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Your search keyword '"Zhu, Shifeng"' showing total 293 results
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293 results on '"Zhu, Shifeng"'

2. Highly parallelizable electronic transport calculations in periodic Rhodium and Copper nanostructures

Author

Zhu, Shifeng, Feldman, Baruch, and Dunham, Scott

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

We extend the highly-parallelizable open-source electronic transport code TRANSEC to perform real-space atomic-scale electronic transport calculations with periodic boundary conditions in the lateral dimensions. We demonstrate the use of TRANSEC in periodic Cu and Rh bulk structures and in large periodic Rh point contacts, in preparation to perform calculations of reflection probability across Rh grain boundaries.

Published
2022
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9. Modeling Electrical Switching of Nonvolatile Phase-Change Integrated Nanophotonic Structures with Graphene Heaters

Author

Zheng, Jiajiu, Zhu, Shifeng, Xu, Peipeng, Dunham, Scott, and Majumdar, Arka

Subjects
Physics - Applied Physics, Physics - Optics
Abstract

Progress in integrated nanophotonics has enabled large-scale programmable photonic integrated circuits (PICs) for general-purpose electronic-photonic systems on a chip. Relying on the weak, volatile thermo-optic or electro-optic effects, such systems usually exhibit limited reconfigurability along with high energy consumption and large footprints. These challenges can be addressed by resorting to chalcogenide phase-change materials (PCMs) such as Ge2Sb2Te5 (GST) that provide substantial optical contrast in a self-holding fashion upon phase transitions. However, current PCM-based integrated photonic applications are limited to single devices or simple PICs due to the poor scalability of the optical or electrical self-heating actuation approaches. Thermal-conduction heating via external electrical heaters, instead, allows large-scale integration and large-area switching, but fast and energy-efficient electrical control is yet to show. Here, we model electrical switching of GST-clad integrated nanophotonic structures with graphene heaters based on the programmable GST-on-silicon platform. Thanks to the ultra-low heat capacity and high in-plane thermal conductivity of graphene, the proposed structures exhibit a high switching speed of ~80 MHz and high energy efficiency of 19.2 aJ/nm^3 (6.6 aJ/nm^3) for crystallization (amorphization) while achieving complete phase transitions to ensure strong attenuation (~6.46 dB/micron) and optical phase (~0.28 dB/micron at 1550 nm) modulation. Compared with indium tin oxide and silicon p-i-n heaters, the structures with graphene heaters display two orders of magnitude higher figure of merits for heating and overall performance. Our work facilitates the analysis and understanding of the thermal-conduction heating-enabled phase transitions on PICs and supports the development of the future large-scale PCM-based electronic-photonic systems.

Published
2020
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10. Nonvolatile electrically reconfigurable integrated photonic switch

Author

Zheng, Jiajiu, Fang, Zhuoran, Wu, Changming, Zhu, Shifeng, Xu, Peipeng, Doylend, Jonathan K., Deshmukh, Sanchit, Pop, Eric, Dunham, Scott, Li, Mo, and Majumdar, Arka

Subjects
Physics - Applied Physics, Physics - Optics
Abstract

Reconfigurability of photonic integrated circuits (PICs) has become increasingly important due to the growing demands for electronic-photonic systems on a chip driven by emerging applications, including neuromorphic computing, quantum information, and microwave photonics. Success in these fields usually requires highly scalable photonic switching units as essential building blocks. Current photonic switches, however, mainly rely on materials with weak, volatile thermo-optic or electro-optic modulation effects, resulting in a large footprint and high energy consumption. As a promising alternative, chalcogenide phase-change materials (PCMs) exhibit strong modulation in a static, self-holding fashion. Here, we demonstrate nonvolatile electrically reconfigurable photonic switches using PCM-clad silicon waveguides and microring resonators that are intrinsically compact and energy-efficient. With phase transitions actuated by in-situ silicon PIN heaters, near-zero additional loss and reversible switching with high endurance are obtained in a complementary metal-oxide-semiconductor (CMOS)-compatible process. Our work can potentially enable very large-scale general-purpose programmable integrated photonic processors.

Published
2019
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18. Application of pneumatic conveying in reactor neutron spectroscopy sample transport

Author

HU Ruirong, WANG Naxiu, XU Bo, ZHANG Hongxin, LI Ling, CAO Yun, and ZHU Shifeng

Subjects
activation method, neutron spectroscopy sample, pneumatic conveying, double-casing tube, gas-solid flow, Nuclear engineering. Atomic power, TK9001-9401
Abstract

BackgroundThe activation method is taken to measure the in-core distribution of neutron spectrum for the designed 10 MW solid-fuel thorium molten-salt reactor (TMSR-SF1). The neutron activation foil sample is loaded outside the reactor and quickly transported to the measurement position in the reactor through the transmission device for irradiation, and then is transferred outside of reactor to the energy spectrum samples for de-spectrographic analysis.PurposeIn order to realize the rapid entry and exit of the neutron activation foil sample into and out of the reactor, a pneumatic conveying system with double-layer casing is designed in this research.MethodsThe principle of the conveying system and the structure of the double-casing tube were adopted in this study. ANSYS Fluent software and 6DOF dynamic grid technology were used to analyze the movement and stress of the sample under different pipe gaps, so as to determine the sample pipe gap value. Then the flow parameters and gas-solid two-phase flow resistance of the conveying system were calculated in detail using the pneumatic conveying theory. Finally, a prototype was developed for experiments to verify the principle of the conveying system.ResultsThe analysis results showed that the sample speed is decreased with the increase of the pipe gap. The experiments results show that the velocity of the sample and the pressure loss of the gas-solid two-phase flow increase with the increase of the gas flow rate. Under the same flow rate, the experimental speed of the sample movement and the pressure loss of the gas-solid two-phase flow are in good agreement with the theoretical calculations.ConclusionsThe pneumatic convey system with double-casing tube can be applied to transport the sample into and out of the reactor, and the theoretical calculations values of pneumatic conveying parameters in this study are reliable.

Published
2023
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42. Efficacy and safety of acupoint embedding therapy compared with western medicine in the treatment of nonalcoholic fatty liver disease: a meta-analysis

Author

Xu, Baixing, Dong, Haicheng, Zhu, Shifeng, Sun, Xiaoying, and Cong, Guodong

Abstract

The purpose of this study is to evaluate the efficacy and safety of acupoint embedding therapy in the treatment of nonalcoholic fatty liver disease (NAFLD). Articles published up to August 2021 were retrieved from PubMed, Embase, Cochrane Library, Web of Science, CNKI, VIP, WanFang, CBM, and the clinical trial registration database. This meta-analysis included 7 RCTs, involving 718 NAFLD patients. There is a statistically significant difference in the total efficacy rate between acupoint embedding therapy and western medicine (RR = 1.22, 95% CI: 1.11-1.34; P< 0.0001; I2= 0%). Acupoint embedding therapy has a huge association with improving TCM syndrome scores (MD = -3.46, 95% CI: -3.98 to -2.94; P< 0.00001; I2= 0%). Acupoint embedding therapy is more effective at treating NAFLD patients.

Published
2024
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