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Illumination system, as one of the main parts of lithography, enables to supply high uniformity intensity distribution on the mask, controls exposure dose and creates off-axis illumination (OAI) modes, which enhance the resolution and enlarge depth of focus of lithography. Quartz crystals exhibit intrinsic birefringence in the x-direction, based on which, quartz crystal polarization device is made, and the polarization state of beam can be controlled by the device. In the lithography machine's lighting system, the resolution ratio and imaging quality can be further improved by the polarization device with off-axis illumination modes assisted. Due to the limitations of traditional quartz crystal growth process and crystal automorphism, largediameter quartz wave plate (diameter above 50 mm) which the polarization device need was always a challenge. In this study, optimized framework seed method was applied to eliminate heritable etch channel defects. Raw material ratio was optimized for further reduce the content of trace elements such as Al3+, and Na+,, etc. Temperature-rising curve was controlled to realize lattice matching on the surface of quartz seed, and weaken inhomogeneous in the epitaxial region of quartz crystal. The parameters (such as temperature, pressure, mineralizer and its concentration, opening rate of throttle flap, et al.) were systematically adjusted for quartz growth. Thereby a high transmittance quartz single crystal suitable for 193 nm wavelength was successfully synthesized and a quartz wave plate blank with maximum size of Φ160 mm was processed, which is the largest size quartz optical wave plate blank reported. Optical properties such as trace element content, internal transmittance, birefringence performance, optical uniformity and laser damage resistance were characterized. The results show that, the total content of trace elements in quartz crystal is controlled within 7 x 10-6, the internal transmittance reaches 99.80%/mm, the unevenness of birefringence difference is less than 0.029 7%, and the PV value of optical uniformity reaches 3.9 x 10-6, (effective aperture Φ140 mm). [ABSTRACT FROM AUTHOR]

In order to solve the problem of Lamb wave dispersion and multi-mode restriction in plate structure and its practical application in ultrasonic nondestructive testing technology, a method based on Bloch-Floquent theory and finite element characteristic frequency method is used to calculate the dispersion curve of plate structure containing mode information in real and pure imaginary wave number domains. Based on the Bloch-Floquent periodic boundary conditions, the dispersion curves of infinite steel plate structures in irreducible Brillouin region and pure imaginary wave number domain are quickly calculated. In this study, Bloch-Floquent extension and Fourier transform are used to obtain the real wave number information of each characteristic mode and overcome the aliasing problem of dispersion curve. In this study, the modal identification is carried out according to the out-of-plane displacements of the upper and lower surfaces of each mode, and the complete dispersion relation of the steel plate is obtained. The calculated results of this method are in good agreement with those obtained by solving the dispersion equation with the traditional dichotomy method, which verifies the validity of this method. [ABSTRACT FROM AUTHOR]

The conventional CBL/VDL sonic log, sector bond log and ultrasonic pulse echo log all are unable to be used to accurately evaluate the quality of well cementing with light-weight cement slurries. To deal with this problem and improve the accuracy of evaluating the quality of well cementing with light-weight cement slurries, an ultrasonic Lamb wave well logging instrument for cementing job quality evaluation was developed based on ultrasonic “pulse-echo” detection mechanism. A model was established describing the relationship among the bending Lamb wave attenuation rate, the vertical echo resonance efficiency and the sonic impedance of medium outside casing. A chart was developed to evaluate the solid-liquid-gas three phase media. With the model and the chart, a new method for evaluating the quality of well cementing based on ultrasonic Lamb wave was developed in connection with light-weight calibration well logs. This new method can be used to effectively evaluate the quality of well cementing with lightweight cement slurries and detect the height of the cement return, thus having solved the difficulties encountered with the lightweight slurries. This technology has provided a clue for examining and evaluating the quality of well cementing with light-weight cement slurries. Meanwhile, the ultrasonic Lamb wave well cementing job quality log instrument can also be used to evaluate the casing eccentricity and casing wear, the results of which can be used as a basis for evaluating the quality of well cementing and the integrity of the wellbore. This new technology will have a broad application prospect. [ABSTRACT FROM AUTHOR]

Water content is crucial to plant growth. Water shortage can cause a decrease in photosynthesis and respiration efficiency during growth, directly leading to the yield of plants and crops. An accurate identification can greatly contribute to the water change of plant leaves in the early stage of water shortage and intervene rapidly. It can greatly reduce the loss of plants and crops due to water shortage. However, there is little change in the water content and no outstanding change in the plant morphology and spectral characteristics during the early stage. It is a high demand for the early identification of plant water content change at present. Two measurements can be widely used in the plant water content. One is the direct measurement (such as drying, and distillation), where the measurement accuracy is higher, generally as the standard of other methods. Another is the indirect measurement using, such as the plant stem diameter, canopy temperature, conductivity, microwave, spectroscopy, and images. In this study, a set of polarized light imaging systems was built to add the light source, and polarizer in the image detection. The polarized light imaging detection was then carried out on the Holly leaves with different water content. The polarization of light that carried the multidimensional vector information was used as the information carrier to transmit more abundant information. The multi-dimensional vector that carried in the light polarization information was used to detect the different water content of Holly leaves, in order to realize the early identification of water content change. The main conclusions of this study were as follows. 1) The m13 and m32 matrix elements in the Mueller matrix image initially reflected the change of water content of Holly leaves, but there was no outstanding difference in the early stage of water content change. 2) The depolarization index image clearly showed the change in the water content of Holly leaves at each stage. Specifically, the depolarization index increased with the continuous decrease of the water content of Holly leaves. This was because the cells inside the leaves were dehydrated gradually, when the water content of the leaves decreased gradually, leading to the increase of multiple scattering. Thus, the overall depolarization index of leaves increased as well. 3) The mapping relationship was obtained between the water content and depolarization index as after fitting. The determination coefficient of the fitting curve was 0.95. Then, different parts of Holly leaves were selected to verify the prediction model. The maximum relative error between the predicted water content and the actual was 4.56%. The polarized light imaging was achieved in the high contrast, strong background noise suppression, and more information, compared with the current commonly used image detection. Furthermore, the cells inside the leaves gradually perished in the process of continuous water loss of Holly leaves, leading to the increase in the multiple scattering of light into the leaves and the increase of depolarization index. Therefore, the depolarization index can be used as an important parameter to identify the early changes in the water content of plants and crops. This finding can provide new insight for the early identification of the water changes in plants and crops. A theoretical basis can also be proved for the rapid nondestructive testing of physiological states, such as salt, acid, and fertilizer stress. Therefore, the integration degree of the system can be optimized to improve the portability of the system in the future. The wave plate can also be replaced with the liquid crystal phase retarder to improve the speed and accuracy of image acquisition. The sample database can be established to constantly optimize the improved model for better accuracy of prediction. [ABSTRACT FROM AUTHOR]

In order to investigate the influence of parameter variation and three‑dimensional effect on the interaction between conical shock wave and plate boundary layer， Menter‑SST two‑equation turbulence model is used to simulate the interaction between three‑dimensional conical shock wave and plate boundary layer in a supersonic Mach 2 flow， and the results are analyzed qualitatively and quantitatively. The influence caused by the change of shock‑wave generator’s half‑cone angle and Reynolds number on the flow in the interference region is studied， and the variation rules of flow separation caused by parameter variation are summarized. Moreover， the two‑dimensional cases which are equivalent to the incident shock wave on the central symmetry plane in corresponding three‑dimensional cases are also calculated， and the results are compared with the three‑dimensional cases. The comparison shows that the interference between conical shock wave and plate boundary layer is obviously different from that of two‑dimensional cases in terms of wall pressure coefficient， separation vortex， vorticity distribution and so on. [ABSTRACT FROM AUTHOR]

Objectives: The Tonga volcano erupted violently on January 15th, 2022, which produced atmospheric gravity waves affecting around the world, and was clearly recorded by all ground strain observation stations in Chinese mainland with the distance from 8-736 km to 12-758 km. Methods: The wavelet analysis method is applied to systematically analyze the spatial-temporal response and frequency characteristics of the data recorded by nearly 200 ground strain observations in China. Results: The results show that the duration of change is about 1.5 hours, in which the strongest energy change is occurred at the first 40 minutes. The average amplitude of surface strain is about 186x10-10, showing a single pulse as rise and fall change, and the patterns have highly consistency with Lamb wave propagation properties. The average velocity of event propagation is 310 m/s, which is consistent with the propagation velocity of atmospheric gravity waves. Most stations also record the effect of atmospheric gravity wave signals on the surface as they arrive twice around the Earth. Conclusions: It is the first time to record the traces of atmospheric gravity waves acting on the surface through a large scale high-precision ground strain meters and it is helpful to understand the mechanism of interaction between crustal movement and atmospheric sphere. [ABSTRACT FROM AUTHOR]

In Lamb wave damage imaging of complicated aircraft structures, the signal wave packets can be easily elongated and deformed due to the dispersion of Lamb wave. The signal resolution is then degraded and the final damage imaging results could be affected. Lamb wave dispersion compensation has become an issue needing to be resolved immediately. However, the traditional dispersion compensation methods usually require the theoretically-calculated dispersion curves of Lamb waves and are hard to be applied in complicated aircraft structures. In this paper, with in-situ measured relative wavenumber curves, the compensation process of linearly-dispersive signal construction (LDSC) is performed to solve the difficult problem of dispersion removal of Lamb waves in complicated aircraft structures. Hereafter, LDSC is used in delay-and-sum imaging to realize high resolution damage imaging, during which the quasi-wideband excitation waveform of 1.5-cycle sine burst is introduced to reduce the influence of complicated aircraft structures. Finally, the proposed methods are verified by the experiment on the actual complicated aircraft beam. [ABSTRACT FROM AUTHOR]

A nonlinear ultrasonic test system is established to meet the needs of evaluating the interface bond quality of composite structure. Epoxy resin is chosen as adhesive to make three sets of specimens which are made up of synthetic glass/adhesive/steel so as to simulate the different bond strengths with three different rations of epoxy resin to curing agent. For the problem of the complexity to determine the mode of lamb using lamb wave approach and the situation of that bond states cant not be evaluated based on second harmonic exciting efficiency using pulse-echo ultrasonic techniques, a method is developed, in which the specimen is excited by a single-frequency ultrasound, and A2/A1², (the ratio of second harmonic A2 to fundamental wave A1²) is used to characterize the degree of nonlinear ultrasonic response. The experimental results indicate that the interface bond quality reduces with the increase in the degree of nonlinearity, and thus it can effectively evaluate the interface bond quality. [ABSTRACT FROM AUTHOR]

Dispersion equation of Lamb wave in underwater elastic plate coated with viscoelastic damping layers is derived, and the phase velocity and attenuation coefficient of Lamb wave propagating in the submerged composite plate at different frequency-thickness products are obtained under the condition of certain elastic modulus. The phase velocities and attenuation coefficients of the first two Lamb wave modes propagating in the composite plate at certain frequency-thickness product are measured by the echo measurement experiment of submerged elastic plate coated with viscoelastic damping layers, the elastic modulus of viscoelastic material is then inversed by substituting the experimental results into the dispersion e-quation. The results show that the phase velocity and attenuation coefficient of composite plate, and the inversed elastic modulus of viscoelastic material coincide with the theoretical values well, error in experiment less than four percent, it's proved to be feasible to inverse elastic modulus of viscoelastic material based on genetic algorithm and echo characteristic. [ABSTRACT FROM AUTHOR]

To further increase the computational efficiency of the time domain spectral finite element method for modeling Lamb wave propagation in plate-like structures, a novel Z-D spectral plate element is proposed which can model the 3-D behavior of Lamb wave propagations. The nodal distribution of the element possesses Lebesgue optimal property and the extended displacement field is adopted in the formulations. Each node has 6 degrees of freedom. The diagonal mass matrix is obtained by using a simple method, equivalent to the row summation of a consistent mass matrix. Results reveal that the proposed spectral plate element has similar behavior as the two widely used spectral elements. Moreover, its computational efficiency is raised due to smaller effort in formulation of the mass matrix, larger critical time step and the ability to model the 3-D behavior of Lamb wave propagation in plates. [ABSTRACT FROM AUTHOR]

Based on Timoshenko beam theory, dispersion relation of Lamb wave in composite laminated beam with different plies is analyzed. Wave reflection and transmission are studied at the joint of a non-uniform composite laminated beam and at the tip of the delamination in a composite laminated beam containing semi-infinite delamination. It is found that Lamb wave modes are coupled with and converted to each other in composite laminated beams. Based upon time-reversion theory, Stokes relations between reflection and transmission in the above two models are proposed. Compared with the method in the reference, wave propagation in a beam structure by simulation verifies the proposed theory resolution. [ABSTRACT FROM AUTHOR]