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11.
In this study, ultrasonic backscattering signals in cancellous bones were obtained by finite difference time domain (FDTD) simulations, and the effect of trabecular material properties on these signals was analyzed. The backscatter coefficient (BSC) and integrated backscatter coefficient (IBC) were numerically investigated for varying trabecular bone material properties, including density, Lame coefficients, viscosities, and resistance coefficients. The results show that the BSC is a complex function of trabecular bone density, and the IBC increases as density increases. The BSC and IBC increase with the first and second Lame coefficients. While not very sensitive to the second viscosity of the trabeculae, the BSC and IBC decrease as the first viscosity and resistance coefficients increase. The results demonstrate that, in addition to bone mineral density (BMD) and microarchitecture, trabecular material properties significantly influence ultrasonic backseattering signals in cancellous bones. This research furthers the understanding of ultrasonic backscattering in cancellous bones and the characterization of cancellous bone status. 相似文献
12.
In this study, a coupled-channel (CC) analysis of the elastic and the inelastic scattering of 20.4 MeV polarized protons from
a 64Zn target leading to the deformed 2 + , 3 −, 22+2_2^+ states was performed. The CC potential parameters and the deformation parameters of the excited states corresponding to the
best fit to the experimental differential cross-sections and the analysing powers data were determined. For 22+2_2^+ excited state, a mixed type was used and a good fit to the data was provided. The CC calculation results were compared to
the pure distorted wave Born approximation (DWBA) calculation results which were calculated using the new parameters. All
calculations were conducted using the computer code ECIS06. 相似文献
13.
基于时频分布的盲信号分离方法研究长骨中的多模式导波信号 总被引:2,自引:0,他引:2
由于超声导波对长骨皮质骨的材料特性及厚度变化非常敏感,因此用导波评价长骨状况的研究已成为近年来的一个研究热点。在接收到的导波中,往往多种模式混叠在一起,使得进一步求取每种导波模式的群速度等与骨质状况密切相关的参数时遇到困难。本文采用基于时频分布的盲信号分离(TFBSS)方法对长骨中混叠的多模式进行分离,然后对分离后的单一导波模式求取群速度。研究结果表明TFBSS方法能够准确的分离出混叠的多模式导波,且实验测量的群速度与其理论值吻合。利用导波的群速度就可以得到长骨皮质骨的厚度,这对诊断其骨质状况具有重要意义。 相似文献
14.
15.
Recently, the notion of an S-metric space is defined and extensively studied as a generalization of a metric space. In this paper, we define the notion of the S∞-space and prove its completeness. We obtain a new generalization of the classical "Picard Theorem". 相似文献
16.
17.
Single pulse excited ultrasonic guided wave surfers high attenuation during the propagation in long bones.This results in small amplitude and low signal-to-noise ratio(SNR)of measured signals.Thus,the Barker code excitation is introduced into long bone detection to improve the quality of received signals,due to its efficiency in increasing amplitude and SNR.Both simulation and in vitro experiment were performed,and the results were decoded by the weighted match filter(WMF) and the finite impulse response- least squares inverse filter(FIRLSIF),respectively.The comparison between the results of Barker code excitation and sine pulse excitation was presented.For 13-bit Barker code excitation,WMF produced 13 times larger amplitude than sine pulse excitation,while FIR-LSIF achieved higher peak-sidelobe-level(PSL) of —63.59 dB and better performance in noise suppression.The results show that the Barker code excited guided waves have the potential to be applied to the long bone detection. 相似文献
18.
YANG Baiding TA De''an WANG Weiqi 《声学学报:英文版》2011,30(3):241-252
Ultrasonic backscatter signals from the cancellous bone can be used to diagnose osteoporosis effectively due to its ability to provide the information of bone microstructure. Mean trabecular bone spacing(MTBS)is one of the important parameters for characterization of bone microstructure.This paper proposed a MTBS estimating method based on the fundamental frequency estimation,which was applied to backscatter signals from simulations, and in vitro bovine trabeculae.The estimated MTBS were compared with those of simplified inverse filter tracking(SIFT)algorithm and autoregressive(AR)cepstrum method.The results demonstrated that the proposed method is very robust for the MTBS estimation with more precise estimates and smaller estimated variance in the presence of a small signal-to-noise ratio (SNR),and a large scattering strength ratio of diffuse scatterers to regular ones. 相似文献
19.
骨折长骨中超声导波传播特性的仿真研究 总被引:5,自引:1,他引:4
采用超声导波评价长骨骨折已成为近两年来的一个研究热点.本文采用混合边界元方法(HBEM)对超声导波在骨裂长骨中的传播情况以及各导波模式的反射系数和透射系数进行了数值分析.研究结果表明,入射导波模式经由裂纹处模式转换后依然保持为主要接收模式不变.对某一裂纹,各模式透射系数常在相近的频率点上达到局部峰值.对于不同深宽比(d/w)裂纹,某些模式透射系数曲线局部峰值所对应的频率存在着相互错开的现象,这些结果可用于选择最优入射导波模式和频率,以便更好地定量评价骨质以及骨裂状况. 相似文献
20.
CHEN Wu-Hua ZHOU Yun-Long TA Hong-Gui HU Zhi-Biao ZHANG Zhu-Sen QIU Ze-Hai ZHANG Li ZENG Qing-Xin 《结构化学》2009,28(12)
The title compound 1 has been synthesized by the reaction of H_2MoO_4, CdCl_2, H_3PO_4, KF, piperazine hexahydrate and water in aqueous solution under mild hydrothermal conditions. Single-crystal X-ray analysis reveals that the title compound crystallizes in the triclinic system, space group P(-1) with a = 14.049(3), b = 15.972(3), c = 20.043(4) (A), α = 85.82(3), β = 81.28(3),γ = 67.15(3)°, V= 4095.9(14) (A)~3, M_r = 3204.62, Z=2,D_c = 2.598 g/cm~3,μ = 2.360 mm~(-1), F(000) = 3124, the final R = 0.0314, wR = 0.0826 and S = 0.989 for 18592 observed reflections with I > 2σ(I). The crystal packing is stabilized by N-H…O and O-H…O intra- and intermolecular hydrogen bonds to form an infinite 3D network. 相似文献