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Multi-revolution low-thrust trajectory optimization using symplectic methods

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Science China(Technological Sciences) 2020年第3期63卷 506-519页

作者： e ZhiBo GUZZeTTI Davide School of Aerospace engineering Tsinghua UniversityBeijing 100084China Department of Aerospace engineering Auburn UniversityAuburn AL 36849USA

Optimization of low-thrust trajectories that involve a larger number of orbit revolutions is considered as a challenging *** paper describes a high-precision symplectic method and optimization techniques to solve the minimum-energy low-thrust multi-revolution orbit transfer problem. First, the optimal orbit transfer problem is posed as a constrained nonlinear optimal control problem. Then, the constrained nonlinear optimal control problem is converted into an equivalent linear quadratic form near a reference solution. The reference solution is updated iteratively by solving a sequence of linear-quadratic optimal control sub-problems, until convergence. each sub-problem is solved via a symplectic method in discrete form. To facilitate the convergence of the algorithm, the spacecraft dynamics are expressed via modified equinoctial elements. Interpolating the non-singular equinoctial orbital elements and the spacecraft mass between the initial point and end point is proven beneficial to accelerate the convergence process. Numerical examples reveal that the proposed method displays high accuracy and efficiency.

关键词： low-thrust trajectory optimization symplectic method multi-revolution transfers

Blast injury risks to humans within a military trench

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Defence Technology（防务技术） 2024年第10期40卷 91-104页

作者： Idan e.edri National Building Research Institute Technion-Israel Institute of TechnologyTechnion CityHaifa 32000Israel

In land warfare,trenches serve as vital defensive fortifications,offering protection to soldiers while engaging in ***,despite their protective function,soldiers often sustain injuries within these *** lack of corresponding blast data alongside empirical injury reports presents a significant knowledge gap,particularly concerning the blast pressures propagating within trench spaces following nearby *** absence hinders the correlation between blast parameters,trench geometry,and reported injury cases,limiting our understanding of blast-related risks within *** paper addresses the critical aspect of blast propagation within trench systems,essential for evaluating potential blast injury risks to individuals within these *** advanced computational fluid dynamics(CFD)simulations,the study comprehensively investigates blast injury risks resulting from explosions near military *** a sophisticated computational model,the research analyzes the dynamic blast effects within trenches,considering both geometrical parameters and blast characteristics influenced by explosive weight and scaled *** numerical simulations yield valuable insights into the impact of these parameters on blast injury risks,particularly focusing on eardrum rupture,lung injury,and traumatic brain injury levels within the *** findings elucidate distinct patterns of high-risk zones,highlighting unique characteristics of internal explosions due to confinement and venting dynamics along the *** study underscores the significance of detailed numerical modeling in assessing blast injury risks and provides a novel knowledge base for understanding risks associated with explosives detonating near military *** insights gained contribute to enhancing safety measures in both military and civilian contexts exposed to blast events near trench structures.

关键词： Trench Blast Injury risk eardrum rupture Lung injury Traumatic brain injury

A comprehensive study for mass attenuation coefficients of different parts of the human body through Monte Carlo methods

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Nuclear Science and Techniques 2016年第3期27卷 31-39页

作者： e.e.ermis F.B.Pilicer e.Pilicer C.Celiktas Physics Department Faculty of ScienceEge University Physics Department Faculty of Arts and ScienceUludag University

The gamma-ray mass attenuation coefficients of blood,bone,lung,eye lens,adipose,tissue,muscle,brain and skin were calculated at different energies(60,80,150,400,500,600,1000,1250,1500,and 2000 keV) by various theoretical methods such as FLUKA,GeANT4 Monte Carlo(MC) methods and XCOM program in this *** coefficients were also compared with the National Institute of Standards and Technology(NIST) *** results were highly in accordance with each other and NIST *** results showed that FLUKA was quite convenient in comparison to GeANT4 in the calculation of the mass attenuation coefficients of the used human body samples for low-energy photons(60,80,and 150 keV) when compared with the NIST values.

关键词：质量衰减系数蒙特卡洛方法 Geant4 部位 NIST 美国国家标准能量计算眼晶状体

Photoluminescence properties of eu3+-doped MgAl2O4 nanoparticles in various surrounding media

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Journal of Rare earths 2019年第8期37卷 806-811,I0001页

作者： I.e.Kolesnikov e.V.Golyeva e.V.Borisov e.Yu Kolesnikov e.Lahderanta A.V.Kurochkin M.D.Mikhailov St.Petersburg State University St.PetersburgRussia Lappeenranta University of Technology LUT LappeenrantaFinland Peter the Great St.Petersburg Polytechnic University St.PetersburgRussia Scientific and Technological Institute of Optical Material Science VNTs S.I.Vavilov State Optical InstituteSt.PetersburgRussia Volga State University of Technology Yoshkar-OlaRussia

eu3+-doped MgAl2O4 nanoparticles were prepared by modified Pechini method.X-ray diffraction analysis shows pure tetragonal spinel phase without any *** average size of synthesized nanoparticles was determined to be about 50-60 nm using scanning electron microscopy and static light scattering *** and excitation spectra as well as lifetimes of MgAl2O4:eu3+ nanophosphors were explored in surrounding media with different refractive *** medium does not affect luminescence bands position,whereas 5D0 lifetime monotonically decreases along with increase of medium refractive *** of surrounding media on radiative and nonradiative decay rates,which were calculated using 4f-4f intensity theory,was studied and *** factor of prepared nanoparticles is defined using both radiative and observed lifetimes.

关键词： eu3+ Nanoparticles Filling factor Luminescence Lifetime Rare earths

DNA Dynamics Studied Using the Homogeneous Balance Method

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Chinese Physics Letters 2012年第8期29卷 9-11页

作者： e.M.e.Zayed A.H.Arnous Mathematics Department Faculty of ScienceZagazig UniversityP.O.Box 44519ZagazigEgypt

We employ the homogeneous balance method to construct the traveling waves of the nonlinear vibrational dynamics modeling of *** new explicit forms of traveling waves are *** is shown that this method provides us with a powerful mathematical tool for solving nonlinear evolution equations in mathematical *** and weaknesses of the proposed method are discussed.

关键词： traveling nonlinear method

effect of Magnetic Field on a p-Type δ-Doped GaAs Layer

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Chinese Physics Letters 2010年第7期27卷 233-236页

作者： e. OZTURK Department of Physics Cumhuriyet University Sivas 58140 Turkey

The energy levels of holes in a p-type δ-doped GaAs structure under a magnetic field are theoretically calculated within the framework of the effective mass approximation for a uniform aceeptor distribution. The electronic structure is calculated by solving the Schrodinger and Poisson equations self-consistently. The effect of the magnetic field on the potential profile changes the degree of the confinement and localization, and thus this behavior can be used to study these systems in regions of interest, without the need to grow many different samples. It is found that the heavy-hole subbands contain many more energy states than the light-hole ones; the population of the heavy-hole levels represents approximately 91 % of all the carriers without magnetic field. With increasing magnetic field the total population of the heavy-holes increases and the number of filled states changes.

关键词： Magnetic field energy Fields Computers Political systems

The Hoeke-Brown failure criterion and GSI-2018 edition

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Journal of Rock Mechanics and Geotechnical engineering 2019年第3期11卷 445-463页

作者： e.Hoek e.T.Brown North Vancouver British ColumbiaV7R 4H7Canada Brisbane Queensland 4169Australia

The HoekeBrown criterion was introduced in 1980 to provide input for the design of underground excavations in *** criterion now incorporates both intact rock and discontinuities,such as joints,characterized by the geological strength index(GSI),into a system designed to estimate the mechanical behaviour of typical rock masses encountered in tunnels,slopes and *** strength and deformation properties of intact rock,derived from laboratory tests,are reduced based on the properties of discontinuities in the rock *** nonlinear HoekeBrown criterion for rock masses is widely accepted and has been applied in many projects around the ***,in general,it has been found to provide satisfactory estimates,there are several questions on the limits of its applicability and on the inaccuracies related to the quality of the input *** paper introduces relatively few fundamental changes,but it does discuss many of the issues of utilization and presents case histories to demonstrate practical applications of the criterion and the GSI system.

关键词： Hoek-Brown criterion Geological strength index(GSI) Rock mass strength Uniaxial compressive strength(UCS) Tension cut-off Rock mass deformation modulus

The Asymptotics of the Heat Semigroup for a General Bounded Domain with Mixed Boundary Conditions

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Acta Mathematica Sinica,english Series 2000年第4期16卷 627-636页

作者： e. M. e. Zayed Mathematics Department. Faculty of Science. Zagazig University. Zagazig. egypt

Small-time asymptotics of the trace of the heat semigroup θ（t）=Σv=1x exp（-tμv）. where {μv} are the eigenvalues of the uegative Laplacian -Δ= -Σβ=12（/xβ）2 in the （x1, x2）-plane. is studied for a general bounded domain Ω with a smooth boundary Ω. where a finite number of Dirichlet. Neumann and Robin boundary conditions, on the piecewise smooth parts Γi（i=1, ..., n） of )Ω such that)Ω=∪i=1nΓ are considered. Some geometrical properties associated with Ω are determined

关键词： Heat semigroup Inverse problem Mixed boundary conditions eigenvalues

enhancement of electric Conductivity in Transparent Glasse—Ceramic Nanocomposites of Bi_2O_3—BaTiO_3 Glasses

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Journal of Materials Science & Technology 2013年第12期29卷 1166-1176页

作者： A.A.Bahgat M.G.Moustafa e.e.Shaisha Department of Physics Faculty of ScienceAl-Azhar University

The frequency and temperature dependent electrical conductivity measurements for heat-treated binary glass system with composition of （lO0-x）Bi203-xBaTi03 （x = 20, 30, 40 and 50, in mol%） were carried out. The glass was prepared by melt quenching technique and their corresponding glass-ceramic nanocomposites were obtained by suitable heat treatment. Nanostructured behavior and electrical properties of these glasses and their corresponding glass-ceramic nanocomposites were studied. X-ray diffraction （XRD） and differential scanning calorimetry confirmed the amorphous nature of the glasses. Moreover, XRD patterns of the samples indicate nanocrystallites embedded in the glass matrix. The Fourier transform infrared spectroscopy （FT-IR） spectral analysis showed that the band positions of glass system are within the wave number range of Bi06, Bi03 and Ti06 structural units. It is observed that the electrical conductivity is enhanced by 102-103 times in the transparent glass-ceramic nanocomposite phase. With further heat treatment, the conductivity decreased considerably in the stage of glass-ceramic nanocomposite phase as compared with the glassy phase sample. Therefore, partially devitrified phase is more suitable as cathode material in secondary batteries compared to its vitreous or fully crystalline counterpart. The conduction mechanism was confirmed to obey the adiabatic small polaron hopping （SPH）. AC conductivity measurements were performed as a function of temperature and frequency, showing a very slow increasing rate at low temperatures and then a fast rate at higher temperatures.

关键词： Barium titanat Transparent glass--ceramic nanocomposites DC electrical conductivity AC electrical conductivity Smallpolaron hopping