解决并行JOIN中数据偏斜的一种方法

1.引言 最近的研究表明,数据库系统也可以利用并行处理来提高更大、更复杂查询的效,因为关系操作是面向集合的操作,本身就具有一定的可并行特性,这为查询优化在选择并行取路径时提供了很大的灵活性。     

薄拱坝极限承载能力研究与应用

根据塑性极限分析的静力法和机构法原理,推导了拱坝极限荷载上、下限值的线性规划数学模型,并选择两座典型薄拱坝为例,采用多拱梁塑性极限分析法计算了极限状态下的超载系数和应力状态、破坏形态,验证了薄拱坝极限承载能力及安全可靠性.     

水泥稳定碎石设计参数研究

基于重载交通和现代测试技术的发展,采用材料试验机(MTS)环向引伸仪法实测了水泥稳定碎石的回弹模量和泊松比,并用BISAR程序计算了回弹模量和泊松比的变化对给定路面结构剪应力和拉应力的影响规律.结果表明:水泥稳定碎石的回弹模量和泊松比均随荷载的增加而增加;水泥稳定碎石回弹模量和泊松比的变化对路面结构剪应力和拉应力的影响不明显;超载对路面结构剪应力和拉应力的不利影响显著.     

Improved Monitoring of Semi-Continuous Anaerobic Digestion of Sugarcane Waste: Effects of Increasing Organic Loading Rate on Methanogenic Community Dynamics

The anaerobic digestion of filter cake and its co-digestion with bagasse, and the effect of gradual increase of the organic loading rate (OLR) from start-up to overload were investigated. Understanding the influence of environmental and technical parameters on the development of particular methanogenic pathway in the biogas process was an important aim for the prediction and prevention of process failure. The rapid accumulation of volatile organic acids at high OLR of 3.0 to 4.0 g_vs·L⁻¹·day⁻¹ indicated strong process inhibition. Methanogenic community dynamics of the reactors was monitored by stable isotope composition of biogas and molecular biological analysis. A potential shift toward the aceticlastic methanogenesis was observed along with the OLR increase under stable reactor operating conditions. Reactor overloading and process failure were indicated by the tendency to return to a predominance of hydrogenotrophic methanogenesis with rising abundances of the orders Methanobacteriales and Methanomicrobiales and drop of the genus Methanosarcina abundance.     

Proposed modifications to the Wheeler retardation model for multiple overloading fatigue life prediction

A number of modifications to the Wheeler fatigue crack retardation model were proposed. The modifications allow the model to account for the delay retardation due to applied overloads, initial crack growth acceleration immediately following an overload, overload interaction and the net section yielding effect observed in the fatigue crack growth retardation behaviour of many materials. The modified model was used to predict the fatigue life of a series of single and multiple overloading fatigue tests conducted on 350 WT steel. The results showed that the modified model predicted the fatigue lives with a greater accuracy than the original model.     

大化水电站扩建左岸高边坡稳定分析及处理

利用简化毕肖普法和摩根斯坦-普莱斯法对大化扩建水电站厂房左岸高边坡两个典型断面进行稳定计算，主要有3点结论：（1）在一定的地质参数下，控制地下水位对保持边坡稳定非常重要；（2）对边坡开挖过程中出现的断层破碎带必须经过处理才能进行下一步的施工；（3）在边坡稳定的前提下，坡顶设置施工用混凝土拌合系统是可行的。     

拱坝的破坏分析及超载问题探讨

以拱坝和周围的岩体为研究对象，采用线弹性 本构模型和不同的破坏追踪方式，对破坏过程中的不同的应力状态应用不同的强度准则和功 能函数，破坏过程的分析按三维随机有限元法分析可靠度指标场，从可靠度指示场中寻找并 联系统中最易出现的破坏轨迹，给出其破坏形式和安全度。同时按逐步增加水的比重和提高 水位两种方法给出拱坝的超载破坏过程，最后指出拱坝的超载是不现实的，也不能给出切合 实际的拱坝安全性。     

Arithmetic equality constraints as C++ statements

Simultaneous equations arise naturally in problems from a variety of application areas. This paper describes how to use two object-oriented features of C++—operator overloading and virtual functions—to allow a programmer to express and to solve a system of simultaneous equations directly in a C++ program.     

Measurement of Truck Transport Vibration Levels in China as a Function of Road Conditions,Truck Speed and Load Level

Transport vibration levels in trucks were measured as a function of truck speed, road conditions and load level. The trucks consisted of one normally loaded truck and one overloaded truck with leaf‐spring suspensions. Truck speeds were divided into three groups: 0–30 km/h, 31–60 km/h and 61–90 km/h. Traffic roads consisted of highways, arterial roads (ARs), secondary roads (SRs) and tertiary roads (TRs). The results revealed that transport vibration levels increased with truck speed; TRs contributed to the highest transport vibration levels, followed by SRs, ARs and highways. The power spectral density peaks were at 3 or 3.5 Hz. Overloading probably suppressed transport vibration levels especially at low speeds. Copyright © 2015 John Wiley & Sons, Ltd.