基于模糊理论的室内环境舒适度监测系统研究

针对温度、湿度等影响室内环境舒适度的主要因素,基于模糊理论完成了温度、湿度数值-符号转换以及舒适度合成,并介绍了其在LabVIEW环境下的实现.最后探讨了在考虑室外环境参数以及人的心情等主观因素的情况下,舒适度合成方法的改进思路.系统既可以实现对室内环境舒适度的实时监测,又可以为室内舒适度控制提供依据.     

行车安全的车内环境综合评价理论研究及车载预警系统设计

分析了车内环境对行车安全的影响,根据车内环境多元化、复杂化的特点研究了对车内环境的评价,进而构建了一套较为完善的综合评价行车安全的车内环境的理论。其中包括:运用改进的韦伯-费希纳定律评价模型确定车内环境分级标准;运用改进的综合集成赋权模型确定各评价指标的权重;基于模糊综合评价模型和检测到的各要素含量,通过计算模糊关系矩阵、指标权重矩阵,得出行车安全的车内环境综合评价结果。在此基础上,利用STM32F103单片机、液晶显示屏、气体传感器、ATK-NEO-6M、ATK-SIM900A等硬件及相关软件,设计了一套能够实时检测、评价、显示、定位、预警、传送车内环境各要素指标的车载预警系统,实测结果表明,该系统达到了预期的检测、评价效果。     

轨道车辆座椅舒适度评价方法及研究展望

目的探讨评价轨道交通工具中座椅装备舒适度的有效方法,以及提升我国轨道交通工具中座椅舒适度的研究方向。方法对国内外相关文献进行比较分析,综述座椅舒适度的一般分析方法和国内外轨道交通工具中座椅舒适度研究现状;举例体压分布指标在动车组一等座椅形面舒适度评价中的应用方法。结论座椅舒适度评价一般采用主观和客观综合评价的方法,体压分布与主观评价有显著关系。提出了我国轨道车辆座椅舒适度的研究思路,包括形成系统全面的评价体系、应用主观和客观综合评价的研究方法、统一座椅尺寸参数定义,更新标准数据。在轨道交通工具座椅实际研发中,基于体压分布指标的分析可快捷有效地对座椅形面造型舒适度进行评价。     

座椅热舒适性客观评价温度模型构建

本文建立了人体一座椅接触面的温度模型,利用实测温度数据验证了模型的精度。从接触面温度特性模型中提取出了三个评价指标：接触面最终温度,接触面温度的最大变化率以及接触面的平均温度,据此建立了座椅舒适度客观评价体系。利用评价体系对三种材料座椅（泡沫、压模和木质座椅）进行评估,结果表明：泡沫座椅的舒适度得分为8．96±2．58,压模座椅的舒适度得分为6．15±1．96,木质座椅的舒适度得分为4．91±1．88。主观测评法得到的座椅舒适度得分为：泡沫座椅的舒适度得分为8．36±1．21,压模座椅的舒适度得分为7．27±1．42,木质座椅的舒适度得分为5．36±3．14。结论,利用人体一座椅接触面温度特性来衡量座椅舒适度的客观评价体系具有一定的实用性和可靠性。     

不同气流组织下冬季空调室内热舒适环境的数值模拟

基于K-ε模型和Fanger提出的热舒适性PMV评价指标,对三种不同气流组织条件下冬季室内热舒适环境进行了数值模拟,模拟结果给出了室内的速度、温度及舒适度PMV指标分布情况。研究结论为改善室内热舒适环境,舒适性空调系统的设计及节能控制提供了参考依据。     

国内外通用室内环境热舒适评价标准的分析与比较

介绍了国内外通用的室内环境热舒适评价标准,即国际ISO7730系列标准、美国ASHRAE 55系列标准和我国国家标准GB/T 50785-2012等标准。从评价指标、模型和方法,热舒适区和适用条件三个方面进行分析,并对国内外通用的室内环境热舒适评价标准各自的发展变化及相互的异同进行了比较,得出了人体热舒适研究的发展趋势,及室内环境热舒适评价标准的优点及局限性,对我国建筑室内热湿环境热舒适的研究和评价标准的改进具有参考价值。     

人行桥随机人行荷载下的振动分析及其舒适度评价的新方法

利用已有的建立在心理物理学方法之上的烦恼率模型以及传统的人行桥振动舒适度评价标准,建立适合于评估人行桥振动烦恼率的舒适度量化指标,提出了考虑人行桥竖向与侧向耦合振动时的综合评价方法,弥补了传统的关于人行桥振动舒适度评价方法的不足.通过模拟人行随机荷载激励对人行桥进行了人致振动时程分析并对其舒适度进行了评价,给出可行的减振措施并预测减振效果.这对今后人行桥人行荷载模拟、人行桥振动舒适度评价以及防振减振研究都具有参考借鉴意义.     

火炮系统效能评价方法研究

在分析火炮系统效能和测试指标影响关系的基础上,建立了火炮系统效能评价指标体系,运用层次分析方法确定了系统的层次结构和权重关系,运用模糊综合评估理论,建立了系统评估模型,并以某型履带式自行火炮武器系统为对象,确定了评估模型的边界条件,进行了实例评价．研究结果为火炮综合评价提供了一种有效的评价方法,对火炮试验鉴定和测试系统综合论证,具有一定的指导意义．     

置换通风室内热舒适性的数值模拟研究

利用CFD方法对一间采用置换通风系统的办公室进行了数值模拟，研究了不同送风参数下的室内流场，并用PPD、PMV等指标评价了室内的热舒适度。结果表明，热舒适度受送风参数的影响较大，并且其受温度的影响大于吹风的影响。最后指出，在送风参数选择合适的情况下，置换通风系统同样能提供良好的热舒适性。     

湖泊水质评价模型研究

水资源是人类日常生活中必不可少的,人们的大部分淡水资源来源于湖泊,对湖泊水的合理评价成为当前研究热点。本文主要基于BOD、氨氮、TN、TP和COD五类指标,结合单因子指标、层次分析法、模糊综合评价以及投影寻踪模型对湖泊水质进行了系统的评价。能够为政府采取措施提供合理意见。     

Health state evaluation of an item: A general framework and graphical representation

This paper presents a general theoretical framework to evaluate the health state of an item based on condition monitoring information. The item's health state is defined in terms of its relative health level and overall health level. The former is evaluated based on the relative magnitude of the composite covariate and the latter is evaluated using a fractile life of the residual life distribution at the decision instant. In addition, a method is developed to graphically represent the degradation model, failure threshold model, and the observation history of the composite covariate. As a result, the health state of the monitored item can be intuitively presented and the evaluated result can be subsequently used in a condition-based maintenance optimization decision model, which is amenable to computer modeling. A numerical example is included to illustrate the proposed approach and its appropriateness.     

超高层建筑中应用风机发电的噪声模拟与评估

世界首创的风机发电“高性能”可持续性建筑-“珠江城”商务写字楼由于风洞口和风机的存在,在气流经过时,将有可能产生较大的噪声。为防止噪声对附近办公室工作人员及居民有较大影响,损害本建筑物的声誉和使用性,有必要对“珠江城”商务写字楼产生的噪声大小及分布进行预测和评估。采用基于SST湍流模型的宽频带噪声源模型方法的数值模拟,得到了“珠江城”商务写字楼风洞口和风机的噪声大小分布,并对比了风洞口风机的存在对大楼噪声分布产生的影响。分析结果表明：一年重现期或者累年最大月平均的风速下,“珠江城”商务写字楼周围局部最大噪声值不会超过《中华人民共和国环境噪声污染防治法》规定的限值。     

Mechanistic evaluation of fatigue cracking in asphalt pavements

Over the last several decades, significant research has been conducted to predict the fatigue cracking performance of asphalt pavements. Recently, the simplified viscoelastic continuum damage (S-VECD) model was developed as an efficient method of characterising the fatigue performance of asphalt mixtures under a wide range of loading conditions. Two important material properties that can be determined from the S-VECD model are the damage characteristic curve that defines how damage evolves in a specimen and the energy-based failure criterion that defines when the specimen fails. These two material functions are unique for a given mixture regardless of temperature, mode of loading, stress/strain amplitude and loading history. This study presents the application of the Layered Viscoelastic Crirtical Distresses (LVECD) programme to predict the fatigue performance of 18 pavement sections from different locations in the United States and Canada. The capability of the LVECD programme to capture crack initiation, crack propagation and damage in the pavement sections is investigated by comparing the simulation results with field observations. This study found reasonable agreement in trends between the damage growth throughout the pavement cross sections as predicted by the LVECD programme and the surface crack growth as evidenced by field observations.     

Choice of standard fracture test for concrete and its statistical evaluation

The main characteristics of the cohesive (or fictitious) crack model, which is now generally accepted as the best simple fracture model for concrete, are (aside from tensile strength) the fracture energies G _F and G _f corresponding to the areas under the complete softening stress-separation curve and under the initial tangent of this curve. Although these are two independent fracture characteristics which both should be measured, the basic (level I) standard test is supposed to measure only one. First, it is argued that the level I test should measure G _f, for statistical reasons and because of relevance to prediction of maximum loads of structures. Second, various methods for measuring G _f (or the corresponding fracture toughness), including the size effect method, the Jenq-Shah method (TPFM), and the Guinea et al. method, are discussed. The last is clearly the most robust and optimal because: (1) it is based on the exact solution of the bilinear cohesive crack model and (2) necessitates nothing more than measurement of the maximum loads of notched specimens of one size, supplemented by tensile strength measurements. Since the identification of material fracture parameters from test data involves two random variables, f_t (tensile strength) and G _f, statistical regression should be applied. But regression is not feasible in the original Guinea et al.'s method. The present study proposes an improved version of Guinea et al.'s method which reduces the statistical problem to linear regression thanks to exploiting the systematic trend of size effect. This is made possible by noting that, according to the cohesive (or fictitious) crack model, the zero-size limit _N0 of nominal strength _N of a notched specimen is independent of F _f and thus can be easily calculated from the measured f_t. Then, the values of _N0 obtained from the measured f_t values, together with the measured _N-values of notched specimens, are used in statistical regression based on the exact size effect curve calculated in advance from the cohesive crack model for the chosen specimen geometry. This has several advantages: (1) the linear regression is the most robust statistical approach; (2) the difficult question of statistical correlation between measured f_t and the nominal strength of notched specimens is bypassed, by virtue of knowing the size effect trend; (3) the resulting coefficient of variation of mean G _f is very different and much more realistic than in the original version; (4) the coefficient of variation of the deviations of individual data from the regression line is very different from the coefficient of variation of individual notched test data and represents a much more realistic measure of scatter; and (5) possible accuracy improvements through the testing of notched specimens with different notch lengths and the same size, or notched specimens of different sizes, are in the regression setting straightforward. For engineering purposes where high accuracy is not needed, the simplest approach is the previously proposed zero-brittleness method, which can be regarded as a simplification of Guinea et al.' method. Finally, the errors of TPFM due to random variability of unloading-reloading properties from one concrete to another are quantitatively estimated.     

Ultrasonic nondestructive evaluation of fibre-reinforced composite materials — a review

A framework is presented for examining the effectiveness of limiting and modelling arguments used in the analysis of fluid flows. It consists of examining the consequences of the arguments on the flow problem as a whole and breaking down the limiting/modelling process into a sequence of steps and associated sequence of flow problems, termed here as ‘lidels’. The notion of validity of lidels is given. Several examples are given to explain the present approach. Invited general lecture at 3rd ACFM, Tokyo, September 1986     

Performance evaluation of ProJet multi-material jetting 3D printer

The purpose of this paper is to quantitatively evaluate the performance of a multi-material jetting 3D printer, ProJet 5500X, especially the capability for micro manufacturing. Unlike other single material 3D printer, ProJet 5500X uses photopolymers as the build material and wax as the support material. The building performance was evaluated by building a modified version of the standard benchmark model with a high-resolution printing mode. The dimensional error, forming quality and surface roughness of the printed parts have been measured and analysed using a microscope, a 3D coordinate measuring machine and a surface profilometer. Using wax as the support material, fine features as small as 0.25?mm, lateral features and sharper edges could all be properly built, despite the rough side surfaces observed in the printed part. Identical features (3?mm pins) were precisely built with an accuracy of 15?µm. The research provides first-hand detailed performance knowledge in the ProJet system for understanding the working principle and comparison with other 3D printing systems.     

Lifetime evaluation of concrete structures under sustained post-peak loading

Experimental tests on crack propagation in concrete under constant post-peak loading are simulated using the finite element method and the cohesive crack model, in both Mode I and Mixed-mode conditions. The time-dependent behaviour of concrete in the process zone is due to the interaction and growth of microcracks, a phenomenon which, for high constant load levels, turns out to be predominant over linear viscoelastic creep in the bulk material. In mechanical systems based on this type of material behaviour (creep and strain-softening taking place simultaneously), the initial value problem is non-parabolic, i.e., the error at one time level is affected by the accumulation of errors introduced at earlier time levels. Despite these difficulties, the scatter in numerical failure lifetime vs. load level turns out to be negligible in Mode I conditions and practically acceptable in Mixed-mode conditions. Therefore the time-dependent behaviour of the process zone can be inferred solely from the results of direct tensile tests.     

基于贝叶斯理论的测量不确定度A类评定

文章介绍了贝叶斯理论，并利用此理论对测量不确定度A类评定进行分析，与基于经典统计方法的不确定度A类评定相比，该方法能充分利用历史测量数据所提供的信息，因此评定时信息量大，使评定更加合理。最后通过实例分析说明了基于贝叶斯理论的不确定度A类评定的合理性和优越性。     

A new rabbit model of implant-related biofilm infection: development and evaluation

This study is to establish a rabbit model for human prosthetic joint infection and biofilm formation. Thirty-two healthy adult rabbits were randomly divided into four groups and implanted with stainless steel screws and ultra-high molecular weight polyethylene (UHMWPE) washers in the non-articular surface of the femoral lateral condyle of the right hind knees. The rabbit knee joints were inoculated with 1 mL saline containing 0, 10², 10³, 10⁴ CFU of Staphylococcus epidermidis (S. epidermidis) isolated from the patient with total knee arthroplasty (TKA) infection, respectively. On the 14th postoperative day, the UHMWPE washers from the optimal 10³ CFU group were further examined. The SEM examination showed a typical biofilm construction that circular S. epidermidis were embedded in a mucous-like matrix. In addition, the LCSM examination showed that the biofilm consisted of the polysaccharide stained bright green fluorescence and S. epidermidis radiating red fluorescence. Thus, we successfully create a rabbit model for prosthetic joint infection and biofilm formation, which should be valuable for biofilm studies.     

机械结构相似度评价及可靠性预计研究

在用传统的相似产品法进行可靠性预计时,所选取的相似产品与评价对象之间差异较大,会造成预计结果的偏差较大。为解决这一问题,提出了一种基于"功能—运动—动作"结构化分解的可靠性预计新方法。通过明确产品的各大运动功能建立功能层,分析完成各功能的机械部件运动建立运动层,确定实现各机械部件运动的元动作运动单元建立元动作层,建立了可靠性预计的"功能—运动—元动作运动单元"层次模型。引入区间层次分析法,确定了"功能—运动—元动作运动单元"层次模型中各子代运动单元对父代运动单元的可靠性影响权重,并构建了由子代运动单元预计父代运动单元可靠性的数学模型。确定影响评价机械结构相似度的因素,构建了区间数综合评判云模型并选取与元动作运动单元相似的参考结构,以区间数综合评价云模型得出的相似度值修正参考结构的可靠性数据来预计元动作运动单元的可靠性。将元动作运动单元的可靠性预计值代入数学模型,层层预计父代运动单元的可靠性,从而得出整个产品的可靠性水平。最后以数控转台为例进行了分析,得出了可靠性预计值,并将该方法与传统方法进行了比较。结果表明,新的可靠性预计方法具有较好的可行性和较高的准确性。