Redistribution Method Research Articles

Collision avoidance for formation of autonomous ships using separation and recovery mechanism combine artificial potential field method

ABSTRACT It is essential to investigate the path planning and tracking problem for maritime autonomous surface ships (MASS). This study proposed an automatic collision avoidance method based on the separation and recovery mechanism with formation of MASS (F-MASS). First, the marine environment model utilized S-57 electric navigation chart (ENC) data for construction. The Scan-searching method was proposed for multipath and path-optimized redistribution method was developed to address MASS congestion. The formation pattern transformation was settled by separation and recovery mechanism. Considered the ‘unmanned–manned’ encounter situation, formulated avoidance strategies for both the MASS formation and manned ships encounters. Finally, the simulation experiment was carried out in the sea near Zhoushan port to verify the effectiveness of the algorithm. The results indicated that the method can satisfy the integrated operation of collision avoidance in a complex environment and can offer effective collision avoidance strategies for F-MASSs navigating in complex marine environments.

Comparison of two hydrodynamic models for their rain-on-grid technique to simulate flash floods in steep catchment

In this study, two hydrodynamic models, TELEMAC-2D and HEC-RAS 2D, were compared for their Rain-on-Grid (RoG) technique with a particular focus on runoff generation processes in a small and steep catchment. Curve number (CN) method was applied in both the models to simulate two single storm events up to 20 h of duration, whereas the Green-Ampt Redistribution (GAR) method was additionally applied in HEC-RAS 2D for a multi-peak flood event with sustained flow between the peaks. CN and GAR methods were compared for this flood event, and a sensitivity analysis of the GAR parameters was also done. Moreover, the two models were compared for their calibration process, computational time, mesh size and shape, and model availability, in general, as well as the results including inundated areas, water depth, and velocity. The results indicate that both the models are capable of reproducing short duration single storm floods. NSE and R2 for both models ranged from 0.70 to 0.90 and from 0.93 to 0.95. However, the models struggled to reproduce the long- duration multi-peak flood event. The sensitivity analysis showed that the results are not very sensitive to the two GAR parameters which are responsible to influence the flow of the second peak in the flood event. Neither the CN nor the GAR infiltration method successfully replicated such events because the hydraulic models permanently lose infiltrated water from the domain. The returned sub-surface flow significantly contributes to river flow during these flood events; however, none of the model incorporates a return flow algorithm.

Fabrication of uniaxially/biaxially tensile-strained Ge by strain redistribution method

Tensile strain is a widely discussed method to improve electron mobility and luminescence of Ge and has been applied in infrared photodetectors. By combining thin film crimping technology with microelectronic processing technology, uniaxial or biaxial tensile strain is achieved in a suspended Ge micro-bridge structure. The strain state can be manipulated by adjusting the sizes of the patterns, and a uniaxial tensile strain of 3.46% and biaxial tensile strain of 0.31% have been demonstrated in this work. The three-dimensional finite element analysis proves that the tensile strain originates from the strain redistribution between the W film and the Ge micro-bridge structure, and finally, the simulation results agree with the experimental data very well.

Collaborative planning algorithm for incomplete navigation graphs

In a complex environment, in order to improve the efficiency of multi-AUV collaborative work, this paper proposes a new collaborative hunting algorithm based on the Bionic Neural Wave Network (BNWN) algorithm. This algorithm integrates search, tracking and capture of targets by multi-AUV under the incomplete navigation graphs. A search mechanism with memory tabu that to avoid redundant search and improve global search efficiency is designed. Then a real-time redistribution method is embedded into this algorithm to ensure the optimal matching state during the tracking and capture process. Further, multi-AUV track and capture prey based on energy consumption models and self-learning models, and recast time-varying navigation maps through the recognition mechanisms, under the whole collaborative operations. Simulation results have proved that the number of multi-AUV path turns is reduced and the execution time is shortened by an average of 81%. In this way, the optimal matching state is maintained, the repeated search and partial self-locking problems are overcome, and the efficient capture of intelligent prey is realized.

Decision Key-Value Feature Construction for Multihoming Big Data Network

The random forest algorithm under the MapReduce framework has too many redundant and irrelevant features, low training feature information, and low parallelization efficiency when dealing with multihoming big data network problems, so parallelism is based on information theory, and norms is proposed for random forest algorithm (PRFITN). In this paper, the technique used first builds a hybrid dimensional reduction approach (DRIGFN) focused on information gain and the Frobenius norm, successfully reducing the number of redundant and irrelevant features; then, an information theory feature is offered. This results in the dimensionality-reduced dataset. Finally, a technique is suggested in the Reduce stage. The features are grouped in the FGSIT strategy, and the stratified sampling approach is employed to assure the information quantity of the training features in the building of the decision tree in the random forest. When datasets are provided as key/value pairs, it is common to want to aggregate statistics across all objects with the same key. To acquire global classification results and achieve a rapid and equal distribution of key-value pairs, a key-value pair redistribution method (RSKP) is used, which improves the cluster’s parallel efficiency. The approach provides a superior classification impact in multihoming large data networks, particularly for datasets with numerous characteristics, according to the experimental findings. We can utilize feature selection and feature extraction together. In addition to minimizing overfitting and redundancy, lowering dimensionality contributes to improved human interpretation and cheaper computing costs through model simplicity.

Analysis of the effect of node attack method on cascading failures in multi-layer directed networks

In order to avoid large-scale cascading failures, we propose a cascading failure model with adjustable parameters in multi-layer directed dependent networks with target nodes. The model sets the initial load and limit capacity, designs load delay judgment mechanism, constructs a load distribution strategy, and analyzes the cascading failure conditions. Finally, the simulation comparison between our method and other four redistribution methods shows that our method can improve the robustness and efficiency of the network. Based on our redistribution method, the same number of nodes are attacked by four attack methods, showing that the cost of attacking the driver node set is small, but can cause cascading failure on a large scale.

Information Entropy-based Edge Importance Identification of Road Network: A Case of Highway in Sichuan Province

Due to the severe damage and huge loss caused by natural disasters to road networks, the protection of the road network is essential. Edge importance identification can help preserve the road network by protecting key edges. This paper proposes a new network performance measure method and introduces a new edge load redistribution method in cascading failure model. To identify different edge importance in the network, this paper proposes three edge importance evaluation metrics, including information entropy of degree values, information entropy of iterative factors and two-dimensional evaluation metric based on the Pareto non-dominated set which combines two single metrics. A case study of highway road in Sichuan province with 204 nodes and 322 edges which was affected by Luding Earthquake is conducted to demonstrate the best one of the three metrics, including data from the Department of Transport of Sichuan Province. The final results of the chi-square test and Kendall’s correlation coefficient comparing the importance ranking of the three metrics with the ranking derived from the network performance assessment model indicate that the two-dimensional evaluation metrics have the best performance and that the road network tends to collapse at the same time when attacked against the road network under different edge rankings, suggesting that the effect of cascading failures should be limited early.

Experiment Study on the properties of Su-53 fracturing fluid

The sand carrying performance of the fracturing fluid is one of the decisive properties of the sand laying form of the proppant in the reservoir, and the sand carrying performance of the seven fracturing fluids on appeal is tested according to the Stokes theoretical formula for two melon samples and five viscoelastic surfactant samples. Single-particle sedimentation test and multi-particle sedimentation test were carried out and the fracturing fluid was optimized based on test data.The treatment of fracturing fluid flowback has always been a problem in the industry. In this paper, a redistribution experiment was carried out on 7 samples according to a redistribution method of fracturing flowback fluid, and viscosity was used as the main reference index. The recyclability of each fracturing fluid was compared based on the retention rate; the fracturing fluid with the most recyclability was selected.

Hybrid Dynamic Mesh Redistribution - Immersed Boundary Method for Acoustic Simulation of Flow Around a Propeller

A novel hybrid dynamic mesh redistribution – immersed boundary method for simulation of turbulent flows around rotating obstacles of complex geometry and analysis of tonal acoustics is proposed. The feasibility of the approach is demonstrated by considering a drone propeller problem. The results of three-dimensional Reynolds-averaged Navier–Stokes simulations using the proposed approach are compared to the results of body-fitted unstructured simulations in noninertial reference frame. The dynamic mesh redistribution method allows the reposition of mesh points taking into account the shape of the moving body while retaining the mesh topology. The cell size and quality of the dynamically redistributed mesh strongly depend on the curvature of the body surface. The position and shape of the moving obstacle is prescribed by a distance function defined on an adaptive octree. The results of simulations using the proposed method are in good agreement with both the results of body-fitted simulations and the experimental data.

Electric vehicle charging guidance based on weighted complex network

The charging station malfunction may deny the charging service for the electric vehicles at the station. As a result, the vehicles need to select other stations. How to make an optimal selection is difficult for the owners. An optimal charging guidance strategy based on a weighted complex network is proposed for the owners to select the optimal station. All the charging stations are modelled as a complex network in which the stations and the roads among them are defined as nodes and edges, respectively. Furthermore, each edge is weighted by the state of charge (SOC) of the vehicle, the charging price, and the distance and traffic conditions between these two stations. The bigger edge weight indicates the smaller probability that the owner at one node of the edge select the other node of the edge for charging, and vice versa. Based on the weighted complex network model, the local load redistribution method is presented to guide the charging of vehicles at the malfunctioning station. Consequently, the optimal scheduling of the vehicles is realized under the guidance strategy proposed in this paper. Finally, some contrast experiments are carried out to illustrate the effectiveness and the superiority of the proposed method.

Enhanced vapor condensation by thermal redistribution on the evaporation surface in heat-localized solar desalination

• The thermal redistribution method is proposed for improving vapor condensation. • The fabricated 3-dimensional evaporation could achieve high evaporation rate. • The condensation rate could be enhanced 30% by thermal redistribution. • The good performance in seawater enables long-term operation of the system. Due to the abundance and cleanliness, Solar energy has been used for desalination and demonstrated great potential to tackle the grand challenges of freshwater shortage. For more efficient solar evaporation, heat-localized solar evaporation was proposed in 2014, in which heat could be localized at the air–water interface. With the high energy efficiency and simple operation, heat-localized solar evaporation systems have drawn great interest recently, and much progress has been made in exploring new materials and structures for better evaporation performance. Especially, many three-dimensional evaporation structures have been proposed, which enhances the evaporation rate of such systems to be higher than 1.5 kg m -2 h −1 . However, most works focused on improving the evaporation part of such 3-dimensional evaporation systems, while the research on the condensation part are rarely seen, which could be more important for freshwater production. Here, we propose a method of thermal redistribution to improve vapor condensation by increasing the average temperature of generated vapor. We firstly prepared the 3-dimensional triangle-shaped evaporation structures with thermal redistribution, which could be bent at different inclination angles to promote evaporation. The vapor condensation performances were compared between structures with and without thermal redistribution, and results show that thermal redistribution could increase the condensation rate by about 30%. This attributes to the increased average temperature of the generated vapor, while low-temperature vapor could hardly condense in practice. This work presents the method of thermal redistribution, which could be further used to increase freshwater production in heat-localized solar desalination systems.

Anisotropic mesh generation and adaptation for quads using the Lp-CVT method

This paper presents a framework for anisotropic unstructured all-quad mesh adaptation. The technique is suitable for use with a diverse class of numerical methods, including the high-order Discontinuous Galerkin solver presented here. Benefiting from the flexibility and efficiency of these methods, improvements in the solution accuracy are targeted by modifying the discretization of the domain. Previous works have tackled this problem for the case of simplex elements using continuous mesh and error models. Our method makes use of novel extensions to allow similar techniques to be applied for the case of tensor product elements. Key aspects of the work will discuss the modified continuous mesh representation and error minimization procedure. Additionally, these ideas have been coupled with mesh generation based on both existing and experimental techniques. As a result, this work will also consider the implementation of an energy minimizing, node redistribution method, that takes place in an anisotropic spatially varying high-order p-norm. Finally, the technique will also be applied to goal-oriented adaption using the adjoint-based error estimation. Overall, the work outlines the adaptive procedure tailored specially to all-quad meshing.

A signal enhancement method based on the reverberation statistical information

This paper proposes a reverberation suppression algorithm utilizing fractional lower-order moments based on statistical properties. As fractional lower-order moments can only be applied on symmetric α-stable random variables, the energy redistribution method is used, so reverberation signals can obtain the characteristic exponents of the symmetric α-stable distribution. To evaluate the proposed algorithm, an experiment involving simulated linear frequency modulation reverberation with the proposed method and comparison methods is performed and discussed. Moreover, an experiment is conducted using reverberation as measured from the lake. The results show that the proposed algorithm can achieve better reverberation suppression and signal enhancement performance compared with other methods.

Preparation and characterization of high temperature resistant thermosetting polyphenylene ether resin

AbstractTo explore high thermal properties, low dielectric constant and loss for copper clad laminates, poly(phenylene oxide) (PPE) with different end groups (allyl and epoxide groups) were successfully prepared. Firstly, low molecular weight polyphenylene ether was synthesized using the redistribution method. Then the polyphenylene ether thermosetting polymers by modifying their terminal hydroxyl groups were reported and their fundamental materials properties were compared. Through property tests and data analyses, it was found that PPE with vinyl end groups had the best performances, especially high glass transition temperature (about 230°C), the thermal conductivity was 0.32–0.38 Wm−1 K−1, low dielectric constant (about 2.5) and low dielectric loss (about 4.4 × 10−3). The possible reason was that the main chain of polyphenylene ether contains non‐polar crosslinkable group (CC). In a word, through properties comparison of thermosets of PPE, the results demonstrated that the materials of all systems were suitable for using as printed circuit boards.

Enforcing detailed balance in the Borgnakke–Larsen redistribution method with temperature dependent relaxation models

For decades, it has been observed that the commonly used Borgnakke–Larsen method for energy redistribution in Direct Simulation Monte Carlo codes fails to satisfy the principle of detailed balance when coupled to a wide variety of temperature dependent relaxation models, while seemingly satisfying detailed balance when coupled to others. Many attempts have been made to remedy the issue, yet much ambiguity remains, and no consensus appears in the literature regarding the root cause of the intermittent compatibility of the Borgnakke–Larsen method with temperature dependent relaxation models. This paper alleviates that ambiguity by presenting a rigorous theoretical derivation of the Borgnakke–Larsen method's requirement for satisfying detailed balance. Specifically, it is shown that the Borgnakke–Larsen method maintains detailed balance if and only if the probability of internal-energy exchange during a collision depends only on collision invariants (e.g., total energy). The consequences of this result are explored in the context of several published definitions of relaxation temperature, including translational, total, and cell-averaged temperatures. Of particular note, it is shown that cell-averaged temperatures, which have been widely discussed in the literature as a way to ensure equilibrium is reached, also fail in a similar, although less dramatic, fashion when the aforementioned relationship is not enforced. The developed theory can be used when implementing existing or new relaxation models and will ensure that detailed balance is satisfied.

Microvibration-based orderly redistribution of wear particles in lubricating oil

On-line monitoring of wear particles in lubricating oil has become an important requirement for engine health management. This paper proposes a new online analysis method for oil wear particles. Exciting with micro-vibration, wear particles in the oil are redistributed on the surface of the vibrating film according to their size such that the collection and analysis of wear particles is realized in an orderly manner. A monolayer horizontal vibrational particle separation model was developed. The distribution law of wear particles in multi-physics field is theoretically deduced. Both a numerical simulation model and a simplified experimental system are established to illustrate the redistribution process of wear particles with different sizes. The numerical and experimental results show that the micro vibration-based redistribution method can separate the aggregation bands of different wear particles under the excitation of a certain frequency.

Spatial-Frequency Redistribution-based Saliency Region Detection for Thai Text Localisation

Saliency region detection plays an important role in computer vision applications and related areas, such as human fixation, figure-ground separation, face detection, and image compression. Nevertheless, state-of-the-art methods can moderately detect the saliency regions of a psychological pattern dataset. Therefore, this paper proposes a spatial-frequency redistribution (SFR) method to improve the efficiency of the detection of the saliency regions. The proposed SFR method consists of two main procedures: (i) adaptive cosine image construction-and-implantation and (ii) saliency region detection using complete multiple-object-implanted images. The former procedure constructs an adaptive cosine image by using a cosine function based on an object structure and then individually implants it into each object detectable. This stage provides the first significant property, spatial redistribution, to the object implanted. The adaptive cosine image redistributes the objects for controllability. Then, the latter procedure transforms a complete multiple object-implanted image into the frequency domain. At this point, the second significant property, frequency redistribution, provides the simple technique for identifying and separating the target object from the unwanted objects and background. In this paper, these properties are referred to as spatial-frequency redistribution. This method was realized as a computer program, and then such program was tested with a psychological pattern dataset and a Thai text dataset. The experimental results, when compared with state-of-the-art methods, show that the proposed SFR method can achieve the clear detection of the attention region in the psychological pattern dataset. Moreover, the proposed method can achieve a F-value of 80.28% with a recall and precision of 76.32% and 85.23%, respectively, for Thai text localisation in the Thai text dataset.

Multistep thrust allocation method based on priority idea for remotely operated underwater vehicle with horizontal thrusters configured as X shape

The horizontal thrusters located as X shape is a commonly used configuration in remotely operated underwater vehicle (ROV). To improve the motion performance of the remotely operated underwater vehicle with this configuration for some typical operation tasks, a multistep thrust allocation method based on priority idea is proposed. Firstly, the thrust allocation result of every single force/moment among the horizontal thrusters is obtained by using a piecewise calculation method. Then, a thrust allocation function of multiple forces and moment is constructed, transforming the thrust allocation problem into a multiparameter optimization problem. The objective function of the optimization problem is established based on priority idea, and limits of the thrusters are considered as constraints. Finally, a thrust redistribution method is adopted in order to further utilize the unsaturated thrusters in the propulsion system. Simulation results show that the proposed thrust allocation method has various advantages over the pseudo-inverse method, which makes the remotely operated underwater vehicle perform perfectly in the given operation task. The proposed method has important practical value and application prospects.

Planning of Hydrogen Refueling Stations in Urban Setting While Considering Hydrogen Redistribution

Electrified transportation systems and renewable energy resources have been recognized as effective environmental-friendly technologies against global warming contributed by greenhouse gas (GHG). Remarkably, hydrogen fuel cell-powered electric vehicles can outperform battery-powered electric vehicles largely in the sense of the driving range and the refueling time. However, both of them require a better coordination of infrastructure system and renewable energy resources to achieve a significant reduction of GHG emissions. This article aims to maximize the long-term profitability for the planning model of hydrogen refueling stations, where the capacitated flow refueling location model is leveraged for maximal traffic flow coverage. Furthermore, we discuss various real-world constraints, such as traffic network constraints, distribution network constraints, hydrogen balance constraints, and energy constraints for electric vehicles, to make the planning model more practical. By considering the uncertainty of the short-term refueling demand across the city, an approach for geographically redistributing hydrogen among the stations is also presented where the minimal cost of redistribution is modeled by one-commodity pickup-and-delivery traveling salesman problem. A real-life case study of Western Sydney is adopted to testify the efficiency of the planning model under current and future cost levels. Finally, a numerical simulation is utilized to demonstrate the validity of the hydrogen redistribution method.

A Two-Dimensional Stabilized Discontinuous Galerkin Method on Curvilinear Embedded Boundary Grids

In this work, we propose a state redistribution method for high order discontinuous Galerkin methods on curvilinear embedded boundary grids. State redistribution relaxes the overly restrictive CFL condition that results from arbitrarily small cut cells when explicit time steppers are used. Thus, the scheme can take take time steps that are proportional to the size of cells in the background grid. The discontinuous Galerkin scheme is stabilized by postprocessing the numerical solution after each stage or step of an explicit time stepping method. This is done by temporarily coarsening, or merging, the small cells into larger, possibly overlapping neighborhoods using a special weighted inner product. Then, the numerical solution on the neighborhoods is refined back onto the base grid in a conservative fashion. The advantage of this approach is that it uses only basic mesh information that is already available in many cut cell codes and does not require complex geometric manipulations. We prove that state redistribution is conservative and $p$-exact. Finally, we solve a number of test problems that demonstrate the encouraging potential of this technique for applications on curvilinear embedded geometries. Numerical experiments reveal that our scheme converges with order $p+1$ in $L_1$ and between $p$ and $p+1$ in $L_\infty$.