Quantitative analysis of fuel-saving potential for waste heat recovery system integrated with hybrid electric vehicle

Hybrid electric vehicles (HEVs) with low fuel consumption, low emissions, and long driving range are the ideal transition models between conventional fuel vehicles and pure electric vehicles. The growing demand for increased vehicle efficiency has motivated the introduction of waste heat recovery (WHR) technology in the automotive industry, with the organic Rankine cycle (ORC) as the most promising measure for recycling waste energy. Currently, only a few studies have been conducted to couple HEV and WHR systems. These studies have mainly focused on the hybrid powertrain control strategy, but lack quantitative methods to comprehensively analyze the fuel-saving potential due to the WHR system. In this study, an HEV-WHR integrated system that includes a mechanism-based dynamic model of ORC and a hybrid diesel-electric truck model is established. Further, a quantitative evaluation method that simultaneously considers the negative integrated effects (increased vehicle weight and increased exhaust back pressure) and the positive impact values of the engine, motor, and WHR system on the fuel-saving potential is proposed. Finally, the influence of two environmental factors (wind speed and ambient temperature) on the fuel-saving performance is analyzed. The results reveal that under the standard highway driving cycle (HWY), the negative integrated effects reduce the ideal fuel-saving potential of the HEV-WHR system from 6.10% to 5.42%. However, the optimized performances of the engine, motor, and WHR system improve the fuel-saving rate by 0.39%, 1.81%, and 3.22%, respectively. The results also indicate that the fuel-saving potential increases from 1.62% to 8.60% with increasing wind speed and decreases from 6.70% to 4.25% with increasing ambient temperature.     

Interference Alignment in Relay-Aided Networks with Imperfect CSIT

In this paper, a relay-aided interference alignment (RIA) strategy was considered based on the benefits offered by relay-based cooperative networks. Along with the benefits offered by cooperative networks, the RIA was shown as a practical solution for a K-user BC network. The relationship between the achievable DoF region of the RIA and the different levels of outdated channel state information (CSI) were derived. The trade-off between the NRIA and RIA were analysed and the specific trade-off region in each outdated CSI assumption was indicated in the numerical results. Through the achievable DoF numerical results, it was recognised that regarding achievable DoF, the RIA outperforms the NRIA in most of the outdated CSI scenarios.

     

Low-complexity transmit antenna selection algorithm formassive MIMO

Massive multiple input multiple output (MIMO) systems can increase capacity and reliability greatly. However,extremely high hardware costs and computational complexity lead to the demand for reasonable antenna selection.Aiming at the problem that the traditional antenna selection algorithm based on maximizing sum capacity has largecomplexity and worse bit error rate (BER) performance, a two-step selection algorithm is proposed, which selectsa part of the antennas based on the norm-based antenna selection (NBS) firstly, and then selects the antenna basedon maximizing capacity via convex optimization. The simulation results show that the improved algorithm has betterBER performance than the traditional algorithms. At the same time, it reduces computational complexity greatly.     

PPAA: a parallel primitive assembly accelerator in graphics processor

Primitive assembly is an inevitable procedure of graphics rendering which performs the objects preparation for the following steps, however, the conventional approaches suffer from some issues, such as the missing of surface attribute, mismatch of color mode for clipped primitives, and performance bottleneck of rendering pipeline. This paper takes all these issues into considerations, and proposes a parallel primitive assembly accelerator (PPAA) which can solve not only the functional problems but also improve the shading performance. The register transfer level (RTL) circuit is designed and the detailed approach is presented. The prototype systems are implemented on Xilinx field programmable gate array (FPGA) XC6VLX550T and Altera FPGA EP2C70F896C6. The experimental results show that PPAA can accomplish the assembly tasks correctly and with higher performance of 1.5x and 2.5x of two previous implementations. For the most frequently independent primitives, the PPAA can efficiently enhance the throughput by squeezing out the pipeline bubbles and by balancing the pipeline stages.     

Local community detection for multi-layer mobile network based on the trust relation

Wireless Networks - With the fast development of mobile Internet, people’s social exchange media has transformed from the traditional social network to mobile network. With the explosion of...     

热处理工艺对Ti-6Al-4V ELI合金厚截面锻件力学性能的影响

针对损伤容限型Ti-6Al-4V ELI合金δ200mm厚截面锻件,开展了β热处理工艺和准β热处理工艺试验,对比分析了热处理工艺对锻件的强度、塑性、断裂韧度、疲劳裂纹扩展速率的影响。研究结果表明,随着第一重退火温度从T_b+15℃升高到T_b+30℃、T_b+60℃,锻件塑性下降明显。准β热处理工艺的塑性明显优于β热处理工艺,源于其β晶粒尺寸较小。强度、断裂韧度和疲劳裂纹扩展速率对β热处理工艺温度不敏感。为达到良好的强度-塑性-韧性的综合性能匹配,Ti-6Al-4V ELI钛合金厚截面锻件宜采用较低热处理温度(如T_β+15℃)的β热处理工艺或准β热处理工艺。     

Experimental study on a small‐scale pumpless organic Rankine cycle with R1233zd(E) as working fluid at low temperature heat source

This paper focuses on the novelty pumpless organic Rankine cycle (ORC) and its choice of working fluids. Based on the selection criteria, the refrigerant of R1233zd(E) is firstly chosen and investigated in the pumpless ORC system. In the system, the feed pump is removed, and the refrigerant flows back and forth between two heat exchangers, which act as the evaporator or condenser, respectively. The impacts of the heating water temperature and loads on the system performance are studied to find out the best operating conditions. The low‐grade heat source is simulated by an electric boiler. The temperature of the heat resource ranges from 80°C to 100°C with the interval of 5°C. The temperature of the cooling water inlet is 10°C and is kept constant. The largest average power output is 127 W under the condition of 100°C heating water with nine loads. Because the cycle efficiency with heating steam temperature of 100°C cannot be determined, the highest energy and exergy efficiencies are 3.5% and 17.1%, respectively, for heating water of 95°C with seven loads. The experimental results show that the energy and exergy efficiencies increase with the increase of the heating temperature. The power and current outputs increase when the loads increase under the condition of the constant heating water temperature, whereas the voltage output decreases meanwhile. The generating time increases when the loads increase. This phenomenon is mainly caused by the increasing evaporating pressure and decreasing condensing pressure when the loads increases.