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101.
In this study, we carried out model tests to investigate the ice failure process and the resistance experienced by a transport vessel navigating in the Arctic region in pack ice conditions. We tested different navigation velocities, ice plate sizes, and ice concentrations. During the tests, we closely observed several phenomena, including the modes of interaction of the ice ship and the moving and failure modes of ice. We also measured the vessel resistances under different conditions. The test results indicate that the navigation velocity is a significant determinant of the moving and failure modes of ice. Moreover, vessel resistance is remarkably dependent on the ice concentration and navigation velocity. The variances of the mean and maximum resistance are also compared and discussed in detail. 相似文献
102.
A transit service quality study based on cluster analysis was performed to extract detailed customer profiles sharing similar appraisals concerning the service. This approach made it possible to detect specific requirements and needs regarding the quality of service and to personalize the marketing strategy. Data from various customer satisfaction surveys conducted by the Transport Consortium of Granada (Spain) were analyzed to distinguish these groups; a decision tree methodology was used to identify the most important service quality attributes influencing passengers’ overall evaluations. Cluster analysis identified four groups of passengers. Comparisons using decision trees among the overall sample of all users and the different groups of passengers identified by cluster analysis led to the discovery of differences in the key attributes encompassed by perceived quality. 相似文献
103.
Recent longitudinal studies of household car ownership have examined factors associated with increases and decreases in car ownership level. The contribution of this panel data analysis is to identify the predictors of different types of car ownership level change (zero to one car, one to two cars and vice versa) and demonstrate that these are quite different in nature. The study develops a large scale data set (n = 19,334), drawing on the first two waves (2009–2011) of the UK Household Longitudinal Study (UKHLS). This has enabled the generation of a comprehensive set of life event and spatial context variables. Changes to composition of households (people arriving and leaving) and to driving licence availability are the strongest predictors of car ownership level changes, followed by employment status and income changes. Households were found to be more likely to relinquish cars in association with an income reduction than they were to acquire cars in association with an income gain. This may be attributed to the economic recession of the time. The effect of having children differs according to car ownership state with it increasing the probability of acquiring a car for non-car owners and increasing the probability of relinquishing a car for two car owners. Sensitivity to spatial context is demonstrated by poorer access to public transport predicting higher probability of a non-car owning household acquiring a car and lower probability of a one-car owning household relinquishing a car. While previous panel studies have had to rely on comparatively small samples, the large scale nature of the UKHLS has provided robust and comprehensive evidence of the factors that determine different car ownership level changes. 相似文献
104.
崔利荣 《上海交通大学学报(英文版)》2016,21(4):509-512
Consistent high-quality and defect-free production is the demand of the day. The product recall not only increases engineering and manufacturing cost but also affects the quality and the reliability of the product in the eye of users. The monitoring and improvement of a manufacturing process are the strength of statistical process control. In this article we propose a process monitoring memory-based scheme for continuous data under the assumption of normality to detect small non-random shift patterns in any manufacturing or service process.The control limits for the proposed scheme are constructed. The in-control and out-of-control average run length(AVL) expressions have been derived for the performance evaluation of the proposed scheme. Robustness to non-normality has been tested after simulation study of the run length distribution of the proposed scheme, and the comparisons with Shewhart and exponentially weighted moving average(EWMA) schemes are presented for various gamma and t-distributions. The proposed scheme is effective and attractive as it has one design parameter which differentiates it from the traditional schemes. Finally, some suggestions and recommendations are made for the future work. 相似文献
105.
The simulation is an important means of performance evaluation of the computer architecture. Nowadays, the serial simulation of general purpose graphics processing unit (GPGPU) architecture is the main bottleneck for the simulation speed. To address this issue, we propose the intra-kernel parallelization on a multicore processor and the inter-kernel parallelization on a multiple-machine platform. We apply these two methods to the GPGPU-sim simulator. The intra-kernel parallelization method firstly parallelizes the serial simulation of multiple compute units in one cycle. Then it parallelizes the timing and functional simulation to reduce the performance loss caused by the synchronization between different compute units. The inter-kernel parallelization method divides multiple kernels of a CUDA program into several groups and distributes these groups across multiple simulation hosts to perform the simulation. Experimental results show that the intra-kernel parallelization method achieves a speed-up of up to 12 with a maximum error rate of 0.009 4% on a 32-core machine, and the inter-kernel parallelization method can accelerate the simulation by a factor of up to 3.9 with a maximum error rate of 0.11% on four simulation hosts. The orthogonality between these two methods allows us to combine them together on multiple multi-core hosts to get further performance improvements. 相似文献
106.
To get the accurate wave loads on wharf composite structure, the wave force on small-scale piles and the uplift force on lower
surface of caisson must be considered. Based on the Reynolds averaged Navier-Stokes (RANS) equations, the pore media theory
and the volume of fluid (VoF) method, a three-dimensional numerical model is established. The model has been developed to
simulate wave interaction with a composite structure including caisson, piles and deck. The numerical results agree very well
with the experimental data on total force. The spatial distributions of the non-dimensional wave height and the maximum of
wave pressure on surface of composite structure are presented and discussed. The effects of relative caisson length, relative
wave height and relative caisson height on horizontal wave force are given. The result indicates that the horizontal wave
force achieves maximum value at the relative caisson length of 0.18 and increases linearly with the increase of the relative
caisson and wave height. It is proved that the model is an accurate and efficient numerical tool to investigate different
problems of wave-structure interaction. 相似文献
107.
Spectrum sensing is an important part of cognitive radio systems to find spectrum hole for transmission which enables cognitive
radio systems coexist with the authorized radio systems without harmful interference. In this paper, an improved cyclostationary
feature detection method is proposed to reduce computational complexity without loss of good performance based on the optimal
parameter selection strategy for choosing detection parameters of cyclic frequency and lag. Taking binary phase shift keying
(BPSK) and quadrature phase shift keying (QPSK) signals as examples, the theoretical analyses are presented for choosing the
optimal parameters. Simulation results are given to certify the correctness of the proposed parameter selection strategy and
show the performance of the proposed method. 相似文献
108.
Aiming at the limitations of the existing knowledge representations in intelligent detection, a novel extension-based knowledge
representation (EKR) is proposed. The definitions, grammar rules, and formal semantics of EKR are presented. A rhombus solving
strategy (RSS) based on EKR is discussed in detail, including creation of the problem oriented model, extension operator,
the solution formation of contradictions problem and extended inference of matter-element. A knowledge base system based on
EKR and RSS is developed, which is applied in intelligent detection in the Dendrobium huoshanense photosynthesis process (DHPP).
More reasonable results are obtained than traditional rule-based system. The EKR is feasible in intelligent detection to solve
the limitations of traditional knowledge representations. 相似文献
109.
The concept of heterogeneity in choice structure is applied in this study to examine individuals’ action space, which is defined
in terms of the reported frequencies of visits. A disaggregate model system that predicts the frequency of visits is condensed
using a nested logit model with multiple choice structures. 相似文献
110.