A Distribution Evolutionary Algorithm for Graph Coloring

Graph Coloring Problem (GCP) is a classic combinatorial optimization problem that has a wide application in theoretical research and engineering. To address complicated GCPs efficiently, a distribution evolutionary algorithm based on population of probability models (DEA-PPM) is proposed. Based on a novel representation of probability model, DEA-PPM employs a Gaussian orthogonal search strategy to explore the probability space, by which global exploration can be realized using a small population. With assistance of local exploitation on a small solution population, DEA-PPM strikes a good balance between exploration and exploitation. Numerical results demonstrate that DEA-PPM performs well on selected complicated GCPs, which contributes to its competitiveness to the state-of-the-art metaheuristics

Research on support vector machine method for comprehensive evaluation after compression

Hydraulic fracturing is one of the important measures to increase production of oil and gas reservoirs. Pressure after the assessment of the existing technology is usually divided into direct and indirect diagnosis of hydraulic fracture. The diversity of evaluation results is due to the uncertainty and immaturity of the technology itself. Up to now, we have not found an economical and accurate hydraulic fracture evaluation method in the development and application of fracturing technology. In this paper, the pressure treatment technology after the comprehensive evaluation of boundary conditions is studied. By introducing the support vector regression theory, an evaluation model and a solution for correcting fracturing parameters are proposed. Fracturing parameters include fracture length, fracture height, fracture width, integrated fracturing fluid leakage coefficient, fracture conductivity, fracture closure pressure, and so on. For the optimization of various parameters, objective and scientific comprehensive evaluation results can be obtained by selecting different kernel functions. The results show that the model and method based on support vector machine are effective and practical

Visibility Extension of 1-D Aperture Synthesis by a Residual CNN for Spatial Resolution Enhancement

In order to improve the spatial resolution of a one-dimensional aperture synthesis (1-D AS) radiometer without increasing the size of the antenna array, the method of visibility extension (VE) is proposed in this article. In the VE method, prior information about the visibility distribution of various scenes is learnt by a residual convolutional neural network (ResCNN). Specifically, the relationship between the distribution of low-frequency visibility and that of high-frequency visibility is learnt. Then, the ResCNN is used to estimate the high-frequency visibility samples from the low-frequency visibility samples obtained by the AS system. Furthermore, the low- and high-frequency visibility samples are combined to reconstruct the brightness temperature image of the scene, to enhance the spatial resolution of AS. The simulation and experiment both demonstrate that the VE method can enhance the spatial resolution of 1-D AS

Visibility Extension of 1-D Aperture Synthesis by a Residual CNN for Spatial Resolution Enhancement

In order to improve the spatial resolution of a one-dimensional aperture synthesis (1-D AS) radiometer without increasing the size of the antenna array, the method of visibility extension (VE) is proposed in this article. In the VE method, prior information about the visibility distribution of various scenes is learnt by a residual convolutional neural network (ResCNN). Specifically, the relationship between the distribution of low-frequency visibility and that of high-frequency visibility is learnt. Then, the ResCNN is used to estimate the high-frequency visibility samples from the low-frequency visibility samples obtained by the AS system. Furthermore, the low- and high-frequency visibility samples are combined to reconstruct the brightness temperature image of the scene, to enhance the spatial resolution of AS. The simulation and experiment both demonstrate that the VE method can enhance the spatial resolution of 1-D AS

Tunable quantum order in bilayer Bi2Te3: Stacking dependent quantum spin Hall states

Recent years have seen the rising importance of interface stacking in determining the electronic properties of multilayer materials stemming from the interlayer coupling; however, the stacking effects on exotic topological quantum orders largely remain to be explored. Here, we show by first-principles studies that bilayer Bi2Te3 host stacking is dependent on quantum spin Hall effects, with a topological phase transition induced by a change in the interlayer stacking pattern. The spin-filtered helical edge states are concomitantly switched on/off along with the changing interlayer stacking pattern. Since few-layer Bi2Te3 has already been experimentally synthesized, the present finding opens an avenue for exploring the fundamental mechanisms and the practical implications of the quantum phenomena associated with band topology in this versatile and intriguing 2D material.</p

An intraoperative device to restore femoral offset in total hip arthroplasty

Abstract Background Leg length discrepancy (LLD) after total hip arthroplasty (THA) can lead to unsatisfactory outcome. Our objective was to design and evaluate a simple and reliable intraoperative device (Length-offset Lever) to minimize leg length discrepancy. Methods This device was used in 51 patients undergoing primary total hip replacements. The leg length discrepancy was measured pre- and postoperatively based on plain radiographs. Results Preoperative radiographic leg length discrepancy averaged 13.5 ± 6.2 mm. Leg length discrepancy showed significant improvement, with a postoperative average of 4.1 ± 2.3 mm (p < 0.0001). There were no complications associated with this device. Conclusions The ‘Length-offset Lever’ is a useful intraoperative tool to restore anatomic femoral offset and height of femoral head

Potential drivers and consequences of regional phosphate depletion in the western subtropical North Pacific

In regions of the nitrogen limited low latitude ocean, phosphate can also be depleted to levels initiating stress responses in marine microbes. Here, we associate a broad region of phosphate depletion in the subtropical North Pacific with different levels of phosphorus stress. Nutrient and aerosol addition experiments demonstrated primary nitrogen limitation of the bulk phytoplankton community, with supply of aerosols relieving this limitation. At northern sites with depleted phosphate, alkaline phosphatase activities were enhanced, indicating elevated phosphorus stress. Analysis of satellite- and model-derived aerosol loading showed that aerosol deposition was elevated in these regions. Surface rate measurements suggested that the regional enhancement in phosphate depletion was predominantly driven by elevated nitrogen fixation, likely stimulated by the coincident supply of aerosol iron. Such observations are important for predicting future biogeochemical responses in the subtropical North Pacific to changing aerosol supply