An Iron-Free Magnetron-Injection-Gun for a 28GHz, 200kW Gyroklystron Amplifier

A design study of a double-anode magnetron-injection-gun is performed to incorporate the electron gun into a high power 28GHz gyroklystron amplifier operating at 70kV and 8.2A. The electron gun is designed to be used in a tapered magnetic field in the cathode region produced from an iron-free superconducting magnet. An electron trajectory code predicts a beam axial velocity spread of 5.9% at = 1.5, 70kV, 8.2A and 10.4kG, which is a high quality electron beam suitable for the high gain, high efficiency, five-cavity gyroklystron amplifier. The successful design of the high quality electron gun is attributed to a longer gap between the modulating anode and the grounded anode compared with the case of the first 28GHz electron gun built with an iron enclosed electromagnet.     

Wigner rotations and Iwasawa decompositions in polarization optics

Wigner rotations and Iwasawa decompositions are manifestations of the internal space-time symmetries of massive and massless particles, respectively. It is shown to be possible to produce combinations of optical filters which exhibit transformations corresponding to Wigner rotations and Iwasawa decompositions. This is possible because the combined effects of rotation, phase-shift, and attenuation filters lead to transformation matrices of the six-parameter Lorentz group applicable to Jones vectors and Stokes parameters for polarized light waves. The symmetry transformations in special relativity lead to a set of experiments which can be performed in optics laboratories.     

High‐quality poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐p‐phenylenevinylene] synthesized by a solid–liquid two‐phase reaction: Characterizations and electroluminescence properties

Poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐p‐phenylenevinylene] (MEH‐PPV) with a molar mass of 26–47 × 10⁴ g mol^?1 and a polydispersity of 2.5–3.2 was synthesized by a liquid–solid two‐phase reaction. The liquid phase was tetrahydrofuran (THF) containing 1,4‐bis(chloromethyl)‐2‐methoxy‐5‐(2′‐ethylhexyloxy)benzene as the monomer and a certain amount of tetrabutylammonium bromide as a phase‐transfer catalyst. The solid phase consisted of potassium hydroxide particles with diameters smaller than 0.5 mm. The reaction was carried out at a low temperature of 0 °C and under nitrogen protection. No gelation was observed during the polymerization process, and the polymer was soluble in the usual organic solvents, such as chloroform, toluene, THF, and xylene. A polymer light‐emitting diode was fabricated with MEH‐PPV as an active luminescent layer. The device had an indium tin oxide/poly(3,4‐ethylenedioxylthiophene) (PEDOT)/MEH‐PPV/Ba/Al configuration. It showed a turn‐on voltage of 3.3 V, a luminescence intensity at 6.1 V of 550 cd/m², a luminescence efficiency of 0.43 cd/A, and a quantum efficiency of 0.57%. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3049–3054, 2004     

Neutron Star Structure in a Nonlinear Realization of Chiral SU(3) Spontaneous Breaking Model

We investigate neutron star properties by constructing a chiral SU(3) spontaneous breaking Lagrangian and using relativistic mean-field approximation. The results show that π- condensate appears at some baryon densities,and hyperons ∑- and A exist in neutron star matter at high density. In this model, neutron star's maximum mass is1.12Ms with corresponding radius about 8 km.     

Compatibilizing effect of polyarylate-polystyrene block copolymer in polyarylate/polystyrene blends

The compatibilizing effect of polyarylate-polystyrene (PAR-PS) block copolymer prepared from macroazo initiator was examined in polyarylate/polystyrene blends from the view-points of morphology, density, and thermal, mechanical, and rheological properties. PARPS block copolymer enhanced the mutual dissolution of the homopolymers. Reduced dispersed-domain size and increased density showed the efficiency of the block copolymer as a compatibilizing agent. Results from mechanical and rheological properties could also be explained by the compatibilizing effect of PAR-PS block copolymer in the blends. © 1994 John Wiley & Sons, Inc.     

三阶非自治微分方程的不稳定性定理

本文运用构造李雅普诺夫函数的方法，给出了一类三阶非自治微分方程零解不稳定的充分条件．     

252Cf冷裂变瞬发γ射线

用四参量关联实验技术研究了²⁵²Cf冷裂变瞬发γ射线发射性质. 孪生屏栅电离室收集极和栅极信号分别用于确定碎片的动能和发射角. 圆柱形电离室轴线上的NaI(T1)晶体用于符合记录裂变瞬发γ射线.结果表明,不仅冷裂变瞬发γ射线角分布系数约为正常二分裂变值的两倍,而且冷裂变轻碎片发射的γ射线数目几乎是重碎片发射数目的三倍.对后一实验事实目前尚未有满意的理论解释.     

Stability of extensional flows and extending viscoelastic fluid sheets

The theory of nearly-extensional flow is developed to study the stability of extensional flow. For such flows a simple constitutive equation is derived for slightly disturbed extensional flow when a ‘short memory’ assumption is admissible.Following Minoshima and White and utilizing the constitutive equation obtained, a stability analysis for non-Newtonian fluid sheets is presented. The theoretical analysis presented is specific for an integral consitutive equation. The influence of the fluid elasticity on the stability behaviour is investigated. It is shown that the fluid sheet stability depends upon λk, where λ is the relaxation time and K is the elongation rate.     

高温超导体YBa2Cu3O7-δ中的元素替代效应

本文综合约20个 YBa₂Cu₃O_7-4的元素替代体系的实验结果,发现:正交晶体结构、氧含量、铜的氧化价态,以及金属-半导体(绝缘体)相变都只是决定Tc的表观因素;存在着CuO₂平面外和CuO₂平面内两类元素替代效应.提出:高温超导体的迁移载流子浓度和CuO₂平面内铜原子之间的动态、短程反铁磁关联程度是决定Tc的两个内禀因素.基于Bi系超导体中有关元素替代效应的实验事实,进一步提出上述结论对各种类型的高温氧化物超导体具有普遍性.