检索结果-南通市图书馆

Surface oxidation study of molten Mg–Al alloys by oxide/metal/oxide sandwich method

维普期刊数据库评论

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 Magnesium and Alloys 2022年第6期10卷 1704-1717页

作者： Mohammad Mahdi Jalilvand Hassan Saghafian mehdi Divandari mehdi Akbarifar School of Materials Science and Engineering Iran University of Science and TechnologyNarmakTehran ***Iran

The dynamic oxidation of molten Mg–Al alloy was investigated via the oxide/metal/oxide(OMO)sandwich *** characteristics of sandwiches were explored using optical microscopy,scanning electron microscopy,X-ray energy dispersive spectroscopy,and X-ray diffraction *** results showed the formation of porous oxide films with varying thicknesses from 0.43 to 16.7 *** the measurements and calculations confirmed the literature findings that the oxidation product consists mainly of MgO and Mg Al_(2)O_(4)*** increase in thickness and amount of folds formed on the oxide films implies the significant effect of aluminum in reducing the oxidation resistance of magnesium.

关键词： OMO sandwich Dynamic oxidation Surface film Oxide morphology Thermodynamics Mg–Al alloys

Dynamic Positioning System Design for A Marine Vessel with Unknown Dynamics Subject to External Disturbances Including Wave Effect

在线全文

学校读者我要写书评

暂无评论

China Ocean Engineering 2020年第5期34卷 651-663页

作者： Alireza HOSSEINNAJAD mehdi LOUEIPOUR Department of Mechanical Engineering Isfahan University of TechnologyIsfahanIran Research Institute for Subsea Science and Technology Isfahan University of TechnologyIsfahanIran

In this paper, a new control system is proposed for dynamic positioning(DP) of marine vessels with unknown dynamics and subject to external disturbances. The control system is composed of a substructure for wave filtering and state estimation together with a nonlinear PD-type controller. For wave filtering and state estimation, a cascade combination of a modified notch filter and an estimation stage is considered. In estimation stage, a modified extended-state observer(ESO) is proposed to estimate vessel velocities and unknown dynamics. The main advantage of the proposed method is its robustness to model uncertainties and external disturbances and it does not require prior knowledge of vessel model parameters. Besides, the stability of the cascade structure is analyzed and input to state stability(ISS) is guaranteed. Later on, a nonlinear PD-type controller with feedforward of filtered estimated dynamics is utilized. Detailed stability analyses are presented for the closed-loop DP control system and global uniform ultimate boundedness is proved using large scale systems method. Simulations are conducted to evaluate the performance of the proposed method for wave filtering and state estimation and comparisons are made with two conventional methods in terms of estimation accuracy and the presence of uncertainties. Besides, comparisons are made in closed-loop control system to demonstrate the performance of the proposed method compared with conventional methods. The proposed control system results in better performance in the presence of uncertainties,external disturbance and even in transients when the vessel is subjected to sudden changes in environmental disturbances.

关键词： dynamic positioning environmental disturbances marine vessel state estimation unknown dynamics wave filtering

Data-Based Filters for Non-Gaussian Dynamic Systems With Unknown Output Noise Covariance

在线全文

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2024年第4期11卷 866-877页

作者： Elham Javanfar mehdi Rahmani the Department of Electrical Engineering Imam Khomeini International UniversityQazvin ***Iran

This paper proposes linear and nonlinear filters for a non-Gaussian dynamic system with an unknown nominal covariance of the output *** challenge of designing a suitable filter in the presence of an unknown covariance matrix is addressed by focusing on the output data set of the *** that data generated from a Gaussian distribution exhibit ellipsoidal scattering,we first propose the weighted sum of norms(SON)clustering method that prioritizes nearby points,reduces distant point influence,and lowers computational ***,by introducing the weighted maximum likelihood,we propose a semi-definite program(SDP)to detect outliers and reduce their impacts on each *** these weights paves the way to obtain an appropriate covariance of the output ***,two filtering approaches are presented:a cluster-based robust linear filter using the maximum a posterior(MAP)estimation and a clusterbased robust nonlinear filter assuming that output noise distribution stems from some Gaussian noise resources according to the ellipsoidal *** last,simulation results demonstrate the effectiveness of our proposed filtering approaches.

关键词： Data-based filter maximum likelihood estimation unknown covariance weighted maximum likelihood estimation weighted sum-of-norms clustering

Reinforcement Learning-Empowered Graph Convolutional Network Framework for Data Integrity Attack Detection in Cyber-Physical Systems

在线全文

学校读者我要写书评

暂无评论

CSEE Journal of Power and Energy Systems 2024年第2期10卷 797-806页

作者： Edeh Vincent mehdi Korki mehdi Seyedmahmoudian Alex Stojcevski Saad Mekhilef School of Science Computingand Engineering TechnologiesSwinburne University of TechnologyMelbourneAustralia

The massive integration of communication and information technology with the large-scale power grid has enhanced the efficiency, safety, and economical operation of cyber-physical systems. However, the open and diversified communication environment of the smart grid is exposed to cyber-attacks. Data integrity attacks that can bypass conventional security techniques have been considered critical threats to the operation of the grid. Current detection techniques cannot learn the dynamic and heterogeneous characteristics of the smart grid and are unable to deal with non-euclidean data types. To address the issue, we propose a novel Deep-Q-Network scheme empowered with a graph convolutional network (GCN) framework to detect data integrity attacks in cyber-physical systems. The simulation results show that the proposed framework is scalable and achieves higher detection accuracy, unlike other benchmark techniques.

关键词： Deep reinforcement learning graph convolutional network heterogeneous smart grid network

The behavior of HfB_2 under neutron irradiation

维普期刊数据库评论

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 2016年第2期27卷 14-17页

作者： Mohammad mehdi Nasseri School of Plasma Physics and Nuclear Fusion Institute of Nuclear Science and Technology (AEOI)

Due to the interesting properties of hafnium diboride(HfB_2) as a ceramic, it has drawn considerabl attention from several researchers. To understand th radiation properties of HfB_2 that may be used in the nuclea industry, the interaction of this composite under neutro irradiation was studied. It is obvious that, because HfB_2 ha Boron, this composite has the potential to absorb neutron particularly in the range of thermal energy. The ^(10)B(n, a7 Li interaction is dominant among other interactions tha produce alpha particles. The results revealed that alph particles have a high fluctuation diagram following a saw tooth spectrum for thermal neutron energy, which has to b carefully analyzed. If HfB_2 is intended to be used in fusio facilities, for example in fusion reactors, its interactio with high neutrons(14 Me V) should be studied. Th results of this case showed that, in the wide range of alph energy, the amount of alpha particles is almost constant, s this continuum spectrum is almost flat and there is just small peak at 2.31 Me V that belongs to the very famou interaction [^(10)B(n, a)~7Li].

关键词：中子辐照相互作用行为能量范围复合材料聚变反应堆 α粒子研究人员

Correlation between platinum-aluminide coating features and tensile behavior of nickel-based superalloy Rene■80

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2024年第10期43卷 5391-5402页

作者： Mohammad mehdi Barjesteh Seyed mehdi Abbasi Karim Zangeneh Madar Kourosh Shirvani Metallic Materials Research Center Malek Ashtar University of Technology(MUT)Tehran 158751774Iran Department of Advanced Materials and New Energies Iranian Research Organization for Science and Technology(IROST)Tehran***Iran

The effect of platinum(a rare metal)-aluminide coating parameters on the tensile properties of nickel-based superalloy Rene■80 was evaluated at 871℃.For this purpose,initial layers of platinum with different thicknesses(2,4,6 and 8μm)were coated on tensile samples Then,low-temperature high-activity(LTHA)and hightemperature low-activity(HTLA)processes were used for *** of microstructural evaluations using scanning electron microscope(SEM)and phase analysis by X-ray diffraction(XRD)showed a three-layer structure coating for different platinum layer thicknesses and both aluminizing *** the thickness of the platinum layer from 2 to 8μm led to the improvement in the final coating thickness from 91.6 to 102.1μm in *** increase was from 128.1 to 148.6μm in *** results of hot tensile tests at 871℃ showed a decrease in strength properties of the coated samples compared to the uncoated ***,HTLA and high thicknesses of the initial platinum layer showed an intense *** results of fractographic evaluations abou uncoated samples showed a ductile *** the other hand,coated samples showed a simultaneous ductile and brittle fracture failure *** the main fracture morphology was brittle cleavage fracture which was for the HTLA.

关键词： Rene■80 Platinum-aluminide Aluminizing Tensile properties Fractography

Fabrication of Modified Fibrous Filters by Electrospinning and Investigating Their Application as Improved Face Masks

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11期42卷 1738-1748,I0010页

作者： mehdi Mahmoudian Fatemeh Zanbili Nanotechnology Research Group Faculty of ScienceUrmia UniversityUrmia57159-404931Iran Department of Nanochemistry Nanotechnology Research CenterUrmia UniversityUrmia57159-404931Iran

Owing to the significant increase in air pollutants and the spread of infectious diseases,it seems that the use of face masks will become an essential item in human ***,there is a need to conduct more research to develop novel types of respirators utilizing upto-date science such as *** this study,we fabricated a nanocomposite fibrous filter containing modified graphene oxide(GO)and zinc oxide(ZnO)*** layer was used as an active filter for absorbing and removing air pollutants,such as suspended submicron particles(below 2.5 microns)and CO_(2),NO_(2),and SO_(2)*** synthesized nanostructures and fibrous filters were characterized by different analysis(FTIR,XRD,TGA,and FESEM),and the performance of the filters was surveyed by tests such as pressure drop,CO_(2),NO_(2),SO_(2)gas rejection,and particulate *** results showed that the stabilization of the modified GO and ZnO nanostructures on the fibrous filter improved the effectiveness of this filter as a mask for removing toxic particles and gases,and the filter containing nanoparticles had the best performance.

关键词： Air pollutants Face masks Nanocomposite fibrous filter Electrospinning

NEW COHORT OF OPTICALLY ACTIVE NANOSTRUCTURE POLY(AMIDEIMIDE)S:PRODUCTION AND PROPERTIES

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2011年第6期29卷 639-649页

作者： Shadpour Mallakpour mehdi Hatami Organic Polymer Chemistry Research Laboratory Department of ChemistryIsfahan University of Technology.Isfahan 84156-83111Iran Nanotechnology and Advanced Materials Institute Isfahan University of TechnologyIsfahan84156-83111Iran Organic Polymer Chemistry Research Laboratory Department of ChemistryIsfahan University of TechnologyIsfahan 84156-83111Iran

Novel aromatic-aliphatic poly（amide-imide）s containing chiral units in the main chain and hydroxyl benzamide units in the side chain have been obtained from the step-growth polymerization of 3,5-diamino-N-（4-hydroxyphenyl） benzamide （2） with different chiral diacid chlorides （la-le）. Theoretical calculations were done by means of computational chemistry methods to narrate the stable conformation and orientation of each diacid chloride monomers under reaction conditions. These polymers were characterized by conventional techniques. The resulting polymers show good thermal stability. Other physical properties of polymers including crystallinity, inherent viscosity and morphological characteristics were also studied.

关键词： Optically active poly(amide-imide)s Amino acid Benzamide units Nano scale.

Multi-objective optimal design of braced frames using hybrid genetic and ant colony optimization

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2016年第4期10卷 472-480页

作者： mehdi BABAEI Ebrahim SANAEI Department of Civil Engineering Faculty of Engineering University of Zanjan Zanjan 45371-38791 Iran

In this article, multi-objective optimization of braced frames is investigated using a novel hybrid algorithm. Initially, the applied evolutionary algorithms, ant colony optimization （ACO） and genetic algorithm （GA） are reviewed, followed by developing the hybrid method. A dynamic hybridization of GA and ACO is proposed as a novel hybrid method which does not appear in the literature for optimal design of steel braced frames. Not only the cross section of the beams, columns and braces are considered to be the design variables, but also the topologies of the braces are taken into account as additional design variables. The hybrid algorithm explores the whole design space for optimum solutions. Weight and maximum displacement of the structure are employed as the objective functions for multi-objective optimal design. Subsequently, using the weighted sum method （WSM）, the two objective problem are converted to a single objective optimization problem and the proposed hybrid genetic ant colony algorithm （HGAC） is developed for optimal design. Assuming different combination for weight coefficients, a trade-offbetween the two objectives are obtained in the numerical example section. To make the final decision easier for designers, related constraint is applied to obtain practical topologies. The achieved results show the capability of HGAC to find optimal topologies and sections for the elements.

关键词： multi-objective hybrid algorithm ant colony genetic algorithm displacement weighted sum method steelbraced frames