• Journal of Navigation and Port Research
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• v.29 no.5 s.101
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• pp.409-413
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• 2005

The existing control techniques for the operation of a container crane satisfy the terminal condition of controlled variables, but the outcome of input computation is inadequate for the operation of the crane due to heavy movement of inputs. In this study, a new control technique employing a nonlinear model of the crane is proposed to compute the inputs approximated with the 4th-order Chevyshev function. The control objective of sum of absolute deviations is minimized, and the optimization is conducted with the simplex algorithm. The inputs and outputs computed from the proposed technique were compared with the results of the previous study to show that they give more stable crane operation than the existing control technique.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.06a
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• pp.13-22
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• 2003

Train speed and infiltration of rainfall causes railway embankment to be unstable and may result in failure. Therefore, the variation in the safety factor of railway embankment should be analyzed as the function of rainfall intensity, rainfall duration, and train speed and the study is accomplished using numerical analysis program. Based on unsaturated soil engineering, the variables in the shear strength function and permeability function are also defined and used for the numerical model for evaluation of railway embankments under rainfall. As a result of the study, in order to secure the safety of train under rainfall, the variation in the safety factor of railway embankment is predicted as the function of rainfall intensity, duration time and the train load as a function of train speed. It is possible to ensure the safety of train under rainfall. Thereafter, the feasibility of the rail-transport operation control with engineering basis was established.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.43-48
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• 2001

To overcome the disadvantages of conventional excavation technology, various trenchless (or excavation free, or no-dig) repair-reinforcement technologies have been developed and tried. But trenchless technologies so fat developed have some brawbacks such as high cost and inconvenience of operation. In this study, a repairing-reinforcing process for underground pipes with glass fiber fabric polymer composites using VARTM(Vacuum Assisted Resin Transfer Molding) has been developed. The developed process requires shorter operation time and lower cost with smaller and simpler operating equipments than those of the conventional trenchless technologies. For the reliable operation of the developed method, a simple method to apply pressure and vacuum to the reinforcement was devised and flexible mold technology was tried. Also, resin filling and cure status during RTM process were monitored with a commercial dielectrometry cure monitoring system, LACOMCURE. From the investigation, it has been found that the developed repairing-reinforcing technology with appropriate process variables and on-line cure monitoring has many advantages over conventional methods.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2004.05a
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• pp.92-95
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• 2004

A mixture experiment is a special type of response surface experiment in which the factors are the ingredients or components of a mixture, and the response is a function of the proportions of each ingredient. Evolutionary operation is useful to improve on-line full-scale manufacturing processes by systematically changing the levels of the process variables without jeopardizing the product. This paper presents an evolutionary operation procedure for large-scale mixture production processes based on simplex search procedure, which can be beneficial to practitioners who should improve on-line mixture process quality while meeting the production schedule of the mixture product.

• Journal of the Korea Society for Simulation
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• v.3 no.1
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• pp.167-178
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• 1994

For the identification of the optimal operating conditions of phosphoric acid plant, an intelligent simulation was performed based on the dissolution reaction of phosphate rock. A phosphoric acid plant consists of three main processes : ball-mill grinding process, rock reaction process and slurry filteration process. The grinding and filteration processes are relatively simple processes and most of the simulation works are on the reaction process. The practical operation data of phosphoric acid plant at Namhae Chemical Corp. were utilized in the simulation. The operation of the phosphoric acid plant is highly dependent on the heuristics of operators and so the expert system technology was employed. The operation of phosphoric acid plant varies with the origin of phosphate rock. Results of the simulation showed the optimal values of major process variables and optimal operating conditions. The knowledgebase for the expert system was constructed based on the interview with the experienced plant operators.

• Journal of Industrial Technology
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• v.26 no.A
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• pp.47-54
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• 2006

To improve passenger safety, seat belt systems with pre-tensioner that tightens seat belt webbing using explosive just before collision are widely used these days. Even though seatbelt must not unlatched without passengers' operation. explosive power of pre-tensioner can cause unlocking of a buckle. To prevent the unlocking, an anti-g mass that blocks displacement of the release button has been attached to the buckle. In this study, the dynamics and statics of locking mechanism associated with operation of anti-g buckle has been theoretically investigated, and important design variables that affect the operation of anti-g buckle have been identified. Through the total seat belt system's dynamic simulation using force and displacement inputs obtained from seat belt sled test, design of the proposed anti-g buckle has been validated.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.12
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• pp.964-970
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• 2006

Vapor compression refrigerators have much critical variables such as the controls of temperature and pressure switches, control durations and operating hours of electronic valves. This study compares and analyzes the data which is obtained from system controlling of the evaporation temperatures which are generally used in automatic pump down operating systems. Through this study, the automatic evaporation control operation system will be more ideal for the system to keep the proper temperature distribution depending on the purpose of evaporation side. The automatic pump down control operation is more appropriate for the system to aim at the effective use of evaporation side without using the temperature difference. And this test will be proved that the changes at the low pressure side didn't have significant impacts on the high pressure side.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1030-1032
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• 2000

Direct torque control algorithm for 3-level inverter-fed induction motors is proposed. Conventional selection method of the stator voltage vector shows problems of stator flux drooping phenomenon and undesirable torque control appeared especially at the low, speed operation. To overcome these problems, a proposed method uses intermediate voltage vectors, which are inherently generated in 3-level inverters. An adaptive observer is also employed to estimate some state-variables and motor parameters, which takes a deep effect on the performance of the low speed operation. Simulation and experiment results verify effectiveness of the proposed algorithm.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.2
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• pp.73-79
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• 1987

This paper describes a new algorithm to evaluate the production cost for a generation system including energy-limited hydroelectric plants. The algorithm is based upon the analytical production costing model developed under the assumption of Gaussian probabilistic distribution of random load fluctuations and plant outages. Hydro operation and pumped storage operation have been dealt with in the previous papers using the concept of peak-shaving operation. In this paper, the hydro problem is solved by using a new version of the gradient projection method that treats the upper / lower bounds of variables saparately and uses a specified initial active constraint set. Accuracy and validity of the algorithm are demonstrated by comparing the result with that of the peak-shaving model.

• Journal of the Korean Society of Safety
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• v.11 no.3
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• pp.104-111
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• 1996

A system was developed that could predict hazardous states for safe operation of chemical plants. This system aimed to prevent hazards of chemical processes from misoperation before real operation. In this study, a data base was organized which consisted of all hazards in the chemical processes. The structure of process was represented by signed direct graph(SDG) of NODEs and ARCs. Each NODE and ARC have property variables ; connected structure and state of processes etc. The hazards that could be occurred in processes were divided into two classes ; one is by operation of unit and the other is by hazardous materials. Using Hazardous States Transition Network, we could recognize transition progress of process states.