纺丝及纤维成形的机理(Ⅵ)

本文依据前报阐述的数学模拟法的基础方程式和解析方法,系统地讨论了在不同泵供量和纺丝速度的情况下,沿纺丝线的丝条温度和固化点的变化,以及沿纺丝线聚合物的纵向运动速度梯度、纤维的细化过程、纺丝张力和纺丝应力的分布,并对与以上有关的主要参数进行了列表归纳。     

Spatial ordering of self-organized InGaAs/AlGaAs quantum disks on GaAs (311)B substrates

We report the control of self-organization of In_xGa_1−xAs/AlGaAs quantum disks on GaAs (311)B surfaces using a novel technique based upon lithography-defined SiN dot arrays. A strained InGaAs island array selectively grown using the SiN dots provides periodic strain field. When the pitch of lateral ordering corresponds with the period of the strain field, self-organized quantum disks stacked on the InGaAs islands are precisely arranged just as the buried SiN dot array. The spacing of the array element is 250–300 nm (x = 0.3) and around 150 nm (x = 0.4). Vertical alignment by strain is achieved at a very thick (95 nm) separating layer. Characterization using atomic force microscopy reveals the size-fluctuation of disk is dramatically improved with spatial ordering.     

Evaluation of hydrogen-assisted cracking behavior of low-alloy steel in the range 95 °C to 350 °C

In this report, hydrogen-assisted cracking (HAC) behavior of low-alloy steel was evaluated using a constant elongation rate tensile test, and the temperature and crack tip strain rate effects were observed. It was found that temperature dependence of the threshold condition (C _σm ^c ) of HAC above about 100 °C followed the relation C _σm ^c = Kexp(−41,300/Rr) whereK is a constant andT is absolute temperature. The relationship between HAC growth rate and crack tip strain rate was established as almost linear, irrespective of temperature and hydrogen concentration at the crack tip. Hydrogen heat release tests were also performed. From these tests, formation and growth of microcracks which are trap sites of hydrogen were thought to be the mechanism of HAC in the steel. From this mechanism, HAC behavior of the low-alloy steel could be qualitatively explained.     

Improvement of diamond X-ray mask membrane: Optical transmittance, surface roughness and irradiation durability

A viable method for the improvement of the polycrystalline diamond X-ray mask membrane is proposed. The use of an ionized cluster beam yields the smoothest surface. Sol-gel planarization film coating with indium tin oxide is the most effective method for obtaining high optical transmittance without sacrificing high synchrotron irradiation durability.     

Electron Spin Resonance of High-Spin Co2+ in Alkali Borate and Alkali Germanate Glasses

Electron spin resonance spectra of high-spin Co²⁺ doped in alkali borate and alkali germanate glasses have been measured at 4.2 K. For comparison, the corresponding spectrum in a 33K₂O·67SiO₂ glass has also been measured. On the basis of the spectral line shape, the observed spectra, together with those in the literature, seem to be classified into four spectral types that represent Co²⁺ ions in octahedral coordination, a mixture of some types of coordination, tetrahedral coordination with nearly axial symmetry, and distorted tetrahedral coordination.     

纺丝及纤维成形的机理(V)

本文以等规聚丙烯为例,继上期学报对熔体纺丝过程的讨论之后,对熔体纺丝纤维的拉伸加工过程中,纤维结构和性能的变化进行了深入的阐述和分析,并根据纺丝的基础方程式介绍了数学模拟的方法。     

1.6 Gbit/s optical receiver at 1.3 ?m with SAW timing retrieval circuit

The performance of a 1.6 Gbit/s optical receiver employing a s.a.w. filter as a timing tank is reported. The error-rate characteristics in a p.c.m. transmission system using a 1.3 ?m In-GaAsP laser and single-mode fibres were studied. The average received optical power at a 10?9 error rate was ?28 dBm. In a 15 km transmission experiment, the receiving level was degraded by 2 dB owing to fibre dispersion. Timing phase margin of 75 degrees after 12 km transmission was confined with the self-timed receiver.     

Magnetic properties of CeC2 and its solid solutions,CeXDy1−XC2

Magnetic properties of CeC₂ and its solid solutions, Ce_XDy_1?XC₂, were investigated. Cerium dicarbide has the highest Neel temperature, 30 K, of the cerium compounds with non-magnetic elements and a positive paramagnetic Curie temperature, +12 K. This Nèel temperature is greatly higher than that expected on the basis of the de Gennes factor. In order to explain this high Nèel temperature we propose an idea that a super exchange interaction via acetylide ion, C₂^2?, contributes much to the total magnetic exchange for CeC₂. The positive paramagnetic Curie temperature observed for CeC₂ are also discussed in terms of the crystal field effects. The Nèel temperature (T_N) for Ce_XDy_1?XC₂ has a minimum on the T_N vs. the de Gennes factor curve, while the paramagnetic Curie temperature (θ_p) varies almost linearly with the de Gennes factor. These behaviors of T_N and θ_p are understood based on a difference in the magnetic exchange between CeC₂ and DyC₂.     

Determination of the cooperativity parameter σ from viscometric data of poly-L-glutamic acid-Na

Summary Viscometry of PLGNa solutions was performed for various degrees of neutralization . The cooperativity parameter in the helix-coil transition was estimated using Ptitsyn's method with some modifications. The increase of thus obtained with decreasing is explained in terms of the a dependence of short-range interactions of PLGNa segments.     

Electrical properties of sintered EuZrO3  EuNbO3 and EuNbO3

Electrical resistivity of two-phase products [yEuZrO₃ + (1 ? y) EuNbO₃] increased continuously with y, and a transition from a metallic to semiconducting characteristic occured at y = 0.14. The resistivity varied almost linearly with temperaure in the range y = 0 to y = 0.24, and thermal coefficients of resistivity at 300 K for the products decreased from +5.9 × 10^?4 K^?1 to ?7.4 × 10^?4 K^?1 according to the value of y. At y = 0.14, the thermal coefficient was almost zero. Thermal coefficients of electrical resistivity for the niobates with various oxygen contents were all positive in the range $\text{2.55 <}\text{O}\text{Nb}\text{< 3.24}$ and exhibited a sharp minimum at $\text{O}\text{Nb}\text{= 2.92}$. In all these niobates, Eu_xNbO₃ was a major phase and Eu₃NbO₆ or EuNbO₂ was detected as a second phase in the range $\text{O}\text{Nb}\text{> 3}$ or $\text{O}\text{Nb}\text{< 3}$ respectively. Peaks in the resistivity curves were correlated with a magnetic ordering temperature for samples with an overall ratio $\text{O}\text{Nb}\text{> 3}$.