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排序方式: 共有2141条查询结果,搜索用时 15 毫秒
11.
Da SHU Baode SUN Ke LI Jun WANG Yaohe ZHOUState Key Laboratory of Metal Matrix Composites Shanghai Jiao Tong University Shanghai China 《材料科学技术学报》2003,19(3):221-225
The continuous separation of inclusions from aluminum melt flowing in a circular pipe using a high frequency magneticfield was investigated both theoretically and experimentally The separation efficiency was calculated based on thetrajectory method and compared with experimental results. It is found that the separation efficiency is a functilnondimensional parameters t_i·d_p~2B_e~2/μ_fμ_eα~2 and α/δ.The effective way to improve the separation efficiency is to increasethe effective magnetic flux density and decrease the pipe radius. and the value of α/δ should be kept about 2 in orderto obtain the optimum separation efficiency. 相似文献
12.
13.
Evaluation of a two-temperature control structure for a two-reactant/two-product type of reactive distillation column 总被引:1,自引:0,他引:1
Devrim B. Kaymak 《Chemical engineering science》2006,61(13):4432-4450
Several different control structures have been proposed for reactive distillation columns. The appropriate control structure depends on the flowsheet and on the type of reactions occurring in the column. If two reactants are involved and if it is desirable to operate the process without any excess of reactant, it is necessary to manage the fresh feed streams so that the stoichiometry is exactly balanced. A composition analyzer that measures an internal composition in the column is often required. However, if two products are produced, it is possible to avoid the use of an analyzer by using two temperatures in the column to adjust the two feed streams. This type of structure was proposed by Roat et al. [Roat, S., Downs. J., Vogel, E., Doss, J., 1986. Integration of rigorous dynamic modeling and control system synthesis for distillation columns. In: Chemical Process Control—CPC III. Elsevier, Amsterdam.] for the ideal reaction A+B↔C+D in one of the earliest papers dealing with reactive distillation control.The purpose of this paper is to explore the effectiveness of this two-temperature control structure for various column designs (number of reactive stages) to quantify the impact of design on controllability. We also discuss the issues of the selection of the trays whose temperatures are to be controlled and the tuning of the two interacting temperature controllers. Disturbances in production rate and fresh feed compositions are made to examine the rangeability of this control structure. Both an ideal reaction system and the methyl acetate system are studied. One of the main conclusions is that the locations of the temperature control trays should be made such that the two temperature controllers both have direct action (an increase in temperature increases feed), which requires negative openloop process gains for both loops. 相似文献
14.
An integrated process based on simultaneous solid-liquid extraction and liquid membrane separation is proposed for recovery and isolation of valuable species from botanicals. This integration provides complete exhausting of the solid material even in the case of very low solubility of the specified solute in the extracting solvent. Selectivity of the liquid membrane ensures a preferential transport of the desired solute from the native extract into the strip solution, while the other co-extracted species remain predominantly in the native extract. 相似文献
15.
A separation distance between adjacent buildings is provided to reduce the risk of pounding of adjacent buildings under seismic excitations. It should be recognized that the evaluation of the critical separation distance is a one-sided barrier crossing problem while the problem of structural design under seismic excitations is a two-sided crossing problem. A procedure for assessing the required separation distance with or without considering possible uncertainty in structural properties was presented based on the reliability methods and random vibration theory. The procedure was used to carry out parametric analyses. It is shown that use of the complete quadratic combination (CQC) rule with the modal responses employed for designing structures may over- or underestimate the critical separation distance, depending on the damping ratios and the closeness of the natural vibration periods of adjacent buildings. This is due to not only one-sided versus two-sided crossing problem but also the approximation in the CQC rule. Further, the effect of the uncertainty in structural properties on the estimated separation is investigated. The results indicate that this uncertainty tends to increase the required critical separation distance. 相似文献
16.
David A. Naumann 《Formal Aspects of Computing》2007,19(2):205-224
In object-oriented programming, reentrant method invocations and shared references make it difficult to achieve adequate encapsulation
for sound modular reasoning. This tutorial paper surveys recent progress using auxiliary state (ghost fields) to describe
and achieve encapsulation. It also compares this technique with encapsulation in the forms provided by separation logic. Encapsulation
is assessed in terms of modular reasoning about invariants and simulations. 相似文献
17.
Numerical prediction of the wind flow and pollutant dispersion over two-dimensional hilly terrain is presented. The wind tunnel
experiments are conducted to validate the numerical results of the flow field. Measured mean velocity profiles, turbulence
characteristics, and surface pressure distributions show good agreement with the numerical predictions. The hypothesis of
Reynolds number independency for an atmospheric boundary layer flow over aerodynamically rough terrain is numerically confirmed.
The linear theory provides generally good prediction of speed-up characteristics for gently sloped low hills. The effect of
two-dimensional double hills on the dispersion of pollutants from continuously or temporally released line source of different
emission heights and locations is also investigated. The ground-level concentrations are considerably reduced as emission
heights are increased. The variances of ground-level concentration with respect to time from a temporally released source
are strongly influenced by the flow separation. 相似文献
18.
首先介绍了小世界理论的概念及其在互联网商业领域中的应用成果。接着分析了小世界理论在蠕虫研制中的应用问题,将实际生活中互相联系的某些潜在攻击目标之间,通过小世界效应产生聚合,最终产生一个可信任的目标网络。利用文章所述的目标网络构建和分析方法,可以清晰地描绘出蠕虫内部传播的网络结构。 相似文献
19.
An algorithmic approach was used to select recoveries for non-sharp sequence designs. Simple distillation columns were employed. The non-key component distribution was modeled using the Fenske equation. The combination of producing impure products and allowing non-key component distribution, results in a large search space. With this large search space size and software limitations, five problems were solved (see summary table in the Design Examples sub-section). The optimal non-key component distribution was found to be significant but not necessarily maximal. Parallel processing was selected as optimal in contrast to the more traditional sequential processing. 相似文献
20.
《矿业科学技术学报(英文版)》2021,31(6):1135-1144
Surprisingly, no investigation has been explored relationships between operating variables and metallurgical responses of coal column flotation (CF) circuits based on industrial databases for under operation plants. As a novel approach, this study implemented a conscious-lab “CL” for filling this gap. In this approach, for developing the CL dedicated to an industrial CF circuit, SHapley Additive exPlanations (SHAP) and extreme gradient boosting (XGBoost) were powerful unique machine learning systems for the first time considered. These explainable artificial intelligence models could effectively convert the dataset to a basis that improves human capabilities for better understanding, reasoning, and planning the unit. SHAP could provide precise multivariable correlation assessments between the CF dataset by using the Tabas Parvadeh coal plant (Kerman, Iran), and showed the importance of solid percentage and washing water on the metallurgical responses of the coal CF circuit. XGBoost could predict metallurgical responses (R-square > 0.88) based on operating variables that showed quite higher accuracy than typical modeling methods (Random Forest and support vector regression). 相似文献