• Restorative Dentistry and Endodontics
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• 제13권2호
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• pp.221-235
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• 1988

The purpose of this study was to observe characteristic properties through the polarization curves and EMPA images from 4 different types of amalgam obtained by using the potentiostats (EG & G PARC) & EPMA (Jeol JSM-35), to investigate the degree of corrosion of each phase of amalgam on the oxidation peak, and to identify corrosion products from the corroded amalgam by use of X-ray diffractometer(Rigaku). After each amlgam alloy and Hg were triturated as the direction of the manufacturer by means of the mechanical amalgamator(Shofu), the triturated mass was inserted into the cylindrical metal mold which was 12mm in diameter and 10mm in height and was condensed by means of routine manner. The specimen was removed from the mold and stored at room temperature for about 7 days. The standard surface preparation was routinely carried out. Anodic polarization measurement was employed to compare the corrosion behaviours of the amalgams in 0.9% saline solution(pH6.8~7.0) and artificial saliva (pH6.8~7.0) at $37^{\circ}C$. The open circuit potential was determined after 30 minutes' immersion of specimen in electrolyte and the potential scan was begun at the potential of 100mV cathodic from the corrosion potential. The scan rate was 1mV/sec and the surface area of amalgam exposed to the solution was 0.64$cm^2$ for each specimen. All the potentials reported are with respect to a saturated calomel electrode (SCE). EPMA images on the determined oxidation peaks of each amalgam in artificial saliva were observed. X-ray diffraction patterns of each sample were recorded before and after polarization in artificial saliva (Aristaloy, Caulk Spherical, Dispersalloy and Tytin: at +770mV, +585mV, +8.10m V and +680m V respectively) by use of a recording diffractometer. Nickel filtered Cu $K_{{\alpha}_1}$ radiation was used and sample was scanned at $4^{\circ}(2{\theta})/min.$ from $25^{\circ}$ to $80^{\circ}$. The following results were obtained. 1. Oxidation peak potential in artificial saliva shifted to more anodic direction than that in saline solution. 2. The corrosion potential of high copper amalgam was more anodic than the potential of low copper amalgam. 3. The current density was lower in artificial saliva than in saline solution. 4. One of the corrosion products, AgCl was identified by X-ray diffraction analysis. 5. ${\gamma}_2$ phase was the most susceptible to corrosion and e phase was stable in low copper amalgam and ${\eta}$' phase and Ag-Cu eutectic were susceptible to corrosion in high copper amalgam.

• 한국게임학회 논문지
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• 제11권6호
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• pp.127-138
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• 2011

네트워크를 통한 정보의 창출 및 교류는 온라인 커뮤니티를 형성하고 온라인 게임과 접목하면서 Social Network Online Game (SNOG)라는 새로운 엔터테인먼트 분야를 만들고 있다. SNOG는 트위터, 페이스북과 같은 Social Network Service (SNS)의 사회적 요소와 게임적 요소를 융합한 서비스로, 소셜 플랫폼에서 동작하며 사용자들의 오락적 유희와 상호작용 관계를 촉진시키고 있다. 국내 SNOG 시장은 현재 빠르게 변화하고 있으며, 급속하게 교체되고 있는 스마트 환경에 따라 빠른 변화가 예상된다. SNOG는 비용적인 측면에서 기존 온라인 게임과 비교해볼 때 경쟁력을 가지기 때문에 더욱 발전될 전망이다. 이와 더불어 페이스북, 트위터 등 해외 SNS 플랫폼 기반 SNOG 서비스와 관련하여 국내 NHN, Daum, SK 컴즈 등에서 개방형 SNS를 선보이면서 SNG 유치를 위한 경쟁이 치열해 질 것이다. 또한, 모바일 연동 기반 서비스와 관련하여 관련 SNOG 개발이 이루어지고 있으며, 관련 국내 인터넷 업체들이 적극적으로 개발 참여하고 있다. 이러한 환경 속에서 본 연구는 SNOG 시장에 비교적 성공적으로 진입한 Nexon 'Maplestory adventure'사례를 연구함으로써 성공적인 SNOG 요인 분석 및 전략을 정리하고 분석하였다. Maplestory adventure 성공 가능 요인으로는 기존의 인기 있는 온라인 게임에 SNS 접목, 기존의 유저를 통한 marketing, NexonStar 실패요인이었던 Platform문제 해결 등을 들 수 있다. 이 연구는 이후 계속 확산 발전될 SNOG 성공 전략 문제에 함의를 제공하여 국내 게임산업 발전에 기여할 수 있으리라 기대된다.

• 한국과학교육학회지
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• 제31권1호
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• pp.1-13
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• 2011

이 연구의 목적은 초임교사를 포함하여 수업전문성 개발이 요구되는 교사를 지원하기 위한 방편으로써 멘토링 체제의 효과와 가능성을 탐구하는 것이다. 최근에는 수업전문성 제고를 통한 교사의 책무성 제고가 요청되며, 여기서 현장 경험 속에서 교사의 수업전문성을 신장시킬 수 있는 효과적인 방법으로 멘토링이 주목되고 있다. 멘토링이란 개별 교사의 전문성과 경력발달과 연계하여 해당 교사가 전문적으로 그리고 개인적으로 성장할 수 있도록 지원하는 것으로 때로는 전문가-초보 관계로 운영된다. 본 연구에서는 교사전문성개발을 지원하기 위한 대안으로서 멘토링 체제 도입 방안에 대하여 살펴보았다. 교과별로 멘토-멘티를 최소 3쌍 정도 구성하여 멘토링을 시범운영해 본 결과를 토대로 멘토링 체제 도입과 관련된 시사점을 논의하였다. 본 연구에서는 동일한 단원의 전 차시 수업에 대하여 멘토와 멘티가 수업동영상을 만들고 그 동영상을 활용하여 수업컨설팅에 초점을 둔 멘토링(video-based discussions)을 진행하였다. 이러한 과정을 통하여 참여교사의 개인적, 집단적 발전을 촉진할 수 있었다. 멘토와 멘티가 협력하여 수업에서 드러난 증거에 기반을 둔 공동탐구를 수행함으로써 반성적 경험을 공유할 수 있게 된다. 과학과 멘토링 체제 적용 결과를 멘토링의 필요성과 목적, 초임교사 지원을 위한 멘토링의 필요성, 역할 기대에 비추어본 멘토의 자격에 초점을 맞추어 논의하였다. 결론에서는 멘토링 체제 운영상의 유의점을 논의하였다.

• 한국보육학회지
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• 제18권1호
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• pp.147-168
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• 2018

본 연구는 유아를 대상으로 지속가능발전교육 활동을 적용하고 그 효과를 검증하는 것이 주된 목적이다. 이를 위해 경기도 P시의 A어린이집 유아 20명을 실험집단(남아11명, 여아9명)으로, G어린이집의 20명을 통제집단(남아11명, 여아9명)으로 구성하고 8주 동안 실험집단에는 지속가능발전교육활동을, 통제집단에게는 누리과정 생활주제와 일상적인 교육활동을 실시하였다. 본 연구의 결과는 다음과 같다. 첫째, 유아 지속가능발전교육 활동을 경험한 실험집단의 유아 배려행동은 증가했다. 둘째, 유아 지속가능발전교육 활동을 경험한 실험집단의 유아 공동체의식은 증가되었다. 셋째, 유아 지속가능발전교육 활동을 경험한 실험집단의 유아 소비자 행동은 긍정적으로 변화하였다. 이에 따라 본 연구에서 구성한 유아 지속가능발전교육 활동은 유아의 배려행동과 공동체의식, 소비자 행동에 긍정적인 효과가 있음을 알 수 있었다. 따라서 유아 지속가능발전교육 활동을 유아교육현장에 적용하는 것은 가치가 있는 것임을 본 연구는 시사하고 있다.

• 한국태양에너지학회 논문집
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• 제25권4호
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• pp.1-11
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• 2005

The stoichiometric mixture of evaporating materials for the $CuInSe_2$ single crystal thin film was prepared from horizontal furnace. Using extrapolation method of X-ray diffraction patterns for the polycrystal $CuInSe_2$, it was found tetragonal structure whose lattice constant $a_0$ and $c_0$ were $5.783\;{\AA}$ and $11.621\;{\AA}$, respectively. To obtain the $CuInSe_2$ single crystal thin film, $CuInSe_2$ mixed crystal was deposited on throughly etched GaAs(100) by the HWE(Hot Wall Epitaxy) system. The source and substrate temperature were $620^{\circ}C$ and $410^{\circ}C$ respectively. The crystalline structure of $CuInSe_2$ single crystal thin film was investigated by the double crystal X-ray diffraction(DCXD). Hall effect on this sample was measured by the method of Van der Pauw and studied on carrier density and mobility depending on temperature. From Hall data, the mobility was likely to be decreased by impurity scattering in the temperature range 30 K to 100 K and by lattice scattering in the temperature range 100 K to 293 K. The temperature dependence of the energy band gap of the $CuInSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=1.1851\;eV-(8.99{\times}10^{-4}\;eV/K)T^2/(T+153\;K)$. The open-circuit voltage, short current density, fill factor, and conversion efficiency of $n-CdS/p-CuGaSe_2$ heterojunction solar cells under $80\;mW/cm^2$ illumination were found to be 0.51V, $29.3\;mA/cm^2$, 0.76 and 14.3 %, respectively.

• 한국태양에너지학회 논문집
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• 제38권1호
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• pp.25-36
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• 2018

The stoichiometric mixture of evaporating materials for the $CaAl_2Se_4$: Co single crystal thin film was prepared from horizontal furnace. Using extrapolation method of X-ray diffraction patterns for the polycrystal $CaAl_2Se_4$, it was found orthorhomic structure whose lattice constant $a_0$, $b_0$ and $c_0$ were 6.4818, $11.1310{\AA}$ and $11.2443{\AA}$, respectively. To obtain the $CaAl_2Se_4$: Co single crystal thin film, $CaAl_2Se_4$: Co mixed crystal was deposited on throughly etched Si (100) by the HWE (Hot Wall Epitaxy) system. The source and substrate temperature were $600^{\circ}C$ and $440^{\circ}C$ respectively. The crystalline structure of $CaAl_2Se_4$: Co single crystal thin film was investigated by the double crystal X-ray diffraction (DCXD). Hall effect on this sample was measured by the method of Van der Pauw and studied on carrier density and mobility depending on temperature. From Hall data, the mobility was likely to be decreased by impurity scattering in the temperature range 30 K to 100 K and by lattice scattering in the temperature range 100 K to 293 K. The temperature dependence of the energy band gap of the $CaAl_2Se_4$: Co obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=3.8239eV-(4.9823{\times}10^{-3}eV/K)T_2/(T+559K)$. The open-circuit voltage, short current density, fill factor, and conversion efficiency of $p-Si/p-CaAl_2Se_4$: Co heterojunction solar cells under $80mW/cm^2$ illumination were found to be 0.42 V, $25.3mA/cm^2$, 0.75 and 9.96%, respectively.

• 한국통신학회논문지
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• 제35권8B호
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• pp.1197-1203
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• 2010

최근 파일 공유를 위해 널리 사용되는 BitTorrent의 강점은 BitTorrent의 핵심 메커니즘인 peer 선택 기법에 기인한다. Peer 선택 기법은 해당 호스트가 업로드 할 peer를 선택하는 것인데, 이 때 자신에게 각 peer가 업로드한 비율을 비교해서 가장 많이 업로드한 peer들에게 업로드를 하게 된다. 그런데 BitTorrent에서는 업로드할 peer의 개수 (즉, unchoked peer 개수)를 4개로 고정하고 있다. 하지만 peer들의 개수나 다운로드 속도, 업로드 속도와 같은 공유집단 (즉, swarm)의 특성은 계속 변하기 때문에 unchoked peer 개수를 고정하는 것은 효율적이지 않다. 본 논문에서는 BitTorrent에서 unchoked peer 개수가 고정된 4개가 아니라 변할 때 전체 시스템 성능에 어떠한 영향이 끼치는지 분석한다. 분석을 위해 본 논문에서는 서울대학교 캠퍼스 망에 테스트베드를 설치하였고, 실제로 널리 사용되는 오픈 소스 BitTorrent 클라이언트를 수정해서 사용하였다. 테스트베드에서의 다양한 실험을 통해 BitTorrent의 성능이 unchoke 개수에 따라 달라지게 되는 것을 보였고, 이에 따라 swarm의 상황을 고려해서 unchoke개수를 적절하게 조절하는 메커니즘이 필요하다는 것을 보였다.

• 한국환경보건학회지
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• 제36권5호
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• pp.343-350
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• 2010

This study was performed to investigate laboratory workers' exposures to airborne nanoparticles at a university laboratory where acid treatment experiments were conducted on the surfaces of engineered carbon nanotubes (CNTs). The surface area concentrations, number concentrations, and mass concentrations of airborne nanoparticles were measured at personal breathing zones (PBZs) for various tasks using direct reading instruments. For all three metrics, airborne nanoparticle concentrations during the experiments were higher than background levels measured before and after the experiments for all three metrics. Among the various tasks that were performed as part of these experiments, one task that involved filtering a mixture of acid and CNTs showed the highest concentrations in all three metrics, with concentrations of $116.6\;{\mu}m^2$/cc, 24320 pt/cc, and $9.0\;{\mu}g/m^3$, respectively. Nanoparticle surface area concentrations measured at a representative area fluctuated with those at the PBZs in the laboratory. This result indicates that nanoparticles generated during the experiments were not just limited to the PBZs of the workers but were also present throughout the room, potentially exposing co-located workers. CNTs were detected by a transmission electron microscope in an air sample collected while handling the CNTs. All the tasks were performed inside fume hoods, with the sliding sashes open to their required heights. It was noted that the capture velocities of the fume hoods were much lower than the American National Standards Institute (ANSI)'s recommendation level (0.4 to 0.6 m/s). In conclusion, this study showed that, due to inadequate control, laboratory researchers performing acid treatment experiments on surfaces of CNTs were exposed to airborne nanoparticles generated during the tasks.

• Genomics & Informatics
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• 제8권3호
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• pp.108-115
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• 2010

Hypertension is the most prevalent disease worldwide and is itself a risk factor for cerebral, cardiac, and renal diseases. The inconsistency of candidate genes suggested by previous genomewide association studies (GWASs) may be due to not only differences in study design and genetic or environmental background but also the difference in the power of analysis between continuous traits and discrete traits. We analyzed 352,228 single nucleotide polymorphisms (SNPs) in 8842 unrelated Koreans obtained from Ansan and Ansung cohorts. We performed a series of GWA analyses using three different phenotype models; young hypertensive cases (278 subjects) versus elderly normotensive controls (680 subjects); the upper 25% (2211 hypertensive cases) versus the lower 25% of the SBP distribution (2211 hypotensive controls); and finally SBP and DBP as continuous traits (8842 subjects). The numbers of young hypertensive cases and elderly normotensive controls were not large enough to achieve genomewide significance. The model comparing the upper 25% subjects to the lower 25% of subjects showed a power that was approximate to that of QTL analysis. Two neighboring SNPs of the ATP2B1 gene, rs17249754 (SBP, p=$2.53^{-10}$; DBP, p=$1.28{\times}10^{-8}$) and rs7136259 (SBP, p=$1.30{\times}10^{-9}$; DBP, p=$6.41{\times}10^{-8}$), were associated with both SBP and DBP. Interestingly, a SNP of the RPL6 gene, rs11066280, revealed a significant genomewide association with SBP in men only (p=$3.85{\times}10^{-8}$), and four SNPs located near the MAN2A1 gene showed a strong association with DBP only in elderly men aged 60-70 years (e.g., rs6421827, p=$4.86{\times}10^{-8}$). However, we did not observe any gene variant attaining genomewide significance consistently in the three phenotype models except for the ATP2B1 gene variants. In general, the association signal with blood pressure was stronger in women than in men. Genes identified in GWASs are expected to open the way for prevention, early diagnosis, and personalized treatment of hypertension.

• 대한지역사회영양학회지
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• 제13권4호
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• pp.489-498
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• 2008

This study was carried out to identify bone mineral density(BMD), body composition, lifestyle and dietary habits of young women by physical measurement and questionnaires. The study subjects, 190 young women living in Seoul, were divided into three age groups: $20{\sim}24$ years(93), $25{\sim}29$ years(44) and $30{\sim}39$ years(53). There was no significant difference in mean body muscle mass, protein, mineral, body fat and BMI among the three age groups. The rate of low weight(18%) in 20 years group was higher that of the 30 years(11.3%). The mean BMD and T-score were $0.44g/cm^2$ and -0.66. BMD and T-score of the forearm bone were significantly higher in the $30{\sim}39$ years group. But BMD and T-score of calcanues were not significantly different among the three age groups. The rate of normal, osteopenia and osteoporosis subjects by BMD were 60.5%, 38.4%, 1.1%, respectively. The rate of osteopenia in $20{\sim}24$ years group was significantly higher than the other age groups. The rate of meal irregularity was significantly higher in $20{\sim}24$ years group. The rate of women who walk and are exposed to sunlight more than 1hr per day were significantly higher in $20{\sim}24$ years group than the others. However, the score of food behaviors is significantly higher(bad) in $20{\sim}24$ years group than the others. The relationship between BMD and frequency of food intake showed significant differences in beans, broom, seaweed and rice wine. In conclusion, the risk rate of BMD was very high, 40% of the subjects, and the risk rate of BMD was higher in 20 years group than 30 years group, and the rate of low weight in 20 years group was higher than in 30 years group. The food habits and behaviors were not healthy enough. Therefore, nutrition education is needed for bone health.