• Advances in aircraft and spacecraft science
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• 제1권1호
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• pp.15-25
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• 2014

The developed concept of smart flow control based on turbulence scale modification was applied to control a flow around a circular cylinder. The concept was realized using arrays of vortex-generators regularly spaced along a cylinder generatrix with a given step. Mechanical and thermal vortex-generators were tested, the latter having been based on the localized surface heating or plasma discharges initiated with microwave radiation near the surface. Thus depending on a particular engineering solution, flow transport properties could be modified in passive or active ways. Matched numerical and experimental investigations showed a possibility to delay flow separation and, accordingly, to improve the aerodynamic performance of blunt bodies.

• 대한기계학회논문집B
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• 제27권1호
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• pp.117-124
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• 2003

Thermal design fur satellite propulsion system has been performed. Overall design requirements and the constitution for propulsion system is described. To meet the thermal design requirements, both a primary and a redundant heater circuit, each with two thermostats placed in series, will protect each hydrazine-wetted components, even if one heater circuit fails to operate. Heater power is turned off if any one of these thermostats is opened at its higher setpoint. Thus, even if one thermostat is failed closed, the second thermostat will turn off the heater. All such components shall be insulated with MLI. Propulsion heater sizing based on the constant worst cold case condition is conducted through thermal analysis. All heaters selected fur propulsion components operate to prevent propellant freezing satisfying the thermal requirements for the propulsion subsystem over the worst case average voltage, i.e. 25 volts.

• 한국항공우주학회지
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• 제38권12호
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• pp.1232-1239
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• 2010

(주)쎄트렉아이는 지구관측위성의 주 탑재체로 사용될 고해상도 전자광학카메라, EOS-C Ver.3.0을 개발 중이다. EOS-C Ver.3.0은 현재 운용중인 DubaiSat-1의 주 탑재체인 EOS-C Ver.2.0 개발 경험을 바탕으로 능동 열제어 방식과 수동 열제어 방식을 적절하게 혼용하여 보다 향상된 성능을 갖도록 설계되었다. 설계를 바탕으로 STM을 개발하여 인증(qualification) 수준의 열진공 시험을 수행하여 설계 여유(design margin)를 확인하였다. 또한 열평형 시험 결과를 이용하여 열제어계 설계에 사용한 열-수치 모델에 대한 검증 작업을 수행하였으며, 열-수치 모델이 실제 열적 특성을 잘 모사하고 있음을 확인하였다.

• 전기전자학회논문지
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• 제17권4호
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• pp.393-397
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• 2013

This paper introduces the T/RX combined compact active channel module which is a key unit of the active phased array antenna(APAA) system. This module is mainly compoased of two parts for TX and RX fabricated on both sides of the active module for size reduction. The TX-part is primarily composed of a 3-stage amplifier, a microstrip phase shifter, a thermal compensation and a power detection circuit. The RX-part is composed of LNAs a microstrip phase shifter and BPFs for TX power rejection. Using the proposed design structure we can realized a compact active channel module having high performance.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.77-82
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• 2001

Thermal design for KOMPSAT-2 propulsion system has been performed. Overall design requirements and the constitution for propulsion system is described. To meet the thermal design requirements, both a primary and a redundant heater circuit, each with two thermostats placed in series, will protect each hydrazine-wetted components, even if one heater circuit fails to operate. Heater power is turned off if any one of these thermostats is opened at its higher setpoint. Thus, even if one thermostat is failed closed, the second thermostat will turn off the heater. All such components shall be insulated with MLI. Propulsion heater sizing based on the constant worst cold case condition is conducted through thermal analysis. All heaters selected for propulsion components operate to prevent propellant freezing satisfying the thermal requirements for the propulsion subsystem over the worst case average voltage, i.e. 25 volts.

• 전기전자학회논문지
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• 제22권3호
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• pp.842-845
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• 2018

본 논문에서는 열전에너지 하베스팅에 의해 구동되는 센서 회로를 저전력으로 동작시킬 수 있는 방법을 제안하였다. 본 논문에서 사용되는 열전소자를 이용하면 에너지 하베스팅 회로에서 8uA의 전류를 얻을 수 있다. 그러나 구동하려고 하는 센서의 전류 소비는 이보다 훨씬 크기 때문에, 본 논문에서는 하드웨어 방법으로 power gating scheme을 이용한 저전력 구동과 소프트웨어적으로 active/sleep control scheme을 이용한 저전력 구동 방법을 센서 회로에 적용하여 센서 회로의 전류 소비를 감소시킬 수 있음을 보였다. 먼저 하드웨어 power gating scheme을 사용할 때에는 파워 게이트의 Toff/Ton의 비를 22보다 더 크게 하면, 센서 회로의 전류 소비가 8uA 이하로 줄어드는 것을 확인하였다. 또한 소프트웨어 기반의 active/sleep control scheme에 의한 저전력 구동에서는 Tslp/Tact의 비를 3 이상으로 설정해주면 전류 소비를 8uA 이하로 줄일 수 있음을 확인하였다. 본 논문에서의 결과는 열전에너지 하베스팅에 의해서 구동되는 다양한 센서 회로 설계 및 구현에 도움이 될 것으로 생각된다.

• 대한기계학회논문집B
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• 제27권10호
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• pp.1377-1384
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• 2003

An analysis has been performed for active thermal control of the KOMPSAT monopropellant rocket engine assembly, i.e., dual thruster module(DTM). The main efforts of this work have been directed at determining proper heater sizes for propellant valves and catalyst beds necessary to maintain their temperatures within specified temperature ranges under KOMPSAT environment and operational conditions. The TAS incorporated with TRASYS thermal radiation analyzer was used to establish a complete heat transfer model which allows to predict the DTM temperature as a function of time. The thermal analysis has been performed in transient mode to verify the appropriate power for catalyst bed heaters necessary to increase catalyst bed temperature to the required value within a specified period of time. Similar analysis has been executed to validate the heater power for the thermostatically controlled primary and redundant heater circuits used to prevent hydrazine freezing, i.e., single fault. Moreover the effect of the radiative property of thermal control coating of heat shield was examined. Thruster firing condition was also simulated for the heat soakback condition. As a consequence, all thermal analysis results for DTM satisfactorily met the thermal requirements for the KOMPSAT DTM under the worst case average voltage, i.e. 25 volt.

• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.274-284
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• 2016

The increasing penetration of distributed energy resources on the distribution networks have brought a number of technical impacts where voltage and thermal variations have been identified as the dominant effects. Active network management in distribution networks aims to integrate distributed energy resources with flexible network management so that distributed energy resources are organized to make better use of existing capacity and infrastructure. This paper propose active solutions which aims to solve the voltage and thermal issues in a distributed manner utilizing a collaborative approach. The proposed algorithms have been fully tested on a distribution network with distributed generation units.

• Structural Engineering and Mechanics
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• 제44권2호
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• pp.127-138
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• 2012

The composite materials may be exposed to environmental (thermal or hygral or both) condition during their service life. The effect of environmental condition is usually adverse from the point of view of design of composite structures. In the present research study the effect of hygrothermal condition on the design of laminated composite structures is investigated. The active fiber composite (AFC) which may be utilized as actuator or sensor is considered in the present analysis. The sensor layer is used to sense the level of response of the composite structures. The sensed voltage is fed back to the actuator through the controller. In this study both displacement and velocity feedback controllers are employed to reduce the response of the composite laminate within acceptable limit. The Newmark direct time integration scheme is employed along with modal superposition method to improve the computational efficiency. It is observed from the numerical study that the laminated composite structures become weak in the presence of hygrothermal load. The response of the structure can be brought to the acceptable level once the AFC layer is activated through the feedback loop.

• 한국정밀공학회지
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• 제29권4호
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• pp.367-372
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• 2012

The biggest factors that lower the machining accuracy are thermal deformation and chatter vibration. In this article, we introduce the study case of technology that can automatically compensate the errors of these factors of a machine during processing on the machine tool's CNC(Computerized Numerical Controller) in real time. This study is related to the detection and compensation of thermal deformation and chatter vibration that can compensate for faster and produce processed goods with more precision by autonomous compensation. In addition, this study is related to the active control of vibration during machining, monitoring of cutting force and auto recognition of machining axes origin. Thus, we attempt to introduce the related contents of the development we have made in this article.