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박동혁,이춘구,박하나,백승환,이중용 한국농업기계학회 2019 바이오시스템공학 Vol.44 No.4
Thediscreteelementmethodcanbeusedtosimulateparticlesystemsandidentifyforcesactingonaparticle,butthesuitabilityof using simulation for the modeling of garlic is undetermined. This study was conducted to evaluate the feasibility of using the EDEM program as a simulation tool for garlic bulbs in a garlic harvester. Simulations were compared with experimental collisions between a bulb and the roller of a garlic harvester. In the collision tests, the behavior and impact of an artificial garlic were observed with a high-speed camera and an accelerometer. The simulated positions and accelerations of the garlic were obtainedinEDEMusingthesameparametersasthoseoftheexperiment.Theimpactsofthegarlicwerecomparedintermsofthe rootmeansquareofacceleration,contactnumber,andaverageforceforrollerspeedsof100–300rpm.Basedonsimilarbehavior observed from photographic images of the experiments, the collision of garlic can be simulated in EDEM. The simulated accelerations were 2.8–7.8 times larger than the measured accelerations, which is attributed to an experimental limitation. The difference was reduced to 1.18 times after applying this limitation to the simulated data. In the simulations, the number of collisions decreased from 185 to 93 as the rotational speed increased, but the average force increased from 3.188 to 6.222 N. EDEM is suitable for simulating the collision of garlic with harvester conveying rollers. Therefore, EDEM can be applied to evaluate the impact forces acting on the garlic and to improve the structure of garlic harvesters.
박동혁,이재진,Park, Dong-Hyuk,Lee, Jae-Jin The Korean Institute of Communications and Informa 2010 韓國通信學會論文誌 Vol.35 No.7c
본 논문에서는 직렬 연접 길쌈 부호와 LDPC 부호를 이용하여 수직자기기록 채널에서의 성능을 조사하였다. 실험과정에서 기록 밀도는 1.7, 2.0, 2.4, 2.8 일 때를 각각 실험하였다. 직렬 연접 길쌈 부호는 LDPC 부호보다 복호기의 구현 복잡도가 더 낮다. 직렬 연접 부호는 순환 구조적 길쌈 부호의 부호기와 복호기, 그리고 프리코더와 인터리버로 이루어져 있다. 본 실험에서 직렬 연접 길쌈 부호의 복호 알고리즘은 메시지 전달 알고리즘을 이용하였으며, LDPC 부호의 복호 알고리즘은 Sum Product 알고리즘을 이용하였다. 신호 검출기와 오류정정부호 사이에 반복 복호 기법을 적용한 터보등화기 기법을 적용하였고, 기록 밀도가 높아짐에 따라 직렬 연접 길쌈 부호가 LDPC 부호 보다 더 효율 적인 것을 보였다. In this paper, we investigate the performances of the serial concatenated convolutional codes (SCCC) and low-density parity-check (LDPC) codes on perpendicular magnetic recording (PMR) channels. We discuss the performance of two systems when user bit-densities are 1.7, 2.0, 2.4 and 2.8, respectively. The SCCC system is less complex than LDPC system. The SCCC system consists of recursive systematic convolutional (RSC) codes encoder/decoder, precoder and random interleaver. The decoding algorithm of the SCCC system is the soft message-passing algorithm and the decoding algorithm of the LDPC system is the log domain sum-product algorithm (SPA). When we apply the iterative decoding between channel detector and the error control codes (ECC) decoder, the SCCC system is compatible with the LDPC system even at the high user bit density.
Modeling of the Inter-Page Interference on the Holographic Data Storage Systems
박동혁,이재진,Park, Dong-Hyuk,Lee, Jae-Jin The Korean Institute of Communications and Informa 2010 韓國通信學會論文誌 Vol.35 No.7c
The holographic data storage system stores multiple data pages by multiplexing. But the inter-page interference(IPI) caused by multiplexing reduces the intensity of the hologram. The simulation of the holographic storage systems has to consider the IPI. Therefore, we introduce a channel modeling that takes care of inter-page interference in the holographic data storage system. We simulate the performance of PRML detection on the hologrpahic data storage system with IPI modeling. 홀로그래픽 저장장치는 여러 장의 데이터 페이지가 멀티플랙싱 기법에 의하여 같은 공간에 저장된다. 그러나 이러한 데이터 저장 밀도의 증가에 따라 페이지 데이터들이 서로에게 간섭이 된다. 같은 공간에 저장되는 모든 페이지들이 서로 간섭을 주게 되며, 그에 대한 영향력을 실험 과정에서 고려해야 한다. 따라서 본 논문에서는 이러한 페이지 간의 간섭에 대한 모델링을 하며, 그에 대한 성능을 분석한다.
Analysis of Inter-particle Contact Parameters of Garlic Cloves Using Discrete Element Method
박동혁,이춘구,양도이,김대현,김준용,이중용 한국농업기계학회 2021 바이오시스템공학 Vol.46 No.4
Purpose The discrete element method (DEM) can be used in agricultural fields such as crop sowing, harvesting, and crop transportation. Nevertheless, modeling complex crops as appropriately shaped particles remains challenging. The modeling of particles and the calibration of input parameters are important for simulating the realistic behaviors of particles using the DEM. Methods In this study, particle models representing the morphological characteristics and size deviations of garlic cloves were proposed. Additionally, the coefficients of friction were analyzed as the contact parameters of the particles based on the heap formation experiments and simultations of the swing-arm method using 150 garlic cloves. Results The simulation results were analyzed that the residual number of particles, a bulk property that can be measured simply in the experiment, is related to the coefficients of friction. In the heap formation experiments with low particle counts, the bulk properties were more clearly differentiated by the residual number of particles than the angle of repose. Moreover, the bulk properties similar to the actual garlic could not be expressed as a spherical particle model. Thus, an equation for predicting the residual number of particles was derived for the non-spherical garlic clove particlemodel. Five sets of coefficients of friction were presented using the prediction equation, and all the simulation results were close to the actual residual number of particles and angle of repose of the garlic. Conclusions Although the sizes of garlic cloves have a wide distribution, appropriate inter-particle contact parameters could be predicted. Therefore, the calibration process of the DEMcan be shortened using the proposed prediction equation for the residual number of particles with non-spherical particles.
한국 노인의 안정시심박수, 상대 악력 및 당뇨병 유병률의 연관성: 2015-2018 국민건강영양조사 자료를 기반으로
박동혁,홍성현,조원희,전용관 한국운동생리학회 2020 운동과학 Vol.29 No.4
PURPOSE: The purpose of this study was to examine the association of resting heart rate (RHR) and relative hand grip strength (RHGS) with diabetes among Korean adult over 65 years old. METHODS: Cross-sectional analyses were performed using the 2015-2018 Korea National Health and Nutrition Examination Survey (KNHANES). Among 31,649, a total of 4,814 adults over 65 years old were included in this study. Participants were divided into tertile according to their RHR and RHGS. Statistical methods included frequency analysis, ANCOVA (Analysis of covariance) and logistic regression. RESULTS: Participants in the 3rd tertile of RHR (RHR over 73 bpm in men, 74 bpm in women) had 2.00 times [95% Confidence Interval (CI): 1.58-2.54] and 1.80 times (95% CI: 1.44-2.26) higher odds of having diabetes in men and women, respectively, compared with participants in the 1st tertile (RHR below 64 bpm in male, 65 bpm in female). Participants in the 1st tertile of RHGS (RHGS below 0.46 in men, 0.31 in women) had 2.51 times (95% CI: 1.76-3.58) and 1.86 times (95% CI: 1.48-2.35) higher odds of having diabetes in men and women, respectively, compared to participants with 3rd tertile (RHGS over 0.54 in men, 0.38 in women). When a joint association of RHR and RHGS with risks of diabetes were analyzed, participants with the highest RHR and the lowest RHGS had 4.23 times (95% CI: 2.74-6.54) and 2.90 times (95% CI: 1.98-4.23) higher odds of having diabetes compared to participants with the lowest RHR and the highest RHGS in men and women, respectively. CONCLUSIONS: The current study showed that higher RHR and lower RHGS were associated with increased risk of diabetes in Korean elderly population.