A Numerical Study of Scheduling Power Efficiency Gain for MIMO-OFDM Networks

2014 ◽  
Author(s):  
Xiangyu Gao ◽  
Yuesheng Zhu
Keyword(s):  
Power Efficiency ◽  
Numerical Study ◽  
Efficiency Gain ◽  
Mimo Ofdm

A Conceptual Model of Flapping-Wing Mechanism Inspired from the Results of Numerical Study

2013 ◽  
Vol 397-400 ◽  
pp. 783-788
Author(s):  
Xing Wei Zhang ◽  
Chao Wang ◽  
Hang Liu
Keyword(s):  
Conceptual Model ◽  
Power Efficiency ◽  
Stokes Equations ◽  
Numerical Study ◽  
Flapping Wing ◽  
Numerical Results ◽  
Navier Stokes ◽  
Active Deformation ◽  
Navier Stokes Equations ◽  
Wing Model

This paper investigates the aerodynamic forces of several plunging wing models by means of computational fluid dynamics. A finite volume method was used to solve the two-dimensional unsteady incompressible Navier-Stokes equations. The forces and power efficiency have been calculated and compared between sets of different models. Current work found that the nonsymmetrical moving can enhance the lift and thrust forces. The numerical results also prove that the flexible wing model can be use to improve the efficiency and reduce the input. Additionally, a new conceptual model for flapping wing mechanism with active deformation and adaptive nonsymmetrical driving motion is proposed base on the numerical results.

Resource Allocation for a Cooperative Broadband MIMO-OFDM System

2010 ◽  
pp. 382-398
Author(s):  
Ibrahim Y. Abualhaol ◽  
Mustafa M. Matalgah
Keyword(s):  
Resource Allocation ◽  
Power Distribution ◽  
Power Efficiency ◽  
Orthogonal Frequency Division Multiplexing ◽  
High Performance ◽  
Ofdm System ◽  
Frequency Space ◽  
Input Multiple Output ◽  
Power Loading ◽  
Mimo Ofdm

In this chapter, a cooperative broadband relay-based resource allocation technique is proposed for adaptive bit and power loading multiple-input-multiple-output/orthogonal frequency division multiplexing (MIMO-OFDM) system. In this technique, sub-channels allocation, M-QAM modulation order, and power distribution among different sub-channels in the relay-based MIMO-OFDM system are jointly optimized according to the channel state information (CSI) of the relay and the direct link. The transmitted stream of bits is divided into two parts according to a suggested cooperative protocol that is based on sub-channel-division. In this protocol, the first part is sent directly from the source to the destination, and the second part is relayed to the destination through an indirect link. Such a cooperative relay-based system enables us to exploit the inherent system diversities in frequency, space and time to maximize the system power efficiency. The BER performance using this cooperative sub-channel-division protocol with adaptive sub-channel assignment and adaptive bit/power loading are presented and compared with a noncooperative ones. The use of cooperation in a broadband relay-based MIMO-OFDM system showed high performance improvement in terms of BER.

Improvement in Savonius Wind Turbines Efficiency by Modification of Blade Designs—A Numerical Study

2019 ◽  
Vol 142 (6) ◽  
Author(s):  
Praveen Laws ◽  
Jaskaran Singh Saini ◽  
Ajit Kumar ◽  
Santanu Mitra
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Power Efficiency ◽  
Numerical Study ◽  
Speed Ratio ◽  
Published Data ◽  
Blade Design ◽  
Simple Modification ◽  
Mesh Structure ◽  
Flow Equations

Abstract Savonius wind turbines are special class of vertical axis wind turbines (VAWTs). These are low-cost drag-driven turbines and are known to be inefficient. It is proposed in this study that a simple modification to the turbine blade design can yield a significant improvement in power efficiency. The performance of the new design is extensively studied on openfoam-v1812, a popular open source computational fluid dynamics (CFD) library. The flow equations coupled with equations of rotation of the turbine are solved on an overset mesh framework. This study also serves as a validation of recently released overset support in openfoam. The turbulence is incorporated by coupling Reynolds-averaged Navier–Stokes (RANS) with shear stress transport (SST) κ − ω eddy viscosity turbulence model. The turbulence parameters are set to produce a flow with the Reynolds number, Re = 4.8 × 105. To have better confidence in simulations, this study also presents a comparison of numerical flow over conventional Savonius turbine designs with the published data. It is observed that a majority of CFD analysis on wind turbine designs are performed for the fixed tip speed ratio on a traditional static mesh structure. But, in this CFD study, a wind-driven rotation of Savonius turbine is simulated on an overset dynamics approach. The results of the study are compared and discussed based on the predicted moment and power coefficients, pressure variation on the blades, flow velocity field, and wake analysis. The study indicates that the blade design presented here has a potential to increase the power efficiency of a Savonius wind turbine by 10–28%.

scholarly journals Energy-Efficiency Analysis of Per-Subcarrier Antenna Selection with Peak-Power Reduction in MIMO-OFDM Wireless Systems

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Ngoc Phuc Le ◽  
Le Chung Tran ◽  
Farzad Safaei
Keyword(s):  
Energy Efficiency ◽  
Power Efficiency ◽  
Peak Power ◽  
Antenna Selection ◽  
Average Power ◽  
Wireless Systems ◽  
Power Reduction ◽  
Cumulative Distribution ◽  
Peak Power Reduction ◽  
Mimo Ofdm

The use of per-subcarrier antenna subset selection in OFDM wireless systems offers higher system capacity and/or improved link reliability. However, the implementation of the conventional per-subcarrier selection scheme may result in significant fluctuations of the average power and peak power across antennas, which affects the potential benefits of the system. In this paper, power efficiency of high-power amplifiers and energy efficiency in per-subcarrier antenna selection MIMO-OFDM systems are investigated. To deliver the maximum overall power efficiency, we propose a two-step strategy for data-subcarrier allocation. This strategy consists of an equal allocation of data subcarriers based on linear optimization and peak-power reduction via cross-antenna permutations. For analysis, we derive the CCDF (complementary cumulative distribution function) of the power efficiency as well as the analytical expressions of the average power efficiency. It is proved from the power-efficiency perspective that the proposed allocation scheme outperforms the conventional scheme. We also show that the improvement in the power efficiency translates into an improved capacity and, in turn, increases energy efficiency of the proposed system. Simulation results are provided to validate our analyses.

Efficient Operation of a Gas Turbine on Methanol Using Chemical Recuperation

2012 ◽  
Author(s):  
Christophe Duwig ◽  
Björn Nyberg ◽  
Marcus Thern
Keyword(s):  
Water Content ◽  
Gas Turbine ◽  
Waste Heat ◽  
Laminar Flame ◽  
Numerical Study ◽  
Co2 Removal ◽  
Efficiency Gain ◽  
Reference Case ◽  
Efficient Operation ◽  
Combustion Properties

Environmental and political concerns, together with new legislations, are pushing for a fuel shift in the power industry and more generally for many thermal applications. Adding to the coming decrease of oil and natural availability (or price increase), it opens avenues for new fuels. Among those, alcohols are strong candidates. In fact, short alcohols are easily produced and stored and require only moderate modifications of existing combustion systems. For example, operating an existing gas turbine (GT) on methanol requires moderate modifications (mainly in the combustion system). However, methanol can be used more efficiently. Unlike methane or other hydrocarbons that decompose at high temperature (1000K), methanol undergoes an endothermic decomposition at low temperatures (400K to 600K) to give CO and H2. It therefore opens avenue for coupling the GT with a chemical recuperation system. In other words, the methanol will be cracked using the waste heat of the flue gases with a gain in fuel heating value hence the original fuel is thermally upgraded. The present study will investigate the upgraded fuel combustion properties. The laminar flame speed of the upgraded fuel/air mixtures will be presented and compared to methane and methanol under conditions relevant to GT combustion. Several upgraded fuel compositions will be considered depending on the water content in the feed methanol. Further, we consider a recuperated micro GT (Turbec T100) based cycle fueled with methanol. The numerical study focuses on different thermodynamic cycles. Firstly, a reference case is considered assuming a direct fueled GT. Further, cycles including the cracker are studied keeping the power constant. The fuel efficiency gain due to the cracker will be investigated as function of the water content in the feed methanol. Finally, a case including CO2-removal will be presented and it will be shown that the cracker enables an efficient carbon capture and sequestration scheme.

Minimizing Axial Energy Loss by Using Vane Turbine in the Propeller Slipstream

2014 ◽  
Vol 664 ◽  
pp. 138-142 ◽  
Author(s):  
S. Leksono ◽  
I Ketut Aria Pria Utama ◽  
Wasis Dwi Aryawan
Keyword(s):  
Energy Loss ◽  
Power Efficiency ◽  
Analytical Investigation ◽  
Efficiency Gain ◽  
Actuator Disc ◽  
Twin Screw ◽  
Ship Performance

The paper describes the results of analytical investigation on the application of vane-turbine in the propeller slipstream. The vane-turbine is attached on single-and twin-screw ships with total number of investigated ships are 20. Performance of the turbine was analyzed by actuator disc method. The effect of vane-turbine on ship performance is investigated. Discussions are focused on two main topics, namely speed loss and power efficiency gain. Final result finds out that the ratio of the thrust-power producing by vane turbine and thrust-power producing by propeller will influence the efficiency gain.

scholarly journals Numerical Study of Parallel Optoelectronic Reservoir Computing to Enhance Nonlinear Channel Equalization

Photonics ◽  
2021 ◽  
Vol 8 (10) ◽  
pp. 406
Author(s):  
Xingxing Feng ◽  
Lu Zhang ◽  
Xiaodan Pang ◽  
Xiazhen Gu ◽  
Xianbin Yu
Keyword(s):  
Signal Processing ◽  
High Power ◽  
Communication Systems ◽  
Power Efficiency ◽  
High Speed ◽  
Numerical Study ◽  
Digital Signal ◽  
Channel Equalization ◽  
Optical Signal ◽  
Reservoir Computing

Nonlinear impairment is one of the critical limits to enhancing the performance of high-speed communication systems. Traditional digital signal processing (DSP)-based nonlinear channel equalization schemes are influenced by limited bandwidth, high power consumption, and high processing latency. Optoelectronic reservoir computing (RC) is considered a promising optical signal processing (OSP) technique with merits such as large bandwidth, high power efficiency, and low training complexity. In this paper, optoelectronic RC was employed to solve the nonlinear channel equalization problem. A parallel optoelectronic RC scheme with a dual-polarization Mach–Zehnder modulator (DPol-MZM) is proposed and demonstrated numerically. The nonlinear channel equalization performance was greatly enhanced compared with the traditional optoelectronic RC and the Volterra-based nonlinear DSP schemes. In addition, the system efficiency was improved with a single DPol-MZM.

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