Order Modes Research Articles

Research on The Internal Control Framework of Large State-owned Enterprises Under Information-based Environment

In the information society and digital era, the information construction of the enterprise internal control framework is particularly important for enterprises to enhance their endogenous power and improve their management efficiency. In order to achieve increasingly powerful control functions and build an efficient overall enterprise internal control framework, we must rely on scientific and precise control means and efficient operation mechanisms. Under such circumstances, large state-owned enterprises should absorb and apply more advanced management concepts and actively innovate and optimize their management mode in order to improve their management level and enhance their comprehensive competitiveness and thus achieve long-term development in the fierce market competition. An important way for large state-owned enterprises to strengthen their management is to build an internal control system. The internal control system can regulate the operation of power, strengthen risk prevention and supervision of internal personnel and be a stimulus to large enterprises to reduce operating costs and increase economic efficiency.

Improvement of the pressure dynamics model in the mask for a powered air purifying respirator as an object of control

Purpose. Justification of the need to improve the simulated model of the powered air-purifying respirator, substantiating the need for planning and conducting additional experiments. Determination of parameters and confirmation of the adequacy of the simulation model to the object of control – a powered air-purifying respirator. Methodology. The research was carried out on an experimental setup by means of an active experiment. To obtain a static characteristic, a sequential increase in the control effect – the speed of rotation of the fan in steps of 200 rpm was performed, and the actual value – pressure in the respirator mask – was recorded. Based on the experimental data, a statistical characteristic was constructed and the dependence of the model amplification factor on the control influence was determined. Verification of the obtained model for adequacy to the control object was performed according to Fisher's adequacy criterion. Findings. According to the results of the study, it was established that the static characteristic of the powered air-purifying respirator according to the channel "speed of rotation of the fan – pressure in the mask" is close to linear, and the amplification factor depends on the value of the control influence. Based on the analysis of the received data, the simulation model of the powered air-purifying respirator was improved. Originality. It was established that the static characteristic of the powered air-purifying respirator in the defined range of control influence is non-linear and the amplification factor depends on the speed of rotation of the fan blades. Practical value. The dependence of the amplification factor on the speed of rotation of the fan blades was determined. Adequacy of the improved simulation model to the control object is 92%. An improved simulation model of a powered air-purifying respirator allows you to perform a study of operating modes in order to determine the requirements for controlling the air supply process to the mask and further synthesis of the control system using various types of regulators.

Dynamic performance of ultra-long stay cable in small-scale extreme winds

The wind-induced vibration and its mitigation of ultra-long stay cables are critical to the safety of long-span bridges. Remarkable progress has been made in understanding and mitigating the vibration of stay cables in normal wind, while the cable response in small-scale extreme winds such as downbursts and tornadoes remains unclear. This study compares the dynamic performance of an ultra-long stay cable in a downburst and a tornado. Firstly, a downburst and its induced vibration of an ultra-long stay cable of a kilometer-level cable-stayed bridge are introduced based on the data recorded by the structural health monitoring system (SHMS). A tornado with the same intensity as the measured downburst is then simulated analytically at the bridge site. The tornado-induced vibration of the stay cable is obtained based on the finite element method. The dynamic performance of the cable under the downburst and the tornado, including the acceleration characteristics, displacement characteristics, and frequency characteristics, are investigated and compared. The result shows that large-amplitude cable vibration is found during the two extreme winds and the out-of-plane acceleration is larger than the in-plane acceleration. For the same wind intensity in this study, the acceleration of the cable caused by the downburst is much larger than that caused by the tornado. During the tornado, the in-plane displacement of the cable is much larger than the out-of-plane displacement, which is the opposite during the downburst. The frequency range of the cable vibration induced by the small-scale extreme winds is similar and it is about 2.5 ∼ 6 Hz, and the mode order is from the 10th to the 25th.

Method for acquisition of orthotropic material parameters and calculation of modal frequencies in permanent magnet synchronous motor

AbstractThis article presents a novel method for fastly obtaining orthotropic material parameters in permanent magnet synchronous motor. First, a theoretical model of the equivalent single cylindrical shell is introduced with three orthotropic material parameters by considering the orthotropic characteristics of the motor. Then, the relationship of three orthotropic material parameters and the axial mode order m, the radial mode order n and modal frequency f is established. On this basis, an analytical method with m = 0 is proposed to acquire three values, and its adaptability is pointed out. Meanwhile, based on the above obtained orthotropic material parameters, the calculation method of modal frequencies is presented. Finally, the modal test and finite‐element method are implemented to verify the rationality of the proposed method.

Optogeometric and waveguiding properties of multimode ZnO planar waveguide sprayed thin films

ZnO thin films with different thicknesses (T1=230.0, T2=450.0, T3=634.0, T4=926.9 and T5=1153.4nm) were deposited by spray pyrolysis on ordinary glass. All of the films had wurtzite crystal structure. The texture coefficient of the (002) plan decreased from 2.74 to 1.64 while that of the (103) increased from 0.65 to 1.23 over the thickness. Flaky shaped grains were observed in the SEM images with a tendency to get larger and hexagonal in shape. The surface evolution was verified by AFM microscopy. The ordinary and extraordinary refractive indices increased with thickness from 1.9344 and 1.9365 to 1.9768 and 1.9830 respectively. The mode order had a significant impact on the confinement of the electric field in the TE mode, therefore the power confinement factor increased by 16.58% with respect to thickness, reaching over 99% whilst it was reduced by 16.39% when the mode order increased from 0 to 4 in T5.

High-power femtosecond vortices generated from a Kerr-lens mode-locked solid-state Hermite-Gaussian oscillator.

We report the generation of high-order transverse modes from a Kerr-lens mode-locked femtosecond laser. Two different orders of Hermite-Gaussian modes were realized by non-collinear pumping, which were converted into the corresponding Laguerre-Gaussian vortex modes using a cylindrical lens mode converter. The mode-locked vortex beams, with an average power of 1.4 W and 0.8 W, contained pulses as short as 126 fs and 170 fs at the first and second Hermite-Gaussian mode orders, respectively. This work demonstrates the possibility of developing Kerr-lens mode-locked bulk lasers with various pure high-order modes and paves the way for generating ultrashort vortex beams.

Design and analysis of MEMS tuning fork gyroscope with dual mode ordering

AbstractThis paper reports a MEMS tuning fork gyroscope which can effectively reduce the acceleration output in both drive and sense directions. The structure adjusts the order of mechanical vibration modes through the design of internal and external lever coupling mechanism, moves the spurious in‐phase mode frequency above the antiphase operating frequency, and provides a large frequency separation between the two modes. It provides true mechanical rejection of external shocks and accelerations. Two comparative tuning fork gyroscopes (TFG) structures are designed, which have traditional coupling in the drive direction and sense direction respectively. Through modal simulation, the internal lever‐coupling brings the antiphase drive mode before the in‐phase drive mode and the external lever‐coupling brings the antiphase sense mode before the in‐phase sense mode. The harmonic response simulation of three stiffness unbalanced TFGs verifies that the mode ordering of two directions can effectively suppress the acceleration output. The results show that the new TFG structure can suppress the acceleration output by more than 80%, and the finite element simulation results are consistent with the theoretical calculation.

Research on Electromagnetic Vibration Characteristics of a Permanent Magnet Synchronous Motor Based on Multi-Physical Field Coupling

Background and Purpose: The stator vibration characteristics are comprehensively mastered by considering the influence of winding and the housing structure on the stator modes. This effect is neglected in the research field of electromagnetic vibration of permanent magnet synchronous motors (PMSMs). Methods: The radial air-gap flux density equations and PMSM’s electromagnetic force density are derived, and then the harmonic characteristics of electromagnetic force density are studied. An equivalent finite element model of the stator is proposed that investigates the impacts of the winding and stator housing rules on the stator modal frequency. Finally, the harmonic response and acoustic analyses of electromagnetic vibration are carried out based on multi-physics field coupling. Results: The equivalent radiated power distribution laws and acoustic field of motor electromagnetic vibration under transient operating conditions are obtained. The theoretical analysis results are consistent with the experimental results. Conclusion: The obtained results show that the spatial order of the radial electromagnetic force is not equal to the order of the radial mode of the motor stator. The reason for this is that structural resonance is induced when the frequency components of the spatial radial electromagnetic force are coupled with the intrinsic frequency of the stator.

Asteroseismology of the DAV star KUV 08368+4026

ABSTRACT As a DAV star, KUV 08368+4026 was observed by Li et al. in 2009 February, 2009 December, 2010 January, and 2012 February. They extracted 30 frequencies from the reported 300 h observation data and identified 17 independent modes. Based on the frequency splitting relationship, 6 l = 1 modes and 1 l = 2 mode are identified. The seven identified modes are reliable and can be used to constrain fitting models. A large sample (7,558,272) DAV star models were established using White Dwarf Evolution Code (wdec; 2018 version). The theoretical modes are calculated and used to fit the observed modes in order to obtain a best-fitting model. The best-fitting model has an average fitting error of σRMS = 0.71 s. The best-fitting model parameters are M* = 0.685 ± 0.005 M⊙, Teff = 11820 ± 40 K, log(MHe/M*) = − 5.00 ± 0.01, and, log(MH/M*) = − 6.90 ± 0.01. The stellar mass M* and effective temperature Teff of the best-fitting model are basically consistent with the results of the spectroscopy. The mass of the He layer is thinner than the results obtained from previous asteroseismic models. The best-fitting model has a small Carbon/Oxygen central core with an oxygen abundance of XO = 0.76. The asteroseismological distance calculated using the luminosity of our best-fitting model is basically consistent with that of the Kiso Schmidt ultraviolet excess survey.

A hybrid generalized TODIM based risk prioritization method for failure mode and effect analysis with linguistic Z-numbers

The traditional failure mode and effect analysis (FMEA), as an effective risk analysis technique, has several limitations in the uncertainty modeling and the weights determination of the risk indicators. This paper aims to propose a hybrid risk prioritization method simultaneously considering the characteristics of the reliability associated with the FMEA team members’ evaluation information and their psychological behavior to enhance the performance of the traditional FMEA model. The hybrid risk prioritization method is developed based on the generalized TODIM method and the weighted entropy measure with the linguistic Z-numbers (LZNs). First, the LZNs are adopted to depict the FMEA team members’ cognition information and the reliability of these information. Second, a weighted entropy measure based on the fuzzy entropy and the LZNs is developed to obtain the risk indicators’ weights. Finally, the generalized TODIM method with the LZNs is constructed to obtain the risk priority orders of failure modes, which can effectively simulate the FMEA team members’ psychological character. The applicability and effectiveness of the proposed risk prioritization method is validated through an illustrative example of an integrated steel plant. The results of sensitivity analysis and comparative analysis indicate that the proposed hybrid risk prioritization method is effective and valid, and can get more accurate and practical risk ranking results to help enterprises formulate accurate risk prevention and control plans.

Tip flow on rotating instability on an axial compressor with different tip clearances

Rotating instability (RI) as an unsteady phenomenon usually occurs at off-design conditions in compressors, featuring a broadband hump in the pressure spectra below the blade passing frequency (BPF). RI phenomenon could not only cause deterioration to the performance, but also lead to tip clearance noise or non-synchronous vibration to the compressor. In this paper a detailed experiment was carried out in a low-pressure single-rotor compressor. By replacing the casing the relative tip clearance size was changed and the time-resolved wall pressure with a distinct RI signature was thus measured under several different conditions through the Kulite pressure transducers both circumferentially and chordwise installed. The temporal-spatial distribution of RI signature evolution with the flow coefficient is interrogated, and its propagation characteristics are also investigated through the cross-correlation method. Moreover, the quasi-instantaneous contour measured by the chordwise transducers shows no distinct flow structure which could be connected to the RI signature, i.e., the prestall disturbance. Therefore, a quasi-SFT method is developed to identify different disturbance counts and the corresponding relationship between the disturbance count per revolution and the azimuthal mode order could thus be strictly established. The prestall disturbance is found to originate from the mid-chord positions as RI initiates and travel upstream as the reduction of flow coefficient, and eventually reaches the leading edge as rotating stall occurs. Furthermore, the location of prestall disturbances is proven to be independent on the blade position. These findings describe the tip flow field when the RI mode orders are relatively high, and provide new insights for the shear layer instability theory as RI mechanism.

Multi-scale modeling of a wind turbine wake in complex terrain

Comparing numerical simulations of wind turbine wakes in neutral atmospheric boundary layer (ABL) flow over complex terrains with full-scale experiments is not always straightforward. Pure neutral ABL conditions are rarely found in the atmosphere as the characteristics of the ABL change during the diurnal cycle. This study presents some insights into how a single wind turbine (WT) and its wake behave under near-neutral ABL conditions in complex terrain. The Perdigão Valley in Portugal was chosen as the test case as it is an excellent case study of three-dimensional flow in complex terrain to validate numerical simulations of WT wake with experimental data due to the availability of extensively deployed remote sensing equipment (e.g., German Aerospace Center (DLR) and Technical University of Denmark (DTU) multi-Doppler lidars). The Weather Research and Forecasting (WRF) [1] model is utilized in large-eddy simulation (LES) mode in order to simulate the period of interest with a multi-scale modeling approach. Five nested domains, with the finest domain having a spatial resolution of 5 m, are used to dynamically downscale mesoscale flow features to microscale. A generalized actuator line (GAL) WT parameterization is used to model the wind turbine-flow interaction. WRF-LES-GAL (hereinafter referred to as WLG) results compare quite well with the experimental data obtained from lidars and meteorological mast, with minor biases between the simulated and observed data. Due to insufficient buoyancy generation from the WRF-LES model, the simulated track wake was found to have lower vertical deflection compared to the lidar data; hence, no recirculation zone is observed in the valley. Overall, the WLG model is able to reproduce the wake characteristics observed on the first ridge top into the valley, as well as the power and thrust generation, and can be used for further analysis of other stability conditions.

Monitoring of the polarized H2O maser emission around the massive protostars W75N(B)-VLA 1 and W75N(B)-VLA 2

Context. Several radio sources have been detected in the high-mass star-forming region W75N(B), with the massive young stellar objects VLA 1 and VLA 2 shown to be of particular interest among them. These objects are thought to be at different evolutionary stages: VLA 1 is in the early stage of photoionization and driving a thermal radio jet, while VLA 2 is a thermal, collimated ionized wind surrounded by a dusty disk or envelope. In both sources, 22 GHz H2O masers have been detected in the past. Those around VLA 1 show a persistent linear distribution along the thermal radio jet, while those around VLA 2 have traced the evolution from a non-collimated to a collimated outflow over a period of ∼20 yr. The magnetic field inferred from the H2O masers has shown an orientation rotation following the direction of the major-axis of the shell around VLA 2, whereas it is immutable around VLA 1. Aims. By monitoring the polarized emission of the 22 GHz H2O masers around both VLA 1 and VLA 2 over a period of six years, we aim to determine whether the H2O maser distributions show any variation over time and whether the magnetic field behaves accordingly. Methods. The European VLBI Network was used in full polarization and phase-reference mode in order to determine the absolute positions of the 22 GHz H2O masers with a beam size of ∼1 mas and to determine the orientation and the strength of the magnetic field. We observed four epochs separated by two years from 2014 to 2020. Results. We detected polarized emission from the H2O masers around both VLA 1 and VLA 2 in all the epochs. By comparing the H2O masers detected in the four epochs, we find that the masers around VLA 1 are tracing a nondissociative shock originating from the expansion of the thermal radio jet, while the masers around VLA 2 are tracing an asymmetric expansion of the gas that is halted in the northeast where the gas likely encounters a very dense medium. We also found that the magnetic field inferred from the H2O masers in each epoch can be considered as a portion of a quasi-static magnetic field estimated in that location rather than in that time. This allowed us to study the morphology of the magnetic field around both VLA 1 and VLA 2 locally across a larger area by considering the vectors estimated in all the epochs as a whole. We find that the magnetic field in VLA 1 is located along the jet axis, bending toward the north and south at the northeasterly and southwesterly ends of the jet, respectively, reconnecting with the large-scale magnetic field. The magnetic field in VLA 2 is perpendicular to the expansion directions until it encounters the denser matter in the northeast, where the magnetic field is parallel to the expansion direction and agrees with the large-scale magnetic field. We also measured the magnetic field strength along the line of sight in three of the four epochs, with resulting values of −764 mG < B||VLA 1 < − 676 mG and −355 mG < B||VLA 2 < −2426 mG.

Photonic Möbius topological insulator from projective symmetry in multiorbital waveguides.

The gauge fields dramatically alter the algebraic structure of spatial symmetries and make them projectively represented, giving rise to novel topological phases. Here, we propose a photonic Möbius topological insulator enabled by projective translation symmetry in multiorbital waveguide arrays, where the artificial π gauge flux is aroused by the inter-orbital coupling between the first (s) and third (d) order modes. In the presence of π flux, the two translation symmetries of rectangular lattices anti-commute with each other. By tuning the spatial spacing between two waveguides to break the translation symmetry, a topological insulator is created with two Möbius twisted edge bands appearing in the bandgap and featuring 4π periodicity. Importantly, the Möbius twists are accompanied by discrete diffraction in beam propagation, which exhibit directional transport by tuning the initial phase of the beam envelope according to the eigenvalues of translation operators. This work manifests the significance of gauge fields in topology and provides an efficient approach to steering the direction of beam transmission.

Multimode damping optimization of a long-span suspension bridge with damped outriggers for suppressing vortex-induced vibrations

Long-span suspension bridges are subjected to wind-induced vibrations due to their large flexibility and low damping. Damped outriggers have been proposed recently to supplement damping and suppress multimode vibrations of main girders of long-span bridges, e.g., vortex-induced vibrations. However, when installed at multiple positions including tower-girder junction points and girder ends to further improve multimode damping effect, damping effects of the damped outriggers are interdependent. Additionally, the frequency curves of adjacent modes with respect to varying parameters of the damping devices could approach and intersect with each other, making it difficult to track mode orders and modal damping variations in design optimization. This study therefore proposes an optimization method to design damped outrigger parameters for maximizing multimode damping of the bridge. First, the bridge with damped outriggers is modeled generally using finite element method for dynamic analysis. Subsequently, two critical issues in the design, i.e., the mode tracking and multi-objective optimization, are respectively addressed by using the modal assurance criterion and the genetic algorithm. The proposed method is then applied to the Xihoumen Bridge with a main span of 1650 m. The results show that through the proposed optimization, 6 out of 7 modes vulnerable to vortex-induced vibrations can reach a damping ratio over 1.0%, which cannot be achieved by using damped outriggers of a uniform size. Furthermore, the required damper coefficients are decreased by 49.4%. The flexibility of the outriggers has been considered in the design. The developed method is promising in the design of other types bridge damping devices, e.g., multiple tuned mass dampers.

Study on the acoustic characteristics of a heavy-duty gas turbine combustor

The acoustic characteristics of combustor are an important theoretical basis for determining whether a gas turbine will undergo thermoacoustic coupled oscillatory combustion. In this paper, the acoustic numerical model of a heavy-duty gas turbine combustor is established and its acoustic characteristics are studied using ANSYS simulation software. The results show that: 1) the acoustic pressure oscillation in the chamber primarily appears as the longitudinal mode below 705 Hz, while above 870 Hz, the transverse mode appears. 2) the effect of temperature on the acoustic natural frequency of the chamber enhances with the order of the acoustic mode. 3) the acoustic frequency of each order of the combustor varies considerably at low load conditions, and no longer varies when the gas turbine load is higher than 80 % rated power. 4) the variation of acoustic frequency with gas turbine load can be fitted by a third-order polynomial, and the acoustic frequency is proportional to the first and third orders.

Shaking table test of multiple-type isolation control strategies for high-rise structure based on friction pendulum

Given the difficulties associated with deploying isolation technique in high-rise structures, this article conducts a comprehensive comparison of three operating systems: friction pendulum system (FPS) base isolation form: FPS-B, FPS inter-story isolation form: FPS-I, and FPS hybrid isolation form: FPS-H. A 9-layer scaled test model is constructed by using third generation benchmark model, and the accompanying FPS model is created and fabricated using the geometric similarity criterion. Considering four typical ground motions and four peak ground acceleration (PGA), the structural seismic responses of the three control systems were analyzed. The result demonstrates that FPS-H technology greatly decreases the superstructure’ top floor acceleration and even the substructure's acceleration impact in both mild and major earthquakes. The working mechanism of FPS-H technology in terms of vibration reduction is similar to the conjunction of tuned mass damper (TMD) and FPS-B structure. The inertia force of superstructure suppresses the substructure since superstructure has FPS inter-story isolation form, and even the substructure is an FPS-B form that can extend the structural period and segregate earthquake energy. The FPS-H technology, which reduces the acceleration response of the structure's 1st -order mode and restrains the dynamic reaction of the high-order mode by changes the dynamic characteristics of whole structure, is primarily responsible for the long-period structure's effective damping.

PALSRaM: A three-detector positron annihilation lifetime spectrometer for [formula omitted]-emitting radioactive materials

A three detector positron annihilation lifetime spectrometer for γ-emitting radioactive materials has been constructed and successfully tested. The equipment operates in triple-coincidence mode in order to reject the false coincidence due to the radioactive background generated when dealing with radioactive samples. The spectrometer has been optimized and tested by comparison of the results of well-known material with and without high background radiation. The time resolution of 155 ps is achieved. This paper reports on the design, stability and performance of this new spectrometer.

Vibrations of joined conical-cylindrical shells with bolt connections: Theory and experiment

This paper investigated the vibration characteristics of joined conical-cylindrical shells (JCCSs) with bolt loosening boundary conditions both theoretically and experimentally. The non-uniform arc constraint model is established to simulate the bolt loosening boundary conditions by the artificial spring technology, which can describe the actual bolt contact pressure distribution. Continuously distributed artificial springs are introduced to realize the connection of the conical and cylindrical shells. Donnell's shell theory and Chebyshev polynomials are adopted to establish the theoretical model, and the dynamic equation is derived from the Lagrange equation. The validity of the present model is verified by the available literature, hammer test and vibration shaker test. The results indicate that the maximum errors of natural frequencies and resonant displacements are less than 4.41% and 18.6%, respectively. It is found that bolt loosening has a significant effect on the fundamental frequency, but it gradually weakens with the increase of the mode order. Increasing bolt loosening degree can lead to an increment of resonant displacement. The developed model is reliable in estimating the dynamic behaviors of bolted JCCSs with different loosening degrees, and it contributes to providing guidance in the design and service process of combined shell structures.

A Novel Nonisolated Buck–Boost DC–DC Converter With Low Voltage Stress on Components

This paper proposes a new non-isolated DC-DC buck-boost converter with low voltage stress on components and enhanced voltage gain. This converter has a high voltage gain in boost mode and is capable of reducing the voltage level significantly in the buck mode, which makes it suitable for renewable energy and other industrial applications. Moreover, the number of components in this converter is low and the input current is continuous. Operational principles of the proposed converter in both CCM and DCM are presented, efficiency analysis is discussed, and small-signal model is derived. Comparisons between the presented converter and related buckboost converters are given in terms of voltage gain, voltage stress on components, number of elements, etc. Besides, a singleinput multi-output converter based on the proposed topology is presented. Experimental results from a lab-scale prototype are given for both buck and boost modes in order to verify the performance of the converter.