Friction Parameters for Flows in Nearly Flat Tidal Channels

A numerical study of friction parameters associated with nearly flat tidal channels is reported. Such empirical parameters are often back-calculated using complex flow equations through a procedure referred to as “inverse problems.” However, estimates of friction parameters of tidal channels are liable to substantial uncertainties if water levels are used in their inverse problems. Even if the parameters are optimized by mathematically comparing gauged and simulated values, the inverse problem must satisfy the quality conditions of “uniqueness,” “identifiability,” and “stability.” To obtain an insight into the problem, this paper focuses on flows where these conditions may not hold. The study concludes that friction parameters can be unidentifiable if the inverse problem employs gauged high tide water levels, because the effect of storage on water level dominates over friction. Gauged discharge values render identifiable, stable, and unique estimates of friction parameters even at high tides, but this is not a practical proposition. Low tide levels should be used to determine friction parameters, as the use of high-tide water levels can make friction parameters, and subsequently simulated discharge values, anomalous.     

Student veterans: A national survey exploring psychological symptoms and suicide risk.

The current study explored psychological symptoms, symptom severity, and suicide risk in a national sample (N = 628) of student veterans. We hypothesized that the rates, types, and severity of problems experienced by student veterans on campus would in many ways mirror those reported by active duty service members as well as the Operation Iraqi Freedom/Operation Enduring Freedom veteran population. Almost 35% of the sample experienced “severe anxiety,” 24% experienced “severe depression,” and almost 46% experienced significant symptoms of posttraumatic stress disorder. Of particular concern, there were significant numbers of participants thinking about suicide (46%), with 20% having a plan, 10.4% thinking about suicide “often or very often,” 7.7% making an attempt, and 3.8% believing that suicide is either “likely” or “very likely.” Implications of the findings are discussed, with a particular focus on college and university campuses. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Friction Factor of Meandering Flows

An expression for the friction factor of rough turbulent meandering flows is suggested: flow cross section is rectangular, the plan shape of the meandering channel is sine-generated. This expression gives the value of the friction factor as a function of position (which is determined by, among other factors, the local channel curvature) and channel sinuosity. The validity of the present expression is tested against results of laboratory measurements. The measurements were carried out in two meandering channels, one typifying “small” sinuosity, the other “large” sinuosity. It is found that the vertically averaged flows in these two channels exhibit two distinctly different (“in-” and “out-going”) flow patterns, depending on whether the channel sinuosity is “large” or “small.” These two radically different flow pictures cannot be supplied by the vertically averaged equations of motion if they are solved for a constant friction factor. The present consideration of the friction factor as a function of position and channel sinuosity is found to yield the computed vertically averaged flows that are in agreement with the flow pictures measured for both large and small values of sinuosity.     

200, 020, and 002 X-ray peaks in tempered Fe-18 Ni-C martensites

Separate 200, 020, and 002 X-ray peaks were recorded for 0.0, 0.4, and 0.8 wt pct carbon (18 pct Ni) martensites after tempering between 25 and 500°C. The carbon bearing martensites studied here have been tempered initially enough to eliminate the “high tetragonality” 002 peak usually recorded for as-quenched martensite and the present results apply to tempered martensite only. The peak maximum is taken to determine the lattice parameter and the peak shape is recorded. At all carbon levels and after all tempering treatments, the “crd parameter is larger than or equal to the “a” or “b”. The relative enlargement is very small (0.08 pct) for the lowest carbon level and for any carbon level after severe tempering (500°C for 15 min). For the two higher carbon alloys tempered at temperatures below 400°C (for 15 min) the “c” parameter is significantly larger than the “a” and “b” and for the 0.4 wt pct C alloy the “b” is significantly smaller than the“a” whereas in the 0.8 pct C alloy the “b” is slightly larger than the “a”. Within experimental error the mean volume of the unit cell does not change during the tempering studied here and is nearly unaffected by the initial carbon content. This indicates that little (at most 0.1 wt pct) carbon is dissolved in tempered martensite. In the low carbon alloy the peaks are symmetric and sharpen symmetrically during tempering. In the higher carbon alloys the peaks are nearly symmetric and sharp after severe tempering. After less severe tempering the 002 peak is asymmetrically broadened toward lower9 values (higher lattice parameters) whereas the 200 and 020 peaks are asymmetrically broadened toward higher 0 values corresponding to lower lattice parameters. This collection of results is tentatively interpreted as being due to strains in martensite due to transformation induced substructure and precipitated carbides.     

Importance of Modeling in Estimation of Properties of Refining Slags

Structures and various properties of refining slags can be estimated by the use of classical molecular dynamics simulation. The appropriateness of the estimation depends on the interatomic potentials used in the simulation. If modeling of the interatomic potentials is sound, the parameter values in the potential functions become equivalent to physical property values and their evaluation based on fitting of calculated properties with the measured values becomes equivalent to the measurement of the “physical properties”. This situation is also applicable to thermodynamic modeling. Once the parameter values, i.e. the “physical properties”, are evaluated by the use of some measurements or ab initio calculations, the simulation by the use of the model and the model itself have the ability of estimating a wide range of properties of refining slags. In this scope, a molecular dynamics approach of molten CaO‐SiO₂, an evaluation method of energy parameter values in the Cell Model as a slag thermodynamic model by the use of NMR measurements are discussed. Estimation of viscosity and relative molar volume of slags by the use of thermodynamic properties is also mentioned.     

Hybrid Approach for Addressing Uncertainty in Risk Assessments

Parameter uncertainty is a major aspect of the model-based estimation of the risk of human exposure to pollutants. The Monte Carlo method, which applies probability theory to address model parameter uncertainty, relies on a statistical representation of available information. In recent years, other uncertainty theories have been proposed as alternative approaches to address model parameter uncertainty in situations where available information is insufficient to identify statistically representative probability distributions, due in particular to data scarcity. The simplest such theory is possibility theory, which uses so-called fuzzy numbers to represent model parameter uncertainty. In practice, it may occur that certain model parameters can be reasonably represented by probability distributions, because there are sufficient data available to substantiate such distributions by statistical analysis, while others are better represented by fuzzy numbers (due to data scarcity). The question then arises as to how these two modes of representation of model parameter uncertainty can be combined for the purpose of estimating the risk of exposure. This paper proposes an approach (termed a hybrid approach) which combines Monte Carlo random sampling of probability distribution functions with fuzzy calculus. The approach is applied to a real case of estimation of human exposure, via vegetable consumption, to cadmium present in the surficial soils of an industrial site located in the north of France. The application illustrates the potential of the proposed approach, which allows the uncertainty affecting model parameters to be represented in a way that is consistent with the information at hand. Also, because the hybrid approach takes advantage of the “rich” information provided by probability distributions, while retaining the conservative character of fuzzy calculus, it is believed to hold value in terms of a “reasonable” application of the precautionary principle.     

Integrated Subsurface Modeling and Risk Assessment of Petroleum-Contaminated Sites in Western Canada

Soil and groundwater contamination can pose a variety of impacts and risks to communities. Identification of management schemes with sound environmental and socio-economic efficiencies is desired. Before any decisions regarding site remediation actions can be made, three major questions may have to be answered. They are namely “What happened underground?”, “What will happen in the future under the given remediation scenarios?”, and “Are there specific risks to the surrounding community?”. In this study, an integrated modeling and risk assessment method is developed for effectively managing petroleum-contaminated sites through technically answering the above questions. It presents an integral concept that integrates issues of multicontaminant transport simulation, biodegradation modeling, health risk assessment, and site remediation for real-world problems within a general decision support framework. The developed method is applied to a petroleum-contaminated groundwater system in western Canada for identifying cost-effective management schemes with improved environmental and socio-economic efficiencies. The research outputs are directly useful for the decision maker to gain insight into the site and to make remediation decisions.     

Reliability Analysis of Partial Safety Factor Design Method for Cantilever Retaining Walls in Granular Soils

Uncertainties in the geotechnical design variables and design equations have a significant impact on the safety of cantilever retaining walls. Traditionally, uncertainties in the geotechnical design are addressed by incorporating a conservative factor of safety in the analytical model. In this paper, a risk-based approach is adopted to assess the influence of the geotechnical variable and design equation uncertainties on the design of cantilever retaining walls in sand using the “partial factor of safety on shear strength” approach. A random model factor based on large-scale laboratory test data from the literature has been incorporated into the reliability analyses to quantify the uncertainty in the geotechnical calculation model. Analyses conducted using Monte Carlo simulation show that the same partial factor can have very different levels of risk depending on the degree of uncertainty of the mean value of the soil friction angle. Calibration studies show the partial factor necessary to achieve target probability values of 1 and 0.1%.     

尊重科学 实事求是——“XGK专利轧机”真相

近年来,媒体上出现了不少XGK"专利轧机"的报导,称该"专利轧机"是"跨世纪发明","国际上三、五十年不可逾越的技术",等等。本文介绍了XGK"专利轧机"质量问题,国家专利复审委作出其专利权全部无效的决定,河南省高院作出专利权全部无效其诉讼请求应予驳回的终审判决以及"专利轧机"的真实水平。     

Effect of Particle Shape on Interface Behavior of DEM‐Simulated Granular Materials

This paper presents a detailed computational investigation of the effect of particle shape on the interface shear behavior of granular materials. The discrete element method (DEM) using clusters to model rough particles is used, expanding the procedure introduced in an earlier paper by Jensen et al. [1]. Seven new cluster shapes (i.e., particle configurations) of varying degrees of roughness are presented herein, and numerical experiments simulating ring shear tests are made using these clusters. From these simulations, the effect of particle shape on void ratio (e) and interface angle of friction between soil and structure surface (δ) is reported. Particle shape characteristics include roundness, angularity, and surface roughness. The results of numerical simulations using the newly formed cluster shapes are in very good qualitative agreement with laboratory tests. Simulation results showed that the void ratio of a particle mass increased as the angularity or roughness of the particles increased. They also showed an increase in interface shear strength between perfectly round DEM particles and the more angular cluster shapes, but no systematic correlations with the various definitions of particle shape parameters was found. It may be necessary to use greater accuracy in modeling the size and shape distributions of a natural medium to further investigate the influence of particle shape on interface friction. The simulations also successfully reflected the relationship between interface friction angle and structure surface roughness as demonstrated in recent physical experiments. The simulations comparing initially “dense” media to initially “loose” media demonstrated behavior that is similar to the behavior of a natural sandy soil observed in experiments.     

Structural Reliability Estimation with Vibration-Based Identified Parameters

This paper presents a unique structural reliability estimation method incorporating structural parameter identification results based on the seismic response measurement. In the shaking table test, a three-bent concrete bridge model was shaken to different damage levels by a sequence of earthquake motions with increasing intensities. Structural parameters, stiffness and damping values of the bridge were identified under damaging seismic events based on the seismic response measurement. A methodology was developed to understand the importance of structural parameter identification in the reliability estimation. Along this line, a set of structural parameters were generated based on the Monte Carlo simulation. Each of them was assigned to the base bridge model. Then, every bridge model was analyzed using nonlinear time history analyses to obtain damage level at the specific locations. Last, reliability estimation was performed for bridges modeled with two sets of structural parameters. The first one was obtained by the nonlinear time history analysis with the Monte Carlo simulated parameters which is called nonupdated structural parameters. The second one was obtained by updating the first set in Bayesian sense based on the vibration-based identification results which is called updated structural parameters. In the scope of this paper, it was shown that residual reliability of the system estimated using the updated structural parameters is lower than the one estimated using the nonupdated structural parameters.     

Sample size and multiple regression analysis.

Despite the development of procedures for calculating sample size as a function of relevant effect size parameters, rules of thumb tend to persist in designs of multiple regression studies. One explanation for their persistence may be the difficulty in formulating a reasonable a priori value of an effect size to be detected. This article presents methods for calculating effect sizes in multiple regression from a variety of perspectives and also introduces a new method based on an exchangeability structure among predictor variables. No single method is deemed superior, but rather examples show that a combination of methods is likely to be most valuable in many situations. A simulation provides a 2nd explanation for why rules of thumb for choosing sample size have persisted but also shows that the outcome of such underpowered studies will be a literature consisting of seemingly contradictory results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Seismic Soil-Pile-Structure Interaction Experiments and Analyses

A dynamic beam on a nonlinear Winkler foundation (or “dynamic p-y”) analysis method for analyzing seismic soil-pile-structure interaction was evaluated against the results of a series of dynamic centrifuge model tests. The centrifuge tests included two different single-pile-supported structures subjected to nine different earthquake events with peak accelerations ranging from 0.02 to 0.7g. The soil profile consisted of soft clay overlying dense sand. Site response and dynamic p-y analyses are described. Input parameters were selected based on existing engineering practices. Reasonably good agreement was obtained between calculated and recorded responses for both structural models in all earthquake events. Sensitivity of the results to dynamic p-y model parameters and site response calculations are evaluated. These results provide experimental support for the use of dynamic p-y analysis methods in seismic soil-pile-structure interaction problems.     

“一带一路”背景下陕西矿产资源国际合作共同体研究

陕西省一直坚持“主合作并购、辅承包转让”的模式与其他国家进行国际矿产资源合作,并取得较多良好成绩。但是,陕西省矿产管理工作中仍存在诸如缺乏完善的风险防范机制、政府服务职能以及有待精简的审批流程等问题。作为“新丝绸之路”的重要组成部分,陕西省在“一带一路”背景下需要开发出一条更加适合未来发展方向的新型矿产资源国际合作之路。研究认为,构建矿产资源国际合作共同体能够从“共担命运”“共同发展”“共享利益”3个方面解决陕西省矿业发展中遇到的问题,应全面坚持政企联动、多元合作、夯实合作关系、强化投资区位选择的方向,积极构建矿产资源国际合作共同体。     

Galerkin Residuals for Adaptive Symmetric-Galerkin Boundary Element Methods

This paper presents a simple a posteriori error estimator and an effective adaptive mesh refinement procedure for the symmetric Galerkin boundary element method. The “hypersingular residuals,” developed for error estimation in a standard collocation BEM, are extended to the symmetric Galerkin setting. This leads to the formulation of “Galerkin residuals,” which are intrinsic to the symmetric Galerkin boundary integral approach and form the basis of the present error estimation scheme. Several computational experiments are conducted to test both the accuracy and the reliability of the proposed technique. These experiments involve potential theory and various problem configurations including mixed boundary conditions, corners, and nonconvex domains. The numerical results indicate that reliable solutions to practical engineering problems can be obtained with this method.     

Design considerations for estimation of exposure effects on disease risk, using aggregate data studies

Previously we proposed an aggregate data study design for estimation of exposure effects from population-based disease rates and covariate data from risk factor surveys in each population group. A basic relative rate model specified for individuals is aggregated to produce a random effects relative rate model for the disease rates. Relative rate parameter estimates from aggregate data studies target the same parameters as individual-level studies but use between-group information in the data. We distinguish aggregate data studies from ecologic studies. Considerations in the design of aggregate studies are motivated by the need to gain clearer understanding of the role of diet in cancer aetiology. Simulation studies show that increasing the number of populations included in an aggregate data study from about 20 to 30-40 gives greater improvement in power than corresponding increases in the size of the survey sample in each population over an initial size of 100 individuals.     

Computer technology for genogenographic study of the gene pool. V. Evaluation of the reliability of maps

An important aspect of gene geography, the estimation of the reliability of interpolation maps, is considered. The introduced quantitative parameter, map reliability, was estimated as the probability of predicted character values in interpolated map regions. The obtained estimates characterize the statistic significance of the mapped values of the character. The estimation algorithm is based on concepts and mathematical methods of the reliability theory. The proposed approach involved the estimation of the reliability at each point of the mapped area and resulted in a new map (a reliability map) expressing the reliability of gene geographic mapping in probability terms. Approaches to estimate the reliability of mapping, as dependent on various parameters of the initial data, were proposed, a general computer-based technology was elaborated, and a standardized reliability scale was proposed. Reliability maps are considered necessary for the correct interpretation of gene geographic maps. The estimation of reliability as dependent on the number and distribution of initially tested populations was illustrated by the example of frequency maps of individual genes (HP*1, HLA*A1) and synthetic maps (100 alleles of 34 polymorphic loci) of Eastern Europe.     

Spatial and Temporal Exposure to Safety Hazards in Construction

Given the dynamic nature of construction sites, analysis of construction activities and their related hazards is inadequate for reliable risk assessment if it does not explicitly account for the likelihood of exposure of potential victims to hazardous situations. In traditional risk level calculations for manufacturing industries, the number of victims is factored with the likelihood of an accident and the potential severity, but the victims are simply assumed to be those typically present at the accident location. In construction, exposure cannot be accounted for at a generic metaproject level: it must be assessed at the level of the activities and the physical context in which they are performed. Conceptually, accidents are “loss-of-control events” to which victims are exposed; without exposure, no accident is assumed to occur. A set of algorithms has been developed to demonstrate estimation of the likelihood of exposure of construction workers to loss-of-control events. The algorithms have been implemented in a prototype software application designed to predict fluctuating risk levels in construction projects. The software implements the “construction hazard assessment with spatial and temporal exposure” model for managing safety in construction, which empowers planners at all levels to adjust construction plans to mitigate high levels of risk or to undertake appropriate proactive measures to ensure safety when high risk levels are unavoidable.     

汽车用合金化热镀锌, IF, 钢表面摩擦系数

采用平板滑动实验研究了表面相组成、表面粗糙度、拉速、压力及涂油品种等因素对汽车用合金化热镀锌IF钢表面摩擦系数的影响。研究发现对于合金化热镀锌IF钢表面存在大量柱状ζ相的镀层表面, 其表面摩擦系数通常大于以粒状δ相为主的镀层表面;以柱状5相为主的镀层表面,当镀层表面存在大量尺寸较大的“火山口”状形貌时,其表面摩擦系数相对较小。