• Journal of Digital Contents Society
• /
• v.5 no.1
• /
• pp.7-11
• /
• 2004

There are many problems that must solve to construct next generation high-speed communication network. Among these, item that must consider basically is characteristics analysis of traffic that nows to network Traffic characteristics of many Internet services that is offered present have shown that network traffic exhibits at a wide range of scals-self-similarity. Self-similarity is expressed by long term dependency, this is contradictory concept with Poisson model that have relativity short term dependency. Therefore, first of all, for design and dimensioning of next generation communication network, traffic model that are reflected burstiness and self-similarity is required. Here self-similarity can be characterized by Hurst parameter. In this paper, the calculation equation is derived considering queueing delay and self-similarity of data traffic art compared with simulation results.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1998.05a
• /
• pp.475-480
• /
• 1998

계면면적 밀도는 two-fluid 모델에서 각 상 간의 상호작용에 영향을 주는 중요한 인자로서 이상유동 현상의 해석을 위하여는 이의 적절한 모델링이 필요하다. 계면면적 밀도의 모델링은 크게 상관식에 의존하는 방법론과 수송 방정식을 사용한 이론적인 접근방식으로 개발되어왔다. 후자는 시간적, 공간적으로 변하고 있는 동적 유동조건에 대하여 계면면적 밀도를 효과적으로 예측할 수 있는 방법론으로서 flow regime의 의존성을 줄이거나 없앨 수 있는 장점을 가진다. 계면면적 수송 방정식은 유체입자의 수밀도에 대한 수송 방정식의 통계적인 모델로부터 유도되며 입자들의 상호작용 및 상변화와 관련된 생성항을 포함하고 있다. 본 연구에서는 계면면적 밀도 수송 방정식 및 그 구성 모델들에 대한 연구현황을 정리하였다.

• Proceedings of the KAIS Fall Conference
• /
• 2012.05a
• /
• pp.25-29
• /
• 2012

본 연구의 목적은 농어촌지역의 음주문제 관련 상담센타, 사업장 중심의 절주 프로그램이나 치료 서비스가 취약한 형편이어서 농어촌 지역 직장인의 음주문제에 대한 대책을 마련하고자 하는데 있다. 본 연구의 대상자는 일 농어촌 지역에 거주하는 20세 이상의 남녀 직장인 530명을 대상으로 하였고, 설문에 동의하여 회수된 설문지는 512부였으며 이중 부실하게 응답한 12명의 자료를 제외한 500명의 자료를 최종 분석대상으로 하였다. 자료수집은 2007년 6월 12일부터 2007년 8월 25일까지 시행되었으며, 설문지의 내용을 이해하며 의사소통이 가능한 자에게 본 연구의 취지를 설명하고 연구에의 참여를 동의한 대상자에게 구조화된 설문지를 이용해 자료를 수집하였다. 1. 본 연구에 참여한 대상자의 음주에 대한 인식은 긍정적 인식의 평균은 2.93, 부정적 인식의 평균은 3.18로 나타났다. 2. 음주행태에서 음주경험여부는 현재 음주자가 79.7%로 가장 많았고, 비음주자 13.1%, 과거 음주자 7.2%로 나타났다. 음주빈도는 음주경험이 있는 대상자 중 '월 2-4회 마시는 경우'가 38.2%로 가장 많았고, 평소 음주량은 '소주 10잔 이상'이 34.6%로 많았으며 '소주 3잔 이상'인 경우가 전체 대상자의 92.2%를 차지하였다. 3. 대상자의 문제음주 정도 및 특성은 전체 대상자 중 CAGE를 통해 선별된 알코올 의존자(4개 문항 중 2개 이상이 그렇다고 응답하면 알코올 의존으로 규정)의 비율이 96명(25.1%)이었고, AUDIT를 통해 선별된 문제성 음주자(8점 이상)의 비율은 241명(64.8%)으로 나타났다. 4. 대상자의 음주로 인한 질병은 위장계 질환이 31.3.%로 가장 많았다. 이상의 연구결과를 종합해볼 때, 농어촌지역 직장인의 음주문제에 관한 구체적인 해결방안으로는 음주 문화에 대한 인식개선과 산업체 중심의 절주사업이 필요하며 농어촌 직장인 중 문제음주자 및 알코올 의존자의 조기발견 및 관리를 위한 알코올중독 예방 교육 및 진단 치료에 관한 교육 프로그램 개발이 필요하다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2003.05b
• /
• pp.1401-1404
• /
• 2003

현재 제공되는 인터넷 서비스들의 동작 특성은 기존에 고려되던 트래픽 특성과는 완전히 다른 자기 유사성(Self·similarity)이라는 성질을 가진다는 것이 증명되었다. 자기 유사성은 장기간 의존성으로 표현되는데, 이것은 단기간 의존성 성질을 갖는 기존의 모델인 포아송(Poisson) 모델과는 상반되는 개념이다. 따라서 차세대 통신망의 설계 및 디멘져닝을 위해서는 무엇보다도 데이터 트래픽의 주요 특성인 버스트성(Burstiness)과 자기유사성이 반영된 트래픽 모델이 요구된다. 여기서 자기유사성은 허스트 파라미터(Hurst Parameter)로 특성화 될 수 있다. 이러한 관점에서 본 논문에서는 데이터 트래픽 특성이 서로 다른 다수의 데이터 트래픽의 통합되어 통신망에 입력되는 경우 주요 파라미터인 Hurst Parameter의 변화를 다양한 환경 하에서 분석하였고 이를 시뮬레이션 결과와도 비교하였다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.9
• /
• pp.1053-1057
• /
• 2012

In this study, the temperature-dependency of the tensile properties of a glass fiber reinforced plastic (GFRP) used in wind turbine blades was examined. The tensile strength, elastic modulus, and Poisson's ratio of the tensile specimen manufactured from uniaxial ($0^{\circ}$) and triaxial ($0/{\pm}45^{\circ}$) laminate composite plates were measured at four different testing temperatures-room temperature, $-30^{\circ}C$, $-50^{\circ}C$, and $60^{\circ}C$. It was found that the tensile strengths and elastic moduli of the uniaxial laminates were greater than those of the triaxial laminates over the testing temperature range. The tensile strength of the two laminates was significantly dependent on the testing temperature, while the dependency of the elastic modulus on the temperature was insignificant. Furthermore, it could be considered that the Poisson's ratio changed slightly with a change in the testing temperature.

• Journal of radiological science and technology
• /
• v.39 no.3
• /
• pp.435-441
• /
• 2016

The importance of radiation dose display of medical X-ray equipment was emphasized, while third edition of IEC(International Electrotechnical Commission) 60601 started to apply. The existing medical X-ray equipment selected a method for attaching the DAP(Dose Area Product) meter when the dose display. However, because the DAP meter was dependent on all of the income, And it did not yet produced in Korea. So, we received the support of Seoul R&BD Program(Grants No. C1152055) to produce DAP meter prototype of the Domestically technology. In this study, the performance of this prototype was evaluated by comparing the German company's product Evaluation item was an electronic capture performance, radiation dose dependence, radiation quality dependence, energy transmittance, repeatability, light transmittance of 6 entries. And IEC 60580 was based on this evaluation. Evaluation results were electronic capture performance intrinsic error 9.5%, radiation dose dependence limits of variation 1%, repeatability coefficient of variation 2%, energy transmittance 91% each assessment was passed. However radiation quality dependence limits of variation 29%, light transmittance 55% was less than acceptance criteria.

• Childhood Kidney Diseases
• /
• v.5 no.2
• /
• pp.117-124
• /
• 2001

Purpose : Since Mendoza(1990)'s report that long term methylprednisolone pulse therapy by Mendoza protocol (MP therapy) is a good treatment option in focal segmental glomerulosclerosis(FSGS), there have been reports of the effects of this therapy in steroid-resistant nephrotic syndrome. However, no studies have been performed on the effects of MP therapy in steroid- dependent nephrotic syndrome and secondary nephrotic syndrome. In this study, we investigated the effects of long term MP therapy in primary and secondary nephrotic syndrome in which previous treatment options were not effective. Methods : We chose 10 children who were diagnosed with steroid-dependent minimal change nephrotic syndrome(SD-MCNS), who had shown frequent relapse during the immunocompromised or cytotoxic therapy Period, and 6 children with FSGS and 5 children with secondary nephrotic syndrome children, who had shown no response during the previous therapy period. We treated these patients according to Mendoza protocol involving infusions of high doses of methylprednisolone, often in combination with oral cyclophosphamide for 82 weeks. Results : In all the 10 children with SD-MCNS, complete remission was visible on average of $18{\pm}9$ days after MP therapy was started. However, all these children relapsed during or after MP therapy. In these children, the mean relapse rate prior to MP therapy was $2.1{\pm}1.0$ relpases/year, which was reduced to $1.4{\pm}0.9$ relapses/year during MP therapy(P>0.05) and rose to $2.7{\pm}1.0$ relapse/year after MP therapy. Of the 6 children with FSGS, 4 children($67\%$) showed complete remission, of whom 3 children($50\%$) remained in the remission status during the follow up period, $1.2{\pm}0.7$ years, after the end of MP therapy. 2 children($33\%$) showed no response. All of the 5 children with secondary nephrotic syndrome showed remission and remained in the remissiom status during the follow up period, $1.7{\pm}0.6$ years The only side effect of MP therapy was transient hypertension in 10 children of ail subjects during the intravenous infusion of methylprednisolone. Conclusion : We conclude that although long term MP therapy is not effective in the treatment of SD-MCNS, it is an effective therapy against intractable FSGS and secondary nephrotic syndrome. (J Korean Soc Pediatr Nephrol 2001 ; 5 : 117-24)

• Journal of the Korean Regional Science Association
• /
• v.40 no.1
• /
• pp.3-17
• /
• 2024

Despite extensive discussions on the repercussions of the prolonged COVID-19 pandemic, there is a lack of analysis on the relationships and changes in relationships between business districts Therefore, this study aims to understand the impact of COVID-19 on retail business districts in Seoul by considering the geographical dependency and interactions of these districts. Using data from the fourth quarters of 2019 to 2021 for 1,490 retail business districts in Seoul, we employed the 3-Stage Least Squares (3SLS) estimation method for simultaneous equation modeling to empirically examine how spatial dependencies among retail business districts in Seoul have evolved due to the influence of COVID-19. The results indicate the existence of spatial dependence among retail business districts in Seoul, with developmental districts exerting a negative influence on nearby districts. Furthermore, the analysis reveals changes in dependency patterns after the onset of COVID-19, interpreted as a decrease in commercial activities in developmental districts due to the impact of the pandemic. The significance of this study lies in providing new insights into Seoul's retail business districts through a spatially dependent analysis, offering a foundation for various stakeholders, including government, local authorities, and small business owners, to respond appropriately to changes in business districts by considering their interrelationships.

• Fire Science and Engineering
• /
• v.24 no.2
• /
• pp.76-81
• /
• 2010

For the safe handling of toluene, explosion limit at $25^{\circ}C$ and the temperature dependence of the explosion limits were investigated. And flash point and AIT (Autoignition Temperature) for toluene were experimented. By using the literature data, the lower and upper explosion limits of toluene recommended 1.13 vol% and 7.9 vol%, respectively. In this study, measured the lower and upper flash points of toluene by air-blowing tester were $5^{\circ}C$ and $40^{\circ}C$, respectively. And measured the upper flash points of toluene by Setaflash tester was $41.5^{\circ}C$. This study measured relationship between the AITs and the ignition delay times by using ASTM E659-78 apparatus for toluene, and the experimental AIT of toluene was $547^{\circ}C$. The new equations for predicting the temperature dependence of the explosion limits of toluene is proposed. The values calculated by the proposed equations were a good agreement with the literature data.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.37 no.5
• /
• pp.9-15
• /
• 2000

The 3 ${\mu}{\textrm}{m}$-thick PVDF (polyvinylidene fluoride) thin film have been prepared using physical vapor deposition with electric field, and its FT-IR spectrum, dielectric property and electric conduction phenomenon have been investigated. Since the characteristic peaks are detected at 509.45 ［$cm^{-1}$ /］ and 1273.6 ［$cm^{-1}$ /］in the FT-IR spectrum, we are confirmed that the $\beta$ -phase is dominant in the PVDF thin film. In the results of dielectric properties, the PVDF thin film shows anomalous dispersion, i.e. gradual decrease of dielectric constant with increase of frequency, and also that the dielectric absorption point changes from 200 Hz to 7000 Hz with increasing temperature of thin film, which is consistent with the Debye's theory. The activation energy ( $\Delta$H) obtained from temperature dependence of dielectric loss is 21.64 ㎉/mole. We confirm that the electric conduction mechanism of PVDF thin film is dominated by ionic conduction by investigating the dependence of the leakage current of the thin film on the temperature and the electric field.