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Temperatures on inaccessible surfaces can be estimated by solving an inverse heat conduction problem (IHCP) based on the measured temperature on accessible surfaces. In this article, the transient temperatures on the front (heated) surface of a three-dimensional (3-D) object is recovered using the conjugate gradient method (CGM) based on temperatures measured on the back surface (opposite to the heated surface). The simulated measurement data are generated from the exact solution obtained by solving the direct problem, in which the front surface of the object is subjected to a moving heat source having an elliptic spot with a Gaussian profile. Random errors are artificially imposed on the back surface data. It is shown that the front-surface temperatures of the 3-D object can be well recovered using the algorithm presented here. Studies are also carried out to test the effect of large measurement errors on the accuracy of the inverse solution. [ABSTRACT FROM AUTHOR]

Temperature and heat flux at the heated surface can be estimated by solving an inverse heat conduction problem (IHCP) based on measured temperature and/or heat flux at the accessible locations (e.g., back surface). Most of the previous studies used temperature measurement data in the objective function, and little work has been done for the inverse numerical algorithm based on heat flux measurement data. In this study, a one-dimensional IHCP in a finite slab is solved by using the conjugate gradient method. The heat flux measurement data are, for the first time, incorporated into the objective function for a nonlinear heat conduction problem with temperature-dependent thermophysical properties. The results clearly show that the inverse approach of using heat flux measurement data in the objective function can provide much better predictions than the traditional approaches in which the temperature measurements are employed in the objective function. Parametric studies are performed to demonstrate the robustness of the formulated IHCP algorithm by testing it for two different materials under different frequencies of the imposed heat flux along with random errors of the measured heat flux at the back surface. [ABSTRACT FROM AUTHOR]

Abstract: Effects of CdCl2 post-growth treatments and annealing under different conditions on the surface and interface properties of CdS/SnO2/glass heterostructure were studied. CdS thin films were grown on SnO2-coated glass substrates for CdS/CdTe heterojunction solar cells by the solution growth technique. It was found that CdCl2 post-growth treatments and annealing enhanced the CdS-related XRD peaks, narrowed the CdS characteristic Raman bands, removed or depressed the disorder related Raman features, and improved the CdS film crystalline quality significantly, which are advantageous to the application in solar cells as a window layer material. [Copyright &y& Elsevier]

Abstract: The effect of temperature and excitation power on the characteristics of InGaN/GaN single quantum well (SQW) and multiple quantum well (MQW) light-emitting diodes (LED) has been investigated in-depth over a broad range of temperatures from 9 to 300K. It was found that the device with a stair-shaped SQW structure exhibited stronger localization effect, as well as had higher internal quantum efficiency than that of the conventional MQW and SQW LEDs. This is interpreted as due to the stair-shaped SQW configuration, which offered a large contribution to the exciton capturing. The adoption of an appropriate heterostructure in active region allows the achievement of improved LED performance. With increasing the excitation power intensity, QW photoluminescence (PL) line broadening and emission peak blue shifts were observed, which are assumed to be caused by the disordering formed in the In-rich heterostructures of QW ensembles. We expect that distinct degree of carrier localization occurs in these samples. [Copyright &y& Elsevier]

New phonon-assisted defect features are observed using photoluminescence (PL) and Raman scattering spectroscopy on 3C-SiC/Si(1 0 0) films grown by chemical vapor deposition (CVD) technique. The ultraviolet excitation room-temperature (RT) PL-Raman spectra show a luminescence band near 2.3 eV due to RT recombination over the 3C-SiC indirect band gap. In addition to the strong Raman lines characteristic of Si substrate and 3C-SiC we also observed weaker impurity modes near 620, 743 and 833 cm-1. These frequencies are compared with the results of Green''s function simulations of impurity modes with plausible defect structures to best support the observed Raman features as well as modes of some prototypical defect center. [Copyright &y& Elsevier]

A model is developed to optimize two aspects of the thermal removal of binder from green ceramic components. The model, which accounts for flow in porous media arising from the thermal decomposition of binder in three-dimensional bodies with anisotropic permeability, describes the pressure within the body as a function of position, time, and temperature during the heating cycle. The model is used with variational calculus to predict the heating profile that minimizes the cycle time for the thermal removal of binder. The model is also used to determine which body geometry maximizes the buildup of pressure in parallelepipeds, a common shape of multilayer ceramic capacitors. [ABSTRACT FROM AUTHOR]

Examines the coupling between the adjacent odd and even modes of water waves using perturbation methods. Development of a criterion for predicting wave type transition; Representation of waves by superposition of standing waves; Identification of amplitude equations governing the slow time dynamics of the amplitude of the odd and even modes.

Discusses the use of the boundary element method combined with the fourth-order Runge-Kutta scheme as time integrator to simulate the dynamics of an acoustically levitated axisymmetric liquid drop. Study of the drop dynamics in an acoustic field in terms of the shape oscillation and translational motion of the drop.

Studies the translational instability of an oscillating bubble. Perturbation analysis; Derivation of amplitude equations; Insignificance of integral relations for motions of bubbles in an infinite perfect liquid; Intimate coupling between the translational motions and amplitudes.

Studies the influence of silicon doping of semiconductors on the infrared reflectance characteristics of gallium nitride grown on sapphire. Calculation of reflectance based on the standard transfer matrix method; Measured reflectance with varying doping levels; Fringes contrast and average reflectivity.

Studies the effects of carbon-aluminum ion coimplanted epitaxial silicon carbide by Raman scattering measured at room temperature. Amorphization and damage to ion implantation; Evidences of the crystallization.

Describes the room-temperature photoluminescence, contactless electroreflectance and x-ray characterization of a double-side delta-doped GaAlAs/InGaAs high electron mobility transistor structure. Observation of signals from every region of the sample; Optical determination of the In composition and channel width.

Describes a uniform radial flow epitaxy-grown indium gallium arsenide/indium phosphide heterostructure using Raman spectroscopy. Preparation of epitaxial films above and below the critical thickness; Analysis of Raman spectra from strained and relaxed films; Formulation of a formula for layer stress evaluation.

Examines the laser-induced coloration of tungsten trioxide. Formation of a melted layer on the surface of the sample; Demonstration of color change by ultraviolet-visible diffuse reflectance; Appearance of conduction band electrons by x-ray photoelectron spectroscopy.

Examines the Raman scattering and x-ray diffraction of lead lanthanum titanate thin films. Use of metalorganic chemical vapor deposition to prepare the thin films; Alignment of crystallographic axes of the films; Decrease in the tetragonality of the crystal structure.

Examines the Raman spectra of lead titanate thin films grown by metalorganic chemical vapor deposition. Use of single-crystal KTaO[sub 3] and fused quartz as substrates; Overview of soft-mode theory; Shift in optical mode frequencies for the thin films and substrates.