• Title/Summary/Keyword: Hybrid evaluation

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A Network-Aware Congestion Control Scheme for Improving the Performance of C-TCP over HBDP Networks (HBDP 네트워크에서 C-TCP의 성능 향상을 위한 네트워크 적응적 혼잡제어 기법)

  • Oh, Junyeol;Yun, Dooyeol;Chung, Kwangsue
    • Journal of KIISE
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    • v.42 no.12
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    • pp.1600-1610
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    • 2015
  • While today's networks have been shown to exhibit HBDP (High Bandwidth Delay Product) characteristics, the legacy TCP increases the size of the congestion window slowly and decreases the size of the congestion window drastically such that it is not suitable for HBDP Networks. In order to solve this problem with the legacy TCP, many congestion control TCP mechanisms have been proposed. C-TCP (Compound-TCP) is a hybrid TCP which is a synergy of delay-based and loss-based approaches. C-TCP adapts the decreasing rate of the delay window without considering the congestion level, leading to degradation of performance. In this paper, we propose a new scheme to improve the performance of C-TCP. By controlling the increasing and decreasing rates according to the congestion level of the network, our proposed scheme can improve the bandwidth occupancy and fairness of C-TCP. Through performance evaluation, we show that our proposed scheme offers better performance in HBDP networks as compared to the legacy C-TCP.

Performance Evaluation of High Strength Concrete with Composite Fibers in Accordance with High Temperature (복합섬유가 혼입된 고강도 콘크리트의 고온가열에 따른 성능 평가)

  • Kim, Seung-Ki;Kim, Woo-Suk
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.19 no.6
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    • pp.63-71
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    • 2015
  • The objective of the present study is to investigate how elevated temperature ranging from $100^{\circ}C$ to $800^{\circ}C$ as well as room temperature affects the variation of mechanical properties of high strength concrete ($over\;f_{ck}=60MPa\;grade$). In this experiment, specimens were exposed for a period of $2^{\circ}C/min$ to temperatures of $20^{\circ}C$, $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$ $400^{\circ}C$, $500^{\circ}C$, $600^{\circ}C$, $700^{\circ}C$ and $800^{\circ}C$, respectively. Accordingly, the study investigated the fire resistance performance of high strength concrete mixed with composite fibers which composed with hybrid fibers and steel fibers. After cooling down to ambient temperature, the following basic mechanical properties were then evaluated and compared with reference values obtained prior to thermal exposure: (i) compressive strength in room temperature; (ii) residual compressive strength; (iii) Poisson's ratio; (iv) weight change; (v) SEM analysis & XRD analysis In addition, XRD and SEM Images analyses were performed to investigate chemical and physical characteristics of high strength concrete with composite fibers according to high temperature.

A R&D Model for Korean SI Companies' International Competitiveness (World Class SI 기업으로의 도약 : 핵심 경쟁력 확보를 위한 R&D 모델 개발)

  • Lee, Yeon-Hee;Choi, Jin-Young
    • Journal of Information Technology Services
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    • v.2 no.2
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    • pp.15-29
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    • 2003
  • This thesis suggests a R&D model for Korean SI companies who aggressively drive oversea business to overcome domestic market limitation and to become world class SI players. Even though there have been a lot of discussions on IT technologies and new business models, scientific approach to a R&D model for SI companies is rare due to its natural distinctiveness from manufacturing and general service domain. Therefore, this will be a flagship thesis to keep up our study. As business market environment gets more competitive, major Korean SI players will be confronted with much more keen competition among themselves. And as they are willing to expand their oversea market presence, they can not help struggling against global SI players. So, here we are presenting SI players the reinforcement of R&D as one of the key components to build up their own core competencies. That is, SI players have to adopt and evaluate fast changing and complicated IT technologies at the right time, and to apply them into a real business with cost-effective service delivery and operation processes internally. The ultimate purpose of all of these activities is to offer a SI company the value added business model based on its innovative technical capabilities and well refined service deliver model. For this purpose, we suggests, SI company's R&D has to play an important role of emerging technology verification/evaluation/utilization, value added business model creation, future innovation lead, standard body participation, and effective service delivery and quality system development. To become a more effective R&D organization, hybrid R&D, in which central R&D and divisional sub R&D work together, is considered as an idea model. The reliability of the R&D model for Korean SI companies', here we suggest, has been checked by SI companies R&D specialists and on-site business people.

Characteristic Evaluation of the Fe-Al Alloy Preform Fabrication by Reactive Sintering Process for the Al Matrix Composites. (반응소결법으로 제조한 Al기 복합재용 Fe-Al합금 예비성형체의 특성평가)

  • Choi, Dap-Chon;Park, Sung-Hyuk;Joo, Hyung-Gon
    • Journal of Korea Foundry Society
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    • v.19 no.6
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    • pp.493-500
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    • 1999
  • Squeeze casting was used for fabricating a light metal base composite having high strength and wearresistance. Reactive sintering was used to prepare the preform of Squeeze casting. To utilize Fe-Al intermetallic compounds and SiC particle as a reinforcement, there needs to prepare Fe-Al mixed powder at 50, 60, 70at.%Al, and add SiC powder to the above mixture at 4, 7, 16, 24wt.%. The prepared mixture with SiC was reactive sintered in a tube furnace at $660^{\circ}C$ to get a porous hybrid preform of intermetallic compound and SiC. The preform prepared above was placed in a metal mold, preheated at $660^{\circ}C$ AC4C matrix was injected into the mold with the temperature of the melt at $610^{\circ}C$ After these processes, 66MPa was applied to the mold for 5 minute to finish the whole procedure. The maximum reaction temperature was increased with the increased Al amount, but decreased with the increased SiC amount. The density of the preform was decreased with SiC amount increase in the compacts due to swelling of the preform. An optical microscope was applied to observe the micro structure and the dispersion of the reinforcements. To analyze phases, We utilized XRD, EDS. Hardness test were chosen to get the information of mechanical properties. There were no significant changes in micro structure between the composite and preform. However, it was shown that uniform dispersion of the reinforcers and complete infiltration of the melt into the preform were achieved through the procedure of the squeeze casting. It was observed that the hardness of the composite is decreased with increased SiC amount, resulting from the volumetric expansion of the preform.

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Development of the Developmental Support Competency Scale for Nurses Caring for Preterm Infants (미숙아 발달지지를 위한 간호역량 측정도구 개발)

  • Kim, Jeong Soon;Shin, Hee Sun
    • Journal of Korean Academy of Nursing
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    • v.46 no.6
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    • pp.793-803
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    • 2016
  • Purpose: Developmental care has been recognized as a very important component for the development and health promotion of preterm infants. However, research on how to assess developmental nursing competency has not been studied as expected. This study was done to develop and evaluate a new scale to measure nursing competency for developmental support of preterm infants. Methods: Concept analysis was done with using the Hybrid model of Schwartz-Barcott and Kim (2000), from which a preliminary new scale (30 items) was developed. To test the validity and reliability of the new scale being developed, data were collected from 122 NICU nurses at 4 hospitals in 3 cities in the Republic of Korea, from December, 2014 to March, 2015. Results: The final version of the Developmental Support Competency Scale for Nurses (DSCS-N) caring for premature infants was a 4-point Likert type scale, consisting of 19 items, and categorized as 6 factors, explaining 62.5% of the total variance. Each of the factors were named as follows; 'environmental support' (4 items), 'parental support' (3 items), 'interaction' (3 items), 'critical thinking' (3 items), 'professional development' (3 items), and 'partnership' (3 items). The Cronbach's ${\alpha}$ coefficient for the scale was .83 and the reliability of the subscales ranged from .60~.76. Conclusion: The psychometric evaluation of the new scale demonstrated an acceptable validity and reliability. Findings indicate that the DSCS-N can be used as the tool to test the effect of educational programs for nurses and contribute to advance developmental care for preterm infants.

Evaluation of SHCC on Direct Tensile Load using Acoustic Emission Technique (음향방출기법을 이용한 혼입되는 섬유의 종류에 따른 SHCC의 직접인장거동특성 평가)

  • Kim, Yun-Su;Yun, Hyun-Do;Jeon, Esther;Park, Wan-Shin
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.177-180
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    • 2008
  • SHCC shows the high energy tolerance capacity due to the interfacial bonding of the fibers to the cement matrix. For effective material design and application of SHCC, it is needed to investigate the damage process and micro-fracture mechanism of cement matrix reinforced with different types of fibers. The objective of this paper is to investigate the direct tensile response of cement composites reinforced with single and hybrid fibers using acoustic emission(AE) technique. In this study, the correlations between AE signal and result of the direct tensile response of SHCC. For these purposes, three kinds of fibers were used: PET1.5%, PET1.0+PE0.5%, PET1.0%+PVA0.5%. The result of the direct tensile response of SHCC, for the same volume fraction of fibers, ultimate strength of PET-PE specimen was 2.7 times higher than specimens with PET fibers. And from AE signal value, AE event numbers and cumulative energy were different according to kind of fiber because of the different material properties of reinforced fiber.

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A Basic Study on the Air Circulation System for Heating using Solar and Geothermal Heat - Focused on Trombe Wall Thermal Storage Performance using Solar Heat - (태양열과 지열을 이용한 난방용 공기순환시스템 기초연구 - 태양열을 이용한 트롬월식의 축열성능 중심으로 -)

  • Kim, Byung-Yun;Choi, Yong-Seok
    • Journal of the Korean Institute of Rural Architecture
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    • v.19 no.4
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    • pp.49-56
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    • 2017
  • Each country in the world currently concentrates on shifting into clean energy, which can be alternative energy, for global environment protection and solution to the problem of fossil fuel depletion. The Korean government is predicted to develop renewable energy, such as solar power, ground power, and offshore wind power, and to increase their supply ratios by ending the use of coals and nuclear power plants. This study conducted experiments on thermal storage performance of Trombe wall thermal storage materials using solar power and simulations in order to offer baseline data for the development of a hybrid air circulation system for heating that can maximize efficiency by simultaneously using solar and geothermal power. The study results are as follows: (1) In all the specimens with 3m, 5m, and 7m in the length of thermal storage pipe, $5.7^{\circ}C$, $7.8^{\circ}C$, and $10.5^{\circ}C$ rose, respectively, as the thermal storage effect of the specimens attaching insulation film and black tape to the general funnel. They were most excellent in terms of thermal storage effect. (2) As a result of thermal performance evaluation on the II type specimens, II-3 ($7.8^{\circ}C$ rise) > II-4 ($5.3^{\circ}C$ rise) > II-1 ($3.9^{\circ}C$ rise) > II-2 ($2.3^{\circ}C$ rise) was revealed, and thus II-3 (insulation film + black tape) was most effective as shown in the I type. (3) This study analyzed air current and temperature distribution inside of the greenhouse by linking actually measured values and simulation interpretation results through the interpretation of CFD (computational fluid dynamics). As a result, the parts absorbing heat and discharging heat around the thermal storage pipe could be visibly classified, and temperature distribution inside of the greenhouse around the thermal storage pipe could be figured out.

Comparison Analysis of Estimation Models of Hourly Horizontal Global Solar Radiation for Busan, Korea (부산지역에 적합한 시간당 수평면 전일사량 산출모델의 비교분석)

  • Kim, Kee Han;Oh, Kie-Whan
    • Journal of the Korean Solar Energy Society
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    • v.33 no.5
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    • pp.9-17
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    • 2013
  • Hourly horizontal global solar radiation has been used as one of significant parameters in a weather file for building energy simulations, which determines the quality of building thermal performance. However, as about twenty two weather stations in Korea have actually measured the horizontal global sola radiation, the weather files collected in other stations requires solar data simulation from the other meteorological parameters. Thus, finding the reliable complicated method that can be used in various weather conditions in Korea is critically important. In this paper, three solar simulation models were selected and evaluated through the reliability test with the simulated hourly horizontal global solar radiation against the actually measured solar data to find the most suitable model for the south east area of Korea. Three selected simulation models were CRM, ZHM, and MRM. The first two models are regression type models using site-fitted coefficients which are derived from the correlation between measured solar data and local meteorological parameters from the previous years, and the last model is a mechanistic type model using the meteorological data to calculate conditions of atmospheric constituents that cause absorption and scattering of the extraterrestrial radiation on the way to the surface on the Earth. The evaluation results show that ZHM is the most reliable model in this area, yet a complicated hybrid simulation methods applying the advantages of each simulation method with the monthly-based weather data is needed.

Design and Energy Performance Evaluation of Plus Energy House (플러스에너지하우스 설계 및 에너지 성능 평가)

  • Kim, Min-Hwi;Lim, Hee-Won;Shin, U-Cheul;Kim, Hyo-Jung;Kim, Hyun-Ki;Kim, Jong-Kyu
    • Journal of the Korean Solar Energy Society
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    • v.38 no.2
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    • pp.55-66
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    • 2018
  • South Korea aims to shift the 20 percent of electricity supplement from the fossil fuel including the nuclear to renewable energy systems by 2030. In order to realize this agenda in the buildings, the plus energy house is necessary to increase the renewable energy supplement beyond the zero energy house. This paper suggested KePSH (KIER Energy-Plus Solar House) and energy performance of house and renewable energy systems was investigated. The KePSH has the target of generating 40% surplus energy than the conventional house energy consumption. The plus energy house is the house that generates surplus energy from the renewable energy sources than that consumes. In order to minimize the cooling and heating load of the house, the shape design and passive parameters design were conducted. Based on the experimental data of the plug load in the typical house, the total energy consumption of the house was estimated. This paper also suggested renewable energy sources integrated HVAC system using air-source heat pump system. Two cases of renewable energy system integration methods were suggested, and energy performance of the cases was investigated using TRNSYS 17 program. The results showed that the BIPV (building integrated photovoltaic) system (i.e., CASE 1) and BIPV and BIST system (i.e., CASE 2) shows 42% and 29% of plus energy rate, respectivey. Also, CASE 1 can generate 59% more surplus energy compared with the CASE 2 under the same installation area.

Elastic Wave Field Calculations (탄성파의 변형 및 응력 계산에 관한 연구)

  • 이정기
    • Computational Structural Engineering
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    • v.10 no.2
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    • pp.213-223
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    • 1997
  • Calculation of elastic wave fields has important applications in a variety of engineering fields including NDE (Non-destructive evaluation). Scattering problems have been investigated by numerous authors with different solution schemes. For simple geometries of the scatterers (e.g., cylinders or spheres), the analysis of steady-state elastic wave scattering has been carried out using analytical techniques. For arbitrary geometries and multiple inclusions, numerical methods have been developed. Special finite element methods, e.g., the infinite element method and a hybrid method called the Global-Local finite element method have also been developed for this purpose. Recently, the boundary integral equation method has been used successfully to solve scattering problems. In this paper, a volume integral equation method (VIEM) is proposed as a new numerical solution scheme for the solution of general elasto-dynamic problems in unbounded solids containing multiple inclusions and voids or cracks. A boundary integral equation method (BIEM) is also presented for elastic wave scattering problems. The relative advantage of the volume and boundary integral equation methods for solving scattering problems is discussed.

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