arXiv subjects

Qing Fang

Publications and source records attributed to Qing Fang.

5 recordsLinked to original sources

arXiv2025

Efficient Computation of Integer-constrained Cones for Conformal Parameterizations

We propose an efficient method to compute a small set of integer-constrained cone singularities, which induce a rotationally seamless conformal parameterization with low distortion. Since the problem only involves discrete variables, i.e., vertex-constrained positions, integer-constrained angles, and the number of cones, we alternately optimize these three types of variables to achieve tractable convergence. Central to high efficiency is an explicit construction algorithm that reduces the optimization problem scale to be slightly greater than the number of integer variables for determining the optimal angles with fixed positions and numbers, even for high-genus surfaces. In addition, we derive a new derivative formula that allows us to move the cones, effectively reducing distortion until convergence. Combined with other strategies, including repositioning and adding cones to decrease distortion, adaptively selecting a constrained number of integer variables for efficient optimization, and pairing cones to reduce the number, we quickly achieve a favorable tradeoff between the number of cones and the parameterization distortion. We demonstrate the effectiveness and practicability of our cones by using them to generate rotationally seamless and low-distortion parameterizations on a massive test data set. Our method demonstrates an order-of-magnitude speedup (30$\times$ faster on average) compared to state-of-the-art approaches while maintaining comparable cone numbers and parameterization distortion.

cs.GR↗

arXiv2025

A Multidimensional Self-Adaptive Numerical Simulation Framework for Semiconductor Boltzmann Transport Equation

This research addresses the numerical simulation of the Boltzmann transport equation for semiconductor devices by proposing a multidimensional self-adaptive numerical simulation framework. This framework is applied to two important generalized forms of the equation: a parabolic equation with singular properties on the unit disk and a continuity equation. The study enhances the alignment of numerical simulations with physical characteristics through polar coordinate transformation and variable drift-diffusion coefficients. Innovatively, a multidimensional adaptive mesh partitioning strategy for radius-angle-time is designed and combined with an adjustable finite difference scheme to construct a highly adaptive numerical simulation method. In the construction of discrete schemes, the Swartztrauber-Sweet method and the control volume method are employed to effectively eliminate the origin singularity caused by polar coordinate transformation. On the programming front, a parallelized MATLAB algorithm is developed to optimize code execution efficiency. Numerical comparative experiments demonstrate that the adaptive method improves the accuracy of the parabolic equation by 1 to 7 times and that of the continuity equation by 10% to 70% while maintaining computational efficiency, significantly enhancing numerical simulation accuracy with high stability. Furthermore, this study systematically verifies the algorithm's convergence, stability, and parameter sensitivity using error visualization and other means. It also explores optimal parameters and establishes tuning optimization criteria. The research provides theoretical support for high-precision and highly adaptive methods in semiconductor device simulation, demonstrating outstanding advantages in handling singular regions.

math.NA↗

arXiv2024

Photoexcited carriers transfer properties in a doped double quantum dots photocell

Identifying the behavior of photoexcited carriers is one method for empirically boosting their transfer efficiencies in doped double quantum dots (DQDs) photocells. The photoexcited carriers transfer qualities were assessed in this study by the output current, power, and output efficiency in the multi-photon absorption process for a doped DQDs photocell, and an optimization technique is theoretically obtained for this proposed photocell model. The results show that some structure parameters caused by doping, such as gaps, incoherent tunneling coupling, and symmetry of structure between two vertically aligned QDs, can remarkably control the photoexcited carriers transfer properties, and that slightly increasing the ambient temperature around room temperature is beneficial to the transfer performance in this doping DQDs photocell model. Thus, our scheme proves a way to optimized strategies for DQDs photocell.

cond-mat.mes-hall↗

arXiv2019

Topology Maintained Structure Encoding

Deep learning has been used as a powerful tool for various tasks in computer vision, such as image segmentation, object recognition and data generation. A key part of end-to-end training is designing the appropriate encoder to extract specific features from the input data. However, few encoders maintain the topological properties of data, such as connection structures and global contours. In this paper, we introduce a Voronoi Diagram encoder based on convex set distance (CSVD) and apply it in edge encoding. The boundaries of Voronoi cells is related to detected edges of structures and contours. The CSVD model improves contour extraction in CNN and structure generation in GAN. We also show the experimental results and demonstrate that the proposed model has great potentiality in different visual problems where topology information should be involved.

cs.CV↗

arXiv2017

Support-Free Hollowing for 3D Printing via Voronoi Diagram of Ellipses

Recent work has demonstrated that the interior material layout of a 3D model can be designed to make a fabricated replica satisfy application-specific demands on its physical properties such as resistance to external loads. A widely used practice to fabricate such models is by layer-based additive manufacturing (AM) or 3D printing, which however suffers from the problem of adding and removing interior supporting structures. In this paper, we present a novel method for generating support-free elliptic hollowing for 3D shapes which can entirely avoid additional supporting structures. To achieve this, we perform the ellipse hollowing in the polygons on parallel section planes and protrude the ellipses of one plane to its neighboring planes. To pack the ellipses in a polygon, we construct the Voronoi diagram of ellipses to efficiently reason the free-space around the ellipses and other geometric features by taking advantage of the available algorithm for the efficient and robust construction of the Voronoi diagram of circles. We demonstrate the effectiveness and feasibility of our proposed method by generating interior designs for and printing various 3D shapes.

cs.CG↗