排序方式: 共有190条查询结果,搜索用时 640 毫秒
181.
鉴于某双层圆柱壳体的机械振动噪声数据结构复杂、维数较高,工程上不宜直接分析,文章提出先对其进行特征提取后再进一步分析的思路,可有效简化数据结构,提高数据分析的准确度。选择工程上常用的主成分分析法(PCA)、核主成分分析法(KPCA)与独立成分分析法(ICA)对文中高维机械振动噪声数据进行特征提取。利用支持向量机(SVM)的分类识别能力,对经特征提取后不同工况下的噪声数据进行分类识别。依据正确识别率大小比较三种方法的特征提取效果,以选择针对某双层圆柱壳体机械振动噪声数据合适的特征提取方法。结论可为深入分析某双层圆柱壳体机械振动噪声数据的规律特点打下良好基础。 相似文献
182.
余豫新 《筑路机械与施工机械化》2013,(11):76-80
系统分析了纵断面设计的关键因素,并且结合某工程实例,为多约束条件的复杂纵断面设计提供了思路和方法;通过研究评价指标与评价方法的对应关系,提出了基于DEA方法的纵断面方案定量评价方法,解决了以往定性选择纵断面方案时易产生的主观性、片面性的问题. 相似文献
183.
绿色生态型城市道路横断面是基于宜居城市生活的追求和能源危机的必然趋势,然而国内研究只是针对城市道路横断面组成要素的布置,在评价体系方面尚是一片空白。因此,基于城市道路横断面体现绿色、生态的影响因素,针对交通安全、降噪、空间伸缩、道路绿化、视觉美感、公众满意度、土地利用、建设投资等方面,提出八大指标评价标准;建立基于模糊重构DEA的绿色生态型城市道路横断面的优化模型;并以天津滨海新区为例,对生态城、中心渔港和西区的典型横断面布置方案进行了优化。结果表明:天津滨海新区西区横断面最优,建议生态城横断面机非分隔带加大至4 m。该方法科学可靠,实用性强,可为城市道路横断面提供有效决策方案。 相似文献
184.
An empirical study of the impacts of operating and market conditions on container-port efficiency and benchmarking 总被引:1,自引:0,他引:1
Despite the growing amount of research on container-port efficiency and benchmarking, the literature on the subject is yet to provide stable and consistent results across researchers and in relation to dynamic operating and market conditions. In this paper, we formulate a number of operational hypotheses to test the sensitivity of benchmarking results to port market and operating conditions namely production scale, cargo mix, transhipment ratio, operating configurations, and working procedures. A series of data envelopment analysis (DEA) models are used to measure the operational efficiency of 420 container terminal decision-making units from 2004 till 2010. The results show that variations in operating conditions highly impact terminal efficiency and that future work on container-port performance and benchmarking should take into account the structure and mechanisms underpinning the operations of container ports and terminals. 相似文献
185.
Conventional data envelopment analysis (DEA) models consider a system as a single-process ‘black box’. There are, however, DEA approaches that consider a system as composed of distinct processes or stages, each one with its own inputs and outputs and with intermediate flows among the stages. In this paper, a network DEA approach to airline efficiency assessment is presented. One conclusion of the study is that the network DEA approach has more discriminative power than the single-process DEA approach and that the computed targets, efficiency scores and rankings are more valid. This is because network DEA allows for a more fine-grained analysis that leads to a more realistic estimation of the overall system production possibility set than the one assumed by conventional DEA. In other words, compared with network DEA the conventional, single-process DEA represents an aggregated analysis that merges all system processes with their inputs and outputs and ignores their internal flows. The main drawbacks are the need for more detailed data (i.e. at the process level) and the greater complexity of the resulting models, especially if there are inputs or outputs that are shared among the processes. 相似文献
186.
Ming-Miin Yu 《运输规划与技术》2013,36(7):697-714
Abstract This paper estimates comprehensive operational performance measures for transport services. A network efficiency approach is used to analyze the production efficiency, service efficiency, and operational efficiency in a unified framework to reflect the transportation service characteristics of airline operations. We show how a modified version of the network data envelopment analysis model can be utilized for evaluating the performance of air route operations. This study considers 15 air routes operated by a domestic airline in Taiwan to highlight the value of the approach. The results of the analysis show the inputs and consumed outputs leading to production inefficiency and service inefficiency respectively as well as the magnitudes of excesses and shortfalls. 相似文献
187.
机场运营效率评价及影响因素分析对科学反映中国主要民用机场运营效率现状,实现中国民航业可持续发展,提高中国机场国际竞争力具有重要意义.本研究首先利用双重导向型DEA模型测算2006-2010年中国27个主要民用机场的运营效率,然后从宏观环境、行业与区域竞争及机场特征三个方面探索机场运营效率的影响因素.研究结果表明,2006-2010年中国主要民用机场的运营效率基本维持在较高水平;各机场的运营效率自2008年始均有不同程度的下降,且机场间运营效率的差异呈现逐年增大的趋势;腹地经济、机场规模、机场级别和一市多场等因素促进了机场运营效率的提升;区域竞争和行业竞争则不利于机场运营效率的提升. 相似文献
188.
采用三阶段DEA模型测度出中国高新技术产业17个行业的平均创新效率,并将其分解为配置效率和研发效率。在此基础上得出我国高技术产业的创新效率的特点:第一,平均创新效率较低主要是由于低配置效率所导致;第二,同时发现我国高新技术产业研发效率主要受制于低规模效率。第三,高技术产业当前推动研发效率提升的同时却是以配置效率的下降为代价。因此,应注重发挥市场对于资源的配置效率,做到研发效率与配置效率的权衡,从而确保效率最大化。 相似文献
189.
Measuring production and consumption efficiencies using the slack‐based measure network data envelopment analysis approach: the case of low‐cost carriers 下载免费PDF全文
One of the most important outcomes of the deregulation of air transportation policy is the emergence of low‐cost carriers (LCCs) around the world. Although LCC airlines have been in operation for more than 30 years, not every LCC is successful. In order to reduce the inefficiencies of LCCs, this paper measures the performance of LCCs by using slack‐based measure network data envelopment analysis. This model combines both the production process with input orientation and the consumption process with output orientation into a unified model. Furthermore, envelopment map analysis LCCs are performed to determine the reasons for the LCCs' inefficiency and how improvements can be made. A sample of 16 low‐cost airlines from Europe, the USA, and Asia were selected for operational performance analysis. The results show that the main reason for easyJet's, US Airways', and Virgin Blue's inefficiency is production inefficiency, so these LCCs should reduce their input quantities to increase efficiency. Jet2, Aer Lingus, and JetBlue were, by contrast, found to be consumption inefficient; these LCCs should increase their output quantities in order to enhance performance. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
190.
文章以折叠式舱口盖为研究对象,结合UG/Open GRIP高效、便捷、交互性能强的编程特点和UG/Open API操作简单、控制用户界面方便的优势,依托UG/Open UIStyler制作灵活、多样的人性化界面和UG/OpenMenuScript生成用户菜单,在对折叠式舱口盖结构分析的基础上,引入UG二次开发技术对折叠式舱口盖进行参数化建模系统设计,达到改变折叠式舱口盖部件参数值输入就能迅速建立新模型的目的。经过对参数化建模系统程序调试,系统能够正确、简便、迅速完成折叠式舱口盖部件参数化建模功能。该系统减少了折叠式舱口盖设计周期,提高了设计效率,为折叠式舱口盖参数化建模设计提供参考依据。 相似文献