• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.1
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• pp.1-14
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• 2008

Eight comprehensive oceanographic cruises on a squared $30{\times}30\;km$ area have been made to investigate the short and long-term impacts on the water qualities due to the sand mining operations at Exclusive Economic Zone (EEZ) in the central Yellow Sea from 2004 to 2007. The area was categorized to 'Sand Mining Zone', 'Potentially Affected Zone', and 'Reference Zone'. The investigation covered suspended solids, nutrients (nitrate, nitrite, ammonium, phosphate), and chlorophyll-a in seawater and several parameters such as water temperature, salinity, pH, and ORP. Additionally, several intensive water collections were made to trace the suspended solids and other parameters along the turbid water by sand mining activities. The comprehensive investigation showed that suspended solids, nitrate, chlorophyll-a and ORP be sensitively responding parameters of seawater by sand mining operations. The intensive collection of seawater near the sand mining operation revealed that each parameter show different distribution pattern: suspended solids showed an oval-shaped distribution of the north-south direction of 8 km wide and the east-west direction of 5 km wide at the surface and bottom layers. On the other hand, phosphate showed so narrow distribution not to traceable. Also ammonium showed a limited distribution, but its boundary was connected to the high nitrate and chlorophyll-a concentrations with high N/P ratios. From the last 4 years of the comprehensive and intensive investigations, we found that suspended solids, ammonium, nitrate, chlorophyll-a, and ORP revealed the sensitive parameters of water quality for tracing the sand mining operations in seawater. Especially suspended solids and ORP would be useful tracers for monitoring the water qualities of remote area like EEZ in Yellow Sea.

• Korean Journal of Applied Biomechanics
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• v.17 no.2
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• pp.61-73
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• 2007

The purpose of this study was to investigate the influence of the muscular endurance on the kinematic factors during a prolonged run. Subjects, 12 males, who were divided into three groups(lower group, general group, and in higher group) after measuring the lower limb's muscular endurance previously. They were asked toe run on the treadmill at 7.4km/h of speed. To analyze the kinematics parameters of the trunk during running, the ProReflex MCU Camera(Qualisys, Sweden) were used. All parameters were sampled from 5 minute, 40 minute, and 60 minute moments during running. An ANOVA with Repeated Measure was used to test the statistic significance between and within groups for all parameters determined with SPSS 11.0. Significance was defined as p<.05. The conclusions were as follows; There was significantly difference within(lapse of running time) groups in the take-off and minimum knee angle event of swing phase of the trunk flexion and extension. In conclusion, the muscular endurance affected on movement of the trunk during a prolonged run. In addition, it showed that there was significant difference in the energy consumption by lapse of running time. Therefore, it seems to be relationships between the muscular endurance and running efficiency.

• International Journal of Aeronautical and Space Sciences
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• v.7 no.2
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• pp.56-69
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• 2006

For a relatively small country like Korea, a radionavigation system using airships can be considered, which is to provide the navigation service utilizing the stratospheric airships that are deployed in the stratosphere at the altitude of around 20-23km, and which is an independent or a back-up radionavigation system other than current GPS or GLONASS. In this paper, a feasibility study on the constellation of stratospheric airships for the navigation system has been performed. A measure of a geometrical condition between a receiver and navigation transmitters. called the DOP (Dilution of Precision), determines the resulting positioning error of the navigation system, if the error of range measurement is predictable. Therefore, with assumption that the range measurement error of the stratospheric airship navigation system is quite similar to GPS. the several DOP values have been used to evaluate the performance of the navigation system with comparing with the DOP values of GPS as the reference values. To provide the position information of the navigation transmitters to users, a receiver cluster system fixed on the ground, called an IGPS (inverted GPS), is proposed, and the error is also evaluated using the DOP values. Five areas around five major cities in South Korea have been selected, and then by numerical simulations the DOP values are compared those of GPS to assess the performance of the proposed navigation system using stratospheric airships. The possible frequency bands have been proposed. and then link budget of the navigation transmitter has been analyzed for the proposed navigation system.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.269-273
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• 2008

기상청(KMA, Korea Meteorological Administration)에서는 기상수치예보모델을 적용하여 수치예보를 하고 있으며 전지구 모델로는 GDAPS(Global Date Assimilation and Prediction System)를 지역모델은 RDAPS(Regional Date Assimilation and Prediction System)를 사용하고 있다. 수치예보결과를 이용하여 유출량을 예측할 경우 일반적으로 해상도가 높은 지역모델인 RDAPS의 수치예보 결과값을 사용한다. RDAPS는 00UTC와 12UTC에 3시간으로 누적된 자료를 30km 격자에 대하여 예측시간으로부터 48시간에 대하여 자료를 생성한다. 일강우자료를 입력자료로 사용하는 강우-유출 모형의 경우 3시간 누적 자료를 나타나는 RDAPS 수치예보 결과를 이용 시 3시간 scale에서 일(day)시간 scale로 변환시켜주어야 한다. 본 연구에서는 RDAPS의 수치예보 결과의 일(day)시간 scale 변환 방법에 따른 정확도를 비교하여 RDAPS 수치예보 결과의 일(day)시간 scale 변환에 대한 정확도를 비교하여 일(day)시간 scale 변환에 대한 지침을 제공하고자 한다. RDAPS 수치예보 결과값의 특징을 이용하여 RDAPS 결과값을 일(day)시간 scale로 변환하는 방법으로 총 9개방법을 적용하였으며, 참 값으로는 기상청 강수자료를 사용하였으며, 금강유역을 대상으로 유역평균강수량을 계산하여 각 변환 방법에 따른 정확도를 비교하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.689-694
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• 2008

댐 유입량은 댐 운영의 필수 인자이기 때문에 매우 중요하고, 하천유량에 비해 신뢰도가 높은 것으로 평가되고 있기 때문에 수자원의 운영 뿐 아니라 계획에도 활용되고 있다. 그러나 계산된 유입량은 평갈수기에 진폭이 너무 크게 나타나고 심지어 음 유입량이 발생하는 등 개선이 요구돼 왔다. 본 연구에서는 시간간격을 10분, 30분, 1시간 등으로 하고, 수위와 방류량이 유입량에 직접 영향을 끼치고, 관측수위의 단위가 크고, 그 진폭이 자연현상과 거리가 있어, 수위 이동평균, 수위 보간, 방류량 이동평균 등의 조합에 따라 댐 유입량의 계산을 개선할 수 있는 방법을 제안하였고, 이를 쉽게 분석, 평가할 수 있도록 시스템으로 개발하였으며, 유역면적 $4,134km^2$인 대청댐과 유역면적 $108,335mi^2$인 미국의 Lake Powell의 사례에서 크게 개선된 결과를 보여주었다. 그러나 정확하게 측정된 댐 유입량 자료가 없기 때문에 개선된 계산 유입량이 참 값이다 주장할 수 없는 것이 본 연구의 한계이며, 연구결과의 신뢰를 높이기 위해 현재 정밀하게 측정된 댐 유입량 사례를 조사 중에 있다. 그림 1은 Lake Powell의 처리전의 댐 유입량 계산 예이고 그림 2는 처리후의 개선된 유입량이다. 그림에서 유입량이 크게 개선돼 계산된 것으로 나타나고 있으나 결과가 참값인지 아직 판단할 수 없다. 대청댐의 경우도 이와 비슷한 결과를 보여주었다.

• Journal of Fisheries and Marine Sciences Education
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• v.14 no.1
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• pp.43-56
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• 2002

(1) This study was carried out to obtain seasonal fluctuations of marine debris in 5 beaches near the Southern Coast of Korea during May, 1999 - April, 2000. The results are as follows: 1. The density of marine debris was remarkably highest at Namhae beach among 5 beaches. The major part of debris in the beach was styrofoam, with the density of 348.5${ea/km}^2$. But, it was Songjung where the largest amount of resin pellets existed. 2. The composition of styrofoam consisted of 51% of the marine debris, wood& papers was 11%, resin pellets & plastics were 8% and others were 16%. 3. Seasonal fluctuations irregularly change in each beach, but the amount of resin pellets were found to be large only in September. It is estimated that resin pellets are beached upon the coastal beaches by the strong warm currents(Tushima currents) during the summer season. 4. Debris fabrication materials that were found had most of parts made up of PE 71.2%, PP 21.2% and EVA 7.7% through these surveys. 5. In the polluted state, the medium one among the 3 specifications(o1d, medium and new state) occupied 88.5% or so.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.5
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• pp.559-564
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• 2011

For the safety of railway, it should be evaluated for the running safety by measuring the derailment coefficient. Although railway has run the fixed and maintained rail, some of railway is derailed. This report shows the results that performed the static load test, main line running test on the basis of the derailment theory and experience. It is executed main line test into more than 90km/h for estimating the curving performance and running safety of depressed center flat car of 3-axle bogie. As the test results, could confirm the curving performance and running safety of depressed center fiat car of 3-axle bogie from the results of the wheel unloading, lateral force, derailment coefficient etc. Derailment coefficient was less than 0.6, and lateral force allowance limit and wheel load reduction ratio were enough safe.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.277-282
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• 2006

Road traffic noise is not produced by any one factor rather occurs as a composition of various factors. Its occurrence is made by running engine noise, tire frictional, and exhaust noise etc. The quality of the noise depends on the size of the vehicles, rotation and engine speed, vehicle load, package state of the road and incline etc. The occurrence of noise level of heavy trucks appears louder than smaller vehicles and the noise levels produced differs according to speed and load etc between similar size vehicles. Other factors such as traffic density, average speed, mixing rate of heavy vehicles, and the distance between vehicles also generate road traffic noise. In this paper we examine 2, 4, and 6-lane roads in Jeonju. Consequently, this study examined the means used to measure road traffic noise. It was found that when there is a large traffic density and the average velocity is below 70 km/hr, the noise level could receive a relative proper value by the current measuring means. But in the case of night-time, it was found that the current measuring method is inapposite.

• Atmosphere
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• v.26 no.2
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• pp.289-299
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• 2016

Optical properties of aerosols associated with haze events over Seoul were examined using ground-based skyradiometer and satellite-borne CALIOP and MODIS measurements over the 2009~2010 period. It is shown that aerosol optical thickness (AOT), ${\AA}ngstr{\ddot{o}}m$ exponents (${\alpha}$), and fine-mode particles increase during the haze events. The CALIOP-measured vertical profiles of aerosol during the haze events revealed that most of aerosols are loaded within layers below 4 km altitude. A large portion of these events appear to be related to the long-range transport of aerosols from China; about 35% and 18% of the haze events observed over Seoul were traced back to northern China and southern China, respectively. Compared with optical properties for locally-induced haze events (25%), these long-range transported aerosols are found to have relatively higher AOTs.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.5
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• pp.812-816
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• 2015

Recently, various monitoring systems have been proposed to detect interaction performance between trains and infrastructure, as well as, various techniques to improve the accuracy and performance of such inspection equipment in high speeds. Especially, it is important to predict electric noise of high speed trains due to its effect on detection system accuracy. In this paper, we analyze various types of electrical noise in electric vehicles to improve the accuracy of the detection module of the inspection car. In detail, analysis of electric noise of high speed railway is performed as a function of speed based on field tests that were carried out by HEMU-430X (Highspeed Eletric Multiple Unit - 430 km/h eXperiment).