• 한국공작기계학회논문집
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• 제16권1호
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• pp.75-79
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• 2007

The cathode design is one of the most important parts in order to enhance the performance of fuel cells. A 3-D model of the porous oxygen reducing cathode with perforated current collectors is analysed for the enhanced design in fuel cells. Simulation is performed using equations of electric potential balance, momentum balance, and mass balance. The gas concentrations are quite large and are significantly affected by the reactions that take place. The weight fraction of oxygen, velocity field for the gas phase, and local overvoltage are illustrated in the porous reactive cathode layer. The current density is also analysed and the result shows the distribution and variation are stated in a wide range. It is found that the rate of reaction and the current production is higher beneath the orifice, and decreases as the distance to the gas inlet increases. The significance of the results is discussed in the viewpoint of the mass transportation phenomena, which is inferred that the mass transport of reactants dictates the efficiency of the electrode in this design and at these conditions.

• 한국식품영양학회지
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• 제18권2호
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• pp.127-134
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• 2005

This study was conducted to investigate the correlations among body composition, athletic ability and nutritional status according to BMI in Korean college students. The anthropometric measurements of three groups showed significant differences in weight, body fat, waist, hip, WHR, skinfold thickness(p<0.001). There were significant difference in vitamin A and niacin by their BMI(p<0.05). There were significant increase in trunk flexion(p<0.05) and maximal oxygen uptake(p<0.05) in subjects as their BMI. There were negative correlation between weight and foot balance, maximal oxygen uptake. Also, foot balance and maximal oxygen uptake were negatively related with BMI. There was a significant positive correlation between BMI and flexion(p<0.50). Grip strenth(p<0.01) and back strenth(p<0.05) were positively related with WHR. Overweight group was significantly inferior in muscular power and endurance but was better in muscular strength than the other groups. Based on this study, the further studies on obesity indice are required for health promotion among young women population.

• Journal of Microbiology and Biotechnology
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• 제11권6호
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• pp.1055-1060
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• 2001

Experimental data for the on-line estimation of cell concentration and growth rate are presented. For this purpose, we utilized the on-line calculation of the oxygen uptake rate (OUR), which was derived from a liquid phase dynamic mass balance for the oxygen during the active growth phase in cyclosporin A (CyA) fermentation. The cell yield coefficient, based on the oxygen $(Y_{x/o})$for both suspended and immobilized cells of Tolypocladium inflatum, was estimated as $1.9 gDCW/gO_2$ from a very good linear correlation between the cell mass produced and the total oxygen consumed. The calculated yield showed a good agreement with the value of $(Y_{x/o})$ generated from the correlation between the cell growth rate and the oxygen uptake rate. In addition, further experimental data are given, which were also applied to determine the specific oxygen uptake rate of T. inflatum cells during the exponential phase of CyA fermentation. A theoretical basis for the analysis of these fermentation parameters is also provided.

• 한국수소및신에너지학회논문집
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• 제32권5호
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• pp.374-387
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• 2021

Basic design of 3 MWth chemical looping combustion system for LNG combustion and steam generation was conducted based on the mass and energy balance and the previous reactivity test results of oxygen carrier particles. Process configuration including fast fluidized bed (air reactor), loop seal and bubbling fluidized bed (fuel reactor) was confirmed and their dimensions were determined by mass balance. Then, the external fluidized bed heat exchanger (FBHE) was adopted based on the energy balance to extract heat from the system. The optimum reactor design and operating condition was confirmed with sensitivity analysis by modifying system configuration based on the mass and energy balance.

• Toxicological Research
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• 제24권2호
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• pp.101-107
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• 2008

Studies on hypoxia-signaling pathways have revealed novel Fe(II) and $\alpha$-ketoglutarate-dependent dioxygenases that hydroxylate prolyl or asparaginyl residues of a transactivator, Hypoxia-Inducible $Factor-\alpha(HIF-\alpha)$ protein. The recognition of these unprecedented dioxygenases has led to open a new paradigm that the hydroxylation mediates an instant post-translational modification of a protein in response to the changes in cellular concentrations of oxygen, reducing agents, or $\alpha$-ketoglutarate. Activity of $HIF-\alpha$ is repressed by two hydroxylases. One is $HIF-\alpha$ specific prolyl-hydroxylases, referred as prolyl-hydroxylase domain(PHD). The other is $HIF-\alpha$ specific asparaginyl-hydroxylase, referred as factor-inhibiting HIF-1(FIH-1). The facts (i) that many dioxygenases commonly use molecular oxygen and reducing agents during detoxification of xenobiotics, (ii) that detoxification reaction produces radicals and reactive oxygen species, and (iii) that activities of both PHD and FIH-1 are regulated by the changes in the balance between oxygen species and reducing agents, imply the possibility that the activity of $HIF-\alpha$ can be increased during detoxification process. The importance of $HIF-\alpha$ in cancer and ischemic diseases has been emphasized since its target genes mediate various hypoxic responses including angiogenesis, erythropoiesis, glycolysis, pH balance, metastasis, invasion and cell survival. Therefore, activators of PHDs and FIH-1 can be potential anticancer drugs which could reduce the activity of HIF, whereas inhibitors, for preventing ischemic diseases. This review highlights these novel dioxygenases, PHDs and FIH-1 as specific target against not only cancers but also ischemic diseases.

• 한국수산과학회지
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• 제24권1호
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• pp.21-30
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• 1991

충무시 북서쪽에 위치한 폐쇄성 내만으로 만 외측에는 굴 양식을 하고 있는 북만의 부영양화현상을 구명하고 수질이 최악에 달하는 하계에 일정수준 이상의 용존산소를 유지하기 위한 적정오염부하량 산정을 위해 1988년 1월부터 동년 12월까지 평균 월 4회 조사한 결과를 요약하면 다음과 같다. 전 조사 지점에서 총무기질소는 $0.10{\~}127.41$(평균: 10.71)$\{mu}g-at/l$, 인산 인은 ND-4.29(평균: 0.40) ${\mu}g-at/l$, Chlorophyll-a는 $0.35{\~}132.75$(평균; 11.90) $mg/m^3$이었고, 여름철 동안 평균농도는 각각 $11.06{\mu}g-at/l,\;0.80\mu g/l,\;11.11mg/m^3$로 이미 부영양상태에 있었다. 용존산소는 전 조사지점에서 $0.00{\~}13.42$(평균:6.45)ml/l 였고, 장마가 끝나고 일정한 기간이 경과한 시점인 7월에 전 지점의 저층에서 평균 2.08ml/l의 저산소수괴가 형성되었으며, 8월이후 증감을 되풀이하면서 점차 회복되는 경향을 보였다. 하계에 북만의 시간에 따른 용존산소 변화곡선은 $DO(ml/l)=15.57-1.40{\times}(day)+0.03{\times}(day)^2+0.0001{\times}(day)^3+......$와 같이 나타낼 수 있었고, 이와 같은 산소변화 특성으로부터 구한 산소소비계수 및 공급계수의 고유치는 각각 0.222/day, 0.018ml/l/day로 북만의 용존산소 수지 특성으로 볼 때 하계에 무산소 또는 저산소 상태를 막고 4ml/l이상의 용존산소를 유지하기 위해서는 이 일대의 해역에 수로의 변경이나 산소 공급장치를 이용 0.856ml/l/day 만큼의 산소를 공급하든지 또는 이 량에 해당되는 유입 BOD 부하를 폐수처리장 건설 등을 통하여 감소시켜야 할 것으로 생각된다.

• 한국주조공학회지
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• 제15권5호
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• pp.477-482
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• 1995

A computer simulation model of various smelting process for melting waste sand was developed by using energy and material balance concept. This model can predict the coal, flux and oxygen consumption and the volume and temperature of off-gas. The major critical variables for smelting process can be explained by using the analysis of energy and material balance. The major conclusions were as follows; 1. The most important variables for smelting process were high post-combustion ratio, high heat transfer efficiency and refractory protection technology. 2. For saving energy in this smelting process, selection of raw materials i.e coal, flux are very important, espacially using of low volatile coal is very profitable. 3. The treatment cost of waste sand is high and environmental restriction is severe, in this reason we must be concerned in the treatment of waste sand by smelting process.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.1996-2000
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• 2008

In autothermal reforming reaction, oxygen to carbon ratio (OCR) and steam to carbon ratio (SCR) are significant factors, which control temperature and carbon deposition into the reactor. The OCR is more sensitive than the SCR to affect the temperature distribution and reforming efficiency. In conventional operation, hydrocarbon fuel, steam, and oxygen was homogeneously mixed and injected into the reactor in order to get hydrogen-rich gas. The temperature was abruptly raised due to fast oxidation reaction in the former part of the reactor. Deactivation of packed catalysts can be accelerated there. In the present study, therefore, the effect of the oxygen distribution is introduced and investigated to suppress the carbon deposition and to maintain the reactor in the mild operating temperature (e.g., $700{\sim}800^{\circ}C$). In order to investigate the effect numerically, the following models are adopted; heterogeneous reaction model and two-medium model for heat balance.

• 한국표면공학회지
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• 제51권5호
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• pp.332-336
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• 2018

Alkaline oxygen electrocatalysis, targeting anion exchange membrane alkaline-based metal-air batteries has become a subject of intensive investigation because of its advantages compared to its acidic counterparts in reaction kinetics and materials stability. However, significant breakthroughs in the design and synthesis of efficient oxygen reduction catalysts from earth-abundant elements instead of precious metals in alkaline media still remain in high demand. One of the most inexpensive alternatives is carbonaceous materials, which have attracted extensive attention either as catalyst supports or as metal-free cathode catalysts for oxygen reduction. Also, carbon composite materials have been recognized as the most promising because of their reasonable balance between catalytic activity, durability, and cost. In particular, heteroatom (e.g., N, B, S or P) doping on carbon materials can tune the electronic and geometric properties of carbon, providing more active sites and enhancing the interaction between carbon structure and active sites. Here, we focused on boron and nitrogen doped nanocarbon composit (BNC nanocarbon) catalysts synthesized by a solution plasma process using the simple precursor of pyridine and boric acid without further annealing process. Additionally, guidance for rational design and synthesis of alkaline ORR catalysts with improved activity is also presented.

• 한국물환경학회지
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• 제26권5호
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• pp.732-739
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• 2010

Two combined autothermal thermophilic aerobic digestion (ATAD) and biofilter (BF) systems were operated to treat the piggery wastewater and the ammonia offgas. Experimental results indicated that the organic removal efficiency of ATAD-2, operated with oxygen, was higher than that of ATAD-1, operated with air. The concentration of ammonia in ATAD-2 offgas was higher compared to ATAD-1 offgas, but the total amount of ammonia produced from ATAD-2 was less than that from ATAD-1 due to the lower oxygen flowrate. The ammonia gas produced from both ATAD reactors was successfully removed by the BF. The BF-1, connected with ATAD-1, removed 93% of ammonia at the loading rate of $9.4g\;NH_3-N/m^3/hr$. The BF-2, connected with ATAD-2, removed 95% of ammonia gas at the loading rate of $8.1g\;NH_3-N/m^3/hr$. As the nitrification process continued, pH value of recirculating solution continuously decreased due to the accumulation of nitrate. When the ammonia loading rate was less than $22.7g\;NH_3-N/m^3/h$, the proper replacing cycle of recirculating solution was in the range of 10 to 11 days. Almost 90% of total mass of nitrogen fed into the each BF was confirmed from the mass balance on nitrogen.