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91.
'Software defined radio' (SDR) is a technology that will appear in future generations of mobile phones, i.e. following the third-generation mobile phone technology that is currently being defined and developed. Early versions of 'pragmatic' SDR will allow the terminal to be reconfigured at any level of its protocol stack. Ultimately, the 'pure' SDR technology will allow a mobile phone or terminal to have its air interface software configured or reconfigured by other software (or software parameters) that have been downloaded to the terminal, e.g. over the air, or from a remote server via the Internet and one's personal computer (PC). A number of security issues arise with downloaded code that implements the air interface functions, and these may not be obvious simply from looking at the way PC software is updated on-line today. This paper starts with an outline of the code that allows a mobile phone to operate over a particular air interface. This sets the baseline for a discussion of the security issues surrounding the change of this code from one that is fixed and downloaded once only, to code that is reconfigurable during the life of a product. 相似文献
92.
93.
T Kita 《Canadian Metallurgical Quarterly》1989,40(16):10816-10830
94.
95.
I. N. Polandov V. K. Novik O. K. Gulish B. P. Bogomolov V. B. Morozov 《Measurement Techniques》1989,32(9):888-890
Translated from Izmeritel'naya Tekhnika, No. 9, pp. 34–35, September, 1989. 相似文献
96.
97.
In this paper, the space-vector transformation used in machine vector control is applied to power system analysis. The proposed method is used to model electric machines, power electronic converters, transformers, and transmission lines and to analyze power sources and loads with different connections (delta and wye). This method can also be applied to analyze steady-state (or transient phenomena) and unbalanced sources, including harmonics. Models obtained with this method are as simple as those of the per-phase approach. With the space-vector transformation, instantaneous active and reactive power concepts can be generalized, and new power system control strategies can be developed when power electronic converters are used. Steady-state, transient behavior, and harmonic analyses examples and applications are presented to illustrate the performance and advantages of the proposed method. This method can be extended to unbalanced systems (e.g., unsymmetric faults) using instantaneous symmetrical components in polyphase balanced circuits. 相似文献
98.
99.
R. Sankarasubramanian C. S. Jog T. A. Abinandanan 《Metallurgical and Materials Transactions A》2002,33(4):1083-1090
We examine the symmetry-breaking transitions in equilibrium shapes of coherent precipitates in two-dimensional (2-D) systems
under a plane-strain condition with the principal misfit strain components ε*
xx
and ε*
yy
. For systems with cubic elastic moduli, we first show all the shape transitions associated with different values of t=ε*
yy
/ε*
xx
. We also characterize each of these transitions, by studying its dependence on elastic anisotropy and inhomogeneity. For
systems with dilatational misfit (t=1) and those with pure shear misfit (t=−1), the transition is from an equiaxed shape to an elongated shape, resulting in a break in rotational symmetry. For systems
with nondilatational misfit (−1<t<1; t ≠ 0), the transition involves a break in mirror symmetries normal to the x- and y-axes. The transition is continuous in all cases, except when 0<t<1. For systems which allow an invariant line (−1≤t<0), the critical size increases with an increase in the particle stiffness. However, for systems which do not allow an invariant
line (0<t≤1), the critical size first decreases, reaches a minimum, and then starts increasing with increasing particle stiffness;
moreover, the transition is also forbidden when the particle stiffness is greater than a critical value. 相似文献
100.
Serum total cholesterol, high density lipoprotein (HDL) cholesterol, and triglyceride levels were studied in healthy male
and female subjects consuming for one-week periods a diet of conventional food (CF) providing 42% of energy as fat, principally
butter fat, and then in random order nutritionally complete, defined formula diets of moderate (32%) to very low (1%) fat
content. Compared to CF, the formula with 32% of energy as corn oil lowered serum cholesterol by 25% and the ratio of total
to HDL-cholesterol by 13%. Low (9%) and very low (1–3%) fat formulas reduced HDL-cholesterol by as much as 40%, raised the
total: HDL-cholesterol ratio by about 20% and raised serum triglyceride levels by as much as 100%. When low and very low fat
formulas were ingested for three weeks, these effects persisted although maximal responses occurred during the first week.
These results demonstrated that a moderate fat formula diet with a high P/S ratio had a more favorable effect on serum lipid
levels than various low fat formulas. Low fat conventional food diets should be studied in long-term controlled metabolic
experiments before such diets are recommended to the general population for coronary heart disease or cancer prevention. 相似文献