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991.
以4%Li3%Cr修饰的25%ZnO/MnO/βAl_2O_3为催化剂,采用固定床反应器,在消除内外扩散的情况下,考察了反应温度和氢酯比对苯甲酸甲酯(MB)加氢制备苯甲醛的影响,并建立苯甲酸甲酯加氢反应的本征动力学模型。以MB转化率和苯甲醛选择性的模型计算值与实验值的残差平方和最小为目标函数,采用Matlab软件中的非线性最小二乘法对实验数据进行拟合,估算出该模型的参数,并对模型的显著性进行了检验。结果表明,动力学模型具有合理性,能较好地描述苯甲酸甲酯加氢反应。 相似文献
992.
Conductivity measurements in PEO30MI polymer electrolytes with M=Li, Na, K, Rb, or Cs over the temperature range from about 65 to 200 °C show an increasing tendency for salt precipitation with increasing cation size. The salt precipitation in these complexes upon heating is revealed by the decrease of the dc conductivity starting at a critical temperature Tc. Whereas LiI and NaI complexes do not show precipitation effects, Tc monotonically decreases from about 140 to 65 °C when changing the salt component from KI via RbI to CsI. For the PEO-RbI system, precipitation is further investigated by nuclear magnetic resonance (NMR) and tracer diffusion experiments. NMR analysis unambiguously demonstrates the onset of RbI salt precipitation and the increase of the precipitate fraction with increasing temperature. In diffusion experiments on PEO30RbI with the radiotracers and , the precipitation effect is manifested by anomalous features in the penetration profiles, however, without noticeable changes in their depth range. Combining the resulting tracer diffusion coefficients with the dc conductivity data enables us to assess crucial parameters characterizing ionic transport in PEO30RbI. 相似文献
993.
The objective of the present study was to investigate farmers' willingness to pay for using recycled water for irrigation purposes in Thessaly region, Greece. The method followed for the above analysis was the contingent valuation method which aims at eliciting individuals' preferences, in monetary terms, for changes in the quantity or quality of nonmarket environmental resources through personal interviewing. Our study was based on data collected from 107 questionnaires, which were answered by farmers in Thessaly region. The region is located in central eastern part of Greece and its main feature is that a relatively high percentage of its population is partly or fully employed in agriculture. Furthermore, Thessaly region suffers from a distinct water shortage in summer period, which is partly attributed to the increased agricultural activity. The group chosen for our study was random and the questionnaires were answered through personal interviews. The questionnaire was divided in 3 sessions. The first one dealt with personal data in order to investigate correlations between socioeconomic characteristics of interviewee and his or her willingness to use recycled water and to pay for it. The second session had as a goal to discover whether farmers are willing to use recycled water for irrigation purposes. Finally, the third session dealt with farmers' willingness to pay for treated wastewater. The data were statistically analyzed with the use of the multinomial logistic regression method. The main results show that Thessaly farmers are willing to pay for recycled water especially during drought spells in the region. 相似文献
994.
为了更好地去除图像中的椒盐噪声、保留图像细节信息,提出了一种广义回归神经网络模型,适用于图像去噪。首先,对传统广义回归神经网络的原理进行了分析,并对采用的广义回归神经网络进行具体设计。然后对广义回归神经网络中的唯一可调参数(平滑因子)进行了优化。采用归一化均方误差和峰值信噪比指标进行具体算法性能分析。仿真试验结果显示:相比径向基神经网络和传统广义回归神经网络,提出算法的去噪能力更强,具有较高的峰值信噪比和较低的归一化均方误差,验证了提出算法的有效性和先进性。 相似文献
995.
Jie Zhang 《Chemical engineering science》2008,63(5):1273-1281
A neural network based batch-to-batch optimal control strategy is proposed in this paper. In order to overcome the difficulty in developing mechanistic models for batch processes, stacked neural network models are developed from process operational data. Stacked neural networks have enhanced model generalisation capability and can also provide model prediction confidence bounds. However, the optimal control policy calculated based on a neural network model may not be optimal when applied to the true process due to model plant mismatches and the presence of unknown disturbances. Due to the repetitive nature of batch processes, it is possible to improve the operation of the next batch using the information of the current and previous batch runs. A batch-to-batch optimal control strategy based on the linearisation of stacked neural network model is proposed in this paper. Applications to a simulated batch polymerisation reactor demonstrate that the proposed method can improve process performance from batch to batch in the presence of model plant mismatches and unknown disturbances. 相似文献
996.
Kechang Xie 《中国化学工程学报》2021,35(7):62-69
It is important to develop the advanced coal to chemicals industry (ACCI) against a backdrop of coal-based energy structures,excessive imported oil and natural gas,and strict environmental con-straints in China.In this study,the technology and industry of China's ACCI are reviewed to explain the effect of using coal to replace oil and natural gas,and the corresponding resource and environmental burdens that this will create.Development trends in technology and industry are also proposed to explore future scenarios.The review shows that although excellent progress has been made on an indus-trial scale,demonstrative level,and in terms of technology and equipment,the lack of strategic under-standing,severe external constraints,partly underdeveloped technologies,and weak foundations must be immediately addressed.Therefore,it is necessary to clarify the importance that the ACCI has on the energy revolution and energy system.Based on technological innovation,a variety of external factors should be considered as a whole with emphasis on filling the knowledge gap of theoretical foundations and industry standards to support high-quality development for ACCI. 相似文献
997.
998.
Diffuse scattering was taken from Ni–23.2 at.% Pt (1 0 0) under grazing incidence at 973 K using photons of 10 keV energy. For comparison, bulk Ni–25.6 at.% Pt was also investigated for a state corresponding to 923 K using Mo Kα radiation. In both cases, the separated short-range order scattering reveals local features of the L12 superstructure – this structure is known for ordered Ni3Pt in the bulk. A much lower degree of local order was found for the (1 0 0) near-surface microstructure than for the bulk, thus suggesting the presence of surface induced disorder. Effective pair interaction parameters determined by the inverse Monte Carlo technique give a dominant nearest-neighbor parameter of ~46 meV for the near-surface microstructure and ~80 meV for the bulk. As ~85 meV was previously noted for Ni–23.2 at.% Pt (1 1 0), the segregation reversal among low-index surfaces seems to be reflected in a different strength for ordering. 相似文献
999.
1000.
在自来水和3.5%NaCl溶液中测试了铸造AZ91D镁合金与铝合金、锌合金、Q235碳钢和Cu偶合后的电偶腐蚀行为,研究了腐蚀环境、偶接材料和阴阳极面积比(CAAR)对铸造AZ91D镁合金电偶腐蚀行为的影响。在电偶腐蚀过程中测量溶液的pH值以及电偶腐蚀电流;用失重法计算了铸造AZ91D镁合金的电偶腐蚀速率,利用SEM观察了AZ91D镁合金的腐蚀形貌,并对腐蚀产物进行XRD分析。结果表明,AZ91D镁合金在电偶腐蚀过程中会使溶液的pH值升高,并伴有以Mg(OH)2为主的腐蚀产物的生成;溶液中Cl-的存在会加速AZ91D镁合金的电偶腐蚀速率;低氢过电位金属Q235碳钢和Cu对AZ91D镁合金的电偶腐蚀加速效果明显高于中氢过电位金属铝合金和锌合金,偶接材料的极化性能对AZ91D镁合金的电偶腐蚀速率有较大影响。同时,大的阴阳极面积比会加速AZ91D镁合金的电偶腐蚀速率,且AZ91D镁合金的电偶腐蚀电流随阴阳极面积比的增大而呈线性增长趋势。 相似文献