11 research outputs found

    Statistical modelling of monthly mean sea level at coastal tide gauge stations along the Indian subcontinent

    No full text
    212-224This study investigates the suitability of statistical models for their predictive potential for the monthly mean sea level at different stations along the west and east coasts of the Indian subcontinent. Statistical modelling of the monthly mean sea level at 15 selected tide gauge stations (8 stations on the west and 7 stations on the east coast) along the coastline of the Indian subcontinent was attempted using autoregressive, sinusoidal and exponentially weighted moving average (EWMA) techniques. Statistics pertaining to the mean seasonal cycle as well as interannual variability are also presented. A strong domination of the annual cycle over the semi-annual cycle was seen at ten stations. The maximum seasonal sea level ranges were observed along the west coast at Bhavnagar (63 cm) and along the east coast at Sagar Island (48 cm). While the autoregressive and sinusoidal models were satisfactory, EWMA technique was found to be the best of all. Tuticorin on the east coast, and Mormugao on the west coast have shown minimum RMSEs for the corresponding coasts for all the three models, while Bhavnagar on west coast has shown very high RMSE values. The EWMA technique (which yields forecast with a lead time of only one month) gave the lowest root mean square errors relative to the verifying observations

    Wave characteristics of the Laccadive Sea (Lakshadweep)

    Get PDF
    211-214Waves in the Laccadive Sea were recorded during March-April 1978 (31st of R V Gaveshani) using a ship-borne wave recorder. Zero-crossing period, significant wave height and spectral width parameter were determined and their distributions studied. Predominant significant wave height and zero-crossing period were 50 to 70 cm and 8 to 8.5 sec respectively. Seasonal variations in the wave characteristics for the area were also studied using the historical data reported by the ships. The predominant wave periods and wave heights were 5-6 sec and 0.5 to 1.5 m respectively during the fair weather season (October-May) and 5-9 sec and 1-3 m respectively during the rough weather season (June-September). A wide range of wave heights 0.5-5 m occurred during the rough season

    Circulation & Water Characteristics on Isanosteric Surfaces in the Northern Arabian Sea during February-April

    Get PDF
    156-165Distribution of water characteristics and circulation were studied on 260, 160, 140, 120 and 80 cl/t surfaces using isanosteric analysis and geostrophic computation. The circulation pattern consisted of several eddies and meanders. The most prominent anticyclonic eddy was located around 24° N and 64° E. Deepest mixed layer occurred in this region. Appreciably deep vertical extension of the eddies was a notable feature. The eddy circulation is proposed to be due to the influence of uneven bottom topography. Persian Gulf water appeared to flow into the Arabian Sea through the northern part of the Gulf of Oman. Distribution of properties was marked by several pockets of high and low values

    Water Masses and General Hydrography along the West Coast of India during Early March

    Get PDF
    82-89Structure of water masses along the west coast of India from Bombay to Trivandrum has been studied through vertical sections of temperature, salinity and density during 3-17 March 1977. The Arabian Sea high salinity water spreads south as a core along the coast at an average depth of 90 m. Influence of the Persian Gulf water in the southern part is found less significant. The northern limit of the Red Sea water is 17 ° N. Low saline waters (<34.2 %) intrude into the southeastern Arabian Sea from the equator around 200 m. Off the Kerala Coast, low saline waters ( <34.5%) occupy the shelf area. A transition zone between 13 ° and 16 ° N separates surface waters of low temperature and high salinity in the north from the surface waters of high temperature and low salinity in the south. Sigma-t surfaces generally slope down towards south indicating very weak onshore flow in the upper layers

    Laser-deposited CoCrMo alloy: Microstructure, wear, and electrochemical properties

    No full text
    CoCrMo alloy was deposited on a metallic substrate using laser engineered net shaping (LENS (TM)) - a laser-based additive manufacturing technique. Several samples with five layers of deposit were fabricated at different combinations of laser power, powder feed rate, and scan velocity to study their influence using L4 Orthogonal array. The deposits were evaluated for their microstructure, hardness, wear resistance, and electrochemical performance. Grey relational grade analysis and analysis of variance were applied to identify optimum process parameters. The x-ray diffraction and microstructural analysis of the deposits showed uniform and fine microstructural features. Our experimental results revealed that the coatings fabricated using high laser power (350 W), low powder feed rate (5 g/min), and high scan velocity (20 mm/s) provide the highest hardness (446 +/- 2.87 Hv) and wear resistance (1.80 +/- 0.0007 mm(3)/Nm). However, the corrosion resistance was observed to be high for the deposits fabricated using low laser power (200 W), low powder feed rate (5 g/min), and low scan velocity (10 mm/s)

    High-Resolution Solid State <sup>13</sup>C NMR Studies of Bent-Core Mesogens of Benzene and Thiophene

    No full text
    Bent-core mesogens are an important class of thermotropic liquid crystals as they exhibit unusual properties as well as morphologies distinctly different from rodlike mesogens. Two bent-core mesogens with differing center rings namely benzene and thiophene are considered and investigated using high-resolution oriented solid state <sup>13</sup>C NMR method in their liquid crystalline phases. The mesogens exhibit different phase sequences with the benzene-based mesogen showing a B<sub>1</sub> phase, while the one based on thiophene showing nematic and smectic C phases. The 2-dimensional separated local field (2D-SLF) NMR method was used to obtain the <sup>13</sup>C–<sup>1</sup>H dipolar couplings of carbons in the center ring as well as in the side-wing phenyl rings. Couplings, characteristic of the type of the center ring, that also provide orientational information on the molecule in the magnetic field were observed. Together with the dipolar couplings of the side-wing phenyl ring carbons from which the local order parameters of the different subunits of the core could be extracted, the bent angle of the mesogenic molecule could be obtained. Accordingly, for the benzene mesogen in its B<sub>1</sub> phase at 145 °C, the center ring methine <sup>13</sup>C–<sup>1</sup>H dipolar couplings were found to be significantly larger (9.5–10.2 kHz) compared to those of the side-wing rings (1.6–2.1 kHz). From the local order parameter values of the center (0.68) as well as the side-wing rings (0.50), a bent-angle of 130.3° for this mesogen was obtained. Interestingly, for the thiophene mesogen in its smectic C phase at 210 °C, the <sup>13</sup>C–<sup>1</sup>H dipolar coupling of the center ring methine carbon (2.11 kHz) is smaller than those of the side-wing phenyl ring carbons (2.75–3.00 kHz) which is a consequence of the different structures of the thiophene and the benzene rings. These values correspond to local order parameters of 0.85 for the center thiophene ring and 0.76 for the first side-wing phenyl ring and a bent-angle of 149.2°. Thus, the significant differences in the dipolar couplings and the order parameter values between different parts in the rigid core of the mesogens are a direct consequence of the nature of the center ring and the bent structure of the molecule. The present investigation thus highlights the ability of the <sup>13</sup>C 2D-SLF technique to provide the geometry of the bent-core mesogens in a straightforward manner through the measurement of the <sup>13</sup>C–<sup>1</sup>H dipolar couplings
    corecore