Comparative Analysis Of CO2 Cycle Enhancements: Ejector Vs. Vapor Injection

In the recent years, Transcritical CO2 refrigeration is gaining popularity. However, operation above critical point at higher ambient temperatures results in significant reduction of CO2 refrigeration cycle efficiency. Vapor injection and ejector are probably the mostly widely applied transcricial cycle enhancement options. The proposed paper includes a description of a simple transcritical one dimensional model of an ejector, based on real gas properties (accessible through Refprop), as well as integration of this model in a refrigeration cycle. Vapor injection cycle is analyzed based on compressor performance and its ability to digest vapor injection stream. An enhancement of traditional compressor performance approximation, enabling to include the vapor injection stream, is presented and vapor injection cycle is analyzed based on that compressor model. Comparison of CO2 cycle performance between two outlined methods at different operation conditions is presented

Spin-Statistics Violations in Superstring Theory

I describe how superstring theory may violate spin-statistics in an experimentally observable manner. Reviewing the basics of superstring interactions and how to utilize these to produce a statistical phase, I then apply these ideas to two specific examples. The first is the case of heterotic worldsheet linkings, whereby one small closed string momentarily enlarges sufficiently to pass over another, producing such a statistical phase. The second is the braneworld model with noncommutative geometry, whereby matter composed of open strings may couple to a background in which spacetime coordinates do not commute, modifying the field (anti)commutator algebra. I conclude with ways to sharpen and experimentally test these exciting avenues to possibly verify superstring theory.Comment: 18 pages, 3 figures; v2: references added and typos correcte

Is violation of Newton's second law possible?

Astrophysical observations (usually explained by dark matter) suggest that classical mechanics could break down when the acceleration becomes extremely small (the approach known as modified Newtonian dynamics, or MOND). I present the first analysis of MOND manifestations in terrestrial (rather than astrophysical) settings. A new effect is reported: around each equinox date, 2 spots emerge on the Earth where static bodies experience spontaneous acceleration due to the possible violation of Newton's second law. Preliminary estimates indicate that an experimental search for this effect can be feasible.Comment: 10 pages; minor changes to match the published versio

Gravitational wave background from coalescing compact stars in eccentric orbits

Stochastic gravitational wave background produced by a stationary coalescing population of binary neutron stars in the Galaxy is calculated. This background is found to constitute a confusion limit within the LISA frequency band up to a limiting frequency \NUlim{}\sim 10^{-3} Hz, leaving the frequency window $\sim 10^{-3}$--$10^{-2}$ Hz open for the potential detection of cosmological stochastic gravitational waves and of signals involving massive black holes out to cosmological distances.Comment: 6 pages, 7 figure

Lunar Superconducting Magnetic Energy Storage (LSMES)

Superconducting Magnetic Energy Storage (SMES) is an energy storage system that stores electrical energy in the form of a magnetic field by passing direct current through a superconducting coil. The conductor for carrying the current operates at cryogenic temperatures where it becomes a superconductor and thus has virtually no resistive losses as it produces the magnetic field. [1]. The energy can be stored in a persistent mode until required [2]. The main terrestrial challenge for SMES is the need for a cryo-cooling system and the cost associated with its deployment, operation and maintenance. For lunar and planetary exploration, this challenge is totally mitigated using the cold environment of the mission to sustain superconductivity temperatures. The permanently shadowed craters on the moon have regolith temperatures between 50-60K (3), which is the operating temperature for High Temperature Superconducting (HTS) wire. SMES provides several ad-vantages over traditional chemical batteries that: 1) incur much energy loss in extremely cold environments due to power needed for heaters, 2) are inefficient due to their inherent redox and side reactions, and 3) fail over time due to charge/discharge cycling changes in their chemical processes

Evidance for an Oxygen Diffusion Model for the Electric Pulse Induced Resistance Change Effect in Oxides

Electric pulse induced resistance (EPIR) switching hysteresis loops for Pr0.7Ca0.7MnO3 (PCMO) perovskite oxide films were found to exhibit an additional sharp "shuttle peak" around the negative pulse maximum for films deposited in an oxygen deficient ambient. The device resistance hysteresis loop consists of stable high resistance and low resistance states, and transition regions between them. The resistance relaxation of the "shuttle peak" and its temperature behavior as well as the resistance relaxation in the transition regions were studied, and indicate that the resistance switching relates to oxygen diffusion with activation energy about 0.4eV. An oxygen diffusion model with the oxygen ions (vacancies) as the active agent is proposed for the non-volatile resistance switching effect in PCMO.Comment: 7 pages, 5 figure

Search for Millicharged Particles at SLAC

Particles with electric charge q < 10^(-3)e and masses in the range 1--100 MeV/c^2 are not excluded by present experiments. An experiment uniquely suited to the production and detection of such "millicharged" particles has been carried out at SLAC. This experiment is sensitive to the infrequent excitation and ionization of matter expected from the passage of such a particle. Analysis of the data rules out a region of mass and charge, establishing, for example, a 95%-confidence upper limit on electric charge of 4.1X10^(-5)e for millicharged particles of mass 1 MeV/c^2 and 5.8X10^(-4)e for mass 100 MeV/c^2.Comment: 4 pages, REVTeX, multicol, 3 figures. Minor typo corrected. Submitted to Physical Review Letter