3-D Model of sound pressure field in a meridinal section plane of fruit

A theoretical model was suggested for qualitative evaluation of a sound pressure field in fruit tissue, as affected by ultrasonic probe dimensions and fruit properties. The classic directivity pattern of an ideal fluid model, expressed by Bessel function of the first kind, was extended to include energy dissipation of a real material. The directional characteristics of wave propagation, as influenced by transmitter frequency and diameter, and by fruit properties, were discussed. The model indicates how to select the parameters of the ultrasonic transducer (transducer diameter, frequency and excitation power) to control the magnitude and directivity of the ultrasonic waves in the fruit tissue. The suggested theoretical model represented fairly well the experimental sound wave distribution over the half-cut surface of potato and avocado (R² > 0.862 and 0.977, respectively); the same theoretical model could not represent the sound wave distribution over a half-cut melon. Results of the study were applied in a new probe design for ultrasonic testing of whole fruit.     

Broadband laser amplifier based on gas-phase dimer molecules pumped by the Sun

We report the design and experimental realization of a solar-pumped dimer gas-laser amplifier. The amplifying medium is Te(2) gas, which is capable of amplifying laser signals over a broad spectral range. A gain of 42% was measured at a wavelength of 632.8 nm. We also present studies of the material characteristics and a brief review of the study of other candidate materials for solar pumping.     

Regular colligations for several commuting operators in Banach space

Several important results of the theory of operator colligations, stated initially for strict commutative colligations in Hilbert space [6] [7], are extended to the more general setting of regular commutative colligations in Banach space, which are defined in the text.     

On the inverse spectral problem for the string equation

The theory of Hilbert spaces of entire functions is used to deduce the changes in the mass distribution of a string effected by a small change in its spectral function. The formula of Gelfand-Levitan emerges as a special case.     

Dielectric microconcentrators for efficiency enhancement in concentrator solar cells

Metal fingers typically cover more than 10% of the active area of concentrator solar cells. Microfabricated dielectric optical designs that can completely eliminate front contact shading losses are explored. Essentially no microconcentrator optical losses need be incurred, series resistance losses can be reduced, and net efficiency gains of roughly 15% (relative) are realistic.     

On the discriminant function of two commuting nonselfadjoint operators

The notion of the discriminant function of two commuting nonselfadjoint operators A₁ and A₂ in a Hilbert space H was defined by M.S. Livic in a recent paper [5].In the present paper we study the discriminant function for two special cases of commuting operators. In one case A₁ and A₂ are rational functions of one and the same operator A in H. In the second case A₁ and A₂ are Kronecker products of the form A I and I B, where I is the identity operator.As an auxiliary result a relation between the Sylvester and Bezoutian matrices of two polynomials is derived.     

Spectral effects in cyclobutane derivatives : The bathochromic-hypochromic shifts in compounds related to verbenone

The bathochromic-hypochromic spectral shifts, observed in bicyclic enones that contain a 4- or a 3-membered ring, are discussed in molecular-mechanical and molecular-orbital terms. It is proposed that the effect, not only by the cyclopropane but also by the cyclobutane ring, is due to extension of the CCCO chromophore, and not to its mere distortion from “normal” geometry. The high-energy absorption of umbellulone (3), 220 nm in ethanol, is characterized as a second π-π^*. 2-Methylbicyclo[3.2.1]oct-2-en-4-one (7) has been synthesized, and its preparation and spectrum are described.     

Thermal stability of Ti–MCM-41

Ti containing mesoporous MCM-41 materials have been synthesized through two methods: heating and non-heating [room temperature (RT)]. The synthesized materials have been characterized using X-ray diffraction, Fourier transform infrared, nitrogen sorption, and X-ray fluorescence methods and their thermal stabilities evaluated using thermogravimetric methods in inert atmosphere. The thermal stabilities have been analyzed based on the synthesis method, as well as on the amount of titanium in the MCM-41 materials. The thermal stability results suggest that uncalcined MCM-41 materials generally show higher mass loss than their calcined counterparts. Also, the RT-synthesized materials showed lower stability than the high-temperature synthesized samples for the uncalcined samples. It is also been found that MCM-41 materials show improved thermal stabilities as the amount of titanium is increased.