NASA Astrophysics Data System (ADS)
Beeby, Stephen P.; Wang, Leran; Zhu, Dibin; Weddell, Alex S.; Merrett, Geoff V.; Stark, Bernard; Szarka, Gyorgy; Al-Hashimi, Bashir M.
2013-07-01
The design of vibration energy harvesters (VEHs) is highly dependent upon the characteristics of the environmental vibrations present in the intended application. VEHs can be linear resonant systems tuned to particular frequencies or nonlinear systems with either bistable operation or a Duffing-type response. This paper provides detailed vibration data from a range of applications, which has been made freely available for download through the Energy Harvesting Network’s online data repository. In particular, this research shows that simulation is essential in designing and selecting the most suitable vibration energy harvester for particular applications. This is illustrated through C-based simulations of different types of VEHs, using real vibration data from a diesel ferry engine, a combined heat and power pump, a petrol car engine and a helicopter. The analysis shows that a bistable energy harvester only has a higher output power than a linear or Duffing-type nonlinear energy harvester with the same Q-factor when it is subjected to white noise vibration. The analysis also indicates that piezoelectric transduction mechanisms are more suitable for bistable energy harvesters than electromagnetic transduction. Furthermore, the linear energy harvester has a higher output power compared to the Duffing-type nonlinear energy harvester with the same Q factor in most cases. The Duffing-type nonlinear energy harvester can generate more power than the linear energy harvester only when it is excited at vibrations with multiple peaks and the frequencies of these peaks are within its bandwidth. Through these new observations, this paper illustrates the importance of simulation in the design of energy harvesting systems, with particular emphasis on the need to incorporate real vibration data.
Linear and nonlinear energy harvesters for powering pacemakers from heart beat vibrations
NASA Astrophysics Data System (ADS)
Karami, M. Amin; Inman, Daniel J.
2011-03-01
Linear and nonlinear piezoelectric devices are introduced to continuously recharge the batteries of the pacemakers by converting the vibrations from the heartbeats to electrical energy. The power requirement of the pacemakers is very low. At the same time, after about 10 years from the original implantation of the pacemakers, patients have to go through another surgical operation just to replace the batteries of their pacemakers. We investigate using vibration energy harvesters to significantly increase the battery life of the pace makers. The major source of vibrations in chest area is due to heartbeats. Linear low frequency and nonlinear mono-stable and bi-stable energy harvesters are designed according to especial signature of heart vibrations. The proposed energy harvesters are robust to variations of heart beat frequency and can meet the power requirement of the pacemakers.
Piezoelectric-based power sources for harvesting energy from platforms with low-frequency vibration
NASA Astrophysics Data System (ADS)
Rastegar, J.; Pereira, C.; Nguyen, H.-L.
2006-03-01
This paper presents a new class of highly efficient piezoelectric based energy harvesting power sources for mounting on platforms that vibrate at very low frequencies as compared to the frequencies at which energy can be efficiently harvested using piezoelectric elements . These energy harvesting power sources have a very simple design and do not require accurate tuning for each application to match the frequency of the platform vibration. The developed method of harvesting mechanical energy and converting it to electrical energy overcomes problems that are usually encountered with harvesting energy from low frequency vibration of various platforms such as ships and other platforms with similar vibratory (rocking or translational) motions. Omnitek Partners has designed several such energy harvesting power sources and is in the process of constructing prototypes for testing. The developed designs are modular and can be used to construct power sources for various power requirements. The amount of mechanical energy available for harvesting is obviously dependent on the frequency and amplitude of vibration of the platform, and the size and mass of the power source.
Powering pacemakers from heartbeat vibrations using linear and nonlinear energy harvesters
NASA Astrophysics Data System (ADS)
Amin Karami, M.; Inman, Daniel J.
2012-01-01
Linear and nonlinear piezoelectric devices are introduced to continuously recharge the batteries of the pacemakers by converting the vibrations from the heartbeats to electrical energy. The power requirement of a pacemaker is very low. However, after few years, patients require another surgical operation just to replace their pacemaker battery. Linear low frequency and nonlinear mono-stable and bi-stable energy harvesters are designed according to the especial signature of heart vibrations. The proposed energy harvesters are robust to variation of heart rate and can meet the power requirement of pacemakers.
Electromagnetic vibration energy harvesting with high power density using a magnet array
NASA Astrophysics Data System (ADS)
Tang, Xiudong; Lin, Teng; Zuo, Lei
2012-04-01
Electromagnetic vibration energy harvesters have been widely used to convert the vibration energy into electricity. However, one of the main challenges of using electromagnetic vibration energy harvesters is that they are usually in very large size with low power density. In this paper, a new type of electromagnetic vibration energy harvester with remarkably high power density is developed. By putting the strong rare-earth magnets in alternating directions and using high-magnetic-conductive casing, magnetic flux density up to 0.9T are obtained. This configuration also has a small current loop with less electrical reluctance, which further increases the high power density when the coil is designed to follow the current loop. The prototype, the size of which is 142x140x86 mm3, can provided up to 727Ns/m damping coefficient, which means 428 kNs/m4 damping density when it is shunt with 70? external resistive load which is set to the same as the internal resistor of the harvester to achieve maximum power. The corresponding power density is 725 ?W/cm3 at 15HZ harmonic force excitation of 2.54mm peak-to-peak amplitude. When shot-circuited, 1091Ns/m damping coefficient and 638 kNs/m4 damping density is achieved. The effectiveness of this novel vibration energy harvester is shown both by FEA and experiments. The eddy current damper is also discussed in this paper for comparison. The proposed configuration of the magnet array can also be extended for both micro-scale and large-scale energy harvesting applications, such as vibration energy harvesting from tall buildings, long bridges and railways.
A Vibration-Based MEMS Piezoelectric Energy Harvester and Power Conditioning Circuit
Yu, Hua; Zhou, Jielin; Deng, Licheng; Wen, Zhiyu
2014-01-01
This paper presents a micro-electro-mechanical system (MEMS) piezoelectric power generator array for vibration energy harvesting. A complete design flow of the vibration-based energy harvester using the finite element method (FEM) is proposed. The modal analysis is selected to calculate the resonant frequency of the harvester, and harmonic analysis is performed to investigate the influence of the geometric parameters on the output voltage. Based on simulation results, a MEMS Pb(Zr,Ti)O3 (PZT) cantilever array with an integrated large Si proof mass is designed and fabricated to improve output voltage and power. Test results show that the fabricated generator, with five cantilever beams (with unit dimensions of about 3 2.4 0.05 mm3) and an individual integrated Si mass dimension of about 8 12.4 0.5 mm3, produces a output power of 66.75 ?W, or a power density of 5.19 ?Wmm?3g?2 with an optimal resistive load of 220 k? from 5 m/s2 vibration acceleration at its resonant frequency of 234.5 Hz. In view of high internal impedance characteristic of the PZT generator, an efficient autonomous power conditioning circuit, with the function of impedance matching, energy storage and voltage regulation, is then presented, finding that the efficiency of the energy storage is greatly improved and up to 64.95%. The proposed self-supplied energy generator with power conditioning circuit could provide a very promising complete power supply solution for wireless sensor node loads. PMID:24556670
A vibration-based MEMS piezoelectric energy harvester and power conditioning circuit.
Yu, Hua; Zhou, Jielin; Deng, Licheng; Wen, Zhiyu
2014-01-01
This paper presents a micro-electro-mechanical system (MEMS) piezoelectric power generator array for vibration energy harvesting. A complete design flow of the vibration-based energy harvester using the finite element method (FEM) is proposed. The modal analysis is selected to calculate the resonant frequency of the harvester, and harmonic analysis is performed to investigate the influence of the geometric parameters on the output voltage. Based on simulation results, a MEMS Pb(Zr,Ti)O3 (PZT) cantilever array with an integrated large Si proof mass is designed and fabricated to improve output voltage and power. Test results show that the fabricated generator, with five cantilever beams (with unit dimensions of about 3 × 2.4 × 0.05 mm3) and an individual integrated Si mass dimension of about 8 × 12.4 × 0.5 mm3, produces a output power of 66.75 μW, or a power density of 5.19 μW∙mm-3∙g-2 with an optimal resistive load of 220 kΩ from 5 m/s2 vibration acceleration at its resonant frequency of 234.5 Hz. In view of high internal impedance characteristic of the PZT generator, an efficient autonomous power conditioning circuit, with the function of impedance matching, energy storage and voltage regulation, is then presented, finding that the efficiency of the energy storage is greatly improved and up to 64.95%. The proposed self-supplied energy generator with power conditioning circuit could provide a very promising complete power supply solution for wireless sensor node loads. PMID:24556670
NASA Astrophysics Data System (ADS)
Du, Sijun; Jia, Yu; Seshia, Ashwin
2015-12-01
A resonant vibration energy harvester typically comprises of a clamped anchor and a vibrating shuttle with a proof mass. Piezoelectric materials are embedded in locations of high strain in order to transduce mechanical deformation into electric charge. Conventional design for piezoelectric vibration energy harvesters (PVEH) usually utilizes piezoelectric material and metal electrode layers covering the entire surface area of the cantilever with no consideration provided to examining the trade-off involved with respect to maximizing output power. This paper reports on the theory and experimental verification underpinning optimization of the active electrode area of a cantilevered PVEH in order to maximize output power. The analytical formulation utilizes Euler-Bernoulli beam theory to model the mechanical response of the cantilever. The expression for output power is reduced to a fifth order polynomial expression as a function of the electrode area. The maximum output power corresponds to the case when 44% area of the cantilever is covered by electrode metal. Experimental results are also provided to verify the theory.
Self-suspended vibration-driven energy harvesting chip for power density maximization
NASA Astrophysics Data System (ADS)
Murillo, Gonzalo; Agustí, Jordi; Abadal, Gabriel
2015-11-01
This work introduces a new concept to integrate energy-harvesting devices with the aim of improving their throughput, mainly in terms of scavenged energy density and frequency tunability. This concept, named energy harvester in package (EHiP), is focused on the heterogeneous integration of a MEMS die, dedicated to scavenging energy, with an auxiliary chip, which can include the control and power management circuitry, sensors and RF transmission capabilities. The main advantages are that the whole die can be used as an inertial mass and the chip area usage is optimized. Based on this concept, in this paper we describe the development and characterization of a MEMS die fully dedicated to harvesting mechanical energy from ambient vibrations through an electrostatic transduction. A test PCB has been fabricated to perform the assembly that allows measurement of the resonance motion of the whole system at 289 Hz. An estimated maximum generated power of around 11 μW has been obtained for an input vibration acceleration of ˜10 m s-2 when the energy harvester operates in a constant-charge cycle for the best-case scenario. Therefore, a maximum scavenged power density of 0.85 mW cm-3 is theoretically expected for the assembled system. These results demonstrate that the generated power density of any vibration-based energy harvester can be significantly increased by applying the EHiP concept, which could become an industrial standard for manufacturing this kind of system, independently of the transduction type, fabrication technology or application.
NASA Astrophysics Data System (ADS)
Truong, Binh Duc; Phu Le, Cuong; Halvorsen, Einar
2015-12-01
This paper presents experiments on how to approach the physical limits on power from vibration energy harvesting under displacement-constrained operation. A MEMS electrostatic vibration energy harvester with voltage-control of the system stiffness is used for this purpose. The power saturation problem, when the proof mass displacement reaches maximum amplitude for sufficient acceleration amplitude, is shifted to higher accelerations by use of load optimization and tunable electromechanical coupling k2. Measurement results show that harvested power can be made to follow the optimal velocity-damped generator also for a range of accelerations that implies displacement constraints. Comparing to the saturated power, the power increases 1.5 times with the optimal load and an electromechanical coupling k2=8.7%. This value is 2.3 times for a higher coupling k2=17.9%. The obtained system effectiveness is beyond 60% under the optimization. This work also shows a first demonstration of reaching optimal power in the intermediate acceleration-range between the two extremes of maximum efficiency and maximum power transfer.
NASA Astrophysics Data System (ADS)
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.
Multi-modal vibration based MEMS energy harvesters for ultra-low power wireless functional nodes
NASA Astrophysics Data System (ADS)
Iannacci, J.; Gottardi, M.; Serra, E.; Di Criscienzo, R.; Borrielli, A.; Bonaldi, M.
2013-05-01
The aim of this contribution is to report and discuss a preliminary study and rough optimization of a novel concept of MEMS device for vibration energy harvesting, based on a multi-modal dynamic behavior. The circular-shaped device features Four-Leaf Clover-like (FLC) double spring-mass cascaded systems, kept constrained to the surrounding frame by means of four straight beams. The combination of flexural bending behavior of the slender beams plus deformable parts of the petals enable to populate the desired vibration frequency range with a number of resonant modes, and improve the energy conversion capability of the micro-transducer. The harvester device, conceived for piezoelectric mechanical into electric energy conversion, is intended to sense environmental vibrations and, thereby, its geometry is optimized to have a large concentration of resonant modes in a frequency range below 5-10 kHz. The results of FEM (Finite Element Method) based analysis performed in ANSYSTM Workbench are reported, both concerning modal and harmonic response, providing important indications related to the device geometry optimization. The analysis reported in this work is limited to the sole mechanical modeling of the proposed MEMS harvester device concept. Future developments of the study will encompass the inclusion of piezoelectric conversion in the FEM simulations, in order to have indications of the actual power levels achievable with the proposed harvester concept. Furthermore, the results of the FEM studies here discussed, will be validated against experimental data, as soon as the MEMS resonator specimens, currently under fabrication, are ready for testing.
NASA Astrophysics Data System (ADS)
Uluşan, H.; Gharehbaghi, K.; Zorlu, Ö.; Muhtaroğlu, A.; Külah, H.
2015-12-01
This study presents a novel hybrid system that combines the power generated simultaneously by a vibration-based Electromagnetic (EM) harvester and a UHF band RF harvester. The novel hybrid scavenger interface uses a power management circuit in 180 nm CMOS technology to step-up and to regulate the combined output. At the first stage of the system, the RF harvester generates positive DC output with a 7-stage threshold compensated rectifier, while the EM harvester generates negative DC output with a self-powered AC/DC negative doubler circuit. At the second stage, the generated voltages are serially added, stepped-up with an on-chip charge pump circuit, and regulated to a typical battery voltage of 3 V. Test results indicate that the hybrid operation enables generation of 9 μW at 3 V output for a wide range of input stimulations, which could not be attained with either harvesting mode by itself. Moreover the hybrid system behaves as a typical battery, and keeps the output voltage stable at 3 V up to 18 μW of output power. The presented system is the first battery-like harvester to our knowledge that generates energy from two independent sources and regulates the output to a stable DC voltage.
Adaptive vibration energy harvesting
NASA Astrophysics Data System (ADS)
Behrens, Sam; Ward, John; Davidson, Josh
2007-04-01
By scavenging energy from their local environment, portable electronic devices such as mobile phones, radios and wireless sensors can achieve greater run-times with potentially lower weight. Vibration energy harvesting is one such approach where energy from parasitic vibrations can be converted into electrical energy, through the use of piezoelectric and electromagnetic transducers. Parasitic vibrations come from a range of sources such as wind, seismic forces and traffic. Existing approaches to vibration energy harvesting typically utilise a rectifier circuit, which is tuned to the resonant frequency of the harvesting structure and the dominant frequency of vibration. We have developed a novel approach to vibration energy harvesting, including adaption to non-periodic vibrations so as to extract the maximum amount of vibration energy available. Experimental results of an experimental apparatus using off-the-shelf transducer (i.e. speaker coil) show mechanical vibration to electrical energy conversion efficiencies of 27 - 34%. However, simulations of a more electro-mechanical efficient and lightly damped transducer show conversion efficiencies in excess of 80%.
NASA Astrophysics Data System (ADS)
Iannacci, J.; Sordo, G.; Serra, E.; Kucera, M.; Schmid, U.
2015-05-01
In this work, we discuss the verification and preliminary experimental characterization of a MEMS-based vibration Energy Harvester (EH) design. The device, named Four-Leaf Clover (FLC), is based on a circular-shaped mechanical resonator with four petal-like mass-spring cascaded systems. This solution introduces several mechanical Degrees of Freedom (DOFs), and therefore enables multiple resonant modes and deformation shapes in the vibrations frequency range of interest. The target is to realize a wideband multi-modal EH-MEMS device, that overcomes the typical narrowband working characteristics of standard cantilevered EHs, by ensuring flexible and adaptable power source to ultra-low power electronics for integrated remote sensing nodes (e.g. Wireless Sensor Networks - WSNs) in the Internet of Things (IoT) scenario, aiming to self-powered and energy autonomous smart systems. Finite Element Method simulations of the FLC EH-MEMS show the presence of several resonant modes for vibrations up to 4-5 kHz, and level of converted power up to a few μW at resonance and in closed-loop conditions (i.e. with resistive load). On the other hand, the first experimental tests of FLC fabricated samples, conducted with a Laser Doppler Vibrometer (LDV), proved the presence of several resonant modes, and allowed to validate the accuracy of the FEM modeling method. Such a good accordance holds validity for what concerns the coupled field behavior of the FLC EH-MEMS, as well. Both measurements and simulations performed at 190 Hz (i.e. out of resonance) showed the generation of power in the range of nW (Root Mean Square - RMS values). Further steps of this work will include the experimental characterization in a full range of vibrations, aiming to prove the whole functionality of the FLC EH-MEMS proposed design concept.
Kim, Moonkeun; Lee, Sang-Kyun; Yang, Yil Suk; Jeong, Jaehwa; Min, Nam Ki; Kwon, Kwang-Ho
2013-12-01
We fabricated dual-beam cantilevers on the microelectromechanical system (MEMS) scale with an integrated Si proof mass. A Pb(Zr,Ti)O3 (PZT) cantilever was designed as a mechanical vibration energy-harvesting system for low power applications. The resonant frequency of the multilayer composition cantilevers were simulated using the finite element method (FEM) with parametric analysis carried out in the design process. According to simulations, the resonant frequency, voltage, and average power of a dual-beam cantilever was 69.1 Hz, 113.9 mV, and 0.303 microW, respectively, at optimal resistance and 0.5 g (gravitational acceleration, m/s2). Based on these data, we subsequently fabricated cantilever devices using dual-beam cantilevers. The harvested power density of the dual-beam cantilever compared favorably with the simulation. Experiments revealed the resonant frequency, voltage, and average power density to be 78.7 Hz, 118.5 mV, and 0.34 microW, respectively. The error between the measured and simulated results was about 10%. The maximum average power and power density of the fabricated dual-beam cantilever at 1 g were 0.803 microW and 1322.80 microW cm(-3), respectively. Furthermore, the possibility of a MEMS-scale power source for energy conversion experiments was also tested. PMID:24266167
Vibration shape effects on the power output in piezoelectric vibro-impact energy harvesters
NASA Astrophysics Data System (ADS)
Twiefel, Jens
2013-04-01
Vibro-Impcact harvesting devices are one concept to increase the bandwidth of resonant operated piezoelectric vibration generators. The fundamental setup is a piezoelectric bending element, where the deflection is limited by two stoppers. After starting the system in resonance operation the bandwidth increases towards higher frequencies as soon the deflection reach the stopper. If the stoppers are rigid, the frequency response gives constant amplitude for increasing frequencies, as long the system is treated as ideal one-DOF system with symmetric stoppers. In consequence, the bandwidth is theoretically unlimited large. However, such a system also has two major drawbacks, firstly the complicated startup mechanism and secondly the tendency to drop from the high constant branch in the frequency response on the much smaller linear branch if the system is disturbed. Nevertheless, the system has its application wherever the startup problem can be solved. Most modeling approaches utilize modal one-DOF models to describe the systems behavior and do not tread the higher harmonics of the beam. This work investigates the effects of the stoppers on the vibration shape of the piezoelectric beam, wherefore a finite element model is used. The used elements are one-dimensional two node elements based on the Timoshenko-beam theory. The finite element code is implemented in Matlab. The model is calculated utilizing time step integration for simulation, to reduce the computation time an auto-resonant calculation method is implemented. A control loop including positive feedback and saturation is used to create a self-excited system. Therefore, the system is always operated in resonance (on the backbone curve) and the frequency is a direct result of the computation. In this case tip velocity is used as feedback. This technique allows effective parametric studies. Investigated parameters include gap, excitation amplitude, tip mass as well as the stiffness of the stopper. The stress and strain distribution as well as the generated electrical power is analyzed with respect to the proper operation range.
Piezoelectric cantilevers optimization for vibration energy harvesting
NASA Astrophysics Data System (ADS)
Cao, Junyi; Zhou, Shengxi; Ren, Xiaolong; Cao, Binggang
2012-04-01
Vibration-based piezoelectric energy harvesters through the conversion of vibration energy to electrical energy has gained increasing attention over the past decade because of the reduced power requirements of small electronic components, especially in industrial condition monitoring applications where sensors may be embedded in machines. The structure parameters of cantilevered piezoelectric energy harvesters are of importance to maximize the output power in accordance with the characteristics of the ambient vibrations. Therefore, a piezoelectric cantilevers optimization method using finite element analysis and SPICE is proposed. This paper models piezoelectric cantilever using Hamilton principle and extracts the vibration modal parameters to establish the circuit model in SPICE. The numerical analysis is addressed to study the effect of parameters. Finally, the optimization analysis and experiment are carried out. The results verify that the optimized cantilevered piezoelectric energy harvesters can produce a 56V peak open-circuit voltage, and that the proposed method is suitable for optimization design of piezoelectric energy harvester.
Piezoelectric cantilevers optimization for vibration energy harvesting
NASA Astrophysics Data System (ADS)
Cao, Junyi; Zhou, Shengxi; Ren, Xiaolong; Cao, Binggang
2011-11-01
Vibration-based piezoelectric energy harvesters through the conversion of vibration energy to electrical energy has gained increasing attention over the past decade because of the reduced power requirements of small electronic components, especially in industrial condition monitoring applications where sensors may be embedded in machines. The structure parameters of cantilevered piezoelectric energy harvesters are of importance to maximize the output power in accordance with the characteristics of the ambient vibrations. Therefore, a piezoelectric cantilevers optimization method using finite element analysis and SPICE is proposed. This paper models piezoelectric cantilever using Hamilton principle and extracts the vibration modal parameters to establish the circuit model in SPICE. The numerical analysis is addressed to study the effect of parameters. Finally, the optimization analysis and experiment are carried out. The results verify that the optimized cantilevered piezoelectric energy harvesters can produce a 56V peak open-circuit voltage, and that the proposed method is suitable for optimization design of piezoelectric energy harvester.
Vibration energy harvester optimization using artificial intelligence
NASA Astrophysics Data System (ADS)
Hadas, Z.; Ondrusek, C.; Kurfurst, J.; Singule, V.
2011-06-01
This paper deals with an optimization study of a vibration energy harvester. This harvester can be used as autonomous source of electrical energy for remote or wireless applications, which are placed in environment excited by ambient mechanical vibrations. The ambient energy of vibrations is usually on very low level but the harvester can be used as alternative source of energy for electronic devices with an expected low level of power consumption of several mW. The optimized design of the vibration energy harvester was based on previous development and the sensitivity of harvester design was improved for effective harvesting from mechanical vibrations in aeronautic applications. The vibration energy harvester is a mechatronic system which generates electrical energy from ambient vibrations due to precision tuning up generator parameters. The optimization study for maximization of harvested power or minimization of volume and weight are the main goals of our development. The optimization study of such complex device is complicated therefore artificial intelligence methods can be used for tuning up optimal harvester parameters.
NASA Astrophysics Data System (ADS)
Asanuma, H.; Hara, M.; Oguchi, H.; Kuwano, H.
2015-10-01
We investigated the dependence of output power, frequency band width, and resonance frequency on the initial air gap for electret-based out-of-plane vibration energy harvesters, both numerically and experimentally. In this investigation, the external acceleration and surface charge densities of the electret were held constant. The numerical investigation predicted the following results: (1) an optimum value exists in the initial air gap to maximize the output power; and (2) enhanced electrostatic forces with decreasing the initial air gap emphasize the soft spring effect, which widens the frequency band width and lowers the resonance frequency. The experimental results showed behaviour consistent with the numerical predictions. The maximum output power in experiment was 4.0??W at the optimum initial air gap of 0.43?mm when the external acceleration and the frequency were 4.9?m?s-2 and 102?Hz, respectively. With reducing the initial air gap to 0.28?mm, the frequency band width increased to 17?Hz, a 2.6-fold increase over the optimum initial air gap. The peak output power at the initial air gap of 0.28?mm was 2.7??W, when the external acceleration and frequency were 4.9?m?s-2 and 96?Hz, respectively.
Energy scavenging from environmental vibration.
Galchev, Tzeno; Apblett, Christopher Alan; Najafi, Khalil
2009-10-01
The goal of this project is to develop an efficient energy scavenger for converting ambient low-frequency vibrations into electrical power. In order to achieve this a novel inertial micro power generator architecture has been developed that utilizes the bi-stable motion of a mechanical mass to convert a broad range of low-frequency (< 30Hz), and large-deflection (>250 {micro}m) ambient vibrations into high-frequency electrical output energy. The generator incorporates a bi-stable mechanical structure to initiate high-frequency mechanical oscillations in an electromagnetic scavenger. This frequency up-conversion technique enhances the electromechanical coupling and increases the generated power. This architecture is called the Parametric Frequency Increased Generator (PFIG). Three generations of the device have been fabricated. It was first demonstrated using a larger bench-top prototype that had a functional volume of 3.7cm3. It generated a peak power of 558{micro}W and an average power of 39.5{micro}W at an input acceleration of 1g applied at 10 Hz. The performance of this device has still not been matched by any other reported work. It yielded the best power density and efficiency for any scavenger operating from low-frequency (<10Hz) vibrations. A second-generation device was then fabricated. It generated a peak power of 288{micro}W and an average power of 5.8{micro}W from an input acceleration of 9.8m/s{sup 2} at 10Hz. The device operates over a frequency range of 20Hz. The internal volume of the generator is 2.1cm{sup 3} (3.7cm{sup 3} including casing), half of a standard AA battery. Lastly, a piezoelectric version of the PFIG is currently being developed. This device clearly demonstrates one of the key features of the PFIG architecture, namely that it is suitable for MEMS integration, more so than resonant generators, by incorporating a brittle bulk piezoelectric ceramic. This is the first micro-scale piezoelectric generator capable of <10Hz operation. The fabricated device currently generates a peak power of 25.9{micro}W and an average power of 1.21{micro}W from an input acceleration of 9.8m/s{sup -} at 10Hz. The device operates over a frequency range of 23Hz. The internal volume of the generator is 1.2cm{sup 3}.
Wireless Inductive Power Device Suppresses Blade Vibrations
NASA Technical Reports Server (NTRS)
Morrison, Carlos R.; Provenza, Andrew J.; Choi, Benjamin B.; Bakhle, Milind A.; Min, James B.; Stefko, George L.; Duffy, Kirsten P.; Fougers, Alan J.
2011-01-01
Vibration in turbomachinery can cause blade failures and leads to the use of heavier, thicker blades that result in lower aerodynamic efficiency and increased noise. Metal and/or composite fatigue in the blades of jet engines has resulted in blade destruction and loss of lives. Techniques for suppressing low-frequency blade vibration, such as gtuned circuit resistive dissipation of vibratory energy, h or simply "passive damping," can require electronics incorporating coils of unwieldy dimensions and adding unwanted weight to the rotor. Other approaches, using vibration-dampening devices or damping material, could add undesirable weight to the blades or hub, making them less efficient. A wireless inductive power device (WIPD) was designed, fabricated, and developed for use in the NASA Glenn's "Dynamic Spin Rig" (DSR) facility. The DSR is used to simulate the functionality of turbomachinery. The relatively small and lightweight device [10 lb (approx.=4.5 kg)] replaces the existing venerable and bulky slip-ring. The goal is the eventual integration of this technology into actual turbomachinery such as jet engines or electric power generators, wherein the device will facilitate the suppression of potentially destructive vibrations in fan blades. This technology obviates slip rings, which require cooling and can prove unreliable or be problematic over time. The WIPD consists of two parts: a remote element, which is positioned on the rotor and provides up to 100 W of electrical power to thin, lightweight piezoelectric patches strategically placed on/in fan blades; and a stationary base unit that wirelessly communicates with the remote unit. The base unit supplies inductive power, and also acts as an input and output corridor for wireless measurement, and active control command to the remote unit. Efficient engine operation necessitates minimal disturbance to the gas flow across the turbine blades in any effort to moderate blade vibration. This innovation makes it possible to moderate vibration on or in turbomachinery blades by providing 100 W of wireless electrical power and actuation control to thin, lightweight vibration-suppressing piezoelectric patches (eight actuation and eight sensor patches in this prototype, for a total of 16 channels) positioned strategically on the surface of, or within, titanium fan blades, or embedded in composite fan blades. This approach moves significantly closer to the ultimate integration of "active" vibration suppression technology into jet engines and other turbomachinery devices such as turbine electrical generators used in the power industry. The novel feature of this device is in its utilization of wireless technology to simultaneously sense and actively control vibration in rotating or stationary turbomachinery blades using piezoelectric patches. In the past, wireless technology was used solely for sensing and diagnostics. This technology, however, will accomplish much more, in terms of simultaneously sensing, suppressing blade vibration, and making it possible for detailed study of vibration impact in turbomachinery blades.
Development of an aeroelastic vibration power harvester
NASA Astrophysics Data System (ADS)
Bryant, Matthew; Garcia, Ephrahim
2009-03-01
Aeroelastic vibration of structures represents a novel energy harvesting opportunity that may offer significant advantages over traditional wind power devices in many applications. Such a system could complement existing alternative energy sources by allowing for distributed power generation and placement in urban areas. The device configuration of a simple two degree aeroelastic system suitable for piezoelectric power harvesting is presented. The mechanical, electromechanical, and aerodynamic equations of motion governing the dynamics and electrical output of the system as a function of incident wind speed are derived. The response and current output of one design for a bench top scale harvester are simulated and presented. Finally, a strategy for expanding the operating envelope of the power harvester is proposed and discussed.
Vibration harvesting in traffic tunnels to power wireless sensor nodes
NASA Astrophysics Data System (ADS)
Wischke, M.; Masur, M.; Kröner, M.; Woias, P.
2011-08-01
Monitoring the traffic and the structural health of traffic tunnels requires numerous sensors. Powering these remote and partially embedded sensors from ambient energies will reduce maintenance costs, and improve the sensor network performance. This work reports on vibration levels detected in railway and road tunnels as a potential energy source for embedded sensors. The measurement results showed that the vibrations at any location in the road tunnel and at the wall in the railway tunnel are too small for useful vibration harvesting. In contrast, the railway sleeper features usable vibrations and sufficient mounting space. For this application site, a robust piezoelectric vibration harvester was designed and equipped with a power interface circuit. Within the field test, it is demonstrated that sufficient energy is harvested to supply a microcontroller with a radio frequency (RF) interface.
Intramolecular vibrational dephasing obeys a power law at intermediate times
Gruebele, M.
1998-01-01
Experimental intramolecular vibrational dephasing transients for several large organic molecules are reanalyzed. Fits to the experimental data, as well as full numerical quantum calculations with a factorized potential surface for all active degrees of freedom of fluorene indicate that power law decays, not exponentials, occur at intermediate times. The results support a proposal that power law decays describe vibrational dephasing dynamics in large molecules at intermediate times because of the local nature of energy flow. PMID:9600900
A vibration powered wireless mote on the Forth Road Bridge
NASA Astrophysics Data System (ADS)
Jia, Yu; Yan, Jize; Feng, Tao; Du, Sijun; Fidler, Paul; Soga, Kenichi; Middleton, Campbell; Seshia, Ashwin A.
2015-12-01
The conventional resonant-approaches to scavenge kinetic energy are typically confined to narrow and single-band frequencies. The vibration energy harvester device reported here combines both direct resonance and parametric resonance in order to enhance the power responsiveness towards more efficient harnessing of real-world ambient vibration. A packaged electromagnetic harvester designed to operate in both of these resonant regimes was tested in situ on the Forth Road Bridge. In the field-site, the harvester, with an operational volume of ∼126 cm3, was capable of recovering in excess of 1 mW average raw AC power from the traffic-induced vibrations in the lateral bracing structures underneath the bridge deck. The harvester was integrated off-board with a power conditioning circuit and a wireless mote. Duty- cycled wireless transmissions from the vibration-powered mote was successfully sustained by the recovered ambient energy. This limited duration field test provides the initial validation for realising vibration-powered wireless structural health monitoring systems in real world infrastructure, where the vibration profile is both broadband and intermittent.
Harvesting Vibrational Energy Using Material Work Functions
Varpula, Aapo; Laakso, Sampo J.; Havia, Tahvo; Kyynäräinen, Jukka; Prunnila, Mika
2014-01-01
Vibration energy harvesters scavenge energy from mechanical vibrations to energise low power electronic devices. In this work, we report on vibration energy harvesting scheme based on the charging phenomenon occurring naturally between two bodies with different work functions. Such work function energy harvester (WFEH) is similar to electrostatic energy harvester with the fundamental distinction that neither external power supplies nor electrets are needed. A theoretical model and description of different operation modes of WFEHs are presented. The WFEH concept is tested with macroscopic experiments, which agree well with the model. The feasibility of miniaturizing WFEHs is shown by simulating a realistic MEMS device. The WFEH can be operated as a charge pump that pushes charge and energy into an energy storage element. We show that such an operation mode is highly desirable for applications and that it can be realised with either a charge shuttle or with switches. The WFEH is shown to give equal or better output power in comparison to traditional electrostatic harvesters. Our findings indicate that WFEH has great potential in energy harvesting applications. PMID:25348004
Harvesting Vibrational Energy Using Material Work Functions
NASA Astrophysics Data System (ADS)
Varpula, Aapo; Laakso, Sampo J.; Havia, Tahvo; Kyynrinen, Jukka; Prunnila, Mika
2014-10-01
Vibration energy harvesters scavenge energy from mechanical vibrations to energise low power electronic devices. In this work, we report on vibration energy harvesting scheme based on the charging phenomenon occurring naturally between two bodies with different work functions. Such work function energy harvester (WFEH) is similar to electrostatic energy harvester with the fundamental distinction that neither external power supplies nor electrets are needed. A theoretical model and description of different operation modes of WFEHs are presented. The WFEH concept is tested with macroscopic experiments, which agree well with the model. The feasibility of miniaturizing WFEHs is shown by simulating a realistic MEMS device. The WFEH can be operated as a charge pump that pushes charge and energy into an energy storage element. We show that such an operation mode is highly desirable for applications and that it can be realised with either a charge shuttle or with switches. The WFEH is shown to give equal or better output power in comparison to traditional electrostatic harvesters. Our findings indicate that WFEH has great potential in energy harvesting applications.
Vibrational Power Flow Analysis of Rods and Beams
NASA Technical Reports Server (NTRS)
Wohlever, James Christopher; Bernhard, R. J.
1988-01-01
A new method to model vibrational power flow and predict the resulting energy density levels in uniform rods and beams is investigated. This method models the flow of vibrational power in a manner analogous to the flow of thermal power in a heat conduction problem. The classical displacement solutions for harmonically excited, hysteretically damped rods and beams are used to derive expressions for the vibrational power flow and energy density in the rod and beam. Under certain conditions, the power flow in these two structural elements will be shown to be proportional to the energy density gradient. Using the relationship between power flow and energy density, an energy balance on differential control volumes in the rod and beam leads to a Poisson's equation which models the energy density distribution in the rod and beam. Coupling the energy density and power flow solutions for rods and beams is also discussed. It is shown that the resonant behavior of finite structures complicates the coupling of solutions, especially when the excitations are single frequency inputs. Two coupling formulations are discussed, the first based on the receptance method, and the second on the travelling wave approach used in Statistical Energy Analysis. The receptance method is the more computationally intensive but is capable of analyzing single frequency excitation cases. The traveling wave approach gives a good approximation of the frequency average of energy density and power flow in coupled systems, and thus, is an efficient technique for use with broadband frequency excitation.
Vibrational power flow analysis of rods and beams. Thesis
NASA Technical Reports Server (NTRS)
Wohlever, James Christopher; Bernhard, R. J.
1988-01-01
A new method to model vibrational power flow and predict the resulting energy density levels in uniform rods and beams is investigated. This method models the flow of vibrational power in a manner analogous to the flow of thermal power in a heat conduction problem. The classical displacement solutions for harmonically excited, hysteretically damped rods and beams are used to derive expressions for the vibrational power flow and energy density in the rod and beam. Under certain conditions, the power flow in these two structural elements will be shown to be proportional to the energy density gradient. Using the relationship between power flow and energy density, an energy balance on differential control volumes in the rod and beam leads to a Poisson's equation which models the energy density distribution in the rod and beam. Coupling the energy density and power flow solutions for rods and beams is also discussed. It is shown that the resonant behavior of finite structures complicates the coupling of solutions, especially when the excitations are single frequency inputs. Two coupling formulations are discussed, the first based on the receptance method, and the second on the travelling wave approach used in Statistical Energy Analysis. The receptance method is the more computationally intensive but is capable of analyzing single frequency excitation cases. The traveling wave approach gives a good approximation of the frequency average of energy density and power flow in coupled systems, and thus, is an efficient technique for use with broadband frequency excitation.
Vibration energy harvesting: fabrication, miniaturisation and applications
NASA Astrophysics Data System (ADS)
Beeby, S. P.; Zhu, D.
2015-05-01
This paper reviews work at the University of Southampton and its spin-out company Perpetuum towards the use of vibration energy harvesting in real applications. Perpetuum have successfully demonstrated vibration-powered condition monitoring systems for rail and industrial applications. They have pursued applications were volume is not a particular constraint and therefore sufficient power can be harvested. Harvester reliability and longevity is a key requirement and this can be a challenging task in high shock environments. The University of Southampton has investigated the miniaturization of the technology. MEMS electromagnetic harvesters were found to be unsuitable although miniaturized devices fabricated using bulk components did perform well. Screen printed piezoelectric harvesters were also found to perform well and were ideally suited to a low profile application where device thickness was limited. Screen printing was not only used to deposit the active piezoelectric material but also an inertial mass ink based on tungsten. This enables the device to be printed entirely by screen printing providing a low-cost route to manufacture. Finally, details of a simulation tool that can take real world vibrations and estimate vibration energy harvester output was presented. This was used to simulate linear and nonlinear harvesters and in many applications with a characteristic resonant frequency the linear approach was found to be the optimum. Bistable nonlinear harvesters were found to work better with more random vibration sources.
Adaptive learning algorithms for vibration energy harvesting
NASA Astrophysics Data System (ADS)
Ward, John K.; Behrens, Sam
2008-06-01
By scavenging energy from their local environment, portable electronic devices such as MEMS devices, mobile phones, radios and wireless sensors can achieve greater run times with potentially lower weight. Vibration energy harvesting is one such approach where energy from parasitic vibrations can be converted into electrical energy through the use of piezoelectric and electromagnetic transducers. Parasitic vibrations come from a range of sources such as human movement, wind, seismic forces and traffic. Existing approaches to vibration energy harvesting typically utilize a rectifier circuit, which is tuned to the resonant frequency of the harvesting structure and the dominant frequency of vibration. We have developed a novel approach to vibration energy harvesting, including adaptation to non-periodic vibrations so as to extract the maximum amount of vibration energy available. Experimental results of an experimental apparatus using an off-the-shelf transducer (i.e. speaker coil) show mechanical vibration to electrical energy conversion efficiencies of 27-34%.
Vibrational excitation energies from vibrational coupled cluster response theory
NASA Astrophysics Data System (ADS)
Seidler, Peter; Christiansen, Ove
2007-05-01
Response theory in the context of vibrational coupled cluster (VCC) theory is introduced and used to obtain vibrational excitation energies. The relation to the vibrational configuration interaction (VCI) approach is described, and the increase in accuracy of VCC response energies relative to VCI energies is discussed theoretically in terms of a perturbational order expansion and demonstrated numerically. To illustrate the theory, a pilot implementation is used to obtain anharmonic vibrational frequencies for fundamental, first overtone and combination excitations of formaldehyde as well as for the fundamental transitions of ethylene.
Microelectromechanical power generator and vibration sensor
Roesler, Alexander W.; Christenson, Todd R.
2006-11-28
A microelectromechanical (MEM) apparatus is disclosed which can be used to generate electrical power in response to an external source of vibrations, or to sense the vibrations and generate an electrical output voltage in response thereto. The MEM apparatus utilizes a meandering electrical pickup located near a shuttle which holds a plurality of permanent magnets. Upon movement of the shuttle in response to vibrations coupled thereto, the permanent magnets move in a direction substantially parallel to the meandering electrical pickup, and this generates a voltage across the meandering electrical pickup. The MEM apparatus can be fabricated by LIGA or micromachining.
A MEMS vibration energy harvester for automotive applications
NASA Astrophysics Data System (ADS)
van Schaijk, R.; Elfrink, R.; Oudenhoven, J.; Pop, V.; Wang, Z.; Renaud, M.
2013-05-01
The objective of this work is to develop MEMS vibration energy harvesters for tire pressure monitoring systems (TPMS), they can be located on the rim or on the inner-liner of the car tire. Nowadays TPMS modules are powered by batteries with a limited lifetime. A large effort is ongoing to replace batteries with small and long lasting power sources like energy harvesters [1]. The operation principle of vibration harvesters is mechanical resonance of a seismic mass, where mechanical energy is converted into electrical energy. In general, vibration energy harvesters are of specific interest for machine environments where random noise or repetitive shock vibrations are present. In this work we present the results for MEMS based vibration energy harvesting for applying on the rim or inner-liner. The vibrations on the rim correspond to random noise. A vibration energy harvester can be described as an under damped mass-spring system acting like a mechanical band-pass filter, and will resonate at its natural frequency [2]. At 0.01 g2/Hz noise amplitude the average power can reach the level that is required to power a simple wireless sensor node, approximately 10 ?W [3]. The dominant vibrations on the inner-liner consist mainly of repetitive high amplitude shocks. With a shock, the seismic mass is displaced, after which the mass will "ring-down" at its natural resonance frequency. During the ring-down period, part of the mechanical energy is harvested. On the inner-liner of the tire repetitive (one per rotation) high amplitude (few hundred g) shocks occur. The harvester enables an average power of a few tens of ?W [4], sufficient to power a more sophisticated wireless sensor node that can measure additional tire-parameters besides pressure. In this work we characterized MEMS vibration energy harvesters for noise and shock excitation. We validated their potential for TPMS modules by measurements and simulation.
Feasibility of structural monitoring with vibration powered sensors
NASA Astrophysics Data System (ADS)
Elvin, Niell G.; Lajnef, Nizar; Elvin, Alex A.
2006-08-01
Wireless sensors and sensor networks are beginning to be used to monitor structures. In general, the longevity, and hence the efficacy, of these sensors are severely limited by their stored power. The ability to convert abundant ambient energy into electric power would eliminate the problem of drained electrical supply, and would allow indefinite monitoring. This paper focuses on vibration in civil engineering structures as a source of ambient energy; the key question is can sufficient energy be produced from vibrations? Earthquake, wind and traffic loads are used as realistic sources of vibration. The theoretical maximum energy levels that can be extracted from these dynamic loads are computed. The same dynamic loads are applied to a piezoelectric generator; the energy is measured experimentally and computed using a mathematical model. The collected energy levels are compared to the energy requirements of various electronic subsystems in a wireless sensor. For a 5 cm3 sensor node (the volume of a typical concrete stone), it is found that only extreme events such as earthquakes can provide sufficient energy to power wireless sensors consisting of modern electronic chips. The results show that the optimal generated electrical power increases approximately linearly with increasing sensor mass. With current technology, it would be possible to self-power a sensor node with a mass between 100 and 1000 g for a bridge under traffic load. Lowering the energy consumption of electronic components is an ongoing research effort. It is likely that, as electronics becomes more efficient in the future, it will be possible to power a wireless sensor node by harvesting vibrations from a volume generator smaller than 5 cm3.
Vibrational energy transfer in fluids
NASA Astrophysics Data System (ADS)
Miller, David W.; Adelman, Steven A.
A review of several of the available theories of vibrational energy transfer (VET) in the gas and liquid phases is presented. First the classical theory of gas phase VET mainly due to Landau and Teller, to Jackson and Mott and to Zener is developed in some detail. Next the Schwartz-Slawsky-Herzfeld theory, a framework for analysing VET data based on the classical theory, is outlined. Experimental tests of the classical theory and theoretical critiques of its assumptions are then described. Next a brief review of the modern ab-initio quantum approach to gas phase VET rates, taking as an example the work of Banks, Clary and Werner, is given. Theories of VET at elevated densities are then discussed. The isolated binary collision model is reviewed and a new molecular approach to the density, temperature and isotope dependences of vibrational energy relaxation rates, due to Adelman and co-workers, is outlined.
Vibration energy harvesting using the Halbach array
NASA Astrophysics Data System (ADS)
Zhu, Dibin; Beeby, Steve; Tudor, John; Harris, Nick
2012-07-01
This paper studies the feasibility of vibration energy harvesting using a Halbach array. A Halbach array is a specific arrangement of permanent magnets that concentrates the magnetic field on one side of the array while cancelling the field to almost zero on the other side. This arrangement can improve electromagnetic coupling in a limited space. The Halbach array offers an advantage over conventional layouts of magnets in terms of its concentrated magnetic field and low-profile structure, which helps improve the output power of electromagnetic energy harvesters while minimizing their size. Another benefit of the Halbach array is that due to the existence of an almost-zero magnetic field zone, electronic components can be placed close to the energy harvester without any chance of interference, which can potentially reduce the overall size of a self-powered device. The first reported example of a low-profile, planar electromagnetic vibration energy harvester utilizing a Halbach array was built and tested. Results were compared to ones for energy harvesters with conventional magnet layouts. By comparison, it is concluded that although energy harvesters with a Halbach array can have higher magnetic field density, a higher output power requires careful design in order to achieve the maximum magnetic flux gradient.
Nonlinear spring-less electromagnetic vibration energy harvesting system
NASA Astrophysics Data System (ADS)
Hadas, Z.; Ondrusek, C.
2015-11-01
This paper deals with a description and modelling of a spring-less electromagnetic vibration energy harvesting system. The presented unique electromagnetic vibration energy harvester consists of a nonlinear resonance mechanism, magnetic circuit with a coil and an electronic load. The mechanical vibrations excite the nonlinear resonance mechanism and the relative movement of the magnetic circuit against fixed coil induces voltage due to Faraday's Law. When the electronics is connected the current flows through the load and output power is harvested. There are several nonlinearities which affects operations of the presented electromagnetic energy harvesting system. The significant nonlinearity of the system is stiffness of the resonance mechanism and it causes extending of an operation bandwidth. The harvesting of electrical energy from mechanical vibrations provides electromagnetic damping feedbacks of the coil to moving magnetic circuit. The feedback depends on the current flow through the electronic load and coil. The using of modern power management circuit with optimal power point provides other nonlinear operation.
Vibration energy harvesting for unmanned aerial vehicles
NASA Astrophysics Data System (ADS)
Anton, Steven R.; Inman, Daniel J.
2008-03-01
Unmanned aerial vehicles (UAVs) are a critical component of many military operations. Over the last few decades, the evolution of UAVs has given rise to increasingly smaller aircraft. Along with the development of smaller UAVs, termed mini UAVs, has come issues involving the endurance of the aircraft. Endurance in mini UAVs is problematic because of the limited size of the fuel systems that can be incorporated into the aircraft. A large portion of the total mass of many electric powered mini UAVs, for example, is the rechargeable battery power source. Energy harvesting is an attractive technology for mini UAVs because it offers the potential to increase their endurance without adding significant mass or the need to increase the size of the fuel system. This paper investigates the possibility of harvesting vibration and solar energy in a mini UAV. Experimentation has been carried out on a remote controlled (RC) glider aircraft with a 1.8 m wing span. This aircraft was chosen to replicate the current electric mini UAVs used by the military today. The RC glider was modified to include two piezoelectric patches placed at the roots of the wings and a cantilevered piezoelectric beam installed in the fuselage to harvest energy from wing vibrations and rigid body motions of the aircraft, as well as two thin film photovoltaic panels attached to the top of the wings to harvest energy from sunlight. Flight testing has been performed and the power output of the piezoelectric and photovoltaic devices has been examined.
Evaluating vehicular-induced bridge vibrations for energy harvesting applications
NASA Astrophysics Data System (ADS)
Reichenbach, Matthew; Fasl, Jeremiah; Samaras, Vasilis A.; Wood, Sharon; Helwig, Todd; Lindenberg, Richard
2012-04-01
Highway bridges are vital links in the transportation network in the United States. Identifying possible safety problems in the approximately 600,000 bridges across the country is generally accomplished through labor-intensive, visual inspections. Ongoing research sponsored by NIST seeks to improve inspection practices by providing real-time, continuous monitoring technology for steel bridges. A wireless sensor network with a service life of ten years that is powered by an integrated energy harvester is targeted. In order to achieve the target ten-year life for the monitoring system, novel approaches to energy harvesting for use in recharging batteries are investigated. Three main sources of energy are evaluated: (a) vibrational energy, (b) solar energy, and (c) wind energy. Assessing the energy produced from vehicular-induced vibrations and converted through electromagnetic induction is the focus of this paper. The goal of the study is to process acceleration data and analyze the vibrational response of steel bridges to moving truck loads. Through spectral analysis and harvester modeling, the feasibility of vibration-based energy harvesting for longterm monitoring can be assessed. The effects of bridge conditions, ambient temperature, truck traffic patterns, and harvester position on the power content of the vibrations are investigated. With sensor nodes continually recharged, the proposed real-time monitoring system will operate off the power grid, thus reducing life cycle costs and enhancing inspection practices for state DOTs. This paper will present the results of estimating the vibration energy of a steel bridge in Texas.
Harvesting vibration energy using two modal vibrations of a folded piezoelectric device
NASA Astrophysics Data System (ADS)
Gong, Li Jiao; Pan, Qiao Sheng; Li, Wei; Yan, Gang Yi; Liu, Yong Bin; Feng, Zhi Hua
2015-07-01
This letter reports a piezoelectric vibration energy harvester that uses the local lateral resonant modes of a folded structure to widen the operation frequency band. In addition, energy conversion efficiency is improved. A prototype energy harvester was fabricated and tested. The output power achieved two power peaks: 0.43 mW at 97 Hz and 6.64 mW at 120.9 Hz. The output power remained above 20 ?W within the operation frequency band that ranged from 88 Hz to 177 Hz when the energy harvester was driven with a vibration of 0.7 g peak acceleration. The output power remained higher than half of one of the maximum power peaks (0.43 mW) between 95 Hz and 101 Hz. Meanwhile, it remained higher than half of the other maximum power peak (6.64 mW) between 120.5 Hz and 123.8 Hz.
Piezoelectric Power Requirements for Active Vibration Control
NASA Technical Reports Server (NTRS)
Brennan, Matthew C.; McGowan, Anna-Maria Rivas
1997-01-01
This paper presents a method for predicting the power consumption of piezoelectric actuators utilized for active vibration control. Analytical developments and experimental tests show that the maximum power required to control a structure using surface-bonded piezoelectric actuators is independent of the dynamics between the piezoelectric actuator and the host structure. The results demonstrate that for a perfectly-controlled system, the power consumption is a function of the quantity and type of piezoelectric actuators and the voltage and frequency of the control law output signal. Furthermore, as control effectiveness decreases, the power consumption of the piezoelectric actuators decreases. In addition, experimental results revealed a non-linear behavior in the material properties of piezoelectric actuators. The material non- linearity displayed a significant increase in capacitance with an increase in excitation voltage. Tests show that if the non-linearity of the capacitance was accounted for, a conservative estimate of the power can easily be determined.
Vibration energy harvesting from random force and motion excitations
NASA Astrophysics Data System (ADS)
Tang, Xiudong; Zuo, Lei
2012-07-01
A vibration energy harvester is typically composed of a spring-mass system with an electromagnetic or piezoelectric transducer connected in parallel with a spring. This configuration has been well studied and optimized for harmonic vibration sources. Recently, a dual-mass harvester, where two masses are connected in series by the energy transducer and a spring, has been proposed. The dual-mass vibration energy harvester is proved to be able to harvest more power and has a broader bandwidth than the single-mass configuration, when the parameters are optimized and the excitation is harmonic. In fact, some dual-mass vibration energy harvesters, such as regenerative vehicle suspensions and buildings with regenerative tuned mass dampers (TMDs), are subjected to random excitations. This paper is to investigate the dual-mass and single-mass vibration harvesters under random excitations using spectrum integration and the residue theorem. The output powers for these two types of vibration energy harvesters, when subjected to different random excitations, namely force, displacement, velocity and acceleration, are obtained analytically with closed-form expressions. It is also very interesting to find that the output power of the vibration energy harvesters under random excitations depends on only a few parameters in very simple and elegant forms. This paper also draws some important conclusions on regenerative vehicle suspensions and buildings with regenerative TMDs, which can be modeled as dual-mass vibration energy harvesters. It is found that, under white-noise random velocity excitation from road irregularity, the harvesting power from vehicle suspensions is proportional to the tire stiffness and road vertical excitation spectrum only. It is independent of the chassis mass, tire-wheel mass, suspension stiffness and damping coefficient. Under random wind force excitation, the power harvested from buildings with regenerative TMD will depends on the building mass only, not on the parameters of the TMD subsystem if the ratio of electrical and mechanical damping is constant.
Internal resonance for nonlinear vibration energy harvesting
NASA Astrophysics Data System (ADS)
Cao, D. X.; Leadenham, S.; Erturk, A.
2015-11-01
The transformation of waste vibration energy into low-power electricity has been heavily researched over the last decade to enable self-sustained wireless electronic components. Monostable and bistable nonlinear oscillators have been explored by several research groups in an effort to enhance the frequency bandwidth of operation. Linear two-degree-of-freedom (2-DOF) configurations as well as the combination of a nonlinear single-DOF harvester with a linear oscillator to constitute a nonlinear 2-DOF harvester have also been explored to develop broadband energy harvesters. In the present work, the concept of nonlinear internal resonance in a continuous frame structure is explored for broadband energy harvesting. The L-shaped beam-mass structure with quadratic nonlinearity was formerly studied in the nonlinear dynamics literature to demonstrate modal energy exchange and the saturation phenomenon when carefully tuned for two-to-one internal resonance. In the current effort, piezoelectric coupling and an electrical load are introduced, and electromechanical equations of the L-shaped energy harvester are employed to explore primary resonance behaviors around the first and the second linear natural frequencies for bandwidth enhancement. Simulations using approximate analytical frequency response equations as well as numerical solutions reveal significant bandwidth enhancement as compared to a typical linear 2-DOF counterpart. Vibration and voltage responses are explored, and the effects of various system parameters on the overall dynamics of the internal resonance-based energy harvesting system are reported.
Parametric energy conversion of thermoacoustic vibrations
NASA Astrophysics Data System (ADS)
Guthy, C.; Van Neste, C. W.; Mitra, S.; Bhattacharjee, S.; Thundat, T.
2012-05-01
We demonstrate a parametric energy conversion method of thermoacoustic (TA) vibrations into electrical oscillations of a LC circuit. The inductance modulation necessary to excite the parametric oscillations is achieved by varying the air gap between two halves of a ferrite E-core coil. As a proof-of-concept, the parametric converter was attached to a Sondhauss tube that converts the heat into acoustic vibrations. The maximum total acoustic power output of this thermoacoustic engine was 5.3 mW. A flexible metallic membrane capping the Sondhauss tube connected to the moving half E-core served as a mechanical oscillator. The resonance frequency of the membrane was matched with the operating frequency (130 Hz) of the Sondhauss tube for resonant energy extraction. We have characterized the power output of the complete system as a function of electrical load. The maximum electrical power of 2.3 mW produced by the system corresponds to an acoustic-to-electric conversion efficiency of 44%.
Efficiency of piezoelectric mechanical vibration energy harvesting
NASA Astrophysics Data System (ADS)
Kim, Miso; Dugundji, John; Wardle, Brian L.
2015-05-01
Harvesting efficiency of a piezoelectric vibration energy harvesting system is investigated to provide design guidelines for harvesting devices with optimal performance. Harvesting power efficiency (?), defined as the ratio of device output power (Pout) to mechanical input power (Pin), is an essential but unexplored metric for comparison of harvesters operating in different power-input environments. Power extracted from piezoelectric harvesters has been of primary interest and proper accounting of mechanical input power and efficiency metrics has not been considered. Here, we present a closed form solution for harvesting efficiency that allows device comparison and furthermore, efficiency-optimized versus power-optimized electrical loading conditions are compared along with a case study. A key finding is that optimal design parameters for efficiency are quite different than optima for output power (e.g., a single optimum versus dual optima at different frequencies), requiring multi-objective design. These new findings provide guidelines on system parameters that can be manipulated for optimized performance in different ambient source conditions.
Active vibration control using minimum actuation power
NASA Astrophysics Data System (ADS)
Chevva, Konda; Sun, Fanping; Blanc, Arthur; Mendoza, Jeff
2015-03-01
Minimum actuation power (MAP) is a novel active vibration control strategy whose theoretical framework is introduced. MAP is an optimal control strategy that minimizes the total input power into the structure by only monitoring and controlling the input power going through the control sources. Implementing MAP control without explicit knowledge about the magnitude of the primary excitation is achieved thanks to the key observation that the real part of the input power from the secondary actuator is zero when the total mechanical input power from the primary and secondary sources is minimum. Piezo-electric actuators provide a simple and robust way to estimate the mechanical input power by measuring the electrical power without additional error sensors. The theory of MAP is developed for a simply supported plate excited by a primary piezo-electric patch actuator and controlled by a secondary piezo-electric patch actuator. The MAP theory is also extended to multi-frequency primary excitation where the discrete frequencies are commensurate.
Vibration Monitoring of Power Distribution Poles
Clark Scott; Gail Heath; John Svoboda
2006-04-01
Some of the most visible and least monitored elements of our national security infrastructure are the poles and towers used for the distribution of our nation’s electrical power. Issues surrounding these elements within the United States include safety such as unauthorized climbing and access, vandalism such as nut/bolt removal or destructive small arms fire, and major vandalism such as the downing of power poles and towers by the cutting of the poles with a chainsaw or torches. The Idaho National Laboratory (INL) has an ongoing research program working to develop inexpensive and sensitive sensor platforms for the monitoring and characterization of damage to the power distribution infrastructure. This presentation covers the results from the instrumentation of a variety of power poles and wires with geophone assemblies and the recording of vibration data when power poles were subjected to a variety of stimuli. Initial results indicate that, for the majority of attacks against power poles, the resulting signal can be seen not only on the targeted pole but on sensors several poles away in the distribution network and a distributed sensor system can be used to monitor remote and critical structures.
Bilgen, Onur; Kenerson, John G; Akpinar-Elci, Muge; Hattery, Rebecca; Hanson, Lisbet M
2015-08-01
The World Health Organization has established recommendations for blood pressure measurement devices for use in low-resource venues, setting the "triple A" expectations of Accuracy, Affordability, and Availability. Because of issues related to training and assessment of proficiency, the pendulum has swung away from manual blood pressure devices and auscultatory techniques towards automatic oscillometric devices. As a result of power challenges in the developing world, there has also been a push towards semiautomatic devices that are not dependent on external power sources or batteries. Beyond solar solutions, disruptive technology related to solid-state vibrational energy harvesting may be the next iterative solution to attain the ultimate goal of a self-powered low-cost validated device that is simple to use and reliable. PMID:25913774
Broadband vibration energy harvesting using triboelectric mechanism
NASA Astrophysics Data System (ADS)
Dhakar, Lokesh; Tay, F. E. H.; Lee, Chengkuo
2015-03-01
This paper demonstrates an approach to vibration energy harvesting using contact electrification or triboelectric mechanism. The device uses a cantilever to realize the contact electrification process when subjected to external vibrations. The device utilizes stiffening in the cantilever beam introduced by contact between two triboelectric layers to broaden the bandwidth of the vibrational energy harvester. The operating bandwidth of the energy harvester is shown to increase from 4.4 Hz to 17.8 Hz at RMS output voltage level of 60mV. The device was also observed to demonstrate continuous improvement in bandwidth as the acceleration level increased.
Piezoelectric energy harvesting from hybrid vibrations
NASA Astrophysics Data System (ADS)
Yan, Zhimiao; Abdelkefi, Abdessattar; Hajj, Muhammad R.
2014-02-01
The concept of harvesting energy from ambient and galloping vibrations of a bluff body with a triangular cross-section geometry is investigated. A piezoelectric transducer is attached to the transverse degree of freedom of the body in order to convert these vibrations to electrical energy. A coupled nonlinear distributed-parameter model is developed that takes into consideration the galloping force and moment nonlinearities and the base excitation effects. The aerodynamic loads are modeled using the quasi-steady approximation. Linear analysis is performed to determine the effects of the electrical load resistance and wind speed on the global damping and frequency of the harvester as well as on the onset of instability. Then, nonlinear analysis is performed to investigate the impact of the base acceleration, wind speed, and electrical load resistance on the performance of the harvester and the associated nonlinear phenomena that take place. The results show that, depending on the interaction between the base and galloping excitations, and the considered values of the wind speed, base acceleration, and electrical load resistance, different nonlinear phenomena arise while others disappear. Short- and open-circuit configurations for different wind speeds and base accelerations are assessed. The results show that the maximum levels of harvested power are accompanied by a minimum transverse displacement when varying the electrical load resistance.
Chen, Jun; Zhu, Guang; Yang, Weiqing; Jing, Qingshen; Bai, Peng; Yang, Ya; Hou, Te-Chien; Wang, Zhong Lin
2013-11-13
A harmonic-resonator-based triboelectric nanogenerator (TENG) is presented as a sustainable power source and an active vibration sensor. It can effectively respond to vibration frequencies ranging from 2 to 200 Hz with a considerably wide working bandwidth of 13.4 Hz. This work not only presents a new principle in the field of vibration energy harvesting but also greatly expands the applicability of TENGs. PMID:23999798
Transient power flow between coupled beams in longitudinal vibrations
NASA Astrophysics Data System (ADS)
Lednik, D.; Pinnington, R. J.
Transient power flow between two coupled beams was investigated in the framework of a research project aimed at developing an approximate method of predicting the vibrational response of equipment aboard Ariane launchers to acoustic and structural shock inputs during the flight phases. Particular emphasis was placed on longitudinal-longitudinal coupling. An exact solution obtained using a mobility approach was compared with WPA (Wave Propagation Analysis) and TSEA (Transient Statistical Energy Analysis) predictions. The agreement between exact and WPA results was very good, indicating that most of the energy was concentrated in the first, direct wave.
On Kinetics Modeling of Vibrational Energy Transfer
NASA Technical Reports Server (NTRS)
Gilmore, John O.; Sharma, Surendra P.; Cavolowsky, John A. (Technical Monitor)
1996-01-01
Two models of vibrational energy exchange are compared at equilibrium to the elementary vibrational exchange reaction for a binary mixture. The first model, non-linear in the species vibrational energies, was derived by Schwartz, Slawsky, and Herzfeld (SSH) by considering the detailed kinetics of vibrational energy levels. This model recovers the result demanded at equilibrium by the elementary reaction. The second model is more recent, and is gaining use in certain areas of computational fluid dynamics. This model, linear in the species vibrational energies, is shown not to recover the required equilibrium result. Further, this more recent model is inconsistent with its suggested rate constants in that those rate constants were inferred from measurements by using the SSH model to reduce the data. The non-linear versus linear nature of these two models can lead to significant differences in vibrational energy coupling. Use of the contemporary model may lead to significant misconceptions, especially when integrated in computer codes considering multiple energy coupling mechanisms.
Potential system efficiencies for MEMS vibration energy harvesting
NASA Astrophysics Data System (ADS)
Behrens, S.
2007-01-01
Reliable power sources are needed for portable micro-electromechanical systems (MEMS) devices such as wireless automobile tire pressure sensors. Vibration is an ubiquitous energy source that maybe 'harvested' as electrical energy at the site of the MEMS device. Existing vibration energy harvesting systems use either a piezoelectric or an electromagnetic transducer to convert vibrations into electrical energy. This electrical energy is then conditioned using a passive rectifier dc-dc converter circuit. Such vibration harvesting techniques have focused on optimising circuit efficiency and, hence, have ignored the system efficiency i.e. mechanical-to-electrical efficiency. Results obtained in the laboratory can be extrapolated to predict potential system efficiencies for MEMS vibration energy harvesting systems. Results to date, using a standard speaker as the electromagnetic transducer, have demonstrated system efficiencies of greater than 14%. Initial estimates suggest a MEMS system efficiency of more than 80% could be achieved with a high performance transducer. Research is continuing to demonstrate these higher system efficiencies with the experimental apparatus.
NASA Astrophysics Data System (ADS)
Ueno, Toshiyuki
2015-05-01
Vibration based power generation technology is utilized effectively in various fields. Author has invented novel vibrational power generation device using magnetostrictive material. The device is based on parallel beam structure consisting of a rod of iron-gallium alloy wound with coil and yoke accompanied with permanent magnet. When bending force is applied on the tip of the device, the magnetization inside the rod varies with induced stress due to the inverse magnetostrictive effect. In vibration, the time variation of the magnetization generates voltage on the wound coil. The magnetostrictive type is advantageous over conventional such using piezoelectric or moving magnet types in high efficiency and high robustness, and low electrical impedance. Here, author has established device configuration, simple, rigid, and high power output endurable for practical applications. In addition, the improved device is lower cost using less volume of Fe-Ga and permanent magnet compared to our conventional, and its assembly by soldering is easy and fast suitable for mass production. Average power of 3 mW/cm3 under resonant vibration of 212 Hz and 1.2 G was obtained in miniature prototype using Fe-Ga rod of 2 × 0.5× 7 mm3. Furthermore, the damping effect was observed, which demonstrates high energy conversion of the generator.
Ueno, Toshiyuki
2015-05-07
Vibration based power generation technology is utilized effectively in various fields. Author has invented novel vibrational power generation device using magnetostrictive material. The device is based on parallel beam structure consisting of a rod of iron-gallium alloy wound with coil and yoke accompanied with permanent magnet. When bending force is applied on the tip of the device, the magnetization inside the rod varies with induced stress due to the inverse magnetostrictive effect. In vibration, the time variation of the magnetization generates voltage on the wound coil. The magnetostrictive type is advantageous over conventional such using piezoelectric or moving magnet types in high efficiency and high robustness, and low electrical impedance. Here, author has established device configuration, simple, rigid, and high power output endurable for practical applications. In addition, the improved device is lower cost using less volume of Fe-Ga and permanent magnet compared to our conventional, and its assembly by soldering is easy and fast suitable for mass production. Average power of 3 mW/cm{sup 3} under resonant vibration of 212 Hz and 1.2 G was obtained in miniature prototype using Fe-Ga rod of 2 × 0.5× 7 mm{sup 3}. Furthermore, the damping effect was observed, which demonstrates high energy conversion of the generator.
Piezoelectric energy harvesting from traffic-induced bridge vibrations
NASA Astrophysics Data System (ADS)
Peigney, Michaël; Siegert, Dominique
2013-09-01
This paper focuses on energy harvesting from traffic-induced vibrations in bridges. Using a pre-stressed concrete highway bridge as a case study, in situ vibration measurements are presented and analysed. From these results, a prototype of a cantilever piezoelectric harvester is designed, tested and modelled. Even though the considered bridge vibrations are characterized by small amplitude and a low frequency (i.e. below 15 Hz), it is shown that mean power of the order of 0.03 mW can be produced, with a controlled voltage between 1.8 and 3.6 V. A simple model is proposed for theoretical prediction of the delivered power in terms of traffic intensity. This model shows good agreement with the experimental results and leads to a simple but effective design rule for piezoelectric harvesters to be used on bridges.
Cryns, Jackson W.; Hatchell, Brian K.; Santiago-Rojas, Emiliano; Silvers, Kurt L.
2013-07-01
Formal journal article Experimental analysis of a piezoelectric energy harvesting system for harmonic, random, and sine on random vibration Abstract: Harvesting power with a piezoelectric vibration powered generator using a full-wave rectifier conditioning circuit is experimentally compared for varying sinusoidal, random and sine on random (SOR) input vibration scenarios. Additionally, the implications of source vibration characteristics on harvester design are discussed. Studies in vibration harvesting have yielded numerous alternatives for harvesting electrical energy from vibrations but piezoceramics arose as the most compact, energy dense means of energy transduction. The rise in popularity of harvesting energy from ambient vibrations has made piezoelectric generators commercially available. Much of the available literature focuses on maximizing harvested power through nonlinear processing circuits that require accurate knowledge of generator internal mechanical and electrical characteristics and idealization of the input vibration source, which cannot be assumed in general application. In this manuscript, variations in source vibration and load resistance are explored for a commercially available piezoelectric generator. We characterize the source vibration by its acceleration response for repeatability and transcription to general application. The results agree with numerical and theoretical predictions for in previous literature that load optimal resistance varies with transducer natural frequency and source type, and the findings demonstrate that significant gains are seen with lower tuned transducer natural frequencies for similar source amplitudes. Going beyond idealized steady state sinusoidal and simplified random vibration input, SOR testing allows for more accurate representation of real world ambient vibration. It is shown that characteristic interactions from more complex vibrational sources significantly alter power generation and power processing requirements by increasing harvested power, shifting optimal conditioning impedance, inducing significant voltage supply fluctuations and ultimately rendering idealized sinusoidal and random analyses insufficient.
Estimating Vibrational Powers Of Parts In Fluid Machinery
NASA Technical Reports Server (NTRS)
Harvey, S. A.; Kwok, L. C.
1995-01-01
In new method of estimating vibrational power associated with component of fluid-machinery system, physics of flow through (or in vicinity of) component regarded as governing vibrations. Devised to generate scaling estimates for design of new parts of rocket engines (e.g., pumps, combustors, nozzles) but applicable to terrestrial pumps, turbines, and other machinery in which turbulent flows and vibrations caused by such flows are significant. Validity of method depends on assumption that fluid flows quasi-steadily and that flow gives rise to uncorrelated acoustic powers in different parts of pump.
Damping and energy dissipation in soft tissue vibrations during running.
Khassetarash, Arash; Hassannejad, Reza; Enders, Hendrik; Ettefagh, Mir Mohammad
2015-01-21
It has been well accepted that the vibrations of soft tissue cannot be simulated by a single sinusoidal function. In fact, these vibrations are a combination of several vibration modes. In this study, these modes are extracted applying a recently developed method namely, partly ensemble empirical mode decomposition (PEEMD). Then, a methodology for estimating the damping properties and energy dissipation caused by damping for each mode is used. Applying this methodology on simulated signals demonstrates high accuracy. This methodology is applied to the acceleration signals of the gastrocnemius muscle during sprinting and the differences between the damping properties of different vibration modes were identified. The results were 1) the damping property of high-frequency mode was higher than that for low-frequency modes. 2) All identified modes were in under damped condition, therefore, the vibrations had an oscillatory nature. 3) The damping ratios of lower modes are about 100% increased compared to higher modes. 4) The energy dissipation occurred in lower modes were much more than that for higher mode; According to the power spectrum of the ground reaction force (GRF), which is the input force into the body, the recent finding supports the muscle tuning paradigm. It is suggested that the damping properties and energy dissipation can be used to distinguish between different running conditions (surface, fatigue, etc.). PMID:25527887
Mechanical vibration to electrical energy converter
Kellogg, Rick Allen; Brotz, Jay Kristoffer
2009-03-03
Electromechanical devices that generate an electrical signal in response to an external source of mechanical vibrations can operate as a sensor of vibrations and as an energy harvester for converting mechanical vibration to electrical energy. The devices incorporate a magnet that is movable through a gap in a ferromagnetic circuit, wherein a coil is wound around a portion of the ferromagnetic circuit. A flexible coupling is used to attach the magnet to a frame for providing alignment of the magnet as it moves or oscillates through the gap in the ferromagnetic circuit. The motion of the magnet can be constrained to occur within a substantially linear range of magnetostatic force that develops due to the motion of the magnet. The devices can have ferromagnetic circuits with multiple arms, an array of magnets having alternating polarity and, encompass micro-electromechanical (MEM) devices.
The bandwidth of optimized nonlinear vibration-based energy harvesters
NASA Astrophysics Data System (ADS)
Cammarano, A.; Neild, S. A.; Burrow, S. G.; Inman, D. J.
2014-05-01
In an attempt to improve the performance of vibration-based energy harvesters, many authors suggest that nonlinearities can be exploited to increase the bandwidths of linear devices. Nevertheless, the complex dependence of the response upon the input excitation has made a realistic comparison of linear harvesters with nonlinear energy harvesters challenging. In a previous work it has been demonstrated that for a given frequency of excitation, it is possible to achieve the same maximum power for a nonlinear harvester as that for a linear harvester, provided that the resistance and the linear stiffness of both are optimized. This work focuses on the bandwidths of linear and nonlinear harvesters and shows which device is more suitable for harvesting energy from vibrations. The work considers different levels of excitation as well as different frequencies of excitation. In addition, the effect of the mechanical damping of the oscillator on the power bandwidth is shown for both the linear and nonlinear cases.
A new figure of merit for wideband vibration energy harvesters
NASA Astrophysics Data System (ADS)
Liu, W. Q.; Badel, A.; Formosa, F.; Wu, Y. P.
2015-12-01
The performance evaluation method is a very important part in the field of vibration energy harvesting. It provides the ability to compare and rate different vibration energy harvesters (VEHs). Considering the lack of a well-recognized tool, this article proposed a new systematic figure of merit for the appraisement of wideband VEHs. Extensive investigations are first performed for some classic figures for linear VEHs. With the common fundamental information obtained, the proposed figure integrates four essential factors: the revised energy harvester effectiveness, the mechanical quality factor, the normalized bandwidth and the effective mass density. Special considerations are devoted to the properties of wideband VEHs about the operation range and the average power in this domain which are related to the performance target of stable power output. Afterward, this new figure is applied to some literature VEHs and demonstrated to present good evaluations of wideband VEHs. Moreover, it exhibits the ability to point out the improvement information of the concerned VEHs further developments.
Vibrational energy storage in high pressure mixtures of diatomic molecules
NASA Astrophysics Data System (ADS)
Plnjes, Elke; Palm, Peter; Lee, Wonchul; Chidley, Matthew D.; Adamovich, Igor V.; Lempert, Walter R.; Rich, J. William
2000-10-01
CO/N 2, CO/Ar/O 2, and CO/N 2/O 2 gas mixtures are optically pumped using a continuous wave CO laser. Carbon monoxide molecules absorb the laser radiation and transfer energy to nitrogen and oxygen by vibration-vibration energy exchange. Infrared emission and spontaneous Raman spectroscopy are used for diagnostics of optically pumped gases. The experiments demonstrate that strong vibrational disequilibrium can be sustained in diatomic gas mixtures at pressures up to 1 atm, with only a few Watts laser power available. At these conditions, measured first level vibrational temperatures of diatomic species are in the range TV=1900-2300 K for N 2, TV=2600-3800 K for CO, and TV=2200-2800 K for O 2. The translational-rotational temperature of the gases does not exceed T=700 K. Line-of-sight averaged CO vibrational level populations up to v=40 are inferred from infrared emission spectra. Vibrational level populations of CO ( v=0-8), N 2 ( v=0-4), and O 2 ( v=0-8) near the axis of the focused CO laser beam are inferred from the Raman spectra of these species. The results demonstrate a possibility of sustaining stable nonequilibrium plasmas in atmospheric pressure air seeded with a few percent of carbon monoxide. The obtained experimental data are compared with modeling calculations that incorporate both major processes of molecular energy transfer and diffusion of vibrationally excited species across the spatially nonuniform excitation region, showing reasonably good agreement.
Effect of electrode configurations on piezoelectric vibration energy harvesting performance
NASA Astrophysics Data System (ADS)
Kim, Miso; Dugundji, John; Wardle, Brian L.
2015-04-01
Piezoelectric vibration energy harvesting is an attractive technology for self-powered wireless sensor networks because of the potential to deliver power to the sensor nodes from mechanical vibration sources in the surrounding medium. Systematic device designs are required in order to increase performance along with materials development of high piezoelectric coefficients and design of circuits with high power transfer efficiency. In this work, we present refined structural and electrical modeling of interdigitated electrodes (IDEs) for piezoelectric vibration energy harvesting, followed by parametric case studies on MEMS devices. Differences in geometric parameters including the size of the electrode and the number of IDE fingers for given device dimensions lead to substantial changes in harvesting performance such as capacitance, system coupling, voltage and power. When compared with parallel plate electrodes, use of IDEs results in much higher voltage generation by a factor of ten times while similar power levels are observed for both {3-1} and {3-3} configurations at optimal electrical loading conditions.
NASA Astrophysics Data System (ADS)
Zaghari, Bahareh; Rustighi, Emiliano; Ghandchi Tehrani, Maryam
2015-03-01
Vibration energy harvesting is the transformation of vibration energy to electrical energy. The motivation of this work is to use vibration energy harvesting to power wireless sensors that could be used in inaccessible or hostile environments to transmit information for condition health monitoring. Although considerable work has been done in the area of energy harvesting, there is still a demand for making a robust and small vibration energy harvesters from random excitations in a real environment that can produce a reliable amount of energy. Parametrically excited harvesters can have time-varying stiffness. Parametric amplification is used to tune vibration energy harvesters to maximize energy gains at system superharmonics, often at twice the first natural frequency. In this paper the parametrically excited harvester with cubic and cubic parametric nonlinearity is introduced as a novel work. The advantages of having cubic and cubic nonlinearity are explained theoretically and experimentally.
Energy harvesting from an autoparametric vibration absorber
NASA Astrophysics Data System (ADS)
Yan, Zhimiao; Hajj, Muhammad R.
2015-11-01
The combined control and energy harvesting characteristics of an autoparametric vibration absorber consisting of a base structure subjected to the external force and a cantilever beam with a tip mass are investigated. The piezoelectric sheets are attached to the cantilever beam to convert the vibrations of the base structure into electrical energy. The coupled nonlinear representative model is developed by using the extended Hamiton’s principle. The effects of the electrical load resistance on the frequency and damping ratio of the cantilever beam are analyzed. The impacts of the external force and load resistance on the structural displacements of the base structure and the beam and on the level of harvested energy are determined. The results show that the initial conditions have a significant impact on the system’s response. The relatively high level of energy harvesting is not necessarily accompanied with the minimum displacements of the base structure.
Efficiency enhancement of a cantilever-based vibration energy harvester.
Kubba, Ali E; Jiang, Kyle
2013-01-01
Extracting energy from ambient vibration to power wireless sensor nodes has been an attractive area of research, particularly in the automotive monitoring field. This article reports the design, analysis and testing of a vibration energy harvesting device based on a miniature asymmetric air-spaced cantilever. The developed design offers high power density, and delivers electric power that is sufficient to support most wireless sensor nodes for structural health monitoring (SHM) applications. The optimized design underwent three evolutionary steps, starting from a simple cantilever design, going through an air-spaced cantilever, and ending up with an optimized air-spaced geometry with boosted power density level. Finite Element Analysis (FEA) was used as an initial tool to compare the three geometries' stiffness (K), output open-circuit voltage (V(ave)), and average normal strain in the piezoelectric transducer (ε(ave)) that directly affect its output voltage. Experimental tests were also carried out in order to examine the energy harvesting level in each of the three designs. The experimental results show how to boost the power output level in a thin air-spaced cantilever beam for energy within the same space envelope. The developed thin air-spaced cantilever (8.37 cm3), has a maximum power output of 2.05 mW (H = 29.29 μJ/cycle). PMID:24366177
Efficiency Enhancement of a Cantilever-Based Vibration Energy Harvester
Kubba, Ali E.; Jiang, Kyle
2014-01-01
Extracting energy from ambient vibration to power wireless sensor nodes has been an attractive area of research, particularly in the automotive monitoring field. This article reports the design, analysis and testing of a vibration energy harvesting device based on a miniature asymmetric air-spaced cantilever. The developed design offers high power density, and delivers electric power that is sufficient to support most wireless sensor nodes for structural health monitoring (SHM) applications. The optimized design underwent three evolutionary steps, starting from a simple cantilever design, going through an air-spaced cantilever, and ending up with an optimized air-spaced geometry with boosted power density level. Finite Element Analysis (FEA) was used as an initial tool to compare the three geometries' stiffness (K), output open-circuit voltage (Vave), and average normal strain in the piezoelectric transducer (?ave) that directly affect its output voltage. Experimental tests were also carried out in order to examine the energy harvesting level in each of the three designs. The experimental results show how to boost the power output level in a thin air-spaced cantilever beam for energy within the same space envelope. The developed thin air-spaced cantilever (8.37 cm3), has a maximum power output of 2.05 mW (H = 29.29 ?J/cycle). PMID:24366177
Vibrationally assisted quantum energy pumps
NASA Astrophysics Data System (ADS)
Myers, C. R.; Milburn, G. J.; Twamley, J.
2015-09-01
We show that directed energy transport in a linear array of coupled quantum dots can be achieved by a coherent coupling of each dot to a single coherently driven mechanical mode. Recent work on light harvesting molecules have implicated the role of discrete mechanical modes in enhancing the energy transport through dipole arrays but say less about directed transport. The study of quantum ratchets indicates how directed energy transport is possible in quantum dot arrays. Inspired by these two apparently unrelated models we show how directed energy transport may be implemented in an engineered quantum systems using a single mechanical degree of freedom. This may have implications for nano-engineered artificial energy harvesting systems.
MARVEL: measured active rotational vibrational energy levels
NASA Astrophysics Data System (ADS)
Furtenbacher, Tibor; Csszr, Attila G.; Tennyson, Jonathan
2007-10-01
An algorithm is proposed, based principally on an earlier proposition of Flaud and co-workers [Mol. Phys. 32 (1976) 499], that inverts the information contained in uniquely assigned experimental rotational-vibrational transitions in order to obtain measured active rotational-vibrational energy levels (MARVEL). The procedure starts with collecting, critically evaluating, selecting, and compiling all available measured transitions, including assignments and uncertainties, into a single database. Then, spectroscopic networks (SN) are determined which contain all interconnecting rotational-vibrational energy levels supported by the grand database of the selected transitions. Adjustment of the uncertainties of the lines is performed next, with the help of a robust weighting strategy, until a self-consistent set of lines and uncertainties is achieved. Inversion of the transitions through a weighted least-squares-type procedure results in MARVEL energy levels and associated uncertainties. Local sensitivity coefficients could be computed for each energy level. The resulting set of MARVEL levels is called active as when new experimental measurements become available the same evaluation, adjustment, and inversion procedure should be repeated in order to obtain more dependable energy levels and uncertainties. MARVEL is tested on the example of the H 217O isotopologue of water and a list of 2736 dependable energy levels, based on 8369 transitions, has been obtained.
Multi-link piezoelectric structure for vibration energy harvesting
NASA Astrophysics Data System (ADS)
Aryanpur, Rameen M.; White, Robert D.
2012-04-01
Work in piezoelectric vibration energy harvesting has typically focused on single member cantilevered structures with transverse tip displacement at a known frequency, taking advantage of the optimal coupling characteristics of piezoceramics in the 3-1 bending mode. Multi-member designs could be advantageous in delivering power to a load in environments with random or wide-band vibrations. The design presented in this work consists of two hinged piezoceramic (PZT-5A) beams x-poled for series operation. Each beam measures 31.8mm x 12.7mm x 0.38mm and consists of two layers of nickel-plated piezoceramic adhered to a brass center shim. The hinge device consists of two custom-machined aluminum attachments epoxied to the end of a beam and connected using a 1.59mm diameter alloy steel dowel. A stainless steel torsion spring is placed over the pin and attached to the aluminum body to provide a restoring torque when under rotation. The design is modeled using the piezoelectric constitutive equations to solve for voltage and power for a set of electromechanical boundary conditions. Experimental measurements on the design are achieved by bolting one end of the structure to a vibration shaker and fixing the other to a rigid framework of industrial aluminum framing material. For a given frequency of vibration, power output of the structure can be obtained by measuring voltage drop across a resistive load.
Electrostatic MEMS vibration energy harvester for HVAC applications
NASA Astrophysics Data System (ADS)
Oxaal, J.; Hella, M.; Borca-Tasciuc, D.-A.
2015-12-01
This paper reports on an electrostatic MEMS vibration energy harvester with gapclosing interdigitated electrodes, designed for and tested on HVAC air ducts. The device is fabricated on SOI wafers using a custom microfabrication process. A dual-level physical stopper system is implemented in order to control the minimum gap between the electrodes and maximize the power output. It utilizes cantilever beams to absorb a portion of the impact energy as the electrodes approach the impact point, and a film of parylene with nanometer thickness deposited on the electrode sidewalls, which defines the absolute minimum gap and provides electrical insulation. The fabricated device was first tested on a vibration shaker to characterize its resonant behavior. The device exhibits spring hardening behavior due to impacts with the stoppers and spring softening behavior with increasing voltage bias. Testing was carried out on HVAC air duct vibrating with an RMS acceleration of 155 mgRMS and a primary frequency of 60 Hz with a PSD of 7.15·10-2 g2/Hz. The peak power measured is 12nW (0.6 nW RMS) with a PSD of 6.9·10-11 W/Hz at 240 Hz (four times of the primary frequency of 60 Hz), which is the highest output reported for similar vibration conditions and biasing voltages.
Vibrational energy transport in the presence of intrasite vibrational energy redistribution.
Schade, Marco; Hamm, Peter
2009-07-28
The mechanism of vibrational energy flow is studied in a regime where a diffusion equation is likely to break down, i.e., on length scales of a few chemical bonds and time scales of a few picoseconds. This situation occurs, for example, during photochemical reactions in protein environment. To that end, a toy model is introduced that on the one hand mimics the vibrational normal mode distribution of proteins, and on the other hand is small enough to numerically time propagate the system fully quantum mechanically. Comparing classical and quantum-mechanical results, the question is addressed to what extent the classical nature of the molecular dynamics simulations (which would be the only choice for the modeling of a real molecular system) affects the vibrational energy flow mechanism. Small differences are found which are due to the different ways classical and quantum mechanics distribute thermal energy over vibrational modes. In either case, a ballistic and a diffusive phase can be identified. For these small length and time scales, the latter is governed by intrasite vibrational energy redistribution, since vibrational energy does not necessarily thermalize completely within individual peptide units. Overall, the model suggests a picture that unifies many of the observations made recently in experiments. PMID:19655898
Vibrational energy transport in the presence of intrasite vibrational energy redistribution
Schade, Marco; Hamm, Peter
2009-07-28
The mechanism of vibrational energy flow is studied in a regime where a diffusion equation is likely to break down, i.e., on length scales of a few chemical bonds and time scales of a few picoseconds. This situation occurs, for example, during photochemical reactions in protein environment. To that end, a toy model is introduced that on the one hand mimics the vibrational normal mode distribution of proteins, and on the other hand is small enough to numerically time propagate the system fully quantum mechanically. Comparing classical and quantum-mechanical results, the question is addressed to what extent the classical nature of the molecular dynamics simulations (which would be the only choice for the modeling of a real molecular system) affects the vibrational energy flow mechanism. Small differences are found which are due to the different ways classical and quantum mechanics distribute thermal energy over vibrational modes. In either case, a ballistic and a diffusive phase can be identified. For these small length and time scales, the latter is governed by intrasite vibrational energy redistribution, since vibrational energy does not necessarily thermalize completely within individual peptide units. Overall, the model suggests a picture that unifies many of the observations made recently in experiments.
A power flow method for evaluating vibration from underground railways
NASA Astrophysics Data System (ADS)
Hussein, M. F. M.; Hunt, H. E. M.
2006-06-01
One of the major sources of ground-borne vibration is the running of trains in underground railway tunnels. Vibration is generated at the wheel-rail interface, from where it propagates through the tunnel and surrounding soil into nearby buildings. An understanding of the dynamic interfaces between track, tunnel and soil is essential before engineering solutions to the vibration problem can be found. A new method has been developed to evaluate the effectiveness of vibration countermeasures. The method is based on calculating the mean power flow from the tunnel, paying attention to that part of the power which radiates upwards to places where buildings' foundations are expected to be found. The mean power is calculated for an infinite train moving through the tunnel with a constant velocity. An elegant mathematical expression for the mean power flow is derived, which can be used with any underground-tunnel model. To evaluate the effect of vibration countermeasures and track properties on power flow, a comprehensive three-dimensional analytical model is used. It consists of Euler-Bernoulli beams to account for the rails and the track slab. These are coupled in the wavenumber-frequency domain to a thin shell representing the tunnel embedded within an infinite continuum, with a cylindrical cavity representing the surrounding soil.
Magnetostrictive vibration damper and energy harvester for rotating machinery
NASA Astrophysics Data System (ADS)
Deng, Zhangxian; Asnani, Vivake M.; Dapino, Marcelo J.
2015-04-01
Vibrations generated by machine driveline components can cause excessive noise and structural dam- age. Magnetostrictive materials, including Galfenol (iron-gallium alloys) and Terfenol-D (terbium-iron- dysprosium alloys), are able to convert mechanical energy to magnetic energy. A magnetostrictive vibration ring is proposed, which generates electrical energy and dampens vibration, when installed in a machine driveline. A 2D axisymmetric finite element (FE) model incorporating magnetic, mechanical, and electrical dynamics is constructed in COMSOL Multiphysics. Based on the model, a parametric study considering magnetostrictive material geometry, pickup coil size, bias magnet strength, flux path design, and electrical load is conducted to maximize loss factor and average electrical output power. By connecting various resistive loads to the pickup coil, the maximum loss factors for Galfenol and Terfenol-D due to electrical energy loss are identified as 0.14 and 0.34, respectively. The maximum av- erage electrical output power for Galfenol and Terfenol-D is 0.21 W and 0.58 W, respectively. The loss factors for Galfenol and Terfenol-D are increased to 0.59 and 1.83, respectively, by using an L-C resonant circuit.
Magnetostrictive Vibration Damper and Energy Harvester for Rotating Machinery
NASA Technical Reports Server (NTRS)
Deng, Zhangxian; Asnani, Vivake M.; Dapino, Marcelo J.
2015-01-01
Vibrations generated by machine driveline components can cause excessive noise and structural damage. Magnetostrictive materials, including Galfenol (iron-gallium alloys) and Terfenol-D (terbium-iron-dysprosium alloys), are able to convert mechanical energy to magnetic energy. A magnetostrictive vibration ring is proposed, which generates electrical energy and dampens vibration, when installed in a machine driveline. A 2D axisymmetric finite element (FE) model incorporating magnetic, mechanical, and electrical dynamics is constructed in COMSOL Multiphysics. Based on the model, a parametric study considering magnetostrictive material geometry, pickup coil size, bias magnet strength, flux path design, and electrical load is conducted to maximize loss factor and average electrical output power. By connecting various resistive loads to the pickup coil, the maximum loss factors for Galfenol and Terfenol-D due to electrical energy loss are identified as 0.14 and 0.34, respectively. The maximum average electrical output power for Galfenol and Terfenol-D is 0.21 W and 0.58 W, respectively. The loss factors for Galfenol and Terfenol-D are increased to 0.59 and 1.83, respectively, by using an L-C resonant circuit.
Energy harvester array using piezoelectric circular diaphragm for rail vibration
NASA Astrophysics Data System (ADS)
Wang, Wei; Huang, Rong-Jin; Huang, Chuan-Jun; Li, Lai-Feng
2014-12-01
Generating electric energy from mechanical vibration using a piezoelectric circular membrane array is presented in this paper. The electrical characteristics of the functional array consisted of three plates with varies tip masses are examined under dynamic conditions. With an optimal load resistor of 11 k?, an output power of 21.4 mW was generated from the array in parallel connection at 150 Hz under a pre-stress of 0.8 N and a vibration acceleration of 9.8 m/s2. Moreover, the broadband energy harvesting using this array still can be realized with different tip masses. Three obvious output power peaks can be obtained in a frequency spectra of 110 Hz to 260 Hz. The results show that using a piezoelectric circular diaphragm array can increase significantly the output of energy compared with the use of a single plate. And by optimizing combination of tip masses with piezoelectric elements in array, the frequency range can be tuned to meet the broadband vibration. This array may possibly be exploited to design the energy harvesting for practical applications such as future high speed rail.
Direct vibrational energy transfer in zeolites
NASA Astrophysics Data System (ADS)
Brugmans, Marco J. P.; Bakker, Huib J.; Lagendijk, Ad
1996-01-01
With two-color picosecond infrared laser spectroscopy the dynamics of O-H and O-D stretch vibrations in zeolites are investigated. Zeolites appear to be good model systems to study transfer of vibrational energy in a solid. For the O-D vibrations, transient spectral holes are burnt in the inhomogeneously broadened absorption bands by saturating the absorption with a strong pump pulse. From the spectral hole widths the homogeneous absorption linewidths are obtained. The excited population lifetimes are determined using a time-resolved pump-probe technique, and in combination with the homogeneous linewidth the pure dephasing time is revealed as well. For high concentrations of O-H oscillators the vibrational stretch excitations are found to diffuse spectrally through the inhomogeneous absorption band. This spectral diffusion process is explained by direct site-to-site transfer of the excitations due to dipole-dipole coupling (Förster transfer). The dependences of the transient spectral signals on oscillator concentration and the results of one-color polarization resolved experiments confirm this explanation. The spectral transients are satisfactorily described by simulations in which the site-to-site transfer by dipole-dipole coupling is taken into account.
Multistable chain for ocean wave vibration energy harvesting
NASA Astrophysics Data System (ADS)
Harne, R. L.; Schoemaker, M. E.; Wang, K. W.
2014-03-01
The heaving of ocean waves is a largely untapped, renewable kinetic energy resource. Conversion of this energy into electrical power could integrate with solar technologies to provide for round-the-clock, portable, and mobile energy supplies usable in a wide variety of marine environments. However, the direct drive conversion methodology of gridintegrated wave energy converters does not efficiently scale down to smaller, portable architectures. This research develops an alternative power conversion approach to harness the extraordinarily large heaving displacements and long oscillation periods as an excitation source for an extendible vibration energy harvesting chain. Building upon related research findings and engineering insights, the proposed system joins together a series of dynamic cells through bistable interfaces. Individual impulse events are generated as the inertial mass of each cell is pulled across a region of negative stiffness to induce local snap through dynamics; the oscillating magnetic inertial mass then generates current in a coil which is connected to energy harvesting circuitry. It is shown that linking the cells into a chain transmits impulses through the system leading to cascades of vibration and enhancement of electrical energy conversion from each impulse event. This paper describes the development of the multistable chain and ways in which realistic design challenges were addressed. Numerical modeling and corresponding experiments demonstrate the response of the chain due to slow and large amplitude input motion. Lastly, experimental studies give evidence that energy conversion efficiency of the chain for wave energy conversion is much higher than using an equal number of cells without connections.
Harvesting energy from the natural vibration of human walking.
Yang, Weiqing; Chen, Jun; Zhu, Guang; Yang, Jin; Bai, Peng; Su, Yuanjie; Jing, Qingsheng; Cao, Xia; Wang, Zhong Lin
2013-12-23
The triboelectric nanogenerator (TENG), a unique technology for harvesting ambient mechanical energy based on the triboelectric effect, has been proven to be a cost-effective, simple, and robust approach for self-powered systems. However, a general challenge is that the output current is usually low. Here, we demonstrated a rationally designed TENG with integrated rhombic gridding, which greatly improved the total current output owing to the structurally multiplied unit cells connected in parallel. With the hybridization of both the contact-separation mode and sliding electrification mode among nanowire arrays and nanopores fabricated onto the surfaces of two contact plates, the newly designed TENG produces an open-circuit voltage up to 428 V, and a short-circuit current of 1.395 mA with the peak power density of 30.7 W/m(2). Relying on the TENG, a self-powered backpack was developed with a vibration-to-electric energy conversion efficiency up to 10.62(±1.19) %. And it was also demonstrated as a direct power source for instantaneously lighting 40 commercial light-emitting diodes by harvesting the vibration energy from natural human walking. The newly designed TENG can be a mobile power source for field engineers, explorers, and disaster-relief workers. PMID:24180642
Vibration behavior of fuel-element vibration suppressors for the advanced power reactor
NASA Technical Reports Server (NTRS)
Adams, D. W.; Fiero, I. B.
1973-01-01
Preliminary shock and vibration tests were performed on vibration suppressors for the advanced power reactor for space application. These suppressors position the fuel pellets in a pin type fuel element. The test determined the effect of varying axial clearance on the behavior of the suppressors when subjected to shock and vibratory loading. The full-size suppressor was tested in a mockup model of fuel and clad which required scaling of test conditions. The test data were correlated with theoretical predictions for suppressor failure. Good agreement was obtained. The maximum difference with damping neglected was about 30 percent. Neglecting damping would result in a conservative design.
Resonant vibrational energy transfer in ice Ih
Shi, L.; Li, F.; Skinner, J. L.
2014-06-28
Fascinating anisotropy decay experiments have recently been performed on H{sub 2}O ice Ih by Timmer and Bakker [R. L. A. Timmer, and H. J. Bakker, J. Phys. Chem. A 114, 4148 (2010)]. The very fast decay (on the order of 100 fs) is indicative of resonant energy transfer between OH stretches on different molecules. Isotope dilution experiments with deuterium show a dramatic dependence on the hydrogen mole fraction, which confirms the energy transfer picture. Timmer and Bakker have interpreted the experiments with a Förster incoherent hopping model, finding that energy transfer within the first solvation shell dominates the relaxation process. We have developed a microscopic theory of vibrational spectroscopy of water and ice, and herein we use this theory to calculate the anisotropy decay in ice as a function of hydrogen mole fraction. We obtain very good agreement with experiment. Interpretation of our results shows that four nearest-neighbor acceptors dominate the energy transfer, and that while the incoherent hopping picture is qualitatively correct, vibrational energy transport is partially coherent on the relevant timescale.
Piezoelectric energy harvesting from heartbeat vibrations for leadless pacemakers
NASA Astrophysics Data System (ADS)
Ansari, M. H.; Karami, M. Amin
2015-12-01
This paper studies energy harvesting from heartbeat vibrations using fan-folded piezoelectric beams. The generated energy from the heartbeat can be used to power a leadless pacemaker. In order to utilize the available 3 dimensional space to the energy harvester, we chose the fan-folded design. The proposed device consists of several piezoelectric beams stacked on top of each other. The size for this energy harvester is 2 cm by 0.5 cm by 1 cm, which makes the natural frequency very high. High natural frequency is one major concern about the micro-scaled energy harvesters. By utilizing the fan-folded geometry and adding tip mass and link mass to the configuration, this natural frequency is reduced to the desired range. This fan-folded design makes it possible to generate more than 10 μW of power. The proposed device does not incorporate magnets and is thus Magnetic resonance imaging (MRI) compatible. Although our device is a linear energy harvester, it is shown that the device is relatively insensitive to the heartrate. The natural frequencies and the mode shapes of the device are calculated. An analytical solution is presented and the method is verified by experimental investigation. We use a closed loop shaker controller and a shaker to simulate the heartbeat vibrations. The developed analytical model is verified through comparison of theoretical and experimental tip displacement and acceleration frequency response functions.
Statistical energy analysis of nonlinear vibrating systems.
Spelman, G M; Langley, R S
2015-09-28
Nonlinearities in practical systems can arise in contacts between components, possibly from friction or impacts. However, it is also known that quadratic and cubic nonlinearity can occur in the stiffness of structural elements undergoing large amplitude vibration, without the need for local contacts. Nonlinearity due purely to large amplitude vibration can then result in significant energy being found in frequency bands other than those being driven by external forces. To analyse this phenomenon, a method is developed here in which the response of the structure in the frequency domain is divided into frequency bands, and the energy flow between the frequency bands is calculated. The frequency bands are assigned an energy variable to describe the mean response and the nonlinear coupling between bands is described in terms of weighted summations of the convolutions of linear modal transfer functions. This represents a nonlinear extension to an established linear theory known as statistical energy analysis (SEA). The nonlinear extension to SEA theory is presented for the case of a plate structure with quadratic and cubic nonlinearity. PMID:26303923
Methods of performing downhole operations using orbital vibrator energy sources
Cole, Jack H.; Weinberg, David M.; Wilson, Dennis R.
2004-02-17
Methods of performing down hole operations in a wellbore. A vibrational source is positioned within a tubular member such that an annulus is formed between the vibrational source and an interior surface of the tubular member. A fluid medium, such as high bulk modulus drilling mud, is disposed within the annulus. The vibrational source forms a fluid coupling with the tubular member through the fluid medium to transfer vibrational energy to the tubular member. The vibrational energy may be used, for example, to free a stuck tubular, consolidate a cement slurry and/or detect voids within a cement slurry prior to the curing thereof.
Production, Delivery and Application of Vibration Energy in Healthcare
NASA Astrophysics Data System (ADS)
Abundo, Paolo; Trombetta, Chiara; Foti, Calogero; Rosato, Nicola
2011-02-01
In Rehabilitation Medicine therapeutic application of vibration energy in specific clinical treatments and in sport rehabilitation is being affirmed more and more.Vibration exposure can have positive or negative effects on the human body depending on the features and time of the characterizing wave. The human body is constantly subjected to different kinds of vibrations, inducing bones and muscles to actively modify their structure and metabolism in order to fulfill the required functions. Like every other machine, the body supports only certain vibration energy levels over which long term impairments can be recognized. As shown in literature anyway, short periods of vibration exposure and specific frequency values can determine positive adjustments.
Autoparametric Resonance Systems for Vibration-Based Energy Harvesters
NASA Astrophysics Data System (ADS)
Kurmann, L.; Hoffmann, D.; Folkmer, B.; Manoli, Y.; Woias, P.; Anderegg, R.
2015-12-01
Motivation for this paper is the creation of a new kind of (vibration) kinetic energy harvester systems that can effectively transfer environmental mechanical vibrations into electrical energy over a wider frequency bandwidth than conventional devices. This paper presents a potential improvement in the 1DoF vibration transducer class and examining therefore analytically the behavior of such systems using strong nonlinear springs. Then a new 2DoF class of vibration transducer is presented having a strong nonlinear characteristic which is well suited for autoparametric resonance vibrations.
NASA Astrophysics Data System (ADS)
Zalesskaya, G. A.; Yakovlev, D. L.; Sambor, E. G.
2000-08-01
Efficiency of vibrational energy transfer (VET) in vibrational quasicontinuum of triplet states was estimated from the dependence of time-resolved delayed fluorescence of benzophenone and anthraquinone on bath gas pressure. The negative temperature dependence for vibration-vibration (V-V) and positive for vibration-translation (V-T) energy transfers from benzophenone and anthraquinone to bath gases (C 2H 4, SF 6, CCl 4, C 5H 12) were obtained between 373 and 553 K. Polarizability and dipole moment of colliding molecules seem to affect the efficiency of V-V relaxation. These data reflect the dominance of long-range attractive interactions in V-V energy transfer and short-range repulsive interactions in V-T energy transfer.
Interface Circuit for Vibration Energy Harvesting with Adjustable Bias Voltage
NASA Astrophysics Data System (ADS)
Wei, J.; Lefeuvre, E.; Mathias, H.; Costa, F.
2015-12-01
This paper presents a new interface circuit for electrostatic vibration energy harvesting with adjustable bias voltage. An electronic switch is used to modify the circuit configuration so that the harvested energy increases the voltage across a biasing capacitor. Decrease of this biasing capacitor voltage occurs naturally due to the circuit imperfections. Such a control of the bias voltage enables to adjust the amount of energy converted by the variable capacitor on each cycle. This feature can be used to optimize the mechanical damping induced by the energy conversion process in order to maximize the harvested power. Another feature of this interface circuit is that it is capable to get high bias voltage whatever the battery voltage with low energy loss.
Dual resonant structure for energy harvesting from random vibration sources at low frequency
NASA Astrophysics Data System (ADS)
Li, Shanshan; Peng, Zhuoteng; Zhang, Ai; Wang, Fei
2016-01-01
We introduce a design with dual resonant structure which can harvest energy from random vibration sources at low frequency range. The dual resonant structure consists of two spring-mass subsystems with different frequency responses, which exhibit strong coupling and broad bandwidth when the two masses collide with each other. Experiments with piezoelectric elements show that the energy harvesting device with dual resonant structure can generate higher power output than the sum of the two separate devices from random vibration sources.
Power management circuit for resonant energy harvesters
NASA Astrophysics Data System (ADS)
Jirku, Tomas; Steinbauer, Miloslav; Kluge, Martin
2009-05-01
This paper deals with the design of the power management circuit for the vibration generator developed in the frame of the European WISE project and its testing in the connection with the generator and the dynamic load simulating the real load. This generator is used as an autonomous energy source for wireless sensor applications. It can be used for example in the aeronautic, automotive and many other applications. The generator output power analysis was based on the vibration spectrum measured on the helicopter engine, provided by the consortium EADS, EUROCOPTER, DASSAULT AVIATION - 6.RP -WIreless SEnsing (WISE) project. This spectrum shows very unstable vibration levels. It was done the statistical analysis of these vibration levels and it was shown that there is a need of the power management circuit, which can provide a stable output voltage for the supplied circuit and if there is a need it can store an immediately unusable generated energy. The generator can't be used as the only energy source for the sensor circuit, because there are not any vibrations when for example a motor is stopped. In these periods and in the time of low vibration levels the circuit must be supplied from battery. The power management circuit described in this paper fulfills these requirements. It has two power inputs - the battery and the generator. It can switch between them at certain defined generator output levels by the threshold detector. Also when there is too much of the generated power, it can store the extra energy in the storage for the later usage. The storage device is the advanced capacitor. The advanced capacitor is a device containing three capacitors. These capacitors are connected (and charged) sequentially so the increasing capacity is provided. The developed power management was tested in the connection with the real vibration generator raised by stable vibration levels and the dynamic load simulating the real sensor in the main operation stages - sampling and data transmitting. It was shown that the generator with output power of 8mW@0,3GRMS with generator weight of 140g together with the described power management circuit can save about 50% of battery energy with the mentioned vibration spectrum. The generator used for the testing was improved, so it is more sensitive and also the sensor power requirements were decreased, so now it can be saved up to 100% battery energy during the generator operation. Also the power management circuit is still refined.
NASA Astrophysics Data System (ADS)
Nishi, Yoshiki; Ueno, Yuta; Nishio, Masachika; Quadrante, Luis Antonio Rodrigues; Kokubun, Kentaroh
2014-05-01
We conducted an experiment in a towing tank to investigate the performance of an energy extraction system using the flow-induced vibration of a circular cylinder. This experiment tested three different cases involving the following arrangements of cylinder(s) of identical diameter: the upstream fixed-downstream movable arrangement (case F); the upstream movable-downstream fixed arrangement (case R); and a movable isolated cylinder (case I). In cases F and R, the separation distance (ratio of the distance between the centers of the two cylinders to their diameters) is fixed at 1.30. Measurement results show that while cases F and I generate vortex-induced vibration (VIV) resonance responses, case R yields wake-induced vibration (WIV) at reduced velocity over 9.0, which is significantly larger than that of the VIV response, leading to the induction of higher electronic power in a generator. Accordingly, primary energy conversion efficiency is higher in the case involving WIV.
Experimental study of a self-powered and sensing MR-damper-based vibration control system
NASA Astrophysics Data System (ADS)
Sapi?ski, Bogdan
2011-10-01
The paper deals with a semi-active vibration control system based on a magnetorheological (MR) damper. The study outlines the model and the structure of the system, and describes its experimental investigation. The conceptual design of this system involves harvesting energy from structural vibrations using an energy extractor based on an electromagnetic transduction mechanism (Faraday's law). The system consists of an electromagnetic induction device (EMI) prototype and an MR damper of RD-1005 series manufactured by Lord Corporation. The energy extracted is applied to control the damping characteristics of the MR damper. The model of the system was used to prove that the proposed vibration control system is feasible. The system was realized in the semi-active control strategy with energy recovery and examined through experiments in the cases where the control coil of the MR damper was voltage-supplied directly from the EMI or voltage-supplied via the rectifier, or supplied with a current control system with two feedback loops. The external loop used the sky-hook algorithm whilst the internal loop used the algorithm switching the photorelay, at the output from the rectifier. Experimental results of the proposed vibration control system were compared with those obtained for the passive system (MR damper is off-state) and for the system with an external power source (conventional system) when the control coil of the MR damper was supplied by a DC power supply and analogue voltage amplifier or a DC power supply and a photorelay. It was demonstrated that the system is able to power-supply the MR damper and can adjust itself to structural vibrations. It was also found that, since the signal of induced voltage from the EMI agrees well with that of the relative velocity signal across the damper, the device can act as a 'velocity-sign' sensor.
Vibration-based energy harvesting with stacked piezoelectrets
Pondrom, P.; Hillenbrand, J.; Sessler, G. M.; Bös, J.; Melz, T.
2014-04-28
Vibration-based energy harvesters with multi-layer piezoelectrets (ferroelectrets) are presented. Using a simple setup with nine layers and a seismic mass of 8 g, it is possible to generate a power up to 1.3 µW at 140 Hz with an input acceleration of 1g. With better coupling between seismic mass and piezoelectret, and thus reduced damping, the power output of a single-layer system is increased to 5 µW at 700 Hz. Simulations indicate that for such improved setups with 10-layer stacks, utilizing seismic masses of 80 g, power levels of 0.1 to 1 mW can be expected below 100 Hz.
Smart nanocoated structure for energy harvesting at low frequency vibration
NASA Astrophysics Data System (ADS)
Sharma, Sudhanshu
Increasing demands of energy which is cleaner and has an unlimited supply has led development in the field of energy harvesting. Piezoelectric materials can be used as a means of transforming ambient vibrations into electrical energy that can be stored and used to power other devices. With the recent surge of micro scale devices, piezoelectric power generation can provide a convenient alternative to traditional power sources. In this research, a piezoelectric power generator composite prototype was developed to maximize the power output of the system. A lead zirconate titanate (PZT) composite structure was formed and mounted on a cantilever bar and was studied to convert vibration energy of the low range vibrations at 30 Hz--1000 Hz. To improve the performance of the PZT, different coatings were made using different percentage of Ferrofluid (FNP) and Zinc Oxide nanoparticles (ZnO) and binder resin. The optimal coating mixture constituent percentage was based on the performance of the composite structure formed by applying the coating on the PZT. The fabricated PZT power generator composite with an effective volume of 0.062 cm3 produced a maximum of 44.5 ?W, or 0.717mW/cm3 at its resonant frequency of 90 Hz. The optimal coating mixture had the composition of 59.9%FNP + 40% ZnO + 1% Resin Binder. The coating utilizes the opto-magneto-electrical properties of ZnO and Magnetic properties of FNP. To further enhance the output, the magneto-electric (ME) effect was increased by subjecting the composite to magnetic field where coating acts as a magnetostrictive material. For the effective volume of 0.0062 cm 3, the composite produced a maximum of 68.5 ?W, or 1.11mW/cm 3 at its resonant frequency of 90 Hz at 160 gauss. The optimal coating mixture had the composition of 59.9% FNP + 40% ZnO + 1% Resin Binder. This research also focused on improving the efficiency of solar cells by utilizing the magnetic effect along with gas plasma etching to improve the internal reflection. Preliminary results showed an improvement in solar cell efficiency from 14.6% to 17.1%.
Improvement of force factor of magnetostrictive vibration power generator for high efficiency
NASA Astrophysics Data System (ADS)
Kita, Shota; Ueno, Toshiyuki; Yamada, Sotoshi
2015-05-01
We develop high power magnetostrictive vibration power generator for battery-free wireless electronics. The generator is based on a cantilever of parallel beam structure consisting of coil-wound Galfenol and stainless plates with permanent magnet for bias. Oscillating force exerted on the tip bends the cantilever in vibration yields stress variation of Galfenol plate, which causes flux variation and generates voltage on coil due to the law of induction. This generator has advantages over conventional, such as piezoelectric or moving magnet types, in the point of high efficiency, highly robust, and low electrical impedance. Our concern is the improvement of energy conversion efficiency dependent on the dimension. Especially, force factor, the conversion ratio of the electromotive force (voltage) on the tip velocity in vibration, has an important role in energy conversion process. First, the theoretical value of the force factor is formulated and then the validity was verified by experiments, where we compare four types of prototype with parameters of the dimension using 7.0 × 1.5 × 50 mm beams of Galfenol with 1606-turn wound coil. In addition, the energy conversion efficiency of the prototypes depending on load resistance was measured. The most efficient prototype exhibits the maximum instantaneous power of 0.73 W and energy of 4.7 mJ at a free vibration of frequency of 202 Hz in the case of applied force is 25 N. Further, it was found that energy conversion efficiency depends not only on the force factor but also on the damping (mechanical loss) of the vibration.
Improvement of force factor of magnetostrictive vibration power generator for high efficiency
Kita, Shota Ueno, Toshiyuki; Yamada, Sotoshi
2015-05-07
We develop high power magnetostrictive vibration power generator for battery-free wireless electronics. The generator is based on a cantilever of parallel beam structure consisting of coil-wound Galfenol and stainless plates with permanent magnet for bias. Oscillating force exerted on the tip bends the cantilever in vibration yields stress variation of Galfenol plate, which causes flux variation and generates voltage on coil due to the law of induction. This generator has advantages over conventional, such as piezoelectric or moving magnet types, in the point of high efficiency, highly robust, and low electrical impedance. Our concern is the improvement of energy conversion efficiency dependent on the dimension. Especially, force factor, the conversion ratio of the electromotive force (voltage) on the tip velocity in vibration, has an important role in energy conversion process. First, the theoretical value of the force factor is formulated and then the validity was verified by experiments, where we compare four types of prototype with parameters of the dimension using 7.0 × 1.5 × 50 mm beams of Galfenol with 1606-turn wound coil. In addition, the energy conversion efficiency of the prototypes depending on load resistance was measured. The most efficient prototype exhibits the maximum instantaneous power of 0.73 W and energy of 4.7 mJ at a free vibration of frequency of 202 Hz in the case of applied force is 25 N. Further, it was found that energy conversion efficiency depends not only on the force factor but also on the damping (mechanical loss) of the vibration.
A dimensionless analysis of a 2DOF piezoelectric vibration energy harvester
NASA Astrophysics Data System (ADS)
Xiao, Han; Wang, Xu; John, Sabu
2015-06-01
In this study, a dimensionless analysis method is proposed to predict the output voltage and harvested power for a 2DOF vibration energy harvesting system. This method allows us to compare the harvesting power and efficiency of the 2DOF vibration energy harvesting system and to evaluate the harvesting system performance regardless the sizes or scales. The analysis method is a hybrid of time domain simulation and frequency response analysis approaches, which would be a useful tool for parametric study, design and optimisation of a 2DOF piezoelectric vibration energy harvester. In a case study, a quarter car suspension model with a piezoelectric material insert is chosen to be studied. The 2DOF vibration energy harvesting system could potentially be applied in a vehicle to convert waste or harmful ambient vibration energy into electrical energy for charging the battery. Especially for its application in a hybrid vehicle or an electrical vehicle, the 2DOF vibration energy harvesting system could improve charge mileage, comfort and reliability.
A Hybrid Indoor Ambient Light and Vibration Energy Harvester for Wireless Sensor Nodes
Yu, Hua; Yue, Qiuqin; Zhou, Jielin; Wang, Wei
2014-01-01
To take advantage of applications where both light and vibration energy are available, a hybrid indoor ambient light and vibration energy harvesting scheme is proposed in this paper. This scheme uses only one power conditioning circuit to condition the combined output power harvested from both energy sources so as to reduce the power dissipation. In order to more accurately predict the instantaneous power harvested from the solar panel, an improved five-parameter model for small-scale solar panel applying in low light illumination is presented. The output voltage is increased by using the MEMS piezoelectric cantilever arrays architecture. It overcomes the disadvantage of traditional MEMS vibration energy harvester with low voltage output. The implementation of the maximum power point tracking (MPPT) for indoor ambient light is implemented using analog discrete components, which improves the whole harvester efficiency significantly compared to the digital signal processor. The output power of the vibration energy harvester is improved by using the impedance matching technique. An efficient mechanism of energy accumulation and bleed-off is also discussed. Experiment results obtained from an amorphous-silicon (a-Si) solar panel of 4.8 2.0 cm2 and a fabricated piezoelectric MEMS generator of 11 12.4 mm2 show that the hybrid energy harvester achieves a maximum efficiency around 76.7%. PMID:24854054
A hybrid indoor ambient light and vibration energy harvester for wireless sensor nodes.
Yu, Hua; Yue, Qiuqin; Zhou, Jielin; Wang, Wei
2014-01-01
To take advantage of applications where both light and vibration energy are available, a hybrid indoor ambient light and vibration energy harvesting scheme is proposed in this paper. This scheme uses only one power conditioning circuit to condition the combined output power harvested from both energy sources so as to reduce the power dissipation. In order to more accurately predict the instantaneous power harvested from the solar panel, an improved five-parameter model for small-scale solar panel applying in low light illumination is presented. The output voltage is increased by using the MEMS piezoelectric cantilever arrays architecture. It overcomes the disadvantage of traditional MEMS vibration energy harvester with low voltage output. The implementation of the maximum power point tracking (MPPT) for indoor ambient light is implemented using analog discrete components, which improves the whole harvester efficiency significantly compared to the digital signal processor. The output power of the vibration energy harvester is improved by using the impedance matching technique. An efficient mechanism of energy accumulation and bleed-off is also discussed. Experiment results obtained from an amorphous-silicon (a-Si) solar panel of 4.8 × 2.0 cm2 and a fabricated piezoelectric MEMS generator of 11 × 12.4 mm2 show that the hybrid energy harvester achieves a maximum efficiency around 76.7%. PMID:24854054
Piezoelectric Vibration Energy Harvester Using Indirect Impact of Springless Proof Mass
NASA Astrophysics Data System (ADS)
Ju, S.; Ji, C.-H.
2015-12-01
This paper presents an impact-based piezoelectric vibration energy harvester using freely movable spherical proof mass and MFC (Macro Fiber Composite) beams as piezoelectric cantilevers. When external vibration is applied, a metal sphere moves freely along the channel and collides with both ends of the cavity, which induces the vibration of parallel- connected MFCs and generates electric power. A proof-of-concept device having the form- factor of a wristwatch has been designed and tested. Moreover, spherical proof mass made of different materials has been tested to analyze the relationship between output power, long-term reliability, and audible noise level during operation. Maximum peak-to-peak open circuit voltage of 41.2V and average power of 908.7 μW have been obtained in response to a 3g vibration at 17Hz for device with parallel-connected MFC beams.
Vibrational energy transfer in shocked molecular crystals.
Hooper, Joe
2010-01-01
We consider the process of establishing thermal equilibrium behind an ideal shock front in molecular crystals and its possible role in initiating chemical reaction at high shock pressures. A new theory of equilibration via multiphonon energy transfer is developed to treat the scattering of shock-induced phonons into internal molecular vibrations. Simple analytic forms are derived for the change in this energy transfer at different Hugoniot end states following shock compression. The total time required for thermal equilibration is found to be an order of magnitude or faster than proposed in previous work; in materials representative of explosive molecular crystals, equilibration is predicted to occur within a few picoseconds following the passage of an ideal shock wave. Recent molecular dynamics calculations are consistent with these time scales. The possibility of defect-induced temperature localization due purely to nonequilibrium phonon processes is studied by means of a simple model of the strain field around an inhomogeneity. The specific case of immobile straight dislocations is studied, and a region of enhanced energy transfer on the order of 5 nm is found. Due to the rapid establishment of thermal equilibrium, these regions are unrelated to the shock sensitivity of a material but may allow temperature localization at high shock pressures. Results also suggest that if any decomposition due to molecular collisions is occurring within the shock front itself, these collisions are not enhanced by any nonequilibrium thermal state. PMID:20078172
NASA Astrophysics Data System (ADS)
Killoran, N.; Huelga, S. F.; Plenio, M. B.
2015-10-01
Recent evidence suggests that quantum effects may have functional importance in biological light-harvesting systems. Along with delocalized electronic excitations, it is now suspected that quantum coherent interactions with certain near-resonant vibrations may contribute to light-harvesting performance. However, the actual quantum advantage offered by such coherent vibrational interactions has not yet been established. We investigate a quantum design principle, whereby coherent exchange of single energy quanta between electronic and vibrational degrees of freedom can enhance a light-harvesting system's power above what is possible by thermal mechanisms alone. We present a prototype quantum heat engine which cleanly illustrates this quantum design principle and quantifies its quantum advantage using thermodynamic measures of performance. We also demonstrate the principle's relevance in parameter regimes connected to natural light-harvesting structures.
Killoran, N; Huelga, S F; Plenio, M B
2015-10-21
Recent evidence suggests that quantum effects may have functional importance in biological light-harvesting systems. Along with delocalized electronic excitations, it is now suspected that quantum coherent interactions with certain near-resonant vibrations may contribute to light-harvesting performance. However, the actual quantum advantage offered by such coherent vibrational interactions has not yet been established. We investigate a quantum design principle, whereby coherent exchange of single energy quanta between electronic and vibrational degrees of freedom can enhance a light-harvesting system's power above what is possible by thermal mechanisms alone. We present a prototype quantum heat engine which cleanly illustrates this quantum design principle and quantifies its quantum advantage using thermodynamic measures of performance. We also demonstrate the principle's relevance in parameter regimes connected to natural light-harvesting structures. PMID:26493926
Extension of vibrational power flow techniques to two-dimensional structures
NASA Technical Reports Server (NTRS)
Cuschieri, J. M.
1987-01-01
In the analysis of the vibration response and structure-borne vibration transmission between elements of a complex structure, statistical energy analysis (SEA) or Finite Element Analysis (FEA) are generally used. However, an alternative method is using vibrational power flow techniques which can be especially useful in the mid- frequencies between the optimum frequency regimes for FEA and SEA. Power flow analysis has in general been used on one-dimensional beam-like structures or between structures with point joints. In this paper, the power flow technique is extended to two-dimensional plate like structures joined along a common edge without frequency or spatial averaging the results, such that the resonant response of the structure is determined. The power flow results are compared to results obtained using FEA at low frequencies and SEA at high frequencies. The agreement with FEA results is good but the power flow technique has an improved computational efficiency. Compared to the SEA results the power flow results show a closer representation of the actual response of the structure.
Extension of vibrational power flow techniques to two-dimensional structures
NASA Technical Reports Server (NTRS)
Cuschieri, Joseph M.
1988-01-01
In the analysis of the vibration response and structure-borne vibration transmission between elements of a complex structure, statistical energy analysis (SEA) or finite element analysis (FEA) are generally used. However, an alternative method is using vibrational power flow techniques which can be especially useful in the mid frequencies between the optimum frequency regimes for SEA and FEA. Power flow analysis has in general been used on 1-D beam-like structures or between structures with point joints. In this paper, the power flow technique is extended to 2-D plate-like structures joined along a common edge without frequency or spatial averaging the results, such that the resonant response of the structure is determined. The power flow results are compared to results obtained using FEA results at low frequencies and SEA at high frequencies. The agreement with FEA results is good but the power flow technique has an improved computational efficiency. Compared to the SEA results the power flow results show a closer representation of the actual response of the structure.
Electret transducer for vibration-based energy harvesting
Hillenbrand, J. Sessler, G. M.; Pondrom, P.
2015-05-04
Vibration-based electret energy harvesters with soft cellular spacer rings are presented. These harvesters are closely related to recently introduced electret accelerometers; however, their development targets are partially differing. Various harvesters with seismic masses from 8 to 23 g and surface potentials in the 500 V regime were built and characterized and powers of up to 8 μW at about 2 kHz and an acceleration of 1 g were measured. An analytical model is presented which, for instance, allows the calculation of the frequency response of the power output into a given load resistance. Finally, experimental and calculated results are compared.
Note: Vibration energy harvesting based on a round acoustic fence
NASA Astrophysics Data System (ADS)
Cui, Xiao-bin; Huang, Cheng-ping; Hu, Jun-hui
2015-07-01
An energy harvester based on a round acoustic fence (RAF) has been proposed and studied. The RAF is composed of cylindrical stubs stuck in a circular array on a thin metal plate, which can confine the acoustic energy efficiently. By removing one stub and thus opening a small gap in the RAF, acoustic leakage with larger intensity can be produced at the gap opening. With the vibration source surrounded by the RAF, the energy harvesting at the gap opening has a wide bandwidth and is insensitive to the position of the vibration source. The results may have potential applications in harvesting the energy of various vibration sources in solid structure.
Coupling analysis of linear vibration energy harvesting systems
NASA Astrophysics Data System (ADS)
Wang, Xu; Liang, Xingyu; Shu, Gequn; Watkins, Simon
2016-03-01
This paper has disclosed the relationship of vibration energy harvester performance with dimensionless force factor. Numerical ranges of the dimensionless force factor have been defined for cases of weak, moderate and strong coupling. The relationships of coupling loss factor, dimensionless force factor, critical coupling strength, coupling quotient, electro-mechanical coupling factor, damping loss factor and modal densities have been established in linear vibration energy harvester systems. The new contribution of this paper is to determine a frequency range where the vibration energy harvesting systems are in a weak coupling and the statistical energy analysis is applicable.
Scaling Rules for Vibrational Energy Transport in Globular Proteins.
Buchenberg, Sebastian; Leitner, David M; Stock, Gerhard
2016-01-01
Computational studies of vibrational energy flow in biomolecules have to date mapped out transport pathways on a case-by-case basis. To provide a more general approach, we derive scaling rules for vibrational energy transport in a globular protein, which are identified from extensive nonequilibrium molecular dynamics simulations of vibrational energy flow in the villin headpiece subdomain HP36. We parametrize a master equation based on inter-residue, residue-solvent, and heater-residue energy-transfer rates, which closely reproduces the results of the all-atom simulations. From that fit, two scaling rules emerge, one for energy transport along the protein backbone which relies on a diffusion model and another for energy transport between tertiary contacts, which is based on a harmonic model. Requiring only the calculation of mean and variance of relatively few atomic distances, the approach holds the potential to predict the pathways and time scales of vibrational energy flow in large proteins. PMID:26650387
Piezoelectric energy harvesting devices for low frequency vibration applications
NASA Astrophysics Data System (ADS)
Shen, Dongna
Energy harvesting, a process of capturing ambient waste energy and converting it into usable electricity, has been attracting more and more researchers' interest because of the limitations of traditional power sources, the increasing demands upon mobile devices such as wireless sensor networks, and the recent advent of the extremely low power electrical and mechanical devices such as microelectromechanical systems (MEMS). In this research, bulk- and wafer-scale of piezoelectric power generator prototypes were developed. The Lead Zirconate Titanate (PZT) bimorph cantilever in bulk scale with a big proof mass at the free end tip was studied to convert ambient vibration energy of 100 Hz and above 1g (1g = 9.81 m/s2) acceleration amplitudes. The optimal design was based on matching the resonant frequency of the device with the environmental exciting frequency, and balancing the power output and the fracture safety factor. The fabricated PZT power generator with an effective volume of 0.0564 cm3 and a safety factor of 10g can produce 6.21 Vpk, 257 microW, or 4558 microW/cm 3 with an optimal resistive load of 75 kO from 1g acceleration at its resonant frequency of 97.6 Hz. To overcome the high fragility of PZT, substitute piezoelectric materials, Macro Fiber Composite (MFC) and polyvinylidene fluoride (PVDF), and alternative operational ambient for power generators were investigated for high vibration amplitude applications. Before fabricating piezoelectric power generators in wafer scale, interlayer effects on the properties of PZT thin film were surveyed. The fabricated device based on Si wafer, with a beam dimension about 4.800 mm x 0.400 mm x 0.036 mm and an integrated Si mass dimension about 1.360 mm x 0.940 mm x 0.456 mm produced 160 mVpk, 2.13 microW, or 3272 microW/cm3 with the optimal resistive load of 6 kO from 2g acceleration at its resonant frequency of 461.15 Hz. To precisely control the resonant frequency of the power generator, Si on insulator (SOI) wafer substitutes for Si wafer. The resonant frequency of the fabricated device is as low as about 184 Hz. The difference between the calculated and measured resonant frequency has been decreased to 4.25%.
Accurate Measurement of Velocity and Acceleration of Seismic Vibrations near Nuclear Power Plants
NASA Astrophysics Data System (ADS)
Arif, Syed Javed; Imdadullah; Asghar, Mohammad Syed Jamil
In spite of all prerequisite geological study based precautions, the sites of nuclear power plants are also susceptible to seismic vibrations and their consequent effects. The effect of the ongoing nuclear tragedy in Japan caused by an earthquake and its consequent tsunami on March 11, 2011 is currently beyond contemplations. It has led to a rethinking on nuclear power stations by various governments around the world. Therefore, the prediction of location and time of large earthquakes has regained a great importance. The earth crust is made up of several wide, thin and rigid plates like blocks which are in constant motion with respect to each other. A series of vibrations on the earth surface are produced by the generation of elastic seismic waves due to sudden rupture within the plates during the release of accumulated strain energy. The range of frequency of seismic vibrations is from 0 to 10 Hz. However, there appears a large variation in magnitude, velocity and acceleration of these vibrations. The response of existing or conventional methods of measurement of seismic vibrations is very slow, which is of the order of tens of seconds. A systematic and high resolution measurement of velocity and acceleration of these vibrations are useful to interpret the pattern of waves and their anomalies more accurately, which are useful for the prediction of an earthquake. In the proposed work, a fast rotating magnetic field (RMF) is used to measure the velocity and acceleration of seismic vibrations in the millisecond range. The broad spectrum of pulses within one second range, measured by proposed method, gives all possible values of instantaneous velocity and instantaneous acceleration of the seismic vibrations. The spectrum of pulses in millisecond range becomes available which is useful to measure the pattern of fore shocks to predict the time and location of large earthquakes more accurately. Moreover, instead of average, the peak values of these quantities are helpful in proper design of earthquake resistant nuclear power plants, buildings and structures. The proposed measurement scheme is successfully tested with a microprocessor based rocking vibration arrangement and the overall performance is recorded at dynamic conditions.
NASA Astrophysics Data System (ADS)
Nili Ahmadabadi, Z.; Khadem, S. E.
2014-09-01
This paper presents an optimal design for a system comprising a nonlinear energy sink (NES) and a piezoelectric-based vibration energy harvester attached to a free-free beam under shock excitation. The energy harvester is used for scavenging vibration energy dissipated by the NES. Grounded and ungrounded configurations are examined and the systems parameters are optimized globally to both maximize the dissipated energy by the NES and increase the harvested energy by piezoelectric element. A satisfactory amount of energy has been harvested as electric power in both configurations. The realization of nonlinear vibration control through one-way irreversible nonlinear energy pumping and optimizing the system parameters result in acquiring up to 78 percent dissipation of the grounded system energy.
[Vibration-vibration energy transfer between highly vibrational excited RbH and H2, N2].
Zhang, Bin; Zhu, Dong-hui; Dai, Kang; Shen, Yi-fan
2012-03-01
Rb-H2 mixture was irradiated with pulses of 696.4 nm radiation from a OPO laser, populating 6D state by two-photon absorption. The vibrational levels of RbH(X1sigma+,v" = 0-2) generated in the reaction of Rb(6D) with H2. Vibrational-state-specific total-removal relaxation rate coefficients, k(v) (M), for RbH(X1sigma+, v" = 15-22) by M = H2 and N2 were investigated in a pump and probe configuration. By the overtone pumping with a cw diode laser, highly vibrational states v" = 15-22 of RbH in its ground electronic state were obtained. Another diode laser was used to probe the prepared vibrational state. The decay signal of laser induced time-resolved fluorescence from A 1sigma+ (v') --> X1sigma+ (v") transition was monitored. Based on the Stern-Volmer equation, the total relaxation rate coefficient k(v) (H2) were yielded. A plot of k(v) (H2 + N2) vs alpha (mole fraction H2) yields a line with a slope of k(v) (H2)-k(v) (N2) and an intercept of k(v) (N2). The values of k(v) (H2) obtained from the slope of the fitted lines compare well with determined values of the k(v) (H2) from the Sern-Volmer plots. At v" < 18, the rate coefficients k(v) (M) increases linearly with vibrational quantum number. This linear region is dominated by single quantum relaxation (deltav = 1) collisional propensity rules. The region (v" > or = 18) where the dependence is much stronger than linear shows significant contribution from multiquantum (deltav > or = 2) relaxation or resonant vibration-vibration energy transfer between highly vibrationally excited RbH and H2 or N2. For RbH(v") + N2 (0), we measured the time-profile of v" = 16 after preparation of v" = 21. A clear bimodal distribution was observed. The first peak is due to resonant vibration-vibration energy transfer: RbH (v" = 21) + N2 (0) --> RbH (v" = 16) + N2 (1). The much broader second peak, at longer time delays, is due to sequential single-quantum relaxation. Although the second process results in a distribution that is much more spread out in time, the peak height is in the same order of magnitude, indicating that the two processes are at least comparable in probability. PMID:22582611
A nanogenerator as a self-powered sensor for measuring the vibration spectrum of a drum membrane.
Yu, Aifang; Zhao, Yong; Jiang, Peng; Wang, Zhong Lin
2013-02-01
A nanogenerator (NG) is a device that converts vibration energy into electricity. Here, a flexible, small size and lightweight NG is successfully demonstrated as an active sensor for detecting the vibration spectrum of a drum membrane without the use of an external power source. The output current/voltage signal of the NG is a direct measure of the strain of the local vibrating drum membrane that contains rich informational content, such as, notably, the vibration frequency, vibration speed and vibration amplitude. In comparison to the laser vibrometer, which is excessively complex and expensive, this kind of small and low cost sensor based on an NG is also capable of detecting the local vibration frequency of a drum membrane accurately. A spatial arrangement of the NGs on the membrane can provide position-dependent vibration information on the surface. The measured frequency spectrum can be understood on the basis of the theoretically calculated vibration modes. This work expands the application of NGs and reveals the potential for developing sound wave detection, environmental/infrastructure monitoring and many more applications. PMID:23306794
A nanogenerator as a self-powered sensor for measuring the vibration spectrum of a drum membrane
NASA Astrophysics Data System (ADS)
Yu, Aifang; Zhao, Yong; Jiang, Peng; Wang, Zhong Lin
2013-02-01
A nanogenerator (NG) is a device that converts vibration energy into electricity. Here, a flexible, small size and lightweight NG is successfully demonstrated as an active sensor for detecting the vibration spectrum of a drum membrane without the use of an external power source. The output current/voltage signal of the NG is a direct measure of the strain of the local vibrating drum membrane that contains rich informational content, such as, notably, the vibration frequency, vibration speed and vibration amplitude. In comparison to the laser vibrometer, which is excessively complex and expensive, this kind of small and low cost sensor based on an NG is also capable of detecting the local vibration frequency of a drum membrane accurately. A spatial arrangement of the NGs on the membrane can provide position-dependent vibration information on the surface. The measured frequency spectrum can be understood on the basis of the theoretically calculated vibration modes. This work expands the application of NGs and reveals the potential for developing sound wave detection, environmental/infrastructure monitoring and many more applications.
A piezoelectric wafer-stack vibration energy harvester for wireless sensor networks
NASA Astrophysics Data System (ADS)
Jiang, Xuezheng; Li, Yancheng; Li, Jianchun
2013-04-01
Over the past few decades, wireless sensor networks have been widely used in civil structure health monitoring application. Currently, most wireless sensor networks are battery-powered and it is costly and unsustainable for maintenance because of the requirement for frequent battery replacements. As an attempt to address such issue, this paper presents a novel piezoelectric vibrational energy harvester to convert the structural vibration into usable electrical energy for powering wireless sensor networks. Unlike the normal cantilever beam structure, the piezoelectric harvester presented in this paper is based on the wafer-stack configuration which is suitable for applications where large force vibration occurs, and therefore can be embedded in civil structures to convert the force induced by vibration of large structures directly into electrical energy. The longitudinal mode of the piezoelectric wafer-stack was developed firstly to illustrate the force-to-voltage relationship of piezoelectric materials and to find the inter-medium force that will be used to convert vibration energy into electrical energy. Then, two electromechanical models (without and with a rectified circuit), considering both the mechanical and electrical aspects of the harvester, were developed to characterize the harvested electrical power under the external load. Exact closed-form expressions of the electromechanical models have been derived to analyze the maximum harvested power and the optimal resistance. Finally, a shake table experimental testing was conducted to prove the feasibility of the presented piezoelectric-wafer-stack harvester under standard sinusoidal loadings. Test results show that the harvester can generate a maximum 45mW (AC) or 16mW (DC) electrical power for sinusoidal loading with 40mm amplitude and 2Hz frequency, and the harvested electrical power is proportional to the levels of exciting vibrational loading.
Energy harvesting from vibration with cross-linked polypropylene piezoelectrets
NASA Astrophysics Data System (ADS)
Zhang, Xiaoqing; Wu, Liming; Sessler, Gerhard M.
2015-07-01
Piezoelectret films are prepared by modification of the microstructure of polypropylene foam sheets cross-linked by electronic irradiation (IXPP), followed by proper corona charging. Young's modulus, relative permittivity, and electromechanical coupling coefficient of the fabricated films, determined by dielectric resonance spectra, are about 0.7 MPa, 1.6, and 0.08, respectively. Dynamic piezoelectric d33 coefficients up to 650 pC/N at 200 Hz are achieved. The figure of merit (FOM, d33 ? g33) for a more typical d33 value of 400 pC/N is about 11.2 GPa-1. Vibration-based energy harvesting with one-layer and two-layer stacks of these films is investigated at various frequencies and load resistances. At an optimum load resistance of 9 M? and a resonance frequency of 800 Hz, a maximum output power of 120 ?W, referred to the acceleration g due to gravity, is obtained for an energy harvester consisting of a one-layer IXPP film with an area of 3.14 cm2 and a seismic mass of 33.7 g. The output power can be further improved by using two-layer stacks of IXPP films in electric series. IXPP energy harvesters could be used to energize low-power electronic devices, such as wireless sensors and LED lights.
Electron-vibration energy exchange models in nitrogen plasma flows
NASA Astrophysics Data System (ADS)
Bourdon, A.; Vervisch, P.
1997-04-01
This work presents an examination of the validity of the simple linear Landau-Teller-type model proposed by Lee for the electron-vibration energy exchange term in nitrogen [in Thermal Design of Aeroassisted Orbital Transfer Vehicles, edited by H. F. Nelson (AIAA, New York, 1985), Vol. 96, p. 3; in Thermophysical Aspects of Re-entry Flows, edited by J. N. Moss and C. D. Scott (AIAA, New York, 1986), Vol. 103, p. 197]. Plasma flow conditions encountered in high enthalpy wind tunnels are considered. The time-dependent relaxation of the vibrational energy of nitrogen due to electron inelastic collisions is calculated. The influence of the anharmonicity of the molecule and of the initial vibrational temperature Tv is studied. With a harmonic oscillator approximation, it is found that a linear Landau-Teller-type model is accurate to describe the vibrational energy relaxation rate for electron temperatures Te in the range 3000 K<=Te<=20 000 K. When Tv
NASA Astrophysics Data System (ADS)
Harne, Ryan L.
2012-03-01
Fundamental studies in vibrational energy harvesting consider the electromechanically coupled devices to be excited by uniform base vibration. Since many harvester devices are mass-spring systems, there is a clear opportunity to exploit the mechanical resonance in a fashion identical to tuned mass dampers to simultaneously suppress the vibration of the host structure via reactive forces while converting the absorbed vibration into electrical power. This paper presents a general analytical model for the coupled electro-elastic dynamics of a vibrating panel to which distributed energy harvesting devices are attached. One such device is described which employs a corrugated piezoelectric spring layer. The model is validated by comparison to measured elastic and electric frequency response functions. Tests on an excited panel show that the device, contributing 1% additional mass to the structure, concurrently attenuates the lowest panel mode accelerance by >20 dB while generating 0.441 W for a panel drive acceleration of 3.29 m s-2. Adjustment of the load resistance connected to the piezoelectric spring layer verifies the analogy between the present harvester device and an electromechanically stiffened and damped vibration absorber. The results show that maximum vibration suppression and energy harvesting objectives occur for nearly the same load resistance in the harvester circuit.
A diamagnetically stabilized horizontally levitated electromagnetic vibration energy harvester
NASA Astrophysics Data System (ADS)
Palagummi, S.; Zou, J.; Yuan, F. G.
2015-04-01
This article investigates a horizontal diamagnetic levitation (HDL) system for vibration energy harvesting. In this configuration, two large magnets, alias lifting magnets, are arranged co-axially at a distance such that in between them a magnet, alias floating magnet, is passively levitated at a laterally offset equilibrium position. The levitation is stabilized in the horizontal direction by two diamagnetic plates made of pyrolytic graphite placed on each side of the floating magnet. This HDL configuration permits large amplitude vibration of the floating magnet and exploits the ability to tailor the geometry to meet specific applications due to its frequency tuning capability. Theoretical modeling techniques are discussed followed by an experimental setup to validate it. At an input root mean square (RMS) acceleration of 0.0434 m/s2 (0.0044 grms) and at a resonant frequency of 1.2 Hz, the prototype generated a RMS power of 3.6 μW with an average system efficiency of 1.93%. Followed by the validation, parametric studies on the geometry of the components are undertaken to show that with the optimized parameters the efficiency can be further enhanced.
Vibrational energy transfer dynamics in ruthenium polypyridine transition metal complexes.
Fedoseeva, Marina; Delor, Milan; Parker, Simon C; Sazanovich, Igor V; Towrie, Michael; Parker, Anthony W; Weinstein, Julia A
2015-01-21
Understanding the dynamics of the initial stages of vibrational energy transfer in transition metal complexes is a challenging fundamental question which is also of crucial importance for many applications, such as improving the performance of solar devices or photocatalysis. The present study investigates vibrational energy transport in the ground and the electronic excited state of Ru(4,4'-(COOEt)2-2,2-bpy)2(NCS)2, a close relative of the efficient "N3" dye used in dye-sensitized solar cells. Using the emerging technique of ultrafast two-dimensional infrared spectroscopy, we show that, similarly to other transition-metal complexes, the central Ru heavy atom acts as a "bottleneck" making the energy transfer from small ligands with high energy vibrational stretching frequencies less favorable and thereby affecting the efficiency of vibrational energy flow in the complex. Comparison of the vibrational relaxation times in the electronic ground and excited state of Ru(4,4'-(COOEt)2-2,2-bpy)2(NCS)2 shows that it is dramatically faster in the latter. We propose to explain this observation by the intramolecular electrostatic interactions between the thiocyanate group and partially oxidised Ru metal center, which increase the degree of vibrational coupling between CN and Ru-N modes in the excited state thus reducing structural and thermodynamic barriers that slow down vibrational relaxation and energy transport in the electronic ground state. As a very similar behavior was earlier observed in another transition-metal complex, Re(4,4'-(COOEt)2-2,2'-bpy)(CO)3Cl, we suggest that this effect in vibrational energy dynamics might be common for transition-metal complexes with heavy central atoms. PMID:25463745
A Detailed Level Kinetics Model of NO Vibrational Energy Distributions
NASA Technical Reports Server (NTRS)
Sharma, Surendra P.; Gilmore, John; Cavolowsky, John A. (Technical Monitor)
1996-01-01
Several contemporary problems have pointed to the desirability of a detailed level kinetics approach to modeling the distribution of vibrational energy in NO. Such a model is necessary when vibrational redistribution reactions are insufficient to maintain a Boltzmann distribution over the vibrational energy states. Recent calculations of the rate constant for the first reaction of the Zeldovich mechanism (N2 + O (goes to) NO + N) have suggested that the product NO is formed in high vibrational states. In shock layer flowfields, the product NO molecules may experience an insufficient number of collisions to establish a Boltzmann distribution over vibrational states, thus necessitating a level kinetics model. In other flows, such as expansions of high temperature air, fast, near-resonance vibrational energy exchanges with N2 and O2 may also require a level specific model for NO because of the relative rates of vibrational exchange and redistribution. The proposed report will integrate computational and experimental components to construct such a model for the NO molecule.
Gao, Xiaotong; Shih, Wei-Heng; Shih, Wan Y.
2010-01-01
We have examined a piezoelectric unimorph cantilever (PUC) with unequal piezoelectric and nonpiezoelectric lengths for vibration energy harvesting theoretically by extending the analysis of a PUC with equal piezoelectric and nonpiezoelectric lengths. The theoretical approach was validated by experiments. A case study showed that for a fixed vibration frequency, the maximum open-circuit induced voltage which was important for charge storage for later use occurred with a PUC that had a nonpiezoelectric-to-piezoelectric length ratio greater than unity, whereas the maximum power when the PUC was connected to a resistor for immediate power consumption occurred at a unity nonpiezoelectric-to-piezoelectric length ratio. PMID:21200444
Power flow prediction in vibrating systems via model reduction
NASA Astrophysics Data System (ADS)
Li, Xianhui
This dissertation focuses on power flow prediction in vibrating systems. Reduced order models (ROMs) are built based on rational Krylov model reduction which preserve power flow information in the original systems over a specified frequency band. Stiffness and mass matrices of the ROMs are obtained by projecting the original system matrices onto the subspaces spanned by forced responses. A matrix-free algorithm is designed to construct ROMs directly from the power quantities at selected interpolation frequencies. Strategies for parallel implementation of the algorithm via message passing interface are proposed. The quality of ROMs is iteratively refined according to the error estimate based on residual norms. Band capacity is proposed to provide a priori estimate of the sizes of good quality ROMs. Frequency averaging is recast as ensemble averaging and Cauchy distribution is used to simplify the computation. Besides model reduction for deterministic systems, details of constructing ROMs for parametric and nonparametric random systems are also presented. Case studies have been conducted on testbeds from Harwell-Boeing collections. Input and coupling power flow are computed for the original systems and the ROMs. Good agreement is observed in all cases.
Vibration Energy Harvesting Characterization of 1 cm2 Poly(vinylidene fluoride) Generators in Vacuum
NASA Astrophysics Data System (ADS)
Cao, Ziping; Zhang, Jinya; Kuwano, Hiroki
2011-09-01
In this study, poly(vinylidene fluoride) (PVDF) was used as a piezoelectric element to fabricate small size (two-dimensional area <1 cm2) generators with low resonant frequency (about 100 Hz) for matching the frequency of vibration sources. To clarify the effect of the air damping on the vibration energy harvesting, PVDF generators were investigated in three measurement conditions: unpackaged in air, packaged in air, and unpackaged in vacuum. It was found that the output power of generators unpackaged in vacuum was almost twice that of generators packaged in air at 0.5g acceleration. With the increase in vibration acceleration, the output power of generators unpackaged in vacuum rapidly increased in a quadratic relationship with the acceleration at low acceleration level, and then the increasing ratio decreased at high acceleration. At 4.31g acceleration, the output power reached 100.833 W.
A resonant electromagnetic vibration energy harvester for intelligent wireless sensor systems
NASA Astrophysics Data System (ADS)
Qiu, Jing; Wen, Yumei; Li, Ping; Liu, Xin; Chen, Hengjia; Yang, Jin
2015-05-01
Vibration energy harvesting is now receiving more interest as a means for powering intelligent wireless sensor systems. In this paper, a resonant electromagnetic vibration energy harvester (VEH) employing double cantilever to convert low-frequency vibration energy into electrical energy is presented. The VEH is made up of two cantilever beams, a coil, and magnetic circuits. The electric output performances of the proposed electromagnetic VEH have been investigated. With the enhancement of turns number N, the optimum peak power of electromagnetic VEH increases sharply and the resonance frequency deceases gradually. When the vibration acceleration is 0.5 g, we obtain the optimum output voltage and power of 9.04 V and 50.8 mW at frequency of 14.9 Hz, respectively. In a word, the prototype device was successfully developed and the experimental results exhibit a great enhancement in the output power and bandwidth compared with other traditional electromagnetic VEHs. Remarkably, the proposed resonant electromagnetic VEH have great potential for applying in intelligent wireless sensor systems.
A resonant electromagnetic vibration energy harvester for intelligent wireless sensor systems
Qiu, Jing Wen, Yumei; Li, Ping; Liu, Xin; Chen, Hengjia; Yang, Jin
2015-05-07
Vibration energy harvesting is now receiving more interest as a means for powering intelligent wireless sensor systems. In this paper, a resonant electromagnetic vibration energy harvester (VEH) employing double cantilever to convert low-frequency vibration energy into electrical energy is presented. The VEH is made up of two cantilever beams, a coil, and magnetic circuits. The electric output performances of the proposed electromagnetic VEH have been investigated. With the enhancement of turns number N, the optimum peak power of electromagnetic VEH increases sharply and the resonance frequency deceases gradually. When the vibration acceleration is 0.5 g, we obtain the optimum output voltage and power of 9.04 V and 50.8 mW at frequency of 14.9 Hz, respectively. In a word, the prototype device was successfully developed and the experimental results exhibit a great enhancement in the output power and bandwidth compared with other traditional electromagnetic VEHs. Remarkably, the proposed resonant electromagnetic VEH have great potential for applying in intelligent wireless sensor systems.
Design improvements for an electret-based MEMS vibrational electrostatic energy harvester
NASA Astrophysics Data System (ADS)
Altena, G.; Renaud, M.; Elfrink, R.; Goedbloed, M. H.; de Nooijer, C.; van Schaijk, R.
2013-12-01
This paper presents several improvements to the design of an electret-based MEMS vibrational electrostatic energy harvester that have led to a two orders of magnitude increase in power compared to a previously presented device. The device in this paper has a footprint of approximately 1 cm2 and generated 175 ?W. The following two improvements to the design are discussed: the electrical connection principle of the harvester and the electrode geometrical configuration. The measured performance of the device is compared with simulations. When exited by sinusoidal vibration, a device employing the two design improvements but with a higher resonance frequency and higher electret potential generated 495 ?W AC power, which is the highest reported value for electret-based MEMS vibrational electrostatic energy harvesters with a similar footprint. This makes this device a promising candidate for the targeted application of wireless tire pressure monitoring systems (TPMS).
Dong, Hui; Lewis, Nicholas H. C.; Oliver, Thomas A. A.; Fleming, Graham R.
2015-05-07
Changes in the electronic structure of pigments in protein environments and of polar molecules in solution inevitably induce a re-adaption of molecular nuclear structure. Both changes of electronic and vibrational energies can be probed with visible or infrared lasers, such as two-dimensional electronic spectroscopy or vibrational spectroscopy. The extent to which the two changes are correlated remains elusive. The recent demonstration of two-dimensional electronic-vibrational (2DEV) spectroscopy potentially enables a direct measurement of this correlation experimentally. However, it has hitherto been unclear how to characterize the correlation from the spectra. In this paper, we present a theoretical formalism to demonstrate the slope of the nodal line between the excited state absorption and ground state bleach peaks in the spectra as a characterization of the correlation between electronic and vibrational transition energies. We also show the dynamics of the nodal line slope is correlated to the vibrational spectral dynamics. Additionally, we demonstrate the fundamental 2DEV spectral line-shape of a monomer with newly developed response functions.
NASA Astrophysics Data System (ADS)
Dong, Hui; Lewis, Nicholas H. C.; Oliver, Thomas A. A.; Fleming, Graham R.
2015-05-01
Changes in the electronic structure of pigments in protein environments and of polar molecules in solution inevitably induce a re-adaption of molecular nuclear structure. Both changes of electronic and vibrational energies can be probed with visible or infrared lasers, such as two-dimensional electronic spectroscopy or vibrational spectroscopy. The extent to which the two changes are correlated remains elusive. The recent demonstration of two-dimensional electronic-vibrational (2DEV) spectroscopy potentially enables a direct measurement of this correlation experimentally. However, it has hitherto been unclear how to characterize the correlation from the spectra. In this paper, we present a theoretical formalism to demonstrate the slope of the nodal line between the excited state absorption and ground state bleach peaks in the spectra as a characterization of the correlation between electronic and vibrational transition energies. We also show the dynamics of the nodal line slope is correlated to the vibrational spectral dynamics. Additionally, we demonstrate the fundamental 2DEV spectral line-shape of a monomer with newly developed response functions.
Development and experiments of a micro piezoelectric vibration energy storage device
NASA Astrophysics Data System (ADS)
Chen, Guangzhu; Meng, Qingchun; Fu, Hailing; Bao, Jiusheng
2013-10-01
According to the difficult replacement and poor endurance of the battery for wireless sensor network nodes, a micro piezoelectric vibration energy storage device was developed in this paper. The electric generating performance of the device was then tested on a self-made experimental system. It is shown that the developed energy storage device can collect effectively surrounding vibrations. What is more, the inherent frequency of the device can be expanded by adjusting the span between its two piezoelectric vibrators. It is also found that the output of the device depends badly on the external load resistance. With the increasing of load resistance, the output voltage increases while the output power increases first then decreases. The output power has an optimal associated load resistance. The output power achieves a maximum value 115.2 ?W when the load resistance is 200 k?. With the energy storing circuit, the output electric energy of the device can effectively act as a power source for any low power micro electron devices such as wireless sensor network nodes. It is believed that this work may be practical for energy supplying of the low power micro electron devices.
Spectroscopic probes of vibrationally excited molecules at chemically significant energies
Rizzo, T.R.
1993-12-01
This project involves the application of multiple-resonance spectroscopic techniques for investigating energy transfer and dissociation dynamics of highly vibrationally excited molecules. Two major goals of this work are: (1) to provide information on potential energy surfaces of combustion related molecules at chemically significant energies, and (2) to test theoretical modes of unimolecular dissociation rates critically via quantum-state resolved measurements.
Researche of the Earth's crust structure with powerful vibrational controlled sources
NASA Astrophysics Data System (ADS)
Alekseev, A.; Glinsky, B.; Kovalevsky, V.
2003-04-01
The paper presents the results of experimental researches of the Earth's structure, geodynamic processes and physical phenomena carried out using vibrational sources in Institutes of Siberian Branch RAS. Powerful seismic vibrators are the large mechanical devises and are installed stationary on the vibroseismic test site near Novosibirsk (Russia). The vibro-DSS experiments were carried out on 100 km-long profile from Novosibirsk to Kuzbass region and on 620 km profile between Novosibirsk and Semipalatinsk test site. Specially developed field recording systems based on multichannel three component seismic arrays were used. It allowed us to observe the main crustal waves and waves refracted on Moho boundary. In the experiments on the 620 km profile the comparison of the seismic vibrator and special 100 tons calibration explosion wave fields was made. The possibility to detect small changes of wave velocities by vibroseismic methods were shown in the experiments on the setoff 356 and 430 km, where the relative variations of velocities of seismic waves about 10-5 - 10-6 caused by the Earth's tides deformations of the crust were defined. Some new physical phenomena connected with resonance mechanism of radiation of seismic energy in low-frequency range, the radiation of acoustic waves simultaneously with seismic waves and their interaction on long distances from vibrators were detected.
NASA Technical Reports Server (NTRS)
Mckenzie, R. L.
1976-01-01
A semiclassical collision model is applied to the study of energy transfer rates between a vibrationally excited diatomic molecule and a structureless atom. The molecule is modeled as an anharmonic oscillator with a multitude of dynamically coupled vibrational states. Three main aspects in the prediction of vibrational energy transfer rates are considered. The applicability of the semiclassical model to an anharmonic oscillator is first evaluated for collinear encounters. Second, the collinear semiclassical model is applied to obtain numerical predictions of the vibrational energy transfer rate dependence on the initial vibrational state quantum number. Thermally averaged vibration-translation rate coefficients are predicted and compared with CO-He experimental values for both ground and excited initial states. The numerical model is also used as a basis for evaluating several less complete but analytic models. Third, the role of rational motion in the dynamics of vibrational energy transfer is examined. A three-dimensional semiclassical collision model is constructed with coupled rotational motion included. Energy transfer within the molecule is shown to be dominated by vibration-rotation transitions with small changes in angular momentum. The rates of vibrational energy transfer in molecules with rational frequencies that are very small in comparison to their vibrational frequency are shown to be adequately treated by the preceding collinear models.
NASA Astrophysics Data System (ADS)
Li, Peng; Zhang, Chongxiao; Kim, Junyoung; Yu, Liangyao; Zuo, Lei
2014-04-01
Regenerative semi-active suspensions can capture the previously dissipated vibration energy and convert it to usable electrical energy for powering on-board electronic devices, while achieve both the better ride comfort and improved road handling performance at the same time when certain control is applied. To achieve this objective, the power electronics interface circuit connecting the energy harvester and the electrical loads, which can perform simultaneous vibration control and energy harvesting function is in need. This paper utilized a buck-boost converter for simultaneous semi-active vibration control and energy harvesting with electromagnetic regenerative shock absorber, which utilizes a rotational generator to converter the vibration energy to electricity. It has been found that when the circuit works in discontinuous current mode (DCM), the ratio between the input voltage and current is only related to the duty cycle of the switch pulse width modulation signal. Using this property, the buck-boost converter can be used to perform semi-active vibration control by controlling the load connected between the terminals of the generator in the electromagnetic shock absorber. While performing the vibration control, the circuit always draw current from the shock absorber and the suspension remain dissipative, and the shock absorber takes no additional energy to perform the vibration control. The working principle and dynamics of the circuit has been analyzed and simulations were performed to validate the concept.
Heavy atom vibrational modes and low-energy vibrational autodetachment in nitromethane anions
Thompson, Michael C.; Weber, J. Mathias; Baraban, Joshua H.; Matthews, Devin A.; Stanton, John F.
2015-06-21
We report infrared spectra of nitromethane anion, CH{sub 3}NO{sub 2}{sup −}, in the region 700–2150 cm{sup −1}, obtained by Ar predissociation spectroscopy and electron detachment spectroscopy. The data are interpreted in the framework of second-order vibrational perturbation theory based on coupled-cluster electronic structure calculations. The modes in the spectroscopic region studied here are mainly based on vibrations involving the heavier atoms; this work complements earlier studies on nitromethane anion that focused on the CH stretching region of the spectrum. Electron detachment begins at photon energies far below the adiabatic electron affinity due to thermal population of excited vibrational states.
A low frequency vibration energy harvester using dual Halbach array suspended in magnetic springs
NASA Astrophysics Data System (ADS)
Salauddin, M.; Halim, M. A.; Park, J. Y.
2015-12-01
An electromagnetic (EM) low frequency vibration energy harvester is newly developed based on dual Halbach array which is suspended in two magnetic springs. Each Halbach array concentrates the magnetic flux lines on one side of the array while suppressing the flux lines on the other side. Dual Halbach array allows the concentrated magnetic flux lines to interact with the same coil in a way where maximum flux linkage occurs. With the goal of higher power generation in low amplitude and low frequency vibrations, the magnetic structures (both the dual Halbach array and the magnetic springs) were optimized in terms of operating frequency and power density. A prototype was fabricated and tested. It is capable of delivering maximum 1.09mW average power to 44? optimum load at 11Hz resonant frequency and 0.5g acceleration. The prototype device offers 33.4?Wcm-3 average power density which is much higher than recently reported electromagnetic energy harvesters.
Pradhan, G. B.; Juanes-Marcos, J. C.; Balakrishnan, N.; Kendrick, Brian K.
2013-11-21
Quantum scattering calculations are reported for state-to-state vibrational relaxation and reactive scattering in O + OH(v = 2 ? 3, j = 0) collisions on the electronically adiabatic ground state {sup 2}A?? potential energy surface of the HO{sub 2} molecule. The time-independent Schrdinger equation in hyperspherical coordinates is solved to determine energy dependent probabilities and cross sections over collision energies ranging from ultracold to 0.35 eV and for total angular momentum quantum number J = 0. A J-shifting approximation is then used to compute initial state selected reactive rate coefficients in the temperature range T = 1 ? 400 K. Results are found to be in reasonable agreement with available quasiclassical trajectory calculations. Results indicate that rate coefficients for O{sub 2} formation increase with increasing the OH vibrational level except at low and ultralow temperatures where OH(v = 0) exhibits a slightly different trend. It is found that vibrational relaxation of OH in v = 2 and v = 3 vibrational levels is dominated by a multi-quantum process.
NASA Astrophysics Data System (ADS)
Pradhan, G. B.; Juanes-Marcos, J. C.; Balakrishnan, N.; Kendrick, Brian K.
2013-11-01
Quantum scattering calculations are reported for state-to-state vibrational relaxation and reactive scattering in O + OH(v = 2 - 3, j = 0) collisions on the electronically adiabatic ground state 2A'' potential energy surface of the HO2 molecule. The time-independent Schrdinger equation in hyperspherical coordinates is solved to determine energy dependent probabilities and cross sections over collision energies ranging from ultracold to 0.35 eV and for total angular momentum quantum number J = 0. A J-shifting approximation is then used to compute initial state selected reactive rate coefficients in the temperature range T = 1 - 400 K. Results are found to be in reasonable agreement with available quasiclassical trajectory calculations. Results indicate that rate coefficients for O2 formation increase with increasing the OH vibrational level except at low and ultralow temperatures where OH(v = 0) exhibits a slightly different trend. It is found that vibrational relaxation of OH in v = 2 and v = 3 vibrational levels is dominated by a multi-quantum process.
NASA Astrophysics Data System (ADS)
Gruenbaum, S. M.; Skinner, J. L.
2013-11-01
Water clustering and connectivity around lipid bilayers strongly influences the properties of membranes and is important for functions such as proton and ion transport. Vibrational anisotropic pump-probe spectroscopy is a powerful tool for understanding such clustering, as the measured anisotropy depends upon the time-scale and degree of intra- and intermolecular vibrational energy transfer. In this article, we use molecular dynamics simulations and theoretical vibrational spectroscopy to help interpret recent experimental measurements of the anisotropy of water in lipid multi-bilayers as a function of both lipid hydration level and isotopic substitution. Our calculations are in satisfactory agreement with the experiments of Piatkowski, Heij, and Bakker, and from our simulations we can directly probe water clustering and connectivity. We find that at low hydration levels, many water molecules are in fact isolated, although up to 70% of hydration water forms small water clusters or chains. At intermediate hydration levels, water forms a wide range of cluster sizes, while at higher hydration levels, the majority of water molecules are part of a large, percolating water cluster. Therefore, the size, number, and nature of water clusters are strongly dependent on lipid hydration level, and the measured anisotropy reflects this through its dependence on intermolecular energy transfer.
Absorption of Energy during Whole-Body Vibration Exposure
NASA Astrophysics Data System (ADS)
Lundstrm, R.; Holmlund, P.
1998-08-01
Absorbed power,PAbs, during exposure to vertical and horizontal whole-body vibration in sitting posture was measured using 15 male and 15 female subjects. Different experimental conditions were applied, such as vibration level (025-14 m/s2), frequency (113-80 Hz), body weight (54-93 kg), relaxed and erect upper body posture. Results show thatPAbswas strongly related to frequency of the vibration peaking, within the range of 4-6 Hz and below 25 Hz for vertical and horizontal directions respectively.PAbsincreased with acceleration level and body weight. If risk assessment is based on the assumption that the amount ofPAbs, independence of the frequency of the vibration, indicates a hazard, then the frequency weighting procedure in ISO-standard 2631 can be questioned. The ISO weighting for horizontal vibration seems to underestimate the risk for frequencies within the range of about 15-3 Hz and overestimate them above about 5 Hz. For the vertical direction the frequency weighting overestimates the risk for frequencies above about 6 Hz. The results also indicate a need for differential guidelines for females and males. Many types of vehicle produce whole-body vibration with frequencies in the range where the highestPAbswas observed. Although not yet thoroughly evaluated,PAbsmay be a better quantity for risk assessment than acceleration as specified in ISO 2631, since it also takes into account the dynamic force applied to the human body.
NASA Astrophysics Data System (ADS)
Bibo, A.; Daqaq, M. F.
2013-06-01
In this letter, a single vibratory energy harvester integrated with an airfoil is proposed to concurrently harness energy from ambient vibrations and wind. In terms of its transduction capabilities and power density, the integrated device is shown to have a superior performance under the combined loading when compared to utilizing two separate devices to harvest energy independently from the two available energy sources. Even below its flutter speed, the proposed device was able to provide 2.5 times the power obtained using two separate harvesters.
NASA Astrophysics Data System (ADS)
Zhao, Nian; Yang, Jin; Yu, Qiangmo; Zhao, Jiangxin; Liu, Jun; Wen, Yumei; Li, Ping
2016-01-01
This work has demonstrated a novel piezoelectric energy harvester without a complex structure and appended component that is capable of scavenging vibration energy from arbitrary directions with multiple resonant frequencies. In this harvester, a spiral-shaped elastic thin beam instead of a traditional thin cantilever beam was adopted to absorb external vibration with arbitrary direction in three-dimensional (3D) spaces owing to its ability to bend flexibly and stretch along arbitrary direction. Furthermore, multiple modes in the elastic thin beam contribute to a possibility to widen the working bandwidth with multiple resonant frequencies. The experimental results show that the harvester was capable of scavenging the vibration energy in 3D arbitrary directions; they also exhibited triple power peaks at about 16 Hz, 21 Hz, and 28 Hz with the powers of 330 μW, 313 μW, and 6 μW, respectively. In addition, human walking and water wave energies were successfully converted into electricity, proving that our harvester was practical to scavenge the time-variant or multi-directional vibration energies in our daily life.
Zhao, Nian; Yang, Jin; Yu, Qiangmo; Zhao, Jiangxin; Liu, Jun; Wen, Yumei; Li, Ping
2016-01-01
This work has demonstrated a novel piezoelectric energy harvester without a complex structure and appended component that is capable of scavenging vibration energy from arbitrary directions with multiple resonant frequencies. In this harvester, a spiral-shaped elastic thin beam instead of a traditional thin cantilever beam was adopted to absorb external vibration with arbitrary direction in three-dimensional (3D) spaces owing to its ability to bend flexibly and stretch along arbitrary direction. Furthermore, multiple modes in the elastic thin beam contribute to a possibility to widen the working bandwidth with multiple resonant frequencies. The experimental results show that the harvester was capable of scavenging the vibration energy in 3D arbitrary directions; they also exhibited triple power peaks at about 16 Hz, 21 Hz, and 28 Hz with the powers of 330 μW, 313 μW, and 6 μW, respectively. In addition, human walking and water wave energies were successfully converted into electricity, proving that our harvester was practical to scavenge the time-variant or multi-directional vibration energies in our daily life. PMID:26827346
Efficiency of Collisional O2 + N2 Vibrational Energy Exchange.
Garcia, E; Kurnosov, A; Lagan, A; Pirani, F; Bartolomei, M; Cacciatore, M
2016-03-01
By following the scheme of the Grid Empowered Molecular Simulator (GEMS), a new O2 + N2 intermolecular potential, built on ab initio calculations and experimental (scattering and second virial coefficient) data, has been coupled with an appropriate intramolecular one. On the resulting potential energy surface detailed rate coefficients for collision induced vibrational energy exchanges have been computed using a semiclassical method. A cross comparison of the computed rate coefficients with the outcomes of previous semiclassical calculations and kinetic experiments has provided a foundation for characterizing the main features of the vibrational energy transfer processes of the title system as well as a critical reading of the trajectory outcomes and kinetic data. On the implemented procedures massive trajectory runs for the proper interval of initial conditions have singled out structures of the vibrational distributions useful to formulate scaling relationships for complex molecular simulations. PMID:26292835
Low Head, Vortex Induced Vibrations River Energy Converter
Bernitsas, Michael B.; Dritz, Tad
2006-06-30
Vortex Induced Vibrations Aquatic Clean Energy (VIVACE) is a novel, demonstrated approach to extracting energy from water currents. This invention is based on a phenomenon called Vortex Induced Vibrations (VIV), which was first observed by Leonardo da Vinci in 1504AD. He called it ‘Aeolian Tones.’ For decades, engineers have attempted to prevent this type of vibration from damaging structures, such as offshore platforms, nuclear fuel rods, cables, buildings, and bridges. The underlying concept of the VIVACE Converter is the following: Strengthen rather than spoil vortex shedding; enhance rather than suppress VIV; harness rather than mitigate VIV energy. By maximizing and utilizing this unique phenomenon, VIVACE takes this “problem” and successfully transforms it into a valuable resource for mankind.
Apparent Mass and Absorbed Power during Exposure to Whole-Body Vibration and Repeated Shocks
NASA Astrophysics Data System (ADS)
MANSFIELD, N. J.; HOLMLUND, P.; LUNDSTRM, R.
2001-11-01
Exposure to mechanical shocks might pose a greater health risk than exposure to continuous vibration. Previous studies have investigated subjective responses, muscle activity or transmission of vibration to the spine or head during shock. If there is a difference between biomechanic responses of the seated body to shocks when compared to continuous vibration, then this may indicate a more, or less, hazardous vibration waveform. This paper presents measurements of apparent mass and absorbed power during exposure to random vibration, repeated shocks and combinations of shocks and random vibration. Eleven male and 13 female subjects were exposed to 15 vibration conditions generated using an electro-dynamic shaker. Subjects were exposed to five 20 s acceleration waveforms with nominally identical power spectra (random vibration, equally spaced shocks, unequally spaced shocks, random combined with equally spaced shocks, random combined with unequally spaced shocks) at each of 05, 10 and 15 m/s2r.m.s. The general shapes of the apparent mass or absorbed power curves were not affected by stimulus type, indicating that the biomechanical response of the body is fundamentally the same when exposed to shocks or random vibration. Two non-linear effects were observed: apparent mass resonance frequencies were slightly higher for exposure to shocks; apparent mass and absorbed power resonance frequencies decreased with increases in vibration magnitude for each stimulus type. It is concluded that the two non-linear mechanisms operate simultaneously: a stiffening effect during exposure to shocks and a softening effect as vibration magnitudes increase. Total absorbed powers were greatest for shock stimuli and least for random vibration.
NASA Astrophysics Data System (ADS)
Hirata, Yoshinori; Okada, Tadashi
1991-12-01
Biphenylene in various solvents is investigated by picosecond time-resolved absorption spectroscopy. The time dependence of the spectral shape of the vibrationally hot S n?S 1 absorption was analyzed by using the Urbach relation. Vibrational energy flow to the solvent molecules in the surroundings from the higher vibrational state of S 1 was proportional to the excess vibrational energy.
Optimization design of high power ultrasonic circular ring radiator in coupled vibration.
Xu, Long; Lin, Shuyu; Hu, Wenxu
2011-10-01
This paper presents a new high power ultrasonic (HPU) radiator, which consists of a transducer, an ultrasonic horn, and a metal circular ring. Both the transducer and horn in longitudinal vibrations are used to drive a metal circular ring in a radial-axial coupled vibration. This coupled vibration cannot only generate ultrasound in both the radial and axial directions, but also focus the ultrasound inside the circular ring. Except for the radial-axial coupled vibration mode, the third longitudinal harmonic vibration mode with relative large vibration amplitude is also detected, which can be used as another operation mode. Overall, the HPU with these two vibration modes should have good potential to be applied in liquid processing, such as sonochemistry, ultrasonic cleaning, and Chinese herbal medicine extraction. PMID:21529873
NASA Astrophysics Data System (ADS)
Galchev, Tzeno; McCullagh, James; Peterson, Rebecca L.; Najafi, Khalil; Mortazawi, Amir
2011-04-01
To power distributed wireless sensor networks on bridges, traditional power cables or battery replacement are excessively expensive or infeasible. This project develops two power harvesting technologies. First, a novel parametric frequency-increased generator (PFIG) is developed. The fabricated PFIG harvests the non-periodic and unprecedentedly low frequency (DC to 30 Hz) and low acceleration (0.55-9.8 m/s2) mechanical energy available on bridges with an average power > 2 ?W. Prototype power conversion and storage electronics were designed and the harvester system was used to charge a capacitor from arbitrary bridge-like vibrations. Second, an RF scavenger operating at medium and shortwave frequencies has been designed and tested. Power scavenging at MHz frequencies allows for lower antenna directivities, reducing sensitivity to antenna positioning. Furthermore, ambient RF signals at these frequencies have higher power levels away from cities and residential areas compared to the UHF and SHF bands utilized for cellular communication systems. An RF power scavenger operating at 1 MHz along with power management and storage circuitry has been demonstrated. It powers a LED at a distance of 10 km from AM radio stations.
NASA Astrophysics Data System (ADS)
Lumentut, M. F.; Howard, I. M.
2013-03-01
Power harvesters that extract energy from vibrating systems via piezoelectric transduction show strong potential for powering smart wireless sensor devices in applications of health condition monitoring of rotating machinery and structures. This paper presents an analytical method for modelling an electromechanical piezoelectric bimorph beam with tip mass under two input base transverse and longitudinal excitations. The Euler-Bernoulli beam equations were used to model the piezoelectric bimorph beam. The polarity-electric field of the piezoelectric element is excited by the strain field caused by base input excitation, resulting in electrical charge. The governing electromechanical dynamic equations were derived analytically using the weak form of the Hamiltonian principle to obtain the constitutive equations. Three constitutive electromechanical dynamic equations based on independent coefficients of virtual displacement vectors were formulated and then further modelled using the normalised Ritz eigenfunction series. The electromechanical formulations include both the series and parallel connections of the piezoelectric bimorph. The multi-mode frequency response functions (FRFs) under varying electrical load resistance were formulated using Laplace transformation for the multi-input mechanical vibrations to provide the multi-output dynamic displacement, velocity, voltage, current and power. The experimental and theoretical validations reduced for the single mode system were shown to provide reasonable predictions. The model results from polar base excitation for off-axis input motions were validated with experimental results showing the change to the electrical power frequency response amplitude as a function of excitation angle, with relevance for practical implementation.
NASA Astrophysics Data System (ADS)
Choi, Yunhee; Ju, Suna; Chae, Song Hee; Jun, Sangbeom; Ji, Chang-Hyeon
2015-06-01
This paper presents a vibration energy harvester using a springless spherical permanent magnet with a non-uniform mass distribution as a proof mass. The magnet has been designed to have the center of mass below the geometrical center, which generates a roly-poly-like motion in response to external vibrations and maintains the upright position. Utilizing this roly-poly-like magnet, proof-of-concept electromagnetic energy harvesters have been fabricated, tested and analyzed. An analytical model which explains the motion of the magnet assembly and resulting output voltage has been developed by finite element analysis of the magnetic field distribution and motion analysis of the magnet assembly. With the fabricated device, a maximum open-circuit voltage of 48.85 mVrms and an output power of 9.03 ?W have been obtained in response to a 20 Hz sinusoidal vibration at 3 g acceleration.
NASA Astrophysics Data System (ADS)
McDowell, Derek Ray
1997-09-01
Collisional energy removal rates from vibrationally excited T1 pyrazine are measured using the refined and validated Competitive Radiationless Decay (CRD) method. Optical excitation followed by intersystem crossing prepares a vibrationally excited vapor sample of T1 pyrazine. Tn/gets T1 transient absorption kinetics, measured with a S/N ratio of ca. 1000, provides the collisional dependence of the average triplet radiationless decay rate constant. Using a calibration between this decay constant and the triplet vibrational energy, the collisional history of the sample's vibrational energy content is deduced. This leads to the rate of collisional energy removal as a function of the triplet pyrazine's vibrational energy content. Results with a variety of small relaxers comprise the most useful database to date on collisional vibrational relaxation of a triplet state polyatomic. We find the following order of relaxer effectiveness per collision: He[<]H2[<]Ne[<]D2[<]Ar[<]N2[<]Kr[<]Xe[<]CO[<]CH4[<]CO2[<]H2OThese triplet state energy removal rates exceed those recently reported for vibrationally excited ground state pyrazine by a factor of ca. 7. In addition, a new method for determining the distribution of vibrational energy contents in an excited polyatomic sample is applied to vibrationally excited T1 pyrazine. The T1 population decays with a distribution of rate constants corresponding to the underlying distribution of vibrational energies. This rate constant distribution is extracted from decay kinetics through the use of a multi-Gaussian distribution model. The calibration between decay constant and triplet vibrational energy is used to deduce the molecular vibrational energy distribution, providing the first experimental view of an excited sample's vibrational energy distribution. Relatively narrow nascent vibrational energy distributions are progressively broadened during the early collisional encounters with a relaxer. These new vibrational energy distributions and the collisional energy removal results suggests a threshold for enhanced relaxation near 2000 cm-1 of donor vibrational energy. These intriguing results should stimulate further theoretical and experimental research into the collisional relaxation of electronically excited molecules.
Coupled analysis of multi-impact energy harvesting from low-frequency wind induced vibrations
NASA Astrophysics Data System (ADS)
Zhu, Jin; Zhang, Wei
2015-04-01
Energy need from off-grid locations has been critical for effective real-time monitoring and control to ensure structural safety and reliability. To harvest energy from ambient environments, the piezoelectric-based energy-harvesting system has been proven very efficient to convert high frequency vibrations into usable electrical energy. However, due to the low frequency nature of the vibrations of civil infrastructures, such as those induced from vehicle impacts, wind, and waves, the application of a traditional piezoelectric-based energy-harvesting system is greatly restrained since the output power drops dramatically with the reduction of vibration frequencies. This paper focuses on the coupled analysis of a proposed piezoelectric multi-impact wind-energy-harvesting device that can effectively up-convert low frequency wind-induced vibrations into high frequency ones. The device consists of an H-shape beam and four bimorph piezoelectric cantilever beams. The H-shape beam, which can be easily triggered to vibrate at a low wind speed, is originated from the first Tacoma Narrows Bridge, which failed at wind speeds of 18.8 m s-1 in 1940. The multi-impact mechanism between the H-shape beam and the bimorph piezoelectric cantilever beams is incorporated to improve the harvesting performance at lower frequencies. During the multi-impact process, a series of sequential impacts between the H-shape beam and the cantilever beams can trigger high frequency vibrations of the cantilever beams and result in high output power with a considerably high efficiency. In the coupled analysis, the coupled structural, aerodynamic, and electrical equations are solved to obtain the dynamic response and the power output of the proposed harvesting device. A parametric study for several parameters in the coupled analysis framework is carried out including the external resistance, wind speed, and the configuration of the H-shape beam. The average harvested power for the piezoelectric cantilever beam reaches 11.77 mW with a power density of 6.11 mW cm-3 under the wind speed of 10 m s-1, which is sufficient to power small sensors. The average harvested power can further reach up to 45 mW under the wind speed of 14 m s-1.
Delayed-feedback vibration absorbers to enhance energy harvesting
NASA Astrophysics Data System (ADS)
Kammer, Ayhan S.; Olgac, Nejat
2016-02-01
Recovering energy from ambient vibrations has recently been a popular research topic. This article is conceived as a concept study that explores new directions to enhance the performance of such energy harvesting devices from base excitation. The main idea revolves around the introduction of delayed feedback sensitization (or tuning) of an active vibration absorber setup. To clarify the concept, the Delayed Resonator theory is reviewed and its suitability for energy harvesting purposes is studied. It is recognized that an actively tuned and purely resonant absorber is infeasible for such applications. The focus is then shifted to alternative tuning schemes that deviate from resonance conditions. Also called Delayed Feedback Vibration Absorbers, these devices may indeed provide significant enhancements in energy harvesting capacity. Analytical developments are presented to study energy generation and consumption characteristics. Effects of excitation frequency and absorber damping are investigated. The influences of time-delayed feedback on the stability and the transient performance of the system are also treated. The analysis starts from a stand-alone absorber, emulating seismic mass type harvesters. The work is then extended to vibration control applications, where an absorber/harvester is coupled with a primary structure. The results are demonstrated with numerical simulations on a case study.
A two-dimensional broadband vibration energy harvester using magnetoelectric transducer
Yang, Jin Wen, Yumei; Li, Ping; Yue, Xihai; Yu, Qiangmo; Bai, Xiaoling
2013-12-09
In this study, a magnetoelectric vibration energy harvester was demonstrated, which aims at addressing the limitations of the existing approaches in single dimensional operation with narrow working bandwidth. A circular cross-section cantilever rod, not a conventional thin cantilever beam, was adopted to extract vibration energy in arbitrary in-plane motion directions. The magnetic interaction not only resulted in a nonlinear motion of the rod with increased frequency bandwidth, but also contributed to a multi-mode motion to exhibit double power peaks. In energy harvesting with in-plane directions, it showed a maximum bandwidth of 4.4 Hz and power of 0.59 mW, with acceleration of 0.6 g (with g = 9.8 m s{sup −2})
Characterization of a water pump for drum-type washing machine by vibration power approach
NASA Astrophysics Data System (ADS)
Heo, YongHwa; Kim, Kwang-joon
2015-03-01
Water pumps used in drum-type washing machines to save water are likely to make the washing process noisier than the one without those because the water pumps attached usually onto cabinet structure work as additional vibration and noise sources. In order to either counteract such vibration and noise problems by stiffness design of the cabinet structure or classify the water pumps from the view point of an acceptance test, characterization of the water pumps as excitation sources would be essential. In this paper, several methods to characterize a water pump as an excitation source are investigated. Measurements by traditional methods of blocked force and/or free velocity for a water pump of 35 W are presented. Two methods of vibration power suggested rather recently are reviewed. Then, another method of the vibration power is proposed. Estimations of the vibration power for the water pump operating on a beam structure are obtained and discussed comparatively.
NASA Astrophysics Data System (ADS)
Alamin Dow, Ali B.; Al-Rubaye, Hasan A.; Koo, David; Schneider, Michael; Bittner, Achim; Schmid, Ulrich; Kherani, Nazir P.
2011-06-01
Piezoelectric energy microgenerators are devices that continuously generate electricity when they are subjected to varying mechanical strain due to vibrations. They can generate electrical power up to 100 ?W which can be used to drive various sensing and actuating MEMS devices. Today, piezoelectric energy harvesters are considered autonomous and reliable energy sources to actuate low power microdevices such as wireless sensor networks, indoor-outdoor monitoring, facility management and biomedical applications. The advantages of piezoelectric energy harvesters including high power density, moderate output power and CMOS compatible fabrication in particular with aluminum nitride (AlN) have fuelled and motivated researchers to develop MEMS based energy harvesters. Recently, the use of AlN as a piezoelectric material has increased fabrication compatibility, enabling the realization of smart integrated systems on chip which include sensors, actuators and energy storage. Piezoelectric MEMS energy microgenerator is used to capture and transform the available ambient mechanical vibrations into usable electric energy via resonant coupling in the thin film piezoelectric material. Analysis and modeling of piezoelectric energy generators are very important aspects for improved performance. Aluminum nitride as the piezoelectric material is sandwiched between two electrodes. The device design includes a silicon cantilever on which the AlN film is deposited and which features a seismic mass at the end of the cantilever. Beam theory and lumped modeling with circuit elements are applied for modeling and analysis of the device operation at various acceleration values. The model shows good agreement with the experimental findings, thus giving confidence in the model.
DEAP-based energy harvesting using vortex-induced vibrations
NASA Astrophysics Data System (ADS)
Hoffstadt, Thorben; Heinze, Robert; Wahl, Tim; Kameier, Frank; Maas, Jürgen
2014-03-01
Generators based on dielectric electroactive polymers (DEAP) convert mechanical strain energy into electrical field energy. In order to harvest renewable energy from ambient sources adequate generator setups have to be developed. Thus, in this contribution a DEAP generator is presented which uses periodic vortex induced vibration of a circular cylinder as excitation mechanism, by which e.g. Flow energy of a wind or water current can be converted. For this purpose a novel generator design consisting of a cylinder that is elastically mounted on DEAP material is presented. Since the effect of vortex induced vibrations depends on the stiffness and damping of the utilized generator's eigenmode, a method to adapt both via the electrostatic pressure and energy conversion is proposed. After the validation of the general functionality of the novel generator design, analyses concerning the control of the overall harvester are carried out.
NASA Technical Reports Server (NTRS)
Inoue, Katsumi; Krantz, Timothy L.
1995-01-01
While the vibration analysis of gear systems has been developed, a systematic approach to the reduction of gearbox vibration has been lacking. The technique of reducing vibration by shifting natural frequencies is proposed here for gearboxes and other thin-plate structures using the theories of finite elements, modal analysis, and optimization. A triangular shell element with 18 degrees of freedom is developed for structural and dynamic analysis. To optimize, the overall vibration energy is adopted as the objective function to be minimized at the excitation frequency by varying the design variable (element thickness) under the constraint of overall constant weight. Modal analysis is used to determine the sensitivity of the vibration energy as a function of the eigenvalues and eigenvectors. The optimum design is found by the gradient projection method and a unidimensional search procedure. By applying the computer code to design problems for beams and plates, it was verified that the proposed method is effective in reducing vibration energy. The computer code is also applied to redesign the NASA Lewis gear noise rig test gearbox housing. As one example, only the shape of the top plate is varied, and the vibration energy levels of all the surfaces are reduced, yielding an overall reduction of 1/5 compared to the initial design. As a second example, the shapes of the top and two side plates are varied to yield an overall reduction in vibration energy of 1/30.
Tunable Vibration Energy Harvester for Condition Monitoring of Maritime Gearboxes
NASA Astrophysics Data System (ADS)
Hoffmann, D.; Willmann, A.; Folkmer, B.; Manoli, Y.
2014-11-01
This paper reports on a new tuning concept, which enables the operation of a vibration generator for energy autonomous condition monitoring of maritime gearboxes. The tuning concept incorporates a circular tuning magnet, which interacts with a coupling magnet attached to the active transducer element. The tuning range can be tailored to the application by careful design of the gap between tuning magnet and coupling magnet. A total rotation angle of only 180° is required for the tuning magnet in order to obtain the full frequency bandwidth. The tuning concept is successfully demonstrated by charging a 0.6 F capacitor on the basis of physical vibration profiles taken from a gearbox.
Comparison of theoretical methods for resonant vibration-vibration energy transfer in liquids
NASA Astrophysics Data System (ADS)
Dodaro, Frank A.; Herman, Michael F.
1998-02-01
The problem of resonant vibration-vibration (V-V) energy transfer in liquids is explored within a simple model in order to compare two calculational methods. Two bromine diatomics are constrained to move between two fixed argon solvent atoms in one dimension. The time-dependent probability for the transfer of a vibrational excitation between the bromine diatomics is computed semiclassically. The results of single-trajectory molecular dynamics methods are compared with those of multiple-trajectory surface hopping methods. It is found that the two methods give similar results, indicating that the simpler single-trajectory method adequately describes the resonant V to V transfer process. The proximity of the nearly degenerate potential energy surfaces leads to a phase coherence time that exceeds the time required for the transition probability to saturate for this model. As a result, the transition probability remains a nonlinear function of time, and this precludes the extraction of a rate constant from the slope of the resonant V-V transition probability curve for this simple one-dimensional model.
Minimization of the vibration energy of thin-plate structure
NASA Technical Reports Server (NTRS)
Inoue, Katsumi; Townsend, Dennis P.; Coy, John J.
1992-01-01
An optimization method is proposed to reduce the vibration of thin plate structures. The method is based on a finite element shell analysis, a modal analysis, and a structural optimization method. In the finite element analysis, a triangular shell element with 18 dof is used. In the optimization, the overall vibration energy of the structure is adopted as the objective function, and it is minimized at the given exciting frequency by varying the thickness of the elements. The technique of modal analysis is used to derive the sensitivity of the vibration energy with respect to the design variables. The sensitivity is represented by the sensitivities of both eigenvalues and eigenvectors. The optimum value is computed by the gradient projection method and a unidimensional search procedure under the constraint condition of constant weight. A computer code, based on the proposed method, is developed and is applied to design problems using a beam and a plate as test cases. It is confirmed that the vibration energy is reduced at the given exciting frequency. For the beam excited by a frequency slightly less than the fundamental natural frequency, the optimized shape is close to the beam of uniform strength.
Electron energy transfer rates for vibrational excitation of N2.
Campbell, L.; Cartwright, D. C.; Tuebner, P. J. O.; Brunger, M. J.
2003-01-01
The calculation of the electron density and electron temperature distribution in our ionosphere (from {approx} 150-600 km) requires a knowledge of the various heating, cooling and energy flow processes that occur. The energy transfer from electrons to neutral gases and ions is one of the dominant electron cooling processes in the ionosphere, and the role of vibrationally excited N2 in this is particularly significant.
NASA Astrophysics Data System (ADS)
Renaud, M.; Fujita, T.; Goedbloed, M.; de Nooijer, C.; van Schaijk, R.
2014-11-01
Current commercial wireless tire pressure monitoring systems (TPMS) require a battery as electrical power source. The battery limits the lifetime of the TPMS. This limit can be circumvented by replacing the battery by a vibration energy harvester. Autonomous wireless TPMS powered by MEMS electret based vibration energy harvester have been demonstrated. A remaining technical challenge to attain the grade of commercial product with these autonomous TPMS is the mechanical reliability of the MEMS harvester. It should survive the harsh conditions imposed by the tire environment, particularly in terms of mechanical shocks. As shown in this article, our first generation of harvesters has a shock resilience of 400 g, which is far from being sufficient for the targeted application. In order to improve this aspect, several types of shock absorbing structures are investigated. With the best proposed solution, the shock resilience of the harvesters is brought above 2500 g.
Optimization of piezoelectric bistable composite plates for broadband vibrational energy harvesting
NASA Astrophysics Data System (ADS)
Betts, David N.; Kim, H. Alicia; Bowen, Christopher R.; Inman, Daniel J.
2012-04-01
This paper presents a unique arrangement of bistable composite plates with piezoelectric patches bonded to its surface to perform broadband vibration-based energy harvesting from ambient mechanical vibrations. These bistable nonlinear devices have been shown to have improved power generation compared to conventional resonant systems and can be designed to occupy smaller volumes than bistable magnetic cantilever systems. This paper presents the results of an optimization study of bistable composites that are capable of generating greater electrical power from a smaller space by discovering the correct geometric configuration for energy harvesting. Optimum solutions are investigated in a series of design parameter studies intended to reveal the complex interactions of the physical constraints and design requirements. The proposed approach considers the optimal choice of device aspect ratio, thickness, laminate stacking sequence, and piezoelectric surface area. Increased electrical output is found for geometries and piezoelectric configurations which have not been considered previously.
NASA Astrophysics Data System (ADS)
MANSFIELD, N. J.; HOLMLUND, P.; LUNDSTRM, R.
2000-02-01
Evaluation of human exposure whole-body vibration (WBV) and shock can be carried out in a variety of ways. The most commonly used standards for predicting discomfort from WBV are BS6841 (1987) and ISO2631-1 (1997) which offer different frequency weightings (Wband Wk) and three methods of assessment: vibration dose value (VDV), estimated VDV (eVDV) and maximum transient vibration value (MTVV). Previous studies have also used DRI and absorbed power for assessments of shock and WBV. This paper reports a laboratory study in which 24 human subjects were exposed to 15 vertical vibration stimuli comprising of random vibration, repeated shocks and combinations of random vibration and shocks at 05, 10 and 15 m/s2r.m.s. Subjects rated the discomfort from the vibration on a numerical scale after each exposure. Acquired acceleration signals were analyzed using VDV, r.m.s. and MTVV for unweighted,Wb , Wkand DRI weighted signals. Acceleration and force were combined to give a measure of absorbed power. Subjective responses were correlated to vibration magnitude for the 13 analysis types. VDV was the best standard method of assessment; MTVV was the worst. Wband Wkfrequency weightings showed slightly greater correlations between vibration magnitude and discomfort than DRI weighted or unweighted signals. For VDV, there were no significant differences between the correlations obtained using any frequency weighting. For assessment of all stimuli types together, absorbed power gave higher correlations with subjective discomfort than acceleration-based methods. It is concluded that the methods described in ISO2631-1 should be clarified and simplified. Due to the difficulty in measuring absorbed power in the field, methods proposed in BS6841 are recommended as the most appropriate for assessment of discomfort from continuous vibration or repeated shocks.
NASA Astrophysics Data System (ADS)
Halim, Miah A.; Park, Jae Y.
2014-03-01
We present a non-resonant, frequency up-converted electromagnetic energy harvester that generates significant power from human-body-induced vibration, e.g., hand-shaking. Upon excitation, a freely movable non-magnetic ball within a cylinder periodically hits two magnets suspended on two helical compression springs located at either ends of the cylinder, allowing those to vibrate with higher frequencies. The device parameters have been designed based on the characteristics of human hand-shaking vibration. A prototype has been developed and tested both by vibration exciter (for non-resonance test) and by manual hand-shaking. The fabricated device generated 110 ?W average power with 15.4 ?W cm-3 average power density, while the energy harvester was mounted on a smart phone and was hand-shaken, indicating its ability in powering portable hand-held smart devices from low frequency (<5 Hz) vibrations.
A Branched Beam-Based Vibration Energy Harvester
NASA Astrophysics Data System (ADS)
Zhang, Guangcheng; Hu, Junhui
2014-11-01
In this paper, a strategy to utilize a branched beam system to improve the frequency response characteristic of vibration energy harvesting is demonstrated. A basic unit of the device consists of several branch beams with proof mass at their ends and one main cantilever beam with a piezoelectric component at its root and proof mass at its end. The device can utilize the resonance of the branch beams and main beam to generate multiple output voltage peaks, providing a better frequency response characteristic than that of the conventional piezoelectric vibration energy harvester. Multiple branch structure and multiple basic units with similar structures can be connected to generate more output voltage peaks in the frequency response characteristic. Only one piezoelectric component is needed in the device, which makes it competitive in the management of harvested electric energy.
NASA Astrophysics Data System (ADS)
Kongsted, Jacob; Christiansen, Ove
2006-09-01
An automatic and general procedure for the calculation of geometrical derivatives of the energy and general property surfaces for molecular systems is developed and implemented. General expressions for an n-mode representation are derived, where the n-mode representation includes only the couplings between n or less degrees of freedom. The general expressions are specialized to derivative force fields and property surfaces, and a scheme for calculation of the numerical derivatives is implemented. The implementation is interfaced to electronic structure programs and may be used for both ground and excited electronic states. The implementation is done in the context of a vibrational structure program and can be used in combination with vibrational self-consistent field (VSCF), vibrational configuration interaction (VCI), vibrational Mller-Plesset, and vibrational coupled cluster calculations of anharmonic wave functions and calculation of vibrational averaged properties at the VSCF and VCI levels. Sample calculations are presented for fundamental vibrational energies and vibrationally averaged dipole moments and frequency dependent polarizabilities and hyperpolarizabilities of water and formaldehyde.
Coherent vibrational energy transfer along a peptide helix
NASA Astrophysics Data System (ADS)
Kobus, Maja; Nguyen, Phuong H.; Stock, Gerhard
2011-03-01
To measure the transport of vibrational energy along a peptide helix, Hamm and co-workers [J. Phys. Chem. B 112, 9091 (2008)] performed time-resolved vibrational experiments, which showed that the energy transport rate increases by at least a factor of 4, when a localized C=O mode of the peptide instead of an attached chromophore is excited. This finding raises the question if coherent excitonic energy transfer between the C=O modes may be of importance for the overall energy transport in peptides. With this idea in mind, nonequilibrium molecular dynamics simulations as well as quantum-classical calculations are performed, which qualitatively reproduce the experimental findings. Moreover, the latter model (an exciton Hamiltonian whose matrix elements depend on the instantaneous positions of the peptide and solvent atoms) indeed exhibits the signatures of coherent quantum energy transport, at least within the first few picoseconds and at low temperatures. The origin of the observed decoherence, the absence of vibrational self-trapping, and the possibility of quantum interference between various transport paths are discussed in some detail.
Vibration exposure for selected power hand tools used in automobile assembly.
Radwin, R G; Armstrong, T J; Vanbergeijk, E
1990-09-01
A practical method for assessing vibration exposure for workers operating vibrating hand tools on an automobile assembly line is presented. Vibration exposure is difficult to assess directly using many fast Fourier transform (FFT) spectral analyzers because of long task cycle times. Exposure time cannot be accurately estimated using time standards because of the high variability between operators and work methods. Furthermore, because workers frequently move about and get into inaccessible spaces, it is difficult to record vibration without interfering with the operation. A work sampling method was used for determining vibration exposure time by attaching accelerometers to the tools and suspending a battery-operated digital data logger from the air hose. Vibration acceleration and frequency spectra for each tool were obtained off-line replicating actual working conditions and analyzed together with exposure time data for determining individual worker vibration exposure. Eight pneumatic vibrating power hand tools, representing tools commonly used in an automobile assembly plant, were studied. Spectra for the rotary and reciprocating power tools and had large distinct dominant fundamental frequencies occurring in a narrow frequency range between 35 Hz and 150 Hz. These frequencies corresponded closely to tool free-running speeds, suggesting that major spectral component frequencies may be predicted on the basis of speed for some tools. PMID:2220569
Accurate ab initio vibrational energies of methyl chloride.
Owens, Alec; Yurchenko, Sergei N; Yachmenev, Andrey; Tennyson, Jonathan; Thiel, Walter
2015-06-28
Two new nine-dimensional potential energy surfaces (PESs) have been generated using high-level ab initio theory for the two main isotopologues of methyl chloride, CH3 (35)Cl and CH3 (37)Cl. The respective PESs, CBS-35(?HL), and CBS-37(?HL), are based on explicitly correlated coupled cluster calculations with extrapolation to the complete basis set (CBS) limit, and incorporate a range of higher-level (HL) additive energy corrections to account for core-valence electron correlation, higher-order coupled cluster terms, scalar relativistic effects, and diagonal Born-Oppenheimer corrections. Variational calculations of the vibrational energy levels were performed using the computer program TROVE, whose functionality has been extended to handle molecules of the form XY 3Z. Fully converged energies were obtained by means of a complete vibrational basis set extrapolation. The CBS-35(?HL) and CBS-37(?HL) PESs reproduce the fundamental term values with root-mean-square errors of 0.75 and 1.00 cm(-1), respectively. An analysis of the combined effect of the HL corrections and CBS extrapolation on the vibrational wavenumbers indicates that both are needed to compute accurate theoretical results for methyl chloride. We believe that it would be extremely challenging to go beyond the accuracy currently achieved for CH3Cl without empirical refinement of the respective PESs. PMID:26133427
Laboratory Measurements of Ozone - M Vibrational Energy Transfer
NASA Astrophysics Data System (ADS)
Castle, K. J.; Rhinehart, J. M.; Dodd, J. A.
2005-12-01
In preliminary work, we explore using a temperature-jump method, similar to what has been used in our ongoing CO2(?2)-O energy transfer studies, to measure vibrational energy transfer efficiencies in O3-M encounters, where M=O2, N2, or O. A lingering concern in the analysis of NASA`s TIMED/SABER data involves the 9.6 micron channel, where the observed radiance is dominated by intense emission from the O3(?3) asymmetric stretch level. Hot band emission trailing to longer wavelengths is also present, arising from vibrationally excited O3 initially populated by O + O2 three-body recombination. Poor knowledge of the relevant collisional quenching rate coefficients constitutes one of the most significant deficiencies in the non-LTE models used to retrieve ozone densities from SABER data. Specifically, accurate rate parameters for the relaxation of vibrationally-excited O3 by the major atmospheric species in the mesosphere and lower thermosphere, N2, O2, and O, are required. The O3(v)-O2, N2quenching rate coefficients derived from existing laboratory measurements vary over a substantial range, and there exists only a single published measurement of O-atom quenching coefficients. The proposed method involves a slow-flowing, dilute mixture of O3 in Xe bath gas. A 266 nm laser pulse is used to dissociate a small fraction of the O3, forming O atoms and stimulating a modest temperature increase. The O3 vibrational level populations redistribute according to the new temperature, and the excited vibrational level populations are monitored via transient diode laser absorption spectroscopy as they return to equilibrium. Rate parameters are determined by effectively plotting the redistributions rates against the quencher concentration. Any promising data or experimental progress will be discussed.
NASA Astrophysics Data System (ADS)
Xiao, Han; Wang, Xu; John, Sabu
2016-02-01
A novel piezoelectric vibration energy harvesting system is proposed whose harvesting performance could be significantly enhanced by introducing one or multiple additional piezoelectric elements placed between every two nearby oscillators. The proposed two degree-of-freedom piezoelectric vibration harvester system is expected to extract 9.78 times more electrical energy than a conventional two degrees of freedom harvester system with only one piezoelectric element inserted close to the base. A parameter study of a multiple degree-of-freedom piezoelectric vibration energy harvester system has been conducted to provide a guideline for tuning its harvesting bandwidth and optimizing its design. Based on the analysis method of the two degrees of freedom piezoelectric vibration harvester system, a generalised MDOF piezoelectric vibration energy harvester with multiple pieces of piezoelectric elements inserted between every two nearby oscillators is studied. The harvested power values of the piezoelectric vibration energy harvesters of 1 to 5 degree-of-freedom have been compared while the total mass and the mass ratio of the oscillators are kept as constants. It is found that the greater numbers of degree-of-freedom of a PVEH with the more additional piezoelectric elements inserted between every two nearby oscillators would enable that system to harvest more energy. The first mode resonant frequency will be shifted to a low-frequency range when the numbers of degree-of-freedom increase.
Investigation of folded spring structures for vibration-based piezoelectric energy harvesting
NASA Astrophysics Data System (ADS)
Lueke, J.; Rezaei, M.; Moussa, W. A.
2014-12-01
This paper presents a fixed-fixed folded spring as an alternative elastic element for beam-based piezoelectric energy harvesting. In order to harvest energy from low frequency vibration in an optimal manner, the natural/operational frequencies of harvesters must be reduced to match low frequency input vibrations. Therefore, natural frequency reduction of vibration-based energy harvesters is critical to maximize output power at low operational frequency. The mechanical optimization of cantilever-based piezoelectric energy harvesters is limited by residual stress-based beam curling that produced through microfabrication adding additional mechanical stiffness to the system. The fixed-fixed folded spring structure presented in this paper allows for increased effective beam length and residual stress relaxation, without out of plane beam curling to further reducing the natural frequency. Multiple designs of folded spring energy harvesters are presented to demonstrate the effect of important design parameters. It is shown that the folded spring harvesters were capable of harvesting electricity at low natural frequencies, ranging from 45 Hz to 3667 Hz. Additionally, the harvesters were shown to be insensitive to microfabrication-based residual stress beam curling. The maximum power output achieved by the folded spring harvesters was 690.5 nW at 226.3 Hz for a single harvesting element of an array, with a PZT layer thickness of 0.24 μm. The work presented in this paper demonstrates that the fixed-fixed folded spring can be used as a viable structural element for low frequency piezoelectric energy harvesting to take advantage of ambient vibrations found in low frequency applications.
Resonant vibrational excitation of CO by low-energy electrons
Poparic, G. B.; Belic, D. S.; Vicic, M. D.
2006-06-15
Electron impact vibrational excitation of the CO molecule, via the {sup 2}{pi} resonance, in the 0-4 eV energy region has been investigated. The energy dependence of the resonant excitation of the first ten vibrational levels, v=1 to v=10, has been measured by use of a crossed-beams double trochoidal electron spectrometer. Obtained relative differential cross sections are normalized to the absolute values. Integral cross sections are determined by using our recent results on scattered electrons angular distributions, which demonstrate clear p-partial wave character of this resonance. Substructures appear in the {sup 2}{pi} resonant excitation of the CO molecule which have not been previously observed.
Internal Conversion and Vibrational Energy Redistribution in Chlorophyll A.
Shenai, Prathamesh M; Fernandez-Alberti, Sebastian; Bricker, William P; Tretiak, Sergei; Zhao, Yang
2016-01-14
We have computationally investigated the role of intramolecular vibrational modes in determining nonradiative relaxation pathways of photoexcited electronic states in isolated chlorophyll A (ChlA) molecules. To simulate the excited state relaxation from the initially excited Soret state to the lowest excited state Qy, the approach of nonadiabatic excited state molecular dynamics has been adopted. The intramolecular vibrational energy relaxation and redistribution that accompany the electronic internal conversion process is followed by analyzing the excited state trajectories in terms of the ground state equilibrium normal modes. The time dependence of the normal mode velocities is determined by projecting instantaneous Cartesian velocities onto the normal mode vectors. Our analysis of the time evolution of the average mode energies uncovers that only a small subset of the medium-to-high frequency normal modes actively participate in the electronic relaxation processes. These active modes are characterized by the highest overlap with the nonadiabatic coupling vectors (NACRs) during the electronic transitions. Further statistical analysis of the nonadiabatic transitions reveals that the electronic and vibrational energy relaxation occurs via two distinct pathways with significantly different time scales on which the hopping from Soret to Qx occurs thereby dictating the overall dynamics. Furthermore, the NACRs corresponding to each of the transitions have been consistently found to be predominantly similar to a set of normal modes that vary depending upon the transition and the identified categories. Each pathway exhibits a differential time scale of energy transfer and also a differential set of predominant active modes. Our present analysis can be considered as a general approach allowing identification of a reduced subset of specific vibrational coordinates associated with nonradiative relaxation pathways. Therefore, it represents an adequate prior strategy that can particularly facilitates mixed quantum-classical approaches. PMID:26651494
NASA Astrophysics Data System (ADS)
Ung, Chandarin; Moss, Scott D.; Chiu, Wing K.; Payne, Owen R.; Vandewater, Luke A.; Galea, Steve C.
2015-04-01
The dominant vibration frequencies exhibited by heavy haul railcars (operating in remote regions of Western Australia) are found to be 5.8 Hz and 14.6 Hz for loaded and unloaded trips respectively. This paper describes the in-service demonstration of two electromagnetic vibration energy harvesting technologies designed to generated power from these railcar vibrations: (i) a coupled two-degree of freedom (2-DoF) device capable of capturing both dominant frequencies of the railcar and (ii) a hybrid rotary-translational harvester device based on a magnetic sphere capable of harvesting from ? 6 Hz. The two devices were laboratory tested prior to mounting on a heavy railcar for in-service demonstration. Within the laboratory the coupled 2-DoF device was found to produce a maximum peak output power of 350 mW from 0.4 g root-mean-square (rms) acceleration at 15 Hz and 230 mW from 6 Hz. The hybrid rotary-translational device based on an oscillating magnetic sphere can produce ?138 mW from host vibration of 0.4 g rms at 5.4 Hz. This paper will discuss and compare the performance of the two prototypes, both within the laboratory and during the in-service demonstration on a heavy heal railcar.
NASA Astrophysics Data System (ADS)
Hu, Mao-Bin; Kong, Xiang-Zhao; Wu, Qing-Song; Zhu, Zhen-Gang
The low frequency vibration energy absorption properties of granular materials have been investigated on an Invert Torsion Pendulum (ITP). The energy absorption rate of granular material changes nonlinearly with amplitude under low frequency vibration. The frequency of ITP system increases a little with granular materials in the holding cup. The vibration frequency of ITP system does not change with time.
Minh, Le Van; Hara, Motoaki; Yokoyama, Tsuyoshi; Nishihara, Tokihiro; Ueda, Masanori; Kuwano, Hiroki
2015-11-01
The first MgZr co-doped AlN-based vibrational energy harvester (VEH) is presented. (MgZr)AlN, which is a new class of doped AlN, provides high piezoelectricity and cost advantage. Using 13%-(MgZr)-doped AlN for micromachined VEHs, maximum output power of 1.3 ?W was achieved with a Q-factor of 400 when resonant frequency, vibration acceleration, load resistance were 792 Hz, 8 m/s(2), and 1.1 M?, respectively. Normalized power density was 8.1 kW.g(-2).m(-3). This was one of the highest values among the currently available piezoelectric VEHs. PMID:26559628
Low-Loss Piezoelectric Transformer Using Energy Trapping of Width Vibration
NASA Astrophysics Data System (ADS)
Wakatsuki, Noboru; Ueda, Masanori; Satoh, Masuji
1993-05-01
Piezoelectric transformers proposed by Rosen have been studied for high-voltage step-up applications. A piezoelectric transformer using LiNbO3 proposed recently by Nakamura and Adachi has low loss and a simple structure. The plate of a conventional piezoelectric transformer was supported only at the node of vibration. Rigid support and loss suppression are required for high-power and high-voltage applications. To apply a piezo-electric transformer to a power circuit, we studied methods for supporting the piezoelectric plate and reducing loss. Based on these studies, we proposed a piezoelectric transformer using energy trapping of the width-shear vibration in a LiNbO3 plate.
White Noise Responsiveness of an AlN Piezoelectric MEMS Cantilever Vibration Energy Harvester
NASA Astrophysics Data System (ADS)
Jia, Y.; Seshia, A. A.
2014-11-01
This paper reports the design, analysis and experimental characterisation of a piezoelectric MEMS cantilever vibration energy harvester, the enhancement of its power output by adding various values of end mass, as well as assessing the responsiveness towards white noise. Devices are fabricated using a 0.5 ?m AlN on 10 ?m doped Si process. Cantilevers with 5 mm length and 2 mm width were tested at either unloaded condition (MC0: fn 577 Hz) or subjected to estimated end masses of 2 mg (MC2: fn 129 Hz) and 5 mg (MC5: fn 80 Hz). While MC0 was able to tolerate a higher drive acceleration prior to saturation (7 g with 0.7 ?W), MC5 exhibited higher peak power attainable at a lower input vibration (2.56 ?W at 3 ms-2). MC5 was also subjected to band-limited (10 Hz to 2 kHz) white noise vibration, where the power response was only a fraction of its resonant counterpart for the same input: peak instantaneous power >1 ?W was only attainable beyond 2 g of white noise, whereas single frequency resonant response only required 2.5 ms-2. Both the first resonant response and the band-limited white noise response were also compared to a numerical model, showing close agreements.
Exploring the vibrational fingerprint of the electronic excitation energy via molecular dynamics
Deyne, Andy Van Yperen-De; Pauwels, Ewald; Ghysels, An; Waroquier, Michel; Van Speybroeck, Veronique; Hemelsoet, Karen; De Meyer, Thierry; Department of Textiles, Ghent University, Technologiepark 907, 9052 Zwijnaarde ; De Clerck, Karen
2014-04-07
A Fourier-based method is presented to relate changes of the molecular structure during a molecular dynamics simulation with fluctuations in the electronic excitation energy. The method implies sampling of the ground state potential energy surface. Subsequently, the power spectrum of the velocities is compared with the power spectrum of the excitation energy computed using time-dependent density functional theory. Peaks in both spectra are compared, and motions exhibiting a linear or quadratic behavior can be distinguished. The quadratically active motions are mainly responsible for the changes in the excitation energy and hence cause shifts between the dynamic and static values of the spectral property. Moreover, information about the potential energy surface of various excited states can be obtained. The procedure is illustrated with three case studies. The first electronic excitation is explored in detail and dominant vibrational motions responsible for changes in the excitation energy are identified for ethylene, biphenyl, and hexamethylbenzene. The proposed method is also extended to other low-energy excitations. Finally, the vibrational fingerprint of the excitation energy of a more complex molecule, in particular the azo dye ethyl orange in a water environment, is analyzed.
Research on the vibration of vertical condensate pumps in nuclear power stations
Tsema, A.D.; Budnik, A.N.; Chelobitchenko, V.A.
1985-01-01
Centrifugal pump units are elements of nuclear power stations, and there are special demands on their operating reliability. Since vibration is the most widespread cause for the failure of these pumps, the task of studying and eliminating the causes of increased vibration is urgent. Dynamically, centrifugal pump units are complex systems consisting of a shaft, casing, and support structures. Vertical pump units have lower natural oscillation frequencies than horizontal units; in some cases, this leads to resonant operating vibrations and, consequently, to early pump failure.
NASA Astrophysics Data System (ADS)
Miller, Lindsay Margaret
Wireless sensor networks (WSNs) have the potential to transform engineering infrastructure, manufacturing, and building controls by allowing condition monitoring, asset tracking, demand response, and other intelligent feedback systems. A wireless sensor node consists of a power supply, sensor(s), power conditioning circuitry, radio transmitter and/or receiver, and a micro controller. Such sensor nodes are used for collecting and communicating data regarding the state of a machine, system, or process. The increasing demand for better ways to power wireless devices and increase operation time on a single battery charge drives an interest in energy harvesting research. Today, wireless sensor nodes are typically powered by a standard single-charge battery, which becomes depleted within a relatively short timeframe depending on the application. This introduces tremendous labor costs associated with battery replacement, especially when there are thousands of nodes in a network, the nodes are remotely located, or widely-distributed. Piezoelectric vibration energy harvesting presents a potential solution to the problems associated with too-short battery life and high maintenance requirements, especially in industrial environments where vibrations are ubiquitous. Energy harvester designs typically use the harvester to trickle charge a rechargeable energy storage device rather than directly powering the electronics with the harvested energy. This allows a buffer between the energy harvester supply and the load where energy can be stored in a "tank". Therefore, the harvester does not need to produce the full required power at every instant to successfully power the node. In general, there are tens of microwatts of power available to be harvested from ambient vibrations using micro scale devices and tens of milliwatts available from ambient vibrations using meso scale devices. Given that the power requirements of wireless sensor nodes range from several microwatts to about one hundred milliwatts and are falling steadily as improvements are made, it is feasible to use energy harvesting to power WSNs. This research begins by presenting the results of a thorough survey of ambient vibrations in the machine room of a large campus building, which found that ambient vibrations are low frequency, low amplitude, time varying, and multi-frequency. The modeling and design of fixed-frequency micro scale energy harvesters are then presented. The model is able to take into account rotational inertia of the harvester's proof mass and it accepts arbitrary measured acceleration input, calculating the energy harvester's voltage as an output. The fabrication of the micro electromechanical system (MEMS) energy harvesters is discussed and results of the devices harvesting energy from ambient vibrations are presented. The harvesters had resonance frequencies ranging from 31 - 232 Hz, which was the lowest reported in literature for a MEMS device, and produced 24 pW/g2 - 10 nW/g2 of harvested power from ambient vibrations. A novel method for frequency modification of the released harvester devices using a dispenser printed mass is then presented, demonstrating a frequency shift of 20 Hz. Optimization of the MEMS energy harvester connected to a resistive load is then presented, finding that the harvested power output can be increased to several microwatts with the optimized design as long as the driving frequency matches the harvester's resonance frequency. A framework is then presented to allow a similar optimization to be conducted with the harvester connected to a synchronously switched pre-bias circuit. With the realization that the optimized energy harvester only produces usable amounts of power if the resonance frequency and driving frequency match, which is an unrealistic situation in the case of ambient vibrations which change over time and are not always known
Bian, Hongtao; Chen, Hailong; Li, Jiebo; Wen, Xiewen; Zheng, Junrong
2011-10-27
The donor/acceptor energy mismatch and vibrational coupling strength dependences of interionic vibrational energy transfer kinetics in electrolyte aqueous solutions were investigated with ultrafast multiple-dimensional vibrational spectroscopy. An analytical equation derived from the Fermi's Golden rule that correlates molecular structural parameters and vibrational energy transfer kinetics was found to be able to describe the intermolecular mode specific vibrational energy transfer. Under the assumption of the dipole-dipole approximation, the distance between anions in the aqueous solutions was obtained from the vibrational energy transfer measurements, confirmed with measurements on the corresponding crystalline samples. The result demonstrates that the mode-specific vibrational energy transfer method holds promise as an angstrom molecular ruler. PMID:21916443
Synergistic use of smart materials for vibration-based energy harvesting
NASA Astrophysics Data System (ADS)
Silva, L. L.; Oliveira, S. A.; Pacheco, P. M. C. L.; Savi, M. A.
2015-11-01
Vibration-based energy harvesting is an approach where available mechanical vibration energy is converted into electrical energy that can be employed for different purposes. This paper deals with the synergistic use of smart materials for energy harvesting purposes. In essence, piezoelectric and shape memory alloys are combined to build an energy harvesting system. The combined effect of these materials can increase the system performance and reduce some limitations. The possibility to control the mechanical stiffness under vibration by a shape memory alloy (SMA) element can provide the ability to tune resonant frequencies in order to increase the output power. The analysis is developed considering a one-degree of freedom mechanical system where the restitution force is provided by an SMA element. The electro-mechanical coupling is provided by a piezoelectric element. Linear piezoelectric constitutive equation is employed together with the Brinson's model for SMA element. Numerical simulations are carried out showing different responses of the system indicating that the inclusion of the SMA element can be used to extend the operational range of the system.
A review of vibration problems in power station boiler feed pumps
NASA Technical Reports Server (NTRS)
France, David
1994-01-01
Boiler feed pump reliability and availability is recognized as important to the overall efficiency of power generation. Vibration monitoring is often used as a part of planned maintenance. This paper reviews a number of different types of boiler feed pump vibration problems describing some methods of solution in the process. It is hoped that this review may assist both designers and users faced with similar problems.
NASA Astrophysics Data System (ADS)
Abed, I.; Kacem, N.; Bouhaddi, N.; Bouazizi, M. L.
2016-02-01
We propose a multi-modal vibration energy harvesting approach based on arrays of coupled levitated magnets. The equations of motion which include the magnetic nonlinearity and the electromagnetic damping are solved using the harmonic balance method coupled with the asymptotic numerical method. A multi-objective optimization procedure is introduced and performed using a non-dominated sorting genetic algorithm for the cases of small magnet arrays in order to select the optimal solutions in term of performances by bringing the eigenmodes close to each other in terms of frequencies and amplitudes. Thanks to the nonlinear coupling and the modal interactions even for only three coupled magnets, the proposed method enable harvesting the vibration energy in the operating frequency range of 4.6–14.5 Hz, with a bandwidth of 190% and a normalized power of 20.2 {mW} {{cm}}-3 {{{g}}}-2.
Skyrmion vibrational energies together with a generalized mass term
Davies, Merlin C.; Marleau, Luc
2009-04-01
We study various properties of a one-parameter mass term for the Skyrme model, originating from the works of Kopeliovich, Piette and Zakrzewski [V. B. Kopeliovich, B. Piette, and W. J. Zakrzewski, Phys. Rev. D 73, 014006 (2006).], through the use of axially symmetric solutions obtained numerically by simulated-annealing. These solutions allow us to observe asymptotic behaviors of the B=2 binding energies that differ to those previously obtained [B. Piette and W. J. Zakrzewski, Phys. Rev. D 77, 074009 (2008).]. We also decipher the characteristics of three distinct vibrational modes that appear as eigenstates of the vibrational Hamiltonian. This analysis further examine the assertion that the one-parameter mass term offers a better account of baryonic matter than the traditional mass term.
Vibrational Energy Distribution Analysis (VEDA): Scopes and limitations
NASA Astrophysics Data System (ADS)
Jamrz, Micha? H.
2013-10-01
The principle of operations of the VEDA program written by the author for Potential Energy Distribution (PED) analysis of theoretical vibrational spectra is described. Nowadays, the PED analysis is indispensible tool in serious analysis of the vibrational spectra. To perform the PED analysis it is necessary to define 3N-6 linearly independent local mode coordinates. Already for 20-atomic molecules it is a difficult task. The VEDA program reads the input data automatically from the Gaussian program output files. Then, VEDA automatically proposes an introductory set of local mode coordinates. Next, the more adequate coordinates are proposed by the program and optimized to obtain maximal elements of each column (internal coordinate) of the PED matrix (the EPM parameter). The possibility for an automatic optimization of PED contributions is a unique feature of the VEDA program absent in any other programs performing PED analysis.
Harvestable vibrational energy from an avian source: theoretical predictions vs. measured values
NASA Astrophysics Data System (ADS)
Shafer, Michael W.; MacCurdy, Robert; Garcia, Ephrahim; Winkler, David
2012-04-01
For many reasons, it would be beneficial to have the capability of powering a wildlife tag over the course of multiple migratory seasons. Such an energy harvesting system would allow for more data collection and eliminate the need to replace depleted batteries. In this work, we investigate energy harvesting on birds and focus on vibrational energy harvesting. We review a method of predicting the amount of power that can be safely harvested from the birds such that the effect on their longterm survivability is not compromised. After showing that the safely harvestable power is significant in comparison to the circuits used in avian tags, we present testing results for the flight accelerations of two species of birds. Using these measured values, we then design harvesters that matched the flight acceleration frequency and are sufficiently low mass to be carried by the birds.
NASA Astrophysics Data System (ADS)
Zhang, Qian; Wang, Yufeng; Zhao, Lurui; Sok Kim, Eun
2016-02-01
This paper presents two microfabrication approaches for multi-layer coils for vibration-energy harvesters. A magnet array is arranged with alternating north- and south-orientation to provide a rapidly changing magnetic field for high electromagnetic energy conversion. Multi-turn spiral coils on silicon wafer are aligned to the magnet array for maximum magnetic flux change. One type of coil is made out of 300 μm-thick copper that is electroplated with silicon mold, and the other is built on 25 μm-thick copper electroplated with photoresist mold. The low resistive coils fabricated by the first approach are integrated in a microfabricated energy harvester of 17 × 7 × 1.7 mm3 (=0.2 cm3) weighing 0.8 g, which generates 14.3 μW power output (into 0.7 Ω load) from vibration amplitude of 6 μm at 250 Hz. The latter approach is used to make a 1080-turn coil for a microfabricated electromagnetic energy harvester with magnet array and plastic spring. Though the size and weight of the harvester are only 44 × 20 × 6 mm3 (=5.3 cm3) and 12 g, respectively, it generates 1.04 mW power output (into 190 Ω load) when it is vibrated at 75 Hz with vibration amplitude of 220 μm.
Harne, Ryan L
2012-07-01
Conversion of ambient vibrational energy into electric power has been the impetus of much modern research. The traditional analysis has focused on absolute electrical power output from the harvesting devices and efficiency defined as the convertibility of an infinite resource of vibration excitation into power. This perspective has limited extensibility when applying resonant harvesters to host resonant structures when the inertial influence of the harvester is more significant. Instead, this work pursues a fundamental understanding of the coupled dynamics of a main mass-spring-damper system to which an electromagnetic or piezoelectric mass-spring-damper is attached. The governing equations are derived, a metric of efficiency is presented, and analysis is undertaken. It is found that electromagnetic energy harvesting efficiency and maximum power output is limited by the strength of the coupling such that no split system resonances are induced for a given mass ratio. For piezoelectric harvesters, only the coupling strength and certain design requirements dictate maximum power and efficiency achievable. Since the harvesting circuitry must "follow" the split resonances as the piezoelectric harvesters become more massive, the optimum design of piezoelectric harvesters appears to be more involved than for electromagnetic devices. PMID:22779465
Electron-vibration energy exchange models in nitrogen-containing plasma flows
NASA Astrophysics Data System (ADS)
Laporta, V.; Bruno, D.
2013-03-01
The physics of vibrational kinetics in nitrogen-containing plasma produced by collisions with electrons is studied on the basis of recently derived cross sections and rate coefficients for the resonant vibrational-excitation by electron-impact. The temporal relaxation of the vibrational energy and of the vibrational distribution function is analyzed in a state-to-state approach. The electron and vibrational temperatures are varied in the range [0-50 000] K. Conclusions are drawn with respect to the derivation of reduced models and to the accuracy of a relaxation time formalism. An analytical fit of the vibrational relaxation time is given.
NASA Astrophysics Data System (ADS)
Haroun, Ahmed; Yamada, Ichiro; Warisawa, Shin`ichi
2015-08-01
This paper presents study of an electromagnetic vibration energy harvesting configuration that can work effectively at low frequencies. Unlike the conventional form of vibration energy harvesters in which the mass is directly connected to a vibrating frame with spring suspension, in the proposed configuration a permanent magnet mass is allowed to move freely within a certain distance inside a frame-carrying coil and make impacts with spring end stops. The free motion distance allows matching lower vibration frequencies with an increase in the relative amplitude at resonance. Hence, significant power could be generated at low frequencies. A nonlinear mathematical model including impact and electromagnetic induction is derived. Study of the dynamic behaviour and investigation of the system performance is carried out with the aid of case study simulation. The proposed harvester shows a unique dynamic behaviour in which different ways of response of the internal relative oscillation appear over the range of input frequencies. A mathematical condition for the response type at which the higher relative amplitude appears is derived, followed by an investigation of the system resonant frequency and relative amplitude. The resonant frequency shows a dependency on the free motion distance as well as the utilized mass and spring stiffness. Simulation and experimental comparisons are carried out between the proposed harvester and similar conventional one tuned at the same input frequency. The power generated by the proposed harvesting configuration can reach more than 12 times at 11 Hz in the simulation case and about 10 times at 10 Hz in the experimental case. Simulation comparison also shows that this power magnification increases by matching lower frequencies which emphasize the advantages of the proposed configuration for low frequency operation.
From MEMS to macro-world: a micro-milling machined wideband vibration piezoelectric energy harvester
NASA Astrophysics Data System (ADS)
Iannacci, J.; Sordo, G.
2015-05-01
In this work, we discuss a novel mechanical resonator design for the realization of vibration Energy Harvester (EH) capable to deliver power levels in the mW range. The device overcomes the typical constraint of frequency narrowband operability of standard cantilevered EHs, by exploiting a circular-shaped resonator with an increased number of mechanical Degrees Of Freedom (DOFs), leading to several resonant modes in the range of vibrations of interest (i.e. multi-modal wideband EH). The device, named Four-Leaf Clover (FLC), is simulated in Ansys Worbench™, showing a significant number of resonant modes up to vibrations of around 2 kHz (modal eigenfrequencies analysis), and exhibiting levels of converted power up to a few mW at resonance (harmonic coupled-field analysis). The sole FLC mechanical structure is realized by micro-milling an Aluminum foil, while a cantilevered test structure also including PolyVinyliDene Fluoride (PVDF) film sheet is assembled in order to collect first experimental feedback on generated power levels. The first lab based tests show peak-to-peak voltages of several Volts when the cantilever is stimulated with a mechanical pulse. Further developments of this work will comprise the assembly of an FLC demonstrator with PVDF pads, and its experimental testing in order to validate the simulated results.
Designing and Testing Energy Harvesters Suitable for Renewable Power Sources
NASA Astrophysics Data System (ADS)
Synkiewicz, B.; Guzdek, P.; Piekarski, J.; Zaraska, K.
2016-01-01
Energy harvesters convert waste power (heat, light and vibration) directly to electric power . Fast progress in their technology, design and areas of application (e.g. “Internet of Things”) has been observed recently. Their effectiveness is steadily growing which makes their application to powering sensor networks with wireless data transfer reasonable. The main advantage is the independence from wired power sources, which is especially important for monitoring state of environmental parameters. In this paper we describe the design and realization of a gas sensor monitoring CO level (powered by TEG) and two, designed an constructed in ITE, autonomous power supply modules powered by modern photovoltaic cells.
NASA Astrophysics Data System (ADS)
Hasbullah Mohd Isa, Wan; Fikri Muhammad, Khairul; Mohd Khairuddin, Ismail; Ishak, Ismayuzri; Razlan Yusoff, Ahmad
2016-02-01
This paper presents the new form of coils for electromagnetic energy harvesting system based on topology optimization method which look-liked a cap to maximize the power output. It could increase the number of magnetic flux linkage interception of a cylindrical permanent magnet which in this case is of 10mm diameter. Several coils with different geometrical properties have been build and tested on a vibration generator with frequency of 100Hz. The results showed that the coil with lowest number of winding transduced highest power output of 680μW while the highest number of windings generated highest voltage output of 0.16V.
NASA Astrophysics Data System (ADS)
Ansari, M. H.; Karami, M. Amin
2016-03-01
This paper studies energy harvesting from heartbeat vibrations for powering leadless pacemakers. Unlike traditional pacemakers, leadless pacemakers are implanted inside the heart and the pacemaker is in direct contact with the myocardium. A leadless pacemaker is in the shape of a cylinder. Thus, in order to utilize the available 3-dimensional space for the energy harvester, we choose a fan-folded 3D energy harvester. The proposed device consists of several piezoelectric beams stacked on top of each other. The volume of the energy harvester is 1 cm3 and its dimensions are 2 cm × 0.5 cm × 1 cm. Although high natural frequency is generally a major concern with micro-scale energy harvesters, by utilizing the fan-folded geometry and adding tip mass and link mass to the configuration, we reduced the natural frequency to the desired range. This fan-folded design makes it possible to generate more than 10 μ W of power per cubic centimeter. The proposed device is compatible with Magnetic Resonance Imaging. Although the proposed device is a linear energy harvester, it is relatively insensitive to the heart rate. The natural frequencies and the mode shapes of the device are calculated analytically. The accuracy of the analytical model is verified by experimental investigations. We use a closed loop shaker system to precisely replicate heartbeat vibrations in vitro.
Prediction of Flow-Induced Structural Vibration and Sound Radiation Using Energy Flow Analysis
NASA Astrophysics Data System (ADS)
Han, F.; Bernhard, R. J.; Mongeau, L. G.
1999-11-01
The energy flow analysis method used to predict the structural vibration response and the radiated sound power of a plate excited by wall pressure fluctuations under turbulent boundary layers, and separated-reattached flows. This method allows the spatially averages energy density and response to be calculated for non-uniform, distributed excitations while taking hydrodynamic flow/structural coupling effects into consideration. The power input was calculated using well known analytical models for the plate mechanical impedance and empirical models for the surface pressure cross-power spectral density and/or wave number-frequency spectral density. The Smol'yakov-Tkachenko model was used to estimate the fluctuation pressure field underneath turbulent boundary layer flows. The Corcos model was used to estimate the wall pressure field under non-uniform, separated-reattached flows. Experiments were performed in order to evaluate the energy flow model. A clamped plate installed in a quiet, low-speed wind tunnel was used. The wall pressure fluctuations, the plate vibration response, and the acoustic pressure radiated from the plate were measured. The energy flow analysis method was found to provide reasonably accurate predictions of the frequency-averaged transverse velocity response of the plate at high frequencies. The acoustic pressure radiated on the quiescent side of the plate was also predicted with comparable accuracy.
Modeling and Tuning for Vibration Energy Harvesting using a Piezoelectric Bimorph
NASA Astrophysics Data System (ADS)
Cao, Yongqing
With the development of wireless sensors and other devices, the need for continuous power supply with high reliability is growing ever more. The traditional battery power supply has the disadvantage of limited duration of continuous power supply capability so that replacement for new batteries has to be done regularly. This can be quite inconvenient and sometimes quite difficult especially when the sensors are located in places not easily accessible such as the inside of a machine or wild field. This situation stimulates the development of renewable power supply which can harvest energy from the environment. The use of piezoelectric materials to converting environment vibration to electrical energy is one of the alternatives of which a broad range of research has been done by many researchers, focusing on different issues. The improvement of efficiency is one of the most important issues in vibration based energy harvesting. For this purpose different methods are devised and more accurate modeling of coupled piezoelectric mechanical systems is investigated. In the current paper, the research is focused on improving voltage generation of a piezoelectric bimorph on a vibration beam, as well as the analytical modeling of the same system. Also an initial study is conducted on the characteristics of the vibration of Zinc oxide (ZnO) nanowire, which is a promising material for its coupled semiconducting and piezoelectric properties. The effect on the voltage generation by different placement of the piezoelectric bimorph on the vibrating beam is investigated. The relation between the voltage output and the curvature is derived which is used to explain the effect of placement on voltage generation. The effect of adding a lumped mass on the modal frequencies of the beam and on the curvature distribution is investigated. The increased voltage output from the piezoelectric bimorph by using appropriately selected mass is proved analytically and also verified by experiment. For the modeling of piezoelectric generator, different methods are employed to modeling the coupled dynamics of a piezoelectric bimorph on a vibrating beam as well as a simple piezoelectric bimorph cantilever. The modeling of piezoelectric bimorph as an alternative current (AC) source with internal capacitance and resistance is used to analyze a piezoelectric bimorph cantilever and to calculate the optimal external load resistance for maximal power output. The couple dynamics method based on Hamilton's Principle is applied in the modeling of the piezoelectric bimorph on a vibrating beam. Impulse response experiment shows this method has a better estimation of the experimental results than the curvature model. The coupled dynamics model is also applied to piezoelectric bimorph cantilever and the external load resistance is also determined by this to maximize the power output. The finite element equations for the piezoelectric materials in the element domain are theoretically derived. The procedure of modeling a piezoelectric on a vibrating beam is demonstrated base on the package of ANSYS. The frequency response of ZnO nanowires with different dimensions is derived analytically for ambient mediums with different damping ratios. With help from nano research lab of Dr. Yong Zhu and the student Feng Xu, an experiment is conducted which indentifies the first modal frequency of ZnO nanowires with different dimensions. The experimental modal frequencies are compared with the numerical results. The influence of the thickness of deposit on the modal frequency is also investigated by finite element modeling.
NASA Astrophysics Data System (ADS)
Tsampas, P.; Roditis, G.; Papadimitriou, V.; Chatzakos, P.; Gan, Tat-Hean
2013-05-01
Increasing demand in mobile, autonomous devices has made energy harvesting a particular point of interest. Systems that can be powered up by a few hundreds of microwatts could feature their own energy extraction module. Energy can be harvested from the environment close to the device. Particularly, the ambient mechanical vibrations conversion via piezoelectric transducers is one of the most investigated fields for energy harvesting. A technique for optimized energy harvesting using piezoelectric actuators called "Synchronized Switching Harvesting" is explored. Comparing to a typical full bridge rectifier, the proposed harvesting technique can highly improve harvesting efficiency, even in a significantly extended frequency window around the piezoelectric actuator's resonance. In this paper, the concept of design, theoretical analysis, modeling, implementation and experimental results using CEDRAT's APA 400M-MD piezoelectric actuator are presented in detail. Moreover, we suggest design guidelines for optimum selection of the storage unit in direct relation to the characteristics of the random vibrations. From a practical aspect, the harvesting unit is based on dedicated electronics that continuously sense the charge level of the actuator's piezoelectric element. When the charge is sensed, to come to a maximum, it is directed to speedily flow into a storage unit. Special care is taken so that electronics operate at low voltages consuming a very small amount of the energy stored. The final prototype developed includes the harvesting circuit implemented with miniaturized, low cost and low consumption electronics and a storage unit consisting of a super capacitors array, forming a truly self-powered system drawing energy from ambient random vibrations of a wide range of characteristics.
Field Telemetry of Blade-rotor Coupled Torsional Vibration at Matuura Power Station Number 1 Unit
NASA Technical Reports Server (NTRS)
Isii, Kuniyoshi; Murakami, Hideaki; Otawara, Yasuhiko; Okabe, Akira
1991-01-01
The quasi-modal reduction technique and finite element model (FEM) were used to construct an analytical model for the blade-rotor coupled torsional vibration of a steam turbine generator of the Matuura Power Station. A single rotor test was executed in order to evaluate umbrella vibration characteristics. Based on the single rotor test results and the quasi-modal procedure, the total rotor system was analyzed to predict coupled torsional frequencies. Finally, field measurement of the vibration of the last stage buckets was made, which confirmed that the double synchronous resonance was 124.2 Hz, meaning that the machine can be safely operated. The measured eigen values are very close to the predicted value. The single rotor test and this analytical procedure thus proved to be a valid technique to estimate coupled torsional vibration.
Optimal design of a vibration-based energy harvester using magnetostrictive material (MsM)
NASA Astrophysics Data System (ADS)
Hu, J.; Xu, F.; Huang, A. Q.; Yuan, F. G.
2011-01-01
In this study, an optimal vibration-based energy harvesting system using magnetostrictive material (MsM) was designed and tested to enable the powering of a wireless sensor. In particular, the conversion efficiency, converting from magnetic to electric energy, is approximately modeled from the magnetic field induced by the beam vibration. A number of factors that affect the output power such as the number of MsM layers, coil design and load matching are analyzed and explored in the design optimization. From the measurements, the open-circuit voltage can reach 1.5 V when the MsM cantilever beam operates at the second natural frequency 324 Hz. The AC output power is 970 W, giving a power density of 279 W cm - 3. The attempt to use electrical reactive components (either inductors or capacitors) to resonate the system at any frequency has also been analyzed and tested experimentally. The results showed that this approach is not feasible to optimize the power. Since the MsM device has low output voltage characteristics, a full-wave quadrupler has been designed to boost the rectified output voltage. To deliver the maximum output power to the load, a complex conjugate impedance matching between the load and the MsM device is implemented using a discontinuous conduction mode (DCM) buck-boost converter. The DC output power after the voltage quadrupler reaches 705 W and the corresponding power density is 202 W cm - 3. The output power delivered to a lithium rechargeable battery is around 630 W, independent of the load resistance.
NASA Astrophysics Data System (ADS)
Muthalif, Asan G. A.; Nordin, N. H. Diyana
2015-03-01
Harvesting energy from the surroundings has become a new trend in saving our environment. Among the established ones are solar panels, wind turbines and hydroelectric generators which have successfully grown in meeting the world's energy demand. However, for low powered electronic devices; especially when being placed in a remote area, micro scale energy harvesting is preferable. One of the popular methods is via vibration energy scavenging which converts mechanical energy (from vibration) to electrical energy by the effect of coupling between mechanical variables and electric or magnetic fields. As the voltage generated greatly depends on the geometry and size of the piezoelectric material, there is a need to define an optimum shape and configuration of the piezoelectric energy scavenger. In this research, mathematical derivations for unimorph piezoelectric energy harvester are presented. Simulation is done using MATLAB and COMSOL Multiphysics software to study the effect of varying the length and shape of the beam to the generated voltage. Experimental results comparing triangular and rectangular shaped piezoelectric beam are also presented.
Hu, Youfan; Yang, Jin; Jing, Qingshen; Niu, Simiao; Wu, Wenzhuo; Wang, Zhong Lin
2013-11-26
An unstable mechanical structure that can self-balance when perturbed is a superior choice for vibration energy harvesting and vibration detection. In this work, a suspended 3D spiral structure is integrated with a triboelectric nanogenerator (TENG) for energy harvesting and sensor applications. The newly designed vertical contact-separation mode TENG has a wide working bandwidth of 30 Hz in low-frequency range with a maximum output power density of 2.76 W/m(2) on a load of 6 MΩ. The position of an in-plane vibration source was identified by placing TENGs at multiple positions as multichannel, self-powered active sensors, and the location of the vibration source was determined with an error less than 6%. The magnitude of the vibration is also measured by the output voltage and current signal of the TENG. By integrating the TENG inside a buoy ball, wave energy harvesting at water surface has been demonstrated and used for lighting illumination light, which shows great potential applications in marine science and environmental/infrastructure monitoring. PMID:24168315
The Acute Effect of Direct Vibration on Muscular Power Performance in Master Athletes.
Cochrane, D J
2016-02-01
This study examined the acute effect of direct vibration on biceps brachii muscular power in master athletes. 10 healthy male national representative master field-hockey players were randomly assigned to receive 10 min of pulsing sinusoidal vibration or no vibration (control) to the right and left biceps brachii. Pre- and post-testing included lifting 2 repetitions of standing dumbbell (DB) biceps curl at 50% 1 RM (repetition maximum). Mechanical peak power (PP), mean concentric power (MCP) and normalised electromyography (EMG) was assessed during the concentric phase of the biceps curl. Following vibration PP increased 44.3±23.6 W (difference pre-post; p=0.013) compared to control (5.9±9.5 W; p=0.334). Similarly, MCP increased 12.0±4.5 W (p=0.002) compared to control (1.5±0.8 W; p=0.397). However, there was no significant difference in normalised EMG between vibration and control (p>0.05). The increase in PP and MCP did not coincide with an increase in EMG and suggests that other mechanisms may be contributing to changes in muscle performance. Given its ease of use and portability the vibratory device may be considered as an alternative warm-up modality immediately prior to explosive activities. PMID:26509379
Copper foil-type vibration-based electromagnetic energy harvester
NASA Astrophysics Data System (ADS)
Khan, Farid; Sassani, Farrokh; Stoeber, Boris
2010-12-01
This paper presents the modeling, simulation, fabrication and experimental results of a vibration-based electromagnetic power generator (EMPG). A novel, low-cost, one-mask technique is used to fabricate the planar coils and the planar spring. This fabrication technique can provide an alternative for processes such as lithographie galvanoformung abformung (LIGA) or SU-8 molding and MEMS electroplating. Commercially available copper foils of 20 m and 350 m thicknesses are used for the planar coils and planar spring, respectively. The design with planar coils on either side of the magnets provides enhanced power generation for the same footprint of the device. The harvester's overall volume is 1 cm3. Excitation of the EMPG, at the fundamental frequency of 371 Hz, base acceleration of 13.5 g and base amplitude of 24.4 m, yields an open circuit voltage of 60.1 mV, as well as 46.3 mV load voltage and 10.7 W power for a 100 ? load resistance. At a matching impedance of 7.5 ? the device produced a maximum power of 23.56 W and a power density of 23.56 W cm-3. The simulations based on the analytical model of the device show good agreement with the experimental results.
NASA Astrophysics Data System (ADS)
Takeya, Kouichi; Sasaki, Eiichi; Kobayashi, Yusuke
2016-01-01
A bridge vibration energy harvester has been proposed in this paper using a tuned dual-mass damper system, named hereafter Tuned Mass Generator (TMG). A linear electromagnetic transducer has been applied to harvest and make use of the unused reserve of energy the aforementioned damper system absorbs. The benefits of using dual-mass systems over single-mass systems for power generation have been clarified according to the theory of vibrations. TMG parameters have been determined considering multi-domain parameters, and TMG has been tuned using a newly proposed parameter design method. Theoretical analysis results have shown that for effective energy harvesting, it is essential that TMG has robustness against uncertainties in bridge vibrations and tuning errors, and the proposed parameter design method for TMG has demonstrated this feature.
The energy fluctuation in the Einstein model of lattice vibration
NASA Astrophysics Data System (ADS)
Nagata, Shoichi
2015-10-01
The temperature variation of the fluctuation in energy in the Einstein model of lattice vibration is calculated. They display particle-like and wave-like properties. The particle-wave duality changes gradually as a function of temperature. With increasing temperature, the dominant contribution to the fluctuation in energy changes at crossover temperature {{T}\\text{pw}} from particle-like to wave-like properties. The crossover point is found to be {{k}\\text{B}}{{T}\\text{pw}}/h? ??=??1.443, where {{k}\\text{B}} is Boltzmanns constant, h is Plancks constant and ? is the frequency of the Einstein model. A detailed comparison of the fluctuation in energy is made between the Einstein model and a two-level system (the so-called Schottky model). This study is developed within the framework of classical quantum theory; nevertheless the obtained results are fairly instructive.
Epistemic uncertainty propagation in energy flows between structural vibrating systems
NASA Astrophysics Data System (ADS)
Xu, Menghui; Du, Xiaoping; Qiu, Zhiping; Wang, Chong
2016-03-01
A dimension-wise method for predicting fuzzy energy flows between structural vibrating systems coupled by joints with epistemic uncertainties is established. Based on its Legendre polynomial approximation at α=0, both the minimum and maximum point vectors of the energy flow of interest are calculated dimension by dimension within the space spanned by the interval parameters determined by fuzzy those at α=0 and the resulted interval bounds are used to assemble the concerned fuzzy energy flows. Besides the proposed method, vertex method as well as two current methods is also applied. Comparisons among results by different methods are accomplished by two numerical examples and the accuracy of all methods is simultaneously verified by Monte Carlo simulation.
Active Vibration Control for Helicopter Interior Noise Reduction Using Power Minimization
NASA Technical Reports Server (NTRS)
Mendoza, J.; Chevva, K.; Sun, F.; Blanc, A.; Kim, S. B.
2014-01-01
This report describes work performed by United Technologies Research Center (UTRC) for NASA Langley Research Center (LaRC) under Contract NNL11AA06C. The objective of this program is to develop technology to reduce helicopter interior noise resulting from multiple gear meshing frequencies. A novel active vibration control approach called Minimum Actuation Power (MAP) is developed. MAP is an optimal control strategy that minimizes the total input power into a structure by monitoring and varying the input power of controlling sources. MAP control was implemented without explicit knowledge of the phasing and magnitude of the excitation sources by driving the real part of the input power from the controlling sources to zero. It is shown that this occurs when the total mechanical input power from the excitation and controlling sources is a minimum. MAP theory is developed for multiple excitation sources with arbitrary relative phasing for single or multiple discrete frequencies and controlled by a single or multiple controlling sources. Simulations and experimental results demonstrate the feasibility of MAP for structural vibration reduction of a realistic rotorcraft interior structure. MAP control resulted in significant average global vibration reduction of a single frequency and multiple frequency excitations with one controlling actuator. Simulations also demonstrate the potential effectiveness of the observed vibration reductions on interior radiated noise.
Zalesskaya, G.A.; Yakovlev, D.L.
1995-02-01
CO{sub 2} laser-induced delayed fluorescence was used to study the collisional vibration-energy exchange between the polyatomic molecules in gases. The efficiency of collisional exchange, the mean amount of energy transfer in one collision, as well as their correlation with the vibration energy and with the size of excited molecule were determined for diacetyl, acetophenone, benzophenone, and anthraquinone molecules form the experimentally observed pressure dependences of the decay rates and fluorescence intensities. It was shown that the mean amount of energy transfer per collision decreases with the molecular size and increases as E{sup m}, with m>2, with increasing the vibration energy. 25 refs., 4 figs., 1 tab.
NASA Astrophysics Data System (ADS)
Wang, Xu
2016-02-01
This paper establishes coupling loss factor of linear vibration energy harvesting systems in a framework of statistical energy analysis under parameter variations and random excitations. The new contributions of this paper are to define the numerical ranges of the dimensionless force factor for the weak, moderate and strong coupling and to study the connections of dimensionless force factor, coupling loss factor, coupling quotient, critical coupling strength, electro-mechanical coupling factor, damping loss factor and modal densities in linear vibration energy harvesting systems. The motivation of this paper is to enable statistical energy analysis of linear vibration energy harvesting systems for reliable performance predictions and design optimisation under parameter variations of materials and manufacturing processes and random ambient environmental excitations.
Low power energy harvesting and storage techniques from ambient human powered energy sources
NASA Astrophysics Data System (ADS)
Yildiz, Faruk
Conventional electrochemical batteries power most of the portable and wireless electronic devices that are operated by electric power. In the past few years, electrochemical batteries and energy storage devices have improved significantly. However, this progress has not been able to keep up with the development of microprocessors, memory storage, and sensors of electronic applications. Battery weight, lifespan and reliability often limit the abilities and the range of such applications of battery powered devices. These conventional devices were designed to be powered with batteries as required, but did not allow scavenging of ambient energy as a power source. In contrast, development in wireless technology and other electronic components are constantly reducing the power and energy needed by many applications. If energy requirements of electronic components decline reasonably, then ambient energy scavenging and conversion could become a viable source of power for many applications. Ambient energy sources can be then considered and used to replace batteries in some electronic applications, to minimize product maintenance and operating cost. The potential ability to satisfy overall power and energy requirements of an application using ambient energy can eliminate some constraints related to conventional power supplies. Also power scavenging may enable electronic devices to be completely self-sustaining so that battery maintenance can eventually be eliminated. Furthermore, ambient energy scavenging could extend the performance and the lifetime of the MEMS (Micro electromechanical systems) and portable electronic devices. These possibilities show that it is important to examine the effectiveness of ambient energy as a source of power. Until recently, only little use has been made of ambient energy resources, especially for wireless networks and portable power devices. Recently, researchers have performed several studies in alternative energy sources that could provide small amounts of electricity to low-power electronic devices. These studies were focused to investigate and obtain power from different energy sources, such as vibration, light, sound, airflow, heat, waste mechanical energy and temperature variations. This research studied forms of ambient energy sources such as waste mechanical (rotational) energy from hydraulic door closers, and fitness exercise bicycles, and its conversion and storage into usable electrical energy. In both of these examples of applications, hydraulic door closers and fitness exercise bicycles, human presence is required. A person has to open the door in order for the hydraulic door closer mechanism to function. Fitness exercise bicycles need somebody to cycle the pedals to generate electricity (while burning calories.) Also vibrations, body motions, and compressions from human interactions were studied using small piezoelectric fiber composites which are capable of recovering waste mechanical energy and converting it to useful electrical energy. Based on ambient energy sources, electrical energy conversion and storage circuits were designed and tested for low power electronic applications. These sources were characterized according to energy harvesting (scavenging) methods, and power and energy density. At the end of the study, the ambient energy sources were matched with possible electronic applications as a viable energy source.
Sassani, Farrokh
2014-01-01
The simulation results for electromagnetic energy harvesters (EMEHs) under broad band stationary Gaussian random excitations indicate the importance of both a high transformation factor and a high mechanical quality factor to achieve favourable mean power, mean square load voltage, and output spectral density. The optimum load is different for random vibrations and for sinusoidal vibration. Reducing the total damping ratio under band-limited random excitation yields a higher mean square load voltage. Reduced bandwidth resulting from decreased mechanical damping can be compensated by increasing the electrical damping (transformation factor) leading to a higher mean square load voltage and power. Nonlinear EMEHs with a Duffing spring and with linear plus cubic damping are modeled using the method of statistical linearization. These nonlinear EMEHs exhibit approximately linear behaviour under low levels of broadband stationary Gaussian random vibration; however, at higher levels of such excitation the central (resonant) frequency of the spectral density of the output voltage shifts due to the increased nonlinear stiffness and the bandwidth broadens slightly. Nonlinear EMEHs exhibit lower maximum output voltage and central frequency of the spectral density with nonlinear damping compared to linear damping. Stronger nonlinear damping yields broader bandwidths at stable resonant frequency. PMID:24605063
Determination of stepsize parameters for intermolecular vibrational energy transfer
Tardy, D.C.
1992-03-01
Intermolecular energy transfer of highly excited polyatomic molecules plays an important role in many complex chemical systems: combustion, high temperature and atmospheric chemistry. By monitoring the relaxation of internal energy we have observed trends in the collisional efficiency ({beta}) for energy transfer as a function of the substrate's excitation energy and the complexities of substrate and deactivator. For a given substrate {beta} increases as the deactivator's mass increase to {approximately}30 amu and then exhibits a nearly constant value; this is due to a mass mismatch between the atoms of the colliders. In a homologous series of substrate molecules (C{sub 3}{minus}C{sub 8}) {beta} decreases as the number of atoms in the substrate increases; replacing F with H increases {beta}. All substrates, except for CF{sub 2}Cl{sub 2} and CF{sub 2}HCl below 10,000 cm{sup {minus}1}, exhibited that {beta} is independent of energy, i.e. <{Delta}E>{sub all} is linear with energy. The results are interpreted with a simple model which considers that {beta} is a function of the ocillators energy and its vibrational frequency. Limitations of current approximations used in high temperature unimolecular reactions were evaluated and better approximations were developed. The importance of energy transfer in product yields was observed for the photoactivation of perfluorocyclopropene and the photoproduction of difluoroethyne. 3 refs., 18 figs., 4 tabs.
DSMC Modeling of Vibration-Vibration Energy Transfer Between Diatomic Molecules
Bondar, Ye. A.; Ivanov, M. S.
2008-12-31
Larsen-Borgnakke model, widely used in the DSMC method to simulate rotation-translation and vibration-translation exchanges in molecular collisions, is applied for the first time to resonant exchange between the vibrational modes of diatomic molecules (VV exchange). The validation of the model is performed through comparisons with experimental data on VV exchange in nitrogen.
NASA Technical Reports Server (NTRS)
Tessarzik, J. M.; Chiang, T.; Badgley, R. H.
1973-01-01
The vibration response of a gas-bearing rotor-support system was analyzed experimentally documented for sinusoidal and random vibration environments. The NASA Brayton Rotating Unit (BRU), 36,000 rpm; 10 KWe turbogenerator; was subjected in the laboratory to sinusoidal and random vibrations to evaluate the capability of the BRU to (1) survive the vibration levels expected to be encountered during periods of nonoperation and (2) operate satisfactorily (that is, without detrimental bearing surface contacts) at the vibration levels expected during normal BRU operation. Response power spectral density was calculated for specified input random excitation, with particular emphasis upon the dynamic motions of the thrust bearing runner and stator. A three-mass model with nonlinear representation of the engine isolator mounts was used to calculate axial rotor-bearing shock response.
Using powerful vibrators for calibration of seismic traces in nuclear explosion monitoring problems.
NASA Astrophysics Data System (ADS)
Glinsky, B.; Kovalevsky, V.; Seleznev, V.; Emanov, A.; Soloviev, V.
2009-04-01
The efficiency of functioning of the International Seismic Monitoring System (ISMS) is connected with the accuracy of the location and identification of a source of seismic waves which can be nuclear explosion. The errors in the determination of the location are caused by local and regional variations of wave hodographs. Empirical approach to solving these problems is to use events for which the locations and times are known, in order to determine a set of corrections to the regional model of wave propagation. The using of powerful vibrators for calibration of seismic traces is a new way in nuclear explosion monitoring problems. Now the 60-100 tons force vibrator can radiate the signals which can be recorded at the distances up to 500 km and can be used for regional calibration of seismic traces. The comparison of the seismic wave fields of powerful vibrators and 100-ton chemical explosion "Omega-3" at the 630-km profile, quarry explosions of the Kuznetsk basin with power from 50 to 700 tons at the distances up to 355 km showed their equivalence in the main types of waves. The paper presents the results of experiments of long-distance recording of seismic signals of powerful vibrators and detailed investigation of the velocity characteristics of the Earth's crust in West Siberia and Altay-Sayan region.
Using powerful vibrators for calibration of seismic traces in nuclear explosion monitoring problems
NASA Astrophysics Data System (ADS)
Glinsky, B.; Kovalevsky, V.; Seleznev, V.; Emanov, A.; Soloviev, V.
2009-04-01
The efficiency of functioning of the International Seismic Monitoring System (ISMS) is connected with the accuracy of the location and identification of a source of seismic waves which can be nuclear explosion. The errors in the determination of the location are caused by local and regional variations of wave hodographs. Empirical approach to solving these problems is to use events for which the locations and times are known, in order to determine a set of corrections to the regional model of wave propagation. The using of powerful vibrators for calibration of seismic traces is a new way in nuclear explosion monitoring problems. Now the 60-100 tons force vibrator can radiate the signals which can be recorded at the distances up to 500 km and can be used for regional calibration of seismic traces. The comparison of the seismic wave fields of powerful vibrators and 100-ton chemical explosion "Omega-3" at the 630-km profile, quarry explosions of the Kuznetsk basin with power from 50 to 700 tons at the distances up to 355 km showed their equivalence in the main types of waves. The paper presents the results of experiments of long-distance recording of seismic signals of powerful vibrators and detailed investigation of the velocity characteristics of the Earth's crust in West Siberia and Altay-Sayan region.
Effect of Vibration Training on Anaerobic Power and Quardroceps Surface EMG in Long Jumpers
ERIC Educational Resources Information Center
Liu, Bin; Luo, Jiong
2015-01-01
Objective: To explore the anaerobic power and surface EMG (sEMG) of quardrocep muscle in lower extremities after single vibration training intervention. Methods: 8 excellent male long jumpers voluntarily participated in this study. Four intervention modes were devised, including high frequency high amplitude (HFHA,30Hz,6mm), low frequency low…
Saffar, Saber; Abdullah, Amir
2014-01-01
The acoustic impedances of matching layers, their internal loss and vibration amplitude are the most important and influential parameters in the performance of high power airborne ultrasonic transducers. In this paper, the optimum acoustic impedances of the transducer matching layers were determined by using a genetic algorithm, the powerful tool for optimizating domain. The analytical results showed that the vibration amplitude increases significantly for low acoustic impedance matching layers. This enhancement is maximum and approximately 200 times higher for the last matching layer where it has the same interface with the air than the vibration amplitude of the source, lead zirconate titanate-pizo electric while transferring the 1 kW is desirable. This large amplitude increases both mechanical failure and temperature of the matching layers due to the internal loss of the matching layers. It has analytically shown that the temperature in last matching layer with having the maximum vibration amplitude is high enough to melt or burn the matching layers. To verify suggested approach, the effect of the amplitude of vibration on the induced temperature has been investigated experimentally. The experimental results displayed good agreement with the theoretical predictions. PMID:23664304
A micromachined low-frequency piezoelectric harvester for vibration and wind energy scavenging
NASA Astrophysics Data System (ADS)
He, Xuefeng; Shang, Zhengguo; Cheng, Yaoqing; Zhu, You
2013-12-01
To efficiently scavenge ambient vibration energy and wind energy at the same time, a low-frequency piezoelectric harvester was designed, fabricated and tested. A lumped-parameter model of the cantilevered piezoelectric energy harvester with a proof mass was established and the closed-form expressions of voltage and power on a resistance load under base acceleration excitation were derived. After effects of the lengths of the proof mass and electrodes on output power were analyzed, a MEMS harvester was optimally designed. By using aluminum nitride as piezoelectric layer, a MEMS energy harvester was fabricated with bulk micromachining process. Experimental results show that the open-circuit frequency of the MEMS harvester is about 134.8 Hz and the matched resistance is about 410 k?. Under the harmonic acceleration excitation of 0.1 g, the maximum output power is about 1.85 W, with the normalized power density of about 6.3 mW cm-3 g-2. The critical wind speed of the device is between 12.7 and 13.2 m s-1 when the wind direction is from the proof mass to the fixed end of the cantilever. The maximum output power under 16.3 m s-1 wind is about 2.27 W.
MEMS based Nonlinear Monostable Electromagnetic Vibrational Energy Harvester for Wider Bandwidth
NASA Astrophysics Data System (ADS)
Mallick, D.; Amann, A.; Roy, S.
2015-12-01
This paper reports a wideband vibrational energy harvesting scheme using a MEMS based nonlinear electromagnetic transducer. The nonlinearity is incorporated in the proposed device through the stretching strain in addition to the bending of the fixed-guided configured beams of the designed structure. The thin spring structure is fabricated on Silicon-On-Insulator substrate with device layer thickness of 50 m. The MEMS spring structure is packaged and characterized with wire wound copper coil (NE1) and micro fabricated double layer copper coil (NE2) for comparison. Measurement results show that ?80 Hz half power bandwidth is obtained for the fabricated devices with maximum load powers of 2.8 W (NE1) and 0.4 W (NE2) respectively at 0.5g which improves the power-bandwidth gain to one of the highest among reported works.
A modal approach to modeling spatially distributed vibration energy dissipation.
Segalman, Daniel Joseph
2010-08-01
The nonlinear behavior of mechanical joints is a confounding element in modeling the dynamic response of structures. Though there has been some progress in recent years in modeling individual joints, modeling the full structure with myriad frictional interfaces has remained an obstinate challenge. A strategy is suggested for structural dynamics modeling that can account for the combined effect of interface friction distributed spatially about the structure. This approach accommodates the following observations: (1) At small to modest amplitudes, the nonlinearity of jointed structures is manifest primarily in the energy dissipation - visible as vibration damping; (2) Correspondingly, measured vibration modes do not change significantly with amplitude; and (3) Significant coupling among the modes does not appear to result at modest amplitudes. The mathematical approach presented here postulates the preservation of linear modes and invests all the nonlinearity in the evolution of the modal coordinates. The constitutive form selected is one that works well in modeling spatially discrete joints. When compared against a mathematical truth model, the distributed dissipation approximation performs well.
A low frequency MEMS vibration sensor for low power missile health monitoring
NASA Astrophysics Data System (ADS)
Horowitz, S. B.; Allen, M. S.; Fox, J. R.; Cortes, J. P.; Barkett, L.; Mathias, A. D.; Hernandez, C.; Martin, A. C.; Sanghadasa, M.; Marotta, S.
This paper addresses the design, fabrication and characterization of a first-generation, low frequency MEMS vibration sensor. The sensor is designed specifically for applications requiring extremely low power vibration detection at only targeted frequencies. For development, lumped element and finite element modeling was performed, driving the design towards a realizable geometry that addresses the targeted performance specs. The sensors were microfabricated using conventional surface micromachining, sol-gel PZT (lead zirconate titanate) thin films, and bulk silicon etching techniques. The completed sensors were then characterized to determine electrical, mechanical and piezoelectric properties at the material and device level. Results demonstrate functional operation with performance close to predicted specifications.
Cantilevers-on-membrane design for broadband MEMS piezoelectric vibration energy harvesting
NASA Astrophysics Data System (ADS)
Jia, Yu; Du, Sijun; Seshia, Ashwin A.
2015-12-01
Most MEMS piezoelectric vibration energy harvesters involve either cantilever-based topologies, doubly-clamped beams or membrane structures. While these traditional designs offer simplicity, their frequency response for broadband excitation are typically inadequate. This paper presents a new integrated cantilever-on-membrane design that attempts to both optimise the strain distribution on a piezoelectric membrane resonator and improve the power responsiveness of the harvester for broadband excitation. While a classic membrane-based resonator has the potential to theoretically offer wider operational frequency bandwidth than its cantilever counterpart, the addition of a centred proof mass neutralises its otherwise high strain energy regions. The proposed topology addresses this issue by relocating the proof mass onto subsidiary cantilevers and integrates the merits of both the membrane and the cantilever designs. When experimentally subjected to a band-limited white noise excitation, up to approximately two folds of power enhancement was observed for the new membrane harvester compared to a classic plain membrane device.
An investigation on vibration energy harvesting using nonlinear dynamic principles inspired by trees
NASA Astrophysics Data System (ADS)
Harne, R. L.; Sun, A.; Wang, K. W.
2015-04-01
Trees exploit intriguing mechanisms such as multimodal frequency distributions and nonlinearities to distribute and dampen the aerodynamically-induced vibration energies to which they are subjected. In dynamical systems, these mechanisms are comparable to the internal resonance phenomenon. In recent years, researchers have harnessed strong nonlinearities, including internal resonance, to induce energetic dynamics that enhance performance of vibration energy harvesting systems. For trees, the internal resonance-like dynamics are evidently useful damping mechanisms in spite of the high variation associated with excitation and structural parameters. Yet for dynamic systems, studies show narrow operating regimes which exhibit internal resonance-based behaviors, suggesting that the energetic dynamics may be deactivated if stochastic inputs corrupt ideal excitation properties. To address these issues, this research evaluates the opportunities enabled by exploiting nonlinear, multimodal motions in an L-shaped energy harvester platform. The system dynamics are probed analytically, numerically, and experimentally for comprehensive insights on the versatility of internal resonance-based behaviors for energy harvesting. It is found that although activating the high amplitude nonlinear dynamics to enhance power generation is robust to significant additive noise in the harmonic excitations, parameter sensitivities may pose practical challenges in application. Discussion is provided on means to address such concerns and on future strategies that may favorably exploit nonlinearity and multimodal dynamics for robust energy harvesting performance.
Chun, Inwoo; Lee, Hyun-Woo; Kwon, Kwang-Ho
2014-12-01
Limited energy sources of ubiquitous sensor networks (USNs) such as fuel cells and batteries have grave drawbacks such as the need for replacements and re-charging owing to their short durability and environmental pollution. Energy harvesting which is converting environmental mechanical vibration into electrical energy has been researched with some piezoelectric materials and various cantilever designs to increase the efficiency of energy-harvesting devices. In this study, we focused on an energy-harvesting cantilever with a broadband vibration frequency. We fabricated a lead zirconate titanate (PZT) cantilever array with various Si proof masses on small beams (5.5 mm x 0.5 mm x 0.5 mm). We obtained broadband resonant frequencies ranging between 127 Hz and 136 Hz using a micro electro-mechanical system (MEMS) process. In order to obtain broadband resonant characteristics, the cantilever array was comprised of six cantilevers with different resonant frequencies. We obtained an output power of about 2.461 μW at an acceleration of 0.23 g and a resistance of 4 kΩ. The measured bandwidth of the resonant frequency was approximately 9 Hz (127-136 Hz), which is about six times wider than the bandwidth of a single cantilever. PMID:25971046
Leveraging nonlinear saturation-based phenomena in an L-shaped vibration energy harvesting system
NASA Astrophysics Data System (ADS)
Harne, R. L.; Sun, A.; Wang, K. W.
2016-02-01
Trees exploit intriguing mechanisms such as multimodal frequency distributions and nonlinearities to distribute and dampen the aerodynamically-induced vibration energies to which they are subjected. In dynamical systems, these mechanisms are comparable to internal resonance phenomena. In recent years, researchers have harnessed strong nonlinearities, including internal resonance, to induce energetic dynamics that enhance performance of vibration energy harvesting systems. For trees, the internal resonance-like dynamics are evidently useful to dampen swaying motions in spite of the high variation associated with excitation and structural parameters. Yet for dynamic systems, studies show narrow operating regimes which exhibit internal resonance-based behaviors; this additionally suggests that the energetic dynamics may be susceptible to deactivation if stochastic inputs corrupt ideal excitation properties. To address these issues and to investigate whether the underlying motivation of exploiting internal resonance-induced saturation dynamics is truly justified, this research evaluates the opportunities enabled by exploiting nonlinear, multimodal motions in an L-shaped energy harvester platform. The system dynamics are probed analytically, numerically, and experimentally for comprehensive insights on the versatility of internal resonance-based behaviors for energy harvesting. It is found that although activating the high amplitude nonlinear dynamics to enhance power generation is robust to significant additive noise in the harmonic excitations, parameter sensitivities may pose practical challenges in application. Discussion is provided on means to address such concerns and on future strategies that may favorably exploit nonlinearity and multimodal dynamics for robust energy harvesting performance.
A novel controller to increase harvested energy from negating vibration-suppression effect
NASA Astrophysics Data System (ADS)
Makihara, Kanjuro; Yamamoto, Yuta; Yoshimizu, Kenji; Horiguchi, Chikahiro; Sakaguchi, Hitoshi; Fujimoto, Katsumi
2015-03-01
This paper proposes an innovative energy-harvesting controller to increase energy harvested from vibrations. Energy harvesting is a process that removes mechanical energy from a vibrating structure, which necessarily results in damping. The damping associated with piezoelectric energy harvesting suppresses the amplitude of mechanical vibration and reduces the harvested energy. To address this critical problem, we devise an energy-harvesting controller that maintains the vibration amplitude as high as possible to increase the harvested energy. Our proposed switching controller is designed to intentionally stop the switching action intermittently. We experimentally demonstrate that the proposed control scheme successfully increases the harvested energy. The piezoelectric voltage with the proposed controller is larger than that with the original synchronized switching harvesting on inductor (SSHI) technique, which increases the harvested energy. The stored energy with our controller is up to 5.7 times greater than that with the conventional SSHI control scheme.
Power management for energy harvesting wireless sensors
NASA Astrophysics Data System (ADS)
Arms, S. W.; Townsend, C. P.; Churchill, D. L.; Galbreath, J. H.; Mundell, S. W.
2005-05-01
The objective of this work was to demonstrate smart wireless sensing nodes capable of operation at extremely low power levels. These systems were designed to be compatible with energy harvesting systems using piezoelectric materials and/or solar cells. The wireless sensing nodes included a microprocessor, on-board memory, sensing means (1000 ohm foil strain gauge), sensor signal conditioning, 2.4 GHz IEEE 802.15.4 radio transceiver, and rechargeable battery. Extremely low power consumption sleep currents combined with periodic, timed wake-up was used to minimize the average power consumption. Furthermore, we deployed pulsed sensor excitation and microprocessor power control of the signal conditioning elements to minimize the sensors" average contribution to power draw. By sleeping in between samples, we were able to demonstrate extremely low average power consumption. At 10 Hz, current consumption was 300 microamps at 3 VDC (900 microwatts); at 5 Hz: 400 microwatts, at 1 Hz: 90 microwatts. When the RF stage was not used, but data were logged to memory, consumption was further reduced. Piezoelectric strain energy harvesting systems delivered ~2000 microwatts under low level vibration conditions. Output power levels were also measured from two miniature solar cells; which provided a wide range of output power (~100 to 1400 microwatts), depending on the light type & distance from the source. In summary, system power consumption may be reduced by: 1) removing the load from the energy harvesting & storage elements while charging, 2) by using sleep modes in between samples, 3) pulsing excitation to the sensing and signal conditioning elements in between samples, and 4) by recording and/or averaging, rather than frequently transmitting, sensor data.
NASA Astrophysics Data System (ADS)
Paxson, Benjamin; Wickenheiser, Adam M.
2014-04-01
In recent years, an increasing number of breakthroughs have been made in the field of small-scale wind energy harvesting, where specialized materials are utilized to convert flow energy into electric power. Several studies on this power extraction rely on a common energy harvester setup in which a stiff cantilever beam is attached to the trailing edge of a miniature bluff body. At these small scales where boundary layer effects are appreciable in the laminar flow regime, periodic vortex shedding can be used to drive transverse vibrations in the beam. Interestingly, the fluid dynamics involved in this unsteady process have been studied for decades not to exploit their characteristics, but instead to eliminate potentially destructive effects. As a result, there is still much room for improvement and expansion on recent design studies. A study of how subtle changes in bluff body trailing edge geometry effect power output of a model will be presented in this paper. The model under consideration consists of a miniature bluff body on the order of tens of millimeters in diameter, to which a piezoelectric cantilever is attached at the trailing edge. This model is specifically designed for laminar to transitional Reynolds Number flows (500-2800) where the periodicity of vortex shedding approaches the natural frequency of the beam. As the flow speed is further increased, the effect of lock-in occurs where the resonant beam motion resists a change in vortex shedding frequency. Vibration amplitudes of the beam reach a maximum under this condition, thus maximizing power generation efficiency of the system and providing an optimal condition to operate the harvester. In an effort to meaningfully compare the results, a number of dimensionless parameters are employed. The influence of parameters such as beam length and natural frequency, fluid flow speed, and trailing edge geometry are studied utilizing COMSOL Multiphysics laminar, fluid-structure interaction simulations in order to create design guidelines for an improved energy harvester.
A high-power linear ultrasonic motor using longitudinal vibration transducers with single foot.
Liu, Yingxiang; Chen, Weishan; Liu, Junkao; Shi, Shengjun
2010-08-01
A high-power linear ultrasonic motor using longitudinal vibration transducers with single foot was proposed in this paper. The stator of proposed motor contains a horizontal transducer and a vertical transducer. Longitudinal vibrations are superimposed in the stator and generate an elliptical trajectory at the driving foot. The sensitivity analysis of structural parameters to the resonance frequencies of two working modes of the stator was performed using the finite element method. The resonance frequencies of two working modes were degenerated by adjusting the structural parameters. The vibration characteristics of stator were studied and discussed. A prototype motor was fabricated and measured. Typical output of the prototype is a no-load speed of 1160 mm/s and maximum thrust force of 20 N at a voltage of 200 V(rms). PMID:20679015
Minimizing the Excitation of Parasitic Modes of Vibration in Slender Power Ultrasonic Devices
NASA Astrophysics Data System (ADS)
Mathieson, A.; Lucas, M.
The design of slender power ultrasonic devices can often be challenging due to the excitation of parasitic modes of vibration during operation. The excitation of these modes is known to manifest from behaviors such as modal coupling which if not controlled or designed out of the system can, under operational conditions, lead to poor device performance and device failure. However, a report published by the authors has indicted that the excitation of these modes of vibration could be minimized through device design, specifically careful location of the piezoceramic stack. This paper illustrates that it is possible, through piezoceramic stack position, to minimize modal coupling between a parasitic mode and the tuned longitudinal mode of vibration for slender ultrasonic devices.
A method of real-time fault diagnosis for power transformers based on vibration analysis
NASA Astrophysics Data System (ADS)
Hong, Kaixing; Huang, Hai; Zhou, Jianping; Shen, Yimin; Li, Yujie
2015-11-01
In this paper, a novel probability-based classification model is proposed for real-time fault detection of power transformers. First, the transformer vibration principle is introduced, and two effective feature extraction techniques are presented. Next, the details of the classification model based on support vector machine (SVM) are shown. The model also includes a binary decision tree (BDT) which divides transformers into different classes according to health state. The trained model produces posterior probabilities of membership to each predefined class for a tested vibration sample. During the experiments, the vibrations of transformers under different conditions are acquired, and the corresponding feature vectors are used to train the SVM classifiers. The effectiveness of this model is illustrated experimentally on typical in-service transformers. The consistency between the results of the proposed model and the actual condition of the test transformers indicates that the model can be used as a reliable method for transformer fault detection.
Energy 101: Concentrating Solar Power
None
2013-05-29
From towers to dishes to linear mirrors to troughs, concentrating solar power (CSP) technologies reflect and collect solar heat to generate electricity. A single CSP plant can generate enough power for about 90,000 homes. This video explains what CSP is, how it works, and how systems like parabolic troughs produce renewable power. For more information on the Office of Energy Efficiency and Renewable Energy's CSP research, see the Solar Energy Technology Program's Concentrating Solar Power Web page at http://www1.eere.energy.gov/solar/csp_program.html.
Energy 101: Concentrating Solar Power
2010-01-01
From towers to dishes to linear mirrors to troughs, concentrating solar power (CSP) technologies reflect and collect solar heat to generate electricity. A single CSP plant can generate enough power for about 90,000 homes. This video explains what CSP is, how it works, and how systems like parabolic troughs produce renewable power. For more information on the Office of Energy Efficiency and Renewable Energy's CSP research, see the Solar Energy Technology Program's Concentrating Solar Power Web page at http://www1.eere.energy.gov/solar/csp_program.html.
Silicon MEMS bistable electromagnetic vibration energy harvester using double-layer micro-coils
NASA Astrophysics Data System (ADS)
Podder, P.; Constantinou, P.; Mallick, D.; Roy, S.
2015-12-01
This work reports the development of a MEMS bistable electromagnetic vibrational energy harvester (EMVEH) consisting of a silicon-on-insulator (SOI) spiral spring, double layer micro-coils and miniaturized NdFeB magnets. Furthermore, with respect to the spiral silicon spring based VEH, four different square micro-coil topologies with different copper track width and number of turns have been investigated to determine the optimal coil dimensions. The micro-generator with the optimal micro-coil generated 0.68 micro-watt load power over an optimum resistive load at 0.1g acceleration, leading to normalized power density of 3.5 kg.s/m3. At higher accelerations the load power increased, and the vibrating magnet collides with the planar micro-coil producing wider bandwidth. Simulation results show that a substantially wider bandwidth could be achieved in the same device by introducing bistable nonlinearity through a repulsive configuration between the moving and fixed permanent magnets.
Harvesting energy from the vibration of a passing train using a single-degree-of-freedom oscillator
NASA Astrophysics Data System (ADS)
Gatti, G.; Brennan, M. J.; Tehrani, M. G.; Thompson, D. J.
2016-01-01
With the advent of wireless sensors, there has been an increasing amount of research in the area of energy harvesting, particularly from vibration, to power these devices. An interesting application is the possibility of harvesting energy from the track-side vibration due to a passing train, as this energy could be used to power remote sensors mounted on the track for strutural health monitoring, for example. This paper describes a fundamental study to determine how much energy could be harvested from a passing train. Using a time history of vertical vibration measured on a sleeper, the optimum mechanical parameters of a linear energy harvesting device are determined. Numerical and analytical investigations are both carried out. It is found that the optimum amount of energy harvested per unit mass is proportional to the product of the square of the input acceleration amplitude and the square of the input duration. For the specific case studied, it was found that the maximum energy that could be harvested per unit mass of the oscillator is about 0.25 J/kg at a frequency of about 17 Hz. The damping ratio for the optimum harvester was found to be about 0.0045, and the corresponding amplitude of the relative displacement of the mass is approximately 5 mm.
Shock reliability analysis and improvement of MEMS electret-based vibration energy harvesters
NASA Astrophysics Data System (ADS)
Renaud, M.; Fujita, T.; Goedbloed, M.; de Nooijer, C.; van Schaijk, R.
2015-10-01
Vibration energy harvesters can serve as a replacement solution to batteries for powering tire pressure monitoring systems (TPMS). Autonomous wireless TPMS powered by microelectromechanical system (MEMS) electret-based vibration energy harvester have been demonstrated. The mechanical reliability of the MEMS harvester still has to be assessed in order to bring the harvester to the requirements of the consumer market. It should survive the mechanical shocks occurring in the tire environment. A testing procedure to quantify the shock resilience of harvesters is described in this article. Our first generation of harvesters has a shock resilience of 400 g, which is far from being sufficient for the targeted application. In order to improve this aspect, the first important aspect is to understand the failure mechanism. Failure is found to occur in the form of fracture of the device’s springs. It results from impacts between the anchors of the springs when the harvester undergoes a shock. The shock resilience of the harvesters can be improved by redirecting these impacts to nonvital parts of the device. With this philosophy in mind, we design three types of shock absorbing structures and test their effect on the shock resilience of our MEMS harvesters. The solution leading to the best results consists of rigid silicon stoppers covered by a layer of Parylene. The shock resilience of the harvesters is brought above 2500 g. Results in the same range are also obtained with flexible silicon bumpers, which are simpler to manufacture.
Orientation of bluff body for designing efficient energy harvesters from vortex-induced vibrations
NASA Astrophysics Data System (ADS)
Dai, H. L.; Abdelkefi, A.; Yang, Y.; Wang, L.
2016-02-01
The characteristics and performances of four distinct vortex-induced vibrations (VIVs) piezoelectric energy harvesters are experimentally investigated and compared. The difference between these VIV energy harvesters is the installation of the cylindrical bluff body at the tip of cantilever beam with different orientations (bottom, top, horizontal, and vertical). Experiments show that the synchronization regions of the bottom, top, and horizontal configurations are almost the same at low wind speeds (around 1.5 m/s). The vertical configuration has the highest wind speed for synchronization (around 3.5 m/s) with the largest harvested power, which is explained by its highest natural frequency and the smallest coupled damping. The results lead to the conclusion that to design efficient VIV energy harvesters, the bluff body should be aligned with the beam for low wind speeds (<2 m/s) and perpendicular to the beam at high wind speeds (>2 m/s).
[Vibrational energy transfer from vibrational levels of RbH(X 1sigma+, v = 0-2) to H2].
Shen, Xiao-Yan; Wang, Shu-Ying; Liu, Jing; Dai, Kang; Shen, Yi-Fan
2011-01-01
The vibrational energy transfer from vibrational levels of RbH(X 1sigma+, v = 0-2) by collision with H2 was determined using the integrated time-resolved laser induced fluorescence (LIF) in a five-arm crossed heat-pipe oven. Rb-H2 mixture was irradiated with pulses of 696.4 nm radiation from a OPO laser, populating 6D state by two-photon absorption. The vibrational levels of RbH(X 1sigma+) generated in the reaction of Rb(6D) and H2 were detected by LIF technique. The nascent quantum state distributions of RbH were obtained when the delay time between the pump and probe laser was 20 ns. The nascent RbH product molecules were found to populate the lowest three vibrational (v = 0, 1, 2) levels of the ground electronic state but could not be detected in any higher vibrational state. The integrated time-resolved LIF excited A 1sigma+ --> X 1sigma+ system in the presence of H2 was recorded with delay time from 0 to 10 micros. The RbH signal of v = 0, 1 levels first increased and then decreased on a larger time scale. RbH was created instantaneously then was quenched by collision and diffused. The rate equations for the population of the vibrational levels were given. The integrated profiles method permitted us to determine the rate coefficients for vibrational transfer of RbH(X 1sigma+, v = 0-2) by collision with H2. The rate coefficients for collisional transfer of RbH(X 1sigma+) by collisions with H2 are (in units of 10-(11) cm3 x s(-1)) 3.4 +/- 0.8 and 2.8 +/- 0.6 for v = 2 --> v = 1 and v = 1 --> v = 0 respectively. The diffusion rates of v = 0, 1, 2 are (in units of 10(5) s(-1)) 4.9 +/- 1.1, 1.0 +/- 0.3 and 0.6 +/- 10.2, respectively. The experiment showed that vibrational relaxation from RbH(X 1sigma+, v = 0-2) was more efficient compared to that of other vibrational levels studied here. PMID:21428051
Computation of acoustic power, vibration response and acoustic pressures of fluid-filled pipes
NASA Astrophysics Data System (ADS)
James, J. H.
1982-05-01
Acoustic power radiated into the fluid around a pipe subjected to time harmonic excitation, the vibration response of the pipe wall, and the pressures in the exterior and interior fluids are computed. Pressure fields and pipe displacements are represented by Fourier transformations, and the acoustic power in the surrounding fluid is obtained from the stationary phase approximation to the far field pressure. The integral representations of fluid pressures, pipe displacements and radiated power are evaluated by a simple numerical quadrature scheme. Decibel level versus frequency plots for the responses in the individual circumferential harmonics of a water filled steel pipe surrounded by air are presented.
Minimizing radiated sound power from vibrating shell structures: Theory and experiment
NASA Astrophysics Data System (ADS)
Constans, Eric William
1998-12-01
A new design methodology is presented here for finding optimal structural designs of shell structures for minimum sound power. Two optimization techniques are presented: the use of lumped masses and tuned absorbers. Thin shell structures were targeted for noise reduction because of their ubiquity in industry. They are used to cover and protect noisy devices, such as gearboxes and electrical transformers, and also to keep dirt and other contaminants away from moving parts, as in the case of automotive valve covers. The design strategy presented here involves three major computational tasks: predicting vibration of the structure, predicting the sound power created by the vibrating structure and finding optimal designs for minimum noise. A discrete Kirchhoff shell finite element is used to calculate vibration response, and a wave superposition boundary element method is used to calculate sound power. A combined gradient- based/stochastic optimization algorithm is used to find optimal lumped mass and absorber locations, as well as absorber design parameters (mass, stiffness and damping.) Three case studies are examined in this research: a flat plate, a half-cylindrical shell and a gearbox enclosure. Numerical and experimental results are presented for each study. It is shown that the optimization strategy presented here is capable of finding optimal designs which produce significant reductions in sound power in all three cases.
Energy transfer of highly vibrationally excited naphthalene: collisions with CHF3, CF4, and Kr.
Chen Hsu, Hsu; Tsai, Ming-Tsang; Dyakov, Yuri A; Ni, Chi-Kung
2011-08-01
Energy transfer of highly vibrationally excited naphthalene in the triplet state in collisions with CHF(3), CF(4), and Kr was studied using a crossed-beam apparatus along with time-sliced velocity map ion imaging techniques. Highly vibrationally excited naphthalene (2.0 eV vibrational energy) was formed via the rapid intersystem crossing of naphthalene initially excited to the S(2) state by 266 nm photons. The shapes of the collisional energy-transfer probability density functions were measured directly from the scattering results of highly vibrationally excited naphthalene. In comparison to Kr atoms, the energy transfer in collisions between CHF(3) and naphthalene shows more forward scatterings, larger cross section for vibrational to translational (V ? T) energy transfer, smaller cross section for translational to vibrational and rotational (T ? VR) energy transfer, and more energy transferred from vibration to translation, especially in the range -?E(d) = -100 to -800 cm(-1). On the other hand, the difference of energy transfer properties between collisional partners Kr and CF(4) is small. The enhancement of the V ? T energy transfer in collisions with CHF(3) is attributed to the large attractive interaction between naphthalene and CHF(3) (1-3 kcal/mol). PMID:21823704
Energy transfer of highly vibrationally excited naphthalene: Collisions with CHF3, CF4, and Kr
NASA Astrophysics Data System (ADS)
Chen Hsu, Hsu; Tsai, Ming-Tsang; Dyakov, Yuri A.; Ni, Chi-Kung
2011-08-01
Energy transfer of highly vibrationally excited naphthalene in the triplet state in collisions with CHF3, CF4, and Kr was studied using a crossed-beam apparatus along with time-sliced velocity map ion imaging techniques. Highly vibrationally excited naphthalene (2.0 eV vibrational energy) was formed via the rapid intersystem crossing of naphthalene initially excited to the S2 state by 266 nm photons. The shapes of the collisional energy-transfer probability density functions were measured directly from the scattering results of highly vibrationally excited naphthalene. In comparison to Kr atoms, the energy transfer in collisions between CHF3 and naphthalene shows more forward scatterings, larger cross section for vibrational to translational (V ? T) energy transfer, smaller cross section for translational to vibrational and rotational (T ? VR) energy transfer, and more energy transferred from vibration to translation, especially in the range -?Ed = -100 to -800 cm-1. On the other hand, the difference of energy transfer properties between collisional partners Kr and CF4 is small. The enhancement of the V ? T energy transfer in collisions with CHF3 is attributed to the large attractive interaction between naphthalene and CHF3 (1-3 kcal/mol).
NASA Astrophysics Data System (ADS)
Karami, Armine; Basset, Philippe; Galayko, Dimitri
2015-12-01
This paper reports for the first time experiments using an electrostatic vibration energy harvester comprised of a low voltage electret-charged MEMS transducer joined to an unstable autosynchronous conditioning circuit with rectangular charge-voltage characteristic, also known as the Bennet's doubler conditioning circuit. The experimental results show that the electret voltage, even if of low value, can be used as the necessary pre-charge for these type of electrostatic vibration energy harvesters. Also, the use of such a conditioning circuit with a low-voltage electret capacitive MEMS tranducer instead of the previously-reported conditioning circuits with direct connection to load or through a rectifier, can be advantageous in terms of maximal harvested power for a low-voltage electret, showing up to 95% higher converted power.
Global Nonlinear Analysis of Piezoelectric Energy Harvesting from Ambient and Aeroelastic Vibrations
NASA Astrophysics Data System (ADS)
Abdelkefi, Abdessattar
Converting vibrations to a usable form of energy has been the topic of many recent investigations. The ultimate goal is to convert ambient or aeroelastic vibrations to operate low-power consumption devices, such as microelectromechanical systems, heath monitoring sensors, wireless sensors or replacing small batteries that have a finite life span or would require hard and expensive maintenance. The transduction mechanisms used for transforming vibrations to electric power include: electromagnetic, electrostatic, and piezoelectric mechanisms. Because it can be used to harvest energy over a wide range of frequencies and because of its ease of application, the piezoelectric option has attracted significant interest. In this work, we investigate the performance of different types of piezoelectric energy harvesters. The objective is to design and enhance the performance of these harvesters. To this end, distributed-parameter and phenomenological models of these harvesters are developed. Global analysis of these models is then performed using modern methods of nonlinear dynamics. In the first part of this Dissertation, global nonlinear distributed-parameter models for piezoelectric energy harvesters under direct and parametric excitations are developed. The method of multiple scales is then used to derive nonlinear forms of the governing equations and associated boundary conditions, which are used to evaluate their performance and determine the effects of the nonlinear piezoelectric coefficients on their behavior in terms of softening or hardening. In the second part, we assess the influence of the linear and nonlinear parameters on the dynamic behavior of a wing-based piezoaeroelastic energy harvester. The system is composed of a rigid airfoil that is constrained to pitch and plunge and supported by linear and nonlinear torsional and flexural springs with a piezoelectric coupling attached to the plunge degree of freedom. Linear analysis is performed to determine the effects of the linear spring coefficients and electrical load resistance on the flutter speed. Then, the normal form of the Hopf bifurcation ( utter) is derived to characterize the type of instability and determine the effects of the aerodynamic nonlinearities and the nonlinear coefficients of the springs on the system's stability near the bifurcation. This is useful to characterize the effects of different parameters on the system's output and ensure that subcritical or "catastrophic" bifurcation does not take place. Both linear and nonlinear analyses are then used to design and enhance the performance of these harvesters. In the last part, the concept of energy harvesting from vortex-induced vibrations of a circular cylinder is investigated. The power levels that can be generated from these vibrations and the variations of these levels with the freestream velocity are determined. A mathematical model that accounts for the coupled lift force, cylinder motion and generated voltage is presented. Linear analysis of the electromechanical model is performed to determine the effects of the electrical load resistance on the natural frequency of the rigid cylinder and the onset of the synchronization region. The impacts of the nonlinearities on the cylinder's response and energy harvesting are then investigated.
Vibration exercise as a warm-up modality for deadlift power output.
Cochrane, Darryl J; Coley, Karl W; Pritchard, Hayden J; Barnes, Matthew J
2015-04-01
Vibration exercise (VbX) has gained popularity as a warm-up modality to enhance performance in golf, baseball, and sprint cycling, but little is known about the efficacy of using VbX as a warm-up before resistance exercise, such as deadlifting. The aim of this study was to compare the effects of a deadlift (DL)-specific warm-up, VbX warm-up, and Control on DL power output (PO). The DL warm-up (DL-WU) included 10, 8, and 5 repetitions performed at 30, 40, and 50% 1-repetition maximum (1RM), respectively, where the number of repetitions was matched by body-weight squats performed with vibration and without vibration (Control). The warm-up conditions were randomized and performed at least 2 days apart. Peak power (PP), mean power, rate of force development (RFD), and electromyography (EMG) were measured during the concentric phase of 2 consecutive DLs (75% 1RM) at 30 seconds and 2:30 minutes after the warm-up conditions. There was no significant (p > 0.05) main effect or interaction effect between the DL-WU, VbX warm-up, and Control for PP, mean power, RFD, and EMG. Vibration exercise warm-up did not exhibit an ergogenic effect to potentiate muscle activity more than the specific DL-WU and Control. Therefore, DL PO is affected to a similar extent, irrespective of the type of stimuli, when the warm-up is not focused on raising muscle temperature. PMID:25353078
NASA Astrophysics Data System (ADS)
Ye, Zhitong; Duan, Zhiyong; Takahata, Kenichi; Su, Yufeng
2015-01-01
In this paper, the force analysis and output performance of the micro-vibration energy harvester are elaborated. The force of the floating magnet in the magnetic field of the lifting magnet is firstly analyzed. Using COMSOL™, the change of magnetic force exerted on the floating magnet versus the vertical distance and the horizontal eccentric distance is obtained for different lifting magnets of a cylinder, a ring and an inner cylinder plus an outer ring, respectively. When the distance between the lifting and floating magnets ranges from 7.3 to 8.1 mm, the change rate of the magnetic force versus the vertical distance for the inner cylinder plus outer ring structure is the smallest, whose value is 619 µN/mm. In other words, if the inner cylinder plus outer ring structure is used as the lifting magnet, the vibration space of the floating magnet is the largest, which is 8 and 7.6 % larger than the cylinder and ring lifting magnets, respectively. The horizontal restoring forces of the three structures are substantially equal to each other at the horizontal eccentric distance of 4 mm, which is around 860 µN. Then the equilibrium position change of the floating magnet is discussed when the energy harvester is in an inclined position. Finally, by the analysis of the vibration model, the output performances of the energy harvester are comparatively calculated under the vertical and inclined positions. At the natural frequency of 6.93 Hz, the maximum power of 66.7 µW is generated.
NASA Astrophysics Data System (ADS)
Ye, Zhitong; Duan, Zhiyong; Takahata, Kenichi; Su, Yufeng
2014-08-01
In this paper, the force analysis and output performance of the micro-vibration energy harvester are elaborated. The force of the floating magnet in the magnetic field of the lifting magnet is firstly analyzed. Using COMSOL, the change of magnetic force exerted on the floating magnet versus the vertical distance and the horizontal eccentric distance is obtained for different lifting magnets of a cylinder, a ring and an inner cylinder plus an outer ring, respectively. When the distance between the lifting and floating magnets ranges from 7.3 to 8.1 mm, the change rate of the magnetic force versus the vertical distance for the inner cylinder plus outer ring structure is the smallest, whose value is 619 N/mm. In other words, if the inner cylinder plus outer ring structure is used as the lifting magnet, the vibration space of the floating magnet is the largest, which is 8 and 7.6 % larger than the cylinder and ring lifting magnets, respectively. The horizontal restoring forces of the three structures are substantially equal to each other at the horizontal eccentric distance of 4 mm, which is around 860 N. Then the equilibrium position change of the floating magnet is discussed when the energy harvester is in an inclined position. Finally, by the analysis of the vibration model, the output performances of the energy harvester are comparatively calculated under the vertical and inclined positions. At the natural frequency of 6.93 Hz, the maximum power of 66.7 W is generated.
Vibration piezoelectric energy harvester with multi-beam
NASA Astrophysics Data System (ADS)
Cui, Yan; Zhang, Qunying; Yao, Minglei; Dong, Weijie; Gao, Shiqiao
2015-04-01
This work presents a novel vibration piezoelectric energy harvester, which is a micro piezoelectric cantilever with multi-beam. The characteristics of the PZT (Pb(Zr0.53Ti0.47)O3) thin film were measured; XRD (X-ray diffraction) pattern and AFM (Atomic Force Microscope) image of the PZT thin film were measured, and show that the PZT (Pb(Zr0.53Ti0.47)O3) thin film is highly (110) crystal oriented; the leakage current is maintained in nA magnitude, the residual polarisation Pr is 37.037 μC/cm2, the coercive field voltage Ec is 27.083 kV/cm, and the piezoelectric constant d33 is 28 pC/N. In order to test the dynamic performance of the energy harvester, a new measuring system was set up. The maximum output voltage of the single beam of the multi-beam can achieve 80.78 mV under an acceleration of 1 g at 260 Hz of frequency; the maximum output voltage of the single beam of the multi-beam is almost 20 mV at 1400 Hz frequency.
NASA Astrophysics Data System (ADS)
Hobeck, J. D.; Inman, D. J.
2014-11-01
Extensive research has been done on the topics of both turbulence-induced vibration and vibration based energy harvesting; however, little effort has been put into bringing these two topics together. Preliminary experimental studies have shown that piezoelectric structures excited by turbulent flow can produce significant amounts of useful power. This research could serve to benefit applications such as powering remote, self-sustained sensors in small rivers or air ventilation systems where turbulent fluid flow is a primary source of ambient energy. A novel solution for harvesting energy in these unpredictable fluid flow environments was explored by the authors in previous work, and a harvester prototype was developed. This prototype, called piezoelectric grass, has been the focus of many experimental studies. In this paper the authors present a theoretical analysis of the piezoelectric grass harvester modeled as a single unimorph cantilever beam exposed to turbulent cross-flow. This distributed parameter model was developed using a combination of both analytical and statistical techniques. The analytical portion uses a Rayleigh-Ritz approximation method to describe the beam dynamics, and utilizes piezoelectric constitutive relationships to define the electromechanical coupling effects. The statistical portion of the model defines the turbulence-induced forcing function distributed across the beam surface. The model presented in this paper was validated using results from several experimental case studies. Preliminary results show that the model agrees quite well with experimental data. A parameter optimization study was performed with the proposed model. This study demonstrated how a new harvester could be designed to achieve maximum power output in a given turbulent fluid flow environment.
Modeling and design of a vibration energy harvester using the magnetic shape memory effect
NASA Astrophysics Data System (ADS)
Saren, A.; Musiienko, D.; Smith, A. R.; Tellinen, J.; Ullakko, K.
2015-09-01
In this study, a vibration energy harvester is investigated which uses a Ni-Mn-Ga sample that is mechanically strained between 130 and 300 Hz while in a constant biasing magnetic field. The crystallographic reorientation of the sample during mechanical actuation changes its magnetic properties due to the magnetic shape memory (MSM) effect. This leads to an oscillation of the magnetic flux in the yoke which generates electrical energy by inducing an alternating current within the pick-up coils. A power of 69.5 mW (with a corresponding power density of 1.37 mW mm-3 compared to the active volume of the MSM element) at 195 Hz was obtained by optimizing the biasing magnetic field, electrical resistance and electrical resonance. The optimization of the electrical resonance increased the energy generated by nearly a factor of four when compared to a circuit with no resonance. These results are strongly supported by a theoretical model and simulation which gives corresponding values with an error of approximately 20% of the experimental data. This model will be used in the design of future MSM energy harvesters and their optimization for specific frequencies and power outputs.
Reliability of vibration energy harvesters of metal-based PZT thin films
NASA Astrophysics Data System (ADS)
Tsujiura, Y.; Suwa, E.; Kurokawa, F.; Hida, H.; Kanno, I.
2014-11-01
This paper describes the reliability of piezoelectric vibration energy harvesters (PVEHs) of Pb(Zr,Ti)O3 (PZT) thin films on metal foil cantilevers. The PZT thin films were directly deposited onto the Pt-coated stainless-steel (SS430) cantilevers by rf-magnetron sputtering, and we observed their aging behavior of power generation characteristics under the resonance vibration condition for three days. During the aging measurement, there was neither fatigue failure nor degradation of dielectric properties in our PVEHs (length: 13 mm, width: 5.0 mm, thickness: 104 ?m) even under a large excitation acceleration of 25 m/s2. However, we observed clear degradation of the generated electric voltage depending on excitation acceleration. The decay rate of the output voltage was 5% from the start of the measurement at 25 m/s2. The transverse piezoelectric coefficient (e31,f) also degraded with almost the same decay rate as that of the output voltage; this indicates that the degradation of output voltage was mainly caused by that of piezoelectric properties. From the decay curves, the output powers are estimated to degrade 7% at 15 m/s2 and 36% at 25 m/s2 if we continue to excite the PVEHs for 30 years.
Low-frequency and wideband vibration energy harvester with flexible frame and interdigital structure
NASA Astrophysics Data System (ADS)
Li, Pengwei; Liu, Ying; Wang, Yanfen; Luo, Cuixian; Li, Gang; Hu, Jie; Liu, Wei; Zhang, Wendong
2015-04-01
As an alternative to traditional cantilever beam structures and their evolutions, a flexible beam based, interdigital structure, vibration energy harvester has been presented and investigated. The proposed interdigital-shaped oscillator consists of a rectangular flexible frame and series of cantilever beams interdigitally bonded to it. In order to achieve low frequency and wide-bandwidth harvesting, Young's modulus of materials, frame size and the amount of the cantilevers have been studied systematically. The measured frequency responses of the designed device (PDMS frame, quintuple piezoelectric cantilever beams) show a 460% increase in bandwidth below 80Hz. When excited at an acceleration of 1.0 g, the energy harvester achieves to a maximum open-circuit voltage of 65V, and the maximum output power 4.5 mW.
NASA Astrophysics Data System (ADS)
Wang, Peihong; Du, Hejun
2015-07-01
Zinc oxide (ZnO) thin film piezoelectric microelectromechanical systems (MEMS) based vibration energy harvesters with two different designs are presented. These harvesters consist of a silicon cantilever, a silicon proof mass, and a ZnO piezoelectric layer. Design I has a large ZnO piezoelectric element and Design II has two smaller and equally sized ZnO piezoelectric elements; however, the total area of ZnO thin film in two designs is equal. The ZnO thin film is deposited by means of radio-frequency magnetron sputtering method and is characterized by means of XRD and SEM techniques. These ZnO energy harvesters are fabricated by using MEMS micromachining. The natural frequencies of the fabricated ZnO energy harvesters are simulated and tested. The test results show that these two energy harvesters with different designs have almost the same natural frequency. Then, the output performance of different ZnO energy harvesters is tested in detail. The effects of series connection and parallel connection of two ZnO elements on the load voltage and power are also analyzed. The experimental results show that the energy harvester with two ZnO piezoelectric elements in parallel connection in Design II has higher load voltage and higher load power than the fabricated energy harvesters with other designs. Its load voltage is 2.06 V under load resistance of 1 M? and its maximal load power is 1.25 ?W under load resistance of 0.6 M?, when it is excited by an external vibration with frequency of 1300.1 Hz and acceleration of 10 m/s2. By contrast, the load voltage of the energy harvester of Design I is 1.77 V under 1 M? resistance and its maximal load power is 0.98 ?W under 0.38 M? load resistance when it is excited by the same vibration.
NASA Astrophysics Data System (ADS)
Halim, M. A.; Cho, H. O.; Park, J. Y.
2014-11-01
We have presented a frequency up-converted hybrid type (Piezoelectric and Electromagnetic) vibration energy harvester that can be used in powering portable and wearable smart devices by handy motion. A transverse impact mechanism has been employed for frequency up-conversion. Use of two transduction mechanisms increases the output power as well as power density. The proposed device consists of a non-magnetic spherical ball (freely movable at handy motion frequency) to impact periodically on the parabolic top of a piezoelectric (PZT) cantilevered mass by sliding over it, allowing it to vibrate at its higher resonant frequency and generates voltage by virtue of piezoelectric effect. A magnet attached to the cantilever vibrates along with it at the same frequency and a relative motion between the magnet and a coil placed below it, induces emf voltage across the coil terminals as well. A macro-scale prototype of the harvester has been fabricated and tested by handy motion. With an optimum magnet-coil overlap, a maximum 0.98mW and 0.64mW peak powers have been obtained from the piezoelectric and the electromagnetic transducers of the proposed device while shaken, respectively. It offers 84.4?Wcm-3 peak power density.
Transition from IVR limited vibrational energy transport to bulk heat transport
NASA Astrophysics Data System (ADS)
Schade, Marco; Hamm, Peter
2012-01-01
In a previous paper [M. Schade, P. Hamm, Vibrational energy transport in the presence of intrasite vibrational energy redistribution, J. Chem. Phys. 131 (2009) 044511], it has been shown that on ultrashort length and time scales, the speed of vibrational energy transport along a molecular chain is limited by intrasite vibrational relaxation rather than the actual intersite propagation. However, since intrasite vibrational relaxation is length independent, the intersite propagation rate is expected to become rate-limiting at some length scale, where propagation approaches the bulk limit. In the present paper, we investigate the transition between both regimes. The response of different types of modes may be very different at early times, depending on how much they contribute directly to energy transport. Surprisingly though, when averaging the energy content over all vibrational modes of the various chain sites, the complexity of the intrasite vibrational relaxation process is completely hidden so that energy transport on the nanoscale can be described by an effective propagation rate, that equals the bulk value, even at short times.
Anharmonic vibrational properties in periodic systems: energy, electron-phonon coupling, and stress
NASA Astrophysics Data System (ADS)
Monserrat, Bartomeu; Drummond, N. D.; Needs, R. J.
2013-04-01
A unified approach is used to study vibrational properties of periodic systems with first-principles methods and including anharmonic effects. Our approach provides a theoretical basis for the determination of phonon-dependent quantities at finite temperatures. The low-energy portion of the Born-Oppenheimer energy surface is mapped and used to calculate the total vibrational energy including anharmonic effects, electron-phonon coupling, and the vibrational contribution to the stress tensor. We report results for the temperature dependence of the electronic band gap and the linear coefficient of thermal expansion of diamond, lithium hydride, and lithium deuteride.
Underwater energy harvesting from vibrations of annular ionic polymer metal composites
NASA Astrophysics Data System (ADS)
Cha, Youngsu; Abdolhamidi, Shervin; Porfiri, Maurizio
2015-04-01
In this paper, we investigate the feasibility of energy harvesting from axisymmetric vibrations of annular ionic polymer metal composites (IPMCs). We consider an in-house fabricated IPMC that is clamped at its inner radius to a moving base and is free at its outer radius. We propose a physics-based model for energy harvesting from underwater vibrations, in which the IPMC is described as a thin annular plate undergoing axisymmetric vibrations with an added mass due to the encompassing fluid. Experiments are performed to elucidate the effect of the shunting resistance and the excitation frequency on energy harvesting.
NASA Astrophysics Data System (ADS)
Palagummi, S.; Yuan, F. G.
2015-04-01
A detailed analysis of a mono-stable vertical diamagnetic levitation (VDL) system for optimal vibration energy harvesting is presented. Initial studies showed that simple analytical techniques such as the dipole model and the image method provide useful guideline for understanding the potential of a diamagnetic levitation system, however, it is discussed here that the more accurate semi-analytical techniques such as the thin coil model and the discrete volume method are needed for quantitative optimization and design of the VDL system. With the semi-analytical techniques, the influence of the cylindrical geometry of the floating magnet, the lifting magnet and the diamagnetic plate are parametrically studied to assess their effects on the levitation gap, size of the system and the natural frequency. For efficient vibration energy harvesting using the VDL system, ways to mitigate eddy current damping and a coil geometry for transduction are critically discussed. With the optimized parameters, an experimental system is realized which showed a hardening type nonlinearity. The results show an overall efficiency of 1.54 percent, a root mean square (rms) power output of 1.72 μW when excited at a peak acceleration of 0.081 m/s2 and at a frequency of 2.1 Hz.
The Effects of Spring Stiffness on Vortex-Induced Vibration for Energy Generation
NASA Astrophysics Data System (ADS)
Zahari, M.; Chan, H. B.; Yong, T. H.; Dol, S. S.
2015-04-01
Vortex-induced vibration (VIV) is the turbulent motion induced on bluff body that generates alternating lift forces and results in irregular movement of the body. VIV-powered system seems a good idea in greening the energy sector and most importantly is its ability to take advantages of low current speed of water to generate electricity. This paper aims to investigate the effects of spring stiffness on the characteristic of VIV. The study is important in order to maximize these potentially destructive vibrations into a valuable resource of energy. Five cylinders with the range of 0.25 to 2.00 inch diameter are tested to study the behavior of VIV. Results from this experiment indicates that, the 2.0 inch cylinder gave the lowest error in frequency ratio which is 1.1% and have a high potential of lock-in condition to occur. In term of maximum amplitude, this cylinder gave the highest amplitude of oscillation motion that is equal to 0.0065 m.
Harvesting broadband kinetic impact energy from mechanical triggering/vibration and water waves.
Wen, Xiaonan; Yang, Weiqing; Jing, Qingshen; Wang, Zhong Lin
2014-07-22
We invented a triboelectric nanogenerator (TENG) that is based on a wavy-structured Cu-Kapton-Cu film sandwiched between two flat nanostructured PTFE films for harvesting energy due to mechanical vibration/impacting/compressing using the triboelectrification effect. This structure design allows the TENG to be self-restorable after impact without the use of extra springs and converts direct impact into lateral sliding, which is proved to be a much more efficient friction mode for energy harvesting. The working mechanism has been elaborated using the capacitor model and finite-element simulation. Vibrational energy from 5 to 500 Hz has been harvested, and the generator's resonance frequency was determined to be ∼100 Hz at a broad full width at half-maximum of over 100 Hz, producing an open-circuit voltage of up to 72 V, a short-circuit current of up to 32 μA, and a peak power density of 0.4 W/m(2). Most importantly, the wavy structure of the TENG can be easily packaged for harvesting the impact energy from water waves, clearly establishing the principle for ocean wave energy harvesting. Considering the advantages of TENGs, such as cost-effectiveness, light weight, and easy scalability, this approach might open the possibility for obtaining green and sustainable energy from the ocean using nanostructured materials. Lastly, different ways of agitating water were studied to trigger the packaged TENG. By analyzing the output signals and their corresponding fast Fourier transform spectra, three ways of agitation were evidently distinguished from each other, demonstrating the potential of the TENG for hydrological analysis. PMID:24964297
Vibration transmission through rolling element bearings. IV - Statistical energy analysis
NASA Technical Reports Server (NTRS)
Lim, T. C.; Singh, R.
1992-01-01
A theoretical broadband coupling-loss factor is developed analytically for use in the statistical energy analysis (SEA) of a shaft-bearing-plate system. The procedure is based on the solution of the boundary-value problem at the plate-bearing interface and incorporates a bearing-stiffness matrix developed by the authors. Three examples are utilized to illustrate the SEA incorporating the coupling-loss factor including: (1) a shaft-bearing-plate system; (2) a plate-cantilevered beam; and (3) a circular-shaft-bearing plate. The coupling-loss factor in the case of the thin plate-cantilevered beam is found to be more accurate than that developed by Lyon and Eichler (1964). The coupling-loss factor is described for the bearing system and extended to describe the mean-square vibratory response of a rectangular plate. The proposed techniques are of interest to the study of vibration and noise in rotating machinery such as gearboxes.
NASA Technical Reports Server (NTRS)
Mckenzie, R. L.
1976-01-01
A semiclassical model of the inelastic collision between a vibrationally excited anharmonic oscillator and a structureless atom is used to predict the variation of thermally averaged vibrational-translational rate coefficients with temperature and initial-state quantum number. Multiple oscillator states are included in a numerical solution for collinear encounters. The results are compared with CO-He experimental values for both ground and excited initial states using several simplified forms of the interaction potential. The numerical model is also used as a basis for evaluating several less complete, but analytic, models. Two computationally simple analytic approximations are found that successfully reproduce the numerical rate coefficients for a wide range of molecular properties and collision partners. Their limitations are identified, and the relative rates of multiple-quantum transitions from excited states are evaluated for several molecular types.
NASA Technical Reports Server (NTRS)
Mckenzie, R. L.
1975-01-01
A semiclassical model of the inelastic collision between a vibrationally excited anharmonic oscillator and a structureless atom was used to predict the variation of thermally averaged vibration-translation rate coefficients with temperature and initial-state quantum number. Multiple oscillator states were included in a numerical solution for collinear encounters. The results are compared with CO-He experimental values for both ground and excited initial states using several simplified forms of the interaction potential. The numerical model was also used as a basis for evaluating several less complete but analytic models. Two computationally simple analytic approximations were found that successfully reproduced the numerical rate coefficients for a wide range of molecular properties and collision partners. Their limitations were also identified. The relative rates of multiple-quantum transitions from excited states were evaluated for several molecular types.
Nakamura, Ryosuke; Hamada, Norio
2015-05-14
Vibrational energy flow in the electronic ground state of photoactive yellow protein (PYP) is studied by ultrafast infrared (IR) pump-visible probe spectroscopy. Vibrational modes of the chromophore and the surrounding protein are excited with a femtosecond IR pump pulse, and the subsequent vibrational dynamics in the chromophore are selectively probed with a visible probe pulse through changes in the absorption spectrum of the chromophore. We thus obtain the vibrational energy flow with four characteristic time constants. The vibrational excitation with an IR pulse at 1340, 1420, 1500, or 1670 cm(-1) results in ultrafast intramolecular vibrational redistribution (IVR) with a time constant of 0.2 ps. The vibrational modes excited through the IVR process relax to the initial ground state with a time constant of 6-8 ps in parallel with vibrational cooling with a time constant of 14 ps. In addition, upon excitation with an IR pulse at 1670 cm(-1), we observe the energy flow from the protein backbone to the chromophore that occurs with a time constant of 4.2 ps. PMID:25896223
Feng, Li; Liu, Jing; Wang, Shu-Ying; Zhang, Wen-Jun; Li, Jia-Ling; Dai, Kang; Shen, Yi-Fan
2014-07-01
The vibrational levels of KH(X1 sigma+ v" = 0-3) were generated in the reaction of K(5P) with H2. The vibrationally excited KH(v" = 17) was populated by an overtone pump-probe configuration Different characteristics of collisional energy transfer in highly and lowly excited vibrational levels of KH and CO2 were investigated through measuring the time-resolved distribution of vibrational energy in KH(v" = 17.3) + CO2 collisions. For KH(v" = 17), there existed three principal regions of vibration temperature (T(v)) in this equilibration process. The initial phase consists of very rapid fall in T(v) within - 5 micros, and the vibrational energy of KH(v" = 17) is mainly transferred to the vibrational levels of CO2 (00 degrees 1) or high rotational levels of CO2 (00 degrees 0). The second phase (5-20 micros) has a slight decline in T(v), and the process of energy transfer to vibrational levels or high rotational levels of CO2 has already finished. The vibration temperature of the third phase has a slightly more rapid decline compared with the last phase. This phase shows that the process of transfer to lowly rotational levels and translation energy of CO2 is accelerated. The equilibration of vibrationally excited KH (v" = 3) in CO2 was also investigated. There are similarities to the behavior of KH (v" = 17) in CO2 plot, but also are significant differences. Once the initial resonant V-R exchange has equalized vibrational temperatures, there is a very slow linear decline in T(v) with equilibrium attained within -80 micros. This same point is reached within 15 micros for KH (v" = 17). The data demonstrate that single rate coefficient measurements are unlikely to capture the complex nature of processes that generally are multistaged with different relaxation rates characterizing each different stage. Examination of the quantum state distributions reveals that these distinct stages reflect the dominance of specific energy transfer mechanisms, some of which are inherently fast and others are much slower. The energy gain into CO2 resulting from collisions with excited KH was probed using transient absorption techniques. Distributions of nascent CO2 rotational populations in both ground (00 degrees 0) state and the vibrationally excited (00 degrees 1) state were determined. A kinetic model was developed to describe rate coefficients for appearance of CO2 states resulting from collisions with excited KH. These experiments show that collisions resulting in CO2 (00 degrees 0) are accompanied by substantial excitation in rotation while the vibrationally excited CO2 (00 degrees 1) state has rotational energy distributions near the initial distributions. PMID:25269275
Dynamical traps lead to the slowing down of intramolecular vibrational energy flow
Manikandan, Paranjothy; Keshavamurthy, Srihari
2014-01-01
The phenomenon of intramolecular vibrational energy redistribution (IVR) is at the heart of chemical reaction dynamics. Statistical rate theories, assuming instantaneous IVR, predict exponential decay of the population with the properties of the transition state essentially determining the mechanism. However, there is growing evidence that IVR competes with the reaction timescales, resulting in deviations from the exponential rate law. Dynamics cannot be ignored in such cases for understanding the reaction mechanisms. Significant insights in this context have come from the state space model of IVR, which predicts power law behavior for the rates with the power law exponent, an effective state space dimensionality, being a measure of the nature and extent of the IVR dynamics. However, whether the effective IVR dimensionality can vary with time and whether the mechanism for the variation is of purely quantum or classical origins are issues that remain unresolved. Such multiple power law scalings can lead to surprising mode specificity in the system, even above the threshold for facile IVR. In this work, choosing the well-studied thiophosgene molecule as an example, we establish the anisotropic and anomalous nature of the quantum IVR dynamics and show that multiple power law scalings do manifest in the system. More importantly, we show that the mechanism of the observed multiple power law scaling has classical origins due to a combination of trapping near resonance junctions in the network of classical nonlinear resonances at short to intermediate times and the influence of weak higher-order resonances at relatively longer times. PMID:25246538
A global ab initio potential for HCN/HNC, exact vibrational energies, and comparison to experiment
NASA Technical Reports Server (NTRS)
Bentley, Joseph A.; Bowman, Joel M.; Gazdy, Bela; Lee, Timothy J.; Dateo, Christopher E.
1992-01-01
An ab initio (i.e., from first principles) calculation of vibrational energies of HCN and HNC is reported. The vibrational calculations were done with a new potential derived from a fit to 1124 ab initio electronic energies which were calculated using the highly accurate CCSD(T) coupled-cluster method in conjunction with a large atomic natural orbital basis set. The properties of this potential are presented, and the vibrational calculations are compared to experiment for 54 vibrational transitions, 39 of which are for zero total angular momentum, J = 0, and 15 of which are for J = 1. The level of agreement with experiment is unprecedented for a triatomic with two nonhydrogen atoms, and demonstrates the capability of the latest computational methods to give reliable predictions on a strongly bound triatomic molecule at very high levels of vibrational excitation.
NASA Technical Reports Server (NTRS)
Tessarzik, J. M.; Chiang, T.; Badgley, R. H.
1973-01-01
The random vibration response of a gas bearing rotor support system has been experimentally and analytically investigated in the amplitude and frequency domains. The NASA Brayton Rotating Unit (BRU), a 36,000 rpm, 10 KWe turbogenerator had previously been subjected in the laboratory to external random vibrations, and the response data recorded on magnetic tape. This data has now been experimentally analyzed for amplitude distribution and magnetic tape. This data has now been experimentally analyzed for amplitude distribution and frequency content. The results of the power spectral density analysis indicate strong vibration responses for the major rotor-bearing system components at frequencies which correspond closely to their resonant frequencies obtained under periodic vibration testing. The results of amplitude analysis indicate an increasing shift towards non-Gaussian distributions as the input level of external vibrations is raised. Analysis of axial random vibration response of the BRU was performed by using a linear three-mass model. Power spectral densities, the root-mean-square value of the thrust bearing surface contact were calculated for specified input random excitation.
NASA Astrophysics Data System (ADS)
Sudakov, A. V.; Slovtsov, S. V.
2013-01-01
Modern methods used to estimate the loading of power equipment elements and their lifetime, which may decrease to an essential extent due to temperature pulsations and vibration loads that are sometimes inherent in the working process in power equipment, and which may lead to equipment failures. Procedures for calculating the longevity of power equipment elements experiencing temperature pulsations during their operation are proposed.
Magma energy for power generation
Dunn, J.C.
1987-01-01
Thermal energy contained in crustal magma bodies represents a large potential resource for the US and magma generated power could become a viable alternative in the future. Engineering feasibility of the magma energy concept is being investigated as part of the Department of Energy's Geothermal Program. This current project follows a seven-year Magma Energy Research Project where scientific feasibility of the concept was concluded.
ERIC Educational Resources Information Center
Holdren, John; Herrera, Philip
The demand of Americans for more and more power, particularly electric power, contrasted by the deep and growing concern for the environment and a desire by private citizens to participate in the public decisions that affect the environment is the dilemma explored in this book. Part One by John Holdren, offers a scientist's overview of the energy
Yuksek, N. S.; Almasri, M.; Feng, Z. C.
2014-09-15
In this paper, we propose an electromagnetic power harvester that uses a transformative multi-impact approach to achieve a wide bandwidth response from low frequency vibration sources through frequency-up conversion. The device consists of a pick-up coil, fixed at the free edge of a cantilever beam with high resonant frequency, and two cantilever beams with low excitation frequencies, each with an impact mass attached at its free edge. One of the two cantilevers is designed to resonate at 25 Hz, while the other resonates at 50 Hz within the range of ambient vibration frequency. When the device is subjected to a low frequency vibration, the two low-frequency cantilevers responded by vibrating at low frequencies, and thus their thick metallic masses made impacts with the high resonance frequency cantilever repeatedly at two locations. This has caused it along with the pick-up coil to oscillate, relative to the permanent magnet, with decaying amplitude at its resonance frequency, and results in a wide bandwidth response from 10 to 63 Hz at 2 g. A wide bandwidth response between 10–51 Hz and 10–58 Hz at acceleration values of 0.5 g and 2 g, respectively, were achieved by adjusting the impact cantilever frequencies closer to each other (25 Hz and 45 Hz). A maximum output power of 85 μW was achieved at 5 g at 30 Hz across a load resistor, 2.68 Ω.
NASA Astrophysics Data System (ADS)
Brusa, E.; Zelenika, S.; Moro, L.; Benasciutti, D.
2009-05-01
One of the main requirements in wireless sensor operation is the availability of autonomous power sources sufficiently compact to be embedded in the same housing and, when the application involves living people, wearable. A possible technological solution satisfying these needs is energy harvesting from the environment. Vibration energy scavenging is one of the most studied approaches in this frame. In this work the conversion of kinetic into electric energy via piezoelectric coupling in resonant beams is studied. Various design approaches are analyzed and relevant parameters are identified. Numerical methods are applied to stress and strain analyses as well as to evaluate the voltage and charge generated by electromechanical coupling. The aim of the work is increasing the specific power generated per unit of scavenger volume by optimizing its shape. Besides the conventional rectangular geometry proposed in literature, two trapezoidal shapes, namely the direct and the reversed trapezoidal configuration, are analyzed. They are modeled to predict their dynamic behavior and energy conversion performance. Analytical and FEM models are compared and resulting figures of merit are drawn. Results of a preliminary experimental validation are also given. A systematic validation of characteristic specimens via an experimental campaign is ongoing.
NASA Astrophysics Data System (ADS)
Colin, M.; Basrour, S.; Rufer, L.
2013-05-01
Current version of implantable cardioverter defibrillators (ICDs) and pacemakers consists of a battery-powered pulse generator connected onto the heart through electrical leads inserted through the veins. However, it is known that long-term lead failure may occur and cause a dysfunction of the device. When required, the removal of the failed leads is a complex procedure associated with a potential risk of mortality. As a consequence, the main players in the field of intracardiac implants prepare a next generation of devices: miniaturized and autonomous leadless implants, which could be directly placed inside the heart. In this paper, we discuss the frequency content of a heart vibration spectrum, and the dimensional restrictions in the case of a leadless pacemaker. In combination with the requirements in terms of useable energy, we will present a design study of a resonant piezoelectric scavenger aimed at powering such a device. In particular, we will show how the frequency-volume-energy requirement leads to new challenges in terms of power densities, which are to be addressed through implementation of innovative piezoelectric thick films fabrication processes. This paper also presents the simulation, fabrication and the testing of an ultralow frequency (15Hz) resonant piezoelectric energy harvester prototype. Using both harmonic (50mg) and real heart-induced vibrations, we obtained an output power of 60?W and 10?W respectively. Finally, we will place emphasis on the new constraint represented by the gravitational (orientation) sensitivity inherent to these ultra low frequency resonant energy harvesters.
NASA Astrophysics Data System (ADS)
Betts, David N.; Bowen, Christopher R.; Inman, Daniel J.; Weaver, Paul M.; Kim, H. A.
2014-04-01
The need for reduced power requirements for small electronic components, such as wireless sensor networks, has prompted interest in recent years for energy harvesting technologies capable of capturing energy from broadband ambient vibrations. Encouraging results have been reported for an arrangement of piezoelectric layers attached to carbon fiber / epoxy laminates which possess bistability by virtue of their specific asymmetric stacking sequence. The inherent bistability of the underlying structure is exploited for energy harvesting since a transition from one stable configuration to another, or `snap-through', is used to repeatedly strain the surface-bonded piezoelectric and generate electrical energy. Existing studies, both experimental and modelling, have been limited to simple geometric laminate shapes, restricting the scope for improved energy harvesting performance by limiting the number of design variables. In this paper we present an analytical model to predict the static shapes of laminates of any desired profile, validated experimentally using a digital image correlation system. Good accuracy in terms of out-of-plane displacements (5-7%) are shown in line with existing square modelling results. The static model is then mapped to a dynamics model and used to compare results against an experimental study of the harvesting performance of an example arbitrary geometry piezoelectric-laminate energy harvester.
A fail-safe magnetorheological energy absorber for shock and vibration isolation
NASA Astrophysics Data System (ADS)
Bai, Xian-Xu; Wereley, Norman M.
2014-05-01
Magnetorheological (MR) energy absorbers (EAs) are an effective adaptive EA technology with which to maximize shock and vibration isolation. However, to realize maximum performance of the semi-active control system, the off-state (i.e., field off) stroking load of the MREA must be minimized at all speeds, and the dynamic range of the MREA must be maximized at high speed. This study presents a fail-safe MREA (MREA-FS) concept that, can produce a greater dynamic range at all piston speeds. A bias damping force is generated in the MREA-FS using permanent magnetic fields, which enables fail-safe behavior in the case of power failure. To investigate the feasibility and capability of the MREA-FS in the context of the semi-active control systems, a single-degree-of-freedom base excited rigid payload is mathematically constructed and simulated with skyhook control.
A fail-safe magnetorheological energy absorber for shock and vibration isolation
Bai, Xian-Xu; Wereley, Norman M.
2014-05-07
Magnetorheological (MR) energy absorbers (EAs) are an effective adaptive EA technology with which to maximize shock and vibration isolation. However, to realize maximum performance of the semi-active control system, the off-state (i.e., field off) stroking load of the MREA must be minimized at all speeds, and the dynamic range of the MREA must be maximized at high speed. This study presents a fail-safe MREA (MREA-FS) concept that, can produce a greater dynamic range at all piston speeds. A bias damping force is generated in the MREA-FS using permanent magnetic fields, which enables fail-safe behavior in the case of power failure. To investigate the feasibility and capability of the MREA-FS in the context of the semi-active control systems, a single-degree-of-freedom base excited rigid payload is mathematically constructed and simulated with skyhook control.
Adaptive tuned piezoelectric MEMS vibration energy harvester using an electrostatic device
NASA Astrophysics Data System (ADS)
Madinei, H.; Khodaparast, H. Haddad; Adhikari, S.; Friswell, M. I.; Fazeli, M.
2015-11-01
In this paper an adaptive tuned piezoelectric vibration based energy harvesting system based on the use of electrostatic device is proposed. The main motivation is to control the resonance frequency of the piezoelectric harvester with the DC voltage applied to the electrostatic system in order to maximize the harvested power. The idea is demonstrated in a hybrid system consisting of a cantilevered piezoelectric harvester combined with an electrostatic harvester which is connected to a variable voltage source. The nonlinear governing differential equation of motion is derived based on Euler Bernoulli theory, and solved to obtain the static and dynamic solutions. The results show that the harvester can be tuned to give a resonant response over a wide range of frequencies, and shows the great potential of this hybrid system.
NASA Astrophysics Data System (ADS)
Tao, K.; Lye, S. W.; Miao, J. M.; Hu, Xiao
2014-11-01
This paper presents a novel out-of-plane electret-based vibrational power generator (EVPG) that has both negative and positive charged electret plates integrated into a single seismic mass system. Compared with the conventional single-charged two-plate configuration, the proposed device not only exhibits an enhanced output voltage magnitude but also has a wide operational bandwidth due to spring softening nonlinearity according to the experimental analysis. With the acceleration changes from 0.1g to 0.5g, the operating 3-dB bandwidth can be increased 2.6 times from 2.5 Hz to 6.5 Hz, which indicates higher energy conversion efficiency than a linear energy harvester in the practical scenario of broadband random vibrations.
Vibrational energy relaxation of naphthalene in the S(1) state in various gases.
Kimura, Y; Abe, D; Terazima, M
2004-09-22
Time-resolved fluorescence spectra of naphthalene in the S(1) state have been measured in various gases below 10(2) kPa. The band shape of the fluorescence changed in an earlier time region after the photoexcitation when an excess energy (3300 cm(-1)) above the 0-0 transition energy was given. The excitation energy dependence of the fluorescence band shape of an isolated naphthalene molecule was measured separately, and the time dependence of the fluorescence band shape in gases was found to be due to the vibrational energy relaxation in the S(1) state. We have succeeded in determining the transient excess vibrational energy by comparing the time-resolved fluorescence band shape with the excitation energy dependence of the fluorescence band shape. The excess vibrational energy decayed almost exponentially. From the slope of the decay rate against the buffer gas pressure, we have determined the collisional decay rate of the excess vibrational energy in various gases. The dependence of the vibrational energy relaxation rate on the buffer gas species was similar to the case of azulene. The comparisons with the results in the low temperature argon and the energy relaxation rate in the S(0) state in nitrogen were also discussed. PMID:15367005
A study of several vortex-induced vibration techniques for piezoelectric wind energy harvesting
NASA Astrophysics Data System (ADS)
Sivadas, Vishak; Wickenheiser, Adam M.
2011-03-01
This paper discusses a preliminary study on harnessing energy from piezoelectric transducers by using bluff body and vortex-induced vibration phenomena. Structures like bridges and buildings tend to deform and crack due to chaotic fluid-structure interactions. The rapid variation of pressure and velocity can be tapped and used to power structural health monitoring systems. The proposed device is a miniature, scalable wind harvesting device. The configuration consists of a bluff body with a flexible piezoelectric cantilever attached to the trailing edge. Tests are run for different characteristic dimensions or shapes for the bluff body and optimized for maximum power over a wide range of flow velocities. The main motive here is to seek a higher synchronized region of frequencies for the oscillation amplitudes. The multi-physics software package COMSOL is used to vary the design parameters to optimize the configuration and to identify the significant parameters in the design. The simulation results obtained show a wider lock-in bandwidth and higher average power for the cylindrical bluff body compared to the other two bluff body shapes investigated, the greatest average power being 0.35mW at a Reynolds number of 900, beam length of 0.04m, and bluff body diameter of 0.02m.
An improved description of the vibrational energy transfers in nitrogen discharges
NASA Astrophysics Data System (ADS)
Guerra, Vasco; Lino da Silva, M.; Goci?, S.; Loureiro, J.
2007-10-01
The vibrational levels of ground-state N2(X) molecules are often the main energy reservoirs in nitrogen discharges and their post-discharges. As a consequence, they have a direct and crucial importance in the understanding of several fundamental phenomena occurring in nitrogen, such as dissociation, ionization, gas heating and the nitrogen pink afterglow. In recent years, nitrogen discharges have been modeled assuming the vibrational levels to be described by a Morse oscillator. Accordingly, the resulting number of bound vibrational states is 45. In this work we investigate how the vibrational energy distribution function of N2(X) molecules and the relaxation of vibrational energy are modified when a more realistic intra-molecular potential is used. To this purpose, the ground-state potential curve has been reconstructed with the RKR method and a total of 59 vibrational bound levels were obtained. The discharge and the afterglow were modeled by solving the electron Boltzmann equation, coupled with a system of rate-balance equations for the creation of the most important heavy- particles. The relevant rate coefficients for vibrational exchanges were obtained using the Forced Harmonic Oscillator theory.
Two-dimensional concentrated-stress low-frequency piezoelectric vibration energy harvesters
NASA Astrophysics Data System (ADS)
Sharpes, Nathan; Abdelkefi, Abdessattar; Priya, Shashank
2015-08-01
Vibration-based energy harvesters using piezoelectric materials have long made use of the cantilever beam structure. Surmounting the deficiencies in one-dimensional cantilever-based energy harvesters has been a major focus in the literature. In this work, we demonstrate a strategy of using two-dimensional beam shapes to harvest energy from low frequency excitations. A characteristic Zigzag-shaped beam is created to compare against the two proposed two-dimensional beam shapes, all of which occupy a 25.4 × 25.4 mm2 area. In addition to maintaining the low-resonance bending frequency, the proposed beam shapes are designed with the goal of realizing a concentrated stress structure, whereby stress in the beam is concentrated in a single area where a piezoelectric layer may be placed, rather than being distributed throughout the beam. It is shown analytically, numerically, and experimentally that one of the proposed harvesters is able to provide significant increase in power production, when the base acceleration is set equal to 0.1 g, with only a minimal change in the resonant frequency compared to the current state-of-the-art Zigzag shape. This is accomplished by eliminating torsional effects, producing a more pure bending motion that is necessary for high electromechanical coupling. In addition, the proposed harvesters have a large effective beam tip whereby large tip mass may be placed while retaining a low-profile, resulting in a low volume harvester and subsequently large power density.
NASA Astrophysics Data System (ADS)
Mercan, Kadir; Demir, Çiğdem; Civalek, Ömer
2016-01-01
In the present manuscript, free vibration response of circular cylindrical shells with functionally graded material (FGM) is investigated. The method of discrete singular convolution (DSC) is used for numerical solution of the related governing equation of motion of FGM cylindrical shell. The constitutive relations are based on the Love's first approximation shell theory. The material properties are graded in the thickness direction according to a volume fraction power law indexes. Frequency values are calculated for different types of boundary conditions, material and geometric parameters. In general, close agreement between the obtained results and those of other researchers has been found.
Zorpette, G
1990-01-01
According to the author, in response to financial and competitive pressures, U.S. utilities have been proposing and consummating mergers on a scale not seen since the 1930s. The author discusses how such proposals have far-reaching consequences for U.S. transmission networks, and, along with concrete proposals for new federal clean air legislation, hint at structural changes in the utility industry. Competitive and environmental concerns are seen as having fostered technical advances, particularly in the harnessing of renewable- and alternative-energy sources and in the use of computers to monitor and control interconnected high-voltage transmission networks.
Chung, Pao-Hung; Lin, Guan-Lun; Liu, Chiang; Chuang, Long-Ren; Shiang, Tzyy-Yuang
2013-01-01
The aim of this study was to determine whether performing Tai Chi Chuan on a customized vibration platform could enhance balance control and lower extremity muscle power more efficiently than Tai Chi Chuan alone in an untrained young population. Forty-eight healthy young adults were randomly assigned to the following three groups: a Tai Chi Chuan combined with vibration training group (TCV), a Tai Chi Chuan group (TCC) or a control group. The TCV group underwent 30 minutes of a reformed Tai Chi Chuan program on a customized vibration platform (32 Hz, 1 mm) three times a week for eight weeks, whereas the TCC group was trained without vibration stimuli. A force platform was used to measure the moving area of a static single leg stance and the heights of two consecutive countermovement jumps. The activation of the knee extensor and flexor was also measured synchronously by surface electromyography in all tests. The results showed that the moving area in the TCV group was significantly decreased by 15.3%. The second jump height in the TCV group was significantly increased by 8.14%, and the activation of the knee extensor/flexor was significantly decreased in the first jump. In conclusion, Tai Chi Chuan combined with vibration training can more efficiently improve balance control, and the positive training effect on the lower extremity muscle power induced by vibration stimuli still remains significant because there is no cross-interaction between the two different types of training methods. Key points Eight weeks of Tai Chi Chuan combined with vibration training can more efficiently improve balance control for an untrained young population. The positive training effect on the lower extremity muscle power induced by vibration stimuli during Tai Chi Chuan movements still remains significant because of SSC mechanism. Combining Tai Chi Chuan with vibration training is more efficient and does not decrease the overall training effects due to a cross-interaction of each other. PMID:24149721
NASA Astrophysics Data System (ADS)
Soloviev, V.; Seleznev, V.; Emanov, A.; Sal`Nikov, A.; Kashun, V.; Glinsky, B.; Kovalevsky, V.; Zhemchugova, I.; Danilov, I.; Liseikin, A.
2004-12-01
There are presented the materials of deep vibroseism researches, carried out in seismic active regions of Siberia with use of stationary (100-tos power) and moveable vibration sources (40-60tons power) and mobile digital recording equipment. There are given some examples of unique, have no world analogues, correlograms from high-power vibrators on distances to 400km and more. Using new vibroseismic technology of deep seismic researches, there were got detail deep sections of the Earth's crust and upper mantle, including time-sections of CDP-DSS up to depth of 80km. Materials of vibroseismic investigations on 2500km of seismic profiles in hard-to-reach regions of the Altay-Sayan region, the Baikal rift zone and Okhotsko-Chukotski regions are evidence of high cost efficiency, ecological safety, possibility to be realized in hard-to-reach region and finally of availability of deep seismic investigations with use of high-power vibration sources.
Mechanism of vibrational energy dissipation of free OH groups at the air–water interface
Hsieh, Cho-Shuen; Campen, R. Kramer; Okuno, Masanari; Backus, Ellen H. G.; Nagata, Yuki; Bonn, Mischa
2013-01-01
Interfaces of liquid water play a critical role in a wide variety of processes that occur in biology, a variety of technologies, and the environment. Many macroscopic observations clarify that the properties of liquid water interfaces significantly differ from those of the bulk liquid. In addition to interfacial molecular structure, knowledge of the rates and mechanisms of the relaxation of excess vibrational energy is indispensable to fully understand physical and chemical processes of water and aqueous solutions, such as chemical reaction rates and pathways, proton transfer, and hydrogen bond dynamics. Here we elucidate the rate and mechanism of vibrational energy dissipation of water molecules at the air–water interface using femtosecond two-color IR-pump/vibrational sum-frequency probe spectroscopy. Vibrational relaxation of nonhydrogen-bonded OH groups occurs at a subpicosecond timescale in a manner fundamentally different from hydrogen-bonded OH groups in bulk, through two competing mechanisms: intramolecular energy transfer and ultrafast reorientational motion that leads to free OH groups becoming hydrogen bonded. Both pathways effectively lead to the transfer of the excited vibrational modes from free to hydrogen-bonded OH groups, from which relaxation readily occurs. Of the overall relaxation rate of interfacial free OH groups at the air–H2O interface, two-thirds are accounted for by intramolecular energy transfer, whereas the remaining one-third is dominated by the reorientational motion. These findings not only shed light on vibrational energy dynamics of interfacial water, but also contribute to our understanding of the impact of structural and vibrational dynamics on the vibrational sum-frequency line shapes of aqueous interfaces. PMID:24191016
Mechanism of vibrational energy dissipation of free OH groups at the air-water interface.
Hsieh, Cho-Shuen; Campen, R Kramer; Okuno, Masanari; Backus, Ellen H G; Nagata, Yuki; Bonn, Mischa
2013-11-19
Interfaces of liquid water play a critical role in a wide variety of processes that occur in biology, a variety of technologies, and the environment. Many macroscopic observations clarify that the properties of liquid water interfaces significantly differ from those of the bulk liquid. In addition to interfacial molecular structure, knowledge of the rates and mechanisms of the relaxation of excess vibrational energy is indispensable to fully understand physical and chemical processes of water and aqueous solutions, such as chemical reaction rates and pathways, proton transfer, and hydrogen bond dynamics. Here we elucidate the rate and mechanism of vibrational energy dissipation of water molecules at the air-water interface using femtosecond two-color IR-pump/vibrational sum-frequency probe spectroscopy. Vibrational relaxation of nonhydrogen-bonded OH groups occurs at a subpicosecond timescale in a manner fundamentally different from hydrogen-bonded OH groups in bulk, through two competing mechanisms: intramolecular energy transfer and ultrafast reorientational motion that leads to free OH groups becoming hydrogen bonded. Both pathways effectively lead to the transfer of the excited vibrational modes from free to hydrogen-bonded OH groups, from which relaxation readily occurs. Of the overall relaxation rate of interfacial free OH groups at the air-H2O interface, two-thirds are accounted for by intramolecular energy transfer, whereas the remaining one-third is dominated by the reorientational motion. These findings not only shed light on vibrational energy dynamics of interfacial water, but also contribute to our understanding of the impact of structural and vibrational dynamics on the vibrational sum-frequency line shapes of aqueous interfaces. PMID:24191016
Voltage tuning of vibrational mode energies in single-molecule junctions
Li, Yajing; Doak, Peter; Kronik, Leeor; Neaton, Jeffrey B.; Natelson, Douglas
2014-01-01
Vibrational modes of molecules are fundamental properties determined by intramolecular bonding, atomic masses, and molecular geometry, and often serve as important channels for dissipation in nanoscale processes. Although single-molecule junctions have been used to manipulate electronic structure and related functional properties of molecules, electrical control of vibrational mode energies has remained elusive. Here we use simultaneous transport and surface-enhanced Raman spectroscopy measurements to demonstrate large, reversible, voltage-driven shifts of vibrational mode energies of C60 molecules in gold junctions. C60 mode energies are found to vary approximately quadratically with bias, but in a manner inconsistent with a simple vibrational Stark effect. Our theoretical model instead suggests that the mode shifts are a signature of bias-driven addition of electronic charge to the molecule. These results imply that voltage-controlled tuning of vibrational modes is a general phenomenon at metal–molecule interfaces and is a means of achieving significant shifts in vibrational energies relative to a pure Stark effect. PMID:24474749
NASA Astrophysics Data System (ADS)
Khbeis, Michael Tawfik
Scavenging energy from environmental sources is an active area of research to enable remote sensing and microsystems applications. Furthermore, as energy demands soar, there is a significant need to explore new sources and curb waste. Vibration energy scavenging is one environmental source for remote applications and a candidate for recouping energy wasted by mechanical sources that can be harnessed to monitor and optimize operation of critical infrastructure (e.g. Smart Grid). Current vibration scavengers are limited by volume and ancillary requirements for operation such as control circuitry overhead and battery sources. This dissertation, for the first time, reports a mass producible hybrid energy scavenger system that employs both piezoelectric and electrostatic transduction on a common MEMS device. The piezoelectric component provides an inherent feedback signal and pre-charge source that enables electrostatic scavenging operation while the electrostatic device provides the proof mass that enables low frequency operation. The piezoelectric beam forms the spring of the resonant mass-spring transducer for converting vibration excitation into an AC electrical output. A serially poled, composite shim, piezoelectric bimorph produces the highest output rectified voltage of over 3.3V and power output of 145muW using g vibration acceleration at 120Hz. Considering solely the volume of the piezoelectric beam and tungsten proof mass, the volume is 0.054cm3, resulting in a power density of 2.68mW/cm3. Incorporation of a simple parallel plate structure that provides the proof mass for low frequency resonant operation in addition to cogeneration via electrostatic energy scavenging provides a 19.82 to 35.29 percent increase in voltage beyond the piezoelectric generated DC rails. This corresponds to approximately 2.1nW additional power from the electrostatic scavenger component and demonstrates the first instance of hybrid energy scavenging using both piezoelectric and synchronous electrostatic transduction. Furthermore, it provides a complete system architecture and development platform for additional enhancements that will enable in excess of 100muW additional power from the electrostatic scavenger.
Power and energy for posterity
NASA Technical Reports Server (NTRS)
Barthelemy, R. F.; Cooper, R. F.
1972-01-01
The use of sophisticated space energy generation and storage systems to benefit the general public was examined. The utilization of these systems for pollution-free generation of energy to satisfy mankind's future electrical, thermal, and propulsion needs was of primary concern. Ground, air, and space transportation; commercial, peaking, and emergency electrical power; and metropolitan and unit thermal energy requirements were considered. Each type of energy system was first analyzed in terms of its utility in satisfying the requirement, and then its potential in reducing the air, noise, thermal, water, and nuclear pollution from future electrical and thermal systems was determined.
Novel vibration-based electrical energy generators for low and variable speed turbo-machinery
NASA Astrophysics Data System (ADS)
Rastegar, J.; Murray, R.
2007-04-01
A novel class of vibration-based electrical energy generators is presented for applications in which the input rotary speed is relatively low and varies significantly over time such as wind mills, turbo-machinery used to harvest tidal flows, and the like. Current technology uses magnet and coil based rotary generators to generate electrical energy in such machinery. However, to make the generation cycle efficient, gearing or other similar mechanisms have to be used to increase the output speed. In addition, variable speed mechanisms are usually needed to achieve high mechanical to electrical energy conversion efficiency since speed variation is usually significant in the aforementioned applications. The objective of the present work is the development of electrical energy generators that do not require the aforementioned gearing and speed control mechanisms, thereby significantly reducing complexity and cost, particularly those related to maintenance and service. This novel class of electrical energy generators operates based on repeated vibration of multiple vibrating elements that are tuned to vibrate at a fixed prescribed frequency. The mechanical energy stored in the vibration elements is transformed into electrical energy using piezoelectric elements. The present generators are very simple, can efficiently operate over a very large range of input speeds, and should require minimal service and maintenance. The project is at the early stages of its development, but the analytical modeling and computer simulation studies using realistic system and component parameters indicate the potentials of this class of piezoelectric-based generators for the indicated applications.
NASA Astrophysics Data System (ADS)
Han, Peng; Bester, Gabriel
2015-02-01
The three-dimensional confinement characterizing a nanocrystal (NC) leads to the formation of discrete electronic states. The energy gap between these states in colloidal NCs can be up to an order of magnitude larger than the vibrational energy of the host material. This large energetic mismatch (not given in self-assembled quantum dots) leads to the expectation that an electron occupying an excited state would be unable to release its energy to vibrations and a "phonon bottleneck" should finally be observed. Using large-scale ab initio calculations and a time-dependent formalism, we show that on the contrary, a phonon bottleneck can be observed only in a narrow window of diameters for CdSe and InAs NCs and should not occur at all in Si NCs. Two relaxation pathways enable fast carrier relaxation. For smaller structures (below 20-Å radius), the coupling strength and energy detuning are such that quantum mechanics allows us to effectively bridge electronic gaps much larger than the vibronic energy. For larger structures, the coupling to passivant modes, although very weak, leads to an efficient picosecond carrier relaxation. This work provides insight into the nature of carrier relaxation in colloidal nanostructures and highlights that defects, of any kind, are not necessary to explain the observed fast carrier relaxation.
Random vibration analysis of the Topaz-II nuclear reactor power system. Master`s thesis
Campbell, S.E.
1995-06-01
The TOPAZ-II Ya-21U is one of six Russian made space nuclear power systems which is based on theomionic power conversion. The U.S. is presently analyzing TOPAZ-II to determine the reliability and feasibility of using this system. A structural analysis test was conducted on the TOPAZ unit in May 1993 to provide data from which modal parameters could be identified. This test showed the fundamental frequency to be 10.5 Hz, yet the test results that the Russians conducted identified a fundamental frequency of 5 Hz. Another finite element model was created incorporating new developments in TOPAZ-II and modifications to the finite element model to better simulate the mass properties of the TOPAZ-II2. A second structural analysis test was conducted on the TOPAZ unit 06-09 September 1994. This thesis focuses on the random vibration analysis of the TOPAZ-II Ya-2lU utilizing the most recent test results and the Master Series (updated version) I-DEAS software. The modal respose of the model and simulated random vibration tests were within 8.33%. This model is a feasible tool which can be used to analyze the TOPAZ unit without testing the unit to fatigue.
NASA Astrophysics Data System (ADS)
Leng, Y. G.; Gao, Y. J.; Tan, D.; Fan, S. B.; Lai, Z. H.
2015-02-01
To overcome the defect of conventional nonlinear piezoelectric cantilever vibration energy harvesters, in this paper we conceive an elastic-support model to study the performance of energy converters under two types of variable-intensity excitation conditions: filtered Gaussian noises and pink noises. When excitation intensity is insufficient, thanks to the system's variable potential function, frequent bistable transition oscillations between two wells occur in elastic-support systems, while only weak oscillations in either well could be observed in rigid-support systems. In practical applications, the structural parameters of energy harvesters are not allowed to make real-time changes. If considered remaining the magnet interval and the spring's elastic stiffness unchanged while receiving stable maximum output voltage, elastic-support systems can be made full use toward variable-intensity filtered Gaussian noises. It has been proven that elastic-support systems are capable of adapting to random excitations with variable intensity, through which maximum power output and sufficient electromechanical energy conversion of the system can be accomplished.
Energy harvesting for self-powered aerostructure actuation
NASA Astrophysics Data System (ADS)
Bryant, Matthew; Pizzonia, Matthew; Mehallow, Michael; Garcia, Ephrahim
2014-04-01
This paper proposes and experimentally investigates applying piezoelectric energy harvesting devices driven by flow induced vibrations to create self-powered actuation of aerostructure surfaces such as tabs, flaps, spoilers, or morphing devices. Recently, we have investigated flow-induced vibrations and limit cycle oscillations due to aeroelastic flutter phenomena in piezoelectric structures as a mechanism to harvest energy from an ambient fluid flow. We will describe how our experimental investigations in a wind tunnel have demonstrated that this harvested energy can be stored and used on-demand to actuate a control surface such as a trailing edge flap in the airflow. This actuated control surface could take the form of a separate and discrete actuated flap, or could constitute rotating or deflecting the oscillating energy harvester itself to produce a non-zero mean angle of attack. Such a rotation of the energy harvester and the associated change in aerodynamic force is shown to influence the operating wind speed range of the device, its limit cycle oscillation (LCO) amplitude, and its harvested power output; hence creating a coupling between the device's performance as an energy harvester and as a control surface. Finally, the induced changes in the lift, pitching moment, and drag acting on a wing model are quantified and compared for a control surface equipped with an oscillating energy harvester and a traditional, static control surface of the same geometry. The results show that when operated in small amplitude LCO the energy harvester adds negligible aerodynamic drag.
NASA Astrophysics Data System (ADS)
Renji, K.; Mahalakshmi, M.
2006-09-01
Vibration energy transfer in a system of three plates separated by a small distance and connected at a few discrete points, like solar panels in a spacecraft, is investigated. Coupling loss factors are obtained experimentally using the power injection technique. The system is then subjected to the acoustic excitation in a reverberant chamber. The measured responses of the inner plate are significant. But the measured responses of the inner plates are higher than the responses estimated based on the coupling loss factors obtained. When the system is subjected to mechanical excitation the measured responses of the inner plate closely match with the estimated responses. The difference is perhaps due to the sound radiated from the outer plates not being considered for the calculation, requiring further studies.
Fedorov, Dmitry A.; Varganov, Sergey A.; Derevianko, Andrei
2014-05-14
We calculate the potential energy curves, the permanent dipole moment curves, and the lifetimes of the ground and excited vibrational states of the heteronuclear alkali dimers XY (X, Y = Li, Na, K, Rb, Cs) in the X{sup 1}?{sup +} electronic state using the coupled cluster with singles doubles and triples method. All-electron quadruple-? basis sets with additional core functions are used for Li and Na, and small-core relativistic effective core potentials with quadruple-? quality basis sets are used for K, Rb, and Cs. The inclusion of the coupled cluster non-perturbative triple excitations is shown to be crucial for obtaining the accurate potential energy curves. A large one-electron basis set with additional core functions is needed for the accurate prediction of permanent dipole moments. The dissociation energies are overestimated by only 14 cm{sup ?1} for LiNa and by no more than 114 cm{sup ?1} for the other molecules. The discrepancies between the experimental and calculated harmonic vibrational frequencies are less than 1.7 cm{sup ?1}, and the discrepancies for the anharmonic correction are less than 0.1 cm{sup ?1}. We show that correlation between atomic electronegativity differences and permanent dipole moment of heteronuclear alkali dimers is not perfect. To obtain the vibrational energies and wave functions the vibrational Schrdinger equation is solved with the B-spline basis set method. The transition dipole moments between all vibrational states, the Einstein coefficients, and the lifetimes of the vibrational states are calculated. We analyze the decay rates of the vibrational states in terms of spontaneous emission, and stimulated emission and absorption induced by black body radiation. In all studied heteronuclear alkali dimers the ground vibrational states have much longer lifetimes than any excited states.
NASA Astrophysics Data System (ADS)
Fedorov, Dmitry A.; Derevianko, Andrei; Varganov, Sergey A.
2014-05-01
We calculate the potential energy curves, the permanent dipole moment curves, and the lifetimes of the ground and excited vibrational states of the heteronuclear alkali dimers XY (X, Y = Li, Na, K, Rb, Cs) in the X1?+ electronic state using the coupled cluster with singles doubles and triples method. All-electron quadruple-? basis sets with additional core functions are used for Li and Na, and small-core relativistic effective core potentials with quadruple-? quality basis sets are used for K, Rb, and Cs. The inclusion of the coupled cluster non-perturbative triple excitations is shown to be crucial for obtaining the accurate potential energy curves. A large one-electron basis set with additional core functions is needed for the accurate prediction of permanent dipole moments. The dissociation energies are overestimated by only 14 cm-1 for LiNa and by no more than 114 cm-1 for the other molecules. The discrepancies between the experimental and calculated harmonic vibrational frequencies are less than 1.7 cm-1, and the discrepancies for the anharmonic correction are less than 0.1 cm-1. We show that correlation between atomic electronegativity differences and permanent dipole moment of heteronuclear alkali dimers is not perfect. To obtain the vibrational energies and wave functions the vibrational Schrdinger equation is solved with the B-spline basis set method. The transition dipole moments between all vibrational states, the Einstein coefficients, and the lifetimes of the vibrational states are calculated. We analyze the decay rates of the vibrational states in terms of spontaneous emission, and stimulated emission and absorption induced by black body radiation. In all studied heteronuclear alkali dimers the ground vibrational states have much longer lifetimes than any excited states.
Ostasevicius, Vytautas; Janusas, Giedrius; Milasauskaite, Ieva; Zilys, Mindaugas; Kizauskiene, Laura
2015-01-01
This paper focuses on several aspects extending the dynamical efficiency of a cantilever beam vibrating in the third mode. A few ways of producing this mode stimulation, namely vibro-impact or forced excitation, as well as its application for energy harvesting devices are proposed. The paper presents numerical and experimental analyses of novel structural dynamics effects along with an optimal configuration of the cantilever beam. The peculiarities of a cantilever beam vibrating in the third mode are related to the significant increase of the level of deformations capable of extracting significant additional amounts of energy compared to the conventional harvester vibrating in the first mode. Two types of a piezoelectric vibrating energy harvester (PVEH) prototype are analysed in this paper: the first one without electrode segmentation, while the second is segmented using electrode segmentation at the strain nodes of the third vibration mode to achieve effective operation at the third resonant frequency. The results of this research revealed that the voltage generated by any segment of the segmented PVEH prototype excited at the third resonant frequency demonstrated a 3.4–4.8-fold increase in comparison with the non-segmented prototype. Simultaneously, the efficiency of the energy harvester prototype also increased at lower resonant frequencies from 16% to 90%. The insights presented in the paper may serve for the development and fabrication of advanced piezoelectric energy harvesters which would be able to generate a considerably increased amount of electrical energy independently of the frequency of kinematical excitation. PMID:26029948
Ostasevicius, Vytautas; Janusas, Giedrius; Milasauskaite, Ieva; Zilys, Mindaugas; Kizauskiene, Laura
2015-01-01
This paper focuses on several aspects extending the dynamical efficiency of a cantilever beam vibrating in the third mode. A few ways of producing this mode stimulation, namely vibro-impact or forced excitation, as well as its application for energy harvesting devices are proposed. The paper presents numerical and experimental analyses of novel structural dynamics effects along with an optimal configuration of the cantilever beam. The peculiarities of a cantilever beam vibrating in the third mode are related to the significant increase of the level of deformations capable of extracting significant additional amounts of energy compared to the conventional harvester vibrating in the first mode. Two types of a piezoelectric vibrating energy harvester (PVEH) prototype are analysed in this paper: the first one without electrode segmentation, while the second is segmented using electrode segmentation at the strain nodes of the third vibration mode to achieve effective operation at the third resonant frequency. The results of this research revealed that the voltage generated by any segment of the segmented PVEH prototype excited at the third resonant frequency demonstrated a 3.4-4.8-fold increase in comparison with the non-segmented prototype. Simultaneously, the efficiency of the energy harvester prototype also increased at lower resonant frequencies from 16% to 90%. The insights presented in the paper may serve for the development and fabrication of advanced piezoelectric energy harvesters which would be able to generate a considerably increased amount of electrical energy independently of the frequency of kinematical excitation. PMID:26029948
Ab initio rotation-vibration energies and intensities for the H 2F + molecule
NASA Astrophysics Data System (ADS)
Bunker, P. R.; Jensen, Per; Wright, J. S.; Hamilton, I. P.
1990-12-01
In a previous publication [I. D. Petsalakis, G. Theodorakopoulos, J. S. Wright, and I. P. Hamilton, J. Chem. Phys., 92, 2440-2449 (1990)] we reported the ab initio multireference configuration interaction calculation of the three-dimensional potential energy surface of the H 2F + molecule in the ground X1A 1 electronic state at 119 nuclear geometries spanning an energy range up to about 50 000 cm -1 above equilibrium. We fitted the 71 points within 33 000 cm -1 of equilibrium to an analytic expression and performed variational calculation of the vibrational energies in Jacobi coordinates using the Discrete Variable Representation and Distributed Gaussian Basis functions (DVR-DGB) technique. In the present paper we examine the effect on the vibrational energies of using a surface obtained by fitting through 52 points within 25 000 cm -1 of equilibrium. We use this surface in a variational calculation of the J = 0, 1, and 2 rotation-vibration energies using the Morse Oscillator Rigid Bender Internal Dynamics Hamiltonian [P. Jensen, J. Mol. Spectrosc., 128, 478-501 (1988); J. Chem. Soc. Faraday Trans. 2, 84, 1315-1340 (1988)]. The vibrational energies obtained are compared with those obtained by the DVR-DGB technique. We also calculate ab initio the dipole moment function and rotation-vibration intensities, and we simulate the ?2 band, which has not yet been observed.
Energy transfer efficiency in the chromophore network strongly coupled to a vibrational mode
NASA Astrophysics Data System (ADS)
Mourokh, Lev G.; Nori, Franco
2015-11-01
Using methods from condensed matter and statistical physics, we examine the transport of excitons through the photosynthetic complex from a receiving antenna to a reaction center. Writing the equations of motion for the exciton creation-annihilation operators, we are able to describe the exciton dynamics, even in the regime when the reorganization energy is of the order of the intrasystem couplings. We determine the exciton transfer efficiency in the presence of a quenching field and protein environment. While the majority of the protein vibrational modes are treated as a heat bath, we address the situation when specific modes are strongly coupled to excitons and examine the effects of these modes on the energy transfer efficiency in the steady-state regime. Using the structural parameters of the Fenna-Matthews-Olson complex, we find that, for vibrational frequencies below 16 meV, the exciton transfer is drastically suppressed. We attribute this effect to the formation of a "mixed exciton-vibrational mode" where the exciton is transferred back and forth between the two pigments with the absorption or emission of vibrational quanta, instead of proceeding to the reaction center. The same effect suppresses the quantum beating at the vibrational frequency of 25 meV. We also show that the efficiency of the energy transfer can be enhanced when the vibrational mode strongly couples to the third pigment only, instead of coupling to the entire system.
NASA Astrophysics Data System (ADS)
Ma, Yongbin; Zhang, Yahui; Kennedy, David
2015-09-01
Based on the concept of the hybrid finite element (FE) analysis and statistical energy analysis (SEA), a new hybrid method is developed for the mid-frequency vibration of a system comprising rectangular thin plates. The wave propagation method based on symplectic analysis is used to describe the vibration of the deterministic plate component. By enforcing the displacement continuity and equilibrium of force at the connection interface, the dynamic coupling between the deterministic plate component and the statistical plate component described by SEA is established. Furthermore, the hybrid solution formulation for the mid-frequency vibration of the system built up by plates is proposed. The symplectic analytical wave describing the deterministic plate component eliminates the boundary condition limitation of the traditional analytical wave propagation method and overcomes the numerical instability of numerical wave propagation methods. Numerical examples compare results from the proposed method with those from the hybrid FE-SEA method and the Monte Carlo method. The comparison illustrates that the proposed method gives good predictions for the mid-frequency behavior of the system considered here with low computational time. In addition, a constant proportionality coefficient between the system coupling power and the energy difference between the plate components can be found, when external forces are applied at different locations on a line perpendicular to the wave propagation direction. Based on this finding, two fast solution techniques are developed for the energy response of the system, and are validated by numerical examples.
Energy Industry Powers CTE Program
ERIC Educational Resources Information Center
Khokhar, Amy
2012-01-01
Michael Fields is a recent graduate of Buckeye Union High School in Buckeye, Arizona. Fields is enrolled in the Estrella Mountain Community College (EMCC) Get Into Energy program, which means he is well on his way to a promising career. Specializing in power plant technology, in two years he will earn a certificate that will all but guarantee a…
Energy Industry Powers CTE Program
ERIC Educational Resources Information Center
Khokhar, Amy
2012-01-01
Michael Fields is a recent graduate of Buckeye Union High School in Buckeye, Arizona. Fields is enrolled in the Estrella Mountain Community College (EMCC) Get Into Energy program, which means he is well on his way to a promising career. Specializing in power plant technology, in two years he will earn a certificate that will all but guarantee a
NASA Astrophysics Data System (ADS)
Soloviev, V. M.; Seleznev, V. S.; Emanov, A. F.; Kashun, V. N.; Elagin, S. A.; Romanenko, I.; Shenmayer, A. E.; Serezhnikov, N.
2013-05-01
The paper presents data of operating vibroseismic observations using high-power stationary 100-tons and moveable 40-tons vibration sources, which have been carried out in Russia for 30 years. It is shown that investigations using high-power vibration sources open new possibilities for study stressedly-deformed condition of the Earth`s crust and the upper mantle and tectonic process in them. Special attention is given to developing operating seismic translucences of the Earth`s crust and the upper mantle using high-power 40-tons vibration sources. As a result of experimental researches there was proved high stability and repeatability of vibration effects. There were carried out long period experiments of many days with vibration source sessions of every two hours with the purpose of monitoring accuracy estimation. It was determined, that repeatability of vibroseismic effects (there was researched time difference of repeated sessions of P- and S-waves from crystal rocks surface) could be estimated as 10-3 - 10-4 sec. It is ten times less than revealed here annual variations of kinematic parameters according to regime vibroseismic observations. It is shown, that on hard high-speed grounds radiation spectrum becomes narrowband and is dislocated to high frequency; at the same time quantity of multiple high-frequency harmonic is growing. At radiation on soft sedimentary grounds (sand, clay) spectrum of vibration source in near zone is more broadband, correlograms are more compact. there Correspondence of wave fields from 40-tons vibration sources and explosions by reference waves from boundaries in he Earth`s crust and the upper mantle at record distance of 400 km was proved by many experiments in various regions of Russia; there was carried out the technique of high-power vibration sources grouping for increase of effectiveness of emanation and increase of record distance. According to results of long-term vibroseismic monitoring near Novosibirsk (1997-2012) there are determined variations in velocities of longitudinal and transverse waves. Both from 100-tons and 40-tons vibration sources there are distinctly determined annual and semiannual variations, and also variations of 120 and 90 days. There is determined correlations of revealed variations of P- and S-wave velocities with drowning of the upper part of the Earth`s crust because of season changes of water volumes in the biggest Novosibirsk water reservoir. There were carried out experiments on aperture widening of operating vibroseismic observations in seismic active zones of the South of Altay. All these results prove possibility of using moveable collapsible 40-tons vibration sources for active monitoring of seismic dangerous zones, nuclear power plants, nuclear waste storage etc.
Spectroscopic probes of vibrationally excited molecules at chemically significant energies
Rizzo, T.R.
1993-04-01
Infrared-optical double resonance is being used to study the unimolecular dissociation dynamics of hydrazoic acid (HN[sub 3]). 6[nu][sub NH] vibrational overtone excitation spectra are given for HN[sub 3]. Work was begun to determine the feasibility of extending the infrared-optical double resonance photofragment spectroscopy to small free radicals, and to be able to monitor atomic dissociation fragments via laser induced fluorescence in the VUV spectrum. 1 fig.
Collisional vibrational energy transfer of OH (A 2Sigma + , v'=1)
NASA Astrophysics Data System (ADS)
Williams, Leah R.; Crosley, David R.
1996-05-01
Vibrational energy transfer (VET) and quenching of the v'=1 level of A 2?+ OH have been studied using laser-induced fluorescence in a discharge flow cell at room temperature. VET cross sections (2) are N2, 30.12.8; O2, 2.80.3; Ar, 0.560.05; H2O, 8.60.6. The rotational energy distribution in v'=0 following the VET event was determined for nine colliders. It is nonthermal, generally populating high rotational levels. There are three broad categories of colliders that cause varying degrees of vibrational to rotational energy transfer; H2, D2, and CH4 show the least; N2, CO2, CF4, and N2O more; and O2 and Ar the most, with about one-third of the vibrational energy appearing as OH rotation.
Do, T. P. T.; Lopes, M. C. A.; Konovalov, D. A.; White, R. D.; Brunger, M. J. E-mail: darryl.jones@flinders.edu.au; Jones, D. B. E-mail: darryl.jones@flinders.edu.au
2015-03-28
We report differential cross sections (DCSs) for electron-impact vibrational-excitation of tetrahydrofuran, at intermediate incident electron energies (15-50 eV) and over the 10°-90° scattered electron angular range. These measurements extend the available DCS data for vibrational excitation for this species, which have previously been obtained at lower incident electron energies (≤20 eV). Where possible, our data are compared to the earlier measurements in the overlapping energy ranges. Here, quite good agreement was generally observed where the measurements overlapped.
A novel two-degree-of-freedom MEMS electromagnetic vibration energy harvester
NASA Astrophysics Data System (ADS)
Tao, Kai; Wu, Jin; Tang, Lihua; Xia, Xin; Woh Lye, Sun; Miao, Jianmin; Hu, Xiao
2016-03-01
In this paper, a vibration-based MEMS electromagnetic energy harvester (EM-EH) device with two-degree-of-freedom (2DOF) configuration has been presented, modeled and characterized. The proposed 2DOF system comprises a primary subsystem for power generation, and an accessory subsystem for frequency tuning. A lumped parametric 2DOF model is built and examined in respect of energy harvesting capabilities. By controlling the mass ratio and frequency ratio, the first two resonances of primary mass can be tuned close to each other while maintaining comparable magnitudes. The 2DOF configuration is expected to be more adaptive and efficient than the conventional 1DOF structure, which could only operate near its sole resonance. The 2DOF EM-EH chip is fabricated on silicon-on-insulator (SOI) wafer through double-sided deep reactive-ion etching (DRIE). Induction coil is only patterned on the primary mass for energy conversion. With current prototype at an acceleration of 0.12 g, two resonances of 326 and 391 Hz with output voltages of 3.6 and 6.5 mV are obtained respectively, providing good validation for the modeling results. This paper offers new insights of implementing a multimodal MEMS EM-EH device.
NASA Astrophysics Data System (ADS)
Pietanza, L. D.; Colonna, G.; D'Ammando, G.; Laricchiuta, A.; Capitelli, M.
2016-01-01
A Boltzmann equation, in the presence of superelastic vibrational and electronic collisions and of electron-electron Coulomb collisions, has been solved in CO2 plasma in discharge and post discharge conditions. Superelastic vibrational collisions play an important role in affecting the electron energy distribution function (eedf) in a wide range of the reduced electric field E/N and of vibrational temperatures characterizing the vibrational modes of CO2. An important result is the dependence of fractional power losses and of the relevant rate coefficients on the vibrational temperatures of the system. Superelastic electronic collisions, on the other hand, are the main processes affecting eedf and related quantities in the post discharge conditions (i.e., E/N = 0). In particular at low vibrational temperatures, the superelastic electronic collisions form an important plateau in the eedf, largely influencing the rate coefficients and the fractional power transfer.
NASA Astrophysics Data System (ADS)
Heo, YongHwa; Kim, Kwang-joon
2015-02-01
While the vibration power for a set of harmonic force and velocity signals is well defined and known, it is not as popular yet for a set of stationary random force and velocity processes, although it can be found in some literatures. In this paper, the definition of the vibration power for a set of non-stationary random force and velocity signals will be derived for the purpose of a time-frequency analysis based on the definitions of the vibration power for the harmonic and stationary random signals. The non-stationary vibration power, defined as the short-time average of the product of the force and velocity over a given frequency range of interest, can be calculated by three methods: the Wigner-Ville distribution, the short-time Fourier transform, and the harmonic wavelet transform. The latter method is selected in this paper because band-pass filtering can be done without phase distortions, and the frequency ranges can be chosen very flexibly for the time-frequency analysis. Three algorithms for the time-frequency analysis of the non-stationary vibration power using the harmonic wavelet transform are discussed. The first is an algorithm for computation according to the full definition, while the others are approximate. Noting that the force and velocity decomposed into frequency ranges of interest by the harmonic wavelet transform are constructed with coefficients and basis functions, for the second algorithm, it is suggested to prepare a table of time integrals of the product of the basis functions in advance, which are independent of the signals under analysis. How to prepare and utilize the integral table are presented. The third algorithm is based on an evolutionary spectrum. Applications of the algorithms to the time-frequency analysis of the vibration power transmitted from an excitation source to a receiver structure in a simple mechanical system consisting of a cantilever beam and a reaction wheel are presented for illustration.
Analysis of vibrational-translational energy transfer using the direct simulation Monte Carlo method
NASA Technical Reports Server (NTRS)
Boyd, Iain D.
1991-01-01
A new model is proposed for energy transfer between the vibrational and translational modes for use in the direct simulation Monte Carlo method (DSMC). The model modifies the Landau-Teller theory for a harmonic oscillator and the rate transition is related to an experimental correlation for the vibrational relaxation time. Assessment of the model is made with respect to three different computations: relaxation in a heat bath, a one-dimensional shock wave, and hypersonic flow over a two-dimensional wedge. These studies verify that the model achieves detailed balance, and excellent agreement with experimental data is obtained in the shock wave calculation. The wedge flow computation reveals that the usual phenomenological method for simulating vibrational nonequilibrium in the DSMC technique predicts much higher vibrational temperatures in the wake region.
Non-classicality of the molecular vibrations assisting exciton energy transfer at room temperature
NASA Astrophysics Data System (ADS)
O'Reilly, Edward J.; Olaya-Castro, Alexandra
2014-01-01
Advancing the debate on quantum effects in light-initiated reactions in biology requires clear identification of non-classical features that these processes can exhibit and utilize. Here we show that in prototype dimers present in a variety of photosynthetic antennae, efficient vibration-assisted energy transfer in the sub-picosecond timescale and at room temperature can manifest and benefit from non-classical fluctuations of collective pigment motions. Non-classicality of initially thermalized vibrations is induced via coherent exciton-vibration interactions and is unambiguously indicated by negativities in the phase-space quasi-probability distribution of the effective collective mode coupled to the electronic dynamics. These quantum effects can be prompted upon incoherent input of excitation. Our results therefore suggest that investigation of the non-classical properties of vibrational motions assisting excitation and charge transport, photoreception and chemical sensing processes could be a touchstone for revealing a role for non-trivial quantum phenomena in biology.
Petit, Pierre-David; Pensini, Manuela; Tessaro, Jol; Desnuelle, Claude; Legros, Patrick; Colson, Serge S
2010-12-01
This study compared the effects of 6-week whole-body vibration (WBV) training programs with different frequency and peak-to-peak displacement settings on knee extensor muscle strength and power. The underlying mechanisms of the expected gains were also investigated. Thirty-two physically active male subjects were randomly assigned to a high-frequency/high peak-to-peak displacement group (HH; n=12), a low-frequency/low peak-to-peak displacement group (LL; n=10) or a sham training group (SHAM; n=10). Maximal voluntary isometric, concentric and eccentric torque of the knee extensors, maximal voluntary isometric torque of the knee flexors, jump performance, voluntary muscle activation, and contractile properties of the knee extensors were assessed before and after the training period. Significant improvement in knee extensor eccentric voluntary torque (P<0.01), knee flexor isometric voluntary torque (P<0.05), and jump performance (P<0.05) was observed only for HH group. Regardless of the group, knee extensor muscle contractile properties (P<0.05) were enhanced. No modification was observed for voluntary muscle activation or electrical activity of agonist and antagonist muscles. We concluded that high-frequency/high peak-to-peak displacement was the most effective vibration setting to enhance knee extensor muscle strength and jump performance during a 6-week WBV training program and that these improvements were not mediated by central neural adaptations. PMID:20801671
NASA Astrophysics Data System (ADS)
Sato, T.; Masuda, A.; Sanada, T.
2015-12-01
This paper presents an experimental verification of a self-excitation control of a resonance- type vibration energy harvester with a Duffing-type nonlinearity which is designed to perform effectively in a wide frequency range. For the conventional linear vibration energy harvester, the performance of the power generation at the resonance frequency and the bandwidth of the resonance peak are trade-off. The resonance frequency band can be expanded by introducing a Duffing-type nonlinear oscillator in order to enable the harvester to generate larger electric power in a wider frequency range. However, since such nonlinear oscillator can have multiple stable steady-state solutions in the resonance band, it is difficult for the nonlinear harvester to maintain the high performance of the power generation constantly. The principle of self-excitation and entrainment has been utilized to provide the global stability to the highest-energy solution by destabilizing other unexpected lower-energy solutions by introducing a switching circuit of the load resistance between positive and the negative values depending on the response amplitude of the oscillator. It has been experimentally validated that this control law imparts the self-excitation capability to the oscillator to show an entrainment into the highest-energy solution.
Vibration energy harvesting by a Timoshenko beam model and piezoelectric transducer
NASA Astrophysics Data System (ADS)
Stoykov, S.; Litak, G.; Manoach, E.
2015-11-01
An electro-mechanical system of vibrational energy harvesting is studied. The beam is excited by external and kinematic periodic forces and damped by an electrical resistor through the coupled piezoelectric transducer. Nonlinearities are introduced by stoppers limiting the transverse displacements of the beam. The interaction between the beam and the stoppers is modeled as Winkler elastic foundation. The mechanical properties of the piezoelectric layer are taken into account and the beam is modeled as a composite structure. For the examined composite beam, the geometrically nonlinear version of the Timoshenko's beam theory is assumed. The equations of motion are derived by the principle of virtual work considering large deflections. An isogeometric approach is applied for space discretization and B-Splines are used as shape functions. Finally, the power output and the efficiency of the system due to harmonic excitations are discussed. The influence of the position of the stoppers and their length on the dynamics of the beam and consequently on the power output are analyzed and presented.
Energy Finite Element Analysis Developments for Vibration Analysis of Composite Aircraft Structures
NASA Technical Reports Server (NTRS)
Vlahopoulos, Nickolas; Schiller, Noah H.
2011-01-01
The Energy Finite Element Analysis (EFEA) has been utilized successfully for modeling complex structural-acoustic systems with isotropic structural material properties. In this paper, a formulation for modeling structures made out of composite materials is presented. An approach based on spectral finite element analysis is utilized first for developing the equivalent material properties for the composite material. These equivalent properties are employed in the EFEA governing differential equations for representing the composite materials and deriving the element level matrices. The power transmission characteristics at connections between members made out of non-isotropic composite material are considered for deriving suitable power transmission coefficients at junctions of interconnected members. These coefficients are utilized for computing the joint matrix that is needed to assemble the global system of EFEA equations. The global system of EFEA equations is solved numerically and the vibration levels within the entire system can be computed. The new EFEA formulation for modeling composite laminate structures is validated through comparison to test data collected from a representative composite aircraft fuselage that is made out of a composite outer shell and composite frames and stiffeners. NASA Langley constructed the composite cylinder and conducted the test measurements utilized in this work.
NASA Astrophysics Data System (ADS)
Emdadul Hoque, Md.; Mizuno, Takeshi; Ishino, Yuji; Takasaki, Masaya
2010-08-01
This paper presents a six-degree-of-freedom hybrid vibration isolation system integrated with an active negative suspension, an active-passive positive suspension and a passive weight support mechanism. The aim of the research consists in maximizing the system and control performances, and minimizing the system development and maintenance costs. The vibration isolation system is, fundamentally, developed by connecting an active negative suspension realized by zero-power control in series with an active-passive positive suspension. The system could effectively isolate ground vibrations in addition to suppress the effect of on-board generated direct disturbances of the six-axis motions, associated with vertical and horizontal directions. The system is further reinforced by introducing a passive weight support mechanism in parallel with the basic system. The modified system with zero-power control allows simplified design of the isolation table without power consumption. It also offers enhanced performance on direct disturbance suppression and large payload supporting capabilities, without degrading transmissibility characteristics. A mathematical model of the system is presented and, therefore, analyzed to demonstrate that zero-compliance to direct disturbance could be generated by the developed system. Experimental demonstrations validate the proposed concept that exhibits high stiffness of the isolation table to static and dynamic direct disturbances, and good transmissibility characteristics against ground vibration. Further improvements of the vibration isolation system and the control system are discussed as well.
Abramavicius, Darius; Valkunas, Leonas
2016-01-01
Oscillatory features of two-dimensional spectra of photosynthetic pigment-protein complexes during few picoseconds after electronic excitations of chlorophylls in various pigment-proteins were recently related to the coherent nuclear vibrations. It has been also speculated that the vibrations may assist the excitonic energy transfer and charge separation, hence contributing to energy transport and energy conversion efficiency. Here, we consider three theoretical approaches usually used for characterization of the excitation dynamics and charge separation, namely Redfield, Frster, and Marcus model descriptions, regarding this question. We show that two out of the three mechanisms require explicit resonances of excitonic splittings and the nuclear vibration frequencies. However, the third one related to the electron transfer is in principle off resonant. PMID:25618783
Intermediate energy electron impact excitation of composite vibrational modes in phenol
NASA Astrophysics Data System (ADS)
Neves, R. F. C.; Jones, D. B.; Lopes, M. C. A.; Nixon, K. L.; de Oliveira, E. M.; da Costa, R. F.; Varella, M. T. do N.; Bettega, M. H. F.; Lima, M. A. P.; da Silva, G. B.; Brunger, M. J.
2015-05-01
We report differential cross section results from an experimental investigation into the electron impact excitation of a number of the low-lying composite (unresolved) vibrational modes in phenol (C6H5OH). The measurements were carried out at incident electron energies in the range 15-40 eV and for scattered-electron angles in the range 10-90. The energy resolution of those measurements was typically 80 meV. Calculations, using the GAMESS code, were also undertaken with a B3LYP/aug-cc-pVDZ level model chemistry, in order to enable us to assign vibrational modes to the features observed in our energy loss spectra. To the best of our knowledge, the present cross sections are the first to be reported for vibrational excitation of the C6H5OH molecule by electron impact.
Intermediate energy electron impact excitation of composite vibrational modes in phenol
Neves, R. F. C.; Jones, D. B.; Lopes, M. C. A.; Nixon, K. L.; Oliveira, E. M. de; Lima, M. A. P.; Costa, R. F. da; Varella, M. T. do N.; Bettega, M. H. F.; Silva, G. B. da; Brunger, M. J.
2015-05-21
We report differential cross section results from an experimental investigation into the electron impact excitation of a number of the low-lying composite (unresolved) vibrational modes in phenol (C{sub 6}H{sub 5}OH). The measurements were carried out at incident electron energies in the range 15–40 eV and for scattered-electron angles in the range 10–90°. The energy resolution of those measurements was typically ∼80 meV. Calculations, using the GAMESS code, were also undertaken with a B3LYP/aug-cc-pVDZ level model chemistry, in order to enable us to assign vibrational modes to the features observed in our energy loss spectra. To the best of our knowledge, the present cross sections are the first to be reported for vibrational excitation of the C{sub 6}H{sub 5}OH molecule by electron impact.
Intermediate energy electron impact excitation of composite vibrational modes in phenol.
Neves, R F C; Jones, D B; Lopes, M C A; Nixon, K L; de Oliveira, E M; da Costa, R F; Varella, M T do N; Bettega, M H F; Lima, M A P; da Silva, G B; Brunger, M J
2015-05-21
We report differential cross section results from an experimental investigation into the electron impact excitation of a number of the low-lying composite (unresolved) vibrational modes in phenol (C6H5OH). The measurements were carried out at incident electron energies in the range 15-40 eV and for scattered-electron angles in the range 10-90°. The energy resolution of those measurements was typically ∼80 meV. Calculations, using the GAMESS code, were also undertaken with a B3LYP/aug-cc-pVDZ level model chemistry, in order to enable us to assign vibrational modes to the features observed in our energy loss spectra. To the best of our knowledge, the present cross sections are the first to be reported for vibrational excitation of the C6H5OH molecule by electron impact. PMID:26001456
Effect of collision energy and vibrational excitation on endothermic ion-molecule reactions
Turner, T.P.
1984-07-01
This thesis is divided into two major parts. In the first part an experimental study of proton and deuteron transfer in H/sub 2//sup +/ + He and HD/sup +/ + He has been carried out as a function of kinetic and vibrational energy. The data gives evidence that at lower kinetic energies, the spectator stripping mechanism indeed plays an important role when H/sub 2//sup +/ or HD/sup +/ is vibrationally excited. The second half of this thesis examines the relative efficiencies between the excitation of C-C stretching vibration and collision energy on the promotion of the H atom transfer reaction of C/sub 2/H/sub 2//sup +/ + H/sub 2/ ..-->.. C/sub 2/H/sub 3//sup +/ + H.
General formulation of the vibrational kinetic energy operator in internal bond-angle coordinates
NASA Astrophysics Data System (ADS)
Frederick, John H.; Woywod, Clemens
1999-10-01
A general formulation of the vibrational kinetic energy operator expressed in internal bond-angle coordinates is presented. This formulation is based on Podolsky's expression for the covariant form of the Laplace-Beltrami operator. When a valid set of internal bond-angle coordinates is employed, it is possible to adapt a systematic approach to solve for the Jacobian determinant governing the coordinate transformation from Cartesian coordinates. In the general case of an arbitrary N-atom system, this Jacobian always factorizes to a simple form. This allows one to evaluate all the terms that contribute to V̂', the effective potential that arises from transforming the kinetic energy operator to internal coordinates. We discuss restrictions on the choice of internal vibrational coordinates that may be included in a valid set. We then provide tabular information from which the vibrational kinetic energy operator for any molecular system can be constructed directly with no matrix inversion or chain rule manipulation required.
Lan, C. B.; Qin, W. Y.
2014-09-15
This letter investigates the energy harvesting from the horizontal coherent resonance of a vertical cantilever beam subjected to the vertical base excitation. The potential energy of the system has two symmetric potential wells. So, under vertical excitation, the system can jump between two potential wells, which will lead to the large vibration in horizontal direction. Two piezoelectric patches are pasted to harvest the energy. From experiment, it is found that the vertical excitation can make the beam turn to be bistable. The system can transform vertical vibration into horizontal vibration of low frequency when excited by harmonic motion. The horizontal coherence resonance can be observed when excited by a vertical white noise. The corresponding output voltages of piezoelectric films reach high values.
ENergy and Power Evaluation Program
1996-11-01
In the late 1970s, national and international attention began to focus on energy issues. Efforts were initiated to design and test analytical tools that could be used to assist energy planners in evaluating energy systems, particularly in developing countries. In 1984, the United States Department of Energy (DOE) commissioned Argonne National Laboratory`s Decision and Information Sciences Division (DIS) to incorporate a set of analytical tools into a personal computer-based package for distribution in developing countries. The package developed by DIS staff, the ENergy and Power Evaluation Program (ENPEP), covers the range of issues that energy planners must face: economic development, energy demand projections, supply-and-demand balancing, energy system expansion, and environmental impact analysis. Following the original DOE-supported development effort, the International Atomic Energy Agency (IAEA), with the assistance from the US Department of State (DOS) and the US Department of Energy (DOE), provided ENPEP training, distribution, and technical support to many countries. ENPEP is now in use in over 60 countries and is an international standard for energy planning tools. More than 500 energy experts have been trained in the use of the entire ENPEP package or some of its modules during the international training courses organized by the IAEA in collaboration with Argonne`s Decision and Information Sciences (DIS) Division and the Division of Educational Programs (DEP). This report contains the ENPEP program which can be download from the internet. Described in this report is the description of ENPEP Program, news, forums, online support and contacts.
A bi-annular-gap magnetorheological energy absorber for shock and vibration mitigation
NASA Astrophysics Data System (ADS)
Bai, Xian-Xu; Wereley, Norman M.; Choi, Young-Tai; Wang, Dai-Hua
2012-04-01
For semi-active shock and vibration mitigation systems using magnetorheological energy absorbers (MREAs), the minimization of the field-off damper force of the MREA at high speed is of particular significance because the damper force due to the viscous damping at high speed becomes too excessive and thus the controllable dynamic force range that is defined by the ratio of the field-on damper force to the field-off damper force is significantly reduced. In this paper, a bi-annular-gap MREA with an inner-set permanent magnet is proposed to decrease the field-off damper force at high speed while keeping appropriate dynamic force range for improving shock and vibration mitigation performance. In the bi-annular-gap MREA, two concentric annular gaps are configured in parallel so as to decrease the baseline damper force and both magnetic activation methods using the electromagnetic coil winding and the permanent magnet are used to keep holding appropriate magnetic intensity in these two concentric annular gaps in the consideration of failure of the electric power supply. An initial field-on damper force is produced by the magnetic field bias generated from the inner-set permanent magnet. The initial damper force of the MREA can be increased (or decreased) through applying positive (or negative) current to the electromagnetic coil winding inside the bi-annular-gap MREA. After establishing the analytical damper force model of the bi-annular-gap MREA using a Bingham-plastic nonlinear fluid model, the principle and magnetic properties of the MREA are analytically validated and analyzed via electromagnetic finite element analysis (FEA). The performance of the bi-annular-gap MREA is also theoretically compared with that of a traditional single-annular- gap MREA with the constraints of an identical volume by the performance matrix, such as the damper force, dynamic force range, and Bingham number with respect to different excitation velocities.
A modified method of vibration surveillance by using the optimal control at energy performance index
NASA Astrophysics Data System (ADS)
Kali?ski, Krzysztof J.; Galewski, Marek A.
2015-06-01
A method of vibration surveillance by using the optimal control at energy performance index has been creatively modified. The suggested original modification depends on consideration of direct relationship between the measured acceleration signal and the optimal control command. The paper presents the results of experiments and Hardware-in-the-loop simulations of a new active vibration reduction algorithm based on the energy performance index idea modified in such a way, that it directly utilises the acceleration feedback signal. Promising prospects towards real application of the modified method in case of the high speed milling are predicted as well.
NASA Astrophysics Data System (ADS)
Blažević, D.; Zelenika, S.
2015-05-01
Scavenging of low-level ambient vibrations i.e. the conversion of kinetic into electric energy, is proven as effective means of powering low consumption electronic devices such as wireless sensor nodes. Cantilever based scavengers are characterised by several advantages and thus thoroughly investigated; analytical models based on a distributed parameter approach, Euler-Bernoulli beam theory and eigenvalue analysis have thus been developed and experimentally verified. Finite element models (FEM) have also been proposed employing different modelling approaches and commercial software packages with coupled analysis capabilities. An approach of using a FEM analysis of a piezoelectric cantilever bimorph under harmonic excitation is used in this work. Modal, harmonic and linear and nonlinear transient analyses are performed. Different complex dynamic effects are observed and compared to the results obtained by using a distributed parameter model. The influence of two types of finite elements and three mesh densities is also investigated. A complex bimorph cantilever, based on commercially available Midé Technology® Volture energy scavengers, is then considered. These scavengers are characterised by an intricate multilayer structure not investigated so far in literature. An experimental set-up is developed to evaluate the behaviour of the considered class of devices. The results of the modal and the harmonic FEM analyses of the behaviour of the multilayer scavengers are verified experimentally for three different tip masses and 12 different electrical load values. A satisfying agreement between numerical and experimental results is achieved.
Vibration transmission through periodic structures using a mobility power flow approach
NASA Technical Reports Server (NTRS)
Cuschieri, J. M.
1990-01-01
The transmission of vibrational power (time averaged) through multiple coupled (periodic) structures is examined. The analysis is performed in the frequency domain and the coupling between the sub-elements of the periodic structure is expressed in terms of structural mobility functions for the junction points and between the junction points of the sub-elements. Equal length spans between stiffeners or supports of the periodic structure are considered. Through the use of the mobility power flow approach, the influence of sub-element and junction parameters, including damping at the joints, can be investigated. The results from the analysis can be in the form of either structural intensity or alternatively structural power content for each of the sub-elements. The examples discussed are for a thin, perfectly periodic beam with a finite number of spans with different types of stiffeners and/or supports between the spans. The excitation of the structure is by a point load located midway along the first span.
NASA Astrophysics Data System (ADS)
Sekiguchi, K.; Shimojima, A.; Kajimoto, O.
2002-04-01
A pump-probe experiment was performed to examine vibrational population relaxation of diiodomethane (CH 2I 2) molecule dissolved in supercritical CO 2. Using an apparatus with femtosecond time resolution, we observed the contributions of intramolecular vibrational energy redistribution (IVR) and intermolecular vibrational energy transfer (VET) separately. IVR and VET rates were measured with varying solvent densities at a constant temperature. It is shown that the IVR rate is not density dependent while the VET rate increases with increasing density from 0.4 to 0.8 g cm-3. This observation suggests that the rate of the VET process is determined by solute-solvent collisions whereas the IVR rate is not much affected by solute-solvent interaction.
NASA Astrophysics Data System (ADS)
Dhote, Sharvari; Zu, Jean; Zhu, Yang
2015-04-01
In this paper, a nonlinear wideband multi-mode piezoelectric vibration-based energy harvester (PVEH) is proposed based on a compliant orthoplanar spring (COPS), which has an advantage of providing multiple vibration modes at relatively low frequencies. The PVEH is made of a tri-leg COPS flexible structure, where three fixed-guided beams are capable of generating strong nonlinear oscillations under certain base excitation. A prototype harvester was fabricated and investigated through both finite-element analysis and experiments. The frequency response shows multiple resonance which corresponds to a hardening type of nonlinear resonance. By adding masses at different locations on the COPS structure, the first three vibration modes are brought close to each other, where the three hardening nonlinear resonances provide a wide bandwidth for the PVEH. The proposed PVEH has enhanced performance of the energy harvester in terms of a wide frequency bandwidth and a high-voltage output under base excitations.
NASA Astrophysics Data System (ADS)
Eltanany, Ali M.; Yoshimura, Takeshi; Fujimura, Norifumi; Elsayed, Nour Z.; Ebied, Mohamed R.; Ali, Mohamed G. S.
2015-10-01
The role of nonlinear stiffness in the performance of the piezoelectric vibrational energy harvester (pVEH) was discussed. Harmonic balance and numerical methods are applied to characterize the electromechanical response of pVEHs based on Duffing oscillator at a deterministic harmonic excitation of fundamental vibration characteristics (2 Hz, 1 m·s-2), which corresponds to human walking. Then, the response to a vibration with two harmonic waves, which has a fixed fundamental frequency (2 Hz, 1 m·s-2) and a frequency varied from 1.5 to 2.5 Hz. The numerical results obtained in this study indicate that nonlinearity does not have a significant advantage on the energy harvesting from human walking.
Dhote, Sharvari Zu, Jean; Zhu, Yang
2015-04-20
In this paper, a nonlinear wideband multi-mode piezoelectric vibration-based energy harvester (PVEH) is proposed based on a compliant orthoplanar spring (COPS), which has an advantage of providing multiple vibration modes at relatively low frequencies. The PVEH is made of a tri-leg COPS flexible structure, where three fixed-guided beams are capable of generating strong nonlinear oscillations under certain base excitation. A prototype harvester was fabricated and investigated through both finite-element analysis and experiments. The frequency response shows multiple resonance which corresponds to a hardening type of nonlinear resonance. By adding masses at different locations on the COPS structure, the first three vibration modes are brought close to each other, where the three hardening nonlinear resonances provide a wide bandwidth for the PVEH. The proposed PVEH has enhanced performance of the energy harvester in terms of a wide frequency bandwidth and a high-voltage output under base excitations.
Theoretical vibrational and rotational energies and intensities of the HNSi and DNSi molecules
NASA Astrophysics Data System (ADS)
Chong, Delano P.; Papousek, Dusan; Chen, Yit-Tsong; Jensen, Per
1993-01-01
Using the DEMON density functional program, 104 points on the potential-energy surface for the ground electronic state of the HNSi molecule were calculated. An analytic function was fitted through these points and used in two different computer programs (called Morse oscillator-rigid bender internal dynamics and TRIATOM) to calculate the vibration-rotational energies of the HNSi and DNSi molecules. Other analytic functions were fitted through the calculated dipole-moment data to compute the vibrational transition moments and the vibrationally averaged dipole moments. The computed fundamentals nu1, nu2, and nu3 for HNSi from the TRIATOM program are 3466, 413, and 1172/cm, respectively, in reasonable agreement with the observed values of 3588, 523, and 1198/cm. Agreement is similar for the Morse oscillator-rigid bender internal dynamics program as well as for DNSi.
Sun, Kyung Ho; Kim, Young-Cheol; Kim, Jae Eun
2014-10-15
While environmental vibrations are usually in the range of a few hundred Hertz, small-form-factor piezoelectric vibration energy harvesters will have higher resonant frequencies due to the structural size effect. To address this issue, we propose a resonant frequency-down conversion based on the theory of dynamic vibration absorber for the design of a small-form-factor piezoelectric vibration energy harvester. The proposed energy harvester consists of two frequency-tuned elastic components for lowering the first resonant frequency of an integrated system but is so configured that an energy harvesting beam component is inverted with respect to the other supporting beam component for a small form factor. Furthermore, in order to change the unwanted modal characteristic of small separation of resonant frequencies, as is the case with an inverted configuration, a proof mass on the supporting beam component is slightly shifted toward a second proof mass on the tip of the energy harvesting beam component. The proposed small-form-factor design capability was experimentally verified using a fabricated prototype with an occupation volume of 20 × 39 × 6.9 mm{sup 3}, which was designed for a target frequency of as low as 100 Hz.
Energy transfer from vibrationally excited pentafluorobenzene to helium, xenon and water vapor
NASA Astrophysics Data System (ADS)
Wallington, Timothy J.; Dagaut, Philippe; Braun, Walter
1988-02-01
Pulsed infrared laser irradiation was used to excite pentafluorobenzene (PFB) in mixtures with helium, argon and water vapor. Measurements of the rates of energy transfer were made as a function of the initial laser excitation energy, total pressure, and composition of the gas mixture using the Hg tracer technique. The results are discussed with respect to the transfer of energy between vibrational, rotational, and translational degrees of freedom.
Zero-point energy, tunneling, and vibrational adiabaticity in the Mu + H2 reaction
Mielke, Steven L.; Garrett, Bruce C.; Fleming, Donald G.; Truhlar, Donald G.
2015-01-09
Abstract: Isotopic substitution of muonium for hydrogen provides an unparalleled opportunity to deepen our understanding of quantum mass effects on chemical reactions. A recent topical review [Aldegunde et al., Mol. Phys. 111, 3169 (2013)] of the thermal and vibrationally-stateselected reaction of Mu with H2 raises a number of issues that are addressed here. We show that some earlier quantum mechanical calculations of the Mu + H2 reaction, which are highlighted in this review and which have been used to benchmark approximate methods, are in error by as much as 19% in the low-temperature limit. We demonstrate that an approximate treatment of the BornOppenheimer diagonal correction that was used in some recent studies is not valid for treating the vibrationally-state-selected reaction. We also discuss why vibrationally adiabatic potentials that neglect bend zero-point energy are not a useful analytical tool for understanding reaction rates and why vibrationally nonadiabatic transitions cannot be understood by considering tunneling through vibrationally adiabatic potentials. Finally, we present calculations on a hierarchical family of potential energy surfaces to assess the sensitivity of rate constants to the quality of the potential surface.
High-level ab initio potential energy surfaces and vibrational energies of H2CS
NASA Astrophysics Data System (ADS)
Yachmenev, Andrey; Yurchenko, Sergei N.; Ribeyre, Tristan; Thiel, Walter
2011-08-01
Six-dimensional (6D) potential energy surfaces (PESs) of H2CS have been generated ab initio using the recently proposed explicitly correlated (F12) singles and doubles coupled cluster method including a perturbational estimate of connected triple excitations, CCSD(T)-F12b [T. B. Adler, G. Knizia, and H.-J. Werner, J. Chem. Phys. 127, 221106 (2007)] in conjunction with F12-optimized correlation consistent basis sets. Core-electron correlation, high-order correlation, scalar relativistic, and diagonal Born-Oppenheimer terms were included as additive high-level (HL) corrections. The resulting 6D PESs were represented by analytical functions which were used in variational calculations of the vibrational term values below 5000 cm-1. The best PESs obtained with and without the HL corrections, VQZ-F12* HL and VQZ-F12*, reproduce the fundamental vibrational wavenumbers with mean absolute deviations of 1.13 and 1.22 cm-1, respectively. A detailed analysis of the effects of the HL corrections shows how the VQZ-F12 results benefit from error cancellation. The present purely ab initio PESs will be useful as starting points for empirical refinements towards an accurate "spectroscopic" PES of H2CS.
A Wind Energy Powered Wireless Temperature Sensor Node
Zhang, Chuang; He, Xue-Feng; Li, Si-Yu; Cheng, Yao-Qing; Rao, Yang
2015-01-01
A wireless temperature sensor node composed of a piezoelectric wind energy harvester, a temperature sensor, a microcontroller, a power management circuit and a wireless transmitting module was developed. The wind-induced vibration energy harvester with a cuboid chamber of 62 mm × 19.6 mm × 10 mm converts ambient wind energy into electrical energy to power the sensor node. A TMP102 temperature sensor and the MSP430 microcontroller are used to measure the temperature. The power management module consists of LTC3588-1 and LT3009 units. The measured temperature is transmitted by the nRF24l01 transceiver. Experimental results show that the critical wind speed of the harvester was about 5.4 m/s and the output power of the harvester was about 1.59 mW for the electrical load of 20 kΩ at wind speed of 11.2 m/s, which was sufficient to power the wireless sensor node to measure and transmit the temperature every 13 s. When the wind speed increased from 6 m/s to 11.5 m/s, the self-powered wireless sensor node worked normally. PMID:25734649
A wind energy powered wireless temperature sensor node.
Zhang, Chuang; He, Xue-Feng; Li, Si-Yu; Cheng, Yao-Qing; Rao, Yang
2015-01-01
A wireless temperature sensor node composed of a piezoelectric wind energy harvester, a temperature sensor, a microcontroller, a power management circuit and a wireless transmitting module was developed. The wind-induced vibration energy harvester with a cuboid chamber of 62 mm 19.6 mm 10 mm converts ambient wind energy into electrical energy to power the sensor node. A TMP102 temperature sensor and the MSP430 microcontroller are used to measure the temperature. The power management module consists of LTC3588-1 and LT3009 units. The measured temperature is transmitted by the nRF24l01 transceiver. Experimental results show that the critical wind speed of the harvester was about 5.4 m/s and the output power of the harvester was about 1.59 mW for the electrical load of 20 k? at wind speed of 11.2 m/s, which was sufficient to power the wireless sensor node to measure and transmit the temperature every 13 s. When the wind speed increased from 6 m/s to 11.5 m/s, the self-powered wireless sensor node worked normally. PMID:25734649
Optimizing the Electrical Power in an Energy Harvesting System
NASA Astrophysics Data System (ADS)
Coccolo, Mattia; Litak, Grzegorz; Seoane, Jess M.; Sanjun, Miguel A. F.
In this paper, we study the vibrational resonance (VR) phenomenon as a useful mechanism for energy harvesting purposes. A system, driven by a low frequency and a high frequency forcing, can give birth to the vibrational resonance phenomenon, when the two forcing amplitudes resonate and a maximum in amplitude is reached. We apply this idea to a bistable oscillator that can convert environmental kinetic energy into electrical energy, that is, an energy harvester. Normally, the VR phenomenon is studied in terms of the forcing amplitudes or of the frequencies, that are not always easy to adjust and change. Here, we study the VR generated by tuning another parameter that is possible to manipulate when the forcing values depend on the environmental conditions. We have investigated the dependence of the maximum response due to the VR for small and large variations in the forcing amplitudes and frequencies. Besides, we have plotted color coded figures in the space of the two forcing amplitudes, in which it is possible to appreciate different patterns in the electrical power generated by the system. These patterns provide useful information on the forcing amplitudes in order to produce the optimal electrical power.
Exploring Energy, Power, and Transportation Technology.
ERIC Educational Resources Information Center
Bowers, Donovan; Kellum, Mary
These teacher's materials for a seven-unit course were developed to help students develop technological literacy, career exploration, and problem-solving skills relative to the communication industries. The seven units include an overview of energy and power, principles of energy and power, power production and conversion, power transmission and
Low-energy vibrational modes of the monolayer adsorbate CO2/NaCl(001)
NASA Astrophysics Data System (ADS)
Lange, G.; Toennies, J. P.; Vollmer, R.; Weiss, H.
1993-06-01
Dispersion curves of surface vibrational modes of monolayer CO2/NaCl(001) have been measured by inelastic He atom scattering along the ?X azimuth. Eight phonon modes could be followed across almost the entire Brillouin zone. The identification of the modes is discussed based on previously calculated normal mode energies at the zone origin.
Effects of reagent translational and vibrational energy on the dynamics of endothermic reactions
Krajnovich, D.; Zhang, Z.; Huisken, F.; Shen, Y.R.; Lee, Y.T.
1981-07-01
The endothermic reactions Br + CH/sub 3/I ..-->.. CH/sub 3/ + IBr (..delta..H/sub 0//sup 0/ = 13 kcal/mole) and Br + CF/sub 3/I ..-->.. CF/sub 3/ + IBr (..delta..H/sub 0//sup 0/ = 11 kcal/mole) have been studied by the crossed molecular beams method. Detailed center-of-mass contour maps of the IBr product flux as a function of recoil velocity and scattering angle are derived. For both systems it is found that the IBr product is sharply backward scattered with respect to the incident Br dirction, and that most of the available energy goes into product translation. Vibrational enhancement of the Br + CF/sub 3/I reaction was investigated by using the infrared multiphoton absorption process to prepare highly vibrationally excited CF/sub 3/I. At a collision energy of 31 kcal/mole (several times the barrier height), reagent vibrational energy appears to be less effective than an equivalent amount of (additional) translational energy in promoting reaction. More forward scattered IBr is produced in reactions of Br with vibrationally hot CF/sub 3/I.
NASA Astrophysics Data System (ADS)
Dudka, A.; Basset, P.; Cottone, F.; Blokhina, E.; Galayko, D.
2013-12-01
This paper reports on an electrostatic Vibration Energy Harvester (e-VEH) system, for which the energy conversion process is initiated with a low bias voltage and is compatible with wideband stochastic external vibrations. The system employs the auto-synchronous conditioning circuit topology with the use of a novel dedicated integrated low-power high-voltage switch that is needed to connect the charge pump and flyback - two main parts of the used conditioning circuit. The proposed switch is designed and implemented in AMS035HV CMOS technology. Thanks to the proposed switch device, which is driven with a low-voltage ground-referenced logic, the e-VEH system may operate within a large voltage range, from a pre-charge low voltage up to several tens volts. With such a high-voltage e-VEH operation, it is possible to obtain a strong mechanical coupling and a high rate of vibration energy conversion. The used transducer/resonator device is fabricated with a batch-processed MEMS technology. When excited with stochastic vibrations having an acceleration level of 0.8 g rms distributed in the band 110-170 Hz, up to 0.75 ?W of net electrical power has been harvested with our system. This work presents an important milestone in the challenge of designing a fully integrated smart conditioning interface for the capacitive e-VEHs.
NASA Astrophysics Data System (ADS)
Shin, Seungha
All energy conversion inefficiencies begin with emission of resonant atomic motions, e.g., vibrations, and are declared as waste heat once these motions thermalize to equilibrium. The nonequilibrium energy occupancy of the vibrational modes can be targeted as a harvestable, low entropy energy source for direct conversion to electric energy. Since the lifetime of these resonant vibrations is short, special nanostructures are required with the appropriate tuning of the kinetics. These in turn require multiscale, multiphysics treatments. Atomic vibration is described with quasiparticle phonon in solid, and the optical phonon emission is dominant relaxation channel in semiconductors. These optical modes become over-occupied when their emission rate becomes larger than their decay rate, thus hindering energy relaxation and transport in devices. Effective removal of these phonons by drifting electrons is investigated by manipulating the electron distribution to have higher population in the low-energy states, thus allowing favorable phonon absorption. This is done through introduction, design and analysis of a heterobarrier conducting current, where the band gap is controlled by alloying, thus creating a spatial variation which is abrupt followed by a linear gradient (to ensure directed current). Self-consistent ensemble Monte Carlo simulations based on interaction kinetics between electron and phonon show that up to 19% of the phonon energy is converted to electric potential with an optimized GaAs/AlxGa1-xAs barrier structure over a range of current and electron densities, and this system is also verified through statistical entropy analysis. This direct energy conversion improves the device performance with lower operation temperature and enhances overall energy conversion efficiency. Through this study, the paradigm for harvesting the resonant atomic vibration is proposed, reversing the general role of phonon as only causing electric potential drop. Fundamentals pertaining to thermal energy transport and conversion are further explored by directly addressing the nonequilibria in phonon and molecular vibration. Enhancement of the laser cooling performance in molecular gas is examined by nonequilibrium interaction kinetics between molecules and photons. Thermal energy transport across interfaces and junctions is also studied, and decomposition of thermal interfacial resistance, atomic restructuring, and phonon wave features are addressed.
Applications of energy harvesting for ultralow power technology
NASA Astrophysics Data System (ADS)
Pop-Vadean, A.; Pop, P. P.; Barz, C.; Chiver, O.
2015-06-01
Ultra-low-power (ULP) technology is enabling a wide range of new applications that harvest ambient energy in very small amounts and need little or no maintenance - self-sustaining devices that are capable of perpetual or nearly perpetual operation. These new systems, which are now appearing in industrial and consumer electronics, also promise great changes in medicine and health. Until recently, the idea of micro-scale energy harvesting, and collecting miniscule amounts of ambient energy to power electronic systems, was still limited to research proposals and laboratory experiments.Today an increasing number of systems are appearing that take advantage of light, vibrations and other forms of previously wasted environmental energy for applications where providing line power or maintaining batteries is inconvenient. In the industrial world, where sensors gather information from remote equipment and hazardous processes; in consumer electronics, where mobility and convenience are served; and in medical systems, with unique requirements for prosthetics and non-invasive monitoring, energy harvesting is rapidly expanding into new applications.This paper serves as a survey for applications of energy harvesting for ultra low power technology based on various technical papers available in the public domain.
Energy-weighted sum rules and the analysis of vibrational structure in molecular spectra
NASA Astrophysics Data System (ADS)
Smith, W. L.
2015-10-01
The energy-weighted sum SV = Σn (E‧n - E″m)|<ψ″m|ψ‧n>|2 = <ψ″m|ΔV|ψ″m> for the vibrational potential functions V‧, V″ associated with transitions between two electronic states of diatomic molecular species is investigated and specific formulae are given using Morse functions for V‧ and V″. It is found that these formulae are useful approximations which provide a convenient way to analyse the vibrational structure of real spectra to give estimates of molecular parameters such as the change in internuclear distance accompanying a transition.
Vibrational energy transfer in OH X 2Pi(i), v = 2 and 1
NASA Technical Reports Server (NTRS)
Raiche, George A.; Jeffries, Jay B.; Rensberger, Karen J.; Crosley, David R.
1990-01-01
Using an IR-pump/UV-probe method in a flow discharge cell, vibrational energy transfer in OH X 2Pi(i) has been studied. OH is prepared in v = 2 by overtone excitation, and the time evolution of population in v = 2 and 1 monitored by laser-induced fluorescence. Rate constants for vibrational relaxation by the colliders H2O, NH3, CO2, and CH4 were measured. Ratios of rate constants for removal from the two states, k2/k1, range from two to five.
Meier, Patrick; Oschetzki, Dominik; Rauhut, Guntram; Berger, Robert
2014-05-14
A transformation of potential energy surfaces (PES) being represented by multi-mode expansions is introduced, which allows for the calculation of anharmonic vibrational spectra of any isotopologue from a single PES. This simplifies the analysis of infrared spectra due to significant CPU-time savings. An investigation of remaining deviations due to truncations and the so-called multi-level approximation is provided. The importance of vibrational-rotational couplings for small molecules is discussed in detail. In addition, an analysis is proposed, which provides information about the quality of the transformation prior to its execution. Benchmark calculations are provided for a set of small molecules.
A flex-compressive-mode piezoelectric transducer for mechanical vibration/strain energy harvesting.
Li, Xiaotian; Guo, Mingsen; Dong, Shuxiang
2011-04-01
A piezoelectric transducer for harvesting energy from ambient mechanical vibrations/strains under pressure condition was developed. The proposed transducer was made of two ring-type piezoelectric stacks, one pair of bow-shaped elastic plates, and one shaft that pre-compresses them. This transducer works in flex-compressive (F-C) mode, which is different from a conventional flex-tensional (F-T) one, to transfer a transversely applied force F into an amplified longitudinal force N pressing against the two piezo-stacks via the two bowshaped elastic plates, generating a large electric voltage output via piezoelectric effect. Our experimental results show that without an electric load, an F-C mode piezo-transducer could generate a maximum electric voltage output of up to 110 Vpp, and with an electric load of 40 ??, it a maximum power output of 14.6 mW under an acceleration excitation of 1 g peak-peak at the resonance frequency of 87 Hz. PMID:21507747
NASA Astrophysics Data System (ADS)
Kruglova, T. V.
2004-01-01
The detailed spectroscope information about highly excited molecules and radicals such us as H+3, H2, HI, H2O, CH2 is needed for a number of applications in the field of laser physics, astrophysics and chemistry. Studies of highly excited molecular vibration-rotation states face several problems connected with slowly convergence or even divergences of perturbation expansions. The physical reason for a perturbation expansion divergence is the large amplitude motion and strong vibration-rotation coupling. In this case one needs to use the special method of series summation. There were a number of papers devoted to this problem: papers 1-10 in the reference list are only example of studies on this topic. The present report is aimed at the application of GET method (Generalized Euler Transformation) to the diatomic molecule. Energy levels of a diatomic molecule is usually represented as Dunham series on rotational J(J+1) and vibrational (V+1/2) quantum numbers (within the perturbation approach). However, perturbation theory is not applicable for highly excited vibration-rotation states because the perturbation expansion in this case becomes divergent. As a consequence one need to use special method for the series summation. The Generalized Euler Transformation (GET) is known to be efficient method for summing of slowly convergent series, it was already used for solving of several quantum problems Refs.13 and 14. In this report the results of Euler transformation of diatomic molecule Dunham series are presented. It is shown that Dunham power series can be represented of functional series that is equivalent to its partial summation. It is also shown that transformed series has the butter convergent properties, than the initial series.
Feasibility of Self Powered Actuation for Flow, Separation and Vibration Control
NASA Technical Reports Server (NTRS)
Shyam, Vikram; Bak, Dillon; Izadnegahdar, Alain
2015-01-01
A gas turbine engine is anywhere from 40-50% efficient. A large amount of energy is wasted as heat. Some of this heat is recoverable through the use of energy harvesting and can be used for powering on-board systems or for storing energy in batteries to replace auxiliary power units (APUs). As hybrid electric aircraft become more common, the use of energy harvesting will see increasingly more benefit and become commonplace in gas turbine engines. For electric aircraft with motors, TEGs would be beneficial for reclaiming waste heat from electric motors. The primary focus of this work was to evaluate the feasibility of harvesting energy from the hot section of a gas turbine engine (for a single aisle Boeing 737 thrust class) using thermoelectric generators (TEGs). The resulting heat could be used to power on-board actuation mechanisms such as plasma actuators and piezoelectric actuators. The work is a result of a two year NASA Center Innovation Fund from 2009 to 2011. The trade-off between thermoelectric harvesting and blade surface temperature were studied to ensure that blade durability is not adversely impacted by embedding a low thermal conductivity TEG. Calculations show that.5-10 Watts can be harvested per blade depending on flow conditions and on the thermoelectric material chosen. BiTe and SiGe were used for this analysis and future thermoelectric generators or multiferroic alloys could considerably improve power output.
Resonant vibrational excitation and de-excitation of N2(v) by low-energy electrons.
Poparić, G B; Ristić, M; Belić, D S
2008-05-01
We have calculated cross sections and rate coefficients for low-energy electron impact excitation of the nitrogen molecule from vibrationally excited levels N2(v) 1-8. Calculations are performed in the 2Pig shape resonance energy region, from 0 to 5 eV. The cross sections are determined by using our recent integral cross section measurements of the ground level vibrational excitation and the most recent cross sections for elastic electron scattering, applying the principle of detailed balance. The rate coefficient calculations are performed for the Maxwellian electron energy distribution. By using extended Monte Carlo simulations, the electron energy distribution functions (EEDF) and the rate coefficients are also determined for the nonequilibrium conditions, in the presence of the homogeneous external electric field for the typical, moderate values of the electric field over gas number density ratios, E/N. PMID:18366195
NASA Astrophysics Data System (ADS)
Dykeman, Eric C.; Sankey, Otto F.
2009-12-01
The vibrational excitation of a tubular M13 bacteriophage capsid is simulated using classical molecular dynamics. The excitation occurs through impulsive stimulated Raman scattering by ultra-short laser pulses which ping the vibrational modes of the capsid. Tuning the laser pulse temporal width determines the frequency region of the capsid that is excited. The simulations reveal that electromagnetic energy transferred to the high frequency modes by ultra-short pulses is funneled via anharmonicity to just five low frequency modes which receive approximately 80% of the funneled energy. A single mode receives most of the funneled energy (3-4% of the total energy delivered) involves swelling and is effective in damaging the capsid. However, the laser intensity necessary to produce damage to the capsid from a single laser pulse is found to be extremely high for this mechanism to be effective.
NASA Technical Reports Server (NTRS)
Tessarzik, J. M.; Chiang, T.; Badgley, R. H.
1974-01-01
A bearing damper, operating on the support flexure of a pivoted pad in a tilting-pad type gas-lubricated journal bearing, has been designed, built, and tested under externally-applied random vibrations. The NASA Brayton Rotating Unit (BRU), a 36,000 rpm, 10-Kwe turbogenerator had previously been subjected in the MTI Vibration Test Laboratory to external random vibrations, and vibration response data had been recorded and analyzed for amplitude distribution and frequency content at a number of locations in the machine. Based on data from that evaluation, a piston-type damper was designed and developed for each of the two flexibly-supported journal bearing pads (one in each of the two three-pad bearings). A modified BRU, with dampers installed, has been re-tested under random vibration conditions. Root-mean-square vibration amplitudes were determined from the test data, and displacement power spectral density analyses have been performed. Results of these data reduction efforts have been compared with vibration tolerance limits. Results of the tests indicate significant reductions in vibration levels in the bearing gas-lubricant films, particularly in the rigidly-mounted pads. The utility of the gas-lubricated damper for limiting rotor-bearing system vibrations in high-speed turbomachinery has thus been demonstrated.
NASA Astrophysics Data System (ADS)
Lu, Y.; Cottone, F.; Boisseau, S.; Galayko, D.; Marty, F.; Basset, P.
2015-12-01
This paper reports for the first time a MEMS electrostatic vibration energy harvester (e-VEH) with corona-charged vertical electrets on its electrodes. The bandwidth of the 1-cm2 device is extended in low and high frequencies by nonlinear elastic stoppers. With a bias voltage of 46 V (electret@21 V + DC external source@25 V) between the electrodes, the RMS power of the device reaches 0.89 μW at 33 Hz and 6.6 μW at 428 Hz. The -3dB frequency band including the hysteresis is 223∼432 Hz, the one excluding the hysteresis 88∼166 Hz. We also demonstrate the charging of a 47 μF capacitor used for powering a wireless and autonomous temperature sensor node with a data transmission beyond 10 m at 868 MHz.
Careers in Geothermal Energy: Power from below
ERIC Educational Resources Information Center
Liming, Drew
2013-01-01
In the search for new energy resources, scientists have discovered ways to use the Earth itself as a valuable source of power. Geothermal power plants use the Earth's natural underground heat to provide clean, renewable energy. The geothermal energy industry has expanded rapidly in recent years as interest in renewable energy has grown. In 2011,…
NASA Astrophysics Data System (ADS)
Hong, Kuang-Sheng
We propose a phenomenon of piezoelectrochemical (PZEC) effect for the direct conversion of mechanical energy to chemical energy. This phenomenon is further applied for generating hydrogen and oxygen via direct water decomposition by means of as-synthesized piezoelectric quartz (SiO2) nano-rods, ZnO microfibers, and BaTiO3 microdendrites. The materials are vibrated with ultrasonic waves leading to a strain-induced electric charge development on their surface. With sufficient electric potential, the strained piezoelectric materials in water triggered the redox reaction of water to produce hydrogen and oxygen gases. All materials have indicated a well response to the external mechanical vibration to drive the desired chemical reactions. ZnO fibers under ultrasonic vibrations showed a stoichiometric ratio of H 2/O2 (2:1) initial gas production from pure water. The efficiency of the piezoelectrochemical effect was calculated by ratio of the chemical energy output over the mechanical energy input of the system. The study of piezoelectrochemical effect is further applied to the environmental cleaning technology. Accordingly, a dissolved orange dye (AO7) was decomposed via mechanical driving force by using BaTiO3 microdendrites. Kinetic details of the dye decomposition through piezoelectrochemical effect were investigated. In addition, the piezoelectrochemical effect was proposed to the implication of tectonic hydrogen in geological systems providing insights of hydrogen generation in active fault zones. The tectonic hydrogen produced through PZEC effect could be a sustainable energy source for subsurface microbial community. This study provides a simple and cost-effective technology for generating hydrogen fuels as well as environmental cleaning by scavenging energy wastes such as noise or stray vibrations from the environment. This new piezoelectrochemical effect may have potential implications in solving the challenging energy and environmental issues that we are facing today and in the future.
Spherical vibrator model with an energy increasing stiffness
NASA Astrophysics Data System (ADS)
Budaca, R.
2015-12-01
A new parameter free collective solution is proposed by inducing a linear energy dependence in the five-dimensional harmonic oscillator potential of the Bohr Hamiltonian and taking the asymptotic limit of the slope. The model preserves the degeneracy features of the U (5) dynamical symmetry but with an expanded energy spectrum and with damped E2 transition probabilities. The 116Cd nucleus is presented as an experimental realization of the model.
Vibrational energy transfer at a gold surface in reacting systems: cyclobutene and nitromethane
Yuan, W.; Rabinovitch, B.S.
1983-06-09
Single collision excitation probabilities were measured for cyclobutene and nitromethane on seasoned polycrystalline gold plane and wire surfaces. Transport above the reaction thresholds for isomerization and decomposition, respectively, for the two substrates was used as the criterion of vibrational energy transfer. Several different seasoning and processing procedures of the surfaces were employed. For cyclobutene, a decreased efficiency relative to strong collider transition probabilities appeared only above 550-600 K; the energy transfer efficiency at a treated gold surface is greater than that at a seasoned silica surface. The vibrational energy transfer efficiency declined above 600 K and fell abruptly to a quasiconstant value in the range 900-1100 K. Above 1100 K the differences between various conditioned surfaces diminished progressively. Unlike cyclobutene, and earlier studies of nitromethane on silica surfaces where reproducible noncatalytic behavior could be attained, nitromethane on gold showed apparent catalytic behavior which the various conditioning treatments failed to repress.
An Ab Initio Calculation of the Low-Frequency Vibrational Energies of the HCl Dimer
NASA Astrophysics Data System (ADS)
Gomez, P. C.; Bunker, P. R.; Karpfen, A.; Lischka, H.
1994-08-01
With the two HCl bond lengths held fixed at the monomer vibrational ground state value ( r0 = 1.284 ) we have calculated a four-dimensional ab initio potential energy surface of the HCl dimer at 400 nuclear geometries covering energies within 1000 cm -1 of the minimum. The electronic basis set is larger than that used earlier (A. Karpfen, P.R. Bunker, and P. Jensen, Chem. Phys. 149, 299-309, (1991) to obtain a surface on which dynamical calculations were carried out. We calculate the lowest 33 vibrational energies (up to 230 cm -1) involving the four large-amplitude modes on this surface using an adiabatic separation of the van der Waals stretching coordinate from the three large-amplitude bending coordinates (following S.C. Althorpe, D.C. Clary, and P. R. Bunker, Chem, Phys. Lett. 187, 345-353, (1991), and we contrast the results with those obtained using electrostatic potentials.
Exploitation of a tristable nonlinear oscillator for improving broadband vibration energy harvesting
NASA Astrophysics Data System (ADS)
Zhou, Shengxi; Cao, Junyi; Lin, Jing; Wang, Zezhou
2014-09-01
Numerical and experimental investigations of a broadband vibration energy harvester with triple-well are presented. The nonlinear restoring force of the tristable oscillator is experimentally identified as a high order polynomial that depends on the relative spacing and locations of the magnets in the magnetically coupled piezoelectric cantilever. Simulations and experiments are performed at different harmonic excitation levels ranging from 10 to 35 Hz. The tristable energy harvester possesses the unique jump characteristics of oscillation center stemming from excitation level and initial displacements. Its broad frequency range of 15.1-32.5 Hz is obtained from the transition among three wells. It is also demonstrated that the tristable nonlinear oscillator will be more helpful to improve the broadband performance for harvesting vibration energy under low frequency excitations.
Potential energy surface and vibrational band origins of the triatomic lithium cation
NASA Astrophysics Data System (ADS)
Searles, Debra J.; Dunne, Simon J.; von Nagy-Felsobuki, Ellak I.
The 104 point CISD Li +3 potential energy surface and its analytical representation is reported. The calculations predict the minimum energy geometry to be an equilateral triangle of side RLi?Li = 3.0 and of energy - 22.20506 E h. A fifth-order MorseDunham type analytical force field is used in the CarneyPorter normal co-ordinate vibrational Hamiltonian, the corresponding eigenvalue problem being solved variationally using a 560 configurational finite-element basis set. The predicted assignment of the vibrational band origins is in accord with that reported for H +3. Moreover, for 6Li +3 and 7Li +3 the lowest i.r. accessible band origin is the overline?0,1,1 predicted to be at 243.6 and 226.0 cm -1 respectively.
Estimating the vibration level of an L-shaped beam using power flow techniques
NASA Technical Reports Server (NTRS)
Cuschieri, J. M.; Mccollum, M.; Rassineux, J. L.; Gilbert, T.
1986-01-01
The response of one component of an L-shaped beam, with point force excitation on the other component, is estimated using the power flow method. The transmitted power from the source component to the receiver component is expressed in terms of the transfer and input mobilities at the excitation point and the joint. The response is estimated both in narrow frequency bands, using the exact geometry of the beams, and as a frequency averaged response using infinite beam models. The results using this power flow technique are compared to the results obtained using finite element analysis (FEA) of the L-shaped beam for the low frequency response and to results obtained using statistical energy analysis (SEA) for the high frequencies. The agreement between the FEA results and the power flow method results at low frequencies is very good. SEA results are in terms of frequency averaged levels and these are in perfect agreement with the results obtained using the infinite beam models in the power flow method. The narrow frequency band results from the power flow method also converge to the SEA results at high frequencies. The advantage of the power flow method is that detail of the response can be retained while reducing computation time, which will allow the narrow frequency band analysis of the response to be extended to higher frequencies.
NASA Astrophysics Data System (ADS)
Kawano, M.; Zhang, Y.; Zheng, R.; Nakano, K.; Kim, B.
2015-12-01
This paper describes extremely simple configuration of novel vibrational energy harvester, which can harness low frequency (less than 5 Hz, such as various environmental vibrations) over a broad frequency band for the first time. A design that utilizes a phenomenon called stochastic resonance can give significantly enhanced vibration mode for increasing efficiency, and simple bi-stable cantilever with tip mass installed a basement vertically fulfils the requirements for stochastic resonance. We fabricated bi-stable cantilever with tip mass and validated whether the cantilever could be used as an effective low frequency vibration energy harvester. In the experiment, when a 1 Hz periodic force and environmental noise vibration were applied, stochastic resonance occurred. The amplitude of the energy harvester increased over tenfold (over 30 mm).
NASA Astrophysics Data System (ADS)
Seo, Jongho; Kim, Jin-Su; Jeong, Un-Chang; Kim, Yong-Dae; Kim, Young-Cheol; Lee, Hanmin; Oh, Jae-Eung
2016-02-01
In this study, we derived an equation of motion for an electromechanical system in view of the components and working mechanism of an electromagnetic-type energy harvester (ETEH). An electromechanical transduction factor (ETF) was calculated using a finite-element analysis (FEA) based on Maxwell's theory. The experimental ETF of the ETEH measured by means of sine wave excitation was compared with and FEA data. Design parameters for the stationary part of the energy harvester were optimized in terms of the power performance by using a response surface method (RSM). With optimized design parameters, the ETEH showed an improvement in performance. We experimented with the optimized ETEH (OETEH) with respect to changes in the external excitation frequency and the load resistance by taking human body vibration in to account. The OETEH achieved a performance improvement of about 30% compared to the initial model.
On the nature of intramolecular vibrational energy transfer in dense molecular environments
NASA Astrophysics Data System (ADS)
von Benten, Rebekka S.; Abel, Bernd
2010-12-01
Transient femtosecond-IR-pump-UV-absorption probe-spectroscopy has been employed to shed light on the nature of intramolecular vibrational energy transfer (IVR) in dense molecular environments ranging from the diluted gas phase to the liquid. A general feature in our experiments and those of others is that IVR proceeds via multiple timescales if overtones or combination vibrations of high frequency modes are excited. It has been found that collisions enhance IVR if its (slower) timescales can compete with collisions. This enhancement is, however, much more weaker and rather inefficient as opposed to the effect of collisions on intermolecular energy transfer which is well known. In a series of experiments we found that IVR depends not significantly on the average energy transferred in a collision but rather on the number of collisions. The collisions are much less efficient in affecting IVR than VET. We conclude that collision induced broadening of vibrational energy levels reduces the energy gaps and enhances existing couplings between tiers. The present results are an important step forward to rationalize and understand apparently different and not consistent results from different groups on different molecular systems between gas and liquid phases.
NASA Astrophysics Data System (ADS)
Komuro, Atsushi; Takahashi, Kazunori; Ando, Akira
2015-10-01
Vibration-to-translation (V-T) energy transfer in atmospheric-pressure streamer discharge is numerically simulated using a two-dimensional electro-hydrodynamic model. The model includes state-to-state vibrational kinetics in humid air and is coupled with the compressible flow equation of the gas fluid. The vibrational distribution of {{\\text{O}}2}(v) reaches equilibrium more quickly than that of {{\\text{N}}2}(v) , whereas the energy released from {{\\text{O}}2}(v) does not increase the gas temperature. In humid air, the decay rate of the vibrational energy of {{\\text{N}}2}(v) is accelerated by the V-T energy transfer through water molecules and the energy heats the gas. However, the increase in gas temperature due to V-T energy transfer is not always seen because it competes with thermal diffusion.
NASA Astrophysics Data System (ADS)
Esquinazi, Pablo
1991-11-01
This review is concerned with effects in the energy dissipation and elastic modulus of superconductors vibrating in a magnetic field. The physics of superconducting vibrating reeds and reeds made of superconducting suspensions is thoroughly described as well as the main features observed in other oscillators applied to flux pinning studies. It is argued that among the diversity of methods to study superconducting and pinning properties as a function of magnetic field and temperature, the vibrating reed technique is one of the most sensitive due to the accurate measurement of frequency and dissipation with feasible magnetometry applications. Results of the elastic coupling between the flux line lattice and the atomic lattice in high- and low- T c superconductors obtained with the vibrating reed are summarized as well as the behavior of vibrating type II superconductors near their lower critical field. Results from mechanical measurements in high-temperature superconductors are reviewed, which support the model of thermally activated depinning and vortex diffusion.
Solar-pumped electronic-to-vibrational energy transfer lasers
NASA Technical Reports Server (NTRS)
Harries, W. L.; Wilson, J. W.
1981-01-01
The possibility of using solar-pumped lasers as solar energy converters is examined. The absorbing media considered are halogens or halogen compounds, which are dissociated to yield excited atoms, which then hand over energy to a molecular lasing medium. Estimates of the temperature effects for a Br2-CO2-He system with He as the cooling gas are given. High temperatures can cause the lower energy levels of the CO2 laser transition to be filled. The inverted populations are calculated and lasing should be possible. However, the efficiency is less than 0.001. Examination of other halogen-molecular lasant combinations (where the rate coefficients are known) indicate efficiencies in all cases of less than 0.005.
Chaos control applied to piezoelectric vibration-based energy harvesting systems
NASA Astrophysics Data System (ADS)
Barbosa, W. O. V.; De Paula, A. S.; Savi, M. A.; Inman, D. J.
2015-11-01
Chaotic behavior presents intrinsic richness due to the existence of an infinity number of unstable periodic orbits (UPOs). The possibility of stabilizing these periodic patterns with a small amount of energy makes this kind of response interesting to various dynamical systems. Energy harvesting has as a goal the use of available mechanical energy by promoting a conversion into electrical energy. The combination of these two approaches may establish autonomous systems where available environmental mechanical energy can be employed for control purposes. Two different goals can be defined as priority, allowing a change between them: vibration reduction and energy harvesting enhancement. This work deals with the use of harvested energy to perform chaos control. Both control actuation and energy harvesting are induced employing piezoelectric materials, in a simultaneous way. A bistable piezomagnetoelastic structure subjected to harmonic excitations is investigated as a case study. Numerical simulations show situations where it is possible to perform chaos control using only the energy generated by the harvesting system.
Power flow analysis for amplifier design and energy harvesting
NASA Astrophysics Data System (ADS)
Vujic, Nikola; Leo, Donald J.; Lindner, Douglas K.
2002-06-01
The power requirements imposed on a active vibration isolation system are quite important to the overall system design. In order to improve the efficiency of an active isolation system we analyze different feedback control strategies which will provide an electrical energy regeneration. In this case, the power is flowing from the mechanical disturbance through the electromechanical actuator and its switching drive into the electrical storage device (batteries or capacitors). We demonstrate that regeneration occurs when controlling one or both of the flow states (velocity and current). This regenerative control strategy also affects the closed loop dynamics. The regenerative control applied to a voice-coil actuator results in a closed loop system which has a reduced amount of damping compared to the initial system. In fact the regenerative control strategy will increase the level of vibration compared to the closed electrical circuit boundary condition in order to make the system absorb more energy, of which a part is transferred to an electrical storage device.
Roles of the Excitation in Harvesting Energy from Vibrations
Zhang, Hui; Ma, Tianwei
2015-01-01
The study investigated the role of excitation in energy harvesting applications. While the energy ultimately comes from the excitation, it was shown that the excitation may not always behave as a source. When the device characteristics do not perfectly match the excitation, the excitation alternately behaves as a source and a sink. The extent to which the excitation behaves as a sink determines the energy harvesting efficiency. Such contradictory roles were shown to be dictated by a generalized phase defined as the instantaneous phase angle between the velocity of the device and the excitation. An inductive prototype device with a diamagnetically levitated seismic mass was proposed to take advantage of the well established phase changing mechanism of vibro-impact to achieve a broader device bandwidth. Results suggest that the vibro-impact can generate an instantaneous, significant phase shift in response velocity that switches the role of the excitation. If introduced properly outside the resonance zone it could dramatically increase the energy harvesting efficiency. PMID:26496183
NASA Astrophysics Data System (ADS)
Mudjijono; Lawrence, Warren D.
1994-06-01
State-to-state branching ratios are reported for vibrational energy transfer (VET) from the 30 2 and 8 2 vibrational levels in S 1 ( 1B 2u) p-difluorobenzene by the collision partners He and Ar in the collision region of a supersonic free-jet expansion. For VET from the 8 2 level, He removes more energy than does Ar. This is the expected light collision partner effect. For the 30 2 level, however, Ar unexpectedly removes more energy than He. The opposing behaviour observed for relaxation by He and Ar from two vibrational levels of the same molecule is inconsistent with a universal 'light collision partner effect'.
Application of Energy Storage in Power Systems
NASA Astrophysics Data System (ADS)
Alqunun, Khalid M.
The purpose of this research is to determine the advantages of using energy storage systems. This study presents a model for energy storage in electric power systems. The model involves methods of reducing the operation cost of a power network and the calculation of capital cost of energy storage systems. Two test systems have been considered, the IEEE six-bus system and the IEEE 118-bus system, to analyze the impact of energy storage on power system economic operation. Properties of energy storage have been considered such as rated power investment cost and rated energy investment cost. Mixed integer programming has been used to formulate the model. A comparison between centralized energy storage system and distributed energy storage system have been proposed. The results show that distributed energy storage system has more impact on reducing total operation cost. Also, an analysis on optimal sizing of energy storage system with fixed investment cost is provided.
Power marketing and renewable energy
Fang, J.M.
1997-09-01
Power marketing refers to wholesale and retail transactions of electric power made by companies other than public power entities and the regulated utilities that own the generation and distribution lines. The growth in power marketing has been a major development in the electric power industry during the last few years, and power marketers are expected to realize even more market opportunities as electric industry deregulation proceeds from wholesale competition to retail competition. This Topical Issues Brief examines the nature of the power marketing business and its relationship with renewable power. The information presented is based on interviews conducted with nine power marketing companies, which accounted for almost 54% of total power sales by power marketers in 1995. These interviews provided information on various viewpoints of power marketers, their experience with renewables, and their respective outlooks for including renewables in their resource portfolios. Some basic differences exist between wholesale and retail competition that should be recognized when discussing power marketing and renewable power. At the wholesale level, the majority of power marketers stress the commodity nature of electricity. The primary criteria for developing resource portfolios are the same as those of their wholesale customers: the cost and reliability of power supplies. At the retail level, electricity may be viewed as a product that includes value-added characteristics or services determined by customer preferences.
Near-resonant energy transfer from highly vibrationally excited OH to N2
NASA Astrophysics Data System (ADS)
Burtt, Kelly D.; Sharma, Ramesh D.
2008-03-01
The probability per collision P(T ) of near-resonant vibration-to-vibration energy transfer (ET) of one quantum of vibrational energy from vibrational levels ? =8 and ? =9 of OH to N2(?=0), OH(? )+N2(0)?OH(?-1)+N2(1), is calculated in the 100-350K temperature range. These processes represent important steps in a model that explains the enhanced 4.3?m emission from CO2 in the nocturnal mesosphere. The calculated energy transfer is mediated by weak long-range dipole-quadrupole interaction. The results of this calculation are very sensitive to the strength of the two transition moments. Because of the long range of the intermolecular potential, the resonance function, a measure of energy that can be efficiently exchanged between translation and vibration-rotation degrees of freedom, is rather narrow. A narrow resonance function coupled with the large rotational constant of OH is shown to render the results of the calculation very sensitive to the rotational distribution, or the rotational temperature if one exists, of this molecule. The calculations are carried out in the first and second orders of perturbation theory with the latter shown to give ET probabilities that are an order of magnitude larger than the former. The reasons for the difference in magnitude and temperature dependence of the first- and second-order calculations are discussed. The results of the calculations are compared with room temperature measurements as well as with an earlier calculation. Our calculated results are in good agreement with the room temperature measurements for the transfer of vibrational energy for the exothermic OH(? =9) ET process but are about an order lower than the room temperature measurements for the exothermic OH(? =8) ET process. The cause of this discrepancy is explored. This calculation does not give the large values of the rate coefficients needed by the model that explains the enhanced 4.3?m emission from CO2 in the nocturnal mesosphere.
Kinetic model for the vibrational energy exchange in flowing molecular gas mixtures. Ph.D. Thesis
NASA Technical Reports Server (NTRS)
Offenhaeuser, F.
1987-01-01
The present study is concerned with the development of a computational model for the description of the vibrational energy exchange in flowing gas mixtures, taking into account a given number of energy levels for each vibrational degree of freedom. It is possible to select an arbitrary number of energy levels. The presented model uses values in the range from 10 to approximately 40. The distribution of energy with respect to these levels can differ from the equilibrium distribution. The kinetic model developed can be employed for arbitrary gaseous mixtures with an arbitrary number of vibrational degrees of freedom for each type of gas. The application of the model to CO2-H2ON2-O2-He mixtures is discussed. The obtained relations can be utilized in a study of the suitability of radiation-related transitional processes, involving the CO2 molecule, for laser applications. It is found that the computational results provided by the model agree very well with experimental data obtained for a CO2 laser. Possibilities for the activation of a 16-micron and 14-micron laser are considered.
Blevins, R.D.
1990-01-01
This book reports on dimensional analysis; ideal fluid models; vortex-induced vibration; galloping and flutter; instability of tube and cylinder arrays; vibrations induced by oscillating flow; vibration induced by turbulence and sound; damping of structures; sound induced by vortex shedding; vibrations of a pipe containing a fluid flow; indices. It covers the analysis of the vibrations of structures exposed to fluid flows; explores applications for offshore platforms and piping; wind-induced vibration of buildings, bridges, and towers; and acoustic and mechanical vibration of heat exchangers, power lines, and process ducting.
NASA Astrophysics Data System (ADS)
Metsala, Markus; Yang, Shengfu; Vaittinen, Olavi; Halonen, Lauri
2002-11-01
The laser-induced dispersed vibration-rotation fluorescence method has been developed further when compared with a previous publication [Saarinen [et al.], J. Chem. Phys. 110, 1424 (1999)]. More than one order of magnitude better signal-to-noise ratio has been achieved in the wave-number region 2900-3500 cm-1 by taking advantage of directionality of the fluorescence signal. The improvement has been applied to overtone spectroscopy of normal acetylene where for high CH stretching excitations separate spectra of ortho and para forms are obtained containing basically just single CH stretching vibrational quantum transitions from the pumped antisymmetric vibrational (nu]1+3[nu]3([Sigmau)+ and nu]2+3[nu]3([Sigmau)+ and close-lying symmetric vibrational local mode (4nu]3([Sigmag)+ and nu]1+[nu]2+2[nu]3 (Σg)+ states. No nuclear spin conversion is observed in these spectra. Two new symmetric vibrational states ν1+2ν2+4ν40 (Σg)+)(29% and (50%)) have been observed and the precision of the spectroscopic parameters of previously published symmetric states has been improved by an order of magnitude. Unexpected fluorescence originating from the antisymmetric CH stretching fundamental state nu3 and some associated states of acetylene have also been observed. These spectra are characterized by both ortho and para forms in normal abundance and by unusual intensity patterns due to strong reabsorption of the fluorescence by ground state acetylene molecules in the sample cell. A simple collisional step-down mechanism is proposed to account for the appearance of the nu3 fluorescence band system. The excess vibrational energy in the sample volume is partly trapped in the form of nu3 mode energy and it decays from the system by radiation.
Performance Studies of the Vibration Wire Monitor on the Test Stand with Low Energy Electron Beam
NASA Astrophysics Data System (ADS)
Okabe, Kota; Yoshimoto, Masahiro; Kinsho, Michikazu
In the high intensity proton accelerator as the Japan Proton Accelerator Research Complex (J-PARC) accelerators, serious radiation and residual dose is induced by a small beam loss such a beam halo. Therefore, diagnostics of the beam halo formation is one of the most important issues to control the beam loss. For the beam halo monitor, the vibration wire monitor (VWM) has a potential for investigating the beam halo and weak beam scanning. The VWM has a wide dynamic range, high resolution and the VWM is not susceptible to secondary electrons and electric noises. We have studied the VWM features as a new beam-halo monitor on the test stand with low energy electron gun. The frequency shift of the irradiated vibration wire was confirmed about wire material and the electron beam profile measured by using the VWM was consistent with the results of the Faraday cup measurement. Also we calculated a temperature distribution on the vibration wire which is irradiated by the electron beam with the numerical simulation. The simulations have been fairly successful in reproducing the transient of the irradiated vibration wire frequency measured by test stand experiments. In this paper, we will report a result of performance evaluation for the VWM on the test stands and discuss the VWM for beam halo diagnostic
Study of vibrational energy transfer at a surface by a time-of-flight method
NASA Astrophysics Data System (ADS)
Yuan, Wei; Rabinovitch, B. S.
1984-02-01
A single collision, time-of-flight extension of the VEM method for the study of molecule-surface vibrational energy transfer is introduced. The technique helps election between possible alternative trial analytic forms of the collisional transition probability function. A Gaussian form is preferred over a Boltzmann-exponential form for cyclobutene isomerization to 1.3-butadiene energized by collisions at a silica surface at 800 K.
Platinum-hydrogen vibrations and low energy electronic excitations of 13-atom Pt nanoclusters.
Keppeler, Melanie; Roduner, Emil
2014-12-28
Two Pt-H vibrational bands at 1679 cm(-1) and 1392 cm(-1) observed with 13-atom Pt clusters supported in LTL zeolite by Fourier Transform Infrared (FTIR) spectroscopy confirms that H atoms bridge two Pt atoms across the edges of the metal cluster. An additional broad absorption band centred near 2200 cm(-1) which exhibits some substructure is assigned to low energy electronic excitations across the HOMO-LUMO gap of the developing band structure of the nanocluster. PMID:25182177
The reduction of rotorcraft power and vibration using optimally controlled active gurney flap
NASA Astrophysics Data System (ADS)
Bae, Eui Sung
The main topic of the present study is the application of active control scheme for the reduction of rotorcraft main rotor power reduction and vibratory load. When the helicopter is operated near its flight boundary, the required power and vibratory loads rapidly increases which impose a limit on the helicopter operation. Various methods were proposed and studied in order to achieve performance improvement under such operating condition. The effect of active control scheme was examined for its impact on the performance improvement and vibration reduction in the present study. Numerical simulations are based on the UH-60A Blackhawk helicopter with an active Gurney flap spanning from 70%R to 80%R of the main rotor. For obtaining the aeroelastic response of the rotor blade, finite element method was used to represent elastic blade. The aerodynamic loads acting on the blade are provided by CFD based 2D lookup table. Prescribed wake model was used to resolve the induced inflow over the rotor disk. The unsteady aerodynamic behavior due to the higher harmonic actuation of active Gurney flap was resolved by the time-domain unsteady aerodynamic model. The first part of preliminary study covers parametric study using Gurney flap. Starting with simple rigid blade representation of the rotor blade, the effect of 1/rev Gurney flap actuation was examined on three different gross weights. The effect of active Gurney flap width, the chordwise location of active Gurney flap, the effect of unsteady aerodynamic model, and the effect of 2/rev actuation frequency were examined. The second part of preliminary study was conducted with the elastic blade model to include the effect of torsion dynamics. Performance improvement using active Gurney flap was examined for maximizing thrust capability at two flight speeds. 1/rev Gurney flap actuation increased the gross weight capability up to 1,000 lbs. Also, 1/rev actuation of Gurney flap increased maximum altitude limit of baseline rotor by 1,400 ft. Furthermore, it was predicted that the maximum level flight speed can be increased by 30 knots with respect to that of the baseline rotor. The effect of active Gurney flap on the vibration reduction was first examined at the stall condition. Using 1/rev actuation, in-plane vibratory force and moment can be reduced by 68% and 44%, respectively. The effects of higher harmonic frequencies were investigated at the high-speed cruise speed, and single frequency phase sweep was conducted to find the best phase angle that minimizes each vibratory components. 3/rev actuation yielded 36% reduction in in-plane vibratory moment. 74% reduction in vertical vibratory force was predicted with 4/rev actuation. With 5/rev actuation, 81% reduction in vertical vibratory load was observed. With the input-output information obtained from single frequency phase sweep, the plant model which correlates active control inputs to helicopter vibratory loads was constructed. Multicyclic controller was applied to the plant model, and 25% reduction in the cost function was reported. Vertical vibratory load was reduced by 51%, and inplane force and moment were reduced by 18%, 22%, respectively.
Energy harvesting to power embedded condition monitoring hardware
NASA Astrophysics Data System (ADS)
Farinholt, Kevin; Brown, Nathan; Siegel, Jake; McQuown, Justin; Humphris, Robert
2015-04-01
The shift toward condition-based monitoring is a key area of research for many military, industrial, and commercial customers who want to lower the overall operating costs of capital equipment and general facilities. Assessing the health of rotating systems such as gearboxes, bearings, pumps and other actuation systems often rely on the need for continuous monitoring to capture transient signals that are evidence of events that could cause (i.e. cavitation), or be the result of (i.e. spalling), damage within a system. In some applications this can be accomplished using line powered analyzers, however for wide-spread monitoring, the use of small-scale embedded electronic systems are more desirable. In such cases the method for powering the electronics becomes a significant design factor. This work presents a multi-source energy harvesting approach meant to provide a robust power source for embedded electronics, capturing energy from vibration, thermal and light sources to operate a low-power sensor node. This paper presents the general design philosophy behind the multi-source harvesting circuit, and how it can be extended from powering electronics developed for periodic monitoring to sensing equipment capable of providing continuous condition-based monitoring.
Zuo, Lei; Cui, Wen
2013-10-01
This paper proposes a novel retrofittable approach for dual-functional energy-harvesting and robust vibration control by integrating the tuned mass damper (TMD) and electromagnetic shunted resonant damping. The viscous dissipative element between the TMD and primary system is replaced by an electromagnetic transducer shunted with a resonant RLC circuit. An efficient gradient based numeric method is presented for the parameter optimization in the control framework for vibration suppression and energy harvesting. A case study is performed based on the Taipei 101 TMD. It is found that by tuning the TMD resonance and circuit resonance close to that of the primary structure, the electromagnetic resonant-shunt TMD achieves the enhanced effectiveness and robustness of double-mass series TMDs, without suffering from the significantly amplified motion stroke. It is also observed that the parameters and performances optimized for vibration suppression are close to those optimized for energy harvesting, and the performance is not sensitive to the resistance of the charging circuit or electrical load. PMID:23918165
Water Power for a Clean Energy Future
2013-04-12
This document describes some of the accomplishments of the Department of Energy Water Power Program, and how those accomplishments are supporting the advancement of renewable energy generated using hydropower technologies and marine and hydrokinetic technologies.
NASA Astrophysics Data System (ADS)
Pfeiffer, Florian; Rauhut, Guntram; Feller, David; Peterson, Kirk A.
2013-01-01
Anharmonic zero point vibrational energies (ZPVEs) calculated using both conventional CCSD(T) and MP2 in combination with vibrational second-order perturbation theory (VPT2) are compared to explicitly correlated CCSD(T)-F12 and MP2-F12 results that utilize vibrational configuration interaction (VCI) theory for 26 molecules of varying size. Sequences of correlation consistent basis sets are used throughout. It is found that the explicitly correlated methods yield results close to the basis set limit even with double-zeta quality basis sets. In particular, the anharmonic contributions to the ZPVE are accurately recovered at just the MP2 (or MP2-F12) level of theory. Somewhat surprisingly, the best vibrational CI results agreed with the VPT2 values with a mean unsigned deviation of just 0.09 kJ/mol and a standard deviation of just 0.11 kJ/mol. The largest difference was observed for C4H4O (0.34 kJ/mol). A simplified version of the vibrational CI procedure that limited the modal expansion to at most 2-mode coupling yielded anharmonic corrections generally within about 0.1 kJ/mol of the full 3- or 4-mode results, except in the cases of C3H8 and C4H4O where the contributions were underestimated by 1.3 and 0.8 kJ/mol, respectively (34% and 40%, respectively). For the molecules considered in this work, accurate anharmonic ZPVEs are most economically obtained by combining CCSD(T)-F12a/cc-pVDZ-F12 harmonic frequencies with either MP2/aug-cc-pVTZ/VPT2 or MP2-F12/cc-pVDZ-F12/VCI anharmonic corrections.
NASA Astrophysics Data System (ADS)
Ha, Jeong Sook; Sibener, S. J.
1991-10-01
High-resolution electron energy loss spectroscopy (HREELS) has been used to study the low-energy vibrational modes of bridge-bonded CO on Ni(111) after a well-ordered c(4 × 2) overlayer structure was formed. In this paper we report the spectroscopic observation of two low-energy modes of bridge-bonded CO on Ni(111) which have not been previously reported, as well as the momentum-resolved scattering for one of these modes. At Ts = 120 K, under impact scattering conditions, a frustrated translation of CO parallel to the surface was observed at an energy loss of 11.8 meV. The dispersion curve measured along the <112> direction of Ni(111) for this mode was dispersionless, indicating that there is no direct lateral interaction between the adjacent CO molecules in this structure. At Ts = 170 K, using a transient negative-ion Σ shape-resonance to enhance our sensitivity, a frustrated rotation for bridge-bonded CO was also observed at an energy loss of 37.5 meV. The energy of this mode is near the value previously estimated from temperature dependent infrared line shape measurements of the CO stretch peak position and lineshape, and is believed to be responsible for vibrational phase relaxation in the c(4 × 2)-CO-Ni(111) system. The energies of the observed modes are also consistent with those derived from a simple cluster calculation.
NASA Astrophysics Data System (ADS)
Strobusch, D.; Scheurer, Ch.
2011-10-01
The hierarchical expansion of the kinetic energy operator in curvilinear coordinates presented earlier for the vibrational self-consistent field technique is extended to the vibrational configuration interaction (VCI) method. The high accuracy of the modified VCI method is demonstrated by computing first excitation energies of the H2O2 molecule using an analytic potential (PCPSDE) and showing convergence to accurate results from full dimensional discrete variable representation calculations.
NASA Astrophysics Data System (ADS)
Kostyukov, V. N.; Tarasov, E. V.
2012-05-01
The report addresses the real-time condition monitoring of technical state and automatic diagnosis of auxiliary equipment for bearings supports vibration, for example, control of the feed-pump operating modes of thermal power stations. The causes that lead to premature birth and development of defects in rolling bearings are identified and the development of activities ensuring safe and continuous operation of the auxiliary equipment of thermal power stations is carried out. Collection and analysis of vibration parameters of pumping units during their operation at the operating modes of the technological process are realized by means of real-time technical condition monitoring. Spectral analysis of vibration parameters of one of the pumps showed the presence of frequency components, which mark violations in the operating practices of the pump, the imbalance development and, as a consequence, the development of defects in the bearings by long-term operation of the unit. Timely warning of the personnel on the operation of the unit with the "INTOLERABLE" technical state and automatic warning issuance of the need to change the technological process allowed to recover the estimated pump operation mode in due time and prevent further development of defects in equipment.
NASA Astrophysics Data System (ADS)
Lumentut, Mikail F.; Howard, Ian M.
2016-02-01
This paper focuses on the primary development of novel numerical and analytical techniques of the modal damped vibration energy harvesters with arbitrary proof mass offset. The key equations of electromechanical finite element discretisation using the extended Lagrangian principle are revealed and simplified to give matrix and scalar forms of the coupled system equations, indicating the most relevant numerical technique for the power harvester research. To evaluate the performance of the numerical study, the analytical closed-form boundary value equations have been developed using the extended Hamiltonian principle. The results from the electromechanical frequency response functions (EFRFs) derived from two theoretical studies show excellent agreement with experimental studies. The benefit of the numerical technique is in providing effective and quick predictions for analysing parametric designs and physical properties of piezoelectric materials. Although analytical technique provides a challenging process for analysing the complex smart structure, it shows complementary study for validating the numerical technique.
Energy regeneration from vibrationally excited methane in catalyst enhanced barrier discharges.
NASA Astrophysics Data System (ADS)
Nozaki, Tomohiro; Muto, Nahoko; Kado, Shigeru; Okazaki, Ken
2002-10-01
Vibrationally excited species are the most abundant in methane-fed barrier discharges due to relatively low electron temperatures ( 5 eV). In the most cases, those exited energy is wasted as heat due to low reactivity. On the other hand, vibrationally excited methane show high-reactivity on a specific transition metal catalyst to dissociation. And we investigated energy regeneration from vibrationally excited methane in catalyst enhanced barrier discharges. The coaxial barrier discharge reactor packed with pellets of either SiO2 or 3wt%Ni/SiO2 was used for this purpose. Methane and water-vapor mixture was fed into the reactor at 200, 400, 600 degC. Catalyst could not activated at 200 degC, so plasma reaction (main products: C2H6, C3H8) become dominant. At 600 degC catalyst reaction was dominant, so main products were CO2 and H2. Most significant plasma and catalyst interaction was observed at 400 degC. Under this condition, methane dissociation by plasma and catalyst was expected.
Mechanism of quasiresonant vibration-rotation energy transfer in atom-diatom encounters
NASA Astrophysics Data System (ADS)
Miklavc, Adolf; Marković, Nikola; Nyman, Gunnar; Harb, Vili; Nordholm, Sture
1992-09-01
We present an analysis based on the quantized version of the effective mass theory and on classical trajectory calculations which leads to an interpretation of all the characteristic features of the striking new phenomenon named rotation-induced quasiresonant vibration-rotation energy transfer and observed recently in Li*2(nvi,Ji) + X → Li*2(nvf,Jf)+ X collision (X=He, Ne, Ar, Xe). The ``ordinary branch'' of the effective mass theory reproduces the broad Jf distribution in the nonresonant internal energy transfer found experimentally at lower Ji values (Ji = 8 and 22). The ``extraordinary branch'' of the same theory gives the narrow, sharply peaked quasiresonant Jf distributions as observed at Ji values 42 and higher. The conclusions derived from the effective mass theory and classical trajectory calculations enable us to elucidate the celebrated experimental correlations between the most probable changes in the rotational and vibrational quantum numbers, as well as the ``locking mechanism'' by which these correlations prevail over large intervals of the initial angular momentum Ji. On the same basis we explain why the total vibrationally inelastic cross section is greatly enhanced by increasing Ji and why the shape of the final Jf distribution is identical (within the experimental uncertainty) for Ne, Ar, and Xe, but not for the He.
Solar energy thermally powered electrical generating system
NASA Technical Reports Server (NTRS)
Owens, William R. (Inventor)
1989-01-01
A thermally powered electrical generating system for use in a space vehicle is disclosed. The rate of storage in a thermal energy storage medium is controlled by varying the rate of generation and dissipation of electrical energy in a thermally powered electrical generating system which is powered from heat stored in the thermal energy storage medium without exceeding a maximum quantity of heat. A control system (10) varies the rate at which electrical energy is generated by the electrical generating system and the rate at which electrical energy is consumed by a variable parasitic electrical load to cause storage of an amount of thermal energy in the thermal energy storage system at the end of a period of insolation which is sufficient to satisfy the scheduled demand for electrical power to be generated during the next period of eclipse. The control system is based upon Kalman filter theory.
Energy harvesting with low-power electronics
NASA Astrophysics Data System (ADS)
Jannson, Tomasz; Forrester, Thomas; Degrood, Kevin; Gans, Eric; Lee, Kang; Nguyen, Kathy; Walter, Kevin; Kostrzewski, Andrew
2010-04-01
In this paper, a novel concept of energy harvesting, applicable to both wired and wireless self-powered low-power electronic devices, is discussed. Types of energy harvesting include solar/optical, thermal, IR, and mechanical. Overall power budgets and control circuitry are discussed, including maximizing Mean Time between Battery Replacement/Recharge values. It is shown that in the case of low-power wireless electronics, surprisingly low amounts of daily direct solar exposure are sufficient to satisfy overall system power consumption.
A new deformed Schiberg-type potential and ro-vibrational energies for some diatomic molecules
NASA Astrophysics Data System (ADS)
Mustafa, Omar
2015-06-01
We suggest a new deformed Schiberg-type potential for diatomic molecules. We show that it is equivalent to Tietz-Hua oscillator potential. We discuss how to relate our deformed Schiberg potential to Morse, to Deng-Fan, to the improved Manning-Rosen, and to the deformed modified Rosen-Morse potential models. We transform our potential into a proper form and use the supersymmetric quantization to find a closed form analytical solution for the ro-vibrational energy levels that are highly accurate over a wide range of vibrational and rotational quantum numbers. We discuss our results using four-diatomic molecules NO?ft( {{X}2}{{\\Pi }r} \\right), {{O}2}?ft( {{X}3}? g- \\right), O2+?ft( {{X}2}{{\\Pi }g} \\right), and {{N}2}?ft( {{X}1}? g+ \\right). Our results turn out to compare excellently with those from a generalized pseudospectral numerical method.
Excitation of vibrational quanta in furfural by intermediate-energy electrons
NASA Astrophysics Data System (ADS)
Jones, D. B.; Neves, R. F. C.; Lopes, M. C. A.; da Costa, R. F.; Varella, M. T. do N.; Bettega, M. H. F.; Lima, M. A. P.; García, G.; Blanco, F.; Brunger, M. J.
2015-12-01
We report cross sections for electron-impact excitation of vibrational quanta in furfural, at intermediate incident electron energies (20, 30, and 40 eV). The present differential cross sections are measured over the scattered electron angular range 10°-90°, with corresponding integral cross sections subsequently being determined. Furfural is a viable plant-derived alternative to petrochemicals, being produced via low-temperature plasma treatment of biomass. Current yields, however, need to be significantly improved, possibly through modelling, with the present cross sections being an important component of such simulations. To the best of our knowledge, there are no other cross sections for vibrational excitation of furfural available in the literature, so the present data are valuable for this important molecule.
Excitation of vibrational quanta in furfural by intermediate-energy electrons.
Jones, D B; Neves, R F C; Lopes, M C A; da Costa, R F; Varella, M T do N; Bettega, M H F; Lima, M A P; Garca, G; Blanco, F; Brunger, M J
2015-12-14
We report cross sections for electron-impact excitation of vibrational quanta in furfural, at intermediate incident electron energies (20, 30, and 40 eV). The present differential cross sections are measured over the scattered electron angular range 10-90, with corresponding integral cross sections subsequently being determined. Furfural is a viable plant-derived alternative to petrochemicals, being produced via low-temperature plasma treatment of biomass. Current yields, however, need to be significantly improved, possibly through modelling, with the present cross sections being an important component of such simulations. To the best of our knowledge, there are no other cross sections for vibrational excitation of furfural available in the literature, so the present data are valuable for this important molecule. PMID:26671372
Energy and vibrational spectrum of the Si(111) (77) surface from empirical potentials
NASA Astrophysics Data System (ADS)
Li, X.-P.; Chen, G.; Allen, P. B.; Broughton, J. Q.
1988-08-01
The stability and vibrational properties of the Si(111) (77) [Takayanagi, or dimer-adatom-stacking-fault structure (DAS)] surface are investigated using the Stillinger-Weber and modified Tersoff interatomic potentials for silicon. The diamond-cubic bulk and surface-terminated bulk and (?3 ?3 ) structures are treated for comparison. The modified Tersoff potential underestimates the bulk transverse-acoustic branch frequencies while the Stillinger-Weber does the opposite. Both potentials produce z expansions away from the idealized (constant-bond-length) structures. The Stillinger-Weber potential produces surface energies in the following order: terminated bulk >~(?3?3)<(77) DAS, whereas the modified Tersoff potential reverses this order in accord with local-density-functional calculations and experiment. The two potentials produce surprisingly similar features in the local densities of vibrational states on surface atoms. In the case of adatoms, a high-frequency state split off from the bulk continuum and a mid-frequency state are observed. The high-frequency state has significant weight in the z direction on the adatom, (x,y) weight (only) on the three first-layer atoms to which the adatom is attached, and z weight again on the second- and third-layer atoms directly beneath; the mid-frequency state corresponds to the z motion of the adatom and the two atoms underneath in phase with each other, while out of phase with the three first-layer atoms attached which symmetrically vibrate in the (x,y) plane as well. Atoms with dangling bonds (first-layer atoms not directly attached to adatoms and atoms in the open site at the corners of the unit cell) have small force constants in the z direction and their local spectra only exhibit weight at low frequencies. The z-polarized adatom vibrations agree nicely with recent inelastic electron-energy-loss spectra by Daum, Ibach, and Mller.
NASA Astrophysics Data System (ADS)
Ferin, G.; Bantignies, C.; Le Khanh, H.; Flesch, E.; Nguyen-Dinh, A.
2015-12-01
Harvesting energy from ambient mechanical vibrations is a smart and efficient way to power autonomous sensors and support innovative developments in IoT (Internet of Things), WSN (Wireless Sensor Network) and even implantable medical devices. Beyond the environmental operating conditions, efficiency of such devices is mainly related to energy source properties like the amplitude of vibrations and its spectral contain and some of these applications exhibit a quite low frequency spectrum where harvesting surrounding mechanical energy make sense, typically 5-50Hz for implantable medical devices or 50Hz-150Hz for industrial machines. Harvesting such low frequency vibrations is a challenge since it leads to adapt the resonator geometries to the targeted frequency or to use out-off band indirect harvesting strategies. In this paper we present a piezoelectric based vibrational energy harvesting device (PEH) which could be integrated into a biocompatible package to power implantable sensor or therapeutic medical devices. The presented architecture is a serial bimorph laminated with ultra-thinned (ranging from 15μm to 100μm) outer PZT “skins” that could operate at a “very low frequency”, below 25Hz typically. The core process flow is disclosed and performances highlighted with regards to other low frequency demonstrations.
Scavenging vibration energy from seismically isolated bridges using an electromagnetic harvester
NASA Astrophysics Data System (ADS)
Lu, Qiuchen; Loong, Chengning; Chang, Chih-Chen; Dimitrakopoulos, Elias G.
2014-04-01
The increasing worldwide efforts in securing renewable energy sources increase incentive for civil engineers to investigate whether the kinetic energy associated with the vibration of larger-scale structures can be harvested. Such a research remains challenging and incomplete despite that hundreds of related articles have been published in the last decade. Base isolation is one of the most popular means of protecting a civil engineering structure against earthquake forces. Seismic isolation hinges on the decoupling of the structure from the shaking ground, hence protecting the structure from stress and damage during an earthquake excitation. The low stiffness isolator inserted between the structure and the ground dominates the response leading to a structural system of longer vibration period. As a consequence of this period shift, the spectral acceleration is reduced, but higher response displacements are produced. To mitigate this side effect, usually isolators are combined with the use of additional energy dissipation. In this study, the feasibility of scavenging the need-to-be dissipated energy from the isolator installed in a seismically isolated bridge using an electromagnetic (EM) energy harvester is investigated. The EM energy harvester consists of an energy harvesting circuit and a capacitor for energy storage. A mathematical model for this proposed EM energy harvester is developed and implemented on an idealized base-isolated single-degree-of-freedom system. The effect of having this EM energy harvester on the performance of this seismic isolated system is analyzed and discussed. The potential of installing such an EM energy harvester on a seismically isolated bridge is also addressed.
ERIC Educational Resources Information Center
Holdren, John; Herrera, Philip
The demand of Americans for more and more power, particularly electric power, contrasted by the deep and growing concern for the environment and a desire by private citizens to participate in the public decisions that affect the environment is the dilemma explored in this book. Part One by John Holdren, offers a scientist's overview of the energy…
Pulsed Power Driven Fusion Energy
SLUTZ,STEPHEN A.
1999-11-22
Pulsed power is a robust and inexpensive technology for obtaining high powers. Considerable progress has been made on developing light ion beams as a means of transporting this power to inertial fusion capsules. However, further progress is hampered by the lack of an adequate ion source. Alternatively, z-pinches can efficiently convert pulsed power into thermal radiation, which can be used to drive an inertial fusion capsule. However, a z-pinch driven fusion explosion will destroy a portion of the transmission line that delivers the electrical power to the z-pinch. They investigate several options for providing standoff for z-pinch driven fusion. Recyclable Transmission Lines (RTLs) appear to be the most promising approach.
NASA Astrophysics Data System (ADS)
Yachmenev, Andrey; Yurchenko, Sergei N.
2015-07-01
We present a new numerical method to construct a rotational-vibrational Hamiltonian of a general polyatomic molecule in the Eckart frame as a power series expansion in terms of curvilinear internal coordinates. The expansion of the kinetic energy operator of an arbitrary order is obtained numerically using an automatic differentiation (AD) technique. The method is applicable to molecules of arbitrary size and structure and is flexible for choosing various types of internal coordinates. A new way of solving the Eckart-frame equations for curvilinear coordinates also based on the AD technique is presented. The resulting accuracy of the high-order expansion coefficients for the kinetic energy operator using our numerical technique is comparable to that obtained by symbolic differentiation, with the advantage of being faster and less demanding in memory. Examples for H2CO, NH3, PH3, and CH3Cl molecules demonstrate the advantages of the curvilinear internal coordinates and the Eckart molecular frame for accurate ro-vibrational calculations. Our results show that very high accuracy and quick convergence can be achieved even with moderate expansions if curvilinear coordinates are employed, which is important for applications involving large polyatomic molecules.
Yachmenev, Andrey; Yurchenko, Sergei N
2015-07-01
We present a new numerical method to construct a rotational-vibrational Hamiltonian of a general polyatomic molecule in the Eckart frame as a power series expansion in terms of curvilinear internal coordinates. The expansion of the kinetic energy operator of an arbitrary order is obtained numerically using an automatic differentiation (AD) technique. The method is applicable to molecules of arbitrary size and structure and is flexible for choosing various types of internal coordinates. A new way of solving the Eckart-frame equations for curvilinear coordinates also based on the AD technique is presented. The resulting accuracy of the high-order expansion coefficients for the kinetic energy operator using our numerical technique is comparable to that obtained by symbolic differentiation, with the advantage of being faster and less demanding in memory. Examples for H2CO, NH3, PH3, and CH3Cl molecules demonstrate the advantages of the curvilinear internal coordinates and the Eckart molecular frame for accurate ro-vibrational calculations. Our results show that very high accuracy and quick convergence can be achieved even with moderate expansions if curvilinear coordinates are employed, which is important for applications involving large polyatomic molecules. PMID:26156463
NASA Astrophysics Data System (ADS)
Wallington, Timothy J.; Scheer, Milton D.; Braun, Walter
1987-08-01
A new technique based upon the Doppler and Lorentz broadening of the isotopic and hyperfine Hg multiplet lines near 254 nm was used to monitor the translational equilibration of vibrationally excited pentafluorobenzene (PFB). Excitation was achieved with a pulsed CO 2 infrared laser focused into a cell containing PFB and a trace amount of Hg. Rates of V? R, T energy transfer were found to be linearly dependent on both the excitation energy and the pressure of PFB. Excitation energies were independently determined by the Hg absorption technique and by measuring the change in absorption by the PFB at 254 nm. For PFB ?-PFB ? collisions, the average energy transferred per collision divided by the average excitation energy of the colliding pair, / < E>, is0.01330.0016.
Shock and vibration tests of uranium mononitride fuel pellets for a space power nuclear reactor
NASA Technical Reports Server (NTRS)
Adams, D. W.
1972-01-01
Shock and vibration tests were conducted on cylindrically shaped, depleted, uranium mononitride (UN) fuel pellets. The structural capabilities of the pellets were determined under exposure to shock and vibration loading which a nuclear reactor may encounter during launching into space. Various combinations of diametral and axial clearances between the pellets and their enclosing structures were tested. The results of these tests indicate that for present fabrication of UN pellets, a diametral clearance of 0.254 millimeter and an axial clearance of 0.025 millimeter are tolerable when subjected to launch-induced loads.
Low-power optical vibration detection by photoconductance monitoring with a laser speckle pattern.
Heinz, Philip; Garmire, Elsa
2005-11-15
We present a quantitative evaluation of the performance of a photoconductance-monitoring sensor array in a speckle-based vibration detection configuration. The device is found to be capable of detecting nanometer-amplitude vibrations in a single shot with incident intensities of only a few microwatts per square centimeter at kilohertz frequencies. This performance indicates that the photoconductance-monitoring array requires approximately 3 orders of magnitude lower intensity to achieve the same displacement sensitivity as competing technologies, such as photo-electromotive-force detectors. PMID:16315710
Low-energy elastic electron scattering from ethylene: Elastic scattering and vibrational excitation
NASA Astrophysics Data System (ADS)
Khakoo, M. A.; Khakoo, S. M.; Sakaamini, A.; Hlousek, B. A.; Hargreaves, L. R.; Lee, J.; Murase, R.
2016-01-01
Normalized experimental differential and integral cross sections for elastic and vibrationally inelastic scattering of low-energy electrons from ethylene (C2H4 ) have been measured over a large number of incident electron energies and angles. The differential cross sections are measured at incident energies from 0.5 to 100 eV and scattering angles from 5 to 130. These measurements are made to monitor the role of the 2g2B(?1.8 eV ) and the higher 2u2B+1u2B+A2g (?7.5 eV ) resonances in the scattering dynamics. Our differential cross section measurements are in very good to excellent agreement with past measurements, and in reasonable agreement with theory as regards forward scattering. A feature in the elastic cross section at 90 scattering angle at ?3.5 eV is tentatively associated with the onset of excitation of the a 1u3B triplet electronic state. Differential cross sections for vibrational excitation of four composite energy features in ethylene are also presented from incident energies of 1.25-15 eV. These results are compared to previous measurements with satisfactory results regarding resonant behavior of these features also concerning the role of the 2g2B (?1.8 eV ) and the higher 2u2B+1u2B+A2g (?7.5 eV ) resonances in the scattering dynamics.
Accurate ab initio potential energy curve of F2. III. The vibration rotation spectrum.
Bytautas, L; Matsunaga, N; Nagata, T; Gordon, M S; Ruedenberg, K
2007-11-28
An analytical expression is found for the accurate ab initio potential energy curve of the fluorine molecule that has been determined in the preceding two papers. With it, the vibrational and rotational energy levels of F(2) are calculated using the discrete variable representation. The comparison of this theoretical spectrum with the experimental spectrum, which had been measured earlier using high-resolution electronic spectroscopy, yields a mean absolute deviation of about 5 cm(-1) over the 22 levels. The dissociation energy with respect to the lowest vibrational energy is calculated within 30 cm(-1) of the experimental value of 12 953+/-8 cm(-1). The reported agreement of the theoretical spectrum and dissociation energy with experiment is contingent upon the inclusion of the effects of core-generated electron correlation, spin-orbit coupling, and scalar relativity. The Dunham analysis [Phys. Rev. 41, 721 (1932)] of the spectrum is found to be very accurate. New values are given for the spectroscopic constants. PMID:18052433
Topology optimization and fabrication of low frequency vibration energy harvesting microdevices
NASA Astrophysics Data System (ADS)
Deng, Jiadong; Rorschach, Katherine; Baker, Evan; Sun, Cheng; Chen, Wei
2015-02-01
Topological design of miniaturized resonating structures capable of harvesting electrical energy from low frequency environmental mechanical vibrations encounters a particular physical challenge, due to the conflicting design requirements: low resonating frequency and miniaturization. In this paper structural static stiffness to resist undesired lateral deformation is included into the objective function, to prevent the structure from degenerating and forcing the solution to be manufacturable. The rational approximation of material properties interpolation scheme is introduced to deal with the problems of local vibration and instability of the low density area induced by the design dependent body forces. Both density and level set based topology optimization (TO) methods are investigated in their parameterization, sensitivity analysis, and applicability for low frequency energy harvester TO problems. Continuum based variation formulations for sensitivity analysis and the material derivative based shape sensitivity analysis are presented for the density method and the level set method, respectively; and their similarities and differences are highlighted. An external damper is introduced to simulate the energy output of the resonator due to electrical damping and the Rayleigh proportional damping is used for mechanical damping. Optimization results for different scenarios are tested to illustrate the influences of dynamic and static loads. To demonstrate manufacturability, the designs are built to scale using a 3D microfabrication method and assembled into vibration energy harvester prototypes. The fabricated devices based on the optimal results from using different TO techniques are tested and compared with the simulation results. The structures obtained by the level set based TO method require less post-processing before fabrication and the structures obtained by the density based TO method have resonating frequency as low as 100 Hz. The electrical voltage response in the experiment matches the trend of the simulation data.
Development of a semi-active friction device to reduce vibration by energy dissipation
NASA Astrophysics Data System (ADS)
Buaka, Paulin; Masson, Patrice; Micheau, Philippe
2003-08-01
Aerospace structures such as antennas and solar panels often consist of truss elements which are connected by bolted joints. Friction damping in these bolted joint connections structures has been identified as a major source of damping. It has been proposed that an improvement in vibration reduction could be obtained by controlling the normal contact force using integrated piezoelectric elements in order to maximize the energy dissipated at the interface between the connected parts. This paper presents analytical and experimental results in order to demonstrate the interest of implementing semi-active vibration reduction by dissipating energy through dry friction contact surfaces. This work fits within the scope of a research project aiming at the development of a semi-active compact piezoelectric friction device which can be bonded to any light structure. In this device, a moving component will rub on two friction surfaces and the normal force on friction surfaces will be controlled so that the distance between moving component and friction surfaces is neither too small (to avoid shock and stiction that cancel the slip between two surfaces and then friction effect) or too large (lose of contact surface). This device will then be positioned on the structure in order to allow the maximum energy dissipation by friction to reduce the vibrations of the structure. Such semi-active device will ensure stability of the control approach and will avoid the spillover effect found with the active approach in addition to reduce energy consumption cost. In this paper, an analytical and experimental study is carried out on two beams assembled by a joint bolted to show the influence of the normal gripping force (tightening torque in this case), directly related to the friction force, on the damping of the modes.
Hu, Junhui; Jong, Januar; Zhao, Chunsheng
2010-01-01
To increase the vibration energy-harvesting capability of the piezoelectric generator based on a cantilever beam, we have proposed a piezoelectric generator that not only uses the strain change of piezoelectric components bonded on a cantilever beam, but also employs the weights at the tip of the cantilever beam to hit piezoelectric components located on the 2 sides of weights. A prototype of the piezoelectric generator has been fabricated and its characteristics have been measured and analyzed. The experimental results show that the piezoelectric components operating in the hit mode can substantially enhance the energy harvesting of the piezoelectric generator on a cantilever beam. Two methods are used and compared in the management of rectified output voltages from different groups of piezoelectric components. In one of them, the DC voltages from rectifiers are connected in series, and then the total DC voltage is applied to a capacitor. In another connection, the DC voltage from each group is applied to different capacitors. It is found that 22.3% of the harvested energy is wasted due to the series connection. The total output electric energy of our piezoelectric generator at nonresonance could be up to 43 nJ for one vibration excitation applied by spring, with initial vibration amplitude (0-p) of 18 mm and frequency of 18.5 Hz, when the rectified voltages from different groups of piezoelectric components are connected to their individual capacitors. In addition, the motion and impact of the weights at the tip of the cantilever beam are theoretically analyzed, which well explains the experimental phenomena and suggests the measures to improve the generator. PMID:20178904
Simonov, B.F.
1986-05-01
Electromagnetic reciprocal-motion transducers (EMT) are being used ever more extensively in modern industry. In particular, rubble to break down bulkiness, slicer drives for coal combines, drilling equipment, etc. are produced on the basis of EMT. This paper is devoted to further refinement of energy conversion questions and their analysis. The energy coming from the supply source in the magnetization of the additionally sucked-in armature volume is determined by the magnetic energy density in the armature section at the pole level. A general expression is deduced for the electromagnetic force of the EMT that sets up the interrelation between the whole system magnetic energy and the coil flux-linkage. It is shown that expressions known earlier for the electromagnetic forces, obtained for the constant current electromagnet and the constant flux-linkage cases, are particular cases of the general expression that is valid without any additional constraints for the condition of the EMT working process.
NASA Astrophysics Data System (ADS)
Cupiał, Piotr
2005-05-01
The paper presents results of the exact three-dimensional analysis of the natural frequencies and mode shapes of a rectangular piezoelectric plate poled along the direction perpendicular to the plate middle plane. The solutions are obtained in non-dimensional form for flexural modes of vibration of a plate simply supported along the plate edges and two types of electrical boundary conditions on the plate faces, namely for the case of short and open circuit. A numerically stable algorithm is described, which allows the calculation of the natural frequencies and mode shapes of the piezoelectric plate. The details of the algorithm have been found to be especially important in the case of equal wavelengths along the two plate edges (e.g. for the lowest flexural mode of a square plate). The natural frequencies of a rectangular plate are given for a rectangular and square plate for the case of short-circuited and open-circuit plate faces, together with the through-thickness distributions of the mechanical and electric fields. Energy balance for piezoelectric continua is used to derive two equivalent formulae which extend the Rayleigh quotient used in free vibration analysis of elastic continua. These expressions are used to verify the consistency of the results and to obtain additional insight into the phenomenon of electromechanical coupling in a vibrating piezoelectric plate.
Vibrational energy flow between modes by dynamic mode coupling in THIATS J-aggregates.
Hasegawa, Daisuke; Nakata, Kazuaki; Tokunaga, Eiji; Okamura, Kotaro; Du, Juan; Kobayashi, Takayoshi
2013-11-14
We performed ultrafast pump-probe spectroscopy of J-aggregates of 3,3'-disulfopropyl-5,5'-dichloro-9-ethyl thiacarbocyanine triethylammonium (THIATS), one of the most typical cyanine dyes, and detected excited molecular vibrations, using a sub-10 fs pulse laser. The time-resolved two-dimensional difference absorption (?A) spectra are observed between -314 and 1267 fs. By performing the Fourier transform and spectrogram analysis, vibrational modes in THIATS are observed at 285, 485, 555, 824, and 1633 cm(-1) and there was a modulation of the vibrational frequencies around 1633 cm(-1) which depend on the delay time, respectively. By the analysis of the modulation, energy flow is found to take place from other modes to the 1633 cm(-1) mode through the low frequency mode with ?50 cm(-1). Also, by fitting the real-time traces of ?A with the sum of two exponential functions and a constant term, the average lifetimes of three electronically excited states were found to be ?1 = 52 5 fs and ?2 = 540 78 fs. By performing single-exponential fitting around the stationary absorption peak at 1.990 eV, in the negative time range, the electronic dephasing time, T2(ele), is determined to be 18.30 fs. PMID:24111914
Intermediate energy cross sections for electron-impact vibrational-excitation of pyrimidine
NASA Astrophysics Data System (ADS)
Jones, D. B.; Ellis-Gibbings, L.; Garca, G.; Nixon, K. L.; Lopes, M. C. A.; Brunger, M. J.
2015-09-01
We report differential cross sections (DCSs) and integral cross sections (ICSs) for electron-impact vibrational-excitation of pyrimidine, at incident electron energies in the range 15-50 eV. The scattered electron angular range for the DCS measurements was 15-90. The measurements at the DCS-level are the first to be reported for vibrational-excitation in pyrimidine via electron impact, while for the ICS we extend the results from the only previous condensed-phase study [P. L. Levesque, M. Michaud, and L. Sanche, J. Chem. Phys. 122, 094701 (2005)], for electron energies ?12 eV, to higher energies. Interestingly, the trend in the magnitude of the lower energy condensed-phase ICSs is much smaller when compared to the corresponding gas phase results. As there is no evidence for the existence of any shape-resonances, in the available pyrimidine total cross sections [Baek et al., Phys. Rev. A 88, 032702 (2013); Fuss et al., ibid. 88, 042702 (2013)], between 10 and 20 eV, this mismatch in absolute magnitude between the condensed-phase and gas-phase ICSs might be indicative for collective-behaviour effects in the condensed-phase results.
Fares, Elie-Jacques; Charrière, Nathalie; Montani, Jean-Pierre; Schutz, Yves; Dulloo, Abdul G.; Miles-Chan, Jennifer L.
2016-01-01
Background and Aim There is increasing recognition about the importance of enhancing energy expenditure (EE) for weight control through increases in low-intensity physical activities comparable with daily life (1.5–4 METS). Whole-body vibration (WBV) increases EE modestly and could present both a useful adjuvant for obesity management and tool for metabolic phenotyping. However, it is unclear whether a “dose-response” exists between commonly-used vibration frequencies (VF) and EE, nor if WBV influences respiratory quotient (RQ), and hence substrate oxidation. We aimed to investigate the EE-VF and RQ-VF relationships across three different frequencies (30, 40, and 50Hz). Methods EE and RQ were measured in 8 healthy young adults by indirect calorimetry at rest, and subsequently during side-alternating WBV at one of 3 VFs (30, 40, and 50 Hz). Each frequency was assessed over 5 cycles of intermittent WBV (30s vibration/30s rest), separated by 5 min seated rest. During the WBV participants stood on the platform with knees flexed sufficiently to maintain comfort, prevent transmission of vibration to the upper body, and minimise voluntary physical exertion. Repeatability was assessed across 3 separate days in a subset of 4 individuals. In order to assess any sequence/habituation effect, an additional group of 6 men underwent 5 cycles of intermittent WBV (30s vibration/30s rest) at 40 Hz, separated by 5 min seated rest. Results Side-alternating WBV increased EE relative to standing, non-vibration levels (+36%, p<0.001). However, no differences in EE were observed across VFs. Similarly, no effect of VF on RQ was found, nor did WBV alter RQ relative to standing without vibration. Conclusion No relationship could be demonstrated between EE and VF in the range of 30-50Hz, and substrate oxidation did not change in response to WBV. Furthermore, the thermogenic effect of intermittent WBV, whilst robust, was quantitatively small (<2 METS). PMID:26974147
Vibrational energy flow in the villin headpiece subdomain: Master equation simulations
Leitner, David M. E-mail: stock@physik.uni-freiburg.de; Buchenberg, Sebastian; Brettel, Paul; Stock, Gerhard E-mail: stock@physik.uni-freiburg.de
2015-02-21
We examine vibrational energy flow in dehydrated and hydrated villin headpiece subdomain HP36 by master equation simulations. Transition rates used in the simulations are obtained from communication maps calculated for HP36. In addition to energy flow along the main chain, we identify pathways for energy transport in HP36 via hydrogen bonding between residues quite far in sequence space. The results of the master equation simulations compare well with all-atom non-equilibrium simulations to about 1 ps following initial excitation of the protein, and quite well at long times, though for some residues we observe deviations between the master equation and all-atom simulations at intermediate times from about 1–10 ps. Those deviations are less noticeable for hydrated than dehydrated HP36 due to energy flow into the water.
Delahaye, Thibault Rey, Michaël Tyuterev, Vladimir G.; Nikitin, Andrei; Szalay, Péter G.
2014-09-14
In this paper we report a new ground state potential energy surface for ethylene (ethene) C{sub 2}H{sub 4} obtained from extended ab initio calculations. The coupled-cluster approach with the perturbative inclusion of the connected triple excitations CCSD(T) and correlation consistent polarized valence basis set cc-pVQZ was employed for computations of electronic ground state energies. The fit of the surface included 82 542 nuclear configurations using sixth order expansion in curvilinear symmetry-adapted coordinates involving 2236 parameters. A good convergence for variationally computed vibrational levels of the C{sub 2}H{sub 4} molecule was obtained with a RMS(Obs.–Calc.) deviation of 2.7 cm{sup −1} for fundamental bands centers and 5.9 cm{sup −1} for vibrational bands up to 7800 cm{sup −1}. Large scale vibrational and rotational calculations for {sup 12}C{sub 2}H{sub 4}, {sup 13}C{sub 2}H{sub 4}, and {sup 12}C{sub 2}D{sub 4} isotopologues were performed using this new surface. Energy levels for J = 20 up to 6000 cm{sup −1} are in a good agreement with observations. This represents a considerable improvement with respect to available global predictions of vibrational levels of {sup 13}C{sub 2}H{sub 4} and {sup 12}C{sub 2}D{sub 4} and rovibrational levels of {sup 12}C{sub 2}H{sub 4}.
NASA Astrophysics Data System (ADS)
D`Amico, R.; Koo, K.; Claeys, C. C.; Pluymers, B.; Desmet, W.
2015-03-01
This paper deals with an efficient strategy to improve the vibro-acoustic behavior of a structure over frequency bands. Genetic Algorithms are used to identify the optimal resonance frequency and location of Dynamic Vibration Absorbers (DVAs) which minimize the band-averaged input power into a plate, leading to an indirect reduction of the radiated acoustic power and global vibration. Instead of classic numerical quadrature schemes, the residue theorem is used to evaluate the band-averaged input power. This results into a considerable reduction of computational effort, as it requires only few function evaluations at complex frequencies, regardless of the analyzed bandwidth. The structural response is simulated by using the Wave Based Method (WBM). Besides an increased convergence rate as compared to classical element-based techniques, the WBM is also free in determining the optimal position of the DVAs, not restricting it to nodal grid locations. Moreover, when point connections are taken into account, only a small part of the WB matrices needs to be recomputed at each iteration, resulting in a strong reduction of the computation time. Numerical examples illustrate the benefits and the efficiency of the proposed optimization strategy.
Teachers Environmental Resource Unit: Energy and Power.
ERIC Educational Resources Information Center
Bemiss, Clair W.
Problems associated with energy production and power are studied in this teacher's guide to better understand the impact of man's energy production on the environment, how he consumes energy, and in what quantities. The resource unit is intended to provide the teacher with basic information that will aid classroom review of these problems. Topics…
Renewable Energy. The Power to Choose.
ERIC Educational Resources Information Center
Deudney, Daniel; Flavin, Christopher
This book, consisting of 13 chapters, charts the progress made in renewable energy in recent years and outlines renewable energy's prospects. Areas addressed include: energy at the crossroads (discussing oil, gas, coal, nuclear power, and the conservation revolution); solar building design; solar collection; sunlight to electricity; wood; energy…
Energy Storage for the Power Grid
Imhoff, Carl; Vaishnav, Dave
2014-07-01
The iron vanadium redox flow battery was developed by researchers at Pacific Northwest National Laboratory as a solution to large-scale energy storage for the power grid. This technology provides the energy industry and the nation with a reliable, stable, safe, and low-cost storage alternative for a cleaner, efficient energy future.
NASA Technical Reports Server (NTRS)
Vlahopoulos, Nickolas
2005-01-01
The Energy Finite Element Analysis (EFEA) is a finite element based computational method for high frequency vibration and acoustic analysis. The EFEA solves with finite elements governing differential equations for energy variables. These equations are developed from wave equations. Recently, an EFEA method for computing high frequency vibration of structures either in vacuum or in contact with a dense fluid has been presented. The presence of fluid loading has been considered through added mass and radiation damping. The EFEA developments were validated by comparing EFEA results to solutions obtained by very dense conventional finite element models and solutions from classical techniques such as statistical energy analysis (SEA) and the modal decomposition method for bodies of revolution. EFEA results have also been compared favorably with test data for the vibration and the radiated noise generated by a large scale submersible vehicle. The primary variable in EFEA is defined as the time averaged over a period and space averaged over a wavelength energy density. A joint matrix computed from the power transmission coefficients is utilized for coupling the energy density variables across any discontinuities, such as change of plate thickness, plate/stiffener junctions etc. When considering the high frequency vibration of a periodically stiffened plate or cylinder, the flexural wavelength is smaller than the interval length between two periodic stiffeners, therefore the stiffener stiffness can not be smeared by computing an equivalent rigidity for the plate or cylinder. The periodic stiffeners must be regarded as coupling components between periodic units. In this paper, Periodic Structure (PS) theory is utilized for computing the coupling joint matrix and for accounting for the periodicity characteristics.
Instantaneous pair theory for high-frequency vibrational energy relaxation in fluids
NASA Astrophysics Data System (ADS)
Larsen, Ross E.; Stratt, Richard M.
1999-01-01
Notwithstanding the long and distinguished history of studies of vibrational energy relaxation, exactly how it is that high frequency vibrations manage to relax in a liquid remains somewhat of a mystery. Both experimental and theoretical approaches seem to say that there is a natural frequency range associated with intermolecular motion in liquids, typically spanning no more than a few hundred cm-1. Landau-Teller-type theories explain rather easily how a solvent can absorb any vibrational energy within this "band," but how is it that molecules can rid themselves of superfluous vibrational energies significantly in excess of these values? In this paper we develop a theory for such processes based on the idea that the crucial liquid motions are those that most rapidly modulate the force on the vibrating coordinate — and that by far the most important of these motions are those involving what we have called the mutual nearest neighbors of the vibrating solute. Specifically, we suggest that whenever there is a single solvent molecule sufficiently close to the solute that the solvent and solute are each other's nearest neighbors, then the instantaneous scattering dynamics of the solute-solvent pair alone suffices to explain the high-frequency relaxation. This highly reduced version of the dynamics has implications for some of the previous theoretical formulations of this problem. Previous instantaneous-normal-mode theories allowed us to understand the origin of a band of liquid frequencies, and even had some success in predicting relaxation within this band, but lacking a sensible picture of the effects of liquid anharmonicity on dynamics, were completely unable to treat higher frequency relaxation. When instantaneous-normal-mode dynamics is used to evaluate the instantaneous pair theory, though, we end up with a multiphonon picture of the relaxation which is in excellent agreement with the exact high-frequency dynamics — suggesting that the critical anharmonicity behind the relaxation is not in the complex, underlying liquid dynamics, but in the relatively easy-to-understand nonlinear solute-solvent coupling. There are implications, as well, for the independent binary collision (IBC) theory of vibrational relaxation in liquids. The success of the instantaneous-pair approach certainly provides a measure of justification for the IBC model's focus on few-body dynamics. However, the pair theory neither needs nor supports the basic IBC factoring of relaxation rates into many-body and few-body dynamical components — into collision rates and relaxation rates per collision. Rather, our results favor taking an instantaneous perspective: the relaxation rate is indeed exercise in few-body dynamics, but a different exercise for each instantaneous liquid configuration. The many-body features therefore appear only in the guise of a purely equilibrium problem, that of finding the likelihood of particularly effective solvent arrangements around the solute. All of these results are tested numerically on model diatomic solutes dissolved in atomic fluids (including the experimentally and theoretically interesting case of I2 dissolved in Xe). The instantaneous pair theory leads to results in quantitative agreement with those obtained from far more laborious exact molecular dynamics simulations.
Low power interface IC's for electrostatic energy harvesting applications
NASA Astrophysics Data System (ADS)
Kempitiya, Asantha
The application of wireless distributed micro-sensor systems ranges from equipment diagnostic and control to real time structural and biomedical monitoring. A major obstacle in developing autonomous micro-sensor networks is the need for local electric power supply, since using a battery is often not a viable solution. This void has sparked significant interest in micro-scale power generators based on electrostatic, piezoelectric and electromagnetic energy conversion that can scavenge ambient energy from the environment. In comparison to existing energy harvesting techniques, electrostatic-based power generation is attractive as it can be integrated using mainstream silicon technologies while providing higher power densities through miniaturization. However the power output of reported electrostatic micro-generators to date does not meet the communication and computation requirements of wireless sensor nodes. The objective of this thesis is to investigate novel CMOS-based energy harvesting circuit (EHC) architectures to increase the level of harvested mechanical energy in electrostatic converters. The electronic circuits that facilitate mechanical to electrical energy conversion employing variable capacitors can either have synchronous or asynchronous architectures. The later does not require synchronization of electrical events with mechanical motion, which eliminates difficulties in gate clocking and the power consumption associated with complex control circuitry. However, the implementation of the EHC with the converter can be detrimental to system performance when done without concurrent optimization of both elements, an aspect mainly overlooked in the literature. System level analysis is performed to show that there is an optimum value for either the storage capacitor or cycle number for maximum scavenging of ambient energy. The analysis also shows that maximum power is extracted when the system approaches synchronous operation. However, there is a region of interest where the storage capacitor can be optimized to produce almost 70% of the ideal power taken as the power harvested with synchronous converters when neglecting the power consumption associated with synchronizing control circuitry. Theoretical predictions are confirmed by measurements on an asynchronous EHC implemented with a macro-scale electrostatic converter prototype. Based on the preceding analysis, the design of a novel ultra low power electrostatic integrated energy harvesting circuit is proposed for efficient harvesting of mechanical energy. The fundamental challenges of designing reliable low power sensing circuits for charge constrained electrostatic energy harvesters with capacity to self power its controller and driver stages are addressed. Experimental results are presented for a controller design implemented in AMI 0.7muM high voltage CMOS process using a macro-scale electrostatic converter prototype. The EHC produces 1.126muW for a power investment of 417nW with combined conduction and controller losses of 450nW which is a 20-30% improvement compared to prior art on electrostatic EHCs operating under charge constrain. Inherently dual plate variable capacitors harvest energy only during half of the mechanical cycle with the other half unutilized for energy conversion. To harvest mechanical energy over the complete mechanical vibration cycle, a low power energy harvesting circuit (EHC) that performs charge constrained synchronous energy conversion on a tri-plate variable capacitor for maximizing energy conversion is proposed. The tri-plate macro electrostatic generator with capacitor variation of 405pF to 1.15nF and 405pF to 1.07nF on two complementary adjacent capacitors is fabricated and used in the characterization of the designed EHC. The integrated circuit fabricated in AMI 0.7muM high voltage CMOS process, produces a total output power of 497nW to a 10muF reservoir capacitor from a 98Hz vibration signal. In summary, the thesis lays out the theoretical and experimental foundation for overcoming the main challenges associated with the design of charge constrained synchronous EHC's, making electrostatic converters a possible candidate for powering emerging communication transceivers and portable electronics.
Alemi, Mallory; Loring, Roger F.
2015-06-07
The optimized mean-trajectory (OMT) approximation is a semiclassical method for computing vibrational response functions from action-quantized classical trajectories connected by discrete transitions that represent radiation-matter interactions. Here, we extend the OMT to include additional vibrational coherence and energy transfer processes. This generalized approximation is applied to a pair of anharmonic chromophores coupled to a bath. The resulting 2D spectra are shown to reflect coherence transfer between normal modes.
NASA Astrophysics Data System (ADS)
Alemi, Mallory; Loring, Roger F.
2015-06-01
The optimized mean-trajectory (OMT) approximation is a semiclassical method for computing vibrational response functions from action-quantized classical trajectories connected by discrete transitions that represent radiation-matter interactions. Here, we extend the OMT to include additional vibrational coherence and energy transfer processes. This generalized approximation is applied to a pair of anharmonic chromophores coupled to a bath. The resulting 2D spectra are shown to reflect coherence transfer between normal modes.
Vibrational energy transfer in OH A 2?+ between 195 and 295 K
NASA Astrophysics Data System (ADS)
Steffens, Kristen L.; Crosley, David R.
2000-06-01
Vibrational energy transfer (VET) v'=1?0 and electronic quenching of v'=1 and 0 in the A 2?+ electronically excited state of the OH radical has been studied over the temperature range 195 to 295 K. The colliders investigated were N2, O2, and CO2. Laser-induced fluorescence experiments were conducted in a flow cell with photolytic production of OH; both fluorescence intensity and time decay measurements were made. The VET cross sections are found to increase with decreasing temperature, suggestive of attractive force interactions in the VET process.
NASA Technical Reports Server (NTRS)
Bauschlicher, Charles W.; Arnold, James O. (Technical Monitor)
1997-01-01
The vibrational frequencies of MO2 are computed at many levels of theory, including HF, B3LYP, BP86, CASSCF, MP2, and CCSD(T). The computed results are compared with the available experimental results. Most of the methods fail for at least one state of the systems considered. The accuracy of the results and the origin of the observed failures are discussed. The B3LYP bond energies are compared with traditional methods for a variety of systems, ranging from FeCOn+ to SiCln and its positive ions. The cases where B3LYP differs from the traditional methods are discussed.
NASA Astrophysics Data System (ADS)
Gnanasekaran, Ramachandran; Leitner, David M.
2011-11-01
Molecular dynamics simulations of the dielectric response and vibrational energy relaxation (VER) from the chromophore to the protein and solvent environment following photoexcitation of photoactive yellow protein are presented. The computed protein response to photoexcitation appears prominently between times of 0.1 and 0.3 ps. Contributions from individual residues to this response are analyzed. The frequency-dependent VER rate also reveals dynamic coupling between the chromophore and residues that hydrogen bond to it. Resonances in the VER rate appear at frequencies comparable to the oscillations observed in recent fluorescence decay studies.
NASA Astrophysics Data System (ADS)
Mori, Kotaro; Horibe, Tadashi; Ishikawa, Shigekazu; Shindo, Yasuhide; Narita, Fumio
2015-12-01
This work deals with the dynamic bending and energy harvesting characteristics of giant magnetostrictive cantilevers with resonant tuning both numerically and experimentally. The giant magnetostrictive cantilever is fabricated using a thin Terfenol-D layer, SUS layer, movable proof mass, etc, and, is designed to automatically adjust its own resonant frequency to match the external vibration frequency in real time. Three-dimensional finite element analysis was conducted, and the resonant frequency, induced voltage and stress in the magnetostrictive cantilevers were predicted. The resonant frequency and induced voltage were also measured, and comparison was made between simulation and experiment. The time-varying behavior and self-tuning ability are discussed in detail.
Self-powered smart blade: helicopter blade energy harvesting
NASA Astrophysics Data System (ADS)
Bryant, Matthew; Fang, Austin; Garcia, Ephrahim
2010-04-01
A novel energy harvesting device powered by aeroelastic flutter vibrations is proposed to generate power for embedded wireless sensors on a helicopter rotor blade. Such wireless sensing and on-board power generation system would eliminate the need for maintenance intensive slip ring systems that are required for hardwired sensors. A model of the system has been developed to predict the response and output of the device as a function of the incident wind speed. A system of coupled equations that describe the structural, aerodynamic, and electromechanical aspects of the system are presented. The model uses semi-empirical, unsteady, nonlinear aerodynamics modeling to predict the aerodynamic forces and moments acting on the structure and to account for the effects of vortex shedding and dynamic stall. These nonlinear effects are included to predict the limit cycle behavior of the system over a range of wind speeds. The model results are compared to preliminary wind tunnel tests of a low speed aeroelastic energy harvesting experiment.
Energy analysis of the solar power satellite.
Herendeen, R A; Kary, T; Rebitzer, J
1979-08-01
The energy requirements to build and operate the proposed Solar Power Satellite are evaluated and compared with the energy it produces. Because the technology is so speculative, uncertainty is explicitly accounted for. For a proposed 10-gigawatt satellite system, the energy ratio, defined as the electrical energy produced divided by the primary nonrenewable energy required over the lifetime of the system, is of order 2, where a ratio of 1 indicates the energy breakeven point. This is significantly below the energy ratio of today's electricity technologies such as light-water nuclear or coal-fired electric plants. PMID:17758765
Power Measurement Methods for Energy Efficient Applications
Calandrini, Guilherme; Gardel, Alfredo; Bravo, Ignacio; Revenga, Pedro; Lzaro, Jos L.; Toledo-Moreo, F. Javier
2013-01-01
Energy consumption constraints on computing systems are more important than ever. Maintenance costs for high performance systems are limiting the applicability of processing devices with large dissipation power. New solutions are needed to increase both the computation capability and the power efficiency. Moreover, energy efficient applications should balance performance vs. consumption. Therefore power data of components are important. This work presents the most remarkable alternatives to measure the power consumption of different types of computing systems, describing the advantages and limitations of available power measurement systems. Finally, a methodology is proposed to select the right power consumption measurement system taking into account precision of the measure, scalability and controllability of the acquisition system. PMID:23778191
SPS Energy Conversion Power Management Workshop
NASA Technical Reports Server (NTRS)
1980-01-01
Energy technology concerning photovoltaic conversion, solar thermal conversion systems, and electrical power distribution processing is discussed. The manufacturing processes involving solar cells and solar array production are summarized. Resource issues concerning gallium arsenides and silicon alternatives are reported. Collector structures for solar construction are described and estimates in their service life, failure rates, and capabilities are presented. Theories of advanced thermal power cycles are summarized. Power distribution system configurations and processing components are presented.
SPS Energy Conversion Power Management Workshop
NASA Astrophysics Data System (ADS)
1980-06-01
Energy technology concerning photovoltaic conversion, solar thermal conversion systems, and electrical power distribution processing is discussed. The manufacturing processes involving solar cells and solar array production are summarized. Resource issues concerning gallium arsenides and silicon alternatives are reported. Collector structures for solar construction are described and estimates in their service life, failure rates, and capabilities are presented. Theories of advanced thermal power cycles are summarized. Power distribution system configurations and processing components are presented.
Duque, H. V.; Chiari, L.; Jones, D. B.; Pettifer, Z.; Silva, G. B. da; Limo-Vieira, P.; Blanco, F.; Garca, G.; White, R. D.; Lopes, M. C. A.; Brunger, M. J.
2014-06-07
Differential and integral cross section measurements, for incident electron energies in the 2050 eV range, are reported for excitation of several composite vibrational modes in ?-tetrahydrofurfuryl alcohol (THFA). Optimisation and frequency calculations, using GAUSSIAN 09 at the B3LYP/aug-cc-pVDZ level, were also undertaken for the two most abundant conformers of THFA, with results being reported for their respective mode classifications and excitation energies. Those calculations assisted us in the experimental assignments of the composite features observed in our measured energy loss spectra. There are, to the best of our knowledge, no other experimental or theoretical data currently available in the literature against which we can compare the present results.
NASA Technical Reports Server (NTRS)
Schwenke, David W.; Langhoff, Stephen R. (Technical Monitor)
1995-01-01
A description is given of an algorithm for computing ro-vibrational energy levels for tetratomic molecules. The expressions required for evaluating transition intensities are also given. The variational principle is used to determine the energy levels and the kinetic energy operator is simple and evaluated exactly. The computational procedure is split up into the determination of one dimensional radial basis functions, the computation of a contracted rotational-bending basis, followed by a final variational step coupling all degrees of freedom. An angular basis is proposed whereby the rotational-bending contraction takes place in three steps. Angular matrix elements of the potential are evaluated by expansion in terms of a suitable basis and the angular integrals are given in a factorized form which simplifies their evaluation. The basis functions in the final variational step have the full permutation symmetries of the identical particles. Sample results are given for HCCH and BH3.
Energy Decisions: Is Solar Power the Solution?
ERIC Educational Resources Information Center
Childress, Vincent W.
2011-01-01
People around the world are concerned about affordable energy. It is needed to power the global economy. Petroleum-based transportation and coal-fired power plants are economic prime movers fueling the global economy, but coal and gasoline are also the leading sources of air pollution. Both of these sources produce greenhouse gases and toxins.…
Energy Decisions: Is Solar Power the Solution?
ERIC Educational Resources Information Center
Childress, Vincent W.
2011-01-01
People around the world are concerned about affordable energy. It is needed to power the global economy. Petroleum-based transportation and coal-fired power plants are economic prime movers fueling the global economy, but coal and gasoline are also the leading sources of air pollution. Both of these sources produce greenhouse gases and toxins.
Power Technologies Energy Data Book - Fourth Edition
Aabakken, J.
2006-08-01
This report, prepared by NREL's Strategic Energy Analysis Center, includes up-to-date information on power technologies, including complete technology profiles. The data book also contains charts on electricity restructuring, power technology forecasts, electricity supply, electricity capability, electricity generation, electricity demand, prices, economic indicators, environmental indicators, and conversion factors.
Energy considerations in central power generating plants
Hammitt, F.G.
1986-01-01
This text covers topics as the cost of availability of the various world energy resources; appropriate breeders and converters; fuel cycle costs and fusion reactor fuel availability; power plant types, including nuclear, fusion, topping cycles, hydroelectric; nuclear reactor cores; safety and environmental considerations; power plant peripheral machinery.
NASA Astrophysics Data System (ADS)
Yu, Hua-Gen; Ndengue, Steve; Li, Jun; Dawes, Richard; Guo, Hua
2015-08-01
Accurate vibrational energy levels of the simplest Criegee intermediate (CH2OO) were determined on a recently developed ab initio based nine-dimensional potential energy surface using three quantum mechanical methods. The first is the iterative Lanczos method using a conventional basis expansion with an exact Hamiltonian. The second and more efficient method is the multi-configurational time-dependent Hartree (MCTDH) method in which the potential energy surface is refit to conform to the sums-of-products requirement of MCTDH. Finally, the energy levels were computed with a vibrational self-consistent field/virtual configuration interaction method in MULTIMODE. The low-lying levels obtained from the three methods are found to be within a few wave numbers of each other, although some larger discrepancies exist at higher levels. The calculated vibrational levels are very well represented by an anharmonic effective Hamiltonian.
Carter, S.; Bowman, J.M.
2000-03-23
The authors report variational calculations of vibrational energies of CH{sub 4}, CH{sub 3}D, CH{sub 2}D{sub 2}, CHD{sub 3}, and CD{sub 4} using the code Multimode and the ab initio force field of Lee and co-workers [Lee, T.J.; Martin, J.M.L.; Taylor, P.R.--J.Chem.Phys. 1995, 102, 254], re-expressed using Morse variables in the stretch displacements. Comparisons are made with experimental energies for CH{sub 4} with this potential, and then small adjustments are made to the potential to improve agreement with experiment for CH{sub 4}. Calculations for the isotopomers are done using the adjusted potential and compared with experiment. Additional vibrational energies and assignments not reported experimentally are also given for CH{sub 4} and the isotopomers. Exact rotational-vibrational energies of CH{sub 4} are also reported for J = 1.
The influence of translational and vibrational energy on the reaction of Cl with CH{sub 3}D
Berke, Andrew E.; Volpa, Ethan H.; Annesley, Christopher J.; Crim, F. Fleming
2013-06-14
The reaction of Cl atoms with CH{sub 3}D proceeds either by abstraction of hydrogen to produce HCl + CH{sub 2}D or by abstraction of deuterium to produce DCl + CH{sub 3}. Using Cl atoms with different amounts of translational energy, produced by photolysis of Cl{sub 2} with 309, 355, or 416 nm light, reveals the influence of translational energy on the relative reaction probability for the two channels. These measurements give an estimate of the energy barrier for the reaction for comparison to theory and indicate that tunneling is the dominant reaction mechanism at low collision energies. Adding two quanta of C-H stretching vibration causes the reaction to proceed readily at all collision energies. Detecting the vibrational state of the CH{sub 2}D product shows that vibrational energy initially in the surviving C-H bond appears as vibrational excitation of the product, an example of spectator behavior in the reaction. The reaction produces both stretch and stretch-bend excited products except at the lowest collision energy. A subtle variation in the reaction probability of the lowest energy rotational states with translational energy may reflect the presence of a van der Waals well in the entrance channel.
NASA Astrophysics Data System (ADS)
Li, Mingfeng; Lim, Teik C.; Shepard, W. Steve, Jr.; Guan, Y. H.
2005-10-01
An experimental study of an active shaft transverse vibration control system for suppressing gear mesh vibratory response due to transmission error excitation in a high power density gearbox is presented. The proposed active control concept employs a piezoelectric stack actuator to deliver the control force through a secondary bearing. A versatile test stand that includes a closed-loop, power recirculating, dual-gearbox set-up capable of high load transfer is specially designed for this work. The underlying controller for computing the actuation signal is based on a modified filtered-x LMS algorithm with a robust frequency estimation technique. In order to avoid the common out-of-band overshoot problem, an integrated adaptive linear enhancer is also applied. Both single mesh frequency and multi-harmonic control cases are examined to evaluate the performance of the active control system. Additionally, the impact of the adaptive linear enhancer order as well as the controller adaptation step size on active control performance is evaluated. The experiments performed show more than 10 dB reduction in housing vibrations at certain targeted mesh harmonics over a range of operating speeds.
A mechanical solution of self-powered SSHI interface for piezoelectric energy harvesting systems
NASA Astrophysics Data System (ADS)
Liu, Haili; Ge, Cong; Liang, Junrui
2015-04-01
The synchronized switch interface circuits, e.g., synchronized switch harvesting on inductor (SSHI), can significantly enhance the harvesting capability of piezoelectric energy harvesting (PEH) systems. In these power conditioning circuits, the piezoelectric voltage is flipped with respect to a bias voltage at the instants when the piezoelectric element is at maximum deforming positions. Voltage peak detection and in time switching action are required for implementing these functions. The state-of-the-art solutions are mostly realized by electronic methods, i.e., both functions are carried out by electronic comparators and electronic switches. However, the peak detectors usually introduce switching phase lag; while the electronic switches function only when the vibration magnitude is above a threshold level. When the vibration is lower than such threshold, the SSHI interface shows no improvement. In this paper, we propose a mechanical solution for constructing the self-powered SSHI interface for PEH systems. This technique is realized by installing a low cost vibration sensor switch (VSS) at the free end of a piezoelectric cantilever. It senses the maximum deflecting places of the cantilever and automatically carries out synchronized switching actions. Compared to the existing electronic solutions, this mechanical solution is compact and has relative low switching threshold. Therefore, with this self-powered solution, the advantage of SSHI interface circuit can be sufficiently released, in particular, at low level vibration. Experiment shows the feasibility of this mechanical solution. The advantages and limitations are also discussed in this paper.
NASA Astrophysics Data System (ADS)
Jurado-Navarro, . A.; Lpez-Puertas, M.; Funke, B.; Garca-Comas, M.; Gardini, A.; Stiller, G. P.; Clarmann, T. von
2015-08-01
We present a retrieval of several vibrational-vibrational (V V) and vibrational-thermal (V-T) collisional rate coefficients affecting the populations of the CO2 levels emitting at 10, 4.3 and 2.7 ?m from high-resolution limb atmospheric spectra taken by Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). This instrument has a high spectral resolution (0.0625 cm-1) and a wide spectral coverage (from 685 to 2410 cm-1) that allow measuring and discriminating among the many bands originating the atmospheric 4.3 ?m radiance. Also its high sensitivity allows measuring the atmospheric limb emission in a wide altitude range, from 20 to 170 km in its middle and upper atmosphere modes, and hence obtain information on the temperature dependence of the collisional rates. In particular, we retrieve the rate coefficients and their temperature dependence in the 130-250 K range of the following processes: CO2(vd,v3)+N2?CO2(vd,v3-1)+N2(1) with vd=2v1+v2=2,3, and 4; CO2(v1,v2,l,1,r)+M?CO2(v1',v2',l',1,r')+M with ?vd=vd'-vd=0 and ?l = 0; and with ?vd=0 and ?l ? 0. In addition we have also retrieved the thermal relaxation of CO2(v3) into the v1 and v2 modes, e.g., CO2(vd,v3)+M?CO2(vd',v3-1)+M with ?vd=2-4 and ?v3=-1 and the efficiency of the excitation of N2(1) by O(1D). All of them were retrieved with a much better accuracy than were known before. The new rates have very important effects on the atmospheric limb radiance in the 10, 4.3 and 2.7 ?m spectral regions (5-8% at 4.3 ?m) and allow a more accurate inversion of the CO2 volume mixing ratio in the mesosphere and lower thermosphere from measurements taken in those spectral regions.
Coal and nuclear power: Illinois' energy future
Not Available
1982-01-01
This conference was sponsored by the Energy Resources Center, University of Illinois at Chicago; the US Department of Energy; the Illinois Energy Resources Commission; and the Illinois Department of Energy and Natural Resources. The theme for the conference, Coal and Nuclear Power: Illinois' Energy Future, was based on two major observations: (1) Illinois has the largest reserves of bituminous coal of any state and is surpassed in total reserves only by North Dakota, and Montana; and (2) Illinois has made a heavy commitment to the use of nuclear power as a source of electrical power generation. Currently, nuclear power represents 30% of the electrical energy produced in the State. The primary objective of the 1982 conference was to review these two energy sources in view of the current energy policy of the Reagan Administration, and to examine the impact these policies have on the Midwest energy scene. The conference dealt with issues unique to Illinois as well as those facing the entire nation. A separate abstract was prepared for each of the 30 individual presentations.
Demand, energy, and power factor. Master's thesis
Gough, M.J.
1994-08-01
This paper briefly presents the results of a study of various utility rate schedules from across the United States and describes a video produced to explain some major features of these rate structures. In particular, the demand, energy and power factor sections of each rate schedule are explored to understand the impacts of selected features on utility costs and on evaluation of energy conservation projects. The accompanying video was produced for the Energy Systems Laboratory's Industrial Assessment Center (IAC) at Texas AM University. This video will be used during industrial audits to explain typical demand, energy and power factor structures and savings potentials that can be realized by implementation of energy conservation retrofit projects, known as energy conservation opportunities (ECO's), that may be presented through the energy audit process.
Wong, Stephanie Y Y; Benoit, David M; Lewerenz, Marius; Brown, Alex; Roy, Pierre-Nicholas
2011-03-01
We have demonstrated the use of ab initio molecular dynamics (AIMD) trajectories to compute the vibrational energy levels of molecular systems in the context of the semiclassical initial value representation (SC-IVR). A relatively low level of electronic structure theory (HF/3-21G) was used in this proof-of-principle study. Formaldehyde was used as a test case for the determination of accurate excited vibrational states. The AIMD-SC-IVR vibrational energies have been compared to those from curvilinear and rectilinear vibrational self-consistent field/vibrational configuration interaction with perturbation selected interactions-second-order perturbation theory (VSCF/VCIPSI-PT2) and correlation-corrected vibrational self-consistent field (cc-VSCF) methods. The survival amplitudes were obtained from selecting different reference wavefunctions using only a single set of molecular dynamics trajectories. We conclude that our approach is a further step in making the SC-IVR method a practical tool for first-principles quantum dynamics simulations. PMID:21384953
Badawi, H M; Al-Saadi, A A; Al-Khaldi, M A A; Al-Abbad, S A; Al-Sunaidi, Z H A
2008-12-15
The structural stability and internal rotations in cyclopropanecarboxylic acid and cyclopropanecarboxamide were investigated by the DFT-B3LYP and the ab initio MP2 calculations using 6-311G** and 6-311+G** basis sets. The computations were extended to the MP4//MP2/6-311G** and CCSD(T)//MP2/6-311G** single-point calculations. From the calculations the molecules were predicted to exist predominantly in the cis (C=O group eclipses the cyclopropane ring) with a cis-trans barrier of about 4-6kcal/mol. The OCOH torsional barrier in the acid was estimated to be about 12-13kcal/mol while the corresponding OCNH torsional barrier in the amide was calculated to be about 20kcal/mol. The equilibrium constant k for the cis<-->trans interconversion in cyclopropanecarboxylic acid was calculated to be 0.1729 at 298.15K that corresponds to an equilibrium mixture of about 85% cis and 15% trans. The vibrational frequencies were computed at the DFT-B3LYP level. Normal coordinate calculations were carried out and potential energy distributions were calculated for the low energy cis conformer of the molecules. Complete vibrational assignments were made on the basis of normal coordinate calculations and comparison with experimental data of the molecules. PMID:18599341
Energy-resolved positron-molecule annihilation: Vibrational Feshbach resonances and bound states
NASA Astrophysics Data System (ADS)
Barnes, Levi Daniel
2005-07-01
This thesis describes a new technique for the measurement of positron annihilation rates for positrons incident on atoms and molecules. Positrons from a radioactive source are collected and cooled in a Penning-Malmberg trap and formed into a magnetically guided beam. The beam is then guided through a cell filled with the molecule to be studied while the gamma ray signal from annihilation events is recorded. As distinguished from previous work, these experiments allow tuning of the positron energy over the range between 50 meV and the threshold for positronium formation. The energy resolution of the beam is 25 meV. A key result in these measurements is the discovery of resonances in the annihilation rates for selected molecules, associated with the vibrations of the target. We attribute these resonances (in accordance with a model proposed by Gribakin [28]) to the presence of a Feshbach resonant state consisting of a positron bound to a vibrationally excited target molecule. The annihilation spectra for a number of molecules are presented including alkane molecules, fluoroalkanes, deuterated alkanes, ring hydrocarbons, noble gases, alkenes and alkynes. The goals of these measurements are to investigate the dependence of these resonant processes on the size, composition and shape of the target molecules, and to provide benchmarks for theoretical descriptions of this process.
NASA Astrophysics Data System (ADS)
Guillen, C. I.; Strom, R. A.; Tobar, J. A.; Panchenko, D. I.; Andrianarijaona, V. M.
2015-04-01
Charge transfer (CT) in H + H2+--> H+ + H2 has fundamental implications because it involves the smallest atomic ion, atom, molecular ion, and molecule possible. The current merged-beam apparatus at Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee, can reliably create and access low collision energies; the existing ion-atom merged beams apparatus there is currently able to benchmark the CT of these fundamental systems at energies below 0.1eV/u (Phys. Rev. A 84, 062716, 2011). A strong contribution from vi = 2 is observed, however, the data analysis still suffers from the lack of information on the vibrational state distribution of H2+.We are exploring the possibility of inserting a three-dimensional imaging technique at the end station of the ORNL apparatus in order to measure the vibrational state distribution of H2+that are produced by the electron cyclotron resonance (ECR) ion source. Discussion of our initial design for the insertion of this technique in the aforementioned system will be presented here. Work supported by the National Science Foundation under Grant No. PHY-1068877.
Fiscalini Farms Renewable Energy Power Generation Project
2009-02-01
Funded by the American Recovery and Reinvestment Act of 2009 Fiscalini Farms L.P., in collaboration with University of the Pacific, Biogas Energy, Inc., and the University of California at Berkeley will measure and analyze the efficiency and regulatory compliance of a renewable energy system for power generation. The system will utilize digester gas from an anaerobic digester located at the Fiscalini Farms dairy for power generation with a reciprocating engine. The project will provide power, efficiency, emissions, and cost/benefit analysis for the system and evaluate its compliance with federal and California emissions standards.
Space solar power - An energy alternative
NASA Technical Reports Server (NTRS)
Johnson, R. W.
1978-01-01
The space solar power concept is concerned with the use of a Space Power Satellite (SPS) which orbits the earth at geostationary altitude. Two large symmetrical solar collectors convert solar energy directly to electricity using photovoltaic cells woven into blankets. The dc electricity is directed to microwave generators incorporated in a transmitting antenna located between the solar collectors. The antenna directs the microwave beam to a receiving antenna on earth where the microwave energy is efficiently converted back to dc electricity. The SPS design promises 30-year and beyond lifetimes. The SPS is relatively pollution free as it promises earth-equivalence of 80-85% efficient ground-based thermal power plant.
On the self-powering of SHM techniques using seismic energy harvesting
NASA Astrophysics Data System (ADS)
Wu, Yi-Chieh; Lallart, Mickal.; Yan, Linjuan; Guyomar, Daniel; Richard, Claude
2013-04-01
Growing demands in self-powered, wireless Structural Health Monitoring (SHM) systems has placed a particular attention on energy harvesting products. While most of works done in this domain considered directly coupled active materials, it may be preferential to use seismic (or indirect-coupled) harvesters for maintenance issues. With a seismic type harvester, a model considering constant vibration magnitude excitation is no longer valid as electrical energy extraction from mechanical vibration leads to a reduction of the vibration magnitude of the harvester because of electromechanical coupling effect. This paper extends a Single Degree of Freedom (SDOF) model with a constant force or acceleration excitation to a Two Degree of Freedom (TDOF) approach to describe the tradeoff between the damping effect on the host structure and the harvested power due to the mechanical to mechanical coupling effect. When the harvester mass to host structure mass ratio is around 10-3, the maximal power is obtained and the host structure has then a sudden displacement reduction due to the strong mechanical to mechanical coupling. Its application to self-powered SHM will be also introduced in the paper.
Saving Energy Through Advanced Power Strips (Poster)
Christensen, D.
2013-10-01
Advanced Power Strips (APS) look just like ordinary power strips, except that they have built-in features that are designed to reduce the amount of energy used by many consumer electronics. There are several different types of APSs on the market, but they all operate on the same basic principle of shutting off the supply power to devices that are not in use. By replacing your standard power strip with an APS, you can signifcantly cut the amount of electricity used by your home office and entertainment center devices, and save money on your electric bill. This illustration summarizes the different options.
Breezy Power: From Wind to Energy
ERIC Educational Resources Information Center
Claymier, Bob
2009-01-01
This lesson combines the science concepts of renewable energy and producing electricity with the technology concepts of design, constraints, and technology's impact on the environment. Over five class periods, sixth-grade students "work" for a fictitious power company as they research wind as an alternative energy source and design and test a…
Breezy Power: From Wind to Energy
ERIC Educational Resources Information Center
Claymier, Bob
2009-01-01
This lesson combines the science concepts of renewable energy and producing electricity with the technology concepts of design, constraints, and technology's impact on the environment. Over five class periods, sixth-grade students "work" for a fictitious power company as they research wind as an alternative energy source and design and test a
Power conditioning system for energy sources
Mazumder, Sudip K. (Chicago, IL); Burra, Rajni K. (Chicago, IL); Acharya, Kaustuva (Chicago, IL)
2008-05-13
Apparatus for conditioning power generated by an energy source includes an inverter for converting a DC input voltage from the energy source to a square wave AC output voltage, and a converter for converting the AC output voltage from the inverter to a sine wave AC output voltage.
Fluid Power Systems. Energy Technology Series.
ERIC Educational Resources Information Center
Center for Occupational Research and Development, Inc., Waco, TX.
This course in fluid power systems is one of 16 courses in the Energy Technology Series developed for an Energy Conservation-and-Use Technology curriculum. Intended for use in two-year postsecondary technical institutions to prepare technicians for employment, the courses are also useful in industry for updating employees in company-sponsored…
A strain energy-based vibrational NDE method applied to an aerospace structure
Osegueda, R. A.; Andre, G.; Ferregut, C. M.; Carrasco, C.; Pereyra, L.; James, G. III; Grygier, M.; Rocha, R.
1999-12-02
An early prototype of the Vertical Stabilizer Assembly (VSA) of the Shuttle Orbiter was modal tested at healthy and damaged states to study vibrational nondestructive damage evaluation in aerospace structures. Frequency Response and Coherence functions were collected with a Laser Vibrometer at 84 points when the healthy and damaged VSA was shaken with a continuous random force from 0 to 300 Hz. The measurements were used to extract the resonant frequencies and modal shapes for the healthy and damaged states. After pairing of the mode shapes between the healthy and damaged states through the Modal Assurance Criterion, the strain energy of the modes were determined through a finite element model of the VSA and normalized. The localization of the damage is achieved through an analysis of the differences between the modal strain energy in the healthy and damaged states and a fusion on the information obtained from several modes. This paper evaluates the detectability and performance of four different methods.
State and species selective energy flow in gas ensembles containing vibrationally excited O2.
McCaffery, Anthony J
2012-10-01
State-to-state, collision-induced, energy transfer is followed to equilibrium through sequences of collision cycles in gas ensembles containing vibrationally excited oxygen molecules (v = 8 and 1) in several different atomic and molecular bath gases. Quantum state distributions for each of the constituent species are available at each stage of the ensemble's evolution and enable the dominant energy exchange mechanisms to be identified. Equilibration is generally a complex process that evolves through several phases of inter- and intra-molecular events, each with their characteristic response rate to collisions. The results suggest that single quantum state population loss rate constants, however precisely determined, may miss key features of the overall equilibration process. PMID:23039593
Energy Servers Deliver Clean, Affordable Power
NASA Technical Reports Server (NTRS)
2010-01-01
K.R. Sridhar developed a fuel cell device for Ames Research Center, that could use solar power to split water into oxygen for breathing and hydrogen for fuel on Mars. Sridhar saw the potential of the technology, when reversed, to create clean energy on Earth. He founded Bloom Energy, of Sunnyvale, California, to advance the technology. Today, the Bloom Energy Server is providing cost-effective, environmentally friendly energy to a host of companies such as eBay, Google, and The Coca-Cola Company. Bloom's NASA-derived Energy Servers generate energy that is about 67-percent cleaner than a typical coal-fired power plant when using fossil fuels and 100-percent cleaner with renewable fuels.
NASA Astrophysics Data System (ADS)
Dhanwani, Manish A.; Sarkar, Abhijit; Patnaik, B. S. V.
2013-11-01
In the present study, a lumped parameter model for vortex-induced vibrations is analysed. In this work, the vortex-induced vibrations of an elastically mounted rigid cylinder are able to move in-line and transverse to the flow with equal mass ratio and natural frequencies. A simplified lumped mass model is proposed to study the two degree of freedom (dof) structural oscillator. A classical van der Pol equation along with acceleration coupling, models the near wake dynamics describing the fluctuating nature of vortex shedding. The model dynamics is investigated analytically and the results are compared for moderate mass ratios. The results predicted using this model show a good agreement with the experimental data. The dependence of stream-wise displacement on mass and damping is explored. The cause of cross-flow displacement magnification due to freedom to move in stream-wise direction is also explored using the proposed model. Apart from these two degrees of freedom, the cylinder can also undergo rotation about its centre of mass. The effect of freedom to move in this rotational degree of freedom is exploited to our advantage by applying it to the VIVACE (Vortex induced vibration aquatic clean energy) design which was originally proposed by Bernitsas et al. (2008). The original design was not reported to be the optimal one and the set-up was shown to work only for a given flow velocity. But, the flow environment keeps changing and hence there is a need to bring in robustness and optimize the proposed design. The values of optimized spring stiffness have been found using the lumped mass model. The design is made robust by exploiting the rotational mode. This mode is triggered by varying the overhang lengths in accordance with the varying flow velocity in order to strike resonance for a certain flow regime.
Adamovich, Igor V.
2014-04-15
A three-dimensional, nonperturbative, semiclassical analytic model of vibrational energy transfer in collisions between a rotating diatomic molecule and an atom, and between two rotating diatomic molecules (Forced Harmonic OscillatorFree Rotation model) has been extended to incorporate rotational relaxation and coupling between vibrational, translational, and rotational energy transfer. The model is based on analysis of semiclassical trajectories of rotating molecules interacting by a repulsive exponential atom-to-atom potential. The model predictions are compared with the results of three-dimensional close-coupled semiclassical trajectory calculations using the same potential energy surface. The comparison demonstrates good agreement between analytic and numerical probabilities of rotational and vibrational energy transfer processes, over a wide range of total collision energies, rotational energies, and impact parameter. The model predicts probabilities of single-quantum and multi-quantum vibrational-rotational transitions and is applicable up to very high collision energies and quantum numbers. Closed-form analytic expressions for these transition probabilities lend themselves to straightforward incorporation into DSMC nonequilibrium flow codes.
NASA Astrophysics Data System (ADS)
Wolfsteiner, Peter; Breuer, Werner
2013-10-01
The assessment of fatigue load under random vibrations is usually based on load spectra. Typically they are computed with counting methods (e.g. Rainflow) based on a time domain signal. Alternatively methods are available (e.g. Dirlik) enabling the estimation of load spectra directly from power spectral densities (PSDs) of the corresponding time signals; the knowledge of the time signal is then not necessary. These PSD based methods have the enormous advantage that if for example the signal to assess results from a finite element method based vibration analysis, the computation time of the simulation of PSDs in the frequency domain outmatches by far the simulation of time signals in the time domain. This is especially true for random vibrations with very long signals in the time domain. The disadvantage of the PSD based simulation of vibrations and also the PSD based load spectra estimation is their limitation to Gaussian distributed time signals. Deviations from this Gaussian distribution cause relevant deviations in the estimated load spectra. In these cases usually only computation time intensive time domain calculations produce accurate results. This paper presents a method dealing with non-Gaussian signals with real statistical properties that is still able to use the efficient PSD approach with its computation time advantages. Essentially it is based on a decomposition of the non-Gaussian signal in Gaussian distributed parts. The PSDs of these rearranged signals are then used to perform usual PSD analyses. In particular, detailed methods are described for the decomposition of time signals and the derivation of PSDs and cross power spectral densities (CPSDs) from multiple real measurements without using inaccurate standard procedures. Furthermore the basic intention is to design a general and integrated method that is not just able to analyse a certain single load case for a small time interval, but to generate representative PSD and CPSD spectra replacing extensive measured loads in time domain without losing the necessary accuracy for the fatigue load results. These long measurements may even represent the whole application range of the railway vehicle. The presented work demonstrates the application of this method to railway vehicle components subjected to random vibrations caused by the wheel rail contact. Extensive measurements of axle box accelerations have been used to verify the proposed procedure for this class of railway vehicle applications. The linearity is not a real limitation, because the structural vibrations caused by the random excitations are usually small for rail vehicle applications. The impact of nonlinearities is usually covered by separate nonlinear models and only needed for the deterministic part of the loads. Linear vibration systems subjected to Gaussian vibrations respond with vibrations having also a Gaussian distribution. A non-Gaussian distribution in the excitation signal produces also a non-Gaussian response with statistical properties different from these excitations. A drawback is the fact that there is no simple mathematical relation between excitation and response concerning these deviations from the Gaussian distribution (see e.g. Ito calculus [6], which is usually not part of commercial codes!). There are a couple of well-established procedures for the prediction of fatigue load spectra from PSDs designed for Gaussian loads (see [4]); the question of the impact of non-Gaussian distributions on the fatigue load prediction has been studied for decades (see e.g. [3,4,11-13]) and is still subject of the ongoing research; e.g. [13] proposed a procedure, capable of considering non-Gaussian broadbanded loads. It is based on the knowledge of the response PSD and some statistical data, defining the non-Gaussian character of the underlying time signal. As already described above, these statistical data are usually not available for a PSD vibration response that has been calculated in the frequency domain. Summarizing the above and considering the fact of having highly non-Gaussian excitations on railway vehicles caused by the wheel rail contact means that the fast PSD analysis in the frequency domain cannot be combined with load spectra prediction methods for PSDs.
Energy storage options for space power
Hoffman, H.W.; Martin, J.F.; Olszewski, M.
1985-01-01
Including energy storage in a space power supply enhances the feasibility of using thermal power cycles (Rankine or Brayton) and providing high-power pulses. Review of storage options (superconducting magnets, capacitors, electrochemical batteries, thermal phase-change materials (PCM), and flywheels) suggests that flywheels and phase-change devices hold the most promise. Latent heat storage using inorganic salts and metallic eutectics offers thermal energy storage densities of 1500 to 2000 kJ/kg at temperatures to 1675/sup 0/K. Innovative techniques allow these media to operate in direct contact with the heat engine working fluid. Enhancing thermal conductivity and/or modifying PCM crystallization habit provide other options. Flywheels of low-strain graphite and Kevlar fibers have achieved mechanical energy storage densities of 300 kJ/kg. With high-strain graphite fibers, storage densities appropriate to space power needs (approx. 550 kJ/kg) seem feasible. Coupling advanced flywheels with emerging high power density homopolar generators and compulsators could result in electric pulse-power storage modules of significantly higher energy density.
Vibration energy harvesting from an array of flexible stalks exposed to airflow: a theoretical study
NASA Astrophysics Data System (ADS)
Gardonio, P.; Zilletti, M.
2016-03-01
This paper investigates the vibration energy harvesting of a system formed by an array of identical artificial flexible stalks connected by equal axial springs. The stalks are excited in bending by the propagating eddies produced by a mixing layer airflow at the top end of the canopy. The energy harvesting is localised in one pivotal stalk, which is equipped with a harvester. The paper first contrasts the spectra of the energy harvested by this system and by a classical system, formed by an equal array of mechanically uncoupled beams, which are all equipped with harvesters. Since the proposed system forms a periodic structure, this analysis considers variations of the stiffness of the harvesting stalk and of the connecting springs, which may lead to natural frequencies veering and mode localisation effects. Finally, the paper presents a parametric study that highlights how the bending stiffness of the harvesting stalk, the axial stiffness of the connecting springs and the energy absorption coefficient of the harvester influence the energy extraction. The study shows that, particularly in presence of strongly correlated drag force excitations produced on the stalks by the airflow, the energy harvested with the proposed system with a single harvester is comparable to that of a more complex and more expensive system formed by a whole array of harvesters.
Reduction of Helicopter BVI Noise, Vibration, and Power Consumption Through Individual Blade Control
NASA Technical Reports Server (NTRS)
Jacklin, Stephen A.; Blaas, Achim; Teves, Dietrich; Kube, Roland; Warmbrodt, William (Technical Monitor)
1994-01-01
A wind tunnel test was conducted with a full-scale BO 105 helicopter rotor to evaluate the potential of open-loop individual blade control (IBC) to improve rotor performance, to reduce blade vortex interaction (BVI) noise, and to alleviate helicopter vibrations. The wind tunnel test was an international collaborative effort between NASA/U.S. Army AFDD, ZF Luftfahrttechnik, Eurocopter Deutschland, and the German Aerospace Laboratory (DLR) and was conducted under the auspices of the U.S./German MOU on Rotorcraft Aeromechanics. In this test the normal blade pitch links of the rotor were replaced by servo-actuators so that the pitch of each blade could be controlled independently of the other blades. The specially designed servoactuators and IBC control system were designed and manufactured by ZF Luftfahrttechnik, GmbH. The wind tunnel test was conducted in the 40- by 80-Foot Wind Tunnel at the NASA Ames Research Center. An extensive amount of measurement information was acquired for each IBC data point. These data include rotor performance, static and dynamic hub forces and moments, rotor loads, control loads, inboard and outboard blade pitch motion, and BVI noise data. The data indicated very significant (80 percent) simultaneous reductions in both BVI noise and hub vibrations could be obtained using multi-harmonic input at the critical descent (terminal approach) condition. The data also showed that performance improvements of up to 7 percent could be obtained using 2P input at high-speed forward flight conditions.
Uranga-Piña, L.; Tremblay, J. C.
2014-08-21
We investigate the effect of inter-mode coupling on the vibrational relaxation dynamics of molecules in weak dissipative environments. The simulations are performed within the reduced density matrix formalism in the Markovian regime, assuming a Lindblad form for the system-bath interaction. The prototypical two-dimensional model system representing two CO molecules approaching a Cu(100) surface is adapted from an ab initio potential, while the diatom-diatom vibrational coupling strength is systematically varied. In the weak system-bath coupling limit and at low temperatures, only first order non-adiabatic uni-modal coupling terms contribute to surface-mediated vibrational relaxation. Since dissipative dynamics is non-unitary, the choice of representation will affect the evolution of the reduced density matrix. Two alternative representations for computing the relaxation rates and the associated operators are thus compared: the fully coupled spectral basis, and a factorizable ansatz. The former is well-established and serves as a benchmark for the solution of Liouville-von Neumann equation. In the latter, a contracted grid basis of potential-optimized discrete variable representation is tailored to incorporate most of the inter-mode coupling, while the Lindblad operators are represented as tensor products of one-dimensional operators, for consistency. This procedure results in a marked reduction of the grid size and in a much more advantageous scaling of the computational cost with respect to the increase of the dimensionality of the system. The factorizable method is found to provide an accurate description of the dissipative quantum dynamics of the model system, specifically of the time evolution of the state populations and of the probability density distribution of the molecular wave packet. The influence of intra-molecular vibrational energy redistribution appears to be properly taken into account by the new model on the whole range of coupling strengths. It demontrates that most of the mode mixing during relaxation is due to the potential part of the Hamiltonian and not to the coupling among relaxation operators.
Observation of vibrational energy exchange in a type-III antifreeze protein.
Lotze, S; Olijve, L L C; Voets, I K; Bakker, H J
2014-07-31
We performed time- and polarization-resolved pump-probe and two-dimensional infrared (2D-IR) experiments to study the dynamics of the amide I vibration of a 7 kDa type-III antifreeze protein. In the pump-probe experiments, we used femtosecond mid-infrared pulses to investigate the vibrational relaxation dynamics of the amide mode. The transient spectra show the presence of two spectral components that decay with different lifetimes, indicative of the presence of two distinct amide subbands. The 2D-IR experiments reveal the coupling between the two bands in the form of cross-peaks. On the basis of previous work by Demirdöven et al. ( J. Am. Chem. Soc. 2004 , 126 , 7981 - 7990 ), we assign the observed bands to the two infrared-active modes α(-) and α(+) found in protein β-sheets. The amplitudes of the cross-peak were found to increase with delay time, indicating that the cross-peaks originate from population transfer between the coupled amide oscillators. The time constant of the energy transfer was found to be 6-7 ps. PMID:25051212
Intramolecular energy transfer in highly vibrationally excited methanol. I. Ultrafast dynamics
NASA Astrophysics Data System (ADS)
Boyarkin, O. V.; Lubich, L.; Settle, R. D. F.; Perry, D. S.; Rizzo, T. R.
1997-11-01
Vibrational overtone excitation of jet-cooled methanol, in combination with infrared laser assisted photofragment spectroscopy (IRLAPS) detection, reveals OH stretch bands that are significantly simplified with respect to room-temperature spectra. The simplification afforded by jet-cooling permits the observation of spectral splitting on the order of 50 cm-1 in the region of the 5?1 OH stretch overtone band. Tracking this splitting as a function of OH stretch vibrational level in combination with isotopic substitution studies allows us to identify the perturbing state as the combination level involving four quanta of OH stretch and one quantum of CH asymmetric stretch, 4?1+?2. Careful examination of the spectra reveals that this strong interaction arises from a fourth-order anharmonic term in the Hamiltonian that couples the OH and CH ends of the molecule. These frequency domain results indicate that subsequent to coherent excitation of the 5?1 band, methanol would undergo energy redistribution to the methyl part of the molecule on a time scale of 130 fs. This work also suggests that similar strong resonances may occur more generally in molecules that possess two different high-frequency oscillators in close proximity.
Accurate variational calculations and analysis of the HOCl vibrational energy spectrum
Skokov, S.; Qi, J.; Bowman, J.M.; Yang, C.; Gray, S.K.; Peterson, K.A.; Mandelshtam, V.A.
1998-12-01
Large scale variational calculations for the vibrational states of HOCl are performed using a recently developed, accurate {ital ab initio} potential energy surface. Three different approaches for obtaining vibrational states are employed and contrasted; a truncation/recoupling scheme with direct diagonalization, the Lanczos method, and Chebyshev iteration with filter diagonalization. The complete spectrum of bound states for nonrotating HOCl is computed and analyzed within a random matrix theory framework. This analysis indicates almost entirely regular dynamics with only a small degree of chaos. The nearly regular spectral structure allows us to make assignments for the most significant part of the spectrum, based on analysis of coordinate expectation values and eigenfunctions. Ground state dipole moments and dipole transition probabilities are also calculated using accurate {ital ab initio} data. Computed values are in good agreement with available experimental data. Some exact rovibrational calculations for J=1, including Coriolis coupling, are performed. The exact results are nearly identical with those obtained from the adiabatic rotation approximation and very close to those from the centrifugal sudden approximation, thus indicating a very small degree of asymmetry and Coriolis coupling for the HOCl molecule. {copyright} {ital 1998 American Institute of Physics.}
NASA Astrophysics Data System (ADS)
Yu, Hua-Gen
2009-08-01
An exact variational algorithm is presented for calculating vibrational energy levels of pentaatomic molecules without any dynamical approximation. The quantum mechanical Hamiltonian of the system is expressed in a set of orthogonal coordinates defined by four scattering vectors in the body-fixed frame. The eigenvalue problem is solved using a two-layer Lanczos iterative diagonalization method in a mixed grid/basis set. A direct product potential-optimized discrete variable representation (PO-DVR) basis is used for the radial coordinates while a non-direct product finite basis representation (FBR) is employed for the angular variables. The two-layer Lanczos method requires only the actions of the Hamiltonian operator on the Lanczos vectors, where the potential-vector products are accomplished via a pseudo-spectral transform technique. By using Jacobi, Radau and orthogonal satellite vectors, we have proposed 21 types of orthogonal coordinate systems so that the algorithm is capable of describing most five-atom systems with small and/or large amplitude vibrational motions. Finally, an universal program ( PetroVib) has been developed. Its applications to the molecules CH and HO2-, and the van der Waals cluster HeCl are also discussed.
Role of energy exchange in vibrational dephasing processes in liquids and solids
Marks, S.
1981-08-01
Three theories which claim relevance to the dephasing of molecular vibrations in condensed phase matter are presented. All of these theories predict (in certain limiting cases) that the widths and shifts of molecular vibrations will obey an Arrhenius temperature dependence. The basic tenets of the theories are detailed so that the differences between them may be used in an experiment to distinguish between them. One model, based on intermolecular energy exchange of low-frequency modes, results in dephasing the high-frequency modes when anharmonic coupling is present. A computer analysis of temperature dependent experimental lineshapes can result in the extraction of various parameters such as the anharmonic shifts and the exchange rates. It is shown that, in order to properly assess the relative validity of the three models, other evidence must be obtained such as the spectral parameters of the low-frequency modes, the combination bands, and the isotopic dilution behavior. This evidence is presented for d/sub 14/-durene (perdeutero-1,2,4,5-tetramethylbenzene) and compared to previous data obtained on pure h/sub 14/-durene. An extension of the (HSC) intermolecular energy exchange model which allows for the p