• 한국습지학회지
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• 제23권2호
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• pp.173-182
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• 2021

수자원의 보전과 관리를 위해서는 갈수시의 유량감쇄 특성을 파악하는 것이 중요한 과제 중에 하나이다. 감쇄특성을 하천 유량자료를 이용하여 표현하기 위해서 여러 복잡한 특성을 고려하여야 하므로, 편의성을 위하여 선형 감쇄분석이 주로 적용되어 왔다. 그러나, 최근의 연구에서 제시된 지하수 유출과 비피압대수층의 저장능력의 비선형성을 고려하면, 비선형 감쇄모형의 적용성이 더 높다고 할 수 있다. 따라서, 본 연구의 목적은 유출자료를 이용하여 지하수의 증발손실, 저류 및 재함양과 같은 비선형 특성을 고찰하는 데 있다. 한강의 상류인 평창강 유역의 유출자료를 이용하여 분석을 수행하였으며, 지하수 수지를 구성하는 주요한 요소인 지하수 유출, 증발손실, 저류, 재함양에 대해서 고찰하고 정량화하였다. 연구결과에 따라서, 식생에 의한 지하수 손실이 감쇄곡선을 편향시키는 것으로 나타났다. 또한, 계절적 강우와 잠재증발산 경향을 감쇄분석에 적용하여 월별 증발산 손실과 지하수 함양량을 정량화하여 제시하였다.

• Archives of Plastic Surgery
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• 제48권4호
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• pp.440-447
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• 2021

Background Brown adipose tissue (BAT) is a potential target for anti-obesity treatments. Previous studies have shown that BAT activation causes an acute metabolic boost and reduces adiposity. Furthermore, BAT and BAT-derived cell transplantation reportedly help treat obesity by regulating glucose and fatty acid metabolism. However, since BAT transplantation leads to whole-body weight loss, we speculated that earlier approaches cause a generalized and unnecessary fat tissue loss, including in breast and hip tissues. Methods We transplanted white adipose tissue-derived or BAT-derived preadipocytes prepared from C57BL/6 mice into one side of the inguinal fat pads of an obese mouse model (db/db mice) to examine whether it would cause fat loss at the peri-transplant site (n=5 each). The same volume of phosphate-buffered saline was injected as a control on the other side. Six weeks after transplantation, the inguinal fat pad was excised and weighed. We also measured the concentrations of glucose, triglycerides, fatty acids, and total cholesterol in the peripheral blood. Results BAT-derived preadipocytes showed abundant mitochondria and high levels of mitochondrial membrane uncoupling protein 1 expression, both in vivo and in vitro, with a remarkable reduction in weight of the inguinal fat pad after transplantation (0.17±0.12 g, P=0.043). Only free fatty acid levels tended to decrease in the BAT-transplanted group, but the difference was not significant (P=0.11). Conclusions Our results suggest that brown adipocytes drive fat degradation around the transplantation site. Thus, local transplantation of BAT-derived preadipocytes may be useful for treating obesity, as well as in cosmetic treatments.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.301-306
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• 2004

In this study, Dual servo mechanism with VCM(Voice Coil Motor) and PZT is designed for a high precision force and position control. We designed the VCM actuator and dual servo mechanism with leaf spring. VCM actuators, with their high linearity, simple structure, low weight, and high efficiency, are increasingly being used in micro-positioning applications. There are many kinds of VCM with a structure. VCM actuators are divided into two types by moving parts. One is moving magnet type and the other moving coil type. We described the properties of these two types of VCM. Design parameters of VCM are defined through the FEM simulation analysis of magnetic field and dynamic model of dual servo mechanism. These researches help to for decreasing loss in the air gap of VCM. We present dual servo mechanism is effective mechanism for a force control in hi h precision, properties of designed VCM.

• Corrosion Science and Technology
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• 제9권3호
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• pp.105-108
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• 2010

The product specification of the Continuous Hot Dip Galvanizing Line (CGL) changes and varies constantly with different customers' requirements, especially in the zinc coating weight which is from 30 to 150 g/$m^2$ on each side. Since the coating weight of zinc changes often, it is very important to reduce time spent in the transfer of target values changed for low production cost and yield loss. The No.2 CGL in China Steel Corporation (CSC) has improved the control of the air knife which is designed by Siemens VAI. CSC proposed an experiment design which is an $L_9(3^4)$ orthogonal array to find the relations between zinc coating weight and the process parameters, such as the line speed, air pressure, gap of air knife and air knife position. A non-linear regression formula was derived from the experimental results and applied in the mathematical model. A new air knife feedforward control system, which is coupled with the regression formula, the air knife control system and the process computer, is implemented into the line. The practical plant operation results have been presented to show the transfer time is obviously shortened while zinc coating weight target changing and the product rejected ratio caused by zinc coating weight out of specification is significantly reduced from 0.5% to 0.15 %.

• Structural Monitoring and Maintenance
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• 제3권2호
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• pp.175-194
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• 2016

Based on the change of traditional viscoelastic damper structure, a brand-new damper is designed to control simultaneously the translational vibration and the rotational vibration for platforms. Experimental study has been carried out on the mechanical properties of viscoelastic material and on its multi-dimensional seismic response control effect of viscoelastic damper. Three types of viscoelastic dampers with different shapes of viscoelastic material are designed to test the influence of excited frequency, strain amplitude and ambient temperature on the mechanical property parameters such as circular dissipation per unit, equivalent stiffness, loss factor and storage shear modulus. Then, shaking table tests are done on a group of single-storey platform systems containing one symmetric platform and three asymmetric platforms with different eccentric forms. Experimental results show that the simulation precision of the restoring force model is rather good for the shear deformation of viscoelastic damper and is also satisfied for the torsion deformation and combined deformations of viscoelastic damper. The shaking table tests have verified that the new-type viscoelastic damper is capable of mitigating the multi-dimensional seismic response of offshore platform.

• Smart Structures and Systems
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• 제22권2호
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• pp.139-150
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• 2018

A variable electromotive-force generator (VEG), which is a modified generator with an adjustable overlap between the rotor and the stator, is proposed to expand the operational range of a regular generator through a simple and robust active control strategy. It has a broad range of applications in hybrid vehicles, wind turbines, water turbines, and similar technologies. A mathematical model of the VEG is developed, and a novel prototype is designed and fabricated. The performance of the VEG with an active control system, which adjusts the overlap ratio based on the desired output power at different rotor speeds for a specific application, is theoretically and experimentally studied. The results show that reducing the overlap between the rotor and the stator of the generator results in reduced torque loss of the generator and an increased rotational speed of the generator rotor. A VEG can improve the fuel efficiency of hybrid vehicles; it can also expand operational ranges of wind turbines and water turbines and harness more power.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.1897-1902
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• 2008

The computer system is used in many application domains and any system error in these domains may either cause critical loss or threaten environment or human life. Though examples of these domains can be found in many areas, the system, which is used in domains for carrying passengers including rolling stocks in particular, is expected to show satisfactory operation all the time. The relay control logic, which is used in rolling stocks, is complex in hardware and occupies considerably large volume. Nevertheless, it has been used for a long time, to let the system safely operate even in the occurrence of an error in the computer system. However, the relay control logic circuit is so complex that the analysis of proper circuit operation and interlocking tends to be dependent only on the designer's experiences instead of being systematically performed. Especially, the analysis following a change, addition and deletion of a previous circuit according to the requirements from a source of demand is significantly limited. In this paper, the accuracy of relay control logic is verified by the use of properties of Petri Net model. In addition, how main circuit breaker (MCB) control circuit is modeled and analyzed by the design methodology is shown.

• Journal of the Optical Society of Korea
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• 제20권6호
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• pp.799-806
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• 2016

We present a polarization-dependent prism array film for controlling the viewing angle distribution of liquid crystal (LC) display panels without loss of light efficiency. On a directional backlight unit, our polarization-dependent prism array film, made into a stacked bilayer with a well-aligned liquid crystalline reactive mesogen (RM) layer on the UV-imprinted prism structure, can continuously control the light refraction function of the prism array by electrically switching incident polarization states of a polarization-controlling layer prepared by a twisted nematic LC mode. The viewing angle control properties of the polarization-dependent prism array film are analyzed under different prism angle and refractive index conditions of the RM layer. A simple analytic model is also presented to describe the intermediate viewing angle distributions with continuously varying applied voltages and incident polarization states.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권5호
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• pp.338-344
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• 2000

This paper proposes a field-oriented control strategy without speed sensor in overall speed range. At low speed region including zero speed, the electrical saliency which is due to the main flux saturation is used in order to estimate an instantaneous flux position. This electrical saliency can be obtained from the difference of high frequency impedance by the high frequency signal injection. This method enables the stable operation at zero speed or stator frequency even under heavily loaded condition. However, because of the high frequency signal injection the loss and noise in motor increase and the voltage margin is reduced as the motor speed increases. Therefore, this algorithm must be supplemented with the algorithm based on the electrical model of motor, which is conventionally used in the region except the low speed. This paper proposes the combination algorithm between the high frequency signal infection method and the adaptive observer, in which the rotor flux and motor speed can be simultaneously estimated by the adaptive control theory. This combination algorithm enables the stable operation of field-oriented speed control without speed sensor in overall speed range. This is verified by experimental results.

• Journal of Power Electronics
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• 제15권2호
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• pp.469-478
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• 2015

In order to promote the application of switched reluctance machines (SRM) in electric vehicles (EVs), the braking torque closed-loop control of a SRM is proposed. A hysteresis current regulator with the soft chopping mode is employed to reduce the switching frequency and switching loss. A torque estimator is designed to estimate the braking torque online and to achieve braking torque feedback. A feed-forward plus saturation compensation torque regulator is designed to decrease the dynamic response time and to improve the steady-state accuracy of the braking torque. The turn-on and turn-off angles are optimized by a genetic algorithm (GA) to reduce the braking torque ripple and to improve the braking energy feedback efficiency. Finally, a simulation model and an experimental platform are built. The simulation and experimental results demonstrate the correctness of the proposed control strategy.