• 한국통신학회논문지
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• 제25권4A호
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• pp.573-578
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• 2000

본 논문은 공유 레이저 광원 및 LED 광원을 이용하는 WDM-PON 구조의 새로운 광 가입자 전송시스템을 제안하고, 제안된 시스템의 타당성을 실험적 시뮬레이션을 통해 고찰하였다. 본 시스템은 고속의 하향전송을 위해서는 공유 레이저 광원을 외부변조하여 이용하는 방식을 채택하였고, 상향전송을 위해서는 LED광원을 직접변조하여 이용하는 구조로 되어 있다. 광 선로구간에서의 파장다중화를 위해서는 채널 결합 및 분기기능을 갖는 AWG(Arrayed Wave-guide Grating) 소자를 이용하였다. 본 연구에서 제안한 전송시스템의 특징은 저가로 시스템을 구현 할 수 있다는 것이다. 이는 하향전송에 대해서는 안정된 고가의 레이저 광원을 공유함으로써 가능하고, 상향전송에는 동일한 LED 광원을 이용함으로써 WDM-PON을 위한 광 송수신장치(ONU; Opticla Network Unit)의 광원 안정화 및 규격화가 쉬워짐에 따라 대량생산을 통한 저가 구현이 가능하다. 본 시스템의 기술적 타당성을 입증하기 위하여 전송속도가 2.5Gbps인 하향전송과 51.84, 155.52 및 622.08Mbps인 상향전송에 대한 시뮬레이션을 실시하였고, 상하향 각 전송속도에 있어서 잘 동작됨을 확인하였다.

• Journal of Korean Neurosurgical Society
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• 제60권1호
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• pp.89-93
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• 2017

Infratentorial cerebral hemorrhage due to a direct carotid-cavernous fistula (CCF) is very rare. To our knowledge, only four such cases have been reported. Cerebellar hemorrhage due to a direct CCF has not been reported. We describe a 63-year-old female who presented with reduced consciousness 3 days after undergoing a maxillectomy for maxillary cancer. Computed tomography showed a cerebellar hemorrhage. Magnetic resonance angiography showed a left-sided direct CCF draining into the left petrosal and cerebellar veins through the left superior petrosal sinus (SPS). Her previous surgery had sacrificed the pterygoid plexus and facial vein. Increased blood flow and reduced drainage could have led to increased venous pressure in infratentorial veins, including the petrosal and cerebellar veins. The cavernous sinus has several drainage routes, but the SPS is one of the most important routes for infratentorial venous drainage. Stenosis or absence of the posterior segment of the SPS can also result in increased pressure in the cerebellar and pontine veins. We emphasize that a direct CCF with cortical venous reflux should be precisely evaluated to determine the hemodynamic status and venous drainage from the cavernous sinus.

• 한국보육지원학회지
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• 제13권1호
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• pp.107-124
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• 2017

Objectives: The purpose of this study was to investigate the effects of children's pride and shame on their interactive peer play, mediated by their daily stress. Methods: The participants of this study were 172 five-year-old children (80 boys and 92 girls) attending kindergartens or child-care centers in Chungbuk, Korea. The data were analyzed by descriptive and correlational analyses, and structural equation modeling using SPSS 19.0 and AMOS 21.0. Results: Children's shame had a significant indirect effect on their interactive peer play, including play-disruption, play-disconnection and play-interactions, mediated by daily stress; children's shame had a significant direct effect on play interaction. However, children's pride did not have a direct effect on daily stress and an indirect effect on their interactive peer play. In other words, high levels of shame among children led to high perceived daily stress. In turn, perceived daily stress increased play-disconnection and play-disruption, while it decreased play-interactions. Meanwhile children's shame led to a low level of play-interaction among young children. Conclusion/Implications: The results imply that children's perceived shame would influence their behaviors in social contexts as well as their psychological wellbeing such as the level of daily stress.

• 한국산학기술학회논문지
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• 제12권5호
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• pp.2054-2060
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• 2011

본 연구의 목적은 경제적이고, 친환경적인 가솔린 직접 분사 인젝터의 분무특성을 연구하는 것에 있다. 분무도달거리, 분무각 그리고 혼합기 형성과 같은 인젝터의 특성을 가시화 실험을 통하여 측정하였다. 특히 분무압력과 분위기압력이 분무 침투거리와 분무각에 미치는 영향을 분석하였다. 가시화 실험을 위하여 정적 연소실과 연료 공급장치를 제작하였다. 초고속 카메라와 LED광원을 이용하여 분무형상을 촬영하였고, 촬영된 영상으로 분무 특성을 분석하였다. 연소실내의 분위기압력이 감소하고, 연료의 분무압력이 증가할수록 도달거리는 증가하였다. 분위기압력과 분무압력에 대해 분무각의 변화는 미소하지만, 분위기압력이 분무각에 더 큰 영향을 미치고 있다.

• 동서간호학연구지
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• 제11권1호
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• pp.58-64
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• 2005

The purpose of this study was to examine impact of hospital computerization on the nursing practice. The study was conducted using the repeated measured design. The subjects were 166 nurses working at surgical nursing care units in a tertiary teaching hospital. A questionnaire was developed based on the Burke's study, and reviewed by a committee for content validity. Eighty-eight nurses responded the questionnaire throughout the study. Indirect nursing care time significantly decreased(p<0.05) after the computerization. These decrease related to time saving in checking physicians' order and writing nursing records. However, the change in direct nursing care time was not clear. In conclusion, the computerization led to the decrease in indirect nursing care time but it did not link to increase in direct nursing care time. Therefore, nurse managers should take into account redesign of the nursing works after computerization.

• Carbon letters
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• 제16권3호
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• pp.198-202
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• 2015

Carbon-supported Pt catalyst systems containing defect adsorption sites on the anode of direct methanol fuel cells were investigated, to elucidate the mechanisms of H₂ dissociation and carbon monoxide (CO) poisoning. Density functional theory calculations were carried out to determine the effect of defect sites located neighboring to or distant from the Pt catalyst on H₂ and CO adsorption properties, based on electronic properties such as adsorption energy and electronic band gap. Interestingly, the presence of neighboring defect sites led to a reduction of H₂ dissociation and CO poisoning due to atomic Pt filling the defect sites. At distant sites, H₂ dissociation was active on Pt, but CO filled the defect sites to form carbon π-π bonds, thus enhancing the oxidation of the carbon surface. It should be noted that defect sites can cause CO poisoning, thereby deactivating the anode gradually.

• 한국분무공학회지
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• 제19권1호
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• pp.9-14
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• 2014

Performance of DI diesel engine with high-pressure fuel injection equipment is directly related to its emission characteristics and fuel consumption. So, the electro-hydraulic injector for the common-rail injection system should be designed to meet the precise high fuel delivery control capability. Currently, most high pressure injector in use has a needle driven by the solenoid coil energy or the piezo actuator controlled by charge-discharge of output pulse current. In this study, macroscopic spray approaching method was applied under constant volume chamber to research the performance of three different injectors : solenoid, indirect-acting piezo and direct-acting piezo type for CR direct-injection. LED back illumination for Mie scattering was applied on the liquid spray visible of direct-acting piezo injector, including hydraulic-servo type solenoid and piezo-driven injectors. As main results, we found that a direct-acting piezo injector had better a spray tip penetration than hydraulic-servo injectors in spray visualization.

• 마이크로전자및패키징학회지
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• 제20권4호
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• pp.13-16
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• 2013

양극산화(anodization)공정으로 제작된 규칙성 나노구조의 다공성 산화알루미늄(Aluminum Anodic Oxide, AAO)는 공정이 적용된 LED 모듈은 비교적 쉽고 경제적이므로 최근 LED용 방열소재로 응용하기 위하여 다양하게 연구가 진행되고 있다. 일반적으로 LED 모듈은 알루미늄/폴리머/구리 회로층으로 구성되며 절연체 역할을 하는 폴리머는 히트스프레더로 구성되어있다. 그러나 열전도도가 낮은 폴리머로 인하여 LED부품의 열 방출이 원활하지 못하므로 LED의 수명단축 및 오작동에 영향을 미친다. 따라서, 본 연구에서는 폴리머 대신 상대적으로 열전도도가 우수한 AAO를 양극산화 공정으로 제작하여 히트스프레더(heat spread)로 사용하였다. 이때, AAO와 금속인 구리 회로층간의 접착력을 향상시키기 위하여 스퍼터링 DBC(direct bonding copper)법으로 시드층(seed layer)을 형성한 뒤 최종적으로 전해도금공정으로 구리회로층을 형성하였다. 본 연구에서는 양극 산화공정으로 AAO와 금속간의 접착강도를 개선하여 1.18~1.45 kgf/cm와 같은 우수한 peel strength 값을 얻었다.

• 한국세라믹학회지
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• 제50권1호
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• pp.75-81
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• 2013

We fabricated translucent opal glass to replace the polycarbonate diffuser in LED lighting systems in order to solve the durability problem. Batch materials of opal glass with a composition of calcium phosphate were created and melted at $1550^{\circ}C$, and the effect of opaqueness was identified by an addition of 1~7% calcium phosphate as an opacifier raw material. As a result, translucent opal glass was obtained by the melting of the mixed batch materials with a composition of more than 5% calcium phosphate glass at $1550^{\circ}C$ for 2 hrs, which had excellent optical properties for the diffuser of a LED lighting system with no dazzling from direct light by a high haze value exceeding 90% and a low parallel transmittance value of about 5%. For the thermal properties, the thermal expansion coefficient was found to be $5.6{\sim}5.9{\times}10^{-6}/^{\circ}C$ and the softening point was $874{\sim}884^{\circ}C$. In addition, good thermal properties such as good thermal shock resistance and feasibility for use with a general manufacturing process during the forming of glass tubes and bulbs were noted. Therefore, it is concluded that this translucent opal glass can be used as a glass diffuser material for LED lighting due to its high heat resistance and high durability as a replacement for a polycarbonate diffuser.

• 한국재료학회지
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• 제22권12호
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• pp.650-657
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• 2012

For the purpose of improving the durability problem, translucent opal glass was fabricated as a substitute for the polycarbonate diffuser of LED lighting. Calcium phosphate was used as an opacifier of opal glass and melted in an electric furnace. The opaque effect was identified according to the change of the cooling procedure. As results, translucent opal glass was obtained by the melting of a batch with a composition of 3.8% calcium phosphate at $1550^{\circ}C$ for 2 hrs and then the cooling of the material in the furnace. For the cooling condition of the glass sample, HTCG (High Temperature Cooled Glass) was found to have better optical properties than LTAG (Low Temperature Annealed Glass). It had excellent optical properties for a diffuser of LED lighting, with no dazzling from direct light due to its high haze value of over 99% and low parallel transmittance value of under 1%. For the thermal properties, it had an expressed thermal expansion coefficient of $5.7{\times}10^{-6}/^{\circ}C$ and a softening point of $876^{\circ}C$; it also had good thermal properties such as good thermal shock resistance and was easy to apply to the general manufacturing process in the forming of glass tubes and bulbs. Therefore, it is concluded that this translucent opal glass can be used as a glass diffuser material for LED lighting with high heat resistance and high durability; this material is suitable as a substitute for polycarbonate diffusers.