Prediction of Microstructure and Mechanical Properties of Hot Rolled Steel Strip: Part I ‐ Description of Models

A metallurgical through‐process model is presented which describes the microstructural evolution and predicts the final mechanical properties of low carbon steel during hot strip rolling. Process models concern the thermal and deformation phenomena, which take into account the strain, strain rate and temperature distribution along the length of the strip. And the metallurgical models cover five modules, which are (i) austenitization of cast slab in reheating furnace, (ii) recrystallization of austenite in hot rolling, (iii) phase transformation of austenite‐ferrite in laminar cooling on the run‐out‐table, (iv) grain growth after coiling, and (v) final structure‐mechanical properties of products. Temperature is the main parameter and has dominant influence on the microstrutural evolution and the mechanical properties. The related temperature variation in hot strip rolling concerns air cooling, scaling, water cooling, heat transmission by roll contact, heat generation by deformation and friction. These complex factors are incorporated into the thermal models to simulate the temperature distribution along the length of the strip from the reheating furnace exit to the down‐coiler. A self‐learning algorithm is employed to improve the calculation accuracy and the computational temperatures are compared with the measured ones at typical locations. In the structure‐property relationships, two key process parameters (e.g., finishing exit temperature (FT7) and coiling temperature (CT)) are introduced in the model to consider the influence of morphology of microstructure on mechanical properties.     

Iconic Animation for Activity-based Construction Simulation

This paper discusses the development of an animation tool for the activity-based construction (ABC) modeling and simulation system. The tool uses an activity-based network diagram, i.e., ABC simulation model, as the animation background image, and uses precreated two-dimensional (2D) iconic images for simulation entities (e.g., resources). The animation process displays the queuing status and dynamic movements of 2D iconic images on the background. It also distinguishes active and idle states of resources and activities. Dynamic reports are available for selected activities with graphs including the production rate and utilization of involved resources. From visualizing the change of status of a simulation process and dynamic interaction between simulation entities in the process, the user can better understand the dynamic nature of the construction process. Animation provides an avenue to demonstrate how dynamic operations are simulated. It also provides an effective tool for the user to verify a simulation model and to validate the obtained simulation results. Compared to other systems, the ABC animation does not require any extra effort in addition to the ABC simulation model constructed for simulation purposes. Therefore, the presented technology greatly reduces the time and cost for achieving animation. A variety of useful information can be observed through animation, and is illustrated using two construction examples.     

Role of Ponded Turbidity Currents in Reservoir Trap Efficiency

The capacity to store water in a reservoir declines as it traps sediment. A river entering a reservoir forms a prograding delta. Coarse sediment (e.g., sand) deposits in the fluvial topset and avalanching foreset of the delta, and is typically trapped with an efficiency near 100%. The trap efficiency of fine sediment (e.g., mud), on the other hand, may be below 100%, because some of this sediment may pass out of the reservoir without settling out. Here, a model of trap efficiency of mud is developed in terms of the mechanics of a turbidity current that plunges on the foreset. The dam causes a sustained turbidity current to reflect and form a muddy pond bounded upstream by a hydraulic jump. If the interface of this muddy pond rises above any vent or overflow point at the dam, the trap efficiency of mud drops below 100%. A model of the coevolution of topset, foreset, and bottomset in a reservoir that captures the dynamics of the internal muddy pond is presented. Numerical implementation, comparison against an experiment, and application to a field-scale case provide the basis for a physical understanding of the processes that determine reservoir trap efficiency.     

Particle Swarm Optimization-Supported Simulation for Construction Operations

This study proposes an integration of particle swarm optimization (PSO) and a construction simulation so as to determine efficiently the optimal resource combination for a construction operation. The particle-flying mechanism is utilized to guide the search process for the PSO-supported simulation optimization. A statistics method, i.e., multiple-comparison procedure, is adopted to compare the random output performances resulting from the stochastic simulation model so as to rank the alternatives (i.e., particle-represented resource combinations) during the search process. The indifference zone and confidence interval facilitate consideration of the secondary performance measure (e.g., productivity) when the main performance measures (e.g., cost) of the competing alternatives are close. The experimental analyses demonstrate the effectiveness and efficiency of the proposed simulation optimization. The study aims to providing an alternative combination of optimization methodology and general construction simulation by utilizing PSO and a statistics method so as to improve the efficiency of simulation in planning construction operations.     

Optimizing Launch‐on‐Time Probability

Future space projects such as space stations, large unmanned space structures, interplanetary spacecraft, and lunar and Mars bases will require highly reliable launch systems for their construction and logistic support. It may also be necessary to provide “guaranteed” commercial launches. These needs will place increased emphasis on mastering every aspect of launch‐vehicle operations, particularly a launch‐on‐time capability. Causes for delay during launch, i.e., unplanned “holds,” are attributable to several sources: weather, range activities, vehicle conditions, human performance, and so forth. In this paper, actual launch data on unscheduled hold distributions of various launch vehicles are presented. The data were supplied by industrial associate companies of the Center for Space Construction of the University of Colorado, Boulder. Probability models that can describe these historical data and be used for several purposes are determined: (1) As inputs to broader simulations of launch‐vehicle logistic space construction support processes; (2) to determine which launch operations sources cause the majority of the unscheduled holds; and (3) to suggest changes that might improve launch on time. The paper demonstrates the ability of a compound distribution probability model to fit the actual data. This model is then manipulated to develop a method for optimally improving launch‐on‐time probability.     

Bridging the gap: Transitive associations between items presented in similar temporal contexts.

In episodic memory tasks, associations are formed between items presented close together in time. The temporal context model (TCM) hypothesizes that this contiguity effect is a consequence of shared temporal context rather than temporal proximity per se. Using double-function lists of paired associates (e.g., A–B, B–C) presented in a random order, the authors examined associations between items that were not presented close together in time but that were presented in similar temporal contexts. After learning, across-pair associations fell off with distance in the list, as if subjects had integrated the pairs into a coherent memory structure. Within-pair associations (e.g., A–B) were strongly asymmetric favoring forward transitions; across-pair associations (e.g., A–C) showed no evidence of asymmetry. While this pattern of results presented a stern challenge for a heteroassociative mediated chaining model, TCM provided an excellent fit to the data. These findings suggest that contiguity effects in episodic memory do not reflect direct associations between items but rather a process of binding, encoding, and retrieval of a gradually changing representation of temporal context. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optimal Planning and Scheduling for Repetitive Construction Projects

This paper presents a multiobjective optimization model for the planning and scheduling of repetitive construction projects. The model enables construction planners to generate and evaluate optimal construction plans that minimize project duration and maximize crew work continuity, simultaneously. The computations in the present model are organized in three major modules: scheduling, optimization, and ranking modules. First, the scheduling module uses a resource-driven scheduling algorithm to develop practical schedules for repetitive construction projects. Second, the optimization module utilizes multiobjective genetic algorithms to search for and identify feasible construction plans that establish optimal tradeoffs between project duration and crew work continuity. Third, the ranking module uses multiattribute utility theory to rank the generated plans in order to facilitate the selection and execution of the best overall plan for the project being considered. An application example is analyzed to illustrate the use of the model demonstrate its new capabilities in optimizing the planning and scheduling of repetitive construction projects.     

Grid-Enabled Simulation-Optimization Framework for Environmental Characterization

Many engineering and environmental problems that involve the determination of unknown system characteristics from observation data can be categorized as inverse problems. A common approach undertaken to solve such problems is the simulation-optimization approach where simulation models are coupled with optimization or search methods. Simulation-optimization approaches, particularly in environmental characterization involving natural systems, are computationally expensive due to the complex three-dimensional simulation models required to represent these systems and the large number of such simulations involved. Emerging grid computing environments (e.g., TeraGrid) show promise for improving the computational tractability of these approaches. However, harnessing grid resources for most computational applications is a nontrivial problem due to the complex hierarchy of heterogeneous and geographically distributed resources involved in a grid. This paper reports and discusses the development and evaluation of a grid-enabled simulation-optimization framework for solving environmental characterization problems. The framework is designed in a modular fashion that simplifies coupling with simulation model executables, allowing application of simulation-optimization approaches across problem domains. The framework architecture utilizes standard communications protocols and the message passing interface with an application programming interface to establish a connection between a centralized search application and simulation models running on TeraGrid resources. Sets of performance and scalability results for solving a groundwater source history reconstruction (SHR) problem are presented. The results show that for a given set of resources, parameters controlling the granularity at various levels of parallelism play an important role in the overall parallel performance. A production run for solving the SHR problem using three geographically distributed grid resources indicates that even in a cross-site grid environment a factor of 90 speedup is possible using 140 computer processors.     

Effets de distribution du voisinage orthographique et d'amor?age par répétition masqué.

This research centres on the effect that the orthographic neighbourhood has in the visual recognition of words. Specifically, we studied to what extent orthographic neighbourhood distribution, that is, the number of letter positions allowing formation of at least one neighbour (Pugh, Rexer, Peter, & Katz, 1994), influences the masked repetition priming effect. In a previous study (Mathey, Robert, & Zagar, 2004), interaction between neighbourhood distribution and orthographic priming was obtained in the lexical decision task. The Interactive Activation Model (IA; McClelland & Rumelhart, 1981) simulated this interaction. With the orthographic priming effect modified for distribution of the neighbourhood of target words, it was necessary to study whether the repetition priming effect also varied as a function of this indicator. Studying this interaction presents a major theoretical issue in specifying the activating and inhibiting processes presented in the IA model. Simulations were produced to obtain precise model predictions regard regarding the neighbourhood distribution effect in a repetitive priming situation for our experimental material. Target words all had two neighbours that were most frequent. These neighbours were isolated, that is, distributed over two letter positions (e.g.: TAUX/faux-toux), or associated, i.e., concentrated on one single position (e.g., SEAU/beaupeau). Targets were preceded by an identical priming (repetitive priming; e.g.: seau-SEAU) or by controlled priming (e.g., &&&&-SEAU). The simulation results obtained using the IA model show the facilitating effects of neighbourhood distribution and repetitive priming, but no interaction between these factors. The experimental results obtained in a lexical decision task confirm these predictions. Thus, the empirical data replicate the neighbourhood distribution's facilitating effect (Mathey & Zagar, 2000) as well as the facilitating effect of masked repetition (Forster & Davis, 1984). Finally, the most interesting result is that the facilitating effect of repetition is comparable for target words with associated neighbours and target words with isolated neighbours. An explanation of the combined effects of the orthographic neighbourhood and orthographic masked repetition priming, integrating data from literature as well as from the current study, is proposed within the framework of the IA model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hybrid Model Incorporating Real Options with Process Centric and System Dynamics Modeling to Assess Value of Investments in Alternative Dispute Resolution Techniques

Project-specific dispute resolution ladders (DRLs) are typically implemented in construction projects to resolve issues arising between the project participants. The DRL typically consists of single or multiple alternative dispute resolution (ADR) techniques to address construction issues at the three levels of escalation: conflicts; disputes; and claims. However, a DRL requires significant investments to cover the direct costs incurred in-house by the project participants or, externally, if construction specialists and lawyers are recruited to assist in the resolution. Thus, the benefits of the DRL implementation in a construction project must outweigh its costs for the implementation to be worthwhile. This paper presents a methodology to study the effect of different resolution strategies on the value of the investment in a DRL using option/real option theories from financial engineering, process centric modeling, and system dynamics methodology. Of particular interest in this paper is the integration of these research methodologies into a computer model to support the evaluation of the DRL investment in a particular construction project by taking into account the characteristics of (1) the project and (2) the different ADR techniques chosen for the DRL implementation. Finally, an example is presented to illustrate the application of the computer model in a real construction project. The results of the simulation serve two main purposes. First, the results of the simulation are used to verify the intended model behavior in terms of proper integration of the three methodologies (i.e., real options, process centric, and system dynamics) in one computer system. Second, the model application to a real construction project using actual project data illustrates the potential of the model in providing the project participants with information related to the expected number of claims and change orders resolved at each level of the DRL, the change in the expected savings during the construction phase, and finally the value of the investment from the perspective of the project owner.     

Stress and Displacement around an Elastic Artificial Rectangular Hole

In engineering practice, rectangular holes (openings) are often encountered. The presence of rectangular holes increases the complexity of the analysis of engineering media (e.g., soils around a diaphragm wall panel) and structural members (e.g., floor slabs). However, there is currently no simple but sufficiently accurate solution readily available for engineers to obtain stress and displacement distributions around an artificial rectangular hole in an elastic plate. This paper presents a simple approximate solution to the problem for an infinite elastic and isotropic plate subjected to uniaxial stress at infinity. A linear elastic plane stress analysis is carried out using complex variables. By introducing a correction factor, simplified and explicitly expressed, a general conformal transformation function that transforms the area outside an arbitrary rectangular hole into the region inside a unit circle is created and used to obtain a solution. The solution is verified by comparing the calculated results using a finite-element method. Displacements caused by the formation of a rectangular hole are investigated. The ease of implementation of the solution is illustrated.     

Optimal Schedule Planning for Multiple, Repetitive Construction Process

This study attempts to develop a construction scheduling model using a conceptual approach to improve the efficiency of construction resources for a multiple, repetitive construction process (MRCP). It is important for a project manager to arrange the number of horizontal repetitive work areas by each crew group to reduce the work interruption period in MRCP. This study suggests some equations for estimating the optimal number of horizontal repetitive work areas for a crew group and pursued a conceptual model for MRCP, which can reduce the loss in manpower and use of construction equipment that is caused by work interruption periods. A computer program developed for the analysis of MRCP shows an appropriate performance through the application to a case study based on the proposed procedure model in this study. Supposing that there is time to spare in the project completion date, the result of the study shows that cost loss could be greatly reduced by the proposed methodology.     

Residential Floor Systems: Wood I-Joist Creep Behavior

A creep study was undertaken to characterize the creep response of a wood I-joist framed and oriented strand board (OSB) sheathed floor system under typical residential in-service loads (e.g., gravity and environmental). The study examined one full-scale floor system constructed of composite wood I-joists and OSB sheathing for 508 days of sustained uniformly distributed loads equivalent to the design dead load, 0.48 kPa (10 psf), plus 25% of the design live load, 0.48 kPa (10 psf). The creep deflection of the system fluctuated with changes in environmental condition (e.g., temperature and relative humidity) but virtually stabilized after 168 days of loading regardless of variation in environmental conditions. The average of the individual floor joist ratios of total creep deflection to initial deflection was 1.66 at 508 days for the floor system. The observed ratio is greater than would be applied in standard United States or most international design practices.     

Viscosities of Slags ‐ an Overview

Viscosities of slags constitute an important physical property needed for an understanding of the mass transfer phenomena in metallurgical processes. Viscosity is also the key that leads to a better understanding of the structure of slags. It is well‐known that the viscosities of silicate slags decrease with the addition of basic oxides due to the breaking of the silicate network. The measurements of slag viscosities often pose experimental challenges, especially with respect to the choice of materials. This paper takes up the experimental problems and the various techniques adopted. Dynamic viscosity measurement, as a powerful tool towards an understanding of the kinetics of some high temperature reactions is brought out. A number of semi‐empirical models have been developed to estimate the slag viscosities in the case of multicomponent slags. A critical survey of these models is presented in this paper. Earlier models by Riboud et al., Urbain et al. and Mills et al. have been developed further into a new generation of models. Some of the current important models are, (1) Model by lida et al., (2) CSIRO model, (3) Pyroresearch Model, (4) Model by Tanaka et al., (5) Model approach by Reddy et al., and (6) KTH‐model. The predictions and capabilities of the various models are compared. Estimations of viscosities from thermodynamic data and prediction of liquidus temperatures from viscosities are presented. The concept of surface viscosities with reference to slags and viscosities of two‐phase mixtures are also taken up in the presentation.     

A method for knowing the statistical reliability of instrumental measurements

The precision of instrumental measurements, usually expressed by SD (standard deviation) or RSD (relative standard deviation) is of importance in a society as well as in a world of analytical chemistry. For example, the detection limit and confidence intervals of calibration lines which are based on the precision are inevitable for regulatory science. As is well-known in statistics, however, a small number of repetitive experiments (e.g., 5) lead to a poor reliability of the precision. This presentation shows a method (called FUMI theory) which can provide a precision from a single measurement of noise and signal without any repetitive measurements. The statistical reliability of the precision from the FUMI theory corresponds to that from the repetitive method of 50 experiments.     

ANSWAPPS: Model for the Analysis of Grass Swale-Perforated Pipe Systems

A computer model for the analysis and design of grass swale perforated pipe systems is presented. The model, which was calibrated and validated using experimental as well as field data, performs detailed computations for flow through the system on a lot by lot basis (i.e., from one catchbasin to another). Several parameters affecting the system performance are considered in the modeling approach. These especially included lot size and imperviousness, grass swale dimensions and its infiltration capacity, pipe length, number of orifices and their configuration, trench dimensions, and native soil infiltration capacity. The model was used to simulate the minimum trench depth required to capture runoff from a 25?mm storm for different native soils and different lot imperviousness ratios. Trench depths varied from 0.3 to 1.4?mm depending on native soil infiltration capacity and lot imperviousness.     

Efficient Repetitive Scheduling for High-Rise Construction

A new scheduling and cost optimization model for high-rise construction is presented in this paper. The model has been formulated with a unique representation of the activities that form the building’s structural core, which need to be dealt with carefully to avoid scheduling errors. In addition, the model has been formulated incorporating: (1) the logical relationships within each floor and among floors of varying sizes; (2) work continuity and crew synchronization; (3) optional estimates and seasonal productivity factors; (4) prespecified deadline, work interruptions, and resource constraints; and (5) a genetic algorithms-based cost optimization that determines the combination of construction methods, number of crews, and work interruptions that meet schedule constraints. A computer prototype was then developed to demonstrate the model’s usefulness on a case study high-rise project. The model is useful to both researchers and practitioners as it better suits the environment of high-rise construction, avoids scheduling errors, optimizes cost, and provides a legible presentation of resource assignments and progress data.     

Processing causal and diagnostic statements in discourse.

Diagnostic statements (e.g., It is raining because the streets are wet) take longer to read than causal statements (e.g., The streets are wet because it is raining). The authors present 4 experiments investigating this phenomenon. In Experiment 1, a reading-time study, the authors demonstrate that this difficulty is reversed when a more complex mental model is cued through the use of phrases like John thinks that and John says that. Experiment 2 shows that the use of a modal construction (e.g., Perhaps it is raining because the streets are wet) makes the processing of diagnostics as easy as processing causals but does not disadvantage causals. The authors explain the pattern of results by proposing that readers build the simplest possible discourse representation during interpretation and that readers adopt a specific pattern of semantic interpretation. These proposals are tested and verified in Experiments 3 and 4. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reasoning by model: The case of multiple quantification.

A theory of deductive reasoning is presented for a major class of inferences that has not been investigated by psychologists: inferences that depend on multiply-quantified premises (e.g., "None of the Princeton letters is in the same place as any of the Dublin letters"). It is argued that reasoners construct mental models based on their knowledge of the meanings of quantifiers (and other terms, including relational expressions). Three experiments corroborate the model theory's prediction that inferences that require the construction of only 1 model will be easier than those that require more than 1 model. The model theory assumes that the logical properties of quantifiers emerge from their meanings and are not mentally represented in rules of inference. How such a semantic process can occur compositionally (i.e., guided by the syntactic analysis of sentences) is described. (PsycINFO Database Record (c) 2010 APA, all rights reserved)