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991.
The paper covers a simple idea. If we sample an aperture, we can obtain valid patterns over a limited angular region about the normal to the aperture. The same expression can be used with near-field measurements. I reduced the expression to a nomograph. A nomograph allows one to rapidly test various choices. In the second half of the paper, I answer questions caused by the February column which discussed polarization (Milligan, IEEE Antennas. Propag. Mag., vol.38, no.1, p.56-8, 1996) 相似文献
992.
通过对相变增韧陶瓷及一种可切削玻璃-陶瓷动态疲劳(恒应力速率)试验中高应力速率区断裂应力下降现象的理论分析,发现这种现象与材料的阻力特性(R-curve)密切相关。确立的σ_f-σ理论关系能够很好地描述整个应力速率区间内的动态疲劳试验结果。高应力速率区σ_f-σ在双对数坐标下为负斜率直线,直线斜率为(m为阻力曲线KR=k(△a)~m的指数),断裂主要由材料阻力行为控制;低应力速率区,σ_f-σ在双对数坐标下为正斜率直线,直线斜率为 (n为应力腐蚀指数),断裂主要由材料应力腐蚀行为控制。建立了测定材料阻力特性的一种新方法,分别用这种方法及压痕/弯曲方法对一种可切削玻璃-陶瓷的阻力特性进行了实验测定,两种方法所得结果有很好的一致性。 相似文献
993.
The formation of mullite was investigated using microcomposite powders which consist of α-alumina cores and amorphous silica coatings. Differential thermal analysis and X-ray diffraction showed that the mullitization reaction was endothermic. In contrast, mullite forms exothermically in samples prepared by sol-gel processing. The results are shown to be consistent with available thermodynamic data for mullite formation from different alumina and silica phases. 相似文献
994.
995.
996.
The objective of this study is to determine the economic and operational impact on energy cost of incorporating large photovoltaic (PV) and wind energy conversion systems (WECS) into the electric utility generation mix. In most cases, PV and WECS power outputs are subtracted from the utility load with the expectation that conventional generation would meet the residual load. This approach is valid for small penetration levels and/or for PV and WECS facilities connected near load centers, However, several constraints such as thermal generation characteristics, fuel supply and delivery, spinning reserve requirements, and hydro availability are not adequately represented in this process. To determine the optimal value of large-scale PV and WECS applications, a new methodology that would take into account the aforementioned constraints as well as a more global penetration is developed. Results indicate that while high hydro availability increases PV penetration levels, high ramping rates can also significantly increase penetration levels 相似文献
997.
A process-inherent NAND2 device is presented for a three-dimensional CMOS integration with epitaxial lateral overgrowth and chemo-mechanical polishing. The required 'OR' function of the two PMOS transistors is achieved by one silicon volume, which is controlled by a back gate and a conventional front gate. Almost symmetrical characteristics are measured for the front and the back gates.<> 相似文献
998.
Kasukawa A. Namegaya T. Fukushima T. Iwai N. Kikuta T. 《Quantum Electronics, IEEE Journal of》1993,29(6):1528-1535
The authors have fabricated 1.3-μm InAsP-InP separate-confinement-heterostructure (SCH) strained-layer double-quantum-well (SL-DQW) laser diodes (LDs) by metalorganic chemical vapor deposition (MOCVD). A low threshold current density of 410 A/cm 2 was obtained. The CW threshold current was as low as 1.8 mA at 20°C, and maximum CW operating temperature of 120°C was obtained. These characteristics are almost the same as those of well-designed GaInAsP-InP SL-QW LDs. Further improvement of the characteristics of InAsP-InP LDs is expected by optimizing the device structure 相似文献
999.
This investigation focuses on the correlation between the crystallographic orientation of grains with respect to magnetic
properties in Co-Cr films. Based on a distribution measured for the (0002) crystallographic pole densities, modified formulae
describing the texture were used to calculate the coercivity Hc, the squareness ratio Rs (Mr⊥/TMs) and the anisotropy field
Ha for Co-Cr films. In general, calculated values for the coercive force He agreed well with the measured values. The calculated
Rs⊥. values were much larger than the measured ones, however, indicating that the influence of the demagnetizing field and
the magnetostriction on the orientation of the magnetization cannot be neglected.
On leave from Institute of Computing Technology, Academia Sinica, P.O.Box 2704-6, Beijing, P.R. China. 相似文献
1000.
An analytic expression of fmax is derived based on a practical HBT circuit model where collector junction capacitance is split up into internal and external parts. It shows that for advanced HBTs, fmax is well characterized by the product of the base resistance and internal collector capacitance. In other words, the external collector capacitance has only a small impact on the determination of fmax. Good agreement between experimental results and numerical circuit simulation confirms the validity of the HBT circuit model. The influence of the external collector capacitance on maximum available gain is also described 相似文献