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Test and Simulation of an Active Vibration Control System for Helicopter Applications
Do-Hyung Kim,Tae-Joo Kim,Se-Un Jung,Dong-Il Kwak 한국항공우주학회 2016 International Journal of Aeronautical and Space Sc Vol.17 No.3
A significant source of vibration in helicopters is the main rotor system, and it is a technical challenge to reduce the vibration in order to ensure the comfort of crew and passengers. Several types of passive devices have been applied to conventional helicopters in order to reduce the vibration. In recent years, helicopter manufacturers have increasingly adopted active vibration control systems (AVCSs) due to their superior performance with lower weight compared with passive devices. AVCSs can also maintain their performance over aircraft configuration and flight condition changes. As part of the development of AVCS software for light civil helicopter (LCH) applications, a test bench is constructed and vibration control tests and simulations are performed in this study. The test bench, which represents the airframe, is excited using a pair of counter rotating force generators (CRFGs) and a multiple input single output (MISO) AVCS that consists of three accelerometer sensors and a pair of CRFGs; a filtered-x least mean square (LMS) algorithm is applied for the vibration reduction. First, the vibration control tests are performed with uniform sensor weights; then, the change in the control performance according to changes in the sensor weight is investigated and compared with the simulation results. It is found that the vibration control performance can be tuned through adjusting the weights of the three sensors, even if only one actuator is used.
Un Sang Yeo,Do Yeon Kwak,Jeom Sig Lee,Woon Goo Ha,Jae Ki Jang,No Bong Park,Sang Jong Lim,Jung Hoon Kang,Ho Yeong Kim,Sae Jun Yang 한국육종학회 2003 한국육종학회지 Vol.35 No.2
This study was carried out to develop a prom ising japonica rice variety resistant to brown planthopper(Bph) through marker-assisted selection(MAS) and backcross breeding methods. 'Milyang 64' which is known as resistant japonica variety to Bph used as a
MS-based illegal food and drug reference library : validation and potentials
Jung Ah Do,sung kwan park,sun young baek,un yong kim,Hyun Joo An,Jaehan Kim 한국당과학회 2016 한국당과학회 학술대회 Vol.2016 No.01
Fast and accurate screening of illegal compounds in food and drugs are crucial for the public safety and health. Mass spectrometric analysis coupled with liquid chromatography enable the fast analysis of compounds and return the vast information for the identification of molecules. Structural information can be obtained from the fragmentation pattern from MS/MS data of compounds at different energy level. For the fast screening of illegal compounds, reference library of MS/MS spectral data has been built using 252 chemicals which frequently observed in food and drugs. In addition to the parent mass and retention time, MS/MS data at different energy levels have been collectively stored to compare the structural characteristics. Each MS/MS data at different energy level were converted to a single representative but artificial mass data sets to compare the fragmentation characteristics. Using this mass spectrometric big data of small compounds, its potential power to segregate the similar compounds to an adjacent cluster and ability to identify the unknown molecules.. For the general acceptability to the public, the cross platform study has been performed by four independent institutes with two different types of mass spectrometry form three companies. Results showed that the reference library are highly reproducible and applicable to identify the compounds. The compounds of structural similarity exhibited the higher similarity of MS/MS dataset that other compounds indicating unique fragmentation patterns. Despite the high similarity value, unique peaks were found as well enabling to distinguishing exact compounds from similar ones.
Apnea–hypopnea index estimation using quantitative analysis of sleep macrostructure
Jung, Da Woon,Hwang, Su Hwan,Lee, Yu Jin,Jeong, Do-Un,Park, Kwang Suk IOP 2016 Physiological measurement Vol.37 No.4
<P>Obstructive sleep apnea, characterized by recurrent cessation or substantial reduction in breathing during sleep, is a prevalent and serious medical condition. Although a significant relationship between obstructive sleep apnea and sleep macrostructure has been revealed in several studies, useful applications of this relationship have been limited. The aim of this study was to suggest a novel approach using quantitative analysis of sleep macrostructure to estimate the apnea–hypopnea index, which is commonly used to assess obstructive sleep apnea. Without being bound by conventional sleep macrostructure parameters, various new sleep macrostructure parameters were extracted from the polysomnographic recordings of 132 subjects. These recordings were split into training and validation sets, each with 66 recordings including 48 recordings with an apnea–hypopnea index greater than 5 events h<SUP>−1</SUP>. The nonlinear regression analysis, performed using the percentage transition probability from non-rapid eye movement sleep stage 2 to stage 1, was most effective in estimating the apnea–hypopnea index. Between the apnea–hypopnea index estimates and the reference values reported from polysomnography, a root mean square error of 7.30 events h<SUP>−1</SUP> was obtained in the validation set. At an apnea–hypopnea index cut-off of ⩾30 events h<SUP>−1</SUP>, the obstructive sleep apnea diagnostic performance was provided with a sensitivity of 90.0%, a specificity of 93.5%, and an accuracy of 92.4% by our method. The developed apnea–hypopnea index estimation model has the potential to be utilized in circumstances in which it is not possible to acquire or analyze respiration signal but it is possible to obtain information on sleep macrostructure.</P>
Nocturnal Awakening and Sleep Efficiency Estimation Using Unobtrusively Measured Ballistocardiogram
Jung, Da Woon,Hwang, Su Hwan,Yoon, Hee Nam,Lee, Yu-Jin G.,Jeong, Do-Un,Park, Kwang Suk IEEE 2014 IEEE Transactions on Biomedical Engineering Vol.61 No.1
<P>Fragmented sleep due to frequent awakenings represents a major cause of impaired daytime performance and adverse health outcomes. Currently, the gold standard for studying and assessing sleep fragmentation is polysomnography (PSG). Here, we propose an alternative method for real-time detection of nocturnal awakening via ballistocardiography using an unobtrusive polyvinylidene fluoride (PVDF) film sensor on a bed mattress. From ballistocardiogram, heart rate and body movement information were extracted to develop an algorithm for classifying sleeping and awakening epochs. In total, ten normal subjects (mean age 38.7 ± 14.6 years) and ten patients with obstructive sleep apnea (OSA) (mean age 44.2 ± 16.5 years) of varying symptom severity participated in this study. Our study detected awakening epochs with an average sensitivity of 85.3% and 85.2%, specificity of 98.4% and 97.7%, accuracy of 97.4% and 96.5%, and Cohen's kappa coefficient of 0.83 and 0.81 for normal subjects and OSA patients, respectively. Also, sleep efficiency was estimated using detected awakening epochs and then compared with PSG results. Mean absolute errors in sleep efficiency were 1.08% and 1.44% for normal subjects and OSA patients, respectively. The results presented here indicate that our suggested method could be reliably applied to real-time nocturnal awakening detection and sleep efficiency estimation. Furthermore, our method may ultimately be an effective tool for long-term, home monitoring of sleep-wake behavior.</P>