555 research outputs found
Phase-resolved PIV measurements of the flow between a pair of corotating disks in a cylindrical enclosure
No full textAnalysis of Single Buffer Random Polling System With State-Dependent Input Process and Server/Station Breakdowns
No full textModels and analytical techniques are developed to evaluate the performance of two variations of single buffers (conventional and buffer relaxation system) multiple queues system. In the conventional system, each queue can have at most one customer at any time and newly arriving customers find the buffer full are lost. In the buffer relaxation system, the queue being served may have two customers, while each of the other queues may have at most one customer. Thomas Y.S. Lee developed a state-dependent non-linear model of uncertainty for analyzing a random polling system with server breakdown/repair, multi-phase service, correlated input processes, and single buffers. The state-dependent non-linear model of uncertainty introduced in this paper allows us to incorporate correlated arrival processes where the customer arrival rate depends on the location of the server and/or the server's mode of operation into the polling model. The author allows the possibility that the server is unreliable. Specifically, when the server visits a queue, Lee assumes that the system is subject to two types of failures: queue-dependent, and general. General failures are observed upon server arrival at a queue. But there are two possibilities that a queue-dependent breakdown (if occurs) can be observed; (i) is observed immediately when it occurs and (ii) is observed only at the end of the current service. In both cases, a repair process is initiated immediately after the queue-dependent breakdown is observed. The author's model allows the possibility of the server breakdowns/repair process to be non-stationary in the number of breakdowns/repairs to reflect that breakdowns/repairs or customer processing may be progressively easier or harder, or that they follow a more general learning curve. Thomas Y.S. Lee will show that his model encompasses a variety of examples. He was able to perform both transient and steady state analysis. The steady state analysis allows us to compute several performance measures including the average customer waiting time, loss probability, throughput and mean cycle time.</jats:p
Underwater spark discharge with long transmission line for cleaning horizontal wells
No full textA transmission line is discussed for application in an underwater spark-discharge technique in the cleaning of a horizontal well by incorporating a power-transmission model into the simulation. The pulsed-spark-discharge technique has been proposed for clogged-well rehabilitation, because it removes incrustations that are attached to well screens by using strong pressure waves that are generated by the rapid expansion of a spark channel. To apply the pulsed-spark-discharge technique to the cleaning of horizontal wells, the coaxial cable between the pulsed power supply and the spark gap as a load needs to be extended to a few hundred meters. Prior to field application, pulsed-spark-discharge experiments were conducted and the role of the transmission line was examined using an improved simulation model. In the model, a non-linear interaction of the spark channel and the capacitor bank is described by the pulse-forming action of the coaxial cable. Based on the accurate physical properties of the water plasma, such as the equation of state and electrical conductivity within the region of interest, the amount of energy contributed to the development of a shock wave was evaluated. The simulation shows that if the initial conditions of the spark channel are the same, no further reduction in strength of the pressure wave occurs, even if the cable length is increased above 50 m. Hence, the degraded peak pressure that was observed in the experiments using the longer cable is attributed to a change in the initial condition of the spark channel. The parametric study suggests that the low initial charging voltage, the high ambient water pressure, and the long cable length yield the low initial spark-channel density, which results in a reduced peak pressure. The simulation of line charging is presented to discuss the principle of disturbing the pre-breakdown process by an extended cable. © 2017 Author(s).OAIID:RECH_ACHV_DSTSH_NO:T201719639RECH_ACHV_FG:RR00200001ADJUST_YN:EMP_ID:A080568CITE_RATE:0DEPT_NM:에너지시스템공학부EMAIL:[email protected]_YN:NN
A Study of Zeolite Membrane Material Balance and Commercialization Potential
No full textabstract: The United States and most of the world is pushing to significantly reduce carbon emissions, with many countries intent on fostering carbon negative energy processes to offset ozone depletion and climate changes. 30% of the U.S. greenhouse gas emissions are generated from the combustion of fossil fuels to generate electricity1. Current commercial IGCC carbon capture processes employ a capital and operating cost intensive water-gas shift reaction facilitated by a high temperature reactor followed by a low temperature reactor and an amine absorber to separate the hydrogen and carbon dioxide streams to capture the carbon. Dr. Jerry Y.S. and his laboratory at Arizona State have developed a hydrogen permselective MFI type ZSM-5 zeolite membrane reactor that effectively facilities the water gas shift reaction with high conversion and separates the CO2 and H2 streams during reaction to generate ultrapure retentate and permeate streams. The membrane, formed by secondary free growth, is synthesized on an ultrapure a-alumina membrane support currently purchased from an outside vendor. The purpose of this study was to design an α-alumina support processing plant with capability to supply one full-scale commercial reactor annually with membranes. The design yielded a DCFRoR of 71% for a 20-year project life. A zeolite membrane processing material balance was conducted using alumina support as the raw material. The study showed very low material costs and consumption rates for all materials except a gas used to refine the membrane after processing. The results of both studies were favorable enough to suggest further study
Democratization and Institutionalization-- A Reflection of Latin American Experience
No full text本文適過解放、自由化、民主化的名詞解析，以比較眼光分析拉丁美洲的民主化困局。作者以此一分析架構，初步檢討拉丁美洲「民主─威權」循環模式的成因及轉型的關鍵因素，可做為分析拉丁美洲政局的一項參考架構。This essay compares and analyses the concepts of liberation, liberalization, democratizations and their interactions in Latin American politics. According to this analytical framework, the author makes a preliminary analysis of the “democracy-authoritarianism-democracy” cycle in the Latin political history. This essay also discusses the causes and consequences of liberalization and democratization during the 1970’s and 1980’s
Development of a soft x-ray (SXR) array diagnostic system on versatile experiment spherical torus (VEST)
No full text© 2022 Author(s).A new soft x-ray (SXR) array diagnostic system has been developed on versatile experiment spherical torus (VEST) for measurements of 2D SXR emissivity profile and identification of poloidal mode structure. Through tomographic inversion techniques, 2D SXR emissivity profile can be acquired from the line-integrated SXR data, which enables the visualization of mode structure of plasma instability, such as the magnetohydrodynamics mode. The SXR array diagnostic system consists of two 20-channel arrays positioned at the middle and the top on the same poloidal plane for horizontal and vertical lines of sight, respectively. Each array of the diagnostic system uses absolute extreme ultraviolet photodiode array as the detector. To apply appropriate filters (up to four) for different energy regimes without breaking the vacuum, a filter wheel and its rotatable vacuum feed-through are installed behind the pinhole. SXR data are acquired with a digitizer at the sampling rate of up to 125 MHz. Finally, we discuss initial measurement data obtained from Ohmic plasma in VEST.N
A bibliometric analysis of the performance of Water Research
Full text link[[abstract]]This paper presents a detailed chronological survey of papers published in the journal titled Water Research which started publication since 1967. This current investigation reviews publication patterns between 1967 and 2008. An analysis of the research performance according to publication output, distribution of words in article title, author keywords, and keywords plus. Performances of countries, institutes, and authors, including total, single, collaborative, first author, and corresponding author publications were analyzed. The most-frequently cited articles each year and the articles of the highest impact in 2008 were also reported. Results showed that ‘‘activated sludge’’ was the most frequently used author keyword, followed by ‘‘adsorption,’’ and ‘‘drinking water.’’ Authors from 114 different countries/territories published in the journal, with the most articles submitted by authors from the USA
Aerobic heterotropoic biodegradation in polluted drains and sewers: The drain and sewer as dual-phase biological reactors
No full textAbstract not availableApplied Science
A finite difference solution for freezing brine on cold substrates of spongy ice
No full textThe process of rapid freezing of a thin layer of brine, suddenly in contact with a cold substrate of brine-spongy ice, is investigated. The mechanism of intermittent ice accretion on cold substrates, which occurs in a short period of time, is different from the slow freezing of salt water and must be evaluated using a differential analysis. Investigation of rapid freezing fills a gap of knowledge related to intermittent icing of superstructures, which has usually been studied using control volume methods. The equation of transient heat conduction through brine-spongy ice is developed. Rapid freezing causes complete solute trapping, which makes the salinity constant and stable at the phase interface. A finite difference method, using uniformly-spaced fixed-grid mesh, is employed as a numerical scheme for calculating the rate of ice accretion. A method is presented for discretization at nodes close to the phase interface for preventing the instability of numerical solutions when the phase interface passes the adjacent nodes. The discretization is based on the Method of Lines (MOL) which is a numerical-iterative method of solution. Numerical results show that higher salinities and lower initial temperatures of brine-spongy substrates have the potential to create a thicker layer of new ice. Experimental studies show that the model and numerical solutions accurately predict the rapid freezing of brine on a cold substrate of brine-spongy ice.Statoil ASA (Norway)MITACSPetroleum Research of Newfoundland & Labrador (PRNL)American Bureau of Shipping (ABS
Water breakup phenomena in wave-impact sea spray on a vessel
No full textBreakup of water in wave-impact sea spray is examined in this paper. The formation of a spray cloud, caused by high energy striking of a sea wave on the bow or hull of a marine vessel, is dependent on the water breakup phenomena and droplet trajectories. The Weber and Reynolds numbers are key parameters defining the thresholds at which breakup begins. The model uses “stripping breakup” and “bag breakup” characteristics to demonstrate the breakup phenomena. A combined breakup model with droplet trajectories is developed in this paper to predict the extent of the breakup phenomena. The governing equations of breakup and trajectories of droplets are solved numerically. Stripping breakup occurs from the beginning of the breakup phenomenon and finishes in front of the vessel. Bag breakup completes the stripping breakup to create stable droplets with constant diameters. A sensitivity analysis evaluates the response of the model to various ranges of initial conditions. Numerical results have reasonable agreement with the size-velocity dependence characteristics at the tip of the bow. The extent of the spray as well as wet heights, obtained by the numerical solutions, are consistent with field observations reported for a Medium-sized Fishing Vessel (MFV).Statoil ASA (Norway)MITACSPetroleum Research of Newfoundland & Labrador (PRNL)American Bureau of Shipping (ABS) Grou
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