• Journal of Advanced Marine Engineering and Technology
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• 제38권3호
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• pp.269-275
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• 2014

본 연구는 PI 개념에 근거한 수처리용 인라인 혼화 및 응집 시스템의 성능특성에 대한 실험적 연구를 목적으로 한다. 3단 인라인 혼화 및 응집 시스템은 처리 원수 저장조, 응집제 주입 정량펌프, 혼화 및 응집관, 침전조 및 제어 판넬로 구성된다. 동일한 응집제와 응집보조제의 주입량 조건에서 응집제의 증가에 따른 탁도 제거율에 비해 응집보조제의 증가에 따른 탁도 제거율이 약 3배 정도 높게 나타났다. 동일한 혼화 및 응집 시간 조건에서 인라인 방식이 기계식에 비해서 평균적으로 약 4.6배 정도 탁도 제거율이 높게 나타났다.

• Geomechanics and Engineering
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• 제20권5호
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• pp.399-410
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• 2020

Cavities often develop behind the vault during the construction of double-arch tunnels, generally in the form of various defects. The study evaluates the impact of cavities behind the vault on the mechanical and failure behaviors of double-arch tunnels. Cavities of the same sizes are introduced at the vault and the shoulder close to the central wall of double-arch tunnels. Physical model tests are performed to investigate the liner stress variation, the earth pressure distribution and the process of progressive failure. Results reveal that the presence of cavities behind the liner causes the re-distribution of the earth pressure and induces stress concentration near the boundaries of cavities, which results in the bending moments in the liner inside the cavity to reverse sign from compression to tension. The liner near the invert becomes the weak region and stress concentration points are created in the outer fiber of the liner at the bottom of the sidewall and central wall. It is suggested that grouting into the foundation soils and backfilling injection should be carried out to ensure the tunnel safety. Changes in the location of cavities significantly impact the failure pattern of the liner close to the vault, e.g., cracks appear in the outer fiber of the liner inside the cavity when a cavity is located at the shoulder close to the central wall, which is different from the case that the cavity locates at the vault, whereas changes in the location of cavities have a little influence on the liner at the bottom of the double-arch tunnels.

• Asian-Australasian Journal of Animal Sciences
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• 제17권12호
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• pp.1652-1656
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• 2004

The aim of this study was to obtain mature ova or embryos at a single cell stage, which can be used in avian transgenesis and nuclear transfer through multiple ovulations, in vitro fertilization and culture. Chicken anterior pituitary extract (CAPE) or acetone-dried chicken anterior pituitary extract (ACAPE) was used to induce multiple ovulations in hens pretreated with pregnant mare' serum gonadotrophin (PMSG). In vitro fertilization of the multiple ovulated ova was performed by inseminating sperm onto the germinal disks in m-Ringer' solution and incubating the ova at 41$^{\circ}C$, 5% $CO_2$ for 10 h in DME-F12 medium containing 20% liquid albumen. The in vitro fertilization process was observed using an environmental scanning electron microscope. When normal laying hens (white Leghorn) were administered daily with PMSG (100 IU), egg laying ceased in most hens within 3 to 8 days. Ovulation began to occur about 7.5 h after injection of CAPE and ACAPE. The number of ovulated ova was 1.00${\pm}$0.00, 2.33${\pm}$0.52 and 2.20${\pm}$0.45, respectively, after receiving 100, 200 and 300 mg CAPE. The number of ovulated ova was 2.00${\pm}$0.00, 2.86${\pm}$0.69 and 3.00${\pm}$1.22, respectively, after receiving 10, 15 and 20 mg ACAPE. The fertilized and cultured ova were able to develop into embryos up to the 32 cell stage. The present experiments demonstrated that multiple ovulations can be induced by CAPE and ACAPE successfully, and the ova resulted from the treatment retained the capability for further fertilization and embryonic development. These data provide new information to support the establishment of an in vitro culture system for future avian transgenesis studies.

• Asian-Australasian Journal of Animal Sciences
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• 제14권2호
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• pp.163-169
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• 2001

Despite the high potency of the retrovirus vector system in gene transfer, one of the main drawbacks of has been difficulty in preparing highly concentrated virus stock. Numerous efforts to boost the virus titer have ended in unsatisfactory results mainly due to fragile property of retrovirus envelope protein. In this study, to overcome this problem, we constructed our own retrovirus vector system producing vector viruses encapsulated with VSV-G (vesicular stomatitis virus G glycoprotein). Concentration process of the virus stock by ultracentrifuge did not sacrifice the virus infectivity, resulting in more than 108 to 109 CFU (colony forming unit) per ml on most of the target cell lines tested. Application of this high-titer retrovirus vector system was tested on chicken embryos. Injection of virus stock beneath the blastoderms of pre-incubated fertilized eggs resulted in chick embryos expressing E. coli LacZ gene with 100% efficiency. Therefore, our results suggest that it is possible to transfer the foreign gene into chicken embryo using our high-titer retrovirus vector.

• 한국식품영양과학회지
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• 제26권5호
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• pp.901-907
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• 1997

The purpose of this study was to investigate the effects of green tea catechin o n free radical generation system and peroxidative damage in the liver of streptozotocin(STZ)-induced diabetic rats. Spragu-Dawley male rats weighing 150$\pm$10gm were randomly assigned to one normal and three STZ-induced diabetic groups; diabetic groups were classified to catechin free diet(DM-oC group), 0.5% catechin diet(DM-0.5C group) and 1% catechin diet(DM-1C group) according to the levels of dietary catechin supplementation. Diabetes was experimentally induced by intravenous injection of 55mg/kg of body wt of STZ in citrate buffer(pH 4.3) after feeding of three experimental diet for 4 weeks. Animals were sacrificed at the 6th day of diabetic states. Activities of serum glutamic oxaloacetic transaminase(GPT) in DM-oC groups were higher than those of the normal group, and those in catechin supplementation group were similar to those of the normal group. Liver lipid peroxide values increased by 153%, 49%, and 27% in Dm-oC, DM-0.5C and DM-0C and Dm-1C but was not significantly different in catechin supplementation groups compared with the normal group, and liver cytochrome $P_{450}$ contents was similar to result of XOD activity. In electron microscopic examination of liver, lysosome was relatively scattered in Dm-oC and Dm-0.5C group and preserved normal shapes in DM-1C group. The present results indicate that STZ-induced diabetic rats are more sensitive to oxidative stress, leading to the acceleration of lipid peroxidation process, but this was reduced by anti-oxidative effect of high level of dietary catechin. It is concluded that dietary catechin serves as powerful antioxidant against lipid peroxidation in diabetic rats.

• Journal of Mechanical Science and Technology
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• 제14권10호
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• pp.1131-1142
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• 2000

In an effort to illustrate the global variation of SMD (Sauter mean diameter, or $D_{32}$) and AMD (Arithmetic mean diameter, or $D_{10}$) at five axial downstream locations (i. e., at Z=30, 50, 80, 120, and 170 mm) under the different experimental conditions, the radial coordinate is normalized by the spray half-width. Experimental data to analyze the atomization characteristics concerning with an internal mixing type have been obtained using a PDPA(Phase Doppler Particle Analyzer). The air injection pressure was varied from 40 kPa to 120 kPa. In this study, counterflowing internal mixing nozzles manufactured at an angle of $15^{\circ}$with axi-symmetric tangential-drilled four holes have been considered. By comparing the results, it is clearly possible to discern the effects of increasing air pressure, suggesting that the disintegration process is enhanced and finer spray droplets can be obtained under higher air assist. The variations in $D_{32}$ are attributed to the characteristic feature of internal mixing nozzle in which the droplets are preferentially ejected downward with strong axial momentum, and dispersed with the larger droplets which are detected in the spray centerline at the near stations and smaller ones are generated due to further subsequent breakup by higher shear stresses at farther axial locations. The poor atomization around the centre close to the nozzle exit is attributed to the fact that the relatively lower rates of spherical particles are detected and these drops are not subject to instantaneous breakup in spite of the strong axial momentum. However, substantial increases in SMD from the central part toward the edge of the spray as they go farther downstream are mainly due to the fact that the relative velocity of droplet is too low to cause any subsequent disintegration.

• 한국추진공학회지
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• 제12권1호
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• pp.57-63
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• 2008

공기흡입식 추진 기관인 스크램제트 엔진은 연소기 내부 유동이 초음속으로 유동장의 연소기 내부 체류 시간이 수 ms로 매우 짧다. 이 짧은 시간동안 연소과정이 모두 이루어져야 하므로 초음속 연소기술에 대한 연구는 매우 중요하다. 본 논문은 초음속 연소 기술 중 연료-공기의 혼합을 증대시키는 방법에 관심을 두고 Cavity를 이용한 방법을 선택하여 높이를 10mm로 고정시키고 길이를 변화시켰으며, Cavity 후류에서 지름 1mm의 분사구를 통해 음속 let을 분사시키는 유동장을 형성하여 3차원 Navier-Stokes 방정식을 통해 점성 유동장을 해석하였다. 해석 결과 Cavity 길이/높이비(L/H)가 클수록 Vorticity가 값이 증가하였고 Vorticity의 증가 영역이 유동장의 위, 옆 방향으로 확장되는 것을 볼 수 있었다. 하지만 Vorticity가 증가하는 만큼 추력특성을 떨어뜨리는 정체압력 손실이 증가하므로 연소기 설계 시 최대의 혼합과 최소의 정체압력 손실을 고려한 최적 형상 설계가 필요하다는 것을 확인하였다.

• 대한환경공학회지
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• 제36권2호
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• pp.147-152
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• 2014

본 연구에서는 폴리설폰 중공사막을 이용하여 화석연료 연소에서 배출되는 온실가스 중 $CO_2$의 회수에 관한 연구를 실시하였다. 고농도의 $CO_2$를 회수하기 위한 막분리 공정에 대한 선행연구이다. 혼합가스 분리거동 관찰을 위하여 이산화탄소가 10% 함유된 배기가스를 사용하였다. 압력, 온도, 주입가스 조성, 다단 막 변화를 주어 스테이지 컷에 따른 분리 성능을 조사하였다. 압력과 온도가 증가 할수록 투과측에 $CO_2$ 농도와 회수율이 증가하였다. 주입 가스 조성 변화 시 $CO_2$의 함량이 높을 경우 회수율 및 분리 효율이 높아졌다. 3단 분리막 시스템을 이용시 $CO_2$ 농도 95% 이상, 회수율 90% 이상 보였으며 1단 분리막 보다 분리율이 향상되었다.

• Journal of Korean Society for Atmospheric Environment
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• 제17권E4호
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• pp.157-162
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• 2001

Jet Bubbling Reactors(JBRs) were operated for the removal of SO$_{x}$ in flue gases produced from many electric power plants. However, many JBR flue gas desulfurization (FGD) facility faced a decrease of SO$_{x}$ removal efficiency and an increase of scale problems with continuous operations. We increased alkalinity of the SO$_{2}$ absorbing medium by adding the dibasic acids (DBAs) to solve these problems more effectively. The SO$_{2}$ removal efficiency, the purity of CaCO$_{3}$ and COD of the wastewater was measured to identify the addition effects of DBAs (150, 200, 250, and 400 ppm) for 2hr in a day into the JBR attached to the large-scale power plants (400 MW$\times$3). Addition of the DBAs resulted in the improvement of the SO$_{2}$ removal efficiency from 2 to 5% and the purity of the gypsum from 1 to 2%; these improvement were due to the alkalinity increase of the absorbing medium and the reduction of a proportion of un-reacted CaCO$_{3}$, respectively. Also, the scale problems formed by un-reacted CaCO$_{3}$ inside the reaction zone of the JBR were substantially reduced. Even though the effluent COD of the wastewater slightly increased from 10~15 to 18~36 mg/l and the erosion problems in the injection pump and duct occurred, this method of increasing SO$_{2}$ removal efficiency by adding the DBAs could be considered as a profitable approach.ach.

• The Korean Journal of Physiology and Pharmacology
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• 제10권1호
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• pp.39-44
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• 2006

Type I diabetes (T1D) is an organ-specific autoimmune disease caused by the T cell-mediated destruction of the insulin-producing ${\beta}$ cells in the pancreatic islets. The onset of T1D is the consequence of a progressive destruction of islet ${\beta}$ cells mediated by an imbalance between effector $CD4^+$ T helper (Th)1 and regulatory $CD4^+$ Th2 cell function. Since interferon-alpha (IFN-${\alpha}$) has been known to modulate immune function and autoimmunity, we investigated whether administration of adenoviralmediated IFN-${\alpha}$ gene would inhibit the diabetic process in NOD mice. The development of diabetes was significantly inhibited by a single injection of adenoviral-mediated IFN-${\alpha}$ gene before 8 weeks of age. Next, we examined the hypothesis that Th2-type cytokines are associated with host protection against autoimmune diabetes, whereas Th1-type cytokines are associated with pathogenesis of T1D. The expression of IFN-${\alpha}$ induced increase of serum IL-4 and IL-6 (Th2 cytokines) levels and decrease of serum IL-12 and IFN-${\gamma}$ (Th1 cytokines) levels. Therefore, overexpression of IFN-${\alpha}$ by adenoviralmediated delivery provides modulation of pathogenic progression and protection of NOD mice from T1D.