For many years, surface wave high frequency radar is used for remote sensing of surface currents in deep water sea and also for measurement of wave velocity and height. The formula and methods are extracted for deep water and, therefore, may be inappropriate to use in shallow water. The Persian Gulf is the shallowest water region that has big area that is suitable for over the horizon radars. Theoretical and experimental analysis of surface waves in shallow water in the presence of the surface current has been done in the past, but in a few papers high frequency radar backscattering in shallow water was considered. In this paper, formulas for water wave velocity when the sea floor interacts with ocean waves were extracted. Also, formulas of Bragg frequency for surface wave high frequency radar when the water has a shear current in shallow water were evaluated. In some cases, the Bragg frequencies will be changed unequally for positive and negative frequencies. Spectrum of echo at surface wave high frequency radar has two resonated frequencies where one is negative and the other is positive according to sea waves travelling away from or toward the high frequency radar, respectively.

Noise most frequently affects hearing system, as it may typically cause a bilateral, progressive sensorineural hearing loss at high frequencies.. This study was designed to compare three different methods to evaluate noise-induced hearing loss (conventional audiometry, high-frequency audiometry, and distortion product otoacoustic emission).. This was a cross-sectional study. Data was analyzed by SPSS (ver. 19) using chi square, T test and repeated measures analysis. Study samples were workers from tile and ceramic industry.. We found that conventional audiometry, extended high-frequency audiometry, low-tone distortion product otoacoustic emission and high-tone distortion product otoacoustic emission had abnormal findings in 29 %, 69 %, 22 %, and 52 % of participants. Most frequently affected frequencies were 4000 and 6000Hz in conventional audiometry, and 14000 and 16000 in extended high-frequency audiometry.. Extended high-frequency audiometry was the most sensitive test for detection of hearing loss in workers exposed to hazardous noise compared with conventional audiometry and distortion product otoacoustic..

As the main findings of our research work, we present a novel theorem on the relationship between the number of extrema of compound sinusoidal signals and its high-frequency component. In the case of signals consisting of the sum of two sine signals, if the high-frequency component has a higher product of the frequency and the amplitude, then we prove that the frequency of the high-frequency component is proportional to the number of extrema in a time interval. This theorem justifies some of the experimental results of other researchers on the relevance of extrema to frequency and amplitude. To confirm the theorem, extrema counting was performed on speech signals and compared with Fourier transform. The experimental results show that the average number of extrema of the compound sinusoidal signal or its derivatives over a time interval can be used to estimate the frequency at its highest frequency band. An important application of this research work is the fast calculation of high frequencies of a signal. This theorem also shows that the number of extrema points can be used as a new effective feature for signal processing, especially speech signals.

Early detection of noise-induced hearing loss (NIHL) is important to prevent the progression of hearing loss at speech frequencies. This study, through a systematic review of literature and meta-analysis, assessed the efficacy of high-frequency audiometry for early detection of NIHL. A systematic literature search was performed in Medline, Scopus, ISI web of science, EMBASE, CINAHL, Health star, and Ovid databases. The mean difference of hearing threshold at normal and high frequencies hearing was considered as the effect size. The pooled and stratum-specific MD were also estimated. From the 3031 articles found in the initial search, 23 and 11 studies were systematically reviewed and meta-analyzed, respectively. The mean difference in the exposed subjects was higher than the non-exposed subjects at most of the hearing frequencies. The effect size was higher at high frequencies, although it was not statistically significant. The research findings indicate that high-frequency audiometry cannot be considered as a method for early detection of NIHL.

Due to leakage current injection to the system ground and high frequency components in DC link resulted from High-speed BLDC motors performance, there are interference with the other equipment performance. Hence it is necessary to overcome electromagnetic interference. In this paper, high-frequency model of BLDC motor is extracted using finite element analysis in the MAXWELL software based on some new solutions. The parameters of high frequency simple model of power switch are valuated using the switch datasheet. A method that uses the filtering method and snubber circuits is proposed to reduce the generated noise. We calculate the frequency spectrum of the DC link current and the leakage current from motor to ground network. The proposed method is effectively capable to reduce the amplitude of the leakage current and weaken considerably the high frequency components of DC link current.

The aim of this study was to assess the accuracy of high-resolution ultrasonography (USG) in the evaluation of rotator cuff tendinopathies and tears with magnetic resonance imaging (MRI) correlation to determine its sensitivity and specificity.
The prospective study was conducted on 40 patients referred to the Department of Radiology for the evaluation of rotator cuff pathologies over a period of 18 months. All the patients underwent high-frequency USG followed by MRI. Variables such as sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), and accuracy of high-frequency USG and MRI were evaluated.
The sensitivity, specificity, NPV, PPV, and accuracy of high-frequency USG in the evaluation of rotator cuff pathologies in comparison to MRI as standard were 90.6%, 87.5%, 96.6%, 70%, and 90%, respectively.
High-frequency USG is almost equally sensitive and specific as MRI for the diagnosis of rotator cuff pathologies, and due to its cost-effectiveness, easy affordability, ease of evaluating contralateral shoulder, more patient compliance, noninvasiveness, and wider applications, we recommend it to be used as a primary modality for evaluating rotator cuff. MRI should be performed in case some extra information is required.

Hearing loss is a social damage affecting the most important aspect of social life i.e. communication. People with high frequency hearing loss do not accept hearing aid easily and resist its using. The purpose of this study was to determine the role of hearing aid in the quality of life of the elderly people with high frequency hearing loss.
This study was performed on 22 elderly people over 60 years old with mild to moderate sensory neural high frequency hearing loss living in Hamadan City, Iran. Hearing Handicap Inventory for the Elderly (HHIE) questionnaire was completed before and three month after using hearing aid. Social, emotional, and total scores before and after intervention were compared, too.
Findings showed significant improvement of social, emotional and total scores before and three months after using hearing aid (p Considering beneficial effects of hearing aid on improving the quality of life in elderly patients with high frequency hearing loss, applying appropriate hearing aid and if needed rehabilitation programs are recommended.

High Electron Mobility Transistors (HEMTs) are the promising devices for high speed structures. In this paper, the electrical characteristics of AlGaN/GaN HEMT have been investigated. The impact of the second gate on the short channel effects (SCEs) and the high frequency performance of presented structurehas been analyzed. All simulations were carried out using 2-D Silvaco software. The threshold voltage, on-state current, off-state current, subthreshold swing have been evaluated. It was shown that SCEs on state current, off state current, subthreshold swing have been evaluated. It was shown that Siftware. The thresignificantly decrease with increasing the number of gates because of the better control of gate in double gate (DG) structure. Also, the high frequency parameters (transconductance, gate capacitance and cut-off frequency) have been calculated. The results show that the cut-off frequency in double gate (DG) structure is more than that of single gate (SG) structure. Therefore, the DG structure is more suitable device for high frequency applications.

In this paper an optimized high frequency lumped model of Induction motor is presented. Model parameters are identified and optimized using Genetic Algorithm (GA). A novel model and approach in an improved high frequency based on GA for parameter identification are used. At first parameters are limited and then fitted using GA for best fitting. The proposed model considered accurate simulation of both differential and common mode behavior in the EMI-frequency range from 100 Hz to 30MHz. model parameters which extracted from GA, is compared with experimental data in both magnitude and phase at the same time and results shown a good accordance between the experimental results and simulation results of the proposed model. A least mean square (LMS) method was used with a GA optimization method to solve the identification problem. The proposed model is suitable to obtain the simulation models for prediction of high frequency conducted Electromagnetic Interference (EMI), over voltage on terminated motor, and common mode current in cable fed induction motor.

Conventional Flux Compression Generators (FCG''s) are used to generate high power DC pulses. A new kind of (FCG''s) with series capacitance called Capacitive Flux Compression Generator (CFCG) will be introduced and explained in this paper. This new kind is used to generate modulated high power pulses. There are some problems to establish a capacitance in high power and high frequency applications. In the present paper several practical methods will be addresed to make capacitance in high power and high frequency applications.