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51.
The potential energy profile of the reaction between dimethyl disulfide and OH? radicals is explored by utilizing ab initio and hybrid meta density functional theory methods. Having the energies and structural data of the stationary points, statistical rate theories, such as transition state theory and variable reaction coordinate-transition state theory, are employed to compute the overall rate constants, and discuss the mechanism and product channels. On the basis of the calculations, the overall rate coefficient is predicted to be 2.49?×?10?10?cm3?molecule?1?s?1 at 298?K. It is found that in the most favorable pathway, the reaction proceeds via formation of the relatively unstable intermediate CH3S?(OH)SCH3 decomposing rapidly to yield CH3S?+CH3SOH. 相似文献
52.
This paper is concerned with the problem of joint input and state estimation for linear stochastic systems with direct feedthrough. Based on the fact that each unknown input between any two time steps is always bounded, a novel improved algorithm is proposed. Compared with existing results, this algorithm can effectively enhance estimation accuracy. Moreover, the stability of the algorithm is also discussed. Finally, an illustrative example is given to demonstrate the effectiveness of the proposed approach. 相似文献
53.
鉴于初期雨水污染为地表水体的主要污染源之一,以儒乐湖初期雨水调蓄池容积确定为例,采用调蓄池工程措施进行截流,以V类水体标准为径流污染控制目标,在《室外排水设计规范》中控制径流污染的分流制初期雨水调蓄池计算公式的基础上,应用模型法模拟得出控制目标下的初期雨水径流累积深度及调蓄池容积。结果表明,截留径流累积深度为7mm,初期雨水调蓄池容积分别为9 250、5 850m^3时,研究区域内能够满足在管网重现期下排水水质达到V类水体标准。研究成果可为初期雨水截流工程实施提供建议及参考。 相似文献
54.
Dwiwahju Sasongko Novan Bayu Nugraha Carolus Borromeus Rasrendra Antonius Indarto 《国际自然能源杂志》2018,39(2):108-116
Direct utilisation of biomass for energy application is less profound due to the problems of low calorific value, high water content, and low grindability of biomass. For this reason, pre-heating treatment, sometimes called torrefaction, is necessary to improve the physical properties of biomass similar to ‘coal-like’ material. Unfortunately, only few comprehensive but simple theoretical models focused on hard-wood biomass were available to describe the torrefaction process. In this discussion, a simple proposed torrefaction model was developed and reported. The model has ability to estimate the yield of product mass and energy after the torrefaction process and determine the optimum conditions. 相似文献
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57.
Aspergillus and their associated metabolites like aflatoxins (AFs) are one of the extremely significant contaminants that affect food production around the world. This species decreases yield and grains quality under suitable environmental conditions. AFs were identified in various food commodities, have been recognized as carcinogenic, mutagenic, teratogenic and immunosuppressive. From 2016 to 2019, a total of 324 samples of maize were obtained from diverse areas of Pakistan and examined for AFs level. AFs were determined using an HPLC validated method through post-column derivatization and fluorescence detection. This study also focused on the effect of climatic conditions on AF production. The total AFs (B1+B2+G1+G2) were detected in 267 (82.4%) samples, ranged between 0.69 and 356.7 μg/kg with a mean of 15.27 ± 0.82 μg/kg. A total of 182 (56.2%) and 85 (26.2%) samples had AFs level above the maximum acceptable limit as accepted by European Union (EU) and United States of America (USA), respectively. The outcomes of the existing study indicated that the climatic situations in the examined areas had a great impact on AFs contamination. Significant differences were found between AFs contamination levels in the samples collected in different months (p < 0.05). The most contaminated samples were identified in July, August and September as the climatic conditions favored the AF production. These outcomes suggested that the food commodities must be regularly examined in order to prevent the health of human and animal from the hazardous effects produced by AFs contamination. 相似文献
58.
从提高流屑角突变模型的预测精度出发,建立了切削状态参数与3个切削控制参数之间关系的新经验公式。提出了一种通过迭代法准确设定有限元仿真软件刀-屑摩擦因数的方法,并通过直角切削Al6061-T6工件的有限元仿真试验,获得了一组不同切削控制参数组合条件下的切削状态参数数据。根据该数据拟合出剪切角φ、刀-屑摩擦角β、剪切应力τs关于刀具前角γ0、进给量f和切削速度v的经验公式,并通过一组直角切削试验,验证了所得经验公式的有效性。将新建经验公式应用于流屑角突变建模过程后,所得模型关于突变临界切削宽度的平均预测误差减小了27.2%。 相似文献
59.
针对变流量制冷(Variable Refrigerant Flow,VRF)系统变吸气状态下带液量的精确控制以及控制元件所引起的滞后或超调现象,以变频滚动转子式制冷系统为研究对象,分别通过恒定频率不同阀开度与恒定阀开度不同频率两个实验,建立其单独控制下的拟合模型,得到其在不同工况下的同步控制方法。结果表明:过热度随阀开度的增大而减小,在过热度为6 K以下,即阀开度为27.8%~30%时,过热度控制难度上升,提高冷冻水温度可改善这一状况;过热度随频率的降低而减小,在过热度为5 K以下,即频率为44.5~46.5 Hz时,控制难度上升;吸气干度随阀开度增大而下降,随频率降低而减小;在某一工况下,以系统质量流量为控制目标,可以拟合得到频率与阀开度的关系式,实现同步控制,在变吸气状态可以精确控制吸气干度,不损坏压缩机,并使系统迅速达到稳定状态。 相似文献
60.
湿式制动器对重型车辆安全具有关键影响,以湿式制动器摩擦副间隙的冷却液压油(Automotive transmission fluid,ATF)为研究对象,考虑车辆初始制动阶段流体的黏性摩擦和层流流动特征,利用积分方法建立了摩擦副流体的非稳态能量方程,并获得了能同时满足轴向和径向边界条件的三维温度和热流密度显式解析表达式,通过简化动量方程和多项式分布假设也获得了径向速度和压力的理论解,与以往试验对比表明,压力和温度解析解与试验结果具有较好的一致性,理论模型有望推广用于液黏离合器等其他HVD装置的ATF速度场、温度场和热流密度场的理论预测。 相似文献