• Membrane and Water Treatment
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• v.1 no.1
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• pp.13-37
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• 2010

The performance of an electrodialyzer for concentrating seawater is predicted by means of a computer simulation, which includes the following five steps; Step 1 mass transport; Step 2 current density distribution; Step 3 cell voltage; Step 4 NaCl concentration in a concentrated solution and energy consumption; Step 5 limiting current density. The program is developed on the basis of the following assumption; (1) Solution leakage and electric current leakage in an electrodialyzer are negligible. (2) Direct current electric resistance of a membrane includes the electric resistance of a boundary layer formed on the desalting surface of the membrane due to concentration polarization. (3) Frequency distribution of solution velocity ratio in desalting cells is equated by the normal distribution. (4) Current density i at x distant from the inlets of desalting cells is approximated by the quadratic equation. (5) Voltage difference between the electrodes at the entrance of desalting cells is equal to the value at the exits. (6) Limiting current density of an electrodialyzer is defined as average current density applied to an electrodialyzer when current density reaches the limit of an ion exchange membrane at the outlet of a desalting cell in which linear velocity and electrolyte concentration are the least. (7) Concentrated solutions are extracted from concentrating cells to the outside of the process. The validity of the computer simulation model is demonstrated by comparing the computed results with the performance of electrodialyzers operating in salt-manufacturing plants. The model makes it possible to discuss optimum specifications and operating conditions of a practical-scale electrodialyzer.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1042-1047
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• 2004

Voltage control is an essential part of the electric energy transmission and distribution system to maintain proper voltage limit at the consumer's terminal. Besides the generating units that provide the basic voltage control, there are many additional voltage-controlling agents e.g., shunt capacitors, shunt reactors, static VAr compensators, regulating transformers mentioned in [1], [2]. The most popular one, among all those agents for controlling voltage levels at the distribution and transmission system, is the on-load tap changer transformer. It serves two functions-energy transformation in different voltage levels and the voltage control. Artificial Neural Network (ANN) has been realized as a convenient tool that can be used in controlling the on load tap changer in the distribution transformers. Usage of the ANN in this area needs suitable training and testing data for performance analysis before the practical application. This paper briefly describes a procedure of processing the data to train an Artificial Neural Network (ANN) to control the tap changer operating decision of parallel transformers for a closed primary bus. The data set are used to train a two layer ANN using three different neural net learning algorithms, namely, Standard Backpropagation [3], Bayesian Regularization [4] and Scaled Conjugate Gradient [5]. The experimental results are presented including performance analysis.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.6
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• pp.71-77
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• 2010

Although the problems of defects and nonmetallic inclusion in metal fatigue are very complicated, it is particularly important to view these problems from the perspective that defects and inclusions are virtually equivalent to small cracks. This concept will help one to understand various fatigue phenomena caused by Ductile Cast Iron. For different ferrite-pearlite matrix structure, containing more than 90% spheroidal ratio of graphite, GCD 45-3, GCD 50, GCD 60 series and 70%, 80%, 90% spheroidal ratio of graphite, GCD 40, GCD 45-1, GCD 45-2 series, this paper has carried out image analyzer, estimated maximum and mean size of graphite, investigated correlation. It was concluded as follows. (1) A good quality of Ductile cast iron using in this experiment, the graphite was separated well. The effect of the interaction by graphite was verified by microscopic observation and by fracture mechanics investigation in surface, interior of the specimen. (2)${\sqrt{area}}_{max}$ of graphite can be used to predict fatigue limit of Ductile Cast Iron. The Statistical distribution of extreme values of ${\sqrt{area}}$ may be used as a guide line for the control of inclusion size in the steel making processes.

• Journal of Distribution Science
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• v.16 no.6
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• pp.25-35
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• 2018

Purpose - Although marketing networks are crucial competitive advantage in terms of firm's new information and resource acquisition ability, their impact on new product development performance remains vague, especially under environmental uncertainty. The principal objective of this research is to provide a better understanding of effects of technological uncertainty and volume uncertainty on first tier supplier's perceived performance of new product development under conditions reflecting varying levels of structural holes. Specifically, this research examines the moderating effect of structural holes on the relationship between environmental uncertainty and new product development performance. Research design, data, and methodology - To test the hypotheses, a questionnaire survey was conducted with a Korean engineering firm's major first-tier suppliers in the context of internal network entities, manufacturer-supplier-subsupplier relationships, and to verify the proposed hypotheses, structural equation modeling was established. Construct measures were based on existing measures and previous research. Results - The survey results indicate that technological uncertainty and volume uncertainty differentially affect NPD performance under conditions of high and low structural holes. Conclusions - This study offer some theoretical and practical implications among distribution channel members, especially, this study suggests that interfirm networks have critical competitive advantage in uncertain environments. The distinctiveness of engineering industry might limit the generalizability of the results. Thus, future research should consider a wider range of industries.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.5
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• pp.1639-1648
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• 1996

Protection of gas turbine blade from its erosion and abrasion at high temperature and pressure is the first goal to cleanup the hot gas upstream for IGCC and PFBC. Ceramic filters represent an attractive technology for particle removal at high temperature and high pressure condition. They have demonstrated being a good system for improvement of thermal efficiency and reduction of effluent pollutants in advanced coal-based power systems such as IGCC and PFBC. Ceramic filter elements currently being developed were evaluated in the previous paper. In this paper, we measured the ash size and distribution on cleaning of ceramic candle filter. The results are as follows : in this experimental range, ceramic candle filter was shown to be fully adequate for the removal process of dust under high temperature and pressure. Also filtration efficiency of ceramic candle filter was higher than 98% compared with the regulation limit of particle size in gas turbine inlet.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.288-295
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• 2003

An adaptive procedure in finite element analysis is presented by p-refinement of meshes in conjunction with a posteriori error estimator that is based on the recovery technique. In case of the recovery technique, the SPR(superconvergent patch recovery) approach has been modified for p-adaptive mesh refinement. The strategy of finding a nearly optimal distribution of polynomial degrees on a fixed finite element mesh is discussed such that a particular element has to be refined automatically to obtain an acceptable level of accuracy by increasing p-levels non-uniformly. To verify the proposed algorithm, the limit value approach is proposed which utilizes the exact strain energy computed from the extrapolation equation. A new pre-processor is developed for the p-version finite element program in which the vector graphic editor is used for the automatic generation of node connection and coordinate by halfedge solid data structure according to uniform or nonuniform p-distribution. The general 2-D algorithm is also developed to generate face modes and internal modes in accordance with different mesh types. The quality of the error estimator is investigated with the help of two mumerical examples. The results show that the sequences of p-distributions obtained by the proposed error indicator closely follow the optimal trajectory.

• Nuclear Engineering and Technology
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• v.51 no.6
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• pp.1616-1625
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• 2019

Measuring occurrence times of random events, aimed to determine the statistical properties of the governing stochastic process, is a basic topic in science and engineering, and has been the subject of numerous mathematical modeling approaches. Often, true statistical properties deviate from measured properties due to the so called dead time phenomenon, where for a certain time period following detection, the detection system is not operational. Understanding the dead time effect is especially important in radiation measurements, often characterized by high count rates and a non-reducible detector dead time (originating in the physics of particle detection). The effect of dead time can be interpreted as a suitable rarefied sequence of the original time sequence. This paper provides a limit theorem for a high rate (diffusion-scale) counter with extendable (Type II) dead time, where the underlying counting process is a renewal process with finite second moment for the inter-event distribution. The results are very general, in the sense that they refer to a general inter arrival time and a random dead time with general distribution. Following the theoretical results, we will demonstrate the applicability of the results in three applications: serially connected components, multiplicity counting and measurements of aerosol spatial distribution.

• PNF and Movement
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• v.17 no.1
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• pp.19-29
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• 2019

Purpose: This study was an investigation of the effects of the bridge exercise with the sensory feedback of combined abdominal drawing-in on transverse abdominal and balance in patients with stroke. Methods: Forty subjects were randomly assigned into two groups. Subjects in the bridge exercise group (BG, n = 20) or feedback drawing-in bridge exercise group (FDBG, n = 20) were studied for 30 minutes each, twice daily, for four weeks. Outcomes were measured using affected weight distribution (AWD), anterior limit of stability (ALOS), posterior limit of stability (PLOS), timed up-and-go test (TUG), the Berg balance scale (BBS), and transverse abdominis thickness (TRA) before and after the four-week intervention period. Results: There were significant effects in the FDBG pre-intervention and post-intervention in AWD, ALOS, PLOS, TUG, BBS, and TRA. Conclusion: The results of this study suggest that the bridge exercise with sensory feedback combined with abdominal drawing-in could be beneficial for patients with stroke in terms of transverse abdominal and balance.

• Analytical Science and Technology
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• v.8 no.4
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• pp.1079-1087
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• 1995

The quality of human life is directly related to the quality of the environment. To assess environmental quality we must first determine the MCLG(Maximum Contaminant Level Goal), MCL(Maximum Contaminant Level), environmental impact and so on. The MCLG is the concentration at which no known adverse health effects occur. The MCLG is determined by risk assessment identifying which process is hazardous assessing, dose-response, human exposure, and characteristics of risk. With consideration of analytical methods, treatment technology, cost and regulatory impact, the MCL is set as close to the MCLG as possible. In this way, determination of the concentration and national distribution of contaminants is important for assessment of environmental quality The analytical sciences pose potential problems in assessing environmental quality. Continuing improvement in the performance of analytical instruments and operating technique has been lowering the limits of detectability. Contaminant concentration below the detection limit has usually been reported as ND(Not-Detected) and this has often been misunderstood as equivalent to zero. Because of this, more the contaminant concentration in the past was below the detection limit, whereas contaminants can be quantified now even though the contaminant concentration might remain the same or may even have decreased. In addition, environmental sampling has various components due to heterogeneous matrices. These samples are used to overestimate the concentration of the contaminant due to large variability, resulting in excess readings for MCL. In this paper, the significance of the analytical sciences is emphasized in both a conceptual and a technical approach to environmental assessment.

• Geomechanics and Engineering
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• v.18 no.6
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• pp.595-603
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• 2019

A modified model combining Kriging and Monte Carlo method (MC) is proposed for probabilistic estimation of tunnel face stability in this paper. In the model, a novel uniform design is adopted to train the Kriging, instead of the existing active learning function. It has advantage of avoiding addition of new training points iteratively, and greatly saves the computational time in model training. The kinematic approach of limit analysis is employed to define the deterministic computational model of face failure, in which the Hoek-Brown failure criterion is introduced to account for the nonlinear behaviors of rock mass. The trained Kriging is used as a surrogate model to perform MC with dramatic reduction of calls to actual limit state function. The parameters in Hoek-Brown failure criterion are considered as random variables in the analysis. The failure probability is estimated by direct MC to test the accuracy and efficiency of the proposed probabilistic model. The influences of uncertainty level, correlation relationship and distribution type of random variables are further discussed using the proposed approach. In summary, the probabilistic model is an accurate and economical alternative to perform probabilistic stability analysis of tunnel face excavated in spatially random Hoek- Brown media.