利用关系数据理论改进装备测试记录存储方法的研究

目前海军装备测试记录的存储大多采用文本文件的形式,不利于数据共享。为解决这一问题,改进原先的存储方法,提出了数据库存储形式,讨论了其开发步骤,并针对应用背景,重点提出了通过现有存储方式的设计文档及相关代码获取设计的需求分析、通过模式分解将测试项目进行划分、通过数据依赖公理验证分解前后是否等价的数据库设计方法,最后通过一个实例对数据库应用系统的开发过程进行了详细说明。与文本文件存储方法相比,数据库存储形式具有利于数据共享、提高数据查询效率、便于装备管理的优点。     

基于可信操作环境的DBMS可信研究

文章给出了支持数据库系统的可信操作环境体系结构,分析DBMS在基于可信操作环境下的可信需求,论述了DBMS可信机制的实施方法,设计了DBMS可信机制中间件,确保数据库系统基础可信和总体安全目标的实现。     

Network sensor health problem

Many existing studies on the sensor health problem determine an individual sensor’s health status based on the statistical characteristics of collected data by the sensor. In this research, we study the sensor health problem at the network level, which is referred to as the network sensor health problem. First, based on the conservation principle of daily flows in a network, we separate all links into base links and non-base links, such that the flows on the latter can be calculated from those on the former. In reality, the network flow conservation principle can be violated due to the existence of unhealthy sensors. Then we define the least inconsistent base set of links as those that minimize the sum of squares of the differences between observed and calculated flows on non-base links. But such least inconsistent base sets may not be unique in a general road network. Finally we define the health index of an individual sensor as the frequency that it appears in all of the least inconsistent base sets. Intuitively, a lower health index suggests that the corresponding sensor is more likely to be unhealthy. We present the brute force method to find all least inconsistent base sets and calculate the health indices. We also propose a greedy search algorithm to calculate the approximate health indices more efficiently. We solve the network sensor health problem for a real-world example with 16 nodes and 30 links, among which 18 links are monitored with loop detectors. Using daily traffic count data from the Caltrans Performance Measurement System (PeMS) database, we use both the brute-force and greedy search methods to calculate the health indices for all the sensors. We find that all the four sensors flagged as unhealthy (high value) by PeMS have the lowest health indices. This confirms that a sensor with a lower health index is more likely to be unhealthy. Therefore, we can use such health indices to determine the relative reliability of different sensors’ data and prioritize the maintenance of sensors.     

Extracting accurate location information from a highly inaccurate traffic accident dataset: A methodology based on a string matching technique

The objective of this research was to develop a model for validating traffic accident locations that would be applicable worldwide, regardless of linguistic or cultural differences. In order to achieve this, a Volunteered Geographic Information (VGI) dataset was used, the OpenStreetMap (OSM) project. To test the developed model, a total of 8550 accidents with fatal or non-fatal injuries that occurred in the City of Zagreb from 2010 to 2014 were evaluated. Traffic accident data was collected using the pen-and-paper method while the traffic accident locations were determined using Global Positioning System (GPS) receivers embedded within police vehicles. This form of data entry invariably introduces errors in both geometric and contextual attributes. To fully counteract these errors, the developed model consists of two key concepts: the Jaro–Winkler string matching technique and the Inverse Distance Weighting method. Over 66% of traffic accident locations were validated, which is an increase of 15% when compared to the classical approach. The model outlined in this paper shows a significant improvement in estimating the correct location of traffic accidents. This in turn results in a drastic decrease in resources needed to estimate the quality of accident locations.     

行人膝关节有限元模型的建立与验证

在前期研究中对下肢长骨和膝关节主要韧带的模型进行了全面验证的基础上,建立了具有详细解剖学结构的行人膝关节有限元模型,并定义了各组织间的接触。依据更符合实际行人事故中膝关节载荷特点的生物力学实验,对膝关节有限元模型进行了动态四点弯曲和动态三点弯剪仿真验证。结果显示膝关节模型的生物力学响应与实验结果吻合,能较好地反映膝关节的损伤和动力学响应,具有较好的生物逼真度。     

某新型压气机的仿真与试验交互验证设计研究

采用增压器台架试验与模拟计算相结合的方法对一新型压气机开展研究。首先针对压气机首轮性能试验与预测相差较大的问题,详细分析了原样机的特性并进行了三维数值模拟,依据样机分析与数值分析的结果针对性地提出了多方面的改进措施,包括变换壳体支撑型式、消除加工误差、优化高压级叶轮等。再对改进后的压气机进行了试验,新一轮样机的台架试验最终满足设计要求。     

公路交通行业工程量清单计价方法研究

阐述了工程量清单的定义和特点以及在我国的应用情况,介绍了国际经验,对比分析了工程量清单计价与定额计价的区别,剖析了我国公路交通行业工程计价的现状及存在的问题,系统研究了公路交通行业工程量清单的计价流程和主要指标,对综合单价指标等关键指标的计算方法进行了重点研究,通过引入价格指数,利用已知的各期价格指数,根据数理统计模型推导出第t期的价格指数,从而计算出第t期的综合单价.分析了公路清单计价优势和实现的基础,研究提出了公路清单计价实现路径大致分为3步:第1步构建统一的计量规则和编码体系,第2步出台公路清单计价编制办法,第3步构建清单数据库;并重点研究了构建清单数据库的路径和方法,最后提出了下一步工作建议.     

知识工程在全回转螺旋桨设计中的应用

针对全回转螺旋桨结构部件数量众多,其建模效率以及建模的准确性受到设计者知识经验的限制,提出了将知识工程应用于全回转螺旋桨设计的方法。该方法基于全回转螺旋桨设计的Access知识库,以Virtual C++6.0为开发平台对SolidWorks进行二次开发,实现智能化的全回转螺旋桨的设计与快速建模,提高了设计效率。根据全回转关键部位的设计实例,表明知识工程技术融入全回转螺旋桨的设计流程能够快速建立标准化模型,解决了设计建模中出现的问题,缩短了建模周期,提高了设计与建模的效率。     

液压组合锚机自动化校核及其诊断系统

用Visual C 编制了船舶液压组合锚机自动化校核与诊断软件,对液压组合锚机进行校核计算,并对计算后的零件进行诊断,针对设备的安全性、匹配性和布局合理性,列出问题的原因和优化建议。用MFC编制了友好的界面,能自动生成校核报告和诊断报告,并保留了ANSYS交互接口和设备可靠性分析的接口。通过实例验证,软件大大地提高了计算效率和计算精度,可以根据给出的诊断建议进行方案改进,能够满足船舶液压锚机厂商的设计需求,并已经被部分厂商采用。     

基于CFD的实船阻力快速预估方法

介绍了一种实船阻力快速预报的方法,通过数值计算得到形状因子(1+k)以及兴波阻力系数,结合实船试航积累的模型-实船相关系数,快速预报船舶的阻力性能。对两型不同类型的船舶应用该方法预报其设计工况附近的阻力性能,预报结果得到实船试航结果的验证,表明该方法具有值得期待的工程应用前景。