High Frequency Energy Research Articles

High energy and high frequency electro-optic Q-switching laser with alternating output of energy amplitude

The high energy and high frequency electro-optic Q-switching laser with alternating output of energy amplitude was the first reported by the temporal delay of pulse energy in 1064 nm laser. The experimental schematic of the output 1064 nm laser with different trigger time were obtained when turn on the Q-switch on the 60 μs. When turn on the Q-switch on the 71 μs, the pulse energy of 1064 nm is distributed in a “high-low” pulse sequence: the pulse energy of the 1st was higher than 2nd, and the 2nd pulse energy was lower than the 3rd is formed repeatedly, when turn on the Q-switch on the 48 μs, the output process of the pulse laser is reversed. To the best of our knowledge, it is the first time to report the high energy and high frequency electro-optic Q-switching laser with alternating output of energy amplitude. In experiment a repetition rate of 100 kHz with a pulse width of 13 ns was achieved when the pump power was 24 J and the charging voltage is 650 V, the total output power of 0.8 J was obtained and the conversion efficiency is 0.3%. And the result of the photon density distributions and the inverse population by numerical calculations are basically agree with the experiment result.

Spectral Decay Parameter (k) of Western Iran Using Accelerograms Recorded up to 2018

An important parameter that controls strong ground motion at high frequencies (higher than 1 Hz) is the spectral decay or kappa (k) parameter. This parameter is a linear decay factor for Fourier spectrum of acceleration on a linear-logarithmic scale within a certain frequency range, which indicates the range of attenuation of high frequency energy. This parameter is used as a key input for the simulation of strong ground motion through a random method. This study aims to estimate the kappa parameter for the west of Iran that has a high seismic activity. Hence 10 reference earthquakes as well as 76 accelerograms recorded from 1973 until 2018 are used, including the 7.3-magnitude Ezgeleh, Kermanshah earthquake on November 12, 2017. The k is derived for the latest seismotectonic zoning map of Iran to enhance the accuracy of calculations and only the records in which the reference earthquake and accelerograms occurred in the same zone are considered in the k equation. The k parameter is calculated separately for each horizontal component and for the mean. Then, the linear relationships between the kappa and distance are separately calculated and analyzed for each seismic zone. An accumulative equation is also proposed for all zones. The presented equations indicate that the near surface attenuation parameter k0 for the west seismic zones of Iran varies from 0.0331 to 0.0398. This parameter can be used effectively to calculate the strong ground motion in the zones using synthetic methods.

Internal tidal currents and solitons in the southern Bay of Bengal

Tidal currents and higher-frequency internal solitons are observed from current and hydrographic fields that were recently measured at six deep-water moorings in the southern Bay of Bengal by the Naval Research Laboratory. Current, temperature and salinity were measured in the upper 500 m of the water column between December 2013 and August 2015. Harmonically-fitted (coherent) tidal currents, in the upper 500 m, showed maximum amplitudes for the M2 constituent, with velocities of the order of 3 cm s−1; M2 tidal ellipses were generally oriented towards the north-northeast. Incoherent internal tides accounted for at least 60% of the total semidiurnal tide energy. Solitons were generated at multiple source regions along the Andaman Islands and contribute significantly to the high frequency energy (greater than 1 cph). Solitons were present throughout the measurement period but their activity was reduced during the 2014–2015 winter monsoon. Soliton and internal-tide amplitudes show a fortnightly modulation, consistent with the spring-neap cycle of the semidiurnal tide. The interaction of tides and the associated high-frequency waves (20–40 min periods) with mesoscale eddies produced regions of enhanced shear and strain in the thermocline. High-strain regions were found within cyclonic eddies and high-shear regions were found within anticyclonic eddies. Shear-strain-based dissipation models indicate that mixing rates can be enhanced by a factor of 3–5 by tidal and higher frequencies during interactions with eddies. This study further suggests that tidal harmonics and internal tides have an important impact on the near-surface currents away from coastal boundaries, in the interior of the Bay of Bengal, while the effects of the depth-averaged tides are more important deeper in the water column.

Detailed analysis of two detected overlaying transient components within the echolocation beam of a bottlenose dolphin (Tursiops truncatus).

Dolphin echolocation clicks measured far off-axis contain two time-separated components. Whether these components overlap and appear as a single signal on axis has received little attention. Here, the scaled reassigned spectrogram analysis was used to examine if bottlenose dolphin (Tursiops truncatus) clicks measured near- or on-axis of the echolocation beam contained overlapping components. Across click trains, the number of overlapping components spatially varied within the echolocation beam. Two overlapping components were found to predominantly occur in the upper portion of the beam, whereas the lower portion of the beam predominantly contained a single component. When components overlapped, the trailing component generally had a higher center frequency and arrived less than 5 μs after the leading component. The spatial relationship of components was consistent with previous findings of two vertically distinct beam lobes with separated frequency content. The two components in the upper portion of the beam possibly result from a single transient click propagating through a geometrically dispersive media; specifically, the slower sound speed of the dolphin melon's core slightly delays the more directional, high frequency energy of the click, whereas the less directional, lower frequency energy propagates through more peripheral but higher sound speed portions of the melon.

Enhanced electrocatalytic activity of Pd and Pd-polyaniline nanoparticles on electrochemically exfoliated graphite sheets

The catalyst support materials play an important role in improving the performance of electrocatalysts for alcohol oxidation reaction. In this work, flexible graphite sheets containing a large number of edge planes were electrochemically exfoliated by the application of large positive and negative potentials in acetonitrile medium. The process described here produces several surface functional groups on graphite sheet surface. In this work, the utility of such a functionalized surface is explored as a solid support for depositing Pd and Pd-PANI nanostructures which are studied for oxidation of alcohols in alkaline medium. The results show that these electrode materials exhibit an excellent electrocatalytic activity with very high turnover frequency and low activation energy values for ethanol oxidation reaction that has the potential to be used in low temperature polymer membrane alkaline fuel cells.

Postural instability in an immersive Virtual Reality adapts with repetition and includes directional and gender specific effects

The ability to handle sensory conflicts and use the most appropriate sensory information is vital for successful recovery of human postural control after injury. The objective was to determine if virtual reality (VR) could provide a vehicle for sensory training, and determine the temporal and spatial nature of such adaptive changes. Twenty healthy subjects participated in the study (10 females). The subjects watched a 90-second VR simulation of railroad (rollercoaster) motion in mountainous terrain during five repeated simulations, while standing on a force platform that recorded their stability. The immediate response to watching the VR movie was an increased level of postural instability. Repeatedly watching the same VR movie significantly reduced both the anteroposterior (62%, p < 0.001) and lateral (47%, p = 0.001) energy used. However, females adapted more slowly to the VR stimuli as reflected by higher use of total (p = 0.007), low frequency (p = 0.027) and high frequency (p = 0.026) energy. Healthy subjects can significantly adapt to a multidirectional, provocative, visual environment after 4–5 repeated sessions of VR. Consequently, VR technology might be an effective tool for rehabilitation involving visual desensitisation. However, some females may require more training sessions to achieve effects with VR.

A High‐Frequency Distance Metric in Ground‐Motion Prediction Equations Based on Seismic Array Backprojections

AbstractTypical ground‐motion prediction equations (GMPEs) measure source‐to‐site distances relative to the closest point on the rupture plane (Rrup). However, for megathrust earthquakes (Mw &gt; 8), the oversimplification of the earthquake source characteristics in distance metrics results in significant bias. Recent studies suggest that the high‐frequency (HF) and low‐frequency (LF) energy tend to emanate from different portions of the megathrusts. This phenomenon motivates an alternative distance metric based on the array backprojection imaging technique that effectively captures regions releasing HF energy. Herein, we define an HF distance metric (Rhf) as the distance from the site to the high‐frequency radiation zone. We study five Mw &gt; 7.2 megathrust earthquakes in Japan and Chile and find that Rhf outperforms Rrup in predicting the ground shaking intensity between 0.5 and 4 Hz. We consider Rhf as a complementary measure to conventional GMPE distance metrics and a more accurate ground‐motion predictor in many cases.

Noble metal NPs and nanoalloys by sonochemistry directly processed on nanocarbon and TiN substrates from aqueous solutions

The sonochemical processing of nanomaterials in a solution is well established and has been advantageously used for a variety of nanomaterials and morphologies thereof. In general, high energy and high frequency ultrasound is applied to a solution containing the ionic species of the elements to be reduced as well as a certain amount of reducing chemicals. For further applications such as catalysis washing, filtering, dispersion and mounting on or mixing in a substrate are necessary. A sonochemical processing of nanomaterials directly on a substrate could make all these steps obsolete. Herein we show that noble metal and nanoalloy nanoparticles (NPs) can directly be processed on nanocarbon and titanium nitride surfaces using a simple ultrasound laboratory cleaner in aqueous solutions that are free from any reducing chemicals. The process is demonstrated on Au-NPs and nanoalloys of AuPd and PdPt which form a dense distribution on the substrate surface. To illustrate the catalytic activity of the NPs, the electrocatalytic performance of one AuPd-nanoalloy is demonstrated. The results are discussed in terms of reduction phenomena occurring at the interface between the ultrasonic cavitation and the substrate. We think that these reduction phenomena are mediated by the formation of reducing radicals at the substrate surface that are in turn driven by OH radicals from water sonolysis. Electrochemical current measurement at 0 V seem to support the existence of reducing currents during measurements under chopped ultrasound in an aqueous solution of HAuCl4 in comparison to measurements in water.

Feature Maps of the Acoustic Spectrum of the Voice

The change in the spectrum of sustained /a/ vowels was mapped over the voice range from low to high fundamental frequency and low to high sound pressure level (SPL), in the form of the so-called voice range profile (VRP). In each interval of one semitone and one decibel, narrowband spectra were averaged both within and across subjects. The subjects were groups of 7 male and 12 female singing students, as well as a group of 16 untrained female voices. For each individual and also for each group, pairs of VRP recordings were made, with stringent separation of the modal/chest and falsetto/head registers. Maps are presented of eight scalar metrics, each of which was chosen to quantify a particular feature of the voice spectrum, over fundamental frequency and SPL. Metrics 1 and 2 chart the role of the fundamental in relation to the rest of the spectrum. Metrics 3 and 4 are used to explore the role of resonances in relation to SPL. Metrics 5 and 6 address the distribution of high frequency energy, while metrics 7 and 8 seek to describe the distribution of energy at the low end of the voice spectrum.Several examples are observed of phenomena that are difficult to predict from linear source-filter theory, and of the voice source being less uniform over the voice range than is conventionally assumed. These include a high-frequency band-limiting at high SPL and an unexpected persistence of the second harmonic at low SPL. The two voice registers give rise to clearly different maps. Only a few effects of training were observed, in the low frequency end below 2 kHz. The results are of potential interest in voice analysis, voice synthesis and for new insights into the voice production mechanism.

Effects of Ultrasound and Green Synthesis ZnO Nanoparticles on Biogas Production from Olive Pomace

Agro-biomass residues can play a crucial role in promoting the fossil-fuel replacement in agro-food farms. Apulia, a region in Southern Italy, concentrates 22% of farms and 57% of total national olive and olive oil production, resulting the leader producer of the Country. So that, a high quantity of biomass (olive pomace) can be recovered from the milling process. This study investigates the biogas production that occurs during the anaerobic digestion of olive pomace by means of an ultrasound pre-treatment or by means of green synthesis of ZnO Nanoparticles mixed with olive pomace, in order to facilitate its digestion or co-digestion. Measurement of dry matter and biogas produced volume during the anaerobic process were investigated starting from 3-phase and 2-phase olive pomace by means of high specific energy and low frequency ultrasound values. The results highlight a promising influence of ultrasound pre-treatment useful at increasing the biogas yield of olive pomace.

Energy Spectrum of Stochastic Signals Caused by Variations of Electrical Resistance

The purpose of the study was to investigate the energy spectrum of stochastic signals caused by the fluctuations of electric resistance of the resistance coils, the metal film resistors and the encephalograms of patients. We have established that all energy spectra of the investigated stochastic signals contain a flicker component that in case of the metal film resistors depends on the defects of their inner structure. We have suggested the reason for the appearance of spectrum flicker-component in the energy spectrum of the stochastic signals of systems of different origin. This reason is the nonequilibrium state of the investigated system. We have shown that it is possible to calculate the flicker noise of the investigated system on any frequencies as well as the flicker noise power, using only two parameters: the value of energy spectrum on the middle and high frequencies (energy spectrum of the equilibrium system) and the relaxation time.

Improving the &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;${Q}$ &lt;/tex-math&gt; &lt;/inline-formula&gt;-Factor of Printed HF RFID Loop Antennas on Flexible Substrates by Condensing the Microstructures of Conductors

High frequency (HF) radio frequency identification (RFID) loop antennas are popular for HF RFID, energy transfer and near field communication applications. One of the major parameters defining the working range of HF RFID antennas is their ${Q}$ -factor. Printing techniques are the ideal method for mass fabrication of HF RFID loop antennas. However, due to the relatively low conductivity of the inks available on the market, the ${Q}$ -factor of the printed HF loop antenna tends to be low and in many cases, fails to meet the working range requirements. This paper reports two methods to condense the microstructures of the conductors in order to improve the ${Q}$ -factors of printed HF RFID loop antennas. Both thermal compression (pressing the sample at elevated temperature) and near-infrared annealing are studied, and the results have demonstrated that both approaches are efficient in improving the ${Q}$ -factors of printed loop antennas.

Non-unit transient based boundary protection for UHV transmission lines

Different from EHV transmission lines, the boundary of UHV transmission lines naturally consists of busbar stray capacitance, shunt reactor and/or series capacitor. The frequency characteristics of the UHV line boundaries with different structures are analyzed deeply, which have significant attenuation on both high frequency signal and low frequency signal. The attenuation is the inherent characteristic of UHV line boundary. Based on the UHV boundary characteristic, a novel boundary protection principle utilizing backward traveling wave is proposed. The fault direction is identified by means of the time-domain energy of the backward traveling wave. The high frequency energy and the low frequency energy of the backward traveling wave are extracted by wavelet transform, and then the forward internal and external faults are discriminated by the product of high frequency energy and low frequency energy. An adaptive setting calculation method in terms of fault type is presented, which is able to improve effectively the right discriminating rate for internal faults. The simulation model of Jindongnan-Nanyang-Jingmen UHV transmission project is established in ATP/EMTP. The simulation results show that the boundary protection possesses stable performance under various fault situations, and the operation time is less than 2 ms, which is appropriate as the non-unit ultra-high-speed protection element for UHV transmission lines.

Thermal effects of Ho: YAG laser lithotripsy: real-time evaluation in an in vitro model.

To evaluate the thermal effect of Ho:YAG laser lithotripsy in a standardized in vitro model via real-time temperature measurement. Our model comprised a 20ml test tube simulating the renal pelvis that was immersed in a 37°C water bath. Two different laser fibers [FlexiFib (15-45W), RigiFib 1000 (45-100W), LISA laser products OHG, Katlenburg-Lindau, Germany] were placed in the test tube. An Ho:YAG 100W laser was used in all experiments (LISA). Each experiment involved 120s of continuous laser application, and was repeated five times. Different laser settings (high vs. low frequency, high vs. low energy, and long vs. short pulse duration), irrigation rates (0 up to 100ml/min, realized by several pumps), and human calcium oxalate stone samples were analyzed. Temperature data were acquired by a real-time data logger with thermocouples (PICO Technology, Cambridgeshire, UK). Real-time measurements were assessed using MatLab®. Laser application with no irrigation results in a rapid increase in temperature up to ∆28K, rising to 68°C at 100W. Low irrigation rates yield significantly higher temperature outcomes. Higher irrigation rates result immediately in a lower temperature rise. High irrigation rates of 100ml/min result in a temperature rise of 5K at the highest laser power setting (100W). Ho:YAG laser lithotripsy might be safe provided that there is sufficient irrigation. However, high power and low irrigation resulted in potentially tissue-damaging temperatures. Laser devices should, therefore, always be applied in conjunction with continuous, closely monitored irrigation whenever performing Ho:YAG laser lithotripsy.

An Electrical Model of a Dielectric Elastomer Generator

Elastomer is an electroactive polymer, which finds popular application in the field of actuators and artificial muscles. Though elastomers are popularly used as actuators, with proper modification to their operating cycle, they can also be used as generators. These dielectric elastomer generators (DEGs), due to properties such as high energy density and frequency independent operation are suitable for different energy harvesting applications. In this letter, a simplified electrical model of the DEG is proposed, which can be used in various simulation platforms to verify compatibility of DEG with electrical circuits and predict its behavior. Detailed process of deriving the model parameters from a physical DEG is discussed at length. Performance of the proposed model is verified by comparing its behavior with a prototype DEG-based energy harvesting system having a DEG of 1.3 nF capacitance. The proposed DEG model was simulated with similar conditions and the simulation results have shown good accuracy with the experimental results.

Feature selection in froth flotation for production condition recognition

At present, a lot of features have been extracted to characterize the froth flotation, but there exist redundant and irrelevant features which may degrade the performance of a classifier and influence the production condition recognition. In this study, a feature selection strategy based on the minimal-redundancy-maximal-relevance criterion (mRMR) is used to find the most useful but less redundant features. Additionally, the least squares support vector machine (LSSVM) optimized by state transition algorithm is proposed to serve as the classifier in feature selection. It is found that hue and energy of high frequency play significant roles in classification of flotation froth images. Experimental results show the effectiveness of the proposed method.

Ureteroscopic Laser Lithotripsy: A Review of Dusting vs Fragmentation with Extraction.

Ureteroscopic laser lithotripsy is becoming the most commonly utilized treatment for patients with urinary calculi. The Holmium:YAG (yttrium aluminum garnet) laser is integral to the operation and is the preferred flexible intracorporeal lithotrite. In recent years, there has been increasing interest in examining the effect of varying the laser settings on the effectiveness of stone treatment. Herein, we review the two primary laser treatment approaches: dusting and fragmentation with extraction. We reviewed PubMed and MEDLINE databases from January 1976 through January 2017. All authors participated in the development of consensus definitions of dusting and fragmentation with extraction. The review protocol adhered to preferred reporting items for systematic reviews and meta-analyses (PRISMA) methodology. When the Holmium:YAG laser is used to treat stones, there are two parameters that can be adjusted: power (J) and frequency (Hz). In one treatment paradigm, which became termed "fragmentation with extraction," laser settings that relied on high energy and low frequency were used. Another paradigm, which became termed "dusting," utilized low energy and high frequency settings, which had the effect of breaking off exceedingly small fragments from the stone. Both dusting and fragmentation with extraction approaches to ureteroscopic stone treatment are effective. In fact, there is little evidence that one approach is better than the other. However, each does have relative advantages and disadvantages, which should be considered. Although dusting tends to be associated with shorter procedure times and a lower risk of ureteral damage, this approach may place the patient at increased risk for future stone events should all of the resultant debris not be expelled from the collecting system. The active removal associated with fragmentation with extraction, in contrast, may provide for a more complete initial stone clearance.

Investigation of an Electromagnetic Wearable Resonance Kinetic Energy Harvester With Ferrofluid

Human motion energy harvester can offer clean and continuous power, and therefore plays an important role in powering mobile devices, which suffer from short standby time because of the limited capability of the battery. In this paper, we investigate an electromagnetic resonance wearable kinetic energy harvester, which is comprised of an oscillator and a carbon fiber tube with two coils wound on its surface. The oscillator is comprised of a columnar PM connected to the two end covers with two elastic strings. The designed resonant frequency is 8-10 Hz, which is higher than the major frequency range of human motion (2-4 Hz), but it can absorb high frequency energy of impulse, such as footfall. Thus, the harvester can wear on legs to absorb the kinetic energy of footfall by resonance. The ferrofluid is adopted to decrease friction, which is one of the main challenges for improving efficiency of this type of energy harvester. The ferrofluid prevents the PM from touching the wall of the tube resulting in significant friction reduction. The FEM simulation results indicate that the ferrofluid can keep the vibrator (a permanent magnet) contactless even subjecting to ten times gravity acceleration. The maximum average output power of 9.5 mW is obtained with a total weight of 80.5 g when running at a speed of 10 km/h. A energy harvest circuit is carried out and an average power of 0.28 s can be stored.

Characterizing egg quality and larval performance from captive mahi-mahiCoryphaena hippurus(Linnaeus, 1758) spawns over time

Mahi-mahi Coryphaena hippurus is a promising species for aquaculture development and has been used as a model species for oil toxicology and physiology studies. This species has one of the fastest growth rates of any marine teleost and a unique reproductive biology due to its high spawning frequency and reproductive energy allocation. These characteristics lend the species to being an excellent model for understanding broodstock nutrition for other high energetic pelagic species. In this study, egg morphometrics and larval survival were tracked over a 10-week period from the initial capture of wild mahi-mahi broodstock. Larval quality from subsequent spawns collected over time was quantified using larval survival activity indices (SAIs) as a metric to assess egg quality. Larval SAIs were maintained and did not significantly decrease (p < .05) over the time course of this study. A multiple linear regression based on the elapsed time in captivity of the broodstock, egg diameter and larval SAI at 1 dph provided the most accurate prediction of larval SAI at 3 dph (R2 = 0.996 p < .05). There were strong positive correlations with larval SAIs at 1 and 3 dph and the key nutrients: eicosapentaenoic acid (C20: 5n-3, EPA) and related fatty acid ratios, vitamin E and nearly all amino acids under investigation. This study demonstrated that larval survival was maintained over time due to the supply of these key nutrients in the broodstock diet.

Speech produced in noise: Relationship between listening difficulty and acoustic and durational parameters.

Conversational speech produced in noise can be characterised by increases in intelligibility relative to such speech produced in quiet. Listening difficulty (LD) is a metric that can be used to evaluate speech transmission performance more sensitively than intelligibility scores in situations in which performance is likely to be high. The objectives of the present study were to evaluate the LD of speech produced in different noise and style conditions, to evaluate the spectral and durational speech modifications associated with these conditions, and to determine whether any of the spectral and durational parameters predicted LD. Nineteen subjects were instructed to speak at normal and loud volumes in the presence of background noise at 40.5 dB(A) and babble noise at 61 dB(A). The speech signals were amplitude-normalised, combined with pink noise to obtain a signal-to-noise ratio of -6 dB, and presented to twenty raters who judged their LD. Vowel duration, fundamental frequency and the proportion of the spectral energy in high vs low frequencies increased with the noise level within both styles. LD was lowest when the speech was produced in the presence of high level noise and at a loud volume, indicating improved intelligibility. Spectrum balance was observed to predict LD.