Frequency-domain design of optimal controllers

Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 41, No. 5, pp. 615–621, May, 1989.     

The four-loop β-function in quantum chromodynamics

We present the analytical calculation of the four-loop QCD β-function within the minimal subtraction scheme.     

Influence of hydrogen bonding on the properties of water molecules adsorbed in zeolite frameworks

Three hydrated aluminosilicate frameworks—LiABW, NaNAT, and BaEDI—are partly optimized with the periodic Hartree–Fock CRYSTAL95 code. In particular, we optimized the positions of the adsorbed water molecules including the positions of the framework cations (ABW, NAT) or part of the framework atomic positions (ABW). This allowed us to compare cation–water clusters in the gas and adsorbed states and discuss the influence of hydrogen bonding to the framework oxygen atoms or to the neighbor water molecules on the atomic properties (quadrupole coupling constant, anisotropy of electric field gradient) of the adsorbed water molecules. The LiBIK structure obtained from X‐ray diffraction is also considered to illustrate the hydrogen bonds occurring between adsorbed water molecules. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003     

The EPR spectra of copper compounds with tetragonal symmetry in glasses

The conditions for the appearance of the additional absorption peak and its position in the EPR spectra of copper compounds with tetragonal symmetry in glasses have been analyzed. It has been found that the constants of the spin hamiltonians A and B should always have negative signs. The resulting theoretical conclusions have been compared with experimental results on the EPR of bis(salicylideneiminato)copper in various solvents and low-temperature glasses.