• Journal of Advanced Marine Engineering and Technology
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• 제39권10호
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• pp.1017-1022
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• 2015

Specific hydrodynamic characteristic of pump-turbine during the start and load rejection process of generating mode causes anomalous increase of water pressure, along with large machine vibration, called "S" characteristic. The aim of this study is to understand and explain the hydrodynamic performance of pump-turbine at "S" characteristic region by using a model of pump-turbine system. The operation in the condition of runway and low discharge in a typical "S" characteristic curve may become unstable and complex flow appears at the passage of guide vane and impeller. Therefore, velocity and pressure distribution are investigated to give an all-sided explanation of the formation and phenomenon of this characteristic, with the assistance of velocity triangle analysis at the impeller inlet. From this study, the internal flow and pressure fluctuation at the normal, runway and low discharge points are explored, giving a deep description of hydrodynamic characteristic when the pump-turbine system operates with "S" characteristic.

• 수산해양교육연구
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• 제24권4호
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• pp.494-506
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• 2012

The purpose of this study was to analyse 3, 4, 5-year-old children's private speech according to their age and task characteristics (structured task vs. unstructured task). In order to achieve the goal, the main effect of age, characteristic of tasks and interaction effect were considered among age and characteristic of tasks on preschool children's private speech. The subjects were each 30 3, 4, 5-year-olds from preschool in Busan, South Korea. The structured task was puzzle task and the unstructured task was drawing task from TCT-DP. The data was analyzed by repeated measurement two way ANOVA: 3(age) ${\times}$ 2((characteristic of task). As a result, firstly, total private speech of 4-year-old was higher than 3-year-old, 5-year-old in both tasks, and total private speech of 5-year-old was higher than 3-year-old in both tasks. Secondly, the task-irrelevant private speech was not affected by main effect of age and characteristic of task and interaction effect between age and characteristic of task. Thirdly, the task-relevant private speech was received both main effects and interaction effects between age and characteristic of task. Finally, the external manifestation of inner speech were not received effect of age but received effect of characteristic of task, and received interaction effect between age and characteristic of task. The results of this study imply that characteristic of task is an important factor inducing children's private speech.

• Journal of applied mathematics & informatics
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• 제34권1_2호
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• pp.19-34
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• 2016

In this paper, we present a split least-squares characteristic mixed finite element method(MFEM) to get the approximate solutions of the convection dominated Sobolev equations. First, to manage both convection term and time derivative term efficiently, we apply a least-squares characteristic MFEM to get the system of equations in the primal unknown and the flux unknown. Then, we obtain a split least-squares characteristic MFEM to convert the coupled system in two unknowns derived from the least-squares characteristic MFEM into two uncoupled systems in the unknowns. We theoretically prove that the approximations constructed by the split least-squares characteristic MFEM converge with the optimal order in L² and H¹ normed spaces for the primal unknown and with the optimal order in L² normed space for the flux unknown. And we provide some numerical results to confirm the validity of our theoretical results.

• 한국농공학회지
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• 제45권6호
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• pp.153-161
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• 2003

The purpose of this paper is to investigate the soil-water characteristic curves for an unsaturated soil. To this ends, a series of suction measured test was conducted on the selected 4 kinds of soils taken from different sites of Korea, using modified pressure plate apparatus. Form the test results, the water contents, degree of saturation and volumetric water contents were analyzed with the suction. And the soil-water characteristic curves of unsaturated soil were drawn from the test results for various factors. The characteristic curves drawn with water content vs matric suction were classified certainly the difference in wet side but were not classified in dry side. The characteristic curves drawn with degree of saturation vs matric suction for unsaturated soil were shown the opposite inclination as compared with the former curve. But the characteristic curve with volumetric water content vs matric suction was described suitably not only in wet side condition but also in dry side. And it was found that the volumetric water contents of loose soil was high at the initial condition but that of dense soil was high at final condition (dry side).

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1231-1234
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• 2003

Pneumatic servo valve which is widely applied in industrial world is advanced technology compounded with electric, electronic and machine. And It is consist of Linear Force Motor. Spool Commutation Mechanism and Microprocessor. In this study, we accomplished test method of Linear Force motor test, Static characteristic test, Dynamic characteristic test for KS(Koran industrial standard) of Pneumatic servo valve. we accomplished study about the main item of Static characteristic test which is related to unload flow characteristic test. And Dynamic characteristic test was step input test and frequency response test. Specially about frequency response test, There was a difficulty resulting from the time delay problem caused by the basic compressibility of air. In order to solve the problem in this study. we proposed two methods. First, displacement of the servo valve spool was directly measured by using a laser sensor. Second, method of calculating control flow by measuring pressure and temperature of chamber.

• 한국산업융합학회 논문집
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• 제13권1호
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• pp.5-13
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• 2010

Industrialization and urbanization occurred-traffic delay, traffic accident and parking problem etc.-variety of transportation problems. Parking problem is one of the transportation problem then transportation engineers would get involved in trying to solve parking problem. A way to overcome a variety of parking problems needs preliminary data for conditions of parking but it lacks the preliminary data to do so. Thus this study analyzed a characteristic of a parking through a field survey for parking in Daegu Metropolitan City. This study analyzed parking characteristic of parking operation method. This study result reveals difference between a toll parking and a no charge parking characteristic. Thus a close examination for a toll parking characteristic and a no charge parking characteristic is a prerequisite for a rational parking policy.

• 한국산업융합학회 논문집
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• 제11권3호
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• pp.113-120
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• 2008

Rapid urbanization occurred a variety of transportation problems. Parking problem is one of the most problems of transportation problem then transportation engineers would get involved in trying to solve parking problem. A way to overcome a variety of parking problems needs preliminary data for conditions of parking but it lacks the preliminary data to do so. Thus this study analyzed a characteristic of a parking through a field survey for parking in Daegu Metropolitan City and Ulsan Metropolitan City. This study analyzed parking turnover, parking use ratio and parking basic unit for characteristic of a parking of each use districts and each cities. This study result reveals difference between the use districts' parking characteristic and cities' parking characteristic. Thus a close examination for use districts' parking characteristic and cities' parking characteristic is a prerequisite for a rational parking policy.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.202-205
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• 2004

A numerical method is presented to determine the characteristic lengths for the failure analysis of composite joints without characteristic length tests. In the conventional methods, compressive characteristic length was determined from the result of a combined bearing test and finite element analysis. The present study, however, shows that the same compressive characteristic length can be obtained by numerical calculation without the bearing test. A new method to define the tensile characteristic length is also introduced so that the tensile characteristic length is numerically determined without the tensile test. Failure loads based on the numerically calculated characteristic lengths are validated by the test results for composite joints

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.743-750
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• 2002

Unsaturated soil has a possibility to induce a negative pore water pressure. Until now, saturated soil is mainly focused on the research of soil mechanics. Recently, soil mechanics is researched on two major parts such as saturated and unsaturated soil mechanics. Negative pore water pressure has a non-linear relationship with the water content changes. Soil-water characteristic curves of soil in Korea are not determined. There is no proper characteristic value such as air-entry value and residual water content. In this study, the characteristic curves of reclaimed soil, sand, and weathered granite soil were determined by laboratory tests. Air-entry value and residual water content were determined by fitting methods. Soil-water characteristic curves were estimated based on the particle-size distribution and compared with the laboratory test results. The results of soil-water characteristic curves estimation indicated that Fredlund and Wilson's model is excellent for sand and weathered granite soil. Arya and Paris's model is excellent for reclaimed soil.

• 대한전기학회논문지:전력기술부문A
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• 제53권8호
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• pp.432-437
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• 2004

Since the characteristic frequency is decreased in proportion to the fault distance, the characteristic frequency component may be insufficiently eliminated by a low-pass filter on a long transmission line. In order to set a standard for the cut-off frequency of the low-pass filter, this paper proposes a method for obtaining the characteristic frequencies due to line faults. The application results of the proposed method are presented for line to ground (LG) faults and line to line (LL) faults on a 345 kV 200 km overhead transmission line. The EMTP is used to generate fault signals under different fault locations and fault inception angles. By comparison between the characteristic frequencies obtained from the proposed method and the EMTP simulation, it is shown that the proposed method accurately obtains the characteristic frequency.