发表论文

2020

  • Wei-Long Zheng, Kunpeng Gao, Gang Li, Wei Liu, Chao Liu, Jing-Quan Liu, Guoxing Wang, Bao-Liang Lu, "Vigilance Estimation Using a Wearable EOG Device in Real Driving Environment," in IEEE Transactions on Intelligent Transportation Systems, vol. 21, no. 1, pp. 170-184, Jan. 2020. Click here to access this paper)
  • Xiaocui Li , Ting Zhou , Yuxin Ji and Yongfu Li, “A 0.35V-to-1.0V Synthesizable Rail-to-Rail Dynamic Voltage Comparator based OAI & AOI Logic”, Analog Integrated Circuits and Signal Processing, pp. 1-6, 2020.
  • Yuhang Zhang , Guanghui He , Guoxing Wang and Yongfu Li, “Efficient and Robust RRAM-based Convolutional Weight Mapping with Shifted and Duplicated Kernel”, IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, pp. 1-1, 2020. Click here to access this paper)
  • D.L.T. Wong , J. Yu , Y. Li , C. J. Deepu , D.H. Ngo , C. Zhou , R.S. Shashi , A.S.L. Koh , R.T.Y. Hong , B. Veeravalli , M. Motani , K.C. Chua , Y. Lian and C.H. Heng, “An Integrated Wearable Wireless Vital Signs Biosensor for Continuous Inpatient Monitoring”, IEEE Sensors Journal, vol. 20, no. 1, pp. 448-462, Jan, 2020. Click here to access this paper)
  • Bo Zhao , Jingna Mao , Jian Zhao , Huazhong Yang and Yong Lian , “The Role and Challenges of Body Channel Communication in Wearable Flexible Electronics”, IEEE Transactions on Biomedical Circuits and Systems, pp. 1-1, 2020. Click here to access this paper)
  • Yuxuan Huang , Jian Zhao , Wenyu Sun , Huazhong Yang and Yongpan Liu ,“Investigation and Modeling of Multi-Node Body Channel Wireless Power Transfer”, Sensors, pp. 156, 2020. Click here to access this paper)

2019

  • Qingsong Xie, Min Wang, Yang Zhao, Ziran He, Yongfu Li, Guoxing Wang, Yong Lian,  "A Personalized Beat-to-Beat Heart Rate Detection System from Ballistocardiogram for Smart Home Applications," in IEEE Transactions on Biomedical Circuits and Systems. ( Early Access )Click here to access this paper)
  • Qingsong Xie, Yongfu Li, Guoxing Wang, Yong Lian , "An Unobtrusive System for Heart Rate Monitoring Based on Ballistocardiogram Using Hilbert Transform and Viterbi Decoding", in IEEE Journal on Emerging and Selected Topics in Circuits and Systems. ( Early Access ) Click here to access this paper)
  • Qingsong Xie, Shikui Tu, Guoxing Wang, Yong Lian, Lei Xu, "Feature Enrichment Based Convolutional Neural Network for Heartbeat Classification From Electrocardiogram", in IEEE Access, vol. 7, pp. 153751-153760, 2019.Click here to access this paper)
  • Boxiao Liu, Guoxing Wang, Yongfu Li, Lei Zeng, Hui Li, Yue Gao, Yixin Ma, Yong Lian, Chun-Huat Heng, "A 13-Channel 1.53-mW 11.28-mm2 Electrical Impedance Tomography SoC Based on Frequency Division Multiplexing for Lung Physiological Imaging", in IEEE Transactions on Biomedical Circuits and Systems, vol. 13, no. 5, pp. 938-949, Oct. 2019. Click here to access this paper)
  • Wei-Long Zheng, Kunpeng Gao, Gang Li, Wei Liu, Chao Liu, Jing-Quan Liu, Guoxing Wang, Bao-Liang Lu, "Vigilance Estimation Using a Wearable EOG Device in Real Driving Environment", in IEEE Transactions on Intelligent Transportation Systems. ( Early Access ) Click here to access this paper)
  • Mingyi Chen, Ho Sung Chun, Iván Dario Castro, Tom Torfs, Qiuyang Lin, Chris van Hoof, Guoxing Wang, Yong Lian, Nick van Helleputte, "A 400 GΩ Input-Impedance Active Electrode for Non-Contact Capacitively Coupled ECG Acquisition With Large Linear-Input-Range and High CM-Interference-Tolerance", in IEEE Transactions on Biomedical Circuits and Systems, vol. 13, no. 2, pp. 376-386, April, 2019. Click here to access this paper)
  • Min Wang, Zhe Li, Qirui Zhang, Guoxing Wang, “Removal of Motion Artifacts in Photoplethysmograph Sensors during Intensive Exercise for Accurate Heart Rate Calculation Based on Frequency Estimation and Notch Filtering”, in MDPI Sensors, vol 19, no.15, pp. 3312, July, 2019. Click here to access this paper)
  • Qirui Zhang, Qingsong Xie, Kefeng Duan, Bo Liang, Min Wang, Guoxing Wang, “A Digital Signal Processor (DSP)-based System for Embedded Continuous-time Cuffless Blood Pressure Monitoring Using Single-channel PPG Signal”, in SCIENCE CHINA Information Sciences, vol.56, no. 1013, pp. 102402. Click here to access this paper)
  • Zhihong Luo, Guoxing Wang, Khalil Yousef, Benjamin Lau, Yong Lian, and Chun-Huat Heng, "A 0.0129mm2 DPLL with 1.6~2.0ps RMS Period Jitter and 0.25-to-2.7 GHz Tunable DCO Frequency Range in 55nm CMOS", in IEEE Transactions on Circuits and Systems II: Express Briefs. ( Early Access ) Click here to access this paper)
  • Mingyi Chen, Hengwei Yu, Guoxing Wang, Yong Lian, "A Batteryless Single-Inductor Boost Converter With 190 mV Self-Startup Voltage for Thermal Energy Harvesting Over a Wide Temperature Range", in IEEE Transactions on Circuits and Systems II: Express Briefs, vol. 66, no. 6, pp. 889-893, June, 2019. Click here to access this paper)
  • Yuting Hou, Jiali Qu, ZhenZhen Tian, Mohamed Atef, Khalil Yousef, Yong Lian, Guoxing Wang, "A 61-nW Level-Crossing ADC With Adaptive Sampling for Biomedical Applications", in IEEE Transactions on Circuits and Systems II: Express Briefs, vol. 66, no. 1, pp. 56-60, Jan, 2019. Click here to access this paper)
  • Y. Luo, K.H. Teng, Y. Li, W. Mao, Y. Lian and C.H. Heng, “A 74-uW 11-Mbp/s Wireless Vital Signs Monitoring SoC for 3-Lead ECG, Respiration Rate, and Body Temperature”, IEEE Transactions on Biomedical Circuits and Systems (TBioCAS), vol. 13, no. 5, pp. 907-917, Oct, 2019. Click here to access this paper)
  • A. Tan, R. T. Toh, A. Lim, Y. Li and Z. H. Kong, “A Simplified Methodology to Evaluate Circuit Complexity: Doherty Power Amplifier as a Case Study”, Electronics, Mar, 2019. Click here to access this paper)
  • W. Mao, Y. Li, C. H. Heng and Y. Lian, “A Low Power 12-bit 1-kS/s SAR ADC for Biomedical Signal Processing”, IEEE Transactions on Circuits and Systems I, vol. 66, no. 2, pp. 477-488, Feb, 2019. Click here to access this paper)
  • D.L.T. Wong, J. Yu, Y. Li, C. J. Deepu, D.H. Ngo, C. Zhou, R.S. Shashi, A.S.L. Koh, R.T.Y. Hong, B. Veeravalli, M. Motani, K.C. Chua, Y. Lian and C.H. Heng, “An Integrated Wearable Wireless Vital Signs Biosensor for Continuous Inpatient Monitoring”, IEEE Sensors Journal, pp. 1-1, 2019. Click here to access this paper)
  • Jian Zhao, Jingna Mao, Wenyu Sun, Yuxuan Huang, Bo Zhao, Yongpan Liu and Huazhong Yang, “An Auto Loss Compensation System for Capacitive Coupled Body Channel Communication”, IEEE Transactions on Biomedical Circuits and Systems, 2019. (Early Access) Click here to access this paper)
  • Wenyu Sun, Jian Zhao, Yuxuan Huang, Yinan Sun, Huazhong Yang and Yongpan Liu, “Dynamic Channel Modeling and OFDM System Analysis for Capacitive Coupling Body Channel Communication”, IEEE Transactions on Biomedical Circuits and Systems, 2019. (Early Access) Click here to access this paper)
  • Chen Lin , Jian Zhao , Zhichao Yao , Qi Fan , Bing Mo and Yan Su, “Vibration modeling of disk resonator gyroscope by wave propagation”, Journal of Sound and Vibration, pp. 85–107, 2019. Click here to access this paper)
  • Zhe Yuan , Yongpan Liu , Jinshan Yue , Yixiong Yang , Jingyu Wang , Xiaoyu Feng , Jian Zhao, Xueqing Li and Huazhong Yang, “STICKER: An Energy-Efficient Multi-Sparsity Compatible Accelerator for Convolutional Neural Networks in 65-nm CMOS”, IEEE Journal of Solid-State Circuits, pp. 1-13, 2019. Click here to access this paper)

2018

  • Mingyi Chen, Min Wang, Hengwei Yu, Yadong Liu, Guanghui He, Yongxin Zhu, Guoxing Wang, "A Self-Powered 3.26-µW 70-meter Wireless Temperature Sensor Node for Power Grid Monitoring," in IEEE Transactions on Industrial Electronics, vol. 65, no. 11, pp. 8956-8965, Nov. 2018. Click here to access this paper)
  • Ting-I Chou, Kwuang-Han Chang, Jia-Yin Jhang, Shih-Wen Chiu, Guoxing Wang, Chia-Hsiang Yang, Herming Chiueh, Hsin Chen, Chih-Cheng Hsieh, Meng-Fan Chang, and Kea-Tiong Tang, "A 1-V 2.6-mW Environmental Compensated Fully Integrated Nose-on-a-Chip," in IEEE Transactions on Circuits and Systems II: Express Briefs, vol. 65, no. 10, pp. 1365-1369, Oct. 2018. Click here to access this paper)
  • Zhe Zhang, Yongfu Li, Guoxing Wang, and Yong Lian, "The Design of an Energy-Efficient IR-UWB Transmitter with Wide-Output Swing and Sub-Microwatt Leakage Current," in IEEE Transactions on Circuits and Systems II: Express Briefs, vol. 65, no. 10, pp. 1485-1489, Oct. 2018. Click here to access this paper)
  • Yuting Hou, Khalil Yousef, Mohamed Atef, Guoxing Wang*; Yong Lian, "A 1-to-1-kHz, 4.2-to-544-nW, Multi-Level Comparator Based Level-Crossing ADC for IoT Applications," in IEEE Transactions on Circuits and Systems II: Express Briefs, vol. 65, no. 10, pp. 1390-1394, Oct. 2018. Click here to access this paper)
  • Xi Chen, Jie Zhou, Xunhua Guo, Zhiheng Zhen, Hui Li, Cheng Chen, Guoxing Wang, "Integrated Circuit Design for Retinal Prosthesis System," in Journal of Shanghai Jiao Tong University, vol. 52, no. 10, pp. 1234-1241, Oct. 2018. (Chinese) Click here to access this paper)
  • Tianyuan Cheng, Chundong Wu, Guoxing Wang, "A Design of Fully Integrated Alternating Dual Slope ADC," in Microelectronics & Computer, vol. 35, no. 10, pp. 62-66, Oct. 2018. (Chinese) Click here to access this paper)
  • Jiali Qu, Guanghui He, Guoxing Wang, "FPGA Implementation of Convolutional Neural Network in Speech Recognition, " in Microelectronics & Computer, vol. 35, no. 9, pp. 37-41 & 46, Sept. 2018. (Chinese) Click here to access this paper)
  • Xianliang Luo, Yingmei Chen, Mohamed Atef, Guoxing Wang, "A 44 Gbit/s Wide-Dynamic Range and High-Linearity Transimpedance Amplifier in 130nm BiCMOS Technology." in IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, vol. E101, issue 2, pp. 438-440, Jan. 2018. Click here to access this paper)
  • Mohamed Atef, Min Wang, Guoxing Wang, "A Fully Integrated High-Sensitivity Wide Dynamic Range PPG Sensor with an Integrated Photodiode and an Automatic Dimming Control LED Driver," in IEEE Sensors Journal, vol. 18, no. 2, pp. 652-659, Jan. 2018. Click here to access this paper)
  • Guoxing Wang, Mohamed Atef, Yong Lian, "Towards a Continuous Non-Invasive Cuffless Blood Pressure Monitoring System Using PPG: Systems and Circuits Review," in IEEE Circuits and Systems Magazine, vol. 18, no. 3, pp. 6-26, thirdquarter 2018. Click here to access this paper)
  • Guoxing Wang, Xiyan Li, Miaorong Wang, Hang Yuan, Wei Xu, "Optimization of a Dual-Band Wireless Power and Data Telemetry System Using Genetic Algorithm," in IEEE Design & Test, vol. 35, no. 3, pp. 54-65, June 2018. Click here to access this paper)

2020

  • S. Zhu , J. Zhao , Y. Li and M. Chen , “A 53%-PTE and 4-Mbps Power and Data Telemetry Circuit based on Adaptive Duty-cycling BPSK Modulated Class-E Amplifier”, ACM International Conference of the Great Lakes Symposium (GLVLSI), pp. 1-6, Sep, 2020.
  • W. Lu , Y. Zhang , Q. Zhang , X. Zhang and Y. Li , “Litho-NeuralODE: Improving Hotspot Detection Accuracy with Advanced Data Augmentation and Neural Ordinary Differential Equations”, ACM International Conference of the Great Lakes Symposium (GLVLSI), pp. 1-6, Sep, 2020.
  • T. Zhou , Y. Ji , M. Chen and Y. Li , “PL-MRO PUF: High Speed Pseudo-LFSR PUF Based on Multiple Ring Oscillators”, IEEE International Symposium on Circuits and Systems (ISCAS), pp. 1-4, May, 2020.
  • M. Attanasio and Y. Li , “A Highly Precise Analog Subtractor with Background Calibration Technique”, IEEE International Symposium on Circuits and Systems (ISCAS), pp. 1-4, May, 2020.

2019

  • Yi Wu, Yilun Jin, Azusa Yokoyama, Chao Wang, Yongfu Li, Yan Liu, Guoxing Wang, "Live Demonstration: An EEG-Based Comparative Study of Light Color Effect on Mental Stress Relief Using an Integrated Mobile Application", 2019 IEEE Biomedical Circuits and Systems Conference (BioCAS), Nara, Japan, pp. 1-1, 2019. Click here to access this paper)
  • Yizhen Wen, Xiangao Qi, Shaoyang Cui, Cheng Chen, Mingyi Chen, Jian Zhao, Guoxing Wang, "A Multi-channel NIRS System for Prefrontal Mental Task Classification Employing Deep Forest Algorithm", 2019 IEEE Biomedical Circuits and Systems Conference (BioCAS), Nara, Japan, pp. 1-4, 2019. Click here to access this paper)
  • Yi Ma, Xinzi Xu, Qing Yu, Yuhang Zhang, Yongfu Li, Jian Zhao, Guoxing Wang, "Live Demo: LungSys - Automatic Digital Stethoscope System For Adventitious Respiratory Sound Detection", 2019 IEEE Biomedical Circuits and Systems Conference (BioCAS), Nara, Japan, pp. 1-1, 2019. Click here to access this paper)
  • Shaoyang Cui, Cheng Chen, Xiangao Qi, Yizhen Wen, Jian Zhao, and Guoxing Wang, "Live Demonstration: Prefrontal Mental Task Classification through a Wearable Near-infrared Spectroscopy System," 2019 IEEE Biomedical Circuits and Systems Conference (BioCAS), Nara, Japan, 2019, pp. 1-1. Click here to access this paper)
  • Yue Gao, Yewangqing Lu, Hui Li, Boxiao Liu, Yongfu Li, Mingyi Chen, Guoxing Wang, Yong Lian, "EIT-CDAE: A 2-D Electrical Impedance Tomography Image Reconstruction Method Based on Auto Encoder Technique", 2019 IEEE Biomedical Circuits and Systems Conference (BioCAS), Nara, Japan, pp. 1-4, 2019. Click here to access this paper)
  • Yi Ma, Xinzi Xu, Qing Yu, Yuhang Zhang, Yongfu Li, Jian Zhao, Guoxing Wang, "LungBRN: A Smart Digital Stethoscope for Detecting Respiratory Disease Using bi-ResNet Deep Learning Algorithm", 2019 IEEE Biomedical Circuits and Systems Conference (BioCAS), Nara, Japan, pp. 1-4, 2019. Click here to access this paper)
  • Qingsong Xie, Yongfu Li, Guoxing Wang, Yong Lian, "Heart Rate Estimation from Ballistocardiogram Using Hilbert Transform and Viterbi Decoding", 2019 IEEE International Conference on Artificial Intelligence Circuits and Systems (AICAS), Hsinchu, Taiwan, pp. 189-193, 2019. Click here to access this paper)
  • Yuhang Zhang, Guanghui He, Kea-Tiong Tang, Guoxing Wang, "On-chip Learning of Multilayer Perceptron Based on Memristors with Limited Multilevel States", 2019 IEEE International Conference on Artificial Intelligence Circuits and Systems (AICAS), Hsinchu, Taiwan, pp. 11-12, 2019. Click here to access this paper)
  • Yue Gao, Boxiao Liu, Hui Li, Yongfu Li, Guoxing Wang, Yong Lian, Chun-Huat Heng, "Live Demonstration: A Pulmonary Conditions Monitor Based on Electrical Impedance Tomography Measurement", 2019 IEEE International Symposium on Circuits and Systems (ISCAS), Sapporo, Japan, pp. 1-1, 2019. Click here to access this paper)
  • Ahmed Reda Mohamed, Mingyi Chen, Guoxing Wang, "Untrimmed CMOS Nano-Ampere Current Reference with Curvature-Compensation Scheme", 2019 IEEE International Symposium on Circuits and Systems (ISCAS), Sapporo, Japan, pp. 1-4, 2019. Click here to access this paper)
  • Tao He, Guoxing Wang, Khalil Yousef, Jing Jin, "A High Conversion Gain Wideband Mixer Design for UWB Applications", 2019 IEEE International Symposium on Circuits and Systems (ISCAS), Sapporo, Japan, pp. 1-4, 2019. Click here to access this paper)
  • Mengdan Lou, Jieyu Li, Guoxing Wang, Guanghui He, "AR-C3D: Action Recognition Accelerator for Human-Computer Interaction on FPGA", 2019 IEEE International Symposium on Circuits and Systems (ISCAS), Sapporo, 2019, pp. 1-4, Japan. Click here to access this paper)
  • Boxiao Liu, Guoxing Wang, Yongfu Li, Hui Li, Yue Gao, Lei Zeng, Yixin Ma, Yong Lian, "22.6 A 13-Channel 1.53-mW 11.28-mm2 Electrical Impedance Tomography SoC Based on Frequency Division Multiplexing with 10× Throughput Reduction", 2019 IEEE International Solid- State Circuits Conference (ISSCC), San Francisco, CA, USA, 2019, pp. 370-372. Click here to access this paper)
  • Fei Zhou, Xiaoli Hu, and Guoxing Wang, "A 32-Kb High–Speed 8T SRAM with Fine-Grained Bitline Stacking for Leakage Reduction in 7nm Technology," 2019 China Semiconductor Technology International Conference (CSTIC), Shanghai, China, 2019, pp. 1-3. Click here to access this paper)

2018

  • Muhammad Adeel Khan, Maya Chennafi, Gang Li, and Guoxing Wang, "Electroencephalogram-Based Comparative Study of Music Effect on Mental Stress Relief," 2018 11th International Congress on Image and Signal Processing, BioMedical Engineering and Informatics (CISP-BMEI), Beijing, China, 2018, pp. 1-5. Click here to access this paper)
  • Zhiheng Zheng, Mingyi Chen, Jie Zhou, and Guoxing Wang, "A CMOS Temperature Sensor with Single-Point Calibration for Retinal Prosthesis," 2018 IEEE Asia Pacific Conference on Circuits and Systems (APCCAS), Chengdu, 2018, pp. 147-150. Click here to access this paper)
  • Kangqi Liu, Mingyi Chen, Yiyu Gong, Songhai Fan, and Guoxing Wang, "A 100μW AC-DC Boost Converter for Electromagnetic Energy Harvesting with 0.2 VPeak Self-starting Voltage and 85% Efficiency," 2018 IEEE Asia Pacific Conference on Circuits and Systems (APCCAS), Chengdu, China, 2018, pp. 493-496. Click here to access this paper)
  • Qingsong Xie, Guoxing Wang and Yong Lian, "Heart Rate Estimation from Ballistocardiography Based on Hilbert Transform and Phase Vocoder," 2018 IEEE Asia Pacific Conference on Circuits and Systems (APCCAS), Chengdu, China, 2018, pp. 139-142. Click here to access this paper)
  • Ziran He, Qingsong Xie, Yong Lian, Guoxing Wang, Zhengchun Peng, Yang Zhao, Min Wang and Bo Meng, "A Heart Rate Measurement System Based on Ballistocardiogram for Smart Furniture," 2018 IEEE Asia Pacific Conference on Circuits and Systems (APCCAS), Chengdu, China, 2018, pp. 151-154. Click here to access this paper)
  • Maya Chennafi, Muhammad Adeel Khan, Gang Li, Yong Lian and Guoxing Wang, "Study of Music Effect on Mental Stress Relief Based on Heart Rate Variability," 2018 IEEE Asia Pacific Conference on Circuits and Systems (APCCAS), Chengdu, China, 2018, pp. 131-134. Click here to access this paper)
  • Hui Li, Boxiao Liu, Yongfu Li, Guoxing Wang and Yong Lian, "A High Accuracy and High Sensitivity System Architecture for Electrical Impedance Tomography System," 2018 IEEE Asia Pacific Conference on Circuits and Systems (APCCAS), Chengdu, China, 2018, pp. 155-158. Click here to access this paper)
  • Boxiao Liu, Chun-Huat Heng, Guoxing Wang, and Yong Lian, "On-chip Data Compression Scheme for Lung EIT Signal Acquisition and Recovery," 2018 IEEE 23rd International Conference on Digital Signal Processing (DSP), Shanghai, China, 2018, pp. 1-5. Click here to access this paper)
  • Qingsong Xie, Guoxing Wang, Zhengchun Peng, and Yong Lian, "Machine Learning Methods for Real-Time Blood Pressure Measurement Based on Photoplethysmography," 2018 IEEE 23rd International Conference on Digital Signal Processing (DSP), Shanghai, China, 2018, pp. 1-5. Click here to access this paper)
  • Qingsong Xie, Qirui Zhang, Guoxing Wang, and Yong Lian, "Combining Adaptive Filter and Phase Vocoder for Heart Rate Monitoring Using Photoplethysmography during Physical Exercise," 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Honolulu, HI, USA, 2018, pp. 3568-3571. Click here to access this paper)
  • Qirui Zhang, Qingsong Xie, Min Wang and Guoxing Wang, "Motion Artifact Removal for PPG Signals Based on Accurate Fundamental Frequency Estimation and Notch Filtering," 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Honolulu, HI, USA, 2018, pp. 2965-2968. Click here to access this paper)
  • Yuting Hou, Jiali Qu, Zhenzhen Tian, Mohamed Atef, Khalil Yousef, Yong Lian, and Guoxing Wang, “A 61-nW Level-Crossing ADC with Adaptive Sampling Function for Biomedical Applications” International Solid-State Circuits Conference, Student Research Preview, San Francisco, USA, 2018. Click here to access this paper)
  • Zhihong Luo, Guoxing Wang, Khalil Yousef, Benjamin Lau, Yong Lian, and Chun-Huat Heng, “A 0.0129 mm2 0.25~2.7 GHz Digital-Filter-Less ADPLL in 55nm CMOS,” 2018 IEEE International Symposium on Circuits and Systems (ISCAS) Late Breaking News, 2018.
  • Hengwei Yu, Mingyi Chen, Chundong Wu, Kea-Tiong Tang, and Guoxing Wang*, "A Batteryless and Single-Inductor DC-DC Boost Converter for Thermoelectric Energy Harvesting Application with 190mV Cold-Start Voltage," 2018 IEEE International Symposium on Circuits and Systems (ISCAS), Florence, Italy, 2018, pp. 1-4. Click here to access this paper)