从铜铁锌酸性液中选择性萃取铜

采用Lix984萃取剂 ,对含铜铁锌酸性浸出液进行选择性萃取铜研究。结果表明 ,萃取剂浓度为 3%时 ,铜的萃取率可达到 99% ,且锌和铁共萃率低 ;萃取混合时间 >2min时 ,铜的萃取率达 96 % ,而铁和锌的萃取率 <5 % ;当相比 (O/A)为 1∶1时 ,铜的萃取效果最佳 ;随萃取值的增大 ,铜的萃取率升高 ,但为了避免萃取污物的大量产生 ,应控制萃取pH <2 .5。反萃试验结果表明 ,铜和铁的反萃率随着反萃剂浓度、反萃相比、反萃时间的增大而升高。     

Surface spectroscopy of apatitic materials: limitations and concerns

The use of x-ray photoelectron spectroscopy for the study of biological materials has provided mixed results. The experimental difficulties associated with the application of this technique to the study of biological materials include the effects of ultra-high vacuum, x-ray exposure, surface charging, and, for insulating materials, the inherent lack of an intrinsic energy reference. Since most biological materials are insulators, the lack of an intrinsic energy reference complicates one's ability to draw direct comparisons between different studies. In this paper, the results from two different apatites are compared with the results obtained from the use of two conventional techniques for referencing binding energies. The results presented here are referenced only to the Pt Fermi level; no further energy modifications are performed. A comparison with the results of other investigators indicates a large difference in binding energies for all involved core levels. These results indicate that, in the study of insulating materials with x-ray photoelectron spectroscopy, it is essential that all data be acquired under exacting conditions on the same experimental system.     

The identification of bias in studies of the diagnostic performance of imaging modalities

The demand for evidence-based healthcare is increasing nationally and internationally and it is equally necessary in both diagnostic and therapeutic practice. Evidence may be collected and combined by means of a systematic literature review of published and unpublished data on a well-defined topic. The output of such reviews is then available to guide health policy, influence good practice or direct research. Published guidelines are available on the performance of systematic reviews, especially those of randomized controlled trials. Although there is an extensive literature base of research data in diagnostic imaging there are few such trials, but it is still possible to perform systematic reviews. With the alternative study designs encountered it is important to be aware of the main threats to study validity. In this paper the biases likely to be encountered in studies of diagnostic performance are reviewed, with particular reference to diagnostic imaging tests. The biases are sub-divided into three categories. The first category is patient selection and covers the validity of generalizing results beyond the study population. The other two, concerning study design and execution and the interpretation of results, affect the likely validity of the results of a study. An understanding of these factors is an essential prerequisite for those undertaking or using a systematic literature review in the field of diagnostic imaging. The definitions form the foundations of a defensible review protocol.     

Property Modification Factors for Seismically Isolated Bridges

An analytical study investigating how changes in the mechanical properties of individual seismic isolators affect the response of isolated bridge structures subjected to earthquake excitation is summarized. Nonlinear response-history analyses are conducted utilizing bins of recorded earthquake ground motion pairs. Twenty bilinear isolation systems are considered so that the results of this study are broadly applicable to the design of seismic isolation systems in the United States. Variations in the mechanical properties are considered using a property modification factor, λ, to modify the appropriate bilinear isolator parameter. The results of analyses considering nominal and modified isolation systems are used to systematically identify changes in system response as a function of the property modification factor. These results are used to determine threshold values of the property modification factor that should aid engineers in the preliminary design and assessment of an isolation system prior to performing the bounding analysis now required by bridge and building design codes.     

Genetic Programming Approach for Prediction of Local Scour Downstream of Hydraulic Structures

This is a pioneer study that presents genetic programming (GP) as a new tool for prediction of local scour downstream of grade-control structures. The objective of this study is to provide an alternative formulation to conventional regression based equations and verify the superiority of GP over regression analysis. The training and testing patterns of the proposed GP formulation are based on well established and widely dispersed experimental results from the literature. Linear and nonlinear regression-based equations were derived throughout regression analysis on dimensionless parameters obtained from dimensional analysis. The GP-based formulation results are compared with experimental results and other equations and found to be more accurate.     

Finite-Element Parametric Study of the Consolidation Behavior of a Trial Embankment on Soft Clay

The paper presents a case study for numerical analysis of the consolidation behavior of an instrumented trial embankment constructed on a soft soil foundation. Details are given to the geological profile, field instrumentation, laboratory test results, and determination of soil parameters for numerical modeling. Embankment settlement is estimated based on one-dimensional consolidation analysis and nonlinear finite-element analysis following Biot’s consolidation theory. Finite-element results are calibrated against the measured field data for a period of more than 3?years. Development and dissipation of excess pore pressure, long-term settlement, and horizontal displacement are predicted and discussed in light of sensitivity of embankment performance to some critical factors through a parametric study.     

稠密气固两相反应流的拉格朗日法

提出了采用欧拉坐标和拉格朗日坐标相结合研究稠密气固两相反应流的方法,建立了稠密两相反应流中两相运动、传热、化学反应的模型与算法,采用该模型与算法研究了循环流化床排烟脱硫装置内的两相反应过程,得到了详细合理的计算结果。结果表明,采用此模型和算法模拟工程意义上的稠密气固两相反应流是可行的。     

The effect of marker heterozygosity on the power to detect linkage disequilibrium

The relationship between marker heterozygosity and the power to detect linkage disequilibrium is examined through the analysis of an example and through a simulation study. The analysis suggests that, despite the penalties for multiple testing incurred with multiple alleles, greater heterozygosity results in greater power. The results of the simulation study are in accord with those of the analysis.     

The advances in the health care management in the Russian Federation on the basis of the analysis of the health personnel

Present the purpose, tasks, methods and programs of a comprehensive study of medical personnel organization and management. The activities of staff departments are proposed to be singled out as a specific service. Some findings of the study are presented, as are the results attained with the introduction into practice of a model of staff service in number of regions and the experience gained with training of specialists for personnel departments.     

Stochastic epidemics: the probability of extinction of an infectious disease at the end of a major outbreak

The aim of this study is to derive an asymptotic expression for the probability that an infectious disease will disappear from a population at the end of a major outbreak ('fade-out'). The study deals with a stochastic SIR-model. Local asymptotic expansions are constructed for the deterministic trajectories of the corresponding deterministic system, in particular for the deterministic trajectory starting in the saddle point. The analytical expression for the probability of extinction is derived by asymptotically solving a boundary value problem based on the Fokker-Planck equation for the stochastic system. The asymptotic results are compared with results obtained by random walk simulations.     

Roaming through the methodology. VIII. Pilot studies: sense and nonsense

A pilot study is often performed before the start of a large study. Its aim is improving the methodological quality and evaluating the feasibility. The results of a pilot study are also often used to gain an impression of the efficacy of an intervention. For this purpose a pilot is absolutely unsuited. However, the estimate of the effect of an intervention in small studies such as pilot studies is determined to a large extent by chance. When conducting small studies the chance of publication bias is large. Small studies of adequate methodological quality should be published, whether the results are positive or negative, significant or non-significant, because combination in a later cumulative meta-analysis may lead to sufficient power to assess the efficacy of an experimental intervention.     

Behavior of FRP Strengthened Reinforced Concrete Beams under Torsion

The use of fiber reinforced plastics (FRPs) for flexural and shear strengthening of reinforced concrete beams has been scrutinized to a considerable depth by researchers worldwide. The area of torsional strengthening however has not been as popular. This paper presents the results of an experimental investigation together with a numerical study on reinforced concrete beams subjected to torsion that are strengthened with FRP wraps in a variety of configurations. In the experimental study, the increase in the ultimate torque for different strengthening configurations, failure mechanisms, crack patterns, and ductility levels are monitored and presented. Experimental results show that FRP wraps can increase the ultimate torque of fully wrapped beams considerably in addition to enhancing the ductility. The experimental results upgrade the weak archival data on torsional strengthening by application of FRP. The numerical section reports on analyses performed by the ANSYS finite element program. Predictions are compared with experimental findings and are in reasonable agreement.     

Flexural Strength of RC Beams with GFRP Laminates

The results of an experimental and numerical study of the flexural behavior of reinforced concrete beams strengthened with glass-fiber-reinforced-polymer (GFRP) laminates are presented in this paper. In the experimental program, ten strengthened beams and two unstrengthened beams are tested to failure under monotonic loading. A number of external GFRP laminate layers and bond length of GFRP laminates in shear span are taken as the test variables. Longitudinal GFRP strain development and interfacial shear stress distribution from the tests are examined. The experimental results generally showed that both flexural strength and stiffness of reinforced concrete beams could be increased by such a bonding technique. In the numerical study, an eight-node interface element is developed to simulate the interface behavior between the concrete and GFRP laminates. This element is implemented into the MARC software package for the finite-element analyses of GFRP laminate strengthened reinforced concrete beams. Reasonably good correlations between experimental and numerical results are achieved.     

Evaluating quality management systems

This study reports how nurse administrators may approach an evaluation of their quality management (QM) initiative. Suggestions are based on the current study of a multiclinic health care system's QM plan. Tips on designing the evaluation and recommendations on how to report results are provided. Collaboration with local university researchers is suggested as a way to strengthen the process.     

EUROPOP--European Programme of Occupational Risks and Pregnancy Outcome--part II

As continuation of their previous paper the authors submit the results of the European study EUROPOP pertaining to the effect of occupation on the course and outcome of pregnancy. The paper contains the first part of results where the authors compare groups of women with premature deliveries (22nd-36th week of pregnancy) with control groups 1/10 deliveries in term (> or = 37 weeks). The groups of abortions in the second trimester which were studied by the authors were relatively small (Czech Republic 49 and in the all-European study 229). To keep the study within a reasonable limits the tables are not presented. Comparison of results describing home work, living conditions of pregnant women, prenatal care and medical problems as well as data on the outcome of pregnancy are presented in part III.     

A longitudinal study of the careers of a cohort of assistant professors in psychology.

Reviews the literature on female psychologists in academe and presents results from a 7-yr longitudinal study of a cohort of 171 male and 174 female assistant professors in psychology. The literature review indicates that women psychologists are less likely to be promoted or receive tenure than men, publish less than men, are less likely to have a PhD, and are less likely to have been an administrator than are men. Women are also limited by constraints of childrearing and mobility necessitated by their husband's career. However, new evidence from the cohort study provides little support for some common assumptions about the career progress of men and women. Instead, results indicate few differences between the career paths of male and female psychologists. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Monte Carlo studies of the hydrocarbon region of lipid bilayers

We present the results of a Monte Carlo study of systems of hydrocarbon chains attached to a plane interface and interacting through hard core repulsive forces only. The chain-order parameters which we find in our studies are compared to experimental results (NMR and ESR). The role of "kink" states and the relevance of our studies to theoretical models are also discussed.     

Laminar and Turbulent Bottom Boundary Layer Induced by Nonlinear Water Waves

Results of a numerical study to investigate wave-induced boundary layer flows are reported. In this study, the writers consider a coupled viscous-inviscid approach, in which the fully nonlinear free surface boundary conditions are satisfied in the inviscid flow calculation, while the viscous flow near the seabed is solved via the Reynolds-averaged Navier-Stokes equations, instead of the thin boundary layer equation. To simulate the turbulent flow, a two-layer k-ε model is applied. Coupling of the viscous and inviscid computations is accomplished by the direct matching of the velocity and pressure distributions on the matching boundaries. Validation of the numerical model is carried out separately for the inviscid and viscous models, and the coupling approach as a whole. The numerical results are compared with theoretical solutions and available experimental data. A parametric study of the laminar and turbulent boundary layers for highly and weakly nonlinear waves is performed using the coupled viscous-inviscid approach. The results are compared with corresponding U-tube simulations, and the discrepancy is highlighted and discussed.     

机架间冷却数学模型计算带钢温度分布

为提高带钢终轧温度的控制精度 ,对精轧过程中导致带钢温度变化的热交换过程进行了分析 ,以此作为机架间冷却控制的传热模型和自学习模型的理论依据 ,给出了带钢厂热轧机组机架间冷却在线控制的传热和自学习模型的算法 ,通过程序开发对精轧机组内带钢的温度分布进行了离线模拟 ,终轧温度计算值与实际生产数据符合较好 ,并对所用数学模型的实际计算结果进行了分析