scholarly journals Stability and vibrations control of a stepped beam using piezoelectric actuation

2018 ◽  
Vol 157 ◽  
pp. 08004
Author(s):  
Krzysztof Kuliński ◽  
Jacek Przybylski
Keyword(s):  
Natural Vibration ◽  
Bottom Surface ◽  
Piezoelectric Actuation ◽  
Beam Loading ◽  
Stepped Beam ◽  
Critical Buckling Force ◽  
Vector Direction ◽  
Residual Force ◽  
The Stability ◽  
Transversal Vibrations

The objects of this studies are the stability and transversal vibrations of the system composed of three segments, where in the centre part of the system two piezoelectric patches are perfectly bonded to the top and bottom surface of the host beam. The system is kinematically loaded as a result of prescribed displacement of one or both end supports. For the analysis purposes three different beam end supports have been taken into consideration, which prevent longitudinal displacements i.e. clamped-clamped, clamped-pinned and pinned-pinned. This type of beam loading not only affect its natural vibration frequencies but also the system’s stability. By introducing the electric field to the piezo patches, depending on its vector direction, in-plane stretching or compressive residual force may be induced. Presented results show that piezo actuation can significantly modify both the critical buckling force and the vibration frequency.

Influence of Gravity and Taper on the Vibration of a Standing Column

2012 ◽  
Vol 4 (04) ◽  
pp. 483-495 ◽  
Author(s):  
C. Y. Wang
Keyword(s):  
Cross Section ◽  
Numerical Stability ◽  
Natural Vibration ◽  
Vibration Frequencies ◽  
Stability Criteria ◽  
Initial Value ◽  
Vertical Column ◽  
Stability Boundaries ◽  
Section Shape ◽  
The Stability

AbstractThe stability and natural vibration of a standing tapered vertical column under its own weight are studied. Exact stability criteria are found for the pointy column and numerical stability boundaries are determined for the blunt tipped column. For vibrations we use an accurate, efficient initial value numerical method for the first three frequencies. Four kinds of columns with linear taper are considered. Both the taper and the cross section shape of the column have large influences on the vibration frequencies. It is found that gravity decreases the frequency while the degree of taper may increase or decrease frequency. Vibrations may occur in two different planes.

scholarly journals Computational neuroscience applied in surface roughness fiber optic sensor

2019 ◽  
Vol 10 (1) ◽  
pp. 70-75 ◽  
Author(s):  
Wei He
Keyword(s):  
Neural Network ◽  
Surface Roughness ◽  
Computational Neuroscience ◽  
Fiber Optic ◽  
Rbf Neural Network ◽  
Fiber Optic Sensor ◽  
Bottom Surface ◽  
Optic Sensor ◽  
Arbitrary Precision ◽  
The Stability

Abstract Computational neuroscience has been widely used in fiber optic sensor signal output. This paper introduces a method for processing the Surface Roughness Fiber Optic Sensor output signals with a radial basis function neural network. The output signal of the sensor and the laser intensity signal as the light source are added to the input of the RBF neural network at the same time, and with the ability of the RBF neural network to approach the non-linear function with arbitrary precision, to achieve the nonlinear compensation of the sensor and reduction of the effect of changes in laser output light intensity at the same time. The Surface Roughness Fiber Optic Sensor adopting this method has low requirements on the stability of the output power of laser, featuring large measuring range, high accuracy, good repeatability, measuring of special surfaces such as minor area, and the bottom surface of holed etc. The measurements were given and various factors that affect the measurement were analyzed and discussed.

THE EFFECT OF CYCLIC STRETCHING SPEED ON THE FORCE DEGRADATION OF ORTHODONTIC ELASTIC BANDS

2013 ◽  
Vol 13 (01) ◽  
pp. 1350017
Author(s):  
DAN-JAE LIN ◽  
TZU-NING HUNG ◽  
MING-TZU TSAI ◽  
JUI-TING HSU ◽  
HENG-LI HUANG ◽  
...  
Keyword(s):  
High Speed ◽  
Artificial Saliva ◽  
Repeated Measure ◽  
Cyclic Stretching ◽  
Measure Analysis ◽  
Repeated Measure Analysis ◽  
Residual Force ◽  
Group 2 ◽  
The Stability ◽  
Initial Force

This study evaluated the effect of the cyclic stretching speed on the force degradation of orthodontic elastics. Forty-five natural rubber bands (3M Unitek™) were stretched at different speeds in three groups: (1) static stretching test, (2) cyclic stretching test at a speed of 80 mm/min, and (3) cyclic stretching at a speed of 160 mm/min. A material tester and customized strain gauge were used to measure the residual force of the elastics in 37°C artificial saliva at different times. One-way repeated-measure analysis of variance followed by Scheffe's post-hoc comparison and t-test were used for statistical analysis. In Group 1, the force of the elastics degraded with time, with two separate phases being observed — distinctive degradation after 15 min and stabilization after 120 min. The cyclic stretching in Group 2 produced a significant deviation in the residual force and the initial force from the first minute, and stabilization after 300 min. After 1,440 min, 60% of the bands had snapped. Under accelerated stretching, no areas of relative stability were observed between the start of stretching to the start of breaking. After 1,440 high-speed stretches, 87% of the elastics in Group 3 snapped. These results indicate that the stretching speed affects the stability of the residual force of elastics. Cyclic stretching at high speed immediately induces a rapid degradation of the elastic's force and increases its probability of breakage.

Battery Charge Affects the Stability of Light Intensity from Light-emitting Diode Light-curing Units

2017 ◽  
Vol 42 (5) ◽  
pp. 497-504 ◽  
Author(s):  
A Tongtaksin ◽  
C Leevailoj
Keyword(s):  
Light Intensity ◽  
Light Emitting Diode ◽  
Resin Composite ◽  
Bottom Surface ◽  
Light Emitting ◽  
Led Light ◽  
Battery Charge ◽  
Light Intensities ◽  
Light Curing ◽  
The Stability

SUMMARY This study investigated the influence of battery charge levels on the stability of light-emitting diode (LED) curing-light intensity by measuring the intensity from fully charged through fully discharged batteries. The microhardness of resin composites polymerized by the light-curing units at various battery charge levels was measured. The light intensities of seven fully charged battery LED light-curing units—1) LY-A180, 2) Bluephase, 3) Woodpecker, 4) Demi Plus, 5) Saab II, 6) Elipar S10, and 7) MiniLED—were measured with a radiometer (Kerr) after every 10 uses (20 seconds per use) until the battery was discharged. Ten 2-mm-thick cylindrical specimens of A3 shade nanofilled resin composite (PREMISE, Kerr) were prepared per LED light-curing unit group. Each specimen was irradiated by the fully charged light-curing unit for 20 seconds. The LED light-curing units were then used until the battery charge fell to 50%. Specimens were prepared again as described above. This was repeated again when the light-curing units' battery charge fell to 25% and when the light intensity had decreased to 400 mW/cm2. The top/bottom surface Knoop hardness ratios of the specimens were determined. The microhardness data were analyzed by one-way analysis of variance with Tukey test at a significance level of 0.05. The Pearson correlation coefficient was used to determine significant correlations between surface hardness and light intensity. We found that the light intensities of the Bluephase, Demi Plus, and Elipar S10 units were stable. The intensity of the MiniLED unit decreased slightly; however, it remained above 400 mW/cm2. In contrast, the intensities of the LY-A180, Woodpecker, and Saab II units decreased below 400 mW/cm2. There was also a significant decrease in the surface microhardnesses of the resin composite specimens treated with MiniLED, LY-A180, Woodpecker, and Saab II. In conclusion, the light intensity of several LED light-curing units decreased as the battery was discharged, with a coincident reduction in the units' ability to polymerize resin composite. Therefore, the intensity of an LED light-curing unit should be evaluated during the life of its battery charge to ensure that sufficient light intensity is being generated.

Self-Excited Vibration of a Plate Supported by Air Pressure in a Floating Conveying Machine

2017 ◽  
Author(s):  
Masakazu Takeda ◽  
Masahiro Watanabe
Keyword(s):  
Air Pressure ◽  
The Self ◽  
Plate Motion ◽  
Bottom Surface ◽  
Fluid Force ◽  
Gap Flow ◽  
Excited Vibration ◽  
Unsteady Fluid ◽  
The Stability ◽  
Work Done

This paper presents experiments and an analysis on self-excited vibration of a plate supported by air pressure in a floating conveying machine. In this study, the instability conditions are examined by theoretical analysis in consideration of the effect of compressibility of air in a chamber. The system’s characteristic equation is derived from the plate motion coupled with equations of the gap flow between the plate and the chamber surface. The vibration characteristics and the instability conditions of the self-excited vibration are examined through experiments. The stability of the plate is affected by an air flow rate, a mass of the plate, a spring stiffness of the plate. We clarified those influences on the instability conditions of the self-excited vibration. The unsteady fluid force acting on the plate (bottom surface) is investigated by measuring the unsteady pressure. The local work done by the unsteady fluid force is also clarified. Lastly, the instability mechanism and important parameters of the self-excited vibration are discussed based on the theoretical model and experimental results.

scholarly journals Effects of Dam Gate Geometry on Pressure Variation Aided by Map Presentation

2020 ◽  
Vol 10 (2) ◽  
pp. 44-52
Author(s):  
Sheeraz M. Ameen ◽  
Thamir M. Ahmed
Keyword(s):  
Power Plants ◽  
High Water ◽  
Water Levels ◽  
Bottom Surface ◽  
Contour Maps ◽  
Hydraulic Design ◽  
Vertical Lift ◽  
High Head ◽  
The Stability ◽  
Surfer Software

The dam vertical lift gate is one of the most important operational parts that regulate the high head water flow to power plants as well as satisfying the water needs for projects and areas downstream of the dam. Due to the high water levels in the dam reservoir, the gates are subjected to many hydrostatic and dynamic pressures that affect their performance and stability. Hence, it became necessary to study all parameters that may cause excessive pressures which may lead to reduce the gate performance efficiency or even cause failure. In the current study, the pressure distribution along the bottom surface of various gate lip shapes has been measured and presented as contour maps using Surfer software. The pressure fluctuation was observed to indicate the intensity of flow separation and reattachment which, in turn, causes a vibration that may threaten the stability of the gate or impede its proper functioning. The pressures in this study are expressed as a dimensional coefficient through the integration of pressure measurements at 8 points distributed over the bottom gate surface. The high intensity of pressure attachment indicates the critical condition for hydraulic design.

scholarly journals STABILITY ANALYSIS OF THE GRAVITY ANCHORAGE OF A SUSPENSION BRIDGE BASED ON LARGE-SCALE FIELD TESTS

2021 ◽  
Vol 30 (1) ◽  
Author(s):  
Zhijun Zhou ◽  
Chaoran Chen ◽  
Longfei Wang ◽  
Yeqing Tian ◽  
Hongming Feng ◽  
...  
Keyword(s):  
Contact Stress ◽  
Large Scale ◽  
Field Tests ◽  
Stability Study ◽  
Bottom Surface ◽  
Suspension Bridges ◽  
Stability Coefficient ◽  
Finite Element Software ◽  
The Stability ◽  
Main Cables

The stability of gravity anchorages is critical to the safe operation of suspension bridges. The purpose of this paper is to study the stability of a gravity anchorage under the tension of main cables. Large-scale load tests and direct shear tests under the nature state and the saturated state were carried out in the adit at the bottom of the gravity anchorage, because the bottom surface of the gravity anchorage is below the design water level of a reservoir to be built. Representative rock samples in the anchorage area were selected for indoor tests. The basic parameters of the rock mass and the characteristic value of subsoil bearing capacity were obtained based on the field and indoor tests results. The static theory was used to calculate the anti-sliding stability coefficient, anti- overturning stability coefficient and contact stress of the gravity anchorage. The finite element software was used to calculate the horizontal displacement, vertical settlement and contact stress of the gravity anchorage. The calculation results met the relevant requirements, and it can be considered that the gravity anchorage was stable under the tension of main cables. It would provide a reference for the stability study of the gravity anchorage of suspension bridges.

scholarly journals Primary Design of Extended Interaction Klystron with Multi-Gap Cavity at 225 GHz

Particles ◽  
2018 ◽  
Vol 1 (1) ◽  
pp. 260-266
Author(s):  
Kaichun Zhang ◽  
Ke Chen ◽  
Qian Xu ◽  
Wangju Xu ◽  
Neng Xiong ◽  
...  
Keyword(s):  
Low Voltage ◽  
Maximum Output Power ◽  
Wave Theory ◽  
Maximum Output ◽  
Coupling Coefficients ◽  
Beam Wave ◽  
Beam Loading ◽  
Beam Voltage ◽  
Extended Interaction ◽  
The Stability

The analytical expressions of the beam–wave coupling coefficients and the beam loading conductance for a 2π mode in a multi-gap cavity is proposed as a circuit of the extended interaction klystron (EIK), are derived by space-charge wave theory. The mechanism of the beam–wave synchronization and the coupling in the multi-gap cavity at 225 GHz are studied in detail by calculating the coupling coefficient and the normalized beam loading conductance as a function of gap number, gap dimension, and beam voltage as well as the perveance. The stability of the circuit is analyzed by considering the quality factor of the electron beam. It is found that the stability of the operating 2π mode is more sensitive to the beam voltage and gap number. Based on the theory and analysis, a 5-gap coupled cavity is proposed as a section of EIK’s circuit. A low voltage EIK with a 4-cavity circuit at 225 GHz is designed and is simulated by a particle-in-cell (PIC) code. The EIK can achieve a maximum output power of ~36 W with more than 30 dB gain at 225 GHz.

scholarly journals Influence of Pier Settlement on Structural Stress of Longitudinal Connected Track in High-Speed Railways

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Hui Fang
Keyword(s):  
High Speed ◽  
Great Influence ◽  
Coupled System ◽  
Bottom Surface ◽  
Structural Stress ◽  
Tensile Stresses ◽  
Control Value ◽  
Practical Engineering ◽  
The Stability ◽  
Track Bridge

Pier settlement is unavoidable in the construction and operation of high-speed railways. This paper presents a work on the influence of pier settlement on additional structural stress of longitudinal connected track (LCT). First of all, the generation mechanism of additional structural stress of LCT caused by pier settlement is described in detail. On this basis, the deformation of LCT caused by pier settlement is analytically deduced and a dynamic model of high-speed train-LCT-bridge coupled system considering pier settlement is established based on the train-track-bridge dynamic interaction theory, adopting which the additional structural stresses of LCT are discussed from static and dynamic perspectives. Results show that pier settlement has a great influence on the stability of LCT. Additional tensile stresses of LCT appear at settlement pier location and two adjacent pier locations. Tensile stresses on top surface of slab and on bottom surface of base should be paid attention to. The behaviors of LCT at adjacent pier locations cannot be ignored in studying the influence of pier settlement on the system. To ensure the stability of LCT and running performance of train, the control value of pier settlement is suggested to be 10.5 mm from the static and dynamic perspectives in practical engineering.

Wave Spring Dynamic Characteristics Analysis

2014 ◽  
Vol 1037 ◽  
pp. 37-40
Author(s):  
Mo Wu Lu ◽  
Tan Wang
Keyword(s):  
Modal Analysis ◽  
Vibration Frequency ◽  
Natural Vibration ◽  
Response Analysis ◽  
Natural Vibration Frequency ◽  
Vibration Direction ◽  
Characteristics Analysis ◽  
Spring System ◽  
Harmonic Response Analysis ◽  
The Stability

The natural vibration frequency and forced vibration amplitude of the spring decides the stability of the whole of the spring system. Take the monolayer wave spring as the research object, do dynamics analysis for the three different kinds of wave spring with the same structure parameters. Obtain the natural vibration frequencies of the three kinds of spring through modal analysis, the result shows that the natural vibration frequency of the integral type wave spring is the highest, then is the wave spring with opening, the natural vibration frequency of the wave spring with lapping is the lowest. Do the harmonic response analysis for the springs based on the modal analysis result, the result shows that the main vibration direction of the wave spring is the symmetry axis direction of the spring, all the three kinds of the spring is much easier resonate in this direction. Through the above provides certain theoretical guidance for the design of the wave spring

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