Satellite appendage tie down cord Patent

Design and construction of satellite appendage tie-down cor

Hierarchical freezing in a lattice model

A certain two-dimensional lattice model with nearest and next-nearest neighbor interactions is known to have a limit-periodic ground state. We show that during a slow quench from the high temperature, disordered phase, the ground state emerges through an infinite sequence of phase transitions. We define appropriate order parameters and show that the transitions are related by renormalizations of the temperature scale. As the temperature is decreased, sublattices with increasingly large lattice constants become ordered. A rapid quench results in glass-like state due to kinetic barriers created by simultaneous freezing on sublattices with different lattice constants.Comment: 6 pages; 5 figures (minor changes, reformatted

Basking behavior of Emydid turtles (Chysemys picta marginata, Graptemys geographica, and Trachemys scripta elegans) in an urban landscape

Basking is common in emydid turtles and is generally accepted to be in thermoregulatory behavior. In 2004, we quantified and described the basking behavior of turtles in the Central Canal of Indianapolis. This canal system runs through an urban landscape that is dominated by fragmented woodlots, residential areas. and commercial areas. We observed that basking turtles exhibited variable basking behavior. with spatial and temporal shins in basking behavior from east-facing banks in the morning to west-facing banks in the afternoon. Turtles in the Central Canal are subject to frequent disturbance, which altered basking behavior. Many turtles forewent aerial basking on emergent substrates for aquatic basking on vegetation mats. which maintained warmer and more consistent temperatures than either emergent substrates or the surrounding water. Living in an intensively managed urban habitat, turtles in the Central Canal are susceptible to frequent anthropogenic perturbations, and future management should consider the life history and ecology of urban turtle population

Topology of the Spin-polarized Charge Density in bcc and fcc Iron

We investigate the topology of the spin-polarized charge density in bcc and fcc iron. While the total spin-density is found to possess the topology of the non-magnetic prototypical structures, in some cases the spin-polarized densities are characterized by unique topologies; for example, the spin-polarized charge densities of bcc and high-spin fcc iron are atypical of any known for non-magnetic materials. In these cases, the two spin-densities are correlated: the spin-minority electrons have directional bond paths with deep minima in the minority density, while the spin-majority electrons fill these holes, reducing bond directionality. The presence of two distinct spin topologies suggests that a well-known magnetic phase transition in iron can be fruitfully reexamined in light of these topological changes. We show that the two phase changes seen in fcc iron (paramagnetic to low-spin and low-spin to high-spin) are different. The former follows the Landau symmetry-breaking paradigm and proceeds without a topological transformation, while the latter also involves a topological catastrophe.Comment: 5 pages, 3 figures. Phys. Rev. Lett. (in press

Electronic Selection Rules Controlling Dislocation Glide in bcc Metals

The validity of the structure-property relationships governing the deformation behavior of bcc metals was brought into question with recent {\it ab initio} density functional studies of isolated screw dislocations in Mo and Ta. These existing relationships were semiclassical in nature, having grown from atomistic investigations of the deformation properties of the groups V and VI transition metals. We find that the correct form for these structure-property relationships is fully quantum mechanical, involving the coupling of electronic states with the strain field at the core of long $a/2$ screw dislocations.Comment: 4 pages, 2 figure

Econometric and Environmental Optimization of Combined Cooling, Heating and Power Plant Operation

Combined Cooling, Heat and Power (CCHP) systems have great potential to recover low-grade thermal energy, resulting in higher energy efficiency, reduced emission rates, lower operating costs and a higher level of energy security. In order to fully realize the benefits of CCHP systems in terms of reduced cost and carbon dioxide emissions, effective optimization and control strategies are required. This work presents an approach for optimizing the operation of the CCHP system using a detailed network energy flow model solved by genetic algorithm. The optimal energy dispatch algorithm provides operational signals associated with resource allocation ensuring that the systems meet campus electricity, heating, and cooling demands. The performance of the system will be compared and evaluated with respect to economic and environmental benefits

Comparison of Steady-State and Dynamic Load-Based Performance Evaluation Methodologies for a Residential Air Conditioner

Space cooling and heating equipment account for nearly 32% of the total residential electricity consumption in the U.S. In the residential space conditioning equipment market, air-conditioning and heat-pumping systems are prevalent, so even a slight improvement in these system efficiencies can have a significant impact on reducing the overall energy consumption. Over the years, the energy efficiency benchmarks established by the U.S. Department of Energy have been successful in encouraging manufacturers to develop higher efficiency equipment. These benchmarks are based on an energy efficiency standard, and these standards are based on a rating test procedure that forms the technical basis. Currently, in the U.S., AHRI 210/240 is the rating procedure for residential air-conditioning and heat-pumping equipment, which is based on a steady-state performance measurement method with a degradation coefficient to account for the cycling losses in part-load conditions. Although it provides a standard metric to compare different equipment performances, there has been a debate that this current methodology fails to appropriately characterize the performance of systems with variable-speed compressors and advanced control design. This is largely attributed to the steady-state nature of this current testing approach, which also involves overriding the equipment native control. In contrast to this, a load-based testing methodology has been developed in which the equipment responds to a simulated virtual building load, and the system dynamic performance is measured with its integrated controls. The load-based testing methodology is described in detail by Hjortland and Braun (2019), Patil et al. (2018), and Cheng et al. (2021), which forms the basis for CSA standard draft EXP07:2019 (CSA, 2019). In this paper, these two performance measurement methodologies, steady-state and dynamic load-based, are compared for application to a 5ton residential heat-pump system. The equipment performance was measured in cooling mode and the seasonal performance estimates based on the two testing approaches are compared. The differences in the two test methodologies\u27 performance evaluation results are discussed with a causal analysis of the observed differences

Demonstration of a Load-Based Testing Methodology for Rooftop Units with Integrated Economizers

Current performance evaluation approaches for commercial packaged air conditioning and heat pump equipment (e.g. AHRI 340/360) utilize full-load steady-state performance tests to estimate system EER (energy efficiency ratio) at different ambient conditions and part-load steady-state tests to estimate an IEER (integrated energy efficiency ratio), a figure of merit for system part-load performance. There are some limitations of the current testing approaches and performance metric estimations, including that they do not consider the effects of: 1) test unit embedded controls and their realistic interactions with the building load; 2) different climate zones and building types; and 3) economizer operation. As a result, the overall performance measurement procedure does not appropriately incentivize the development of better performing controls and economizers. In this paper, an improved testing procedure applied to packaged air conditioning equipment, such as rooftop units (RTUs), that include the effects of embedded controls, economizers, climate, and building type is presented. The testing approach is based on allowing the integrated equipment system and controls to respond naturally to a “virtual building load”. This is termed load-based testing and involves dynamically adjusting the indoor room temperature and humidity setpoints for the psychrometric chamber reconditioning system in a manner that emulates the response of a building’s sensible and latent loads to the test equipment controls. The developed test methodology is demonstrated to evaluate the dynamic performance of a 5-ton variable-speed RTU with an integrated economizer in a psychrometric test facility