Synthesis and microstructure of SrTiO<Subscript>3</Subscript> and BaTiO<Subscript>3</Subscript> ceramics by a reaction-sintering process

Strontium titanate and barium titanate ceramics prepared by a reaction-sintering process were investigated. The mixture of raw materials of stoichiometric SrTiO₃ and BaTiO₃ was pressed and sintered into ceramics without any calcination stage involved. A density 4.99 g/cm³ (97.5% of the theoretic value) was found in SrTiO₃ after 6 h sintering at 1,370 °C. Grains less than 1.5 μm were formed at 1,300–1,330 °C and became 2.2–3.3 μm at 1,350–1,370 °C SrTiO₃. A density 5.89 g/cm³ (97.9% of the theoretic value) was found in BaTiO₃ after 6 h sintering at 1,400 °C. Merged grains were observed in BaTiO₃ and were less than 10 μm after sintered at 1,400 °C.     

Preparation and phase formation of perovskite Pb(Ni<Subscript>1/3</Subscript>Nb<Subscript>2/3</Subscript>)O<Subscript>3</Subscript> by a reaction-sintering process

Pyrochlore-free Pb(Ni_1/3Nb_2/3)O₃ perovskite ceramics produced by a simple and effective reaction-sintering process were investigated. Without any calcination, the mixture of PbO, Ni(NO₃)₂ and Nb₂O₅ was pressed and sintered directly into PNN ceramics. Density of 98.5% of theoretical value was obtained after sintered at 1230 °C for 2 h in air. 99.3% of theoretical density was obtained after sintered at 1,200 °C for 2 h in PbO compensated atmosphere. PNN ceramic with dielectric constant 1,680 at 25 °C and 1 kHz has been obtained.     

基于内容的反垃圾邮件过滤器研究

本文论述了基于内容的反垃圾邮件过滤器的构造方法。介绍了邮件表示中的几个技术问题:特征定义和选择,以及特征权值的估计;探讨了以朴素贝叶斯、支持向量机和最大熵模型为代表的机器学习方法如何构造反垃圾邮件过滤器,并对它们作了简要的评价;介绍了几个常用的衡量邮件过滤器性能的指标。     

阿公店水庫越域引水路工程泥岩隧道之設計

阿公店水庫位於高雄縣燕巢鄉境,係以防洪為主並兼具灌溉及公共給水之多目標水庫,惟因庫區淤積情況嚴重,為恢復水庫原有功能並達水資源永續利用之目的,經核定辦理"阿公店水庫更新工程計畫",採台灣首創排潤蓄清之空庫防淤操作,輔以越域引水路導引旗山溪潔淨水源蓄存運用,以同時解決水庫防洪、淤積及給水問题於一舉。隧道基於水理及施工性考量採4.0m内徑2R-3R-3R之正馬蹄型斷面,隧道開挖主要可能遭遇問題包括擠壓破壞及砂岩夾層蕴藏地下水狀況,由於泥岩隧道岩體分類及支撐設計不盡適用CSIR-RMR及NGI-Q值之經驗設計法則,遂採近似Terzaghi之岩壓估算方式,輔以數值分析法計算隧道變形與岩體-支撐之應力,俾檢核支撐設計之適用性,施工期間並彙整監測资料進行反算分析回饑設計,以期達兼顧安全與經濟之合理設計。考量儘早有效抑制隧道岩體擠壓及潛變變形,確保隧道長期之穩定性,並可維護洞内施工動綜提升施工效率,隧道仰拱設計以預鑄混凝土版進行斷面支撐閉合。     

改善工业级干酪素色泽的研究

针对用曲拉原料生产的干酪素颜色发黄、无光泽等问题,采用离心过滤,亚硫酸盐,抗氧化剂处理,研究其对产品色泽改善的效果。同时,对漂白剂和抗氧化剂的用量及作用条件进行了研究。     

Surface-enhanced infrared spectroscopic studies of the catalytic behavior of silver nanoparticles on a germanium substrate

The catalytic activity of silver nanoparticles (AgNPs) on a germanium substrate is reported. Para-nitrothiophenol (pNTP) that had been adsorbed on this substrate is converted to p-aminothiophenol (pATP) under very mild reaction conditions, such as simply soaking in water. The AgNPs may be formed either by physical vapor deposition or by electroless deposition from a solution of silver nitrate. Analogous reactions were not observed on copper nanoparticles on germanium or AgNPs on silicon or zinc selenide even though very slow conversion of pNTP to pATP was observed with Au nanoparticles (AuNPs) on Ge under controlled reaction conditions. The effects of factors that could influence the catalytic reaction were examined; these included the particle size of the AgNPs, reaction temperature, concentration and chemical nature of other ions present in the solution, the pH of the water, and the nature of the substrate. The reaction rate was approximately independent of the particle size for AgNPs between 50 and 150 nm in diameter. Increasing the temperature accelerates the reaction significantly; at temperatures above 40 °C, the adsorbed pNTP is completely converted by water within five minutes. Not surprisingly, the reaction rate was increased as the pH of the solution was decreased, as the reduction of each nitro group to an amino group requires six protons. The presence of Br(-) and I(-) ions accelerated the reaction to the point that even at 4 °C, the conversion of the nitro group was still observable, while solutions containing chloride ions had to be heated to 40 °C before their effect became apparent. Apparently, Br(-) and I(-) ions remove the oxide layer from the surface of the germanium substrate, facilitating transfer of electrons from the germanium to the nitro group of the pNTP.     

Electrical and thermal transport properties of electrically stressed Bi-Sb-Te nanocrystalline thin films

Nanoscale size effect is beneficial for enhancing thermoelectric figure-of-merit of Bi-Sb-Te compounds due to the decrease of thermal conductivity. Bi-Sb-Te nanocrystalline thin films prepared by sputtering at room temperature, in general, require a post-deposition treatment to improve their electrical transport properties by eliminating residual crystal defects. In this study we present an electric current stressing treatment to effectively eliminate crystal defects in sputtered Bi-Sb-Te films at low temperature. By maintaining a low thermal conductivity of 0.6-0.7 W/mK, the electrically stressed Bi-Sb-Te nanocrystalline films possess highly enhanced Hall mobility and moderately reduced carrier concentration as compared to the films thermally treated at the same temperature. Carrier concentration, mobility and Seebeck measurement results suggest that the change of electrical transport properties involves the elimination of Sb_Te antisite defects as supported by the observation of some Sb-rich precipitates in the thermally/electrically treated Bi-Sb-Te films. Besides, crystal defects are also suggested to be preferentially removed in the (00l)-oriented grains due to anisotropic diffusion and electrical transport properties in the electrically stressed Bi-Sb-Te films.     

A fully on-chip ESD protection UWB-band low noise amplifier using GaAs enhancement-mode dual-gate pHEMT technology

This paper presents the development of a novel ESD protected wideband low noise amplifier (LNA) using enhancement-mode (E-mode) pHEMT dual-gate clamps. The proposed novel clamp possesses a low on-state resistance, uniform parasitic capacitance, and flexibility to adjust the trigger voltage for different ESD applications. Implementation of the LNA demonstrates that RF performance can be maintained after human body mode (HBM) ESD test while at the same time endure more than +2.5 kV and −2 kV HBM ESD stress voltage. In addition, the incorporated clamps use a fewer number of diodes than the conventional diode stacks, thereby making it size efficient and low effort impedance matching co-design which allow this approach to be an attractive solution for ESD protection.     

New and bioactive lignans from the fruits of Schisandra sphenanthera

Phytochemical investigation of the ethanol extract from the fruits of Schisandra sphenanthera has resulted in isolation of seven new oxygenated lignans (1–7), in addition to 11 known compounds (8–18). Their structures were determined on the basis of 2D-NMR (COSY, HMQC, HMBC and NOESY) analyses. The isolated components were evaluated with a reporter gene assay that measures their anti-liver fibrosis activity. Compounds 1, 2, 4, 11, 13, 14 and 18 exhibited significant anti-inflammatory activity on HSC-T6 test.     

广义原函数与广义不定积分

利用积分限函数定义了可积函数的原函数－广义原函数与可积函数的不定积分－广义不定积分，并给出 了利用广义原函数计算可积函数定积的分式。