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181.
It has been a focus of debate for a large time on construction methods for large-span loess tunnel. Reasonable construction
method has much effect on stability of tunnel and construction schedule. Deformation and failure of surrounding rock are quite
complex. Associating with the large-span loess tunnel of Zhengzhou—Xi’an high-speed passenger rail line in China, large scale
model test with geometric proportion 1:20 is applied to study on dynamic mechanical behavior of various construction methods.
They include full-face excavation with support and no support, and benching method with support. It is found that pre-deformation
and stress accumulation take place ahead of working face. The effects of three construction methods are further studied, particularly
in terms of tunnel displacement and stress changes. It is revealed that benching method transfers load to an unexcavated area,
limits horizontal deformation, reduces stress concentration effectively, lengthens the distance between location of peak for
stress concentration and working face, and consequently increases stability. The model test results not only supply theoretical
foundation for determination of reasonable construction method, but also can act as reference for similar tunnel and underground
engineering construction. 相似文献
182.
In the field of 3D model matching and retrieval, an effective method for feature extraction is spherical harmonic or its mutations,
and is acted on the spherical images. But the obtainment of spherical images from 3D models is very time-consuming, which
greatly restrains the responding speed of such systems. In this paper, we propose a quantitative evaluation of the whole process
and give a detailed two-sided analysis based on the comparative size between pixels and voxels. The experiments show that
the resultant optimized parameters are fit for the practical application and exhibit a satisfactory performance. 相似文献
183.
This paper presents a full-scale solution to the detection of the traffic data using laser device. Range images, gathered
by a particular laser camera, are used in the multi-threshold segmentation. The multi-threshold segmentation is based on the
height of the moving objects. In order to get the precise height of the moving objects, mapping of the original terrain is
performed on the first step. On each layer, the clustering algorithm called iteration-self organizing data analysis techniques
algorithm (ISODATA) is conducted afterwards. Kalman filtering technique is applied to recognize and track the moving objects.
Extensive experiments show that these algorithms are effective in object recognition and tracking, as well as robust in the
applications. 相似文献
184.
The purpose of remote sensing images fusion is to produce a fused image that contains more clear, accurate and comprehensive
information than any single image. A novel fusion method is proposed in this paper based on nonsubsampled contourlet transform
(NSCT) and region segmentation. Firstly, the multispectral image is transformed to intensity-hue-saturation (IHS) system.
Secondly, the panchromatic image and the component intensity of the multispectral image are decomposed by NSCT. Then the NSCT
coefficients of high and low frequency subbands are fused by different rules, respectively. For the high frequency subbands,
the fusion rules are also unalike in the smooth and edge regions. The two regions are segregated in the panchromatic image,
and the segmentation is based on particle swarm optimization. Finally, the fusion image can be obtained by performing inverse
NSCT and inverse IHS transform. The experimental results are evaluated by both subjective and objective criteria. It is shown
that the proposed method can obtain superior results to others. 相似文献
185.
To tackle the key-exposure problem in signature settings, this paper introduces a new cryptographic primitive named threshold
key-insulated signature (TKIS) and proposes a concrete TKIS scheme. For a TKIS system, at least k out of n helpers are needed to update a user’s temporary private key. On the one hand, even if up to k−1 helpers are compromised in addition to the exposure of any of temporary private keys, security of the non-exposed periods
is still assured. On the other hand, even if all the n helpers are compromised, we can still ensure the security of all periods as long as none of temporary private keys is exposed.
Compared with traditional key-insulated signature (KIS) schemes, the proposed TKIS scheme not only greatly enhances the security
of the system, but also provides flexibility and efficiency. 相似文献
186.
The development of an innovative H
∞ controller for looper and tension control in hot strip finishing mills is traced based on approximately linearized model.
This solution has been considered thanks to its well-known robustness and simplicity characteristics concerning disturbances’
attenuation. The controller is designed based on an optimal problem with linear matrix inequality (LMI) constraints, and the
problem is solved by the mincx function of Matlab LMI Toolbox. Simulation results show the effectiveness of the proposed controller
compared with conventional ones. 相似文献
187.
Numerical simulation of macrosegregation during steel ingot solidification using continuum model 总被引:1,自引:0,他引:1
A continuum model is adopted to study the macrosegregation phenomena during solidification of large steel ingots. Evolution
of temperature, melt velocity, and compositional concentration field during a 22 t steel ingot solidification are illustrated
by using the finite volume method. Numerical results of temperature distribution are validated by experiments. The influence
of local permeability relates to the friction that the melt experienced in mushy region is investigated. It is shown that
the continuum model is able to predict the temperature field, and the variation of permeability obviously affects the melt
flowing behavior and the final compositional distribution. 相似文献
188.
High performance computer is often required by model predictive control (MPC) systems due to the heavy online computation
burden. To extend MPC to more application cases with low-cost computation facilities, the implementation of MPC controller
on field programmable gate array (FPGA) system is studied. For the dynamic matrix control (DMC) algorithm, the main design
idea and the implemental strategy of DMC controller are introduced based on a FPGA’s embedded system. The performance tests
show that both the computation efficiency and the accuracy of the proposed controller can be satisfied due to the parallel
computing capability of FPGA. 相似文献
189.
Packet analysis is very important in our digital life. But what protocol analyzers can do is limited because they can only
process data in determined format. This paper puts forward a solution to decode raw data in an unknown format. It is certain
that data can be cut into packets because there are usually characteristic bit sequences in packet headers. The key to solve
the problem is how to find out those characteristic sequences. We present an efficient way of bit sequence enumeration. Both
Aho-Corasick (AC) algorithm and data mining method are used to reduce the cost of the process. 相似文献
190.
An efficient method is proposed for the design of finite impulse response (FIR) filter with arbitrary pass band edge, stop
band edge frequencies and transition width. The proposed FIR band stop filter is designed using craziness based particle swarm
optimization (CRPSO) approach. Given the filter specifications to be realized, the CRPSO algorithm generates a set of optimal
filter coefficients and tries to meet the ideal frequency response characteristics. In this paper, for the given problem,
the realizations of the optimal FIR band pass filters of different orders have been performed. The simulation results have
been compared with those obtained by the well accepted evolutionary algorithms, such as Parks and McClellan algorithm (PMA),
genetic algorithm (GA) and classical particle swarm optimization (PSO). Several numerical design examples justify that the
proposed optimal filter design approach using CRPSO outperforms PMA and PSO, not only in the accuracy of the designed filter
but also in the convergence speed and solution quality. 相似文献