Effects Of Different Frequencies Research Articles

Lift-Off Effect of Koch and Circular Differential Pickup Eddy Current Probes

A flexible or planar eddy current probe with a differential structure can suppress the lift-off noise during the inspection of defects. However, the extent of the lift-off effect on differential probes, including different coil structures, varies. In this study, two planar eddy current probes with differential pickup structures and the same size, Koch and circular probes, were used to compare lift-off effects. The eddy current distributions of the probes perturbed by 0° and 90° cracks were obtained by finite element analysis. The analysis results show that the 90° crack can impede the eddy current induced by the Koch probe even further at relatively low lift-off distance. The peak-to-peak values of the signal output from the two probes were compared at different lift-off distances using finite element analysis and experimental methods. In addition, the effects of different frequencies on the lift-off were studied experimentally. The results show that the signal peak-to-peak value of the Koch probe for the inspection of cracks in 90° orientation is larger than that of the circular probe when the lift-off distance is smaller than 1.2 mm. In addition, the influence of the lift-off distance on the peak-to-peak signal value of the two probes was studied via normalization. This indicates that the influence becomes more evident with an increase in excitation frequency. This research discloses the lift-off effect of differential planar eddy current probes with different coil shapes and proves the detection merit of the Koch probe for 90° cracks at low lift-off distances.

Acoustic scattering characteristics of underwater buried oil pipeline

With the development of offshore oil resources, subsea oil pipelines have emerged. As a fast, economical, and safe way to transport oil resources, subsea pipelines are known as the “lifeline” of offshore oil projects. However, the detection of submarine pipelines is very difficult due to the complex underwater environment. One of the mainstream methods to detect submarine pipelines is the employment of sonar. Hence, the acoustic scattering characteristics of submarine pipelines play an important role in detecting themselves. In this study, the acoustic scattering model of the buried pipeline is established using the finite element method, and the scattering mechanism of the buried pipeline is analyzed. The effects of different frequencies, grazing angles, burial depth, and other factors on the acoustic scattering characteristics of the buried pipeline are investigated, providing the reference significance for detecting submarine pipelines.

Low-frequency band noise generated by industrial recirculating aquaculture systems exhibits a greater impact on Micropterus salmoidess

The effect of underwater noise environment generated by equipment in industrial recirculating aquaculture systems (RAS) on fish is evident. However, different equipment generate noise in various frequency ranges. Understanding the effects of different frequency ranges noise on cultured species is important for optimizing the underwater acoustic environment in RAS. Given this, the effects of underwater noise across various frequency bands in RAS on the growth, physiology, and collective behavior of juvenile largemouth bass (Micropterus salmoides) were comprehensively evaluated here. In this study, three control groups were established: low-frequency noise group (80–1000 Hz, 117 dB re 1μPa RMS), high-frequency noise group (1–19 kHz, 117 dB re 1μPa RMS), and ambient group. During a 30-day experiment, it was found that: 1) industrial RAS noise with different frequency bands all had a certain inhibitory effect on the growth of fish, which the weight gain rate and product of length and depth of caudal peduncle in the ambient group were significantly higher than those of the two noise groups, with the low-frequency noise group showing significantly lower values than the high-frequency noise group; 2) industrial RAS noise had a certain degree of adverse effect on the digestive ability of fish, with the low-frequency noise group being more affected; 3) industrial RAS noise affected the collective feeding behavior of fish, with the collective feeding signal propagation efficiency and feeding intensity of the noise groups being significantly lower than those of the ambient group, and the high-frequency noise group performing better than the low-frequency noise group as a whole therein. From the above, the underwater noise across different frequency bands generated by equipment operation in industrial RAS both had an impact on juvenile largemouth bass, with the low-frequency noise group being more severely affected.

BORS/BJR TRAVELLING FELLOWSHIP: A COMPARISON OF THE EFFECTS ON BONE TISSUE OF TWO ULTRASONIC CUTTING DEVICES OPERATING AT DIFFERENT FREQUENCIES

AbstractIntroductionUltrasonic cutting in surgery has great potential. However, a key limitation is heat created by friction between the bone and the blade. Bone has poor thermal conductivity which hinders the dissipation of heat, causing cell death near the cut site In addition, ultrasonic vibration may create microcracks. It was hypothesised that these effects on bone would vary with the frequency and displacement of the ultrasonically powered blade. Therefore varying frequencies and displacements of the tip of the blade were studied to find the combination with fewest microcracks and lowest temperature rise at the bone-tool interface.AimTo explore the effect of different frequencies and tip displacements of ultrasonic cutting devices on the amount of thermal and mechanical damage.MethodsIn vitro tests were conducted on fresh rat femoral shafts using two different frequencies; 20kHz and 35kHz.Two displacement amplitudes of two different frequencies were used: 23.9 μm (p-p) and 7.5 μm (p-p) both at 20kHz and 18.7 μm (p-p) and 27 μm (p-p) both at 35kHz and. Cooling was used to emulate clinical conditions. Histological examination (H & E and TUNEL) was performed to identify live and dead cells. Further rat femoral shafts (n=6) were exposed to the same number of cuts by each tool to identify any micro-damage induced by different electrical currents using Micro-CT and confocal Laser scanning microscope. All experimental data were expressed as mean ± standard deviation. Statistical analysis was performed using one-way ANOVA, followed by Post Hoc multiple comparisons test. Differences between groups were considered statistically significant at p < 0.05.ResultsThe cut site at 7.5 μm (p-p) in 20kHz displayed only indentation instead of a cut, and was excluded. Histological examination revealed a high incidence of cell death at the cutting edge, in both frequencies. At 35kHz and 27 μm (p-p) some charring was evident, while at 20kHz and 23.9 μm (p-p) more irregularities were seen on the surface of the cut indicating instability during cutting when this setting was used. In contrast, the 35kHz at 18.7 μm (p-p) resulted in a smoother cutting surface. The highest cell death percentage ranged from 25% (at 35kHz, 18.7 μm (p-p)) to 44 % (at 35kHz, 27 μm (p-p)). Most of the tool's effect was located within 25 µm of the cut surface. There was a significant decrease to < 5 % at 200 µm. No cell death was found over 200 µm from the cut surface in both frequencies (35 kHz and 20 kHz). No significant difference in total percentage cell death was found between cutting at 35kHz and 18.7 μm (p-p) and at 20kHz and 23.9 μm (p-p). No microcracks were detected along the depth of the cut site at either frequency.ConclusionOf the 2 ultrasonic cutting frequencies tested, the combination of the higher vibration frequency (35kHz) and the lower displacement amplitude (18.7 μm (p-p) demonstrated least damage to the bone tissue. No microcracks were displayed when using either of the ultrasonic cutting frequencies.Declaration of Interest(b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Electromagnetic shielding tests of a permanent magnet generator

In the present work, some tests on the electromagnetic interference issues of a new designed and constructed axial flux permanent magnet generator have been presented. The machine itself has multiple special laminated cores (i.e., 12) and 24 windings in the stator component with two active sides. Machine operates in 3 phases and uses disc type permanent magnets on two rotors at two sides in a sandwiched formation. Rotors have 32 magnets and freely rotates at the vicinity of stable stator within a certain air gap. The electromagnetic interference measurements have been realized for different distances and directions from the machine. Besides, the effects of different frequencies are also evaluated following the tests. It has been concluded that the shielding material shape is very important for the optimum shielding results.

Effect of Different Frequencies of Dental Visits on Dental Caries and Periodontal Disease: A Scoping Review.

Recommending dental visits every six months is commonplace among dental practitioners worldwide. A scoping review was conducted by electronically searching PubMed, Scopus and Embase to identify and map the nature of evidence for the effect of different frequencies of dental visits on dental caries and periodontal disease. Studies were written in English on the frequency of dental visits and published between January 2008 and April 2023. Three systematic reviews that evaluated the risk of bias, strength of studies and certainty of evidence were included from the 4537 articles yielded through the search strategy. The available evidence was weak and of low quality for the currently recommended frequencies of dental visits, whether these are fixed or universal. For adults, there was little to no effect of making biannual, biennial or risk-based dental visits on dental caries and periodontal disease, which was supported by moderate- to high-certainty evidence. Accordingly, it is suggested that dental professionals and dental insurance providers make individually tailored, customised and risk-based recommendations for dental visits, rather than encouraging fixed or universal frequencies of dental visits. For children and adolescents, further research on this issue warrants well-designed randomised controlled trials (RCTs) and cohort studies of sufficient duration with an adequate number of participants.

Estimation of Electromagnetic Radiation Distribution in the Human Heart Rate at Different Frequencies‏‏

The health implications of electromagnetic radiation have been extensively debated due to the sharp increase in the usage of cell phones, Wi-Fi transmitters and other microwave equipment. Electromagnetic radiation affects the autonomic nervous system, heart rate, blood pressure and other cardiovascular functions. This study aims to present a Numerical Simulation of Electromagnetic Radiation (EMR) on the human heart tissue and to explore the effect of different frequencies in the spectral range (900, 1,800 and 2,400 MHz) on Specific Absorption Rate (SAR), power density, the Distribution of Electromagnetic Fields by Matlab program, and Finite-Difference Time-Domain (FDTD) method in One Dimension (1D). A 1-dimensional finite difference method was used to solve Maxwell’s equations in heart tissue. The heart model was subjected to electromagnetic radiation that has dielectric properties according to frequency. Frequency was chosen and the operation of the software program as Matlab and the dielectric attribute has been calculated. Concurring with the Frequency in a private program, are the conductivity, relative permittivity, wavelength and infiltration profundity. The amplitudes of the reflected and transmitted sinusoid waves, relative to the occurrence wave, were portrayed by the reflection coefficient and the transmission coefficient, which relate to the amplitudes of the electric field wave. The electric field, magnetic field and power density were simulated along the line X = Y = 0. The study showed that the impact of electromagnetic radiation depends on the frequency of the wave which hit the heart. It was found that the heart tissue reacts more at 900 MHz compared to 1,800 and 2,400 MHz, and the tissue absorption is higher at the lower frequency. There was a relation between the magnetic field in the y-dimension and the time step the in x-dimension. HIGHLIGHTS The effect of electromagnetic has been theoretically studied where the electromagnetic fields produced from electromagnetic radiation at 900 MHz,1800 MHz, and 2400 MHz on layered biological tissues (heart model) by the finite difference time domain (FDTD) method A one-dimensional finite difference method was used to solve Maxwell's equations in heart tissue The amplitudes of the reflected and transmitted sinusoid waves, relative to the occurrence wave, were portrayed by the reflection coefficient and the transmission coefficient, which relate to the amplitudes of the electric field wave The impact of electromagnetic radiation depends on the frequency of the wave which hit the heart. There was a relation between the magnetic field in the y-dimension and the time step the in x-dimension GRAPHICAL ABSTRACT

Growth of pecan rootstocks with the use of liquid humus in an organic production system

Pecan farming is a long-term investment which needs quality seedlings to establish an orchard. Pecan rootstocksmust have a vigorous radicular system to form quality seedlings. Liquid humus, which acts as an agent thatpromotes their growth and development, is a bioinput that is specially used in organic production systems.This study aimed at evaluating effects of different frequencies of liquid humus application on pecan rootstockgrowth and development in an organic system. Liquid humus at 30% was applied every 7, 14, 21 and 28 days.The control treatment consisted of water application. The experiment was carried out with ‘Barton’ rootstocksin a greenhouse at the Embrapa Clima Temperado located in Pelotas, RS, Brazil. The following variables wereevaluated 280 and 480 days after transplantation: plant height; stem diameter; leaf area; fresh and dry massesof the aerial part; main and secondary root lengths; fresh and dry masses of roots; fresh and dry masses of themain root; fresh and dry masses of secondary roots; and the Dickson Quality Index. Liquid humus increasedsecondary root length of pecan rootstocks, mainly when it was applied every seven days. Thus, the bioinputmay be used for this purpose.

Effects of Different Frequencies of Physical Therapy Visits on Shoulder Function After Arthroscopic Rotator Cuff Repair.

There is no consensus about the optimal frequency of patient visits during the rehabilitation program after arthroscopic rotator cuff repair (ARCR). This study aimed to investigate the short- and long-term effects of high-frequency (HF) and low-frequency (LF) visits of the patients in the first 12weeks of rehabilitation after ARCR. This was a quasi-randomized study with 2 parallel groups. Forty-seven patients with ARCR were included in 2 different patient visit frequency protocols (HF = 23, LF = 24) in 12weeks of postoperative rehabilitation. Patients in the HF group visited the clinic twice a week, whereas patients in the LF group visited once every 2weeks for the first 6weeks and once a week for the following 6weeks. Both groups performed the same exercise protocol. Outcome measurements were pain and range of motion measured at baseline; at the 3rd, 5th, 8th, 12th, and 24th weeks; and at 1-year follow-up. Shoulder function was assessed at the 12th and 24th weeks and at 1-year follow-up with an American Shoulder and Elbow Surgeons score. There was a significant group × time interaction in pain intensity during the activity between the groups. The activity pain intensity was higher in the LF group (4.2 points) at 8 weeks post surgery than in the HF group (2.7 points) (mean difference: 1.5 points, P < .05), whereas it was similar in both groups at other time periods. The interaction term was not significant between the groups for pain intensity during rest and night through the 1-year follow-up. No group × time interactions were observed in shoulder range of motion and American Shoulder and Elbow Surgeons score over the postoperative period. Both rehabilitation programs at different visit frequencies after ARCR showed similar clinical results in the long term. A supervised, controlled rehabilitation program with LF visits in the first 12weeks after surgery can be sufficient to achieve optimal clinical results and reduce rehabilitation-related costs after ARCR. This study highlights that LF treatment protocols under the supervision of the therapist can be adopted after the arthroscopic rotator cuff repair to achieve successful results while decreasing the treatment costs. Physical therapists should plan the treatment sessions efficiently for the compliance of the patients to the exercise treatment. If you are a patient with arthroscopic rotator cuff repair, a supervised, controlled rehabilitation program with low-frequency visits in the first 12weeks after surgery could help you achieve the best outcome and help lower the costs of rehabilitation. A total of 3 visits in the first 6weeks might be sufficient (once every 2weeks). More frequent visits (1-2 visits a week) should happen 6 to 12weeks after the surgery.

Treatment strategy of different enhanced external counterpulsation frequencies for coronary heart disease and cerebral ischemic stroke: A hemodynamic numerical simulation study

Background and objectivesCurrently, enhanced external counterpulsation (EECP) devices mainly produce one counterpulsation per cardiac cycle. However, the effect of other frequencies of EECP on the hemodynamics of coronary and cerebral arteries is still unclear. It should be investigated whether one counterpulsation per cardiac cycle leads to the optimal therapeutic effect in patients with different clinical indications. Therefore, we measured the effects of different frequencies of EECP on the hemodynamics of coronary and cerebral arteries to determine the optimal counterpulsation frequency for the treatment of coronary heart disease and cerebral ischemic stroke. MethodsWe established 0D/3D geometric multi-scale hemodynamics model of coronary and cerebral arteries in two healthy individuals, and performed clinical trials of EECP to verify the accuracy of the multi-scale hemodynamics model. The pressure amplitude (35 kPa) and pressurization duration (0.6 s) were fixed. The global and local hemodynamics of coronary and cerebral arteries were studied by changing counterpulsation frequency. Three frequency modes, including one counterpulsation in one, two and three cardiac cycles, were applied. Global hemodynamic indicators included diastolic / systolic blood pressure (D/S), mean arterial pressure (MAP), coronary artery flow (CAF), and cerebral blood flow (CBF), whereas local hemodynamic effects included area-time-averaged wall shear stress (ATAWSS) and oscillatory shear index (OSI). The optimal counterpulsation frequency was verified by analyzing the hemodynamic effects of different frequency modes of counterpulsation cycles and full cycles. ResultsIn the full cycle, CAF, CBF and ATAWSS of coronary and cerebral arteries were the highest when one counterpulsation per cardiac cycle was applied. However, in the counterpulsation cycle, the global and local hemodynamic indicators of coronary and cerebral artery reached the highest when one counterpulsation in one cardiac cycle or two cardiac cycles was applied. ConclusionsFor clinical application, the results of global hemodynamic indicators in the full cycle have more clinical practical significance. Combined with the comprehensive analysis of local hemodynamic indicators, it can be concluded that for coronary heart disease and cerebral ischemic stroke, applying one counterpulsation per cardiac cycle may provide the optimal benefit.

A modified sonic black hole structure for improving and broadening sound absorption

In order to improve and broaden the absorption performance of Sonic Black Hole (SBH), we propose a modified SBH structure with micro-perforated panels which is embedded the multiple resonator cavities, and investigate the sound absorption effect of the structure. Characteristics of acoustic streaming effects are embodied in sound pressure and flow velocity distribution. Further, proposed SBH structure can achieve high sound absorption under 6.0 kHz. Based on the symmetry of the structure, the Two-dimensional axisymmetric Finite Element Method (FEM) model is proposed to study the sound absorption mechanism, which shows that the change of flow velocity gradient of acoustic medium leads to the loss of acoustic energy inside the structure. By discussion on acoustic streaming effects of different frequencies, the resonator cavity and micro-perforated panels contributes more to the sound absorption performance at low frequencies, and SBH produces a sound absorption advantage at high frequencies.The theoretical calculation and simulation result match and prove the correctness of the sound streaming effect. Sound absorption tests by acoustic impedance tube confirm that the proposed structure can maintain a sound absorption coefficient of over 0.5 in the range of 0.05–6.0 kHz. The combination of micro-perforated panels and SBH structure is widely applicable to muffler design and has good application prospects.

High-frequency chest wall oscillation multiple times daily can better reduce the loss of pulmonary surfactant and improve lung compliance in mechanically ventilated patients

BackgroundHigh-frequency chest wall oscillation (HFCWO) has been widely recognized for its airway secretion clearance effectiveness in critically ill ICU patients. ObjectivesThe purpose of this randomized controlled trial is to validate and compare the effects of different frequencies of HFCWO on oxygenation, lung compliance, and pulmonary surfactant proteins (SPs) in critically ill patients admitted to the intensive care unit (ICU). MethodsSixty patients with severe craniocerebral injury treated with a tracheostomy and mechanical ventilation were randomized into three groups (20 patients in each group): a single group (treated with 30 minutes of HFCWO once daily) and a double group (treated with 30 minutes of HFCWO twice daily), and a blank group (treated without HFCWO). Primary outcome measures included results on several specific proteins (SP-A, SP-B, SP-C, and SP-D) in serum and alveolar lavage fluid. Secondary outcome measures were lung static compliance test and oxygenation. ResultsPatients in both the single and double groups exhibited significant oxygenation and static compliance improvement. Similar results were observed in changes in SPs concentrations in the alveolar lavage fluid. However, a significant reduction of SPs levels was observed in the serum. In the group comparison analysis for the same variables between the single and double group, twice daily HFCWO treatments showed a significantly better result. ConclusionCompared with HFCWO once daily, HFCWO twice daily is advantageous in patients with tracheostomy and prolonged ventilation, which demonstrated significantly greater effectiveness in improving oxygenation and lung static compliance linked to the increase of and SPs contents in the airways as well as a reduction of SPs shift from airways to the blood.

Textural, Rheological, and Sensory Modifications in Oaxaca Cheese Made with Ultrasonicated Raw Milk

In this research, we evaluated the effects of different frequencies (25 and 45 kHz) and times (15 and 30 min) of high-intensity ultrasound (HIU) applied to fresh raw milk on the textural properties of Oaxaca cheese. When HIU was applied for 15 min, the cheese melting time was reduced by up to 23.4 s compared to the control. The cheeses produced with ultrasonicated milk at 45 kHz presented larger melting and exudate areas. They were softer, but consumer acceptability was lower. Frequencies of 25 and 45 kHz (15 or 30 min) reduced the temperature of the solid–liquid transition by 1.9–3.6 °C and 0.6–1.8 °C, respectively, compared to controls. Consequently, the melting time in ultrasonicated cheese was significantly reduced. The strands were perfectly aligned and well organized in the direction of stretching with 25 kHz ultrasonication. In addition, these cheeses were more consistent, chewy, and rubbery. Consequently, they were preferred and more accepted in flavor, aroma, and texture, with high general acceptability. HIU is a promising technology to improve the textural and rheological properties of Oaxaca cheese made with raw milk, as HIU produced cheeses with better sensory acceptability by consumers and with a high melting capacity and thread formation.

Fire Needling Therapy of Different Frequencies versus External Diclofenac Diethylamine Emulgel for Knee Osteoarthritis: Study Protocol for a Pilot Randomized Controlled Trial.

Knee osteoarthritis (KOA) is regarded as one of the leading musculoskeletal diseases. Although the efficacy is under exploration, fire needling therapy is considered an effective alternative for KOA. This trial aims to investigate the effectiveness of different frequencies of fire needling therapy in attenuating pain and promoting function in KOA patients. This is a study protocol for a pilot, three-arm, single-center, randomized controlled trial. A total of 90 participants with KOA will be recruited and randomly assigned to the high-frequency fire needling group (3 sessions per week, for 6 weeks), the low-frequency fire needling group (1 session per week, for 6 weeks) or the positive control group (Diclofenac Diethylamine Emulgel, 3 times per day, for 6 weeks) in a 1:1:1 ratio. Participants will accomplish the trial at Week 14 after a follow-up evaluation. The response rate will be set as the primary outcome that the proportion of participants obtaining a minimal clinically important difference, which is identified as ≥2 units on the numerical rating scale (NRS) and ≥6 units on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) function score at Week 6 compared with Week 0. Secondary outcomes are NRS, WOMAC, Brief Pain Inventory, Short-Form Health Survey-12, TimedUpandGoTest, and pain threshold. This is the first standardized protocol comparing fire needling therapy and positive control drugs. This trial may provide reliable evidence for the effectiveness of fire needling therapy and dose-effect property of it in KOA. Trial registration: The trial has been registered on Chinese Clinical Trial Registry (Registered number: ChiCTR2100043041), registered on 4 February 2021.

Research on the Different Frequencies of Transcutaneous Electrical Acupoint Stimulation for Postpartum Pelvic Girdle Pain

Objective: To observe the clinical effect of different frequencies of transcutaneous electrical acupoint stimulation in treating postpartum pelvic girdle pain and promoting postpartum rehabilitation. Methods: From January to September 2022, 300 patients with pelvic girdle pain after spontaneous delivery in a hospital in Shaanxi Province were selected and randomly divided into three groups, low frequency, high frequency, and alternating frequency, with 100 cases in each group. In addition to routine postpartum care and psychological counseling, the three groups received transcutaneous electrical acupoint stimulation at low-frequency (2 Hz,) high-frequency (100 Hz), and alternating frequency (2/100 Hz), respectively. The differences in initial pain, pain scores before and after treatment, satisfaction with analgesic effect, and postpartum rehabilitation effect were evaluated among the three groups of patients. Results: There was a significant correlation between maternal age and postpartum pelvic girdle pain (P &lt; 0.001), but no correlation was observed between newborn birth weight and postpartum pelvic girdle pain (P &gt; 0.05). After 1d/2d of treatment, the pain scores and rehabilitation effect of patients in the alternating-frequency group and low-frequency group were significantly better than those in the high-frequency group, and the postpartum curative effect of patients in the alternating-frequency group was the best, followed by the low-frequency group, and the high-frequency group; the differences were statistically significant (P &lt; 0.001). Among the three groups, the alternating-frequency group had the highest satisfaction with the analgesic effect and the highest rate of selecting the same analgesic regimen the next time; the differences were statistically significant (P &lt; 0.001). Conclusion: Transcutaneous electrical acupoint stimulation at different frequencies is safe and effective in treating postpartum pelvic girdle pain and beneficial to postpartum rehabilitation. Sparse-dense wave stimulation is effective in treating postpartum pelvic girdle pain. It has the best effect in promoting postpartum rehabilitation and the highest patient satisfaction. Therefore, its application in clinical practice is highly recommended.

Investigation of the effect of frequency on shear strength and damping of pure sand and sand stabilised with rice husk ash using cyclic triaxial tests

Rice husk ash (RHA), owing to its pozzolanic properties and wide abundance, is an additive that can be used as an alternative to cement to improve a variety of soils. Damping and shear modulus are two important soil dynamic parameters used to predict soil behaviour under dynamic loading. Therefore, in this study, materials were prepared and their specifications were determined. A cyclic triaxial device was used to determine the dynamic parameters (stress control). Subsequently, the results related to shear modulus and damping calculated for pure sand before and after stabilisation were analysed according to different percentages of stabilisers for two frequencies of 0.5 and 1 Hz. The results revealed the effect of different frequencies on the damping of pure sand, which differed for stabilised sand. In all stabilised specimens, the shear modulus decreased with increasing frequency. Additionally, the damping decreased with increasing frequency in the stabilised samples. The shear modulus increases with the increase in the amount of stabilisers. The results also showed the positive effect of partially replacing cement with RHA.

Dielectric constant, dielectric loss, conductivity, capacitance and model analysis of electronic electroactive polymers

In this study, the dielectric constant, dielectric loss, conductivity and capacitance of the electronic electroactive polymer (EEAP) were systematically tested experimentally, and the effects of different frequencies, effective voltages, electrode types, and specimen thicknesses on the dielectric relaxation properties of polymers were analyzed, and finally the Debye, Cole-Cole and Havriliak-Negami functions were used to model the dielectric constants. The experimental results show that the dielectric constant of the polymer depends strongly on the frequency, especially in the low frequency stage from 10−1 to 100 Hz. The effect of different effective voltages on the dielectric properties is basically identical, and the accuracy of the test can be improved at this AC voltage avoiding the effect of electrostatic stress. At the same effective voltage and thickness, the polymer with G-C electrodes shows the best electrical parameters, the composite electrode form of G-C electrodes contributes to the conductive properties of the polymer and can be applied to the later design of actuators. Compared with the Debye model, the errors of the experimental and calculated values of the Cole-Cole and Havriliak-Negami models are smaller, 1.1102 and 0.7130, respectively. The dielectric behavior of EEAPs differs from that of epoxy materials, probably due to the influence of electric dipole moments, bound charges, and dipole effects. The paper has some reference value for further revealing the dielectric properties and relaxation time distribution of the polymer, and provides guidance for the later application of EEAP materials in flexible robots.

Effect of different weekly frequencies of plyometric-jump and linear-sprint training on youth male futsal athlete’s physical fitness

Introduction: This prospective cross-sectional intervention study aimed to compare the effect of different frequencies (equated for total repetitions) of plyometric-jump and linear-sprint training on U-18 (age, 17,0 ± 1,05) male futsal athlete’s physical fitness. Methods: Athletes (33) were randomly distributed into groups with one (1-TSW, n = 10), two (2-TSW, n = 11), and three (3-TSW, n = 12) training session per week (TSW), during 4 weeks of their regular futsal training routine. Plyometric-jump training involved bipedal and unipedal horizontal maximum-intensity jumps. Linear-sprint training involved maximal-intensity 10-msprints with 30 seconds of rest between sprints. Results: The three training groups completed an equal number of total jumps (n = 780) and sprints (n = 260). A two-way ANOVA with repeated measures on time revealed significant main effects of time for all physical fitness outcomes, i.e., squat jump and counter-movement jump height, power, relative power, standing long jump distance, 10-m and 20-m sprint time, and change of direction sprint time in the T-test (all p &lt; 0.001; d = 0.36-0.69), without significant group × time interaction effects (p = 0.133-0.861; d = 0.01-0.13). Conclusion, Adding plyometric-jump and linear-sprint training to the standard training of youth male futsal athlete’s improves their physical fitness, with similar improvements regardless of the training frequency.

Effects of different frequencies of pricking-bloodletting at auricular points plus auricular point sticking therapy on the serum levels of related factors in patients with acne vulgaris

Effects of different frequencies of pricking-bloodletting at auricular points plus auricular point sticking therapy on the serum levels of related factors in patients with acne vulgaris

Effects of different frequencies of repetitive transcranial magnetic stimulation on simultaneously recorded electrocorticograms and motor evoked potentials in monkeys

Effects of different frequencies of repetitive transcranial magnetic stimulation on simultaneously recorded electrocorticograms and motor evoked potentials in monkeys