螺旋侧板厚度对浮式风力机Spar平台涡激载荷的影响

Spar平台因其特殊的深吃水立柱式结构,在来流影响下极易发生涡激运动。为探究不同厚度螺旋侧板对浮式风力机Spar平台涡激载荷的影响,基于CFD方法,针对不同厚度螺旋侧板,对平台进行了数值模拟并详细分析平台的升阻力系数、压力场及涡量场等流场参数。结果表明:螺旋侧板可有效抑制涡激载荷,且随厚度增加,升力系数幅值先增加后减小,阻力系数逐步减小;在研究范围内,螺旋侧板厚度为0.10 D时,升力系数幅值最小,阻力系数与原型平台在同一范围内,对涡激载荷的抑制效果最好。     

BaTiO3系PTC热敏电阻用施主加入物的研究

阐述了常用的施主加入物、施主加入量、影响施主加入量的主要因素及各施主加入物的特点。研究了常用的施主加入物的理化指标对ＰＴＣ热敏电阻性能的影响，并据此提出了其技术标准。     

框架结构护岸新技术在城市河道中的应用

好溪堰河是贯穿浙江省丽水市主城区的一条千年古河道,在河道整治过程中,受制于河道周边的密集建筑物,传统的河道护岸技术均难以同时满足水利、市政、交通及景观的多元化要求。在分析其他创新河道护岸技术特点及存在问题的基础上,提出了适用于城市河道的桩柱式、框柱式两种框架结构护岸新技术,这两种护岸在维护河道周边建筑物稳定的同时,均具有不加深河床就可拓宽河道过流断面、不减少河岸用地、保持岸路畅通、改善水质及生态效果、提高亲水性等优点,在丽水好溪堰河水系整治工程中应用较为成功。     

Credal classification rule for uncertain data based on belief functions

In this paper we present a new credal classification rule (CCR) based on belief functions to deal with the uncertain data. CCR allows the objects to belong (with different masses of belief) not only to the specific classes, but also to the sets of classes called meta-classes which correspond to the disjunction of several specific classes. Each specific class is characterized by a class center (i.e. prototype), and consists of all the objects that are sufficiently close to the center. The belief of the assignment of a given object to classify with a specific class is determined from the Mahalanobis distance between the object and the center of the corresponding class. The meta-classes are used to capture the imprecision in the classification of the objects when they are difficult to correctly classify because of the poor quality of available attributes. The selection of meta-classes depends on the application and the context, and a measure of the degree of indistinguishability between classes is introduced. In this new CCR approach, the objects assigned to a meta-class should be close to the center of this meta-class having similar distances to all the involved specific classes? centers, and the objects too far from the others will be considered as outliers (noise). CCR provides robust credal classification results with a relatively low computational burden. Several experiments using both artificial and real data sets are presented at the end of this paper to evaluate and compare the performances of this CCR method with respect to other classification methods.     

A heuristic approach to selecting views for materialization

XML data warehouses are becoming more popular as data is harvested from the web or as output from web services. As these warehouses tend to grow significantly over time, various techniques for expediting queries have been developed. One such technique is to materialize some or all of the queries in advance of query processing. These views are then subject to change either when underlying data changes or view definitions themselves are modified by users. The work in this paper focuses on changes to view definitions or view adaptation as it is known. Our approach is to segment the materialized view into fragments to minimize the effect of view changes. One crucial aspect to this approach is how to select the best fragments for materialization. In this paper, we introduce a new approach to selecting fragments based on heuristics derived from costs associated with the view graph. Copyright © 2013 John Wiley & Sons, Ltd.     

An integrated portfolio optimisation procedure based on data envelopment analysis,artificial bee colony algorithm and genetic programming

Portfolio optimisation is an important issue in the field of investment/financial decision-making and has received considerable attention from both researchers and practitioners. However, besides portfolio optimisation, a complete investment procedure should also include the selection of profitable investment targets and determine the optimal timing for buying/selling the investment targets. In this study, an integrated procedure using data envelopment analysis (DEA), artificial bee colony (ABC) and genetic programming (GP) is proposed to resolve a portfolio optimisation problem. The proposed procedure is evaluated through a case study on investing in stocks in the semiconductor sub-section of the Taiwan stock market for 4 years. The potential average 6-month return on investment of 9.31% from 1 November 2007 to 31 October 2011 indicates that the proposed procedure can be considered a feasible and effective tool for making outstanding investment plans, and thus making profits in the Taiwan stock market. Moreover, it is a strategy that can help investors to make profits even when the overall stock market suffers a loss.     

String analysis by sliding positioning strategy

Discovering frequent factors from long strings is an important problem in many applications, such as biosequence mining. In classical approaches, the algorithms process a vast database of small strings. However, in this paper we analyze a small database of long strings. The main difference resides in the high number of patterns to analyze. To tackle the problem, we have developed a new algorithm for discovering frequent factors in long strings. We present an Apriori-like solution which exploits the fact that any super-pattern of a non-frequent pattern cannot be frequent. The SANSPOS algorithm does a multiple-pass, candidate generation and test approach. Multiple length patterns can be generated in a pass. This algorithm uses a new data structure to arrange nodes in a trie. A Positioning Matrix is defined as a new positioning strategy. By using Positioning Matrices, we can apply advanced prune heuristics in a trie with a minimal computational cost. The Positioning Matrices let us process strings including Short Tandem Repeats and calculate different interestingness measures efficiently. Furthermore, in our algorithm we apply parallelism to transverse different sections of the input strings concurrently, speeding up the resulting running time. The algorithm has been successfully used in natural language and biological sequence contexts.     

离子交换法处理含Cr(Ⅵ)废水的研究

采用201×7强碱性阴离子交换树脂处理模拟含Cr(Ⅵ)废水,探讨了废水酸度、交换时间、浓度对Cr(Ⅵ)去除率的影响以及树脂再生所需的合适温度和再生剂浓度。结果表明,201×7强碱性阴离子交换树脂处理模拟含Cr(Ⅵ)废水,具有交换容量大、交换效果好、树脂再生条件较简单等优点。并对实际含铬废水进行了处理,废水中Cr(Ⅵ)的初始浓度为1 540 mg/L,处理量达52 BV(床体积)时,出水中Cr(Ⅵ)的浓度仍小于0.5 mg/L,达到国家排放标准。树脂交换容量约80 mg/g。用8%NaOH溶液,在50℃条件下进行再生效果较好,再生率大于95%,可实现树脂的重复使用。     

Revisiting the two-stage choice model: an empirical study of consumer choice on brand website visits

In consumer choice behaviour literature, a two-stage choice model serves as a base theory where choice behaviour is decomposed into a consideration stage plus a choice stage. Yet, this default model has been increasingly challenged by the ‘limited consumer search’ school of thought because consumers do not necessarily review all products in a choice set before making decisions, but frequently draw on external information as mental short cuts. Methodologically, the choice behaviour in stage 1 has traditionally been latent because data that directly observe how consumers form their consideration sets by eliminating alternatives are lacking. This study continues the ‘limited consumer search’ line of reasoning and proposes an aided non-compensatory process in choice stage 1, where consumers reduce brand website alternatives by using online ratings to arrive at a consideration set. We use observed Web analytics data to unveil the stage 1 choice process and also the transition from stage 1 to stage 2, which is in need of further research based on extant literature. Lastly, we cross-validate our model with two types of websites (i.e. search vs. experience/credence) and find our model is contingent on the type of website content, where consumers’ inclination to use online ratings for decision-making varies.     

723型阳离子交换树脂催化合成甲基叔丁基醚

本文研究利用723型阳离子交换树脂催化合成MTBE，采用正交设计的统计方法，对影响产率的各因素如反应温度，反应时间，催化剂用量和原料摩尔比进行组合，找到合适的工艺路线，最佳反应条件为：催化剂用量为5g，甲醇与叔丁醇比为3：1，反应时间为7h。