• 설비공학논문집
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• 제17권9호
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• pp.830-838
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• 2005

The present study investigated the optimization of the absorption performance of the vertical absorber tube with falling film by considering heat and mass transfer simultaneously. Effects of film Reynolds number, geometric parameters by insert device (spring) and flow pattern on heat and mass transfer performances have been also investigated. Especially, effects of coolant flow rate and the flow pattern by geometric parameters has been observed for the total heat and mass transfer rates through both numerical and experimental studies. Based on both predicted values, the optimal coolant flow rate was predicted as 1.98 L/min. The maximum absorption rate of the spring inserted tube was increased by the maximum of $20.0\%$ than those for uniform film of bare tube. Average Sherwood numbers and Nusselt numbers were increased as Reynolds numbers increased under the dynamic and geometric conditions showing the maximum absorption performance.

• 한국소음진동공학회논문집
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• 제18권1호
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• pp.110-122
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• 2008

Pneumatic vibration isolator typically consisting of dual-chamber pneumatic springs and a rigid table are widely employed for proper operation of precision instruments such as optical devices or nano-scale equipments owing to their low stiffness- and high damping-characteristics. As environmental vibration regulations for precision instruments become more stringent, it is required to improve further the isolation performance. In order to facilitate their design optimization or active control, a more accurate mathematical model or complex stiffness is needed. Experimental results we obtained rigorously for a dual-chamber pneumatic spring exhibit significantly amplitude dependent behavior, which cannot be described by linear models in earlier researches. In this paper, an improvement for the complex stiffness model is presented by taking two major considerations. One is to consider the amplitude dependent complex stiffness of diaphragm necessarily employed for prevention of air leakage. The other is to employ a nonlinear model for the air flow in capillary tube connecting the two pneumatic chambers. The proposed amplitude-dependent complex stiffness model which reflects dependency on both frequency and excitation amplitude is shown to be very valid by comparison with the experimental measurements. Such an accurate nonlinear model for the dual-chamber pneumatic springs would contribute to more effective design or control of vibration isolation systems.

• 한국환경생태학회지
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• 제34권1호
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• pp.55-62
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• 2020

이 연구는 강원대학교 학술림 내의 산지계류를 대상으로 2년간(2017~2018)의 현지 모니터링에 기초하여 수온과 강우, 유량 및 기온 등 환경인자간의 관계를 분석하고, 계절별 산지계류의 수온변화 예측기법에 대하여 검토하였다. 동절기를 제외한 봄, 여름 및 가을철로 구분하여 단계적 다중선형회귀분석을 실시하였으며, 계절별 산지계류의 수온변화에 미치는 환경인자의 영향을 분석하였다. 그 결과, 산지계류의 일평균 수온은 봄철 6.9~17.7℃로 기온과 유의적 관계를 나타내었고, 여름철 12.2~26.3℃로 기온, 유량과 유의적 관계를 나타냈으며, 가을철 3.6~19.3℃로 기온 및 유량과 유의적 관계를 나타내는 등 계절별로 산지계류의 수온에 미치는 영향인자는 다르게 나타났다. 다중선형회귀식은 봄철 (0.553×기온)+(0.086×유량)+4.145(R²=0.505; p<0.01), 여름철 (0.756×기온)+(-0.072×유량)+2.670(R²=0.510; p<0.01), 가을철 (0.738×기온)+(0.028×강우)+2.660(R²=0.844; p<0.01)이었다. 도출된 모든 회귀식의 결정계수(R²)는 기온만으로 예측한 경우보다 높게 나타났고, 봄철에서 가을철로 갈수록 증가하였다. 향후 정밀도 높은 산지계류의 수온변화 예측을 위해서는 지속적인 현지 모니터링과 함께 시·공간적 데이터의 확보가 중요하다고 판단된다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.299-304
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• 2009

A hybrid electromagnetic actuator with an air spring is designed so as to achieve the desired isolation reduce the vibration efficiency on the floor vibration. The performance specification of the hybrid electromagnetic actuator is determined based on the vibration criterion for vibration-sensitive equipment. In basic design stage of the electromagnetic actuator, the simple reluctance method is adapted to analyze magnetic circuits. The result is verified by finite element analysis using ANSYS Emag. Finally, some design parameters are optimized under several constraint conditions. Through this study, the design procedure for a specific electromagnetic actuator is set up using a simple reluctance method.

• 한국반도체및디스플레이장비학회:학술대회논문집
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• 한국반도체및디스플레이장비학회 2006년도 추계학술대회 발표 논문집
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• pp.184-189
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• 2006

In the process of accurate manufacture and measurement, it is necessarily required to isolate external or internal vibration due to external disturbance and internal actuators. The higher vibration isolation system gets damping around resonance, the better it is generally. This paper analyzes the performance of an existing passive air-spring for vibration isolation table by rising experiment and simulation. Optimal design for a passive air spring can be obtained by fluting the size of the orifice. Also design for an active isolation system is carried out by applying PID controller and considering non-linearity of pneumatic characteristics with help of look-up table. We have developed the act ive vibration isolation table wi th the bet ter isolation performance.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.459-462
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• 2003

This paper presents a force model of the clean tube system, which was developed as a means for transferring the air-floated wafers inside the closed tube filled with the super clean air. The recovering force from the holes for floating wafers is modeled as a linear spring and thus the wafer motion is modeled as a mass-spring-damper system. The propelling forces are modeled as linear along with the wafer location. The paper also proposes the control method to emit and stop a wafer at the center of a control unit. It shows the minimum value of the propelling force to leave from the control unit. In order to stop the wafer, it utilizes the exact time when a wafer arrives at the position to activate the propelling force. Experiments with the clean tube system built for 12 inch wafer shows the validity of the proposed model and the algorithm.

• 설비공학논문집
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• 제22권5호
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• pp.296-303
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• 2010

An experimental study was carried out to investigate performance characteristics of the hybrid solar system during spring season. The system operating condition, each load, and heat pump performance were analyzed with the cloud cover. As a results, the collector heat, solar fraction, and hot water load were decreased with a rise of the cloud. The heating load was considerably effected by the ambient temperature regardless of the cloud cover. Besides, the temperature of hot water increased with the solar radiation. The COP of the heat pump was significantly influenced by the ambient temperature, that was 2.09~2.46 for gray day and 1.94~2.71 for fair day, respectively.

• 설비공학논문집
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• 제25권11호
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• pp.612-616
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• 2013

A circular CAV damper has been developed, based on the investigation of the pressure loss, and the flow-resisting moment by the damper blade. When a torsional spring is attached to the damper axle, and the setting angle is adjusted to around $82^{\circ}$, the volume rate across the damper is almost independent of the static pressure. Such a CAV characteristic appears at an opening angle between $40^{\circ}$ and $60^{\circ}$, where the normalized moment decreases linearly with the angle. In addition, by adjusting the setting angle, the volume rate can be controlled to within 10% error, regardless of the pressure loss.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(III)
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• pp.389-394
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• 2003

Subway has been used one of major public transportations because of overpopulation and heavy traffic problems in the metropolitan areas. So, the air pollution has been serious. In this study, continuous date of PM-10 (particles with aerodynamic diameter < $10{\mu}m$) and heavy metal concentration measurements for winter, spring and summer. These measurements have been carried out in the outdoor, concourse, platform, tunnel. The study results showed that the average seasonally concentration of PM-10 particles were $141.57{\mu}g/m^3$ in winter. $129.34{\mu}g/m^3$ in spring and $122.73{\mu}g/m^3$. The average concentration of PM-l0 particles at indoor higher than outdoor. The concentration of Fe, Cu, showed the largest peak concentrations during the respective season.

• International Journal of Air-Conditioning and Refrigeration
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• 제13권3호
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• pp.158-166
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• 2005

The present study investigated experimentally and numerically the enhancement of absorption performance due to the waviness of falling film in the vertical absorber tube. The momentum, energy and mass diffusion equations were utilized to find out temperature and concentration profiles at both the interfaces of liquid solution and refrigerant vapor and the wall. Flow visualization was performed to find out the wetting characteristics of the falling film. The maximum heat transfer coefficient was obtained for the wavy flow using spring as an insert device through both numerical and experimental studies. Based on the numerical and experimental results, the maximum absorption rate was found for the wavy-flow using spring as the insert device. The differences between experimental and analytical results ranged from $5.0\;to\;25\%\;when\;Re_j>100$.