• 한국통신학회논문지
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• 제27권4B호
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• pp.345-352
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• 2002

본 논문에서는 백색잡음과 페이딩환경에서 IS-95 시스템 역방향의 성능을 평가하는데 있어 컴퓨터 수행시간을 개선할 수 있는 획기적인 방법을 제안하고 제안된 방법의 효율성은 샘플수의 형태로 입증된다. 현재 통신 시스템의 성능분석에 가장 많이 사용되는 MC(Monte Carlo) 시뮬레이션 기법은 낮은 에러율에서 많은 시뮬레이션 수행시간을 요구한다. 때문에 MC 방법은 컴퓨터 수행속도의 한계를 피할 수 없게 된다. 이러한 문제점을 해결하기 위해 제안된 방식인 센트랄 모멘트 기법을 IS-95 시스템 역방향에 적용하여 MC 방법에서 요구되는 데이터 샘플수보다 적은 수신신호의 N차 센트랄 모멘트로부터 이산 확률밀집함수를 얻을 수 있다. 연속된 누적확률분포 함수는 보간법을 통해 정확하게 되고 샘플수에서의 개선 효과가 입증된다.

• 한국항공우주학회지
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• 제36권5호
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• pp.483-490
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• 2008

마이크로 추진장치에서 노즐의 소형화는 많은 유동손실을 유발한다. 이러한 유동손실을 극복하기 위해 본 연구에서는 열적발산원리를 이용한 마이크로 추진장치에 대한 기초연구를 진행하였다. 움직이는 부품 없이 오직 온도구배만으로 추진제를 낮은 온도에서 높은 온도로 자체 펌핑이 가능한 열적발산장치를 설계, 제작 하였으며, 진공환경에서 누센수에 따른 맴브레인 압력구배효율을 분석하였다. 실험결과 천이영역에서는 두꺼운 맴브레인의 효율이 다소 높았으며, 자유분자영역에서는 두께에 관계없이 최대 압력구배 효율이 82%까지 증가하는 것을 확인할 수 있었다.

• 한국도서관정보학회지
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• 제44권4호
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• pp.399-419
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• 2013

이 연구는 우리나라 공공도서관의 규모를 나타내는 8가지 변인을 대상으로 2011년도 통계데이터를 적용한 분포에서 어떤 독특한 특성이 나타나는지를 실증적으로 분석하였다. 그 결과 8가지 규모변인들 모두에서 멱함수 법칙이 나타나는 복잡계 현상이 발견되었다. 우리나라 공공도서관의 규모에서 양극화가 발생한 것이다. 특히 연면적, 직원수, 도서수, 예산의 변인에서는 지프의 법칙이 나타났다. 그리고 등록회원수, 자료실 이용자수, 대출자수, 대출권수의 변인에서는 지프의 법칙보다 더 심하게 불균등한 분포가 나타났다. 따라서 우리나라 공공도서관 규모의 양극화 현상을 해소할 수 있는 정책의 개발이 요구된다.

• Journal of Nutrition and Health
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• 제31권3호
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• pp.354-362
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• 1998

The purposes of this study were to develop standardized indices of staffing needs in each school, foodservice system through work sampling methodology . Conventional school foodservices were classified into 5 groups depending on size of meals served. Commissary school foodservices were also classified into 5 groups by cluster analysis using number of meals served, number of satellite schools, and time for transportation of food. Work measurement through work sampling methodology was conducted in 15 conventional and 21 commissary foodservices during 3 consecutive days from September to October in 1995. Statistical data analysis was completed using the SAS programs for descriptive analysis, cluster analysis, and simple linear regression. The results were as follows : Average points of leveling factors of conventional and commissary foodservices were 1.066 and 1.061 , respectively. Mean labor hours per work force was 328 minutes and 366 minutes in conventional and commissary foodservice , respectively. Standardized work time was calculated using leveling factor, ILO allowance rate (175) , and observational work time. The model for standardized indices of staffing needs was developed based on simple linear regression in each school foodservice system. In conventional school foodservice systems(for 100-1,900 meals per day) standardized staffing needs=3.2497 +0.005267$\times$number of meals served (F=273.1, R-square 0.9750, p<0.001). In commissary school foodservice systems (for 200-1,600 meals per day ) Standardized staffing needs=3.393384 +0.0063$\times$number of meals served (F=30.78, R-square 0.6580, p<0.001).

• 한국농공학회지
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• 제35권3호
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• pp.63-73
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• 1993

For a systematic approach to rural settlement planning, socio-economic and land use potentialities were analysed in 10 villages("Ri", the lowest-order administrative unit in Korea)of Izuk-myun, Anseong-gun, Kyeonggi province, the model area in this study. Socio-economic potentialities, sub-grouped into rural and urban related ones, were analysed by the principal component analysis technique, while land use potentialities by the land suitability system of which the physical analysis is based on geographical information system. The principal component of rurality is strongly related with 5 key variables such as annual increasing rate of farm households, ratio of over 1ha-households, ratio of full-time farmers, ratio of animal rearing households and the principal component of urbanity with 6 key ones such as population density, number of schools, number of shops and servicing facilities, number of daily bus routes, number of non-farm households, percentage of area of housing sites. The analysis procedure of land suitability using the geographical information system were generalized and the results of analysis on village sites and paddy and upland fields were presented. The whole land use planning was presented by the criteria of the land suitability rank and the priority order of land use. land use.

• 디지털콘텐츠학회 논문지
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• 제4권1호
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• pp.1-10
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• 2003

본 연구는 인터넷에서 사용하는 주문형 전자카드 서비스 방법 및 시스템설계에 관한 것으로, 사용자의 신용카드번호, 선불카드번호, 은행계좌 등을 포함하는 신용정보를 입력받는 단계부터 시작하여 주문형 전자카드의 승인여부, 거래대금지불승인여부를 거쳐, 지급단계까지의 서비스를 시스템에 관한 연구이다. 이는 사용자가 전자카드의 사용한도. 사용횟수, 유효기간, 충전가능 여부 익명사용여부 등을 사용하고자 하는 거래 형태에 맞추어 직접 설계할 수 있으므로 사용자의 편의성을 보다. 증진시킬 수 있다. 또한 사용자의 설계범위 내에서만 결제가 이루어지므로 카드번호의 분실시에도 그 피해를 설계범위내로 최소화할 수 있다.

• Journal of Mechanical Science and Technology
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• 제15권2호
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• pp.268-276
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• 2001

In order to improve the efficiency of a direct contact heat exchanger for a solar thermal energy system, the working fluid should be dispersed into small and uniform droplets, and stay within a heat exchanger for a long time. Therefore, installation of meshes in a direct contact heat exchanger is suggested in the present study, and the performance of the direct contact heat exchanger with several layers of meshes is experimentally investigated. Diethyl phthalate is used as the working fluid, and the performance of the heat exchanger is tested for several different operating conditions and compared to that of the heat exchanger without meshes. The results of this investigation show that meshes make droplets uniform and small when the flow rate is low. The relationship between the Peclet number and the Nusselt number becomes linear if it is steady. And, the Nusselt number for the direct contact heat exchanger with meshes becomes greater than that without meshes as the Peclet number increases.

• 산업경영시스템학회지
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• 제17권32호
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• pp.243-253
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• 1994

Work environments have been changed with the advent of new technologies, such as computer technology. The newer technologies, the more changes in our work conditions. However, human cognitive limits can't keep up with the change of work environments. Mental workload has been an important factors in designing modem work environments such as human-computer interaction. Designing man-machine systems requires knowledge and evaluation of the human cognitive processes which control information flow workload. Futhermore, under an urgent situation, human operator may suffer the work stress, work error, and resultant deleterious work performance. To describe the work performance in the urgent work situations, with time stress and dynamic event occurence, a new concept of information density was introduced. For a series of experiments performed for this study, three independent variables(information amount system processing time, information density) were evaluated using such dependent variables as reaction time, number of error, and number of failure. The results of statistical anlysiss indicate that the amount of information effected on all of five dependent measure. Number of failure and number of secondary task score were effected by both amount of information and operational speed of system, but reaction time of secondary task were effected by both amount of information and information density.

• 전자공학회논문지A
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• 제31A권4호
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• pp.11-20
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• 1994

The error rate equation of DS-CDMA/DQPSK skgnal adopting ARQ scheme has been derived in indoor radio channel which is characterized by AWGN, multi-user interference (MUI) and Rician fading, Using the derived equation the error performance has been evaluated and shown in figures as a function of direct to diffuse signal power ratio(KS1rT), the number of active users (K), PN code sequence length (N), the number of parity bit of linear code (b), forward channel BER, and ES1bT/NS1OT. From the results it is known that in severe fading environments (KS1rT=6) the performance of DS-CDMA/DQPSK system is not reliable so it is needed to adopt techniques for improvement. When an ARQ scheme is adopted, as a method for improving error performance, the performance improves compared with that of non-ARQ scheme and the degree of improvement is proportional to the number of parity bits of linear code. As increasing the number of parity bits, system performance is improved vut system throughput efficiency must be considered. In severe fading channel Hybrid ARQ scheme is more effective than ARQ scheme. As a result, ARQ scheme is appropriate for the high-reliability data communication systems over the radio channel in which the real time processing is not required.

• Asian-Australasian Journal of Animal Sciences
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• 제26권4호
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• pp.545-551
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• 2013

This study aimed to present a mouse model of ovalbumin (OVA) induced allergic diarrhea under a sub-barrier system and investigate the development of gut microbiota in this model. Male BALB/c mice were systemically sensitized with OVA or sham-sensitized with saline, and followed by oral OVA intubation, leading to OVA-specific acute diarrhea. Compared with sham-sensitized mice, sera OVA-specific IgG1 and total IgE in OVA-sensitized mice were dramatically elevated, and the number of mast cells was greatly increased in the jejunum of the OVA-sensitized mice. Principle component analysis of the DGGE profile showed that samples from group of OVA-sensitized mice and group of sham-sensitized mice were scattered into two different regions. Real-time PCR analysis showed that the number of 16S rRNA gene copies of Lactobacillus in the colon of OVA-sensitized mice decreased significantly, while there was no significant difference in the number of Bifidobacterium and total bacteria. In conclusion, OVA-specific allergic diarrhea was successfully induced under a sub-barrier system, and changes of allergic reactions during induction was coupled with changes in gut microbiota, especially the number of colonic Lactobacillus, but the role of gut microbiota in the development of food allergic reactions needs to be further evaluated.