检索结果-南通市图书馆

The 3D Inverse Problem of the Wave equation for a General Multi-connected Vibrating Membrane with a Finite Number of Piecewise Smooth Boundary Conditions

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

Acta Mathematica Sinica,english Series 2005年第4期21卷 733-752页

作者： e.M.e.ZAYeD Mathematics Department Faculty of ScienceZagazig UniversityZagazig.Egypt

The trace of the wave kernel μ（t） =∑ω=1^∞ exp（-iteω^1/2）, where {eω}ω^∞=1 are the eigenvalues of the negative Laplacian -△↓2 = -∑k^3=1 （δ/δxk）^2 in the （x^1, x^2, x^3）-space, is studied for a variety of bounded domains, where -∞ 〈 t 〈 ∞ and i= √-1. The dependence of μ （t） on the connectivity of bounded domains and the Dirichlet, Neumann and Robin boundary conditions are analyzed. Particular attention is given for a multi-connected vibrating membrane Ω in Ra surrounded by simply connected bounded domains Ω j with smooth bounding surfaces S j （j = 1,……, n）, where a finite number of piecewise smooth Dirichlet, Neumann and Robin boundary conditions on the piecewise smooth components Si^＊（i = 1 ＋ kj-1,……, kj） of the bounding surfaces S j are considered, such that S j = Ui-1＋kj-1^kj Si^＊, where k0=0. The basic problem is to extract information on the geometry Ω by using the wave equation approach from a complete knowledge of its eigenvalues. Some geometrical quantities of Ω （e.g. the volume, the surface area, the mean curvuture and the Gaussian curvature） are determined from the asymptotic expansion ofexpansion of μ（t） for small │t│.

关键词： Inverse problem Wave kernal eigenvalues Greens function Multi-connected vibrating membrane Negative Laplacian Heat kernel

The Asymptotics of the Two-Dimensional Wave equation for a General Multi-Connected Vibrating Membrane with Piecewise Smooth Robin Boundary Conditions

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,english Series 2004年第2期20卷 209-222页

作者： e.M.e.ZAYeD Department of Mathematics Faculty of ScienceZagazig UniversityZagazigEgypt

The asymptotic expansion for small |t| of the trace of the wave kernel , where and are the eigenvalues of the negative Laplacian in the (x 2,x 2)-plane, is studied for a multi-connected vibrating membrane ? in R 2 surrounded by simply connected bounded domains ? j with smooth boundaries ?? j (j = 1, ..., n), where a finite number of piecewise smooth Robin boundary conditions on the piecewise smooth components Γ i (i = 1+k j?1, ..., k j ) of the boundaries ?? j are considered, such that and k 0 = 0. The basic problem is to extract information on the geometry of ? using the wave equation approach. Some geometric quantities of ? (e. g. the area of ?, the total lengths of its boundary, the curvature of its boundary, the number of the holes of ?, etc.) are determined from the asymptotic expansion of the trace of the wave kernel for small |t|.

关键词： Inverse problem Wave kernel eigenvalues Robin boundary conditions Vibrating membrane Hearing the shape of a drum

Asymptotic expansions of the Heat Kernel of the Laplacian for General Annular Bounded Domains with Robin Boundary Conditions：Further Results

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,english Series 2003年第4期19卷 679-694页

作者： e.M.e.ZAYeD DepartmentofMathematics FacultyofScienceZagazigUniversityZagazigEgypt

The asymptotic expansions of the trace of the heat kernel Θ(t) = Σ_(v =1)~∞exp(-tλ_v) for small positive t, where {λ_v} are the eigenvalues of the negative Laplacian-△_n = -Σ_(i = 1)~n(partial deriv/(partial deriv)x^i)~2 in R^n (n = 2 or 3), are studied for ageneral annular bounded domain Ω with a smooth inner boundary (partial deriv)Ω_1 and a smoothouter boundary (partial deriv)Ω_2, where a finite number of piecewise smooth Robin boundaryconditions (partial deriv/(partial deriv)n_j + γ_j)φ = 0 on the components Γ_j(j = 1, …, k) of(partial deriv)Ω_1 and on the components Γ_j(j = k + 1, …, m) of (partial deriv)Ω_2 areconsidered such that (partial deriv)Ω_1 = ∪_(j = 1)~kΓ_j and (partial deriv)Ω_2 = ∪_(j = k +1)~mΓ_j and where the coefficients γ_j(j = 1, …, m) are piecewise smooth positive functions. Someapplications of Θ(t) for an ideal gas enclosed in the general annular bounded domain Ω are *** results are also obtained.

关键词： inverse problem heat kernel eigenvalues Robin boundary conditions classical ideal gas

Systematic review of centrifugal valving based on digital twin modeling towards highly integrated lab-on-a-disc systems

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

Microsystems & Nanoengineering 2021年第6期7卷 45-70页

作者： Jens Ducrée School of Physical Sciences Dublin City UniversityDublinIreland

Current,application-driven trends towards larger-scale integration(LSI)of microfluidic systems for comprehensive assay automation and multiplexing pose significant technological and economical challenges to *** virtue of their intrinsic capability for powerful sample preparation,centrifugal systems have attracted significant interest in academia and business since the early *** review models common,rotationally controlled valving schemes at the heart of such“Lab-on-a-Disc”(LoaD)platforms to predict critical spin rates and reliability of flow control which mainly depend on geometries,location and liquid volumes to be processed,and their experimental *** absence of larger-scale manufacturing facilities during product development,the method presented here facilitates efficient simulation tools for virtual prototyping and characterization and algorithmic design optimization according to key performance *** virtual in silico approach thus significantly accelerates,de-risks and lowers costs along the critical advancement from idea,layout,fluidic testing,bioanalytical validation,and scale-up to commercial mass manufacture.

关键词： centrifugal advancement modeling

New DySrAlO_4 Compound Synthesis and Formation Process Correlations for LnSrAlO_4(Ln=Nd,Gd,Dy) Series

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

Acta Metallurgica Sinica(english Letters) 2016年第5期29卷 450-456页

作者： e.A.Tugova New Inorganic Materials Laboratory Ioffe Institute

For the first time, DySrA104 of K2NiF4-type structure was synthesized. The parameters of DySrA104 ele- mentary unit cell are determined as follows： a = 0.368 （4） nm, c = 1.229 （2） nm, V = 0.166 （4） nm3. The research of the complex aluminates ZnSrA104 （Ln = Nd, Gd, Dy） solid-state process demonstrated the change of the formation mecha- nism among LnSrA104 （Ln = Nd, Gd, Dy） series from DySrA104 oxide. The performed analysis provided a possibility to realize why chemists couldn＇t get DySrA104 for a long period of time.

关键词： Rare earths Oxide materials K2NiF4-type structure Solid-state reactions Phase formation

城区复杂条件下V形墩钢-混组合连续梁桥临时工程专项设计研究

在线全文

学校读者我要写书评

暂无评论

科学技术创新 2025年第2期 142-145页

作者：赵娥黄辉中交二航局第二工程有限公司重庆

本研究以双桥路道路工程施工为平台,开展城区复杂条件下V形墩钢-混组合连续梁桥支架体系研究。结合项目地形、地质特点及受限空间等多方面工况,利用三维建模及结构计算等手段综合考虑设计一套安全风险可控、经济价值高的临时工程体系,同... 详细信息

本研究以双桥路道路工程施工为平台,开展城区复杂条件下V形墩钢-混组合连续梁桥支架体系研究。结合项目地形、地质特点及受限空间等多方面工况,利用三维建模及结构计算等手段综合考虑设计一套安全风险可控、经济价值高的临时工程体系,同时,结合施工工序,将下部结构V形墩、钢箱梁顶推、上部结构混凝土箱梁等主要结构的支架统筹考虑,周转利用,节约施工工期,降低施工成本。

关键词： V形墩一体化支架体系受限空间钢箱梁拱圈拱架地质条件

Multi-revolution low-thrust trajectory optimization using symplectic methods

在线全文

学校读者我要写书评

暂无评论

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

在线全文

学校读者我要写书评

暂无评论

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

在线全文

学校读者我要写书评

暂无评论

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