• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.9-9
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• 2017

입자거동해석소프트웨어(EDEM)은 DEM(Discrete Element Method)기법을 이용한 입자 거동 전용 해석툴로 입자 유입량, 위치 등을 조절하여 입자거동과 관련된 제품 개발, 프로세스 최적화를 위한 비용 및 시간 절감에 활용도가 뛰어난 소프트웨어이다. EDEM을 활용하기 위해선 적용대상에 대한 물성치를 적용하여야 한다. 따라서 본 연구에서는 EDEM를 이용하여 현재 연구개발 중인 카드클리너 방식의 고추 선별기의 성능을 분석을 수행하기 위해 고추 물성측정 실험을 수행 하였다. EDEM을 이용한 입자거동해석에 필요한 개인 물성치에는 포아송비, 전단탄성계수, 밀도가 있다. 또한 입자-입자, 입자-Geometry 간의 상호관계를 위한 물성치인 반발계수, 정지마찰계수, 구름마찰계수가 필요하다. 공시 시료인 고추는 광주광역시 남구 승촌동 소재의 개인농가 Plastic 온실로 재배된 '천상'품종을 사용하였다. 푸아송 비와, 전단 탄성계수를 측정하기 위한 인장시험기기로는 만능인장시험기(TA-XT2, Stable Micro, 영국)를 이용하였으며, 인장에 의한 고추의 변형량 축정은 초고속카메라(NX4-SI, IDT, 미국)을 이용하였다. 밀도는 비중병법에 기초하여 질량과 부피를 측정하여 밀도를 계산하였다. 반발계수는 고추의 충돌 실험을 통해 변화한 높이를 이용하여 계산하였고, 충동 실험을 통해 변화한 높이는 초고속카메라를 이용하여 측정하였다. 정지마찰계수와 구름마찰계수는 고추의 미끄러짐이 시작하는 각도와 등속도 운동으로 구르는 각도를 초고속카메라를 이용하여 측정 후 계산하였다. 모든 실험은 3번 반복을 통해 평균값을 시험 결과 값으로 이용하였다. 고추의 대한 물성치 실험결과 고추의 푸아송 비는 0.294(std : 0.2), 전단탄성계수 4.624E+06 Pa, 밀도 $600kg/m^3$로 나타났다. 또한 입자-입자 간의 물성치인 반발계수는 0.383, 정지마찰계수는 0.455, 구름마찰 계수는 0.043로 나타났다. 추후 본 연구에서 측정한 고추의 물성치를 적용한 EDEM 입자거동해석 시뮬레이션을 통해 카드클리너 방식의 고추 선별기의 성능에 대한 분석을 하고자 한다.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.65-65
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• 2017

밭작물 중 양파와 마늘은 높은 노동투하시간, 노임의 상승, 복잡한 수거 과정 등으로 최근 재배면적이 감소하는 추세이다. 밭농업 활성화 방안으로 생산비 절감과 작업 속도 향상을 위한 수확기계 개발 연구로 줄기절단기가 개발되었다. 이 연구는 줄기절단기 예취날의 설치각이 절단부하에 미치는 영향을 분립체 해석 기법으로 분석하고자 하였다. 실험에 사용한 시뮬레이션은 EDEM으로 인장탄성계수, 전단탄성 계수, 중첩길이, 입자 반경 및 질량, 상대속도를 이용하여 충돌시 힘을 해석하고 인장 및 전단강도, 한계, 결합 길이를 통해 입자간 결합을 설정할 수 있다. 시제품으로 설계된 줄기절단기의 치수를 활용하여 프로그램 상에서 줄기 절단 시뮬레이션을 진행하여 절단부하 결과를 얻도록 하였고 칼날 설치각을 30도, 45도, 60도로 변경하여 각각의 부하를 분석하여 경향성을 파악하고자 하였다. 실험에서 사용한 프로그램은 EDEM 2.7.1 Academic Research 버전이며 시뮬레이션을 진행한 PC의 사양은 Intel(R) $Core^{TM}$ i7-4790 CPU @ 3.60GHz, Memory 16.0GB이다. 줄기 절단 시뮬레이션에 적용시킨 줄기 모델은 마늘의 조건을 적용시켜 직경 1mm의 입자로 이루어진 지름 12mm, 높이 214mm의 원통형 모델이며 60.32N의 최대절단력을 가지고 있다. 줄기절단기는 2개의 회전날을 가지고 있으나 좌우대칭을 적용하여 절반에 대한 해석으로 하나의 회전날로 절단을 하도록 줄기 모델은 4조로 하여 3열을 140mm 간격으로 위치시켰다. 줄기절단기의 칼날은 반경 350mm로 회전하며 진행속도는 1.65m/s, 회전속도는 1680rpm으로 작업하도록 하였다. 시뮬레이션은 0.5초의 시간에 대해 해석하도록 하였으며 0.003초 간격으로 칼날에 가해지는 힘을 구하여 저장하도록 하였다. 시뮬레이션 해석시간은 약 116시간이었으며 설치각별 시간에 따른 칼날에 가해지는 압축력 값과 그래프를 얻을 수 있었다. 대부분의 시간에서 절단이 이루어지지 않으므로 0의 값을 나타내었으며 절단이 이루어지는 시점에 절단부하가 나타났다. 결과 해석을 위해 그래프의 피크 값들을 이용하였으며 그 중 상위 6개의 값으로 분석하였다. 30도, 45도, 60도의 설치각에 따른 절단부하의 평균 값은 각각 105.4N, 160.5N, 215.9N으로 나타났다. 설치각에 따른 절단부하의 경향성은 유의수준은 3.93%로 각각의 차이가 유의미하게 나타났으며 상관계수는 0.489로 증가하는 경향이 보였다. 그러나 $R^2$는 0.2394로 낮은 값을 보여 데이터 처리 방법의 개선과 적절한 회귀 모델의 적용이 필요하다. 향후 포장시험을 진행하고 복합적으로 분석하여 경향성을 자세히 분석하고자 한다.

• Journal of Korean Society of Disaster and Security
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• v.12 no.2
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• pp.57-63
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• 2019

The road sinks in the sewer line or subway section are affected by the ground characteristics. Therefore, it is necessary to accurately identify the relationship between the soil properties and the ground motion in the area where cavities occurred in order to establish a countermeasure against the road sink. In this paper, simulation was performed by using EDEM program, which is one of the Discrete Element Method programs, for sandy soil and clayey soil, which are most common in alluvial deposits, with different locations and sizes of cavities in the underground. As a result, it was found that the sink size occurred more in the sandy soil than in the cohesive soil. Deeper and larger cavity is more likely to occur the road sink In the sand soil model while road sink in the clay model is easy to occur when the cavity is more shallower.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.372.2-372
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• 2002

This paper presents an efficient modeling method fur open cracked beam structures. An equivalent bending spring model is introduced to represent the structural weakening effect in the presence of open cracks. The proposed method adopts the exact dynamic element method (EDEM) to avoid the difficulty and numerical errors in association with re-meshing the structure. The proposed method is rigorously compared with a commercial finite element code. (omitted)

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.3
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• pp.187-192
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• 2020

To reduce fuel consumption by reducing the weight of the deck of a dump truck and to design an eco-friendly deck, accurate structural analysis is required. To date, the load on the deck has been calculated based on the hydrostatic pressure or by applying the earth pressure theory. However, these methods cannot be used to determine the non-uniformity of the load on the deck. Load distribution varies depending on the size distribution and interaction of aggregate particles. Compared with the finite element method, the discrete element method can simulate the behavior of aggregate particles more effectively. In this study, major properties were obtained by measuring bulk density and repose. The deck of a 15 ton dump truck was simulated using the obtained properties and bumping, breaking, and turning load conditions were applied. EDEM, which is a discrete element analysis software, was employed. The stress and strain distribution of the deck were calculated by NASTRAN and compared with the measured values. The study revealed that the results derived from a DEM simulation were more accurate than those based on mathematical assumption.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.725-730
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• 2002

This paper presents an efficient modeling method for open cracked beam structures. An equivalent bending spring model is introduced to represent the structural weakening effect in the presence of open cracks. The proposed method adopts the exact dynamic element method (EDEM) to avoid the difficulty and numerical errors in association with re-meshing the structure. The proposed method is rigorously compared with a commercial finite element code. Experiments are also performed to validate the proposed modeling method. Finally, a diagnostic scheme for open cracked beam structures is proposed and demonstrated through a numerical example.

• Journal of KSNVE
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• v.9 no.5
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• pp.966-974
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• 1999

This paper introduces modeling and its modal analysis procedure for exact and closed form solution of in-plane vibrations of general Timoshenko frame structures using exact dynamic element method(EDEM). The derivation procedure of the exact system dynamic matrices for Timoshenko beam frames is described. A new modal analysis procedure is also proposed since the conventional modal analysis schemes are not adequate for the proposed, exact system dynamic matrix. The proposed method provides exact modal parameters as well as all kinds of closed form solutions for general frame structures. Two numerical examples are presented for validating and illustrating the proposed method. The numerical study proves that the proposed method is useful for dynamic analysis of frame structures.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.6
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• pp.197-204
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• 2003

This paper presents an efficient modeling and dynamic analysis method for open cracked beam structures. An equivalent bending spring model is introduced to represent the structural weakening effect in the presence of cracks. The proposed method adopts the exact dynamic element method (EDEM) to avoid the inconvenience and numerical errors in association with re-meshing the structural model with the crack position changed. The proposed modeling method is validated through a series of simulation and experiments. First, the proposed method is rigorously compared with a commercial finite element code. Then, two kinds of experiments are performed to validate the proposed modeling method. Finally, a diagnostic scheme fur open cracked beam structures is proposed and demonstrated through a numerical example.

• The Korea Journal of Herbology
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• v.27 no.3
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• pp.57-65
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• 2012

Objective : For the purpose of developing Korean herbology of the plants to Polyporaceae in Korea, the literatures of the successive generations have been thoroughly investigated to prepare this article. Methods : The examined herbological books and research paper which published domestically and abroad. Results : 1. Polyporacease plants (raised in Korea) are devided into 31 classes with 59 species. Among them, 26 species in 19 classes were found serviceable, which indicates 44 % of all Polyporacease plants. 2. Among those 59 species, $Coriolus$ $Phellinus$ $Trametes$ includes 5 species. $Ganoderma$, a medicinal plant, includes 3 species. 3. Dividing the serviceable plants of Polyporacease, the fruit body family had the largest number; 25. 4. Out of plants Polyporacease, neutral taste plants was 17 species and sweet taste was 14 species. 5. Only 8 species of Polyporaceae plants were found to enterd into the spleen and heart. 6. 11 species were found to prevent cancer, 7 species were found to dispel wind-dampness and Alleviate edem antittusive and antasth matic. 7. There were no toxic species in the Plyporaceae. Conclusion : There were totaled to 31 genera and 59 species in Polyporaceae in Korea and among them medicinal plants are 19genera, 26 species, some 44% in total.

• Journal of Distribution Science
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• v.17 no.9
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• pp.67-81
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• 2019

Purpose - The overarching aim of this study is to empirically test the effect of ex-post control mechanisms on multi-dimensional trust and channel performance in franchise systems. Although the franchise system is a vertical marketing channel based on trust between the franchisor and the franchisees, issues related to franchisee's opportunistic behavior have persisted and thus requires research into the effective control system of franchise headquarters. Research design, data, and methodology - In this study, data was collected from 150 franchises to identify the effect of two types of franchising headquarters' control system on the multi-dimensional trust and franchise channel outcome between franchisor and franchisee. To test the hypotheses intended to achieve this aim, structural equations modeling technique is utilized. Results - The results of this research reveal that among the two formal control systems studied (output and process control), output control positively and significantly affects multidimensional trust. Additionally, among the three dimensions of trust employed in this study, only expertise has a positive and significant effect on contract compliance. Equally, only expertise and integrity have a negative and significant effect on opportunistic behavior. Conclusions - The study provides managerial and theoretical insights into understanding ex-post control mechanisms, trust, compliance and opportunistic behaviors in franchise systems.