振动类型的识别

1　柴油发动机振动性质的识别图 1所示柴油发动机 ,在运转时发生振动 ,与它固结着1号加速度传感器 ,此发动机搁置在底盘的悬置减震器上 ,减震器的作用是使发动机振动进行控制 ,减少传递到驾驶室底板及座椅上。在底板上也固结着另一个 2号加速度传感器。对 1号传感器的振动时域信号进行处理 ,得幅值域的概率密度函数ｐ(ｘ1)和累积概率分布函数Ｐ(ｘ1) ,可以看出振动性质是周期性振动加上随机振动的两者组合 ,幅值域的有效值或标准离差σｘ1 =348ｍｍ/ｓ2 。　　　注 :图 2对应 1号加速度传感器 ,图 3对应 2号加速度传感器从自相关函数Φｘ1 …     

简议矿山地质灾害的几种类型与防治方法

我国矿山种类繁多、分布广、户数多、规模小、富矿少、基础差,由于技术、管理、效益等原因,资源开发中的安全隐患相当严重,地质灾害频发,尤其是矿山闭矿留下的矿坑、塌陷、尾矿坝等给当地的人民生产生活带来很大的威胁。对矿山地质灾害必须予以足够的重视,灾害的治理需要从源头抓起,才能放患于未然。本文对产生地质灾害几种类型及防治措施作了简要的论述。     

桥梁工程常见病害类型浅析

本文主要对现阶段桥梁工程几种常见质量缺陷的形成原因进行分类探讨,以期通过查找问题、分析问题来更好地了解这些缺陷,同时提出了一些有针对性、建设性的技术防范措施,以达到对桥梁病害进行有效预防、防治结合的根本目的。     

桥梁常见裂缝类型浅析

本人结合多年参与公路桥梁现场施工工作实践,对部分桥梁在建设过程中或建成通车后常见的一些裂缝类型进行归类总结,通过查找原因分析问题,才能让我们真正地了解各种裂缝的引发成因,进而制订防范措施,达到预防布控之目的。     

常见硬盘数据损坏的类型及恢复方法

随着信息技术的不断发展,微机与网络在各单位的日常工作中愈发占有更加重要的地位,在给工作带来便捷的同时,也带来一个问题,就是一旦操作失误或者硬盘出现问题,将导致数据丢失,从而造成不可挽回的损失,下面,就常见的硬盘损坏类型以及处理方式介绍给大家,希望能给单位网管或普通用户能有所帮助。     

小议森林病虫害的常见类型及防治

我国林木结构分布十分不合理,树种单一,林木抵抗能力低下,导致病虫害盛行。本文从分析森林病虫害的常见类型人手,并进一步提出了综合治理对策。     

探讨石油地质类型对石油勘探的作用

近年来,随着社会经济的飞速发展和能源资源的需求量越来越大,石油勘探技术也有了很大程度的提高。石油地质类型对石油勘探有着非常重要的意义,它是石油勘探的基础。本文将对石油地质类型进行分析,并在此基础上研究其对石油勘探的作用,以期为我国石油开采事业的发展提供一些参考。     

矿山地质灾害的常见类型及防治办法

我国丰富的矿产资源和近年来的大力开发,采矿业成为促进国民经济发展的重要推动力量。但是扩张期高速发展重效益、重速度,对矿山环境、周边地质相对忽视,矿山地质灾害屡有发生。在这样的背景下,有必要对矿山地质灾害的常见类型及防治办法进行分析讨论。本文从矿山地质灾害的常见类型探讨入手,详细探讨了矿山地质灾害的多层次的防治办法,以期总结经验,为我国矿山开采和地质灾害防治提供思路。     

基于类型间关系学习的细粒度实体分类

细粒度实体分类旨在为构建知识图谱过程中所抽取的实体或实体提及确定一个或多个层次化、细粒度的类型,以便更好地为下游任务提供支持。现有细粒度实体分类方法存在细粒度分类精度不高、部分实体难以有效分类的问题。另一方面,直观来说,掌握细粒度类型之间的语义区别有助于实体的细粒度分类。但由于已有面向该任务的数据集缺少可用于学习细粒度类型间语义差别的数据,因此目前没有将细粒度类型之间的语义区别应用于细粒度实体分类的研究。为此,本文提出一种基于Freebase知识库学习细粒度类型语义区别的方法,并将学习到的语义信息应用在细粒度实体分类任务中。具体地,利用SPARQL从Freebase中获取类型之间的关系数据,据此学习细粒度实体类型之间的语义区别信息,进而结合实体提及及其上下文的文本信息进行细粒度实体分类。实验表明,本文提出的方法可以有效学习细粒度类型之间的语义区别,能够达到提升细粒度实体分类准确率的效果。     

浅论试题类型对考试作弊的防范作用

考试作弊是高校课程考试中普遍存在的问题之一，尽管各校对作弊行为都有严厉的处罚规定，但仍有不步平时不努力学习的学生寄希望于考场，企图作弊过关。作弊的成功，会进一步助长这些学生的不学习行为，并对其它同学的学习积极性产生不利影响。考试成绩是衡     

Misspecification analysis of two-phase gamma-Wiener degradation models

A degradation model is used to analyze degradation data and product reliability. Owing to model uncertainty, the assumed degradation model may be improper, which can create a difference between the evaluated and actual product reliabilities. Thus, model misspecification analysis is essential. Recent studies on misspecification analysis have mainly considered single-phase degradation models; two-phase degradation models have not been investigated intensively. In this study, an approach to model misspecification analysis was developed for a two-phase gamma-Wiener process, where the change point was assumed to be known. The gamma and Wiener processes in a two-phase degradation model may be incorrectly assumed, so five misspecified degradation models were considered: the two-phase Wiener process, two-phase gamma process, two-phase Wiener-gamma process, one-phase Wiener process, and one-phase gamma process. A Monte Carlo simulation was performed to examine the effects of model misspecification on the relative bias and relative variability. A case study was performed to examine the effects of model misspecification on the evaluated mean time to failure and median lifetime of a product for different sample sizes, termination time, and change points. The results clearly demonstrated the effects of model misspecification on the evaluated reliability of a product.     

Traffic analysis zone level crash estimation models based on land use characteristics

The objective of this paper is to develop crash estimation models at traffic analysis zone (TAZ) level as a function of land use characteristics. Crash data and land use data for the City of Charlotte, Mecklenburg County, North Carolina were used to illustrate the development of TAZ level crash estimation models. Negative binomial count models (with log-link) were developed as data was observed to be over-dispersed. Demographic/socio-economic characteristics such as population, the number of household units and employment, traffic indicators such as trip productions and attractions, and, on-network characteristics such as center-lane miles by speed limit were observed to be correlated to land use characteristics, and, hence were not considered in the development of TAZ level crash estimation models. Urban residential commercial, rural district and mixed use district land use variables were observed to be correlated to other land use variables and were also not considered in the development of the models. Results obtained indicate that land use characteristics such as mixed use development, urban residential, single-family residential, multi-family residential, business and, office district are strongly associated and play a statistically significant role in estimating TAZ level crashes. The coefficient for single-family residential area was observed to be negative, indicating a decrease in the number of crashes with an increase in single-family residential area. Models were also developed to estimate these crashes by severity (injury and property damage only crashes). The outcomes can be used in safety conscious planning, land use decisions, long range transportation plans, and, to proactively apply safety treatments in high risk TAZs.     

The integration of product and process models for design

A structural correspondence is demostrated between product and process models through the definition of generic units, called roles. Relationships and communication between roles are discussed as are the types of knowledge required for design. The blackboard and prototype frameworks are presented as implementation strategies that could integrate product and process models for design.     

Global sensitivity analysis of computer models with functional inputs

Global sensitivity analysis is used to quantify the influence of uncertain model inputs on the response variability of a numerical model. The common quantitative methods are appropriate with computer codes having scalar model inputs. This paper aims at illustrating different variance-based sensitivity analysis techniques, based on the so-called Sobol's indices, when some model inputs are functional, such as stochastic processes or random spatial fields. In this work, we focus on large cpu time computer codes which need a preliminary metamodeling step before performing the sensitivity analysis. We propose the use of the joint modeling approach, i.e., modeling simultaneously the mean and the dispersion of the code outputs using two interlinked generalized linear models (GLMs) or generalized additive models (GAMs). The “mean model” allows to estimate the sensitivity indices of each scalar model inputs, while the “dispersion model” allows to derive the total sensitivity index of the functional model inputs. The proposed approach is compared to some classical sensitivity analysis methodologies on an analytical function. Lastly, the new methodology is applied to an industrial computer code that simulates the nuclear fuel irradiation.     

The use of models in reliability

The paper reviews the scientific and philosophical basis of the use of models in engineering, particularly in reliability engineering, and their credibility in predicting future outcomes.     

几种植酸酶活测定方法的修正与差异比较

对目前文献所见到的植酸酶活的测定方法选取三种进行了分析和修正,并用两种温度下的酶活定义检验修正过的测定方法的差异。根据显色剂吸收光谱和磷化合物的吸收光谱的比较,确定FeSO_4—钼蓝法选取大于720nm、VC—钼蓝法选取620～660nm、丙酮法选取400～420nm的波长为测量适宜波长。在同样温度下(即对一种酶活定义来说,)用这三种方法测定曲霉发酵液的植酸酶活,结果酶活大小基本一致(平均差率小于5％),说明这三种方法在测定植酸酶活时都有相等的可靠性和准确性。     

The use of multiplicative models for analysis of road safety data

Accident ratios are analysed with regard to the variables road-surface skidding resistance and hourly traffic volume. In a first analysis the Additive Conjoint Measurement model (ACM) is used to investigate to what extent the accident ratios can be described as a result of independent contributions of skidding resistance and traffic volume. Furthermore it is considered whether these contributions have to be combined in an additive or multiplicative way. Based on the results of this investigation a second analysis takes place in which a stochastic interpretation of the data is combined with the multiplicative model. This Weighted Poisson model (WPM) is in fact a generalisation of the log-linear model, recently proposed for the analysis of contingency tables. It is concluded that the multiplicative model describes the data better than the additive model. Moreover, there is no interaction between skidding resistance and traffic volume in their effect on accident ratios. The relation between accident ratios and both variables are shown, and the statistics regarding the contributions of the variables are given.     

空分流程中几个基本热力过程的分析

简介了的概念及计算方法 ,对空分流程中几个基本热力过程进行了分析 ,从更深层次揭示了这些基本热力过程的实质 ,从而为优化这些热力过程、进一步降低不可逆损失指明方向。把这些基本的分析方法用于整体空分流程 ,将会对流程的改进和优化有较好的指导作用。     

The use of best design practices: An analysis of US navy contractors

Rapid and successful introduction of new products is a potentially significant source of competitive advantage for manufacturing firms. Organizations need to identify and manage those critical elements of the product development process (PDP) that have a positive influence on new product success. This research identifies the distinctive product development and design practices, policies and tools currently followed by companies (Navy contractors) that participated in an empirical research study known as the Best Manufacturing Practices Program. A summary of practices reported in the case studies is compiled using content analysis techniques, and the most interesting practices by individual companies are highlighted. We find numerous examples of sophisticated CAD techniques being used to enhance the development process, including expert system design advisers, computer simulation, and design databases. Companies are emphasizing the design policies of concurrent engineering and teamwork, and documenting design process knowledge into design manuals. Company effort still appear focused primarily on the phase of detailed design rather than the concept selection phase.     

粘结磁体的研究现状及发展趋势

本文从理论和生产实际出发,对粘结磁体作了简要介绍,主要综述了粘结磁体的研究背景、生产和研究现状及发展趋势,并对粘结磁体的原料及生产工艺现状进行了概括,涉及原料(永磁磁粉、粘结剂及配合剂等几个方面)及原料配比、制备工艺过程等产品生产的全过程,也对不同成型工艺的适用对象和优缺点作了简单描述,以便使人们对粘结磁体的现状及发展趋势能有基本的认识.最后,对粘结磁体的发展趋势和存在的问题进行了总结并提出了一些看法,以供研究和生产粘结磁体的同行参考.