• 한국유체기계학회 논문집
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• 제2권3호
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• pp.45-51
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• 1999

Centrifugal fans are widely used and the noise generated by these machines causes one of the most serious problems. In general, the centrifugal fan noise is often dominated by tones at BPF(blade passage frequency) and its higher harmonics. This is a consequence of the strong interaction between the flow discharged from the impeller and the cutoff in the casing. However, only a few researches have been carried out on predicting the noise due to the difficulty in obtaining detailed information about the flow field and casing effects on noise radiation. The objective of this study is to develop a prediction method for the unsteady flow field and the acoustic pressure field of a centrifugal fan and to calculate the effects of rotating velocity, flow rate, cut-off distance and the number of blades and its effects on the noise of the fan. We assume that the impeller rotates with a constant angular velocity and the flow field around the impeller is incompressible and inviscid. So, a discrete vortex method (DVM) is used to model the centrifugal fan and to calculate the flow field. The force of each element on the blade is calculated with the unsteady Bernoulli equation. Lowson's method is used to predict the acoustic source. The cut-off distance is the most important factor effecting the noise generation. Acoustic pressure is proportional to 2.8, which shows the same scaling index as the experimental result. In this paper, the cut-off distance is found to be the dominant parameter offecting the acoustic pressure.

• 대한치과보철학회지
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• 제45권2호
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• pp.216-227
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• 2007

Statement of problem: For the long-term success of removable partial dentures, the bonding between metal framework and denture base resin is one of the important factors. To improve bonding between those, macro-mechanical retentive form that is included metal framework design has been generally used. However it has been known that sealing at the interface between metal framework and denture base resin is very weak, because this method uses mechanical bonding. Purpose: Many studies has been made to find a simple method which induces chemical bond, now various bonding system is applied to clinic. In this experiment, shear bond strengths of heat-cured denture base resin to the surface-treated Co-Cr alloy were measured before and after thermocycling. Chemically treated groups with Alloy $Primer^{TM}$, Super-Bond $C&B^{TM}$, and tribochemically treated group with $Rocatec^{TM}$ system were compared to the beadtreated control group. The data were analyzed with two-way ANOVA. Result: 1. Shear bond strength of bead-treated group is highest, and Alloy $Primer^{TM}$ treated group, Super-Bond $C&B^{TM}$ treated group, RocatecTM system treated group were followed. Statistically significant differences were found in each treated group(p<0.05). 2. Surface treatment and thermocycling affected shear bond strength(p<0.05), however there was no interaction between two factors(p>0.05). 3. Shear bond strengths of bead-treated group and Alloy $Primer^{TM}$ treated group showed no statistically significant difference before and after thermocycling(p>0.05), and those of Super-Bond $C&B^{TM}$ treated group and $Rocatec^{TM}$ system treated group showed statistically significant difference after thermocycling(p<0.05).

• Journal of Radiation Protection and Research
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• 제26권2호
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• pp.67-71
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• 2001

극저준위 방사능측정시스템의 백그라운드에 영향을 주는 중성자를 차폐하기 위한 차폐체를 설계하였다. 중성자 차폐방법은 고 밀도 폴리에틸렌을 이용하여 고속중성자를 감속한 후 $B_4C$를 이용하여 감속된 열중성자를 흡수하는 방법을 이용하였다. 몬테카를로 모사방법인 MCNP4B 코드를 이용하여 계산한 결과 고 밀도 폴리에틸렌의 두께가 10 cm 일 때 열중성자속이 최대가 되는 것으로 나타났으며 감속된 중성자의 흡수는 용제에 자연상태의 $B_4C$ 분말을 30 w% 섞을 경우 2 mm의 두께에서 94%의 중성자 흡수가 일어나는 것으로 나타났다. 또한 몬테카를로 모사를 통한 계산결과의 타당성 여부를 조사하기 위하여 중성자 차폐실험 장치를 제작하여 실험 결과와 비교하였으며, 비교 결과 실험값과 일치하는 것으로 나타났다.

• 한국전자통신학회논문지
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• 제13권3호
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• pp.593-600
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• 2018

효과적인 암호시스템 설계에 셀룰라 오토마타(이하 CA)가 적용되고 있다. CA는 국소적 상호작용에 의해 상태가 동시에 업데이트되는 성질이 있어서 LFSR보다 랜덤성이 우수하다. 이런 CA를 암호 시스템에 적용하기 위해 주어진 다항식에 대응하는 CA를 합성하는 방법에 대한 연구가 진행되었다. 본 논문에서는 90 UCA의 특성다항식과 전이규칙이 <$00{\cdots}001$>인 90/150 CA의 특성다항식의 점화관계를 분석한다. 또한 f(x)=f(x+1)을 만족하는 삼항다항식 $x^{2^n}+x+1$에 대응하는 90/150 CA를 90 UCA 전이규칙 블록과 특별한 전이규칙 블록을 이용하여 합성한다. 또한 $x^{2^n}+x+1$의 기약인수에 관한 성질을 분석한 후 $x^{2^n}+x^{2^m}+1(n{\geq}2,n-m{\geq}2)$에 대응하는 90/150 CA 합성 알고리즘을 제안한다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제10권3호
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• pp.192-197
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• 2005

The effects of macronutrients $(NO_3^-,\; NH_4^+\;and\;PO_4^{3-})$ on cell growth and triterpenoids production in Centella asiatica cell suspension cultures were analyzed using the Box­Behnken response surface model experimental design. In screening and optimization experiments, $PO_4^{3-}$ as a single factor significantly influenced cell growth where increasing the phosphate level from 0.1 to 2.4 or 2.6 mM, elevated cell growth from 3.9 to $14\~16g/L$. The optimum values predicted from the response surface model are 5.05mM $NH_4^+$, 15.0mM $NO_3^-$ and 2.6mM $PO_4^{3-}$, yielding 16.0g/L cell dry weight with $99\%$ fitness to the experimental data. While the $NH_4^+-NO_3^-$ interaction influenced cell growth positively in the optimization experiment, $NH_4^+$ and $NO_3^-$ as single factors; and interactions of $NO_3^--PO_4^{3-},\;NH_4^+-PO_4^{3-}$ and $NH_4^+-NO_3^-$ were all negative in the screening experiment. Cell growth and the final pH level were positively affected by $PO_4^{3-}$, but negatively affected by $NH_4^+\;and\;NH_4^+-PO_4^{3-}$ interactions. The different effects of factors and their interactions on cell growth and final pH are influenced by a broad or narrow range of macronutrient concentrations. The productions of triterpenoids however were lower than 4mg/g cell dry weight.

• 한국의류학회지
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• 제36권10호
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• pp.1058-1073
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• 2012

This study examines the effects of collaboration type and brand sensitivity on consumer responses toward fashion collaboration brands. For this study, six brands of fashion collaboration were selected by collaboration types: collaboration with same industry (Uniqlo-Jill Sander, H&M-Sonia Rykiel, and Levis-Jean Paul Gaultier) and collaboration with different industries (LG-Prada, Samsung-Armani, and LG-Levis). A selfadministered questionnaire was developed based on the literature that mainly included brand sensitivity, consumer response (brand association, brand values, and purchase intention), and marketing strategic elements in the context of fashion collaboration. For collecting the data, respondents were asked to choose and assess a previously purchased brand. A total of 299 usable data responses were obtained from Korean consumers aged from 15 to 40 years old. The consumer response toward the fashion collaboration brand consisted of four factors: Emotional value, perceived quality, symbolic value, and brand association. The results showed that the collaboration type had the main effect on emotional value, symbolic value, and purchase intention. Brand sensitivity had the main effect on brand association, emotional value, symbolic value, and purchase intention. There was also an interaction effect on emotional value. With respect to strategic marketing elements, product differentiation, premium pricing, and value pricing had partially positive effect on consumer responses; however, promotion had a negative effect on consumer responses (e.g., perceived quality, and emotional value). In addition, collaboration type or brand sensitivity moderated the effect of strategic marketing elements on consumer responses. This study discussed a managerial implication to develop a strategic brand alliance to manage brand equity in the fashion marketplace.

• 한국수학교육학회지시리즈A:수학교육
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• 제56권3호
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• pp.281-300
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• 2017

This study analyzed the difficulties of middle school students in computer simulation of the law of large numbers through eye movement analysis. Some students did not attend to the simulation results and could not make meaningful inferences. It is observed that students keep the existing concept even though they observe the simulation results which are inconsistent with the misconceptions they have. Since probabilistic intuition influence student's thinking very strongly, it is necessary to design a task that allows students to clearly recognize the difference between their erroneous intuitions and simulation results. In addition, we could confirm through eye movements analysis that students could not make meaningful observations and inferences if too much reasoning was needed even though the simulation included a rich context. It is necessary to use visual representations such as graphs to provide immediate feedback to students, to encourage students to attend to the results in a certain intentional way to discover the underlying mathematical structure rather than simply presenting experimental data. Some students focused their attention on the visually salient feature of the experimental results and have made incorrect conclusion. The simulation should be designed so that the patterns of the experimental results that the student must discover are not visually distorted and allow the students to perform a sufficient number of simulations. Based on the results of this study, we suggested that cumulative relative frequency graph showing multiple results at the same time, and the term 'generally tends to get closer' should be used in learning of the law of large numbers. In addition, it was confirmed that eye-tracking method is a useful tool for analyzing interaction in technology-based probabilistic learning.

• 응용통계연구
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• 제8권2호
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• pp.87-97
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• 1995

$2 \times 2$ 요인계획법에서 주효과가 전혀 존재하지 않거나 단지 하나만이 존재하는 경우의 교호작용을 위한 일반적인 F 검정과 순위변환을 이용한 F 검정 (FR 검정)의 제1종 오류율과 검정력은 전반적으로 비슷한 수준이나 정규분포보다는 지수분포하에서의 FR 검정의 검정력이 상당히 높은 수준임을 알 수 있다. 반면에 주효과들이 모두 존재하는 경우의 FR 검정의 제1종 오류율은 F 검정에 비하여 효과의 크기가 증가할수록 감소하고 주효과의 구성방법에도 영향을 받으며, 검정력은 효과의 크기와 표본의 크기를 크게할수록 증가하되 FR 검정의 검정력은 F 검정에 비하여 낮은 수준이며 주효과의 구성방법 및 모집단의 분포형태에 따라 민감하게 변화함을 알 수 있다.

• International Journal of Industrial Entomology and Biomaterials
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• 제30권2호
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• pp.31-39
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• 2015

Antheraea mylitta Drury (Lepidoptera: Saturniidae) is a commercial silk producing forest insect of India, but it has never been experimented in Uttarakhand state in spite of the huge availability of its forestry host plants. This is the first study on A. mylitta in Uttarakhand. The goal of this study is to introduce forest based commercial rearing of A. mylitta, in tropical forest areas of Uttarakhand to reduce poverty among forest dependent people. In current study, we assessed the effect of seven forest tree species, rearing seasons, and their interactions on cocoon productivity of Daba (bivoltine) ecorace of A. mylitta in the New Forest of FRI, Dehra Dun during 2012 and 2013 and collected the data that was analysed by two-way completely randomized block factorial design. Post HOC Tukey's HSD test was carried out to compare the homogeneous pairs of means. We also carried out Evaluation Index analysis to rank the tested forestry host plants for better growth and development of A. mylitta under the climatic condition of Uttarakhand. Analysis of variance indicated that cocoon yield of A. mylitta differed significantly between rearing seasons (DF=1, F=88.24, p<0.05) and host plants (DF 6, F= 368.63, p<0.05); however, their interactions were found insignificant (DF=6, F=0.99, p>0.05). In first rearing season of July-August, there was higher cocoon yield than the second season of September-November. Results indicated that Terminalia alata fed larvae showed significantly higher cocoon yield (164.11 cocoons/300 larvae); followed by, T. tomentosa (148.89 cocoons), T. arjuna (140.00 cocoons) and Lagerstroemia speciosa (129.47 cocoons) fed larvae. Whereas, Lagerstroemia tomentosa fed larvae that was used by the first time in India, showed lowest cocoon yield (48.81 cocoons), followed by T. chebula (72.53 cocoons) fed larvae. Cocoon yield of T. tomentosa and T. arjuna fed larvae of A. mylitta did not differ significantly with each other.

• 대한교통학회지
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• 제17권2호
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• pp.149-162
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• 1999

양방향 2차로 도로의 설계, 용량 및 운영분석의 단계에서 고려되어야 할 핵심사항으로 화물차와 같은 중차량이 교통류에 미치는 영향을 들 수 있다. 중차량이 교통류에 미치는 영향은 승용차환산계수로 표현할 수 있으며, 이는 교통류 운영분석의 주 MOE's로 사용되는 교통량, 운행속도, 지체시간, 주행의 자유 등에 대하여 중차량이 미치는 영향을 계산하여 승용차 몇 대에 해당하는가를 나타낸 것이다. PCE환산에 있어서 중요한 것은 중차량을 승용차로 환산하는 척도이며, 이러한 승용차 환산 척도는 계량화가 가능하고 교통류특성을 반영할 수 있는 특성을 지녀야 한다. 본 연구에서는 PCE 산정의 척도로서 지체시간을 선정하였으며, 이의 계산을 위하여 도로구간을 추월가능구간과 추월금지구간으로 나누어 지체시간을 계산하였다. PCE의 환산은 Werner와 Morrall이 제시한 것처럼 Walker's Method를 이용하여 교통류 상호간에 발생하는 지체시간과 중차량 1대의 유입으로 인해 유발되는 지체시간을 비교하여 결정하였다. 또한 추월가능 및 금지구간 뿐만 아니라, 추월가능구간과 추월금지구간이 조합되어 연속적으로 나타나는 도로구간의 평균 PC료를 산정할 수 있는 방법을 제시하였다.