Triangles of Minimal Perimeter Circumscribed about a Convex n-Gon

An algorithm for finding a circumscribed triangle of the minimal perimeter is suggested. Properties of such a triangle are described. Bibliography: 1 title.     

A study of polarized low-frequency spectra of the solid solution of paradibromobenzene with parachloronitrobenzene in the α phase

Polarized spectra of low-frequency Raman scattering in solid solutions of paradibromobenzene with parachloronitrobenzene in the α phase are studied at temperatures of 293 and 77 K. The solid solution spectrum is found to be similar to the paradibromobenzene spectrum (in accordance with the X-ray diffraction data), but has a series of additional low-intensity lines resulting from disordering. As the parachloronitrobenzene concentration increases, frequencies of the solid solution orientation vibrations decrease steadily, and the half-widths grow. Frequency spectra of the mixed crystal are calculated by the Dean method.     

Photovaractor for remote optical control of microwave circuits

A photovaractor for the remote optical control of microwave circuits was studied. The photovaractor was fabricated as a p-i-n photodiode placed in a pigtailed fiber optical module. The study of the impedance in the frequency range up to 3 GHz in darkness and under illumination has shown that the photovaractor capacitance strongly depends on the incident optical power. The capacitance variation of the photovaractor diode under illumination is discussed     

Characterization of rectangular waveguide with a pseudochiral /spl Omega/ slab

A mode matching approach has been employed for evaluating the matrix S of the section of rectangular waveguide with pseudochiral /spl Omega/ slab. Scattering characteristics for different localizations of the /spl Omega/ slab in the guide are predicted numerically and verified by measurements. Based on the numerical analysis, the scattering properties of the guides are discussed. Scattering parameters are next applied in an optimization procedure to extract constitutive parameters of the /spl Omega/ slab used in experiment.     

Analysis of the structure of an amorphous sediment obtained upon decomposition of potassium oxofluroniobate in water

An amorphous sediment was prepared by the decomposition of potassium oxofluoroniobate K_{2 ? x} Nb₄O₃(O, F)₃F in water. For this sediment, the atomic radial distribution function was analyzed with the use of a fragment model, which allows one to interpret expanded coordination spheres as being formed by first several strongest diffusion maxima. These spheres carry the most reliable information on the structure. It is shown that the amorphous sediment consists of the randomly packed Nb(O,F)₆-octahedra with interatomic distances close to those observed in the ordered region in the N-Nb₂O₅ structure. During decomposition in water, the initial K_{2 ? x} Nb₄O₃(O, F)₃F phase loses KF-layers, whereas Nb₆ clusters with metal bonds are destroyed.     

LIDAR mapping of ozone-episode dynamics in Paris and intercomparison with spot analyzers Supplementary material available at http://link.springer.de/journals/apb

Continuous mapping of an ozone episode in Paris in June 1999 has been performed using a differential absorption lidar system. The 2D ozone concentration vertical maps recorded over 33 h at the Champ de Mars are compiled in a video clip that gives access to local photochemical dynamics with unprecedented precision. The lidar data are compared over the whole period with point monitors located at 0-, 50-, and 300-m altitudes on the Eiffel Tower. Very good agreement is found when spatial resolution, acquisition time, and required concentration accuracy are optimized. Sensitivity to these parameters for successful intercomparison in urban areas is discussed. Received: 11 February 2002 / Published online: 14 March 2002     

Amplified spontaneous emission and its application for population of resonant states of the Xe and Kr atoms

To extend the capabilities of the existing spectroscopic methods of investigation and diagnostics of gaseous media, we consider a macroscopic effect of an increase in the rate of spontaneous emission, which results in the transition of a considerable part of excited molecules to lower-lying optically accessible states with light pulse emission along the direction of propagation of the exciting laser radiation. As an application of the effect of amplified spontaneous emission, we propose the population with its help of optically inaccessible electronic states of atoms and molecules.     

Mechanism analysis of gate-induced drain leakage in off-state n-MOSFET

An analytical expression for both band-to-band and band-trap-band indirect tunnelings is used to study the gate-induced drain leakage (GIDL) current of MOSFETs measured before and after hot-carrier stress. The voltage and temperature dependence of GIDL are characterized. Both results show that interface traps situated near the midgap participate in the conduction of GIDL, and band-trap-band indirect tunneling could be the major mechanism. This is further supported by the fact that the percentage increase in GIDL induced by hot-carrier stress is about the same as the corresponding increase in interface-trap density. On the other hand, under low-field conditions, trap-assisted Poole–Frenkle emission dominates over tunneling for temperatures even well below room temperature.     

Ka-band solid-state pulsed Gunn oscillator and power combiner

GaAs Gunn diodes were fabricated for pulse source application at 8 mm wave band and operated with pulsewidths of 0.05 to 2.0 microseconds and duty cycles of 0.001 to 0.01. Peak pulse output power levels of 0.8–1.2W are achieved and the maximum available power is 1.6W with the highest efficiency of 6.5 percent. A simple and compact pulsed power combiner is also given in this paper.