• Title/Summary/Keyword: Channel optimization

Search Result 567, Processing Time 0.022 seconds

A Numerical Study on the Heat Transfer Characteristics of the Multiple Slot Impinging Jet (다양한 노즐 수 변화에 따른 충돌 제트의 열전달 특성에 관한 수치적 연구)

  • Kim, Sang-Keun;Ha, Man-Yeong;Son, Chang-Min
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.23 no.11
    • /
    • pp.754-761
    • /
    • 2011
  • The present study numerically investigates two-dimensional flow and heat transfer in the multiple confined impinging slot jet. Numerical simulations are performed for the different Reynolds numbers(Re=100 and 200) in the range of nozzles from 1 to 9 and height ratios(H/D) from 2 to 5, where H/D is the ratio of the channel height to the slot width. The vector plots of velocity profile, stagnation and averaged Nusselt number distributions are presented in this paper. The dependency of thermal fields on the Reynolds number, nozzle number and height ratio can be clarified by observing the Nusselt number as heat transfer characteristic at the stagnation point and impingement surface. The Nusselt number at the stagnation point of the central slot shows unsteadiness at H/D=3 and Re=200. The value of Nusselt number at the stagnation point of the central slot decreases with higher Reynolds number and number of nozzle although overall area averaged Nusselt number increases. Hence careful selection of geometrical parameters and number of nozzle are necessary for optimization of the heat transfer performance of multiple slot impinging jet.

Giga-Hertz-Level Electromagnetic Field Analysis for Equivalent Inductance Modeling of High-Performance SoC and SiP Designs

  • Yao Jason J.;Chang Keh-Jeng;Chuang Wei-Che;Wang, Jimmy S.
    • JSTS:Journal of Semiconductor Technology and Science
    • /
    • v.5 no.4
    • /
    • pp.255-261
    • /
    • 2005
  • With the advent of sub-90nm technologies, the system-on-chip (SoC) and system-in-package (SiP) are becoming the trend in delivering low-cost, low-power, and small-form-factor consumer electronic systems running at multiple GHz. The shortened transistor channel length reduces the transistor switching cycles to the range of several picoseconds, yet the time-of-flights of the critical on-chip and off-chip interconnects are in the range of 10 picoseconds for 1.5mm-long wires and 100 picoseconds for 15mm-long wires. Designers realize the bottleneck today often lies at chip-to-chip interconnects and the industry needs a good model to compute the inductance in these parts of circuits. In this paper we propose a new method for extracting accurate equivalent inductance circuit models for SPICE-level circuit simulations of system-on-chip (SoC) and system-in-package (SiP) designs. In our method, geometrical meshes are created and numerical methods are used to find the solutions for the electromagnetic fields over the fine meshes. In this way, multiple-GHz SoC and SiP designers can use accurate inductance modeling and interconnect optimization to achieve high yields.

Simulation of 4H-SiC MESFET for High Power and High Frequency Response

  • Chattopadhyay, S.N.;Pandey, P.;Overton, C.B.;Krishnamoorthy, S.;Leong, S.K.
    • JSTS:Journal of Semiconductor Technology and Science
    • /
    • v.8 no.3
    • /
    • pp.251-263
    • /
    • 2008
  • In this paper, we report an analytical modeling and 2-D Synopsys Sentaurus TCAD simulation of ion implanted silicon carbide MESFETs. The model has been developed to obtain the threshold voltage, drain-source current, intrinsic parameters such as, gate capacitance, drain-source resistance and transconductance considering different fabrication parameters such as ion dose, ion energy, ion range and annealing effect parameters. The model is useful in determining the ion implantation fabrication parameters from the optimization of the active implanted channel thickness for different ion doses resulting in the desired pinch off voltage needed for high drain current and high breakdown voltage. The drain current of approximately 10 A obtained from the analytical model agrees well with that of the Synopsys Sentaurus TCAD simulation and the breakdown voltage approximately 85 V obtained from the TCAD simulation agrees well with published experimental results. The gate-to-source capacitance and gate-to-drain capacitance, drain-source resistance and trans-conductance were studied to understand the device frequency response. Cut off and maximum frequencies of approximately 10 GHz and 29 GHz respectively were obtained from Sentaurus TCAD and verified by the Smith's chart.

Minimum Distance based Precoder Design for General MIMO Systems using Gram Matrix

  • Chen, Zhiyong;Xu, Xiaodong
    • Journal of Communications and Networks
    • /
    • v.17 no.6
    • /
    • pp.634-646
    • /
    • 2015
  • Assuming perfect channel state information (CSI) at the transmitter and receiver, the optimization problem of maximizing the minimum Euclidean distance between two received signals by a linear precoder is considered for multiple-input multiple-output (MIMO) systems with arbitrary dimensions and arbitraryary quadrature amplitude modulation (QAM) input. A general precoding framework is first presented based on the Gram matrix, which is shown for 2-dimensional (2-D) and 3-dimensional (3-D) MIMO systems when employing the ellipse expanding method (EEM). An extended precoder for high-dimensional MIMO system is proposed following the precoding framework, where the Gram matrix for high-dimensional precoding matrix can be generated through those chosen from 2-D and 3-D results in association with a permutation matrix. A complexity-reduced maximum likelihood detector is also obtained according to the special structure of the proposed precoder. The analytical and numerical results indicate that the proposed precoder outperforms the other precoding schemes in terms of both minimum distance and bit error rate (BER).

Resource Allocation Method for Improving Energy Efficiency and Receiver Fairness in Wireless Networks (무선 네트워크의 전력 효율성과 수신기 공평성 향상을 위한 자원 할당 방안)

  • Lee, Kisong;Cho, Dong-Ho;Chung, Byung Chang
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.40 no.5
    • /
    • pp.826-832
    • /
    • 2015
  • In wireless networks, it is important to guarantee the energy efficiency and receiver fairness for satisfying service provider and customer at the same time. In this paper, we propose a resource allocation algorithm which improves energy efficiency as well as receiver fairness based on optimization techniques. In the proposed algorithm, subchannel and power are allocated to receivers iteratively in the consideration of channel state information, amount of dissipated power, and receiver rate, in order to improve energy efficiency and receiver fairness. Through simulation, we show the effectiveness and superiority of the proposed algorithm in terms of energy efficiency and receiver fairness.

Optimal Amplify-and-Forward Scheme for Parallel Relay Networks with Correlated Relay Noise

  • Liu, Binyue;Yang, Ye
    • ETRI Journal
    • /
    • v.36 no.4
    • /
    • pp.599-608
    • /
    • 2014
  • This paper studies a parallel relay network where the relays employ an amplify-and-forward (AF) relaying scheme and are subjected to individual power constraints. We consider correlated effective relay noise arising from practical scenarios when the relays are exposed to common interferers. Assuming that the noise covariance and the full channel state information are available, we investigate the problem of finding the optimal AF scheme in terms of maximum end-to-end transmission rate. It is shown that the maximization problem can be equivalently transformed to a convex semi-definite program, which can be efficiently solved. Then an upper bound on the maximum achievable AF rate of this network is provided to further evaluate the performance of the optimal AF scheme. It is proved that the upper bound can be asymptotically achieved in two special regimes when the transmit power of the source node or the relays is sufficiently large. Finally, both theoretical and numerical results are given to show that, on average, noise correlation is beneficial to the transmission rate - whether the relays know the noise covariance matrix or not.

Minimum Wave Resistance Hull Form Derived from Center Plane Source Distribution and its Application to Hull Form Design (선체중심선면(船體中心線面)에 분포(分布)된 특이점계(特異點系)로부터 얻어지는 최소조파저항선형(最少造波抵抗船型)과 그 응용(應用))

  • Hyo-Chul,Kim;B.S.,Hyun
    • Bulletin of the Society of Naval Architects of Korea
    • /
    • v.19 no.4
    • /
    • pp.31-37
    • /
    • 1982
  • Developing a minimum wave resistance hull form which is satisfying the given requirements such as displacement and speed is one of the important problems in ship hydrodynamics. The theoretical approach conducted by Pien was successful in developing an optimized hull form, however, which can not be applied directly to practical hull form without manual lines fairing process. To avoid this difficulty, source distribution which arrived after the optimization was put into a fictitious restricted channel and as a result practicably modified hull form was derived by stream line tracing. The wave resistance of the hull thus obtained was calculated by solving the simplified integral equation suggested by Kan. The resistance at design point is almost same with that of the original hull which was represented by source distribution on the vertical rectangular center plane. It is therefore recommended to use the derived hull form for the hull which obtained after manual lines fairing process at Pienoid method. Further researches both in theory and experiment are necessary before this concept is put into practical application.

  • PDF

SUPERCRITICAL WATER LOOP DESIGN FOR CORROSION AND WATER CHEMISTRY TESTS UNDER IRRADIATION

  • Ruzickova, Mariana;Hajek, Petr;Smida, Stepan;Vsolak, Rudolf;Petr, Jan;Kysela, Jan
    • Nuclear Engineering and Technology
    • /
    • v.40 no.2
    • /
    • pp.127-132
    • /
    • 2008
  • An experimental loop operating with water at supercritical conditions(25MPa, 600C in the test section) is designed for operation in the research reactor LVR-15 in UJV Rez, Czech Republic. The loop should serve as an experimental facility for corrosion tests of materials for in-core as well as out-of-core structures, for testing and optimization of suitable water chemistry for a future HPLWR and for studies of radiolysis of water at supercritical conditions, which remains the domain where very few experimental data are available. At present, final necessary calculations(thermalhydraulic, neutronic, strength) are being performed on the irradiation channel, which is the most challenging part of the loop. The concept of the primary and auxiliary circuits has been completed. The design of the loop shall be finished in the course of the year 2007 to start the construction, out-of-pile testing to verify proper functioning of all systems and as such to be ready for in-pile tests by the end of the HPLWR Phase 2 European project by the end of 2009.

RRM Optimization for the Throughput Enhancement of WiFi AP (WiFi AP 성능 향상을 위한 무선 자원 관리 최적화)

  • Jeong, Kil Hyun
    • Journal of the Korea Society of Computer and Information
    • /
    • v.17 no.12
    • /
    • pp.131-136
    • /
    • 2012
  • In these days, with the diffusion of mobile equipments, the number of WiFi Access Point (AP) is increasing, and the growth of WiFi AP causes the throughput degradation due to interferences between APs. This recent phenomenon demands the method able to be utilized with current WiFi network to improve the throughput of Wireless LANs. This paper studied the channel assignment method and several throughput enhancement methods to optimize Radio Resource Management (RRM) for distributed infrastructure WLANs. As a result, it was able to put AP independently, improve older allocation error, and improve execution speed.

Cross-Layer Reduction of Wireless Network Card Idle Time to Optimize Energy Consumption of Pull Thin Client Protocols

  • Simoens, Pieter;Ali, Farhan Azmat;Vankeirsbilck, Bert;Deboosere, Lien;Turck, Filip De;Dhoedt, Bart;Demeester, Piet;Torrea-Duran, Rodolfo;Perre, Liesbet Van der;Dejonghe, Antoine
    • Journal of Communications and Networks
    • /
    • v.14 no.1
    • /
    • pp.75-90
    • /
    • 2012
  • Thin client computing trades local processing for network bandwidth consumption by offloading application logic to remote servers. User input and display updates are exchanged between client and server through a thin client protocol. On wireless devices, the thin client protocol traffic can lead to a significantly higher power consumption of the radio interface. In this article, a cross-layer framework is presented that transitions the wireless network interface card (WNIC) to the energy-conserving sleep mode when no traffic from the server is expected. The approach is validated for different wireless channel conditions, such as path loss and available bandwidth, as well as for different network roundtrip time values. Using this cross-layer algorithm for sample scenario with a remote text editor, and through experiments based on actual user traces, a reduction of the WNIC energy consumption of up to 36.82% is obtained, without degrading the application's reactivity.