Vibrations and Stability: Solved Problems
DEFF Research Database (Denmark)
Thomsen, Jon Juel
Worked out solutions for exercise problems in J. J. Thomsen 'Vibrations and Stability: Advanced Theory, Analysis, and Tools', Springer, Berlin - Heidelberg, 2003.......Worked out solutions for exercise problems in J. J. Thomsen 'Vibrations and Stability: Advanced Theory, Analysis, and Tools', Springer, Berlin - Heidelberg, 2003....
Analysis of potential helicopter vibration reduction concepts
Landgrebe, A. J.; Davis, M. W.
1985-01-01
Results of analytical investigations to develop, understand, and evaluate potential helicopter vibration reduction concepts are presented in the following areas: identification of the fundamental sources of vibratory loads, blade design for low vibration, application of design optimization techniques, active higher harmonic control, blade appended aeromechanical devices, and the prediction of vibratory airloads. Primary sources of vibration are identified for a selected four-bladed articulated rotor operating in high speed level flight. The application of analytical design procedures and optimization techniques are shown to have the potential for establishing reduced vibration blade designs through variations in blade mass and stiffness distributions, and chordwise center-of-gravity location.
Acoustic vibration problem for dissipative fluids
Lepe, Felipe; Meddahi, Salim; Mora, David; Rodríguez, Rodolfo
2016-01-01
In this paper we analyze a finite element method for solving a quadratic eigenvalue problem derived from the acoustic vibration problem for a heterogeneous dissipative fluid. The problem is shown to be equivalent to the spectral problem for a noncompact operator and athorough spectral characterization is given. The numerical discretization of the problem is based on Raviart-Thomas finite elements. The method is proved to be free of spurious modes and to converge with optimal order. Finally, w...
Terfenol-D driven flaps for helicopter vibration reduction
Fenn, Ralph C.; Downer, James R.; Bushko, Dariusz A.; Gondhalekar, Vijay; Ham, Norman D.
1996-02-01
The utility of helicopter aviation is limited by the high vibration levels caused by the interaction of each rotor blade with the wake of preceding blades. Existing full-blade actuation using a swashplate has various problems such as insufficient bandwidth, limitations in the number of harmonics controlled, high maintenance, and lack of spanwise lift variation. These problems are avoided by the proposed flap operated, individual blade control system, which uses magnetostrictive actuation technology. Terfenol-D actuation has many advantages over competing technologies such as hydraulic systems, electric motors, and piezoelectric elements. These benefits include all-electric operation, simplicity and reliability, low mass, low voltage, and insensitivity to centripetal acceleration. A blade mounted Terfenol-D actuator was developed for the high-weight-penalty helicopter application. The optimum coil to Terfenol-D volume ratio was derived that gives the highest mechanical power output for a small actuator envelope and mass. A fixed ability to dissipate coil resistive losses is assumed. The magnetostrictive actuation system will weigh less than 1% of gross vehicle weight, and use only 0.7% of cruise power. Other required subsystems of the vibration reduction system are available from commercial sources or are described in the literature. Helicopter vibration reduction greater than 90% is predicted because of superior actuator performance and individual blade control. This magnetostrictive actuator technology will also produce future helicopter systems having lower noise and higher performance. Such advances will significantly improve the utility and competitiveness of helicopters for civilian and military transportation.
Vibration for Pain Reduction in a Plastic Surgery Clinic.
Eichhorn, Mitchell George; Karadsheh, Murad Jehad; Krebiehl, Johanna Ruth; Ford, Dawn Marie; Ford, Ronald D
2016-01-01
Patients can experience significant pain during routine procedures in the plastic surgery clinic. Methods for clinical pain reduction are often impractical, time-consuming, or ineffective. Vibration is a safe, inexpensive, and highly applicable modality for pain reduction that can be readily utilized for a wide variety of procedures. This study evaluated the use of vibration as a viable pain-reduction strategy in the clinical plastic surgery setting. Patients requiring at least 2 consecutive procedures that are considered painful were enrolled in the study. These included injections, staple removal, and suture removal. In the same patient, one half of the procedures were performed without vibration and the other half with vibration. After completing the procedures, the patients rated their pain with vibration and without vibration. The patient and the researcher also described the experience with a short questionnaire. Twenty-eight patients were enrolled in the study. Patients reported significantly less pain on the Numeric Rating Scale pain scale when vibration was used compared with the control group (p vibration and 1.93 with vibration, and vibration with injections resulted in the greatest improvement. Eighty-six percent of the patients claimed that vibration significantly reduced their pain. Vibration is an effective method of pain reduction. It significantly reduces the pain experienced by patients during minor office procedures. Given its practicality and ease of use, it is a welcome tool in the plastic surgery clinic.
10th International Conference on Vibration Problems
Horáček, Jaromír; Okrouhlík, Miloslav; Marvalová, Bohdana; Verhulst, Ferdinand; Sawicki, Jerzy; Vibration Problems ICOVP 2011
2011-01-01
This volume presents the Proceedings of the 10th International Conference on Vibration Problems, September 5-8, 2011, Prague, Czech Republic. Since they started in 1990 the ICOVP conferences have matured into a reference platform reflecting the state-of-the-art of dynamics in the broadest sense, bringing together scientists from different backgrounds who are actively working on vibration-related problems in theoretical, experimental and applied dynamics, thus facilitating a lively exchange of ideas, methods and results. Dynamics as a scientific discipline draws inspiration from a large variety of engineering areas, such as Mechanical and Civil Engineering, Aero and Space Technology, Wind and Earthquake Engineering and Transport and Building Machinery. Moreover, the basic research in dynamics nowadays includes many fields of theoretical physics and various interdisciplinary subject areas. ICOVP 2011 covers all branches of dynamics and offers the most up-to-date results and developments in a high-quality select...
Inoue, Katsumi; Krantz, Timothy L.
1995-01-01
While the vibration analysis of gear systems has been developed, a systematic approach to the reduction of gearbox vibration has been lacking. The technique of reducing vibration by shifting natural frequencies is proposed here for gearboxes and other thin-plate structures using the theories of finite elements, modal analysis, and optimization. A triangular shell element with 18 degrees of freedom is developed for structural and dynamic analysis. To optimize, the overall vibration energy is adopted as the objective function to be minimized at the excitation frequency by varying the design variable (element thickness) under the constraint of overall constant weight. Modal analysis is used to determine the sensitivity of the vibration energy as a function of the eigenvalues and eigenvectors. The optimum design is found by the gradient projection method and a unidimensional search procedure. By applying the computer code to design problems for beams and plates, it was verified that the proposed method is effective in reducing vibration energy. The computer code is also applied to redesign the NASA Lewis gear noise rig test gearbox housing. As one example, only the shape of the top plate is varied, and the vibration energy levels of all the surfaces are reduced, yielding an overall reduction of 1/5 compared to the initial design. As a second example, the shapes of the top and two side plates are varied to yield an overall reduction in vibration energy of 1/30.
Application of system concept in vibration and noise reduction
Directory of Open Access Journals (Sweden)
SHENG Meiping
2017-08-01
Full Text Available Although certain vibration and noise control technologies are maturing, such as vibration absorption, vibration isolation, sound absorption and sound insulation, and new methods for specific frequency bands or special environments have been proposed unceasingly, there is still no guarantee that practical effective vibration and noise reduction can be obtained. An important constraint for vibration and noise reduction is the lack of a system concept, and the integrity and relevance of such practical systems as ship structure have not obtained enough attention. We have tried to use the system engineering theory in guiding vibration and noise reduction, and have already achieved certain effects. Based on the system concept, the noise control of a petroleum pipeline production workshop has been completed satisfactorily, and the abnormal noise source identification of an airplane has been accomplished successfully. We want to share our experience and suggestions to promote the popularization of the system engineering theory in vibration and noise control.
Rotor Vibration Reduction via Active Hybrid Bearings
DEFF Research Database (Denmark)
Nicoletti, Rodrigo; Santos, Ilmar
2002-01-01
The use of fluid power to reduce and control rotor vibration in rotating machines is investigated. An active hybrid bearing is studied, whose main objective is to reduce wear and vibration between rotating and stationary machinery parts. By injecting pressurised oil into the oil film, through...... with experiment, and simulations show the feasibility of controlling shaft vibration through this active device....
Feedback Linearisation for Nonlinear Vibration Problems
Directory of Open Access Journals (Sweden)
S. Jiffri
2014-01-01
Full Text Available Feedback linearisation is a well-known technique in the controls community but has not been widely taken up in the vibrations community. It has the advantage of linearising nonlinear system models, thereby enabling the avoidance of the complicated mathematics associated with nonlinear problems. A particular and common class of problems is considered, where the nonlinearity is present in a system parameter and a formulation in terms of the usual second-order matrix differential equation is presented. The classical texts all cast the feedback linearisation problem in first-order form, requiring repeated differentiation of the output, usually presented in the Lie algebra notation. This becomes unnecessary when using second-order matrix equations of the problem class considered herein. Analysis is presented for the general multidegree of freedom system for those cases when a full set of sensors and actuators is available at every degree of freedom and when the number of sensors and actuators is fewer than the number of degrees of freedom. Adaptive feedback linearisation is used to address the problem of nonlinearity that is not known precisely. The theory is illustrated by means of a three-degree-of-freedom nonlinear aeroelastic model, with results demonstrating the effectiveness of the method in suppressing flutter.
Reactor vibration reduction based on giant magnetostrictive materials
Directory of Open Access Journals (Sweden)
Yan Rongge
2017-05-01
Full Text Available The vibration of reactors not only produces noise pollution, but also affects the safe operation of reactors. Giant magnetostrictive materials can generate huge expansion and shrinkage deformation in a magnetic field. With the principle of mutual offset between the giant magnetostrictive force produced by the giant magnetostrictive material and the original vibration force of the reactor, the vibration of the reactor can be reduced. In this paper, magnetization and magnetostriction characteristics in silicon steel and the giant magnetostrictive material are measured, respectively. According to the presented magneto-mechanical coupling model including the electromagnetic force and the magnetostrictive force, reactor vibration is calculated. By comparing the vibration of the reactor with different inserted materials in the air gaps between the reactor cores, the vibration reduction effectiveness of the giant magnetostrictive material is validated.
Reactor vibration reduction based on giant magnetostrictive materials
Rongge, Yan; Weiying, Liu; Yuechao, Wu; Menghua, Duan; Xiaohong, Zhang; Lihua, Zhu; Ling, Weng; Ying, Sun
2017-05-01
The vibration of reactors not only produces noise pollution, but also affects the safe operation of reactors. Giant magnetostrictive materials can generate huge expansion and shrinkage deformation in a magnetic field. With the principle of mutual offset between the giant magnetostrictive force produced by the giant magnetostrictive material and the original vibration force of the reactor, the vibration of the reactor can be reduced. In this paper, magnetization and magnetostriction characteristics in silicon steel and the giant magnetostrictive material are measured, respectively. According to the presented magneto-mechanical coupling model including the electromagnetic force and the magnetostrictive force, reactor vibration is calculated. By comparing the vibration of the reactor with different inserted materials in the air gaps between the reactor cores, the vibration reduction effectiveness of the giant magnetostrictive material is validated.
Magnetostrictively actuated control flaps for vibration reduction in helicopter rotors
Energy Technology Data Exchange (ETDEWEB)
Millott, T.; Friedmann, P.P. [Univ. of California, Los Angeles, CA (United States). Mechanical, Aerospace and Nuclear Engineering Dept.
1994-12-31
High vibration levels can impose constraints on helicopter operations and hinder passenger acceptance. Vibration reduction using blade root pitch control introduces a significant power penalty and may adversely affect the airworthiness of the flight control system. Comparable levels of vibration reduction can be achieved using considerably less power through an actively controlled trailing edge flap mounted on the blade. Such a device would have no effect on helicopter airworthiness since it is controlled by a loop separate from the primary flight control system which utilizes the swashplate. Control flap actuation using the magnetostrictive material Terfenol-D is studied in this paper by designing a minimum weight actuator, subject to a set of actuation and stress constraints. The resulting device is capable of producing vibration reduction in excess of 90% at cruise conditions.
Rotor Vibration Reduction Using Multi-Element Multi-Path Design
Su, Keye
Multi-Element Multi-Path (MEMP) structural design is a new concept for rotor vibration reduction. This thesis explores the possibility of applying MEMP design to helicopter rotor blades. A conceptual design is developed to investigate the MEMP blade's vibration reduction performance. In the design, the rotor blade is characterized by two centrifugally loaded beams which are connected to each other through linear and torsional springs. A computer program is built to simulate the behavior of such structures. Detailed parametric studies are conducted. The main challenges in this thesis involve the blade hub load vibration analysis, the blade thickness constraint and the blade parameter selection. The results show substantial vibration reduction for the MEMP design but the large relative deflection between the two beams, conceptualized as an internal spar and airfoil shell, remains a problem for further study.
Tiltrotor Vibration Reduction Through Higher Harmonic Control
Nixon, Mark W.; Kvaternik, Raymond G.; Settle, T. Ben
1997-01-01
The results of a joint NASA/Army/Bell Helicopter Textron wind-tunnel test to assess the potential of higher harmonic control (HHC) for reducing vibrations in tiltrotor aircraft operating in the airplane mode of flight, and to evaluate the effectiveness of a Bell-developed HHC algorithm called MAVSS (Multipoint Adaptive Vibration Suppression System) are presented. The test was conducted in the Langley Transonic Dynamics Tunnel using an unpowered 1/5-scale semispan aeroelastic model of the V-22 which was modified to incorporate an HHC system employing both the rotor swashplate and the wing flaperon. The effectiveness of the swashplate and the flaperon acting either singly or in combination in reducing IP and 3P wing vibrations over a wide range of tunnel airspeeds and rotor rotational speeds was demonstrated. The MAVSS algorithm was found to be robust to variations in tunnel airspeed and rotor speed, requiring only occasional on-line recalculations of the system transfer matrix. HHC had only a small (usually beneficial) effect on blade loads but increased pitch link loads by 25%. No degradation in aeroelastic stability was noted for any of the conditions tested.
Higher Harmonic Control for Tiltrotor Vibration Reduction
Nixon, Mark W.; Kvaternik, Raymond G.; Settle, T. Ben
1997-01-01
The results of a joint NASA/Army/Bell Helicopter Textron wind-tunnel test to assess the potential of higher harmonic control (HHC) for reducing vibrations in tiltrotor aircraft operating in the airplane mode of flight, and to evaluate the effectiveness of a Bell-developed HHC algorithm called MAVSS (Multipoint Adaptive Vibration Suppression System) are presented. The test was conducted in the Langley Transonic Dynamics Tunnel using an unpowered 1/5- scale semispan aeroelastic model of the V-22 which was modified to incorporate an HHC system employing both the rotor swashplate and the wing flaperon. The effectiveness of the swashplate and the flaperon acting either singly or in combination in reducing 1P and 3P wing vibrations over a wide range of tunnel airspeeds and rotor rotational speeds was demonstrated. The MAVSS algorithm was found to be robust to variations in tunnel airspeed and rotor speed, requiring only occasion-al on-line recalculations of the system transfer matrix.
New Damped-Jerk trajectory for vibration reduction
BEAREE, Richard
2014-01-01
This paper derives a jerk-shaped profile to address the vibration reduction of underdamped flexible dynamics of motion system. The jerk-limited profile is a widespread smooth command pattern used by modern motion systems. The ability of the jerk-limited profile to cancel the residual vibration of an undamped flexible mode is clearly explained using an equivalent continuous filter representation and the input shaping formalism. This motivates the design of a new jerk-shaped profile, named Damp...
Lead-Lag Control for Helicopter Vibration and Noise Reduction
Gandhi, Farhan
1995-01-01
, meant to achieve lag motion amplitudes up to 45 degrees. In order to reduce the required actuation force, the blade hinges were moved to 40% of the blade radius to increase the rotating lag frequency to approximately 1/rev. The blade hinges were redesigned to produce a flap-lag coupling so the large flapwise aerodynamic loads could be exploited to actuate the blades in the lag direction. A wind tunnel test of this rotor concept revealed actuation and blade motion scheduling problems. The project was eventually discontinued due to these problems and high blade stresses. Around the same time, at Boelkow in Germany, a similar lead-lag rotor program was conducted under the leadership of Hans Derschmidt. Here, too, the blade hinges were moved outboard to 34% radius to reduce the actuation loads. The main difference between this and the United Aircraft program was the use of a mechanical actuation scheme with maximum lead-lag motions of 400. This program was also discontinued for unclear reasons. The present study is directed toward conducting a comprehensive analytical examination to evaluate the effectiveness of controlled lead-lag motions in reducing vibratory hub loads and increasing maximum flight speed. Since both previous studies on this subject were purely experimental, only a limited data set and physical understanding of the problem was obtained. With the currently available analytical models and computational resources, the present effort is geared toward developing an in-depth physical understanding of the precise underlying mechanisms by which vibration reduction may be achieved. Additionally, in recognition of the fact that large amplitude lead-lag motions would - (i) be difficult to implement, and (ii) produce very large blade stresses; the present study examines the potential of only moderate-to-small lead-lag motions for reduction of vibratory hub loads. Using such an approach, the emphasis is not on eliminating the periodic variations in tangential velocity
Reduction of personnel vibration hazards in underground coal mines
Energy Technology Data Exchange (ETDEWEB)
Oh, X.; Middlin, A. (Vipac Engineers and Scientists Ltd. (Australia))
1991-03-01
Whole-Body Vibration (WBV) due to the 'rough ride' in vehicles is a major source of back and neck injury in underground coal mines. Hand-Arm Vibration (HAV) from hand held equipment can also cause long term health damage. Surveys in three collieries in NSW have been conducted to measure the vibration levels to which miners are being exposed and to assess them according to the two relevant Australian Standards namely AS2670 and AS2763. WBV results indicated that shock loadings must be the source of back and neck injuries that are occurring due to 'rough ride'. Existing off-the-shelf seat suspensions were demonstrated to be inadequate for providing effective shock isolation, due to them being prone to bottoming out under rough conditions, and due their scissor action mechanism becoming rapidly jammed by dirt to the point where they become rigid. Commercially available seats were evaluated and tested on a hydraulic shaker, but none proved able to provide the required vibration isolation. A prototype seat suspension was developed by Vipac. This suspension was shaker tested and trialled in low loaders at two collieries. The seat proved capable of cushioning shock loads without bottoming out, as well as attenuating the dominant vibration at 2.5 Hz and higher. This suspension with encapsulated mechanism could be readily adapted to suit a wide range of underground vehicles. The HAV survey results identified the Wombat roof-bolter as the major item requiring vibration level reductions. Extensive investigations resulted in the design of a prototype vibration isolated handle. During field tests this prototype handle reduced the HAV level such that the Exposure Time (10th percentile) was increased from 7 to 11.5 years. Guidelines are presented for additional developments which would further improve this performance and result in a handle design suitable for retrofitting to existing roof bolters.
Adaptive control of an active seat for occupant vibration reduction
Gan, Zengkang; Hillis, Andrew J.; Darling, Jocelyn
2015-08-01
The harmful effects on human performance and health caused by unwanted vibration from vehicle seats are of increasing concern. This paper presents an active seat system to reduce the vibration level transmitted to the seat pan and the occupants' body under low frequency periodic excitation. Firstly, the detail of the mechanical structure is given and the active seat dynamics without external load are characterized by vibration transmissibility and frequency responses under different excitation forces. Owing the nonlinear and time-varying behaviour of the proposed system, a Filtered-x least-mean-square (FXLMS) adaptive control algorithm with on-line Fast-block LMS (FBLMS) identification process is employed to manage the system operation for high vibration cancellation performance. The effectiveness of the active seat system is assessed through real-time experimental tests using different excitation profiles. The system identification results show that an accurate estimation of the secondary path is achieved by using the FBLMS on-line technique. Substantial reduction is found for cancelling periodic vibration containing single and multiple frequencies. Additionally, the robustness and stability of the control system are validated through transient switching frequency tests.
Dynamically Tuned Blade Pitch Links for Vibration Reduction
Milgram, Judah; Chopra, Inderjit; Kottapalli, Sesi
1994-01-01
A passive vibration reduction device in which the conventional main rotor blade pitch link is replaced by a spring/damper element is investigated using a comprehensive rotorcraft analysis code. A case study is conducted for a modern articulated helicopter main rotor. Correlation of vibratory pitch link loads with wind tunnel test data is satisfactory for lower harmonics. Inclusion of unsteady aerodynamics had little effect on the correlation. In the absence of pushrod damping, reduction in pushrod stiffness from the baseline value had an adverse effect on vibratory hub loads in forward flight. However, pushrod damping in combination with reduced pushrod stiffness resulted in modest improvements in fixed and rotating system hub loads.
Terfenol-D-driven flaps for helicopter vibration reduction
Fenn, Ralph C.; Downer, James R.; Bushko, Dariusz A.; Gondhalekar, Vijay; Ham, Norman D.
1993-09-01
The utility of helicopter aviation is limited by the high vibration levels caused by interaction of each rotor blade with the wake of preceding blades. Existing full blade actuation using a swashplate has various problems such as insufficient bandwidth, limitations in the number of harmonics controlled, high maintenance, and lack of spanwise lift variation. These problems are avoided by the proposed flap operated, individual blade control system, which uses magnetostrictive actuation technology. Terfenol-D actuation has many advantages over competing technologies such as hydraulic systems, electric motors, and piezoelectric elements. These benefits include all-electric operation, simplicity and reliability, low mass, low voltage, and insensitivity to centripetal acceleration.
Topology optimization of vibration and wave propagation problems
DEFF Research Database (Denmark)
Jensen, Jakob Søndergaard
2007-01-01
The method of topology optimization is a versatile method to determine optimal material layouts in mechanical structures. The method relies on, in principle, unlimited design freedom that can be used to design materials, structures and devices with significantly improved performance and sometimes...... novel functionality. This paper addresses basic issues in simulation and topology design of vibration and wave propagation problems. Steady-state and transient wave propagation problems are addressed and application examples for both cases are presented....
PREFACE: International Conference on Vibration Problems (ICOVP-2015)
2015-12-01
Vibrations produced by operating machine cause deleterious effect including excessive stresses in mechanical components and reduce the machine performance. Hence, it is important to minimize the vibrations to improve the machine performance. Machines need the materials wherein vibration characteristics such as frequency and amplitude are lower. The vibration characteristics depend on strength and other elastic constants. Therefore, study of the relation between vibration characteristics and the elastic constants of the material is very much important. In the domain of seismology, the knowledge of vibrations associated with an earthquake is needed for the mitigation plans. With the increased use of strong and light weight structures especially in defence and aero-space engineering applications, wherein, precision is very important, problems of vibrations arise. The knowledge of quality (mechanical properties) of bones comes from the study of vibrations in it. This knowledge may, for exmple, help to answer bone tissue remodelling problems. Unfortunately, vibrations mostly deal with destructive areas such as manufacturing industry, seismology, and bonemechanics. These days, mathematics has become a very important tool for Non- Destructive Evaluation (NDE) in the destructive areas. A very common issue in the said domains is that the pertinent problems result in non-linear coupled differential equations which are not easily solvable. Keeping the above facts in mind, the Department of Mathematics, Kakatiya University has organized the International Conference on Vibration Problems (ICOVP-2015) from February, 18-20, 2015 in collaboration with the Department of Mechanical Engineering, Kakatiya University, and Von-Karman Society, West Bengal. This association has already succeeded in organizing the Wave Mechanics and Vibration Conference (WMVC) in the year 2010. In the Conference, new research results were presented by the experts from eight countries. There were more than
Application of Vibrational Power Flow to a Passenger Car for Reduction of Interior Noise
Directory of Open Access Journals (Sweden)
S.K. Lee
2000-01-01
Full Text Available Reduction of structure-borne noise in the compartment of a car is an important task in automotive engineering. Transfer path analysis using the vibroacoustic reciprocity technique or multiple path decomposition method has generally been used for structure-borne noise path analysis. These methods are useful for solving a particular problem, but they do not quantify the effectiveness of vibration isolation of each isolator of a vehicle. To quantify the effectiveness of vibration isolation, vibrational power flow has been used for a simple isolation system or a laboratory-based isolation system. It is often difficult to apply the vibrational power flow technique to a complex isolation system like a car. In this paper, a simple equation is derived for calculation of the vibrational power flow of an isolation system with multiple isolators such as a car. It is successfully applied not only to quantifying the relative contributions of eighteen isolators, but also to reducing the structure-borne noise of a passenger car. According to the results, the main contributor of the eighteen isolators is the rear roll mount of an engine. The reduced structure-borne noise level is about 5dBA.
THE PROBLEM OF IMPROVEMENT OF THE AVIONIC EQUIPMENT VIBRATION RESISTANCE
Directory of Open Access Journals (Sweden)
E. A. Danilova
2017-01-01
Full Text Available The article gives an approach to a solution of the problem of improvement the avionic equipment vibration resistance. It is shown that the use of the tests, which are provided by the state standards do not insure the required level of the failures caused by mechanical damages. Due to the fact that the tests are carried out restrictedly they do not completely reveal the main resonant phenomena, which define the structure vibrational strength. It is shown that the main challenges of the improvement are to increase the adequacy of test and real modes of vibration, to increase the accuracy of reproduction of the test modes on shake tables and also to increase the reliability of measuring information about the modes of vibration and dynamic responses of an object of researches and to increase the information capacity of the vibrational tests. To ensure the equivalence of the test modes to the modes of maintenance the modes of tests are provided, they are not created by in-phase submission of a test signal in points of fixing the printed circuit boards. It is shown that with the help of control over the amplitudes and phases of affecting signals on resonance frequencies the displacement of maxima deflection in the area of the printed circuit board is possible and, thereby, it is enable to increase the reliability. The received results of mathematical simulation and their correlation with the results of full-scale tests specified on the limitation of vibration tests by means of standard techniques. The conclusion about the necessity of full-scale tests modifications is drawn.
An electroactive polymer based concept for vibration reduction via adaptive supports
Wolf, Kai; Röglin, Tobias; Haase, Frerk; Finnberg, Torsten; Steinhoff, Bernd
2008-03-01
A concept for the suppression of resonant vibration of an elastic system undergoing forced vibration coupled to electroactive polymer (EAP) actuators based on dielectric elastomers is demonstrated. The actuators are utilized to vary the stiffness of the end support of a clamped beam, which is forced to harmonic vibration via a piezoelectric patch. Due to the nonlinear dependency of the elastic modulus of the EAP material, the modulus can be changed by inducing an electrostrictive deformation. The resulting change in stiffness of the EAP actuator leads to a shift of the resonance frequencies of the vibrating beam, enabling an effective reduction of the vibration amplitude by an external electric signal. Using a custom-built setup employing an aluminum vibrating beam coupled on both sides to electrodized strips of VHB tape, a significant reduction of the resonance amplitude was achieved. The effectiveness of this concept compared to other active and passive concepts of vibration reduction is discussed.
Vibration reduction using autoparametric resonance in a high-Tc superconducting levitation system
Yamasaki, Hiroshi; Takazakura, Toyoki; Sakaguchi, Ryunosuke; Sugiura, Toshihiko
2014-05-01
High-Tc superconducting levitation systems have very small damping and enable stable levitation without control. Therefore, they can be applied to various kinds of application. However, there are some problems that small damping produces large vibration and nonlinearity of magnetic force can generate complicated phenomena. Accordingly, analysis of these phenomena and reduction of vibration occurring in the system are important. In this study, we examined reduction of vibration without using any absorbers, but utilizing autoparametric resonance caused by nonlinear coupling between vertical oscillation and horizontal oscillation. We conducted numerical analysis and experiments in order to investigate motions of a rigid bar levitated by the electromagnetic force from high-Tc superconductors. As a result, if the ratio of the natural frequency of vertical oscillation and that of horizontal oscillation is two to one, the vertical oscillation decreases while the horizontal oscillation is excited. Thus, it was confirmed that the amplitude of a primary resonance can be reduced by occurrence of autoparametric resonance without using any absorbers.
Model reduction using the Vorobyev moment problem
Strakoš, Zdeněk
2009-07-01
Given a nonsingular complex matrix and complex vectors v and w of length N, one may wish to estimate the quadratic form w * A - 1 v, where w * denotes the conjugate transpose of w. This problem appears in many applications, and Gene Golub was the key figure in its investigations for decades. He focused mainly on the case A Hermitian positive definite (HPD) and emphasized the relationship of the algebraically formulated problems with classical topics in analysis - moments, orthogonal polynomials and quadrature. The essence of his view can be found in his contribution Matrix Computations and the Theory of Moments, given at the International Congress of Mathematicians in Zürich in 1994. As in many other areas, Gene Golub has inspired a long list of coauthors for work on the problem, and our contribution can also be seen as a consequence of his lasting inspiration. In this paper we will consider a general mathematical concept of matching moments model reduction, which as well as its use in many other applications, is the basis for the development of various approaches for estimation of the quadratic form above. The idea of model reduction via matching moments is well known and widely used in approximation of dynamical systems, but it goes back to Stieltjes, with some preceding work done by Chebyshev and Heine. The algebraic moment matching problem can for A HPD be formulated as a variant of the Stieltjes moment problem, and can be solved using Gauss-Christoffel quadrature. Using the operator moment problem suggested by Vorobyev, we will generalize model reduction based on matching moments to the non-Hermitian case in a straightforward way. Unlike in the model reduction literature, the presented proofs follow directly from the construction of the Vorobyev moment problem.
Environmental vibration reduction utilizing an array of mass scatterers
DEFF Research Database (Denmark)
Peplow, Andrew; Andersen, Lars Vabbersgaard; Bucinskas, Paulius
2017-01-01
Ground vibration generated by rail and road traffic is a major source of environmental noise and vibration pollution in the low-frequency range. A promising and cost effective mitigation method can be the use of heavy masses placed as a periodic array on the ground surface near the road or track (e.......g. concrete or stone blocks, specially designed brick walls, etc.). The natural frequencies of vibration for such blocks depend on the local ground stiffness and on the mass of the blocks which can be chosen to provide resonance at specified frequencies. This work concerns the effectiveness of such “blocking...
Active Vibration Reduction of the Advanced Stirling Convertor
Wilson, Scott D.; Metscher, Jonathan F.; Schifer, Nicholas A.
2016-01-01
Stirling Radioisotope Power Systems (RPS) are being developed as an option to provide power on future space science missions where robotic spacecraft will orbit, flyby, land or rove. A Stirling Radioisotope Generator (SRG) could offer space missions a more efficient power system that uses one fourth of the nuclear fuel and decreases the thermal footprint compared to the current state of the art. The Stirling Cycle Technology Development (SCTD) Project is funded by the RPS Program to developing Stirling-based subsystems, including convertors and controller maturation efforts that have resulted in high fidelity hardware like the Advanced Stirling Radioisotope Generator (ASRG), Advanced Stirling Convertor (ASC), and ASC Controller Unit (ACU). The SCTD Project also performs research to develop less mature technologies with a wide variety of objectives, including increasing temperature capability to enable new environments, improving system reliability or fault tolerance, reducing mass or size, and developing advanced concepts that are mission enabling. Active vibration reduction systems (AVRS), or "balancers", have historically been developed and characterized to provide fault tolerance for generator designs that incorporate dual-opposed Stirling convertors or enable single convertor, or small RPS, missions. Balancers reduce the dynamic disturbance forces created by the power piston and displacer internal moving components of a single operating convertor to meet spacecraft requirements for induced disturbance force. To improve fault tolerance for dual-opposed configurations and enable single convertor configurations, a breadboard AVRS was implemented on the Advanced Stirling Convertor (ASC). The AVRS included a linear motor, a motor mount, and a closed-loop controller able to balance out the transmitted peak dynamic disturbance using acceleration feedback. Test objectives included quantifying power and mass penalty and reduction in transmitted force over a range of ASC
Vibrations in lightweight structures - Efficiency and reduction of numerical models
Flodén, Ola
2014-01-01
Multi-storey wood buildings have been increasing in popularity since a century-old ban on the construction of such buildings was lifted in 1994. Compared to conventional concrete structures, it is more difficult to build lightweight structures in such a way that noise and disturbing vibrations is avoided. To design buildings of high performance regarding sound and vibrations, it is desirable to have tools for predicting the effects of structural modifications prior to construction. The long-t...
A magnetic damper for first mode vibration reduction in multimass flexible rotors
Kasarda, M. E. F.; Allaire, P. E.; Humphris, R. R.; Barrett, L. E.
1989-01-01
Many rotating machines such as compressors, turbines and pumps have long thin shafts with resulting vibration problems, and would benefit from additional damping near the center of the shaft. Magnetic dampers have the potential to be employed in these machines because they can operate in the working fluid environment unlike conventional bearings. An experimental test rig is described which was set up with a long thin shaft and several masses to represent a flexible shaft machine. An active magnetic damper was placed in three locations: near the midspan, near one end disk, and close to the bearing. With typical control parameter settings, the midspan location reduced the first mode vibration 82 percent, the disk location reduced it 75 percent and the bearing location attained a 74 percent reduction. Magnetic damper stiffness and damping values used to obtain these reductions were only a few percent of the bearing stiffness and damping values. A theoretical model of both the rotor and the damper was developed and compared to the measured results. The agreement was good.
Steps for Vibration Reduction of 50kg-Class Micro-Satellite Structure
Nakamura, Masato; Furukawa, Takuya; Chiba, Masakatsu; Okubo, Hiroshi; Akita, Takeshi; Sugiyama, Yoshihiko; Nakamura, Yosuke; Imamura, Hiroaki; Umehara, Nobuhito
The paper reports several steps taken to reduce vibration responses of a 50kg-class micro-satellite structure, which is subjected to severe mechanical/vibratory environment during launching. In order to satisfy the required mechanical interface conditions, anti-vibration design of satellite structure was modified to enhance damping capacity of the structure by applying adherent aisogrid-panel, honeycomb panel, polyimid-tape-inserted connections, and damping pads. Considerable reduction of vibration responses was confirmed by vibration test of structural-thermal model.
Directory of Open Access Journals (Sweden)
Kaihua Lu
2017-01-01
Full Text Available A novel type of integral squeeze film damper (ISFD is proposed to reduce and isolate vibration excitations of the gear system through bearing to the foundation. Four ISFD designs were tested experimentally with an open first-grade spur gear system. Vibration reduction characteristics were experimentally studied at different speeds for cases where ISFD elastic damping supports were simultaneously installed on the driving and driven shafts, installed on the driven shaft, or only installed on the driving shaft. Experimental results show that the ISFD elastic damping support can effectively reduce shock vibration of the gear system. Additionally, resonant modulation in gear shafts caused by meshing impact was significantly reduced. Different vibration amplitudes of gear shafts with ISFD installed only on driven or driving shafts were compared. Results indicated that vibration reduction is better when ISFD is only installed on the driven shaft than on the driving shaft.
Environmental vibration reduction utilizing an array of mass scatterers
DEFF Research Database (Denmark)
Peplow, Andrew; Andersen, Lars Vabbersgaard; Bucinskas, Paulius
2017-01-01
Ground vibration generated by rail and road traffic is a major source of environmental noise and vibration pollution in the low-frequency range. A promising and cost effective mitigation method can be the use of heavy masses placed as a periodic array on the ground surface near the road or track (e......” resonating masses. A semi-analytical lumped-parameter method is utilized assuming that the blocks are point masses situated on an elastic half-space. The work is enhanced by examples highlighting advantages and disadvantages of single-mass scatterers and periodic scatterers. © 2017 The Authors. Published...
Coupled rotor-fuselage vibration reduction with multiple frequency blade pitch control
Papavassiliou, I.; Friedmann, P. P.; Venkatesan, C.
1991-01-01
A nonlinear coupled rotor/flexible fuselage analysis has been developed and used to study the effects of higher harmonic blade pitch control on the vibratory hub loads and fuselage acceleration levels. Previous results, obtained with this model have shown that conventional higher harmonic control (HHC) inputs aimed at hub shear reduction cause an increase in the fuselage accelerations and vice-versa. It was also found that for simultaneous reduction of hub shears and fuselage accelerations, a pitch input representing a combination of two higher harmonic components of different frequencies was needed. Subsequently, it was found that this input could not be implemented through a conventional swashplate. This paper corrects a mistake originally made in the representation of the multiple frequency pitch input and shows that such a pitch input can be only implemented in the rotating reference frame. A rigorous mathematical solution is found, for the pitch input in the rotating reference frame, which produces simultaneous reduction of hub shears and fuselage acceleration. New insight on vibration reduction in coupled rotor/fuselage systems is obtained from the sensitivity of hub shears to the frequency and amplitude of the open loop HHC signal in the rotating reference frame. Finally the role of fuselage flexibility in this class of problems is determined.
Directory of Open Access Journals (Sweden)
Zhou Danfeng
2017-01-01
Full Text Available The maglev vehicle-girder coupled vibration problem has been encountered in many maglev test or commercial lines, which significantly degrade the performance of the maglev train. In previous research on the principle of the coupled vibration problem, it has been discovered that the fundamental model of the maglev girder can be simplified as a series of mass-spring resonators of different but related resonance frequencies, and that the stability of the vehicle-girder coupled system can be investigated by separately examining the stability of each mass-spring resonator – electromagnet coupled system. Based on this conclusion, a maglev test platform, which includes a single electromagnetic suspension control system, is built for experimental study of the coupled vibration problem. The guideway of the test platform is supported by a number of springs so as to change its flexibility. The mass of the guideway can also be changed by adjusting extra weights attached to it. By changing the flexibility and mass of the guideway, the rules of the maglev vehicle-girder coupled vibration problem are to be examined through experiments, and related theory on the vehicle-girder self-excited vibration proposed in previous research is also testified.
Model reduction and analysis of a vibrating beam microgyroscope
Ghommem, Mehdi
2012-05-08
The present work is concerned with the nonlinear dynamic analysis of a vibrating beam microgyroscope composed of a rotating cantilever beam with a tip mass at its end. The rigid mass is coupled to two orthogonal electrodes in the drive and sense directions, which are attached to the rotating base. The microbeam is driven by an AC voltage in the drive direction, which induces vibrations in the orthogonal sense direction due to rotation about the microbeam axis. The electrode placed in the sense direction is used to measure the induced motions and extract the underlying angular speed. A reduced-order model of the gyroscope is developed using the method of multiple scales and used to examine its dynamic behavior. © The Author(s) 2012 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.
Actively Controlled Landing Gear for Aircraft Vibration Reduction
Horta, Lucas G.; Daugherty, Robert H.; Martinson, Veloria J.
1999-01-01
Concepts for long-range air travel are characterized by airframe designs with long, slender, relatively flexible fuselages. One aspect often overlooked is ground induced vibration of these aircraft. This paper presents an analytical and experimental study of reducing ground-induced aircraft vibration loads using actively controlled landing gears. A facility has been developed to test various active landing gear control concepts and their performance. The facility uses a NAVY A6-intruder landing gear fitted with an auxiliary hydraulic supply electronically controlled by servo valves. An analytical model of the gear is presented including modifications to actuate the gear externally and test data is used to validate the model. The control design is described and closed-loop test and analysis comparisons are presented.
Energy Technology Data Exchange (ETDEWEB)
Balci, Murat [Dept. of Mechanical Engineering, Bayburt University, Bayburt (Turkmenistan); Gundogdu, Omer [Dept. of Mechanical Engineering, Ataturk University, Erzurum (Turkmenistan)
2017-01-15
In this study, estimation of some physical properties of a laminated composite plate was conducted via the inverse vibration problem. Laminated composite plate was modelled and simulated to obtain vibration responses for different length-to-thickness ratio in ANSYS. Furthermore, a numerical finite element model was developed for the laminated composite utilizing the Kirchhoff plate theory and programmed in MATLAB for simulations. Optimizing the difference between these two vibration responses, inverse vibration problem was solved to obtain some of the physical properties of the laminated composite using genetic algorithms. The estimated parameters are compared with the theoretical results, and a very good correspondence was observed.
Electrochemical CO2 Reduction: A Classification Problem.
Bagger, Alexander; Ju, Wen; Varela, Ana Sofia; Strasser, Peter; Rossmeisl, Jan
2017-11-17
In this work, we propose four non-coupled binding energies of intermediates as descriptors, or "genes", for predicting the product distribution in CO2 electroreduction. Simple reactions can be understood by the Sabatier principle (catalytic activity vs. one descriptor), while more complex reactions tend to give multiple very different products and consequently the product selectivity is a more complex property to understand. We approach this, as a logistical classification problem, by grouping metals according to their major experimental product from CO2 electroreduction: H2 , CO, formic acid and beyond CO* (hydrocarbons or alcohols). We compare the groups in terms of multiple binding energies of intermediates calculated by density functional theory. Here, we find three descriptors to explain the grouping: the adsorption energies of H*, COOH*, and CO*. To further classify products beyond CO*, we carry out formaldehyde experiments on Cu, Ag, and Au and combine these results with the literature to group and differentiate alcohol or hydrocarbon products. We find that the oxygen binding (adsorption energy of CH3 O*) is an additional descriptor to explain the alcohol formation in reduction processes. Finally, the adsorption energy of the four intermediates, H*, COOH*, CO*, and CH3 O*, can be used to differentiate, group, and explain products in electrochemical reduction processes involving CO2 , CO, and carbon-oxygen compounds. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
A model to study the reduction of turbine blade vibration using the snubbing mechanism
Pennacchi, Paolo; Chatterton, Steven; Bachschmid, Nicolò; Pesatori, Emanuel; Turozzi, Giorgio
2011-05-01
Blade vibration reduction is an important task in high performance turbo machinery for power generation, in order to avoid the risk of blade failure due to the overcoming of fatigue limit. A possible way to obtain this result is a contact related phenomenon, i.e. by physically limiting the vibration amplitude on the blade tip leaving a small gap between the shrouds of adjacent blades. When the relative displacement between adjacent blades exceeds the gap, in a certain vibration mode of the blade row, a contact occurs between the shrouds, the relative motion is restricted and energy is dissipated by friction and impact during the contact. This is called the snubbing mechanism. In this paper, an original simplified model of bladed disks, in which the snubbing mechanism can occur, is presented and numerical integration in time domain furnishes the time histories of the vibrations of the blades. The level of vibration reduction is then evaluated in some different modes that could be excited for instance by the fluid flow. It is also shown that unlucky combinations of system and excitation parameters can effect also a certain magnification instead of a reduction of the vibration amplitudes. Experimental results on single blade and blade groups of a steam turbine are used to tune the parameters of the system.
Energy Technology Data Exchange (ETDEWEB)
Lee, Hyun; Kim, Yeon Whan [Korea Electric Power Corp. (KEPCO), Taejon (Korea, Republic of). Research Center; Kim, Tae Ryong; Park, Jin Ho [Korea Atomic Energy Research Inst., Daeduk (Korea, Republic of)
1996-08-01
The main steam piping of nuclear power plant which runs between steam generator and high pressure turbine has been experienced to have a severe effect on the safe operation of the plant due to the vibration induced by the steam flowing inside the piping. The imposed cyclic loads by the vibration could result in the degradation of the related structures such as connection parts between main instruments, valves, pipe supports and building. The objective of the study is to reduce the vibration level of Wolsung nuclear power plant unit 1 main steam pipeline by analyzing vibration characteristics of the piping, identifying sources of the vibration and developing a vibration reduction method .The location of the maximum vibration is piping between the main steam header and steam chest .The stress level was found to be within the allowable limit .The main vibration frequency was found to be 4{approx}6 Hz which is the same as the natural frequency from model test .A vibration reduction method using pipe supports of energy absorbing type(WEAR)is selected .The measured vibration level after WEAR installation was reduced about 36{approx}77% in displacement unit (author). 36 refs., 188 figs.
Kim, Heung Soo; Sohn, Jung Woo; Jeon, Juncheol; Choi, Seung-Bok
2013-02-06
In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structural vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs) were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structural vibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active vibration control of the underwater structure is a useful means to reduce structure-borne noise in water.
Directory of Open Access Journals (Sweden)
Seung-Bok Choi
2013-02-01
Full Text Available In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structural vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structural vibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active vibration control of the underwater structure is a useful means to reduce structure-borne noise in water.
Adsorption-induced symmetry reduction of metal-phthalocyanines studied by vibrational spectroscopy
Sforzini, J.; Bocquet, F. C.; Tautz, F. S.
2017-10-01
We investigate the vibrational properties of Pt- and Pd-phthalocyanine (PtPc and PdPc) molecules on Ag(111) with high-resolution electron energy loss spectroscopy (HREELS). In the monolayer regime, both molecules exhibit long-range order. The vibrational spectra prove a flat adsorption geometry. The redshift of specific vibrational modes suggests a moderate interaction of the molecules with the substrate. The presence of asymmetric vibrational peaks indicates an interfacial dynamical charge transfer (IDCT). The molecular orbital that is involved in IDCT is the former Eg lowest unoccupied molecular orbital (LUMO) of the molecules that becomes partially occupied upon adsorption. A group-theoretical analysis of the IDCT modes, based on calculated vibrational frequencies and line shape fits, provides proof for the reduction of the symmetry of the molecule-substrate complex from fourfold D4 h to C2 v(σv) , Cs(σv) , or C2 and the ensuing lifting of the degeneracy of the former LUMO of the molecule. The vibration-based analysis of orbital degeneracies, as carried out here for PtPc/Ag(111) and PdPc/Ag(111), is particularly useful whenever the presence of multiple molecular in-plane orientations at the interface makes the analysis of orbital degeneracies with angle-resolved photoemission spectroscopy difficult.
Application of higher harmonic blade feathering on the OH-6A helicopter for vibration reduction
Straub, F. K.; Byrns, E. V., Jr.
1986-01-01
The design, implementation, and flight test results of higher harmonic blade feathering for vibration reduction on the OH-6A helicopter are described. The higher harmonic control (HHC) system superimposes fourth harmonic inputs upon the stationary swashplate. These inputs are transformed into 3P, 4P and 5P blade feathering angles. This results in modified blade loads and reduced fuselage vibrations. The primary elements of this adaptive vibration suppression system are: (1) acceleration transducers sensing the vibratory response of the fuselage; (2) a higher harmonic blade pitch actuator system; (3) a flightworthy microcomputer, incorporating the algorithm for reducing vibrations, and (4) a signal conditioning system, interfacing between the sensors, the microcomputer and the HHC actuators. The program consisted of three distinct phases. First, the HHC system was designed and implemented on the MDHC OH-6A helicopter. Then, the open loop, or manual controlled, flight tests were performed, and finally, the closed loop adaptive control system was tested. In 1983, one portion of the closed loop testing was performed, and in 1984, additional closed loop tests were conducted with improved software. With the HHC system engaged, the 4P pilot seat vibration levels were significantly lower than the baseline ON-6A levels. Moreover, the system did not adversely affect blade loads or helicopter performance. In conclusion, this successful proof of concept project demonstrated HHC to be a viable vibration suppression mechanism.
Modern Data Analysis techniques in Noise and Vibration Problems
1981-11-01
ce cours (commun a l’acoustique et aux vibrations) conduit de fagon naturelle a presenter, parallelement aux methodologies, les aspects fondamentaux...without knowledge to first order of the shear stress and entropy fluctuations. Finally, when mean motion is appreciable, convection of the stress...some right-hand side "equivalent source" terms to the left-hand side to represent these mean convection effects as distinct from "generation
Reduction of Structural Vibrations by Passive and Semiactively Controlled Friction Dampers
Directory of Open Access Journals (Sweden)
L. Gaul
2014-01-01
Full Text Available Reduction of structural vibrations is of major interest in mechanical engineering for lowering sound emission of vibrating structures, improving accuracy of machines, and increasing structure durability. Besides optimization of the mechanical design or various types of passive damping treatments, active structural vibration control concepts are efficient means to reduce unwanted vibrations. In this contribution, two different semiactive control concepts for vibration reduction are proposed that adapt to the normal force of attached friction dampers. Thereby, semiactive control concepts generally possess the advantage over active control in that the closed loop is intrinsically stable and that less energy is required for the actuation than in active control. In the chosen experimental implementation, a piezoelectric stack actuator is used to apply adjustable normal forces between a structure and an attached friction damper. Simulation and experimental results of a benchmark structure with passive and semiactively controlled friction dampers are compared for stationary narrowband excitation. For simulations of the control performance, transient simulations must be employed to predict the achieved vibration damping. It is well known that transient simulation of systems with friction and normal contact requires excessive computational power due to the nonlinear constitutive laws and the high contact stiffnesses involved. However, commercial finite-element codes do not allow simulating feedback control in a general way. As a remedy, a special simulation framework is developed which allows efficiently modeling interfaces with friction and normal contact by appropriate constitutive laws which are implemented by contact elements in a finite-element model. Furthermore, special model reduction techniques using a substructuring approach are employed for faster simulation.
Energy Technology Data Exchange (ETDEWEB)
Cho, Seon Woog [Silla Univ., Pusan (Korea, Republic of)
2002-02-01
It is shown that one-electron reduction of nitric oxide (NO) to nitroxyl anion (NO{sup -}) can be accelerated by vibrational energy. Potential energy surfaces of NO and NO{sup -} reveal that the vertical transition between them has favorable energetics for vibrationally excited molecule. Also, Franck-Condon factors between NO and NO{sup -} vibrational wave functions are calculated. It shows that the number of open channels increases with increased vibrational energy. These results mean that we can control the rate of reduction of NO to NO{sup -} by radiating an appropriate light.
Similitude design for the vibration problems of plates and shells: A review
Zhu, Yunpeng; Wang, You; Luo, Zhong; Han, Qingkai; Wang, Deyou
2017-06-01
Similitude design plays a vital role in the analysis of vibration and shock problems encountered in large engineering equipment. Similitude design, including dimensional analysis and governing equation method, is founded on the dynamic similitude theory. This study reviews the application of similitude design methods in engineering practice and summarizes the major achievements of the dynamic similitude theory in structural vibration and shock problems in different fields, including marine structures, civil engineering structures, and large power equipment. This study also reviews the dynamic similitude design methods for thin-walled and composite material plates and shells, including the most recent work published by the authors. Structure sensitivity analysis is used to evaluate the scaling factors to attain accurate distorted scaling laws. Finally, this study discusses the existing problems and the potential of the dynamic similitude theory for the analysis of vibration and shock problems of structures.
Optimization of Vibration Reduction Ability of Ladder Tracks by FEM Coupled with ACO
Directory of Open Access Journals (Sweden)
Hao Jin
2015-01-01
Full Text Available Ladder track, which has drawn increased attention in scientific communities, is an effective method for reducing vibrations from underground railways. In order to optimize the vibration reduction ability of ladder track, a new method, that is, the finite element method (FEM coupled with ant colony optimization (ACO, has been proposed in this paper. We describe how to build the FEM model verified by the vibration tests in the Track Vibration Abatement and Control Laboratory and how to couple the FEM with ACO. The density and elasticity modulus of the sleeper pad are optimized using this method. After optimization, the vibration acceleration level of the supporting platform in the 1–200 Hz range was reduced from 102.8 dB to 94.4 dB. The optimized density of the sleeper pad is 620 kg/m3, and the optimized elasticity modulus of the sleeper pad is 6.25 × 106 N/m2.
Vibration reduction in helicopter rotors using an active control surface located on the blade
Millott, T. A.; Friedmann, P. P.
1992-01-01
A feasibility study of vibration reduction in a four-bladed helicopter rotor using individual blade control (IBC), which is implemented by an individually controlled aerodynamic surface located on each blade, is presented. For this exploratory study, a simple offset-hinged spring restrained model of the blade is used with fully coupled flap-lag-torsional dynamics for each blade. Deterministic controllers based on local and global system models are implemented to reduce 4/rev hub loads using both an actively controlled aerodynamic surface on each blade as well as conventional IBC, where the complete blade undergoes cyclic pitch change. The effectiveness of the two approaches for simultaneous reduction of the 4/rev hub shears and hub moments is compared. Conventional IBC requires considerably more power to achieve approximately the same level of vibration reduction as that obtained by implementing IBC using an active control surface located on the outboard segment of the blade. The effect of blade torsional flexibility on the vibration reduction effectiveness of the actively controlled surface was also considered and it was found that this parameter has a very substantial influence.
Adaptive inverse control for rotorcraft vibration reduction. Ph.D. Thesis
Jacklin, S. A.
1985-01-01
The Least Mean Square (LMS) algorithm is extended to solve the multiple-input, multiple-output problem of alleviating N/Rev helicopter fuselage vibration by means of adaptive inverse control. A frequency domain locally linear model is used to represent the transfer matrix relating the high harmonic pitch control inputs to the harmonic vibration outputs to be controlled. By using the inverse matrix as the controller gain matrix, an adaptive inverse regulator is formed to alleviate the N/Rev vibration. The stability and rate of convergence properties of the extended LMS algorithm are discussed. It is shown that the stability ranges for the elements of the stability gain matrix are directly related to the eigenvalues of the vibration signal information matrix for the learning phase, but not for the control phase. The overall conclusion is that the LMS adaptive inverse control method can form a robust vibration control system, but will require some tuning of the input sensor gains, the stability gain matrix, and the amount of control relaxation to be used. The learning curve of the controller during the learning phase is shown to be quantitatively close to that predicted by averaging the learning curves of the normal modes. It is shown that the best selections of the stability gain matrix elements and the amount of control relaxation is basically a compromise between slow, stable convergence and fast convergence with increased possibility of unstable identification.
Cribbs, Richard Clay
This dissertation describes the development of a coupled rotor/flexible fuselage aeroelastic response model including rotor/fuselage aerodynamic interactions. This model is used to investigate fuselage vibrations and their suppression using active control of structural response (ACSR). The fuselage, modeled by a three dimensional structural dynamic finite element model, is combined with a flexible, four-bladed, hingeless rotor. Each rotor blade is structurally modeled as an isotropic Euler-Bernoulli beam with coupled flap-lag-torsional dynamics assuming moderate deflections. A free wake model is incorporated into the aeroelastic response model and is validated against previous studies. Two and three dimensional sources model the fuselage aerodynamics. Direct aerodynamic influences of the rotor and wake on the fuselage are calculated by integrating pressures over the surface of the fuselage. The fuselage distorts the wake and influences the air velocities at the rotor which alters the aerodynamic loading. This produces fully coupled rotor/fuselage aerodynamic interactions. The influence of the aerodynamic refinements on vibrations is studied in detail. Results indicate that a free wake model and the inclusion of fuselage aerodynamic effects on the rotor and wake are necessary for vibration prediction at all forward speeds. The direct influence of rotor and wake aerodynamics on the fuselage plays a minor role in vibrations. Accelerations with the improved aerodynamic model are significantly greater than uniform inflow results. The influence of vertical separation between the rotor and fuselage on vibrations is also studied. An ACSR control algorithm is developed that preferentially reduces accelerations at selected airframe locations of importance. Vibration reduction studies are carried out using this improved control algorithm and a basic algorithm studied previously at UCLA. Both ACSR methods markedly reduce acceleration amplitudes with no impact on the rotor
On a Non-Symmetric Eigenvalue Problem Governing Interior Structural–Acoustic Vibrations
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Heinrich Voss
2016-06-01
Full Text Available Small amplitude vibrations of a structure completely filled with a fluid are considered. Describing the structure by displacements and the fluid by its pressure field, the free vibrations are governed by a non-self-adjoint eigenvalue problem. This survey reports on a framework for taking advantage of the structure of the non-symmetric eigenvalue problem allowing for a variational characterization of its eigenvalues. Structure-preserving iterative projection methods of the the Arnoldi and of the Jacobi–Davidson type and an automated multi-level sub-structuring method are reviewed. The reliability and efficiency of the methods are demonstrated by a numerical example.
Daraji, A. H.; Hale, J. M.
2014-10-01
This study concerns new investigation of active vibration reduction of a stiffened plate bonded with discrete sensor/actuator pairs located optimally using genetic algorithms based on a developed finite element modeling. An isotropic plate element stiffened by a number of beam elements on its edges and having a piezoelectric sensor and actuator pair bonded to its surfaces is modeled using the finite element method and Hamilton’s principle, taking into account the effects of piezoelectric mass, stiffness and electromechanical coupling. The modeling is based on the first order shear deformation theory taking into account the effects of bending, membrane and shear deformation for the plate, the stiffening beam and the piezoelectric patches. A Matlab finite element program has been built for the stiffened plate model and verified with ANSYS and also experimentally. Optimal placement of ten piezoelectric sensor/actuator pairs and optimal feedback gain for active vibration reduction are investigated for a plate stiffened by two beams arranged in the form of a cross. The genetic algorithm was set up for optimization of sensor/actuator placement and feedback gain based on the minimization of the optimal linear quadratic index as an objective function to suppress the first six modes of vibration. Comparison study is presented for active vibration reduction of a square cantilever plate stiffened by crossed beams with two sensor/actuator configurations: firstly, ten piezoelectric sensor/actuator pairs are located in optimal positions; secondly, a piezoelectric layer of single sensor/actuator pair covering the whole of the stiffened plate as a SISO system.
Is the Coupling of C3V Internal Rotation and Normal Vibrations a Tractable Problem?
Pearson, John; Groner, Peter; Daly, Adam M.
2016-06-01
The solution of a C3V internal rotation problem for the torsional manifold of an isolated vibrational state such as the ground state is well established. However, once an interacting small amplitude vibrational state is involved the path to a solution becomes far less clear and there is little guidance in the literature on how to proceed. The fundamental challenge is that the torsional problem and the internal axis system are unique to each torsional manifold of a specific vibrational state. In an asymmetric top molecule vibrational angular momentum can be rotated away, but this sort of rotation changes the angle between the internal rotation axis and the principle axis when there is an internal rotor. This means that there is an angle between the internal axis systems of each torsional manifold of a vibrational state. The net result is that the coupling between the two states must account for the difference in internal axis angle and will have some significant consequences to the selection rules and interactions. Two cases will be discussed, methanol and ethyl cyanide.
Inverse Problem for the Vibrating Beam in the Free/Clamped Configuration,
1979-01-01
such as in seismic prospecting wherr this stripping-off is usually carried out in the time domain (Berkhout & van Wulfften Palthe , 1979). The Stielties...multiplicity of solutions of the inverse problem for a vibrating beam. SIAM 37, 605-613. Berkhout, A.J. & van Wulfften Palthe , D. W. 1979 Migration in
Application of HPEM to investigate the response and stability of nonlinear problems in vibration
DEFF Research Database (Denmark)
Mohammadi, M.H.; Mohammadi, A.; Kimiaeifar, A.
2010-01-01
In this work, a powerful analytical method, called He's Parameter Expanding Methods (HPEM) is used to obtain the exact solution of nonlinear problems in nonlinear vibration. In this work, the governing equation is obtained by using Lagrange method, then the nonlinear governing equation is solved ...
THE REDUCTION OF VIBRATIONS IN A CAR – THE PRINCIPLE OF PNEUMATIC DUAL MASS FLYWHEEL
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Robert GREGA
2014-09-01
Full Text Available The dual-mass flywheel replaces the classic flywheel in such way that it is divided into two masses (the primary mass and the secondary mass, which are jointed together by means of a flexible interconnection. This kind of the flywheel solution enables to change resonance areas of the engine with regard to the engine dynamic behaviour what leads to a reduction of vibrations consequently. However, there is also a disadvantage of the dualmass flywheels. The disadvantage is its short-time durability. There was projected a new type of the dual-mass flywheel in the framework of our workplace in order to eliminate disadvantages of the present dual-mass flywheels, i.e. we projected the pneumatic dual-mass flywheel, taking into consideration our experiences obtained during investigation of vibrations.
The Power of Data Reduction : Kernels for Fundamental Graph Problems
Jansen, B.M.P.|info:eu-repo/dai/nl/326093605
2013-01-01
The purpose of this thesis is to give a mathematical analysis of the power of data reduction for dealing with fundamental NP-hard graph problems. It has often been observed that the use of heuristic reduction rules in a preprocessing phase gives significant performance gains when solving such
METHOD OF COMPENSATING LOADS FOR SHALLOW SHELLS. VIBRATION AND STABILITY PROBLEMS
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Tran Duc Chinh
2015-12-01
Full Text Available Based on the integral representation of the displacements functions through Green's functions, the author proposed a method to solve the system of differential equations of the given problem. The equations were solved approximately by reducing to algebraic equations by finite difference techniques in Samarsky scheme. Some examples are given for calculation of eigenvalues of shallow shell vibration problem, which are compared with results received by Onyashvili using Galerkin method.
Rotation in vibration, optimization, and aeroelastic stability problems. Ph.D. Thesis
Kaza, K. R. V.
1974-01-01
The effects of rotation in the areas of vibrations, dynamic stability, optimization, and aeroelasticity were studied. The governing equations of motion for the study of vibration and dynamic stability of a rapidly rotating deformable body were developed starting from the nonlinear theory of elasticity. Some common features such as the limitations of the classical theory of elasticity, the choice of axis system, the property of self-adjointness, the phenomenon of frequency splitting, shortcomings of stability methods as applied to gyroscopic systems, and the effect of internal and external damping on stability in gyroscopic systems are identified and discussed, and are then applied to three specific problems.
Active Vibration Reduction of Titanium Alloy Fan Blades (FAN1) Using Piezoelectric Materials
Choi, Benjamin; Kauffman, Jeffrey; Duffy, Kirsten; Provenza, Andrew; Morrison, Carlos
2010-01-01
The NASA Glenn Research Center is developing smart adaptive structures to improve fan blade damping at resonances using piezoelectric (PE) transducers. In this paper, a digital resonant control technique emulating passive shunt circuits is used to demonstrate vibration reduction of FAN1 Ti real fan blade at the several target modes. Single-mode control and multi-mode control using one piezoelectric material are demonstrated. Also a conceptual study of how to implement this digital control system into the rotating fan blade is discussed.
Optimized design of suspension systems for hand-arm transmitted vibration reduction
Saggin, Bortolino; Scaccabarozzi, Diego; Tarabini, Marco
2012-05-01
This paper describes a systematic approach for optimizing suspension systems to reduce the vibrations transmitted to workers by hand-held power tools. The optimization is based on modeling tool-operator interactions using a mobility scheme. The tool is modeled as a vibration generator, and its internal impedance is included. A hand-arm impedance matrix is used to model the operator upper limbs. The mobility model is used to identify the optimal suspension characteristics, which in our study were the set of parameters that minimizes the frequency-weighted acceleration at the hand-tool interface. Different handling conditions (one and two hands) and different working cycles with the same tools can be included in the optimization process. The constraints derived from the limitation on the increase in the tool mass and the static deflection of the mounting system under the working loads are also considered. The proposed method has been applied to the reduction of the vibrations transmitted to the operator by a small pneumatic hammer. The designed system reduced the worker's exposure so that it is within the limits of the EU directive. The agreement between the model predictions and the measured suspension performances validates the effectiveness of this approach.
Taylor, R. B.; Zwicke, P. E.; Gold, P.; Miao, W.
1980-01-01
An analytical study was conducted to define the basic configuration of an active control system for helicopter vibration and gust response alleviation. The study culminated in a control system design which has two separate systems: narrow band loop for vibration reduction and wider band loop for gust response alleviation. The narrow band vibration loop utilizes the standard swashplate control configuration to input controller for the vibration loop is based on adaptive optimal control theory and is designed to adapt to any flight condition including maneuvers and transients. The prime characteristics of the vibration control system is its real time capability. The gust alleviation control system studied consists of optimal sampled data feedback gains together with an optimal one-step-ahead prediction. The prediction permits the estimation of the gust disturbance which can then be used to minimize the gust effects on the helicopter.
Samani, Farhad S.; Pellicano, Francesco
2012-05-01
The goal of the present work is to assess the performances of dynamic vibration absorbers (DVA) in suppressing the vibrations of a simply supported beam subjected to an infinite sequence of regularly spaced concentrated moving loads. In particular, several types of DVA are considered: linear, cubic, higher odd-order monomials and piecewise linear stiffness; linear, cubic and linear-quadratic viscous damping. The purpose is to clarify if nonlinear DVAs show improvements with respect to the classical linear devices. The dynamic scenario is deeply investigated in a wide range of operating conditions, spanning the parameter space of the DVA (damping, stiffness). Nonlinear stiffness can lead to complex dynamics such as quasi-periodic, chaotic and sub-harmonic responses; moreover, acting on the stiffness nonlinearity no improvement is found with respect to the linear DVA. A nonlinear non-symmetric dissipation in the DVA leads to a great reduction of the beam response, the reduction is larger with respect to the linear DVA.
Millott, T. A.; Friedmann, P. P.
1994-06-01
This report describes an analytical study of vibration reduction in a four-bladed helicopter rotor using an actively controlled, partial span, trailing edge flap located on the blade. The vibration reduction produced by the actively controlled flap (ACF) is compared with that obtained using individual blade control (IBC), in which the entire blade is oscillated in pitch. For both cases a deterministic feedback controller is implemented to reduce the 4/rev hub loads. For all cases considered, the ACF produced vibration reduction comparable with that obtained using IBC, but consumed only 10-30% of the power required to implement IBC. A careful parametric study is conducted to determine the influence of blade torsional stiffness, spanwise location of the control flap, and hinge moment correction on the vibration reduction characteristics of the ACF. The results clearly demonstrate the feasibility of this new approach to vibration reduction. It should be emphasized than the ACF, used together with a conventional swashplate, is completely decoupled from the primary flight control system and thus it has no influence on the airworthiness of the helicopter. This attribute is potentially a significant advantage when compared to IBC.
Pan, Minghao; Yang, Yongmin; Guan, Fengjiao; Hu, Haifeng; Xu, Hailong
2017-01-01
The accurate monitoring of blade vibration under operating conditions is essential in turbo-machinery testing. Blade tip timing (BTT) is a promising non-contact technique for the measurement of blade vibrations. However, the BTT sampling data are inherently under-sampled and contaminated with several measurement uncertainties. How to recover frequency spectra of blade vibrations though processing these under-sampled biased signals is a bottleneck problem. A novel method of BTT signal processing for alleviating measurement uncertainties in recovery of multi-mode blade vibration frequency spectrum is proposed in this paper. The method can be divided into four phases. First, a single measurement vector model is built by exploiting that the blade vibration signals are sparse in frequency spectra. Secondly, the uniqueness of the nonnegative sparse solution is studied to achieve the vibration frequency spectrum. Thirdly, typical sources of BTT measurement uncertainties are quantitatively analyzed. Finally, an improved vibration frequency spectra recovery method is proposed to get a guaranteed level of sparse solution when measurement results are biased. Simulations and experiments are performed to prove the feasibility of the proposed method. The most outstanding advantage is that this method can prevent the recovered multi-mode vibration spectra from being affected by BTT measurement uncertainties without increasing the probe number. PMID:28758952
Dimensionality Reduction and Uncertainty Quantification for Inverse Problems
van Leeuwen, Tristan
2015-01-01
Many inverse problems in science and engineering involve multi-experiment data and thus require a large number of forward simulations. Dimensionality reduction techniques aim at reducing the number of forward solves by (randomly) subsampling the data. In the special case of non-linear least-squares
Data-Driven Model Order Reduction for Bayesian Inverse Problems
Cui, Tiangang
2014-01-06
One of the major challenges in using MCMC for the solution of inverse problems is the repeated evaluation of computationally expensive numerical models. We develop a data-driven projection- based model order reduction technique to reduce the computational cost of numerical PDE evaluations in this context.
Model reduction for optimization of structural-acoustic coupling problems
DEFF Research Database (Denmark)
Creixell Mediante, Ester; Jensen, Jakob Søndergaard; Brunskog, Jonas
2016-01-01
-acoustic coupling, for which two different approaches to constructing a modal reduction base are discussed. The efficiency and accuracy of the CMS and the MMR methods are strongly model-dependent; in this paper, they are compared for two optimization problems in the hearing aid context, where the MMR technique......Fully coupled structural-acoustic models of complex systems, such as those used in the hearing aid field, may have several hundreds of thousands of nodes. When there is a strong structure-acoustic interaction, performing optimization on one part requires the complete model to be taken into account......, which becomes highly time consuming since many iterations may be required. The use of model reduction techniques to speed up the computations is studied in this work. The Component Mode Synthesis (CMS) method and the Multi-Model Reduction (MMR) method are adapted for problems with structure...
Reduction of Helicopter BVI Noise, Vibration, and Power Consumption Through Individual Blade Control
Jacklin, Stephen A.; Blaas, Achim; Teves, Dietrich; Kube, Roland; Warmbrodt, William (Technical Monitor)
1994-01-01
A wind tunnel test was conducted with a full-scale BO 105 helicopter rotor to evaluate the potential of open-loop individual blade control (IBC) to improve rotor performance, to reduce blade vortex interaction (BVI) noise, and to alleviate helicopter vibrations. The wind tunnel test was an international collaborative effort between NASA/U.S. Army AFDD, ZF Luftfahrttechnik, Eurocopter Deutschland, and the German Aerospace Laboratory (DLR) and was conducted under the auspices of the U.S./German MOU on Rotorcraft Aeromechanics. In this test the normal blade pitch links of the rotor were replaced by servo-actuators so that the pitch of each blade could be controlled independently of the other blades. The specially designed servoactuators and IBC control system were designed and manufactured by ZF Luftfahrttechnik, GmbH. The wind tunnel test was conducted in the 40- by 80-Foot Wind Tunnel at the NASA Ames Research Center. An extensive amount of measurement information was acquired for each IBC data point. These data include rotor performance, static and dynamic hub forces and moments, rotor loads, control loads, inboard and outboard blade pitch motion, and BVI noise data. The data indicated very significant (80 percent) simultaneous reductions in both BVI noise and hub vibrations could be obtained using multi-harmonic input at the critical descent (terminal approach) condition. The data also showed that performance improvements of up to 7 percent could be obtained using 2P input at high-speed forward flight conditions.
The problem of margin calculation and its reduction via the p-median problem model
Goldengorin, B.; Krushynskyi, D.; Kuzmenko, V.; Mastorakis, NE; Demiralp, M; Mladenov,; Bojkovic, Z
2009-01-01
The paper deals with a model for calculation of the regulatory margin on brokerage accounts. The model is based on the p-Median problem (PMP) that is known to be NP-hard. We use a pseudo-Boolean representation of the PMP and propose several problem size reduction and preprocessing techniques. Our
Inverse problem of the vibrational band gap of periodically supported beam
Shi, Xiaona; Shu, Haisheng; Dong, Fuzhen; Zhao, Lei
2017-04-01
The researches of periodic structures have a long history with the main contents confined in the field of forward problem. In this paper, the inverse problem is considered and an overall frame is proposed which includes two main stages, i.e., the band gap criterion and its optimization. As a preliminary investigation, the inverse problem of the flexural vibrational band gap of a periodically supported beam is analyzed. According to existing knowledge of its forward problem, the band gap criterion is given in implicit form. Then, two cases with three independent parameters, namely the double supported case and the triple one, are studied in detail and the explicit expressions of the feasible domain are constructed by numerical fitting. Finally, the parameter optimization of the double supported case with three variables is conducted using genetic algorithm aiming for the best mean attenuation within specified frequency band.
Fu-yao Zhao; Er-xiang Song; Jun Yang
2015-01-01
The rotary vibration of rigid friction pile can be seen approximately as a central symmetry plane problem in elasticity. The stress general solution of central symmetry plane problem in elasticity can be constructed by technique such as the Laurent expansion of the volume force. This solution has some decoupling, generalized, and convergent properties, and it can be used in stress analysis of the rotary vibration of pile. The analysis results show that the maximum value of displacement will n...
Directory of Open Access Journals (Sweden)
Young H. YOU
2017-08-01
Full Text Available The best active twist schedules exploiting various waveform types are sought taking advantage of the global search algorithm for the reduction of hub vibration and/or power required of a rotor in high-speed conditions. The active twist schedules include two non-harmonic inputs formed based on segmented step functions as well as the simple harmonic waveform input. An advanced Particle Swarm assisted Genetic Algorithm (PSGA is employed for the optimizer. A rotorcraft Computational Structural Dynamics (CSD code CAMRAD II is used to perform the rotor aeromechanics analysis. A Computation Fluid Dynamics (CFD code is coupled with CSD for verification and some physical insights. The PSGA optimization results are verified against the parameter sweep study performed using the harmonic actuation. The optimum twist schedules according to the performance and/or vibration reduction strategy are obtained and their optimization gains are compared between the actuation cases. A two-phase non-harmonic actuation schedule demonstrates the best outcome in decreasing the power required while a four-phase non-harmonic schedule results in the best vibration reduction as well as the simultaneous reductions in the power required and vibration. The mechanism of reduction to the performance gains is identified illustrating the section airloads, angle-of-attack distribution, and elastic twist deformation predicted by the present approaches.
Multigrid Reduction in Time for Nonlinear Parabolic Problems
Energy Technology Data Exchange (ETDEWEB)
Falgout, R. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Manteuffel, T. A. [Univ. of Colorado, Boulder, CO (United States); O' Neill, B. [Univ. of Colorado, Boulder, CO (United States); Schroder, J. B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2016-01-04
The need for parallel-in-time is being driven by changes in computer architectures, where future speed-ups will be available through greater concurrency, but not faster clock speeds, which are stagnant.This leads to a bottleneck for sequential time marching schemes, because they lack parallelism in the time dimension. Multigrid Reduction in Time (MGRIT) is an iterative procedure that allows for temporal parallelism by utilizing multigrid reduction techniques and a multilevel hierarchy of coarse time grids. MGRIT has been shown to be effective for linear problems, with speedups of up to 50 times. The goal of this work is the efficient solution of nonlinear problems with MGRIT, where efficient is defined as achieving similar performance when compared to a corresponding linear problem. As our benchmark, we use the p-Laplacian, where p = 4 corresponds to a well-known nonlinear diffusion equation and p = 2 corresponds to our benchmark linear diffusion problem. When considering linear problems and implicit methods, the use of optimal spatial solvers such as spatial multigrid imply that the cost of one time step evaluation is fixed across temporal levels, which have a large variation in time step sizes. This is not the case for nonlinear problems, where the work required increases dramatically on coarser time grids, where relatively large time steps lead to worse conditioned nonlinear solves and increased nonlinear iteration counts per time step evaluation. This is the key difficulty explored by this paper. We show that by using a variety of strategies, most importantly, spatial coarsening and an alternate initial guess to the nonlinear time-step solver, we can reduce the work per time step evaluation over all temporal levels to a range similar with the corresponding linear problem. This allows for parallel scaling behavior comparable to the corresponding linear problem.
Granular dampers for the reduction of vibrations of an oscillatory saw
Heckel, Michael; Sack, Achim; Kollmer, Jonathan E.; Pöschel, Thorsten
2012-10-01
Instruments for surgical and dental application based on oscillatory mechanics submit unwanted vibrations to the operator's hand. Frequently the weight of the instrument's body is increased to dampen its vibration. Based on recent research regarding the optimization of granular damping we developed a prototype granular damper that attenuates the vibrations of an oscillatory saw twice as efficiently as a comparable solid mass.
Zhen, Chong; Jiffri, Shakir; Li, Daochun; Xiang, Jinwu; Mottershead, John E.
2018-01-01
New output feedback-linearisation theory is presented for the treatment of nonlinear vibration problems by a receptance-based approach. An important aspect is a new formulation for investigating the stability of the zero dynamics. The overall methodology possesses the usual benefits of the receptance method, namely that the system matrices (with associated assumptions and approximations) do not have to be known. In addition, it has the distinction of not requiring the form and parameter values of the nonlinearity when the input and output degrees of freedom are away from the nonlinearity itself. This represents a valuable advance over the conventional time-domain feedback linearisation approach.
Liu, Shibing; Yang, Bingen
2017-10-01
Flexible multistage rotor systems with water-lubricated rubber bearings (WLRBs) have a variety of engineering applications. Filling a technical gap in the literature, this effort proposes a method of optimal bearing placement that minimizes the vibration amplitude of a WLRB-supported flexible rotor system with a minimum number of bearings. In the development, a new model of WLRBs and a distributed transfer function formulation are used to define a mixed continuous-and-discrete optimization problem. To deal with the case of uncertain number of WLRBs in rotor design, a virtual bearing method is devised. Solution of the optimization problem by a real-coded genetic algorithm yields the locations and lengths of water-lubricated rubber bearings, by which the prescribed operational requirements for the rotor system are satisfied. The proposed method is applicable either to preliminary design of a new rotor system with the number of bearings unforeknown or to redesign of an existing rotor system with a given number of bearings. Numerical examples show that the proposed optimal bearing placement is efficient, accurate and versatile in different design cases.
Marichal, N.; Tomas-Rodriguez, M.; Hernandez, A.; Castillo, S; Campoy, P.
2014-01-01
In this paper, an intelligent control approach based on neuro-fuzzy systems performance is presented, with the objective of counteracting the vibrations that affect the low-cost vision platform onboard an unmanned aerial system of rotating nature. A scaled dynamical model of a helicopter is used to simulate vibrations on its fuselage. The impact of these vibrations on the low-cost vision system will be assessed and an intelligent control approach will be derived in order to reduce its detrime...
Active vibration control for underwater signature reduction of a navy ship
Basten, T.G.H.; Berkhoff, Arthur P.; Vermeulen, Ruud
2010-01-01
Dutch navy ships are designed and built to have a low underwater signature. For low frequencies however, tonal vibrations of a gearbox can occur, which might lead to increased acoustic signatures. These vibrations are hard to reduce by passive means. To investigate the possibilities of active
SOLUTION TO THE PROBLEM OF THERMOELASTIC VIBRATION OF A PLATE IN SPECIAL BOUNDARY CONDITIONS
Directory of Open Access Journals (Sweden)
Egorychev Oleg Aleksandrovich
2012-10-01
Full Text Available Operating conditions of uneven non-stationary heating can cause changes in physical and mechanical properties of materials. The awareness of the value and nature of thermal stresses is needed to perform a comprehensive analysis of structural strength. The authors provide their solution to the problem of identification of natural frequencies of vibrations of rectangular plates, whenever a thermal factor is taken into account. In the introductory section of the paper, the authors provide the equation describing the thermoelastic vibration of a plate and set the initial and boundary conditions. Furthermore, the authors provide a frequency equation derivation for the problem that has an analytical solution available (if all edges are simply supported at zero temperature. The equation derived by the authors has no analytical solution and can be solved only numerically. In the middle of the paper, the authors describe a method of frequency equation derivation for plates exposed to special boundary conditions, if the two opposite edges are simply supported at zero temperature, while the two other edges have arbitrary types of fixation and arbitrary thermal modes. For this boundary condition derived as a general solution, varying fixation of the two edges makes it possible to obtain transcendental trigonometric equations reducible to algebraic frequency equations by using expending in series. Thus, the obtaining frequency equations different from the general solution becomes possible for different types of boundary conditions. The final section of the paper covers the practical testing of the described method for the problem that has an analytical solution (all edges are simply supported at zero temperature as solved above. An approximate equation provided in the research leads to the analytical solution that is already available.
Vibration Anesthesia for Pain Reduction During Intralesional Steroid Injection for Keloid Treatment.
Park, Kui Young; Lee, Yohan; Hong, Ji Yeon; Chung, Won Soon; Kim, Myeung Nam; Kim, Beom Joon
2017-05-01
Patients suffer significant pain during intralesional steroid injection treatment for keloids and hypertrophic scars. Vibration anesthesia has been shown to effectively and safely alleviate pain sensations, likely by reducing pain transmission from peripheral receptors to the brain. The objective was to evaluate the efficacy, safety, and patient satisfaction associated with vibration anesthesia for reducing pain during intralesional corticosteroid injection. The authors recruited 40 patients with 58 keloids who were scheduled to undergo intralesional triamcinolone acetonide (TA) injections. Half of each keloid was injected with concomitant vibration anesthesia, whereas the other half was injected without vibration anesthesia. Pain experienced by patients during both procedures was assessed according to visual analog scale (VAS) score. The authors also assessed procedure safety. The mean VAS score during intralesional TA injection therapy without vibration was 5.88 ± 2.34. By contrast, the same patients yielded a mean VAS score during intralesional TA injection therapy with vibration of 3.28 ± 1.85; the difference between the mean scores was significant (p Vibration anesthesia is a promising option for reducing pain during keloid treatment with intralesional steroid injection.
Cazzulani, Gabriele; Resta, Ferruccio; Ripamonti, Francesco
2012-04-01
Large mechanical structures are often affected by high level vibrations due to their flexibility. These vibrations can reduce the system performances and lifetime and the use of active vibration control strategies becomes very attractive. In this paper a combination of resonant control and a disturbance estimator is proposed. This solution is able to improve the system performances during the transient motion and also to reject the disturbance forces acting on the system. Both control logics are based on a modal approach, since it allows to describe the structure dynamics considering only few degrees of freedom.
Model reduction for optimization of structural-acoustic coupling problems
DEFF Research Database (Denmark)
Creixell Mediante, Ester; Jensen, Jakob Søndergaard; Brunskog, Jonas
2016-01-01
Fully coupled structural-acoustic models of complex systems, such as those used in the hearing aid field, may have several hundreds of thousands of nodes. When there is a strong structure-acoustic interaction, performing optimization on one part requires the complete model to be taken into account......-acoustic coupling, for which two different approaches to constructing a modal reduction base are discussed. The efficiency and accuracy of the CMS and the MMR methods are strongly model-dependent; in this paper, they are compared for two optimization problems in the hearing aid context, where the MMR technique...... is found to be the most efficient, speeding up the optimizations up to 6 times compared to the full model....
Vibration Reduction Methods and Techniques for Rotorcraft Utilizing On-Blade Active Control Project
National Aeronautics and Space Administration — Rotor blades adapted for vibration control have the added benefit of extended blade and rotor life, as well as improved passenger comfort. Approaches that have been...
Higher harmonic control analysis for vibration reduction of helicopter rotor systems
Nguyen, Khanh Q.
1994-01-01
An advanced higher harmonic control (HHC) analysis has been developed and applied to investigate its effect on vibration reduction levels, blade and control system fatigue loads, rotor performance, and power requirements of servo-actuators. The analysis is based on a finite element method in space and time. A nonlinear time domain unsteady aerodynamic model, based on the indicial response formulation, is used to calculate the airloads. The rotor induced inflow is computed using a free wake model. The vehicle trim controls and blade steady responses are solved as one coupled solution using a modified Newton method. A linear frequency-domain quasi-steady transfer matrix is used to relate the harmonics of the vibratory hub loads to the harmonics of the HHC inputs. Optimal HHC is calculated from the minimization of the vibratory hub loads expressed in term of a quadratic performance index. Predicted vibratory hub shears are correlated with wind tunnel data. The fixed-gain HHC controller suppresses completely the vibratory hub shears for most of steady or quasi-steady flight conditions. HHC actuator amplitudes and power increase significantly at high forward speeds (above 100 knots). Due to the applied HHC, the blade torsional stresses and control loads are increased substantially. For flight conditions where the blades are stalled considerably, the HHC input-output model is quite nonlinear. For such cases, the adaptive-gain controller is effective in suppressing vibratory hub loads, even though HHC may actually increase stall areas on the rotor disk. The fixed-gain controller performs poorly for such flight conditions. Comparison study of different rotor systems indicates that a soft-inplane hingeless rotor requires less actuator power at high speeds (above 130 knots) than an articulated rotor, and a stiff-inplane hingeless rotor generally requires more actuator power than an articulated or a soft-inplane hingeless rotor. Parametric studies for a hingeless rotor
VIBRATION REDUCTION ON SINGLE-LINK FLEXIBLE MANIPULATOR USING H∞ CONTROL
Directory of Open Access Journals (Sweden)
Roberd Saragih
2012-06-01
Full Text Available This paper is concerned with the vibration and position control of a single link flexible manipulator. Robot link manipulators are widely used in various industrial applications. It is desirable to build light weight flexible manipulators. Light flexible manipulators have a variety of applications, most significantly in space exploration,manufacturing automation, construction, mining, and hazardous operation. Timoshenko beam theory is used to derive mathematical model of a flexible manipulator. The dynamic equations of motion are obtained using the Lagrange's formulation of dynamics.The H∞ controller is designed for vibration and position control of the system. Simulations are presented and show that vibration and position control of a single flexible link can be controlled with the designed H∞ controller.
Key Intermediates of Carbon Dioxide Reduction on Silver from Vibrational Nanospectroscopy
Jain, Prashant
2017-06-01
The design of efficacious, selective heterogeneous catalysts relies on the knowledge of the nature of active sites and reactive intermediates involved in the catalytic transformation. This is also true in the case of carbon dioxide reduction, an important scientific and technological problem. With the goal of furthering mechanistic understanding of a complex transformation that yields multiple products, we are employing surface enhanced Raman scattering (SERS) to image carbon dioxide photoreduction on individual Ag nanoparticles within a heterogeneous dispersion. The lack of ensemble-averaging is allowing us to detect fleeting intermediates in the adsorption and catalytic photoreduction processes. In particular, we have detected on some sites physisorbed CO_{2} and at others chemisorbed CO_{2}^{-} anion radical, a critical intermediate in carbon dioxide reduction. The primary product formed also appears to vary from one catalytic nanoparticle to another: CO, formaldehyde, or formic acid. The origin of such heterogeneities in adsorption and photoreduction behavior are being traced to differences in nanoparticle structure or surface composition, from which structure/activity relationships will be established, with aid from electronic structure theory. This single-nanoparticle approach is providing molecular-level insights into a broad range of industrially and environmentally relevant catalytic transformations.
A Simple Reduction Process for the Normal Vibrational Modes Occurring in Linear Molecules
McInerny, William
2005-01-01
The students in molecular spectroscopy courses are often required to determine the permitted normal vibrations for linear molecules that belong to particular groups. The reducible group representations generated by the use of Cartesian coordinates can be reduced by the use of a simple algebraic process applied to the group representations. The…
A unified control strategy for the active reduction of sound and vibration
Doelman, N.J.
1991-01-01
The generalized minimum variance (GMV) control strategy is proposed as an effective strategy for active sound and vibration control systems. The GMV strategy is shown to unify well-known adaptive filtering approaches based on LMS-type algorithms and purely feedback strategies as used in other types
Some problems of control of dynamical conditions of technological vibrating machines
Kuznetsov, N. K.; Lapshin, V. L.; Eliseev, A. V.
2017-10-01
The possibility of control of dynamical condition of the shakers that are designed for vibration treatment of parts interacting with granular media is discussed. The aim of this article is to develop the methodological basis of technology of creation of mathematical models of shake tables and the development of principles of formation of vibrational fields, estimation of their parameters and control of the structure vibration fields. Approaches to build mathematical models that take into account unilateral constraints, the relationships between elements, with the vibrating surface are developed. Methods intended to construct mathematical model of linear mechanical oscillation systems are used. Small oscillations about the position of static equilibrium are performed. The original method of correction of vibration fields by introduction of the oscillating system additional ties to the structure are proposed. Additional ties are implemented in the form of a mass-inertial device for changing the inertial parameters of the working body of the vibration table by moving the mass-inertial elements. The concept of monitoring the dynamic state of the vibration table based on the original measuring devices is proposed. Estimation for possible changes in dynamic properties is produced. The article is of interest for specialists in the field of creation of vibration technology machines and equipment.
Petrenko, Taras; Rauhut, Guntram
2017-03-28
Vibrational configuration interaction theory is a common method for calculating vibrational levels and associated IR and Raman spectra of small and medium-sized molecules. When combined with appropriate configuration selection procedures, the method allows the treatment of configuration spaces with up to 1010 configurations. In general, this approach pursues the construction of the eigenstates with significant contributions of physically relevant configurations. The corresponding eigenfunctions are evaluated in the subspace of selected configurations. However, it can easily reach the dimension which is not tractable for conventional eigenvalue solvers. Although Davidson and Lanczos methods are the methods of choice for calculating exterior eigenvalues, they usually fall into stagnation when applied to interior states. The latter are commonly treated by the Jacobi-Davidson method. This approach in conjunction with matrix factorization for solving the correction equation (CE) is prohibitive for larger problems, and it has limited efficiency if the solution of the CE is based on Krylov's subspace algorithms. We propose an iterative subspace method that targets the eigenvectors with significant contributions to a given reference vector and is based on the optimality condition for the residual norm corresponding to the error in the solution vector. The subspace extraction and expansion are modified according to these principles which allow very efficient calculation of interior vibrational states with a strong multireference character in different vibrational structure problems. The convergence behavior of the method and its performance in comparison with the aforementioned algorithms are investigated in a set of benchmark calculations.
Petrenko, Taras; Rauhut, Guntram
2017-03-01
Vibrational configuration interaction theory is a common method for calculating vibrational levels and associated IR and Raman spectra of small and medium-sized molecules. When combined with appropriate configuration selection procedures, the method allows the treatment of configuration spaces with up to 1010 configurations. In general, this approach pursues the construction of the eigenstates with significant contributions of physically relevant configurations. The corresponding eigenfunctions are evaluated in the subspace of selected configurations. However, it can easily reach the dimension which is not tractable for conventional eigenvalue solvers. Although Davidson and Lanczos methods are the methods of choice for calculating exterior eigenvalues, they usually fall into stagnation when applied to interior states. The latter are commonly treated by the Jacobi-Davidson method. This approach in conjunction with matrix factorization for solving the correction equation (CE) is prohibitive for larger problems, and it has limited efficiency if the solution of the CE is based on Krylov's subspace algorithms. We propose an iterative subspace method that targets the eigenvectors with significant contributions to a given reference vector and is based on the optimality condition for the residual norm corresponding to the error in the solution vector. The subspace extraction and expansion are modified according to these principles which allow very efficient calculation of interior vibrational states with a strong multireference character in different vibrational structure problems. The convergence behavior of the method and its performance in comparison with the aforementioned algorithms are investigated in a set of benchmark calculations.
Integrated vibration-based maintenance: an approach for continuous reduction in LCC. A case study
Energy Technology Data Exchange (ETDEWEB)
Najjar, B. [ER Konsult Utveckling AB, Vaexjoe (Sweden)
1998-12-31
The biggest thread in achieving and maintaining high equipment effectiveness can be stated as: whether the improved manufacturing processes capable of producing quality products at a competitive cost. The effect of a new vibration-based maintenance concept, called Total Quality Maintenance (TQMain), is introduced. It aims to make intensive use of the real-time data acquisition and analysis to detect causes behind product quality deviation and failures in machinery, and following defect development at an early stage to increase machine mean effective life and improve company`s economics. The effect of TQMain on LCC of machinery and company`s economics is discussed. A case study to reveal savings in maintenance cost when a vibration-based policy involved, is presented. Using TQMain, company`s economics can be improved effectively through continuous improvement of the technical and economic effectiveness of production processes. (orig.) 14 refs.
Assessment of FGPM shunt damping for vibration reduction of laminated composite beams
Lezgy-Nazargah, M.; Divandar, S. M.; Vidal, P.; Polit, O.
2017-02-01
This work addresses theoretical and finite element investigations of functionally graded piezoelectric materials (FGPMs) for shunted passive vibration damping of laminated composite beams. The properties of piezoelectric patches are assumed to vary through the thickness direction following the exponent or power law distribution in terms of the volume fractions of the constituent materials. By employing Hamilton's principle, the governing differential equations of motion are derived. The resulting system of equations of vibration is solved by employing an efficient three-nodded beam element which is based on a refined sinus piezoelectric model. The effects of effective electromechanical coupling coefficients (EEMCCs), different electric shunt circuits and different material compositions on the shunted damping performance are investigated. The optimal values of the electric components belonging to each shunt circuit are numerically determined.
Reduction of Ground Vibration by Means of Barriers or Soil Improvement along a Railway Track
DEFF Research Database (Denmark)
Andersen, Lars; Nielsen, Søren R.K.
2005-01-01
Trains running in built-up areas are a source to ground-borne noise. A careful design of the track may be one way of minimizing the vibrations in the surroundings. For example, open or infilled trenches may be constructed along the track, or the soil underneath the track may be improved. In this ......Trains running in built-up areas are a source to ground-borne noise. A careful design of the track may be one way of minimizing the vibrations in the surroundings. For example, open or infilled trenches may be constructed along the track, or the soil underneath the track may be improved...... is of paramount importance. For example, the response outside a shallow open trench may change dramatically when horizontal load is applied instead of vertical load....
Directory of Open Access Journals (Sweden)
Kwark Jong-Won
2015-01-01
Full Text Available The dynamic flexural behaviour of railway bridges is influenced by the torsional behaviour, and the flexural response tends to be amplified as the flexural natural frequency (the 1st vibrational mode and torsional frequency (the 2nd vibrational mode are adjoining. To avoid this phenomenon, the installation of concrete segment panels was considered for the reinforcement of torsional stiffness by connecting bottom flanges between girders. This alternative can increase the torsional stiffness by providing the restraint in torsional vibration and reduce the influence of torsional behaviour on the amplification of flexural responses. This study investigates the effect of the concrete segment panels on the control of torsional dynamic responses and on the increment of torsional frequency. The excitation tests on a full-size bridge specimen with 30 m span length were conducted with respect to the installation length of concrete panels up to 7 m from each ends. The results show that the installation of concrete segment panel augments the torsional frequency up to 22 % while the flexural frequency keeps its original value. It is concluded that the dynamic behaviour of girder bridges can be controlled by the adjustment of installation length of concrete panels, thereby reducing the torsional responses.
Dimension Reduction and Discretization in Stochastic Problems by Regression Method
DEFF Research Database (Denmark)
Ditlevsen, Ove Dalager
1996-01-01
The chapter mainly deals with dimension reduction and field discretizations based directly on the concept of linear regression. Several examples of interesting applications in stochastic mechanics are also given.Keywords: Random fields discretization, Linear regression, Stochastic interpolation...
A dimensionality reduction technique for scattering problems in photonics
Ivanova, Alyona; Stoffer, Remco; Lohmeyer, Manfred
2008-01-01
Optical scattering problems in guided wave photonics are addressed. We represent the unknown optical fields as superpositions of 1D slab modes bounded by PMLs. By applying a variational principle, the problems are reduced to lower dimensional systems of differential equations for the unknown
Energy Technology Data Exchange (ETDEWEB)
Hohenberg, Guenter [IVD Prof. Hohenberg GmbH, Graz (Austria); Beidl, Christian [Technische Univ. Darmstadt (Germany). VKM; Hoefler, Dieter [tectos gmbh, Graz (Austria)
2013-08-01
Plug-in hybrid drives will be, in the foreseeable future, the dominant variant for the electrification of vehicles, with the trend clearly pointing to combustion engines with a low number of cylinders and low engine operating speeds. However, the considerable torsional vibration and its impact on the drive train as well as the engine mount pose a problem. The conventional mechanical solutions with dual mass flywheels and pendulum support etc. have clearly reached their limit when it comes to improving the noise vibration harshness (NVH) behavior. Operating the drive engine with low speed values which are relevant for the fuel consumption is therefore only possible to a limited extent. This paper introduces a technique as a solution to the problem, where the excitation frequency can be doubled with the existing E-motor by generating additional torque pulses. This will achieve the excitation of the drive train and the engine mount as would be the case with a combustion engine with twice the number of cylinders. This technique, referred to as directE strategy, is particularly interesting for 2 und 3-cylinder engines. By combining the individual components into a highly integrated directE hybrid module a simple combination of existing combustion engines and gearboxes can be implemented. This paper describes the technique in more detail, which is followed by a discussion of its advantages, disadvantages and the first practical results. (orig.)
Directory of Open Access Journals (Sweden)
Fu-yao Zhao
2015-01-01
Full Text Available The rotary vibration of rigid friction pile can be seen approximately as a central symmetry plane problem in elasticity. The stress general solution of central symmetry plane problem in elasticity can be constructed by technique such as the Laurent expansion of the volume force. This solution has some decoupling, generalized, and convergent properties, and it can be used in stress analysis of the rotary vibration of pile. The analysis results show that the maximum value of displacement will not occur at the edge of the pile and the assumption that pile cross section remains unchanged is no longer applicable, if the value of one dimensionless quantity, reflecting the angular frequency of the rotation, radius, and material properties of the pile, is larger than 1.84. Once the rotary vibration of rigid friction pile happens, the pile may lose its bearing capacity under the comprehensive effect of normal and shear stress of the pile-soil interface and it will be very difficult to recover.
Complete reduction of the Euler-Poinsot problem
Deprit, Andre; Elipe, Antonio
1993-10-01
We propose a new way of defining the Serret-Andoyer variables that does not call on spherical trigonometry. We use those variables to present a complete solution of the Euler-Poinsot problem in the phase space determined by the components of the angular momentum along the principal axes of inertia. We use the solution to convert directly the Serret-Andoyer variables into action and angle variables, thereby making the Hamiltonian dependent on only two momenta.
Vibration Reduction of Wind Turbines Using Tuned Liquid Column Damper Using Stochastic Analysis
Alkmim, M. H.; de Morais, M. V. G.; Fabro, A. T.
2016-09-01
Passive energy dissipation systems encompass a range of materials and devices for enhancing damping. They can be used both for natural hazard mitigation and for rehabilitation of aging or deficient structures. Among the current passive energy dissipation systems, tuned liquid column damper (TLCD), a class of passive control that utilizes liquid in a “U” shape reservoir to control structural vibration of the primary system, has been widely researched in a variety of applications. This paper focus in TLCD application for wind turbines presenting the mathematical model as well as the methods used to overcome the nonlinearity embedded in the system. Optimization methods are used to determine optimum parameters of the system. Additionally, a comparative analysis is done considering the equivalent linearized system and the nonlinear system under random excitation with the goal of compare the nonlinear model with the linear equivalent and investigated the effectiveness of the TLCD. The results are shown using two types of random excitation, a white noise and a first order filters spectrum, the latter presents more satisfactory results since the excitation spectrum is physically more realistic than white noise spectrum model. The results indicate that TLCDs at optimal tuning can significantly dissipate energy of the primary structure between 3 to 11%.
Takahata, Ryoichi; Wakui, Shinichi; Miyata, Kenji; Noma, Keiji; Senoo, Masaharu
Recently, global warming and the problem with successfully incorporating environmental safeguards have promoted the need for a more power-efficient motor. Therefore, as a driving source, permanent magnet synchronous motor (PMSM) with concentrated winding is widely used as the important device for a variety of fields. However, a PMSM with concentrated winding generates more vibrations than that with distributed winding because of a radial electromagnetic force. This paper describes the influence of a new skewed rotor on the characteristics of a concentrated winding PMSM. We investigated the influence by using a three-dimensional finite element analysis (3-D FEM) and several measurements. In addition, we presented that the proposed rotor is effective in reducing the radial electromagnetic force without decreasing the motor efficiency.
A finite-dimensional reduction method for slightly supercritical elliptic problems
Directory of Open Access Journals (Sweden)
Riccardo Molle
2004-01-01
Full Text Available We describe a finite-dimensional reduction method to find solutions for a class of slightly supercritical elliptic problems. A suitable truncation argument allows us to work in the usual Sobolev space even in the presence of supercritical nonlinearities: we modify the supercritical term in such a way to have subcritical approximating problems; for these problems, the finite-dimensional reduction can be obtained applying the methods already developed in the subcritical case; finally, we show that, if the truncation is realized at a sufficiently large level, then the solutions of the approximating problems, given by these methods, also solve the supercritical problems when the parameter is small enough.
Directory of Open Access Journals (Sweden)
Mahmoud Bayat
Full Text Available This review features a survey of some recent developments in asymptotic techniques and new developments, which are valid not only for weakly nonlinear equations, but also for strongly ones. Further, the achieved approximate analytical solutions are valid for the whole solution domain. The limitations of traditional perturbation methods are illustrated, various modified perturbation techniques are proposed, and some mathematical tools such as variational theory, homotopy technology, and iteration technique are introduced to over-come the shortcomings.In this review we have applied different powerful analytical methods to solve high nonlinear problems in engineering vibrations. Some patterns are given to illustrate the effectiveness and convenience of the methodologies.
Rahman, Md. Saifur; Lee, Yiu-Yin
2017-10-01
In this study, a new modified multi-level residue harmonic balance method is presented and adopted to investigate the forced nonlinear vibrations of axially loaded double beams. Although numerous nonlinear beam or linear double-beam problems have been tackled and solved, there have been few studies of this nonlinear double-beam problem. The geometric nonlinear formulations for a double-beam model are developed. The main advantage of the proposed method is that a set of decoupled nonlinear algebraic equations is generated at each solution level. This heavily reduces the computational effort compared with solving the coupled nonlinear algebraic equations generated in the classical harmonic balance method. The proposed method can generate the higher-level nonlinear solutions that are neglected by the previous modified harmonic balance method. The results from the proposed method agree reasonably well with those from the classical harmonic balance method. The effects of damping, axial force, and excitation magnitude on the nonlinear vibrational behaviour are examined.
National Research Council Canada - National Science Library
Slep, Amy
2004-01-01
This project aims to enhance the capacity of the Air Force (AP) to reduce death, injury, and degraded force readiness via reduction of he prevalence and impact of family - maltreatment, suicidality, and alcohol/drug problems...
Directory of Open Access Journals (Sweden)
Zhengchao Xie
2009-01-01
Full Text Available Due to the large number of design variables that can be present in complex systems incorporating visco-elastic damping, this work examines the application of genetic algorithms in optimizing the response of these structures. To demonstrate the applicability of genetic algorithms (GAs, the approach is applied to a simple viscoelastically damped constrained-layer beam. To that end, a finite element model (FEM derived by Zapfe, which was based on Rao's formulation, was used for a beam with constrained-layer damping. Then, a genetic algorithm is applied to simultaneously determine the thicknesses of the viscoelastic damping layer and the constraining layer that provide the best response. While the targeted response is ultimately at the discretion of the designer, a few different choices for the fitness function are shown along with their corresponding impact on the vibratory response. By integrating the FEM code within the GA routine, it is easier to include the frequency-dependence of both the shear modulus and the loss factors for the viscoelastic layer. Examples are provided to demonstrate the capabilities of the method. It is shown that while a multi-mode optimization target provides significant reductions, the response for that configuration is inferior to the response when only single-mode reduction is considered. The results also reveal that the optimum configuration has a lower response level than when a thick layer of damping material is used. By demonstrating the applicability of GA for a simple beam structure, the approach can be extended to more complex damped structures.
Theory of vibration protection
Karnovsky, Igor A
2016-01-01
This text is an advancement of the theory of vibration protection of mechanical systems with lumped and distributed parameters. The book offers various concepts and methods of solving vibration protection problems, discusses the advantages and disadvantages of different methods, and the fields of their effective applications. Fundamental approaches of vibration protection, which are considered in this book, are the passive, parametric and optimal active vibration protection. The passive vibration protection is based on vibration isolation, vibration damping and dynamic absorbers. Parametric vibration protection theory is based on the Shchipanov-Luzin invariance principle. Optimal active vibration protection theory is based on the Pontryagin principle and the Krein moment method. The book also contains special topics such as suppression of vibrations at the source of their occurrence and the harmful influence of vibrations on humans. Numerous examples, which illustrate the theoretical ideas of each chapter, ar...
Schindler, Holly Reed; Horner, Robert H.
2005-01-01
The effects of functional communication training on the generalized reduction of problem behavior with three 4- to 5-year-old children with autism and problem behavior were evaluated. Participants were assessed in primary teaching settings and in three secondary, generalization settings. Through baseline analysis, lower effort interventions in the…
Directory of Open Access Journals (Sweden)
M Pomarède
2016-09-01
Full Text Available Numerical simulation of Vortex-Induced-Vibrations (VIV of a rigid circular elastically-mounted cylinder submitted to a fluid cross-flow has been extensively studied over the past decades, both experimentally and numerically, because of its theoretical and practical interest for understanding Flow-Induced-Vibrations (FIV problems. In this context, the present article aims to expose a numerical study based on fully-coupled fluid-solid computations compared to previously published work [34], [36]. The computational procedure relies on a partitioned method ensuring the coupling between fluid and structure solvers. The fluid solver involves a moving mesh formulation for simulation of the fluid structure interface motion. Energy exchanges between fluid and solid models are ensured through convenient numerical schemes. The present study is devoted to a low Reynolds number configuration. Cylinder motion magnitude, hydrodynamic forces, oscillation frequency and fluid vortex shedding modes are investigated and the “lock-in” phenomenon is reproduced numerically. These numerical results are proposed for code validation purposes before investigating larger industrial applications such as configurations involving tube arrays under cross-flows [4].
Lecoq, D.; Pézerat, C.; Thomas, J.-H.; Bi, W. P.
2014-06-01
An improvement of the Force Analysis Technique (FAT), an inverse method of vibration, is proposed to identify the low wavenumbers including the acoustic component of a turbulent flow that excites a plate. This method is a significant progress since the usual techniques of measurements with flush-mounted sensors are not able to separate the acoustic and the aerodynamic energies of the excitation because the aerodynamic component is too high. Moreover, the main cause of vibration or acoustic radiation of the structure might be due to the acoustic part by a phenomenon of spatial coincidence between the acoustic wavelengths and those of the plate. This underlines the need to extract the acoustic part. In this work, numerical experiments are performed to solve both the direct and inverse problems of vibration. The excitation is a turbulent boundary layer and combines the pressure field of the Corcos model and a diffuse acoustic field. These pressures are obtained by a synthesis method based on the Cholesky decomposition of the cross-spectra matrices and are used to excite a plate. Thus, the application of the inverse problem FAT that requires only the vibration data shows that the method is able to identify and to isolate the acoustic part of the excitation. Indeed, the discretization of the inverse operator (motion equation of the plate) acts as a low-pass wavenumber filter. In addition, this method is simple to implement because it can be applied locally (no need to know the boundary conditions), and measurements can be carried out on the opposite side of the plate without affecting the flow. Finally, an improvement of FAT is proposed. It regularizes optimally and automatically the inverse problem by analyzing the mean quadratic pressure of the reconstructed force distribution. This optimized FAT, in the case of the turbulent flow, has the advantage of measuring the acoustic component up to higher frequencies even in the presence of noise. the aerodynamic component
The Shock and Vibration Bulletin. Part 4. Underwater Problems, Environments and Measurements
1974-08-01
CENTER OF PERCUSSION ROADARM DESIGN D.D. Ustick, U.S. Army Tank-Automotive Command, Warren, Michigan SYNCHRONIZATION AND PHASE ANGLE OF TWO...OF MECHANICAL IMPEDANCE CONCEPTS TO THE COUPLING PROBLEM OF STRUCTURES IN SHOCK ENVIRONMENT Robert AQUILINA Centre d"Etudes et Recherches...French submarines. Measu- rements are extended to the low frequency range with percussion excitation. HI - MODAL IDENTIFICATION OF THE FIXED BASE
A spectral dynamic stiffness method for free vibration analysis of plane elastodynamic problems
Liu, X.; Banerjee, J. R.
2017-03-01
A highly efficient and accurate analytical spectral dynamic stiffness (SDS) method for modal analysis of plane elastodynamic problems based on both plane stress and plane strain assumptions is presented in this paper. First, the general solution satisfying the governing differential equation exactly is derived by applying two types of one-dimensional modified Fourier series. Then the SDS matrix for an element is formulated symbolically using the general solution. The SDS matrices are assembled directly in a similar way to that of the finite element method, demonstrating the method's capability to model complex structures. Any arbitrary boundary conditions are represented accurately in the form of the modified Fourier series. The Wittrick-Williams algorithm is then used as the solution technique where the mode count problem (J0) of a fully-clamped element is resolved. The proposed method gives highly accurate solutions with remarkable computational efficiency, covering low, medium and high frequency ranges. The method is applied to both plane stress and plane strain problems with simple as well as complex geometries. All results from the theory in this paper are accurate up to the last figures quoted to serve as benchmarks.
González Cornejo, Felipe A.; Cruchaga, Marcela A.; Celentano, Diego J.
2017-11-01
The present work reports a fluid-rigid solid interaction formulation described within the framework of a fixed-mesh technique. The numerical analysis is focussed on the study of a vortex-induced vibration (VIV) of a circular cylinder at low Reynolds number. The proposed numerical scheme encompasses the fluid dynamics computation in an Eulerian domain where the body is embedded using a collection of markers to describe its shape, and the rigid solid's motion is obtained with the well-known Newton's law. The body's velocity is imposed on the fluid domain through a penalty technique on the embedded fluid-solid interface. The fluid tractions acting on the solid are computed from the fluid dynamic solution of the flow around the body. The resulting forces are considered to solve the solid motion. The numerical code is validated by contrasting the obtained results with those reported in the literature using different approaches for simulating the flow past a fixed circular cylinder as a benchmark problem. Moreover, a mesh convergence analysis is also done providing a satisfactory response. In particular, a VIV problem is analyzed, emphasizing the description of the synchronization phenomenon.
Lyashko, A. D.
2017-11-01
A new analytical presentation of the solution for steady-state oscillations of orthotopic rectangular prism is found. The corresponding infinite system of linear algebraic equations has been deduced by the superposition method. A countable set of precise eigenfrequencies and elementary eigenforms is found. The identities are found which make it possible to improve the convergence of all the infinite series in the solution of the problem. All the infinite series in presentation of solution are analytically summed up. Numerical calculations of stresses in the rectangular orthotropic prism with a uniform along the border and harmonic in time load on two opposite faces have been performed.
An Integral Equation Method for the First-Passage Problem in Random Vibration
DEFF Research Database (Denmark)
Madsen, Peter Hauge; Krenk, Steen
1984-01-01
The first-passage problem for a nonstationary stochastic process is formulated as an integral identity, which produces known bounds and series expansions as special cases, while approximation of the kernel leads to an integral equation for the first-passage probability density function. An accurate......, explicit approximation formula for the kernel is derived, and the influence of uni or multi modal frequency content of the process is investigated. Numerical results provide comparisons with simulation results and alternative methods for narrow band processes, and also the case of a multimodal...
Turtles all the way down? Psychometric approaches to the reduction problem
Kievit, R.A.
2014-01-01
The question of how different explanatory levels in scientific inquiry are related to each other is known as the reduction problem. This thesis focuses on a specific domain of this question, namely how we should relate brains to (psychological) behaviour. The central position of this thesis is that
An Inverse Eigenvalue Problem for a Vibrating String with Two Dirichlet Spectra
Rundell, William
2013-04-23
A classical inverse problem is "can you hear the density of a string clamped at both ends?" The mathematical model gives rise to an inverse Sturm-Liouville problem for the unknown density ñ, and it is well known that the answer is negative: the Dirichlet spectrum from the clamped end-point conditions is insufficient. There are many known ways to add additional information to gain a positive answer, and these include changing one of the boundary conditions and recomputing the spectrum or giving the energy in each eigenmode-the so-called norming constants. We make the assumption that neither of these changes are possible. Instead we will add known mass-densities to the string in a way we can prescribe and remeasure the Dirichlet spectrum. We will not be able to answer the uniqueness question in its most general form, but will give some insight to what "added masses" should be chosen and how this can lead to a reconstruction of the original string density. © 2013 Society for Industrial and Applied Mathematics.
Directory of Open Access Journals (Sweden)
Uğbreve;ur Dalli
2011-01-01
Full Text Available An active control method utilizing the multiple trailing edge flap configuration for rotorcraft vibration suppression and blade loads control is presented. A comprehensive model for rotor blade with active trailing edge flaps is used to calculate the vibration characteristics, natural frequencies and mode shapes of any complex composite helicopter rotor blade. A computer program is developed to calculate the system response, rotor blade root forces and moments under aerodynamic forcing conditions. Rotor blade system response is calculated using the proposed solution method and the developed program depending on any structural and aerodynamic properties of rotor blades, structural properties of trailing edge flaps and properties of trailing edge flap actuator inputs. Rotor blade loads are determined first on a nominal rotor blade without multiple active trailing edge flaps and then the effects of the active flap motions on the existing rotor blade loads are investigated. Multiple active trailing edge flaps are controlled by using open loop controllers to identify the effects of the actuator signal output properties such as frequency, amplitude and phase on the system response. Effects of using multiple trailing edge flaps on controlling rotor blade vibrations are investigated and some design criteria are determined for the design of trailing edge flap controller that will provide actuator signal outputs to minimize the rotor blade root loads. It is calculated that using the developed active trailing edge rotor blade model, helicopter rotor blade vibrations can be reduced up to 36% of the nominal rotor blade vibrations.
Directory of Open Access Journals (Sweden)
Khomenko Andrei P.
2018-01-01
Full Text Available The article deals with the development of mathematical models and evaluation criteria of the vibration field in the dynamic interactions of the elements of the vibrational technological machines for the processes of vibrational strengthening of long-length parts with help of a steel balls working medium. The study forms a theoretical understanding of the modes of motions of material particles in interaction with a vibrating surface of the working body of the vibration machine. The generalized approach to the assessment of the dynamic quality of the work of vibrating machines in multiple modes of tossing, when the period of free flight of particles is a multiple of the period of the surface oscillations of the working body, is developed in the article. For the correction of vibration field of the working body, the characteristics of dynamic interactions of granular elements of the medium are taken into account using original sensors. The sensors that can detect different particularities of interaction of the granular medium elements at different points of the working body are proposed to evaluate the deviation from a homogeneous and one-dimensional mode of vibration field. Specially developed sensors are able to register interactions between a single granule, a system of granules in filamentous structures, and multipoint interactions of the elements in a close-spaced cylindrical structure. The system of regularization of the structure of vibration fields based on the introduction of motion translation devices is proposed using the multi-point sensor locations on the working body. The article refers to analytical approaches of the theory of vibration displacements. For the experimental data assessment, the methods of statistical analysis are applied. It is shown that the peculiar features of the motion of granular medium registered by the sensors can be used to build active control systems of field vibration.
Schwenke, David W.
1992-01-01
The optimization of the wave functions is considered for coupled vibrations represented by linear combinations of products of functions depending only on a single vibrational coordinate. The functions themselves are optimized as well as configuration list. For the H2O molecule highly accurate results are obtained for the lowest 15 levels using significantly shorter expansions than would otherwise be possible.
Directory of Open Access Journals (Sweden)
Khayam-Bashi
2009-07-01
Full Text Available Introduction: Delayed Onset Muscle Soreness (DOMS is a common strain resulting during therapeutic exercise with eccentric contractions. This pain can result in loss of interest by the patient and eventually in cancellation of the routine. The purpose of the present study was to determine whether vibration could have an affect on delayed onset muscle soreness. We hypothesized that the vibration training would decrease DOMS. Methods: Subjects comprised of 30 male athletes aged 18-26 years. The athletes were involved in regular sports activities since at least three years. Subjects were assigned randomly into two VT (n=15 and Non-VT (n=15 groups. The measurements included the flexed knee angle (FANG, pressure pain threshold (PPT, muscle soreness (SOR of right quadriceps muscle and maximal isometric force (MIF of both quadriceps muscles together (Base-line. A vibrator was used to apply 50 Hz vibration on the left and right quadriceps muscles for 1 min in the VT group. Then both groups trained eccentric exercise. All parameters were determined again 24 hours post-exercise (After- activity. Results: All subjects showed a loss in MIF, decrease in PPT, FANG and increase in SOR 24h after eccentric exercise (p=0/000. But the parameters were statistically significantly different in the VT and Non-VT groups [MIF (p=0/000, PPT (p=0/001, FANG (p=0/02, SOR (p=0/003]. Conclusion: Therapeutic exercise with eccentric contractions results in DOMS, but vibration training before exercise is effective and beneficial in decreasing DOMS.
Energy Technology Data Exchange (ETDEWEB)
Teng, C. [Carrier Corp., Indianapolis, IN (United States); Reynolds, D.D. [Univ. of Nevada, Las Vegas, NV (United States). Dept. of Mechanical Engineering
1998-10-01
Vibration modes associated with a fan impeller, motor, and motor mounting assembly in small air-conditioning units can be excited by motor torque pulsations in single-phase motors. Experimental procedures were developed that can be used to measure the torsional resonance frequencies of the stationary parts (motor stator and motor mounting assembly) and the rotating parts (fan impeller and motor rotor and shaft assembly) of a propeller fan assembly. Impact test procedures, test procedures in which the fan motor is set up to act as a torsional shaker, and procedures that employ the use of a microphone in an anechoic room are presented in this paper.
Vibration of hydraulic machinery
Wu, Yulin; Liu, Shuhong; Dou, Hua-Shu; Qian, Zhongdong
2013-01-01
Vibration of Hydraulic Machinery deals with the vibration problem which has significant influence on the safety and reliable operation of hydraulic machinery. It provides new achievements and the latest developments in these areas, even in the basic areas of this subject. The present book covers the fundamentals of mechanical vibration and rotordynamics as well as their main numerical models and analysis methods for the vibration prediction. The mechanical and hydraulic excitations to the vibration are analyzed, and the pressure fluctuations induced by the unsteady turbulent flow is predicted in order to obtain the unsteady loads. This book also discusses the loads, constraint conditions and the elastic and damping characters of the mechanical system, the structure dynamic analysis, the rotor dynamic analysis and the system instability of hydraulic machines, including the illustration of monitoring system for the instability and the vibration in hydraulic units. All the problems are necessary for vibration pr...
Human population reduction is not a quick fix for environmental problems.
Bradshaw, Corey J A; Brook, Barry W
2014-11-18
The inexorable demographic momentum of the global human population is rapidly eroding Earth's life-support system. There are consequently more frequent calls to address environmental problems by advocating further reductions in human fertility. To examine how quickly this could lead to a smaller human population, we used scenario-based matrix modeling to project the global population to the year 2100. Assuming a continuation of current trends in mortality reduction, even a rapid transition to a worldwide one-child policy leads to a population similar to today's by 2100. Even a catastrophic mass mortality event of 2 billion deaths over a hypothetical 5-y window in the mid-21(st) century would still yield around 8.5 billion people by 2100. In the absence of catastrophe or large fertility reductions (to fewer than two children per female worldwide), the greatest threats to ecosystems--as measured by regional projections within the 35 global Biodiversity Hotspots--indicate that Africa and South Asia will experience the greatest human pressures on future ecosystems. Humanity's large demographic momentum means that there are no easy policy levers to change the size of the human population substantially over coming decades, short of extreme and rapid reductions in female fertility; it will take centuries, and the long-term target remains unclear. However, some reduction could be achieved by midcentury and lead to hundreds of millions fewer people to feed. More immediate results for sustainability would emerge from policies and technologies that reverse rising consumption of natural resources.
Directory of Open Access Journals (Sweden)
Chen Ying Jie
2016-01-01
Full Text Available In this paper, with the principle of least action with variables to solve the problems of forced vibration of the Rectangular plate with three clamped and the other free with concentrated load, and the stable solution can be worked out. We can compare the results with the literate; it also can be proved to be true. So the results by calculating not only it have important academic value, but also it can be directly referred in the actual work.
Two-Aircraft optimal control problem. The in-flight noise reduction*, **
Directory of Open Access Journals (Sweden)
Ndimubandi Jean
2012-04-01
Full Text Available The aim of this paper is to present and solve a mathematical model of a two-aircraft optimal control problem reducing the noise on the ground during the approach. The mathematical modelization of this problem is a non-convex optimal control governed by ordinary non-linear differential equations. To solve this problem, A direct method and a Runge-Kutta RK4 discretization schema are used. This discretization schema is chosed because it is a sufficiently high order and it does-not require computation of the partial derivatives of the aircraft dynamic. The Nonlinear Interior point Trust Region Optimization solver KNITRO is applied. A large set of numerical experiments is presented. The obtained results give feasible trajectories with a significant noise reduction.
Flow distribution and tube vibration in heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Anderson, H.L.
1985-07-01
A project was initiated to study flow distribution and tube vibration in heat exchangers. An experimental program was carried out on a full-size heat exchanger in four test phases of parametric study. The flow induced vibration data were used to quantify and develop non-intrusive vibration monitoring techniques for online problem evaluation and to study the influence of design features and conditions on the vibration. The in-tube vibration data obtained have shown that the vibroacoustic and microphone monitoring techniques to be reliable and accurate methods for the detection of tube impacting in an operating heat exchanger. Development of work on the use of a two-accelerator vibroacoustic technique for the location of impacting zones in a bundle showed promise and is currently being employed in the field. The in-tube vibration data have demonstrated the effects that changes in the design of a bundle can have on tube vibration in that bundle. These results indicate that an important factor in bundle design is the local flow distribution in areas of high vibration susceptibility. The in-tube data have demonstrated that tubes in zones other than the inlet region can be susceptible to a form of periodic resonant excitation. This observation has implications for cases where flow reduction is implemented to avoid an instability problem. Such a reduction could bring the tube bundle into a flow regime where it is susceptible to the resonant excitation. 10 refs., 55 figs., 4 tabs.
Dickson, Laurie M.; Derevensky, Jeffrey L.; Gupta, Rina
2004-01-01
Despite the growing popularity of the harm reduction approach in the field of adolescent alcohol and substance abuse, a harm reduction approach to prevention and treatment of youth problem gambling remains largely unexplored. This article poses the question of whether the harm reduction paradigm is a promising approach to the prevention of…
Bao, Xingxian; Cao, Aixia; Zhang, Jing
2016-07-01
Modal parameters estimation plays an important role for structural health monitoring. Accurately estimating the modal parameters of structures is more challenging as the measured vibration response signals are contaminated with noise. This study develops a mathematical algorithm of solving the partially described inverse singular value problem (PDISVP) combined with the complex exponential (CE) method to estimate the modal parameters. The PDISVP solving method is to reconstruct an L2-norm optimized (filtered) data matrix from the measured (noisy) data matrix, when the prescribed data constraints are one or several sets of singular triplets of the matrix. The measured data matrix is Hankel structured, which is constructed based on the measured impulse response function (IRF). The reconstructed matrix must maintain the Hankel structure, and be lowered in rank as well. Once the filtered IRF is obtained, the CE method can be applied to extract the modal parameters. Two physical experiments, including a steel cantilever beam with 10 accelerometers mounted, and a steel plate with 30 accelerometers mounted, excited by an impulsive load, respectively, are investigated to test the applicability of the proposed scheme. In addition, the consistency diagram is proposed to exam the agreement among the modal parameters estimated from those different accelerometers. Results indicate that the PDISVP-CE method can significantly remove noise from measured signals and accurately estimate the modal frequencies and damping ratios.
Variance reduction techniques for 14 MeV neutron streaming problem in rectangular annular bent duct
Energy Technology Data Exchange (ETDEWEB)
Ueki, Kotaro [Ship Research Inst., Mitaka, Tokyo (Japan)
1998-03-01
Monte Carlo method is the powerful technique for solving wide range of radiation transport problems. Its features are that it can solve the Boltzmann`s transport equation almost without approximation, and that the complexity of the systems to be treated rarely becomes a problem. However, the Monte Carlo calculation is always accompanied by statistical errors called variance. In shielding calculation, standard deviation or fractional standard deviation (FSD) is used frequently. The expression of the FSD is shown. Radiation shielding problems are roughly divided into transmission through deep layer and streaming problem. In the streaming problem, the large difference in the weight depending on the history of particles makes the FSD of Monte Carlo calculation worse. The streaming experiment in the 14 MeV neutron rectangular annular bent duct, which is the typical streaming bench mark experiment carried out of the OKTAVIAN of Osaka University, was analyzed by MCNP 4B, and the reduction of variance or FSD was attempted. The experimental system is shown. The analysis model by MCNP 4B, the input data and the results of analysis are reported, and the comparison with the experimental results was examined. (K.I.)
Mallick, Rajnish; Ganguli, Ranjan; Seetharama Bhat, M.
2015-09-01
The objective of this study is to determine an optimal trailing edge flap configuration and flap location to achieve minimum hub vibration levels and flap actuation power simultaneously. An aeroelastic analysis of a soft in-plane four-bladed rotor is performed in conjunction with optimal control. A second-order polynomial response surface based on an orthogonal array (OA) with 3-level design describes both the objectives adequately. Two new orthogonal arrays called MGB2P-OA and MGB4P-OA are proposed to generate nonlinear response surfaces with all interaction terms for two and four parameters, respectively. A multi-objective bat algorithm (MOBA) approach is used to obtain the optimal design point for the mutually conflicting objectives. MOBA is a recently developed nature-inspired metaheuristic optimization algorithm that is based on the echolocation behaviour of bats. It is found that MOBA inspired Pareto optimal trailing edge flap design reduces vibration levels by 73% and flap actuation power by 27% in comparison with the baseline design.
Basok, B. I.; Gotsulenko, V. V.; Gotsulenko, V. N.
2012-11-01
The reason for the decrease in the amplitude of longitudinal vibration combustion self-oscillations in the combustion chamber of a liquid-propellant rocket engine by means of antipulse partitions has been justified. A mathematical model of the development of combustion instability in such a chamber on attachment of a Helmholtz resonator to it has been obtained. The character of the damping of vibration combustion self-oscillations excited by the action of the Crocco mechanisms and negative thermal resistance, when varying the acoustic parameters of the resonator and of the pressure head characteristics of combustion chamber is established.
Liang, Shuang; Zhang, Liang; Jiang, Feng
2016-09-01
Nitrate dosing is commonly used to control hydrogen sulfide production in sewer systems. However, quick rebound of the sulfide concentration after nitrate depletion has been observed and results in more serious odor and corrosion problem. To investigate the mechanism of sulfide regeneration in the nitrate-free period, a laboratory-scale sewer reactor was run for 30 days to simulate sulfide production and oxidation with intermittent nitrate addition. The results show that nitrate addition substantially reduced the sulfide concentration, but the produced elemental sulfur was then quickly reduced back to sulfide in nitrate-free periods. This induced more and more sulfide production in the sewer reactor. Elemental sulfur and polysulfide reductions were found in the sewage in nitrate-free periods, showing their contributions to the sulfide regeneration. Through batch tests, polysulfide was confirmed as the key intermediate for accelerating sulfur reduction during the nitrate-free period in the sewer. Sulfide production rates significantly increased by 65% and 59% in the presences of tetrasulfide and sulfur with sulfide, respectively, at the beginning of the test. While polysulfide formation was prevented by the ferrous chloride addition, the sulfur reduction rate remarkably decreased from 12.8 mgS/L-h to 1.8 mgS/L-h. This indicates that direct sulfur reduction was significantly slower than the indirect sulfur reduction via polysulfide; the latter process could be the cause for the quick rebound of the sulfide concentration in the sewer with intermittent nitrate dosing. Thus, the pathways of sulfur transformations in a sewer, both in the presence and absence of nitrate, were proposed. Microbial community analysis results reveal that some common sulfate-reducing bacteria (SRB) genera in sewer sediment were possible sulfur reducers. According to this finding, the effect and strategy of nitrate dosing for hydrogen sulfide control in sewers should be re-evaluated and re
Less reduction of psychosocial problems among adolescents with unmet communication needs.
Jager, Margot; Reijneveld, Sijmen A; Almansa, Josue; Metselaar, Janneke; Knorth, Erik J; De Winter, Andrea F
2017-04-01
Patient-professional communication has been suggested to be a major determinant of treatment outcomes in psychosocial care for children and adolescents. However, the mechanisms involved are largely unknown and no longitudinal studies have been performed. Our aim was, therefore, to assess over the course of 1 year, the impact of patient-centered communication on psychosocial problems of adolescents in psychosocial care, including the routes mediating this impact. We obtained data on 315 adolescents, aged 12-18 years, enrolled in child and adolescent social or mental health care. We assessed patient-centered communication by comparing the needs and experiences of adolescents with regard to three aspects of communication: affective quality, information provision, and shared decision-making. Changes in psychosocial problems comprised those reported by adolescents and their parents between baseline and 1 year thereafter. Potential mediators were treatment adherence, improvement of understanding, and improvement in self-confidence. We found a relationship between unmet needs for affective quality, information provision, and shared decision-making and less reduction of psychosocial problems. The association between the unmet need to share in decision-making and less reduction of psychosocial problems were partially mediated by less improvement in self-confidence (30 %). We found no mediators regarding affective quality and information provision. Our findings confirm that patient-centered communication is a major determinant of treatment outcomes in psychosocial care for adolescents. Professionals should be aware that tailoring their communication to individual patients' needs is vital to the effectiveness of psychosocial care.
Ding, Ruqi; Xu, Bing; Zhang, Junhui; Cheng, Min
2017-08-01
Independent metering control systems are promising fluid power technologies compared with traditional valve controlled systems. By breaking the mechanical coupling between the inlet and outlet, the meter-out valve can open as large as possible to reduce energy consumptions. However, the lack of damping in outlet causes stronger vibrations. To address the problem, the paper designs a hybrid control method combining dynamic pressure-feedback and active damping control. The innovation resides in the optimization of damping by introducing pressure feedback to make trade-offs between high stability and fast response. To achieve this goal, the dynamic response pertaining to the control parameters consisting of feedback gain and cut-off frequency, are analyzed via pole-zero locations. Accordingly, these parameters are tuned online in terms of guaranteed dominant pole placement such that the optimal damping can be accurately captured under a considerable variation of operating conditions. The experiment is deployed in a mini-excavator. The results pertaining to different control parameters confirm the theoretical expectations via pole-zero locations. By using proposed self-tuning controller, the vibrations are almost eliminated after only one overshoot for different operation conditions. The overshoots are also reduced with less decrease of the response time. In addition, the energy-saving capability of independent metering system is still not affected by the improvement of controllability.
Directory of Open Access Journals (Sweden)
Egorychev Oleg Aleksandrovich
2012-10-01
Full Text Available Operating conditions of uneven heating can cause changes in the physical and mechanical properties of materials. Awareness of the values and nature of thermal stresses are required for a comprehensive structural strength analysis. The authors propose their solution to the problem of identification of natural frequencies of vibrations of rectangular plates using a thermal factor. The introductory part of the paper covers the derivation of equations of (a the thermoelastic vibration of a plate, (b initial and boundary conditions. In the next part of the paper, the authors describe a method of frequency equation derivation for plates exposed to special boundary conditions, if the two opposite edges of the plate are simply supported, the temperature of the plate surface is equal to zero degrees Celsius, while the two other edges have an arbitrary type of fixation and an arbitrary thermal mode. The authors have derived a general solution for the above boundary conditions, and by altering the method of fixation of the two edges of a plate, the authors obtain transcendental trigonometric equations reducible to algebraic frequency equations by using expanding in series. Thus, derivation of frequency equations different from the general solution is feasible for various types of boundary conditions. The final part of the paper contains a derivation of the solution to the selected problem using the proposed method. The results demonstrate that the thermoelastic plate has four natural frequencies, two of them being equal to the frequencies of a plate free from the temperature influence, while the other two are close to the frequency of free vibrations of a plate.
Model Reduction of a 2-Dimenional Sedimentary Texture Groundwater-Flow Model for Inverse Problems
Boyce, S. E.; Yeh, W.
2013-12-01
pattern by defining the 57,888 elements with a fraction of coarse- and fine-grained sediment. This highly-heterogeneous model is reduced by selecting combinations of the global coarse and fine hydraulic conductivity at a set power of the power mean. The dimensionality of the Texture Oristano model for power-mean powers of 0, 0.8, and 1 are reduced from a system of 29,197 ordinary differential equations to 60, 42, and 45 equations, respectively. The application of the parameter-independent model reduction reduces the CPU time by 90% for a single model run. The robustness of the three reduced models, which differ in the power-mean power, are evaluated by solving a synthetic inverse problem with the BFGS algorithm. The three reduced models produced the same optimal coarse and fine hydraulic conductivity as the full model's result from BFGS. This study demonstrates that parameter-independent model reduction is possible for a highly, heterogeneous groundwater model and the inverse problem can be solved with the reduced model at a fraction of the time required by the full model.
Vibrations of rotating machinery
Matsushita, Osami; Kanki, Hiroshi; Kobayashi, Masao; Keogh, Patrick
2017-01-01
This book opens with an explanation of the vibrations of a single degree-of-freedom (dof) system for all beginners. Subsequently, vibration analysis of multi-dof systems is explained by modal analysis. Mode synthesis modeling is then introduced for system reduction, which aids understanding in a simplified manner of how complicated rotors behave. Rotor balancing techniques are offered for rigid and flexible rotors through several examples. Consideration of gyroscopic influences on the rotordynamics is then provided and vibration evaluation of a rotor-bearing system is emphasized in terms of forward and backward whirl rotor motions through eigenvalue (natural frequency and damping ratio) analysis. In addition to these rotordynamics concerning rotating shaft vibration measured in a stationary reference frame, blade vibrations are analyzed with Coriolis forces expressed in a rotating reference frame. Other phenomena that may be assessed in stationary and rotating reference frames include stability characteristic...
Vibration Antiresonance Design for a Spacecraft Multifunctional Structure
Directory of Open Access Journals (Sweden)
Dong-Xu Li
2017-01-01
Full Text Available Spacecraft must withstand rigorous mechanical environment experiences such as acceleration, noise, vibration, and shock during the process of launching, satellite-vehicle separation, and so on. In this paper, a new spacecraft multifunctional structure concept designed by us is introduced. The multifunctional structure has the functions of not only load bearing, but also vibration reduction, energy source, thermal control, and so on, and we adopt a series of viscoelastic parts as connections between substructures. Especially in this paper, a vibration antiresonance design method is proposed to realize the vibration reduction. The complex zero-point equations of the vibration system are firstly established, and then the vibration antiresonance design for the system is achieved. For solving the difficulties due to viscoelastic characteristics of the connecting parts, we present the determining formulas to obtain the structural parameters, so that the complex zero-point equations can be satisfied. Numerical simulation and ground experiment demonstrate the correctness and effectiveness of the proposed method. This method can solve the structural vibration control problem under the function constraints of load bearing and energy supplying and will expand the performance of spacecraft functional modules.
Indian Academy of Sciences (India)
The vibrating string problem is the source of much mathematicsand physics. This article describes Lagrange's formulationof a discretised version of the problem and its solution.This is also the first instance of an eigenvalue problem. Author Affiliations. Rajendra Bhatia1. Ashoka University, Rai, Haryana 131 029, India.
Directory of Open Access Journals (Sweden)
Małgorzata Kowalska
2010-06-01
Full Text Available The leading idea of the article is defined by a quotation from Fichte concerning the opposition between idealism and “dogmatism”, or naturalism. That opposition is interpreted as a result of two alternative “reductions of consciousness”: according to the first, or the idealistic one, it is possible to reduce the world to consciousness (or to its “constituted correlate”, to a pure phenomenon, while according to the second, the naturalistic one, it is possible to reduce consciousness to the world conceived as a material whole of particles and physical laws. The logics of the idealistic reduction is developed on the example of Husserlian “pure phenomenology”; this of the naturalistic one is illustrated by the proposals of Paul Churchland and John Searle. The reconstruction of the two alternative modes of reductions aims at revealing their symmetry and, also, the insufficiency of either of them. In the last paragraph, the possibility of a “third way” between idealism and naturalism is briefly examined (on the examples of several, both classical and contemporary, “continental” and “analytical” ideas, but the conclusions are skeptical.
Manela, A.; Pogorelyuk, L.
2015-12-01
We study the effect of surface heating on sound radiation by a vibrating boundary. Focusing on a setup of an infinite planar wall interacting with a semi-infinite expanse of a gas, the system response to arbitrary (small-amplitude) vibro-thermal excitation is investigated. Starting with the case of sinusoidal actuations, the superposed effect of boundary heat-flux excitation at a common frequency ω is examined. The entire range of frequencies is considered, where, depending on the ratio between ω and gas kinetic collision frequency ωcoll, fundamentally different flow regimes follow. The two limit cases of ω ≪ωcoll (continuum-flow conditions) and ω ≫ωcoll (ballistic flow regime) are investigated analytically, based on continuum equations and collisionless Boltzmann equation, respectively. In between, an intermediate interval of frequencies ω ~ωcoll is analyzed numerically, based on the direct simulation Monte Carlo method. In search for optimal conditions for acoustic sound reduction, it is found that effective attenuation is obtained when boundary heat flux is applied at opposite phase to surface actuation. Amplitude-wise, conditions for minimization of the acoustic field vary between the limits: at low-frequency conditions, wave radiation extends over large distances from the wall, and optimal sound reduction is achieved when the ratio between wall-inserted thermal and kinetic energies |Eq/Ek|opt equals γ /(γ - 1) (with γ denoting the ratio between gas specific heat capacities). At high-frequency conditions, wall signal affects only a thin gas layer (of the order of the mean free path) in the vicinity of the boundary, and optimal attenuation is achieved when |Eq/Ek|opt = 1. The analysis is extended to consider the system response to non-periodic excitations, for the specific case of a delta-function input. Making use of the above collisionless- and continuum-limit analyses, early- and late-time system responses are computed. While conditions for
Review of the logging residue problem and its reduction through marketing practices.
Thomas C. Adams; Richard C. Smith
1976-01-01
This study notes the increasing concern over logging residue in forest land management and describes the various administrative and technological means for accomplishing reductions of logging residue. Alternative sales arrangements can include such things as reduction of stumpage charges for low quality logs or required yarding of unutilized material to the landing or...
Asami, Takuya; Tamada, Yosuke; Higuchi, Yusuke; Miura, Hikaru
2017-07-01
Conventional ultrasonic metal welding for joining dissimilar metals uses a linear vibration locus, although this method suffers from problems such as low overall weld strength. Our previous studies have shown that ultrasonic welding with a planar vibration locus improves the weld strength. However, the vibration source in our previous studies had problems in longitudinal-torsional vibration controllability and small welding tip. Therefore, the study of the optimal shape of the vibration locus was difficult. Furthermore, improvement of weld strength cannot be expected. We have developed a new ultrasonic vibration source that can control the longitudinal-torsional vibration and can connect to a large welding tip. In this study, we clarified the longitudinal-torsional vibration controllability of the developed ultrasonic vibration source. Moreover, we clarified that using the planar locus of the developed vibration source produced a higher weld strength than our previous studies, and clarified the optimal shape of the vibration locus.
Czech Academy of Sciences Publication Activity Database
Ferfecki, P.; Zapoměl, Jaroslav; Kozánek, Jan
2017-01-01
Roč. 104, February (2017), s. 1-11 ISSN 0965-9978 R&D Projects: GA ČR GA15-06621S Institutional support: RVO:61388998 Keywords : magnetorheological squeeze film dampers * magnetorheological oils * closed form formulas * multiphysical problem Subject RIV: JR - Other Machinery Impact factor: 3.000, year: 2016
Zariffa, José; Popovic, Milos R.
2008-06-01
Improving our ability to localize bioelectric sources within a peripheral nerve would help us to monitor the control signals flowing to and from any limb or organ. This technology would provide a useful neuroscience tool, and could perhaps be incorporated into a neuroprosthesis interface. We propose to use measurements from a multi-contact nerve cuff to solve an inverse problem of bioelectric source localization within the peripheral nerve. Before the inverse problem can be addressed, the forward problem is solved using finite element modeling. A fine mesh improves the accuracy of the forward problem solution, but increases the number of variables to be solved for in the inverse problem. To alleviate this problem, variables corresponding to mesh elements that are not distinguishable by the measurement setup are grouped together, thus reducing the dimension of the inverse problem without impacting on the forward problem accuracy. A quantitative criterion for element distinguishability is derived using the columns of the leadfield matrix and information about the uncertainty in the measurements. Our results indicate that the number of variables in the inverse problem can be reduced by more than half using the proposed method, without having a detrimental impact on the quality of the localization.
Reduction to condensed form for the eigenvalue problem on distributed memory architectures
Energy Technology Data Exchange (ETDEWEB)
Dongarra, J.J. [Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science]|[Oak Ridge National Lab., TN (United States). Mathematical Sciences Section; van de Geijn, R.A. [Texas Univ., Austin, TX (United States). Dept. of Computer Sciences
1992-01-01
In this paper, we describe a parallel implementation for the reduction of general and symmetric matrices to Hessenberg and tridiagonal form, respectively. The methods are based on LAPACK sequential codes and use a panel-wrapped mapping of matrices to nodes. Results from experiments on the Intel Touchstone Delta are given.
DEFF Research Database (Denmark)
Asmussen, J. C.; Nielsen, Søren R. K.
The present collection of MATLAB exercises has been published as a supplement to the textbook, Svingningsteori, Bind 1 and the collection of exercises in Vibration theory, Vol. 1A, Solved Problems. Throughout the exercise references are made to these books. The purpose of the MATLAB exercises...... is to give a better understanding of the physical problems in linear vibration theory and to surpress the mathematical analysis used to solve the problems. For this purpose the MATLAB environment is excellent....
Martínez-Hidalgo, Mª Nieves; Lorenzo-Sánchez, Elena; López García, Juan José; Regadera, Juan José
2017-12-13
This study assessed the effectiveness of a social contact program between young adults and adolescents with and without mental health problems. It was evaluated if the development of a social contact program in a non-segregated space and respecting criteria of contact hypothesis reduced Self-Stigma and Public Stigma and, increased Self-Esteem. A pre-post intervention design was used with a sample of 47 subjects, 25 with different mental health diagnoses (Psychotic Disorder, Anxiety Disorder, Depression, Autism Spectrum Disorder and Attention Deficit Hyperactivity Disorder) and 22 without mental health problems, aged between 15 and 35 years. Five workshops of social contact and creativity were carried out during five months with a 2-h weekly meeting. The results analysis revealed a significant reduction in Self-Stigma for participants with mental health problems and may suggest a slight reduction in Public Stigma as well as a slight increase in the level of Self-Esteem of all participants. These findings suggest that programs of this nature reduce Self-Stigma and facilitate social inclusion in young adults and adolescents with and without mental health problems. Copyright © 2017 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
W. Merlijn van Spengen
2010-12-01
Full Text Available We have replaced the periodic Prandtl–Tomlinson model with an atomic-scale friction model with a random roughness term describing the surface roughness of micro-electromechanical systems (MEMS devices with sliding surfaces. This new model is shown to exhibit the same features as previously reported experimental MEMS friction loop data. The correlation function of the surface roughness is shown to play a critical role in the modelling. It is experimentally obtained by probing the sidewall surfaces of a MEMS device flipped upright in on-chip hinges with an AFM (atomic force microscope. The addition of a modulation term to the model allows us to also simulate the effect of vibration-induced friction reduction (normal-force modulation, as a function of both vibration amplitude and frequency. The results obtained agree very well with measurement data reported previously.
Quality problems root cause identification and variability reduction in casting processes
Directory of Open Access Journals (Sweden)
G. Furgał
2009-01-01
Full Text Available Increasing customer requirements and production costs force casting manufacturers to adopt a methodological approach to manufacturingprocesses, in order to deliver increasingly more repeatable, predictable and competitive products. One of the methods of achieving such results is the reduction of variability of manufacturing processes and the optimization of their control. This paper presents the possibilities granted by the Six Sigma methodology in efficient identification of special factors influencing pre-heat of ceramic moulds and castingparameters, in the minimization of the frequency at which they occur, and in the reduction of key process parameters variability. This paper also shows the usability of the method in achieving measurable business advantages for the company using the example of one DMAIC methodology based project realized in the Investment Foundry Department of WSK “PZL-Rzeszow” S.A.
Van Volsem, Sofie; Verdiesen, Johannes
2010-01-01
In this paper, we investigate the trade-off between investing in product quality improvement and lead time reduction in a B2B single-supplier, single-buyer environment. To this end, a discrete event simulation model is proposed, based on the integrated inventory model defined in Ouyang et al. (2006). Furthermore, the possibility of using alternative failure mechanisms and capital investment functions are studied. ity of using alternative failure mechanisms and capital investment functions...
Avoid heat transfer equipment vibration
Energy Technology Data Exchange (ETDEWEB)
Ganapathy, V.
1987-06-01
Tube bundles in heat exchangers, boilers, superheaters and heaters are often subject to vibration and noise problems. Vibration can lead to tube thinning and wear, resulting in tube failures. Excessive noise can be a problem to plant operating personnel. Large gas pressure drop across the equipment is also a side effect, which results in large operating costs. With the design checks presented in this paper, one can predict during design if problems associated with noise and vibration are likely to occur in petroleum refineries.
Xu, Peiliang
2013-12-01
Reduction can be important to aid quickly attaining the integer least squares (ILS) estimate from noisy data. We present an improved LLL algorithm with fixed complexity by extending a parallel reduction method for positive definite quadratic forms to lattice vectors. We propose the minimum angle of a reduced basis as an alternative quality measure of orthogonality, which is intuitively more appealing to measure the extent of orthogonality of a reduced basis. Although the LLL algorithm and its variants have been widely used in practice, experimental simulations were only carried out recently and limited to the quality measures of the Hermite factor, practical running behaviors and reduced Gram-Schmidt coefficients. We conduct a large scale of experiments to comprehensively evaluate and compare five reduction methods for decorrelating ILS problems, including the LLL algorithm, its variant with deep insertions and our improved LLL algorithm with fixed complexity, based on six quality measures of reduction. We use the results of the experiments to investigate the mean running behaviors of the LLL algorithm and its variants with deep insertions and the sorted QR ordering, respectively. The improved LLL algorithm with fixed complexity is shown to perform as well as the LLL algorithm with deep insertions with respect to the quality measures on length reduction but significantly better than this LLL variant with respect to the other quality measures. In particular, our algorithm is of fixed complexity, but the LLL algorithm with deep insertions could seemingly not be terminated in polynomial time of the dimension of an ILS problem. It is shown to perform much better than the other three reduction methods with respect to all the six quality measures. More than six millions of the reduced Gram-Schmidt coefficients from each of the five reduction methods clearly show that they are not uniformly distributed but depend on the reduction algorithms used. The simulation results of
Autoclave reduction of jarosites and other metal sulfates : a new approach to major waste problems
Hage, J.L.T.
1999-01-01
Industrial jarosite is a waste product of the zinc industry. It is considered a serious environmental problem, due to the quantity produced and the mobile hazardous metals it contains. Over 50 million tons are already stored worldwide. The jarosite sludge autoclave treatment process described in
A Multi-Model Reduction Technique for Optimization of Coupled Structural-Acoustic Problems
DEFF Research Database (Denmark)
Creixell Mediante, Ester; Jensen, Jakob Søndergaard; Brunskog, Jonas
2016-01-01
Finite Element models of structural-acoustic coupled systems can become very large for complex structures with multiple connected parts. Optimization of the performance of the structure based on harmonic analysis of the system requires solving the coupled problem iteratively and for several...
Reduction of Severe Behavior Problems in the Community Using a Multicomponent Treatment Approach.
Carr, Edward G.; Carlson, Jane I.
1993-01-01
A multicomponent intervention to change problem behavior, which prevented community integration of three adolescents with autism, was evaluated. The intervention (implemented in a supermarket setting) included choice making, embedding, functional communication training, building tolerance for delay of reinforcement, and presenting discriminative…
Nasertdinova, A. D.; Bochkarev, V. V.
2017-11-01
Deep neural networks with a large number of parameters are a powerful tool for solving problems of pattern recognition, prediction and classification. Nevertheless, overfitting remains a serious problem in the use of such networks. A method of solving the problem of overfitting is proposed in this article. This method is based on reducing the number of independent parameters of a neural network model using the principal component analysis, and can be implemented using existing libraries of neural computing. The algorithm was tested on the problem of recognition of handwritten symbols from the MNIST database, as well as on the task of predicting time series (rows of the average monthly number of sunspots and series of the Lorentz system were used). It is shown that the application of the principal component analysis enables reducing the number of parameters of the neural network model when the results are good. The average error rate for the recognition of handwritten figures from the MNIST database was 1.12% (which is comparable to the results obtained using the "Deep training" methods), while the number of parameters of the neural network can be reduced to 130 times.
Jóźwiak, Grzegorz
2017-03-01
Scanning probe microscopy (SPM) is a well known tool used for the investigation of phenomena in objects in the nanometer size range. However, quantitative results are limited by the size and the shape of the nanoprobe used in experiments. Blind tip reconstruction (BTR) is a very popular method used to reconstruct the upper boundary on the shape of the probe. This method is known to be very sensitive to all kinds of interference in the atomic force microscopy (AFM) image. Due to mathematical morphology calculus, the interference makes the BTR results biased rather than randomly disrupted. For this reason, the careful choice of methods used for image enhancement and denoising, as well as the shape of a calibration sample are very important. In the paper, the results of thorough investigations on the shape of a calibration standard are shown. A novel shape is proposed and a tool for the simulation of AFM images of this calibration standard was designed. It was shown that careful choice of the initial tip allows us to use images of hole structures to blindly reconstruct the shape of a probe. The simulator was used to test the impact of modern filtration algorithms on the BTR process. These techniques are based on sparse approximation with function dictionaries learned on the basis of an image itself. Various learning algorithms and parameters were tested to determine the optimal combination for sparse representation. It was observed that the strong reduction of noise does not guarantee strong reduction in reconstruction errors. It seems that further improvements will be possible by the combination of BTR and a noise reduction procedure.
Effect of shelf aging on vibration transmissibility of anti-vibration gloves.
Shibata, Nobuyuki
2017-10-05
Anti-vibration gloves have been used in real workplaces to reduce vibration transmitted through hand-held power tools to the hand. Generally materials used for vibration attenuation in gloves are resilient materials composed of certain synthetic and/or composite polymers. The mechanical characteristics of the resilient materials used in anti-vibration gloves are prone to be influenced by environmental conditions such as temperature, humidity, and photo-irradiation, which cause material degradation and aging. This study focused on the influence of shelf aging on the vibration attenuation performance of air-packaged anti-vibration gloves following 2 years of shelf aging. Effects of shelf aging on the vibration attenuation performance of anti-vibration gloves were examined according to the Japan industrial standard JIS T8114 test protocol. The findings indicate that shelf aging induces the reduction of vibration attenuation performance in air-packaged anti-vibration gloves.
A paradigm shift in policing: Crime reduction through problem oriented policing
Murat Ozkan
2016-01-01
The opportunity theories of crime regards opportunity as a root cause and focus attention on the crime rather than the criminal. In the practical crime prevention efforts, this theoretical framework paved the way for innovative policing strategies like problem oriented policing and situational crime prevention. Policy makers and practitioners accept the motivated offender as given and gather the efforts to prevent offenders accessing sufficient means and opportunities for a crime to occur. Th...
VIBRATION ISOLATION SYSTEM PROBABILITY ANALYSIS
Directory of Open Access Journals (Sweden)
Smirnov Vladimir Alexandrovich
2012-10-01
Full Text Available The article deals with the probability analysis for a vibration isolation system of high-precision equipment, which is extremely sensitive to low-frequency oscillations even of submicron amplitude. The external sources of low-frequency vibrations may include the natural city background or internal low-frequency sources inside buildings (pedestrian activity, HVAC. Taking Gauss distribution into account, the author estimates the probability of the relative displacement of the isolated mass being still lower than the vibration criteria. This problem is being solved in the three dimensional space, evolved by the system parameters, including damping and natural frequency. According to this probability distribution, the chance of exceeding the vibration criteria for a vibration isolation system is evaluated. Optimal system parameters - damping and natural frequency - are being developed, thus the possibility of exceeding vibration criteria VC-E and VC-D is assumed to be less than 0.04.
The Problem with Templates: Learning from Organic Gang-Related Violence Reduction
Directory of Open Access Journals (Sweden)
Dennis Rodgers
2015-10-01
Full Text Available This article considers what demobilisation, disarmament, and reintegration (DDR programmes might learn from research on gangs and the problems associated with government-instituted ‘wars on gangs’ putatively aimed at reducing or fighting gang-related violence. It begins by considering interventions associated with the global war on gangs, and compares their underlying premises and practices with those of DDR programmes while highlighting how both are plagued with problems associated with drawing on de-contextualized templates. Drawing on long-term ethnographic research carried out in Nicaragua and South Africa, the article then goes on to explore why individuals leave gangs, focusing in particular on the more organic processes that deplete gangs of their members, as well as the consequences that the different possible occupational trajectories of ex-gang members can have for patterns of violence. These offer a number of potential lessons for DDR programmes, particularly with regard to reducing violence in a realistic and sustainable manner.
Energy Technology Data Exchange (ETDEWEB)
Arimatsu, M.; Kawakami, T. [Nissan Motor Co. Ltd., Tokyo (Japan)
1997-10-01
With the reduction of vehicle noise, the requirements for an efficient method to reduce transmission gear noise have become stronger yearly. So far efforts to reduce gear noise have generally focused on ways of improving the gears themselves. In addition to these traditional methods, it proved very beneficial to us to optimize the gear train structure. Nissan has just released the new Belt CVT for 2.0L Front wheel drive vehicles. We have been analyzing vibration of the gear train by using a finite element model since the early development stage, and we could achieve the quiet gears effectively. 2 refs., 9 figs.
Kornilov, V. I.; Boiko, A. V.
2017-10-01
Problems of experimental modeling of the process of air blowing into turbulent boundary layer of incompressible fluid through finely perforated wall are discussed. Particular attention is paid to the analysis of both the main factors responsible for the effectiveness of blowing and the possibility of studying the factors in artificially generated turbulent boundary layer. It was shown that uniformity of the injected gas is one of the main requirements to enhance the effectiveness of this method of flow control. An example of the successful application of this technology exhibiting a significant reduction of the turbulent skin friction is provided.
Energy Technology Data Exchange (ETDEWEB)
Tiryaki, B. [Hacettepe University (Turkey). Dept. of Mining Engineering
2003-12-01
The paper examines the prediction and optimisation of machine vibrations in longwall shearers. Underground studies were carried out at the Middle Anatolian Lignite Mine, between 1993 and 1997. Several shearer drums with different pick lacing arrangements were designed and tested on double-ended ranging longwall shearers employed at the mine. A computer program called the Vibration Analysis Program (VAP) was developed for analysing machine vibrations in longwall shearers. Shearer drums that were tested underground, as well as some provided by leading manufacturers, were analyzed using these programs. The results of the experiments and computer analyses are given in the article. 4 refs., 9 figs.
Nonlinear frequency response analysis of structural vibrations
Weeger, Oliver; Wever, Utz; Simeon, Bernd
2014-12-01
In this paper we present a method for nonlinear frequency response analysis of mechanical vibrations of 3-dimensional solid structures. For computing nonlinear frequency response to periodic excitations, we employ the well-established harmonic balance method. A fundamental aspect for allowing a large-scale application of the method is model order reduction of the discretized equation of motion. Therefore we propose the utilization of a modal projection method enhanced with modal derivatives, providing second-order information. For an efficient spatial discretization of continuum mechanics nonlinear partial differential equations, including large deformations and hyperelastic material laws, we employ the concept of isogeometric analysis. Isogeometric finite element methods have already been shown to possess advantages over classical finite element discretizations in terms of higher accuracy of numerical approximations in the fields of linear vibration and static large deformation analysis. With several computational examples, we demonstrate the applicability and accuracy of the modal derivative reduction method for nonlinear static computations and vibration analysis. Thus, the presented method opens a promising perspective on application of nonlinear frequency analysis to large-scale industrial problems.
Lyubetsky, Vassily; Gershgorin, Roman; Gorbunov, Konstantin
2017-12-06
Chromosome structure is a very limited model of the genome including the information about its chromosomes such as their linear or circular organization, the order of genes on them, and the DNA strand encoding a gene. Gene lengths, nucleotide composition, and intergenic regions are ignored. Although highly incomplete, such structure can be used in many cases, e.g., to reconstruct phylogeny and evolutionary events, to identify gene synteny, regulatory elements and promoters (considering highly conserved elements), etc. Three problems are considered; all assume unequal gene content and the presence of gene paralogs. The distance problem is to determine the minimum number of operations required to transform one chromosome structure into another and the corresponding transformation itself including the identification of paralogs in two structures. We use the DCJ model which is one of the most studied combinatorial rearrangement models. Double-, sesqui-, and single-operations as well as deletion and insertion of a chromosome region are considered in the model; the single ones comprise cut and join. In the reconstruction problem, a phylogenetic tree with chromosome structures in the leaves is given. It is necessary to assign the structures to inner nodes of the tree to minimize the sum of distances between terminal structures of each edge and to identify the mutual paralogs in a fairly large set of structures. A linear algorithm is known for the distance problem without paralogs, while the presence of paralogs makes it NP-hard. If paralogs are allowed but the insertion and deletion operations are missing (and special constraints are imposed), the reduction of the distance problem to integer linear programming is known. Apparently, the reconstruction problem is NP-hard even in the absence of paralogs. The problem of contigs is to find the optimal arrangements for each given set of contigs, which also includes the mutual identification of paralogs. We proved that these
Jaworske, D. A.; Palaszewski, B. A.; Kulis, M. J.; Gokoglu, S. A.
2015-01-01
Human space missions generate waste materials. A 70-kg crewmember creates a waste stream of 1 kg per day, and a four-person crew on a deep space habitat for a 400+ day mission would create over 1600 kg of waste. Converted into methane, the carbon could be used as a fuel for propulsion or power. The NASA Advanced Exploration Systems (AES) Logistics Reduction and Repurposing (LRR) project is investing in space resource utilization with an emphasis on repurposing logistics materials for useful purposes and has selected steam reforming among many different competitive processes as the preferred method for repurposing organic waste into methane. Already demonstrated at the relevant processing rate of 5.4 kg of waste per day, high temperature oxygenated steam consumes waste and produces carbon dioxide, carbon monoxide, and hydrogen which can then be converted into methane catalytically. However, the steam reforming process has not been studied in microgravity. Data are critically needed to understand the mechanisms that allow use of steam reforming in a reduced gravity environment. This paper reviews the relevant literature, identifies gravity-dependent mechanisms within the steam gasification process, and describes an innovative experiment to acquire the crucial kinetic information in a small-scale reactor specifically designed to operate within the requirements of a reduced gravity aircraft flight. The experiment will determine if the steam reformer process is mass-transport limited, and if so, what level of forced convection will be needed to obtain performance comparable to that in 1-g.
A new model order reduction strategy adapted to nonlinear problems in earthquake engineering.
Bamer, Franz; Amiri, Abbas Kazemi; Bucher, Christian
2017-04-10
Earthquake dynamic response analysis of large complex structures, especially in the presence of nonlinearities, usually turns out to be computationally expensive. In this paper, the methodical developments of a new model order reduction strategy (MOR) based on the proper orthogonal decomposition (POD) method as well as its practical applicability to a realistic building structure are presented. The seismic performance of the building structure, a medical complex, is to be improved by means of base isolation realized by frictional pendulum bearings. According to the new introduced MOR strategy, a set of deterministic POD modes (transformation matrix) is assembled, which is derived based on the information of parts of the response history, so-called snapshots, of the structure under a representative earthquake excitation. Subsequently, this transformation matrix is utilized to create reduced-order models of the structure subjected to different earthquake excitations. These sets of nonlinear low-order representations are now solved in a fractional amount of time in comparison with the computations of the full (non-reduced) systems. The results demonstrate accurate approximations of the physical (full) responses by means of this new MOR strategy if the probable behavior of the structure has already been captured in the POD snapshots. Copyright © 2016 The Authors. Earthquake Engineering & Structural Dynamics Published by John Wiley & Sons Ltd.
Energy Technology Data Exchange (ETDEWEB)
Chuang, Tzu-Shien [Department of Electrical Engineering, Ming Chi University of Technology, 84 Gungjuan Road, Taishan, Taipei 24301 (China); Liang, Jin-Wei [Department of Mechanical Engineering, Ming Chi University of Technology (China)
2008-11-15
In this paper, a stator flux oriented current vector control of a sensorless three-phase 6/4 switched reluctance motor without position sensors is presented. Space current vector control technology based on torque angle estimation was used to reduce the acoustic noise and vibration of the motor drive system. The power converter for the 6/4 switched reluctance motor is three-phase full bridge inverter. The experimental results show that the maximum level of acoustic noises and vibration are 73 dB and 8 dB; m/s/s, respectively, and the steady speed error of the drive system is less than 0.1% operated at the rated load when the drive system was operated below 1500 rpm. In addition, the transient speed performance is also satisfactory. (author)
Bigg, D
2001-01-01
Disease (particularly HIV) has increased our motivation to reconsider how the current help system deals with drug-related problems. A more concrete focus on disease prevention as an additional goal has, for many, lead to a reevaluation of the goals of drug help work. Such a critical examination shows how much there is to improve within the system even in the absence of blood borne disease. Integrating the heart of harm reduction--respecting work on any positive change as a person defines it for his/herself--into treatment fashions a health sensitive alternative to the predominant practice of abstinence-only assistance for the relief of drug problems. This new approach is called substance use management (SUM), as it no longer requires abstinence but instead focuses on a range of options for improvements while still including abstinence among the possible self-selected outcomes. SUM is suggested as a framework for change within the treatment system that would maximize treatment's constructive impact, cost-effectiveness and maturation as a distinct discipline that can appropriately attract support and gain stature for making society healthier. This article describes a formalized system for applying some of the main principles of harm reduction within the treatment system. Viable options for a SUM treatment focus are suggested herein as well as a critical process, based on respect and collaboration, for use with these options.
Kozlov, Victor; Ivanova, Alevtina; Schipitsyn, Vitalii; Stambouli, Moncef
2014-10-01
The paper is concerned with dynamics of light solid in cavity with liquid subjected to rotational vibration in the external force field. New vibrational phenomenon - diving of a light cylinder to the cavity bottom is found. The experimental investigation of a horizontal annulus with a partition has shown that under vibration a light body situated in the upper part of the layer is displaced in a threshold manner some distance away from the boundary. In this case the body executes symmetric tangential oscillations. An increase of the vibration intensity leads to a tangential displacement of the body near the external boundary. This displacement is caused by the tangential component of the vibrational lift force, which appears as soon as the oscillations lose symmetry. In this case the trajectory of the body oscillatory motion has the form of a loop. The tangential lift force makes stable the position of the body on the inclined section of the layer and even in its lower part. A theoretical interpretation has been proposed, which explains stabilization of a quasi-equilibrium state of a light body near the cavity bottom in the framework of vibrational hydromechanics.
Wenner, Michael T.
Obtaining the solution to the linear Boltzmann equation is often is often a daunting task. The time-independent form is an equation of six independent variables which cannot be solved analytically in all but some special problems. Instead, numerical approaches have been devised. This work focuses on improving Monte Carlo methods for its solution in eigenvalue form. First, a statistical method of stationarity detection called the KPSS test adapted as a Monte Carlo eigenvalue source convergence test. The KPSS test analyzes the source center of mass series which was chosen since it should be indicative of overall source behavior, and is physically easy to understand. A source center of mass plot alone serves as a good visual source convergence diagnostic. The KPSS test and three different information theoretic diagnostics were implemented into the well known KENOV.a code inside of the SCALE (version 5) code package from Oak Ridge National Laboratory and compared through analysis of a simple problem and several difficult source convergence benchmarks. Results showed that the KPSS test can add to the overall confidence by identifying more problematic simulations than without its usage. Not only this, the source center of mass information on hand visually aids in the understanding of the problem physics. The second major focus of this dissertation concerned variance reduction methodologies for Monte Carlo eigenvalue problems. The CADIS methodology, based on importance sampling, was adapted to the eigenvalue problems. It was shown that the straight adaption of importance sampling can provide a significant variance reduction in determination of keff (in cases studied up to 30%?). A modified version of this methodology was developed which utilizes independent deterministic importance simulations. In this new methodology, each particle is simulated multiple times, once to every other discretized source region utilizing the importance for that region only. Since each particle
Rotary-wing aeroservoelastic problems
Friedmann, Peretz P.
1992-01-01
The state-of-the-art in the field of alleviating rotary-wing aeroservoelastic problems (by using active controls that modify the pitch of a helicopter rotor blade so as to alleviate dynamic effects) is assessed, and the more promising developments are identified. Special attention is given to the active control of aeromechanical and aeroelastic problems, such as the active control of ground resonance, active control of air resonance, and active control of blade aeroelastic instabilities; individual blade control; active control of vibration reduction using a conventional swashplate; and coupled rotor/fuselage vibration reduction using open-loop active control. Some results are presented for each of these topics, illustrating the efficiency of the techniques which have been developed.
Ma, Chiyuan; Liu, An; Sun, Miao; Zhu, Hanxiao; Wu, Haobo
2016-02-17
To examine whole-body vibration (WBV) effect on bone mineral density (BMD) and fall prevention in postmenopausal women, we performed a meta-analysis and systematic review of prospective randomized controlled trials (RCTs) comparing change in BMD of the femoral neck and lumbar spine and related factors of falls between WBV group and control group. EMBASE, PubMed, Cochrane Central Register of Controlled Trials, ISI Web of Science, and China National Knowledge Infrastructure (CNKI) were searched up to April 2015; search strategy was used as follows: (vibration) AND (osteoporo* OR muscle* OR bone mineral density OR BMD). All prospective randomized controlled trials comparing related factors of falls and BMD change in the femoral neck and lumbar spine between WBV group and control group were retrieved. Eight of 3599 studies with 1014 patients were included, 477 in the WBV group, and 537 in the control group. We found that there was no significant difference in all magnitude groups of the femoral neck (N = 936, WMD: 0.00 (-0.00, 0.01); p = 0.18). A statistical significance showed in the all magnitude groups (N = 1014, WMD: 0.01 (0.00, 0.01); p = 0.01) and low-magnitude group (N = 838, WMD: 0.01 (0.00, 0.01); p = 0.007) of the lumbar spine. No significant difference was found in high-magnitude group of the lumbar spine (N = 176, WMD: 0.00 (-0.01, 0.02); p = 0.47), low-magnitude group (N = 838, WMD: 0.00 (-0.00, 0.00); p = 0.92) and high-magnitude group (N = 98, WMD: 0.02 (-0.00, 0.05); p = 0.06) of the femoral neck. All the studies provided data of related factors of falls such as strength of the lower limb, balance, and fall rate reported effectiveness of WBV therapy. In addition, no complication was reported. Low-magnitude whole-body vibration therapy can provide a significant improvement in reducing bone loss in the lumbar spine in postmenopausal women. Moreover, whole-body vibration can be used as an intervention for fall prevention.
Active vibration isolation of a rigidly mounted turbo pump
Basten, T.G.H.; Doppenberg, E.J.J.
2006-01-01
Manufacturers of precision equipment are constantly aiming at increased accuracy. Elimination of disturbing vibrations is therefore getting more and more important. The technical limitations of passive isolation methods require alternative strategies for vibration reduction, such as active
Reducing vibration transfer from power plants by active methods
Kiryukhin, A. V.; Milman, O. O.; Ptakhin, A. V.
2017-12-01
The possibility of applying the methods of active damping of vibration and pressure pulsations for reducing their transfer from power plants into the environment, the seating, and the industrial premises are considered. The results of experimental works implemented by the authors on the active broadband damping of vibration and dynamic forces after shock-absorption up to 15 dB in the frequency band up to 150 Hz, of water pressure pulsations in the pipeline up to 20 dB in the frequency band up to 600 Hz, and of spatial low-frequency air noise indoors of a diesel generator at discrete frequency up to 20 dB are presented. It is shown that a reduction of vibration transfer through a vibration-isolating junction (expansion joints) of pipelines with liquid is the most complicated and has hardly been developed so far. This problem is essential for vibration isolation of power equipment from the seating and the environment through pipelines with water and steam in the power and transport engineering, shipbuilding, and in oil and gas pipelines in pumping stations. For improving efficiency, reducing the energy consumption, and decreasing the overall dimensions of equipment, it is advisable to combine the work of an active system with passive damping means, the use of which is not always sufficient. The executive component of the systems of active damping should be placed behind the vibration isolators (expansion joints). It is shown that the existence of working medium and connection of vibration with pressure pulsations in existing designs of pipeline expansion joints lead to growth of vibration stiffness of the expansion joint with the environment by two and more orders as compared with the static stiffness and makes difficulties for using the active methods. For active damping of vibration transfer through expansion joints of pipelines with a liquid, it is necessary to develop expansion joint structures with minimal connection of vibrations and pulsations and minimal
Haidar, Azzam
2011-01-01
This paper introduces a novel implementation in reducing a symmetric dense matrix to tridiagonal form, which is the preprocessing step toward solving symmetric eigenvalue problems. Based on tile algorithms, the reduction follows a two-stage approach, where the tile matrix is first reduced to symmetric band form prior to the final condensed structure. The challenging trade-off between algorithmic performance and task granularity has been tackled through a grouping technique, which consists of aggregating fine-grained and memory-aware computational tasks during both stages, while sustaining the application\\'s overall high performance. A dynamic runtime environment system then schedules the different tasks in an out-of-order fashion. The performance for the tridiagonal reduction reported in this paper is unprecedented. Our implementation results in up to 50-fold and 12-fold improvement (130 Gflop/s) compared to the equivalent routines from LAPACK V3.2 and Intel MKL V10.3, respectively, on an eight socket hexa-core AMD Opteron multicore shared-memory system with a matrix size of 24000×24000. Copyright 2011 ACM.
Rehm, Jürgen; Gmel, Gerrit; Sierra, Cristina; Gual, Antoni
2018-01-01
Through a simulation study, we estimated the potential effects of better detection of hypertension and improved screening for alcohol problems with subsequent interventions. Results showed that if 50% of Spanish males between 40 and 64 years of age who are currently unaware of their hypertension become aware of their condition and receive the usual treatment, and 50% of these males with hypertension are screened for alcohol and are treated for hazardous drinking or alcohol use disorders, then the percentage of uncontrolled hypertension among men with hypertension decreases from 61.2% to 55.9%, i.e. by 8.6%, with about 1/3 of the effect due to the alcohol intervention. For women, likewise, these interventions would decrease the percentage of women in the same age group with uncontrolled hypertension by 7.4% (about 40% due to the alcohol intervention). The reduction of blood pressure in the population would avoid 412 premature CVD deaths (346 in men, 66 in women) within one year. Therefore, better detection of hypertension and screening for alcohol with subsequent interventions would result in marked reductions of uncontrolled hypertension and CVD mortality.
A two scale modeling and computational framework for vibration-induced Raynaud syndrome.
Hua, Yue; Lemerle, Pierre; Ganghoffer, Jean-François
2017-07-01
Hand-Arm Vibration syndrome (HAVS), usually caused by long-term use of hand-held power tools, can in certain manifestations alter the peripheral blood circulation in the hand-arm region. HAVS typically occurs after exposure to cold, causing an abnormally strong vasoconstriction of blood vessels. A pathoanatomical mechanism suggests that a reduction of the lumen of the blood vessels in VWF (Vibration White Finger) subjects, due to either hypertrophy or thickening of the vessel wall, may be at the origin of the disease. However, the direct and indirect effects of the load of the hand-held tools on the structure of blood vessels remain controversial:.one hypothesis is the mechanical action of vibration on the local acral dysregulation and/or on the vessel histomorphological modifications. Another hypothesis is the participation of the sympathetic nervous system to this dysregulation. In this paper, we assume the modifications as mechanobiological growth and the load-effect relationship may be interpreted as directly or indirectly induced. This work is the first attempt to model the effect of vibration through soft tissues onto the distal capillaries, addressing the double paradigm of multi space-time scales, i.e. low period vibration versus high time constant of the growth phenomenon as well as vibrations propagating in the macroscopic tissue including the microscopic capillary structures subjected to a pathological microstructural evolution. The objective is to lay down the theoretical basis of growth modeling for the small distal artery, with the ability to predict the geometrical and structural changes of the arterial walls caused by vibration exposure. We adopt the key idea of splitting the problem into one global vibration problem at the macroscopic scale and one local growth problem at the micro level. The macroscopic hyperelastic viscous dynamic model of the fingertip cross-section is validated by fitting experimental data. It is then used in steady
Directory of Open Access Journals (Sweden)
Patrik Flegner
2015-12-01
Full Text Available The process of separation of a rock massif by rotary drilling belongs to the most frequently used geotechnologies. Since their energy costs are significant, it makes sense to pay sufficient consideration to the subject of an efficient mode of drilling. Only an efficient drilling mode can guarantee the overall quality of this process. This contribution builds upon previous works of the authors in the area of utilization of abstract Hilbert spaces in control of specific processes. In this paper, some possibilities and aspects of visualization of concurrent vibrations with respect to efficient control of drilling are pointed out. The result of implementing the vibration signal as a vector in Hilbert space is the algorithm for recognition of the class into which the rock being separated belongs based on its geomechanical properties. The algorithm is based on geometrical interpretation of time or frequency characteristics of the concurrent vibrations. The method was applied to concurrent vibrations from drilling on an experimental stand and also from tunneling. The achieved results confirm the suitability of the proposed algorithm for its application in the system of automated setting of an efficient mode of drilling of rock massif.
2009-01-01
Ed Witten is one of the leading scientists in the field of string theory, the theory that describes elementary particles as vibrating strings. This week he leaves CERN after having spent a few months here on sabbatical. His wish is that the LHC will unveil supersymmetry.
Vibrations on board and health effects
DEFF Research Database (Denmark)
Jensen, Anker; Jepsen, Jørgen Riis
2014-01-01
for such relation among seafarers except for fishermen, who, however, are also exposed to additional recognised physical risk factors at work. The assessment and reduction of vibrations by naval architects relates to technical implications of this impact for the ships’ construction, but has limited value......There is only limited knowledge of the exposure to vibrations of ships’ crews and their risk of vibration-induced health effects. Exposure to hand-arm vibrations from the use of vibrating tools at sea does not differ from that in the land-based trades. However, in contrast to most other work places...... of the health consequences of whole body vibrations in land-transportation, such exposure at sea may affect ships’ passengers and crews. While the relation of back disorders to high levels of whole body vibration has been demonstrated among e.g. tractor drivers, there are no reported epidemiological evidence...
Directory of Open Access Journals (Sweden)
Setyamartana Parman
1999-01-01
Full Text Available A three-dimensional rest-to-rest attitude maneuver of flexible spacecraft equipped by on-off reaction jets is studied. Equations of motion of the spacecraft is developed by employing a hybrid system of coordinates and Lagrangian formulation. The finite element method is used to examine discrete elastic deformations of a particular model of satellite carrying flexible solar panels by modelling the panels as flat plate structures in bending. Results indicate that, under an unshaped input, the maneuvers induce undesirable attitude angle motions of the satellite as well as vibration of the solar panels. An input shaper is then applied to reduce the residual oscillation of its motion at several natural frequencies in order to get an expected pointing precision of the satellite. Once the shaped input is given to the satellite, the performance improves significantly.
Vibration characteristics of casing string under the exciting force of an electric vibrator
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Yiyong Yin
2017-11-01
Full Text Available Vibration cementing is a new technique that can significantly improve the bond strength of cementing interface. To popularize this technique, it is necessary to solve the key problem of how to make cementing string generate downhole radial vibration in the WOC stage. For this purpose, an electric vibrator was developed. With this vibrator, electric energy is converted into mechanical energy by means of a high-temperature motor vibration unit. The motor vibration unit rotates the eccentric block through an output shaft to generate an exciting source, which produces an axial-rotating exciting force at the bottom of the casing string. Then, the vibration characteristics of vertical well casing string under the exciting force were analyzed by using the principal coordinate analysis method, and the response model of casing string to an electric vibrator was developed. Finally, the effects of casing string length, exciting force and vibration frequency on the vibration amplitude at the lowermost of the casing string were analyzed based on a certain casing program. It is indicated that the casing string length and the square of vibration frequency are inversely proportional to the vibration amplitude at the lowermost of the casing string, and the exciting force is proportional to the vibration amplitude at the lowermost of the casing string. These research results provide a theoretical support for the application of vibration cementing technology to the cementing sites with different requirements on well depth and amplitude.
Problems in differential equations
Brenner, J L
2013-01-01
More than 900 problems and answers explore applications of differential equations to vibrations, electrical engineering, mechanics, and physics. Problem types include both routine and nonroutine, and stars indicate advanced problems. 1963 edition.
Molino, C G R C; Carnevale, Renata Cavalcanti; Rodrigues, Aline Teotonio; Moriel, Patricia; Mazzola, Priscila Gava
2017-07-01
Background: Highly active antiretroviral therapy (HAART) is complex and many factors contribute to a patient's response to initial therapy including adherence, drug effectiveness, and tolerance. Close HAART follow-up is needed, particularly when there are concurrent therapies such as prophylactic antibiotics and medications for the treatment of comorbidities. Objective: To assess the effectiveness of pharmacist intervention in reducing drug related problems in HIV/AIDS outpatients (intervention group) and in improving clinical parameters in the intervention group compared to the control group. Methods: We conducted a prospective controlled intervention study with patients paired by gender and initial T CD4+ lymphocyte (CD4) count. HIV-infected patients of a public outpatient service were enrolled for the study by consecutive and convenience sampling. Patients selected for the study were divided into a control group and an intervention group. Both groups were followed for one year; however, only the intervention group received pharmaceutical care. The primary outcome was the drug related problem (DRP) analysis for the intervention group. Secondary outcomes were CD4 count and viral load evaluation for both groups. Results: There was a total of 143 patients enrolled in this study, with 53 (37.06%) patients in the control group and 90 (62.94%) patients in the intervention group. A total of 202 pharmacist interventions with 193 pharmacist-patient and 9 pharmacist-physician interventions were proposed. After one year of pharmaceutical care, a reduction of 38.43% between the initial and final DRP was found (p = 0.0001). The most common DRPs found were related to medication safety. The intervention group showed a mean increase of 84% for the CD4 count in comparison with that observed in the control group. The viral load was not significantly different between the final and initial mean values for both groups. Conclusion: Pharmacist appointments enabled identification
DEFF Research Database (Denmark)
Morrison, Ann; Knudsen, L.; Andersen, Hans Jørgen
2012-01-01
lab studies in that we found a decreased detection rate in busy environments. Here we test with a much larger sample and age range, and contribute with the first vibration sensitivity testing outside the lab in an urban public...
Coupled rotor/airframe vibration analysis
Sopher, R.; Studwell, R. E.; Cassarino, S.; Kottapalli, S. B. R.
1982-01-01
A coupled rotor/airframe vibration analysis developed as a design tool for predicting helicopter vibrations and a research tool to quantify the effects of structural properties, aerodynamic interactions, and vibration reduction devices on vehicle vibration levels is described. The analysis consists of a base program utilizing an impedance matching technique to represent the coupled rotor/airframe dynamics of the system supported by inputs from several external programs supplying sophisticated rotor and airframe aerodynamic and structural dynamic representation. The theoretical background, computer program capabilities and limited correlation results are presented in this report. Correlation results using scale model wind tunnel results show that the analysis can adequately predict trends of vibration variations with airspeed and higher harmonic control effects. Predictions of absolute values of vibration levels were found to be very sensitive to modal characteristics and results were not representative of measured values.
Neece, Cameron L
2014-03-01
Parents of children with developmental delays (DD) typically report elevated levels of parental stress compared with parents of typically developing children. Children with DD are also at high risk for exhibiting significant behaviour problems. Parental stress has been shown to impact the development of these behaviour problems; however, it is rarely addressed in interventions aimed at reducing child behaviour problems. The current study examined the efficacy of mindfulness-based stress reduction (MBSR) for parents of children with DD by investigating whether this intervention is effective in reducing parenting stress and whether decreases in parenting stress lead to reductions in behaviour problems among children with DD. Forty six parents of children with DD were randomly assigned to an immediate treatment or wait list-control group. Participants completed questionnaires assessing parental stress and child behaviour problems at intake and at a second assessment, which took place after only the immediate treatment group had received the MBSR. Parents who participated in MBSR reported significantly less stress and depression as well as greater life satisfaction compared with wait list-control parents. Regarding child outcomes, children whose parents participated in MBSR were reported to have fewer behaviour problems following the intervention, specifically in the areas of attention problems and ADHD symptomatology. Results indicated that MBSR may be an effective intervention for ameliorating parental stress and mental health problems among parents of children with DD. Additionally, these benefits may 'spill over' and improve behaviour challenges among these children. © 2013 John Wiley & Sons Ltd.
Oteer, Rabee
2015-01-01
This study aimed to identify the work-related stress and its subsequent problems among teachers of the public schools which operated the school-based Violence Reduction Program (VRP) in the governorate of Tulkarm during the second semester of 2015-2016. Besides, it aimed to identify the effect of specific variables, such as gender, specialization,…
Directory of Open Access Journals (Sweden)
V. S. Zarubin
2016-01-01
dependence of the absorption factor on the local intensity of this radiation. Furthermore, it can be a significant dependence of this factor on the local value of the material temperature, reflecting the above-mentioned relationship between the absorption of electromagnetic wave energy and the excitation of material microparticles. This process can be described by Boltzmann distribution function that comprises the energy to activate microparticles and the local value of temperature.This paper presents a variational formulation of the nonlinear problem of stationary heat conduction in a plate for the case when the radiation reduction factor in relation to the Bouguer law depends on the local temperature. This formulation includes a functional that can have several fixed points corresponding to different steady states of the plate temperature. Analysis of the properties of this functional enabled us to identify the stationary points, which correspond to the realized temperature distribution in the plate.
DOE/ANL/HTRI heat exchanger tube vibration data bank
Energy Technology Data Exchange (ETDEWEB)
Halle, H.; Chenoweth, J.M.; Wambsganss, M.W.
1981-01-01
This addendum to the DOE/ANL/HTRI Heat Exchanger Tube Vibration Data Bank includes 16 new case histories of field experiences. The cases include several exchangers that did not experience vibration problems and several for which acoustic vibration was reported.
DEFF Research Database (Denmark)
Nielsen, Søren R. K.
The present collection of solved problems has been published as a supplement to the textbook Svingningsteori. Bind 1. Lineær svingningsteori,Aalborg tekniske Universitetsforlag, 1991, whicj is used in the introductory course on linear vibration theory that is being given on th e8th semester...
Reliability Analysis of Random Vibration Transmission Path Systems
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Wei Zhao
2017-01-01
Full Text Available The vibration transmission path systems are generally composed of the vibration source, the vibration transfer path, and the vibration receiving structure. The transfer path is the medium of the vibration transmission. Moreover, the randomness of transfer path influences the transfer reliability greatly. In this paper, based on the matrix calculus, the generalized second moment technique, and the stochastic finite element theory, the effective approach for the transfer reliability of vibration transfer path systems was provided. The transfer reliability of vibration transfer path system with uncertain path parameters including path mass and path stiffness was analyzed theoretically and computed numerically, and the correlated mathematical expressions were derived. Thus, it provides the theoretical foundation for the dynamic design of vibration systems in practical project, so that most random path parameters can be considered to solve the random problems for vibration transfer path systems, which can avoid the system resonance failure.
Innovative Techniques Simplify Vibration Analysis
2010-01-01
In the early years of development, Marshall Space Flight Center engineers encountered challenges related to components in the space shuttle main engine. To assess the problems, they evaluated the effects of vibration and oscillation. To enhance the method of vibration signal analysis, Marshall awarded Small Business Innovation Research (SBIR) contracts to AI Signal Research, Inc. (ASRI), in Huntsville, Alabama. ASRI developed a software package called PC-SIGNAL that NASA now employs on a daily basis, and in 2009, the PKP-Module won Marshall s Software of the Year award. The technology is also used in many industries: aircraft and helicopter, rocket engine manufacturing, transportation, and nuclear power."
1990-06-01
The project was an evaluation of the potential for the legal liability of alcoholic beverage servers to stimulate preventative serving practices and thus reduce alcohol-involved traffic problems. Legal analyses of judicial and legislative actions wit...
1990-06-01
The project was an evaluation of the potential for the legal liability of alcoholic beverage servers to stimulate preventative serving practices and thus reduce alcohol-involved traffic problems. Legal analyses of judicial and legislative actions wit...
Gebler, Malte
2013-01-01
Summary Transport systems face significant input- and output-related challenges in the upcoming decades. To tackle climate change – the major output challenge - an 80% CO2 reduction has to be achieved by 2050 (base year 1990). This requires a sustainabi
Free-Vibration Analysis of Structures
Gupta, K. K.
1985-01-01
Improved numerical procedure more than twice as fast as previous methods. Unified numerical algorithm efficiently solves free-vibration problems of stationary or spinning structures with or without viscous or structural damping. Algorithm used to solve static problems involving multiple loads and to solve quadratic matrix eigenvalue problems associated with finite-dynamic-element structural discretization.
Watanabe, Takao; Stoorvogel, Antonie Arij
2001-01-01
This paper establishes a new class of the reduced-order controllers in the continuous-time as well as discrete-time $H_\\infty$ control problems. The reduced-order controllers are characterized by unstable transmission zeros of off-diagonal subsystems in the generalized plant. Algorithms to obtain
F.D. Barb
2004-01-01
textabstractIn this paper we address the problem of reducing the order of a linear system affected by uncertainties from the robust dissipative perspective introduced in Barb. Firstly, we show that all major balanced truncation techniques developed and reported in the literature of the last two
Nieuwsma, Jason A; Wray, Laura O; Voils, Corrine I; Gierisch, Jennifer M; Dundon, Margaret; Coffman, Cynthia J; Jackson, George L; Merwin, Rhonda; Vair, Christina; Juntilla, Karen; White-Clark, Courtney; Jeffreys, Amy S; Harris, Amy; Owings, Michael; Marr, Johnpatrick; Edelman, David
2017-09-01
Health behaviors related to diet, tobacco usage, physical activity, medication adherence, and alcohol use are highly determinative of risk for developing cardiovascular disease. This paper describes a study protocol to evaluate a problem-solving intervention that aims to help patients at risk for developing cardiovascular disease address barriers to adopting positive health behaviors in order to reduce cardiovascular risk. Eligible patients are adults enrolled in Veterans Affairs (VA) health care who have not experienced a cardiovascular event but are at elevated risk based on their Framingham Risk Score (FRS). Participants in this two-site study are randomized to either the intervention or care as usual, with a target of 400 participants. The study intervention, Healthy Living Problem-Solving (HELPS), consists of six group sessions conducted approximately monthly interspersed with individualized coaching calls to help participants apply problem-solving principles. The primary outcome is FRS, analyzed at the beginning and end of the study intervention (6months). Participants also complete measures of physical activity, caloric intake, self-efficacy, group cohesion, problem-solving capacities, and demographic characteristics. Results of this trial will inform behavioral interventions to change health behaviors in those at risk for cardiovascular disease and other health conditions. ClinicalTrials.gov identifier NCT01838226. Published by Elsevier Inc.
Modeling Displacement Measurement using Vibration Transducers
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AGOSTON Katalin
2014-05-01
Full Text Available This paper presents some aspects regarding to small displacement measurement using vibration transducers. Mechanical faults, usages, slackness’s, cause different noises and vibrations with different amplitude and frequency against the normal sound and movement of the equipment. The vibration transducers, accelerometers and microphone are used for noise and/or sound and vibration detection with fault detection purpose. The output signal of the vibration transducers or accelerometers is an acceleration signal and can be converted to either velocity or displacement, depending on the preferred measurement parameter. Displacement characteristics are used to indicate when the machine condition has changed. There are many problems using accelerometers to measure position or displacement. It is important to determine displacement over time. To determinate the movement from acceleration a double integration is needed. A transfer function and Simulink model was determinate for accelerometers with capacitive sensing element. Using these models the displacement was reproduced by low frequency input.
High Energy Vibration for Gas Piping
Lee, Gary Y. H.; Chan, K. B.; Lee, Aylwin Y. S.; Jia, ShengXiang
2017-07-01
In September 2016, a gas compressor in offshore Sarawak has its rotor changed out. Prior to this change-out, pipe vibration study was carried-out by the project team to evaluate any potential high energy pipe vibration problems at the compressor’s existing relief valve downstream pipes due to process condition changes after rotor change out. This paper covers high frequency acoustic excitation (HFAE) vibration also known as acoustic induced vibration (AIV) study and discusses detailed methodologies as a companion to the Energy Institute Guidelines for the avoidance of vibration induced fatigue failure, which is a common industry practice to assess and mitigate for AIV induced fatigue failure. Such detailed theoretical studies can help to minimize or totally avoid physical pipe modification, leading to reduce offshore plant shutdown days to plant shutdowns only being required to accommodate gas compressor upgrades, reducing cost without compromising process safety.
NOISE AND VIBRATION DAMPING FOR YACHT INTERIOR
Directory of Open Access Journals (Sweden)
Murat Aydın
2016-12-01
Full Text Available Vibration damping and sound insulation are essential for all vehicles. Because moving parts and external factors such as wind, tracks, etc. can cause vibration and noise. Wave which is a dynamic force, drive system and HVAC systems are the main vibration and noise generators in a vessel. These all can affect comfort level on board yachts. Different types of isolators and absorbers such as sylomer®, cork panels, etc. are used to reduce these effects. Comfort level on board yachts can be increased using these types of materials. Otherwise, discomfort of passenger and crew may increase. These materials not only reduce structure-borne and air-borne noise and vibrations from waves, air, engines, pumps, generators and HVAC systems but also protect vibration sensitive interior or fittings. Noise and vibration evaluation is an important issue for this reason. And, measurement tools must be used not only to minimize this problem but also fulfill the regulations such as “comfort class”. Besides, providing quiet and low vibration increases the costs too. From this point of view, this study aims to explain clearly how noise and vibration damping can be done in a yacht.
DOWNHOLE VIBRATION MONITORING & CONTROL SYSTEM
Energy Technology Data Exchange (ETDEWEB)
Martin E. Cobern
2004-08-31
The deep hard rock drilling environment induces severe vibrations into the drillstring, which can cause reduced rates of penetration (ROP) and premature failure of the equipment. The only current means of controlling vibration under varying conditions is to change either the rotary speed or the weight-on-bit (WOB). These changes often reduce drilling efficiency. Conventional shock subs are useful in some situations, but often exacerbate the problems. The objective of this project is development of a unique system to monitor and control drilling vibrations in a ''smart'' drilling system. This system has two primary elements: (1) The first is an active vibration damper (AVD) to minimize harmful axial, lateral and torsional vibrations. The hardness of this damper will be continuously adjusted using a robust, fast-acting and reliable unique technology. (2) The second is a real-time system to monitor drillstring vibration, and related parameters. This monitor adjusts the damper according to local conditions. In some configurations, it may also send diagnostic information to the surface via real-time telemetry. The AVD is implemented in a configuration using magnetorheological (MR) fluid. By applying a current to the magnetic coils in the damper, the viscosity of the fluid can be changed rapidly, thereby altering the damping coefficient in response to the measured motion of the tool. Phase I of this program entailed modeling and design of the necessary subsystems and design, manufacture and test of a full laboratory prototype. Phase I of the project was completed by the revised end date of May 31, 2004. The objectives of this phase were met, and all prerequisites for Phase II have been completed.
DOWNHOLE VIBRATION MONITORING & CONTROL SYSTEM
Energy Technology Data Exchange (ETDEWEB)
Martin E. Cobern
2004-10-13
The deep hard rock drilling environment induces severe vibrations into the drillstring, which can cause reduced rates of penetration (ROP) and premature failure of the equipment. The only current means of controlling vibration under varying conditions is to change either the rotary speed or the weight-on-bit (WOB). These changes often reduce drilling efficiency. Conventional shock subs are useful in some situations, but often exacerbate the problems. The objective of this project is development of a unique system to monitor and control drilling vibrations in a ''smart'' drilling system. This system has two primary elements: (1) The first is an active vibration damper (AVD) to minimize harmful axial, lateral and torsional vibrations. The hardness of this damper will be continuously adjusted using a robust, fast-acting and reliable unique technology. (2) The second is a real-time system to monitor drillstring vibration, and related parameters. This monitor adjusts the damper according to local conditions. In some configurations, it may also send diagnostic information to the surface via real-time telemetry. The AVD is implemented in a configuration using magnetorheological (MR) fluid. By applying a current to the magnetic coils in the damper, the viscosity of the fluid can be changed rapidly, thereby altering the damping coefficient in response to the measured motion of the tool. Phase I of this program entailed modeling and design of the necessary subsystems and design, manufacture and test of a full laboratory prototype. Phase I of the project was completed by the revised end date of May 31, 2004. The objectives of this phase were met, and all prerequisites for Phase II have been completed. The month of June, 2004 was primarily occupied with the writing of the Phase I Final Report, the sole deliverable of Phase I, which will be submitted in the next quarter. Redesign of the laboratory prototype and design of the downhole (Phase II) prototype was
Active structural elements within a general vibration control framework
Holterman, J.; de Vries, Theodorus J.A.; Isermann, R.
2000-01-01
High-precision machines typically suffer from small but annoying vibrations. As the most appropriate solution to a particular vibration problem is not always obvious, it may be convenient to cast the problem in a more general framework. This framework may then be used for frequency response
Tunable Passive Vibration Suppressor
Boechler, Nicholas (Inventor); Dillon, Robert Peter (Inventor); Daraio, Chiara (Inventor); Davis, Gregory L. (Inventor); Shapiro, Andrew A. (Inventor); Borgonia, John Paul C. (Inventor); Kahn, Daniel Louis (Inventor)
2016-01-01
An apparatus and method for vibration suppression using a granular particle chain. The granular particle chain is statically compressed and the end particles of the chain are attached to a payload and vibration source. The properties of the granular particles along with the amount of static compression are chosen to provide desired filtering of vibrations.
Indian Academy of Sciences (India)
We make music by causing strings, membranes, or air columns to vibrate. Engineers design safe structures by control- ling vibrations. I will describe to you a very simple vibrating system and the mathematics needed to analyse it. The ideas were born in the work of Joseph-Louis Lagrange (1736–1813), and I begin by quot-.
Vibrations of Damaged Functionally Graded Cantilever Beams
Byrd, Larry W.; Birman, Victor
2008-02-01
The paper discusses closed-form solutions of the problems of free and forced vibrations of a functionally graded cantilever FGM beam with and without damage. The mode of damage considered in the paper is represented by cracks that are perpendicular to the axis of the beam. Notably, such mode of damage was observed in experiments on representative FGM beams. Forced vibrations considered in the paper were generated by a kinematic excitation of the clamped end of the beam.
Agarwal, Mukul
2010-01-01
Consider a scenerio where various users want to communicate with each other over an unknown network to within a fidelity criterion. Thus, there are various users. Each user has a source that it wants to send to another user to within some distortion level. We abstract this problem as that of universal communication of random sources over networks to within a distortion criterion. We compute ta universally reliably achievable region for a set of networks where networks in the set are defined in terms of end to end distortion that they achieve for transmission of independent signals between various nodes assuming that there is common randomness between sender and corresponding receiver. Using this, we provide results for when communication of independent signals to within particular fidelity criteria is possible in terms of when reliable communication is possible. Using this, we show that when the sources at the various nodes are independent of each other, it is sufficient to consider separation architectures: ...
Vibration analysis of cryocoolers
Tomaru, Takayuki; Suzuki, Toshikazu; Haruyama, Tomiyoshi; Shintomi, Takakazu; Yamamoto, Akira; Koyama, Tomohiro; Li, Rui
2004-05-01
The vibrations of Gifford-McMahon (GM) and pulse-tube (PT) cryocoolers were measured and analyzed. The vibrations of the cold-stage and cold-head were measured separately to investigate their vibration mechanisms. The measurements were performed while maintaining the thermal conditions of the cryocoolers at a steady state. We found that the vibration of the cold-head for the 4 K PT cryocooler was two orders of magnitude smaller than that of the 4 K GM cryocooler. On the other hand, the vibration of the cold-stages for both cryocoolers was of the same order of magnitude. From a spectral analysis of the vibrations and a simulation, we concluded that the vibration of the cold-stage is caused by an elastic deformation of the pulse tubes (or cylinders) due to the pressure oscillation of the working gas.
Vibration analysis of cryocoolers
Energy Technology Data Exchange (ETDEWEB)
Tomaru, Takayuki; Suzuki, Toshikazu; Haruyama, Tomiyoshi; Shintomi, Takakazu; Yamamoto, Akira [High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki (Japan); Koyama, Tomohiro; Rui Li [Sumitomo Heavy Industries Ltd., Tokyo (Japan)
2004-05-01
The vibrations of Gifford-McMahon (GM) and pulse-tube (PT) cryocoolers were measured and analyzed. The vibrations of the cold-stage and cold-head were measured separately to investigate their vibration mechanisms. The measurements were performed while maintaining the thermal conditions of the cryocoolers at a steady state. We found that the vibration of the cold-head for the 4 K PT cryocooler was two orders of magnitude smaller than that of the 4 K GM cryocooler. On the other hand, the vibration of the cold-stages for both cryocoolers was of the same order of magnitude. From a spectral analysis of the vibrations and a simulation, we concluded that the vibration of the cold-stage is caused by an elastic deformation of the pulse tubes (or cylinders) due to the pressure oscillation of the working gas. (Author)
Vibration of imperfect rotating disk
Directory of Open Access Journals (Sweden)
Půst L.
2011-12-01
Full Text Available This study is concerned with the theoretical and numerical calculations of the flexural vibrations of a bladed disk. The main focus of this study is to elaborate the basic background for diagnostic and identification methods for ascertaining the main properties of the real structure or an experimental model of turbine disks. The reduction of undesirable vibrations of blades is proposed by using damping heads, which on the experimental model of turbine disk are applied only on a limited number of blades. This partial setting of damping heads introduces imperfection in mass, stiffness and damping distribution on the periphery and leads to more complicated dynamic properties than those of a perfect disk. Calculation of FEM model and analytic—numerical solution of disk behaviour in the limited (two modes frequency range shows the splitting of resonance with an increasing speed of disk rotation. The spectrum of resonance is twice denser than that of a perfect disk.
Hand-Arm vibration assessment among tiller operator
Directory of Open Access Journals (Sweden)
P. Nassiri
2013-08-01
Result: Results of the present study indicated that in all measured situations, exposure to hand arm vibration was higher than the standard limit suggested by Iranian occupational health committee and there was risk of vibration-induced disorders. The maximum exposure to vibration is in plowing ground. Exposure to hand arm vibration in three modes of plowing, transmission and natural, were respectively 16.95, 14.16 and 8.65 meters per second squared. Additionally, in all situations, vibration exposure was highest in the X-axis in comparison with Z- and Y-axes. .Conclusion: This study emphasizes on the need to provide intervention and controlling and managing strategies in order to eliminate or reduce vibration transmitted from tiller to operators hand and arm and also prevent to serious problems including neurovascular disorders, discomfort and white finger syndrome. Meanwhile, more studies are necessary to identify the sources of vibration on different models of tiller.
Simulation studies for multichannel active vibration control
Prakash, Shashikala; Balasubramaniam, R.; Praseetha, K. K.
2003-10-01
Traditional approach to vibration control uses passive techniques, which are relatively large, costly and ineffective at low frequencies. Active Vibration Control (AVC) is used to overcome these problems & in AVC additional sources (secondary) are used to cancel vibration from primary source based on the principle of superposition theorem Since the characteristics of the vibration source and environment are time varying, the AVC system must be adaptive. Adaptive systems have the ability to track time varying disturbances and provide optimal control over a much broader range of conditions than conventional fixed control systems. In multi channel AVC vibration fields in large dimensions are controlled & is more complicated. Therefore to actively control low frequency vibrations on large structures, multi channel AVC requires a control system that uses multiple secondary sources to control the vibration field simultaneously at multiple error sensor locations. The error criterion that can be directly measured is the sum of squares of outputs of number of sensors. The adaptive algorithm is designed to minimize this & the algorithm implemented is the "Multiple error LMS algorithm." The best known applications of multiple channel FXLMS algorithm is in real time AVC and system identification. More wider applications are in the control of propeller induced noise in flight cabin interiors. In the present paper the results of simulation studies carried out in MATLAB as well as on TMS320C32 DSP processor will be brought out for a two-channel case.
Vibrations and stability of complex beam systems
Stojanović, Vladimir
2015-01-01
This book reports on solved problems concerning vibrations and stability of complex beam systems. The complexity of a system is considered from two points of view: the complexity originating from the nature of the structure, in the case of two or more elastically connected beams; and the complexity derived from the dynamic behavior of the system, in the case of a damaged single beam, resulting from the harm done to its simple structure. Furthermore, the book describes the analytical derivation of equations of two or more elastically connected beams, using four different theories (Euler, Rayleigh, Timoshenko and Reddy-Bickford). It also reports on a new, improved p-version of the finite element method for geometrically nonlinear vibrations. The new method provides more accurate approximations of solutions, while also allowing us to analyze geometrically nonlinear vibrations. The book describes the appearance of longitudinal vibrations of damaged clamped-clamped beams as a result of discontinuity (damage). It...
Vision Influence on Whole-Body Human Vibration Comfort Levels
Duarte, Maria Lúcia Machado; de Brito Pereira, Matheus
2006-01-01
The well being of people needs to be a priority in the modern world. In that respect, vibration cannot be one more cause of stress. Besides that, vibration comfort is very important, since high levels may cause health or even tasks' accomplishment problems. Several parameters may influence the levels of vibration a human being supports. Among them, one can mention the influence of gender, age, corporeal mass index (CMI), temperature, humor, anxiety, hearing, posture, vision, etc. The first th...
14th International Conference on Acoustics and Vibration of Mechanical Structures
Marinca, Vasile
2018-01-01
This book is a collection of papers presented at Acoustics and Vibration of Mechanical Structures 2017 – AVMS 2017 – highlighting the current trends and state-of-the-art developments in the field. It covers a broad range of topics, such as noise and vibration control, noise and vibration generation and propagation, the effects of noise and vibration, condition monitoring and vibration testing, modeling, prediction and simulation of noise and vibration, environmental and occupational noise and vibration, noise and vibration attenuators, as well as biomechanics and bioacoustics. The book also presents analytical, numerical and experimental techniques for evaluating linear and non-linear noise and vibration problems (including strong nonlinearity). It is primarily intended for academics, researchers and professionals, as well as PhD students in various fields of the acoustics and vibration of mechanical structures.
Whole body vibration improves body mass, flexibility and strength in ...
African Journals Online (AJOL)
related fitness benefits; not only those associated with obesity, but also the reduction ... The use of whole body vibration (WBV) as an exercise intervention for health ..... muscular strength, muscular endurance and aerobic capacity. In addition ...
Application of eigenfunction orthogonalities to vibration problems
CSIR Research Space (South Africa)
Fedotov, I
2009-07-01
Full Text Available II WCE 2009, July 1 - 3, 2009, London, U.K. ISBN:978-988-18210-1-0 WCE 2009 the variation of the action ∫= 2 1 t t LdtS must be equal to zero for all 1t and 2t . [5]. Thus ∫ == 2 1 0 t t LdtS δδ (2) (It... ′ ′ + + = ∫ where ).1()0()( 21 2 0 1 0 22 2 nn yydxxyy nn αα ++′= ∫ (18) Proceedings of the World Congress on Engineering 2009 Vol II WCE 2009, July 1 - 3, 2009, London, U.K. ISBN:978-988-18210-1-0 WCE 2009 In the case α₀ = 1α =0 orthogonality...
Using periodicity to mitigate ground vibration
DEFF Research Database (Denmark)
Andersen, Lars Vabbersgaard
2015-01-01
Introduction of trenches, barriers and wave impeding blocks on the transmission path between a source and receiver can be used for mitigation of ground vibration. However, to be effective a barrier must have a depth of about one wavelength of the waves to be mitigated. Hence, while great reductions...
Lambda-matrices and vibrating systems
Lancaster, Peter; Stark, M; Kahane, J P
1966-01-01
Lambda-Matrices and Vibrating Systems presents aspects and solutions to problems concerned with linear vibrating systems with a finite degrees of freedom and the theory of matrices. The book discusses some parts of the theory of matrices that will account for the solutions of the problems. The text starts with an outline of matrix theory, and some theorems are proved. The Jordan canonical form is also applied to understand the structure of square matrices. Classical theorems are discussed further by applying the Jordan canonical form, the Rayleigh quotient, and simple matrix pencils with late
Noise and vibration in friction systems
Sergienko, Vladimir P
2015-01-01
The book analyzes the basic problems of oscillation processes and theoretical aspects of noise and vibration in friction systems. It presents generalized information available in literature data and results of the authors in vibroacoustics of friction joints, including car brakes and transmissions. The authors consider the main approaches to abatement of noise and vibration in non-stationary friction processes. Special attention is paid to materials science aspects, in particular to advanced composite materials used to improve the vibroacoustic characteristics of tribopairs The book is intended for researchers and technicians, students and post-graduates specializing in mechanical engineering, maintenance of machines and transport means, production certification, problems of friction and vibroacoustics.
Muellmann, S; Landgraf-Rauf, K; Brand, T; Zeeb, H; Pischke, C R
2017-04-01
Objective: To summarize the current evidence on the effectiveness of school-based interventions for the maintenance of mental health and the prevention of psychosocial problems among pupils. Methods: A systematic literature search of reviews published between 2007 and 2015 was carried out. Databases searched included Medline, PsycINFO, Campbell Library, Cochrane Library, NICE, ERIC, and Web of Science. Study selection, data extraction, and quality assessment (using AMSTAR criteria) were performed by 2 independent reviewers. Results: 6 reviews covering 331 primary studies were included in this review of reviews. Findings of three reviews with a focus on the maintenance and/or promotion of mental health and general well-being suggested that interventions aimed at changes in the social and the school environment were more effective than those that only targeted individual behavior change among pupils. Interventions for the reduction of mobbing/bullying were most effective if they comprised organizational changes at schools, such as playground and schoolyard supervision, and disciplinary measures. One review suggested strong evidence for the effectiveness of classroom management to reduce violent behavior among pupils. Conclusions: Participation in interventions promoting changes in the school environment, in addition to individual behavior change, appears to be associated with improved mental health among pupils and reductions in mobbing/bullying and violent behavior at schools. © Georg Thieme Verlag KG Stuttgart · New York.
Experimental study on titanium wire drawing with ultrasonic vibration.
Liu, Shen; Shan, Xiaobiao; Guo, Kai; Yang, Yuancai; Xie, Tao
2018-02-01
Titanium and its alloys have been widely used in aerospace and biomedical industries, however, they are classified as difficult-to-machine materials. In this paper, ultrasonic vibration is imposed on the die to overcome the difficulties during conventional titanium wire drawing processes at the room temperature. Numerical simulations were performed to investigate the variation of axial stress within the contacting region and study the change of the drawing stress with several factors in terms of the longitudinal amplitude and frequency of the applied ultrasonic vibration, the diameter reduction ratio, and the drawing force. An experimental testing equipment was established to measure the drawing torque and rotational velocity of the coiler drum during the wire drawing process. The result indicates the drawing force increases with the growth of the drawing velocity and the reduction ratio, whether with or without vibrations. Application of either form of ultrasonic vibrations contributes to the further decrease of the drawing force, especially the longitudinal vibration with larger amplitude. SEM was employed to detect the surface morphology of the processed wires drawn under the three circumstances. The surface quality of the drawn wires with ultrasonic vibrations was apparently improved compared with those using conventional method. In addition, the longitudinal and torsional composite vibration was more effective for surface quality improvement than pure longitudinal vibration, however, at the cost of weakened drawing force reduction effect. Copyright © 2017 Elsevier B.V. All rights reserved.
Turner, Sarah; Torode, Margaret; Climstein, Mike; Naughton, Geraldine; Greene, David; Baker, Michael K.; Fiatarone Singh, Maria A.
2011-01-01
Purpose. To examine the effects of two doses of low-frequency (12 Hz), low-magnitude (0.3 g), whole body vibration on markers of bone formation and resorption in postmenopausal women. Methods. Women were recruited and randomized into a sham vibration control group, one time per week vibration group (1×/week), or three times per week vibration group (3×/week). Vibration exposure consisted of 20 minutes of intermittent vibration for the 1×/week and 3×/week groups, and sham vibration (vibration group but not in the 1×/wk vibration group compared with sham control (P vibration 3×/week for eight weeks in postmenopausal women results in a significant reduction in NTx/Cr, a marker of bone resorption, when compared with sham vibration exposure. PMID:21772975
Plagiarism: Problem, Behaviour and Reduction
kiran Malik; Pritee
2012-01-01
Plagiarism has been troubling academic world since long.With the invention of electronic resources like internet inrecent times, it has become easier and more accessible forstudents than ever before. Practice of plagiarism bystudents has resulted negative consequences in theacademic field, and university teachers are now facingproblems that are more challenging. This has led to theproduction and submission of assignments and researchworks that are not properly referenced and cited or, worsest...
Sensitivity of Footbridge Vibrations to Stochastic Walking Parameters
DEFF Research Database (Denmark)
Pedersen, Lars; Frier, Christian
2010-01-01
Some footbridges are so slender that pedestrian traffic can cause excessive vibrations and serviceability problems. Design guidelines outline procedures for vibration serviceability checks, but it is noticeable that they rely on the assumption that the action is deterministic, although in fact it...
Locomotor problems of supersonic aviation and astronautics.
Remes, P
1989-04-01
Modern high-speed aviation and space flight are fraught with many problems and require a high standard of health and fitness. Those responsible for the health of pilots must appreciate the importance of early diagnosis even before symptoms appear. This is particularly true in terms of preventing spinal injuries where even a single Schmorl's node may make a pilot unfit for high-speed flying. Spinal fractures are frequent during emergency ejection and landing. Helicopter crews are particularly prone to spinal disc degeneration due to vibration. By effective lowering of vibration by changes in the seats, a reduction in such lesions is possible. The osteoporosis and muscle atrophy occurring among astronauts subjected to prolonged weightlessness can be prevented by regular physical exercises.
Model Indepedent Vibration Control
Yuan, Jing
2010-01-01
A NMIFC system is proposed for broadband vibration control. It has two important features. Feature F1 is that the NMIFC is stable without introducing any invasive effects, such as probing signals or controller perturbations, into the vibration system; feature F2 is
DEFF Research Database (Denmark)
Nielsen, Søren R. K.
The present textbook has been written based on previous lecture notes for a course on stochastic vibration theory that is being given on the 9th semester at Aalborg University for M. Sc. students in structural engineering. The present 4th edition of this textbook on linear stochastic vibration...
DEFF Research Database (Denmark)
Nielsen, Søren R. K.
The present textbook has been written based on previous lecture notes for a course on stochastic vibration theory that is being given on the 9th semester at Aalborg University for M. Sc. students in structural engineering. The present 2nd edition of this textbook on linear stochastic vibration...
Hydroelastic Vibrations of Ships
DEFF Research Database (Denmark)
Jensen, Jørgen Juncher; Folsø, Rasmus
2002-01-01
A formula for the necessary hull girder bending stiffness required to avoid serious springing vibrations is derived. The expression takes into account the zero crossing period of the waves, the ship speed and main dimensions. For whipping vibrations the probability of exceedance for the combined...
Gearbox vibration diagnostic analyzer
1992-01-01
This report describes the Gearbox Vibration Diagnostic Analyzer installed in the NASA Lewis Research Center's 500 HP Helicopter Transmission Test Stand to monitor gearbox testing. The vibration of the gearbox is analyzed using diagnostic algorithms to calculate a parameter indicating damaged components.
Mechanical vibration and shock analysis, sinusoidal vibration
Lalanne, Christian
2014-01-01
Everything engineers need to know about mechanical vibration and shock...in one authoritative reference work! This fully updated and revised 3rd edition addresses the entire field of mechanical vibration and shock as one of the most important types of load and stress applied to structures, machines and components in the real world. Examples include everything from the regular and predictable loads applied to turbines, motors or helicopters by the spinning of their constituent parts to the ability of buildings to withstand damage from wind loads or explosions, and the need for cars to m
Package security recorder of vibration
Wang, Xiao-na; Hu, Jin-liang; Song, Shi-de
2013-08-01
This paper introduces a new kind of electronic product — Package Security Recorder of Vibration. It utilizes STC89C54RD+ LQFP-44 MCU as its main controller. At the same time, it also utilizes Freescale MMA845A 3-Axis 8-bit/12-bit Digital Accelerometer and Maxim DS1302 Trickle Charge Timekeeping Chip. It utilizes the MCU to read the value of the accelerometer and the value of the timekeeping chip, and records the data into the inner E2PROM of MCU. The whole device achieves measuring, reading and recording the time of the vibration and the intensity of the vibration. When we need the data, we can read them out. The data can be used in analyzing the condition of the cargo when it transported. The device can be applied to monitor the security of package. It solves the problem of responsibility affirming, when the valuable cargo are damaged while it transported. It offers powerful safeguard for the package. It's very value for application.
The Effect of a Vibration Absorber on the Damping Properties of Alpine Skis
Directory of Open Access Journals (Sweden)
Stefan Schwanitz
2018-02-01
Full Text Available Coupled bending-torsion vibrations at the shovel are a severe problem when running an alpine ski at high velocities on hard or icy slopes. Thus, a major goal for ski manufacturers is to dampen vibrations through a proper multi-material design and/or additional absorbers. The aim of this study was to examine the effectiveness of a particular vibration absorber on a commercial slalom ski through a series of laboratory tests as well as a subjective field evaluation. Therefore, two identical pairs of ski were used and the absorber was deactivated on one pair. Laboratory tests revealed reductions of 5% to 49% of bending vibrations on skis with activated absorber. Subjective evaluation by 6 subjects suggested minor differences in the mean of the evaluated criteria turnablity, edge grip, steering behavior and stability towards a better performance of the skis with activated absorber. Subjects were able to identify the absorber mode with a success rate of 61.1%.
Resonant vibration control of wind turbine blades
DEFF Research Database (Denmark)
Svendsen, Martin Nymann; Krenk, Steen; Høgsberg, Jan Becker
2010-01-01
The paper deals with introduction of damping to specific vibration modes of wind turbine blades, using a resonant controller with acceleration feedback. The wind turbine blade is represented by three-dimensional, two-node finite elements in a local, rotating frame of reference. The element....... The efficiency of the resonant controller is demonstrated for a representative turbine blade exposed to turbulent wind loading. It is found that the present explicit tuning procedure yields close to optimal tuning, with very limited modal spill-over and effective reduction of the vibration amplitudes....
Active Vibration Control in a Rotor System by an Active Suspension with Linear Actuators
Directory of Open Access Journals (Sweden)
M. Arias-Montiel
2014-10-01
Full Text Available In this paper the problem of modeling, analysis and unbalance response control of a rotor system with two disks in an asymmetrical configuration is treated. The Finite Element Method (FEM is used to get the system model including the gyroscopic effects and then, the obtained model is experimentally validated. Rotordynamic analysis is carried out using the finite element model obtaining the Campbell diagram, the natural frequencies and the critical speeds of the rotor system. An asymptotic observer is designed to estimate the full state vector which is used to synthesize a Linear Quadratic Regulator (LQR to reduce the vibration amplitudes when the system passes through the first critical speed. Some numerical simulations are carried out to verify the closed-loop system behavior. The active vibration control scheme is experimentally validated using an active suspension with electromechanical linear actuators, obtaining significant reductions in the resonant peak.
Sreekanta Murthy, T.
1992-01-01
Results of the investigation of formal nonlinear programming-based numerical optimization techniques of helicopter airframe vibration reduction are summarized. The objective and constraint function and the sensitivity expressions used in the formulation of airframe vibration optimization problems are presented and discussed. Implementation of a new computational procedure based on MSC/NASTRAN and CONMIN in a computer program system called DYNOPT for optimizing airframes subject to strength, frequency, dynamic response, and dynamic stress constraints is described. An optimization methodology is proposed which is thought to provide a new way of applying formal optimization techniques during the various phases of the airframe design process. Numerical results obtained from the application of the DYNOPT optimization code to a helicopter airframe are discussed.
Directory of Open Access Journals (Sweden)
J.-J. Sinou
2017-01-01
Full Text Available During the past decades, the problem of friction-induced vibration and noise has been the subject of a huge amount of works. Various numerical simulations with finite elements models have been largely investigated to predict squeal events. Although a nonlinear analysis is more predictive than Complex Eigenvalues Analysis, one of the main drawbacks of the time analysis is the need of large computational efforts. In view of the complexity of the subject, this approach appears still computationally too expensive to be used in industry for finite element models. In this study, the potential of a new reduced model based on a double modal synthesis (i.e., a classical modal reduction via Craig and Bampton plus a condensation at the frictional interface based on complex modes for the prediction of self-excited vibrations of brake squeal is discussed. The effectiveness of the proposed modal reduction is tested on a finite element model of a simplified brake system. It will be shown that numerical results of times analysis by applying the proposed reduction correlate well with those of the nonlinear analysis based on a reference model, hence demonstrating the potential of using adapted modal reductions to predict the squeal propensity and to estimate self-excited vibrations and noise.
Wind-induced vibration of stay cables
2007-08-01
Cable-stayed bridges have become the form of choice over the past several decades for bridges in the medium- to long-span range. In some cases, serviceability problems involving large amplitude vibrations of stay cables under certain wind and rain co...
Lambda-matrices and vibrating systems
Lancaster, Peter
2002-01-01
Features aspects and solutions of problems of linear vibrating systems with a finite number of degrees of freedom. Starts with development of necessary tools in matrix theory, followed by numerical procedures for relevant matrix formulations and relevant theory of differential equations. Minimum of mathematical abstraction; assumes a familiarity with matrix theory, elementary calculus. 1966 edition.
Damping of Torsional Beam Vibrations by Control of Warping Displacement
DEFF Research Database (Denmark)
Høgsberg, Jan Becker; Hoffmeyer, David; Ejlersen, Christian
2016-01-01
Supplemental damping of torsional beam vibrations is considered by viscous bimoments acting on the axial warping displacement at the beam supports. The concept is illustrated by solving the governing eigenvalue problem for various support configurations with the applied bimoments represented...
Structural Stability and Vibration
DEFF Research Database (Denmark)
Wiggers, Sine Leergaard; Pedersen, Pauli
This book offers an integrated introduction to the topic of stability and vibration. Strikingly, it describes stability as a function of boundary conditions and eigenfrequency as a function of both boundary conditions and column force. Based on a post graduate course held by the author at the Uni......This book offers an integrated introduction to the topic of stability and vibration. Strikingly, it describes stability as a function of boundary conditions and eigenfrequency as a function of both boundary conditions and column force. Based on a post graduate course held by the author...... and their derivation, thus stimulating them to write interactive and dynamic programs to analyze instability and vibrational modes....
Dynamics and vibrations progress in nonlinear analysis
Kachapi, Seyed Habibollah Hashemi
2014-01-01
Dynamical and vibratory systems are basically an application of mathematics and applied sciences to the solution of real world problems. Before being able to solve real world problems, it is necessary to carefully study dynamical and vibratory systems and solve all available problems in case of linear and nonlinear equations using analytical and numerical methods. It is of great importance to study nonlinearity in dynamics and vibration; because almost all applied processes act nonlinearly, and on the other hand, nonlinear analysis of complex systems is one of the most important and complicated tasks, especially in engineering and applied sciences problems. There are probably a handful of books on nonlinear dynamics and vibrations analysis. Some of these books are written at a fundamental level that may not meet ambitious engineering program requirements. Others are specialized in certain fields of oscillatory systems, including modeling and simulations. In this book, we attempt to strike a balance between th...
Directory of Open Access Journals (Sweden)
Hakan Yazici
2016-01-01
Full Text Available This paper deals with the design of an observed based optimal state feedback controller having pole location constraints for an active vibration mitigation problem of an aircraft system. An eleven-degree-of-freedom detailed full aircraft mathematical model having active landing gears and a seated pilot body is developed to control and analyze aircraft vibrations caused by runway excitation, when the aircraft is taxiing. Ground induced vibration can contribute to the reduction of pilot’s capability to control the aircraft and cause the safety problem before take-off and after landing. Since the state variables of the pilot body are not available for measurement in practice, an observed based optimal controller is designed via Linear Matrix Inequalities (LMIs approach. In addition, classical LQR controller is designed to investigate effectiveness of the proposed controller. The system is then simulated against the bump and random runway excitation. The simulation results demonstrate that the proposed controller provides significant improvements in reducing vibration amplitudes of aircraft fuselage and pilot’s head and maintains the safety requirements in terms of suspension stroke and tire deflection.
Vibration Analysis and the Accelerometer
Hammer, Paul
2011-01-01
Have you ever put your hand on an electric motor or motor-driven electric appliance and felt it vibrate? Ever wonder why it vibrates? What is there about the operation of the motor, or the object to which it is attached, that causes the vibrations? Is there anything "regular" about the vibrations, or are they the result of random causes? In this…
Modeling of vibration for functionally graded beams
Yiğit Gülsemay; Şahin Ali; Bayram Mustafa
2016-01-01
In this study, a vibration problem of Euler-Bernoulli beam manufactured with Functionally Graded Material (FGM), which is modelled by fourth-order partial differential equations with variable coefficients, is examined by using the Adomian Decomposition Method (ADM).The method is one of the useful and powerful methods which can be easily applied to linear and nonlinear initial and boundary value problems. As to functionally graded materials, they are composites mixed by two or more materials a...
Free vibrations of circular cylindrical shells
Armenàkas, Anthony E; Herrmann, George
1969-01-01
Free Vibrations of Circular Cylindrical Shells deals with thin-walled structures that undergo dynamic loads application, thereby resulting in some vibrations. Part I discusses the treatment of problems associated with the propagation of plane harmonic waves in a hollow circular cylinder. In such search for solutions, the text employs the framework of the three-dimensional theory of elasticity. The text explains the use of tables of natural frequencies and graphs of representative mode shapes of harmonic elastic waves bounding in an infinitely long isotropic hollow cylinder. The tables are
DEFF Research Database (Denmark)
Thomsen, Jon Juel
About this textbook An ideal text for students that ties together classical and modern topics of advanced vibration analysis in an interesting and lucid manner. It provides students with a background in elementary vibrations with the tools necessary for understanding and analyzing more complex...... dynamical phenomena that can be encountered in engineering and scientific practice. It progresses steadily from linear vibration theory over various levels of nonlinearity to bifurcation analysis, global dynamics and chaotic vibrations. It trains the student to analyze simple models, recognize nonlinear...... phenomena and work with advanced tools such as perturbation analysis and bifurcation analysis. Explaining theory in terms of relevant examples from real systems, this book is user-friendly and meets the increasing interest in non-linear dynamics in mechanical/structural engineering and applied mathematics...
Topology optimization of free vibrations of fiber laser packages
DEFF Research Database (Denmark)
Hansen, Lars Voxen
2005-01-01
The optimization problems described in the present paper are inspired by the problem of fiber laser package design for vibrating environments. The optical frequency of tuned fiber lasers glued to stiff packages is sensitive to acoustic or other mechanical vibrations. The paper presents a method...... for reducing this sensitivity by limiting the glue point movement on the package while using only a limited knowledge of vibrating external forces. By use of topology optimization a density distribution for the package is obtained, where the critical eigenmode of the package only effects a small elongation...
Flow-Induced Vibration of Circular Cylindrical Structures
Energy Technology Data Exchange (ETDEWEB)
Chen, Shoei-Sheng [Argonne National Lab. (ANL), Argonne, IL (United States). Components Technology Division
1985-06-01
Flow-induced vibration is a term to denote those phenomena associated with the response of structures placed in or conveying fluid flow. More specifically, the terra covers those cases in which an interaction develops between fluid-dynamic forces and the inertia, damping or elastic forces in the structures. The study of these phenomena draws on three disciplines: (1) structural mechanics, (2) mechanical vibration, and (3) fluid dynamics. The vibration of circular cylinders subject to flow has been known to man since ancient times; the vibration of a wire at its natural frequency in response to vortex shedding was known in ancient Greece as aeolian tones. But systematic studies of the problem were not made until a century ago when Strouhal established the relationship between vortex shedding frequency and flow velocity for a given cylinder diameter. The early research in this area has beer summarized by Zdravkovich (1985) and Goldstein (1965). Flow-induced structural vibration has been experienced in numerous fields, including the aerospace industry, power generation/transmission (turbine blades, heat exchanger tubes, nuclear reactor components), civil engineering (bridges, building, smoke stacks), and undersea technology. The problems have usually been encountered or created accidentally through improper design. In most cases, a structural or mechanical component, designed to meet specific objectives, develops problems when the undesired effects of flow field have not been accounted for in the design. When a flow-induced vibration problem is noted in the design stage, the engineer has different options to eliminate the detrimental vibration. Unfortunately, in many situations, the problems occur after the components are already in operation; the "fix" usually is very costly. Flow-induced vibration comprises complex and diverse phenomena; subcritical vibration of nuclear fuel assemblies, galloping of transmission lines, flutter of pipes conveying fluid, and whirling
Vibration exposure and prevention in Japan.
Futatsuka, M; Ueno, T; Yamada, S
1994-05-01
Working conditions of vibration exposure have generally improved, but many difficult problems must be solved such as (1) hygienic improvements in a variety of vibrating tools; (2) improving working conditions, for example, by limiting the time of operation in spite of economic difficulties such as those faced by those who work on a piece rate basis; (3) gathering more complete information about the risk population because of the large number of self-employed in informal employment sectors; and (4) finding work places after rehabilitation for patients, particularly in mountainous rural areas or in small scale industries. Historical observation of vibration and preventive measures in Japanese national forests was presented on the basis of the results of a retrospective cohort study in Kyushu, Japan. Prevalence rate of VWF remarkably changed from 58.4% in the groups that began to operate chain saws in 1960 to only a few cases in the groups who started the operation after 1971. When we compare the relationships between the results of long term cohort study and the consequences of preventive measures of vibration syndrome, the most important factor is the decrease of vibration exposure (improvement in chain saws plus the time restriction system). The comprehensive prevention system used in Japanese national forests consists of the following: (1) Health care system; (2) Work regulation system; (3) System for improving mechanized tools; (4) Warming system to protect against cold conditions; and (5) Education and training system.
Vibration Isolation for Parallel Hydraulic Hybrid Vehicles
Directory of Open Access Journals (Sweden)
The M. Nguyen
2008-01-01
Full Text Available In recent decades, several types of hybrid vehicles have been developed in order to improve the fuel economy and to reduce the pollution. Hybrid electric vehicles (HEV have shown a significant improvement in fuel efficiency for small and medium-sized passenger vehicles and SUVs. HEV has several limitations when applied to heavy vehicles; one is that larger vehicles demand more power, which requires significantly larger battery capacities. As an alternative solution, hydraulic hybrid technology has been found effective for heavy duty vehicle because of its high power density. The mechanical batteries used in hydraulic hybrid vehicles (HHV can be charged and discharged remarkably faster than chemical batteries. This feature is essential for heavy vehicle hybridization. One of the main problems that should be solved for the successful commercialization of HHV is the excessive noise and vibration involving with the hydraulic systems. This study focuses on using magnetorheological (MR technology to reduce the noise and vibration transmissibility from the hydraulic system to the vehicle body. In order to study the noise and vibration of HHV, a hydraulic hybrid subsystem in parallel design is analyzed. This research shows that the MR elements play an important role in reducing the transmitted noise and vibration to the vehicle body. Additionally, locations and orientations of the isolation system also affect the efficiency of the noise and vibration mitigation. In simulations, a skyhook control algorithm is used to achieve the highest possible effectiveness of the MR isolation system.
AbouEisha, Hassan M.
2014-01-01
The problem of attribute reduction is an important problem related to feature selection and knowledge discovery. The problem of finding reducts with minimum cardinality is NP-hard. This paper suggests a new algorithm for finding exact reducts with minimum cardinality. This algorithm transforms the initial table to a decision table of a special kind, apply a set of simplification steps to this table, and use a dynamic programming algorithm to finish the construction of an optimal reduct. I present results of computer experiments for a collection of decision tables from UCIML Repository. For many of the experimented tables, the simplification steps solved the problem.
Vibration and Deflection Behavior of a Coal Auger Working Mechanism
Directory of Open Access Journals (Sweden)
Songyong Liu
2016-01-01
Full Text Available Because coal auger working mechanism faces problems such as excessive vibration, serious deflection, and low drilling efficiency, a new five-bit coal auger working mechanism test model was established to explore the influence factor on vibration and deflection under different conditions. Additionally, a simulation model was built to further research the effect of partial load and stabilizer arrangement, the correctness of which was proved by experiments. The results show that the vibration and deflection increase with drilling depth in the x direction, and they first increase and then gradually become stable in the y direction. In addition, the vibration, deflection, and deflection force increase with the partial load. By arranging the stabilizer every five drill-rod section intervals, the vibration and deflection can be decreased by 30% and 40% in the x direction and by 14.3% and 65.7% in y direction, respectively.
Vision Influence on Whole-Body Human Vibration Comfort Levels
Directory of Open Access Journals (Sweden)
Maria Lúcia Machado Duarte
2006-01-01
Full Text Available The well being of people needs to be a priority in the modern world. In that respect, vibration cannot be one more cause of stress. Besides that, vibration comfort is very important, since high levels may cause health or even tasks' accomplishment problems. Several parameters may influence the levels of vibration a human being supports. Among them, one can mention the influence of gender, age, corporeal mass index (CMI, temperature, humor, anxiety, hearing, posture, vision, etc. The first three parameters mentioned were already investigated in previous studies undertaken by GRAVI (Group of Acoustics and Vibration researchers. In this paper, the influence of vision is evaluated. The main objective with this series of tests performed is to try to quantify in a future the influence of each parameter in a global vibration comfort level. Conclusions are presented for the parameter investigated.
Nonlinear vibration with control for flexible and adaptive structures
Wagg, David
2015-01-01
This book provides a comprehensive discussion of nonlinear multi-modal structural vibration problems, and shows how vibration suppression can be applied to such systems by considering a sample set of relevant control techniques. It covers the basic principles of nonlinear vibrations that occur in flexible and/or adaptive structures, with an emphasis on engineering analysis and relevant control techniques. Understanding nonlinear vibrations is becoming increasingly important in a range of engineering applications, particularly in the design of flexible structures such as aircraft, satellites, bridges, and sports stadia. There is an increasing trend towards lighter structures, with increased slenderness, often made of new composite materials and requiring some form of deployment and/or active vibration control. There are also applications in the areas of robotics, mechatronics, micro electrical mechanical systems, non-destructive testing and related disciplines such as structural health monitoring. Two broader ...
Lyu, Bai-cheng; Wu, Wen-hua; Yao, Wei-an; Du, Yu
2017-06-01
Mooring system is the key equipment of FPSO safe operation. The soft yoke mooring system is regarded as one of the best shallow water mooring strategies and widely applied to the oil exploitation in the Bohai Bay in China and the Gulf of Mexico. Based on the analysis of numerous monitoring data obtained by the prototype monitoring system of one FPSO in the Bohai Bay, the on-site lateral vibration behaviors found on the site of the soft yoke subject to wave load were analyzed. ADAMS simulation and model experiment were utilized to analyze the soft yoke lateral vibration and it was determined that lateral vibration was resonance behaviors caused by wave excitation. On the basis of the soft yoke longitudinal restoring force being guaranteed, a TLD-based vibration damper system was constructed and the vibration reduction experiments with multi-tank space and multi-load conditions were developed. The experimental results demonstrated that the proposed TLD vibration reduction system can effectively reduce lateral vibration of soft yoke structures.
Time-resolved vibrational spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Tokmakoff, Andrei [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Champion, Paul [Northeastern Univ., Boston, MA (United States); Heilweil, Edwin J. [National Inst. of Standards and Technology (NIST), Boulder, CO (United States); Nelson, Keith A. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Ziegler, Larry [Boston Univ., MA (United States)
2009-05-14
This document contains the Proceedings from the 14th International Conference on Time-Resolved Vibrational Spectroscopy, which was held in Meredith, NH from May 9-14, 2009. The study of molecular dynamics in chemical reaction and biological processes using time-resolved spectroscopy plays an important role in our understanding of energy conversion, storage, and utilization problems. Fundamental studies of chemical reactivity, molecular rearrangements, and charge transport are broadly supported by the DOE's Office of Science because of their role in the development of alternative energy sources, the understanding of biological energy conversion processes, the efficient utilization of existing energy resources, and the mitigation of reactive intermediates in radiation chemistry. In addition, time-resolved spectroscopy is central to all fiveof DOE's grand challenges for fundamental energy science. The Time-Resolved Vibrational Spectroscopy conference is organized biennially to bring the leaders in this field from around the globe together with young scientists to discuss the most recent scientific and technological advances. The latest technology in ultrafast infrared, Raman, and terahertz spectroscopy and the scientific advances that these methods enable were covered. Particular emphasis was placed on new experimental methods used to probe molecular dynamics in liquids, solids, interfaces, nanostructured materials, and biomolecules.
Vibrational spectroscopy of resveratrol
Billes, Ferenc; Mohammed-Ziegler, Ildikó; Mikosch, Hans; Tyihák, Ernő
2007-11-01
In this article the authors deal with the experimental and theoretical interpretation of the vibrational spectra of trans-resveratrol (3,5,4'-trihydroxy- trans-stilbene) of diverse beneficial biological activity. Infrared and Raman spectra of the compound were recorded; density functional calculations were carried out resulting in the optimized geometry and several properties of the molecule. Based on the calculated force constants, a normal coordinate analysis yielded the character of the vibrational modes and the assignment of the measured spectral bands.
Bumblebee vibration activated foraging
Su, Dan Kuan-Nien
2009-01-01
The ability use vibrational signals to activate nestmate foraging is found in the highly social bees, stingless bees and honey bees, and has been hypothesized to exist in the closely related, primitively eusocial bumble bees. We provide the first strong and direct evidence that this is correct. Inside the nest, bumble bee foragers produce brief bursts of vibration (foraging activation pulses) at 594.5 Hz for 63±26 ms (velocityRMS=0.46±0.02mm/s, forceRMS=0.8±0.2 mN. Production of these vibrati...
DEFF Research Database (Denmark)
Jönsson, Jeppe; Hansen, Lars Pilegaard
1994-01-01
concerned with spectator-induced vertical vibrations on grandstands. The idea is to use impulse response analysis and base the load description on the load impulse. If the method is feasable, it could be used in connection with the formulation of requirements in building codes. During the last two decades...... work has been done on the measurement of the exact load functions and related reponse analysis. A recent work using a spectral description has been performed by Per-Erik Erikson and includes a good literature survey. Bachmann and Ammann give a good overview of vibrations caused by human activity. Other...
Kaliski, S
2013-01-01
This book gives a comprehensive overview of wave phenomena in different media with interacting mechanical, electromagnetic and other fields. Equations describing wave propagation in linear and non-linear elastic media are followed by equations of rheological models, models with internal rotational degrees of freedom and non-local interactions. Equations for coupled fields: thermal, elastic, electromagnetic, piezoelectric, and magneto-spin with adequate boundary conditions are also included. Together with its companion volume Vibrations and Waves. Part A: Vibrations this work provides a wealth
Heterogeneous Dynamics of Coupled Vibrations
Cringus, Dan; Jansen, Thomas I. C.; Pshenichnikov, Maxim S.; Schoenlein, RW; Corkum, P; DeSilvestri, S; Nelson, KA; Riedle, E
2009-01-01
Frequency-dependent dynamics of coupled stretch vibrations of a water molecule are revealed by 2D IR correlation spectroscopy. These are caused by non-Gaussian fluctuations of the environment around the individual OH stretch vibrations.
Review of vibration effect during piling installation to adjacent structure
Rahman, Nurul Aishah Abd; Musir, Adhilla Ainun; Dahalan, Nurol Huda; Ghani, Abdul Naser Abdul; Khalil, Muhamad Kasimi Abd
2017-12-01
Basically, many major structures across the world such as towers, high rise building, houses and bridges utilize pile as a support material. The use of pile is important to strengthen the structures. However, this has led to another problem to the nearest surrounding structures resulted from pile driving. As part of a construction work, unavoidable pile driving activity generates a vibration towards the surrounding structures if uncontrolled may cause damage to the adjacent structure. As the current construction works are frequently located in urban areas where the distance between the nearest building structures is not far, vibration may cause damage to nearby structures. Knowing which part of the building that is mostly affected by various vibration patterns from the impact of pile driving is crucial. Thus, it is very important to predict the impact of vibration during piling installation work. This paper reviews the vibrations generated by piling activity toward surrounding structures in terms sources of vibration, impact of piling installation, pile-soil interaction, and factors affecting the vibration impact of building as well as to study the parameters involved in vibration generation during piling works.
VIBRATIONS DETECTION IN INDUSTRIAL PUMPS BASED ON SPECTRAL ANALYSIS TO INCREASE THEIR EFFICIENCY
Directory of Open Access Journals (Sweden)
Belhadef RACHID
2016-01-01
Full Text Available Spectral analysis is the key tool for the study of vibration signals in rotating machinery. In this work, the vibration analy-sis applied for conditional preventive maintenance of such machines is proposed, as part of resolved problems related to vibration detection on the organs of these machines. The vibration signal of a centrifugal pump was treated to mount the benefits of the approach proposed. The obtained results present the signal estimation of a pump vibration using Fourier transform technique compared by the spectral analysis methods based on Prony approach.
Real eigenvalue analysis in NASTRAN by the tridiagonal reduction (FEER) method
Newman, M.; Flanagen, P. F.; Rogers, J. L., Jr.
1976-01-01
Implementation of the tridiagonal reduction method for real eigenvalue extraction in structural vibration and buckling problems is described. The basic concepts underlying the method are summarized and special features, such as the computation of error bounds and default modes of operation are discussed. In addition, the new user information and error messages and optional diagnostic output relating to the tridiagonal reduction method are presented. Some numerical results and initial experiences relating to usage in the NASTRAN environment are provided, including comparisons with other existing NASTRAN eigenvalue methods.
Directory of Open Access Journals (Sweden)
Rossikhin Yury A.
2018-01-01
Full Text Available Non-linear damped vibrations of a cylindrical shell embedded into a fractional derivative medium are investigated for the case of the combinational internal resonance, resulting in modal interaction, using two different numerical methods with further comparison of the results obtained. The damping properties of the surrounding medium are described by the fractional derivative Kelvin-Voigt model utilizing the Riemann-Liouville fractional derivatives. Within the first method, the generalized displacements of a coupled set of nonlinear ordinary differential equations of the second order are estimated using numerical solution of nonlinear multi-term fractional differential equations by the procedure based on the reduction of the problem to a system of fractional differential equations. According to the second method, the amplitudes and phases of nonlinear vibrations are estimated from the governing nonlinear differential equations describing amplitude-and-phase modulations for the case of the combinational internal resonance. A good agreement in results is declared.
Composite Struts Would Damp Vibrations
Dolgin, Benjamin P.
1991-01-01
New design of composite-material (fiber/matrix laminate) struts increases damping of longitudinal vibrations without decreasing longitudinal stiffness or increasing weight significantly. Plies with opposing chevron patterns of fibers convert longitudinal vibrational stresses into shear stresses in intermediate viscoelastic layer, which dissipate vibrational energy. Composite strut stronger than aluminum strut of same weight and stiffness.
1989-07-01
Frachtschiffen," Werft Reederie Hafen, 1925. 4-21 Noonan, E. F. "Vibration Considerations for 120,000 CM LNG Ships," NKF: Preliminary Report No. 7107, 25...Ship Response to Ice - A Second Season by C. Daley, J. W. St. John, R. Brown, J. Meyer , and I. Glen 1990 SSC-340 Ice Forces and Ship Response to Ice
Ivanco, Thomas G. (Inventor)
2014-01-01
A vibration damper includes a rigid base with a mass coupled thereto for linear movement thereon. Springs coupled to the mass compress in response to the linear movement along either of two opposing directions. A converter coupled to the mass converts the linear movement to a corresponding rotational movement. A rotary damper coupled to the converter damps the rotational movement.
Blade Vibration Measurement System
Platt, Michael J.
2014-01-01
The Phase I project successfully demonstrated that an advanced noncontacting stress measurement system (NSMS) could improve classification of blade vibration response in terms of mistuning and closely spaced modes. The Phase II work confirmed the microwave sensor design process, modified the sensor so it is compatible as an upgrade to existing NSMS, and improved and finalized the NSMS software. The result will be stand-alone radar/tip timing radar signal conditioning for current conventional NSMS users (as an upgrade) and new users. The hybrid system will use frequency data and relative mode vibration levels from the radar sensor to provide substantially superior capabilities over current blade-vibration measurement technology. This frequency data, coupled with a reduced number of tip timing probes, will result in a system capable of detecting complex blade vibrations that would confound traditional NSMS systems. The hardware and software package was validated on a compressor rig at Mechanical Solutions, Inc. (MSI). Finally, the hybrid radar/tip timing NSMS software package and associated sensor hardware will be installed for use in the NASA Glenn spin pit test facility.
Vibration Sensitive Keystroke Analysis
Lopatka, M.; Peetz, M.-H.; van Erp, M.; Stehouwer, H.; van Zaanen, M.
2009-01-01
We present a novel method for performing non-invasive biometric analysis on habitual keystroke patterns using a vibration-based feature space. With the increasing availability of 3-D accelerometer chips in laptop computers, conventional methods using time vectors may be augmented using a distinct
Egger, Philipp; Caracoglia, Luca
2015-09-01
Impact dampers are often used in the field of civil, mechanical and aerospace engineering for reducing structural vibrations. The behavior of this type of passive control device has been investigated for several decades. In this research a distributed-mass impact damper, similar to the "chain damper" used in wind engineering, has been examined and applied to the vibration reduction on a slender line-like structural element (stay-cable). This study is motivated by a practical problem and describes the derivation of a reduced-order model for explaining the behavior, observed during a field experiment on a prototype system. In its simplest form, the dynamics of the apparatus is modeled as a "resilient damper", composed of mass-spring-dashpot secondary elements, attached to the primary structure. Various sources of excitation are analyzed: free vibration, external harmonic force and random excitation. The proposed model is general and potentially applicable to the analysis of several structural systems. The study also shows that the model can adequately describe and explain the experimentally observed behavior.
Harmonic vibrations and waves in a cylindrical helically anisotropic shell
Panfilov, I. A.; Ustinov, Yu. A.
2012-04-01
A Kirchhoff-Love type applied theory is used to study the specific characteristics of harmonic waves and vibrations of a helically anisotropic shell. Special attention is paid to axisymmetric and bending vibrations. In both cases, the dispersion equations are constructed and a qualitative and numerical analysis of their roots and the corresponding elementary solutions is performed. It is shown that the skew anisotropy in the axisymmetric case generates a relation between the longitudinal and torsional vibrations which is mathematically described by the amplitude coefficients of homogeneous waves. In the case of a shell with rigidly fixed end surfaces, the dependence of the first two natural frequencies on the shell length and the helical line slope α, i.e., the geometric parameter of helical anisotropy, is studied. A boundary value problem in which longitudinal vibrations are generated on one of the end surfaces and the other end is free of forces and moments is considered to analyze the degree of transformation of longitudinal vibrations into longitudinally torsional vibrations. In the case of bending vibrations, two problems for a half-infinite shell are studied as well. In the first problem, the waves are excited kinematically by generating harmonic vibrations of the shell end surface in the plane of the axial cross-section, and it is shown that the axis generally moves in some closed trajectories far from the end surface. In the second problem, the reflection of a homogeneous wave incident on the shell end is examined. It is shown that the "boundary resonance" phenomenon can arise in some cases.
Neece, Cameron L.
2014-01-01
Background: Parents of children with developmental delays (DD) typically report elevated levels of parental stress compared with parents of typically developing children. Children with DD are also at high risk for exhibiting significant behaviour problems. Parental stress has been shown to impact the development of these behaviour problems;…
Spross, Christian; Zeledon, Rebeca; Zdravkovic, Vilijam; Jost, Bernhard
2017-09-01
With the introduction of the deltoid tuberosity index (DTI), a simple radiographic tool has become available to measure bone mineral density of the proximal humerus. The aim of this study was to assess the influence of local bone mineral density on the early failure rate after angular stable open reduction-internal fixation of proximal humeral fractures (PHFs). We retrospectively followed up all patients treated with angular stable implants for PHFs from 2007 to 2014. The fractures were classified according to Neer, and the DTI, metaphyseal head extension (MHE), medial hinge displacement, and quality of reduction were assessed. Failures were defined as head screw cutouts. The study included 146 patients (mean age, 66 years; range, 20-94 years). The mean follow-up period was 11 months (range, 3-94 months). Of the fractures, 91% were classified as 2- or 3-part fractures and 9% as 4-part fractures. The mean DTI was 1.44 (range, 1.19-2.11), and the mean MHE was 12 mm (range, 0-48 mm). The reduction result was at least acceptable in 80% of fractures. Screw cutouts were found in 23%. The DTI and MHE were the most significant preoperative predictors for the reduction result. The DTI (P = .036) and age (P = .02) were independent preoperative factors, and a good reduction (P = .001) was the only intraoperative factor influencing cutout. This study proves that good bone quality and a long MHE are helpful for the reduction. Furthermore, good bone quality, a younger age, and a good reduction prevent later cutout. We conclude that local bone quality is a relevant factor in the treatment plan for PHFs. Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.
Design for Vibration Monitoring: A Methodology for Reliable and Cost-Effective Vibration Monitoring
Tumer, Irem Y.; Koga, Dennis (Technical Monitor)
2001-01-01
The purpose of health monitoring systems is to detect failures or defects for increased safety and performance and to provide on-condition maintenance with reduced costs. The problems associated with health monitoring systems include high rates of false alarms and missed failures, which make monitoring an unreliable and costly task. The reason for this is that unaccounted variations invalidate signal modeling assumptions. Our approach was to focus on vibration monitoring of rotating components. We analyzed baseline signals to determine statistical variations, identify and model factors that influence vibrations (pre-production vs. post-production variations), determine hit and false alarm rates with baseline flight data, model and predict effects of defects and variations on vibrations, and develop algorithms and metrics for failure and anomaly detection in the presence of variations.
Integrated cable vibration control system using wireless sensors
Jeong, Seunghoo; Cho, Soojin; Sim, Sung-Han
2017-04-01
As the number of long-span bridges is increasing worldwide, maintaining their structural integrity and safety become an important issue. Because the stay cable is a critical member in most long-span bridges and vulnerable to wind-induced vibrations, vibration mitigation has been of interest both in academia and practice. While active and semi-active control schemes are known to be quite effective in vibration reduction compared to the passive control, requirements for equipment including data acquisition, control devices, and power supply prevent a widespread adoption in real-world applications. This study develops an integrated system for vibration control of stay-cables using wireless sensors implementing a semi-active control. Arduino, a low-cost single board system, is employed with a MEMS digital accelerometer and a Zigbee wireless communication module to build the wireless sensor. The magneto-rheological (MR) damper is selected as a damping device, controlled by an optimal control algorithm implemented on the Arduino sensing system. The developed integrated system is tested in a laboratory environment using a cable to demonstrate the effectiveness of the proposed system on vibration reduction. The proposed system is shown to reduce the vibration of stay-cables with low operating power effectively.
Vibration Control via Stiffness Switching of Magnetostrictive Transducers
Scheidler, Justin J.; Asnani, Vivake M.; Dapino, Marcelo J.
2016-01-01
This paper presents a computational study of structural vibration control that is realized by switching a magnetostrictive transducer between high and low stiffness states. Switching is accomplished by either changing the applied magnetic field with a voltage excitation or changing the shunt impedance on the transducer's coil (i.e., the magnetostrictive material's magnetic boundary condition). Switched-stiffness vibration control is simulated using a lumped mass supported by a damper and the magnetostrictive transducer (mount), which is represented by a nonlinear, electromechanical model. Free vibration of the mass is calculated while varying the mount's stiffness according to a reference switched-stiffness vibration control law. The results reveal that switching the magnetic field produces the desired change in stiffness, but also an undesired actuation force that can significantly degrade the vibration control. Hence, a modified switched-stiffness control law that accounts for the actuation force is proposed and implemented for voltage-controlled stiffness switching. The influence of the magnetomechanical bias condition is also discussed. Voltage-controlled stiffness switching is found to introduce damping equivalent to a viscous damping factor up to about 0.25; this is shown to primarily result from active vibration reduction caused by the actuation force. The merit of magnetostrictive switched-stiffness vibration control is then quantified by comparing the results of voltage- and shunt-controlled stiffness switching to the performance of optimal magnetostrictive shunt damping.
Animal Communications Through Seismic Vibrations
Energy Technology Data Exchange (ETDEWEB)
Hill, Peggy (University of Tulsa)
2001-05-02
Substrate vibration has been important to animals as a channel of communication for millions of years, but our literature on vibration in this context of biologically relevant information is only decades old. The jaw mechanism of the earliest land vertebrates allowed them to perceive substrate vibrations as their heads lay on the ground long before airborne sounds could be heard. Although the exact mechanism of vibration production and the precise nature of the wave produced are not always understood, recent development of affordable instrumentation to detect and measure vibrations has allowed researchers to answer increasingly sophisticated questions about how animals send and receive vibration signals. We now know that vibration provides information used in predator defense, prey detection, recruitment to food, mate choice, intrasexual competition, and maternal/brood social interactions in a variety of insect orders, spiders, crabs, scorpions, chameleons, frogs, golden moles, mole rats, kangaroos rats, wallabies, elephants and bison.
Moradi, H.; Bakhtiari-Nejad, F.; Movahhedy, M. R.
2008-11-01
Dynamic vibration absorbers are used to reduce the undesirable vibrations in many applications such as electrical transmission lines, helicopters, gas turbines, engines, bridges, etc. Tuneable vibration absorbers (TVA) are also used as semi-active controllers. In this paper, the application of a TVA for suppression of chatter vibrations in the boring manufacturing process is presented. The boring bar is modeled as a cantilever Euler-Bernoulli beam and the TVA is composed of mass, spring and dashpot elements. In addition, the effect of spring mass is considered in this analysis. After formulation of the problem, the optimum specifications of the absorber such as spring stiffness, absorber mass and its position are determined using an algorithm based on the mode summation method. The analog-simulated block diagram of the system is developed and the effects of various excitations such as step, ramp, etc. on the absorbed system are simulated. In addition, chatter stability is analyzed in dominant modes of boring bar. Results show that at higher modes, larger critical widths of cut and consequently more material removal rate (MRR) can be achieved. In the case of self-excited vibration, which is associated with a delay differential equation, the optimum absorber suppresses the chatter and increases the limit of stability.
Tomilin, A. K.; Kurilskaya, N. F.
2017-10-01
A model problem of transversal vibrations of an elastic conducting rod in the magnetic field is studied. Vibrations in the rod are excited due to kinematic and force factors. A partial differential equation of motion containing the integral term for the electromagnetic force was constructed. After applying the Fourier procedure, the problem is reduced to a set of ODEs. The condition for passive stabilization of the main vibrational mode’s amplitude is derived. A method of active electromagnetic suppression of certain vibrational modes is proposed.
Structure-borne sound structural vibrations and sound radiation at audio frequencies
Cremer, L; Petersson, Björn AT
2005-01-01
Structure-Borne Sound"" is a thorough introduction to structural vibrations with emphasis on audio frequencies and the associated radiation of sound. The book presents in-depth discussions of fundamental principles and basic problems, in order to enable the reader to understand and solve his own problems. It includes chapters dealing with measurement and generation of vibrations and sound, various types of structural wave motion, structural damping and its effects, impedances and vibration responses of the important types of structures, as well as with attenuation of vibrations, and sound radi
Vibration Attenuation of Plate Using Multiple Vibration Absorbers
Directory of Open Access Journals (Sweden)
Zaman Izzuddin
2014-07-01
Full Text Available Vibrations are undesired phenomenon and it can cause harm, distress and unsettling influence to the systems or structures, for example, aircraft, automobile, machinery and building. One of the approach to limit this vibration by introducing passive vibration absorber attached to the structure. In this paper, the adequacy of utilizing passive vibration absorbers are investigated. The vibration absorber system is designed to minimize the vibration of a thin plate fixed along edges. The plate’s vibration characteristics, such as, natural frequency and mode shape are determined using three techniques: theoretical equations, finite element (FE analysis and experiment. The results demonstrate that the first four natural frequencies of fixed-fixed ends plate are 48, 121, 193 and 242 Hz, and these results are corroborated well with theoretical, FE simulation and experiment. The experiment work is further carried out with attached single and multiple vibration absorbers onto plate by tuning the absorber’s frequency to match with the excitation frequency. The outcomes depict that multiple vibration absorbers are more viable in lessening the global structural vibration.
Good vibrations. [Hydraulic turbines
Energy Technology Data Exchange (ETDEWEB)
Reynolds, P.
1994-07-01
The latest developments in the Voith Turbine Control and Automation System (VTLS), which couples digital control technology to hydropower plant equipment, are described. Prominent among these is the vibration diagnostics module for hydraulic turbines. It provides machine-specific diagnostic logic for a vibration monitoring and analysis system. Of the two other VTLS modules described, the operation module optimizes the control of a power plant with three or more turbines by considering the individual properties of each in turn, recommending which should be run, and how, in order to partition the load for a required power output. The cavitation module is a diagnostic system which enables the limits of operation of the turbines to be extended to bands just outside those determined by cavitation calculations. (3 figures). (UK)
On Coulomb and Viscosity damped single-degree-of-freedom vibrating systems
DEFF Research Database (Denmark)
Jakobsen, J.; Sivebæk, Ion Marius
2016-01-01
Attention on friction damping mechanisms could be of interest for vibration reduction, and appears therefore to be desirable. Presentations of textbook analyses on mechanical vibration of a viscosity damped single degree system [mass, spring and eventually damping] are numerous. Often they begin...
Low-frequency vibration isolation in six degrees of freedom: the Hummingbird
Rijnveld, N.; Braber, R. van den; Fraanje, P.R.; Dool, T.C. van den
2010-01-01
TNO Science and Industry and MECAL have developed a six degree of freedom vibration isolation system that suppresses both floor vibrations and direct forces on a table top. The achieved reduction of transmissibility and compliance is 40 dB between 1 and 50 Hz in vertical direction, and 30 dB between
Katarina Anthony
2015-01-01
In preparation for the civil engineering work on the HL-LHC, vibration measurements were carried out at the LHC’s Point 1 last month. These measurements will help evaluate how civil engineering work could impact the beam, and will provide crucial details about the site’s geological make-up before construction begins. A seismic truck at Point 1 generated wave-like vibrations measured by EN/MME. From carrying out R&D to produce state-of-the-art magnets to developing innovative, robust materials capable of withstanding beam impact, the HL-LHC is a multi-faceted project involving many groups and teams across CERN’s departments. It was in this framework that the project management mandated CERN's Mechanical and Materials Engineering (EN/MME) group to measure the propagation of vibrations around Point 1. Their question: can civil engineering work for the HL-LHC – the bulk of which is scheduled for LS2 – begin while the LHC is running? Alth...
Vibrational stability of graphene
Directory of Open Access Journals (Sweden)
Yangfan Hu
2013-05-01
Full Text Available The mechanical stability of graphene as temperature rises is analyzed based on three different self-consistent phonon (SCP models. Compared with three-dimensional (3-D materials, the critical temperature Ti at which instability occurs for graphene is much closer to its melting temperature Tm obtained from Monte Carlo simulation (Ti ≃ 2Tm, K. V. Zakharchenko, A. Fasolino, J. H. Los, and M. I. Katsnelson, J. Phys. Condens. Matter 23, 202202. This suggests that thermal vibration plays a significant role in melting of graphene while melting for 3-D materials is often dominated by topologic defects. This peculiar property of graphene derives from its high structural anisotropy, which is characterized by the vibrational anisotropic coefficient (VAC, defined upon its Lindermann ratios in different directions. For any carbon based material with a graphene-like structure, the VAC value must be smaller than 5.4 to maintain its stability. It is also found that the high VAC value of graphene is responsible for its negative thermal expansion coefficient at low temperature range. We believe that the VAC can be regarded as a new criterion concerning the vibrational stability of any low-dimensional (low-D materials.
High-damping-performance magnetorheological material for passive or active vibration control
Liu, Taixiang; Yang, Ke; Yan, Hongwei; Yuan, Xiaodong; Xu, Yangguang
2016-10-01
Optical assembly and alignment system plays a crucial role for the construction of high-power or high-energy laser facility, which attempts to ignite fusion reaction and go further to make fusion energy usable. In the optical assembly and alignment system, the vibration control is a key problem needs to be well handled and a material with higher damping performance is much desirable. Recently, a new kind of smart magneto-sensitive polymeric composite material, named magnetorheological plastomer (MRP), was synthesized and reported as a high-performance magnetorheological material and this material has a magneto-enhanced high-damping performance. The MRP behaves usually in an intermediate state between fluid-like magnetorheological fluid and solid-like magnetorheological elastomer. The state of MRP, as well as the damping performance of MRP, can be tuned by adjusting the ratio of hard segments and soft segments, which are ingredients to synthesize the polymeric matrix. In this work, a series of MRP are prepared by dispersing micron-sized, magneto-sensitive carbonyl iron powders with related additives into polyurethane-based, magnetically insensitive matrix. It is found that the damping performance of MRP depends much on magnetic strength, shear rate, carbonyl iron content and shear strain amplitude. Especially, the damping capacity of MRP can be tuned in a large range by adjusting external magnetic field. It is promising that the MRP will have much application in passive and active vibration control, such as vibration reduction in optical assembly and alignment system, vibration isolation or absorption in vehicle suspension system, etc.
Chi, Feng; Zhou, Jun; Zhang, Qi; Wang, Yong; Huang, Panling
2017-03-08
The vibration control of a construction vehicle must be carried out in order to meet the aims of sustainable environmental development and to avoid the potential human health hazards. In this paper, based on market feedback, the driver seat vibration of a type of wheel loader in the left and right direction, is found to be significant over a certain speed range. In order to find abnormal vibration components, the order tracking technique (OTT) and transmission path analysis (TPA) were used to analyze the vibration sources of the wheel loader. Through this analysis, it can be seen that the abnormal vibration comes from the interaction between the tire tread and the road, and this is because the vibration was amplified by the cab mount, which was eventually transmitted to the cab seat. Finally, the seat vibration amplitudes were decreased by up to 50.8%, after implementing the vibration reduction strategy.
A Detailed Level Kinetics Model of NO Vibrational Energy Distributions
Sharma, Surendra P.; Gilmore, John; Cavolowsky, John A. (Technical Monitor)
1996-01-01
Several contemporary problems have pointed to the desirability of a detailed level kinetics approach to modeling the distribution of vibrational energy in NO. Such a model is necessary when vibrational redistribution reactions are insufficient to maintain a Boltzmann distribution over the vibrational energy states. Recent calculations of the rate constant for the first reaction of the Zeldovich mechanism (N2 + O (goes to) NO + N) have suggested that the product NO is formed in high vibrational states. In shock layer flowfields, the product NO molecules may experience an insufficient number of collisions to establish a Boltzmann distribution over vibrational states, thus necessitating a level kinetics model. In other flows, such as expansions of high temperature air, fast, near-resonance vibrational energy exchanges with N2 and O2 may also require a level specific model for NO because of the relative rates of vibrational exchange and redistribution. The proposed report will integrate computational and experimental components to construct such a model for the NO molecule.
Kappa Delta Award. Low back pain and whole body vibration.
Pope, M H; Magnusson, M; Wilder, D G
1998-09-01
The investigators describe their multifaceted approach to the study of the relationship between whole body vibration and low back pain. The epidemiologic study was a two center study of drivers and sedentary workers in the United States and Sweden. The vibration exposure was measured in the vehicles. It was found that the career vibration exposure was related to low back, neck, and shoulder pain. However, disability was related to job satisfaction. In vivo experiments, using percutaneous pin mounted accelerometers have shown that the natural frequency is at 4.5 Hz. The frequency response is affected by posture, seating, and seat back inclination. The response appears to be determined largely by the rocking of the pelvis. Electromyographic studies have shown that muscle fatigue occurs under whole body vibration. After whole body vibration exposure the muscle response to a sudden load has greater latency. Vehicle driving may be a reason for low back pain or herniated nucleus pulposus. Prolonged seating exposure, coupled with the whole body vibration, should be reduced for those recovering from these problems. Vibration attenuating seats and correct ergonomic layout of the cabs may reduce the risks of recurrence.
Super-multiplex vibrational imaging
Wei, Lu; Chen, Zhixing; Shi, Lixue; Long, Rong; Anzalone, Andrew V.; Zhang, Luyuan; Hu, Fanghao; Yuste, Rafael; Cornish, Virginia W.; Min, Wei
2017-04-01
The ability to visualize directly a large number of distinct molecular species inside cells is increasingly essential for understanding complex systems and processes. Even though existing methods have successfully been used to explore structure-function relationships in nervous systems, to profile RNA in situ, to reveal the heterogeneity of tumour microenvironments and to study dynamic macromolecular assembly, it remains challenging to image many species with high selectivity and sensitivity under biological conditions. For instance, fluorescence microscopy faces a ‘colour barrier’, owing to the intrinsically broad (about 1,500 inverse centimetres) and featureless nature of fluorescence spectra that limits the number of resolvable colours to two to five (or seven to nine if using complicated instrumentation and analysis). Spontaneous Raman microscopy probes vibrational transitions with much narrower resonances (peak width of about 10 inverse centimetres) and so does not suffer from this problem, but weak signals make many bio-imaging applications impossible. Although surface-enhanced Raman scattering offers high sensitivity and multiplicity, it cannot be readily used to image specific molecular targets quantitatively inside live cells. Here we use stimulated Raman scattering under electronic pre-resonance conditions to image target molecules inside living cells with very high vibrational selectivity and sensitivity (down to 250 nanomolar with a time constant of 1 millisecond). We create a palette of triple-bond-conjugated near-infrared dyes that each displays a single peak in the cell-silent Raman spectral window; when combined with available fluorescent probes, this palette provides 24 resolvable colours, with the potential for further expansion. Proof-of-principle experiments on neuronal co-cultures and brain tissues reveal cell-type-dependent heterogeneities in DNA and protein metabolism under physiological and pathological conditions, underscoring the
Vibration Analysis of a Residential Building
Directory of Open Access Journals (Sweden)
Sampaio Regina Augusta
2015-01-01
Full Text Available The aim of this paper is to present the results of a study regarding vibration problems in a 17 storey residential building during pile driving in its vicinity. The structural design of the building was checked according to the Brazilian standards NBR6118 and NBR6123, and using commercial finite element software. An experimental analysis was also carried out using low frequency piezo-accelerometers attached to the building structure. Structure vibrations were recorded under ambient conditions. Four monitoring tests were performed on different days. The objective of the first monitoring test was an experimental modal analysis. To obtain de modal parameters, data was processed in the commercial software ARTEMIS employing two methods: the Stochastic Subspace Identification and the Frequency Domain Decomposition. Human comfort was investigated considering the International Standard ISO 2631. The Portuguese standard, NP2074, was also used as a reference, since it aims to limit the adverse effects of vibrations in structures caused by pile driving in the vicinity of the structure. The carried out experimental tests have shown that, according to ISO2301, the measure vibration levels are above the acceptance limits. However, velocity peaks are below the limits established by NP2074. It was concluded that, although the structure has adequate capacity to resist internal forces according to normative criteria, it has low horizontal stiffness, which could be verified by observing the vibration frequencies and mode shapes obtained with the finite element models, and its similarity with the experimental results. Thus, the analyses indicate the occurrence of discomfort by the residents.
Piezoelectric Vibration Damping Study for Rotating Composite Fan Blades
Min, James B.; Duffy, Kirsten P.; Choi, Benjamin B.; Provenza, Andrew J.; Kray, Nicholas
2012-01-01
Resonant vibrations of aircraft engine blades cause blade fatigue problems in engines, which can lead to thicker and aerodynamically lower performing blade designs, increasing engine weight, fuel burn, and maintenance costs. In order to mitigate undesirable blade vibration levels, active piezoelectric vibration control has been investigated, potentially enabling thinner blade designs for higher performing blades and minimizing blade fatigue problems. While the piezoelectric damping idea has been investigated by other researchers over the years, very little study has been done including rotational effects. The present study attempts to fill this void. The particular objectives of this study were: (a) to develop and analyze a multiphysics piezoelectric finite element composite blade model for harmonic forced vibration response analysis coupled with a tuned RLC circuit for rotating engine blade conditions, (b) to validate a numerical model with experimental test data, and (c) to achieve a cost-effective numerical modeling capability which enables simulation of rotating blades within the NASA Glenn Research Center (GRC) Dynamic Spin Rig Facility. A numerical and experimental study for rotating piezoelectric composite subscale fan blades was performed. It was also proved that the proposed numerical method is feasible and effective when applied to the rotating blade base excitation model. The experimental test and multiphysics finite element modeling technique described in this paper show that piezoelectric vibration damping can significantly reduce vibrations of aircraft engine composite fan blades.
Modal and Vibration Analysis of Filter System in Petrochemical Plant
Directory of Open Access Journals (Sweden)
Zhongchi Liu
2017-01-01
Full Text Available Filter systems are widely used in petrochemical plants for removing solid impurities from hydrocarbon oils. The backwash is the cleaning process used to remove the impurities on the sieves of the filters without a need to interrupt the operation of the entire system. This paper presents a case study based on the actual project of a filter system in a petrochemical plant, to demonstrate the significant effect of vibration on the structural integrity of piping. The induced vibration had led to the structural fatigue failure of the pipes connecting the filter system. A preliminary assessment suggested that the vibrations are caused by the operation of backwashing of the filter system. A process for solving the vibration problem based on the modal analysis of the filter system using the commercial finite element software for simulation is therefore proposed. The computed natural frequencies of the system and the vibration data measured on site are assessed based on the resonance effect of the complete system including the piping connected to the filters. Several approaches are proposed to adjust the natural frequencies of the system in such a way that an optimal and a reasonable solution for solving the vibration problem is obtained.
Forced Vibration Analysis for a FGPM Cylindrical Shell
Directory of Open Access Journals (Sweden)
Hong-Liang Dai
2013-01-01
Full Text Available This article presents an analytical study for forced vibration of a cylindrical shell which is composed of a functionally graded piezoelectric material (FGPM. The cylindrical shell is assumed to have two-constituent material distributions through the thickness of the structure, and material properties of the cylindrical shell are assumed to vary according to a power-law distribution in terms of the volume fractions for constituent materials, the exact solution for the forced vibration problem is presented. Numerical results are presented to show the effect of electric excitation, thermal load, mechanical load and volume exponent on the static and force vibration of the FGPM cylindrical shell. The goal of this investigation is to optimize the FGPM cylindrical shell in engineering, also the present solution can be used in the forced vibration analysis of cylindrical smart elements.
Efficiency of Nearly Periodic Structures for Mitigation of Ground Vibration
DEFF Research Database (Denmark)
Andersen, Lars Vabbersgaard; Peplow, Andrew; Bucinskas, Paulius
2017-01-01
be introduced by periodic inclusions or changes to the ground surface geometry. However, for vibration mitigation in the context of real civil-engineering problems related to ground-borne noise from railways, for example, the excitation is not strictly harmonic and a steady state of the response is usually......Periodic structures are known to produce passbands and stopbands for propagation of vibration energy within the frequency domain. Sources vibrating harmonically at a frequency within a passband can lead to propagation of energy through propagating modes over long distances. However, sources...... vibrating at a frequency within a stopband excite only nearfields in the form of attenuating and evanescent modes, and the energy decays with distance. The decay phenomena are due to destructive interference of waves reflected and scattered by interfaces or obstacles placed periodically within or between...
Vibration Analysis Of a Self-Excited Elastic Beam
Directory of Open Access Journals (Sweden)
M. A. Barrón-M
2010-08-01
Full Text Available The vibration behavior and the energy exchange among the normal modes of a clamped-free self-excited elasticbeam are analyzed in this work. To model this kind of beam, the damping term of a van der Pol oscillator is directlyadded to the equation of a linear elastic beam, yielding a single nonlinear partial differential equation. To solve thisequation, a spectral method is employed. Three vibration modes are considered in the analysis, and the values of theself-exciting constant are varied in order to cover from linear to nonlinear vibration behavior. Multiple frequencies ofthe nonlinear beam are determined through the power spectral density of the beam free-end time series. Given thatthis relatively simple model mimics at least in a qualitative way some key issues of the fluid-structure problem, it couldbe potentially useful for fatigue studies and vibration analysis of rotating blades in turbomachinery.
Mistuned Vibration of Radial Inflow Turbine Impeller
Hattori, Hiroaki; Unno, Masaru; Hayashi, Masazumi
This paper is concerned with the numerical prediction of impeller blade vibration due to excitation by the wake of nozzle guide vanes in turbochargers. This problem is particularly important as turbochargers are used in a broad range of operation conditions, leading to some unavoidable resonant frequencies. In the paper, first the unsteady pressure distributions on the rotor blades are analyzed and structural response analysis is performed for the excitation component with largest contribution to pressure fluctuation. In a parametric survey, pressure expansion ratio and inlet flow temperature are varied in order to investigate the impact on vibration response. Unsteady CFD+FEM prediction well explains the qualitative trends that appeared in experimental survey. The result also points out that a fluctuation in natural frequency among the blades of only a few percent may cause large magnification factors. Finally, adjustment of disk thickness is suggested as a measure to reduce the magnification factor and its effectiveness demonstrated numerically as well as experimentally.
Random vibrations theory and practice
Wirsching, Paul H; Ortiz, Keith
1995-01-01
Random Vibrations: Theory and Practice covers the theory and analysis of mechanical and structural systems undergoing random oscillations due to any number of phenomena— from engine noise, turbulent flow, and acoustic noise to wind, ocean waves, earthquakes, and rough pavement. For systems operating in such environments, a random vibration analysis is essential to the safety and reliability of the system. By far the most comprehensive text available on random vibrations, Random Vibrations: Theory and Practice is designed for readers who are new to the subject as well as those who are familiar with the fundamentals and wish to study a particular topic or use the text as an authoritative reference. It is divided into three major sections: fundamental background, random vibration development and applications to design, and random signal analysis. Introductory chapters cover topics in probability, statistics, and random processes that prepare the reader for the development of the theory of random vibrations a...
Cooley, Christopher G.
2017-09-01
This study investigates the vibration and dynamic response of a system of coupled electromagnetic vibration energy harvesting devices that each consist of a proof mass, elastic structure, electromagnetic generator, and energy harvesting circuit with inductance, resistance, and capacitance. The governing equations for the coupled electromechanical system are derived using Newtonian mechanics and Kirchhoff circuit laws for an arbitrary number of these subsystems. The equations are cast in matrix operator form to expose the device's vibration properties. The device's complex-valued eigenvalues and eigenvectors are related to physical characteristics of its vibration. Because the electrical circuit has dynamics, these devices have more natural frequencies than typical electromagnetic vibration energy harvesters that have purely resistive circuits. Closed-form expressions for the steady state dynamic response and average power harvested are derived for devices with a single subsystem. Example numerical results for single and double subsystem devices show that the natural frequencies and vibration modes obtained from the eigenvalue problem agree with the resonance locations and response amplitudes obtained independently from forced response calculations. This agreement demonstrates the usefulness of solving eigenvalue problems for these devices. The average power harvested by the device differs substantially at each resonance. Devices with multiple subsystems have multiple modes where large amounts of power are harvested.
Reducing whole body vibration in forklift drivers.
Motmans, R
2012-01-01
Forklift drivers in warehouses are often exposed to whole body vibration (WBV) during the total day. There is however an association between working as a forklift operator and the development of low back pain. In this study the exposure to WBV was measured in five forklift drivers who performed a standardised order picking task during 10 minutes. The effect of driving surface (uneven concrete vs. new flat concrete), driving speed (15 km/h vs. 8 km/h) and seat suspension (mechanical suspension vs. air suspension) was investigated. Improving the driving surface was the most effective preventive measure by reducing the whole body vibration with 39%, from 1.14 to 0.69 m/s2. Lowering the speed limit resulted in a reduction of WBV with 26% (1.05 vs. 0.78 m/s2). An air suspension seat was 22% more effective compared to mechanical suspension (1.02 vs. 0.80 m/s2). On uneven concrete an air suspension seat performed even better by reducing the WBV by 29% (1.33 vs. 0.95 m/s2). A combination of a new driving surface, limiting the maximum speed and the introduction of an air suspension seat reduced the whole body vibrations below the action limit of 0.5 m/s2 as mentioned in the European directive. None of the interventions were effective enough on their own.
Strömberg, Carl; Aboagye, Emmanuel; Hagberg, Jan; Bergström, Gunnar; Lohela-Karlsson, Malin
2017-09-01
The aim of this study was to propose wage multipliers that can be used to estimate the costs of productivity loss for employers in economic evaluations, using detailed information from managers. Data were collected in a survey panel of 758 managers from different sectors of the labor market. Based on assumed scenarios of a period of absenteeism due to sickness, presenteeism and work environment-related problem episodes, and specified job characteristics (i.e., explanatory variables), managers assessed their impact on group productivity and cost (i.e., the dependent variable). In an ordered probit model, the extent of productivity loss resulting from job characteristics is predicted. The predicted values are used to derive wage multipliers based on the cost of productivity estimates provided by the managers. The results indicate that job characteristics (i.e., degree of time sensitivity of output, teamwork, or difficulty in replacing a worker) are linked to productivity loss as a result of health-related and work environment-related problems. The impact of impaired performance on productivity differs among various occupations. The mean wage multiplier is 1.97 for absenteeism, 1.70 for acute presenteeism, 1.54 for chronic presenteeism, and 1.72 for problems related to the work environment. This implies that the costs of health-related and work environment-related problems to organizations can exceed the worker's wage. The use of wage multipliers is recommended for calculating the cost of health-related and work environment-related productivity loss to properly account for actual costs. Copyright © 2017 International Society for Pharmacoeconomics and Outcomes Research (ISPOR). Published by Elsevier Inc. All rights reserved.
Chaotic vortex induced vibrations
Energy Technology Data Exchange (ETDEWEB)
Zhao, J.; Sheridan, J. [Fluids Laboratory for Aeronautical and Industrial Research (FLAIR), Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, Victoria 3800 (Australia); Leontini, J. S. [Department of Mechanical and Product Design Engineering, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia); Lo Jacono, D. [Institut de Mécanique des Fluides de Toulouse (IMFT), CNRS, UPS and Université de Toulouse, 31400 Toulouse (France)
2014-12-15
This study investigates the nature of the dynamic response of an elastically mounted cylinder immersed in a free stream. A novel method is utilized, where the motion of the body during a free vibration experiment is accurately recorded, and then a second experiment is conducted where the cylinder is externally forced to follow this recorded trajectory. Generally, the flow response during both experiments is identical. However, particular regimes exist where the flow response is significantly different. This is taken as evidence of chaos in these regimes.
Lattice Vibrations in Chlorobenzenes:
DEFF Research Database (Denmark)
Reynolds, P. A.; Kjems, Jørgen; White, J. W.
1974-01-01
Lattice vibrational dispersion curves for the ``intermolecular'' modes in the triclinic, one molecule per unit cell β phase of p‐C6D4Cl2 and p‐C6H4Cl2 have been obtained by inelastic neutron scattering. The deuterated sample was investigated at 295 and at 90°K and a linear extrapolation to 0°K...... was applied in order to correct for anharmonic effects. Calculations based on the atom‐atom model for van der Waals' interaction and on general potential parameters for the aromatic compounds agree reasonably well with the experimental observations. There is no substantial improvement in fit obtained either...
Active vibrations and noise control for turboprop application research program activities
Paonessa, A.; Concilio, A.; Lecce, Leonardo V.
1992-01-01
The objectives of this work include the following: (1) development of active noise control techniques to alleviate inefficiencies and drawbacks of passive noise control approach especially at low frequencies; (2) reduction of structurally radiated noise applying external forces to the vibrating structure by means of force actuators made of piezoelectric material; and (3) reduction of fuselage vibration levels in propeller driven aircraft by means of distributed piezoelectric actuators that are actively controlled.
Subspace Methods for Eigenvalue Problems
Hochstenbach, Michiel Erik
2003-01-01
This thesis treats a number of aspects of subspace methods for various eigenvalue problems. Vibrations and their corresponding eigenvalues (or frequencies) arise in science, engineering, and daily life. Matrix eigenvalue problems come from a large number of areas, such as chemistry,
Quantum dynamics of vibrational excitations and vibrational charge ...
Indian Academy of Sciences (India)
Quantum dynamics of vibrational excitations and vibrational charge transfer processes in H+ + O2 collisions at collision energy 23 eV ... The Fritz Haber Research Centre and The Department of Physical Chemisry, Hebrew University of Jerusalem, Jerusalem, Israel 91904; Department of Chemistry, Indian Institute of ...
Literature survey on anti-vibration gloves
CSIR Research Space (South Africa)
Sampson, E
2003-08-01
Full Text Available ............................................................................................................... 1 2. HAND ARM VIBRATION SYNDROME (HAVS).......................................................... 2 2.1 Hand-arm vibration................................................. Error! Bookmark not defined. 2.2 Human Response to vibration...
STABILITY AND NATURAL VIBRATIONS OF INHOMOGENEOUS SHELLS TAKING INTO ACCOUNT THE STRESS STATE
Directory of Open Access Journals (Sweden)
Bazhenov V.A.
2015-12-01
Full Text Available The work is devoted to the problem of developing a unified methodology based on the efficient numerical analysis of problems of stability and natural vibrations of a wide class of inhomogeneous shells, thin and medium thickness. In problems of its natural vibrations takes into account the presence of a pre-stressed state of the structure from the action of static loads, which significantly affect the spectrum of natural vibrations and allows determining the bifurcation point and the value of the critical force of buckling by dynamic criteria.
Alexander, B. X. S.
Flywheel energy storage has distinct advantages over conventional energy storage methods such as electrochemical batteries. Because the energy density of a flywheel rotor increases quadratically with its speed, the foremost goal in flywheel design is to achieve sustainable high speeds of the rotor. Many issues exist with the flywheel rotor operation at high and varying speeds. A prominent problem is synchronous rotor vibration, which can drastically limit the sustainable rotor speed. In a set of projects, the novel Active Disturbance Rejection Control (ADRC) is applied to various problems of flywheel rotor operation. These applications include rotor levitation, steady state rotation at high speeds and accelerating operation. Several models such as the lumped mass model and distributed three-mass models have been analyzed. In each of these applications, the ADRC has been extended to cope with disturbance, noise, and control effort optimization; it also has been compared to various industry-standard controllers such as PID and PD/observer, and is proven to be superior. The control performance of the PID controller and the PD/observer currently used at NASA Glenn has been improved by as much as an order of magnitude. Due to the universality of the second order system, the results obtained in the rotor vibration problem can be straightforwardly extended to other vibrational systems, particularly, the MEMS gyroscope. Potential uses of a new nonlinear controller, which inherits the ease of use of the traditional PID, are also discussed.
Prototype observation and influencing factors of environmental vibration induced by flood discharge
Directory of Open Access Journals (Sweden)
Xin Wang
2017-01-01
Full Text Available Due to a wide range of field vibration problems caused by flood discharge at the Xiangjiaba Hydropower Station, vibration characteristics and influencing factors were investigated based on prototype observation. The results indicate that field vibrations caused by flood discharge have distinctive characteristics of constancy, low frequency, small amplitude, and randomness with impact, which significantly differ from the common high-frequency vibration characteristics. Field vibrations have a main frequency of about 0.5–3.0 Hz and the characteristics of long propagation distance and large-scale impact. The vibration of a stilling basin slab runs mainly in the vertical direction. The vibration response of the guide wall perpendicular to the flow is significantly stronger than it is in other directions and decreases linearly downstream along the guide wall. The vibration response of the underground turbine floor is mainly caused by the load of unit operation. Urban environmental vibration has particular distribution characteristics and change patterns, and is greatly affected by discharge, scheduling modes, and geological conditions. Along with the increase of the height of residential buildings, vibration responses show a significant amplification effect. The horizontal and vertical vibrations of the 7th floor are, respectively, about 6 times and 1.5 times stronger than the corresponding vibrations of the 1st floor. The vibration of a large-scale chemical plant presents the combined action of flood discharge and working machines. Meanwhile, it is very difficult to reduce the low-frequency environmental vibrations. Optimization of the discharge scheduling mode is one of the effective measures of reducing the flow impact loads at present. Choosing reasonable dam sites is crucial.
NON-HOLONOMIC DYNAMICS OF WHIRLING VIBRATIONS OF DEEP DRILL COLUMNS
Directory of Open Access Journals (Sweden)
Gaidaichuk V.V.
2014-06-01
Full Text Available On the basis of the non-holonomic mechanics methods, the problem of the whirling vibrations of a bit of a drillstring, which is prestressed by longitudinal force and rotates under the applied forces is stated. The analysis of the mechanism of the vibration self-excitation is performed. It is shown that they can be both stable and unstable.
Vibrational Sensing in Marine Invertebrates
1997-09-30
VIBRATIONAL SENSING IN MARINE INVERTEBRATES Peter A. Jumars School of Oceanography University of Washington Box 357940 Seattle, WA 98195-7940 (206...DATES COVERED 00-00-1997 to 00-00-1997 4. TITLE AND SUBTITLE Vibrational Sensing in Marine Invertebrates 5a. CONTRACT NUMBER 5b. GRANT NUMBER
Szajna, Waldemar St.
2017-03-01
The paper presents a standard vibrating table for fresh concrete testing adopted for determination of maximum dry density (ρdmax) of sand. Vibration is an efficient method for coarse soil compaction therefore vibrating tables are useful for ρdmax determination. Acceleration that the soil is subject to is one of the basic parameters of efficient compaction. A vibrating table with inertial excitation was supplemented by a frequency converter and subjected to dynamic tests. The results of measurements of dynamic parameters are included. The paper presents problems connected with this method and describes the relationship between efficiency of compaction and accelerations which the soil is subjected to.
A Novel Control System Design for Vibrational MEMS Gyroscopes
Directory of Open Access Journals (Sweden)
Qing Zheng
2007-04-01
Full Text Available There are two major control problems associated with vibrational MEMS gyroscopes: to control two vibrating axes (or modes of the gyroscope, and to estimate a time-varying rotation rate. This paper demonstrates how a novel active disturbance rejection control addresses these problems in the presence of the mismatch of natural frequencies between two axes, mechanical-thermal noises, Quadrature errors, and parameter variations. A demodulation approach based on the estimated dynamics of the system by an extended state observer is used to estimate the rotation rate. The simulation results on a Z-axis MEMS gyroscope show that the controller is very effective by driving the output of the drive axis to a desired trajectory, forcing the vibration of the sense axis to zero for a force-to-rebalance operation and precisely estimating the rotation rate.
VIBRATION OF FRAME BUILDING STRUCTURES CAUSED BY UNDERGROUND TRAINS
Directory of Open Access Journals (Sweden)
P. V. Аliavdin
2011-01-01
Full Text Available The paper contains investigations on element vibration of a real residential 9-storeyed reinforced-concrete frame building induced by train movement in the shallow subway. A design model for a problem on propagation of bending waves within the limits of the typical fragment of a skeleton is presented in the paper. The steady state vibrations of a column and reinforced-concrete slab induced by an excited force which is equivalent to the impact of the subway trains have been investigated in the paper. The problem has been solved numerically on the basis of the ANSYS FEA program. Numerical results have been compared with an approximate analytical solution and data on full-scale experiment. A prediction technique for vibration propagation in the designed buildings is offered in the paper.
MR Damper Controlled Vibration Absorber for Enhanced Mitigation of Harmonic Vibrations
Directory of Open Access Journals (Sweden)
Felix Weber
2016-12-01
Full Text Available This paper describes a semi-active vibration absorber (SVA concept based on a real-time controlled magnetorheological damper (MR-SVA for the enhanced mitigation of structural vibrations due to harmonic disturbing forces. The force of the MR damper is controlled in real-time to generate the frequency and damping controls according to the behaviour of the undamped vibration absorber for the actual frequency of vibration. As stiffness and damping emulations in semi-active actuators are coupled quantities the control is formulated to prioritize the frequency control by the controlled stiffness. The control algorithm is augmented by a stiffness correction method ensuring precise frequency control when the desired control force is constrained by the semi-active restriction and residual force of the MR damper. The force tracking task is solved by a model-based feed forward with feedback correction. The MR-SVA is numerically and experimentally validated for the primary structure with nominal eigenfrequency and when de-tuning of −10%, −5%, +5% and +10% is present. Both validations demonstrate that the MR-SVA improves the vibration reduction in the primary structure by up to 55% compared to the passive tuned mass damper (TMD. Furthermore, it is shown that the MR-SVA with only 80% of tuned mass leads to approximately the same enhanced performance while the associated increased relative motion amplitude of the tuned mass is more than compensated be the reduced dimensions of the mass. Therefore, the MR-SVA is an appropriate solution for the mitigation of tall buildings where the pendulum mass can be up to several thousands of metric tonnes and space for the pendulum damper is limited.
The origins of vibration theory
Dimarogonas, A. D.
1990-07-01
The Ionian School of natural philosophy introduced the scientific method of dealing with natural phenomena and the rigorous proofs for abstract propositions. Vibration theory was initiated by the Pythagoreans in the fifth century BC, in association with the theory of music and the theory of acoustics. They observed the natural frequency of vibrating systems and proved that it is a system property and that it does not depend on the excitation. Pythagoreans determined the fundamental natural frequencies of several simple systems, such as vibrating strings, pipes, vessels and circular plates. Aristoteles and the Peripatetic School founded mechanics and developed a fundamental understanding of statics and dynamics. In Alexandrian times there were substantial engineering developments in the field of vibration. The pendulum as a vibration, and probably time, measuring device was known in antiquity, and was further developed by the end of the first millennium AD.
Sun, Liangming; Xie, Weiping; He, Xingwen; Hayashikawa, Toshiro
2016-03-01
In this study a 3D numerical analysis approach is developed to predict the ground vibration around rigid-frame viaducts induced by running high-speed trains. The train-bridge-ground interaction system is divided into two subsystems: the train-bridge interaction and the soil-structure interaction. First, the analytical program to simulate bridge vibration with consideration of train-bridge interaction is developed to obtain the vibration reaction forces at the pier bottoms. The highspeed train is described by a multi-DOFs vibration system and the rigid-frame viaduct is modeled with 3D beam elements. Second, applying these vibration reaction forces as input external excitations, the ground vibration is simulated by using a general-purpose program that includes soil-structure interaction effects. The validity of the analytical procedure is confirmed by comparing analytical and experimental results. The characteristics of high-speed train-induced vibrations, including the location of predominant vibration, are clarified. Based on this information a proposed vibration countermeasure using steel strut and new barrier is found effective in reducing train-induced vibrations and it satisfies environmental vibration requirements. The vibration screening efficiency is evaluated by reduction VAL based on 1/3 octave band spectral analysis.
Optimization of the impact multi-mass vibration absorbers
Directory of Open Access Journals (Sweden)
Ivan Kernytskyy
2017-09-01
Full Text Available The problem of attaching dynamic vibration absorber (DVA to a discrete multi-degree-of-freedom or continuous structure has been outlined in many papers and monographs. An impact damping system can overcome some limitations by impact as the damping medium and impact mass interaction as the damping mechanism. The paper contemplates the provision of DVA with the several of the impact masses. Such originally designed absorbers reduce vibration selectively in maximum vibration mode without introducing vibration in other modes. An impact damper is a passive control device which takes the form of a freely moving mass, constrained by stops attached to the structure under control, i.e. the primary structure. The damping results from the exchange of momentum during impacts between the mass and the stops as the structure vibrates. The paper contemplates the provision of the impact multi-mass DVA’s with masses collisions for additional damping. For some cases of DVA optimization such a design seems more effective than conventional multi-mass DVA with independent mass moving. A technique is developed to give the optimal DVA’s for the elimination of excessive vibration in harmonic stochastic and impact loaded systems.
Seventh international conference on time-resolved vibrational spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Dyer, R.B.; Martinez, M.A.D.; Shreve, A.; Woodruff, W.H. [comps.
1997-04-01
The International Conference on Time-Resolved Vibrational Spectroscopy (TRVS) is widely recognized as the major international forum for the discussion of advances in this rapidly growing field. The 1995 conference was the seventh in a series that began at Lake Placid, New York, 1982. Santa Fe, New Mexico, was the site of the Seventh International Conference on Time-Resolved Vibrational Spectroscopy, held from June 11 to 16, 1995. TRVS-7 was attended by 157 participants from 16 countries and 85 institutions, and research ranging across the full breadth of the field of time-resolved vibrational spectroscopy was presented. Advances in both experimental capabilities for time-resolved vibrational measurements and in theoretical descriptions of time-resolved vibrational methods continue to occur, and several sessions of the conference were devoted to discussion of these advances and the associated new directions in TRVS. Continuing the interdisciplinary tradition of the TRVS meetings, applications of time-resolved vibrational methods to problems in physics, biology, materials science, and chemistry comprised a large portion of the papers presented at the conference.
Buffoni, Boris; Groves, Mark D.; Wahlén, Erik
2017-12-01
Fully localised solitary waves are travelling-wave solutions of the three- dimensional gravity-capillary water wave problem which decay to zero in every horizontal spatial direction. Their existence has been predicted on the basis of numerical simulations and model equations (in which context they are usually referred to as `lumps'), and a mathematically rigorous existence theory for strong surface tension (Bond number {β} greater than {1/3} ) has recently been given. In this article we present an existence theory for the physically more realistic case {0 < β < 1/3} . A classical variational principle for fully localised solitary waves is reduced to a locally equivalent variational principle featuring a perturbation of the functional associated with the Davey-Stewartson equation. A nontrivial critical point of the reduced functional is found by minimising it over its natural constraint set.
Prinz, R J; Dumas, J E; Smith, E P; Laughlin, J E
2000-06-01
This paper describes a preventive intervention trial called EARLY ALLIANCE which is aimed at reducing risk for three adverse outcomes in childhood and adolescence: conduct problems, substance abuse, and school failure. The structure of the prevention trial is unique because two linked designs are being implemented concurrently. The primary design focuses on children at elevated risk for adverse outcomes, and compares a targeted, multicontextual preventive intervention with family, classroom, peer relational, and academic components to a universal, schoolwide preventive intervention that emphasizes peaceful conflict management and serves as a "usual care" control condition. The secondary design focuses on children at lower risk for adverse outcomes and compares a universally administered classroom program to the control condition. The paper describes the theoretical foundation for EARLY ALLIANCE, the goals of the prevention trial, the rationale for design choices, and the methods employed.
Distributed measurement of acoustic vibration location with frequency multiplexed phase-OTDR
Iida, Daisuke; Toge, Kunihiro; Manabe, Tetsuya
2017-07-01
All-fiber distributed vibration sensing is attracting attention in relation to structural health monitoring because it is cost effective, offers high coverage of the monitored area and can detect various structural problems. And in particular the demand for high-speed vibration sensing operating at more than 10 kHz has increased because high frequency vibration indicates high energy and severe trouble in the monitored object. Optical fiber vibration sensing with phase-sensitive optical time domain reflectometry (phase-OTDR) has long been studied because it can be used for distributed vibration sensing in optical fiber. However, pulse reflectometry such as OTDR cannot measure high-frequency vibration whose cycle is shorter than the repetition time of the OTDR. That is, the maximum detectable frequency depends on fiber length. In this paper, we describe a vibration sensing technique with frequency-multiplexed OTDR that can detect the entire distribution of a high-frequency vibration thus allowing us to locate a high-speed vibration point. We can measure the position, frequency and dynamic change of a high-frequency vibration whose cycle is shorter than the repetition time. Both frequency and position are visualized simultaneously for a 5-km fiber with an 80-kHz frequency response and a 20-m spatial resolution.
Control of noise and structural vibration a MATLAB-based approach
Mao, Qibo
2013-01-01
Control of Noise and Structural Vibration presents a MATLAB®-based approach to solving the problems of undesirable noise generation and transmission by structures and of undesirable vibration within structures in response to environmental or operational forces. The fundamentals of acoustics, vibration and coupling between vibrating structures and the sound fields they generate are introduced including a discussion of the finite element method for vibration analysis. Following this, the treatment of sound and vibration control begins, illustrated by example systems such as beams, plates and double plate structures. Sensor and actuator placement is explained as is the idea of modal sensor–actuators. The design of appropriate feedback systems includes consideration of basic stability criteria and robust active structural acoustic control. Single and multi-mode positive position feedback (PPF) control systems are also described in the context of loudspeaker–duct model with non-collocated loudspeaker–microp...
Instantaneous Purified Orbit: A New Tool for Analysis of Nonstationary Vibration of Rotor System
Directory of Open Access Journals (Sweden)
Shi Dongfeng
2001-01-01
Full Text Available In some circumstances, vibration signals of large rotating machinery possess time-varying characteristics to some extent. Traditional diagnosis methods, such as FFT spectrum and orbit diagram, are confronted with a huge challenge to deal with this problem. This work aims at studying the four intrinsic drawbacks of conventional vibration signal processing method and instantaneous purified orbit (IPO on the basis of improved Fourier spectrum (IFS to analyze nonstationary vibration. On account of integration, the benefits of short period Fourier transform (SPFT and regular holospectrum, this method can intuitively reflect vibration characteristics of’a rotor system by means of parameter analysis for corresponding frequency ellipses. Practical examples, such as transient vibration in run-up stages and bistable condition of rotor show that IPO is a powerful tool for diagnosis and analysis of the vibration behavior of rotor systems.
Local vibrations and lift performance of low Reynolds number airfoil
Directory of Open Access Journals (Sweden)
TariqAmin Khan
2017-06-01
Full Text Available The 2D incompressible Navier-Stokes equations are solved based on the finite volume method and dynamic mesh technique is used to carry out partial fluid structure interaction. The local flexible structure (hereinafter termed as flexible structure vibrates in a single mode located on the upper surface of the airfoil. The Influence of vibration frequency and amplitude are examined and the corresponding fluid flow characteristics are investigated which add complexity to the inherent problem in unsteady flow. The study is conducted for flow over NACA0012 airfoil at 600≤Re≤3000 at a low angle of attack. Vibration of flexible structure induces a secondary vortex which modifies the pressure distribution and lift performance of the airfoil. At some moderate vibration amplitude, frequency synchronization or lock-in phenomenon occurs when the vibration frequency is close to the characteristic frequency of rigid airfoil. Evolution and shedding of vortices corresponding to the deformation of flexible structure depends on the Reynolds number. In the case of Re≤1000, the deformation of flexible structure is considered in-phase with the vortex shedding i.e., increasing maximum lift is linked with the positive deformation of flexible structure. At Re=1500 a phase shift of about 1/π exists while they are out-of-phase at Re>1500. Moreover, the oscillation amplitude of lift coefficient increases with increasing vibration amplitude for Re≤1500 while it decreases with increasing vibration amplitude for Re>1500. As a result of frequency lock-in, the average lift coefficient is increased with increasing vibration amplitude for all investigated Reynolds numbers (Re. The maximum increase in the average lift coefficient is 19.72% within the range of investigated parameters.
Vibrational optical activity principles and applications
Nafie, Laurence A
2011-01-01
This unique book stands as the only comprehensive introduction to vibrational optical activity (VOA) and is the first single book that serves as a complete reference for this relatively new, but increasingly important area of molecular spectroscopy. Key features:A single-source reference on this topic that introduces, describes the background and foundation of this area of spectroscopy.Serves as a guide on how to use it to carry out applications with relevant problem solving.Depth and breadth of the subject is presented in a logical, complete and progressive fashion. A
Zhou, Danfeng; Yu, Peichang; Wang, Lianchun; Li, Jie
2017-11-01
The levitation gap of the urban maglev train is around 8 mm, which puts a rather high requirement on the smoothness of the track. In practice, it is found that the track irregularity may cause stability problems when the maglev train is traveling. In this paper, the dynamic response of the levitation module, which is the basic levitation structure of the urban maglev train, is investigated in the presence of track irregularities. Analyses show that due to the structural configuration of the levitation module, the vibration of the levitation gap may be amplified and "resonances" may be observed under some specified track wavelengths and train speeds; besides, it is found that the gap vibration of the rear levitation unit in a levitation module is more significant than that of the front levitation unit, which agrees well with practice. To suppress the vibration of the rear levitation gap, an adaptive vibration control method is proposed, which utilizes the information of the front levitation unit as a reference. A pair of mirror FIR (finite impulse response) filters are designed and tuned by an adaptive mechanism, and they produce a compensation signal for the rear levitation controller to cancel the disturbance brought by the track irregularity. Simulations under some typical track conditions, including the sinusoidal track profile, random track irregularity, as well as track steps, indicate that the adaptive vibration control scheme can significantly reduce the amplitude of the rear gap vibration, which provides a method to improve the stability and ride comfort of the maglev train.
Vibration analysis of the synchronous motor of a propane compressor
Energy Technology Data Exchange (ETDEWEB)
Nogueira, D.; Rangel Junior, J. de S. [Petroleo Brasileiro S.A. - PETROBRAS, Rio de Janeiro, RJ (Brazil)], Emails: diananogueira@petrobras.com.br, joilson_jr@petrobras.com.br; Moreira, R.G. [Petroleo Brasileiro S.A. - PETROBRAS, Cabiunas, RJ (Brazil)], E-mail: ricgmoreira@petrobras.com.br
2010-07-01
This paper aims at describing the Analysis of a synchronous electric motor which presented high vibration levels (shaft displacement and bearing housing vibration) during the commissioning process, as well as propose the best practices for the solution of vibration problems in similar situations. This motor belongs to the propane centrifugal compressor installed at a Gas Compression Station. The methodology used in this study conducted an investigation of the problems presented in the motor through the execution of many types of tests and the analysis of the results. The main evaluations were performed, such as the vibration analysis and the rotor dynamic analysis. The electric motor was shipped back to the manufacturer's shop, where the manufacturer made certain modifications to the motor structure so as to improve the structure stiffness, such as the improvement of the support and the increase of the thickness of the structural plates. In addition to that, the dynamic balancing of the rotating set was checked. Finally, the excitation at a critical speed close to the rated speed was found after Rotor Dynamics Analysis was performed again, because of the increase in bearing clearances. The bearing shells were replaced so as to increase the separation margin between these frequencies. In order to verify the final condition of the motor, the manufacturer repeated the standard tests - FAT (Factory Acceptance Tests) - according to internal procedure and international standards. As a result of this work, it was possible to conclude that there was a significant increase in the vibration levels due to unbalance conditions. It was also possible to conclude that there are close relationships between high vibration levels and unbalance conditions, as well as between high vibration levels and the stiffness of the system and its support. Certain points of attention related to the manufacturing process of the motor compressor are described at the end of this paper, based
Performance of active vibration control technology: the ACTEX flight experiments
Nye, T. W.; Manning, R. A.; Qassim, K.
1999-12-01
This paper discusses the development and results of two intelligent structures space-flight experiments, each of which could affect architecture designs of future spacecraft. The first, the advanced controls technology experiment I (ACTEX I), is a variable stiffness tripod structure riding as a secondary payload on a classified spacecraft. It has been operating well past its expected life since becoming operational in 1996. Over 60 on-orbit experiments have been run on the ACTEX I flight experiment. These experiments form the basis for in-space controller design problems and for concluding lifetime/reliability data on the active control components. Transfer functions taken during the life of ACTEX I have shown consistent predictability and stability in structural behavior, including consistency with those measurements taken on the ground prior to a three year storage period and the launch event. ACTEX I can change its modal characteristics by employing its dynamic change mechanism that varies preloads in portions of its structure. Active control experiments have demonstrated maximum vibration reductions of 29 dB and 16 dB in the first two variable modes of the system, while operating over a remarkable on-orbit temperature range of -80 °C to 129 °C. The second experiment, ACTEX II, was successfully designed, ground-tested, and integrated on an experimental Department of Defense satellite prior to its loss during a launch vehicle failure in 1995. ACTEX II also had variable modal behavior by virtue of a two-axis gimbal and added challenges of structural flexibility by being a large deployable appendage. Although the loss of ACTEX II did not provide space environment experience, ground testing resulted in space qualifying the hardware and demonstrated 21 dB, 14 dB, and 8 dB reductions in amplitude of the first three primary structural modes. ACTEX II could use either active and/or passive techniques to affect vibration suppression. Both experiments trailblazed
Diesel engine torsional vibration control coupling with speed control system
Guo, Yibin; Li, Wanyou; Yu, Shuwen; Han, Xiao; Yuan, Yunbo; Wang, Zhipeng; Ma, Xiuzhen
2017-09-01
The coupling problems between shafting torsional vibration and speed control system of diesel engine are very common. Neglecting the coupling problems sometimes lead to serious oscillation and vibration during the operation of engines. For example, during the propulsion shafting operation of a diesel engine, the oscillation of engine speed and the severe vibration of gear box occur which cause the engine is unable to operate. To find the cause of the malfunctions, a simulation model coupling the speed control system with the torsional vibration of deformable shafting is proposed and investigated. In the coupling model, the shafting is simplified to be a deformable one which consists of several inertias and shaft sections and with characteristics of torsional vibration. The results of instantaneous rotation speed from this proposed model agree with the test results very well and are successful in reflecting the real oscillation state of the engine operation. Furthermore, using the proposed model, the speed control parameters can be tuned up to predict the diesel engine a stable and safe running. The results from the tests on the diesel engine with a set of tuned control parameters are consistent with the simulation results very well.
Effect of vibration versus suspension therapy on balance in children ...
African Journals Online (AJOL)
Most cerebral palsy children have deficits in balance, co-ordination, and gait throughout childhood and adulthood. So, it is essential to seek an ideal physical therapy program to help in solving such widespread problem. The present study was conducted to compare between the effect of vibration training and suspension ...
Reliability of vibration predictions in civil engineering applications
Wit, M.S. de; Waarts, P.H.; Hölscher, P.; Stuit, H.G.
2003-01-01
The reliability of vibration predictions distinguishes itself from other reliability problems be-cause of the highly non-linear behavior of the underlying models. Over the last two years, a combination of four institutes in the Netherlands has studied the reliability in this type of predictions. For
On the resonant behavior of longitudinally vibrating accreting rods
CSIR Research Space (South Africa)
Shatalov, M
2012-09-01
Full Text Available subjected to longitudinal vibrations. This problem is described it terms of the linear classical, Rayleigh-Love and Rayleigh-Bishop models. It is assumed that the rod is fixed at one end and free at the other end and its length is increasing. For solution...
Torsional vibration of thin-walled elastic beams with doubly ...
African Journals Online (AJOL)
In this paper, the problem of analyzing the torsional vibration of thin-walled elastic beams, with open cross-sections that are doubly symmetric and traversed by moving concentrated masses at constant speeds is addressed. The mathematical model adopted accounts for both the gravitational and inertial effects of the ...
Vibrations of thin piezoelectric shallow shells: Two-dimensional ...
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
of the three-dimensional piezoelectric shells converge to the eigensolutions of a two- dimensional eigenvalue problem. Keywords. Vibrations; piezoelectricity; shallow shells. 1. Introduction. Lower dimensional models of shells are preferred in numerical computations to three- dimensional models when the thickness of the ...
PROBABILISTIC ESTIMATION OF VIBRATION INFLUENCE ON SENSITIVE SYSTEM ELEMENTS
Directory of Open Access Journals (Sweden)
A. A. Lobaty
2009-01-01
Full Text Available The paper considers a problem pertaining to an estimation of vibration influence on sensitive system elements. Dependences of intensity and probability of a process exit characterizing a condition of a system element for the preset range that allow to estimate serviceability and no-failure operation of the system have been obtained analytically in the paper
Vibration analysis of a completely free elliptical plate
Beres, D. P.
1974-01-01
The Ritz method is applied to the variation analysis of a completely free elliptical plate as an efficient alternative to a procedure using a truncated series of regular and modified Mathieu functions. It is shown that a solution as accurate as desired can be obtained with the Ritz method in solving thin plate vibration problems with difficult geometries.
Quantum control of vibrational excitations in a heteronuclear ...
Indian Academy of Sciences (India)
Optimal control theory is applied to obtain infrared laser pulses for selective vibrational excitation in a heteronuclear diatomic molecule. The problem of finding the optimized field is phrased as a maximization of a cost functional which depends on the laser field. A time dependent Gaussian factor is introduced in the field ...
Aeroelastic vibrations and stability of plates and shells
Algazin, Sergey D
2015-01-01
Back-action of wind onto wings causes vibrations, endangering the whole structure. By careful choices of geometry, materials and damping, hazardous effects on wind engines, planes, turbines and cars can be avoided. This book gives an overview of aerodynamics and mechanics behind these problems and describes a range of mechanical effects. Numerical and analytical met
Random vibration test of Mars Exploration Rover spacecraft
Scharton, T.; Lee, D.
2003-01-01
The primary objective of the random vibration test was to identify any hardware problems, which might compromise the mission. The test objectives, configuration, and requirements are briefly described in this presentation, and a representative sample of the measured data is presented.
Speckle reduction in THz imaging systems with multiple phase patterns
Jaeger, Irina; Stiens, Johan; Koers, Gaetan; Poesen, Gert; Vounckx, Roger
2006-04-01
THz technology makes possible imaging of phenomena, inaccessible to both visible and infrared radiation, but the imaging is still in its early stages of development. This paper draws attention to the aspects of speckle reduction to improve the image quality. Because all existing THz sources are coherent - speckle is an ultimate limiting factor of the free-space imaging techniques. Speckle arises when coherent light scattered from a rough surface is detected by an intensity detector with a finite aperture, hiding the image information. This problem is of special importance for THz imaging, because surface roughness is closer to the object dimension as in optical imaging. The reduction of speckle is highly desirable and we propose here a Hadamard matrix solution. Hadamard diffuser for mm-wave frequency range have been designed, built and tested. We report 50% speckle reduction measurements using a free-space vector network analyzer over the full W-band (75-110 GHz). The advantage of the mm-wave Hadamard technology over optical: the diffuser doesn't have to be moved (vibrated) any more to accomplish the technology of speckle reduction. Temporal optical effect is substituted here by spatial quasi-optical: Hadamard coding in each scan pixel. Second method delivers realistic system parameters for the speckle reduction with polychromatic light for aviation security.
Vibration response of misaligned rotors
Patel, Tejas H.; Darpe, Ashish K.
2009-08-01
Misalignment is one of the common faults observed in rotors. Effect of misalignment on vibration response of coupled rotors is investigated in the present study. The coupled rotor system is modelled using Timoshenko beam elements with all six dof. An experimental approach is proposed for the first time for determination of magnitude and harmonic nature of the misalignment excitation. Misalignment effect at coupling location of rotor FE model is simulated using nodal force vector. The force vector is found using misalignment coupling stiffness matrix, derived from experimental data and applied misalignment between the two rotors. Steady-state vibration response is studied for sub-critical speeds. Effect of the types of misalignment (parallel and angular) on the vibration behaviour of the coupled rotor is examined. Along with lateral vibrations, axial and torsional vibrations are also investigated and nature of the vibration response is also examined. It has been found that the misalignment couples vibrations in bending, longitudinal and torsional modes. Some diagnostic features in the fast Fourier transform (FFT) of torsional and longitudinal response related to parallel and angular misalignment have been revealed. Full spectra and orbit plots are effectively used to reveal the unique nature of misalignment fault leading to reliable misalignment diagnostic information, not clearly brought out by earlier studies.
Active Control of Panel Vibrations Induced by a Boundary Layer Flow
Chow, Pao-Liu
1998-01-01
In recent years, active and passive control of sound and vibration in aeroelastic structures have received a great deal of attention due to many potential applications to aerospace and other industries. There exists a great deal of research work done in this area. Recent advances in the control of sound and vibration can be found in the several conference proceedings. In this report we will summarize our research findings supported by the NASA grant NAG-1-1175. The problems of active and passive control of sound and vibration has been investigated by many researchers for a number of years. However, few of the articles are concerned with the sound and vibration with flow-structure interaction. Experimental and numerical studies on the coupling between panel vibration and acoustic radiation due to flow excitation have been done by Maestrello and his associates at NASA/Langley Research Center. Since the coupled system of nonlinear partial differential equations is formidable, an analytical solution to the full problem seems impossible. For this reason, we have to simplify the problem to that of the nonlinear panel vibration induced by a uniform flow or a boundary-layer flow with a given wall pressure distribution. Based on this simplified model, we have been able to study the control and stabilization of the nonlinear panel vibration, which have not been treated satisfactorily by other authors. The vibration suppression will clearly reduce the sound radiation power from the panel. The major research findings will be presented in the next three sections. In Section II we shall describe our results on the boundary control of nonlinear panel vibration, with or without flow excitation. Section III is concerned with active control of the vibration and sound radiation from a nonlinear elastic panel. A detailed description of our work on the parametric vibrational control of nonlinear elastic panel will be presented in Section IV. This paper will be submitted to the Journal
Tissue vibration in prolonged running.
Friesenbichler, Bernd; Stirling, Lisa M; Federolf, Peter; Nigg, Benno M
2011-01-04
The impact force in heel-toe running initiates vibrations of soft-tissue compartments of the leg that are heavily dampened by muscle activity. This study investigated if the damping and frequency of these soft-tissue vibrations are affected by fatigue, which was categorized by the time into an exhaustive exercise. The hypotheses were tested that (H1) the vibration intensity of the triceps surae increases with increasing fatigue and (H2) the vibration frequency of the triceps surae decreases with increasing fatigue. Tissue vibrations of the triceps surae were measured with tri-axial accelerometers in 10 subjects during a run towards exhaustion. The frequency content was quantified with power spectra and wavelet analysis. Maxima of local vibration intensities were compared between the non-fatigued and fatigued states of all subjects. In axial (i.e. parallel to the tibia) and medio-lateral direction, most local maxima increased with fatigue (supporting the first hypothesis). In anterior-posterior direction no systematic changes were found. Vibration frequency was minimally affected by fatigue and frequency changes did not occur systematically, which requires the rejection of the second hypothesis. Relative to heel-strike, the maximum vibration intensity occurred significantly later in the fatigued condition in all three directions. With fatigue, the soft tissue of the triceps surae oscillated for an extended duration at increased vibration magnitudes, possibly due to the effects of fatigue on type II muscle fibers. Thus, the protective mechanism of muscle tuning seems to be reduced in a fatigued muscle and the risk of potential harm to the tissue may increase. Copyright © 2010 Elsevier Ltd. All rights reserved.
Development and evaluation of a generic active helicopter vibration controller
Davis, M. W.
1984-01-01
A computerized generic active controller is developed, which alleviates helicopter vibration by closed-loop implementation of higher harmonic control (HHC). In the system, the higher harmonic blade pitch is input through a standard helicopter swashplate; for a four-blade helicopter rotor the 4/rev vibration in the rotorcraft is minimized by inducing cyclic pitch motions at 3, 4, and 5/rev in the rotating system. The controller employs the deterministic, cautious, and dual control approaches and two linear system models (local and global), as well as several methods of limiting control. Based on model testing, performed at moderate to high values of forward velocity and rotor thrust, reductions in the rotor test apparatus vibration from 75 to 95 percent are predicted, with HHC pitch amplitudes of less than one degree. Good performance is also noted for short-duration maneuvers.
Optimal Search Strategy of Robotic Assembly Based on Neural Vibration Learning
Directory of Open Access Journals (Sweden)
Lejla Banjanovic-Mehmedovic
2011-01-01
Full Text Available This paper presents implementation of optimal search strategy (OSS in verification of assembly process based on neural vibration learning. The application problem is the complex robot assembly of miniature parts in the example of mating the gears of one multistage planetary speed reducer. Assembly of tube over the planetary gears was noticed as the most difficult problem of overall assembly. The favourable influence of vibration and rotation movement on compensation of tolerance was also observed. With the proposed neural-network-based learning algorithm, it is possible to find extended scope of vibration state parameter. Using optimal search strategy based on minimal distance path between vibration parameter stage sets (amplitude and frequencies of robots gripe vibration and recovery parameter algorithm, we can improve the robot assembly behaviour, that is, allow the fastest possible way of mating. We have verified by using simulation programs that search strategy is suitable for the situation of unexpected events due to uncertainties.
A self-adaptive anti-vibration pipeline-filtering algorithm
Wu, Houde; Wang, Bin; Zhao, Ming; Xu, Wenhai
2015-03-01
The mobile pipeline-filtering algorithm is a real-time algorithm that performs well in detecting small dim targets, but it is particularly sensitive to interframe vibration of sequence images. When searching for small dim targets at sea based on an infrared imaging system, irregular and random vibration of the airborne imaging platform causes huge interference problems for the mobile pipeline-filtering. This paper puts forward a pipeline-filtering algorithm that has a good performance on self-adaptive anti-vibration. In the block matching method using the normalized cross-correlations coefficient (NCC), the interframe vibration of sequence images is acquired in real time and used to correct coordinates of the single-frame detection results, and then the corrected detection results are used to complete the mobile pipelinefiltering. Experimental results show that the algorithm can overcome the problem of interframe vibration of sequence images, thus realizing accurate detection of small dim maritime targets.
Mechanics problems in undergraduate physics
Strelkov, S P
2013-01-01
Problems in Undergraduate Physics, Volume I: Mechanics focuses on solutions to problems in physics. The book first discusses the fundamental problems in physics. Topics include laws of conservation of momentum and energy; dynamics of a point particle in circular motion; dynamics of a rotating rigid body; hydrostatics and aerostatics; and acoustics. The text also offers information on solutions to problems in physics. Answers to problems in kinematics, statics, gravity, elastic deformations, vibrations, and hydrostatics and aerostatics are discussed. Solutions to problems related to the laws of
Molecular vibrations the theory of infrared and Raman vibrational spectra
Wilson, E Bright; Cross, Paul C
1980-01-01
Pedagogical classic and essential reference focuses on mathematics of detailed vibrational analyses of polyatomic molecules, advancing from application of wave mechanics to potential functions and methods of solving secular determinant.
The Influence of Tractor-Seat Height above the Ground on Lateral Vibrations
Gomez-Gil, Jaime; Gomez-Gil, Francisco Javier; Martin-de-Leon, Rebeca
2014-01-01
Farmers experience whole-body vibrations when they drive tractors. Among the various factors that influence the vibrations to which the driver is exposed are terrain roughness, tractor speed, tire type and pressure, rear axle width, and tractor seat height above the ground. In this paper the influence of tractor seat height above the ground on the lateral vibrations to which the tractor driver is exposed is studied by means of a geometrical and an experimental analysis. Both analyses show that: (i) lateral vibrations experienced by a tractor driver increase linearly with tractor-seat height above the ground; (ii) lateral vibrations to which the tractor driver is exposed can equal or exceed vertical vibrations; (iii) in medium-size tractors, a feasible 30 cm reduction in the height of the tractor seat, which represents only 15% of its current height, will reduce the lateral vibrations by around 20%; and (iv) vertical vibrations are scarcely influenced by tractor-seat height above the ground. The results suggest that manufacturers could increase the comfort of tractors by lowering tractor-seat height above the ground, which will reduce lateral vibrations. PMID:25340448
The Influence of Tractor-Seat Height above the Ground on Lateral Vibrations
Directory of Open Access Journals (Sweden)
Jaime Gomez-Gil
2014-10-01
Full Text Available Farmers experience whole-body vibrations when they drive tractors. Among the various factors that influence the vibrations to which the driver is exposed are terrain roughness, tractor speed, tire type and pressure, rear axle width, and tractor seat height above the ground. In this paper the influence of tractor seat height above the ground on the lateral vibrations to which the tractor driver is exposed is studied by means of a geometrical and an experimental analysis. Both analyses show that: (i lateral vibrations experienced by a tractor driver increase linearly with tractor-seat height above the ground; (ii lateral vibrations to which the tractor driver is exposed can equal or exceed vertical vibrations; (iii in medium-size tractors, a feasible 30 cm reduction in the height of the tractor seat, which represents only 15% of its current height, will reduce the lateral vibrations by around 20%; and (iv vertical vibrations are scarcely influenced by tractor-seat height above the ground. The results suggest that manufacturers could increase the comfort of tractors by lowering tractor-seat height above the ground, which will reduce lateral vibrations.
Vibration Control via Stiffness Switching of Magnetostrictive Transducers
Scheidler, Justin J.; Asnani, Vivake M.; Dapino, Marcelo J.
2016-01-01
In this paper, a computational study is presented of structural vibration control that is realized by switching a magnetostrictive transducer between high and low stiffness states. Switching is accomplished by either changing the applied magnetic field with a voltage excitation or changing the shunt impedance on the transducer's coil (i.e., the magnetostrictive material's magnetic boundary condition). Switched-stiffness vibration control is simulated using a lumped mass supported by a damper and the magnetostrictive transducer (mount), which is represented by a nonlinear, electromechanical model. Free vibration of the mass is calculated while varying the mount's stiffness according to a reference switched-stiffness vibration control law. The results reveal that switching the magnetic field produces the desired change in stiffness, but also an undesired actuation force that can significantly degrade the vibration control. Hence, a modified switched-stiffness control law that accounts for the actuation force is proposed and implemented for voltage-controlled stiffness switching. The influence of the magneto-mechanical bias condition is also discussed. Voltage-controlled stiffness switching is found to introduce damping equivalent to a viscous damping factor up to about 0.13; this is shown to primarily result from active vibration reduction caused by the actuation force. The merit of magnetostrictive switched-stiffness vibration control is then quantified by comparing the results of voltage- and shunt-controlled stiffness switching to the performance of optimal magnetostrictive shunt damping. For the cases considered, optimal resistive shunt damping performed considerably better than both voltage- and shunt-controlled stiffness switching.
Vibrational and thermal noise reduction for cryogenic detectors
Energy Technology Data Exchange (ETDEWEB)
Pirro, S. E-mail: stefano.pirro@lngs.infn.it; Alessandrello, A.; Brofferio, C.; Bucci, C.; Cremonesi, O.; Coccia, E.; Fiorini, E.; Fafone, V.; Giuliani, A.; Nucciotti, A.; Pavan, M.; Pessina, G.; Previtali, E.; Vanzini, M.; Zanotti, L
2000-04-07
In this paper we present the excellent results obtained by mechanical decoupling of our thermal detectors from the cryostat. The starting point of this work is the necessity to improve the performances of thermal detectors and, besides, to eliminate the non-constant noise resulting from the overall cryogenic facility; this second point results to be crucial for rare-events experiments and the fundamental task for Dark Matter search. Tested on our bolometer, consisting of a 750 g tellurium oxide absorber coupled with an NTD thermistor and operated at {approx}9 mK in an Oxford 200 dilution refrigerator, this powerful technique can, moreover, provide advantages for a large variety of thermal detectors. A good energy resolution of 3.9 keV FWHM was obtained for 2.615 MeV {gamma}-rays. The 4.2 keV average FWHM resolution for the 5407 keV {sup 210}Po {alpha} decay line is the best ever obtained for {alpha}-particles with any type of detector.
Vibrational and thermal noise reduction for cryogenic detectors
Pirro, S.; Alessandrello, A.; Brofferio, C.; Bucci, C.; Cremonesi, O.; Coccia, E.; Fiorini, E.; Fafone, V.; Giuliani, A.; Nucciotti, A.; Pavan, M.; Pessina, G.; Previtali, E.; Vanzini, M.; Zanotti, L.
2000-04-01
In this paper we present the excellent results obtained by mechanical decoupling of our thermal detectors from the cryostat. The starting point of this work is the necessity to improve the performances of thermal detectors and, besides, to eliminate the non-constant noise resulting from the overall cryogenic facility; this second point results to be crucial for rare-events experiments and the fundamental task for Dark Matter search. Tested on our bolometer, consisting of a 750 g tellurium oxide absorber coupled with an NTD thermistor and operated at ˜9 mK in an Oxford 200 dilution refrigerator, this powerful technique can, moreover, provide advantages for a large variety of thermal detectors. A good energy resolution of 3.9 keV FWHM was obtained for 2.615 MeV γ-rays. The 4.2 keV average FWHM resolution for the 5407 keV 210Po α decay line is the best ever obtained for α-particles with any type of detector.
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration. 33.63 Section 33.63 Aeronautics... STANDARDS: AIRCRAFT ENGINES Design and Construction; Turbine Aircraft Engines § 33.63 Vibration. Each engine... because of vibration and without imparting excessive vibration forces to the aircraft structure. ...
14 CFR 33.83 - Vibration test.
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration test. 33.83 Section 33.83... STANDARDS: AIRCRAFT ENGINES Block Tests; Turbine Aircraft Engines § 33.83 Vibration test. (a) Each engine must undergo vibration surveys to establish that the vibration characteristics of those components that...
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration. 33.33 Section 33.33 Aeronautics... STANDARDS: AIRCRAFT ENGINES Design and Construction; Reciprocating Aircraft Engines § 33.33 Vibration. The... vibration and without imparting excessive vibration forces to the aircraft structure. ...
14 CFR 33.43 - Vibration test.
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration test. 33.43 Section 33.43... STANDARDS: AIRCRAFT ENGINES Block Tests; Reciprocating Aircraft Engines § 33.43 Vibration test. (a) Each engine must undergo a vibration survey to establish the torsional and bending vibration characteristics...
49 CFR 178.819 - Vibration test.
2010-10-01
... 49 Transportation 2 2010-10-01 2010-10-01 false Vibration test. 178.819 Section 178.819... Testing of IBCs § 178.819 Vibration test. (a) General. The vibration test must be conducted for the... vibration test. (b) Test method. (1) A sample IBC, selected at random, must be filled and closed as for...
Rectangular Parallelepiped Vibration in Plane Strain State
Hanckowiak, Jerzy
2004-01-01
In this paper we present a vibration spectrum of a homogenous parallelepiped (HP) under the action of volume and surface forces resulting from the exponent displacements entering the Fourier transforms. Vibration under the action of axial surface tractions and the free vibration are described separately. A relationship between the high frequency vibration and boundary conditions (BC) is also considered.
Windshield wiper motor noise reduction; Jidoshayo waipa mota no soon teigen
Energy Technology Data Exchange (ETDEWEB)
Murata, Y.; Ohashi, Y.; Ishikawa, M.; Teshirogi, I.; Sakakibara, M.; Aoki, K. [Jidosha Denki Kogyo Co. Ltd., Yokohama (Japan)
1997-02-01
Regarding automobile wipers, manual wipers were attached to a car in the beginning of 1916, pneumatic motor driven wipers were introduced in 1930, electric motor driven wipers appeared in 1950`s, and the existing style of wiper was perfected in 1957. The reduction of running noise of wiper motors in recent years has shown the most significant progress. In this article, the approaches towards reduction of running noise of wiper motors in recent years are described. First the basic structure of wiper motor is shown, then the sources of generation of vibration and the routes of its propagation are shown. The vibration from the direct current motor section consists of dynamic balance of rotor, vibration by fluctuation of magnetism, vibration due to the 3rd brush, brush noise, vibration from the reduction section and inversion noise. Their propagation routes are divided into radiation from the motor and propagation noise through body panels, and the respective evaluation methods are introduced. Concerning a method to reduce the running noise of motor, reduction of vibration of the direct current motor section (improvement of dynamic balance of rotor, reduction of vibrations by fluctuation of magnetism as well as the 3rd brush, and reduction of brush noise) and reduction of vibration from the reduction section are explained. 10 figs.
Meng, Fanwei; Liu, Chengying; Li, Zhijun; Wang, Liping
2013-01-01
Due to low damping ratio, flat permanent magnet linear synchronous motor's vibration is difficult to be damped and the accuracy is limited. The vibration suppressing results are not good enough in the existing research because only the longitudinal direction vibration is considered while the normal direction vibration is neglected. The parameters of the direct-axis current controller are set to be the same as those of the quadrature-axis current controller commonly. This causes contradiction between signal noise and response. To suppress the vibration, the electromagnetic force model of the flat permanent magnet synchronous linear motor is formulated first. Through the analysis of the effect that direct-axis current noise and quadrature-axis current noise have on both direction vibration, it can be declared that the conclusion that longitudinal direction vibration is only related to the quadrature-axis current noise while the normal direction vibration is related to both the quadrature-axis current noise and direct-axis current noise. Then, the simulation test on current loop with a low-pass filter is conducted and the results show that the low-pass filter can not suppress the vibration but makes the vibration more severe. So a vibration suppressing strategy that the proportional gain of direct-axis current controller adapted according to quadrature-axis reference current is proposed. This control strategy can suppress motor vibration by suppressing direct-axis current noise. The experiments results about the effect of K p and T i on normal direction vibration, longitudinal vibration and the position step response show that this strategy suppresses vibration effectively while the motor's motion performance is not affected. The maximum reduction of vibration can be up to 40%. In addition, current test under rated load condition is also conducted and the results show that the control strategy can avoid the conflict between the direct-axis current and the quadrature
DESIGN OF VIBRATION AND NOISE CONTROL SYSTEM FOR FLEXIBLE STRUCTURES
Directory of Open Access Journals (Sweden)
В. Макаренко
2012-04-01
Full Text Available In the article the control system is created, which is able to reduce steady-state vibration response of thinwalled flexible structure in the wide band of low frequencies. It is supposed, that the flexible structure is subject to external harmonic force with variable frequencies, and parameters of that force are available for the usage by the control system. The control system is based on pattern search algorithm and suggestion about the dependence of signal, which is formed by the control system, from the steady-state vibration response of the flexible structure. Developed software allows to use pattern search algorithm as the control system for plate vibration in real-time. The influence on control system operation of signal delay of executive device of compensating path and transition process after the change of control signal parameters is done by the usage of the additional idle time. During idle time the control signal is supported. It has parameters that have taken place before the beginning of idle mode. Step reset option for resuming of search after the long-term steady-state vibration of flexible structure do not derange control system operation, because step change take place only after polling cycle termination. The efficiency of proposed system is illustrated experimentally on the example of clamped plate. Experimental results analysis showed the necessity of multiple compensating devices application for vibration reduction in wide frequency range.
Vibration analysis of structural elements using differential quadrature method
Directory of Open Access Journals (Sweden)
Mohamed Nassar
2013-01-01
Full Text Available The method of differential quadrature is employed to analyze the free vibration of a cracked cantilever beam resting on elastic foundation. The beam is made of a functionally graded material and rests on a Winkler–Pasternak foundation. The crack action is simulated by a line spring model. Also, the differential quadrature method with a geometric mapping are applied to study the free vibration of irregular plates. The obtained results agreed with the previous studies in the literature. Further, a parametric study is introduced to investigate the effects of geometric and elastic characteristics of the problem on the natural frequencies.
Vibration Analysis of Structures with Rotation and Reflection Symmetry
Directory of Open Access Journals (Sweden)
Baojian Li
1996-01-01
Full Text Available The article applies group representation theory to the vibration analysis of structures with Cnv symmetry, and presents a new structural vibration analysis method. The eigenvalue problem of the whole structure is divided into much smaller subproblems by forming the mass and stiffness matrices of one substructure and than modifying them to form mass and stiffness matrices in each irreducible subspace, resulting in the saving of computer time and memory. The modal characteristics of structures with Cnv symmetry are derived from theoretical analysis. Computation and modal testing are used to verify the validity of the theoretical deductions.
Some heuristic procedures for analyzing random vibration of nonlinear oscillators.
Crandall, S. H.
1971-01-01
The stationary response of a lightly damped nonlinear oscillator subjected to wideband random excitation can be examined as an example of thermal equilibrium. It may be assumed that the response consists of a series of free-vibration cycles with small random fluctuations in phase and amplitude. Certain statistical properties of the response can be estimated by averaging corresponding properties of the free vibration with respect to cycle amplitude distributions. Such heuristic procedures for determining the expected frequency and the autocorrelation function of the stationary response are outlined. Some additional results concerning first-passage problems for nonlinear oscillators are included.
Nonlinear Vibration of Oscillation Systems using Frequency-Amplitude Formulation
Directory of Open Access Journals (Sweden)
A. Fereidoon
2012-01-01
Full Text Available In this paper we study the periodic solutions of free vibration of mechanical systems with third and fifth-order nonlinearity for two examples using He's Frequency-Amplitude Formulation (HFAF.The effectiveness and convenience of the method is illustrated in these examples. It will be shown that the solutions obtained with current method have a fabulous conformity with those achieved from time marching solution. HFAF is easy with powerful concepts and the high accuracy, so it can be found widely applicable in vibrations, especially strong nonlinearity oscillatory problems.
Isogeometric Shape Optimization of Vibrating Membranes
DEFF Research Database (Denmark)
Nguyen, Dang Manh; Evgrafov, Anton; Gersborg, Allan Roulund
2011-01-01
We consider a model problem of isogeometric shape optimization of vibrating membranes whose shapes are allowed to vary freely. The main obstacle we face is the need for robust and inexpensive extension of a B-spline parametrization from the boundary of a domain onto its interior, a task which has...... perform a number of numerical experiments with our isogeometric shape optimization algorithm and present smooth, optimized membrane shapes. Our conclusion is that isogeometric analysis fits well with shape optimization.......We consider a model problem of isogeometric shape optimization of vibrating membranes whose shapes are allowed to vary freely. The main obstacle we face is the need for robust and inexpensive extension of a B-spline parametrization from the boundary of a domain onto its interior, a task which has...... to be performed in every optimization iteration. We experiment with two numerical methods (one is based on the idea of constructing a quasi-conformal mapping, whereas the other is based on a spring-based mesh model) for carrying out this task, which turn out to work sufficiently well in the present situation. We...
Suppression of wind-induced vibrations of a seesaw-type oscillator by means of a dynamic absorber
Lumbantobing, H.
2003-01-01
In this paper the suppression of wind-induced vibrations of a seesaw-type oscillator by means of a dynamic absorber is considered. With suppression the shift of the critical flow velocity to higher values as well as the reduction of vibration amplitudes is meant. The equations of motion are derived
Vibrational Damping of Composite Materials
Biggerstaff, Janet M.
2006-01-01
The purpose of this research was to develop new methods of vibrational damping in polymeric composite materials along with expanding the knowledge of currently used vibrational damping methods. A new barrier layer technique that dramatically increased damping in viscoelastic damping materials that interacted with the composite resin was created. A method for testing the shear strength of damping materials cocured in composites was developed. Directional damping materials, where the loss facto...
Harmonic vibrations of multispan beams
DEFF Research Database (Denmark)
Dyrbye, Claes
1996-01-01
Free and forced harmonic vibrations of multispan beams are determined by a method which implies 1 equation regardless of the configuration. The necessary formulas are given in the paper. For beams with simple supports and the same length of all (n) spans, there is a rather big difference between...... the n´th and the (n+1)´th eigenfrequency. The reason for this phenomenon is explained.Keywords: Vibrations, Eigenfrequencies, Beams....
Smart accelerometer. [vibration damage detection
Bozeman, Richard J., Jr. (Inventor)
1994-01-01
The invention discloses methods and apparatus for detecting vibrations from machines which indicate an impending malfunction for the purpose of preventing additional damage and allowing for an orderly shutdown or a change in mode of operation. The method and apparatus is especially suited for reliable operation in providing thruster control data concerning unstable vibration in an electrical environment which is typically noisy and in which unrecognized ground loops may exist.
Improved Predictions for Geotechnical Vibrations
Macijauskas, Darius
2015-01-01
In urban areas where the infrastructure is dense and construction of new structures is near existing and sensitive buildings, frequently vibrations, caused by human activities, occur. Generated waves in the soil may adversely affect surrounding buildings. These vibrations have to be predicted a priori by using currently available knowledge of the soil dynamics. Current research, conducted by Deltares research institute, showed that the reliability of methods for prediction of m...
Stress analysis of vibrating pipelines
Zachwieja, Janusz
2017-03-01
The pipelines are subject to various constraints variable in time. Those vibrations, if not monitored for amplitude and frequency, may result in both the fatigue damage in the pipeline profile at high stress concentration and the damage to the pipeline supports. If the constraint forces are known, the system response may be determined with high accuracy using analytical or numerical methods. In most cases, it may be difficult to determine the constraint parameters, since the industrial pipeline vibrations occur due to the dynamic effects of the medium in the pipeline. In that case, a vibration analysis is a suitable alternative method to determine the stress strain state in the pipeline profile. Monitoring the pipeline vibration levels involves a comparison between the measured vibration parameters and the permissible values as depicted in the graphs for a specific pipeline type. Unfortunately, in most cases, the studies relate to the petrochemical industry and thus large diameter, long and straight pipelines. For a pipeline section supported on both ends, the response in any profile at the entire section length can be determined by measuring the vibration parameters at two different profiles between the pipeline supports. For a straight pipeline section, the bending moments, variable in time, at the ends of the analysed section are a source of the pipe excitation. If a straight pipe section supported on both ends is excited by the bending moments in the support profile, the starting point for the stress analysis are the strains, determined from the Euler-Bernoulli equation. In practice, it is easier to determine the displacement using the experimental methods, since the factors causing vibrations are unknown. The industrial system pipelines, unlike the transfer pipelines, are straight sections at some points only, which makes it more difficult to formulate the equation of motion. In those cases, numerical methods can be used to determine stresses using the
Vibrationally coupled electron transport through single-molecule junctions
Energy Technology Data Exchange (ETDEWEB)
Haertle, Rainer
2012-04-26
Single-molecule junctions are among the smallest electric circuits. They consist of a molecule that is bound to a left and a right electrode. With such a molecular nanocontact, the flow of electrical currents through a single molecule can be studied and controlled. Experiments on single-molecule junctions show that a single molecule carries electrical currents that can even be in the microampere regime. Thereby, a number of transport phenomena have been observed, such as, for example, diode- or transistor-like behavior, negative differential resistance and conductance switching. An objective of this field, which is commonly referred to as molecular electronics, is to relate these transport phenomena to the properties of the molecule in the contact. To this end, theoretical model calculations are employed, which facilitate an understanding of the underlying transport processes and mechanisms. Thereby, one has to take into account that molecules are flexible structures, which respond to a change of their charge state by a profound reorganization of their geometrical structure or may even dissociate. It is thus important to understand the interrelation between the vibrational degrees of freedom of a singlemolecule junction and the electrical current flowing through the contact. In this thesis, we investigate vibrational effects in electron transport through singlemolecule junctions. For these studies, we calculate and analyze transport characteristics of both generic and first-principles based model systems of a molecular contact. To this end, we employ a master equation and a nonequilibrium Green's function approach. Both methods are suitable to describe this nonequilibrium transport problem and treat the interactions of the tunneling electrons on the molecular bridge non-perturbatively. This is particularly important with respect to the vibrational degrees of freedom, which may strongly interact with the tunneling electrons. We show in detail that the resulting
Vibrational modes of nanolines
Heyliger, Paul R.; Flannery, Colm M.; Johnson, Ward L.
2008-04-01
Brillouin-light-scattering spectra previously have been shown to provide information on acoustic modes of polymeric lines fabricated by nanoimprint lithography. Finite-element methods for modeling such modes are presented here. These methods provide a theoretical framework for determining elastic constants and dimensions of nanolines from measured spectra in the low gigahertz range. To make the calculations feasible for future incorporation in inversion algorithms, two approximations of the boundary conditions are employed in the calculations: the rigidity of the nanoline/substrate interface and sinusoidal variation of displacements along the nanoline length. The accuracy of these approximations is evaluated as a function of wavenumber and frequency. The great advantage of finite-element methods over other methods previously employed for nanolines is the ability to model any cross-sectional geometry. Dispersion curves and displacement patterns are calculated for modes of polymethyl methacrylate nanolines with cross-sectional dimensions of 65 nm × 140 nm and rectangular or semicircular tops. The vibrational displacements and dispersion curves are qualitatively similar for the two geometries and include a series of flexural, Rayleigh-like, and Sezawa-like modes. This paper is a contribution of the National Institute of Standards and Technology and is not subject to copyright in the United States.
Energy Technology Data Exchange (ETDEWEB)
Oh, Seok Gyu; Choi, Tae Wan [Chinju National University (Korea); Lee, Jong Gun [Kumho Electronics Co., Ltd. (Korea)
2001-06-01
SRM drives generate large vibration and acoustic noise because it is rotated by step pulse mmf and switching commutation mechanism. The main vibration source of SRM drive is generated by rapidly variation of radial force when phase winding current is extinguished for commutation action. So the rapidly variation of radial force is repressed firstly to reduce vibrating force of SRM drive. This paper suggests an SRM excitation scheme using unidirect-short compensation winding to reduce vibration of the motor. The motor is excited by a two stage commutation method during commutation period. This reduction effect of vibration is verified with the result obtained in the test of prototype machine. (author). 7 refs., 11 figs.
Active Vibration Control of a Railway Vehicle Carbody Using Piezoelectric Elements
Molatefi, Habibollah; Ayoubi, Pejman; Mozafari, Hozhabr
2017-07-01
In recent years and according to modern transportation development, rail vehicles are manufactured lighter to achieve higher speed and lower transportation costs. On the other hand, weight reduction of rail vehicles leads to increase the structural vibration. In this study, Active Vibration Control of a rail vehicle using piezoelectric elements is investigated. The optimal control employed as the control approach regard to the first two modes of vibration. A simplified Car body structure is modeled in Matlab using the finite element theory by considering six DOF beam element and then the Eigen functions and mode shapes are derived. The surface roughness of different classes of rail tracks have been obtained using random vibration theory and applied to the secondary suspension as the excitation of the structure; Then piezoelectric mounted where the greatest moments were captured. The effectiveness of Piezoelectric in structural vibrations attenuation of car body is demonstrated through the state space equations and its effect on modal coefficient.
Shunted Piezoelectric Vibration Damping Analysis Including Centrifugal Loading Effects
Min, James B.; Duffy, Kirsten P.; Provenza, Andrew J.
2011-01-01
Excessive vibration of turbomachinery blades causes high cycle fatigue problems which require damping treatments to mitigate vibration levels. One method is the use of piezoelectric materials as passive or active dampers. Based on the technical challenges and requirements learned from previous turbomachinery rotor blades research, an effort has been made to investigate the effectiveness of a shunted piezoelectric for the turbomachinery rotor blades vibration control, specifically for a condition with centrifugal rotation. While ample research has been performed on the use of a piezoelectric material with electric circuits to attempt to control the structural vibration damping, very little study has been done regarding rotational effects. The present study attempts to fill this void. Specifically, the objectives of this study are: (a) to create and analyze finite element models for harmonic forced response vibration analysis coupled with shunted piezoelectric circuits for engine blade operational conditions, (b) to validate the experimental test approaches with numerical results and vice versa, and (c) to establish a numerical modeling capability for vibration control using shunted piezoelectric circuits under rotation. Study has focused on a resonant damping control using shunted piezoelectric patches on plate specimens. Tests and analyses were performed for both non-spinning and spinning conditions. The finite element (FE) shunted piezoelectric circuit damping simulations were performed using the ANSYS Multiphysics code for the resistive and inductive circuit piezoelectric simulations of both conditions. The FE results showed a good correlation with experimental test results. Tests and analyses of shunted piezoelectric damping control, demonstrating with plate specimens, show a great potential to reduce blade vibrations under centrifugal loading.
Stochastic unilateral free vibration of an in-plane cable network
Giaccu, Gian Felice; Barbiellini, Bernardo; Caracoglia, Luca
2015-03-01
Cross-ties are often used on cable-stayed bridges for mitigating wind-induced stay vibration since they can be easily installed on existing systems. The system obtained by connecting two (or more) stays with a transverse restrainer is designated as an "in-plane cable-network". Failures in the restrainers of an existing network have been observed. In a previous study [1] a model was proposed to explain the failures in the cross-ties as being related to a loss in the initial pre-tensioning force imparted to the connector. This effect leads to the "unilateral" free vibration of the network. Deterministic free vibrations of a three-cable network were investigated by using the "equivalent linearization method". Since the value of the initial vibration amplitude is often not well known due to the complex aeroelastic vibration regimes, which can be experienced by the stays, the stochastic nature of the problem must be considered. This issue is investigated in the present paper. Free-vibration dynamics of the cable network, driven by an initial stochastic disturbance associated with uncertain vibration amplitudes, is examined. The corresponding random eigen-value problem for the vibration frequencies is solved through an implementation of Stochastic Approximation, (SA) based on the Robbins-Monro Theorem. Monte-Carlo methods are also used for validating the SA results.
Report of workshop on vibration related to fluid in atomic energy field. 7
Energy Technology Data Exchange (ETDEWEB)
NONE
1997-12-31
Because of the nonlinearity of the equation that governs flow, sometimes vibration occurs in an unexpected system, and it causes trouble. This 7th workshop on vibration related to fluid in atomic energy field was held at Nuclear Engineering Research Laboratory of University of Tokyo on August 25 and 26, 1997. Two themes were ``Vibration of liquid surface by flow`` and ``Numerical analysis of coupled vibration of fluid-structures``. The former is related to the problem in the development of a demonstration FBR, and the latter is related to the numerical analysis technology such as the handling of boundary conditions and the method of taking position, moving velocity and acceleration into account. This workshop aims at thoroughly discussing a small number of themes, and deepening the understanding. In this report, the summaries of 17 papers are collected, of which the titles are as follows. Liquid surface self-exciting vibration by flow, vibration of upper plenum liquid surface of fast reactor, stability analysis of multiple liquid surfaces, flow instability phenomena of multi-loop system, sloshing in a vessel in which fluid flows, the mechanism of occurrence of self-exciting sloshing in a vessel elucidated by numerical analysis, numerical analysis of manometer vibration excited by flow, numerical analysis of flutter phenomena of aircraft, numerical analysis of aerodynamic elastic problem, mechanism of in-line excitation, numerical analysis of hydrodynamic elastic vibration of tube nest and so on. (K.I.)
Effect of horizontal wave barriers on ground vibration propagation.
Grau, L; Laulagnet, B
2015-09-01
The aim of this article is to introduce a method to mitigate ground surface vibration through a flexural plate coupled to the ground and acting as a horizontal wave barrier. Using the thin plate hypothesis, two flexural plates are coupled to the ground, the first plate being the excited plate and the second plate the horizontal wave barrier. For instance, the first plate may represent a slab track and be excited by the tramway wheels. A solution to the problem can be found using a spatial two-dimensional Fourier transform of the elastodynamics equation for the ground and a modal decomposition for the flexural plate vibration. The authors show that vibration is substantially mitigated by the horizontal wave barrier and depends on its thickness and width. When the top surface wavelength becomes smaller than twice the plate width, the horizontal wave barrier acts as a wave barrier in the frequency range of interest, i.e., from 20 Hz.
Free Vibration Analysis of Multiple Cracked Functionally Graded Timoshenko Beams
Directory of Open Access Journals (Sweden)
Tran Van Lien
Full Text Available Abstract In this paper, authors present the study of free vibration of bending multiple cracked functionally graded material (FGM beam. Vibration equations of multiple cracked FGM beam were established by using the rotational spring model of cracks, dynamic stiffness method (DSM and actual position of neutral plane. The frequency equation obtained was in a simple form, that provides an effective approach to study not only free vibration of the beams but also inverse problems like identification of material and crack parameters in structure. The obtained numerical results show good agreement with other previous published results. Thence, numerical computation has been carried out to investigate the effect of each crack, the number of cracks, material and geometric parameters on the natural frequencies of multiple cracked Timoshenko FGM beams.
Planetary Gearbox Vibration Signal Characteristics Analysis and Fault Diagnosis
Directory of Open Access Journals (Sweden)
Qiang Miao
2015-01-01
Full Text Available Planetary gearboxes are widely used in helicopters, wind turbines, mining machinery, and so forth. The structure and motion type of a planetary gearbox are more complex in comparison with a fixed-shaft one, which makes condition monitoring and fault diagnosis of planetary gearbox a challenging issue in practical applications. In order to understand the fundamental nature of planetary gearbox vibration, this paper conducts an investigation on vibration characteristics of a single-stage planetary gearbox. Assuming that the gearbox and the sensor revolve inversely at the speed of planet carrier, the problem can be transformed into two easier parts: research on fixed-shaft gearbox signal model and research on influence of sensor spinning. Based on this assumption, a vibration signal model of planetary gearbox is obtained. Experimental data are used to validate the model.
Vehicle Vibration Analysis in Changeable Speeds Solved by Pseudoexcitation Method
Directory of Open Access Journals (Sweden)
Li-Xin Guo
2010-01-01
Full Text Available The vehicle driving comfort has become one of the important factors of vehicle quality and receives increasing attention. In this paper, the mechanical and mathematical models of the half-car, five degrees of freedom (DOF of a vehicle were established, as well as the pseudoexcitation model of road conditions for the front wheel and the rear wheel. By the pseudoexcitation method, the equations of transient response and power spectrum density were established. After numerical simulation to vehicle vibration response of changeable driving, the results show that the pseudoexcitation method is more convenient than the traditional method and effectively solves the smoothness computation problems of vehicles while the pseudoexcitation method is used to analyze vehicle vibration under nonstationary random vibration environments.
Whole-body vibration therapy in intensive care patients: A feasibility and safety study.
Boeselt, Tobias; Nell, Christoph; Kehr, Katahrina; Holland, Angélique; Dresel, Marc; Greulich, Timm; Tackenberg, Björn; Kenn, Klaus; Boeder, Johannes; Klapdor, Benjamin; Kirschbaum, Andreas; Vogelmeier, Claus; Alter, Peter; Koczulla, Andreas Rembert
2016-03-01
Admission to the intensive care unit is associated with sustained loss of muscle mass, reduced quality of life and increased mortality. Early rehabilitation measures may counteract this process. New approaches to rehabilitation while the patient remains in bed are whole-body vibration alone and whole-body vibration with a dumbbell. The aims of this study are to determine the safety of whole-body vibration for patients admitted to the intensive care unit, and to compare the effects of these techniques in intensive care unit patients and healthy subjects. Twelve intensive care unit patients and 12 healthy subjects using whole-body vibration for the first time were examined while lying in bed. First both groups performed whole body vibration over 3 min. In a second step whole body vibration with dumbbell was performed. In order to determine the safety of the training intensity, heart rate, oxygen saturation and blood pressure were measured. The study was approved by the Marburg ethics committee. There were minor reversible and transient increases in diastolic blood pressure (p = 0.005) and heart rate (p = 0.001) in the control group with whole-body vibration with a dumbbell. In intensive care patients receiving whole-body vibration alone, there were increases in diastolic blood pressure (p = 0.011) and heart rate (p vibration and whole-body vibration with a dumbbell for intensive care unit in-bed patients. No clinically significant safety problems were found. Whole-body vibration and whole-body vibration with a dumbbell might therefore be alternative methods for use in early in-bed rehabilitation, not only for hospitalized patients.
Optimum design of a gearbox for low vibration
Inoue, Katsumi; Townsend, Dennis P.; Coy, John J.
1992-01-01
A computer program was developed for designing a low vibration gearbox. The code is based on a finite element shell analysis, a modal analysis, and a structural optimization method. In the finite element analysis, a triangular shell element with 18 degrees-of-freedom is used. In the optimization method, the overall vibration energy of the gearbox is used as the objective function and is minimized at the exciting frequency by varying the finite element thickness. Modal analysis is used to derive the sensitivity of the vibration energy with respect to the design variable. The sensitivity is representative of both eigenvalues and eigenvectors. The optimum value is computed by the gradient projection method and a unidimensional search procedure under the constraint condition of constant weight. The computer code is applied to a design problem derived from an experimental gearbox in use at the NASA Lewis Research Center. The top plate and two side plates of the gearbox are redesigned and the contribution of each surface to the total vibration is determined. Results show that optimization of the top plate alone is effective in reducing total gearbox vibration.
Evaluation of hand-arm vibration reducing effect of anti-vibration glove
樹野, 淳也; 前田, 節雄; 横田, 和樹; 平, 雄一郎
2015-01-01
Many kinds of the anti-vibration glove have been developed for reducing hand-arm vibration during the operation with vibration tools. International standard ISO 10819 evaluates the physical effect of gloves' vibration transmissibility but not evaluates the physiological effect of human hands. Thus, in this paper, we proposed the evaluation using the temporary threshold shift of vibrotactile perception threshold to evaluate the hand-arm vibration reducing effect of anti-vibration glove. We per...
A concept for semi-active vibration control with a serial-stiffness-switch system
Min, Chaoqing; Dahlmann, Martin; Sattel, Thomas
2017-09-01
This work deals with a new semi-active vibration control concept with a serial-stiffness-switch system (SSSS), which can be seen as one and a half degree-of-freedom system. The proposed switched system is mainly composed of two serial elements, each of which consists of one spring and one switch in parallel with each other. This mechanical structure benefits from a specified switching law based on the zero crossing of velocity in order to realize vibration reduction. In contrast with conventional ways, the new system is capable of harvesting vibration energy as potential energy stored in springs, and then applies it to vibration reduction. In this paper, the concept is characterized, simulated, evaluated, and proven to be able to improve the system response. The equivalent stiffness and natural frequency of the switched system are mathematically formulated and verified.
Localised Muscle Tissue Oxygenation During Dynamic Exercise With Whole Body Vibration
Robbins, Daniel; Elwell, Clare; Jimenez, Alfonso; Goss-Sampson, Mark
2012-01-01
Despite increasing use of whole body vibration during exercise an understanding of the exact role of vibration and the supporting physiological mechanisms is still limited. An important aspect of exercise analysis is the utilisation of oxygen, however, there have been limited studies considering tissue oxygenation parameters, particularly during dynamic whole body vibration (WBV) exercise. The aim of this study was to determine the effect of adding WBV during heel raise exercises and assessing changes in tissue oxygenation parameters of the lateral gastrocnemius using Near Infra Red Spectroscopy (NIRS). Twenty healthy subjects completed ten alternating sets of 15 heel raises (vibration vs. no vibration). Synchronous oxygenation and motion data were captured prior to exercise to determine baseline levels, for the duration of the exercise and 20 sec post exercise for the recovery period. Both vibration and no vibration conditions elicited a characteristic increase in deoxyhaemoglobin and decreases in oxyhaemoglobin, total haemoglobin, tissue oxygenation index and normalised tissue haemoglobin index which are indicative of local tissue hypoxia. However, the addition of vibration elicited significantly lower (p < 0. 001) depletions in oxyhaemoglobin, total haemoglobin, normalised tissue haemoglobin index but no significant differences in deoxyhaemoglobin. These findings suggest that addition of vibration to exercise does not increase the cost of the exercise for the lateral gastrocnemius muscle, but does decrease the reduction in local muscle oxygenation parameters, potentially resulting from increased blood flow to the calf or a vasospastic response in the feet. However, further studies are needed to establish the mechanisms underlying these findings. Key pointsWhole body vibration affects tissue oxygenation of the lateral gastrocnemius.The underlying mechanism could be either increased blood flow or a vasospastic response in the feet.The local metabolic cost of heel
Vibrations of wind power plants; Schwingungen von Windenergieanlagen
Energy Technology Data Exchange (ETDEWEB)
NONE
2010-07-01
Within the meeting of the department vibration engineering of the Association of German Engineers (Duesseldorf, Federal Republic of Germany) between 3rd and 4th February, 2010 in Hanover (Federal Republic of Germany) the following lectures are presented: (1) Reduction of forced strengths generated by wagging and snaking of the rotor in the power strain of wind power plants (F. Mitsch); (2) Reduction of vibrations at wind power plants by means of active additional systems (S. Katz, S. Pankoke, N. Loix); (3) Reduction of vibrations by means of balancing and alignment (E. Becker, M. Kenzler); (4) Active absorber for reducing tonal emissions of vibration at wind power plants (R. Neugebauer, M. Linke, H. Kunze, M. Ulrich); (5) Control structures for damping torsion vibrations and peak loads in the power strain of wind power converters (C. Sourkounis); (6) Possibilities of a non-contact investigation of vibrations at wind power plants (R. Behrendt, E. Reimers, H. Wiegers); (7) Influences on the loadability of CMS statements (R. Wirth); (8) Recording modal structural properties with sensor grids and methods of operational modal analysis (A. Friedmann, D. Mayer, M. Koch, M. Kauba, T. Melz); (9) Early failure detection of damages of roller bearings in wind power gear units with variable speed (B. Hacke, G. Poll); (10) Condition monitoring in wind power plants - structure monitoring and life time monitoring of wind power plants (SCMS and LCMS) (H. Lange); (11) Development of a model-based structural health monitoring system for condition monitoring of rotor blades (C. Ebert, H. Friedmann, F.O. Henkel, B. Frankenstein, L. Schubert); (12) Efficient remote monitoring at wind power plants by means of an external diagnosis centre (G. Ceglarek); (13) Accurate turbine modelling at component and assembly level for durability and acoustic analysis (D. v. Werner, W. Hendricx); (14) Possibilities of the investigation of the dynamic behaviour of power strains in wind power plants by
Optimal Placement of Piezoelectric Plates to Control Multimode Vibrations of a Beam
Directory of Open Access Journals (Sweden)
Fabio Botta
2013-01-01
Full Text Available Damping of vibrations is often required to improve both the performance and the integrity of engineering structures, for example, gas turbine blades. In this paper, we explore the possibility of using piezoelectric plates to control the multimode vibrations of a cantilever beam. To develop an effective control strategy and optimize the placement of the active piezoelectric elements in terms of vibrations amplitude reduction, a procedure has been developed and a new analytical solution has been proposed. The results obtained have been corroborated by comparison with the results from a multiphysics finite elements package (COMSOL, results available in the literature, and experimental investigations carried out by the authors.
Directory of Open Access Journals (Sweden)
Ze Zhang
2014-01-01
Full Text Available A feedback control method based on an extended state observer (ESO method is implemented to vibration reduction in a typical semiactive suspension (SAS system using a magnetorheological (MR damper as actuator. By considering the dynamic equations of the SAS system and the MR damper model, an active disturbance rejection control (ADRC is designed based on the ESO. Numerical simulation and real-time experiments are carried out with similar vibration disturbances. Both the simulation and experimental results illustrate the effectiveness of the proposed controller in vibration suppression for a SAS system.
Vibration Isolation Technology (VIT) ATD Project
Lubomski, Joseph F.; Grodsinsky, Carlos M.; Logsdon, Kirk A.; Rohn, Douglas A.; Ramachandran, N.
1994-01-01
A fundamental advantage for performing material processing and fluid physics experiments in an orbital environment is the reduction in gravity driven phenomena. However, experience with manned spacecraft such as the Space Transportation System (STS) has demonstrated a dynamic acceleration environment far from being characterized as a 'microgravity' platform. Vibrations and transient disturbances from crew motions, thruster firings, rotating machinery etc. can have detrimental effects on many proposed microgravity science experiments. These same disturbances are also to be expected on the future space station. The Microgravity Science and Applications Division (MSAD) of the Office of Life and Microgravity Sciences and Applications (OLMSA), NASA Headquarters recognized the need for addressing this fundamental issue. As a result an Advanced Technology Development (ATD) project was initiated in the area of Vibration Isolation Technology (VIT) to develop methodologies for meeting future microgravity science needs. The objective of the Vibration Isolation Technology ATD project was to provide technology for the isolation of microgravity science experiments by developing methods to maintain a predictable, well defined, well characterized, and reproducible low-gravity environment, consistent with the needs of the microgravity science community. Included implicitly in this objective was the goal of advising the science community and hardware developers of the fundamental need to address the importance of maintaining, and how to maintain, a microgravity environment. This document will summarize the accomplishments of the VIT ATD which is now completed. There were three specific thrusts involved in the ATD effort. An analytical effort was performed at the Marshall Space Flight Center to define the sensitivity of selected experiments to residual and dynamic accelerations. This effort was redirected about half way through the ATD focusing specifically on the sensitivity of
Feed-forward control of gear mesh vibration using piezoelectric actuators
Montague, Gerald T.; Kascak, Albert F.; Palazzolo, Alan; Manchala, Daniel; Thomas, Erwin
1994-01-01
This paper presents a novel means for suppressing gear mesh-related vibrations. The key components in this approach are piezoelectric actuators and a high-frequency, analog feed-forward controller. Test results are presented and show up to a 70-percent reduction in gear mesh acceleration and vibration control up to 4500 Hz. The principle of the approach is explained by an analysis of a harmonically excited, general linear vibratory system.
Hirotsuka, Isao; Tsuboi, Kazuo
The capacitor motor (CRM) is widely used to drive industrial equipments and electric home appliances. Recently, the reduction in the vibration and noise of the CRM has become increasingly important from the standpoint of environmental improvement. However, the electromagnetic vibration of the CRM under load has not been analyzed sufficiently. Therefore, we have studied the electromagnetic vibration of CRM for the purpose of reducing it. In a previous paper, the relationships for a backward magnetic field, the equivalent circuit current, and the vibration of the CRM were clarified. The present paper theoretically and experimentally discusses the effect of the slot combination and skewed slot on the electromagnetic vibration of CRM under load. The primary conclusions are as follows: (1) In the case of 4-pole and 6-pole CRMs, the dominant electromagnetic vibration of CRMs was theoretically attributed to three types of electromagnetic force waves. Two types of electromagnetic force waves are generated: one wave is generated by the interaction of two forward magnetic fluxes, such as those of a three-phase squirrel-cage induction motor, and the other wave is generated under the influence of a backward magnetic flux. (2) The characteristics of dominant electromagnetic vibration depending on load and running capacitor were classified theoretically and experimentally into three types based on the characteristics of the electromagnetic force wave and equivalent circuit current. (3) The influences of magnetic saturation in dominant electromagnetic vibration were verified experimentally and their causes were clarified theoretically in relation to electromagnetic force waves.
Blade Vibration Measurement System for Unducted Fans
Marscher, William
2014-01-01
With propulsion research programs focused on new levels of efficiency and noise reduction, two avenues for advanced gas turbine technology are emerging: the geared turbofan and ultrahigh bypass ratio fan engines. Both of these candidates are being pursued as collaborative research projects between NASA and the engine manufacturers. The high bypass concept from GE Aviation is an unducted fan that features a bypass ratio of over 30 along with the accompanying benefits in fuel efficiency. This project improved the test and measurement capabilities of the unducted fan blade dynamic response. In the course of this project, Mechanical Solutions, Inc. (MSI) collaborated with GE Aviation to (1) define the requirements for fan blade measurements; (2) leverage MSI's radar-based system for compressor and turbine blade monitoring; and (3) develop, validate, and deliver a noncontacting blade vibration measurement system for unducted fans.
Development of Novel Methods for the Reduction of Noise and Weight in Helicopter Transmissions
Dimofte, Florin; Keith, Theo G., Jr.
2003-01-01
Over the 70-year evolution of the helicopter, man's understanding of vibration control has greatly increased. However, in spite of the increased performance, the extent of helicopter vibration problems has not significantly diminished. Crew vibration and noise remains important factors in the design of all current helicopters. With more complex and critical demands being placed on aircrews, it is essential that vibration and noise not impair their performance. A major source of helicopter cabin noise (which has been measured at a sound pressure level of over 100 dB) is the gearbox. Reduction of this noise has been a goal of NASA and the U.S. Army. Gear mesh noise is typically in the frequency range of 1000 to 3000 Hz, a range important for speech. A requirement for U.S. Army/NASA Advanced Rotorcraft Transmission project has been a 10-dB reduction compared to current designs. A combined analytical/experimental effort has been underway, since the end of the 80's, to study effects of design parameters on noise production. The noise generated by the gear mesh can be transmitted to the surrounding media through the bearings that support the gear shaft. Therefore, the use of fluid film bearings instead of rolling element bearings could reduce the transmission noise by 10 dB. In addition, the fluid film bearings that support the gear shaft can change the dynamics of the gear assembly by providing damping to the system and by being softer than rolling element bearings. Wave bearings can attenuate, and filter, the noise generated by a machine component due to the dynamic stiffness and damping coefficients. The attenuation ratio could be as large as 35-40 dB. The noise components at higher frequencies than a synchronous frequency can be almost eliminated.
Directory of Open Access Journals (Sweden)
Wei Zhu
2014-01-01
Full Text Available A vibration control system is put forward using a magnetorheological damper (MRD and a magnetorheological elastomer (MRE connected in series. In order to model the hysteresis of the MRD, a Bouc-Wen model and a corresponding parameter identification method are developed for the MRD. The experimental results validate the proposed Bouc-Wen model that can predict the hysteretic behavior of the MRD accurately. The role of the MRE is illustrated by an example of a single degree-of-freedom system. A semiactive vibration control strategy of the proposed vibration control system is proposed. To validate this new approach, experiments are conducted and the results highlight significantly improved vibration reduction effect of the proposed vibration control system than the vibration control system only using the MRD.
A 6-DOF vibration isolation system for hydraulic hybrid vehicles
Nguyen, The; Elahinia, Mohammad; Olson, Walter W.; Fontaine, Paul
2006-03-01
This paper presents the results of vibration isolation analysis for the pump/motor component of hydraulic hybrid vehicles (HHVs). The HHVs are designed to combine gasoline/diesel engine and hydraulic power in order to improve the fuel efficiency and reduce the pollution. Electric hybrid technology is being applied to passenger cars with small and medium engines to improve the fuel economy. However, for heavy duty vehicles such as large SUVs, trucks, and buses, which require more power, the hydraulic hybridization is a more efficient choice. In function, the hydraulic hybrid subsystem improves the fuel efficiency of the vehicle by recovering some of the energy that is otherwise wasted in friction brakes. Since the operation of the main component of HHVs involves with rotating parts and moving fluid, noise and vibration are an issue that affects both passengers (ride comfort) as well as surrounding people (drive-by noise). This study looks into the possibility of reducing the transmitted noise and vibration from the hydraulic subsystem to the vehicle's chassis by using magnetorheological (MR) fluid mounts. To this end, the hydraulic subsystem is modeled as a six degree of freedom (6-DOF) rigid body. A 6-DOF isolation system, consisting of five mounts connected to the pump/motor at five different locations, is modeled and simulated. The mounts are designed by combining regular elastomer components with MR fluids. In the simulation, the real loading and working conditions of the hydraulic subsystem are considered and the effects of both shock and vibration are analyzed. The transmissibility of the isolation system is monitored in a wide range of frequencies. The geometry of the isolation system is considered in order to sustain the weight of the hydraulic system without affecting the design of the chassis and the effectiveness of the vibration isolating ability. The simulation results shows reduction in the transmitted vibration force for different working cycles of
Reviving Vibration Energy Harvesting and Self-Powered Sensing by a Triboelectric Nanogenerator
Chen, Jun
2017-10-10
Vibration energy harvesting and sensing is a traditional and growing research field in which various working mechanisms and designs have been developed for an improved performance. Relying on a coupling effect of contact electrification and electrostatic induction, in the past 5 years, triboelectric nanogenerator (TENG) has been applied as a fundamentally new technology to revive the field of vibration energy harvesting and self-powered sensing, especially for low-frequency vibrations such as human motion, automobile, machine, and bridge vibrations. The demonstrated instantaneous energy conversion efficiency of ∼70% and a total efficiency up to 85% distinguished TENG from traditional techniques. In this article, both TENG-enabled vibration energy harvesting and self-powered active sensing are comprehensively reviewed. Moving toward future development, problems pressing for solutions and onward research directions are also posed to deliver a coherent picture.
Characterization of a water pump for drum-type washing machine by vibration power approach
Heo, YongHwa; Kim, Kwang-joon
2015-03-01
Water pumps used in drum-type washing machines to save water are likely to make the washing process noisier than the one without those because the water pumps attached usually onto cabinet structure work as additional vibration and noise sources. In order to either counteract such vibration and noise problems by stiffness design of the cabinet structure or classify the water pumps from the view point of an acceptance test, characterization of the water pumps as excitation sources would be essential. In this paper, several methods to characterize a water pump as an excitation source are investigated. Measurements by traditional methods of blocked force and/or free velocity for a water pump of 35 W are presented. Two methods of vibration power suggested rather recently are reviewed. Then, another method of the vibration power is proposed. Estimations of the vibration power for the water pump operating on a beam structure are obtained and discussed comparatively.
Possible Mechanisms of Low Back Pain due to Whole-Body Vibration
Pope, M. H.; Wilder, D. G.; Magnusson, M.
1998-08-01
The investigators describe their multifaceted approach to the study of the relationship between whole-body vibration and low back pain.In vitroexperiments, using percutaneous pin-mounted accelerometers have shown that the natural frequency is at 4·5 Hz. The frequency response was affected by posture, seating, and seat-back inclination. The response appears to be largely determined by the rocking of the pelvis. Electromyographic studies have shown that muscle fatigue occurs under whole body vibration. After whole body vibration exposure the muscle response to a sudden load has greater latency. Vehicle driving may be a reason for low back pain or herniated nucleus pulposus. Prolonged seating exposure, coupled with the whole body vibration should be reduced for those recovering from these problems. Vibration attenuating seats, and correct ergonomic layout of the cabs may reduce the risks of recurrence.
Analysis and control of the vibration of doubly fed wind turbine
Yu, Manye; Lin, Ying
2017-01-01
The fault phenomena of the violent vibration of certain doubly-fed wind turbine were researched comprehensively, and the dynamic characteristics, load and fault conditions of the system were discussed. Firstly, the structural dynamics analysis of wind turbine is made, and the dynamics mold is built. Secondly, the vibration testing of wind turbine is done with the German test and analysis systems BBM. Thirdly, signal should be analyzed and dealt with. Based on the experiment, spectrum analysis of the motor dynamic balance can be made by using signal processing toolbox of MATLAB software, and the analysis conclusions show that the vibration of wind turbine is caused by dynamic imbalance. The results show that integrating mechanical system dynamics theory with advanced test technology can solve the vibration problem more successfully, which is important in vibration diagnosis of mechanical equipment.
Research of rotating machinery vibration parameters - Shaft speed relationship
Kostyukov, V. N.; Kostyukov, A. V.; Zaytsev, A. V.; Teterin, A. O.
2017-08-01
The paper considers the relationship between the parameters of the vibration arising in rotating machinery during operation and the shaft speed. The goal of this paper is to determine the dependence of the vibration parameters on the shaft speed for solving applied engineering problems. To properly evaluate the technical condition of bearing assemblies, we should take into account the pattern of the rotating machinery vibration parameters-shaft speed relationship, which will allow creating new diagnostic features, the totality of which will ensure an increased reliability of diagnosis. We took the check for a correlation between the factor and resultative feature parameters as the correlation analysis method. A high pair linear correlation between the diagnostic features (acceleration, velocity, displacement) and the shaft speed was determined on the basis of the check for correlation between the vibration parameters and the shaft speed, and also the linear correlation coefficients can be used to solve the applied engineering problems of diagnosing the bearing assemblies of the rotating machinery.
Mechanical Vibrations Modeling and Measurement
Schmitz, Tony L
2012-01-01
Mechanical Vibrations:Modeling and Measurement describes essential concepts in vibration analysis of mechanical systems. It incorporates the required mathematics, experimental techniques, fundamentals of modal analysis, and beam theory into a unified framework that is written to be accessible to undergraduate students,researchers, and practicing engineers. To unify the various concepts, a single experimental platform is used throughout the text to provide experimental data and evaluation. Engineering drawings for the platform are included in an appendix. Additionally, MATLAB programming solutions are integrated into the content throughout the text. This book also: Discusses model development using frequency response function measurements Presents a clear connection between continuous beam models and finite degree of freedom models Includes MATLAB code to support numerical examples that are integrated into the text narrative Uses mathematics to support vibrations theory and emphasizes the practical significanc...
Directory of Open Access Journals (Sweden)
2012-12-01
Full Text Available Introduction: Today’s, defective and faulty equipments lose a large part of them energy as noise and vibration which beside their financial costs can be hazardous to the health of people. Vibration as a physical agent can cause an adverse health effect on human to nervous system. These effects, based on body region can be as specific or general systems. Digestion system has a natural vibration of 3-8Hz frequency. When the digestive system is exposed by such vibration, it can make impairment on that system. This study aimed to study vibration effect on digestion irregularities. . Material and Method: This was a retrospective case-control study conducted in a food industry. The number of 103 workers digestive problem and 431 healthy workers were selected as population study. Exposure to the vibration in the different parts were measured. People with more than 100 dB was considered exposed group. Then, after determining the number of exposed and non exposed groups, data were analyzed using statistical methodologies. .Result: The acceleration level of vibration was 109.8 dB in the packing section, which was less than standard limit (118.8 dB. Study population had a managed of 24-57 years old with 4-15 years of job tenure. In 59.2% of case comparing to 22.7% of control group were exposed to the vibration. The odds ratio (OR of prevalence rate of digestive problem among exposed group was 6.3 times more than non exposed group people, in risk of gastrointestinal complications. .Conclusion: Beside of the other risk factors of digestive problem, vibration can be also an effective cause of adverse health problem: Even by lower level of digestive problem can be seen in the exposed people. So, we suggest in the workplace with vibration risk factor, a digestive health exam be take general medical beside periodic examination. Moreover, it is recommended that researches related to the vibration is widely developed and the vibration standard limits is revised
Stroboscopic shearography for vibration analysis
Steinchen, Wolfgang; Kupfer, Gerhard; Maeckel, Peter; Voessing, Frank
1999-09-01
Digital Shearography, a laser interferometric technique in conjunction with the digital image processing, has the potential for vibration analysis due to its simple optical system and insensitivity against small rigid body motions. This paper will focus on its recent developments for vibration analysis and for nondestructive testing (NDT) by dynamic (harmonical) excitation. With the introduction of real time observation using automatically refreshing reference frame, both small and large rigid body motions are greatly suppressed. The development of a smaller and more mobile measuring device in conjunction with a user guided comfortable program Shearwin enables the digital shearography to be applied easily as an industrial online testing tool.
Vibrational Collapse of Hexapod Packings
Zhao, Yuchen; Ding, Jingqiu; Barés, Jonathan; Zheng, Hu; Dierichs, Karola; Menges, Achim; Behringer, Robert
2017-06-01
Columns made of convex noncohesive grains like sand collapse after being released from a confining container. However, structures built from non-convex grains can be stable without external support. In the current experiments, we investigate the effect of vibration on destroying such columns. The change of column height during vertical vibration, can be well characterized by stretched exponential relaxation when the column is short, which is in agreement with previous work, while a faster collapse happens when the column is tall. We investigate the collapse after the fast process including its dependence on column geometry, and on interparticle and basal friction.
Krajnak, Kristine; Raju, Sandya G; Miller, G Roger; Johnson, Claud; Waugh, Stacey; Kashon, Michael L; Riley, Danny A
2016-01-01
Repeated exposure to hand-transmitted vibration through the use of powered hand tools may result in pain and progressive reductions in tactile sensitivity. The goal of the present study was to use an established animal model of vibration-induced injury to characterize changes in sensory nerve function and cellular mechanisms associated with these alterations. Sensory nerve function was assessed weekly using the current perception threshold test and tail-flick analgesia test in male Sprague-Dawley rats exposed to 28 d of tail vibration. After 28 d of exposure, Aβ fiber sensitivity was reduced. This reduction in sensitivity was partly attributed to structural disruption of myelin. In addition, the decrease in sensitivity was also associated with a reduction in myelin basic protein and 2',3'- cyclic nucleotide phosphodiasterase (CNPase) staining in tail nerves, and an increase in circulating calcitonin gene-related peptide (CGRP) concentrations. Changes in Aβ fiber sensitivity and CGRP concentrations may serve as early markers of vibration-induced injury in peripheral nerves. It is conceivable that these markers may be utilized to monitor sensorineural alterations in workers exposed to vibration to potentially prevent additional injury.
Bostic, Susan W.; Fulton, Robert E.
1987-01-01
Eigenvalue analyses of complex structures is a computationally intensive task which can benefit significantly from new and impending parallel computers. This study reports on a parallel computer implementation of the Lanczos method for free vibration analysis. The approach used here subdivides the major Lanczos calculation tasks into subtasks and introduces parallelism down to the subtask levels such as matrix decomposition and forward/backward substitution. The method was implemented on a commercial parallel computer and results were obtained for a long flexible space structure. While parallel computing efficiency is problem and computer dependent, the efficiency for the Lanczos method was good for a moderate number of processors for the test problem. The greatest reduction in time was realized for the decomposition of the stiffness matrix, a calculation which took 70 percent of the time in the sequential program and which took 25 percent of the time on eight processors. For a sample calculation of the twenty lowest frequencies of a 486 degree of freedom problem, the total sequential computing time was reduced by almost a factor of ten using 16 processors.
... Women Hair Loss Hand/Wrist/Arm Problems Headaches Hearing Problems Hip Problems Knee Problems Leg Problems Lower Back ... have ear pain or redness but is having problems hearing?YesNo Back to Questions Step 3 Possible Causes ...
Energy Technology Data Exchange (ETDEWEB)
Marienfeld, P.M.; Karkosch, H.J. [ContiTech Vibration Control GmbH, Hannover (Germany); Bohn, C. [Technische Univ. Clausthal (Germany); Svaricek, F. [Univ. der Bundeswehr Muenchen (Germany); Knake-Langhorst, S. [Deutsches Zentrum fuer Luft- und Raumfahrt, Braunschweig (Germany)
2008-07-01
In the automotive industry passive vibration absorbers are a well established method to reduce structural vibrations in automotive vehicles. Designing a vibration absorber consists of selecting its mechanical properties. Usually extensive tests are necessary with different absorbers in the vehicle and subjective as well as objective evaluation of the results. This requires hardware modifications between different tests. In this paper, an approach is proposed that can assist in the development of vibration absorbers. It is based on tuning an active vibration control system such that it reproduces the behavior of a specified vibration absorber. This behavior can then be changed electronically without modifying the hardware. Two different control approaches are compared. In the first approach, the apparent physical properties of a vibration absorber are directly modified through acceleration, velocity or displacement feedback. In the second approach, a desired dynamic mass transfer function for the vibration absorber is prescribed and an H2-norm optimal model matching problem is solved. Experimental results obtained with this approach are presented. (orig.)
DEFF Research Database (Denmark)
Jalkanen, Karl J.
2003-01-01
Here we present several low energy conformers of Leu-enkephalin (LeuE) calculated with the density functional theory using the Becke 3LYP hybrid functional and the 6-31G* basis set. The structures, conformational energies, vibrational frequencies, vibrational absorption (VA) intensities......, vibrational circular dichroism (VCD) intensities and Raman scattering intensities are reported for the conformers of LeuE which are expected to be populated at room temperature. The species of LeuE-present in non-polar solvents is the neutral non-ionic species with the NH2 and CO2H groups, in contrast...... to the zwitterionic neutral species with the NH3+ and CO2- groups which predominates in aqueous solution and in the crystal. All of our attempts to find the zwitterionic species in the isolated state failed, with the result that a hydrogen atom from the positively charged N-terminus ammonium group transferred either...
Optical properties of a vibrationally modulated solid state Mott insulator.
Kaiser, S; Clark, S R; Nicoletti, D; Cotugno, G; Tobey, R I; Dean, N; Lupi, S; Okamoto, H; Hasegawa, T; Jaksch, D; Cavalleri, A
2014-01-22
Optical pulses at THz and mid-infrared frequencies tuned to specific vibrational resonances modulate the lattice along chosen normal mode coordinates. In this way, solids can be switched between competing electronic phases and new states are created. Here, we use vibrational modulation to make electronic interactions (Hubbard-U) in Mott-insulator time dependent. Mid-infrared optical pulses excite localized molecular vibrations in ET-F2TCNQ, a prototypical one-dimensional Mott-insulator. A broadband ultrafast probe interrogates the resulting optical spectrum between THz and visible frequencies. A red-shifted charge-transfer resonance is observed, consistent with a time-averaged reduction of the electronic correlation strength U. Secondly, a sideband manifold inside of the Mott-gap appears, resulting from a periodically modulated U. The response is compared to computations based on a quantum-modulated dynamic Hubbard model. Heuristic fitting suggests asymmetric holon-doublon coupling to the molecules and that electron double-occupancies strongly squeeze the vibrational mode.
Resonant vibration control of rotating beams
DEFF Research Database (Denmark)
Svendsen, Martin Nymann; Krenk, Steen; Høgsberg, Jan Becker
2011-01-01
Rotatingstructures,like e.g.wind turbine blades, may be prone to vibrations associated with particular modes of vibration. It is demonstrated, how this type of vibrations can be reduced by using a collocated sensor–actuator system, governed by a resonant controller. The theory is here demonstrated...... modal connectivity, only very limited modal spill-over is generated. The controller acts by resonance and therefore has only a moderate energy consumption, and successfully reduces modal vibrations at the resonance frequency....
Vibration Transfer Path Analysis and Path Ranking for NVH Optimization of a Vehicle Interior
Directory of Open Access Journals (Sweden)
B. Sakhaei
2014-01-01
Full Text Available By new advancements in vehicle manufacturing, evaluation of vehicle quality assurance has got a more critical issue. Today noise and vibration generated inside and outside the vehicles are more important factors for customers than before. So far several researchers have focused on interior noise transfer path analysis and the results have been published in related papers but each method has its own limitations. In present work, the vibration transfer path analysis and vibration path ranking of a car interior have been performed. As interior vibration is a source of structural borne noise problem, thus, the results of this research can be used to present the structural borne noise state in a vehicle. The proposed method in this paper does not need to disassemble the powertrain from the chassis. The procedure shows a good ability of vibration path ranking in a vehicle and is an effective tool to diagnose the vibration problem inside the vehicle. The simulated vibration spectrums in different speeds of the engine have a good compliance with the tested results; however, some incompatibilities exist and have been discussed in detail. The simulated results show the strength of the method in engine mount optimization.
A fractional-order controller for vibration suppression of uncertain structures.
Aghababa, Mohammad Pourmahmood
2013-11-01
The problem of active control of vibration structures has attracted much attention over the past decades. A general description of the control problem of vibration systems is to design an active controller to suppress the vibrations of the system induced by external disturbances such as an earthquake. In this paper, a novel fractional-order sliding mode control is introduced to attenuate the vibrations of structures with uncertainties and disturbances. After establishing a stable fractional sliding surface, a sliding mode control law is proposed. Then, the global asymptotic stability of the closed-loop system is analytically proved using fractional Lyapunov stability theorem. Finally, the robustness and applicability of the technique are verified using two examples, including a three degree of freedom structure and a two-story shear building. Copyright © 2013 ISA. Published by Elsevier Ltd. All rights reserved.
Adaptive and robust active vibration control methodology and tests
Landau, Ioan Doré; Castellanos-Silva, Abraham; Constantinescu, Aurelian
2017-01-01
This book approaches the design of active vibration control systems from the perspective of today’s ideas of computer control. It formulates the various design problems encountered in the active management of vibration as control problems and searches for the most appropriate tools to solve them. The experimental validation of the solutions proposed on relevant tests benches is also addressed. To promote the widespread acceptance of these techniques, the presentation eliminates unnecessary theoretical developments (which can be found elsewhere) and focuses on algorithms and their use. The solutions proposed cannot be fully understood and creatively exploited without a clear understanding of the basic concepts and methods, so these are considered in depth. The focus is on enhancing motivations, algorithm presentation and experimental evaluation. MATLAB®routines, Simulink® diagrams and bench-test data are available for download and encourage easy assimilation of the experimental and exemplary material. Thre...
Influence of dynamic soil-structure interaction on building response to ground vibration
DEFF Research Database (Denmark)
Andersen, Lars Vabbersgaard
2014-01-01
must be used. In this regard it is often assumed that a no significant back coupling from the building to the ground exists. Thus, a model with free-field vibrations from the ground provides input at the base of the building model. The aim of the present paper is to examine whether—and to which extent......Vibration from traffic and pile driving are an increasing problem in densely populated areas. To assess vibration levels in new or existing buildings near construction sites, roads or railways in the design phase, valid models for prediction of wave transmission via the ground and into a building...
Feedback Controller Stabilizing Vibrations of a Flexible Cable Related to an Overhead Crane
Directory of Open Access Journals (Sweden)
Abdelhadi Elharfi
2010-01-01
Full Text Available The problem of stabilizing vibrations of flexible cable related to an overhead crane is considered. The cable vibrations are described by a hyperbolic partial differential equation (HPDE with an update boundary condition. We provide in this paper a systematic way to derive a boundary feedback law which restores in a closed form the cable vibrations to the desired zero equilibrium. Such a control law is explicitly constructed in terms of the solution of an appropriate kernel PDE. The pursued approach combines the “backstepping method” and “semigroup theory”.
Low-energy isovector quadrupole vibrations
Energy Technology Data Exchange (ETDEWEB)
Faessler, A.; Nojarov, R.
1986-01-23
The low-lying isovector quadrupole vibrations are described by an extension of the vibrational model allowing independent proton and neutron vibrations coupled by the symmetry energy. The recently detected low-lying isovector states in nearly spherical nuclei with N=84 are described well concerning their energies and E2/M1 mixing ratios. (orig.).
Ground Vibration Measurements at LHC Point 4
Energy Technology Data Exchange (ETDEWEB)
Bertsche, Kirk; /SLAC; Gaddi, Andrea; /CERN
2012-09-17
Ground vibration was measured at Large Hadron Collider (LHC) Point 4 during the winter shutdown in February 2012. This report contains the results, including power and coherence spectra. We plan to collect and analyze vibration data from representative collider halls to inform specifications for future linear colliders, such as ILC and CLIC. We are especially interested in vibration correlations between final focus lens locations.
33 CFR 159.103 - Vibration test.
2010-07-01
... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Vibration test. 159.103 Section...) POLLUTION MARINE SANITATION DEVICES Design, Construction, and Testing § 159.103 Vibration test. The device... subjected to a sinusoidal vibration for a period of 12 hours, 4 hours in each of the x, y, and z planes, at...
14 CFR 27.907 - Engine vibration.
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Engine vibration. 27.907 Section 27.907... STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant General § 27.907 Engine vibration. (a) Each engine must be installed to prevent the harmful vibration of any part of the engine or rotorcraft. (b) The addition of the...
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration. 29.251 Section 29.251... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Flight Miscellaneous Flight Requirements § 29.251 Vibration. Each part of the rotorcraft must be free from excessive vibration under each appropriate speed and power...
14 CFR 29.907 - Engine vibration.
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Engine vibration. 29.907 Section 29.907... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant General § 29.907 Engine vibration. (a) Each engine must be installed to prevent the harmful vibration of any part of the engine or rotorcraft. (b) The...
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration. 27.251 Section 27.251... STANDARDS: NORMAL CATEGORY ROTORCRAFT Flight Miscellaneous Flight Requirements § 27.251 Vibration. Each part of the rotorcraft must be free from excessive vibration under each appropriate speed and power...
49 CFR 178.608 - Vibration standard.
2010-10-01
... 49 Transportation 2 2010-10-01 2010-10-01 false Vibration standard. 178.608 Section 178.608... Testing of Non-bulk Packagings and Packages § 178.608 Vibration standard. (a) Each packaging must be capable of withstanding, without rupture or leakage, the vibration test procedure outlined in this section...
49 CFR 178.985 - Vibration test.
2010-10-01
... 49 Transportation 2 2010-10-01 2010-10-01 false Vibration test. 178.985 Section 178.985... Testing of Large Packagings § 178.985 Vibration test. (a) General. All rigid Large Packaging and flexible Large Packaging design types must be capable of withstanding the vibration test. (b) Test method. (1) A...
Vibration measurements on timber frame floors
Kuilen, J.W.G. van de; Oosterhout, G.P.C. van; Donkervoort, R.
1998-01-01
In the design of lightweight floors vibrational aspects become more and more important. With the foreseen introduction of Eurocode 5 the vibration of timber floors becomes a part of the design for serviceability. Design rules for the vibrational behaviour are given in Eurocode 5. The first rule is
Vibrations in a moving flexible robot arm
Wang, P. K. C.; Wei, Jin-Duo
1987-01-01
The vibration in a flexible robot arm modeled by a moving slender prismatic beam is considered. It is found that the extending and contracting motions have destabilizing and stabilizing effects on the vibratory motions, respectively. The vibration analysis is based on a Galerkin approximation with time-dependent basis functions. Typical numerical results are presented to illustrate the qualitative features of vibrations.
Vibration Damping Circuit Card Assembly
Hunt, Ronald Allen (Inventor)
2016-01-01
A vibration damping circuit card assembly includes a populated circuit card having a mass M. A closed metal container is coupled to a surface of the populated circuit card at approximately a geometric center of the populated circuit card. Tungsten balls fill approximately 90% of the metal container with a collective mass of the tungsten balls being approximately (0.07) M.
Wideband Piezomagnetoelastic Vibration Energy Harvesting
DEFF Research Database (Denmark)
Lei, Anders; Thomsen, Erik Vilain
2014-01-01
This work presents a small-scale wideband piezomagnetoelastic vibration energy harvester (VEH) aimed for operation at frequencies of a few hundred Hz. The VEH consists of a tape-casted PZT cantilever with thin sheets of iron foil attached on each side of the free tip. The wideband operation...
Ultrafast vibrations of gold nanorings
DEFF Research Database (Denmark)
Kelf, T; Tanaka, Y; Matsuda, O
2011-01-01
We investigate the vibrational modes of gold nanorings on a silica substrate with an ultrafast optical technique. By comparison with numerical simulations, we identify several resonances in the gigahertz range associated with axially symmetric deformations of the nanoring and substrate. We...
Madsen, Niels Kristian; Godtliebsen, Ian H; Losilla, Sergio A; Christiansen, Ove
2018-01-14
A new implementation of vibrational coupled-cluster (VCC) theory is presented, where all amplitude tensors are represented in the canonical polyadic (CP) format. The CP-VCC algorithm solves the non-linear VCC equations without ever constructing the amplitudes or error vectors in full dimension but still formally includes the full parameter space of the VCC[n] model in question resulting in the same vibrational energies as the conventional method. In a previous publication, we have described the non-linear-equation solver for CP-VCC calculations. In this work, we discuss the general algorithm for evaluating VCC error vectors in CP format including the rank-reduction methods used during the summation of the many terms in the VCC amplitude equations. Benchmark calculations for studying the computational scaling and memory usage of the CP-VCC algorithm are performed on a set of molecules including thiadiazole and an array of polycyclic aromatic hydrocarbons. The results show that the reduced scaling and memory requirements of the CP-VCC algorithm allows for performing high-order VCC calculations on systems with up to 66 vibrational modes (anthracene), which indeed are not possible using the conventional VCC method. This paves the way for obtaining highly accurate vibrational spectra and properties of larger molecules.
Madsen, Niels Kristian; Godtliebsen, Ian H.; Losilla, Sergio A.; Christiansen, Ove
2018-01-01
A new implementation of vibrational coupled-cluster (VCC) theory is presented, where all amplitude tensors are represented in the canonical polyadic (CP) format. The CP-VCC algorithm solves the non-linear VCC equations without ever constructing the amplitudes or error vectors in full dimension but still formally includes the full parameter space of the VCC[n] model in question resulting in the same vibrational energies as the conventional method. In a previous publication, we have described the non-linear-equation solver for CP-VCC calculations. In this work, we discuss the general algorithm for evaluating VCC error vectors in CP format including the rank-reduction methods used during the summation of the many terms in the VCC amplitude equations. Benchmark calculations for studying the computational scaling and memory usage of the CP-VCC algorithm are performed on a set of molecules including thiadiazole and an array of polycyclic aromatic hydrocarbons. The results show that the reduced scaling and memory requirements of the CP-VCC algorithm allows for performing high-order VCC calculations on systems with up to 66 vibrational modes (anthracene), which indeed are not possible using the conventional VCC method. This paves the way for obtaining highly accurate vibrational spectra and properties of larger molecules.
Using Car Vibration Data for Road Prominency Identification
Bratarčuks, S; Dubovska, R
2014-01-01
Research is devoted to the problem of computer recognition of vibrations that car receives while moving by the road. Roads’ roughness, holes cause additional mechanical load on a car and may lead to its damage. For timely reaction of road service on roads’ impairments is necessary to create geographical information system that allows gathering operative data about the condition of roads. During the era of mobile devices this data can be gathered by traffic participants. Ways of gathering data...
Calculation of characteristics of torsionally vibrating mechatronic system
A. Buchacz
2007-01-01
Purpose: of this paper is the application of the approximate method to solve the task of assigning the frequencymodalanalysis and characteristics of a mechatronic system.Design/methodology/approach: was the formulated and solved as a problem in the form of a set of differentialequations of motion and state equations of the considered mechatronic model of an object. To obtain thesolution, Galerkin’s method was used. The discussed torsionally vibrating mechanical system is a continuousbar of ci...
Vibrations of structurally orthotropic laminated shells under thermal power loading
Kogan, E. A.; Lopanitsyn, E. A.
2017-05-01
On the basis of the linearized version of equations obtained in a geometrically nonlinear statement and describing the nonaxisymmetric strain of nonshallow sandwich structure orthotropic shells under thermal power loading, the Rayleigh-Ritz method with polynomial approximation of displacements and shear strains is used to solve the problem of small free vibrations of axisymmetrically thermally preloaded freely supported three-layer conical shell. The causes of dynamical fracture of the shell under study are revealed.
Fundamental vibrational mode in a highly inhomogeneous star
Bastrukov, S. I.; Chang, H. -K.; Wu, E. -H.; Molodtsova, I. V.
2008-01-01
The eigenfrequency problem of fundamental vibrational mode in a highly inhomogeneous star, modeled by self-gravitating mass of viscous liquid with singular density at the center, is considered in juxtaposition with that for Kelvin fundamental mode in the liquid star model with uniform density. Particular attention is given to the difference between spectral equations for the frequency and lifetime of f-mode in the singular and homogeneous star models. The newly obtained results are discussed ...
Solutions to Mitigate Vibrations and Noise Produced by Tramways (State of Art
Directory of Open Access Journals (Sweden)
Mihaela - Dorica Stroia
2009-10-01
Full Text Available Vibrations and noises produced by daily human activities represent a major issue of nowadays, having a negative impact both on environment and on people. These negative effects occur with the human evolution and development and remain a problem that needs to be solved. The paper describes a part of the methods used on vibrations and noise damping, caused by road traffic, with reference in particular to tramways.
Energy Dissipation from Vibrating Floor Slabs due to Human-Structure Interaction
Directory of Open Access Journals (Sweden)
James M.W. Brownjohn
2001-01-01
Full Text Available Lightweight pre-cast flooring systems using post-tensioning to increase strength but not stiffness are increasingly popular, and vibration serviceability problems tend to govern design of such floors where human occupants are increasingly concerned with vibrations. At the same time as inducing response, stationary human observers can also participate in the response as mitigating influence and it is clear that a human behaves as a highly effective damper, even when seated.
Forced Vibrations of a Two-Layer Orthotropic Shell with an Incomplete Contact Between Layers
Ghulghazaryan, L. G.; Khachatryan, L. V.
2018-01-01
Forced vibrations of a two-layer orthotropic shell, with incomplete contact conditions between layers, when the upper face of the shell is free and the lower one is subjected to a dynamic action are considered. By an asymptotic method, the solution of the corresponding dynamic equations and correlations of a 3D problem of elasticity theory is obtained. The amplitudes of forced vibrations are determined, and resonance conditions are established.
Wavelets, vibrations and scalings
Meyer, Yves
1997-01-01
Physicists and mathematicians are intensely studying fractal sets of fractal curves. Mandelbrot advocated modeling of real-life signals by fractal or multifractal functions. One example is fractional Brownian motion, where large-scale behavior is related to a corresponding infrared divergence. Self-similarities and scaling laws play a key role in this new area. There is a widely accepted belief that wavelet analysis should provide the best available tool to unveil such scaling laws. And orthonormal wavelet bases are the only existing bases which are structurally invariant through dyadic dilations. This book discusses the relevance of wavelet analysis to problems in which self-similarities are important. Among the conclusions drawn are the following: 1) A weak form of self-similarity can be given a simple characterization through size estimates on wavelet coefficients, and 2) Wavelet bases can be tuned in order to provide a sharper characterization of this self-similarity. A pioneer of the wavelet "saga", Meye...
Huang, Yu; Griffin, Michael J
2012-06-01
The relative discomfort caused by noise and vibration, how this depends on the level of noise and the magnitude of vibration, and whether the noise and vibration are presented simultaneously or sequentially has been investigated in a laboratory study with 20 subjects. Noise and vertical vibration were reproduced with all 49 combinations of 7 levels of noise and 7 magnitudes of vibration to allow the discomfort caused by one of the stimuli to be judged relative to the other stimulus using magnitude estimation. In four sessions, subjects judged noise relative to vibration and vibration relative to noise, with both simultaneous and sequential presentations of the stimuli. The equivalence of noise and vibration was not greatly dependent on whether the stimuli were simultaneous or sequential, but highly dependent on whether noise was judged relative to vibration or vibration was judged relative to noise. When judging noise, higher magnitude vibrations appeared to mask the discomfort caused by low levels of noise. When judging vibration, higher level noises appeared to mask the discomfort caused by low magnitudes of vibration. The judgment of vibration discomfort was more influenced by noise than the judgment of noise discomfort was influenced by vibration.
NATURAL TRANSVERSE VIBRATIONS OF A PRESTRESSED ORTHOTROPIC PLATE-STRIPE
Directory of Open Access Journals (Sweden)
Egorychev Oleg Aleksandrovich
2012-10-01
Full Text Available The article represents a new outlook at the boundary-value problem of natural vibrations of a homogeneous pre-stressed orthotropic plate-stripe. In the paper, the motion equation represents a new approximate hyperbolic equation (rather than a parabolic equation used in the majority of papers covering the same problem describing the vibration of a homogeneous orthotropic plate-stripe. The proposed research is based on newly derived boundary conditions describing the pin-edge, rigid, and elastic (vertical types of fixing, as well as the boundary conditions applicable to the unfixed edge of the plate. The paper contemplates the application of the Laplace transformation and a non-standard representation of a homogeneous differential equation with fixed factors. The article proposes a detailed representation of the problem of natural vibrations of a homogeneous orthotropic plate-stripe if rigidly fixed at opposite sides; besides, the article also provides frequency equations (no conclusions describing the plate characterized by the following boundary conditions: rigid fixing at one side and pin-edge fixing at the opposite side; pin-edge fixing at one side and free (unfixed other side; rigid fixing at one side and elastic fixing at the other side. The results described in the article may be helpful if applied in the construction sector whenever flat structural elements are considered. Moreover, specialists in solid mechanics and theory of elasticity may benefit from the ideas proposed in the article.
Identification and Addressing Reduction-Related Misconceptions
Gal-Ezer, Judith; Trakhtenbrot, Mark
2016-01-01
Reduction is one of the key techniques used for problem-solving in computer science. In particular, in the theory of computation and complexity (TCC), mapping and polynomial reductions are used for analysis of decidability and computational complexity of problems, including the core concept of NP-completeness. Reduction is a highly abstract…
Transient vibration of wind turbine blades
Li, Yuanzhe; Li, Minghai; Jiang, Feng
2017-09-01
This article aims to the transient vibration of wind turbine blades. We firstly introduce transient vibration and previous studies in this area. The report then shows the fundamental equations and derivation of Euler Equation. A 3-D beam are created to compare the analytical and numerical result. In addition we operate the existing result and Patran result of a truncation wedge beam, especially the frequencies of free vibration and transient vibration. Transient vibration cannot be vanished but in some case it can be reduced.
Rinck, Philipp M.; Sitzberger, Sebastian; Zaeh, Michael F.
2017-06-01
In vibration assisted machining, an additional high-frequency oscillation is superimposed on the kinematics of the conventional machining process. This generates oscillations on the cutting edge in the range of a few micrometers, thereby causing a high-frequency change in the cutting speed or the feed. Consequently, a reduction of cutting forces, an increase of the tool life as well as an improvement of the workpiece quality can be achieved. In milling and grinding it has been shown that these effects are already partially present in the case of a vibration excitation in axial direction relative to the workpiece, which is perpendicular to the cutting direction. Further improvements of the process results can be achieved by superimposing a vibration in cutting direction and thus modifying the cutting speed at high frequency. The presented work shows the design of an ultrasonic actuator that enables vibration-assisted milling and grinding with ultrasonically modulated cutting speed. The actuator system superimposes a longitudinal torsional ultrasonic oscillation to the milling or grinding tool. It uses a bolt clamped Langevin transducer and a helically slotted horn, which degenerates the longitudinal vibration into a combined longitudinal torsional (L-T) vibration at the output surface. A finite element analysis is used to determine the vibration resonance frequency and mode shapes to maximize the torsional output. Afterwards, the simulation has been experimentally validated.
Effect of nonlinearity of connecting dampers on vibration control of connected building structures
Directory of Open Access Journals (Sweden)
Masatoshi eKasagi
2016-01-01
Full Text Available The connection of two building structures with dampers is one of effective vibration control systems. In this vibration control system, both buildings have to possess different vibration properties in order to provide a higher vibration reduction performance. In addition to such condition of different vibration properties of both buildings, the connecting dampers also play an important role in the vibration control mechanism. In this paper, the effect of nonlinearity of connecting dampers on the vibration control of connected building structures is investigated in detail. A high-damping rubber damper and an oil damper with and without relief mechanism are treated. It is shown that, while the high-damping rubber damper is effective in a rather small deformation level, the linear oil damper is effective in a relatively large deformation level. It is further shown that, while the oil dampers reduce the response in the same phase as the case without dampers, the high-damping rubber dampers change the phase. The merit is that the high-damping rubber can reduce the damper deformation and keep the sufficient space between both buildings. This can mitigate the risk of building pounding.
Multiple Rabi Splittings under Ultrastrong Vibrational Coupling.
George, Jino; Chervy, Thibault; Shalabney, Atef; Devaux, Eloïse; Hiura, Hidefumi; Genet, Cyriaque; Ebbesen, Thomas W
2016-10-07
From the high vibrational dipolar strength offered by molecular liquids, we demonstrate that a molecular vibration can be ultrastrongly coupled to multiple IR cavity modes, with Rabi splittings reaching 24% of the vibration frequencies. As a proof of the ultrastrong coupling regime, our experimental data unambiguously reveal the contributions to the polaritonic dynamics coming from the antiresonant terms in the interaction energy and from the dipolar self-energy of the molecular vibrations themselves. In particular, we measure the opening of a genuine vibrational polaritonic band gap of ca. 60 meV. We also demonstrate that the multimode splitting effect defines a whole vibrational ladder of heavy polaritonic states perfectly resolved. These findings reveal the broad possibilities in the vibrational ultrastrong coupling regime which impact both the optical and the molecular properties of such coupled systems, in particular, in the context of mode-selective chemistry.
Semiactive Vibration Control of a Wind Turbine Tower using an MR Damper
DEFF Research Database (Denmark)
Kirkegaard, Poul Henning; Nielsen, Søren R. K.; Poulsen, B. L.
2002-01-01
For fatigue vibration reduction modern wind turbines are installed with different kind of passive systems such as a tuned mass damper or a tuned liquid damper. However, passive control systems are limited because they cannot adapt to broadbanded loading conditions, i.e. they perform well...... or semiactive system for reducing the fatigue will be more optimal than a passive control system. This paper presents a numerically and experimentally investigation of semiactive vibration control of wind turbine tower vibrations by using a magnetorheological (MR) fluid damper. Numerical simulations as well...... as experimental laboratory results indicate that the MR damper approach is superior to a traditional tuned mass damper for reducing the vibration of wind turbine towers....
Vibrational damping of composite materials
Biggerstaff, Janet M.
The purpose of this research was to develop new methods of vibrational damping in polymeric composite materials along with expanding the knowledge of currently used vibrational damping methods. A new barrier layer technique that dramatically increased damping in viscoelastic damping materials that interacted with the composite resin was created. A method for testing the shear strength of damping materials cocured in composites was developed. Directional damping materials, where the loss factor and modulus could be tailored by changing the angle, were produced and investigated. The addition of particles between composite prepreg layers to increase damping was studied. Electroviscoelastic materials that drastically changed properties such as loss factor and modulus with an applied voltage were manufactured and tested.
Dynamical response of vibrating ferromagnets
Gaganidze, E; Ziese, M
2000-01-01
The resonance frequency of vibrating ferromagnetic reeds in a homogeneous magnetic field can be substantially modified by intrinsic and extrinsic field-related contributions. Searching for the physical reasons of the field-induced resonance frequency change and to study the influence of the spin glass state on it, we have measured the low-temperature magnetoelastic behavior and the dynamical response of vibrating amorphous and polycrystalline ferromagnetic ribbons. We show that the magnetoelastic properties depend strongly on the direction of the applied magnetic field. The influence of the re-entrant spin glass transition on these properties is discussed. We present clear experimental evidence that for applied fields perpendicular to the main area of the samples the behavior of ferromagnetic reeds is rather independent of the material composition and magnetic state, exhibiting a large decrease of the resonance frequency. This effect can be very well explained with a model based on the dynamical response of t...
Vibrational coupling in plasmonic molecules.
Yi, Chongyue; Dongare, Pratiksha D; Su, Man-Nung; Wang, Wenxiao; Chakraborty, Debadi; Wen, Fangfang; Chang, Wei-Shun; Sader, John E; Nordlander, Peter; Halas, Naomi J; Link, Stephan
2017-10-31
Plasmon hybridization theory, inspired by molecular orbital theory, has been extremely successful in describing the near-field coupling in clusters of plasmonic nanoparticles, also known as plasmonic molecules. However, the vibrational modes of plasmonic molecules have been virtually unexplored. By designing precisely configured plasmonic molecules of varying complexity and probing them at the individual plasmonic molecule level, intramolecular coupling of acoustic modes, mediated by the underlying substrate, is observed. The strength of this coupling can be manipulated through the configuration of the plasmonic molecules. Surprisingly, classical continuum elastic theory fails to account for the experimental trends, which are well described by a simple coupled oscillator picture that assumes the vibrational coupling is mediated by coherent phonons with low energies. These findings provide a route to the systematic optical control of the gigahertz response of metallic nanostructures, opening the door to new optomechanical device strategies. Published under the PNAS license.
2002-01-01
Next week-end, the Geneva Science History Museum invites you to a Science Night under the banner of waves and vibrations. Scientists, artists and storytellers from more than forty institutes and local or regional associations will show that waves and vibrations form an integral part of our environment. You will be able to get in contact with the nature of waves through interactive exhibitions on sound and light and through hands-on demonstrations arranged in the Park of the Perle du Lac. On the CERN stand, you will be able to measure the speed of light with a bar of chocolate, and understand the scattering of waves with plastic ducks. Amazing, no? In addition to the stands, the Night will offer many other activities: reconstructions of experiments, a play, a concert of crystal glasses, an illuminated fountain, a house of spirits. More information Science Night, 6 and 7 July, Park of the Perle du Lac, Geneva
Free vibration analysis by BEM using particular integrals
Ahmad, S.; Banerjee, P. K.
1986-01-01
A new method for the free-vibration analysis using the boundary element technique is presented. The method utilizes a fictitious vector function to approximate the inertia forces and then uses the well-known concept of complementary functions and particular integrals to solve the resulting governing differential equations. The necessary particular integrals are defined for the two and three-dimensional analyses, and the present formulation is applied to a number of two-dimensional problems to show its accuracy and efficiency in the solution of realistic engineering problems.
[Actuator placement for active sound and vibration control
1997-01-01
Two refereed journal publications and ten talks given at conferences, seminars, and colloquia resulted from research supported by NASA. They are itemized in this report. The two publications were entitled "Reactive Tabu and Search Sensor Selection in Active Structural Acoustic Control Problems" and "Quelling Cabin Noise in Turboprop Aircraft via Active Control." The conference presentations covered various aspects of actuator placement, including location problems, for active sound and vibration control of cylinders, of commuter jets, of propeller driven or turboprop aircraft, and for quelling aircraft cabin or interior noise.
Vibration Control in Periodic Structures
DEFF Research Database (Denmark)
Høgsberg, Jan Becker
2017-01-01
Within the framework of periodic structures, the calibration of RL shunted piezoelectric inclusions is investigated with respect to maximum damping of a particular wave form. A finite element setting is assumed, with local shunted inclusions inside the unit cell. The effect of the shunts is repre....... The presentation contains dispersion diagrams and vibration amplitude curves for the optimally calibrated RL shunt system in a 1-D periodic structure with local piezoelectric inclusions....
Chronic sleep reduction in adolescents
Dewald-Kaufmann, J.F.
2012-01-01
Based on the results of this thesis, it can be concluded that sleep problems and chronic sleep reduction have a high impact on adolescents’ daytime functioning. Additionally, this research shows that gradual sleep extension can improve adolescents’ sleep and especially their chronic sleep reduction. This approach has beneficial effects on adolescents’ depressive symptoms and their cognitive performance.
Chronic sleep reduction in adolescents
Dewald-Kaufmann, J.F.
2012-01-01
Based on the results of this thesis, it can be concluded that sleep problems and chronic sleep reduction have a high impact on adolescents’ daytime functioning. Additionally, this research shows that gradual sleep extension can improve adolescents’ sleep and especially their chronic sleep reduction.
Casting light on harm reduction
DEFF Research Database (Denmark)
Jourdan, Michael
2009-01-01
Background: Harm reduction is commonly regarded as complementary to other drug problem responses - as the fourth tier. Yet even core examples of harm reduction such as the provision of injection equipment and methadone treatment has over and over encountered considerable opposition, and harm redu...
Ergonomic Evaluation of Vibrations of a Rototiller with New Blade
Directory of Open Access Journals (Sweden)
H Gholami
2017-10-01
Full Text Available Introduction One of the most important problems arising with operation of the conventional rototillers is severe vibration of the machine handle which is transmitted to the user’s hands, arms and shoulders. Long period exposure of the hand-transmitted vibration may cause various diseases such as white finger syndrome. Therefore in this study, vibrations of a new type of rototiller with ridged blades were investigated at the position of handle/hand interface in different working conditions. Finally, the maximum allowable exposure time to the rototiller users in continuous tillage operation was obtained according to ISO 5349-1. Materials and Methods Experiments were carried out in one of the farms with silty clay soil texture, located in Sari city, Mazandaran province, Iran. Vibration measurements were performed according to ISO 5349-1 and ISO 5349-2 standards in two different modes, including in situ mode and tillage mode. Vibrational parameters were obtained in three blade rotational speeds, i.e., low speed (140-170 rpm, medium speed (170-200, and high speed (200-230. Blade rotational speed varied by changing engine speed using the throttle control lever. In each experiment, different vibrational values were individually recorded in three directions (x, y, and z. Experimental design and data analysis were performed in a Randomized Complete Block Design with three replications using the SPSS16 software. Results and Discussion Based on the obtained results in this study, the RMS of acceleration increased by increasing in rotational speed for all of the conducted experiments. The reason is that number of cutting per unit of time and consequently the frequency of changing in the dynamic forces exerting on the blades dramatically increases with increasing the rotational speed of the blades. Noteworthy is that in most cases the variation of acceleration in the tillage mode showed similar trend with vibrational values in the idling mode. This
SDBI 1904: Human Factors Assessment of Vibration Effects on Visual Performance during Launch
Thompson, Shelby G.; Holden, Kritina; Root, Phillip; Ebert, Douglas; Jones, Jeffery; Adelstein, Bernard
2009-01-01
The primary objective of the of Human Factors Short Duration Bioastronautics Investigation (SDBI) 1904 is to determine visual performance limits during operational vibration and g-loads, specifically through the determination of minimal usable font sized using Orion-type display formats. Currently there is little to no data available to quantify human visual performance under these extreme conditions. Existing data on shuttle vibration magnitude and frequency is incomplete, does not address sear and crew vibration in the current configuration, and does not address human visual performance. There have been anecdotal reports of performance decrements from shuttle crews, but no structured data has been collected. The SDBI is a companion effort to the Detailed Test Objective (DTO) 695, which will measure shuttle seat accelerations (vibration) during ascent. Data fro the SDBI will serve an important role in interpreting the DTO vibration data. This data will be collected during the ascent phase of three shuttle missions (STS-119, 127, and 128). Both SDBI1904 and DTO 695 are low impact with respect to flight resources, and combined they represent an efficient and focused problem solving approach. The SDBI and DTO data will be correlated to determine the nature of perceived visual performance under varying vibrations and g-loads. This project will provide: 1) Immediate data for developing preliminary human performance vibration requirements; 2) Flight validated inputs for ongoing and future ground-based research; and 3) Information of functional needs that will drive Orion display format design decisions.
A new compound control method for sine-on-random mixed vibration test
Zhang, Buyun; Wang, Ruochen; Zeng, Falin
2017-09-01
Vibration environmental test (VET) is one of the important and effective methods to provide supports for the strength design, reliability and durability test of mechanical products. A new separation control strategy was proposed to apply in multiple-input multiple-output (MIMO) sine on random (SOR) mixed mode vibration test, which is the advanced and intensive test type of VET. As the key problem of the strategy, correlation integral method was applied to separate the mixed signals which included random and sinusoidal components. The feedback control formula of MIMO linear random vibration system was systematically deduced in frequency domain, and Jacobi control algorithm was proposed in view of the elements, such as self-spectrum, coherence, and phase of power spectral density (PSD) matrix. Based on the excessive correction of excitation in sine vibration test, compression factor was introduced to reduce the excitation correction, avoiding the destruction to vibration table or other devices. The two methods were synthesized to be applied in MIMO SOR vibration test system. In the final, verification test system with the vibration of a cantilever beam as the control object was established to verify the reliability and effectiveness of the methods proposed in the paper. The test results show that the exceeding values can be controlled in the tolerance range of references accurately, and the method can supply theory and application supports for mechanical engineering.
Importance of Added Mass and Damping in Flow-Induced Vibration Analysis of Tubes Bundle: An Overview
Directory of Open Access Journals (Sweden)
Faisal Karim Shami
2012-01-01
Full Text Available Flow-induced vibration is of prime concern to the designers of heat exchangers subjected to high flows of gases or liquids. Excessive vibration may cause tube failure due to fatigue or fretting-wear. Tube failure results in, expensive plant upholding and suffers loss of production. Therefore, tube failure due to unwarranted vibration must be avoided in process heat exchangers and nuclear steam generators, preferably at design stage. Such vibration problems may be avoided through a comprehensive flowinduced vibration analysis before fabrication of heat exchangers. However, it requires an understanding of vibration mechanism and parameters related to flow-induced vibration. For an accurate vibration analysis, it is of prime importance to have good estimates of structural and flow related dynamic parameters. Thus dynamic parameters such as added mass and damping are of significant concern in a flow regime. The purpose of this paper is to provide an overview of our state of knowledge and role of dynamic parameters in flow-induced vibration on tube bundles due to current trend of larger heat exchangers. The present paper provides published data, analysis, evaluation, formulation, and experimental studies related to hydrodynamic mass and damping by a large number of researchers. Guidelines for experimental research and heat exchangers design related to added mass and damping mechanisms subjected to both single and two-phase flow are outlined in this paper.
Asymmetric Vibrations of a Circular Elastic Plate on an Elastic Half Space
DEFF Research Database (Denmark)
Schmidt, H.; Krenk, Steen
1982-01-01
The asymmetric problem of a vibrating circular elastic plate in frictionless contact with an elastic half space is solved by an integral equation method, where the contact stress appears as the unknown function. By a trigonometric expansion, the problem is reduced to a number of uncoupled two......-dimensional problems. The radial variations of contact stresses and surface displacements are represented by polynomials, the coefficients of which are directly related by an infinite matrix that is a function of the vibration frequency. The results include a parametric study of the power input as a function...... of the vibration frequency of various plate stiffnesses and the normal component of the surface displacement field for simple excitation of the plate and passage of a plane Rayleigh wave....
Directory of Open Access Journals (Sweden)
M.M. Rahman
2011-12-01
Full Text Available Trains and cars are the most important modes of transportation throughout the world. In highly developed countries, trains have become essential for human use as the most well-known form of public transportation, whereas the car plays a significant role in prompt human travel from one place to another. The high magnitude of vibration caused by trains and cars may cause health problems in humans, especially low back pain. The aim of this study was to evaluate and validate the values of daily exposure to vibration A(8 and the vibration dose value (VDV in passengers travelling by train and car and to assess the effects produced by this exposure on the human body. Moreover, this study introduces a newly developed whole-body vibration measurement instrumentation system. One train travelling from the east coast to the south of Malaysia was chosen to conduct the study. Whole-body vibration exposure was measured over 8 hours, which is equal to the duration of normal occupational exposure. One car was chosen randomly and whole-body vibration exposure was measured for 5 min and 10 min. All the data were computed using an IEPE(ICPTM accelerometer sensor connected to a DT9837 device which is capable of effectively measuring and analysing vibration. The vibration results were displayed on a personal computer using a custom graphical user interface (GUI. Matlab software was used to interpret the data. From the results, the whole-body vibration exposure level could be determined. It can be concluded that the whole-body vibration absorbed by the human body is enhanced when the magnitude of the vibration exposure experienced by the passengers increased. This was shown by the increased values of daily exposure to vibration A(8 and VDV calculated in the study.
DEFF Research Database (Denmark)
Almegaard, Henrik
2014-01-01
The majority of literature on engineering design methods is focused on the processes of fulfilling the design goals as efficiently as possible. This paper will focus on - and discuss - the processes of determining the design goals: the specifications. The purpose is to draw attention to the inher...... to the inherent problems, dilemmas and possibilities in these processes bearing in mind that that the most important decisions in a design project are taken in the beginning of the project....
... it could be a sign of a balance problem. Balance problems can make you feel unsteady. You may also ... injuries, such as a hip fracture. Some balance problems are due to problems in the inner ear. ...
Highly indefinite multigrid for eigenvalue problems
Energy Technology Data Exchange (ETDEWEB)
Borges, L.; Oliveira, S.
1996-12-31
Eigenvalue problems are extremely important in understanding dynamic processes such as vibrations and control systems. Large scale eigenvalue problems can be very difficult to solve, especially if a large number of eigenvalues and the corresponding eigenvectors need to be computed. For solving this problem a multigrid preconditioned algorithm is presented in {open_quotes}The Davidson Algorithm, preconditioning and misconvergence{close_quotes}. Another approach for solving eigenvalue problems is by developing efficient solutions for highly indefinite problems. In this paper we concentrate on the use of new highly indefinite multigrid algorithms for the eigenvalue problem.
Use of wavelet energy for spinal cord vibration analysis during spinal surgery.
Dai, Yu; Zhang, Jianxun; Xue, Yuan
2013-12-01
An online non-contact measurement system using a laser displacement sensor was developed for obtaining the vibration amplitude of spinal cord and hard tissue. The discrete wavelet transform was used to extract the distinctive features of tissue vibration signals. The spinal cord and spinal cancellous bone can be discriminated by the comparison of wavelet energy over a characteristic scale. We also derived the integro-differential equation of motion to describe the spinal cord vibration excited by the motion of bone. Experimental results show that the method works well in identifying spinal cord and bone. However, available viscoelastic constants cannot describe the high-frequency features of spinal cord. The examined issue of tissue vibration due to the operation power device is a significant problem. The proposed method can be used by a surgery robot, and then spinal surgery may greatly benefit from the enhanced safety of robotics. Copyright © 2012 John Wiley & Sons, Ltd.
Methodology for Analysing Controllability and Observability of Bladed Disc Coupled Vibrations
DEFF Research Database (Denmark)
Christensen, Rene Hardam; Santos, Ilmar
2004-01-01
and observability of bladed discs. The aim is to determine where to locate actuators and sensors in order to be capable of controlling and monitoring both disc lateral and blade vibrations. The analysis methodology is based on the time-variant modal analysis. A numerical example of the methodogy is provided....... A tuned rotating bladed disc is analysed. The analysis shows that blade actuators and sensors are inevitable in order to control and monitor the vibrations. Moreover, it shows that the controllability and observability depends very strongly on the rotational speed.......Many bladed rotating machines such as helicopters, turbines and compressors are susceptible to blade faults due to vibration problems. Typically, blade vibrations in this kind of machines are suppressed by using passive mechanical components. However, when passive control techniques...
Vibrations of composite steel-concrete floors induced by human activities
Directory of Open Access Journals (Sweden)
Gluhović Nina
2016-01-01
Full Text Available The latest demands in construction design towards slender structures with large spans, large open interiors, unconventional shapes and constructional solutions are leading to the extensive problems related to the serviceability limit state. Slender structures with large spans have lower natural frequencies and lower natural damping, considerably influencing the dynamic response of the structure. Annoying vibrations induced by human activities can significantly affect the structure's functionality, comfort of people and quality of life. Design recommendations for composite steel-concrete floor vibrations can be found in different standards. This paper presents a short overview of design procedures for vibrations of composite steel-concrete beams and design recommendations of floor vibrations induced by human activities, through two design criteria.
Study on measuring vibration displacement by shear interference based on sinusoidal phase modulation
He, Guotian; Tang, Feng; Song, Li; Jiang, Helun
2009-05-01
The semiconductor laser (LD) Taimangelin interferometer based on sinusoidal phase modulation is vulnerable to external vibration, temperature changes, vibration, and other air interference which causes great measurement error. This paper presents a new semiconductor laser sinusoidal phase modulation shear interference technology and anti-jamming wavelet transform algorithm which is not sensitive to environment interference. It changes the original optical technology in the plane mirror to three pyramid-shear, causing a certain amount of displacement of reference light and object light. and partial use of high resolution wavelet transform algorithm solves the problem in measuring the vibration displacement of measured object..Vibration shear interferometry expression is launched, and theoretically discusses the measurement principle. Using MATLAB before and after the improvement of the methods to simulate contrast obtains the impact of shear volume size on measurement accuracy with experimental test. Experimental results show that it effectively reduces the impact of outside interference on measurement accuracy.
Flow-induced vibration of component cooling water heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Yeh, Y.S.; Chen, S.S. (Taiwan Power Co., Taipei (Taiwan). Nuclear Engineering Dept.; Argonne National Lab., IL (USA))
1990-01-01
This paper presents an evaluation of flow-induced vibration problems of component cooling water heat exchangers in one of Taipower's nuclear power stations. Specifically, it describes flow-induced vibration phenomena, tests to identify the excitation mechanisms, measurement of response characteristics, analyses to predict tube response and wear, various design alterations, and modifications of the original design. Several unique features associated with the heat exchangers are demonstrated, including energy-trapping modes, existence of tube-support-plate (TSP)-inactive modes, and fluidelastic instability of TSP-active and -inactive modes. On the basis of this evaluation, the difficulties and future research needs for the evaluation of heat exchangers are identified. 11 refs., 19 figs., 3 tabs.
NASTRAN nonlinear vibration analysis of beam and frame structures
Mei, C.; Rogers, J. L., Jr.
1975-01-01
A capability for the nonlinear vibration analysis of beam and frame structures suitable for use with NASTRAN level 15.5 is described. The nonlinearity considered is due to the presence of axial loads induced by longitudinal end restraints and lateral displacements that are large compared to the beam height. A brief discussion is included of the mathematical analysis and the geometrical stiffness matrix for a prismatic beam (BAR) element. Also included are a brief discussion of the equivalent linearization iterative process used to determine the nonlinear frequency, the required modifications to subroutines DBAR and XMPLBD of the NASTRAN code, and the appropriate vibration capability, four example problems are presented. Comparisons with existing experimental and analytical results show that excellent accuracy is achieved with NASTRAN in all cases.
Numerical analysis of free vibrations of damped rotating structures
Gupta, K. K.
1977-01-01
This paper is concerned with the efficient numerical solution of damped and undamped free vibration problems of rotating structures. While structural discretization is achieved by the finite element method, the associated eigenproblem solution is effected by a combined Sturm sequence and inverse iteration technique that enables the computation of a few required roots only without having to compute any other. For structures of complex configurations, a modal synthesis technique is also presented, which is based on appropriate combinations of eigenproblem solution of various structural components. Such numerical procedures are general in nature, which fully exploit matrix sparsity inherent in finite element discretizations, and prove to be most efficient for the vibration analysis of any damped rotating structure, such as rotating machineries, helicopter and turbine blades, spinning space stations, among others.
Nonlinear Vibrations of Cantilever Timoshenko Beams: A Homotopy Analysis
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Shahram Shahlaei-Far
Full Text Available Abstract This study analyzes the fourth-order nonlinear free vibration of a Timoshenko beam. We discretize the governing differential equation by Galerkin's procedure and then apply the homotopy analysis method (HAM to the obtained ordinary differential equation of the generalized coordinate. We derive novel analytical solutions for the nonlinear natural frequency and displacement to investigate the effects of rotary inertia, shear deformation, pre-tensile loads and slenderness ratios on the beam. In comparison to results achieved by perturbation techniques, this study demonstrates that a first-order approximation of HAM leads to highly accurate solutions, valid for a wide range of amplitude vibrations, of a high-order strongly nonlinear problem.