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“Blocking and rebalance”mechanism-guided design strategies of bimetallic doped 2D a-phosphorus carbide as efficient catalysts for N_(2) electroreduction

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Journal of Energy Chemistry 2024年第10期97卷 68-78,I0003页

作者： Cheng He Jianglong Ma shen xi Wenxue Zhang State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi'an Jiaotong UniversityXian 710049ShanxiChina School of Materials Science and Engineering Chang'an UniversityXi'an 710064ShaanxiChina

Compared to single atom catalysts(SACs),the introduction of dual atom catalysts(DACs)has a significantly positive effect on improving the efficiency in the electrocatalytic nitrogen reduction reaction(NRR)which provides an environmental alternative to the Haber-Bosch ***,the research on the mechanism and strategy of designing bimetallic combinations for better performance is still in its early ***,based on"blocking and rebalance"mechanism,45 combinations of bimetallic pair dopedα-phosphorus carbide(TM_(A)TM_(B)@PC)are investigated as efficient NRR catalysts through density functional theory and machine learning *** a multi-step screening,the combinations of TiV,TiFe,MnMo,and FeW exhibit highly efficient catalytic performance with significantly lower limiting potentials(-0.17,-0.18,-0.14,and-0.30 V,respectively).Excitingly,the limiting potential for CrMo and CrW combinations is 0 V,which are considered to be extremely suitable for the NRR *** mechanism of"blocking and rebalance"is revealed by the exploration of charge transfer for phosphorus atoms in electron blocking ***,the descriptorφis proposed with machine learning,which provides design strategies and accurate prediction for finding efficient *** work not only offers promising catalysts TM_(A)TM_(B)@PC for NRR process but also provides design strategies by presenting the descriptorφ.

关键词： DACs Nitrogen reduction reaction 2D a-phosphorus carbide Inherent attributes Machine learning

Characteristics of diffuse pollution of nitrogen and phosphorous from a small town in the hilly area of the central Sichuan Basin,China

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Journal of Mountain Science 2016年第2期13卷 292-301页

作者： YANG xiao-lin shen xi ZHU Bo Key Laboratory of Mountain Surface Processes and Ecological Regulation Institute of Mountain Hazards and EnvironmentChinese Academy of Sciences Safety and Emergency Management Research Center Henan Polytechnic University

Hydrological and hydro-chemical monitoring of nitrogen(N) and phosphorus(P) in a small urbanized catchment was conducted in the hilly area of the central Sichuan Basin,China,from 2010 through *** diffuse N and P loadings in different forms of total nitrogen(TN) and phosphorus(TP),dissolved nitrogen(DN) and phosphorus(DP),as well as particulate nitrogen(PN) and phosphorus(PP) were calculated based on runoff discharges and chemical *** results revealed that the diffuse pollution concentrations of TN,DN,PN,TP,DP and PP exhibited large variations during rainfall events,with peak concentrations occurring during the initial *** all of the measured parameters,the event mean concentrations(EMCs) were observed to clearly vary among rainfall *** EMCs of TN,DN,PN,TP,DP and PP(for all of the observed rainfall events) were 10.04,6.62,3.42,1.30,0.47 and0.83 mg/L,*** losses of diffuse N and P exhibited clear seasonal patterns and mainly occurred during the period from July through September,when the losses totaled 99.3 and 9.6 kg/ha for TN and TP,respectively,accounting for 75% and 74% of the total annual *** mean annual loadings of TN and TP were 124.6 and 12.9 kg/ha,*** results indicate that residential areas in the hilly areaof the central Sichuan Basin are subject to high diffuse N and P loadings,posing a serious risk to the receiving water *** buffering belts are recommended to incorporate into the urbanized catchment to reduce diffuse pollution.

关键词： Nitrogen transport Phosphorus transport Event mean concentration Pollution loading Pollution sources Non-point-source pollution Yanting Agro-ecological Station

Dynamic Simulation of Pelagic Longline Retrieval

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Journal of Ocean University of China 2019年第2期18卷 455-466页

作者： SONG Liming QI Yukun LI Jie shen Zhibin ZHANG xinfeng shen xi College of Marine Sciences Shanghai Ocean University National Engineering Research Centre for Oceanic Fisheries Shanghai Ocean University Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources (Shanghai Ocean University) Ministry of Education Collaboration Innovation Center for National Distant-Water Fisheries

To improve fishing gear efficiency, it is important to understand the interactions among sea current, fishing vessel, line hauler, and catches during pelagic longline gear retrieval. In this study, fishing gear configuration parameters, operational parameters, and 3 D ocean current data were collected from Indian Ocean. Dynamic models of pelagic longline gear retrieval were built using the lumped mass method and solved using the Euler-Trapezoidal method. From the results, the pulling force of line hauler exerted on the gear was 2800–3600 N. There were no significant differences(P > 0.05) between the time of the hook retrieval measured at sea and that obtained from the simulation. The absolute values of the movement velocity at representative nodes along the X, Y, and Z axes were 0.01–25.5 m s^(-1). These results suggest that the dynamic model of longline fishing gear retrieval can be used to analyze the interactions among sea current, fishing vessel, line hauler, longline gear, and catches, and to acquire the basic data for optimizing the design of the line hauler. Moreover, the model can serve as a reference to study the hydrodynamic performance of other fishing gears during the hauling process.

关键词： pelagic longline retrieval dynamic simulation visualization

Heterogeneous MXene-based films with graded electrical conductivity towards highly efficient EMI shielding and electrothermal heating

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Nano Research 2024年第8期17卷 7264-7274页

作者： Yu Zhang Guangcheng Zhang Zhonglei Ma Jianbin Qin xi shen Department of Aeronautical and Aviation Engineering The Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina Shaanxi Key Laboratory of Macromolecular Science and Technology School of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi’an 710072China Research Institute for Sports Science and Technology The Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina

The increasing need for electromagnetic interference(EMI)shielding of electronics in cold environments such as those in aircraft,space exploration,and wearable heaters to avoid hazardous icing conditions or hypothermia requires the development of thin and lightweight EMI shielding materials preferably by absorbing rather than reflecting electromagnetic(EM)waves while also generating heat through energy-efficient electrothermal ***,it is challenging to achieve absorption-dominant EMI shielding and energy-efficient electrothermal heating simultaneously in a thin and lightweight ***,we develop a heterogeneous composite film comprising a porous multi-walled carbon nanotubes(MWCNTs)/bacterial cellulose(BC)film and an aligned MXene/Ag nanowires(NWs)backing via a sequential vacuum filtration *** porous film contains random conductive networks of MWCNTs with moderate conductivity while the aligned MXene sheets atop Ag NWs network affords high conductivity in the backing,giving rise to graded electrical conductivity for absorption-dominant EMI *** increasing Ag NW coverage leads to significantly increased electrical conductivity without increasing the EM wave reflection as well as the density and thickness of the film,yielding excellent specific EMI shielding effectiveness(>8500 dB/(g·cm^(2))),low driving voltage for energy-efficient electrothermal heating(163℃at 2.5 V),and fast response time(60 s)at a low areal density of 0.015 mg/cm^(2).Combining EMI shielding and electrothermal heating,the heterogeneous film developed here are promising contenders for the protection of electronic equipment in low-temperature environment.

关键词： heterogenous composite film MXene electromagnetic interference(EMI)shielding thermal management

Dynamic spectrum allocations in multi-cells and intra-cell of cognitive network to enhance system performance

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High Technology Letters 2010年第3期16卷 280-287页

作者： Su xi shen Shuqun Li Zheng Zhang Lei School of Electronic Engineering Beijing University of Posts and Telecommunications Beijing 100876 P.R. China

In this study, we propose new dynamic spectrum allocations in multi-cells and intra-cell of cognitive network to enhance system performance in terms of decreasing probability of interruption and spectrum handoff of communication services in a cognitive system. The inter-cells of the spectrum allocation mechanism is designed to share the risk of vacating spectrum caused by licensed incumbents re-occupying the spectrum and minimize probability of service interruption in the cognitive network. This mechanism also can guarantee fairness among multi-cells. The intra-cell of the proposed spectrum allocation is based on a service data hierarchical model and establishes a mapping mechanism between layered data and the spectrum. It can reduce probability of spectrum handoff. Finally, simulation results are given and show that the new mechanism can reduce service interruption ratio and the probability of spectrum handoff caused by licensed incumbents with re-occupying the spectrum.

关键词： cognitive radio dynamic spectrum allocation spectrum analysis risk sharing hierarchical model

Decadal Variation of the Impact of La Nina on the Winter Arctic Stratosphere

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Advances in Atmospheric Sciences 2017年第5期34卷 679-684页

作者： Shuangyan YANG Tim LI Jinggao HU xi shen Key Laboratory of Meteorological Disaster Ministry of Education/Joint International Research Laboratory of Climate and Environmental Change/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of lnformation Science and Technology Nanjing 210044 China International Pacific Research Center and Department of Atmospheric Sciences University of Hawaii at Manoa Honolulu Hawaii 96822 USA

The impact of La Ni?a on the winter Arctic stratosphere has thus far been an ambiguous topic of research. Contradictory results have been reported depending on the La Ni?a events considered. This study shows that this is mainly due to the decadal variation of La Ni?a’s impact on the winter Arctic stratosphere since the late 1970 s. Specifically,during the period1951–78,the tropospheric La Ni?a teleconnection exhibits a typical negative Pacific–North America pattern,which strongly inhibits the propagation of the planetary waves from the extratropical troposphere to the stratosphere,and leads to a significantly strengthened stratospheric polar vortex. In contrast,during 1979–2015,the La Ni?a teleconnection shifts eastwards,with an anomalous high concentrated in the northeastern Pacific. The destructive interference of the La Ni?a teleconnection with climatological stationary waves seen in the earlier period reduces greatly,which prevents the drastic reduction of planetary wave activities in the extratropical stratosphere. Correspondingly,the stratospheric response shows a less disturbed stratospheric polar vortex in winter.

关键词： La Nina stratospheric polar vortex decadal variation planetary waves

Dynamically reconfigurable radio-over-fiber network with medium access control protocol to provide network access to train passengers

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Science China(Information Sciences) 2013年第10期56卷 134-143页

作者： shen xi XU Kun SUN xiaoQiang WU Jian LIN JinTong State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications

An innovative dynamically reconfgurable radio-over-fber(RoF)network equipped with an intelligent medium access control(MAC)protocol is proposed to provide broadband access to train passengers in railway high-speed mobile *** proposed RoF network architecture is based on a reconfgurable control station and remote access unit(RAU)that is equipped with a fxed flter and tunable *** proposed hybrid frequency-division multiplexing/time division multiple access(FDM/TDMA)based MAC protocol realizes failure detection/recovery and dynamic wavelength allocation to remote access *** result shows that with the proposed MAC protocol,the control station can detect failures and recover and dynamic wavelength allocation can increase the wavelength resource utilization to maintain network performance.

关键词： radio over fber medium access control protocol wavelength allocation failure detection failure recovery

Tree‑Inspired Structurally Graded Aerogel with Synergistic Water,Salt,and Thermal Transport for High‑Salinity Solar‑Powered Evaporation

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Nano-Micro Letters 2024年第11期16卷 19-37页

作者： xiaomeng Zhao Heng Zhang Kit‑Ying Chan xinyue Huang Yunfei Yang xi shen Department of Aeronautical and Aviation Engineering The Hong Kong Polytechnic UniversityHung HomKowloonHong Kong SARPeople’s Republic of China Research Institute for Sports Science and Technology The Hong Kong Polytechnic UniversityHung HomKowloonHong Kong SARPeople’s Republic of China Research Institute for Advanced Manufacturing The Hong Kong Polytechnic UniversityHung HomKowloonHong Kong SARPeople’s Republic of China

Solar-powered interfacial evaporation is an energy-efficient solution for water *** requires solar absorbers to facilitate upward water transport and limit the heat to the surface for efficient ***,downward salt ion transport is also desired to prevent salt ***,achieving simultaneously fast water uptake,downward salt transport,and heat localization is challenging due to highly coupled water,mass,and thermal ***,we develop a structurally graded aerogel inspired by tree transport systems to collectively optimize water,salt,and thermal *** arched aerogel features root-like,fan-shaped microchannels for rapid water uptake and downward salt diffusion,and horizontally aligned pores near the surface for heat localization through maximizing solar absorption and minimizing conductive heat *** structural characteristics gave rise to consistent evaporation rates of 2.09 kg m^(-2) h^(-1) under one-sun illumination in a 3.5 wt%NaCl solution for 7 days without *** in a high-salinity solution of 20 wt%NaCl,the evaporation rates maintained stable at 1.94 kg m^(-2) h^(-1) for 8 h without salt crystal *** work offers a novel microstructural design to address the complex interplay of water,salt,and thermal transport.

关键词： Composite aerogel Graded structure Solar-powered evaporation Thermal insulation Salt rejection

Effect of rich air/fuel ratio and temperature on NO_x desorption of lean NO_x trap

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第11期14卷 835-842页

作者： Lei LIU Zhi-jun LI Hong-yang ZHANG Qing CHANG Bo-xi shen State Key Laboratory of Engines Tianjin University

An experimental and model-based study of the effect of rich air/fuel ratios(AFRs) and temperature on the NOx slip of a lean NOx trap(LNT) was conducted in a lean-burn gasoline engine with an LNT after-treatment system. The emissions of the engine test bench and the inlet temperature of the LNT were used as the major inlet boundary conditions of the LNT. The engine periodically operated between a constant lean AFR of 23 with alterable rich AFRs of 10, 11, 12, 13, and 14. A decrease in the rich AFR of the engine strengthened the desorption atmosphere in the LNT, an effect closely related to the number of reductants, and further heightened the NOx desorption of the LNT, but with a penalty in fuel consumption. To eliminate that penalty, the inlet boundary conditions of the LNT were varied by adjusting the inlet temperature within a range between 200℃ and 400℃. An increase in inlet temperature heightened the NOx desorption of the LNT, and a NOx breakthrough occurred after the inlet temperature exceeded 390℃. To control NOx breakthrough, the inlet temperature can be adjusted to offset the strong desorption atmosphere in the LNT commonly created by a rich AFR.

关键词： Lean NOx trap (LNT) Air/fuel ratio (AFR) Temperature NOx adsorption NOx desorption