EVALUATION OF ACCIDENTS WITH DOMINO EFFECT IN LPG STORAGE AREAS

The term domino effect denotes a chain of accidents, or situations, in which a fire/explosion load generated by an accident in one unit in an industry causes secondary and higher order accidents in other units. Such chains of accidents have a greater propensity to cause damage than stand-alone accidents. Most of the past risk assessment studies deal with accident in a single industry, more so in one of the units of an industry. But, often, accident in one unit causes a secondary accident in a nearby unit, which in turn may trigger a tertiary accident, and so on. The probability of occurrence and adverse impacts of such domino or cascading effects are increasing due to increasing congestion in industrial complexes and increasing density of human population around such complexes. Accidents with domino effect are seldom studied. LPG storage areas could produce the worst possible consequences in the event of an unforeseen incident. This work illustrates the application of models to evaluate the impacts of events with fire and explosion in LPG tanks on other similar units in the park and the possibility of occurrence of a domino effect. The criteria for occurrence of accidents with domino effect adopted in this work were 37.5 kW/m2 in case of fire radiation and an overpressure of 0.7 atm in explosion cases in a receptor body. The spacing between LPG tanks was evaluated. The results show that such spacing is minimal and does not represent, as it should, a parameter indicating a safe distance able to prevent the propagation of an accident with domino effect

Is Urinary Density An Adequate Predictor Of Urinary Osmolality?

Background: Urinary density (UD) has been routinely used for decades as a surrogate marker for urine osmolality (U-osm). We asked if UD can accurately estimate U-osm both in healthy subjects and in different clinical scenarios of kidney disease. Methods: UD was assessed by refractometry. U-osm was measured by freezing point depression in spot urines obtained from healthy volunteers (N = 97) and in 319 inpatients with acute kidney injury (N = 95), primary glomerulophaties (N = 118) or chronic kidney disease (N = 106). Results: UD and U-osm correlated in all groups (p < 0.05). However, a wide range of U-osm values was associated with each UD value. When UD was <= 1.010, 28.4% of samples had U-osm above 350 mOsm/kg. Conversely, in 61.6% of samples with UD above 1.020, U-osm was below 600 mOsm/kg. As expected, U-osm exhibited a strong relationship with serum creatinine (S-creat), whereas a much weaker correlation was found between UD and Screat. Conclusion: We found that UD is not a substitute for U-osm. Although UD was significantly correlated with U-osm, the wide dispersion makes it impossible to use UD as a dependable clinical estimate of U-osm. Evaluation of the renal concentrating ability should be based on direct determination of U-osm.1

Inverting Time-Dependent Harmonic Oscillator Potential by a Unitary Transformation and a New Class of Exactly Solvable Oscillators

A time-dependent unitary (canonical) transformation is found which maps the Hamiltonian for a harmonic oscillator with time-dependent real mass and real frequency to that of a generalized harmonic oscillator with time-dependent real mass and imaginary frequency. The latter may be reduced to an ordinary harmonic oscillator by means of another unitary (canonical) transformation. A simple analysis of the resulting system leads to the identification of a previously unknown class of exactly solvable time-dependent oscillators. Furthermore, it is shown how one can apply these results to establish a canonical equivalence between some real and imaginary frequency oscillators. In particular it is shown that a harmonic oscillator whose frequency is constant and whose mass grows linearly in time is canonically equivalent with an oscillator whose frequency changes from being real to imaginary and vice versa repeatedly.Comment: 7 pages, 1 figure include

Tuning the crystalline electric field and magnetic anisotropy along the CeCuBi2−x_{2-x}Sbx_{x} series

We have performed X-ray powder diffraction, magnetization, electrical resistivity, heat capacity and inelastic neutron scattering (INS) to investigate the physical properties of the intermetallic series of compounds CeCuBi$_{2-x}$Sb$_{x}$. These compounds crystallize in a tetragonal structure with space group $P4/nmm$ and present antiferromagnetic transition temperatures ranging from 3.6 K to 16 K. Remarkably, the magnetization easy axis changes along the series, which is closely related to the variations of the tetragonal crystalline electric field (CEF) parameters. This evolution was analyzed using a mean field model, which included anisotropic nearest-neighbor interactions and the tetragonal CEF Hamiltonian. The CEF parameters were obtained by fitting the magnetic susceptibility data with the constraints given by the INS measurements. Finally, we discuss how this CEF evolution can affect the Kondo physics and the search for a superconducting state in this family.Comment: 7 pages, 6 figures. To be published in Physical Review

The VISCACHA survey -- V. Rejuvenating three faint SMC clusters

We present the analysis of three faint clusters of the Small Magellanic Cloud RZ82, HW42 and RZ158. We employed the SOAR telescope instrument SAM with adaptive optics, allowing us to reach to V~23-24 mag, unprecedentedly, a depth sufficient to measure ages of up to about 10-12Gyr. All three clusters are resolved to their centres, and the resulting colour-magnitude diagrams (CMDs) allow us to derive ages of 3.9, 2.6, and 4.8Gyr respectively. These results are significantly younger than previous determinations (7.1, 5.0, and 8.3Gyr, respectively), based on integrated photometry or shallower CMDs. We rule out older ages for these clusters based on deep photometry and statistical isochrone fitting. We also estimate metallicities for the three clusters of [Fe/H]=-0.68, -0.57 and -0.90, respectively. These updated ages and metallicities are in good agreement with the age-metallicity relation for the bulk of SMC clusters. Total cluster masses ranging from ~7-11x10^3Mo were estimated from integrated flux, consistent with masses estimated for other SMC clusters of similar ages. These results reduce the number of SMC clusters known to be older than about 5 Gyr and highlight the need of deep and spatially resolved photometry to determine accurate ages for older, low-luminosity SMC star clusters.Comment: Accepted for publication as MNRAS letter, 5 pages, 5 figure

Twist-averaged Boundary Conditions in Continuum Quantum Monte Carlo

We develop and test Quantum Monte Carlo algorithms which use a``twist'' or a phase in the wave function for fermions in periodic boundary conditions. For metallic systems, averaging over the twist results in faster convergence to the thermodynamic limit than periodic boundary conditions for properties involving the kinetic energy with the same computational complexity. We determine exponents for the rate of convergence to the thermodynamic limit for the components of the energy of coulomb systems. We show results with twist averaged variational Monte Carlo on free particles, the Stoner model and the electron gas using Hartree-Fock, Slater-Jastrow, three-body and backflow wavefunction. We also discuss the use of twist averaging in the grand canonical ensemble, and numerical methods to accomplish the twist averaging.Comment: 8 figures, 12 page