• Journal of the Korean Wood Science and Technology
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• 제32권5호
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• pp.66-74
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• 2004

내화 성능은 표준 화염 조건에 노출된 목구조물의 안전성 평가를 위한 중요한 기준이 된다. 내화 성능의 기준으로 여러 나라에서 지속 시간과 파괴 시까지의 시간이 사용되고 있다. 본 연구에서는 화염에 대한 신뢰성 설계의 기초 연구로서 화염에 노출된 목재 마루 시스템의 신뢰성 해석이 진행되었다. 해석은 수치 해석적 방법과 결정론적 방법 두 가지를 모두 사용하였다. 두 방법 간에는 큰 차이를 보이지 않았다. 화염에 노출된 마루시스템의 신뢰도는 부재의 변이계수에 크게 의존하였으며 부재의 강도나 하중은 신뢰도에 크게 영향하지 않았다.

• Geomechanics and Engineering
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• 재33권6호
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• pp.543-552
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• 2023

The design of foundations based on a deterministic approach may not be safe and reliable occasionally, since soils sometimes show considerable spatial variability, and thus, significant uncertainties in turn affect the estimation of footing bearing capacity. The design of footing on cohesionless stratums on the basis of reliability analysis has not received much attention. This paper performs two-dimensional random finite difference analyses of shallow strip footings on a spatially variable frictional soil considering correlation structure. Friction angle (ϕ) is considered as a log-normally distributed random variable and Monte Carlo Simulation is then performed to determine the statistical response based on the random fields. A new approach reliability-based safety factor is defined based on various reliability levels by considering the coefficient of variation of ϕ and correlation length in both the horizontal and vertical directions. The comparison of the probabilistic safety factor and the conventional one illustrates the limitations of the deterministic safety factor and provides insight into how the heterogeneity of soils properties affects the required safety factor. Results show that the conventional safety factor of 3 can be conservative in some cases, especially for soil with low values of mean ϕ and COV_ϕ.

• Physical Therapy Rehabilitation Science
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• 제12권3호
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• pp.251-258
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• 2023

Objective: The practice of breathing exercises involves altering the depth and frequency of respiration. Strengthening respiratory muscles plays a crucial role in maintaining overall health and well-being. The efficiency of the respiratory system affects not only physical activity but also various physiological processes including cardiovascular health, lung function, and cognitive abilities. The study evaluated the reliability of the developed device for inspiratory/expiratory training using pressure sensors and Bluetooth connectivity with a smartphone application. Design: Design & development research Methods: The research methodology involved connecting a custom-made respiratory sensor to an IMT-PEP BIC Breath device. Various pressure conditions were measured, and statistical analyses were performed to assess reliability and consistency. Results showed high Intraclass Coefficient Correlation (ICC) values for both inspiratory and expiratory pressures, indicating strong test-retest reliability. The device was designed for ease of use and wireless monitoring through a smartphone app. Results: This study conducted at expiratory pressure confirmed the proper operation of the IMT/PEP breathing trainer at the specified pressure setting in the product. The pressure sensor demonstrated high test-retest reliability with an ICC value of 0.999 for both expiratory and inspiratory pressure measurements. Conclusions: The developed respiratory training device measured and monitored inspiratory and expiratory pressures, demonstrating its reliability for respiratory training. The system could be utilized to record training frequency and intensity, providing potential benefits for patients requiring respiratory interventions. Further research is needed to assess the full potential of the device in diverse populations and applications.

• 한국구조물진단유지관리공학회 논문집
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• 제12권6호
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• pp.241-248
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• 2008

민감도 해석은 구조 모델링 변수의 변화에 따른 역학적인 거동의 특성을 찾는 것을 목적으로 한다. 따라서 건물의 구조 진단과 보수 보강 분야에서 특히 중요한 설계 자료로서 활용되고 있다. 본 연구는 구조물의 위상학적 최적 모델링에서 중요하게 다루어지는 민감도 해석을 다양한 방법을 사용하여 공식화하였다. 감차법과 변분법을 적용하여 직접법과 수반법으로서 최종적인 해석적인 민감도 식들을 유도하였다. 구조 해석에 관한 간단한 수치예제를 통하여 유도된 민감도 식들의 해가 적절함을 수치적인 민감도 해석치와 비교하여 검증하였고, 최종적으로 이산화 민감도 해석에 의한 밀도분배법의 위상학적 최적 모델링을 수행하여 민감도 공식들을 위상 최적화 문제에서 정식화하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.123-130
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• 2003

The estimation of key soil properties and subsequent quantitative assessment of the associated uncertainties has always been an important issue in geotechnical engineering. It is well recognized that soil properties vary spatially as a result of depositional and post-depositional processes. The stochastic nature of spatially varying soil properties can be treated as a random field. A practical statistical approach that can be used to systematically model various sources of uncertainty is presented in the context of reliability analysis of slope stability Newly developed expressions for probabilistic characterization of soil properties incorporate sampling and measurement errors, as well as spatial variability and its reduced variance due to spatial averaging. Reliability analyses of the probability of slope failure using the different statistical representations of soil properties show that the incorporation of spatial correlation and conditional simulation leads to significantly lower probability of failure than obtained using simple random variable approach.

• International Journal of Advanced Culture Technology
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• 제8권1호
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• pp.248-256
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• 2020

This study investigated whether the schema modes have validity in Korean adults. We examined the validity and reliability of the Schema Mode Inventory (SMI) in a Korean adult sample (N = 768; Mean age = 22.29 years; range = 19-55 years; 69.3% Males). Psychometric properties, such as factor structure, internal reliability, as well as intercorrelations among subscales were assessed. Confirmatory factor analyses yield satisfying fits for a 61-item Korean Schema Mode Inventory. Thirteen Schema Mode Inventory scales were found to have adequate reliability of the original 14 schema factors. Furthermore, the SMI scales differentiated between depressed and non-depressed participants as theoretically predicted. These findings imply that the SMI is a sound instrument to measure the schema mode model in a Korean setting for assessment prior to schema therapy.

• 대한안전경영과학회지
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• 제6권2호
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• pp.231-239
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• 2004

To keep an enterprise's competitiveness on the condition of the automatic manufacturing system such as FA, FMS and CIM, all the maintenance problems should be considered seriously in not only in production and maintenance but also in related industrial productivity. This paper presents the study of equipment reliability improvement for rotary-machine vibration analysis. Based on these analyses, the maintenance management information system, and the machinery condition diagnosis technique are studied by using of the real-time diagnostic. Therefore, it is expected to improve the efficiency of business processes in the production and safety when we use this system.

• 한국경영과학회지
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• 제34권1호
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• pp.11-28
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• 2009

Intelligent investment in setup cost reduction and process reliability improvement is crucial to an emerging integrated lean six sigma practice today. This study examines a cost-minimizing problem of jointly determining production lot size, setup cost reduction, and process reliability improvement decisions for a manufacturer with an imperfect production process. We develop models for previously untapped discrete shipping in a supply chain context as well as continuous shipping and solve them optimally using differential calculus and nonlinear programming. We also conduct analytic and numerical sensitivity analyses to provide various important managerial insights into practices.

• 한국IT서비스학회지
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• 제17권2호
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• pp.101-110
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• 2018

Analytic Hierarchy Process (AHP) is a systematic and objective decision method that stratifies multiple criteria to determine various evaluation factors' order of priority. Since AHP requires several stages of analysis with complicated attributes, they normally rely on computer programs for the execution of such analyses. However, the existing AHP analytic tools carry the inconvenience of having to repeatedly input massive amounts data generated in every stage. This repetitious data entry process results in prolonged analysis times and higher possibility of errors, leading to decreased reliability of the results. Thus, in this study, we develop an analytic tool that effectively simplifies the data entry process in AHP analysis, for the purpose of reducing analysis times and increasing the reliability of the results.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.22.2-22.2
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• 2011

Reliability and degradation mechanism of conventional phosphor-converted white GaN-based light-emitting diodes (LEDs) were investigated. Under electro-thermal stress condition, the optical output degraded rapidly at the initial stress time accompanied by the change of chromatic properties. This could be attributed to the optical degradation of packaged materials, in particular, the browning of encapsulants and the darkening of reflective packages. At longer stress times, the optical output gradually decreased according to the degree of the reverse leakage currents, namely, the generation ofnonradiative recombination defects. This indicates that the optical degradation of white LEDs are dominated by the darkening of packaged materials and the generation of defects depending on the injection current and ambient temperatures. Using analyses of electroluminescence spectra, optical microscopy, electrical, optical, and thermal properties, optical degradations of white LEDs are discussed.