Yun PENG  Xin LIN  Byron CHOI  Bingsheng HE 《Frontiers of Computer Science》2021,15(4):154610

Graph coloring has a wide range of real world applications, such as in the operations research, communication network, computational biology and compiler optimization fields. In our recent work [1], we propose a divide-andconquer approach for graph coloring, called VColor. Such an approach has three generic subroutines. (i) Graph partition subroutine: VColor partitions a graph G into a vertex cut partition (VP), which comprises a vertex cut component (VCC) and small non-overlapping connected components (CCs). (ii) Component coloring subroutine: VColor colors the VCC and the CCs by efficient algorithms. (iii) Color combination subroutine: VColor combines the local colors by exploiting the maximum matchings of color combination bigraphs (CCBs). VColor has revealed some major bottlenecks of efficiency in these subroutines. Therefore, in this paper, we propose VColor*, an approach which addresses these efficiency bottlenecks without using more colors both theoretically and experimentally. The technical novelties of this paper are the following. (i) We propose the augmented VP to index the crossing edges of the VCC and the CCs and propose an optimized CCB construction algorithm. (ii) For sparse CCs, we propose using a greedy coloring algorithm that is of polynomial time complexity in the worst case, while preserving the approximation ratio. (iii) We propose a distributed graph coloring algorithm. Our extensive experimental evaluation on real-world graphs confirms the efficiency of VColor*. In particular, VColor* is 20X and 50X faster than VColor and uses the same number of colors with VColor on the Pokec and PA datasets, respectively. VColor* also significantly outperforms the state-ofthe- art graph coloring methods.  相似文献   

    

Jinyoung YOON  Byoung Il CHOI  Jae Hong KIM 《Frontiers of Structural and Civil Engineering》2022,16(4):506

The cement dispersion performance of a polycarboxylate (PCE)-based superplasticizer is highly related to their adsorption behaviors as a function of time. This study evaluated effects of PCEs on rheological properties of cementitious materials. First, characteristics of PCEs were characterized via permeation chromatography (GPC) and Fourier-transform infrared spectrometry (FT-IR). The adsorption behavior of single and blended PCEs on cementitious composites was identified using total organic carbon analyzer (TOC). Based on the measurement of PCE adsorption, the changes of rheological properties of cementitious materials as well as the number of dispersed cement particles were characterized using a rheometer and laser spectroscopy, respectively. The experimental results support the systematic mechanism of PCE adsorption, cement dispersion, and the decrease in viscosity of cementitious materials.  相似文献   

    

Tsan-Ming CHOI  Alexandre DOLGUI  Guo LI  Suresh P. SETHI  Xiaohang YUE 《工程管理前沿(英文版)》2023,10(1):1

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H J YEOM  D H CHOI  Y S LEE  et al. 《等离子体科学和技术》2019,21(6):64007-57

In this study, plasma density measurements were performed near the plume region of the remote plasma source (RPS) in Ar/ NF₃ gas mixtures using a microwave cutoff probe. The measured plasma density is in the range of 10 ¹⁰ –10 ¹¹ cm ⁻³ in the discharge conditions with RPS powers of 2–4 kW and gas pressures of 0.87–4 Torr. The plasma density decreased with increasing gas pressures and RPS powers under various Ar/ NF₃ mixing ratios. This decrease in the plasma density measured at the fixed measurement position (plume region) can be understood by the reduction of the electron energy relaxation length with increases in the gas pressures and mixing ratio of NF₃/(Ar / NF₃). We also performed downstream etching of silicon and silicon oxide films in this system. The etch rate of the silicon films significantly increases while the silicon oxide is slightly etched with the gas pressures and powers. It was also found that the etch rate strongly depends on the wafer position on the processing chamber electrode, and that the etch selectivity reached 96–131 in the discharge conditions of RF powers (3730–4180 W) and gas pressures (3.6–4 Torr).  相似文献   

    

KIM Jinhyu ;SONG Inseon ;CHOI Sangban 《中南大学学报(英文版)》2015,22(5)

A wireless body area network offers cost-effective solutions for healthcare infrastructure. An adaptive transmission algorithm is designed to handle channel efficiency, which adjusts packet size according to the difference in feature-point values that indicate biomedical signal characteristics. Furthermore, we propose a priority-adjustment method that enhances quality of service while guaranteeing signal integrity. A large number of simulations were carried out for performance evaluation. We use electrocardiogram and electromyogram signals as reference biomedical signals for performance verification. From the simulation results, we find that the average packet latency of proposed scheme is enhanced by 30% compared to conventional method. The simulation results also demonstrate that the proposed algorithm achieves significant performance improvement in terms of drop rates of high-priority packets around 0.3%-0.9 %.  相似文献   

    

CHOI Hoon-k ;YOO Geun-jon ;KIM Churl-hwa 《中南大学学报(英文版)》2011,18(3)

Numerical study was performed to evaluate the characteristics of combined heat transfer of radiation, conduction and convection in indirect near infrared ray (NIR) heating chamber. The effects of important design parameters such as the shape of heat absorbing cylinder and heat releasing fin on the pressure drop and heat transfer coefficient were analyzed with different Reynolds numbers. The Reynolds numbers were varied from 10³ to 3×10⁶, which was defined based on the hydraulic diameter of the heat absorbing cylinder. Analyses were performed to obtain the inner and outer flow and the temperature distributions in the heat absorbing cylinder and the rates of radiation heat transfer and convection heat transfer. As the Reynolds number increases, the convection heat transfer rate is increased while the radiation heat transfer rate is decreased. The average convection heat transfer rate follows a power rule of the Reynolds number. Addition of three-dimensional heat releasing fin to the outside of the heat absorbing cylinder enhances the , convection heat transfer.  相似文献   

    

HUR Yone-gi  CHOI Young-kiu 《钢铁研究学报(英文版)》2011,18(3):17-23

 The strip shape in the stainless steel process has made an issue of the strip quality. The objective of the shape control is to minimize the shape deviation and to maintain symmetrical shape patterns in the lateral direction. The method of the shape recognition employs the least square method. The shape deviation is controlled by the fuzzy shape controller (FSC). The experiments have been performed online for various stainless materials, thicknesses, and strip widths. The test results show very efficient performances in respect of stable target tracking and symmetrical and minimal fluctuation of the strip shape.  相似文献   

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Joung-han LEE  In-ho CHOI  Seung-ho HONG 《测试科学与仪器》2011,2(1):42-46

Recently,the use of ubiquitous sensor network technology has spread vastly.The ubiquitous sensor networks are widely deployed in factory automation as they provide effective measuring solution for instruments.The wired/wireless network module,which provides the interface to connect to the u-sensor network,is needed but there is no perfect standardization about the interface.In this situation,the interface compatibility between measuring instrument can be maintained using the IEEE1451 international standard.In this paper,the Wireless Transducer Interface Module（WTIM）based on IEEE1451.5 was designed.It connects to the measuring instrument,like the multi-meter,power meter,and etc.,to support the RS232 interface.As these devices cannot connect to network without a module,we use the WTIM to help these devices connect to network system.Its function was verified through the ubiquitous network connection and data transfer between monitoring PC and measuring instrument.This technology is expected to reduce cost in order to construct the wireless industry automation system using existing devices.  相似文献   

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Jee-Hun KO  Sooseok CHOI  Hyun-Woo PARK  Dong-Wha PARK 《等离子体科学和技术》2013,15(9):923-927

The low power arc plasma is characterized by extremely high enthalpy and temperature and it is easy to generate and control,and thus thermal decomposition process based on the plasma torch is receiving a great attention for decomposing non-degradable greenhouse gases.In order to elevate the economic feasibility,the efects of input power,waste gas flow rate and additive gases on the destruction and removal efciency(DRE) of NF3 are examined.Specific energy density(SED) deceases as the flow rate increases,and accordingly,the DRE is reduced.The DRE is basically determined by the specific energy density.The highest DRE of NF3 was 97% for the waste gas flow rate of 100 L/min at a low input power level of 2 kW with the help of hydrogen additional gas.The inlet and outlet concentration of NF3 was analyzed using Fourier transform infrared spectroscopy(FT-IR) for DRE of NF3 evaluation.As a result,large amount of NF3 can be efciently decomposed by low power arc plasma systems.  相似文献   

    

YANG Myung-seo ;KANG Nam-ky ;KIM Yun-jeon ;KIM Jae-so ;CHOI Kwang-na ;KIM Young-ku 《中南大学学报(英文版)》2013,20(8)

This work aims to implement expert and collaborative group recommendation services through an analysis of expertise and network relations NTIS. First of all, expertise database has been constructed by extracting keywords after indexing national R&D information in Korea (human resources, project and outcome) and applying expertise calculation algorithm. In consideration of the characteristics of national R&D information, weight values have been selected. Then, expertise points were calculated by applying weighted values. In addition, joint research and collaborative relations were implemented in a knowledge map format through network analysis using national R&D information.  相似文献