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1.
有效缓发中子份额(βeff)是研究反应堆动力学特性的关键参数。在液态燃料熔盐堆(MSR)中,燃料流动引起缓发中子先驱核(DNP)在堆内的再分布,并使部分DNP在堆外回路衰变,从而导致βeff的计算方法与固态燃料反应堆不同。为评估石墨慢化通道式熔盐堆内燃料流动引起的反应性损失,研究缓发中子随燃料的流动行为,同时为堆设计和安全分析提供依据,分别基于解析方法和数值方法推导了计算βeff的数学模型,计算了熔盐实验堆(MSRE)在额定工况下的DNP损失份额和堆内DNP浓度分布,并分析了燃料在堆外流动时间和入口流量对βeff的影响。结果表明:两种方法均可对DNP行为提供合理描述;固定燃料在堆外流动时间,βeff随入口流量的增加而减小;固定入口流量,βeff随燃料在堆外流动时间的增加而减小,80 s后趋于稳定。  相似文献   
2.
以化工流程模拟软件Aspen Plus为工具,通过模拟数据与文献数据对比,确定选用SR-POLAR热力学方程模拟研究体系。利用残余曲线、蒸馏边界理论对三乙胺、乙醇和水混合液模拟分析,确定采用变压精馏技术分离共沸混合物设计方案,利用灵敏度分析对流程进行优化设计。结果表明:低压精馏塔理论塔板数为25、回流比为5,原料进料位置在第21块塔板;加压精馏塔理论塔板数为20、回流比为2,进料位置在第11块塔板。在此条件下,塔底产品三乙胺的质量纯度在99.9%以上,达到了预期的分离效果。  相似文献   
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A novel La2MgGeO6 ceramic was synthesized through a solid-state reaction process within a sintering temperature range of 1450–1550 °C. By a combination of X-ray diffraction and Rietveld refinement analyses, the ceramics were found to have a pure hexagonal phase structure belonging to space group R3/146. The scanning electron microscopy images revealed that the ceramic grains were closely connected. The effects of internal (lattice energy, valence bond, and fraction packing) and external factors (density) on the microwave properties of ceramics were also studied. The ceramic exhibited excellent microwave dielectric performances, with a relative permittivity (?r) of 21.2, a quality factor (Q × f) of 52 360 GHz, and a temperature coefficient of resonant frequency (τf) of ?44.2 ppm/°C, when sintered at 1500 °C for 4 h. The τf value of the La2MgGeO6 ceramic doped with CaTiO3 could be adjusted to zero. Particularly, 0.2La2MgGeO6-0.8CaTiO3 ceramics have good microwave dielectric properties with τf = +2.1 ppm/°C, Q × f = 15 610 GHz, and ?r = 40.3.  相似文献   
4.
Perovskite materials with compositions in the vicinity of the steep morphotropic phase boundary (MPB) exhibit various intriguing properties including giant piezoelectricity and large dielectric constant. Aside from composition, the phase configuration of the perovskites is also strongly related to the ambient temperature. Here, we report a giant piezoelectricity of 10 980 pm/V at 93°C in the 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) single crystals which is more than five times larger than that at room temperature. The enhanced piezoelectricity can be attributed to the instability of the thermally induced tetragonal phase which can be converted to the orthorhombic phase by the external electric field in the <011> oriented single crystal. The transverse piezoelectricity has been investigated by measuring the electric-field-dependent ferromagnetic resonance (FMR) field in the CoFeB/PMN-PT magnetoelectric (ME) heterostructures. The ME coupling coefficient has been increased from 49.3 to 476 Oe cm/kV as temperature increased from 25 to 90°C. The findings reveal that both longitudinal and transverse piezoelectricity in the PMN-PT single crystals can be greatly enhanced by proper setting of ambient temperature, indicating an effective route for the design of strain-mediated tunable devices with ultralow driving voltage.  相似文献   
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Along with the implementation of electricity sales-side reform and incremental power distribution investment liberalization under China's new round of electricity market reform, the main subjects of distributed generation investment, construction, and operations have become more various, and the approaches as well as the ways that distributed generation takes part in the market have been more flexible. How to operate distributed generation economically and efficiently in this market environment has become an urgent issue to be addressed. Based on the domestic development situation of China's distributed generation, this paper introduces typical existing business models of distributed generation, and elaborates the correlation between electricity market reform and business models of distributed generation in depth in combination with the contents of electricity market reform. At last, several business models of distributed generation which are feasible to be implemented in China have been proposed under the new electricity market reform based on successful international distributed generation operation experiences in the terms of stimulating stakeholders' participation in the investment and operations of distributed generation. Characteristics of these recommended models are compared and analyzed as well.  相似文献   
7.
Bio‐based amphiphilic triblock copolymers with 100% renewably sourced poly(trimethylene ether) glycol (PO3G) as the hydrophobic blocks and statistical copolymer of 2‐(2‐methoxyethoxy)ethyl methacrylate (MEO2MA) and oligo(ethylene glycol)methacrylate (OEGMA) [P(MEO2MA‐stat‐OEGMA)] as the hydrophilic blocks are synthesized and characterized. It is found that the molar ratio of MEO2MA/OEGMA among the resulting copolymers is approximately 70/30. The degree of polymerization (DP) of P(MEO2MA‐stat‐OEGMA) block ranges from 16 to 90, and the DP of PO3G block is fixed at 35. The amphiphilic copolymers could form core‐shell micelles self‐assembly in aqueous solution at low concentrations, and the micelles are in spherical shape with sizes varying from 121 to 188 nm. With the increasing length of hydrophilic blocks, the critical micelle concentration increases from 2.15 to 13.8 mg L?1, and the lower critical solution temperature improves from 32.5 to 38.4 °C. The in vitro doxorubicin (DOX) release study shows that all DOX‐loaded micelles have a higher release rate at 37 °C than that at 25 °C. Cytotoxicity test reveals that the blank micelles are nearly nontoxic. These results indicate that the block copolymer micelles containing 100% renewably sourced PO3G can serve as a potential drug delivery carrier. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46112.  相似文献   
8.
Zhang  Xin  Xie  Yuxiang  Luan  Xidao  He  Jingmeng  Zhang  Lili  Wu  Lingda 《Wireless Personal Communications》2018,103(1):401-416
Wireless Personal Communications - This paper introduces a novel content-based video copy detection method using the deep CNN features. An efficient deep CNN feature is employed to encode the image...  相似文献   
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