• Korean Journal of Remote Sensing
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• v.28 no.1
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• pp.1-9
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• 2012

The diurnal variation in pollen vertical distributions in the atmosphere was observed by a surface-based lidar remote sensing technique. Aerosol extinction coefficient and depolarization ratio at 532 nm were obtained from lidar measurements in spring ($4^{th}$ May - $2^{nd}$ June) 2009 at Gwangju Institute of Science & Technology (GIST) located in Gwangju, Korea ($35.15^{\circ}E$, $126.53^{\circ}N$). Unusual variations of depolarization ratio were observed for six days from $4^{th}$ to $9^{th}$ May. Depolarization ratios varied from 0.08 to 0.14 were detected at the low altitude in the morning. The altitude with those high depolarization ratios was increased up to 1.5 - 2.0 km at the time interval between 12:00 and 14:00 LT and then decreased. The temporal variations in high values of depolarization ratios from lidar measurements show good agreement in patterns with the sampled pollen concentrations measured using the Burkard trap sampler. This study demonstrates that the pollen distribution data obtained by lidar measurements can be a useful tool for investigating spatial and temporal characteristic of pollen particles.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1385-1391
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• 2010

In this study, we present small-size, low-power, and high-speed electromagnetic flapping shutters for phone cameras. These shutters are composed of trapezoidal twin blades suspended by H-type torsional springs. The existing electrostatic rolling and flapping shutters need high input voltage, while the existing electromagnetic rotating shutters are too big to be used for phone cameras. To achieve low-power and high-speed angle motion for small-size electromagnetic flapping shutters for camera phones, low-inertia trapezoidal twin blades, each suspended by the low-stiffness H-type torsional springs, are employed. The electromagnetic flapping shutters used in this experimental study have steady-state rotational angles of $48.8{\pm}1.4^{\circ}$ and $64.4{\pm}1.0^{\circ}$ in the magentic fields of 0.15 T and 0.30 T, respectively, for an input current of 60 mA; the maximum overshoot angles are $80.2{\pm}3.5^{\circ}$ and $90.0{\pm}1.0^{\circ}$ in the magentic fields of 0.15 T and 0.30 T, respectively. The rising/settling times of the shutter while opening are 1.0 ms/20.0 ms, while those while closing are 1.7 ms/10.3 ms. Thus, we experimentally demonstrated that the smallsize (${\sim}8{\times}8{\times}2\;mm^3$), low-power (${\leq}60\;mA$), and high-speed (~1/370 s) electromagnetic flapping shutters are suitable for phone cameras.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.4
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• pp.344-353
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• 2016

The cause of abnormal tidal residuals was examined by analyzing sea levels, sea surface atmospheric pressures, winds at ten tide stations, and current, measured at the coast of the Yellow Sea from the night of November $24^{th}$ to the morning of the $25^{th}$ in 2013, along with weather chart. Additionally, the cross-correlations among the measured data were also examined. The 'abnormal tidal residuals' mentioned in this study refer to differences between maximum and minium tidal residuals. The largest abnormal tidal residual was identified to be a difference of 176 cm occurring over 4 hours and 1 minute at YeongJongDo (YJD) with a maximum tidal residual of 111 cm and minimum of -65 cm. The smallest abnormal tidal residual was 68 cm at MoSeulPo (MSP) during 8 hours 52 minutes. The cause of these abnormal tidal residuals was not a meteo-tsunami generated by an atmospheric pressure jump but wind generated by the pressure patterns. The flow speed due to these abnormal tidal residuals as measured at ten tide stations was not negligible, representing 16 ~ 41 % of the annual average ebb current speed. From the cross correlation among the tidal residuals, winds, and tidal residual currents, we learned the northern flow, due to southerly winds, raised the sea level at Incheon when a low pressure center located on the left side of the Korean Peninsula. After passing the Korean Peninsula, a southern flow due to northerly winds decreased the sea level.

• Korean Chemical Engineering Research
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• v.50 no.6
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• pp.1021-1026
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• 2012

The transient mass transfer in a single droplet system consisting of 1-octanol (continuous phase)/aqueous succinic acid solution (dispersed phase) was investigated in the presence of chemical reaction, which is acid/anion exchange reaction of succinic acid and tri-n-octylamine (TOA). This succinic acid extraction by TOA can be considered to occur at the interface between organic and aqueous phase, that is, heterogeneous reaction system. The basic properties of the system such as viscosity, density, distribution coefficient, terminal velocity of droplet, and diffusion coefficient were measured experimentally or calculated theoretically, and used for theoretical calculation of characteristic parameters of mass transfer later. The effects of succinic acid concentration on the terminal velocity was negligible in the existence of TOA, although the terminal velocity increases with succinic acid concentration in the absence of TOA. On the contrary, the terminal velocity decreases with TOA concentration. While droplets falls through organic phase, the trajectory of droplets is observed to oscillate around its vertical path. A mass trnasfer cell was prepared to monitor the mass transfer behavior in a single droplet and used to measure the mean concentration of succinic acid inside droplet. The results are expressed with dimensionless parameters. Under 50 g/L succinic acid condition, the system with 0.1 mol/kg TOA showed that the molar flux decreases in proportion to the decrease of concentration gradient, while in the case of 0.5 mol/kg TOA Sh increases rapidly with time indicating the molar flux of succinic acid decreases relatively slowly compared to the decrease in concentration gradient.

• Tunnel and Underground Space
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• v.25 no.6
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• pp.568-576
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• 2015

In this study, scenarios based on the leakage of highly compressed air and fire occurrence turned out to be high risks in an operation stage of CAES facility were constructed and estimated. By combining Bernoulli equation with momentum equation, an expression to calculate an impact force of a jet flow of compressed air was derived. An impact force was found to be proportional to the square of diameter of fracture and the pressure of compressed air. Four types of fire scenarios were composed to evaluate an effects that seasonal change and location of fire source have on the spread behavior of smoke. Smoke from the fire ignited in the vicinity of CAES opening descended more quickly below the limit line of breathing than one from the fire occurred 10 m away from CAES opening, which is expected to occur due to a propagation of wave front of smoke. It was shown that a rate of smoke spread of the winter fire is faster than one of the summer fire and smoke from the winter fire spreads farther than one of the summer fire, which are dependent on the direction of air flow into access opening. Evacuation simulation indicated that the required safe evacuation time(RSET) of the summer and winter fires are 262, 670 s each.

• Bulletin of Food Technology
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• v.25 no.2
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• pp.116-128
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• 2012

식품동결에 의한 품질손상에 있어 크게 영향을 미치는 인자 중의 하나가 체적변화에 의한 조직 파괴이므로 식육 및 과채류의 냉동시 내부압력에 따른 조직파괴를 방지하기 위한 기초연구로 다양한 동결방법에 따른 내부압력 변화에 대하여 조사한 결과, 급속 및 완만동결시 우육의 내부압력 변화 경향은 동결 직전에 급격히 상승한 후 동결 초기부터 최대빙결정생성대를 통과하는 동안은 급격히 감소하다가 다시 온도가 내려감에 따라 압력변화는 증가와 감소를 반복하여 상승하는 경향을 보여 주었고, 동결시의 내부압력 크기는 약 8~10 psig 수준이며, 내부압력의 변화 경향은 정지공기식보다 침지식에서 약 1 psig 정도 크게 나타났다. 냉동냉장시에 일어나는 내부압력의 상하변화는 돈육의 품온차가 ${\pm}1^{\circ}C$일 때, 시료중량에 따라 1.84~2.32 psig 정도의 내부압력 차가 반복적으로 발생됨을 알 수 있었다. 또한, 돈육의 해동시 내부압력은 해동 개시 후 급격히 상승하여 5분 이내에 최고압력에 도달한 이후에는 서서히 하강하였으며, 해동시에 발생한 내부압력의 값은 동결시의 내부압력 값보다도 대부분 크게 나타났다. 또한, 균온처리한 우육의 동결시 내부압력 값은 약 1~4 psig 수준으로 균온처리하지 않은 우육에 비하여 매우 적게 나타났으며, 동결소요시간도 약 10~20% 정도 짧게 나타났다. 그리고 균온처리 및 다양한 동결방법에 따른 동결식육의 조직과 냉동냉장 중의 품질변화를 비교 검토한 결과, 동결방법에 따른 드립손실율은 우육의 경우 정지공기식으로 처리한 시료는 타 처리구에 비해 계속 높게 나타났으며, 돈육은 우육에 비해 상대적으로 드립손실량이 적게 나타났으나 송풍식으로 처리한 시료에서 저장 40일째, 7.39%로 가장 높게 나타났다. 동결 우육 및 돈육의 pH변화는 뚜렷한 차이를 나타내지 않았으며, VBN 및 TBA값에 있어서는 균온 처리한 시료가 완만 및 급속동결 처리한 타 시료에 비해 저장 200일까지 가장 변화가 없었다. 동결저장온도의 상하변동에 있어서는 온도변동 횟수가 증가할수록 pH 및 수분함량은 뚜렷한 변화가 없었으나 드립손실율, VBN 및 TBA값은 온도 변동횟수가 증가할수록 서서히 증가하는 경향을 보여 주었다.

• Korean Journal of Applied Biomechanics
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• v.18 no.1
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• pp.97-105
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• 2008

The kinematic variables for swimming and fin-swimming start motions were analyzed and compared using 3-dimensional cinematography. For the swimming start, the arm segment moved towards the upper rear and trunk towards the upper front followed by a descent towards the lower front, while the fin-swimming start motion showed movement towards the lower front for all segments. The total body center of gravity for the swimming start showed horizontal movement far to the front followed by a rapid descent while the fin-swimming start showed close movement towards the lower front in a short period of time. Upon entering the water, the center of gravity for swimming showed high vertical velocities while fin swimming had high horizontal velocities. For both swimming and fin swimming, the upper extremity velocity had more influence on the total center of gravity velocity than the lower extremities. Flexion of the hip joint was observed before the jump for the fin swimming start while the swimming start showed two flexions in mid-air succeeding the jump. The flexion and extension movements at the knee joint during the fin-swimming start motion were shown to be larger and more rapid than those of fin-swimming.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.1
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• pp.16-21
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• 2002

In this paper, a dual type PFD(Phase Frequency Detector) for high speed PLL to improve output characteristics using TSPC(True Single Phase Clocking) circuit is proposed. The conventional 3-state PFD has problems with large dead-zone and long delay time. Therefore, it is not applicable to high-speed PLL(Phase-Locked Loop). A dynamic PFD with dynamic CMOS logic circuit is proposed to improve these problems. But, it has the disadvantage of jitter noise due to the variation of the duty cycle. In order to solve the problems of previous PFD, the proposed PFD improves not only the dead zone and duty cycle but also jitter noise and response characteristics by the TSPC circuit and dual structured PFD circuit. The PFD is consists of a P-PFD(Positive edge triggered PFD) and a N-PFD(Negative edge triggered PFD) and improves response characteristics to increase PFD gain. The Hspice simulation is performed to evaluate the performance of proposed PFD. From the experimental results, it has the better dead zone, duty cycle and response characteristics than conventional PFDs.

• Microbiology and Biotechnology Letters
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• v.18 no.5
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• pp.541-546
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• 1990

Bacillus sphaericus ts-Dl290 was characterized by SDS-PAGE produced by the mutant at $30^{\circ}C$ and $42^{\circ}C$. The total amount of proteins produced by the mutant at $42^{\circ}C$ decreased to one-fifth of those at $30^{\circ}C$; however, when the culture was shifted down from $42^{\circ}C$ after 4 to $30^{\circ}C$, the total amount of protein decreased to one-third and the 221 kd protein did not appear, but the 155 kd appeared remarkably. When the mutant and the wild type strain were cultured in the media containing 80$\mu g$ per ml of chloramphenicol at $42^{\circ}C$, the wild type strain synthesized half amounts of the total proteins than those at $30^{\circ}C$, and the mutant produced one-tenth of the total protein amounts. When the both strains were cultured in the media containing chloramphenicol, the 155 kd protein was produced was produced in lesser amounts than those without chloramphenicol. The 150 kd protein showed lethal activity to Culex pipiens 3rd instar larvae.

• Journal of the Korean Geotechnical Society
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• v.21 no.3
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• pp.119-131
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• 2005

Seepage analysis through unsaturated zone based on the theory of unsaturated flow is commonly performed to evaluate dam safety. However, the concepts of unsaturated soil behavior have not been transferred into the hands of practicing geotechnical engineers since the problems involving unsaturated soils often have the appearances of being extremely complex. The behavior of dam such as seepage rate and the pore water pressure distribution is different according to the unsaturated hydraulic properties, but nevertheless simply assumed properties have been used due to insufficient data from domestic soils. In this paper, the effect of unsaturated hydraulic properties on the behavior of dam was studied through a series of numerical analyses, and then the results were discussed. It is observed that water table moves at a (aster rate, as the values of unsaturated soil parameter a and n increase. The value of m showed opposite trend. The sensitivity calculated using the approximation form showed maximum values near the water table. And the value of n that is related to the slope of soil water characteristic curve gives greatest influence on the change of sensitivity with time.