检索结果-南通市图书馆

Fusing Geometrical and Visual Information via Superpoints for the Semantic Segmentation of 3D Road Scenes

在线全文

学校读者我要写书评

暂无评论

Tsinghua Science and Technology 2020年第4期25卷 498-507页

作者： liuyuan Deng Ming Yang Zhidong Liang Yuesheng He Chunxiang Wang the Department of Automation Shanghai Jiao Tong UniversityShanghai 200240China the Key Laboratory of System Control and Information Processing Ministry of Education of ChinaShanghai 200240China the Research Institute of Robotics Shanghai Jiao Tong UniversityShanghai 200240China

This paper addresses the problem of the semantic segmentation of large-scale 3D road scenes by incorporating the complementary advantages of point clouds and *** make full use of geometrical and visual information,this paper extracts 3D geometric features from a point cloud using a deep neural network for 3D semantic segmentation and extracts 2D visual features from images using a Convolutional Neural Network(CNN)for 2D semantic *** order to bridge the features of the two modalities,this paper uses superpoints as an intermediate representation to connect the 2D features with the 3D features.A superpoint-based pooling method is proposed to fuse the features from the two different modalities for joint *** evaluate the approach,the paper generates 3D scenes from the Virtual KITTI *** results of the experiments demonstrate that the proposed approach is capable of segmenting large-scale 3D road scenes based on the compact and semantically homogeneous superpoints,and that it achieves considerable improvements over the 2D image and 3D point cloud semantic segmentation methods.

关键词： scene understanding point cloud semantic segmentation multi-modal information fusion deep learning

On cyclic oscillation in granular gas

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2005年第8期50卷 726-730页

作者： MIAOTiande liuyuan MIAOFuxing MUQingsong DeparmentofMechanics LanzhouUniversityLanzhou730000China DeparmentofMechanics LanzhouUniversityLanzhou730000China//SchoolofCivilEngineeringLanzhouJiaotongUniversityLanzhou730070China

In a Maxwell’s demon experiment on a dilute granular gas made up of two species of particles placed in two closely connected containers, a cyclic oscillation similar to the chemical oscillations is recognized that the two species of particles cluster alternately in the two containers. Then the nonlinear behavior is qualitatively explained based on a flux model.

关键词：粒状气体循环摆动非线性运动流量模型

Fabrication of High Quality Three-Dimensional Photonic Crystals

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2004年第7期21卷 1289-1291页

作者： HUXiao-Yong liuyuan-Hao CHENGBing-Ying ZHANGDao-Zhong MENGQing-Bo OpticalPhysicsLaboratory InstituteofPhysicsChineseAcademyofSciencesBeijing100080 StateKeyLaboratoryforSurfacePhysics InstituteofPhysicsChineseAcademyofSciencesBeijing100080

High quality colloidal photonic crystals made from polystyrene spheres with diameter 240 nm are fabricated by the vertical deposition method. The scanning electron microscopy (SEM) and the transmittance spectrum are used to characterize the properties of the photonic crystal. The SEM images show that there are few lattice defects. The transmittance of the photonic crystal is above 75% in the pass band at 700 nm and is lower than 5% at the centre of the band gap, respectively. It is found that proper concentration is a very important factor to fabricate the photonic crystal when the diameter of the spheres is lower than 300 nm.

关键词： Soft matter liquids and polymers Condensed matter: electrical magnetic and optical Surfaces interfaces and thin films Optics quantum optics and lasers Condensed matter: structural mechanical & thermal Chemical physics and physical chemistry

Phase Transitions of a Dilute O（n） Model

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2004年第6期41卷 911-916页

作者： GUOWen-An HenkW.J.B1ote liuyuan-Yuan PhysicsDepartment BeijingNormalUniversityBeijing100875~China FacultyofAppliedSciences DelftUniversityofTechnologyP.O.Box50462600GADelftTheNetherlands

We investigate tricritical behavior of the O(n) model in two dimensions by means of transfer-matrix and finite-size scaling methods. For this purpose we consider an O(n) symmetric spin model on the honeycomb lattice with vacancies; the tricritical behavior is associated with the percolation threshold of the vacancies. The vacancies are represented by face variables on the elementary hexagons of thelattice. We apply a mapping of the spin degrees of freedom model on a non-intersecting-loop model, in which the number n of spin components assumes the role of a continuously variable parameter. This loop model serves as a suitable basis for the construction of the transfer *** results reveal the existence of a tricritical line, parametrized by n, which connects the known universality classes of the tricritical Ising model and the theta point describing the collapse of a polymer. On the other side of theIsing point,the tricritical line extends to the n = 2 point describing a tricritical O(2) model.

关键词： phase transition dilute O(n) model tricritical behavior transfer matrix

The mid-high latitude whistler mode chorus waves observed around substorm onsets

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2008年第10期51卷 1648-1658页

作者： YANG JunYing CAO JinBin YAN ChunXiao LI liuyuan MA YuDuan Key Laboratory of Space Weather Center for Space Science and Applied ResearchChinese Academy of SciencesBeijing 100080China Graduate University of Chinese Academy of Sciences Beijing 100039China

Using the data of LFEW/TC-2, we studied the dawn side chorus around substorm onsets during a strong geomagnetic storm in November 2004. During this storm, LFEW/TC-2 observed 14 dawnside chorus events. Nine of them were associated with substorms and occurred within 40 min around the substorm onsets. The fre-quencies of waves have a very good correlation with the half equatorial electron cyclotron frequencies. Chorus can be excited in the region near magnetic equato-rial plane and then propagate to the mid and high latitudes. When the wave fre-quencies reach the local lower hybrid frequencies, chorus can be reflected due to the lower hybrid resonance. The time delay between the chorus and its echo is about 28 min. Previous observations show that the chorus can propagate at most to the magnetic latitudes of 40°. LFEW/ TC-2 found for the first time that the chorus in space could propagate to the magnetic latitude of 70°. Since most of the previous chorus observations are made close to the magnetic equatorial plane, our results are important for the studies of excitation and propagation of whistler mode wave, and relevant relativistic electron acceleration in the magnetosphere.

关键词： chorus substorm onset electron acceleration

Response of magnetic fields at geosynchronous orbit and on the ground to the sudden changes of IMF B_Z

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2014年第2期57卷 360-367页

作者： DONG YiXuan CAO JinBin LIU WenLong ZHANG Lei LI liuyuan Beijing Institute of Spacecraft Environment Engineering Space Science Institute School of Astronautics Beihang University Institute of Telecommunication Satellite China Academy of Space Technology

The rapid change in the Earth’s magnetosphere caused by solar wind disturbances has been an important part of the solar wind-magnetosphere *** most of the previous studies focused on the perturbation of the Earth’s magnetic field caused by solar wind dynamic pressure *** this paper,we studied the response of geosynchronous magnetic field and the magnetic field to the rapid southward turning of interplanetary magnetic field during the interval 1350 1420 UT on 7May *** this event,BZ component of the interplanetary magnetic field decreased from 15 nT to 10 nT within 3 min(1403 1406 UT).The geosynchronous magnetic field measured by three geosynchronous satellites(GOES 10 12)first increased and then *** variations of magnetic field strength in the morning sector(9 10 LT)were much larger than those in the dawn sector(5 LT).Meanwhile,the H components of geomagnetic field on the ground have similar response features but exhibit latitude and LT dependent *** with H components,the D components do not have regular *** the solar wind dynamical pressure encounters small variations,the magnetic field both in space and on the ground does not display similar ***,the increase of geomagnetic field in the dawn sector is caused by the southward turning of IMF(interplanetary magnetic field)*** results will help to better understand the coupling process of geomagnetic filed and interplanetary magnetic field.

关键词： interplanetary magnetic field (IMF) solar wind geosynchronous orbit geomagnetic field

Fast Frequency Offset Acquisition and Accurate Tracking in OFDM Systems

在线全文

学校读者我要写书评

暂无评论

The Journal of China Universities of Posts and Telecommunications 2004年第1期11卷 6-11页

作者： ZHANGZhong-shan ZHAOMing liuyuan-an (WirelessCommunicationCenter.BeijingUniversityofPostsandTelecommunications Beijing100876P.R.China

A new carrier frequency offset estimation scheme for Orthogonal Frequency-Division Multiplexing (OFDM) systems is proposed. The carrier frequency offset estimation includes acquisition and tracking. The acquisition range of the proposed algorithm is as large as one half of the overall signal bandwidth. Comparison of the proposed scheme with Schmidl's algorithm by computer simulation illustrates the superior performance of the proposed scheme with regard to estimation accuracy in both AWGN channel and multipath channels.

关键词： synchronization frequency offset estimation OFDM

Performance Modeling of the Fast and Reliable Two-Layer Retransmission for CDMA Systems

在线全文

学校读者我要写书评

暂无评论

The Journal of China Universities of Posts and Telecommunications 2005年第1期12卷 101-106页

作者： LIUFang KONGJian WANGWen-bo liuyuan-an BeijingUniversityofPostsandTelecommunications Beijing100876P.R.China

In this paper, an analytical model of two-layer retransmission scheme isproposed for CDMA systems in which selective repeat Automatic Repeat reQuest (ARQ) is used at theRadio Link Protocol (RLP) layer and n-channel Stop-and-Wait hybrid ARQ at the Medium Access control(MAC) layer. The retransmission mechanism in the RLP has considerable amount of delay associatedwith it, which might not be able to sustain real-time communications with strict delay *** done at a lower layer, such as the MAC, enhance the performance of the system. Weshow how the joint reliability varies with respect to the maximum retransmission number of RLP layerand MAC layer. We also consider that soft packet combining at the MAC layer of receiver issupported, which effectively lowers the Frame Error Rate (FER). Compared with the RLP Layer ARQ usedin IS-99, the two-layer retransmission scheme shows shorter packet transmission delay and smallerpacket error rate. The results show that it can offer the faster and more reliable communicationthan conventional scheme used in IS-99.

关键词： TCP ARQ CDMA

Loading Schemes for Downlink OFDMA Systems

在线全文

学校读者我要写书评

暂无评论

The Journal of China Universities of Posts and Telecommunications 2004年第4期11卷 86-90页

作者： KONGJian LIUFang WANGWen-bo liuyuan-an SchoolofTelecommunicationEngineering BeijingUniversityofPostsandTelecommunicationsBeijing100876P.R.China

In this paper we study the subcarrier and bit allocation strategies for downlink OFDMA *** opti-mization objective is to find optimum subcarrier and bit assignment minimizing the total transmitted power with the con-straints on BER and data rate for all *** divide this problem into three steps:resource allocation,subcarrier assign-ment and single-user power and bit *** the first two steps we propose new *** loading schemesconstitute by combining these algorithms as well as algorithms proposed in Ref.[6].Simulation results demonstrate thatour proposed suboptimal loading scheme can achieve performance closer to the near optimal algorithm in Ref.[8]withmuch lower complexity than schemes in Ref.[6].

关键词： loading downlink OFDMA