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Spatiotemporal variation of rainy season span and precipitation recorded by lacustrine laminated pollen in the Tibetan Plateau during the past two millennia

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Science China Earth Sciences 2024年第3期67卷 789-801页

作者： Anning CUI Houyuan LU Juzhi HOU Xingqi liu Deke XU Key Laboratory of Cenozoic Geology and Environment Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Innovation Academy for Earth Science Chinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China Group of Alpine Paleoecology and Human Adaptation State Key Laboratory of Tibetan Plateau Earth SystemResources and EnvironmentInstitute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Capital Normal University College of Resource Environment and Tourism Beijing 100048China

The quantitative reconstruction of the length of the rainy season and precipitation on the Tibetan Plateau(TP) is crucial for revealing the spatiotemporal evolution of the Westerlies and Asian summer monsoon, as well as its ecological and environmental effects. Accurately determining the start and end times of the rainy season on the Plateau remains *** study determined the start and end times of the rainy season in different locations on the Plateau by identify.ng precipitation inflection points. We calculated the duration and precipitation amount of the rainy season and established a transfer function between the modern pollen assemblages and them. Then, we reconstructed the rainy season variations in Kusai Lake(northern TP) and Jiang Co(central TP) during the past two millennia. The results showed that, the rainy season precipitation in Kusai Lake recorded five periods of high precipitation: AD 580–680, 1000–1100, 1200–1450, 1550–1780, and 1920–present, corresponding to the stages with long rainy season. The rainy season precipitation sequence in Jiang Co recorded four periods of high precipitation: AD 80–500, 800–950, 1250–1450, and 1780–present, which is consistent with the long rainy season before AD 1000 but unclear afterward. Spatially, rainy season precipitation on the Plateau exhibited four patterns: “wet in both north and south” may be related to abnormally strong summer monsoons;“dry in both north and south” likely associated with weak Westerly wind and weak summer monsoon;“wet in the south and dry in the north” linked to strong summer monsoon and weak Westerly wind;and “dry in the south and wet in the north” connected to weak summer monsoon and strong Westerly wind. This study revealed the spatiotemporal evolution pattern of the rainy season onset and end, duration, and precipitation amount on the Plateau over the past two millennia. It provides natural background support for further understanding the coupling between Westerly wind and Asia

关键词： Tibetan Plateau Past two millennia Rainy season length Rainy season precipitation Quantitative reconstruction

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Switched-capacitor Based Seven-level Boost Inverter with a Reduced Number of Devices

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CSEE Journal of Power and Energy Systems 2024年第1期10卷 381-391页

作者： Weijie lin Jun Zeng Bo Fu Zhixing yan Junfeng liu School of Electric Power Engineering South China University of TechnologyGuangzhou 510641China WISDRI Engineering&Research Incorporation limited Wuhan 430074China Department of Energy Aalborg UniversityAalborg 9220Denmark School of Automation Science and Engineering South China University of TechnologyGuangzhou 510641China

The conventional multilevel inverters(Mlis)have the disadvantages of numerous devices,incapacity of boost,unbalance for capacitor’s voltage,high complexity for control,and *** by this issue,a seven-level boost inverter(7LBI)based on a switched capacitor is presented for singlephase applications in this *** proposed 7LBI using only seven transistors can achieve seven output levels,1.5 voltage gain,and natural balance of capacitors’voltages without sensors or other auxiliary methods,which illustrates its suitability for the applications of renewable energy *** configuration of topology and operating principles are illustrated in *** natural balance of capacitors and capacitance calculations are deduced as ***,the comparative study is conducted for different types of *** results illustrate the merits of the proposed 7LBI with respect to reduced devices,lower voltage stress,and less power ***,a simulation for the proposed 7LBI with PWM modulation is realized based on the theoretical analysis;an experimental prototype is also implemented,verify.ng multilevel output,boost ability,natural balance for switched capacitors,and performance of transient response.

关键词： Multilevel inverters voltage gain natural balance renewable energy generation reduced number of elements

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Voltage rise rate-related generalised probabilistic lifetime model of turn-to-turn insulation in inverter-fed motors

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High Voltage 2024年第1期9卷 46-55页

作者： yan y.ng Xuey.ng Bai yuxing Lei Kai liu Guangning Wu School of Electrical Engineering Southwest Jiaotong UniversityChengduChina

The lifetime model of turn-to-turn insulation in inverter-fed motors is studied.A lifetime model has been built by considering the effect of inverter-generated high voltage rise rate(dv/dt up to 20 V/ns).This model is followed by the generalised probabilistic model,in which the lifetime is proportional to the nth power of the voltage rise ***,by investigating the effect of voltage rise rate on the partial discharge characteristics,it is found that the effect of voltage rise rate on the charge transport process in a voltage cycle is similar to that of the voltage *** enhanced partial discharge activity and induced charges are responsible for accelerated ageing and thus determine the final lifetime of turn-to-turn *** this case,the generalised probabilistic electric lifetime model is applicable to the voltage rise rate as well as the voltage amplitude.

关键词： lifetime inverter insulation

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Trojan horses in tumor:engineered pyroelectric and photodynamic nanocomposites for NIR-induced cell apoptosis and tumor growth inhibition

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Science China Chemistry 2024年第9期67卷 3050-3062页

作者： yanxi y.ng Xinru Kong Xueli Ren yandai lin Zhe liu Academy of Medical Engineering and Translational Medicine Tianjin UniversityTianjin 300072China Tianjin Key Laboratory of Brain Science and Neural Engineering Tianjin UniversityTianjin 300072China

It is desirable but always challenging to develop a cutting-edge tumor treatment strategy with high therapeutic efficacy,lesiontargeted precision and mild *** to traditional treatment modalities,photodynamic therapy has been widely studied since the generation of reactive oxygen species(ROS)at cancerous lesions unprecedentedly offers a convenient approach for localized tumor ***,the consumption of oxygen for ROS production in a hypoxic tumor microenvironment has dramatically limited its feasibility and ***,the engineered nanocomposites of BTO@PDA-ICGHA with photodynamic and pyroelectric performances have been fabricated and applied to the photodynamic-pyroelectric dynamic *** continuing ROS production derived from intracellular oxygen(O_(2))and water(H_(2)O)by laser irradiation contributed to the superb tumor cell apoptosis and significant tumor growth ***,this study has validated a new concept by depositing the engineered nanocomposites at the tumor just like Trojan horses,facilitating ROS release as killers and exerting the NIR-induced cell apoptosis and tumor growth inhibition with high therapeutic efficiency and expectable translational perspectives.

关键词： nanocomposites pyroelectric effect photodynamic therapy cell apoptosis tumor growth inhibition

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Double-layer probiotic encapsulation for enhanced bacteriotherapy against inflammatory bowel disease

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Nano Research 2024年第10期17卷 9103-9110页

作者： yixin Wang Jun liu Sichen yuan yawen you Quanyin Hu Pharmaceutical Sciences Division School of PharmacyUniversity of Wisconsin-MadisonMadisonWI 53705USA Carbone Cancer Center School of Medicine and Public HealthUniversity of Wisconsin-MadisonMadisonWI 53705USA Wisconsin Center for NanoBioSystems School of PharmacyUniversity of Wisconsin-MadisonMadisonWI 53705USA

Inflammatory bowel disease(IBD)is inflammatory intestinal disorders associated with dysregulated gut *** that leverages bacteria as therapeutics has shown tremendous promise in resolving gut dysbiosis and reducing inflammatory mediators to treat *** delivered probiotics,such as Escherichia coli Nissle 1917(EcN),can produce beneficial ingredients,competitively inhibit the proliferation of pathogens,and promote the restoration of gut microbiome ***,environmental stresses(such as gastric acids)in the gastrointestinal(GI)tract pose an enormous challenge to the probiotics following oral administration,leading to decreases in viability and activity of ***,the inferior mucoadhesive capability of probiotics results in low colonization efficacy,further compromising their therapeutic *** probiotics with functional biomaterials may protect them from elimination and prolong their retention in the GI ***,we developed a facile double-layer electrostatic assembly technique to encapsulate EcN bacteria in protective layers of mucoadhesive chitosan(CS)and immunomodulatory hyaluronic acid(HA)to generate *** biomaterials confer the coated EcN resistance to environmental assault and enhanced mucoadhesion in the GI *** probiotics equipped with the multifunctional shield can thus suppress inflammation and reshape the intestinal microenvironment to enhance therapeutic efficacy for the prevention and treatment of ***,this study presents a novel probiotic coating strategy to augment the outcome of bacteriotherapy to combat IBD.

关键词： probiotics biomaterial coating inflammatory bowel disease mucoadhesion oral administration

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Ultralow-phase-noise and broadband frequency-hopping coupled optoelectronic oscillator under quiet point operation

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Photonics Research 2024年第8期12卷 1785-1793页

作者： HUI liu MIngy.ng GUO TIAN ZHAng JIAN DAI KUN XU State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and TelecommunicationsBeijing 100876China School of Electronic Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China

Advancements in microwave photonics have yielded novel approaches for generating high-purity microwave *** these,optoelectronic oscillators(OEOs)and coupled optoelectronic oscillators(COEOs)have demonstrated the capability to generate frequency-independent microwaves with exceptionally low phase ***,the tunability of the oscillators is rather limited due to the necessity for narrowband electronic bandpass filters,presenting challenges in achieving both wide and rapid tuning ***,we present a COEO featuring ultralow phase noise,flexible tuning capability,and high *** is achieved through a quiet point(QP)-operated harmonic mode-locked fiber laser,which effectively mitigates optical amplifier noise and supermode competition,thus significantly diminishing the necessity for ultra-narrow electronic *** to the liberated tuning ability,we present an oscillator that can be tuned from 2 GHz to 18 GHz,with phase noise as low as-140 d Bc/Hz at 10 k Hz under the QP *** then illustrate the practical application of the proposed oscillator in generating frequency-hopping signals with consistent spurious modes less than-85 d Bc,absolute phase noise below-135 d Bc/Hz at 10 k Hz,hopping resolution of 1.25 MHz,and fractional frequency stability below 6.1×10^(-12)at 1 s averaging time when locked to a *** presented COEO structure emerges as a compelling solution for agile and low-noise microwave sources in advanced wireless communication and radar systems.

关键词： optoelectronic tuning amplifier

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Metal–phenolic coordination crystals derived magnetic hollow carbon spheres for ultrahigh electromagnetic wave absorption

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Nano Research 2024年第3期17卷 1616-1624页

作者： Hanxiao Xu Zizhuang He yiruo Wang Xiangru Ren Panbo liu School of Chemistry and Chemical Engineering Northwestern Polytechnical UniversityXi’an 710129China

Owing to the tunable compositions and versatile functionality,the development of eco-friendly metal–phenolic coordination crystals derivatives is highly anticipated for electromagnetic wave *** this study,three kinds of magnetic hollow carbon spheres(HCSs)with macro-meso-microporous characteristics,including Fe/HCS,Co/HCS,and CoNi/HCS,are successfully fabricated via the co-operative hard template and self-assembling process,in which magnetic particles are encapsulated in carbon shell matrix after the pyrolysis of metal–polyphenol coordination crystals and further subsequent template *** the one hand,hierarchical macro-meso-micropores effectively balance the impedance gap between absorbers and air and introduce structural defects or distortion,leading to matched impedance and enhanced dipolar/defect *** the other hand,wrapped magnetic particles provide uncountable hetero-interfaces and induce ferromagnetic resonance,resulting in strengthened interfacial polarization and additional magnetic *** particular,enhanced minimum reflection loss(RL,min)and broadband effective absorption bandwidth(EAB)are achieved with only 10 wt.%filler ***,the RL,min and EAB values are-57.5 dB and 7.2 GHz for Fe/HCS,-50.0 dB and 5.8 GHz for Co/HCS,and-52.1 dB and 6.7 GHz for CoNi/HCS,***,this work provides us a modular-assembly strategy to regulate the hollow cavity of absorbers and simultaneously manipulates the chemical components of absorbers to regulate electromagnetic wave absorption performance.

关键词： hollow engineering hierarchical pores hetero-interfaces synergetic effect electromagnetic wave absorption

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Counterion-Mediated Hydrogen Bonding Making Strong Polyelectrolytes pH-Responsive:Current Understanding and Perspectives

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Chinese Journal of Polymer Science 2024年第9期42卷 1270-1277,I0005页

作者： yue Huang Guang-Tao Mei Zan Hua Guang-Ming liu Hefei National Research Center for Physical Sciences at the Microscale Department of Chemical PhysicsKey Laboratory of Surface and Interface Chemistry and Energy Catalysis of Anhui Higher Education InstitutesUniversity of Science and Technology of ChinaHefei230026China The Key Laboratory of Functional Molecular Solids Ministry of Educationand Department of Materials ChemistrySchool of Chemistry and Materials ScienceAnhui Normal UniversityWuhu214002China

The counterion-mediated hydrogen bonding(CMHB)is related to the hydrogen bonding between bound counterions and polyelectrolyte chains in polyelectrolyte systems,where the counterions can both electrostatically bind to the charged groups of polyelectrolyte chains and act as hydrogen bond donors or acceptors to form hydrogen bonds with the hydrogen bond sites associated with polyelectrolyte chains simultaneously.A large number of literatures illustrate that strong polyelectrolytes(SPs)are insensitive to pH,which severely limmits the applications of SPs as smart ***,our studies have demonstrated that the CMHB makes SPs *** perspective discusses the mechanism of pH responsiveness of SPs and the pH-tunable properties of SPs,based on the pH-controlled CMHB *** future research directions on the pH responsiveness of SPs are also discussed *** is anticipated that the study of the pH responsiveness of SPs not only will provide a new understanding of the fundamental properties of SPs,but also will greatly expand the applications of SPs in the field of smart materials.

关键词： Counterion binding Hydrogen bond Polyelectrolyte brush Polyelectrolyte complexation

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Highly Strong,Tough,and Cryogenically Adaptive Hydrogel Ionic Conductors via Coordination Interactions

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Research 2024年第3期2024卷 703-713页

作者： Zhuomin Wang Siheng Wang Lei Zhang He liu Xu Xu Institute of Chemical Industry of Forestry Products Key Laboratory of Biomass Energy and MaterialJiangsu ProvinceKey Laboratory of Chemical Engineering of Forest ProductsNational Forestry and Grassland AdministrationNational Engineering Research Center of Low-Carbon Processing and Utilization of Forest BiomassJiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest ResourcesChinese Academy of ForestryNanjing 210042China College of Chemical Engineering Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest ResourcesNanjing Forestry UniversityNanjing 210037China.

Despite the promise of high flexibility and conformability of hydrogel ionic conductors,existing polymeric conductive hydrogels have long suffered from compromises in mechanical,electrical,and cryoadaptive properties due to monotonous functional improvement strategies,leading to lingering ***,we propose an all-in-one strategy for the preparation of poly(acrylic acid)/cellulose(PAA/Cel)hydrogel ionic conductors in a facile yet effective manner combining acrylic acid and salt-dissolved cellulose,in which abundant zinc ions simultaneously form strong coordination interactions with the two polymers,while free solute salts contribute to ionic conductivity and bind water molecules to prevent ***,the developed PAA/Cel hydrogel simultaneously achieved excellent mechanical,conductive,and cryogenically adaptive properties,with performances of 42.5 MPa for compressive strength,1.6 MPa for tensile strength,896.9%for stretchability,9.2 MJ m^(−3)for toughness,59.5 kJ m^(−2)for fracture energy,and 13.9 and 6.2 mS cm^(−1)for ionic conductivity at 25 and−70°C,*** by these features,the resultant hydrogel ionic conductor is further demonstrated to be assembled as a self-powered electronic skin(e-skin)with high signal-to-noise ratio for use in monitoring movement and physiological signals regardless of cold temperatures,with hinting that could go beyond high-performance hydrogel ionic conductors.

关键词： Highly freezing salts

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Significantly improved near-field communication antennas based on novel Ho^(3+)and Co^(2+)ions co-doped Ni-Zn ferrites

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Journal of Advanced Ceramics 2024年第3期13卷 293-309页

作者： Pao y.ng Zhiqing liu Hongbin Qi Xiuli Fu Zhijian Peng School of Science China University of GeosciencesBeijing 100083China School of Science Beijing University of Posts and TelecommunicationsBeijing 100876China Kunshan Guoli Electronic Technology Co. Ltd.Kunshan 215300China

In near-field communication(NFC)antennas,soft magnetic ferrites are usually applied as a substrate to reduce eddy current loss and increase magnetic field *** this purpose,the applied ferrites are required to have high permeability and saturation magnetization together with low magnetic loss and dielectric ***,for most soft magnetic ferrites,it is difficult to meet all the *** novel Ni-Zn ferrite ceramics co-doped by Ho^(3+)and Co^(2+)ions with chemical formula Ni_(0.5-x)Zn_(0.5)Ho_(0.02)Co_(x)Fe_(1.98)O_(4)(x=0-0.2)were designed and prepared to balance these needs on the basis of molten salt synthesis with metal nitrates as raw materials and potassium hydroxide(KOH)as the precipitation agent and molten salt *** the substitution of Ho^(3+),the saturation magnetization and initial permeability decrease,but with further doping of Co^(2+),the saturation magnetization gradually increases,while the initial permeability continues to *** x=0.1,the sample will have the lowest dielectric constant,magnetic and dielectric loss,as well as the highest Curie temperature(305℃).Moreover,the acquired Ni-Zn ferrites have been applied simulatively in NFC antennas,revealing that the device manufactured with the optimal Ni_(0.4)Zn_(0.5)Ho_(0.02)Co_(0.1)Fe_(1.98)O_(4)ferrite ceramics would have significantly improved performance at 13.56 MHz with low leakage and long transmit distance of magnetic ***,the Ni_(0.4)Zn_(0.5)Ho_(0.02)Co_(0.1)Fe_(1.98)O_(4)ferrite ceramics would be a good candidate for NFC antenna substrates.

关键词： electromagnetic properties co-doping microstrip antennas Ni-Zn ferrite

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