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排序方式: 共有157条查询结果,搜索用时 15 毫秒
1.
Quadrature spatial modulation (QSM) utilizes the in‐phase and quadrature spatial dimensions to transmit the real and imaginary parts of a single signal symbol, respectively. The improved QSM (IQSM) transmits two signal symbols per channel use through a combination of two antennas for each of the real and imaginary parts. The main contributions of this study can be summarized as follows. First, we derive an upper bound for the error performance of the IQSM. We then design constellation sets that minimize the error performance of the IQSM for several system configurations. Second, we propose a double QSM (DQSM) that transmits the real and imaginary parts of two signal symbols through any available transmit antennas. Finally, we propose a parallel IQSM (PIQSM) that splits the antenna set into equal subsets and performs IQSM within each subset using the same two signal symbols. Simulation results demonstrate that the proposed constellations significantly outperform conventional constellations. Additionally, DQSM and PIQSM provide a performance similar to that of IQSM while requiring a smaller number of transmit antennas and outperform IQSM with the same number of transmit antennas.  相似文献   
2.
This paper aims to provide a systematic and comprehensive survey of state-of-the-art machine learning techniques and their potential applications in IoT-integrated power systems.  相似文献   
3.
A hybrid approach between the Taguchi method and grey relational analysis (GRA) with entropy measurement was applied to determine a single optimum setting for reaction factors of the proposed ethylene dimerization catalyst having overall selectivity to 1-butene (S1-btn (%)) and turnover frequency (TOF (h-1)) as multiple quality characteristics. Titanium tetrabutoxide (Ti(OC4H9)4) catalyst precursor in combination with triethyl aluminum (TEA) activator, 1,4-dioxane as a suitable modifier, and ethylene dichloride (EDC) as a novel promoter were used in the catalysis. Control factors of temperature, pressure, Al/Ti, 1,4-dioxane/Ti, and EDC/Ti mol ratios were investigated on three levels and their main effects were discussed. The effect of the binary interaction between temperature, pressure, and Al/Ti mol ratio was also examined. Weight of the responses was determined using entropy. Analysis of variance (ANOVA) for data obtained from GRA indicated that EDC/Ti mol ratio with 27.64% contribution had the most profound effect on the multiple quality characteristics. Development of the weighted Grey-Taguchi method used the Taguchi method as its basic structure, adopted GRA to deal with multiple responses, and entropy to enhance the reasonability of the comprehensive index produced by GRA to make the results more objective and accurate. Overall, these combined mathematical techniques improved catalytic performance for 1-butene production.  相似文献   
4.
T. Kairn  M.L. Matin  I.K. Snook 《Polymer》2004,45(7):2453-2464
We study the concentration dependence of the conformational and viscometric behaviour of short-chain polymer solutions in shear flow by conducting a series of non-equilibrium molecular dynamics simulations, covering the entire concentration range. Our model explicitly incorporates all of the important generic features of real polymer solutions—excluded volume, hydrodynamic interactions and finite chain extensibility. Hydrodynamic interactions are included exactly by treating the solvent explicitly as an atomic fluid. The polymer molecules studied consist of 20-site bead-rod model molecules, which correspond approximately to 12 Kuhn steps in the melt. For polyethylene, this represents a molar mass of 1800 g mol−1. In some respects, our results are consistent with experimental and theoretical results obtained for long-chain polymer solutions. We calculate the Flory-Fox constant and find a value that agrees reasonably well with results for long chain polymer solutions. Due to the short chain length of the molecules investigated, no semidilute region exists for these solutions. However, the radius of gyration and viscosity still exhibit strong concentration dependence, which is well described by power series, rather than power law expressions, in contrast to the behaviour usually observed in long-chain polymer solutions.  相似文献   
5.
Reviews the history of saccadic suppression and describes the suggested causes of the phenomenon. Primary emphasis is placed on "ordinary" saccadic suppression (i.e., decreased sensitivity for stimulation received from the outside environment either during or within a few hundred milliseconds of the time of occurrence of a saccade). However, the suppression of afterimages and entopic images is also considered. Some suggestions are made about the role of suppression in maintaining a stable visual world (constancy of visual direction) when voluntary saccades occur. (98 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
6.
The physical elevation corresponding to visually perceived eye level (VPEL) changes linearly with the pitch of a visual field. Deviations from true eye level average more than 0.5 times the angle of pitch over a 65° pitch range. A visual field consisting of 2 dim, isolated vertical lines in darkness is more than 4/5 as effective as that of a complexly structured visual field; 2 horizontal lines have a small and inconsistent effect. Differences in influence on VPEL between pitched-from-vertical and horizontal lines were predicted from an analysis that extracted differences in retinal perspective resulting from changes in pitch. The Great Circle Model (GCM), based on a spherical approximation to the erect, stationary eye, predicts the present results and results of 8 other sets of experiments. The model treats the influence of a single line on VPEL as systematically related to the elevation of the intersection between the great circle containing the image of the line and the central vertical retinal meridian; generalized GCM combines visual inputs with inputs from the body-referenced mechanism and maps onto the central nervous system. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
7.
The use of design-build delivery methods and building information modeling (BIM) tools in the construction industry has been growing rapidly in recent years due to the increasing demand for more efficient construction project management. The successful implementation of these?tools by engineering firms on projects, however, is still not being achieved consistently. This paper shares the experiences of the implementation of an in-house BIM tool by a large engineering, procurement, and construction firm that has an extensive reputation for design-build projects. A new workflow was proposed that takes full advantage of the BIM tool to both enhance the construction management performance and to minimize the impact on the firm’s existing workflow. The development of a new workflow was conducted by interviewing key personnel in various departments of the firm and by carefully examining probable impacts of the BIM tool’s introduction into the firm’s business processes.  相似文献   
8.
Two-dimensional phase Doppler anemometry techniques have been used to achieve simultaneous measurement of the velocity and size of individual droplets entrained into the gas core during upward annular gas-liquid flow. Data rates greatly exceeding those of other experimental techniques have been achieved. Information is presented on the centreline variation of droplet velocity and droplet size, together with size and velocity correlations, for a range of flowrates and hydrodynamic development lengths from 135 to 228.  相似文献   
9.
Strategic Resource Development Options in England and Wales   总被引:1,自引:0,他引:1  
This paper describes the options which had to be considered for new water resources in the development of the † National Rivers Authority's water resource strategy for England and Wales. The options included interregional transfers, strategic reservoirs, and a range of unconventional schemes including aquifer recharge, effluent re-use, groundwater abstraction where levels are rising, desalination, and transfer by sea. The main options are described and comparative costs are presented.  相似文献   
10.
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