Ruled surfaces play an important role in many manufacturing and construction applications. In this work, we explore a multi-dimensional dynamic programming based ruled surface fitting scheme to a given freeform ration...
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Ruled surfaces play an important role in many manufacturing and construction applications. In this work, we explore a multi-dimensional dynamic programming based ruled surface fitting scheme to a given freeform rational surface, S. Considering two initial opposite boundaries of S, sampled into a discrete piecewise linear polyline representation, the ruled surface fitting problem is reduced to a pairing-search between the polylines and elevations above the polylines, in the normal directions of S. A four-dimensionaldynamicprogramming solution is sought for the four dimensions prescribed by the two polylines and the two elevation levels along the surface normals. This multi-dimensional dynamic programming is evaluated using highly parallel algorithms running on GPUs that ensures the best fit to the sampled data. In order to evaluate the fitting error with respect to S, we derive a scheme to compute a bound from above on the maximal error between a bilinear surface patch (formed by two consecutive point-pairs) and its corresponding surface region on S. Surface-surface composition is employed to extract the corresponding surface region on S to compare against. Finally, the above ruled surface fitting approach is also extended into a discrete algorithm to find the non-isoparametric subdivision curve on S when a discrete recursive piecewise-ruled surface fitting is considered. A five- or seven-dimensionaldynamicprogramming solution is employed towards this end and once again, surface-surface composition is employed to extract the two subdivided patches as tensor products. (C) 2014 Elsevier Ltd. All rights reserved.
Hybrid storage systems consisting of battery and ultra-capacitor have recently emerged as an alternative to the conventional single buffer layout in hybrid vehicles. Their high power and energy density could improve t...
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Hybrid storage systems consisting of battery and ultra-capacitor have recently emerged as an alternative to the conventional single buffer layout in hybrid vehicles. Their high power and energy density could improve the performance indices of the vehicle, provided that an optimal energy management strategy is employed that could handle systems with multiple degrees of freedom (DOF). The majority of existing energy management strategies is limited to a single DOF and the small body of work on multi-DOF systems is mainly heuristic-based. We propose an optimal solution to the energy management problem in fuel-cell hybrid vehicles with dual storage buffer for fuel economy in a standard driving cycle using multi-dimensional dynamic programming (MDDP). An efficient MDDP code is developed using MATLAB (TM)'s vectorization feature that helps reduce the inherently high computational cost of MDDP. Results of multiple simulated experiments are presented to demonstrate the applicability and performance of the proposed strategy. A comparison is also made between a single and a double buffer fuel-cell hybrid vehicle in various driving cycles to determine the maximum reduction in fuel consumption that can be achieved by the addition of an ultra-capacitor. (C) 2013 Elsevier B.V. All rights reserved.
The "curse of dimensionality" of dynamicprogramming (DP) has always been a great challenge to the cascade reservoirs operation optimization (CROO) because computer memory and computational time increase exp...
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The "curse of dimensionality" of dynamicprogramming (DP) has always been a great challenge to the cascade reservoirs operation optimization (CROO) because computer memory and computational time increase exponentially with the increasing number of reservoirs. It is an effective measure to combine DP with the parallel processing technology to improve the performance. This paper proposes three parallel modes for multi-dimensional dynamic programming (MDP) based on .NET4 Parallel Extensions, i.e., the stages parallel mode, state combinations parallel mode and hybrid parallel mode. A cascade reservoirs of Li Xiangjiang River in China is used as the study instance in this paper, and a detailed contrastive analysis of the three parallel modes on run-time, parallel acceleration ratio, parallel efficiency and memory usage has been implemented based on the parallel computing results. Results show that all the three parallel modes can effectively shorten the run-time so that to alleviate the "curse of dimensionality" of MDP, but relatively, the state combinations parallel mode is the optimal, the hybrid parallel is suboptimal and the stages parallel mode is poor. (C) 2015 Elsevier B.V. All rights reserved.
An efficient reservoir operation technique plays a very important role in improving the water resources and energy efficiency of reservoirs. In order to effectively avoid or alleviate the "curse of dimensionality...
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An efficient reservoir operation technique plays a very important role in improving the water resources and energy efficiency of reservoirs. In order to effectively avoid or alleviate the "curse of dimensionality" of multi-dimensional dynamic programming (MDP) in the application of cascade reservoirs operation optimization (CROO) and keep a global convergence at the same time, two dimension reduction methods are proposed in this paper. One is a hybrid algorithm of MDP and a Progressive Optimality Algorithm (POA), named MDP-POA, which combines the global convergence of MDP and the strong local search ability of POA. MDP-POA first takes the global optimal trajectory of MDP in a low discrete degree as the initial trajectory of the POA, and then implements further optimization to the obtained initial trajectory by the POA with a high discrete degree, so as to avoid the "curse of dimensionality" of MDP in high discrete degree and the dependency of the POA for the initial trajectory. The other is an improved MDP (IMDP), which first constructs a corridor by the optimal trajectory of MDP in a lower discrete degree, and then implements further optimization in the corridor by MDP with a relatively high discrete degree, so as to avoid a large number of unnecessary calculations, and shorten the run-time effectively. In a case study, the results of MDP-POA, IMDP, and MDP are compared and analyzed from the aspects of power generation and run-time. The analysis indicates that the proposed MDP-POA and IMDP both have a good application effect and are worthy of further promotion.
In this study, a comprehensive energy-thermal coupling model for stratospheric airships is established to address the dual challenges of energy and buoyancy balance for long-duration missions. A multi-dimensional Dyna...
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In this study, a comprehensive energy-thermal coupling model for stratospheric airships is established to address the dual challenges of energy and buoyancy balance for long-duration missions. A multi-dimensional dynamic programming (MDP) energy management framework is introduced to significantly accelerate the optimization process for hybrid energy system including solar array, battery, and RFC (Regenerative Fuel Cell), achieving 4 % greater maneuverability, 25.42 % less curtailment, and 3.4 % fewer gas loss,. The efficiency of the MDP optimization process is enhanced by the implementation of vectorization and state-to-state traversal with feasibility checks and state reduction, achieving speed improvements of over 1000 times compared to traditional methods. State variables and time steps are appropriately discretized to balance feasible search regions and control resolution. The global search capability of the MDP algorithm allows for stable power consumption and distribution, resulting in lower curtailment rates and higher maneuverability. Additionally, a 10.9 % increase in endurance to 1301h and 1835 km h cumulative boundary exceedance decrease, obtained by hierarchical online energy management, are achieved by extracting rules from deterministic global algorithms, incorporating energy consumption prediction, energy harvesting prediction, residency prediction, temperature following, and RFC power stabilization.
Automated segmentation approaches for the left ventricle (LV) in real-time 3D echocardiography (RT3DE) often rely on manual initialization. So far, little effort has been put in automating the initialization procedure...
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ISBN:
(纸本)9781424413836
Automated segmentation approaches for the left ventricle (LV) in real-time 3D echocardiography (RT3DE) often rely on manual initialization. So far, little effort has been put in automating the initialization procedure to get to a fully automatic segmentation approach. We propose a fully automatic method for the detection of the LV long axis (LAX) and the mitral valve plane (MVP) over the full cardiac cycle, for the initialization of segmentation algorithms in 3DE. It assigns probabilities to candidate LV center points through a Hough transform for circles, and detects the LV LAX by combining dynamicprogramming detections on these probabilities in 3D and 2D + time, to obtain a time-continuous solution. Subsequently, the mitral valve plane is detected in a projection of the data on a plane through the previously detected LAX. The method easily adjusts to different acquisition routines and combines robustness with good accuracy and low computational costs. Automatic detection was evaluated using patient data acquired with the Fast Rotating Utrasound (FRU-) transducer (11 patients) and with the Philips Sonos 7500 ultrasound system with the X4 matrix transducer (14 patients). For the FRU data, the LAX was estimated with a distance of 2.85 +/- 1.70 mm (Av +/- SD) and an angle of 5.25 +/- 3.17 degrees;the mitral valve plane was estimated with a distance of -1.54 +/- 4.31 mm. For the matrix data these distances were 1.96 +/- 1.30 mm with an angle error of 5.95 +/- 2.11 and -1.66 +/- 5.27 mm for the mitral valve plane. These results confirm that the method is very well suitable for automatic detection of the LV LAX and MVP. It provides a basis for further automatic exploration of the LV and could therefore replace manual initialization of 3D segmentation approaches.
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