Forced-air precooling of spherical foods in bulk: A parametric study

In this paper, a mathematical model for forced-air precooling of spherical food products in bulk is developed. The foods are arranged in horizontal layers stacked one above the other to form a rectangular parallelepiped with a vertical gap in between the product layers. The foods are cooled by chilled air blown along the height of the package. The governing equations for the conduction heat transfer in the foods, simultaneous heat and mass transfer at the food-air interface and in the air stream are solved numerically using finite-difference methods. A comprehensive numerical study is performed by varying the process parameters over a wide range. Typical results showing the variation of moist air properties along the height of the package and the effect of each parameter on the process time are presented. The ranges of parameters for advantageous operation of the precooling system are identified. Correlations are obtained for the process time based on the product center and mass-averaged temperatures in terms of process parameters.     

Intensity ratios of mesonic x-ray linesK_{\alpha _1 } , K_{\alpha _2 } andL_{\alpha _1 } , L_{\beta _2 }

Intensity ratios ofμ-mesonic x-rays in some heavy elements are discussed. Intensity ratios of the \(K_{\alpha _1 } /K_{\alpha _2 } \) and \(L_{\alpha _1 } /L_{\beta _2 } \) lines have been calculated for²⁰⁶Pb,²⁰⁹Bi and²³⁸U with relativistic wavefunctions and retardation effect. Though for a refined calculation, it is necessary to take into consideration several features that are peculiar to mesonic atoms, the present calculations have shown that the observed intensity ratios of mesonic x-rays are not anomalous.     

Reinvestigation of the second negative (A 2 Π u−X 2 Π g) band system of O 2 +

TheA ² Π _ustate of O₂ ⁺ was earlier established as an inverted state contrary to previous assumptions. The rotational analysis of a few more bands of theA-X system of O₂ ⁺ has now been completed. These studies show that the spin-orbit coupling constantA in theA ² Π _ustate gradually varies with the vibrational quantum numberν and is found to be positive forν⩾6. It has also been observed that the spia-rotation interaction is not negligible in theA ² Π _ustate. The spin splitting constantγ is reported for various vibrational levels of this electronic state.     

Photoelectric cross-sections of light elements and compounds at low photon energies

Total photon mass attenuation coefficients in C, Al, S, Ti, B₂O₃, LiF, ZnO, Y₂O₃ and H₈O₂C₅ (perspex) are measured on a good geometry set-up using proportional counter, Si(Li) and Ge(Li) detecting systems in the energy region from 6.47 to 52.014 keV employing x-rays and gamma rays from radioactive sources. The deduced photoelectric cross-sections are found to agree with the theoretical values of Storm and Israel, Scofield and semiexperimental values of Veigele wherever available within a few percent. The photo-electric cross-sections in elements, S, Ti and Y at their respectiveK-edges obtained by extrapolation technique agree with the theoretical values of Storm and Israel and Scofield at the respectiveK-edges except in S. In the case of S both the theoretical values atK-edges are found to be underestimations, more in the case of Scofield evaluations.     

Isotope shift studies of the ultra-violet and visible bands of P16O and P18O

The spectra of P¹⁶O and P¹⁸O were excited in sealed discharge tubes containing neon (2–3 mm. pressure), oxygen gas enriched to 65 per cent. of¹⁸O and trace amounts of phosphorus vapour and photographed on a 3 m. grating spectrograph at a dispersion of 2·5 Å/mm. Isotope shift studies in theβ-bands confirmed the earlier vibrational scheme of Curryet al. and showed conclusively that the red as well as the violet degraded bands belonged to the sameβ-system. The present studies of isotope shifts also confirmed the vibrational assignments of the extensive ultraviolet bands involving the² Σ ^??X² Π transition and theγ-bands (A² Σ ⁺?X² Π). In the case of the visible bands, they provided evidence for the first time that the bands at 5585 Å, 5962 Å and 6385 Å belonged to one system and involved 0–0, 0–1 and 0–2 transitions respectively.     

Photoelectric effect in some alloys in the region of absorption edges

Summary Photoelectric effect in alloys using the transmission method in the energy range (17.8÷138) keV, at energies in the region of absorption edges of the various elements in the alloys, have been measured and compared with the respective theoretical estimates.     

High spin states in102Ag

High spin states are populated in¹⁰²Ag using the reaction¹⁶O+⁸⁹Y with projectile energies in the energy range 60–80 MeV. Gamma multipolarities are inferred from DCO ratios and coincidence relationships are established among the gamma rays assigned to¹⁰²Ag. A comprehensive level scheme is constructed with four band systems, two of positive parity and the other two of negative parity. The present study extended spins upto 19^– in the main negative parity band. A new band is populated in the present work and is similar to the one observed in¹⁰⁶Ag.The authors wish to thank and record their appreciation to Dr. S.K. Parthasaradhi, VECC, Calcutta for preparing the target used in this experiment. The authors gratefully acknowledge useful discussions with Dr. Rakhesh Popli. The authors record their grateful thanks to Prof. A.P. Patro and Prof. G.K. Mehta, former and present directors of the Nuclear Science Centre, for their interest in this work, helpful discussions and providing excellent facilities. The authors also thank Dr. S.K. Datta of the Nuclear Science Centre for his continued interest and helpful discussions and accelerator staff of N.S.C. for their efficient services in delivering the beam. Grateful thanks are also due to the University Grants Commission for providing financial support.