隧穿问题的数值算法

本文给出一种新的数值方法，用以计算隧道效应中的透射系数和相移。这个方法适用于任意形状的势垒，不仅可以计算透射系数，还可以计算透射波和反射波的相位。分析表明该方法具有很高的精度。     

Change of characteristics of desulfurization and denitrification by combustion flue gas composition and electrode configuration under pulsed corona discharge

Laboratory-scale and parametric experiments of SO₂ and NO_x removal from the simulated combustion gas by pulsed corona discharge have been performed by changing the combustion gas composition and temperature, the electrode configuration of plasma reactor, and the polarity of high-voltage electrode. The following results are obtained: 1) the higher the concentration of H₂O and O₂, the higher the efficiency of desulfurization and denitrification at the same specific input; 2) the pulsed corona discharge with a voltage pulsewidth as short as 200 ns of negative polarity shows the possibility to attain almost 90 percent deSO_x and deNO_x efficiency at the specific discharge input of 20 J/g, which is almost the same as the specific input in the electron-beam process; 3) the deNO_x characteristics show a little temperature dependence in the range of 70 to 130°C, but the deSO_x efficiency increases rapidly in the temperature region below 100°C suggesting the thermochemical dependence of deSO_x reaction; 4) when desulfurization and denitrification proceed, the white dendritic powder deposits on the plasma reactor whose composition is identified to be 49 mol% (NH₄)₂SO₄ and 47 mol% of 2NH₄NO₃ · (NH₄)₂SO₄, and the ratio of SO₂, NO and NH₃ of the deposit is almost equal to that of supplied gas.     

The polar cluster like behavior in Ti substituted BaZrO3 ceramics

In this paper we report the evolution of the polar cluster like behavior with the incorporation of Ti⁴⁺ ion in BaZrO₃ Ceramics. Dielectric behavior of BaZr_xTi_(1−x)O₃ (x = 1.00, 0.95, 0.90, 0.85) ceramics is studied in the temperature range from 300 to 30 K. Polar cluster like behavior becomes more prominent with the increase in content of Ti⁴⁺ ion. The dielectric relaxation is analyzed by Vogel–Fulcher relation and Arrhenius law. Frequency dependence of dielectric constant and low loss tangent of these materials can be useful for the potential applications at low temperature.     

Formation of low-resistivity poly-Si and SiNx films by Cat-CVD for ULSI application

In this paper, bulk-Si metal–oxide–semiconductor field effect transistors (MOSFETs) are fabricated using the catalytic chemical vapor deposition (Cat-CVD) method as an alternative technology to the conventional high-temperature thermal chemical vapor deposition. Particularly, formation of low-resistivity phosphorus (P)-doped poly-Si films is attempted by using Cat-CVD-deposited amorphous silicon (a-Si) films and successive rapid thermal annealing (RTA) of them. Even after RTA processes, neither peeling nor bubbling are observed, since hydrogen contents in Cat-CVD a-Si films can be as low as 1.1%. Both the crystallization and low resistivity of 0.004 Ω·cm are realized by RTA at 1000 °C for only 5 s. It is also revealed that Cat-CVD SiN_x films prepared at 250 °C show excellent oxidation resistance, when the thickness of films is larger than approximately 10 nm for wet O₂ oxidation at 1100 °C. It is found that the thickness required to stop oxygen penetration is equivalent to that for thermal CVD SiN_x prepared at 750 °C. Finally, complementary MOSFETs (CMOSs) of single-crystalline Si were fabricated by using Cat-CVD poly-Si for gate electrodes and SiN_x films for masks of local oxidation of silicon (LOCOS). At 3.3 V operation, less than 1.0 pA μm⁻¹ of OFF leakage current and ON/OFF ratio of 10⁷–10⁸ are realized, i.e. the devices can operate similarly to conventional thermal CVD process.     

High‐pressure processing effects on the mechanical,barrier and mass transfer properties of food packaging flexible structures: a critical review

Food products can be high‐pressure processed (HPP) either in bulk or prepackaged in flexible or semi‐rigid packaging materials. In the latter case the packaging material is subjected, together with the food, to high‐pressure treatment. A number of studies have been performed to quantify the effects of high‐pressure processing on the physical and barrier properties of the packaging material, since the integrity of the package during and after processing is of paramount importance to the safety and quality of the food product. This article reviews the results of published research concerning the effect of HPP on packaging materials. Copyright © 2004 John Wiley & Sons, Ltd.     

纯铜双层辉光离子渗钛组织形成机理及性能分析

采用双层辉光离子渗金属技术对纯铜进行了渗钛处理。用配有能谱仪(EDS)的扫描电子显微镜(SEM)、X射线衍射仪和透射电子显微镜对合金层的显微组织形貌、钛含量分布、相组成及相结构类型进行了观察与测定，对合金层的形成机理进行了探讨，并对其性能进行了对比测定。结果表明：渗钛层由合金层和扩散层组成，合金层主要由TiCu (Cu)固溶体 TiCu4构成，TiCu4为Dla型有序相，TiCu为B2型有序相，扩散层为(Cu)固溶体。渗钛处理后纯铜的表面得到显著强化。     

Thermally stimulated discharge current studies in pure and fe-doped polystyrene films

Studies were made on the thermally stimulated discharge currents (TSDCs) in pure (undoped) and Fe-doped polystyrene films as a function of polarizing field, polarizing temperature and dopant concentration. While undoped films exhibited a single peak, doped films showed two peaks one at low temperatures and another at high temperatures. The low temperature peak, which exhibits a shift towards lower temperatures with increasing dopant concentration, is attributed to the relaxation of the main chain, while the high temperature peak, which shows a tendency to shift towards higher temperatures with dopant concentration, is due to space charge polarization. The TSDCs were higher for low dopant concentrations than their undoped counterparts, while for high concentrations of the dopant, the TSDCs decreased. Formation of charge transfer complexes at low dopant concentrations and molecular aggregates at higher dopant concentrations are suggested as the possible reasons for this behaviour.     

Changes in the dielectric relaxations of water in epoxy resin as a function of the extent of water ingress in carbon fibre composites

Dielectric relaxation measurements are reported over a frequency range from 10⁻¹ to 10⁹ Hz as a function of exposure time for an epoxy resin-carbon fibre composite, ageing at 60 °C in water. Investigation of the nature of the dipole relaxation of the water molecules, indicates the nature of their interaction with the polymer matrix. Analysis of the dielectric relaxation spectra allow identification of processes that can be attributed to ‘free’ and ‘bonded’ water, water in micro-cracking, located in carbon fibre disbonds and plasticizing the polymer matrix. Identification of the various types of location in which water exists was aided by use of the N_g factor from the Kirkwood-Frölich equation, which describes the constraints on free dipole ration nature imposed by the environment in which it is located. These data indicate the power of the dielectric technique for quantitative analysis of water ingress into epoxy composites.     

氧气放电辅助激光淀积原位制备高T_c超导薄膜

采用低压氧气放电辅助的激光淀积方法,原位外延生长出零电阻温度91K,临界电流密度10~5A/cm~2的Y-Ba-Cu-O高温超导薄膜。扫描电镜和X光衍射分析结果表明,薄膜中超导相晶粒的生长具有c轴垂直于表面的择优取向。     

Electrical characterization of waterside corrosion films formed on ZrNb(1%)O(0.13%)

Oxide films formed by water oxidation at 360°C on ZrNb(1%)O(0.13%) for several durations (50-300 days) were studied by impedance spectroscopy (IS) in gaseous atmosphere. The electrical behavior of oxide layers was investigated as a function of the temperature (25-300°C) at constant oxygen partial pressure (0.3 Pa). Cole-Cole diagrams suggest a frequency-temperature equivalence. A simple electrical model has been derived from the as-deduced 14 decade master curve. Equivalent circuit includes a series association of two layers exhibiting different dielectric properties: a dense layer near the oxide-metal interface and a porous layer at the waterside. Electronic conductivity is predominant within the whole temperature range, but ionic contribution was proposed to increase for temperature higher than 170°C. During the parabolic oxidation step, the oxide thickness of the barrier layer increases but oxide growth would not be only a geometrical one. The kinetic modification to a constant oxidation rate was observed to be correlated to the increase of the dense layer thickness. Such a behavior suggests that the mechanism controlling oxidation rate is not a pure mechanism of oxygen diffusion through this layer. Finally, a qualitative model of activated electrons transport based on an hopping mechanism was proposed in order to take into account that the Arrhenius diagrams of both total conductivity and dispersion factor are characterized by a break point with two activation energy values.