• ETRI Journal
• /
• 제28권5호
• /
• pp.660-663
• /
• 2006

In this letter, we propose a frame-size adaptive MAC protocol for high rate wireless personal area networks (WPANs). In the proposed scheme, during communication, frame error rate is periodically reported to a transmitting device and the frame size is changed according to the measured results. Thus, the channel can be more effectively utilized by adapting to variable radio conditions. Analytical results show that this scheme achieves a much higher throughput than a non-frame-size adaptive media access control protocol in high-rate WPANs.

• Fisheries and Aquatic Sciences
• /
• 제5권3호
• /
• pp.183-190
• /
• 2002

To determine the effect of body size on the clearance rate and ingestion rate of small intertidal bivalves, Glauconome chinensis, feeding experiments were conducted on individuals of 12 different size classes, from 4 to 16 mm in shell length. Relationships between morphological parameters were also determined. The clearance and ingestion rates of G. chinensis responded similarly to their body size, ranging from 1.3 to 28.2 mL/hr/ind. and from 24.0 to 458.5, ${\mu}gC/hr/ind$., respectively. Both rates increased significantly (p<0.001) as shell length increased from 4 to 9 mm, although neither rate changed significantly when shell length was in the range from 12 to 16 mm. The weight-specific clearance rate $(CR_w)$ and ingestion rate $(IR_w)$ decreased with increasing body size, with values from 1.0 to 3.1 L/hr/g and from 17.9 to 51.3 mgC/hr/g, respectively. The $CR_w$ of G. chinensis was intermediate compared to those of larger bivalve species. The clearance rate (CR) relative to flesh dry weight (FDW) of G. chinensis were fitted well to the power function: $CR=0.43\times(FDW)^{0.71}\;(r^2=0.89)$. The exponent of fitting equation (0.71) of G. chinensis was higher than those of Mytilus edulis (Walne, 1972), Crassostrea gigas (Walne, 1972), and Placopecten magellanicus (MacDonald and Thompson, 1986).

• 환경생물
• /
• 제29권4호
• /
• pp.274-279
• /
• 2011

식물의 초기 생활사가 종자크기에 따라 어떤 영향을 받는지를 알아보기 위하여 우리나라 산림군락에서 상수리나무, 굴참나무, 갈참나무, 졸참나무 참나무 4종의 열매를 3등급의 크기(대, 중, 소)로 구분하고, 그에 따른 4종의 발아율, 겨울철 생존율과 초기 생장율을 측정하였다. 평균 발아율은 종자가 큰 상수리나무와 굴참나무에서 높았고, 상대적으로 크기가 작은 갈참나무와 졸참나무에서 낮았다. 그러나 종 내 종자크기에 따른 발아율은 굴참나무에서만 종자가 작을수록 높았고, 나머지 3종은 종자크기에 따른 경향성이 없었다. 평균 초기 생장율은 종자크기에 비례하여 상수리나무, 굴참나무>갈참나무>졸참나무 순으로 낮았다. 초기 생장율은 상수리나무와 굴참나무에서 종자가 크거나 중간인 것이 작은 것보다 높았으나, 종자가 작은 갈참나무와 졸참나무 내에서는 종자크기에 따른 차이는 없었다. 겨울 동안의 생존율은 4종 모두 중간 크기의 종자에서 가장 높았으나, 졸참나무나 굴참나무는 작거나 큰 종자에서는 전혀 생존하지 않았다. 결론적으로 발아와 초기 생장에는 큰 종자가, 생존에는 중간크기 종자가 각각 유리하였다. 이것은 종자의 크기가 식물의 생활사에 미치는 영향은 생장단계에 따라 서로 다름을 의미한다.

• 한국식품조리과학회지
• /
• 제22권4호통권94호
• /
• pp.521-534
• /
• 2006

The Kimchi intake of elementary students in both school and home is decreasing due to their westernized eating habits which have been affected by the rapid economic growth and industrialization in our modem society. The purposes of this study were to examine the influence of menu selections on the Kimchi intake rate and to provide basic data for an appropriate Kimchi serving size to reduce the plate-waste rate. The results showed that the average daily intake rate of Kimchi of low-grade students was 58.2%, equating to 6${\sim}$18 g, compared to 64.6% for high-grade students, equivalent to 13${\sim}$24 g. Correlation analysis of the intake rate of menu items and Kimchi showed that the Kimchi intake rate increased with increasing total meal intake rate, rice intake rate, soup intake rate, rice mixed with grains intake rate, clear soup intake rate and soybean-paste soup intake rate, but that it decreased as the intake rate of seasoned uncooked vegetables of high-grade students increased. This study is expected to be utilized as a solution to increase the Kimchi intake rate of elementary school students, and also to determine the proper serving size per person on the menu items by grade.

• 한국안전학회지
• /
• 제9권1호
• /
• pp.76-82
• /
• 1994

Combustion phenomena(characteristics) of organic solvents including various alcohols Immobilized on ceramic balls were studied. Experiments were performed by burning methyl, ethyl, and propyl alcohol immobilized on sands (particle size 0.35mm) and coramic balls(particle size 1~5mm) to measure mass burning rate, height burning rate and combustion temperature. The longer time from ignition to extinguishment was resualted from the larger particle size of ceramic balls and the smaller size of ceramic balls exhibited the higher mass burning rate. Of alcohols tested the relative magnitude of facilitation of combustion was methyl >ethyl >propyl. Combustion temperatare of alcohols, without regard to the types of alcohols, was not increased with smaller ceramic balls(up to 3mm of particle size). However, with larger ceramic balls, combustion temperatare of alcohols was increased by 40~5$0^{\circ}C$ and the highest combustion temperatare was obtained with sands(particle size 0.35mm). Also, second rising was occurred at the combustion time of I5-20min. and this second rising time was increased with the smaller particle. These results will be able to be used for petrochemical industries using particles to evaluate the danger of fire and explosion.

• 한국음향학회지
• /
• 제28권8호
• /
• pp.815-821
• /
• 2009

소음이 존재하고, 신호의 전달 시스템이 가변적인 환경에서 신호처리는 일반적으로 적응 알고리즘에 의해 이뤄진다. 다양한 적응 알고리즘들 중에서 LMS 알고리즘은 연산량이 적고, 구현이 쉬우며, 성능이 훌륭해 가장 널리 쓰이는 알고리즘이 되었다. LMS 알고리즘의 성능에 영향을 미치는 가장 중요한 요소 중 하나가 Step Size이다. 일반적으로, Step Size가 크면, 알고리즘 수렴 속도는 빨라지지만, 수렴 오차는 커지게 되고, Step Size가 작으면 수렴 오차는 작아지지만, 수렴 속도는 느려진다. Step Size의 이러한 특성을 상호 보완하고자 많은 방법들이 제안되어 오고 있다. 본 논문에서는 오차 제곱 변화 곡선의 기울기로부터 현재 상태에 대한 카테고리를 분류하여, Step Size를 매 단계마다 적절하게 가변시킴으로써, 결과적으로 수렴 속도와 정확도, 연산량을 향상시킨 새로운 개념의 Categorized 가변 스텝 사이즈 LMS 알고리즘을 제시하고, 그 성능은 실험을 통하여 수렴 속도와 Excessive Mean Square Error (EMSE), 연산량의 관점에서 향상되었음을 검증하였다.

• 대한기계학회논문집
• /
• 제8권1호
• /
• pp.34-40
• /
• 1984

In this study, martensite-ferrite dual phase steel composed of martensite in hard phase and ferrite in soft phase is made as model material, and the difference of fatigue crack propagation behavior resulted from the structural size is investigated by fracture mechanics and microstructural method. The main results obtained are as follows; 1)Fatigue crack propagation rate is influenced by ferrite grain size. In other words, in the low .DELTA. K region fatigue crack propagation rate is decreased with decreasing of grain size but the difference of propagation rate resulted from the structural size is decreased as .DELTA.K is increased. 2)The above result is explained by the degree of crack arrest effect of second phase for fatigue crack propagation depending on the ratio of reversed plastic zone size to ferrite grain size.

• 한국정보처리학회논문지
• /
• 제4권9호
• /
• pp.2366-2377
• /
• 1997

본 논문은 ATM망의 트래픽 제어에서 예방적 기법인 가변 토큰풀(Variable Token Pool : VTP)을 이용한 적응적 사용 파라메터 제어에 관한 메카니즘을 제안한다. 가변 토큰풀 메카니즘은 ON-OFF형 트래픽의 버스트 기간과 침묵 기간을 장기간 감시하여 토큰풀을 가변시킴으로서 최대 비트율 뿐만 아니라 평균 비트율과 버스트 기간 위반을 함께 감시할 수 있다. 또한 제안된 메카니즘은 버스트 기간과 평균 비트율 위반에 대한 민감성을 개선할 수 있고, 위반 사항에 대한 반응이 빨리 나타난다. VTP 크기는 버스트와 침묵 구간마다 계단 형태로 변하고, 하향 간격 (Down_size)과 상향 간격 (Up_size)의 값에 따라 제어된다. 본 논문에서 제안한 메카니즘을 시뮬레이션을 통해 LB와 JW 메카니즘과의 성능을 비교 분석하였다. VTP메카니즘은 기존에 제안된 메카니즘보다 좀더 엄격한 제어 능력을 보였다. VTP 메카니즘의 셀 손실율은 VTP의 파라메터 (Down_size, Up_size)값의 증감에 따라 다르게 나타났으며, 두 파라메터 값이 트래픽 상황에 따라 적당한 값으로 결정되어야 함을 보여주었다.

• Transactions on Electrical and Electronic Materials
• /
• 제7권4호
• /
• pp.167-172
• /
• 2006

Submicron colloidal silica coated with ceria were prepared by mixing of silica and nano ceria particles and modified by hydrothermal reaction. The polishing efficiency of the ceria coated silica slurry was tested over oxide film on silicon wafer. By changing the polishing pressure in the range of $140{\sim}420g/cm^2$ with the ceria coated silica slurries in $100{\sim}300nm$, rates, WIWNU and friction force were measured. The removal rate was in the order of 200, 100, and 300 nm size silica coated with ceria. It was known that the smaller particle size gives the higher removal rate with higher contact area in Cu slurry. In the case of oxide film, the indentation volume as well as contact area gives effect on the removal rate depending on the size of abrasives. The indentation volume increase with the size of abrasive particles, which results to higher removal rate. The highest removal rate in 200 nm silica core coated with ceria is discussed as proper combination of indentation and contact area effect.

• 대한안전경영과학회지
• /
• 제1권1호
• /
• pp.231-239
• /
• 1999

CAPM explains the rate of return for the risk asset by $\beta$, systematic risk. There are some assumption in CAPM. But CAPM can not explain the movement of stock price sufficiently due to limitation of the assumptions. Therefore many scholars study which variables with the exception of $\beta$ effect on the rate of return of risk asset for supplementing this limitation by using PER, size of firm etc.. But it will be natural that PER, size of firm etc. to be determinant factors of $\beta$ also effect on the abnormal rate of return, because PER, size of firm etc. used in their studies already effect on determination of $\beta$, . That is, the determinant factors of $\beta$ effect on determination of abnormal rate of return according as $\beta$, effects on abnormal rate of return. Therefore, this study tests empirically how the determinant factors of $\beta$, effect on determination of$\beta$, ,and how $\beta$ and the determinant factor of $\beta$ effect on the abnormal rate of return in CAPM.