Three-colours photoelectric observations of W UMA-system BB Pegasi

The paper givesUBV photoelectric light curves of the eclipsing binary BB Peg obtained in one of the nights in August 1982 and four nights of November 1984. A comparison has been made with previous light curves of this binary system. Two salient points arise from the light curves, (i) the depth of the primary eclipse could be variable, (ii) the period of the system has probably been increased.     

Spectral photometry of selected areas of the lunar surface during maximum solar activity

Photoelectric observations have been carried out during maximum solar activity in order to investigate the variation of the brightness of the lunar surface with the solar cycle and to detect the possiblity of existing colour anomaly. The brightness data, using a wide-passband filter, do not show any evidence of variation with the solar cycle. No colour anomaly is found for the investigated lunar regions, and the doubt that has been felt by some investigators about the nonexistence of certain colour indices' variation with phase is not confirmed.     

Photoelectric studies of DK Cyg

UBV photoelectric light curves of the eclipsing variable DK Cyg, were obtained in four nights of September 1986. They are compared with the previous light curves of the system. The primary shows a transit, so the star maybe classified with the A-type WUMa systems. Two salient points arise from the light curves: first, the secondary maximum is increasing in brightness, and secondly, the secondary minimum is varying in depth. These changing patterns of surface brightness may be due to the instabilities of an energy transfer process between the components. The (O-C) diagram shows a parabolic trend, indicating a seculariy increasing period.     

Numerical versus field studies of delayed yield in response to a moving water-table

As pumping proceeds in an unconfined aquifer the water-table is lowered and slowly drains out of the initially saturated material giving a delayed yield from storage. Although considerable work has been carried out on delayed yield, a definitive solution is still lacking. The unsaturated zone was treated here as a significant factor in delayed yield analysis. The one-dimensional unsaturated flow equation was solved numerically to simulate the flow in the zone located between successive water levels in the unconfined aquifer for the case with zero flux at the upper boundary. The moisture content distribution curve was integrated numerically to determine the amount of water drained with time. The study shows that the numerical results are in close agreement with the monitored field data, which implies the important role of the unsaturated zone and the reliability of the numerical simulation in describing this physical phenomenon. The results show that the relationship between the flux and time is sensibly in exponential form, which agrees with the general applicability of Boulton's assumption.     

Study of photoelectric observations of the eclipsing binary system FZ-Delphinus

Photoelectric observations in B and V for the FZ Del system are presented and its light curves are analyzed. Absolute parameters are obtained. The system shows a near contact subgaint secondary component with a likely K1 spectral type. The O-C curve is presented and probably a secular orbital period variations is detected on a timescale of about 6.9×10⁶ yrs, suggesting thermal timescale mass transfer. A new light elements for the system have been obtained. The system can be considered as an early stage of conservative case of mass transfer. This revised version was published online in August 2006 with corrections to the Cover Date.     

A photometric light variation and a 1500 days secondary period in the W UMa system TZ bootis

Photoelectric observations of the eclipsing variable TZ Bootis, obtained in 1983 and 1986, in the two coloursB andV are presented: They are compared with the previous light curves of the system. The light curve changes show that the system TZ Bootis has a solar-like activity cycle with a period of 1500 days. The primary shows a transit, whereas the secondary shows an occultation minima. The maxima exhibit a large difference suggesting a large complication in the system. The (O-C) trend indicates that the period did not remain constant; a satisfactory representation of all the observed time of minimum light was obtaiend assuming a linear trend in the (O-C)s. The star may be classified to A-type W UMa systems.     

The system WY Cnc and derivation of absolute information at the lower end of the Main Sequence

Photometric and spectrographic observations of the system WY Cnc are presented and analysed. It is concluded that the system consists of two Main Sequence stars: a G5 primary and a low mass secondary star with a mass of about 0.4M , corresponding to a spectral type of around M2. The possibility of deriving absolute information on this low mass Main Sequence object lends significance to this study.Also there is evidence concerning the role of scattering by the atmosphere of the cool comparison.     

Photoelectric UBV observations and period study of AK Herculis system

New photoelectric UBV observations of the W Ursae Majoris-type eclipsing binary AK Her are presented. The system exhibits many phenomena such as O'Connell effect, unequal depth, phase shift and different duration in secondary eclipse due to its totality, which have been studied. O'Connell effect-duration relation may be exist. The (O-C) curve has been obtained and the new light elements have been calculated. The analysis of the minima-times data of the system reveals possible sinusoidal orbital period variation (LITE). The study of the (O-C)curve, the light curves, O'Connell effect and the duration effect have led to that the system is likely a case which undergoes cyclic around the marginal contact state conservatively with mass transfers between its components, i.e.in TRO mode. This revised version was published online in July 2006 with corrections to the Cover Date.     

Solar spectrum distribution and optical depth of Bahrain's sky

The solar spectrum of wavelength 350–800 nm has been measured for the four seasons. The intensity of the solar radiation in W m^-2 nm^-1 has been calculated and used to estimate the monochromatic optical depth of Bahrain's sky. It was found that the optical depth (i.e., extinction coefficient,k) is least in winter and highest in summer. Comparison of the hourly variation of the optical depth between Bahrain's atmosphere and that of Dhahran (Saudi Arabia) shows that the abundance of small size particles in the former is more than in the latter. This causes more extinction effect in Bahrain than in Dhahran, especially in the wavelengths 350–525 nm. The relation betweenk and for each season in Bahrain is in the formk =A ⁿ , whereA is a constant andn is a negative integer, is reported in this study.     

Perturbed earth processes due to thermally induced deformation in a discontinuous granite mass

Summary The effect of thermally induced stress on fractured granite is considered, using mathematics to solve an engineering problem that includes: (1) physical information translated into a mathematical form; (2) a mathematical model proposing a solution of the problem and (3) interpretation of the solution in physical terms.This procedure, applied to an engineering problem demonstrates that theory and its physical applications are related.