Modulation Index Research Articles

Evaluation of pseudoexfoliation syndrome patients with systemic immune indexes.

The aim of this study was to investigate the level of peripheral blood systemic immune indexes in pseudoexfoliation syndrome (PXS) patients and to compare the results with healthy controls. This study included 143 healthy controls (group 1) and 100 patients (group 2). Peripheral blood samples were collected from all participants. Neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), monocyte to lymphocyte ratio (MLR), systemic immune inflammation index (SIII), systemic inflammation response index (SIRI), systemic inflammation modulation index (SIMI) and aggregate systemic inflammation index (AISI) were calculated. According to complete blood count, leukocyte, monocyte and platelet counts showed a statistically significant difference between the two groups (p < 0.001 for all). Systemic immune indexes (NLR, PLR, SIII, SIRI, SIMI and AISI) in group 2 were statistically significantly higher compared to group 1 (PLR for p = 0.011, others p < 0.001). In conclusion, systemic immune indexes (NLR, MLR, PLR, SIII, SIRI, AISI and SIMI) were elevated in PXS patients compared to healthy controls. These indexes may serve as an easy, simple and cost-effective tool to assess the degree of systemic inflammation in patients, playing an important role in recognizing the underlying mechanisms of diseases and thus potentially guiding treatment.

Self-mixing thinly sliced ruby laser for laser Doppler velocimetry with high optical sensitivity

In self-mixing laser Doppler velocimetry (LDV), the motion of a moving target is observed by using intensity-modulated laser light detected by a simple photodetector. Here, the self-mixing laser output modulation takes place, reflecting the pronounced effective loss modulation index, which is proportional to the fluorescence-to-photon lifetime ratio. The fluorescence lifetime of a ruby laser is extremely long, so if a ruby crystal can be used as a laser light source for a self-mixing LDV system, high-sensitivity LDV measurements can be performed with it. We describe a method for velocimetry of moving targets using self-mixing LDV in which a CW oscillating ruby laser is the light source. The oscillation mechanism of the thin-slice ruby laser with a large fluorescence-to-photon lifetime ratio, which is suitable for LDV measurements, is clarified and the results of highly sensitive LDV measurements are presented, featuring nonlinear dynamics observed associated with the self-mixing velocimetry experiment. The measurement accuracy is clarified by measuring the rotating disc with various conditions using self-mixing LDV.

CHAOTIC RANDOMIZED SPACE VECTOR PULSE WIDTH MODULATION INTENDED FOR INDUCTION MOTOR DRIVES IN INDUSTRIAL APPLICATIONS

In this industrial era, induction motor control plays a vital role, especially in speed control. Adjustment of speed is essential in all control strategies from the application perspective. There are different pulse width modulation methodologies to tune the speed and reduce harmonics. Among various pulse width modulation (PWM) strategies, space vector PWM (SVPWM) proves best for harmonic reduction in drive applications of variable frequency. SVPWM topology is modified by incorporating some randomness, generating switching pulses for the inverter, thereby controlling induction motor drives. A chaotic-based randomized algorithm is synthesized in primitive SVPWM and termed chaotic random SVPWM (CRSVPWM). It is proved from the results that the efficiency and performance are higher for chaotic randomized SVPWM induction drives than all conventional methods of PWM, having higher harmonics, lower modulation index, and less flexibility. CRSVPWM shows the advantages of better fundamental output voltage, more straightforward digital realization, improved harmonic performance, and extreme simplicity in vector selection. It is simulated through MATLAB 2021R, and hardware-based experimental validation was done using the Vivado design suite environment with Spartans-6 FPGA (XC6SLX9-2tqg144).

FPGA Realization of an Image Encryption System Using a 16-CPSK Modulation Technique

Nowadays, M-Quadrature Amplitude Modulation (M-QAM) techniques are widely used to modulate information by bit packets due to their ability to increase transfer rates. These techniques require more power when increasing the modulation index M to avoid interference between symbols. This article proposes a technique that does not suffer from interference between symbols, but instead uses memory elements to store the modulation symbols. In addition, the aim of this paper is to implement a four-dimensional reconfigurable chaotic oscillator that generates 16-Chaotic Phase Shift Keying (16-CPSK) modulation–demodulation carriers. An encryption and modulation transmitter module, a reception module, and a master–slave Hamiltonian synchronization module make up the system. A 16-CPSK modulation scheme implemented in Field Programmable Gate Array (FPGA) and applied to a red-green-blue (RGB) and grayscale image encryption system are the main contributions of this work. Matlab and Vivado were used to verify the modulation–demodulation scheme and synchronization. This proposal achieved excellent correlation coefficients according to various investigations, the lowest being −15.9×10−6 and 0.13×10−3 for RGB and grayscale format images, respectively. The FPGA implementation of the 16-CPSK modulation–demodulation system was carried out using a manufacturer’s card, Xilinx’s Artix-7 AC701 (XC7A200TFBG676-2).

A novel carrier index M‐ary differential chaos shift keying modulation scheme

AbstractTo obtain better spectral efficiency and higher bit rate, a novel carrier index M‐ary differential chaos shift keying modulation scheme is proposed. In this system, part of subcarriers is assigned to the chaotic reference so that it can carry extra data bits through carrier index modulation, while one of the remaining subcarriers is activated to transmit the data‐bearing signal. In addition, M‐ary DCSK modulation is also applied to data‐bearing signals based on the constellation theory and Walsh codes. Theoretical bit error rate expressions are derived over the multipath Rayleigh fading and additive white Gaussian noise channels. Simulations and comparisons are performed with various combinations of chaotic sequence lengths, subcarrier numbers and constellation sizes. Results show that the proposed scheme can outperform other counterparts in both spectral efficiency and bit error rate performances.

Irregular RIS Pattern Array-Based Index Modulation for Next-Generation RIS Communication

Irregular RIS Pattern Array-Based Index Modulation for Next-Generation RIS Communication

The effect of photo-thermo-induced crystallization on the properties and microstructure of transmission volume Bragg gratings

Volume Bragg gratings (VBGs) recored on photo-thermo-refractive (PTR) glass are extensively utilized in high power lasers, optical communication, holographic display fields, etc. In the majority of application fields, high refractive index modulation (RIM) value and high transmittance are the required parameters for transmission Volume Bragg gratings (TVBGs) devices. This study indicates that the RIM values and transmittance of TVBGs strongly depend on the size and concentration of sodium fluoride (NaF) crystals within the grating periodic structure. Increasing the UV exposure dose causes a reduction in the size of NaF crystals, leading to a finitely rise in the RIM value of TVBGs. Prolonging the crystallization heat treatment time and elevating the temperature effectively enhance the RIM value of TVBGs, which also significantly enlarge the size of NaF crystals in the grating periodic structure. By fine-tuning the process parameters of photothermal induced crystallization, a RIM value of 20–320 ppm is freely controlled. For 1.5 mm thick TVBGs, the above RIM value range can meet the application requirements of achieving high diffraction efficiency in the visible to near-infrared range. Following UV exposure at a dose of 5 J/cm2 and nucleation at 480 °C for 120 min, crystallization treatments at 550 °C for 30–60 min and at 570 °C for 60–120 min are determined as optimal for fabricating TVBGs with high diffraction efficiency and transmittance in the visible (532 nm) and near-infrared (1053 nm) bands, respectively.

High-Efficiency e-Powertrain Topology by Integrating Open-End Winding and Winding Changeover for Improving Fuel Economy of Electric Vehicles

The fuel economy of electric vehicles (EVs) is an important factor in determining the competitiveness of EVs. Since the fuel economy is affected by the efficiency of an e-powertrain composed of a motor and inverter, it is necessary to select a high-efficiency topology for the e-powertrain. In this paper, a novel topology of e-powertrains to improve the fuel economy of EVs is proposed. The proposed topology aims to improve the system efficiency by integrating open-end winding (OEW) and winding changeover (WC). The proposed OEW-PMSM with WC enables to drive a permanent magnet synchronous motor (PMSM) in four different modes. Each mode can increase inverter efficiency and motor efficiency by changing motor parameters and maximum modulation index. In this paper, the system efficiency of the proposed topology was evaluated using electromagnetic finite element analysis and a loss model of power semiconductors. In addition, the vehicle simulations were performed to evaluate the fuel economy of the proposed topology, thereby proving the superiority of the proposed topology compared with the conventional PMSM.

Enhancing Robustness and Imperceptibility with a Texture-Based Adaptive QIM Approach

This paper proposes a new approach for image data hiding that aims to improve both robustness and imperceptibility. The proposed approach is based on a texture-adaptive quantization index modulation (QIM) method that takes into account the local characteristics of the image texture to optimize the embedding process. The approach is evaluated using various image datasets and compared to existing state-of-the-art techniques. The results show that the proposed approach achieves better performance in terms of robustness against various image processing attacks, with BERs of zero in some attacks, while maintaining a high level of imperceptibility with PSNRs exceeding 46 decibels. It can be deduced that adaptation and normalization of the embedding strength arguments can enhance the QIM methods’ performance. The proposed approach has potential applications in image authentication, copyright protection, and data hiding.

Recording Reflection Volume Holographic Gratings with Enhanced Performance by Two‐Stage Photopolymers Containing Bifunctional Monomers

AbstractA holographic optical waveguide (HOW) is an optimal solution for augmented reality (AR) displays, in which reflection volume holographic gratings are core optical elements. In this study, five high‐refractive‐index (≈1.6) bifunctional acrylate monomers (TPBSAs) are designed and synthesized. A series of two‐stage photopolymers are prepared using TPBSAs as writing monomers. Among them, one containing 9 wt.% TPBSA‐3 shows the best holographic recording performance with a sensitivity as high as 26.59 cm mJ−1. Using it as the recording medium, a reflection VHG can be obtained with high spatial frequency (5634 lines per mm), diffraction efficiency (97.14%), refractive index modulation (0.029), and good transparency within 400−800 nm after photobleaching. Furthermore, a HOW capable of achieving virtual and real image fusion is fabricated.

Synthetic assessment of cardiac autonomic modulation and Baevsky stress index in patients with synucleinopathies

Abstract Background The Baevsky Stress Index (BSTRi), calculated from Heart Rate Variability (HRV) data, has been proposed for quantitative assessment of physiological stress, with higher scores indicating higher levels of physical and/or psychological stress [1]. Cardiac autonomic modulation can be synthetically quantified by calculating the parasympathetic (PNSi) and the sympathetic (SNSi) indexes. The values of the BSTRi, SNSi, and PNSi in patients with synucleinopathies of different prognoses have not been reported yet. Purpose To quantify, in patients with Parkinson's disease (PD) and Multisystem Atrophy (MSA), the BSTRi, its correlation with the PNSi and the SNSi indexes, and their potential value for a synthetic assessment of cardiac autonomic modulation and early differential diagnosis between PD and MSA. Methods Holter ECG data of 66 patients with Parkinsonian syndromes were retrospectively analyzed after 10 years of follow-up. Out of them, 34 patients with a certain diagnosis of PD (17) and MSA (17) were selected for this study. HRV was analyzed with the Kubios software (version 4.0), providing automatic calculation of the BSTRi, PNSi, and SNSi [2], as well as of time domain (TD), frequency domain (FD), nonlinear (NL), and time-varying (TV) HRV parameters. HRV was calculated from selected short-term intervals (of 5 minutes), during daily activity (ACT5’), and non-REM sleep (NREM5’), and from 24-hours Holter recordings. Patients’ HRV findings were compared with those of 51 age-matched healthy subjects (HS). Results An example of individual automatic graphic summary is shown in Figure 1. Both short-term and 24-hour BSTRi and SNSi values were significantly (p &amp;lt; 0.05) higher in PD and MSA compared to those of HS, in all investigated conditions. Short-term PNSi was significantly higher in HS than in PD in all conditions, but only during NREM5’ in MSA patients (Table 1). No significant difference was found between the indexes of PD and MSA patients. As in HS (R=92), BSTRi was positively correlated with the SNSi in MSA (average R= 0.83 and 0.89 during ACT5’ and NREM5’, respectively), but less evident in PD (R=0.67). The inverse correlation between PNSi and SNSi (R=0.75 in HS) was lost in both MSA and PD. Conclusions Higher values of BSTRi in PD and MSA compared to HS suggest that patients with synucleinopathies do experience higher levels of psychophysiological stress, which may affect their quality of life negatively. However, since no significant difference was found in this study between BSTRi values of PD and MSA patients, BSTRi seems at present unreliable for early differentiation between the two diseases. Telematic assessment of BSTRi, SNSi, and PNSi could be useful for remote monitoring of PD and MSA patients’ psychophysiological stress, to provide timely intervention and adaptive treatment.Fig.1 Example of graphic summary (ACT5')

An Improved Type of Synchronized Space Vector PWM Based on Switching Angles for High‐Power AC Drive Application

Synchronized space vector pulse width modulation (SSVPWM) is widely employed in high‐power AC drive systems. The existing methods are carrier‐based, in which the carrier ratio, position of samples, and switching sequences used to generate every sample for a given SSVPWM are settled, which causes two problems: (i) the control delay changes, and a voltage phase modulation error appears suddenly during transition between different SSVPWMs with different carrier ratios, which causes motor current spikes; (ii) due to the particular switching sequences, some kinds of SSVPWM cannot get into six‐step operation by overmodulation. This paper proposes an improved type of SSVPWM based on switching angles, in which the carrier ratio of a given SSVPWM can change flexibly, and the problems mentioned above can be solved. Theories including switching angle calculation, overmodulation strategy, carrier ratio setting principle, and transition rules between different SSVPWM modes are given in this paper. Meanwhile, the switching angles change linearly with modulation index which makes it easy to implement, and the modulation error in the overmodulation region is effectively limited so that the proposed scheme is suitable in the whole modulation index range. A case study of a 5.5‐kW experimental platform is presented to validate the proposed method. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Quasi-modified-Newton method-based selective harmonic elimination in cascaded H bridge inverters

Multilevel converters have gained significant popularity in medium-voltage and high-power applications due to their numerous advantages over traditional two-level converters. These advantages include reduced harmonic distortion, improved efficiency, and lower stress on power semiconductors. Selective harmonic elimination (SHE) is a modulation method that can be employed with multilevel converters to achieve high-quality output voltage waveforms. In this work, an extension of Broyden’s method, known as the Quasi-Modified Newton Method, is implemented for selective harmonic elimination and accurate calculation of switching angles for a wide range of modulation indices. The proposed method is applied to cascaded H bridge inverters operating at levels 5, 7, and 9. The method offers simplicity, reduced computational burden, and faster convergence, making it easily implementable, reducing total harmonic distortion (THD), and reducing RMSE and MAD errors. The paper includes simulation and experimental results that validate the accuracy and effectiveness of the proposed approach.

Study of modulation in complex refractive indices induced by ultrafast relativistic electrons using infrared and THz probe pulses.

Objective &#xD;Achieving ultra-precise temporal resolution in ionizing radiation detection is essential, particularly in positron emission tomography, where precise timing enhances signal-to-noise ratios and may enable reconstruction-less imaging. A promising approach involves utilizing ultrafast modulation of the complex refractive index, where sending probe pulses to the detection crystals will result in changes in picoseconds (ps), and thus a sub - 10 ps coincidence time resolution can be realized. Towards this goal, here, we aim to first measure the ps changes in probe pulses using an ionizing radiation source with high time resolution.&#xD;Approach &#xD;We used relativistic, ultrafast electrons to induce complex refractive index and use probe pulses in the near-infrared (800 nm) and terahertz (THz, 300 µm) regimes to test the hypothesized wavelength-squared increase in absorption coefficient in the Drude free-carrier absorption model. We measured BGO, ZnSe, BaF2, ZnS, PBG, and PWO with 1 mm thickness to control the deposited energy of the 3 MeV electrons, simulating ionization energy of the 511 keV photons. &#xD;Main results &#xD;Both with the 800 nm and THz probe pulses, transmission decreased across most samples, indicating the free carrier absorption, with an induced signal change of 11% in BaF2, but without the predicted Drude modulation increase. To understand this discrepancy, we simulated ionization tracks and examined the geometry of the free carrier distribution, attributing the mismatch in THz modulations to the sub-wavelength diameter of trajectories, despite the lengths reaching 500 µm to 1 mm. Additionally, thin samples truncated the final segments of the ionization tracks, and the measured initial segments have larger inter-inelastic collision distances due to lower stopping power (dE/dx) for high-energy electrons, exacerbating diffraction-limited resolution. &#xD;Significance&#xD;Our work offers insights into ultrafast radiation detection using complex refractive index modulation and highlights critical considerations in sample preparation, probe wavelength, and probe-charge carrier coupling scenarios.

Single-pulse Emissions of PSRs J1611–0114 and J1617+1123

In this paper, the emissions from two pulsars, PSRs J1611−0114 and J1617+1123, were investigated using the Five-hundred-meter Aperture Spherical radio Telescope operating at a central frequency of 1250 MHz. The average pulse profile of PSR J1611−0114 shows two components, the first of which is relatively weak in intensity. The two-dimensional pulse stack exhibits an obvious nulling phenomenon, with an estimated nulling fraction of 40.1% ± 5.4%. The durations of the nulls and bursts are consistent with power-law distributions, and no periodic nulling phenomenon is found. The results from PSR J1617+1123 demonstrate that the average pulse profile is composed of four components. The peak intensity of the fourth component varies significantly, causing an unstable integrated profile. In addition, the modulation characteristics of J1611−0114 and J1617+1123 were studied by analyzing the modulation index, longitude resolved fluctuation spectrum and two-dimensional fluctuation spectrum using the software PSRSALSA. It was found that the two pulsars exhibit intensity modulation. In particular, J1611−0114 displays even–odd modulation, with the modulation period of approximately two pulses. The modulation period of J1617+1123 is relatively broad. There is an obvious subpulse drift phenomenon, and the value of P 2 is ∼0.125c/P 0, corresponding to 12 pulse longitude bins, and the drift rate (P 2/P 3) is about 0.29.

Design and Analysis of Reliable and High Data Rate Multicarrier DCSK Transceiver With Index Modulation and Noise Suppression

Design and Analysis of Reliable and High Data Rate Multicarrier DCSK Transceiver With Index Modulation and Noise Suppression

Intelligent Index Recognition for OFDM With Index Modulation in Underwater OWC Systems

Intelligent Index Recognition for OFDM With Index Modulation in Underwater OWC Systems

Mode conversion in graded-index few-mode fiber via hollow cylindrical long-period fiber gratings.

We demonstrate the realization of mode conversion using hollow cylindrical long-period fiber gratings (LPFGs) inscribed in graded-index few-mode fibers (FMFs) by a femtosecond laser. By precisely shaping the refractive index modulation into a hollow cylindrical structure, we enable efficient coupling from the fundamental mode to high-order modes (LP11, LP02, LP21, LP12, LP31, LP03, and LP22 modes). The method achieves high-efficiency and low-loss mode conversion across various mode groups, marking a first for graded-index FMFs with different grating periods. The influence of the hollow cylindrical LPFG radius on mode conversion efficiency and spectral characteristics is thoroughly investigated. Additionally, incorporating a linear polarizer allowed for distinguishing between LP modes within a mode group, enhancing the tunability of the mode converter. These mode conversion devices have significant potential for applications in mode gain equalization and mode scrambling for mode division multiplexing (MDM) systems.

High‐Resolution Optical Convolutional Neural Networks Using Phase‐Change Material‐Based Microring Hybrid Waveguides

In the More‐than‐Moore era, the explosive growth of data and information has driven the exploration of alternative non‐von Neumann computational paradigms. Photonic neuromorphic computing has emerged as a promising approach, offering high speed, wide bandwidth, and massive parallelism. Herein, a high‐resolution optical convolutional neural network (OCNN) is introduced using phase‐change material Ge2Sb2Te5 (GST)‐based microring hybrid waveguides. This on‐chip optical computing platform integrates GST into photonic devices, enabling versatile programming and in‐memory computing capabilities. Central to this platform is a photonic convolutional computational kernel, constructed from photonic switching cells embedded with GST on a microring resonator. This programmable photonic switch leverages the refractive index modulation during the GST phase transition to achieve up to 64 discrete levels of transmission contrast, suitable for representing matrix elements in neural network algorithms with 6‐bit resolution. Using these matrix elements, an OCNN capable of performing parallelized image edge detection and digital recognition tasks with high accuracy is demonstrated. The architecture is scalable for large‐scale photonic neural networks, offering ultrahigh computational throughput, a compact design, complementary metal‐oxide‐semiconductor‐compatible fabrication, and broad bandwidth.

Exit pupil uniformity improvement of holographic waveguide displays based on a genetic algorithm

Waveguide displays based on a volume holographic grating (VHG) have the benefit of expanding the exit pupil. Exit pupil size and exit pupil uniformity are two important indicators of waveguide displays. Most current optimizations for exit pupil uniformity are based on the central viewing angle. However, this does not ensure satisfied exit pupil uniformity for other viewing angles. In this paper, a method based on a genetic algorithm to optimize the exit pupil uniformity under the whole horizontal field of view (HFOV) is proposed. First, the ray-tracing-based mathematical model to analyze the uniformity of the whole HFOV at all wavelengths is established. Based on the mathematical model, the objective function can be defined, which can optimize the refractive index modulation distribution on several regions of the out-coupling VHG. The simulation results show that for a holographic waveguide display with the exit pupil size of 16mm×12mm, the average exit pupil uniformity can reach 86.87% at a diagonal field of view (DFOV) of 30°, a 9.16% improvement over the previous method. The genetic-algorithm-based method proposed in the paper can effectively improve the exit pupil uniformity.