A review of compact modeling for phase change memory

Phase change memory(PCM)attracts wide attention for the memory-centric computing and neuromorphic comput-ing.For circuit and system designs,PCM compact models are mandatory and their status are reviewed in this work.Macro mod-els and physics-based models have been proposed in different stages of the PCM technology developments.Compact model-ing of PCM is indeed more complex than the transistor modeling due to their multi-physics nature including electrical,thermal and phase transition dynamics as well as their interactions.Realizations of the PCM operations including threshold switching,set and reset programming in these models are diverse,which also differs from the perspective of circuit simulations.For the purpose of efficient and reliable designs of the PCM technology,open issues and challenges of the compact modeling are also discussed.     

Design optimization of a solar tower power plant heliostat field by considering different heliostat shapes

The present study focuses on the optimization of solar tower power plant heliostat field by considering different heliostat shapes including rectangular, square, pentagon, hexagon, heptagon, octagon, and circular heliostat shapes. The optimization is carried out using an in-house developed code-based MATLAB program. The developed in-house code is validated first on a well-known PS10 Solar Thermal Power plant having rectangular heliostats shape and the resulting yearly unweighted heliostat field efficiency of about 64.43% could be obtained. The optimized PS10 heliostat field using different heliostat shapes showed that the circular and octagon heliostat shapes provide better efficiency with minimum land area. The yearly efficiency is increased from 69.65% for the rectangular heliostat shape to 70.96% and 71% for the octagon and circular shapes, respectively. In addition, the calculated field area (land area) is reduced for the case of circular and octagon heliostat shapes with a gain of about 11.10% and 10.93% (about 42.0436 × 10³ and 41.4036 × 10³ m²), respectively, in comparison with the PS10 field area.     

Land Cover Classification and Mapping based on Segmentation Optimized Hierarchical Object Classification System

With the wide application of high-resolution satellite，Object based Image Analysis (OBIA) has gradually become main stream of extracting land cover information.Segmentation optimization is a fundamental step in OBIA.Different land cover types usually have different optimized segmentation parameters.How to make full use of the optimal Multi-Resolution Segmentation (MRS) to establish a segmentation classification hierarchy and to achieve high-precision land cover mapping，is a challenge in object-oriented image analysis.based on the optimal segmentation parameters of different land cover types，this paper explores a method to construct a segmentation optimized hierarchical classification system based on the minimum optimized segmentation unit.Experiments show that this method can effectively reduce the dependence on the operator's personal experience when setting up the classification hierarchy system，improve the classification accuracy，and meet the requirements of automatic drawing.     

Automatic Video Segmentation Based on Information Centroid and Optimized SaliencyCut

Journal of Computer Science and Technology - We propose an automatic video segmentation method based on an optimized SaliencyCut equipped with information centroid (IC) detection according to level...     

Compact finite volume methods for the diffusion equation

We describe an approach to treating initial-boundary-value problems by finite volume methods in which the parallel between differential and difference arguments is closely maintained. By using intrinsic geometrical properties of the volume elements, we are able to describe discrete versions of the div, curl, and grad operators which lead, using summation-by-parts techniques, to familiar energy equations as well as the div curl=0 and curl grad=0 identities. For the diffusion equation, these operators describe compact schemes whose convergence is assured by the energy equations and which yield both the potential and the flux vector with second-order accuracy. A simplified potential form is especially useful for obtaining numerical results by multigrid and ADI methods. The treatment of general curvilinear coordinates is shown to result from a specialization of these general results.     

结合数值计算与模型试验进行调压室参数优化

由于特殊的地形地质条件，大桥电站差动式调压室高度大，水流条件复杂，荷载特殊，需全面优化其参数．虽然该种调压室已有了实用的计算方法及公式，但在工程实践中仍有不少参数处于不好把握的状况．为此以大桥电站调压室为背景，综合运用电算与实验手段对差动式调压室各参数的变化规律及相互关系进行了探讨，增强了对该类调压室的进一步认识，并获得了大桥电站调压室的优化参数和水力条件，同时说明电算与试验结合是取得优化结果和成果可靠性的保证．     

AN ALE METHOD AND DDM WITH HIGH ACCURATE COMPACT SCHEMES FOR VORTEX-INDUCED VIBRATIONS OF AN ELASTIC CIRCULAR CYLINDER

A numerical study was conducted for the vortex-induced vibrations of an elastic circular cylinder at low Reynolds numbers. An Arbitrary Lagrangian-Eulerian (ALE) method was employed to deal with the fluid-structure interaction with an H-O type of non-staggered grids incorporating the domain decomposition method(DDM), which could save the computational CPU time due to re-meshing. The computational domain was divided into nine sub-domains including one ALE sub-domain and eight Eulerian sub-domains. The convection term and dissipation term in the N-S equations were discretized using the third-order upwind compact scheme and the fourth-order central compact scheme, respectively. The motion of the cylinder was modeled by a spring-damper-mass system and solved using the Runge-Kutta method. By simulating the non-linear fluid-structure interaction, the “lock-in”,“beating” and “phase switch” phenomena were successfully captured, and the results agree with experimental data. Furthermore, the vortex structure, the unsteady lift and drag on the cylinder, and the cylinder displacement at various natural frequency of the cylinder for Re 200 were discussed in detail,by which a jump transition of the wake structure was captured.     

优化射孔技术在百色油田的应用

解志恒，张继果．优化射孔技术在百色油田的应用．测井技术，１９９５，１９（３）：２０８～２１９针对百色油田第三系砂岩储层那读组、百色岗组的地质特点的技术现状，开展了射孔参数优选的理论和实验研究。详细介绍了射孔液、负压射孔、射孔枪弹和射孔参数的优化设计和无法进行完井试验的情况下如何进行较为科学的射后效果评价。指出了在现场建立简易射孔靶以进行枪弹性能试验的重要性，１９９３年１０月至１９９４年７月在百色油田推广应用上述优化射孔技术，优化射孔３５口井，取得良好效果，平均流动效率从０．３６５４提高到０．８８４３，平均表皮系数从１１．０１５４下降到１．６０９，仅补孔作业２７口井净增原油１０２２．４８ｔ，有效地恢复和改善了百色油田百岗组、那续组砂岩储层的生产能力。     

A quasi-optimal scheduling of intermediate signatures for multiple signature analysis compaction testing schemes

In this article, a strategy based on the use of intermediate signatures is proposed that enables the exact fault coverage of compact testing schemes to be determined in a feasible computation time. Two models to predict fault simulation time, a fault simulator dependent and independent model, are developed and used by a dynamic programming based algorithm to find the optimal scheduling of the signatures with respect to the total simulation time. Simulation results for both models are then presented demonstrating the feasibility of the proposed strategy.This work was supported in part by grants from the Natural Sciences and Engineering Research Council (NSERC) of Canada, the Canadian Microelectronics Corporation (CMC) and the British Columbia Advanced Systems Institute (B.C. A.S.I.).     

紧凑式轧机对横列式小型轧机的改造问题

以横列式小型机轧机的生产能力，确定了紧凑式轧机使用珠基准速度，进而分析了紧凑式轧机与横列小型轧机在生产有力匹配上所存在的问题，指出改造应向连续化方向发展。