Papers by Keyword: Frequency Response

Abstract: A three-dimensional parametric model was employed to recreate the free response laminated composite plate constructed from different materials. Simulation of the modal analysis is powerful when extreme localized modes are of problem, and it demands dependable material structural models along with correct modelling methodologies. A classical theory-based finite element approach was created to explore the effect of material attributes upon the natural vibration behavior for thin laminated plates. The approach was validated using three-dimensional deformation findings and also achieved based on the theory's results with those derived from commercial programs, including Solidworks. The results obtained from software are in good agreement for some cases and significantly differ for free vibration and is highly dependent on the material properties and boundary conditions. For simply supported boundary condition, the results showed that the maximum fundamentals frequency was 1808.5Hz Hz for the carbon/epoxy material. An established computational technique, depending on finite element method, has been proposed for the computation of free vibration in reinforcement laminated composite components. a good result for estimate the natural frequency and mode shape.

Abstract: Visible light communication has advantages over acoustic and radio wave transmissions in free-space and underwater. The optical transmitters are usually light emitting diodes or laser diodes, and the optical receivers are usually photodiodes or its variants. Solar panels are used for solar energy harvesting to electricity, but the panels are also available in small sizes, and hence, are finding increasing use in optical communications due to larger aperture compared to photodiodes. This work investigated by experiments the characteristics of solar panels as receivers in visible light communication (VLC). In the work, four solar panels of different physical sizes were selected for experiments and measurement. Two characteristics important to communication were investigated. First is the internal resistance at different low illumination levels of white light. Second is response to sinusoidally varying intensity of white light at varying frequencies. For the first study, two of the four panels were investigated; and for the second study, the four solar panels were investigated. An array of seven white LEDs was used as the light source. Also, underwater data communication in saline water was performed for one of the solar panels, and a photodiode in comparison. Results showed that under steady illumination, the internal resistance is both illumination level-dependent and surface area-dependent. It decreases with increase in illumination level, and surface area. Also, the rate of decrease of the internal resistance with illumination increases with surface area. For the frequency response, the cut-off frequency of the solar panel is surface area-dependent, and load-dependent. It decreases with increase in surface area, and increases with decrease in load resistance values (increased loading). For data communication, the maximum data rate obtainable with the solar panel is less to that of the photodiode. The frequency response is important in considering the bandwidth of the solar panels, which also varies with the load, while the internal resistance is important in maximum power point tracking and impedance matching with front end circuits in optical communication receivers.

Abstract: This paper presents a simulation of three different types of lead-free piezoelectric materials for energy harvesting. Polyvinylidene Fluoride (PVDF), Zinc Sulfide (ZnS), and Cadmium Sulfide (CdS) are simulated using COMSOL Multiphysics to evaluate the frequency response and electrical potential for each materials. The simulation consisted of two parts which is 3D block cantilever for simulating frequency response and total displacement. The second part is 2D block bimorph to simulate power generated by varying frequency responses. The simulated result for the first shows that frequency response for each materials is differents for ZnS, PVDF and CdS which 30.897 kHz, 8.517 kHz, and 22.118 kHz. For total displacement is 303 µm which same for each materials. Each material is simulated for various cantilever beam thicknesses ranging from 1-4 µm and result ZnS having the greatest frequency response. For 2D block bimorph model, the highest electric potential is 0.75 V at 60 Hz frequency for ZnS. Meanwhile for CdS and PVDF has less electric potential which 0.6 V and 0.4V at 60 Hz frequency response. For power disspation, ZnS generate 10% more power compare to CdS and PVDF. In the end of the paper, ZnS is excellent lead free material compared to CdS and PVDF in term of aforementioned parameter studied.

Abstract: Collaboration with professionals, particularly in the production of a key test of audio material, consider not only commonplace, but a necessary condition for objectification of input values of research whose content is aural component of the learning material. To get near the practice tests were filmed in three versions for voice, lower male voice, higher male voice and a female voice. Professional presenters under the leadership of literary director for us were the guarantee of a precise pronunciation of speech therapy without defects.

Abstract: Power system stability is the ability of an electric power system unit, for giving operating conditions beginning to recover operating state of equilibrium after being subjected to a physical interference. Power system stability has been recognized as an important problem for safe operation of system unit. Stability of power system is similar to the stability of any dynamic system, and has basic mathematical. Concepts from the mathematics and theoretical stability control are first revised to provide background information related to stability of dynamic system generally and establish a connection theoretical. This paper presents to improve of dynamic power system stability using frequency response as tuning of system stabilizer. It is started by electrical power systems mathematic modeling in state variable equation then set the expertise function of frequency response as tuning of system stabilizer. The plant controlled by function of frequency response is tuned to left half plane (LHP) as system stabilizer which their input from the rotor speed. When the system occur fault, the rotor speed should be synchronized, for this case one electrical controller is needed to make sure the system is stable.

Abstract: To explore the isolation mechanism and optimize the performance of the porous material in a dynamic viewpoint, a nonlinear porous material vibration isolator is modeled in this work. The stiffness of the isolator is regarded to be a piecewise linear, according to the stress–strain characteristics of porous material. Averaging method is employed to analyze the amplitude-frequency characteristics when the system excited by harmonic excitation. It is found that the vibration system represents linear, bilinear and tri-linear characteristics, when the porous material isolator works in linear-elastic phase, plateau phase and densification phase, respectively. The result shows that the amplitude response of the system in the plateau stage is much less than the linear isolator.

Abstract: Vibration reduction in term of lower acoustic noise level increases e.g. the passenger comfort, fulfills acoustic manufacturing standards, decreases the transportation influence on the environment etc. The basic sheet metal structure is complemented with damping layer which absorbs the vibration energy. The frequency response experiment analysis of the component structure with damping material helps to validate the separate material models used for predictive simulations.

Abstract: The mechanical part of the 2D servo valve is mainly a hydraulic servo screw mechanism, by which the rotary motion of the spool is turned to linear sliding. A step motor is utilized to rotate the spool and functions as the electrical-to-mechanical transformer. For studying the different influences of 2D valve's pilot circular and full arch structure on its dynamic characteristics of servo screw mechanism, a step response and sine response experiment device was designed, and the experiments were done. The experimental results show that the full arch structure type step response time is about 1.6 ms (abbreviation of millisecond), the circular type about 3ms, proved that the full bow structure can significantly improve the dynamic characteristic of servo screw mechanism, it is also be proved by sinusoidal frequency response experiments.

Abstract: In recent years, piezoelectric energy harvester which can replace the traditional battery supply has become a hot topic in global research field of microelectronic devices. Characteristics of a trapezoidal-loop piezoelectric energy harvester (TLPEH) were analyzed through finite-element analysis. The output voltage density is 4.251V/cm2 when 0.1N force is applied to the free end of ten-arm energy harvester. Comparisons of the resonant frequencies and output voltages were made. The first order resonant frequency could reach 15Hz by increasing the number of arms. Meanwhile, the output voltage is improved greatly when excited at first-order resonant frequencies. The trapezoidal-loop structure of TLPEH could enhance frequency response, which means scavenging energy more efficiently in vibration environment. The TLPEH mentioned here might be useful for the future structure design of piezoelectric energy harvester with low resonance frequency.

Abstract: MEMS resonator represents currently one of the important research areas of Microelectromechanical Systems (MEMS). The usual applications of MEMS resonators are the radio-frequency electromechanical devices, MEMS gyroscopes and resonant sensors. The main part of a MEMS resonator is the mechanical vibrating structure that can be fabricated as microcantilevers, microbridges or in a more complex configuration as micromembranes. The scope of this paper is to investigate the dynamic behavior of an electrostatically actuated MEMS cantilever under different oscillating modes in order to determine the resonant frequency, amplitude and velocity of oscillations. Moreover, based on the resonant frequency experimental curves, the quality factor for different oscillating modes is determined. The effect of operating conditions on the frequency response of investigated microcantilever is monitored. As a consequence, the experimental tests are performed both in ambient conditions and in vacuum. The dynamic response of microcantilever in vacuum is influenced by the intrinsic dissipation energy and the sample behavior in air depends on the intrinsic losses as well as the extrinsic dissipation energy.