An accurate and efficient finite-difference method for solving the incompressible Navier-Stokes equations on curvilinear grids is developed. This method combines the favorable features of the staggered grid and semist...
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An accurate and efficient finite-difference method for solving the incompressible Navier-Stokes equations on curvilinear grids is developed. This method combines the favorable features of the staggered grid and semistaggered grid approaches. All components of velocity are stored at the corner vertices, and pressure is stored at the grid cell centers. All components of the momentum equations are discretized at cell vertices, facilitating a consistent discretization of the diffusive and convective terms as the boundaries are approached. The Christoffel symbol does not appear in the transformed equations and the cost of computation is comparable to that of the staggered-grid approach. A projection method is used to effectively evolve the discrete system in time, while ensuring a divergence-free velocity field. The discrete divergence and gradient operators of the projection step are constructed on a staggered gird layout leading to exact satisfaction of the discrete continuity. The solution of the Poisson-Neumann equation in the projection step is free of any spurious eigenmodes. The validity of the method is demonstrated on four benchmark problems. The Taylor-Green vortex problem is solved on a curvilinear grid with highly skewed cells and a second-order convergence in l-norm is observed. The mixed convection in a lid-driven cavity is solved on a highly curvilinear grid and excellent agreement with literature is obtained. The results for flow past a cylinder and pusatile flow in a 90 degrees bend are compared with the existing experimental data in the literature. The predictions agree well with the measured data, and validate the approach used.
We note that the seal can function stably in the fluid friction mode (for thechosen design characteristics of the seal unit) when the axial rigidity of the lifting layer at thecontact of the parr of surfaces of the fa...
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We note that the seal can function stably in the fluid friction mode (for thechosen design characteristics of the seal unit) when the axial rigidity of the lifting layer at thecontact of the parr of surfaces of the face seal ring pair is high. That rigidity is the parameterfor optimizing a seal with a wedge-shaped slot. When designing the unit, the designer must strive tocreate a face seal with the highest attainable lifting layer rigidity in the contact of the facesurfaces of the ring pair.
The performance descending of current congested link inference algorithms is obviously in dynamic routing IP network, such as the most classical algorithm CLINK. To overcome this problem, based on the assumptions of M...
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The performance descending of current congested link inference algorithms is obviously in dynamic routing IP network, such as the most classical algorithm CLINK. To overcome this problem, based on the assumptions of Markov property and time homogeneity, we build a kind of Variable Structure Discrete Dynamic Bayesian (VSDDB) network simplified model of dynamic routing IP network. Under the simplified VSDDB model, based on the Bayesian Maximum A Posteriori (BMAP) and Rest Bayesian Network Model (RBNM), we proposed an Improved CLINK (ICLINK) algorithm. Considering the concurrent phenomenon of multiple link congestion usually happens, we also proposed algorithm CLILRS (Congested Link Inference algorithm based on Lagrangian Relaxation Subgradient) to infer the set of congested links. We validated our results by the experiments of analogy, simulation, and actual Internet.
In this study, standard penetration test dependent bore-log charts of different boreholes were collected for selected locations in order to prepare the datasets. Datasets were applied to the Idriss and Boulanger metho...
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In this study, standard penetration test dependent bore-log charts of different boreholes were collected for selected locations in order to prepare the datasets. Datasets were applied to the Idriss and Boulanger method to evaluate liquefaction potential. Complete datasets were used for development of neural network and neuro-fuzzy models. Feed forward backpropagation algorithm with a multilayer perceptron network is utilized to analyze the liquefaction occurrence in different locations. To meet the objective, 159 sets of geotechnical data were collected, out of which 133 datasets were used for development of models and 26 datasets were used for validation. Neural network models were trained with six input vectors by optimum numbers of hidden layers, epoch, and suitable transfer functions. Neuro-fuzzy models have been developed using the Takagi-Sugeno-Kang reliant approach. The predicted values of liquefaction potential by artificial neural networks and neuro-fuzzy models were compared with an empirical method (i.e., Idriss and Boulanger method). The compared values of liquefaction potential obtained by neural network and neuro-fuzzy models shows that trained artificial neural network models' prediction capability are better than that of neuro-fuzzy models.
Direction of arrival (DOA) estimation of a gunshot is an important issue in shooter localisation. As the distance between the firing position and the sensor array increases, the signal-to-noise ratio decreases, which ...
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Direction of arrival (DOA) estimation of a gunshot is an important issue in shooter localisation. As the distance between the firing position and the sensor array increases, the signal-to-noise ratio decreases, which degrades the accuracy of the DOA estimation. Strong noise may lead to false peaks in cross-correlation functions, which may result in spurious time difference of arrival (TDOA) estimates and hence spurious DOA estimates. The proposed gunshot DOA estimation algorithm [exhaustive search-searching consistent fundamental loop (ES-SCFL)] reduces this problem by combining the methods of standard estimation, ES, and SCFL. The ES-SCFL method looks for the best set of microphone pairs and the correct peaks of their cross-correlation functions, and uses the time lags of these peaks as the TDOA estimates for DOA estimation. The performance of the proposed algorithm is evaluated using real gunshot data recorded from a field experiment.
Many spectral matching algorithms, ranging from the traditional clustering techniques to the recent automated matching models, have evolved. This paper provides a review and up-to-date information on the past and curr...
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Many spectral matching algorithms, ranging from the traditional clustering techniques to the recent automated matching models, have evolved. This paper provides a review and up-to-date information on the past and current role of the spectral matching approaches adopted in hyperspectral satellite image processing. The need for spectral matching has been deliberated and a list of spectral matching algorithms has been compared and described. A review of the conventional spectral angle measures and the advanced automated spectral matching tools indicates that, for better performance of target detection, there is a need for combining two or more spectral matching techniques. From the studies of several authors, it is inferred that continuous improvement in the matching techniques over the past few years is due to the need to handle and analyse hyperspectral image data for various applications. The need to develop a well-built and specialized spectral library to accommodate the resources from enormous spectral data is suggested. This may improve accuracy in mineral and soil mapping, vegetation species identification and health monitoring, and target detection. The future role of cloud computing in accessing globally distributed spectral libraries and performing spectral matching is highlighted. Rather than inferring that a particular matching algorithm is the best, this paper points out the requirements of an ideal algorithm. With increasing usage of hyperspectral data for resources mapping, the review presented in this paper will certainly benefit the large and emerging community of hyperspectral image users.
作者：
Yellin, DMIBM Corp
Div Res Thomas J Watson Res Ctr Yorktown Hts NY 10598 USA
As component-based development matures, more and more applications are built by integrating multiple distributed components. We suggest providing components with multiple implementations, each optimized for a particul...
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As component-based development matures, more and more applications are built by integrating multiple distributed components. We suggest providing components with multiple implementations, each optimized for a particular workload,and augmenting the component run-time environment with a mechanism for switching between implementations. This mechanism monitors the types of requests the component is receiving, and adaptively switches implementations for optimal application performance. Achieving this optimal performance depends on making good choices as to when and how to switch implementations, a problem, we refer to as the adaptive component problem. We first formalize the generic problem and then provide an algorithm, named Delta, for switching implementations in the special case when the component has exactly two implementations. We show that this algorithm is (3 + epsilon)-competitive with respect to the optimal algorithm, where epsilon is a small fraction. We establish a 3-competitve lower bound for the problem, which implies that Delta is close to optimal. We describe the application of these results to the distributed pub/sub problem, and the data structure selection problem.
The object tracking problem is an important research topic in computer vision. For real applications such as vehicle tracking and face tracking, there are many efficient and real-time algorithms. In this study, we wil...
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The object tracking problem is an important research topic in computer vision. For real applications such as vehicle tracking and face tracking, there are many efficient and real-time algorithms. In this study, we will focus on the Lucas-Kanade (LK) algorithm for object tracking. Although this method is time consuming, it is effective in tracking accuracy and environment adaptation. In the standard LK method, the sum of squared errors is used as the cost function, while least trimmed squares is adopted as the cost function in this study. The resulting estimator is robust against outliers caused by noises and occlusions in the tracking process. Simulations are provided to show that the proposed algorithm outperforms the standard LK method in the sense that it is robust against the outliers in the object tracking problems.
Distribution network planning is a very complicated, non-linear, large scale multi-objective and multi-constraint combinatorial optimisation problem. The capacity, location and power supply range of the substation and...
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Distribution network planning is a very complicated, non-linear, large scale multi-objective and multi-constraint combinatorial optimisation problem. The capacity, location and power supply range of the substation and the distribution network are optimised based on the load forecasting. In previous studies, this problem usually decomposes into two sub-problems, one is substation planning and the other is distribution network planning. The authors propose a method based on the self-adjustment weighted Voronoi diagram (WVD) using genetic algorithms and particle swarm optimisation for planning substations, which can optimise the location and power range of the substations when both the number and capacity of the substations are known. The weight is calculated according to the substation capacity and load distribution, and then the authors form the self-adjusted WVD whose weight can be adaptively adjusted. This method ensures the convergence of the algorithm and also makes the location and power supply range of the substations more reasonable. On this basis, the self-adjusted WVD based on the elitist selection genetic algorithm (ESGA-WVD) or the particle swarm optimisation algorithm (PSO-WVD) is achieved using the global search feature of the ESGA or the PSO. Numerical results show that ESGA-WVD and PSO-WVD are more reliable and reasonable than single ESGA, PSO or WVD;both in the determination of substation location and in the division of the substation power supply range. Compared with ESGA-WVD, PSO-WVD is better in terms of running time, convergence rate and investment costs.
The article highlights the success of pair programming based on a 'pair programming survey,' in context of Robert L. Fulgham's essay titled 'All I Really Need to Know I Learned in Kindergarten.' Th...
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The article highlights the success of pair programming based on a 'pair programming survey,' in context of Robert L. Fulgham's essay titled 'All I Really Need to Know I Learned in Kindergarten.' The article reports that when it comes to programming practices, studies show two heads are almost better than one. Pair programming is a practice in which two programmers work side-by-side at one computer, continuously collaborating on the same design, algorithm, code, or test. Anecdotal and initial statistical evidence indicates pair programming is highly beneficial, which is also attributed by Extreme programming. In the case of transition to pair programming from solitary programming, to avoid hesitation and to work successfully, some principles referred to are sharing of the work, sharing of key board typing and continuous analysis, avoiding negative thoughts, leaving ego etc. As a final thought, the article points out that making transition to pair programming involves breaking down some personal barriers. The success lies in hands of them in understanding the value of intercommunication skills, in confidently sharing the work and accepting the ownership of the partner's work. INSET: All I Really Need to Know I Learned in Kindergarten..
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