Modulation Method Research Articles

Measurement of plasma electron energy distribution functions by Langmuir probe using a modified AC modulation method

Abstract In the diagnosis of vacuum discharge plasma using the Langmuir probe, the electron energy distribution function (EEDF) is closely related to the second derivative of current to voltage (d 2 I/dV 2) on the Langmuir probe. While d 2 I/dV 2 is very sensitive to probe noise, its accuracy directly affects the measurement results of the EEDF. In this paper, a modified AC modulation method is proposed to improve the measurement accuracy of the EEDF. First, two small AC signals of different amplitudes are modulated on the measured DC scanning voltage of the Langmuir probe, and the probe current signal is measured. Then, the fundamental amplitudes of the two AC signals are corrected by spectral analysis and using the all-phase fast Fourier transformation—fast Fourier transformation amplitude correction algorithm. Then the accurate first-order derivative of the probe current to voltage (dI/dV) is obtained using the AC modulation derivative correction algorithm, and finally the EEDF is obtained by numerically differentiating dI/dV to obtain d 2 I/dV 2. The method of this paper is compared with the traditional data processing method through experiments, and the results show the superiority and effectiveness of the method.

Performance evaluation of magic square based spatial modulation in UAV communication

This study proposes a method to reduce the bit error rate (BER) in communications by unmanned aerial vehicles (UAVs). The method involves using specific active antennas that transmit at precise times with a particular mapping, ensuring orthogonality among transmitting antennas. This technique can accommodate numerous transmit antennas and amplitude-phase modulation orders. When applied to spatial modulation (SM) and generalized spatial modulation (GSM), it demonstrates clear superiority and significantly improved results compared to traditional SM and GSM methods, especially at high altitudes where conventional methods result in high BER. Introducing a new modulation method called magic square (MS) further enhances the results. The MS method provides a unique orthogonality pattern for the transmitting antenna sets. Additionally, the study introduces the utilization of magic squares in the modulation field. The MS-based SM model shows a BER rate almost 103 times lower than traditional SM at the 25 dB signal-to-noise ratio (SNR) level for various fly altitudes. Similarly, the MS-based GSM model demonstrates a BER rate almost 100 times lower than traditional GSM. The proposed method yields better results as the altitude increases, making it suitable for UAV communication at various altitudes.

Nonlinear acoustic modulation utilizing designed acoustic bubble array.

Acoustic modulation has attracted significant investigative interest for their outstanding promising application scenes. Furthermore, acoustic bubble array has shown anticipated foreground in signal processing and acoustic manipulation. Here, we demonstrate a nonlinear acoustic modulation method via designed acoustic bubble array. Numerical calculations have been conducted to analyze several influential parameters and the corresponding effects on the vibrational behaviors of the acoustic bubbles. Appropriate corrections have been added on the numerical model to elucidate the physical scene. Experimental validation has confirmed the practicability and validity of the designation. Potential applications in biological tissue imaging and unidirectional sound transmission can be expected with further research.

Analysis of methods for reducing the signal PAPR under the influence of the Doppler effect in hybrid communication networks

Background. For further development of communication networks, it is planned to use hybrid satellite networks for traffic transmission. However, satellite communication channels have features such as distortion caused by the Doppler effect and increased energy efficiency requirements. Aim of this study is to analyze variants of orthogonal frequency multiplexing methods and modulation methods in order to choose the most stable technology, taking into account destabilizing factors. Method. Comparing different signal processing technologies and studying their resistance to bit errors is the imitation modeling of the communication channel in the Matlab environment. This approach allows creating a model of the communication network, taking into account the main parameters of communication channels, such as the Doppler effect, energy deficiency and destabilizing factors. Results. The distribution of the bit error coefficient for various signal processing technologies, depending on the signal-to-noise ratio, is compared. The method of frequency multiplexing is defined, providing the minimum peak factor and the most resistant to bit error. It is also noted that the effectiveness of all the studied technologies depends on the spacing and modulation constellations, and that it is necessary to adjust the characteristics of the system for each case. Conclusion. The results of this study can be used to improve the quality of communication in difficult interference conditions of hybrid mobile networks of 5 and 6 generations using the satellite segment.

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.

Accelerating T1 relaxation time measurements of noble gas using transverse low-frequency square-wave magnetic field modulation.

The longitudinal relaxation time (T1) of noble gas nuclear spins is a critical parameter for evaluating the performance of an atomic comagnetometer, significantly influencing the signal-to-noise ratio of the system. Traditional measurement techniques, such as the free induction decay method combined with the spin growth technique (FIDSG), are time-consuming for gases with extended T1 durations, such as 21Ne, and are prone to substantial environmental variability. Here, we propose the transverse low-frequency square-wave magnetic field modulation (LSMM) method for the rapid measurement of T1. The experiment indicates that the LSMM significantly condenses the measurement time to 19.2% of the original, thereby diminishing the robustness demands of the system. Although a minor discrepancy of up to 3 min (or 1.3%) exists between LSMM and FIDSG results, the LSMM method provides strong support for calibrating the performance of comagnetometer cells and conducting various nuclear spin polarization experiments, thereby improving efficiency and reducing energy loss.

Modulating TTN gene expression in human iPSC-CMs to investigate mechanisms and therapies in TTN-associated dilated cardiomyopathy

Abstract Background Familial dilated cardiomyopathy (DCM) is a common and harmful condition, and no available therapies target the underlying genetic mechanisms. Truncating variants in TTN are the most commonly identified genetic cause of DCM. However, it remains unclear how TTN variants drive disease. Contemporary thinking identifies haploinsufficiency, dominant negative effects, or a combination of both as likely driving mechanisms. There is competing evidence as to whether I-band and A-band mutations differ in severity or in the relative roles of haploinsufficiency and dominant-negative effects. Clarifying disease mechanisms will help pave the way to targeted genetic therapies. Purpose To modulate TTN gene expression in human-induced stem cell-derived cardiomyocyte (hiPSC-CM) models of TTN-associated DCM carrying I-band or A-band variants to provide insight into the comparative roles of haploinsufficiency and dominant negative mechanisms in DCM, and to identify novel therapeutic strategies. Methods We used CRISPR-Cas9 gene-editing to generate hiPSC lines with known disease-causing heterozygous truncating mutations in the I-band or A-band of TTN. These were screened for off-target mutations and pluripotency. hiPSCs were differentiated into hiPSC-CMs for phenotyping. We assayed TTN mRNA and titin protein levels. We trialled approaches for modulating TTN expression including CRISPR activation. Results Two hiPSC lines with heterozygous mutations in the I-band and A-band of TTN were generated using CRISPR/Cas-9 gene-editing. These hiPSC lines were successfully differentiated into hiPSC-CMs. Both cell lines demonstrated unchanged TTN mRNA expression compared to wildtype controls, but had reduced expression of full-length titin protein and identifiable truncated protein products. TTN mRNA expression was subsequently increased in these models using modulators of gene expression. Conclusions hiPSC-CM models of DCM with truncating mutations in the I-band or A-band of TTN were generated and phenotyped. These models were then used to trial gene expression modulation methods. This provides a human cellular system that can be used to better understand disease mechanisms of TTN-associated DCM, with the ultimate aim of establishing gene therapies for TTN-associated DCM.

Real‐time reliability evaluation method for IGBT module in MMC based on junction temperature and bond wire failure online monitoring

AbstractThe lack of an MMC reliability evaluation approach that incorporates data on essential components' health monitoring in the already related research prevents reliability from being further improved. Therefore, this article proposes a real‐time reliability evaluation method of the multi‐state IGBT module in MMC through iterative calculation of the Markov chain model. The degradation process of the IGBT module is divided into multiple states based on the monitored bond wire failure, and the failure rate of the IGBT module is updated in real time using the accumulated monitoring data of junction temperature. The proposed method can more accurately reflect the real state of MMC compared with the binary state evaluation method. Besides, a multi‐channel high‐speed data acquisition board is designed to measuring the gate voltage and collector voltage of the IGBT for the health evaluation of IGBT modules in MMC; the typically measured results validate the effectiveness of the data acquisition board.

Model analysis for optical frequency comb Faraday modulation rotation spectroscopy.

Modulating the signal is a common method in spectroscopy for reducing noise. However, for broadband coherent light sources like optical frequency combs (OFCs), modulation methods typically involve the use of optical modulators, making the experimental setup cumbersome. This study proposes and successfully implements a broadband Faraday modulation rotation spectroscopy (FAMOS) method combined with an OFC. The development of this method by extending the modulation frequency of the OFC from tens of MHz down to the kHz level, effectively relaxes the stringent demands for high-speed electronics and optoelectronic devices, making modulation spectroscopy techniques more practically useful for diverse real-world environments. Moreover, through specifically designed modulation strategies, this method can effectively suppress low-frequency noise, thereby significantly improving the signal-to-noise ratio of the measurements without sacrificing measurement accuracy.

Enhanced Active Voltage Regulation Capability for Three-Level NPC Converters with the Space Vector Modulation Method

Enhanced Active Voltage Regulation Capability for Three-Level NPC Converters with the Space Vector Modulation Method

Research on the generation and modulation of active pressure wave for pipelines leak diagnosis

In this paper, a novel device that uses compressed air to generate pressure waves in the liquid pipeline is proposed. Experimental investigations are carried out to explore the modulation method of the pressure wave generated and the application potential of the device in leak diagnosis. The consequences show that the device can generate safe, stable and controllable pressure waves. The characteristics of produced pressure wave under different excitation frequencies and inflation pressure are investigated with the combination of experiments and theory analysis. The parameters that affect the excitation behaviors of the device are pointed out theoretically. Finally, the performance of the device under continuous excitation and single excitation is tested in the leaking pipe. Through the extraction and analysis of the signal features in the frequency domain, the leakage can be diagnosed and distinguished under both excitation methods.

2D Fe/Co-MOF/SOX cascade reactors for fast noninvasive detection of sarcosine level in prostate cancer urine

Sarcosine plays a key role in screening for early prostate cancer. However, the several already reported peroxidase mimics immobilized with sarcosine oxidase (SOX) utilized to detect uriary sarcosine still have some limitations such as complex synthesis process, using of expensive heavy metals to mimic enzyme activity and long color development time. Herein, an inexpensive peroxidase-like 2D Fe/Co-MOF nanosheet was prepared by a simple solvent modulation method. The resultant 2D Fe/Co-MOF nanosheets have strong peroxidase activity, with its Vmax value for H2O2 of 15.3 × 10-8 M/s, being 1.76 times that of HRP. Then, using the 2D Fe/Co-MOF as a peroxidase model for anchoring natural SOX to construct 2D Fe/Co-MOF/SOX , which can act as a cascade reactor for detection of sarcosine. Considering the above properties, a platform for the detection of sarcosine was built based on a colorimetric method. Because of presence of the high ratio of Fe2+ caused by the electron transfer from Co2+ to Fe3+, large specific surface area and plentiful active sites, 2D Fe/Co-MOF/SOX with TMB (3,3′,5,5′-tetramethylbenzidine) colorimetric reagent could have fast color development and can be applied conveniently and fastly in an early screening tool for prostate cancer patients. The sarcosine could be quantified by peroxidase activity with a detection range of 1–400 μM and a limit of detection (LOD) of 0.324 μM. More importantly, the average sarcosine concentration of 21.367 μM and 1.871 μM was detected in patient’s and normal urine (n = 5), respectively, which showed an excellent screening effect and a great potential in early prostate cancer.

Modelling and DPWM control of continuous switched boost inverter

ABSTRACT In this paper, a new type of three-phase continuous switched boost inverter (CSBI) is proposed. The proposed inverter has a new impedance network that can obtain a high voltage boost ratio. It also can make the system work in continuous conduction mode (CCM). The shoot-through is allowed in the operating mode of the CSBI, which eliminates the dead time and leads to better EMI immunity. The modified discontinuous pulse-width modulation (DPWM) strategy is proposed to operate the CSBI. Compared with the space vector pulse-width modulation (SVPWM) method, the new modulation strategy can reduce the switching loss effectively. Meanwhile, the state space averaging method is used to design the inverter structure and calculate the impedance parameters. To investigate the dynamic performance of the CSBI impedance parameters, the small signal model analysis is used. A test bench of CSBI is built in laboratory. The operating strategy and the theoretical analysis of the proposed inverter are validated by the results of simulation and experiment.

Perspectives on non-genetic optoelectronic modulation biointerfaces for advancing healthcare

AbstractAdvancements in optoelectronic biointerfaces have revolutionized healthcare by enabling targeted stimulation and monitoring of cells, tissues, and organs. Photostimulation, a key application, offers precise control over biological processes, surpassing traditional modulation methods with increased spatial resolution and reduced invasiveness. This perspective highlights three approaches in non-genetic optoelectronic photostimulation: nanostructured phototransducers for cellular stimulation, micropatterned photoelectrode arrays for tissue stimulation, and thin-film flexible photoelectrodes for multiscale stimulation. Nanostructured phototransducers provide localized stimulation at the cellular or subcellular level, facilitating cellular therapy and regenerative medicine. Micropatterned photoelectrode arrays offer precise tissue stimulation, critical for targeted therapeutic interventions. Thin-film flexible photoelectrodes combine flexibility and biocompatibility for scalable medical applications. Beyond neuromodulation, optoelectronic biointerfaces hold promise in cardiology, oncology, wound healing, and endocrine and respiratory therapies. Future directions include integrating these devices with advanced imaging and feedback systems, developing wireless and biocompatible devices for long-term use, and creating multifunctional devices that combine photostimulation with other therapies. The integration of light and electronics through these biointerfaces paves the way for innovative, less invasive, and more accurate medical treatments, promising a transformative impact on patient care across various medical fields.

Spatiotemporal Information, Near-Field Perception, and Service for Tourists by Distributed Camera and BeiDou Positioning System in Mountainous Scenic Areas

The collaborative use of camera near-field sensors for monitoring the number and status of tourists is a crucial aspect of smart scenic spot management. This paper proposes a near-field perception technical system that achieves dynamic and accurate detection of tourist targets in mountainous scenic areas, addressing the challenges of real-time passive perception and safety management of tourists. The technical framework involves the following steps: Firstly, real-time video stream signals are collected from multiple cameras to create a distributed perception network. Then, the YOLOX network model is enhanced with the CBAM module and ASFF method to improve the dynamic recognition of preliminary tourist targets in complex scenes. Additionally, the BYTE target dynamic tracking algorithm is employed to address the issue of target occlusion in mountainous scenic areas, thereby enhancing the accuracy of model detection. Finally, the video target monocular spatial positioning algorithm is utilized to determine the actual geographic location of tourists based on the image coordinates. The algorithm was deployed in the Tianmeng Scenic Area of Yimeng Mountain in Shandong Province, and the results demonstrate that this technical system effectively assists in accurately perceiving and spatially positioning tourists in mountainous scenic spots. The system demonstrates an overall accuracy in tourist perception of over 90%, with spatial positioning errors less than 1.0 m and a root mean square error (RMSE) of less than 1.14. This provides auxiliary technical support and effective data support for passive real-time dynamic precise perception and safety management of regional tourist targets in mountainous scenic areas with no/weak satellite navigation signals.

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.

Multi-Terminal DC Transformer for Renewable Energy Cluster Grid Connection

An AC (alternative current) power integration of distributed energies faces multi-fold challenges such as synchronization and weak grid-induced instability. In this study, a multi-terminal DC transformer is proposed for renewable energy clusters grid connection. The DC transformer provides multiple DC input ports for renewable energy collection, while the load port is connected to the medium-voltage DC grid via a modular multilevel converter (MMC). The multi-port topology enables flexible power transfer between multiple input sources to the load without additional components. The carrier layer modulation strategy is implemented to balance the MMC module voltage; bidirectional power transmission between multiple input sources is achieved through the phase shift modulation (PSM) method. First, we provided a detailed introduction of the proposed topology and working principle. A simulation model was built using the SIMULINK, and the simulation results verified the effectiveness of the proposed converter modulation strategy and phase shift modulation method. A corresponding hardware experimental platform was designed and built, and the modulation and voltage equalization functions of modular multilevel rectifiers were presented as well as the measured results of power transmission modulation of the converter under single-input and multi-input conditions. The results indicate that the proposed transformer can achieve multiple DC inputs and has multi-channel power transmission capabilities, making it suitable for renewable energy clusters grid connection.

Spatial-temporal modulation method of nanosecond laser for the double-cone ignition scheme.

In order to improve the stability of the pulse, realize the high requirements of the direct drive ignition design for the uniformity of the target irradiation, reduce the interference of laser plasma instability, and improve the laser-target coupling efficiency, a nanosecond laser spatial-temporal modulation of high-power laser driver for double-cone ignition (DCI) research was proposed. Under the premise of satisfying the near-isentropic compression waveform of driving implosion, the time-power curves of all sub-beams in the facility are redistributed to reduce the waveform contrast ratio of each sub-beam. A fewer number of sub-beams are utilized to generate low-power foot pulses, which are focused on the target surface of the initial radius. And the remaining sub-beams are utilized to generate high-power driving main pulses, which are focused on a relatively small target surface. It is shown that the stability of the time-power curve of each sub-beam and the power balance control ability can be effectively improved by redistributing. At the same time, the variable focal spot control can be realized to reduce the influence of cross-beam energy transfer (CBET).

A bibliometric analysis of oncolytic virotherapy combined with immunotherapy

ABSTRACT Oncolytic virotherapy in combination with immunotherapy has demonstrated significant survival benefits in some types of cancer. Here, we summarized the development, research hotpots and potential trends of the combination therapy using visual bibliometric analysis. A total of 712 articles were retrieved on June 21, 2023. The USA was the top contributors of any country (325, 45.65%), and the Rluk Research Libraries UK ranked first (43, 6.03%) of any institutions. The Journal for ImmunoTherapy of Cancer was with the largest publications (60, 8.43%). ‘Tumor microenvironment’ and ‘delivery’ were citation keywords with the strongest ongoing bursts. Research fronts in the future may focus on the methods of virus delivery and tumor microenvironment modulation. Futhermore, the most extensively studied cancer were melanoma, glioma and hepatocellular carcinoma.

Research on a Thirteen-Level Switched Capacitor Inverter with Low Switching Loss

This paper presents a 13-level switched capacitor inverter with a novel modulation method designed to minimize the number of switches and significantly reduce switching losses. The inverter stands out for its simplicity, requiring only ten semiconductor switches to generate 13 levels. A key feature is the inherent self-voltage balancing of the capacitors, which eliminates the need for additional control mechanisms. The inverter’s unique architecture, comprising high-voltage and low-voltage modules, enables modulation using a hybrid PWM approach that combines step waveform modulation with level-shifted PWM (LS-PWM). This innovative technique dramatically lowers the switching frequency of the high-voltage module’s switches, independent of the carrier frequency, thereby limiting the number of switches in high-frequency operation and achieving substantial reductions in switching losses. This paper provides a detailed analysis of the inverter’s operating modes, voltage-balancing mechanisms, and parameter calculations. The advantages of the topology presented in this paper are demonstrated by comparison. Finally, the simulation and experimental results confirm the practicality and effectiveness of the proposed inverter and its modulation strategy.