适用于云计算的面向查询数据库数据分布策略

为满足海量数据的处理需求,业界提出了多种解决方案。云计算是目前较为热门的一种,它主要用廉价PC组成超大规模集群服务器来进行数据存储和处理。随着云计算技术的发展,越来越多的应用将转移到云中,数据库系统也不例外。但数据库系统要求的ACID特性在数据分布存储时可能导致部分操作性能低下,如连接查询操作。为在数据分布存储下提高数据库系统的性能,提出了一种面向查询的数据分布策略(Selection Oriented Distribution,SOD),即根据数据库的查询情况确定数据的分布算法。该算法适用于云计算,能明显提高系统的查询性能。

Dust-Cloud Structures behind a Shock Wave Moving Over a Deposited Layer of Fine Particles

The present paper investigates dispersed-phase flow structures of a dust cloud induced by a normal shock wave moving at a constant speed over a flat surface deposited with fine particles. In the shock-fitted coordinates, the general equations of dusty-gas

Fast Computing For Lurr Of Earthquake Prediction

The LURR theory is a new approach for earthquake prediction, which achieves good results in earthquake prediction within the China mainland and regions in America, Japan and Australia. However, the expansion of the prediction region leads to the refinement of its longitude and latitude, and the increase of the time period. This requires increasingly more computations, and the volume of data reaches the order of GB, which will be very difficult for a single CPU. In this paper, a new method was introduced to solve this problem. Adopting the technology of domain decomposition and parallelizing using MPI, we developed a new parallel tempo-spatial scanning program.

Shock-Induced Dust Cloud Over a Deposit Layer of Fine Particles

The present paper investigates particle density pro les of a dust cloud induced by a normal shock wave moving at a constant speed along a at surface deposited with ne particles. In shock-fixxed coordinates, numerical simulation of ow structures of the carrier- and dispersed- phases was performed for the M = 2 case. The neness and non-uniformity of the particle size are taken into account and their effcts on the dust cloud are discussed in detail.

Parallel optical negabinary signed-digit computing: algorithm and optical implementation

Negabinary is a component of the positional number system. A complete set of negabinary arithmetic operations are presented, including the basic addition/subtraction logic, the two-step carry-free addition/subtraction algorithm based on negabinary signed-digit (NSD) representation, parallel multiplication, and the fast conversion from NSD to the normal negabinary in the carry-look-ahead mode. All the arithmetic operations can be performed with binary logic. By programming the binary reference bits, addition and subtraction can be realized in parallel with the same binary logic functions. This offers a technique to perform space-variant arithmetic-logic functions with space-invariant instructions. Multiplication can be performed in the tree structure and it is simpler than the modified signed-digit (MSD) counterpart. The parallelism of the algorithms is very suitable for optical implementation. Correspondingly, a general-purpose optical logic system using an electron trapping device is suggested. Various complex logic functions can be performed by programming the illumination of the data arrays without additional temporal latency of the intermediate results. The system can be compact. These properties make the proposed negabinary arithmetic-logic system a strong candidate for future applications in digital optical computing with the development of smart pixel arrays. (C) 1999 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(99)00803-X].