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1.
Harish C. Bahl Stanley Zionts 《The Journal of the Operational Research Society》1987,38(12):1141-1148
Scheduling the production of several items requires the determination of production quantities in different periods in the presence of resource constraints. Several approximate and heuristic algorithms have been proposed to solve this problem. However, no method for finding an optimal solution has as yet been developed. It is shown that the problem may be solved advantageously using Benders' decomposition. The subproblem in Benders' decomposition is shown to be a transportation problem, and some strategies for solving the master problem are indicated. The paper concludes with a sample problem demonstrating the application of the method. 相似文献
2.
We have chemically prepared a sample of antiferromagnetic alpha-Fe2O3 nanoparticles by a gel-sol technique. M?ssbauer spectra of the as-prepared sample showed that superparamagnetic relaxation was suppressed due to strong magnetic interparticle interactions even at room temperature. However, subsequent grinding of the sample by hand in a mortar for some minutes resulted in fast superparamagnetic relaxation of some of the particles. The effect was even more dramatic if the alpha-Fe2O3 powder was ground for a longer time or together with nonmagnetic eta-Al2O3 nanoparticles. Similar effects were found after low-energy ball milling. Thus it is found that the agglomeration of the nanoparticles during preparation under wet conditions results in strong magnetic interparticle interaction, but a relatively gentle mechanical treatment is sufficient to break up the agglomerates, resulting in much weaker interactions. We show that these effects can also be seen when a soil sample containing magnetic nanoparticles is ground. 相似文献
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5.
R. Bjørk C.R.H. Bahl A. Smith N. Pryds 《Journal of magnetism and magnetic materials》2010,322(22):3664-3671
A permanent magnet assembly in which the flux density can be altered by a mechanical operation is often significantly smaller than comparable electromagnets and also requires no electrical power to operate. In this paper five permanent magnet designs in which the magnetic flux density can be altered are analyzed using numerical simulations, and compared based on the generated magnetic flux density in a sample volume and the amount of magnet material used. The designs are the concentric Halbach cylinder, the two half Halbach cylinders, the two linear Halbach arrays and the four and six rod mangle. The concentric Halbach cylinder design is found to be the best performing design, i.e. the design that provides the most magnetic flux density using the least amount of magnet material. A concentric Halbach cylinder has been constructed and the magnetic flux density, the homogeneity and the direction of the magnetic field are measured and compared with numerical simulation and a good agrement is found. 相似文献
6.
C. R.H. Bahl J. Garde K. Lefmann T. B.S. Jensen P.-A. Lindgård D. E. Madsen S. Mørup 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(1):53-57
In magnetic nanoparticles the uniform precession
(q = 0 spin wave) mode gives the predominant contribution
to the magnetic excitations. We have calculated the energy of the
uniform mode in antiferromagnetic nanoparticles with uncompensated
magnetic moments, using the coherent potential approximation. In
the presence of uncompensated moments, an antiferromagnetic
nanoparticle must be considered as a kind of a ferrimagnet. Two
magnetic anisotropy terms are considered, a planar term confining
the spins to the basal plane, and an axial term determining an
easy axis in this plane. Excitation energies are calculated for
various combinations of these two anisotropy terms, ranging from
the simple uniaxial case to the planar case with a strong
out-of-plane anisotropy. In the simple uniaxial case, the
uncompensated moment has a large influence on the excitation
energy, but in the planar case it is much less important. The
calculations explain recent neutron scattering measurements on
nanoparticles of antiferromagnetic α-Fe2O3 and NiO. 相似文献
7.
Background
Growth hormone (GH) plays an incompletely understood role in the development of the central nervous system (CNS). In this study, we use transgenic mice expressing a growth hormone antagonist (GHA) to explore the role of GH in regulating postnatal brain, spinal cord and body growth into adulthood. The GHA transgene encodes a protein that inhibits the binding of GH to its receptor, specifically antagonizing the trophic effects of endogenous GH. 相似文献8.
Diwan Chand Bahl 《Colloid and polymer science》1932,59(1):60-68
Ohne Zusammenfassung
übersetzt von E. Lottermoser (Dresden). 相似文献
9.
X-ray K-absorption studies of molybdenum sulphide, selenides and tellurides have been carried out using 400-mm bent crystal (mica) spectrograph. K-absorption edge of molybdenum in its selenides, tellurides and sulphide lies on the higher energy side with respect to that in the molybdenum metal; the shift in higher selenide and telluride, namely MoSe2 and MoTe2 being smaller than that in the lower selenide and telluride, Mo3Se4 and Mo3Te4 respectively. On the other hand selenium K-absorption edge changes from low energy side in Mo3Se4 to higher energy side in MoSe2 with respect to that in the selenium metal. 相似文献
10.
R. Bjørk C.R.H. Bahl A. Smith D.V. Christensen N. Pryds 《Journal of magnetism and magnetic materials》2010,322(21):3324-3328
A magnet designed for use in a magnetic refrigeration device is presented. The magnet is designed by applying two general schemes for improving a magnet design to a concentric Halbach cylinder magnet design and dimensioning and segmenting this design in an optimum way followed by the construction of the actual magnet. The final design generates a peak value of 1.24 T, an average flux density of 0.9 T in a volume of 2 L using only 7.3 L of magnet, and has an average low flux density of 0.08 T also in a 2 L volume. The working point of all the permanent magnet blocks in the design is very close to the maximum energy density. The final design is characterized in terms of a performance parameter, and it is shown that it is one of the best performing magnet designs published for magnetic refrigeration. 相似文献