Photometric elements and evolutionary status of eclipsing binary DI Pegasi

The light curves of eclipsing binary DI Pegasi inU, B. andV filters have been presented and discussed. Photometric elements of the system have been determined. Using the colour indices, we estimate absolute dimensions and discuss the evolutionary status of the system.     

A Numerical Study on Coastal Defence at Chennai and Related Management Strategies

Chennai coast, right from the inception of Madras harbourin the year 1876, has been experiencinghostile conditions such as (i) coastal erosion, (ii) sandbar formation at the entrance to inlets, (iii) sea water ingression and (iv) change insea bed elevation, etc. In addition, construction of a new satellite harbour, about18 km north of Madras harbour has produced a negative impact on the delicatecoastal features such as (i) Pulicat lake, (ii) Ennore shoals, etc. Construction ofthis satellite harbour has led to the accumulation of sand south of the southbreakwater of the harbour and its accelerated growth is of concern to an inletlocated 2.6~km south of the harbour. `Coastal erosion', a perennial problemassociated with north Chennai sea front for the past 100 years has been addressedin this paper. The paper discusses on a long term solution and details of themethodologies to be adopted for effective management of the coast. Thesolution presented in this paper is based on numerical model study consideringthe nearshore currents and wave induced sediment transports.     

Effect of wave amplitude on turbulent flow in a wavy channel by direct numerical simulation

The present study numerically investigates the characteristics of three-dimensional turbulent flow in a wavy channel. For the purpose of a careful observation of the effect of the wave amplitude on the turbulent flow, numerical simulations are performed at a various range of the wave amplitude to wavelength ratio (0.01?α/λ?0.05), where the wavelength is fixed with the same value of the mean channel height (H). The immersed boundary method is used to handle the wavy surface in a rectangular grid system, using the finite volume method. The Reynolds number (Re=U_bH/ν) based on the bulk velocity (U_b) is fixed at 6760. The present computational results for a wavy surface are well compared with those of references. When α/λ=0.02, the small recirculating flow occurs near the trough at the instant, but the mean reverse flow is not observed. In the mean flow field, the reverse flow appears from α/λ=0.03 among the wave amplitude considered in this study. The domain of the mean reverse flow defined by the locations of separation and reattachment depends strongly on the wave amplitude. The pressure drag coefficient augments with increasing the wave amplitude. The friction drag coefficient shows the increase and decrease behavior according to the wave amplitude. The quantitative information about the flow variables such as the distribution of pressure and shear stress on the wavy surface is highlighted.     

Some basic notions in geographical synthesis

Modern geography is based on ecological thinking. In this paper some geoecological notions are discussed: the scales and levels regarding spatial magnitude and complexity, the “hierarchy” of landscape units and espcially the scale of time and the concept of the supper-imposing “stamps”. This last mentioned concept is very important in relation to the problem regarding regionalization and its possibilities. Three “stamps” are recognized: 1. the substrate, 2. the climatic conditions, 3. the human (noötic) influence. Holistic regionalization in which all elements (including the human influences) are telling to full advantage, is unsatisfactory.     

Cosmogenic nuclide measurements in southernmost South America and implications for landscape change

We measured in situ ¹⁰Be, ²⁶Al and³⁶Cl on glacial deposits as old as 1.1 Myr in the southernmost part of Patagonia and on northern Tierra del Fuego to understand boulder and moraine and, by inference, landscape changes. Nuclide concentrations indicate that surface boulders have been exposed for far less time than the ages of moraines they sit upon. The moraine ages are themselves constrained by previously obtained ⁴⁰Ar/³⁹Ar ages on interbedded lava flows or U-series and amino acid measurements on related (non-glacial) marine deposits. We suggest that a combination of boulder erosion and their exhumation from the moraine matrix could cause the erratics to have a large age variance and often short exposure histories, despite the fact that some moraine landforms are demonstrably 1 Myr old. We hypothesize that fast or episodic rates of landscape change occurred during glacial times or near the sea during interglacials. Comparison with boulder erosion rates and exhumation histories derived for the middle latitudes of semi-arid Patagonia imply different geomorphic processes operating in southernmost South America. We infer a faster rate of landscape degradation towards the higher latitudes where conditions have been colder and wetter.     

Determination of solar wind elemental abundances from M/Q observations during three periods in 1980

Mass spectra in the range 2 ≦ M/Q ≦ 3 provided by a high resolution mode of the ISEE-3 Plasma Composition Experiment were evaluated for three selected periods during early 1980. The observed Ne/O ratios are compatible with estimated solar abundance ratios. In two of the three periods, the He/Ne-ratios agree with the Apollo foil results. Freezing-in temperatures for oxygen are similar to those obtained by other groups. Possible reasons for an unexpectedly high flux at M/Q = 2.4 are discussed.     

Quasi-Biennial Oscillations of Global Solar-Activity Indices

Quasi-biennial oscillations of solar activity are investigated using several global indices. The Singular Spectrum Analysis is used to separate out and study quasi-biennial oscillations; this method is one of the modifications of the main components method. The principal components of the solar cycle are stable 11-year, secular, and quasi-biennial variations. The periods and shapes of individual variations in each quasi-biennial train depend on the length and power of the particular 11-year cycle.