Enhanced utilization bound of Rate-Monotonic scheduling in Controller Area Networks

When priorities to message streams are assigned using Rate Monotonic (RM) for a Controller Area Network (CAN), the utilization bound is known to be about 25% for CAN 2.0A and 29% for CAN 2.0B. In this letter, we present a higher utilization bound than the existing ones with a reasonable constraint. The new utilization bounds are approximately 34% for CAN 2.0A and 41% for CAN 2.0B if no single message stream's utilization exceeds 46% or 27% of the total utilization for CAN 2.0A or CAN 2.0B, respectively.     

双向搜索多约束路由启发式计算方法

为提高大型通信网络中搜索满足多约束条件路由的速度,提出一种双向搜索路由的计算方法.首先从源和目的节点同时出发,计算到达各中间节点的可达路径.然后在各可达路径中进行路径的筛选.可达路径是采用邻接矩阵变换方式获得的,筛选路径是根据非线性开销函数,采用启发方式择优选取.当两方向搜索的节点数累计达到n-2后,对接合并两方向到达中间节点的路径,从中再选择最佳路径作为路由输出.通过算例详细介绍了可达路径计算及启发式选优方法.阐述了算法的正确性及特点,分析了最大时间杂性.通过仿真实验评估,不仅更进一步验证了新算法的正确性,而且表明新算法在搜索路由速度上要优于其他算法.     

Fabrication of Titanium Aluminides via Powder-Cored Wire Arc Additive Manufacturing: Microstructural and Mechanical Characterization

Herein, an innovative powder-cored wire arc additive manufacturing (PC-WAAM) process is proposed to fabricate γ-TiAl thin-walled intermetallic alloy. The metallography, phase composition, and mechanical properties at different thin-wall locations are characterized. The results show that the alternatively distributed layer-like microstructure composed of α₂ (Ti₃Al) and γ (TiAl) phases is obtained along the building direction. The content of α₂ phase exhibits the tendency of decreasing from the bottom to top region. This unique microstructure characteristic is closely related to the typical thermal cycling history during deposition. Moreover, the tensile strength and microhardness of the top region are lower than the middle and bottom region. In general, the current PC-WAAM technique shows promising capability of fabricating γ-TiAl intermetallic alloy with low cost. This work becomes a valuable reference for understanding the evolution mechanism of microstructure and paves the way for the flexible and customized additive manufacturing of γ-TiAl alloy.     

基于MDA的代码生成器设计与实现

针对如何将业务模型转换为程序代码的问题,提出一种代码生成器设计方案,用以实现模型驱动架构中代码的自动生成。介绍采用XML描述的面向业务对象的平台无关模型,在此基础上设计实现代码生成器,完成从平台无关模型到代码的自动转换,以支持在业务模型变化后系统行为的快速变化和代码的自动生成,通过实例演示该代码生成器的应用。     

两阶段多供应商选择采购模型

针对如何从众多供应商中选择出适合需求的供货商进行准时采购这一问题,提出两阶段多供应商选择采购模型。利用层次分析方法对各个供应商按照定性准则进行分析评价,利用定量准则所建立的多供应商选择采购的成本优化模型对初步选择的供应商做进一步选择,从而确定最终的供货商及供货数量。实际应用结果表明,该模型不但能使企业选择出符合要求的供货商,而且能使企业降低采购成本和产品成本。     

Spatial and temporal variations in algal blooms in the coastal waters of the western South China Sea

Algal blooms occur frequently in the coastal waters of the western South China Sea (SCS). This paper reports spatial and temporal variations of algal bloom events in these waters from 1993 to 2007. Twenty-five algal bloom events occurred in summer in the coastal waters of South and Central Vietnam where they were associated with wind-induced, coastal, nutrient upwelling and river discharges; a further eight events occurred in the coastal waters of North Vietnam. A greater number of algal bloom events were observed in 1999 and 2002, and were accompanied by several previously unobserved species for the study period. These events may be related to the El Niño events of 1998 and 2002. Furthermore, the bloom-causative species Trichodesmium erythraeum (Cyanophyta) entirely dominated the phytoplankton community of algal blooms during 1993–1999 whereas the species Phaeocystis globosa (Haptophyta) dominated blooms after 2002. This study establishes a basis for further long-term research of algal bloom event variations, and provides a compiled scientific reference that may be used for later prediction of Harmful algal blooms (HABs).     

对流方程的交替分组显示方法

提出了求解对流方程初边值问题绝对稳定的二阶精度交替分组显示方法.模型问题的数值结果表明,本方法忧于陈景良和陆金甫的分组显示方法.     

High-performance two-electrode electron gun lenses: Beyond the Butler gun

High-performance two-electrode electron gun lens designs with lower spherical and chromatic aberration coefficients than the Butler gun are presented. It is shown that the Butler gun is a specific solution to the general class of one-interval polynomial lenses of degree three. It is found that the higher-order (> 3) polynomial lenses have equipotential angles at the saddle points which differ from 54°44′08″. Reductions in aberration disks of 60% are possible using the new lenses instead of the Butler gun. Retarding-mode performance of the lenses is considered for potential application to low voltage microscopy. A simple design of a scanning gun microscope is considered.     

On the multiple melting transitions of starch/monoglyceride systems

Thermal analysis of rice starch/1-monoglyceride mixtures at intermediate water content (50%) was carried out using Differential Scanning Calorimetry (DSC) and Thermo-Mechanical Analysis (TMA). The DSC thermal profiles revealed multiple melting characteristics for the amylose-monoglyceride complexes. A mechanism based on partial melting followed by recrystallization (exothermic effect) and remelting is invoked to explain such behavior. Crystallization of amylose-lipid complexes occurs during starch gelatinization with a rate that is determined by the molecular nucleation step. The latter is strongly dependent on the nature of the complexing ligand molecule. Monoglycerides of good amylose complexing ability rapidly induce metastable (small size and/or less perfected) crystallites in the melted polysaccharide matrix which are inclined to reorganization/annealing on subsequent heating in the DSC. The overall thermal behavior of these systems is best rationalized by considering the interactions between solvent and polymer, the morphology of the semicrystalline structure, as well as the kinetic effects inherent with the dynamic character of the thermoanalytical techniques employed. Due to the irreversible/non-equilibrium melting of amylose-lipid complexes, complications can arise in attempting to analyze melting data by the polymer-diluent method (Flory-Huggins equation). The general features of the TMA volume expansion curves suggested that lipids can retard granule swelling at low temperatures.