109 research outputs found
Mid-Neoproterozoic intraplate magmatism in the northern margin of the Southern Granulite Terrane, India: constraints from geochemistry, zircon U-Pb geochronology and Lu-Hf isotopes
No full textAbstract not availableT.R. Deeju, M. Santosh, Qiong-Yan Yang, A.P. Pradeepkumar, E. Shaj
Crustal evolution in the western margin of the Nilgiri Block, southern India: insights from zircon U–Pb and Lu–Hf data on Neoarchean magmatic suite
No full textAbstract not availableQiong-Yan Yang, M. Santosh, A.P. Pradeepkumar, E. Shaji, R.S. Prasanth, S.G. Dhanil De
Metamorphic phase equilibria modelling and zircon U–Pb geochronology of ultrahigh-temperature cordierite granulites from the Madurai Block, India: implications for hot Gondwana crust
No full textThe Madurai Block (MB) is the largest Precambrian crustal block in the Southern Granulite Terrane (SGT) of India and hosts rare cordierite- and orthopyroxene-bearing granulites. Investigations based on field study, petrology, metamorphic P–T estimation, and detrital zircon geochronology of these granulites are crucial for understanding the ultrahigh-temperature (UHT) metamorphism and crustal evolution in this block. Here we investigate the petrology and zircon U–Pb geochronology of two new localities of cordierite granulites at Kottayam (southern MB; SMB) and Munnar (central MB; CMB). Petrographic observations and phase equilibria modelling results indicate that these rocks experienced UHT metamorphism with the peak temperature exceeding 950℃ and involving clockwise P–T paths. The prograde mineral assemblages define the P–T conditions of 6.8–8.7 kbar and 750–875℃. The peak conditions are estimated using pseudosection modelling and geothermometry, which yield P–T estimates of 7.1–9.1 kbar and 955–985℃. The retrograde cooling and decompression are inferred at 860–790℃ and <6.5 kbar, respectively. Partial melting played an important role during metamorphism and contributed to the overgrowth around detrital zircons. The melt production process was probably related to biotite dehydration melting, and was mainly triggered by heating, with or without the effect of decompression. Detrital zircons in cordierite granulite samples from the two localities show similar age distributions and have dominantly Neoproterozoic ages (1024–760 Ma). The zircon cores show oscillatory zoning with a wide range of Th/U ratios (0.01–0.96), implying complex protoliths from multiple Neoproterozoic provenances from both southern and central domains of the MBs. Zircon rims and homogeneous bright zircons yield mean ages of 549 ± 5 Ma, 536 ± 6 Ma, and 544 ± 6 Ma, which are interpreted to represent zircon overgrowths during the post-peak cooling and decompression process. The timing of peak UHT metamorphism is constrained as 549–599 Ma, which coincides with the assembly of the Gondwana supercontinent.Li Tang, S. Rajesh, M. Santosh, Toshiaki Tsunogae, A.P. Pradeepkumar, Yukiyasu Tsutsumi and Yusuke Takamur
A Systems Framework and Analysis Tool for Rapid Conceptual Design of Aerocapture Missions
No full textAerocapture offers a near propellantless and quick method of orbit insertion at atmosphere bearing planetary destinations. Compared to conventional propulsive insertion, the primary advantage of using aerocapture is the savings in propellant mass which could be used to accommodate more useful payload. To protect the spacecraft from the aerodynamic heating during the maneuver, the spacecraft must be enclosed in a protective aeroshell or deployable drag device which also provides aerodynamic control authority to target the desired conditions at atmospheric exit. For inner planets such as Mars and Venus, aerocapture offers a very attractive option for inserting small satellites or constellations into very low circular orbits such as those used for imaging or radar observations. The large amount of propellant required for orbit insertion at outer planets such as Uranus and Neptune severely limits the useful payload mass that can delivered to orbit as well as the achievable flight time. For outer planet missions, aerocapture opens up an entirely new class of short time of flight trajectories which are infeasible with propulsive insertion. A systems framework for rapid conceptual design of aerocapture missions considering the interdependencies between various elements such as interplanetary trajectory and vehicle control performance for aerocapture is presented. The framework provides a step-by-step procedure to formulate an aerocapture mission starting from a set of mission objectives. At the core of the framework is the “aerocapture feasibility chart”, a graphical method to visualize the various constraints arising from control authority requirement, peak deceleration, stagnation-point peak heat rate, and total heat load as a function of vehicle aerodynamic performance and interplanetary arrival conditions. Aerocapture feasibility charts have been compiled for all atmosphere-bearing Solar System destinations for both lift and drag modulation control techniques. The framework is illustrated by its application to conceptual design of a Venus small satellite mission and a Flagship-class Neptune mission using heritage blunt-body aeroshells. The framework is implemented in the Aerocapture Mission Analysis Tool (AMAT), a free and open-source Python package, to enable scientists and mission designers perform rapid conceptual design of aerocapture missions. AMAT can also be used for rapid Entry, Descent, and Landing (EDL) studies for atmospheric probes and landers at any atmosphere-bearing destination
Analysis of a 115MW, 3 shaft, helium Brayton cycle
No full textThis research theme is originated from a development project that is going on in
South Africa, for the design and construction of a closed cycle gas turbine plant using
gas-cooled reactor as the heat source to generate 115 MW of electricity. South African
Power utility company, Eskom, promotes this developmental work through its
subsidiary called PBMR (Pebble Bed Modular Reactor). Some of the attractive features
of this plant are the inherent and passive safety features, modular geometry, small
evacuation area, small infrastructure requirements for the installation and running of the
plant, small construction time, quick starting and stopping and also low operational
cost.
This exercise is looking at the operational aspects of a closed cycle gas turbine,
the finding of which will have a direct input towards the successful development and
commissioning of the plant. A thorough understanding of the fluid dynamics in this
three-shaft system and its transient performance analysis were the two main objectives
of this research work. A computer programme called GTSI, developed by a previous
Cranfield University research student, has been used in this as a base programme for the
performance analysis. Some modifications were done on this programme to improve its
control abilities. The areas covered in the performance analysis are Start-up, Shutdown
and Load ramping. A detailed literature survey has been conducted to learn from the
helium Turbo machinery experiences, though it is very limited. A critical analysis on
the design philosophy of the PBMR is also carried out as part of this research work.
The performance analysis has shown the advantage, disadvantage and impact of
various power modulation methods suggested for the PBMR. It has tracked the effect of
the operations of the various valves included in the PBMR design. The start-up using a
hot gas injection has been analysed in detail and a successful start region has been
mapped. A start-up procedure is also written based on this. The analysis on the normal
and emergency load rejection using various power modulation devices has been done
and it stress the importance of more control facilities during full load rejection due to
generator faults.
A computational fluid dynamics (CFD) analysis, using commercial software, has
been carried out on some geometry of the PBMR design to find out whether its flow
characteristic will have any serious impact on the performance on the cycle during the
load control of the plant. The analysis has demonstrated that there will not be much
impact on the performance, during load control using pressure level changes, from this
geometry. However, some locations in the geometry have been identified as areas where
the flow is experiencing comparatively high pressure losses. Recommendations, which
include modification in the physical design, were made to improve this.
The CFD analysis has extended to a cascade to compare the flow behaviour of
Air and Helium with an objective of using air, being inexpensive, to test the helium
flow characteristic in a test rig to simulate the behavioural pattern of helium in the
PBMR pressure vessel. The specification of a hypothetical test rig and the necessary
scaling parameters has been derived from this exercise. This will be useful for designing
test rigs during the developmental and operational stage of the PBMR project
Feminist issues in Vairamuthu's works
No full textMen and women have separate levels of value in society. From ancient times, men were held in high esteem because of their physical strength and their ability to earn money. The idea that woman is not equal to man is still prevalent. Since women have been subservient to men from time immemorial, the aim and function of feminism is to make them aware and give them equal respect as men. A woman is a benevolent woman who gives birth and nurtures life and loves others. However, the suppression and suppression of women and femininity in society is widespread. In this way, Vairamuthu examines what Vairamuthu says about women through his poems
Experimental Investigation and Optimization of Machining Process Parameters in AISI D2 Steel Under Conventional EDM and Cryogenically Cooled EDM Process
No full textGrowth and characterization of divalent transition metal ions doped zinc hydrogen phosphate single crystals
No full textAerocapture Performance Analysis for a Neptune Mission Using a Heritage Blunt-Body Aeroshell
No full textThe large navigation and atmospheric uncertainties at Neptune have historically driven the need for a mid-lift-to-drag L/D vehicle with L/D of 0.6--0.8. All planetary entry vehicles flown to date are low-L/D blunt-body aeroshells with L/D less than 0.4. The lack of a heritage mid-L/D aeroshell presents a long pole for Neptune aerocapture, as the development and testing of a new entry vehicle incurs significant cost, risk, and time. Techniques which may allow Neptune aerocapture to be performed using heritage low-L/D blunt-body aeroshells are investigated, and obviate the need for mid-L/D aeroshells. A navigation study is performed to quantify the delivery errors, and a new guidance algorithm with on-board density estimation is developed to accommodate atmospheric uncertainties. Monte Carlo simulation is used to analyze aerocapture performance of a vehicle with L/D = 0.4. One hundred percent of the cases captured successfully and show a 99.87% probability of achieving the desired science orbit with a total of 396 m/s propulsive Delta V budget, even with worst-case atmospheric uncertainties
Tobacco use in Kerala: Findings from three recent studies
No full textBackground. We reviewed the literature on tobacco use in Kerala and present data from three recently conducted unpublished studies.Methods. Three cross-sectional studies were conducted; a community-based study of 1298 individuals aged 15 years and above (mean age 37.4 years, men 630), a school-based study of 132 3 boys (mean age 14.7 years), and a college-based study of 1254 male students (mean age 18.2 years). Information on tobacco use and sociodemographic variables was collected using pre-tested, structured interview schedules and questionnaires.Results. In the community study, 72% of men and 6% of women had ever used tobacco. Compared to men with > 12 years of schooling, those with 44 years. In the school study, the age at initiation among boys aged: 13 years was 10.7 years compared with 13.2 years among 2:16-year-old boys. Boys whose fathers and friends used tobacco were 2 times and 2.9 times more likely to use tobacco (OR 2.0, Cl 1.3-3.1 and OR 2.9, Cl 1.6-5.1), respectively, compared with their counterparts. In the college study, 29% of the commerce students used tobacco compared with 5.3% of polytechnic students (p<0.001).Conclusion. Survey data suggest that the age at initiation of tobacco use appears to be failing. A series of cross-sectional studies with larger sample sizes of the youth is required to confirm this impression. Tobacco use habits of fathers and peers are significant influences on youth smoking. There is a need to focus on particular types of colleges as these appear to have high-risk tobacco use environments
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