kHz Frequency Research Articles

Comparison of conducted emissions due to electric vehicle charging processes under isolated and on-line conditions in the 9–500 kHz frequency range

This paper aims at comparing the conducted emissions generated by Electric Vehicle Charging Processes (EVCPs) under isolated and on-line conditions in the frequency and time domains, covering the 9–500 kHz frequency range. The isolated conditions correspond to the use of a Line Impedance Stabilization Network (LISN), whereas measurements in the Low Voltage (LV) grid where the EV is connected are referred to as on-line conditions. Regarding the frequency analysis, the results lead to conclude that different amplitude and spectral features of the Non-Intentional Emissions (NIEs) are measured depending on the measurement conditions, registering higher-amplitude NIEs when the measurements are conducted in the LV grid. Moreover, the paper also shows that the spectral characteristics of the NIEs correspond to tonal and narrowband emissions at specific frequencies in the 9–150 kHz frequency range, while background noise with low-amplitude emissions (in the case of isolated conditions) and colored noise (in the case of on-line conditions) are reported in the 150–500 kHz band. In the time domain, a periodic time-dependent behavior within the fundamental cycle of the mains (20 ms) is reported in all the analyzed cases, except for the tonal emissions with oscillating central frequency generated by a specific EV model. The time variability between both measurement configurations only differs by more than 3 dB for three out of the twelve analyzed EVCPs, where a higher variability is observed if the measurements are carried out using a LISN. As a conclusion, considering the differences in the frequency and time characteristics of the NIEs under isolated and on-line conditions, evaluating the emissions generated by EVCPs might lead to an underestimation of the NIEs in real LV grids.

Numerical study on temperature distribution during magnetic hyperthermia of different tumor tissues

In recent years, nanotechnology has made an invasion in biomedical applications which has gained much more attention because of its high efficiency and low side effects.One such applicationis magnetic hyperthermia (MHT) where magnetic nanoparticles (MNPs) are used to generate heat to kill the cancerous tissues over an alternating magnetic field.The heat generated by the nanoparticles is caused by hysteresis and Neel and Brownian relaxation.In this paper, a finite element method-based numerical modelling with the help of COMSOL is used to obtain temperature distribution on different tumor tissues (liver, lungs, and kidney) embedded with nanoparticles during magnetic hyperthermia by varying different magnetic field strengths (4000–6000 A/m), different frequencies (100–500 kHz) and different volume fractions of nanoparticles (0.1––0.5 %). Results show that at 500 kHz frequency, the temperature at the centre of the tumor is elevated marginally by 8 %, 4 %, and 2 % for the lungs, liver, and kidney respectively. Similarly, at 6000 A/m magnetic field strength, the temperature at the given point of tumor enhances moderately by 25 %, 14 %, and 8 % in the case of lungs, liver, and kidney respectively. The temperature at the same location increases majorly by 81 %, 45 %, and 20 % for the case of lungs, liver, and kidney respectively at 0.5 % volume fraction of nanoparticles. In the study, the effect of the volume fraction of nanoparticles on temperature rise is found to be more significant compared to other cases. The heat transfer rate is maximum in the lungs followed by the liver and kidney respectively.

Microencapsulation of Vitis vinifera grape pulp phenolic extract using maltodextrin and its application in gummy candy enrichment.

Phenolic extract of Vitis vinifera grape pulp was prepared using ultrasonication at frequencies of 28, 40, and 28-40 kHz with a 1:10, 1:15, and 1:20 ratio of solid (grape pulp) to water. The 1:10 ratio and 40 kHz frequency were considered optimal conditions for the preparation of red grape pulp extract (RGPE). Then, RGPE was encapsulated within maltodextrin using a spray drying technique, and the produced powder was used in the gummy candy production. The results revealed that the phenolic content of the powder was almost constant during the storage time. The solubility of the powder decreased, whereas its moisture content increased during the 45-day storage period. The results of scanning electron microscopy showed that the produced microparticles had spherical shapes with a micron size. Fourier-transform infrared spectroscopy and X-ray diffraction showed that RGPE was encapsulated in the structure of maltodextrin through the formation of hydrogen bonds, considering the amorphous structure of the powder. The antioxidant properties of the microencapsulated RGPE containing gummy candy were preserved. Sensory evaluation and colorimetric values of the enriched gummy candy had acceptable results compared to the control sample. In general, microencapsulation of RGPE within maltodextrin as a carrier using the spray drying technique and its application in gummy candy enrichment could be useful.

Frequency pushing enhanced by an exceptional point in an atom–cavity coupled system

We observed the frequency pushing of the cavity resonance as a result of the coupling of the cavity field with the ground state 138Ba in a high-Q cavity. A weak probe laser propagated along the axis of a Fabry–Pérot cavity while ground-state barium atoms traversed the cavity mode perpendicularly. By operating the atom–cavity composite in the vicinity of an exceptional point, we could observe a greatly enhanced frequency shift of the cavity transmission peak, which was pushed away from the atomic resonance, resulting in up to 41 ± 7 kHz frequency shift per atom from the empty cavity resonance. We analyzed our results by using the Maxwell–Schrödinger equation and obtained good agreement with the measurements.

The impact of the Cochlear™ Osia® 2 System on patients with mixed or conductive hearing loss: A comparison with Cochlear™ Baha® Attract System outcomes.

This prospective study assessed the efficacy of the Cochlear™ Osia® 2 System compared to the previous Baha® Attract System in patients with mixed or conductive hearing loss (MHL/CHL). In this prospective case-control study, 10 patients (2 men and 8 women) with MHL/CHL were implanted with the Osia® 2 System. Their audiological outcomes were compared with 13 patients (2 men and 11 women) who had previously been implanted with the transcutaneous Baha® Attract system. We compared the complications and compliance of the two groups. Also, in the Osia 2 System group, subjective satisfaction was assessed using the Korean version of the International Outcome Inventory for Hearing Aids (K-IOI-HA) questionnaire and the Abbreviated Profile of Hearing Aid Benefit (APHAB) questionnaire. Complications such as poor magnetization, pain & infection, and abnormal noise were more common in the Baha Attract group, although not statistically significant. Also, the Osia 2 group exhibited better compliance. Subjective satisfaction was assessed using the K-IOI-HA and APHAB questionnaires with the Osia 2 group, revealing significantly improved scores in ease of communication, reverberation, background noise, and higher K-IOI-HA scores post-implantation. Postoperative-aided thresholds with both systems were significantly lower than preoperative-unaided thresholds, with the Osia 2 System demonstrating notably high satisfaction levels. Although both systems showed similar preoperative and postoperative word-recognition scores, the Osia 2 System provided greater audiological gain, especially at 2 kHz and 4 kHz frequencies. Additionally, the functional gain of both systems was comparable across all frequencies. The Osia 2 System demonstrated high subjective satisfaction and improved audiological outcomes compared to the Baha Attract system in patients with conductive or mixed hearing loss. Its superior audiological gain, particularly at critical frequencies, along with better compliance, suggests it as a favorable option for this patient population.

Neural activity of retinal ganglion cells under continuous, dynamically-modulated high frequency electrical stimulation

Objective. Current retinal prosthetics are limited in their ability to precisely control firing patterns of functionally distinct retinal ganglion cell (RGC) types. The aim of this study was to characterise RGC responses to continuous, kilohertz-frequency-varying stimulation to assess its utility in controlling RGC activity. Approach. We used in vitro patch-clamp experiments to assess electrically-evoked ON and OFF RGC responses to frequency-varying pulse train sequences. In each sequence, the stimulation amplitude was kept constant while the stimulation frequency (0.5–10 kHz) was changed every 40 ms, in either a linearly increasing, linearly decreasing or randomised manner. The stimulation amplitude across sequences was increased from 10 to 300 µA. Main results. We found that continuous stimulation without rest periods caused complex and irreproducible stimulus-response relationships, primarily due to strong stimulus-induced response adaptation and influence of the preceding stimulus frequency on the response to a subsequent stimulus. In addition, ON and OFF populations showed different sensitivities to continuous, frequency-varying pulse trains, with OFF cells generally exhibiting more dependency on frequency changes within a sequence. Finally, the ability to maintain spiking behaviour to continuous stimulation in RGCs significantly reduced over longer stimulation durations irrespective of the frequency order. Significance. This study represents an important step in advancing and understanding the utility of continuous frequency modulation in controlling functionally distinct RGCs. Our results indicate that continuous, kHz-frequency-varying stimulation sequences provide very limited control of RGC firing patterns due to inter-dependency between adjacent frequencies and generally, different RGC types do not display different frequency preferences under such stimulation conditions. For future stimulation strategies using kHz frequencies, careful consideration must be given to design appropriate pauses in stimulation, stimulation frequency order and the length of continuous stimulation duration.

Chronic Toxoplasma gondii Infection Modulates Hearing Ability across the Adult Life Span.

While several studies have shown associations between hearing disorders and congenital toxoplasmosis, the present study investigated the impact of chronic, latent Toxoplasma gondii (T. gondii) infection on hearing loss. We used a regression analysis to explore whether latent T. gondii infection modulates changes in hearing thresholds over an age range from 20 to 70 years. We analyzed audiometric data of 162 T. gondii IgG-positive and 430 T. gondii-negative participants, collected in the Dortmund Vital Study (DVS, ClinicalTrials.gov Identifier: NCT05155397), a prospective study on healthy cognitive aging. The regression analysis indicated that latent toxoplasmosis was associated with an accelerated development in hearing loss over the observed age range. Hearing loss was less frequent in IgG-positive than in IgG-negative participants up to the age of about 40 for a low (0.125-1 kHz)-frequency range. For high (2-8 kHz) frequencies, this pattern reversed for ages above 65 years. We discuss these findings on hearing function in the context of a recently proposed model, suggesting that latent toxoplasmosis can differentially affect brain functions across a lifespan.

Rancang Bangun Alat Ukur Tingkat Manis Buah Jeruk Menggunakan Sensor Kapasitor Semi Silinder Berbasis Arduino

It has been realized the design of the orange based sweet level measuring device using an arduino based semi cylinder capacitor sensor. This study was conducted by providing input to the capacitor plates using an oscillator with a variety of frequency values of 10 KHz, 100 KHz, and 1 MHz. The oscillator used is the IC XR-2206 type. The sweet level of orange fruit is measured using a pocket refractometer otago pal-α. Semi cylinder capacitor sensor testing is carried out on 16 oranges. The most optimal measurement results are obtained in a 100 KHz frequency variation because the graph of the measurement results drops linearly. The voltage range at a frequency of 100 KHz is 200 - 2000 mV, with a brix value obtained between 13.8 - 16.7%. The higher the orange voltage, the lower the Brix value contained in oranges. Brix value 13.8 - 15.6% states the sweet level of orange fruit is sour, while the Brix value 16.7% states the sweet level of orange fruit is sweet. The results of testing the tool obtained an average error value of 0,004% and a tool accuracy value of 99,6%.

Harmonic Emission of Large PV Installations Case Study of a 1 MW Solar Campus

Extensive measurements were carried out at a 1 MW photovoltaic (PV) installation with focus on the analysis of harmonic emission both for classical harmonics below 2.5 kHz and higher frequency emission in the range of 2-150 kHz. The installation consists of multiple inverters with different rated power. Beside the measurement of total emission of all inverters, in one part of the measurement the inverters were switched off and on stepwise following a predefined schedule. This provides a comprehensive basis for a detailed characterisation of the interactions between the inverters in terms of harmonic emission. After a description of the measurement setup the paper discusses the total emission of the installation, the dependency of the emission on the supply voltage distortion and the potential of harmonic cancellation due to phase angle diversity between the different inverters. The results enable a better understanding of the harmonic emission behaviour of large PV installations. The paper is intended to be an contribution to the development and improvement of respective harmonic models.

Optimized designed [formula omitted]-shape impedance in voltage type [formula omitted]-Source inverter based on average modeling

The Z-source inverter is a desirable power converter topology for voltage source and current source converter applications, which is an exciting alternative for replacing the popular conventional type.This paper presents a novel method for designing voltage-type Z-Source inverters that are innovated based on good voltage source and DC-Link prerequisites such as its current and voltage value. This method is caused to reduce the size of the capacitor and inductor as well as the total cost of the converter, which is applicable in hybrid electric vehicle development. Z-Source inverter‘s output based on its input variables and effects has been investigated to propose to optimize the design/control method. State space equations are obtained, and its model is analyzed to illustrate how the undesired effects of these changes can be omitted or compensated. It has been used to optimize the designed parameters. A prototype experimental Z-Source inverter with a rated power of 500W and switching frequency of 20kHz is developed to demonstrate the validity of the design process. The Simulation and experimental results verify that the proposed method successfully optimizes the x-shape Impedance design.

Audiologic and vestibular assessment in children and adolescents with transfusion dependent beta thalassemia major: The era of deferasirox film coated tablet

BackgroundHearing impairment has frequently been described in β-thalassemia patients with a significant impact on the patients’ quality of life. Most studies provided evidence of deferoxamine (DFO) dose-related ototoxicity, however, the data is scarce regarding deferasirox (DFX) as a sole iron chelator. AimWe aimed to assess the prevalence and risk factors of sensorineural hearing loss (SNHL) and vestibular dysfunction in regularly transfused β-thalassemia patients who had been treated with DFX film coated tablets. MethodsWe conducted a case control study on 57 transfusion dependent β-thalassemia patients with a mean age of 15.3 years who received DFX FCT as monotherapy for at least one consecutive year, and 57 healthy age and sex-matching controls. Comprehensive audiological evaluations using pure tone audiometry (PTA) and transient evoked otoacoustic emission (TEOAE) as well as vestibular evaluation using Video-nystagmography (VNG) were done. ResultsSNHL was identified in 12 patients (21.1 %) using PTA and a statistically significant difference was detected between controls and patients at 6 KHz and 12 KHz frequencies. A higher incidence of SNHL was detected using TEOAE, 22 patients (43.1 %) failed to pass TEOAE, with a statistically significant decrease in the signal at frequencies 1, 4 KHz bilaterally and at frequencies 1.5, 2 KHz in the right ear compared to controls. Canal paresis was detected in 21 (36.8 %) of thalassemic children using bithermal caloric test with significantly more unilateral weakness than control children (P = 0.008). We found no significant correlation between audio-vestibular dysfunction and age, sex, serum ferritin, frequency of blood transfusion and dose of DFX FCT in thalassemic children. ConclusionWe conclude that the incidence of SNHL and vestibular dysfunction was high among transfusion dependent β-thalassemia patients. Therefore, we recommend performing pre-treatment baseline audio-vestibular assessment and yearly audio-vestibular monitoring to early detect high risk patients and initiate timely management to prevent permanent damage.

Dielectric Property, AC Conductivity, and Electric Modulus Studies of Pristine and Green‐Synthesized ZnO Nanoparticles

Frequency‐dependent dielectric constant and dielectric loss of pristine and green‐synthesized (using Tabernaemontana divaricata flower extract) ZnO nanoparticles (NPs) are studied at different temperatures. Below 1 kHz frequency and at temperatures above 100 °C, ZnO NPs have giant dielectric constant values (≈3 × 104). At lower frequencies and at/below 100 °C, the nature of temperature dependence of dielectric constant for pristine and green‐synthesized ZnO NPs are reversed, and this anomalous temperature dependence is correlated with the in‐plane and out‐of‐plane thermal expansions of ZnO. A temperature‐dependent poly‐dispersive relaxation mechanism in ZnO has been observed. The electrical conduction mechanism is found to be significantly modulated by the use of flower extract. The electric modulus study suggests similar mechanism of electrical conduction and dielectric polarization followed in these materials. A plausible growth mechanism of the ZnO NPs in presence of the flower extract is explored. Variations in the dielectric constant, dielectric loss, conductivity, and polarization mechanisms of the ZnO NPs are understood as signatures of the capping effect of the phytochemicals present in the flower extract on the crystal growth and formation of grain boundaries.

Development of a cost-effective compact diode-laser-based photoacoustic sensing instrument for breast tissue diagnosis.

The photoacoustic (PA) technique, a noninvasive pump-probe technique, has found interesting applications in biomedical tissue diagnosis over the last decade. To take it a step further to clinical applications, the PA technique needs to be designed as an instrument focusing on a compact design, reducing the cost, and quickly providing a quantitative diagnosis. This work presents a design and characterization of a cost-effective, compact PA sensing instrument for biomedical tissue diagnosis. A compact laser diode case design is developed to house several laser diodes for PA excitation, and a pulsed current supply unit is also developed in-house to power the laser diodes to generate a 25ns current pulse at a frequency of 20kHz. After PA experimental data acquisition, the signal's frequency spectra were calculated to characterize the tissue quantitatively and correlated with their mechanobiological properties. The corresponding dominant frequency peak in the PA spectral response (PASR) study was low in the fibrofatty normal breast tissue , compared to the dominant frequency peak of in the fibrocystic disease tissue, which had increased glandular and stromal elements, thereby increased tissue density. The histopathological findings correlated with the PASR results, and the fibrocystic breast disease tissue exhibited a higher dominant frequency peak and energy compared to the normal breast tissue. We experimented with an in vitro PASR study of fibrocystic human breast tissues and successfully differentiated different tissue types using quantitative spectral parameters peak frequency, mean frequency, and spectral energy. This gives the potential to take this technique further for cost-effective and quick clinical applications.

Lung disease detection using EasyNet

One of the major causes of deaths worldwide is the pulmonary diseases. There is an increasing need for an efficient technique that can automatically diagnose these diseases with high accuracy. In this paper, we propose a deep learning architecture to automatically detect pulmonary diseases. The raw pulmonary sound signals are taken from two popular datasets: ICBHI and KAUH datasets. These signals have diverse sampling frequencies of 4 kHz, 10 kHz or 44.1 kHz. The signals from KAUH dataset have a duration of minimum 5 s, while ICBHI signals have a duration of 10 to 90 s. These signals undergo pre-processing, which involves re-sampling them to a common 4 kHz frequency, and segmenting them into frames lasting 3 s. The frames are then normalized and passed to the proposed EasyNet model for training and classification. The EasyNet architecture contains only two convolution layers, which reduces the model complexity. The model’s performance is analyzed for both binary detection as well as multi-class detection. Our method performs well in all the considered evaluation scenarios, and yields an accuracy, sensitivity, and specificity of 1.0 for the KAUH dataset, while for the ICBHI dataset, an accuracy of 0.997, sensitivity of 0.999, and specificity of 0.997 is achieved. For the combined dataset, we have achieved an accuracy of 0.998, with a sensitivity and specificity of 0.999. These values are better than the existing state-of-the-art methods. The proposed architecture is quite simple yet effective in detecting lung diseases.

A Wide-Band Magnetoelectric Sensor Based on a Negative-Feedback Compensated Readout Circuit.

Magnetoelectric (ME) sensors cannot effectively detect broadband magnetic field signals due to their narrow bandwidth, and existing readout circuits are unable to vary the bandwidth of the sensors. To expand the bandwidth, this paper introduces a negative-feedback readout circuit, fabricated by introducing a negative-feedback compensation circuit based on the direct readout circuit of the ME sensor. The negative-feedback compensation circuit contains a current amplifier, a feedback resistor, and a feedback coil. For this purpose, a Metglas/PVDF/Metglas ME sensor was prepared. Experimental measurements show that there is a six-fold difference between the maximum and minimum values of the ME voltage coefficients in the 6-39 kHz frequency band for the ME sensor without the negative-feedback compensation circuit when the sensor operates at the optimal bias magnetic field. However, the ME voltage coefficient in this band remains stable, at 900 V/T, after the charge amplification of the direct-reading circuit and the negative-feedback circuit. In addition, experimental results show that this negative-feedback readout circuit does not increase the equivalent magnetic noise of the sensor, with a noise level of 240 pT/√Hz in the frequency band lower than 25 kHz, 63 pT/√Hz around the resonance frequency of 30 kHz, and 620 pT/√Hz at 39 kHz. This paper proposes a negative-feedback readout circuit based on the direct readout circuit, which greatly increases the bandwidth of ME sensors and promotes the widespread application of ME sensors in the fields of broadband weak magnetic signal detection and DBS electrode positioning.

Si/Ge phototransistor with responsivity >1000A/W on a silicon photonics platform.

In this article, we report a Si/Ge waveguide phototransistor with high responsivity and low dark current under low bias voltages, due to an engineered electric field distribution. The photodetector consists of n-i-p-i-n doping regions and shows a responsivity of 606 A/W at 1 V bias, and 1032 A/W at 2.8V bias with an input optical power of -50 dBm, and dark current of 4 µA and 42 µA respectively. This is achieved by placing two p+-doped regions in the silicon slab region beneath the Ge epitaxial layer. A measured small signal -3 dB bandwidth of 1.5 GHz with a -80 dBc/Hz phase noise response at 1 KHz frequency offset were demonstrated experimentally.

Efficient Metal Recovery from Industrial Wastewater: Potential Oscillation and Turbulence Mode for Electrochemical System

Efficient metal recovery from industrial wastewater facilitates addressing of the environmental hazards and resource requirements of heavy metals. The conventional electrodeposition recovery method is hampered by the limitations of interfacial ion transport in charge-transfer reactions, creating challenges for simultaneous rapid and high-quality metal recovery. Therefore, we proposed integrating a transient electric field (TE) and swirling flow (SF) to synchronously enhance bulk mass transfer and promote interfacial ion transport. We investigated the effects of the operation mode, transient frequency, and flow rate on metal recovery, enabling determination of the optimal operating conditions for rapid and efficient sequential recovery of Cu in TE&SF mode. These conditions included low and high electric levels of 0 and 4 V, a 50% duty cycle, 1 kHz frequency, and 400 L·h−1 flow rate. The kinetic coefficients of TE&SF electrodeposition were 3.5–4.3 and 1.37–1.97 times that of single TE and SF electrodeposition, respectively. Simulating the deposition process under TE and SF conditions confirmed the efficient concurrence of interfacial ion transport and charge transfer under TE and SF synergy, which achieved rapid and high-quality metal recovery. Therefore, the combined deposition strategy is considered an effective technique for reducing metal pollution and promoting resource recycling.

Stomata damage, photosynthesis, and transpiration evaluation of aquatic lirium after ultrasound irradiation

Purpose Evaluate the structural damage and the changes in the photosynthesis and transpiration rates of aquatic lirium leaves caused by ultrasound (US) irradiation in search of environmentally friendly methodologies for the control of this weed. Materials and methods Aquatic lirium plants were extracted from Xochimilco water canals in Mexico City. A part of the group of plants was selected for irradiation, and the rest formed the control group. The irradiation plants group was exposed to US irradiation of 17 kHz frequency and 30 W × 4 output power for 2 h, at noon and 25 °C room temperature. The structural analysis was done with a MOTICAM 1 digital camera, 800 × 600 pixels, incorporated into the MOTIC PSM-1000 optical microscope and edited with Motic Images Plus 2.0 ML software. The total stomata density and the damaged stomata density were determined by dividing the numbers of total and damaged stomata by the visual field area (67,917 mm2), respectively. The leaves’ photosynthesis and transpiration rates were measured using an LI-6400XT Portable Photosynthesis System. Results Significant damage was observed in the stomata and epidermal cells, finding that the average ratio between the damaged and total stomata densities as a function of time (days) showed an exponential increase described by a Box–Lucas equation with a saturation value near unity and a maximum rate of change of the density of damaged stomata on zero-day (immediately after irradiation), decreasing as the days go by. The transpiration rate showed a sudden increase during the first hour after irradiation, reaching a maximum of 36% of its value before irradiation. It then quickly fell during the next 6 days and more slowly until the 21st day, decreasing 79.9% of its value before irradiation. The photosynthetic rate showed similar behavior with a 37.7% maximum increment and a 73.6% minimum decrease of its value before irradiation. Conclusions The results of structural stomata damage on the ultrasound-irradiated aquatic lirium leaves are consistent with an excessive ultrasound stimulation on stomata’s mechanical operation by guard cells that produce the measured significant increase of the photosynthetic and transpiration rates during the first hour after irradiation. The initial high evaporation could alter the water potential gradient, with a possible generation of tensions in the xylem that could cause embolism in their conduits. The loss of xylem conductivity or hydraulic failure would be consistent with the observed significant fall in the photosynthesis and transpiration rates of the aquatic lirium leaves after its sudden rise in the first hour after irradiation.

Overall performance of Ni-Co-WC nanocomposite coatings prepared by ultrasonic vibration-assisted scanning jet electrodeposition

To obtain a high-performance Ni-Co-WC nanocomposite coating on 45# steel, this work proposed a novel ultrasonic vibration-assisted scanning jet electrodeposition and used the range of WC nanoparticles concentration (3-12 g/L) in the electrolyte as the key variable in this study. Through harmonic response analysis, a 31 kHz frequency ultrasonic transducer was selected as the vibration source to achieve better vibration effects. The type of current mode that we employed was DC mode. The influence of ultrasonic vibration and the concentration of WC nanoparticles in the electrolyte on the surface morphology, micro-texture, microhardness, adhesion, and corrosion resistance of the nanocomposite coating were investigated by using SEM, XRD, Vickers microhardness tester, scratch tester and electrochemical workstation respectively. Compared to conventional scanning jet electrodeposition, the results indicated that the ultrasonic vibration improved the surface morphology, mechanical properties, and corrosion resistance of the coating, with the hardness increased by 15.9 % and the adhesion strength increased by 76.1 % as well as the corrosion current density decreased by 13.0 %. When the WC concentration in the electrolyte was 6 g/L, the Ni-Co-WC nanocomposite coating prepared by ultrasonic vibration-assisted composite scanning jet electrodeposition exhibited the best surface quality and properties. The microhardness of the coating was the highest at 590 HV, the adhesion strength was the largest at 33.4 N and the corrosion current density was as low as 4.104 μA·cm−2. Compared with the WC concentration of 3 g/L, when the WC concentration was 6 g/L, the hardness increased by 7.8 %, the adhesion strength increased by 41.5 % whereas the corrosion current density decreased by 30.6 %. In addition, molecular dynamics simulation was employed to calculate the effect of WC content in the coating on the binding energy between the coating and the substrate. The simulation results confirmed that the adhesive strength between the composite coating and substrate was directly proportional to the WC content in the composite coating. Therefore, this research is of great significance for the protection of offshore platform support structure materials and the improvement of their service life.

Effect of polymerization on free water in polyacrylamide hydrogels observed with Brillouin spectroscopy.

Brillouin spectroscopy is used to determine the effects of polymer concentration, crosslinking density, and polymerization on the longitudinal storage and loss moduli of polyacrylamide hydrogels. The model established by Chiarelli et al. is implemented to calculate the speed of sound in the free water [Chiarelli et al., The Journal of the Acoustical Society of America, 2010, 127(3), 1197-1207]. The polymer concentration has the greatest effect on the moduli of the polymer matrix. We determined that the crosslink density has no measurable effect on the logitudinal storage or loss modulus of polyacrylamide hydrogels when measurements are made at GHz frequencies, in contrast to measurements made at kHz frequencies as documented by other studies. However, the moduli are independent of monomer concentration if the acrylamide is not polymerized. We show at the GHz frequency that the incorporation of acrylamide polymer chains affects the mechanical properties of the free water. The speed of sound in the free water is reduced by the introduction of polymerized acrylamide. The long polymer chains and their interactions with the bounded water disrupt the bonding organization of the unbound water, causing a reduction of the average hydrogen bond strength between free water molecules. This results in a decreased speed of sound in the free water and an increase in the longitudinal storage modulus of the hydrogel.