Adaptive Pulse Research Articles

Atherosclerotic plaque mechanical characterization coupled with vector Doppler imaging in atherosclerotic carotid arteries in-vivo.

Methods used in clinical practice to diagnose and monitor atherosclerosis present limitations. Imaging the mechanical properties of the arterial wall has demonstrated the potential evaluate plaque vulnerability and assess the risk for stroke. Adaptive Pulse Wave Imaging (PWI) is a non-invasive ultrasound imaging technique, which automatically detects points of spatial mechanical inhomogeneity along the imaged artery and provides piecewise stiffness characterization. The aims of the present study are to: 1) demonstrate the initial feasibility of adaptive PWI to image the mechanical properties of an atherosclerotic plaque 2) demonstrate the feasibility to combine adaptive PWI with vector Doppler in a single imaging modality in order to simultaneously obtain information plaque mechanical properties and plaque hemodynamics. The common carotid arteries of 1 healthy subject and 2 carotid artery disease patients were scanned in vivo. One of the patients underwent carotid endarterectomy and a plaque sample was retrieved. In this patient, a higher compliance value of the stenotic segment was estimated by Adaptive PWI as compared with the adjacent arterial wall, and the healthy carotid artery. This was corroborated by histological staining of the plaque sample, which revealed the presence of a large necrotic core and a thrombus, characteristics associated with reduced stiffness. Moreover, the same sequence demonstrated the feasibility to obtain both stiffness maps and vector flow information, showing promise in atherosclerosis diagnosis and patient care.

ICI Mitigation in OFDM System Using Negative Peak Augmented Raised Cosine Power Pulse

Orthogonal frequency division multiplexing (OFDM) is a digital modulation technique generally which is utilized in modern wireless applications to support high data rates. The carrier frequency offset (CFO), which models the frequency discrepancy between the transmitter and receiver oscillators, gives rise to inter carrier interference (ICI), along with destroying the orthogonality between the OFDM subcarriers. Thus the alleviation of an ICI power is extremely important in an OFDM system. Pulse shaping functions is a standout amongst the most generally utilized solutions with the end goal of lessening the ICI power. In this paper, an Adaptive pulse shaping filter based on the concept of Negative Peak Augmentation is proposed to mitigate the ICI and to enhance the performance of the OFDM system. The simulation results demonstrate the impact of the proposed pulse shaping function and performance investigation in terms of SIR, SNR and BER is carried out to show the superiority of the proposed pulse shaping function.

회로 및 시스템] LED 디스플레이 장치의 휘도개선을 위한 점등율 향상에 대한 연구

LED 디스플레이 장치의 LED 소자의 전기 광학 특성으로 인한 열화는 고유 휘도 값을 낮추어 휘도 값 및 화질 저하로 인한 휘도 불균형을 초래한다. 따라서 본 논문에서는 휘도 불균형을 보상하기 위해 적응적 휘도 구현 비트와 펄스를 휘도 값 감소에 비례하여 휘도를 증가시켜 픽셀 간의 휘도 불균형을 보상하는 휘도 및 색상 제어 기법을 제안 하였다. A degradation due to the electro-optical characteristics of LED devices in LED display lowers the intrinsic luminance value, resulting in luminance unbalance due to a decrease in luminance value and image quality. Therefore, in this paper, we proposed a luminance and color control technique that applies adaptive luminance implementation bits and pulses to compensate for luminance imbalance between pixels by increasing luminance in proportion to the decreased luminance value to compensate for luminance imbalance caused by degradation, respectively.

Fast pulse sampling module for real-time neutron–gamma discrimination

An adaptable and compact fast pulse sampling module was developed for the neutron–gamma discrimination. The developed module is well suited for low-cost and low-power consumption applications. It is based on the Domino Ring Sampler 4 (DRS4) chip, which offers fast sampling speeds up to 5.12 giga samples per second (GSPS) to digitize pulses from front-end detectors. The high-resolution GSPS data is useful for obtaining precise real-time neutron–gamma discrimination results directly in this module. In this study, we have implemented real-time data analysis in a field programmable gate array. Real-time data analysis involves two aspects: digital waveform integral and digital pulse shape discrimination (PSD). It can significantly reduce the system dead time and data rate processed offline. Plastic scintillators (EJ-299-33), which have proven capable of PSD, were adopted as neutron detectors in the experiments. A photomultiplier tube (PMT) (model #XP2020) was coupled to one end of a detector to collect the output light from it. The pulse output from the anode of the PMT was directly passed onto the fast sampling module. The fast pulse sampling module was operated at 1 GSPS and 2 GSPS in these experiments, and the AmBe-241 source was used to examine the neutron–gamma discrimination quality. The PSD results with different sampling rates and energy thresholds were evaluated. The figure of merit (FOM) was used to describe the neutron–gamma discrimination quality. The best FOM value of 0.91 was obtained at 2 GSPS and 1 GSPS sampling rates with an energy threshold of 1.5 MeVee (electron equivalent).

Adaptive pulse edge detection algorithm based on short-time Fourier transforms and difference of box filter

Precise radar pulse detection is of great significance for estimating parameters in electronic countermeasure and reconnaissance. An adaptive detection algorithm is proposed, which considers short-time Fourier transforms (STFT), constant false alarm rate (CFAR) in frequency domain, and difference of box (DOB) filter. First, STFT with the Gaussian window is used to acquire the time-frequency spectrum of the radar pulse signal. Second, in order to determine the existence of the pulse, CFAR detector is introduced into the frequency domain to generate an adaptive threshold, and then the rough pulse edges are obtained by mn method. Finally, the data where the rough pulse edges locate are processed by the refined STFT and DOB filter to get the precise pulse edges. The proposed algorithm is processed in the time-frequency domain, which cannot only adapt to low signal-to-noise ratio, but also has a high measurement accuracy. We also draw parallels to the conventional energy-based detection method, the results validate that the proposed algorithm is more robust and effective in practice. Simulations via various noisy input pulse data demonstrate the viability and validity of our proposed algorithm. The algorithm has been implemented in a spaceborne radar receiver.

Design and implementation of adaptive SVPWM algorithm for multilevel inverters in renewable energy applications

This paper presents a design and an implementation of a generalized adaptive multi-objectives Space Vector Pulse Width Modulation (SVPWM) algorithm for multilevel inverters (MLIs). SVPWM is considered as an influential and resilient tool for optimizing the performance of MLIs. Innumerable objectives can be attained by the proper selection of switching times and states. The performance of MLIs can be improved, as well. Hitherto, achieving multiple objectives could be a challenging mission in the SVPWM algorithms scheming. In this paper, an objective function has been demarcated based on the weighted sum of the desired performance parameters. Then, considering this chosen objective function, the proposed algorithm nominates the optimum switching sequence from valid switching sequences. With this algorithm, the objective function can be weighted for the sake of reaching different performance parameter combinations; to outfit different applications and operating points. Furthermore, different SVPWM design cases for enhancing the operation of MLIs can be accomplished. Voltage balance over the DC-link capacitors in MLIs has been implemented, as a study case, using the proposed SVPWM. Both simulation and experimental platforms have been utilized. The results visibly illustrate the generality of the proposed algorithm, and it can improve different performance limitations of MLI such as; achieving a fast balance of the capacitors voltages with reduced power losses. The selected case study has achieved 21.62% faster voltage balance with 17.61% reduction in the power losses compared to conventional SVPWM method. Notwithstanding its straightforwardness to be implemented without complex calculations, the proposed algorithm can maintain the high operating efficiency of the MLI system for a wide range of operation.

Investigation of forming heat affected zone of the deposited weld metal in adaptive-pulse welding in low climatic temperatures

This article discusses the possibilities of forming the structure of the heat-affected zone (HAZ) in adaptive pulsed welding at low temperatures. It is determined that the use of adaptive pulsed welding allows the formation of a dispersed and uniform structure of the heat-affected zone. In order to identify the effect of current pulses on the formation of HAZ, the same technological parameters of the welding process were maintained. The results showed the possibility of determining the optimal algorithms for adaptive pulse control of welding processes, both positive and negative temperatures. Metallographic studies showed that in all deposited specimens, the weld structures have a dendritic structure: in the zone adjacent to the transition zone in the form of columnar formations, and closer to the outer surface, the dendrites have a disoriented structure. It was revealed that when using adaptive pulsed welding, the grain size in the heat-affected zone is reduced by 1.3 times both at positive and negative climatic temperatures, which undoubtedly positively affects the increase in the strength characteristics of the welded joint.

Two-stage fast charging method using dual-switch flyback converter

To improve the charging speed, a new two-stage charging method with dual-switch fly-back converter for Li-ion battery is proposed in this paper. The proposed charging method adopts a two-stage charging of constant current and adaptive pulse current (CC-APC) charging to reduce the charging time for batteries. A dual-switch fly-back converter has the features of simple topology, low cost, galvanic isolation, low voltage stress, no need of additional RCD clamp, and the leakage inductance energy is recovered to the input voltage when the switch is off. Based on the above advantages, a dual-switch fly-back converter is used and designed for the charging system. With the proposed charging method, the charging time is reduced by about 34% compared with the traditional constant current-constant voltage charging method, and the charging time is reduced by about 6% compared with the constant current-fixed duty cycle pulse charging method. The simulation results are provided to verify the system performance.

非下采样Contourlet变换域内结合模糊逻辑和自适应脉冲耦合神经网络的图像融合

非下采样Contourlet变换域内结合模糊逻辑和自适应脉冲耦合神经网络的图像融合

The PAN and MS Image Pansharpening Algorithm Based on Adaptive Neural Network and Sparse Representation in the NSST Domain

How to improve the spatial resolution as much as possible while maintaining the spectral information of multi-spectral (MS) image in the field of image fusion is of great significance for practical applications, such as map updating, feature classification, and target recognition. To analyze the coefficients of the subband distribution characteristics, in this paper, we propose a new panchromatic (PAN) and MS image pansharpening model based on an adaptive neural network and sparse representation in the non-subsample shearlet transform (NSST) domain. First, this algorithm is specific to regional directional characteristics in the high-frequency subband of PAN and MS images, and we propose an adaptive pulse coupled neural network (PCNN) model. The model can adaptively calculate the link strength of a neural cell based on the region energy. Furthermore, we apply the model to the high-frequency fusing process with the corresponding fusion rule, and the rule can distinguish the high-frequency coefficients by ignition times, which can more effectively capture the geometric texture information and detailed information in the PAN image, enhancing the spatial resolution of the fused image. Second, because of the low-frequency sub-bands from the PAN image and I component obtained by intensity-hue-saturation (IHS) transformation of the MS images with high similarity to the original image but poor sparsity, we select a set of PAN images for learning, a more targeted over-complete dictionary for low-frequency sub-band sparse representation is obtained. Then, the larger absolute value of the sparse matrix is selected to obtain the low-frequency coefficients for the fusion image while maintaining the MS spectral information effectively, and the representation of characteristic information of low-frequency subband is more effective. A large number of simulation experiments verify the effectiveness of the proposed method.

Data Transmission at 14.4kb/s OVER 32kb/s ADPCM Channel

Abstract This paper presents new modified QAM modem that operates at data rate of 14.4kb/s to be transmitted over 32kb/s Adaptive Differential Pulse Code Modulation (ADPCM). The purpose of this modified QAM modem is to reduce the nonlinear distortion introduced by ADPCM. The performance of ADPCM is studied considering the standard QAM modem and modified QAM modem with different constellations. The simulation results show that the performance of ADPCM with modified QAM modem is better than its performance with standard QAM modem. Also, the performance with circular constellation is better than rectangular one.

Automatic segmentation of vertebrae in 3D CT images using adaptive fast 3D pulse coupled neural networks.

Two systems are presented for segmentation of vertebrae in a 3D computed tomography (CT) image. The first method extracts seven features from each voxel and uses a multi-layer perceptron neural network (MLPNN) to classify the voxel as vertebrae or background. In the second method, the segmentation is completed in two steps: first, a newly developed adaptive pulse coupled neural network (APCNN) directly applied to a given image segments vertebrae, then the result is refined using a median filter. In the developed APCNN, the values for the user-defined parameters of the pulse coupled neural networks (PCNN) are adaptively adjusted for each image individually, instead of using one value for all images as in conventional PCNN. The performance of both systems in terms of Dice index (DI) was evaluated and compared against the state-of-the-art segmentation methods using seventeen clinical and standard CT images. Overall, both systems demonstrated statistically similar and promising performance with average DI > 95%. Compared to existing PCNN-based segmentation algorithms, the accuracy of the proposed APCNN improved by 29.3% on average. The developed APCNN-based system is more accurate than MLPNN-based system and existing PCNN-based algorithms in segmentation of vertebrae with blurred and weak boundaries and in the images contaminated by salt- and- pepper noise. In terms of computation time, the APCNN-based system is 16 times faster than the MLPNN-based system. Consequently, the presented APCNN-based algorithm is both accurate and fast and could be used in clinical environment for segmentation of vertebrae in 3D CT images.

Modified‐adaptive pulse compression repair algorithm based on post‐processing for eclipsing effects

The problem of resolving and detecting masked weak moving targets in the presence of fast strong targets is particularly difficult due to side lobes produced by ordinary signal processing techniques and becomes even harder when a partially returned signal is received. Where return signals coincide with the transmission of a pulse, pulse eclipsing can occur which results in detection performance loss. In this approach, the output of a matched filter (MF) was utilised as the input to the post-processing reiterative minimum mean square error (RMMSE) algorithm. The mismatch created in the received signal by Doppler phase shift and pulse eclipsing degrades adaptive pulse compression (APC) filter performance. This study presents a new method to account for both Doppler phase shift and pulse eclipsing using the modified APC repair (MAPCR) algorithm. Simulation results show that the proposed MAPCR algorithm mitigates the eclipsing effect and reduces range side lobes significantly, in addition to providing improved range resolution. The authors compare their results for single point and extended targets placed in the eclipsed region with other algorithms such as the standard MF, pulse compression repair, APC-eclipsing repair and MF-RMMSE.

Tuning up-conversion luminescence in Er3+-doped glass ceramic by phase-shaped femtosecond laser field with optimal feedback control

Tuning the color output of rare-earth ion doped luminescent nanomaterials has important scientific significance for further extending applications in color displays, laser sources, optoelectronic devices, and biolabeling. In previous studies, pre-designed phase modulation of the femtosecond laser field has been proven to be effective in tuning the luminescence of doped rare-earth ions. Owing to the complex light–matter interaction in the actual experiment, the dynamic range and optimal efficiency for color tuning cannot be determined with the pre-designed phase modulation. This article shares the development of an adaptive femtosecond pulse shaping method based on a genetic algorithm, and its use to manipulate the green and red luminescence tuning in an Er3+-doped glass ceramic under 800-nm femtosecond laser field excitation for the first time. Experimental results show that the intensity ratio of the green and red UC luminescence of the doped Er3+ ions can be either increased or decreased conveniently by the phase-shaped femtosecond laser field with an optimal feedback control. The physical control mechanisms for the color tuning are also explained in detail. This article demonstrates the potential applications of the adaptive femtosecond pulse shaping technique in controlling the color output of doped rare-earth ions.

Features of Formation of Structure and Physical and Mechanical Properties of Permanent Welded Joints of Low-Alloy Steels by Methods of Adaptive Pulse Control of Energy Parameters of Welding Mode

The features of the formation of the structure and physical and mechanical properties of all-in-one compounds of low-alloy steels are studied. It is shown that the quality and strength properties of permanent joints depend on the energy parameters of the technological process of their manufacture. The technological process is accompanied by melting, transfer and crystallization of the weld metal from the melt, which has a dominant effect on the structure, indicators of static and dynamic strength of welded joints. The ranges of welding modes that have the greatest impact on the structural and mechanical properties of the zone of permanent joints in the temperature range from +20 degrees to minus 60 degrees Celsius. The results of the research can be widely used in the practice of repair and installation works of structures of the Northern design, working in conditions of naturally low climatic temperatures.

Adaptive pulse width modulation design for power converters based on affine switched systems

In this work we propose a novel adaptive switching strategy for the design of pulse width modulation signals in power converters. Instead of an uncertain averaged model of the power converter, an uncertain switched model is considered, which can better represent the actual power converter dynamics. Uncertainties in the power converters parameters are handled via an adaptive control approach, and all circuit parameters of the switched model are assumed to be unknown (including the load and parasitic effects). After defining the pulse width modulation in terms of a reverse mode-dependent dwell time, an elementary-time-unit Lyapunov function is used to derive a set of linear matrix inequalities (LMIs) based on global uniformly ultimately boundedness of the switched system. The LMIs are solved in an adaptive fashion using an exploitation–exploration mechanism: exploitation is achieved by solving the LMIs based on the estimated switched model, while exploration is achieved by a persistently exciting input voltage source, which guarantees convergence of the estimated parameters to the true system parameters.

Construction of adaptive pulse coupled neural network for abnormality detection in medical images

ABSTRACTIn this article, we propose a customized pulse coupled neural network for image segmentation to detect the different classes of skin lesions by minimizing the number of pixels as image harmonics. In addition, we have used a distribution similar to primary visual cortex for internal activation function. This helps in transforming the visual behavior of the cortex. The developed neural synchrony of adaptive pulse coupled neural network helps in classifying the lesion patterns in dermoscopy images. We evaluate our proposed approach on 240 gold standard dermofit images of lesions. Our results have shown significant improvement in the accuracy and efficiency when compared with existing methods.

Arbitrary temporal shape pulsed fiber laser based on SPGD algorithm

A novel adaptive pulse shaping method for a pulsed master oscillator power amplifier fiber laser to deliver an arbitrary pulse shape is demonstrated. Numerical simulation has been performed to validate the feasibility of the scheme and provide meaningful guidance for the design of the algorithm control parameters. In the proof-of-concept experiment, information on the temporal property of the laser is exchanged and evaluated through a local area network, and the laser adjusted the parameters of the seed laser according to the monitored output of the system automatically. Various pulse shapes, including a rectangular shape, ‘M’ shape, and elliptical shape are achieved through experimental iterations.

A novel fusion framework of visible light and infrared images based on singular value decomposition and adaptive DUAL-PCNN in NSST domain

Visible light and infrared images fusion has been a significant subject in imaging science. As a new contribution to this field, a novel fusion framework of visible light and infrared images based on adaptive dual-channel unit-linking pulse coupled neural networks with singular value decomposition (ADS-PCNN) in non-subsampled shearlet transform (NSST) domain is present in this paper. First, the source images are decomposed into multi-direction and multi-scale sub-images by NSST. Furthermore, an improved novel sum modified-Laplacian (INSML) of low-pass sub-image and an improved average gradient (IAVG) of high-pass sub-images are input to stimulate the ADS-PCNN, respectively. To address the large spectral difference between infrared and visible light and the occurrence of black artifacts in fused images, a local structure information operator (LSI), which comes from local area singular value decomposition in each source image, is regarded as the adaptive linking strength that enhances fusion accuracy. Compared with PCNN models in other studies, the proposed method simplifies certain peripheral parameters, and the time matrix is utilized to decide the iteration number adaptively. A series of images from diverse scenes are used for fusion experiments and the fusion results are evaluated subjectively and objectively. The results of the subjective and objective evaluation show that our algorithm exhibits superior fusion performance and is more effective than the existing typical fusion techniques.

A Fuzzy adaptive hysteresis band controller for three phase four wire UPQC

Unified Power Quality Compensator (UPQC) is used to protect the sensitive loads in the distribution system from voltage and current disturbances. The compensation capability of UPQC depends on the control strategies used for shunt and series converters. Conventional adaptive hysteresis controller pulse width modulation technique had failed to track exactly during transient conditions and disturbances at load and source side. In paper fuzzy adaptive hysteresis controller is proposed for three phase four wire UPQC for compensating voltage sag/swell, current harmonics, voltage harmonics and neutral current compensation. Fuzzy adaptive hysteresis controller can effectively compensate the power quality problems during the transient conditions. A comparative simulation analysis of proposed and conventional methods are presented in this paper using MATLAB/SIMULINK tool.