Principle Of Modulation Research Articles

Trends in Guided Growth for Correction of Angular Deformities around the Knee: Past, Present, and Future

The principles of guided growth have been followed in orthopaedics since historic times . The bent tree braced to a stake to make it grow upward and straight is the first reference to the principles of growth modulation in the annals of orthopaedic history Keywords: Guided Growth, Epiphysiodesis, Hemiepiphysiodesis, growth modulation, eight plates, genu varum, genu valgum, deformity correction, pediatric orthopaedics, growth plate

Distributed spatial media-based modulation for relay networks with RF mirrors

A novel distributed spatial media-based modulation scheme is proposed in this paper by cleverly utilizing distributed spatial modulation (DSM) and media-based modulation (MBM) principles. This proposed scheme is referred to as distributed channel modulation (DCM) for relay networks. In this scheme, decode-and-forward relaying protocol is adopted, and the channel states are exploited for transmitting extra information bits by using a number of radio frequency (RF) mirrors that are placed near each relay. To provide a fair comparison with the conventional state-of-the-art schemes, the symbol error rate (SER) performance of DSM scheme is evaluated. Besides, a low complexity detection technique known as iterative maximum ratio combining (i-MRC) is used in order to reduce the receiver complexity of the proposed scheme. Simulation results demonstrate that the proposed DCM scheme significantly outperforms DSM scheme for the same average rate. It is also shown that there is a negligible degradation in the SER performance of the proposed DCM scheme when i-MRC detection is used as compared to the performance with maximum likelihood (ML) detection. Furthermore, a significant reduction in the receiver complexity is achieved by using i-MRC detection technique in contrast to the results with ML detector. It has been also revealed that the proposed DCM scheme shows a performance drop of about 3 dB when the availability of an imperfect channel state information (CSI) is assumed with the presence of channel estimation errors (CEEs). Finally, simulation results have confirmed the analytical findings.

Signal modulation system measuring device

The design can measure and display other parameters such as the modulation system of the measured signal output by the signal source, identify and display the modulation mode of the measured signal, and output the demodulation signal. The measurement module is composed of an automatic gain amplifier circuit, a broadband amplifier, a low-pass filter circuit, a DDS signal generation circuit, an amplification circuit, and a display circuit. The working principle of the signal modulation measuring device is that the demodulated AM signal is obtained after the spectrum is transmitted by the multiplier, and the high-frequency signal is filtered out by the low-pass filter and amplified by the fixed gain amplifier. After the amplification circuit, the output waveform is sampled by the onboard ADC of MSP432E401Y, and then the fast Fourier transform is performed to obtain various parameters, which are finally displayed on the serial screen.

Research on Slot-pole Combination in High-power Direct-drive PM Vernier Generator for Fractional Frequency Transmission System

Offshore wind energy is an important part of clean energy, and the adoption of wind energy to generate electricity will contribute to the implementation of the carbon peaking and carbon neutrality goals. The combination of the fractional frequency transmission system (FFTS) and the direct-drive wind turbine generator will be beneficial to the development of the offshore wind power industry. The use of fractional frequency in FFTS is beneficial to the transmission of electrical energy, but it will also lead to an increase in the volume and weight of the generator, which is unfavorable for wind power generation. Improving the torque density of the generator can effectively reduce the volume of the generators. The vernier permanent magnet machine (VPM) operates on the magnetic flux modulation principle and has the merits of high torque density. In the field of electric machines, the vernier machine based on the principle of magnetic flux modulation has been proved its feasibility to reduce the volume and weight. However, in the field of low-speed direct-drive machines for high-power fractional frequency power generation, there are still few related researches. Therefore, this paper studies the application of magnetic flux modulation in fractional frequency and high-power direct-drive wind turbine generators, mainly analyzes the influence of different pole ratios and different pole pairs on the generator, and draws some conclusions to provide reference for the design of wind turbine generators.

РАСЧЕТНО-ЭКСПЕРИМЕНТАЛЬНОЕ ИССЛЕДОВАНИЕ ДИНАМИЧЕСКОЙ НАГРУЖЕННОСТИ ЭНЕРГОСИЛОВОГО БЛОКА ТРАНСПОРТНОЙ МАШИНЫ

The article presents the results of a computational and experimental study of the dynamic loading of the transmission of a transport vehicle with an increased power diesel engine. The novelty of the study is substantiated in the scientifically based applicability of elastic torsion shafts between the engine and transmission as a torsional vibration damper, as well as in the development of a new experimental definition of the dynamic value of torque based on the principle of modulation of high-frequency oscillations of the signal of standard pulse speed sensors by modulating vibrations occurring in the power unit of the transport vehicle. As a result, the main calculated motor-frequency function of acceleration (torque) is obtained, including engine harmonics, harmonic components formed by the mechanisms of the connecting rod-piston and gas distribution mechanisms of the engine, the generator drive, vibrations in the transmission, etc. It is established that the reason for the limitation of the durability of torsion shafts is their operation in off-design modes due to the occurrence of a phenomenon called “task conflict”. On the basis of probabilistic calculations, a high comparative assessment of the probability of sudden fracture of elastic shafts at design and off-design loading modes is carried out. Based on the research results, a conclusion is made on the applicability of torsion shafts as dampers of torsional vibrations in the power unit with increased power.

Research on Magnetic Coupling Characteristic of a Double Rotor Flux-Switching PM Machine From the Perspective of Air-Gap Harmonic Groups

The magnetic coupling phenomenon widely exists in the type of double rotor motor, which is difficult to be eliminated completely due to the interactions between two layers of air-gap magnetic fields in a compact geometry structure. This article studies magnetic coupling in the perspective of air-gap harmonic groups, where the novelty is to propose the concept of positive coupling harmonics and the negative one. And, a double rotor flux-switching PM machine is chosen as the research subject. Then, the article begins with the analytical investigation of the modulation principle considering magnetic coupling, where the coupling harmonic group factor is defined. According to this factor, the coupling harmonics are analyzed and selected, and the positive and negative coupling harmonic groups are further determined. Next, the influence of coupling harmonic group on the machine performance is investigated in detail, including the back-EMF, torque performances, overload capability, and so on. The results show that the raise of positive coupling harmonic group factor brings the improvement of machine performances. In addition, a prototype machine is manufactured for experimental testing. Overall, theoretical analysis, simulation and test results verify the validation of the whole investigation to a large extent.

Origin and Acceleration of Insoluble Li2 S2 -Li2 S Reduction Catalysis in Ferromagnetic Atoms-based Lithium-Sulfur Battery Cathodes.

Accelerating insoluble Li2 S2 -Li2 S reduction catalysis to mitigate the shuttle effect has emerged as an innovative paradigm for high-efficient lithium-sulfur battery cathodes, such as single-atom catalysts by offering high-density active sites to realize in situ reaction with solid Li2 S2 . However, the profound origin of diverse single-atom species on solid-solid sulfur reduction catalysis and modulation principles remains ambiguous. Here we disclose the fundamental origin of Li2 S2 -Li2 S reduction catalysis in ferromagnetic elements-based single-atom materials to be from their spin density and magnetic moments. The experimental and theoretical studies disclose that the Fe-N4 -based cathodes exhibit the fastest deposition kinetics of Li2 S (226 mAh g-1 ) and the lowest thermodynamic energy barriers (0.56 eV). We believe that the accelerated Li2 S2 -Li2 S reduction catalysis enabled via spin polarization of ferromagnetic atoms provides practical opportunities towards long-life batteries.

Origin and Acceleration of Insoluble Li2S2−Li2S Reduction Catalysis in Ferromagnetic Atoms‐based Lithium‐Sulfur Battery Cathodes

AbstractAccelerating insoluble Li2S2−Li2S reduction catalysis to mitigate the shuttle effect has emerged as an innovative paradigm for high‐efficient lithium‐sulfur battery cathodes, such as single‐atom catalysts by offering high‐density active sites to realize in situ reaction with solid Li2S2. However, the profound origin of diverse single‐atom species on solid‐solid sulfur reduction catalysis and modulation principles remains ambiguous. Here we disclose the fundamental origin of Li2S2−Li2S reduction catalysis in ferromagnetic elements‐based single‐atom materials to be from their spin density and magnetic moments. The experimental and theoretical studies disclose that the Fe−N4‐based cathodes exhibit the fastest deposition kinetics of Li2S (226 mAh g−1) and the lowest thermodynamic energy barriers (0.56 eV). We believe that the accelerated Li2S2−Li2S reduction catalysis enabled via spin polarization of ferromagnetic atoms provides practical opportunities towards long‐life batteries.

Analysis of DC Winding Induced Voltage in Wound-Rotor Synchronous Machines by Using the Air-Gap Field Modulation Principle

In order to analyze the DC winding induced voltage in the wound-rotor synchronous machine, this paper uses the air-gap field modulation principle to investigate its operation mechanism and harmonic order. By establishing the analytical magneto-motive force (MMF)-permeance model, the DC winding induced voltage per electrical cycle under open-circuit condition, armature reaction condition and on-load condition are deduced. Analytical analysis shows that the MMF function, stator and rotor permeance function are critical factors that influence the harmonic order of the DC winding induced voltage. The analysis results are compared with those predicted by the finite element analysis (FEA). Both non-linear steel and linear steel conditions are accounted in the FEA analysis, and the results show that the analytical deduction result agrees well with the FEA analysis result.

Angular Rate Measurement Method of Magnetically Suspended Control and Sensing Gyroscope Using Component-Level Rotation Modulation

Magnetically suspended control and sensing gyroscope (MSCSG) is a novel concept gyroscope with attitude control and attitude measurement. In order to eliminate constant drift error and improve the angular rate measurement accuracy of MSCSG, a high-precision angular rate measurement method based on component-level rotation modulation (CLRM) is proposed in this article. First, the structure of MSCSG, the Lorentz force magnetic bearing (LFMB), and the angular rate measurement principle of MSCSG are analyzed. Second, the basic principle of rotational modulation is introduced. Third, based on the principle of CLRM angle measurement, the high-precision measurement of angular rate based on MSCSG is realized by taking the derivative of the angle and sliding smoothing. After CLRM processing, the angular rate measurement error of MSCSG is quantified and the installation error is analyzed and compensated. Finally, the error compensation of CRLM and installation error compensation effect is verified by simulation. The feasibility of the proposed method is verified by experiments. The method of CLRM can reduce the MSCSG drift error by two orders of magnitude. The method proposed in this article can be used as a reference for MSCSG attitude measurement and attitude control integration.

Efficiency of the autonomous modular system in the implementation of the spray application process in the vineyard

Autonomous modular system mounted on a conventional (CON) sprayer operating on the principle of pulse-width modulation (PWM) control of electromagnetic valves represents state-of-the-art technology for implementation controlled application of spray mixture without changing the operating parameters of the sprayer (e.g. spray pressure, nozzle size). In accordance with the principles of precision viticulture, the pulse width modulation control is the primary technology, which allows the application of the required amount of spray mixture exclusively to the target areas of the vine without changing the droplet size spectrum and allows for even deposit quality and reducing the drift outside the target areas. In the vineyard, we tested an autonomous axial sprayer prototype throughout the entire spraying season in 2021 on which we have installed an autonomous modular system with enabled pulse-width control. We tested two modes of operation of the sprayer prototype, namely autonomous (continuous duty cycle control (DC: 0 to 100%)) and conventional (nozzle fully open at all time), at a steady spray speed of 6 kmh-1. We compared the amount of PPP expressed as a percentage between autonomous and conventional mode of operation of the sprayer through individual nozzles on the sprayer. The maximum saving of the spray mixture of 69.8%, through an individual nozzle was measured at phenological stage of the vine BBCH 55. A comparative analysis between the CON and PWM mode of the spray mixture application showed that we saved 626.24 l per year in the automated mode of operation.

Magneto-optical Intensity Modulation for Optical Vortex Beams with Orbital Angular Momentum

Here we theoretically and experimentally demonstrate a way to control the intensity of optical vortices by a magnetic field directed along the beam axis. We describe the principle of an optical vortex modulator and switch based on the Faraday effect in an iron garnet film. Importantly, the magnetic field influences only the polarization plane of the vortex and keeps its topological charge.

Role of growth modulation in the management of idiopathic scoliosis: A narrative review of literature

Scoliosis is a condition in which there is a lateral curve to the spine. The cause of scoliosis is unknown, but different aetiologies have been suggested, but mostly cause has been idiopathic in nature. Muscle spasms, cerebral palsy, Marfan syndrome, and tumours (neurofibromatosis) are some of the suggested aetiologies. Progressive adolescent idiopathic scoliosis (AIS) affects mainly girls and anterior spinal overgrowth during the second growth spurt appear to be a significant cause. The diagnosis of scoliosis is primarily a clinical suspicion followed by an AP and lateral X ray of spine in standing position. Measurement of the Cobb angle is the standard method of assessing the curvature in a quantitative manner. It is the angle between two lines, drawn perpendicular to the upper endplate of the first vertebra involved and the lower endplate of the last vertebra involved. Cobb angles are followed for both curves for those with two curves. Risser classification grades the skeletal maturity on X rays and is considered along with the Cobb angle to making a decision towards surgery. Indications for surgical correction of scoliosis is not clearly defined however, the treatment of scoliosis is based on the severity and progressive nature of the curve. Cobb angle above 40 degrees, rapidly progressing curve, major thoracic deformity affecting the function such as breathing and cosmetic reasons, are some of the indications for surgery. There are several modalities of surgical correction. Main method has been correction of the deformity and fixation with one or two rods and pedicle screws followed by bone grafting. Harrington rods were the primarily used system, but with time many spinal instrumentation systems and rods have been introduced to the market. Apart from using rods some have tried anterior vertebral body stapling and anterior vertebral body tethering for correction scoliosis using the principle of growth modulation.
 We conducted a systematic review to answer the question, 'What is the role of growth modulation in the management of idiopathic scoliosis?' All articles / publications published from 2010 May to 2019 October were used as research data. A health, related database (PubMed) was used for the search. Search criteria revealed 99 articles initially and 37 articles after filtered based on title reading. Then 18 articles were selected for the final analysis after being filtered manually by reading summary and abstracts of each article.

Classification of primary dysmenorrhea by brain effective connectivity of the amygdala: a machine learning study.

The amygdala plays a crucial role in the central pathogenesis mechanism of primary dysmenorrhea (PDM). However, the detailed pain modulation principles of the amygdala in PDM remain unclear. Here, we applied the Granger causality analysis (GCA) to investigate the directional effective connectivity (EC) alterations in the amygdala network of PDM patients. Thirty-seven patients with PDM and 38 healthy controls were enrolled in this study and underwent resting-state functional magnetic resonance imaging scans during the pain-free stage. GCA was employed to explore the amygdala-based EC network alteration in PDM. A multivariate pattern analysis (MVPA)-based machine learning approach was used to explore whether the altered amygdala EC could serve as an fMRI-based marker for classifying PDM and HC participants. Compared to the healthy control group, patients with PDM showed significantly decreased EC from the amygdala to the right superior frontal gyrus (SFG), right superior parietal lobe/middle occipital gyrus, and left middle cingulate cortex, whereas increased EC was found from the amygdala to the bilateral medial orbitofrontal cortex. In addition, increased EC was found from the bilateral SFG to the amygdala, and decreased EC was found from the medial orbitofrontal cortex, caudate nucleus to the amygdala. The increased EC from the right SFG to the amygdala was associated with a plasma prostaglandin E2 level in PDM. The MVPA based on an altered amygdala EC pattern yielded a total accuracy of 86.84% for classifying the patients with PDM and HC. Our study is the first to combine MVPA and EC to explore brain function alteration in PDM. The results could advance understanding of the neural theory of PDM in specifying the pain-free period.

Electro-optic modulation aberration correction algorithm based on phase difference compensation.

In order to achieve wide field-of-view, high-resolution LIDAR, a gating imaging structure combining an electro-optic crystal and an electron multiplication CCD is constructed. According to the index ellipsoid theory, a 3D ray tracing model is established to explore the principle of electro-optic modulation. The field-of-view and interference intensity distribution of the LiNbO3(LN) crystal electro-optic modulation are studied by using the proposed model. In order to solve the problem that the interference light intensity at the edge of the field-of-view of crystal electro-optic modulation is not homogeneous, we study and propose an electro-optic modulation aberration correction algorithm based on phase difference compensation. The corrected interference light intensity at the edge of the field-of-view increased from 0.87 to 0.94. Finally, a LIDAR imaging simulation system is established to image the target at a distance of 2000m. The results show that under the condition of a 1° wide field-of-view, the imaging accuracy of the system is 5mm, and the average imaging error introduced by the crystal electro-optic modulation is less than 2cm.

Simulation Research on Improved Small Signal Model of VSC Converter

Small signal model is the basis of stability analysis and control design of VSC-HVDC. In this paper, the small signal model of VSC-MTDC applies to Voltage Source Converters (VSC) in different conditions through theoretical analysis and derivation. The model of ac system can be widely used by choosing d-q synchronous reference frame flexible. Then according to voltage source converter (VSC) modulation principle, the converter model is revised through the coupling mechanism between ac and dc of converter. This article has constructed three kinds of improved small signal models applied to different conditions. By comparing of Electromagnetic transient simulation and the small-signal model simulation, the small-signal model has high accuracy.

An Embedded Communication Method for In-Home Energy Routers With Power/Signal Dual Modulation

This article proposes a novel embedded communication strategy for in-home energy routers (IHERs). It is based on the power/signal dual modulation (PSDM) principle and applied in the small-scale community energy local area network (E-LAN). The proposed communication strategy multiplexes power converters as data transmitters, and thus high cooperation and synchronization between power flow and information flow are achieved. In addition, system reliability is enhanced since communication module has practically the same reliability as the power module. A typical IHER’s structure and operation principles are presented, based on which the detailed design of embedded communication is proposed. For distributed power management of community E-LAN, both intra-IHER communication and inter-IHERs communication are involved, and their channels are modeled mathematically. IHER interconnection interface converters (IICs) play a significant role in power exchange between IHERs, and their operation modes are analyzed in detail. Finally, an experimental prototype is built to validate the feasibility of the proposed method.

Recent Progress of Terahertz Spatial Light Modulators: Materials, Principles and Applications.

Terahertz (THz) technology offers unparalleled opportunities in a wide variety of applications, ranging from imaging and spectroscopy to communications and quality control, where lack of efficient modulation devices poses a major bottleneck. Spatial modulation allows for dynamically encoding various spatial information into the THz wavefront by electrical or optical control. It plays a key role in single-pixel imaging, beam scanning and wavefront shaping. Although mature techniques from the microwave and optical band are not readily applicable when scaled to the THz band, the rise of metasurfaces and the advance of new materials do inspire new possibilities. In this review, we summarize the recent progress of THz spatial light modulators from the perspective of functional materials and analyze their modulation principles, specifications, applications and possible challenges. We envision new advances of this technique in the near future to promote THz applications in different fields.

Sliding-boundary-constrained cantilever structure for vibration isolation via nonlinear stiffness modulation

In this paper, a novel sliding-boundary-constrained cantilever structure with nonlinear stiffness modulation (SCS-NSM) is proposed and systematically investigated for vibration isolation. The SCS-NSM is composed of a hemisphere-constrained cantilever structure (HCCS) and a pair of repulsive magnets. The nonlinear stiffness modulation mechanism for achieving quasi-zero stiffness (QZS), that is, using the hardening stiffness of the magnets to modulate the negative stiffness of HCCS, is fully revealed by static analysis. Furthermore, the QZS is adjustable to respond to different loads, and the modulation principle is clarified. Compared with conventional QZS isolators (paralleling negative and linear stiffness), the proposed SCS-NSM shows the advantages of wide load range and small static deflection. Static tests are performed to verify the effectiveness of the nonlinear stiffness modulation mechanism. Dynamic analysis shows that the SCS-NSM has a low resonant frequency and a wide vibration isolation frequency band due to its low stiffness. Periodic, sweep and random excitation tests are implemented to evaluate the vibration isolation performance of SCS-NSM. Experimental results validate the dynamic model and demonstrate that the vibration with a frequency higher than 4.6 Hz can be effectively attenuated. The proposed SCS-NSM provides a new perspective on low-frequency vibration isolation, and the nonlinear stiffness modulation mechanism has reference significance for designing QZS isolators with wide-bearing capacity and high compactness.

Minimum-Output-Current-Ripple Control of Current-Fed Three-Level Phase-Shift Full-Bridge Converter

Electrified ports using medium-voltage DC (MVDC) renewable energy microgrids require current-fed dc/dc converters in application scenarios such as battery or ultracapacitor charging units and hydrogen production systems. This paper designs a three-level phase-shift full-bridge (TL-PSFB) converter that interfaces with the MVDC microgrid. Its operation in the current source mode requires a wide output voltage range and small output current ripple. Firstly, the dual-output TL-PSFB topology is introduced, and the principle of phase-shift pulse width modulation (PS-PWM) is presented. Secondly, the principle of the traditional constant-conduction-duty-cycle (CCDC) strategy is analyzed. Then, a minimum-output-current-ripple (MOCR) strategy is proposed by analyzing the relationship between output current ripple, conducting-duty cycle, and phase-shift duty cycle, and a constant current control combined with the MOCR strategy is designed. The output current ripple of the MOCR strategy is smaller than that of the CCDC strategy in a full range of operating conditions. Under the same output current ripple design index, the value and loss of the filter inductor can be reduced with the MOCR strategy. In addition, the MOCR strategy can widen the output voltage regulation range and increase the bus voltage utilization without causing significant changes to the total harmonic distortion (THD) of primary voltage. Finally, experimental results verify the correctness of the theoretical analysis.