Determination of Physical Properties for Discrete Element Model on the Nanji-Type Garlic Cloves

한현우,임동우,조승제,박영준 한국농업기계학회 2022 바이오시스템공학 Vol.47 No.4

Purpose Agricultural machines, which increase the convenience of agricultural work and enable mass production, are mechanical systems that inevitably interact with organisms based on the characteristics of handling agricultural products. Such crop-mechanical systems often form discrete systems by integrating a large number of agricultural products within the machines. The discrete element method (DEM) is an efective numerical method that is applicable to such discontinuous mechanical systems. However, the information required for a DEM model, such as the shapes, weights, and mechanical properties of crops, is difcult to obtain based on the characteristics of organisms with atypical and large dispersion. Therefore, this study aimed to develop a calibration process that can estimate and verify DEM model parameters for Nanji-type garlic cloves. Methods The DEM model considers the statistical properties and shape parameters of 500 garlic clove samples and is a cluster model composed of three spherical particles. The Hertz–Mindlin contact model was adopted, and the required parameters for the contact model, including the equivalent Young’s modulus and friction coefcient, were estimated, compared, and verifed based on actual compression and shear test results. Results Simulation results using the calibrated DEM model are in good agreement with the results of compression and shear tests. Further, the statistical properties of crop shape and weight were refected in the DEM model. Conclusion The fndings will aid the analysis of crop-mechanical systems. In particular, the proposed method has applicability in the design and analysis of planters and harvesters.

중증지체장애인의 자립생활에 미치는 영향 : 장애수용의 매개효과를 중심으로

한현우,이수민 한국성인계속교육학회 2023 성인계속교육연구 Vol.14 No.4

This study aims to analyze the factors that influence the independent living of people with severe physical disabilities, verifying the mediating effects of independent variables such as physical function level, disability acceptance, and self-esteem. The study involved 131 patients from A Rehabilitation Hospital and was conducted through descriptive statistical analysis, T-tests, regression analysis, and bootstrapping. The results of the study are as follows: First, the perception of independent living was higher in the paradigmatic perception of rehabilitation. Second, between the patients with spinal cord injuries and the with brain diseases, the level of disability acceptance was significantly higher in the with brain diseases, while self-esteem was significantly higher in the with spinal cord injuries. Third, in the regression analysis of variables related to independent living, self-esteem did not have a significant impact. Fourth, the level of physical function showed a partial mediating effect on disability acceptance in relation to independent living.

콰크 質量差의 下限界

韓賢愚 서울産業大學校 1994 논문집 Vol.39 No.1

Using a general potential-model approximation to quantum chromodynamics, mass formulae of ground state mesons and baryons are establised as eigenvalues of Hamiltonians. Inputting experimental masses of ground state mesons and baryons, lower bounds on the constituent-quark mass differences are calculated in these mass formulae. We obtain quark mass differences ->4.10.3MeV, ->183 0.3MeV, ->11800.3MeV, ->33430.3MeV respectively. The most constituent-quark masses of mesons and baryons which predicted by many authors are different values, but these masses are satisfied very well to our lower bounds. And we find that current -quark mass differences and invariant-quark mass differences are the same as constituent-quark mass differences.

승차감 평가를 위한 100 kW급 농업용 트랙터 운전자의 전신 진동 분석

한현우,김경대,임원홍,김지만,조승제,박영준 경상대학교 농업생명과학연구원 2022 농업생명과학연구 Vol.56 No.2

진동은 농업용 트랙터 운전자의 쾌적한 작업 환경 조성을 방해하고, 건강을 위협하는 요소이다. 본 연구에서는 국제 표준안(ISO 2631-1)에 따라 트랙터 운전자의 전신 진동을 평가하였다. 진동 시험은 재현성과 반복성이 뛰어난 four-post road simulator 상에서 6가지 노면 조건을 적용하여 수행하였다. 취득한 진동 신호의 파고율, 최대 진동 진폭, 피폭 진동 누적량, 실효치 등을 이용하여 진동 특성을 분석하였다. 최종적으로 건강 지도 위험 수준과 안락도에 대한 반응도를 평가 방법에 따른 실효치와 피폭 진동 누적량에 적용하여 농업용 트랙터의 운전자 전신 진동을 정량적으로 평가하였다. A vibration is a factor that impairs an working environment of agricultural tractor drivers and threatens their health. This study focused on the evaluation of whole-body vibration for the agricultural tractor driver according to an international standard (ISO 2631-1). Vibration tests were performed by applying six road conditions on a four-post road simulator that guarantees reproducibility and repeatability. The vibration characteristics were analyzed using the crest factor, maximum transient vibration value, vibration dose value, and weighted root-mean-square acceleration from the obtained vibration signals. Finally, the whole body vibration of the agricultural tractor driver were quantitatively evaluated by applying the health guidance caution level, and the comfort reactions for vibration environment to the root-mean-square acceleration and the vibration dose value according to the evaluation methods.

공간담론과 박물관교육

한현우,이병준 한국문화교육학회 2016 한국문화교육학회 학술대회지 Vol.2016 No.-

한국청년의 초기경력개발 과정에서의 전이에 관한 연구 -대학생을 중심으로

한현우,이병준 한독교육학회 2016 한독교육학회 학술대회 자료집 Vol.2016 No.3

High-speed continuous production of polymeric nanoparticles with improved stability using a self-aligned coaxial turbulent jet mixer

한현우,윤정훈,Gi-Ra Yi,최원일,임종민 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.97 No.-

Continuous synthesis of polymeric nanoparticles (NPs) has been intensively studied due to its greatpotential to produce NPs with the physicochemical properties of reproducibility and controllability. Here,we developed a self-aligned coaxial turbulent jet mixer for high-speed continuous synthesis of polymericNPs. The coaxial turbulent jet mixer can be constructed using commercial tubefittings and tubes. Sincethosefluidic components are self-aligned coaxially, leak-free jet mixers can be assembled without theuse of tools or specialized skills in robust manner. Using the jet mixer with polystyrene (PS) solution,uniform polymeric NPs can be synthesized in a fully continuous manner, for which diaphragm pumpsand pulsation dampers are used for continuous control of theflow. We also improved the dispersionstability of the PS NPs in aqueous solution against centrifugation by introducing polystyrene-poly(ethylene oxide) diblock copolymer (PS-b-PEO) as steric stabilizer. The NPs prepared using the coaxialturbulent jet mixer were smaller and more uniform in size compared to NPs synthesized by a bulknanoprecipitation method.

物理學에 나타나는 二陛偏微分方程式의 境界條件에 關하여

韓賢愚 서울産業大學校 1984 논문집 Vol.20 No.1

The boundary conditions and physical characteristics of the second order partial differential equations in theoretical physics were investigated in order to satisfy physical meaning. By applying difference equations, the boundary conditions and physical characteristics appeared in form apparently different form each other in elliptic, parabolic and hyperbolic equations.

次元行列을 利用한 物理量의 單位轉換

韓賢愚 서울産業大學校 1985 논문집 Vol.21 No.1

It is shown how matrix methods in dimensional analysis can be used to convert numerical values and units of electromagnetic quantities from the mks unit system to the Gaussian unit system and those of mechanical quantities from the SI unit system to the engineering unit system. Examples are given to illustrate that these methods are valid and useful.

λφ⁴/4! 理論의 再規格化

韓賢愚 서울産業大學校 1988 논문집 Vol.27 No.1

Renormalization of ? thoery have been studied. The pole in the propagator asked for mass renormalization,propagator renormalization,and wave function renormalizationin the presence of interaction. Divergences in the vertex were indentified as ultraviolet. Those structure and renormalization were revealed by ultraviolet cut-off method. The same results have been gained by dimensional method and its evaluation was more swifter and simpler than the ultraviolet cut-off method.