石油化工过程中控制与联锁自保系统的仿真

本文介绍了石油化工过程中控制与联锁自保系统的仿真模型的建立方法，并附以相应程序。     

并行工程产品开发过程的建模方法学

在并行工程中，为了实现产品开发过程的集成、并行和最优化，首先要建立能够充分反映产品开发过程各方面信息的产品开发过程模型。通过对模型的仿真分析和优化，指导产品开发过程的实施。本文首先提出了并行工程产品开发过程模型是集成多视图模型，随后提出了采用集成多视图建模理论的并行工程产品开发过程建模、分析和管理的方法学框架     

植物多糖提取液的几种脱蛋白方法的比较分析

多糖对肿瘤、病毒、心血管等方面具有独特的生物活性,且细胞毒性很低,因此多糖的分离及纯化一直是一个很有意义的研究课题.实验以多糖损失率和脱蛋白率(r)为衡量指标,通过对几种脱蛋白方法的比较,优化出植物多糖提取液的脱蛋白方法,为多糖的纯化提供了一定的参考.选用了3种较为常见的方法:三氯乙酸法、盐酸法及沙维积法(Sevag 法)对植物多糖提取液进行脱蛋白处理.三氯乙酸法、盐酸法及Sevag法的脱蛋白率分别为46.1%、72.5%和42.3%,多糖损失率分别为6.1%、15.1%和14.3%.盐酸法脱蛋白率高,但它的多糖损失率较高;三氯乙酸法较温和,但除蛋白效率不高;Sevag法的脱蛋白效果不及前两种方法.     

金佛山甑子岩物种多样性保护研究

用稀疏曲线法、丰富度指数、多样性指数和均匀度指数分析了金佛山甑子岩植物群落的物种丰富度、多样性和均匀度。结果表明：该地区距离人群居住地越近、海拔越低的地方其植物群落的丰富度指数、多样性指数和均匀度指数越低，并且该地区植物群落处于严重退化状态，说明该地区植物群落的退化主要是由于过度放牧和滥伐造成的。     

In-plane elastic stability of fixed parabolic shallow arches

The nonlinear behavior of fixed parabolic shallow arches subjected to a vertical uniform load is investigated to evaluate the in-plane buckling load.The virtual work principle method is used to establish the non-linear equilibrium and buckling equations.Analytical solutions for the non-linear in-plane symmetric snap-through and antisymmetric bifurcation buckling loads are obtained.Based on the least square method,an approximation for the symmetric buckling load of fixed parabolic arch is proposed to simplif...     

A perturbation-incremental scheme for studying Hopf bifurcation in delayed differential systems

A new method,called perturbation-incremental scheme (PIS),is presented to investigate the periodic solution derived from Hopf bifurcation due to time delay in a system of first-order delayed differential equations.The method is summarized as three steps,namely linear analysis at critical value,perturbation and increment for continuation.The PIS can bypass and avoid the tedious calculation of the center manifold reduction (CMR) and normal form.Meanwhile,the PIS not only inherits the advantages of the method ...     

Improved generalized cell mapping for global analysis of dynamical systems

Three main parts of generalized cell mapping are improved for global analysis.A simple method,which is not based on the theory of digraphs,is presented to locate complete self-cycling sets that correspond to attractors and unstable invariant sets involving saddle,unstable periodic orbit and chaotic saddle.Refinement for complete self-cycling sets is developed to locate attractors and unstable invariant sets with high degree of accuracy,which can start with a coarse cell structure.A nonuniformly interior-and...     

Examination of dynamic recrystallization during compression of AZ31 magnesium

This study aimed to investigate dynamic recrystallization(DRX)behavior during compression of magnesium alloy AZ31. Cylinder samples were cut from the extruded rod and hot rolled sheet AZ31 for compression test.The samples were compressed using a Gleeble 1500D at a temperature of 300℃and a strain rate of 0.01 s-1.Grain orientations and misorientation angles across grain boundaries for the tested samples were obtained by using electron backscatter diffraction(EBSD)technique.The results showed that strong basal texture was observed after 50%compression(ε=0.69)on both the extruded and hot rolled samples,which have different initial textures.It was observed that with increased strain,DRX grains gradually rotated to basal orientation,and grain boundaries with misorientation angle of near 30°was formed in the samples.At the strain of 0.69,a high fraction of high-angle(60°)boundaries was present in the extruded sample,whereas almost no high angle boundaries were observed in the hot rolled sheet sample.     

Effects of electromagnetic field and lubricate condition on the surface quality of magnesium alloy billet during LFEC processing

The microstructures of the magnesium billets could be improved markedly by low-frequency electromagnetic casting(LFEC)processing.In fact,the low-frequency electromagnetic field(LFEF)also has favorite effect on the surface quality of billet.However,few public reports on the surface quality of LFEC magnesium billets could be found.Therefore,a new crystallizer with a metal internal sleeve together with a kind of lubricant was designed aiming at lowing surface turning quantity,and the effects of casting velocit...     

Net-shape forming of composite packages with high thermal conductivity

The continuing miniaturization of electronic devices in microelectronics and semiconductors drives the development of new packaging materials with enhanced thermal conductivity to dissipate the heat generated in electronic packages.In recent years,several promising composite materials with high thermal conductivity have been developed successfully for high performance electronic equipment to replace the traditional Kovar and Cu/W or Cu/Mo alloys,such as SiCp/Al,SICp/Cu,diamond/Al and diamond/Cu.However,thes...