• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2021-2025
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• 2007

Performance of single cell at solid oxide fuel cell (SOFC) system is largely affected by electrocatalytic and thermal properties of cathode. Samarium-based perovskite oxide material is recently recognized as promising cathode material for intermediate temperature-operating SOFC due to its high electrocatalytic property. Perovskite structured $Sm_{0.5}Sr_{0.5}CoO_{3-\delta}$ and its composite material, $Sm_{0.5}Sr_{0.5}CoO_{3-\delta}/Sm_{0.2}Ce_{0.8}O_{1.9}$ were investigated in terms of area specific resistance (ASR), thermal expansion coefficient (TEC), thermal cycling and long term performance. $Sm_{0.2}Ce_{0.8}O_{1.9}$ was used as electrolyte material. Electrochemical ac impedance spectroscopy (EIS) and dilatometer were used to measure the cathodic properties. Composite cathode ($Sm_{0.5}Sr_{0.5}CoO_{3-\delta}$: $Sm_{0.2}Ce_{0.8}O_{1.9}$ = 6:4) showed a good ASR of 0.13${\Omega}$ $cm^2$ at 650$^{\circ}C$ and its TEC value was 12.3${\times}$10-6/K at 600$^{\circ}C$ which is similar to the value of ceria-based electrolyte of 11.9${\times}$10-6/K. Performance of composite cathode was maintained with no degradation even after 13 times thermal cycle test.

• 한국정보통신학회논문지
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• 제17권10호
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• pp.2281-2287
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• 2013

네트워크 코딩은 통신의 새로운 패러다임이다. 네트워크 코딩에서 중간 노드는 입력 패킷을 조합하여 새로운 패킷을 생성하여 이웃 노드에게 방송한다. 네트워크 코딩은 실제 네트워크에 폭넓게 적용될 수 있기 때문에 정보 이론의 주요 연구 분야로 빠르게 떠오르고 있다. 네트워크 코딩은 무선 멀티홉 네트워크에서 처리량과 채널 효율을 향상시킬 것으로 예상된다. 관련 선행연구들이 무선 Ad-hoc 네트워크 분야에서 활발히 이루어지고 있다. 우리의 연구에서 중간노드는 네트워크 코딩을 하기위해서 단일홉 양방향 패킷을 식별한다. 우리는 제안된 기법이 네트워크 패킷의 디코딩 성공률을 증가시킬 수 있을 것으로 기대한다. 컴퓨터 시뮬레이션에서 제안된 네트워크 코딩기법은 코딩 이득과 패킷 전송률에서 기존의 네트워크 코딩기법보다 나은 성능을 얻을 수 있었다.

• 한국해양공학회지
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• 제29권1호
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• pp.34-44
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• 2015

A hydraulic tensile test machine (HSTM) is one of the devices used to obtain the flow stress of a material during high-speed elongation. This paper first describes some features of a newly built HSTM. The improvement histories of the upper and lower jigs, which are the most vital parts of the HSTM, are also presented. We have frequently witnessed test failures with 1st generation jigs and specimens due to slip between the jig and specimen. 2nd generation jigs provide more stable test results, but the use of a longer upper jig induces excessive vibration and consequently makes it difficult to attach an environment chamber. 3rd generation jigs have some advances in terms of the symmetric fastening between the upper jig and specimen, as well as an exemption from direct contact between the lower jig and specimen. The performance of an environment chamber is verified by high and low temperature tests. A high-speed displacement measurement system is introduced based on a high-speed camera and motion-tracking software with aid of a surface grid device for the specimen.

• Journal of Preventive Medicine and Public Health
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• 제45권2호
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• pp.90-97
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• 2012

Objectives: While there have been many quantitative studies on the public's attitude towards mental illnesses, it is hard to find quantitative study which focused on the contextual effect on the public's attitude. The purpose of this study was to identify factors that affect the public's beliefs and attitudes including contextual effects. Methods: We analyzed survey on the public's beliefs and attitudes towards mental illness in Korea with multi-level analysis. We analyzed the public's beliefs and attitudes in terms of prejudice as an intermediate outcome and social distance as a final outcome. Then, we focused on the associations of factors, which were individual and regional socioeconomic factors, familiarity, and knowledge based on the comparison of the intermediate and final outcomes. Results: Prejudice was not explained by regional variables but was only correlated with individual factors. Prejudice increased with age and decreased by high education level. However, social distance controlling for prejudice increased in females, in people with a high education level, and in regions with a high education level and a high proportion of the old. Therefore, social distance without controlling for prejudice increased in females, in the elderly, in highly educated people, and in regions with a high education and aged community. Conclusions: The result of the multi-level analysis for the regional variables suggests that social distance for mental illness are not only determined by individual factors but also influenced by the surroundings so that it could be tackled sufficiently with appropriate considering of the relevant regional context with individual characteristics.

• Journal of Yeungnam Medical Science
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• 제29권2호
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• pp.89-95
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• 2012

Background: As Mycoplasma pneumoniae pneumonia has increased in Korea, its relevance to infants, toddlers, and adolescents has magnified as well as. However, it is difficult to perform the serological test and PCR test routinely for diagnosis in actual clinical practice. Thus, the authors conducted this study to help clinicians do presumptive diagnosis of Mycoplasma pneumoniae pneumonia using clinical, radiological, and hematological findings. Methods: The study population consisted of 224 children between 1 month and 14 years old, hospitalized for radiographically confirmed pneumonia. Patients were divided into two groups of 100 children with Mycoplasma pneumoniae pneumonia, as diagnosed using the ELISA method. Groups with negative result in Mycoplasma IgM antibody test were classified into the viral group (98 patients with respiratory virus) and the bacterial group (46 patients with the bacteria detected in the blood sputum culture or antibiotic treatment except macrolide improved the patient's condition). These groups were compared and analyzed using clinical, hematological, and radiographic differences and scoring system. Results: Clinical, hematological, and radiographic characteristics of Mycoplasma pneumoniae pneumonia have shown the intermediate level results between bacterial pneumonia and viral pneumonia. In terms of scoring system, the mean score of Mycoplasma pneumoniae pneumonia was 4.23, which was the intermediate level between bacterial pneumonia (mean score=6.67) and viral pneumonia (mean score=1.48). Conclusion: Results suggest that the combination of the scoring system information can increase the accuracy in the diagnosis even if they may have difficulties on diagnosis, because clinical manifestations, hematological, and radiographic findings are nonspecific.

• 한국조경학회지
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• 제27권1호
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• pp.79-89
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• 1999

Recent expansion of urban parks has been partly successful in terms of providing urban outdoor recreation space. Unfortunately we paid very little attention to the importance of providing regional identity to urban parks until recently. Thus one of the most important tasks of the contemporary landscape architects of Korea is to investigate ways to improve regional identity of urban parks. This study is aimed at evaluating how well the current urban parks have realized their own regional identity. To test the effectiveness of the concept of 'identity', the identity items were created, while a research model was developed by using such variables as in urban park identity, park satisfaction, belongingness to the region, and residential satisfaction. In order to test the model, the causations were analyzed. Meanwhile, the scales to evaluating identity were reviewed by means of the unstructures group interview, and were finally determined as 10 items; culture, uniqueness, symbolic, historic nature, homogeneity, harmony, difference, public benefit, nativeness and traditionality. Data from three new towns in the capital region-Bundang, Ilsan and Sanbon-were collected, and their central parks were referred to a questionnaire survey. The data were processed using descriptive statistics, correlation analysis, multiple regression analysis and path analysis. It was found through this survey that subjects 'sentiments regarding the sample towns' regional identity differed slightly. Residents of Bundang felt the strongest amount of regional identity, followed by those of Ilsan and Sanbon. In addition, the most important scale on regional identity is 'park satisfaction', followed by 'belongingness to the region' and 'residental satisfaction'. The path analysis was conducted to interpret the causations in a more detailed and comprehensive way than correlation analysis. As a result, it was proven that the regional identity affects 'belingingness to region' through the intermediated variable 'park satisfaction', while affecting ' residential satisfaction' through the intermediate variables 'park satisfaction' and 'beligningness to region'. In other words, although the regional identity of a park does not directly affect 'belongingness to region' or 'residental satisfaction', it has indirect effects on them through intermediate variables.

• 대한지역사회영양학회지
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• 제15권5호
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• pp.648-655
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• 2010

This study is attempted to propose a quality evaluation method of the materials for nutrition education by applying readability test of printed materials for nutrition education. It is significantly important for the teaching class with nutrition education materials to consider students understanding level and education materials topics or choosing words in developed printed materials. This study performed an evaluation of the readability of text in teachers' guidebook, which is devised for elementary school students' education material about sugar, sodium and trans-fat and attempted to estimate the developing materials through analyzing difficulty level of the text. We utilized "The Teacher's Guidebook for Cooking Activity" that had been developed for elementary school by Ministry Education Science and Technology, as the readability evaluation standard. Compared with the average score of readability about "The Teacher's Guidebook for Cooking Activity", $72.94{\pm}6.85$, "Sugar Guidebook" was 70.94{\pm}7.46, "Sodium Guidebook" was $68.76{\pm}14.50$, and "Trans-fat Guidebook" was $58.87{\pm}10.79$. Considering the subjects careers or ages, "The Teacher's Guidebook for Cooking Activity" has little deviation by the subjects careers or ages and was "intermediate" or "easy" level; however, "Sugar Guidebook", "Sodium Guidebook", "Trans-fat Guidebook" was "intermediate" or "difficult" level (p < 0.05). Readability score was especially low when the contents of some particular subjects were too professionalized or scientific terms were frequently used, and thes results were definitely seen in the "Sodium Guidebook" and "Trans-fat Guidebook". With Cloze test score, the readability evaluation will be using as an evaluation tool for the nutrition education materials.

• 전자공학회논문지
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• 제54권6호
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• pp.72-79
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• 2017

본 논문에서는 웨이블릿 부밴드의 상호 정보량을 이용한 새로운 세일리언시 검출 방법을 제시한다. 본 논문의 방법은 웨이블릿 고주파 계수에 대한 승수와 가우시안 블러링을 이용하여 중간 세일리언시 지도를 형성한다. 웨이블릿 방향에 따른 세 개의 중간 세일리언시 지도를 방향별로 결합한 후 최소 엔트로피를 가지는 주 방향성 성분을 찾는다. 최소 엔트로피를 가지는 부밴드를 중심으로 각 부밴드의 상호 정보량을 구하고, 이를 이용한 가중치를 계산하고, Minkowski 합을 이용하여 최종 세일리언시를 검출한다. CAT2000 및 ECSSD 데이터베이스 대한 실험 결과, 본 논문의 방법은 기존 방법과 비교하여 적은 계산시간으로 ROC 및 AUC 관점에서 우수한 검출 결과를 보였다.

• Bulletin of the Korean Chemical Society
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• 제19권6호
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• pp.671-676
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• 1998

The formation and dissociation rates of $Ce^{3+}$ Complexes of the 1,4,7,10-tetraaza-13,16-dioxacyclooctadecane-NN', N",N"'-tetraacetic acid (1), 1,4,7,10-tetraaza-13,16-dioxacyclooctadecane-N,N',N",N"'-tetramethylacetic acid (2), and 1,4,7,10-tetraaza-13,16-dioxacyclooctadecane-N,N',N",N"'-tetrapropionic acid (3) have been measured by the use of stopped-flow spectrophotometry. Observations were made at 25.0±0.1 ℃ and at an ionic strength of 0.10 M $NaClO_4$. The complexation of $Ce^{3+}$ ion with 1 and 2 proceeds through the formation of an intermediate complex $(CeH_3L^{2+})^*$ in which the $Ce^{3+}$ ion is incompletely coordinated. This may then lead to be a final product in the rate-determining step. Between pH 4.76 and 5.76, the diprotonated $(H_2L^{2-})$ from is revealed to be a kinetically active species despite of its low concentration. The stability constants $(logK(CeH_3L^{2+}))$ and specific water-assisted rate constants $(k_{OH})$ of intermediate complexes have been determined from the kinetic data. The dissociation reactions of $Ce^{3+}$ complexes of 1, 2, and 3 were investigated with $Cu^{2+}$, ions as a scavenger in acetate buffer. All complexes exhibit acid-independent and acid-catalyzed contributions. The effect of buffer and $Cu^{2+}$ concentration on the dissociation rate has also been investigated. The ligand effect on the dissociation rate of $Ce^{3+}$ complexes is discussed in terms of the side-pendant arms and the chelate ring sizes of the ligands.

• Steel and Composite Structures
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• 제33권4호
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• pp.595-614
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• 2019

In cold-formed steel (CFS) structures, such as trusses, transmission towers and portal frames, the use of back-to-back built-up CFS unequal angle sections are becoming increasingly popular. In such an arrangement, intermediate welds or screw fasteners are required at discrete points along the length, preventing the angle sections from buckling independently. Limited research is available in the literature on axial strength of back-to-back built-up CFS unequal angle sections. The issue is addressed herein. This paper presents an experimental investigation on both the welded and screw fastened back-to-back built-up CFS unequal angle sections under axial compression. The load-axial shortening and the load verses lateral displacement behaviour along with the deformed shapes at failure are reported. A nonlinear finite element (FE) model was then developed, which includes material non-linearity, geometric imperfections and modelling of intermediate fasteners. The FE model was validated against the experimental test results, which showed good agreement, both in terms of failure loads and deformed shapes at failure. The validated FE model was then used for the purpose of a parametric study to investigate the effect of different thicknesses, lengths and, yield stresses of steel on axial strength of back-to-back built-up CFS unequal angle sections. Five different thicknesses and seven different lengths (stub to slender columns) with two different yield stresses were investigated in the parametric study. Axial strengths obtained from the experimental tests and FE analyses were used to assess the performance of the current design guidelines as per the Direct Strength Method (DSM); obtained comparisons show that the current DSM is conservative by only 7% on average, while predicting the axial strengths of back-to-back built-up CFS unequal angle sections.