• Wind and Structures
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• v.30 no.4
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• pp.367-378
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• 2020

Two-dimensional Delayed Detached Eddy Simulation (DDES) was carried out to investigate the uniform flow over a twin-box bridge deck (TBBD) with various gap ratios of L/C=5.1%, 12.8%, 25.6%, 38.5%, 73.3% and 108.2% (L: the gap-width between two girders, C: the chord length of a single girder) at Reynolds number, Re=4×104. The aerodynamic coefficients of the prototype deck with gap ratio of 73.3% obtained from the present simulation were compared with the previous experimental and numerical data for different attack angles to validate the present numerical method. Particular attention is devoted to the fluctuating pressure distribution and forces, shear layer reattachment position, wake velocity and flow pattern in order to understand the effects of gap ratio on dynamic flow interaction with the twin-box bridge deck. The flow structure is sensitive to the gap, thus a change in L/C thus leads to single-side shedding regime at L/C≤25.6%, and co-shedding regime at L/C≥35.8% distinguished by drastic changes in flow structure and vortex shedding. The gap-ratio-dependent Strouhal number gradually increases from 0.12 to 0.27, though the domain frequencies of vortices shedding from two girders are identical. The mean and fluctuating pressure distributions is significantly influenced by the flow pattern, and thus the fluctuating lift force on two girders increases or decreases with increasing of L/C in the single-side shedding and co-shedding regime, respectively. In addition, the flow mechanisms for the variation in aerodynamic performance with respect to gap ratios are discussed in detail.

• Journal of the Korean Chemical Society
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• v.9 no.1
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• pp.49-54
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• 1965

One of the difficult and time consuming problems in the production of magnesia from sea water is a settling rate of magnesium hydroxide. In this experiments, authors attempted to accelerate its settling rate by addition of various sedimenting agents as C.M.C., Separan and Starch, and sought for optimum calcination temperature for domestic dolomite, as alkali source, mole ratio of dolomite milk to bittern. It is observed through experiments that the small amounts of sedimenting agents, C.M.C., Separan, starch, 20 mg/l, 40 mg/l, 400mg/l, respectively increase the settling rate of magnesium hydroxide by 8 times or more. The following conditions resulted in good yield of magnesium hydroxide from sea water with relatively tolerable calcium oxide contaminated for the magnesium clinker. Calcinating temperature, $1,100{\sim}1,200^{\circ}C$, mole ratio of 10% dolomite milk to magnesium salts in sea water or bittern, 1. 2 : 1.

• Environmental Engineering Research
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• v.20 no.3
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• pp.246-253
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• 2015

The effects of carbon-to-nitrogen (C/N) ratio in simulated rice straw hydrolysates using glucose and ammonium chloride on polyhydroxyalkanoates (PHA) accumulation by Cupriavidus necator was investigated. In general, PHA accumulation rate was higher under higher degrees of N-deficient conditions (e.g., C/N ratio of 360:1) than lower degrees of N-deficient conditions (e.g., C/N ratio of 3.6:1 and 36:1). Also, the most PHA accumulation was observed during the first 12 h after the PHA accumulation initiation. This study showed that the similar PHA accumulation could be achieved by using different accumulation periods depending on C/N ratios. N source presence was important for new cell production, supported by approximately ten times greater PHA accumulation under the N-deficient condition ($NH_4Cl$ 0.01 g/L) than the N-free (without $NH_4Cl$) condition after 96 h. C/N ratio of the rice straw hydrolysate was approximately 160:1, based on the glucose content, and this accumulated $0.36{\pm}0.0033g/L$ PHA with PHA content of $21{\pm}3.1%$ after 12 h. Since external C or N source addition for C/N ratio adjustment increases production cost, an appropriate accumulation period may be used for PHA accumulation from organic wastes, based on the PHA accumulation patterns observed at various C/N ratios and C and N concentrations.

• Steel and Composite Structures
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• v.21 no.2
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• pp.323-342
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• 2016

To study the effect of collar-plate reinforcement on the static strength of tubular T-joints under axial loading, fundamental research work is carried out from both experimental test and finite element (FE) simulation. Through experimental tests on 7 collar-plate reinforced and 7 corresponding un-reinforced tubular T-joints under axial loading, the reinforcing efficiency is investigated. Thereafter, the static strengths of the above 14 models are analyzed by using FE method, and it is found that the numerical results agree reasonably well with the experimental data to prove the accuracy of the presented FE model. Additionally, a parametric study is conducted to analyze the effect of some geometrical parameters, i.e., the brace-to-chord diameter ratio ${\beta}$, the chord diameter-to-chord wall thickness ratio $2{\gamma}$, collar-plate thickness to chord wall thickness ratio ${\tau}_c$, and collar-plate length to brace diameter ratio $l_c/d_1$, on the static strength of a tubular T-joint. The parametric study shows that the static strength can be greatly improved by increasing the collar-plate thickness to chord wall thickness ratio ${\tau}_c$ and the collar-plate length to brace diameter ratio $l_c/d_1$. Based on the numerical results, parametric equations are obtained from curving fitting technique to estimate the static strength of a tubular T-joint with collar-plate reinforcement under axial loading, and the accuracy of these equations is also evaluated from error analysis.

• Food Science and Preservation
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• v.15 no.1
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• pp.66-73
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• 2008

Response surface methodology (RSM) was applied for monitor the yields of desirable substances from fig (Ficus carica L) under different extraction conditions. The maximum yield was 66.46% at 22.08 mL/g of solvent to sample ratio, $90.59^{\circ}C$ extraction temperature and 148.04 min extraction time. The maximum total phenolics was $121.31{\mu}g/mL$ at 17.87 mL/g, $98.82^{\circ}C$, and 130.80 min. The maximum electron donating ability was 54.09% at $121.31{\mu}g/mL$, 18.13 mL/g, and $98.81^{\circ}C$. The maximum value of protease activity was 54.51 unit/min at 17.45 mL/g, $99.01^{\circ}C$, and 131.43 min. In addition, the maximum value of reducing sugar content was 19.14 mg/mL in 22.66 mL/g, $86.30^{\circ}C$, and 153.59 min. The optimum conditions estimated by RSM for maximal extraction of the effective components were $17{\sim}25$ mL/g of solvent to sample ratio, $80{\sim}100^{\circ}C$ of extraction temperature, and $100{\sim}170$ min of extraction time.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.4
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• pp.197-204
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• 2003

Honeycomb structure has been fabricated by brazing method using 0.1 wt%C and 1.0wt%C carbon steel core and STS304 stainless steel face sheet. Core shear strength ratio in W and L directions was 1:1.03 in 7 mm cell size, whereas 1:1.45 in 4 mm cell size. Flexural strength on face sheet was 166.4 MPa (0.1 wt%C, W direction), 171.1 MPa (0.1 wt%C, L direction), and 120.2 MPa (1.0 wt%C, W direction) in 7 mm cell size. And in 4mm cell size specimen, it was 169.2 MPa (0.1 wt%C, W direction), 224.2 MPa (0.1 wt%C, L direction). This means that flexural strength of 0.1 wt%C core material was higher than that of 1.0wt%C core material, which was contrary to expectation. SEM and EDS analysis represented that grain boundary diffusion had occurred in0.1 wt%C core, but no grain boundary diffusion in 1.0 wt%C core. And corrugated surface of 0.1 wt%C core was flat, whereas that of 1.0 wt%C core was not flat. As a result, contact area between two 1.0 wt%C cores was much less than that of 0.1 wt% cores, It is thought to be main reason for lower flexural strength of 1.0 wt%C core.

• KSBB Journal
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• v.19 no.1
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• pp.78-82
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• 2004

Experiments were carried out to select an organic nitrogen source and optimize the culture conditions for the production of arachidonic acid by Mortierella alpina DSA-12. Corn steep powder(CSP) was selected as an organic nitrogen source based on arachidonic acid production and raw material price. The optimum C/N ratio was in the range of 15 to 17 with the medium containing glucose as carbon source and CSP as nitrogen source. The optimum culture conditions for arachidonic acid production showed 500 rpm agitation and 25$^{\circ}C$ culture temperature at 0.5 vvm aeration. Under the optimum conditions, the concentration of cell, total lipid and arachidonic acid were 21.8 g/L, 10.2 g/L and 3.70 g/L, respectively, from 50 g/L glucose and 18 g/L CSP. In the 500 L fermenter with 0.5 vvm aeration and 200 rpm agitation, the concentration of cell, total lipid and arachidonic acid were 19.8 g/L, 9.1 g/L and 3.67 g/L, respectively, from 50 g/L glucose and 18 g/L CSP. This result showed that an arachidonic acid production could be possible with a bench-scale fermenter using corn steep powder as a nitrogen source.

• Korean Journal of Remote Sensing
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• v.23 no.2
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• pp.89-101
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• 2007

This paper investigates the effects of the fusion of multifrequency (C and L bands) polarimetric SAR data in land-cover classification. NASA JPL AIRSAR C and L bands data were used to supervised classification in an agricultural area to simulate the integration of ALOS PALSAR and Radarsat-2 SAR data to be available. Several scattering features derived from target decomposition based on eigen value/vector analysis were used as input for a support vector machines classifier and then the posteriori probabilities for each frequency SAR data were integrated by applying a probabilistic ratio model as a decision level fusion methodology. From the case study results, L band data had the proper amount of penetration power and showed better classification accuracy improvement (about 22%) over C band data which did not have enough penetration. When all frequency data were fused for the classification, a significant improvement of about 10% in overall classification accuracy was achieved thanks to an increase of discrimination capability for each class, compared with the case of L band Shh data.

• Journal of Environmental Science International
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• v.25 no.11
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• pp.1493-1498
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• 2016

The efficiencies of Gang-Byeon sewage treatment facilities, which are based on GPS-X modelling, were analysed and used to design recycle water treatment processes. The effluent of an aeration tank contained total kjeldahl nitrogen (TKN) of 1.8 mg/L with both C-1 and C-2 conditions, confirming that most ammonia nitrogen ($NH_3{^+}-N$) was converted to nitrate nitrogen ($NO_3{^-}-N$). The concentrations of $NH_3{^+}-N$ and $NO_3{^-}-N$ were found to be 222.5 and 227.2 mg/L, respectively, with C-1 conditions and 212.2 and 80.4 mg/L with C-2 conditions. Although C-2 conditions with higher organic matter yielded a slightly higher nitrogen removal efficiency, sufficient denitrification was not observed to meet the discharge standards. For the total nitrogen (T-N) removal efficiency, the final effluent concentrations of T-N were 293.8 mg/L with biochemical oxygen demand (BOD) of 2,500 mg/L, being about 1.5 times lower than that (445.3 mg/L) with BOD of 2,000 mg/L. Therefore, an external carbon source to increase the C/N ratio was required to get sufficient denitrification. During the winter period with temperature less than $10^{\circ}C$, the denitrification efficiency was dropped rapidly even with a high TKN concentration (1,500 mg/L). This indicates that unit reactors (anoxic/aerobic tanks) for winter need to be installed to increase the hydraulic retention time. Thus, to enhance nitrification and denitrification efficiencies, flexible operations with seasons are recommended for nitrification/anoxic/denitrification tanks.

• Asian-Australasian Journal of Animal Sciences
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• v.21 no.1
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• pp.90-96
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• 2008

We compared the effects of supplementing $L-lysine{\cdot}SO_4$ to L-lysine HCl on growth performance, nutrient digestibility and nitrogen retention in weaning pigs. A total of 96 crossbred pigs, weaned at $21{\pm}3$ days of age and with an average initial body weight (BW) $6.23{\pm}0.01kg$, were given one of 4 treatments, which translated into 6 replicates of 4 pigs in each pen. The animals were randomly assigned to four dietary treatments according to a randomized completely block design (RCBD) as follows: 1) control-no synthetic lysine, lysine deficient (0.80% total lysine); 2) L-C (= 0.2% L-lysine HCl); 3) K-L-S (= 0.332% $L-lysine{\cdot}SO_4$, A company); 4) C-L-S (= 0.332% $L-lysine{\cdot}SO_4$, B company). Diets were formulated with corn, soy bean meal, and corn gluten meal as the major ingredients, and all nutrients except the lysine met or exceeded NRC requirements (1998). The lysine content of supplemented synthetic lysine was the same in all treatment groups except the control. No clinical health problems associated with the dietary treatments were observed. During the entire experimental period, body weight, average daily gain (ADG) and feed efficiency (G:F ratio) increased (p<0.01) in pigs fed the experimental diets supplemented with L-lysine??HCl or $L-lysine{\cdot}SO_4$ produced by A company, irrespective of the two synthetic lysine sources. Although the supplementation of $L-lysine{\cdot}SO_4$ produced by B company tended to improve the ADG and G:F ratio, significant differences were not seen among all treatments and tended to be lower than the L-C (L-lysine HCl) and K-L-S ($L-lysine{\cdot}SO_4$ groups using the product from A company). The digestibility of crude protein (CP) was increased by the supplementation of synthetic lysine (p<0.05), irrespective of the L-lysine source (L-C, K-L-S, C-L-S). The results of this study showed that ADG, G:F ratio, and CP digestibility improved when $L-lysine{\cdot}SO_4$ or L-lysine HCl was supplemented into the weaning pigs' diet. There was a clear difference in efficacy between the two $lysine{\cdot}SO_4$ products based upon the growth performance of weaning pigs. Consequently, the bioavailability of $lysine{\cdot}SO_4$ products should be evaluated before supplementation of synthetic lysine in swine diets.