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排序方式: 共有7049条查询结果,搜索用时 15 毫秒
1.
Steven S. Ross 《网络电信》2008,(8):13-13
Perhaps the most powerful claim that advocates of fiber can make,on top of the massive bandwidthfiber makes possible today, is that fiber is future-proof. That is, the fiber that is laid today can be upgraded so that the same strands of glass can carry massively more bandwidth in the future. 相似文献
2.
We demonstrate differences between reducibilities and corresponding completeness notions for nondeterministic time and space classes. For time classes the studied completeness notions under polynomial-time bounded (even logarithmic-space bounded) reducibilities turn out to be different for any class containingNE. For space classes the completeness notions under logspace reducibilities can be separated for any class properly containingLOGSPACE. Key observation in obtaining the separations is the honesty property of reductions, which was recently observed to hold for the time classes and can be shown to hold for space classes.The work of S. Homer was supported in part by National Science Foundation Grants MIP-8608137 and CCR-8814339 and a Fulbright-Hays Research Fellowship. Some of this research was done while he was a Guest Professor at the Mathematics Institute of Heidelberg University. 相似文献
3.
Amit Chourasia Steve Cutchin Yifeng Cui Reagan W Moore Kim Olsen Steven M Day J Bernard Minster Philip Maechling Thomas H Jordan 《Computer Graphics and Applications, IEEE》2007,27(5):28-34
This study focuses on the visualization of a series of large earthquake simulations collectively called TeraShake. The simulation series aims to assess the impact of San Andreas Fault earthquake scenarios in Southern California. We discuss the role of visualization in gaining scientific insight and aiding unexpected discoveries. 相似文献
4.
5.
Bellovin Steven M. Benzel Terry V. Blakley Bob Denning Dorothy E. Diffie Whitfield Epstein Jeremy Verissimo Paulo 《Security & Privacy, IEEE》2008,6(1):16-23
A virtual roundtable (featuring panelists Steven Bellovin, Terry Benzel, Bob Blakely, Dorothy Denning, Whitfield Diffie, Jeremy Epstein, and Paulo Verissimo) discussing the next 15 years in computer security. 相似文献
6.
Steven Spier 《The Journal of Architecture》1998,3(2):135-146
William Forsythe's research into ways of engendering and organising movement has led him to pursue counterpoint, proprioperception, entrainment, and authenticity for organisational principles that also allow improvisation. Artistic director and choreographer of the Ballett Frankfurt, and himself trained in ballet, Forsythe shows an appreciation of and often a critical engagement with classical dance, transforming and revitalising it. When he works collaboratively, Forsythe challenges the traditional distinction between choreographer and dancer, thus questioning hierarchy, authorship, and disciplinary boundaries. 相似文献
7.
8.
Toward a comprehensive assessment of fundamental motivation: Factor structure of the Reiss Profiles.
Two instruments were developed to provide a comprehensive assessment of the strength of a person's fundamental end goals and motivational sensitivities. One instrument was a self-report inventory for adolescents and adults in general, and the other was an informant-rating scale for adolescents and adults with mental retardation and development disabilities. Exploratory and confirmatory factor analyses and test-retest reliabilities are reported in 7 studies, with independent samples of participants from diverse geographical areas, occupations, and social groups, N?=?2,548. Each instrument was found to have a 15-factor solution, and the 2 solutions were similar to one another. Because the factors assess universal motives that are also seen in animals, a genetics-behavior-cognitive model of fundamental motivation is suggested. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
A model for the compressive buckling of extended chain polymers 总被引:1,自引:0,他引:1
Steven J. DeTeresa Roger S. Porter Richard J. Farris 《Journal of Materials Science》1985,20(5):1645-1659
A model for the compressive buckling of an extended polymer chain is presented. The application of classical elastic instability analysis to an idealized polymer chain reveals that the bending rigidity and critical buckling loads for a chain are proportional to the force constants for valence bond angle bending and torsion. Highly oriented polymer fibres are treated as a collection of elastic chains that interact laterally. The critical stresses to buckle this collection of chains are calculated following a procedure developed to predict the compressive strengths of fibre-reinforced composites. This buckling stress is predicted to be equal to the shear modulus of the fibres and is the limiting value of compressive strength. Comparison of experimental and predicted values shows that the theory overestimates the compressive strength, but that there is a correlation of shear modulus with axial compressive strength. Consideration of flaws in both the theory and the material indicate that the compressive strength should be proportional to either the shear modulus or shear strength of the fibres.Nomenclature
P
axial compressive load (force)
-
P
cr
critical buckling load (force)
-
M,M
i
bending moments
-
l
length of a link
-
p
number of links
-
k
elastic hinge constant
-
,
i
angular rotation of hinges
-
L
overall chain or column length
-
v,v
i
lateral deflection of buckled chain or column
-
x, y, z
Cartesian coordinate axes
-
E
Young's modulus of isotropic column
-
I
moment of inertia
-
a
ij
matrix coefficients
-
A
p
coefficient for exact buckling loads of chains
- T
energy change due to work of external load on buckled column or chain
- U
1
bending strain energy change of buckled column or chain
- U
2, U
2
e
, U
2
s
strain energy changes in elastic foundation, where e refers to extension mode buckling and s refers to shear mode buckling
-
E
t
transverse modulus
-
G
longitudinal shear modulus
-
b
dimension associated with chain packing
-
A
cross-sectional area per chain (=b
2)
-
f(x)
curve fitted to shape of buckled chain
-
m,n,r
integers
-
a
n
coefficients of trigonometric series
-
y
normal strain iny-direction
-
y
normal stress iny-direction
-
xy
shear strain inxy plane
-
xy
shear stress inxy plane
-
u
x
displacement inx-direction
-
u
y
displacement iny-direction
-
V
volume 相似文献
10.
Reed M. Izatt Steven R. Izatt Don W. Mcbride Jr. Jerald S. Bradshaw James J. Christensen 《Israel journal of chemistry》1985,25(1):27-32
Macrocycle-mediated fluxes of Cd(NO3)2 and of several binary mixtures of Cd(NO3)2 with the nitrate salt of either Na+, K+, Rb+ Cs+, Ag+, Ca2+, Sr2+, Pb2+, Zn2+, or Cu2+ have been determined in a H2O-CHCl3–H2O liquid membrane system. Of the macrocycles studied, 2.2 and 2.2DD most successfully transported Cd2+ In the Cd2+–Mn+ mixtures, Cd2+ was transported selectively with 2.2 when Mn+ was either an alkali or an alkaline earth cation. However, when Mn+ was either Ag+, Pb2+, or Cu2+ the Cd2+ flux was reduced sharply. Generally, cation flux was greater for 2.2DD than for 2.2 with selectivity for Cd2+ being altered also in several cases. Relative fluxes from binary cation mixtures depend on metal cation radius, macrocycle cavity diameter, ligand ring substituent and log K for metal ion-macrocycle interaction. 相似文献