• Proceedings of the KSRS Conference
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• 1998.09a
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• pp.313-318
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• 1998

Electro-Optical Camera(EOC) is the main payload of Korea Multi-Purpose SATellite(KOMPSAT) with the mission of cartography to build up a digital map of Korean territory including Digital Terrain Elevation Map(DTEM). This instrument which comprises EOC Sensor Assembly and EOC Electronics Assembly produces the panchromatic images of 6.6 m GSD with a swath wider than 17 km by push-broom scanning and spacecraft body pointing in a visible range of wavelength, 510 ~ 730 nm. The high resolution panchromatic image is to be collected for 2 minutes during 98 minutes of orbit cycle covering about 800 km along ground track, over the mission lifetime of 3 years with the functions of programmable rain/offset and on-board image data storage. The image of 8 bit digitization, which is collected by a full reflective type F8.3 triplet without obscuration, is to be transmitted to Ground Station at a rate less than 25 Mbps. EOC was elaborated to have the performance which meets or surpasses its requirements of design phase. The spectral response the modulation transfer function, and the uniformity of all the 2592 pixel of CCD of EOC are illustrated as they were measured for the convenience of end-user. The spectral response was measured with respect to each gain setup of EOC and this is expected to give the capability of generating more accurate panchromatic image to the EOC data users. The modulation transfer function of EOC was measured as greater than 16% at Nyquist frequency over the entire field of view which exceeds its requirement of larger than 10%, The uniformity that shows the relative response of each pixel of CCD was measured at every pixel of the Focal Plane Array of EOC and is illustrated for the data processing.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.2
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• pp.108-115
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• 2015

Electro-mechanical actuator installed on aircraft consists of a decelerator which magnifies the torque in order to rotate an axis connected with aircraft control surface, a control section which controls the motor assembly through receiving orders from cockpit and a motor assembly which rotates the decelerator. Electro-mechanical actuator controls aircraft altitude, position, landing, takeoff, etc. It is an important part of a aircraft. Aircraft maneuvering causes vibrations to electro-mechanical actuator. Vibrations may result in structural fatigue. For that reason, it is necessary to analyze the system structural safety. In order to analyze the system structural safety. It is needed reasonable finite element model and structural response stress closed to real value. In this paper, analytic model is derived by using the simplified finite element model, and damping ratio which is closely related to response stress is derived by using modal test. So, we developed analytic model in less than 10 % error rate, compared with modal test. Vibration response stress close to real value was estimated from analytic model modified with modal experimental damping ratio. Estimation method for damping ratio with empirical formula was suggested partly. Finally, It was proved that electro-mechanical actuator had reasonable structure margin of safety at environmental random $3{\sigma}$ stress during life cycle.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.2
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• pp.54-59
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• 2005

Nonlinear aeroelastic analyses of a missile control fin are performed considering backlash and dynamic stiffness of actuator. Doublet-Hybrid method is used for the calculation of subsonic unsteady aerodynamic forces, and aerodynamic forces are approximated by the minimum-state approximation. For nonlinear flutter analysis backlash is represented by a free-play and is linearized by using the describing function method. Also, dynamic stiffness is function of frequency and is calculated by solving equation of motion for actuator. The linear and nonlinear flutter analyses show that the aeroelastic characteristics are significantly dependent on the backlash and dynamic stiffness. From the nonlinear flutter analysis, various types of limit cycle oscillations are observed in a range of air speeds below the linear divergent flutter boundary. The nonlinear flutter characteristics and the nonlinear aeroelastic responses are also investigated in the time domain.

• Proceedings of the KSEE Conference
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• 2006.10a
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• pp.119-140
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• 2006

The rock excavation work by doing blasting breaks the rock by using a shock pressure and gas pressure produced when explosive explodes and the shock wave by shock pressure propagated three-dimensionally from the exploding center is on the decrease notably to the distance, however, $0.5{\sim}20%$ of energy produced by blasting propagates into the ground outside a crack zone by the shape of an elastic wave, on the ground it appears as a ground vibration with a seismic amplitude and a seismic cycle, it is called a blasting vibration. on the other side, what propagated in the air is called a blasting sound. The blasting sound of both means the things which the shock sound within the range the audible frequency($20{\sim}20000Hz$) of the elastic wave in the air influences the response system of a human body, it doesn't harm physically to any structures but influences unreasonably a work accomplishment, such as a work discontinuance due to the outbreak of a public complaint by a mental pain, reduction of a blasting scale, etc.. So, this study is examined at about 20 sites on the installation time and method of soundproofing facilities for reduction of the sound accompanied with a tunnel blasting work.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2436-2441
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• 2015

BSR noise from automobiles is largely issued in recent as an emotional quality. This study describes the two test methods for determining BSR noise occurred in automotive seat system. First, the sine sweep test is found to be an effective excitation method for determining BSR noise with high frequency. Second, BSR operation test is introduced in such a way that BSR noise during operation of seat height system is measured by several accelerometer at each 800 cycles until 6400 cycles. The periodic noise signal is captured during one cycle after many cycles of operation. Two test method presented in this paper can be analyzed more efficiently BSR noise of the seat.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.72-72
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• 2018

A dynamic fatigue characteristic of dental implant system has been evaluated with applying single axial compressive shear loading based on the ISO 14801 standard. For the advanced dynamic fatigue test, multi-directional force and motion needed to be accompanied for more information of mechanical properties as based on mastication in oral environment. In this study, we have prepared loading and motion protocol for the multi-directional fatigue test of dental implant system with single (Apical/Occlusal; AO), and additional mastication motion (Lingual/Facial; LF, Mesial/Distal; MD). As following the prepared protocol (with modification of ISO 14801), fatigue test was conducted to verify the worst case results for the development of highly stabilized dental implant system. Mechanical testing was performed using an universal testing machine (MTS Bionix 858, MN, USA) for static compression and single directional loading fatigue, while the multi-directional loading was performed with joint simulator (ADL-Force 5, MA, USA) under load control. Basically, all mechanical test was performed according to the ISO 14801:2016 standard. Static compression test was performed to identify the maximum fracture force with loading speed of 1.0 mm/min. A dynamic fatigue test was performed with 40 % value of maximum fracture force and 5 Hz loading frequency. A single directional fatigue test was performed with only apical/occlusal (AO) force application, while multi directional fatigue tests were applied $2^{\circ}$ of facial/lingual (FL) or mesial/distal (MD) movement. Fatigue failure cycles were entirely different between applying single-directional loading and multi-directional loading. As a comparison of these loading factor, the failure cycle was around 5 times lower than single-directional loading while applied multi-directional loading. Also, the displacement change with accumulated multi-directional fatigue cycles was higher than that of single directional cycles.

• Korean Journal of Animal Reproduction
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• v.10 no.1
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• pp.58-65
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• 1986

The results from a survery on the reproduction of a, pp.oximately 500 dairy cows raised in four different farming areas including Cheju city, Jochun, Hallim and Sung-up are summarized as follows; 1. At the occurrence of first estrus, the average age of the heifers was 15.1 months (330 Kg/B.W.), and at first conception 18.0 months (354Kg/B.W.). There was no regional differences. 2. The average interval of the estrous cycle was 20.4 days. And the repetition of esturs after unsuccessful insemination occurred on an average of 1.6 times, especially 2.0 times in the herds of the Jochun district. 3. The ages at the first calving were similar to the data recorded for the domestic mainland's herds at 27.1 months. But some regional differences were recognized within the four districts: i.e. 28.6 (Cheju city), 27.4(Jochun), 27.1(Hallim) and 25.3 months (Sung-up). There was no significant differences in sex ratio of newborns at 50.4%(♂) and 49.6%(♀). 4. The intervals of esturs recurrence and the following conception after calving were 80.0 and 95.8 days respectively. In the followsing conception intervals after cavling, 90.6-97.4 days were average for the herds of Cheju city and Jochun districts, 62.4-69.7 days for those of Hallim and Sung-up districts. 5. The average gestation period was 279.8 days, and was almost identical in the four districts. 6. The calving intervals was 377.7 days in average, and it was shorter than the data recorded for the domestic mainland's herds. Also it was reduce gradually according to the calving frequency.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1995.05a
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• pp.185-198
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• 1995

This is an experimental study conducted to visualize the nucleate boiling phenomena and flow regimes occurring inside the liquid pool in a closed two-phase thermosyphon. To meet this purpose, an annular-type thermosyphon was designed and manufactured using a glass tube and a stainless steel tube, being assembled axisymmetrically. The heat to be supplied to the working fluid is generated within a very thin layer of stainless steel tube wall by applying a high frequency electromagnetic field through the induction coil, axisymmetrically set around the evaporator zone. Some important results were as follows ; 1) Considering the structural complexity of the tested thermosyphon, it showed good performance for the range of heat flux 2＜ q" ＜25kW/$m^2$ and saturation vapor pressure, 0.1＜Pv＜1.1bar 2) different type of nucleating boiling regimes were observed as described below, -Pulse boiling regime : Flow pattern changed cyclically with time during 1 cycle of pulse boiling process. The onset of Nucleation was followed by expulsive growing of vapor bubble, resulting in the so called blow-up phenomenon, massive expulsion of large amount of liquid around the bubble. -Transient : Some spherical vapor bobbles were observed growing out from 2~3 nucleating sites, that was dispersed at the lower part of the heated tube wall in the liquid pool. But the rest upper region above the nucleating sites were filled with churns or bubbles of vapor. -Continuous nucleate boiling regime : The whole zone of evaporator was filled with lots of spherical vapor bubbles, and the bubbles showed tendency to decrease in diameter as the heat flux increased.ased.

• Sleep Medicine and Psychophysiology
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• v.2 no.2
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• pp.146-155
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• 1995

Jet lag can be defined as the cumulative physiological and psychological effects of rapid air travel across multiple time zone. The consequences of jet lag include fatigue, general malaise, sleep disturbances, and reductions of cognitive and psychomotor performance, all of which have been documented in experimental biological and air crew personnel studies. Thus authors tried to study the jet lag of natural travellers by modified self reporting sleep log. Total 61 healthy travellers was studied for 3 days before and 7 days after jet-flights across seven to ten time zone. The eastbound travelling group was 38 persons, aged 19 -70 and westbound travelling group was 23 persons, aged 13 - 69. Sleep onset time, wake-up time, sleep latency, awakening frequency on night sleep, awakening duration on night sleep, sleepiness at wake-up and nap length were evaluated. Our results suggested that the 7 to 10 time zone shift gave significant influence to traveller's sleep-wake cycles. The date which subjective physical condition was recovered on was $5.16{\pm}1.50$ day after arrivals for eastbound, while for westbound, $4.91{\pm}1.62$ day. In eastbound travelling, sleep onset time became later than baselines and could not recover until 7th day. But in westbound, it became earlier than baseline and could recover until 6th day. The mean score of 24-hour sleepiness was greater in eastboumd than westbound. Therefore the eastbound travelling caused more sleep-wake cycle disturbance and daytime dysfunction than westbound travelling. In other parameters, there was no definite difference between east and westbound. From our results, it was suggested that the symptom severity of jet lag was dependent on the travelling direction. To demonstrate more definite evidence, large sized data collections and comparision by age difference were needed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.1
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• pp.92-95
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• 2016

In this paper, an UHF-band 1 kW solid-state pulsed power amplifier was designed and implemented for the thermoacoustic imaging(TAI) at 900 MHz. The designed power amplifier has a pulse width of $80{\mu}s$ and a duty cycle of 1 % for short-pulse operation. The overall amplifier was implemented by combining of 16 single-power amplifiers adopting MRFE6P9220HR3 LDMOSFET using wilkinson power dividers. The solid-state pulsed power amplifier shows 25 % drain efficiency with a gain of 76.2 dB when the output power is 60.2 dBm for a -16 dBm input power at center frequency.