Solar Cycle variations of ƒoF2 from IGY to 1990

Noontime monthly median values of F2-layer critical frequency ƒoF2 (m) for some ionospheric stations representing low- and mid-latitudes are examined for their dependence on solar activity for the years 1957 (IGY) to 1990. This is the period for which ionospheric data in digital form is available in two CD-ROMs at the World Data Center, Boulder. It is observed that at mid-latitudes, foF2 (m) shows nearly a linear relationship with R12 (the 12-month running average of the Zurich sunspot number), though this relation is nonlinear for low-latitudes. These results indicate some departures from the existing information often used in theoretical and applied areas of space research

Micromechanical analysis of influence of voids and interface properties on ultimate strength of composite laminates

The influence of fiber-matrix interface fracture properties, fiber waviness, and voids on the response of fiber-reinforced composites are investigated in this paper via three dimensional finite element analysis. We specifically employ augmented finite element method (AFEM) to provide high-fidelity data on damage initiation and propagation along with micromechanical analysis. Stochastic process of model preparation is programmed in Python code and linked to the Abaqus software. Crack initiation and propagation in AFEM are autonomously determined based on the loading conditions, laminate configuration and properties, and distribution of defects and waviness. Within micromechanical analysis, the effects of fiber volume fractions, fiber shapes are also considered to capture the stochastic behavior of the composite under tensile loading. In order to investigate the effects of voids and defects on ultimate strength of composite, we carry out simulations with random voids and defects. These results strongly show the importance of including defects and voids in the finite element analysis. The results reveal that the response of RVE with constant interface properties overestimates the composite transverse strength. It is also seen that the damage initiation and propagation locations are controlled by the distributions of fracture properties, fibers’ shapes, and defects

Design/Development of Mini/Micro Air Vehicles through Modelling and Simulation: Case of an Autonomous Quadrotor

Design and development of an autonomous quadrotor micro aerial vehicle is undertaken following a systematic approach. A fairly detailed model was constructed and simulations were then carried out with the purpose of refining the baseline design, building a controller, and testing the flying qualities of the vehicle on a ground-based flight simulator. Following this, a smooth transition to rig and flight testing has been enabled in a cost- and time-effective manner, meeting all the design requirements.Defence Science Journal, 2011, 61(4), pp.337-345, DOI:http://dx.doi.org/10.14429/dsj.61.108

International Disease Epidemics and the Shadow Economy

Adding to the emerging body of research related to the current coronavirus crisis, this paper studies the impact of disease epidemics on the worldwide prevalence of the shadow or the underground economy. The informal sector undermines compliance with government regulations and lowers tax collections. Our main hypothesis is that epidemics positively impacts the spread of the shadow economy. Using data on nearly 130 nations and nesting the empirical analysis in the broader literature on the drivers of the shadow sector, we find that both the incidence and the intensity of epidemics positively and significantly contribute to the spread of the underground sector. Numerically, a ten percent increase in the intensity of epidemics leads to an increase in the prevalence of the shadow economy by about 2.1 percent. These findings about the spillovers from epidemics have implications for economic policies in the current times of coronavirus. JEL-Codes: I150, K420

Impact of health education on unmet needs of contraception in urban slums of Chandigarh, India

Background: Unmet need points to gap between some women reproductive intention and their contraceptive behavior. Unmet need for contraception is mainly attributed to lack of information, negative attitude, fear of adverse effects and social influences. The objective of this study was to investigate awareness and practice of contraceptive usage. And to estimate unmet need of contraception in the studied population and to identify the factors associated with it, and to evaluate impact of health education on unmet needs of contraception.Methods: A community-based longitudinal study was conducted in four randomly selected urban slum areas (colonies) of Chandigarh, India. A systematic two-stage random sample design was adopted.Results: Overall contraceptive awareness rates among women and men were increased from 84.1% to 96.3% and from 82.2% to 95.5% in post-interventional survey as compared to baseline survey. Contraceptive prevalence rates were found to be 57.3% and 65.5% respectively in pre interventional and post interventional surveys, against contraceptive awareness rates of 81.7% and 95.5% respectively, resulting in gaps between knowledge and practice to be unmet needs of contraception to the extents of 24.4% and 30.0% respectively in the two surveys.Conclusions: There is an urgent need of adopting some population specific integral strategies for changing social norms and attitudes of couples regarding reproductive issues, increase in contraceptives awareness as well as practice for reductions in unmet needs of contraception and unwanted/unplanned pregnancies