• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.544-545
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• 2010

전자식 안정기의 초기구동 시, 발생되는 입력단의 높은 돌입전류는 전자식 안정기 내의 전파정류다이오드 및 능동 역률보상회로의 파손원인이 되며, 제품의 신뢰성을 감소시키는 큰 요인으로 지목된다. 따라서 안정기의 입력에서 발생되는 돌입전류를 분석하고 제한하는 방법이 필요하다. 본 논문은 250W CDM(Ceramic Discharge Metal-halide) 램프용 DBI(Dual Buck Inverter) 구조의 전자식 안정기에서 초기 구동 시 높은 돌입전류가 발생되는 원인을 분석하고, 해결책을 제시하였다.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.6
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• pp.1089-1094
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• 2021

In order to support the restoration and construction work of port infrastructure facilities damaged or damaged due to disasters and disasters, it is linked with work equipment based on the performance of duties such as regular patrol in the port, monitoring the underwater environment, and acquisition of underwater configuration information in the port, Define content related to AUV platform analysis and design that can support construction.

• Korean Journal of Child Studies
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• v.24 no.3
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• pp.73-85
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• 2003

The purpose of this study was to examine whether adolescents' parental rule obedience moderates the relationship between maternalmonitoring and problem behavior (drinking and vandalism). Participants were 398 adolescents attending a middle school (6th through 8th grades) in a semi-rural mid-Atlantic community in the USA. Data were collected by questionnaires including items regarding relationships with parents, problem behavior, and peer relationships. Hierarchical multiple regression was usedto analyze the data. Results indicate that maternal monitoring is negatively related with adolescent drinking and vandalism. However, the negative relationship varies as a function of adolescents' parental rule obedience. The relationship was stronger among adolescents with lower level of parental rule obedience than among adolescents with higher level of parental rule obedience. Findings from this study suggest that research on maternal monitoring during adolescence needs to take adolescents' personal characteristics into account to better understand the process. They also suggest that parents could lower the possibility that their children's will be involved in drinking and vandalism by maintaining quality relationships with their children because children are more likely to internalize their parents' rules and standards when they have positive relationships with parents.

• Vending industry
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• v.4 no.3 s.11
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• pp.52-54
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• 2004

100원, 500원 동전을 가장 요긴하게 활용할 수 있는 유통수단은 자판기이다. 자판기를 통해 제공되는 커피, 캔음료의 가격대가 1000원 이하이다 보니 동전사용이 엄청나게 많이 이루어진다. 이렇게 소액결제의 대명사인 자판기가 동전사용의 비중이 높다 보니 이로 인해 파생되는 문제 역시 다양하다. 항시 자판기내 동전보관이 되어 있는 만큼 도난 파손의 문제가 작용하기도 하고, 화폐가치 차이가 있는 제3국 동전을 넣는다거나, 이물질을 넣는 문제가 발생하기도 한다. 또 애써 모은 동전을 은행이 교환해 주지 않아 골머리를 앓기도 한다. 한쪽에서는 무시를 받고, 또 한쪽에서는 한탕의 수단으로 혈안이 되게 만드는 게 자판기 동전이다. 인간사 다양한 이치처럼 자판기 동전으로 인해 파생되는 문제도 다양하다. 이번 정책초점에서는 자판기 동전 문제를 보는 두 가지 시각을 조명하고자 한다. 필리핀 동전 1페소가 국내 자판기에 유통되는 문제와 은행들의 교환거부로 애물단지로 전락한 자판기 동전 문제를 분석 정리했다.

• The Journal of the Acoustical Society of Korea
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• v.41 no.6
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• pp.680-690
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• 2022

Vibrations in the pipe system trigger fatigue-related issues and lead to fatal other problems caused by pipe damage. There are numerous studies to analyze and reduce the cause of pipe vibration, among which a small number of studies are being conducted on pipe vibration reduction using friction supports. The study of friction supports, however, focused only on predicting and evaluating the performance of the friction supports and seldomly considered the design perspective of the install location of the supports. Therefore, this study intends to suggest the optimization process for finding the best installation region of friction support to attenuate the vibration of entire piping system. The optimal position of the friction support is predicted only by linear analysis to guarantee optimization efficiency in the design process. The designed friction support location is verified by time domain analysis.

• Composites Research
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• v.16 no.3
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• pp.18-24
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• 2003

Sandwich structures have been widely used in the applications of vessel industry, where high structural stiffness is required with small addition of weight. It is so significant to think of the effect of the variables in the design process of the sandwich structure for the concentrated loads. This paper describes the influence of design variables, such as core density, core thickness and face thickness ratio, on the strength of sandwich beam. The theoretical failure loads based on the 2-D elasticity theory agree well with the experimental yield or failure loads, which are measured at the three point bending laboratory test using AS4/3501-6 facing and polyurethane foam core sandwich beam. The comparison of those yield or failure loads was also done with the ratio of the top to bottom face thickness. The theoretical optimum condition is obtained by finding the intersection point of failure modes involved, which gives optimum core density of the sandwich beam for strength and stiffness. In the addition, the effect of unequal face thickness for the optimized and off-optimized sandwich beams for the strength was compared with the ratio of loading length to beam length, and the variations of strength and stiffness were discussed with the relative ratio of core to face mass.

• Composites Research
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• v.37 no.5
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• pp.409-415
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• 2024

In this study, we present a progressive fatigue damage model for accurately predicting the fatigue life of laminated composites. The proposed model simulates intralaminar damage progression within composites based on the continuum mechanics and employs the LaRC05 failure criteria to predict the initiation of damage in both the fibers and matrix. A damage variable is introduced to capture the degradation of material properties under cyclic loading, which accumulates progressively with each fatigue cycle, enabling reliable fatigue life prediction. The model comprehensively accounts for key failure mechanisms, including fiber fracture, matrix cracking, fiber kinking, and fiber splitting and provides a detailed analysis of the damage evolution within the composite. The algorithm is implemented into the UMAT subroutine of ABAQUS. To validate the model, simulations were conducted using T700/2510 composite laminates, evaluating fatigue life with various stacking sequences and stress ratios. The simulation results were compared with experimental S-N curves, and showed a strong correlation, thereby confirming the accuracy and reliability of the proposed model.

• The Journal of the Acoustical Society of Korea
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• v.36 no.5
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• pp.314-320
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• 2017

A pressure relief valve is generally used to prevent piping systems from being broken due to high pressure gas flows. However, the sudden pressure drop caused by the pressure relief valve produces high acoustic energy which propagates in the form of compressible acoustic waves in the pipe and sometimes causes severe vibration of the pipe structure, thereby resulting in its failure. In this study, internal aerodynamic noise due to valve flow is estimated for a simple contraction-expansion pipe by combining the LES (Large-Eddy Simulation) technique with the wavenumber-frequency analysis, which allows the decomposition of fluctuating pressure into incompressible hydrodynamic pressure and compressible acoustic pressure. In order to increase the convergence, the steady Reynolds-Averaged Navier-Stokes equations are numerically solved. And then, for the unsteady flow analysis with high accuracy, the unsteady LES is performed with the steady result as the initial value. The wavenumber-frequency analysis is finally performed using the unsteady flow simulation results. The wavenumber-frequency analysis is shown to separate the compressible pressure fluctuation in the flow field from the incompressible one. This result can provide the accurate information for the source causing so-called acoustic-induced-vibration of a piping system.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1369-1374
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• 2007

We carried out a vibration test to analyze causes of the damage in the plate of Bell Crank of the high speed Line turnout, at the section where the plate of high speed railway turnout get damaged from May 8th to 9th in 2006. In addition, through a test of the material quality, we performed an analysis of the qualities (of the components) composing the plate. The result indicates that the main cause of faults of the high speed line turnout, which is installed in the section of Chil-gok IEC, is the vibration. In this paper, effects on track-side equipments from vibration, and measurements to protect them from it are mainly analyzed and checked.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.1
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• pp.91-99
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• 2001

에너지 수송배관은 경제성과 실용성으로 인해 총 설치 길이가 크게 증가하고 있으며, 최근에는 대륙관통 배관망 등의 건설이 지구촌 곳곳에서 진행되고 있다. 이러한 수송용 배관은 운송대상인 오일이나 가스의 폭발특성이나 환경오염 위험성으로 인해 무엇보다 철저한 안전관리가 이루어져야 한다. 선진 각 국에서는 이미 1960년대부터 배관파손의 원인을 분석하고 원인별 대책마련을 위해 부단한 노력을 기울이고 있다. 본고에서는 에너지 수송배관에 발생하는 대표적 결함 종류들에 대해, 선진 각 국에서 사용중인 안전성평가 방법을 정리함으로써, 국내 수송배관 안전성평가 대책 마련을 위한 기초자료로 제시하고자 한다.