arXiv subjects

Liang Zhu

Publications and source records attributed to Liang Zhu.

29 records · Page 2Linked to original sources

arXiv2020

An improved sample size calculation method for score tests in generalized linear models

Self and Mauritsen (1988) developed a sample size determination procedure for score tests in generalized linear models under contiguous alternatives. Its performance may deteriorate when the effect size is large. We propose a modification of the Self-Mauritsen method by taking into account of the variance of the score statistic under both the null and alternative hypotheses, and extend the method to noninferiority trials. The modified approach is employed to calculate the sample size for the logistic regression and negative binomial regression in superiority and noninferiority trials. We further explain why the formulae recently derived by Zhu and Lakkis tend to underestimate the required sample size for the negative binomial regression. Numerical examples are used to demonstrate the accuracy of the proposed method.

stat.ME↗

arXiv2020

MOTS: Multiple Object Tracking for General Categories Based On Few-Shot Method

Most modern Multi-Object Tracking (MOT) systems typically apply REID-based paradigm to hold a balance between computational efficiency and performance. In the past few years, numerous attempts have been made to perfect the systems. Although they presented favorable performance, they were constrained to track specified category. Drawing on the ideas of few shot method, we pioneered a new multi-target tracking system, named MOTS, which is based on metrics but not limited to track specific category. It contains two stages in series: In the first stage, we design the self-Adaptive-matching module to perform simple targets matching, which can complete 88.76% assignments without sacrificing performance on MOT16 training set. In the second stage, a Fine-match Network was carefully designed for unmatched targets. With a newly built TRACK-REID data-set, the Fine-match Network can perform matching of 31 category targets, even generalizes to unseen categories.

cs.CV↗

arXiv2020

Tailored pore gradient in phenolic membranes for adjustable permselectivity by leveraging different poloxamers

Cost-affordable phenolic membranes having gradient nanostructures can be facilely synthesized from resol oligomers in the presence of ZnCl2 and poloxamers. The gradient nanostructures are formed by stacking phenolic nanoparticles with gradually enlarged diameters as the distance from the upper surface increases. The use of poloxamers for creating gelation surroundings is of great significance for controlling the growth of phenolic nanoparticles, which in turn dictates the performance of the phenolic membranes thus-produced. Hence, a study of the effects of poloxamers species on the preparation of the phenolic membranes is highly demanded since such robust membranes have much potential to be scale up for mass production. Herein, the poloxamer Pluronic F127 (EO106-PO70-EO106; EO = ethyleneoxide, PO = propyleneoxide) was introduced in the membrane-forming formulations. As opposed to P123 (EO20-PO70-EO20) that we used previously, F127 possessing extended PEO chains can delay the gelation during membrane formation. Hence, the phenolic nucleates are able to grow for longer durations, leading to the generation of more distinct gradient nanostructures in the phenolic membranes. Enhanced permeance can then be realized with F127-derived phenolic membranes. We also demonstrate that L31 (EO1-PO22-EO1) with merely single terminal EO units at the ends of the PPO block could be used to prepare gradient phenolic membranes. This work is not only much helpful to deeply understand the design of the structural gradient in phenolic membranes, but capable of sheding light on the development of such intriguing structures for water purification.

physics.app-ph↗

arXiv2020

Tunable THz generation and enhanced nonlinear effects with active and passive graphene hyperbolic metamaterials

The active and nonlinear graphene properties are limited due to weak light matter interaction between the ultrathin graphene and the incident light. In this work, we present enhanced nonlinear effects at the low terahertz (THz) range by designing a new patterned graphene hyperbolic metamaterial (GHMM). More specifically, it is demonstrated that the third harmonic generation (THG) can be significantly enhanced by the proposed GHMM due to the field enhancement at the resonance as well as the supported slow light response that fosters strong light matter interaction.

physics.optics↗

arXiv2019

Dual Path Multi-Scale Fusion Networks with Attention for Crowd Counting

The task of crowd counting in varying density scenes is an extremely difficult challenge due to large scale variations. In this paper, we propose a novel dual path multi-scale fusion network architecture with attention mechanism named SFANet that can perform accurate count estimation as well as present high-resolution density maps for highly congested crowd scenes. The proposed SFANet contains two main components: a VGG backbone convolutional neural network (CNN) as the front-end feature map extractor and a dual path multi-scale fusion networks as the back-end to generate density map. These dual path multi-scale fusion networks have the same structure, one path is responsible for generating attention map by highlighting crowd regions in images, the other path is responsible for fusing multi-scale features as well as attention map to generate the final high-quality high-resolution density maps. SFANet can be easily trained in an end-to-end way by dual path joint training. We have evaluated our method on four crowd counting datasets (ShanghaiTech, UCF CC 50, UCSD and UCF-QRNF). The results demonstrate that with attention mechanism and multi-scale feature fusion, the proposed SFANet achieves the best performance on all these datasets and generates better quality density maps compared with other state-of-the-art approaches.

cs.CV↗

arXiv2018

Tunable Terahertz Amplification Based on Photoexcited Active Graphene Hyperbolic Metamaterials

The efficient amplification and lasing of electromagnetic radiation at terahertz (THz) frequencies is a non-trivial task achieved mainly by quantum cascade laser configurations with limited tunability and narrowband functionality. There is a strong need of compact and efficient THz electromagnetic sources with reconfigurable operation in a broad frequency range. Photoexcited graphene can act as the gain medium to produce coherent radiation at low THz frequencies but its response is very weak due to its ultrathin thickness. In this work, we demonstrate an alternative design to achieve efficient tunable and compact THz amplifiers and lasers with broadband operation based on active THz hyperbolic metamaterials (HMM) designed by multiple stacked photoexcited graphene layers separated by thin dielectric sheets. The hyperbolic THz response of the proposed ultrathin active HMM is analytically and numerically studied and characterized. When the graphene-based HMM structure is periodically patterned, a broadband slow-wave propagation regime is identified, thanks to the hyperbolic dispersion. In this scenario, reconfigurable amplification of THz waves in a broad frequency range is obtained, which can be made tunable by varying the quasi-Fermi level of graphene. We demonstrate that the THz response of the presented tunable THz amplifiers or lasers is controlled by the incident optical pumping (photodoping) and the loaded dielectric materials in the HMM waveguide array, an interesting property that can have great potential for THz amplification, emission, and sensing applications.

physics.optics↗

arXiv2018

Qiniu Submission to ActivityNet Challenge 2018

In this paper, we introduce our submissions for the tasks of trimmed activity recognition (Kinetics) and trimmed event recognition (Moments in Time) for Activitynet Challenge 2018. In the two tasks, non-local neural networks and temporal segment networks are implemented as our base models. Multi-modal cues such as RGB image, optical flow and acoustic signal have also been used in our method. We also propose new non-local-based models for further improvement on the recognition accuracy. The final submissions after ensembling the models achieve 83.5% top-1 accuracy and 96.8% top-5 accuracy on the Kinetics validation set, 35.81% top-1 accuracy and 62.59% top-5 accuracy on the MIT validation set.

cs.CV↗

arXiv2018

Land use mapping in the Three Gorges Reservoir Area based on semantic segmentation deep learning method

The Three Gorges Dam, a massive cross-century project spans the Yangtze River by the town of Sandouping, located in Yichang, Hubei province, China, was built to provide great power, improve the River shipping, control floods in the upper reaches of the Yangtze River, and increase the dry season flow in the middle and lower reaches of the Yangtze River. Benefits are enormous and comprehensive. However, the social and environmental impacts are also immense and far-reaching to its surrounding areas. Mapping land use /land cover changed (LUCC) is critical for tracking the impacts. Remote sensing has been proved to be an effective way to map and monitor land use change in real time and in large areas such as the Three Gorges Reservoir Area(TGRA) by using pixel based or oriented based classifier in different resolution. In this paper, we first test the state of the art semantic segmentation deep learning classifiers for LUCC mapping with 7 categories in the TGRA area with rapideye 5m resolution data. The topographic information was also added for better accuracy in mountain area. By compared with the pixel-based classifier, the semantic segmentation deep learning method has better accuracy and robustness at 5m resolution level.

cs.CV↗

arXiv2016

Multilayer network analysis of nuclear reactions

The nuclear reaction network is usually studied via precise calculation of differential equation sets, and much research interest has been focused on the characteristics of nuclides, such as half-life and size limit. In this paper, however, we adopt the methods from both multilayer and reaction networks, and obtain a distinctive view by mapping all the nuclear reactions in JINA REACLIB database into a directed network with 4 layers: neutron, proton, $^4$He and the remainder. The layer names correspond to reaction types decided by the currency particles consumed. This combined approach reveals that, in the remainder layer, the $β$-stability has high correlation with node degree difference and overlapping coefficient. Moreover, when reaction rates are considered as node strength, we find that, at lower temperatures, nuclide half-life scales reciprocally with its out-strength. The connection between physical properties and topological characteristics may help to explore the boundary of the nuclide chart.

nucl-th↗

arXiv2016

Photoluminescence of InGaAs/GaAsBi/InGaAs type-II quantum well grown by gas source molecular beam epitaxy

InGaAs/GaAsBi/InGaAs quantum wells (QWs) were grown on GaAs substrates by gas source molecular beam epitaxy for realizing the type II band-edge line-up. Both type I and type II transitions were observed in the Bi containing W QWs and the photoluminescence intensity was enhanced in the sample with a high Bi content, which is mainly due to the improvement of carrier confinement. Blue-shift of type II transitions at high excitation power density was observed and ascribed to the band-bending effect. The calculated transition energies based on 8 band k.p model fit well with the experiment results. The experimental and theoretical results show that the type-II QW design is a new promising candidate for realizing long wavelength GaAs-based light emitting devices near 1.3 um.

cond-mat.mtrl-sci↗

arXiv2013

Study on the Energy Dependence of the Radii of Jets by the HBT Correlation Method in e+e- collisions

The energy dependence of the radii size of jets are studied in detail by the HBT correlation method using Monte Carlo Simulation generator Jetset7.4 to produce 40,000,000 events of e$^+$e$^-$ collisions at $\sqrt s =30$, 50, 70, 91.2, 110, 130, 150 and 170 GeV. The radii of jets are measured using the HBT correlation method with the indistinguishability of identical final state pions. It is found that the average radii of quark-jets and gluon-jets are independent of the c.m. energy of e$^+$e$^-$ collisions. The average radius of quark-jets are obviously larger than that of gluon-jets. The invariable average radii of quark-jets and gluon-jets in e$^+$e$^-$ collisions are obtained at the end of parton evolvement.

hep-ph↗