不同弯沉检测技术在路基检测中的应用对比

在高等级公路路基弯沉现场测试实践中,较为常用的检测方法包括BB法和FWD法两种,上述两种方法分属于两种不同的荷载类型。本文以高等级公路路基弯沉指标检测为研究对象,详细分析了BB法和FWD法的检测原理及相关流程,选定省内某等级公路路基弯沉检测标段作为试验段,对比了两种检测技术对应的指标结果,论证了FWD法在公路路基弯沉指标检测中的优势。     

A comparison of impact measures from hybrid and synthetic techniques: A case study of the Foothills Model Forest

This article presents an applied framework for selective precision in the insertion of superior data into hybrid regional models where regional purchasing coefficients are absent or unattainable. Due to the lack of regional-level data, crude top-down methods are the most frequently applied methods in Canadian regional studies. However, they may lead to inaccurate policy analysis where significant variation exists between the technical coefficients and trade flows of two economies. This article discusses an alternative, hybrid approach that involves the collection of region-specific information and therefore promises greater accuracy and validity of impact analysis. The robustness of the hybrid model is tested against the results derived from a synthetically regionalized model. The Foothills Model Forest (FMF) in west-central Alberta is used as a case study for the development of a sub-provincial economic database for the purpose of regional impact modeling. Received: September 1999/Accepted: September 2001     

Sediment oxygen demand techniques: A review and comparison of laboratory and in situ systems

Sediment oxygen demand (SOD) measurement techniques are reviewed and suggestions offered for improving their performance, including an experimental approach toward standardizing the SOD methodology. Five principal analytical systems are used to evaluate SOD. These are conveniently classified as: (1) batch (laboratory and in situ); (2) continuous flow; (3) manometric; (4) electrolytic and (5) dehydrogenase activity. Comparison of SOD methods requires establishing certain criteria which should be met for a given method to be considered acceptable. These criteria are: (1) consistency; (2) reproducibility and (3) efficiency. Laboratory techniques can meet the acceptability criteria more easily than in situ techniques. A SOD reaction chamber used in our laboratory provided reproducible data for replicate analyses of stream and lakes sediments and met our acceptability criteria.     

电力监控系统在长大隧道机电工程中的应用

以某高速公路长大隧道机电工程为背景,详细介绍了电力监控系统的监控对象及内容、系统的结构和组成等,并归纳了该系统的主要功能,为高速公路隧道全线供电系统的安全可靠运行提供了保障。     

Pipe network leak detection: comparison between statistical and machine learning techniques

ABSTRACT

This paper investigates an inverse analysis technique to find leaks in water networks and compares different solution strategies. Although a number of strategies have been proposed by different authors to identify leaks on a vast selection of pipe networks, limited research has been done to compare strategies and point out their weakness. Three strategies, a Bayesian probabilistic analysis, a support vector machine and, an artificial neural network were combined with the inverse analysis technique on different numerical and experimental networks to point out each strategy’s weakness. Two numerical networks are investigated and one experimental network. It is shown that the Bayesian probabilistic analysis struggles to find unique solutions when a few observations are available, while the support vector machine and the artificial neural network struggle when only flow measurements are available. Additionally it is shown that the artificial neural network struggles to estimate unique solutions for leak size and location.     

A study of the blast wave from deflagrative explosions

The research reported here is an experimental and theoretical study of the overpressures produced by unconfined vapour-cloud explosions (UVCE) in deflagration. Using the analogy of accidental explosions, the experiments were conducted in the open air using samples of hydrocarbons (propane, n-pentane and n-octane) in the range 0.31 – 313.0 kg by mass. The features observed in the overpressure profiles and their impulses were thoroughly studied by comparison with the results calculated from a simulation model that assumed a propagating flame that was a spherically expanding piston. This model was useful for determining the blast-wave parameters of ideal cases of UVCEs in deflagration. The behaviour of blast waves in dimensionless space was dependent on only the initial flame speed and was independent of mass, that is, it followed a kind of scaling law.     

A data fusion scheme for building automation systems of building central chilling plants

Accurate and reliable building load measurement is essential for robust chiller sequencing control, building air-conditioning system performance monitoring and optimization. This paper presents a scheme adopting the data fusion technique to improve the quality of building cooling load measurement of building automation systems. The strategy uses two types of measurement information on the cooling load, i.e., “direct measurement” of building cooling load, which is calculated directly using the differential water temperature and water flow rate measurements, and “indirect measurement” of building cooling load, which is calculated using a model using the instantaneous chiller electrical power input. Capitalizing their own advantages and disadvantages, a data fusion algorithm is developed to merge these two types of data to remove outliers and system errors as well as to reduce the impacts of measurement noises. Meanwhile, a method is implemented to provide quantitative evaluation of the degree of reliability of the merged measurement. Validation of the data fusion algorithm is conducted using field data collected from a chiller plant in a high-rising building in Hong Kong.     

Elasticity and urban vacancy: A longitudinal comparison of U.S. cities

The effects of urban expansion and population change on vacant land patterns are not fully understood. While the majority of previous research documents that depopulation can result in increased vacant urban areas, there are conflicting findings in regards to the effects of urban expansion. What remains unclear is whether higher urban elasticity (expansion in size) contributes to increases in urban vacancies, or the inverse. While elastic cities extend their boundaries and develop outwardly, inelastic cities contract or stay the same in size and utilize infill development. This research sought to determine if urban elasticity plays a significant role in contributing to urban vacancy increases through an exploratory, quasi-experimental longitudinal analysis of vacant address data from 40 U.S. cities of over 100,000 persons from 2000 to 2010. We compared the top 20 elastic (boundaries expanded the most) and inelastic (boundaries contracted the most) cities. A fixed effects panel model was developed to observe changes over time and differences in total, residential, and business land uses. Results indicate that aggressive urban expansion can contribute to increased urban vacancies, specifically in reference to residential land uses. This finding clarifies what had heretofore been a murky aspect of the urban studies literature.     

A comparison of in situ and extractive measurement techniques for monitoring SO2 emissions from a stationary source

Recently, an investigation has been completed which compared both extractive and in situ electro-optical instrumentation for the measurement of SO₂ emissions from a pulverized-coal power generating boiler. An assessment was made of individual system performance under field conditions. To accomplish this, particular areas of interest in this study included: (1) an investigation of the effects of variations in fuel composition, boiler operating conditions and fly ash emissions on the various measurement systems; (2) a correlation of instrument response with standard EPA compliance test methods; and (3) a determination of several instrument operating criteria such as zero drift, span drift, and maintenance.     

山西省高速公路机电系统维护管理初探

研究了山西省高速公路机电系统维护管理现状,指出了机电设备维护管理过程中存在的问题,从建立健全维护体系、提高维护效率、加强专项维护工程的统一高效管理三方面探讨了提高机电系统管理维护水平的思路,以确保高速公路机电系统的正常运行.     

A comparison of dilution adjustment methods for urinary enzymes.

Urinary dilution adjustment methods can be used to reduce the intra-individual variability in concentrations of metals and other substances in urine due to variability in urinary flow. In this study linear and non-linear dilution adjustments with urinary flow, creatinine (CREAT) and urinary density (UD) were compared for the urinary enzymes alanine amino peptidase (AAP), beta-galactosidase (beta GAL) and N-acetyl-beta, D-glucosaminidase (NAG). The most optimal dilution adjustment for AAP was: AAPadjusted = AAPmeasured/(CREATmeasured)0.824 The optimal dilution adjustment for beta GAL was: beta GALadjusted = beta GALmeasured/(CREATmeasured)0.878 For NAG the optimal dilution adjustment parameter was the conventional linear adjustment with SG. It could not be determined whether urinary dilution methods can be useful for population based reference intervals of urinary enzymes. If personal reference intervals can be calculated, urinary dilution adjustment methods may be useful by reduction of intraindividual variability.     

A review of development of better prediction equations for blast fragmentation

The paper reviews the development of prediction formulas for the fragmentation from bench blasting.Much attention has been paid to the Kuz-Ram model,its development and errors,and the mean vs.median misunderstanding.The work by the US Bureau of Mines(USBM) and Chung and Katsabanis are also reviewed,as well as the two Julius Kruttschnitt Mineral Research Centre(JKMRC) models,i.e.the crush zone model(CZM) and the two-component model(TCM),which were developed to cope with the underestimation of blasting fines.The change brought by the Swebrec distribution and the associated Kuznetsov-Cunningham-Ouchterlony(KCO) model is described.Studying distribution-free fragment sizes xp for an arbitrary mass passing P led to the discovery of the fragnmentation-energy fan,and with the help of dimensional analysis,to the new fragmentation prediction model xp-frag,which has much lower errors than those of the Kuz-Ram and CZM models.     

宝钢二号高炉炉体框架的加固设计

宝钢二号高炉大修时采用了炉体整体提升的方法,炉体框架在高炉大修时要承受整体提升50000kN的荷载作用,远远超过其现有的承载能力,必须对原框架进行加固处理。仅为满足承受50000kN荷载作用时,框架很容易加固,但在大修过程中由于运输荷载的大小和作用位置的变化,使得炉体框架的局部构件的内力发生变化,又由于高炉框架上连接的附属结构众多,因而使得加固工作变得复杂。本文根据高炉大修时的具体工艺,将高炉大修时的荷载作用情况分为4个工况进行计算,得到结构的加固方案。对加固后的炉体框架进行了内力计算,并按现行的相关规范(规程)进行了强度、稳定和变形验算。     

福州地区水泥混凝土路面破碎技术工艺效果对比研究

结合福州地区相关的技术应用情况和试验路监测数据,重点对冲击压实破碎、打裂压稳、碎石化等旧水泥混凝土路面破碎化技术的原理、机械、工艺和效果进行了比较。研究发现:旧板实际破碎尺寸除与特定破碎技术有关外,还依赖于旧路结构。不同破碎改建技术得到的旧板承载力差别较大,碎石化处理后的旧路承载能力损失最多,冲击压实其次,打裂压稳损失最小。所需加铺沥青层厚度各异,改建工程造价需结合加铺结构费用进行综合对比。根据福州地区工程经验,建议打裂压稳尺寸在60~80cm以下,碎石化顶面混凝土块尺寸在7~10cm之间,同时应检测旧路顶面弯沉或回弹模量,软弱路段要进行补强。     

Safety of engineered structures against blast vibrations:A case study

Blasting used for rock excavation is associated with ground vibrations having potential damage to surrounding structures.The extent of damage produced in a structure depends largely on ground motion characteristics,dynamic characteristics of structure and the type of geological strata on which it is founded.The safety of surrounding structures against blast vibrations is a cause of concern.However,use of a systematic approach to rock blasting helps to complete the excavation safely in time without endangering the safety of surrounding structures.Various steps are commonly adopted at construction sites to ensure safety of engineered structures against blast vibrations,e.g.adopting a suitable safe vibration level,developing site-specific attenuation relation,estimating safe charges for different distances,designing blasting pattern,and monitoring vibrations during actual blasting.The paper describes the details of studies conducted for ensuring safety of an 85 years old masonry dam and green concrete of varying ages during excavation of about 30,000 m~3 of hard rock in Maharashtra,India.The studies helped to complete the rock excavation safely in time and the safety of the dam was ensured by monitoring blast vibrations during actual rock excavation.     

美国和欧洲消防防化服技术标准之比较

本文从防化服的耐磨性能、抗渗透性能、测试环境温度和耐火焰性能四个方面 ,比较了以美国消防协会标准 NFPA1991和欧盟标准 EN 934为代表 ,涉及消防防化服的两个主要国际标准 ;并介绍了一次性 (简易 )防化服的特点 ,以及封闭空间等特殊工作环境对消防防化服的要求进行了简介。     

A multiphysics-viscoplastic cap model for simulating blast response of cemented tailings backfill

Although a large number of previous researches have significantly contributed to the understanding of the quasi-static mechanical behavior of cemented tailings backfill,an evolutive porous medium used in underground mine cavities,very few efforts have been made to improve the knowledge on its response under sudden dynamic loading during the curing process.In fact,there is a great need for such information given that cemented backfill structures are often subjected to blast loadings due to mine exploitations.In this study,a coupled thermo-hydro-mechanical-chemical(THMC)-viscoplastic cap model is developed to describe the behavior of cementing mine backfill material under blast loading.A THMC model for cemented backfill is adopted to evaluate its behavior and evolution of its properties in curing processes with coupled thermal,hydraulic,mechanical and chemical factors.Then,the model is coupled to a Perzyna type of viscoplastic model with a modified smooth surface cap envelope and a variable bulk modulus,in order to reasonably capture the nonlinear and rate-dependent behaviors of the cemented tailings backfill under blast loading.All of the parameters required for the variable-modulus viscoplastic cap model were obtained by applying the THMC model to reproducing evolution of cemented paste backfill(CPB)properties in the curing process.Thus,the behavior of hydrating cemented backfill under high-rate impacts can be evaluated under any curing time of concern.The validation results of the proposed model indicate a good agreement between the experimental and the simulated results.The authors believe that the proposed model will contribute to a better understanding of the performance of hydrating cemented backfill under blasting,and also to practical risk management of backfill structures associated with such a dynamic condition.     

A comparison of two methods to project regional and state populations for the U.S.

This paper is a comparison of two contrasting methods for projecting population at the regional and state levels. A projection of the U.S. Bureau of the Census employs standard demographic methods, while the population projection by Data Resources, Inc., is based on economic opportunity. The methodological differences between these two projections are discussed, and the projections for the year 2000 are compared. While both projections use the same national control total for population in the year 2000, some of the regional and state projections are very different. The U.S. Bureau of the Census projects population decline in the Northeast and rapid growth in the West while Data Resources, Inc., projects some population growth in the Northeast and less rapid growth in the West.Funding for this project was provided by the U.S. Department of Energy under Contract W-31-109-Eng-38.The authors hope that this paper has illustrated the extent to which such a change in the growth pattern established in the 1970s may matter to the regions and states.