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User Profiling Based on Multimodal Fusion Technology
ZHANG Zhuang, FENG Xiaonian, QIAN Tieyun
Acta Scientiarum Naturalium Universitatis Pekinensis    2020, 56 (1): 105-111.   DOI: 10.13209/j.0479-8023.2019.097
Abstract1480)   HTML    PDF(pc) (802KB)(340)       Save
Existing studies in user profiling are unable to fully utilize the multimodal information. This paper presents a cross-modal joint representation learning network, and develop a multi-modal fusion model. Firstly, a stacking method is adopted to learn the joint representation network which fuse the cross-modal information. Then, attention mechanism is introduced to automatically learn the contribution of different modal to the prediction task. Proposed model has a well defined loss function and network structure, which enables combining the related features in various models by learning the joint representations after feature-level and decision-level fusion. The extensive experiments on real data sets show that proposed model outperforms the baselines.
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A Design of 10B SAR ADC with Novel Mixed-Monotonic Capacitor Switching Scheme
GE Binjie, LI Yan, YU Hang, FENG Xiaoxing
Acta Scientiarum Naturalium Universitatis Pekinensis    2018, 54 (5): 927-934.   DOI: 10.13209/j.0479-8023.2018.048
Abstract1175)   HTML    PDF(pc) (7091KB)(170)       Save

A mixed-monotonic capacitor switching scheme which can provide stable common-mode voltage (Vcm) without any additional voltage regulator and compensation capacitor array is proposed for the successive approximation register (SAR) analog-to-digital (ADC). The proposed scheme contains two equal amplitude but opposite monotonicity switched capacitor arrays, the stabilization of the common mode voltage is achieved with self-complementation of the differential voltage. Based on this technique, a 10-bit 50 MS/s prototype is designed in CMOS 0.18 μm technology. A window opening SAR logic is used to reduce the transmission time from the comparator out to DAC control signal. An adaptive delay chain is used in the comparator loop to reduce the conversion time of lower bit in the SAR ADC. Measurement result shows that the SAR ADC can achieve a SNDR equal to 57.31 dB, and INL and DNL are equal to 1.81 LSB and 0.98 LSB respectively.

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Lagrange Equation Applied to Continuum Mechanics
FENG Xiaojiu, LIANG Lifu
Acta Scientiarum Naturalium Universitatis Pekinensis    2016, 52 (4): 597-607.   DOI: 10.13209/j.0479-8023.2016.076
Abstract1319)   HTML    PDF(pc) (418KB)(1410)       Save

How to apply the Lagrange equation to the continuous medium mechanics has been a theoretical issue of academic circles. Using variational derivative concepts and operational rules, the properties of variational derivative in Lagrange equation are studied. The Lagrange equation is applied to linear elastic dynamics and nonlinear elastic dynamics, and some corresponding numerical examples are given. The result shows that it is a feasible way to solve the problem of the application of Lagrange equation to the mechanics of continuous media by using the variational integral calculus.

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Common Problems and Technical Innovation of Travel Survey in Old Town: A Case Study in Qianmen Area in Beijing
ZHAO Pengjun, FENG Xiao, LI Shengxiao
Acta Scientiarum Naturalium Universitatis Pekinensis    2016, 52 (3): 486-492.   DOI: 10.13209/j.0479-8023.2015.155
Abstract1233)   HTML    PDF(pc) (407KB)(1167)       Save

This study targets on the practical process of travel survey in Qianmen, Beijing and examines the problems derived from the survey. Their characteristics and the reasons of being generated are stated. The paper focuses on survey organization and its institutional obstacles, the survey design, survey sampling techniques, the choice and training of surveyors and the survey timing. Based on the theoretical researches, the advices towards the innovation of travel survey methods are proposed.

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Top-Down Design for MASH21 Sigma-Delta Modulator
GE Binjie,WANG Xin’an,ZHANG Xing,FENG Xiaoxing,WANG Qingqin
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract787)            Save
The authors propose a top-down design process for MASH21 modulator. In system level, coefficient scaling is used to limit integrator’s output; in circuit level, integrator transient modeling is used to analyze the effect caused by OP’s non-ideality, and get the optimized design region for SNR, area and power. A MASH21 modulator for digital audio application is designed to verify the proposed design criteria. This experimental prototype is implemented with TSMC18MMRF, operates under a single 1.8 V power supply, and achieves a measured SNDR of 91dB.
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A Passive UHF RFID Transponder with Novel Clock Generator
FENG Xiaoxing,WANG Xin’an,ZHANG Xing,GE Binjie
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract547)            Save
An ultra-low power passive UHF RFID transponder complying with ISO/IEC 18000-6B protocol is presented. In order to provide an accurate clock for the digital baseband processing, an ultra-low power and self-calibrated clock generator is designed and implemented in the transponder with a clock variation within 4% against temperature from -50℃ to 120 ℃ or supply voltage from 0.7 to 1.6 V. Total power consumption of the novel clock generator is only 364 nW with 0.7V supply voltage. Further, a low voltage bandgap reference which generates 0.96 V with 100 nA current consumption is introduced. In digital baseband, clock gating and module reuse strategies are employed to further reduce the power consumption to 1.17 μW. This design is fabricated in 0.18 μm mix-signal CMOS process with a die size of 0.75 mm×0.75 mm. Measurement results show that the proposed RFID transponder operates with a sensitivity of -10 dBm.
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A New Baseband Decoder for Mobile RFID Reader
ZHONG Jinsi,WANG Xinan,FENG Xiaoxing,CAO Wei,QI Yongzhen
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract796)            Save
A digital baseband receiver which supports both ISO 18000-6B and 6Cfor UHF RFIDradio frequency identification reader is described. The digital baseband receiver includes deci mation filters, dc-removed filters, phase-recovery module, and so on. A novel decoder in digital baseband is also proposed. An approach to compensate the effect of zero-point excursion based on the zero-detect method is presented in the decoder. Simulation and verification results indicate that the new approach needs less hardware resources and less time to decodethe signal, compared with the correlation based demodulation method. Total chip area without test pads is 730 μm ×3375 μm @0. 18 μm CMOSprocess and consumes 32. 89 mW, whilethe decoder occupies the 1% of total area and consumes 0. 23mW.
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