• Journal of the Optical Society of Korea
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• 제17권2호
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• pp.117-129
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• 2013

We briefly review the recent progress in passively mode-locked fiber lasers (PMLFLs) based on semiconductor saturable absorber mirrors (SESAMs) and discuss the detailed characterization of a SESAM-based, passively mode-locked erbium-doped fiber (EDF) laser operating in the 1.5-${\mu}m$ spectral range for various configurations. A simple and compact design of the laser cavity enables the PMLFL to generate either femtosecond or wavelength-tunable picosecond pulses with high stability as the intra-cavity filtering method is altered. All the cavities investigated in our experiments present self-starting, continuous-wave mode-locking with no Q-switching instabilities. The excellent stability of the source eventually enables the wavelength-tunable PMLFL to be used as a master oscillator for a power-amplifier source based on a large-core EDF, generating picosecond pulses of >10-kW peak power and >100-nJ pulse energy.

• Structural Engineering and Mechanics
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• 제11권5호
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• pp.503-518
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• 2001

In this paper, the procedure for deriving an infinite element that is compatible with the quadrilateral Q8 element is first summarized. Enhanced by a self mesh-expansion procedure for generating the impedance matrices of different frequencies for the region extending to infinity, the infinite element is used to simulate the far field of the soil-structure system. The structure considered here is of the box type and the soils are either homogeneous or resting on a bedrock. Using the finite/infinite element approach, a parametric study is conducted to investigate the effect of open and in-filled trenches in reducing the structural vibration caused by a train passing nearby, which is simulated as a harmonic line load. The key parameters that dominate the performance of wave barriers in reducing the structural vibrations are identified. The results presented herein serve as a useful guideline for the design of open and in-filled trenches concerning wave reduction.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2003년도 ISIS 2003
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• pp.74-77
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• 2003

In this paper, we propose a new personal agent for generating the combinational services from using history of appliances in the home network environment. In such environment, it is required that flexible services can be provided by combining services of appliances and unskillful users can use these services without knowledge. So, it is needed to satisfy following: (1) combinational services can be suggested automatically and (2) the increase of services can be followed. Then, we propose a new personal agent that suggests combinational services by learning the lifestyle. Its learning mechanism is based on Self-Organizing Map (SOM), and can follow the increase of services. We implemented the the agent, and use history of a user for two weeks was made to learn. As the result, we confirmed that the agent can extract services related with time or location and can suggest combinational services.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.537-542
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• 1996

In the present work the influence of various physical parameters on the two-phase flow behavior in a self-heated porous medium has been studied using a numerical model, that is, the effects of heat generation rate, of porosity, of particle size, and of system pressure on the dryout process. To analyze the effect of these parameters, the variation of both liquid volumetric fraction and liquid axial velocity is evaluated at the steady state or at the onset of a first boiled-out region. The analysis of computational results indicate that a qualitative tendency exists between the parameters such as heat generation rate, porosity, effective particle diameter and the temporal development of the liquid volumetric fraction field up to dryout. In addition to these parameters, a variation of fluid properties such as phase density, phase viscosity due to a change of system pressure can be used for gaining insight into the nature of two-phase flow behavior up to dryout.

• 한국농공학회논문집
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• 제47권7호
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• pp.13-22
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• 2005

Main purpose of this article is to classify reservoirs corresponding to their physical characteristics, for example, dam height, dam width, age, repair-works history. First of all, data set of 13,976 reservoirs was analyzed using k means and self organized maps. As a result of these analysis, lots of reservoirs have been classified into four clusters. Factors and their critical values to classify the reservoirs into four groups have been founded by generating a decision tree. The path rules to each group seem reasonable since their survivor function showed unique pattern.

• 대한공업교육학회지
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• 제30권1호
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• pp.1-18
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• 2005

The purpose of this study was to development a model of problem solving instruction for improving practical skill-competence in technical high school. For the study, various literature researches were reviewed intensively about problem solving process, laboratory instruction's approaches and learning principals. The problem solving instruction process was composed with identifying problems, generating alternative solutions, investigation and research, choosing a solution, acting on a plan, modeling of problem solving, testing and evaluating, redesigning and improving. The skills schema combines a four domain of skilled activity, that is, cognitive skills, psychomotor skills, reactive skills and interactive skills. The problem solving instruction was composed with five major learning systems-emotional, social, cognitive, physical, and reflective-that can be used extensively as generic lesson plashing. The teacher serves as a coach or guide for student learning. As a facilitator, the teacher challenges, questions, and stimulates the students in their thinking, problem solving and self-directed study. In this process, students represent problem with think aloud, assume responsibility for their learning and move from teacher-centered to student-centered education.

• 한국소음진동공학회논문집
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• 제19권4호
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• pp.393-399
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• 2009

Historically, industrial condition monitoring has been performed by costly hard-wired sensors or infrequent checks by maintenance personnel equipped with hand held monitoring equipment. Self- powered wireless condition monitoring systems provides on-line monitoring of critical plant and machinery providing major operating cost benefits. A vibration energy harvester(VEH) is a device that converts kinetic energy occurred by machine vibration into useable electrical energy. Using VEHs to power wireless monitoring systems can yield significant benefits: increased reliability, lower life time costs and no battery disposal issues, etc. This paper proposes the novel prototype design and manufacturing of a VEH that can eliminate the effect by failed batteries.

• 한국지역사회생활과학회지
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• 제14권3호
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• pp.3-11
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• 2003

The objectives of the study were to analyze the current conditions of the“NONGCHON ILGAM GATCI”project (an income generating project for rural areas) and to suggest possible improvements. Among the 567 business which have been supported by the project, implemented in 1990 by the Department of Rural-Home-Improvement of the Rural Development Administration, 361 (63.7%) can be categorized as being in the self-supporting stage. Another 126 (22.2%) can be said to be in the incubation stage. Data for the case study was collected from 20 project sites. The“NONGCHON ILGAM GATCI”project has been progressing successfully when compared with other rural development projects. However, there are still some problems. Among the problems are the lack of a business mindset and management abilities in individuals, and the fact that the businesses and their products are not well hewn on the market. To remedy these problems, education toward improving business and management skills, a unified public relations system, and institutional support from the government are greatly needed.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 추계 학술발표회
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• pp.169-178
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• 2006

The pumped-storage power system is the one of the hydroelectric power systems, generating electricity with hydraulic head difference. In this system, the electricity is produced during the hours of peak demand by using water that has been pumped into an upper reservoir from a lower reservoir during the hours of low demand. Generally, the system consists of an under-ground power house and tunnels such as the headrace, pressure, and tailrace tunnels. The Chungsong pumped-storage power station is the sixth one In the pumped-storage power station in Korea. Both the regional self-government and the population of chungsong -Goon had made a great effort to draw this power station construction into this area. The proposed Chungsong pumped-power station construction project was accepted by the central government as a part of the national electricity plan for the first time in Korea.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.522-526
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• 2004

High cost of crude oil imposes a heavy burden on vehicle users. Thus, much efforts are given to the development of alternative energies in advanced countries as well as our country. Among them, fuel cell is emerged as the most promising one for transportation. There is no harmful emission with hydrogen energy of which sources are abundant on the earth. The use of both fuel cell with self-generating system and electromanetic guidance system will be able to make urban track rapid transit operate even in the city areas of very limited infrastructure space with flexibility and on time accessibility. The high efficiency is also expected with clean environment and easy riding for both the old and the handicapped.