Jianhua Lu

ORCID

Publication Activity (10 Years)

Years Active: 1997-2023
Publications (10 Years): 188

Top Venues

GLOBECOM

CoRR

ICC

IEEE Trans. Veh. Technol.

Queen's University Belfast, UK (PHD)

Education History

Queen's University Belfast, UK

PHD

Publications

Danlan Huang, Feifei Gao, Xiaoming Tao, Qiyuan Du, Jianhua Lu
Toward Semantic Communications: Deep Learning-Based Image Semantic Coding. IEEE J. Sel. Areas Commun. 41 (1) (2023)
Chaoyang Zheng, Zhipeng Chen, Jianhua Lu, Yan Ma, Yumei Huang, Zhiliang Hong
A 400M-510MHz On-Chip Transformer-Based RF Power Amplifier with 22.5dBm Output Power and 48% PAE. ASICON (2023)
Jin Zhang, Daoye Wang, Kai Liu, Jianhua Lu
A Multi-Table Programmable Parser for Satellite Networks. HPSR (2023)
Zhiming Wang, Yuxiao Li, Danlan Huang, Juan Wang, Ning Ge, Jianhua Lu
DeformSg2im: Scene graph based multi-instance image generation with a deformable geometric layout. Neurocomputing 558 (2023)
Haodi Li, Jing Wu, Jianhua Lu, Ziyu Chen, Ping Zhang, Wei Hu
A Task Level-Aware Scheduling Algorithm for Energy Consumption Constrained Parallel Applications on Heterogeneous Computing Systems. ICIC (1) (2023)
Tuanwei Tian, Hao Deng, Guchong Li, Jianhua Lu
Hybrid/Reflective Beamforming for IRS-Assisted Dual-Function Radar-Communication System. IEEE Internet Things J. 10 (22) (2023)
Jiachen Sun, Ning Ge, Xu Chen, Wei Feng, Jianhua Lu
Truthful Transaction Protocol for E-Commerce Networks Based on Double Auction. IEEE Trans. Netw. Sci. Eng. 10 (2) (2023)
Haoge Jia, Chunxiao Jiang, Linling Kuang, Jianhua Lu
An Analytic Approach for Modeling Uplink Performance of Mega Constellations. IEEE Trans. Veh. Technol. 72 (2) (2023)
Ping Zhang, Jing Wu, Di Cheng, Jianhua Lu, Wei Hu
A Task-Duplication Based Clustering Scheduling Algorithm for Heterogeneous Computing System. ICIC (1) (2023)
Haoge Jia, Chunxiao Jiang, Linling Kuang, Jianhua Lu
Adaptive Random Access and Data Transmission Scheme With Mixed Traffic in NGSO Satellite Networks. IEEE Trans. Veh. Technol. 72 (5) (2023)
Zhiming Wang, Juan Wang, Ning Ge, Jianhua Lu
HiMoReNet: A Hierarchical Model for Human Motion Refinement. IEEE Signal Process. Lett. 30 (2023)
Mayank Kulkarni, Aoxiao Zhong, Nicolas Guenon des Mesnards, Sahar Movaghati, Mukund Sridhar, He Xie, Jianhua Lu
An Empirical Analysis of Leveraging Knowledge for Low-Resource Task-Oriented Semantic Parsing. ACL (Findings) (2023)
Yingxu Wang, Bernard Widrow, C. A. R. Hoare, Witold Pedrycz, Robert C. Berwick, Konstantinos N. Plataniotis, Imre J. Rudas, Jianhua Lu, Janusz Kacprzyk
The odyssey to next-generation computers: cognitive computers (κC) inspired by the brain and powered by intelligent mathematics. Frontiers Comput. Sci. 5 (2023)
Yantian Luo, Xu Chen, Ning Ge, Wei Feng, Jianhua Lu
Transformer-Based Device-Type Identification in Heterogeneous IoT Traffic. IEEE Internet Things J. 10 (6, March 15) (2023)
Yaqiang Zhang, Xiaoming Tao, Zhoujuan Cui, Yiping Duan, Jianhua Lu
Safety Stock Forecasting based on Materials Correlation. WCSP (2023)
Yue Gao, Xiaolin Liu, Jianhua Lu
Tropical Surface Temperature and Atmospheric Latent Heating: A Whole-Tropics Perspective Based on TRMM and ERA5 Datasets. Remote. Sens. 15 (11) (2023)
Zhiming Wang, Yantian Luo, Danlan Huang, Ning Ge, Jianhua Lu
Category-Adaptive Domain Adaptation for Semantic Segmentation. ICASSP (2022)
Jack FitzGerald, Shankar Ananthakrishnan, Konstantine Arkoudas, Davide Bernardi, Abhishek Bhagia, Claudio Delli Bovi, Jin Cao, Rakesh Chada, Amit Chauhan, Luoxin Chen, Anurag Dwarakanath, Satyam Dwivedi, Turan Gojayev, Karthik Gopalakrishnan, Thomas Gueudre, Dilek Hakkani-Tur, Wael Hamza, Jonathan J. Hüser, Kevin Martin Jose, Haidar Khan, Beiye Liu, Jianhua Lu, Alessandro Manzotti, Pradeep Natarajan, Karolina Owczarzak, Gokmen Oz, Enrico Palumbo, Charith Peris, Chandana Satya Prakash, Stephen Rawls, Andy Rosenbaum, Anjali Shenoy, Saleh Soltan, Mukund Harakere Sridhar, Lizhen Tan, Fabian Triefenbach, Pan Wei, Haiyang Yu, Shuai Zheng, Gökhan Tür, Prem Natarajan
Alexa Teacher Model: Pretraining and Distilling Multi-Billion-Parameter Encoders for Natural Language Understanding Systems. KDD (2022)
Weiwei Jiang, Yafeng Zhan, Xi Shen, Defeng David Huang, Jianhua Lu
Compressive Sensing-Based 3-D Rain Field Tomographic Reconstruction Using Simulated Satellite Signals. IEEE Trans. Geosci. Remote. Sens. 60 (2022)
Tuanwei Tian, Guchong Li, Hao Deng, Jianhua Lu
Adaptive Bit/Power Allocation With Beamforming for Dual-Function Radar-Communication. IEEE Wirel. Commun. Lett. 11 (6) (2022)
Haoran Xie, Yafeng Zhan, Shuqian Ren, Jianhua Lu
Kernel Extreme Learning Machine-Based Dynamic Interval Construction for Outlier Detection of Telemetry Data. VTC Fall (2022)
Yantian Luo, Xu Chen, Ning Ge, Wei Feng, Jianhua Lu
Transformer-Based Malicious Traffic Detection for Internet of Things. ICC (2022)
Haoge Jia, Zuyao Ni, Chunxiao Jiang, Linling Kuang, Jianhua Lu
Uplink Interference and Performance Analysis for Megasatellite Constellation. IEEE Internet Things J. 9 (6) (2022)
Shuzhan Hu, Yiping Duan, Xiaoming Tao, Geoffrey Ye Li, Jianhua Lu
Human Perception Measurement by Electroencephalography for Facial Image Compression. IEEE Signal Process. Lett. 29 (2022)
Haoge Jia, Chunxiao Jiang, Linling Kuang, Jianhua Lu
Adaptive Access Control and Resource Allocation for Random Access in NGSO Satellite Networks. IEEE Trans. Netw. Sci. Eng. 9 (4) (2022)
Danlan Huang, Feifei Gao, Xiaoming Tao, Qiyuan Du, Jianhua Lu
Towards Semantic Communications: Deep Learning-Based Image Semantic Coding. CoRR (2022)
Khaled B. Letaief, Yuanming Shi, Jianmin Lu, Jianhua Lu
Edge Artificial Intelligence for 6G: Vision, Enabling Technologies, and Applications. IEEE J. Sel. Areas Commun. 40 (1) (2022)
Weiwei Jiang, Yafeng Zhan, Guanming Zeng, Jianhua Lu
Probabilistic-Forecasting-Based Admission Control for Network Slicing in Software-Defined Networks. IEEE Internet Things J. 9 (15) (2022)
Fang Li, Gang Wu, Jianhua Lu, Mingye Jin, Haitao An, Junxiong Lin
SmartCMP: A Cloud Cost Optimization Governance Practice of Smart Cloud Management Platform. SmartCloud (2022)
Dingcheng Gao, Bing Du, Xiaoming Tao, Jianhua Lu
Driver Vigilance Detection from EEG Signals using Transformer Networks. GLOBECOM (2022)
Gui-Lu Long, Dong Pan, Yu-Bo Sheng, Qikun Xue, Jianhua Lu, Lajos Hanzo
An Evolutionary Pathway for the Quantum Internet Relying on Secure Classical Repeaters. IEEE Netw. 36 (3) (2022)
Xiang Peng, Zhijin Qin, Danlan Huang, Xiaoming Tao, Jianhua Lu, Guangyi Liu, Chengkang Pan
A Robust Deep Learning Enabled Semantic Communication System for Text. GLOBECOM (2022)
Jack FitzGerald, Shankar Ananthakrishnan, Konstantine Arkoudas, Davide Bernardi, Abhishek Bhagia, Claudio Delli Bovi, Jin Cao, Rakesh Chada, Amit Chauhan, Luoxin Chen, Anurag Dwarakanath, Satyam Dwivedi, Turan Gojayev, Karthik Gopalakrishnan, Thomas Gueudre, Dilek Hakkani-Tur, Wael Hamza, Jonathan J. Hüser, Kevin Martin Jose, Haidar Khan, Beiye Liu, Jianhua Lu, Alessandro Manzotti, Pradeep Natarajan, Karolina Owczarzak, Gokmen Oz, Enrico Palumbo, Charith Peris, Chandana Satya Prakash, Stephen Rawls, Andy Rosenbaum, Anjali Shenoy, Saleh Soltan, Mukund Harakere Sridhar, Liz Tan, Fabian Triefenbach, Pan Wei, Haiyang Yu, Shuai Zheng, Gökhan Tür, Prem Natarajan
Alexa Teacher Model: Pretraining and Distilling Multi-Billion-Parameter Encoders for Natural Language Understanding Systems. CoRR (2022)
Zhijin Qin, Xiaoming Tao, Jianhua Lu, Geoffrey Ye Li
Semantic Communications: Principles and Challenges. CoRR (2022)
Khaled B. Letaief, Yuanming Shi, Jianmin Lu, Jianhua Lu
Edge Artificial Intelligence for 6G: Vision, Enabling Technologies, and Applications. CoRR (2021)
Juan Wang, Yiping Duan, Xiaoming Tao, Mai Xu, Jianhua Lu
Semantic Perceptual Image Compression With a Laplacian Pyramid of Convolutional Networks. IEEE Trans. Image Process. 30 (2021)
Danlan Huang, Xiaoming Tao, Feifei Gao, Jianhua Lu
Deep Learning-Based Image Semantic Coding for Semantic Communications. GLOBECOM (2021)
Luoxin Chen, Francisco Garcia, Varun Kumar, He Xie, Jianhua Lu
Industry Scale Semi-Supervised Learning for Natural Language Understanding. CoRR (2021)
Jianyu Cao, Wei Feng, Ning Ge, Jianhua Lu
Delay Characterization of Mobile-Edge Computing for 6G Time-Sensitive Services. IEEE Internet Things J. 8 (5) (2021)
Baili Zhang, Kejie Wen, Jianhua Lu, Mingjun Zhong
A Top-K QoS-Optimal Service Composition Approach Based on Service Dependency Graph. J. Organ. End User Comput. 33 (3) (2021)
Hongying Liu, Derong Xu, Tianwen Zhu, Fanhua Shang, Yuanyuan Liu, Jianhua Lu, Ri Yang
Graph Convolutional Networks by Architecture Search for PolSAR Image Classification. Remote. Sens. 13 (7) (2021)
Nan Li, Zengqi Wang, Weitian Liu, Qiao Zhang, Jichao Zhan, Na Yan, Tingting Han, Mi Tian, Weiqiang Zhu, Zhijian Li, Jianhua Lu
0.5W X-Band SOI 4-Channel Beamforming TR IC. ASICON (2021)
Zhen Li, Chunxiao Jiang, Jianhua Lu
Distributed Service Migration in Satellite Mobile Edge Computing. GLOBECOM (2021)
Luoxin Chen, Francisco Garcia, Varun Kumar, He Xie, Jianhua Lu
Industry Scale Semi-Supervised Learning for Natural Language Understanding. NAACL-HLT (Industry Papers) (2021)
Chaoyi Han, Yiping Duan, Xiaoming Tao, Jianhua Lu
Perceptual Image Restoration with High-Quality Priori and Degradation Learning. CoRR (2021)
Di Cheng, Wei Hu, Jing Liu, Yu Gan, Jianhua Lu
Permanent fault-tolerant scheduling in heterogeneous multi-core real-time systems. SMC (2021)
Zhen Sun, Zhao Chen, Liuguo Yin, Jianhua Lu
Design of LDBCH Codes for Ultra Reliable Low Latency Communications. IEEE Commun. Lett. 25 (9) (2021)
Yantian Luo, Zhiming Wang, Danlan Huang, Ning Ge, Jianhua Lu
Get away from Style: Category-Guided Domain Adaptation for Semantic Segmentation. CoRR (2021)
Yantian Luo, Xu Chen, Ning Ge, Jianhua Lu
Deep Learning Based Device Classification Method for Safeguarding Internet of Things. GLOBECOM (2021)
Shuzhan Hu, Yiping Duan, Xiaoming Tao, Geoffrey Ye Li, Jianhua Lu
Brain-Inspired Image Quality Assessment Method based on Electroencephalography Feature Learning. GLOBECOM (2021)
Zhiming Wang, Yuxiao Li, Danlan Huang, Yantian Luo, Ning Ge, Jianhua Lu
Deformable Geometry based Semantic Reconstruction from Scene Graphs. GLOBECOM (2021)
Tuanwei Tian, Hao Deng, Jianhua Lu, Xianxiang Yu, Xianyuan Wang
Simultaneous Radar Sensing and Communication Enabled by Joint Transmit-Receive Beamforming. ICCC Workshops (2021)
Te Wei, Wei Feng, Yunfei Chen, Cheng-Xiang Wang, Ning Ge, Jianhua Lu
Hybrid Satellite-Terrestrial Communication Networks for the Maritime Internet of Things: Key Technologies, Opportunities, and Challenges. IEEE Internet Things J. 8 (11) (2021)
Zhenyu Han, Fengli Xu, Yong Li, Tao Jiang, Depeng Jin, Jianhua Lu, James A. Evans
Policy-Aware Mobility Model Explains the Growth of COVID-19 in Cities. CoRR (2021)
Puyang Wang, Pengfei Guo, Jianhua Lu, Jinyuan Zhou, Shanshan Jiang, Vishal M. Patel
Improving Amide Proton Transfer-Weighted MRI Reconstruction Using T2-Weighted Images. MICCAI (2) (2020)
Haoge Jia, Zuyao Ni, Linling Kuang, Jianhua Lu
Joint Occlusion Detection and Phase Estimation Algorithm for Helicopter Satellite Communication. IEEE Trans. Aerosp. Electron. Syst. 56 (1) (2020)
Zhen Sun, Liyuan Song, Qin Huang, Liuguo Yin, Guilu Long, Jianhua Lu, Lajos Hanzo
Toward Practical Quantum Secure Direct Communication: A Quantum-Memory-Free Protocol and Code Design. IEEE Trans. Commun. 68 (9) (2020)
Jianyu Cao, Wei Feng, Ning Ge, Jianhua Lu
Delay Characterization of Mobile Edge Computing for 6G Time-Sensitive Services. CoRR (2020)
Yiping Duan, Chaoyi Han, Xiaoming Tao, Bingrui Geng, Yunfei Du, Jianhua Lu
Panoramic Image Generation: From 2-D Sketch to Spherical Image. IEEE J. Sel. Top. Signal Process. 14 (1) (2020)
Shuzhan Hu, Yiping Duan, Xiaoming Tao, Yongjia Liu, Xuming Zhang, Jianhua Lu
Content-aware Facial Image Compression with Deep Learning Method. WCSP (2020)
Xiaoming Tao, Yiping Duan, Cheng Yang, Haijun Zhang, Shuai Liu, Jianhua Lu
Representation Learning in Wireless Multimedia Communications. IEEE Wirel. Commun. 27 (2) (2020)
Luoxin Chen, Xinyue Liu, Weitong Ruan, Jianhua Lu
Enhance Robustness of Sequence Labelling with Masked Adversarial Training. EMNLP (Findings) (2020)
Bingkun Liu, Chunxiao Jiang, Linling Kuang, Jianhua Lu
Joint User Grouping and Beamwidth Optimization for Satellite Multicast with Phased Array Antennas. GLOBECOM (2020)
Juan Wang, Yiping Duan, Xiaoming Tao, Jianhua Lu
Local-to-Global Semantic Supervised Learning for Image Captioning. ICC (2020)
Danlan Huang, Xiaoming Tao, Chunxiao Jiang, Shuguang Cui, Jianhua Lu
Trace-Driven QoE-Aware Proactive Caching for Mobile Video Streaming in Metropolis. IEEE Trans. Wirel. Commun. 19 (1) (2020)
Te Wei, Wei Feng, Ning Ge, Jianhua Lu
Environment-Aware Coverage Optimization for Space-Ground Integrated Maritime Communications. IEEE Access 8 (2020)
Yiping Duan, Zhe Li, Xiaoming Tao, Qiang Li, Shuzhan Hu, Jianhua Lu
EEG-Based Maritime Object Detection for IoT-Driven Surveillance Systems in Smart Ocean. IEEE Internet Things J. 7 (10) (2020)
Chaoyi Han, Yiping Duan, Xiaoming Tao, Mai Xu, Jianhua Lu
Toward Variable-Rate Generative Compression by Reducing the Channel Redundancy. IEEE Trans. Circuits Syst. Video Technol. 30 (7) (2020)
Xiwen Liu, Xiaoming Tao, Mai Xu, Yafeng Zhan, Jianhua Lu
An EEG-Based Study on Perception of Video Distortion Under Various Content Motion Conditions. IEEE Trans. Multim. 22 (4) (2020)
Baihong Lin, Xiaoming Tao, Jianhua Lu
Hyperspectral Image Denoising via Matrix Factorization and Deep Prior Regularization. IEEE Trans. Image Process. 29 (2020)
Hao Wu, Jian Yan, Jianhua Lu
FlowTrace: Maximizing the Service Payoff of Heterogeneous Communications Networks. IEEE Trans. Netw. Sci. Eng. 7 (4) (2020)
Bingrui Geng, Ke Liu, Yiping Duan, Qiwei Song, Xiaoming Tao, Jianhua Lu, Jincheng Shi
A Novel EEG Based Directed Transfer Function for Investigating Human Perception to Audio Noise. IWCMC (2020)
Luoxin Chen, Weitong Ruan, Xinyue Liu, Jianhua Lu
SeqVAT: Virtual Adversarial Training for Semi-Supervised Sequence Labeling. ACL (2020)
Danlan Huang, Xiaoming Tao, Jianhua Lu, Minh N. Do
Geometry-Aware GAN for Face Attribute Transfer. IEEE Access 7 (2019)
Haoge Jia, Zuyao Ni, Chunxiao Jiang, Linling Kuang, Song Guo, Jianhua Lu
Enhanced Irregular Repetition Slotted ALOHA with Degree Distribution Adjustment in Satellite Network. GLOBECOM (2019)
Te Wei, Wei Feng, Jue Wang, Ning Ge, Jianhua Lu
Exploiting the Shipping Lane Information for Energy-Efficient Maritime Communications. IEEE Trans. Veh. Technol. 68 (7) (2019)
Xiaoming Tao, Chunxiao Jiang, Jie Liu, Ailing Xiao, Yi Qian, Jianhua Lu
QoE Driven Resource Allocation in Next Generation Wireless Networks. IEEE Wirel. Commun. 26 (2) (2019)
Xiwen Liu, Xiaoming Tao, Li Wang, Yafeng Zhan, Jianhua Lu
Developing a QoE Monitoring Approach for Video Service Based on Mobile Terminals. ICNC (2019)
Yanan Miao, Xiaoming Tao, Xiaolin Xu, Jianhua Lu
Joint 3-D Shape Estimation and Landmark Localization From Monocular Cameras of Intelligent Vehicles. IEEE Internet Things J. 6 (1) (2019)
Te Wei, Wei Feng, Yunfei Chen, Cheng-Xiang Wang, Ning Ge, Jianhua Lu
Hybrid Satellite-Terrestrial Communication Networks for the Maritime Internet of Things: Key Technologies, Opportunities, and Challenges. CoRR (2019)
Wei Feng, Jingchao Wang, Yunfei Chen, Xuanxuan Wang, Ning Ge, Jianhua Lu
UAV-Aided MIMO Communications for 5G Internet of Things. IEEE Internet Things J. 6 (2) (2019)
Xiaoming Tao, Yiping Duan, Mai Xu, Zhishen Meng, Jianhua Lu
Learning QoE of Mobile Video Transmission With Deep Neural Network: A Data-Driven Approach. IEEE J. Sel. Areas Commun. 37 (6) (2019)
Te Wei, Wei Feng, Jue Wang, Ning Ge, Jianhua Lu
Exploiting the Shipping Lane Information for Energy-Efficient Maritime Communications. CoRR (2019)
Danlan Huang, Xiaoming Tao, Jianhua Lu, Minh N. Do
Geometry-Aware GAN for Face Attribute Transfer. ICIP (2019)
Chaoyi Han, Yiping Duan, Xiaoming Tao, Jianhua Lu
Dense Convolutional Networks for Semantic Segmentation. IEEE Access 7 (2019)
Xiaoming Tao, Zhao Chen, Mai Xu, Jianhua Lu
Rebuffering Optimization for DASH via Pricing and EEG-Based QoE Modeling. IEEE J. Sel. Areas Commun. 37 (7) (2019)
Juan Wang, Xiaoming Tao, Mai Xu, Jianhua Lu
Semantic Perceptual Image Compression with a Laplacian Pyramid of Convolutional Networks. ICIP (2019)
Ping Wang, Liuguo Yin, Jianhua Lu
Spatially Coupled Generalized Low-Density Parity-Check Codes Over Class-A Impulsive Noise Channels. IEEE Access 7 (2019)
Xiangming Zhu, Chunxiao Jiang, Linling Kuang, Ning Ge, Song Guo, Jianhua Lu
Cooperative Transmission in Integrated Terrestrial-Satellite Networks. IEEE Netw. 33 (3) (2019)
Xiwen Liu, Xiaoming Tao, Yafeng Zhan, Jianhua Lu
Peripheral Sensing: Monitoring Quality of Experience for Video Services Based on Mobile Terminals. IEEE Access 7 (2019)
Jie Liu, Xiaoming Tao, Jianhua Lu
Mobility-Aware Centralized Reinforcement Learning for Dynamic Resource Allocation in HetNets. GLOBECOM (2019)
Yiping Duan, Yaqiang Zhang, Xiaoming Tao, Chaoyi Han, Mai Xu, Cheng Yang, Jianhua Lu
Content-aware Deep Perceptual Image Compression. WCSP (2019)
Jie Liu, Xiaoming Tao, Jianhua Lu
QoE-Oriented Rate Adaptation for DASH With Enhanced Deep Q-Learning. IEEE Access 7 (2019)
Yiping Duan, Xiaoming Tao, Mai Xu, Chaoyi Han, Jianhua Lu
GAN-NL: Unsupervised Representation Learning for Remote Sensing Image Classification. GlobalSIP (2018)
Zhen Sun, Ruoyang Qi, Zaisheng Lin, Liuguo Yin, Guilu Long, Jianhua Lu
Design and Implementation of a Practical Quantum Secure Direct Communication System. GLOBECOM Workshops (2018)
Yingxu Wang, Jianhua Lu, Marina L. Gavrilova, Rodolfo A. Fiorini, Janusz Kacprzyk
Brain-Inspired Systems (BIS): Cognitive Foundations and Applications. SMC (2018)
Baihong Lin, Xiaoming Tao, Xiaowei Qin, Yiping Duan, Jianhua Lu
Hyperspectral Image Denoising via Nonnegative Matrix Factorization and Convolutional Neural Networks. IGARSS (2018)
Jianhua Lu, Ningyun Lu, Sipei Ma, Baili Zhang
Edit Distance Based Similarity Search of Heterogeneous Information Networks. DEXA (2) (2018)
Yanan Miao, Xiaoming Tao, Jianhua Lu
Robust Monocular 3D Car Shape Estimation From 2D Landmarks. IEEE Trans. Circuits Syst. Video Technol. 28 (3) (2018)
Juan Wang, Xiaoming Tao, Mai Xu, Jianhua Lu
Boundary Objectness Network for Object Detection and Localization. ICASSP (2018)

Jianhua Lu.css-eqlu8i{font-size:small;padding-left:4px;}

Publication Activity (10 Years)

Top Topics

Top Venues

Jianhua Lu