bluuebunny/crossref_metadata_2025_split huggingface dataset:
Primary mouse embryonic fibroblasts: A model of mesenchymal cartilage formation
Authors: Lengner Christopher J. , Lepper Christoph , van Wijnen Andre J. , Stein Janet L. , Stein Gary S. , Lian Jane B. 
Published: June 2004

AbstractCartilage formation is an intricate process that requires temporal and spatial organization of regulatory factors in order for a mesenchymal progenitor cell to differentiate through the distinct stages of chondrogenesis. Gene function during this process has best been studied by analysis of in vivo cartilage formation in genetically altered mouse models. Mouse embryonic fibroblasts (MEFs) isolated from such mouse models have been widely used for the study of growth control and DNA damage response. Here, we address the potential of MEFs to undergo chondrogenic differentiation. We demonstrate for the first time that MEFs can enter and complete the program of chondrogenic differentiation ex vivo, from undifferentiated progenitor cells to mature, hypertrophic chondrocytes. We show that chondrogenic differentiation can be induced by cell–cell contact or BMP‐2 treatment, while in combination, these conditions synergistically enhance chondrocyte differentiation resulting in the formation of 3‐dimensional (3‐D) cartilaginous tissue ex vivo. Temporal expression profiles of pro‐chondrogenic transcription factors Bapx1 and Sox9 and cartilaginous extracellular matrix (ECM) proteins Collagen Type II and X (Coll II and Coll X) demonstrate that the in vivo progression of chondrocyte maturation is recapitulated in the MEF model system. Our findings establish the MEF as a powerful tool for the generation of cartilaginous tissue ex vivo and for the study of gene function during chondrogenesis. © 2004 Wiley‐Liss, Inc.
Quasistatic and dynamic problems in viscoplasticity theory—non‐linearities with power growth
Authors: Pompe Waldemar 
Published: June 2004

AbstractWe find a common abstract formulation of the quasistatic and dynamic problems from viscoplasticity theory. Based on this formulation we show existence and uniqueness of the solution to this abstract problem by choosing appropriate spaces and by reducing the problem to an evolution equation, which can be treated by the general theory of monotone operators in Hilbert space. Our proof is valid for non‐linearities in the constitutive equation with power law growth. Copyright © 2004 John Wiley & Sons, Ltd.
A three dimensional embedded beam element for reinforced geomaterials
Authors: Sadek Machhour , Shahrour Isam 
Published: June 2004

AbstractThis paper presents the formulation and verification of a 3D embedded beam element, which is intended for numerical modelling of three dimensional problems concerned by reinforced geomaterials. This element permits analysis of reinforced geomaterial structures with simplified meshes, that do not need to account for reinforcement orientation. The paper is composed of four sections. Section 1 discusses the need for the development of a particular beam element for soil reinforcement, which can be easily used in practical applications. Section 2 describes the mathematical formulation of this element, while Section 3 deals with its verification on various examples. Section 4 illustrates an application of this element by analysing the behaviour of a group of micropiles containing inclined elements and subjected to lateral loading. Copyright © 2004 John Wiley & Sons, Ltd.
Deterministic and stochastic scheduling with teamwork tasks
Authors: Cai Xiaoqiang , Zhou Xian 
Published: June 2004

AbstractWe study a class of new scheduling problems which involve types of teamwork tasks. Each teamwork task consists of several components, and requires a team of processors to complete, with each team member to process a particular component of the task. Once the processor completes its work on the task, it will be available immediately to work on the next task regardless of whether the other components of the last task have been completed or not. Thus, the processors in a team neither have to start, nor have to finish, at the same time as they process a task. A task is completed only when all of its components have been processed. The problem is to find an optimal schedule to process all tasks, under a given objective measure. We consider both deterministic and stochastic models. For the deterministic model, we find that the optimal schedule exhibits the pattern that all processors must adopt the same sequence to process the tasks, even under a general objective function GC = F(f1(C1), f2(C2), … , fn(Cn)), where fi(Ci) is a general, nondecreasing function of the completion time Ci of task i. We show that the optimal sequence to minimize the maximum cost MC = max fi(Ci) can be derived by a simple rule if there exists an order f1(t) ≤ … ≤ fn(t) for all t between the functions {fi(t)}. We further show that the optimal sequence to minimize the total cost TC = ∑ fi(Ci) can be constructed by a dynamic programming algorithm. For the stochastic model, we study three optimization criteria: (A) almost sure minimization; (B) stochastic ordering; and (C) expected cost minimization. For criterion (A), we show that the results for the corresponding deterministic model can be easily generalized. However, stochastic problems with criteria (B) and (C) become quite difficult. Conditions under which the optimal solutions can be found for these two criteria are derived. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004
Stochastic scheduling subject to machine breakdowns: The preemptive‐repeat model with discounted reward and other criteria
Authors: Cai Xiaoqiang , Sun Xiaoqian , Zhou Xian 
Published: June 2004

AbstractWe consider the problem of scheduling a set of jobs on a single machine subject to random breakdowns. We focus on the preemptive‐repeat model, which addresses the situation where, if a machine breaks down during the processing of a job, the work done on the job prior to the breakdown is lost and the job will have to be started from the beginning again when the machine resumes its work. We allow that (i) the uptimes and downtimes of the machine follow general probability distributions, (ii) the breakdown process of the machine depends upon the job being processed, (iii) the processing times of the jobs are random variables following arbitrary distributions, and (iv) after a breakdown, the processing time of a job may either remain a same but unknown amount, or be resampled according to its probability distribution. We first derive the optimal policy for a class of problems under the criterion to maximize the expected discounted reward earned from completing all jobs. The result is then applied to further obtain the optimal policies for other due date‐related criteria. We also discuss a method to compute the moments and probability distributions of job completion times by using their Laplace transforms, which can convert a general stochastic scheduling problem to its deterministic equivalent. The weighted squared flowtime problem and the maintenance checkup and repair problem are analyzed as applications. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004
Wavefront reduction using graphs, neural networks and genetic algorithm
Authors: Kaveh A. , Bondarabady H. A. Rahimi 
Published: June 2004

AbstractThis paper presents an algorithm for nodal numbering in order to obtain a small wavefront. Element clique graphs are employed as the mathematical models of finite element meshes. A priority function containing five vectors is used, which can be viewed as a generalization of Sloan's function. These vectors represent different connectivity properties of the graph models. Unlike Sloan's algorithm, which uses two fixed coefficients, here, five coefficients are employed, based on an evaluation by artificial neural networks. The networks weights are obtained using a simple genetic algorithm. Examples are included to illustrate the performance of the present hybrid method. Copyright © 2004 John Wiley & Sons, Ltd.
Radical copolymerization of maleimide with ethyl α‐ethylacrylate and α‐ethylacrylic acid via RAFT
Authors: Ren Yong , Zhu Zhongliang , Huang Junlian 
Published: June 2004

AbstractThe copolymerization of maleimide (MI) with α‐ethylacrylic acid (EAA) and with ethyl α‐ethylacrylate (EEA) in the presence of 2‐phenylprop‐2‐yl dithiobenzoate (PPDB) was investigated. The copolymerization of MI and EAA was difficult to conduct with the reversible addition–fragmentation chain transfer (RAFT) mechanism because reinitiation of expelled radicals by fragmentation chain transfer was inhibited by the association of EAA in polar solvent and the strong interaction of the imino of MI with the carboxyl of EAA between the propagation chains. When the carboxylic group of EAA was esterified, then the copolymerization went well via RAFT, and alternating copolymers with controlled molecular weight were obtained. Combining by electron spin resonance showed a different result. It was found that before 30% of the comonomer conversion had occurred, the copolymer poly(EEA‐co‐MI) showed increasing molecular weight with the conversion and a rather narrow molecular weight distribution; then the molecular weight of the copolymer began to retard. This phenomenon of retardation was aggravated at high temperature. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3828–3835, 2004
Permeability of N2, Ar, He, O2, and CO2 through as‐extruded amorphous and biaxially oriented polyester films: Dependence on chain mobility
Authors: McGonigle E.‐A. , Liggat J. J. , Pethrick R. A. , Jenkins S. D. , Daly J. H. , Hayward D. 
Published: June 2004

AbstractFor as‐extruded amorphous and biaxially orientated polyester films based on poly(ethylene terephthalate), poly(ethylene naphthalate), and copolymers containing poly(ethylene terephthalate) and poly(ethylene naphthalate) moieties, permeability, diffusion, and solubility coefficients are interpreted in terms of chain mobility. The influence of polymer morphology is determined by comparison of the data for as‐extruded amorphous sheets and materials produced with different biaxial draw ratios. The crystallinities of the samples were assessed using differential scanning calorimetry and density measurements. Changes in mobility at a molecular level were investigated using dielectric spectroscopy and dynamic mechanical thermal analysis. The study, in conjunction with our earlier work, leads to the conclusion that the key to understanding differences in gas transport is the difference in local chain motions rather than in free volume. This was illustrated by the permeability results for He, Ar, N2, and O2 in the range of polyesters. However, the permeability of CO2 was found to require alternative explanations because of polymer–penetrant interactions. For biaxially oriented samples, the differences in diffusivity are not only due to differences in local chain motions, but also additional constraints resulting from the increased crystallinity and chain rigidity—which also act to hinder segmental mobility. The effectiveness of the reduction in permeability in the biaxially oriented films is consequently determined by the ability of the polymer chains to effectively align and form crystalline structures. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2916–2929, 2004
Statistical evaluation of Lower Flammability Distance (LFD) using four hazardous release models
Authors: Kumar Ashok , Luo Jie , Bennett Gary F. 
Published: June 2004

AbstractUsing four hazardous dispersion models, the ability to predict Lower Flammability Distance (LFD), the distance from a release through which the released gas is present in concentration below flammable range, has been evaluated using a set of large‐scale propane release field experiment data. The four models evaluated were the DEGADIS model, the SLAB model, the OME Simple Gas model and the OME Heavy Gas model (1983). The observed LFDs were compared with the predicted LFDs for three atmospheric conditions. The complete data set was broken into two parts: (1) the cyclone type releases (representing instantaneous release situations) and (2) the nozzle type releases (representing horizontal jet releases). A procedure based on the USEPA guidelines on air quality models was followed to evaluate the models.The complex models (DEGADIS and SLAB models) appear unreasonably weak in predicting LFD's compared with the relatively simple Gaussian model used in the OME Simple Gas model for instantaneous releases. The OME simple gas model is significantly better than the DEGADIS and SLAB models for cyclone type (instantaneous) releases under unstable and neutral atmospheric conditions; and the DEGASIS model is significantly better than the SLAB model for nozzle type (horizontal jet) releases under stable atmospheric conditions. Since the size of the data set is not large enough (n = 20 for cyclone type release and n = 18 for nozzle type release), it is difficult to show 95% significant differences between models.
Static hazards using flexible intermediate bulk containers for powder handling
Authors: Britton Laurence G. 
Published: June 2004

AbstractFIBC use is increasing rapidly owing principally to improved handling efficiency and product quality improvement. However, selection of the proper FIBC has many aspects, of which safety is paramount. Numerous accidents have occurred when emptying flammable powders from FIBCs, both with and without flammable vapors additionally present. Owing to the mode of operation and speed of emptying, not only is there a high probability of static generation but also a high probability of one or more operators being in the flash fire zone should ignition occur. Apart from the flash fire produced by a dust cloud and/or flammable vapors displaced from a receiving vessel, a flame may in some cases propagate into the FIBC, which might then explode. This paper discusses the FIBC selection problem, a series of case histories, and available literature. Since no FIBC loading incidents are known, the paper will focus on emptying. In particular it should be appeciated that the potential for operator grounding error and sudden nemesis can be very high.
Dispersion of instantaneous jets
Authors: Landis John G. , Linney Robert E. , Hanley Brian F. 
Published: June 2004

AbstractWhen a gas under pressure is released, the momentum imparted to it causes the gas to mix with the surrounding air. A series of tests was carried out, and a model was used to determine the dynamics of the gas and air mixing for releases of a very short time duration. The amount of mixing that occurs when a pressurized fluid is released was determined by filling a container with varying mixtures of fumed silica and nitrogen, by bursting the container's rupture disks at fixed pressures, and by measuring the cloud velocity, location, and size at successive time intervals. A two‐stage model was developed to predict the location, size, and fluid concentration (i.e., degree of dilution) of the cloud resulting from the release of a two‐phase fluid composed of a non‐flashing or non‐evaporating dense phase. The dimensionless form of the model (ρ0u0t/ρ0r0) was found to correlate the cloud properties over initial pressures ranging from 3.1 to 70.7 barg (46 to 1025 psig), and gas quality ranging from 0.2 to 0.7 (gas mass fraction). Both the model and the data showed that the initial fluid concentration was reduced by factor of 300 to 1000 as a result of the momentum imparted mixing. This dilution is in addition to that resulting from atmospheric dispersion. Combining the predicted dilution effect from the instantaneous release with atmospheric dispersion to predict both near field and far‐field concentration is an important application of this two stage model.
Safety and chemical engineering education
Authors: Louvar J. F. , Kubias F. O. 
Published: June 2004

AbstractSACHE, or Safety and Chemical Engineering Education, is a project under the auspices of AIChE's Center for Chemical Process Safety (CCPS). SACHE's mission is to assist universities to add an element of process safety to their undergraduate curriculum.This project is funded by university members ($300/year/school) and CCPS ($30,000 annually). With the current membership of 72 universities, this gives SACHE an annual budget of $52,000 to produce teaching aids for universities. The teaching aids which have been produced and distributed to member universities include slide packages with scripts, videos, problems for use in class, and instructional modules covering technical subjects or case histories.The SACHE products are primarily developed for universities; therefore, they contain (a) the fundamentals, (b) good illustrations, and (c) text to assist the professors develop effective educational exercises. Industry is also discovering that these products are valuable training aids; products are available via CCPS publications.
Static electricity hazards of flexible intermediate bulk container (FIBC)
Authors: Dahn C. James , Kashani A. , Reyes B. 
Published: June 2004

AbstractFlexible intermediate bulk containers are being widely used. Much concern has been expressed regarding the electrostatic discharge hazards around flammable vapor/air mixtures and some very sensitive dust clouds. Methods were developed to analyze and test powders with FIBC materials to predict full scale electrostatic charging characteristics. Comparison with full scale FIBC operations shows very good correlation. Operations using FIBCs, including grounded versions are not recommended in flammable vapor environments. When dusty powders with low dust cloud ignition energies are used for FIBC systems, engineering analysis and testing is required to assure ESD safety.
Investigation of a thermal runaway hazard‐drum storage of thionyl chloride/ethyl acetate mixture
Authors: Wang Steve S. Y. , Kiang San , Merkl William 
Published: June 2004

AbstractThionyl chlorie is routinely shipped in galvanized drums. The compatibility of this drum for the storage of a mixture of thionyl chloride and ethyl acetate was investigated by thermochemical studies, condensed phase and off gas analysis. The chemical incompatibility of the ternary mixtures (thionyl chloride/ethyl acetate/zinc) resulted in an exothermic runaway reaction with extensive gas evolution, which has not been heretofore described in the literature. Storage in a drum was simulated in a half‐liter, high pressure containment vessel. Adiabatic calorimeter data are also presented to illustrate the mass transfer process involved in the induction period and the runaway reaction characteristics. Ethyl acetate is inert with thionyl chloride. However, in the presence of metallic zinc, an equimolar amount of each component are consumed by the reaction to generate ethyl chloride (g), sulfur dioxide (g), acetyl chloride (l) and sulfur (s). It was also found that the rate of gas evolution is highly dependent on the molar ratio of the thionyl chloride or ethyl acetate to metallic zinc in the solution. Based on the semi‐batch process experiments, the reaction mechanism is proposed. A potential hazard indication based on the oxygen balance for the reaction mixture is also discussed. Data on similar ternary mixtures are presented.
Loss prevention in a modern ethylene plant
Authors: Olivo John 
Published: June 2004

AbstractQuantum's Deer Park Ethylene Plant was built with a philosophy of risk management which was based on loss prevention. To this end, the plant incorporates a number of concepts designed to effect early detection containment and dispersion of hydrocarbon releases. Features include a gas detection grid system, water curtain in the furnace/boiler area with open path IR detector, extensive deluge systems on equipment and in pipe racks, remote television monitoring, large portable monitors (as well as the more standard plant safety systems such as hydrants), fixed monitors, and foam generators.The systems described are monitored by means of a graphic panel and alarm console located in the Central Control Room. This centralized facility enables the operator to monitor and activate the proper subsystems and provide a visual interface between the operator and the physical plant.
An accurate methodology for modeling the characteristics of explosion effects
Authors: Madsen Warren W. , Wagner Robert C. 
Published: June 2004

AbstractA new means for modeling blast effects of all types of reactants including vapor cloud explosions has been developed and verified against empirical data. Methods such as the TNT‐equivalency model are still being widely used to simulate vapor cloud explosions and blast effects. However, many limitations exist in the accuracy of those models. Use of such flawed models could potentially provide for deleterious results from an explosion such as loss of property and/or life as well as the ramifications of liability. This should be of extreme interest to not only the chemical process industry, but also to insurerers who must understand the nature of the risk that is being under written, government safety compliance organizations and the legal profession which must either defend or litigate liability cases resulting from explosions.The computer code, CMBWAT, models the physics of detonations and deflagrations occurring in the reaction zone and the resulting shock wave which attenuates with distance. It computes static and stagnation pressure, velocity and the shock wave impulse delivered to target surfaces within the flow field, all as a function of time, both for the incident and reflected waves. Data resulting from these analyses are used to examine the structural response of the object due to the resulting shock and to determine proper risk mitigation solutions to minimize damage effects. The model can also examine the physics of solid or vapor reactants including nuclear explosions.Systems Integration Corporation has developed this code which was independently verified against actual test data by Sandia National Laboratory. The Nuclear Regulatory Agency is currently revising its REG GUIDE 131 as a result of this work.
Improved fire and explosion index hazard classification
Authors: Scheffler Norman E. 
Published: June 2004

AbstractThe Fire and Explosion Index (F&EI) is one of the most widely used hazard indices for chemical process plants. It was developed by The Dow Chemical Company in 1964 and has been improved, enhanced and simplified through the publishing of six editions. This paper describes the latest 7th edition and the improvements it contains. The F&EI is to serve as a guide for evaluating the hazard potential for separate major units of chemical process plants, is to aid in determining the consequences of a fire or an explosion and is to help determine appropriate loss prevention features to be used.Efforts have been made to make the task of completing the F&EI form easier and the results more consistent based on the most current and accurate material property data. Some of the major features of the revised F&EI are:

Improvement of readability and corrections to previous edition.
Addition of F&EI versus Degree of Hazard table.
Major upgrading of data table which gives key chemical properties and materials factors.
Revised, streamlined F&EI forms available in computer spreadsheet form.
Improvement in data plots with equations developed for ease of calculations.
Adjustments and updating of credit factors and check lists.
The main purpose for creating the 7th edition is to update information, procedures and data to make the F&EI and auxiliary calculations more accurate and easier to perform. There are no fundamental changes in the methodology. Use of the new Fire & Explosion Index Hazard Classification Guide should lead to better determination of this important hazard index which is a valuable tool for analyzing risks for chemical process plants and selection of appropriate measures. The revised F&EI guideline will be made available as an AIChE publication as it has been since 1966.