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71.
72.
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。 相似文献
73.
74.
Zhang Li Chun Jin Hai Yan Ye Hong Fei Gao Yu Zhi Ning Bao Jun Mo Bang Xian 《Electron Devices, IEEE Transactions on》2002,49(6):1075-1076
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 相似文献
75.
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. 相似文献
76.
77.
Hong Jeong Jeong‐Ho Park 《International Journal of Adaptive Control and Signal Processing》2002,16(1):1-23
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. 相似文献
78.
比较了几种长距离传动方式的特点与适用场合,重点探讨了实现长距离精密传动的技术要点。结合实际工程,完成了长距离钢带精密传动的应用,并指出张紧机构的设计与应用是钢带实现长距离精密传动的关键。为此文中对钢带传动的典型张紧机构进行了比较,并分析了这几类张紧机构的应用情况,有参考和应用价值。 相似文献
79.
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. 相似文献
80.
采用被动式工艺生产冷轧带肋钢筋须经过减径、成型两台轧机连续轧制.要求钢材的秒流量相等,否则将造成断线停产或线材在拉丝机卷筒上打滑,致使卷筒严重磨损.用双层卷筒拉丝机提供动力生产冷轧带肋钢筋时,线材直径与卷筒直径的匹配是在一个小的调整范围,通过轧机拉力控制在一定范围变化,可保证成品尺寸符合公差要求而不产生打滑,从而避免了卷筒严重磨损. 相似文献