α-蒎烯催化加氢反应的研究

以FYX - 2G型高压搅拌釜为加氢反应器 ,测定了在不同搅拌器型式和搅拌转速下高压釜的持气量和反应效果 ,认识到α 蒎烯催化加氢是外扩散控制的反应 ,当搅拌转速为 6 0 0r/min时 ,基本上能消除外扩散的影响。考察了Raney镍和Pd/C催化剂、反应温度在 35 3～ 499K ,压力在 4 0～ 10MPa的条件下对α 蒎烯加氢转化率和选择性的影响 ,结果表明Raney镍更适宜于α 蒎烯催化加氢 ,其转化率随温度、压力增加而提高 ,但选择性下降。采用温度 35 3～ 433K、压力 4 0～ 7 0MPa的操作序列 ,克服了α 蒎烯加氢转化率与选择性互为逆向的缺点 ,缩短了反应时间 ,制得了顺反比高达 18 2∶1的蒎烷 ,并且发现加氢反应从温度 433K开始有副产物对烷生成 ,当温度超过 45 6K时 ,加氢过程还出现飞温现象。     

NBR/PP热塑性弹性体研究进展

阐述了NBR／PP共混热塑性弹性体动态硫化胶的国内外研究进展、微观相态结构、性能、应用及展望。     

浅析嵌入式电脑及其发展趋势

主要介绍嵌入式电脑的构成特点、应用与发展前景。     

Improvement of RCA transistor using RTA annealing after theformation of interfacial oxide

A polysilicon emitter RCA transistor (an ultra-thin interfacial oxide layer exists between polysilicon and silicon emitter) is presented which can operate at 77 K for the first time. An ultra-thin (1.5 nm) interfacial oxide layer is grown deliberately between polysilicon and silicon emitter using RCA oxidation and excellent device stability is obtained after rapid thermal annealing (RTA) treatment in nitrogen atmosphere. The RCA transistor exhibits good electrical performance at very low temperature for an emitter area of 3 × 8 μm². The maximum toggle frequency of a 1:2 static divider is 1.2 GHz and 732 MHz at 300 K and 77 K, respectively     

The influence of viewing distance on subjective impairment assessment

In this paper, the influence of viewing distance on subjective assessment of the impairment in video sequences is investigated. Subjective tests using the double-stimulus impairment scale variant II (DSIS II) method have been conducted at viewing distances of 5H (where H stands for the screen height) and 3H, respectively. Several statistical measures have been used to analyze the influence, including correlations and ANOVA (analysis of variance) tests. The results reveal that there is a very high correlation between the subjective scores, the variances are similar under the two viewing distances, the means of subjective data at these two viewing distances are the same, and there is no interaction between the viewing distance and the other two factors, i.e., the codec system and the source sequence. Throughout the tests, there is no evidence that a closer viewing distance such as 3H will vary the subjective test result statistically significantly.     

数字化制模新技术

数字化制模技术是将三维CAD模型直接转化成为铸造用模的新技术。文中介绍了华中科技大学开发的HRP系列数字化制模技术的原理及制模工艺。与传统制模方法相比 ,具有制模速度快、精度高、质量好、价格便宜等优点。文中还以制作轿车制动器卡钳体模样、搅拌叶片模样、蜗壳凸样为例说明了运用数字化制模新技术的优点     

An EM‐based adaptive multiple target tracking filter

Tracking targets of interest is one of the major research areas in radar surveillance systems. We formulate the problem as incomplete data estimation and apply EM to the MAP estimate. The resulting filter has a recursive structure analogous to the Kalman filter. The advantage is that the measurement‐update deals with multiple measurements in parallel and the parameter‐update estimates the system parameters on the fly. Experiments tracking separate targets in parallel show that tracking maintenance ratio of the proposed system is better than that of NNF and RMS position error is smaller than that of PDAF. Also, the system parameters are correctly obtained even from incorrect initial values. Copyright © 2001 John Wiley & Sons, Ltd.     

入侵检测及网络层安全的研究

随着计算机网络的迅速发展，网络安全问题正变得日益重要。文章介绍了计算机网络系统IP层安全概况和入侵者对IP层常采用的入侵手段，以及为防止这种入侵所采取的措施。     

A novel cyclic process using CaSO4/CaS pellets for converting sulfur dioxide to elemental sulfur without generating secondary pollutants: Part II. Hydrogen reduction of calcium-sulfate pellets to calcium sulfide

The reduction of calcium sulfate to produce calcium sulfide is a part of the cyclic process for converting sulfur dioxide to elemental sulfur that is described in Part I. The kinetics of the hydrogen reduction of nickel-catalyzed calcium-sulfate pellets were investigated using a thermogravimetric analysis (TGA) technique at reaction temperatures between 1023 and 1088 K and hydrogen partial pressures between 12.9 and 86.1 kPa. The reactivity of nickel-catalyzed calcium-sulfate pellets was demonstrated by the conversion of 70 pct fresh nickel-catalyzed calcium sulfate to calcium sulfide in 20 minutes at 1073 K under a hydrogen partial pressure of 86.1 kPa. Furthermore, the reactivity remained relatively intact after ten cycles of reactions and regenerations. This observed characteristic of the pellets is important because the solids must be reusable for repeated cycles to avoid generating secondary pollutants. The nucleation and growth rate expression was found to be useful in describing the kinetics of the reaction, which had an activation energy of about 167 kJ/mol (∼40 kcal/mol) in all reaction cycles except for the first regenerated samples that were lower at 146 kJ/mol (35 kcal/mol). The reaction order with respect to hydrogen partial pressure was 0.22 in all cycles with the exception of the first regenerated sample for which it was 0.37.     

马家河水电站的设计

马家河水电站通过在马家河和毛家河上游分别建底栏栅坝和低拱坝 ,经各自的引水系统将水引至两河口汇合流入前池发电。本文介绍了电站的开发方案 ,厂区、引水工程和取水枢纽的布置和设计