• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.9
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• pp.1646-1653
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• 2008

In this paper, we propose multicarrier CDMA system using the concept of the modulation level-controlled system in order to make the system robust to the frequency selectivity and to provide a maximum data rate maintaining an acceptable transmission quality over various channel environments. This system selects higher data rate when the channel experiences the low delay spread and slow fading. On the other hand, when the fading changes very fast and the delay spread is very long, the system selects lower data rate. In both cases, the system controls the number of serial-to-parallel converted streams and the number of fed streams. This system has the fixed number of sub-carriers. So the product of tile number of serial-to-parallel converted streams and the number of fed streams is always kept constant. With the same data fed at different sub-carriers, the frequency diversity is achieved. And a RAKE receiver also is utilized to achieve path (time) diversity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5202-5207
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• 2011

A temperature control system is very important part in many industrial applications. Typical development procedures for temperature control system consist of several stages such as conceptual system design, construction of physical system, controller design based on the mathematical model for the system, and performance test. Since the mathematical model is usually obtained with the aid of system identification technique based on repeated experiments after construction of the physical system, the above procedures require very large amount of time and cost. It takes also large amount of time in the controller design and performance test procedures. In this paper, a virtual development scheme, which can predict the performance of the temperature control system prior to construction of physical system, for rapid validation of the initial system design is proposed. The effectiveness of the proposed scheme is shown by using SISO (Single Input Single Output) example.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.11
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• pp.77-84
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• 2003

This paper presents a multi-functional microstrip spital antenna that operates in dual frequency bands. Several types of beam shape can be selected by controlling the phase difference of two spiral arms with the phase shifters located on each feed line. It has a normal beam at the lower frequency band, and four different patterns at the higher frequency band: normal beam, conical beam and two types of tilted beam. The antenna exhibits more than 10% of bandwidth at each band. The antenna is fabricated with conductor backed electromagnetic absorber in order to attain unidirectional radiation pattern and confirmed the multi-functionality by measurements.

• Korean Journal of Food Science and Technology
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• v.25 no.4
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• pp.313-320
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• 1993

A sublimation model of the freeze drying process, which accounted for the removal of free water, was presented and used to study the operation conditions of freeze driers for carrot juice. It was found that the shortest drying time was obtained when the condenser temperature and chamber pressure were kept at heir lowest values and the plate temperature was controlled independently so that the scorch and melting constraints were both held throughout the drying period. The effect of sample thickness on the drying time was significant. Optimal policies were investigated experimentally in laboratory freeze dryer.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.17 no.4
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• pp.36-45
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• 2021

In this study, to improve the indoor thermal environment of the radiant floor heating system, a study was conducted on the temperature change characteristics and energy consumption according to the change of the indoor air set temperature, the supply hot water temperature and the outdoor temperature. As for the control method, the on/off control and the thermal difference proportional control method proposed through previous studies were applied. In addition, in consideration of field applicability, numerical analysis was performed for the case where the indoor air temperature sensor was affected by the wall temperature. As a result, it was found that the temperature difference proportional control method is more effective for thermal comfort and energy saving than on/off control.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.4
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• pp.472-483
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• 1997

An experimental facility consisting of two $3{\times}4.4{\times}3.8m$ rooms identical in construction is built. Each room has a control system and storage tank supplying hot water to the radiant floor heating system. The facility enables simultaneous comparision of two different control stratigies each implemented in a separate room. The operating performance of three kinds of flow control scheme is tested and compared in this study : (i) conventional on-off control based on feedback from room air temperature (ii) TPSC(two parameter switching control) (iii) TPOC(two parameter on-off control). Results show that TPSC and TPOC using room air and surface temperature sequentially as feedback signal to control hot water supply is the better temperature regulation scheme than conventional control based on feedback from only room air temperature. They are good candidates for the room with radiant floor heating system under continuous and intermittent heating mode.

• Journal of the Korea Society of Computer and Information
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• v.17 no.12
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• pp.41-47
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• 2012

Every object over $O^{\circ}K$ emits radiant energy based on its own temperature. Uncooled thermal imaging system displays the detected incident radiant energy as an image by signal processing. Recently, the uncooled thermal imaging system is applied to various areas such as medical, industrial, and military applications. Also, several researches are in progress to find new applications of the uncooled thermal imaging system. In this paper, we present effective method for controlling TEC-less detector in the uncooled thermal imaging system and also present the efficient control scheme for maximizing the accuracy of temperature measurement. The proposed scheme is to apply TEC-less and temperature detection algorithm in Uncooled thermal imaging system. In results of tests performed by using the actual chamber, we acquired images of better quality than the former system and temperature measurement accuracy was improved to less than $1^{\circ}C$.

• Journal of computational fluids engineering
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• v.12 no.3
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• pp.62-68
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• 2007

A conceptual thermal design is performed for the optical payload system of a geostationary satellite. The optical payload considered in this paper is GOCI(Geostationary Ocean Color Imager) of COMS of Korea. The radiative thermal control system is employed in order to expect a small thermal gradient in the telescope structure of GOCl. Two design margins are applied to the dedicated radiator dimensioning, and three kinds of configuration to the heater power sizing. A Monte-Carlo ray tracing method and a network analysis method are utilized to calculate radiative couplings and thermal responses respectively. At the level of conceptual design, sizing thresholds are presented for the radiator and heater on the purpose of determining the mass and power budget of the spacecraft.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.06a
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• pp.47-49
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• 2013

본 논문에서는 기존 중앙집중형 방식의 텔레프레즌스 시스템에서의 확장성 문제를 해결하기 위해서 미디어 트래픽을 분산해서 처리 할 수 있는 구조와 서비스를 확장하기 위해서 제어 플랜과 미디어 플랜을 분리하는 구조를 제안하고자 한다. 트래픽 분산 기술을 적용한 텔레프레즌스는 제어 플랜과 미디어 플랜이 분리되어 수행하기 때문에, 트래픽 분산 및 서비스 확장에 용이하며, 여러 개의 미디어 분산 처리기(DP)가 클라이언트의 트래픽을 나누어서 중계하고 전달하기 때문에, 중앙집중형 텔레프레즌스 구조에 비해서 어느 한 시스템에 많은 트래픽이 집중되지 않는다. 또한, 서버에서 클라이언트로 직접 트래픽이 전달되지 않고 미디어 분산 처리기와 미디어 분산 처리기 사이에 트래픽이 우선 전달되고, 로컬에서 트래픽이 복사되어 여러 개의 클라이언트로 전달되기 때문에 네트워크 코아망에서의 트래픽을 감소시키는 장점이 있다.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.618-620
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• 1999

웨이퍼내의 온도 균일도를 확보하는 것은 고속열처리공정장비(RTP)에 있어서 입력신호 수집을 통해 달성해야 할 중요한 제어 요소이며, 이러한 온도의 균일도를 향상시키기 위해서는 웨이퍼의 각 지점에 대한 정확한 온도 계측이 필수적으로 선행되어야 한다. 그러나 RTP의 구조적 특징과 동작특성 때문에 정확한 온도계측이 매우 어려운 면이 있다. 온도계측은 주로 고온계를 통해 이루어지는데 대류와 복사 등 여러 가지 원인에 의해서 웨이퍼내에 온도가 불균일하게 되는 경우 한정된 개수의 고온계로 온도 분포를 정확히 추정할 수 없는 한계를 지니고 있다. 본 논문에서는 RTP 공정을 열역학적으로 접근하여 단일점 온도 계측에 의한 전체 온도 분포 추정 기법을 연구하고 이것을 다중점 온도 계측에 의한 온도 분포 추정 기법으로 확장 발전시켜 웨이퍼에 상대적으로 영향을 끼치는 요소 중 예측 불가능하거나 측정 불가능한 요소까지 포함하여 최소의 측정치를 활용하여, 적절한 제어입력 유도에 필요한 형태로 웨이퍼상의 온도계측을 가능하게 하였다.