• Title/Summary/Keyword: heterogeneous

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A Virtual-Queue based Backpressure Scheduling Algorithm for Heterogeneous Multi-Hop Wireless Networks

  • Jiao, Zhenzhen;Zhang, Baoxian;Zheng, Jun
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.9 no.12
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    • pp.4856-4871
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    • 2015
  • Backpressure based scheduling has been considered as a promising technique for improving the throughput of a wide range of communication networks. However, this scheduling technique has not been well studied for heterogeneous wireless networks. In this paper, we propose a virtual-queue based backpressure scheduling (VQB) algorithm for heterogeneous multi-hop wireless networks. The VQB algorithm introduces a simple virtual queue for each flow at a node for backpressure scheduling, whose length depends on the cache size of the node. When calculating flow weights and making scheduling decisions, the length of a virtual queue is used instead of the length of a real queue. We theoretically prove that VQB is throughput-optimal. Simulation results show that the VQB algorithm significantly outperforms a classical backpressure scheduling algorithm in heterogeneous multi-hop wireless networks in terms of the packet delivery ratio, packet delivery time, and average sum of the queue lengths of all nodes per timeslot.

A Novel Power-Efficient BS Operation Scheme for Green Heterogeneous Cellular Networks

  • Kim, Jun Yeop;Kim, Junsu;Kang, Chang Soon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.41 no.12
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    • pp.1721-1735
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    • 2016
  • Power-efficient base station (BS) operation is one of the important issues in future green cellular networks. Previously well-known BS operation schemes, the cell zooming scheme and the cell wilting and blossoming scheme, require tight cooperation between cells in cellular networks. With the previous schemes, the non-cooperative BSs of a serving cell and neighboring cells could cause coverage holes between the cells, thereby seriously degrading the quality of service as well as the power saving efficiency of the cellular networks. In this paper, we propose a novel power-efficient BS operation scheme for green downlink heterogeneous cellular networks, in which the networks virtually adjust the coverage of a serving macrocell (SM) and neighboring macrocells (NMs) without adjusting the transmission power of the BSs when the SM is lightly loaded, and the networks turn off the BS of the SM when none of active users are associated with the SM. Simulation results show that our proposed scheme significantly improves the power saving efficiency without degrading the quality of service (e.g., system throughput) of a downlink heterogeneous LTE network and outperforms the previous schemes in terms of system throughput and power saving efficiency. In particular, with the proposed scheme, macrocells are able to operate independently without the cooperation of a SM and NMs for green heterogeneous cellular networks.

Basic Study on the Spatial Structure Analysis of the Evaporative Diesel Spray (증발디젤분무의 공간적 구조해석에 관한 기초 연구)

  • Yeom, J.K.
    • Journal of Power System Engineering
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    • v.14 no.3
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    • pp.5-12
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    • 2010
  • The purpose of this study is to analyze heterogeneous distribution of branch-like structure at downstream region of inner spray. The previous many studies about diesel spray structure have yet stayed in the analysis of 2-D structure, and there are very few of informations which are concerned with 3-D analysis of the structure. The heterogeneous distribution of droplets in inner spray affects the mixture formation of diesel spray, and also the combustion characteristics of the diesel engines. Therefore, in order to investigate 3-D structure of evaporative spray the laser beam of 2-D plane was used in this study. Liquid fuel was injected from a single-hole nozzle (l/d=5) into a constant-volume vessel under high pressure and temperature in order to visualize the spray phenomena. The incident laser beam was offset on the central axis. From the images analysis taken by offset of laser beam, we examine formation mechanism of heterogeneous distribution by vortex flow at the downstream of the diesel spray. As the experimental results, the branch-like structure formed heterogeneous distribution of the droplets consists of high concentration of vapor phase in the periphery of droplets and spray tip of branch-like structure. Also the 3-D spatial structure of the evaporative diesel spray can be verified by images obtained from 2-D measurement methods.

The Effect of Corporate Social Responsibility Activities on Investors' Heterogeneous Beliefs: A Study of Korea's Data Set

  • JUNG, Hyun-Uk;MUN, Tae-Hyoung;KIM, Young Ei
    • The Journal of Asian Finance, Economics and Business
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    • v.7 no.10
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    • pp.95-107
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    • 2020
  • This study analyzes the effect of corporate social responsibility (CSR) activity on investors' heterogeneous beliefs. The hypothesis of this study is based on the conflicting effects of CSR activities on firm value and earning's quality. Investors' heterogeneous beliefs used in the empirical analysis of this study are trading volume, and CSR activity is measured by the KEJI Index (Korea Economic Justice Institute Index). This study performs an empirical analysis using regression analysis including control variables. CSR activities are found to have a positive relationship with trading volume. This is consistent regardless of the low and high accounting information (earning's quality). It can be interpreted that Korea's CSR activity acts as an incentive to increase investors' heterogeneous beliefs about target companies. In other words, it implies that the investor judges CSR activities negatively when evaluating firm value. This study could have a policy implication in that it analyzes how CSR activities affect investors' decision-making. In other words, this study analyzed CSR activities from the perspective of shareholders. Therefore, this study is expected to provide useful information for policymaking by regulatory agencies. In particular, its contribution is to presents data that CSR activities can be a negative factor in evaluating firm values.

Comparing Cilk and MPI on a heterogeneous cluster system (이기종 클러스터 시스템에서 Cilk와 MPI 특성 비교)

  • Lee, Kyu-Ho;Kim, Jun-Seong
    • Journal of the Institute of Electronics Engineers of Korea CI
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    • v.44 no.4 s.316
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    • pp.21-27
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    • 2007
  • Recently cluster system built from personal computers and network devices are easily and economically constructed. Rapid technological change discloses new processors on the market yielding cluster systems heterogeneity. A parallel system in heterogeneous environment needs work managers for utilizing the full power of the heterogeneous cluster system. In this paper, we compare MPI and Cilk in a heterogeneous cluster system in terms of performance and code complexity. Experimental results show that Cilk is better than MPI with small sizes of data transfers while MPI outperforms Cilk with big sizes of data transfers. Also, We find that Cilk requires less programming efforts to write a parallel program.

Ultrasonic Processing of Polymer Foam (고분자 포움의 초음파 가공)

  • 변성광;윤재륜
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.13 no.4
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    • pp.618-624
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    • 1989
  • Ultrasonically induced bubble formation in thermoplastic matrix was investigated experimentally and theoretically. polystyrene was saturated with nitrogen under the pressure of 0.2 to 3.45 MPa in a pressure chamber, followed by pressure release and ultrasonic bubble nucleation. Zinc stearate was added to polystyrene as the nucleating agent to induce heterogeneous nucleation. Various mixture of low density polyethylene and polyethylene wax was also saturated with the gas. The foamed specimens with or without ultrasonically induced bubble nucleation was modeled by modifying the classical nucleation theory. The rate of ultrasonic nucleation was predicted for homogeneous and heterogeneous nucleation at a conical cavity. This study showed that the heterogeneous and heterogeneous nucleation at a conical cavity. This study showed that the heterogeneous nucleation must be employed for ultrasonic production of bubbles in a viscous fluid and the homogeneous nucleation for ultrasonic production of bubbles in a low viscosity fluid.

An Effective Method of Sharing Heterogeneous Components of OPRoS and RTM

  • Salov, Andrey D.;Park, Hong Seong;Han, Soohee;Lee, Dooam
    • Journal of Electrical Engineering and Technology
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    • v.9 no.2
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    • pp.755-761
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    • 2014
  • Heterogeneous components have different component models, which prevents such components from sharing the functionalities of other components based on the different models. As one of methods for linking heterogeneous components, this paper suggests a proxy component to construct a bridge between heterogeneous components of OPRoS (Open Platform for Robotic Service) and RTM (Robot Technology Middleware). The proxy component consists of two types of components called Adaptor and Interceptor, via which the heterogeneous components can exchange data and services easily. The proposed method enables adaptor and interceptor components to directly invoke the services of the latter and the former, respectively, in order to exchange data and services on a real-time basis. The proxy component can be implemented for OPRoS and RT (Robot Technology) component models to connect with RT and OPRoS ones, respectively. It is shown through a simple experiment that the proposed method works well for real-time control.

A Simultaneous Delivery and Pick-up Heterogeneous Vehicle Routing Problem with Separate Loading Area (다품종 독립 적재공간을 갖는 배달과 수거를 동시에 고려한 차량경로문제)

  • Kim, Gak-Gyu;Kim, Seong-Woo;Kim, Seong-Woo
    • Journal of Korean Institute of Industrial Engineers
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    • v.39 no.6
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    • pp.554-561
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    • 2013
  • As a special topic of the vehicle routing problems (VRP), VRPSDP extends the vehicle routing problem as considering simultaneous pickup and delivery for goods. The past studies have mainly dealt with a only weight constraint of a loading capacity for heterogeneous products. However. this study suggests VRPSDP considering separate loading area according to characteristics of loading species. The objective is to design a set of minimum distance routes for the vehicle routing assignment with independent capacity for heterogeneous species. And then we present a another HVRPSDP model which is easy to utilizes in a unique circumstance that is a guarantee of executing a task simultaneously from the various areas under restricted time and raising an application of vehicles that returns at the depot for the next mission like the military group. The optimal results of the suggested mathematical models are solved by the ILOG CPLEX software ver. 12.4 that is provided by IBM company.

Comparative Study on Static Task Scheduling Algorithms in Global Heterogeneous Environment (전역 이기종 환경에서의 정적 태스크 스케줄링의 비교 연구)

  • Kim Jung-Hwan
    • The KIPS Transactions:PartA
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    • v.13A no.2 s.99
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    • pp.163-170
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    • 2006
  • Most scheduling problems including DAG(Directed Acyclic Graph)-based are known to be NP-complete, so many heuristic-based scheduling algorithms have been researched. HEFT and CPOP are such algorithms which have been devised to be effective in heterogeneous environment. We proposed, in the previous research, three scheduling algorithms which are effective in realistic global heterogeneous environment: CPOC, eCPOPC and eCPOP. In this paper, the heuristics which are used in the above five algorithms will be systematically analyzed. Those algorithms will be also studied experimentally using various benchmarks. Experimental results show that the eCPOC generates better schedules than any other algorithms and the heuristics which are used in the proposed algorithms are effective in the global heterogeneous environment.

Improved Heterogeneous-Ants-Based Path Planner using RRT* (RRT*를 활용하여 향상된 이종의 개미군집 기반 경로 계획 알고리즘)

  • Lee, Joonwoo
    • The Journal of Korea Robotics Society
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    • v.14 no.4
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    • pp.285-292
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    • 2019
  • Path planning is an important problem to solve in robotics and there has been many related studies so far. In the previous research, we proposed the Heterogeneous-Ants-Based Path Planner (HAB-PP) for the global path planning of mobile robots. The conventional path planners using grid map had discrete state transitions that constrain the only movement of an agent to multiples of 45 degrees. The HAB-PP provided the smoother path using the heterogeneous ants unlike the conventional path planners based on Ant Colony Optimization (ACO) algorithm. The planner, however, has the problem that the optimization of the path once found is fast but it takes a lot of time to find the first path to the goal point. Also, the HAB-PP often falls into a local optimum solution. To solve these problems, this paper proposes an improved ant-inspired path planner using the Rapidly-exploring Random Tree-star ($RRT^*$). The key ideas are to use $RRT^*$ as the characteristic of another heterogeneous ant and to share the information for the found path through the pheromone field. The comparative simulations with several scenarios verify the performance of the improved HAB-PP.