Northwestern Polytechnical University

About: Northwestern Polytechnical University is a education organization based out in Xi'an, China. It is known for research contribution in the topics: Microstructure & Computer science. The organization has 47497 authors who have published 56067 publications receiving 657071 citations. The organization is also known as: Xīběi Gōngyè Dàxué & State Northwest Institute of Engineering.

A competition on generalized software-based face presentation attack detection in mobile scenarios

Abstract: In recent years, software-based face presentation attack detection (PAD) methods have seen a great progress. However, most existing schemes are not able to generalize well in more realistic conditions. The objective of this competition is to evaluate and compare the generalization performances of mobile face PAD techniques under some real-world variations, including unseen input sensors, presentation attack instruments (PAI) and illumination conditions, on a larger scale OULU-NPU dataset using its standard evaluation protocols and metrics. Thirteen teams from academic and industrial institutions across the world participated in this competition. This time typical liveness detection based on physiological signs of life was totally discarded. Instead, every submitted system relies practically on some sort of feature representation extracted from the face and/or background regions using hand-crafted, learned or hybrid descriptors. Interesting results and findings are presented and discussed in this paper.

Breast ultrasound image segmentation: a survey

Abstract: Breast cancer is the most common form of cancer among women worldwide. Ultrasound imaging is one of the most frequently used diagnostic tools to detect and classify abnormalities of the breast. Recently, computer-aided diagnosis (CAD) systems using ultrasound images have been developed to help radiologists to increase diagnosis accuracy. However, accurate ultrasound image segmentation remains a challenging problem due to various ultrasound artifacts. In this paper, we investigate approaches developed for breast ultrasound (BUS) image segmentation. In this paper, we reviewed the literature on the segmentation of BUS images according to the techniques adopted, especially over the past 10 years. By dividing into seven classes (i.e., thresholding-based, clustering-based, watershed-based, graph-based, active contour model, Markov random field and neural network), we have introduced corresponding techniques and representative papers accordingly. We have summarized and compared many techniques on BUS image segmentation and found that all these techniques have their own pros and cons. However, BUS image segmentation is still an open and challenging problem due to various ultrasound artifacts introduced in the process of imaging, including high speckle noise, low contrast, blurry boundaries, low signal-to-noise ratio and intensity inhomogeneity To the best of our knowledge, this is the first comprehensive review of the approaches developed for segmentation of BUS images. With most techniques involved, this paper will be useful and helpful for researchers working on segmentation of ultrasound images, and for BUS CAD system developers.

Ultrathin flexible poly(vinylidene fluoride)/MXene/silver nanowire film with outstanding specific EMI shielding and high heat dissipation

Abstract: Herein, ultrathin flexible poly(vinylidene fluoride) (PVDF) composite films with MXenes and silver nanowires (AgNWs) were prepared via solution casting method. Due to the synergistic effects induced by MXene/AgNW network, the electrical conductivity, thermal conductivity, and electromagnetic interference (EMI) shielding of PVDF/MXene/AgNW films were higher than the corresponding PVDF/MXene and PVDF/AgNW films, and the values of PVDF/MXene/AgNW films at 300 μm thickness were reached 1.08 S/m, 0.78 W/(mK), and 25.87 dB, respectively. Additionally, due to the ultrathin thickness, the high specific shielding value of 1091 dB cm2/g was achieved. Moreover, the total shielding effectiveness increased from 19.31 to 41.26 dB as the thickness was increased from 150 to 600 μm. The main EMI shielding mechanism is contribution to the absorption. The possible synergistic mechanisms for enhancing EMI shielding and mechanical performance are discussed. This work offers a promising solution for EMI shielding challenges in modern smaller and smaller wearable devices. Ultrathin flexible PVDF/MXenes/AgNWs films shows 1.08 S/m electrical conductivity, 0.78 W/(mK) thermal conductivity and 1091 dBcm2/g specific EMI shielding.

Fluorinated, Sulfur-Rich, Covalent Triazine Frameworks for Enhanced Confinement of Polysulfides in Lithium-Sulfur Batteries.

Abstract: Lithium–sulfur battery represents a promising class of energy storage technology owing to its high theoretical energy density and low cost. However, the insulating nature, shuttling of soluble polysulfides and volumetric expansion of sulfur electrodes seriously give rise to the rapid capacity fading and low utilization. In this work, these issues are significantly alleviated by both physically and chemically restricting sulfur species in fluorinated porous triazine-based frameworks (FCTF-S). One-step trimerization of perfluorinated aromatic nitrile monomers with elemental sulfur allows the simultaneous formation of fluorinated triazine-based frameworks, covalent attachment of sulfur and its homogeneous distribution within the pores. The incorporation of electronegative fluorine in frameworks provides a strong anchoring effect to suppress the dissolution and accelerate the conversion of polysulfides. Together with covalent chemical binding and physical nanopore-confinement effects, the FCTF-S demonstrates ...