Design and performance of a compact superconducting duplexer at VHF-band

This paper presents the design, fabrication, and performance of a compact high temperature superconducting duplexer at VHF-band. The duplexer consists of a T-junction and two four-pole filters with an ultra-narrow bandwidth of 400 kHz at 216 MHz and 220 MHz, respectively. By using gap-coupled feedlines in the filter design procedure, the duplexer is constructed by connecting the two filters using a T-junction with short-length branches. The two filters are fabricated on separate substrates and are carefully packaged to achieve a high isolation between the duplexer channels. The duplexer has a compact size of 41.6 mm × 28 mm. The measured results at 73 K show a high performance. The return loss is −17 dB, the insertion losses of both channels are less than 0.16 dB, and the out-of-band rejections are higher than 60 dB. The isolation between the two channels is better than 76 dB.     

冷端温度对无极灯253.7nm共振谱线的影响

无极灯是一种长寿命、低汞害、无频闪的新型电光源,其光效在很大程度上取决于253.7nm共振谱线的辐射效率。通过原子发射光谱分析,实验研究了冷端温度对253.7nm共振谱线的影响规律。研究发现,253.7nm共振谱线的辐射效率随冷端温度变化近似呈正态分布,即无极灯工作存在一个最佳冷端温度。运用气体放电理论对实验结果进行了定性分析,对无极灯光效的提高具有指导意义。     

浙江省综合自然区划新方案

综合自然区划是一项综合性很强的科学研究。1980年以来,我们同时进行了两项科研工作,一是浙江省土地类型研究,二是浙江省综合自然区划。到1981年取得初步成果,一是编制了“浙江省1∶50万土地类型图”,二是写出《浙江省的土地类型及其1∶50万土地类型图的编制》一文,三是编写了《浙江省简明综合自然区划》。此后,我们继续上述研究工作,并着重将浙江省自然区划与浙江省土地类型研究结合起来,互相促进和补充,逐步深入。本文讨论的浙江省综合自然区划新方案,就是依据浙江省土地类型拟订的。     

Mathematical Modeling of Multicomponent Nonisothermal Adsorption in Sorbent Particles Under Pressure Swing Conditions

A detailed model for nonisothermal sorption of multicomponent mixtures in a single sorbent particle (monodisperse or bidisperse with negligible intracrystalline mass transport limitations) under pressure swing conditions is developed in this study. The dusty-gas model is used to describe the coupling of the molar fluxes, the temperature, the partial pressures and the partial pressure gradients of the components in the pore space of the particle. The variations of the temperature are described by an energy equation in which both convective and conductive modes of heat transport are accounted for. No limitations are imposed on the number of the components in the mixture and on the type of the adsorption isotherm. The model is applied in the investigation of the industrially important air-zeolite 5A system. Two cases with respect to the surrounding gas phase are examined: infinite environment, which is representative for single particle experiments, and finite environment, which is representative for the situation in packed bed adsorbers. It is found that in an infinite environment the external and internal temperature gradients are equally important while in a finite environment the external heat transport limitations are negligible. It is concluded that in modeling the nonisothermal operation of adsorption processes occurring in packed beds it is not necessary to allow for the temperature differences between the gas phase and the surface of the adsorbing particles. Furthermore, if the temperature gradients within the particles can be neglected, only a single temperature equation is needed to describe the energy transport in the bed.     

Demixing in polystyrene/methylcyclohexane solutions

Cloudpoint data for polystyrene/methylcyclohexane solutions extending over moderate ranges of pressure and molecular weight are available in the literature. Those data are supplemented with new results from this laboratory to fill in gaps and extend the MW range (to 761 ≤ MW/amu ≤ 2 × 10⁷). The resulting data net is discussed and reasons to extend studies to higher pressure are presented. © 1996 John Wiley & Sons, Inc.     

Preparation and characterization of poly(m-xylylene oxamide) and its copolymer

New polyoxamides, poly(m-xylylene oxamide) (PMXD2) and its copolymer with 2-methyl-1,5- pentanediamine (P(MXD2/M52)) with relative viscosity up to 4.6 were synthesized via spray/solid state polymerization. The obtained polyoxamides were characterized by FTIR, NMR, WAXD, DSC and TGA. The T_m of the copolymers decreased with increasing percentage of poly(2-methyl-1,5- pentaneoxamide) (PM52) in the copolymer from 346°C for 100% poly(meta-xylyleneoxamide) (PMXD2) to 277°C for copolymers of PMXD/PM52 (60/40). TGA analysis revealed that the thermal stability of the copolymers compared well with commercial PA6 and XRD studies suggested the copolymers possessed high crystallinity. DMA profile of the PMXD/PM52 (70/30) copolymer showed better mechanical performance with a storage modulus of about 7.2 GPa as compared to 1.8 GPa of PA6 at 25°C.     

New Prospective Ni-catalytic Materials

IR spectroscopy was applied to investigate the non-isothermal redox processes in Ni/NiO-gas phase system involving the elimination of CO₂. At the Curie temperature (T _c=633 K for Ni), a change in the mechanism of CO catalytic oxidation on NiO was observed. It was established by means of temperature-programmed desorption with mass-spectroscopic registration that fluctuations in the oxygen density on the NiO surface are generated at this temperature. Under the given chemical reaction conditions, these fluctuations bring about the formation of Ni microheterogeneity on the NiO surface. X-ray diffraction, electronic and magnetometric measurements were employed to determine the dimensions of the Ni particles. It was shown that an increase in the Ni dispersity in Ni/NiO may be responsible for an increased number of active surface sites. This was verified for the NiO/thermo-exfoliated graphite system. This revised version was published online in August 2006 with corrections to the Cover Date.     

Crystallization Behavior of Sol-Gel Derived Films by Self-Seeding Process

We propose the novel preparation method, Self-seeding Process, based on the following concept for low temperature crystallization of oxide films. Introduction of desirable inhomogeneity should give lowering of a crystallization temperature through heterogeneous nucleation accompanied with reduced activation energy. We carried out inspection of the above concept through use of PZT films. PZT gel films with the desirable inhomogeneity of microstructure were prepared, and their crystallization behaviors was examined. The PZT film was successfully crystallized at 500°C by the self-seeding process. The single phase (001) oriented PZT film with 0.55 m in thickness was obtained at 550°C for 5 min. The self-seeding process by microstructure control is efficient for the low temperature process of the oxide thin film.     

Melt Behaviour of Poly(p-xylylene) (PPX) Coated Gel-spun UHMW-PE Fibers As Revealed by Temperature Modulated DSC

The method of temperature modulated DSC has been applied to obtain additional information about the effect of constraints on the melting behaviour of gel-spun ultra high molecular mass polyethylene (UHMW-PE) fibers coated with a high temperature stable poly(p-xylylene) (PPX) polymer. The underlying signal, corresponding to the normal DSC signal, reveals two endothermic peaks for the coated PE fibers. A shift in the underlying and magnitude signal from 142 to 145°C at 0.1 K min^–1 , a relative small magnitude signal, together with a vanishing step-like change in the phase signal with increasing PPX coating layer thickness characterize the constraints in terms of a hindrance of the melting of the unconstrained orthorhombic crystal fraction. The time constant of the melting process can be estimated as larger than the reciprocal angular frequency 1/ω=5 s of the modulation. This revised version was published online in July 2006 with corrections to the Cover Date.     

片状催化剂F-T合成宏观动力学

采用固定床积分反应器,在工业条件下,对压片Ｆｅ－Ｃｕ－Ｋ催化剂进行了Ｆ－Ｔ合成宏观动力学考查。在稳态下,用集总的方法,在保持一定的轴向温度分布及取其平均温度条件下,求得两组宏观动力学方程,两者分别与实验数据吻合较好,同时两者之间也存在较好的一致性。