Generalization of p-Injective Rings and Projective Modules

Any left R-module M is said to be p-injective if for every principal left ideal I of R and any R-homomorphism g: I®M, there exists y ÎM such that  for all b in I.  We find that RM is p-injective iff for each rÎR, xÎM if xÏrM then there exists cÎR with cr = 0 and cx ¹0.  A ring R is said to be epp-ring if every projective R-module is p-injective.  Any ring R is right epp-ring iff the trace of projective right R-module on itself is p-injective.  A left epp-ring which is not right epp-ring has been constructed. Key words: P-injective, epp-ring, f-injective, Artinian, Noetherian. Subject Classification code: 16D40, 16D50, 16P20

Excitations of a Bose-condensed gas in anisotropic traps

We investigate the zero-temperature collective excitations of a Bose-condensed atomic gas in anisotropic parabolic traps. The condensate density is determined by solving the Gross-Pitaevskii (GP) equation using a spherical harmonic expansion. The GP eigenfunctions are then used to solve the Bogoliubov equations to obtain the collective excitation frequencies and mode densities. The frequencies of the various modes, classified by their parity and the axial angular momentum quantum number, m, are mapped out as a function of the axial anisotropy. Specific emphasis is placed upon the evolution of these modes from the modes in the limit of an isotropic trap.Comment: 7 pages Revtex, 9 Postscript figure

Mean field effects in a trapped classical gas

In this article, we investigate mean field effects for a bosonic gas harmonically trapped above the transition temperature in the collisionless regime. We point out that those effects can play also a role in low dimensional system. Our treatment relies on the Boltzmann equation with the inclusion of the mean field term. The equilibrium state is first discussed. The dispersion relation for collective oscillations (monopole, quadrupole, dipole modes) is then derived. In particular, our treatment gives the frequency of the monopole mode in an isotropic and harmonic trap in the presence of mean field in all dimensions.Comment: 4 pages, no figure submitted to Phys. Rev.

Comparison of porcine brain mechanical properties to potential tissue simulant materials in quasi-static and sinusoidal compression

The final publication is available at Elsevier via https://doi.org/10.1016/j.jbiomech.2019.05.033. © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/In both finite element and physical surrogate models of head blast injury, accurate material properties of the brain and/or tissue simulants are necessary to ensure biofidelity in predicted response. Thus, there is a need for experimental comparisons between tissue and simulant materials under the same experimental conditions. This study compares the response of porcine brain tissue and a variety of brain tissue simulants in quasi-static and sinusoidal compression tests. Fresh porcine brain tissue was obtained from a local abattoir and tested within 4 h post mortem. Additionally, the effect of post mortem time was investigated by comparing samples stored at room temperature and stored frozen (−18 °C), at various time intervals. The brain tissue simulants tested were bovine gelatin (3%, 5%, and 10% concentration), agarose gelatin (e0.4%, 0.6%, 0.8% concentration), and Sylgard 527. The experiments were performed using a DMA apparatus (TA Instruments Q800). The quasi-static compression data were fit to Ogden hyperelastic functions so that parameters could be compared. It was found that bovine gelatin at 3% and 5% concentration demonstrated the closest response to brain tissue in quasi-static compression. Conversely, in sinusoidal compression, the agarose gel and Sylgard 527 were found to be in closer agreement with the tissue, than bovine gel. In terms of post mortem time and storage, there was no statistically significant difference detected in the response of tissue samples after 48 h, regardless of storage method. However, samples stored at room temperature after 48 h appeared to demonstrate a reduction in stiffness.The authors would like to acknowledge DRDC Suffield, and the Natural Sciences and Engineering Research Council (NSERC) of Canada for their financial and technical contributions that made this work possible

Component-wise exergy analysis using adaptive neuro-fuzzy inference system in vapor compression refrigeration system

In this work, the adaptive neuro-fuzzy inference (ANFIS) system as an artificial intelligence method was used to predict the destruction of exergy in components (compressor, condenser, capillary tube and evaporator) of a vapor compression refrigeration system using a mixture of R134a and LPG refrigerant (consisting of R134a and LPG in a ratio of 28:72 by mass fraction). For this purpose, ANFIS models were developed to predict the destruction of exergy in each component using some experimental data recently published in author previous publication, and the remaining data were used to validate the developed models. It was found that the predictions of ANFIS models are in good agreement with the experimental results and give an absolute fraction of variance in range of 0.996–0.999, a root mean square error in range of 0.0296–0.1726 W and mean absolute percentage error in range of 0.108– 0.176%, respectively. The results suggest that the ANFIS models can predict the destruction of exergy in the components of refrigeration system quickly and with high accuracy

Exergy analysis of vapor compression refrigeration system using R450A as a replacement of R134a

This paper experimentally investigated exergetic performance analysis of vapor compression refrigeration system using R450a as a replacement for R134a at different evaporator and condenser temperatures within controlled environmental conditions. The exergetic performance analysis of the vapor compression refrigeration system with test parameters including efficiency defects in the components, total irreversibility, and exergy efficiency of the refrigeration system was performed. Findings showed that the total irreversibility and exergy efficiency of the vapor compression refrigeration system using R450A refrigerant were lower and higher than R134a by about 15.25–27.32% and 10.07–130.93%, respectively. However, the efficiency defect in the condenser, compressor, and evaporator of the R450A refrigeration system was lower than R134a by about 16.99–26.08%, 5.03–20.11%, and 1.85– 15.85%, respectively. Conversely, efficiency defect in the capillary tube of the R450A refrigeration system was higher than R134a by about 14.66–78.97% under similar operating conditions. Overall, it was found that the most efficient component was the evaporator, and the least efficient component was the compressor for both refrigerants

Two-hole bound states in modified t-J model

We consider modified $t-J$ model with minimum of single-hole dispersion at the points $(0,\pm \pi)$, $(\pm \pi,0)$. It is shown that two holes on antiferromagnetic background produce a bound state which properties strongly differs from the states known in the unmodified $t-J$ model. The bound state is d-wave, it has four nodes on the face of the magnetic Brillouin zone. However, in the coordinate representation it looks like as usual s-wave.Comment: LaTeX 9 page

Multiagent cooperation for solving global optimization problems: an extendible framework with example cooperation strategies

This paper proposes the use of multiagent cooperation for solving global optimization problems through the introduction of a new multiagent environment, MANGO. The strength of the environment lays in itsflexible structure based on communicating software agents that attempt to solve a problem cooperatively. This structure allows the execution of a wide range of global optimization algorithms described as a set of interacting operations. At one extreme, MANGO welcomes an individual non-cooperating agent, which is basically the traditional way of solving a global optimization problem. At the other extreme, autonomous agents existing in the environment cooperate as they see fit during run time. We explain the development and communication tools provided in the environment as well as examples of agent realizations and cooperation scenarios. We also show how the multiagent structure is more effective than having a single nonlinear optimization algorithm with randomly selected initial points

Disordered Bosons: Condensate and Excitations

The disordered Bose Hubbard model is studied numerically within the Bogoliubov approximation. First, the spatially varying condensate wavefunction in the presence of disorder is found by solving a nonlinear Schrodinger equation. Using the Bogoliubov approximation to find the excitations above this condensate, we calculate the condensate fraction, superfluid density, and density of states for a two-dimensional disordered system. These results are compared with experiments done with ${}^4{\rm He}$ adsorbed in porous media.Comment: RevTeX, 26 pages and 10 postscript figures appended (Figure 9 has three separate plots, so 12 postcript files altogether

Elementary excitations of trapped Bose gas in the large-gas-parameter regime

We study the effect of going beyond the Gross-Pitaevskii theory on the frequencies of collective oscillations of a trapped Bose gas in the large gas parameter regime. We go beyond the Gross-Pitaevskii regime by including a higher-order term in the interatomic correlation energy. To calculate the frequencies we employ the sum-rule approach of many-body response theory coupled with a variational method for the determination of ground-state properties. We show that going beyond the Gross-Pitaevskii approximation introduces significant corrections to the collective frequencies of the compressional mode.Comment: 17 pages with 4 figures. To be published in Phys. Rev.