Measurement Of Dynamic Characteristics Research Articles

Quantitative assessment and dynamic characteristic measurement of regional resilience: from the perspective of post-earthquakes effects

Strong geological disasters have caused persistent losses in society, economy, and ecological environments. Given the unique geographical settings of the stricken areas, their resilience is prone to damage or even loss. Comprehensive risk assessment of natural disasters is the core content and important foundation for building regional resilience. Therefore, conducting dynamic characteristics analysis of resilience in mountainous disaster areas impacted by strong earthquake geological disasters is vital for ensuring the region's high-quality and sustainable development. This article takes the 51 stricken areas of Wenchuan earthquake as the research object. To this end, social, economic and ecological environmental data from 2008 to 2020 was hereby collected. Initially, a regional resilience assessment system based on "socio-economic-ecological environment" was established, considering the long-term and spatial heterogeneity of geological disasters. Secondly, the regional resilience assessment model was constructed using Spectral clustering-genetic algorithm-improved entropy weight method. Following that, the dynamic characteristics of regional resilience were quantitatively analyzed from two aspects, including change velocity state and change rate trend. Finally, based on the regional resilience characteristics, differentiated resilience enhancement strategies were proposed. Collectively, the results revealed that: (1) From a geological disaster standpoint, the risk in post-earthquake disaster areas exhibited a strikingly rapid decline, with the spatial distribution of geological disaster risk being notably higher in the central areas and diminishing towards the peripheries. (2) Overall, the regional resilience of the 51 stricken areas showed a "V-shaped" trend, with a significant upturn since 2012. (3) From the perspective of dynamic characteristics, more counties (cities) presented an upward trend. (4) The 51 stricken areas were hereby divided into the "benchmarking type", the "declination type", the "backward type", and the "potential type". In conclusion, the current study enhances the technical framework for evaluating regional resilience and provides technical support for the construction of resilient cities.

Structural design and performance testing of respiratory sensor based on optical fiber end-face coupling

An optical fiber sensor based on the principle of intensity modulation is proposed, which is composed of plastic optical fibers and silicone tubes. The displacement measurement is achieved by stretching the optical fibers to cause changes in the angle between the end faces, resulting in changes in the coupling efficiency between the end faces. To address the challenges in the performance calibration of fiber optic respiratory sensors, it is proposed to convert the dynamic characteristics measurement of the respiratory sensor into the static performance analysis of the displacement sensor, so as to obtain the characteristics such as sensitivity, linearity, and repeatability, etc. It is further proposed to use a stepper motor to simulate the periodic stretching process of the optical fibers caused by the respiratory process, enabling the analysis of frequency measurement accuracy under different respiratory strengths. Simulation and experimental results demonstrate that the proposed sensor has high linearity, good repeatability, high sensitivity, and a wide measurement range. It can accurately measure respiratory frequency and display amplitude information, providing comprehensive information for respiratory monitoring.

A Theoretical Methodology and Measurement of Dynamic Characteristics of Wind Turbines with Composite Bucket Foundations

A composite bucket foundation (CBF) is a new type of supporting structure in offshore wind engineering. Its huge transition part is the key difference compared to other offshore foundations. Firstly, the vibration measurement system of a wind turbine with the CBF is introduced. A finite element method (FEM) was developed, and the rigid deformation performance of the transition part was characterized. Then, to clarify the influence of the transition part brings to wind turbines with CBFs, a three-DOF theoretical model was established by simplifying the transition part as a rigid body. Horizontal and rotational foundation stiffness were considered to present the constraint effect below the mudline. Sensitivity studies were conducted on the parameters (including mass, moment of inertia and mass center height) of the transition part. Further, the vibration properties of the CBF structures under different operation load conditions were compared through the theoretical model and the in situ data. The results show that the relative errors between the theoretical model and FEM model are 3.78% to 5.03%, satisfying the accuracy requirements. The parameters of the transition part have varying degrees of influence on the natural frequency, foundation stiffness and vibration response of the wind turbines with CBFs. Compared to wind and 1P loads, the 3P load has a greater influence if the 3P frequency is close to the natural frequency of the wind turbine.

Dynamic Characteristics Measurement and Analysis of HTS Maglev Vehicle Driven by Permanent Magnet Electrodynamic Wheel

Dynamic Characteristics Measurement and Analysis of HTS Maglev Vehicle Driven by Permanent Magnet Electrodynamic Wheel

Experimental Measurement of Dynamic Characteristics of Structural Units

The aim of this study is to investigate and optimize the dynamic properties of an entire structural unit. Using modal analysis and experimental measurements of the propulsion system, natural frequencies with close agreement were identified. The drive was able to work within the frequency range during start-up and normal operation, but due to various influences, including the inherent oscillations of structural elements, complex dynamic phenomena occurred. The presence of a conveyor with rubber and plastic wheels also affected the results. Important information on the input shaft, tooth frequency, driveline oscillation and output shaft was obtained. Research has identified resonant frequencies and increased drive oscillation that are created by the interaction between the input shaft and tooth frequency. The significant frequency of bent screws in the conveyor pipe affects the shafts and the drive screw, which in turn causes problems with material fatigue and microcracks. Corrective measures include the possibility of replacing or balancing the screw and increasing the diameter of the pipe. Regular monitoring and diagnostics have a preventive nature and serve to minimize serious consequences. Implementing a controller with a PID system offers the potential to suppress oscillations and improve dynamic and strength characteristics, while accurate calibration of this implementation is of key importance.

Dynamic characteristic measurement of precast and cast in‐situ walls in abandoned high‐rise building using ambient and forced vibration methods

AbstractThis study evaluates the dynamic characteristics of an abandoned reinforced concrete building with structural deterioration and defects in its precast and cast in‐situ walls. Using ambient vibration and forced excitation, the dynamic characteristics (i.e., modal frequency, modal damping, and strain patterns) were extracted to evaluate existing performances. Then, the numerical modal analysis was conducted with the dynamic properties at the initial service stage since the joint degradation was not accounted. In general, modal frequency obtained from field measurement was approximately 19.8%–20.8% smaller than that obtained from the numerical analysis, indicating the degraded stiffness due to existing cracks at joint connections. In addition, the measured strain patterns and neutral axis location were eventually compared with the analytical results, proving the potential indicators for identifying local imperfections of the targeted high‐rise buildings.

Experimental Measurement of Structural Static and Dynamic Characteristics of Glass/Banana Hybrid Composite

Experimental Measurement of Structural Static and Dynamic Characteristics of Glass/Banana Hybrid Composite

Устройства и методы измерения параметров RFTES-болометра

Several new approaches to the measurement of intrinsic noise and dynamic characteristics of superconducting bolometers based on the RFTES technology are demonstrated. The developed methods were tested with an experimental 550–750 GHz sample at reading frequency of ~1.5 GHz at a temperature of 400 mK. The absorption of thin-film resistive coatings on sapphire and quartz substrates was studied, and the emissivity of the experimental heat source was estimated as ~14%. A shot noise source based on Al/AlOx/Al tunnel junction was developed, and the noise temperature of the 1.35–1.6 GHz buffer amplifier referred to the detector output was determined as ~20 K. The response time of RFTES with a hafnium film sized 6 µm × 2 µm × 0.08 µm was evaluated as ~3 µs via microwave heat modulation at the second resonance at ~4.2 GHz; the dynamic range at a modulation frequency of 10 kHz was more than 23 dB. The data obtained made it possible to determine the RFTES sensitivity as 1∙10-17 W/√Hz ± 30%, that coincided with the theoretical value up to the measurement error.

AUTOMATED MONITORING OF TIME SYNCHRONISATION DEVICES AND DIGITAL PROCESSING OF VECTOR MEASUREMENTS OF DYNAMIC CHARACTERISTICS OF SMART GRID POWER SYSTEMS

Currently, customers of energy companies use devices to generate electricity (solar panels, windmills, etc.) and return energy to the grid to save costs or generate income. Therefore, it is urgent to solve the problem of creating an automated system for diagnosing the quality of electricity for consumers who use renewable sources of electricity. The purpose of this study was to improve the efficiency of management in intelligent SMART Grid power systems. To fulfil the said purpose, it was proposed to use an automated system for monitoring synchro signals of PMU microprocessor equipment and software tools for digital processing and statistical analysis of the results of synchronised vector measurements of dynamic characteristics of power grids. Software tools for digital processing and statistical analysis of the obtained vector measurement data were developed. Linear regression, Random Forest Regression, and Ridge regression methods were employed to analyse and predict electricity quality indicators. The results of a comparative analysis of the obtained results of the predictive model were presented. To conduct experimental studies, a laboratory sample of a quality control device for generating synchro signals was developed and manufactured, which directly affects the reliability of digital data from distributed synchronised vector measurements in transient modes (in real time). The multichannel nature of the device increases the performance and reliability of the automated monitoring system. The paper presents the results of experimental studies of the device as a part of the developed laboratory stand, which is connected to the current local IP network of the National University of Life and Environmental Sciences of Ukraine. The practical significance of the conducted experimental studies lies in the establishment of the technical possibility of simultaneous monitoring of time synchronisation signals generated by two GPS receivers. In this case, it is obvious to increase the performance of the developed and manufactured device for monitoring the quality of clock signal generation, compared to a single-channel one. This material can be useful for engineers who design electrical systems connected to renewable energy sources.

Метод построения МИС СВЧ ограничителей мощности для повышения порога сгорания

The article shows the method of constructing the MMIC power limiter. The purpose of this research is to increase the burnout level. We considered a classical two-stage cir-cuit on anti-parallel p-i-n diodes. The idea of increasing the burnout level is to redis-tribute currents, so that at the burnout power at the first and second stages, the current is equal to the saturation current – 0.41–0.45 A / 100 µm. To do this, a simulation of the circuits was carried out – the ratio of the capacity of the first to the second stage 1:1, 2:1, 3:1 and 4:1. The design circuits were manufactured at p-i-n diode GaAs tech-nology of JSC RPC “Istok” named after Shokin, the height of the diode barrier is 1,1 V / 1 mA, the breakdown voltage is 45 V / 100 µA. The results of probe measurements S-parameters of power limiters and measure-ments of dynamic characteristics in the fix-ture are presented. Devices in the frequency range from 1 GHz to 16 GHz have losses less than 0.8 dB and VSWR input and output less than 2. The burnout level in continu-ous power at a frequency of 10 GHz was: for topology 1:1 — 45.3 dBm, 2:1 — 48.3 dBm and for topology 3:1 — 49.6 dBm. Under the same conditions, serial MMIC power limiters of foreign company were investigated. The burnout power density was ~20 W / 100 µm of the periphery, for the JSC RPC “Istok” named after Shokin technology, which exceeds the level of the investigated foreign analogues.

Development of portable device for measurement of dynamic and static light-emission WOLED characteristics

The research object of this work is the parameters of organic light-emitting diodes, namely power and luminous flux. Determination of these parameters can be carried out using a photodiode and requires measuring the dark current of the sensor (photodiode), measuring the current of the photodiode when illuminated by the LED under investigation. And also take into account the relationship between the light flux received by the sensor and its output current, and take into account the spectral characteristics of the sensor. Calculate the investigated parameters of the LED based on the measurements. Carrying out these measurements requires laboratory instruments and workplace organization, and further calculations are routine work. It is possible to increase the measurement accuracy by improving the existing methods for measuring the required parameters, and it is possible to automate the process of measurements and calculations using a modern microprocessor radioelement base. Microcontrollers are widespread such radioelements. They have the necessary peripherals for independent operation and have sufficient computing power to implement the required measuring device. Its application makes it possible to automate the measurement process, carry out the necessary calculations, save correction constants, accumulate and process the obtained data, analyze these received data, exchange data with a computer, etc. So, the work is aimed at developing a methodology that will allow the simultaneous measurement of power and luminous flux of planar light sources. And also on the feasibility of this technique in the device and software with the ability to measure the power of the light source in an arbitrary band of the spectral visible range. Thus, it is possible to determine what power in watts a light source emits with the dynamics of supply currents in the optical bands, knowing the spectrum of this source without using glass filters. So, the result of applying the technique is to determine the power of light radiation (in watts) or the luminous flux (in lumens) of the emitter (light sources).

Test Results for the Static and Rotordynamic Characteristics of a Long (L/D = 0.75) Smooth Seal in Two-Phase (Mainly Gas) Conditions With a 62-Bar Inlet Pressure

Abstract Recent multiphase-pump developments encountered several rotordynamic issues with smooth balance-piston seals, creating a need to better understand the performance of annular seals under multiphase-flow operation. This paper presents measurements of static and dynamic characteristics of a long smooth seal (L/D = 0.75, D = 114.686 mm, and Cr = 0.200 mm) operating under pure- and mainly air condition in which air is mixed with silicone oil (PSF-5cSt). Tests are performed at a supply pressure of 62.1 bars-g, three rotation speeds (5, 10, and 15 krpm), three pressure ratios (PRs) (0.6, 0.5, 0.4), for a range of inlet liquid volume fraction (LVFi) from 0% to 8%. The results are then compared to: (1) the previous test reported by Zhang et al. (2017, “Experimental Study of the Static and Dynamic Characteristics of a Long Smooth Seal with Two-Phase, Mainly-air Mixtures,” ASME J. Eng. Gas Turbines Power, 139(12), p. 122504) with similar testing condition but a different seal geometry (L/D = 0.65, D = 89.306 mm, and Cr = 0.188 mm) and (2) the predictions from a bulk-flow model developed by San Andrés (2012, “Rotordynamic Force Coefficients of Bubbly Mixture Annular Pressure Seals,” ASME J. Eng. Gas Turbines Power, 134(2), p. 022503). Results show a significant increase of direct dynamic stiffness KΩ as LVFi increases, especially at low PR. Test results reported by Zhang et al. (2017, “Experimental Study of the Static and Dynamic Characteristics of a Long Smooth Seal with Two-Phase, Mainly-air Mixtures,” ASME J. Eng. Gas Turbines Power, 139(12), p. 122504) has an opposite tendency of KΩ as an impact of increasing LVFi values. Concerning cross-coupled dynamic stiffness kΩ and cross-coupled damping c, the results from Zhang et al. (2017) and the present results agree to the effects of changing speed, PR, and LVFi under pure- and mainly air conditions. As LVFi increases, direct damping C increases while test results reported by Zhang et al. (2017, “Experimental Study of the Static and Dynamic Characteristics of a Long Smooth Seal with Two-Phase, Mainly-air Mixtures,” ASME J. Eng. Gas Turbines Power, 139(12), p. 122504) showed no significant increase. A steady-state computational fluid dynamics (CFD) result for a testing case suggests a significant difference happening inside the two seals (present seal and Zhang et al.'s (2017, “Experimental Study of the Static and Dynamic Characteristics of a Long Smooth Seal with Two-Phase, Mainly-air Mixtures,” ASME J. Eng. Gas Turbines Power, 139(12), p. 122504) seal). A full investigation in CFD is needed. Except for the direct dynamic stiffness and the impact of changing LVFi on the cross-coupled dynamic stiffness, the bulk-flow model of San Andrés (2012, “Rotordynamic Force Coefficients of Bubbly Mixture Annular Pressure Seals,” ASME J. Eng. Gas Turbines Power, 134(2), p. 022503) predicts decently the tendencies and magnitudes of the rotordynamic coefficients.

Application of seismic multi-attribute inversion based on wireless network sensor in Dongying delta foreset

Seismic attributes, which are extracted from seismic information, are physical indexes used specifically for the measurement of geometric, dynamic, or statistical characteristics of seismic data. Current methods for seismic multi-attribute inversion include linear and nonlinear methods. By adopting the wireless module of NFC24l01, combined with the seismic data acquisition sensor, constitutes an intelligent network sensor, and then it sends the collected data to the topmost machine for analysis. Methods for the nonlinear inversion of seismic multi-attributes usually employ tools such as neural networks and support vector machines (SVMs) for mapping. Hence, inversion results obtained via nonlinear methods are more accurate than those obtained via linear methods. In this work, with spontaneous-potential (SP) curves as the objective of nonlinear inversion, an optimized seismic attribute combination for the inversion of SP curves was identified, and the nonlinear inversion of seismic multi-attributes was achieved via the use of a deep neural network (DNN) to obtain 3D SP data. Finally, the foresetting process of a sand body of the intermediate section in Member 3 of the Shahejie Formation in the Dongying Delta was illustrated via the horizon slice of the SP data.

Measurement of Dynamic Characteristics of Partially Textured Journal Bearings

Measurement of Dynamic Characteristics of Partially Textured Journal Bearings

Theoretical analysis and experimental measurement of coupling dynamic characteristics for transversely isotropic rectangular plate based on modified FSDT assumption

The theoretical analysis of thick plate vibration behavior has been investigated in the literature, but most of the studies were focused on flexural dynamic characteristics and lack experimental verification. In this study, the analytical solutions based on the superposition method for both the flexural and extensional vibrations are presented to obtain resonant frequencies and associated mode shapes for a transversely isotropic thick rectangular plate. The displacement equilibrium equations and boundary conditions of the modified first-order shear deformation theory (FSDT) are derived by utilizing Hamilton’s principle and the variation method. To verify the validity of the theoretical model, the finite-element method (FEM) and impact experiment results for thick plates are employed in this work. Excellent agreement of resonant frequencies and associated mode shapes is obtained for FEM calculation and theoretical analysis. To excite vibrations of a thick rectangular plate, a steel ball controlled by an electromagnet is utilized. A steel ball is dropped freely from a height of 231 mm on the top of the plate surface, and a transient wave will be generated after the ball impact on the specimen. The frequency spectrum of the thick rectangular plate is constructed by using the fast Fourier transform of the time-domain transient response. The excited resonant frequencies obtained from experimental measurement are compared with theoretical results. The comparisons show that the modified FSDT provides an excellent prediction of the resonant frequencies and mode shapes for the dynamic characteristics of thick rectangular plates.

The direct measurement of the cylinder block dynamic characteristics based on a non-contact method in an axial piston pump

The cylinder block is the main rotating part in axial piston pump, and its dynamic characteristics can reflect the health condition of the pump more directly than the external characteristics. In this paper, a less modification measurement scheme is proposed to acquire the dynamic characteristics of the cylinder block accurately. The less modified pump minimizes the influence of the test equipment on the cylinder block motion. The radial displacements of the cylinder block surface in two cross-sections along the perpendicular directions are measured under different operating conditions. Moreover, the translational motion and the tilt behavior of the cylinder block are calculated when the run-out signals of the cylinder block surface are removed from the measurement signals. The vibration signals are measured synchronously and compared with the movement of the cylinder block. Finally, the dynamic characteristics of the cylinder block under different operating pressure are presented and analyzed in detail.

Dynamic load test analysis of upper bearing arch bridge

The bridge load test is an important means to evaluate the completed performance, construction quality and structural bearing capacity of the bridge structure, including determining the dynamic load test to determine the natural frequency, damping ratio and vibration mode of the bridge structure or structure, so as to determine the structural rigidity. The quality is an important factor to determine the basis. However, for the dynamic characteristics measurement method of the upper bearing arch bridge, the specification does not give a detailed detection method or recommendations. Combining with the analysis results of the field test data of the upper bearing arch bridge, this paper obtains a more accurate arrangement of test points.

Oxidation-boosted charge trapping in ultra-sensitive van der Waals materials for artificial synaptic features

Exploitation of the oxidation behaviour in an environmentally sensitive semiconductor is significant to modulate its electronic properties and develop unique applications. Here, we demonstrate a native oxidation-inspired InSe field-effect transistor as an artificial synapse in device level that benefits from the boosted charge trapping under ambient conditions. A thin InOx layer is confirmed under the InSe channel, which can serve as an effective charge trapping layer for information storage. The dynamic characteristic measurement is further performed to reveal the corresponding uniform charge trapping and releasing process, which coincides with its surface-effect-governed carrier fluctuations. As a result, the oxide-decorated InSe device exhibits nonvolatile memory characteristics with flexible programming/erasing operations. Furthermore, an InSe-based artificial synapse is implemented to emulate the essential synaptic functions. The pattern recognition capability of the designed artificial neural network is believed to provide an excellent paradigm for ultra-sensitive van der Waals materials to develop electric-modulated neuromorphic computation architectures.

High Frequency Modal Testing of the Multiblade Packets Using a Noncontact Measurement and Excitation System

High cycle failure of blades and vanes caused by the vibration is one of the major causes reducing the lifetime of turbomachines. For multiblade packets, the failure may occur at vibrations with high frequencies that can reach up to tens of kHz. The experimental modal testing of blades is crucial for the validation of numerical models and for the optimization of turbomachine design. In this paper, the test rig and procedure for measurements of dynamic characteristics of lightweight multiblade packets in wide and high frequency ranges are developed. The measurements are based on a noncontact excitation and noncontact measurement method, which allows the determination of the modal characteristics of the packets with high accuracy in wide frequency ranges. The responses of the multiblade packets are measured using a Scanning Laser Doppler Vibrometry (SLDV), while vibrations are excited by the acoustic excitation technique. Modal tests of the blade packet comprising 18 vane blades connected by shrouds are performed. The measurements are performed within the high frequency range of 0–30 kHz, and the natural frequencies and mode shapes are obtained for first 97 modes. To capture the complex high frequency blade mode shapes, each blade in the packet is scanned over 25 reference points uniformly distributed over the blade concave surface. In order to obtain the high frequency resolution, the frequency range used for the measurements is split into several frequency intervals accordingly to the number of spectral lines available in the used data acquisition system, and for each such interval, the test is performed separately. The finite model of the packet is created, and the numerical modal analysis is performed to compare the calculated natural frequencies and mode shapes with the experimental measurements. The comparison shows the satisfactory with those from finite element analysis. It illustrates the measurement method described in this work is effective and reliable.

Measurement of Oil Film Dynamic Characteristics of Partially Textured Journal Bearings

Measurement of Oil Film Dynamic Characteristics of Partially Textured Journal Bearings