Solitons in Triangular and Honeycomb Dynamical Lattices with the Cubic Nonlinearity

We study the existence and stability of localized states in the discrete nonlinear Schr{\"o}dinger equation (DNLS) on two-dimensional non-square lattices. The model includes both the nearest-neighbor and long-range interactions. For the fundamental strongly localized soliton, the results depend on the coordination number, i.e., on the particular type of the lattice. The long-range interactions additionally destabilize the discrete soliton, or make it more stable, if the sign of the interaction is, respectively, the same as or opposite to the sign of the short-range interaction. We also explore more complicated solutions, such as twisted localized modes (TLM's) and solutions carrying multiple topological charge (vortices) that are specific to the triangular and honeycomb lattices. In the cases when such vortices are unstable, direct simulations demonstrate that they turn into zero-vorticity fundamental solitons.Comment: 17 pages, 13 figures, Phys. Rev.

Adsorption air conditioner for electric vehicle applications. Revision 1

This paper shows an analysis of the applicability of an adsorption system for electric vehicle (EV) air conditioning. Adsorption systems are designed and optimized to provide the required cooling for four combinations of vehicle characteristics and driving cycles. The resulting adsorption systems are compared with vapor compression air conditioners that can satisfy the cooling load. The objective function is the overall system weight, which includes the cooling system weight and the weight of the battery necessary to provide energy for air conditioner operation. The system with the minimum overall weight is considered to be the best, because a lower weight results in an increased vehicle range. The results indicate that, for the conditions analyzed in this paper, vapor compression air conditioners are superior to adsorption systems not only because they are lighter, but also because they have a higher COP and are more compact

Thermal analysis of simulated Pantex pit storage

This report investigates potential pit storage configurations that could be used at the Mason and Hanger Pantex Plant. The study utilizes data from a thermal test series performed at Lawrence Livermore National Laboratory (LLNL) that simulated these storage configurations. The heat output values used in the LLNL test series do not represent actual pits but are rounded numbers that were chosen for convenience to allow parameter excursions. Specifically in this project, we are modeling the heat transfer and air flow around cylindrical storage containers in Pantex magazines in order to predict container temperatures. This difficult problem in thermal- fluid mechanics involves transient, three-dimensional (3-D) natural convection and thermal radiation around interacting containers with various heat generation rates. Our approach is to link together two computational methods in order to synthesize a modeling procedure for a large array of pit storage containers. The approach employs a finite element analysis of a few containers, followed by a lumped- parameter model of an array of containers. The modeling procedure we developed was applied in the simulation of a recent experiment where temperatures of pit storage containers were monitored in a steady- state, controlled environment. Our calculated pit container temperatures are comparable with data from that experiment. We found it absolutely necessary to include thermal radiation between containers in order to predict temperatures accurately, although the assumption of black-body radiation appears to be sufficient. When radiation is neglected the calculated temperatures are 4 to 6 {degrees}C higher than temperature data from the experiment. We also investigated our model`s sensitivity to variations in the natural convection heat transfer coefficient and found that with a 50% drop in the coefficient, calculated temperatures are approximately I {degree}C higher. Finally, with a modified lumped-parameter model, we demonstrate how an entire Pantex magazine can be simulated

Thermodynamics of insulated pressure vessels for vehicular hydrogen storage

This paper studies the application of insulated pressure vessels for hydrogen-fueled light-duty vehicles. Insulated pressure vessels can store liquid hydrogen (LH2); low-temperature (90 K) compressed hydrogen (CH2); or ambient temperature CH2. In this analysis, hydrogen temperatures, pressures and venting losses am calculated for insulated pressure vessels fueled with LH2 or with low-temperature CH2, and the results are compared to those obtained in low-pressure LH2 tanks. Hydrogen losses are calculated as a function of daily driving distance during normal operation; as a function of time during long periods of vehicle inactivity; and as a function of initial vessel temperature during fueling. The number of days before any venting losses occur is also calculated as a function of the daily driving distance. The results show that insulated pressure vessels have packaging characteristics comparable to those of conventional, low-pressure LH2 tanks (low weight and volume), with greatly improved dormancy and much lower boil-off. Insulated pressure vessels used in a 17 km/l (40 mpg) car do not lose any hydrogen when the car is driven at least 15 km/day in average. Since almost all cars are driven for longer distances, most cars would never lose any hydrogen. Losses during long periods of parking are also relatively small. Due to their high-pressure capacity, these vessels would retain about a third of their full charge even after a very long dormancy, so that the owner would not risk running out of fuel. If an insulated pressure vessel reaches ambient temperature, it can be cooled down very effectively by fueling it with LH2 with no losses during fueling. The vessel has good thermal performance even when thermally insulated with inexpensive microsphere insulation. In addition, the insulated pressure vessels greatly ease fuel availability and infrastructure requirements, since it would be compatible with both compressed and cryogenic hydrogen reveling

Applied Thermal Engineering

Several technologies are being researched to address the challenges of cryogenic heat transfer in liquefied natural gas (LNG) production. Single mixed refrigerant (SMR) or dual mixed refrigerant (DMR) systems have advantages vs. pure refrigerant-based systems (e.g., cascade or inverted Brayton cycle with nitrogen) due to compact design suitable for small-scale units. However, the selection of mixed refrigerant composition is a challenge. Several methods have been published, typically using heuristic and computational techniques; with power consumption, efficiency, and/or exergy as the figure of merit. This paper presents an alternative approach for the determination of optimum refrigerant mixture composition based on nonlinear thermodynamic equations relating heat exchanger composite curves and mass flow of LNG produced. Three case studies demonstrate the effectiveness of the approach, indicating that single mixed refrigerant systems can be used for cost-effective LNG production while improving LNG production per unit of refrigerant flow rate by as much as 6.5 % vs. conventional approaches. The research is applicable to current needs of the gas extraction industry because it helps increase LNG production in small-scale cryogenic systems, thereby enabling economic gas recovery and reducing flaring during fracking operation, as is typical in e.g., the Bakken formation of North Dakota.Sciencie Directhttps://www.sciencedirect.com/science/article/abs/pii/S1359431122014156#kg00

Automated modelling of complex refrigeration cycles through topological structure analysis

We have developed a computational method for analysis of refrigeration cycles. The method is well suited for automated analysis of complex refrigeration systems. The refrigerator is specified through a description of flows representing thermodynamic sates at system locations; components that modify the thermodynamic state of a flow; and controls that specify flow characteristics at selected points in the diagram. A system of equations is then established for the refrigerator, based on mass, energy and momentum balances for each of the system components. Controls specify the values of certain system variables, thereby reducing the number of unknowns. It is found that the system of equations for the refrigerator may contain a number of redundant or duplicate equations, and therefore further equations are necessary for a full characterization. The number of additional equations is related to the number of loops in the cycle, and this is calculated by a matrix-based topological method. The methodology is demonstrated through an analysis of a two-stage refrigeration cycle. © 2009 Elsevier Ltd. All rights reserved

Effect of an Exogenous Phytase on Growth Performance in Growing Holstein Calves

The aim of this study was to evaluate the effect on the productive performance, apparent digestibility of DM, serum phosphorus and phosphorus balance in Holstein calves which received a high concentrate diet with different doses of exogenous phytase for a period of 60d. The experiment was conducted with a completely randomized design with three treatments of eight calves each, the treatment included dietary supplementation of exogenous phytase at 0, 12 and 24 g/ton. Phytase inclusion increased (P<0.05) average daily gain when phytase was supplemented at 24 (850g) as compared to 0 (816g) or 12 (809g) g/ton. However, it had no effect (P>0.05) on DM intake, feed conversion and DM digestibility. Adding phytase in the diet decreased phosphorus excretion in faeces (P<0.05) showing a significant linear increase with increasing level of supplementation (the values being 9.96, 9.14 and 8.13 g/d) which, in turn, increased the P retention (4.69, 5.37 and 6.45 g/d, resectively, for the three groups). In conclusion, supplementation of phytase could improve the growth performance of calves without any discernible effects on feed intake or digestibility of nutrients