncertainty induced by insufficient experimental data as well as the inherent variability of the products. In this paper, a confidence-based model validation method that captures the variability and the uncertainty, and that corrects model bias at a user-specified target confidence level, has been developed. The developed model validation helps RBDO to obtain a conservative RBDO optimum design at the target confidence level. The RBDO with model validation may have a convergence issue because the feasible domain changes as the design moves (i.e., a moving-target problem). To resolve the issue, a practical optimization procedure is proposed. Furthermore, the efficiency is achieved by carrying out deterministic design optimization (DDO) and RBDO without model validation, followed by RBDO with confidence-based model validation. Finally, we demonstrate that the proposed RBDO approach can achieve a conservative and practical optimum design given a limited number of experimental data. [ABSTRACT FROM AUTHOR]

Deals with a study which demonstrated the reduction of photoconductive gain in quantum well infrared photodetectors from its classical value. Noise properties of a quantum well infrared photodetector; Information on an inhomogeneous electron decay function used in the study; Uses of the quantum model curve.

Presents a study which demonstrated an efficient detector based on localized bound-state-extended-continuum-state absorption in doped gallium arsenide/aluminum[subx]gallium[sub1-x]arsenide quantum wells. Measurement of the optical transitions from the bound state to the continuum states; Significance of decreasing the size of quantum well that contains two bound states; Conclusion.