查看更多>>摘要：We report the acquired of Fano resonance based on metal-insulator-metal (MIM) waveguide structure, which first consists of a branched semi-closed T-shaped waveguide coupled to an open square ring resonator, demonstrate that the Fano resonance has an highly sensitive, observe rapid detection of glucose concentration and the Fano resonance spectrum redshift with increasing the glucose level. zong These features provide a solid foundation for the application of these novel MIM structures in the field of biochemical sensing.
查看更多>>摘要：Rolling contact fatigue (RCF) cracks are one of the typical surface-breaking defects that impairs the rail service life. RCF cracks propagation can deviate from regular semi-ellipse shapes, turning into asymmetrical profiles. RCF crack measurements using the alternating current field measurement (ACFM) method are unable to accurately characterise asymmetrical cracks, as the sizing algorithm is developed based on regular crack shapes. In this paper, the development of modelling capability to consider asymmetrical RCF cracks and the influence of asymmetrical shapes on ACFM signals are presented. A novel grid scan method using ACFM probe sensor for characterizing asymmetrical crack shapes is proposed. The influences of rail head profile on crack sizing are studied and result shows that it gives maximum 2 mm underestimation in crack depth if the worn rail head profile is not considered in ACFM sizing algorithm.
查看更多>>摘要：Accurate estimations of the time of arrival (TOA) are essential in ultrasonic nondestructive testing. The parameters of ultrasonic pulse echoes are usually estimated by detecting the peak value of the envelope with a Hilbert transformation (HT). However, ultrasonic pulse echoes are likely to be polluted by noise in the propagation process, distorting the envelope signal and preventing the TOA from being accurately estimated. This paper proposes an algorithm for estimating the parameters of ultrasonic echo signals based on joint sparse representation and the flower pollination algorithm (FPA). An improved matching pursuit algorithm is developed to eliminate the noise and improve the envelope extraction of the echo signals. This reduces the superposition of repeated signals and improves the reconstruction accuracy. The signal envelope is then extracted by an HT. Finally, FPA is used to fit the envelope and estimate the parameters. Numerical simulations and experimental results show that the parameters estimated by the proposed method are highly accurate and have a mean square error that is close to the Cramer-Rao lower bound.
查看更多>>摘要：On-machine measurement based on chromatic confocal principle is an effective method for quality control in precision manufacturing. However, angular misalignment between the measurement axis and the optical axis of probe will introduce cosine error, and the probe offset will cause rotational deviation. These alignment errors, which negatively affect measurement accuracy, are represented by beam vector deviations. In this paper, the influence of the beam vector deviation is first quantitatively analyzed. Then, an effective calibration method using standrad parts is proposed. The accuracy of the calibration method is verified by measuring standard sphere profile, and the uncertainty considering indication error, random error, sampling strategy and fitting optimization algorithm is evaluated. The feasibility of the proposed method is demonstrated by practical on-machine measurement experiments of a typical high-gradient freeform surface. Trajectory deviation is cor-rected based on virtual rotation center planning. The results agree well with offline measurements.
查看更多>>摘要：Acoustic grating metamaterials (AGMs) with exotic enhancement property and remarkable directional response are promising candidates to advance the metamaterial-based acoustic sensing. In this paper, a graded reflection AGM (GRAGM) is proposed to broaden the working bandwidth and reduce the device volume. In contrast with conventional periodic AGM, GRAGM with graded slit width can be viewed as a series of combined Fabry-Perotlike (FP-like) resonators. As a result, the working band is broadened twice by combining multiple resonant bands. The added reflection plate is capable of reducing the working frequency of GRAGM by manipulating the reflection phase at the boundaries with the maximum variation over than 280 Hz, which enables the GRAGM to work in a deep subwavelength scale. Moreover, the strong directional response of the GRAGM is able to localize sound sources. These exotic properties promise a number of potential applications, such as sound source localization, condition monitoring, and remote whispering.
查看更多>>摘要：The choice of the grain interaction model is a critical element of residual stress analysis using diffraction methods. For the near-surface region of a mechanically polished austenitic steel, it is shown that the application of the widely used Eshelby-Kro & BULL;ner model does not lead to a satisfactory agreement with experimental observations. Therefore, a new grain interaction model called 'tunable free-surface' is proposed, allowing for the determination of the in-depth evolution of the elastic interaction between grains. It has a strong physical justification and is adjusted to experimental data using three complementary verification methods. It is shown that a significant relaxation of the intergranular stresses perpendicular to the sample surface occurs in the subsurface layer having a thickness comparable with the average size of the grain. Using the new type of X-ray Stress Factors, the in-depth evolution (up to the depth of 45 mu m) of residual stresses and of the strain-free lattice parameter is determined.
查看更多>>摘要：This paper describes an application of ultrasound techniques to solid-liquid fluidized beds. The ultrasonic methods, experimental setups, and the signal processing for obtaining velocity profiles, particle size distribution, and solids volume fraction are discussed. The techniques are based on the measurement of the ultrasound attenuation coefficient, sound speed, and frequency shift of the propagated sound wave. The ultrasound propagation speed in solid-liquid fluidized bed was measured to be between 1504 m/s and 1565 m/s for glass particles with volume fractions spanning from 27% to 70% in water. The solid velocity profiles were measured for liquid superficial velocities varying from 0.84 cm/s to 4.24 cm/s. The particle size distributions were measured for four different sizes of glass particles ranging from 500 mu m to 1250 mu m at a solid volume fraction of 35%. This paper also reports the importance of the techniques as a diagnostic tool to investigate the particles segregation behaviour in solid-liquid fluidized beds at different fluidization conditions. The results indicated that ultrasound techniques are a powerful tool that can characterise in real-time highly concentrated solid-liquid systems.
查看更多>>摘要：A serial-parallel conversion test strategy is proposed for the test path optimization of digital microfluidic biochip which is parallelly tested by multiple droplets. It can solve the problem of the test path repetition in the partition method, as well as the droplet fluid conflict in the traditional non-partition method. Firstly, a hybrid algorithm based on priority strategy and genetic algorithm is designed to optimize the parallel test path of the biochip, so as to avoid the problem that the search process is too random when only a single intelligent algorithm is used to optimize the test path. Then an adaptive method is proposed to adjust the amount of test tasks, which can improve the average distribution method of test tasks and further optimize the parallel test of the digital microfluidic biochip. The test simulation of nine different array chips shows that the serial-parallel conversion strategy proposed in this paper is better than the partition strategy, and the experimental results show that the proposed method can improve the test efficiency of digital microfluidic biochips and reduce the test cost.
查看更多>>摘要：To obtain precise and continuous attitude information, this paper proposed a data fusion scheme that exploits the complementary advantages of a microelectromechanical system (MEMS) magnetic, angular rate, and gravity (MARG) sensor and a low-cost global navigation satellite system (GNSS) receiver. A quaternion-based error state Kalman filter is designed to integrate the different data sources, where the attitude error and gyro bias variation are taken as the error states. The gyro-measured angular rates are continuously integrated to propagate the attitude quaternion, while the accelerometer and magnetometer readings or the GNSS pitch and heading angles estimated by the precise carrier phase observations are utilized to perform the measurement update. The system kinematic model remains constant when the aiding source changes, only the measurement model alternates accordingly. A vehicular dynamical test was conducted to evaluate the proposed algorithm, the test results show that the attitude estimation accuracy of the integrated algorithm is apparently improved.
查看更多>>摘要：The paper presents and discusses the results of research aimed at developing the optimal System for Generation of the fast-changing Rotating Magnetic Field (SGRMF) that causes the hyperthermic effect in magnetic liquids. In the calculations and design of the SGRMF, the three-dimensional (3D), original approach of the Finite Element Method (FEM) has been used. The FEM software prepared by the authors is based on the dl-T0 formulation with nodal values of the scalar potential dl to describe the magnetic field, and edge values of the electric vector potential T0 to define currents in windings. In the prepared model of the SGRMF, the relations describing the conversion of electromagnetic energy into thermal energy in magnetic fluids have been taken into consideration. The results of the proposed FEM model and elaborated software are presented and compared with the results obtained from the measurements on the specialized test stand. The prototype of the SGRMF system has been designed and built. Finally, the application of this prototype in the investigations of the hyper-thermal effect in a selected magnetic fluid of APG 513 type is given and discussed.
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Elsevier