Preset Frequency Research Articles

Short-term effects of simultaneous cardiovascular workout and personal music device use on the outer hair cell function of young adults

Background: Recreational noise exposure, including personal music device use (PMD), has become a growing public health concern, as it may potentially result in the development of hearing difficulties.Objectives: The aim of the study was to determine the differential impact and short-term effects of simultaneous cardiovascular workout and PMD use on the outer hair cell (OHC) function of young adults.Method: A quantitative research approach was followed. In this study a pre-test post-test approach was used and twelve subjects participated in three 1 h testing conditions with altered variables including: (i) exposure to PMD use in isolation, (ii) exposure to cardiovascular workout in isolation, and (iii) simultaneous exposure to the latter mentioned. Distortion product otoacoustic emissions (DPOAEs) were conducted pree and post exposure for each testing condition as primary indicator of cochlear responses. The process consisted of a cycling procedure through the preset stimulus frequency sequence, measuring the 2f₁—f₂ (75—70 dBSPL) and constructing a plot of DPOAE levels as a function offrequency.Results: Individual testing conditions did not result in statistically significant changes of the DPOAE response, however a significantly different profile in the DPOAE response level increase/decrease for the higher frequencies (6—8 kHz) was obtained when comparing the different sessions. Exposure to cardiovascular workout condition in isolation indicated a clear trend of an increased DPOAE response level between the pre-exposure and post exposuretesting from 2 kHz to 8 kHz with a maximum increase at 6 kHz. Both the music-only condition and the combined condition resulted in a clear trend of decreased DPOAE response amplitudes between the pre-exposure and post-exposure testing for the higher frequencies.Conclusion: Findings support the notion of a clear effect of cardiovascular workout with and without music exposure on the OHC function at higher test frequencies, as measured by DPOAEs. Decreased DPOAE amplitudes between 2 kHz and 8 kHz were observed with music exposure and the opposite effect was observed for cardiovascular workout in isolation.

Short-term effects of simultaneous cardiovascular workout and personal music device use on the outer hair cell function of young adults

BackgroundRecreational noise exposure, including personal music device use (PMD), has become a growing public health concern, as it may potentially result in the development of hearing difficulties. ObjectivesThe aim of the study was to determine the differential impact and short-term effects of simultaneous cardiovascular workout and PMD use on the outer hair cell (OHC) function of young adults. MethodA quantitative research approach was followed. In this study a pre-test post-test approach was used and twelve subjects participated in three 1 h testing conditions with altered variables including: (i) exposure to PMD use in isolation, (ii) exposure to cardiovascular workout in isolation, and (iii) simultaneous exposure to the latter mentioned. Distortion product otoacoustic emissions (DPOAEs) were conducted pre– and post-exposure for each testing condition as primary indicator of cochlear responses. The process consisted of a cycling procedure through the preset stimulus frequency sequence, measuring the 2f₁–f₂ (75–70 dBSPL) and constructing a plot of DPOAE levels as a function of frequency. ResultsIndividual testing conditions did not result in statistically significant changes of the DPOAE response, however a significantly different profile in the DPOAE response level increase/decrease for the higher frequencies (6–8 kHz) was obtained when comparing the different sessions. Exposure to cardiovascular workout condition in isolation indicated a clear trend of an increased DPOAE response level between the pre-exposure and post-exposure testing from 2 kHz to 8 kHz with a maximum increase at 6 kHz. Both the music-only condition and the combined condition resulted in a clear trend of decreased DPOAE response amplitudes between the pre-exposure and post-exposure testing for the higher frequencies. ConclusionFindings support the notion of a clear effect of cardiovascular workout with and without music exposure on the OHC function at higher test frequencies, as measured by DPOAEs. Decreased DPOAE amplitudes between 2 kHz and 8 kHz were observed with music exposure and the opposite effect was observed for cardiovascular workout in isolation.

Cloud based Real-time Multi-robot Collision Avoidance for Swarm Robotics

Nowadays, Cloud Computing has brought many new and efficient approaches for computation-intensive application areas. One typical area is Cloud based real-time device control system, such as the IoT Cloud Platform. This kind of platform shifts computation load from devices to the Cloud and provides powerful processing capabilities to a simple device. In Swarm robotics, robots are supposed to be small, energy efficient and low-cost, but still smart enough to carry out individual and swarm intelligence. These two goals are normally contradictory to each other. Besides, in real world robot control, real-time on-line data processing is required, but most of the current Cloud Robotic Systems are focusing on off-line batch processing. However, Cloud based real-time device control system may provide a way that leads this research area out of its dilemma. This paper explores the availability of Cloud based real-time control of massive complex robots by implementing a relatively complicated but better performed local collision avoidance algorithm. The Cloud based application and corresponding Cloud driver, which connects the robot and the Cloud, are developed and deployed in Cloud environment. Simulation tests are carried out and the results show that, when the number of robots increases, by simply scaling computation resources for the application, the algorithm can still maintain the preset control frequency. Such characteristics verify that the Cloud Computing environment is a new platform for studying massive complex robots in swarm robotics.

PZT Based Smart Aggregate for Unified Health Monitoring of RC Structures

The most familiar civil engineering structure is reinforced concrete (RC) structure. Performance of structure undergoes changes during their service life with time. Thus, it is of great concern to monitor the health of RC structure. Structural health monitoring (SHM) is the art of detecting the changes in structure that influences its performance. Various techniques to monitor the health of structure are broadly studied worldwide. PZT based smart aggregate can play an effective role as an advanced tool in the development of structural health monitoring. This research work contributes for proposing a more generous Non-Destructive Evaluation (NDE) technique for structural health monitoring by using smart materials. If performance of a structure deviates from the design parameters with time, appropriate and effective maintenance is required. Considering the relevant need of RC structures, a more sensitive and cost-effective approach by using Electro-Mechanical Impedance (EMI) technique has been proposed for implementation in real-life situations. In general, surface bonded PZT transducer is used for SHM. Since PZT transducers are of very small dimension and brittle in nature, for consistent characteristics, they should be protected from severe environmental condition and other external interruptions. For this reason, PZT transducer is embedded in structure at the time of construction and manufacturing of the embedded transducer is simple. The proposed EMI technique assesses the health of RC structures more rationally by embedding PZT transducer in the structure, whose health is to be monitored over the user specified preset frequency range. The conductance and susceptance signatures are acquired by using LCR meter. At any future point of time, when it is desired to assess the health of structure, the conductance and susceptance signatures are acquired and further utilized for damage detection and quantification. The Root Mean Square Deviation (RMSD) is used to specify damage severity.

Media with zero refractive index at a preset frequency

The refraction of a plane s-polarized electromagnetic wave on the vacuum–metamaterial interface is considered. It is established that, under certain conditions, a medium consisting of electric and magnetic dipoles or entirely of electric dipoles can behave as possessing a zero refractive index at a preset frequency.

A Method for Synthesis of Frequency-Time Radio Images in Non-Radiating Radars

We propose a modification of the known method used to synthesize frequency time radio images in non-radiating radars and based on minimization of the r.m.s. deviation of the observation data vector from its linear model with an additional limitation imposed on the L1 norm of the vector of the evaluated amplitudes of two-dimensional signal distribution in the range of delays and Doppler frequencies. The essence of the modification is that instead of solving the problem of conditional minimization at a full array in the “time delay—Doppler frequency shift” coordinates, this problem is solved sequentially for the zeroth and a preset frequency shift. In combination with additional computational tricks, the proposed modification allows one to increase the computational efficiency of image formation by three orders of magnitude.

Multi‐frequency high frequency surface wave radar based on phase offset

Multi-frequency high frequency surface wave radar (MHFSWR) shows good capability of anti-interference, sea-state information extraction and target detection. The authors develop a new technique to produce a specified Doppler frequency offset on the echoes spectra for each operating frequency in simultaneous MHFSWR system. The radar transmits frequency modulated interrupted continuous wave signals with different linear phase offsets which are counted up from sweep cycle to sweep cycle. After the echoes being demodulated, the signals of different operating frequencies from same range can be distinguished by the preset frequency offsets in a single Doppler spectrum, though they are indiscernible in the A-Scope display. In the receiver, both the data transmission channel and the signal processing channel of different operating frequency, including digital down-conversion, data rate conversion and range–Doppler transform, are shared significantly reducing the hardware cost and system complexity. The simulation results and the initial observations obtained by the radar verify the feasibility of the proposed technique. This technique is applicable in monostatic radars, bistatic radars and networking radars to apply multi-frequency observations simultaneously.

Arbitrary frequency stabilization of a diode laser based on visual Labview PID VI and sound card output**Project supported by the National Basic Research Program of China (Grant No. 2012CB921603), the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China (Grant No. IRT13076), the Major Research Plan of the National Natural Science Foundation of

We report a robust method of directly stabilizing a grating feedback diode laser to an arbitrary frequency in a large range. The error signal, induced from the difference between the frequency measured by a wavelength meter and the preset target frequency, is fed back to the piezoelectric transducer module of the diode laser via a sound card in the computer. A visual Labview procedure is developed to realize a feedback system. In our experiment the frequency drift of the diode laser is reduced to 8 MHz within 25 min. The robust scheme can be adapted to realize the arbitrary frequency stabilization for many other kinds of lasers.

A Hydrogen Management Method in Residential Distributed Generation Systems with Photovoltaic Cells and Hydrogen‐Storage Type Fuel Cells

SUMMARYRecently, renewable energy has been attracting attention as a result of global warming and the depletion of fossil fuels. Photovoltaic (PV) systems have spread rapidly around the world because they generate electric power quietly and can be installed in many places. The output power generated in a PV system fluctuates with changes in solar irradiance and panel temperature. The reverse flow of surplus power in output spikes may have a negative effect on electric power quality, such as on the frequency and voltage in a power system. A residential distributed generation (DG) system composed of a fuel cell (FC) unit, an electrolyzer (EL) unit, and a PV system has been proposed in order to resolve these problems. In order to operate this system without interruption, the hydrogen storage volume must be managed. This paper proposes a novel hydrogen management method for a residential DG system with PV cells and hydrogen‐storage type FCs. The hydrogen storage volume is maintained at the preset frequency by operating the FC unit and the EL unit. Models of the PV, FC, and EL were constructed for a simulation. In the simulation, we showed that the proposed management method is viable for a residential DG system with PV cells and hydrogen‐storage FCs.

On voluntary rhythmic leg movement behaviour and control during pedalling.

The overall purpose of the present dissertation was to contribute to the understanding of voluntary human rhythmic leg movement behaviour and control. This was achieved by applying pedalling as a movement model and exposing healthy and recreationally active individuals as well as trained cyclists to for example cardiopulmonary and mechanical loading, fatiguing exercise, and heavy strength training. As a part of the background, the effect of pedalling frequency on diverse relevant biomechanical, physiological, and psychophysiological variables as well as on performance was initially explored. Freely chosen pedalling frequency is considerably higher than the energetically optimal pedalling frequency. This has been shown by others and was confirmed in the present work. As a result, pedal force is relatively low while rates of VO2 and energy turnover are relatively high during freely chosen pedalling as compared to a condition where a lower and more efficient pedalling frequency is imposed. The freely chosen pedalling frequency was in the present work, and by others, found to most likely be less advantageous than the lower energetically optimal pedalling frequency with respect to performance during intensive cycling following prolonged submaximal cycling. This stimulates the motivation to understand the behaviour and control of the freely chosen pedalling frequency during cycling. Freely chosen pedalling frequency was in the present work shown to be highly individual. In addition, the pedalling frequency was shown to be steady in a longitudinal perspective across 12 weeks. Further, it was shown to be unaffected by both fatiguing hip extension exercise and hip flexion exercise as well as by increased loading on the cardiopulmonary system at constant mechanical loading, and vice versa. Based on this, the freely chosen pedalling frequency is considered to be characterised as a highly individual, steady, and robust innate voluntary motor rhythm under primary influence of central pattern generators. The last part of the characterisation is largely based on, and supported by, work of other researchers in the field. Despite the robustness of the freely chosen pedalling frequency, it may be affected by some particular factors. As an example from the present work, freely chosen pedalling frequency during treadmill cycling increased by on average 15 to 17 rpm when power output was increased from a value corresponding to 86% and up to 165% of Wmax . This phenomenon is supported by other studies. As another example from the present work, freely chosen pedalling frequency decreased by on average 9 to 14 rpm following heavy strength training that involved both hip extension and hip flexion. Further, the present work suggested that the latter phenomenon occurred within the first week of training and was caused by in particular the hip extension strength training rather than the hip flexion strength training. The fast response to the strength training indicated that neural adaptations presumably caused the observed changes in movement behaviour. The internal organisation of the central pattern generator is by some other researchers in the field considered to be functionally separated into two components, in which, one is responsible for movement frequency and another is responsible for movement pattern. For the present dissertation, the freely chosen pedalling frequency was considered to reflect the rhythmic movement frequency of the voluntary rhythmic leg movement of pedalling. The tangential pedal force profile was considered to reflect the rhythmic movement pattern. The present work showed that fatiguing hip flexion exercise in healthy and recreationally active individuals modified the tangential pedal force profile during cycling at a pre-set target pedalling frequency in a way that the minimum tangential pedal force became more negative, the maximum tangential pedal force increased, and the phase with negative tangential pedal force increased. In other words, the legs were "actively lifted" to a lesser extent in the upstroke phase. Fatiguing hip extension exercise did not have that effect. And none of the fatiguing exercises affected the freely chosen pedalling frequency. The present work furthermore showed that the primary effect of hip extension strength training was that it decreased the freely chosen pedalling frequency. An interpretation of this could be that the hip extension strength training, in particular, influenced the output from the component of the central pattern generator that may be responsible for rhythmic movement frequency.

Medium with unity refractive index at preset frequency

It is shown that, under certain conditions, a medium consisting of electric and magnetic dipoles will neither reflect nor refract incident radiation at a preset frequency.

Automatic Calibration System for Digital-Display Vibrometers Based on Machine Vision

Abstract Considering the low efficiency during the process of traditional calibration for digital-display vibrometers, an automatic calibration system for vibrometers based on machine vision is developed. First, an automatic vibration control system is established on the basis of a personal computer, and the output of a vibration exciter on which a digital-display vibrometer to be calibrated is installed, is automatically adjusted to vibrate at a preset vibration level and a preset frequency. Then the display of the vibrometer is captured by a digital camera and identified by means of image recognition. According to the vibration level of the exciter measured by a laser interferometer and the recognized display of the vibrometer, the properties of the vibrometer are calculated and output by the computer. Image recognition algorithms for the display of the vibrometer with a high recognition rate are presented, and the recognition for vibrating digits and alternating digits is especially analyzed in detail. Experimental results on the built-up system show that the prposed image recognition methods are very effective and the system could liberate operators from boring and intense calibration work for digital-display vibrometers

The Influence of Preset Frequency, Loading Condition, and Exercise Type on the Mechanical Behavior of a Novel Vibratory Bar

This study aimed to analyze the influence of different vibration frequencies, loading conditions, and exercise types on the mechanical behavior of a novel vibratory bar (VB). Fourteen healthy men were asked to hold the VB during lying row (pulling) and bench press (pushing) static exercise as steadily as possible for 10 seconds with loads of 20, 50, and 80% of the maximum sustained load (MSL) and at preset vibration frequencies (f(in)) of 20, 35, and 50 Hz. Root mean square vibration acceleration (a(RMS)), peak-to-peak displacement (D), and frequency (f(out)) were gained from a 3-dimensional accelerometer fixed to the VB. Increasing vibration frequency (from 20 to 50 Hz) resulted in a progressive and sizeable increase in VB a(RMS) and f(out) (both p ≤ 0.001) with smaller variations of D (≤5.9%, p ≤ 0.001). Adding weight to the VB (progressive overload from 20 to 80% MSL) did not affect D and minimally altered a(RMS) (<4.2%, p = 0.014) and f(out) (<1.7%, p = 0.002). Altering the type of exercise (pulling vs. pushing) did not affect VB a(RMS), D, and f(out). In conclusion, this study establishes the validity of a novel VB and legitimates its use for effective and safe upper-body static exercise with a wide range of vibration frequencies and loading conditions in the context of physical training or rehabilitation.

Application of Inductive Topological Transfer Function Generation for a Cascaded Low-Pass Filter

This work presents applications of an inductive topological approach in the calculation of the transfer function of a cascading network control system. The method provides a very versatile and effective way of counting all the graphs that contribute and of translating them into their algebraic contribution. The contributing graphs are very simple and reflect the morphology of the original control system signal flow graph. Application of the method and results are presented for an n-cell RC network. We derive an analytical formula relating ω(3 dB) to the filter size (n) and RjCj (j=1,2,…,n). This formula can be used for designing preset frequency range self-loaded LP filters by varying their size. We also derive general expressions for the sensitivities which we use to observe a sensitivity-insensitivity filter transition for various frequency ranges, relaxation times, and, most importantly, filter sizes.

Workforce Management in Periodic Delivery Operations

Service quality and driver efficiency in the delivery industry may be enhanced by increasing the regularity with which a driver visits the same set of customers. However, effectively managing a workforce of drivers may increase travel distance, a traditional metric of the vehicle routing problem (VRP). This paper evaluates the effect that workforce management has on routing costs, providing insight for managerial decision making. The analysis is presented in the context of the period vehicle routing problem (PVRP), an extension of the VRP with vehicle routes constructed to service customers according to preset visit frequencies over an established period of time. We develop models to apply workforce management principles. Through a computational study with standard PVRP test cases and real-world delivery data, we show that multiobjective PVRP models can achieve a balance between workforce management and travel distance goals. With the proper parameters in place, workforce management principles may be successfully applied without sacrificing other operational objectives.

A Hydrogen Management Method in Residential Distributed Generation Systems with Photovoltaic Cells and Hydrogen-Storage Type Fuel Cells

SUMMARY Recently, renewable energy has been attracting attention as a result of global warming and the depletion of fossil fuels. Photovoltaic (PV) systems have spread rapidly around the world because they generate electric power quietly and can be installed in many places. The output power generated in a PV system fluctuates with changes in solar irradiance and panel temperature. The reverse flow of surplus power in output spikes may have a negative effect on electric power quality, such as on the frequency and voltage in a power system. A residential distributed generation (DG) system composed of a fuel cell (FC) unit, an electrolyzer (EL) unit, and a PV system has been proposed in order to resolve these problems. In order to operate this system without interruption, the hydrogen storage volume must be managed. This paper proposes a novel hydrogen management method for a residential DG system with PV cells and hydrogen-storage type FCs. The hydrogen storage volume is maintained at the preset frequency by operating the FC unit and the EL unit. Models of the PV, FC, and EL were constructed for a simulation. In the simulation, we showed that the proposed management method is viable for a residential DG system with PV cells and hydrogen-storage FCs.

The isolated buck boost dc to dc converter with high efficiency for higher input voltages

An isolated buck–boost dc/dc converter for wide input-voltage range is proposed in this paper, and the fullbridge (FB) boost converter, being one of the typical topologies, is analyzed. Due to the existence of the resonant inductor (including the leakage inductor), the FB-boost converter can only adopt the two-edgemodulation (TEM) scheme with the FB cell being leading-edge modulated and the boost cell being trailing-edge modulated to minimize the inductor current ripple over the inputvoltage range, and a phase-shift-controlscheme-based TEM with the use of the market available controller IC such as UC3895 is proposed, which realizes phase-shifted control for the FB cell to achieve zero-voltage switching. In order to improve the reliability and efficiency of the FB-boost converter, a three-mode dual-frequency control scheme is proposed, in which the FBboost converter operates in boost, FB-boost and FB modes in low, medium and high input voltage regions, respectively, and for which the expression of the inductor current ripple is derived in this paper. As the input voltage in the FB-boost mode is close to the output voltage, the inductor current ripple in this mode is much smaller than that in the other modes, and the switching frequency of the boost cell in this mode can be lowered to one-(2N+1)th of the preset switching frequency to reduce the switching loss, and hence, to improve the efficiency. A 250–500 V input, 360 V output, and 6 kW rated power prototype is fabricated to verify the effectiveness of the design and control method. The average efficiency over the input-voltage range is 96.5%, and the highest efficiency attained is 97.2%. Key wordsbuck, boost,, buck-boost, Isolated buck–boost converter ,full-bridge boost converter, inductor current ripple,pulse width modulation(PWM), two-edge modulation (TEM),hysteresis modulation .

Aluminum particle combustion in turbulent flames

Predictive mechanisms for particle ignition and combustion rates are required in order to develop optimized propellant and energetic formulations using micron-sized metal powders, such as aluminum. Most current descriptions are based on laboratory experiments performed in stationary or laminar combustion configurations. However, turbulent environments exist in most applications and validity of the present descriptions for such environments has not been established. This experimental study is aimed to measure burn times for aluminum particles burning in environments with different levels of turbulence. A laminar air-acetylene flame is produced, and auxiliary tangential jets of air with adjustable flow rates are used to achieve different controlled levels of turbulence. Fine spherical aluminum powder is injected in the flame axially using a flow of nitrogen. The streaks of burning particles are photographed using a camera placed behind a mechanical chopper interrupting the photo-exposure with a pre-set frequency. The obtained dashed streaks are used to measure the particle burn times for different flow conditions. The particle burn times are correlated with the particle size distribution to obtain the burn time as a function of the particle size. The results are processed to obtain a correction for the Al particle burn rate as a function of the turbulence intensity, I. The measured burn times are longer than predicted for the micron-sized Al particles using a correlation based on survey of earlier experiments, mostly with coarser Al powders. Increased turbulence intensity results in substantial reduction of the particle burn time. Present data suggest that the burn rate for particle combustion in a laminar environment should be multiplied by 1+18.2I, to estimate the acceleration of aluminum combustion in turbulent environments.

Sound decay in a rectangular room with impedance walls

The problem of sound decay in a rectangular room is considered for the case of a room with walls the acoustic properties of which are described by the impedance, which implies a dependence of the absorption coefficient on the angle of incidence of sound waves. The ray approximation is used to determine the sound decay laws for different distributions of wall absorption. It is shown that, in a room with impedance walls, the sound decay is slower than in the conventional reverberation model, in which the wall absorption coefficient is independent of the angle of incidence. The problem is also solved in the wave approximation to determine the decay law for a preset frequency band.

Design and implementation of a low-cost multiple-range digital phase detector

This article describes the design, simulation, implementation and testing of a novel low-cost multiple-range programmable digital phase detector. The detector receives two periodic signals and calculates the ratio of the time difference to the time period to measure and display the phase difference. The resulting output values are in integer form ranging from −180° to 180°. Users can select the detector pre-set operation frequency ranges using a three-bit pre-scalar. This enables to use the detector for various applications. The proposed detector can be programmed over a frequency range of 10 Hz to 25 kHz by configuring its clock divider circuit. Detector simulations were conducted and verified using ModelSim and the design was implemented and tested using an Altera Cyclone II field-programmable gate array board. Both the simulation and actual circuit testing results showed that the phase detector has a magnitude of error of only 1°. The detector is ideal for applications such as power factor measurement and correction, self-tuning resonant circuits and in metal detection systems. Unlike other stand-alone phase detection systems, the reported system has the ability to be programmed to several frequency ranges, hence expanding its bandwidth.