Polycrystalline silicon solar cells on low cost foreign substrates

The use of polycrystalline silicon layers on low-cost substrates is a promising approach for the fabrication of low-cost solar cells. Using low-carbon steel and graphite as substrates, solar cell structures have been deposited by the thermal decomposition of silane and appropriate dopants.Steel was selected as a substrate on the sole basis of its low cost. However, steel and silicon are not compatible in their properties, and an interlayer of a diffusion barrier, such as borosilicate, must be used to minimize the diffusion of iron from the substrate into the deposit. The deposited silicon on borosilicate/steel substrates is polycrystalline with a grain size of 1–5 μm, depending on deposition conditions. P-n junction solar cells were found to have low open-circuit voltages and poor current-voltage characteristics, and Schottky-barrier solar cells were found to show negligible photovoltages.Graphite is more compatible with silicon in properties than steel, and silicon deposited on graphite substrates shows considerably better microstructures. A number of solar cells, 2·5×2·5 cm in area, have been fabricated from n⁺-silicon/p-silicon/p⁺-silicon/graphite structures. The best cell to date had a V_oc of 0·35 V and an AMO efficiency of 1·5% (no antireflection coating). This type of solar cell is very promising because of the simplicity in fabrication.     

Identification of inorganic pigments used in porcelain cards based on fusing Raman and X-ray fluorescence (XRF) data

Raman spectroscopy and X-ray fluorescence (XRF) spectroscopy are often used as complementary techniques that are well suited for the analysis of art objects because both techniques are fast, sensitive, and noninvasive and measurements can take place in situ. In most of these studies, both techniques are used separately, in the sense that the spectra are evaluated independently and single conclusions are obtained, considering both results. This paper presents a data fusion procedure for Raman and XRF data for the characterization of pigments used in porcelain cards. For the classification of the analyzed points of the porcelain cards principal component analysis (PCA) was used. A first attempt was made to develop a new procedure for the identification of the pigments using a database containing the fused Raman-XRF data of 24 reference pigments. The results show that the classification based on the fused Raman-XRF data is significantly better than the classifications based on the Raman data or the XRF data separately.     

An improved Wigner Monte-Carlo technique for the self-consistent simulation of RTDs

We present an original approach to including quantum transport into classical Ensemble Monte Carlo (EMC) simulations. The method, based on the Wigner transport equation, is fully self-consistent, and includes impurity and phonon scattering according to the Fermi Golden rule. It is inspired by an approach suggested by Shifren et al. [IEEE Trans. Electron Dev. 50, 769 (2003)], with some major improvements that make possible successful comparison with other simulation techniques and experiments.     

Complex-subband transform for subband-based motionestimation/compensation and coding

This paper introduces the complex subband transform (CST) that can be applied for both subband signal decomposition and motion estimation, which are the two major processes in subband-based image sequence coding. In the experiments, we compare the CST-based subband motion compensation with conventional block matching motion compensation, and find that the former has (i) higher peak signal-to-noise ratio (PSNR) of the reconstructed images and (ii) lower prediction error entropy of the motion vectors.     

Discrete energy conservation law and reciprocity relationship for one-dimensional wave propagation problems

A mathematical derivation is presentcd to establish the discrete energy conservation law and reciprocity relationship for explaining the insensitive phenomenon round in the previous investigations of a one-dimensional wave propagation problem. It is shown that there do exist certain discretized differential and variational systems which can preserve the energy conservation and reciprocity relationships. This then excludes the use of these relationships in error estimation.     

Usefulness of transesophageal echocardiography in the treatment of critically ill patients

To evaluate the usefulness of transesophageal echocardiography (TEE) in the treatment of critically ill patients, 80 patients (51 male and 29 female; mean age, 53 years) undergoing both transthoracic echocardiography (TTE) and TEE were studied in a 2-year period. Of these, 48 patients were studied in the ICU, while the other 32 patients were directly referred from the emergency departments. Indications for the study included suspected aortic dissection (34 patients), hemodynamic instability (22 patients), suspected cardiac source of embolism (11 patients), evaluation of the severity of mitral regurgitation (7 patients), and suspected infective endocarditis (6 patients). The probe was passed successfully in 78 of 80 attempts (98 percent). No significant complications were recorded during the transesophageal echocardiographic study. Transesophageal echocardiography provided critical information that was not obtained by TTE in 39 of 78 studies (50 percent, p < 0.005). Cardiac surgery was prompted by TEE findings in 14 patients (18 percent) and these findings were all confirmed at operation. Transesophageal echocardiography was a safe, well-tolerated, and valuable diagnostic approach for the rapid detection of specific cardiac abnormalities in patients with critical illness; TEE should be considered in the treatment of critically ill patients especially when TTE provided inadequate information.     

Corandomization of fats improves absorption in rats

Human milk fat is well absorbed despite its large concentration of long-chain saturated fatty acids (LCSFA), particularly palmitic acid. The superior absorption has been ascribed in part to the uncommonly high proportion of the palmitic acid in the sn-2 position of the triglycerides, 70% in human milk triglycerides compared with 10-15% in the fats and oils commonly used in infant formula blends. Colipase-dependent pancreatic lipase selectively hydrolyzes the fatty acids at the sn-1 and 3 positions, yielding free fatty acids and the 2-monoglyceride, which are absorbable. Free palmitic acid, but not monopalmitin, can be lost as calcium soaps in the feces. The present study demonstrated that mixtures of coconut oil and palm olein are better absorbed by rats if the proportion of LCSFA in the sn-2 position is increased by the process of chemical randomization, in which the fatty acids of the native oils are redistributed equally to all three positions in the rearranged triglycerides. The fecal excretion of total fatty acids, essentially LCSFA, from the mixtures in which the oils were randomized together (corandomized) was 30 to 60% less than from the mixtures of native oils.     

Reduction of free-edge stress intensities in anisotropic bimaterials

We investigate the free-edge stresses in anisotropic bimaterials through the use of the free-edge stress intensity factor, Kf. This requires a determination of the singularity order at the free-surface as well as a calculation of the near-field stresses. We determine the order of the singularity for arbitrary free-surface orientation of the upper material using an eigenvalue analysis for anisotropic bimaterials. The interfacial stresses are determined using a boundary element calculation based on anisotropic, bimaterial Green's functions. The variation of Kf with free-surface orientation is determined. We find that the free-edge singularity vanishes for certain angles dependent on the anisotropic elastic constants. This revised version was published online in August 2006 with corrections to the Cover Date.