• Smart Structures and Systems
• /
• 제31권5호
• /
• pp.517-529
• /
• 2023

Using a device composed of two lateral pressure plates (LPPs) and a steel reinforcement bar to apply horizontal pressure on slope surfaces, a newly developed prestress-reinforced embankment (PRE) is proposed, to which can be adopted in strengthening railway subgrades. In this study, an analytical model, which is available of calculating additional confining stress (σ_H) at any point in a PRE, was established based on the theory of elasticity. In addition, to verify the proposed analytical model, three dimensional (3D) finite element analyses were conducted and the feasibility in application was also identified and discussed. In order to study the performance of the PRE, the propagation of σ_H in a PRE was analyzed and discussed based on the analytical model. For the aim of convenience in application, calculation charts were developed in terms of three dimensionless parameters, and they can be used to accurately and efficiently predict the σ_H in a PRE regardless of the embankment slope ratio and LPP side length ratio. Finally, the potential applications of the proposed analytical model were discussed.

• 운동영양학회지
• /
• 제16권1호
• /
• pp.11-17
• /
• 2012

The purposes of this study were to investigate the effects of acute exercise on blood vaspin, glucose level, and inflammatory cytokines in middle-aged women with pre-diabetes. Nineteen middle-aged women (normal women, n = 11) and women with pre-diabetes(n = 8), who were apparently healthy and not taking any medications affecting their blood pressure or blood glucose, participated. Body fatness parameters including body mass index, body fat percentage, and waist circumference were measured using a bio-impedance analyzer. Resting blood pressure was measured in duplicate, and mean values were used for the data analysis. Regardless of group assignments, all subjects participated in a 3-day consecutive walking exercise at an intensity of 65% VO_2max targeting an energy expenditure of 1200 kcal (400 kcal per day). The major outcome variables included total cholesterol, triglycerides, high-density lipoprotein cholesterol, glucose, vaspin, interleukin-6, and adiponectin levels. Unlike normal women, women with pre-diabetes had a significant improvement in the homeostatic model assessment of insulin resistance (p < 0.025) with no significant group difference in response to acute exercise. The findings suggest that acute exercise results in a significant improvement in insulin sensitivity without any change in serum vaspin levels in women with pre-diabetes.

• 한국가스학회지
• /
• 제15권6호
• /
• pp.38-43
• /
• 2011

천연가스 액화공정은 극저온에서 운전되며 에너지 소비가 매우 크기 때문에 압축기의 에너지 소모를 최소화하는 것이 공정의 효율 측면에서 중요하다. 여러 가지 천연가스 액화공정 중 C3-MR(Propane Pre-cooled Mixed Refrigerant) 공정의 경우 순수냉매인 프로판과 혼합냉매를 사용하는 두 개의 냉각 사이클로 구성되어있다. 본 연구에서는 C3-MR 공정에서 최적의 프로판 압력 레벨을 찾기 위해 프로판 사이클을 별개로 구성하여 모사하였다. 또한, 압력 레벨에 따른 조건을 변화시켜가며 사례 연구를 수행하고 이를 통해 압축기에서 소모되는 에너지양을 비교하였다. 그 결과 압력 레벨이 높을수록 총 에너지 소모량이 감소하는 것을 확인 할 수 있었다. 압력 레벨이 3일때 보다 압력 레벨이 5일 때 에너지 소모는 약 23.7% 감소하는 값을 얻을 수 있었다.

• Geomechanics and Engineering
• /
• 제24권6호
• /
• pp.573-588
• /
• 2021

The interaction of cracks and water significantly affects the fracture mechanism of rocks. In this study, laboratory tests were conducted using sandstone samples containing a single fissure to explore the hydro-mechanical behaviors in the failure process of pre-cracked rocks. The internal crack characteristics were also analyzed using X-ray CT scanning. The results show that the confining pressure has the greatest effect on the mechanical properties (e.g., strengths, elastic modulus, and Poisson's ratio), followed by the fissure inclination and water pressure. At a lower fissure inclination, the confining pressure may control the type main cracks that form, and an increase in the water pressure increases the number of anti-wing cracks and the length of wing cracks and branch cracks. However, the fracture behaviors of samples with a higher fissure inclination are only slightly affected by the confining pressures and water pressures. The effect of fissure inclination on the internal crack area is reduced with the propagation from the fissure tips to the sample ends. The fissure inclination mainly affects the value of permeability but not affect the trend. The impact of pre-existing fissure on permeability is smaller than that of confining pressure and water pressure.

• 플랜트 저널
• /
• 제14권2호
• /
• pp.39-44
• /
• 2018

본 연구에서는 870 MW 대형 석탄화력 발전소에서 출력을 고정시키고 과잉공기비 조정만으로 통풍계통 안정 및 보일러 효율에 어떠한 변화가 있는지를 분석하였으며 이에 따른 적정 과잉공기비를 선정하였다. 과잉공기비 조정에 따라 공기예열기 압력강하, 유인송풍기 실속여유 등이 변하므로 통풍계통 안정화를 위해 적정 과잉공기비 선정은 반드시 필요하다. 따라서 본 연구에서는 과잉공기비를 통상 운전 값인 1.153에서 운전지침서상의 하한 값인 1.127까지 단계적으로 조정하여 공기예열기 압력강하, 유인송풍기 1차 실속여유, 보일러 효율, 각종 손실 등을 측정하였고 보일러 효율도 동등수준이상으로 유지하면서 통풍계통도 위험수준에서 안전하게 이격시켜 안정화에 기여할 수 있는 적정 과잉공기비를 선정하였다. 적정 과잉공기비는 운전지침서 상의 하한 값인 1.127까지 낮추어 운전하는 것이 바람직하다고 판단된다.

• 동서간호학연구지
• /
• 제16권1호
• /
• pp.11-18
• /
• 2010

Purpose: The aim of this study was to examine the characteristics of hypertension-related nursing intervention programs and their effects on systolic and diastolic blood pressure. Methods: Fifteen studies were selected from four databases (Korean studies, Riss4U, RICHIS, and JKAN) published as of 2009. They were analyzed by meta-analysis method. The selected studies contained a control group with pre-test and post-test design, measured blood pressure as a dependent variable, and used a reported statistical value for blood pressure to measure the size of effects. Results: The hypertension-related nursing intervention programs were relatively effective in lowering both systolic and diastolic blood pressure, although they were more efficient to decrease diastolic pressure. Among the hypertension-related intervention programs, complementary and alternative therapies were more effective in lowering blood pressure compared to lifestyle change intervention. Conclusions: To acquire substantial data of intervention effects, and complementary and alternative therapy, subjects in pre-hypertensive stage, and elderly people, better industrial and scholastic research methods need to be developed for future research. Further studies are needed to establish complementary and alternative therapies. Studies with different group of participants and studies using effective research design are in need as well.

• 한국식품저장유통학회지
• /
• 제22권3호
• /
• pp.421-427
• /
• 2015

고품질 참외와인을 제조하기 위하여 브랜칭 및 착즙 처리를 하여 발효와 숙성에 따른 이화학적 특성 및 항산화능을 조사하였다. 발효 중 참외와인의 이화학적 특성은 모든 처리구가 유사한 추이를 보였으며, 브랜칭 및 착즙 처리가 알코올 발효에 영향을 미치지 않았다. 숙성 후 이화학적 특성을 측정한 결과는 알코올 함량, 가용성 고형분 함량, 환원당 함량, 적정 산도, pH가 각각 11.5~11.8%, 10.7~11.2%, 0.25~0.49 g/100 mL, 0.60~0.81%, 3.75~3.89 범위로 나타났으며, 숙성 전에 비하여 가용성 고형분, 환원당, 알코올 함량, 적정산도는 감소하고 pH는 증가하는 것으로 나타났다. 항산화능은 DPPH 라디칼 소거 활성, FRAP 활성이 각각 $563.00{\sim}785.00{\mu}M\;TE$, $504.60{\sim}811.93{\mu}M\;TE$ 범위로 나타났으며, 브랜칭 처리구의 항산화 활성이 높았다. 총페놀성 화합물 함량은 287.53~312.08 mg/L 범위로 전처리 방법에 따른 유의적인 차이가 나타나지 않았으며(p<0.05), 총플라보노이드 함량은 39.06~141.03 mg/L 범위로 브랜칭 처리구의 함량이 높았다. 또한 QDA profile 결과는 색, 맛, 풋내, 이취, 종합적 기호도 항목에서 모두 브랜칭 처리구가 더 높은 점수를 얻었다. 브랜칭 처리는 참외와인의 항산화능을 증가시키고 기호성을 좋게 하는 반면, 착즙 처리는 참외와인 제조 시 영향을 미치지 않는 것으로 나타났다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
• /
• pp.370-373
• /
• 1999

Si direct bonding (SDB) technology is very attractive for both Si-on-insulator(SOI) electric devices and MEMS applications because of its stress free structure and stability. This paper presents on- pre treatment conditions in Si wafer direct bonding, The paper resents on pre-bonding according to HF pre-treatment conditions in Si wafer direct bonding. The characteristics of bonded sample were measured under different bonding conditions of HF concentration, applied pressure and annealing temperature(200~ 100$0^{\circ}C$) after pre-bonding. The bonding strength was evaluated by tensile strength method. The bonded interface and the void were analyzed by using SEM and IR camera, respectively, Components existed in the interlayer were analyzed by using FT-IR. The bond strength depends on the HF pre-treatment condition before pre-bonding(Min 2.4kgf/$\textrm{cm}^2$~ Max : 14.kgf/$\textrm{cm}^2$)

• 대한환경공학회지
• /
• 제33권9호
• /
• pp.656-661
• /
• 2011

본 연구에서는 공경 $0.1{\mu}m$, 막여과 유속$3.0m^3/m^2{\cdot}d$의 국산 세라믹 막을 이용하여 음용수를 생산하는 기술에 대해 조사하였다. 세라믹 막의 성능 평가를 위해 $1m^3/d$ 규모의 pilot-scale 실험장치를 제작하였으며, 역세주기에 따른 차압변화와 전오존이 차압변화에 미치는 영향을 조사하였다. 차압상승률은 역세주기에 비례하여 증가하였으나, 전오존 주입을 통해 차압상승률을 낮출 수 있었다. 이 결과는 전오존이 파울링 감소에 효과가 있음을 의미한다. 1 mg/L의 전오존을 주입하고 5 min간 접촉하였을 때, 역세주기 1시간에서 차압상승률은 약 30% 감소하였다. 전오존 접촉시간을 5~15 min으로 변경하면서 운전한 결과, 접촉시간에 따른 차압상승률에는 차이가 없었다. 그러나, 차압상승률은 오존 주입농도가 증가하면 감소하는 경향을 보였다.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.4-5
• /
• 2006

An update and the latest results on molten metal atomization using a Pressure-Gas-Atomizer will be given. This atomizer combines a swirl-pressure atomizer, to generate a liquid hollow cone film and a gas atomizer to atomize the film and/or the fragments of the film. The paper is focused on powder production, but this atomization system is also applicable for deposition purposes. Different alloys (Sn, SnCu) were atomized to study the characteristics of the Pressure-Gas-Atomizer.