• Journal of Communications and Networks
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• 제16권4호
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• pp.430-435
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• 2014

The performance of a distributed database system depends particularly on the site-allocation of the fragments. Queries access different fragments among the sites, and an originating site exists for each query. A data allocation algorithm should distribute the fragments to minimize the transfer and settlement costs of executing the query plans. The primary cost for a data allocation algorithm is the cost of the data transmission across the network. The data allocation problem in a distributed database is NP-complete, and scalable evolutionary algorithms were developed to minimize the execution costs of the query plans. In this paper, quadratic assignment problem heuristics were designed and implemented for the data allocation problem. The proposed algorithms find near-optimal solutions for the data allocation problem. In addition to the fast ant colony, robust tabu search, and genetic algorithm solutions to this problem, we propose a fast and scalable hybrid genetic multi-start tabu search algorithm that outperforms the other well-known heuristics in terms of execution time and solution quality.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2007년도 하계종합학술대회 논문집
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• pp.193-194
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• 2007

We propose The Fast Join Mechanism for overlay multicast. This mechanism is provided with RP(Rendezvous Point), SM(Session Manager) and overlay multicast nodes. The RP provides data transfer to overlay multicast nodes and the Session Manager controls overlay multicast nodes to maintain the overlay topology.

• 천문학논총
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• 제11권1호
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• pp.91-107
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• 1996

We determine analytically the onset of thin-shell formation time of fast wind bubble with power-law energy injection $E_{in}=E_0t^s$, and power-law ambient density structure, ${\rho}_0(r)={\bar{\rho}}(r/{\bar{r}})^{-{\omega}}$. Thin-shell formation time, $t_{sf}$ can be estimated by minimizing the total time elapsed before the complete cooling of shocked gas. For uniform medium (${\omega}=0$) and constant energy injection (s = 1), the onset of shell formation is found to be at $t_{sf}=5.2{\times}10^3yr$, which agrees Quite well with the results of FCT 1D numerical calculation. We solve the line transfer problem with previous result derived by numerical calculation in order to calculate line profile of [OIII] (${\lambda}=5007{\AA}$) forbidden line. In general, radiative outer shell causes the formation of double peaked line profile. Each peak corresponds to approaching and receeding shells with large velocities. Our line profiles show good agreements with observation of expanding shell structure.

• Nuclear Engineering and Technology
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• 제52권1호
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• pp.51-58
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• 2020

Despite the recent growth of interest in molten salt reactor technology and the crucial role which heat transfer plays in the design of power reactors, specific studies on the design of heat exchangers for the Molten Salt Fast Reactor have not yet been performed. In this work we deliver a preliminary but quantitative analysis of the intermediate heat exchangers, based on reference design data from the SAMOFAR H2020-Euratom project. Two different promising reference technologies are selected for study thanks to their compactness features, the Printed Circuit and the Helical Coil heat exchangers. We present preliminary design results for each technology, based on simplified design tools. Results highlight the limiting effects of the compactness constraints imposed on the fuel salt inventory and the allowed size. Large pressure drops on both flow sides are to be expected, with negative consequences on pumping power and natural circulation capabilities. The small size required for the flow channels also represents possible fabrication issues and safety concerns regarding channel blockage.

• Journal of Biosystems Engineering
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• 제27권6호
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• pp.529-536
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• 2002

The performance of stilting engine, in particular, its energy conversion efficiencies are critically influenced by the regenerator characteristics. The regenerator characteristics are influenced by effectiveness, void fraction. heat transfer loss and fluid friction loss in the regenerator matrix. These factors were influenced by the surface geometry and material properties of the regenerator matrix. The regenerator design goals arc good heat transfer and low pressure drop of working Bas across the regenerator. Various data for designing a wire screen matrix have been given by Kays and London(1984). The mesh number of their experiment. however, was confined below the No. 60. which seems rather small for the Stirling engine applications. In this paper. in order to provide a basic data for the design of regenerator matrix, characteristics of heat transfer and flow friction loss were investigated by a packed mettled of matrix in oscillating flow as the same condition of operation in a Stirling engine. Seven kinds of sing1e wire screen meshes were used as the regenerator matrices. The results are summarized as follows; 1. While the working fluid flew slowly in the regenerator. the temperature difference was great at the both hot-blow(the working fluid flows from healer to cooler) and cold-blow(the working fluid flows from cooler to healer). On the other hand. while the working fluid flew fast. the temperature difference was not distinguished. 2. The No.150 wire screen used as the regenerator matrix showed excellent performance than tile others. 3. Phase angle variation and filling rate affected heat transfer or regenerator matrices. 4. Temperature difference between the inlet and outlet of the regenerator is very hish in degree of 120 phase angle.

• 에너지공학
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• 제26권4호
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• pp.57-66
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• 2017

열은 전력과 같이 이동속도가 빠르지 못하고 전력에 비해 손실이 비교적 크게 발생하므로 전력거래와 같이 한개의 운용센터를 두고 열 연계 시스템을 운용하는 것은 현실성이 없다. 현재 열 연계가 모두 이루어지고 있는 한국지역난방공사의 경우에도 인접한 2~4개 정도의 열병합발전소간에만 열 거래가 이루어지고 있는 실정이다. 따라서 본 논문에서는 열 거래를 위한 통합운용센터를 몇 개의 권역으로 나누어 각 권역마다 권역의 Hub 통합운용발전소를 두고 운용하는 것이 열매체의 특성을 반영하는데 적정하고 타당한 것으로 판단하여 집단에너지 사업자간 열 연계 메커니즘을 제안하였다. 제안된 메커니즘에 최적으로 열 거래를 행할 수 있는 알고리즘을 개발하고 이를 실제 사업자에 적용하여 제안한 알고리즘의 유용성을 검증하였다.

• Asian Pacific Journal of Cancer Prevention
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• 제16권14호
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• pp.5993-5999
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• 2015

Background: Molecular testing for human papillomavirus (HPV) is the most objective and reproducible of all cervical cancer screening tests and also less demanding in terms of training and quality assurance. However, there is an impending need for cost effective molecular HPV testing methods with sampling ease, easy storage measures and minimum turn around times suitable for a low resource setting. Objective : Our aim was to evaluate the feasibility of using a fast transfer analysis (FTA) mini elute cartridge for cervical sampling to identify high risk HPV by real time PCR and to compare molecular HPV testing and Pap cytology testing to predict histologically confirmed cervical precancer (CIN 2+ lesions) in a cervical cancer prevention program. Materials and Methods: This was conducted as a pilot study (n=200) on women sampled using FTA mini elute cartridges, genotyped by two different real time PCR assays, detecting 13 high risk HPV (HR HPV) species, including HPV16 along with its physical DNA status. Results obtained from each of the tests were compared and analysed using suitable statistical tests. Results: With FTA mini elute cartridge samples HR HPV positivity was seen in 48/200 (24%). Of these, presence of HPV 16 DNA was observed in 28/48 (58.3%) women. High risk HPV was positive in 20% (37/185) of women with benign cytology and 73.3% (11/15) of women with abnormal cytology findings. A very significant correlation (${\chi}^2=22.090$ ; p=0.000) was observed between cytology and HR HPV findings showing an increasing trend of HR HPV prevalence in 50% (1/2) of LSIL, 75% (3/4) of HSIL and 100% (3/3) of SCC. Of the CIN 2+ lesions identified by histopathology, 88.9% (8/9) had HR HPV. A significant association (${\chi}^2=11.223$ ; p=0.001) of HR HPV and histopathologically confirmed CIN 2+ lesions was found. Sensitivity of the two tests were comparable but specificity of Pap testing was better (90.7% vs 70.4%) to predict histopathologically diagnosed cervical precancers. Conclusions: The current study explored the feasibility of using a FTA mini elute cartridge for cervical sampling for the first time in India as a part of a community based cervical cancer prevention program. We suggest that FTA based sampling is suitable and feasible for real time based HPV testing. Molecular HR HPV testing can be more sensitive and useful to identify high risk women requiring Pap testing which is more specific to detect histologically confirmed cervical precancer.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.151-157
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• 2004

In this paper, we propose a simple control scheme, based on second order sliding modes, which guarantees a fast and precise container transfer and the swing suppression during the container movement, despite of model uncertainties and unmodeled dynamic actuators. In the actual case, the swing suppression is obtained by constraining the system motion on a suitable surface which involves both the desired path and the swing angle. Strictly speaking, the trolley velocity is modified on-line, on the actual swing angle, to obtain the suppression of the oscillations not only at the end of the transport but during transfer as well. Such controller has been tested on a laboratory-size model of the 3Dcrane, and some experimental results are reported.

• Smart Structures and Systems
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• 제3권1호
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• pp.115-131
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• 2007

The electromechanical integrated toroidal drive is a new drive system. For the control of the drive, the torque fluctuation and the steady-state errors should be removed and the fast response to the input change should be achieved. In this paper, the torque fluctuation of the drive system is analyzed and expressed as Fourier series forms. The transfer function of the torque control for the drive system is derived from its electromechanical coupled dynamic equations. A 2-DOF control method is used to control the drive system. Using definite parameter relationship of the 2-DOF control system, the steady errors of the torque control for the drive system is removed. Influences of the drive parameters on the control system are investigated. Using proper drive parameters, the response time of the control system is reduced and the quick torque response of the drive system is realized. Using a compensated input voltage, the torque fluctuation of the drive system is removed as well. The compensated input voltage can be obtained from the torque fluctuation equation and the transfer function. These research results are useful for designing control system of the new drive.

• 한국압력기기공학회 논문집
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• 제12권1호
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• pp.107-114
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• 2016

Four cylindrically shaped IHXs(Intermediate Heat Exchangers) are installed in the PHTS(Primary Heat Transfer System) of the PGSFR(Prototype Gen IV Sodium cooled Fast Reactor). As for the IHX, the temperature difference of structure is inevitable result caused by heat transfer between primary coolant sodium and IHTS(Intermediate Heat Transport System) sodium. It is necessary to evaluate the high temperature structural integrity of IHXs which operate at the elevated temperature condition over the creep temperature. In this paper, the high temperature structural integrity of IHX under assumed loading conditions has been reviewed according to ASME code.