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China Ocean Engineering 2014年第5期28卷 645-657页

作者： S.Sakthivel MURUGAN V.NATARAJAN K.MAHESWARAN ECE Department SSN College of Engineering Instrumentation Department MIT Campus Anna University Infosys Chennai India

Sonar generated acoustic signals transmitted in underwater channel for distant communications are affected by numerous factors like ambient noise, making them nonlinear and non-stationary in nature. In recent years, the application of Empirical Mode Decomposition(EMD) technique to analyze nonlinear and non-stationary signals has gained much attention. It is an empirical approach to decompose a signal into a set of oscillatory modes known as intrinsic mode functions(IMFs). In general, Hilbert transform is used in EMD for the identification of oscillatory signals. In this paper a new EMD algorithm is proposed using FFT to identify and extract the acoustic signals available in the underwater channel that are corrupted due to various ambient noises over a range of 100 Hz to 10 kHz in a shallow water region. Data for analysis are collected at a depth of 5 m and 10 m offshore Chennai at the Bay of Bengal. The algorithm is validated for different sets of known and unknown reference signals. It is observed that the proposed EMD algorithm identifies and extracts the reference signals against various ambient noises. Significant SNR improvement is also achieved for underwater acoustic signals.

关键词： EMD IMF SNR ambient noises underwater acoustic signals FFT

Establishment and Assessment of Plasma Disruption and Warning Databases from EAST

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Plasma Science and Technology 2016年第12期18卷 1162-1168页

作者：王勃 Robert GRANETZ 肖炳甲李建刚杨飞李君君陈大龙 University of Science and Technology of China mit Plasma Science and Fusion Center Institute of Plasma Physics Chinese Academy of Sciences

Disruption database and disruption warning database of the EAST tokamak had been established by a disruption research group. The disruption database, based on Structured Query Language（SQL）, comprises 41 disruption parameters, which include current quench characteristics, EFIT equilibrium characteristics, kinetic parameters, halo currents,and vertical motion. Presently most disruption databases are based on plasma experiments of non-superconducting tokamak devices. The purposes of the EAST database are to find disruption characteristics and disruption statistics to the fully superconducting tokamak EAST,to elucidate the physics underlying tokamak disruptions, to explore the influence of disruption on superconducting magnets and to extrapolate toward future burning plasma devices. In order to quantitatively assess the usefulness of various plasma parameters for predicting disruptions,a similar SQL database to Alcator C-Mod for EAST has been created by compiling values for a number of proposed disruption-relevant parameters sampled from all plasma discharges in the2015 campaign. The detailed statistic results and analysis of two databases on the EAST tokamak are presented.

关键词： disruption database disruption warning database data analysis

Moduli of Polarized Calabi–Yau Pairs

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Acta Mathematica Sinica,English Series 2020年第6期36卷 631-637页

作者： János KOLLáR Chen Yang XU Princeton University Princeton NJ 08544-1000USA mit CambridgeMA 02139-4307USA

We prove that the irreducible components of the moduli space of polarized Calabi–Yau pairs are projective.

关键词： Polarized Calabi–Yau stable pairs Moduli spaces

On the performance of shared autonomous bicycles:A simulation study

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Communications in Transportation Research 2022年第1期2卷 116-151页

作者： Naroa Coretti Sanchez Inigo Martinez Luis Alonso Pastor Kent Larson mit Media Lab CambridgeMAUSA University of Navarra San SebastianSpain

As society faces global challenges such as population growth and climate change,rethinking cities is now more imperative than *** design of cities can not be abstracted from the design of their mobility ***,efficient solutions must be found to transport people and goods throughout the city efficiently and *** autonomous bicycle-sharing system would combine the most relevant benefits of vehicle-sharing,autonomy,and micro-mobility,increasing the efficiency and convenience of bicycle-sharing systems and incentivizing more people to bike and enjoy their cities in an environmentally friendly *** to the novelty of introducing autonomous driving technology into bicycle-sharing systems and their inherent complexity,there is a need to quantify the potential impact of autonomy on fleet performance and user *** paper presents the results of an agent-based simulation that provides an in-depth understanding of the fleet behavior of autonomous bicycle-sharing systems in realistic scenarios,including a rebalancing system based on demand *** addition,this work describes the impact of different parameters on system efficiency and service ***,it quantifies the extent to which an autonomous system would outperform current station-based and dockless bicycle-sharing *** obtained results show that with a fleet size three and a half times smaller than a station-based system and eight times smaller than a dockless system,an autonomous system can improve overall performance and user experience even with no rebalancing.

关键词： Future mobility Bicycle-sharing systems Autonomous vehicles Micro-mobility Agent-based simulation Multi-agent systems

A new mathematical model for studying fully ionized plasma flows in MPD thrusters

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International Journal of Modeling, Simulation, and Scientific Computing 2016年第3期7卷 87-106页

作者： Vijai Kumar S Thanigaiarasu S Department of Aerospace Engineering MIT Campus Anna UniversityChennaiTamilnadu 600044India

The paper describes a novel mathematical model to study the physics of fully ionized plasma flow through MPD thrusters otherwise known as magnetoplasmadynamic *** developed model consists of a set of differential equations obtained by coupling the Navier–Stokes equations with Maxwell’s *** model developed was tested for various 1D and 1.5D *** simulations have been carried out for a special case of geometries called Tikhonov fitted geometries for alleviating the instability phenomenon commonly known as onset phenomenon in self-field MPD *** work was also extended to applied field MPD thrusters.A new equation for magnetic field was introduced to incorporate a virtual *** the computations were carried out using a higher order integration *** results obtained were found to be in good agreement with the previous work done on similar models.

关键词： MPD thrusters computational fluid dynamics mathematical modeling

Helicase-assisted continuous editing for programmable mutagenesis of endogenous genomes

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四川生理科学杂志 2024年第10期46卷 2326-2326页

作者： Xi Dawn Chen Gene Regulation Observatory Broad Institute of MIT and Harvard Cambridge MA 02142 USA. Department of Stem Cell and Regenerative Biology Harvard University Cambridge MA 02138 USA. Systems Synthetic and Quantitative Biology PhD Program Harvard University Cambridge MA 02138 USA. Department of Cancer Biology Dana-Farber Cancer Institute Boston MA 02215 USA. Department of Cell Biology and Pathology Harvard Medical School Boston MA 02115 USA. Department of Chemistry and Chemical Biology Harvard University Cambridge MA 02138 USA. Cancer Program Broad Institute of MIT and Harvard Cambridge MA 02142 USA. Cecil H. and Ida Green Center for Reproductive Biology Sciences University of Texas Southwestern Medical Center Dallas TX 75390 USA. Department of Obstetrics and Gynecology University of Texas Southwestern Medical Center Dallas TX 75390 USA. The Novo Nordisk Foundation Center for Genomic Mechanisms of Disease Broad Institute of MIT and Harvard Cambridge MA 02142 USA.

Deciphering the context-specific relationship between sequence and function is a major challenge in *** tools for inducing locus-specific hypermutation and evolution in the native genome context are *** we present a programmable platform for long-range,locus-specific hypermutation called helicase-assisted continuous editing(HACE).HACE leverages CRISPR-Cas9 to target a processive helicase-deaminase fusion that incurs mutations across large(>1000-base pair)genomic *** applied HACE to identify mutations in mitogen-activated protein kinase kinase 1(MEK1)that confer kinase inhibitor resistance,to dissect the impact of individual variants in splicing factor 3B subunit 1(SF3B1)-dependent missplicing,and to evaluate noncoding variants in a stimulation-dependent immune enhancer of *** provides a powerful tool for investigating coding and noncoding variants,uncovering combinatorial sequence-to-function relationships,and evolving new biological functions.

关键词： endogenous stimulation continuous

Tracking Co-evolution of Behavior and Relationships with Mobile Phones

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Tsinghua Science and Technology 2012年第2期17卷 136-151页

作者： Wen Dong Bruno Lepri Sandy Pentland mit Media Laboratory Cambridge MA 02142 USA FBK Povo-Trento Italy

The co-evolution of social relationships and individual behavior in time and space has important implications, but is poorly understood because of the difficulty of closely tracking the everyday life of a com- plete community. We offer evidence that relationships and behavior co-evolve in a student dormitory, based on monthly surveys and location tracking through resident cellular phones over a period of nine months. We demonstrate that a Markov jump process could capture the co-evolution in terms of the rates at which resi- dents visit places and friends. Our co-evolution model will be useful in bridging sensor networks data and organizational dynamics theories, simulating different ways to shape behavior and relationships, and turning mobile phone data into data products.

关键词： social computing human dynamics living labs sensor networks organizational dynamics stochastic process multi-agent model

FLNL:Fuzzy entropy and lion neural learner for EDoS attack mitigation in cloud computing

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International Journal of Modeling, Simulation, and Scientific Computing 2018年第6期9卷 1-18页

作者： Sukhada Bhingarkar Deven Shah mit College of Engineering PuneIndia Thakur College of Engineering and Technology MumbaiIndia

Cloud computing is a technology that allows the end-users to access the network through a shared area of *** the demand for the cloud computing increases,vulnerabilities in the service provision also *** is one of the attacks that take over the provider,financially affecting the various organizations which use the cloud *** paper utilizes fuzzy entropy and lion neural learner(FLNL)for the classification of cloud users to mitigate EDoS attacks in the *** technique includes a training phase,which creates a log file using various parameters and then transforms the features into database considering certain key *** are two important stages in this classification approach:feature selection and ***,the fuzzy entropy function is utilized for feature selection which effectively selects useful features without information *** classification is performed using lion neural learner(LNL)which incorporates Lion algorithm(LA)into the neural network and uses Levenberg–Marquardt(LM)*** experimental results finalize that the proposed FLNL is effective with 89%precision,78%recall,and 83.13%of f-measure compared with the existing Na¨ıve Bayes(NB),Neural Network+Back Propagation(NN+BP),and Neural Network+Levenberg–Marquardt(NN+LM).

关键词： Cloud computing EDoS attacks fuzzy entropy feature selection neural network.

Group Velocity of Anisotropic Waves-Part Ⅰ: Mathematical Expression

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Advances in Atmospheric Sciences 1993年第4期10卷 393-406页

作者： Yong L.McHall Department of Earth Atmospheric and Planetary Sciences MIT MA 02139 USA

The group velocity used in meteorology in the last 30 years was derived in terms of conservation of wave energy or crests in wave propagation. The conservation principle is a necessary but not a sufficient condition for deriving the mathematical form of group velocity, because it cannot specify a unique direction in which wave energy or crests propagate. The derived mathematical expression is available only for isotropic waves. But for anisotropic waves, the traditional group velocity may have no a definite direction, because it varies with rotation of coordinates. For these reasons, it cannot be considered as a general expression of group velocity. A ray defined by using this group velocity may not be the trajectory of a reference point in an anisotropic wave train. The more general and precise expression of group velocity which is applicable for both isotropic and anisotropic waves and is independent of coordinates will be derived following the displacement of not only a wave envelope phase but also a wave reference point on the phase.

关键词： Isotropic group velocity General group velocity Oblique group velocity

Large Scale Perturbations in Extratropical Atmosphere-Part Ⅱ: On Geostrophic Waves

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Advances in Atmospheric Sciences 1993年第2期10卷 181-192页

作者： Y.L. McHall Department of Earth Atmospheric and Planetary Sciences MIT MA 02139 USA

We have examined, in Part Ⅰ, the propagation mechanism and geostrophic property of classical Rossby waves in a non-divergent barotropic atmosphere. As we found that the non-divergent Rossby waves do not propagate in a hydrostatically equilibrium atmosphere, and do not manifest a good geostrophic property, an alternative large scale circulation pattern of geostrophic waves has been proposed (McHall, 1991a). The propagation mechanism and geostrophic property of these waves are examined in the present study.

关键词： On Geostrophic Waves Large Scale Perturbations in Extratropical Atmosphere-Part