• 한국위성정보통신학회논문지
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• 제10권4호
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• pp.71-76
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• 2015

본 연구는 LTE, 5G의 무선 통신네트워크망에서 효율적으로 무선에너지하비스팅과 데이터 전송 실시하기 위한 시스템 모델을 제시한다. 수신 된 신호의 파워를 타임 스위칭(Time Switching)과 파워 스플릿팅(Power Splitting) 기법을 통해 우리가 원하는 무선에너지하비스팅 효율과 데이터 전송률을 만족시키기 위한최적의 타암 & 파워 비율을 찾는다. 그래서 최적의 시간 & 파워 비율을 선정함으로써 우리는 효율적으로 데이터 전송과 에너지하비스팅이 가능하다. 또 이상적인 수신기와 제안한 시스템 모델의 비교를 통해 성능 분석을 실시하고, 앞으로의 연구방향을 제시한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권10호
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• pp.3321-3341
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• 2014

This paper investigates the outage performance and optimization for the four-phase two-way transmission network with an energy harvesting (EH) relay. To enable the simultaneous information processing and energy harvesting at the relay, we firstly propose a power splitting-based two-way relaying protocol (PSTWR). Then, we discuss its outage performance theoretically and derive an explicit expression for the system outage probability. In order to find the optimal system configuration parameters such as the optimal power splitting ratio and the optimal transmit power redistribution factor, we formulate an outage-minimized optimization problem. As the problem is difficult to solve, we design a genetic algorithm (GA) based algorithm for it. Besides, we also investigate the effects of the power splitting ratio, the power redistribution factor at the relay, and the source to relay distance on the system outage performance. Finally, extensive simulation results are provided to demonstrate the accuracy of the analytical results and the effectiveness of the GA-based algorithm. Moreover, it is also shown that, the relay position greatly affects the system performance, where relatively worse outage performance is achieved when the EH relay is placed in the middle of the two sources.

• 한국건설순환자원학회논문집
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• 제2권1호
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• pp.52-59
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• 2014

이 연구에서는 플라이애쉬와 고로슬래그를 혼합한 지오폴리머 콘크리트의 역학성능을 평가하기 위하여 압축강도, 탄성계수 및 쪼갬인장강도에 대해 검토하였다. 또한 다양한 변수에 대한 비교분석을 하기 위해 분체량, 알칼리 활성화제 첨가율 및 실리카퓸 혼입률에 대해서도 동일한 시험을 수행하였으며, 국내 외의 규준식과 비교하였다. 그 결과, 알칼리 활성화제의 첨가율은 18%가 적정하고 실리카퓸 치환율은 5%가 유리한 것으로 나타났다. 지오폴리머 콘크리트의 탄성계수는 변수 및 재령별로 압축강도가 증진됨에 따라 탄성계수가 소폭 상승되는 것으로 나타났으며, 국내 외 규준식에 의한 예측값보다 작은 것으로 나타났다. 또한 응력-변형률 선도를 분석한 결과, 지오폴리머 콘크리트가 일반 OPC 콘크리트 보다 연성적인 거동을 하는 것으로 분석되었다. 쪼갬인장강도는 분체량 $400kg/m^3$와 알칼리 활성화제 첨가율 18%에서 높은 강도를 보였으며, 압축강도에 대한 쪼갬인장강도의 비가 8.7~10.2% 수준인 것으로 분석되었다.

• 대한기계학회논문집
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• 제18권3호
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• pp.653-661
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• 1994

In this paper the CSCM type upwind flux difference splitting Navier-Stokes method has been applied to study the ARL-SL19 supersonic/transonic compressor cascade flow. H-type grid was chosen for its simplicity in applying cyclic tridiagonal matrix algorithm along with conventional slip/no-slip boundary conditions. The thin-layer algebraic model of Baldwin-Lomax was employed for the calculation of turbulent flows. The test case inlet Mach No. was 1.612 and inlet/exit pressure ratio($P_2/P_1$) was 2.15. The results were compared with experimental results from current method were compared well in suction surface with the experiments and other computational results; however, not well in pressure surface. It might be due to the complex flowfields such as shock/boundary layer interaction, turbulence, and flow separation, etc. In the future, a proper turbulence modelling and adaptive grid system will be studied to improve the solution quality.

• 전자공학회논문지D
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• 제35D권7호
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• pp.102-108
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• 1998

A new 1*4 optical waveguide power divider is proposed and fabricated. It consists of a 1*4 multi-branch structure with a beam separator and two beam expanders that can control the splitting ratios between the output ports. The proposed optical waveguide power divider is designed by employing the two dimensional finite difference beam propagation method and is fabricated by a reactive ion etching method. The splitting ratio of fabricatd device is 25.0 : 25.7 : 25.3 : 24.0 for TE mode and 25.7 : 25.2 : 24.1 : 25.0 for TM mode. Comapred with the conventional Y-branch structure, the proposed structure shortens the length of a 1*N divider by the factor 3. Thus it reduces the total propagation loss and the total radiation loss at the branch points. furthermore, the splitting ratios between the output ports may be controlled in this structure for some special applications.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.13-16
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• 2006

Electro-electrodialysis (EED) experiments were carried out for the HI concentration from HIx $(HI-H_2O-I_2)$ solution to improve the Hl decomposition reaction in the thermochemical water-splitting is (iodine-Sulfur) process. EED cell is composed of the collector electrode and electrolyte. Nafion 117 which was cation exchange membrane used as an electrolyte, and the activated carbon cloth used as an electrode. The HI concentration experiment was carried out using the HIx solution and molar ratio of the $I_2$ were varied from 1 to 3 mole. The cell voltages were decreased as temperature increase. And, membrane properties such as transport number of proton and electro-osmosis coefficient were decreased as temperature increase

• 대한조선학회논문집
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• 제47권1호
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• pp.11-19
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• 2010

A code is developed to simulate incompressible free surface flows using the Roe's flux-difference splitting scheme. An interface of two fluids is considered as a moving contact discontinuity. The continuities of pressure and normal velocity across the interface are enforced by the conservation law in the integral sense. The fluxes are computed using the Roe's flux-difference splitting scheme for two incompressible fluids. The interface can be identified based on the computed density distribution. However, no additional treatment is required along the interface during the whole computations. Complicated time evolution of the interface including topological change can be captured without any difficulties. The developed code is applied to simulate the Rayleigh-Taylor instability of two incompressible fluids in the density ratio of 7.2:1 and the broken dam problem of water-air. The present results are compared with other available results and good agreements are achieved for the both cases.

• International Journal of Concrete Structures and Materials
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• 제8권4호
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• pp.301-307
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• 2014

Rice husk ash (RHA) is classified as a highly reactive pozzolan. It has a very high silica content similar to that of silica fume (SF). Using less-expensive and locally available RHA as a mineral admixture in concrete brings ample benefits to the costs, the technical properties of concrete as well as to the environment. An experimental study of the effect of RHA blending on workability, strength and durability of high performance fine-grained concrete (HPFGC) is presented. The results show that the addition of RHA to HPFGC improved significantly compressive strength, splitting tensile strength and chloride penetration resistance. Interestingly, the ratio of compressive strength to splitting tensile strength of HPFGC was lower than that of ordinary concrete, especially for the concrete made with 20 % RHA. Compressive strength and splitting tensile strength of HPFGC containing RHA was similar and slightly higher, respectively, than for HPFGC containing SF. Chloride penetration resistance of HPFGC containing 10-15 % RHA was comparable with that of HPFGC containing 10 % SF.

• 한국분무공학회지
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• 제25권3호
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• pp.103-110
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• 2020

In this study, the behavior of water droplet impacting on a thin horizontal wire was visualized by time-delay photography. The impact behavior modes, critical capture speed and trapped mass were analyzed by changing the droplet size, velocity, wire diameter and eccentricity ratio. As the Weber number increased, the hanging, merging, and splitting modes appeared sequentially for the case of central impact, and the hanging and non-splitting modes appeared for the case of off-center impact. The boundary We number of each mode was affected by the diameter ratio. The critical capture speed was affected much by the degree of eccentricity. For all diameter ratios, it was higher for the case of central impact than for off-center impact. The trapped mass was larger for the case of central impact than for off-center impact and it increased with the smaller We number and the larger diameter ratio.

• 한국농공학회지
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• 제31권3호
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• pp.81-91
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• 1989

The aims of this study were to determine mechanical properties of steel-fiber reinforced concrete under splitting tensile, flexural and compressive loading, and thus to improve the possible applications of concrete. The major factors experimentally investigated in this study were the fiber content and the length and the diameter of fibers. The major results obtained are summarized as follows : 1.The strength, strain, elastic modulus and energy obsorption capability of steel-fiber reinforced concrete under splitting tensile loading were significantly improved by increasing the fiber content or the aspect ratio. 2.The flexural strength, central deflection, and flexural toughness of steel4iber reinforced beams were significantly improved by increasing the fiber content or the aspect ratio. And flexural behavior characteristic was good at the aspect ratio of about 60 to 75. 3.The strength, strain, and energy absorption capability in compression were increased with the increase of the fiber content. These effects were not so sensitive to the aspect ratio. The energy absorption capability was improved only slightly with the increase of the fiber length. 4.The elastic modulus, transverse strains, and poisson's ratios in compression were not influenced by the fiber content. 5.The steel-fibers were considered to be appropriated as the materials covering the weakness of concrete because the mechanical properties of concrete in tension and flexure were significantly improved by steel-fiber reinforcement.