温州地区近地强风特性实测研究

为研究我国沿海地区的近地强风特性,基于设置在温州大学的风场观测点(离地约30m高),对台风“海鸥”影响温州时的风场状况进行了监测,获取了台风期间近地风场的实测数据。通过对台风影响过程的风速和风向、湍流度、阵风因子、湍流积分尺度、脉动风速功率谱密度函数和空间相干性等参数的分析,研究了台风“海鸥”影响温州时的近地风场特性。结果表明：台风“海鸥”的湍流度和阵风因子较大,顺风向和横风向湍流度接近;顺风向与横风向湍流积分尺度的均值分别为70.4m和66.6m;实测风速谱与von Karman谱基本符合;实测两点的脉动风速空间相干系数在零频率处与Shiotami经验公式计算结果一致。     

凯威特型索穹顶结构多种张拉成形方案模型试验研究

张拉成形技术属于索穹顶结构的关键技术。为分析比较各种张拉成形方案的施工可行性和方便性,同时深入理解预应力生成机理,对一凯威特型索穹顶结构模型进行了逐步张拉外圈斜索成形、一次性张拉外圈斜索成形及由外及里逐步调节压杆到原长成形等三种成形方案的张拉成形试验,跟踪了张拉成形全过程。试验研究表明：三种张拉成形方案都是可行有效的,其中一次性张拉外圈斜索成形方案施工较为方便;逐步调节压杆长度到原长成形方案精度相对较高;控制构件原长的张拉成形控制技术不仅适用于单整体自应力模态体系,也适用于多整体自应力模态体系;体系预应力伴随着构件的逐步张拉到位而逐步生成。     

Optimized energy storage performance in BF-BT-based lead-free ferroelectric ceramics with local compositional fluctuation

BiFeO₃-based lead-free ferroelectric is considered a potential candidate for energy storage applications owing to its high spontaneous polarization. To tackle the compromise between high polarization and energy storage density, NaNbO₃ (NN) was introduced into 0.7BiFeO₃-0.3Ba(Hf_0.05Ti_0.95)O₃ (BF-BHfT) ceramics, where Nb⁵⁺ ions enter the BF-BHfT lattices and enhance resistivity, while Na⁺ ions occupied on the A-sites and smash the long-range ferroelectric order into polar nanoregions. Consequently, the ceramics could maintain high maximum polarization and low remanent polarization. High recoverable energy density (W_rec) of 5.2 J/cm³ and efficiency (88%) were recorded in 0.53BF-0.3BHfT-0.17NN ceramics. Besides, it exhibited good thermostability up to 120 °C (W_rec variation < 5%), frequency stability from 10 to 200 Hz (W_rec variation < 7%) and excellent fatigue resistance after 10⁴ cycles (W_rec variation < 0.2%). Under different electric fields the efficiency still maintains nearly constant. In charge-discharge test a W_dis of 3.7 J/cm³ was recorded, which proved 0.5³BF-0.3BHfT-0.17NN ceramics a promising candidate for energy storage applications.     

Multistep kinetic study of Fe2O3 reduction by H2 based on isothermal thermogravimetric analysis data deconvolution

The multistep kinetics of Fe₂O₃ reduction by H₂ is investigated by data deconvolution in this study. The reduction process was conducted in a TGA apparatus isothermally in the temperature range of 750–950 °C. The stepwise reduction of Fe₂O₃, i.e. Fe₂O₃–Fe₃O₄, Fe₃O₄–FeO, and FeO–Fe, was successfully decoupled from each other without controlling the reduction gas atmosphere. The overlapping, as well as the reaction rate, of each reduction step can be described by the deconvoluted data with R² > 0.995 for all the tested temperatures. Based on the deconvolution, relatively stable activation energy with increasing the conversion was obtained for each step with the model-free iso-conversion method, indicating the rationality of the decoupled multistep profiles. Master plot was then applied to evaluate the suitability of kinetic models reported in the open literature. The JMA model (Avrami-Erofe'ev equation), corresponding to the nucleation and growth mechanism, was found to be most suitable for describing each reduction step. The activation energies obtained by the JMA model fitting for Fe₂O₃–Fe₃O₄, Fe₃O₄–FeO, and FeO–Fe were 10.3, 26.7, and 24.8 kJ/mol, respectively, which also agree well with the E_a obtained by the model-free method.     

楠溪江干流香鱼栖息地水生态调查分析

香鱼是楠溪江较为名贵且对环境敏感的一种鱼类,由于人类活动影响,香鱼栖息地遭到破坏,导致香鱼数量急剧减少。为进一步开展楠溪江香鱼栖息地的水生态保护与修复工作,本文对楠溪江香鱼栖息地水质及着生藻类进行了现场调查与分析,结果表明:香鱼产卵期的产卵场及育肥期的育肥场水质相对较好,能为香鱼的产卵、育肥提供较好的水质环境;上溯期的中游产卵场河段及下游感潮河段水质均较差,不利于香鱼从下游河段向育肥场迁移。产卵场和育肥场着生藻类生物量丰富,以硅藻为主,有利于香鱼的产卵和育肥。为促进楠溪江香鱼栖息地的保护与修复,针对楠溪江下游感潮河段开展水环境综合治理工作,提出了重点关注TN的削减的建议。     

Effect of sintering temperature on the transparency and mechanical properties of lutetium aluminum garnet fabricated by spark plasma sintering

Transparent lutetium aluminum garnet (Lu₃Al₅O₁₂, LuAG) was fabricated by reactive spark plasma sintering. The effect of sintering temperature on the crystal phase, microstructure, transparency and mechanical properties of LuAG bodies was investigated. Fully dense and single-phase LuAG bodies were obtained at sintering temperatures 1573–1923 K. The average grain size increased from 0.18 to 0.52 μm with increasing sintering temperature from 1573 to 1773 K, and grain growth became significant at 1823 K. Transmittance showed a maximum value of 77.8% at 2000 nm at a sintering temperature of 1773 K after annealing at 1423 K in air for 43.2 ks. The Vickers hardness increased from 14.2 to 17.2 GPa with decreasing grain size from 7.45 to 0.23 μm.     

Structural,linear and third-order nonlinear optical properties of Cu nanocrystal in sodium borosilicate glass

Cu nanocrystals embedded in sodium borosilicate glass of varied Cu contents from 0.5 to 1.5 wt% have been successfully prepared through a sol–gel process. According to the results of X-ray diffraction (XRD) and the energy dispersive X-ray spectrometry (EDS), the metal Cu nanocrystals in cubic crystal system were well distributed inside glass matrix. Fourier Transform Infrared (FTIR) indicated the sodium borosilicate matrix had no major structural change for gels with different Cu contents. The optical absorption peaks due to the surface plasmon resonance of Cu particles were observed in the wavelength range of 550–600 nm. The absorption peak showed a red-shift trend with increasing Cu contents from 0.5 to 1.5 wt%. Transmission electron microscopy (TEM) revealed the existence of spherical Cu nanocrystals in the matrix. The diameter of Cu nanocrystals varied from 1 to 3.5 nm. Furthermore, the third-order nonlinear optical properties were investigated by Z-scan technique at 800 nm. Experimental results indicated the Cu nanocrystals have obvious positive refractive nonlinearities and reverse saturated absorption performance.     

The dynamic behaviors of diblock copolymer/nanorod mixtures under equilibrium and nonequilibrium conditions

Cylindrical diblock copolymer/anisotropic nanorod composites under equilibrium and nonquilibrium conditions, have been modeled and simulated using dissipative particle dynamics. The aim of our present study is to understand how the anisotropic NRs affect the equilibrium self-assembled structure of diblock copolymers (DBCPs) melts and how the shear flow induces the dynamic behaviors of DBCPs/NRs composites, especially the orientation and distribution of NRs in diblock matrix. We consider two different shear directions categorized with respect to the flow velocity parallel or perpendicular to the orientation of initial structures, which are defined as z-axis shear flow and x-axis shear flow, respectively. Our results show the shear flow not only aligns the orientation of DBCPs template and the dispersed NRs toward the flow direction, but also regulates the orientational and positional order of NRs. The final self-assembly behaviors of DBCPs/NRs nanocomposites is determined by the interplay between shear-induced polymer thinning and NRs dispersion. This work provides us a viable strategy for creating polymer nanocomposites with tunable and enhanced processing properties.     

SP0810色谱柱上D-塔格糖和D-半乳糖Henry常数的测定

利用高效液相色谱测定在SP0810色谱柱上吸附的Henry常数,以超纯水作为流动相,在流速为0.5 mL/min,柱温为35℃,进样20μL的条件下,测定D-半乳糖的Henry常数为0.56,D-塔格糖Henry常数为1.28。此外,研究了柱温对Henry常数的影响,估算了D-塔格糖及D-半乳糖的吸附焓。     

Modified extremal optimization for the hard maximum satisfiability problem

Based on our recent study on probability distributions for evolution in extremal optimization (EO),we propose a modified framework called EOSAT to approximate ground states of the hard maximum satisfia...