Synthesis,cure, and composite properties of mixed allyl/propargyl cyclopentadiene resins

A series of thermosetting resins were synthesized via phase transfer reaction of allyl chloride and propargyl bromide with cyclopentadiene in the presence of a strong base. Feed ratios of 1 : 1, 3 : 1, and 5 : 1 allyl chloride to propargyl bromide were used to give resins with varying amounts of propargyl and allyl functionality. In all cases the resins could be thermally cured, without added catalyst, at temperatures below 275°C to give black, glassy, brittle materials with densities of 1.15. TGA evaluation of the resins, with heating to 1000°C, resulted in carbon yields ranging from 48 to 66% with increasing propargyl functionality causing increased values. Physical mixtures of ACP and PCP resins were also made and evaluated. Cure of the mixed materials also occurred below 275°C, and carbon yields were comparable to the corresponding APCP resin. APCP/carbon fiber composites gave good mechanical properties with flexural modulus values of 115–130 GPa and flexural strength values of 1000 MPa. Carbonization of 1 : 1 APCP/carbon fiber composites provided materials with interlaminar strength values of approximately 1.14 MPa. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2869–2876, 1998     

Charge division mechanism in low energy binary fission and the passage of prompt fragments towards theβ-stable products in terms of the double core model

The postulates of the double core model of binary fission are examined against the two well-known charge division mechanisms of fission, namelyucd andecd. An analytic expression of the modifieducd formula is obtained. Radiochemical distribution of mass and charge, formulated from the model, is found to agree satisfactorily with available experimental results. Finally, the most probable charge and mass values of the radiochemical heavy and light products, the average number of neutron andβ-emissions per fragment, are calculated, and found to agree with experimental observations.     

甲胺分子共振增强多光子电离的波长依赖性

使用激光多光子电离质谱技术，研究了甲胺分子在４２５ｎｍ－４９５ｎｍ波长范围内共振增强多光子电离碎裂过程，记录了母体离子和与碎片离子产额与波长的依赖关系。由于共振增强多光子电离母体离子与碎片离子谱的相似性，可用探测总离子信号的方法来替代单独的母离子探测，有效地提高痕量探测的灵敏度。     

Yields and energy spectra of light charged particles emitted in neutron induced fission of235U

The yields and energy spectra of light charged particles emitted in the fission of²³⁵U have been measured in the neutron energy range of 100 keV to 1 MeV. The yield of long range alpha particles is found to increase around 200 keV neutron energy compared to thermal fission. A low energy component observed in the energy spectrum was assigned to the tritons emitted in fission. The yield of this triton component is seen to have a marked increase around 500 keV. These results indicate that LCP yield is influenced by the transition state level characteristics.     

Measurement of K shell radiative transition probabilities and K, L2 and L3 shell/subshell fluorescence yields of some elements in the atomic number range 30 ≤ Z ≤ 40

K shell radiative transition probabilities and K, L₂ and L₃ shell/subshell fluorescence yields were measured using the K_β/K_α intensity ratio for seven elements in the atomic number range 30≤Z≤40 (Zn, As, Se, Rb, Sr, Y and Zr). The targets were irradiated with γ photons of energy 59.5 keV from Am-241. The obtained values were compared with the theoretical values. It was observed that the present values agree with previous theoretical results. The L₂ and L₃ subshell fluorescence yields were the first measured for the present elements.     

Selectivity of hydrogenations. Part 4 6- and 8-substituted quinaldines yield of tetrahydroderivatives and basicities of quinolines

Hydrogenation of 6- or 8-R-substituted quinaldines [R=H, CH₃, CH(CH₃)₂, C(CH₃)₃, or CF₃] over platinum in trifluoroacetic acid gave higher yields (90%) of 5,6,7,8-tetrahydroderivatives than hydrogenation of the corresponding quinolines. ThepKa-values of 20 quinolines and quinaldines were determined by measuring the half-neutralization potentials in acetic anhydride. More basic quinolines gave higher yields of 5,6,7,8-tetrahydroproduct; exceptions are 6- and 8-methylquinoline and 8-tert. butylquinoline. Explanations for these observations are suggested.Dedicated to Prof. Dr.K. Schlögl on the occasion of his 60th birthday.     

两级生产与需求不确定的供应链收益共享契约机制

研究原材料生产、产成品生产以及市场需求不确定下供应链收益共享契约机制.分析了独立无协调决策下,供应链系统的生产与订购决策.构建了收益分享协调契约与模型,研究了收益分享契约下供应链收益分配模型与机制,最后进行了算例分析.研究表明,收益共享协调机制可以减少两级生产与需求不确定性对供应链的影响,使得基于收益共享的供应链利润达到了集中决策供应链的利润水平.     

厚靶D（d,n）^3He反应加速器中子源的产额、能谱和角分布

给出一种计算氘钛厚靶D(d,n)3He反应加速器中子源的产额、能谱和角分布的方法,并发展了一个计算机模拟程序,程序能够计算氘束流能量小于1.0 MeV的中子源的产额、能谱和角分布.计算时使用推荐的D(d,n)3He反应截面数据和来自SRIM-2003程序的氘在氘钛靶中的阻止本领数据.给出一些典型计算结果,包括中子积分产额、中子能谱和角分布.     

Investigation of the Photochemistry and Quantum Yields of Triazines Using Polychromatic Irradiation and UV-Spectros Copy as Analytical Tool

Abstract

Photochemical reactions of atrazine, propazine, simazine, terbuthylazine, ametryn and atraton were investigated in aqueous and buffered (pH=7–9) solutions (containing a few percent of acetonitrile) using a polychromatic Xe light source at T=22[ddot]C. For terbuthylazine the photochemistry is investigated in detail, including solvent-, temperature-and pH-dependence and products found. The role of polychromatic light sources used in investigations of the photochemistry of triazines is discussed.

For the first time, quantum yield measurements were performed in the UV-band between 240–300 nm of the chlorotriazines and ametryn. Isosbestic points were found in the UV-spectra at different irradiation times, and UV-spectroscopy was used to obtain kinetic information.

Quantum yields in aqueous solutions at T=22[ddot]C for the chlorotriazines (Φ=0.048–0.062) and for ametryn (Φ=0.043) are comparable. The temperature dependence of the photoreaction of terbuthylazine leads to an activation energy of about 13 kJ mol^?1. Quantum yields in acetonitrile and hexane for terbuthylazine are about half of the values found in aqueous solution.

Atraton was not degradable under the conditions used, and the quantum yield could only be estimated to be Φ < 0.002.     

The synthesis and photophysical properties of novel cationic tetra pyridiloxy substituted aluminium, silicon and titanium phthalocyanines in water

This work reports on the synthesis, characterisation and photophysical properties of new unquaternized β-2,(3)-tetra-(2 pyridiloxy) aluminium(III) (3a), silicon(IV) (3b), titanium(IV) (3c) phthalocyanines and their water-soluble quaternized counterparts, 4a, 4b and 4c, respectively. The water-soluble silicon(IV) (4b) and titanium(IV) (4c) phthalocyanine derivatives were found to be aggregated in aqueous media but were partially or fully disaggregated in the presence of a surfactant Cremophor^® EL (CEL). The photophysical properties of aggregated complexes were investigated both in the presence of CEL and in pH 11 alone. Low triplet and fluorescence yield were obtained in pH 11 but an improvement was achieved upon addition of CEL for the aggregated complexes. The unquaternized silicon(IV) phthalocyanine complex (3b) gave the highest triplet quantum yield of 0.77 in DMF followed by its quaternized derivative (4b) with triplet yield of 0.73 in pH 11 plus CEL. The highest triplet lifetime of 220 μs was obtained for 4b in the presence of CEL. Higher fluorescence yields of 0.23 were obtained for quaternized water-soluble aluminium(III) phthalocyanine derivative (4a) in the presence of CEL.