Shot noise in diffusive ferromagnetic metals

We show that shot noise in a diffusive ferromagnetic wire connected by tunnel contacts to two ferromagnetic electrodes can probe the intrinsic density of states and the extrinsic impurity scattering spin-polarization contributions in the polarization of the wire conductivity. The effect is more pronounced when the electrodes are perfectly polarized in opposite directions. While in this case the shot noise has a weak dependence on the impurity scattering polarization, it is strongly affected by the polarization of the density of states. For a finite spin-flip scattering rate the shot noise increases well above the normal state value and can reach the full Poissonian value when the density of states tends to be perfectly polarized. For the parallel configuration we find that the shot noise depends on the relative sign of the intrinsic and the extrinsic polarizations.Comment: 4 pages, 3 figure

Taguchi parametric study on the radial and tangential cutting forces in Dry High Speed Machining (DHSM)

In this paper, L8 Taguchi array is applied to find the most important parameters effects on the radial and tangential cutting forces of a Ti–6Al-4V ELI titanium alloy in dry high speed machining (DHSM). The experiments are performed in four cutting speeds of 150, 200, 250, and 300 m/min and two feed rates of 0.03 and 0.06 mm/rev. Also, two cutting tools in types of XOMX090308TR-ME06 of uncoated (H25) and TiAlN+TiN coated (F40M) are used. Results confirm that to minimize the resultant cutting force and radial cutting force, utilizing the lower feed rate and higher cutting speeds were considered as the best levels of factors to reach to its goal

The study of nano technology utilization in upgrading the quality of construction industry with fire-engineering approach

Today, the first requirement for increasing quality and strength in construction industry is utilization of appropriate and high quality materials so that usage of these materials, in addition to reducing maintenance costs and also upgrading the structure's longevity, in engineering respect through change on weight reduction and increasing strength in used materials, can cause general strength of the structure against earthquakes and probable runs due to natural disasters. This requirement is very significant in passive defense scope and this task will be considered in used material in main structure of a building and also in used materials in its frontage and in terminology elaborate work. Given that one of the effects of fire on the building part and parcel of passive defense, so, this look from the perspective of fire engineering is also of particular significance. Wide studies have been performed in this ground and various factories are trying to increase their produced materials quality in today competitive world with utilization of various technologies. One of technologies considered today is Nano technology which in fact by changing the molecular structure of a material causes creating special properties in it and utilization of these properties can answer needs of producers and users for increasing quality, longevity, strength and weight reduction. In this study, it is tried to introduce materials produced by Nano technology which have special properties like resistance against fire, settlement and weight reduction and increasing resistance in tolerance of strike and injected loads to the structure in defensive point of view in civil engineering scope. Keywords: Nano technology; passive defense; building material

Biosuper as a phosphate fertilizer in a calcareous soil with low available phosphorus

Laboratory assays were conducted to produce phosphorus (P) biofertilizers from rock phosphate (RP), applying sulphur at different rates of 10, 15 and 20% and inoculated with Thiobacillus. A greenhouse experiment was carried out to evaluate the effect of the biofertilizers in a calcareous soil with low available P from the Qazvin plain of “Qazvin State”, grown with corn (Zea mays L.). The treatments were: rock phosphate (RP), biofertilizers produced in laboratory with sulphur and Thiobacillus (Biof1, Biof2 and Biof3), rock phosphate with sulphur (10, 15 and 20%) without Thiobacillus (Nbiof1, Nbiof2 and Nbiof3), Triple Super Phosphate (TSP) and a control without phosphorus. In this experiment, shoot dry matter, total P, Fe and Zn in shoots, and also soil available P, Fe and Zn were determined. Higher rates of measured parameters were obtained from biofertilizers with sulphur and Thiobacillus (Biof) and in Triple Super Phosphate (TSP). Biofertilizers with sulphur and Thiobacillus (Biof) and TSP increased plant parameters significantly compared with control or rock phosphate

Counting flags in triangle-free digraphs

Motivated by the Caccetta-Haggkvist Conjecture, we prove that every digraph on n vertices with minimum outdegree 0.3465n contains an oriented triangle. This improves the bound of 0.3532n of Hamburger, Haxell and Kostochka. The main new tool we use in our proof is the theory of flag algebras developed recently by Razborov.Comment: 19 pages, 7 figures; this is the final version to appear in Combinatoric

Integrality gaps of semidefinite programs for Vertex Cover and relations to ell1_1 embeddability of negative type metrics

We study various SDP formulations for Vertex Cover by adding different constraints to the standard formulation. We rule out approximations better than even when we add the so-called pentagonal inequality constraints to the standard SDP formulation, and thus almost meet the best upper bound known due to Karakostas, of . We further show the surprising fact that by strengthening the SDP with the (intractable) requirement that the metric interpretation of the solution embeds into &#8467;1 with no distortion, we get an exact relaxation (integrality gap is 1), and on the other hand if the solution is arbitrarily close to being &#8467;1 embeddable, the integrality gap is 2&#8201;&#8722;&#8201;o(1). Finally, inspired by the above findings, we use ideas from the integrality gap construction of Charikar to provide a family of simple examples for negative type metrics that cannot be embedded into &#8467;1 with distortion better than 8/7&#8201;&#8722;&#8201;&#949;. To this end we prove a new isoperimetric inequality for the hypercube. </div

Conductance of bilayer graphene in the presence of a magnetic field: Effects of disorder

We investigate the electronic transport properties of unbiased and biased bilayer graphene nanoribbon in n-p and n-n junctions subject to a perpendicular magnetic field. Using the non-equilibrium Green's function method and the Landauer-B\"{u}ttiker formalism, the conductance is studied for the cases of clean, on-site, and edge disordered bilayer graphene. We show that the lowest Hall plateau remains unchanged in the presence of disorder, whereas asymmetry destroys both the plateaus and conductance quantization. In addition, we show that disorder induces an enhancement of the conductance in the n-p region in the presence of magnetic fields. Finally, we show that the equilibration of quantum Hall edge states between distinctively doped regions causes Hall plateaus to appear in the regime of complete mode mixing.Comment: 8 pages, 7 figures. Accepted to Phys. Rev.