• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.264-265
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• 2010

최근, nanorod나 nanowire와 같은 1차원의 나노구조가 나노디바이스로 각광을 받고 있다. [1] 특히 InN는 3족 질화물 반도체 중 가장 작은 밴드갭 에너지와 뛰어난 수송 특성을 가지고 있어 나노디바이스로의 응용에 적합한 물질이다. [2] 그러나 InN는 큰 평형증기압을 가지므로 쉽게 인듐과 질소로 분해되는 특성이 있어 나노구조로의 성장이 쉽지 않음이 알려져 있다. [3] 최근 연구결과에 따르면, InN 나노구조는 금속 catalyst를 사용한 방법이나, 기판 위 패턴을 이용하여 성장하는 방법, 염소를 사용한 방법이 널리 쓰이고 있다. [4,5,6] 그러나 이 방법들은 의도치 않은 불순물의 원인이 되거나 다른 추가적인 과정을 필요로 한다는 문제점도 일부 가지고 있다. 본 연구에서는 catalyst-free 유기 금속 화학 증착법 (MOCVD)를 이용하여 $Al_2O_3$ (0001)면 위에 InN nanostructure를 성장하였다. InN nanostructure 성장 시 트리메틸인듐(TMIn)과 암모니아($NH_3$) 를 전구체로 사용하였으며, 캐리어 가스로는 질소를 사용하였다. 또한 모든 샘플의 성장시간은 60분으로 고정하였으나, 성장 시 온도의 의존성을 보기 위해 $680-710^{\circ}C$ 의 온도범위에서 성장을 진행하였다. 그 결과 InN는 본 실험에서 적용된 성장온도범위 내에서 온도가 증가함에 따라 초기에는 columnar구조로 성장된 박막의 형태에서 wall이 배열된 형태로 변화하며 결국 $710^{\circ}C$ 의 온도에서 nanorod로 성장하게 된다. 성장된 InN의 나노구조는 X-선 회절 측정법, 주사 전자 현미경 그리고 투과 전자 현미경을 이용하여 각각의 구조적 특성을 분석하였다. X-선 회절 측정법과 주사 전자 현미경을 통한 분석결과에서는 이들 nanorods가 대부분 c 방향으로 수직하게 정렬되어 있음을 확인 할 수 있었다. 또한, $690^{\circ}C$ 에서 60분간 성장된 InN의 wall 구조의 두께는 200 nm, 길이는 $2-2.5\;{\mu}m$로 관찰되었으며, $710^{\circ}C$에서 60분간 성장된 InN nanorod의 지름은 150 nm, 길이는 $3\;{\mu}m$ 정도로 관찰되었다. 이를 통하여 볼 때 성장 온도가 InN의 나노구조 형성 시 표면의 모폴로지변화에 중요한 변수로 작용함을 알 수 있다. 본 발표에서는 이러한 표면 형상 및 구조 변화가 성장온도에 따른 관계성을 가짐을 InN의 분해와 성장의 경쟁적인 관계에 의해 논의할 것이다.

• Smart Media Journal
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• v.5 no.4
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• pp.75-82
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• 2016

Although Korea's economic and domestic automobile market through the change of road environment are growth, the traffic accident rate has also increased, and the casualties is at a serious level. For this reason, the government is establishing and promoting policies to open traffic accident data and solve problems. In this paper, describe the method of predicting traffic accidents by eliminating the class imbalance using the traffic accident data and constructing the Hybrid Model. Using the original traffic accident data and the sampled data as learning data which use FP-Growth algorithm it learn patterns associated with traffic accident injury severity. Accordingly, In this paper purpose a method for predicting the severity of a victim of a traffic accident by analyzing the association patterns of two learning data, we can extract the same related patterns, when a decision tree and multinomial logistic regression analysis are performed, a hybrid model is constructed by assigning weights to related attributes.

• Journal of Korea Society of Industrial Information Systems
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• v.7 no.5
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• pp.39-48
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• 2002

long with the rapid spread of the Internet, a new class of commercial applications which process transactions with respect to electronic dictionaries become popular Typical examples are Internet search engines. In this paper, we present a new approach to achieving high performance electronic dictionaries. Different from the conventional approach which use Trie data structures for the implementation of electronic dictionaries, our approach used multi-dimensional binary trees. In this paper, we present the implementation of our electronic dictionary ED-MBT(Electronic Dictionary based on Multidimensional Binary Tree). Exhaustive performance study is also presented to assess the performance impact of ED-MBT on the real world applications.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.941-943
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• 1998

Exploitation of equipment with cross linked polyethylene (XLPE) insulation requires its condition monitoring and diagnostic. Traditionally diagnostics of insulation is carried out by means of partial discharge detection. Many researchers have developed a lot of methods to identify the defect by the PD form. However, such identification of a defect, for example, void, inclusion or treeing, does not say about its danger from a point of view of full insulation gap breakdown and insulation construction failure. The information about the form and size of formed upon high voltage treeing is necessary for prediction of the remained resource of XLPE insulation. For this purpose we carry out experimental research for determination of the dependencies between PD characteristics in XLPE upon time and three dimension PD patterns of corresponding treeing. The investigations were carried out by means of electrical measurement of PD current and simultaneous optical recording of treeing image. Test results show that the PD patterns can be applied for detecting tree growth well.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.293-296
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• 1998

Surface electrical conduction in insulator is most important factor to assess the insulation performances of outdoor insulating materials. In this paper, contamination performance of the widely used materials for outdoor insulator - porcelain, EPDM, Silicone rubber - were discussed by measuring properties of average leakage current and scintillation discharge pulses under artificial contamination conditions. The artificial contaminations used were deionized distilled water fog, 0.5wt% NaCl salt fog of light pollution and 2wt% NaCl salt fog of medium pollution. The average leakage current was appeared linearly with applied voltage at dry and clean surface condition. The magnitude of leakage current was almost same at different kinds of samples. In case of deionized distilled water fog, the characteristics of leakage current and applied voltage was most different to that in case of dry and clean condition. In case of salt fog pollution condition, The leakage current was increased above critical voltage. The scintillation discharges were also activated at the level. the leakage current and scintillation discharges were increased with increasing pollution degree. The resistance to pollution properties of silicone rubber appeared excellent among them.

• Journal of Yeungnam Medical Science
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• v.7 no.1
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• pp.191-195
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• 1990

A case of sporotrichosis misdiagnosed as lupus vulgaris was presented. A 56-year-old woman had bean to pea sized, nontender pustules and a hypertrophic-sear-like nodule on the right thigh. She denied any trauma before the lesions developed. Histopathologic findings from the lesion showed tuberculosis-like granulomatous changes. And she was diagnosed as lupus vuagaris. She also had pulmonary tuberculosis and had been treated with antituberculous drugs for 1 year. But skin lesions was not cleared. We suspected the lesions as one of deep mycoses and could confirm sporotrichosis by mycologic studies. They showed characteristic gross colonies and microscopic findings of Sporothrix schenckii.

• The KIPS Transactions:PartD
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• v.18D no.3
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• pp.169-178
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• 2011

Recently, data sharing between enterprises or organizations is required matter for task cooperation. In this process, when the enterprise opens its database to the affiliates, it can be occurred to problem leaked sensitive information. To resolve this problem it is needed to hide sensitive information from the database. Previous research hiding sensitive information applied different heuristic algorithms to maintain quality of the database. But there have been few studies analyzing the effects on the items modified during the hiding process and trying to minimize the hided items. This paper suggests eFP-Tree(Extended Frequent Pattern Tree) based FP-Tree(Frequent Pattern Tree) to hide sensitive frequent itemsets. Node formation of eFP-Tree uses border to minimize impacts of non sensitive frequent itemsets in hiding process, by organizing all transaction, sensitive and border information differently to before. As a result to apply eFP-Tree to the example transaction database, the lost items were less than 10%, proving it is more effective than the existing algorithm and maintain the quality of database to the optimal.

• Archives of design research
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• v.13 no.3
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• pp.221-234
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• 2000

This thesis aims to study the space concept of the constructive mode in the work space of the postmodernism artists since 1970s. According to the changing view of the world artists, they are searching for the characteristics of having the parameter of formative organization on how they are related to the constructive system which represents the work styles. First, this study searches for the theoretical approaches of the constructive system and parameters that were studied by Le Corbusier - the module concept as the meaning of order system being used for the basic formative construction Second, when it is regarded as a formative construction in making art as the'principles of organization'(the law of living form), which was defined by Suzanne Langer in the formative theory as the organized structure shown in growth structure in mu and ecological system, the principles governing the module rules were arthmetically analysed art-work space through the dynamic symmetry of Jay Hambidge. Therefore, this study shows the principles working on the parameters for new formative organization as follows: First, the module in the work space should be designed and built from the dynamic symmetry. Second, the module should satisfy the human needs that it must be acceptable, efficient, flexible, which are the necessary and sufficient condition for the dynamic symmetry. Third, the dynamic symmetry which has the principle of Reciprocity and the principle of Complement as its primary construction principle has the common properties and the reciprocity in the construction of the work space and when it has the self similarity, it segments organically the total space without damaging the continuum.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.4
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• pp.645-650
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• 1998

Alumina- and yttria-coated SiC powder was prepared by the surface-induced precipitation method, and sintered properties of silicon carbide prepared from this powder were investigated. After a well dispersion of SiC powders in the aqueous solution of $Al_2(SO_4)_3$ and $Y_2(SO_4)_3$, the mixed precursors of aluminum hydroxide, aluminum carbonate, yttrium hydroxide, and yttrium carbonate were precipitated on the surfaces of SiC particles through the hydrolysis reaction of urea. SiC specimens with alumina and yttria exhibit, 97.8% of theoretical density after the sintering at $1900^{\circ}C$ for 2 hrs. During annealing at $2000^{\circ}C$, $\beta$longrightarrow$\alpha$ phase transformation of SiC had taken place and resulted with a rodlike microstructure. Toughness of sintered SiC was enhanced by crack deflection around the rodlike grains. In case of annealing less than that of 3 hr, the fracture toughness of SiC was slightly improved with increasing the amount of sintering aid. However, annealed specimens for a long time showed constant fracture toughness even though the amount of sintering aid increased. It is resulted that the main factor for toughening in annealed SiC for a long time is the pullout effect of rodlike grains during the propagation of cracks, and the amount of sintering aids is less effective on the fracture toughness of SiC.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.5
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• pp.255-264
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• 2013

Cobalt aluminate ($CoAl_2O_4$) is a highly stable pigment with excellent resistance to light, weather, etc., which has resulted in widespread use as a ceramic pigment. Due to the unique optical characteristics, $CoAl_2O_4$ is generally used as a coloring agent to decorate porcelain products, glass, paints and plastics. Here, $CoAl_2O_4$ pigments were synthesized by polymerized complex method and solid state reaction. Then $CoAl_2O_4$ pigment were grinded using the attrition milling with 1 mm size zirconia ball for 3 hours. The attrition milling process was performed at the constant speed of 800 rpm and ball to powder weight ratio (BPR) was 100 : 1. The characteristics of synthesized pigment were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), particle size analyser (PSA) and CIE $L^*a^*b^*$. The XRD patterns of $CoAl_2O_4$ show single phase spinel structure. The particle size of $CoAl_2O_4$ measured by FE-SEM, TEM and PSA analysis was in the range of 100~200 nm. The blue color of obtained $CoAl_2O_4$ pigments could be confirmed through CIE $L^*a^*b^*$ measurement.