• 환경위생공학
• /
• 제14권4호
• /
• pp.77-84
• /
• 1999

Most river quality problems are generated by pollutants which are discharged into the river as a consequence of human activities. And eutrophication occurs when water is over enriched with nutrients, principally nitrate and phosphate. Both these nutrients are found in many waste products, especially sewage even when the waste is treated. Eutrophication is concerned in lakes, but it also causes problems in river. Wide growth of Phytoplankton in rivers, leads to blockage of channels, but the main concern is deoxygenation because of the increase in plant life's demand for oxygen in revers. Fish, plant and animals die due to lack of oxygen. The increase of algae floating on the tops of water looks ugly and has attracted public attention and concern in recent years. One way of controlling eutrophication is to restrict the amount of waste carrying nitrate or phosphate from entering the water in the first place. another way is to remove it from the water after it has been entered. This study was carried out to investigate on the trophic state, nutrients and Chlorophyll-a concentration in the Han River. The results were as follows:1. Concentrations of total nitrogen were 2.208~9.221(5.133)mg/$\ell$2. Concentrations of total phosphate were 0.045~0.614(0.195)mg/$\ell$3. Chlorophyll-a concentration were $0.0-25.3(9.6)mg/m^3$.4. The correlation coefficient between T-P and Chlorophyll-a concentration was r=-0.856 at Sungsan sampling site.5. The correlation coefficient was r=-0.578~-0.767, between Paldang Dam outflow and Chlorophyll-a concentration at all sampling sites.

• Environmental Engineering Research
• /
• 제23권1호
• /
• pp.99-106
• /
• 2018

Lack of information on the Biochemical Oxygen Demand (BOD) decay rates of river water under the tropical environment has triggered this study with an aim to fill the gap. Raw sewage, treated sewage, river water and tap water were mixed in different proportions to represent river water receiving varying amounts and types of wastewater and fed in a laboratory flume in batch mode. Water samples were recirculated in the flume for 30 h and BOD and Carbonaceous BOD (CBOD) concentrations were measured at least six times. Decay rates were obtained by fitting the measured data in the first order kinetic equation. After conducting 12 experiments, the range of BOD and CBOD decay rates were found to be 0.191 to 0.92 per day and 0.107 to 0.875 per day, respectively. Median decay rates were 0.344 and 0.258 per day for BOD and CBOD, respectively, which are slightly higher than the reported values in literatures. A relationship between CBOD decay rate and BOD decay rate is proposed as $k_{CBOD}=0.8642_{k_{BOD}}-0.0349$ where, $k_{CBOD}$ is CBOD decay rate and $k_{BOD}$ is BOD decay rate. The equation can be useful to extrapolate either of the decay rates when any of the rates is unknown.

• 한국물환경학회지
• /
• 제28권5호
• /
• pp.717-722
• /
• 2012

Fluoride can be easily found in semiconductor and display industry. However, there is a lack of research for its effects on the related wastewater treatment. The objective of this study is to evaluate the microbial inhibitory effect by fluoride injection. The research entailed the assessment of removal efficiency of $TCOD_{Cr}$ according to the fluoride concentration and also the Specific Oxygen Uptake Rate (SOUR) was measured. The laboratory scale reactor was prepared and operated with the fluoride concentrations of 0, 10, 50, 100, and 200 mg/L based on concentrations frequently occurring in the wastewater. The results from this study showed that, as the fluoride concentration increase, the Specific Substrate Utilization Rate (SSUR) tend to decrease as expected. Also, the increase in fluoride concentrations resulted in the decrease in SOUR. It is determined that fluoride injection affects the microbial activity. Especially, The addition of above 200 mg/L fluoride into reactor caused rapidly decreased SSUR and SOUR due to the inhibitory effects of fluoride.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2006년도 춘계학술대회
• /
• pp.59-62
• /
• 2006

Formability is requested to successfully develop of a metal bipolar plate for mass production. From this point of view, wider channel and land width is more helpful to improve formability. But the performance of the fuel cell can be affected by its channel and land shape. So it is very important to select proper channel and land shape not to deteriorate the fuel cell performance. In this work, 3-dimensional, non-isothermal numerical simulation was performed to analyse the effects of channel and land width on the fuel cell performance. 3 types of straight channel were selected for the numerical simulation. The simulation results reveal that wide channel and land width lower fuel cell performance and decrease voltage at a high current density region. Water activity, temperature, oxygen concentration distributions were investigated to find the reasons of performance degradation. The results show that wide channel and land width give an bad effect on fuel cell performance because of low cool ins efficiency and lack of oxygen gas under the land.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
• /
• pp.97-100
• /
• 2011

액체로켓엔진의 점화는 그 시퀀스가 대단히 중요하며 시퀀스에 따라 엔진에 손상이 갈 수도 있다. 따라서 시동 시 hard start가 일어나지 않도록 많은 연구가 이루어지고 있다. 액체로켓의 점화 방법은 점화성 연료를 많이 사용하며 그 중 TEAL 역시 대기 중의 산소과 접촉하면 발화되는 자연발화 물질이다. TEAL을 사용하는 점화방법은 케로신-액체산소 엔진의 주요한 점화방식 중의 하나이나 아직까지 국내에서는 다단연소사이클 산화제 과잉 예연소기에 TEAL을 사용하여 점화 시험을 실시한 경험이 거의 없기 때문에 본격적인 시험에 앞서 이를 예측해 보고자 한다.

• 동의생리병리학회지
• /
• 제21권1호
• /
• pp.117-125
• /
• 2007

Neuronal ischemia is a pathological process caused by a lack of oxygen (anoxia) and glucose (hypoglycemia), resulting in neuronal death. It is believed that apoptosis is one of the mechanisms involved in ischemic cell death. Neuronal apoptosis is a process characterized by nuclear DNA fragmentation, changes of plasma membrane organization. To elucidate the mechanism of neuronal death following ischemic insult and to develop neuroprotective effects of Daebowonjeon(DBWJ) against ischemic damage, in vitro models are used. In vitro models of cell death have been devloped with pheochromocytoma (PC12) cell, which have become widely used as neuronal models of oxidative stress, trophic factor, serum deprivation and chemical hypoxia. Using a special ischemic device and PC12 cultures, we investigated an in vitro model of ischemia based on combined Oxygen and Glucose Deprivation (OGD) insult, followed by reoxygenation, mimicking the pathological conditions of ischemia. In this study, Daebowonjeon rescued PC12 cells from Oxygen-Glucose Deprivation (OGD)-induced cell death in a dose-dependent manner The nuclear staining of PC12 cells clearly showed that DBWJ attenuated nuclear condensation and fragmentation which represent typical neuronal apoptotic characteristics. DBWJ also prevents the LDH release and induction of Hypoxia Inducing Factor (HIF)-1 by OGD-exposed PC12 cells. Furthermore, DBWJ reduced the activation of polyADP-ribose polymerase (PARP) by OGO-exposed PC12 cells. These results suggest that apoptosis is an important characteristic of OGD-induced neuronal death and that oriental medicine, such as DBWJ, may prevent PC12 cell from OG D-induced neuronal death by inhibiting the apoptotic process.

• Journal of Microbiology and Biotechnology
• /
• 제25권11호
• /
• pp.1819-1826
• /
• 2015

Poly(ε-ʟ-lysine) (ε-PL) is a novel bioactive polymer secreted by filamentous bacteria. Owing to lack of a genetic system for most ε-PL-producing strains, very little research on enhancing ε-PL biosynthesis by genetic manipulation has been reported. In this study, an effective genetic system was established via intergeneric conjugal transfer for Streptomyces albulus PD-1, a famous ε-PL-producing strain. Using the established genetic system, the Vitreoscilla hemoglobin (VHb) gene was integrated into the chromosome of S. albulus PD-1 to alleviate oxygen limitation and to enhance the biosynthesis of ε-PL in submerged fermentation. Ultimately, the production of ε-PL increased from 22.7 g/l to 34.2 g/l after fed-batch culture in a 5 L bioreactor. Determination of the oxygen uptake rate, transcriptional level of ε-PL synthetase gene, and ATP level unveiled that the expression of VHb in S. albulus PD-1 enhanced ε-PL biosynthesis by improving respiration and ATP supply. To the best of our knowledge, this is the first report on enhancing ε-PL production by chromosomal integration of the VHb gene in an ε-PL-producing strain, and it will open a new avenue for ε-PL production.

• 한국재료학회지
• /
• 제22권4호
• /
• pp.202-206
• /
• 2012

$CoSi_2$ was formed through annealing of atomic layer deposition Co thin films. Co ALD was carried out using bis(N,N'-diisopropylacetamidinato) cobalt ($Co(iPr-AMD)_2$) as a precursor and $NH_3$ as a reactant; this reaction produced a highly conformal Co film with low resistivity ($50\;{\mu}{\Omega}cm$). To prevent oxygen contamination, $ex-situ$ sputtered Ti and $in-situ$ ALD Ru were used as capping layers, and the silicide formation prepared by rapid thermal annealing (RTA) was used for comparison. Ru ALD was carried out with (Dimethylcyclopendienyl)(Ethylcyclopentadienyl) Ruthenium ((DMPD)(EtCp)Ru) and $O_2$ as a precursor and reactant, respectively; the resulting material has good conformality of as much as 90% in structure of high aspect ratio. X-ray diffraction showed that $CoSi_2$ was in a poly-crystalline state and formed at over $800^{\circ}C$ of annealing temperature for both cases. To investigate the as-deposited and annealed sample with each capping layer, high resolution scanning transmission electron microscopy (STEM) was employed with electron energy loss spectroscopy (EELS). After annealing, in the case of the Ti capping layer, $CoSi_2$ about 40 nm thick was formed while the $SiO_x$ interlayer, which is the native oxide, became thinner due to oxygen scavenging property of Ti. Although Si diffusion toward the outside occurred in the Ru capping layer case, and the Ru layer was not as good as the sputtered Ti layer, in terms of the lack of scavenging oxygen, the Ru layer prepared by the ALD process, with high conformality, acted as a capping layer, resulting in the prevention of oxidation and the formation of $CoSi_2$.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
• /
• pp.77.1-77.1
• /
• 2013

Atomic layer deposition (ALD) is known for its self-limiting reaction, which offers atomic-level controllability of the growth of thin films for a wide range of applications. The self-limiting mechanism leads to very useful properties, such as excellent uniformity over a large area and superior conformality on complex structures. These unique features of ALD provide promising opportunities for future electronics. Although the ALD of Al2O3 film (using trimethyl-aluminum and water as a metal precursor and oxygen source, respectively) can be regarded as a representative example of an ideal ALD based on the completely self-limiting reaction, there are many cases deviating from the ideal ALD reaction in recently developed ALD processes. The nonconventional aspects of the ALD reactions may strongly influence the various properties of the functional materials grown by ALD, and the lack of comprehension of these aspects has made ALD difficult to control. In this respect, several dominant factors that complicate ALD reactions, including the types of metal precursors, non-metal precursors (oxygen sources or reducing agents), and substrates, will be discussed in this presentation. Several functional materials for future electronics, such as higher-k dielectrics (TiO2, SrTiO3) for DRAM application, and resistive switching materials (NiO) for RRAM application, will be addressed in this talk. Unwanted supply of oxygen atoms from the substrate or other component oxide to the incoming precursors during the precursor pulse step, and outward diffusion of substrate atoms to the growing film surface even during the steady-state growth influenced the growth, crystal structure, and properties of the various films.

• 한국안전학회지
• /
• 제33권2호
• /
• pp.32-38
• /
• 2018

The sprinkler system is a basic fire extinguishing system widely used, but there is a lack of quantitative assessment of its performance. In this study, to evaluate the fire extinguishing performance of the sprinkler head according to the discharge coefficients, experiments were conducted. Experimental sprinkler heads were selected with heads having K50, K80 and K115 water discharge coefficients, and the fire source was assumed to be an indoor fire in Class A Model 1. As experimental results, the time required for the fire chamber to cool down to $200^{\circ}C$ was 26 seconds for the K115 head, 414 seconds for the K80 head, and 481 seconds for the K50 head, so the cooling time of the K115 head was decreased by 94.5% compared to K50 head. In the case of restoring the oxygen concentration to 15%, the K115 head did not decrease below the oxygen concentration of 15%, and the K80 head took 145 seconds and the K50 head took 484 seconds. The lowest oxygen concentration in the fire chamber was 16.1% for the K115 head, 14.33% for the K80 head, and 11.28% for the K50 head, indicating that the K115 head was superior to the K80 and K50 heads by 13.1% and 43.7%, respectively. As the experimental results show, there is big difference in the extinguishing performance depending on the discharge coefficients of the sprinkler head. Therefore, in designing the sprinkler system, the discharge coefficients of the sprinkler head should be selected considering the heat release rate at the installation site and the fire extinguishing characteristics of sprinkler head.