• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.4
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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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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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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• v.27 no.10
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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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• v.7 no.2
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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%.

• Journal of the Korean Institute of Landscape Architecture
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• v.33 no.3 s.110
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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.

• Korean Journal of Environmental Biology
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• v.22 no.1
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• pp.101-110
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• 2004

The growth and niche breath of four species, i.e., native plants such as Bidens tripauita and B. bipinnata and naturalized plants such as B. frondosa and B. pilosa var. minor, were studied as related with environmental gradients including light intensity, soil moisture and soil nutrient. There were no significant differences in the phonology within each environmental gradients while considerable differences were found between species; the two naturalized species bloomed and produced fruit later than the two native species. Two naturalized species exhibited relatively higher total dry weight than the two native counterparts within all environmental gradients. Total dry weight showed positive responses to light intensity and soil moisture, and negatively to soil nutrient. The relative contribution of the environmental factors to total dry weight decreased in the order of soil nutrient, soil moisture and light intensity. Both B. bipinnata and B. pilosa var. minor showed significantly higher net assimilation rate (NAR) than other species. Also, NARs of B. bipinnata and B. pilosa var. minor decreased with increasing soil nutrient. Relative growth rate (RGR) decreased in order of B. tripartita, B. bipinnata, B. frondosa and B. pilosa var. minor in response to light intensity. In addition, RGRs of B. bipinnata and B. piEosa yay. minor increased in response to soil moisture, while those of B. pilosa var. minor and B. tripartita decreased with increment of soil nutrient. No significant fluctuations of shoot/root ratio were not observed in three species, but a native species, B. tripartita showed n decreased shoot/root ratio in response to soil nutrient. Comparing the growth characteristics of the species, B. pitosa var. minor and 3. tripartita revealed vigorous growth on barren soil. On the other hand, B. frondosa exhibited vigorous growth on fertile soil. Morphologically, B. tripartita adapted to light and required considerable moisture. On the contrary, the leaves of B. bipinnata did not change considerably in their area, although it preferred habitat with abundant light. In terms of niche breadth, B. bipinnata showed the widest ranges of 0.875 and 0.845 for light intensity and soil moisture gradients, respectively. B. pilosa var. minor showed a value of 0.933 for soil nutrient gradient. B. tripartita showed narrow ranges for the three environmental factors, whereas B. frondosa showed wide values for light intensity and soil nutrient, but relatively narrow value for soil moisture.

• Wind and Structures
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• v.22 no.2
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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%.

• Journal of the Korean Society of Food Science and Nutrition
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• v.3 no.1
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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).

• International Journal of Concrete Structures and Materials
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• v.7 no.4
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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.

• Structural Engineering and Mechanics
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• v.74 no.6
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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.