Strength Reduction in Electrical and Elastic Networks

Particular aspects of problems ranging from dielectric breakdown to metal insu- lator transition can be studied using electrical o elastic networks. We present an expression for the mean breakdown strength of such networks.First, we intro- duce a method to evaluate the redistribution of current due to the removal of a finite number of elements from a hyper-cubic network of conducatances.It is used to determine the reduction of breakdown strength due to a fracture of size $\kappa$.Numerical analysis is used to show that the analogous reduction due to random removal of elements from electrical and elastic networks follow a similar form.One possible application, namely the use of bone density as a diagnostic tools for osteorosporosis,is discussed.Comment: one compressed file includes: 9 PostScrpt figures and a text fil

Finite-size Effects in a Two-Dimensional Electron Gas with Rashba Spin-Orbit Interaction

Within the Kubo formalism, we estimate the spin-Hall conductivity in a two-dimensional electron gas with Rashba spin-orbit interaction and study its variation as a function of disorder strength and system size. The numerical algorithm employed in the calculation is based on the direct numerical integration of the time-dependent Schrodinger equation in a spin-dependent variant of the particle source method. We find that the spin-precession length, L_s controlled by the strength of the Rashba coupling, establishes the critical lengthscale that marks the significant reduction of the spin-Hall conductivity in bulk systems. In contrast, the electron mean free path, inversely proportional to the strength of disorder, appears to have only a minor effect.Comment: 5 pages, 3 figure

Optimization and analysis of cutting parameters using cryogenic media in machining of high strength alloy steel

In this research, liquid Argon is used as a cryogenic media to optimize the cutting parameters for evaluation of tool flank wear width of Tungsten Carbide Insert (CNMG 120404-WF 4215) while turning high strength alloy steel. Robust design concept of Taguchi L9 (34) method is applied to determine the optimum conditions. This analysis revealed is revealed that cryogenic impact is more significant in reduction of the tool flank wear

Magnetic torque oscillations from warped helical surface states in topological insulators

A magnetic torque method is proposed that probes the warping and mass gap of Dirac cone surface states in topological insulators like Bi2X3 (X=Se,Te). A rotating field parallel to the surface induces a paramagnetic moment in the helical surface states for nonzero warping. It is non-collinear with the applied field and therefore produces torque oscillations as function of the field angle which are a direct signature of the surface states. The torque dependence on field strength and angle, the chemical potential and the Dirac cone parameters like warping strength and mass gap is calculated. It is shown that the latter leads to a symmetry reduction in the fourfold torque oscillations.Comment: 6 pages, 4 figure

Labial Reduction Guide for Laminate Veneer Preparation

This article describes a method of fabricating a labial reduction guide for laminate veneer preparations by using a digital tire tread depth gauge and orthodontic wire. The labial reduction guide can help clinicians to achieve accurate reduction of the labial surface. Minimally invasive porcelain laminate veneers have become a popular option in esthetic dentistry. Porcelain laminate veneers require only 25% to 50% of the amount of tooth reduction required for complete coverage restorations.Nevertheless, adequate labial reduction is important in creating optimal esthetics. However, excessive reduction can lead to compromised bond strength due to penetration of the enamel surface. Typically, the appropriate reduction is determined from a diagnostic waxing, and then a silicone index or thermoplastic matrix is made to guide preparation. Verifying the amount of reduction during tooth preparation from the guide can be problematic because the range of labial reduction for laminate veneers is small (0.3 to 0.9 mm). Freehand labial reduction can result in insufficient tooth removal.The purpose of this article was to describe the fabrication and use of a labial reduction guide (LRG) for laminate veneers

Advanced sheet metal forming

Weight reduction of vehicles can be achieved by using high strength steels or aluminum. The formability of aluminum can be improved by applying the forming process at elevated temperatures. A thermo-mechanically coupled material model and shell element is developed to accurately simulate the forming process at elevated temperatures. The use of high strength steels enlarges the risk of wrinkling. Wrinkling indicators are developed which are used to drive a local mesh refinement procedure to be able to properly capture wrinkling. Besides, to intensify the use of implicit finite element codes for solving large-scale problems, a method is developed which decreases the computational time of implicit codes by factors. The method is based on introducing inertia effects into the implicit finite element code. It is concluded that the computation time is decreased by a factor 5-10 for large-scale problems

Local dielectric spectroscopy of near-surface glassy polymer dynamics

A non-contact scanning-probe-microscopy method was used to probe local near-surface dielectric susceptibility and dielectric relaxation in poly-vinyl-acetate (PVAc) near the glass transition. Dielectric spectra were measured from 10-4 Hz to 102 Hz as a function of temperature. The measurements probed a 20 nm thick layer below the free-surface of a bulk film. A small (4 K) reduction in glass transition temperature and moderate narrowing of the distribution of relaxation times was found. In contrast to results for ultra-thin-films confined on or between metallic electrodes, no reduction in the dielectric strength was found, inconsistent with the immobilization of slower modes.Comment: submitte