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Multiscale causes of the 2022 Yangtze mega-flash drought under climate change

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Science China Earth Sciences 2024年第8期67卷 2649-2660页

作者： Xing YUAN Yumiao wang Shiyu ZHOU Hua LI Chenyuan LI School of Hydrology and Water Resources Nanjing University of Information Science and Technology Institute of Atmospheric Physics Chinese Academy of Sciences Key Laboratory of Hydrometeorological Disaster Mechanism and Warning of Ministry of Water Resources Nanjing University of Information Science and Technology

The 2022 Yangtze mega-flash drought is characterized by strong intensity and rapid development both in time and space, accompanied by a persistent anticyclonic circulation anomaly. However, the causes of the extreme event remain elusive given the multiscale nature of drought. Here we presented a brief overview for the oceanic and terrestrial causes of the megaflash drought during the summer of 2022, and estimated the risk in a changing climate. Using the soil moisture percentile as the drought index, it was found that the drought expanded to the entire Yangtze River basin within two months, with 80% of basin under severe drought conditions at the end of August. Both the intensity and onset speed of the 2022 mega-flash drought were ranked as the first during the past 62 years, with return periods of 86 and 259 years, respectively. The results of composite analysis showed that the spring La Ni?a can facilitate the abrupt change from a wet/normal condition in May–June to drought in July–August over the Yangtze River basin, which was beneficial for the increase of flash drought intensity and onset speed in2022. The analysis through the linear regression also indicated that the unprecedented intensity was associated with the negative phase of the Pacific Decadal Oscillation. Quantified by a coupling strength index for soil moisture and vapor pressure deficit, it was found that there was a strong land-atmosphere coupling over the Yangtze River basin during July–August 2022. The attribution by using CMIP6 climate models suggested that land-atmosphere coupling increased the risks of flash drought intensity and onset speed like 2022 by 61%±6% and 64%±7% under natural climate forcings, and the synergy of coupling and anthropogenic climate change would increase the risks by 75%±22% and 85%±12%. Our findings emphasized the role of landatmosphere coupling combined with anthropogenic climate change in intensifying flash droughts.

关键词： Flash drought Yangtze River basin Land-atmosphere coupling Climate change Attribution

Investigating the Effects of VC MXene on Improving the Switching Stability and Reducing the Operation Voltages of TiO-Based Memristors

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Chinese Journal of Electronics 2024年

作者： Nan HE Lei wang Yi TONG College of Electronic and Optical Engineering and College of Flexible Electronics (Future Technology) College of Integrated Circuit Science and Engineering Nanjing University of Posts and Telecommunications Gusu Laboratory of Materials

Three-atoms-type V2C MXene, an emerging class of transition metal carbides, has attracted tremendous attention in the fabrication of advanced memristive devices due to its excellent electrochemical properties. However, the inserted and behind physical effects of inserting V2C on traditional TiO2-based memristors have not been clearly explored. In this work, exhaustive electrical characterizations of the V2C/TiO2-based devices exhibit enhanced performance（e.g., improved switching stability and lower operating voltages） compared to the TiO2-based counterparts. In addition, the advantaged influences of the inserted V2C have also been studied by means of firstprinciples calculations, confirming that V2C MXene enables controllable internal ionic process and facilitated formation mechanism of the Ag conductive filaments. This work demonstrates a way to combine experimental and theoretical investigations to reveal the positive effects of introducing V2C MXene on memristor, which is beneficial for fabricating performance-enhanced memristors.

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Asymptotic Behavior of Singular Solution to the k-Hessian Equation with a Matukuma-Type Source

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Wuhan University Journal of Natural Sciences 2024年第3期 242-256页

作者： LIU Jinyu wang Biao CHANG Caihong College of Science Xi'an University of Science and Technology

This paper is concerned with radially positive solutions of the k-Hessian equation involving a Matukuma-type source■ x ∈ Ω, where Sk(D2（-φ）) is the k-Hessian operator, q > k > 1,λ > 0,n > 2k,k ∈ N, and Ω is a suitable bounded do-main in R~n. It turns out that there are two different types of radially positive solutions for k > 1, i.e., M-solution（singular at r = 0） and Esolution（regular at r = 0）, which is distinct from the case when k = 1. For 1 < q < [（n-2 + λ）k]（n-2k）, we apply an iterative approach to improve accuracy of asymptotic expansions of M-solution step by step to the desired extend. In contrast to the case k = 1, we require a more precise range of parameters due to repeated application of Taylor expansions, which also makes asymptotic expansions need more delicate investigation.

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纤维素/海藻酸钠/明胶复合水凝胶的制备与性能

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高分子材料科学与工程 2024年第3期40卷 133-142页

作者：王斐昊许波王平王强江南大学纺织科学与工程学院江苏无锡214122

纤维素作为一种来源丰富的天然高分子材料,具有优异的生物相容性和可降解性,但其难溶特性限制了其应用。文中采用离子液体1-烯丙基-3-甲基咪唑氯化物(AmimCl)溶解纤维素(Cel),海藻酸钠(SA)与明胶(Gel)混合水溶液作为凝固浴进行纤维素再... 详细信息

纤维素作为一种来源丰富的天然高分子材料,具有优异的生物相容性和可降解性,但其难溶特性限制了其应用。文中采用离子液体1-烯丙基-3-甲基咪唑氯化物(AmimCl)溶解纤维素(Cel),海藻酸钠(SA)与明胶(Gel)混合水溶液作为凝固浴进行纤维素再生,进一步通过浸泡氯化钙(CaCl_(2))溶液交联海藻酸钠,制备了一种透明、高强度的复合水凝胶。分别探究了纤维素浓度(3%,4%,5%,6%,7%和8%)及不同的海藻酸钠/明胶质量比(0:10,2:8,4:6,6:4,8:2和10:0)对水凝胶性能的影响。利用傅里叶变换红外光谱、扫描电子显微镜、X射线衍射仪、紫外可见分光光度计和万能材料试验机对水凝胶进行了表征。结果表明,水凝胶中各组分之间的氢键作用及海藻酸钠与Ca^(2+)之间的离子相互作用赋予水凝胶优异的力学性能,相比于纯水作为凝固浴制备的再生纤维素水凝胶,强度提高了26.36%。随着纤维素浓度的增加,水凝胶的结晶度和网络结构的致密性增加,水凝胶的力学性能显著提升。此外,海藻酸钠/明胶的比例也对水凝胶的力学性能有显著影响,当海藻酸钠与明胶质量比为6:4时,水凝胶力学性能最好,最高达到2.349 MPa。生物降解性分析表明,水凝胶具有良好的生物降解性,在食品包装和生物医药领域具有潜在应用价值。

关键词：纤维素海藻酸钠明胶水凝胶离子液体

A robust viscoelastic surfactant tolerating 20% HCl up to 150℃ for oil well stimulation

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Petroleum Science 2024年第3期21卷 1865-1874页

作者： Ji wang Ning Qi Hong-Yao Yin Yu-Jun Feng Polymer Research Institute State Key Laboratory of Polymer Materials Engineering Sichuan University Tianfu Yongxing Laboratory New Theory and Technology of CO School of Petroleum Engineering China University of Petroleum (East China)

Viscoelastic surfactants（VES） are often used as viscous diverters in acidizing stimulation to prolong the acid consumption time and maximize zonal coverage of the acid for improving well productivity.However, the ceiling temperature of commercial VES cannot exceed 120℃ in practical use because of the poor thermal stability and fragile molecular structure, hindering their implementation in hightemperature oil reservoirs, i.e., ≥150℃. Here we synthesized a novel C22-tailed diamine, N-erucaminopropyl-N,N-dimethylamine（EDPA）, and examined comparatively its rheological behavior, assemblies morphology and molecular stability in 20 wt% HCl with a commercial VES, erucyl dimethyl amidopropyl betaine（EDAB）. The feasibility of EDPA for acidizing stimulation was assessed by acid etching of carbonate rock with its HCl solution at 150℃. Rheological results showed that the 2.5 wt% EDPA—20 wt%HCl solution maintains stable viscosity of 90 m Pa s at 150℃ for 60 min, while that of 2.0 wt% EDAB HCl solution is just 1 m Pa s under identical conditions.1H NMR spectra and cryo-TEM observations revealed that the chemical structure and self-assembled architectures of EDPA remained intact in such context,but the EDAB suffered from degradation due to the hydrolysis of the amide group, accounting for the poor heat-resistance and acid-tolerance. The reaction rate of 2.5 wt% EDPA HCl solution with carbonate rock was one order of magnitude lower than that of 20 wt% HCl solution at 150℃, underpinning the potential of EDPA to be used in the high-temperature reservoirs acidizing. This work improved the thermal tolerance of VES in highly concentrated HCl solution, paving a feasible way for the acidization of high-temperature reservoir environments（～150℃）.

关键词： Viscoelastic surfactants Thermal stability Self-diverting acid Wormlike micelles Acidizing stimulation

Underwater self-interference suppression method based on multistage delay estimation and transfer function fitting

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Chinese Journal of Acoustics 2024年第2期43卷 199-217页

作者： wang Boheng ZHANG Qunfei SHI Wentao School of Marine Science and Technology Northwestern Polytechnical UniversityXi'an 710072

In order to suppress strong self-interference signals in received signals, a selfinterference suppression method based on transfer function fitting and multistage delay estimation is proposed. Firstly, the transfer function of transmitting leakage is estimated by frequency domain deconvolution to construct the basic cancellation signal. Then, the multistage delay estimation based on the cross correlation method and the cross spectrum method is used to accurately compensate the cancelling signals to obtain a good selfinterference suppression effect. The processing results of the actual sea trial data indicate that the suppression ratio of the proposed method can reach 36 d B, and the signal-tointerference ratio of the detectable echo can be reduced from-30 d B to-55 d B when the unmanned undersea vehicle(UUV) integrated system is used to transmit multi-frame linear frequency modulated(LFM) signals in the working sector of the side array for active detection of the target ship. The same suppression effect is found for the subsequent selfinterference signals. The above results indicate that the method can suppress the strong self-interference signal, and presents stability, so that the echo signal submerged in the strong self-interference signal can be detected.

关键词： estimation delay function

Electricity Carbon Quota Trading Scheme based on Certificateless Signature and Blockchain

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Computer Modeling in Engineering & Sciences 2024年第2期138卷 1695-1712页

作者： Xiaodong Yang Runze Diao Tao Liu Haoqi Wen Caifen wang College of Computer Science and Engineering Northwest Normal UniversityLanzhou730070China Institute of China TelecomWanwei China TelecomWanwei Information Technology Co.Ltd.Lanzhou730030China College of Big Data and Internet Shenzhen Technology UniversityShenzhen518118China Key Laboratory of Cryptography and Data Analytics Northwest Normal UniversityLanzhou730070China

The carbon tradingmarket can promote“carbon peaking”and“carbon neutrality”at low cost,but carbon emission quotas face attacks such as data forgery,tampering,counterfeiting,and replay in the electricity trading market.Certificateless signatures are a new cryptographic technology that can address traditional cryptography’s general essential certificate requirements and avoid the problem of crucial escrowbased on identity cryptography.However,most certificateless signatures still suffer fromvarious security flaws.We present a secure and efficient certificateless signing scheme by examining the security of existing certificateless signature schemes.To ensure the integrity and verifiability of electricity carbon quota trading,we propose an electricity carbon quota trading scheme based on a certificateless signature and blockchain.Our scheme utilizes certificateless signatures to ensure the validity and nonrepudiation of transactions and adopts blockchain technology to achieve immutability and traceability in electricity carbon quota transactions.In addition,validating electricity carbon quota transactions does not require time-consuming bilinear pairing operations.The results of the analysis indicate that our scheme meets existential unforgeability under adaptive selective message attacks,offers conditional identity privacy protection,resists replay attacks,and demonstrates high computing and communication performance.

关键词： Electricity carbon trading certificateless signature blockchain forgery attack carbon quota

Learning Discriminatory Information for Object Detection on Urine Sediment Image

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工程与科学中的计算机建模(英文) 2024年第1期138卷 411-428页

作者： Sixian Chan Binghui Wu Guodao Zhang Yuan Yao Hongqiang wang College of Computer Science and Technology Zhejiang University of TechnologyHangzhou310023China The Hefei Institutes of Physical Science Chinese Academy of SciencesHefei230071China Department of Digital Media Technology Hangzhou Dianzi UniversityHangzhou310018China School of Computer Science University of Nottingham Ningbo ChinaNingbo315100China

In clinical practice,the microscopic examination of urine sediment is considered an important in vitro examination with many broad applications.Measuring the amount of each type of urine sediment allows for screening,diagnosis and evaluation of kidney and urinary tract disease,providing insight into the specific type and severity.However,manual urine sediment examination is labor-intensive,time-consuming,and subjective.Traditional machine learning based object detection methods require hand-crafted features for localization and classification,which have poor generalization capabilities and are difficult to quickly and accurately detect the number of urine sediments.Deep learning based object detection methods have the potential to address the challenges mentioned above,but these methods require access to large urine sediment image datasets.Unfortunately,only a limited number of publicly available urine sediment datasets are currently available.To alleviate the lack of urine sediment datasets in medical image analysis,we propose a new dataset named UriSed2K,which contains 2465 high-quality images annotated with expert guidance.Two main challenges are associated with our dataset:a large number of small objects and the occlusion between these small objects.Our manuscript focuses on applying deep learning object detection methods to the urine sediment dataset and addressing the challenges presented by this dataset.Specifically,our goal is to improve the accuracy and efficiency of the detection algorithm and,in doing so,provide medical professionals with an automatic detector that saves time and effort.We propose an improved lightweight one-stage object detection algorithm called Discriminatory-YOLO.The proposed algorithm comprises a local context attention module and a global background suppression module,which aid the detector in distinguishing urine sediment features in the image.The local context attention module captures context information beyond the object region,while the global background suppression module e

关键词： Object detection attention mechanism medical image urine sediment

Longitudinal transducer driven by NiMnGa magnetic shape memory alloy

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Chinese Journal of Acoustics 2024年第2期43卷 232-247页

作者： LAN Yu wang Houqi LU Wei National Key Laboratory of Underwater Acoustic Technology Harbin Engineering UniversityHarbin 150001 Key Laboratory of Marine Information Acquisition and Security(Harbin Engineering University) Ministry of Industry and Information TechnologyHarbin 150001 College of Underwater Acoustic Engineering Harbin Engineering UniversityHarbin 150001

In order to realize a low-frequency and small-size underwater acoustic source,an underwater acoustic transducer has been designed by using Ni Mn Ga alloy, which has the advantages of large strain, rapid response and high energy density. Based on the deformation principle of Ni Mn Ga alloy, a physical model of a Ni Mn Ga longitudinal transducer is established, and the equivalentcircuit of the transducer is derived.A multi-physics coupling model of electromagnetic, mechanical and acoustic fields is established by using the finite element method to predict the underwater acoustic performance of the transducer.A small-scale prototype of the Ni Mn Ga longitudinal transducer is fabricated and its sound source level is tested in water within the frequency range from 500 Hz to 800 Hz. Experimental results demonstrate that the Ni Mn Ga transducer with an 8 mm diameter of the radiation surface, achieves sound source level of 115.5 d B at 700 Hz.

关键词： alloy NiMnGa density