Flow tracing fidelity of scattering aerosol in laser Doppler velocimetry

An experimental method for determinating the flow tracing fidelity of a scattering aerosol used in laser Doppler velocimeters was developed with particular reference to the subsonic turbulence measurements. The method employs the measurement of the dynamic response of a flow seeding aerosol excited by acoustic waves. The amplitude and frequency of excitation were controlled to simulate the corresponding values of fluid turbulence components. Experimental results are presented on the dynamic response of aerosols over the size range from 0.1 to 2.0 microns in diameter and over the frequency range 100 Hz to 100 kHz. It was observed that unit density spherical scatterers with diameters of 0.2 microns followed subsonic air turbulence frequency components up to 100 kHz with 98 percent fidelity

Temporal evolution of mesoscopic structure of some non-Euclidean systems using a Monte Carlo model

A Monte Carlo based computer model is presented to comprehend the contrasting observations of Mazumder et al. [Phys. Rev. Lett. 93, 255704 (2004) and Phys. Rev. B 72, 224208 (2005)], based on neutron-scattering measurements, on temporal evolution of effective fractal dimension and characteristic length for hydration of cement with light and heavy water. In this context, a theoretical model is also proposed to elucidate the same.Comment: 31 Pages, 13 Figure

An effectual template bank for the detection of gravitational waves from inspiralling compact binaries with generic spins

We report the construction of a three-dimensional template bank for the search for gravitational waves from inspiralling binaries consisting of spinning compact objects. The parameter space consists of two dimensions describing the mass parameters and one "reduced-spin" parameter, which describes the secular (non-precessing) spin effects in the waveform. The template placement is based on an efficient stochastic algorithm and makes use of the semi-analytical computation of a metric in the parameter space. We demonstrate that for "low-mass" ($m_1 + m_2 \lesssim 12\,M_\odot$) binaries, this template bank achieves effective fitting factors $\sim0.92$--$0.99$ towards signals from generic spinning binaries in the advanced detector era over the entire parameter space of interest (including binary neutron stars, binary black holes, and black hole-neutron star binaries). This provides a powerful and viable method for searching for gravitational waves from generic spinning low-mass compact binaries. Under the assumption that spin magnitudes of black-holes [neutron-stars] are uniformly distributed between 0--0.98 [0 -- 0.4] and spin angles are isotropically distributed, the expected improvement in the average detection volume (at a fixed signal-to-noise-ratio threshold) of a search using this reduced-spin bank is $\sim20-52\%$, as compared to a search using a non-spinning bank.Comment: Minor changes, version appeared in Phys. Rev.

A comparative analysis of the wear characteristics of glazes generated on the ordinary Portland cement surface of concrete by means of CO2 and high power diode laser radiation

The wear characteristics of a glaze generated on the ordinary Portland cement (OPC) surface of concrete using a 2 kW high power diode laser (HPDL) and a 3 kW CO2 laser have been determined. Within both normal and corrosive environmental conditions, the wear rate of the CO2 and HPDL generated glazes were consistently higher than the untreated OPC surface of concrete. Life assessment testing revealed that surface glazing of the OPC with both the CO2 and the HPDL effected an increase in wear life of 1.3 to 17.7 times over an untreated OPC surface, depending upon the corrosive environment. The reasons for these marked improvements in the wear resistance and wear life of the CO2 and HPDL generated glazes over the untreated OPC surface of concrete can be attributed to the partial (CO2 laser) and full (HPDL) vitrification of the OPC surface after laser treatment which subsequently created a much more dense and consolidated surface with improved microstructure and phase characteristics which is more resistant in corrosive environments. In addition, the wear life and the wear rate of the HPDL glaze was found to be consistently higher than that of the CO2 laser glaze. This is due to the fact that CO2 and HPDLs have very different wavelengths; consequently, differences exist between the CO2 and HPDL beam absorption characteristics of the OPC. Such differences give rise to different cooling rates, solidification speeds, etc and are, therefore, the cause of the distinct glaze characteristics which furnishing each microstructure with its own unique wear resistance characteristics

Numerical simulation of heat transfer and fluid flow in coaxial laser cladding process for direct metal deposition

The coaxial laser cladding process is the heart of direct metal deposition (DMD). Rapid materials processing, such as DMD, is steadily becoming a tool for synthesis of materials, as well as rapid manufacturing. Mathematical models to develop the fundamental understanding of the physical phenomena associated with the coaxial laser cladding process are essential to further develop the science base. A three-dimensional transient model was developed for a coaxial powder injection laser cladding process. Physical phenomena including heat transfer, melting and solidification phase changes, mass addition, and fluid flow in the melt pool, were modeled in a self-consistent manner. Interactions between the laser beam and the coaxial powder flow, including the attenuation of beam intensity and temperature rise of powder particles before reaching the melt pool were modeled with a simple heat balance equation. The level-set method was implemented to track the free surface movement of the melt pool, in a continuous laser cladding process. The governing equations were discretized using the finite volume approach. Temperature and fluid velocity were solved for in a coupled manner. Simulation results such as the melt pool width and length, and the height of solidified cladding track were compared with experimental results and found to be reasonably matched.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87766/2/024903_1.pd

Symmetric and anti-symmetric Landau parameters and magnetic properties of dense quark matter

We calculate the dimensionless Fermi liquid parameters (FLPs), $F_{0,1}^{sym}$ and $F_{0,1}^{asym}$, for spin asymmetric dense quark matter. In general, the FLPs are infrared divergent due to the exchange of massless gluons. To remove such divergences, the Hard Density Loop (HDL) corrected gluon propagator is used. The FLPs so determined are then invoked to calculate magnetic properties such as magnetization $\langle M\rangle$ and magnetic susceptibility $\chi_M$ of spin polarized quark matter. Finally, we investigate the possibility of magnetic instability by studying the density dependence of $\langle M\rangle$ and $\chi_M$.Comment: 14 pages, 5 figures, abstract and introduction modifified. Published in Phys. Rev. C. 81, 054906 (2010

Surface glazing of concrete using a 2.5 kW high power diode laser and the effects of large beam geometry

Interaction of a 2.5 kW high power diode laser (HPDL) beam with the ordinary Portland cement (OPC) surface of concrete has been investigated, resulting in the generation of a tough, inexpensive amorphous glaze. Life assessment testing revealed that the OPC glaze had an increase in wear life of 1.3 to 14.8 times over an untreated OPC surface, depending upon the corrosive environment. Also, variations in the width of the HPDL beam were seen to have a considerable affect on the melt depth. Furthermore, the maximum coverage rate that it may be possible to achieve using the HPDL was calculated as being 1.94 m2/h. It is a distinct possibility that the economic and material benefits to be gained from the deployment of such an effective and efficient large area coating on OPC could be significant

Energy and momentum relaxation of heavy fermion in dense and warm plasma

We determine the drag and the momentum diffusion coefficients of heavy fermion in dense plasma. It is seen that in degenerate matter drag coefficient at the leading order mediated by transverse photon is proportional to $(E-\mu)^2$ while for the longitudinal exchange this goes as $(E-\mu)^3$. We also calculate the longitudinal diffusion coefficient to obtain the Einstein relation in a relativistic degenerate plasma. Finally, finite temperature corrections are included both for the drag and the diffusion coefficients.Comment: 8 pages, 1 eps figure, typos corrected and paragraphs rearranged. Accepted for publication in Physical Review

Control of the wetting properties of an AISI 316L stainless steel surface by femtosecond laser-induced surface modification

A simple and effective method without vacuum to control the wetting properties of AISI 316L stainless steel using femtosecond laser pulses at high repetition rate has been developed. Both hydrophilic and hydrophobic surfaces were formed by creating micro-conical structures on the surface with femtosecond laser irradiation in air. The scan speed was found to be an effective parameter in controlling micro-cone morphology, size and number densities and contact angles during surface wettability experiments. It was found during surface wettability experiments that the contact angle of water varied from 0° (superhydrophilic) to 113° on laser micro-cone textured surfaces depending on processing conditions. Additionally, a superhydrophobic AISI 316L stainless steel surface was created (contact angle ∼150°) with a functionalized silane coating on already hydrophobic surface geometry.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98609/1/0960-1317_22_10_105019.pd