Square-wave Signal Research Articles

Influence of Load Signal Form and Variable Amplitude Loading on the Corrosion Fatigue Behaviour of Aluminium Alloys

Aluminium alloys are used for a large variety of safety relevant applications for example in the automotive and aviation industries. With the introduction of high strength but possibly less corrosion resistant alloys it is essential to determine if an enhanced sensitisation against corrosion comes into effect under simultaneous mechanical and corrosive loading. Within this work corrosion fatigue tests under constant and variable amplitude loading were carried out on aluminium alloys established for chassis applications such as EN AW-5018 with slightly elevated magnesium content (AlMg3.5Mn), EN AW-6082-T6, EN AW-6110A-T6 and EN AC‑42100-T6 as well as alloys sensitised to corrosion. Sensitisation was obtained by a borderline (17 h at 130 °C) and an excessive (500 h at 130 °C) thermal ageing treatment and elevated copper contents for the forged and cast alloys. Aforementioned alloys and material conditions were assessed concerning the impact of mechanical loading conditions such as load signal type (sinusoidal and square-wave signal), strain rate and load spectra on the damaging process and on corrosion fatigue life. Fatigue tests were complemented by simultaneous determination of electrochemical characteristics as well as the type of corrosion by metallographic investigations.

A methodology for memristance calculation

A memristor is a newly found fundamental circuit element whose behavior can be predicted using either the charge-dependent function called memristance or the flux-dependent function called memductance. Therefore, it is important to find the memristance or memductance function of a memristor. To the best of our knowledge, there is no methodology describing how to obtain the memristance function or memristor characteristic in the literature for this purpose as of yet. In this work, a methodology is suggested to find the memristance or memductance functions. The methodology suggests first doing several experiments with a memristor using a square-wave signal to acquire data and then using an algorithm inspired by the experience on ionic memristors reported in the literature to obtain its memristance and memductance functions. The methodology is applied to calculate the memristance function and memristor characteristic of a memristor emulator. Justifications for this method are also given.

Design and performance of a polymer Mach-Zehnder interferometer electro-optic modulator at 1.55 μm

Based on poled guest-host electro-optic (EO) polymer DR1/SU-8, a Mach-Zehnder interferometer (MZI) EO modulator operated at 1.55 μm is proposed. For achieving high response speed and high EO modulation efficiency, both waveguide structure and electrode structure are especially optimized. The impedance match and less index mismatch are achieved. The final characteristic impedance of electrode is about 49.4 Ω, and the microwave index and the light-wave index are 1.5616 and 1.6006, respectively. The device is fabricated using wet-etching technique and inductively coupled plasma (ICP) etching technique, and its performance is measured at 1.55 μm. Experimental results show that when the applied voltage is tuned, the modulator can be changed from ON state to OFF state. The insertion loss at ON state is 12 dB and the extinction ratio between ON and OFF states is about 10 dB. The high response speed is in nanosecond level for a square-wave signal. Therefore, the modulator possesses potential applications in high-speed optical networks on chip.

Relaxation Oscillator-Based Active Bridge Circuit for Linearly Converting Resistance to Frequency of Resistive Sensor

An easily implementable signal conditioning circuit for resistive humidity and temperature sensors is presented. It is based on a relaxation oscillator in which both the frequency and the duty-cycle of the square-wave output signal simultaneously carry information from two different types of sensors. The output frequency is linearly related to the resistive unbalance of an active bridge, whereas the duty-cycle is independently controlled by a thermal sensor for controlling temperature error of the humidity sensor (RH). The design, analysis, and experimental characterization of the circuit and its application to a sol-gel thin film porous γ-Al2O3-based humidity sensor and resistance temperature detector are reported. Experimental results confirm the theoretical value predicted. The circuit covering wide resistance measurement range has the potential for remotely monitoring measurement parameters accurately.

Robust square-wave polarization switching in vertical-cavity surface-emitting lasers

We study theoretically and experimentally the combined effects of polarization-selective optical feedback and of crossed-polarization reinjection in a vertical-cavity surface-emitting laser. We show that the application of polarization-selective optical feedback, which induces an effective dichroism in the system, allows one to generate a robust and regular square-wave output signal in each polarization component. The period of the square-wave signal is determined by twice the reinjection delay. We analyze the regularity of the induced modulation as a function of laser bias current, dichroism, and of the levels and delays of reinjection and feedback, thus revealing the robustness of the square-wave emission in the parameter space. We also show that the feedback is more effective when acting on the long-wavelength polarization mode, which can be traced to the asymmetry of the bistable region of the vertical-cavity surface-emitting lasers for low dichroism.

Study of data format transform with optical waveguide resonators

Based on the linear property of silicon microring resonators, we experimentally observed that such resonator can transform square-wave signal into pulse-wave signal, and the output waveform is strongly dependent on the input wavelength. We then proposed a mathematical model, which utilized linear coupling mode theory, Fourier transform and electro-optical Mach-Zehnder (MZ) intensity modulation functions. The numerical simulation results fit well with the experimental results. Besides, we gave a detailed explanation based on the transfer function of microrings. Furthermore, we have studied the case when the ring resonator is deviated from the critical coupling condition, and found that the coupling state, over coupling or under coupling, can be easily judged through the output waveform.

Amplitude Control of Phase Modulation for Dithered Closed-loop Fiber Optic Gyroscope

The amplitude error of phase modulator used in closed-loop fiber optic gyroscope has occurred by the temperature dependency of the electro-optic coefficient, and also can be due to the square-wave dither signal which is generally applied for eliminating the deadzone. This error can cause bias drift and scale factor error. This paper analyzes the temperature dependency of the modulation amplitude and the relationship with the scale factor of the gyroscope, and deals with an amplitude control method. The error calculation logic considering the dither signal is implemented on the signal processing module. The result of experiments from a prototype gyroscope shows the effect of the modulation amplitude control and a considerable improvement on performances.

A new inertial piezoelectric rotary actuator based on changing the normal pressure

A new inertial rotary actuator using two piezoelectric stacks as the power converter is proposed. The actuator rotates by regulating the friction force, which is controlled by the normal pressure, and driven by a square-wave or triangular-wave signal. Dynamic and simulation models of the actuator are established to evaluate the performance of the actuator in terms of distance, speed, radial run-out and positioning repeatability. A 40 mm wide and 32 mm high prototype was compared with the simulated model. The results show that the angular speed is proportional to the amplitude and frequency of the driving signal. A 10 μrad angular displacement resolution is obtained by applying a of 15 Vp–p square wave with a frequency of 10 Hz.

Multivariate modeling of cognitive-motor stimulation on neurovascular coupling: transcranial Doppler used to characterize myogenic and metabolic influences

Neural activation induces changes in cerebral blood flow velocity (CBFV) with separate contributions from resistance-area product (V(RAP)) and critical closing pressure (V(CrCP)). We modeled the dependence of V(RAP) and V(CrCP) on arterial blood pressure (ABP), end-tidal CO(2) (EtCO(2)), and cognitive stimulation to test the hypothesis that V(RAP) reflects myogenic activity while V(CrCP) reflects metabolic pathways. In 14 healthy subjects, CBFV was measured with transcranial Doppler ultrasound, ABP with the Finapres device and EtCO(2) with infrared capnography. Two different paradigms (word or puzzle) were repeated 10 times (30 s on-off), and the corresponding square-wave signal was used, together with ABP and EtCO(2), as inputs to autoregressive-moving average (ARMA) models, which allowed identification of the separate contributions of the three inputs to either V(RAP) or V(CrCP). For both paradigms, the contribution of ABP was mainly manifested through V(RAP) (P < 0.005 for word; P < 0.004 for puzzle), while stimulation mainly contributed to V(CrCP) (P < 0.002 for word; P < 0.033, for puzzle). The contribution of EtCO(2) was relatively small (<10%) with greater contribution to V(CrCP) (P < 0.01 for puzzle; not significant for word). Separate step responses were also obtained for each of the three inputs. ARMA modeling of V(RAP) and V(CrCP) allows the separation of the effects of cerebral autoregulation and CO(2) reactivity from the main effects of cognitive-motor stimulation and have the potential to improve the diagnostic value of neurovascular coupling testing in physiological and clinical studies.

Effect of Time-Delay in a Time-Delayed Mono-Stable System Subject to White Noise and Dichotomous Noise

The stochastic resonance (SR) for a time-delayed mono-stable system, driven by periodic square-wave signal, a dichotomous noise and a static force as well as multiplicative and additive noise is considered. It is found that the output signal-to-noise ratio (SNR) increases monotonically with the increase of the delayed time. The SNR varies non-monotonically with the intensities of the dichotomous noise and multiplicative and additive noise as well as the system parameter and the amplitude of the input square-wave signal.

Design and Fabrication of Thermocapillary Micro Bubble Pump

In this paper, a novel MEMS-fabricated thermal bubble pump is proposed. By using thermocapillary effect in a microchannel loop, bubbles are designed to move only in one direction of the loop. Driving heater with a square-wave signal, bubble nucleates and grows asymmetrically above the heater. As soon as the heating pulse is turned off, an interesting phenomenon is found. Instead of bubble collapse, bubble moves toward growing direction. Continuous bubbles grow and move periodically when square-wave pulsing signals are applied. Thermocapillary pumping phenomena are achieved successfully in the experiments. By adjusting background temperature field, thermocapillary pumping phenomena can be sustained. Detailed mechanism for pumping force will be discussed in this paper.

Stochastic Resonance Enhanced by Colored Multiplicative and Additive Noises in a Time-Delayed Bistable System

The phenomenon of stochastic resonance (SR) in a time-delayed bistable system with square-wave signal, a constant force, with asymmetric dichotomous noise and multiplicative and additive colored noise is investigated. It is found that, the SR behavior can be observed on the signal-to-noise ratio (SNR) curves as a function of the intensity and asymmetry of the dichotomous noise, as a function of the amplitude of the square-wave, the constant force, as well as of the strength of the colored noises.

Evaluation of damage to DNA induced by UV-C radiation and chemical agents using electrochemical biosensor based on low molecular weight DNA and screen-printed carbon electrode

There is great interest and need to detect and evaluate damage to DNA by environmental factors. In the present paper, simple electrochemical DNA biosensors composed of commercially available screen-printed carbon electrode (SPCE) and low molecular weight double-stranded DNA (dsDNA) recognition layer are reported and applied to the detection of damage to DNA by UV-C radiation and reactive oxygen species produced by the Fenton type reaction in model as well as mineral water samples with additives. Complex DNA biosensor response is based on square-wave voltammetric intrinsic signal of the guanine moiety as well as that of the intercalative indicator thioridazine, cyclic voltammetric response of the [Fe(CN)6]3−/4− indicator in solution and on electrochemical impedance spectroscopy when the measurements can be performed in the same solution. For the last two types of measurements, the biosensor was also used with an interface between the SPCE and DNA formed by a composite of carboxylated single-walled carbon nanotubes and chitosan to enhance the transducer conductivity. Individual electrochemical/electrical signals depend on the time of biosensor incubation in a cleavage medium and their profiles characterize process of deep DNA degradation.

Electrochemical Characterization of and Stripping Voltammetry at Screen Printed Electrodes Modified with Different Brands of Multiwall Carbon Nanotubes and Bismuth Films

A screen-printed electrode sensor has been fabricated by modifying the carbon ink surface with different brands of multiwall carbon nanotubes (MWCNTs) and bismuth film (BiF) for the determination of traces of lead, cadmium and zinc ions by square wave anodic stripping voltammetry. The MWCNTs, from three different sources, were functionalized and dispersed in Nafion (MWCNT-Nafion) solution and placed on screen printed electrodes (MWCNT-Nafion/SPE); bismuth films were then prepared by ex-situ plating of bismuth onto the MWCNT-Nafion/SPE electrodes. The electrochemical characteristics of BiF/MWCNT-Nafion/SPE/ were examined by electrochemical impedance spectroscopy and showed differences; the charge transfer resistance tends to decrease with negative applied potentials. After optimizing the experimental conditions, the square-wave peak current signal is linear in the nmol L−1 range. The lowest limit of detection found for the separate determination of lead, cadmium and zinc were 0.7 nmol L−1, 1.5 nmol L−1, and 11.1 nmol L−1, respectively, with a 120 s deposition time.

A novel mode of air supply for aircraft cabin ventilation

Aircraft cabin ventilation is essential during commercial passenger flights. Efficient fresh air delivery has become an important research issue in the field of HVAC. This study proposes a novel mode of air supply, which has the potential to improve ventilation performance, without increasing the fresh air supply rate. The velocity at the cabin inlet is set to follow a square-wave signal. Under this periodic supply condition, the fresh air jet, after entering the cabin, appears to oscillate. This motion is able to continue, for an interval of time, during which the mixing between fresh and residual cabin air is enhanced, if the periodic supply signal is properly defined. Consequently, when compared to a traditional steady supply air delivery at the average rate of the periodic supply, the periodic condition may achieve better ventilation, as indicated by the performance measures considered in this study. Note that the reported improvements may need further justification by field tests, due to the somewhat limited capability of a numerical simulation to fully reflect the complexity of real boundary conditions.

Phenomenon of entropic stochastic resonance with asymmetric dichotomous noise and white noise

The entropic stochastic resonance (ESR) in a confined system subject to asymmetric dichotomous noise, white noise, and a periodic square-wave signal is investigated. Under the adiabatic approximation condition, by use of the properties of the dichotomous noise, we obtain the expression of the output signal-to-noise ratio (SNR) based on two-state theory. The SNR is shown to be a nonmonotonic function of the strength and asymmetry of the dichotomous noise, the intensity of the white noise, and the amplitude of the square-wave signal. The SNR varies non-monotonically with increases in the parameters of the confined structure. The influence of the correlation rate of the dichotomous noise and the frequency of the external constant force on the SNR is also discussed.

Synchronization ability of coupled cell-cycle oscillators in changing environments

BackgroundThe biochemical oscillator that controls periodic events during the Xenopus embryonic cell cycle is centered on the activity of CDKs, and the cell cycle is driven by a protein circuit that is centered on the cyclin-dependent protein kinase CDK1 and the anaphase-promoting complex (APC). Many studies have been conducted to confirm that the interactions in the cell cycle can produce oscillations and predict behaviors such as synchronization, but much less is known about how the various elaborations and collective behavior of the basic oscillators can affect the robustness of the system. Therefore, in this study, we investigate and model a multi-cell system of the Xenopus embryonic cell cycle oscillators that are coupled through a common complex protein, and then analyze their synchronization ability under four different external stimuli, including a constant input signal, a square-wave periodic signal, a sinusoidal signal and a noise signal.ResultsThrough bifurcation analysis and numerical simulations, we obtain synchronization intervals of the sensitive parameters in the individual oscillator and the coupling parameters in the coupled oscillators. Then, we analyze the effects of these parameters on the synchronization period and amplitude, and find interesting phenomena, e.g., there are two synchronization intervals with activation coefficient in the Hill function of the activated CDK1 that activates the Plk1, and different synchronization intervals have distinct influences on the synchronization period and amplitude. To quantify the speediness and robustness of the synchronization, we use two quantities, the synchronization time and the robustness index, to evaluate the synchronization ability. More interestingly, we find that the coupled system has an optimal signal strength that maximizes the synchronization index under different external stimuli. Simulation results also show that the ability and robustness of the synchronization for the square-wave periodic signal of cyclin synthesis is strongest in comparison to the other three different signals.ConclusionsThese results suggest that the reaction process in which the activated cyclin-CDK1 activates the Plk1 has a very important influence on the synchronization ability of the coupled system, and the square-wave periodic signal of cyclin synthesis is more conducive to the synchronization and robustness of the coupled cell-cycle oscillators. Our study provides insight into the internal mechanisms of the cell cycle system and helps to generate hypotheses for further research.

Determination of hematocrit using on-line conductance cell

Hematocrit has been considered as an important marker of oxygen carrying capacity of the blood associated with whole blood viscosity to assess the mortality risk of both cardiovascular, cerebral, and kidney diseases. The present study developed a new on-line conductivity cell to measure the hematocrit of whole blood using a bipolar square-wave voltage signal at a frequency of 5kHz. By applying such a voltage signal to a blood flowing in a range of 1.2–3.0mL/min, the electrolyte effect of blood plasma, the conductive and capacitive effects of blood cells, and the sedimentation effect of erythrocytes on the conductivity of whole blood could be minimized for an accurate hematocrit measurement. The coefficient of correlation between the present method and conventional microcentrifuge method showed an excellent linear relationship. A new equation between the specific conductance and Hct of whole blood was obtained: C=12.561−0.1527 Hct (P<0.001).

DBD reactor instrumentation for NOxdegradation

The design and construction of an instrumentation for NO X degradation in a dielectric-barrier discharge reactor (DBDR) is presented. This is endowed with a parallel plane electrode glass-glass (GG) circular geometry configuration. A solid-state multi-cellular power supply was produced in order to generate the plasma discharge. The power supply is based on a full-bridge voltage inverter commanded by three 4.33 kHz square-wave signals. Thus, the output converter signal is filtered by a resonant LC circuit, providing a 13 kHz sine wave to the DBDR. Initial results showing high removal efficiencies of about 97% have been obtained by means of this instrumentation.

STOCHASTIC RESONANCE ENHANCED BY WHITE NOISE IN A STOCHASTIC BISTABLE SYSTEM

The stochastic resonance (SR) for a stochastic bistable system driven by a static force and a periodic square-wave signal as well as by additive white noise is considered from the view of signal-to-noise ratio (SNR). It is found that the SNR appears SR behavior when it is plotted as a function of the additive noise strength or as a function of the system parameters. Moreover, the influence of the static force is opposite to that of the amplitude of the stochastic potential.