The observational evidence pertinent to possible kick mechanisms in neutron stars

We examine available observations on pulsars for evidence pertaining to mechanisms proposed to explain the origin of their velocities. We find that mechanisms predicting a correlation between the rotation axis and the pulsar velocity are ruled out. Also, that there is no significant correlation between pulsar magnetic field strengths and velocities. With respect to recent suggestions postulating asymmetric impulses at birth being solely responsible for both the spins and velocities of pulsars, single impulses of any duration and multiple extended duration impulses appear ruled out.Comment: 7 pages. Accepted for publication in Astronomy & Astrophysic

Safety Instrumented Bypass Management

PresentationProper management of Safety Instrumented Function (SIF) bypasses during process plant operation can be challenging and could compromise process safety if the SIF is bypassed longer than its allowable maximum time interval. Safety bypass procedures are usually written on site to comply with OSHA 1910.119 and IEC61511. However, in practice, safety bypass management can be difficult due to a lack of readily available process safety information, lack of operator awareness and the existence of a production throughput oriented culture. For many operating sites, process safety information (PSI) is only available in Process Hazard Analysis (PHA) reports. Commercial databases are available which display process safety information and make it readily available to operations and maintenance to properly implement and handle safety bypasses. An alternative approach is the creation of an in-house process safety database to provide easily-accessed process safety information. This paper will present a case-study on how TOTAL-Port Arthur Refinery developed and implemented such a system. The paper will include our flow chart for bypass approval, how we perform a bypass risk assessment and how we developed our SIS database. This SIS database has also proven useful for ‘operator training’ on the risks associated with the process unit and the available safeguards to manage those risks

D0 Dimuon Asymmetry in Bs−BˉsB_s - \bar B_s Mixing and Constraints on New Physics

We study the consequences of the large dimuon asymmetry observed at D0. Physics beyond the standard model (SM) in $B_s-\bar B_s$ mixing is required to explain the data. We first present a detailed analysis for model independent constraints on physics beyond the SM, and then study the implications for theoretical models which modify the SM results in different ways, such as $Z'$ with FCNC and R-parity violating SUSY contributions.Comment: RevTex 13 pages, 6 figures. References added. Modified some discussions. Version to appear in PR

Instantaneous Radio Spectra of Giant Pulses from the Crab Pulsar from Decimeter to Decameter Wavelengths

The results of simultaneous multifrequency observations of giant radio pulses from the Crab pulsar, PSR B0531+21, at 23, 111, and 600 MHz are presented and analyzed. Giant pulses were detected at a frequency as low as 23 MHz for the first time. Of the 45 giant pulses detected at 23 MHz, 12 were identified with counterparts observed simultaneously at 600 MHz. Of the 128 giant pulses detected at 111 MHz, 21 were identified with counterparts observed simultaneously at 600 MHz. The spectral indices for the power-law frequency dependence of the giant-pulse energies are from -3.1 to -1.6. The mean spectral index is -2.7 +/- 0.1 and is the same for both frequency combinations (600-111 MHz and 600-23 MHz). The large scatter in the spectral indices of the individual pulses and the large number of unidentified giant pulses suggest that the spectra of the individual giant pulses do not actually follow a simple power law. The observed shapes of the giant pulses at all three frequencies are determined by scattering on interstellar plasma irregularities. The scatter broadening of the pulses and its frequency dependence were determined as tau_sc=20*(f/100)^(-3.5 +/- 0.1) ms, where the frequency f is in MHz.Comment: 13 pages, 1 figure, 1 table (originally published in Russian in Astronomicheskii Zhurnal, 2006, vol. 83, No. 7, pp. 630-637), translated by Georgii Rudnitski

A Separate Higgs?

We investigate the possibility of a multi-Higgs doublet model where the lightest neutral Higgs boson ($h^0$) decouples from the fermion sector. We are partially motivated by the four $\ell^+\ell^-\gamma\gamma$ events with $M_{\gamma\gamma}\simeq60$\,GeV recently observed by the L3 collaboration, which could be a signal for $Z\to (Z^*\to \ell^+\ell^-)+(h^0\to \gamma\gamma)$. Collider signatures for the additional physical Higgs bosons present in such models are discussed.Comment: 8 pages (plus 2 figures, available by request), latex, ANL-HEP-PR-92-10

Radical Artificial Intelligence: A Postmodern Approach

The dynamic response of end-clamped monolithic beams and sandwich beams has been measured by loading the beams at mid-span using metal foam projectiles. The AISI 304 stainless-steel sandwich beams comprise two identical face sheets and either prismatic Y-frame or corrugated cores. The resistance to shock loading is quantified by the permanent transverse deflection at mid-span of the beams as a function of projectile momentum. The prismatic cores are aligned either longitudinally along the beam length or transversely. It is found that the sandwich beams with a longitudinal core orientation have a higher shock resistance than the monolithic beams of equal mass. In contrast, the performance of the sandwich beams with a transverse core orientation is very similar to that of the monolithic beams. Three-dimensional finite element (FE) simulations are in good agreement with the measured responses. The FE calculations indicate that strain concentrations in the sandwich beams occur at joints within the cores and between the core and face sheets; the level of maximum strain is similar for the Y-frame and corrugated core beams for a given value of projectile momentum. The experimental and FE results taken together reveal that Y-frame and corrugated core sandwich beams of equal mass have similar dynamic performances in terms of rear-face deflection, degree of core compression and level of strain within the beam

Gas–liquid flow in stirred reactors: Trailing vortices and gas accumulation behind impeller blades

In a gas–liquid stirred reactor, gas tends to accumulate in low-pressure regions behind the impeller blades. Such gas accumulation significantly alters impeller performance characteristics. We have computationally investigated gas–liquid flow generated by a Rushton (disc) turbine. Rotating Rushton turbine generates trailing vortices behind the blades, which influence the gas accumulation in the impeller region. Characteristics of these trailing vortices were first investigated by considering a model problem of flow over a single impeller blade. Predicted results were compared with the published experimental data. Circulation velocity and turbulent kinetic energy of the trailing vortices were found to scale with blade tip velocity. Several numerical experiments were carried out to understand interaction of gas bubbles and trailing vortices. Gas–liquid flow in stirred vessel was then simulated by extending the computational snapshot approach of Ranade and Dometti (Chem. Engng Res. Des., 74, 476–484, 1996). The approach was able to capture the main features of gas–liquid flow in stirred vessels. The detailed analysis of predicted results with reference to experimental data and the results obtained for flow over a single impeller blade will be useful for extending the scope of computational fluid dynamics (CFD) based tools for engineering gas–liquid stirred reactors

Study of Ge Doped Garnet Type Li7La3Zr2O12 as Solid Electrolyte for Li-ion Battery Application

Li7-4xGexLa3Zr2O12 has been synthesized using the conventional solid-state reaction method by substituting Germanium (Ge) at the Li site, which increases the Li-ion vacancies and leads to an increase in conductivity with x varying from 0.05-0.20. The formation of cubic phase is confirmed by using XRD analysis. The surface morphology and elemental distribution have been studied using SEM characterization which gives the average particle size of the sample. The densities of the samples were calculated. For the confirmation of functional groups present within the sample, IR spectroscopy has been studied. The modulus and ac conductivity studies have also been studied. A complex impedance study has been done in the frequency range 20Hz -20 MHz. Increase in ionic conductivity by one order has been observed in the sample with x=0.10. The minimum value of 0.56 eV activation energy is associated with the highest conductivity value of 7.23 x 10-6 S/cm at room temperature. Thus increment in ionic conductivity at room temperature makes this material a promising solid electrolyte for future sustainable energy storage devices