• 한국인터넷방송통신학회논문지
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• 제11권3호
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• pp.41-46
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• 2011

요 약 주행 중인 차량의 타이어에서 발생하는 초음파 신호의 포락선에서 손상 물질에 의한 특징 신호의 주기를 검출하여 타이어 손상을 분별하는 방법을 연구하였다. 손상된 타이어는 주행 시 회전에 의해 주기성을 갖는 신호를 발생하기 때문에 이를 펄스화하고 펄스 간의 시간 간격을 밀도함수로 나타내어 우성 주기를 검출하였다. 펄스화하기 위한 임계값은 포락선 신호를 이동평균필터 처리하여 결정하였다. 손상물질이 한 개이고, 주행속도가 약 50km/h, 80km/h일 때, 시간밀도함수의 결과는 제 1 피크시간이 156ms, 102ms로 주행속도에 따라 계산한 타이어의 회전주기와 일치하였고, 한 개 이상의 손상물질의 경우에는 각 피크시간의 합이 타이어의 회전주기와 동일한 결과를 얻을 수 있었다.

• 한국대기환경학회지
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• 제15권4호
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• pp.441-455
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• 1999

Meteorological characteristics of three high-ozone episodes in the Greater Seoul Area, selected on the basis of morning-average wind direction and speed for the 1990~1997 period, were investigated. Three high-ozone episodes thus selected were seven days of July 3~9, 1992, nine days of July 21~29, 1994, and three days of August 22~24, 1994. Along with surface meteorological data from the Seoul Weather Station, surface and 850-hPa wind fields over the Northest Asia around the Korean Peninsula were used for the analysis. In the July 1992 episode, westerly winds were most frequent as a result of the influence of a high-pressure system in the west behind the trough. In contrast, in the July 1994 episode, easterly winds were most frequent due to the effect of a typhoon moving north from the south of Japan. Despite different prevailing wind directions in the two episodes, the peak ozone concentration of each episode always occurred when a sea-land breeze developed in association with weak synoptic forcing. The August 1994 episode, selected as being representative of calm conditions, was another typical example in which peak ozone concentration rose to 322 ppb under the well-developed sea-land breeze. All three high-ozone episodes were terminated by precipitation, and subsequent rises in ozone concentrations were also suppressed by a series of precipitation afterwards. In particular, two heavy rainfalls were the main reason why the August 1994 episode, with the highest and second-highest ozone concentrations during the 1990~1997 period, lasted for only a few days.

• 한국미생물·생명공학회지
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• 제21권4호
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• pp.354-365
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• 1993

A novel control method with automatic tuning of PID controller parameters has been developed for efficient regulation of dissolved oxygen concentration in fed-batch fermentations of Escherichia coli. Agitation speed and oxygen partial pressure in the inlet gas stream were chosen to be the manipulated variables. A heuristic reasoning allowed improved tuning decisions from the supervision of control performance indices and it coule obviate the needs for process assumptions or disturbance patterns. The control input consisted of feedback and feedforword parts. The feedback part was determined by PID control and the feedforward part is determined from the feed rate. The proportional gain was updated on-line by a set of heuristics rules based on the supervision of three performance indices. These indices were output error covariance, the average value of output error, and input covariance, which were calculated on-line using a moving window. The integral and derivative time constants were determined from the period of output response. The specific growth rate was maintained at a low level to avoid acetic acid accumulation and thus to achieve a high cell density. The specific growthe rate was estimated from the carbon dioxide evolution rate. In fed-batch fermentation, the simutaneous control of dissolved oxygen concentration (at 0.2; fraction of saturated value) and specific growth rate (at 0.25$hr^{-1}$) was satisfactory for the entire culture period in spite of the changes in the feed rate and the switching of control input.

• 한국농공학회지
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• 제19권3호
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• pp.4472-4482
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• 1977

In order to estimate furture consumtive use, some statistical characteristics of 22-year pan evaporation data at four selected stations were calculated in this study. Districal distribution, trend analysis and time-series, statistical and periodic analysis for annual, monethly and ten-day values were performed in the statistical analysis. The stations are Seoul, Taeku, Jeonju and Mokpo for monthly data, and Suweon data are compared to the reported Penman values. The results are as followed: 1. Annual evaporation ranged to 990-1,375mm varying with the locations of the stations. The Districal distribution of evaporation in the Republic is shown in Fig. 1. 2. The trend analysis for annual evaporation resulted in detail in Table 2 and Fig. 2, through simple moving average methods. The results show relatively short-period data of about 10 years would be acceptable for field use. 3. The means and dispersions of monthly evaporation at four stations are detailed in Table 3. 4. The monthly evaporation approached to the trend of normal distribution Fig. 3 showed the examples of normal distribution for each typical monthly data. 5. The correlograms detailed in Fig. 4, shows the time-series characteristics of monthly evaporation, whose periodic term should be twelve months. 6. The periodic analysis for monthly evapolation results in Table 4. Fig. 5 shows the comparison of estimated values to actual and the trend approaches Shuster's periodic trend. 7. A periodic description of days after March 1 for irrigation periods was developed to predict ten-day evaporation in Fig. 6. The ten-day etraporation is different in the distribution form and occurence period of maximum values from the reported Penman's man's evapotranspiration.

• Structural Engineering and Mechanics
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• 제24권3호
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• pp.375-393
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• 2006

Under high velocity, pulse type near source earthquakes semi-active control systems are very effective in reducing seismic response base isolated structures. Semi-active control systems can be classified as: 1) independently variable stiffness, 2) independently variable damping, and 3) combined variable stiffness and damping systems. Several researchers have studied the effectiveness of independently varying damping systems for seismic response reduction of base isolated structures. In this study effectiveness of a combined system consisting of a semi-active independently variable stiffness (SAIVS) device and a magnetorheological (MR) damper in reducing seismic response of base isolated structures is analytically investigated. The SAIVS device can vary the stiffness, and hence the period, of the isolation system; whereas, the MR damper enhances the energy dissipation characteristics of the isolation system. Two separate control algorithms, i.e., a nonlinear tangential stiffness moving average control algorithm for smooth switching of the SAIVS device and a Lyapunov based control algorithm for damping variation of MR damper, are developed. Single and multi degree of freedom systems consisting of sliding base isolation system and both the SAIVS device and MR damper are considered. Results are presented in the form of nonlinear response spectra, and effectiveness of combined variable stiffness and variable damping system in reducing seismic response of sliding base isolated structures is evaluated. It is shown that the combined variable stiffness and variable damping system leads to significant response reduction over cases with variable stiffness or variable damping systems acting independently, over a broad period range.

• 대한토목학회논문집
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• 제34권2호
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• pp.597-604
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• 2014

본 연구는 현재 국내 BIS에서 버스도착시간 안내를 위해 개별노선 단위로 산정되고 있는 정류소간 통행시간 기반의 버스도착시간 추정 모형의 한계점을 제시하고, 이를 극복하기 위한 방안을 제시하였다. 정류소간 운행시간을 기반으로 산출되는 버스도착시간정보의 특성을 이용하여 버스노선번호에 관계없이 버스정류소에 도착한 동일 구간을 운행하는 모든 버스의 정보를 순서대로 이용하여 버스도착시간을 추정하는 버스도착시간 추정모형을 제안하였다. 제안한 모형은 실제 버스운행정보를 수집하여 RMSE를 기준으로 검증을 실시하였으며, 분석결과 오차는 기존 모형 대비 최대 20%가 감소하였고 버스도착시간정보의 정확도와 직결될 수 있는 데이터 업데이트 주기는 절반수준으로 감소하였다. 이를 통해 버스도착시간의 급격한 증가나 감소, 동일한 구간을 운행하는 다른 노선의 도착예정시간 차이, 운행계획과 다르게 운행시의 정보제공 불가함 등의 문제가 해결될 것으로 기대된다.

• Asian-Australasian Journal of Animal Sciences
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• 제14권11호
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• pp.1527-1533
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• 2001

Garole is a prolific, rare, less known and small size Indian sheep breed found in low and humid Sunderban region of West Bengal. Although information on stored Garole ram liquid semen upto 24 h is available, but there is a need to further investigate the short-term and long-term preservability of Garole ram semen for extensive utilization of this valuable germplasm by artificial insemination. The aim of the present study was to apply computer-assisted sperm analysis technique for assessing the motion characteristics of Garole ram semen stored (i) in liquid state at refrigeration temperature for short-term preservation upto 48 h and (ii) in frozen state at $-196^{\circ}C$ for long-term preservation after packaging in mini straws. Short-term preservation had a significant effect on motility (p<0.01) as the motility progressively decreased from 90.1% at 0 h to 85.5% and 73.2% after 24 and 48 h of storage, respectively. Although the decline in rapid moving sperms was also significant (p<0.01) on storage but the decrease was more pronounced at 48 h as compared to 24 h of storage period. Storage of chilled semen had also a significant effect on % linearity (p<0.05), % straightness (p<0.01), sperm velocities (p<0.01), amplitude of lateral head displacement (p<0.01) and beat frequency (pO.Ol) of spermatozoa. The replication had a significant effect for all the variables except average path and straight line velocity. However, the interactions of short-term storage and replication were non-significant for most of the variables except % of medium moving sperms, sperm velocities and beat frequency. On long-term preservation of Garole ram spermatozoa under controlled conditions the mean post-thaw recovery of 70.4 and 71.4% motile spermatozoa was achieved having 48.8 and 48.9% of rapidly motile spermatozoa, respectively in both the replicates. The effect of replication on cryopreservation was significant (p<0.05) on amplitude of lateral head displacement and beat frequency, but there was no significant effect on motility, rapidly motile spermatozoa, linearity, straightness and sperm velocities of frozen-thawed spermatozoa. It can be concluded from these results that an average 70% motility can be achieved on storage of Garole ram semen in chilled liquid state upto 48 h or in liquid nitrogen after freezing under controlled conditions in straws. However, further studies are required to evaluate the fertility of short-term and long-term preserved Garole ram semen for extensive use of this prolific sheep breed.

• 가정과삶의질연구
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• 제26권3호
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• pp.37-52
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• 2008

The purpose of this study was to provide the valid data about residential-linked pension insurance development. The development was a part of national housing projects, which was an incentive for rural living of retired people, in order to relieve residential issues of elderly and revitalize rural communities by residents moving from cities. The insuring intent, decisive insuring factors and the residential service demand degree of people preparing retirement were analyzed. Data was collected in October, 2007. 364 Sample Subjects lived in Seoul Metropolitan area. Firstly, more than 90% of respondents had intention to purchase a residential-linked pension insurance and about 50% of them necessarily desired receiving premium for moving in. This indicated that it could be developed as an insurance which helped to meet housing expenses by housing-linked system, and in the mean time, it met the original purpose of pension insurance as the pension benefit could be guaranteed for all the insurance subscribers. Secondly, the respondents, whose income and private assets were higher, were able to pay more for insurance compared to average. Therefore, It was necessary to regulate monthly insurance bill and the payment period according to asset states of insurance subscribers after establishing certain amount of total insurance payment. Thirdly, by and large, it indicated the tendency that the less they prepare for older age the later they wanted to move into the pension insurance residence. It was inferred that in the case of insufficient preparation for older age, people preferred preparing behind time by postponing move in to moving in early to enjoy retired life, due to uncertainties. lastly, the respondents understood the significance of health, medical treatment and emergency management service and these two services were preferred as essential provided services. Because of the necessity of developing residential-linked pension insurance was found to be positive, further research to find the real cost, directives for operation and institutional support for this type of pension insurance might be needed.

• 한국해양환경ㆍ에너지학회지
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• 제13권4호
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• pp.279-287
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• 2010

고성만 해역의 수질 특성 및 정체성을 알기 위해 1987년~2009년간의 만내 1개 정점에 대한 표.저층 수질에 대한 장기관측 자료를 분석하였다. 그 결과 고성만 해역의 수질은 chlorophyll-a, DIP, DIN을 기준으로 중영양(Mesotrophic) 단계이고, 화학적산소요구량(COD) 기준으로 해역등급 2등급으로 볼 수 있어, 고성만은 만내에 유입된 물질수지의 확산이 비교적 더딘 폐쇄성 내만임에도 불구하고 수질은 비교적 양호한 것으로 판단된다. 조사기간 전 기간에 걸친 수질성분에 대해 이동평균 시계열분석, 상관분석 및 회귀분석한 결과 고성만 해역은 시간의 경과에 따라 용존무기인(DIP)은 축적되고, 용존무기질소(DIN)는 감소하는 추세를 보였다. 또한 고성만 해역의 식물성플랑크톤 성장의 제한인자는 용존무기질소(DIN)이고, chlrophyll-a의 농도는 8월의 $4.60{\mu}g/L$로 가장 높았다. 계절 평균 및 계절지수는 11월이 가장 높아 고성만의 영양염 수지는 담수 등에 의한 외부유입보다 만의 내부 즉 수산생물의 대량 양식 및 저층 퇴적물에서의 용출 등이 더 큰 요인으로 작용하는 특징을 보였다. 따라서 고성만 해역의 수질 또는 해역 관리를 위해서는 목적에 따라 동 해역의 용존무기인(DIP), 용존무기질소(DIN) 등의 영양염 수지에 대한 고려가 필요한 것으로 보여진다.

• 한국수자원학회논문집
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• 제36권4호
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• pp.561-573
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• 2003

본 연구에서는 서울지점 월강수량 자료에 나타난 가뭄의 재현 및 지속특성을 관측자료의 분석하고, 아울러 포아송 과정을 적용하여 비교하였다. 가뭄을 나타내는 지수로서 표준강수지수(SPI)를 이용하였으며, 10개월의 지속기간을 적용하였다. 관측자료의 분석을 위한 절단수준으로는 -1.00, -1.50, -2.00을 적용하였다. 관측자료의 분석을 통해서 나타난 서울지점 가뭄의 재현 및 지속특성은, 먼저, 보통 가뭄은 대략 2년에 한번 발생하며, 평균 지속기간은 4∼5개월 정도이다. 심한 가뭄은 대략 3∼5년 정도에 한번 발생하며, 평균 지속기간은 대략 2∼4개월 정도로 나타났다. 아주 심한 가룸의 경우에는 8∼23년에 한번 발생하며, 그 평균 지속기간은 2∼4개월 정도이다. 특히, 심한 가뭄의 경우(절단수준 -1.5 및 -2.0 기준)에는 장기 건조기 전반부가 후반부에 비하여 그 재현기간이 매우 크게 나타났으며, 반대로 지속기간은 매우 짧았던 것으로 나타났다. 이는 기본적으로 장기건조기 전반부에 강수 자체의 변동성이 더 컷다는 데서 그 원인을 찾을 수 있으며, 여기에 겨울철 강설량이 포함되지 않은 강수량을 사용한 것도 한 원인으로 작용한 것으로 판단된다. 마지막으로, 관측치에 나타난 결과와 포아송 과정을 적용한 결과를 비교해 본 결과 포아송 과정이 가뭄의 재현 및 지속특성을 잘 설명하고 있음을 파악할 수 있었다.