• Geomechanics and Engineering
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• 제28권3호
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• pp.265-281
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• 2022

A set of slurry shield test system capable of cutter cutting and slurry automatic circulation is used to investigate the deformation characteristics, the evolution characteristics of support resistance and the distribution and evolution process of earth pressure during excavating and collapsing of slurry shield tunneling in circular-gravel layer. The influence of cover-span ratio on surface subsidence, support resistance and failure mode of excavation face is also discussed. Three-dimensional numerical calculations are performed to verify the reliability of the test results. The results show that, with the decrease of the supporting force of the excavation face, the surface subsidence goes through four stages: insensitivity, slow growth, rapid growth and stability. The influence of shield excavation on the axial earth pressure of the front soil is greater than that of the vertical earth pressure. When the support resistance of the excavation face decreases to the critical value, the soil in front of the excavation face collapses. The shape of the collapse is similar to that of a bucket. The ultimate support resistance increase with the increase of the cover-span ratio, however, the angle between the bottom of the collapsed body and the direction of the tunnel excavation axis when the excavation face is damaged increase first and then becomes stable. The surface settlement value and the range of settlement trough decrease with the increase of cover-span ratio. The numerical results are basically consistent with the model test results.

• 대한한의학회지
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• 제43권4호
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• pp.145-158
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• 2022

Objectives: To identify changes in the subjects and methods of Herbal Medicine Consumption Survey, and analyze trend of the key results Methods: The population, methods, and items of the basic reports of all Surveys on Consumption of Herbal Medicine(HM) were organized in a time-series manner. The analysis items were trend in the purchase of standardized HM; consumption value share, and price of prepared HM; type of herbal dispensary; and awareness of HM policy in Koran Medicine(KM) institutions. Results: The price of HM preparations showed an upward trend in 2011, 2014, and 2017 surveys, and decreased in the 2020 survey. However, despite this recent decrease, the 2021 survey also saw the highest proportion of HM users reporting that price of herbal decoction is expensive. Furthermore, the demand for expanded coverage of herbal decoction was the greatest for the expansion of health insurance benefits. Efforts such as adjusting the number of covered diseases and the cost of health insurance coverage would be necessary. Regarding decoction dispensaries the proportion of HM hospitals using only extramural herbal dispensaries increased. Finally, the consumption of HM and the size of the HM industry has continued to expand due to the large-scale branding of KM institutions and the expansion of health insurance coverage. Conclusion: Future surveys must standardize and unify the items for the time-series continuity and compare the results with government statistics reports on HM to increase reliability. Moreover, specialized survey items may be developed for KM, to establish a better and efficient distribution system for domestic HMs.

• 한국유기농업학회지
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• 제28권3호
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• pp.367-386
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• 2020

The significance of this study was to analyze the quality value of organic livestock pork for the first time based on the results of managing and testing the cycling organic farming of black pork and vegetables within farm for two years. The results of analysis could be summarized as follows. First, the pork of experimental group with crop-livestock cycling farming showed the excellent quality and high consumer preference compared to the control group of general pork or pork from non-crop-livestock cycling organic farming. In the content ratio of Omega-3 as a representative essential fatty acid, it was 1.46 that was about 2.8 times more than general pork (0.52). In case of Omega-6, it had about 2.5 times more than general pork. Especially, the U/S ratio value which was the content ratio of Unsaturated Fatty Acid (UFA, U) of Saturated Fatty Acid (SFA, S), was largely shown in pork (2.93) from cycling organic farming. Second, it would be necessary to maintain the economies of scope shown in crop-livestock cycling organic farming, and the high quality value of livestock products. For this, there should be a value chain model that could realize the economies of scope and economies of scale at the same time based on scaling and diversification through cooperative organization between farmers. Through this, it would be possible to establish a cycling model called 'community cooperative agriculture' by forming local internal markets through cooperation of production-processing and integration of distribution-sale-consumption. For the managerial activation of this cooperative organization, the government should promote/support the small crop-livestock cycling organic farming cooperative organization in local unit. For securing the reliability of crop-livestock cycling organic agricultural products and crop-livestock cycling organic livestock products, it would be necessary to review the introduction of Participatory Guarantee System (PGS).

• 산업경영시스템학회지
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• 제37권3호
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• pp.36-42
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• 2014

Domestic 105mm HE (High Explosive) shell is composed of three parts that are Fuze, Projectile and Propellants. Among three parts, propelling charge of propellants part consists of single base propellants. It has been known that the lifespan of single base propellants is affected by a storage period. These are because Nitrocellulose (NC) which is the main component of propelling gunpowder can be naturally decomposed to unstable substances similar with other nitric acid ester. Even though it cannot be prevented fundamentally from being disassembled, a decomposition product ($NO_2$, $NO_3$, and $HNO_3$) and tranquillizer DPA (Diphenylamine) having high reactivity are added into a propellant to restrain induction of automatic catalysis by a decomposition product. The decay rate of the tranquillizer is also affected by a production rate of the decomposition product of NC. Therefore, an accurate prediction of the Self-Life is required to ensure against risks such as explosion. Hereupon, this paper presents a new methodology to estimate the shelf-life of single base propellants using data of ASRP (Ammunition Stockpile Reliability Program) to domestic 105mm HE (propelling charge of propellants part). We selected four attributes that are inferred to have influence on distribution of the DPA amount in a propellant from the ASRP dataset through data mining processes. Then the selected attributes were used as independent variables in a regression analysis in order to estimate the shelf-life of single base propellants.

• The Journal of Asian Finance, Economics and Business
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• 제7권8호
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• pp.425-433
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• 2020

This paper aims to develop a conceptual framework for evaluating the impact of motivational factors on the work results of lecturers at Vietnam National University, Hanoi (VNU), one of two leading multidisciplinary and multi-sectoral national universities in Vietnam. This study has considered wages and other benefits (WB), training and development (TD), working environment (WE) and working motivation (WM) as motivational factors, and proposed a structural model of the impact of motivational factors on the work results of lecturers at VNU. The empirical analysis used data from the survey data of 321 university lecturers. Comprehensive, valid, and reliable tools (SPSS 26 and SmartPLS 3.0 software) are used to evaluate rigorous statistical tests including convergence validity, discriminatory validity, reliability, and average variance extracted to analyze and verify the gathered data, and the hypotheses developed. The result of path analysis shows that four motivational factors constitute a structured system with different degrees of influence on the work results of lecturers. There is also a positive relationship between the motivational factors and the work results of lecturers. As a result, it can be concluded that all hypotheses developed are supported. Several recommendations are further suggested to improve the performance of lecturers at VNU.

• 대한교통학회지
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• 제23권2호
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• pp.151-160
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• 2005

버스와 같은 대중교통의 경우에는 서비스수준을 평가하는 효과철도에 확률의 개념이 사용되어, 확률값의 선형비례적인 수치를 기준으로 A~F의 서비스수준의 등급을 구분하기도 한다.(TCQSM: Transit Capacity and Quality of Service Manual-2nd Edition, TRB, Washington DC., 2003) 이 경우 운전자나 승객이 느끼는 정도와 확률값이 선형비례 관계에 있지 않을 수 있는데 이는 서비스수준을 적절하게 반영한다고 볼 수 있다. 본 연구에서는 TCQSM에서 제시하고 있는 버스 운행의 정시성 평가 사례를 통해 확률값의 선형비례적인 수치를 기준으로 서비스수준의 등급을 구분할 때 발생하는 문제점을 분석하고, 이러한 문제점을 보완하는 적절한 서비스수준 기준을 산정하는 방법론을 제시하였다. 본 연구에서 제시한 차두간격 분산계수 분포의 확률밀도를 기준으로 서비스수준의 기준을 산정하는 방법은 승객의 평균 대기시간을 적절하게 반영하고, 실제 버스 운행 자료를 사용하여 적용한 결과, TCQSM에서 제시한 방법보다 더 적절하게 버스의 운행 신뢰성을 평가하는 것으로 나타났다. 그러나 효용함수를 이용하여 서비스수준의 기준을 산정하는 방법은 이용자가 느끼는 서비스수준과 효용차이의 관계에 대한 추가적인 연구가 필요한 것으로 본 연구의 한계로 남는다.

• 한국인터넷방송통신학회논문지
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• 제18권6호
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• pp.181-186
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• 2018

산업화의 추세에 따라 수요가 급증하고 있는 고전력을 생산하기 위하여 시설장비 및 부하의 대용량화가 수반되고 있다. 전기설비의 규모는 점차 복잡해 지고, 대규모화 됨으로써 고도 정보화 사회로의 발전에 크게 기여하고 있다. 그러나, 발전 설비에서 불의의 사고가 발생하여 전기의 생산이 중단된다면, 전기에 의존하여 작동 중인 수 많은 장비가 지장을 받게되고, 산업사회에 막대한 경제적 손실 및 장애를 초래하게 된다. 사고가 발생한 발전설비를 복구하기 위해서는 많은 시간과 비용이 소요되어 국가 산업 활동에 막대한 경제적 피해를 끼치게 된다. 사고를 미연에 방지하기 위하여 케이블의 동작 상태를 정기적으로 감시 확인하여야 한다. 우리는 사고가 가장 빈번하게 발생하는 접속부에 대해 안정적인 사용을 위한 진단의 정확성과 신뢰성을 향상시키기 위한 연구를 하였다. 이 논문에서 데이터 취득을 하고, 통계적 처리를 하기 위한 방법을 제시한다.

• Advances in nano research
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• 제9권1호
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• pp.1-13
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• 2020

In this work, the electrical potential (EP) technique with an artificial neural networks (ANNs) for monitoring of nanostructures are used for the first time. This study employs an expert system to identify size and localize hidden nano-delamination (N.Del) inside layers of nano-pipe (N.P) manufactured from Basalt Fiber Reinforced Polymer (BFRP) laminate composite by using low-cost monitoring method of electrical potential (EP) technique with an artificial neural networks (ANNs), which are combined to decrease detection effort to discern N.Del location/size inside the N.P layers, with high accuracy, simple and low-cost. The dielectric properties of the N.P material are measured before and after N.Del introduced using arrays of electrical contacts and the variation in capacitance values, capacitance change and node potential distribution are analyzed. Using these changes in electrical potential due to N.Del, a finite element (FE) simulation model for N.Del location/size detection is generated by ANSYS and MATLAB, which are combined to simulate sensor characteristic, therefore, FE analyses are employed to make sets of data for the learning of the ANNs. The method is applied for the N.Del monitoring, to minimize the number of FE analysis in order to keep the cost and save the time of the assessment to a minimum. The FE results are in excellent agreement with an ANN and the experimental results available in the literature, thus validating the accuracy and reliability of the proposed technique.

• 한국안전학회지
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• 제19권4호
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• pp.141-149
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• 2004

가솔린 엔진을 장착한 자동차는 고전압발생장치인 점화코일을 이용하여 고전압을 발생 연소실 내의 혼합기를 점화 및 연소시킴으로써 동력을 얻고 엔진을 구동하게 된다. 점화코일은 1차측 낮은 전압을 스위칭 작용으로 2차측 높은 전압을 발생시키고, 이를 전극으로 보내는데, 점화코일에 작은 결함이 발생하게 되면 제 성능을 발휘하지 못한다. 본 연구에서는 현재 사용하고 있는 에폭시 성형 점화코일과 절연재료인 에폭시수지를 시료로 선택하여 시료에 전압이 인가될 때 발생하는 부분방전 특성을 측정하여 전압변화에 따른 위상각, 방전전하량 및 발생빈도 수 등의 분포를 연구하고 검토한 결과를 실제 자동차점화장치에 접목시켜 점화코일의 성능향상과 전기장치의 신뢰성 확보에 기여하고자 한다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.258-265
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• 2017

고속추진체계의 시험평가에는 많은 비용과 시간이 필요하므로 시험자료의 양은 항상 부족하고, 설사 있더라도 지상시험 환경이 실제 비행조건과 일치하는 경우가 드물다. 이러한 이유로 설계자들은 설계결과에 대한 불확실성을 정량적인 확률로 제시하는데 어려움을 가지고 있다. 본 논문에서는 Evidence 기법을 이용하여, 시험자료 대신 개발자들의 경험과 공학적인 지식을 바탕으로 불확실성을 모델링하는 방법을 연구하였다. 연소효율은 이중연소램제트 엔진의 초기설계단계에서 가장 예측하기 어려운 변수중의 하나이다. 유사분야의 경험을 가진 설계자들이 이 값을 제시하는 것으로 가정하여 이중연소램제트 엔진의 설계결과에 대한 불확실성을 산출하였다. 나아가 흡입구와 연소기 출구면적으로 설계변수로, 추력성능과 thermal choking의 가능성을 제약함수로 하는 신뢰성 최적설계를 수행함으로써 시스템의 안전성을 확보하면서 최적의 성능을 얻을 수 있는 설계기법을 탐색하였다.