Development and Testing of a Kilohertz Solar-to-Acoustic Energy Converter

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Kuan Chen ◽  
Mohammed Albonaeem ◽  
Yeongmin Kim ◽  
Nam Jin Kim ◽  
Sang Hoon Lim ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Fresnel Lens ◽  
Pulse Frequency ◽  
Acoustic Energy ◽  
Sound Waves ◽  
Energy Converter ◽  
Low Frequencies ◽  
High Frequencies ◽  
The Relationship ◽  
Acoustical Energy

A thermal-to-acoustic energy converter (TAC) was developed and tested to produce sound waves in the kilohertz range directly from solar energy. The converter consisted of a glass window and a small amount of steel wool in the shape of a disk sealed in an aluminum housing. A Fresnel lens and a chopper wheel with 60 holes in it were employed to generate a pulsed sunbeam of approximately 200 sun intensity as the heat source of the TAC. Various designs and techniques were tested to improve the sound amplitude and signal-to-noise ratio of the converter at high frequencies. Reduction in air volume, better cooling, and improvement in air tightness were found to be effective in enhancing the sound amplitude. A shockproof mount commonly used in radio studios to reduce microphone vibration was essential in noise reduction for the TAC at high chopper wheel rotations. The sound amplitude was found to rapidly decrease with the increase in pulse frequency of the sunbeam at low frequencies. The relationship between the decibel value and frequency of the generated sound waves was changed to linear for sunbeam frequencies above 1 kHz. This is the frequency at which the penetration of surface temperature fluctuations into the aluminum housing becomes comparable with the aluminum housing thickness. At a given frequency, the sound amplitude increased almost exponentially with the increase in solar flux intensity. To the best of our knowledge, the 3 kHz sound frequency measured in our experiments is by far the highest frequency produced by a solar-to-acoustical energy converter.

Hearing loss in diabetics

1993 ◽  
Vol 107 (3) ◽  
pp. 179-182 ◽  
Author(s):  
J. R. Cullen ◽  
M. J. Cinnamond
Keyword(s):  
Hearing Loss ◽  
Sensorineural Deafness ◽  
Insulin Dosage ◽  
Speech Discrimination ◽  
Low Frequencies ◽  
High Frequencies ◽  
History Of ◽  
Insulin Dependent ◽  
Stapedial Reflex ◽  
The Relationship

The relationship between diabetes and senbsorineural hearing loss has been disputed. This study compares 44 insulin-dependent diabetics with 38 age and sex matched controls. All had pure tone and speech audiometry performed, with any diabetics showing sensorineural deafness undergoing stapedial reflecx decat tests. In 14 diabetics stapedial reflex tests showed no tone decay in any patient, but seven showed evidence of recruitment. Analysis of vaiance showed the diabetics to be significantly deafer than the control population.The hearing loss affected high frequencies in both sexes, but also low frequencies in the male. Speech discrimination scores showed no differences. Further analysis by sex showed the males to account for most of the differences. Analysys of the audiograms showered mostly a high tone loss. Finally duration of disbetes, insulin dosage and family history of diabtes were not found to have a significant effect on threshold.

Relations among Nightmare Frequency and Ego Strength, Death Anxiety, and Sex of College Students

1989 ◽  
Vol 69 (3-2) ◽  
pp. 1107-1113 ◽  
Author(s):  
Ross Levin
Keyword(s):  
Death Anxiety ◽  
Significant Negative Correlation ◽  
Anxiety Scale ◽  
Ego Strength ◽  
Low Frequencies ◽  
Men And Women ◽  
High Frequencies ◽  
Self Reports ◽  
Mediating Factor ◽  
The Relationship

The present study was designed to investigate empirically the relationship between self-reports of nightmare frequency and ego strength and death anxiety in both men and women. In addition, the interrelations among these variables were assessed. 20 undergraduates with high frequencies of nightmares and 20 with low frequencies (10 men and 10 women per group) were administered the Barron Ego Strength Scale and a death anxiety scale. Significant differences were found between nightmare groups on the Barron scale for men and women but none on the death anxiety scale either by nightmare frequency or sex. A significant negative correlation of -.47 between death anxiety and ego strength was found for women and in one high frequency group. Women with high frequencies of nightmares showed the highest correlation, -.83. These data suggest that nightmare frequency may be a mediating factor in the relationship between ego strength, death anxiety, and sex of subject.

scholarly journals Attenuation of sound in glacier ice from 2 to 35 kHz

2019 ◽  
Vol 13 (4) ◽  
pp. 1381-1394 ◽  
Author(s):  
Alexander Meyer ◽  
Dmitry Eliseev ◽  
Dirk Heinen ◽  
Peter Linder ◽  
Franziska Scholz ◽  
...  
Keyword(s):  
Physical Property ◽  
Sound Waves ◽  
Attenuation Length ◽  
Low Frequencies ◽  
Acoustic Damping ◽  
High Frequencies ◽  
Systematic Uncertainties ◽  
Glacier Ice

Abstract. The acoustic damping of sound waves in natural glaciers is a largely unexplored physical property that has relevance for various applications. We present measurements of the attenuation of sound in ice with a dedicated measurement setup in situ on the Italian glacier Langenferner from August 2017. The tested frequency ranges from 2 kHz to 35 kHz and probed distances between 5 m and 90 m. The attenuation length has been determined by two different methods including detailed investigations of systematic uncertainties. The attenuation length decreases with increasing frequencies. Observed values range between 13 m for low frequencies and 5 m for high frequencies. The presented results improve in accuracy with respect to previous measurements. However, the observed attenuation is found to be remarkably similar to observations at very different locations.

Relations among Nightmare Frequency and Ego Strength, Death Anxiety, and Sex of College Students

1989 ◽  
Vol 69 (3_suppl) ◽  
pp. 1107-1113 ◽  
Author(s):  
Ross Levin
Keyword(s):  
Death Anxiety ◽  
Significant Negative Correlation ◽  
Anxiety Scale ◽  
Ego Strength ◽  
Low Frequencies ◽  
Men And Women ◽  
High Frequencies ◽  
Self Reports ◽  
Mediating Factor ◽  
The Relationship

The present study was designed to investigate empirically the relationship between self-reports of nightmare frequency and ego strength and death anxiety in both men and women. In addition, the interrelations among these variables were assessed. 20 undergraduates with high frequencies of nightmares and 20 with low frequencies (10 men and 10 women per group) were administered the Barron Ego Strength Scale and a death anxiety scale. Significant differences were found between nightmare groups on the Barron scale for men and women but none on the death anxiety scale either by nightmare frequency or sex. A significant negative correlation of −.47 between death anxiety and ego strength was found for women and in one high frequency group. Women with high frequencies of nightmares showed the highest correlation, −.83. These data suggest that nightmare frequency may be a mediating factor in the relationship between ego strength, death anxiety, and sex of subject.

scholarly journals The construction and testing of an acoustic energy harvester consisting of a Helmholtz resonator and a loudspeaker

2020 ◽  
Vol 4 (1) ◽  
pp. 8
Author(s):  
Ikhsan Setiawan ◽  
Mulaiyinatus Sifa
Keyword(s):  
Energy Harvester ◽  
Helmholtz Resonator ◽  
Acoustic Energy ◽  
Sound Waves ◽  
Low Frequencies ◽  
Resonator Cavity ◽  
Alternating Electric Current ◽  
Load Resistor ◽  
Inner Diameter ◽  
Frequency Variations

Sound energy is all around but not properly utilized despite being a source of electricity. This research was conducted to construct and test an acoustic energy harvester consisting of a Helmholtz resonator and a loudspeaker. The resonator cavity was made of 10 mm-thick cube-shaped acrylic plates with an inner side length of 300 mm while its neck was made of PVC (polyvinyl chloride) pipes with an inner diameter of 55 mm and three length variations at 50 mm, 70 mm, and 90 mm. A 6-inch subwoofer loudspeaker was mounted on the resonator back wall facing the cavity with its terminals connected to a 100-ohm load resistor. The sound waves entering the resonator cavity through the neck were converted into the alternating electric current flowing through the resistor. The test was conducted experimentally by exposing the harvester to sound waves at a maximum sound pressure level (SPL) of 100 dB and frequency variations from 25 Hz to 200 Hz. The root-mean-square (rms) voltages across the resistor were measured to calculate the output rms values for electric power. The results showed seven spectrum peaks which appeared at frequencies of 31 Hz, 37 Hz, 41 Hz, 49 Hz, 58 Hz, 73 Hz, and 82 Hz. Moreover, a shorter neck was also observed to have produced higher output power as indicated by the highest value of 2.75 mW obtained by using a 50 mm-long resonator neck at 37 Hz frequency and 100 dB SPL. These findings showed the acoustic energy harvester used to be effective due to its ability to produce electricity even at low frequencies below 100 Hz.

scholarly journals The Potential of Cylindrical Piezoelectric Transducers for High-Frequency Acoustic Energy Harvesting

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5845
Author(s):  
Shehab Salem ◽  
Karel Fraňa ◽  
Iva Nová
Keyword(s):  
Energy Harvesting ◽  
Lead Zirconate Titanate ◽  
High Frequency ◽  
Lead Zirconate ◽  
Open Circuit ◽  
Piezoelectric Transducers ◽  
Acoustic Energy ◽  
Sound Waves ◽  
Acoustic Energy Harvesting ◽  
The Relationship

The work presented in this paper studies the potential of cylindrical piezoelectric transducers for harvesting high-frequency acoustic energy. The cylinder was made of a modified PZT (lead zirconate titanate) and had the shape of a squared cylinder with a side length of 4 cm and a wall thickness of 1 mm. The study used open-circuit measurements to study the relationship between the sound wavelength and the cylinder size and its effect on the performance of energy harvesting. The cylinder was found to give the best performance at a frequency of 20 kHz. In addition to open-circuit measurements, closed-circuit measurements were performed to demonstrate the ability to dissipate energy harvested from 20 kHz sound waves across an electric load. The load was designed in a series of experimental steps that aimed at optimizing an impedance-matched energy harvester. Finally, the cylinder was tested at the optimized load conditions, and it was possible to harvest and store energy with a power of 67.6 μW and harvesting efficiency of 86.1%.

scholarly journals Clarifying the relationship between efficiency and resonance for flexible inertial swimmers

2018 ◽  
Vol 853 ◽  
pp. 271-300 ◽  
Author(s):  
Daniel Floryan ◽  
Clarence W. Rowley
Keyword(s):  
Travelling Wave ◽  
Power Coefficient ◽  
Mass Ratio ◽  
Eigenvalues And Eigenfunctions ◽  
Trailing Edge ◽  
Thrust Coefficient ◽  
Low Frequencies ◽  
High Frequencies ◽  
Wave Kinematics ◽  
The Relationship

We study a linear inviscid model of a passively flexible swimmer, calculating its propulsive performance, eigenvalues and eigenfunctions with an eye towards clarifying the relationship between efficiency and resonance. The frequencies of actuation and stiffness ratios we consider span a large range, while the mass ratio is mostly fixed to a low value representative of swimmers. We present results showing how the trailing edge deflection, thrust coefficient, power coefficient and efficiency vary in the stiffness–frequency plane. The trailing edge deflection, thrust coefficient and power coefficient show sharp ridges of resonant behaviour for mid-to-high frequencies and stiffnesses, whereas the efficiency does not show resonant behaviour anywhere. For low frequencies and stiffnesses, the resonant peaks smear together and the efficiency is high. In this region, flutter modes emerge, inducing travelling wave kinematics which make the swimmer more efficient. We also consider the effects of a finite Reynolds number in the form of streamwise drag. The drag adds an offset to the net thrust produced by the swimmer, causing resonant peaks to appear in the efficiency (as observed in experiments in the literature).

scholarly journals A Bootstrap Method to Test Granger-Causality in the Frequency Domain

2021 ◽  
Author(s):  
Matteo Farnè ◽  
Angela Montanari
Keyword(s):  
Stochastic Process ◽  
Frequency Domain ◽  
Granger Causality ◽  
Bootstrap Method ◽  
Money Stock ◽  
Bootstrap Test ◽  
Low Frequencies ◽  
Economic Output ◽  
Stationary Bootstrap ◽  
The Relationship

AbstractWe propose a bootstrap test for unconditional and conditional Granger-causality spectra in the frequency domain. Our test aims to detect if the causality at a particular frequency is systematically different from zero. In particular, we consider a stochastic process derived applying independently the stationary bootstrap to the original series. At each frequency, we test the sample causality against the distribution of the median causality across frequencies estimated for that process. Via our procedure, we infer about the relationship between money stock and GDP in the Euro Area during the period 1999–2017. We point out that the money stock aggregate M1 had a significant impact on economic output at all frequencies, while the opposite relationship is significant only at low frequencies.

Effect of Blowing Agent on Cell Morphology and Acoustic Absorption of Natural Rubber Foam

2015 ◽  
Vol 804 ◽  
pp. 25-29 ◽  
Author(s):  
Wanlop Harnnarongchai ◽  
Kantima Chaochanchaikul
Keyword(s):  
Natural Rubber ◽  
Cell Size ◽  
Cell Morphology ◽  
Foam Cell ◽  
Adsorption Coefficient ◽  
Low Frequencies ◽  
Potassium Oleate ◽  
High Frequencies ◽  
Blowing Agent ◽  
Open Cell Foam

The sound absorbing efficiency of natural rubber (NR) foam is affected by the cell morphology of foam. Potassium oleate (K-oleate) and sodium bicarbonate (NaHCO3) were used as blowing agents to create open-cell foam. Amounts of the blowing agent were varied from 0.5 to 8.0 part per hundred of rubber (phr) to evaluate cell size and number of foam cell as well as sound adsorption coefficient of NR foam. The NR foam specimens were prepared using mould and air-circulating oven for vulcanizing and foaming processes. The results indicated that K-oleate at 2.0 phr and NaHCO3 at 0.5 phr led to form NR foam with the smallest cell size and the largest number of foam cell. At low frequencies, the optimum sound adsorption coefficient of NR foam was caused by filling K-oleate 2 phr. However, that of NR foam at high frequencies was provided by 0.5 phr-NaHCO3 addition.

Reproductive hormone secretion and spermatogenic function in thyroidectomized rams receiving graded doses of exogenous thyroxine

1986 ◽  
Vol 111 (2) ◽  
pp. 245-253 ◽  
Author(s):  
Y. Chandrasekhar ◽  
M. J. D'Occhio ◽  
B. P. Setchell
Keyword(s):  
Hormone Secretion ◽  
Reproductive Function ◽  
Pulse Frequency ◽  
Endocrine Function ◽  
Sex Hormone Binding Globulin ◽  
Testosterone Levels ◽  
Reproductive Endocrine ◽  
Lh Release ◽  
Lh Releasing Hormone ◽  
The Relationship

ABSTRACT This study aimed to obtain a better understanding of the relationship between circulating thyroxine (T4) concentrations and reproductive endocrine function in the ram. Mature Merino rams were thyroidectomized and supplemented with 0, 30, 100 and 300% of normal T4 for 10 weeks. Thyroidectomy had no apparent effect on spermatogenic function but interfered with sperm maturation, the latter being returned to normal by 30% T4 replacement. Circulating testosterone levels were reduced by thyroidectomy and restored to control levels by 30% T4; when T4 levels were supranormal (300%), circulating testosterone levels were again reduced. The lowered circulating testosterone levels in thyroidectomized rams occurred as a result of suppressed testosterone secretion from the testis, observed under basal conditions and also following LH-releasing hormone (LHRH) and human chorionic gonadotrophin injection. In thyroidectomized rams, sex hormone binding globulin (SHBG) levels were depressed without changes in testosterone clearance rate (TCR), while in rams with supranormal T4 levels, TCR was increased without changes in SHBG levels. Subnormal levels of T4 also restored to normal the reduced LH pulse frequency in thyroidectomized rams. Reduced LH pulse frequency, together with diminished LH release following LHRH injection in thyroidectomized rams, suggested effects of T4 at the hypothalamo-pituitary axis. The present study demonstrates that complete lack of thyroid hormones suppresses normal reproductive endocrine function in the ram, but that this can be restored to normal by 30% T4 replacement. The results support the theory that T4 plays a permissive rather than a regulatory role in reproductive function in males. J. Endocr. (1986) 111, 245–253

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