• 조명전기설비학회논문지
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• 제30권2호
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• pp.71-77
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• 2016

The dielectric barrier discharge (DBD) has low efficiency due to about 70% input power is consumed as thermal energy in the discharge space. However, because of the usage of DBD ozone generator is easier than other methods. The DBD ozone generator has been widely applied for high concentration ozone generation in the industrial application. But, the low-capacity compact DBD ozone generator is not applied so far. Therefore, the DBD ozone generator is necessary to improve ozone production efficiency and reduce the capacity. In this paper, the stainless steel pipe inner electrode was designed with hall type and screw type to improve the ozone production yield. The manufactured two inner electrodes were experimented with normal type for comparison of the discharge characteristics and the ozone generating characteristics. As the experimental results, the discharge current effective value of designed inner electrodes with hall type and screw type are higher than the normal type, due to unequal electric field is formed at the boundary. However, the difference of designed and original electrodes is less than 0.1mA that has no effect on the discharge characteristic. On the other hand, the screw type inner electrode increased higher than original model about 7 times when the flow rate of the oxygen source gas was increased from $0.6{\ell}/min$ to $1.0{\ell}/min$ The reason was assumed by the flow rate of the raw gas through the inner electrode was became fast that has a cooling effect. The designed hall type and screw type inner electrodes have shown good performances in ozone generation and ozone production that better than normal type in the same electrode surface area.

• Geomechanics and Engineering
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• 제16권4호
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• pp.385-397
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• 2018

This study evaluates the interfacial properties of composite specimens consisting of shotcrete and sprayed waterproofing membrane. Two different membrane prototypes were first produced and tested for their waterproofing ability. Then composite specimens were prepared and their interfacial properties assessed in direct shear and uniaxial compression tests. The direct shear test showed the peak shear strength and shear stiffness of the composites' interface decreased as the membrane layer became thicker. The shear stiffness, a key input parameter for numerical analysis, was estimated to be 0.32-1.74 GPa/m. Shear stress transfer at the interface between the shotcrete and membrane clearly emerged when measuring peak shear strengths (1-3 MPa) under given normal stress conditions of 0.3-1.5 MPa. The failure mechanism was predominantly shear failure at the interface in most composite specimens, and shear failure in the membranes. The uniaxial compression test yielded normal stiffness values for the composite specimens of 5-24 GPa/m. The composite specimens appeared to fail by the compressive force forming transverse tension cracks, mainly around the shotcrete surface perpendicular to the membrane layer. Even though the composite specimens had strength and stiffness values sufficient for shear stress transfer at the interfaces of the two shotcrete layers and the membrane, the sprayed waterproofing membrane should be as thin as possible whilst ensuring waterproofing so as to obtain higher strength and stiffness at the interface.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2017년도 춘계공동학술대회
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• pp.135-135
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• 2017

Greenhouse have been developed to provide the plants with good environmental conditions for cultivation crop, two major factors of which are the inside air temperature and humidity. The inside temperature are influenced by the heating systems, ventilators and for systems among others, which in turn are geverned by some type of controller. Likewise, humidity environment is the result of complex mass exchanges between the inside air and the several elements of the greenhouse and the outside boundaries. Most of the existing models are based on the energy balance method and heat balance equation for modelling the heat and mass fluxes and generating dynamic elements. However, greenhouse are classified as complex system, and need to make a sophisticated modeling. Furthermore, there is a difficulty in using classical control methods for complex process system due to the process are non linear and multi-output(MIMO) systems. In order to predict the time evolution of conditions in certain greenhouse as a function, we present here to use of recurrent neural networks(RNN) which has been used to implement the direct dynamics of the inside temperature and inside humidity of greenhouse. For the training, we used algorithm of a backpropagation Through Time (BPTT). Because the environmental parameters are shared by all time steps in the network, the gradient at each output depends not only on the calculations of the current time step, but also the previous time steps. The training data was emulated to 13 input variables during March 1 to 7, and the model was tested with database file of March 8. The RMSE of results of the temperature modeling was $0.976^{\circ}C$, and the RMSE of humidity simulation was 4.11%, which will be given to prove the performance of RNN in prediction of the greenhouse environment.

• 전자공학회논문지 IE
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• 제47권2호
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• pp.13-20
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• 2010

본 논문에서는 PWM을 활용한 전류모드 고효율 PWM DC-DC 전원변환 집적회로(Integrated Circuit)를 설계하였다. IC에 인가할 수 있는 최대 전압은 40[V]이며 입력 전압이 DC 2.8[V]~330[V]일 때 출력 전압을 이 보다 높은 전압으로 바꿀 수 있는 한편 외부 저항비나 트랜스의 권선비를 조정하여 원하는 DC 전압을 만들어 낼 수 있다. 출력전압의 3[%] 오차를 유지하면서 3[A] 이상의 전류를 부하에 공급할 수 있도록 구현하였다. 제작공정은 0.6[um], 2P_2M CMOS 공정을 사용하였다. 전원전압이 3.6[V]일 때 대기상태에서 소비전력은 1[mW]이하이고 최대 전력변환 효율은 약 86[%]이다. 칩 사이즈는 2100*2000[um2]이며, 칩을 소형패키지에 내장하여 조립하였기 때문에 휴대형기기나 소형 전자기기에 적용이 편리하게 되어 있다.

• 전력전자학회논문지
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• 제11권3호
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• pp.193-200
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• 2006

본 논문에서는 효율을 개선하고 인버터 스위칭 주파수를 줄이기 위하여 벅-부스트 형식을 기반의 PWM 전류형 인버터를 내장한 6-pulse-shift 컨버터 구조를 제안한다. 이는 에너지 저장장치 없이 태양광 시스템과 전력계통 사이를 연계하는 시스템으로 사용할 수 있다. 제안된 회로는 초퍼로 동작하는 6개의 전류형 벅-부스트 컨버터와 교류 출력의 극성을 결정하는 한 개의 전파 브리지 인버터로 구성된다. 따라서 제안된 인버터는 스위칭 손실을 줄이고 단위 역률운전을 구현하는 장점을 갖는다. 본 논문에서 이론적인 배경을 논하고 TMS320F2812를 사용하여 구현된 인버터 시작품에 대한 입출력 특성을 실험적으로 입증하였다.

• 한국광학회지
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• 제14권4호
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• pp.383-391
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• 2003

개인의 신원정보 보호를 위하여 새로운 광 정보보호 시스템을 제안하였다. 개인 신원정보의 확인과 인증을 위하여 얼굴영상과 개인식별번호로 구성된 신원정보를 사용하였다. 영상 암호화는 4-f 광상관기의 입력과 푸리에영역에서 랜덤위상패턴을 사용하는 위상암호화 기술을 사용하였다. 그렇지만 암호화된 영상을 복원하는 과정에서 개인의 신원정보가 유출될 가능성이 있다. 이에 대처하기 위하여 신원확인 과정에서 영상을 복원하지 않고 암호화된 영상을 그대로 사용하였다. 암호화된 개인식별번호는 제안된 MMACE_p 필터를 사용하여 분류ㆍ인식하였고, 개인정보의 인증은 OWMF를 사용하여 얼굴영상의 상관치를 구하여 확인하였다. 제안된 MMACE_p 필터는 10개의 암호화된 숫자를 한꺼번에 인식할 수 있도록 4개의 MACE_p필터를 다중화하여 합성하였고, OWMF는 얼굴영상의 분리인식 능력과 SNR을 향상시킬 수 있도록 하였다. 컴퓨터 시뮤레이션을 통하여 제안된 정보보호기술이 개인신원정보 보호에 적용될 수 있음을 보였다.

• 터널과지하공간
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• 제2권1호
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• pp.95-101
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• 1992

Norwegian technology related to preinvestigations, planning, design and construction of large underground caverns is wellknown worldwide. However, so far this technology is only slightly verified through scientiffic reports and documentation. The "Rock cavern stadium" research program is an interdisciplinary program related to the ongoing building and future use of Gjovik Olympic Subsite which is the largest cavern in the world for public purposes with a span of 61 meters and a height of 25 meters. The estimated budget for this program is about USD 4 million which is made possible through grants from The Royal Norwegian Council for Scientific and Industrial Research as well as through contributions from Norwegian and Swedish companies that are participating. The program is carried out in collaboration with The Foundation for Scientific and Industrial Research at the Norwegian Institute of Technology. The Norwegian Geotechnical Institute and The Eastern Norway Research Center. The research program will continue until the end of 1994 to ensure that input comes from a full period of use in this stadium with different activities like exhibitions, conferences, concerts etc being included as verification through full-scale measurements and observations. The research program has five subtasks. Three of these are related to subjects like Energy consumption. HVAC installations. Fire safety design, Engineering geology and Rock mechanics, Environmental aspects. The fourth subtask is concerned with the collection of basic data, results and experience from these three subtasks to provide a basis for national Norwegian guidelines related to this interdisciplinary subject area. The guidelines will first be presented as a manual for planning and engineering purposes. The realization of this research program is a unique opportunity to enhance the expertise that has been acquired from this cavern stadium. By involving research in this extraordinary project from the excavation and building phase to its subsequent use. this will give the participants know-how and expertise which is very much in demand internationally. The coordination of the international activities between the participants as well as preparation of participations and presentations in international conferences and symposium are included in the fifth task of this national research program.

• 한국생산제조학회지
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• 제22권1호
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• pp.22-28
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• 2013

Robotic GMA (Gas Metal Arc) welding process is one of widely acceptable metal joining process. The heat and mass inputs are coupled and transferred by the weld arc to the molten weld pool and by the molten metal that is being transferred to the weld pool. The amount and distribution of the input energy are basically controlled by the obvious and careful choices of welding process parameters in order to accomplish the optimal bead geometry and the desired quality of the weldment. To make effective use of automated and robotic GMA welding, it is imperative to predict online faults for bead geometry and welding quality with respect to welding parameters, applicable to all welding positions and covering a wide range of material thickness. MD (Mahalanobis Distance) technique was employed for investigating and modeling the GMA welding process and significance test techniques were applied for the interpretation of the experimental data. To successfully accomplish this objective, two sets of experiment were performed with different welding parameters; the welded samples from SM 490A steel flats. First, a set of weldments without any faults were generated in a number of repeated sessions in order to be used as references. The experimental results of current and voltage waveforms were used to predict the magnitude of bead geometry and welding quality, and to establish the relationships between weld process parameters and online welding faults. Statistical models developed from experimental results which can be used to quantify the welding quality with respect to process parameters in order to achieve the desired bead geometry based on weld quality criteria.

• 자원환경지질
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• 제45권2호
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• pp.195-204
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• 2012

미생물에 의한 광물합성은 지화학적 순환 및 미생물의 독성에 대한 저항기작을 위해 주로 연구되어져 왔으나 본 논문에서는 NanoFermentation을 통한 경제적, 친환경적, 저에너지, 대량생산이 가능한 나노입자 크기의 자철석 합성연구를 소개하고 또한 초상자성(Superparamagnetism)과 준강자성(Ferrimagnetism)을 결정짓는 입자크기에 대한 조절인자를 살펴보고자 한다. NanoFermentation을 통한 자철석의 합성 시 입자 크기의 조절 인자는 선택된 미생물 종 및 배양 온도, 배양액의 화학적 조성, 배양기간, 치환된 원소의 조성 및 함량, 자철석 전조물질(Precursor)의 형태, 반응 부피의 증가 및 자철석 전조물질의 농도와 같은 조건들의 조합에 의해 결정되어지며 주로 핵형성 및 결정 성장의 균형에 의해 조절된다. 생광물화 작용을 통한 무기재료의 합성 연구는 앞서 언급한 지표에서의 원소의 순환 및 미생물 생리학적 측면뿐만 아니라 최종 산물인 나노입자의 대량 생산을 통해 재료학적 응용 분야에도 많은 파급 효과가 예상된다.

• 한국대기환경학회지
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• 제30권6호
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• pp.577-585
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• 2014

A series of experiments using atmospheric-pressure non-thermal plasma coupled with transition metal catalysts were performed to remove ethylene from agricultural storage facilities. The non-thermal plasma was created by dielectric barrier discharge, which was in direct contact with the catalyst pellets. The transition metals such as Ag and $V_2O_5$ were supported on ${\gamma}-Al_2O_3$. The effect of catalyst type, specific input energy (SIE) and oxygen content on the removal of ethylene was examined to understand the behavior of the hybrid plasma-catalytic reactor system. With the other parameters kept constant, the plasma-catalytic activity for the removal of ethylene was in order of $V_2O_5/{\gamma}-Al_2O_3$ > $Ag/{\gamma}-Al_2O_3$ > ${\gamma}-Al_2O_3$ from high to low. Interestingly, the rate of plasma-catalytic ozone generation was in order of $V_2O_5/{\gamma}-Al_2O_3$ > ${\gamma}-Al_2O_3$ > $Ag/{\gamma}-Al_2O_3$, implying that the catalyst activation mechanisms by plasma are different for different catalysts. The results obtained by varying the oxygen content indicated that nitrogen-derived reactive species dominated the removal of ethylene under oxygen-lean condition, while ozone and oxygen atoms were mainly involved in the removal under oxygen-rich condition. When the plasma was coupled with $V_2O_5/{\gamma}-Al_2O_3$, nearly complete removal of ethylene was achieved at oxygen contents higher than 5% by volume (inlet ethylene: 250 ppm; gas flow rate: $1.0Lmin^{-1}$; SIE: ${\sim}355JL^{-1}$).