• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.235-240
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• 2003

Methods to predict fatigue crack growth are compared in a quantitative manner for crack growth test data of 2024-T351 aluminum alloy under narrow and wide band random loading. In order to account for the effect of load ratio, crack closure model, Hater's equation and NASGRO's equation have been employed. Load interaction effect under random loading has been considered by crack closure model, Willenborg's model and Wheeler's model. The prediction method using the measured crack opening results provides the best result among the prediction methods discussed for narrow and wide band random loading data.

• 대한기계학회논문집A
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• 제27권10호
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• pp.1785-1792
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• 2003

Methods to predict fatigue crack growth are compared in a quantitative manner for crack growth test data of 2024- T351 aluninum alloy under narrow and wide band random loading. In order to account for the effect of load ratio, crack closure model, Hater's equation and NASGRO's equation have been employed. Load interaction effect under random loading has been considered by crack closure model, Willenborg's model and Wheeler's model. The prediction method using the measured crack opening results provides the best result among the prediction methods discussed for narrow and wide band random loading data.

• Journal of Power Electronics
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• 제19권6호
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• pp.1403-1412
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• 2019

A coupled inductor-dual boost-inverter (CIDBI) with a differential structure has been presented for application to a micro-inverter photovoltaic module system due to its turn ratio of a high-voltage level. However, it is difficult to design a CIDBI converter with a conventional PI regulator to be stable and achieve good dynamic performance, given the fact that it is a high order system. In view of this situation, a sliding mode control (SMC) strategy is introduced in this paper, and two different sliding mode controllers (SMCs) are proposed and adopted in the left and right side of two Boost sub-circuits to implement the corresponding regulation of the voltage and current. The schemes of the SMCs have been elaborated in this paper including the establishment of a system variable structure model, selection of the sliding surface, determination of the control law, and presentation of the reaching conditions and sliding domain. Finally, the mathematic analysis and the proposed SMC are verified by experimental results.

• 천문학논총
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• 제8권1호
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• pp.169-177
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• 1993

Observed spectra of supernovae allow the empirical classification of supernovae into two basic categories, Type I with little or no evidence of hydrogen, and Type II with obvious evidence for hydrogen. The broad class of Type I can be subdivided depending on whether helium or silicon and other intermediate mass elements is observed. Understanding the physical processes that underlie these classifications---the progenitor evolution. the explosion mechanism, and end products---requires calculation of radiative transfer and model spectra. While most Type II occur in evolved massive stars that undergo core collapse. some may span the dividing line between degenerate and non-degenerate carbon burning and involve both core collapse and thermonuclear explosion. Type Ia are still most plausibly explained as thermonuclear explosions in carbon/oxygen white dwarfs in binary systems. Type Ib reveal helium atmospheres and are probably the result of core collapse in the helium core of a massive star that has lost its hydrogen envelope to a binary companion or to a wind. Type Ic supernovae are probably related to Type Ib but have also lost their helium envelope to reveal a mantle rich in oxygen.

• Journal of Acupuncture Research
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• 제36권1호
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• pp.1-11
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• 2019

Models of traditional Chinese medicine (TCM) are still difficult to grasp from the view of a Western-cultural background. For proper integration into science and clinical research, it is vital to think "out of the box" of classical sciences. Modern sciences, such as quantum physics, system theory, and information theory offer new models, that reveal TCM as a method to process information. For this purpose, we apply concepts of information theory to propose a "Chinese black box model," that allows for a non-deterministic, bottom-up approach. Considering a patient as an undeterminable complex system, the process of getting information about an individual in Chinese diagnostics is compared to the input-process-output principle of information theory and quantum physics, which is further illustrated by Wheeler's "surprise 20 questions." In TCM, an observer uses a decision-making algorithm to qualify diagnostic information by the binary polarities of "yang" (latin activity) and "yin" (latin structivity) according to the so called "8 principles" (latin 8 guiding criteria). A systematic reconstruction of ancient Chinese terms and concepts illuminates a scattered scientific method, which is specified in a medical context by Latin terminology of the sinologist Porkert [definitions of the Latin terms are presented in Porkert's appendix [1] (cf. Limitations)].

• 한국해양공학회지
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• 제13권3호통권33호
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• pp.36-48
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• 1999

Fatigue life and crack retardation behavior after penetration were experimentally examined using surface pre-cracked specimens of aluminium alloy 5083. The Wheeler model retardation parameter was used successfully to predict crack growth behavior after penetration. By using a crack propagation rule, the change in crack shape after penetration can be evaluated quantitatively. Advanced, waveform-based acoustic emission (AE) techniques have been successfully used to evaluate signal characteristics obtained form fatigue crack propagation and penetratin behavior in 6061 aluminum plate with surface crack under fatigue stress. Surface defects in the structural members are apt to be origins of fatigue crack growth, which may cause serious failure of the whole structure. The nondestructive analysis on the crack growth and penetration from these defects may, therefore, be one of the most important subjects on the reliability of the leak before break (LBB) design. The goal of the present study is to determine if different sources of the AE could be identified by characteristics of the waveforms produced from the crack growth and penetration. AE signals detected in four stages were found to have different signal per stage. With analysis of waveform and power spectrum in 6061 aluminum alloys with a surface crack, it is found to be capabilities on real-time monitoring for the crack propagation and penetration behavior of various damages and defects in structural members.

• 한국산업정보학회논문지
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• 제5권1호
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• pp.102-107
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• 2000

일반적으로 문자와 영상이 갖는 특성이 서로 다르기 때문에 문자 압축 기법들을 영상 압축에 직접 사용하지 않는다. 최근 문자 압축에 뛰어난 결과를 얻을 수 있는 블록 정렬 알고리즘인 BW 변환이 소개되었으나 BW 변환을 직접 영상에 적용하면 만족할 만한 결과를 얻을 수가 없다. 따라서 BW 변환을 영상에 적용할 때 무손실 압축성능 개선을 위한 새로운 방법을 제안한다. 제안한 방법의 구성은 3단계로 나누어지며 SSKF 필터에 의한 10개 영역으로 계층적 대역 분할을 하고 BW 변환에 의한 블록 정렬 알고리즘을 수행하여 적응적 산술 부호화에 의한 중복성를 제거한다. 실험 결과 제안한 방법이 무손실 JPEG 표준안과 LZ계열의 PKZIP 보다 뛰어난 압축 성능을 가졌다.

• Safety and Health at Work
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• 제8권2호
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• pp.206-211
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• 2017

Background: Self-reported low back pain (LBP) has been evaluated in relation to material handling lifting tasks, but little research has focused on relating quantifiable stressors to LBP at the individual level. The National Institute for Occupational Safety and Health (NIOSH) Composite Lifting Index (CLI) has been used to quantify stressors for lifting tasks. A chemical exposure can be readily used as an exposure metric or stressor for chemical risk assessment (RA). Defining and quantifying lifting nonchemical stressors and related adverse responses is more difficult. Stressor-response models appropriate for CLI and LBP associations do not easily fit in common chemical RA modeling techniques (e.g., Benchmark Dose methods), so different approaches were tried. Methods: This work used prospective data from 138 manufacturing workers to consider the linkage of the occupational stressor of material lifting to LBP. The final model used a Bayesian random threshold approach to estimate the probability of an increase in LBP as a threshold step function. Results: Using maximal and mean CLI values, a significant increase in the probability of LBP for values above 1.5 was found. Conclusion: A risk of LBP associated with CLI values > 1.5 existed in this worker population. The relevance for other populations requires further study.

• Restorative Dentistry and Endodontics
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• 제24권1호
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• pp.67-75
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• 1999

The use of composite restorative materials is established due to continuing improvements in the materials and restorative techniques. Composite resins are widely used for the restoration of cervical lesions because of esthetics, good physical properties and working time. There are several types of cavity design for class V composite resin filling, but inappropriate cavity form may affect bonding failure, microleakage and fracture during mastication. Cavity preparations for composite materials should be as conservative as possible. The extent of the preparation is usually determined by the size, shape, and location of the defect. The design of the cavity preparation to receive a composite restoration may vary depending on several factors. In this study, 5 types of class V cavity were prepared on each maxillary central incisor. The types are; 1) V-shape, 2) round(U) shape, 3) box form, 4) box form with incisal bevel and 5) box form with incisal bevel and grooves for axial line angles. After restoration, in order to observe the concentration of stress at bonding surfaces of teeth and restorations, developing a 2-dimensional finite element model of labiopalatal section in tooth, surrounding bone, periodontal ligament and gingiva, based on the measurements by Wheeler, loading force from direction of 45 degrees from lingual side near the incisal edge was applied. This study analysed Von Mises stress with SuperSap finite element analysis program(Algor Interactive System, Inc.). The results were as follows : 1. Stress concentration was prevalent at tooth-resin bonding surface of cervical side on each model. 2. In model 2 without line angle, stress was distributed evenly. 3. Preparing bevel eliminated stress concentration much or less at line angle. 4. Model with round-shape distributed stress concentration more evenly than box-type model with sharp line angle, therefore decreased possibility of fracture. 5. Adding grooves to line angles had no effect of decreasing stress concentration to the area.

• 한국유통학회지:유통연구
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• 제15권5호
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• pp.127-153
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• 2010

본 연구는 지난 10년간 급격하게 변화하여 온 온라인 쇼핑산업에 대해 성장의 동력을 이론적으로 확인하고, 이들에 의한 이론적 설명을 시도한 탐색적 연구이다. 이러한 과정에서 이론적으로 선점이론에 대한 검토를 통해 이 이론이 유통구조에서 온라인 유통산업에서 발생하고 있는 재중간상화와 배치됨을 확인하였고, 이에 따라서 동적 역량이론을 활용한 온라인 산업에 대한 이론적 적용모델인 NEBIC에 대한 검토를 통해 동적성장이론인 이중나선구조 모형을 제안하였다. 또한 이론의 현실적합성을 확인하기 위해 2000년에서 2008년 한국 온라인 쇼핑산업의 발전과정을 재구성하고 각 기업의 매출자료 및 총매출액을 검토하여 현재 진행 중인 온라인 유통업의 동적 성장과정에서 각 기업의 역량이 시장에 적용되어지는 과정을 확인하고 새로운 진화방향을 제시하고자 하였다. 이러한 과정을 통해 보았을 때, 오픈마켓의 주도를 통한 시장 발전은 한계에 봉착한 것으로 보인다. 따라서 향후 온라인 쇼핑몰은 자기 기반 역량 위에서 유통경로 구조 전반에 걸친 유통기능의 개발과 상품개발을 통해 경로구조를 통합하는 방향으로 발전할 것으로 잠정적 결론을 내릴 수 있을 것이다. 이러한 결론에 기반하여 오픈마켓에서 육성된 대형 판매자들의 전문몰화, 상장기업화를 유도하는 한편, 상품취급범위를 제한하는 다양한 정책 및 규제를 통합운영하고 조정하는 컨트롤 타워의 구축, 그리고 오픈마켓의 중소 상인육성기능을 강화하기 위한 인센티브의 구성과 같은 정책적 제안이 제시되었다.