• 한국통신학회논문지
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• 제33권10C호
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• pp.764-777
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• 2008

차세대 모바일 통신 기술로 불리는 4G는 인터넷 기술의 급격한 발전 및 이기종망 간의 통합으로 인해 핸드폰, PMP, UMPC 등과 같은 모바일 단말을 사용한 무선 인터넷의 이용이 증가할 것으로 전망된다. 이로 인해 사용자는 유선 인터넷 뿐만 아니라 무선 인터넷 환경에서도 개인정보의 불법적인 사용을 예방하고 효율적으로 관리할 수 있는 전자ID(Digital ID) 기술이 필요하다. 본 논문에서는 다양한 전자ID 관리 기술을 분석하고, 사용자가 직접 개인정보를 통제할 수 있는 사용자 중심의 전자ID 관리 기술에 대한 요구사항을 정의한다. 또한 4G 표준기술로 주목받고 있는 3GPP(3rd Generation Partnership Project)의 LTE/SAE(Long Term Evolution/System Architecture Evolution) 네트워크에서 모바일 응용을 위한 인증 메커니즘을 제안한 후에 이와 연동이 가능한 사용자 중심의 모바일 전자ID지갑 메커니즘을 제안한다.

• 한국해양공학회지
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• 제23권6호
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• pp.71-76
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• 2009

This paper describes a statistical analysis method for predicting a coast fishing boat's effective horsepower. The EHP estimation method for small coast fishing boats was developed, based on a statistical regression analysis of model test results in a circulating water channel. The statistical regression formula of a fishing boat's effective horsepower is determined from the regression analysis of the resistance test results for 15 actual coast fishing boats. This method was applied to the effective horsepower prediction of a G/T 4 ton class coast fishing boat. From the estimation of the effective horsepower using this regression formula and the experimental model test of the G/T 4 ton class coast fishing boat, the estimation accuracy was verified under 10 percent of the design speed. However, the effective horsepower prediction method for coast fishing boats using the regression formula will be used at the initial design and hull-form development stage.

• 대한조선학회논문집
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• 제44권4호
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• pp.349-359
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• 2007

In this study the hull form design with minimum resistance of domestic coastal fishing boat using a computer design procedure is carried out. The target boat is G/T 4.99 ton class fishing boat. which is one of the most popular boat in the coastal sea. For the task, the design parameters needed in preliminary stage are selected or determined from the existing boat. which has excellent resistances characteristics. In the EHP estimation during the design procedure, the main objective function is the hull resistance, and the initial hull forms before the optimization are selected from the boats that are in operation now. The EHP values from the hull after optimization process are also compared with those of the original hull to confirm its effect. Also, optimizing is investigated for the hull form to reestimate such factors as stability, laboring environment for the best design. it is expected that the results of this study here can be effectively used to improve the present design status of domestic small fishing boats.

• 한국조경학회지
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• 제30권5호
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• pp.107-115
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• 2002

This study was carried out to compare artificial soil formulated by blending calcined clay and coconut peat with perlite, then to evaluate this soil as a perlite substitute for use as an artificial planting medium. To achieve this, a determination of the physico-chemical properties and it's effect on plant growth were conducted by comparing those with large perlite grains and small grains. The results are summarized as follows: 1) The bulk density was 0.41g/㎤. This density was lower than that of field soil, but higher than that of large perlite grain(0.23g/㎤) and small grain(0.25g/㎤). The porosity, field capacity, and saturated hydraulic conductivity were 71.3%, 49.2%, and 3.8$\times$10-2cm/s, respectively. The air-permeability, water holding capacity, and drainage were better than or equal to that both large and small perlite grain. 2) It was near-neutral in reaction(pH=6.6). It had a high organic carbon content(65.8g/kg) and a low available phosphoric acid content(84.7mg/kg). It was similar to crop soil in cation exchange capacity(11.4cmol/kg). It had a low exchangeable calcium content(0.71cmol/kg), a low exchangeable magnesium content(0.68cmol/kg), a high exchangeable potassium content(2.54cmol/kg), and a high exchangeable sodium content(1.12cmol/kg). Except for the exchangeable potassium and sodium content, the chemical properties were better than or equal to both large and small grain perlite. The excessive exchangeable potassium or sodium content will inhibit plant growth. 3) In Experiment 1, the plant growth tended to be higher compared to that of large and small perlite gains. But in Experiment 2, it tended to be lower. This might be linked to the excessive exchangeable potassium or sodium content. 4) It could be considered as a renewable perlite substitute for greening of artificial soil. But, it would be necessary to leach the excessive exchangeable potassium or sodium to avoid the risk of inhibiting plant growth.

• Bulletin of the Korean Chemical Society
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• 제29권6호
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• pp.1167-1172
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• 2008

We investigated the glass transition temperatures ($T_g$) of dendrons consisting of conformationally mobile aliphatic polyether dendritic cores plus glassy peripheral polystyrenes (PSs), and linear PSs in the molecular weight range of 1000-8500 g/mol. We compared their $T_g$ behavior depending on their polymeric architecture. The linear PSs show a typical growth of $T_g$ up to 92.5 ${^{\circ}C}$ as the molecular weight increases to 8300 g/mol, while the dendrons display nearly constant $T_g$ values of 58-61 ${^{\circ}C}$, despite the increase of molecular weight with each generation. The striking contrast of Tg behavior would be mainly attributed to the fact that the dendrons keep the ratio of $N_e$/M ($N_e$: number of peripheral chain ends, M: molecular weight) over all the generations. Additionally, for the influence of dendritic spacers on glass transition temperature we prepared dimeric PSs with different linkage groups such as aliphatic ether, ester and amide bonds. We found that the dimer with the ether spacer exhibited the lowest glass transition at 55.4 ${^{\circ}C}$, while the amide linked dimer showed the highest glass transition temperature at 74.2 ${^{\circ}C}$. This indicates that the peripheral PS chains are effectively decoupled by the conformationally flexible ether spacer. The results from this study demonstrated that polymeric architecture and dendritic core structures play a crucial role in the determination of glass transition behavior, providing a strategy for the systematic engineering of polymer chain mobility.

• 한국조경학회지
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• 제30권2호
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• pp.88-94
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• 2002

This study was conducted to select suitable turfarasses for use at 2002 world cup soccer fields in Korea. A 1/1000 scale Inchon worldcup soccer dome was constructed for this research. Species and seeding rates of cool-season grasses used inside and outside the dome were Kentuck bleugrass 10g/$m^2$ (KB), Kentucky bleugrass 10g/$m^2$+ perennial ryegrass 10g/$m^2$ mixture (KB+PR) and Kentucky bleugrass 6g/$m^2$+tall fescue 14g/$m^2$+ perennial ryegrass 4g/$m^2$ mixture (KB+TF+PR). Warm-season grasses also used in this study were Zoysia japonica 'Anyangjungzii' (ZA) and Zoysia japonica 'Zenith'(ZZ) which were layed as sod. So, total 5 types of grasses were used inside and outside the dome. The rootzone was constructed by the multi-layer method(United States Golf Association method). The plots were designed by randomized block design. Cool-season grasses(KB, KB+PR, KB+TF+PR) were found to be better performers for visual rating and visual color than the zoysiagrasses(ZA, ZZ). There were no significant differences in turf performance within cool-season grasses, while ZA showed better turf performances than ZZ within zoysiagrasses. The green color was maintained for about 10 months in the col-season grasses(KB, KB+PR, KB+TF+PR) compared to about 5~6 months in the zoysiagrasses. Root length and density data revealed higher values for KB, KB+PR and KB+TF+PR compared to ZA and ZZ. Root performance of 22 was better than ZA within zoysiagrasses which was the opposite result of turf performances. There was also no significant difference between U performance inside and outside the dome. However, the decreasing tendency of turf quality inside the dome at the end of the study showed that more proper maintenance technology was needed inside the d[me. It could be concluded by this study that cool-season grasses(KB, KB+PR, KB+TF+PR) were more suitable turfgrasses than waits-season zoysiagrasses(ZA, ZZ) for use at 2002 world cup soccer fields in Korea.

• 한국산업정보학회논문지
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• 제17권1호
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• pp.31-38
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• 2012

Next generation cellular applications and smart phone usage generate very heavy wireless data traffic. It becomes ineluctable for mobile network operators to have multiple core network entities such as Serving Gateway and Packet Data Network Gateway in 4G-LTE to share this high traffic generated. A typical configuration consists of multiple serving gateways behind a load-balancer which would determine which serving gateway would service a end-users'request. Such hardware is expensive, has a rigid policy set, and is a single point of failure. Another perspective of today's increasingly high data traffic is that besides it is being widely accepted that the high bandwidth L TE provides is creating bottlenecks for service providers by the increasing user bandwidth demands without creating any corresponding revenue improvements, a hidden problem that is also passively advancing on the newly emerging 4G-LTE that may need more immediate attention is the network signaling traffic, also known as the control-plane traffic that is generated by the applications developed for smartphones and tablets. With this as starting point, in this paper, we propose a solution, by a new approach considering OpenFlow switch connected to a controller, which gains flexibility in policy, costs less, and has the potential to be more robust to failure with future generations of switches. This also solves the problem of scaling the control-plane traffic that is imperative to preserve revenue and ensure customer satisfaction. Thus, with the proposed architecture with OpenFlow, mobile network operators could manipulate the traffic generated by the control-plane signaling separated from the data-plane, besides also reducing the cost in installing multiple core-network entities.

• 한국조경학회지
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• 제46권4호
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• pp.61-75
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• 2018

본 연구의 목적은 도시계획시설로 조성되는 완충녹지가 $PM_{2.5}$(초미세먼지) 저감에 효과가 있는지를 규명하고, 도로변 완충녹지의 구조, 녹량(녹지용적), 식재유형에 따른 초미세먼지 변화량을 분석하여 초미세먼지 저감을 위한 완충녹지 조성 시 활용할 수 있는 요소들을 도출하는 것이었다. 연구대상지는 송파구를 선정하였고, 양재대로, 송파대로에 인접한 5개의 완충녹지에서 16개 조사구를 선정해 현장조사를 실시하였다. $PM_{2.5}$ 농도 측정결과, 조사구별 평균농도는 계절 상관없이 보도 $46.6{\mu}g/m^3$, 녹지 $45.5{\mu}g/m^3$, 주거지 $42.9{\mu}g/m^3$로 모두 도로($53.2{\mu}g/m^3$)보다 낮았으며, 주거지 농도 값이 가장 낮았다. 완충녹지의 농도 저감효과 확인을 위해 완충녹지의 녹량과 초미세먼지 상대비율간의 상관관계 분석결과, 교목과 관목 전체 녹량이 높은 그룹의 상대비율이 낮은 것으로 확인되어 완충녹지 녹량의 영향력을 증명했으며, 관목 부족형이 교목 부족형보다 농도상대비율이 더 높은 것으로 확인되어 관목의 영향이 더 큰 것으로 판단되었다. 교목과 관목의 식재구조에 따른 녹피율과 녹지용적계수가 복합적으로 $PM_{2.5}$ 농도 저감에 영향을 미치고 있었으며, 교목의 열수와 관목의 층위구조가 $PM_{2.5}$ 농도 저감에 중요한 영향요인으로 판단되었다. 특히, 초미세먼지 농도가 높은 겨울철 완충녹지의 $PM_{2.5}$ 농도저감 특성 분석결과, 관목의 녹피율이 중요한 요인이었다.

• 한국정보통신학회논문지
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• 제9권5호
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• pp.1031-1038
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• 2005

본 논문에서는 패럴렉스 배리어 방식의 2D/3D 겸용 PC 및 핸드폰용 LCD를 위한 화소단위의 실시간 3D 영상변환 구조를 제안하고, 이를 FPGA 기반으로 설계한 후에 전체적인 동작을 위한 시스템으로 구현하였다. PC로부터 출력되는 아날로그 형태의 영상신호를 A/D 변환한 후에 디지털 형태의 신호를 입력된 영상의 형태에 따라서 3D 형태의 영상으로 재구성한다. 3D 형태의 영상으로 재구성하는 알고리즘은 패럴렉스 배리어에 많은 부분 의존하고 하는데, 입력되는 영상의 포맷에 따라서 R, G, B의 화소 단위로 영상을 인터리빙 하는 방식을 사용한다. 제안한 구조는 고속의 메모리 처리기법과 함께 다시점 2D 영상을 3D 영상으로 변환하는 FPGA로 설계되고, 고속의 데이터 저장 및 처리를 위해 4개의 SDRAM을 사용한다. 구현된 전체 시스템은 A/D 변환기를 위한 시스템과 디지털화된 2D 영상신호를 3D 디스플레이를 위한 영상신호로 변환하는 FPGA 시스템 그리고 3D영상을 디스플레이할 수 있는 LCD 패널로 구성된다.

• 대한조선학회논문집
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• 제52권4호
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• pp.305-314
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• 2015

In this paper, a numerical analysis is carried out to study the drag of conical cavitators, supercavity generation devices for the high-speed underwater vehicle. The realizable k-∊ turbulence model and the Schnerr-Sauer cavitation model are applied to calculate steady-state supercavitating flows around cones of various cone angles. The calculated drags of the cones are decomposed of the pressure and the friction parts and their dependency on the geometry and the flow conditions have been analyzed. It is confirmed that the pressure drag coefficients of the cones can be estimated by a simple function of both the cone angle and the cavitation number while the friction drag coefficients approximately by well-known empirical formulas, e.g., Schults-Grunow's for the drag of the flat plate. Finally a practical method for estimating the total drags of supercavitating cones is suggested, which can be useful consequently for the design of conical cavitaors.