发动机水套方案优选

某涡轮增压发动机开发过程中,出现了缸垫黏结、机油积炭、缸孔轻微拉伤等过热问题。针对这些问题制订了5个发动机水套优化方案,然后通过制造工艺性、制造经济性、发动机可靠性、CAE计算结果多方面综合评估,优选出2个相对较好的方案。对优选出的方案进行样件试制、试验测试,确认优化效果。结合试验测试结果,确定出最终工程实施的技术方案。最终通过台架耐久性测试及试验后发动机拆解分析,确认过热问题得到解决。     

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基于空中交通复杂程度刻画管制工作负荷是当前空中交通管理领域的研究热点。本文采集了厦门空管站的雷达数据,计算得出10个空中交通复杂性评价指标数值,通过共线性诊断发现复杂性指标间存在较强的多重共线性。在利用岭迹图对复杂性评价指标进行筛选的基础上,建立岭回归—BP神经网络组合模型对管制员工作负荷进行预测,并通过实测陆空通话数据进行验证。结果表明,本文提出的岭回归—BP神经网络组合模型收敛速度快、训练时间少;组合模型的均方误差、均方根误差、平均绝对误差、平均绝对相对误差等4项性能指标都相对较小,预测精度较高。     

Challenges and Myths in Norwegian Coastal Zone Management

Abstract

This paper is written in response to a recent publication (Walker, 1973) which questions both the biological basis for wetlands preservation and the usefulnesss of scientific participation in the formulation of management policies. Our major points are that: (1) considerable evidence exists linking wetlands primary production to aquatic secondary production, (2) all available information suggests that large‐scale wetlands destruction results in lowered production of estuarine organisms of interest to man, (3) more than economics needs to be considered in attempts to analyze the procedures by which the wetlands controversy is to be resolved, and (4) uncertainty about the applicability of scientific findings to a particular problem situation does not destroy the usefulness of those findings in reaching a solution to a public controversy.     

Improving the efficiency of repeated dynamic network loading through marginal simulation

Currently, the applicability of macroscopic Dynamic Network Loading (DNL) models for large-scale problems such as network-wide traffic management, reliability and vulnerability studies, network design, traffic flow optimization and dynamic origin–destination (OD) estimation is computationally problematic. The main reason is that these applications require a large number of DNL runs to be performed. Marginal DNL simulation, introduced in this paper, exploits the fact that the successive simulations often exhibit a large overlap. Through marginal simulation, repeated DNL simulations can be performed much faster by approximating each simulation as a variation to a base scenario. Thus, repetition of identical calculations is largely avoided. The marginal DNL algorithm that is presented, the Marginal Computation (MaC) algorithm, is based on first order kinematic wave theory. Hence, it realistically captures congestion dynamics. MaC can simulate both demand and supply variations, making it useful for a wide range of DNL applications. Case studies on different types of networks are presented to illustrate its performance.     

汽车空调风道系统CFD研究与优化

基于对某种风道的CFD分析。对后风道和中心导风管进行了优化设计，改善了风量分配同时增加了总风量。分析结果显示改进能够满足要求。     

汽车空调除霜风道结构优化研究

建立了3种汽车空调除霜风道模型，用以研究除霜风道内空气流动情况。利用商业软件Fluent，对速度场进行数值分析、计算流量。通过比较，得到效果较好的除霜风道结构。     

Radar Emitter Signal Recognition Based on Complexity Features

Intra-pulse characteristics of different radar emitter signals reflect on signal waveform by way of changing frequency, phase and amplitude. A novel approach was proposed to extract complexity features of radar emitter signals in a wide range of signal-to-noise ratio ( SNR), and radial basis probability neural network (RBPNN) was used to recognize different radar emitter signals. Complexity features, including Lempel-Ziv complexity (LZC) and correlation dimension (CD), can measure the complexity and irregularity of signals, which mirrors the intra-pulse modulation laws of radar emitter signals. In an experiment, LZC and CD features of 10 typical radar emitter signals were extracted and RBPNN was applied to identify the 10 radar emitter signals. Simulation results show that the proposed approach is effective and has good application values because average accurate recognition rate is high when SNR varies in a wide range.     

基于近似网页聚类的Web文本数据挖掘技术

提出一种针对小文本的基于近似网页聚类算法的Web文本数据挖掘技术,以获得用户感兴趣的近似网页簇系列。试验证明,该算法在保证查全率和查准率的基础上大大提高了搜索效率。由于是针对小文本的数据挖掘,研究的算法时间和空间复杂度都不高,因此,有望成为一种实用、有效的信息检索技术。     

基于云模型的基坑工程地质条件复杂性评价研究

针对基坑工程地质条件复杂性评价具有模糊性和随机性的问题,基于云模型理论处理地质指标的模糊性和随机性,提出一种定量指标为区间数的云模型确定方法。分析归纳福建地区的地质特点和基坑工程施工过程中可能存在风险,构建基坑工程地质条件复杂性评价体系及各指标的量化标准,将各评价等级划分为“简单”、 “一般”、 “较复杂”、 “复杂”,将其映射到区间［0,2.5)、［2.5,5.0)、［5.0,7.5)、［7.5,10.0］上,并确定对应云模型的数字特征。将所提理论及方法应用于福州地铁2号线某车站基坑工程中,基于评价结果针对性地提出地下水、软土等的处理方案,工程实践验证了该评价方法的可行性和有效性。     

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为改进航空器计量方法在评估交通态势复杂度时的局限性,本文建立了一种空中交通复杂性评估模型.基于空中交通的结构因素,模型构建了距离因子和冲突因子,能够反映航空器之间的相对距离与航迹交叉作用对于复杂性的影响.针对广州区域扇区进行的交通复杂性指标评估结果表明：航空器数量的变化会引起目标空域交通复杂性的变化,但后者对前者的响应并非完全同步;两者的变化程度不完全相同,且变化趋势可能相反.对相应交通态势的回溯和分析表明,相比基于航空器数量的评估方法,交通复杂性指标能够更加客观地反映空域状态的变化特征.