检索结果-南通市图书馆

Communications in Theoretical Physics 2024年第1期76卷 76-81页

作者： Cheng Xu Zhen-Hao Yang Xiao-mei Kuang Rui-Hong Yue Center for Gravitation and Cosmology College of Physical Science and TechnologyYangzhou UniversityYangzhou225009China

The scalar-free black hole could be unstable against the scalar field perturbation when it is coupled to a Gauss–Bonnet(GB)invariant in a special *** is known that the tachyonic instability in this scenario is triggered by the sufficiently strong GB *** this paper,we focus on the time domain analysis of massive scalar field perturbation around the Schwarzschild de-Sitter black hole in Einstein-scalar–Gauss–Bonnet *** analyzing the scalar field propagation,we find that the scalar field will finally grow when the GB coupling is large *** could lead to the instability of the background black ***,we demonstrate how the mass of the scalar field and the GB coupling strength affect the onset of tachyonic instability.

关键词： black hole perturbation scalar-Einstein-Gauss-Bonnet gravity time domain evolution me

A new class of spectrally arbitrary complex sign pattern

在线全文

学校读者我要写书评

暂无评论

Frontiers of Mathematics in China 2024年第1期19卷 13-24页

作者： Yinzhen mei Peng WANG School of Mathematics North University of ChinaTaiyuan 030051China

Assume that S is an nth-order complex sign *** for every nth degree complex coefficient polynomial f(λ)with a leading coefficient of 1,there exists a complex matrix C∈Q(S)such that the characteristic polynomial of C is f(λ),then S is called a spectrally arbitrary complex sign *** is,if the spectrum of nth-order complex sign pattern S is a set comprised of all spectra of nth-order complex matrices,then S is called a spectrally arbitrary complex sign *** paper presents a class of spectrally arbitrary complex sign pattern with only 3n nonzero elements by adopting the method of Schur complement and row reduction.

关键词： Complex sign pattern potentially nilpotent spectrally arbitrary

Global Spillovers of China's Monetary Policy

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

China & World Economy 2024年第3期32卷 1-30页

作者： Wenni Lei Dongzhou mei Mi Zhang School of Economics Minzu University of ChinaChina School of International Trade and Economics Central University of Finance and EconomicsChina

Spillovers from China's monetary policy have become increasingly obvious with China's growing importance in the global economy and its close economic and trade ties with the *** study establishes a proxy structure vector autoregression model to investigate the magnitude and transmission channel of spillovers from China to global and regional economies,taking advantage of high-frequency changes in asset prices in the financial markets to identify monetary policy *** analysis reveals that China's monetary policy can affect the global economy by influencing international trade and commodity prices but there is no evidence of China's monetary policy affecting global financial *** in China's monetary policy can cause a decline in world output whereas expansion in monetary policy can support global trade and *** study also finds that the response of emerging Asian economies to China's monetary policy shock was nearly twice that of developed economies,while the transmission path did not *** results of this study are consistent with the stylized fact that China's monetary policy plays an important role in the global trade and commodity cycle,although it does not drive the global financial cycle.

关键词： China's monetary policy commodity prices external instruments global trade spillovers

Local search yields a PTAS for fixed-dimensional k-means problem with penalties

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of the Operations Research Society of China 2024年第2期12卷 351-362页

作者： Fan Yuan Da-Chuan Xu Dong-Lei Du Dong-mei Zhang Beijing Institute for Scientific and Engineering Computing Beijing University of TechnologyBeijing 100124China Faculty of Management University of New BrunswickFrederictonNB E3B 9Y2Canada School of Computer Science and Technology Shandong Jianzhu UniversityJinan 250101ShandongChina

We study a problem called the k-means problem with penalties(k-MPWP),which is a natural generalization of the typical k-means *** this problem,we have a set D of client points in R^(d),a set F of possible centers in R^(d),and a penalty cost Pj>O for each point j∈*** are also given an integer k which is the size of the center point *** want to find a center point set S■F with size k,choose a penalized subset of clients P■D,and assign every client in D\P to its open *** goal is to minimize the sum of the squared distances between every point in D\P to its assigned centre point and the sum of the penalty costs for all clients in *** using the multi-swap local search technique and under the fixed-dimensional Euclidean space setting,we present a polynomial-time approximation scheme(PTAS)for the k-MPWP.

关键词： Approximation algorithm k-means Local search Penalty

Fault Diagnosis Scheme for Railway Switch Machine Using Multi-Sensor Fusion Tensor Machine

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2024年第6期79卷 4533-4549页

作者： Chen Chen Zhongwei Xu Meng mei Kai Huang Siu Ming Lo School of Electronic and Information Engineering Tongji UniversityShanghai201804China Department of Architecture and Civil Engineering City University of Hong KongHong KongChina School of Computer Engineering Jimei UniversityXiamen361021China

Railway switch machine is essential for maintaining the safety and punctuality of train operations.A data-driven fault diagnosis scheme for railway switch machine using tensor machine and multi-representation monitoring data is developed *** existing methods,this approach takes into account the spatial information of the time series monitoring data,aligning with the domain expertise of on-site manual ***,a multi-sensor fusion tensor machine is designed to improve single signal data’s limitations in insufficient ***,one-dimensional signal data is preprocessed and transformed into two-dimensional ***,the fusion feature tensor is created by utilizing the images of the three-phase current and employing the CANDE-COMP/PARAFAC(CP)decomposition ***,the tensor learning-based model is built using the extracted fusion feature *** developed fault diagnosis scheme is valid with the field three-phase current *** experiment indicates an enhanced performance of the developed fault diagnosis scheme over the current approach,particularly in terms of recall,precision,and F1-score.

关键词： Railway switch machine tensor machine fault diagnosis

Ultrahigh spatiotemporal resolution beam signal reconstruction with bunch phase compensation

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2024年第5期35卷 99-108页

作者： You-Ming Deng Yong-Bin Leng Xing-Yi Xu Jian Chen Yi-mei Zhou Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of the Chinese Academy of Sciences Beijing 100049China Shanghai Synchrotron Radiation Facility Chinese Academy of SciencesShanghai 201204China University of Science and Technology of China Hefei 230026China Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201204China

Various electromagnetic signals are excited by the beam in the acceleration and beam-diagnostic elements of a particle *** is important to obtain time-domain waveforms of these signals with high temporal resolution for research,such as the study of beam–cavity interactions and bunch-by-bunch parameter ***,a signal reconstruction algorithm with ultrahigh spatiotemporal resolution and bunch phase compensation based on equivalent sampling is proposed in this *** with traditional equivalent sampling,the use of phase compensation and setting the bunch signal zero-crossing point as the time reference can construct a more accurate reconstructed *** basic principles of the method,simulation,and experimental comparison are also *** on the beam test platform of the Shanghai Synchrotron Radiation Facility(SSRF)and the method of experimental verification,the factors that affect the reconstructed signal quality are analyzed and discussed,including the depth of the sampled data,quantization noise of analog-to-digital converter,beam transverse oscillation,and longitudinal *** results of the beam experiments show that under the user operation conditions of the SSRF,a beam excitation signal with an amplitude uncertainty of 2%can be reconstructed.

关键词： Turn-by-turn bunch phase compensation technique Equivalent sampling Signal reconstruction algorithm Ultrahigh spatiotemporal resolution SSRF

Simultaneous removal of sulfur dioxide and nitrogen oxide from flue gas by phosphorus sludge:The performance and absorption mechanism

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2024年第1期65卷 212-221页

作者： Yuanyuan Yin Xujun Wang Lei Xu Binbin He Yunxiang Nie Yi mei Faculty of Chemical Engineering Kunming University of Science and TechnologyKunming 650500China Yunnan Provincial Key Laboratory of Energy Saving in Phosphorus Chemical Engineering and New Phosphorus Materials Kunming 650500China The Higher Educational Key Laboratory for Phosphorus Chemical Engineering of Yunnan Province Kunming 650500China

Developing low-cost and green simultaneous desulfurization and denitrification technologies is of great significance for sulfur dioxide(SO_(2))and nitrogen oxide(NO_(x))emission control at low temperatures,especially for small and medium-sized coal-fired boilers and ***,phosphorus sludge,an industrial waste from the production process of yellow phosphorus,has been developed to simultaneously eliminate SO_(2)and NO_(x)from coal-fired flue *** key factors affecting the experimental results indicate that desulfurization and denitrification efficiency of over 95%can be achieved at a low temperature of 55℃.Further,the absorption mechanism was investigated by characterizing the solid and liquid phases of the phosphorus sludge during the absorption *** efficient removal of SO_(2)is attributed to the abundance of iron(Fe^(3+))and manganese(Mn^(2+))in the ***_(2)can be rapidly catalyzed and converted to SO_(4)^(2-)by *** key to NOx removal is the oxidation of NO toward watersoluble high-valent nitrogen oxides by oxidizing reactive substances induced via yellow phosphorus,which are then absorbed by water and converted to NO_(3)^(-).Meanwhile,yellow phosphorus is oxidized to phosphoric acid(H_(3)PO_(4)).The spent absorption slurry can be reused through wet process phosphoric acid production,as it contains sulfuric acid(H_(2)SO_(4)),nitric acid(HNO_(3)),and H_(3)PO_(4).Accordingly,this is a technology with broad application prospects.

关键词： Absorption Oxidation Multiphase reaction Phosphorus sludge Yellow phosphorus Low temperature

A Low Cost, Green Sustainable and Biodegradable Biomass-based Fluorine-free Water and Oil Repellent

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2024年第4期42卷 480-491页

作者： Zhi-Wei Shen Shu-Feng Hu Chen Zeng Wei-Qing Kong mei-Fang Zhu State Key Laboratory for Modification of Chemical Fibers&Polymer Materials College of Materials Science and EngineeringDonghua UniversityShanghai201620China State Key Laboratory of Pulp and Paper Engineering School of Light Industry and EngineeringSouth China University of TechnologyGuangzhou510630China

With the global ban on plastics intensifying, the substitution of plastic with paper has garnered increasing attention. However, the inadequate water and oil repellency of pulp molding hinders its practical applications. Currently, the common method to enhance the oil and water repellency of pulp molding is by adding fluorinated water and oil repellents. Nevertheless, fluorinated compounds are environmentally and physiologically harmful. Therefore, the development of fluorine-free, water and oil repellent alternatives is crucial. In this study, chitosan and stearic acid were utilized as the first and second layers of the oil and water repellent coatings, respectively. The coated samples exhibited favorable water repellency, with a water contact angle of 116.4°, and excellent oil repellency, achieving a 12/12 rating on the kit scale. Importantly, the samples did not exhibit any leakage after being soaked in hot water and hot oil at 95±5℃ for 30 min, demonstrating remarkable performance as a barrier against hot water and oil. Moreover, the coated samples displayed outstanding mechanical properties, thermal stability, biodegradability, and recyclability. The approach presented in this study is simple, cost-effective, environmentally friendly, and represents a promising technique for producing fluoride-free, oil-and water-resistant pulp molding products.

关键词： Biomass Fluoride-free Oil-andwater-resistant Plasticfree

Rational Design of Cost-Effective Metal-Doped ZrO_(2)for Oxygen Evolution Reaction

在线全文

学校读者我要写书评

暂无评论

Nano-Micro Letters 2024年第9期16卷 385-396页

作者： Yuefeng Zhang Tianyi Wang Liang mei Ruijie Yang Weiwei Guo Hao Li Zhiyuan Zeng Department of Materials Science and Engineering and State Key Laboratory of Marine PollutionCity University of Hong Kong83 Tat Chee AvenueKowloon 999077Hong KongPeople’s Republic of China Advanced Institute for Materials Research(WPI‑AIMR) Tohoku UniversitySendai 980‑8577Japan Shenzhen Research Institute City University of Hong KongShenzhen 518057People’s Republic of China Shanxi Supercomputing Center Lvliang 033000ShanxiPeople’s Republic of China

The design of cost-effective electrocatalysts is an open challenging for oxygen evolution reaction(OER)due to the“stable-oractive”*** dioxide(ZrO_(2)),a versatile and low-cost material that can be stable under OER operating conditions,exhibits inherently poor OER activity from experimental ***,we doped a series of metal elements to regulate the ZrO_(2)catalytic activity in OER via spin-polarized density functional theory calculations with van der Waals *** modeling as a function of the OER activity descriptor(G_(O*)-G_(HO*))displays that 16 metal dopants enable to enhance OER activities over a thermodynamically stable ZrO_(2)surface,among which Fe and Rh(in the form of single-atom dopant)reach the volcano peak(*** optimal activity of OER under the potential of interest),indicating excellent OER *** energy diagram calculations,density of states,and ab initio molecular dynamics simulations further showed that Fe and Rh are the effective dopants for ZrO_(2),leading to low OER overpotential,high conductivity,and good *** cost-effectiveness,single-atom Fe doped ZrO_(2)emerged as the most promising catalyst for *** finding offers a valuable perspective and reference for experimental researchers to design cost-effective catalysts for the industrial-scale OER production.

关键词： Oxygen evolution reaction Metal oxide Electrocatalysis Surface Pourbaix analysis Doping

Optical Transient Source AT2021lfa:A Possible“Dirty Fireball”

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2024年第4期24卷 124-133页

作者： Xue-mei Ye Da-Ming Wei Yi-Ming Zhu Zhi-Ping Jin Key Laboratory of Dark Matter and Space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210023China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China National Astronomical Observatories/Nanjing Institute of Astronomical Optics&Technology Chinese Academy of SciencesNanjing 210042China CAS Key Laboratory of Astronomical Optics&Technology Nanjing Institute of Astronomical Optics&TechnologyNanjing 210042China

AT2021lfa,also known as ZTF21aayokph,was detected by the Zwicky Transient Facility on 2021 May 4,a 05:34:48 ***-up observations were conducted using a range of ground-based optical telescopes,as wel as Swift/XRT and VLA ***2021lfa is classified as an“orphan afterglow”candidate due to its rapid flux decline and its reddened color(g-r=0.17±0.14 mag).For an optical transient source without promp gamma-ray detection,one key point is to determine its burst *** we measure the burst time through fitting the initial bump feature of AT2021lfa and obtain its burst time as 2021 May 3,at 22:09:50 *** afterglowpy,we model the multi-band afterglow of AT2021lfa and find that the standard model canno reproduce the late radio observations *** that the microphysical parameters ε_(e),ε_(B)(the energy fraction given to electrons and magnetic field),andξN(the fraction of accelerated electrons)may vary with time we then model the afterglow of AT2021lfa taking into account the temporal evolution of the physical parameters ε_(e),ε^(B),and ξ_(N) and find in this case the multi-wavelength observations can be reproduced *** initial Lorentz factor of AT2021lfa can be estimated from the peak time of the early afterglow,which yields a value of about 18 suggesting that AT2021lfa should be classified as a“dirty fireball.”From the upper limit for the prompt emission energy of AT2021lfa,we obtain that the radiation efficiency is less than 0.02%,which is much smaller than that of ordinary gamma-ray bursts(GRBs).It is also interesting that the fitted values of jet angle and viewing angle are very large,θ_(c)~0.66 rad,θ_(v)~0.53 rad,which may lead to the low Lorentz factor and radiation *** compared with GRB afterglow samples,it is evident that the onset bump timescale of AT2021lfa satisfies the empirical relationships observed in GRB ***,the luminosity of AT2021lfa falls within the range of observations for GRB samples;howeve

关键词： gamma-rays:ISM methods:numerical radiation mechanisms:non-thermal