基于回归分析的爆破振速预测保护古建筑

爆破振动多采用萨道夫斯基经验公式法预测,但由于影响爆破振动效应因素较多,导致回归系数离散程度较大.尤其在保护重要对象时,若采用单一的衰减公式,可能存在安全隐患或降低施工效率.结合一起为保护古建筑进行的爆破振动监测,利用多组爆破试验数据进行回归分析,充分分析不同组合的回归结果.针对不同的爆破条件选用相应的衰减系数,科学地预测爆破药量.不仅有效地控制了爆破振动,而且提高了施工效率.     

古建筑的爆破安全允许振动限值研究

古建筑由于建筑结构和材料与现代建筑不同,而且历时漫长可能遭受到自然和人为的破坏,因此在保护此类建筑不受爆破振动破坏时,其安全允许振动限值应经论证选取。本文结合一起为保护国家级文物(六胜塔)进行的爆破振动监测,通过脉动测试和试爆测试,分析古塔结构反应,确定古塔的安全允许振速,更科学地控制爆破施工对古建筑的振动影响。     

基于经验格林函数方法的爆破振动预测

通过单孔爆破振动监测实验,获取点振源的经验格林函数,利用单孔振源的格林函数来叠加合成群孔爆破振动时程。根据经验格林函数法原理建立了相应的爆破振动预测方法,编制了专用的预测分析软件。通过实例验证,若应用电子雷管精确控制起爆时差,预测目标点的群孔爆破振动波形与实测结果相当吻合。该方法获得的爆破振动预测准确度显著高于传统的回归统计分析法,不仅可以预报爆破振动峰值速度,也可对频率及持续振动时间进行预测.充分体现了爆破地震波的时频域信息,爆破振动的预测结果更全面。     

基于经验格林函数方法的爆破振动预测

通过单孔爆破振动监测实验,获取点振源的经验格林函数,利用单孔振源的格林函数来叠加合成群孔爆破振动时程。根据经验格林函数法原理建立了相应的爆破振动预测方法,编制了专用的预测分析软件。通过实例验证,若应用电子雷管精确控制起爆时差,预测目标点的群孔爆破振动波形与实测结果相当吻合。该方法获得的爆破振动预测准确度显著高于传统的回归统计分析法,不仅可以预报爆破振动峰值速度,也可对频率及持续振动时间进行预测.充分体现了爆破地震波的时频域信息,爆破振动的预测结果更全面。     

基于BP神经网络的爆破振速峰值预测

在分析爆破振动主要影响因素的基础上,建立了对爆破振动质点速度峰值进行预测的BP神经网络模型.将某露天铁矿的爆破振动监测数据分别与模型预测结果和应用传统经验公式进行预测的结果比较,发现由于每次爆破的地震波传播不同,直接应用萨氏公式的K、α值进行预测会引起较大误差,相比之下,BP网络模型的预测结果更为准确和可靠.     

前白枣山铁矿地面爆破振动预测

地面振动是爆破作业过程中最严重、最复杂的环境问题之一.爆破振动会对预留的边坡和构筑物产生不利影响,从而影响建筑物结构的完整性.因此,在爆破过程中准确预测地面振动具有重要意义.研究的主要目的是对矿山爆破引起的地面振动进行高精度预测,以减少地面振动对周围环境的影响.为此,提出神经网络(ANN)模型用于前白枣山铁矿爆破振动预...     

高边坡爆破振动传播规律及其控制技术

为了分析及预测广西某航运过坝工程高边坡爆破振动的传播与衰减规律,进而减弱爆破振动效应,保护既有建(构)筑物,通过无量纲分析,推导出了反映高程效应的爆破振动传播规律预测模型。采用爆破测振仪在爆区附近设置5个监测点,对爆破所产生的振动进行监测、记录。根据实测数据,进行了非线性回归分析,对比了2种不同预测模型的预测精度。研究结果表明:高程对爆破振动效应具有较大的影响,传统预测经验公式的预测精度为83.48%,采用改进后的反映高程效应的模型的预测精确度较高,达97.03%,在复杂环境下,采用综合减振技术具有较好的降振效果。     

高边坡爆破振动传播规律及其控制技术

为了分析及预测广西某航运过坝工程高边坡爆破振动的传播与衰减规律,进而减弱爆破振动效应,保护既有建(构)筑物,通过无量纲分析,推导出了反映高程效应的爆破振动传播规律预测模型。采用爆破测振仪在爆区附近设置5个监测点,对爆破所产生的振动进行监测、记录。根据实测数据,进行了非线性回归分析,对比了2种不同预测模型的预测精度。研究结果表明:高程对爆破振动效应具有较大的影响,传统预测经验公式的预测精度为83.48%,采用改进后的反映高程效应的模型的预测精确度较高,达97.03%,在复杂环境下,采用综合减振技术具有较好的降振效果。     

隧洞开挖爆破振动监测与振速预测分析

根据盛洪卿隧道泄水洞开挖爆破施工实际情况,选定合适的爆破监测方案.结合现场监测数据,分别采用经验公式线性回归法和BP神经网络法对爆破振动速度进行预测并将2种预测结果进行了比较分析.结果表明,线性回归法对地质条件具有依赖性,而BP神经网络方法可以较全面地考虑爆破振动速度的多种影响因素,且具有误差小、精度高等特性,因而应用BP神经网络方法预测爆破振动速度是有效可行的.     

基于量纲理论的爆破振动频率分析

为了探究影响爆破振动频率的各种因素,采用量纲分析方法研究了爆破地震波的产生和传播效应.基于小波包分析基本理论,将地震波中的低频波段进行细化,参照萨道夫斯基公式得到了爆破振动频率的预测方程,并进行了工程验证.结果表明,该预测方程的回归参数有较好的一致性,可以为爆破振动危害控制提供参考依据.     

往复式压缩机出口管线振动的分析与改造

某厂220×104t/a加氢处理装置在实际生产中发现加氢精制装置高分压力控制不稳,引起往复式压缩机出口管线振动。本文首先对往复式压缩机出口管线振动的原因进行分析,得出压力脉动为主要因素。然后,通过对管系的重要区段进行改造,将往复式压缩机采用的Ⅰ回Ⅰ,Ⅱ回Ⅱ的控制方案改为Ⅱ回Ⅰ的控制方案。并对改造前后的方案分别采用DDC控制系统进行动态模拟实验,得到高分压力随时间变化的关系图,并进行压力不均匀度计算。最后,对比二种方案高分压力随时间变化的关系图以及压力不均匀度,得出Ⅱ回Ⅰ的控制方案比Ⅰ回Ⅰ,Ⅱ回Ⅱ控制方案大大降低管线振动,使压力控制平稳。     

振动试验夹具的优化设计及模态试验

将优化设计引入到夹具的设计环节中,运用拓扑优化和尺寸优化来合理布置材料分布以及优化板件厚度尺寸,提高夹具设计效率和设计质量,采用数字信号处理的方法对加工出来的夹具进行模态试验,将模态试验的结果与有限元模态分析的结果进行对比。证明了优化设计在夹具设计中的可靠性和适用性,为今后夹具的动态设计提供有价值的参考。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...