• International Journal of Contents
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• 제12권1호
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• pp.65-69
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• 2016

Wireless communication chipsets have fixed transmission rate and communication distance. Although there are many kinds of chipsets with throughput and distance purpose, they cannot support various types of wireless applications. This paper provides theoretic research results in order to support various wireless applications requiring different throughput, delayed quality-of-service (QoS), and different communication distances by using a wireless communication chipset with fixed rate and transmission power. As a performance metric, the probability for a data frame that successfully receives at a desired receiver is adopted. Based on this probability, the average number of transmission in order to make a successful frame transmission is derived. Equations are utilized to analyze the performance of a single-hop with channel coding and a dual-hop without error correction matter transmission system. Our results revealed that single-hop transmission assisted by channel coding could extend its communication distance. However, communication range extending effect of the single-hop system was limited. Accordingly, dual-hop transmission is needed to overcome the communication distance limit of a chipset.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 I
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• pp.318-321
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• 2003

In this paper, path loss and delay profile characteristics are measured in the subway platform. To evaluate the fading characteristics of the measured signals, the standard deviations are computed. The standard deviation is bigger for shorter distance. The shorter the distance, the bigger the phase difference between direct wave and reflected waves according the distance, which results in heavy fading. To compute the path loss according to distance, the average values of path loss exponent(n) is evaluated. The path loss exponents measured in the subway environment for Omni-VP(omni-directional vertical polarization) antenna and CP(circular polarization) antenna are 1.418 and 1.680, respectively, which are considerably less than 2.0, the free space path loss exponent.

• 대한인간공학회지
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• 제6권2호
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• pp.9-18
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• 1987

The purpose of this study was to find the optimal stroke width-to-height ratio of the Korean character (Hangeul) which yields the greatest reading distance. In this study, black characters on a white background were used under 200 lux conditions in-doors, with the stroke width-to-height ratios ranging from a very thin 1:125 to heavier 1: 8.3. The criterion was the average reading distance at which three subjects (male university students) having normal visual acuity (1.2) could read the characters. Using the data obtained from the experi- ment, we analyzed the relationship between stroke width-to-height ratio and reading distance. In the case of the black characters on a white background, the greatest reading distances occurred with a range from 1:11.4 to 1:17.9.

• Educational Technology International
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• 제17권1호
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• pp.59-85
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• 2016

The purpose of the study is to report differences in the effects of learner characteristics on the self-regulated learning (SRL) abilities between Chinese and Korean distance learners by using a structured SRL scale. A standardized 54-item self-regulated learning scale (SRAS) was used. The reliability was tested both in China and Korea which showed the scale had good reliability. The comparative study were conducted by administering the SRAS on 1999 Chinese distance learners from the Open Distance Education Center of Beijing Normal University and 1941 Korean distance learners from H Cyber University. Data on four dimensions of SRL - planning, control, regulating, and evaluation - were analyzed using 't-test' and 'ANOVA' with regards to the learner characteristics such as gender, age, prior education level, semesters, location and major. Results indicated that the average participant had an above medium level of SRL ability in all of the four dimensions. There were significant differences in the self-regulated learning ability between Chinese and Korean distance learners. Chinese distance learners scored higher in SRAS than Korean distance learners. The effects of learner characteristics on the SRL ability showed different patterns in the two countries. As for gender, male learners scored better in SRL than female learners in China, whereas it was just the opposite in Korea. No age differences were found in China, but Korean data exhibited a consistent age effect in all dimensions. In Korea, the age group older than 46 scored the highest, followed by the group between 35 to 45 years old, the group between 26 to 35 years old and the group younger than 25. As for location, Korean distance students from metropolitan were better than those from other regions, whereas it was on the contrary in China, albeit the location effect was not statistically significant. Prior education level had a clear and consistent effect on the SRL ability in both countries: the distance learners from junior colleges had better planning, regulating and evaluating abilities than those who came from senior high schools. These results have been discussed in various contexts of distance/online education as well as in relation to different culture between China and Korea. The results will also have implications for designing distance and online learning generally.

• 한국축산시설환경학회지
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• 제17권2호
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• pp.93-100
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• 2011

본 연구는 로봇 착유시스템의 유두인식을 위한 기초연구로 레이저 스캔 센서를 이용하여 모형유두의 위치정보를 획득 및 분석하고 이를 통하여 로봇 착유시스템에 적용가능성을 알아보고자 하였다. 이를 위하여 실제유두와 같은 모양과 크기의 모형유두를 제작하였으며, 각 모형의 재질에 따른 특성을 파악하고 센서의 거리에 따른 오차, 각도에 따른 오차를 분석하였다. 또한 4개 유두모형을 이용하여 각 유두의 2차원 거리정보를 동시에 획득하였으며 결과는 다음과 같다. 1. 모형유두의 재질선택을 위한 실험에서 손가락의 경우 거리오차가 최대 4.3 mm, 최소 1.3 mm, 평균 2.8 mm로 가장 작게 나타났으며, 고무재질의 모형유두가 평균 4.3 mm로 나타나 모형유두로 가장 적합한 것으로 판단되었다. 2. 거리에 따른 오차는 기준거리 100 mm에서 가장 크게 나타났으며, 거리가 증가할수록 감소하다 300 mm를 지나 다시 증가한 후 다시 감소하는 경향을 나타내었다. 3. 각도별 오차는 $170^{\circ}$에서 10.1 mm로 최대오차가 발생하였으며, $70^{\circ}$일 때 0.2 mm로 최소 오차를 나타내었다. 각도에 따른 오차는 특별한 경향을 나타내지 않는 것으로 판단되었다. 4. 4개 모형유두에 대한 2차원 위치오차를 측정한 결과 거리오차의 경우 최소 3.8 mm, 최대 7.2 mm로 나타났으며, 각도 오차는 최대 $1.2^{\circ}$로 오차가 발생한 것으로 나타났다. 모든 오차가 센서 정밀도 내에 포함되며, 센서의 측정 속도와 착유컵의 구멍크기 등을 고려해 볼 때 로봇 착유시스템을 위한 유두의 거리측정에 적용이 가능할 것으로 판단되었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.534-539
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• 2001

An experimental investigation of heat transfer characteristics on confined jet impinging plate using multiple slot jets has been performed. The effects of jet Reynolds numbers(Re=2000, 3950, 5900, 7900), dimensionlesss slot-to-plate distances(H/B=2, 4, 6, 8) and jet-to-jet distances(S=16B, 20B, 24B, 30B) on the local and average heat transfer coefficients have been examined. To clarify local heat transfer characteristics, naphthalene sublimation technique were used. From the experimental results, it was found that the local and average heat transfer rates increase with increasing jet Reynolds number. Measurements of local heat transfer coefficients produced by multiple of slot jets have given an indication of the nature of the interaction between jets and of the uniformity of heat transfer obtainable with various arrangements. At S/B=20, Re=7900 and H/B=6, maximum average Nusselt number is obtained.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.274-279
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• 2001

An experimental investigation of heat transfer characteristics at the surface of two-dimensional protruding heated blocks using confined impinging multiple slot jets has been performed. The effects of jet-to-jet distances(S=16B, 24B), dimensionless nozzle-to-block distances(H/B=2, 6) and jet Reynolds numbers(Re=2000, 3900, 5800, 7800) on the local and average heat transfer coefficients have been examined with five isothermally heated blocks at streamwise block spacing(p/w=1). To clarify local heat transfer characteristics, naphthalene sublimation technique was used. From the results, it was found that the local and average heat transfer of heated blocks increases with decreasing jet-to-jet distance and increasing jet Reynolds number. Measurements of local heat transfer coefficients have given an indication of the nature of the interaction between jets and of the uniformity of heat transfer obtainable with various arrangements. In the case of S/B=16, H/B=6 and Re=7800, maximum average Nusselt number of overall blocks was obtained.

• 한국식생활문화학회지
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• 제30권4호
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• pp.439-446
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• 2015

This study considered network quotient (NQ) of deluxe hotel employees and schematized characteristic attributes of being selected by employees with image through correspondence analysis in terms of cognition degree. Self-administrated questionnaires were completed by employees (292 samples) and data were analysed by frequency, t-test, one-way ANOVA, reliability and correspondence analysis. First, the hotel employees indicated the high average value in "participating in special education or seminar for improving ability ($3.85{\pm}0.76$). Second, as a result of analyzing difference according to gender, the average value in men was higher than in women. It was indicated that the higher age and career lead to a rise even in the average value of relationship index. Third, in consequence of carrying out correspondence analysis in order to prepare image map according to cognition level on relationship index in hotel employees, the measurement item that is placed in the closest distance to the response as saying of not so very was the response as saying of "having a lunch (dinner) engagement twice or three times a week." On the other hand, the response as saying of "tending to have many acquaintances compared to coworkers" was schematized in the close distance to the response as saying of very so.

• 한국동물학회지
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• 제32권1호
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• pp.14-21
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• 1989

한국산 포유동물 6목 24종 279표본의 4개 외부형질과 22개 두골형질들을 측정하였으며, 측정치를 ordination법과 clustering법에 의해서 분석하였다. 형태적 분석의 결과는 족제비, 청서 및 토마스 땃쥐가 현존 분류체계상의 위치와 다르게 나타났다. 한국산 포유동물의 목 수준에서의 mrophological difference는 다른 포유동물보다는 크게 나타났으나, 목 이하의 수준에서는 별 차이가 없었다. 분류학적 체계에서의 단계가 높아질 수록 average taxonomic distance morphological difference의 수치는 커졌으며, 두 행렬식간의 상관계수는 0.59였다.

• 천문학회보
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• 제44권1호
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• pp.34.3-34.3
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• 2019

We report our discovery of observational evidence for the coherence between galaxy rotation and the average motion of neighbors. Using the Calar Alto Legacy Integral Field Area (CALIFA) survey data analyzed with the Python CALIFA STARLIGHT Synthesis Organizer (PyCASSO) platform, and the NASA-Sloan Atlas (NSA) catalog, we estimate the angular momentum vectors of 445 CALIFA galaxies and build composite maps of their neighbor galaxies on the parameter space of velocity versus distance. The composite radial profiles of the luminosity-weighted mean velocity of neighbors show striking evidence for dynamical coherence between the rotational direction of the CALIFA galaxies and the average moving direction of their neighbor galaxies. The signal of such dynamical coherence is significant for the neighbors within 800 kpc distance from the CALIFA galaxies with a confidence level of $3.5{\sigma}$, when the angular momentum is measured at the outskirt ($Re<R{\leq}2Re$) of each CALIFA galaxy. We also find that faint or kinematically misaligned galaxies show stronger coherence with neighbor motions than bright or kinematically well-aligned galaxies do. Our results show that the rotation of a galaxy, particularly at its outskirt, may be significantly influenced by recent interactions with its neighbors.