The accuracy of ultrasonography and 201Tl-99mTc subtraction scan in localization of parathyroid lesions

Pulsed xenon chloride excimer and holmium laser-tissue interaction is primarily based on tissue water vaporization. Consequently, each ablative laser pulse produces a rapidly expanding and imploding vapour bubble in blood or the target tissue. In experimental studies, explosive water vaporization is the major mechanical cause of observed tissue dissections. By reduction of the induced bubble volume, a reduction in experimentally and clinically observed dissections after coronary excimer laser angioplasty is to be expected. This reduction of mechanical damage, however, in combination with efficient and substantial plaque debulking is the major challenge in the development of laser angioplasty.     

Near-field scattering by physical theory of diffraction andshooting and bouncing rays

This paper proposes a method to compute the near-field RCS and Doppler spectrum of a target when the distances to the antennas are comparable to the target size. By dealing with a small piece of the target surface at a time, the transmitting antenna, and the receiving antenna are in the far-field zone of the small piece of the induced currents. The electromagnetic field produced by this small piece of induced currents can be written as a spherical wave. Sum up all spherical waves produced by every small piece of induced currents and we can obtain the total scattered field at the receiving antenna. The physical theory of diffraction (PTD) and the method of shooting and bouncing rays (SBR) are modified to evaluate the received signals. Numerical results based on these techniques are obtained and discussed. The formulation applies the simple concepts of “equivalent” image and vector effective height, which are believed to be novel     

Fast codeword search technique for the encoding of variable-ratevector quantisers

The authors present a fast search algorithm for the encoding of variable-rate vector quantisers (VQs). The optimal encoder for the variable-rate full-search VQs considers both the squared distance and channel index length for the search of codewords. Therefore, the existing fast search algorithms for the fixed-rate full-search VQs might not be able to effectively reduce the computational complexities for the variable-rate VQs. An algorithm is presented which solves this problem using a two-stage search process. A large number of undesired codewords are removed at the first stage of the search with a small computational overhead. At the second stage, the optimal codeword are searched among the remaining codewords using the partial distance search technique in the transform domain. Simulation results show that the algorithm is more effective than other fast search algorithms for the variable-rate VQs     

Reflection and transmission characteristics of single-layerperiodic composite structures for TE case

A periodic surface-integral formulation is proposed to analyze the reflection and transmission characteristics of a single-layer lossy periodic composite structure for the TE case. Theoretically, the equivalence principle, involving unknown electric and magnetic currents over material discontinuity interfaces, the structure periodicity, and the Poisson summation formula are used to reduce the problem to a periodic cell. These surface-integral equations are solved numerically by the method of moments with pulse bases and point matching. In this study, the numerical results such as reflected, transmitted, and dissipated powers for a single-layer graphite/epoxy composite structure with both circular and square fibers are presented for the TE case. The effects of frequency, incident angle, fiber area, fiber conductivity, and embedding dielectric etc. are examined in detail. Convergence study and comparison with the previous published results are also included to confirm the accuracy of the new formulation     

An SBR/image approach for radio wave propagation in indoorenvironments with metallic furniture

In this paper, we propose a deterministic approach to model the radio wave propagation channels in complex indoor environments. This technique applies the modified shooting-and-bouncing-ray (SBR) method to find the equivalent sources (images) for each launched ray tube. In addition, the first-order wedge diffraction from furniture is included and the diffracted rays also can be attributed to the corresponding images. By summing the contributions of all these images coherently, we can obtain the total received field at a receiver. Besides, the vector-effective height (VEH) of an antenna is introduced to consider the polarization coupling effect resulting from multiple reflection inside the rooms. We verify this approach by comparing the numerical results in three canonical examples where closed-form solutions exist. The good agreement indicates that our method can provide a good approximation of high-frequency radio propagation inside rooms where multiple reflection is dominant. Work reported in this paper has shown that the propagation loss in indoor environments varies considerably according to furniture and polarizations     

POST WELD HEAT TREATMENT EFFECTS ON FATIGUE CRACK PROPAGATION IN AN ELECTRON BEAM WELDMENT

This paper studies the effect of two post-weld heat treatment processes on the fatigue behaviour of an electron beam weldment in 9 mm AISI 4130 steel. Electron beam tempering, in a vacuum chamber, immediately after welding and a traditional furnace tempering treatment were compared. Fatigue crack propagation resistance was assessed by a linear elastic fracture mechanics analysis. The resistance to fatigue crack growth was improved with post weld heat treatment due to residual stress relief and the existence of a toughened tempered microstructure. The specimens with an electron beam post-weld heat treatment showed better fatigue properties than those of furnace-treated specimens. An electron beam post-weld heat treatment causes the fatigue crack growth rate to decrease with increasing energy input and decreasing micro-dot-pattern width. For a furnace post-weld heat treatment, the fatigue crack growth rate decreases with increasing tempering temperature.     

A new variational theory for linear field problems and its application to electrostatics

Abstract

A new theory, based on the concept of formally adjoint operator, is proposed to construct a variational formulation for a linear field problem, interior or exterior, with Dirichlet, Neumann, and continuity conditions. When our result is applied to the interface problem, a useful variational expression, which competes with integral equation formulation in its capability of reducing the problem dimensionality, can be obtained. The usefulness of this novel theory is demonstrated through its application to electrostatics. Three examples are also included to confirm its validity.     

Forced Convection of Metallic Foam Heat Sink under Laminar Slot Jet Confined by Parallel Wall

This investigation numerically explores the fluid flow and heat transfer characteristics of the metallic foam heat sink under the laminar slot jet confined by a parallel wall. The Prandtl number is 0.7, and the range of Reynolds numbers is 100–500. The parameters of interest in this work are the porosity (?), pore density (PPI), effective solid conductivity (k _s *), jet nozzle width (W), ratio of the porous sink length to the jet nozzle width (L/W), ratio of the jet-to-sink distance to the jet nozzle width (C/W), and ratio of the porous sink height to the jet nozzle width (H/W). The simulation data reveal that the Nusselt number of the system with a metallic porous heat sink was much better than that of the system without a porous sink, for a given volumetric flow rate and value of (C+H)/W. The porous properties (such as ? and k _s *) and the system configurations (such as L/W and H/W) strongly influenced the cooling performance. The effect of the PPI, W, and C/W values on the heat transfer characteristics of the system was negligible. The effect of the fluid flow on the thermal results was examined. Finally, the correlations of the stagnation Nusselt number and the average Nusselt number were also determined using the numerical data for a system with the size of a common multi-chips module.