二维双曲守恒律标量方程的三阶CWENO-型熵相容算法

应用提出的中心加权基本无振荡(CWENO)-型熵相容格式求解了二维双曲守恒律方程初边值问题,对所得数值结果进行了分析与讨论,并通过与准确解的比较发现该数值求解格式稳定性条件可以取到0.6,而激波过渡带只有1~2个网格单元。实验结果表明该数值求解格式分辨率高且数值稳定性好。     

基于FIM赋权的水资源配置方案模糊物元评价

针对水资源配置的多目标、多层次和群决策等问题,探索了合理有效的配置方案评价方法,以济宁市水资源配置方案评价为例,采用关联度函数构建了模糊物元评价模型,利用模糊区间映射法确定指标权重。实例结果表明,该方法合理有效,改进了专家评点估值的难度。     

Design and analysis of permutation-based pyramid broadcasting

Periodic broadcasting can be used to support near-video-on-demand for popular videos. For a given bandwidth allocation, pyramid broadcasting schemes substantially reduce the viewer latency (waiting) time compared to conventional broadcasting schemes. Nevertheless, such pyramid schemes typically have substantial storage requirements at the client end, and this results in set-top boxes needing disks with high transfer rate capabilities. In this paper, we present a permutation-based pyramid scheme in which the storage requirements and disk transfer rates are greatly reduced, and yet the viewer latency is also smaller. Under the proposed approach, each video is partitioned into contiguous segments of geometrically increasing sizes, and each segment is further divided into blocks, where a block is the basic unit of transmission. As in the original pyramid scheme, frequencies of transmission for the different segments of a video vary in a manner inversely proportional to their size. Instead of transmitting the blocks in each segment in sequential order, the proposed scheme transmits these blocks in a prespecified cyclic permutation to save on storage requirements in the client end. Performance analyses are provided to quantify the benefits of the new scheme.     

Feebates promoting energy-efficient cars: Design options to address more consumers and possible counteracting effects

An increasing number of countries have implemented or are evaluating feebate systems in order to reduce energy consumption of new vehicle registrations. We distinguish between absolute feebates based strictly on a vehicle's energy consumption and relative feebates normalizing energy consumption by a given car utility. This paper analyzes whether absolute or relative feebates encourage more consumers to change to vehicles with lower energy consumption. We combine an analysis of all car models on sale at the end of 2005 with survey data from 326 potential new car buyers. Analysis of the car fleet with regard to behavioral changes assumed as realistic shows that relative systems succeed better in offering more consumer groups cars that are eligible for incentives. Survey results suggest that consumers show some, but limited, willingness to change behavior to obtain an incentive. However, a relative system potentially allows people to switch to cars with higher relative efficiency without actually lowering absolute CO₂ emissions. We discuss this inherent dilemma of simultaneously addressing more consumers and limiting counteracting effects. In order to find the optimal trade-off, we suggest assessing different parameters operationalizing vehicle utility by means of micro-simulation with detailed car fleet and differentiated consumer segments.     

Characteristics of hydrogen production by a plasma–catalyst hybrid converter with energy saving schemes under atmospheric pressure

This paper investigated the production of hydrogen from methane under atmospheric pressure using a plasma–catalyst hybrid converter with emphasis on energy conservation. A spark discharge was used to ionize the hydrocarbon fuel and air mixture with a catalyst to enhance hydrogen production using two energy saving schemes, namely, heat recycling and heat insulation. The experimental results showed that higher methane feeding rate resulted in higher reformate gas temperature and a corresponding increase in methane conversion efficiency. The energy saving systems also enabled the oxygen/carbon ratio to be decreased to reduce oxidation of hydrogen and carbon monoxide and thereby improving the concentrations of hydrogen and carbon monoxide. By heat recycling, a lower methane feeding rate showed an 8.7% improvement in methane conversion efficiency whilst improvement was not apparent with higher methane supply rates due to the already high conversion efficiency. Moreover, it was shown that hydrogen production increased significantly with the reaction from water–gas shifting under the same operation parameters but with high methane selectivity. The best combination resulting in a total thermal efficiency of 77.11% was 10 L/min methane feeding rate and 0.8 O₂/C ratio. With water–gas shifting (S/C ratio=0.5), an 86.26% hydrogen yield, equating to 17.25 L/min hydrogen production rate could be achieved. The equilibrium production rate was calculated using the commercialized HSC Chemistry software (^©ChemSW Software, Inc.). Good correlation was obtained between the calculations and the experimental results.     

特高压线路铁塔施工关键技术研究

特高压线路的铁塔重量大、铁塔高、横担长、结构复杂。介绍根据不同的塔型、地形和交通状况,选择合适的组塔方案,配备合适的组塔抱杆,并探讨内抱杆组立铁塔施工技术、施工工艺、受力计算和工器具选择。     

特高压输电线路煤矿采动影响区铁塔基础设计研究

晋东南-南阳-荆门1000kV交流输电线路是我国第1条特高压试验示范工程,优化后的线路路径不可避免地经过煤矿采动影响区,基于对采动影响区铁塔基础设计相关技术及地基稳定性评价和逐基塔位地基变形量化分析及计算比较专题研究,本着安全可靠、先进可行、经济合理的目标,确定了煤矿采动影响区铁塔基础设计的原则、合理可行的基础型式和设计方案,为确保特高压输电线路工程安全、稳定运行打下了基础。     

Numerical study of a nuclear fuel element dissipating fission heat into its surrounding fluid medium

The objective of the present work is twofold – the first to establish the criterion for the boundary layer solution to be accurate enough in the study of conjugate heat transfer problem associated with a rectangular nuclear fuel element washed by upward moving coolant and the second to predict the critical thermal performance characteristics of the fuel element with uniform volumetric energy generation. Accordingly, employing stream function–vorticity formulation, equations governing the steady, two-dimensional flow and thermal fields in the coolant are solved simultaneously with the steady, two-dimensional heat conduction equation for the fuel element using second-order accurate finite difference schemes. Keeping the Prandtl number constant at 0.005 for liquid sodium as coolant, numerical results are presented for wide range of aspect ratio, conduction–convection parameter, energy generation parameter and Reynolds number. It is found that for all value of aspect ratio greater than 15, numerical prediction using the boundary layer approximation based model is quite accurate enough. It is also concluded that other parameters being kept constant, the increase in the maximum fuel element temperature due to increase in aspect ratio beyond 15 is negligible. Further, it is found that a relatively higher value of conduction–convection parameter reduces the coolant pumping power requirement to a large extent.     

信息表的闭离散化方案研究

提出对象域U的有序划分概念,讨论一种特殊的离散化方案（闭离散化方案）。给出对象域U的有序划分对应的闭离散化方案获取算法CDA,分析闭离散化方案与对象域U的有序划分之间的关系,证明了闭离散化方案在离散格到划分格的映射f下能保持交并运算。     

膜下滴灌墒情监测点布设方案研究

研究了膜下滴灌墒情监测点的布设方案,为降低监测成本,提高田间信息采集精度提供了理论指导。在新疆库尔勒市包头湖农场48 m×56 m(一根支管控制)的区域内,制定了3种墒情监测点布设方案,并对方案合理性进行了分析,结果表明,此3种监测点布设方案下插值后计算出的土壤含水率与实测样本土壤含水率,在显著性水平0.05下,没有显著性差异;综合考虑农田规格、合理监测点数目、以及监测点位置等因素,一根支管控制区域内土壤墒情测布设方案可采用30 m×10 m网格。更多还原