An Efficient Output-Size Sensitive Parallel Algorithm for Hidden-Surface Removal for Terrains

We describe an efficient parallel algorithm for hidden-surface removal for terrain maps. The algorithm runs in O(log ⁴ n) steps on the CREW PRAM model with a work bound of O((n+k) \polylog ( n)) where n and k are the input and output sizes, respectively. In order to achieve the work bound we use a number of techniques, among which our use of persistent data structures is somewhat novel in the context of parallel algorithms. Received July 29, 1998; revised October 5, 1999.     

Symbolic gray code as a multikey hashing function

In this paper, we extend the binary Gray code to symbolic Gray code. We then show that this symbolic Gray code can be used as a multikey hashing function for storing symbolic records. The record stored at location k and the record stored at location k + 1 will be nearest neighbors if this hashing function is used. Thus, this symbolic Gray code hashing function exhibits some kind of clustering property which will group similar records together. This property is a desirable property for designing nearest neighbor searching (also called best match searching) systems. There are many other interesting properties of this hashing function. For instance, there exists an address-to-key transformation which can be used to determine the record stored at certain location k if this hashing function is used. Besides, if there are totally M records, we only have to reserve exactly M locations; there are no collisions and wasting of memory storage. At the end of this paper, it is shown that the resulting file exhibits the multiple-attribute tree structure.     

An adaptive model-free resource and power management approach for multi-tier cloud environments

With the development of cloud environments serving as a unified infrastructure, the resource management and energy consumption issues become more important in the operations of such systems. In this paper, we investigate adaptive model-free approaches for resource allocation and energy management under time-varying workloads and heterogeneous multi-tier applications. Specifically, we make use of measurable metrics, including throughput, rejection amount, queuing state, and so on, to design resource adjustment schemes and to make control decisions adaptively. The ultimate objective is to guarantee the summarized revenue of the resource provider while saving energy and operational costs. To validate the effectiveness, performance evaluation experiments are performed in a simulated environment, with realistic workloads considered. Results show that with the combination of long-term adaptation and short-term adaptation, the fluctuation of unpredictable workloads can be captured, and thus the total revenue can be preserved while balancing the power consumption as needed. Furthermore, the proposed approach can achieve better effect and efficiency than the model-based approaches in dealing with real-world workloads.     

Model test of helical angle effect on coal loading performance of shear drum

The work presented in this paper focuses on improving coal loading performance of shear drum.Employing the similarity theory,we carried out a dimensional analysis of the correlation parameters which in...     

乙烯装置裂解气分馏及冷却的模拟计算

对于含有众多复什碳氢化合物的裂解汽油、裂解柴油和裂解燃料油等宽馏分以及氢、轻烃、大量水分的裂解气，采用虚拟组分以减少组分总数、用惰性气体描述水在烃类中的相行为，以物流混合和闪蒸过程组成一个闪蒸平衡级，并以逐级闪蒸计算来描述乙烯装置的裂解气分馏塔。     

全电动注塑机的特点及应用领域

重点分析了全电动注塑机与全液压注塑机的不同之处,简单地概述了国内塑料工业发展落后的现状以及把我国建成注塑机生产强国的突破口。详细介绍了全电动注塑机的应用领域,并展望了全电动注塑机的发展。     

Decision-feedback detection for block differential space-time modulation

Time variation on fading channels hinders accurate channel estimation in differential space-time modulation and deteriorates the performance. Decision-feedback differential detection is studied for block differential space-time modulation, and compared with conventional differential space-time modulation. It is observed that the proposed scheme does not suffer effective fading bandwidth expansion, as does the conventional scheme. An improved effective signal-to-noise ratio approach is proposed for analyzing the performance of the proposed scheme in time-varying flat Rayleigh fading. Theoretical analysis and simulations show the improved performance of the proposed scheme over the conventional scheme.     

室温固相反应法制备纳米氧化锆及表征

以ZrOCl2.8H2O和NH4HCO3为原料,在适量表面活性剂(PEG-400)存在下,先在室温下充分混合研磨进行固相反应,得到的反应混合物再用水洗去其中的可溶性无机盐并烘干,即得氧化锆前驱体。前驱体经530℃下热解3h即得氧化锆产品,采用TG/DTA,XRD和TEM对前驱体及产品进行了表征。结果表明,所得产品氧化锆为结晶良好、以四方相为主的混合晶相,其平均粒径约为25nm。     

成人高等教育专业导师制学生管理模式初探

文章对如何在成人高等院校实施专业导师制学生管理模式进行了探讨，指出专业导师制能适应成人高等教育业余学习的特点，并对继续教育的顺利发展起到积极作用。