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901.
In this paper, the effects of hardening exponent, yield strength and elastic modulus on the deformability of near hemispherical
shells are investigated by means of finite element method and orthogonal experiment design. The largest eccentric angle during
the deformation process and thickness reduction after the deformation are introduced to estimate the deformability quantitatively
according to the deformation characteristics of near hemispherical shells. The results indicate that the hardening exponent
is the most influential parameter, followed by elastic modulus and yield strength. The shell exhibits good deformability when
the hardening exponent and elastic modulus are in the range of 0.1–0.125 and 70–108 GPa, respectively. 相似文献
902.
In this paper, we consider a floating raft isolation system with elastic limiters. The limiters might be “contact” or “no
contact”, thus forming a unilateral system generating possible contacts. In order to avoid the large displacement of the floating
raft under shock, limiters might be adopted but good limiters design requires the values of the gaps. Based on the contact
dynamics, the multi-degree-freedom dynamic model of floating raft isolation system with elastic limiters is established. The
artificial neural network has been developed to dingtinguish the contact state of elastic limiters at each step. The example
analysis shows that the algorithm of neural network for contact can shorten the time of caclaution. From the example analysis,
we get some interesting results that may be useful to the ship engineering. 相似文献
903.
A biomechanical musculo-skeletal model of upper limb is presented in this paper, which can provide accurate representations
of muscles and joints, and capture important interactions between joints. The upper limb model is made up of seven segments:
ribs, sternum, clavicle, scapular, humerus, radius and ulna, considered as a single rigid body respectively and includes 22
muscles. The individual muscle forces can be calculated by using an electromyography (EMG) assisted method, which is verified
by comparing the simulation results with other researches of an elbow flexion motion. These comparisons show that the muscle
forces and the estimated joint moment match well with previous literatures. 相似文献
904.
The feasibility of electromagnetically stimulated thermography non-destructive testing (NDT) for the detection of defects
in metallic conductive materials has been carried out by finite element analysis. Aluminum plates with defects of different
diameters, depths, locations, shapes and orientation with respect to eddy current are numerically investigated. ANSYS software
is used to solve the coupled electromagnetic and temperature field equations. The peak temperatures on the top surface of
circular defects with different diameters and depths are calculated at varying excitation frequencies. It is demonstrated
that the obtained temperature inreases with increase of the defect diameter and decrease of its depth. The dependence of the
temperature over the top surface of the defect on its location and orientation is also presented. The results indicate that
we can detect the subsurface defect and estimate its depth and location by choosing a suitable coil-specimen configuration. 相似文献
905.
Solar energy is considered as one of the best alternative energy in the future. Multicrystalline silicon ingot casting is
the main production process for major supply of solar cell. However, the casting process cannot be understood clearly because
of some difficulties, such as enclosed furnace, long cycle time of production and so on. In this paper, an integrated model,
including casting process analysis, quality prediction and production parameters optimization, is proposed and the preliminary
results are acquired. The framework of the proposed model is introduced and the numerical simulation results on the temperature
field and grain growth process are also given out and discussed. 相似文献
906.
Secret sharing schemes are multi-party protocols related to key establishment. They also facilitate distributed trust or shared
control for critical activities (e.g., signing corporate cheques and opening bank vaults), by gating the critical action on
cooperation from t(t ∈ Z
+) of n(n ∈ Z
+) users. A (t, n) threshold scheme (t < n) is a method by which a trusted party computes secret shares Γ
i
(1 ⩽ i ⩽ n) from an initial secret Γ
0 and securely distributes Γ
i
to user. Any t or more users who pool their shares may easily recover Γ
0, but any group knowing only t−1 or fewer shares may not. By the ElGamal public key cryptophytes and the Schnorr’s signature scheme, this paper proposes
a new (t, n) threshold signature scheme with (k,m) (k,m ∈ Z
+) threshold verification based on the multivariate linear polynomial. 相似文献
907.
In an identity based proxy signature (IBPS) scheme, a designated proxy signer can generate the signature on behalf of an original
signer. Traditional IBPS schemes normally rely on the assumption that private keys are kept perfectly secure. However, due
to viruses, worms or other break-ins allowed by operating-system holes, key exposure seems inevitable. To minimize the damage
caused by key exposure in IBPS, we propose an identity-based key-insulated proxy signature (IBKIPS) scheme in the standard
model, i.e. without random oracles. 相似文献
908.
Giles Thomas Stefan Winkler Michael Davis Damien Holloway Shinsuke Matsubara Jason Lavroff Ben French 《Journal of Marine Science and Technology》2011,16(1):8-21
Slam events experienced by high-speed catamarans in irregular waves were characterised through experiments using a hydroelastic
segmented model. The model was designed to represent the dynamic behaviour of the full-scale Incat 112 m vessel and to allow
the measurement of the slam load on the centrebow and wet deck. It was tested in irregular head seas at two speeds relating
to Froude numbers of 0.32 and 0.60. Nearly 300 slams were identified in the test data and analysed with respect to kinematic
parameters. Slams were found to have a large range of magnitudes, with the largest equivalent to 1785 tonnes full scale (approximately
70% of vessel displacement); however, the majority of events were of relatively low severity. Differences in slam characteristics
were found for the two model speeds tested; slams at the slower speed generally occurred further forward on the hull, prior
to the wave crest and with a bow down pitch angle. Immersion of the centrebow to the two-dimensional filling height of the
cross-section between the centrebow and demihulls is shown to be a better indicator of slam occurrence than immersion to the
top of the archway. 相似文献
909.
Sloshing waves in moving tanks is an important engineering problem, and most studies of this phenomenon have focused on tanks
that are excited by forcing motion in a limited number of directions and with fixed excitation frequencies throughout the
forcing. In practice, the excitation comprises multiple degree of freedom motion that potentially couples surge, sway, heave,
pitch, roll, and yaw motions. In the present study, a time-independent finite difference method is used to simulate fluid
sloshing in three-dimensional tanks filled to an arbitrary depth for various excitation frequencies and multiple degree of
freedom motion. The numerical scheme developed here was verified by rigorous benchmark tests. The coupled motions of surge
and sway are simulated for various excitation angles, frequencies and water depths. Five kinds of sloshing waves found under
coupled surge–sway motions: diagonal, single-directional, square-like, swirling, and irregular waves. The effect of excitation
angle on the frequency responses of different sloshing waves is analyzed and discussed in the present study. Further, the
components of horizontal force of various sloshing waves are also presented. The coupled effect of surge, sway and heave motions
is also discussed, and the results show that unstable sloshing occurs when the excitation frequency of the heave motion is
twice the fundamental natural frequency. Moreover, the effects of heave motion on the different types of sloshing waves are
explored. It is found that heave motion causes all of the sloshing waves to change type. 相似文献
910.
The dynamic response of planing vessels in regular head seas is investigated numerically. Nonlinear time domain simulations
were performed using a 2D + t theory (two-dimensional plus time dependent theory). A prismatic hull form was assumed. We employed a two-dimensional (2D)
boundary element method to solve the initial boundary value problems in 2D cross planes, in which nonlinear free-surface conditions
and exact body boundary conditions were satisfied. At each time step, the total force and moment on the hull could be obtained
by using the sectional forces calculated in those 2D planes. Heave and pitch motions were then acquired by solving the equations
for those motions. The calculated heave and pitch responses were compared with the experiments by Fridsma (A systematic study
of the rough-water performance of planing boats. Davidson Laboratory Report R-1275, 1969) for two different Froude numbers. Three-dimensional (3D) corrections at the transom stern were applied to show the influence
of the 3D effect at the stern on the numerical results. Ship motions were affected by the 3D corrections, especially near
the resonance frequency, while the phase angles were slightly affected and the acceleration peaks at the bow near the resonance
frequency were sensitive to the 3D corrections. Other error sources in the theoretical results are also mentioned. 相似文献