Load Modulation Research Articles

A Modified Triaxial Apparatus for Soils under High-Frequency, Low-Amplitude Vibrations

Abstract A modified triaxial apparatus was developed to explore the behavior of cohesionless soil subjected to high-frequency, low-amplitude vibrations, such as those induced by high-speed trains. It was based on a conventional Bishop-type triaxial apparatus to utilize its existing static loading module. The major modification was an added dynamic loading module with a low-inertia linear voice coil actuator mounted coaxially with the vertical loading rod. Through a signal generator and an amplifier connected to the voice coil actuator, a vibration input with wide range of frequencies and amplitudes could be superimposed to a monotonic loading process. A series of tests under different conditions were performed to demonstrate the effectiveness and performance of the modified triaxial apparatus, with the focus being placed on the reduction of shear resistance and accumulative deformation of sand induced by high-frequency, low-amplitude vibrations.

Bandwidth-Increased Ripple-Mitigating Scheduling Algorithm for Dynamically Reconfigurable Batteries

Modular cascaded circuits offer attractive qualities in reconfigurable battery applications, including improved fault tolerance and flexibility. In contrast to conventional hard-wired dc battery packs, however, cascaded topologies, such as modular multilevel circuits (MMC) with serial or serial and parallel connectivity, load modules with substantial low-frequency current ripple, which generates additional loss and can accelerate battery aging. Recent studies reveal that low-frequency ripple can cause noticeable battery aging, whereas high frequencies are insignificant, presumably mainly as they can be absorbed by the dielectric electrode capacitance, and reduce heating associated with lower high-frequency battery impedance. Previous MMC–battery control methods solely focus on state-of-charge and thermal balancing of individual modules, while the few existing methods for suppressing ripple tend to form low-frequency patterns in the modules’ load, which increase battery cycling as well as loss. This paper presents a ripple-oriented high-bandwidth control technique that minimizes low-frequency components in the module load spectrum and improves battery treatment, while maintaining the average switching frequency. The control method takes limitations related to module data acquisition into account and enhances the feedback bandwidth using observers. It works with a wide range of topologies including modules with series connectivity only as well as series/parallel. The measurements in the laboratory verify the shift of the module load from the 10 – 100 Hz range to ~5 kHz and a reduction of battery losses by up to 20 %.

A Nine-Level Inverter With Single DC-Link and Low-Voltage Capacitors as Stacked Voltage Sources With Capacitor Voltage Control Irrespective of Load Power Factor

This paper proposes a multilevel inverter topology with a single DC-link and series-connected capacitors as stacked voltage sources for multilevel voltage generation. The voltage deviation of a DC-link capacitor will occur whenever a phase terminal connects to the balanced neutral points (NPs: terminal joints of DC-link capacitors). On the contrary, if the voltage of a DC-link capacitor deviates from the nominal voltage, the same phase currents can be utilised to balance these neutral points. This new technique is being proposed for the first time in literature. Any voltage disturbance of the DC-link capacitors is balanced using the motor phase currents, irrespective of load power factor and modulation indices. For the balanced neutral points, whenever a phase connects to a neutral point, the other phase terminal tapping positions are varied on the DC-link to establish <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$i_{A}+i_{B}+i_{C}=0$</tex-math></inline-formula> for that neutral point. The pole voltage level variation at motor phase terminals is undisturbed by adding extra cascaded H-bridges (CHBs) at each phase leg. The voltages of CHB capacitors are controlled conventionally by inverter pole voltage redundancies. The detailed experimental results for open-loop V/ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> and closed-loop field-oriented control on an induction motor are presented using a nine-level laboratory prototype.

The Prediction of Cracking Load and Peak Load of UHPC‐NC Composite Structure

In this study, models for calculating the cracking load and a peak load of the UHPC‐NC structures are established. The effects of UHPC's high tensile strength, reinforced steel bars in NC, reinforce steel bars in UHPC, and prestress tendons in UHPC on cracking load and peak load are considered. In the cracking load model, UHPC is considered to be elastic and the stress distribution is triangular, the stress of steel bars and prestressing tendons is also calculated according to the plane section assumption and elastic theory. In the peak load module, UHPC is assumed to be partially elastic and partially plastic. The plastic part is represented by a rectangular stress block diagram, and the stress value reduction factor and rectangular stress frame height reduction factor are obtained by trial calculation. Compared with the experimental data of UHPC‐NC beams with different types of combinations collected from references, the calculated results have a high matching degree, which is suitable for various types of UHPC‐NC, both cracking loads and peak loads.

Prototype of Simulation model of Socio-epidemiological and economic consequences on the example of Russian Federation subjects

Processes associated with extraordinary events that are difficult to control and evaluate, as a rule, are built on patterns of past events or historical analogues, but the spread of coronavirus infection is a kind of unique phenomenon that has affected all spheres of life of states and the world as a whole. This article is a continuation of a study related to the assessment of the socio-epidemiological and economic consequences that led to the spread of COVID-19. Previously, the architecture of the model was created taking into account world practices for building such blocks for simulation models. The prototype combines three fully functional blocks. At this stage of the study, a prototype model was formed, which takes into account demographic, epidemiological and economic processes that are closely related to each other. The simulation has been running continuously since 2018 and covers three chronological periods - before the pandemic, during the pandemic and the forecast period. The experiment ends in 2025, after which a set of statistical indicators is produced for the three aligned blocks. The prototype model has prospects for expansion to all subjects of the Russian Federation. Also, if you add a loading module, it can be launched using supercomputer technologies on a scale of 1: 1 in terms of the number of agents that form an artificial society on the basis of which scenario experiments were carried out.

THE INFLUENCE OF THE LOADING-DISTRIBUTING MODULE ON THE TECHNOLOGICAL CHARACTERISTICS OF THE WHEELED TRANSPORT UNIT

The Amur Region is the main agricultural region of the Far Eastern Federal District. In terms of the volume of grown products (soybeans), the Amur Region accounts for over 40 percent of the total gross harvest of the Russian Federation. (Research purpose) The research purpose is to study the effect of the loading-distributing module on the technological characteristics of a wheeled transport unit. (Materials and methods) The main task when harvesting crops in conditions of the weak bearing capacity of soil is to timely transport the resulting crop out of the fields. The weak bearing capacity of the soil is because of that during the harvesting period (August-October) there is greatest amount of precipitation falls. One of the ways to solve this problem is to increase the traction properties of the energy vehicle due to the rational distribution of the coupling weight with an increase in the support area of its propellers. (Results and discussion) The article presents the results of improving the traction properties of a road train as part of a KamAZ-4350 car and a 2PN-4M trailer due to the use of a loading module for a truck and the installation of arched tires. These make it possible to expand the technological characteristics of the unit in cross-country ability and reduce the anthropogenic impact of its running system on the fertile soil layer in motion. The proposed method makes it possible to increase the increasing of power and traction characteristics of the propulsion by 12-14 percent compared to the serial KAMAZ-4350 on arched tires. (Conclusions) An increase in the efficiency of transport and technological support of the harvesting process is possible by increasing the traction properties of the car due to the redistribution of the coupling weight in the system of the transport unit, directly between the trailer and the car.

Millimeter-Wave Power Amplifier ICs for High Dynamic Range Signals

The next-generation 5G and beyond- 5G wireless systems have stimulated a substantial growth in research, development, and deployment of mm-Wave electronic systems and antenna arrays at various scales. It is also envisioned that large dynamic range modulation signals with high spectral efficiency will be ubiquitously employed in future communication and sensing systems. As the interface between the antennas and transceiver electronics, power amplifiers (PAs) typically govern the output power, energy efficiency, and reliability of the entire wireless systems. However, the wide use of high dynamic range signals at mm- Wave carrier frequencies substantially complicates the design of PAs and demands an ultimate balance of energy efficiency and linearity as well as other PA performances. In this review paper, we will first introduce the system-level requirements and design challenges on mm-Waves PAs due to high dynamic range signals. We will review advanced active load modulation architectures for mm-Wave PAs and power devices. We will then introduce recent advances in mm-Wave PA technologies and innovations with several design examples. Special design considerations on mm-Wave PAs for phased array MIMOs and high mm-Wave frequencies will be outlined. We will also share our vision on future technology trends and innovation opportunities.

A Compact CMOS Broadband Bidirectional Digital Transceiver Frontend With Capacitor Bank and Transformer Matching Network Reuse

This article presents a fully integrated bidirectional class-G digital Doherty switched capacitor transmitter (TX) and N-path Quadrature receiver (RX) in CMOS. Through sharing on-chip capacitor banks, typically occupying a major portion of the digital TX or RX chip area, as well as the RF passive matching networks, the overall size can be radically reduced. Moreover, the overall performance could be further improved by eliminating the need for an integrated T/RX switch and its corresponding loss and area overhead. The class-G operation is used within the Doherty TX to increase the output power and backoff efficiency, while the capacitive stacking technique is used in the RX to increase the voltage gain. A transformer network is used to present the optimum impedance for both the parallel Doherty TX and RX mode of operation, as well as the class-G Doherty active load modulation. As a proof-of-concept, the joint bidirectional class-G digital Doherty switched-capacitor TX and N-path Quadrature RX through capacitor bank sharing is implemented in a 45-nm CMOS SOI process. The TX demonstrates a P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</sub> 1dB bandwidth (BW) of 1.6-3.1 GHz, a fractional BW >63%, and peak output power (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</sub> ) of 22.5dBm at 2.4GHz. The peak drain efficiency (DE) of the TX is 49.5% at 1.8GHz and 41.5%/38.7%/31.6%/18.1% for the peak/2.5/6/12dB power back off (PBO) at 2.4GHz. The DE improvement compared to class-B PA is 1.24×/1.51×/1.72× at 2.5/6/12dB PBO. The TX is measured using 64-QAM/20MHz modulation without the use of AM-PM pre-distortion or pattern based DPD. It achieves an excellent -27.1dB EVM, -31.31dBc ACLR, 14.6dBm average P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</sub> and 25.8% average DE at 1.6GHz. The RX achieves a noise figure (NF) of 7.6dB at 2.2GHz and a conversion gain of 17dB with a 12 MHz bandwidth. In addition, the proposed RX front-end achieves < -60 dBm LO leakage over the operating frequency range.

Induction Heating for Variably Sized Ferrous and Non-Ferrous Materials through Load Modulation

Induction heating (IH) is a process of heating the electrically conducting materials especially ferromagnetic materials with the help of electromagnetic induction through generating heat in an object by eddy currents. A well-entrenched way of IH is to design a heating system pertaining to the usage of ferromagnetic materials such as stainless steel, iron, etc., which restricts the end user’s choice of using utensils made of ferromagnetic only. This research article proposes a new scheme of induction heating that is equally effective for heating ferromagnetic and non-ferromagnetic materials such as aluminium and copper. This is achieved by having a competent IH system that embodies a series resonant inverter and controller where a competent flexible load modulation (FLM) is deployed. FLM facilitates change in operating frequency in accordance with the type of material chosen for heating. The recent attempts by researchers on all metal IH have not addressed much on the variable shapes and sizes of the material, whereas this research attempts to address that issue as well. The proposed induction heating system is verified for a 2 kW system and is compatible with both industrial and domestic applications.

A novel single source multilevel inverter with hybrid switching technique

SummaryA novel multilevel inverter (MLI) configuration with the hybrid switching technique is presented in this paper. The proposed MLI consists of the H‐bridge combination with unidirectional switches, half‐bridges, and transformers. The suggested MLI with the additional cascaded connection increases to higher voltage levels. The number of employed components in this topology is drastically minimized. Therefore, the complexity, cost, and volume of the proposed topology are also reduced. The operation of the suggested topology is tested through the improved novel switching technique. This modulation method reduces the total harmonic distortion (THD) and produces high root mean square (RMS) voltage. Further, a comprehensive comparison with the recent MLI topologies is performed to validate the merits of the suggested inverter. Simulation and experimental results verify the suggested topology performance using the new modulation technique at different loading conditions and modulation indices.

A Hybrid Self-Voltage Balanced Multilevel Inverter Topologies for Induction Motors

A hybrid structured asymmetric switching capacitor multilevel inverter (ASC-MLI) is suggested in this work. The notion behind presenting this topology is to reduce the device count and DC sources as compared with conventional MLI. The step by step operating mode of single phase ASC-MLI is presented and by doing slight modifications the same configuration is used in three phase utility application and electric drive. The proposed configurations utilize major benefits of self-voltage balancing capability of capacitor voltage, which is independent from different load type and modulations index. To generate the switching pulse for corresponding switches the multi-carrier based sinusoidal pulse width modulation (MCS-PWM) technique is used; in addition to this simulation result are obtained using MATLAB/Simulink 2016b software version. Simulation results of an induction motor drive connected as three phase load highlights good performance of 17-level MLI.

Frequency analysis of load modulation networks for asymmetric Doherty power amplifiers in GaN

AbstractThis paper investigates the frequency response of load modulation networks for asymmetric Doherty power amplifiers (ADPA) with an output back-off power level larger than 6 dB and a power ratio of peak to main amplifier (N − 1) larger than 1. The influence of the main path impedance transformer (IT) on the Doherty impedances at main and peak path as well as on the ADPA's efficiency is analyzed. Scaling of the main IT's characteristic impedance via ξ indicates a maximum broadband matching for an input voltage Vin of ξ · Vin,max. By weighting the frequency- and ξ-dependent efficiency curves using a probability density function (PDF), an optimum is obtained for ξ = 1/N. To verify the theory, three ADPAs with different ξ-scaled ITs are designed, measured, and compared. For the design at 3.6 GHz, a gallium nitride (GaN) transistor is used. By means of the intrinsic node matching technique, matching at the current source plane is obtained. In laboratory measurements, the ADPA with ξ = 1/N achieves a power-added efficiency (PAE) of 63% at 42 dBm output power and a PDF-weighted average PAE of 38.8% within 400 MHz bandwidth for 8 dB peak-to-average power ratio. Comparison with similar state-of-the-art ADPAs in GaN technology shows highest PAE and operation power gain GP for center frequencies larger than 3.0 GHz.

Ka-Band CMOS Power Amplifier Based on Transmission Line Transformers With Single-Ended Doherty Network

A <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ka</i> -band CMOS two-stage Doherty power amplifier (DPA) is presented, whose back-off efficiency is improved by voltage-mode Doherty load modulation. The input and output networks of its power stage are composed of transmission line transformers (TLTs) and single-ended Doherty networks implemented with lumped elements. An adaptive bias circuit to boost the Doherty operation is included in the gate network of the auxiliary amplifier. It shows a power gain of 16.2 dB with 48.2% peak drain efficiency (DE) and 25% 6-dB back-off DE at 26 GHz. It has two times higher 6-dB back-off efficiency in comparison to that of a theoretical class-A power amplifier. It is fabricated in a 28-nm bulk CMOS process and occupies 0.094-mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> core size.

Simulation of impact load modulation device based on drill string vibration

The longitudinal vibration of the bottom drill string is violent and the law is complex during the deep well drilling. The vibration of the drill string brings many adverse effects on the drilling pipe fracture and bit trampoling. Generally speaking, the effective way to control the vibration of drill string is to install damping device in bottom hole. The research group proposes a device that uses the longitudinal vibration energy of the deep well drill string to modulate the impact dynamic load, which converts the vibration energy of the downhole drill string that is not conducive to drilling into the mechanical impact energy that improves the rock breaking capacity of the bit. The impact load modulation device can use the drill string to apply the “mechanical WOB” and the differential pressure between the upper and lower piston to produce the “hydraulic WOB”, The simulation results show that the adjustable range of output load is 2 ~ 7T, and the change of each time is about 2T. The modulation law of impact load under the influence of longitudinal vibration of drill string and different parameters is analyzed. Through ground experiment and simulation, the damping performance and speed-up effect of the modulation device are compared and analyzed, and the impact load output characteristics of the device are analyzed, which provides a thinking for the design of damping and pressurization tools.

Modeling of the Rail Type Electromagnetic Launch System With Superconducting Pulsed Power Supply Considering Resistance

In the rail type electromagnetic launch system, when the projectile accelerates in orbit, it is affected by not only the electromagnetic force, but also various resistances, such as sliding friction, air resistance and so on. These resistances affect the characteristics of the pulsed power supply (PS). Nowadays, in order to analyze and design the pulsed PS conveniently, researchers usually ignore the influence of various resistors, and use fixed loads including resistors and inductors to simulate the rail load module, which will cause large errors. So, the mathematical model of the orbital electromagnetic launch system with superconducting is established, including the pulsed PS model with the multiple high-temperature superconducting pulsed power transformer (HTSPPT) and the dynamic rail load model considering various forces. The simulation results indicate that the dynamic rail load model considering various forces can reduce the error of capacitor voltage, load current and other parameters, the features of pulsed PS can be studied more precisely.

Effect of countermeasure bodygear on cardiac-vascular-respiratory coupling during 6-degree head-down tilt: An earth-based microgravity study

Prolonged exposure to microgravity causes physiological deconditioning in humans. Herein, a novel designed countermeasure gravitational load modulation bodygear has been developed to deal with the ill effects of the microgravity environment. The bodygear is designed to provide the wearer an axial loading from the shoulder to the feet that simulate Earth's gravity. The present study aims to evaluate the effect of bodygear on cardiac, vascular and respiratory systems during head-down tilt (HDT) microgravity analogue. In this, 30 healthy male subjects have volunteered and their average age, height and weight were 24.56 ± 3.87 yr, 168.4 ± 9.17 cm and 65.9 ± 10.51 kg respectively. The physiological signals such as electrocardiogram (ECG), blood pressure (BP) and respiration were recorded non-invasively using Biopac MP100. The signals were sampled at 1,000 Hz and processed using MATLAB 2018b. The signals were analysed in linear well as non-linear domains. The ECG and BP were used to derive R-R interval (RRI) and systolic blood pressure (SBP). The respiration time series (RSP) was derived by extracting R-peaks from the ECG signal and using these peaks to find the respiration amplitude. The non-linear domain analysis was used for the detection and quantification of information flow among the recorded signals. Repeated measure analysis of variance with Bonferroni post-hoc paired t-test was used for statistical analysis with the p < 0.05. The experimental results show that the 6-degree HDT activates the parasympathetic system and decreased the RRI effect on SBP (p = 0.005). Interestingly with the bodygear usage, the sympathetic system activated, mean RRI decreased (p = 0.018) and blood pressure increased (p = 0.031) as compared to baseline. Further, it was also observed that the effect of RRI on SBP (p = 0.029) and SBP on RRI (p = 0.012) was increased with bodygear as compared to HDT without bodygear. The conditional entropy technique aided in analyzing the effect of bodygear on information flow variation in the cardiovascular system of the human body.

A new multi-function servo control dynamic shear apparatus for geomechanics

In this paper, we report a new multi-function servo control dynamic shear test apparatus, DJZ-500. This apparatus consists of five parts, including power system, loading frame, servo control unit, cooling system and PC console. The normal load and shear load are measured by load cells with an accuracy of 0.1 kN; normal and shear displacement are measured by LVDTs with an accuracy of 0.1 μm. DJZ-500 has the dynamic and static loading modules, which can perform the force and displacement servo control experiments in both vertical and horizontal directions. In addition, the dynamic loading modules can execute the custom waveforms, which can be utilized to investigate the seismic response of rock and soil masses. We presented six sets of representative tests on sands to demonstrate these functions. Moreover, DJZ-500 can also preform the coupled shear-flow test with the pumping system to investigate the flow behavior in sheared rock fractures. This device makes up for the deficiency of the existing equipment, and promotes the study of frictional properties of geomaterials.

The Discovery and Biosynthesis of Nicotinic Myxochelins from an Archangium sp. SDU34

Myxobacteria are a prolific source of structurally diverse natural products, and one of the best-studied myxobacterial products is the siderophore myxochelin. Herein, we report two new compounds, myxochelins N (1) and O (2), that are nicotinic paralogs of myxochelin A, from the terrestrial myxobacterium Archangium sp. SDU34; 2 is functionalized with a rare 2-oxazolidinone. A precursor-feeding experiment implied that the biosynthesis of 1 or 2 was due to altered substrate specificity of the loading module of MxcE, which likely accepts nicotinic acid and benzoic acid instead of more conventional 2,3-dihydroxybenzoic acid. We also employed a phylogenomic approach to map the evolutionary relationships of the myxochelin biosynthetic gene clusters (BGCs) in all the available myxobacterial genomes, to pave the way for the future discovery of potentially hidden myxochelin derivatives. Although the biological function of 1 and 2 is unclear yet, this work underpins that even extensively studied BGCs in myxobacteria can still produce new chemistry.

Receiver-Feedback-Free Cavity Resonant Wireless Power Transfer Based on In Situ S-Parameter Estimation Using a Parasitic Antenna

This letter proposes a novel cavity resonant wireless power transfer that can optimize the load condition of a parasitic antenna without receiver feedback or the need to know the S-parameter <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a priori</i> . In this letter, it is hypothesized that the transmission efficiency to a receiver can be indirectly maximized by minimizing reflection observed at the signal source, and the proposed method is based on this. Furthermore, an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> S-parameter estimation based on load modulation is proposed. This estimation provides a closed-form optimum load condition for minimizing reflection, and avoids the need for a brute force search with load sweeping. Experiments carried out in a 200 mm conductive cube cavity successfully demonstrate the effectiveness of the proposed method, which obtains a high transmission efficiency of 42.2% that is comparable to the achievable maximum.

Analyzing the biosynthetic potential of antimicrobial-producing actinobacteria originating from Indonesia

We investigated the biosynthetic potential of soil-associated actinobacteria originating from Indonesia, identified as Streptomyces luridus and as Streptomyces luteosporeus. Antimicrobial assays indicated inhibitory activity by both strains against the pathogen Pseudomonas aeruginosa, with S. luteosporeus particularly inhibiting the growth of Bacillus subtilis. PCR-amplification, cloning, and sequencing of ketosynthase (KS) domains of type I modular polyketide (PKS-I) and adenylation (AD) domains of non-ribosomal peptide synthetase (NRPS) indicated the diversity of KS and AD domains derived from both Indonesian Streptomyces. Further phylogenetic analysis showed that KS domains from the subclass cis-AT PKS can be classified as being a part of a loading module or an extension module, along with their predicted substrate specificity. The results suggest that both strains are a potential source of novel biosynthetic pathways. This genetic analysis approach can be used as a fast guide to obtain insight into natural product biosynthetic gene diversity in microorganisms.