Scattering by a Periodic Array of Collinear Cracks

This paper deals with the problem of scattering of an in-plane wave by a periodic array of collinear cracks in an elastic solid. The work is of interest for the detection of cracked zone in both quantitative evaluation of materials and seismology.</p

Features of chromophobe cell renal carcinoma on 3.0T MR imaging

Objective: To analyze the MRI features of chromophobe cell renal carcinoma. Methods: MRI features of 14 cases with histologically proved chromophobe cell renal carcinoma were studied retrospectively. Tumor size, position, borderline, homogeneousness, pseudo capsule, signal intensity, ADC values and enhancement features were evaluated. Results: All 14 cases were unilateral and single disease. In all cases, 64.28% (9/14) were regular in shape; 85.71% (12/14) had clear borderline; 64.28% (9/14) had pseudo capsule. On T1WI, 50.00% (7/14) showed homointensity, on T2WI, 85.71% (12/14) showed hypointesity. For 13 cases with DWI, the mean ADC value of tumor was 1.38×10-3 mm 2/s, the mean ADC value of kidney was 2.34×10 -3mm2/s. On contrast enhanced images, 72.73% (8/11) showed mild enhancement, 72.73% (8/11) showed homogenous enhancement; 5 cases showed spoke-like enhancement, 2 cases showed flowed-out blood vessels in the tumor. Conclusion: Chromophobe cell renal carcinoma has some unique feature on MR imaging which provides posibility to correct diagnosis.link_to_subscribed_fulltex

Economic Development and Agricultural Land Loss in the Pearl River Delta

organized by Department of Geography, Hong Kong Baptist University and Centre of Urban Planning and Environmental Management, University of Hong Kon

Rationale for using nickel-titanium instruments by hand

The NDE of real-life situations is based on elastic (ultrasonic) wave propagation, diffraction and scattering in dissipative inhomogeneous isotropic or anisotropic media. Physical phenomena of elastic waves are described by linear Cauchy’s equation of motion and equation of deformation rate [1, 2]. Interpretation of the very complicated behavior of elastic waves, especially in inhomogeneous anisotropic media, requires powerful computational tools to model and study advanced NDT situations. Such a tool is the well-established Elastodynamic Finite Integration Technique (EFIT) basically formulated by Fellinger [3, 4]. Recently, EFIT has been extented to simulate elastic waves in dissipative (viscoelastic) and homogeneous anisotropic media [5, 6]

Wave Propagation in Discontinuous Media by the Scattering Matrix Method

Propagation of elastic waves in discontinuous media is studied in this paper by the scattering matrix method (SMM). An electromagnetic transmission line analogy is also used to set up the mathematical model. The SMM operates in the frequency domain and allows for all wave polarizations (P, SV and SH). Rock masses are examples of discontinuous media in which the discontinuities (fractures or joints) influence wave propagation. Both elastic and viscoelastic joints are considered and the latter are described by Kelvin-Voigt, Maxwell and Burgers models. Rock joints with Coulomb slip behavior are also analyzed, by applying the averaging principle of Caughy (J Appl Mech 27:640-643, 1960). The evaluation of the effects of periodic discontinuities in a homogeneous medium is presented by introducing the concept of Bloch waves. The dispersion curves of these waves are useful to explain the existence of frequency bands of strong attenuation, also in the case of lossless (perfectly elastic) structures. Simple expressions of transmission and reflection coefficients are obtained. Finally, the SMM results are compared with those computed via the distinct element method (DEM). The comparisons are performed on a medium with joints with Coulomb slip behavior and the agreement is satisfactory, although the SMM must be applied in conjunction with the equivalent linearization technique. Even if the DEM is much more general, the SMM in these simple cases is extremely faster and provides a higher physical insigh