The lifetime cost of a magnetic refrigerator

The total cost of a 25 W average load magnetic refrigerator using commercial grade Gd is calculated using a numerical model. The price of magnetocaloric material, magnet material and cost of operation are considered, and all influence the total cost. The lowest combined total cost with a device lifetime of 15 years is found to be in the range \$150-\$400 depending on the price of the magnetocaloric and magnet material. The cost of the magnet is largest, followed closely by the cost of operation, while the cost of the magnetocaloric material is almost negligible. For the lowest cost device, the optimal magnetic field is about 1.4 T, the particle size is 0.23 mm, the length of the regenerator is 40-50 mm and the utilization is about 0.2, for all device lifetimes and material and magnet prices, while the operating frequency vary as function of device lifetime. The considered performance characteristics are based on the performance of a conventional A$^{+++}$ refrigeration unit. In a rough life time cost comparison between the magnetic refrigeration device and such a unit we find similar costs, the former being slightly cheaper, assuming the cost of the magnet can be recuperated at end of life.Comment: 17 pages, 17 figure

Stability of Viscous Flow between Two Concentric Rotating Porous Cylinders

The stability of a viscous flow between two concentric rotating porous cylinders has been examined when the difference in radii of the cylinders is small in comparison with their mean radius. Critical Taylor numbers have been calculated for various wave numbers and velocity ratios of the cylinders. Theroetical results show that injection at the outer cylinder improves the stability of the flow whereas suction has an opposite effect

Digital Solution of Power-flow Problems by Newton\u27s Method of Using a Hybrid Matrix

The last decade and a half has witnessed dramatic developments in the application of digital computers for solving power-flow problems. Previously these problems were analyzed on the direct analog computers called a-c calculating boards. With the enormous growth of the interconnected power systems during this period of time, digital computers established a distinct advantage over the analog computers for such reasons as: (a) Their ability to analyze large-size systems (with such features as automatic tap setting, automatic area interchange control, and control of reactive constraints of generators). (b) Elimination of human error in reading data and recording information on the system diagram. (c) Accessibility and economy in making only a few changes from the base case. (d) Availability of additional information such as the total transmission loss by easy extension of the power-flow program. The power-flow problem can be solved by both direct and iterative methods. In fact, all the methods are iterative in the sense that the load flow problem involves the solution of a system of nonlinear equations. However, the so-called direct methods employ the direct solution of a related linear system in the iterative algorithm, whereas the iterative methods use a scheme of successive displacements such as Gauss-Seidel. Newton\u27s method has an advantage over an iterative method because of its much faster (quadratic) convergence to a solution, thus saving computer time. The usual approach has been to use the bus admittance matrix for the network-defining equations. The purpose of this investigation has been to apply. Newton \u27s method for the solution of power-flow problems employing a hybrid matrix for the network-defining equations in order to confirm the possibility of affecting further saving in computer time. A sample 6-bus problem was solved on an. IBM 360 Model 40 computer with 1 28 K core memory with single precision programming for the precision indices of 1 x 10-3 and 1 x 10-S for real and reactive power mismatches at the busses. A double precision program was written for the precision index of 5 x l0-7. The hybrid matrix was formed by considering generator busses (1 and 2) as voltage-corrected and load busses (3 to 6) as current-corrected. Bus 1 is considered the swing bus

Parallelised max-log-MAP model

A paralleliscd max-Log-MAP model (P-max-Log-MAP) that exploits the sub-word parallelism and very long instruction word architccture of a microprocessor or a digital signal processor (DSP) is presented. The proposed model rcduccs considerably thc computational complexity of the max-Log-MAP algorithm; valid therefore facilitates easy implementation

Bound electron nonlinearity beyond the ionization threshold

Although high field laser-induced ionization is a fundamental process underlying many applications, there have been no absolute measurements of the nonlinear polarizability of atoms and molecules in the presence of ionization. Such information is crucial, for example, for understanding the propagation of high intensity ultrashort pulses in matter. Here, we present absolute space- and time-resolved measurements of the ultrafast laser-driven nonlinear polarizability in argon, krypton, xenon, nitrogen, and oxygen up to an ionization fraction of a few percent. These measurements enable determination of the non-perturbative bound electron nonlinearity well beyond the ionization threshold, where it is found to be approximately linear in intensity