水流含沙量和流速对水轮机磨蚀性能的影响

水流含沙量和流速是影响水轮机磨蚀性能的非常重要的两大因素,其影响规律对水轮机磨蚀的防治有很重要的理论意义和参考价值.采用黄河原型沙,通过试验研究不同泥沙含量和不同水流流速条件下水轮机材料的磨蚀外貌、磨蚀失重量和磨蚀失重率.通过对试验结果进行定性和定量分析,得到水轮机磨蚀与水流含沙量、磨蚀与水流流速之间的关系,并得到数学回归式,找出水轮机磨蚀的基本规律,为多泥沙河流水轮机的参数选择与磨蚀防治提供了依据.     

Economic assessment of climate adaptation options for urban drainage design in Odense, Denmark

Climate change is likely to influence the water cycle by changing the precipitation patterns, in some cases leading to increased occurrences of precipitation extremes. Urban landscapes are vulnerable to such changes due to the concentrated population and socio-economic values in cities. Feasible adaptation requires better flood risk quantification and assessment of appropriate adaptation actions in term of costs and benefits. This paper presents an economic assessment of three prevailing climate adaptation options for urban drainage design in a Danish case study, Odense. A risk-based evaluation framework is used to give detailed insights of the physical and economic feasibilities of each option. Estimation of marginal benefits of adaptation options are carried out through a step-by-step cost-benefit analysis. The results are aimed at providing important information for decision making on how best to adapt to urban pluvial flooding due to climate impacts in cities.     

水电站水工闸门运行事故及对策

水电站水工闸门曾因疏于管理、操作失误、重大缺陷没有及时消除,以及闸门启闭电源不可靠等原因,而发生多次运行事故,不仅影响发电等效益的发挥,有的甚至对大坝和下游人民生命财产造成危害.为了防止水工闸门运行事故的发生,应规范闸门操作运行,杜绝人为操作失误,及时消除重大隐患,设置柴油发电应急备用电源,若采用远方操控闸门的运行方式,必须严格实行大坝现场监护人制度.     

Gravity filtration performances of the bio-diatomite dynamic membrane reactor for slightly polluted surface water purification

A bio-diatomite dynamic membrane (BDDM) reactor for surface water treatment under a water head of 30, 40, 50, 60 and 70 cm, respectively, was investigated, which was very effective for pollutants removal. The water head exerted strong influences on filtration flux of BDDM during the precoating process, as well as on the formation of BDDM and turbidity variations. A high filtration flux (approximately 200-300 L/m2 h) could be achieved in the long filtration times of BDDM with a stable effluent turbidity of approximately 0.11-0.25 NTU. The BDDM could remove particles larger than 25 μm completely. The adopted sintered diatomite mainly consisted of macro pores, which were beneficial for improving the filtration flux of BDDM. During the backwash stage, the BDDM could be removed completely by the air backwash.     

一种新颖的CDMA系统下多目标无线定位方法

利用Marginalized粒子滤波算法,处理CDMA(Code Division Multiple Access)系统中多目标无线定位及跟踪问题。在CDMA系统中,由于数据的非线性导致了过大的计算复杂度,并影响到定位的精度。论文主要从CDMA系统中多目标联合检测和建立基于边缘化粒子滤波器的数据融合模型两方面进行研究和分析,解决CDMA中多用户的辨别、定位精度和计算复杂度之间的矛盾。仿真结果证明其方法能够保证多目标定位的精度,并极大地减少计算复杂度。     

Aggregate keyword search on large relational databases

Keyword search has been recently extended to relational databases to retrieve information from text-rich attributes. However, all the existing methods focus on finding individual tuples matching a set of query keywords from one table or the join of multiple tables. In this paper, we motivate a novel problem of aggregate keyword search: finding minimal group-bys covering a set of query keywords well, which is useful in many applications. We develop two interesting approaches to tackle the problem. We further extend our methods to allow partial matches and matches using a keyword ontology. An extensive empirical evaluation using both real data sets and synthetic data sets is reported to verify the effectiveness of aggregate keyword search and the efficiency of our methods.     

Optimal cyclic single crane scheduling for two parallel train oilcan repairing lines

Crane is widely used to move a heavy object from one place to another not only in manufacturing industry but also service industry. As an important resource in the train oilcan repairing, crane scheduling affects directly the productivity of the systems. In this paper, we study cyclic single crane scheduling problem with two parallel train oilcan repairing lines, where jobs are loaded into the line at one end and unloaded at the other end. The processing time at each workstation must be within a given range. There is no buffer between these stations. A crane is used to move jobs between the workstations in two parallel lines. The objective is to schedule the moves to minimize the production cycle. We proposed a time way diagram for two parallel lines and developed a mixed integer linear programming model. Then we extended the model to the scheduling problem with multi-station to eliminate the bottleneck in lines. Examples are given to demonstrate the effectiveness of the model.     

Tree-turn routing: an efficient deadlock-free routing algorithm for irregular networks

In this paper, we propose a general turn model, called a Tree-turn model, for tree-based routing algorithms on irregular topologies. In the Tree-turn model, links are classified as either a tree link or a cross link and six directions are associated with the channels of links. Then we can prohibit some of the turns formed by these six directions such that an efficient deadlock-free routing algorithm, Tree-turn routing, can be derived. There are three phases to develop the Tree-turn routing. First, a coordinated tree for a given topology is created. Second, a communication graph is constructed based on the topology and the corresponding coordinated tree. Third, the forwarding table is set up by using all-pairs shortest path algorithm according to the prohibited turns in the Tree-turn model and the directions of the channels in the communication graph. To evaluate the performance of the proposed Tree-turn routing, we develop a simulator and implement Tree-turn routing along with up*/down* routing, L-turn routing, and up*/down* routing with DFS methodology. The simulation results show that Tree-turn routing outperforms other routing algorithms for all the test cases.     

Contextual correlation based thread detection in short text message streams

Short text message streams are produced by Instant Messaging and Short Message Service which are wildly used nowadays. Each stream contains more than one thread usually. Detecting threads in the streams is helpful to various applications, such as business intelligence, investigation of crime and public opinion analysis. Existing works which are mainly based on text similarity encounter many challenges including the sparse eigenvector and anomaly of short text message. This paper introduces a novel concept of contextual correlation instead of the traditional text similarity into single-pass clustering algorithm to cover the challenges of thread detection. We firstly analyze the contextually correlative nature of conversations in short text message streams, and then propose an unsupervised method to compute the correlative degree. As a reference, a single-pass algorithm employing the contextual correlation is developed to detect threads in massive short text stream. Experiments on large real-life online chat logs show that our approach improves the performance by 11% when compared with the best similarity-based algorithm in terms of F1 measure.     

Relevance feature mapping for content-based multimedia information retrieval

This paper presents a novel ranking framework for content-based multimedia information retrieval (CBMIR). The framework introduces relevance features and a new ranking scheme. Each relevance feature measures the relevance of an instance with respect to a profile of the targeted multimedia database. We show that the task of CBMIR can be done more effectively using the relevance features than the original features. Furthermore, additional performance gain is achieved by incorporating our new ranking scheme which modifies instance rankings based on the weighted average of relevance feature values. Experiments on image and music databases validate the efficacy and efficiency of the proposed framework.