• Journal of the Korean institute of surface engineering
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• v.42 no.1
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• pp.1-7
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• 2009

Resistive heating sources are widely used to prepare thin films by vapor deposition because they are cheap, and easy to install and handle in vacuum system. Graphite is one of materials used to make the resistive heating source, but until now only limited applications have been possible as it reacts easily with evaporating materials at high temperature. In this study, evaporation characteristics of aluminum have been investigated by using graphite boat thermally treated with BN powder. The employed graphite boat has been prepared by spray-coating BN power onto the cavity surface of the boat and thermal treatment with aluminum in vacuum at the temperature of more than $1400^{\circ}C$. The voltage-current characteristics as well as resistivity changes of the graphite boat have been investigated during aluminum evaporation according to the applied voltage and time. The evaporation aspect has been picturized during flash evaporation for 40 seconds based on the characterization results. The evaporation rate of the graphite boat has been compared with that of BN boat. The graphite boat showed some different characteristics compared with BN boat, in that the evaporation occurred at the last stage of flash evaporation. The film appearance according to the applied voltage has been compared, and also the reflectance of the resulting film has been investigated according to the film thickness. It has been found that the graphite boat thermally treated with BN powder can be used for aluminum evaporation without problem.

• Journal of KIISE:Software and Applications
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• v.34 no.6
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• pp.549-561
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• 2007

Vision-based scene understanding is to infer and interpret the context of a scene based on the evidences by analyzing the images. A probabilistic approach using Bayesian networks is actively researched, which is favorable for modeling and inferencing cause-and-effects. However, it is difficult to gather meaningful evidences sufficiently and design the model by human because the real situations are dynamic and uncertain. In this paper, we propose a learning method of Bayesian network that reduces the computational complexity and enhances the accuracy by searching an efficient BN structure in spite of insufficient evidences and training data. This method represents the domain knowledge as ontology and builds an efficient hierarchical BN structure under constraint rules that come from the ontology. To evaluate the proposed method, we have collected 90 images in nine types of circumstances. The result of experiments indicates that the proposed method shows good performance in the uncertain environment in spite of few evidences and it takes less time to learn.

• Journal of the Korean Magnetics Society
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• v.8 no.5
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• pp.249-254
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• 1998

In relation to the application of magnetic method to the evaluation of irradiation damage (embrittlement) changes in the magnetic parameters(hysteresis loop and Barkhausen noise) and Vickers microhardness due to neutron irradiation and heat treatment were measured and compared. In the case of irradiation $(2.3{\times}10^{19}\;n/cm^2,\; E{\ge}1\;Mev,\; 288{\circ}C)$ hysteresis loop measurements show that susceptibility decreases as coercivity increase. Saturation magnetization do not show any change. Barkhausen noise amplitude and Barkhausen noise energy have decreased while Vickers microhardness has increased. For isothermally heat treated condition of irradiated specimen at 470 $^{\circ}C$ and 540 $^{\circ}C$, Barkhausen noise energy has increased while Vickers microhardness has decreased. Results of BNE and Vickers microhardness are reversed to the results on irradiated condition. All these consistent changes in magnetic parameter and Vickers microhardness measurement, which are thought to be resulted from the interaction between irradiation-induced defects and dislocation, and magnetic domain, respectively, show a possibility that magnetic measurement may be used to the evaluation of material degradation and recovery due to neutron irradiation and heat treatment, respectively, if a relevant large database in prepared.

• Polymer(Korea)
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• v.37 no.6
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• pp.722-729
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• 2013

In order to enhance the thermal conductivity of poly(dimethyl siloxane) (PDMS), boron nitride (BN) and carbon nanotubes (CNTs) were incorporated as the thermally conductive fillers. The amount of BN was increased from 0 to 100 phr (parts per hundred rubber) and the amount of CNTs was increased from 0 to 4 phr at a fixed amount of the boron nitride (100 phr). The thermal conductivity of the composites increased with an increasing concentration of BN, but the incorporation of CNTs had only a slight effect on the enhancement of thermal conductivity. Unexpectedly, the thermal degradation of the composites was accelerated by the addition of CNTs in 100 phr BN filled PDMS. Activation energy for thermal decomposition of the composites was calculated using the Horowitz-Metzger method. The curing behavior, electrical resistivity, and mechanical properties of PDMS filled with BN and CNTs were investigated.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.6
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• pp.760-766
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• 2018

The present study investigates the effect of PMMA and BN content on microstructure, mechanical and dielectric properties of silicon nitride($Si_3N_4$) ceramics in $Y_2O_3-Al_2O_3$ additive system. The total additive content was fixed at 8 wt.% and the amount of PMMA varies from 0 to 40 wt.% and BN varies from 0 to 36 wt.%, respectively. The crystalline phases of the samples were determined by X-ray diffraction analysis. All the sintered sample shows complete transformation of ${\alpha}$ to ${\beta}-Si_3N_4$ during the sintering process indicated that the phase transformation was unaffected by the PMMA or BN content. However, the microstructure shows that the residual porosity increased with increasing PMMA and BN content. In addition, the flexural strength and the dielectric constant decrease with addition of PMMA and BN due to the residual porosity. This article provides empirical study of design parameters for $Si_3N_4$-based radome materials.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.63.1-63.1
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• 2015

The next generation electronics need to not only be smaller but also be more flexible. To meet such demands, van der Waals (vdW) heterostructures using two dimensional (2D) atomic crystals such as graphene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDCs) have been attracted intensely. In particular, for high performance of vdW heterostructures device, ultraclean interface between stacked 2D atomic crystals should be guaranteed. In this talk, I will present fabrication and characterization of the vdW field effect transistors toward performance enhancement by employing TMDCs channel, h-BN insulating layer and graphene electrode. Furthermore, it will also be introduced the characterization and surface engineering of graphene for gas molecule sensor.

• Journal of Embryo Transfer
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• v.6 no.1
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• pp.46-55
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• 1991

본연구의 목적은 흰쥐의 임신 초기에 있어서 착상의 유발에 PAF의 관련여부를 PAF의 수용체 길항제인 BN-52021d의 작용과 비교하여 결정하기 위함이다. 임신초기 각일에 점증하는 용량의 BN-52021 (체중 200g당 10$\mu$g 내지 1.25mg)이 근육내로 주사되었을때 10$\mu$g내지 250$\mu$g 용량에서는 대조구에 비하여 착상부위의 수 혹은 이것을 가진 흰쥐의 수에 대하여 현저한 영향을 미치지 아니하였으나 1.25mg투여 경우에는 현저히 감소된 효과를 나타내었다.(P<0.05). PAF(1$\mu$g) 경우에는 대조구와 비교하여 현저한 차이는 없었다. 임신 초기 각일에 BN-52021(1.25mg)과 검증하는 용량의 PAF(0.04$\mu$g 내지 1.0$\mu$g)가 동시에 투여된 경우에는 PAF의 농도가 증가함에 따라서 착상 부위의 수도 증가하는 경향이었으나 현저하지는 아니하였다. 본 실험 결과는 PAF는 흰쥐의 임신 초기 반응에 관련된다는 사실을 보여준다.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.1
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• pp.61-70
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• 2004

Generally, ceramics are very difficult-to-cut materials because of its high strength and hardness. The machining process of ceramics can be characterized by cracking and brittle fracture. In the machining of ceramics, edge chipping and crack propagation are the principal reasons to cause surface integrity deterioration. Such phenomenon can cause not only poor dimensional and geometric accuracy, but also possible failure of the ceramic parts. Ceramics can be machined with traditional method such as grinding and polishing. However, such processes are generally cost-expensive and have low material removal rate. Thus, in this paper, to overcome these problems. BN powder, which gives good cutting property, is added for the fabrication of machinable ceramics by volume of 5,10,15,20,25 and 30%. And, mechanical properties, R-curve behavior and machining tests are carried out to evaluate the machining properties of the manufactured machinable ceramics.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05b
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• pp.1381-1384
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• 2003

본 논문에서는 ad hoc 네트워크의 성능 향상을 위해서 두개의 네트워크 인터페이스를 갖는 이질적인 노드를 활용하여 구성한 계층적인 ad hoc 네트워크(HANA)를 소개한다. HANA 는 두 계층으로 구성되며, 하위계층을 구성하는 노드(TN)들은 ad hoc 네트워크의 대표적 라우팅 프로토콜인 AODV를 수행하고, 상위계층을 구성하는 백본 노드(BN)는 두개의 네트워크 인터페이스를 갖고 자동 구성(auto-configuration)을 통해서 토폴로지 등 네트워크를 초기화한다. 또한, 본 논문에서는 HANA 구조를 효율적으로 활용하기 위해서 상위계층에서 운용할 라우팅 프로토콜(Extended-AODV)을 제안한다. BN 은 하위계층의 노드들이 발생시키는 AODV 메시지를 통해서 자신이 관할하는 지역에 있는 TN노드의 정보를 얻어내며, 확장된 AODV 메시지를 통해서 BN 상호간 정보를 교환하여 Proactive한 라우팅 정보를 수집한다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.6 no.3
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• pp.197-201
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• 2006

In the implementation of a smart home, activity recognition technology using simple sensors is very important. In this paper, we propose a new activity recognition method based on Bayesian network (BN). The structure of the BN is learned by K2 algorithm and is composed of sensor nodes, activity nodes and time node whose state is quantized with reasonable interval. In the proposed method, the BN has less complexity and provides better activity recognition rate than the previous method.