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Generating Adversarial Samples on Multivariate Time Series using Variational Autoencoders

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IEEE/CAA Journal of Automatica Sinica 2021年第9期8卷 1523-1538页

作者： Samuel Harford Fazle Karim Houshang darabi Department of Mechanical and Industrial Engineering University of Illinois at ChicagoChicagoIL 60607 USA

Classification models for multivariate time series have drawn the interest of many researchers to the field with the objective of developing accurate and efficient ***,limited research has been conducted on generating adversarial samples for multivariate time series classification *** samples could become a security concern in systems with complex sets of *** study proposes extending the existing gradient adversarial transformation network(GATN)in combination with adversarial autoencoders to attack multivariate time series classification *** proposed model attacks classification models by utilizing a distilled model to imitate the output of the multivariate time series classification *** addition,the adversarial generator function is replaced with a variational autoencoder to enhance the adversarial *** developed methodology is tested on two multivariate time series classification models:1-nearest neighbor dynamic time warping(1-NN DTW)and a fully convolutional network(FCN).This study utilizes 30 multivariate time series benchmarks provided by the University of East Anglia(UEA)and University of California Riverside(UCR).The use of adversarial autoencoders shows an increase in the fraction of successful adversaries generated on multivariate time *** the best of our knowledge,this is the first study to explore adversarial attacks on multivariate time ***,we recommend future research utilizing the generated latent space from the variational autoencoders.

关键词： Adversarial machine learning deep learning multivariate time series perturbation methods

Applied statistical functions and multivariate analysis of geochemical compositional data to evaluate mineralization in Glojeh polymetallic deposit,NW Iran

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Frontiers of Earth Science 2019年第1期13卷 229-246页

作者： F darabi-GOLESTAN A HEZARKHANI Department of Mining and Metallurgical Engineering Amirkabir University of TechnologyTehranIran

Various genesis of epithermal veins as well as host rock cause complication in the modeling process. Thus LINEST and controlling function were applied to improve the accuracy and the quality of the *** LINEST is a model which is based on multiple linear regression and refers to a branch of applied *** method concerns directly to the application oft-test (TINV and TDIST to analyses of variables in the model)and F- test (FDIST,F-statistic to compare different models) *** elimination technique is applied to reduce the number of variables in the model through all the borehole *** 18 steps,an optimized reduced model (ORM)was constructed and ranked in order of importance as Pb >Ag >P >Hg>Mn>Nb >U>Sr>Sn>As > Cu,with the lowest confidence level (CL)of 92% for *** to the epigenetic vein genesis of Glojeh polymetallic deposit,determination of spatial pattems and elemental associations accompanied by anomaly separation were conducted by K-means cluster and robust factor analysis method based on centered log-ratio (clr)transformed ***,12 samples (cluster 2)with the maximum distance from centroid,indicates the intensity of vein polymetallic mineralization in the *** addition, an ORM for vein population was extracted for Sb >A1 > As >Mg >Pb >Cu >Ag elements with the R2 up to 0.99. On the other hand,after 23 steps of optimization process at the host rock population,an ORM Was conducted by Ag >Te >Hg >Pb >Mg >A1 >Sb >As represented in descending order *** revealed that Te and Hg can be considered as pathfinder elements for Au at the host *** on the ORMs at each population Ag,Pb,and As were often associated with Au *** concentration ratio of (tSb × tA1)vein/(tSb × tA1)baekground as an enrichment index can intensify the mineralization ***,Glojeh deposit was evaluated to be classified as a vein-style Au (Ag,Pb,As)-polymetallic mineralization.

关键词： LINEST and controlling function optimized reduced model log-ratio (clr)transformation K-means cluster robust factor analysis pathfinder elements veinstyle Glojeh polymetallic mineralization

Simplified modeling of frequency behavior in photonic crystal vertical cavity surface emitting laser with tunnel injection quantum dot in active region

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Chinese Physics B 2017年第2期26卷 260-267页

作者： Mehdi Riahinasab Vahid Ahmadi Elham darabi Department of Electrical Engineering Science and Research Branch Islamic Azad University Tehran Iran Department of Electrical Engineering Tarbiat Modares University Tehran Iran Plasma Physics Research Center Science and Research Branch Islamic Azad University Tehran Iran

In this work, the characteristics of the photonic crystal tunneling injection quantum dot vertical cavity surface emitting lasers（Ph C-TIQD-VCSEL） are studied through analyzing a modified modulation transfer function. The function is based on the rate equations describing the carrier dynamics at different energy levels of dot and injector well. Although the frequency modulation response component associated with carrier dynamics in wetting layer（WL） and at excited state（ES） levels of dots limits the total bandwidth in conventional QD-VCSEL, our study shows that it can be compensated for by electron tunneling from the injector well into the dot in TIQD structure. Carrier back tunneling time is one of the most important parameters, and by increment of that, the bias current dependence of the total bandwidth will be insignificant. It is proved that at high bias current, the limitation of the WL-ES level plays an important role in reducing the total bandwidth and results in rollovers on 3-d B bandwidth-I curves. In such a way, for smaller air hole diameter of photonic crystal, the effect of this reduction is stronger.

关键词： modulation transfer function photonic crystal(PhC) tunnel injection quantum dot(TIQD) vertical cavity surface emitting laser(VCSEL)

Discrimination geochemical interaction effects on mineralization at the polymetallic Glojeh deposit,NW Iran by interative backward quadratic modeling

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Acta Geochimica 2020年第2期39卷 236-254页

作者： Farshad darabi-Golestan Ardeshir Hezarkhani Department of Mining and Metallurgical Engineering Amirkabir University of Technology424 Hafez AveTehran 15875-4413Iran

The physico-chemical exchanges between hydrothermal fluids and the host rock are usually controlled by elemental interaction effects.A criterion-based backward elimination approach applies the iterative regression analysis and analysis of variance to investigate the geochemical features of the polymetallic Glojeh(Au-Ag-CuPb-Zn)deposit in NW Iran.A statistical definition of the elemental interaction effects(X(i-j)^2,Xi×Xj)could elucidate the relationship between variables and the performance of a full quadratic polynomial model(QPM).The model optimization procedure was carried out by the removal of insignificant predictors(P value 95%CL)based on R^2(pred.)*** order to straighten the convergent trend with R^2 and R^2(adj.),R^2(pred.)gradually increased from 0%to 77.8%by 15-steps *** miniature-scale geochemical changes indicate double ordinal Au(Ag,Pb)and Au(Ag,Zn)interactions within the vein and host rock,in *** show that the Au(Pb-Zn)commonly presents ordinal effect at the vein and disordinal interaction at the host *** ordinal-disordinal interaction revealed that elements Pb and Zn have similar geochemical features during *** addition,Akima's polynomial contour map confirms the results from Pb-Zn interaction effects by dependency tracing between Au-Pb-Zn at different ***,it is noteworthy that Pb and Zn occur together in the second phase of Pb-Zn-Cu±(Ag±Cd)sulfide mineralization at Glojeh,which implies intergrowth and interaction of Pb-Zn on Au *** and Zn demonstrate relatively high mobility and are generally concentrated in the near surface *** is an immobile element during alteration and high content Hg zone is mainly restricted to narrow stripes above ore vein and veinlets.

关键词： Backward Elimination Quadratic polynomial model Miniature-scale changes Ordinal–disordinal interaction effect Akima's polynomial contour map Immobile element

Two-color light-emitting diodes with polarization-sensitive high extraction efficiency based on graphene

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Chinese Physics B 2016年第5期25卷 474-478页

作者： H Sattarian S Shojaei E darabi Plasma Physics Research Center Science and Research Branch Islamic Azad University Photonics Department Research Institute for Applied Physics & Astronomy University of Tabriz

In the present study, graphene photonic crystals are employed to enhance the light extraction efficiency（LEE） of two-color, red and blue, light-emitting diode（LED）. The transmission characteristics of one-dimensional（1D） Fibonacci graphene photonic crystal LED（FGPC-LED） are investigated by using the transfer matrix method and the scaling study is presented. We analyzed the influence of period, thickness, and permittivity in the structure to enhance the LEE. The transmission spectrum of 1D FGPC has been optimized in detail. In addition, the effects of the angle of incidence and the state of polarization are investigated. As the main result, we found the optimum values of relevant parameters to enhance the extraction of red and blue light from an LED as well as provide perfect omnidirectional and high peak transmission filters for the TE and TM modes.

关键词： photonic crystal blue light emitting diode graphene transfer matrix method

Free vibrations of beam-mass-spring systems:analytical analysis with numerical confirmation

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Acta Mechanica Sinica 2012年第2期28卷 468-481页

作者： Mohammad A.darabi Siavash Kazemirad Mergen H.Ghayesh Department of Mechanical Engineering University of GuilanRasht Department of Mechanical Engineering McGill UniversityMontrealQuebecCanada H3A 2K6

Free vibrations of a beam-mass-spring system with different boundary conditions are analyzed both analyt- ically and numerically. In the analytical analysis, the system is divided into three subsystems and the effects of the spring and the point mass are considered as internal boundary con- ditions between any two neighboring subsystems. The par- tial differential equations governing the motion of the sub- systems and internal boundary conditions are then solved us- ing the method of separation of variables. In the numerical analysis, the whole system is considered as a single system and the effects of the spring and point mass are introduced using the Dirac delta function. The Galerkin method is then employed to discretize the equation of motion and the result- ing set of ordinary differential equations are solved via eigen- value analysis. Analytical and numerical results are shown to be in very good agreement.

关键词： beam-mass-spring systems Vibrations Para- metric study

Effects of Pits and Mounds Following Windthrow Events on Soil Features and Greenhouse Gas Fluxes in a Temperate Forest

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Pedosphere 2015年第6期25卷 853-867页

作者： Yahya KOOCH Sakineh Mollaei darabi Seyed Mohsen HOSSEINI Department of Forestry Faculty of Natural Resources & Marine SciencesTarbiat Modares University

Pit and mound micro-relief(resultant microsites from trees uprooted by windthrow) could have regimes of microclimate and soil features that differ from areas of undisturbed soil. In an attempt to provide a comprehensive evaluation of the significance of pits and mounds on soil features and also the dynamics of greenhouse gas(GHG) fluxes at local scale, this study was carried out in a reserved area of Darabkola forest in Mazandaran Province, northern Iran. The age of a pit and mound was considered equal to the degree of decay of the blown down tree. Three microsites were distinguished, consisting of pit bottom(PB), mound top(MT) and undisturbed area(UA). Soil samples were taken at 0–15 and 15–30 cm depths from all microsites and analysed for soil physical, chemical and biological features. Our findings suggested that in context of forest ecology, pits and mounds following windthrow events should be considered as an effective factor influencing soil features(i.e., density, texture, water content, p H, organic C, total N, available nutrients and earthworm density/biomass) and especially GHG fluxes. Results showed that MT acted as a sink for N2O(-0.010 mg N2 O m-2d-1) and CH4(-0.257 mg CH4m-2d-1) fluxes and also produced lower CO2 concentrations(0.095 mg CO2 m-2d-1) than PB(0.207 mg CO2 m-2d-1) and UA(0.098 mg CO2 m-2d-1). As a consequence, a separation into pits/mounds would be important for a precise budgeting of greenhouse gases.

关键词： carbon dioxide, methane microsite, nitrous oxide oriental beech, uprooted tree

Surface stress effect on the vibration and instability of nanoscale pipes conveying fluid based on a size-dependent Timoshenko beam model

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Acta Mechanica Sinica 2015年第5期31卷 708-719页

作者： R.Ansari R.Gholami A.Norouzzadeh M.A.darabi Department of Mechanical Engineering University of Guilan Department of Mechanical Engineering Lahijan BranchIslamic Azad University

Presented in this paper is a precise investigation of the effect of surface stress on the vibration characteristics and instability of fluid-conveying nanoscale *** this end,the nanoscale pipe is modeled as a Timoshenko *** equations of motion of the nanoscale pipe are obtained based on Hamilton＇s principle and the Gurtin-Murdoch continuum elasticity incorporating the surface stress ***,the generalized differential quadrature method is employed to discretize the governing equations and associated boundary *** what extent important parameters such as the thickness,material and surface stress modulus,residual surface stress,surface density,and boundary conditions influence the natural frequency of nanoscale pipes and the critical velocity of fluid is discussed.

关键词： Fluid-conveying pipes Vibration and instability Surface stress Gurtin-Murdoch elasticity continuum Generalized differential quadrature method

Guest Editorial for Special Issue on Time Series Classification

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IEEE/CAA Journal of Automatica Sinica 2019年第6期6卷 1291-1292页

作者： Houshang darabi Georgiana Ifrim Patrick Schafer Diego Furtado Silva Department of Mechanical and Industrial Engineering University of Illinois at Chicago(UIC) University of Bucharest Romania University of Berlin Sciences(ICMC) University of Sao Paulo

TIME series classification research and applications have recently received a lot of *** the rapid advancement of technological devices,time series data are being collected by a wide variety of devices,resulting in a wide range of research and *** fields of studies,ranging from healthcare to weather readings,require time series *** and action recognition using time series data from fitness trackers are commonly being ***,a new generation of algorithms and techniques are being used to classify time series data that are extensively available to the research *** example,recently deep learning techniques that utilize convolutions and recurrent neural networks are being used to classify epileptic seizures from EEG recordings made available at the University of California-Irvine data repository.

关键词： classify utilize recording