Research on Frequency Doubling Effect of Thermoacoustic Speaker Based on Graphene Film

In this work, the frequency doubling effect of thermoacoustic speakers is studied, and a method is analyzed to suppress the frequency doubling effect. Three cases were analyzed by superimposing the DC bias on the AC excitation: (1) DC is less than AC; (2) DC is equal to AC; (3) DC is greater than AC. We found that the frequency doubling effect can be well suppressed by superimposing a larger DC excitation on the AC excitation. The laser scribing technology was used to prepare graphene film in only one step, and the screen printing technology was used to prepare conductive electrodes. The microphone and B&K system was used to record the sound pressure level and study the suppression of frequency doubling effect. Finally, the sound pressure levels with the three different kinds of excitations were measured. The measured results show that they have a good agreement with the theoretical results. The suppression effect will be better when DC amplitude is greater than AC amplitude. Therefore, this work has certain reference significance for the further study and application of thermoacoustic speakers.

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Two-step computational aeroacoustics approach for underhood cooling fan application

INTER-NOISE and NOISE-CON Congress and Conference Proceedings ◽

10.3397/in-2021-2467 ◽

2021 ◽

Vol 263 (3) ◽

pp. 3615-3624

Author(s):

Parag Chaudhari ◽

Jose Magalhaes ◽

Aparna Salunkhe

Keyword(s):

Flow Field ◽

Sound Pressure ◽

Acoustic Analysis ◽

Air Flow ◽

Computational Aeroacoustics ◽

Noise Sources ◽

Fan Noise ◽

Cooling Fan ◽

Sound Pressure Levels ◽

One Step

Aeroacoustic noise is one of the important characteristics of the fan design. Computational Aeroacoustics (CAA) can provide better design options without relying on physical prototypes and reduce the development time and cost. There are two ways of performing CAA analysis; one-step and two-step approach. In one-step CAA, air flow and acoustic analysis are carried out in a single software. In two-step approach, air flow and acoustic analysis are carried out in separate software. Two-step CAA approach can expedite the calculation process and can be implemented in larger and complex domain problems. For the work presented in this paper, a mockup of an underhood cooling fan was designed. The sound pressure levels were measured for different installation configurations. The sound pressure level for one of the configurations was calculated with two-step approach and compared with test data. The compressible fluid flow field was first computed in a commercially available computational fluid dynamics software. This flow field was imported in a separate software where fan noise sources were computed and further used to predict the sound pressure levels at various microphone locations. The results show an excellent correlation between test and simulation for both tonal and broadband components of the fan noise.

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Electroanalytical Performance of Nitrogen-Doped Graphene Films Processed in One Step by Pulsed Laser Deposition Directly Coupled with Thermal Annealing

Materials ◽

10.3390/ma12040666 ◽

2019 ◽

Vol 12 (4) ◽

pp. 666 ◽

Cited By ~ 7

Author(s):

Florent Bourquard ◽

Yannick Bleu ◽

Anne-Sophie Loir ◽

Borja Caja-Munoz ◽

José Avila ◽

...

Keyword(s):

High Temperature ◽

Pulsed Laser Deposition ◽

Graphene Film ◽

Pulsed Laser ◽

Laser Deposition ◽

Synthesis Process ◽

Nitrogen Doped ◽

Nitrogen Doped Graphene ◽

Doped Graphene ◽

One Step

Graphene-based materials are widely studied to enable significant improvements in electroanalytical devices requiring new generations of robust, sensitive and low-cost electrodes. In this paper, we present a direct one-step route to synthetize a functional nitrogen-doped graphene film onto a Ni-covered silicon electrode substrate heated at high temperature, by pulsed laser deposition of carbon in the presence of a surrounding nitrogen atmosphere, with no post-deposition transfer of the film. With the ferrocene methanol system, the functionalized electrode exhibits excellent reversibility, close to the theoretical value of 59 mV, and very high sensitivity to hydrogen peroxide oxidation. Our electroanalytical results were correlated with the composition and nanoarchitecture of the N-doped graphene film containing 1.75 at % of nitrogen and identified as a few-layer defected and textured graphene film containing a balanced mixture of graphitic-N and pyrrolic-N chemical functions. The absence of nitrogen dopant in the graphene film considerably degraded some electroanalytical performances. Heat treatment extended beyond the high temperature graphene synthesis did not significantly improve any of the performances. This work contributes to a better understanding of the electrochemical mechanisms of doped graphene-based electrodes obtained by a direct and controlled synthesis process.

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Research on sound pressure level of graphene loudspeaker with AC and AC/DC excitation

Japanese Journal of Applied Physics ◽

10.7567/1347-4065/ab4692 ◽

2019 ◽

Vol 58 (11) ◽

pp. 116502

Author(s):

Debo Wang ◽

Jihao Xin ◽

Xingyue He ◽

Dong Zhang

Keyword(s):

Sound Pressure Level ◽

Sound Pressure ◽

Pressure Level ◽

Dc Excitation

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Fe3O4@L-arginine as a Reusable Catalyst for the Synthesis of Polysubstituted 2-Pyrrolidinones

Current Organocatalysis ◽

10.2174/2213337206666181211125226 ◽

2019 ◽

Vol 6 (1) ◽

pp. 61-68 ◽

Cited By ~ 1

Author(s):

Mohammad Ali Ghasemzadeh ◽

Mohammad Hossein Abdollahi-Basir ◽

Zahra Elyasi

Keyword(s):

Heterocyclic Compounds ◽

Structure Elucidation ◽

Reaction Times ◽

Biologically Active ◽

Reusable Catalyst ◽

Particle Sizes ◽

Magnetic Nanocatalyst ◽

Green Method ◽

One Step ◽

Good Agreement

Background: This research introduces an effective and green method for the synthesis of polysubstituted 2-pyrrolidinone derivatives as biologically-active heterocyclic compounds using multi- component reactions using Fe3O4@L-arginine as a reusable organocatalyst. Material and Method: The Fe3O4@L-arginine nanoparticles were prepared by a facile one-step approach and the structure elucidation of the magnetic nanocatalyst has been done using various spectroscopy techniques. Results: L-arginine-functionalized magnetite nanoparticles were obtained with particle sizes around 10 nm. Fe3O4@L-arginine exhibited strong catalytic activity to obtain some polysubstituted 2- pyrrolidinone. Conclusion: The considerable advantages of this research are short reaction times, excellent yields, simple workup procedure and reusability of the nanocatalyst which is in good agreement with green chemistry disciplines. The study on the reusability of the Fe3O4@L-arginine nanoparticles showed that the recovered catalyst could be reused six consecutive times.

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Discrete Frequency Noise From Lifting Fans

Journal of Engineering for Power ◽

10.1115/1.3445603 ◽

1971 ◽

Vol 93 (4) ◽

pp. 431-440

Author(s):

A. N. Abdelhamid

Keyword(s):

Sound Pressure ◽

Frequency Noise ◽

Noise Emission ◽

Aerodynamic Forces ◽

Fan Noise ◽

Unsteady Forces ◽

Discrete Frequency ◽

Unsteady Aerodynamic ◽

Noise Characteristics ◽

Good Agreement

Discrete frequency noise characteristics of a research lifting fan is investigated analytically. Based on steady aerodynamic data of the fan, unsteady aerodynamic forces acting on the rotor and stator blades were calculated using the results of previous investigators and an analysis which determines the effect of fluctuating velocity disturbance parallel to blade chord on the unsteady lift of cambered thin airfoils. The calculated unsteady forces were then used to determine the characteristics of discrete frequency noise emission from the fan. For the fan under consideration it is shown that the rotor interaction noise dominates the fan noise. Comparison between the predicted sound pressure levels and experimental observations shows good agreement. Based on the calculated detailed contributions of the different force harmonics acting on the blades to the fan noise, possible means of reducing lifting fan noise are discussed.

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R Dump Converter without DC Link Capacitor for an 8/6 SRM: Experimental Investigation

The Scientific World JOURNAL ◽

10.1155/2015/393629 ◽

2015 ◽

Vol 2015 ◽

pp. 1-13 ◽

Cited By ~ 2

Author(s):

Pasumalaithevan Kavitha ◽

Bhaskaran Umamaheswari

Keyword(s):

Torque Ripple ◽

Current Control ◽

Experimental Investigations ◽

Switched Reluctance ◽

Hysteresis Current Control ◽

Reluctance Motor ◽

Dc Excitation ◽

Sinusoidal Current ◽

Ac Excitation ◽

Control Constant

The objective of this paper is to investigate the performance of 8/6 switched reluctance motor (SRM) when excited with sinusoidal voltage. The conventional R dump converter provides DC excitation with the help of capacitor. In this paper the converter used is the modified R dump converter without DC link capacitor providing AC or sinusoidal excitation. Torque ripple and speed ripple are investigated based on hysteresis current control. Constant and sinusoidal current references are considered for comparison in both DC and AC excitation. Extensive theoretical and experimental investigations are made to bring out the merits and demerits of AC versus DC excitation. It is shown that the constructionally simple SRM can be favorably controlled with simple R dump converter with direct AC excitation without need for DC link capacitor. A 4-phase 8/6 0.5 kW SRM is used for experimentation.

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Noise Prediction for Multi-Element Airfoil Based on FW-H Equation

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.52-54.1388 ◽

2011 ◽

Vol 52-54 ◽

pp. 1388-1393

Author(s):

Jun Tao ◽

Gang Sun ◽

Ying Hu ◽

Miao Zhang

Keyword(s):

Flow Field ◽

Sound Pressure ◽

Near Field ◽

Pressure Level ◽

Aerodynamic Noise ◽

Noise Prediction ◽

Far Field ◽

Acoustic Analogy ◽

Acoustic Information ◽

Good Agreement

In this article, four observation points are selected in the flow field when predicting aerodynamic noise of a multi-element airfoil for both a coarser grid and a finer grid. Numerical simulation of N-S equations is employed to obtain near-field acoustic information, then far-field acoustic information is obtained through acoustic analogy theory combined with FW-H equation. Computation indicates: the codes calculate the flow field in good agreement with the experimental data; The finer the grid is, the more stable the calculated sound pressure level (SPL) is and the more regularly d(SPL)/d(St) varies.

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Evaluation of Bionike One-Step Tests for the Detection of Drugs of Abuse in Urine

Annals of Clinical Biochemistry International Journal of Laboratory Medicine ◽

10.1177/000456329703400111 ◽

1997 ◽

Vol 34 (1) ◽

pp. 74-80 ◽

Cited By ~ 7

Author(s):

E R S Brown ◽

D R Jarvie ◽

D Simpson

Keyword(s):

Mass Spectrometry ◽

Gas Chromatography ◽

Drugs Of Abuse ◽

Urine Samples ◽

Gas Chromatography Mass Spectrometry ◽

Site Testing ◽

Immunoassay Technique ◽

Or Groups ◽

One Step ◽

Good Agreement

Bionike one-step tests were used to screen urine samples for amphetamines, methamphetamines, benzodiazepines, cannabinoids, methadone and opiates, and results were compared with those obtained using enzyme multiplied immunoassay technique d.a.u. assays. Taking into consideration different threshold levels and possible differences in cross-reactivities, there was good agreement between the methods. Results of Bionike tests correlated well with amphetamines, methadone and opiates detected in urine using gas chromatography—mass spectrometry. Bionike methods are rapid, simple to use, and relatively inexpensive for on-site testing of individual drugs or groups of drugs in urine.

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Investigation of the Multielement Capability of Laser-Enhanced Ionization Spectrometry in Flames for Analysis of Trace Elements in Water Solutions

Applied Spectroscopy ◽

10.1366/0003702874868160 ◽

1987 ◽

Vol 41 (1) ◽

pp. 19-26 ◽

Cited By ~ 46

Author(s):

O. Axner ◽

I. Magnusson ◽

J. Petersson ◽

S. Sjöström

Keyword(s):

Trace Elements ◽

Detection Limit ◽

Trace Element Analysis ◽

Frequency Doubling ◽

Ultraviolet Region ◽

Element Analysis ◽

Coumarin 153 ◽

One Step ◽

Trace Elements In Water ◽

First Time

One-step Laser-Enhanced Ionization (LEI) spectrometry of 23 different elements in aqueous solutions has been performed in an acetylene/air flame. All elements were detected by light in the ultraviolet region, produced by frequency doubling of the output from the dye Coumarin 153. This was done in order to investigate the multielement capability of LEI in flames that has been made possible by the recent development of commercially available, widely tunable dyes. Among the elements detected, 9 (As, Au, In, Mn, Pb, Sb, Tl, W, Yb) show detection limits which are superior to those reported in the literature for one-step LEI. The lowest detection limit obtained in this investigation was 1 pg/mL for In. Four of the elements (As, Sb, Yb, W) are reported as being detected by LEI for the first time. The multielement capabilities of LEI as a method for trace element analysis are discussed.

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