Urban Growth Models (UGMs) are very essential for a sustainable development of a city as they predict the future urbanization based on the present scenario. Neural Network based Cellular Automata models have proved to...Urban Growth Models (UGMs) are very essential for a sustainable development of a city as they predict the future urbanization based on the present scenario. Neural Network based Cellular Automata models have proved to predict the urban growth more close to reality. Recently, deep learning based techniques are being used for the prediction of urban growth. In this current study, urban growth of Chennai Metropolitan Area (CMA) of 2017 was predicted using Neural Network based Cellular Automata (NN-CA) model and Deep belief based Cellular Automata (DB-CA) model using 2010 and 2013 urban maps. Since the study area experienced congested type of urban growth, “Existing Built-Up” of 2013 alone was used as the agent of urbanization to predict urban growth in 2017. Upon validating, DB-CA model proved to be the better model, as it predicted 524.14 km2 of the study area as urban with higher accuracy (kappa co-efficient: 0.73) when compared to NN-CA model which predicted only 502.42 km2 as urban (kappa co-efficient: 0.71), while the observed urban cover of CMA in 2017 was 572.11 km2. This study also aimed at analyzing the effects of different types of neighbourhood configurations (Rectangular: 3 × 3, 5 × 5, 7 × 7 and Circular: 3 × 3) on the prediction output based on DB-CA model. To understand the direction and type of the urban growth, the study area was divided into five distance based zones with the State Secretariat as the center and entropy values were calculated for the zones. Results reveal that Chennai Corporation and its periphery experience congested urbanization whereas areas away from the Corporation boundary follow dispersed type of urban growth in 2017.展开更多
Manual investigation of chest radiography(CXR)images by physicians is crucial for effective decision-making in COVID-19 diagnosis.However,the high demand during the pandemic necessitates auxiliary help through image a...Manual investigation of chest radiography(CXR)images by physicians is crucial for effective decision-making in COVID-19 diagnosis.However,the high demand during the pandemic necessitates auxiliary help through image analysis and machine learning techniques.This study presents a multi-threshold-based segmentation technique to probe high pixel intensity regions in CXR images of various pathologies,including normal cases.Texture information is extracted using gray co-occurrence matrix(GLCM)-based features,while vessel-like features are obtained using Frangi,Sato,and Meijering filters.Machine learning models employing Decision Tree(DT)and RandomForest(RF)approaches are designed to categorize CXR images into common lung infections,lung opacity(LO),COVID-19,and viral pneumonia(VP).The results demonstrate that the fusion of texture and vesselbased features provides an effective ML model for aiding diagnosis.The ML model validation using performance measures,including an accuracy of approximately 91.8%with an RF-based classifier,supports the usefulness of the feature set and classifier model in categorizing the four different pathologies.Furthermore,the study investigates the importance of the devised features in identifying the underlying pathology and incorporates histogrambased analysis.This analysis reveals varying natural pixel distributions in CXR images belonging to the normal,COVID-19,LO,and VP groups,motivating the incorporation of additional features such as mean,standard deviation,skewness,and percentile based on the filtered images.Notably,the study achieves a considerable improvement in categorizing COVID-19 from LO,with a true positive rate of 97%,further substantiating the effectiveness of the methodology implemented.展开更多
Banded iron formations （BIFs） are major rock units having hematite layers intermittent with silica rich layers and formed by sedimentary processes during late Archean to mid Proterozoic time. In terrestrial environm...Banded iron formations （BIFs） are major rock units having hematite layers intermittent with silica rich layers and formed by sedimentary processes during late Archean to mid Proterozoic time. In terrestrial environment, hematite deposits are mainly found associated with banded iron formations. The BIFs in Lake Superior （Canada） and Carajas （Brazil） have been studied by planetary scientists to trace the evolution of hematite deposits on Mars. Hematite deposits are extensively identified in Meridiani region on Mars. Many hypotheses have been proposed to decipher the mechanism for the formation of these deposits. On the basis of geomorphological and mineralogical studies, aqueous environment of deposition is found to be the most supportive mechanism for its secondary iron rich deposits. In the present study, we examined the spectral characteristics of banded iron formations of Joda and Daitari located in Singhbhum craton in eastern India to check its potentiality as an analog to the aqueous/marine environment on Mars. The prominent banding feature of banded iron formations is in the range of few millimeters to few centimeters in thickness. Fe rich bands are darker （gray） in color compared to the light reddish jaspilitic chert bands. Thin quartz veins （〈4 mm） are occasionally observed in the handspecimens of banded iron formations. Spectral investigations have been conducted in VIS/NIR region of electromagnetic spectrum in the laboratory conditions. Optimum absorption bands identified include 0.65, 0.86, 1.4 and 1.9 μm, in which 0.56 and 0.86 μm absorption bands are due to ferric iron and 1.4 and 1,9 μm bands are due to OH/H2O. To validate the mineralogical results obtained from VlS/NIR spectral radiometry, laser Raman and Fourier transform infrared spectroscopic techniques were utilized and the results were found to be similar. Goethite-hematite association in banded iron formation in Singhbhum craton suggests dehydration activity, which has altered the primary iron oxide phases into the secondary iron oxide phases. The optimum bands identified for the minerals using various spectroscopic techniques can be used as reference for similar mineral deposits on any remote area on Earth or on other hydrated planetary surfaces like Mars.展开更多
Leveraging the high resolution,sensitivity,and wide frequency coverage of the Atacama Large Millimeter/submillimeter Array(ALMA),the QUARKS survey,standing for“Querying Underlying mechanisms of massive star formation...Leveraging the high resolution,sensitivity,and wide frequency coverage of the Atacama Large Millimeter/submillimeter Array(ALMA),the QUARKS survey,standing for“Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures”,is observing 139 massive starforming clumps at ALMA Band 6(λ~1.3 mm).This paper introduces the Atacama Compact Array(ACA)7 m data of the QUARKS survey,describing the ACA observations and data reduction.Combining multiwavelength data,we provide the first edition of QUARKS atlas,offering insights into the multiscale and multiphase interstellar medium in high-mass star formation.The ACA 1.3 mm catalog includes 207 continuum sources that are called ACA sources.Their gas kinetic temperatures are estimated using three formaldehyde transitions with a non-LTE radiation transfer model,and the mass and density are derived from a dust emission model.The ACA sources are massive(16–84 percentile values of 6–160 M_(⊙)),gravity-dominated(M∝R^(1.1))fragments within massive clumps,with supersonic turbulence(M>1)and embedded star-forming protoclusters.We find a linear correlation between the masses of the fragments and the massive clumps,with a ratio of 6%between the two.When considering fragments as representative of dense gas,the ratio indicates a dense gas fraction(DGF)of 6%,although with a wide scatter ranging from 1%to 10%.If we consider the QUARKS massive clumps to be what is observed at various scales,then the size-independent DGF indicates a self-similar fragmentation or collapsing mode in protocluster formation.With the ACA data over four orders of magnitude of luminosity-to-mass ratio(L/M),we find that the DGF increases significantly with L/M,which indicates clump evolutionary stage.We observed a limited fragmentation at the subclump scale,which can be explained by a dynamic global collapse process.展开更多
We present a detailed investigation of the evolution of observed net vertical current using a time series of vector magnetograms of the active region （AR） NOAA 11158 obtained from the Helioseismic and Magnetic Image...We present a detailed investigation of the evolution of observed net vertical current using a time series of vector magnetograms of the active region （AR） NOAA 11158 obtained from the Helioseismic and Magnetic Imager. We also discuss the relation of net current to the observed eruptive events. The AR evolved from the βγ to βγδ3 configuration over a period of six days. The AR had two sub-regions of activity with opposite chirality： one dominated by sunspot rotation producing a strong CME, and the other showing large shear motions producing a strong flare. The net current in each polarity over the CME producing sub-region increased to a maximum and then decreased when the sunspots were separated. The time profile of net current in this sub-region followed the time profile of the rotation rate of the south-polarity sunspot in the same sub-region. The net current in the flaring sub-region showed a sudden increase at the time of the strong flare and remained unchanged until the end of the observation, while the sunspots maintained their close proximity. The systematic evo- lution of the observed net current is seen to follow the time evolution of total length of strongly sheared polarity inversion lines in both of the sub-regions. The observed photospheric net current could be explained as an inevitable product of the emergence of a twisted flux rope, from a higher pressure confinement below the photosphere into the lower pressure environment of the photosphere.展开更多
Development of asymptotic magnitude Bode plots for integer-order transfer functions is a well-established topic in the control theory.However,construction of such plots for the fractional-order transfer functions has ...Development of asymptotic magnitude Bode plots for integer-order transfer functions is a well-established topic in the control theory.However,construction of such plots for the fractional-order transfer functions has not received much attention in the existing literature.In the present paper,we investigate in this direction and derive the procedures for sketching asymptotic magnitude Bode plots for some of the popular fractional-order controllers such as PI^α,[PI]^α,PD^β,[PD]^β,and PI^αD^β.In addition,we deduce these plots for general fractional commensurate-order transfer functions as well.As applications of this work,we illustrate 1)the analysis of the designed fractional-control loop and 2)the identification of fractional-order transfer function from a given plot.展开更多
TCP performance degrades when end-to-end connections extend over wireless links which are characterized by high Bit Error Rate and intermittent connectivity. Such degradation is mainly accounted for TCP’s unnecessary...TCP performance degrades when end-to-end connections extend over wireless links which are characterized by high Bit Error Rate and intermittent connectivity. Such degradation is mainly accounted for TCP’s unnecessary congestion control actions while attempting TCP loss recovery. Several independent link loss recovery approaches are proposed by researchers to reduce number of losses visible at TCP. In this paper we first presented a survey of loss mitigation techniques at wireless link layer. Secondly performance evaluation for TCP through Type 0 Automatic Retransmission Request mechanism in erroneous Wireless LAN is presented. In particular, simulations are performed taking into account the wireless errors introduced over IEEE 802.11 link using a well-established 2-State Markov model. TCP performance is evaluated under different settings for maximum link retransmissions allowed for each frame. Simulation results show that, link retransmission improves TCP performance by reducing losses perceived at TCP sender. However, such improvement is often associated with adverse effect on other TCP parameters that may cost a lot in return under extreme network conditions. In this paper an attempt is made to observe impact of link retransmissions on the performance of multiple TCP flows competing with each other. The analysis presented in this paper signifies the scope for maximizing TCP’s throughput at the least possible cost.展开更多
This paper presents an overview of the QUARKS survey,which stands for Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures."The QUARKS survey is observing139 m...This paper presents an overview of the QUARKS survey,which stands for Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures."The QUARKS survey is observing139 massive clumps covered by 156 pointings at Atacama Large Millimeter/submillimeter Array(ALMA)Band 6(λ~1.3 mm).In conjunction with data obtained from the ALMA-ATOMS survey at Band 3(λ~3 mm),QUARKS aims to carry out an unbiased statistical investigation of massive star formation process within protoclusters down to a scale of 1000 au.This overview paper describes the observations and data reduction of the QUARKS survey,and gives a first look at an exemplar source,the mini-starburst Sgr B2(M).The wide-b and width(7.5 GHz)and high-angular-resolution(~0."3)observations of the QUARKS survey allow for the resolution of much more compact cores than those could be done by the ATOMS survey,and to detect previously unrevealed fainter filamentary structures.The spectral windows cover transitions of species including CO,SO,N_(2)D^(+),SiO,H_(30)α,H_(2)CO,CH_(3)CN,and many other complex organic molecules,tracing gas components with different temperatures and spatial extents.QUARKS aims to deepen our understanding of several scientific topics of massive star formation,such as the mass transport within protoclusters by(hub-)filamentary structures,the existence of massive starless cores,the physical and chemical properties of dense cores within protoclusters,and the feedback from already formed high-mass young protostars.展开更多
Thermally insulating and fire-resistant carbon composite foams are prepared by consolidating natural cotton fibre dispersed in aqueous sucrose solution by filter-pressing followed by drying and carbonization.The compr...Thermally insulating and fire-resistant carbon composite foams are prepared by consolidating natural cotton fibre dispersed in aqueous sucrose solution by filter-pressing followed by drying and carbonization.The compressive strength(5 kPa to 1.4 MPa)and thermal conductivity(0.069 to 0.185 W m^(-1)K^(-1))depend on the foam density(0.06 to 0.31 g cm^(-3))which is modulated by varying the sucrose solutions concentration(100 to 700 g L^(-1)).Partially flexible to the rigid transition of the carbon composite foams occurs at sucrose concentration above 200 g L^(-1).The tubular carbon fibre formed from cotton is welded at their contact points by the amorphous carbon produced from sucrose leading to partial flexibility at low sucrose concentration and advancement of fibre-to-fibre bonding area at higher sucrose concentration results in rigid foam.The porosity in the inter-fibre space and lumen of the carbonized cotton fibre contributes to the low thermal conductivity.The carbon composite foams prepared at a sucrose solution concentration of 500 g L^(-1) and above are amenable to machining using conventional machines and tools.The rigid carbon foams show EMI shielding effectiveness and specific shielding effectiveness in the ranges of 21.5 to 38.9 d B and 108-138 dB cm^(3) g^(-1),respectively.展开更多
Composite solid propellant is prepared using tri-modal Ammonium perchlorate(AP)containing coarse,fine and ultrafine fractions of AP with average particle size(APS)340,40 and 5 mm respectively,in various compositions a...Composite solid propellant is prepared using tri-modal Ammonium perchlorate(AP)containing coarse,fine and ultrafine fractions of AP with average particle size(APS)340,40 and 5 mm respectively,in various compositions and their rheological,mechanical and burn rate characteristics are evaluated.The optimum combination of AP coarse to fine to ultrafine weight fraction was obtained by testing of series of propellant samples by varying the AP fractions at fixed solid loading.The concentration of aluminium was maintained constant throughout the experiments for ballistics requirement.The propellant formulation prepared using AP with coarse to fine to ultrafine ratio of 67:24:9 has lowest viscosity for the propellant paste and highest tensile strength due to dense packing as supported by the literature.A minimum modulus value was also observed at 9 wt.%of ultrafine AP concentration indicates the maximum solids packing density at this ratio of AP fractions.The burn rate is evaluated at different pressures to obtain pressure exponent.Incorporation of ultrafine fraction of AP in propellant increased burn rate without adversely affecting the pressure exponent.Higher solid loading propellants are prepared by increased AP concentration from 67 to 71 wt.%using AP with coarse to fine to ultrafine ratio of67:24:9.Higher solid content up to 89 wt.%was achieved and hence increased solid motor performance.The unloading viscosity showed a trend with increased AP content and the propellant couldn't able to cast beyond 71 wt.%of AP.Mechanical properties were also studied and from the experiments noticed that%elongation decreased with increased AP content from 67 to 71 wt.%,whereas tensile strength and modulus increased.Burn rate increased with increased AP content and observed that pressure exponent also increased and it is high for the propellant containing with 71 wt.%of AP due to increased oxidiser to fuel ratio.Catalysed composite solid propellant is prepared by using burn rate modifiers Copper chromite and Iron oxide.Addition of Copper chromite and Iron oxide has enhanced the burn rate of tri-modal AP based composite solid propellant.The catalytic propensity of copper chromite is higher than that of iron oxide.The pressure exponent increased with the catalyst concentration and the values obtained are compatible for solid rocket motor applications.展开更多
The incompressible miscible displacement problem in porous media is modeled by a coupled system of two nonlinear partial differential equations,the pressure–velocity equation and the concentration equation.In this pa...The incompressible miscible displacement problem in porous media is modeled by a coupled system of two nonlinear partial differential equations,the pressure–velocity equation and the concentration equation.In this paper,we present a mixed finite volume element method(FVEM)for the approximation of the pressure–velocity equation and a standard FVEM for the concentration equation.A priori error estimates in L^(∞)(L^(2))are derived for velocity,pressure and concentration.Numerical results are presented to substantiate the validity of the theoretical results.展开更多
Tungsten disulfide(WS_(2))stands out as a fascinating member of the transition metal dichalcogenides(TMDs)family.Recently,there has been a focus on introducing WS_(2)nanosheets into various polymers to expand their ap...Tungsten disulfide(WS_(2))stands out as a fascinating member of the transition metal dichalcogenides(TMDs)family.Recently,there has been a focus on introducing WS_(2)nanosheets into various polymers to expand their application in different fields.This study explores the innovative application of WS_(2)nanosheets in natural rubber latex(NRL)using tannic acid(TA)as a green exfoliating agent.WS_(2)nanosheets were synthesized through sand grinding of bulk WS_(2)with the assistance of TA.The resulting TA-modified WS_(2)nanosheets(WT)were then dispersed in NRL,leading to the fabrication of NR/WS_(2)(NWT)nanocomposites via the latex double-dipping method.An insertion of 1.5 phr of WT significantly enhanced the mechanical,thermal,and antibacterial properties,as well as the biocompatibility of natural rubber(NR).These improvements were attributed to the uniform dispersion of WT nanosheets in NRL,the interaction between WS_(2)and NR through TA,and the reinforcement effect from excess TA.This advancement demonstrates the potential of WS_(2)nanosheets-based NR nanocomposites for industrial development and innovation in various fields,especially the biomedical field.展开更多
Film cooling in combination with regenerative cooling is presently considered as an efficient method to guarantee safe operation of liquid rocket engines having higher heat flux densities for long duration.This paper ...Film cooling in combination with regenerative cooling is presently considered as an efficient method to guarantee safe operation of liquid rocket engines having higher heat flux densities for long duration.This paper aims to bring all the research carried out in the field of liquid rocket engine film cooling since 1950.The analytical and numerical procedure followed,experimental facilities and measurements made and major inferences drawn are reviewed in detail,and compared where ever possible.Review has been made through a discussion of the analyses methodologies and the factors that influence film cooling performance.An effort has also been made to determine the status of the research,pointing out critical gaps,which are still to be explained and addressed by future generations.展开更多
In this paper,we discuss the trajectory controllability of linear and nonlinear fractional dynamical systems represented by the fractional differential equations in the sense of Caputo fractional derivative by using t...In this paper,we discuss the trajectory controllability of linear and nonlinear fractional dynamical systems represented by the fractional differential equations in the sense of Caputo fractional derivative by using the Mittag-Leffler function and Gronwall-Bellman inequality.For the nonlinear system,we assume Lipschitz-type conditions on the nonlinearity.Examples are given to illustrate the theoretical results.展开更多
A finite element model for piezoelectric smart beam in extension mode based on First-order Shear Deformation Theory(FSDT)with an appropriate through-thickness distribution of electric potential is presented.Accuracy o...A finite element model for piezoelectric smart beam in extension mode based on First-order Shear Deformation Theory(FSDT)with an appropriate through-thickness distribution of electric potential is presented.Accuracy of piezoelectric finite element formulations depends on the selection of assumed mechanical and electrical fields.Most of the conventional FSDT-based piezoelectric beam formulations available in the literature use linear through-thickness distribution of electric potential which is actually nonlinear.Here,a novel quadratic profile of the through-thickness electric potential is proposed to include the nonlinear effects.The results obtained show that the accuracy of conventional formulations with linear through-thickness potential approximation is affected by the material configuration,especially when the piezoelectric material dominates the beam cross section.It is shown that the present formulation gives the same level of accuracy for all regimes of material configurations in the beam cross section.Also,a modified form of the FSDT displacements is employed,which utilizes the shear angle as a degree of freedom instead of section rotation.Such a FSDT displacement field shows improved performance compared to the conventional field.The present formulation is validated by comparing the results with ANSYS 2D simulation.The comparison of results proves the improved efficiency and accuracy of the present formulation over the conventional formulations.展开更多
Experimental and computational analysis has been carried out by many researchers on supersonic cavity flow,but detailed analysis based on Rossiter’s model still requires some insight.In the current study an open rect...Experimental and computational analysis has been carried out by many researchers on supersonic cavity flow,but detailed analysis based on Rossiter’s model still requires some insight.In the current study an open rectangular cavity with a length to depth ratio of 2(L/D=2)and Mach number at the inlet as 1.71,was considered as a baseline configuration for experimental analysis.Statistical techniques such as power spectral density(PSD),correlation,and overall sound pressure level(OASPL)were carried out on the unsteady pressure data,to analyze the aero-acoustic flow physics.High-speed schlieren images were processed to obtain spatially coherent modes by proper orthogonal decomposition(POD).The analysis was extended for different dimensions of subcavities on the aft,floor,and front wall.This detailed analysis of these configurations with different dimensions and combinations revealed the various flow features and mode frequencies in supersonic cavity.As the front wall subcavity act as a passive control device,reducing the overall sound pressure level inside the cavity whereas,the aft wall subcavity acts as a passive resonator with distinct harmonic fluidresonant modes,a similar phenomenon was observed for floor subcavity at different locations.A novel method was employed to analyze Rossiter’s model and its applicability in estimating experimental modes was verified,as it accurately predicted the dominant frequencies with a maximum of 2.74% uncertainty among all the configurations.展开更多
Development of an Advection Upstream Splitting Method(AUSM+-up)scheme-based Unstructured Finite Volume(UFVM)solver for the simulation of two-dimensional axisymmetric/planar high speed compressible turbulent reacting s...Development of an Advection Upstream Splitting Method(AUSM+-up)scheme-based Unstructured Finite Volume(UFVM)solver for the simulation of two-dimensional axisymmetric/planar high speed compressible turbulent reacting shear layers is presented.The inviscid numerical flux is evaluated using AUSM+-up upwind scheme.An eight-step hydrogen–oxygen finite rate chemistry model is used to model the development of chemical species in a supersonic reacting flow field.The chemical species terms are alone solved implicitly in this explicit flow solver by rescaling the equation in time.The turbulence modeling has been done using RNG-based k–model.Three-stage Runge–Kutta method has been used for explicit time integration.The nonreacting twodimensional Cartesian version of the same solver has been successfully validated against experimental and numerical results reported for the wall static pressure data in sonic slot injection to supersonic stream.Detailed validation studies for reacting flow solver has been done using experimental results reported for a coaxial supersonic combustor,in which species profile at various axial locations has been compared.Present numerical solver is useful in simulating combustors of high speed air-breathing propulsion devices.展开更多
Recent developments in space technology and exponential increase in demand of earth observation data from space have generated a requirement of a data processing environment,where users can discover the data and proce...Recent developments in space technology and exponential increase in demand of earth observation data from space have generated a requirement of a data processing environment,where users can discover the data and process,based on their requirements.Grid Services for Earth Observation Image Data Processing(GEOID)is proposed with a motivation to cater to future earth observation applications requirements of digital earth.This paper discusses the overview of the GEOID architecture,its deployment scenario,use-cases and simulation results.Core technologies used for implementation include Grid computing and Service Oriented Architecture.GEOID provides capability to address require-ments of applications such as real-time monitoring,time series data processing and processing with user required quality to meet the requirements of end user applications.GEOID allows users to access the archive products or the raw satellite data stream and process their area of interest.Simulations show that applications such as time series analysis show considerable improvement in processing time by using GEOID.展开更多
MI-Jet or medium independent jet engine is a new conceptual design which can be used in any gaseous atmosphere or in any planets with an ISP greafer than that of the existing rocket engines.MI engine's thermodynam...MI-Jet or medium independent jet engine is a new conceptual design which can be used in any gaseous atmosphere or in any planets with an ISP greafer than that of the existing rocket engines.MI engine's thermodynamic concept could be utilized to develop turbojet,ramjet and scramjet engines that can operate in Martian environment with higher ISP.The same concept could be extended for the development of MI-Turbojet,M-Ramjet and MI-Scramjet engine for Earth atmosphere with an ISP as high as 200% of the ISP of existing rocket engines,but less than that of the conventional scramjet or other air-breathing engine.However the operational complexity of the MI-Jet will be significantly lower than that of the existing scramjet engine.展开更多
文摘Urban Growth Models (UGMs) are very essential for a sustainable development of a city as they predict the future urbanization based on the present scenario. Neural Network based Cellular Automata models have proved to predict the urban growth more close to reality. Recently, deep learning based techniques are being used for the prediction of urban growth. In this current study, urban growth of Chennai Metropolitan Area (CMA) of 2017 was predicted using Neural Network based Cellular Automata (NN-CA) model and Deep belief based Cellular Automata (DB-CA) model using 2010 and 2013 urban maps. Since the study area experienced congested type of urban growth, “Existing Built-Up” of 2013 alone was used as the agent of urbanization to predict urban growth in 2017. Upon validating, DB-CA model proved to be the better model, as it predicted 524.14 km2 of the study area as urban with higher accuracy (kappa co-efficient: 0.73) when compared to NN-CA model which predicted only 502.42 km2 as urban (kappa co-efficient: 0.71), while the observed urban cover of CMA in 2017 was 572.11 km2. This study also aimed at analyzing the effects of different types of neighbourhood configurations (Rectangular: 3 × 3, 5 × 5, 7 × 7 and Circular: 3 × 3) on the prediction output based on DB-CA model. To understand the direction and type of the urban growth, the study area was divided into five distance based zones with the State Secretariat as the center and entropy values were calculated for the zones. Results reveal that Chennai Corporation and its periphery experience congested urbanization whereas areas away from the Corporation boundary follow dispersed type of urban growth in 2017.
文摘Manual investigation of chest radiography(CXR)images by physicians is crucial for effective decision-making in COVID-19 diagnosis.However,the high demand during the pandemic necessitates auxiliary help through image analysis and machine learning techniques.This study presents a multi-threshold-based segmentation technique to probe high pixel intensity regions in CXR images of various pathologies,including normal cases.Texture information is extracted using gray co-occurrence matrix(GLCM)-based features,while vessel-like features are obtained using Frangi,Sato,and Meijering filters.Machine learning models employing Decision Tree(DT)and RandomForest(RF)approaches are designed to categorize CXR images into common lung infections,lung opacity(LO),COVID-19,and viral pneumonia(VP).The results demonstrate that the fusion of texture and vesselbased features provides an effective ML model for aiding diagnosis.The ML model validation using performance measures,including an accuracy of approximately 91.8%with an RF-based classifier,supports the usefulness of the feature set and classifier model in categorizing the four different pathologies.Furthermore,the study investigates the importance of the devised features in identifying the underlying pathology and incorporates histogrambased analysis.This analysis reveals varying natural pixel distributions in CXR images belonging to the normal,COVID-19,LO,and VP groups,motivating the incorporation of additional features such as mean,standard deviation,skewness,and percentile based on the filtered images.Notably,the study achieves a considerable improvement in categorizing COVID-19 from LO,with a true positive rate of 97%,further substantiating the effectiveness of the methodology implemented.
基金financially supported by Indian Institute of Space Science and Technology(IIST),Thiruvananthapuram
文摘Banded iron formations （BIFs） are major rock units having hematite layers intermittent with silica rich layers and formed by sedimentary processes during late Archean to mid Proterozoic time. In terrestrial environment, hematite deposits are mainly found associated with banded iron formations. The BIFs in Lake Superior （Canada） and Carajas （Brazil） have been studied by planetary scientists to trace the evolution of hematite deposits on Mars. Hematite deposits are extensively identified in Meridiani region on Mars. Many hypotheses have been proposed to decipher the mechanism for the formation of these deposits. On the basis of geomorphological and mineralogical studies, aqueous environment of deposition is found to be the most supportive mechanism for its secondary iron rich deposits. In the present study, we examined the spectral characteristics of banded iron formations of Joda and Daitari located in Singhbhum craton in eastern India to check its potentiality as an analog to the aqueous/marine environment on Mars. The prominent banding feature of banded iron formations is in the range of few millimeters to few centimeters in thickness. Fe rich bands are darker （gray） in color compared to the light reddish jaspilitic chert bands. Thin quartz veins （〈4 mm） are occasionally observed in the handspecimens of banded iron formations. Spectral investigations have been conducted in VIS/NIR region of electromagnetic spectrum in the laboratory conditions. Optimum absorption bands identified include 0.65, 0.86, 1.4 and 1.9 μm, in which 0.56 and 0.86 μm absorption bands are due to ferric iron and 1.4 and 1,9 μm bands are due to OH/H2O. To validate the mineralogical results obtained from VlS/NIR spectral radiometry, laser Raman and Fourier transform infrared spectroscopic techniques were utilized and the results were found to be similar. Goethite-hematite association in banded iron formation in Singhbhum craton suggests dehydration activity, which has altered the primary iron oxide phases into the secondary iron oxide phases. The optimum bands identified for the minerals using various spectroscopic techniques can be used as reference for similar mineral deposits on any remote area on Earth or on other hydrated planetary surfaces like Mars.
基金upported by the National Natural Science Foundation of China(NSFC,Grant No.12033005)the National Key R&D Program of China(No.2022YFA1603102)+2 种基金the China Manned Space Project(CMS-CSST-2021-A09,CMS-CSST-2021-B06)the China-Chile Joint Research Fund(CCJRF No.2211)support from the Tianchi Talent Program of Xinjiang Uygur Autonomous Region。
文摘Leveraging the high resolution,sensitivity,and wide frequency coverage of the Atacama Large Millimeter/submillimeter Array(ALMA),the QUARKS survey,standing for“Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures”,is observing 139 massive starforming clumps at ALMA Band 6(λ~1.3 mm).This paper introduces the Atacama Compact Array(ACA)7 m data of the QUARKS survey,describing the ACA observations and data reduction.Combining multiwavelength data,we provide the first edition of QUARKS atlas,offering insights into the multiscale and multiphase interstellar medium in high-mass star formation.The ACA 1.3 mm catalog includes 207 continuum sources that are called ACA sources.Their gas kinetic temperatures are estimated using three formaldehyde transitions with a non-LTE radiation transfer model,and the mass and density are derived from a dust emission model.The ACA sources are massive(16–84 percentile values of 6–160 M_(⊙)),gravity-dominated(M∝R^(1.1))fragments within massive clumps,with supersonic turbulence(M>1)and embedded star-forming protoclusters.We find a linear correlation between the masses of the fragments and the massive clumps,with a ratio of 6%between the two.When considering fragments as representative of dense gas,the ratio indicates a dense gas fraction(DGF)of 6%,although with a wide scatter ranging from 1%to 10%.If we consider the QUARKS massive clumps to be what is observed at various scales,then the size-independent DGF indicates a self-similar fragmentation or collapsing mode in protocluster formation.With the ACA data over four orders of magnitude of luminosity-to-mass ratio(L/M),we find that the DGF increases significantly with L/M,which indicates clump evolutionary stage.We observed a limited fragmentation at the subclump scale,which can be explained by a dynamic global collapse process.
基金supported by an INSPIRE grant under the AORC scheme of the Department of Science and Technology
文摘We present a detailed investigation of the evolution of observed net vertical current using a time series of vector magnetograms of the active region （AR） NOAA 11158 obtained from the Helioseismic and Magnetic Imager. We also discuss the relation of net current to the observed eruptive events. The AR evolved from the βγ to βγδ3 configuration over a period of six days. The AR had two sub-regions of activity with opposite chirality： one dominated by sunspot rotation producing a strong CME, and the other showing large shear motions producing a strong flare. The net current in each polarity over the CME producing sub-region increased to a maximum and then decreased when the sunspots were separated. The time profile of net current in this sub-region followed the time profile of the rotation rate of the south-polarity sunspot in the same sub-region. The net current in the flaring sub-region showed a sudden increase at the time of the strong flare and remained unchanged until the end of the observation, while the sunspots maintained their close proximity. The systematic evo- lution of the observed net current is seen to follow the time evolution of total length of strongly sheared polarity inversion lines in both of the sub-regions. The observed photospheric net current could be explained as an inevitable product of the emergence of a twisted flux rope, from a higher pressure confinement below the photosphere into the lower pressure environment of the photosphere.
文摘Development of asymptotic magnitude Bode plots for integer-order transfer functions is a well-established topic in the control theory.However,construction of such plots for the fractional-order transfer functions has not received much attention in the existing literature.In the present paper,we investigate in this direction and derive the procedures for sketching asymptotic magnitude Bode plots for some of the popular fractional-order controllers such as PI^α,[PI]^α,PD^β,[PD]^β,and PI^αD^β.In addition,we deduce these plots for general fractional commensurate-order transfer functions as well.As applications of this work,we illustrate 1)the analysis of the designed fractional-control loop and 2)the identification of fractional-order transfer function from a given plot.
文摘TCP performance degrades when end-to-end connections extend over wireless links which are characterized by high Bit Error Rate and intermittent connectivity. Such degradation is mainly accounted for TCP’s unnecessary congestion control actions while attempting TCP loss recovery. Several independent link loss recovery approaches are proposed by researchers to reduce number of losses visible at TCP. In this paper we first presented a survey of loss mitigation techniques at wireless link layer. Secondly performance evaluation for TCP through Type 0 Automatic Retransmission Request mechanism in erroneous Wireless LAN is presented. In particular, simulations are performed taking into account the wireless errors introduced over IEEE 802.11 link using a well-established 2-State Markov model. TCP performance is evaluated under different settings for maximum link retransmissions allowed for each frame. Simulation results show that, link retransmission improves TCP performance by reducing losses perceived at TCP sender. However, such improvement is often associated with adverse effect on other TCP parameters that may cost a lot in return under extreme network conditions. In this paper an attempt is made to observe impact of link retransmissions on the performance of multiple TCP flows competing with each other. The analysis presented in this paper signifies the scope for maximizing TCP’s throughput at the least possible cost.
基金supported by the National Key R&D Program of China(No.2022YFA1603100)the National Natural Science Foundation of China(NSFC)through grants Nos.12203086,12033005,12073061,12122307,and 12103045+12 种基金supported by CPSF No.2022M723278the international partnership program of Chinese Academy of Sciences through grant No.114231K YSB20200009Shanghai Pujiang Program 20PJ1415500the science research grants from the China Manned Space Project with no.CMS-CSST-2021-B06Yunnan Fundamental Research Project(grant No.202301AT070118)sponsored by Natural Science Foundation of Shanghai(No.23ZR1482100)support from the National Natural Science Foundation of China(NSFC)through grants Nos.12273090&12322305the Chinese Academy of Sciences(CAS)‘Light of West China’Program(No.xbzgzdsys-202212)support from the ANID BASAL project FB210003support from the Fondecyt Regular(project code 1220610)partially supported by a Grant-in-Aid for Scientific Research(KAKENHI Number JP22H01271 and JP23H01221)of JSPSsupported by JSPS KAKENHI(grant No.JP20H05645)sponsored(in part)by the Chinese Academy of Sciences(CAS),through a grant to the CAS South America Center for Astronomy(CASSACA)in Santiago,Chile。
文摘This paper presents an overview of the QUARKS survey,which stands for Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures."The QUARKS survey is observing139 massive clumps covered by 156 pointings at Atacama Large Millimeter/submillimeter Array(ALMA)Band 6(λ~1.3 mm).In conjunction with data obtained from the ALMA-ATOMS survey at Band 3(λ~3 mm),QUARKS aims to carry out an unbiased statistical investigation of massive star formation process within protoclusters down to a scale of 1000 au.This overview paper describes the observations and data reduction of the QUARKS survey,and gives a first look at an exemplar source,the mini-starburst Sgr B2(M).The wide-b and width(7.5 GHz)and high-angular-resolution(~0."3)observations of the QUARKS survey allow for the resolution of much more compact cores than those could be done by the ATOMS survey,and to detect previously unrevealed fainter filamentary structures.The spectral windows cover transitions of species including CO,SO,N_(2)D^(+),SiO,H_(30)α,H_(2)CO,CH_(3)CN,and many other complex organic molecules,tracing gas components with different temperatures and spatial extents.QUARKS aims to deepen our understanding of several scientific topics of massive star formation,such as the mass transport within protoclusters by(hub-)filamentary structures,the existence of massive starless cores,the physical and chemical properties of dense cores within protoclusters,and the feedback from already formed high-mass young protostars.
文摘Thermally insulating and fire-resistant carbon composite foams are prepared by consolidating natural cotton fibre dispersed in aqueous sucrose solution by filter-pressing followed by drying and carbonization.The compressive strength(5 kPa to 1.4 MPa)and thermal conductivity(0.069 to 0.185 W m^(-1)K^(-1))depend on the foam density(0.06 to 0.31 g cm^(-3))which is modulated by varying the sucrose solutions concentration(100 to 700 g L^(-1)).Partially flexible to the rigid transition of the carbon composite foams occurs at sucrose concentration above 200 g L^(-1).The tubular carbon fibre formed from cotton is welded at their contact points by the amorphous carbon produced from sucrose leading to partial flexibility at low sucrose concentration and advancement of fibre-to-fibre bonding area at higher sucrose concentration results in rigid foam.The porosity in the inter-fibre space and lumen of the carbonized cotton fibre contributes to the low thermal conductivity.The carbon composite foams prepared at a sucrose solution concentration of 500 g L^(-1) and above are amenable to machining using conventional machines and tools.The rigid carbon foams show EMI shielding effectiveness and specific shielding effectiveness in the ranges of 21.5 to 38.9 d B and 108-138 dB cm^(3) g^(-1),respectively.
文摘Composite solid propellant is prepared using tri-modal Ammonium perchlorate(AP)containing coarse,fine and ultrafine fractions of AP with average particle size(APS)340,40 and 5 mm respectively,in various compositions and their rheological,mechanical and burn rate characteristics are evaluated.The optimum combination of AP coarse to fine to ultrafine weight fraction was obtained by testing of series of propellant samples by varying the AP fractions at fixed solid loading.The concentration of aluminium was maintained constant throughout the experiments for ballistics requirement.The propellant formulation prepared using AP with coarse to fine to ultrafine ratio of 67:24:9 has lowest viscosity for the propellant paste and highest tensile strength due to dense packing as supported by the literature.A minimum modulus value was also observed at 9 wt.%of ultrafine AP concentration indicates the maximum solids packing density at this ratio of AP fractions.The burn rate is evaluated at different pressures to obtain pressure exponent.Incorporation of ultrafine fraction of AP in propellant increased burn rate without adversely affecting the pressure exponent.Higher solid loading propellants are prepared by increased AP concentration from 67 to 71 wt.%using AP with coarse to fine to ultrafine ratio of67:24:9.Higher solid content up to 89 wt.%was achieved and hence increased solid motor performance.The unloading viscosity showed a trend with increased AP content and the propellant couldn't able to cast beyond 71 wt.%of AP.Mechanical properties were also studied and from the experiments noticed that%elongation decreased with increased AP content from 67 to 71 wt.%,whereas tensile strength and modulus increased.Burn rate increased with increased AP content and observed that pressure exponent also increased and it is high for the propellant containing with 71 wt.%of AP due to increased oxidiser to fuel ratio.Catalysed composite solid propellant is prepared by using burn rate modifiers Copper chromite and Iron oxide.Addition of Copper chromite and Iron oxide has enhanced the burn rate of tri-modal AP based composite solid propellant.The catalytic propensity of copper chromite is higher than that of iron oxide.The pressure exponent increased with the catalyst concentration and the values obtained are compatible for solid rocket motor applications.
文摘The incompressible miscible displacement problem in porous media is modeled by a coupled system of two nonlinear partial differential equations,the pressure–velocity equation and the concentration equation.In this paper,we present a mixed finite volume element method(FVEM)for the approximation of the pressure–velocity equation and a standard FVEM for the concentration equation.A priori error estimates in L^(∞)(L^(2))are derived for velocity,pressure and concentration.Numerical results are presented to substantiate the validity of the theoretical results.
文摘Tungsten disulfide(WS_(2))stands out as a fascinating member of the transition metal dichalcogenides(TMDs)family.Recently,there has been a focus on introducing WS_(2)nanosheets into various polymers to expand their application in different fields.This study explores the innovative application of WS_(2)nanosheets in natural rubber latex(NRL)using tannic acid(TA)as a green exfoliating agent.WS_(2)nanosheets were synthesized through sand grinding of bulk WS_(2)with the assistance of TA.The resulting TA-modified WS_(2)nanosheets(WT)were then dispersed in NRL,leading to the fabrication of NR/WS_(2)(NWT)nanocomposites via the latex double-dipping method.An insertion of 1.5 phr of WT significantly enhanced the mechanical,thermal,and antibacterial properties,as well as the biocompatibility of natural rubber(NR).These improvements were attributed to the uniform dispersion of WT nanosheets in NRL,the interaction between WS_(2)and NR through TA,and the reinforcement effect from excess TA.This advancement demonstrates the potential of WS_(2)nanosheets-based NR nanocomposites for industrial development and innovation in various fields,especially the biomedical field.
文摘Film cooling in combination with regenerative cooling is presently considered as an efficient method to guarantee safe operation of liquid rocket engines having higher heat flux densities for long duration.This paper aims to bring all the research carried out in the field of liquid rocket engine film cooling since 1950.The analytical and numerical procedure followed,experimental facilities and measurements made and major inferences drawn are reviewed in detail,and compared where ever possible.Review has been made through a discussion of the analyses methodologies and the factors that influence film cooling performance.An effort has also been made to determine the status of the research,pointing out critical gaps,which are still to be explained and addressed by future generations.
基金the National Board for Higher Mathematics(Department of Atomic Energy,India)for the financial support through the Post-Doctoral Fellowship[2/40(9)/2014/R&D-II/319]the Second author would like to thank the IIT Mandi for providing the financial support through the Seed Grant[IITMandi/SG/2015/05-01].
文摘In this paper,we discuss the trajectory controllability of linear and nonlinear fractional dynamical systems represented by the fractional differential equations in the sense of Caputo fractional derivative by using the Mittag-Leffler function and Gronwall-Bellman inequality.For the nonlinear system,we assume Lipschitz-type conditions on the nonlinearity.Examples are given to illustrate the theoretical results.
文摘A finite element model for piezoelectric smart beam in extension mode based on First-order Shear Deformation Theory(FSDT)with an appropriate through-thickness distribution of electric potential is presented.Accuracy of piezoelectric finite element formulations depends on the selection of assumed mechanical and electrical fields.Most of the conventional FSDT-based piezoelectric beam formulations available in the literature use linear through-thickness distribution of electric potential which is actually nonlinear.Here,a novel quadratic profile of the through-thickness electric potential is proposed to include the nonlinear effects.The results obtained show that the accuracy of conventional formulations with linear through-thickness potential approximation is affected by the material configuration,especially when the piezoelectric material dominates the beam cross section.It is shown that the present formulation gives the same level of accuracy for all regimes of material configurations in the beam cross section.Also,a modified form of the FSDT displacements is employed,which utilizes the shear angle as a degree of freedom instead of section rotation.Such a FSDT displacement field shows improved performance compared to the conventional field.The present formulation is validated by comparing the results with ANSYS 2D simulation.The comparison of results proves the improved efficiency and accuracy of the present formulation over the conventional formulations.
基金the support provided by the Department of Aerospace Engineering,IIST,Trivandrum,India,in carrying out this research work.
文摘Experimental and computational analysis has been carried out by many researchers on supersonic cavity flow,but detailed analysis based on Rossiter’s model still requires some insight.In the current study an open rectangular cavity with a length to depth ratio of 2(L/D=2)and Mach number at the inlet as 1.71,was considered as a baseline configuration for experimental analysis.Statistical techniques such as power spectral density(PSD),correlation,and overall sound pressure level(OASPL)were carried out on the unsteady pressure data,to analyze the aero-acoustic flow physics.High-speed schlieren images were processed to obtain spatially coherent modes by proper orthogonal decomposition(POD).The analysis was extended for different dimensions of subcavities on the aft,floor,and front wall.This detailed analysis of these configurations with different dimensions and combinations revealed the various flow features and mode frequencies in supersonic cavity.As the front wall subcavity act as a passive control device,reducing the overall sound pressure level inside the cavity whereas,the aft wall subcavity acts as a passive resonator with distinct harmonic fluidresonant modes,a similar phenomenon was observed for floor subcavity at different locations.A novel method was employed to analyze Rossiter’s model and its applicability in estimating experimental modes was verified,as it accurately predicted the dominant frequencies with a maximum of 2.74% uncertainty among all the configurations.
文摘Development of an Advection Upstream Splitting Method(AUSM+-up)scheme-based Unstructured Finite Volume(UFVM)solver for the simulation of two-dimensional axisymmetric/planar high speed compressible turbulent reacting shear layers is presented.The inviscid numerical flux is evaluated using AUSM+-up upwind scheme.An eight-step hydrogen–oxygen finite rate chemistry model is used to model the development of chemical species in a supersonic reacting flow field.The chemical species terms are alone solved implicitly in this explicit flow solver by rescaling the equation in time.The turbulence modeling has been done using RNG-based k–model.Three-stage Runge–Kutta method has been used for explicit time integration.The nonreacting twodimensional Cartesian version of the same solver has been successfully validated against experimental and numerical results reported for the wall static pressure data in sonic slot injection to supersonic stream.Detailed validation studies for reacting flow solver has been done using experimental results reported for a coaxial supersonic combustor,in which species profile at various axial locations has been compared.Present numerical solver is useful in simulating combustors of high speed air-breathing propulsion devices.
文摘Recent developments in space technology and exponential increase in demand of earth observation data from space have generated a requirement of a data processing environment,where users can discover the data and process,based on their requirements.Grid Services for Earth Observation Image Data Processing(GEOID)is proposed with a motivation to cater to future earth observation applications requirements of digital earth.This paper discusses the overview of the GEOID architecture,its deployment scenario,use-cases and simulation results.Core technologies used for implementation include Grid computing and Service Oriented Architecture.GEOID provides capability to address require-ments of applications such as real-time monitoring,time series data processing and processing with user required quality to meet the requirements of end user applications.GEOID allows users to access the archive products or the raw satellite data stream and process their area of interest.Simulations show that applications such as time series analysis show considerable improvement in processing time by using GEOID.
文摘MI-Jet or medium independent jet engine is a new conceptual design which can be used in any gaseous atmosphere or in any planets with an ISP greafer than that of the existing rocket engines.MI engine's thermodynamic concept could be utilized to develop turbojet,ramjet and scramjet engines that can operate in Martian environment with higher ISP.The same concept could be extended for the development of MI-Turbojet,M-Ramjet and MI-Scramjet engine for Earth atmosphere with an ISP as high as 200% of the ISP of existing rocket engines,but less than that of the conventional scramjet or other air-breathing engine.However the operational complexity of the MI-Jet will be significantly lower than that of the existing scramjet engine.
