Balanced Mode Research Articles

Pneumatic Experimental Design for Strain Rate Sensitive Forming Limit Evaluation of 7075 Aluminum Alloy Sheets under Biaxial Stretching Modes at Elevated Temperature

A pneumatic experimental design to evaluate strain rate sensitive biaxial stretching forming limits for 7075 aluminum alloy sheets was attempted with the finite element method. It was composed of apparatus geometric design with pressure optimization as the process design. The 7075 aluminum alloy material was characterized by conventional Voce-type hardening law with power law strain rate sensitivity relationship. For optimization of the die shape design, the ratio of minor to major die radius (k) and profile radius (R) were parametrically studied. The final shape of die was determined by how the history of targeted deformation mode was well maintained and whether the fracture was induced at the pole (specimen center), thereby preventing unexpected failure at other locations. As a result, a circular die with k = 1.0 and an elliptic die with k = 0.25 were selected for the balanced biaxial mode and near plane strain mode, respectively. Lastly, the pressure inducing fracture at the targeted strain rate was studied as the process design. An analytical solution that had been previously studied to maintain constant strain rate was properly modified for the designed model. The results of the integrated design were compared with real experimental results. The shape and thickness distribution of numerical simulation showed good agreement with those of the experiment.

Charging equaliser based on wireless power transfer for electric scooters

It is more convenient and safer to employ wireless power transfer (WPT) systems to charge the battery pack of electric scooters (ESs) than conventional plug-in systems. A charging equaliser suitable for ESs is proposed to achieve constant current (CC) output without communication link between the transmitter side and the receiver side. The full-bridge rectifier and select switches utilised at the receiver side are employed to be operated once to change from the balancing mode to charging modes. The characteristics of the load-independent current output in the CC mode are achieved by properly selecting the parameters of the circuit so that no sophisticated control strategies are required to regulate the output as per the charging profile. The experimental results show that when the voltage of battery pack is charged at 32 or 4.2 V, the current is 1.02 or 1.12 A, respectively. Therefore, the proposed system can be considered as a CC system.

Sensor Selection With Cost Constraints for Dynamically Relevant Bases

We consider cost-constrained sparse sensor selection for full-state reconstruction, applying a well-known greedy algorithm to dynamical systems for which the usual singular value decomposition (SVD) basis may not be available or preferred. We apply the cost-modified, column-pivoted QR decomposition to a physically relevant basis—the pivots correspond to sensor locations, and these locations are penalized with a heterogeneous cost function. In considering different bases, we are able to account for the dynamics of the particular system, yielding sensor arrays that are nearly Pareto optimal in sensor cost and performance in the chosen basis. This flexibility extends our framework to include actuation and dynamic estimation, and to select sensors without training data. We provide three examples from the physical and engineering sciences and evaluate sensor selection in three dynamically relevant bases: truncated balanced modes for control systems, dynamic mode decomposition (DMD) modes, and a basis of analytic modes. We find that these bases all yield effective sensor arrays and reconstructions for their respective systems. When possible, we compare to results using an SVD basis and evaluate tradeoffs between methods.

Real-Time Mission-Motion Planner for Multi-UUVs Cooperative Work Using Tri-Level Programing

This article develops a novel mission-motion planner for unmanned underwater vehicles (UUVs) when dispatching them to visit a set of marine stations in a vast and time-varying environment. Specifically, a tri-level optimization model is built for the planner to finish the task with less energy cost. The lower-level is a motion planner, which provides safe and efficient paths with local environmental information. The middle-level is a mission planner, which designs a balanced station allocation mode as well as economical visitation sequences for each UUV concerning global information. The upper-level is a commander, which manages and synchronizes the two levels, so that UUVs can autonomously decide the next destination and corresponding paths in real-time. Thereafter, different heuristic algorithms are chosen according to each level property, and their initialization processes are modified to solve the optimization efficiently. Finally, the proposed model and algorithms present their outstanding performance in complex and large-scale cases.

Dual-wavelength Mach-Zehnder interferometry-assisted photothermal spectroscopy for characterization of surface contaminants.

Photothermal spectroscopy (PTS) working in the mid-infrared region is an effective technique for in-situ characterization of the chemical composition of surface contaminants. The sensitivity relies on the way that the laser-induced response of the sample is detected. We present a highly-sensitive PTS assisted with a dual-wavelength Mach-Zehnder interferometer (MZI), MZI-PST in short. The MZI aims to sense all the phase delays taking place at the sample and air when the heat produced by resonance absorption of the contaminant is transferred into its surroundings and further to amplify the total phase delay to a large intensity difference of a probe beam. To guarantee a stable quadrature phase bias of the MZI working in the balanced detection mode, we employ two separate wavelengths, one for sensing and the other for phase bias feedback, to lock the working point to the quadrature point in real time. The MZI is expected to have a 7.8-fold sensitivity enhancement compared with the conventional phase-sensitive PTS in theory. The results of the proof-of-concept experiment on the olive oil contaminated on a wafer surface verify the spectral fidelity and the sensitivity enhancement as well as the capability of photothermal spectral imaging of the MZI-PST.

Automotive Battery Equalizers Based on Joint Switched-Capacitor and Buck-Boost Converters

A series of integrated equalizers based on joint buck-boost (BB) and switched-capacitor (SC) converters are proposed for balancing the voltages of series-connected battery packs. All these equalizers realize the any-cells-to-any-cells (AC2AC) equalization mode without increasing the count of MOSFETs and drivers. Corresponding operational principles are analyzed and the expressions of balancing currents are derived by analytical methods and verified by experimental waveforms. According to the comparative balancing experiments for four and six series-connected Li-ion cells, one proposed CBB-PCSC equalizer, which achieves the dual AC2AC balancing modes through the integration of both coupled buck-boost (CBB) and parallel-connected switched-capacitor (PCSC) converters, leads to the highest balancing speed and efficiency. Moreover, compared with several conventional equalizers, this CBB-PCSC topology also has the compact size and low cost, making it become a well-performing integrated topology for automotive battery voltages equalization.

A Multilevel Mobile Fog Computing Offloading Model Based on UAV-Assisted and Heterogeneous Network

The mobile fog computing (MFC) network that integrates unmanned aerial vehicles (UAV) fully exerts its advantages of flexible deployment, load balance, and rapid response. Under complex network environment, proposing a reasonable offloading model and according resource optimization of the MFC network is important to satisfy high-requirement offloading standard. In this paper, a multilevel MFC offloading model where UAV and fog nod undertake relay nodes and offloading computing nodes are established for computation-intensive and latency-critical tasks, considering heterogeneous network selection , dynamic channel quality and central cloud access . With the total system utility optimality function including reward function maximization as the goal, the MDP algorithm is applied to solve the best offloading decision of the computing task and the balanced load mode of the MFC network. Finally, the simulation section verifies the excellent performance of the proposed multilevel MFC offloading model in network resource utilization. Simulation results show that the model can optimize the relative position of service nodes in MFC network and ensure the offloading reliability of terminal equipment.

S-Parameter Analysis for Balanced and Unbalanced Modes Corresponding Dissipated Power of a Small Antenna

In this paper, an analysis method for calculating balanced and unbalanced modes of a small antenna is summarized. Modal condactances which relate dissipated power of the antenna are directly obtained from standard S-parameters that we can measure by a 2-port network analyzer. We demonstrate the validity and effectiveness of the proposed method by simulation and measurement for a dipole antenna with unbalaned feed. The ratio of unbalanced-mode power to the total power (unbalanced-mode power ratio) calculated by the proposed method agrees precisely with that yielded by the conventional method using measured radiation patterns. Furthermore, we analyze a small loop antenna with unbalanced feed by the proposed method and show that the self-balancing characteristic appears when the loop is set in resonant state by loading capacitances or the whole length of the loop is less than 1/20th the wavelength.

Structure and morphology of CrSi<sub>2</sub> layers formed by rapid thermal treatment

The formation of chromium disilicide layers on n-type single crystal silicon substrates (111) during rapid thermal annealing in heat balance mode by the methods of Rutherford backscattering, X-ray diffraction and transmission electron microscopy of cross sections was investigated. Chromium films of about 30 nm thickness were deposited by magnetron sputtering of a chromium target with argon ions onto silicon substrates at room temperature. The rapid thermal treatment was carried out in a temperature range of 200 to 550 °C in a heat balance mode by irradiating the substrates backside with a non-coherent light flux of quartz halogen lamps in a nitrogen ambient for 7 s. It was established that hexagonal phase of chromium disilicide formation with grain size of 150–300 nm occurs in a threshold manner when the temperature of rapid thermal treatment exceeds 400 °C. At the same time, there are strong changes in the films surface morphology and surface roughness, and a silicide-silicon interface occur. In this case the wavy film surface morphology practically repeats silicide-silicon interface morphology (the surface exactly replicates the interface). The mechanism of CrSi2/Si interface structure roughness formation based on consideration of Kirkendall effect and deformation-stimulated diffusion of vacancies is proposed and discussed. The research results of the structure and morphology of CrSi2 layers on silicon are well-correlated with the results of the Schottky barrier electrophysical measurements. The results obtained can be used in microelectronics for forming rectifying contacts and interconnects metallization for integrated circuits, as well as for thermoelectric and optoelectronic applications.

Non-linear Mathematical Model of a Quad-Tiltrotor UAV Spatial Motion

The article presents a design scheme of a quad-tiltrotor unmanned aerial vehicle (UAV), which combines a safe vertical take-off and landing procedures and a relatively large flight range inherent in the aircraft. In order to reduce the cost and weight of the quad-tiltrotor UAV, to increase its reliability, a circuit with minimization of movable executive drives is considered. Namely, in the proposed structural scheme of the quad-tiltrotor UAV there are no deflectable airfoils. In addition, the rotors of all four engines are rotated by the same setting angle in the longitudinal plane using a single actuator. The research results showed that the quadtiltrotor UAV of the proposed scheme as a whole is statically controlled. All the necessary balancing forces and moments are formed independently of each other only by a coordinated change in engine speed and control of the overall setting angle of their thrust vectors. It is also shown that there is a so-called degenerate flight mode in which static controllability is not provided. Theoretically, this is reflected in the degeneracy of the linear equation system matrix for determining the balance values of engine thrusts. Physically, the specified mode corresponds to the case when the resulting thrust vector of the engines lies on a straight line passing through the centre of gravity of the aircraft, and therefore it cannot create a pitch moment. The paper proposes two ways to overcome this limitation. The constructive method offers a special arrangement of rotor bushings. The algorithmic method carries out a quick transition through a degenerate balancing mode using a control system.

Decentralized vibration control of smart constrained layer damping plate

The traditional centralized control strategy to vibration suppression of large-scale thin plate structures may increase the design difficulty of the controller. In this article, a decentralized vibration active control method is proposed to suppress the vibration of the thin plate structure with smart constrained layer damping treatment. First, the dynamics model of the smart constrained layer damping plate is established based on the finite element method, and the characteristics of viscoelastic materials with temperature and frequency are described by Golla-Hughes-McTavish damping model. Subsequently, a decentralized subsystem control model is obtained from the balanced model reduction method and complex mode truncation method. The modal test proves that the theoretical model is accurate. Then, the particular emphasis is placed on the stability and vibration attenuation of a decentralized system, which is composed of multiple subsystems. The local state feedback stabilization, using interaction of local state feedback and output feedback, is introduced to achieve system stability. To solve the practical problem of local state feedback, a decentralized controller with an observer is developed by adopting the pole placement method. Finally, the numerical simulation and hardware-in-the-loop experiment under different excitation are performed to investigate the effectiveness of decentralized vibration active control. The results demonstrate that the decentralized controller can effectively suppress the vibration, especially under mixed periodic signal and Gauss white noise signal.

Potential Vorticity and Balanced and Unbalanced Moisture

Abstract Atmospheric flows are often decomposed into balanced (low frequency) and unbalanced (high frequency) components. For a dry atmosphere, it is known that a single mode, the potential vorticity (PV), is enough to describe the balanced flow and determine its evolution. For a moist atmosphere with phase changes, on the other hand, balanced–unbalanced decompositions involve additional complexity. In this paper, we illustrate that additional balanced modes, beyond PV, arise from the moisture. To support and motivate the discussion, we consider balanced–unbalanced decompositions arising from a simplified Boussinesq numerical simulation and a hemispheric-sized channel simulation using the Weather Research and Forecasting (WRF) Model. One important role of the balanced moist modes is in the inversion principle that is used to recover the moist balanced flow: rather than traditional PV inversion that involves only the PV variable, it is PV-and-M inversion that is needed, involving M variables that describe the moist balanced modes. In examples of PV-and-M inversion, we show that one can decompose all significant atmospheric variables, including total water or water vapor, into balanced (vortical mode) and unbalanced (inertio-gravity wave) components. The moist inversion, thus, extends the traditional dry PV inversion to allow for moisture and phase changes. In addition, we illustrate that the moist balanced modes are essentially conserved quantities of the flow, and they act qualitatively as additional PV-like modes of the system that track balanced moisture.

Balanced-to-Doherty Mode-Reconfigurable Power Amplifier With High Efficiency and Linearity Against Load Mismatch

A balanced-to-Doherty (B2D) mode-reconfigurable power amplifier (PA) is presented in this article, which is endowed with a unique capability of maintaining high linearity and high efficiency against load mismatch. The Doherty operation of this PA is based on a new Doherty PA (DPA) architecture configured from an ideal balanced amplifier, named quasi-balanced DPA (QB-DPA). This article, for the first time, analytically proves that the QB-DPA is functionally equivalent to a standard DPA. Most importantly, this new discovery enables PA reconfiguration between the Doherty and balanced modes. With the tunability implemented using a silicon-on-insulator (SOI)-based single-poledouble-throw (SPDT) switch, a reconfigurable B2D PA prototype using GaN technology is demonstrated at 3.5 GHz, exhibiting the state-of-the-art linear DPA performance in the nominal 50-Ω load condition. Specifically, the Doherty mode achieves a continuous-wave measurement efficiency of 70% and 54.5% at the maximum output power of 41.9 dBm and 6-dB power backoff, respectively. In the modulated long-term evolution (LTE) evaluation, the DPA exhibits -37-dB adjacent channel power leakage (ACPR) and 2.36% error vector magnitude (EVM) at the maximum rated power of 34.5 dBm while achieving a 42.4% efficiency. It is experimentally demonstrated that the Doherty (QB-DPA) mode is well resistant to load mismatch with high efficiency across a majority portion of the 2:1 voltage standing wave ratio (VSWR) circle, while the combination of Doherty and balanced modes can ensure a constantly linear performance of the B2D PA (e.g., 2.2%-5% of EVM) under the entire mismatch condition.

Design and Realization of a Low Cross-Polarization Conical Horn With Thin Metasurface Walls

A Ku -band low cross-polarization conical horn based on thin metasurface (MTS) walls is presented in this article, along with the relevant design method. The necessary boundary conditions are realized by printing a tensor MTS on the internal walls of the horn, which yields a radiation performance similar to a standard corrugated Gaussian horn yet with the benefits of thin walls. The design method is based on the adiabatic approximate solution for the hybrid mode of a conical waveguide with generic balanced impedance walls, which allows the determination of the impedance profile supporting a single balanced mode. The impedance design is based on the usual locally flat approximation of the wall and on the assumption of plane wave incidence. This approach results in an analytic design method that requires no optimization. The design has been first validated by solving the problem with homogenized impedance boundary conditions through a body of revolution (BoR) method of moments. The actual structure, including impedance wall implementation, is then simulated in full detail with a full-wave fast code. Finally, the horn has been realized and experimentally characterized; measurements show excellent agreement both with theory and with simulations, with a cross-polarization level below −20 dB over a 2 GHz bandwidth.

INFLUENCE OF TIME MODES OF THERMAL TREATMENT ON Pt-Si SYSTEM MICROSTRUCTURE

The paper is purposed to establish the principles of the micro-structural changes of Pt-Si system during the rapid thermal treatment. The Pt films 43.7 nm thick were applied on the substrates of mono-crystal silicon KEF 0.5 with orientation (111) by means of the magnetron platinum target sputtering (purity of 99.95 %) on the unit MPC 603 with the cryogen pumping to the pressure of no less than 5∙10-5 Pa. Argon was used as a working medium, whose purity constituted 99.933 %. Rapid thermal treatment was performed in the mode of the thermal balance with irradiation of the reverse side of the wafer by means of the non-coherent light flow in the nitrogen medium within the temperature range from 200 to 550 °C with a step of 50 °С during 7 s. In parallel, the solid phase synthesis was performed of platinum silicide by means of the standard method with application of the continuous single stage thermal treatment in the analogue medium (T = 550 °C, t = 30 min). Temperature monitoring was performed by means of the thermal couple method with accuracy of ±0.5 °C. The grain size was determined by the translucent electron microscopy method. Thickness of platinum silicide under formation, its surface micro-relief and the separation boundaries with silicon were determined by means of the raster electron microscopy. It is demonstrated, that with the rise of the rapid thermal treatment one can observe growth of the platinum film on silicon. A comparative analysis was conducted of the average size of grains, micro-relief of the PtSi surface and its separation boundary with silicon for two methods of its formation with application of the rapid thermal treatment and with application of the traditional continuous thermal treatment at the temperature of 550 °C during 30 min in the nitrogen atmosphere. By means of the raster electron microscopy method it is demonstrated, that size of the micro-relief on the separation boundary of PtSi-Si does not exceed 15.9 nm and the size of grains is 37.7 nm. This is in 2.5 and 3.1 times smaller, then in the case of the traditional single stage continuous thermal treatment.

Improved historical simulation by enhancing moist physical parameterizations in the climate system model NESM3.0

The third version of the Nanjing University of Information Science and Technology (NUIST) Earth System Model (NESM3.0) has been recently developed for sub-seasonal to seasonal climate prediction and projection of future climate change. This requires realistic simulation of both internal modes of climate variability and global energy balance and climate sensitivity. In the historical experiments based on the coupled model intercomparison project (CMIP6) forcings, the original version of NESM3.0 does a reasonably good job in capturing warming trends and climate sensitivity to external forcing, but not in simulating climatology and climate variability. For our project we modified the deep and shallow convective scheme, cloud cover, and cloud microphysics in the atmospheric model. We then conducted hundreds of experiments to test the results in the fully coupled model with comprehensive metrics to ensure that any individual targeted improvement does not affect the overall performance. The modifications in moist physics improved the model’s climatology and internal variability significantly without degrading global energy balance and climate sensitivity. The key was to reduce the model’s warm sea surface temperature (SST) bias and associated excessive precipitation bias in the tropics by reducing convective precipitation and increasing large-scale stable precipitation. This effort leads to more realistic simulation of the zonal mean circulation and temperature structure, global monsoon, and ocean salinity. The El Nino Southern Oscillation (ENSO) simulation was improved by reducing wind stress biases associated with ENSO in the central and eastern Pacific. Better ENSO leads to better teleconnection in mid-latitudes, particularly over the North Pacific and Atlantic Ocean. The eastward propagation of the Madden–Julian Oscillation (MJO) was significantly improved by enhancing the interaction between the boundary layer and lower tropospheric heating. These results suggest that improvement in moist physical parameterizations is an effective way to improve simulation of climatology and major modes of internal variability without degrading the global energy balance and climate sensitivity in the historical run.

EFFECT OF RAPID THERMAL TREATMENT ТЕMPERATURE ON ELECTROPHYSICAL PROPERTIES OF NICKEL FILMS ON SILICON

Present work is devoted to determination the regularity of change of specific resistance and Schottky barrier height of nickel films on n-type silicon (111) at their rapid thermal treatment in the temperatures range from 200 to 550 °C. Nickel films of about 60 nm thickness were deposited by magnetron sputtering onto the silicon substrates having a resistivity of 0.58 to 0.53 Ohms×cm. The rapid thermal treatment was carried out in the range of 200 to 550 °C under heat balance mode by irradiating the backside of the substrates with non-coherent light flux in nitrogen ambient for 7 seconds. The thickness of the nickel films was determined by scanning electron microscopy. The sheet resistance of the samples was measured by a four-probe method. The Schottky barrier height was determined from I-V plots. It is shown that at a temperatureы of rapid thermal treatment of Ni/n-Si (111) 200–250 °C nickel will be transformed to Ni2Si, increasing in thickness by 1.15–1.33 times, specific resistance increases to 26–30 μOhm×cm, and Schottky barrier height decreases from 0.66 to 0.6 V. At a rapid thermal treatment temperature of 300°C the initial nickel film thickness increases by 1.93 times, the resistivity and Schottky barrier height decrease to 26–30 μOhm×cm and 0.59 V respectively due to the conversion of the Ni2Si into NiSi and the fixation of the barrier height by surface states at the silicidesilicon interface. Rapid thermal treatment of 350–550 °C transforms the original nickel film into NiSi, increases its thickness by 2.26–2.67 times, reduces its resistivity to 15–18 μOhm×cm and increases the Schottky barrier height to 0.62–0.64 V. The minimum defects and better reproducibility of electrophysical properties are characterized by NiSi films formed by rapid thermal treatment of nickel films on n-type silicon at a temperature of 400–450 °C. The results obtained can be used in the technology of integrated electronics products containing rectifying contacts.

Current and power quality multi-objective control of virtual synchronous generators under unbalanced grid conditions

In recent years, with the large-scale application of distributed power sources in the power grid, the power grid is moving toward low inertia and low damping. The virtual synchronous generator (VSG) has become a hot topic for scholars since it can simulate the moment of inertia, damping and frequency modulation of synchronous generators. Due to its unbalanced load distribution and the random variation of power loads, grid voltage is asymmetrical. Under grid voltage asymmetry, a VSG experiences output current imbalance and power oscillation. The grid current imbalance further reduces the transformer’s three-phase voltage, which makes it unequal, cyclic, and very easy to cause electricity accidents. Aiming at this problem, this paper proposes three modes of current balance, reactive power balance and active power balance without changing the characteristics of VSGs. The output current balance and power are constant when the grid voltage is asymmetrical. The effectiveness and feasibility of the control strategy are verified by simulation and experimental results, which provides an effective scheme for balanced and stable operation of the grid.

A Digital Closed-Loop Sense MEMS Disk Resonator Gyroscope Circuit Design Based on Integrated Analog Front-end.

A digital closed-loop system design of a microelectromechanical systems (MEMS) disk resonator gyroscope (DRG) is proposed in this paper. Vibration models with non-ideal factors are provided based on the structure characteristics and operation mode of the sensing element. The DRG operates in force balance mode with four control loops. A closed self-excited loop realizes stable vibration amplitude on the basis of peak detection technology and phase control loop. Force-to-rebalance technology is employed for the closed sense loop. A high-frequency carrier loaded on an anchor weakens the effect of parasitic capacitances coupling. The signal detected by the charge amplifier is demodulated and converted into a digital output for subsequent processing. Considering compatibility with digital circuits and output precision demands, a low passband sigma-delta (ΣΔ) analog-to-digital converter (ADC) is implemented with a 111.8dB signal-to-noise ratio (SNR). The analog front-end and digital closed self-excited loop is manufactured with a standard 0.35 µm complementary metal-oxide-semiconductor (CMOS) technology. The experimental results show a bias instability of 2.1 °/h and a nonlinearity of 0.035% over the ± 400° full-scale range.

A Hybrid Optimization Technique Using Exchange Market and Genetic Algorithms

This paper proposes a hybrid optimization technique combining genetic and exchange market algorithms. These algorithms are two evolutionary algorithms that facilitate finding optimal solutions for different optimization problems. The genetic algorithm's high execution time decreases its efficiency. Because of the genetic algorithm's strength in surveying solution space, it can be combined with a proper exploitation-based algorithm to improve the optimization efficiency. The exchange market algorithm is an optimization algorithm that can effectively find the global optimum of the objective functions in an efficient manner. According to the trade's inherent situation, the stock market works under unbalanced and balanced modes. In order to gain maximum profit, shareholders take specific decisions based on the existing conditions. The exchange market algorithm has two searching and two absorbent operators for acquiring the best-simulated form of the stock market. Simulations on twelve benchmarks with the different dimensions and variables prove the effectiveness of this algorithm compared to eight optimization algorithms.