• 대한기계학회논문집B
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• 제24권4호
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• pp.512-518
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• 2000

A wall fuel-film flow model is developed to predict the effect of a wall-fuel-film on air-fuel ratio in an SI engine in transient conditions. Fuel redistribution in the intake port resulting from charge backflow and a simple liquid fuel behavior in the cylinder are included in this model. Liquid fuel film flow is calculated of every crank angle degree using the instantaneous air flow rate. The model is validated by comparing the calculated results and corresponding engine experiment results of a commercial 4 cylinder DOHC engine. The predicted results match well with the experimental results. To maintain the constant air-fuel ratio during transient operation. the fuel injection rate control can be obtained from the simulation result.

• 대한기계학회논문집B
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• 제28권11호
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• pp.1449-1458
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• 2004

The influence of eccentric(=staggeredness) ratio between stationary upstream circular cylinders on heat transfer characteristics of a heated downstream circular cylinder installed in a channel was investigated experimentally. In order to enhance the heat transfer rate of the heated downstream cylinder surface, we have changed the configuration of upstream cylinder. As a result, we were able to obtain local time-averaged convective heat transfer enhancement of the heated cylinder by the relative replacement of upstream cylinder. This is basically attributed to the mean flow structure change, such as flow separation, vortex shedding, and recirculation of the upstream cylinder including the reattachment and new thermal boundary developed at the downstream cylinder which are the results of the increase of the staggeredness ratio.

• Bulletin of the Korean Chemical Society
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• 제27권10호
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• pp.1609-1612
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• 2006

The determination of the boron isotopic ratio in solutions was achieved by means of a solid state track detector by using an alpha track. The neutron flux was optimized by using a Cd-foil to find the optimum conditions for counting the number of alpha tracks on the selected solid detector caused by the (n, $\alpha$) nuclear reaction of boron. The home-made multi-dot detector plate was utilized in this study to increase the reproducibility of the measurement by uniformly drying the boron solution within the marked circle area on the detector plate. The experimental results of this study verified that the $^{11}B/^{10}B $ isotopic ratio can be measured by observing the number of alpha tracks for different concentrated standard solutions with various isotopic compositions. This technique was applied to the determination of $^{10}B$ enrichment factor in a biological sample for a boron neutron capture therapy.

• Journal of Advanced Marine Engineering and Technology
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• 제7권2호
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• pp.15-21
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• 1983

Preparing for treatment and management of the emulsified fuel oil which will be generalized henceforth, this paper is an attempt to examine the viscosity-temperature characteristics of emulsified heavy fuel oil which is mixed with water and emulsifier in various mixture ratio by mechanical mixer. The experimental results are summarized as follows: 1. The viscosity-temperature characteristics of the emulsified C & B grade heavy fuel oil mixed with water of same or less weight, is changed according to log.log(v+0.6)=b-3.8log T. 2. The emulsifier has to be added to the emulsified A grade heavy fuel oil mixed with water of same or less weight, because it is instable. Especially if the emulsifier is sodium stearate, it is added more than 0.3% of the weight of oil and water. 3. In the emulsified A grade heavy fuel oil mixed with water and emulsifier, the higher the ratio of water addition becomes, the higher the viscosity is and the more the viscosity-temperature slope decreases. But the higher the ratio of emulsifier addition is, the more the viscosity-temperature slope increases. In this case, the linearity of viscosity-temperature characteristic curve is poorer than that of B and C grade heavy fuel oil. 4. In the emulsified A grade heavy fuel oil mixed with emulsifier of 0.3% or less, the emulsion type is O/W type when water addition ratio is 40%, but it is W/O type when it is 10%, 20%, 30% and 50%.

• 한국조경학회지
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• 제33권3호
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• pp.84-93
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• 2005

The purpose of this study is to analyze the economic feasibility of the construction of a new ecological park, based on the case of a plan in Yeongcheon City. For fulfilling the purpose of this study, questionnaire survey was conducted in Yeongcheon City. Based on the survey data, cost-benefit analysis is conducted. For this study, costs and benefits of the project are estimated. Then, using NPV, IRR, and B/C ratio criteria, cost-benefit analysis for this study is conducted. from the empirical cost-benefit analysis, NPV of the proposed project is estimated at 5,420 million Won, IRR is estimated at 12.16%, and B/C ratio is estimated at 1.44. Thus, it is found that the construction of a new ecological park in this area would be feasible from the economic point of view.

• 환경생물
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• 제22권1호
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• pp.101-110
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• 2004

자생종인 가막사리 (Bidens tripartita), 도깨비바늘 (B. bipinnata), 귀화종인 미국가막사리 (B. frondosa), 흰도깨비바늘 (B. pilosa var. minor)의 도깨비바늘속(Bidens) 4분류군의 성장반응과 생태적 지위폭을 비교ㆍ분석하기 위하여 광도, 토양함수량, 토양무기영양소의 3가지 환경요인별, 구배별 재배실험을 하였다. Phonology는 구배별로 큰 차이가 없으나, 종별로는 차이를 나타내어 귀화종인 2종이 자생종인 2종에 비해 개화 및 결실시기가 늦다. 총 건중량은 자생종인 2종에 비해 귀화종인 2종이 대체로 높으며, 구배별로는 광도와 토양함수량이 증가할수록 건중량도 증가하였고, 토양무기영양소 구배에는 반대의 경향이 나타났다. 환경요인별 총건중량은 토양무기영양소, 토양함수량, 광도의 순으로 낮아졌다. NAR은 B. bipinnata와 B. pilosa var minor에서 광도와 함수량증가에 따른 증가속도가 크며, 반대로 B. tripartita와 B. frondosa는 그 증가속도가 작았다. 그러나 토양무기영양소에 대해서는 영양소 증가에 따라 B, bipinnata와 B. pilosa var. minor가 오히려 감소하는 경향을 나타냈다. RGR은 광도의 증가에 따라 B. tripartita, B. bipinnata, B. frondosa, B. pilosa var. minor의 순서로 작아졌으며, 토양함수량 구배에서는 B. bipinnata와 B. pilosa var. minor에서 증가경향이 컸다. 토양 무기영양소 구배에서는 B. pilosa와 B. tripartita는 토양무기영양소 증가에 따라 RGR이 작아지는 경향을 나타냈다. Shoot/root ratio는 환경요인별로 종별 변동이 크지 않으나, 자생종인 B. tripartita는 Shoot/root ratio에서 각 환경요인 별로 감소 경향이 뚜렷하다. 종별 성장특성의 비교결과 B. pilosa var. minor와 B. tripartita는 양분이 척박한 입지에서 생육이 왕성한 특징을 보이며, B. frondosa는 양분이 풍부한 입지에서 생육이 왕성한 종으로 분석된다. B. tripartita는 광에 대한 형태적 적응이 크고 수분을 좋아하는 특성이 있으며, B. bipinnata는 잎에 대한 형태적 형질은 크게 변화시키지 않으나 광이 풍부한 입지를 선호한다. Niche breadth는 B. bipinnata가 광도와 토양함수량 구배에서 0.875, 0.845로 가장 넓으며, 토양 무기영양소 에서는 B. pilosa var. minor가 0.933으로 넓게 나타났다. B. tripartita는 세 가지 환경요인에서 Niche breadth가 모두 좁았고, B. frondosa는 광도와 토양 무기영양소에서 넓고 토양함수량에서는 가장 좁은 값을 나타냈다.

• Wind and Structures
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• 제22권2호
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• pp.185-209
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• 2016

Across-wind aerodynamic damping ratios are identified from the wind-induced acceleration responses of 15 aeroelastic models of rectangular super-high-rise buildings in various simulated wind conditions by using the random decrement technique. The influences of amplitude-dependent structural damping ratio and natural frequency on the estimation of the aerodynamic damping ratio are discussed and the identifying method for aerodynamic damping is improved at first. Based on these works, effects of turbulence intensity $I_u$, aspect ratio H/B, and side ratio B/D on the across-wind aerodynamic damping ratio are investigated. The results indicate that turbulence intensity and side ratio are the most important factors that affect across-wind aerodynamic damping ratio, whereas aspect ratio indirectly affects the aerodynamic damping ratio by changing the response amplitude. Furthermore, empirical aerodynamic damping functions are proposed to estimate aerodynamic damping ratios at low and high reduced speeds for rectangular super-high-rise buildings with an aspect ratio in the range of 5 to 10, a side ratio of 1/3 to 3, and turbulence intensity varying from 1.7% to 25%.

• International Journal of Concrete Structures and Materials
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• 제7권4호
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• pp.287-293
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• 2013

Strength and some durability properties of concrete containing rice husk ash (RHA) predominantly composed of amorphous silica at a specific surface of 235 $m^2/kg$ produced using a charcoal incinerator were determined. The maximum ordinary Portland cement (OPC) replacement with the RHA increased with increase in water/binder (w/b) ratio of the concrete mixes. The results show that 15 % OPC could be substituted by the RHAwithout strength loss at w/b ratio of 0.50. The split tensile strength generally increased with increase in RHA content for the mixes.

• 한국식품영양과학회지
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• 제3권1호
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• pp.43-46
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• 1974

It was reported that the digestion ratio of chlorella was low because it had a low metabolic rate in body. Generally, the thickness of a cell membrane of it is $200-250\;{\AA}$, the weight of it is approximatly 13% of the total weight of a dry cell. And it is composed of protein, lipid, hemicellulose and ash etc. So, in order to elevate the digestion ratio of chlorella in body, we experimented the crude treatment methods of chlorella. The results obtained in this experiment are summarized as follows : 1. The digestion ratios calculated from ordinary N- balance method were 83.05% for 10% chl. (b) plus diastase group ; 81.25% for 10% chl. (b) plus amylase group, and 79.23% for 10% chl. (b), 58.55% for 10% chl. (a). 2. Biological values from this method were 80.25% for 10% chl. (b) plus diastase group, and 60% for 10% for chlorella(a).

• Structural Engineering and Mechanics
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• 제74권6호
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• pp.747-756
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• 2020

High-strength concrete (HSC) generally is made with high amount of cement which may release large amount of hydration heat at early age. The hydration heat will increase the internal temperature of slab and may cause potential cracking. In this study, slab specimens with a dimension of 600 × 600 × 100 mm were cast with concrete incorporating silica fume for test. The thermistors were embedded in the slabs therein to investigate the interior temperature development. The test variables include water-to-binder ratio (0.25, 0.35, 0.40), the cement replacement ratio of silica fume (RSF; 5 %, 10 %, 15 %) and fly ash (RFA; 10 %, 20 %, 30 %). Test results show that reducing the W/B ratio of HSC will enhance the temperature of first heat peak by hydration. The increase of W/B decrease the appearance time of second heat peak, but increase the corresponding maximum temperature. Increase the RSF or decrease the RFA may decrease the appearance time of second heat peak and increase the maximum central temperature of slab. HSC slab with the range of W/B ratio of 0.25 to 0.40 may occur cracking within 4 hours after casting. Reducing W/B may lead to intensive cracking damage, such as more crack number, and larger crack width and length.