• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 봄 학술발표회 논문집
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• pp.138-145
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• 2001

This paper presents F.E.M. analysis result about the behavior of R.C. beam repaired with steel plate and fiber sheet. The effect of repairing varies with reinforcement ratio of R.C. beam, plate thickness, numbers of fiber sheet, and repairing length, etc. F.E.M. analysis using a program, DIANA, was carried out taking these factors as parameter in this study. Analysis result shows that repaired R.C. beam behaves differently according to parameters and certain cases imply that repairing is useless or may lay structure in dangerous condition. F.E.M. model considers that interfacial behavior between different two parts of repaired beam is rigid based on an assumption that adhesive failure does not appear before yielding of reinforcement and its analysis shows the result coincides with that of experiment.

• 상하수도학회지
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• 제13권4호
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• pp.27-34
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• 1999

An experimental study on improvement of the paper-mill wastewater treatment using the pure oxygen activated sludge process was conducted. The effects of hydraulic retention time(HRT) and BOD loading on organic removal efficiency were investigated. The BOD removal efficiencies were above 90% under all examined HRTs except for HRT of 3 hours. The increase of HRT from 3 hours to 6 hours, and to 12 hours significantly improved BOD and COD removal efficiencies, respectively. However, additional increase of HRT did not affect organic removal efficiency. F/M ratio change at fixed HRT did not affect organic removal efficiency. However, F/M ratio investigated in this study(0.11~1.98kgBOD/kgMLVSS/day) was 5 times greater in maximum than that of conventional activated sludge process, which implies that pure oxygen activated sludge process can treat wastewater with high organic strength. Under the same HRT, the volumetric BOD loading change cause no effect on organic removal efficiency also.

• 한국환경보건학회지
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• 제33권6호
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• pp.493-496
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• 2007

The influences of contact time and ratio of food to microorganism (F/M) on uptake of wastewater organic matter in a short contact process were investigated using three activated sludge batch reactors fed with synthetic wastewater, sewage and livestock wastewater. About 64% of influent soluble chemical oxygen demand (SCOD) in the synthetic wastewater and 61% of SCOD in the sewage and 43% of SCOD in the diluted livestock wastewater were adsorbed into the activated sludge within 30 min. The specific mass of organic matter uptaken in the synthetic wastewater was 55 mg SCOD/g mixed liquor suspended solids (MLSS). In the same manner, 20 and 14 mg SCOD/g MLSS were calculated as the values in the sewage and livestock wastewater, respectively.

• 한국수산과학회지
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• 제55권2호
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• pp.91-101
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• 2022

In this study, we analyzed the compositional characteristics of Melosira nummuloides mass-cultured using Jeju lava seawater. M. nummuloides showed the highest growth rate when cultured for 14 days at 17-20℃ and 15,000 lx. Proximate composition of raw-material (RM) and freeze-dried M. nummuloides (FM) showed high ash content (65-72%), while ethanol-extracted M. nummuloides (EM) had low ash and high lipid contents. The predominantly occurring mineral, Si, was 334 g/kg in RM and 269 g/kg in FM, but EM contained only 1.97 g/kg. The ratio of essential amino acids was similar in RM (38.93%) and FM (36.89%) lower in EM (17.83%), but branched chain amino acids required for muscle metabolism was high (63.40%). The polyunsaturated fatty acids of EM (34.74%) was 11% more than that in RM (23.81%), and the ratio of omega-6 to omega-3 fatty acids was 1:3.6. Furthermore, the concentration of total chlorophyll was higher by 5.15 times (62.32 mg/g) and that of fucoxanthin by 7.06 times (11.02 mg/g) in EM than in RM (12.11, 1.56 mg/g, respectively). The mass cultivation and filtration of M. nummuloides using lava seawater has high prospects of commercialization as a competitive bio silica, cosmetic and healthy functional food material.

• 한국대기환경학회지
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• 제2권3호
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• pp.27-33
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• 1986

Atmospheric particulate matter (A. P. M.) was collected and size-fractionated by an Andersen high-volume air sampler over 15 month period from Jan. 1985 to Feb. 1986 in Seoul. The concentration of chloride, nitrate and sulfate were extracted in an ultrasonic bath and were analyzed by ion chromatography. The annual arithmetical mean of A. P. M. was 128.54 $\mug/m^3$. The concentration of anions were 2.88 $\mug/m^3$ for chloride, 3.86$\mug/m^3$ for nitrate, and 25.44$\mug/m^3$ for sulfate. The content of A. P. M. was lowest in the particle size range 1.1 $\sim 3.3\mum$ and increased as the particle size increased or decreased. And the anions exhibited a seasonal variation in the isize distribution. The contents of anions were higher in winter than summer. Ther ratio of fine particles to the total particles defined by F/T for chloride, nitrate and sulfate. The F\ulcornerT of these anion generally decrease with increasing air temperature. This tendency was prevalent in the chloride and nitrate.

• 대한금속재료학회지
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• 제49권2호
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• pp.104-111
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• 2011

An ultrafine grained Mg-9Al-1Zn magnesium alloy with the mean grain size less than $1{\mu}m$ was produced by using high-ratio differential speed rolling. The processed alloy exhibited excellent superplasticity at relatively low temperatures. The micro-forming tests were carried out using a micro-forging apparatus with micro V-grooved shaped dies made of silicon and the micro-formability was evaluated by means of micro-formability index, $R_f$ ($=A_f/A_g$, $A_f$: formed and inflowed area into the V-groove, $A_g$: area of the V-groove). The $R_f$ value increased with temperature up to $280^{\circ}C$ and then decreased beyond $300^{\circ}C$. The decrease of the $R_f$ value at $300^{\circ}C$ was attributed to the accelerated grain coarsening. Increasing the micro-forging pressure increased the $R_f$ values. At a given die geometry, die filling ability decreased as the die position moved away from the die center to the end. FEM simulation predicted this behavior and a method of improving this problem was proposed.

• Earthquakes and Structures
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• 제22권6호
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• pp.597-608
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• 2022

One of the most important parameters affecting nonlinearsoil-structure interaction, especially rocking foundation, is the vertical factor of safety (F.S_v). In this research, the effect of F.S_v on the behavior of rocking foundations was experimentally investigated. A set of slow, cyclic, horizontal loading tests was conducted on elastic SDOF structures with different shallow foundations. Vertical bearing capacity tests also were conducted to determine the F.S_v more precisely. Furthermore, 10% silt was mixed with the dry sand at a 5% moisture content to reach the minimum apparent cohesion. The results of the vertical bearing capacity tests showed that the bearing capacity coefficients (N_c and N_γ) were influenced by the scaling effect. The results of horizontal cyclic loading tests showed that the trend of increase in capacity was substantially related to the source of nonlinearity and it varied by changing F.S_v. Stiffness degradation was found to occur in the final cycles of loading. The results indicated that the moment capacity and damping ratio of the system in models with lower F.S_v values depended on soil specifications such cohesiveness or non-cohesiveness and were not just a function of F.S_v.

• Journal of electromagnetic engineering and science
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• 제6권3호
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• pp.189-195
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• 2006

In this paper, the derivation of the protection ratio for the digital microwave system with diversity is newly suggested for a basic guidance of initial planning for frequency coordination, and computational results are presented for an actual radio frequency band. The net filter discrimination has been also examined to see the effect of the adjacent channel protection ratio caused by adjacent channel interference. In addition, the protection ratios for the space or frequency diversity system are analyzed in terms of diversity improvement factors to find out an equivalent allowable noise-to-interference ratio (N/I) from degraded fade margin. According to results for 6.2 GHz system, with the space diversity of 25 m distance between antennas or the frequency diversity of ${\Delta}f/f=0.05$, under 64-QAM and 60 km at BER $10^{-6}$, the protection ratio can be greatly reduced in comparison to the non-diversity system. So, assuming that only the same protection ratio as the non-diversity system is kept, it is shown that the system with diversity may get more interference level of N/I allowing from 9.0 to - 5.9 dB or from 6.0 to - 4.3 dB for the space or frequency diversity. In consequence, it is concluded that the diversity system is more robust or tolerable for interferences or fades, which may play an important role in overcoming N/I to some extent.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권4호
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• pp.199-203
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• 2006

This paper presents an ASER (Accelerated Soft Error Rate) integral model. The model is based on the facts that the generated EHP/s(electron hole pairs) are diminished after some residual range of the incident alpha particle, where residual range is a function of the incident angle and the capping layer thickness over the semiconductor junction. The ASER is influenced by the flux of the alpha particles, the junction area ratio, the alpha particle incident angle when the critical charge is same as the collected charge, and the sizes of the alpha source and the chip. The model was examined with 8M static RAM samples. The measured ASER data showed good agreement with the calculated values using the model. The ASER decreased exponentially with respect to the operational voltage. As the capping layer thickness increases up to $16{\mu}m$, the ASER increases, and after that thickness, the ASER decreases. The ASER increased as the depth of BNW increased from $0{\mu}m\;to\;4{\mu}m$. and then saturated. The ASER decreased as the node capacitance increased from 2fF to 5fF.

• Journal of Nutrition and Health
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• 제35권2호
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• pp.229-236
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• 2002

Cataracts are the leading cause of blindness worldwide and are characterized by increased opacity of the lens that significantly diminishes visual acuity. It has been suggested that increased risk of lens opacities are associated with age, exposure to sunlight, diabetes, smoking, and poor nutrition. Antioxidant nutrients have born demonstrated to protect the lens membrane and protein against damage due to oxidative stress. The purpose of this study was to investigate the antioxidant system in the blood of cataract patients. The status of the blood antioxidant system was evaluated based on the levels of antioxidant vitamins and minerals as well as glutathione peroxidase (GSH-Px) and malondialdehyde (M7A) activity in 34 patients with cataracts (17 male and 17 female) and 45 control subjects (20 male and 25 female). After adjusting for age, the results showed significantly lower levels of antioxidant vitamins such as lycopene (M : p < 0.05, F: p < 0.01), zeaxanthin (F: p < 0.01), ${\gamma}$-tocopherol (F: p < 0.01) and ascorbic arid (M: p < 0.05) in the cataract patients than in the control subjects. In contrast, the concentration of cryptoxanthin (F : p < 0.07) showed a significantly higher value in the cataract patients. The serum level of the antioxidant mineral Zn (M : p < 0.01) was found to be significantly lower in the cataract patients while the ratio of cu/zn appeared significantly higher (M : p < 0.05). Significantly higher (M : p < 0.01, F: p < 0.05) concentrations of MDA in serum was found in the cataract patients as compared to the control subjects. GSH-Px activity was significantly lower (F: p < 0.05) in 71e cataract patients. In conclusion, the antioxidant system may play an important roll in cataract creation. Further studies are needed to clarify the mechanisms underlying these findings and to establish preventive measures with an emphasis on antioxidant nutrition for cataract patients.