微型热驱动热声热机热端换热器的优化设计

该文基于热声环境,采用厘米级扁管和deltaE数值计算对微型热声换热器进行了优化设计。     

荧光光谱法研究蛋白质构象的电磁-温度协同效应

长期以来电磁生物效应受到人们普遍关注，近年来从各个角度进行了相关研究。电磁－温度协同效应是当前的热点。本研究通过电磁场及温度协同对蛋白质影响的研究，发现蛋白质在电磁场作用下的不可逆变性，而且这种变性也遵循Arrhenius规律，并进一步得出电磁－温度协同作用的蛋白质变性模型。本文从分子反应动力学的角度解释了电磁－温度协同效应，并对非热效应作了一定的探讨。     

高温超导薄膜微波非线性研究的进展

文章介绍了高温超导薄膜微波非线性的主要特征，阐述了高温超导薄膜微波非线性产生的原因和相关的研究现状，指出了高温超导薄膜非线性研究中遇到的困难和尚未解决的问题．     

Thermal stability of poly(mono-n-alkylitaconates) and mono-n-alkylitaconate-co-vinylpyrrolidone copolymers I

Poly(monoitaconates) containing octyl, decyl and dodecyl groups and random monoalkylitaconate-co-vinylpyrrolidone copolymers were studied by thermogravimetric analysis. Copolymers of mono-n-octylitaconate (MOI), mono-n-decylitaconate (MDI), and mono-n-dodecylitaconate (MDoI), respectively, with N-vinyl-2-pyrrolidone (VP) of different compositions were studied by dynamic thermogravimetric analysis. The thermal stability of the copolymers depends on the structure of the monoitaconate comonomer and on the composition of the copolymer The kinetic analysis of the degradation data shows that the thermal decomposition of these copolymers can be described by several kinetic orders depending on the copolymer and on the composition. The relative thermal stability of the copolymers increases as the VP content increases and as the length of the side chain of the itaconate increases, following the same trend as the flexibility of the copolymers in solution.     

Resonant Raman scattering from a spin density wave insulator

We present a calculation of the electronic Raman cross section for the scattering of light across the energy gap of an antiferromagnetic insulator. The antiferromagnet is described in terms of a spin density wave state for the Hubbard model at half filling. We consider the coupling of the light to the current density and the inverse mass tensor on equal footing. A comparison of the cross section for different scattering geometries is given.     

Molecular modeling study on surface,thermal, mechanical and gas diffusion properties of chitosan

The motivation of this work is to provide reliable and accurate modeling studies of the physical (surface, thermal, mechanical and gas diffusion) properties of chitosan (CS) polymer. Our computational efforts have been devoted to make a comparison of the structural bulk properties of CS with similar type of polymers such as chitin and cellulose through cohesive energy density, solubility parameter, hydrogen bonding, and free volume distribution calculations. Atomistic modeling on CS polymer using molecular mechanics (MM) and molecular dynamics (MD) simulations has been carried out in three dimensionally periodic and effective two dimensionally periodic condensed phases. From the equilibrated structures, surface energies were computed. The equilibrium structure of the films shows an interior region of mass density close to the value in the bulk state. Various components of energetic interactions have been examined in detail to acquire a better insight into the interactions between bulk structure and the film surface. MD simulation (NPT ensemble) has also been used to obtain polymer specific volume as a function of temperature. It is demonstrated that these V–T curves can be used to locate the volumetric glass transition temperature (T_g) reliably. The mechanical properties of CS have been obtained using the strain deformation method. Diffusion coefficients of O₂, N₂, and CO₂ gas molecules at 300 K in CS have been estimated. The calculated properties of CS are comparable with the experimental values reported in the literature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1260–1270, 2007     

Influence of temperature on phosphorescence spectra of Pd-porphine in Shpol’skii matrices

We have studied the temperature dependence of the radiative deactivation of the Pd-porphine triplet states in Shpol’skii matrices in the temperature range 1.2–210 K. A substantial transformation of the phosphorescence spectra is observed as the temperature increases and is due to the inclusion of thermally activated Pd-porphine states in the radiative deactivation processes. The activation energy E_a of these Pd-porphine states is measured in matrices of n-octane and n-nonane. The splitting of the lowest quasidegenerate triplet state ΔE(T₂−T₁) is determined for planar and distorted conformations of the Pd-porphine macrocycle in the n-octane matrix as 40 and 57 cm⁻¹, respectively. The ability to use the temperature dependence of the phosphorescence properties of Pd-porphine to fabricate molecular thermometers for the low-temperature range is analyzed. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 460–464, July–August, 2007.     

Anomalies in the Absorption and Reflection of a High-Power Ultrashort Laser Pulse by a Plasma with a Solid-State Density

The patterns of absorption and reflection of an ultrashort laser pulse by a plasma with a solid-state density, which are realized in the mode of the normal skin effect, are studied. It is shown that a decrease in low-power pulse duration shorter than the period corresponding to the fundamental frequency of radiation leads to an increase in the absorption coefficient. If the pulse power is so high as to provide electron heating during a time shorter than the reciprocal fundamental frequency, nonlinear suppression of absorption takes place and the spectrum of the reflected radiation contains odd harmonics of the fundamental frequency.     

基于半导体材料的新型光纤温度传感器

提出利用全反射定律以半导体材料作为敏感器件的光纤温度传感器，着重阐述半导体材料的温度敏感特性及传感原理，介绍传感器构造，并给出初步实验方案。     

Electrical characterization of low temperature deposited TiO2 films on strained-SiGe layers

Thin films of titanium dioxide have been deposited on strained Si_0.82Ge_0.18 epitaxial layers using titanium tetrakis-isopropoxide [TTIP, Ti(O-i-C₃H₇)₄] and oxygen by microwave plasma enhanced chemical vapor deposition (PECVD). The films have been characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Dielectric constant, equivalent oxide thickness (EOT), interface state density (D_it), fixed oxide charge density (Q_f/q) and flat-band voltage (V_FB) of as-deposited films were found to be 13.2, 40.6 Å, 6×10¹¹ eV⁻¹ cm⁻², 3.1×10¹¹ cm⁻² and −1.4 V, respectively. The capacitance–voltage (C–V), current–voltage (I–V) characteristics and charge trapping behavior of the films under constant current stressing exhibit an excellent interface quality and high dielectric reliability making the films suitable for microelectronic applications.