卫星通信之父克拉克先生90年的人生

亚瑟·C·克拉克（Arthur C·Clarke）是将科学专业和诗意想象有机结合的作家，也是太空时代的导师。克拉克于2008年3月19日上午在斯里兰卡的科伦坡溘然去世，享年90岁，他从1956年开始就一直居住在科伦坡。     

Heat-treated chromium doped rutile used in an L-band travelling-wave maser

The net. gain of n travelling-wave maser operating at 4-2°K in the frequency range 1680-1050 MHK haa been improved by heat treatment of the active material, chromium-doped rutile (Cr-TiO₂). The heat treatments investigated, diffusion doping, quenching, and annealing were performed in a nearly hydrogen-free atmosphere of oxygen at 1200°C. The maximum net gain with a 3dB bandwidth of 6 MHz was 35 dB at 4·2°K and 1800 MHz. The length of the slow-wave structure was 55 mm. The net gain per unit length is the highest hitherto obtained.     

Plasma-assisted molecular beam epitaxy of ZnO on in-situ grown GaN/4H-SiC buffer layers

Plasma-assisted molecular beam epitaxy (MBE) was used to grow ZnO(0001) layers on GaN(0001)/4H-SiC buffer layers deposited in the same growth chamber equipped with both N- and O-plasma sources. The GaN buffer layers were grown immediately before initiating the growth of ZnO. Using a substrate temperature of 440°C–445°C and an O₂ flow rate of 2.0–2.5 sccm, we obtained ZnO layers with smooth surfaces having a root-mean-square roughness of 0.3 nm and a peak-to-valley distance of 3 nm shown by AFM. The FWHM for X-ray rocking curves recorded across the ZnO(0002) and ZnO(101ˉ5) reflections were 200 and 950 arcsec, respectively. These values showed that the mosaicity (tilt and twist) of the ZnO film was comparable to corresponding values of the underlying GaN buffer. It was found that a substrate temperature >450°C and a high Zn-flux always resulted in a rough ZnO surface morphology. Reciprocal space maps showed that the in-plane relaxation of the GaN and ZnO layers was 82.3% and 73.0%, respectively and the relaxation occurred abruptly during the growth. Room-temperature Hall-effect measurements showed that the layers were intrinsically n-type with an electron concentration of 10¹⁹ cm^–3 and a Hall mobility of 50 cm²·V^–1·s^–1.     

Rheological Studies of Water-Soluble (1–3),(1–4)-β-D-Glucans from Milling Fractions of Oat

We studied the rheological properties of water-soluble, mixed-linkage β-glucans of high purity (88–99.5%) isolated from oats. Comparing the β-glucan fractions at the same concentration (1.3 mg/g) the mean value of the bran fraction viscosities was larger (by 5X) than the mean viscosity of endosperm fractions. Both mean values had a relative standard deviation of ～20%. Heat treatment of oats did not alter the viscous properties of the extracted β-glucans. Activation energies for the bran fraction at two shear rates were E_r=5.81= 42 kJ/mole and E_r=581= 17 kJ/mole. The variation in G′and G′ with frequency for the β-glucan from bran fractions could be qualitatively described by a superposition of two single Maxwell models with widely different relaxation time. These data can help predict potential processing effects on such fractions incorporated as food components.     

High-temperature fatigue crack growth in Inconel 718 subjected to high strain amplitudes

Fatigue crack growth experiments in Inconel 718 subjected to high strain amplitudes at 650 °C have been conducted. In the study the effects of load amplitude, ratio and frequency have been investigated. It was found that crack growth is a mixture of cyclic and time dependent mechanisms, depending on the load frequency. The load frequency was also found to have a strong influence on the crack growth rate. Also, crack closure was found to play an important role. By using an effective J‐integral and including a frequency compensation term it was possible to summarize crack growth data into an empirical life prediction law, which seems to be in reasonable agreement with data from other studies.     

设计研究及其对于学科方法论发展的意义

1题目及假设 我将使用编辑所建议的题目来对设计研究与学科方法论发展之间的关系进行探讨。这两个概念都未能得到充分的澄清。＂设计研究……是系统性的探究,其目标在于认知或者具体化那些人造事物或系统中的构型、构成、结构、意图、