• Journal of Biosystems Engineering
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• v.17 no.1
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• pp.18-26
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• 1992

A mechanical-hydraulic hitch control system has been adapted to most agricultural tractors. But it has various defects due to friction, inertia and hysteresis. Recently a number of electronic-hydraulic hitch control systems have been developed in several countries to improve control performance of the agricultural tractors equipped with a mechanical-hydraulic hitch control system. This study was conducted to develop a new electronic-hydraulic hitch control system using an electro-hydraulic servo valve instead of an on-off valve and to carry out computer simulation of the system. According to the result of computer simulation, the control system showed the best performance when the proportional constants were 9 and 4 for position and draft control respectively. The step and frequency responses were improved as flow rate increased.

• Journal of Biosystems Engineering
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• v.15 no.4
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• pp.290-297
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• 1990

The purposes of this study were to perform theoretical analysis of an electronic-hydraulic hitch control system for position and draft control of tractor implements and to investigate the performance of the control system through computer simulation. Computer simulation models which could predict the responses of the system to the step and sinusoidal inputs in position and draft controls were developed using the simulation package "TUTSIM". The effects of control mode, hydraulic flow rate, deadband, and proportional constant on control performance of the system were investigated. The simulated results were compard with the experimental ones to verify the simulation models. The simulation models appeared to be a useful means for the analysis and the design of the electronic-hydraulic hitch control system.

• Journal of Aerospace System Engineering
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• v.16 no.5
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• pp.8-16
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• 2022

This paper presents the orbital control for positioning micro synthetic aperture radar (SAR) satellites for all-weather monitoring around the Korean Peninsula. In Small SAR technology experimental project (S-STEP) developed in Korea, multiple satellites are placed at equal intervals in multiple orbital planes to secure an average revisit period for the region around the Korean Peninsula. Satellites entering the same orbital plane use ion thrusters to control their orbits and the separation velocity from the launch vehicle to distribute them evenly across the orbit. For an orbital that places the satellites equally spaced in the same orbital plane, the shape of the satellite constellation is formed by adjusting the difference in drift rates between the satellites. This paper presents, different types of satellite constellations, and the results of satellite constellation placement according to launch strategies are presented. In addition, a method and limitations in shortening the duration of orbital deployment are presented.

• Journal of Preventive Medicine and Public Health
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• v.34 no.1
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• pp.73-79
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• 2001

Objectives : To examine predictors of successful control for selfishness, dishonesty, resentment, and fear(SDRF) among Korean Alcoholics Anonymous(AA) members. Methods : This study was a cross-sectional study. The study group included members from 18 different AA groups which were enrolled in the Korean AA Association in 1998. 207 Out of 300 self administered questionnaires were completed by AA members (response rate 69.0%). Alcoholics who attended AA meetings were divided into two groups according to their self reported level of success in SDRF control; one with very successful experience after AA participation and the other with little or no success. In this study, the general characteristics, AA activities, relapse experience, and degree of effort exerted for SDRF control were compared between two groups. In order to study predictors of successful SDRF control after joining AA, 4 logistic regression analyses were performed for each of the 4 SDRF indices. Results : The proportion of those reporting a 'very successful' experience was 19.9% for selfishness, 20.7% for dishonesty, 25.5% for resentment, and 24.7% for fear. After control for the effect of general characteristics, the practice of the 12th step(taking alcoholics to an AA meeting after conveying messages) was found to be a significant predictor for the successful control of both selfishness(OR=6.04) and the dishonesty(OR=7.77). And individuals making every effort for SDRF control showed more successful control of selfishness(OR=4.10), dishonesty(OR=4.01, and fear(OR=34.89). Conclusions : Bivariate and multivariate analyses demonstrated that especially practicing the 12th step and making every effort themselves, may help alcoholics to control SDRF successfully after joining AA.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.3 s.192
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• pp.67-75
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• 2007

This paper deals with a problem of vibration suppression of a piezoelectric beam using a self-sensing algorithm. Two methods, which are PPF(positive position feedback) and SRF(strain rate feedback), are considered to suppress a residual vibration of a piezoelectric beam developed during the step positioning of a beam end point. A self-sensing algorithm treated here is basically a strain rate estimator of a beam movement and is to be used for the closed loop control. The efficacy of the proposed idea is evaluated through experiments.

• Journal of Biosystems Engineering
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• v.31 no.3 s.116
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• pp.203-208
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• 2006

This study was conducted to improve the control performance of a current variable-rate controller for granular fertilizers. Simulation model was developed. Optimized proportional, integral and derivative gains were determined by simulation model using 2nd order PID gain learning algorithm, and these control gains were evaluated through the field tests. Important results of this study are as follows; 1. Principles of pre-existing variable-rate application of granular fertilizers were investigated. 2. Simulation model of a PID controller that could simulate the control system was developed by using Matlab/Simulink program. The program was to determine PID control coefficients through the simulation model and 2nd order PID gain learning algorithm. 3. PID control coefficients obtained from the simulation were applied to the developed model. When the step input was given, Maximum overshoot were 1.96%, rise time were 0.05 sec, settling time were 0.06 sec and steady state error were 0.21 % respectively. 4. The simulation model was verified through field tests. The errors of maximum overshoot were 10%, rise time were 0.11 sec, settling time were 0.40 sec and steady state error were 8% because of loads and noises. Rise time was decreased to one third of that of the pre-existing system. 5. If the speed of a fertilizing machine is $0.3{\sim}0.6\;m/s$ and the maximum rotation speed of a discharging roller is 64 rpm, rise time would be 0.26 sec and fertilizing machine would cover the distance of $0.07{\sim}0.15\;m$ with settling time of 0.4 sec, fertilizing machine would cover the distance of $0.12{\sim}0.24\;m$.

• Bulletin of the Korean Chemical Society
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• v.27 no.10
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• pp.1618-1622
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• 2006

Bacteriophage T7 gp4A' is a ring-shaped hexameric DNA helicase that catalyzes duplex DNA unwinding using dTTP hydrolysis as an energy source. To investigate the effect of single-stranded DNA (ssDNA) on the kinetic pathway of dTTP hydrolysis by the T7 DNA helicase complexed with ssDNA, we have first determined optimal concentration of long circular M13 single-stranded DNA and pre-incubation time in the absence of $Mg^{2+}$ which is necessary for the helicase-ssDNA complex formation. Steady state dTTP hydrolysis in the absence of $Mg^{2+}$ by the helicase-ssDNA complex provided $k_{cat}$ of $8.5\;{\times}\;10^{-3}\;sec^{-1}$. Pre-steady state kinetics of the dTTP hydrolysis by the pre-assembled hexameric helicase was monitored by using the rapid chemical quench-flow technique both in the presence and absence of M13 ssDNA. Pre-steady state dTTP hydrolysis showed distinct burst kinetics in both cases, indicating that product release step is slower than dTTP hydrolysis step. Pre-steady state burst rates were similar both in the presence and absence of ssDNA, while steady state dTTP hydrolysis rate in the presence of ssDNA was much faster than in the absence of ssDNA. These results suggest that single-stranded DNA stimulates dTTP hydrolysis reaction by T7 helicase by enhancing the rate of product release step.

• Polymer(Korea)
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• v.36 no.3
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• pp.309-314
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• 2012

To control degradation rate of biodegradable poly(lactide)s (PLA), the stereochemical PLAs with different ratios of $d$-lactide and $l$-lactide units were synthesized by the ring open polymerization and a degradation behavior was measured by a Langmuir film balance. Degradation rates of mixture monolayers on alkaline subphase were investigated as a function of optical purity of mixture component, 100, 99, 97 and 95%. As increasing their optical purity, melting temperatures of mixtures from stereocomplexation increased. The degradation rate of mixture monolayer with 100% optical purity was much slower than that of each homopolymer one and the others showed 2 step degradation behaviors. In the first step, the degradation which is faster than that of each homopolymer occurs in the uncomplexed region, and secondly, the degradation occurred in the complexed region which showed similar degradation rate to that of 100% optical purity. These results indicate that the alkaline degradation of stereochemical PLAs could be controlled by stereochemistry and stereocomplexation between enantiomer PLAs.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.1060-1062
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• 1999

Pulsed Nd:YAG laser is used widely for materials processing and instrumentation. It is very important to control the laser energy density in materials processing by a pulsed Nd:YAG laser. A pulse repetition rate and a pulse width are regarded as the most dominant factors to control the energy density of laser beam. In this study, the alternating charge-discharge system was designed to adjust a pulse repetition rate. And the parallel mesh is added to increase laser output power. This system is controlled by one chip microprocessor and allows to replace an expensive condenser for high frequency to a cheap condenser for low frequency. In addition, we have investigated the current pulse shape of flashlamp and the operating characteristics of a pulsed Nd:YAG laser. As a result, it is found that the laser output of the power supply using the parallel mesh and the alternating charge-discharge system is not less than that of typical power supply. As the pulse repetition rate rises from 10pps to 110pps by the step of 20pps at 1000V and 1200V, it is found that the laser efficiency decreases but the laser output power increases about 5W at each step.

• Journal of Korean Physical Therapy Science
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• v.10 no.1
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• pp.7-17
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• 2003

The purpose of this study was to investigate the effect of the involved lower limb weight bearing training on symmetrical weight supporting rate improvement and gait characteristics of patients with hemiplegia including their gait velocity, cadence, stride length, step length of the non affected side, step length of the affected side, foot angle of the non affected side, foot angle of the affected side, base of support, and so on. The subject of the study was 28 men and women patients with hemiplegia from 22 to 77 age, among patients who doctor diagnosed as hemiplegia due to stroke or traumatic brain injury, were possible to do independent gait more than 45m without others assistance, the flexion contracture of hip pint was less than $15^{\circ}$, did not have contracture for knee pint and one more than $5^{\circ}$ for ankle joint, did not have contraindication for exercise or gait did not show visual defect due to brain injury. The patients, the subject of the study, were classified into 14 patients of treatment. group applying continuous involved weight bearing with general therapeutic exercise and 14 patients of control group applying general therapeutic exercise, and then analyzed their gait before and after exercise. Temporal distance gait analysis(Boening, 1977) was used to analyze their gait, and ink foot-print was applied as one of measurement methods. However, it was statistically signifiant in the change rate(%) of gait characteristics, and treatment group's patients with hemiplegia had been highly changed in gait characteristics in comparison with control group. From the above-mentioned results, could find that continuous involved weight bearing training for patients with hemiplegia was effective to improve their gait ability and it could increase the ability in comparison with general exercise.