Coupling an Underflow Model to a Three-Dimensional Hydrodynamic Model

A separate underflow model is coupled to the three-dimensional (3D) estuary and lake computer model. The underflow equations are solved on a two-dimensional (2D) grid underlying the 3D model grid. The underflow model entrains ambient water whose properties are given by the fluid properties of the bottom boundary cells in the 3D model. This new approach allows improved representation of underflow effects in z-coordinate models by reducing numerical convective entrainment. An idealized case is used to illustrate the benefits of the underflow model. Comparisons of model results and field data for a saline underflow event in Lake Ogawara and a cold-water underflow in Lake Kinneret demonstrate improved model capability in representing underflow events that are thin compared to the vertical grid scale.     

Contemporary Design-Bid-Build Model

Empirical research was performed into the hypothesis that a substantial number of building performance engineering tasks on design-bid-build projects are typically provided by entities associated with the construction phase, not with the architect-engineer (AE) of record. This hypothesis is contrary to the traditional understanding of design-bid-build and is theorized to result from increased time pressures on AEs, decreased AE profit margins, AEs’ attempts to minimize liability, increased design and construction specialization, and increased prefabrication. Project technical specifications were analyzed for 20 $5–45M building construction projects and 16 individuals directly associated with these projects were interviewed. It was found that 35 building performance engineering tasks were required by the project specifications to be performed by entities associated with the construction of the buildings. This large number of delegated design tasks suggests the conventional understanding of the design-bid-build process is not accurate. The increasing fragmentation of the design and construction process may have implications for the efficiency of communication on design-bid-build projects, lean construction processes, and constructability.     

Transitional Markov Chain Monte Carlo Method for Bayesian Model Updating, Model Class Selection, and Model Averaging

This paper presents a newly developed simulation-based approach for Bayesian model updating, model class selection, and model averaging called the transitional Markov chain Monte Carlo (TMCMC) approach. The idea behind TMCMC is to avoid the problem of sampling from difficult target probability density functions (PDFs) but sampling from a series of intermediate PDFs that converge to the target PDF and are easier to sample. The TMCMC approach is motivated by the adaptive Metropolis–Hastings method developed by Beck and Au in 2002 and is based on Markov chain Monte Carlo. It is shown that TMCMC is able to draw samples from some difficult PDFs (e.g., multimodal PDFs, very peaked PDFs, and PDFs with flat manifold). The TMCMC approach can also estimate evidence of the chosen probabilistic model class conditioning on the measured data, a key component for Bayesian model class selection and model averaging. Three examples are used to demonstrate the effectiveness of the TMCMC approach in Bayesian model updating, model class selection, and model averaging.     

Random Uncertainties Model in Dynamic Substructuring Using a Nonparametric Probabilistic Model

This paper presents a new approach, called a nonparametric approach, for constructing a model of random uncertainties in dynamic substructuring in order to predict the matrix-valued frequency response functions of complex structures. Such an approach allows nonhomogeneous uncertainties to be modeled with the nonparametric approach. The Craig–Bampton dynamic substructuring method is used. For each substructure, a nonparametric model of random uncertainties is introduced. This nonparametric model does not require identifying uncertain parameters in the reduced matrix model of each substructure as is usually done for the parametric approach. This nonparametric model of random uncertainties is based on the use of a probability model for symmetric positive-definite real random matrices using the entropy optimization principle. The theory and a numerical example are presented in the context of the finite-element method. The numerical results obtained show the efficiency of the model proposed.     

FRP-Confined Concrete Model

A uniaxial model for concrete confined with fiber-reinforced polymers (FRP), but also with steel jackets or conventional transverse reinforcement, is presented. The model, which is suitable to be inserted into fiber-type beam-column models, explicitly accounts for the continuous interaction with the confining device due to the lateral strain of concrete, through an incremental-iterative approach. The relation between the axial and lateral strains is implicitly derived through equilibrium between the (dilating) confined concrete and the confining device. This relation allows one to trace the state of strain in the jacket and to detect its failure. The model is compared with a set of experimental tests and shows very good agreement in both the stress-strain and the stress-lateral strain response. Evidence of the main aspects of the behavior of FRP-confined concrete is given that points out differences in the response when using fiberglass or carbonfiber. Predictive equations to determine the ultimate strength and strain of concrete confined with FRP are derived and tested on a number of experimental data.     

Practical Subgrade Model for Improved Soil-Structure Interaction Analysis: Model Development

This note outlines the theoretical development of a new subgrade model with inherent spring coupling called the modified Kerr-Reissner (MK-R) model. The MK-R model is a novel hybrid that synergistically combines the advantages of mechanical and simplified-continuum subgrade models with the specific objective of producing a model that is straightforward to implement in routine practice.     

中小企业供应链融资模式相关问题分析

随着改革开放的逐渐深入,传统融资模式已不足以满足中小企业的需求.新兴的供应链融资模式拓宽了企业融资渠道,降低了融资成本,但该模式仍然存在供应链整体潜在风险、信用风险、信息不对称等问题.针对这些问题,提出了一些完善中小企业供应链融资的对策及建议,为企业融资探寻新的思路.     

Deterministic-Based Model of Slow Sand Filtration. II: Model Application

This paper describes the use of a deterministic slow sand filter process model to investigate and assess some of the fundamental aspects and mechanisms operating during slow sand filtration (SSF). These include the role of the schmutzdecke, biomass development, and the initial condition of the filter, to the overall process performance. The SSF process model has been developed recently and is described in a companion paper by Campos et al., in 2006. It attempts to provide a simulation of the physicochemical and biological processes responsible for the filtration mechanisms operating in SSF. The simulation of filter runs has been carried out with the help of extensive pilot plant data provided by Thames Water Utilities Ltd., involving both uncovered and covered filter beds. The results demonstrate that the presence and nature of a schmutzdecke layer profoundly influence the spatial and temporal development of interstitial biomass within the sand and, consequently, the headloss profile. Microbial interactions in the filter bed play a fundamental role in the process and are involved in setting the pattern and magnitude of headloss development. The model also demonstrates the significance of residual deposits within the filter after surface cleaning, on the subsequent filter behavior.     

冷轧平整机模型研究与仿真

对鞍钢1450 mm平整机过程控制系统数学模型进行了研究,分析了轧制力、张力等模型设定参数,提出了修正轧制力公式及提高模型设定计算精度的方法。同时利用VB开发了模型参数设定计算仿真程序。仿真程序能够结合实际生产运行数据,离线准确地计算出各轧制参数设定值,为提高冷轧薄板成品质量提供支持。     

Tripartite Cohesive Crack Model

A new multicomponent cohesive crack model for concrete is presented. The model, which is directly applicable to interface finite elements, has three main components termed undamaged, bridging, and fully debonded. The relative sizes of these components, each of which simulates a proportion of a representative material volume, change according to evolution functions that are developed from data from uniaxial cyclic tests on notched concrete specimens. The undamaged component is treated as elastic damaging, the bridging component has two subcomponents, which are elastoplastic and elastic with contact, and the fully debonded component is elastoplastic with contact. The relationships governing the normal-shear interactions are developed from experimental data on combined shear-tension tests on cracked concrete specimens. Comparisons with experimental data illustrate that the model is able to represent the cyclic behavior of cracked concrete in tension, full crack closure, the interaction between shear and normal behavior, and aggregate interlock behavior.     

成本预测模型

：本文以样本年数据为基础,通过数理统计确定占成本构成份额98％的18种物资;在计算模型设计中,引进与机时产量成反比的“生产系数”和与品种总成本成正比的品种系数;解决费用分排问题。企业的成本要素一旦发生变化,本计算模型可立即计算出企业的全部有关产品生产成本和销售成本。     

Fundamental Mathematical Model for AOD Process. Part II: Model validation

A fundamental mathematical model for AOD process has been developed and proposed in “Fundamental Mathematical Model for AOD Process. Part I: Derivation of the Model” 1 . Validation of the model with process data, measured from full scale AOD process, is presented in this paper. A broad selection of input data for the model was exported from various types of full scale industrial AOD heats. In this study 6 different types of heats were studied and simulated. Process data was measured from two AOD converters (95 t, 150 t). Validation of the model was then done by comparing simulated and measured values for carbon and chromium content, carbon release rate, melt composition, slag composition and bath temperature during final stages of carbon removal. The validation results showed that the model was in good agreement with the measured process data, and same model parameters were valid in all of the simulated heats.     

Gates’ Bidding Model

In evaluating closed-bid competitive procurement auctions, the most crucial issue is to determine the probability of placing a winning bid for a given markup level. There has long been disagreement on how this should be done due to the absence of a mathematical derivation of one of the main evaluation techniques—Gates’ method. Gates’ method is shown in this paper to be valid if, and only if, bids can be described using the proportional hazards family of statistical distributions. When markup values are included in Gates’ method, it is seen that the underlying statistical distribution required for the method to work is closely related to the Weibull distribution. Likelihood based methods are suggested for parameter estimation and an illustrative example is provided by analysis of Shaffer and Micheau's 1971 construction contract bidding data.     

Lunar Base Parametric Model

A steady-state model for first-order magnitude estimates of lunar base masses is presented. The main focus of the model is the derivation of initial and annual resupply mass estimates for a lunar base at certain development stages. These estimates are not only a function of several thousand input parameters and boundary conditions such as crew size; lunar base location; and environmental conditions, but also specific system masses; specific power requirements; and specific thermal loads. This integrated lunar base model indicates which systems and subsystems have the greatest mass impact on the overall base. Also, brief overviews of possible activities at a lunar base and of lunar development strategies are given.     

Model of Compaction Grouting

Compaction grouting is an important soil improvement and underpinning technique that involves injection of a very stiff grout material into the soil. The objective is to displace and compact the surrounding soil without permeating or hydrofracturing it. Compaction grouting has been developed and used almost entirely on the basis of practical experience. The present study proposes a theoretical model that describes the mechanics of the compaction grouting process and rationally considers the different soil and grouting parameters that govern the overall design and performance of the method. The theoretical basis of the model draws from the theory of cavity expansion as well as the conical shear failure above the grout bulb. This model was validated using limited available data. The results indicate reasonable agreement and show a good potential of the proposed model for rationally optimizing the design of compaction grouting operations.