Mode Of Operation Research Articles

Epidemiological features of 1,332 cases of hip fracture in Shanghai, China (2015–2020)

PurposeThis study aimed to analyze the epidemiological characteristics of hip fracture in all age groups in Shanghai, and to evaluate the hospitalization cost of patients with hip fracture.MethodsA total of 1,332 hip fracture patients admitted to a tertiary general hospital between January 2015 and May 2020 in Shanghai were included. Age, sex, diagnosis, cause of injury and site, fracture type, comorbidities, length of stay, treatment, outcomes (at discharge) and hospitalization expenses were recorded. The epidemiological characteristics of hip fracture were analyzed by using SPSS 26.0 software.ResultsThe average age of hip fracture was 77.24 ± 12.66 years, and 69.0% of the patients were female. Overall, 886 patients had femoral neck fracture, and 446 patients suffered from intertrochanteric fracture. Most of the fractures caused by falls at the same level and falls from a height occurred in those aged 81–90 years; and traffic accident injuries mostly took place in patients aged 50–60. Among the 1,302 hip fracture patients who underwent surgical treatment, hip replacement was the major choice for femoral neck fracture, accounting for 49.2%. Internal fixation was the main treatment choice for intertrochanteric fracture, making up 97.8%. The median length of hospital stay lasted 8 days and at cost of hospitalization was ¥49,138.18 RMB.ConclusionThis epidemiological study found that patients with hip fracture had certain distribution characteristics in age, sex, type of fracture, injury season, cause of injury, mode of operation, length of stay, cost, and so on. Proper medical management, social preventive measures, and prevention of falls are needed to reduce the risk of hip fracture and the socioeconomic burden.

Fuzzy controlled modified reduced switch converter for switched reluctance motor under dynamic loading

In this paper, modified reduced switch converter topology is used to drive 8/6 pole, 7500 W switched reluctance motor (SRM) with an electric vehicle (EV) load. Fuzzy logic control (FLC) is developed for the modified converter topology and its performance is compared with the proportional integral (PI) controller. Analytical equations, switching pulses and different mode of operation are presented for modified reduced switch converter using double phase magnetization scheme. The converter topology adopts a modified switching sequence i.e., magnetization then freewheeling before demagnetization. It offers lesser torque ripples, reduced phase current and need only four switches for a 4-phase SRM drive. Modified reduced switch converter is simulated in MATLAB-simulation to investigate and compare the steady state waveforms and transient speed response of the PI and FLC. Torque ripple in modified converter is 50% less than the classical converter. Peak overshoot and settling time performance of FLC is superior as compared to PI, when applied to modified converter with EV loading.

Studying the Effect of Fireball Position in the Furnace on the Coal Fired Boiler’s Operation Mode

Studying the Effect of Fireball Position in the Furnace on the Coal Fired Boiler’s Operation Mode

Numerical simulation and experimental study on seafloor sampling of an anchor-type mud collector based on SPH-FEM coupling method

Marine sediments are important for research in scientific fields such as marine geology, environmental testing of waters, marine biology and seabed resource exploration. Among them, mud miner is an important way to obtain sediments. However, due to the complexity of the marine environment, the seabed sampling operation is a relatively difficult and complicated project. The structural design of the sampler, the operation mode, and the interaction between the sampler and the sediment affect the sampling effect, which leads to the low efficiency of the sampler operation. In order to investigate the main factors affecting the drag force of the sampler during seafloor sampling, this paper takes a simple and portable anchor-type mud collector surface sediment sampler as a study. This paper introduces the mechanical structure and working principle of an anchor-type mud collector, establishes a mechanical model of the mud collector seafloor sampling process and derives the main factors affecting the dragging force: internal friction angle; the horizontal angle of the bi-directional shaft rod; undercut angle [Formula: see text] of bottom cover and dragging speed. A FEM-SPH method based on the coupling of the finite element method (FEM) and the smooth particle hydrodynamics method (SPH) was proposed to simulate the dynamic process of mud collector subsea sampling, and the mechanical data of fine sand and clay were obtained through land-based experiments. Based on the comparison between experimental data and numerical simulation data, the simulation validity of the FEM-SPH method was verified. The results show that the drag force of the clay was greater than that of the fine sand in the experiment of cutting the lower cover of the mud collector into the fine sand and clay, the internal friction angle of the clay is greater than that of the fine sand; with the increase in horizontal inclination angle and the decrease in undercut angle, the dragging force gradually increased; The dragging speed ranged from 0.2 to 0.6 m/s, with an increase in the mass of clay and fine sand collected with increasing speed, resulting in a gradual increase in dragging force. This paper provides a new method to study the force of the mud collector, provides a theoretical method to reduce the intensity and difficulty of manual work in the sampling process and increase the efficiency of sampling.

Monolithically integrated multimode interference coupler-based master oscillator power amplifier with dual-wavelength emission around 830 nm

A monolithically integrated dual-wavelength multimode interference coupler-based master oscillator power amplifier is presented. It consists of two shallowly etched, laterally separated ridge waveguide laser cavities as master oscillators with individual distributed Bragg reflector gratings as cavity mirrors. A deeply etched coupling section containing S-bend shaped waveguides and a multimode interference coupler is used to couple the laser emission of the master oscillators into a shallowly etched single waveguide serving as power amplifier. Changing the etch depth for the coupling section enables a compact device layout. In addition, increased radiation angles of modes not coupled into the power amplifier help to suppress beam steering, otherwise indicated by laterally separated far-field intensity distributions. The device provides 0.5 W of dual-wavelength emission around 830 nm in individual and common operation. As designed, both emission wavelengths are separated by 0.5 nm with spectral widths below 20 pm, limited by the spectral resolution of the spectrometer. Both peak wavelengths remain within spectral windows of 50 pm within the available power range. This enables full flexibility selecting operating points for applications such as shifted excitation Raman difference spectroscopy and the generation of THz emission by photomixing. The emission wavelengths can additionally be non-continuously tuned by applying a heater current to resistors implemented next to the distributed Bragg reflector gratings. As an example, selected spectral distances of 0.5 nm, 1.0 nm, 1.5 nm, and 2.0 nm are demonstrated. Near field widths of 5 μm and far field angles of 17° result in beam propagation ratios of 1.4 (1/e2) in all operation modes and enable easy beam shaping or optical single-mode fiber coupling.

Analysis, design, and reliability evaluation of a modified multi‐port quasi‐resonant converter with high gain

AbstractHigh‐gain converters play a vital role in all industrial applications such as automobiles, motor drives, renewable energy systems, and railway transportation sectors. The conventional converters have low gain owing to high‐voltage stress on active MOSFET, diode and low efficiency related with high operating pulse ratio. To overcome the limitations associated with the conventional converters, this study proposes a non‐isolated configuration of multiport quasi‐resonant converter (MP‐QRC) with high gain. The proposed MP‐QRC has the merits of high‐voltage gain, reduced number of components, minimum conduction losses, realization of soft switching in the devices and improved reliability. Moreover, the proposed converter is scalable and can serve as a good candidate in microgrid environment where the integration of more than one input is essential. In this paper, first a comprehensive analysis of various operation modes and design constraints are presented. Further, the study is supported with a reliability evaluation of proposed converter based on component failure. Also, the futuristic behaviour of MP‐QRC under continuous conduction mode as a function of operational and environmental variables is investigated to ascertain the reliability. The steady‐state operation of the converter is demonstrated for off‐board electric vehilce (EV) charging using MATLAB/SIMULINK and experiments performed on a 300‐W test rig.

A Review on Cooling Methods of Lithium-Ion Battery Pack for Electric Vehicles Applications

The thermal concerns, such as capacity loss, uneven temperature distribution and thermal runaway of the battery packs made of lithium-ion batteries (LIB) used in electric vehicles (EV), limits its applicability, especially in situations of high-power demand. This article analyses the causes of heat generation in lithium-ion battery packs, focusing on their dominance over total heat generation. It discusses the thermal issues arising from heat generation, their root causes, and influencing parameters. Further, it examines the effect of cooling systems on peak battery temperature and temperature uniformity, as well as their design, operating, and performance parameters. The review suggests that, when designing a cooling system, entropic heating should be considered alongside Joule heating during low discharge rates and high temperatures, which are the conditions that prevail when an EV cruises on highways in hot weather. Capacity fade of battery is caused by temperature-dependent factors such as the growth of the SEI layer, rise in separator resistance, and active material loss. Hence an effective battery cooling system should maintain a temperature range of 15°C to 35°C and ‘ΔTmax’ below 6°C. Out of the reviewed cooling systems, air cooling is found to be simple and cost effective, but inefficient for large battery packs. PCM based cooling technique offers greater temperature uniformity but is sensitive to melting point. Liquid cooling is most efficient but adds cost and complexity. Evaporative cooling can serve as a middle ground between air and liquid cooling with further research to put it into practice. The future research in battery thermal management may focus lowering the energy consumption of the cooling systems by taking into account, the precise cooling needs as per the modes of battery operation.

Research of static and dynamic characteristics of a process system ‘electric drive-fluid-handling machine-pipeline’

<p>The paper offers the obtained quantitative assessment of the performance and energy parameters of a process system composed of an asynchronous motor, a fluid-handling machine and a pipeline when using two methods of performance control, in particular, throttling and speed control methods. Taking into account nonlinearity of mathematical representation of fluid-handling machines and asynchronous drive motors, the starting conditions were analysed using nonlinear differential calculus. The calculations for the models were performed using the MATLAB software package. Transient profiles of flow and head, stator current, angular frequency and torque of an asynchronous motor were obtained at pump startup and control of pump capacity. It has been found that the developed mathematical model of a process system composed of an asynchronous motor, a fluid-handling machine and a pipeline allows obtaining quantitative estimation of the performance and energy parameters of the unit when using two methods of the pump capacity control. The use of frequency method allows to decrease the pump rotation speed and significantly reduce the power consumed by the unit and provide energy-saving mode of operation, the economic efficiency of which depends on the range of feed control.</p>

Three-Level DC-DC Boost Converter for Wind Energy Conversion

In recent years, advancements in power converter technology for wind energy conversion systems have aimed to enhance power output, increase reliability, and improve overall efficiency. However, achieving a fixed and high-power DC output remains a challenge. This study explores three modes of operation for a DC-DC boost converter to enhance fixed DC output, essential for various applications like battery charging and electronics. The research categorizes DC system topologies based on factors such as setup complexity, cost-effectiveness, and performance metrics. It proposes a DC/DC conversion approach that offers cost-effectiveness and efficiency, aiming to set a new standard in topology for future converters. The study addresses key challenges in the efficiency of the step-up process of DC/DC converters, focusing on parameter design, operational principles, and control strategies. Simulation results confirm the effectiveness of the suggested approach, emphasizing its future potential for non-isolated high step-up DC/DC converters. Reduced device voltage stress and increased efficiency represent the two advantages of the suggested three-level DC-DC boost converter, which combines a standard boost converter with a switched capacitor function to supply three capacitors in series. Simulation results demonstrate the converter’s effectiveness in a wind energy conversion system, showcasing its potential for high-power applications.

АНАЛІЗ РЕЗУЛЬТАТІВ ЕКСПЕРИМЕНТАЛЬНИХ ДОСЛІДЖЕНЬ НЕОДНОРІДНОСТІ МЕРЕЖІ ПОСТІЙНОГО СТРУМУ

The modes of breakage of one line of network sections with parallel lines in electrical distribution networks of power supply to consumers of direct current electric transport have been studied. An analysis of the experimental data was carried out, the results of which indicate the presence of a dependence of the value of the variable component in the rectified current on the distance to the damaged area. Mathematical modeling of the breakage mode of one of the line sections in the network with a serial connection of three sections, each of which has parallel lines, has been carried out. The obtained results of mathematical modeling of the modes of operation of a direct current network with heterogeneity of different sections also indicate the possibility of using the sixth harmonic of the current to determine the occurrence of heterogeneity and the section with this heterogeneity. To reduce the influence of load changes when determining an inhomogeneous section, it is proposed to control the input impedance of the network at a frequency of 300 Hz. It has been established that in these regimes the resistance angle changes the most. A method for determining the occurrence of local damage to a direct current line and the distance to this damage location is proposed, which is based on moni-toring the value of the line current and the input resistance of the line at a frequency of 300 Hz. References 7, Figures 4, Tables 2.

Recovering Differential Forces From the GRACE‐D Accelerometer

AbstractThe reduction of non‐gravitational accelerations through an onboard accelerometer is a vital part of accurately estimating gravity fields for Gravity Recovery and Climate Experiment (GRACE) Follow‐On (GRACE‐FO). Current accelerometer quality, specifically a defect on the GRACE‐D accelerometer, necessitates the use of extensive calibration techniques to optimally utilize the accelerometer measurements. This paper describes these techniques and correction algorithms as they are used for the official GRACE‐FO accelerometer products, which rest on the information present in the partially functional GRACE‐D accelerometer. First, transplanted data from GRACE‐C is used to remove common effects between the spacecraft. Then, GRACE‐D data is utilized to compute a correction to the transplanted data to account for solar radiation pressure (SRP) and albedo using a parity argument and to account for non‐common drag and thruster leaks in the attitude control system. The SRP and albedo term predominantly improves C3,0 while the drag and leaky thruster term improves the gravity field across the entire spectrum. Finally, some comments on alternative data usage, initial modifications to the algorithms to account for other spacecraft operational modes, and future outlook are provided.

Development of Biomechanical Response Curves for the Calibration of Biofidelic Measuring Devices Used in Robot Collision Testing.

Collaborative robots (cobots) can be employed in close proximity to human workers without safety fences. The operation mode Power and Force Limiting requires that cobots not exceed the biomechanical limits of ISO/TS 15066 to ensure protection against injuries caused by collisions with them. Collision tests must be performed to prove that cobots cannot exceed the biomechanical limits. Such tests are performed with a biofidelic measuring device that measures contact forces and replicates the biomechanics of the human body. Biomechanical response curves serve as a reference for the calibration of such devices. In order to be able to compare measurements and limits correctly and reliably, the limits and response curves for calibration must be obtained from the same data with the same methodology. In this article, we present a new technique for developing biomechanical response curves, which employs a statistical model we used to calculate biomechanical limits for cobots in a previous study. This technique's development process entails normalizing the data over force, resampling them and then fitting the newly obtained samples to a log-normal distribution. The statistical model makes it possible to produce response curves for the same quantile we used for the limits. Our technique adds a confidence region around each response curve to express the sufficiency of the available data. We have produced response curves for 24 different body locations for which we have calculated limits. These curves will enable manufacturers of cobot testing equipment to calibrate their measuring devices precisely.

Research on the spatial effect of digital economy development on urban carbon reduction

Cities are one of the main sources of regional carbon emissions, and reducing urban carbon emission is the key to reducing emissions. The digital economy has transformed the economic operation mode, and it is a significant approach to support the “dual carbon goals” (carbon peaking and carbon neutrality). This article considers the externalities of the digital economy and carbon emissions. And we use spatial econometric models to analyze the effectiveness of digital economy in empowering carbon emissions reduction. Besides, we explore the static and dynamic spillover effects, and use spatial Durbin panel quantile model to analyze the digital economy’s heterogeneity on carbon emissions. Research has shown that the digital economy has a remarkable carbon reduction effect, and the conclusion remains valid after considering robustness tests such as replacing the weight matrices, calculation methods, and proxy variables. The analysis of static and dynamic spillover effects indicates that the degree of the digital economy’s impact on carbon emissions are significantly different. Heterogeneity analysis shows that as the digital economy develops from a low level to a high level, its impact on carbon emissions also shifts from positive promotion to negative suppression. This paper proposes a policy reference to help the development of digital economy and promote carbon neutrality in the face of severe environmental challenges.

ДИНАМІЧНА МОДЕЛЬ РЕЗОНАНСНОГО ПЕРЕТВОРЮВАЧА ДЛЯ ВПЛИВУ ЗІ СТОРОНИ ЖИВЛЕННЯ

In the paper, a discrete dynamic model of a full-bridge resonant converter with a symmetrical operating mode has been obtained, which describes the resonant converter as a transfer link with an supply voltage input side and a load current output side. The dynamic model is based on a linear mathematical model of the resonant converter built according to the superposition principle. The structure of the resonant converter with the processes outline function is given and analyzed. The structure of the discrete dynamic model of the resonant converter of the nth order is presented. It is proved that the transfer function of the discrete dynamic model for the outline function can be determined by the transfer function of the continuous system. The resulting dependencies describing the discrete transfer functions of the resonant converter are used to obtain the discrete dynamic model of the double-circuit transformer resonant converter in a synchronous rectifier. For this, the sequence of actions is defined: definition of the transfer function of the continuous dynamic model; obtaining the system of equations in vector-matrix form describing electromagnetic processes in the converter; definition of the system of discrete equations; definition of the transfer function of the circuit. The obtained theoretical results were verified by means of simulation modeling of the considered double-circuit resonant converter. The proposed dynamic model makes it possible to analyze the influence of instability and low-frequency fluctuations of the supply voltage of the resonant converter on the output values. The presented results can be used in the development and improvement of single- or multi-circuit bridge high-frequency resonant converters as the secondary power sources and converters used in ship demagnetization systems. References 25, figures 8, tables 2.

Selection of Asynchronized Turbogenerators Parameters Taking into Account the Operating Mode

The purpose of the work is to develop an algorithm for calculating currents in the asynchro-nized turbogenerator rotor windings when it operates at a power system with a variable load. Typically, synchronous turbogenerators of thermal power plants are used to maintain the balance of active and reactive power in the power system. But they cannot fully ensure the maintenance of balance by switch-ing to non-nominal modes: during periods of power consumption dips, reduce power to 50-70% and switch to under-excitation mode to compensate for reactive power. Therefore, it is promising to install asynchronized turbogenerators at power plants in parallel with synchronous turbogenerators, which re-main stable over a wide range of changes in active and reactive power. The work analyzed data from the operation of asynchronous turbogenerators in different countries. The subject of the study was an ASTG-200-2U3 asynchronized turbogenerator with two identical field windings. The goal of the work was achieved by calculating the field windings currents using the finite element method and modeling in the FEMM program when the load magnitude and nature changes. The most important results of the work are the proposed algorithm for calculating the asynchronized turbogenerators field currents de-pending on the load size and nature in order to maintain the frequency and voltage nominal values. The significance of the results obtained lies in the fact that practical recommendations have been obtained for choosing the asynchronized generator load angle depending on the load size and nature, including in the modes of consumption of reactive energy.

Impact of Dual-Gate Configuration on the Endurance of Ferroelectric Thin-Film Transistors With Nanosheet Polycrystalline-Silicon Channel Film

This work explores the characteristics of ferroelectric thin-film transistors (FeTFTs) utilizing an asymmetric dual-gate (DG) structure in both single-gate (SG) and DG operation modes. In the transfer characteristics, DG mode exhibits a memory window (MW) of 1.075 V, smaller than SG mode’s MW of 1.402 V, attributed to the back-gate bias effect causing a reduction in the device’s threshold voltage. However, DG mode demonstrates superior endurance characteristics with 106 cycles compared to SG mode’s 105 cycles. Additionally, the increase in erase pulse voltage (VERS) exacerbates the polycrystalline-silicon channel lattice damage of FeTFT, resulting in subthreshold swing (SS) degradation. Nevertheless, the extent of SS degradation from DG mode operation is significantly lower than that of SG mode, contributing to the superior endurance of DG mode. The elevation of program pulse voltage (VPRG) induces imprint and charge-trapping effects in the top-gate ferroelectric dielectric, leading to reduced endurance. Due to the use of SiO2 as the back-gate dielectric in FeTFT, DG mode exhibits lower impacts of charge-trapping effects from the top-gate ferroelectric dielectric layer, resulting in better endurance compared to SG mode. The asymmetric DG structure provides greater tolerance in the selection of VPRG and VERS.

Research on optimal power flow of AC/DC hybrid system for civil more electric aircraft

Modern civil more electric aircraft often use AC/DC systems instead of AC systems to reduce the weight of the power system. Compared with the AC/DC system of the land power grid, the aircraft power system needs to pursue economic operation mode under more complex security constraints. This paper establishes the optimal power flow model of the AC/DC hybrid system of more electric aircraft, which takes minimizing the active power loss of the line as the optimization objective, including the steady-state operation constraints and security constraints of the AC/DC system. The interior point method and prediction correction interior point method are used to solve the model. Then, based on the simplified steady-state model of the B787 power system, the model and algorithm are verified by experiments. The experimental results show that by optimizing the power flow distribution of the power system, the power utilization efficiency of the system has been significantly improved, and its stability and reliability can also be better guaranteed.

Prediction of power generation output of compressed air energy storage tank based on temperature limitation

The pressure and temperature of the CAES system drop during the power generation process. This generation will be forced to stop when the temperature reaches the metal material limit. To avert the power generation process from stopping due to the temperature dropping too low, it is necessary to monitor and predict the power output of the CAES system in real time. By setting the relevant control operation logic, according to the temperature limit value of the gas canister, the minimum allowable temperature of the gas canister design, and the maximum value of the minimum allowable temperature of the pipe design between the gas canister and the heat exchanger, the minimum allowable temperature of the gas canister is obtained. the residual energy release energy and residual energy release time of the gas storage tank can be calculated by collecting relevant parameters in real time. It is verified by the simulation experiment of the 10 MW CAES system model. By monitoring the changes in parameters such as the temperature of the gas canister during the energy release process, the prediction model can calculate the compressed gas in the gas canister more accurately, and the power generation output can be predicted in the operation of the CASE system. Mastering the residual energy release energy and residual energy release time of the gas canister can arrange the operation mode in advance and improve the reliability of unit operation.

A Low-Noise Low-Power 0.001Hz-1kHz Neural Recording System-on-Chip With Sample-Level Duty-Cycling.

Advances in brain-machine interfaces and wearable biomedical sensors for healthcare and human-computer interactions call for precision electrophysiology to resolve a variety of biopotential signals across the body that cover a wide range of frequencies, from the mHz-range electrogastrogram (EGG) to the kHz-range electroneurogram (ENG). Existing integrated wearable solutions for minimally invasive biopotential recordings are limited in detection range and accuracy due to trade-offs in bandwidth, noise, input impedance, and power consumption. This article presents a 16-channel wide-band ultra-low-noise neural recording system-on-chip (SoC) fabricated in 65nm CMOS for chronic use in mobile healthcare settings that spans a bandwidth of 0.001 Hz to 1 kHz through a featured sample-level duty-cycling (SLDC) mode. Each recording channel is implemented by a delta-sigma analog-to-digital converter (ADC) achieving 1.0 μ V rms input-referred noise over 1Hz-1kHz bandwidth with a Noise Efficiency Factor (NEF) of 2.93 in continuous operation mode. In SLDC mode, the power supply is duty-cycled while maintaining consistently low input-referred noise levels at ultra-low frequencies (1.1 μV rms over 0.001Hz-1Hz) and 435 M Ω input impedance. The functionalities of the proposed SoC are validated with two human electrophysiology applications: recording low-amplitude electroencephalogram (EEG) through electrodes fixated on the forehead to monitor brain waves, and ultra-slow-wave electrogastrogram (EGG) through electrodes fixated on the abdomen to monitor digestion.

Feasibility Study of Three-Phase Modular Converter for Dual-Purpose Application in DC and AC Microgrids

The modern concept of a universal converter is intended as a power converter suitable for application in both dc or ac grids using the same external connectors. This novel family was recently proposed to allow an easier integration of renewable energy sources and energy storage systems, interfacing with dc/ac grids and/or loads with a minimum redundancy of power switches and passive elements. This kind of solution and applications are expected to be a reality in the nearest decade, as ac and dc low voltage distribution networks will coexist. Nevertheless, the initial solutions proposed as universal converter were focused on ac single-phase power conversion systems. In this sense, this article proposes and describes a new member of the universal converter family suitable for dc to dc and dc to ac power conversion (both in three-phase three-wire and in three-phase four-wire). The proposed power topology is derived as a modular extension from the single buck-boost bidirectional cell. Its main operation modes (buck and boost) are discussed, and a pulse-width-modulation technique is developed to generate the corresponding switching patterns. The proposed solution is successfully validated in open-loop mode both in simulation and experimentally with a laboratory prototype. The measured efficiency of the power converter was above 97% in the dc to ac mode and around 99% in the dc to dc mode.