Journal articles: 'Half-power bandwidth method'

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Wu, Baisheng. "A correction of the half-power bandwidth method for estimating damping." Archive of Applied Mechanics 85, no. 2 (August 17, 2014): 315–20. http://dx.doi.org/10.1007/s00419-014-0908-0.

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Lozia, Zbigniew, and Piotr Zdanowicz. "Simulation assessment of the half-power bandwidth method in testing shock absorbers." Open Engineering 11, no. 1 (December 12, 2020): 120–29. http://dx.doi.org/10.1515/eng-2021-0011.

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AbstractThe work deals with usability of the half-power bandwidth method in the diagnostic testing of automotive shock absorbers. In all the simulation tests, the front and rear suspension system of a present-day medium-classmotor car was considered. At the first stage, calculations were made in the frequency domain for a linear “quarter-car” model with two degrees of freedom; then, simulations were carried out in the time domain with using a similar but strongly nonlinear model. In the latter case, actual characteristics (corresponding to those obtained from test rig measurements) of shock absorber damping, suspension and tire elasticity, sliding friction in the suspension, and “wheel hop” were considered. The calculations were carried out every time for twelve levels of viscous damping in the suspension system, which made 48 calculation series in total. The factors of gain in the vertical force between the tester’s vibration plate and the vehicle tire (relative to the input force applied) and the dimensionless coefficients of viscous damping in the suspension system, determined by the half-power bandwidth method, were thoroughly analyzed. The calculation results were presented in graphical form. Attention was also paid to the distortions caused by the force of inertia of the tester’s vibration plate.

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Yerrawar, R. N., and R. R. Arakerimath. "Experimental investigations of damping characteristic for MR strut by half-power bandwidth method." Journal of Measurements in Engineering 6, no. 3 (September 30, 2018): 163–72. http://dx.doi.org/10.21595/jme.2018.20122.

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Guo, Zhi Wei, Mei Ping Sheng, and Jian Gang Ma. "Negative Ten Decibels Method for Damping Identification of Light Damping Structure." Applied Mechanics and Materials 577 (July 2014): 170–73. http://dx.doi.org/10.4028/www.scientific.net/amm.577.170.

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Half power method is commonly used in structural damping identification because of its simplicity in algorithm. But when the damping is very small, half power method will lead a big error. In order to get more accurate result of small damping structure, this paper suggests using negative ten decibels method (N-10dB) instead of half power method. N-10dB method takes 10-dB bandwidth into consideration, differs from 3-dB of half-power method. The theory of this method is given firstly and proves that it is very simple in algorithm. Subsequent simulation and experiment show that, compared with half power method, N-10dB method have stronger noise resistance, higer precision and is more stable in repeated measurements. Except that, the N-10dB method is also practical in engineering test.

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Siva Sankara Rao, Yemineni, Kutchibotla Mallikarjuna Rao, and V. V. Subba Rao. "Estimation of damping in riveted short cantilever beams." Journal of Vibration and Control 26, no. 23-24 (March 20, 2020): 2163–73. http://dx.doi.org/10.1177/1077546320915313.

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In layered and riveted structures, vibration damping happens because of a micro slip that occurs because of a relative motion at the common interfaces of the respective jointed layers. Other parameters that influence the damping mechanism in layered and riveted beams are the amplitude of initial excitation, overall length of the beam, rivet diameter, overall beam thickness, and many layers. In this investigation, using the analytical models such as the Euler–Bernoulli beam theory and Timoshenko beam theory and half-power bandwidth method, the free transverse vibration analysis of layered and riveted short cantilever beams is carried out for observing the damping mechanism by estimating the damping ratio, and the obtained results from the Euler–Bernoulli beam theory and Timoshenko beam theory analytical models are validated by the half-power bandwidth method. Although the Euler–Bernoulli beam model overestimates the damping ratio value by a very less fraction, both the models can be used to evaluate damping for short riveted cantilever beams along with the half-power bandwidth method.

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Papagiannopoulos, George A., and George D. Hatzigeorgiou. "On the use of the half-power bandwidth method to estimate damping in building structures." Soil Dynamics and Earthquake Engineering 31, no. 7 (July 2011): 1075–79. http://dx.doi.org/10.1016/j.soildyn.2011.02.007.

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Wang, Jin-Ting, Feng Jin, and Chu-Han Zhang. "Estimation error of the half-power bandwidth method in identifying damping for multi-DOF systems." Soil Dynamics and Earthquake Engineering 39 (August 2012): 138–42. http://dx.doi.org/10.1016/j.soildyn.2012.02.008.

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Olmos, Bertha A., and Jose M. Roesset. "Evaluation of the half-power bandwidth method to estimate damping in systems without real modes." Earthquake Engineering & Structural Dynamics 39, no. 14 (October 26, 2010): 1671–86. http://dx.doi.org/10.1002/eqe.1010.

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Fu, Jingcheng, Jun Huang, Li-Bo Wang, and Lei Song. "Oscillation mode flight data analysis based on FFT." Aircraft Engineering and Aerospace Technology 91, no. 1 (January 7, 2018): 157–62. http://dx.doi.org/10.1108/aeat-04-2018-0139.

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Purpose The purpose of this paper is to propose an identification method of acquiring aircraft mode characteristics based on fast Fourier transform and half-power bandwidth method, aiming at the common oscillation met in flight test. Design/methodology/approach The feasibility of this method is demonstrated through derivation; the robustness analysis is conducted through three examples, and finally the method was applied on a set of sideslip angle record from flight test. Findings The derivation and numerical analysis both show that the presented method can have high accuracy and good robustness under coupled mode and noise condition. Practical implications The method proposed is of robustness, and it is concise and easy to apply on flight data record. Originality/value This paper demonstrates the feasibility of half power bandwidth to be applied on oscillation mode characteristics identification from flight data record, which is different from other method applied.

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Szulej, Jacek. "The method of determining damping coefficients of vibration for complex structures." Budownictwo i Architektura 5, no. 2 (December 13, 2009): 039–59. http://dx.doi.org/10.35784/bud-arch.2344.

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The purpose of this paper is to present methods of determining damping coefficient of vibration. The methods, such as: collocation method, two energetic methods and half-power bandwidth method, concern composite structures. Verification of methods was taken into account in this research. Real compound models and numerical models were created. Time histories of vibrations of these models were measured or calculated. Comparison of methods were made on a basis of obtained results.

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Ching Yu, Low, and Muhammad Ramlee Kamarudin. "5G Fixed Beam Switching on Microstrip Patch Antenna." International Journal of Electrical and Computer Engineering (IJECE) 7, no. 2 (April 1, 2017): 975. http://dx.doi.org/10.11591/ijece.v7i2.pp975-980.

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<span lang="EN-US">5G technology is using millimeter-wave band to improve the wireless communication system. However, narrow transmitter and receiver beams have caused the beam coverage area to be limited. Due to propagation limitations of mm wave band, beam forming technology with multi-beam based communication system, has been focused to overcome the problem. In this letter, a fixed beam switching method is introduced. By changing the switches, four different configurations of patch array antennas are designed to investigate their performances in terms of radiation patterns, beam forming angle, gain, half-power bandwidth and impedance bandwidth at 28 GHz operating frequency for 5G application. Mircostrip antenna is preferred due to its low profile, easy in feeding and array configurations. Three different beam directions had been formed at -15°, 0°, and 15° with half-power bandwidth of range 45˚ to 50˚.</span>

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Flaga, Andrzej, Jacek Szulej, and Piotr Wielgos. "Comparison of determination methods of vibration’s damping coefficients for complex structures." Budownictwo i Architektura 3, no. 2 (December 11, 2008): 053–61. http://dx.doi.org/10.35784/bud-arch.2322.

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The purpose of this paper is to present methods of vibrations damping coefficient determination. The methods, such as collocation method, two energetic methods and half-power bandwidth method concern composite structures. The verification of methods has been taken into account in this work. Two real compound models and two numerical models have been created. Time series of vibrations of these models have been measured and calculated. The comparison of four methods has been made on the basis of obtained results.

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Zhu, Chengwei, Jingjing Yan, Ye Zhuang, Xueliang Gao, Qiang Chen, Jiannan Wei, and Haitao Ding. "A novel evaluation on rolling resistance characteristics of truck tire through the simplified experimental modal analysis." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 234, no. 12 (July 16, 2020): 2771–82. http://dx.doi.org/10.1177/0954407020920032.

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A novel evaluation method for the rolling resistance characteristics of truck tire is proposed, in which a simplified modal experiment is suggested through a single-point vibration sampling from the tire surface with a polyvinylidene fluoride (PVDF) piezoelectric film. Three truck tires are utilized in the modal experiments, and the half-power bandwidth method is employed to identify the damping characteristics of the three tires. The damping characteristics of the tires are ranked by their values. These values are compared with their corresponding rolling resistance coefficients to manifest their correlative relationship. The experimental results, which are obtained from the modal experiment and the rolling resistance test, indicate that the modal parameters and the half-power bandwidth of the tire are exactly correlated to the rolling resistance coefficients. Furthermore, the damping ratios of the tires are correlated well with the rolling resistance coefficients among the tires. Overall, the proposed evaluation method could effectively evaluate the rolling resistance characteristics of the tire, which enable it to be a simple and economical alternative over the conventional tire rolling resistance experiments.

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Badsar, S. A., M. Schevenels, W. Haegeman, and G. Degrande. "Determination of the material damping ratio in the soil from SASW tests using the half-power bandwidth method." Geophysical Journal International 182, no. 3 (July 8, 2010): 1493–508. http://dx.doi.org/10.1111/j.1365-246x.2010.04690.x.

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Treszkai, Marcell Ferenc, Balázs Vehovszky, and Dániel Feszty. "Damping determination by the half power bandwidth method for a rectangular flat plate with bitumen damping layer application." Journal of Vibroengineering 23, no. 5 (May 27, 2021): 1267–77. http://dx.doi.org/10.21595/jve.2021.21938.

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Ding, Hong Gang, Ze Yu Weng, Hong Wu You, Bo Lu, and Xue Zhe Tang. "Resin Concrete Specimens Attenuation Characteristics Research." Applied Mechanics and Materials 141 (November 2011): 478–82. http://dx.doi.org/10.4028/www.scientific.net/amm.141.478.

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This paper introduces a method of manufacturing process of resin concrete, made three tubular cast-iron specimens filled with resin concrete. This paper detected the amplitude-frequency response curve of specimens in experimental method, and calculated the damping ratio of specimens through half power bandwidth method. The damping ratio of specimens is compared. It provided a good reference for the design of the machine tool on the dynamic characteristics.

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Treszkai, Marcell Ferenc, David Sipos, and Daniel Feszty. "Damping Determination by Half-Power Bandwidth Method for a Slightly Damped Rectangular Steel Plate in the Mid-Frequency Range." Acta Technica Jaurinensis 13, no. 3 (August 5, 2020): 177–96. http://dx.doi.org/10.14513/actatechjaur.v13.n3.545.

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This paper presents a novel methodology for measuring the Damping Loss Factor (DLF) of a slightly damped plate in the mid-frequency range (400-1000 Hz) by the Half Power Bandwidth Method (HPBM). A steel flat plate of 650 x 550 x 2 mm was considered as the test case, which was excited by both a shaker and an impact hammer to quantify the effect of the excitation type for slightly damped plate. Since the HPBM is based on extracting the damping data from the modal resonance peaks, working with the correct Frequency Response Functions (FRF) was found to be a crucial factor. Therefore, the effects of coherence and resolution of the sampling frequency were examined in detail in the measurements. The obtained DLF results were statistically analysed and then applied in SEA simulations. Comparison of the simulation and experimental results showed that the method of extracting the DLF data from the measurements can have as much as 10 dB influence on the simulation results. The best results, with only 2 dB difference between measurement and simulation, were obtained when the statistical expected value of the data was used as the input in the SEA simulations.

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Wang, Jinting, Dandan Lü, Feng Jin, and Chuhan Zhang. "Accuracy of the half-power bandwidth method with a third-order correction for estimating damping in multi-DOF systems." Earthquake Engineering and Engineering Vibration 12, no. 1 (March 2013): 33–38. http://dx.doi.org/10.1007/s11803-013-0149-1.

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Naghipour, M., M. Mehrzadi, F. Taheri, and G. P. Zou. "Polynomial correction function for half-power bandwidth (HPB) method of damping of glulam beams reinforced with e-glass reinforced epoxy polymer (GRP)." Canadian Journal of Civil Engineering 36, no. 2 (February 2009): 241–52. http://dx.doi.org/10.1139/l08-097.

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Analytical and experimental investigation into dynamic properties of glued–laminated (glulam) beams reinforced with various lay ups of e-glass reinforced epoxy polymer (GRP) composites are discussed. Three unreinforced glulam (control) beams and 11 glulam beams reinforced with GRP on their bottom surface were clamped in a cantilever condition and tested using an instrumental hammer. The natural frequencies of all beams determined by the impact dynamic (hammer) method using power spectral density (PSD) were used to estimate damping ratio of all the beams through both time domain and frequency domain methods. In the time domain analysis, the method of logarithmic decrement analysis (LDA) and the Hilbert transform analysis (HTA) were considered; in the frequency domain analysis, both moving block analysis (MBA) and half-power bandwidth (HPB) were applied to the data and a new approach HPB method with a polynomial correction function was numerically established. A comparison between the results obtained from all the methods of analysis and a new approach shows that this method may improve the accuracy of the HPB method in evaluation of vibration damping properties of glulam reinforced composite beams because glulam beams have high level damping ratios and that this method should be modified especially when used with materials having high level damping ratios.

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Hasanvand, Hamed, and Mohammad Reza Zamani. "Robust control of static Var compensator-based power oscillation dampers using polynomial control in power systems." Transactions of the Institute of Measurement and Control 40, no. 5 (January 24, 2017): 1395–406. http://dx.doi.org/10.1177/0142331216683774.

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A static Var compensator (SVC) installed in a power transmission network can be effectively exploited to enhance the damping of low frequency electromechanical oscillations. The application of robust control theory offers more reliable and robust damping controller to achieve desired damping level considering variations in the operating conditions of power system. This paper presents a new approach to design a robust proportional-integral (PI) controller for stabilizing power system oscillations. The variability in operating conditions is captured using an interval polynomial and then, Kharitonov’s theorem is used to design the desired damping controller. The proposed method is based on plotting the stability boundary locus in the ( kp-ki) plane and then computing the stabilizing values of the parameters of a PI controller. Besides stabilization, computation of stabilizing PI controllers that achieve user specified gain margin (Gm), phase margin (Pm) and bandwidth is studied simultaneously. This novel method enables designers to make the convenient trade-off between stability and performance by choosing the proper margins and bandwidth specifications. In addition, the most appropriate stabilizing input signal is selected using Hankel singular value (HSV) and right half plane-zeros (RHP-zeros) for the SVC-based supplementary damping controller. The effectiveness and robustness of the proposed controller are demonstrated using eigenvalue analysis and time-domain simulation for a 16 machine 68-bus test system. The simulations and analysis are implemented in matrix laboratory environment and power system analysis toolbox.

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Djouane, Lotfi, Sami Bedra, Randa Bedra, and Tarek Fortaki. "Neurospectral modeling of rectangular patch with rectangular aperture in the ground plane." International Journal of Microwave and Wireless Technologies 7, no. 6 (July 24, 2014): 759–68. http://dx.doi.org/10.1017/s1759078714001007.

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In this study, we propose an artificial neural network in conjunction with spectral domain approach (SDA), for fast and accurate determination of the resonant frequency and half-power bandwidth of rectangular patch over the ground plane with rectangular aperture. The performances evaluation of the neurospectral method reveals superiority over the conventional SDA model in terms of errors and time. The results obtained from the neurospectral method are in very good agreement with the experimental and theoretical results available in the literature. Finally, numerical results for the effect of rectangular aperture dimensions on the resonant characteristics of the rectangular patch are also investigated.

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Abdulhamid, Mohanad, and Eugene Ochieng. "Review Design of Slot Antenna Based on Ansoft HFSS Software." Technological Engineering 16, no. 1 (October 1, 2019): 65–68. http://dx.doi.org/10.1515/teen-2019-0010.

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Abstract In this paper, a micro-strip fed slot antenna array for application in the 2.4GHz industrial, scientific and medical(ISM) band is implemented using the Ansoft HFSS software. Standard formulas are used to calculate different antenna parameters. The proposed antenna is designed to work at 2.4GHz frequency band. A half power beam width(HPBW) of 57°. A bandwidth of around 7.7% is attained. This may have been brought about by poor impedance matching and a high level of surface waves. A way of improving the bandwidth would have been to use proximity coupling feeding method which offers the highest bandwidth and is somewhat easy to model and has low spurious radiation. However, its fabrication would have been more difficult. A directivity of 2.01 dB is achieved. This is a fairly high though directivity increase could have been studied through use of different substrate material and thickness. Adjusting length and width of narrow slot loop antenna will influence on the resonance frequency and bandwidth. By using HFSS software, the characteristics of antenna are investigated and analyzed, including voltage standing wave ratio (VSWR), return loss and far field radiation patterns.

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Piotr Zdanowicz and Marek Guzek. "Diagnostics of the On-Vehicle Shock Absorber Testing." Communications - Scientific letters of the University of Zilina 23, no. 3 (July 1, 2021): B178—B186. http://dx.doi.org/10.26552/com.c.2021.3.b178-b186.

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The practical problems that usually come up during the on-vehicle testing of motor car shock absorbers have been discussed. Results of example tests carried out to the EUSAMA standard procedure were compared to the test results obtained with using newer methods, i.e. the phase angle method and half power bandwidth method (HPBM). The issue of incompatibility of the typical excitation applied by diagnostic suspension testers with one that often occurs in the road conditions has also been raised. It has also been shown that the wear of shock absorbers may affect the value of braking deceleration of cars with ABS (anti-lock braking system) when moving on uneven ground. The main objective of the work was to assess usefulness and reliability of various diagnostic methods intended for the on-vehicle testing of car shock absorbers.

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Luo, Jian Lin, Zhong Dong Duan, Tie Jun Zhao, and Qiu Yi Li. "Cement-Based Composite with Carbon Nanotubes Reinforcement Tailored for Structural Damping." Advanced Materials Research 150-151 (October 2010): 526–29. http://dx.doi.org/10.4028/www.scientific.net/amr.150-151.526.

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Cement-based composites filled with some multi-walled carbon nanotubes (MWNTs) (MWNT/CC) were fabricated using surfactant enwrapping, ultrasonic treatment, and subsequently intensive shear mixing. The damping capacities of the cured nanocomposites were characterized with forced vibration testing and half-power bandwidth identification method. Results show that, the MWNTs can greatly enhance the structural damping capacity of the MWNT/CC beam with balanced strength reinforcement. There exists 44.5%, 10% increase in the damping ratio, and fundamental frequency of the MWNT/CC with 1.0 wt% MWNTs addition, along with strength reinforcement, as compared to the reference, respectively.

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Pesterev, I. S., N. N. Sosnovsky, and B. G. Stepanov. "Radiation by Transducer of Waveguide Type into Conical Half-Spaces Coaxial With It." Journal of the Russian Universities. Radioelectronics 23, no. 1 (February 28, 2020): 70–82. http://dx.doi.org/10.32603/1993-8985-2020-23-1-70-82.

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Introduction. The present stage of development of hydroacoustic equipment is characterized by a constant improvement of an element base and by an increase in computing power. However, in solving of applied problems one is increasingly faced with a restriction on the realized bandwidth of electroacoustic transducers and antennas. The most of well-known methods of bandwidth expansion do not provide a linear character of the phase-frequency characteristic (PFC) of radiation in the working frequency band, which is of primary importance for the effective formation of relatively short, frequency-tunable, and complex acoustic signals. From this position, the use of a transducer of waveguide type (TWT) is preferential. Its construction and electrical excitation method provides a close to linear phase response of radiation.Aim. The development of a generalized computational model. It has to include particular cases of TWT radiation into cylindrical waveguides coaxial with it and into half-spaces, and also to take into account the influence of waves reflected from the boundaries of the TWT on its field characteristics.Materials and methods. The TWT was presented by a coaxial set of identical water filled piezocylinders with amplitude-phase excitation, provided a mode of broadband radiation in the form of traveling waves. The usage of the method of partial regions allowed one to obtain a solution of the problem of TWT radiation through water filled apertures into the conical adjacent half-spaces, variable in angle.Results. Frequency characteristics of TWT sound pressure results calculated in accordance with the solution of the synthesis problem in the frontal and rear directions for different angles of cone opening were presented and analyzed. Using the proposed computational model of TWT, the possibility of obtaining a bandwidth of the order of 3 octaves was demonstrated. An influence of the thickness of the passive flanges, which are used to link the TWT in the antennas was estimated. The possibility of radiation in the working frequency band of TWT of ultrashort ultra-short single-period pulses for different angles of cone opening was considered. A comparative assessment of the result of calculation with other particular solutions (the radiation by TWT in coaxial water-filled waveguides and also – in half-spaces) was presentedConclusion. An expedient to use a generalized computational model for a more accurate description of the acoustic fields of real antenna models made up of TWT was concluded.

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Du, Guang Yu, Zhen Tan, Kun Liu, Hao Chai, and De Chun Ba. "Research on Damping Properties of TiN Coating Prepared with Arc Ion Plating." Applied Mechanics and Materials 184-185 (June 2012): 1167–70. http://dx.doi.org/10.4028/www.scientific.net/amm.184-185.1167.

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In this paper TiN coating was prepared on stainless steel substrate using arc ion plating technique. The coating samples’ phases, surface morphology, micro-determination chemical composition, loss factor and damping ratio were tested. The phases of TiN coating were determined by X-ray diffraction (XRD) technique. The surface morphology and chemical composition of the TiN coating were analyzed by scanning electron microscope (SEM) and Energy Dispersive Spectrometer (EDS), respectively. The damping performance of the samples was measured by hammering activation according half power bandwidth method. The loss factor or damping ratio of samples were obtained according frequency response curve. The results showed that damping performance of samples was considerably improved by TiN coatings.

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Chakkour, Mounia, Otman Aghzout, and Fahd Chaoui. "Theoretical Analysis of a Novel WDM Optical Long-Haul Network Using the Split-Step Fourier Method." International Journal of Optics 2020 (March 1, 2020): 1–9. http://dx.doi.org/10.1155/2020/3436729.

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In this paper, a new optical transmission model was investigated and developed in order to improve the performance of Wavelength Division Multiplexing optical transmission systems. For this purpose, an efficient theoretical method combining a Fiber Bragg Grating (FBG) and Erbium Doped Fiber Amplifier (EDFA) was implemented. Enhancements on the transmitted signal amplitudes with important compensation of the chromatic dispersions and large reduction on the nonlinear effects were obtained. The reflectivity peak, the full width at half maximum bandwidth, and the side lobe level have been studied in depth to demonstrate the efficiency of the proposed method. To apply the new method, we considered a complicated system of 16-channel wavelengths, where the split-step fourier method was used to solve the nonlinear Schrödinger equations, and the transfer matrix method was applied to describe the coupled mode equations. The wavelengths corresponding to different values of reflectivity peaks calculated previously in the FBG outputs section were injected as EDFA inputs to determine the output power and the gain of the new transmission system. All results are analyzed using Matlab program.

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Nagasankar, P., S. Balasivanandha Prabu, Velmurugan Ramachandran, and R. Paskaramoorthy. "Experimental Investigation on Dynamic Characteristics of Polypropylene Honeycomb Sandwich Structures under the Influences of Different Temperatures." Applied Mechanics and Materials 606 (August 2014): 153–57. http://dx.doi.org/10.4028/www.scientific.net/amm.606.153.

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The dynamic characteristics of the Polypropylene honeycomb (PPHC) sandwich composites have been investigated under various temperatures (30°,35°,40°,45°,50°,55°,60°, 65°,70°,75° and 80°C) and different orientations (0° and 90°) of the glass fibers in the composites. Since the thermal properties of the constituent materials (glass fiber, epoxy resin and PPHC core) of the PPHC sandwich composites are different and the in-plane effect of the composites varies with the two different orientations (0° and 90°) of the fibers, the variation of the loss factor under the various temperatures are also different for these orientations. A two stage layup technique has been used to fabricate the sandwich composite specimens. Impulse technique associated with the half power bandwidth method, has been used to evaluate the natural frequency and damping values of the sandwich composite under different temperatures.

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Xu, Le, Rui Li, Xiaoqun Chen, Feng Wei, and Xiaowei Shi. "Wideband Frequency Invariant Array Synthesis Based on Matrix Singular Value Decomposition." Electronics 10, no. 16 (August 23, 2021): 2039. http://dx.doi.org/10.3390/electronics10162039.

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In this paper, an analytic method for frequency invariant (FI) array synthesis is proposed based on matrix singular value decomposition. By grouping the elements of FI array into a few subarrays, the FI pattern in the whole frequency band is realized. Using this algorithm, the number of sub arrays is reduced. Simulation results show that the proposed algorithm can synthesize the 64-element broadband FI array in 0.52 s. For the 18-element linear array, the half power beam width (HPBW) changes less than 0.6 degrees in the bandwidth. Moreover, the range of HPBW variation decreases rapidly along with the increase in the number of elements. Furthermore, the effectiveness of the algorithm is verified by synthesizing FI array with low side lobe level (SLL), beam scanning, and notch requirements. The examples in this paper show that the proposed algorithm can achieve better pattern characteristics with fewer elements. Finally, a broadband antenna with 2:1 bandwidth is improved, and two FI arrays of 23 elements and 64 elements are formed by using the antenna. The active pattern of the array element is introduced into the proposed algorithm, and two FI arrays synthesized by the algorithm are simulated by full wave software.

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Khanh, Ngo Tan Vu, and Van Dinh Nguyen. "Max-Min Fairness and Sum Throughput Maximization for In-Band Full-Duplex IoT Networks: User Grouping, Bandwidth and Power Allocation." Electronics 9, no. 12 (December 18, 2020): 2182. http://dx.doi.org/10.3390/electronics9122182.

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The skyrocketing growth in the number of Internet of Things (IoT) devices has posed a huge traffic demand for fifth-generation (5G) wireless networks and beyond. In-band full-duplex (IBFD), which is theoretically expected to double the spectral efficiency of a half-duplex wireless channel and connect more devices, has been considered as a promising technology in order to accelerate the development of IoT. In order to exploit the full potential of IBFD, the key challenge is how to handle network interference (including self-interference, co-channel interference, and multiuser interference) more effectively. In this paper, we propose a simple yet efficient user grouping method, where a base station (BS) serves strong downlink users and weak uplink users and vice versa in different frequency bands, mitigating severe network interference. First, we aim to maximize a minimum rate among all of the users subject to bandwidth and power constraints, which is formulated as a nonconvex optimization problem. By leveraging the inner approximation framework, we develop a very efficient iterative algorithm for solving this problem, which guarantees at least a local optimal solution. The proposed iterative algorithm solves a simple convex program at each iteration, which can be further cast to a conic quadratic program. We then formulate the optimization problem of sum throughput maximization, which can be solved by the proposed algorithm after some slight modifications. Extensive numerical results are provided to show not only the benefit of using full-duplex radio at BS, but also the advantage of the proposed user grouping method.

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Avil, Esma, Ferhat Kadioglu, and Cevdet Kaynak. "Contribution of carbon nanotubes to vibration damping behavior of epoxy and its carbon fiber composites." Journal of Reinforced Plastics and Composites 39, no. 7-8 (February 12, 2020): 311–23. http://dx.doi.org/10.1177/0731684420906609.

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The main objective of this study was to investigate contribution of the non-functionalized multi-walled carbon nanotubes on the vibration damping behavior of first neat epoxy resin and then unidirectional and bidirectional continuous carbon fiber reinforced epoxy matrix composites. Epoxy/carbon nanotubes nanocomposites were produced by ultrasonic solution mixing method, while the continuous carbon fiber reinforced composite laminates were obtained via resin-infusion technique. Vibration analysis data of the specimens were evaluated by half-power bandwidth method; and the mechanical properties of the specimens were determined with three-point bending flexural tests, including morphological analyses under scanning electron microscopy. It was generally concluded that when even only 0.1 wt% carbon nanotubes were incorporated into neat epoxy resin, they have contributed not only to the mechanical properties (flexural strength and modulus), but also to the vibration behavior (damping ratio) of the epoxy. When 0.1 or 0.5 wt% carbon nanotubes were incorporated into continuous carbon fiber reinforced epoxy matrix composites, although they have no additional contribution to the mechanical properties, their contribution in terms of damping ratio of the composites were significant.

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Gao, Qi, Jinzhi Feng, Songlin Zheng, and Xuyun Qiu. "Research on Compilation Method of Multi-Axial Loading Spectrum for Cylindrical Shock Absorber." International Journal of Reliability, Quality and Safety Engineering 24, no. 05 (September 27, 2017): 1750023. http://dx.doi.org/10.1142/s0218539317500231.

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The main failure mode of cylindrical shock absorbers (CSAs) used by taxis in China’s Zhejiang Province is oil leakage because of a large horizontal force loaded on the cylinder wall by a questionnaire survey. The previous CSA durability bench test methods, which do not involve the interaction between horizontal load and vertical load and do not consider the user road spectrum, cannot simulate the real fatigue phenomena of it. In order to preferably reproduce the failure mode and accurately to predict the failure time of the CSA used in the area, a compilation method of multi-axial loading spectrum is proposed based on the road spectrum. The vertical loading spectrum is compiled by using the way of sine on sine, in which high frequency (HF) signal superimposed on low frequency (LF) signal. The LF is determined by the half-power bandwidth theory, which can reflect the power spectral density distribution of the random road spectrum. The HF is determined by the maximum line velocity principle to effectively reduce test time. The loading cycles and amplitudes of them are determined by using the rain-flow counting method. In addition, the horizontal loading force is taken into consideration in the multi-axial loading spectrum. To prove the validation and efficiency of the method described in this paper, the compiled multi-axial loading spectrum was used to conduct the durability bench test. The results show that the mean failure mileage of specimens is close to the mean mileage time of field samples. The failure modes of the specimens are the same as those of field samples. Thus the proposed method can be used as a reference for durability bench test of CSA. The test data can also be used to accurately study the reliability of CSA.

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Liang, Ruijun, Wenlong Hao, Wenfeng Ran, and Wenhua Ye. "Analysis of the Creeping Phenomenon of Linear Feed System Based on the Rigid-Flexible Coupling Model." Shock and Vibration 2021 (July 2, 2021): 1–11. http://dx.doi.org/10.1155/2021/9928733.

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A mathematical model of the creeping phenomenon based on the mechanical model of the linear feed system was established. The dynamic characteristic parameters of each fixed joint were obtained by Yoshimura’s integral. Using the method, only the dynamic characteristic parameters of the joint surface per unit area with simple structure need to be studied, and then, the dynamic characteristic parameters of the whole joint surface can be obtained by integration. Based on the principle of the half-power bandwidth method and the frequency response function identification, the dynamic parameters of each moving joint were solved by the method of experimental modal analysis. Through the parameters of the fixed and moving joints, a rigid body model of the feed system and a flexible body model including the power transmission parts (ball screw pair) and the motion guide parts (guide slide pair and rolling bearing) were, respectively, established. And then, a rigid-flexible coupling dynamic model of the feed system was obtained through the constraint relationships between joints. The influence of both the external load and the feed rate on the fluctuation of motion speed of the system was analyzed from this model. The difference between the experimental results and the simulation results on a feed system platform is not greater than 10%, which verifies the creeping phenomenon. This conclusion can provide a basis for the optimization of the dynamic performance of the ball screw linear-feeding workbench.

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Łabuński, Piotr, and Lucjan Witek. "EXPERIMENTAL ANALYSIS OF DAMPING PROPERTIES OF VISCOELASTIC MATERIALS." Acta Metallurgica Slovaca 27, no. 2 (June 1, 2021): 63–67. http://dx.doi.org/10.36547/ams.27.2.896.

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This study presents results of an experimental investigations of the materials used in passive damping vibrations. The main purpose of this paper was to examine the damping properties of selected viscoelastic materials (VEM), using the modal analysis. In presented analysis three configurations of specimens were considered. At first, the separated steel beam was analyzed. As results of this analysis, the frequencies and amplitudes of the beam during resonance were obtained. In next part of the work the modified specimen was investigated. In this modification the bitumen-based material (as a damper) was fixed to the surface of the beam. This method is known as free layer damping (FLD) treatment. In last configuration, the butyl rubber layer was connected to the steel beam. Using the Unholtz-Dickie UDCO-TA250 electrodynamic vibration system, the natural frequencies and amplitudes of free vibrations for all examined specimens were obtained. The vibration amplitude of the beam was measured using piezoelectric acceleration sensors. In order to define the damping capabilities of both the bitumen based material and the butyl rubber, the relative amplitude of specimens and the loss factor using half-power bandwidth method were calculated.

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Wang, Yilin, Shilei Li, Jie-Yun Yan, Chao Li, Ping Jiang, Lulu Wang, and Li Yu. "Bidirectional to unidirectional emission of fluorescence controlled by optical traveling wave antennas." Nanophotonics 8, no. 7 (July 15, 2019): 1271–78. http://dx.doi.org/10.1515/nanoph-2019-0121.

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AbstractTailoring the fluorescence emission of quantum emitters to a desired direction is a crucial issue to achieve high efficient photodetection and realize unique optoelectronic devices. In this study, the directional emission of quantum dots controlled by optical traveling wave antennas based on 1D silver nanowires (NWs) was investigated. Both leaky waves and surface waves on a single NW are utilized for fluorescence emission control, and we show that the coupled fluorescence transforms from bidirectional to unidirectional emission when the surrounding medium changes from air to water. Moreover, in the unidirectional case, we obtain an ultra-narrow half-power bandwidth about 20°. Finite-difference time-domain simulations and Green’s function method in a stratified medium are used to calculate the far-field emission patterns of the hybrid structures, which agree well with the experiments. Further analyses based on typical modes and the dipole-chain model also reveal the mechanism behind the bidirectional and unidirectional fluorescence emission. These results show that the structures have great potential in integrated on-chip, sensing and photon-collection devices.

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Armstrong, M. A., M. Ravasio, W. G. Versteijlen, D. J. Verschuur, A. V. Metrikine, and K. N. van Dalen. "Seismic inversion of soil damping and stiffness using multichannel analysis of surface wave measurements in the marine environment." Geophysical Journal International 221, no. 2 (February 14, 2020): 1439–49. http://dx.doi.org/10.1093/gji/ggaa080.

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SUMMARY Determination of soil material damping is known to be difficult and uncertain, especially in the offshore environment. Using an advanced inversion methodology based on multichannel spectral analysis, Scholte and Love wave measurements are used to characterize subsea soil from a North Sea site. After normalization, a determinant-based objective function is used in a genetic algorithm optimization to estimate the soil shear modulus. The inverted shear-modulus profile is comparable to previously published results for the same data, although a higher degree of certainty is achieved in the near-surface layers. The half-power bandwidth method is used for extracting the attenuation curve from the measurements and efficient reference data points are chosen based on wavelet compression. The material-damping ratio inversion is performed using a modified stochastic optimization algorithm. Accounting for measurement errors, the material-damping ratio profile is retrieved from the fundamental-mode Scholte wave with a high degree of certainty. Furthermore, a method is proposed for identifying the frequency dependence of the material-damping ratio from in situ measurements. No evidence for frequency dependence is found and the small-strain soil material-damping ratio at this site can be said to be frequency independent for the measured conditions.

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Tsai, Ming-Fa, Chung-Shi Tseng, and Po-Jen Cheng. "Implementation of an FPGA-Based Current Control and SVPWM ASIC with Asymmetric Five-Segment Switching Scheme for AC Motor Drives." Energies 14, no. 5 (March 7, 2021): 1462. http://dx.doi.org/10.3390/en14051462.

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This paper presents the design and implementation of an application-specific integrated circuit (ASIC) for a discrete-time current control and space-vector pulse-width modulation (SVPWM) with asymmetric five-segment switching scheme for AC motor drives. As compared to a conventional three-phase symmetric seven-segment switching SVPWM scheme, the proposed method involves five-segment two-phase switching in each switching period, so the inverter switching times and power loss can be reduced by 33%. In addition, the produced PWM signal is asymmetric with respect to the center-symmetric triangular carrier wave, and the voltage command signal from the discrete-time current control output can be given in each half period of the PWM switching time interval, hence increasing the system bandwidth and allowing the motor drive system with better dynamic response. For the verification of the proposed SVPWM modulation scheme, the current control function in the stationary reference frame is also included in the design of the ASIC. The design is firstly verified by using PSIM simulation tool. Then, a DE0-nano field programmable gate array (FPGA) control board is employed to drive a 300W permanent-magnet synchronous motor (PMSM) for the experimental verification of the ASIC.

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Asokan, Darvind, and Jawaid I. Inayat Hussain. "Loss Factor of Elastomeric Dampers for Rotating Machinery Application." International Journal of Engineering & Technology 7, no. 4.35 (November 30, 2018): 107. http://dx.doi.org/10.14419/ijet.v7i4.35.22337.

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Elastomeric dampers have potential application in rotating machinery vibration control. They are however not widely used due to lack of reliable data on their loss factor. Most available data on these dampers are obtained from testing undertaken during stationary condition of the shaft. When the shaft rotates, the dampers are subjected to rotating load that may affect their loss factor. The effect of shaft rotation on the loss factor is experimentally examined in this work. Impact test was used to determine the frequency response function (FRF) of the dampers. For the dampers subjected to rotating load, the loss factor values derived from the FRF was found to be in good agreement with those determined from the half-power bandwidth method. The results further showed that the loss factor at resonant frequency determined from testing of the dampers under stationary shaft condition underestimates the values of the loss factor when the shaft is rotating. The effect of shaft rotation on the values of the damper’s loss factor was more noticeable for the response in the X-direction as opposed to the Y-direction, indicating that pre-strain plays a more dominant role in influencing the loss factor of the dampers compared to the dynamic amplitude.

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Jiang, Shijie, Mingyu Sun, Yang Zhan, Hui Li, and Wei Sun. "A dynamic model of laminated material extrusion additive manufacturing plate with the property of orthogonal anisotropy." Rapid Prototyping Journal 27, no. 4 (May 21, 2021): 785–96. http://dx.doi.org/10.1108/rpj-04-2020-0075.

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Purpose The purpose of this study is to set up a dynamic model of material extrusion (ME) additive manufacturing plates for the prediction of their dynamic behavior (i.e. dynamic inherent characteristic, resonant response and damping) and also carry out its experimental validation and sensitivity analysis. Design/methodology/approach Based on the classical laminated plate theory, a dynamic model is established using the orthogonal polynomials method, taking into account the effect of lamination and orthogonal anisotropy. The dynamic inherent characteristics of the ME plate are worked out by Ritz method. The frequency-domain dynamic equations are then derived to solve the plates’ resonant responses, with which the damping ratio is figured out according to the half-power bandwidth method. Subsequently, a series of experimental tests are performed on the ME samples to obtain the measured data. Findings It is shown that the predictions and measurements in terms of dynamic behavior are in good agreement, validating the accuracy of the developed model. In addition, sensitivity analysis shows that increasing the elastic modulus or Poisson’s ratio will increase the corresponding natural frequency of the ME plate but decrease the resonant response. When the density is increased, both the natural frequency and resonant response will be decreased. Research limitations/implications Future research can be focused on using the proposed model to investigate the effect of processing parameters on the ME parts’ dynamic behavior. Practical implications This study shows theoretical basis and technical insight into improving the forming quality and reliability of the ME parts. Originality/value A novel reliable dynamic model is set up to provide theoretical basis and principle to reveal the physical phenomena and mechanism of ME parts.

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Sun, W. P., Y. H. Sun, Y. P. Yu, and B. S. Wu. "A Comparison of the Improved and Classic Half-Power Bandwidth Methods in Estimating Damping for Multi-DOF Systems." Journal of Vibration Engineering & Technologies 6, no. 3 (June 2018): 219–25. http://dx.doi.org/10.1007/s42417-018-0034-3.

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Zhang, Qi, Bihua Zhou, Jianbao Wang, and Cheng Gao. "Full-Wave Analysis of Field-to-Line Coupling Effects Using 1D FDTD Method under Exciting Source with Different Bandwidths." Mathematical Problems in Engineering 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/890181.

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With the aim to analyze field-to-line coupling effects based on energy spectrum, parallel finite-difference time-domain (FDTD) method is applied to calculate the induced voltage on overhead lines under high-power electromagnetic (HPEM) environment. Firstly, the energy distribution laws of HEMP (IEC 61000-2-9), HEMP (Bell Laboratory), HEMP (Paulino et al., 2010), and LEMP (IEC61000-4-5) are given. Due to the air-earth stratified medium, both the absorbing boundary and the connecting boundary applied to scattering by finite-length objects are separately set in aerial and underground parts. Moreover, the influence of line length on induced voltage is analyzed and discussed. The results indicate that the half-peak width is wider with the increase of the line length. But the steepness of induced voltage on the overhead line is invariable. There is no further increase in the peak of induced voltage especially when the line length increases to be equivalent to the wavelength of the frequency bands with the maximum energy.

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Shahbazi, Maryam, Amy B. Cerato, Shawn Allred, M. Hesham El Naggar, and Ahmed Elgamal. "Damping characteristics of full-scale grouped helical piles in dense sands subjected to small and large shaking events." Canadian Geotechnical Journal 57, no. 6 (June 2020): 801–14. http://dx.doi.org/10.1139/cgj-2018-0769.

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A full-scale pile testing program was implemented using the large outdoor shake table at the University of California – San Diego. Nine steel helical piles with varying geometry were embedded in dense sand and tested individually and in 2×2 groups, comparing fixed and pinned pile head connections. The test piles were subjected to shake motions ranging from pulses and white noise to replicated earthquakes. Strain gauges attached to the exterior pile walls and accelerometers placed on the pile caps and within the soil provided data for analyzing the behavior of these piles. Foundation damping (herein soil–pile system) is a substantial parameter in seismic design of the foundation–structure. Therefore, the damping characteristics of the soil bed along with the combined soil–pile system consisting of single and grouped helical piles are discussed based on the experimental pulse, white noise, and shake excitations. Several methods, including logarithmic decrement, half-power bandwidth, and energy (equivalent) methods, were implemented to estimate the damping ratio over a range of strains. Based on the experimental data gathered from this study, the suitability and accuracy of different computational methods to determine damping ratio as well as the effect of type and location of instrumentation on the calculated damping ratio were evaluated.

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Sengar, Kanchan, and Arun Kumar. "Fractional Order Capacitor in First-Order and Second-Order Filter." Micro and Nanosystems 12, no. 1 (January 21, 2020): 75–78. http://dx.doi.org/10.2174/1876402911666190821100400.

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Background: Fractional order Butterworth and Chebyshev (low-pass filter circuits, highpass filter circuits and band-pass filters circuits) types of first and second order filter circuits have been simulated and their transfer function are derived. The effect of change of the fractional order α on the behavior of the circuits is investigated. Objective: This paper presents the use of fractional order capacitor in active filters. The expressions for the magnitude, phase, the quality factor, the right-phase frequencies, and the half power frequencies are derived and compared with their previous counterpart. Methods: The circuits have been simulated using Orcad as well as MATLAB for the different value of α. We have developed the fractional gain and phase equations for low pass filter circuits, high pass filter circuits and band pass filter circuits in Sallen-Key topology. Results: It is observed that the bandwidth increases significantly with fractional order other than unity for the low pass as well as high pass and band pass filters. Conclusion: We have also seen that in the frequency domain, the magnitude and phase plots in the stop band change nearly linearly with the fractional order. If we compare the fractional Butterworth filters for low-pass and high-pass type with conventional filters then we find that the roll-off rate is equal to the next higher order filter.

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Su, Benyu, and Yasuhiro Fujimitsu. "Research on Heavy Oil Thermal Recovery by CO2 Steam Flooding with Help of Combination of Borehole-Surface Electric Potential and Cross-Borehole Electric Potential." Energy Exploration & Exploitation 29, no. 6 (December 2011): 797–815. http://dx.doi.org/10.1260/0144-5987.29.6.797.

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With an increasing tendency towards more demand for energy resources, the supply of energy as a focus of global strategy is attracting more and more attention from the world. However, on the one hand, conventional hydrocarbon resources are decreasing gradually, and therefore it is definitely an urgent task to search for renewable and replaceable resources at the present time. On the other hand, it has been proved that the total reserves of heavy oil are already up to 1105×108 tons around the world, which means that exploring heavy oil can be a beneficial supplement for alleviating the shortage of oil and gas. Moreover, it is noteworthy that because the heavy oil can be exploited by heated CO2, collecting and consuming CO2 during the production process will help to relieve global warming. In this study, we take the feasibility of heavy oil recovery by CO2 steam into consideration only from the viewpoint of geophysics. In the process of research, with the help of borehole-surface electric potential and cross-borehole electric potential, the entire procedures from heating heavy oil reservoir and optimizing the location of well to deciding the layer of perforation are exhibited completely. In the course of calculation, potential distributions corresponding to a point source of current are acquired by solving the Poisson equation using a direct and explicit finite difference technique for a lower half-space with 3-D distribution of conductivity. As for computation of a large sparse matrix, the technique of nonzero bandwidth storage and the Incomplete Cholesky Conjugate Gradient method are adopted. The consequences prove that with the assistance of cross-borehole electric potential combining with borehole-surface electric potential, the project of heavy oil recovery by CO2 steam is feasible and effective.

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Wang, Ivan. "An Analysis of Higher Order Effects in the Half Power Method for Calculating Damping." Journal of Applied Mechanics 78, no. 1 (October 8, 2010). http://dx.doi.org/10.1115/1.4002208.

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The half power method is a technique commonly used for calculating the system damping using frequency response curves. Past derivations typically assume a small damping ratio but do not keep track of the order of magnitude when simplifying results and focus mainly on displacement frequency response curves. This paper provides two separate and rigorous derivations of the half power bandwidth for displacement and acceleration frequency response functions. The exact expressions are simplified systematically using binomial expansions to include third order effects. The third order and classical approximations are compared with the exact expressions, and the truncation errors are presented for both displacement and acceleration cases. The high order effects are more apparent and the truncation errors are greater for the acceleration case. The classical method is sufficiently accurate for many practical cases where the damping ratio is less than 0.1 but higher order corrections may be used to reduce truncation error for systems where the damping ratio is higher.

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Gómez, S. S., and A. V. Metrikine. "The Energy Flow Analysis as a Tool for Identification of Damping in Tall Buildings Subjected to Wind: Contributions of the Foundation and the Building Structure." Journal of Vibration and Acoustics 141, no. 1 (September 10, 2018). http://dx.doi.org/10.1115/1.4040975.

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In this paper, the energy dissipated in a tall building is identified by means of the energy flow analysis. This approach allows assessing energy dissipation within a specific domain or element of the structure. In this work, the focus is placed on the superstructure, which is the part of the building above the ground, and on the foundation. Damping operators for the superstructure and the foundation are formulated based on the identified energy dissipation in these parts of the building. The obtained damping operators are used to compute the modal damping ratios in a simplified model of the building. The modal damping ratios of the three lowest modes of vibration are compared to those identified in full-scale measurements by means of the half-power bandwidth method.

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Tai, Wei-Che, Mingyi Liu, Yue Yuan, and Lei Zuo. "On Improvement of the Frequency Bandwidth of Nonlinear Vibration Energy Harvesters Using a Mechanical Motion Rectifier." Journal of Vibration and Acoustics 140, no. 5 (April 19, 2018). http://dx.doi.org/10.1115/1.4039534.

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This paper presents a broadband vibration energy harvester (VEH) which consists of a monostable Duffing oscillator connected to an electromagnetic generator via a mechanical motion rectifier. The mechanical motion rectifier converts the bidirectional vibratory motion of the oscillator induced by ambient environment vibrations into unidirectional rotation of the generator and causes the harvester to periodically switch between a large- and small-inertia system, resulting in nonlinearity in inertia. By means of analytical and numerical methods, this inertia nonlinearity is shown to have two advantages. First, it allows for more stiffness nonlinearity without inducing nonuniqueness of energy branches and enhances bandwidths of energy harvesting. The effect of mitigating nonuniqueness of energy branches occurs to steady-state and transient responses of the harvester and is experimentally verified by a prototype. The experimental results show a nearly 50% increase in the half power bandwidth via mechanical motion rectification (MMR). Second, it enlarges the basin of attraction of the high-energy branch when multiple energy branches are present. A numerical example shows that a more than 50% increase in the basin area can be achieved via MMR.

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"Cavity Backed Circular Half Mode SIW Array for Microwave Communications." International Journal of Innovative Technology and Exploring Engineering 9, no. 4 (April 10, 2020): 1741–45. http://dx.doi.org/10.35940/ijitee.f4706.049620.

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A two element array of circular shaped cavity backed substrate integrated waveguide (SIW) based antenna is proposed in this work. The elements are backed by a dielectric cavity of FR4 epoxy and fed by SIW slot coupling mechanism. Keeping the advantages of the conventional waveguides, the bandwidth of the radiation can be increased by choosing proper dimensions to the slots and circular patches. The two element array configuration in the design contributed to the comfortable uplift of the gain. The impedance matching is achieved by inserting a two arm power divider with pre-calculated dimensions. The accurate formulation of the electromagnetic problem of analyzing the SIW antenna is achieved by using integral equation based methods which can be solved numerically. The designed top layer of the antenna is analyzed with well known Method of Moments (MoM) and the results are compared. The functioning of the antenna is compared in terms of Return losses, radiation pattern and gain. The antenna exhibits 72% of bandwidth with peak gain of 4.2dB in the range of 4.4GHz to9.9GHz with the resonating frequency of 7.54GHz and well suited for C-band microwave communication applications.

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Aimer, Younes, Boubakar Seddik Bouazza, Smail Bachir, and Claude Duvanaud. "Shaping code in conjunction with DCT for PAPR reduction in multicarrier system." EURASIP Journal on Wireless Communications and Networking 2021, no. 1 (February 23, 2021). http://dx.doi.org/10.1186/s13638-021-01928-0.

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AbstractNonlinear behavior and power efficiency of the Power Amplifier (PA) contradictorily depend on the input signal amplitude distribution. The transmitted signal in multi-carrier modulation exhibits high Peak-to-Average Power Ratio (PAPR) and large bandwidths, leading to the degradation of the radio link and additional generation out-of-band interferences, which degrade the quality of the transmission. Practical solutions exist, like a power back-off, but with unacceptable efficiency performances of the transmitter. This paper deals with efficiency and linearity improvement using a new PAPR reduction method based on the combination of Discrete Cosine Transform and shaping technique. The main principle is to determine an optimal coding scheme according to a trade-off between coding complexity and performance benefits in the presence of PA nonlinearities. Simulation and experimental results in the context of OFDM signal and using a 20 W–3.7 GHz Radio-Frequency Power Amplifier show an improvement on PAPR reduction of about 3.25 dB. Also, the communication criteria like Bit Error Rate and Error Vector Magnitude are improved by about one decade and a half and $$8\%$$ 8 % , respectively.

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Moran, J. E., and D. S. Weaver. "On the Damping in Tube Arrays Subjected to Two-Phase Cross-Flow." Journal of Pressure Vessel Technology 135, no. 3 (May 21, 2013). http://dx.doi.org/10.1115/1.4023421.

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An experimental study was conducted to investigate the mechanism of damping in tube arrays subjected to two-phase cross-flow, mainly focusing on the influence of void fraction and flow regime. The model tube bundle had a parallel-triangular configuration, with a pitch ratio of 1.49. The two-phase flow loop used in this research utilized Refrigerant 11 as the working fluid, which better models steam-water than air-water mixtures in terms of vapour-liquid mass ratio as well as permitting phase changes due to pressure fluctuations. The void fraction was measured using a gamma densitometer, introducing an improvement over the homogeneous equilibrium model (HEM). Three different damping measurement methodologies were implemented and compared in order to obtain a more reliable damping estimate: the traditionally used half-power bandwidth, the logarithmic decrement and an exponential fitting to the tube decay response. The experiments showed that the half-power bandwidth produces higher damping values than the other two methods, due to the tube frequency shifting triggered by fluctuations in the added mass and coupling between the tubes, which depend on void fraction and flow regime. The exponential fitting proved to be the more consistent and reliable approach to estimating damping. A dimensional analysis was carried out to investigate the relationship between damping and two-phase flow related parameters. As a result, the inclusion of surface tension in the form of the capillary number appears to be useful when combined with the two-phase component of the damping ratio (interfacial damping). A strong dependence of damping on flow regime was observed when plotting the interfacial damping versus the void fraction, introducing an improvement over the previous results obtained by normalizing the two-phase damping, which does not exhibit this behavior.

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Journal articles on the topic 'Half-power bandwidth method'

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