Use of thermo‐Raman spectroscopy and chemometric analysis to identify dehydration steps of hydrated inorganic samples—application to copper sulfate pentahydrate

In situ thermo‐Raman spectroscopy (TRS) measurements were performed in order to investigate solid‐phase transformation of the copper sulfate pentahydrate from room temperature up to 300 °C. Band‐target entropy minimization (BTEM), a blind‐source separation algorithm, was employed in order to identify and reconstruct the pure component spectra of the species involved in the dehydration process. In spite of low signal‐to‐noise ratio and elevated baseline spectral data, BTEM was successfully utilized to identify and reconstruct four pure component spectra of copper sulfate pentahydrate, trihydrate, monohydrate, and anhydrate, which were formed during this thermally induced process. Subsequent mapping of these four pure component spectral estimates back onto the preprocessed spectra yielded the relative concentrations of each individual species. Finally, the transition temperatures of each dehydration step could be unambiguously deduced from the obtained concentration profile. The current study shows that combined thermo‐Raman spectroscopy and chemometric analysis provides an effective tool to determine the dehydration temperatures as well as to identify the structures of each individual species involved in a solid‐phase dehydration process. Copyright © 2009 John Wiley & Sons, Ltd.     

Infrared moving target detection and tracking based on tensor locality preserving projection

This paper presents an algorithm for detecting and tracking dim moving target in IR image sequence with low SNR. The algorithm, which is designed based on the locality preserving projection, accepts tensors as inputs. The justification for the algorithm comes from the role of the generalized eigenvalue problem in providing an optimal embedding for the manifold. Not only does the proposed method inherit the attractive characteristics of the locality preserving projections in terms of exploiting the intrinsic manifold structure, it is also appealing in terms of significant reduction in both space complexity and time complexity. Experimental results on two IR image sequences demonstrate the effectiveness of the proposed algorithm.     

空调冷凝热热回收技术研究现状及发展趋势

界定了空调冷凝热热回收系统的分类,总结了国内外空调冷凝热热回收技术的研究现状,提出了空调冷凝热热回收技术的发展趋势。     

密度泛函理论计算内掺氢分子富勒烯H2@C60及其二聚体的几何结构和电子结构

采用密度泛函理论中的广义梯度近似(generalized gradient approximation, 简称GGA),对内掺氢分子富勒烯H2@C60及其二聚体的几何结构和电子结构进行了计算研究.发现无论是在H2@C60单体,还是在其二聚体中,氢倾向以分子形式存在于碳笼中心处,且在室温下氢分子可以做自由旋转.电子结构分析表明,氢分子掺入到C60和C120中,仅对距离费米能级以下-8eV至-5eV能级处有一定的贡献,其他能级的分布和能隙几乎没有变化.     

Two-vibron bound states in the β--Fermi--Pasta--Ulam model

This paper studies the two-vibron bound states in the β- Fermi Pasta-Ulam model by means of the number conserving approximation combined with the number state method. The results indicate that on-site, adjacent-site and mixed two-vibron bound states may exist in the model. Specially, wave number has a significant effect on such bound states, which may be considered as the quantum effects of the localized states in quantum systems.     

Study on the temperature distribution of heated falling liquid films

A 2-D theoretical model was derived to present the temperature distribution of falling liquid films flowing over a vertical heated/cooled plate with constant temperature. And the temperature gradients for different flow rates and fluids were also discussed for different liquid films. The temperature distributions for liquid films of water, ethanol aqueous solutions and glycerol aqueous solutions were experimentally investigated with a sensitive thermal imaging system. It is found that the surface temperature of a film flowing over a vertical heated solid plate has a characteristic relationship with the film flow distance. A lower flow rate of the film or a higher temperature of the wall generally leads to a higher surface temperature in the film inception. For films of glycerol aqueous solutions under the same heating conditions, a lower glycerol concentration causes a higher surface temperature of the film, due to the decrease of the liquid viscosity, whereas the ethanol concentration is found to have little influence on the temperature distribution of the film surface. Comparisons of the experimental data and the theoretical model show that the model can adequately describe the surface temperature distribution of a heated falling liquid film.     

Subluminal and Superluminal Phenomena in a Four-Level Atom

In a four-level atomic system, we investigate the light pulse propagation properties interacting with only one laser field. It is shown that in the steady state, the group velocity of the light pulse can be changed from subluminal to superluminal by varying the field detuning. Meanwhile, the effects of the field intensity on the group velocity are also shown. At last, with special parameters, the analytical solution for the group index is also obtained.     

The magnetic and magnetocaloric effect of (Mn0.5Co0.5)65Ge35 alloy in low magnetic field

The crystal structure and magnetocaloric effect (MCE) of water-quenched and annealed (Mn_0.5Co_0.5)₆₅Ge₃₅ alloys were studied in this paper. A CoMnGe-single phase was formed in the water-quenched alloy, and mixture phases of CoMnGe and Mn+2O in the annealed alloy. The annealed alloy has a smaller crystal parameter than the water-quenched alloy. The Curie temperature is 275 and 298 K for the water-quenched and annealed alloys, respectively, which means that the magnetic-transition temperature in this material can be controlled by anneal. In addition, the same magnetic entropy change was found in these two alloys, even though their Curie temperatures have a significant difference.     

BaTiO3 thin-film waveguide modulator with a low voltage-length product at near-infrared wavelengths of 0.98 and 1.55 microm

A BaTiO3 thin-film electro-optic waveguide modulator with a low half-wave voltage-length product has been demonstrated at near-infrared wavelengths of 1-1.6 microm. Half-wave voltage-length products as small as 0.25 and 0.5 V cm were measured for a 5-mm-long device at wavelengths of 973 and 1561 nm, respectively. The effective electro-optic coefficients were calculated as 420 pm/V at 973 nm and 360 pm/V at 1561 nm. Further improvements in device performance by optimizing the ferroelectric domain structure are anticipated.