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111.
对实腹式波形顶板-UHPC(超高性能混凝土)组合桥面板进行了改进, 采用空腹式结构建立波形钢板-UHPC组合桥面板有限元模型, 研究UHPC层厚度、波形钢板厚度、波形长度、下缘板宽度和波形高度等截面参数变化对组合桥面板受力特性的影响, 并确定其合理取值范围. 在此基础上, 通过理想点法对参数组合进行优化, 得到合理的参数匹配. 研究结果表明 相较于实腹式组合桥面板, 优化后的组合桥面板自重减小35%, 钢板弯折处应力减小16%; 相较于正交异性钢桥面板, 桥面板用钢量减小7%, 顶板与U肋连接位置应力减小47%. 相似文献
112.
113.
采用flat-joint粘结模型,建立多孔铁电陶瓷在一维应变冲击压缩下的PFC (particle flow code)颗粒流离散元模型,通过数值模拟再现了平板撞击实验中实测的自由面速度剖面历史,并揭示了多孔铁电陶瓷在冲击压缩下的响应过程与损伤演化机制。多孔铁电陶瓷在冲击压缩下的响应过程可分4个阶段:弹性变形、失效蔓延、冲击压溃变形、冲击Hugoniot平衡状态;其中,失效蔓延的内在机制是由剪切裂纹的成核与增长,而冲击压溃变形的主要机制是孔洞的塌缩以及层状剪切裂纹的形成与扩展;冲击速度与孔隙率对铁电陶瓷的响应有显著的影响,Hugoniot弹性极限强烈依赖于孔隙率,但与冲击速度的大小无关,宏观损伤累积随着冲击速度和孔隙率的增加而增加。 相似文献
114.
Complex networks with binary-state dynamics represent many meaningful behaviors in a variety of contexts. Reconstruction of networked systems hosting delayed binary processes with hidden nodes becomes an outstanding challenge in this field. To address this issue, we extend the statistical inference method to complex networked systems with distinct binary-state dynamics in presence of time delay and missing data. By exploiting the expectation-maximization (EM) algorithm, we implement the statistical inference based approach to different (i.e., random, small world, and scale-free) networks hosting delayed-binary processes. Our framework is completely data driven, and does not require any a prior knowledge about the detailed dynamical process on the network; especially, our method can independently infer each physical connectivity and estimate the time delay solely from the data of a pair of nodes in this link. We provide a physical understanding of the underlying mechanism; and extensive numerical simulations validate the robustness, efficiency, and accuracy of our method. 相似文献
115.
The regioselectivity of Diels-Alder cycloaddition of 1,3-butadiene to C59XH (X=N, B) has been studied theoretically by means of the semiempirical AM1 and DFT (B3LYP/6-31G*) methods. The mechanisms of the cycloaddition on some selected 6.6 bonds of C59XH (X=N, B) have been analyzed. For C59NH, the activation energies become lower with the addition site increasingly farther from the N atom; however, they are all higher than that of the reaction of 1,3-butadiene with C60. In contrast to C59NH, for the cycloaddition to C59BH, the activation energies corresponding to 2,12/r- and 2,12/f-transition states, in which the addition sites are the nearest ones to the B atom, are the lowest ones, and are lower than that of the reaction of 1,3-butadiene with C60 by over 18 kJ·mol−1, and the products corresponding to these two transition states are the most stable ones. The different electronic natures of N and B atoms results in different effects on the Diels-Alder reactions of 1,3-butadiene with C59NH and C59BH; the former makes the reactivity of C59NH reduced and the latter makes the reactivity of C59BH enhanced, relative to that of C60. 相似文献
116.
Nie Q Li X Dai S Xu T Jin Z Zhang X 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(3):537-541
Nd(2)O(3)-doped 70Bi(2)O(3)-20B(2)O(3)-10SiO(2)-xNd(2)O(3) (x=0.1, 0.3, 0.5, 0.7, 1.0, 1.5 mol%) bismuth glasses were prepared by the conventional melt-quenching method, and the Nd(3+):(4)F(3/2)-->(4)I(13/2) fluorescence properties had been studied for different Nd(3+) concentrations. The Judd-Ofelt analysis for Nd(3+) ions in bismuth boron silicate glasses was also performed on the base of absorption spectrum. The transition probabilities, excited state lifetimes, the fluorescence branching ratios, quantum efficiency and the stimulated emission cross-sections of (4)F(3/2)-->(4)I(13/2) transition were calculated and discussed. Based on the electric dipole-dipole interaction theory, the interaction parameters: C(DD), for the energy migration rate (4)F(3/2), (4)I(9/2)-->(4)F(3/2), (4)I(9/2) and C(DA), for cross-relaxation rate (4)F(3/2), (4)I(9/2)-->(4)I(15/2), (4)I(15/2), and/or (4)F(3/2), (4)I(9/2)-->(4)I(13/2), (4)I(15/2) in bismuth boron silicate glasses were about 18.4 x 10(-40)cm(6)/s and 3.4 x 10(-40)cm(6)/s, respectively. 相似文献
117.
Hao Lei~a Hai-yin Yu~a Ying Lu~b Xiao-long Lu~c Zhi-kang Xu~ 《高分子科学》2008,(1):105-110
A novel approach for the surface modification of poly(vinylidene fluoride)(PVDF)membrane was successfully realized through alkaline treatment,UV-induced bromine addition,and followed by surface-initiated atom transfer radical polymerization(ATRP)of methyl methacrylate(MMA).Chemical changes on the PVDF membrane before and after modification were analyzed with attenuated total reflectance Fourier transform infrared spectroscopy(ATR/FT-IR)and X-ray photoelectron spectroscopy(XPS).Primary kinetic study revea... 相似文献
118.
《Arabian Journal of Chemistry》2023,16(6):104718
Identification and determination of chiral pharmaceutical residues is still a challenging analytical puzzle. In this work, a simple, rapid, and effective method for chiral D/L-tetraiodothyronine (T4) separation and quantitative was developed based on host–guest recognition using ion mobility spectrometry-mass spectrometry (IMS-MS). The D/L-T4 enantiomers were mobility separated by their diastereomeric complexes through mixing with cyclodextrin (CD) and metal ions. D/L-T4 was first separated by complexing with host molecule (α-, β-, γ-CD), observing weak peak-to-peak resolution (Rp-p) by the formed binary complex [CD + D/L-T4-H]+, and the Rp-p decreased with the CD size increasing. However, the separation effect of D/L-T4 was much improved with the addition of divalent metal ions (G2+) by the formed ternary complex [CD + D/L-T4 + G]2+. In comparison, α-CD related complexes can possess the best separation effect for D/L-T4 in most cases. Considering the high selectivity, non-toxic, and chemically stable of β-CD, [β-CD + D/L-T4 + Ca]2+ was selected for D/L-T4 analysis (RP-P = 0.764). Whereafter, chemical theoretical conformations for [β-CD + D/L-T4 + H]+ and [β-CD + D/L-T4 + Ca]2+ were optimized, discovering similar micro-interaction modes between [β-CD + D-T4 + H]+ and [β-CD + L-T4 + H]+; while with the addition of Ca2+, significantly different interaction modes were observed between [β-CD + D-T4 + Ca]2+ and [β-CD + L-T4 + Ca]2+. And theoretical collision cross section (CCS) trends for the complexes were consistent with that of the experimental results. Additionally, calibration curves were linear within 1.00 to 104 ng mL?1 with coefficient (R2 > 0.99), gaining the limit of detection (LODs) calculation of 0.11 ng mL?1, and the detection range between D-T4 and L-T4 of 45.6:1 to 1:59.8. Finally, the method was applied for D/L-T4 detection in Levothyroxine tablets, the detection content has good consistency on drug labeling. Because the proposed method exhibited good analytical performance in terms of speed, selectivity, sensitivity, and reproducibility of the measurements, that can be a promising strategy for effective D/L-T4 detection in pharmaceutical industries or other practical samples. 相似文献
119.
In this work, a series of high performance bio-based polyurethanes(bio-PUs) were synthesized from polylactide(PLA)-based diols, different diisocyanates(TDI, MDI, HDI, IPDI) and chain extender 1,4-butanediol, in which different soft and hard segments are used to adjust their transition temperatures and mechanical properties. Poly(lactide-co-caprolactone)copolymer diols(co-PLAols) instead of PLA diols as the soft segment improved the thermal stability and mechanical properties of the synthesized bio-PUs. Among them, MDI-based bio-PUs have the highest T_g(43.8 °C), tensile strength(23.5 MPa) and modulus(380.8 MPa), while HDI-based bio-PUs have the lowest T_g(21.4 °C) and highest elongation at break(580%). Especially, the bio-PUs synthesized from co-PLAols and MDI demonstrate better mechanical properties,closed to petroleum-based commodities. Furthermore, the obtained bio-PUs display good shape memory properties at body temperature and cytocompatibility. Therefore, these bio-PUs are promising for applications in biomedical fields. 相似文献
120.
Variable-weight optical orthogonal codes(OOCs) were introduced by G. C. YANG for multimedia optical CDMA systems with multiple quality of service(Qo S) requirements. In this paper, some infinite classes of optimal cyclic packing are presented. Optimal(24u, {3, 4}, 1,{2/3, 1/3})-OOCs for any positive integer u > 1 are established. 相似文献