System and method for damping vibration in a drill string

Science.gov (United States)

Wassell, Mark Ellsworth; Turner, William Evans; Burgess, Daniel E; Perry, Carl Allison

2014-03-04

A system for damping vibration in a drill string can include a valve assembly having a supply of a fluid, a first member, and a second member capable of moving in relation to first member in response to vibration of the drill bit. The first and second members define a first and a second chamber for holding the fluid. Fluid can flow between the first and second chambers in response to the movement of the second member in relation to the first member. The valve assembly can also include a coil or a valve for varying a resistance of the fluid to flow between the first and second chambers.

Robust, accurate, and non-contacting vibration measurement systems: Summary of comparison measurements of the robust laser interferometer and typical accelerometer systems. Volume 1

International Nuclear Information System (INIS)

Goodenow, T.C.; Shipman, R.L.; Holland, H.M.

1995-06-01

Epoch Engineering, Incorporated (EEI) has completed a series of vibration measurements comparing their newly-developed Robust Laser Interferometer (RLI) with accelerometer-based instrumentation systems. EEI has successfully demonstrated, on several pieces of commonplace machinery, that non-contact, line-of-sight measurements are practical and yield results equal to or, in some cases, better than customary field implementations of accelerometers. The demonstration included analysis and comparison of such phenomena as nonlinearity, transverse sensitivity, harmonics, and signal-to-noise ratio. Fast Fourier Transformations were performed on the accelerometer and the laser system outputs to provide a comparison basis. The RLI was demonstrated, within the limits of the task, to be a viable, line-of-sight, non-contact alternative to accelerometer systems. Several different kinds of machinery were instrumented and compared, including a small pump, a gear-driven cement mixer, a rotor kit, and two small fans. Known machinery vibration sources were verified and RLI system output file formats were verified to be compatible with commercial computer programs used for vibration monitoring and trend analysis. The RLI was also observed to be less subject to electromagnetic interference (EMI) and more capable at very low frequencies

Measurement Model and Precision Analysis of Accelerometers for Maglev Vibration Isolation Platforms.

Science.gov (United States)

Wu, Qianqian; Yue, Honghao; Liu, Rongqiang; Zhang, Xiaoyou; Ding, Liang; Liang, Tian; Deng, Zongquan

2015-08-14

High precision measurement of acceleration levels is required to allow active control for vibration isolation platforms. It is necessary to propose an accelerometer configuration measurement model that yields such a high measuring precision. In this paper, an accelerometer configuration to improve measurement accuracy is proposed. The corresponding calculation formulas of the angular acceleration were derived through theoretical analysis. A method is presented to minimize angular acceleration noise based on analysis of the root mean square noise of the angular acceleration. Moreover, the influence of installation position errors and accelerometer orientation errors on the calculation precision of the angular acceleration is studied. Comparisons of the output differences between the proposed configuration and the previous planar triangle configuration under the same installation errors are conducted by simulation. The simulation results show that installation errors have a relatively small impact on the calculation accuracy of the proposed configuration. To further verify the high calculation precision of the proposed configuration, experiments are carried out for both the proposed configuration and the planar triangle configuration. On the basis of the results of simulations and experiments, it can be concluded that the proposed configuration has higher angular acceleration calculation precision and can be applied to different platforms.

Measurement Model and Precision Analysis of Accelerometers for Maglev Vibration Isolation Platforms

Directory of Open Access Journals (Sweden)

Qianqian Wu

2015-08-01

Full Text Available High precision measurement of acceleration levels is required to allow active control for vibration isolation platforms. It is necessary to propose an accelerometer configuration measurement model that yields such a high measuring precision. In this paper, an accelerometer configuration to improve measurement accuracy is proposed. The corresponding calculation formulas of the angular acceleration were derived through theoretical analysis. A method is presented to minimize angular acceleration noise based on analysis of the root mean square noise of the angular acceleration. Moreover, the influence of installation position errors and accelerometer orientation errors on the calculation precision of the angular acceleration is studied. Comparisons of the output differences between the proposed configuration and the previous planar triangle configuration under the same installation errors are conducted by simulation. The simulation results show that installation errors have a relatively small impact on the calculation accuracy of the proposed configuration. To further verify the high calculation precision of the proposed configuration, experiments are carried out for both the proposed configuration and the planar triangle configuration. On the basis of the results of simulations and experiments, it can be concluded that the proposed configuration has higher angular acceleration calculation precision and can be applied to different platforms.

Full-field vibration measurements of the violin using digital stroboscopic holographic interferometry and electromagnetic stimulation of the strings

Science.gov (United States)

Keersmaekers, Lissa; Keustermans, William; De Greef, Daniël; Dirckx, Joris J. J.

2016-06-01

We developed a setup in which the strings of the violin are driven electromagnetically, and the resulting vibration of the instrument is measured with digital stroboscopic holography. A 250mW single mode green laser beam is chopped using an acousto-optic modulator, generating illumination pulses of 2% of the vibration period. The phase of the illumination pulse is controlled by a programmable function generator so that digital holograms can be recorded on a number of subsequent time positions within the vibration phase. From these recordings, the out of plane motion as a function of time is reconstructed in full field. We show results of full-field vibration amplitude and vibration phase maps, and time resolved full-field deformations of the violin back plane. Time resolved measurements show in detail how the deformation of the violin plane changes as a function of time at different frequencies. We found very different behavior under acoustic stimulation of the instrument and when using electromagnetic stimulation of a string. The aim of the work it to gather data which can be used in power flow calculations to study how the energy of the strings is conducted to the body of the violin and eventually is radiated as sound.

Full-field vibration measurements of the violin using digital stroboscopic holographic interferometry and electromagnetic stimulation of the strings

International Nuclear Information System (INIS)

Keersmaekers, Lissa; Keustermans, William; De Greef, Daniël; Dirckx, Joris J. J.

2016-01-01

We developed a setup in which the strings of the violin are driven electromagnetically, and the resulting vibration of the instrument is measured with digital stroboscopic holography. A 250 mW single mode green laser beam is chopped using an acousto-optic modulator, generating illumination pulses of 2% of the vibration period. The phase of the illumination pulse is controlled by a programmable function generator so that digital holograms can be recorded on a number of subsequent time positions within the vibration phase. From these recordings, the out of plane motion as a function of time is reconstructed in full field. We show results of full-field vibration amplitude and vibration phase maps, and time resolved full-field deformations of the violin back plane. Time resolved measurements show in detail how the deformation of the violin plane changes as a function of time at different frequencies. We found very different behavior under acoustic stimulation of the instrument and when using electromagnetic stimulation of a string. The aim of the work it to gather data which can be used in power flow calculations to study how the energy of the strings is conducted to the body of the violin and eventually is radiated as sound.

Full-field vibration measurements of the violin using digital stroboscopic holographic interferometry and electromagnetic stimulation of the strings

Energy Technology Data Exchange (ETDEWEB)

Keersmaekers, Lissa; Keustermans, William, E-mail: william.keustermans@uantwerpen.be; De Greef, Daniël; Dirckx, Joris J. J. [University of Antwerp, Laboratory of Biophysics and Biomedical Physics, Groenenborgerlaan 171, 2020 Antwerp (Belgium)

2016-06-28

We developed a setup in which the strings of the violin are driven electromagnetically, and the resulting vibration of the instrument is measured with digital stroboscopic holography. A 250 mW single mode green laser beam is chopped using an acousto-optic modulator, generating illumination pulses of 2% of the vibration period. The phase of the illumination pulse is controlled by a programmable function generator so that digital holograms can be recorded on a number of subsequent time positions within the vibration phase. From these recordings, the out of plane motion as a function of time is reconstructed in full field. We show results of full-field vibration amplitude and vibration phase maps, and time resolved full-field deformations of the violin back plane. Time resolved measurements show in detail how the deformation of the violin plane changes as a function of time at different frequencies. We found very different behavior under acoustic stimulation of the instrument and when using electromagnetic stimulation of a string. The aim of the work it to gather data which can be used in power flow calculations to study how the energy of the strings is conducted to the body of the violin and eventually is radiated as sound.

Magnitude of Neck-Surface Vibration as an Estimate of Subglottal Pressure during Modulations of Vocal Effort and Intensity in Healthy Speakers

Science.gov (United States)

McKenna, Victoria S.; Llico, Andres F.; Mehta, Daryush D.; Perkell, Joseph S.; Stepp, Cara E.

2017-01-01

Purpose: This study examined the relationship between the magnitude of neck-surface vibration (NSV[subscript Mag]; transduced with an accelerometer) and intraoral estimates of subglottal pressure (P'[subscript sg]) during variations in vocal effort at 3 intensity levels. Method: Twelve vocally healthy adults produced strings of /p?/ syllables in 3…

Free and forced vibrations of an eccentrically rotating string on a viscoelastic foundation

Science.gov (United States)

Soedel, S. M.; Soedel, W.

1989-12-01

Equations of motion of an eccentrically rotating cord on a viscoelastic foundation, derived by way of Hamilton's principle, are solved for free and forced vibrations. The natural frequencies during rotation are bifurcations of the stationary string values. The natural modes are complex and can be interpreted as mode pairs spinning with and against the string rotation. The general forced solution is expanded in terms of these complex modes. Results are given for an example of steady state harmonic response because of its practical significance to aircraft or automobile tire design.

Vibrations of axially moving strings with in-plane oscillating supports

DEFF Research Database (Denmark)

Fuglede, Niels; Thomsen, Jon Juel

a uniform, heavy string moving at subcritical speed with prescribed endpoint motion, and ignoring longitudinal inertia, one obtains a continuous, nonlinear, gyroscopic, parametrically and externally excited system. By employing a single-mode approximation, using velocity dependent mode shapes, the system...... response is approximated using the method of multiple scales. Vibrations from support oscillations characteristic of roller chain drives are investigated. Conclusions about critical values for chain drive parameters such as pretension and meshing frequency are sought and identified....

Robust, accurate, and non-contacting vibration measurement systems: Supplemental appendices presenting comparison measurements of the robust laser interferometer and typical accelerometer systems. Volume 2

International Nuclear Information System (INIS)

Goodenow, T.C.; Shipman, R.L.; Holland, H.M.

1995-06-01

Epoch Engineering, Incorporated (EEI) has completed a series of vibration measurements comparing their newly-developed Robust Laser Interferometer (RLI) with accelerometer-based instrumentation systems. EEI has successfully demonstrated, on several pieces of commonplace machinery, that non-contact, line-of-sight measurements are practical and yield results equal to or, in some cases, better than customary field implementations of accelerometers. The demonstration included analysis and comparison of such phenomena as nonlinearity, transverse sensitivity, harmonics, and signal-to-noise ratio. Fast Fourier Transformations were performed on the accelerometer and the laser system outputs to provide a comparison basis. The RLI was demonstrated, within the limits o the task, to be a viable, line-of-sight, non-contact alternative to accelerometer systems. Several different kinds of machinery were instrumented and. compared, including a small pump, a gear-driven cement mixer, a rotor kit, and two small fans. Known machinery vibration sources were verified and RLI system output file formats were verified to be compatible with commercial computer programs used for vibration monitoring and trend analysis. The RLI was also observed to be less subject to electromagnetic interference (EMI) and more capable at very low frequencies. This document, Volume 2, provides the appendices to this report

Are Stopped Strings Preferred in Sad Music?

OpenAIRE

David Huron; Caitlyn Trevor

2017-01-01

String instruments may be played either with open strings (where the string vibrates between the bridge and a hard wooden nut) or with stopped strings (where the string vibrates between the bridge and a performer's finger pressed against the fingerboard). Compared with open strings, stopped strings permit the use of vibrato and exhibit a darker timbre. Inspired by research on the timbre of sad speech, we test whether there is a tendency to use stopped strings in nominally sad music. Specifica...

Effect of detector size and position on measured vibration spectra of strings and rods

International Nuclear Information System (INIS)

Lipcsei, S.; Kiss, S.; Por, G.

1993-04-01

Weight functions of string and rod vibrations are described by standing and travelling wave models. The effects of detector size and position on the measured vibration spectra was investigated, and the main characteristics of the transfer function were calculated by a simple standing wave model. The theoretical results were compared with data from laboratory rod vibration experiments, and with pressure fluctuation spectra obtained at the Paks Nuclear Power Plant. In addition, some fundamental physical consequences can be made using the theory of superposition of travelling waves and their reflection on clamped rod ends. (R.P.) 5 refs.; 10 figs

Natural frequencies, modeshapes and modal interactions for strings vibrating against an obstacle: Relevance to Sitar and Veena

Science.gov (United States)

Mandal, A. K.; Wahi, P.

2015-03-01

We study the vibration characteristics of a string with a smooth unilateral obstacle placed at one of the ends similar to the strings in musical instruments like sitar and veena. In particular, we explore the correlation between the string vibrations and some unique sound characteristics of these instruments like less inharmonicity in the frequencies, a large number of overtones and the presence of both frequency and amplitude modulations. At the obstacle, we have a moving boundary due to the wrapping of the string and an appropriate scaling of the spatial variable leads to a fixed boundary at the cost of introducing nonlinearity in the governing equation. Reduced order system of equations has been obtained by assuming a functional form for the string displacement which satisfies all the boundary conditions and gives the free length of the string in terms of the modal coordinates. To study the natural frequencies and mode-shapes, the nonlinear governing equation is linearized about the static configuration. The natural frequencies have been found to be harmonic and they depend on the shape of the obstacle through the effective free length of the string. Expressions have been obtained for the time-varying mode-shapes as well as the variation of the nodal points. Modal interactions due to coupling have been studied which show the appearance of higher overtones as well as amplitude modulations in our theoretical model akin to the experimental observations. All the obtained results have been verified with an alternate formulation based on the assumed mode method with polynomial shape functions.

A Review of the Evaluation, Control, and Application Technologies for Drill String Vibrations and Shocks in Oil and Gas Well

Directory of Open Access Journals (Sweden)

Guangjian Dong

2016-01-01

Full Text Available Drill string vibrations and shocks (V&S can limit the optimization of drilling performance, which is a key problem for trajectory optimizing, wellbore design, increasing drill tools life, rate of penetration, and intelligent drilling. The directional wells and other special trajectory drilling technologies are often used in deep water, deep well, hard rock, and brittle shale formations. In drilling these complex wells, the cost caused by V&S increases. According to past theories, indoor experiments, and field studies, the relations among ten kinds of V&S, which contain basic forms, response frequency, and amplitude, are summarized and discussed. Two evaluation methods are compared systematically, such as theoretical and measurement methods. Typical vibration measurement tools are investigated and discussed. The control technologies for drill string V&S are divided into passive control, active control, and semiactive control. Key methods for and critical equipment of three control types are compared. Based on the past development, a controlling program of drill string V&S is devised. Application technologies of the drill string V&S are discussed, such as improving the rate of penetration, controlling borehole trajectory, finding source of seismic while drilling, and reducing the friction of drill string. Related discussions and recommendations for evaluating, controlling, and applying the drill string V&S are made.

Accelerometer having integral fault null

Science.gov (United States)

Bozeman, Richard J., Jr.

1995-08-01

An improved accelerometer is introduced. It comprises a transducer responsive to vibration in machinery which produces an electrical signal related to the magnitude and frequency of the vibration; and a decoding circuit responsive to the transducer signal which produces a first fault signal to produce a second fault signal in which ground shift effects are nullified.

Self Diagnostic Accelerometer Testing on the C-17 Aircraft

Science.gov (United States)

Tokars, Roger P.; Lekki, John D.

2013-01-01

The self diagnostic accelerometer (SDA) developed by the NASA Glenn Research Center was tested for the first time in an aircraft engine environment as part of the Vehicle Integrated Propulsion Research (VIPR) program. The VIPR program includes testing multiple critical flight sensor technologies. One such sensor, the accelerometer, measures vibrations to detect faults in the engine. In order to rely upon the accelerometer, the health of the accelerometer must be ensured. The SDA is a sensor system designed to actively determine the accelerometer structural health and attachment condition, in addition to vibration measurements. The SDA uses a signal conditioning unit that sends an electrical chirp to the accelerometer and recognizes changes in the response due to changes in the accelerometer health and attachment condition. To demonstrate the SDAs flight worthiness and robustness, multiple SDAs were mounted and tested on a C-17 aircraft engine. The engine test conditions varied from engine off, to idle, to maximum power. The SDA attachment conditions were varied from fully tight to loose. The newly developed SDA health algorithm described herein uses cross correlation pattern recognition to discriminate a healthy from a faulty SDA. The VIPR test results demonstrate for the first.

Analytical Analysis on Nonlinear Parametric Vibration of an Axially Moving String with Fractional Viscoelastic Damping

Directory of Open Access Journals (Sweden)

Ying Li

2017-01-01

Full Text Available The nonlinear parametric vibration of an axially moving string made by rubber-like materials is studied in the paper. The fractional viscoelastic model is used to describe the damping of the string. Then, a new nonlinear fractional mathematical model governing transverse motion of the string is derived based on Newton’s second law, the Euler beam theory, and the Lagrangian strain. Taking into consideration the fractional calculus law of Riemann-Liouville form, the principal parametric resonance is analytically investigated via applying the direct multiscale method. Numerical results are presented to show the influences of the fractional order, the stiffness constant, the viscosity coefficient, and the axial-speed fluctuation amplitude on steady-state responses. It is noticeable that the amplitudes and existing intervals of steady-state responses predicted by Kirchhoff’s fractional material model are much larger than those predicted by Mote’s fractional material model.

Are Stopped Strings Preferred in Sad Music?

Directory of Open Access Journals (Sweden)

David Huron

2017-01-01

Full Text Available String instruments may be played either with open strings (where the string vibrates between the bridge and a hard wooden nut or with stopped strings (where the string vibrates between the bridge and a performer's finger pressed against the fingerboard. Compared with open strings, stopped strings permit the use of vibrato and exhibit a darker timbre. Inspired by research on the timbre of sad speech, we test whether there is a tendency to use stopped strings in nominally sad music. Specifically, we compare the proportion of potentially open-to-stopped strings in a sample of slow, minor-mode movements with matched major-mode movements. By way of illustration, a preliminary analysis of Samuel Barber's famous Adagio from his Opus 11 string quartet shows that the selected key (B-flat minor provides the optimum key for minimizing open string tones. However, examination of a broader controlled sample of quartet movements by Haydn, Mozart and Beethoven failed to exhibit the conjectured relationship. Instead, major-mode movements were found to avoid possible open strings more than slow minor-mode movements.

Testing accelerometer rectification error caused by multidimensional composite inputs with double turntable centrifuge.

Science.gov (United States)

Guan, W; Meng, X F; Dong, X M

2014-12-01

Rectification error is a critical characteristic of inertial accelerometers. Accelerometers working in operational situations are stimulated by composite inputs, including constant acceleration and vibration, from multiple directions. However, traditional methods for evaluating rectification error only use one-dimensional vibration. In this paper, a double turntable centrifuge (DTC) was utilized to produce the constant acceleration and vibration simultaneously and we tested the rectification error due to the composite accelerations. At first, we deduced the expression of the rectification error with the output of the DTC and a static model of the single-axis pendulous accelerometer under test. Theoretical investigation and analysis were carried out in accordance with the rectification error model. Then a detailed experimental procedure and testing results were described. We measured the rectification error with various constant accelerations at different frequencies and amplitudes of the vibration. The experimental results showed the distinguished characteristics of the rectification error caused by the composite accelerations. The linear relation between the constant acceleration and the rectification error was proved. The experimental procedure and results presented in this context can be referenced for the investigation of the characteristics of accelerometer with multiple inputs.

Extended Galilean symmetries of non-relativistic strings

Energy Technology Data Exchange (ETDEWEB)

Batlle, Carles [Departament de Matemàtiques and IOC, Universitat Politècnica de Catalunya, EPSEVG,Av. V. Balaguer 1, E-08808 Vilanova i la Geltrú (Spain); Gomis, Joaquim; Not, Daniel [Departament de Física Quàntica i Astrofísica and Institut de Ciències del Cosmos (ICCUB),Universitat de Barcelona,Martí i Franquès 1, E-08028 Barcelona (Spain)

2017-02-09

We consider two non-relativistic strings and their Galilean symmetries. These strings are obtained as the two possible non-relativistic (NR) limits of a relativistic string. One of them is non-vibrating and represents a continuum of non-relativistic massless particles, and the other one is a non-relativistic vibrating string. For both cases we write the generator of the most general point transformation and impose the condition of Noether symmetry. As a result we obtain two sets of non-relativistic Killing equations for the vector fields that generate the symmetry transformations. Solving these equations shows that NR strings exhibit two extended, infinite dimensional space-time symmetries which contain, as a subset, the Galilean symmetries. For each case, we compute the associated conserved charges and discuss the existence of non-central extensions.

A state-the-art report on the development of the piezoelectric accelerometer sensor

Energy Technology Data Exchange (ETDEWEB)

Park, Jee Yun; Oh, Suk Jin; Kim, Kyung Hoh; Kim, Sun Jae; Kang, Dae Kab [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1994-12-01

A state-of-the art surveys on the application and the manufacturing technology of a piezoelectric accelerometer sensor. An accelerometer sensor is applied to the monitoring of acoustic leak, reactor coolant pump vibration and loose parts in the reactor, and the measurement of vibration and stress of large equipments such as pump, tubes, etc.. The performance of an accelerometer consisted of piezoelectric ceramic, mass, base, case and cable is depend on the characteristics of each component and the assembling method. Sensitivity, linearity and dynamic range, transverse sensitivity, phase response, transient temperature response, frequency response, base strain sensitivity, magnetic sensitivity, acoustic sensitivity, humidity effect and radiation effect must be measured and evaluated for conforming quality of the developed accelerometer sensor. 35 figs., 29 tabs., 38 refs. (Author).

A state-the-art report on the development of the piezoelectric accelerometer sensor

International Nuclear Information System (INIS)

Park, Jee Yun; Oh, Suk Jin; Kim, Kyung Hoh; Kim, Sun Jae; Kang, Dae Kab

1994-12-01

A state-of-the art surveys on the application and the manufacturing technology of a piezoelectric accelerometer sensor. An accelerometer sensor is applied to the monitoring of acoustic leak, reactor coolant pump vibration and loose parts in the reactor, and the measurement of vibration and stress of large equipments such as pump, tubes, etc.. The performance of an accelerometer consisted of piezoelectric ceramic, mass, base, case and cable is depend on the characteristics of each component and the assembling method. Sensitivity, linearity and dynamic range, transverse sensitivity, phase response, transient temperature response, frequency response, base strain sensitivity, magnetic sensitivity, acoustic sensitivity, humidity effect and radiation effect must be measured and evaluated for conforming quality of the developed accelerometer sensor. 35 figs., 29 tabs., 38 refs. (Author)

Accelerometer method and apparatus for integral display and control functions

Science.gov (United States)

Bozeman, Richard J., Jr.

1992-06-01

Vibration analysis has been used for years to provide a determination of the proper functioning of different types of machinery, including rotating machinery and rocket engines. A determination of a malfunction, if detected at a relatively early stage in its development, will allow changes in operating mode or a sequenced shutdown of the machinery prior to a total failure. Such preventative measures result in less extensive and/or less expensive repairs, and can also prevent a sometimes catastrophic failure of equipment. Standard vibration analyzers are generally rather complex, expensive, and of limited portability. They also usually result in displays and controls being located remotely from the machinery being monitored. Consequently, a need exists for improvements in accelerometer electronic display and control functions which are more suitable for operation directly on machines and which are not so expensive and complex. The invention includes methods and apparatus for detecting mechanical vibrations and outputting a signal in response thereto. The apparatus includes an accelerometer package having integral display and control functions. The accelerometer package is suitable for mounting upon the machinery to be monitored. Display circuitry provides signals to a bar graph display which may be used to monitor machine condition over a period of time. Control switches may be set which correspond to elements in the bar graph to provide an alert if vibration signals increase over the selected trip point. The circuitry is shock mounted within the accelerometer housing. The method provides for outputting a broadband analog accelerometer signal, integrating this signal to produce a velocity signal, integrating and calibrating the velocity signal before application to a display driver, and selecting a trip point at which a digitally compatible output signal is generated. The benefits of a vibration recording and monitoring system with controls and displays readily

Smart accelerometer. [vibration damage detection

Science.gov (United States)

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.

The Shock and Vibration Digest. Volume 15, Number 8

Science.gov (United States)

1983-08-01

three revolute clearances is analyzed to illustrate the procedure. STRINGS AND ROPES 83-1574 Longitudinal Vibrations in Violin Strings A.R, Lee and...Strings, Violins , Mutical instruments. Longi- tudinal vibration The observation of longitudinal vibrations In violin strings excited by bowing it...few existing exam - ples is encouraging but inconclusive. Better overall agreement is demonstrated with fairly comprehensive measurements from a

Self Diagnostic Accelerometer Ground Testing on a C-17 Aircraft Engine

Science.gov (United States)

Tokars, Roger P.; Lekki, John D.

2013-01-01

The self diagnostic accelerometer (SDA) developed by the NASA Glenn Research Center was tested for the first time in an aircraft engine environment as part of the Vehicle Integrated Propulsion Research (VIPR) program. The VIPR program includes testing multiple critical flight sensor technologies. One such sensor, the accelerometer, measures vibrations to detect faults in the engine. In order to rely upon the accelerometer, the health of the accelerometer must be ensured. Sensor system malfunction is a significant contributor to propulsion in flight shutdowns (IFSD) which can lead to aircraft accidents when the issue is compounded with an inappropriate crew response. The development of the SDA is important for both reducing the IFSD rate, and hence reducing the rate at which this component failure type can put an aircraft in jeopardy, and also as a critical enabling technology for future automated malfunction diagnostic systems. The SDA is a sensor system designed to actively determine the accelerometer structural health and attachment condition, in addition to making vibration measurements. The SDA uses a signal conditioning unit that sends an electrical chirp to the accelerometer and recognizes changes in the response due to changes in the accelerometer health and attachment condition. In an effort toward demonstrating the SDAs flight worthiness and robustness, multiple SDAs were mounted and tested on a C-17 aircraft engine. The engine test conditions varied from engine off, to idle, to maximum power. The two SDA attachment conditions used were fully tight and loose. The newly developed SDA health algorithm described herein uses cross correlation pattern recognition to discriminate a healthy from a faulty SDA. The VIPR test results demonstrate for the first time the robustness of the SDA in an engine environment characterized by high vibration levels.

A modal-based approach to the nonlinear vibration of strings against a unilateral obstacle: Simulations and experiments in the pointwise case

Science.gov (United States)

Issanchou, Clara; Bilbao, Stefan; Le Carrou, Jean-Loïc; Touzé, Cyril; Doaré, Olivier

2017-04-01

This article is concerned with the vibration of a stiff linear string in the presence of a rigid obstacle. A numerical method for unilateral and arbitrary-shaped obstacles is developed, based on a modal approach in order to take into account the frequency dependence of losses in strings. The contact force of the barrier interaction is treated using a penalty approach, while a conservative scheme is derived for time integration, in order to ensure long-term numerical stability. In this way, the linear behaviour of the string when not in contact with the barrier can be controlled via a mode by mode fitting, so that the model is particularly well suited for comparisons with experiments. An experimental configuration is used with a point obstacle either centered or near an extremity of the string. In this latter case, such a pointwise obstruction approximates the end condition found in the tanpura, an Indian stringed instrument. The second polarisation of the string is also analysed and included in the model. Numerical results are compared against experiments, showing good accuracy over a long time scale.

Accelerometer-based estimation and modal velocity feedback vibration control of a stress-ribbon bridge with pneumatic muscles

International Nuclear Information System (INIS)

Liu, Xiaohan; Goldack, Arndt; Schlaich, Mike; Schauer, Thomas; Bleicher, Achim

2016-01-01

Lightweight footbridges are very elegant but also prone to vibration. By employing active vibration control, smart footbridges could accomplish not only the architectural concept but also the required serviceability and comfort. Inertial sensors such as accelerometers allow the estimation of nodal velocities and displacements. A Kalman filter together with a band-limited multiple Fourier linear combiner (BMFLC) is applied to enable a drift-free estimation of these signals for the quasi-periodic motion under pedestrian excitation without extra information from other kinds of auxiliary sensors. The modal velocities of the structure are determined by using a second Kalman filter with the known applied actuator forces as inputs and the estimated nodal displacement and velocities as measurements. The obtained multi-modal velocities are then used for feedback control. An ultra-lightweight stress-ribbon footbridge built in the Peter-Behrens- Halle at the Technische Universitat Berlin served as the research object. Using two inertial sensors in optimal points we can estimate the dominant modal characteristics of this bridge. Real-time implementation and evaluation results of the proposed estimator will be presented in comparison to signals derived from classical displacement encoders. The real-time estimated modal velocities were applied in a multi-modal velocity feedback vibration control scheme with lightweight pneumatic muscle actuators. Experimental results demonstrate the feasibility of using inertial sensors for active vibration control of lightweight footbridges. (paper)

Accelerometer-based estimation and modal velocity feedback vibration control of a stress-ribbon bridge with pneumatic muscles

Science.gov (United States)

Liu, Xiaohan; Schauer, Thomas; Goldack, Arndt; Bleicher, Achim; Schlaich, Mike

2016-09-01

Lightweight footbridges are very elegant but also prone to vibration. By employing active vibration control, smart footbridges could accomplish not only the architectural concept but also the required serviceability and comfort. Inertial sensors such as accelerometers allow the estimation of nodal velocities and displacements. A Kalman filter together with a band-limited multiple Fourier linear combiner (BMFLC) is applied to enable a drift-free estimation of these signals for the quasi-periodic motion under pedestrian excitation without extra information from other kinds of auxiliary sensors. The modal velocities of the structure are determined by using a second Kalman filter with the known applied actuator forces as inputs and the estimated nodal displacement and velocities as measurements. The obtained multi-modal velocities are then used for feedback control. An ultra-lightweight stress-ribbon footbridge built in the Peter-Behrens- Halle at the Technische Universitat Berlin served as the research object. Using two inertial sensors in optimal points we can estimate the dominant modal characteristics of this bridge. Real-time implementation and evaluation results of the proposed estimator will be presented in comparison to signals derived from classical displacement encoders. The real-time estimated modal velocities were applied in a multi-modal velocity feedback vibration control scheme with lightweight pneumatic muscle actuators. Experimental results demonstrate the feasibility of using inertial sensors for active vibration control of lightweight footbridges.

On the planar and whirling motion of a stretched string due to a parametric harmonic excitation

NARCIS (Netherlands)

Van der Burgh, A.H.P.; Van Horssen, W.T.

2004-01-01

In this paper a model of the dynamics of a stretched string is derived. The sag of the string due to gravity is neglected. The string is suspended between a fixed support and a vibrating support. Due to the vibrating support the oscillation of the string in vertical direction is influenced by a

Simulation and experimental study of a three-axis fiber Bragg grating accelerometer based on the pull-push mechanism

Science.gov (United States)

Jiang, Qi; Yang, Meng

2013-11-01

A three-axis fiber Bragg grating accelerometer, which has uniform sensitivities to three axes, has been developed for seismic application. This paper presents the design, simulation and calibration of the three-axis accelerometer. A series of experiments were performed to measure harmonic vibration and shock vibration. The precise acceleration was measured by a PZT accelerometer which provided high sensitivity. The fully described dynamic sensitivity of three-axis accelerometers represented by a 3-by-3 matrix is given. The results indicate that the accelerometer has a sensitivity of 0.068 V g-1 in a measured full scale of ±2.5 m s-2. The cross-axis sensitivity was measured as -75.5 dB, -75.5 dB and -78.2 dB, respectively.

String Theory - The Physics of String-Bending and Other Electric Guitar Techniques

Science.gov (United States)

Grimes, David Robert

2014-01-01

Electric guitar playing is ubiquitous in practically all modern music genres. In the hands of an experienced player, electric guitars can sound as expressive and distinct as a human voice. Unlike other more quantised instruments where pitch is a discrete function, guitarists can incorporate micro-tonality and, as a result, vibrato and sting-bending are idiosyncratic hallmarks of a player. Similarly, a wide variety of techniques unique to the electric guitar have emerged. While the mechano-acoustics of stringed instruments and vibrating strings are well studied, there has been comparatively little work dedicated to the underlying physics of unique electric guitar techniques and strings, nor the mechanical factors influencing vibrato, string-bending, fretting force and whammy-bar dynamics. In this work, models for these processes are derived and the implications for guitar and string design discussed. The string-bending model is experimentally validated using a variety of strings and vibrato dynamics are simulated. The implications of these findings on the configuration and design of guitars is also discussed. PMID:25054880

String theory--the physics of string-bending and other electric guitar techniques.

Directory of Open Access Journals (Sweden)

David Robert Grimes

Full Text Available Electric guitar playing is ubiquitous in practically all modern music genres. In the hands of an experienced player, electric guitars can sound as expressive and distinct as a human voice. Unlike other more quantised instruments where pitch is a discrete function, guitarists can incorporate micro-tonality and, as a result, vibrato and sting-bending are idiosyncratic hallmarks of a player. Similarly, a wide variety of techniques unique to the electric guitar have emerged. While the mechano-acoustics of stringed instruments and vibrating strings are well studied, there has been comparatively little work dedicated to the underlying physics of unique electric guitar techniques and strings, nor the mechanical factors influencing vibrato, string-bending, fretting force and whammy-bar dynamics. In this work, models for these processes are derived and the implications for guitar and string design discussed. The string-bending model is experimentally validated using a variety of strings and vibrato dynamics are simulated. The implications of these findings on the configuration and design of guitars is also discussed.

String theory--the physics of string-bending and other electric guitar techniques.

Science.gov (United States)

Grimes, David Robert

2014-01-01

Electric guitar playing is ubiquitous in practically all modern music genres. In the hands of an experienced player, electric guitars can sound as expressive and distinct as a human voice. Unlike other more quantised instruments where pitch is a discrete function, guitarists can incorporate micro-tonality and, as a result, vibrato and sting-bending are idiosyncratic hallmarks of a player. Similarly, a wide variety of techniques unique to the electric guitar have emerged. While the mechano-acoustics of stringed instruments and vibrating strings are well studied, there has been comparatively little work dedicated to the underlying physics of unique electric guitar techniques and strings, nor the mechanical factors influencing vibrato, string-bending, fretting force and whammy-bar dynamics. In this work, models for these processes are derived and the implications for guitar and string design discussed. The string-bending model is experimentally validated using a variety of strings and vibrato dynamics are simulated. The implications of these findings on the configuration and design of guitars is also discussed.

Progress in string theory research

CERN Document Server

2016-01-01

At the first look, the String Theory seems just an interesting and non-trivial application of the quantum mechanics and the special relativity to vibrating strings. By itself, the quantization of relativistic strings does not call the attention of the particle physicist as a significant paradigm shift. However, when the string quantization is performed by applying the standard rules of the perturbative Quantum Field Theory, one discovers that the strings in certain states have the same physical properties as the gravity in the flat space-time. Chapter one of this book reviews the construction of the thermal bosonic string and D-brane in the framework of the Thermo Field Dynamics (TFD). It briefly recalls the wellknown light-cone quantization of the bosonic string in the conformal gauge in flat space-time, and gives a bird’s eye view of the fundamental concepts of the TFD. Chapter two examines a visual model inspired by string theory, on the system of interacting anyons. Chapter three investigate the late-ti...

Vibrating minds

CERN Multimedia

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.

Design of a Piezoelectric Accelerometer with High Sensitivity and Low Transverse Effect

Directory of Open Access Journals (Sweden)

Bian Tian

2016-09-01

Full Text Available In order to meet the requirements of cable fault detection, a new structure of piezoelectric accelerometer was designed and analyzed in detail. The structure was composed of a seismic mass, two sensitive beams, and two added beams. Then, simulations including the maximum stress, natural frequency, and output voltage were carried out. Moreover, comparisons with traditional structures of piezoelectric accelerometer were made. To verify which vibration mode is the dominant one on the acceleration and the space between the mass and glass, mode analysis and deflection analysis were carried out. Fabricated on an n-type single crystal silicon wafer, the sensor chips were wire-bonged to printed circuit boards (PCBs and simply packaged for experiments. Finally, a vibration test was conducted. The results show that the proposed piezoelectric accelerometer has high sensitivity, low resonance frequency, and low transverse effect.

In- and out-of-plane response of a stretched string due to an in-plane harmonic excitation

NARCIS (Netherlands)

Van Horssen, W.T.; Van der Burgh, A.H.P

2004-01-01

In this paper a model of the dynamics of a stretched string is derived. The sag of the string due to gravity is neglected. The string is suspended between a fixed support and a vibrating support. Due to the vibrating support the oscillation of the string in vertical direction is influenced by a

Simulation and experimental study of a three-axis fiber Bragg grating accelerometer based on the pull–push mechanism

International Nuclear Information System (INIS)

Jiang, Qi; Yang, Meng

2013-01-01

A three-axis fiber Bragg grating accelerometer, which has uniform sensitivities to three axes, has been developed for seismic application. This paper presents the design, simulation and calibration of the three-axis accelerometer. A series of experiments were performed to measure harmonic vibration and shock vibration. The precise acceleration was measured by a PZT accelerometer which provided high sensitivity. The fully described dynamic sensitivity of three-axis accelerometers represented by a 3-by-3 matrix is given. The results indicate that the accelerometer has a sensitivity of 0.068 V g −1 in a measured full scale of ±2.5 m s −2 . The cross-axis sensitivity was measured as −75.5 dB, −75.5 dB and −78.2 dB, respectively. (paper)

Plucked Strings and the Harpsichord

Science.gov (United States)

GIORDANO, N.; WINANS, J. P.

1999-07-01

The excitation of a harpsichord string when it is set into motion, i.e., plucked, by a plectrum is studied. We find that the amplitude of the resulting string vibration is approximately independent of the velocity with which the key is depressed. This result is in accord with conventional wisdom, but at odds with a recent theoretical model. A more realistic theoretical treatment of the plucking process is then described, and shown to be consistent with our measurements. The experiments reveal several other interesting aspects of the plectrum-string interaction.

Thimble vibration analysis and monitoring on 1300 and 900 MW reactors using accelerometers and in core neutron noise

International Nuclear Information System (INIS)

Trenty, A.; Puyal, C.; Vincent, C.; Baeyens, R.; Messainguiral-Bruynooghe, C.; Lagarde, G.

1988-01-01

The axial flow along the thimbles of the in core instrumentation induces vibration and shocks against their guides in the vessel, producing wear and even leakage, either on the thimbles, or on the instrumentation tube of the fuel assemblies. In order to characterize the phenomenon and help to reduce or suppress vibration of the thimbles, two methods have been developed and applied to French and Belgian reactors. The first one consists of an analysis of the shocks perceived on the thimbles tubes by accelerometers; this analysis, based on the study of statistical distribution (amplitude, impulse rate of shocks...) has allowed to choose among the different solutions proposed to solve the problem; this choice has been confirmed by direct wear measurements made later. The second method is based on spectral and time analysis of the fluctuating signals from in core neutron chambers. The correlation appears clearly between shocks and fluctuations. An estimation of the thimble model shape in the instrumentation tube of the assembly, has been made. These two analysis methods have been widely applied during start-up of the first eight 1300 MW reactors: they have contributed to solve the problem and to increase the availability of these plants. On the 900 MW reactors, where the problem is less severe, the approach has been to study the mechanical behaviour of one new plant, Chinon B3: all in core guide tubes have been equipped with accelerometers and an on line monitoring system directly transmits to Chatou the parameters of shocks, in order to define an acoustic parameter able to characterize wear, and so, to define a new type of maintenance for the thimbles. The first results are presented. (author)

Vibration transducer calibration techniques

Science.gov (United States)

Brinkley, D. J.

1980-09-01

Techniques for the calibration of vibration transducers used in the Aeronautical Quality Assurance Directorate of the British Ministry of Defence are presented. Following a review of the types of measurements necessary in the calibration of vibration transducers, the performance requirements of vibration transducers, which can be used to measure acceleration, velocity or vibration amplitude, are discussed, with particular attention given to the piezoelectric accelerometer. Techniques for the accurate measurement of sinusoidal vibration amplitude in reference-grade transducers are then considered, including the use of a position sensitive photocell and the use of a Michelson laser interferometer. Means of comparing the output of working-grade accelerometers with that of previously calibrated reference-grade devices are then outlined, with attention given to a method employing a capacitance bridge technique and a method to be used at temperatures between -50 and 200 C. Automatic calibration procedures developed to speed up the calibration process are outlined, and future possible extensions of system software are indicated.

A Low Frequency FBG Accelerometer with Symmetrical Bended Spring Plates

Directory of Open Access Journals (Sweden)

Fufei Liu

2017-01-01

Full Text Available To meet the requirements for low-frequency vibration monitoring, a new type of FBG (fiber Bragg grating accelerometer with a bended spring plate is proposed. Two symmetrical bended spring plates are used as elastic elements, which drive the FBG to produce axial strains equal in magnitude but opposite in direction when exciting vibrations exist, leading to doubling the wavelength shift of the FBG. The mechanics model and a numerical method are presented in this paper, with which the influence of the structural parameters on the sensitivity and the eigenfrequency are discussed. The test results show that the sensitivity of the accelerometer is more than 1000 pm/g when the frequency is within the 0.7–20 Hz range.

Investigation of PDC bit failure base on stick-slip vibration analysis of drilling string system plus drill bit

Science.gov (United States)

Huang, Zhiqiang; Xie, Dou; Xie, Bing; Zhang, Wenlin; Zhang, Fuxiao; He, Lei

2018-03-01

The undesired stick-slip vibration is the main source of PDC bit failure, such as tooth fracture and tooth loss. So, the study of PDC bit failure base on stick-slip vibration analysis is crucial to prolonging the service life of PDC bit and improving ROP (rate of penetration). For this purpose, a piecewise-smooth torsional model with 4-DOF (degree of freedom) of drilling string system plus PDC bit is proposed to simulate non-impact drilling. In this model, both the friction and cutting behaviors of PDC bit are innovatively introduced. The results reveal that PDC bit is easier to fail than other drilling tools due to the severer stick-slip vibration. Moreover, reducing WOB (weight on bit) and improving driving torque can effectively mitigate the stick-slip vibration of PDC bit. Therefore, PDC bit failure can be alleviated by optimizing drilling parameters. In addition, a new 4-DOF torsional model is established to simulate torsional impact drilling and the effect of torsional impact on PDC bit's stick-slip vibration is analyzed by use of an engineering example. It can be concluded that torsional impact can mitigate stick-slip vibration, prolonging the service life of PDC bit and improving drilling efficiency, which is consistent with the field experiment results.

On the transversal vibrations of a conveyor belt with a low and time-varying velocity : Part I: the string-like case

NARCIS (Netherlands)

Suweken, G.; Van Horssen, W.T.

2001-01-01

In this paper initial-boundary value problems for a linear wave (string) equation are considered. These problems can be used as simple models to describe the vertical vibrations of a conveyor belt, for which the velocity is small with respect to the wave speed. In this paper the belt is assumed to

Vibrations and Eigenvalues

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-.

The Effect of String Tension Variation on the Perceived Pitch of a Classical Guitar

Directory of Open Access Journals (Sweden)

Wanda Jadwiga Lewis

2014-09-01

Full Text Available Actual motion of a vibrating guitar string is a superposition of many possible shapes (modes in which it could vibrate. Each of these modes has a corresponding frequency, and the lowest frequency is associated with a shape idealised as a single wave, referred to as the fundamental mode. The other contributing modes, each with their own progressively higher frequency, are referred to as overtones, or harmonics. By attaching a string to a medium (a soundboard capable of a response to the vibrating string, sound waves are generated. The sound heard is dominated by the fundamental mode, ‘coloured’ by contributions from the overtones, as explained by the classical theory of vibration. The classical theory, however, assumes that the string tension remains constant during vibration, and this cannot be strictly true; when considering just the fundamental mode, string tension will reach two maximum changes, as it oscillates up and down. These changes, occurring twice during the fundamental period match the frequency of the octave higher, 1st overtone. It is therefore plausible to think that the changing tension effect, through increased force on the bridge and, therefore, greater soundboard deflection, could be amplifying the colouring effect of (at least the 1st overtone. In this paper, we examine the possible influence of string tension variation on tonal response of a classical guitar. We use a perturbation model based on the classical result for a string in general vibration in conjunction with a novel method of assessment of plucking force that incorporates the engineering concept of geometric stiffness, to assess the magnitude of the normal force exerted by the string on the bridge. The results of our model show that the effect of tension variation is significantly smaller than that due to the installed initial static tension, and affects predominantly the force contribution arising from the fundamental mode. We, therefore, conclude that string

Structural Design of a Compact in-Plane Nano-Grating Accelerometer

International Nuclear Information System (INIS)

Yao Bao-Yin; Zhou Zhen; Feng Li-Shuang; Wang Wen-Pu; Wang Xiao

2012-01-01

A combination of large mass, weak spring and nano-grating is the key for a nano-grating accelerometer to measure nano-G acceleration. A novel compact nano-grating accelerometer integrating a large mass with nano-grating is proposed. First, the numbers of diffraction orders are calculated. Then, structure parameters are optimized by finite element analysis to achieve a high sensitivity in an ideal vibration mode. Finally, we design the fabrication method to form such a compact nano-grating accelerometer and successfully fabricate the uniform and well-designed nano-gratings with a period of 847 nm, crater of 451 nm by an FIB/SEM dual beam system. Based on the ANSYS simulation, a nano-grating accelerometer is predicted to work in the first modal and enables the accelerometer to have displacement sensitivity at 197 nm/G with a measurement range of ±1 G, corresponding to zeroth diffraction beam optical sensitivity 1%/mG. The nano-gratings fabricated are very close to those designed ones within experimental error to lay the foundation for the sequent fabrication. These results provide a theoretical basis for the design and fabrication of nano-grating accelerometers

Quality factor improvement of silicon nitride micro string resonators

DEFF Research Database (Denmark)

Schmid, Silvan; Malm, Bjarke; Boisen, Anja

2011-01-01

Resonant micro and nano strings are of interest for sensor applications due to their extraordinary high quality factors, low mass and tunable resonant frequency. It has been found that the quality factor of strings is usually limited by clamping loss. In this work, clamping loss has been addressed...... by varying the clamping design and string geometry. We present silicon nitride micro strings with quality factors (Q) of up to 4 million in high vacuum achieved by minimizing clamping loss. For applications such as for chemical sensing, strings need to vibrate at atmospheric pressure. Maximal quality factor...

On small vibrations of a damped Stieltjes string

Directory of Open Access Journals (Sweden)

Olga Boyko

2015-01-01

Full Text Available Inverse problem of recovering masses, coefficients of damping and lengths of the intervals between the masses using two spectra of boundary value problems and the total length of the Stieltjes string (an elastic thread bearing point masses is considered. For the case of point-wise damping at the first counting from the right end mass the problem of recovering the masses, the damping coefficient and the lengths of the subintervals by one spectrum and the total length of the string is solved.

New technologies for acceleration and vibration measurements inside operating nuclear power reactors

International Nuclear Information System (INIS)

Runkel, J.; Stegemann, D.; Fiedler, J.; Heidemann, P.; Blaser, R.; Schmid, F.; Trobitz, M.; Hirsch, L.; Thoma, K.

2000-01-01

A miniature bi-axial in-core accelerometer has been inserted temporarily inside the travelling in-core probe (TIP) systems of operating 1300 MW el boiling water reactors (BWR) during full power operation. In-core acceleration measurements can be performed in any position of the TIP system. This provides new features of control technologies to preserve the integrity of reactor internals. The radial and axial position where fretting or impacting of instrumentation string tubes or other structures might occur can be localised inside the reactor pressure vessel. The efficiency and long-term performance of subsequent improvements of the mechanical or operating conditions can be controlled with high local resolution and sensitivity. Low frequency vibrations of the instrumentation tubes were measured inside the core. Neutron-mechanical scale factors were determined from neutron noise, measured by the standard in-core neutron instrumentation and from displacements of the TIP tubes, calculated by integration of the measured in-core acceleration signals. The scale factors contribute to qualitative and quantitative monitoring of BWR internals' vibrations only by the use of neutron signals. (authors)

Experiment on interface separation detection of concrete-filled steel tubular arch bridge using accelerometer array

Science.gov (United States)

Pan, Shengshan; Zhao, Xuefeng; Zhao, Hailiang; Mao, Jian

2015-04-01

Based on the vibration testing principle, and taking the local vibration of steel tube at the interface separation area as the study object, a real-time monitoring and the damage detection method of the interface separation of concrete-filled steel tube by accelerometer array through quantitative transient self-excitation is proposed. The accelerometers are arranged on the steel tube area with or without void respectively, and the signals of accelerometers are collected at the same time and compared under different transient excitation points. The results show that compared with the signal of compact area, the peak value of accelerometer signal at void area increases and attenuation speed slows down obviously, and the spectrum peaks of the void area are much more and disordered and the amplitude increases obviously. whether the input point of transient excitation is on void area or not is irrelevant with qualitative identification results. So the qualitative identification of the interface separation of concrete-filled steel tube based on the signal of acceleration transducer is feasible and valid.

Six Degree-of-Freedom Haptic Simulation of a Stringed Musical Instrument for Triggering Sounds.

Science.gov (United States)

Dangxiao Wang; Xiaohan Zhao; Youjiao Shi; Yuru Zhang; Jing Xiao

2017-01-01

Six degree-of-freedom (DoF) haptic rendering of multi-region contacts between a moving hand avatar and varied-shaped components of a music instrument is fundamental to realizing interactive simulation of music playing. There are two aspects of computational challenges: first, some components have significantly small sizes in some dimensions, such as the strings on a seven-string plucked instrument (e.g., Guqin), which makes it challenging to avoid pop-through during multi-region contact scenarios. Second, deformable strings may produce high-frequency vibration, which requires simulating diversified and subtle force sensations when a hand interacts with strings in different ways. In this paper, we propose a constraint-based approach to haptic interaction and simulation between a moving hand avatar and various parts of a string instrument, using a cylinder model for the string that has a large length-radius ratio and a sphere-tree model for the other parts that have complex shapes. Collision response algorithms based on configuration-based optimization is adapted to solve for the contact configuration of the hand avatar interacting with thin strings without penetration. To simulate the deformation and vibration of a string, a cylindrical volume with variable diameters is defined with response to the interaction force applied by the operator. Experimental results have validated the stability and efficiency of the proposed approach. Subtle force feelings can be simulated to reflect varied interaction patterns, to differentiate collisions between the hand avatar with a static or vibrating string and the effects of various colliding forces and touch locations on the strings.

Windings of twisted strings

Science.gov (United States)

Casali, Eduardo; Tourkine, Piotr

2018-03-01

Twistor string models have been known for more than a decade now but have come back under the spotlight recently with the advent of the scattering equation formalism which has greatly generalized the scope of these models. A striking ubiquitous feature of these models has always been that, contrary to usual string theory, they do not admit vibrational modes and thus describe only conventional field theory. In this paper we report on the surprising discovery of a whole new sector of one of these theories which we call "twisted strings," when spacetime has compact directions. We find that the spectrum is enhanced from a finite number of states to an infinite number of interacting higher spin massive states. We describe both bosonic and world sheet supersymmetric models, their spectra and scattering amplitudes. These models have distinctive features of both string and field theory, for example they are invariant under stringy T-duality but have the high energy behavior typical of field theory. Therefore they describe a new kind of field theories in target space, sitting on their own halfway between string and field theory.

Modeling Friction Performance of Drill String Torsional Oscillation Using Dynamic Friction Model

Directory of Open Access Journals (Sweden)

Xingming Wang

2017-01-01

Full Text Available Drill string torsional and longitudinal oscillation can significantly reduce axial drag in horizontal drilling. An improved theoretical model for the analysis of the frictional force was proposed based on microscopic contact deformation theory and a bristle model. The established model, an improved dynamic friction model established for drill strings in a wellbore, was used to determine the relationship of friction force changes and the drill string torsional vibration. The model results were in good agreement with the experimental data, verifying the accuracy of the established model. The analysis of the influence of drilling mud properties indicated that there is an approximately linear relationship between the axial friction force and dynamic shear and viscosity. The influence of drill string torsional oscillation on the axial friction force is discussed. The results indicated that the drill string transverse velocity is a prerequisite for reducing axial friction. In addition, low amplitude of torsional vibration speed can significantly reduce axial friction. Then, increasing the amplitude of transverse vibration speed, the effect of axial reduction is not significant. In addition, by involving general field drilling parameters, this model can accurately describe the friction behavior and quantitatively predict the frictional resistance in horizontal drilling.

Development of multiple performance indices and system parameter study for the design of a MEMS accelerometer

International Nuclear Information System (INIS)

Kim, Yong Il; Choi, Chan Kyu; Yoo, Hong Hee

2012-01-01

For the design of a MEMS accelerometer, proper performance indices should be defined and employed. Performance indices are obtained using either an experimental method or a numerical method. In the present study, a vibration analysis model of a MEMS accelerometer is introduced to calculate three performance indices: sensitivity, measurable acceleration range, and measurable frequency range. The accuracy of the vibration analysis model is first validated by comparing its modal and transient results with those of a commercial finite element code. Measurable acceleration and frequency ranges versus allowable errors for electrical and mechanical sensitivities are obtained and the effects of system parameter variations on the three performance indices are investigated

Vibration Disturbance Damping System Design to Protect Payload of the Rocket

Directory of Open Access Journals (Sweden)

Sutisno Sutisno

2012-12-01

Full Text Available Rocket motor generates vibrations acting on whole rocket body including its contents. Part of the body which is sensitive to disturbance is the rocket payload. The payload consists of various electronic instruments including: transmitter, various sensors, accelerometer, gyro, the embedded controller system, and others. This paper presents research on rocket vibration influence to the payload and the method to avoid disturbance. Avoiding influence of vibration disturbance can be done using silicone gel material whose typical damping factors are relatively high. The rocket vibration was simulated using electromagnetic motor, and the vibrations were measured using an accelerometer sensor. The measurement results were displayed in the form of curve, indicating the vibration level on some parts of the tested material. Some measurement results can be applied to determine the good material to attenuate vibration disturbance on the instruments of the payload.

Principle Research on a Single Mass Piezoelectric Six-Degrees-of-Freedom Accelerometer

Directory of Open Access Journals (Sweden)

Jingcheng Liu

2013-08-01

Full Text Available A signal mass piezoelectric six-degrees-of-freedom (six-DOF accelerometer is put forward in response to the need for health monitoring of the dynamic vibration characteristics of high grade digitally controlled machine tools. The operating principle of the piezoelectric six-degrees-of-freedom accelerometer is analyzed, and its structure model is constructed. The numerical simulation model (finite element model of the six axis accelerometer is established. Piezoelectric quartz is chosen for the acceleration sensing element and conversion element, and its static sensitivity, static coupling interference and dynamic natural frequency, dynamic cross coupling are analyzed by ANSYS software. Research results show that the piezoelectric six-DOF accelerometer has advantages of simple and rational structure, correct sensing principle and mathematic model, good linearity, high rigidity, and theoretical natural frequency is more than 25 kHz, no nonlinear cross coupling and no complex decoupling work.

Citizen Sensors for SHM: Use of Accelerometer Data from Smartphones

Directory of Open Access Journals (Sweden)

Maria Feng

2015-01-01

Full Text Available Ubiquitous smartphones have created a significant opportunity to form a low-cost wireless Citizen Sensor network and produce big data for monitoring structural integrity and safety under operational and extreme loads. Such data are particularly useful for rapid assessment of structural damage in a large urban setting after a major event such as an earthquake. This study explores the utilization of smartphone accelerometers for measuring structural vibration, from which structural health and post-event damage can be diagnosed. Widely available smartphones are tested under sinusoidal wave excitations with frequencies in the range relevant to civil engineering structures. Large-scale seismic shaking table tests, observing input ground motion and response of a structural model, are carried out to evaluate the accuracy of smartphone accelerometers under operational, white-noise and earthquake excitations of different intensity. Finally, the smartphone accelerometers are tested on a dynamically loaded bridge. The extensive experiments show satisfactory agreements between the reference and smartphone sensor measurements in both time and frequency domains, demonstrating the capability of the smartphone sensors to measure structural responses ranging from low-amplitude ambient vibration to high-amplitude seismic response. Encouraged by the results of this study, the authors are developing a citizen-engaging and data-analytics crowdsourcing platform towards a smartphone-based Citizen Sensor network for structural health monitoring and post-event damage assessment applications.

Citizen sensors for SHM: use of accelerometer data from smartphones.

Science.gov (United States)

Feng, Maria; Fukuda, Yoshio; Mizuta, Masato; Ozer, Ekin

2015-01-29

Ubiquitous smartphones have created a significant opportunity to form a low-cost wireless Citizen Sensor network and produce big data for monitoring structural integrity and safety under operational and extreme loads. Such data are particularly useful for rapid assessment of structural damage in a large urban setting after a major event such as an earthquake. This study explores the utilization of smartphone accelerometers for measuring structural vibration, from which structural health and post-event damage can be diagnosed. Widely available smartphones are tested under sinusoidal wave excitations with frequencies in the range relevant to civil engineering structures. Large-scale seismic shaking table tests, observing input ground motion and response of a structural model, are carried out to evaluate the accuracy of smartphone accelerometers under operational, white-noise and earthquake excitations of different intensity. Finally, the smartphone accelerometers are tested on a dynamically loaded bridge. The extensive experiments show satisfactory agreements between the reference and smartphone sensor measurements in both time and frequency domains, demonstrating the capability of the smartphone sensors to measure structural responses ranging from low-amplitude ambient vibration to high-amplitude seismic response. Encouraged by the results of this study, the authors are developing a citizen-engaging and data-analytics crowdsourcing platform towards a smartphone-based Citizen Sensor network for structural health monitoring and post-event damage assessment applications.

System and method for damping vibration in a drill string using a magnetorheological damper

Science.gov (United States)

Wassell, Mark Ellsworth; Burgess, Daniel E.; Barbely, Jason R.; Thompson, Fred Lamar

2018-05-22

A system for damping vibration in a drill string can include a magnetorheological fluid valve assembly having a supply of a magnetorheological fluid. A remanent magnetic field is induced in the valve during operation that can be used to provide the magnetic field for operating the valve so as to eliminate the need to energize the coils except temporarily when changing the amount of damping required. The current to be supplied to the coil for inducing a desired magnetic field in the valve is determined based on the limiting hysteresis curve of the valve and the history of the magnetization of the value using a binary search methodology. The history of the magnetization of the valve is expressed as a series of sets of current and it resulting magnetization at which the current experienced a reversal compared to prior values of the current.

Tapered Polymer Fiber Sensors for Reinforced Concrete Beam Vibration Detection.

Science.gov (United States)

Luo, Dong; Ibrahim, Zainah; Ma, Jianxun; Ismail, Zubaidah; Iseley, David Thomas

2016-12-16

In this study, tapered polymer fiber sensors (TPFSs) have been employed to detect the vibration of a reinforced concrete beam (RC beam). The sensing principle was based on transmission modes theory. The natural frequency of an RC beam was theoretically analyzed. Experiments were carried out with sensors mounted on the surface or embedded in the RC beam. Vibration detection results agreed well with Kistler accelerometers. The experimental results found that both the accelerometer and TPFS detected the natural frequency function of a vibrated RC beam well. The mode shapes of the RC beam were also found by using the TPFSs. The proposed vibration detection method provides a cost-comparable solution for a structural health monitoring (SHM) system in civil engineering.

Stringed converters on a basis of Ge1-xSix monocrystals

International Nuclear Information System (INIS)

Abbasov, Sh.M.; Abbasov, Sh. I.; Baytsar, R.I

2003-01-01

Full Text: The representing electromechanical resonator on elastic vibrations of monocrystal strings from semiconductor materials rather simple in manufacturing of stringed tenzoconverter on the basis of Ge-Si monocrystals was described. The examples os such class of converters using in concrete designs of devices for measurement of various physical parameters were reported

Physics is in trouble, the string theory has failed

International Nuclear Information System (INIS)

Smolin, L.

2007-01-01

The popularity of the string theory is based on its claim to explain both the very big and the very small: gravity and elementary particles. The string theory assumes that the real world contains dimensions that have not yet been observed and that any elementary particle is a vibration of a unique entity called string that obeys simple and elegant laws. Most theoretical physicists and mathematicians have focused their attention on this theory for the last 25 years and the diagnosis is clear: string theory fails to cope with the standard model and to explain the existence of dark matter or the mass of neutrinos. The string theory is hailed for its beauty or elegancy but this theory has never been backed by experimental data. While science has made significant progress in numerous domains, particle physics seems to have reached a dead-end. It is high time we officially questioned the string theory and opened the gate for alternative theories. (A.C.)

Development and Application of the Downhole Drilling String Shock-Absorption and Hydraulic Supercharging Device

Directory of Open Access Journals (Sweden)

Yongwang Liu

2016-01-01

Full Text Available It is a hot topic for deep/ultradeep wells to improve rock-breaking efficiency and drilling speed by available downhole energy. Based on different downhole energies and working conditions, specialized plunger pump is proposed to convert longitudinal vibration of drilling string into rock-breaking energy. Technical design is developed to generate high-pressure water jet. And then a simulation model is built to verify feasibility of the technical design. Through simulation, the influence law of key factors is obtained. On this basis, this device is tested in several wells. The result indicates this device can increase drilling speed as much as 136%. Meanwhile the harmful vibration can be absorbed. The energy from drilling string vibration is of high frequency and increases as well depth and formation anisotropy increase. By reducing adverse vibration, this device is able to increase the drilling speed and the service life also meets the demand of field application. The longest working time lasts for more than 130 hours. The performance of this device demonstrates great application prospect in deep/ultradeep resources exploration. To provide more equipment support for deep/ultradeep wells, more effort should be put into fundamental study on downhole drill string vibration and related equipment.

Low-frequency characteristics extension for vibration sensors

Institute of Scientific and Technical Information of China (English)

杨学山; 高峰; 候兴民

2004-01-01

Traditional magneto-electric vibration sensors and servo accelerometers have severe shortcomings when used to measure vibration where low frequency components predominate. A low frequency characteristic extension for velocity vibration sensors is presented in this paper. The passive circuit technology, active compensation technology and the closedcycle pole compensation technology are used to extend the measurable range and to improve low frequency characteristics of sensors. Thses three types of low frequency velocity vibration sensors have been developed and widely adopted in China.

Piezoelectric Accelerometers Development

DEFF Research Database (Denmark)

Liu, Bin; Bang, Lisbet Fogh

1999-01-01

The paper describes the development of piezoelectric accelerometers using Finite Element (FE) approach. Brüel & Kjær Accelerometer Type 8325 is chosen as an example to illustrate the advanced accelerometer development procedure. The deviation between simulated results and measured results of Type...... 8325 are below 6%. It is proved that the specifications of the accelerometer can be effectively predicted using the FE method, especially when modifications of the accelerometer are required. The development process of piezoelectric accelerometers in Brüel & Kjær is becoming more efficient...

Separation of traveling and standing waves in a finite dispersive string with partial or continuous viscoelastic foundation

Science.gov (United States)

Cheng, Xiangle; Blanchard, Antoine; Tan, Chin An; Lu, Huancai; Bergman, Lawrence A.; McFarland, D. Michael; Vakakis, Alexander F.

2017-12-01

The free and forced vibrations of a linear string with a local spring-damper on a partial elastic foundation, as well as a linear string on a viscoelastic foundation conceptualized as a continuous distribution of springs and dampers, are studied in this paper. Exact, analytical results are obtained for the free and forced response to a harmonic excitation applied at one end of the string. Relations between mode complexity and energy confinement with the dispersion in the string system are examined for the steady-state forced vibration, and numerical methods are applied to simulate the transient evolution of energy propagation. Eigenvalue loci veering and normal mode localization are observed for weakly coupled subsystems, when the foundation stiffness is sufficiently large, for both the spatially symmetric and asymmetric systems. The forced vibration results show that nonproportional damping-induced mode complexity, for which there are co-existing regions of purely traveling waves and standing waves, is attainable for the dispersive string system. However, this wave transition phenomenon depends strongly on the location of the attached discrete spring-damper relative to the foundation and whether the excitation frequency Ω is above or below the cutoff frequency ωc. When Ωcontrol strategies.

Evaluation Of Vibration-Monitoring Gear-Diagnostic System

Science.gov (United States)

Townsend, Dennis P.; Zakrajsek, James J.

1995-01-01

Report describes experimental evaluation of commercial electronic system designed to monitor vibration signal from accelerometer on gear-box to detect vibrations indicative of damage to gears. System includes signal-conditioning subsystem and personal computer in which analog-to-digital converter installed. Results show system fairly effective in detecting surface fatigue pits on spur-gear teeth.

Identification of Capacitive MEMS Accelerometer Structure Parameters for Human Body Dynamics Measurements

Directory of Open Access Journals (Sweden)

Vincas Benevicius

2013-08-01

Full Text Available Due to their small size, low weight, low cost and low energy consumption, MEMS accelerometers have achieved great commercial success in recent decades. The aim of this research work is to identify a MEMS accelerometer structure for human body dynamics measurements. Photogrammetry was used in order to measure possible maximum accelerations of human body parts and the bandwidth of the digital acceleration signal. As the primary structure the capacitive accelerometer configuration is chosen in such a way that sensing part measures on all three axes as it is 3D accelerometer and sensitivity on each axis is equal. Hill climbing optimization was used to find the structure parameters. Proof-mass displacements were simulated for all the acceleration range that was given by the optimization problem constraints. The final model was constructed in Comsol Multiphysics. Eigenfrequencies were calculated and model’s response was found, when vibration stand displacement data was fed into the model as the base excitation law. Model output comparison with experimental data was conducted for all excitation frequencies used during the experiments.

Analysis of friction-induced limit cycling in an experimental drill-string system

NARCIS (Netherlands)

Mihajlovic, N.; Veggel, van A.A.; Wouw, van de N.; Nijmeijer, H.

2004-01-01

In this paper, we aim for an improved understanding of the causes for torsional vibrations that appear in rotary drilling systems used for the exploration of oil and gas. For this purpose, an experimental drill-string setup is considered. In that system, torsional vibrations with and without

Vibrations and Eigenvalues

Indian Academy of Sciences (India)

The vibrating string problem is the source of much mathe- matics and physics. ... ing this science [mechanics],and the art of solving the problems pertaining to it, to .... used tools for finding maxima and minima of functions of several variables.

Accuracy improvement in a calibration test bench for accelerometers by a vision system

International Nuclear Information System (INIS)

D’Emilia, Giulio; Di Gasbarro, David; Gaspari, Antonella; Natale, Emanuela

2016-01-01

A procedure is described in this paper for the accuracy improvement of calibration of low-cost accelerometers in a prototype rotary test bench, driven by a brushless servo-motor and operating in a low frequency range of vibrations (0 to 5 Hz). Vibration measurements by a vision system based on a low frequency camera have been carried out, in order to reduce the uncertainty of the real acceleration evaluation at the installation point of the sensor to be calibrated. A preliminary test device has been realized and operated in order to evaluate the metrological performances of the vision system, showing a satisfactory behavior if the uncertainty measurement is taken into account. A combination of suitable settings of the control parameters of the motion control system and of the information gained by the vision system allowed to fit the information about the reference acceleration at the installation point to the needs of the procedure for static and dynamic calibration of three-axis accelerometers.

Accuracy improvement in a calibration test bench for accelerometers by a vision system

Energy Technology Data Exchange (ETDEWEB)

D’Emilia, Giulio, E-mail: giulio.demilia@univaq.it; Di Gasbarro, David, E-mail: david.digasbarro@graduate.univaq.it; Gaspari, Antonella, E-mail: antonella.gaspari@graduate.univaq.it; Natale, Emanuela, E-mail: emanuela.natale@univaq.it [University of L’Aquila, Department of Industrial and Information Engineering and Economics (DIIIE), via G. Gronchi, 18, 67100 L’Aquila (Italy)

2016-06-28

A procedure is described in this paper for the accuracy improvement of calibration of low-cost accelerometers in a prototype rotary test bench, driven by a brushless servo-motor and operating in a low frequency range of vibrations (0 to 5 Hz). Vibration measurements by a vision system based on a low frequency camera have been carried out, in order to reduce the uncertainty of the real acceleration evaluation at the installation point of the sensor to be calibrated. A preliminary test device has been realized and operated in order to evaluate the metrological performances of the vision system, showing a satisfactory behavior if the uncertainty measurement is taken into account. A combination of suitable settings of the control parameters of the motion control system and of the information gained by the vision system allowed to fit the information about the reference acceleration at the installation point to the needs of the procedure for static and dynamic calibration of three-axis accelerometers.

Vibration-based SHM System: Application to Wind Turbine Blades

DEFF Research Database (Denmark)

Tcherniak, D.; Mølgaard, Lasse Lohilahti

2015-01-01

propagate along the blade and are measured by an array of accelerometers. Unsupervised learning is applied to the data: the vibration patterns corresponding to the undamaged blade are used to create a statistical model of the reference state. During the detection stage, the current vibration pattern...

Changes in vibrational properties of coated wood through ti me from application of varnish, with recipes used in European or Iranian string instruments making

OpenAIRE

Brémaud , Iris; Karami , Elham; Bardet , Sandrine; Gilles , Nicolas; Perego , François; Zare , Samad; Gril , Joseph ,

2016-01-01

International audience; The influence of vanishing process on the vibrational properties of the wood+coating systems was studied using different types and recipes of instrument making varnishes, used in traditional Iranian string instruments making, or in European violin-quartet making. The focus is on the time evolution of these properties, that can be involved in the changing behaviour of newly made instruments. The different tested varnishes recipes were applied on wood representative of e...

Melde's Experiment on a Vibrating Liquid Foam Microchannel

Science.gov (United States)

Cohen, Alexandre; Fraysse, Nathalie; Raufaste, Christophe

2017-12-01

We subject a single Plateau border channel to a transverse harmonic excitation, in an experiment reminiscent of the historical one by Melde on vibrating strings, to study foam stability and wave properties. At low driving amplitudes, the liquid string exhibits regular oscillations. At large ones, a nonlinear regime appears and the acoustic radiation splits the channel into two zones of different cross section area, vibration amplitude, and phase difference with the neighboring soap films. The channel experiences an inertial dilatancy that is accounted for by a new Bernoulli-like relation.

Research In Diagnosing Bearing Defects From Vibrations

Science.gov (United States)

Zoladz, T.; Earhart, E.; Fiorucci, T.

1995-01-01

Report describes research in bearing-defect signature analysis - use of vibration-signal analysis to diagnose defects in roller and ball bearings. Experiments performed on bearings in good condition and other bearings in which various parts scratched to provide known defects correlated with vibration signals. Experiments performed on highly instrumented motor-driven rotor assembly at speeds up to 10,050 r/min, using accelerometers, velocity probes, and proximity sensors mounted at various locations on assembly to measure vibrations.

Vibration control for the ARGOS laser launch path

Science.gov (United States)

Peter, Diethard; Gässler, Wolfgang; Borelli, Jose; Barl, Lothar; Rabien, S.

2012-07-01

Present and future adaptive optics systems aim for the correction of the atmospheric turbulence over a large field of view combined with large sky coverage. To achieve this goal the telescope is equipped with multiple laser beacons. Still, to measure tip-tilt aberrations a natural guide star is used. For some fields such a tilt-star is not available and a correction on the laser beacons alone is applied. For this method to work well the laser beacons must not be affected by telescope vibrations on their up-link path. For the ARGOS system the jitter of the beacons is specified to be below 0.05. To achieve this goal a vibration compensation system is necessary to mitigate the mechanical disturbances. The ARGOS vibration compensation system is an accelerometer based feed forward system. The accelerometer measurements are fed into a real time controller. To achieve high performance the controller of the system is model based. The output is applied to a fast steering mirror. This paper presents the concept of the ARGOS vibration compensation, the hardware, and laboratory results.

Fault Diagnosis using Audio and Vibration Signals in a Circulating Pump

International Nuclear Information System (INIS)

Henríquez, P; Alonso, J B; Ferrer, M A; Travieso, C M; Gómez, G

2012-01-01

This paper presents the use of audio and vibration signals in fault diagnosis of a circulating pump. The novelty of this paper is the use of audio signals acquired by microphones. The objective of this paper is to determine if audio signals are capable to distinguish between normal and different abnormal conditions in a circulating pump. In order to compare results, vibration signals are also acquired and analysed. Wavelet package is used to obtain the energies in different frequency bands from the audio and vibration signals. Neural networks are used to evaluate the discrimination ability of the extracted features between normal and fault conditions. The results show that information from sound signals can distinguish between normal and different faulty conditions with a success rate of 83.33%, 98% and 91.33% for each microphone respectively. These success rates are similar and even higher that those obtained from accelerometers (68%, 90.67% and 71.33% for each accelerometer respectively). Success rates also show that the position of microphones and accelerometers affects on the final results.

Fabrication of nano piezoelectric based vibration accelerometer for mechanical sensing

Science.gov (United States)

Murugan, S.; Prasad, M. V. N.; Jayakumar, K.

2016-05-01

An electromechanical sensor unit has been fabricated using nano PZT embedded in PVDF polymer. Such a polymer nano composite has been used as vibration sensor element and sensitivity, detection of mechanical vibration, and linearity measurements have been investigated. It is found from its performance, that this nano composite sensor is suitable for mechanical sensing applications.

Dynamic tire pressure sensor for measuring ground vibration.

Science.gov (United States)

Wang, Qi; McDaniel, James Gregory; Wang, Ming L

2012-11-07

This work presents a convenient and non-contact acoustic sensing approach for measuring ground vibration. This approach, which uses an instantaneous dynamic tire pressure sensor (DTPS), possesses the capability to replace the accelerometer or directional microphone currently being used for inspecting pavement conditions. By measuring dynamic pressure changes inside the tire, ground vibration can be amplified and isolated from environmental noise. In this work, verifications of the DTPS concept of sensing inside the tire have been carried out. In addition, comparisons between a DTPS, ground-mounted accelerometer, and directional microphone are made. A data analysis algorithm has been developed and optimized to reconstruct ground acceleration from DTPS data. Numerical and experimental studies of this DTPS reveal a strong potential for measuring ground vibration caused by a moving vehicle. A calibration of transfer function between dynamic tire pressure change and ground acceleration may be needed for different tire system or for more accurate application.

Ultraminiature resonator accelerometer

Energy Technology Data Exchange (ETDEWEB)

Koehler, D.R.; Kravitz, S.H.; Vianco, P.T.

1996-04-01

A new family of microminiature sensors and clocks is being developed with widespread application potential for missile and weapons applications, as biomedical sensors, as vehicle status monitors, and as high-volume animal identification and health sensors. To satisfy fundamental technology development needs, a micromachined clock and an accelerometer have initially been undertaken as development projects. A thickness-mode quartz resonator housed in a micromachined silicon package is used as the frequency-modulated basic component of the sensor family. Resonator design philosophy follows trapped energy principles and temperature compensation methodology through crystal orientation control, with operation in the 20--100 MHz range, corresponding to quartz wafer thicknesses in the 75--15 micron range. High-volume batch-processing manufacturing is utilized, with package and resonator assembly at the wafer level. Chemical etching of quartz, as well as micromachining of silicon, achieves the surface and volume mechanical features necessary to fashion the resonating element and the mating package. Integration of the associated oscillator and signal analysis circuitry into the silicon package is inherent to the realization of a size reduction requirement. A low temperature In and In/Sn bonding technology allows assembly of the dissimilar quartz and silicon materials, an otherwise challenging task. Unique design features include robust vibration and shock performance, capacitance sensing with micromachined diaphragms, circuit integration, capacitance-to-frequency transduction, and extremely small dimensioning. Accelerometer sensitivities were measured in the 1--3 ppm/g range for the milligram proof-mass structures employed in the prototypes evaluated to date.

Quantification of mouse in vivo whole-body vibration amplitude from motion-blur using x-ray imaging

International Nuclear Information System (INIS)

Hu, Zhengyi; Yuan, Xunhua; Pollmann, Steven I; Nikolov, Hristo N; Holdsworth, David W; Welch, Ian

2015-01-01

Musculoskeletal effects of whole-body vibration on animals and humans have become an intensely studied topic recently, due to the potential of applying this method as a non-pharmacological therapy for strengthening bones. It is relatively easy to quantify the transmission of whole-body mechanical vibration through the human skeletal system using accelerometers. However, this is not the case for small-animal pre-clinical studies because currently available accelerometers have a large mass, relative to the mass of the animals, which causes the accelerometers themselves to affect the way vibration is transmitted. Additionally, live animals do not typically remain motionless for long periods, unless they are anesthetized, and they are required to maintain a static standing posture during these studies. These challenges provide the motivation for the development of a method to quantify vibrational transmission in small animals. We present a novel imaging technique to quantify whole-body vibration transmission in small animals using 280 μm diameter tungsten carbide beads implanted into the hind limbs of mice. Employing time-exposure digital x-ray imaging, vibrational amplitude is quantified based on the blurring of the implanted beads caused by the vibrational motion. Our in vivo results have shown this technique is capable of measuring vibration amplitudes as small as 0.1 mm, with precision as small as  ±10 μm, allowing us to distinguish differences in the transmitted vibration at different locations on the hindlimbs of mice. (paper)

Quantification of mouse in vivo whole-body vibration amplitude from motion-blur using x-ray imaging

Science.gov (United States)

Hu, Zhengyi; Welch, Ian; Yuan, Xunhua; Pollmann, Steven I.; Nikolov, Hristo N.; Holdsworth, David W.

2015-08-01

Musculoskeletal effects of whole-body vibration on animals and humans have become an intensely studied topic recently, due to the potential of applying this method as a non-pharmacological therapy for strengthening bones. It is relatively easy to quantify the transmission of whole-body mechanical vibration through the human skeletal system using accelerometers. However, this is not the case for small-animal pre-clinical studies because currently available accelerometers have a large mass, relative to the mass of the animals, which causes the accelerometers themselves to affect the way vibration is transmitted. Additionally, live animals do not typically remain motionless for long periods, unless they are anesthetized, and they are required to maintain a static standing posture during these studies. These challenges provide the motivation for the development of a method to quantify vibrational transmission in small animals. We present a novel imaging technique to quantify whole-body vibration transmission in small animals using 280 μm diameter tungsten carbide beads implanted into the hind limbs of mice. Employing time-exposure digital x-ray imaging, vibrational amplitude is quantified based on the blurring of the implanted beads caused by the vibrational motion. Our in vivo results have shown this technique is capable of measuring vibration amplitudes as small as 0.1 mm, with precision as small as  ±10 μm, allowing us to distinguish differences in the transmitted vibration at different locations on the hindlimbs of mice.

High-precision and low-cost vibration generator for low-frequency calibration system

Science.gov (United States)

Li, Rui-Jun; Lei, Ying-Jun; Zhang, Lian-Sheng; Chang, Zhen-Xin; Fan, Kuang-Chao; Cheng, Zhen-Ying; Hu, Peng-Hao

2018-03-01

Low-frequency vibration is one of the harmful factors that affect the accuracy of micro-/nano-measuring machines because its amplitude is significantly small and it is very difficult to avoid. In this paper, a low-cost and high-precision vibration generator was developed to calibrate an optical accelerometer, which is self-designed to detect low-frequency vibration. A piezoelectric actuator is used as vibration exciter, a leaf spring made of beryllium copper is used as an elastic component, and a high-resolution, low-thermal-drift eddy current sensor is applied to investigate the vibrator’s performance. Experimental results demonstrate that the vibration generator can achieve steady output displacement with frequency range from 0.6 Hz to 50 Hz, an analytical displacement resolution of 3.1 nm and an acceleration range from 3.72 mm s-2 to 1935.41 mm s-2 with a relative standard deviation less than 1.79%. The effectiveness of the high-precision and low-cost vibration generator was verified by calibrating our optical accelerometer.

A mathematical model for source separation of MMG signals recorded with a coupled microphone-accelerometer sensor pair.

Science.gov (United States)

Silva, Jorge; Chau, Tom

2005-09-01

Recent advances in sensor technology for muscle activity monitoring have resulted in the development of a coupled microphone-accelerometer sensor pair for physiological acousti signal recording. This sensor can be used to eliminate interfering sources in practical settings where the contamination of an acoustic signal by ambient noise confounds detection but cannot be easily removed [e.g., mechanomyography (MMG), swallowing sounds, respiration, and heart sounds]. This paper presents a mathematical model for the coupled microphone-accelerometer vibration sensor pair, specifically applied to muscle activity monitoring (i.e., MMG) and noise discrimination in externally powered prostheses for below-elbow amputees. While the model provides a simple and reliable source separation technique for MMG signals, it can also be easily adapted to other aplications where the recording of low-frequency (< 1 kHz) physiological vibration signals is required.

Customized DSP-based vibration measurement for wind turbines

Energy Technology Data Exchange (ETDEWEB)

LaWhite, N.E.; Cohn, K.E. [Second Wind Inc., Somerville, MA (United States)

1996-12-31

As part of its Advanced Distributed Monitoring System (ADMS) project funded by NREL, Second Wind Inc. is developing a new vibration measurement system for use with wind turbines. The system uses low-cost accelerometers originally designed for automobile airbag crash-detection coupled with new software executed on a Digital Signal Processor (DSP) device. The system is envisioned as a means to monitor the mechanical {open_quotes}health{close_quotes} of the wind turbine over its lifetime. In addition the system holds promise as a customized emergency vibration detector. The two goals are very different and it is expected that different software programs will be executed for each function. While a fast Fourier transform (FFT) signature under given operating conditions can yield much information regarding turbine condition, the sampling period and processing requirements make it inappropriate for emergency condition monitoring. This paper briefly reviews the development of prototype DSP and accelerometer hardware. More importantly, it reviews our work to design prototype vibration alarm filters. Two-axis accelerometer test data from the experimental FloWind vertical axis wind turbine is analyzed and used as a development guide. Two levels of signal processing are considered. The first uses narrow band pre-processing filters at key fundamental frequencies such as the 1P, 2P and 3P. The total vibration energy in each frequency band is calculated and evaluated as a possible alarm trigger. In the second level of signal processing, the total vibration energy in each frequency band is further decomposed using the two-axis directional information. Directional statistics are calculated to differentiate between linear translations and circular translations. After analyzing the acceleration statistics for normal and unusual operating conditions, the acceleration processing system described could be used in automatic early detection of fault conditions. 9 figs.

ACCELEROMETERS IN FLOW FIELDS: A STRUCTURAL ANALYSIS OF THE CHOPPED DUMMY INPILE TUBE

Energy Technology Data Exchange (ETDEWEB)

Howard, T. K.; Marcum, W. R.; Latimer, G. D.; Weiss, A.; Jones, W. F.; Phillips, A. M.; Woolstenhulme, N.; Holdaway, K.; Campbell, J.

2016-06-01

Four tests characterizing the structural response of the Chopped-Dummy In-Pile tube (CDIPT) experiment design were measured in the Hydro-Mechanical Fuel Test Facility (HMFTF). Four different test configurations were tried. These configurations tested the pressure drop and flow impact of various plate configurations and flow control orifices to be used later at different reactor power levels. Accelerometers were placed on the test vehicle and flow simulation housing. A total of five accelerometers were used with one on the top and bottom of the flow simulator and vehicle, and one on the outside of the flow simulator. Data were collected at a series of flow rates for 5 seconds each at an acquisition rate of 2 kHz for a Nyquist frequency of 1 kHz. The data were then analyzed using a Fast Fourier Transform (FFT) algorithm. The results show very coherent vibrations of the CDIPT experiment on the order of 50 Hz in frequency and 0.01 m/s2 in magnitude. The coherent vibrations, although small in magnitude pose a potential design problem if the frequencies coincide with the natural frequency of the fueled plates or test vehicle. The accelerometer data was integrated and combined to create a 3D trace of the experiment during the test. The merits of this data as well as further anomalies and artifacts are also discussed as well as their relation to the instrumentation and experiment design.

System for Monitoring and Analysis of Vibrations at Electric Motors

OpenAIRE

Gabriela Rață; Mihai Rață

2014-01-01

The monitoring of vibration occurring at the electric motors is of paramount importance to ensure their optimal functioning. This paper presents a monitoring system of vibrations occurring at two different types of electric motors, using a piezoelectric accelerometer (ICP 603C11) and a data acquisition board from National Instruments (NI 6009). Vibration signals taken from different parts of electric motors are transferred to computer through the acquisition board. A virtual...

Feasibility of heart sounds measurements from an accelerometer within an ICD pulse generator.

Science.gov (United States)

Siejko, Krzysztof Z; Thakur, Pramodsingh H; Maile, Keith; Patangay, Abhilash; Olivari, Maria-Teresa

2013-03-01

The feasibility of detecting heart sounds (HS) from an accelerometer sensor enclosed within an implantable cardioverter defibrillator (ICD) pulse generator (PG) was explored in a noninvasive pilot study on heart failure (HF) patients with audible third HS (S3). Accelerometer circuitry enhanced for HS was incorporated into non-functional ICDs. A study was conducted on 30 HF patients and 10 normal subjects without history of cardiac disease. The devices were taped to the skin surface over both left and right pectoral regions to simulate subcutaneous implants. A lightweight reference accelerometer was taped over the cardiac apex. Waveforms were recorded simultaneously with a surface electrocardiogram for 2 minutes. Algorithms were developed to perform off-line automatic detection of HS and HS time intervals (HSTIs). S1, S2, and S3 vibrations were detected in all accelerometer locations for all 40 subjects, including 16 subjects without an audible S3. A substantial proportion of S3 energy was infrasonic (remote ambulatory monitoring of HF progression and the detection of the onset of HF decompensation. ©2012, The Authors. Journal compilation ©2012 Wiley Periodicals, Inc.

Non-material finite element modelling of large vibrations of axially moving strings and beams

Science.gov (United States)

Vetyukov, Yury

2018-02-01

We present a new mathematical model for the dynamics of a beam or a string, which moves in a given axial direction across a particular domain. Large in-plane vibrations are coupled with the gross axial motion, and a Lagrangian (material) form of the equations of structural mechanics becomes inefficient. The proposed mixed Eulerian-Lagrangian description features mechanical fields as functions of a spatial coordinate in the axial direction. The material travels across a finite element mesh, and the boundary conditions are applied in fixed nodes. Beginning with the variational equation of virtual work in its material form, we analytically derive the Lagrange's equations of motion of the second kind for the considered case of a discretized non-material control domain and for geometrically exact kinematics. The dynamic analysis is straightforward as soon as the strain and the kinetic energies of the control domain are available. In numerical simulations we demonstrate the rapid mesh convergence of the model, the effect of the bending stiffness and the dynamic instability when the axial velocity gets high. We also show correspondence to the results of fully Lagrangian benchmark solutions.

Fourier Analysis of a Vibrating String through a Low-Cost Experimental Setup and a Smartphone

Science.gov (United States)

Pereyra, C. J.; Osorio, M.; Laguarda, A.; Gau, D. L.

2018-01-01

In this work we present a simple and low-cost setup to illustrate the dependence of the behaviour of a standing wave in a guitar string with the initial conditions. To do so, we impose two kinds of initial conditions; in the first instance, the initial shape of the string is varied. Secondly, different nodes are imposed on the string. This…

Vibration analysis of the sulky accessory for a commercial walk-behind lawn mower to determine operator comfort and health.

Science.gov (United States)

Thrailkill, Elizabeth A; Lowndes, Bethany R; Hallbeck, M Susan

2013-01-01

A sulky is a single-wheeled platform attachment on which the operator of a commercial walk-behind lawn mower rides while standing. The effects of sulky vibration on operator comfort and health have not been investigated. In this study, tri-axial accelerometers measured sulky vibration during mower use by two commercial mowers on varied terrain and 12 volunteer mowers over a controlled course. The accelerometer data were processed according to methods established in ISO 2631. Results indicate the mean frequency-weighted root mean square (RMS) acceleration sums fall into the 'very uncomfortable' range for vibration of standing persons (1.9 ± 0.48 m s⁻²). Additionally, vibration dose values indicated that the mean vibration dosages exceeded the daily exposure limit values established in Directive 2002 /44/EC (z-axis A(8) value of 1.30 ± 34 m s⁻²; VDV(exp) value of 28.1 ± 6.25 m s⁻¹·⁷⁵). This information suggests that modifications including vibration damping should be added to the sulky to reduce rider discomfort and health risks. This study investigated the effects of vibration during use of a commercial lawn mowing sulky. Findings from accelerometer data suggest that the vibration experienced by sulky operators is significant enough to cause discomfort and health risks which may lead to personnel turnover or long-term effects for the operator.

System for Monitoring and Analysis of Vibrations at Electric Motors

Directory of Open Access Journals (Sweden)

Gabriela Rață

2014-09-01

Full Text Available The monitoring of vibration occurring at the electric motors is of paramount importance to ensure their optimal functioning. This paper presents a monitoring system of vibrations occurring at two different types of electric motors, using a piezoelectric accelerometer (ICP 603C11 and a data acquisition board from National Instruments (NI 6009. Vibration signals taken from different parts of electric motors are transferred to computer through the acquisition board. A virtual instrument that allows real-time monitoring and Fourier analysis of signals from the vibration sensor was implemented in LabVIEW.

VibeComm: Radio-Free Wireless Communication for Smart Devices Using Vibration

Directory of Open Access Journals (Sweden)

Inhwan Hwang

2014-11-01

Full Text Available This paper proposes VibeComm, a novel communication method for smart devices using a built-in vibrator and accelerometer. The proposed approach is ideal for low-rate off-line communication, and its communication medium is an object on which smart devices are placed, such as tables and desks. When more than two smart devices are placed on an object and one device wants to transmit a message to the other devices, the transmitting device generates a sequence of vibrations. The vibrations are propagated through the object on which the devices are placed. The receiving devices analyze their accelerometer readings to decode incoming messages. The proposed method can be the alternative communication method when general types of radio communication methods are not available. VibeComm is implemented on Android smartphones, and a comprehensive set of experiments is conducted to show its feasibility.

击弦乐器乐声特性与演奏手法的关系%Relationship between hammered string instrument musical sound characteristic and playing skills

Institute of Scientific and Technical Information of China (English)

任静锋; 王旸; 龙姝明

2012-01-01

给定初值条件,解弦振动波动定解问题,计算演奏手法变化引起的击弦乐器振动驻波能谱结构变化.探索击弦乐器乐声的音调、音色与弦振动驻波能谱结构的关系.用Mathematica编程模拟击弦乐器弦振动乐声,用听觉体验和频谱分析研究击弦乐器音调、音色与演奏手法的关系.%Given initial conditions, string vibration wave problem was solved. By changing playing techniques, calculation of the change caused by hammered string instrument vibration energy spectrum. Explore the relationship of the hammered string instrument tone and timbre and string vibration energy spectrum was exploved. Mathematics programming was used to simulate the hammered string instrument music. By auditory experience and spectrum analysis, the relationship between the hammered string instrument tone and timbre and playing techniques was studied.

Interacting-string picture of the fermionic string

International Nuclear Information System (INIS)

Mandelstam, S.

1986-01-01

This report gives a review of the interacting-string picture of the Bose string. In the present lecture, the author outlines a similar treatment of the Fermionic string. The quantization of the free Fermionic string is carried out to the degrees of freedom x, representing the displacement of the string. Also presented are Grassman degrees of freedom S distributed along the string. The report pictures the fermionic string as a string of dipoles. The general picture of the interaction of such strings by joining and splitting is the same as for the Bose string. The author does not at present have the simplest formula for fermion string scattering amplitudes. A less detailed treatment is given than for the Bose string. The report sets up the functional-integration formalism, derives the analog mode, and indicates in general, terms how the conformal transformation to the z-plane may be performed. The paper concludes by stating without proof the formula for the N-article tree amplitude in the manifestly supersymmetric formalism

An Inverse Eigenvalue Problem for a Vibrating String with Two Dirichlet Spectra

KAUST Repository

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.

Characterization and synthesis of random acceleration vibration specifications

NARCIS (Netherlands)

Wijker, Jacob J; Ellenbroek, Marcellinus Hermannus Maria; de Boer, Andries; Papadrakakis, M.; Lagaros, N.D.; Plevris, V.

2013-01-01

Random acceleration vibration specifications for subsystems, i.e. instruments, equipment, are most times based on measurement during acoustic noise tests on system level, i.e. a spacecraft and measured by accelerometers, placed in the neighborhood of the interface between spacecraft and subsystem.

A new exact solution to the classical equations of motion of the relativistic string with massive ends

International Nuclear Information System (INIS)

Barbashov, B.M.; Chervyakov, A.M.

1991-01-01

The classical histories of the relativistic string with massive ends in space-time are examined in terms of geometric invariants of both the string world surface and world lines of the point masses at the string ends. In this formulation the string variables are completely defined by means of the constant curvatures and torsions of the endpoint trajectories which are subjected to a system of differential equations with a delayed arguments that incorporates retardation effects of the interaction of two point masses through the string. The well-known example of the rotating straight-line string with massive ends corresponds to a particular solution of this system for the constant torsions. A new exact solution for the periodic torsions of the world trajectories of the massive string ends is found. In this case the string coordinates are represented in terms of normal elliptic integrals and describe a more intricate motion including its transverse vibrations than rotation of a stretched string in a given plane. 17 refs

Failure modes and natural control time for distributed vibrating systems

International Nuclear Information System (INIS)

Reid, R.M.

1994-01-01

The eigenstructure of the Gram matrix of frequency exponentials is used to study linear vibrating systems of hyperbolic type with distributed control. Using control norm as a practical measure of controllability and the vibrating string as a prototype, it is demonstrated that hyperbolic systems have a natural control time, even when only finitely many modes are excited. For shorter control times there are identifiable control failure modes which can be steered to zero only with very high cost in control norm. Both natural control time and the associated failure modes are constructed for linear fluids, strings, and beams, making note of the essential algorithms and Mathematica code, and displaying results graphically

Micro-/nanosized cantilever beams and mass sensors under applied axial tensile/compressive force vibrating in vacuum and viscous fluid

Directory of Open Access Journals (Sweden)

Ivo Stachiv

2015-11-01

Full Text Available Vibrating micro-/nanosized cantilever beams under an applied axial force are the key components of various devices used in nanotechnology. In this study, we perform a complete theoretical investigation of the cantilever beams under an arbitrary value of the axial force vibrating in a specific environment such as vacuum, air or viscous fluid. Based on the results easy accessible expressions enabling one the fast and highly accurate estimations of changes in the Q-factor and resonant frequencies of beam oscillating in viscous fluid caused by the applied axial force are derived and analyzed. It has been also shown that for beam-to-string and string vibrational regimes the mode shape starts to significantly deviate from the one known for a beam without axial force. Moreover, a linear dependency of the vibrational amplitude in resonance on the dimensionless tension parameter has been found. We revealed that only a large axial force, i.e. the string vibrational regime, significantly improves the Q-factor of beams submerged in fluid, while an increase of the axial force in beam and beam-to-string transition regimes has a negligibly small impact on the Q-factor enhancement. Experiments carried out on the carbon nanotubes and nanowires are in a good agreement with present theoretical predictions.

Evaluation of MEMS-Based Wireless Accelerometer Sensors in Detecting Gear Tooth Faults in Helicopter Transmissions

Science.gov (United States)

Lewicki, David George; Lambert, Nicholas A.; Wagoner, Robert S.

2015-01-01

The diagnostics capability of micro-electro-mechanical systems (MEMS) based rotating accelerometer sensors in detecting gear tooth crack failures in helicopter main-rotor transmissions was evaluated. MEMS sensors were installed on a pre-notched OH-58C spiral-bevel pinion gear. Endurance tests were performed and the gear was run to tooth fracture failure. Results from the MEMS sensor were compared to conventional accelerometers mounted on the transmission housing. Most of the four stationary accelerometers mounted on the gear box housing and most of the CI's used gave indications of failure at the end of the test. The MEMS system performed well and lasted the entire test. All MEMS accelerometers gave an indication of failure at the end of the test. The MEMS systems performed as well, if not better, than the stationary accelerometers mounted on the gear box housing with regards to gear tooth fault detection. For both the MEMS sensors and stationary sensors, the fault detection time was not much sooner than the actual tooth fracture time. The MEMS sensor spectrum data showed large first order shaft frequency sidebands due to the measurement rotating frame of reference. The method of constructing a pseudo tach signal from periodic characteristics of the vibration data was successful in deriving a TSA signal without an actual tach and proved as an effective way to improve fault detection for the MEMS.

Design and characterization of a fully differential MEMS accelerometer fabricated using MetalMUMPs technology.

Science.gov (United States)

Qu, Peng; Qu, Hongwei

2013-05-02

This paper presents a fully differential single-axis accelerometer fabricated using the MetalMUMPs process. The unique structural configuration and common-centriod wiring of the metal electrodes enables a fully differential sensing scheme with robust metal sensing structures. CoventorWare is used in structural and electrical design and simulation of the fully differential accelerometer. The MUMPs foundry fabrication process of the sensor allows for high yield, good process consistency and provides 20 μm structural thickness of the sensing element, which makes the capacitive sensing eligible. In device characterization, surface profile of the fabricated device is measured using a Veeco surface profilometer; and mean and gradient residual stress in the nickel structure are calculated as approximately 94.7 MPa and -5.27 MPa/μm, respectively. Dynamic characterization of the sensor is performed using a vibration shaker with a high-end commercial calibrating accelerometer as reference. The sensitivity of the sensor is measured as 0.52 mV/g prior to off-chip amplification. Temperature dependence of the sensing capacitance is also characterized. A -0.021fF/°C is observed. The findings in the presented work will provide useful information for design of sensors and actuators such as accelerometers, gyroscopes and electrothermal actuators that are to be fabricated using MetalMUMPs technology.

Error Correction of Measured Unstructured Road Profiles Based on Accelerometer and Gyroscope Data

Directory of Open Access Journals (Sweden)

Jinhua Han

2017-01-01

Full Text Available This paper describes a noncontact acquisition system composed of several time synchronized laser height sensors, accelerometers, gyroscope, and so forth in order to collect the road profiles of vehicle riding on the unstructured roads. A method of correcting road profiles based on the accelerometer and gyroscope data is proposed to eliminate the adverse impacts of vehicle vibration and attitudes change. Because the power spectral density (PSD of gyro attitudes concentrates in the low frequency band, a method called frequency division is presented to divide the road profiles into two parts: high frequency part and low frequency part. The vibration error of road profiles is corrected by displacement data obtained through two times integration of measured acceleration data. After building the mathematical model between gyro attitudes and road profiles, the gyro attitudes signals are separated from low frequency road profile by the method of sliding block overlap based on correlation analysis. The accuracy and limitations of the system have been analyzed, and its validity has been verified by implementing the system on wheeled equipment for road profiles’ measuring of vehicle testing ground. The paper offers an accurate and practical approach to obtaining unstructured road profiles for road simulation test.

Deriving the four-string and open-closed string interactions from geometric string field theory

International Nuclear Information System (INIS)

Kaku, M.

1990-01-01

One of the questions concerning the covariant open string field theory is why there are two distinct BRST theories and why the four-string interaction appears in one version but not the other. The authors solve this mystery by showing that both theories are gauge-fixed versions of a higher gauge theory, called the geometric string field theory, with a new field, a string verbein e μσ νρ , which allows us to gauge the string length and σ parametrization. By fixing the gauge, the authors can derive the endpoint gauge (the covariantized light cone gauge), the midpoint gauge of Witten, or the interpolating gauge with arbitrary string length. The authors show explicitly that the four-string interaction is a gauge artifact of the geometric theory (the counterpart of the four-fermion instantaneous Coulomb term of QED). By choosing the interpolating gauge, they produce a new class of four-string interactions which smoothly interpolate between the endpoint gauge and the midpoint gauge (where it vanishes). Similarly, they can extract the closed string as a bound state of the open string, which appears in the endpoint gauge but vanishes in the midpoint gauge. Thus, the four-string and open-closed string interactions do not have to be added to the action as long as the string vierbein is included

Racquet string tension directly affects force experienced at the elbow: implications for the development of lateral epicondylitis in tennis players

Science.gov (United States)

Mohandhas, Badri R; Makaram, Navnit; Drew, Tim S; Wang, Weijie; Arnold, Graham P

2016-01-01

Background Lateral epicondylitis (LE) occurs in almost half of all tennis players. Racket-string tension is considered to be an important factor influencing the development of LE. No literature yet exists that substantiates how string-tension affects force transmission to the elbow, as implicated in LE development. We establish a quantitative relationship between string-tension and elbow loading, analyzing tennis strokes using rackets with varying string-tensions. Methods Twenty recreational tennis players simulated backhand tennis strokes using three rackets strung at tensions of 200 N, 222 N and 245 N. Accelerometers recorded accelerations at the elbow, wrist and racket handle. Average peak acceleration was determined to correlate string-tension with elbow loading. Results Statistically significant differences (p elbow at 200 N string-tension (acceleration of 5.58 m/s2) was compared with that at 222 N tension (acceleration of 6.83 m/s2) and 245 N tension (acceleration of 7.45 m/s2). The 200 N racket induced the least acceleration at the elbow. Conclusions Although parameters determining force transmission to the elbow during a tennis stroke are complex, the present study was able to control these parameters, isolating the effect of string-tension. Lower string-tensions transmit less force to the elbow in backhand strokes. Reducing string-tension should be considered favourably with respect to reducing the risk of developing LE. PMID:27583017

Racquet string tension directly affects force experienced at the elbow: implications for the development of lateral epicondylitis in tennis players.

Science.gov (United States)

Mohandhas, Badri R; Makaram, Navnit; Drew, Tim S; Wang, Weijie; Arnold, Graham P; Abboud, Rami J

2016-07-01

Lateral epicondylitis (LE) occurs in almost half of all tennis players. Racket-string tension is considered to be an important factor influencing the development of LE. No literature yet exists that substantiates how string-tension affects force transmission to the elbow, as implicated in LE development. We establish a quantitative relationship between string-tension and elbow loading, analyzing tennis strokes using rackets with varying string-tensions. Twenty recreational tennis players simulated backhand tennis strokes using three rackets strung at tensions of 200 N, 222 N and 245 N. Accelerometers recorded accelerations at the elbow, wrist and racket handle. Average peak acceleration was determined to correlate string-tension with elbow loading. Statistically significant differences (p < 0.05) were observed when average peak acceleration at the elbow at 200 N string-tension (acceleration of 5.58 m/s(2)) was compared with that at 222 N tension (acceleration of 6.83 m/s(2)) and 245 N tension (acceleration of 7.45 m/s(2)). The 200 N racket induced the least acceleration at the elbow. Although parameters determining force transmission to the elbow during a tennis stroke are complex, the present study was able to control these parameters, isolating the effect of string-tension. Lower string-tensions transmit less force to the elbow in backhand strokes. Reducing string-tension should be considered favourably with respect to reducing the risk of developing LE.

Honeybee Colony Vibrational Measurements to Highlight the Brood Cycle.

Directory of Open Access Journals (Sweden)

Martin Bencsik

Full Text Available Insect pollination is of great importance to crop production worldwide and honey bees are amongst its chief facilitators. Because of the decline of managed colonies, the use of sensor technology is growing in popularity and it is of interest to develop new methods which can more accurately and less invasively assess honey bee colony status. Our approach is to use accelerometers to measure vibrations in order to provide information on colony activity and development. The accelerometers provide amplitude and frequency information which is recorded every three minutes and analysed for night time only. Vibrational data were validated by comparison to visual inspection data, particularly the brood development. We show a strong correlation between vibrational amplitude data and the brood cycle in the vicinity of the sensor. We have further explored the minimum data that is required, when frequency information is also included, to accurately predict the current point in the brood cycle. Such a technique should enable beekeepers to reduce the frequency with which visual inspections are required, reducing the stress this places on the colony and saving the beekeeper time.

The vibration compensation system for ARGOS

Science.gov (United States)

Peter, D.; Gaessler, W.; Borelli, J.; Kulas, M.

2011-09-01

For every adaptive optics system telescope vibrations can strongly reduce the performance. This is true for the receiver part of the system i.e. the telescope and wave front sensor part as well as for the transmitter part in the case of a laser guide star system. Especially observations in deep fields observed with a laser guide star system without any tip-tilt star will be greatly spoiled by telescope vibrations. The ARGOS GLAO system actually being built for the LBT aims to implement this kind of mode where wave front correction will rely purely on signals from the laser beacons. To remove the vibrations from the uplink path a vibration compensation system will be installed. This system uses accelerometers to measure the vibrations and corrects their effect with a small fast tip-tilt mirror. The controller of the system is built based on the assumption that the vibrations take place at a few distinct frequencies. Here I present a lab set-up of this system and show first results of the performance.

Compact Circuit Preprocesses Accelerometer Output

Science.gov (United States)

Bozeman, Richard J., Jr.

1993-01-01

Compact electronic circuit transfers dc power to, and preprocesses ac output of, accelerometer and associated preamplifier. Incorporated into accelerometer case during initial fabrication or retrofit onto commercial accelerometer. Made of commercial integrated circuits and other conventional components; made smaller by use of micrologic and surface-mount technology.

Violin Pedagogy and the Physics of the Bowed String

Science.gov (United States)

McLeod, Alexander Rhodes

The paper describes the mechanics of violin tone production using non-specialist language, in order to present a scientific understanding of tone production accessible to a broad readership. As well as offering an objective understanding of tone production, this model provides a powerful tool for analyzing the technique of string playing. The interaction between the bow and the string is quite complex. Literature reviewed for this study reveals that scientific investigations have provided important insights into the mechanics of string playing, offering explanations for factors which both contribute to and limit the range of tone colours and dynamics that stringed instruments can produce. Also examined in the literature review are significant works of twentieth century violin pedagogy exploring tone production on the violin, based on the practical experience of generations of teachers and performers. Hermann von Helmholtz described the stick-slip cycle which drives the string in 1863, which replaced earlier ideas about the vibration of violin strings. Later, scientists such as John Schelleng and Lothar Cremer were able to demonstrate how the mechanics of the bow-string interaction can create different tone colours. Recent research by Anders Askenfelt, Knut Guettler, and Erwin Schoonderwaldt have continued to refine earlier research in this area. The writings of Lucien Capet, Leopold Auer, Carl Flesch, Paul Rolland, Kato Havas, Ivan Galamian, and Simon Fischer are examined and analyzed. Each author describes a different approach to tone production on the violin, representing a different understanding of the underlying mechanism. Analyzing these writings within the context of a scientific understanding of tone production makes it possible to compare these approaches more consistently, and to synthesize different concepts drawn from the diverse sources evaluated.

Piezoelectric accelerometers with integral electronics

CERN Document Server

Levinzon, Felix

2014-01-01

This book provides an invaluable reference to Piezoelectric Accelerometers with Integral Electronics (IEPE). It describes the design and performance parameters of IEPE accelerometers and their key elements, PE transducers and FET-input amplifiers. Coverage includes recently designed, low-noise and high temperature IEPE accelerometers. Readers will benefit from the detailed noise analysis of the IEPE accelerometer, which enables estimation of its noise floor and noise limits. Other topics useful for designers of low-noise, high temperature silicon-based electronics include noise analysis of FET

Design and Characterization of a Fully Differential MEMS Accelerometer Fabricated Using MetalMUMPs Technology

Directory of Open Access Journals (Sweden)

Hongwei Qu

2013-05-01

Full Text Available This paper presents a fully differential single-axis accelerometer fabricated using the MetalMUMPs process. The unique structural configuration and common-centriod wiring of the metal electrodes enables a fully differential sensing scheme with robust metal sensing structures. CoventorWare is used in structural and electrical design and simulation of the fully differential accelerometer. The MUMPs foundry fabrication process of the sensor allows for high yield, good process consistency and provides 20 μm structural thickness of the sensing element, which makes the capacitive sensing eligible. In device characterization, surface profile of the fabricated device is measured using a Veeco surface profilometer; and mean and gradient residual stress in the nickel structure are calculated as approximately 94.7 MPa and −5.27 MPa/μm, respectively. Dynamic characterization of the sensor is performed using a vibration shaker with a high-end commercial calibrating accelerometer as reference. The sensitivity of the sensor is measured as 0.52 mV/g prior to off-chip amplification. Temperature dependence of the sensing capacitance is also characterized. A −0.021fF/°C is observed. The findings in the presented work will provide useful information for design of sensors and actuators such as accelerometers, gyroscopes and electrothermal actuators that are to be fabricated using MetalMUMPs technology.

Topographic analysis of the skull vibration-induced nystagmus test with piezoelectric accelerometers and force sensors.

Science.gov (United States)

Dumas, Georges; Lion, Alexis; Perrin, Philippe; Ouedraogo, Evariste; Schmerber, Sébastien

2016-03-23

Vibration-induced nystagmus is elicited by skull or posterior cervical muscle stimulations in patients with vestibular diseases. Skull vibrations delivered by the skull vibration-induced nystagmus test are known to stimulate the inner ear structures directly. This study aimed to measure the vibration transfer at different cranium locations and posterior cervical regions to contribute toward stimulus topographic optimization (experiment 1) and to determine the force applied on the skull with a hand-held vibrator to study the test reproducibility and provide recommendations for good clinical practices (experiment 2). In experiment 1, a 100 Hz hand-held vibrator was applied on the skull (vertex, mastoids) and posterior cervical muscles in 11 healthy participants. Vibration transfer was measured by piezoelectric sensors. In experiment 2, the vibrator was applied 30 times by two experimenters with dominant and nondominant hands on a mannequin equipped to measure the force. Experiment 1 showed that after unilateral mastoid vibratory stimulation, the signal transfer was higher when recorded on the contralateral mastoid than on the vertex or posterior cervical muscles (Pskull vibration-induced nystagmus test in patients with unilateral vestibular lesions and enables a stronger stimulation of the healthy side. In clinical practice, the vibrator should be placed on the mastoid and should be held by the clinician's dominant hand.

Testing of Tools for Measurement Vibration in Car

Directory of Open Access Journals (Sweden)

Martin JURÁNEK

2009-06-01

Full Text Available This work is specialized on testing of several sensors for measurement vibration, that be applicable for measurement on vehicles also behind running. These sensors are connected to PC and universal mobile measuring system cRIO (National Instruments with analog I/O module for measurement vibration, that is described in diploma work: [JURÁNEK 2008]. This system has upped mechanical and heat imunity, small proportions and is therefore acceptable also measurement behind ride vehicles. It compose from two head parts. First is measuring part, composite from instruments cRIO. First part is controlled and monitored by PDA there is connected of wireless (second part hereof system. To system cRIO is possible connect sensors by four BNC connector or after small software change is possible add sensor to other analog modul cRIO. Here will be test several different types of accelerometers (USB sensor company Phidgets, MEMS sensor company Freescale, piezoresistiv and Delta Tron accelerometers company Brüel&Kjær. These sensors is attach to stiff board, board is attach to vibrator and excite by proper signal. Testing will realized with reference to using for measurement in cars. Results will be compared with professional signal analyser LabShop pulse from company Brüel&Kjær.

A comparison between swallowing sounds and vibrations in patients with dysphagia

Science.gov (United States)

Movahedi, Faezeh; Kurosu, Atsuko; Coyle, James L.; Perera, Subashan

2017-01-01

The cervical auscultation refers to the observation and analysis of sounds or vibrations captured during swallowing using either a stethoscope or acoustic/vibratory detectors. Microphones and accelerometers have recently become two common sensors used in modern cervical auscultation methods. There are open questions about whether swallowing signals recorded by these two sensors provide unique or complementary information about swallowing function; or whether they present interchangeable information. The aim of this study is to present a broad comparison of swallowing signals recorded by a microphone and a tri-axial accelerometer from 72 patients (mean age 63.94 ± 12.58 years, 42 male, 30 female), who underwent videofluoroscopic examination. The participants swallowed one or more boluses of thickened liquids of different consistencies, including thin liquids, nectar-thick liquids, and pudding. A comfortable self-selected volume from a cup or a controlled volume by the examiner from a 5ml spoon was given to the participants. A comprehensive set of features was extracted in time, information-theoretic, and frequency domains from each of 881 swallows presented in this study. The swallowing sounds exhibited significantly higher frequency content and kurtosis values than the swallowing vibrations. In addition, the Lempel-Ziv complexity was lower for swallowing sounds than those for swallowing vibrations. To conclude, information provided by microphones and accelerometers about swallowing function are unique and these two transducers are not interchangeable. Consequently, the selection of transducer would be a vital step in future studies. PMID:28495001

Wavy strings: Black or bright?

International Nuclear Information System (INIS)

Kaloper, N.; Myers, R.C.; Roussel, H.

1997-01-01

Recent developments in string theory have brought forth considerable interest in time-dependent hair on extended objects. This novel new hair is typically characterized by a wave profile along the horizon and angular momentum quantum numbers l,m in the transverse space. In this work, we present an extensive treatment of such oscillating black objects, focusing on their geometric properties. We first give a theorem of purely geometric nature, stating that such wavy hair cannot be detected by any scalar invariant built out of the curvature and/or matter fields. However, we show that the tidal forces detected by an infalling observer diverge at the open-quotes horizonclose quotes of a black string superposed with a vibration in any mode with l≥1. The same argument applied to longitudinal (l=0) waves detects only finite leading-order tidal forces. We also provide an example with a manifestly smooth metric, proving that at least a certain class of these longitudinal waves have regular horizons. copyright 1997 The American Physical Society

Parameter definition using vibration prediction software leads to significant drilling performance improvements

Energy Technology Data Exchange (ETDEWEB)

Amorim, Dalmo; Hanley, Chris Hanley; Fonseca, Isaac; Santos, Juliana [National Oilwell Varco, Houston TX (United States); Leite, Daltro J.; Borella, Augusto; Gozzi, Danilo [Petroleo Brasileiro S.A. (PETROBRAS), Rio de Janeiro, RJ (Brazil)

2012-07-01

The understanding and mitigation of downhole vibration has been a heavily researched subject in the oil industry as it results in more expensive drilling operations, as vibrations significantly diminish the amount of effective drilling energy available to the bit and generate forces that can push the bit or the Bottom Hole Assembly (BHA) off its concentric axis of rotation, producing high magnitude impacts with the borehole wall. In order to drill ahead, a sufficient amount of energy must be supplied by the rig to overcome the resistance of the drilling system, including the reactive torque of the system, drag forces, fluid pressure losses and energy dissipated by downhole vibrations, then providing the bit with the energy required to fail the rock. If the drill string enters resonant modes of vibration, not only does it decreases the amount of available energy to drill, but increases the potential for catastrophic downhole equipment and drilling bit failures. In this sense, the mitigation of downhole vibrations will result in faster, smoother, and cheaper drilling operations. A software tool using Finite Element Analysis (FEA) has been developed to provide better understanding of downhole vibration phenomena in drilling environments. The software tool calculates the response of the drilling system at various input conditions, based on the design of the wellbore along with the geometry of the Bottom Hole Assembly (BHA) and the drill string. It identifies where undesired levels of resonant vibration will be driven by certain combinations of specific drilling parameters, and also which combinations of drilling parameters will result in lower levels of vibration, so the least shocks, the highest penetration rate and the lowest cost per foot can be achieved. With the growing performance of personal computers, complex software systems modeling the drilling vibrations using FEA has been accessible to a wider audience of field users, further complimenting with real time

Quantitative Accelerated Life Testing of MEMS Accelerometers.

Science.gov (United States)

Bâzu, Marius; Gălăţeanu, Lucian; Ilian, Virgil Emil; Loicq, Jerome; Habraken, Serge; Collette, Jean-Paul

2007-11-20

Quantitative Accelerated Life Testing (QALT) is a solution for assessing thereliability of Micro Electro Mechanical Systems (MEMS). A procedure for QALT is shownin this paper and an attempt to assess the reliability level for a batch of MEMSaccelerometers is reported. The testing plan is application-driven and contains combinedtests: thermal (high temperature) and mechanical stress. Two variants of mechanical stressare used: vibration (at a fixed frequency) and tilting. Original equipment for testing at tiltingand high temperature is used. Tilting is appropriate as application-driven stress, because thetilt movement is a natural environment for devices used for automotive and aerospaceapplications. Also, tilting is used by MEMS accelerometers for anti-theft systems. The testresults demonstrated the excellent reliability of the studied devices, the failure rate in the"worst case" being smaller than 10 -7 h -1 .

Influence of Installation Errors On the Output Data of the Piezoelectric Vibrations Transducers

Science.gov (United States)

Kozuch, Barbara; Chelmecki, Jaroslaw; Tatara, Tadeusz

2017-10-01

The paper examines an influence of installation errors of the piezoelectric vibrations transducers on the output data. PCB Piezotronics piezoelectric accelerometers were used to perform calibrations by comparison. The measurements were performed with TMS 9155 Calibration Workstation version 5.4.0 at frequency in the range of 5Hz - 2000Hz. Accelerometers were fixed on the calibration station in a so-called back-to-back configuration in accordance with the applicable international standard - ISO 16063-21: Methods for the calibration of vibration and shock transducers - Part 21: Vibration calibration by comparison to a reference transducer. The first accelerometer was calibrated by suitable methods with traceability to a primary reference transducer. Each subsequent calibration was performed when changing one setting in relation to the original calibration. The alterations were related to negligence and failures in relation to the above-mentioned standards and operating guidelines - e.g. the sensor was not tightened or appropriate substance was not placed. Also, there was modified the method of connection which was in the standards requirements. Different kind of wax, light oil, grease and other assembly methods were used. The aim of the study was to verify the significance of standards requirements and to estimate of their validity. The authors also wanted to highlight the most significant calibration errors. Moreover, relation between various appropriate methods of the connection was demonstrated.

Role of curvatures in determining the characteristics of a string vibrating against a doubly curved obstacle

Science.gov (United States)

Singh, Harkirat; Wahi, Pankaj

2017-08-01

The motion of a string in the presence of a doubly curved obstacle is investigated. A mathematical model has been developed for a general shape of the obstacle. However, detailed analysis has been performed for a shape relevant to the Indian stringed musical instruments like Tanpura and Sitar. In particular, we explore the effect of obstacle's curvature in the plane perpendicular to the string axis on its motion. This geometrical feature of the obstacle introduces a coupling between motions in mutually perpendicular directions over and above the coupling due to the stretching nonlinearity. We find that only one planar motion is possible for our system. Small amplitude planar motions are stable to perturbations in the perpendicular direction resulting in non-whirling motions while large amplitude oscillations lead to whirling motions. The critical amplitude of oscillations, across which there is a transition in the qualitative behavior of the non-planar trajectories, is determined using Floquet theory. Our analysis reveals that a small obstacle curvature in a direction perpendicular to the string axis leads to a considerable reduction in the critical amplitudes required for initiation of whirling motions. Hence, this obstacle curvature has a destabilizing effect on the planar motions in contrast to the curvature along the string axis which stabilizes planar motions.

Exactly soluble dynamics of (p,q) string near macroscopic fundamental strings

International Nuclear Information System (INIS)

Bak, Dongsu; Rey, Soojong; Yee, Houng

2004-01-01

We study dynamics of type-IIB bound-state of a Dirichlet string and n fundamental strings in the background of N fundamental strings. Because of supergravity potential, the bound-state string is pulled to the background fundamental strings, whose motion is described by open string rolling radion field. The string coupling can be made controllably weak and, in the limit 1 2 st n 2 st N, the bound-state energy involved is small compared to the string scale. We thus propose rolling dynamics of open string radion in this system as an exactly solvable analog for rolling dynamics of open string tachyon in decaying D-brane. The dynamics bears a novel feature that the worldsheet electric field increases monotonically to the critical value as the bound-state string falls into the background string. Close to the background string, D string constituent inside the bound-state string decouples from fundamental string constituents. (author)

Does a String-Particle Dualism Indicate the Uncertainty Principle's Philosophical Dichotomy?

Science.gov (United States)

Mc Leod, David; Mc Leod, Roger

2007-04-01

String theory may allow resonances of neutrino-wave-strings to account for all experimentally detected phenomena. Particle theory logically, and physically, provides an alternate, contradictory dualism. Is it contradictory to symbolically and simultaneously state that λp = h, but, the product of position and momentum must be greater than, or equal to, the same (scaled) Plank's constant? Our previous electron and positron models require `membrane' vibrations of string-linked neutrinos, in closed loops, to behave like traveling waves, Tws, intermittently metamorphosing into alternately ascending and descending standing waves, Sws, between the nodes, which advance sequentially through 360 degrees. Accumulated time passages as Tws detail required ``loop currents'' supplying magnetic moments. Remaining time partitions into the Sws' alternately ascending and descending phases: the physical basis of the experimentally established 3D modes of these ``particles.'' Waves seem to indicate that point mass cannot be required to exist instantaneously at one point; Mott's and Sneddon's Wave Mechanics says that a constant, [mass], is present. String-like resonances may also account for homeopathy's efficacy, dark matter, and constellations' ``stick-figure projections,'' as indicated by some traditional cultures, all possibly involving neutrino strings. To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.NES07.C2.5

BRST invariant mixed string vertex for the bosonic string

International Nuclear Information System (INIS)

Clarizia, A.; Pezzella, F.

1987-09-01

We construct a BRST invariant (N+M)-string vertex including both open and closed string states. When we saturate it with N open string and M closed string physical states it reproduces their corresponding scattering amplitude. As a particular case we obtain BRST invariant vertex for the open-closed string transition. (orig.)

Calibration of tri-axial MEMS accelerometers in the low-frequency range – Part 2: Uncertainty assessment

Directory of Open Access Journals (Sweden)

G. D'Emilia

2018-05-01

Full Text Available A comparison among three methods for the calibration of tri-axial accelerometers, in particular MEMS, is presented in this paper, paying attention to the uncertainty assessment of each method. The first method is performed according to the ISO 16063 standards. Two innovative methods are analysed, both suitable for in-field application. The effects on the whole uncertainty of the following aspects have been evaluated: the test bench performances in realizing the reference motion, the vibration reference sensor, the geometrical parameters and the data processing techniques. The uncertainty contributions due to the offset and the transverse sensitivity are also studied, by calibrating two different types of accelerometers, a piezoelectric one and a capacitive one, to check their effect on the accuracy of the methods under comparison. The reproducibility of methods is demonstrated. Relative uncertainty of methods ranges from 3 to 5 %, depending on the complexity of the model and of the requested operations. The results appear promising for low-cost calibration of new tri-axial accelerometers of MEMS type.

Introduction to string theory and string compactifications

International Nuclear Information System (INIS)

GarcIa-Compean, Hugo

2005-01-01

Basics of some topics on perturbative and non-perturbative string theory are reviewed. After a mathematical survey of the Standard Model of particle physics and GUTs, the bosonic string kinematics for the free case and with interaction is described. The effective action of the bosonic string and the spectrum is also discussed. T-duality in closed and open strings and the definition of D-brane are surveyed. Five perturbative superstring theories and their spectra is briefly outlined. Calabi-Yau three-fold compactifications of heterotic strings and their relation to some four-dimensional physics are given. Finally, non-perturbative issues like S-duality, M-theory and F-theory are also reviewed

Observer based output-feedback control to eliminate rorsional drill-string vibrations

NARCIS (Netherlands)

Vromen, T.G.M.; van de Wouw, N.; Doris, A.; Astrid, P.; Nijmeijer, H.

2014-01-01

Torsional stick-slip vibrations decrease the performance and reliability of drilling systems used for the exploration of energy and mineral resources. In this work, we present the design of a nonlinear observer-based outputfeedback control strategy to eliminate these vibrations. We apply the

Open-closed string correspondence in open string field theory

International Nuclear Information System (INIS)

Baumgartl, M.; Sachs, I.

2008-01-01

We address the problem of describing different closed string backgrounds in background independent open string field theory: A shift in the closed string background corresponds to a collective excitation of open strings. As an illustration we apply the formalism to the case where the closed string background is a group manifold. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

Observer-based output-feedback control to eliminate torsional drill-string vibrations

NARCIS (Netherlands)

Vromen, T.G.M.; Wouw, van de N.; Doris, A.; Astrid, P.; Nijmeijer, H.

2014-01-01

Torsional stick-slip vibrations decrease the performance and reliability of drilling systems used for the exploration of energy and mineral resources. In this work, we present the design of a nonlinear observer-based output-feedback control strategy to eliminate these vibrations. We apply the

Development of S-wave portable vibrator; S ha potable vibrator shingen no kaihatsu

Energy Technology Data Exchange (ETDEWEB)

Kaida, Y; Matsubara, Y [OYO Corp., Tokyo (Japan); Nijhof, V; Brouwer, J

1996-05-01

An S-wave portable vibrator to serve as a seismic source has been developed for the purpose of applying the shallow-layer reflection method to the study of the soil ground. The author, et al., who previously developed a P-wave portable vibrator has now developed an S-wave version, considering the advantage of the S-wave over the P-wave in that, for example, the S-wave velocity may be directly compared with the N-value representing ground strength and that the S-wave travels more slowly than the P-wave through sticky soil promising a higher-resolution exploration. The experimentally constructed S-wave vibrator consists of a conventional P-wave vibrator and an L-type wooden base plate combined therewith. Serving as the monitor for vibration is a conventional accelerometer without any modification. The applicability test was carried out at a location where a plank hammering test was once conducted for reflection aided exploration, and the result was compared with that of the plank hammering test. As the result, it was found that after some preliminary treatment the results of the two tests were roughly the same but that both reflected waves were a little sharper in the S-wave vibrator test than in the plank hammering test. 4 refs., 9 figs., 1 tab.

An Inverse Eigenvalue Problem for a Vibrating String with Two Dirichlet Spectra

KAUST Repository

Rundell, William; Sacks, Paul

2013-01-01

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

Analysis of tube vibrations in D-4 steam generator

International Nuclear Information System (INIS)

Mavko, B.; Peterlin, G.; Boltezar, M.

1983-01-01

Accelerometer data for the most exposed tube in steam generator D-4 were recorded on magnetic tape. Procedures for calculations of the most characteristic parameters were prepared for spectral analyzer on SD 360. Parameters which most satisfactorily describe the vibrations are power spectral densities peak to peak acceleration volume and root mean square displacement. Computer program was written to calculate the natural frequencies of a multispaned tube. Procedures and the computer program will be used for independent analysis of tube vibrations in Krsko D-4 type steam generator. (author)

Screening of inorganic gases released from firework-rockets by a gas chromatography/whistle-accelerometer method.

Science.gov (United States)

Chen, Kuan-Fu; Wu, Hui-Hsin; Lin, Chien-Hung; Lin, Cheng-Huang

2013-08-30

The use of an accelerometer for detecting inorganic gases in gas chromatography (GC) is described. A milli-whistle was connected to the outlet of the GC capillary and was used instead of a classical GC detector. When the GC carrier gases and the sample gases pass through the milli-whistle, a sound is produced, leading to vibrational changes, which can be recorded using an accelerometer. Inorganic gases, including SO2, N2 and CO2, which are released from traditional Chinese firework-rockets at relatively high levels as the result of burning the propellant and explosive material inside could be rapidly determined using the GC/whistle-accelerometer system. The method described herein is safe, the instrumentation is compact and has potential to be modified so as to be portable for use in the field. It also can be used in conjunction with FID (flame ionization detector) or TCD (thermal conductivity detector), in which either no response for FID (CO2, N2, NO2, SO2, etc.) or helium gas is needed for TCD, respectively. Copyright © 2013 Elsevier B.V. All rights reserved.

Surface Acoustic Wave Vibration Sensors for Measuring Aircraft Flutter

Science.gov (United States)

Wilson, William C.; Moore, Jason P.; Juarez, Peter D.

2016-01-01

Under NASA's Advanced Air Vehicles Program the Advanced Air Transport Technology (AATT) Project is investigating flutter effects on aeroelastic wings. To support that work a new method for measuring vibrations due to flutter has been developed. The method employs low power Surface Acoustic Wave (SAW) sensors. To demonstrate the ability of the SAW sensor to detect flutter vibrations the sensors were attached to a Carbon fiber-reinforced polymer (CFRP) composite panel which was vibrated at six frequencies from 1Hz to 50Hz. The SAW data was compared to accelerometer data and was found to resemble sine waves and match each other closely. The SAW module design and results from the tests are presented here.

A digital output accelerometer using MEMS-based piezoelectric accelerometers and arrayed CMOS inverters with satellite capacitors

International Nuclear Information System (INIS)

Kobayashi, T; Okada, H; Maeda, R; Itoh, T; Masuda, T

2011-01-01

The present paper describes the development of a digital output accelerometer composed of microelectromechanical systems (MEMS)-based piezoelectric accelerometers and arrayed complementary metal–oxide–semiconductor (CMOS) inverters accompanied by capacitors. The piezoelectric accelerometers were fabricated from multilayers of Pt/Ti/PZT/Pt/Ti/SiO 2 deposited on silicon-on-insulator (SOI) wafers. The fabricated piezoelectric accelerometers were connected to arrayed CMOS inverters. Each of the CMOS inverters was accompanied by a capacitor with a different capacitance called a 'satellite capacitor'. We have confirmed that the output voltage generated from the piezoelectric accelerometers can vary the output of the CMOS inverters from a high to a low level; the state of the CMOS inverters has turned from the 'off-state' into the 'on-state' when the output voltage of the piezoelectric accelerometers is larger than the threshold voltage of the CMOS inverters. We have also confirmed that the CMOS inverters accompanied by the larger satellite capacitor have become 'on-state' at a lower acceleration. On increasing the acceleration, the number of on-state CMOS inverters has increased. Assuming that the on-state and off-state of CMOS inverters correspond to logic '0' and '1', the present digital output accelerometers have expressed the accelerations of 2.0, 3.0, 5.0, and 5.5 m s −2 as digital outputs of 111, 110, 100, and 000, respectively

Fuel Rod Vibration Measurement Method using a Flap and its Verification

Energy Technology Data Exchange (ETDEWEB)

Yoo, Joo Young; Park, Nam Gyu; Suh, Jung Min; Jeon, Kyeong Lak [KEPCO NF Co., Daejeon (Korea, Republic of)

2011-10-15

Flow-induced vibration is a critical factor for the mechanical integrity of a fuel rod. This vibration can cause leaked fuel through the mechanism, such as grid to rod fretting. To minimize the failures caused by flow-induced vibration, a robust design is needed which takes into account vibrational characteristics. That is, the spacer grid design should be developed to avoid any excessive vibration. On the one hand, if fuel rod vibration can be measured, an estimation of the excitation forces, which are a critical cause of rod failure, should be possible. Therefore, by applying an external force, flow-induced vibration can be roughly estimated when the fuel rod vibration model is used. KEPCO Nuclear Fuel developed the test loop to research flow-induced vibration as shown in Fig.1. The investigation flow-induced vibration (INFINIT) - the test facility - can measure the grid strap vibration and pressure drop of a 5x5 small scale fuel bundle. Basically, using a Laser Doppler Vibrometer (LDV), the vibration of a structure immersed in high speed fluid can be measured. Grid strap vibration is easily measured using an LDV. However, it is quite difficult to measure fuel rod vibration because of the round surface shape of the rods. In addition, measuring current method using the LDV, it was only possible to directly measure fuel rod vibration at the first row of the bundle as the rods behind the first row are obscured. To solve this problem, a thin flap, as shown in Fig. 2(a) can be used as a reflecting target, gaining access to rods within the bundle. The flap is attached to the fuel rod, as in Fig. 2(b). As a result, most of the inner rod vibration can be measured. Before using a flap to measure fuel rod vibration, a verification process was needed to show whether the LDV signal from the flap vibration provided equivalent and reliable signals. Therefore, impact testing was carried out on the fuel rod using a flap. The LDV signals were then compared with accelerometer

Hyperbolic strings

International Nuclear Information System (INIS)

Popov, A.D.

1991-01-01

We introduce hyperbolic strings as closed bosonic strings with the target space R d-1,1 xT q+1,1 which has an additional time-like dimension in the internal space. The Fock spaces of the q-parametric family of standard bosonic, fermionic and heterotic strings with the target spaces of dimension n≤d+q are shown to be embedded into the Fock space of hyperbolic strings. The condition of the absence of anomaly fixes d and q for all three types of strings written in a bosonized form. (orig.)

Efficient synthesis of tension modulation in strings and membranes based on energy estimation.

Science.gov (United States)

Avanzini, Federico; Marogna, Riccardo; Bank, Balázs

2012-01-01

String and membrane vibrations cannot be considered as linear above a certain amplitude due to the variation in string or membrane tension. A relevant special case is when the tension is spatially constant and varies in time only in dependence of the overall string length or membrane surface. The most apparent perceptual effect of this tension modulation phenomenon is the exponential decay of pitch in time. Pitch glides due to tension modulation are an important timbral characteristic of several musical instruments, including the electric guitar and tom-tom drum, and many ethnic instruments. This paper presents a unified formulation to the tension modulation problem for one-dimensional (1-D) (string) and two-dimensional (2-D) (membrane) cases. In addition, it shows that the short-time average of the tension variation, which is responsible for pitch glides, is approximately proportional to the system energy. This proportionality allows the efficient physics-based sound synthesis of pitch glides. The proposed models require only slightly more computational resources than linear models as opposed to earlier tension-modulated models of higher complexity. © 2012 Acoustical Society of America.

String theory

International Nuclear Information System (INIS)

Chan Hongmo.

1987-10-01

The paper traces the development of the String Theory, and was presented at Professor Sir Rudolf Peierls' 80sup(th) Birthday Symposium. The String theory is discussed with respect to the interaction of strings, the inclusion of both gauge theory and gravitation, inconsistencies in the theory, and the role of space-time. The physical principles underlying string theory are also outlined. (U.K.)

Strings draw theorists together

International Nuclear Information System (INIS)

Green, Michael

2000-01-01

Theorists are confident that they are closer than ever to finding a quantum theory that unites gravity with the three other fundamental forces in nature. Many of the leading figures in the world of string theory met at the California Institute of Technology in January to discuss recent progress in the field and to reflect on the state of the theory. The enthusiastic mood of the gathering was based on the fact that string theory provides an elegant framework for a unified theory of all the forces and particles in nature, and also gives a consistent quantum-mechanical description of general relativity. String theory, and more precisely superstring theory, describes the assortment of elementary particles such as quarks and leptons, and the gauge bosons responsible for mediating forces in a unified manner as different modes of vibration of a single extended string. This version of the theory also embodies supersymmetry a conjectured symmetry that unifies fermions and bosons. Furthermore, the fact that the string has a fundamental length scale - the ''string length'' - apparently cures the short-distance problems of uniting general relativity with quantum theory. The main problem with the early formulations of superstring theory was that they emphasized the ''perturbative'' point of view, an approximation that describes string-like quantum-mechanical particles moving through classical (that is non quantum-mechanical) space-time. However, very general arguments require that any quantum theory of gravity should also describe space-time geometry in a quantum-mechanical manner. The classical geometry of space-time should then emerge as an approximate description at distance scales much larger than the so-called Planck scale of 10 -33 m. This requires an understanding of the theory beyond the perturbative approximation. It is the quest for this more fundamental description of string theory that has provided the main challenge for string theorists over the past decade. Much

Duality relation between charged elastic strings and superconducting cosmic strings

International Nuclear Information System (INIS)

Carter, B.

1989-01-01

The mechanical properties of macroscopic electromagnetically coupled string models in a flat or curved background are treated using a covariant formalism allowing the construction of a duality transformation that relates the category of uniform ''electric'' string models, constructed as the (nonconducting) charged generalisation of ordinary uncoupled (violin type) elastic strings, to a category of ''magnetic'' string models comprising recently discussed varieties of ''superconducting cosmic strings''. (orig.)

A reduced covariant string model for the extrinsic string

International Nuclear Information System (INIS)

Botelho, L.C.L.

1989-01-01

It is studied a reduced covariant string model for the extrinsic string by using Polyakov's path integral formalism. On the basis of this reduced model it is suggested that the extrinsic string has its critical dimension given by 13. Additionally, it is calculated in a simple way Poliakov's renormalization group law for the string rigidity coupling constants. (A.C.A.S.) [pt

Low-cost vibration sensor based on dual fiber Bragg gratings and light intensity measurement.

Science.gov (United States)

Gao, Xueqing; Wang, Yongjiao; Yuan, Bo; Yuan, Yinquan; Dai, Yawen; Xu, Gang

2013-09-20

A vibration monitoring system based on light intensity measurement has been constructed, and the designed accelerometer is based on steel cantilever frame and dual fiber Bragg gratings (FBGs). By using numerical simulations for the dual FBGs, the dependence relationship of the area of main lobes on the difference of initial central wavelengths is obtained and the most optimal choice for the initial value and the vibration amplitude of the difference of central wavelengths of two FBGs is suggested. The vibration monitoring experiments are finished, and the measured data are identical to the simulated results.

The heterotic string

International Nuclear Information System (INIS)

Gross, D.J.

1986-01-01

Traditional string theories, either bosonic or supersymmetric, came in two varieties, closed string theories and open string theories. Closed string are neutral objects which describe at low energies gravity or supergravity. Open strings have geometrically invariant ends to which charge can be attached, thereby obtaining, in addition to gravity, Yang-Mills gauge interactions. Recently a new kind of string theory was discovered--the heterotic string, which is a chiral hybrid of the closed superstring and the closed bosonic string, and which produces by an internal dynamical mechanism gauge interactions of a totally specified kind. Although this theory is found in an attempt to produce a superstring theory which would yield a low energy E/sub 8/xE/sub 8/ supersymmetric, anomaly free, gauge theory, as suggested by the anomaly cancellation mechanism of Green and Schwarz, it fits naturally into the general framework of consistent string theories

String Gas Cosmology

OpenAIRE

Brandenberger, Robert H.

2008-01-01

String gas cosmology is a string theory-based approach to early universe cosmology which is based on making use of robust features of string theory such as the existence of new states and new symmetries. A first goal of string gas cosmology is to understand how string theory can effect the earliest moments of cosmology before the effective field theory approach which underlies standard and inflationary cosmology becomes valid. String gas cosmology may also provide an alternative to the curren...

Strings draw theorists together

Energy Technology Data Exchange (ETDEWEB)

Green, Michael [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge (United Kingdom)

2000-03-01

Theorists are confident that they are closer than ever to finding a quantum theory that unites gravity with the three other fundamental forces in nature. Many of the leading figures in the world of string theory met at the California Institute of Technology in January to discuss recent progress in the field and to reflect on the state of the theory. The enthusiastic mood of the gathering was based on the fact that string theory provides an elegant framework for a unified theory of all the forces and particles in nature, and also gives a consistent quantum-mechanical description of general relativity. String theory, and more precisely superstring theory, describes the assortment of elementary particles such as quarks and leptons, and the gauge bosons responsible for mediating forces in a unified manner as different modes of vibration of a single extended string. This version of the theory also embodies supersymmetry a conjectured symmetry that unifies fermions and bosons. Furthermore, the fact that the string has a fundamental length scale - the ''string length'' - apparently cures the short-distance problems of uniting general relativity with quantum theory. The main problem with the early formulations of superstring theory was that they emphasized the ''perturbative'' point of view, an approximation that describes string-like quantum-mechanical particles moving through classical (that is non quantum-mechanical) space-time. However, very general arguments require that any quantum theory of gravity should also describe space-time geometry in a quantum-mechanical manner. The classical geometry of space-time should then emerge as an approximate description at distance scales much larger than the so-called Planck scale of 10{sup -33} m. This requires an understanding of the theory beyond the perturbative approximation. It is the quest for this more fundamental description of string theory that has provided the main challenge for

Chern-Simons couplings for dielectric F-strings in matrix string theory

International Nuclear Information System (INIS)

Brecher, Dominic; Janssen, Bert; Lozano, Yolanda

2002-01-01

We compute the non-abelian couplings in the Chern-Simons action for a set of coinciding fundamental strings in both the type IIA and type IIB Matrix string theories. Starting from Matrix theory in a weakly curved background, we construct the linear couplings of closed string fields to type IIA Matrix strings. Further dualities give a type IIB Matrix string theory and a type IIA theory of Matrix strings with winding. (Abstract Copyright[2002], Wiley Periodicals, Inc.)

A string theory which isn't about strings

Science.gov (United States)

Lee, Kanghoon; Rey, Soo-Jong; Rosabal, J. A.

2017-11-01

Quantization of closed string proceeds with a suitable choice of worldsheet vacuum. A priori, the vacuum may be chosen independently for left-moving and right-moving sectors. We construct ab initio quantized bosonic string theory with left-right asymmetric worldsheet vacuum and explore its consequences and implications. We critically examine the validity of new vacuum and carry out first-quantization using standard operator formalism. Remarkably, the string spectrum consists only of a finite number of degrees of freedom: string gravity (massless spin-two, Kalb-Ramond and dilaton fields) and two massive spin-two Fierz-Pauli fields. The massive spin-two fields have negative norm, opposite mass-squared, and provides a Lee-Wick type extension of string gravity. We compute two physical observables: tree-level scattering amplitudes and one-loop cosmological constant. Scattering amplitude of four dilatons is shown to be a rational function of kinematic invariants, and in D = 26 factorizes into contributions of massless spin-two and a pair of massive spin-two fields. The string one loop partition function is shown to perfectly agree with one loop Feynman diagram of string gravity and two massive spin-two fields. In particular, it does not exhibit modular invariance. We critically compare our construction with recent studies and contrast differences.

Sensor agent robot with servo-accelerometer for structural health monitoring

Science.gov (United States)

Lee, Nobukazu; Mita, Akira

2012-04-01

SHM systems are becoming feasible with the growth of computer and sensor technologies during the last decade. However, high cost prevents SHM to become common in general homes. The reason of this high cost is partially due to many accelerometers. In this research, we propose a moving sensor agent robot with accelerometers and a laser range finder (LRF). If this robot can properly measure accurate acceleration data, the cost of SHM would be cut down and resulting in the spread of SHM systems. Our goal is to develop a platform for SHM using the sensor agent robot. We designed the prototype robot to correctly detect the floor vibrations and acquire the micro tremor information. When the sensor agent robot is set in the mode of acquiring the data, the dynamics of the robot should be tuned not to be affected by its flexibility. To achieve this purpose the robot frame was modified to move down to the ground and to provide enough rigidity to obtain good data. In addition to this mechanism, we tested an algorithm to correctly know the location of the robot and the map of the floor to be used in the SHM system using the LRF and Simultaneously Localization and Mapping (SLAM).

Computational modelling of string body interaction for the violin family and simulation of wolf notes

Science.gov (United States)

Inácio, O.; Antunes, J.; Wright, M. C. M.

2008-02-01

Most theoretical studies of bowed-string instruments deal with isolated strings, pinned on fixed supports. In others, the instrument body dynamics have been accounted by using extremely simplified models of the string-body interaction through the instrument bridge. Such models have, nevertheless, been instrumental to the understanding of a very common and musically undesirable phenomenon known as the wolf note—a strong beating interplay between string and body vibrations. Cellos, bad and good, are particularly prone to this problem. In previous work, a computational method that allows efficient time-domain modelling of bowed strings based on a modal approach has been introduced. This has been extended to incorporate the complex dynamics of real-life instrument bodies, and their coupling to the string motions, using experimental dynamical body data. The string is modelled using its unconstrained modes, assuming pinned-pinned boundary conditions at the tailpiece and the nut. At the intermediary bridge location, the string-body coupling is enforced using the body impulse-response or modal data, as measured at the instrument bridge. In the present paper, this computational approach is applied to a specific cello, which provided experimental wolf-behaviour data under several bowing conditions, as well as laboratory measurements of the bridge impulse responses on which the numerical simulations were based. Interesting aspects of the string-body dynamical responses are highlighted by numerical simulations and the corresponding sounds and animations produced. Finally, a qualitative (and, when possible, quantitative) comparison of the experimental and numerical results is presented.

Vortex-strings in N=2 SQCD and bulk-string decoupling

Science.gov (United States)

Gerchkovitz, Efrat; Karasik, Avner

2018-02-01

We study vortex-strings in four-dimensional N=2 supersymmetric SU( N c ) × U(1) gauge theories with N f hypermultiplets in the fundamental representation of SU( N c ) and general U(1) charges. If N f > N c , the vacuum is not gapped and the low-energy theory contains both the vacuum massless excitations and the string zero-modes. The question we address in this work is whether the vacuum and the string moduli decouple at low energies, allowing a description of the low-energy dynamics in terms of a two-dimensional theory on the string worldsheet. We find a simple condition controlling the bulk-string coupling: if there exist two flavors such that the product of their U(1) charge difference with the magnetic flux carried by the string configuration is not an integer multiple of 2 π, the string has zero-modes that decay slower than 1 /r, where r is the radial distance from the string core. These modes are coupled to the vacuum massless excitations even at low energies. If, however, all such products are integer multiples of 2 π, long-range modes of this type do not exist and the string moduli decouple from the bulk at low energies. This condition turns out to coincide with the condition of trivial Aharonov-Bohm phases for the particles in the spectrum. In addition to a derivation of the bulk-string decoupling criterion using classical analysis of the string zero-modes, we provide a non-perturbative derivation of the criterion, which uses supersymmetric localization techniques.

StringForce

DEFF Research Database (Denmark)

Barendregt, Wolmet; Börjesson, Peter; Eriksson, Eva

2017-01-01

In this paper, we present the forced collaborative interaction game StringForce. StringForce is developed for a special education context to support training of collaboration skills, using readily available technologies and avoiding the creation of a "mobile bubble". In order to play String......Force two or four physically collocated tablets are required. These tablets are connected to form one large shared game area. The game can only be played by collaborating. StringForce extends previous work, both technologically and regarding social-emotional training. We believe String......Force to be an interesting demo for the IDC community, as it intertwines several relevant research fields, such as mobile interaction and collaborative gaming in the special education context....

Bosonic strings

CERN Document Server

Jost, Jürgen

2007-01-01

This book presents a mathematical treatment of Bosonic string theory from the point of view of global geometry. As motivation, Jost presents the theory of point particles and Feynman path integrals. He provides detailed background material, including the geometry of Teichmüller space, the conformal and complex geometry of Riemann surfaces, and the subtleties of boundary regularity questions. The high point is the description of the partition function for Bosonic strings as a finite-dimensional integral over a moduli space of Riemann surfaces. Jost concludes with some topics related to open and closed strings and D-branes. Bosonic Strings is suitable for graduate students and researchers interested in the mathematics underlying string theory.

Determination of vibration amplitudes and neutron-mechanical scale factors in the PWR nuclear power plant

International Nuclear Information System (INIS)

Kostic, Lj.; Heidemann, P.; Runkel, J.

1997-01-01

Displacements of vibrating reactor components which can not be measured by other means during normal reactor operation can be determined through the scale factors from the neutron spectra of signals measured by the standard in-core neutron instrumentation. Neutron-mechanical scale factors are determined for the vibrations of fuel assemblies and reactor pressure vessel/core barrel system using the signals of in-core neutron detectors and accelerometers. (author)

String cosmology. Large-field inflation in string theory

International Nuclear Information System (INIS)

Westphal, Alexander

2014-09-01

This is a short review of string cosmology. We wish to connect string-scale physics as closely as possible to observables accessible to current or near-future experiments. Our possible best hope to do so is a description of inflation in string theory. The energy scale of inflation can be as high as that of Grand Unification (GUT). If this is the case, this is the closest we can possibly get in energy scales to string-scale physics. Hence, GUT-scale inflation may be our best candidate phenomenon to preserve traces of string-scale dynamics. Our chance to look for such traces is the primordial gravitational wave, or tensor mode signal produced during inflation. For GUT-scale inflation this is strong enough to be potentially visible as a B-mode polarization of the cosmic microwave background (CMB). Moreover, a GUT-scale inflation model has a trans-Planckian excursion of the inflaton scalar field during the observable amount of inflation. Such large-field models of inflation have a clear need for symmetry protection against quantum corrections. This makes them ideal candidates for a description in a candidate fundamental theory like string theory. At the same time the need of large-field inflation models for UV completion makes them particularly susceptible to preserve imprints of their string-scale dynamics in the inflationary observables, the spectral index n s and the fractional tensor mode power r. Hence, we focus this review on axion monodromy inflation as a mechanism of large-field inflation in string theory.

Boundary string field theory and an open string one-loop

International Nuclear Information System (INIS)

Lee, Tae Jin; Viswanathan, K. S.; Yang, Yi

2003-01-01

We discuss the open string one-loop partition function in the tachyon condensation background of an unstable D-brane system. We evaluate the partition function by using the boundary-state formulation and find that it is in complete agreement with the result obtained in the boundary string field theory. This suggests that the open string higher loop diagrams may be produced consistently by using a closed string field theory, where the D-brane plays the role of a source for the closed string field

Vibrations on pulse tube based Dry Dilution Refrigerators for low noise measurements

Energy Technology Data Exchange (ETDEWEB)

Olivieri, E. [CSNSM, Univ. Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, 91405 Orsay (France); Billard, J.; De Jesus, M.; Juillard, A. [Univ Lyon, Université Lyon 1, CNRS/IN2P3, IPN-Lyon, F-69622 Villeurbanne (France); Leder, A. [Massachussets Institute of Technology, Laboratory for Nuclear Science, 77 Massachusetts Avenue Cambridge, MA 02139-4307 (United States)

2017-06-21

Dry Dilution Refrigerators (DDR) based on pulse tube cryo-coolers have started to replace Wet Dilution Refrigerators (WDR) due to the ease and low cost of operation. However these advantages come at the cost of increased vibrations, induced by the pulse tube. In this work, we present the vibration measurements performed on three different commercial DDRs. We describe in detail the vibration measurement system we assembled, based on commercial accelerometers, conditioner and DAQ, and examined the effects of the various damping solutions utilized on three different DDRs, both in the low and high frequency regions. Finally, we ran low temperature, pseudo-massive (30 and 250 g) germanium bolometers in the best vibration-performing system under study and report on the results.

Integrated cable vibration control system using wireless sensors

Science.gov (United States)

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.

Hot String Soup

OpenAIRE

Lowe, D. A.; Thorlacius, L.

1994-01-01

Above the Hagedorn energy density closed fundamental strings form a long string phase. The dynamics of weakly interacting long strings is described by a simple Boltzmann equation which can be solved explicitly for equilibrium distributions. The average total number of long strings grows logarithmically with total energy in the microcanonical ensemble. This is consistent with calculations of the free single string density of states provided the thermodynamic limit is carefully defined. If the ...

String-driven inflation

International Nuclear Information System (INIS)

Turok, N.

1988-01-01

It is argued that, in fundamental string theories, as one traces the universe back in time a point is reached when the expansion rate is so fast that the rate of string creation due to quantum effects balances the dilution of the string density due to the expansion. One is therefore led into a phase of constant string density and an exponentially expanding universe. Fundamental strings therefore seem to lead naturally to inflation

Cosmic global strings

International Nuclear Information System (INIS)

Sikivie, P.

1991-01-01

The topics are: global strings; the gravitational field of a straight global string; how do global strings behave?; the axion cosmological energy density; computer simulations of the motion and decay of global strings; electromagnetic radiation from the conversion of Nambu-Goldstone bosons in astrophysical magnetic fields. (orig.)

Construction of a Vibration Monitoring System for HANARO's Rotating Machinery and Analysis of Pump Vibration Signals

International Nuclear Information System (INIS)

Ryu, Jeong Soo; Yoon, Doo Byung

2005-01-01

HANARO is an open-tank-in-pool type research reactor with a thermal power of 30MW. In order to remove the heat generated by the reactor core and the reflector vessel, primary cooling pumps and reflector cooling pumps circulate coolant. These pumps are installed at the RCI(Reactor Concrete Island) which is covered by heavy concrete hatches. For the prevention of an abnormal operation of these pumps in the RCI, it is necessary to construct a vibration monitoring system that provides an alarm signal to the reactor control room when the rotating speed or the vibration level exceeds the allowable limit. The first objective of this work is to construct a vibration monitoring system for HANARO's rotating machinery. The second objective is to verify the possibility of condition monitoring of the rotating machinery. To construct a vibration monitoring system, as a first step, the standards and references related to the vibration monitoring system were investigated. In addition, to determine the number and the location of sensors that can effectively characterize the overall vibration of a pump, the vibration of the primary cooling pumps and the reflector cooling pumps were measured. Based on these results, detailed construction plans for the vibration monitoring system for HANARO were established. Then, in accordance with the construction plans, the vibration monitoring system for HANARO's rotating machinery was manufactured and installed at HANARO. To achieve the second objective, FFT analysis and bearing fault detection of the measured vibration signals were performed. The analysis results demonstrate that the accelerometers mounted at the bearing locations of the pumps can effectively monitor the pump condition

The use of pulsed lasers for vibration analysis in the nuclear power industry

International Nuclear Information System (INIS)

Tozer, B.A.

1987-01-01

The structural engineer's interest in vibration can generally be summarised as a desire to know the modes of vibration which an engineering structure can assume, the resonant frequencies, the sharpness of the resonances (related to the damping forces in and on the structure) and their amplitudes under given driving forces. Most of all he is interested in the non-resonant vibration of the structure under the influence of a random driving force, and he would like to determine the direction (in three dimensional space), as well as amplitude, of the motions involved. In industries in which exceptionally high levels of structural integrity are required through long periods of continuous or near continuous operation, such as the aeronautical or nuclear industries, accurate vibration analysis is an essential first step towards an assessment of the fatigue life of the structure. In this case the most important factor is the dynamic stress in the structural material. Measurement tools available to the engineer, in order to obtain the information he needs, are numerous, varied in character, and generally unable to meet all the needs outlined above. They may be contacting (e.g. accelerometers or straingauges) or non contacting (for example holographic interferometry, ESPI or SPATE). They may provide data continuous in space (holographic interferometry), with limited spatial resolution (ESPI), or discrete point measurements (accelerometers, laser vibrometers)

A Hybrid Resynthesis Model for Hammer-String Interaction of Piano Tones

Directory of Open Access Journals (Sweden)

Jensen Kristoffer

2004-01-01

Full Text Available This paper presents a source/resonator model of hammer-string interaction that produces realistic piano sound. The source is generated using a subtractive signal model. Digital waveguides are used to simulate the propagation of waves in the resonator. This hybrid model allows resynthesis of the vibration measured on an experimental setup. In particular, the nonlinear behavior of the hammer-string interaction is taken into account in the source model and is well reproduced. The behavior of the model parameters (the resonant part and the excitation part is studied with respect to the velocities and the notes played. This model exhibits physically and perceptually related parameters, allowing easy control of the sound produced. This research is an essential step in the design of a complete piano model.

String driven inflation

International Nuclear Information System (INIS)

Turok, N.

1987-11-01

It is argued that, in fundamental string theories, as one traces the universe back in time a point is reached when the expansion rate is so fast that the rate of string creation due to quantum effects balances the dilution of the string density due to the expansion. One is therefore led into a phase of constant string density and an exponentially expanding universe. Fundamental strings therefore seem to lead naturally to inflation. 17 refs., 1 fig

Vibration noise control in laser satellite communication

Science.gov (United States)

Saksonov, Avigdor; Shlomi, Arnon; Kopeika, Norman S.

2001-08-01

Laser satellite communication has become especially attractive in recent years. Because the laser beam width is narrow than in the RF or microwave range, the transmitted optical power may be significantly reduced. This leads to development of miniature communication systems with extremely low power consumption. On the other hand, the laser communication channel is very sensitive to vibrations of the optical platform. These vibrations cause angular noise in laser beam pointing, comparable to the laser beam width. As result, as significant portion of the optical power between transmitter and receiver is lost and the bit error rate is increased. Consequently, vibration noise control is a critical problem in laser satellite communication. The direction of the laser beam is corrected with a fast steering mirror (FSM). In this paper are presented two approaches for the FSM control. One is the feedback control that uses an LQG algorithm. The second is the direct feed- forward control when vibration noise is measured by three orthogonal accelerometers and drives directly the F SM. The performances of each approach are evaluated using MATLAB simulations.

Transducers for Sound and Vibration - FEM Based Design

DEFF Research Database (Denmark)

Liu, Bin

2001-01-01

Design of transducers for measurement of vibration (piezoelectric accelerometers) and sound (condenser microphones) is a very labour intensive work. The design work is mostly based on experience and on simple analogies to electrical circuit design. Often a time consuming itterative loop is used......: Specification of the transducer, production of a physical prototype, measurements on the prototype, changed specification of the transducer etc. Furthermore are many transducers made based on customer requirements which also increases the amount of required design work. For these reasons there is a need...... for methods that can reduce the design time consumption and the number of itterations. The present work proposes to use finite element based programs for simulating the behaviour of a transducer with a given set of specifications. A simulation program for accelerometers was developed and has been tested...

Tomographic elastography of contracting skeletal muscles from their natural vibrations

Science.gov (United States)

Sabra, Karim G.; Archer, Akibi

2009-11-01

Conventional elastography techniques require an external mechanical or radiation excitation to measure noninvasively the viscoelastic properties of skeletal muscles and thus monitor human motor functions. We developed instead a passive elastography technique using only an array of skin-mounted accelerometers to record the low-frequency vibrations of the biceps brachii muscle naturally generated during voluntary contractions and to determine their two-dimensional directionality. Cross-correlating these recordings provided travel-times measurements of these muscle vibrations between multiple sensor pairs. Travel-time tomographic inversions yielded spatial variations of their propagation velocity during isometric elbow flexions which indicated a nonuniform longitudinal stiffening of the biceps.

Evaluation of protective gloves and working techniques for reducing hand-arm vibration exposure in the workplace.

Science.gov (United States)

Milosevic, Matija; McConville, Kristiina M Valter

2012-01-01

Operation of handheld power tools results in exposure to hand-arm vibrations, which over time lead to numerous health complications. The objective of this study was to evaluate protective equipment and working techniques for the reduction of vibration exposure. Vibration transmissions were recorded during different work techniques: with one- and two-handed grip, while wearing protective gloves (standard, air and anti-vibration gloves) and while holding a foam-covered tool handle. The effect was examined by analyzing the reduction of transmitted vibrations at the wrist. The vibration transmission was recorded with a portable device using a triaxial accelerometer. The results suggest large and significant reductions of vibration with appropriate safety equipment. Reductions of 85.6% were achieved when anti-vibration gloves were used. Our results indicated that transmitted vibrations were affected by several factors and could be measured and significantly reduced.

String field theory solution for any open string background

Czech Academy of Sciences Publication Activity Database

Erler, T.; Maccaferri, Carlo

2014-01-01

Roč. 10, Oct (2014), 1-37 ISSN 1029-8479 R&D Projects: GA ČR GBP201/12/G028 Institutional support: RVO:68378271 Keywords : tachyon condensation * string field theory * conformal field models in string theory * bosonic strings Subject RIV: BE - Theoretical Physics Impact factor: 6.111, year: 2014

Lattice strings

International Nuclear Information System (INIS)

Thorn, C.B.

1988-01-01

The possibility of studying non-perturbative effects in string theory using a world sheet lattice is discussed. The light-cone lattice string model of Giles and Thorn is studied numerically to assess the accuracy of ''coarse lattice'' approximations. For free strings a 5 by 15 lattice seems sufficient to obtain better than 10% accuracy for the bosonic string tachyon mass squared. In addition a crude lattice model simulating string like interactions is studied to find out how easily a coarse lattice calculation can pick out effects such as bound states which would qualitatively alter the spectrum of the free theory. The role of the critical dimension in obtaining a finite continuum limit is discussed. Instead of the ''gaussian'' lattice model one could use one of the vertex models, whose continuum limit is the same as a gaussian model on a torus of any radius. Indeed, any critical 2 dimensional statistical system will have a stringy continuum limit in the absence of string interactions. 8 refs., 1 fig. , 9 tabs

Study on antilock brake system with elastic membrane vibration generated by controlled solenoid excitation

International Nuclear Information System (INIS)

Wibowo,; Zakaria,; Lambang, Lullus; Triyono,; Muhayat, Nurul

2016-01-01

The most effective chassis control system for improving vehicle safety during severe braking is anti-lock braking system (ABS). Antilock effect can be gained by vibrate the pad brake at 7 to 20 cycle per second. The aim of this study is to design a new method of antilock braking system with membrane elastic vibrated by solenoid. The influence of the pressure fluctuations of brake fluid is investigated. Vibration data is collected using a small portable accelerometer-slam stick. The experiment results that the vibration of brake pad caused by controlled solenoid excitation at 10 Hz is obtained by our new method. The result of measurements can be altered by varying brake fluid pressure.

Study on antilock brake system with elastic membrane vibration generated by controlled solenoid excitation

Energy Technology Data Exchange (ETDEWEB)

Wibowo,, E-mail: wibowo-uns@yahoo.com; Zakaria,, E-mail: zakaaria27@gmail.com; Lambang, Lullus, E-mail: lulus-l@yahoo.com; Triyono,, E-mail: tyon-bila@yahoo.co.id; Muhayat, Nurul, E-mail: nurulmuhayat@ymail.com [Mechanical Engineering Department, Sebelas Maret University, Surakarta 57128 (Indonesia)

2016-03-29

The most effective chassis control system for improving vehicle safety during severe braking is anti-lock braking system (ABS). Antilock effect can be gained by vibrate the pad brake at 7 to 20 cycle per second. The aim of this study is to design a new method of antilock braking system with membrane elastic vibrated by solenoid. The influence of the pressure fluctuations of brake fluid is investigated. Vibration data is collected using a small portable accelerometer-slam stick. The experiment results that the vibration of brake pad caused by controlled solenoid excitation at 10 Hz is obtained by our new method. The result of measurements can be altered by varying brake fluid pressure.

Problems in Modelling Charge Output Accelerometers

Directory of Open Access Journals (Sweden)

Tomczyk Krzysztof

2016-12-01

Full Text Available The paper presents major issues associated with the problem of modelling change output accelerometers. The presented solutions are based on the weighted least squares (WLS method using transformation of the complex frequency response of the sensors. The main assumptions of the WLS method and a mathematical model of charge output accelerometers are presented in first two sections of this paper. In the next sections applying the WLS method to estimation of the accelerometer model parameters is discussed and the associated uncertainties are determined. Finally, the results of modelling a PCB357B73 charge output accelerometer are analysed in the last section of this paper. All calculations were executed using the MathCad software program. The main stages of these calculations are presented in Appendices A−E.

String-coupling constant and dilaton vacuum expectation value in string field theory

International Nuclear Information System (INIS)

Yoneya, Tamiaki

1987-01-01

In the first quantized approaches to strings, it is well known that the string-coupling constant is determined by the vacuum expectation value of the dilaton field. This property, however, has never been demonstrated within the framework of string field theory. An explicit reparametrization of the string field associated with the shifts of the dilaton vacuum expectation value and the string-coupling constant is constructed exhibiting the above property in the light-cone field theory of the closed bosonic string. (orig.)

Closed string field theory

International Nuclear Information System (INIS)

Strominger, A.

1987-01-01

A gauge invariant cubic action describing bosonic closed string field theory is constructed. The gauge symmetries include local spacetime diffeomorphisms. The conventional closed string spectrum and trilinear couplings are reproduced after spontaneous symmetry breaking. The action S is constructed from the usual ''open string'' field of ghost number minus one half. It is given by the associator of the string field product which is non-vanishing because of associativity anomalies. S does not describe open string propagation because open string states associate and can thereby be shifted away. A field theory of closed and open strings can be obtained by adding to S the cubic open string action. (orig.)

Conformal techniques in string theory and string field theory

International Nuclear Information System (INIS)

Giddings, S.B.

1987-01-01

The application of some conformal and Riemann surface techniques to string theory and string field theory is described. First a brief review of Riemann surface techniques and of the Polyakov approach to string theory is presented. This is followed by a discussion of some features of string field theory and of its Feynman rules. Specifically, it is shown that the Feynman diagrams for Witten's string field theory respect modular invariance, and in particular give a triangulation of moduli space. The Polyakov formalism is then used to derive the Feynman rules that should follow from this theory upon gauge-fixing. It should also be possible to apply this derivation to deduce the Feynman rules for other gauge-fixed string field theories. Following this, Riemann surface techniques are turned to the problem of proving the equivalence of the Polyakov and light-cone formalisms. It is first shown that the light-cone diagrams triangulate moduli space. Then the Polyakov measure is worked out for these diagrams, and shown to equal that deduced from the light-cone gauge fixed formalism. Also presented is a short description of the comparison of physical states in the two formalisms. The equivalence of the two formalisms in particular constitutes a proof of the unitarity of the Polyakov framework for the closed bosonic string

Fast Fourier transformation in vibration analysis of physically active systems

International Nuclear Information System (INIS)

Hafeez, T.; Amir, M.; Farooq, U.; Day, P.

2003-01-01

Vibration of all physical systems may be expressed as the summation of an infinite number of sine and cosine terms known as Fourier series. The basic vibration analysis tool used is the frequency 'spectrum' (a graph of vibration where the amplitude of vibration is plotted against frequency). When a particular rotating component begins to fail, its vibration tends to increase. Spectra graphs are powerful diagnostic tool for detecting components' degradation. Spectra obtained with accelerometers located at the various locations on the components and their analysis in practice from rotating machines enable early detecting of incipient failure. Consequence of unexpected failure can be catastrophic and costly. This study provides basis to relate defective component by its constituent frequencies and then to the known discrete frequency of its 'signature' or 'thumbprint' to predict and verify the sustained dynamic behavior of machine designs harmful effects of forced vibration. The spectra for gearbox of a vane with teeth damaged fault are presented here which signified the importance of FFT analysis as diagnostic tool. This may be helpful to predictive maintenance of the machinery. (author)

On the elliptic genus of three E-strings and heterotic strings

International Nuclear Information System (INIS)

Cai, Wenhe; Huang, Min-xin; Sun, Kaiwen

2015-01-01

A precise formula for the elliptic genus of three E-strings is presented. The related refined free energy coincides with the result calculated from topological string on local half K3 Calabi-Yau threefold up to genus twelve. The elliptic genus of three heterotic strings computed from M9 domain walls matches with the result from orbifold formula to high orders. This confirms the n=3 case of the recent conjecture that n pairs of E-strings can recombine into n heterotic strings.

Peri-prosthetic fracture vibration testing

Energy Technology Data Exchange (ETDEWEB)

Cruce, Jesse R [Los Alamos National Laboratory; Erwin, Jenny R [Los Alamos National Laboratory; Remick, Kevin R [Los Alamos National Laboratory; Cornwell, Phillip J [Los Alamos National Laboratory; Menegini, R. Michael [INDIANA UNIV.; Racanelli, Joe [STRYKER ORTHOPARDICS

2010-11-08

The purpose of this study was to establish a test setup and vibration analysis method to predict femoral stem seating and prevent bone fracture using accelerometer and force response data from an instrumented stem and impactor. This study builds upon earlier studies to identify a means to supplement a surgeon's tactile and auditory senses by using damage identification techniques normally used for civil and mechanical structures. Testing was conducted using foam cortical shell sawbones prepared for stems of different geometries. Each stem was instrumented with an accelerometer. Two impactor designs were compared: a monolithic impactor and a two-piece impactor, each with an integrated load cell and accelerometer. Acceleration and force measurements were taken in the direction of impaction. Comparisons between different methods of applying an impacting force were made, including a drop tower and a surgical hammer. The effect of varying compliance on the data was also investigated. The ultimate goal of this study was to assist in the design of an integrated portable data acquisition system capable of being used in future cadaveric testing. This paper will discuss the experimental setup and the subsequent results of the comparisons made between impactors, prosthetic geometries, compliances, and impact methods. The results of this study can be used for both future replicate testing as well as in a cadaveric environment.

Minimal open strings

International Nuclear Information System (INIS)

Hosomichi, Kazuo

2008-01-01

We study FZZT-branes and open string amplitudes in (p, q) minimal string theory. We focus on the simplest boundary changing operators in two-matrix models, and identify the corresponding operators in worldsheet theory through the comparison of amplitudes. Along the way, we find a novel linear relation among FZZT boundary states in minimal string theory. We also show that the boundary ground ring is realized on physical open string operators in a very simple manner, and discuss its use for perturbative computation of higher open string amplitudes.

Verification of the Microgravity Active Vibration Isolation System based on Parabolic Flight

Science.gov (United States)

Zhang, Yong-kang; Dong, Wen-bo; Liu, Wei; Li, Zong-feng; Lv, Shi-meng; Sang, Xiao-ru; Yang, Yang

2017-12-01

The Microgravity active vibration isolation system (MAIS) is a device to reduce on-orbit vibration and to provide a lower gravity level for certain scientific experiments. MAIS system is made up of a stator and a floater, the stator is fixed on the spacecraft, and the floater is suspended by electromagnetic force so as to reduce the vibration from the stator. The system has 3 position sensors, 3 accelerometers, 8 Lorentz actuators, signal processing circuits and a central controller embedded in the operating software and control algorithms. For the experiments on parabolic flights, a laptop is added to MAIS for monitoring and operation, and a power module is for electric power converting. The principle of MAIS is as follows: the system samples the vibration acceleration of the floater from accelerometers, measures the displacement between stator and floater from position sensitive detectors, and computes Lorentz force current for each actuator so as to eliminate the vibration of the scientific payload, and meanwhile to avoid crashing between the stator and the floater. This is a motion control technic in 6 degrees of freedom (6-DOF) and its function could only be verified in a microgravity environment. Thanks for DLR and Novespace, we get a chance to take the DLR 27th parabolic flight campaign to make experiments to verify the 6-DOF control technic. The experiment results validate that the 6-DOF motion control technique is effective, and vibration isolation performance perfectly matches what we expected based on theoretical analysis and simulation. The MAIS has been planned on Chinese manned spacecraft for many microgravity scientific experiments, and the verification on parabolic flights is very important for its following mission. Additionally, we also test some additional function by microgravity electromagnetic suspension, such as automatic catching and locking and working in fault mode. The parabolic flight produces much useful data for these experiments.

Whole-Body Vibrations Associated With Alpine Skiing: A Risk Factor for Low Back Pain?

Directory of Open Access Journals (Sweden)

Matej Supej

2018-03-01

Full Text Available Alpine skiing, both recreational and competitive, is associated with high rates of injury. Numerous studies have shown that occupational exposure to whole-body vibrations is strongly related to lower back pain and some suggest that, in particular, vibrations of lower frequencies could lead to overuse injuries of the back in connection with alpine ski racing. However, it is not yet known which forms of skiing involve stronger vibrations and whether these exceed safety thresholds set by existing standards and directives. Therefore, this study was designed to examine whole-body vibrations connected with different types of skiing and the associated potential risk of developing low back pain. Eight highly skilled ski instructors, all former competitive ski racers and equipped with five accelerometers and a Global Satellite Navigation System to measure vibrations and speed, respectively, performed six different forms of skiing: straight running, plowing, snow-plow swinging, basic swinging, short swinging, and carved turns. To estimate exposure to periodic, random and transient vibrations the power spectrum density (PSD and standard ISO 2631-1:1997 parameters [i.e., the weighted root-mean-square acceleration (RMS, crest factor, maximum transient vibration value and the fourth-power vibration dose value (VDV] were calculated. Ground reaction forces were estimated from data provided by accelerometers attached to the pelvis. The major novel findings were that all of the forms of skiing tested produced whole-body vibrations, with highest PSD values of 1.5–8 Hz. Intensified PSD between 8.5 and 35 Hz was observed only when skidding was involved. The RMS values for 10 min of short swinging or carved turns, as well as all 10-min equivalent VDV values exceeded the limits set by European Directive 2002/44/EC for health and safety. Thus, whole-body vibrations, particularly in connection with high ground reaction forces, contribute to a high risk for low back

A review of micromachined thermal accelerometers

Science.gov (United States)

Mukherjee, Rahul; Basu, Joydeep; Mandal, Pradip; Guha, Prasanta Kumar

2017-12-01

A thermal convection based micro-electromechanical accelerometer is a relatively new kind of acceleration sensor that does not require a solid proof mass, yielding unique benefits like high shock survival rating, low production cost, and integrability with CMOS integrated circuit technology. This article provides a comprehensive survey of the research, development, and current trends in the field of thermal acceleration sensors, with detailed enumeration on the theory, operation, modeling, and numerical simulation of such devices. Different reported varieties and structures of thermal accelerometers have been reviewed highlighting key design, implementation, and performance aspects. Materials and technologies used for fabrication of such sensors have also been discussed. Further, the advantages and challenges for thermal accelerometers vis-à-vis other prominent accelerometer types have been presented, followed by an overview of associated signal conditioning circuitry and potential applications.

String necklaces and primordial black holes from type IIB strings

International Nuclear Information System (INIS)

Lake, Matthew; Thomas, Steve; Ward, John

2009-01-01

We consider a model of static cosmic string loops in type IIB string theory, where the strings wrap cycles within the internal space. The strings are not topologically stabilised, however the presence of a lifting potential traps the windings giving rise to kinky cycloops. We find that PBH formation occurs at early times in a small window, whilst at late times we observe the formation of dark matter relics in the scaling regime. This is in stark contrast to previous predictions based on field theoretic models. We also consider the PBH contribution to the mass density of the universe, and use the experimental data to impose bounds on the string theory parameters.

The Development of Piezoelectric Accelerometers Using Finite Element Analysis

DEFF Research Database (Denmark)

Liu, Bin

1999-01-01

This paper describes the application of Finite Element (FE) approach for the development of piezoelectric accelerometers. An accelerometer is simulated using the FE approach as an example. Good agreement is achieved between simulated results and calibrated results. It is proved that the FE modeling...... can be effectively used to predict the specifications of the accelerometer, especially when modification of the accelerometer is required. The FE developing technology forms the bases of fast responsiveness and flexible customized design of piezoelectric accelerometers....

The Development of Piezoelectric Accelerometers Using Finite Elemen Analysis

DEFF Research Database (Denmark)

Liu, Bin; Yao, Q.; Kriegbaum, B.

1999-01-01

This paper describes the application of Finite Element (FE) approach for the development of piezoelectric accelerometers. An accelerometer is simulated using the FE approach as an example. Good agreement is achieved between simulated results and calibrated results. It is proved that the FE modeling...... can be effectively used to predict the specifications of the accelerometer, especially when modification of the accelerometer is required. The FE developing technology forms the bases of fast responsiveness and flexible customized design of piezoelectric accelerometers...

Reliability of the input admittance of bowed-string instruments measured by the hammer method.

Science.gov (United States)

Zhang, Ailin; Woodhouse, Jim

2014-12-01

The input admittance at the bridge, measured by hammer testing, is often regarded as the most useful and convenient measurement of the vibrational behavior of a bowed string instrument. However, this method has been questioned, due especially to differences between human bowing and hammer impact. The goal of the research presented here is to investigate the reliability and accuracy of this classic hammer method. Experimental studies were carried out on cellos, with three different driving conditions and three different boundary conditions. Results suggest that there is nothing fundamentally different about the hammer method, compared to other kinds of excitation. The third series of experiments offers an opportunity to explore the difference between the input admittance measuring from one bridge corner to another and that of single strings. The classic measurement is found to give a reasonable approximation to that of all four strings. Some possible differences between the hammer method and normal bowing and implications of the acoustical results are also discussed.

Coulomb string tension, asymptotic string tension, and the gluon chain

OpenAIRE

Greensite, Jeff; Szczepaniak, Adam P.

2014-01-01

We compute, via numerical simulations, the non-perturbative Coulomb potential of pure SU(3) gauge theory in Coulomb gauge. We find that that the Coulomb potential scales nicely in accordance with asymptotic freedom, that the Coulomb potential is linear in the infrared, and that the Coulomb string tension is about four times larger than the asymptotic string tension. We explain how it is possible that the asymptotic string tension can be lower than the Coulomb string tension by a factor of four.

Planetary Gearbox Fault Detection Using Vibration Separation Techniques

Science.gov (United States)

Lewicki, David G.; LaBerge, Kelsen E.; Ehinger, Ryan T.; Fetty, Jason

2011-01-01

Studies were performed to demonstrate the capability to detect planetary gear and bearing faults in helicopter main-rotor transmissions. The work supported the Operations Support and Sustainment (OSST) program with the U.S. Army Aviation Applied Technology Directorate (AATD) and Bell Helicopter Textron. Vibration data from the OH-58C planetary system were collected on a healthy transmission as well as with various seeded-fault components. Planetary fault detection algorithms were used with the collected data to evaluate fault detection effectiveness. Planet gear tooth cracks and spalls were detectable using the vibration separation techniques. Sun gear tooth cracks were not discernibly detectable from the vibration separation process. Sun gear tooth spall defects were detectable. Ring gear tooth cracks were only clearly detectable by accelerometers located near the crack location or directly across from the crack. Enveloping provided an effective method for planet bearing inner- and outer-race spalling fault detection.

Intelligent vibration control of ELTs and large AO hardware

Science.gov (United States)

Pott, J.-U.; Kürster, M.; Trowitzsch, J.; Borelli, J.; Rohloff, R.-R.; Herbst, T.; Böhm, M.; Keck, A.; Ruppel, T.; Sawodny, O.

2012-07-01

MPIA leads the construction of the LINC-NIRVANA instrument, the MCAO-supported Fizeau imager for the LBT, serves as pathfinder for future ELT-AO imagers in terms of size and technology. In this contribution, we review recent results and significant progress made on the development of key items of our stratgey to achieve a piston stability of up to 100nm during a science exposure. We present an overview of our vibration control strategies for optical path and tip-tilt stabilization, involving accelerometer based real-time vibration measurements, vibration sensitive active control of actuators, and the development of a dynamical model of the LBT. MPIA also co-develops the E-ELT first-light NIR imager MICADO (both SCAO and MCAO assisted). Our experiences, made with LINC-NIRVANA, will be fed into the MICADO structural AO design to reach highest on-sky sensitivity.

On Field Theory of Open Strings, Tachyon Condensation and Closed Strings

OpenAIRE

Shatashvili, Samson L.

2001-01-01

I review the physical properties of different vacua in the background independent open string field theory. Talk presented at Strings 2001, Mumbai, India, http://theory.theory.tifr.res.in/strings/Proceedings/#sha-s.

Closed Strings From Nothing

Energy Technology Data Exchange (ETDEWEB)

Lawrence, Albion

2001-07-25

We study the physics of open strings in bosonic and type II string theories in the presence of unstable D-branes. When the potential energy of the open string tachyon is at its minimum, Sen has argued that only closed strings remain in the perturbative spectrum. We explore the scenario of Yi and of Bergman, Hori and Yi, who argue that the open string degrees of freedom are strongly coupled and disappear through confinement. We discuss arguments using open string field theory and worldsheet boundary RG flows, which seem to indicate otherwise. We then describe a solitonic excitation of the open string tachyon and gauge field with the charge and tension of a fundamental closed string. This requires a double scaling limit where the tachyon is taken to its minimal value and the electric field is taken to its maximum value. The resulting flux tube has an unconstrained spatial profile; and for large fundamental string charge, it appears to have light, weakly coupled open strings living in the core. We argue that the flux tube acquires a size or order {alpha}' through sigma model and string coupling effects; and we argue that confinement effects make the light degrees of freedom heavy and strongly interacting.

Closed Strings From Nothing

International Nuclear Information System (INIS)

Lawrence, Albion

2001-01-01

We study the physics of open strings in bosonic and type II string theories in the presence of unstable D-branes. When the potential energy of the open string tachyon is at its minimum, Sen has argued that only closed strings remain in the perturbative spectrum. We explore the scenario of Yi and of Bergman, Hori and Yi, who argue that the open string degrees of freedom are strongly coupled and disappear through confinement. We discuss arguments using open string field theory and worldsheet boundary RG flows, which seem to indicate otherwise. We then describe a solitonic excitation of the open string tachyon and gauge field with the charge and tension of a fundamental closed string. This requires a double scaling limit where the tachyon is taken to its minimal value and the electric field is taken to its maximum value. The resulting flux tube has an unconstrained spatial profile; and for large fundamental string charge, it appears to have light, weakly coupled open strings living in the core. We argue that the flux tube acquires a size or order α' through sigma model and string coupling effects; and we argue that confinement effects make the light degrees of freedom heavy and strongly interacting

How to simulate global cosmic strings with large string tension

Energy Technology Data Exchange (ETDEWEB)

Klaer, Vincent B.; Moore, Guy D., E-mail: vklaer@theorie.ikp.physik.tu-darmstadt.de, E-mail: guy.moore@physik.tu-darmstadt.de [Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstraße 2, Darmstadt, D-64289 Germany (Germany)

2017-10-01

Global string networks may be relevant in axion production in the early Universe, as well as other cosmological scenarios. Such networks contain a large hierarchy of scales between the string core scale and the Hubble scale, ln( f {sub a} / H ) ∼ 70, which influences the network dynamics by giving the strings large tensions T ≅ π f {sub a} {sup 2} ln( f {sub a} / H ). We present a new numerical approach to simulate such global string networks, capturing the tension without an exponentially large lattice.

String field theory

International Nuclear Information System (INIS)

Kaku, M.

1987-01-01

In this article, the authors summarize the rapid progress in constructing string field theory actions, such as the development of the covariant BRST theory. They also present the newer geometric formulation of string field theory, from which the BRST theory and the older light cone theory can be derived from first principles. This geometric formulation allows us to derive the complete field theory of strings from two geometric principles, in the same way that general relativity and Yang-Mills theory can be derived from two principles based on global and local symmetry. The geometric formalism therefore reduces string field theory to a problem of finding an invariant under a new local gauge group they call the universal string group (USG). Thus, string field theory is the gauge theory of the universal string group in much the same way that Yang-Mills theory is the gauge theory of SU(N). The geometric formulation places superstring theory on the same rigorous group theoretical level as general relativity and gauge theory

Wind Turbine Bearing Diagnostics Based on Vibration Monitoring

Science.gov (United States)

Kadhim, H. T.; Mahmood, F. H.; Resen, A. K.

2018-05-01

Reliability maintenance can be considered as an accurate condition monitoring system which increasing beneficial and decreasing the cost production of wind energy. Supporting low friction of wind turbine rotating shaft is the main task of rolling element bearing and it is the main part that suffers from failure. The rolling failures elements have an economic impact and may lead to malfunctions and catastrophic failures. This paper concentrates on the vibration monitoring as a Non-Destructive Technique for assessing and demonstrates the feasibility of vibration monitoring for small wind turbine bearing defects based on LabVIEW software. Many bearings defects were created, such as inner race defect, outer race defect, and ball spin defect. The spectra data were recorded and compared with the theoretical results. The accelerometer with 4331 NI USB DAQ was utilized to acquiring, analyzed, and recorded. The experimental results were showed the vibration technique is suitable for diagnostic the defects that will be occurred in the small wind turbine bearings and developing a fault in the bearing which leads to increasing the vibration amplitude or peaks in the spectrum.

Assessment of Differing Definitions of Accelerometer Nonwear Time

Science.gov (United States)

Evenson, Kelly R.; Terry, James W., Jr.

2009-01-01

Measuring physical activity with objective tools, such as accelerometers, is becoming more common. Accelerometers measure acceleration multiple times within a given frequency and summarize this as a count over a pre-specified time period or epoch. The resultant count represents acceleration over the epoch length. Accelerometers eliminate biases…

BPS limit of multi- D- and DF-strings in boundary string field theory

International Nuclear Information System (INIS)

Go, Gyungchoon; Ishida, Akira; Kim, Yoonbai

2007-01-01

A BPS limit is systematically derived for straight multi- D- and DF-strings from the D3D-bar3 system in the context of boundary superstring field theory. The BPS limit is obtained in the limit of thin D(F)-strings, where the Bogomolny equation supports singular static multi-D(F)-string solutions. For the BPS multi-string configurations with arbitrary separations, BPS sum rule is fulfilled under a Gaussian type tachyon potential and reproduces exactly the descent relation. For the DF-strings ((p,q)-strings), the distribution of fundamental string charge density coincides with its energy density and the Hamiltonian density takes the BPS formula of square-root form

Estimation of sound pressure levels of voiced speech from skin vibration of the neck

NARCIS (Netherlands)

Svec, JG; Titze, IR; Popolo, PS

How accurately can sound pressure levels (SPLs) of speech be estimated from skin vibration of the neck? Measurements using a small accelerometer were carried out in 27 subjects (10 males and 17 females) who read Rainbow and Marvin Williams passages in soft, comfortable, and loud voice, while skin

The arithmetic of strings

International Nuclear Information System (INIS)

Freund, P.G.O.

1988-01-01

According to the author nobody has succeeded as yet in extracting any new numbers from string theory. This paper discusses how if one cannot get new numbers from string theory, maybe one can get new strings out of number theory. Number theory is generally regarded as the purest form of mathematics. So how can it conceivably make contact with physics which aims at describing nature? The author discusses how the connecting link of these two disciplines is provided by the compact Riemann surfaces. These appear as world sheets of interacting strings. For instance, string-string scattering at the three-loop level involves the four external strings attaching themselves to a genus three compact surface

Bowed Strings

Science.gov (United States)

Rossing, Thomas D.; Hanson, Roger J.

In the next eight chapters, we consider some aspects of the science of bowed string instruments, old and new. In this chapter, we present a brief discussion of bowed strings, a subject that will be developed much more thoroughly in Chap. 16. Chapters 13-15 discuss the violin, the cello, and the double bass. Chapter 17 discusses viols and other historic string instruments, and Chap. 18 discusses the Hutchins-Schelleng violin octet.

The theta-structure in string theories - 1: bosonic strings

International Nuclear Information System (INIS)

Li Miao.

1985-09-01

We explored the theta-structures in bosonic string theories which are similar to those in gauge field theories. The theta-structure of string is due to the multiply connected spatial compact subspace of space-time. The work of this paper shows that there is an energy band E(theta) in the string theory and one may move the tachyon out in theory by choosing some proper theta parameters. (author)

Kac-Moody Eisenstein series in string theory

Energy Technology Data Exchange (ETDEWEB)

Fleig, Philipp

2013-12-19

Understanding nature on its very smallest 'physical-length' scale has always been a central goal of physics. Theoretical investigations into this problem over the last fifty years or so were largely driven by the aim of reconciling the theory of general relativity, the theory which describes the fundamental force of gravity and therefore the dynamics of space-time, with the theory of quantum mechanics, which dominates the physical phenomena on very small (sub-atomic) scales, within one big framework, referred to as the theory of quantum gravity. One candidate for such a theory is string theory. The fundamental assumption of this theory is that the smallest constituents of nature are not given by point particles, but rather by one dimensional strings the size of the Planck length. Through their different vibrational modes, strings are thought to produce the different properties of the observed spectrum of particles in nature. With this basic idea, string theory is not only predicted to describe the gravitational force, but also all other known forces of nature, and therefore extends far beyond the concept of only being a theory of quantised gravity. Since its initial proposal, the theory has developed into a vast and complex mathematical web of different theories, which all seem to be part of a larger, all-encompassing theory. Key to understanding the complicated mathematical structure of this theory is the concept of symmetries. Such symmetries, which are also known as duality relations, for instance manifest themselves in special mathematical functions, contained in the amplitudes that capture information about the interaction processes of strings with one another. A particularly relevant example of such a function is given by the so-called Eisenstein series, which display invariance under certain discrete duality groups. The central goal of this thesis is to study the properties of Eisenstein series invariant under special, particularly large (in fact

Kac-Moody Eisenstein series in string theory

International Nuclear Information System (INIS)

Fleig, Philipp

2013-01-01

Understanding nature on its very smallest 'physical-length' scale has always been a central goal of physics. Theoretical investigations into this problem over the last fifty years or so were largely driven by the aim of reconciling the theory of general relativity, the theory which describes the fundamental force of gravity and therefore the dynamics of space-time, with the theory of quantum mechanics, which dominates the physical phenomena on very small (sub-atomic) scales, within one big framework, referred to as the theory of quantum gravity. One candidate for such a theory is string theory. The fundamental assumption of this theory is that the smallest constituents of nature are not given by point particles, but rather by one dimensional strings the size of the Planck length. Through their different vibrational modes, strings are thought to produce the different properties of the observed spectrum of particles in nature. With this basic idea, string theory is not only predicted to describe the gravitational force, but also all other known forces of nature, and therefore extends far beyond the concept of only being a theory of quantised gravity. Since its initial proposal, the theory has developed into a vast and complex mathematical web of different theories, which all seem to be part of a larger, all-encompassing theory. Key to understanding the complicated mathematical structure of this theory is the concept of symmetries. Such symmetries, which are also known as duality relations, for instance manifest themselves in special mathematical functions, contained in the amplitudes that capture information about the interaction processes of strings with one another. A particularly relevant example of such a function is given by the so-called Eisenstein series, which display invariance under certain discrete duality groups. The central goal of this thesis is to study the properties of Eisenstein series invariant under special, particularly large (in fact infinite

Bevel Gearbox Fault Diagnosis using Vibration Measurements

Directory of Open Access Journals (Sweden)

Hartono Dennis

2016-01-01

Full Text Available The use of vibration measurementanalysis has been proven to be effective for gearbox fault diagnosis. However, the complexity of vibration signals observed from a gearbox makes it difficult to accurately detectfaults in the gearbox. This work is based on a comparative studyof several time-frequency signal processing methods that can be used to extract information from transient vibration signals containing useful diagnostic information. Experiments were performed on a bevel gearbox test rig using vibration measurements obtained from accelerometers. Initially, thediscrete wavelet transform was implementedfor vibration signal analysis to extract the frequency content of signal from the relevant frequency region. Several time-frequency signal processing methods werethen incorporated to extract the fault features of vibration signals and their diagnostic performances were compared. It was shown thatthe Short Time Fourier Transform (STFT could not offer a good time resolution to detect the periodicity of the faulty gear tooth due the difficulty in choosing an appropriate window length to capture the impulse signal. The Continuous Wavelet Transform (CWT, on the other hand, was suitable to detection of vibration transients generated by localized fault from a gearbox due to its multi-scale property. However, both methods still require a thorough visual inspection. In contrast, it was shown from the experiments that the diagnostic method using the Cepstrumanalysis could provide a direct indication of the faulty tooth without the need of a thorough visual inspection as required by CWT and STFT.

Cosmic strings

International Nuclear Information System (INIS)

Bennett, D.P.

1988-07-01

Cosmic strings are linear topological defects that are predicted by some grand unified theories to form during a spontaneous symmetry breaking phase transition in the early universe. They are the basis for the only theories of galaxy formation aside from quantum fluctuations from inflation that are based on fundamental physics. In contrast to inflation, they can also be observed directly through gravitational lensing and their characteristic microwave background anistropy. It has recently been discovered by F. Bouchet and myself that details of cosmic string evolution are very different from the so-called ''standard model'' that has been assumed in most of the string induced galaxy formation calculations. Therefore, the details of galaxy formation in the cosmic string models are currently very uncertain. 29 refs., 9 figs

Why string theory?

CERN Document Server

Conlon, Joseph

2016-01-01

Is string theory a fraud or one of the great scientific advances? Why do so many physicists work on string theory if it cannot be tested? This book provides insight into why such a theory, with little direct experimental support, plays such a prominent role in theoretical physics. The book gives a modern and accurate account of string theory and science, explaining what string theory is, why it is regarded as so promising, and why it is hard to test.

Vision-based measurement system for structural vibration monitoring using non-projection quasi-interferogram fringe density enhanced by spectrum correction method

International Nuclear Information System (INIS)

Zhong, Jianfeng; Zhong, Shuncong; Zhang, Qiukun; Lu, Huancai; Zhuang, Yizhou; Fu, Xinbin

2017-01-01

A non-projection fringe vision measurement system suitable for vibration monitoring was proposed by using the concept of a 2D optical coherence vibration tomography (2D-OCVT) technique. An artificial quasi-interferogram fringe pattern (QIFP), similar to the interferogram of the 2D-OCVT system, was pasted onto the surface of a vibrating structure as a sensor. Image sequences of the QIFP were captured by a high-speed CMOS camera that worked as a detector. It was possible to obtain both the in-plane and out-of-plane vibration simultaneously. The in-plane vibration was obtained by tracking the center of the imaged QIFP using an image cross-correlation method, whilst the out-of-plane vibration was obtained from the changes in period density of the imaged QIFP. The influence of the noise sources from the CMOS image sensor, together with the effect of the imaging distance, the period density of the QIFP and also the key parameters of the fringe density enhanced by the spectrum correction method on the accuracy of the displacement measurement, were investigated by numerical simulations and experiments. Compared with the results from a conventional accelerometer-based measurement system, the proposed method was demonstrated to be an effective and accurate technique for measuring structural vibration without introducing any extra mass from the accelerometer. The significant advantages of this method include its simple installation and real-time dynamic response measurement capability, making the measurement system ideal for the low- and high-frequency vibration monitoring of engineering structures. (paper)

Multiflavor string-net models

Science.gov (United States)

Lin, Chien-Hung

2017-05-01

We generalize the string-net construction to multiple flavors of strings, each of which is labeled by the elements of an Abelian group Gi. The same flavor of strings can branch, while different flavors of strings can cross one another and thus they form intersecting string nets. We systematically construct the exactly soluble lattice Hamiltonians and the ground-state wave functions for the intersecting string-net condensed phases. We analyze the braiding statistics of the low-energy quasiparticle excitations and find that our model can realize all the topological phases as the string-net model with group G =∏iGi . In this respect, our construction provides various ways of building lattice models which realize topological order G , corresponding to different partitions of G and thus different flavors of string nets. In fact, our construction concretely demonstrates the Künneth formula by constructing various lattice models with the same topological order. As an example, we construct the G =Z2×Z2×Z2 string-net model which realizes a non-Abelian topological phase by properly intersecting three copies of toric codes.

Heterotic cosmic strings

International Nuclear Information System (INIS)

Becker, Katrin; Becker, Melanie; Krause, Axel

2006-01-01

We show that all three conditions for the cosmological relevance of heterotic cosmic strings, the right tension, stability and a production mechanism at the end of inflation, can be met in the strongly coupled M-theory regime. Whereas cosmic strings generated from weakly coupled heterotic strings have the well-known problems posed by Witten in 1985, we show that strings arising from M5-branes wrapped around 4-cycles (divisors) of a Calabi-Yau in heterotic M-theory compactifications solve these problems in an elegant fashion

A novel string field theory solving string theory by liberating left and right movers

International Nuclear Information System (INIS)

Nielsen, Holger B.; Ninomiya, Masao

2014-01-01

We put forward ideas to a novel string field theory based on making some “objects” that essentially describe “liberated” left- and right- mover fields X L μ (τ+σ) and X R μ (τ−σ) on the string. Our novel string field theory is completely definitely different from any other string theory in as far as a “null set” of information in the string field theory Fock space has been removed relatively, to the usual string field theories. So our theory is definitely new. The main progress is that we manage to make our novel string field theory provide the correct mass square spectrum for the string. We finally suggest how to obtain the Veneziano amplitude in our model

Accelerometer vs. geophone response : a field case history

Energy Technology Data Exchange (ETDEWEB)

Hons, M.S.; Stewart, R.R.; Lawton, D.C.; Bertram, M.B. [Calgary Univ., AB (Canada); Hauer, G. [ARAM Systems Ltd, Calgary, AB (Canada)

2008-07-01

The geophysical community has shown interest in the use of MEMS accelerometers as a new sensor for acquiring seismic data. Accelerometers, with their flat response in acceleration, may have advantages over geophones at low frequencies as well as high frequencies due to greater sensitivity. In this study, geophones and accelerometers were considered as simple harmonic oscillators. A method was developed to calculate ground acceleration from geophone data using a frequency-domain inverse filter and an empirical scaling constant. A comparison of acceleration-domain spectra from geophones and MEMS accelerometers from an oilfield survey at Violet Grove, Alberta, Canada revealed a distinct similarity between the geophone and accelerometer data, over a band of 5-200 Hz. The accelerometer amplitudes were larger than the geophones below 5 Hz and there were some differences at very high frequencies. Significant events related to the first breaks were not observed on the accelerometer records at some stations. It was concluded that both types of sensors can record ground motion similarly. If data from the two sensor types must be merged, a scaling factor based on matching amplitude spectra should be found. The spectra should be similar once the appropriate scaling is found, particularly around the dominant frequency. Some of the differences in data were related to high frequencies, very low frequencies, and near the first breaks. 4 refs., 6 figs.

Fingers' vibration transmission and grip strength preservation performance of vibration reducing gloves.

Science.gov (United States)

Hamouda, K; Rakheja, S; Dewangan, K N; Marcotte, P

2018-01-01

The vibration isolation performances of vibration reducing (VR) gloves are invariably assessed in terms of power tools' handle vibration transmission to the palm of the hand using the method described in ISO 10819 (2013), while the nature of vibration transmitted to the fingers is ignored. Moreover, the VR gloves with relatively low stiffness viscoelastic materials affect the grip strength in an adverse manner. This study is aimed at performance assessments of 12 different VR gloves on the basis of handle vibration transmission to the palm and the fingers of the gloved hand, together with reduction in the grip strength. The gloves included 3 different air bladder, 3 gel, 3 hybrid, and 2 gel-foam gloves in addition to a leather glove. Two Velcro finger adapters, each instrumented with a three-axis accelerometer, were used to measure vibration responses of the index and middle fingers near the mid-phalanges. Vibration transmitted to the palm was measured using the standardized palm adapter. The vibration transmissibility responses of the VR gloves were measured in the laboratory using the instrumented cylindrical handle, also described in the standard, mounted on a vibration exciter. A total of 12 healthy male subjects participated in the study. The instrumented handle was also used to measure grip strength of the subjects with and without the VR gloves. The results of the study showed that the VR gloves, with only a few exceptions, attenuate handle vibration transmitted to the fingers only in the 10-200 Hz and amplify middle finger vibration at frequencies exceeding 200 Hz. Many of the gloves, however, provided considerable reduction in vibration transmitted to the palm, especially at higher frequencies. These suggest that the characteristics of vibration transmitted to fingers differ considerably from those at the palm. Four of the test gloves satisfied the screening criteria of the ISO 10819 (2013) based on the palm vibration alone, even though these caused

Three Three-Axis IEPE Accelerometers on the Inner Liner of a Tire for Finding the Tire-Road Friction Potential Indicators.

Science.gov (United States)

Niskanen, Arto; Tuononen, Ari J

2015-08-05

Direct tire-road contact friction estimation is essential for future autonomous cars and active safety systems. Friction estimation methods have been proposed earlier for driving conditions in the presence of a slip angle or slip ratio. However, the estimation of the friction from a freely-rolling tire is still an unsolved topic. Knowing the existing friction potential would be beneficial since vehicle control systems could be adjusted before any remarkable tire force has been produced. Since accelerometers are well-known and robust, and thus a promising sensor type for intelligent tires, this study uses three three-axis IEPE accelerometers on the inner liner of a tire to detect friction potential indicators on two equally smooth surfaces with different friction levels. The equal roughness was chosen for both surfaces in order to study the friction phenomena by neglecting the effect of surface texture on vibrations. The acceleration data before the contact is used to differentiate the two friction levels between the tire and the road. In addition, the contact lengths from the three accelerometers are used to validate the acceleration data. A method to differentiate the friction levels on the basis of the acceleration signal is also introduced.

Exceptional groups from open strings

International Nuclear Information System (INIS)

Gaberdiel, M.R.; Zwiebach, B.

1998-01-01

We consider type IIB theory compactified on a two-sphere in the presence of mutually non-local 7-branes. The BPS states associated with the gauge vectors of exceptional groups are seen to arise from open strings connecting the 7-branes, and multi-pronged open strings capable of ending on more than two 7-branes. These multi-pronged strings are built from open string junctions that arise naturally when strings cross 7-branes. The different string configurations can be multiplied as traditional open strings, and are shown to generate the structure of exceptional groups. (orig.)

Evidence for string substructure

International Nuclear Information System (INIS)

Bergman, O.

1996-06-01

The author argues that the behavior of string theory at high temperature and high longitudinal boosts, combined with the emergence of p-branes as necessary ingredients in various string dualities, point to a possible reformulation of strings, as well as p-branes, as composites of bits. He reviews the string-bit models, and suggests generalizations to incorporate p-branes

Experimental investigation of torsional vibration isolation using Magneto Rheological Elastomer

Directory of Open Access Journals (Sweden)

Praveen Shenoy K

2018-01-01

Full Text Available Rotating systems suffer from lateral and torsional vibrations which have detrimental effect on the roto-dynamic performance. Many available technologies such as vibration isolators and vibration absorbers deal with the torsional vibrations to a certain extent, however passive isolators and absorbers find less application when the input conditions are dynamic. The present work discusses use of a smart material called as Magneto Rheological Elastomer (MRE, whose properties can be changed based on magnetic field input, as a potential isolator for torsional vibrations under dynamic loading conditions. Carbonyl Iron Particles (CIP of average size 5 μm were mixed with RTV Silicone rubber to form the MRE. The effect of magnetic field on the system parameters was comprehended under impulse loading conditions using a custom built in-house system. Series arrangement of accelerometers were used to differentiate between the torsional and the bending modes of vibration of the system. Impact hammer tests were carried out on the torsional system to study its response, in the presence and absence of magnetic field. The tests revealed a shift in torsional frequency in the presence of magnetic field which elucidates the ability of MRE to work as a potential vibration isolator for torsional systems.

Strings, texture, and inflation

International Nuclear Information System (INIS)

Hodges, H.M.; Primack, J.R.

1991-01-01

We examine mechanisms, several of which are proposed here, to generate structure formation, or to just add large-scale features, through either gauged or global cosmic strings or global texture, within the framework of inflation. We first explore the possibility that strings or texture form if there is no coupling between the topological theory and the inflaton or spacetime curvature, via (1) quantum creation, and (2) a sufficiently high reheat temperature. In addition, we examine the prospects for the inflaton field itself to generate strings or texture. Then, models with the string/texture field coupled to the curvature, and an equivalent model with coupling to the inflaton field, are considered in detail. The requirement that inflationary density fluctuations are not so large as to conflict with observations leads to a number of constraints on model parameters. We find that strings of relevance for structure formation can form in the absence of coupling to the inflaton or curvature through the process of quantum creation, but only if the strings are strongly type I, or if they are global strings. If formed after reheating, naturalness suggests that gauged cosmic strings correspond to a type-I superconductor. Similarly, gauged strings formed during inflation via conformal coupling ξ=1/6 to the spacetime curvature (in a model suggested by Yokoyama in order to evade the millisecond pulsar constraint on cosmic strings) are expected to be strongly type I

Piezoelectric Accelerometers Modification Based on the Finite Element Method

DEFF Research Database (Denmark)

Liu, Bin; Kriegbaum, B.

2000-01-01

The paper describes the modification of piezoelectric accelerometers using a Finite Element (FE) method. Brüel & Kjær Accelerometer Type 8325 is chosen as an example to illustrate the advanced accelerometer development procedure. The deviation between the measurement and FE simulation results...

A Self-Diagnostic System for the M6 Accelerometer

Science.gov (United States)

Flanagan, Patrick M.; Lekki, John

2001-01-01

The design of a Self-Diagnostic (SD) accelerometer system for the Space Shuttle Main Engine is presented. This retrofit system connects diagnostic electronic hardware and software to the current M6 accelerometer system. This paper discusses the general operation of the M6 accelerometer SD system and procedures for developing and evaluating the SD system. Signal processing techniques using M6 accelerometer diagnostic data are explained. Test results include diagnostic data responding to changing ambient temperature, mounting torque and base mounting impedance.

String Theory and M-Theory

Science.gov (United States)

Becker, Katrin; Becker, Melanie; Schwarz, John H.

String theory is one of the most exciting and challenging areas of modern theoretical physics. This book guides the reader from the basics of string theory to recent developments. It introduces the basics of perturbative string theory, world-sheet supersymmetry, space-time supersymmetry, conformal field theory and the heterotic string, before describing modern developments, including D-branes, string dualities and M-theory. It then covers string geometry and flux compactifications, applications to cosmology and particle physics, black holes in string theory and M-theory, and the microscopic origin of black-hole entropy. It concludes with Matrix theory, the AdS/CFT duality and its generalizations. This book is ideal for graduate students and researchers in modern string theory, and will make an excellent textbook for a one-year course on string theory. It contains over 120 exercises with solutions, and over 200 homework problems with solutions available on a password protected website for lecturers at www.cambridge.org/9780521860697. Comprehensive coverage of topics from basics of string theory to recent developments Ideal textbook for a one-year course in string theory Includes over 100 exercises with solutions Contains over 200 homework problems with solutions available to lecturers on-line

New expressions for string loop amplitudes leading to an ultra-simple conception of string dynamics

International Nuclear Information System (INIS)

Chan Hongmo; Tsou Sheungtsun; Bordes, J.; Nellen, L.

1990-11-01

New expressions are derived for string loop amplitudes as overlap integrals of string wave functionals. They are shown to take the form of exchange terms coming from the Bose-Einstein symmetrisation between string segments. One is thus led to the ultra-simple conception that string theory is basically free, and that 'string interactions' are due merely to the fact that strings are composite objects with Bose-Einstein segments as constituents. (author)

Stretching cosmic strings

International Nuclear Information System (INIS)

Turok, N.; Bhattacharjee, P.

1984-01-01

The evolution of a network of strings produced at a grand-unification phase transition in an expanding universe is discussed, with particular reference to the processes of energy exchange between the strings and the rest of the universe. This is supported by numerical calculations simulating the behavior of strings in an expanding universe. It is found that in order that the energy density of the strings does not come to dominate the total energy density there must be an efficient mechanism for energy loss: the only plausible one being the production of closed loops and their subsequent decay via gravitational radiation

M-strings, Elliptic Genera and N=4 String Amplitudes

CERN Document Server

Hohenegger, Stefan

2014-01-01

We study mass-deformed N=2 gauge theories from various points of view. Their partition functions can be computed via three dual approaches: firstly, (p,q)-brane webs in type II string theory using Nekrasov's instanton calculus, secondly, the (refined) topological string using the topological vertex formalism and thirdly, M theory via the elliptic genus of certain M-strings configurations. We argue for a large class of theories that these approaches yield the same gauge theory partition function which we study in detail. To make their modular properties more tangible, we consider a fourth approach by connecting the partition function to the equivariant elliptic genus of R^4 through a (singular) theta-transform. This form appears naturally as a specific class of one-loop scattering amplitudes in type II string theory on T^2, which we calculate explicitly.

String Math 2017

CERN Document Server

The series of String-Math conferences has developed into a central event on the interface between mathematics and physics related to string theory, quantum field theory and neighboring subjects. The conference will take place from July 24-28 in the main building of Hamburg university. The String-Math conference is organised by the University of Hamburg jointly with DESY Hamburg.

EMBEDDED SYSTEMS FOR VIBRATION MONITORING

Directory of Open Access Journals (Sweden)

Miloš Milovančević

2014-08-01

Full Text Available The purpose of the research presented in this paper is the development of the optimal micro configuration for vibration monitoring of pumping aggregate, based on Microchip’s microcontroller (MC. Hardware used is 10-bit MC, upgraded with 12/bit A/D converter. Software for acquisition and data analysis is optimized for testing turbo pumps with rotation speed up to 2000 rpm. This software limitation is set for automatic diagnostics and for individual and manual vibro-diagnostic; the only limitation is set by accelerometer performance. The authors have performed numerous measurements on a wide range of turbo aggregates for establishing the operational condition of pumping aggregates.

Recoil and Vibration in an Archery Bow Equipped with a Multi-Rod Stabilizer

Directory of Open Access Journals (Sweden)

Igor Zaniewski

2012-01-01

Full Text Available The aim of this research is to create a mechanical and mathematical model of a multi-rod stabilizer for the sport archery bow and to analyze its capability to damp disagreeable recoil and vibration of the bow during internal ballistic motion. The research methods are based on the Euler-Bernoulli theory of beam bending, Lagrange equations of the second kind, the Cauchy problem, and the Runge-Kutta method. A mathematical software package was used to analyze the problem. The approach to the problem of sport-bow stabilization in the vertical plane that is proposed in this paper addresses the practical needs both of applied engineering mechanics and of the sport of archery. Numerical results from computer simulation are presented in both tabular and graphical form. The common motion of the string and arrow (internal ballistic motion is accompanied by intense vibration which is caused by disruption of the static force balance at the moment of string release.

Calibration and comparison of accelerometer cut points in preschool children.

Science.gov (United States)

van Cauwenberghe, Eveline; Labarque, Valery; Trost, Stewart G; de Bourdeaudhuij, Ilse; Cardon, Greet

2011-06-01

The present study aimed to develop accelerometer cut points to classify physical activities (PA) by intensity in preschoolers and to investigate discrepancies in PA levels when applying various accelerometer cut points. To calibrate the accelerometer, 18 preschoolers (5.8 ± 0.4 years) performed eleven structured activities and one free play session while wearing a GT1M ActiGraph accelerometer using 15 s epochs. The structured activities were chosen based on the direct observation system Children's Activity Rating Scale (CARS) while the criterion measure of PA intensity during free play was provided using a second-by-second observation protocol (modified CARS). Receiver Operating Characteristic (ROC) curve analyses were used to determine the accelerometer cut points. To examine the classification differences, accelerometer data of four consecutive days from 114 preschoolers (5.5 ± 0.3 years) were classified by intensity according to previously published and the newly developed accelerometer cut points. Differences in predicted PA levels were evaluated using repeated measures ANOVA and Chi Square test. Cut points were identified at 373 counts/15 s for light (sensitivity: 86%; specificity: 91%; Area under ROC curve: 0.95), 585 counts/15 s for moderate (87%; 82%; 0.91) and 881 counts/15 s for vigorous PA (88%; 91%; 0.94). Further, applying various accelerometer cut points to the same data resulted in statistically and biologically significant differences in PA. Accelerometer cut points were developed with good discriminatory power for differentiating between PA levels in preschoolers and the choice of accelerometer cut points can result in large discrepancies.

Investigation and analysis the vibration of handles of chainsaw without cutting

Directory of Open Access Journals (Sweden)

M Feyzi

2016-04-01

Full Text Available Introduction: Nowadays most of the agricultural and industrial tasks are performed using different machines and almost any people are exposed to the vibration of these machines. Just as sound can be either music to the ear or irritating noise, human vibrations can either be pleasant or unpleasant. Whole-body vibration and hand-arm vibration are two main types of unpleasant vibration. The hand-arm transmitted vibration can cause complex vascular, neurological and musculoskeletal disorder, collectively named as hand-arm vibration syndrome. The chainsaw is a portable machine, powered by a two-stroke engine. This machine is used by tree surgeons to fell trees, remove branches, and other activities such as prune trees. The chainsaw exposes own operators to high level of hand-arm vibration which can lead to problems such as vibration white finger syndrome and Raynaud's phenomenon. White finger syndrome affects the nerves, blood vessels, muscles, and joints of the hand, wrist and arm. It is clear that before trying to control the vibrations, the level of vibrations should be identified. Therefore, an investigation on the vibration level of this machine is crucial. Materials and Methods: The Stihl-MS230 chainsaw was selected in this study. The size of this type of chainsaw is middle and it is equipped with anti-vibration system. According to the ISO-7505 standard, vibration must be measured at three speed level of engine. First at idling speed, second at nominal speed and third at 133% of the nominal speed or maximum speed of engine whichever is less (Racing. So 2800, 10000, and 13300 RPM Engine speed were selected. One of the employed accessories was ARMA ETI-TACHO tachometer which had been fabricated in Taiwan. The vibrations were measured and analyzed using the portable data acquisition system (Easy Viber. During the measurements, data acquisition system was powered by internal batteries. The vibrations were sensed by the piezoelectric accelerometer

Wireless vibration monitoring in a US coal-fired plant

Energy Technology Data Exchange (ETDEWEB)

Gbur, G.L.; Wier, W.; Bark, T.

2006-07-15

Choosing a reliable wireless systems able to provide data on vibration magnitudes in a coal pulveriser was never going to be easy, so two systems were tested alongside each other. One was the Wireless MCT System produced by SKF Reliability Systems; the other was from an alternative vendor. A replacement wireless vibration monitor was required at the Baldwin Energy Complex near Decartar, Illinois, USA. A single CE-Raymond model 923.RP pulverizer equipped with eight Wilcox on 786A accelerometers was chosen for monitoring. Five days after installation, the pulverizer experienced a failure. The wireless system provided vibration magnitudes to Dynegy's OSI PI Historian software. Analysis of this data coupled with an unsuccessful attempt to adjust the grinding roll, revealed that the number two grinding roll bearing had failed. The SKF Reliability System proved to detect the fault earlier than the non-SKF system and was chosen for the plant. 10 figs., 1 tab.

A Simple Instrumentation System for Large Structure Vibration Monitoring

Directory of Open Access Journals (Sweden)

Didik R. Santoso

2010-12-01

Full Text Available Traditional instrumentation systems used for monitoring vibration of large-scale infrastructure building such as bridges, railway, and others structural building, generally have a complex design. Makes it simple would be very useful both in terms of low-cost and easy maintenance. This paper describes how to develop the instrumentation system. The system is built based on distributed network, with field bus topology, using single-master multi-slave architecture. Master is a control unit, built based on a PC equipped with RS-485 interface. Slave is a sensing unit; each slave was built by integrating a 3-axis vibration sensor with a microcontroller based data acquisition system. Vibration sensor is designed using the main components of a MEMS accelerometer. While the software is developed for two functions: as a control system hardware and data processing. To verify performance of the developed instrumentation system, several laboratory tests have been performed. The result shows that the system has good performance.

Hybrid motion sensing and experimental modal analysis using collocated smartphone camera and accelerometers

International Nuclear Information System (INIS)

Ozer, Ekin; Feng, Dongming; Feng, Maria Q

2017-01-01

State-of-the-art multisensory technologies and heterogeneous sensor networks propose a wide range of response measurement opportunities for structural health monitoring (SHM). Measuring and fusing different physical quantities in terms of structural vibrations can provide alternative acquisition methods and improve the quality of the modal testing results. In this study, a recently introduced SHM concept, SHM with smartphones, is focused to utilize multisensory smartphone features for a hybridized structural vibration response measurement framework. Based on vibration testing of a small-scale multistory laboratory model, displacement and acceleration responses are monitored using two different smartphone sensors, an embedded camera and accelerometer, respectively. Double-integration or differentiation among different measurement types is performed to combine multisensory measurements on a comparative basis. In addition, distributed sensor signals from collocated devices are processed for modal identification, and performance of smartphone-based sensing platforms are tested under different configuration scenarios and heterogeneity levels. The results of these tests show a novel and successful implementation of a hybrid motion sensing platform through multiple sensor type and device integration. Despite the heterogeneity of motion data obtained from different smartphone devices and technologies, it is shown that multisensory response measurements can be blended for experimental modal analysis. Getting benefit from the accessibility of smartphone technology, similar smartphone-based dynamic testing methodologies can provide innovative SHM solutions with mobile, programmable, and cost-free interfaces. (paper)

Hybrid motion sensing and experimental modal analysis using collocated smartphone camera and accelerometers

Science.gov (United States)

Ozer, Ekin; Feng, Dongming; Feng, Maria Q.

2017-10-01

State-of-the-art multisensory technologies and heterogeneous sensor networks propose a wide range of response measurement opportunities for structural health monitoring (SHM). Measuring and fusing different physical quantities in terms of structural vibrations can provide alternative acquisition methods and improve the quality of the modal testing results. In this study, a recently introduced SHM concept, SHM with smartphones, is focused to utilize multisensory smartphone features for a hybridized structural vibration response measurement framework. Based on vibration testing of a small-scale multistory laboratory model, displacement and acceleration responses are monitored using two different smartphone sensors, an embedded camera and accelerometer, respectively. Double-integration or differentiation among different measurement types is performed to combine multisensory measurements on a comparative basis. In addition, distributed sensor signals from collocated devices are processed for modal identification, and performance of smartphone-based sensing platforms are tested under different configuration scenarios and heterogeneity levels. The results of these tests show a novel and successful implementation of a hybrid motion sensing platform through multiple sensor type and device integration. Despite the heterogeneity of motion data obtained from different smartphone devices and technologies, it is shown that multisensory response measurements can be blended for experimental modal analysis. Getting benefit from the accessibility of smartphone technology, similar smartphone-based dynamic testing methodologies can provide innovative SHM solutions with mobile, programmable, and cost-free interfaces.

Gravitational effects of global strings

International Nuclear Information System (INIS)

Aryal, M.; Everett, A.E.

1986-01-01

We have obtained the gravitational field, in the weak-field approximation, of cosmic strings formed in a phase transition in which a global symmetry is broken (global strings). The effect of this field on light rays passing a global string is found, and the resulting formation of double images and production of discontinuities in the microwave background temperature compared with the corresponding results for gauge strings. There are some differences in the case of global strings, reflecting the fact that the space surrounding such strings is not purely conical. However, the differences between gauge and global strings with masses suitable to explain galaxy formation are small, and the task of distinguishing them observationally appears difficult at best

International conference on string theory

CERN Document Server

2017-01-01

The Strings 2017 conference is part of the "Strings" series of annual conferences, that bring the entire string theory community together. It will include reviews of major developments in the field, and specialized talks on specific topics. There will also be several public lectures given by conference participants, a pre-Strings school at the Technion, and a post-Strings workshop at the Weizmann Institute.

Cosmic strings and inflation

International Nuclear Information System (INIS)

Vishniac, E.T.

1987-01-01

We examine the compatibility of inflation with the cosmic string theory for galaxy formation. There is a general conflict between having sufficient string tension to effect galaxy formation, and reheating after inflation to a high enough temperature that strings may form in a thermal phase transition. To escape this conflict, we propose a class of models where the inflation is coupled to the string-producing field. The strings are formed late in inflation as the inflaton rolls towards its zero-temperature value. A large subset of these models have a novel large-scale distribution of galaxies that is fractal, displays biasing without dynamics or feedback mechanisms, and contains voids. (orig.)

Fabrication of a Miniaturized ZnO Nanowire Accelerometer and Its Performance Tests

Directory of Open Access Journals (Sweden)

Hyun Chan Kim

2016-09-01

Full Text Available This paper reports a miniaturized piezoelectric accelerometer suitable for a small haptic actuator array. The accelerometer is made with zinc oxide (ZnO nanowire (NW grown on a copper wafer by a hydrothermal process. The size of the accelerometer is 1.5 × 1.5 mm2, thus fitting the 1.8 × 1.8 mm2 haptic actuator array cell. The detailed fabrication process of the miniaturized accelerometer is illustrated. Performance evaluation of the fabricated accelerometer is conducted by comparing it with a commercial piezoelectric accelerometer. The output current of the fabricated accelerometer increases linearly with the acceleration. The miniaturized ZnO NW accelerometer is feasible for acceleration measurement of small and lightweight devices.

String-Math 2015

CERN Document Server

2015-01-01

Welcome to String-Math 2015 at Sanya. The conference will be opened in December 31, 2015- January 4, 2016. String theory plays a central role in theoretical physics as a candidate for the quantum theory unifying gravity with other interactions. It has profound connections with broad branches of modern mathematics ever since the birth. In the last decades, the prosperous interaction, built upon the joint efforts from both mathematicians and physicists, has given rise to marvelous deep results in supersymmetric gauge theory, topological string, M-theory and duality on the physics side as well as in algebraic geometry, differential geometry, algebraic topology, representation theory and number theory on the mathematics side. The interplay is two-fold. The mathematics has provided powerful tools to fulfill the physical interconnection of ideas and clarify physical structures to understand the nature of string theory. On the other hand, ideas from string theory and quantum field theory have been a source of sign...

A non-invasive acoustic and vibration analysis technique for evaluation of hip joint conditions.

Science.gov (United States)

Glaser, Diana; Komistek, Richard D; Cates, Harold E; Mahfouz, Mohamed R

2010-02-10

The performance evaluation of THA outcome is difficult and surgeons often use invasive methods to investigate effectiveness. A non-invasive acoustic and vibration analysis technique has recently been developed for more-in-depth evaluation of in vivo hip conditions. Gait kinematics, corresponding vibration and sound measurement of five THA subjects were analyzed post-operatively using video-fluoroscopy, sound and accelerometer measurements while walking on a treadmill. The sound sensor and a pair of tri-axial accelerometers, externally attached to the pelvic and femoral bone prominences, detected frequencies that are propagated through the femoral head and acetabular cup interactions. A data acquisition system was used to amplify the signal and filter out noise generated by undesired frequencies. In vivo kinematics and femoral head sliding quantified using video fluoroscopy were correlated to the sound and acceleration measurements. Distinct variations between the different subjects were identified. A correlation of sound and acceleration impulses with separation has been achieved. Although, in vivo sounds are quite variable in nature and all correlated well with the visual images. This is the first study to document and correlate visual and audible effects of THA under in-vivo conditions. This study has shown that the development of the acoustic and vibration technique provides a practical method and generates new possibilities for a better understanding of THA performance. Copyright 2009 Elsevier Ltd. All rights reserved.

Deterministic indexing for packed strings

DEFF Research Database (Denmark)

Bille, Philip; Gørtz, Inge Li; Skjoldjensen, Frederik Rye

2017-01-01

Given a string S of length n, the classic string indexing problem is to preprocess S into a compact data structure that supports efficient subsequent pattern queries. In the deterministic variant the goal is to solve the string indexing problem without any randomization (at preprocessing time...... or query time). In the packed variant the strings are stored with several character in a single word, giving us the opportunity to read multiple characters simultaneously. Our main result is a new string index in the deterministic and packed setting. Given a packed string S of length n over an alphabet σ...

Topics in string theory

International Nuclear Information System (INIS)

Neveu, A.

1986-01-01

There exist several string models. In the first lecture, the simplest one, the open bosonic string, which turns out to live most naturally in 26 dimensions will be described in some detail. In the second lecture, the closed bosonic strings, and the open and closed 10-dimensional strings (superstrings) are reviewed. In the third lecture, various compactification schemes which have been proposed to deal with the extra space dimensions, from 4 to 10 or 26 are dealt with; in particular, the Frenkel-Kac construction which builds non-Abelian internal symmetry groups out of the compactified dimensions, and the resulting heterotic string are described. Finally, in the fourth lecture, the important problem of the second quantization of string theories, and of the underlying gauge invariance which is responsible for the possibility of dealing, in a consistent fashion, with interacting high-spin states without negative metric is addressed. 41 references, 8 figures

Fiber-optical accelerometers based on polymer optical fiber Bragg gratings

DEFF Research Database (Denmark)

Yuan, Scott Wu; Stefani, Alessio; Bang, Ole

2010-01-01

Fiber-optical accelerometers based on polymer optical fiber Bragg gratings (FBGs) are reported. We have written 3mm FBGs for 1550nm operation, characterized their temperature and strain response, and tested their performance in a prototype accelerometer.......Fiber-optical accelerometers based on polymer optical fiber Bragg gratings (FBGs) are reported. We have written 3mm FBGs for 1550nm operation, characterized their temperature and strain response, and tested their performance in a prototype accelerometer....

Oriented open-closed string theory revisited

International Nuclear Information System (INIS)

Zwiebach, B.

1998-01-01

String theory on D-brane backgrounds is open-closed string theory. Given the relevance of this fact, we give details and elaborate upon our earlier construction of oriented open-closed string field theory. In order to incorporate explicitly closed strings, the classical sector of this theory is open strings with a homotopy associative A ∞ algebraic structure. We build a suitable Batalin-Vilkovisky algebra on moduli spaces of bordered Ricmann surfaces, the construction of which involves a few subtleties arising from the open string punctures and cyclicity conditions. All vertices coupling open and closed strings through disks are described explicitly. Subalgebras of the algebra of surfaces with boundaries are used to discuss symmetries of classical open string theory induced by the closed string sector, and to write classical open string field theory on general closed string backgrounds. We give a preliminary analysis of the ghost-dilaton theorem. copyright 1998 Academic Press, Inc

Multiquark strings

International Nuclear Information System (INIS)

Wang, F.; Chun, W.

1985-01-01

The use of basis states described as hadronic (or hadron-hadron) or hidden-colour (or colour-colour) for a system of quarks does not necessarily imply that connected exotic multiquark hadrons do exist. Antisymmetrization of quark wave functions tends to make these descriptions ill defined. It appears necessary to have stable collective structures called strings or bags to provide the physical connections required by quark confinement. The masses of multiquark hadrons can then be estimated by using semplified string, bag and NR potential models. The results turn out to be qualitatively similar in all these models. The stability problem for multiquark strings is briefly discussed

Vibration Suppression for Improving the Estimation of Kinematic Parameters on Industrial Robots

Directory of Open Access Journals (Sweden)

David Alejandro Elvira-Ortiz

2016-01-01

Full Text Available Vibration is a phenomenon that is present on every industrial system such as CNC machines and industrial robots. Moreover, sensors used to estimate angular position of a joint in an industrial robot are severely affected by vibrations and lead to wrong estimations. This paper proposes a methodology for improving the estimation of kinematic parameters on industrial robots through a proper suppression of the vibration components present on signals acquired from two primary sensors: accelerometer and gyroscope. A Kalman filter is responsible for the filtering of spurious vibration. Additionally, a sensor fusion technique is used to merge information from both sensors and improve the results obtained using each sensor separately. The methodology is implemented in a proprietary hardware signal processor and tested in an ABB IRB 140 industrial robot, first by analyzing the motion profile of only one joint and then by estimating the path tracking of two welding tasks: one rectangular and another one circular. Results from this work prove that the sensor fusion technique accompanied by proper suppression of vibrations delivers better estimation than other proposed techniques.

Open string model building

International Nuclear Information System (INIS)

Ishibashi, Nobuyuki; Onogi, Tetsuya

1989-01-01

Consistency conditions of open string theories, which can be a powerful tool in open string model building, are proposed. By making use of these conditions and assuming a simple prescription for the Chan-Paton factors, open string theories in several backgrounds are studied. We show that 1. there exist a large number of consistent bosonic open string theories on Z 2 orbifolds, 2. SO(32) type I superstring is the unique consistent model among fermionic string theories on the ten-dimensional flat Minkowski space, and 3. with our prescription for the Chan-Paton factors, there exist no consistent open superstring theories on (six-dimensional Minkowski space-time) x (Z 2 orbifold). (orig.)

Cosmic strings and galaxy formation

International Nuclear Information System (INIS)

Bertschinger, E.

1989-01-01

Cosmic strings have become increasingly popular candidates as seeds for the formation of structure in the universe. This scenario, remains a serious cosmogonical model despite close scrutiny. In constrast, magnetic monopoles and domain walls - relic topological defects as are cosmic strings - are disastrous for cosmology if they are left over from the early universe. The production of heavy cosmic strings is speculative, as it depends on the details of ultrahigh energy physics. Fortunately, speculation about cosmic strings is not entirely idle because, if they exist and are heavy enough to seed galaxy formation, cosmic strings can be detected astronomically. Failure to detect cosmic strings would impose some constraints on grand unified theories (GUTs); their discovery would have exciting consequences for high energy physics and cosmology. This article reviews the basic physics of nonsuperconducting cosmic strings, highlighting the field theory aspects, and provides a progress report on calculations of structure formation with cosmic strings

String-localized quantum fields

International Nuclear Information System (INIS)

Mund, Jens; Santos, Jose Amancio dos; Silva, Cristhiano Duarte; Oliveira, Erichardson de

2009-01-01

Full text. The principles of physics admit (unobservable) quantum fields which are localized not on points, but on strings in the sense of Mandelstam: a string emanates from a point in Minkowski space and extends to infinity in some space-like direction. This type of localization might permit the construction of new models, for various reasons: (a) in general, weaker localization implies better UV behaviour. Therefore, the class of renormalizable interactions in the string-localized has a chance to be larger than in the point-localized case; (b) for certain particle types, there are no point-localized (free) quantum fields - for example Anyons in d = 2 + 1, and Wigner's massless 'infinite spin' particles. For the latter, free string-localized quantum fields have been constructed; (c) in contrast to the point-localized case, string-localization admits covariant vector/tensor potentials for fotons and gravitons in a Hilbert space representation with positive energy. We shall present free string-localized quantum fields for various particle types, and some ideas about the perturbative construction of interacting string-localized fields. A central point will be an analogue of gauge theories, completely within a Hilbert space and without ghosts, trading gauge dependence with dependence on the direction of the localization string. In order to discuss renormalizability (item (a)), methods from microlocal analysis (wave front set and scaling degree) are needed. (author)

Device for balancing parallel strings

Science.gov (United States)

Mashikian, Matthew S.

1985-01-01

A battery plant is described which features magnetic circuit means in association with each of the battery strings in the battery plant for balancing the electrical current flow through the battery strings by equalizing the voltage across each of the battery strings. Each of the magnetic circuit means generally comprises means for sensing the electrical current flow through one of the battery strings, and a saturable reactor having a main winding connected electrically in series with the battery string, a bias winding connected to a source of alternating current and a control winding connected to a variable source of direct current controlled by the sensing means. Each of the battery strings is formed by a plurality of batteries connected electrically in series, and these battery strings are connected electrically in parallel across common bus conductors.

Strings in the Sun?

International Nuclear Information System (INIS)

Chudnovsky, E.; Vilenkin, A.

1988-01-01

If light superconducting strings were formed in the early Universe, then it is very likely that now they exist in abundance in the interstellar plasma and in stars. The dynamics of such strings can be dominated by friction, so that they are ''frozen'' into the plasma. Turbulence of the plasma twists and stretches the strings, forming a stochastic string network. Such networks must generate particles and magnetic fields, and may play an important role in the physics of stars and of the Galaxy

Thermodynamics of quantum strings

CERN Document Server

Morgan, M J

1994-01-01

A statistical mechanical analysis of an ideal gas of non-relativistic quantum strings is presented, in which the thermodynamic properties of the string gas are calculated from a canonical partition function. This toy model enables students to gain insight into the thermodynamics of a simple 'quantum field' theory, and provides a useful pedagogical introduction to the more complicated relativistic string theories. A review is also given of the thermodynamics of the open bosonic string gas and the type I (open) superstring gas. (author)

Dynamics of Carroll strings

Energy Technology Data Exchange (ETDEWEB)

Cardona, Biel [Departament d’Estructura i Constituents de la Matèriaand Institut de Ciències del Cosmos (ICCUB) Facultat de Física, Universitat de Barcelona,Diagonal 647, E-08028 Barcelona, Catalonia (Spain); Gomis, Joaquim [Departament d’Estructura i Constituents de la Matèriaand Institut de Ciències del Cosmos (ICCUB) Facultat de Física, Universitat de Barcelona,Diagonal 647, E-08028 Barcelona, Catalonia (Spain); Department of Physics, Faculty of Science, Chulalongkorn University,Bangkok 10330 (Thailand); Pons, Josep M. [Departament d’Estructura i Constituents de la Matèriaand Institut de Ciències del Cosmos (ICCUB) Facultat de Física, Universitat de Barcelona,Diagonal 647, E-08028 Barcelona, Catalonia (Spain)

2016-07-11

We construct the canonical action of a Carroll string doing the Carroll limit of a canonical relativistic string. We also study the Killing symmetries of the Carroll string, which close under an infinite dimensional algebra. The tensionless limit and the Carroll p-brane action are also discussed.

Cosmic strings and cosmic structure

International Nuclear Information System (INIS)

Albrecht, A.; Brandenberger, R.; Turok, N.

1987-01-01

The paper concerns the application of the theory of cosmic strings to explain the structure of the Universe. The formation of cosmic strings in the early Universe is outlined, along with the Big Bang theory, Grand Unified theories, and the first three minutes after the Big Bang. A description is given of the shaping of the Universe by cosmic strings, including the evolution of the string. The possibility for direct observation of cosmic strings is discussed. (U.K.)

Three Three-Axis IEPE Accelerometers on the Inner Liner of a Tire for Finding the Tire-Road Friction Potential Indicators

Directory of Open Access Journals (Sweden)

Arto Niskanen

2015-08-01

Full Text Available Direct tire-road contact friction estimation is essential for future autonomous cars and active safety systems. Friction estimation methods have been proposed earlier for driving conditions in the presence of a slip angle or slip ratio. However, the estimation of the friction from a freely-rolling tire is still an unsolved topic. Knowing the existing friction potential would be beneficial since vehicle control systems could be adjusted before any remarkable tire force has been produced. Since accelerometers are well-known and robust, and thus a promising sensor type for intelligent tires, this study uses three three-axis IEPE accelerometers on the inner liner of a tire to detect friction potential indicators on two equally smooth surfaces with different friction levels. The equal roughness was chosen for both surfaces in order to study the friction phenomena by neglecting the effect of surface texture on vibrations. The acceleration data before the contact is used to differentiate the two friction levels between the tire and the road. In addition, the contact lengths from the three accelerometers are used to validate the acceleration data. A method to differentiate the friction levels on the basis of the acceleration signal is also introduced.

Using tri-axial accelerometers to identify wild polar bear behaviors

Science.gov (United States)

Pagano, Anthony M.; Rode, Karyn D.; Cutting, A.; Owen, M.A.; Jensen, S.; Ware, J.V.; Robbins, C.T.; Durner, George M.; Atwood, Todd C.; Obbard, M.E.; Middel, K.R.; Thiemann, G.W.; Williams, T.M.

2017-01-01

Tri-axial accelerometers have been used to remotely identify the behaviors of a wide range of taxa. Assigning behaviors to accelerometer data often involves the use of captive animals or surrogate species, as their accelerometer signatures are generally assumed to be similar to those of their wild counterparts. However, this has rarely been tested. Validated accelerometer data are needed for polar bears Ursus maritimus to understand how habitat conditions may influence behavior and energy demands. We used accelerometer and water conductivity data to remotely distinguish 10 polar bear behaviors. We calibrated accelerometer and conductivity data collected from collars with behaviors observed from video-recorded captive polar bears and brown bears U. arctos, and with video from camera collars deployed on free-ranging polar bears on sea ice and on land. We used random forest models to predict behaviors and found strong ability to discriminate the most common wild polar bear behaviors using a combination of accelerometer and conductivity sensor data from captive or wild polar bears. In contrast, models using data from captive brown bears failed to reliably distinguish most active behaviors in wild polar bears. Our ability to discriminate behavior was greatest when species- and habitat-specific data from wild individuals were used to train models. Data from captive individuals may be suitable for calibrating accelerometers, but may provide reduced ability to discriminate some behaviors. The accelerometer calibrations developed here provide a method to quantify polar bear behaviors to evaluate the impacts of declines in Arctic sea ice.

Random surfaces and strings

International Nuclear Information System (INIS)

Ambjoern, J.

1987-08-01

The theory of strings is the theory of random surfaces. I review the present attempts to regularize the world sheet of the string by triangulation. The corresponding statistical theory of triangulated random surfaces has a surprising rich structure, but the connection to conventional string theory seems non-trivial. (orig.)

Hagedorn Behavior of Little String Theories from string corrections to NS5-branes

DEFF Research Database (Denmark)

Harmark, Troels; Obers, N. A.

2000-01-01

We examine the Hagedorn behavior of little string theory using its conjectured duality with near-horizon NS5-branes. In particular, by studying the string-corrected NS5-brane supergravity solution, it is shown that tree-level corrections to the temperature vanish, while the leading one-loop string...... correction generates the correct temperature dependence of the entropy near the Hagedorn temperature. Finally, the Hagedorn behavior of ODp-brane theories, which are deformed versions of little string theory, is considered via their supergravity duals....

Lectures on strings and dualities

International Nuclear Information System (INIS)

Vafa, C.

1997-01-01

In this set of lectures I review recent developments in string theory emphasizing their non-perturbative aspects and their recently discovered duality symmetries. The goal of the lectures is to make the recent exciting developments in string theory accessible to those with no previous background in string theory who wish to join the research effort in this area. Topics covered include a brief review of string theory, its compactifications, solitons and D-branes, black hole entropy and wed of string dualities. (author)

String GUTs

International Nuclear Information System (INIS)

Aldazabal, G.; Ibanez, L.E.; Uranga, A.M.

1995-01-01

Standard SUSY-GUTs such as those based on SU(5) or SO(10) lead to predictions for the values of α s and sin 2 θ W in amazing agreement with experiment. In this article we investigate how these models may be obtained from string theory, thus bringing them into the only known consistent framework for quantum gravity. String models with matter in standard GUT representations require the realization of affine Lie algebras at higher levels. We start by describing some methods to build level k=2 symmetric orbifold string models with gauge groups SU(5) or SO(10). We present several examples and identify generic features of the type of models constructed. Chiral fields appropriate to break the symmetry down to the standard model generically appear in the massless spectrum. However, unlike in standard SUSY-GUTs, they often behave as string moduli, i.e., they do not have self-couplings. We also discuss briefly the doublet-triplet Higgs splitting. We find that, in some models, built-in sliding-singlet type of couplings exist. (orig.)

Vibration Analysis Of Automotive Structures Using Holographic Interferometry

Science.gov (United States)

Brown, G. M.; Wales, R. R.

1983-10-01

Since 1979, Ford Motor Company has been developing holographic interferometry to supplement more conventional test methods to measure vehicle component vibrations. An Apollo PHK-1 Double Pulse Holographic Laser System was employed to visualize a variety of complex vibration modes, primarily on current production and prototype powertrain components. Design improvements to reduce powertrain response to problem excitations have been deter-mined through pulsed laser holography, and have, in several cases, been put into production in Ford vehicles. Whole-field definition of vibration related deflections provide continuity of information missed by accelerometer/modal analysis techniaues. Certain opera-tional problems, common among pulsed ruby holographic lasers, have reauired ongoing hardware and electronics improvements to minimize system downtime. Real-time, time-averaged and stroboscopic C. W. laser holographic techniques are being developed at Ford to complement the double pulse capabilities and provide rapid identification of modal frequencies and nodal lines for analysis of powertrain structures. Methods for mounting and exciting powertrains to minimize rigid body motions are discussed. Work at Ford will continue toward development of C. W. holographic techniques to provide refined test methodology dedicated to noise and vibration diagnostics with particular emphasis on semi-automated methods for quantifying displacement and relative phase using high resolution digitized video and computers. Continued use of refined pulsed and CW laser holographic interferometry for the analysis of complex structure vibrations seems assured.

Different grades MEMS accelerometers error characteristics

Science.gov (United States)

Pachwicewicz, M.; Weremczuk, J.

2017-08-01

The paper presents calibration effects of two different MEMS accelerometers of different price and quality grades and discusses different accelerometers errors types. The calibration for error determining is provided by reference centrifugal measurements. The design and measurement errors of the centrifuge are discussed as well. It is shown that error characteristics of the sensors are very different and it is not possible to use simple calibration methods presented in the literature in both cases.

String theory and water waves

International Nuclear Information System (INIS)

Iyer, Ramakrishnan; Johnson, Clifford V; Pennington, Jeffrey S

2011-01-01

We uncover a remarkable role that an infinite hierarchy of nonlinear differential equations plays in organizing and connecting certain c-hat <1 string theories non-perturbatively. We are able to embed the type 0A and 0B (A, A) minimal string theories into this single framework. The string theories arise as special limits of a rich system of equations underpinned by an integrable system known as the dispersive water wave hierarchy. We observe that there are several other string-like limits of the system, and conjecture that some of them are type IIA and IIB (A, D) minimal string backgrounds. We explain how these and several string-like special points arise and are connected. In some cases, the framework endows the theories with a non-perturbative definition for the first time. Notably, we discover that the Painleve IV equation plays a key role in organizing the string theory physics, joining its siblings, Painleve I and II, whose roles have previously been identified in this minimal string context.

Prediction of Gap Asymmetry in Differential Micro Accelerometers

Directory of Open Access Journals (Sweden)

Xiaoping He

2012-05-01

Full Text Available Gap asymmetry in differential capacitors is the primary source of the zero bias output of force-balanced micro accelerometers. It is also used to evaluate the applicability of differential structures in MEMS manufacturing. Therefore, determining the asymmetry level has considerable significance for the design of MEMS devices. This paper proposes an experimental-theoretical method for predicting gap asymmetry in differential sensing capacitors of micro accelerometers. The method involves three processes: first, bi-directional measurement, which can sharply reduce the influence of the feedback circuit on bias output, is proposed. Experiments are then carried out on a centrifuge to obtain the input and output data of an accelerometer. Second, the analytical input-output relationship of the accelerometer with gap asymmetry and circuit error is theoretically derived. Finally, the prediction methodology combines the measurement results and analytical derivation to identify the asymmetric error of 30 accelerometers fabricated by DRIE. Results indicate that the level of asymmetry induced by fabrication uncertainty is about ±5 × 10⁻², and that the absolute error is about ±0.2 µm under a 4 µm gap.

Smartphone MEMS accelerometers and earthquake early warning

Science.gov (United States)

Kong, Q.; Allen, R. M.; Schreier, L.; Kwon, Y. W.

2015-12-01

The low cost MEMS accelerometers in the smartphones are attracting more and more attentions from the science community due to the vast number and potential applications in various areas. We are using the accelerometers inside the smartphones to detect the earthquakes. We did shake table tests to show these accelerometers are also suitable to record large shakings caused by earthquakes. We developed an android app - MyShake, which can even distinguish earthquake movements from daily human activities from the recordings recorded by the accelerometers in personal smartphones and upload trigger information/waveform to our server for further analysis. The data from these smartphones forms a unique datasets for seismological applications, such as earthquake early warning. In this talk I will layout the method we used to recognize earthquake-like movement from single smartphone, and the overview of the whole system that harness the information from a network of smartphones for rapid earthquake detection. This type of system can be easily deployed and scaled up around the global and provides additional insights of the earthquake hazards.

Macroscopic fundamental strings in cosmology

Energy Technology Data Exchange (ETDEWEB)

Aharonov, Y; Englert, F; Orloff, J

1987-12-24

We show that, when D greater than or equal to 4, theories of closed strings of closed strings in D, non-compact space-time dimensions exhibit a phase transition. The high-temperature phase is characterized by a condensate of arbitrarily long strings with Hausdorff dimension two (area filling curves). We suggest that this stringy phase is the ancestor of the adiabatic era. Fundamental strings could then both drive the inflation and seed, in a way reminiscent of the cosmic string mechanism, the large structures in the universe.

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.

Interpolating string field theories

International Nuclear Information System (INIS)

Zwiebach, B.

1992-01-01

This paper reports that a minimal area problem imposing different length conditions on open and closed curves is shown to define a one-parameter family of covariant open-closed quantum string field theories. These interpolate from a recently proposed factorizable open-closed theory up to an extended version of Witten's open string field theory capable of incorporating on shell closed strings. The string diagrams of the latter define a new decomposition of the moduli spaces of Riemann surfaces with punctures and boundaries based on quadratic differentials with both first order and second order poles

Baryon string model

International Nuclear Information System (INIS)

Klimenko, S.V.; Kochin, V.N.; Plyushchaj, M.S.; Pron'ko, G.P.; Razumov, A.V.; Samarin, A.V.

1985-01-01

Partial solutions to classical equations of three-string motion are considered. Simplest solutions, when three-string center moving with high velocity, are co nsidered. Single-mode solutions are studied. Explicit form of their parametrization is obtained and three-string dynamics visualization is made. Means of graphic packet ''Atom'' were used for visualization. A set of processes for graphic representation of multiparametric functions is developed. Peculiarity of these processes is a wide class of functions, which are represented by parametric, coordinate and functional isolines

String theory compactifications

CERN Document Server

Graña, Mariana

2017-01-01

The lectures in this book provide graduate students and non-specialist researchers with a concise introduction to the concepts and formalism required to reduce the ten-dimensional string theories to the observable four-dimensional space-time - a procedure called string compactification. The text starts with a very brief introduction to string theory, first working out its massless spectrum and showing how the condition on the number of dimensions arises. It then dwells on the different possible internal manifolds, from the simplest to the most relevant phenomenologically, thereby showing that the most elegant description is through an extension of ordinary Riemannian geometry termed generalized geometry, which was first introduced by Hitchin. Last but not least, the authors review open problems in string phenomenology, such as the embedding of the Standard Model and obtaining de Sitter solutions.

Retina as Reciprocal Spatial Fourier Transform Space Implies ``Wave-transformation'' Functions, String Theory, the Inappropriate Uncertainty Principle, and Predicts ``Quarked'' Protons.

Science.gov (United States)

Mc Leod, Roger David; Mc Leod, David M.

2007-10-01

Vision, via transform space: ``Nature behaves in a reciprocal way;' also, Rect x pressure-input sense-reports as Sinc p, indicating brain interprets reciprocal ``p'' space as object space. Use Mott's and Sneddon's Wave Mechanics and Its Applications. Wave transformation functions are strings of positron, electron, proton, and neutron; uncertainty is a semantic artifact. Neutrino-string de Broglie-Schr"odinger wave-function models for electron, positron, suggest three-quark models for protons, neutrons. Variably vibrating neutrino-quills of this model, with appropriate mass-energy, can be a vertical proton string, quills leftward; thread string circumferentially, forming three interlinked circles with ``overpasses''. Diameters are 2:1:2, center circle has quills radially outward; call it a down quark, charge --1/3, charge 2/3 for outward quills, the up quarks of outer circles. String overlap summations are nodes; nodes also far left and right. Strong nuclear forces may be --px. ``Dislodging" positron with neutrino switches quark-circle configuration to 1:2:1, `downers' outside. Unstable neutron charge is 0. Atoms build. With scale factors, retinal/vision's, and quantum mechanics,' spatial Fourier transforms/inverses are equivalent.

Observation of Motion of Bowed Strings and Resonant Strings in Violin Performances

Science.gov (United States)

Matsutani, Akihiro

2013-10-01

The motion of a bowed string and a resonant string of a violin were simultaneously observed for the first time. The results of the direct observation of string motion in double stops and harmonics are also presented. The importance of the resonance was experimentally demonstrated from these observations. It is suggested that players should take account of the resonance and ideal Helmholtz motion in violin performances.

Maximal unbordered factors of random strings

DEFF Research Database (Denmark)

Cording, Patrick Hagge; Knudsen, Mathias Bæk Tejs

2016-01-01

A border of a string is a non-empty prefix of the string that is also a suffix of the string, and a string is unbordered if it has no border. Loptev, Kucherov, and Starikovskaya [CPM 2015] conjectured the following: If we pick a string of length n from a fixed alphabet uniformly at random...

Non-critical Poincare invariant bosonic string backgrounds and closed string tachyons

International Nuclear Information System (INIS)

Alvarez, Enrique; Gomez, Cesar; Hernandez, Lorenzo

2001-01-01

A new family of non critical bosonic string backgrounds in arbitrary space-time dimension D and with ISO(1,D-2) Poincare invariance are presented. The metric warping factor and dilaton agree asymptotically with the linear dilaton background. The closed string tachyon equation of motion enjoys, in the linear approximation, an exact solution of 'kink' type interpolating between different expectation values. A renormalization group flow interpretation, based on a closed string tachyon potential of type -T 2 e -T , is suggested

Quantum backreaction in string theory

International Nuclear Information System (INIS)

Evnin, O.

2012-01-01

There are situations in string theory when a finite number of string quanta induce a significant backreaction upon the background and render the perturbation theory infrared-divergent. The simplest example is D0-brane recoil under an impact by closed strings. A more physically interesting case is backreaction on the evolution of a totally compact universe due to closed string gas. Such situations necessitate qualitative amendments to the traditional formulation of string theory in a fixed classical background. In this contribution to the proceedings of the XVII European Workshop on String Theory in Padua, I review solved problems and current investigations in relation to this kind of quantum backreaction effects. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

String model of elementary particles

International Nuclear Information System (INIS)

Kikkawa, Keiji

1975-01-01

Recent development of the models of elementary particles is described. The principal features of elementary particle physics can be expressed by quark model, mass spectrum, the Regge behavior of scattering amplitude, and duality. Venezians showed in 1968 that the B function can express these features. From the analysis of mass spectrum, the string model was introduced. The quantization of the string is performed with the same procedure as the ordinary quantum mechanics. The motion of the string is determined by the Nambu-Goto action integral, and the Schroedinger equation is obtained. Mass spectrum from the string model was same as that from the duality model such as Veneziano model. The interaction between strings can be introduced, and the Lagrangian can be formulated. The relation between the string model and the duality model has been studied. The string model is the first theory of non-local field, and the further development is attractive. The relation between this model and the quark model is still not clear. (Kato, T.)

Inflationary string theory?

Indian Academy of Sciences (India)

strongly motivate a detailed search for inflation within string theory, although it has ... between string theory and observations provides a strong incentive for ..... sonably be expected to arise for any system having very many degrees of freedom.

Open strings on AdS2 branes

International Nuclear Information System (INIS)

Lee, Peter; Ooguri, Hirosi.; Park, Jongwon; Tannenhauser, Jonathan

2001-01-01

We study the spectrum of open strings on AdS 2 branes in AdS 3 in an NS-NS background, using the SL(2,R) WZW model. When the brane carries no fundamental string charge, the open string spectrum is the holomorphic square root of the spectrum of closed strings in AdS 3 . It contains short and long strings, and is invariant under spectral flow. When the brane carries fundamental string charge, the open string spectrum again contains short and long strings in all winding sectors. However, branes with fundamental string charge break half the spectral flow symmetry. This has different implications for short and long strings. As the fundamental string charge increases, the brane approaches the boundary of AdS 3 . In this limit, the induced electric field on the worldvolume reaches its critical value, producing noncommutative open string theory on AdS 2

String Theory for Pedestrians (1/3)

CERN Multimedia

CERN. Geneva

2009-01-01

This is a non-technical rapid course on string theory. Lecture 1 is an introduction to the basics of the subject: classical and quantum strings, D(irichlet) branes and string-string dualities. In lecture 2 I will discuss string unification of the fundamental forces, covering both its successes and failures. Finally in lecture 3 I will review string models of black hole microstates, the holographic gauge/gravity duality and, if time permits, potential applications to the physics of the strong interactions.

String Theory for Pedestrians (2/3)

CERN Multimedia

CERN. Geneva

2009-01-01

This is a non-technical rapid course on string theory. Lecture 1 is an introduction to the basics of the subject: classical and quantum strings, D(irichlet) branes and string-string dualities. In lecture 2 I will discuss string unification of the fundamental forces, covering both its successes and failures. Finally in lecture 3 I will review string models of black hole microstates, the holographic gauge/gravity duality and, if time permits, potential applications to the physics of the strong interactions.

String Theory for Pedestrians (3/3)

CERN Multimedia

CERN. Geneva

2009-01-01

This is a non-technical rapid course on string theory. Lecture 1 is an introduction to the basics of the subject: classical and quantum strings, D(irichlet) branes and string-string dualities. In lecture 2 I will discuss string unification of the fundamental forces, covering both its successes and failures. Finally in lecture 3 I will review string models of black hole microstates, the holographic gauge/gravity duality and, if time permits, potential applications to the physics of the strong interactions.

6d string chains

Science.gov (United States)

Gadde, Abhijit; Haghighat, Babak; Kim, Joonho; Kim, Seok; Lockhart, Guglielmo; Vafa, Cumrun

2018-02-01

We consider bound states of strings which arise in 6d (1,0) SCFTs that are realized in F-theory in terms of linear chains of spheres with negative self-intersections 1,2, and 4. These include the strings associated to N small E 8 instantons, as well as the ones associated to M5 branes probing A and D type singularities in M-theory or D5 branes probing ADE singularities in Type IIB string theory. We find that these bound states of strings admit (0,4) supersymmetric quiver descriptions and show how one can compute their elliptic genera.

Instability of colliding metastable strings

International Nuclear Information System (INIS)

Hiramatsu, Takashi; Kobayashi, Tatsuo; Ookouchi, Yutaka; Kyoto Univ.

2013-04-01

We investigate the collision dynamics of two metastable strings which can be viewed as tube-like domain walls with winding numbers interpolating a false vacuum and a true vacuum. We find that depending on the relative angle and speed of two strings, instability of strings increases and the false vacuum is filled out by rapid expansion of the strings or of a remnant of the collision.

String theory in four dimensions

International Nuclear Information System (INIS)

Dine, M.

1988-01-01

A representative sample of current ideas about how one might develop a string phenomenology is presented. Some of the obstacles which lie in between string theory and contact with experiment are described. It is hoped that this volume will provide the reader with ways of thinking about string theory in four dimensions and provide tools for asking questions about string theory and ordinary physics. 102 refs

Instability of colliding metastable strings

Energy Technology Data Exchange (ETDEWEB)

Hiramatsu, Takashi [Kyoto Univ. (Japan). Yukawa Inst. for Theoretical Physics; Eto, Minoru [Yamagata Univ. (Japan). Dept. of Physics; Kamada, Kohei [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kobayashi, Tatsuo [Kyoto Univ. (Japan). Dept. of Physics; Ookouchi, Yutaka [Kyoto Univ. (Japan). Dept. of Physics; Kyoto Univ. (Japan). The Hakubi Center for Advanced Research

2013-04-15

We investigate the collision dynamics of two metastable strings which can be viewed as tube-like domain walls with winding numbers interpolating a false vacuum and a true vacuum. We find that depending on the relative angle and speed of two strings, instability of strings increases and the false vacuum is filled out by rapid expansion of the strings or of a remnant of the collision.

Superconducting cosmic strings

International Nuclear Information System (INIS)

Chudnovsky, E.M.; Field, G.B.; Spergel, D.N.; Vilenkin, A.

1986-01-01

Superconducting loops of string formed in the early Universe, if they are relatively light, can be an important source of relativistic particles in the Galaxy. They can be observed as sources of synchrotron radiation at centimeter wavelengths. We propose a string model for two recently discovered radio sources, the ''thread'' in the galactic center and the source G357.7-0.1, and predict that the filaments in these sources should move at relativistic speeds. We also consider superheavy superconducting strings, and the possibility that they be observed as extragalactic radio sources

Metabolic effect of bodyweight whole-body vibration in a 20-min exercise session: A crossover study using verified vibration stimulus.

Directory of Open Access Journals (Sweden)

Chiara Milanese

Full Text Available The ability of whole body vibration (WBV to increase energy expenditure (EE has been investigated to some extent in the past using short-term single exercises or sets of single exercises. However, the current practice in WBV training for fitness is based on the execution of multiple exercises during a WBV training session for a period of at least 20 min; nevertheless, very limited and inconsistent data are available on EE during long term WBV training session. This crossover study was designed to demonstrate, in an adequately powered sample of participants, the ability of WBV to increase the metabolic cost of exercise vs. no vibration over the time span of a typical WBV session for fitness (20 min. Twenty-two physically active young males exercised on a vibration platform (three identical sets of six different exercises using an accelerometer-verified vibration stimulus in both the WBV and no vibration condition. Oxygen consumption was measured with indirect calorimetry and expressed as area under the curve (O2(AUC. Results showed that, in the overall 20-min training session, WBV increased both the O2(AUC and the estimated EE vs. no vibration by about 22% and 20%, respectively (P<0.001 for both, partial eta squared [η2] ≥0.35 as well as the metabolic equivalent of task (+5.5%, P = 0.043; η2 = 0.02 and the rate of perceived exertion (+13%, P<0.001; ŋ2 = 0.16. Results demonstrated that vibration is able to significantly increase the metabolic cost of exercise in a 20-min WBV training session.

Superconducting accelerometer using niobium-on-sapphire rf resonator

International Nuclear Information System (INIS)

Blair, D.G.

1979-01-01

An accelerometer is described which uses a rf niobium-on-sapphire resonator as its sensor element. The accelerometer uses a magnetically levitated spool as a test mass and the spool modulates the inductance of the resonator; its position is servo controlled to maintain the resonator at the external rf excitation frequency. The accelerometer has high sensitivity over the full audio frequency range, but is optimized for frequencies between 100 Hz and 1 kHz, where the calculated displacement sensitivity approaches 10 -15 cm for a 1 Hz measurement bandwidth. The system noise sources are analyzed and possible improvements are discussed

Transverse structure of the QCD string

International Nuclear Information System (INIS)

Meyer, Harvey B.

2010-01-01

The characterization of the transverse structure of the QCD string is discussed. We formulate a conjecture as to how the stress-energy tensor of the underlying gauge theory couples to the string degrees of freedom. A consequence of the conjecture is that the energy density and the longitudinal-stress operators measure the distribution of the transverse position of the string, to leading order in the string fluctuations, whereas the transverse-stress operator does not. We interpret recent numerical measurements of the transverse size of the confining string and show that the difference of the energy and longitudinal-stress operators is a particularly natural probe at next-to-leading order. Second, we derive the constraints imposed by open-closed string duality on the transverse structure of the string. We show that a total of three independent ''gravitational'' form factors characterize the transverse profile of the closed string, and obtain the interpretation of recent effective string theory calculations: the square radius of a closed string of length β defined from the slope of its gravitational form factor, is given by (d-1/2πσ)log(β/4r 0 ) in d space dimensions. This is to be compared with the well-known result that the width of the open string at midpoint grows as (d-1/2πσ)log(r/r 0 ). We also obtain predictions for transition form factors among closed-string states.

New capacitive low-g triaxial accelerometer with low cross-axis sensitivity

International Nuclear Information System (INIS)

Hsu, Yu-Wen; Chen, Jen-Yi; Chien, Hsin-Tang; Chen, Sheah; Lin, Shih-Ting; Liao, Lu-Po

2010-01-01

This work describes a compact accelerometer, which integrates three spring-proof mass systems into a single structure to sense triaxial motion. It has a size of 1.3 × 1.28 mm 2 and an operating range of ±1 g. Silicon-on-glass (SOG) micromachining and deep reactive-ion etching (DRIE)-based process are adopted to fabricate this accelerometer with a high-aspect-ratio sensing structure. The accelerometer has an excellent z-axis output sensitivity of 1.434 V g −1 and a high resolution of 49 µg Hz −1/2 . The sensitivity and minimum cross-axis sensitivity of the x-axis in-plane accelerometer are 1.442 V g −1 and 0.03% and those of the y-axis accelerometer are 1.241 V g −1 and 0.21%, respectively. The new in-plane and out-of-plane accelerometer design exhibits high cross-axis sensitivity immunity, high sensitivity and high linearity suggesting that the triaxial accelerometer has the potential for use in future applications in consumer goods and the cellular phone marketþ

Analysis of generator bearing vibration data for diagnosing rotor circuit malfunction in DFIGs

DEFF Research Database (Denmark)

Skrimpas, Georgios Alexandros; Sweeney, Christian W.; Jensen, Bogi Bech

2014-01-01

Doubly fed induction generators (DFIGs) are the most popular configuration met in the wind energy sector occu- pying approximately 65 % of the total market share. Condition monitoring of wind turbine generators is performed based on vibration data collected from accelerometers mounted on the drive....... In this paper generator bearing vibration signature for a DFIG under operation with one rotor phase coil open is analysed and presented. Further this failure mode is compared to rotor dynamics fault, such as rotational looseness, and the difference in signature is discussed. Vibration data from a multi...... end and non-drive end bearings, meeting the requirements of numerous turbine operators for condition based maintenance. In a DFIG the voltage applied to the rotor is controlled by a converter, where electric connection between the two is accom- plished by using slip rings. Improper connection between...

A first course in vibrations and waves

CERN Document Server

Samiullah, Mohammad

2015-01-01

This book builds on introductory physics and emphasizes understanding of vibratory motion and waves based on first principles. The book is divided into three parts. Part I contains a preliminary chapter that serves as a review of relevant ideas of mechanics and complex numbers. Part II is devoted to a detailed discussion of vibrations of mechanical systems. This part covers a simple harmonic oscillator, coupled oscillators, normal coordinates, beaded string, continuous string, standing waves, and Fourier series. Part II ends with a presentation of stationary solutions of driven finite systems. Part III is concerned with waves. Here, the emphasis is on the discussion of common aspects of all types of waves. The applications to sound, electromagnetic, and matter waves are illustrated. The book also includes examples from water waves and electromagnetic waves on a transmission line. The emphasis of the book is to bring out the similarities among various types of waves. The book includes treatment of reflection a...

Disordered chaotic strings

DEFF Research Database (Denmark)

Schäfer, Mirko; Greiner, Martin

2011-01-01

to chaotic strings. Inhomogeneous coupling weights as well as small-world perturbations of the ring-network structure are discussed. It is found that certain combinations of coupling and network disorder preserve the empirical relationship between chaotic strings and the weak and strong sector...

QCD and string theories

International Nuclear Information System (INIS)

Cohen-Tannoudji, G.

1990-01-01

This paper is devoted to a review of the connections between quantumchromodynamics (QCD) and string theories. One reviews the phenomenological models leading to string pictures in non perturbative QCD and the string effects, related to soft gluon coherence, which arise in perturbative QCD. One tries to build a string theory which goes to QCD at the zero slope limit. A specific model, based on superstring theories is shown to agree with QCD four point amplitudes at the Born approximation and with one loop corrections. One shows how this approach can provide a theoretical framework to account for the phenomenological property of parton-hadron duality

QCD and hadronic strings

International Nuclear Information System (INIS)

Cohen-Tannoudji, G.

1989-01-01

This series of lectures is devoted to review ot he connections between QCD and string theories. One reviews the phenomenological models leading to string pictures in non perturbative QCD and the string effects, related to soft gluon coherence, which arise in perturbative QCD. One tries to build a string theory which goes to QCD at the zero slope limit. A specific model, based on superstring theories is shown to agree with QCD four point amplitudes at the Born approximation and with one loop corrections. One shows how this approach can provide a theoretical framework to account for the phenomenological property of parton-hadron duality.(author)

Tadpole resummations in string theory

International Nuclear Information System (INIS)

Kitazawa, Noriaki

2008-01-01

While R-R tadpoles should be canceled for consistency, string models with broken supersymmetry generally have uncanceled NS-NS tadpoles. Their presence signals that the background does not solve the field equations, so that these models are in 'wrong' vacua. In this Letter we investigate, with reference to some prototype examples, whether the true values of physical quantities can be recovered resumming the NS-NS tadpoles, hence by an approach that is related to the analysis based on String Field Theory by open-closed duality. We show that, indeed, the positive classical vacuum energy of a Dp-brane of the bosonic string is exactly canceled by the negative contribution arising from tree-level tadpole resummation, in complete agreement with Sen's conjecture on open-string tachyon condensation and with the consequent analysis based on String Field Theory. We also show that the vanishing classical vacuum energy of the SO(8192) unoriented bosonic open-string theory does not receive any tree-level corrections from the tadpole resummation. This result is consistent with the fact that this (unstable) configuration is free from tadpoles of massless closed-string modes, although there is a tadpole of the closed string tachyon. The application of this method to superstring models with broken supersymmetry is also discussed

Laser vibrometry measurements of vibration and sound fields of a bowed violin

Science.gov (United States)

Gren, Per; Tatar, Kourosh; Granström, Jan; Molin, N.-E.; Jansson, Erik V.

2006-04-01

Laser vibrometry measurements on a bowed violin are performed. A rotating disc apparatus, acting as a violin bow, is developed. It produces a continuous, long, repeatable, multi-frequency sound from the instrument that imitates the real bow-string interaction for a 'very long bow'. What mainly differs is that the back and forward motion of the real bow is replaced by the rotating motion with constant velocity of the disc and constant bowing force (bowing pressure). This procedure is repeatable. It is long lasting and allows laser vibrometry techniques to be used, which measure forced vibrations by bowing at all excited frequencies simultaneously. A chain of interacting parts of the played violin is studied: the string, the bridge and the plates as well as the emitted sound field. A description of the mechanics and the sound production of the bowed violin is given, i.e. the production chain from the bowed string to the produced tone.

String bit models for superstring

International Nuclear Information System (INIS)

Bergman, O.; Thorn, C.B.

1995-01-01

The authors extend the model of string as a polymer of string bits to the case of superstring. They mainly concentrate on type II-B superstring, with some discussion of the obstacles presented by not II-B superstring, together with possible strategies for surmounting them. As with previous work on bosonic string work within the light-cone gauge. The bit model possesses a good deal less symmetry than the continuous string theory. For one thing, the bit model is formulated as a Galilei invariant theory in (D - 2) + 1 dimensional space-time. This means that Poincare invariance is reduced to the Galilei subgroup in D - 2 space dimensions. Naturally the supersymmetry present in the bit model is likewise dramatically reduced. Continuous string can arise in the bit models with the formation of infinitely long polymers of string bits. Under the right circumstances (at the critical dimension) these polymers can behave as string moving in D dimensional space-time enjoying the full N = 2 Poincare supersymmetric dynamics of type II-B superstring

String bit models for superstring

Energy Technology Data Exchange (ETDEWEB)

Bergman, O.; Thorn, C.B.

1995-12-31

The authors extend the model of string as a polymer of string bits to the case of superstring. They mainly concentrate on type II-B superstring, with some discussion of the obstacles presented by not II-B superstring, together with possible strategies for surmounting them. As with previous work on bosonic string work within the light-cone gauge. The bit model possesses a good deal less symmetry than the continuous string theory. For one thing, the bit model is formulated as a Galilei invariant theory in (D {minus} 2) + 1 dimensional space-time. This means that Poincare invariance is reduced to the Galilei subgroup in D {minus} 2 space dimensions. Naturally the supersymmetry present in the bit model is likewise dramatically reduced. Continuous string can arise in the bit models with the formation of infinitely long polymers of string bits. Under the right circumstances (at the critical dimension) these polymers can behave as string moving in D dimensional space-time enjoying the full N = 2 Poincare supersymmetric dynamics of type II-B superstring.

String-math 2012

CERN Document Server

Katz, Sheldon; Klemm, Albrecht; Morrison, David R

2015-01-01

This volume contains the proceedings of the conference String-Math 2012, which was held July 16-21, 2012, at the Hausdorff Center for Mathematics, Universitat Bonn. This was the second in a series of annual large meetings devoted to the interface of mathematics and string theory. These meetings have rapidly become the flagship conferences in the field. Topics include super Riemann surfaces and their super moduli, generalized moonshine and K3 surfaces, the latest developments in supersymmetric and topological field theory, localization techniques, applications to knot theory, and many more. The contributors include many leaders in the field, such as Sergio Cecotti, Matthias Gaberdiel, Rahul Pandharipande, Albert Schwarz, Anne Taormina, Johannes Walcher, Katrin Wendland, and Edward Witten. This book will be essential reading for researchers and students in this area and for all mathematicians and string theorists who want to update themselves on developments in the math-string interface.

Fast Searching in Packed Strings

DEFF Research Database (Denmark)

Bille, Philip

2009-01-01

Given strings P and Q the (exact) string matching problem is to find all positions of substrings in Q matching P. The classical Knuth-Morris-Pratt algorithm [SIAM J. Comput., 1977] solves the string matching problem in linear time which is optimal if we can only read one character at the time....... However, most strings are stored in a computer in a packed representation with several characters in a single word, giving us the opportunity to read multiple characters simultaneously. In this paper we study the worst-case complexity of string matching on strings given in packed representation. Let m...... word-RAM with logarithmic word size we present an algorithm using time O(n/log(sigma) n + m + occ) Here occ is the number of occurrences of P in Q. For m = o(n) this improves the O(n) bound...

Comparing double string theory actions

International Nuclear Information System (INIS)

De Angelis, L.; Gionti, S.J.G.; Marotta, R.; Pezzella, F.

2014-01-01

Aimed to a deeper comprehension of a manifestly T-dual invariant formulation of string theory, in this paper a detailed comparison between the non-covariant action proposed by Tseytlin and the covariant one proposed by Hull is done. These are obtained by making both the string coordinates and their duals explicitly appear, on the same footing, in the world-sheet action, so “doubling” the string coordinates along the compact dimensions. After a discussion on the nature of the constraints in both the models and the relative quantization, it results that the string coordinates and their duals behave like “non-commuting” phase space coordinates but their expressions in terms of Fourier modes generate the oscillator algebra of the standard bosonic string. A proof of the equivalence of the two formulations is given. Furthermore, open-string solutions are also discussed

Comparing double string theory actions

Energy Technology Data Exchange (ETDEWEB)

De Angelis, L. [Dipartimento di Fisica, Università degli Studi “Federico II” di Napoli,Complesso Universitario Monte S. Angelo ed. 6, via Cintia, 80126 Napoli (Italy); Gionti, S.J.G. [Specola Vaticana, Vatican City, V-00120, Vatican City State and Vatican Observatory Research Group, Steward Observatory, The University Of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721 (United States); Marotta, R.; Pezzella, F. [Istituto Nazionale di Fisica Nucleare, Sezione di Napoli,Complesso Universitario di Monte S. Angelo ed. 6, via Cintia, 80126 Napoli (Italy)

2014-04-28

Aimed to a deeper comprehension of a manifestly T-dual invariant formulation of string theory, in this paper a detailed comparison between the non-covariant action proposed by Tseytlin and the covariant one proposed by Hull is done. These are obtained by making both the string coordinates and their duals explicitly appear, on the same footing, in the world-sheet action, so “doubling” the string coordinates along the compact dimensions. After a discussion on the nature of the constraints in both the models and the relative quantization, it results that the string coordinates and their duals behave like “non-commuting” phase space coordinates but their expressions in terms of Fourier modes generate the oscillator algebra of the standard bosonic string. A proof of the equivalence of the two formulations is given. Furthermore, open-string solutions are also discussed.

A mechanical model of the smartphone's accelerometer

OpenAIRE

Gallitto, Aurelio Agliolo; Lupo, Lucia

2015-01-01

To increase the attention of students, several physics experiments can be performed at school, as well at home, by using the smartphone as laboratory tools. In the paper we describe a mechanical model of the smartphone's accelerometer, which can be used in classroom to allow students to better understand the principle of the accelerometer even by students at the beginning of the study in physics.

A low-noise MEMS accelerometer for unattended ground sensor applications

Science.gov (United States)

Speller, Kevin E.; Yu, Duli

2004-09-01

A low-noise micro-machined servo accelerometer has been developed for use in Unattended Ground Sensors (UGS). Compared to conventional coil-and-magnet based velocity transducers, this Micro-Electro-Mechanical System (MEMS) accelerometer offers several key benefits for battlefield monitoring. Many UGS require a compass to determine deployment orientation with respect to magnetic North. This orientation information is critical for determining the bearing of incoming signals. Conventional sensors with sensing technology based on a permanent magnet can cause interference with a compass when used in close proximity. This problem is solved with a MEMS accelerometer which does not require any magnetic materials. Frequency information below 10 Hz is valuable for identification of signal sources. Conventional seismometers used in UGS are typically limited in frequency response from 20 to 200 Hz. The MEMS accelerometer has a flat frequency response from DC to 5 kHz. The wider spectrum of signals received improves detection, classification and monitoring on the battlefield. The DC-coupled output of the MEMS accelerometer also has the added benefit of providing tilt orientation data for the deployed UGS. Other performance parameters of the MEMS accelerometer that are important to UGS such as size, weight, shock survivability, phase response, distortion, and cross-axis rejection will be discussed. Additionally, field test data from human footsteps recorded with the MEMS accelerometer will be presented.

Metastable cosmic strings in realistic models

International Nuclear Information System (INIS)

Holman, R.

1992-01-01

The stability of the electroweak Z-string is investigated at high temperatures. The results show that, while finite temperature corrections can improve the stability of the Z-string, their effect is not strong enough to stabilize the Z-string in the standard electroweak model. Consequently, the Z-string will be unstable even under the conditions present during the electroweak phase transition. Phenomenologically viable models based on the gauge group SU(2) L x SU(2) R x U(1) B-L are then considered, and it is shown that metastable strings exist and are stable to small perturbations for a large region of the parameter space for these models. It is also shown that these strings are superconducting with bosonic charge carriers. The string superconductivity may be able to stabilize segments and loops against dynamical contraction. Possible implications of these strings for cosmology are discussed

Measurement and prediction of cutting forces and vibrations on longwall shearers

Energy Technology Data Exchange (ETDEWEB)

Bulent Tiryaki [CRCMining (Australia)

2006-12-15

CRCMining has developed the Cutting Head Performance Analysis Software (CPAS) to predict cutter motor power, ranging arm reaction forces, and vibrations for different drum designs, coal seams, and shearer operational conditions. This project describes the work on THE DBT EL3000 shearer at Beltana to validate/update CPAS by measuring the cutter motor power, ranging arm vibrations, and reaction forces through an online data acquisition system called Cutting Head Performance Monitoring System (CPMS). This system records the outputs of six strain gauge bridges, six accelerometers, and two pressure transducers on ranging arms during underground coal production. CPAS2 has then been developed in order to eliminate the needs for performing coal cutting tests for the target coal seam. CPAS2 simulations for cutter motor power, vertical reaction force, and vibrations were also close to those measured in the trials. CRCMining will release the CPAS code including fully functioning software code on CD to Australian coal mining industry.

Vibration analysis of cooling system of upgraded PARR-1: (primary pumps)

International Nuclear Information System (INIS)

Ayazuddin, S.K.; Baig, R.; Pervez, S.

1992-12-01

During the conversion and up gradation of PARR-1, major changes were made in the cooling system of the reactor with the addition of new heat exchanger assemblies and cooling tower. It was therefore, planned to perform vibration analysis on the cooling system to check proper installation and investigate any abnormality in the operation. As a first step, vibration measurements was made on the primary pumps PW-P1 and PW-P2. Power spectral density (PSD) or frequency spectrum of the signal produced from an accelerometer placed on the pump motor assembly was analysed to identify faults which are commonly found in rotating and reciprocating machinery such as unbalance, shaft misalignment and bearing instability. The root mean square (RMS) of the signal was compared with the vibration criterion chart to determine the operating condition of the pump motor assembly. The procedure used for the analysis and faults detected in the primary pump-motor system are discussed. 9 figs. (author)

Constraints on cosmic strings due to black holes formed from collapsed cosmic string loops

International Nuclear Information System (INIS)

Caldwell, R.R.; Gates, E.

1993-05-01

The cosmological features of primordial black holes formed from collapsed cosmic string loops are studied. Observational restrictions on a population of primordial black holes are used to restrict f, the fraction of cosmic string loops which collapse to form black holes, and μ, the cosmic string mass-per-unit-length. Using a realistic model of cosmic strings, we find the strongest restriction on the parameters f and μ is due to the energy density in 100MeV photons radiated by the black holes. We also find that inert black hole remnants cannot serve as the dark matter. If earlier, crude estimates of f are reliable, our results severely restrict μ, and therefore limit the viability of the cosmic string large-scale structure scenario

String Chopping and Time-ordered Products of Linear String-localized Quantum Fields

Science.gov (United States)

Cardoso, Lucas T.; Mund, Jens; Várilly, Joseph C.

2018-03-01

For a renormalizability proof of perturbative models in the Epstein-Glaser scheme with string-localized quantum fields, one needs to know what freedom one has in the definition of time-ordered products of the interaction Lagrangian. This paper provides a first step in that direction. The basic issue is the presence of an open set of n-tuples of strings which cannot be chronologically ordered. We resolve it by showing that almost all such string configurations can be dissected into finitely many pieces which can indeed be chronologically ordered. This fixes the time-ordered products of linear field factors outside a nullset of string configurations. (The extension across the nullset, as well as the definition of time-ordered products of Wick monomials, will be discussed elsewhere).

Prediction of vibration characteristics of a planar mechanism having imperfect joints using neural network

International Nuclear Information System (INIS)

Erkaya, Selcuk

2012-01-01

Clearance is inevitable in the joints of mechanisms due primarily to the design, manufacturing and assembly processes or a wear effect. Excessive value of joint clearance plays a crucial role and has a significant effect on the kinematic and dynamic performances of the mechanism. In this study, effects of joint clearances on bearing vibrations of mechanism are investigated. An experimental test rig is set up, and a planar slider-crank mechanism having two imperfect joints with radial clearance is used as a model mechanism. Three accelerometers are positioned at different points to measure the bearing vibrations during the mechanism motion. For the different running speeds and clearance sizes, this work provides a neural model to predict and estimate the bearing vibrations of the mechanical systems having imperfect joints. The results show that radial basis function (RBF) neural network has a superior performance for predicting and estimating the vibration characteristics of the mechanical system

Modeling fluid forces and response of a tube bundle in cross-flow induced vibrations

International Nuclear Information System (INIS)

Khushnood, Shahab; Khan, Zaffar M.; Malik, M. Afzaal; Koreshi, Zafarullah; Khan, Mahmood Anwar

2003-01-01

Flow induced vibrations occur in process heat exchangers, condensers, boilers and nuclear steam generators. Under certain flow conditions and fluid velocities, the fluid forces result in tube vibrations and possible damage of tube, tube sheet or baffle due to fretting and fatigue. Prediction of these forces is an important consideration. The characteristics of vibration depend greatly on the fluid dynamic forces and structure of the tube bundle. It is undesirable for the tube bundles to vibrate excessively under normal operating conditions because tubes wear and eventual leakage can occur leading to costly shutdowns. In this paper modeling of fluid forces and vibration response of a tube in a heat exchanger bundle has been carried out. Experimental validation has been performed on an existing refinery heat exchanger tube bundle. The target tube has been instrumented with an accelerometer and strain gages. The bundle has been studied for pulse, sinusoidal and random excitations. Natural frequencies and damping of the tubes have also been computed. Experimental fluid forces and response shows a reasonable agreement with the predictions. (author)

What is the most effective posture to conduct vibration from the lower to the upper extremities during whole-body vibration exercise?

Directory of Open Access Journals (Sweden)

Tsukahara Y

2016-01-01

Full Text Available Yuka Tsukahara, Jun Iwamoto, Kosui Iwashita, Takuma Shinjo, Koichiro Azuma, Hideo MatsumotoInstitute for Integrated Sports Medicine, Keio University School of Medicine, Tokyo, Japan Background: Whole-body vibration (WBV exercise is widely used for training and rehabilitation. However, the optimal posture for training both the upper and lower extremities simultaneously remains to be established. Objectives: The objective of this study was to search for an effective posture to conduct vibration from the lower to the upper extremities while performing WBV exercises without any adverse effects. Methods: Twelve healthy volunteers (age: 22–34 years were enrolled in the study. To measure the magnitude of vibration, four accelerometers were attached to the upper arm, back, thigh, and calf of each subject. Vibrations were produced using a WBV platform (Galileo 900 with an amplitude of 4 mm at two frequencies, 15 and 30 Hz. The following three postures were examined: posture A, standing posture with the knees flexed at 30°; posture B, crouching position with no direct contact between the knees and elbows; and posture C, crouching position with direct contact between the knees and elbows. The ratio of the magnitude of vibration at the thigh, back, and upper arm relative to that at the calf was used as an index of vibration conduction. Results: Posture B was associated with a greater magnitude of vibration to the calf than posture A at 15 Hz, and postures B and C were associated with greater magnitudes of vibration than posture A at 30 Hz. Posture C was associated with a vibration conduction to the upper arm that was 4.62 times and 8.26 times greater than that for posture A at 15 and 30 Hz, respectively. Conclusion: This study revealed that a crouching position on a WBV platform with direct contact between the knees and elbows was effective for conducting vibration from the lower to the upper extremities. Keywords: whole-body vibration exercise, upper

Perspectives on string phenomenology

CERN Document Server

Kane, Gordon; Kumar, Piyush

2015-01-01

The remarkable recent discovery of the Higgs boson at the CERN Large Hadron Collider completed the Standard Model of particle physics and has paved the way for understanding the physics which may lie beyond it. String/M theory has emerged as a broad framework for describing a plethora of diverse physical systems, which includes condensed matter systems, gravitational systems as well as elementary particle physics interactions. If string/M theory is to be considered as a candidate theory of Nature, it must contain an effectively four-dimensional universe among its solutions that is indistinguishable from our own. In these solutions, the extra dimensions of string/M Theory are “compactified” on tiny scales which are often comparable to the Planck length. String phenomenology is the branch of string/M theory that studies such solutions, relates their properties to data, and aims to answer many of the outstanding questions of particle physics beyond the Standard Model. This book contains perspectives on stri...

Malfunction tests and vibration analysis of P.W.R. internal structures

International Nuclear Information System (INIS)

Puyal, C.; Carre, J.C.; Epstein, A.

1987-01-01

To diagnose changes liable to occur in the vibration behavior of internals, it is important to understand the influence of changes in the mechanical properties of elements on the output signals obtained from neutron chambers placed out of core and accelerometers fixed to the reactor vessel. To do this, the effects of changes liable to occur in the hold-down springs and the flexures were simulated on the SAFRAN loop, using a representative hydroelastic mock-up. The results obtained experimentally on SAFRAN for different characteristics of the hold-down spring, which lies between the upper part of the core barrel and the vessel head, have been published. In this paper, we propose to present the results of the investigation of the fracture of one or more flexures which connect the cylindrical thermal shield to the core barrel. This work is in two parts: a) Computation based on a hydroelastic model using the substructuration computer program TRISTANA of the CASTEM system. b) Tests simulating flexure fracture: 1 - in air, for an understanding of the mechanisms involved; 2 - on the SAFRAN loop with a representative flow in order to estimate the strains liable to exist on the vibration signatures recorded on displacement transducers and accelerometers. Good agreement was observed between the computation results with the theoretical model employed and those obtained experimentally [fr

Cosmic strings and galaxy formation

Science.gov (United States)

Bertschinger, Edmund

1989-01-01

The cosmogonical model proposed by Zel'dovich and Vilenkin (1981), in which superconducting cosmic strings act as seeds for the origin of structure in the universe, is discussed, summarizing the results of recent theoretical investigations. Consideration is given to the formation of cosmic strings, the microscopic structure of strings, gravitational effects, cosmic string evolution, and the formation of galaxies and large-scale structure. Simulation results are presented in graphs, and several outstanding issues are listed and briefly characterized.

On the null origin of the ambitwistor string

Energy Technology Data Exchange (ETDEWEB)

Casali, Eduardo [Mathematical Institute, University of Oxford,Woodstock Road, Oxford, OX2 6GG (United Kingdom); Tourkine, Piotr [Department of Applied Mathematics and Theoretical Physics,Wilberforce Road, Cambridge, CB3 0WA (United Kingdom)

2016-11-07

In this paper we present the null string origin of the ambitwistor string. Classically, the null string is the tensionless limit of string theory, and so too is the ambitwistor string. Both have as constraint algebra the Galilean Conformal Algebra in two dimensions. But something interesting happens in the quantum theory since there is an ambiguity in quantizing the null string. We show that, given a particular choice of quantization scheme and a particular gauge, the null string coincides with the ambitwistor string both classically and quantum mechanically. We also show that the same holds for the spinning versions of the null string and ambitwistor string. With these results we clarify the relationship between the ambitwistor string, the null string, the usual string and the Hohm-Siegel-Zwiebach theory.

The QCD Effective String

International Nuclear Information System (INIS)

Espriu, D.

2003-01-01

QCD can be described in a certain kinematical regime by an effective string theory. This string must couple to background chiral fields in a chirally invariant manner, thus taking into account the true chirally non-invariant QCD vacuum. By requiring conformal symmetry of the string and the unitarity constraint on chiral fields we reconstruct the equations of motion for the latter ones. These provide a consistent background for the propagation of the string. By further requiring locality of the effective action we recover the Lagrangian of non-linear sigma model of pion interactions. The prediction is unambiguous and parameter-free. The estimated chiral structural constants of Gasser and Leutwyler fit very well the phenomenological values. (author)

A New Annular Shear Piezoelectric Accelerometer

DEFF Research Database (Denmark)

Liu, Bin; Kriegbaum, B.

2000-01-01

This paper describes the construction and performance of a recently introduced Annular Shear piezoelectric accelerometer, Type 4511. The design has insulated and double-shielded case. The accelerometer housing is made of stainless steel, AISI 316L. Piezoceramic PZ23 is used. The seismic mass...... prototype. Reasonable agreement between the experimental results of the physical prototype and the simulation results is achieved. The design becomes more efficient. In addition, Type 4511 has a built in DeltaTronâ charge amplifier with ID and complies with IEEE-P1451.4 standard, which is a smart transducer...

Minimal string theories and integrable hierarchies

Science.gov (United States)

Iyer, Ramakrishnan

Well-defined, non-perturbative formulations of the physics of string theories in specific minimal or superminimal model backgrounds can be obtained by solving matrix models in the double scaling limit. They provide us with the first examples of completely solvable string theories. Despite being relatively simple compared to higher dimensional critical string theories, they furnish non-perturbative descriptions of interesting physical phenomena such as geometrical transitions between D-branes and fluxes, tachyon condensation and holography. The physics of these theories in the minimal model backgrounds is succinctly encoded in a non-linear differential equation known as the string equation, along with an associated hierarchy of integrable partial differential equations (PDEs). The bosonic string in (2,2m-1) conformal minimal model backgrounds and the type 0A string in (2,4 m) superconformal minimal model backgrounds have the Korteweg-de Vries system, while type 0B in (2,4m) backgrounds has the Zakharov-Shabat system. The integrable PDE hierarchy governs flows between backgrounds with different m. In this thesis, we explore this interesting connection between minimal string theories and integrable hierarchies further. We uncover the remarkable role that an infinite hierarchy of non-linear differential equations plays in organizing and connecting certain minimal string theories non-perturbatively. We are able to embed the type 0A and 0B (A,A) minimal string theories into this single framework. The string theories arise as special limits of a rich system of equations underpinned by an integrable system known as the dispersive water wave hierarchy. We find that there are several other string-like limits of the system, and conjecture that some of them are type IIA and IIB (A,D) minimal string backgrounds. We explain how these and several other string-like special points arise and are connected. In some cases, the framework endows the theories with a non

Identification of the excitation source of the pressure vessel vibration in a Soviet built WWER PWR with signal transmission path analysis

International Nuclear Information System (INIS)

Antonopoulos-Domis, M.; Mourtzanos, K.; Por, G.

1996-01-01

Signal transmission path analysis via multivariate auto-regressive modelling was applied at signals recorded at a WWER power reactor (Paks reactor, Hungary). The core is equipped with strings of self-powered neutron detectors (SPNDs). Each string has seven SPNDs. The signals were high pass filtered with cut-off at 0.03 Hz and low pass-filtered with cut-off at 25 Hz. The analysis suggests that the source of excitation of all signals at 25 Hz is due to main coolant pump vibration. It was confirmed that there is vibration of main coolant pumps at this frequency due to a bearing problem. Signal transmission path analysis also suggests direct paths from outlet coolant to inlet coolant pressure and in-core neutron detectors at the upper part of the core. (author)

The basis property of eigenfunctions in the problem of a nonhomogeneous damped string

Directory of Open Access Journals (Sweden)

Łukasz Rzepnicki

2017-01-01

Full Text Available The equation which describes the small vibrations of a nonhomogeneous damped string can be rewritten as an abstract Cauchy problem for the densely defined closed operator \\(i A\\. We prove that the set of root vectors of the operator \\(A\\ forms a basis of subspaces in a certain Hilbert space \\(H\\. Furthermore, we give the rate of convergence for the decomposition with respect to this basis. In the second main result we show that with additional assumptions the set of root vectors of the operator \\(A\\ is a Riesz basis for \\(H\\.

Test particle trajectories near cosmic strings

Indian Academy of Sciences (India)

We present a detailed analysis of the motion of test particle in the gravitational field of cosmic strings in different situations using the Hamilton–Jacobi (H–J) formalism. We have discussed the trajectories near static cosmic string, cosmic string in Brans–Dicke theory and cosmic string in dilaton gravity.

Accelerometer and GPS Analysis of Trail Use and Associations With Physical Activity.

Science.gov (United States)

Tamura, Kosuke; Wilson, Jeffrey S; Puett, Robin C; Klenosky, David B; Harper, William A; Troped, Philip J

2018-03-26

Concurrent use of accelerometers and global positioning system (GPS) data can be used to quantify physical activity (PA) occurring on trails. This study examined associations of trail use with PA and sedentary behavior (SB) and quantified on trail PA using a combination of accelerometer and GPS data. Adults (N = 142) wore accelerometer and GPS units for 1-4 days. Trail use was defined as a minimum of 2 consecutive minutes occurring on a trail, based on GPS data. We examined associations between trail use and PA and SB. On trail minutes of light-intensity, moderate-intensity, and vigorous-intensity PA, and SB were quantified in 2 ways, using accelerometer counts only and with a combination of GPS speed and accelerometer data. Trail use was positively associated with total PA, moderate-intensity PA, and light-intensity PA (P GPS and accelerometer data for quantifying on trail activity may be more accurate than accelerometer data alone and is useful for classifying intensity of activities such as bicycling.

Worldsheet factorization for twistor-strings

Energy Technology Data Exchange (ETDEWEB)

Adamo, Tim [Department of Applied Mathematics & Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)

2014-04-10

We study the multiparticle factorization properties of two worldsheet theories which — at tree-level — describe the scattering of massless particles in four dimensions: the Berkovits-Witten twistor-string for N=4 super-Yang-Mills coupled to N=4 conformal supergravity, and the Skinner twistor-string for N=8 supergravity. By considering these string-like theories, we can study factorization at the level of the worldsheet before any Wick contractions or integrals have been performed; this is much simpler than considering the factorization properties of the amplitudes themselves. In Skinner’s twistor-string this entails the addition of worldsheet gravity as well as a formalism that represents all external states in a manifestly symmetric way, which we develop explicitly at genus zero. We confirm that the scattering amplitudes of Skinner’s theory, as well as the gauge theory amplitudes for the planar sector of the Berkovits-Witten theory, factorize appropriately at genus zero. In the non-planar sector, we find behavior indicative of conformal gravity in the Berkovits-Witten twistor-string. We contrast factorization in twistor-strings with the story in ordinary string theory, and also make some remarks on higher genus factorization and disconnected prescriptions.

Worldsheet factorization for twistor-strings

International Nuclear Information System (INIS)

Adamo, Tim

2014-01-01

We study the multiparticle factorization properties of two worldsheet theories which — at tree-level — describe the scattering of massless particles in four dimensions: the Berkovits-Witten twistor-string for N=4 super-Yang-Mills coupled to N=4 conformal supergravity, and the Skinner twistor-string for N=8 supergravity. By considering these string-like theories, we can study factorization at the level of the worldsheet before any Wick contractions or integrals have been performed; this is much simpler than considering the factorization properties of the amplitudes themselves. In Skinner’s twistor-string this entails the addition of worldsheet gravity as well as a formalism that represents all external states in a manifestly symmetric way, which we develop explicitly at genus zero. We confirm that the scattering amplitudes of Skinner’s theory, as well as the gauge theory amplitudes for the planar sector of the Berkovits-Witten theory, factorize appropriately at genus zero. In the non-planar sector, we find behavior indicative of conformal gravity in the Berkovits-Witten twistor-string. We contrast factorization in twistor-strings with the story in ordinary string theory, and also make some remarks on higher genus factorization and disconnected prescriptions

Fermions on the electroweak string

CERN Document Server

Moreno, J M; Quirós, Mariano; Moreno, J M; Oaknin, D H; Quiros, M

1995-01-01

We construct a simple class of exact solutions of the electroweak theory including the naked Z--string and fermion fields. It consists in the Z--string configuration (\\phi,Z_\\theta), the {\\it time} and z components of the neutral gauge bosons (Z_{0,3},A_{0,3}) and a fermion condensate (lepton or quark) zero mode. The Z--string is not altered (no feed back from the rest of fields on the Z--string) while fermion condensates are zero modes of the Dirac equation in the presence of the Z--string background (no feed back from the {\\it time} and z components of the neutral gauge bosons on the fermion fields). For the case of the n--vortex Z--string the number of zero modes found for charged leptons and quarks is (according to previous results by Jackiw and Rossi) equal to |n|, while for (massless) neutrinos is |n|-1. The presence of fermion fields in its core make the obtained configuration a superconducting string, but their presence (as well as that of Z_{0,3},A_{0,3}) does not enhance the stability of the Z--stri...

The STRING database in 2011

DEFF Research Database (Denmark)

Szklarczyk, Damian; Franceschini, Andrea; Kuhn, Michael

2011-01-01

present an update on the online database resource Search Tool for the Retrieval of Interacting Genes (STRING); it provides uniquely comprehensive coverage and ease of access to both experimental as well as predicted interaction information. Interactions in STRING are provided with a confidence score...... models, extensive data updates and strongly improved connectivity and integration with third-party resources. Version 9.0 of STRING covers more than 1100 completely sequenced organisms; the resource can be reached at http://string-db.org....

Racetrack inflation and cosmic strings

Energy Technology Data Exchange (ETDEWEB)

Brax, P. [CEA-Saclay, Gif sur Yvette (France). CEA/DSM/SPhT, Unite de Recherche Associee au CNRS, Service de Physique Theorique; Bruck, C. van de [Sheffield Univ. (United Kingdom). Dept. of Applied Mathematics; Davis, A.C.; Davis, S.C. [Cambridge Univ. (United Kingdom). DAMTP, Centre for Mathematical Sciences; Jeannerot, R. [Instituut-Lorentz for Theoretical Physics, Leiden (Netherlands); Postma, M. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)]|[Nationaal Inst. voor Kernfysica en Hoge-Energiefysica (NIKHEF), Amsterdam (Netherlands)

2008-05-15

We consider the coupling of racetrack inflation to matter fields as realised in the D3/D7 brane system. In particular, we investigate the possibility of cosmic string formation in this system. We find that string formation before or at the onset of racetrack inflation is possible, but they are then inflated away. Furthermore, string formation at the end of inflation is prevented by the presence of the moduli sector. As a consequence, no strings survive racetrack inflation. (orig.)

Racetrack inflation and cosmic strings

International Nuclear Information System (INIS)

Brax, P.; Postma, M.

2008-05-01

We consider the coupling of racetrack inflation to matter fields as realised in the D3/D7 brane system. In particular, we investigate the possibility of cosmic string formation in this system. We find that string formation before or at the onset of racetrack inflation is possible, but they are then inflated away. Furthermore, string formation at the end of inflation is prevented by the presence of the moduli sector. As a consequence, no strings survive racetrack inflation. (orig.)

Geometric derivation of string field theory from first principles: Closed strings and modular invariance

International Nuclear Information System (INIS)

Kaku, M.

1988-01-01

We present an entirely new approach to closed-string field theory, called Igeometric string field theory R, which avoids the complications found in Becchi-Rouet-Stora-Tyutin string field theory (e.g., ghost counting, infinite overcounting of diagrams, midpoints, lack of modular invariance). Following the analogy with general relativity and Yang-Mills theory, we define a new infinite-dimensional local gauge group, called the unified string group, which uniquely specifies the connection fields, the curvature tensor, the measure and tensor calculus, and finally the action itself. Geometric field theory, when gauge fixed, yields an entirely new class of gauges called the interpolating gauge which allows us to smoothly interpolate between the midpoint gauge and the end-point gauge (''covariantized light-cone gauge''). We can show that geometric string field theory reproduces one copy of the Shapiro-Virasoro model. Surprisingly, after the gauge is broken, a new Iclosed four-string interactionR emerges as the counterpart of the instantaneous four-fermion Coulomb term in QED. This term restores modular invariance and precisely fills the missing region of the complex plane

MEMS Accelerometer with Screen Printed Piezoelectric Thick Film

DEFF Research Database (Denmark)

Hindrichsen, Christian Carstensen; Lau-Moeller, R.; Bove, T.

2006-01-01

A bulk-micromachined piezoelectric MEMS accelerometer with screen printed piezoelectric Pb(ZrxTil )O3(PZT) thick film (TF) as the sensing material has been fabricated and characterized. The accelerometer has a four beam structure with a central seismic mass (3600x3600x500 pm3) and a total chip size...

Finite Element Based Design and Optimization for Piezoelectric Accelerometers

DEFF Research Database (Denmark)

Liu, Bin; Kriegbaum, B.; Yao, Q.

1998-01-01

A systematic Finite Element design and optimisation procedure is implemented for the development of piezoelectric accelerometers. Most of the specifications of accelerometers can be obtained using the Finite Element simulations. The deviations between the simulated and calibrated sensitivities...

String theory as a Lilliputian world

International Nuclear Information System (INIS)

Ambjørn, J.; Makeenko, Y.

2016-01-01

Lattice regularizations of the bosonic string do not allow us to probe the tachyon. This has often been viewed as the reason why these theories have never managed to make any contact to standard continuum string theories when the dimension of spacetime is larger than two. We study the continuum string theory in large spacetime dimensions where simple mean field theory is reliable. By keeping carefully the cutoff we show that precisely the existence of a tachyon makes it possible to take a scaling limit which reproduces the lattice-string results. We compare this scaling limit with another scaling limit which reproduces standard continuum-string results. If the people working with lattice regularizations of string theories are akin to Gulliver they will view the standard string-world as a Lilliputian world no larger than a few lattice spacings.

String theory as a Lilliputian world

Energy Technology Data Exchange (ETDEWEB)

Ambjørn, J., E-mail: ambjorn@nbi.dk [The Niels Bohr Institute, Copenhagen University, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); IMAPP, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen (Netherlands); Makeenko, Y., E-mail: makeenko@nbi.dk [The Niels Bohr Institute, Copenhagen University, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Institute of Theoretical and Experimental Physics, B. Cheremushkinskaya 25, 117218 Moscow (Russian Federation)

2016-05-10

Lattice regularizations of the bosonic string do not allow us to probe the tachyon. This has often been viewed as the reason why these theories have never managed to make any contact to standard continuum string theories when the dimension of spacetime is larger than two. We study the continuum string theory in large spacetime dimensions where simple mean field theory is reliable. By keeping carefully the cutoff we show that precisely the existence of a tachyon makes it possible to take a scaling limit which reproduces the lattice-string results. We compare this scaling limit with another scaling limit which reproduces standard continuum-string results. If the people working with lattice regularizations of string theories are akin to Gulliver they will view the standard string-world as a Lilliputian world no larger than a few lattice spacings.

Relativistic classical strings. II

International Nuclear Information System (INIS)

Galvao, C.A.P.

1985-01-01

The interactions of strings with electromagnetic and gravitational fields are extensively discussed. Some concepts of differential geometry are reviewed. Strings in Kaluza-Klein manifolds are studied. (L.C.) [pt

A rotating string

International Nuclear Information System (INIS)

Jensen, B.

1993-06-01

The author presents a global solution of Einstein's equations which represents a rotating cosmic string with a finite coreradius. The importance of pressure for the generation of closed timelike curves outside the coreregion of such strings is clearly displayed in this model due to the simplicity of the source. 10 refs

The ABCDEFG of Little Strings

OpenAIRE

Haouzi, Nathan; Kozçaz, Can

2017-01-01

Starting from type IIB string theory on an $ADE$ singularity, the (2,0) little string arises when one takes the string coupling $g_s$ to 0. In this setup, we give a unified description of the codimension-two defects of the little string, for any simple Lie algebra ${\\mathfrak{g}}$. Geometrically, these are D5 branes wrapping 2-cycles of the singularity. Equivalently, the defects are specified by a certain set of weights of $^L {\\mathfrak{g}}$, the Langlands dual of ${\\mathfrak{g}}$. As a firs...

Open problems in string cosmology

International Nuclear Information System (INIS)

Toumbas, N.

2010-01-01

Some of the open problems in string cosmology are highlighted within the context of the recently constructed thermal and quantum superstring cosmological solutions. Emphasis is given on the high temperature cosmological regime, where it is argued that thermal string vacua in the presence of gravito-magnetic fluxes can be used to bypass the Hagedorn instabilities of string gas cosmology. This article is based on a talk given at the workshop on ''Cosmology and Strings'', Corfu, September 6-13, 2009. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

SOI Digital Accelerometer Based on Pull-in Time Configuration

NARCIS (Netherlands)

Pakula, L.S.; Rajaraman, V.; French, P.J.

2009-01-01

The operation principle, design, fabrication and measurement results of a quasi digital accelerometer fabricated on a thin silicon-on-insulator (SOI) substrate is presented. The accelerometer features quasi-digital output, therefore eliminating the need for analogue signal conditioning. The

Strings, conformal fields and topology

International Nuclear Information System (INIS)

Kaku, Michio

1991-01-01

String Theory has advanced at an astonishing pace in the last few years, and this book aims to acquaint the reader with the most active topics of research in the field. Building on the foundations laid in his Introduction to Superstrings, Professor Kaku discusses such topics as the classification of conformal string theories, knot theory, the Yang-Baxter relation, quantum groups, the non-polynominal closed string field theory, matrix models, and topological field theory. Several chapters review the fundamentals of string theory, making the presentation of the material self-contained while keeping overlap with the earlier book to a minimum. The book conveys the vitality of current research in string theory and places readers at its forefront. (orig.) With 40 figs. in 50 parts

Basic concepts of string theory

International Nuclear Information System (INIS)

Blumenhagen, Ralph

2013-01-01

The purpose of this book is to thoroughly prepare the reader for research in string theory. It is intended as a textbook in the sense that, starting from the basics, the material is presented in a pedagogical and self-contained fashion. The emphasis is on the world-sheet perspective of closed strings and of open strings ending on D-branes, where two-dimensional conformal field theory is the main tool. Compactifications of string theory, with and without fluxes, and string dualities are also discussed from the space-time point of view, i.e. in geometric language. End-of-chapter references have been added to guide the reader intending to pursue further studies or to start research in the topics covered by this book.

String fragmentation; La fragmentation des cordes

Energy Technology Data Exchange (ETDEWEB)

Drescher, H.J.; Werner, K. [Laboratoire de Physique Subatomique et des Technologies Associees - SUBATECH, Centre National de la Recherche Scientifique, 44 - Nantes (France)

1997-10-01

The classical string model is used in VENUS as a fragmentation model. For the soft domain simple 2-parton strings were sufficient, whereas for higher energies up to LHC, the perturbative regime of the QCD gives additional soft gluons, which are mapped on the string as so called kinks, energy singularities between the leading partons. The kinky string model is chosen to handle fragmentation of these strings by application of the Lorentz invariant area law. The `kinky strings` model, corresponding to the perturbative gluons coming from pQCD, takes into consideration this effect by treating the partons and gluons on the same footing. The decay law is always the Artru-Menessier area law which is the most realistic since it is invariant to the Lorentz and gauge transformations. For low mass strings a manipulation of the rupture point is necessary if the string corresponds already to an elementary particle determined by the mass and the flavor content. By means of the fragmentation model it will be possible to simulate the data from future experiments at LHC and RHIC 3 refs.

Querying and Mining Strings Made Easy

KAUST Repository

Sahli, Majed

2017-10-13

With the advent of large string datasets in several scientific and business applications, there is a growing need to perform ad-hoc analysis on strings. Currently, strings are stored, managed, and queried using procedural codes. This limits users to certain operations supported by existing procedural applications and requires manual query planning with limited tuning opportunities. This paper presents StarQL, a generic and declarative query language for strings. StarQL is based on a native string data model that allows StarQL to support a large variety of string operations and provide semantic-based query optimization. String analytic queries are too intricate to be solved on one machine. Therefore, we propose a scalable and efficient data structure that allows StarQL implementations to handle large sets of strings and utilize large computing infrastructures. Our evaluation shows that StarQL is able to express workloads of application-specific tools, such as BLAST and KAT in bioinformatics, and to mine Wikipedia text for interesting patterns using declarative queries. Furthermore, the StarQL query optimizer shows an order of magnitude reduction in query execution time.

First quantized noncritical relativistic Polyakov string

International Nuclear Information System (INIS)

Jaskolski, Z.; Meissner, K.A.

1994-01-01

The first quantization of the relativistic Brink-DiVecchia-Howe-Polyakov (BDHP) string in the range 1 < d 25 is considered. It is shown that using the Polyakov sum over bordered surfaces in the Feynman path integral quantization scheme one gets a consistent quantum mechanics of relativistic 1-dim extended objects in the range 1 < d < 25. In particular, the BDHP string propagator is exactly calculated for arbitrary initial and final string configurations and the Hilbert space of physical states of noncritical BDHP string is explicitly constructed. The resulting theory is equivalent to the Fairlie-Chodos-Thorn massive string model. In contrast to the conventional conformal field theory approach to noncritical string and random surfaces in the Euclidean target space the path integral formulation of the Fairlie-Chodos-Thorn string obtained in this paper does not rely on the principle of conformal invariance. Some consequences of this feature for constructing a consistent relativistic string theory based on the ''splitting-joining'' interaction are discussed. (author). 42 refs, 1 fig

Functional integral approach to string theories

International Nuclear Information System (INIS)

Sakita, B.

1987-01-01

Fermionic string theory can be made supersymmetric: the superstring. It contains among others mass zero gauge fields of spin 1 and 2. The recent revival of interests in string field theories is due to the recognition of the compactified superstring theory as a viable theory of grandunification of all interactions, especially after Green and Schwarz's discovery of the gauge and gravitational anomaly cancellation in 0(32) superstring theory. New developments include string phenomenology, general discussions of compactification, new models, especially the heterotic string. These are either applications or extensions of string field theories. Although these are very exciting developments, the author limits his attention to the basics of the bosonic string theory

Black string in dRGT massive gravity

Energy Technology Data Exchange (ETDEWEB)

Tannukij, Lunchakorn [Mahidol University, Department of Physics, Faculty of Science, Bangkok (Thailand); Hanyang University, Department of Physics, Seoul (Korea, Republic of); Naresuan University, The Institute for Fundamental Study, Phitsanulok (Thailand); Wongjun, Pitayuth [Naresuan University, The Institute for Fundamental Study, Phitsanulok (Thailand); Ministry of Education, Thailand Center of Excellence in Physics, Bangkok (Thailand); Ghosh, Suchant G. [Jamia Millia Islamia, Centre of Theoretical Physics, New Delhi (India); University of Kwazulu-Natal, Astrophysics and Cosmology Research Unit, School of Mathematical Sciences, Durban (South Africa)

2017-12-15

We present a cylindrically symmetric solution, both charged and uncharged, which is known as a black string solution to the nonlinear ghost-free massive gravity found by de Rham, Gabadadze, and Tolley (dRGT). This ''dRGT black string'' can be thought of as a generalization of the black string solution found by Lemos. Moreover, the dRGT black string solution includes other classes of black string solution such as the monopole-black string ones since the graviton mass contributes to the global monopole term as well as the cosmological-constant term. To investigate the solution, we compute mass, temperature, and entropy of the dRGT black string. We found that the existence of the graviton mass drastically affects the thermodynamics of the black string. Furthermore, the Hawking-Page phase transition is found to be possible for the dRGT black string as well as the charged dRGT black string. The dRGT black string solution is thermodynamically stable for r > r{sub c} with negative thermodynamical potential and positive heat capacity while it is unstable for r < r{sub c} where the potential is positive. (orig.)

Strings and quantum gravity

International Nuclear Information System (INIS)

Vega, H.J. de

1990-01-01

One of the main challenges in theoretical physics today is the unification of all interactions including gravity. At present, string theories appear as the most promising candidates to achieve such a unification. However, gravity has not completely been incorporated in string theory, many technical and conceptual problems remain and a full quantum theory of gravity is still non-existent. Our aim is to properly understand strings in the context of quantum gravity. Attempts towards this are reviewed. (author)

Magnetic strings

International Nuclear Information System (INIS)

Chaves, Max

2006-01-01

The conception of the magnetic string is presented as an infinitely thin bundle of magnetic flux lines. The magnetic strings are surrounded by a film of current that rotates around them, and are a solution of Maxwell's equations. The magnetic potential contains a line singularity, and its stability can be established topologically. A few comments are added on the possibility that they may exist at a cosmological scale as relics of the Big Bang. (author) [es

Effect of changing of the parameters of the cable network of monitoring systems of high-rise buildings on the basis of string converters on their operability

Science.gov (United States)

Gusev, Nikolay; Svatovskaya, Larisa; Kucherenko, Alexandr

2018-03-01

The article is devoted to the problem of improving the reliability of monitoring systems for the technical conditions of high-rise buildings. The improvement is based on string sensors with an impulsed excitation method ensuring the maximum signal-to-noise ratio at their output. The influence of the parameters of the monitoring system on the shape of the excitation impulses of the string, and, consequently, on the amplitude of the string vibration of the string converter is also considered in the article. It has been experimentally proved that the parameters of the excitation impulses of the string converters. The article presents the results of the experiments showing the effect of the fronts duration of the excitation impulses on the amplitude of the oscillations of the strings. The influence of the fronts duration of the excitation impulse with the frontal lengths up to 0.5 ms is studied at the excitation impulse duration not exceeding 0.5 times the duration of natural oscillation periods of the string. The experimental data are compared with the theoretical ones and hypotheses explaining their difference are advanced. The article suggests some methods of reducing the influence of the cable-switching equipment system parameters on the amplitude of string oscillations. The possibilities of improving the reliability of the systems developed on the basis of string sensors with an impulsed excitation method and used for monitoring the technical conditions of the high-rise buildings are proposed.

Vibration test of 1/5 scale H-II launch vehicle

Science.gov (United States)

Morino, Yoshiki; Komatsu, Keiji; Sano, Masaaki; Minegishi, Masakatsu; Morita, Toshiyuki; Kohsetsu, Y.

In order to predict dynamic loads on the newly designed Japanese H-II launch vehicle, the adequacy of prediction methods has been assessed by the dynamic scale model testing. The three-dimensional dynamic model was used in the analysis to express coupling effects among axial, lateral (pitch and yaw) and torsional vibrations. The liquid/tank interaction was considered by use of a boundary element method. The 1/5 scale model of the H-II launch vehicle was designed to simulate stiffness and mass properties of important structural parts, such as core/SRB junctions, first and second stage Lox tanks and engine mount structures. Modal excitation of the test vehicle was accomplished with 100-1000 N shakers which produced random or sinusoidal vibrational forces. The vibrational response of the test vehicle was measured at various locations with accelerometers and pressure sensor. In the lower frequency range, corresmpondence between analysis and experiment was generally good. The basic procedures in analysis seem to be adequate so far, but some improvements in mathematical modeling are suggested by comparison of test and analysis.

String Theory in a Nutshell

CERN Document Server

Kiritsis, Elias

2007-01-01

This book is the essential new introduction to modern string theory, by one of the world's authorities on the subject. Concise, clearly presented, and up-to-date, String Theory in a Nutshell brings together the best understood and most important aspects of a theory that has been evolving since the early 1980s. A core model of physics that substitutes one-dimensional extended ""strings"" for zero-dimensional point-like particles (as in quantum field theory), string theory has been the leading candidate for a theory that would successfully unify all fundamental forces of nature, includin

String theory and quark confinement

International Nuclear Information System (INIS)

Polyakov, A.M.

1998-01-01

This article is based on a talk given at the ''Strings '97'' conference. It discusses the search for the universality class of confining strings. The key ingredients include the loop equations, the zigzag symmetry, the non-linear renormalization group. Some new tests for the equivalence between gauge fields and strings are proposed. (orig.)

Open bosonic string in background electromagnetic field

International Nuclear Information System (INIS)

Nesterenko, V.V.

1987-01-01

The classical and quantum dynamics of an open string propagating in the D-dimensional space-time in the presence of a background electromagnetic field is investigated. An important point in this consideration is the use of the generalized light-like gauge. There are considered the strings of two types; the neutral strings with charges at their ends obeying the condition q 1 +q 2 =0 and the charged strings having a net charge q 1 +q 2 ≠ 0. The consistency of theory demands that the background electric field does not exceed its critical value. The distance between the mass levels of the neutral open string decreases (1-e 2 ) times in comparison with the free string, where e is the dimensionless strength of the electric field. The magnetic field does not affect this distance. It is shown that at a classical level the squared mass of the neutral open string has a tachyonic contribution due to the motion of the string as a whole in transverse directions. The tachyonic term disappears if one considers, instead of M 2 , the string energy in a special reference frame where the projection of the total canonical momentum of the string onto the electric field vanishes. The contributions due to zero point fluctuations to the energy spectrum of the neutral string and to the Virasoro operators in the theory of charged string are found

A Subnano-g Electrostatic Force-Rebalanced Flexure Accelerometer for Gravity Gradient Instruments

Directory of Open Access Journals (Sweden)

Shitao Yan

2017-11-01

Full Text Available A subnano-g electrostatic force-rebalanced flexure accelerometer is designed for the rotating accelerometer gravity gradient instrument. This accelerometer has a large proof mass, which is supported inversely by two pairs of parallel leaf springs and is centered between two fixed capacitor plates. This novel design enables the proof mass to move exactly along the sensitive direction and exhibits a high rejection ratio at its cross-axis directions. Benefiting from large proof mass, high vacuum packaging, and air-tight sealing, the thermal Brownian noise of the accelerometer is lowered down to less than 0.2 ng / Hz with a quality factor of 15 and a natural resonant frequency of about 7.4 Hz . The accelerometer’s designed measurement range is about ±1 mg. Based on the correlation analysis between a commercial triaxial seismometer and our accelerometer, the demonstrated self-noise of our accelerometers is reduced to lower than 0.3 ng / Hz over the frequency ranging from 0.2 to 2 Hz, which meets the requirement of the rotating accelerometer gravity gradiometer.

Casimir energy of a nonuniform string

Science.gov (United States)

Hadasz, L.; Lambiase, G.; Nesterenko, V. V.

2000-07-01

The Casimir energy of a nonuniform string built up from two pieces with different speeds of sound is calculated. A standard procedure of subtracting the energy of an infinite uniform string is applied, the subtraction being interpreted as the renormalization of the string tension. It is shown that in the case of a homogeneous string this method is completely equivalent to zeta renormalization.

A Note on Tensionless Strings in M-Theory

OpenAIRE

Davis, K.

1996-01-01

In this article we examine the appearance of tensionless strings in M-Theory. We subsequently interpret these tensionless strings in a String Theory context. In particular, we examine tensionless strings appearing in M-Theory on $S^{1}$, M-Theory on $S^{1} / {\\bf Z}_{2}$, and M-Theory on $T^{2}$; we then interpret the appearance of such strings in a String Theory context. Then we reverse this process and examine the appearance of some tensionless strings in String Theory. Subsequently we inte...

Open strings in the SL(2, R) WZWN model with solution for a rigidly rotating string

DEFF Research Database (Denmark)

Lomholt, Michael Andersen; Larsen, A.L.

2003-01-01

Boundary conditions and gluing conditions for open strings and D-branes in the SL(2, R) WZWN model, corresponding to AdS , are discussed. Some boundary conditions and gluing conditions previously considered in the literature are shown to be incompatible with the variation principle. We then consi......Boundary conditions and gluing conditions for open strings and D-branes in the SL(2, R) WZWN model, corresponding to AdS , are discussed. Some boundary conditions and gluing conditions previously considered in the literature are shown to be incompatible with the variation principle. We...... then consider open string boundary conditions corresponding to a certain field-dependent gluing condition. This allows us to consider open strings with constant energy and angular momentum. Classically, these open strings naturally generalize the open strings in flat Minkowski space. For rigidly rotating open...

Poisson hierarchy of discrete strings

International Nuclear Information System (INIS)

Ioannidou, Theodora; Niemi, Antti J.

2016-01-01

The Poisson geometry of a discrete string in three dimensional Euclidean space is investigated. For this the Frenet frames are converted into a spinorial representation, the discrete spinor Frenet equation is interpreted in terms of a transfer matrix formalism, and Poisson brackets are introduced in terms of the spinor components. The construction is then generalised, in a self-similar manner, into an infinite hierarchy of Poisson algebras. As an example, the classical Virasoro (Witt) algebra that determines reparametrisation diffeomorphism along a continuous string, is identified as a particular sub-algebra, in the hierarchy of the discrete string Poisson algebra. - Highlights: • Witt (classical Virasoro) algebra is derived in the case of discrete string. • Infinite dimensional hierarchy of Poisson bracket algebras is constructed for discrete strings. • Spinor representation of discrete Frenet equations is developed.

Basic Concepts of String Theory

CERN Document Server

Blumenhagen, Ralph; Theisen, Stefan

2013-01-01

The purpose of this book is to thoroughly prepare the reader for research in string theory. It is intended as a textbook in the sense that, starting from the basics, the material is presented in a pedagogical and self-contained fashion. The emphasis is on the world-sheet perspective of closed strings and of open strings ending on D-branes, where two-dimensional conformal field theory is the main tool. Compactifications of string theory, with and without fluxes, and string dualities are also discussed from the space-time point of view, i.e. in geometric language. End-of-chapter references have been added to guide the reader intending to pursue further studies or to start research in the topics covered by this book.

Poisson hierarchy of discrete strings

Energy Technology Data Exchange (ETDEWEB)

Ioannidou, Theodora, E-mail: ti3@auth.gr [Faculty of Civil Engineering, School of Engineering, Aristotle University of Thessaloniki, 54249, Thessaloniki (Greece); Niemi, Antti J., E-mail: Antti.Niemi@physics.uu.se [Department of Physics and Astronomy, Uppsala University, P.O. Box 803, S-75108, Uppsala (Sweden); Laboratoire de Mathematiques et Physique Theorique CNRS UMR 6083, Fédération Denis Poisson, Université de Tours, Parc de Grandmont, F37200, Tours (France); Department of Physics, Beijing Institute of Technology, Haidian District, Beijing 100081 (China)

2016-01-28

The Poisson geometry of a discrete string in three dimensional Euclidean space is investigated. For this the Frenet frames are converted into a spinorial representation, the discrete spinor Frenet equation is interpreted in terms of a transfer matrix formalism, and Poisson brackets are introduced in terms of the spinor components. The construction is then generalised, in a self-similar manner, into an infinite hierarchy of Poisson algebras. As an example, the classical Virasoro (Witt) algebra that determines reparametrisation diffeomorphism along a continuous string, is identified as a particular sub-algebra, in the hierarchy of the discrete string Poisson algebra. - Highlights: • Witt (classical Virasoro) algebra is derived in the case of discrete string. • Infinite dimensional hierarchy of Poisson bracket algebras is constructed for discrete strings. • Spinor representation of discrete Frenet equations is developed.

Testing string theory at LHC?

CERN Multimedia

CERN. Geneva

2002-01-01

A theory with such mathematical beauty cannot be wrong: this is one of the main arguments in favour of string theory, which unifies all known physical theories of fundamental interactions in a single coherent description of the universe. But no one has ever observed strings, not even indirectly, nor the space of extra dimensions where they live. However there are good reasons to believe that the 'hidden' dimensions of string theory may be much larger than what we thought in the past and that they may be within experimental reach in the near future - together with the strings themselves. In my talk, I will give an elementary introduction of string theory and describe the main experimental predictions.Organiser(s): Jasper Kirkby / EP DivisionNote: Tea & coffee will be served at 16.00 hrs.

String theory and quantum gravity '92

International Nuclear Information System (INIS)

Harvey, J.; Iengo, R.; Narain, K.S.; Randjbar Daemi, S.; Verlinde, H.

1993-01-01

These proceedings of the 1992 Trieste Spring School and Workshop on String Theory and Quantum Gravity contains introductions and overviews of recent work on the use of two-dimensional string inspired models in the study of black holes, a lecture on gravitational scattering at planckian energies, another on the physical properties of higher-dimensional black holes and black strings in string theory, a discussion on N=2 superconformal field theories, a lecture about the application of matrix model techniques to the study of string theory in two dimensions, and an overview of the current status and developments in string field theory. Connections with models in statistical mechanics are also discussed. These proceedings contain seven lectures and ten contributions. Refs and figs

Real-time vibration compensation for large telescopes

Science.gov (United States)

Böhm, M.; Pott, J.-U.; Sawodny, O.; Herbst, T.; Kürster, M.

2014-08-01

We compare different strategies for minimizing the effects of telescope vibrations to the differential piston (optical pathway difference) for the Near-InfraRed/Visible Adaptive Camera and INterferometer for Astronomy (LINC-NIRVANA) at the Large Binocular Telescope (LBT) using an accelerometer feedforward compensation approach. We summarize, why this technology is important for LINC-NIRVANA, and also for future telescopes and already existing instruments. The main objective is outlining a solution for the estimation problem in general and its specifics at the LBT. Emphasis is put on realistic evaluation of the used algorithms in the laboratory, such that predictions for the expected performance at the LBT can be made. Model-based estimation and broad-band filtering techniques can be used to solve the estimation task, and the differences are discussed. Simulation results and measurements are shown to motivate our choice of the estimation algorithm for LINC-NIRVANA. The laboratory setup is aimed at imitating the vibration behaviour at the LBT in general, and the M2 as main contributor in particular. For our measurements, we introduce a disturbance time series which has a frequency spectrum comparable to what can be measured at the LBT on a typical night. The controllers' ability to suppress vibrations in the critical frequency range of 8-60 Hz is demonstrated. The experimental results are promising, indicating the ability to suppress differential piston induced by telescope vibrations by a factor of about 5 (rms), which is significantly better than any currently commissioned system.

Collisions of cosmic F- and D-strings

International Nuclear Information System (INIS)

Jones, N.

2004-01-01

Recent theoretical advances and upcoming experimental measurements make the testing of generic predictions of string theory models of cosmology feasible. Brane anti-brane models of inflation within superstring theory are promising as string theory descriptions of the physics of the early universe. While varied in their construction, these models can have the generic and observable consequence that cosmic strings will be abundant in the early universe. This leads to possible detectable effects in the cosmic microwave background, gravitational wave physics and gravitational lensing. Detailed calculations of cosmic string interactions within string theory are presented, in order to distinguish these cosmic strings from those in more conventional theories; these interaction probabilities can be very different from conventional 4-dimension strings, providing the possibility of experimental tests of string theory. (authors)

Strings and superstrings. Electron linear colliders

International Nuclear Information System (INIS)

Alessandrini, V.; Bambade, P.; Binetruy, P.; Kounnas, C.; Le Duff, J.; Schwimmer, A.

1989-01-01

Basic string theory; strings in interaction; construction of strings and superstrings in arbitrary space-time dimensions; compactification and phenomenology; linear e+e- colliders; and the Stanford linear collider were discussed [fr

Dynamical evolution of cosmic strings

International Nuclear Information System (INIS)

Bouchet, F.R.

1988-01-01

The author have studied by means of numerical simulations the dynamical evolution of a network of cosmic strings, both in the radiation and matter era. Our basic conclusion is that a scaling solution exists, i.e., the string energy density evolves as t -2 . This means that the process by which long strings dump their energy into closed loops (which can gravitationally radiate away) is efficient enough to prevent the string domination over other forms of energy. This conclusion does not depend on the initial string energy density, nor on the various numerical parameters. On the other hand, the generated spectrum of loop sizes does depend on the value of our numerical lower cutoff (i.e., the minimum length of loop we allow to be chopped off the network). Furthermore, the network evolution is very different from what was assumed before), namely the creation of a few horizon sized loops per horizon volume and per hubble time, which subsequently fragment into about 10 smaller daughter loops. Rather, many tiny loops are directly cut from the network of infinite strings, and it appears that the only fundamental scale (the horizon) has been lost. This is probably because a fundamental ingredient had been overlooked, namely the kinks. These kinks are created in pairs at each intercommutation, and very rapidly, the long strings appear to be very kinky. Thus the number of long strings per horizon is still of the order of a few, but their total length is fairly large. Furthermore, a large number of kinks favors the formation of small loops, and their sizes might well be governed by the kink density along the long strings. Finally, we computed the two-point correlation function of the loops and found significant differences from the work of Turok

Demonstration of non-collocated vibration control of a flexible manipulator using electrical dynamic absorbers

International Nuclear Information System (INIS)

Kim, Sang-Myeong; Kim, Heungseob; Boo, Kwangsuck; Brennan, Michael J

2013-01-01

This paper describes an experimental study into the vibration control of a servo system comprising a servo motor and a flexible manipulator. Two modes of the system are controlled by using the servo motor and an accelerometer attached to the tip of the flexible manipulator. The control system is thus non-collocated. It consists of two electrical dynamic absorbers, each of which consists of a modal filter and, in case of an out-of-phase mode, a phase inverter. The experimental results show that each absorber acts as a mechanical dynamic vibration absorber attached to each mode and significantly reduces the settling time for the system response to a step input. (technical note)

Fast searching in packed strings

DEFF Research Database (Denmark)

Bille, Philip

2011-01-01

Given strings P and Q the (exact) string matching problem is to find all positions of substrings in Q matching P. The classical Knuth–Morris–Pratt algorithm [SIAM J. Comput. 6 (2) (1977) 323–350] solves the string matching problem in linear time which is optimal if we can only read one character...... at the time. However, most strings are stored in a computer in a packed representation with several characters in a single word, giving us the opportunity to read multiple characters simultaneously. In this paper we study the worst-case complexity of string matching on strings given in packed representation....... Let m⩽n be the lengths P and Q, respectively, and let σ denote the size of the alphabet. On a standard unit-cost word-RAM with logarithmic word size we present an algorithm using timeO(nlogσn+m+occ). Here occ is the number of occurrences of P in Q. For m=o(n) this improves the O(n) bound of the Knuth...

Dynamics of strings between walls

International Nuclear Information System (INIS)

Eto, Minoru; Fujimori, Toshiaki; Nagashima, Takayuki; Nitta, Muneto; Ohashi, Keisuke; Sakai, Norisuke

2009-01-01

Configurations of vortex strings stretched between or ending on domain walls were previously found to be 1/4 Bogomol'nyi-Prasad-Sommerfield (BPS) states in N=2 supersymmetric gauge theories in 3+1 dimensions. Among zero modes of string positions, the center of mass of strings in each region between two adjacent domain walls is shown to be non-normalizable whereas the rests are normalizable. We study dynamics of vortex strings stretched between separated domain walls by using two methods, the moduli space (geodesic) approximation of full 1/4 BPS states and the charged particle approximation for string end points in the wall effective action. In the first method we explicitly obtain the effective Lagrangian in the strong coupling limit, which is written in terms of hypergeometric functions, and find the 90 deg. scattering for head-on collision. In the second method the domain wall effective action is assumed to be U(1) N gauge theory, and we find a good agreement between two methods for well-separated strings.

Experimental observation of Bethe strings

Science.gov (United States)

Wang, Zhe; Wu, Jianda; Yang, Wang; Bera, Anup Kumar; Kamenskyi, Dmytro; Islam, A. T. M. Nazmul; Xu, Shenglong; Law, Joseph Matthew; Lake, Bella; Wu, Congjun; Loidl, Alois

2018-02-01

Almost a century ago, string states—complex bound states of magnetic excitations—were predicted to exist in one-dimensional quantum magnets. However, despite many theoretical studies, the experimental realization and identification of string states in a condensed-matter system have yet to be achieved. Here we use high-resolution terahertz spectroscopy to resolve string states in the antiferromagnetic Heisenberg-Ising chain SrCo2V2O8 in strong longitudinal magnetic fields. In the field-induced quantum-critical regime, we identify strings and fractional magnetic excitations that are accurately described by the Bethe ansatz. Close to quantum criticality, the string excitations govern the quantum spin dynamics, whereas the fractional excitations, which are dominant at low energies, reflect the antiferromagnetic quantum fluctuations. Today, Bethe’s result is important not only in the field of quantum magnetism but also more broadly, including in the study of cold atoms and in string theory; hence, we anticipate that our work will shed light on the study of complex many-body systems in general.

A new approach to strings and superstrings

International Nuclear Information System (INIS)

Sparano, G.

1988-01-01

The subject of this thesis is a new, more general, action principle for strings, superstrings, and extended objects in any number of dimensions. The origin and motivations for this approach can be found in the context of the study of the symmetries of string theories and, more specifically, are related to the application of K.S.K. (Kirillov, Souriau, Kostant) construction to strings. The main results we find are: (A) A classification of string theories analogous to the classification of relativistic point particles as massive, massless and tachionic with or without spin. Nambu-Goto string and Schild null string emerge as special cases of a more general classification of strings. (B) A new method to introduce spin in strings by using a Wess-Zumino term in the action. (C) Several results are obtained through the study of the configuration space which shows a rich topological structure: for the Nambu-Goto string in any number of dimensions it is found the existence of theta states analogous to the theta-vacua of nonabelian gauge theories. For the closed Schild Null string, in four dimensions, this analysis shows Z2 solitons and the possibility of quantizing the system so that the states are spinorial (have half odd integral spin) even though the Lagrangian consists only of bosonic variables. (D) Unlike Nambu-Goto string, the quantization of Schild Null string is consistent in any number of space-time dimensions. Besides these concrete results, the formalism we introduce will hopefully give also new insights in the problem of the hidden symmetries of the string

Hydroball string sensing system

International Nuclear Information System (INIS)

Hurwitz, M.J.; Ekeroth, D.E.; Squarer, D.

1991-01-01

This patent describes a hydroball string sensing system for a nuclear reactor having a core containing a fluid at a fluid pressure. It comprises a tube connectable to the nuclear reactor so that the fluid can flow within the tube at a fluid pressure that is substantially the same as the fluid pressure of the nuclear reactor core; a hydroball string including - a string member having objects positioned therealong with a specified spacing, the object including a plurality of hydroballs, and bullet members positioned at opposing ends of the string member; first sensor means, positioned outside a first segment of the tube, for sensing one of the objects being positioned within the first segment, and for providing a sensing signal responsive to the sensing of the first sensing means

Field theory of strings

International Nuclear Information System (INIS)

Ramond, P.

1987-01-01

We review the construction of the free equations of motion for open and closed strings in 26 dimensions, using the methods of the Florida Group. Differing from previous treatments, we argue that the constraint L 0 -anti L 0 =0 should not be imposed on all the fields of the closed string in the gauge invariant formalism; we show that it can be incorporated in the gauge invariant formalism at the price of being unable to extract the equations of motion from a Langrangian. We then describe our purely algebraic method to introduce interactions, which works equally well for open and closed strings. Quartic interactions are absent except in the Physical Gauge. Finally, we speculate on the role of the measure of the open string path functional. (orig.)

Gearbox Fault Features Extraction Using Vibration Measurements and Novel Adaptive Filtering Scheme

Directory of Open Access Journals (Sweden)

Ghalib R. Ibrahim

2012-01-01

Full Text Available Vibration signals measured from a gearbox are complex multicomponent signals, generated by tooth meshing, gear shaft rotation, gearbox resonance vibration signatures, and a substantial amount of noise. This paper presents a novel scheme for extracting gearbox fault features using adaptive filtering techniques for enhancing condition features, meshing frequency sidebands. A modified least mean square (LMS algorithm is examined and validated using only one accelerometer, instead of using two accelerometers in traditional arrangement, as the main signal and a desired signal is artificially generated from the measured shaft speed and gear meshing frequencies. The proposed scheme is applied to a signal simulated from gearbox frequencies with a numerous values of step size. Findings confirm that 10−5 step size invariably produces more accurate results and there has been a substantial improvement in signal clarity (better signal-to-noise ratio, which makes meshing frequency sidebands more discernible. The developed scheme is validated via a number of experiments carried out using two-stage helical gearbox for a healthy pair of gears and a pair suffering from a tooth breakage with severity fault 1 (25% tooth removal and fault 2 (50% tooth removal under loads (0%, and 80% of the total load. The experimental results show remarkable improvements and enhance gear condition features. This paper illustrates that the new approach offers a more effective way to detect early faults.

String theory in four dimensions

CERN Document Server

1988-01-01

``String Theory in Four Dimensions'' contains a representative collection of papers dealing with various aspects of string phenomenology, including compactifications on smooth manifolds and more general conformal field theories. Together with the lucid introduction by M. Dine, this material gives the reader a good working knowledge of our present ideas for connecting string theory to nature.

One testing method of dynamic linearity of an accelerometer

Directory of Open Access Journals (Sweden)

Lei Jing-Yu

2015-01-01

Full Text Available To effectively test dynamic linearity of an accelerometer over a wide rang of 104 g to about 20 × 104g, one published patent technology is first experimentally verified and analysed, and its deficient is presented, then based on stress wave propagation theory on the thin long bar, the relation between the strain signal and the corresponding acceleration signal is obtained, one special link of two coaxial projectile is developed. These two coaxial metal cylinders (inner cylinder and circular tube are used as projectiles, to prevent their mutual slip inside the gun barrel during movement, the one end of two projectiles is always fastened by small screws. Ti6-AL4-V bar with diameter of 30 mm is used to propagate loading stress pulse. The resultant compression wave can be measured by the strain gauges on the bar, and a half –sine strain pulse is obtained. The measuring accelerometer is attached on the other end of the bar by a vacuum clamp. In this clamp, the accelerometer only bear compression wave, the reflected tension pulse make the accelerometer off the bar. Using this system, dynamic linearity measurement of accelerometer can be easily tested in wider range of acceleration values. And a really measuring results are presented.

A microelectromechanical accelerometer fabricated using printed circuit processing techniques

Science.gov (United States)

Rogers, J. E.; Ramadoss, R.; Ozmun, P. M.; Dean, R. N.

2008-01-01

A microelectromechanical systems (MEMS) capacitive-type accelerometer fabricated using printed circuit processing techniques is presented. A Kapton polymide film is used as the structural layer for fabricating the MEMS accelerometer. The accelerometer proof mass along with four suspension beams is defined in the Kapton polyimide film. The proof mass is suspended above a Teflon substrate using a spacer. The deflection of the proof mass is detected using a pair of capacitive sensing electrodes. The top electrode of the accelerometer is defined on the top surface of the Kapton film. The bottom electrode is defined in the metallization on the Teflon substrate. The initial gap height is determined by the distance between the bottom electrode and the Kapton film. For an applied external acceleration (normal to the proof mass), the proof mass deflects toward or away from the fixed bottom electrode due to inertial force. This deflection causes either a decrease or increase in the air-gap height thereby either increasing or decreasing the capacitance between the top and the bottom electrodes. An example PCB MEMS accelerometer with a square proof mass of membrane area 6.4 mm × 6.4 mm is reported. The measured resonant frequency is 375 Hz and the Q-factor in air is 0.52.

A microelectromechanical accelerometer fabricated using printed circuit processing techniques

International Nuclear Information System (INIS)

Rogers, J E; Ramadoss, R; Ozmun, P M; Dean, R N

2008-01-01

A microelectromechanical systems (MEMS) capacitive-type accelerometer fabricated using printed circuit processing techniques is presented. A Kapton polymide film is used as the structural layer for fabricating the MEMS accelerometer. The accelerometer proof mass along with four suspension beams is defined in the Kapton polyimide film. The proof mass is suspended above a Teflon substrate using a spacer. The deflection of the proof mass is detected using a pair of capacitive sensing electrodes. The top electrode of the accelerometer is defined on the top surface of the Kapton film. The bottom electrode is defined in the metallization on the Teflon substrate. The initial gap height is determined by the distance between the bottom electrode and the Kapton film. For an applied external acceleration (normal to the proof mass), the proof mass deflects toward or away from the fixed bottom electrode due to inertial force. This deflection causes either a decrease or increase in the air-gap height thereby either increasing or decreasing the capacitance between the top and the bottom electrodes. An example PCB MEMS accelerometer with a square proof mass of membrane area 6.4 mm × 6.4 mm is reported. The measured resonant frequency is 375 Hz and the Q-factor in air is 0.52

One-loop masses of open-string scalar fields in string theory

International Nuclear Information System (INIS)

Kitazawa, Noriaki

2008-01-01

In phenomenological models with D-branes, there are in general open-string massless scalar fields, in addition to closed-string massless moduli fields corresponding to the compactification. It is interesting to focus on the fate of such scalar fields in models with broken supersymmetry, because no symmetry forbids their masses. The one-loop effect may give non-zero masses to them, and in some cases mass squared may become negative, which means the radiative gauge symmetry breaking. In this article we investigate and propose a simple method for calculating the one-loop corrections using the boundary state formalism. There are two categories of massless open-string scalar fields. One consists the gauge potential fields corresponding to compactified directions, which can be understood as scalar fields in uncompactified space-time (related with Wilson line degrees of freedom). The other consists 'gauge potential fields' corresponding to transverse directions of D-brane, which emerge as scalar fields in D-brane world-volume (related with brane moduli fields). The D-brane boundary states with constant backgrounds of these scalar fields are constructed, and one-loop scalar masses are calculated in the closed string picture. Explicit calculations are given in the following four concrete models: one D25-brane with a circle compactification in bosonic string theory, one D9-brane with a circle compactification in superstring theory, D3-branes at a supersymmetric C 3 /Z 3 orbifold singularity, and a model of brane supersymmetry breaking with D3-branes and anti-D7-branes at a supersymmetric C 3 /Z 3 orbifold singularity. We show that the sign of the mass squared has a strong correlation with the sign of the related open-string one-loop vacuum amplitude.

Interacting bosonic strings in subcritical dimensions

International Nuclear Information System (INIS)

Hwang, S.; Marnelius, R.

1988-01-01

Interaction theory for relativistic bosonic string in spacetime dimensions below the critical value 26 is formulated using BRST techniques with an extra scalar field. One-loop zero-point amplitudes for closed strings are modular invariant. For a free scalar field, vertex operators are constructed leading to, e.g., the old dual N-tachyon tree amplitudes in D < 26. The N-tachyon one-loop expressions contain closed string poles for open strings, and are modular invariant for closed strings. However, the threshold cuts are wrong in D < 25. Only for D=25 to the considered vertex operators lead to consistency. (orig.)

Micro string resonators as temperature sensors

DEFF Research Database (Denmark)

Larsen, T.; Schmid, S.; Boisen, A.

2013-01-01

The resonance frequency of strings is highly sensitive to temperature. In this work we have investigated the applicability of micro string resonators as temperature sensors. The resonance frequency of strings is a function of the tensile stress which is coupled to temperature by the thermal...... to the low thermal mass of the strings. A temperature resolution of 2.5×10-4 °C has been achieved with silicon nitride strings. The theoretical limit for the temperature resolution of 8×10-8 °C has not been reached yet and requires further improvement of the sensor....

A primer on string theory

CERN Document Server

Schomerus, Volker

2017-01-01

Since its conception in the 1960s, string theory has been hailed as one of the most promising routes we have to unify quantum mechanics and general relativity. This book provides a concise introduction to string theory explaining central concepts, mathematical tools and covering recent developments in physics including compactifications and gauge/string dualities. With string theory being a multidisciplinary field interfacing with high energy physics, mathematics and quantum field theory, this book is ideal for both students with no previous knowledge of the field and scholars from other disciplines who are looking for an introduction to basic concepts.

Splitting strings on integrable backgrounds

Energy Technology Data Exchange (ETDEWEB)

Vicedo, Benoit

2011-05-15

We use integrability to construct the general classical splitting string solution on R x S{sup 3}. Namely, given any incoming string solution satisfying a necessary self-intersection property at some given instant in time, we use the integrability of the worldsheet {sigma}-model to construct the pair of outgoing strings resulting from a split. The solution for each outgoing string is expressed recursively through a sequence of dressing transformations, the parameters of which are determined by the solutions to Birkhoff factorization problems in an appropriate real form of the loop group of SL{sub 2}(C). (orig.)

T-Duality Group for Open String Theory

OpenAIRE

Kajiura, Hiroshige

2001-01-01

We study T-duality for open strings on tori $\\T^d$. The general boundary conditions for the open strings are constructed, and it is shown that T-duality group, which preserves the mass spectrum of closed strings, preserves also the mass spectrum of the open strings. The open strings are transformed to those with different boundary conditions by T-duality. We also discuss the T-duality for D-brane mass spectrum, and show that the D-branes and the open strings with both ends on them are transfo...

Integrated hydraulic booster/tool string technology for unfreezing of stuck downhole strings in horizontal wells

Science.gov (United States)

Tian, Q. Z.

2017-12-01

It is common to use a jarring tool to unfreeze stuck downhole string. However, in a horizontal well, influenced by the friction caused by the deviated section, jarring effect is poor; on the other hand, the forcing point can be located in the horizontal section by a hydraulic booster and the friction can be reduced, but it is time-consuming and easy to break downhole string using a large-tonnage and constant pull force. A hydraulic booster - jar tool string has been developed for unfreezing operation in horizontal wells. The technical solution involves three elements: a two-stage parallel spring cylinder structure for increasing the energy storage capacity of spring accelerators; multiple groups of spring accelerators connected in series to increase the working stroke; a hydraulic booster intensifying jarring force. The integrated unfreezing tool string based on these three elements can effectively overcome the friction caused by a deviated borehole, and thus unfreeze a stuck string with the interaction of the hydraulic booster and the mechanical jar which form an alternatively dynamic load. Experimental results show that the jarring performance parameters of the hydraulic booster-jar unfreezing tool string for the horizontal wells are in accordance with original design requirements. Then field technical parameters were developed based on numerical simulation and experimental data. Field application shows that the hydraulic booster-jar unfreezing tool string is effective to free stuck downhole tools in a horizontal well, and it reduces hook load by 80% and lessens the requirement of workover equipment. This provides a new technology to unfreeze stuck downhole string in a horizontal well.

Introduction to field theory of strings

International Nuclear Information System (INIS)

Kikkawa, K.

1987-01-01

The field theory of bosonic string is reviewed. First, theory is treated in a light-cone gauge. After a brief survey of the first quantized theory of free string, the second quantization is discussed. All possible interactions of strings are introduced based on a smoothness condition of work sheets swept out by strings. Perturbation theory is developed. Finally a possible way to the manifest covariant formalism is discussed

Vibration Based Diagnosis for Planetary Gearboxes Using an Analytical Model

Directory of Open Access Journals (Sweden)

Liu Hong

2016-01-01

Full Text Available The application of conventional vibration based diagnostic techniques to planetary gearboxes is a challenge because of the complexity of frequency components in the measured spectrum, which is the result of relative motions between the rotary planets and the fixed accelerometer. In practice, since the fault signatures are usually contaminated by noises and vibrations from other mechanical components of gearboxes, the diagnostic efficacy may further deteriorate. Thus, it is essential to develop a novel vibration based scheme to diagnose gear failures for planetary gearboxes. Following a brief literature review, the paper begins with the introduction of an analytical model of planetary gear-sets developed by the authors in previous works, which can predict the distinct behaviors of fault introduced sidebands. This analytical model is easy to implement because the only prerequisite information is the basic geometry of the planetary gear-set. Afterwards, an automated diagnostic scheme is proposed to cope with the challenges associated with the characteristic configuration of planetary gearboxes. The proposed vibration based scheme integrates the analytical model, a denoising algorithm, and frequency domain indicators into one synergistic system for the detection and identification of damaged gear teeth in planetary gearboxes. Its performance is validated with the dynamic simulations and the experimental data from a planetary gearbox test rig.

Covariant N-string amplitude

International Nuclear Information System (INIS)

Di Vecchia, P.; Sciuto, S.; Nakayama, R.; Petersen, J.L.; Sidenius, J.R.

1986-11-01

The BRST-invariant N-Reggeon vertex (for the bosonic string) previously given by us in the operator formulation is considered in more detail. In particular we present a direct derivation from the string path integral. Several crucial symmetry properties found a posteriori before, become a priori clearer in this formulation. A number of delicate points related to zero modes, cut off procedures and normal ordering prescriptions are treated in some detail. The old technique of letting the string field acquire a small dimension ε/2 → 0 + is found especially elegant. (orig.)

A disintegrating cosmic string

International Nuclear Information System (INIS)

Griffiths, J B; Docherty, P

2002-01-01

We present a simple sandwich gravitational wave of the Robinson-Trautman family. This is interpreted as representing a shock wave with a spherical wavefront which propagates into a Minkowski background minus a wedge (i.e. the background contains a cosmic string). The deficit angle (the tension) of the string decreases through the gravitational wave, which then ceases. This leaves an expanding spherical region of Minkowski space behind it. The decay of the cosmic string over a finite interval of retarded time may be considered to generate the gravitational wave. (letter to the editor)

Strings for quantumchromodynamics

International Nuclear Information System (INIS)

Schomerus, V.

2007-04-01

During the last decade, intriguing dualities between gauge and string theory have been found and explored. they provide a novel window on strongly couplde gauge physics, including QCD-like models. Based on a short historical review of modern string theory, we explain how so-called AdS/CFT dualities emerged at the end of the 1990s. Some of their concrete implications and remarkable recent progress are then illustrated for the simplest example, namely the multicolor limit of N=4 SYM theory in four dimensions. We end with a few comments on existing extensions to more realistic models and applications, in particular to the sQGP. This text is meant as a non-technical introduction to gauge/string dualities for (particle) physicists. (orig.)

Strings for quantumchromodynamics

Energy Technology Data Exchange (ETDEWEB)

Schomerus, V.

2007-04-15

During the last decade, intriguing dualities between gauge and string theory have been found and explored. they provide a novel window on strongly couplde gauge physics, including QCD-like models. Based on a short historical review of modern string theory, we explain how so-called AdS/CFT dualities emerged at the end of the 1990s. Some of their concrete implications and remarkable recent progress are then illustrated for the simplest example, namely the multicolor limit of N=4 SYM theory in four dimensions. We end with a few comments on existing extensions to more realistic models and applications, in particular to the sQGP. This text is meant as a non-technical introduction to gauge/string dualities for (particle) physicists. (orig.)

Remarks on entanglement entropy in string theory

Science.gov (United States)

Balasubramanian, Vijay; Parrikar, Onkar

2018-03-01

Entanglement entropy for spatial subregions is difficult to define in string theory because of the extended nature of strings. Here we propose a definition for bosonic open strings using the framework of string field theory. The key difference (compared to ordinary quantum field theory) is that the subregion is chosen inside a Cauchy surface in the "space of open string configurations." We first present a simple calculation of this entanglement entropy in free light-cone string field theory, ignoring subtleties related to the factorization of the Hilbert space. We reproduce the answer expected from an effective field theory point of view, namely a sum over the one-loop entanglement entropies corresponding to all the particle-excitations of the string, and further show that the full string theory regulates ultraviolet divergences in the entanglement entropy. We then revisit the question of factorization of the Hilbert space by analyzing the covariant phase-space associated with a subregion in Witten's covariant string field theory. We show that the pure gauge (i.e., BRST exact) modes in the string field become dynamical at the entanglement cut. Thus, a proper definition of the entropy must involve an extended Hilbert space, with new stringy edge modes localized at the entanglement cut.

Is the string theory doomed?

International Nuclear Information System (INIS)

Le Meur, H.; Daninos, F.; Bachas, C.

2007-01-01

Since its beginning, in the sixties, the string theory has succeeded in overcoming a lot of theoretical difficulties but now the complete absence of experimental validation entertains doubts about its ability to represent the real world and questions its hegemony in today's theoretical physics. Other space-time theories like the twistors, or the non-commutative geometry, or the loop quantum gravity, or the causal dynamics triangulation might begin receiving more attention. Despite all that, the string theory can be given credit for 4 achievements. First, the string theory has provided a consistent quantum description of gravity. Secondly, the string theory has built a theoretical frame that has allowed the unification of the 4 basic interactions. Thirdly, the string theory applied to astrophysics issues has demonstrated that the evaporation of a black hole does not necessarily lead to a loss of information which comforts the universality of the conservation of the quantity of information in any system and as a consequence put a fatal blow to the so-called paradox observed in black holes. Fourthly, the string theory has given a new and original meaning on the true nature of space-time. (A.C.)

Introduction to string theory

CERN Multimedia

CERN. Geneva. Audiovisual Unit

2002-01-01

I will present a simple and non-technical overview of string theory, aimed for non-experts who like to get some idea what string theory is about. Besides introductory material, I intend to cover also some of the more recent developments.

Unification of string dualities

International Nuclear Information System (INIS)

Sen, A.

1997-01-01

We argue that all conjectured dualities involving various string, M- and F-theory compactifications can be 'derived' from the conjectured duality between type I and SO(32) heterotic string theory, T-dualities and the definition of M-and F-theories. (orig.)

Hosotani model in closed string theory

International Nuclear Information System (INIS)

Shiraishi, Kiyoshi.

1988-11-01

Hosotani mechanism in the closed string theory with current algebra symmetry is described by the (old covariant) operator method. We compare the gauge symmetry breaking mechanism in a string theory which has SU(2) symmetry with the one in an equivalent compactified closed string theory. We also investigate the difference between Hosotani mechanism and Higgs mechanism in closed string theories by calculation of a fourpoint amplitude of 'Higgs' bosons at tree level. (author)

String breaking with Wilson loops?

CERN Document Server

Kratochvila, S; Kratochvila, Slavo; Forcrand, Philippe de

2003-01-01

A convincing, uncontroversial observation of string breaking, when the static potential is extracted from Wilson loops only, is still missing. This failure can be understood if the overlap of the Wilson loop with the broken string is exponentially small. In that case, the broken string ground state will only be seen if the Wilson loop is long enough. Our preliminary results show string breaking in the context of the 3d SU(2) adjoint static potential, using the L\\"uscher-Weisz exponential variance reduction approach. As a by-product, we measure the fundamental SU(2) static potential with improved accuracy and see clear deviations from Casimir scaling.

Architectures and representations for string transduction

NARCIS (Netherlands)

Chrupala, Grzegorz

2015-01-01

String transduction problems are ubiquitous in natural language processing: they include transliteration, grapheme-to-phoneme conversion, text normalization and translation. String transduction can be reduced to the simpler problems of sequence labeling by expressing the target string as a sequence

Introduction to strings and superstrings

International Nuclear Information System (INIS)

Traubenberg, M.R. de.

1988-01-01

We discuss the main features on the formulation of string theory that, in a primitive level, describe the hadronic phenomenon of duality. We also study an extension of the models of closed and strings with spin. Then, by using supersymmetry, it is formulated the theory of superstrings and heterotic strings with the aim of unify the fundamental interactions and matter. (M.W.O.) [pt

Singleton strings

International Nuclear Information System (INIS)

Engquist, J.; Sundell, P.; Tamassia, L.

2007-01-01

The group theoretical structure underlying physics in anti de Sitter (AdS) spacetime is intrinsically different with respect to the flat case, due to the presence of special ultra-short representations, named singletons, that do not admit a flat space limit. The purpose of this collaboration is to exploit this feature in the study of string and brane dynamics in AdS spacetime, in particular while trying to establish a connection between String Theory in AdS backgrounds (in the tensionless limit) and Higher-Spin Gauge Theory. (orig.)

Aspects of some dualities in string theory

Science.gov (United States)

Kim, Bom Soo

AdS/CFT correspondence in string theory has changed landscape of the theoretical physics. Through this celebrated duality between gravity theory and field theory, one can investigate analytically strongly coupled gauge theories such as Quantum Chromodynamics (QCD) in terms of weakly coupled string theory such as supergravity theory and vice versa. In the first part of this thesis we used this duality to construct a new type of nonlocal field theory, called Puff Field Theory, in terms of D3 branes in type IIB string theory with a geometric twist. In addition to the strong-weak duality of AdS/CFT, there also exists a weak-weak duality, called Twistor String Theory. Twistor technique is successfully used to calculate the SYM scattering amplitude in an elegant fashion. Yet, the progress in the string theory side was hindered by a non-unitary conformal gravity. We extend the Twistor string theory by introducing mass terms, in the second part of the thesis. A chiral mass term is identified as a vacuum expectation value of a conformal supergravity field and is tied with the breaking of the conformal symmetry of gravity. As a prime candidate for a quantum theory of gravity, string theory revealed many promising successes such as counting the number of microstates in supersymmetric Black Holes thermodynamics and resolution of timelike and null singularities, to name a few. Yet, the fundamental string and M-theroy formulations are not yet available. Various string theories without gravity, such as Non-Commutative Open String (NCOS) and Open Membrane (OM) theories, are very nice playground to investigate the fundamental structure of string and M-theory without the complication of gravity. In the last part of the thesis, simpler Non-Relativistic String Theories are constructed and investigated. One important motivation for those theories is related to the connection between Non-Relativistic String Theories and Non-critical String Theories through the bosonization of betagamma

String cosmology modern string theory concepts from the cosmic structure

CERN Document Server

2009-01-01

The field of string cosmology has matured considerably over the past few years, attracting many new adherents to this multidisciplinary Field. This book fills a critical gap by bringing together strains of current research into one single volume. The resulting collection of selected articles presents the latest, ongoing results from renowned experts currently working in the field. This offers the possibility for practitioners to become conversant with many different aspects of string cosmology

Semilocal and electroweak strings

NARCIS (Netherlands)

Achucarro, A; Vachaspati, T

We review a class of non-topological defects in the standard electroweak model, and their implications. Starting with the semilocal string, which provides a counterexample to many well-known properties of topological vortices, we discuss electroweak strings and their stability with and without

Vibration analysis method for detection of abnormal movement of material in a rotary dissolver

International Nuclear Information System (INIS)

Smith, C.M.; Fry, D.N.

1978-11-01

Vibration signals generated by the movement of simulated nuclear fuel material through a three-stage, continuous, rotary dissolver were frequency analyzed to determine whether these signals contained characteristic signal patterns that would identify each of five phases of operation in the dissolver and, thus, would indicate the proper movement of material through the dissolver. This characterization of the signals is the first step in the development of a system for monitoring the flow of material through a dissolver to be developed for reprocessing spent nuclear fuel. Vibration signals from accelerometers mounted on the dissolver roller supports were analyzed in a bandwidth from 0 to 10 kHz. The analysis established that (1) all five phases of dissolver operation can be characterized by vibration signatures; (2) four of the five phases of operation can be readily and directly identified by a characteristic vibration signature during continuous, prototypic operation; (3) the transfer of material from the inlet to the dissolution stage can be indirectly monitored by one of the other four vibration signatures (the mixing signature) during prototypic operation; (4) a simulated blockage between the dissolution and exit stages can be detected by changes in one or more characteristic vibration signatures; and (5) a simulated blockage of the exit chute cannot be detected

Twenty-five questions for string theorists

Energy Technology Data Exchange (ETDEWEB)

Binetruy, Pierre; /Orsay, LPT; Kane, G.L.; /Michigan U., MCTP; Lykken, Joseph D.; /Fermilab; Nelson, Brent D.; /Pennsylvania U.

2005-09-01

In an effort to promote communication between the formal and phenomenological branches of the high-energy theory community, we provide a description of some important issues in supersymmetric and string phenomenology. We describe each within the context of string constructions, illustrating them with specific examples where applicable. Each topic culminates in a set of questions that we believe are amenable to direct consideration by string theorists, and whose answers we think could help connect string theory and phenomenology.

Nonrelativistic closed string theory

International Nuclear Information System (INIS)

Gomis, Jaume; Ooguri, Hirosi

2001-01-01

We construct a Galilean invariant nongravitational closed string theory whose excitations satisfy a nonrelativistic dispersion relation. This theory can be obtained by taking a consistent low energy limit of any of the conventional string theories, including the heterotic string. We give a finite first order worldsheet Hamiltonian for this theory and show that this string theory has a sensible perturbative expansion, interesting high energy behavior of scattering amplitudes and a Hagedorn transition of the thermal ensemble. The strong coupling duals of the Galilean superstring theories are considered and are shown to be described by an eleven-dimensional Galilean invariant theory of light membrane fluctuations. A new class of Galilean invariant nongravitational theories of light-brane excitations are obtained. We exhibit dual formulations of the strong coupling limits of these Galilean invariant theories and show that they exhibit many of the conventional dualities of M theory in a nonrelativistic setting

Non-linear σ-models and string theories

International Nuclear Information System (INIS)

Sen, A.

1986-10-01

The connection between σ-models and string theories is discussed, as well as how the σ-models can be used as tools to prove various results in string theories. Closed bosonic string theory in the light cone gauge is very briefly introduced. Then, closed bosonic string theory in the presence of massless background fields is discussed. The light cone gauge is used, and it is shown that in order to obtain a Lorentz invariant theory, the string theory in the presence of background fields must be described by a two-dimensional conformally invariant theory. The resulting constraints on the background fields are found to be the equations of motion of the string theory. The analysis is extended to the case of the heterotic string theory and the superstring theory in the presence of the massless background fields. It is then shown how to use these results to obtain nontrivial solutions to the string field equations. Another application of these results is shown, namely to prove that the effective cosmological constant after compactification vanishes as a consequence of the classical equations of motion of the string theory. 34 refs

Boundary terms in Nambu-Goto string action

OpenAIRE

Hadasz, Leszek; Wegrzyn, Pawel

1994-01-01

We investigate classical strings defined by the Nambu-Goto action with the boundary term added. We demonstrate that the latter term has a significant bearing on the string dynamics. It is confirmed that new action terms that depend on higher order derivatives of string coordinates cannot be considered as continuous perturbations from the starting string functional. In the case the boundary term reduces to the Gauss-Bonnet term, a stability analysis is performed on the rotating rigid string so...

Charting the Landscape of Supercritical String Theory

International Nuclear Information System (INIS)

Hellerman, Simeon; Swanson, Ian

2007-01-01

Special solutions of string theory in supercritical dimensions can interpolate in time between theories with different numbers of spacetime dimensions and different amounts of world sheet supersymmetry. These solutions connect supercritical string theories to the more familiar string duality web in ten dimensions and provide a precise link between supersymmetric and purely bosonic string theories. Dimension quenching and c duality appear to be natural concepts in string theory, giving rise to large networks of interconnected theories

E(lementary) Strings in Six-Dimensional Heterotic F-Theory

OpenAIRE

Choi, Kang-Sin; Rey, Soo-Jong

2017-01-01

Using E-strings, we can analyze not only six-dimensional superconformal field theories but also probe vacua of non-perturabative heterotic string. We study strings made of D3-branes wrapped on various two-cycles in the global F-theory setup. We claim that E-strings are elementary in the sense that various combinations of E-strings can form M-strings as well as heterotic strings and new kind of strings, called G-strings. Using them, we show that emissions and combinations of heterotic small in...

A novel piezoresistive polymer nanocomposite MEMS accelerometer

International Nuclear Information System (INIS)

Seena, V; Hari, K; Prajakta, S; Ramgopal Rao, V; Pratap, Rudra

2017-01-01

A novel polymer MEMS (micro electro mechanical systems) accelerometer with photo-patternable polymer nanocomposite as a piezoresistor is presented in this work. Polymer MEMS Accelerometer with beam thicknesses of 3.3 µ m and embedded nanocomposite piezoresistive layer having a gauge factor of 90 were fabricated. The photosensitive nanocomposite samples were prepared and characterized for analyzing the mechanical and electrical properties and thereby ensuring proper process parameters for incorporating the piezoresistive layer into the polymer MEMS accelerometer. The microfabrication process flow and unit processes followed are extremely low cost with process temperatures below 100 °C. This also opens up a new possibility for easy integration of such polymer MEMS with CMOS (complementary metal oxide semiconductor) devices and circuits. The fabricated devices were characterized using laser Doppler vibrometer (LDV) and the devices exhibited a resonant frequency of 10.8 kHz and a response sensitivity of 280 nm g −1 at resonance. The main focus of this paper is on the SU-8/CB nanocomposite piezoresistive MEMS accelerometer technology development which covers the material and the fabrication aspects of these devices. CoventorWare FEA analysis performed using the extracted material properties from the experimental characterization which are in close agreement to performance parameters of the fabricated devices is also discussed. The simulated piezoresistive polymer MEMS devices showed an acceleration sensitivity of 126 nm g −1 and 82 ppm of Δ R / R per 1 g of acceleration. (paper)

Differential geometry in string models

International Nuclear Information System (INIS)

Alvarez, O.

1986-01-01

In this article the author reviews the differential geometric approach to the quantization of strings. A seminal paper demonstrates the connection between the trace anomaly and the critical dimension. The role played by the Faddeev-Popov ghosts has been instrumental in much of the subsequent work on the quantization of strings. This paper discusses the differential geometry of two dimensional surfaces and its importance in the quantization of strings. The path integral quantization approach to strings will be carefully analyzed to determine the correct effective measure for string theories. The choice of measure for the path integral is determined by differential geometric considerations. Once the measure is determined, the manifest diffeomorphism invariance of the theory will have to be broken by using the Faddeev-Popov ansatz. The gauge fixed theory is studied in detail with emphasis on the role of conformal and gravitational anomalies. In the analysis, the path integral formulation of the gauge fixed theory requires summing over all the distinct complex structures on the manifold

Hollow micro string based calorimeter device

DEFF Research Database (Denmark)

2014-01-01

positions so as to form a free released double clamped string in-between said two longitudinally distanced positions said micro-channel string comprising a microfluidic channel having a closed cross section and extending in the longitudinal direction of the hollow string, acoustical means adapted...

Experimenting with string musical instruments

Science.gov (United States)

LoPresto, Michael C.

2012-03-01

What follows are several investigations involving string musical instruments developed for and used in a Science of Sound & Light course. The experiments make use of a guitar, orchestral string instruments and data collection and graphing software. They are designed to provide students with concrete examples of how mathematical formulae, when used in physics, represent reality that can actually be observed, in this case, the operation of string musical instruments.

Triaxial Accelerometer Error Coefficients Identification with a Novel Artificial Fish Swarm Algorithm

Directory of Open Access Journals (Sweden)

Yanbin Gao

2015-01-01

Full Text Available Artificial fish swarm algorithm (AFSA is one of the state-of-the-art swarm intelligence techniques, which is widely utilized for optimization purposes. Triaxial accelerometer error coefficients are relatively unstable with the environmental disturbances and aging of the instrument. Therefore, identifying triaxial accelerometer error coefficients accurately and being with lower costs are of great importance to improve the overall performance of triaxial accelerometer-based strapdown inertial navigation system (SINS. In this study, a novel artificial fish swarm algorithm (NAFSA that eliminated the demerits (lack of using artificial fishes’ previous experiences, lack of existing balance between exploration and exploitation, and high computational cost of AFSA is introduced at first. In NAFSA, functional behaviors and overall procedure of AFSA have been improved with some parameters variations. Second, a hybrid accelerometer error coefficients identification algorithm has been proposed based on NAFSA and Monte Carlo simulation (MCS approaches. This combination leads to maximum utilization of the involved approaches for triaxial accelerometer error coefficients identification. Furthermore, the NAFSA-identified coefficients are testified with 24-position verification experiment and triaxial accelerometer-based SINS navigation experiment. The priorities of MCS-NAFSA are compared with that of conventional calibration method and optimal AFSA. Finally, both experiments results demonstrate high efficiency of MCS-NAFSA on triaxial accelerometer error coefficients identification.

Final Report: "Strings 2014"

Energy Technology Data Exchange (ETDEWEB)

Witten, Edward

2015-10-21

The Strings 2014 meeting was held at Princeton University June 23-27, 2014, co-sponsored by Princeton University and the Institute for Advanced Study. The goal of the meeting was to provide a stimulating and up-to-date overview of research in string theory and its relations to other areas of physics and mathematics, ranging from geometry to quantum field theory, condensed matter physics, and more. This brief report lists committee members and speakers but contains no scientific information. Note that the talks at Strings 2014 were videotaped and are available on the conference website: http://physics.princeton.edustrings2014/Talk_titles.shtml.

Vibration characteristics of tubes in a heat exchanger

International Nuclear Information System (INIS)

Simonis; Steininger, D.

1985-01-01

Circumferential tube cracking has occurred in the once-through steam generators used in nuclear power plants. Analyses of failed tubes indicate that a fatigue process induced by tube vibration could cause the leaks. To investigate the vibration amplitude of tube spans during reactor operation, twenty-three tube spans were instrumented with accelerometers and strain gages at Three Mile Island Unit 2. To aid in the interpretation of the operational vibration measurements, tests were performed, in air, to determine the predominant resonant frequencies and mode shapes of selected tubes. By adapting modal analysis techniques, the two predominant response frequencies were determined for 100 randomly selected tube spans and the 23 instrumented tube spans; plus, the predominant mode shape was determined for five tube spans bounded by the tube sheet and the fifteenth support plate and one tube span bounded by the ninth and tenth support plate. The average value for the first and second predominant response frequency was 65 Hz and 170 Hz, respectively. The predominant frequencies for the individual tube spans are distributed randomly with no spatial orientation. The first predominant mode shape for the six tube spans tested corresponded to a classical beam with elastic supports. The equivalent stiffness of the elastic supports depend upon the tube span tested

Implementation of a robust hybrid rotary-translational vibration energy harvester for autonomous self-powered acceleration measurement

Science.gov (United States)

Payne, Owen R.; Vandewater, Luke A.; Ung, Chandarin; Moss, Scott D.

2015-04-01

In this paper, a self-powered wireless sensor node utilising ambient vibrations for power is described. The device consists of a vibration energy harvester, power management system, microcontroller, accelerometer, RF transmitter/receiver and external LED indicators. The vibration energy harvester is adapted from a previously reported hybrid rotary-translational device and uses a pair of copper coil transducers to convert the mechanical energy of a magnetic sphere into usable electricity. The device requires less than 0.8 mW of power to operate continuously in its present setup (with LED indicators off) while measuring acceleration at a sample rate of 200 Hz, with the power source providing 39.7 mW of power from 500 mg excitations at 5.5 Hz. When usable input energy is removed, the device will continue to transmit data for more than 5 minutes.

String Formatting Considered Harmful for Novice Programmers

Science.gov (United States)

Hughes, Michael C.; Jadud, Matthew C.; Rodrigo, Ma. Mercedes T.

2010-01-01

In Java, "System.out.printf" and "String.format" consume a specialised kind of string commonly known as a format string. In our study of first-year students at the Ateneo de Manila University, we discovered that format strings present a substantial challenge for novice programmers. Focusing on their first laboratory we found…

Strings and fundamental physics

International Nuclear Information System (INIS)

Baumgartl, Marco; Brunner, Ilka; Haack, Michael

2012-01-01

The basic idea, simple and revolutionary at the same time, to replace the concept of a point particle with a one-dimensional string, has opened up a whole new field of research. Even today, four decades later, its multifaceted consequences are still not fully conceivable. Up to now string theory has offered a new way to view particles as different excitations of the same fundamental object. It has celebrated success in discovering the graviton in its spectrum, and it has naturally led scientists to posit space-times with more than four dimensions - which in turn has triggered numerous interesting developments in fields as varied as condensed matter physics and pure mathematics. This book collects pedagogical lectures by leading experts in string theory, introducing the non-specialist reader to some of the newest developments in the field. The carefully selected topics are at the cutting edge of research in string theory and include new developments in topological strings, AdS/CFT dualities, as well as newly emerging subfields such as doubled field theory and holography in the hydrodynamic regime. The contributions to this book have been selected and arranged in such a way as to form a self-contained, graduate level textbook. (orig.)

Strings and fundamental physics

Energy Technology Data Exchange (ETDEWEB)

Baumgartl, Marco [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Brunner, Ilka; Haack, Michael (eds.) [Muenchen Univ. (Germany). Fakultaet fuer Physik

2012-07-01

The basic idea, simple and revolutionary at the same time, to replace the concept of a point particle with a one-dimensional string, has opened up a whole new field of research. Even today, four decades later, its multifaceted consequences are still not fully conceivable. Up to now string theory has offered a new way to view particles as different excitations of the same fundamental object. It has celebrated success in discovering the graviton in its spectrum, and it has naturally led scientists to posit space-times with more than four dimensions - which in turn has triggered numerous interesting developments in fields as varied as condensed matter physics and pure mathematics. This book collects pedagogical lectures by leading experts in string theory, introducing the non-specialist reader to some of the newest developments in the field. The carefully selected topics are at the cutting edge of research in string theory and include new developments in topological strings, AdS/CFT dualities, as well as newly emerging subfields such as doubled field theory and holography in the hydrodynamic regime. The contributions to this book have been selected and arranged in such a way as to form a self-contained, graduate level textbook. (orig.)

Spin chains and string theory.

Science.gov (United States)

Kruczenski, Martin

2004-10-15

Recently, an important test of the anti de Sitter/conformal field theory correspondence has been done using rotating strings with two angular momenta. We show that such a test can be described more generally as the agreement between two actions: one a low energy description of a spin chain appearing in the field theory side, and the other a limit of the string action in AdS5xS5. This gives a map between the mean value of the spin in the boundary theory and the position of the string in the bulk, and shows how a string action can emerge from a gauge theory in the large-N limit.

Using the GOCE star trackers for validating the calibration of its accelerometers

Science.gov (United States)

Visser, P. N. A. M.

2017-12-01

A method for validating the calibration parameters of the six accelerometers on board the Gravity field and steady-state Ocean Circulation Explorer (GOCE) from star tracker observations that was originally tested by an end-to-end simulation, has been updated and applied to real data from GOCE. It is shown that the method provides estimates of scale factors for all three axes of the six GOCE accelerometers that are consistent at a level significantly better than 0.01 compared to the a priori calibrated value of 1. In addition, relative accelerometer biases and drift terms were estimated consistent with values obtained by precise orbit determination, where the first GOCE accelerometer served as reference. The calibration results clearly reveal the different behavior of the sensitive and less-sensitive accelerometer axes.

Development of a High-Sensitivity Wireless Accelerometer for Structural Health Monitoring.

Science.gov (United States)

Zhu, Li; Fu, Yuguang; Chow, Raymond; Spencer, Billie F; Park, Jong Woong; Mechitov, Kirill

2018-01-17

Structural health monitoring (SHM) is playing an increasingly important role in ensuring the safety of structures. A shift of SHM research away from traditional wired methods toward the use of wireless smart sensors (WSS) has been motivated by the attractive features of wireless smart sensor networks (WSSN). The progress achieved in Micro Electro-Mechanical System (MEMS) technologies and wireless data transmission, has extended the effectiveness and range of applicability of WSSNs. One of the most common sensors employed in SHM strategies is the accelerometer; however, most accelerometers in WSS nodes have inadequate resolution for measurement of the typical accelerations found in many SHM applications. In this study, a high-resolution and low-noise tri-axial digital MEMS accelerometer is incorporated in a next-generation WSS platform, the Xnode. In addition to meeting the acceleration sensing demands of large-scale civil infrastructure applications, this new WSS node provides powerful hardware and a robust software framework to enable edge computing that can deliver actionable information. Hardware and software integration challenges are presented, and the associate resolutions are discussed. The performance of the wireless accelerometer is demonstrated experimentally through comparison with high-sensitivity wired accelerometers. This new high-sensitivity wireless accelerometer will extend the use of WSSN to a broader class of SHM applications.