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Over the last two decades, spaceborne polarimetric synthetic aperture radar (PolSAR) has been widely used to penetrate sea ice surfaces to achieve fully polarimetric high-resolution imaging at all times of day and in a range of weather conditions. Model-based polarimetric decomposition is a powerful tool used to extract useful physical and geometric information about sea ice from the matrix datasets acquired by PolSAR. The volume scattering of sea ice is usually modeled as the incoherent average of scatterings of a large volume of oriented ellipsoid particles that are uniformly distributed in 3D space. This uniform spatial distribution is often approximated as a uniform orientation distribution (UOD), i.e., the particles are uniformly oriented in all directions. This is achieved in the existing literature by ensuring the canting angle φ and tilt angle τ of particles uniformly distributed in their respective ranges and introducing a factor cos⁡τ in the ensemble average. However, we find this implementation of UOD is not always effective, while a real UOD can be realized by distributing the solid angles of particles uniformly in 3D space. By deriving the total solid angle of the canting-tilt cell spanned by particles and combining the differential relationship between solid angle and Euler angles φ and τ, a complete expression of the joint probability density function pφ,τ that can always ensure the uniform orientation of particles of sea ice is realized. By ensemble integrating the coherency matrix of φ,τ-oriented particle with pφ,τ, a generalized modeling of the volume coherency matrix of 3D uniformly oriented spheroid particles is obtained, which covers factors such as radar observation geometry, particle shape, canting geometry, tilt geometry and transmission effect in a multiplicative way. The existing volume scattering models of sea ice constitute special cases. The performance of the model in the characterization of the volume behaviors was investigated via simulations on a volume of oblate and prolate particles with the differential reflectivity ZDR, polarimetric entropy H and scattering α angle as descriptors. Based on the model, several interesting orientation geometries were also studied, including the aligned orientation, complement tilt geometry and reflection symmetry, among which the complement tilt geometry is specifically highlighted. It involves three volume models that correspond to the horizontal tilt, vertical tilt and random tilt of particles within sea ice, respectively. To match the models to PolSAR data for adaptive decomposition, two selection strategies are provided. One is based on ZDR, and the other is based on the maximum power fitting. The scattering power that reduces the rank of coherency matrix by exactly one without violating the physical realizability condition is obtained to make full use of the polarimetric scattering information. Both the models and decomposition were finally validated on the Gaofen-3 PolSAR data of a young ice area in Prydz Bay, Antarctica. The adaptive decomposition result demonstrates not only the dominant vertical tilt preference of brine inclusions within sea ice, but also the subordinate random tilt preference and non-negligible horizontal tilt preference, which are consistent with the geometric selection mechanism that the c-axes of polycrystallines within sea ice would gradually align with depth. The experiment also indicates that, compared to the strategy based on ZDR, the maximum power fitting is preferable because it is entirely driven by the model and data and is independent of any empirical thresholds. Such soft thresholding enables this strategy to adaptively estimate the negative ZDR offset introduced by the transmission effect, which provides a novel inversion of the refractive index of sea ice based on polarimetric model-based decomposition.

The cladding layer of Ti-6Al-4V alloy was treated by traditional forging and ultrasonic-assisted forging with the self-made forging device. The forged titanium alloy cladding layer was characterize...

Cancer-related systemic inflammation affects many aspects of malignancy. The platelet-to-lymphocyte ratio (PLR), an easily applicable inflammatory marker based on platelet and lymphocyte counts, is associated with the clinical outcome of some cancers. The present study aimed to investigate the prognostic significance of the preoperative PLR in a cohort of colorectal cancer (CRC) patients. A total of 138 patients with CRC were enrolled in this retrospective study. The optimal cutoff value for the PLR was calculated using receiver operating curve (ROC) analysis. The correlation of PLR with the clinicopathological characteristics of patients was explored. Cox proportional hazard analysis was applied to determine the independent prognostic effect of PLR. PLR of 248 yielded the most optimal predictive value for the prognosis of CRC [area under the curve (AUC) = 0.820]. High level of PLR was significantly associated with lymph node and distance metastasis (P

One-dimensional tool ultrasonic vibration system was designed and manufactured, and the influence law of air gap, axis deviation, axis deflection on the coupling coefficient and the transmission efficiency were studied.The influence of the cross-sectional area, air gap and axis deflection angle on the coupling coefficient and transmission efficiency are very obvious, so must be paid special attention in the design and installation.

Carbon/carbon composite is composite material using carbon fiber as reinforcement and carbon as matrix. However, it is the difficult-to-machine material due to some characteristics of the material. The thesis uses ultrasonic milling cutting in order to improve the surface quality. Surface quality becomes better with the improvement of milling speed; surface quality becomes poor with the increases of per tooth feed and cutting depth; Skuincreases after adding ultrasonic, and which explains that the mechanism of ultrasonic milling is different from that of ordinary milling; the increase of Salindicates that surface defects of all kinds reduces in ultrasonic milling and the surface quality is better than that of ordinary milling.

This paper Studied the milling thickness and milling force on two directions ultrasonic vibration assisted milling. X direction ultrasonic vibration assisted milling periodic can generate periodic separation between the tool tip and the workpiece during the cutting process, so the milling force can be reduced, and the effect of the pulse cutting can be produced. Y direction ultrasonic vibration assisted milling can reduce the average cutting force, and milling width can be increased in Y direction ultrasonic vibration assisted milling, so the surface quality can be improved.

Carbon fiber reinforced plastics (CFRP) have been used widely in airplanes, spaceships, automobiles and sport equipment, etc. But the machining is very difficult due to the rigidity of its internal reinforced-phase. In order to settle the difficult machining problem of CFRP, ultrasonic vibration is introduced to common cutting. Through the experiment of common milling and ultrasonic milling of CFRP, the influences of different parameters on milling force are studied. The experimental results shows that the milling forces of ultrasonic milling are significantly lower than common milling using the same milling parameters. The processing vibration of ultrasonic milling is lesser and the process is more stable than the common milling.

This paper proposes to use a method of ultrasonic milling on the composite materials processing, we mainly studies the effect of the length of the tool rod, tool rod diameter on the acoustic resonant frequency, amplitude, to ensure processing quality and improving the tool's vibration effect.

Composite materials have good mechanical properties. In order to solve the difficult process of composite materials, this paper proposes to use a method of ultrasonic milling on the composite materials processing, we mainly studies the effect of the length of the arbor, arbor diameter and arbor end milling platform on the acoustic resonant frequency, amplitude, and anti-resonance frequency. With the decreased in the length of the tool bar, tool bar's resonant frequency increased，and the oscillation amplitude also obviously increased. In the vicinity of 35 KHz amplitude of vibration are largest. Along with tool bar diameter's increasing, the resonant frequency is increases gradually. Milling platform has little effect on the resonant frequency and amplitude.

The machanism of oppositely rotating twin screw conveyer. is analyzed and studied experimentally and theoretically formulating the semiempirical equation of output. Factors affecting the output of twin screw conveyer suchas speed, properties of material, pitch, direction fo rotation, the form of blade and of the openings, etc. are also studied.