scholarly journals Vibrations of thin plates with small clamped patches

2015 ◽  
Vol 471 (2184) ◽  
pp. 20150474 ◽  
Author(s):  
A. E. Lindsay ◽  
W. Hao ◽  
A. J. Sommese
Keyword(s):  
Eigenvalue Problem ◽  
Vibrational Frequency ◽  
Dirichlet Condition ◽  
Thin Plates ◽  
Thin Elastic Plate ◽  
Numerical Algebraic Geometry ◽  
Local Maxima ◽  
Out Of Plane ◽  
Modes Of Vibration ◽  
New Type

Eigenvalues of fourth-order elliptic operators feature prominently in stability analysis of elastic structures. This paper considers out-of-plane modes of vibration of a thin elastic plate perforated by a collection of small clamped patches. As the radius of each patch shrinks to zero, a point constraint eigenvalue problem is derived in which each patch is replaced by a homogeneous Dirichlet condition at its centre. The limiting problem is consequently not the eigenvalue problem with no patches, but a new type of spectral problem. The discrepancy between the eigenvalues of the patch-free and point constraint problems is calculated. The dependence of the point constraint eigenvalues on the location(s) of clamping is studied numerically using techniques from numerical algebraic geometry. The vibrational frequencies are found to depend very sensitively on the number and centre(s) of the clamped patches. For a range of number of punctures, we find spatial clamping patterns that correspond to local maxima of the base vibrational frequency of the plate.

scholarly journals Region-Based CNN Method with Deformable Modules for Visually Classifying Concrete Cracks

2020 ◽  
Vol 10 (7) ◽  
pp. 2528 ◽  
Author(s):  
Lu Deng ◽  
Hong-Hu Chu ◽  
Peng Shi ◽  
Wei Wang ◽  
Xuan Kong
Keyword(s):  
Crack Detection ◽  
Detection Methods ◽  
Convolutional Networks ◽  
Fully Convolutional Networks ◽  
Out Of Plane ◽  
Intelligent Detection ◽  
New Type ◽  
Feature Pyramid ◽  
Crack Detector ◽  
Core Idea

Cracks are often the most intuitive indicators for assessing the condition of in-service structures. Intelligent detection methods based on regular convolutional neural networks (CNNs) have been widely applied to the field of crack detection in recently years; however, these methods exhibit unsatisfying performance on the detection of out-of-plane cracks. To overcome this drawback, a new type of region-based CNN (R-CNN) crack detector with deformable modules is proposed in the present study. The core idea of the method is to replace the traditional regular convolution and pooling operation with a deformable convolution operation and a deformable pooling operation. The idea is implemented on three different regular detectors, namely the Faster R-CNN, region-based fully convolutional networks (R-FCN), and feature pyramid network (FPN)-based Faster R-CNN. To examine the advantages of the proposed method, the results obtained from the proposed detector and corresponding regular detectors are compared. The results show that the addition of deformable modules improves the mean average precisions (mAPs) achieved by the Faster R-CNN, R-FCN, and FPN-based Faster R-CNN for crack detection. More importantly, adding deformable modules enables these detectors to detect the out-of-plane cracks that are difficult for regular detectors to detect.

Conditions for the planes of symmetry of an elastically supported rigid body

2009 ◽  
Vol 223 (8) ◽  
pp. 1755-1766 ◽  
Author(s):  
S J Jang ◽  
Y J Choi
Keyword(s):  
Rigid Body ◽  
Eigenvalue Problems ◽  
Mass Matrix ◽  
Equations Of Motion ◽  
Mass Matrices ◽  
Out Of Plane ◽  
Modes Of Vibration ◽  
Compliance Matrices ◽  
Special Points ◽  
Elastically Supported

Introducing the planes of symmetry into an oscillating rigid body suspended by springs simplifies the complexity of the equations of motion and decouples the modes of vibration into in-plane and out-of-plane modes. There have been some research results from the investigation into the conditions for planes of symmetry in which prior conditions for the simplification of the equations of motion are required. In this article, the conditions for the planes of symmetry that do not need prior conditions for simplification are presented. The conditions are derived from direct expansions of eigenvalue problems for stiffness and mass matrices that are expressed in terms of in-plane and out-of-plane modes and the orthogonality condition with respect to the mass matrix. Two special points, the planar couple point and the perpendicular translation point are identified, where the expressions for stiffness and compliance matrices can be greatly simplified. The simplified expressions are utilized to obtain the analytical expressions for the axes of vibration of a vibration system with planes of symmetry.

Synthesis and optical properties of tetrapyrazinoporphyrazine containing phenylene dendron unit as a peripheral substituent

2009 ◽  
Vol 13 (08n09) ◽  
pp. 939-948 ◽  
Author(s):  
Chun Keun Jang ◽  
Jae Yun Jaung
Keyword(s):  
Catalytic Properties ◽  
Diels Alder ◽  
Laser Desorption Ionization ◽  
Visible Spectroscopy ◽  
Ionization Time ◽  
H Nmr ◽  
Flight Mass Spectrometry ◽  
Out Of Plane ◽  
New Type ◽  
Uv Visible

A dendritic shell can create a distinct micro-environment within its core. It also has the advantage of possessing unique photochemical, photophysical, electrochemical, and catalytic properties. Polyphenylene dendrons, which are characterized by their shape-persistent structures and out-of-plane twisted phenyl components, have previously been successfully attached to various functional groups. We have recently developed a convenient method for synthesizing a new type of porphyrazine that contains both flexible (linear) and more rigid (dendritic) groups. The synthesis of this completely aromatic and dendronic structure is unique in that it is based on a [2+4] Diels-Alder cycloaddition of tetraphenylcyclopentadienone to an ethynyl compound, followed by the elimination of carbon monoxide. In this study, tetrapyrazinoporphyrazinato metal and metal-free complexes were prepared by mixing 2,3-dicyano-5-polyphenylpyrazines with magnesium in n-butanol. The synthesized tetrapyrazinoporphyrazines were characterized by UV-visible spectroscopy, MALDI-TOF-MS (matrix-assisted laser desorption/ionization time-of-flight mass) spectrometry, elemental analysis and 1 H NMR spectroscopy.

scholarly journals Frequencies and Normal Modes of Vibration of Benz[a]anthracene Radical Ions

2005 ◽  
Vol 60 (3) ◽  
pp. 158-164
Author(s):  
Rehab M. Kubba ◽  
Raghida I. Al-ani ◽  
Muthana Shanshal
Keyword(s):  
Radical Cation ◽  
Normal Modes ◽  
Equilibrium Geometry ◽  
Vibration Frequencies ◽  
Radical Ions ◽  
Normal Coordinates ◽  
Bond Alternation ◽  
Out Of Plane ◽  
Modes Of Vibration ◽  
Stretching Vibrations

MINDO/3-FORCES calculations were carried out for the radical ions of benz[a]anthracene. Both ions exhibit Cs symmetry with C-C bond alternation in all four rings. The obtained equilibrium geometry was applied for the calculation of all 3N − 6 vibration frequencies of each ion, and for the analysis of their normal coordinates. The so calculated frequencies of the radical cation were close to the experimental frequencies and those of the ab initio calculations. They fall in the ranges νCHstr. (3034 - 3087 cm−1), νCCstr. (1237 - 1609 cm−1), δCH (1142 - 1216 cm−1). Interesting correlations could be obtained for the frequencies of similar vibrations, e. g. νsymCHstr. >νasymCHstr. Exception is the frequency of vibration of CHα in ring A for the radical cation and the same bond in ring D for the radical anion. The vibration frequencies for the CH bonds depend on the σ -electron densities of the corresponding carbon atoms, i. e. νCH.+str. >νCHstr. >νCH.−str., where σ −ρĊ+ >σ −ρC >σ −ρĊ− . For the C-C stretching vibrations the relation ν(C-C)str. >ν(C-C).−str. >ν(C-C).+str. holds, with the exception of the Cβ -Cβ bond, for which the relation ν(C-C)str. >ν(C-C).+str. >ν(C-C).−str. is found. As for the in-plane and out of-plane deformations, the following general correlations δ (CH) >δ (CH).− >δ (CH).+ and γ (CC) >γ (CC).− >γ (CC).+.

scholarly journals Photo Alignment Behaviour of Polyethene Imine Having Cyano Azobenzene Side Chain

2015 ◽  
Vol 63 (2) ◽  
pp. 67-72
Author(s):  
Mohammad Kamruzzaman ◽  
Seiji Kurihara
Keyword(s):  
Molecular Orientation ◽  
Uv Light ◽  
Side Chain ◽  
Reaction Parameters ◽  
Reaction Conditions ◽  
Out Of Plane ◽  
Solid Film ◽  
New Type ◽  
Photo Alignment ◽  
Random State

New type of polyethene imine having cyano (-CN) side chain through six methylene spacer group (PEI6C) was successfully synthesised and characterised. The effect of reaction parameters on degree of substitution of PEI6C was also studied and the reaction conditions were optimised. Photochemical as well as photoorientational behaviour of the polymer were investigated. PEI6C in solid film exhibited photoresponsive properties upon irradiation with UV and visible light. PEI6C film also exhibited reversible molecular orientation from random state to out-of-plane and from out-of-plane to random state upon non-polarised visible and UV light irradiation.Dhaka Univ. J. Sci. 63(2): 67-72, 2015 (July)

scholarly journals Experimental Study on Out-of-Plane Seismic Performance of New Type Masonry System

2021 ◽  
Vol 11 (24) ◽  
pp. 11736
Author(s):  
Ho Choi ◽  
Kang-Seok Lee
Keyword(s):  
Seismic Performance ◽  
Masonry Wall ◽  
Shaking Table ◽  
Shaking Table Tests ◽  
Preliminary Calculation ◽  
Four Point Bending ◽  
Out Of Plane ◽  
New Type ◽  
Block Wall ◽  
Joint Mortar

The authors developed two types of block systems, consisting only of main and key blocks, without joint mortar, to improve the in- and out-of-plane seismic performances and enhance the workability. Two types of block systems have different key block shapes. One is the peanuts shape, and the other is the H shape. The proposed block systems have a half-height difference between the main and key blocks, to significantly improve seismic performance in in- and out-of-plane directions, compared to typical masonry wall with joint mortar. In this study, in order to evaluate the out-of-plane seismic performance of the proposed block systems, two types of block walls are experimentally investigated, including the typical block wall. Firstly, the shaking table tests are carried out to investigate the fundamental out-of-plane behaviors of three specimens. Next, four-point bending tests are planned to evaluate the out-of-plane seismic performance, since all specimens do not occur the out-of-plane collapse in the shaking table tests from the preliminary calculation. In this paper, the development of predominant period, profiles of acceleration and displacement, and maximum tensile strength of each specimen are discussed in detail. As a result, the maximum loads of the proposed block walls were about three to four times that of the typical block wall. This result means that the proposed block system has significantly improved seismic performance in the out-of-plane direction.

scholarly journals Mechanical Behavior of Single-Layer Two-Way Grid Cylindrical Latticed Shell with Out-of-Plane Tension Members

2014 ◽  
Vol 8 (1) ◽  
pp. 311-319 ◽  
Author(s):  
Zhang Zhonghao ◽  
Ma Huihuan ◽  
Fujimoto Masumi ◽  
Fu Qiang
Keyword(s):  
Load Distribution ◽  
Single Layer ◽  
Distribution Patterns ◽  
Stability Behavior ◽  
Initial Imperfections ◽  
Tension Member ◽  
Grid Shell ◽  
Out Of Plane ◽  
New Type ◽  
Tension Members

Single layer two-way grid shell with in-plane and out-of-plane tension members is a new type of single-layer latticed shell roof. This study treats the effects of tension member installation on the buckling load and strength of a single layer two-way grid cylindrical shell roof by the numerical method. The tension members are installed to stiffen the rigidity of a single layer two-way grid shell roof and improve its stability behavior. Tension member installation and placement pattern is focused as both diagonal members of two-way grids and out-of-plane stiffened members in a cylindrical surface. The diagonal member and the out-of-plane member are used to increase the in-plane and the out-of-plane rigidity of a single layer two-way grid shell, respectively. The tension member placement pattern, the load distribution patterns, the initial imperfections and the initial axial force are considered for the numerical calculation parameters. It is confirmed by the numerical analysis that the tension members in out-of-plane and diagonals caused the increase in the buckling and strength of two-way grid shell.

Non-Contact Mechanical Testing and Characterization of Micro-Scale Structures

2006 ◽  
Author(s):  
Jian Chen ◽  
Ganesh Subramanian ◽  
Justin Ricci ◽  
Liang Ban ◽  
Cetin Cetinkaya
Keyword(s):  
Plane Motion ◽  
Cantilever Beams ◽  
Micro Scale ◽  
New Class ◽  
Sensor Platform ◽  
Out Of Plane ◽  
Modes Of Vibration ◽  
Scale Structures ◽  
Micro Cantilever

A non-contact testing and characterization method based on air-coupled acoustic excitation and interferometric displacement measurements of micro-scale MEMS structures at room conditions is introduced. In demonstrating its potential uses in testing and characterization, the present non-contact approach is applied to (i) micro-cantilever beams and (ii) rotational disk oscillators. Air-coupled multi-mode excitation of micromechanical cantilever-type oscillators under a pulsed acoustic field generated by an air-coupled transducer is demonstrated and reported. Also, the testing and characterization of a micro-scale rotational disk oscillator developed for a new class of sensor platform is demonstrated. The main design objective of the rotational disk oscillator class is to overcome the out-of-plane motion related sensitivity limitations of the cantilever-based sensors at high frequency operations. The dynamics of the rotational disk oscillators is more complex than micro-cantilever beams due to its in-plane motion in addition to its various out-of-plane modes of vibration. The fabrication of a rotational disk oscillator requires a suspended disk whose underside is visibly inaccessible due to a narrow micro-gap. In addition to the dynamic characterization of the cantilever beams and rotational disk oscillators, the current investigation demonstrates that the presented approach can address unique structural concerns such as the verification of a gap separation of the rotational oscillator from the underlying silicon substrate. Utilizing the proposed technique, the resonant frequencies of the oscillator structures are obtained and its potential uses in the testing and characterization of micro-scale structures are discussed. The major specific advantages of the introduced approach include that (i) its noncontact nature can eliminate testing problems associated with stiction and adhesion, and (ii) it allows direct mechanical characterization and testing of components and sub-components of a micro-scale devices.

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