• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.186-186
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• 2011

태양전지의 효율을 증가시키기 위해서는 표면에서의 Fresnel 반사를 줄여 입사된 빛이 흡수층까지 잘 도달되도록 해야 한다. 그러나 결정질 실리콘의 경우, 굴절률이 높아 32% 이상의 표면반사율을 보이고 있어, 실리콘 태양전지 표면에 단일 또는 다중 박막의 무반사 코팅을 통해 반사율을 낮추는 방법이 널리 사용 되어 오고 있었다. 하지만, 이와 같은 코팅 방법은 열적팽창 불일치, 물질 선택의 어려움뿐만 아니라 낮은 반사율을 포함하는 파장 및 빛의 입사각 영역의 제한 등 여러 문제점을 지니고 있다. 이러한 문제점을 보완하기 위해, 표면에 서브파장의 주기를 갖는 나노구조(subwavelength structure, SWS)의 형성에 관한 연구가 활발히 진행되고 있다. 습식 식각보다 건식 식각을 이용한 SWS 제작 방법이 표면 profile을 제어하기 용이하나 패턴 형성을 위해 식각 마스크가 필요하다. 최근, 복잡하고 고가의 전자빔 또는 나노임프린트를 이용한 패턴 형성보다, 간단/저렴하며 대면적 제작이 용이한 금속 나노입자 마스크를 이용한 SWS의 제작에 대한 연구가 활발히 진행되고 있다. 또한 SWS의 무반사 특성은 표면 profile에 따라 크게 영향을 받는다. 따라서 본 실험에서는 열적 응집현상에 의해 형성되는 self-assembled Pt 나노입자 식각 마스크 및 $SiCl_4$가스를 사용한 유도결합 플라즈마(inductively coupled plasma, ICP) 장비를 이용하여 무반사 실리콘 SWS를 제작하였으며, SWS 표면 profile에 따른 구조적 및 무반사 특성을 조사하기 위해 다양한 공정조건을 변화시켰다. 실리콘 기판 위의 Pt 박막은 전자빔 증착(e-beaml evaporation)법을 사용하였고, 급속 열처리(RTA)를 통해 Pt 나노입자의 식각 마스크를 형성시켰다. Pt 나노입자들의 패턴 및 제작된 무반사 실리콘 SWS의 식각 profile은 scanning electron microscope를 사용하여 관찰하였으며, UV-VIR-NIR spectrophotometer를 사용하여 350~1050 nm 파장 영역에서의 반사율을 측정하였다. ICP 식각 조건을 변화시켜 5% 이하의 낮은 반사율을 갖는 높이가 높고 쐐기 형태의 실리콘 SWS를 도출하였다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.49 no.3
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• pp.74-80
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• 2012

In resolution-constrained quantization, the size of Voronoi cell varies depending on probability density function of the input data, which causes large amount of distortion outliers. We propose a vector quantization method that reduces distortion outliers by combining the generalized Lloyd algorithm (GLA) and the cell-size constrained vector quantization (CCVQ) scheme. The training data are divided into the inside and outside regions according to the size of Voronoi cell, and consequently CCVQ and GLA are applied to each region, respectively. As CCVQ is applied to the densely populated region of the source instead of GLA, the number of centroids for the outside region can be increased such that distortion outliers can be decreased. In real-world environment, source mismatch between training and test data is inevitable. For the source mismatch case, the proposed algorithm improves performance in terms of average distortion and distortion outliers.

• Journal of KIISE:Software and Applications
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• v.36 no.10
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• pp.861-873
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• 2009

There are many reasons that fail to get appropriate information in information retrieval. Allomorph is one of the reasons for search failure due to keyword mismatch. This research proposes a method to construct alternative word candidates automatically in order to minimize search failure due to keyword mismatch. Assuming that two words have similar meaning if they have similar co-occurrence words, the proposed method uses the concept of concentration, association word set, cosine similarity between association word sets and a filtering technique using confidence. Performance of the proposed method is evaluated using a manually extracted alternative list. Evaluation results show that the proposed method outperforms the context window overlapping in precision and recall.

• Journal of Korea Multimedia Society
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• v.14 no.3
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• pp.433-439
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• 2011

The positioning system based on wireless AP collects AP information distributed in the real world, stores it into database, and measures the position objects by comparing with searched AP information. The existing fingerprinting method is a probabilistic modeling method that acquires much of the data collected from one location upon database composition, and stores the average of the data for the sake of use it in positioning objects. Using the average value, however, may cause the probability of errors Such errors are fatal weaknesses for services based on the accurate position. This paper described the characteristics and problems of the previously used wireless AP positioning system, and proposed a method of using the AP DB and an MSS mechanism for outdoor positioning in order to solve the aforementioned problems. And the results obtained from experimental tests showed that the proposed method achieved very low error rate(27%) compared with the existing method.

• Journal of Korea Water Resources Association
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• v.44 no.12
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• pp.967-974
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• 2011

Based on daily time series from RDAPS numerical weather forecast, Streamflow prediction was simulated and the result of ESP analysis was implemented considering quantitative mid- and long-term forecast to compare the results and review applicability. The result of ESP, ESP considering quantitative weather forecast, and flow forecast from RDAPS numerical weather forecast were compared and analyzed with average observed streamflow in Guem River Basin. Through this process, the improvement effect per method was estimated. The result of ESP considering weather information was satisfactory relatively based on long-term flow forecast simulation result. Discrepancy ratio analysis for estimating accuracy of probability forecast had similar result. It is expected to simulate more accurate flow forecast for RDAPS numerical weather forecast with improved daily scenario including time resolution, which is able to accumulate 3 hours rainfall or continuous simulation estimation.

• Journal of Korea Water Resources Association
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• v.43 no.11
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• pp.977-984
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• 2010

In order to determine the optimal sediment discharge formula for Hyeongsan river, some statistical approaches have been applied to analyze the simulated results of long-term bed change by HEC-6. The field measurements have been conducted to obtain the data for model calibration and verification such as sediment discharge, bed material, and channel geometry. Several sediment discharge formulae have been verified according to the bias, RMSE, RRMSE, discrepancy ratio, and S/N ratio of bed change along the thalweg. Comparing the formulae, Laursen formula(modified by Copeland) have shown the best performance to simulate the long-term bed change of Hyeongsan river.

• Journal of the korean academy of Pediatric Dentistry
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• v.39 no.2
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• pp.166-173
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• 2012

Dilaceration is a developmental disturbance in shape of teeth. It refers to an angulation, or a sharp bend or curve, in the root or crown of a formed tooth. Dilacerations are estimated to occur in 3% of all permanent dentitions. However, the etiology of dilaceration is not yet fully understood. Traumatic injury to the deciduous predecessors and ectopic development of the tooth germ are the two commonly cited causes of this anomaly. The involved tooth is usually the maxillary central incisor and it also shows high prevalence of impaction. At first, We tried to do surgical exposure with orthodontic traction but to no avail. After then surgical repositioning of the dilacerated tooth was performed. Finally, Satisfactory results were obtained at the end of treatment, with improvement in dental esthetics and functional aspects.

• Tunnel and Underground Space
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• v.26 no.6
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• pp.508-515
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• 2016

In this study, we compared the stability of the pillars by using room and pillar mining method with the four models with different stiffness and pillar overlap ratio. The experimental models consist of two plaster models (overlap ratio 0%, 100%) and two cement models(overlap ratio 0%, 100%). The soft and hard rocks are modeled by plaster and cement models respectively. In these experiments, the model materials with strength values reflecting the calculated scaled factors not been used, so it is not a true scaled model test that reproduces in situ state in the laboratory. Experimental results show that the different overlap ratio pillars are one of the factors that can affect the stability of the mine.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.6
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• pp.155-159
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• 2013

This article employs Naive Bayesian Classifier to realize a system that can distinguish the sex of a name. Unlike foreign names, in Korean names, the pronoun referring to a person shows discordance with sex. With the characteristics of Korean names, however, the study distinguishes names frequently used for men and for women. And as it also includes names of which sex is rather ambiguous such as proper nouns, the accuracy of it is somewhat low. The result of the experiment conducted in this article indicates 84% accuracy for Korean men and 88% for Korean women; thus, the total accuracy equals 86%. Meanwhile, about foreign names, men show 80% accuracy, and women 84%, so the total accuracy equals 83%.

• Journal of Food Hygiene and Safety
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• v.38 no.1
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• pp.12-18
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• 2023

Beef traceability systems help prevent the distribution of Hanwoo (Korean native cattle) meat as imported beef. In particular, assigning a traceability number to each cattle can provide all information regarding the purchased Hanwoo meat to the consumers. In the present study, a DNA identity test was conducted on 344 samples of Hanwoo meat from large livestock product stores in Seoul between 2021 and 2022 to determine the authenticity of important label information, such as the traceability number. Traceability number mismatch was confirmed in 45 cases (13.1%). The mismatch rate decreased to 11.3% in 2022 from 14.7% in 2021, and the mismatch rate was higher in the northern region (16.9%) than in the southern region (10.2%). In addition, of the six brands, B and D showed satisfactory traceability system management, whereas E and A showed poor traceability system management, with significant differences (P<0.001). The actual traceability number confirmation rate was only 53.9% among the mismatch samples. However, examination of the authenticity of label information of the samples within the identified range revealed false marking in the order of the traceability number (13.1%), sex (2.9%), slaughterhouse name (2.2%), and grade (1.6%); no false marking of breed (Hanwoo) was noted. To prevent the distribution of erroneously marked livestock products, the authenticity of label information must be determined promptly. Therefore, a legal basis must be established mandating the filling of a daily work sheet, including the traceability number of beef, in partial meat subdivisions. Our findings can be used as reference data to guide the management direction of traceability systems for ensuring transparency in the distribution of livestock products.