一维新型阶梯函数光子晶体透射特性

研究了阶梯型折射率n22、n11(阶梯分布高度)的大小、对应的分布厚度、不同入射角以及缺陷模对阶梯函数型光子晶体透射特性的影响.由费马原理给出光在函数光子晶体中的运动方程,再由电磁传播理论给出函数光子晶体的传输矩阵,进一步推导出函数光子晶体的透射率以及电场分布的表达式.研究表明,1)随n22,n11大小或者厚度改变,其禁带变宽;2)随光的入射角增加,其禁带变窄;3)当加入缺陷层时,随着缺陷层介质折射率增加,缺陷模强度减小且位置发生红移;4)在函数光子晶体中,缺陷层前电场分布保持不变,而在缺陷层处以及之后的电场强度都明显增强,这不同于常规光子晶体的电场分布仅在缺陷层处局域增强.     

天目铁木愈伤组织和芽苗诱导技术

以天目铁木嫩茎尖为外植体,应用均匀设计法筛选其基部愈伤组织诱导和愈伤组织再分化芽苗的最适合培养基.结果表明,最适合的嫩茎尖基部愈伤组织诱导培养基为1/2DR+TDZ 2.30 mg·L^-1+2,4-D 0.55 mg·L^-1,诱导率为93.5%;愈伤组织芽苗再分化培养基为1/2DR+TDZ 3.30 mg·L^-1+KT 0.70 mg·L^-1,分化率达99.8%以上. 成功建立了天目铁木嫩茎尖离体诱导愈伤组织和芽苗再分化体系,且再生芽苗与野生植株染色体数目相同.     

非线性A_f-B_g型自由基交替共聚反应的固化理论

利用高分子反应统计理论 ,给出了非线性Af-Bg 型自由基交替共聚反应的溶胶 -凝胶分配方程和反应体系的凝胶化条件 ,这些结果是进一步研究与凝胶网络性能相关的网络结构参数的基础     

热敏显色微胶囊的制备与表征

热敏显色微胶囊是用于传真、条形码系统、医用图像、各种打印等领域的重要材料,它是一种内部含有染料隐色体的球形胶囊。染料隐色体是一种内酯结构的无色染料,在一定条件下,与显色剂发生显色反应。由于染料隐色体的化学惰性不够理想,易受外界因素的干扰,因而在应用中受到一定限制,所以为了克服其存在的不足,常将其微胶囊化。微胶囊的芯壁结构可以将芯材与外界隔离,提高芯材的稳定性,同时保留芯材原有的化学性质。当环境温度在微胶囊的玻璃化温度以上时,由于形成微胶囊壁的物质透过性显著增加,因此显色成分接触而发生显色反应。本文利用界面聚合法,以聚乙烯醇为保护胶体,曲拉通X-100为表面活性剂,聚氨酯为壁材,染料隐色体为芯材,合成了聚氨酯热敏显色微胶囊。研究了三个主要因素对微胶囊的粒径及其分布、表面形貌和热敏显色性能的影响。结果表明,增大保护胶体浓度,提高乳化速度,增加乳化剂用量,微胶囊的平均粒径变小,粒径分布变窄,表面变得光滑而且致密,具有较高的热敏显色密度。利用红外光谱仪确认了微胶囊的结构,在最优条件下,所制备的微胶囊玻璃化温度为131 ℃,并具有良好的热稳定性。     

非线性Af—Bg型自由基交替共聚反应的固化理论

利用高分子反应统计理论,给出了非线性Ａｆ－Ｂｇ型自由基交替共聚反应的溶胶－凝胶分配方程和反应体系的凝凝胶化条件,这些结果是进一步研究与凝胶网络性能相关的网络结构参数的基础。     

Tapered copolymers of styrene and 4-vinylbenzocyclobutene via carbanionic polymerization for crosslinkable polymer films

Well-defined polystyrene homopolymers with surface-adhesive triethoxysilyl end group were synthesized via living carbanionic polymerization, epoxide end-functionalization and subsequent hydrosilylation with triethoxysilane. Grafting-to performance of polymers with various molecular weight (M_n = 3000–14,000 g mol⁻¹) to a silicon surface was examined in dependence of reaction time, polymer concentration, solvent and number of alkoxysilyl end groups. Crosslinkable polymers for surface modification were synthesized by statistical carbanionic copolymerization of 4-vinylbenzocyclobutene (4-VBCB) and styrene, followed by epoxide end-functionalization and triethoxysilane modification (M_n = 4000–14,000 g mol⁻¹). The copolymers were characterized by ¹H-NMR, THF-SEC, and matrix-assisted laser desorption and ionization time-of-flight mass spectrometry. In situ ¹H-NMR kinetic studies in cyclohexane-d₁₂ provided information regarding the monomer gradient in the polymer chains, with styrene being the more reactive monomer (r_s = 2.75, r_4-VBCB = 0.23). Thin polymer films on silicon wafers were prepared by grafting-to surface modification under conditions derived for the polystyrene homopolymer. The traceless, thermally induced crosslinking reaction of the benzocyclobutene units was studied by DSC in bulk as well as in 3–6 nm thick polymer films. Crosslinked films were analyzed by atomic force microscopy, ellipsometry, and nanoindentation, showing smooth polymer films with an increased modulus. © 2019 The Authors. Journal of Polymer Science published by Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 181–192     

Pulverized coal plasma gasification

A number of experiments on the plasma-vapor gasification of brown coals of three types have been carried out using an experimental plant with an electric-arc reactor of the combined type. On the basis of the material and heat balances, process parameters have been obtained: the degree of carbon gasification (_c), the level of sulfur conversion into the gas phase (_s), the synthesis gas concentration (CO+Hz) in the gaseous products, and the specific power consumption for the gasification process. The degree of gasification was 90.5-95.0%, the concentration of the synthesis gas amounted to 84.7–85.7%, and the level of sulfur conversion into the gas phase was 94.3–96.7%. Numerical study of the process of plasma gasification of coals was carried out using a mathematical model of motion, heating, and gasification of polydisperse coal particles in an electric-arc reactor of the combined type with an internal heat source (arc). The initial conditions for a conjugate system of nonlinear differential equations of the gas dynamics and kinetics of a pulverized coal stream interacting with the electric arc and oxidizer (water vapor) agree with the initial conditions of the experiments. The computation results satisfactorily correlate with the experimental data. The mathematical model can be used for the determination of reagent residence time and geometrical dimensions of the plasma reactor for the gasification of coals.Nomenclature c _i volume concentration of components (kmol m^–3) - x longitudinal coordinate (m) - f _i source members, determined by variation of the ith component due to chemical reactions in unit volume in unit time (kmol m^–3s^–1) - velocity (m s^–1) - M _s ash mass in one particle (kg) - C _D particle drag coefficient - 3.14 - r _s particle radius (m) - d particle diameter (m) - density (kg m^–3) - C _p heat capacity of components (J mol^t– K^–1) - Q _j thermal effect of reaction (J kmol^–1) - E_j activation energy of reaction - N _l volume concentration of particles of thelth fraction (m^–3) - T temperature (K) - emissivity factor of coal particles - 5.67 × 10^–8, blackbody emissivity coefficient (W m^–2 K^–4) - P pressure (Pa) - S reactor cross section (m²) - D reactor diameter (m) - V reactor volume (m³) - L _R reactor length (m) - F _W friction force on the wall (N) - f _g friction coefficient - residence time (s) - Nu Nusselt number - Re Reynolds number - Pr Prandtl number - thermal conductivity of gas (J m^– s^–1 K^–1) - R 8.3 × 10³, universal gas constant (J kmol K^–1) - µ _i molecular mass of component (kg kmol^–1) - dynamic viscosity coefficient of gas (kg m^–1 s^–1) - thermal efficiency of plasma reactor - q_arc specific heat flow from arc (W m^–3) - P ₁ heat supplied in vapor at T = 405 K (W) - P ₂ heat loss to wall (W) - P ₃ heat loss in the gas and slag separator chamber (W) - P ₄ heat loss in the synthesis gas oxidation chamber (W) - P ₅ heat loss in the slag catcher (W) - P ₆ heat carried away in the off-gas (W) - P heat input of arc (W) - P _arc electric power of arc (W) - Q_sp specific power consumption (kw Hr kg^–1) - d _w specific heat flow to wall (W m^–2) - _c degree of carbon gasification (%) - _s level of sulfur conversion into gas phase (%)     

A Study of the Probe Effect on the Apparent Image of Biological Atomic Force Microscopy

The atomic force microscopy (AFM) possesses high spatial resolution and it is compatible with liquid environments. AFM can provide possibility to study a wide range of biological problems at the molecular level and acquire topological information at nanometre resolution under physiological conditions1,2. However, a major problem for image reconstruction of biological specimens is that structures of most biological molecules are very soft and delicate, which could be easily deformed and dama…     

含芴共轭单元的超支化聚合物的合成及表征

以芴和季戊四醇为初始物,分别合成了具有芴共轭单元和季戊四醇多臂结构的两种聚合单体,进一步采用Suzuki反应合成出一种结构新颖的部分共轭结构的超支化聚合物.利用紫外吸收光谱和荧光发射光谱对聚合物予以表征,结果表明,超支化聚合物具有与模型化合物分子相似的发光行为,既可以发出纯正的蓝光,又表现出支化结构对荧光发射的影响.差...     

A planar tetracoordinate carbon and unusual bonding in an organodimetallic propynylidene complex arising from double C-H activation of an allene ligand

Reduction of the organoditantalum allene complex (eta-C5Me4R)2Ta2(mu-X)X3(mu-eta1,eta3-C3H4) (R = Me (Cp*), Et; X = Cl, Br) with sodium amalgam leads to the propynylidene complex (eta-C5Me4R)2Ta2(mu-H)2X2(mu-HCCCH) by a formal double 1,3-C-H activation of the allene ligand. The solid-state molecular structure contains a planar HCCCH ligand bridging, in parallel coordination mode, the two tantalum atoms, with the HCCCH and Ta atoms coplanar. Key structural features are a Ta-Ta distance of 2.8817(7) A, propynylidene C-C-C angle of 153.7(13) degrees , C-C distance of 1.370(8) A, Ta-C(central) distance of 2.194(9) A, and Ta-C(terminal) distance of 1.970(9) A. Molecular orbital calculations on the complex at the RHF/SBK(d) and B3LYP/LanL2dz levels of theory demonstrate that the propynylidene ligand is best viewed formally as an allenediylidene(4-) ligand bonded to two d0 tantalum atoms via two Ta=C(terminal) double bonds and an unusual three-center, two-electron bridge bond involving both tantalum atoms and a lone pair on the planar, tetracoordinate central carbon. There is no net Ta-Ta bonding based on the orbital analysis.