Adjustable Waveform Research Articles

Terahertz waveform synthesis in scattering systems via nonlinear ghost imaging

Terahertz Nonlinear Ghost Imaging introduces a groundbreaking method for object sampling at spatial-temporal levels, achieving super-resolution (i.e., beyond the diffraction limit). Our theoretical and experimental endeavour seeks to leverage this technique, enabling arbitrary field-level waveform manipulation through intricate propagation in scattering environments. This approach facilitates essential agile waveform adjustment, made possible through near-field interactions between terahertz sources and scattering media.

Photoplethysmography-Based Distance Estimation for True Wireless Stereo.

Recently, supplying healthcare services with wearable devices has been investigated. To realize this for true wireless stereo (TWS), which has limited resources (e.g. space, power consumption, and area), implementing multiple functions with one sensor simultaneously is required. The Photoplethysmography (PPG) sensor is a representative healthcare sensor that measures repeated data according to the heart rate. However, since the PPG data are biological, they are influenced by motion artifact and subject characteristics. Hence, noise reduction is needed for PPG data. In this paper, we propose the distance estimation algorithm for PPG signals of TWS. For distance estimation, we designed a waveform adjustment (WA) filter that minimizes noise while maintaining the relationship between before and after data, a lightweight deep learning model called MobileNet, and a PPG monitoring testbed. The number of criteria for distance estimation was set to three. In order to verify the proposed algorithm, we compared several metrics with other filters and AI models. The highest accuracy, precision, recall, and f1 score of the proposed algorithm were 92.5%, 92.6%, 92.8%, and 0.927, respectively, when the signal length was 15. Experimental results of other algorithms showed higher metrics than the proposed algorithm in some cases, but the proposed model showed the fastest inference time.

Research on Chinese Speech Emotion Recognition Based on Deep Neural Network and Acoustic Features.

In recent years, the use of Artificial Intelligence for emotion recognition has attracted much attention. The industrial applicability of emotion recognition is quite comprehensive and has good development potential. This research uses voice emotion recognition technology to apply it to Chinese speech emotion recognition. The main purpose of this research is to transform gradually popularized smart home voice assistants or AI system service robots from a touch-sensitive interface to a voice operation. This research proposed a specifically designed Deep Neural Network (DNN) model to develop a Chinese speech emotion recognition system. In this research, 29 acoustic characteristics in acoustic theory are used as the training attributes of the proposed model. This research also proposes a variety of audio adjustment methods to amplify datasets and enhance training accuracy, including waveform adjustment, pitch adjustment, and pre-emphasize. This study achieved an average emotion recognition accuracy of 88.9% in the CASIA Chinese sentiment corpus. The results show that the deep learning model and audio adjustment method proposed in this study can effectively identify the emotions of Chinese short sentences and can be applied to Chinese voice assistants or integrated with other dialogue applications.

Nonsinusoidal motion effect on a self-propelled heaving foil

In order to explore the mechanism of bionic propulsion and bionic robots, to make up for the limitations of traditional propulsion with a uniform incoming flow, numerical methods are used to couple fluid dynamics and flapping foil motions, and a flapping-fluid coupling self-propulsion calculation model is established in this paper. K is used as the waveform adjustment parameter to change the waveform from triangle wave to sine wave and square wave. The self-propulsion performances of non-sinusoidal heave motion under two frequency-heaving amplitude combinations are numerically simulated to study the influence of different motion waveforms on self-propulsion velocity, efficiency and flow field structure in still water. The results show that the non-sinusoidal waveform has a great influence on the self-propulsion. With the increase of K, the closer to the square wave, the more violent the speed oscillation, the faster the starting acceleration, the greater the forward displacement and the average speed, as K decreases, self-propulsion efficiency and energy utilization continue to increase. The results of this study have certain guiding significance for the design of bionic underwater vehicles.

A Simplified Model of a Surge Arrester and Its Application in Residual Voltage Tests

A simplified and accurate model of a surge arrester used in the residual voltage test is proposed in this paper. With the help of a genetic algorithm, the measured impulse current and residual voltage waveforms are utilized to determine circuit parameters of the proposed model and the generation circuit precisely. The technique starts from the circuit parameter determination using the preliminary experimental data with a lower current peak than that specified by the standard. From the determined model and with the help of the genetic algorithm, the circuit parameters and the charging voltage to obtain the specified current peak and the residual voltage can be estimated accurately. The validity of the proposed technique has been verified by experiments for the estimation of the appropriate current circuit parameters, the charging voltage, and the residual voltage. In addition, the application of the proposed model in the residual voltage tests is presented. From comparison of simulated and experimental results with the determined parameters, the impulse current and residual voltage waveforms are determined precisely. It is confirmed that the proposed model and technique are attractive in the appropriate circuit parameter determination and the residual voltage estimation in the residual voltage tests of surge arresters. The proposed method also provides a good advantage for reduction of the number of trial and error experiments for obtaining the current waveform according to the standard requirement. Moreover, the unintentional damages of the arrester during the process of the waveform adjustment will be reduced significantly.

An Algorithm for Circuit Parameter Identification in Lightning Impulse Voltage Generation for Low-Inductance Loads

This paper presents an effective technique based on an artificial neural network algorithm utilized for circuit parameter identification in lightning impulse generation for low inductance loads such as low voltage windings of a power transformer, a large distribution transformer and an air core reactor. The limitation of the combination between Glaninger’s circuit and the circuit parameter selection from Feser’s suggestions in term of producing an impulse waveform to be compliant with standard requirements when working with a low inductance load is discussed. In Feser’s approach, the circuit parameters of the generation circuit need to be further adjusted to obtain the waveform compliant with the standard requirement. In this process, trial and error approaches based on test engineers’ experience are employed in the circuit parameter selection. To avoid the unintentional damage from electrical field stress during the voltage waveform adjustment process, circuit simulators, such as Pspice and EMTP/ATP, are very useful to examine the generated voltage waveform before the experiments on the test object are carried out. In this paper, a system parameter identification based on an artificial neural network algorithm is applied to determine the appropriate circuit parameters in the test circuit. This impulse voltage generation with the selected circuit parameters was verified by simulations and an experiment. It was found that the generation circuit gives satisfactory impulse voltage waveforms in accordance with the standard requirement for the maximum charging capacitance of 10 µF and the load inductance from 400 µH to 4 mH. From the simulation and experimental results of all cases, the approach proposed in this paper is useful for test engineers in selection of appropriate circuit components for impulse voltage tests with low inductance loads instead of employing conventional trial and error in circuit component selection.

Waveform adjustment for obtaining higher quality droplets based on a multi-satellite droplet monitoring system

In the field of printed electronics, there are many kinds of ink with a variety of performance and parameters. In order to generate high-quality droplets, it is necessary to eject droplet for testing in order to discover the appropriate excitation voltage and waveform shape. Consequently, a real-time and efficient droplet monitoring system is needed to monitor droplet formation quality. A multi-satellite droplet monitoring system is proposed in this paper. It can not only monitor the droplet with multiple satellites but also can generate the instantaneous droplet position curve, length curve and velocity curve. The waveform voltage and dwell time can be adjusted in real-time to obtain droplets with higher quality and efficiency.

T022 Shaping the temporal characteristics of transcranial magnetic stimulation

The pulse waveform of transcranial magnetic stimulation (TMS) affects the degree to which various neuronal elements and populations are activated as well as the strength of neuromodulation resulting from repetitive TMS. Conventional TMS devices allow very limited pulse waveform adjustment; therefore we developed TMS devices with controllable pulse parameters (cTMS). So far cTMS has been used, by our and other groups, to study strength-duration curves in motor cortex and the associated neural membrane time constants; pulse-width dependence of motor input–output curves, cortical neuron recruitment, paired-pulse paradigms, and scalp sensation; and pulse-shape dependence of neuromodulatory effects. These studies show that changing the pulse width, shape, and/or direction may alter the neural elements that are preferentially activated in cortex, as evidenced by differences in motor evoked potential latencies and membrane time constants. These parameters also affect the changes of neural excitability resulting from 1 Hz and intermittent theta burst stimulation. For the 1 Hz protocol, the near rectangular cTMS pulses produced stronger inhibition than conventional sinusoidal pulses, with unidirectional cTMS pulses having the strongest effect. As well, cTMS has been used to optimize new repetitive paired-pulse stimulation protocols. cTMS was also used to show that the slope of motor input–output curves depends on pulse width via the same mechanism driving the strength-duration relationship of motor threshold. Finally, the pulse width affects the perceived scalp sensation of TMS, with briefer pulses feeling sharper and slightly more uncomfortable than longer pulses. In parallel with exploring the capabilities afforded by cTMS, we are developing a next generation ultraflexible TMS device called a modular pulse synthesizer (MPS) that would allow the generation of essentially any pulse shape and pulse sequence/train within the energy levels practical for TMS. The development and adoption of cTMS and MPS could enable expanded utilization of the temporal characteristics of TMS as a means of enhancing functional targeting, noninvasive biomarkers, neuromodulatory potency, and tolerability.

Defibrillation Waveform Duration Adjustment Increases the Proportion of Acceptable Defibrillation Thresholds in Patients Implanted with Single-Coil Defibrillation Leads

The aim of this study was to determine whether defibrillation waveform duration adjustment with single-coil defibrillation leads can be used to increase the proportion of patients with satisfactory defibrillation thresholds (DFTs). A retrospective analysis of the DFT levels for 105 patients with implantable cardioverter-defibrillator devices and a single-coil defibrillation lead was performed. Two groups of patients were compared: 34 patients who had undergone waveform tuning (group A) and 71 patients with a fixed-tilt waveform (group B). Additional data including demographics, etiology, New York Heart Association functional class, left ventricular ejection fraction, high-voltage lead impedance and medications were gathered to determine what effect these variables had on the DFT levels. Of the 34 patients who had undergone waveform adjustment (group A), 27 (79%) were found to have satisfactory DFTs, while 41 (58%) of the 71 patients with fixed-tilt devices (group B) had satisfactory DFTs. Waveform duration adjustment was found to significantly increase the proportion of patients with satisfactory DFTs (p = 0.03).

Relation analysis between cathode ablation and voltage for a magnetically insulated transmission line oscillator

Through the particle-in-cell simulation and experimental investigation, the relation between the cathode ablation and the input voltage waveform of a magnetically insulated transmission line oscillator (MILO) is analyzed. And the key factor that results in the cathode ablation is found. The figures and process that the electron beam bombards back the cathode are obviously presented. By waveform adjustment of the low impedance accelerator, the reverse voltage of the input voltage to MILO is restrained, and the cathode ablation problem of the MILO driven by the low impedance accelerator is solved. Analysis results show that the electron beam which has been hauled from the cathode by the right direction voltage moves back, which the reverse voltage with adequate amplitude driven, and the beam bombards back the the cathode. The reverse current is formed and the cathode of the MILO device is ablated. Therefore, the reverse voltage immediately following the down slope of the input voltage is a key factor.

A Design of Cascaded Multilevel Inverter Snubber Circuit

The high frequency induction heating power supply has received increasing attention from researchers, multilevel converter is a high voltage large power application areas of research focus and core, it solves the problem of the multilevel inverter output voltage waveform adjustment, avoids the problem of two times reversing that the load voltage in the commutation during the dead period occurred. An effective way to improve efficiency is to keep the power device of low voltage stress and less switching loss. A passive lossless snubber circuit is designed for inhibiting the reverse recovery current of diode and improving the turn-on condition of powers switch. The operation process of snubber circuit is analyzed and the parameter design method is given. The results of simulation have verified the validity of design methods and the conclusions given by theoretically analyzing in this paper.

Direct Microjoining of Copper Materials Using Laser Beams

Direct microjoining using Yttrium-Aluminium-Garnet (YAG) laser beams of copper wire and a plate or substrate board was carried out. The control of the behavior of the molten wire was extremely important to prevent joining defects such as evaporation or constriction of the wire. Both the contact angle between the wire and the plate and the distance from the tip of the wire to the laser irradiation point affected the improvement of the defect. Controlling the input heat by pulse waveform adjustment was also effective in controlling the melt behavior of the wire. Therefore, for plates 100 and 200µm thick, high peeling strength of 4N with little dispersion was obtained. However, for copper foil 70µm thick, the strength was poor and the dispersion was high. Because of the low heat capacity of the foil, the thermal condition of the wire extremely severe. Therefore, more details on input heat control are required.

Inductive plasma current start-up by the outer vertical field coil in a spherical tokamak

Plasma current-start up induced by an outer vertical field coil is studied during the ignition access phase in a spherical tokamak reactor. We have illustrated the concept that the plasma current of ~50 MA could be induced by the outer vertical field coil in the proposed spherical tokamak with the help of the small central solenoid flux of ±5 V s and the strong heating power less than 100 MW for the internal inductance of i~0.4-0.8 without the help of bootstrap current and non-inductive current drive power. The required condition to achieve this operation scenario is that the flux produced by the equilibrium vertical field is larger than the inductive flux. Current start-up operation is achieved by adding the small ohmic heating solenoid flux for the flux waveform adjustment because the flux from the outer vertical field coil cannot solely induce the desired plasma current waveform in the case of the preprogramming of the heating power.

Graticules for Judging Television Waveforms

The following three papers deal with the subject of using a graticule or overlay on an oscilloscope to help determine whether or not a television waveform will produce a subjectively acceptable picture. Aspects of this subject have been discussed as far back as 1947–1948. The concept of echo weighting and several data involved in the concept were described in a Journal paper of May 1953 (Influence of Television Transmission Echoes). — It is interesting to see how the concept has become more definite and formalized and how the requirements have become somewhat less severe. In the early days, the communications people were scared of picture deterioration and afraid of the consequences of possible miscalulation. Present-day engineers are more firmly certain, because of the widespread experience, of their tolerances. For a long time, because of the limited precision and stability of cathode-ray oscilloscopes, it was deemed impractical to use graticules as indicators, but engineers can now predict with some confidence the result of a particular waveform adjustment. It is now reasonable to assert that the industry should settle on a standard graticule for evaluating television transmission in North America.