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The relationship between night work and involuntary weight change
Jongho Kwon,Jung-Woo Park,Jin-Soo Park,Seyoung Kim,Hyunrim Choi,Sinye Lim 대한직업환경의학회 2016 대한직업환경의학회지 Vol.28 No.-
Background: Previous studies on the association between shift or night work and weight change have been focused on finding the risk of weight gain caused by shift or night work. In this study, we aimed to reveal the risk of weight gain and weight loss associated with night work by using a nationwide representative data. Methods: This study was performed on 1605 full-time wage workers between the age of 20 and 69 based on the fifth Korea National Health and Nutrition Examination Survey (KNHANES 2010–2012). The association between night work and involuntary weight change in the previous year was divided into the categories of weight gain and weight loss and studied with modifications in socio-demographic variables, health behavior-related variables, and occupational characteristic variables. Results: The participants working in night work accounted for 10.6 % of total study participants (male; 11.9 %, female 7.4 %). Workers who worked more than 48 hours per week on average accounted for 41.6 % of the total study participants (male; 46.3 %, female 29.1 %). Odds ratio (OR) of weight loss associated with night work in male workers was 0.34 (95 % confidence interval (CI) 0.16–0.76) after controlling for several related factors. OR of weight loss associated with night work in female workers with long working hours was 1.95 (95 % CI 0.47–80.86) and that of weight gain was 2.83 (95 % CI 0.12–69.83) after adjusting associated factors. Conclusions: In this cross-sectional study with national representative sample, night work may lower the risk of weight loss in male workers and induce weight change (weight loss or weight gain) in female workers with long working hours. Therefore, future studies with cohort study design for night workers are needed to reveal the mechanisms and health effects of weight change associated with night work and establish proper management solutions with health and labor policies for Korean night workers.
Park, Jongho,Kam, Minchul,Trippe, Sascha,Kang, Sincheol,Byun, Do-Young,Kim, Dae-Won,Algaba, Juan-Carlos,Lee, Sang-Sung,Zhao, Guang-Yao,Kino, Motoki,Shin, Naeun,Hada, Kazuhiro,Lee, Taeseok,Oh, Junghwan American Astronomical Society 2018 The Astrophysical journal Vol.860 No.2
<P>We study the linear polarization of the radio cores of eight blazars simultaneously at 22, 43, and 86 GHz with observations obtained by the Korean VLBI Network (KVN) in three epochs between late 2016 and early 2017 in the frame of the Plasma-physics of Active Galactic Nuclei project. We investigate the Faraday rotation measure (RM) of the cores; the RM is expected to increase with observing frequency if core positions depend on frequency owing to synchrotron self-absorption. We find a systematic increase of RMs at higher observing frequencies in our targets. The RM-nu relations follow power laws with indices distributed around 2, indicating conically expanding outflows serving as Faraday rotating media. Comparing our KVN data with contemporaneous optical polarization data from the Steward Observatory for a few sources, we find indications that the increase of RM with frequency saturates at frequencies of a few hundred gigahertz. This suggests that blazar cores are physical structures rather than simple tau = 1 surfaces. A single region, e.g., a recollimation shock, might dominate the jet emission downstream of the jet-launching region. We detect a sign change in the observed RMs of CTA 102 on a timescale of approximate to 1 month, which might be related to new superluminal components emerging from its core undergoing acceleration/deceleration and/or bending. We see indications for quasars having higher core RMs than BL Lac objects, which could be due to denser inflows/outflows in quasars.</P>
Park, Jongho,Hwang, Jae-Yeol,Lee, Kyu Hyoung,Kim, Seong-Gon,Lee, Kimoon,Kim, Sung Wng American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.48
<P>We report that the spin-alignment of interstitial anionic electrons (IAEs) in two-dimensional (2D) interlayer spacing can be tuned by chemical pressure that controls the magnetic properties of 2D electrides. It was clarified from the isovalent Sc substitution on the Y site in the 2D Y<SUB>2</SUB>C electride that the localization degree of IAEs at the interlayer becomes stronger as the unit cell volume and <I>c</I>-axis lattice parameter were systematically reduced by increasing the Sc contents, thus eventually enhancing superparamagnetic behavior originated from the increase in ferromagnetic particle concentration. It was also found that the spin-aligned localized IAEs dominated the electrical conduction of heavily Sc-substituted Y<SUB>2</SUB>C electride. These results indicate that the physcial properties of 2D electrides can be tailored by adjusting the localization of IAEs at interlayer spacing via structural modification that controls the spin instability as found in three-dimensional elemental electrides of pressurized potassium metals.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2017/jacsat.2017.139.issue-48/jacs.7b10338/production/images/medium/ja-2017-103387_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja7b10338'>ACS Electronic Supporting Info</A></P>
Park, Jongho,Trippe, Sascha American Astronomical Society 2017 The Astrophysical journal Vol.834 No.2
<P>We study the long-term (approximate to 30 years) radio variability of 43 radio-bright active galactic nuclei (AGNs) by exploiting the database of the University of Michigan Radio Astronomy Observatory monitoring program. We model the periodograms (temporal power spectra) of the observed light. curves as simple power-law noise (red noise, spectral power P(f) proportional to f-beta) using Monte Carlo simulations, taking into account windowing effects (red-noise leak, aliasing). The power spectra of 39 (out of 43) sources are in good agreement with the models, yielding a range in power spectral index (beta) from approximate to 1 to approximate to 3. We fit a Gaussian function to each flare in a given light curve to obtain the flare duration. We discover a correlation between beta and the median duration of the flares. We use the derivative of a light curve to obtain a characteristic variability timescale, which does not depend on the assumed functional form of the flares, incomplete fitting, and so on. We find that, once the effects of relativistic Doppler boosting are corrected for, the variability timescales of our sources are proportional to the accretion rate to the power of 0.25 +/- 0.03 over five orders of magnitude in accretion rate, regardless of source type. We further find that modeling the periodograms of four of our sources requires the assumption of broken power-law spectra. From simulating light curves as superpositions of exponential flares, we conclude that strong overlap of flares leads to featureless simple power-law periodograms of AGNs at radio wavelengths in most cases.</P>
Multiclass Classification Fault Diagnosis of Multirotor UAVs Utilizing a Deep Neural Network
Jongho Park,Yeondeuk Jung,Jong-Han Kim 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.4
A fault diagnosis algorithm using a deep neural network for an octocopter Unmanned Aerial Vehicle (UAV) is proposed. All eight rotors are considered in the multiclass classification fault diagnosis problem. The latest angle time history is fed to the proposed algorithm to determine rotor failure in real time. The normal case and fault case of each rotor are considered with appropriate output pairs to form a dataset. The proposed classifier can distinguish a failed rotor from the others with the help of different patterns of Euler angles during the training process. Two hidden layers are constructed using sigmoid and softmax activation functions. A generalized delta rule is adopted, and a stochastic gradient descent scheme is used to calculate the weight update of the neural network. The proposed fault diagnosis algorithm can be augmented to a fault-tolerant controller to construct an integrated system that involves solving a convex optimization problem. Numerical simulations are conducted to validate the performance of the proposed diagnostic algorithm. It is demonstrated that the performance can be adjusted by controlling the design parameters.
Jongho Park,Youdan Kim,Sungwan Kim Institute of Electrical and Electronics Engineers 2015 IEEE transactions on control systems technology Vol. No.
<P>An enhanced search algorithm of a landing site on unknown terrain using stereo vision information for a quadrotor unmanned aerial vehicle is developed. For the development, a quadrotor dynamic model, including nonlinear actuator dynamics, is constructed and guidance and control system is designed based on feedback linearization and linear quadratic tracker. Stereo vision sensor is used to acquire depth map information of the terrain and flatness information of the topography is obtained by extracting the edge of the depth map and performing Euclidean distance transform. Energy consumption of the quadrotor is also considered. The three measures of: 1) the depth; 2) the flatness; and 3) the energy consumption are combined to propose a performance index to determine the safe landing spot of the quadrotor. Numerical simulation is performed to verify the performance of the proposed algorithm and hardware system applicable to practical implementation is also included.</P>