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박동혁 (사)방송기자연합회 2019 방송기자 Vol.48 No.-

나는 청소년이다. 고로 체육활동 할 권리가 있다.

박동혁,박현신,이정훈,이준헌,조동진,최다빈 한국스포츠교육학회 2010 우리체육 Vol.- No.6

조선어문 열독교수에서의 인문화교육

박동혁 길림성민족사무위원회 2001 중국조선어문 Vol.114 No.-

유효우량 산정을 위한 NRCS-CN 모형의 초기손실량 산정방법 개선

박동혁,무하마드 아즈말,안재현,김태웅,Park, Dong-Hyeok,Ajmal, Muhammad,Ahn, Jae-Hyun,Kim, Tae-Woong 한국수자원학회 2015 한국수자원학회논문집 Vol.48 No.6

본 연구는 NRCS-CN 방법이 산정하는 유출량의 정확성을 향상시키기 위하여 강우량과 최대잠재보유수량을 초기손실량 계산과정의 주요 기여인자로 고려하였으며, 우리나라 15개 유역에서 관측된 658개의 강우량과 유출량 자료를 이용하여 초기손실량의 수정모형을 제안하였다. 유효우량을 산정하는 방법으로는 NRCS-CN 방법(M1), NRCS-CN 방법에서 초기손실량계수를 감소시킨 방법(M2), 관측 강우-유출 관계를 바탕으로 본 연구에서 제안하는 방법(M3)을 적용하였다. 또한 USDA에서 제시하는 CN값($CN_T$), 관측자료로 부터 계산된 CN값($CN_C$) 그리고 최소자승법으로 추정한 CN값($CN_{LSF}$)을 각각의 방법에 적용하였다. 적용 결과는 RRMSE, NSE 그리고 PBIAS 등을 이용하여 평가되었다. 그 결과 $CN_T$를 M1, M2, M3에 적용한 경우 각 유역에서 평균적으로 [RMSE (23.60, 18.12, 16.04), NSE (0.54, 0.73, 0.79), PBIAS (36.54, 20.25, 12.00)]로 나타났다. 이와 비슷하게 $CN_C$를 M1과 M2에 적용하고, $CN_{LSF}$를 M3에 적용하였을 경우 각 유역에서 평균적으로 [RMSE (17.17, 15.88, 13.82), NSE (0.76, 0.80, 0.85), PBIAS (3.06, 4.47, 0.11)]로 나타났다. 따라서 본 연구에서 제안된 M3 방법을 사용하여 추정한 유효우량이 관측된 직접유출량과 통계학적으로 가장 가까운 값을 제공하는 것으로 나타났다. In order to improve the runoff estimation accuracy of the Natural Resources Conservation Service (NRCS) curve number (CN) model, this study incorporated rainfall and maximum potential retention as contributors for initial abstraction. The modification was proposed based on 658 rank-order data of rainfall and subsequent runoff from 15 watersheds. The NRCS-CN model (M1), one of its inspired modified model (M2), and the proposed model (M3) were analyzed employing different CN approaches. Using tabulated, calculated and least squares fitted CNs ($CN_T$, $CN_C$, $CN_{LSF}$, respectively), the models' performances were evaluated based on Root Mean Square Error (RMSE), Nash-Sutcliffe Efficiency (NSE), and Percent Bias (PBIAS). Applications of model M1, M2, and M3, respectively exhibited watershed cumulative mean [RMSE (23.60, 18.12, 16.04), NSE (0.54, 0.73, 0.79), and PBIAS (36.54, 20.25, 12.00)]. Similarly, using CNC (for M1 and M2 model) and $CN_{LSF}$ (for M3 model), the performance of three models respectively were assessed based on watershed cumulative mean [RMSE (17.17, 15.88, 13.82), NSE (0.76, 0.80, 0.85), and PBIAS (3.06, 4.47, 0.11)]. The proposed model (M3) that linked all of the NRCS-CN variants showed more statistically significant agreement between the observed and estimated data.

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.

주행 시뮬레이터 기반 C-ITS 정보제공 서비스 평가

박동혁,강가원,박준영,허희범 한국ITS학회 2022 한국ITS학회 학술대회 Vol.2022 No.06

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.

수직자기기록 채널에서 LDPC를 이용한 메시지 전달 방식의 채널 검출 성능비교

박동혁,이재진 한국통신학회 2008 韓國通信學會論文誌 Vol.33 No.4

수직자기기록 채널에서는 PRML(Partial-Response Maximum Likelihood) 검출방법이나 NPML(Noise-Predictive Maximum Likelihood) 검출방법을 이용한 방식으로 더 이상의 성능 향상을 기대하기 힘들게 되었다. 따라서 LDPCO(Low-Density Parity-Check) 부호를 이용한 성능의 향상을 기대하게 되었는데, 본 논문에서는 메시지 전달 방식을 이용한 채널 검출기와 LDPC 부호를 결합시켜 병렬적으로 채널 반복복호를 수행하여 수직자기기록 채널에서의 성능을 보았다. 또한 메시지 전달 방식의 채널 검출기의 구현 복잡도를 근사화 방식을 이용하여 간단히 하였다.

Evaluation of the Mechanical Properties of ZnO Nanorods Treated with Oxygen Plasma using Atomic Force Microscopy

박동혁,양이준,김관래 대한금속·재료학회 2021 대한금속·재료학회지 Vol.59 No.3

Zinc oxide (ZnO) simultaneously exhibits semiconducting and piezoelectric properties. ZnO in the form of nanorods has been studied intensively for application in self-powering devices. The power generation in piezoelectric nanogenerators based on ZnO nanorods can be improved via several approaches, including an oxygen plasma treatment. When ZnO nanorods are exposed to oxygen plasma, the charge carrier concentration decreases and the piezoelectric output voltage consequently increases. However, the effects of oxygen plasma on the mechanical properties of ZnO nanorods has not been systematically studied using a precise measurement technique. Given the size of ZnO nanorods, atomic force microscopy (AFM) is a suitable method for manipulating individual ZnO nanorods and measuring their elastic properties. In the present work, we observed the effects of oxygen plasma on the elemental composition and microstructure of ZnO nanorods. First of all, the surface roughness of the ZnO nanorods was analyzed using AFM, revealing that it increased due to the etching effect of the oxygen plasma. From X-ray photoelectron spectroscopy (XPS) measurements, three distinct peaks corresponding to lattice oxygen, oxygen vacancies, and absorbed oxygen on the surface were identified. The XPS analysis results showed that oxygen vacancy defects on the ZnO nanorods were decreased by oxygen plasma treatment. Next, the effects of oxygen plasma on the elastic properties of ZnO nanorods were studied using lateral force microscopy. It was confirmed that the elastic modulus of ZnO nanorods increased due to the reduced number of defects originating from oxygen vacancies.

A Comparative Study of BaTiO3/PDMS Composite Film and a PVDF Nanofiber Mat for Application to Flexible Pressure Sensors

박동혁,김관래 대한금속·재료학회 2021 대한금속·재료학회지 Vol.59 No.6

Intensive research has been conducted to develop flexible piezoelectric pressure sensors, since selfpowering devices are advantageous for wearable electronic applications. Recently, two types of piezoelectric devices, ceramic-PDMS composite film and PVDF nanofiber mats, have drawn attention in the research community. Piezoelectric ceramics such as BaTiO3 (BTO) and PZT exhibit outstanding piezoelectric coefficients, while PDMS provides flexibility. In contrast, a PVDF nanofiber mat simultaneously exhibits piezoelectricity and flexibility. In the present study, a comparative analysis of BTO-PDMS composite film and a PVDF nanofiber mat for application to flexible pressure sensors was carried out. First, step-wise electric poling was conducted on these two types of pressure sensors, after which the open-circuit voltage (Voc) was measured under compressive force. The 1.8 V peak-to-peak Voc was measured in a BTO-PDMS composite with a 30 wt.% BTO content that was poled by 10 kV/mm electric field for 15 min. This peak-to-peak Voc of the BTO-PDMS composite increased further to ~ 4 V when it was poled for 24 hr. Unlike the BTO-PDMS composite films, the maximum Voc (1.1 V) was measured in a PVDF nanofiber mat that did not undergo subsequent electric poling. A BTO-PDMS composite film and a PVDF nanofiber mat were fabricated, and the compressive force and strain-rate dependencies of Voc and the short-circuit current (Isc) were investigated. Overall, the Voc and Isc of the BTO-PDMS composite film exceeded those of the PVDF nanofiber mat in a force range of 1 − 25 N and frequency range of 0.5 − 2.0 Hz. However, the Voc and Isc signals from the PVDF nanofiber mat were more stable than those from the BTO-PDMS composite film due to the longer lifetime of the signals.