• 한국표면공학회지
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• 제51권3호
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• pp.149-156
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• 2018

The corrosion and strength degradation characteristics of 1.25Cr-0.5Mo steels were studied under $650^{\circ}C$ in $76%N_2+6%O_2+16%CO_2+2%SO_2$ gas condition up to 500 hrs. Corroded specimens were characterized by weight gain, scanning electron microscope(SEM), energy dispersive X-ray spectroscopy(EDS), and X-ray diffraction(XRD). The tensile test was conducted to evaluate the mechanical strength and fracture mode with corrosion at high temperature. As the results of the experiments, thick Fe-rich oxide layers over $200{\mu}m$ were formed on the surface within 500 hrs. The thick oxide layers are formed with reduction of the cross-sectional area of the specimens. Thus, the strength tended to decrease with reduction of the cross-sectional area.

• Toxicological Research
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• 제19권3호
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• pp.227-234
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• 2003

2-Bromopropane (2-BP), a halogenated propane analogue, is a substitute for chlorofluorocarbones (CFCs) which have a great potential to destroy the ozone layer and to warm the earth's environment. The present study was undertaken to evaluate the potential adverse effects of 2-BP on pregnant dams and embryo-fetal development after maternal exposure during the gestational days (GD) 6 through 17 in ICR mice. The test chemical was administered subcutaneously to pregnant mice at dose levels of 0, 313, 625 or 1,250 mg/kg/day. All dams were subjected to caesarean section on GD 18 and their fetuses were examined for external, visceral and skeletal abnormalities. In the 1,250 mg/kg group, maternal toxicity included an increase in the incidence of abnormal clinical signs and a decrease in the maternal body weight, body weight gain, and corrected body weight. Developmental toxicity included a decrease in the fetal body weight, a reduction in the placental weight, an increase in the fetal skeletal variation and ossification delay. There were no adverse effects on either pregnant dams or embryo-fetal development in the 313 and 625 mg/kg groups. These results suggest that a 12-day subcutaneous dose of 2-BP is embryotoxic at a maternally toxic dose (i.e., 1,250 mg/kg/day) in ICR mice. In the present experimental condition, the no-observed-adverse-effect level of 2-BP is considered to be 625 mg/kg/day for dams and embryo-fetuses, respectively.

• 자원리싸이클링
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• 제12권5호
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• pp.42-49
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• 2003

넓은 입도분포를 가지는 헤마타이트 철광석을 사용하여 $H_2$ 및 $H_2$-CO 혼합가스 분위기에서 환원 및 탄회특성에 대하여 고찰하였다. 환원에 의한 활성화에너지 값은 약 20kJ/mol 였다. 환원 및 탄화단계에서 무게변화는 환원단계에서는 약 28% 감소하였고, 탄화단계에서는 약 5%증가하였다. 이는 이론 계산식에 의한 값과 거의 일치하였다. 온도, 입도 및 가스비($_H2$/CO=1～5 범위)에 따른 탄화속도는 온도가 낮을수록 입자가 작을수록 그리고 가스비가 작을수록 탄화속도가 증가하였다. 또한 $H_2$의 가스비($H_2$/CO=1)가 낮을 때는 유리카본(C, free carbon)이 발생하였다. 수소가스를 혼합하였을 경우가 탄화속도는 증가하였으나, 수소분율에 비례하여 증가하지는 않았다. 혼합가스 중 수소분율($X_{H2}$ )이 0.5일 때 ($H_2$/CO=1) 탄화속도가 최대였다. 이때 수소가 탄화철 생성과정에 있어서 촉매역할을 한 것으로 추정된다.

• 한국철도학회논문집
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• 제18권6호
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• pp.522-532
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• 2015

본 연구에서는 철도 교량 위를 주행하는 철도 소음에 의한 고층 공동주택 거주민들의 철도 소음 피해를 최소화할 뿐 아니라, 방음시설에 미치는 풍하중 및 자중을 동시에 감소시키는 방안으로 터널형 방음벽의 벽면부 개방을 검토하였다. 광음향기법, 전산 유체 역학 및 구조 역학을 이용하여 방음 효과, 유동 효과 및 구조 경량화가 고려된 터널형 방음벽 설계 및 효과를 예측하였다. 해석결과, 벽면부를 부분 개방하여 경량화 및 풍하중 감소 효과를 얻을 수 있었으며, 방음시설의 풍하중은 최대 30% 감소되었다. 부분 개방으로 인해 철도소음의 피해가 특정 높이에서 증가하기 때문에 이를 보완하기 위하여 개방된 부분에 소음기 형태의 음향 루우버 설치를 검토하였다. 음향 루우버의 경우 기존 방음재료의 차음성능과 유사한 성능이 존재하도록 개공율에 따른 유동 해석과 차음성능 해석을 수행하였다. 개공율 30~40% 개방 시, 차음성능 10dB를 만족하며 풍하중이 약 25% 저감되는 것으로 분석되었다. 결과적으로 터널형 방음벽의 벽면부 개방과 음향 루우버 설치는 경량화 및 풍하중에는 긍정적인 효과를 보여주며, 부분 개방과 함께 적절한 방음 재료와 방음설계가 동시에 적용될 경우, 거주민들이 요구하는 5-10dB 수준의 소음저감 효과가 나타나는 것으로 분석되었다.

• 한국축산식품학회지
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• 제33권2호
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• pp.276-280
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• 2013

본 연구의 목적은 가르시니아 캄보지아 추출물이 함유된 육류용 딥소스의 항비만 효과를 동물실험을 통하여 검증하기 위하여 고지방 식이로 유도한 비만 쥐의 체중 및 지방조직의 변화, 혈중 지질성분의 변화를 5주령 흰쥐 18마리를 정상식이에 식염수 투여군(NCD), 고지방 식이에 가르시니아 캄보지아 추출물-비함유 육류용 딥소스 투여군(HFD), 고지방 식이에 2% 가르시니아 캄보지아 추출물-함유 육류용 딥소스 투여군(HFD+GC)으로 나누어 90일 간 실시하였다. HFD군의 흰쥐에서의 체중 중가가 가장 두드러지게 나타났고, 이러한 체증증가는 HFD+GC군의 흰쥐에서 유의 있게 감소되는 것을 확인할 수 있었다. 또한 개복 후 부고환 및 신장주변 지방 조직을 적출하여 무게를 확인한 결과에서도 HFD+GC군의 흰쥐에서 지방의 무게가 유의하게 감소된 것을 확인할 수 있었다. 또한, 혈청 중의 지질성분인 total cholesterol, triglycerol, total lipid의 함량이 다른 식이 군에 비해 유의하게 감소한 결과도 HFD+GC군에서 확인할 수 있었다. 이상의 결과들은 가르시니아 캄보지아 추출물이 비만 유도 실험 모델 쥐에서 비만과 관련된 각종 지표들을 억제함으로써 항비만 효과를 나타내고 있음을 확인할 수 있었고, 이러한 효과는 가르시니아 캄보지아 추출물이 함유된 육류용 딥소스를 비만을 유발할 수 있는 음식과 동시에 섭취하여도 효과가 있음이 시사되었다.

• Food Science and Biotechnology
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• 제17권2호
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• pp.362-366
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• 2008

Anti-lipogenic effects of tannic acid on 3T3-L1 adipocytes as well as on rats fed high fat diet (HFD) were investigated. Tannic acid stimulated lipolysis through suppression of the leptin secretion and an increase of glycerol release in a dose dependent manner in 3T3-L1 adipocytes. For animal study, the rats were fed either HFD or HFD supplemented with 1%(w/w) tannic acid (HFDT) for 12 weeks, respectively. Body weight gain, liver weight, and visceral fat mass in rats fed HFDT were significantly decreased compared to those of rats fed HFD. The lipid profiles of HFDT group were significantly decreased compared with HFD group in the serum and liver, whereas fecal total cholesterol excretion was increased in HFDT group. These results suggest that anti-lipogenic effect of tannic acid in 3T3-L1 adipocytes and in rats fed HFD may be due to the stimulation of lipolysis and the reduction of lipid levels.

• 동의생리병리학회지
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• 제25권5호
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• pp.870-875
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• 2011

Arthritis of the knee is the most common type of joint inflammatory disorder and it is associated with pain and inflammation of the joint capsule. The aim of present study was to investigate the endogenous effect of low intensity laser acupuncture on collagen-induced arthritis in rats. Forty Sprague-Dawley rats were randomly divided into normal group, arthritis group, low laser group with 10 rats in each group. Arthritis in rats was induced by subcutaneous injection of type II collagen combined with complete Freund's adjuvant. Here we investigated the effects of low intensity laser therapy in experimentally induced rat knee arthritis. To evaluate preventive and therapeutic effects of low intensity laser acupuncture on collagen-induced arthritis rats. In collagen induced arthritic rats, there was significant increase in rat paw volume and decrease in body weight increment, whereas low intensity laser therapy groups, showed significant reduction in paw volume and normal gain in body weight. The altered biochemical parameters(blood urea, serum creatinine, total proteins and acute phase proteins) in the arthritic rats were significantly brought back to near normal by the low intensity laser therapy. Therefore, low intensity laser acupuncture may be a useful treatment in the prevention and treatment of collagen-induced arthritis.

• Molecular & Cellular Toxicology
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• 제4권2호
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• pp.138-143
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• 2008

We investigated if Chlorella vulgaris (CV) has protective effects on cadmium (Cd) induced liver damage in male Sprague-Dawley (SD) rats. Forty rats, aged 5 weeks old and weighed 90-110g, were divided into a control (with Cd free water), 50 ppm of $CdCl_2$ in drinking water treated groups (Chlorella 0% diet group (Cd/CV0%), Chlorella 5% diet group (Cd/CV5%) or Chlorella 10% diet group (Cd/CV10%). All the rats had freely access to water and diet for 8 weeks. The results show that body weight gain and relative liver weight had significantly lower in Cd/CV0%-treated group than in Cd/CV-treated groups. Hepatic Cd contents showed significantly less by feeding CV (P<0.05). Cd/CV0%-treated rats had significantly (P<0.05) higher hepatic T-MTs, and Cd-MTs concentrations, compared to Cd/CV5% or Cd/CV10% treated rats. The MT I/II mRNA was expressed in the liver of all experimental rats. Its expression was more increased in Cd/CV5%- or Cd/CV10%-treated rats, compared to control and Cd-treated rats. Thus, this study suggested that CV would have a protective effect on Cd-treated liver injury by the reduction of Cd concentrations and stimulation of Cd-MT binds in the liver. However, more studies are needed to identify the proper mechanism of CV and liver toxicity.

• 한국의류학회지
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• 제39권6호
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• pp.812-825
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• 2015

This study explored various issues related to the quality-of-life for obese Korean men. In-depth interviews were conducted with thirty men over BMI 25 whose age ranged from 20's to 50's. Projective techniques along with semi-structured interviews were used. The results of interviews were analyzed based on grounded theory. "Stress" was the main phenomenon resulting from the causal conditions of obesity and stigma. Stress consisted of social, psychological, physical and environmental factors. Contextual conditions mediating the relationship between causal conditions and main phenomenon were obesity level, pressure, and public appearance. Avoidance, change of personal traits, and insensitivity were the action/reactions to the main phenomenon. Various factors due to obesity disappeared and quality-of-life increased when they succeed in weight reduction; however, factors related to obesity and lowered condition of quality-of-life continued if they experienced a weight gain/loss yo-yo.

• Journal of Power Electronics
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• 제13권5호
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• pp.737-745
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• 2013

Offshore wind farms are rapidly growing owing to their comparatively more stable wind conditions than onshore and land-based wind farms. The power capacity of offshore wind turbines has been increased to 5MW in order to capture a larger amount of wind energy, which results in an increase of each component's size. Furthermore, the weight of the marine turbine components installed in the nacelle directly influences the total mechanical design, as well as the operation and maintenance (O&M) costs. A reduction in the weight of the nacelle allows for cost-effective tower and foundation structures. On the other hand, longer transmission distances from an offshore wind turbine to the load leads to higher energy losses. In this regard, DC transmission is more useful than AC transmission in terms of efficiency because no reactive power is generated/consumed by DC transmission cables. This paper describes some of the challenges and difficulties faced in designing high-power-density power conversion systems (HPDPCSs) for offshore wind turbines. A new approach for high gain/high voltage systems is introduced using transformerless power conversion technologies. Finally, the proposed converter is evaluated in terms of step-up conversion ratio, device number, modulation, and costs.