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Long-term changes in the effect of drought stress on ecosystems across global drylands

Science China Earth Sciences 2023年第1期66卷 146-160页

作者： Xiaojing YU Lixia zhang Tianjun ZHOU Xing Zhang LASG Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science&TechnologyNanjing 210044China

Droughts are one of the climate extremes that occur frequently in drylands,constraining the terrestrial carbon uptake and water cycle processes.Studies about the long-term changes in the effect of drought stress on dryland ecosystems under global warming are still insufficient so far.Here we comprehensively investigate long-term changes in droughts and the effect of drought stresses on ecosystems across global drylands for 1982–2015,and further reveal changes in the configurations of the key meteorological and ecological factors of droughts,by using observation and reanalysis datasets.Climatically,the spatial patterns of intensity,occurrence,duration and severity of all drought categories across global drylands are highly consistent with each other.Associated with severe droughts,drylands witness insufficient precipitation(-12.4 mm mon^(-1)area-averaged over global drylands),warmer temperature(0.6℃),water deficit(-19.0 mm mon^(-1)),higher atmospheric aridity(0.06 k Pa),lower soil moisture(-0.03 m^(3)m^(-3)),suppressed vegetation growth and declined carbon uptake(-0.13 g C m^(-2)d^(-1)).The affected area,occurrence,duration and severity for mild to severe droughts in drylands and the anomalies of meteorological and ecological factors for all drought categories have increased significantly during 1982-2015.Specifically,when droughts occur,the precipitation deficit is weakened at a rate of 3.7–9.6 mm mon^(-1)(30 yr)^(-1),the higher temperature(atmospheric aridity)is further intensified at 0.71–0.87-1(30 yr)^(-1)(39–47 Pa(30 yr)^(-1)),the water(soil moisture)deficit is relieved at 1.7–5.1 mm mon^(-1)(30yr)^(-1)(4.1×10^(-3)–7.4×10^(-3)m^(3)m^(-3)(30 yr)^(-1)),and the suppressed vegetation growth is generally alleviated at 0.98×10^(-2)–1.2×10^(-2)(30 yr)^(-1).Since the 2000s,the increasing trend in the suppressed vegetation growth during droughts tends to stagnate over about 50%of the dryland area.By checking the probability density function,the configurations of the key meteorological and ecological factors of drought

关键词： Global drylands Droughts Drought stress for ecosystem Global warming

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Study of Polymer Flooding in Heterogeneous Porous Media by Using Nuclear Magnetic Resonance

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Energy Engineering 2021年第5期118卷 1453-1467页

作者： Xing Zhang Shengli Oil Field Sinopec GroupDongying257000China

Polymer has been successfully used to enhance crude oil recovery at high water cut stage.However,the application of polymer flooding is limited by the heterogeneity of reservoir.In this work,the role of polymer flooding in heterogeneous reservoir was explored by nuclear magnetic resonance(NMR)spectroscopy.Parallel core displacement experiments were carried out to study polymer flooding in heterogeneous formation.The results showed that the polymer flooding area was related to permeability and pore connectivity.At the end of the water flooding stage,the residual oil was not evenly distributed in porous media.The percent crude oil recovery increased with the increase of pore diameter.Crude oil recovery from cores with larger pores was higher,and water broke through the highly permeable core first.After 0.3 PV polymer injection,the water mobility of the high permeability core decreased.Polymer injection showed a dual effect,an oil displacement effect and a traction effect.The oil displacement effect was responsible for driving out the crude oil in large pores,whereas the traction effect was responsible for driving out residual oil from small pores.After 1 PV polymer injection,the polymer solution channeled through the highly permeable core rapidly.The crude oil in large pores was washed out completely.The NMR water-phase spectrum line of the highly permeable core was much higher than that of the low permeable core.Under different core permeability and porosity,the NMR peak of the crude oil-phase spectrum line indicated that the polymer flooding is mainly effective on pores>40μm.

关键词： Nuclear magnetic resonance relaxation time polymer flooding displacement effect traction effect

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Current status of stationary fuel cells for coal power generation

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Clean Energy 2018年第2期2卷 126-139页

作者： Xing Zhang IEA Clean Coal Centre 176 Upper Richmond RdLondon SW152SHUK

Fuel cells electrochemically convert chemical energy in fuels into electrical energy(and heat)and so can produce power efficiently with low environmental impact.Applications of fuel cells include stationary power generation,distributed combined heat and power(CHP)and portable power.Recently,research has been conducted on direct carbon fuel cell(DCFC)technology that converts the chemical energy in solid carbon directly into electricity.This article discusses these technologies and their development status.For small-to medium-sized stationary power systems and CHP,the USA ranks first for fuel cell capacity and Japan leads for delivery systems.South Korea is home to the world’s largest fuel cell power plant:the 59-MW Gyeonggi Green Energy park in Hwasung City.Deployment of fuel cell systems is driven by support from governments in the form of tax credits and other incentives.For large stationary power generation,current interest is in integrating a coal gasification process with high-temperature fuel cells(IGFC)to create ultra-high-efficiency,low-emissions power generation systems.The first IGFC demonstration plant with CCS may be in Japan in 2021 as a result of the CoolGen project.DCFC is still in its infancy and far from demonstration.The overall challenges for stationary fuel cells are cost and cell durability.Experience gained from research,designing,building and operating commercially available systems and the IGFC demonstration plant should lead to further development of the technologies and reduced costs,making them a realistic option for power generation.

关键词： stationary fuel cells power generation efficiency carbon capture and storage IGCC IGFC DCFC coal

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A brief review on the recent development of phonon engineering and manipulation at nanoscales

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International Journal of Extreme Manufacturing 2024年第1期6卷 177-206页

作者： Siqi Xie Hongxin Zhu Xing Zhang Haidong Wang Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Engineering MechanicsTsinghua UniversityBeijing 100084People’s Republic of China

Phonons are the quantum mechanical descriptions of vibrational modes that manifest themselves in many physical properties of condensed matter systems. As the size of electronic devices continues to decrease below mean free paths of acoustic phonons, the engineering of phonon spectra at the nanoscale becomes an important topic. Phonon manipulation allows for active control and management of heat fow, enabling functions such as regulated heat transport. At the same time, phonon transmission, as a novel signal transmission method, holds great potential to revolutionize modern industry like microelectronics technology, and boasts wide-ranging applications. Unlike fermions such as electrons, polarity regulation is difficult to act on phonons as bosons, making the development of effective phonon modulation methods a daunting task.This work reviews the development of phonon engineering and strategies of phonon manipulation at different scales, reports the latest research progress of nanophononic devices such as thermal rectifiers, thermal transistors, thermal memories, and thermoelectric devices,and analyzes the phonon transport mechanisms involved. Lastly, we survey feasible perspectives and research directions of phonon engineering. Thermoelectric analogies, external field regulation, and acousto-optic co-optimization are expected to become future research hotspots.

关键词： phonon engineering phononic device nanoscale

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The epigenetic landscape of exercise in cardiac health and disease

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Journal of Sport and Health Science 2021年第6期10卷 648-659,I0001,F0003页

作者： Guiling Wu Xing Zhang Feng Gao School of Aerospace Medicine Fourth Military Medical UniversityXi’an 710032China

With the rising incidence of cardiovascular diseases,the concomitant mortality and morbidity impose huge burdens on quality of life and societal costs.It is generally accepted that physical inactivity is one of the major risk factors for cardiac disease and that exercise benefits the heart in both physiological and pathologic conditions.However,the molecular mechanisms governing the cardioprotective effects exerted by exercise remain incompletely understood.Most recently,an increasing number of studies indicate the involvement of epigenetic modifications in the promotion of cardiac health and prevention of cardiac disease.Exercise and other lifestyle factors extensively induce epigenetic modifications,including DNA/RNA methylation,histone post-translational modifications,and non-coding RNAs in multiple tissues,which may contribute to their positive effects in human health and diseases.In addition,several studies have shown that maternal or paternal exercise prevents age-associated or high-fat dietinduced metabolic dysfunction in the offspring,reinforcing the importance of epigenetics in mediating the beneficial effects of exercise.It has been shown that exercise can directly modify cardiac epigenetics to promote cardiac health and protect the heart against various pathological processes,or it can modify epigenetics in other tissues,which reduces the risk of cardiac disease and affords cardioprotection through exerkines.An in-depth understanding of the epigenetic landscape of cardioprotective response to exercise will provide new therapeutic targets for cardiac diseases.This review,therefore,aimed to acquaint the cardiac community with the rapidly advancing and evolving field of exercise and epigenetics.

关键词： Cardioprotection DNA methylation Epigenetics Exercise Histone post-translational modifications Non-coding RNAs

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Analysis and Optimization on Partition-Based Caching and Delivery in Satellite-Terrestrial Edge Computing Networks

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China Communications 2023年第3期20卷 252-285页

作者： Peng Wang Xing Zhang Jiaxin zhang Shuang Zheng Wenhao Liu Wireless Signal Processing and Network Laboratory Key Laboratory of Universal Wireless CommunicationMinistry of EducationSchool of Information and Communication EngineeringBeijing University of Posts and TelecommunicationsBeijing 100876China

As a viable component of 6G wireless communication architecture,satellite-terrestrial networks support efficient file delivery by leveraging the innate broadcast ability of satellite and the enhanced powerful file transmission approaches of multi-tier terrestrial networks.In the paper,we introduce edge computing technology into the satellite-terrestrial network and propose a partition-based cache and delivery strategy to make full use of the integrated resources and reducing the backhaul load.Focusing on the interference effect from varied nodes in different geographical distances,we derive the file successful transmission probability of the typical user and by utilizing the tool of stochastic geometry.Considering the constraint of nodes cache space and file sets parameters,we propose a near-optimal partition-based cache and delivery strategy by optimizing the asymptotic successful transmission probability of the typical user.The complex nonlinear programming problem is settled by jointly utilizing standard particle-based swarm optimization(PSO)method and greedy based multiple knapsack choice problem(MKCP)optimization method.Numerical results show that compared with the terrestrial only cache strategy,Ground Popular Strategy,Satellite Popular Strategy,and Independent and identically distributed popularity strategy,the performance of the proposed scheme improve by 30.5%,9.3%,12.5%and 13.7%.

关键词： edge computing satellite terrestrial net-works caching deployment stochastic geometry 6G networks

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Improved Fractional-order Damping Method for Voltage-controlled DFIG System Under Weak Grid

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Journal of Modern Power Systems and Clean Energy 2022年第6期10卷 1531-1541页

作者： Zhen Xie Xiang Gao Shuying Yang Xing Zhang School of Electrical Engineering and Automation Hefei University of TechnologyHefeiChina

When a doubly-fed induction generator(DFIG)is connected to a weak grid,the coupling between the grid and the DFIG itself will increase,which will cause stability problems.It is difficult to maintain the tracking accuracy and robustness of the phase-locked loop(PLL)in the weak grid,and the risk of instability of the current-controlled DFIG(CC-DFIG)system will increase.In this paper,a new type of voltage-controlled DFIG(VC-DFIG)mode is adopted,which is a grid-forming structure that can independently support the voltage and frequency with a certain adaptability in the weak grid.A small-signal impedance model of the VC-DFIG system is also established.The impedance of DFIG inevitably generates coupling with the grid impedance in the weak grid,especially in parallel compensation grids,and results in resonance.On the basis of the VC-DFIG,impedance stability analysis is performed to study the influences of the control structure and short-circuit ratio.Then,a feedforward damping method is proposed to modify the impedance of the VC-DFIG system at resonance frequencies.The proposed fractional order damping is utilized,which can enhance the robustness and rapidity of resonance suppression under parameter fluctuations.Finally,the experimental results are presented to validate the effectiveness of the proposed control strategy.

关键词： Weak grid voltage-controlled doubly-fed induction generator(DFIG) resonance feedforward damping fractional-order damping

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Molecular toxicity and defense mechanisms induced by silver nanoparticles in Drosophila melanogaster

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Journal of Environmental Sciences 2023年第3期125卷 616-629页

作者： Zhidi Wang Liying zhang xing Wang College of Resources and Environmental Sciences China Agricultural UniversityBeijing 100193China Beijing Key Laboratory of Biodiversity and Organic Farming Beijing 100193China

The widely use of silver nanoparticles(AgNPs) as antimicrobial agents gives rise to potential environmental risks. AgNPs exposure have been reported to cause toxicity in animals.Nevertheless, the known mechanisms of AgNPs toxicity are still limited. In this study, we systematically investigated the toxicity of AgNPs exposure using Drosophila melanogaster.We show here that AgNPs significantly decreased Drosophila fecundity, the third-instar larvae weight and rates of pupation and eclosion in a dose-dependent manner. AgNPs reduced fat body cell viability in MTT(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)assays. AgNPs caused DNA damage in hemocytes and S2 cells. Interestingly, the mRNA levels of the entire metallothionein gene family were increased under AgNPs exposure as determined by RNA-seq analysis and validated by qRT-PCR, indicating that Drosophila responded to the metal toxicity of AgNPs by producing metallothioneins for detoxification. These findings provide a better understanding of the mechanisms of AgNPs toxicity and may provide clues to effect on other organisms, including humans.

关键词： Drosophila melanogaster Silver nanoparticles(AgNPs) Reactive oxygen species(ROS) DNA damage RNA-seq Metallothionein

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Bioinspired polymeric heart valves derived from polyurethane and natural cellulose fibers

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Journal of Materials Science & Technology 2023年第13期144卷 178-187页

作者： Feng Guo Rizheng Han Jishan Ying Zeping zhang Rui Yang Xing Zhang Institute of Metal Research Chinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China

In this work,bioinspired anisotropic polymeric heart valves were fabricated using composite materials from polyurethane(PU)and natural cellulose fiber bundles.Cellulose fibers with good alignment were obtained from balsa wood by a top-down process,which were then distributed in polyurethane to pre-pare cellulose fiber bundles reinforced polyurethane(CPU)by hot pressing.The storage modulus of the CPU along the direction parallel to the fiber alignment was 16.70±0.80 MPa,whereas that along the direction perpendicular to the fiber alignment was 8.41±0.94 MPa by dynamic mechanical analysis(DMA)tests at 1 Hz,comparable to aortic valve leaflets.Moreover,2-methacryloyloxyethyl phosphoryl-choline(MPC)was grafted onto the CPU surface(CPU-MPC)to improve hemocompatibility.With MPC modification,the water contact angle decreased significantly from 54.58°±2.98°to 26.42°±3.50°,and the platelet adhesion was reduced by 92%,compared to the original CPU.In vitro cell culture proved that both CPU and CPU-MPC samples did not show any cytotoxicity.Furthermore,the CPU composites were used to fabricate polymeric heart valves,which showed excellent hydrodynamic performance with a large orifice area(1.70 cm 2)and low regurgitation fraction(0.7%),meeting the requirements of ISO 5840-2 standard.

关键词： Polymeric heart valve Anisotropy Cellulose fibers Polyurethane

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An Update Review on Performance Enhancement of Refrigeration Systems Using Nano-Fluids

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Journal of Thermal Science 2022年第4期31卷 1236-1251页

作者： xing Meibo zhang Hongfa zhang Cancan Beijing Engineering Research Center of Sustainable Energy and Buildings School of Environment and Energy EngineeringBeijing University of Civil Engineering and ArchitectureBeijing 100044China MOE Key Laboratory of Enhanced Heat Transfer and Energy Conservation Beijing Key Laboratory of Heat Transfer and Energy ConversionBeijing University ofTechnologyBeijing 100124China

Considering the issues of energy saving and environment protection,the performance of refrigeration systems requires to be improved.In recent years,nano-fluids have attracted greatly attention from the researchers due to their outstanding thermal characteristics.In this work,the published investigations on the preparation and characterization of nano-fluids have been discussed at first.Furthermore,the key thermo-physical properties of nano-fluids,such as thermal conductivity,viscosity,specific heat and density have been summarized.Finally,the performance enhancements in different types of refrigeration systems by using nano-fluids have been reviewed.It is concluded that nano-fluids as refrigerant,lubricant or secondary fluid have wide potential application in refrigeration systems.

关键词： nano-fluids performance enhancement nano-refrigerant nano-lubricant nano-secondary fluid refrigeration

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