• 대한기계학회논문집
• /
• 제15권1호
• /
• pp.252-261
• /
• 1991

본 연구에서는 2상 횡분류의 평균 유동특성을 비교적 정확히 예측할 수 있는 방법을 제시하는데 있다. 이를 위하여 2상 기체 분류속에 유입되는 자유흐름의 질량 유입을 Keffer와 Baines의 유입함수를 이용하기로 하며, 입자와 기체분류사이의 궤적 이탈을 고려하기로 한다. 이런 모델을 이용하여 2상 횡분류의 분출초기의 입자와 기 체분류의 속도비(particle to gas velocity ratio at the jet exit)가 유동에 미치는 영향을 알아보고자 한다.

• 한국정밀공학회지
• /
• 제10권1호
• /
• pp.134-141
• /
• 1993

Electro-Rheological(ER) fluids undergo a phase-change when subjected to an external electic field, and this phase-change typically manifests itself as a many-order-of-magnitude change in the rheological behavior. This phenomenon permits the global stiffness and energy- dissipation properties of the beam structures to be tuned in order to synthesize the desired vibration characteristics. This paper reports on a proof-of-concept experimental investigation focussed on evaluation the vibration properties of hollow cantilevered beams filled with an ER fluid. and consequently deriving an empirical model for predicting field-dependent vibration characteristics. A hydrous-based ER fluid consisting of corn starch and silicone oil is employed. The beams are considered to be uniform viscoelastic materials and modelled as a viscously-damped harmonic oscillator. Natural frequency, damping ratio and elastic modulus are evaluated with respect to the electric field and compared among three different beams: two types of different volume fraction of ER fluid and one type of different particle concentration of ER fluid by weight. Transient and forced vibration responses are examined in time domain to demonstrate the validity of the proposed empirical model and to evaluate the feasibility of using the ERfluid as an actuator in a closed-loop control system.

• 태양에너지
• /
• 제6권2호
• /
• pp.43-53
• /
• 1986

The objective of this study is to report on the characterics of convective flow and heat transfer during metling process in order to provide design information for thermal energy storage systems which use phase change material. In present study, flow and heat transfer characteristics of the Phase Change Material in the Open Top Model (O.T.M) and in the Closed Top Model (C.T.M) were studied numerically by the control volume formulation using the algebraic non-orthogonal coordinate transformation. For the calculation procedure, the physical properties of fluid are assumed to be constant except density which is linely dependent on temperature in the bouyancy term of momentum equations. At start of melting process, the thickness of melting layer is assumed from the Stefan Problem assumption. The heat transfer results of Open Top Model and Closed Top Model are compared with the parameters of Grashof number and aspect ratio. It was found that heat transfer phenomena in melted region was greatly affected by buoyancy-driven natural convection and the melting distance of Open Top Model at the upper region is greater than that of Closed Top Model.

• Advances in concrete construction
• /
• 제11권2호
• /
• pp.99-109
• /
• 2021

Slag blended concrete is widely used as a mineral admixture in the modern concrete industry. This study shows an optimization process that determines the optimal mixture of air-entrained slag blended concrete considering carbonation durability, frost durability, CO2 emission, and materials cost. First, the aim of optimization is set as total cost, which equals material cost plus CO2 emission cost. The constraints of optimization consist of strength, workability, carbonation durability with climate change, frost durability, range of components and component ratio, and absolute volume. A genetic algorithm is used to determine optimal mixtures considering aim function and various constraints. Second, mixture design examples are shown considering four different cases, namely, mixtures without considering carbonation (Case 1), mixtures considering carbonation (Case 2), mixtures considering carbonation coupled with climate change (Case 3), and mixtures of high strength concrete (Case 4). The results show that the carbonization is the controlling factor of the mixture design of the concrete with ordinary strength (the designed strength is 30MPa). To meet the challenge of climate change, stronger concrete must be used. For high-strength slag blended concrete (design strength is 55MPa), strength is the control factor of mixture design.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2005년도 춘계 학술기술논문발표대회 논문집
• /
• pp.93-98
• /
• 2005

The purpose of this study was to analyze the compression strength research by aerated concrete as mixing ratio This Study used foaming-agent and produced aerated concrete by pre-foam way that is used in construction site. An experiment changes unit cement amount, w/c and the glass fiber mixing rate and 'measured capacity change, unit capacity weight and compressive strength. The results obtained from experimental study are as following; Research to reduce unit capacity weight in condition more than unit cement amount 500kgf is considered should be gone side by side. The highest compressive strength result appeared in aerated concrete that cement amount 600kgf and w/c ratio $45\%$, $50\%$. compressive strength was increased maximum $34%$ when glass fiber $0.7\%$ addition cause by coherence enlargement to enlargement of cement paste and glass fiber addition per unit volume

• The Journal of Korean Physical Therapy
• /
• 제26권5호
• /
• pp.302-307
• /
• 2014

Purpose: This study was conducted in order to determine the changes in pain and breathing function when kinesio taping is applied to patients with myofacial trigger points on sternocleidomastoid (SCM) muscle. Methods: The subjects were 25 males and females aged 20 to 30 years (male 10, female 15). They were randomly divided into the control group and the experimental group to be applied with kinesio taping. Kinesio taping was applied to SCM muscle three times per week for two weeks. Pain triggered when the taut band or nodule was palpated was measured. Pain intensity was measured using the visual analog scale (VAS). The breathing function was measured using forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and FEV1/FVC ratio. In all subjects, VAS, breathing function was measured before and after intervention. Results: In the experimental group, pain in the SCM was relieved as VAS showed a significant decrease and FVC, FEV1, and FEV1/FVC ratio showed a significant increase. Comparison between the groups, showed significant differences in VAS and the FVC, FEV1, and FEV1/FVC ratio. Conclusion: These results suggest that myofascial pain on SCM muscle is thought a factor that affects the breathing function.

• 한국분무공학회지
• /
• 제6권1호
• /
• pp.25-34
• /
• 2001

Several efforts to meet the exhaust gas regulation have been undertaken by many researchers in recent years. Main researches are on development of design techniques of intake port and combustion chamber, atomisation of fuel and precise control of air-fuel ratio, post-treatment of exhaust gas and so on. Engine technology is changed from PFI to GDI to correspond with exhaust gas regulation. GDI technique makes it possible to preserve lean air-fuel ratio and control accurate air-fuel ratio. Nevertheless, It is not cleared that information of spray characteristics and atomization process are very dependent on fluctuation of pressure and change of temperature in intake stroke. In this study, a constant volume combustion chamber is manufactured to investigate various fluctuations of in-cylinder pressure for injection duration. It is taken photographs of injection process of conventional GDI injector using PMAS. Then, it was verified experimently that ambient conditions as temperature and pressure of combustion chamber have effects on process of spray growth and atomization of fuel.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.13-18
• /
• 2003

Heat pipes with binary mixture fabricated and tested for applications where condenser temperature is in a range of $10^{\circ}C$ to $130^{\circ}C$. The pipe materials 8.0 mm O.D. cupper tube and the working fluids are ethanol-water mixtures. The total length of test of the heat pipe was 1710mm in which evaporator section was 1570mm, adiabatic section was 50mm and condenser section was 90mm. Mixing ratios of ethanol and water could be variable in mole fraction. Temperature of condenser section was $10^{\circ}C$, $80^{\circ}C$ and $130^{\circ}C$. Heat pipe performance experimental study was accomplished with change of mixing ratio in these temperatures. The fill charge ratio was 20% of the heat pipe volume. Wick structure was woven-wire and method of experimental work was that thermal load was increased 20W step until the heat pipe wall temperature reached at $150^{\circ}C$. Results were following: At coolant $10^{\circ}C$ and $130^{\circ}C$, mixing ratio that have beat thermal performance was 0.8M+ and at coolant $80^{\circ}C$, was 0.3 ${\sim}$ 0.5 M+.

• 한국재료학회지
• /
• 제15권12호
• /
• pp.773-779
• /
• 2005

Properties of Ni-base superalloys of Nimonic 80A alloy system were investigated by the observation of microstructures, precipitates ana hardness as a function of the chemical compositions ana the paths of heat treatment. The higher hardness values showed, the higher Ti/Al ratio among high compositions of Cr and Co element. The lower (Ti+Al) and Fe contents decreased in the same Ti/Al ratio, the higher hardness values showed. This results are considered that coherent deformation was increased with increasing Ti/Al ratio. Hardness showed higher value when Cr contents was $18 wt\%$ less than $21wt\%Cr$. In $3.15 wt\%$Co alloy, $\gamma'$ phase was very fine as around 50nm and, its volume fraction and hardness showed the highest value by 2step-aging treatment.

• 한국건축시공학회지
• /
• 제13권3호
• /
• pp.282-290
• /
• 2013

본 연구는 혼화재의 다량 치환 시 배합 요인의 조정 범위를 검토하기 위한 목적으로 일반 콘크리트에서 혼화재 다량 치환 콘크리트로의 배합변경 데이터를 확보하고자 하였다. 실험결과를 요약하면, 일반 범용적 배합내에서 혼화재 다량 치환 콘크리트로 배합을 변경 시 적정 품질을 확보하기 위한 단위수량의 경우 $20{\sim}30kg/m^3$ 하향 조정, 잔골재율은 W/B 5 % 하향조정 시 약 1 %, 총 치환율 5 % 증가 시약 0.12 %로 중복 하향 조정, AE제는 FA 치환율 5 % 증가 시 컨벤셔널 대비 약 20~30 % 정도 상향 조정, W/B는 FA 및 BS의 치환율이 5 % 상향 시 W/B를 약 1~4 % 정도 하향 조정함으로써 콘크리트의 기본 물성을 확보할 수 있는 것으로 나타났다.