Enhanced Adjacent Extreme-point Search and Tabu Search for the Minimum Concave-cost Uncapacitated Transshipment Problem

Practicable methods for optimising concave-cost, uncapacitated transshipment networks are non exact. In this paper, one such effective method, that of adjacent extreme point search, is further developed to enhance its overall computational efficiency. The enhanced search algorithm is then imbedded in a tabu search scheme which proved capable of finding better solutions, by a wide margin in some instances. Another tabu search scheme, somewhat inferior in terms of solution quality but computationally more efficient, is also developed to provide an alternative solution vehicle for larger networks. Results of extensive computational testing are included.     

Kinetic Nonlinear Buneman's Instability in Field-Free Isothermal Collisonal Plasma

A nonlinear dispersion relation is derived and solved for a 1-D electron-ion two-stream (Buneman) instability excited in an isothermal field-free plasma. The major nonlinear mechanism is the qualilinear modification of the background distribution function. We take into consideration the effect of Coulomb collisions which describes the broadening of the Cherenkov interaction of waves with particles. Nonlinear effects seem to lead, in field-free plasma, to the increase in the current velocity and consequently, to the growth of the instability and a rapid turbulent heating of plasma electrons. The methods used here to solve the Vlasov's kinetic equation may also be used to investigate other types of current micro-instabilities in plasmas.     

Mixed insoluble acidic salts of tetravalent metals IV. Crystalline mixed zirconium — Titanium phosphates

Mixed crystalline alpha zirconium — titanium phosphates with variable zirconium to titanium ratios have been prepared both by the well known gel reflux method and a modified HF method. Chemical analysis, X-ray, i.r. and thermal analysis were used to characterize the materials. Exchange capacities for these ion-exchangers have been evaluated by pH-titration combined with radioisotope tract technique for Na⁺, K⁺, Rb⁺ and Cs⁺.     

QCD asymptotics and kinematic thresholds in deep inelastic scattering

The Nachtmann moments of deep inelastic scattering structure functions are required by kinematics to contain a so far neglected threshold factor which is dependent on both n and q². Its presence significantly affects the “moment analysis” in the usual QCD phenomenology and it resolves the difficulties connected with improper threshold behavior of the “ξ-scaling” analysis of structure functions.     

Effect of magnetic field on nonlinear interactions of electromagnetic and surface waves in a plasma layer

Investigation is made for nonlinear interaction between incident radiation and a surface wave in a magnetized plasma layer. Both interacting waves are ofP polarization. We get the generated currents and fields at combination frequencies analytically. Unlike theS-polarized interacting waves, the magnetic field affects the fundamental waves and leads to an amplification of generated waves when their frequencies approach the cyclotron frequency.     

Ligand-induced distortion of a tetranuclear manganese butterfly complex

The reaction of the pentadentate Schiff-base ligand 1,3-bis(salicylideneamino)-2-propanol (salproH3) with [Mn3O(O2CR)6(py)3] (R = Me, Et, But) gives the corresponding tetranuclear manganese product [Mn4O2O2CR)5(salpro)] (4Mn(III)). The syntheses, structure and magnetochemical characterization of these complexes are reported. The structure of the [Mn4(mu3-O)2]8+ is butterfly-like much more closed than in previous complexes with this core as a result of the alkoxide oxygen of the salpro ligand bridging the two wingtip Mn atoms. Variable-temperature, solid-state magnetic susceptibility studies reveal that these complexes possess S = 0 ground state spins. Fitting of the magnetic susceptibility data to the theoretical chiMT vs. T expression derived for a C2v symmetry complex, assuming an isotropic Heisenberg spin-Hamiltonian and using the Van Vleck equation, revealed that the various exchange parameters are all antiferromagnetic, and the core thus experiences spin frustration effects.