检索结果-南通市图书馆

Beam Training and Tracking in mmWave Communication:A Survey

在线全文

学校读者我要写书评

暂无评论

China Communications 2024年第6期21卷 1-22页

作者： Wang yi Wei Zhiqing Feng Zhiyong Yangtze Delta Region Institute(Quzhou) University of Electronic Science and Technology of ChinaQuzhou 324003China School of Information and Communication Engineering University of Electronic Science and Technology of ChinaChengdu 611731China Key Laboratory of Universal Wireless Communications Ministry of EducationBeijing University of Posts and TelecommunicationsBeijing 100876China

Communicating on millimeter wave(mmWave)bands is ushering in a new epoch of mobile communication which provides the availability of 10 Gbps high data rate transmission.However,mmWave links are easily prone to short transmission range communication because of the serious free space path loss and the blockage by obstacles.To overcome these challenges,highly directional beams are exploited to achieve robust links by hybrid beamforming.Accurately aligning the transmitter and receiver beams,i.***.beam training,is vitally important to high data rate transmission.However,it may cause huge overhead which has negative effects on initial access,handover,and tracking.Besides,the mobility patterns of users are complicated and dynamic,which may cause tracking error and large tracking latency.An efficient beam tracking method has a positive effect on sustaining robust links.This article provides an overview of the beam training and tracking technologies on mmWave bands and reveals the insights for future research in the 6th Generation(6G)mobile network.Especially,some open research problems are proposed to realize fast,accurate,and robust beam training and tracking.We hope that this survey provides guidelines for the researchers in the area of mmWave communications.

关键词： 6G beam tracking beam training beamforming mmWave

Design,fabrication,and characterization of hierarchical mechanical metamaterials

在线全文

学校读者我要写书评

暂无评论

Frontiers of Mechanical Engineering 2024年第1期19卷 73-83页

作者： Jian SONG Junfei YAN Bengang yi Automotive Engineering Research Institute BYD Auto Industry Co.Ltd.Shenzhen 518000China College of Civil and Transportation Engineering Shenzhen UniversityShenzhen 518060China

Natural mechanical materials,such as bamboo and bone,often exhibit superior specific mechanical properties due to their hierarchical porous architectures.Using the principle of hierarchy as inspiration can facilitate the development of hierarchical mechanical metamaterials(HMMs)across multiple length scales via 3D printing.In this work,we propose self-similar HMMs that combine octet-truss(OCT)architecture as the first and second orders,with cubic architecture as the third or more orders.These HMMs were fabricated using stereolithography 3D printing,with the length sizes ranging from approximately 200µm to the centimeter scale.The compressive stress–strain behaviors of HMMs exhibit a zigzag characteristic,and the toughness and energy absorption can be significantly enhanced by the hierarchical architecture.The compressive moduli are comparable to that of natural materials,and the strengths are superior to that of most polymer/metal foams,alumina hollow/carbon lattices,and other natural materials.Furthermore,the flexural stress–strain curves exhibit a nonlinear behavior,which can be attributed to the hierarchical architecture and local damage propagation.The relatively high mechanical properties can be attributed to the synergistic effect of the stretch-dominated OCT architecture and the bending-dominated cube architecture.Lastly,an ultralight HMM-integrated unmanned aerial vehicle(HMM-UAV)was successfully designed and printed.The HMM-UAV is~85%lighter than its bulk counterpart,remarkably extending the flight duration time(~53%).This work not only provides an effective design strategy for HMMs but also further expands the application benchmark of HMMs.

关键词： 3D printing mechanical metamaterials hierarchical architecture mechanical behavior unmanned aerial vehicle(UAV)

Fatigue-resistant Hydrogels

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2024年第1期40卷 64-77页

作者： LI Luofei LEI Hai CAO yi Collaborative Innovation Center of Advanced Microstructures National Laboratory of Solid State MicrostructureDepartment of PhysicsNanjing UniversityNanjing 210093P.R.China Department of Physics Zhejiang UniversityHangzhou 310027P.R.China

Hydrogels have been extensively studied for applications in various fields, such as tissue engineering and soft robotics, as determined by their mechanical properties. The mechanical design of hydrogels typically focuses on the modulus, toughness, and deformability. These characteristics play important roles and make great achievements for hydrogel use. In recent years, a growing body of research has concentrated on the fatigue property of hydrogels, which determines their resistance to crack propagation in the networks during cyclic mechanical loads for applications. However, knowledge of hydrogel fatigue behavior remains notably deficient. Here, we present a brief overview of the fatigue behavior of hydrogels, encompassing the general experimental methods to measure the fatigue property and fundamental theoretical calculation models. Then, we highlight multiple strategies to enhance the fatigue resistance of hydrogels. Finally, we present our perspectives on fatigue-resistant hydrogels, outstanding challenges and potential directions for future research.

关键词： Hydrogel Fatigue-resistant Fracture

Atomistic study on the microscopic mechanism of grain boundary embrittlement induced by small dense helium bubbles in iron

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2024年第3期35卷 84-95页

作者： Lei Peng Yong-Jie Sun Jing-yi Shi yi-Fei Liu Shang-Ming Chen Liu-Liu Li State Key Laboratory of Particle Detection and Electronics University of Science and Technology of ChinaHefei 230026China School of Nuclear Science and Technology University of Science and Technology of ChinaHefei 230027China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of ChinaChengdu 610213China

The helium bubbles induced by 14 MeV neutron irradiation can cause intergranular fractures in reduced activation ferritic martensitic steel,which is a candidate structural material for fusion reactors.In order to elucidate the susceptibility of different grain boundaries(GBs)to helium-induced embrittlement,the tensile fracture processes of 10 types of GBs with and without helium bubbles in body-centered cubic(bcc)iron at the relevant service temperature of 600 K were investigated via molecular dynamics methods.The results indicate that in the absence of helium bubbles,the GBs studied here can be classified into two distinct categories:brittle GBs and ductile GBs.The atomic scale analysis shows that the plastic deformation of ductile GB at high temperatures originates from complex plastic deformation mechanisms,including the Bain/Burgers path phase transition and deformation twinning,in which the Bain path phase transition is the most dominant plastic deformation mechanism.However,the presence of helium bubbles severely inhibits the plastic deformation channels of the GBs,resulting in a significant decrease in elongation at fractures.For bubble-decorated GBs,the ultimate tensile strength increases with the increase in the misorientation angle.Interestingly,the coherent twin boundary∑3{112}was found to maintain relatively high fracture strength and maximum failure strain under the influence of helium bubbles.

关键词： Helium bubble Grain boundary Embrittlement Reduced activation ferritic martensitic steel Molecular dynamics Bain path

Differentially private SGD with random features

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics(A Journal of Chinese Universities) 2024年第1期39卷 1-23页

作者： WANG yi-guang GUO Zheng-chu Polytechnic Institute of Zhejiang University Zhejiang UniversityHangzhou 310015China School of Mathematical Sciences Zhejiang UniversityHangzhou 310058China

In the realm of large-scale machine learning,it is crucial to explore methods for reducing computational complexity and memory demands while maintaining generalization performance.Additionally,since the collected data may contain some sensitive information,it is also of great significance to study privacy-preserving machine learning algorithms.This paper focuses on the performance of the differentially private stochastic gradient descent(SGD)algorithm based on random features.To begin,the algorithm maps the original data into a lowdimensional space,thereby avoiding the traditional kernel method for large-scale data storage requirement.Subsequently,the algorithm iteratively optimizes parameters using the stochastic gradient descent approach.Lastly,the output perturbation mechanism is employed to introduce random noise,ensuring algorithmic privacy.We prove that the proposed algorithm satisfies the differential privacy while achieving fast convergence rates under some mild conditions.

关键词： learning theory differential privacy stochastic gradient descent random features reproducing kernel Hilbert spaces

Improved multi-scale inverse bottleneck residual network based on triplet parallel attention for apple leaf disease identification

在线全文

学校读者我要写书评

暂无评论

Journal of Integrative Agriculture 2024年第3期23卷 901-922页

作者： Lei Tang Jizheng yi Xiaoyao Li College of Computer&Information Engineering Central South University of Forestry and TechnologyChangsha 410004China Yuelushan Laboratory Carbon Sinks Forests Variety Innovation Center Changsha 410000China

Accurate diagnosis of apple leaf diseases is crucial for improving the quality of apple production and promoting the development of the apple industry. However, apple leaf diseases do not differ significantly from image texture and structural information. The difficulties in disease feature extraction in complex backgrounds slow the related research progress. To address the problems, this paper proposes an improved multi-scale inverse bottleneck residual network model based on a triplet parallel attention mechanism, which is built upon ResNet-50, while improving and combining the inception module and ResNext inverse bottleneck blocks, to recognize seven types of apple leaf(including six diseases of alternaria leaf spot, brown spot, grey spot, mosaic, rust, scab, and one healthy). First, the 3×3 convolutions in some of the residual modules are replaced by multi-scale residual convolutions, the convolution kernels of different sizes contained in each branch of the multi-scale convolution are applied to extract feature maps of different sizes, and the outputs of these branches are multi-scale fused by summing to enrich the output features of the images. Second, the global layer-wise dynamic coordinated inverse bottleneck structure is used to reduce the network feature loss. The inverse bottleneck structure makes the image information less lossy when transforming from different dimensional feature spaces. The fusion of multi-scale and layer-wise dynamic coordinated inverse bottlenecks makes the model effectively balances computational efficiency and feature representation capability, and more robust with a combination of horizontal and vertical features in the fine identification of apple leaf diseases. Finally, after each improved module, a triplet parallel attention module is integrated with cross-dimensional interactions among channels through rotations and residual transformations, which improves the parallel search efficiency of important features and the recognition rate of the network with relatively small com

关键词： multi-scale module inverse bottleneck structure triplet parallel attention apple leaf disease

Incidence of surgical site infection in minimally invasive colorectal surgery

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastrointestinal Surgery 2024年第4期16卷 1121-1129页

作者： Lu-Ting Ni Ru Zhao yi-Ru Ye yi-Ming Ouyang Xin Chen Department of Surgery The First Affiliated Hospital of Soochow UniversitySuzhou 215000Jiangsu ProvinceChina

BACKGROUND Surgical site infection(SSI)is a common complication of colorectal surgery.Minimally invasive surgery notably reduces the incidence of SSI.This study aimed to compare the incidences of SSI after robot-assisted colorectal surgery(RACS)vs that after laparoscopic assisted colorectal surgery(LACS)and to analyze associated risk factors for SSI in minimally invasive colorectal surgery.AIM To compare the incidences of SSI after RACS and LACS,and to analyze the risk factors associated with SSI after minimally invasive colorectal surgery.METHODS Clinical data derived from patients who underwent minimally invasive colorectal surgery between October 2020 and October 2022 at the First Affiliated Hospital of Soochow University were collated.Differences in clinical characteristics and surgeryrelated information associated with RACS and LACS were compared,and possible risk factors for SSI were identified.RESULTS A total of 246 patients(112 LACS and 134 RACS)were included in the study.Fortythree(17.5%)developed SSI.The proportions of patients who developed SSI were similar in the two groups(17.9%vs 17.2%,P=0.887).Diabetes mellitus,intraoperative blood loss≥100 mL,and incision length were independent risk factors for SSI.Possible additional risk factors included neoadjuvant therapy,lesion site,and operation time.CONCLUSION There was no difference in SSI incidence in the RACS and LACS groups.Diabetes mellitus,intraoperative blood loss≥100 mL,and incision length were independent risk factors for postoperative SSI.

关键词： Colorectal surgery Minimally invasive surgery Surgical site infection

Metal-organic frameworks on 3D interconnected macroporous sponge foams for large-scale water decontamination:A mini review

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2024年第5期35卷 77-84页

作者： Xiao-Hong yi Chong-Chen Wang Beijing Key Laboratory of Functional Materials for Building Structure and Environment Remediation School of Environment and Energy EngineeringBeijing University of Civil Engineering and ArchitectureBeijing 100044China

Water pollution caused by global population growth,urban expansion and industrialization development is one of the urgent issues that need to be addressed in the 21st century.Up to now,it was challenging for metal-organic frameworks(MOFs)to be used in the actual water treatment due to that the powder MOFs suffered from difficult reuse,poor water stability and easy corrosion.It is an effective strategy to immobilize MOFs powder onto porous sponge foam carriers for accomplishing large flux,facile recycling,easy processing water treatment setups.In this review article,the fabrication approaches and applications of different MOFs/sponge composites were highlighted,in which the fluorescence detection of pollutants,adsorption and separation of pollutants,catalytic reduction and oxidation of pollutants were included.Finally,the future challenges and opportunities of MOF/sponge for water treatment are proposed,aiming to provide in-depth guidance for the future design and manufacture of the immobilized MOFs onto sponge foams.

关键词： Metal-organic frameworks Sponge foam Water decontamination Adsorption Catalysis

Comprehensive evaluation of rare case:From diagnosis to treatment of a sigmoid Schwannoma:A case report

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastrointestinal Oncology 2024年第1期16卷 244-250页

作者： Jing-yi Li Xi-Zhuang Gao Jian Zhang Xiang-Zheng Meng yi-Xian Cao Kun Zhao Clinical Medical College of Jining Medical University Jining Medical UniversityJining 272000Shandong ProvinceChina Department of Gastroenterology The First People's Hospital of JiningJining 272000Shandong ProvinceChina

BACKGROUND Schwannomas are uncommon tumors originating from Schwann cells,forming the neural sheath.They account for approximately 2%-6%of all mesenchymal tumors and are most commonly identified in peripheral nerve trunks,with rarity in the gastrointestinal tract.Among gastrointestinal locations,the stomach harbors the majority of nerve sheath tumors,while such occurrences in the sigmoid colon are exceptionally infrequent.CASE SUMMARY This study presented a clinical case involving a 60-year-old female patient who,during colonoscopy,was diagnosed with a submucosal lesion that was later identified as a nerve sheath tumor.The patient underwent surgical resection,and the diagnosis was confirmed through immunohistochemistry.This study highlighted an exceptionally uncommon occurrence of a nerve sheath tumor in the sigmoid colon,which was effectively managed within our department.Additionally,a comprehensive review of relevant studies was conducted.CONCLUSION The preoperative diagnosis of nerve sheath tumors poses challenges,as the definitive diagnosis still relies on pathology and immunohistochemistry.Although categorized as benign,these tumors have the potential to demonstrate malignant behavior.Consequently,the optimal treatment approach entails the complete surgical excision of the tumor,ensuring the absence of residual lesions at the margins.

关键词： Schwannoma Gastrointestinal stromal tumors Treatment Sigmoid colon Case report