Solar Wind and its Evolution

By using our previous results of magnetohydrodynamical simulations for the solar wind from open flux tubes, I discuss how the solar wind in the past is different from the current solar wind. The simulations are performed in fixed one-dimensional super-radially open magnetic flux tubes by inputing various types of fluctuations from the photosphere, which automatically determines solar wind properties in a forward manner. The three important parameters which determine physical properties of the solar wind are surface fluctuation, magnetic field strengths, and the configuration of magnetic flux tubes. Adjusting these parameters to the sun at earlier times in a qualitative sense, I infer that the quasi-steady-state component of the solar wind in the past was denser and slightly slower if the effect of the magneto-centrifugal force is not significant. I also discuss effects of magneto-centrifugal force and roles of coronal mass ejections.Comment: 6 pages, 1 figure, Earth, Planets, & Space in press (based on 5th Alfven Conference) correction of discussion on a related pape

Efficient UC Commitment Extension with Homomorphism for Free (and Applications)

Homomorphic universally composable (UC) commitments allow for the sender to reveal the result of additions and multiplications of values contained in commitments without revealing the values themselves while assuring the receiver of the correctness of such computation on committed values. In this work, we construct essentially optimal additively homomorphic UC commitments from any (not necessarily UC or homomorphic) extractable commitment. We obtain amortized linear computational complexity in the length of the input messages and rate 1. Next, we show how to extend our scheme to also obtain multiplicative homomorphism at the cost of asymptotic optimality but retaining low concrete complexity for practical parameters. While the previously best constructions use UC oblivious transfer as the main building block, our constructions only require extractable commitments and PRGs, achieving better concrete efficiency and offering new insights into the sufficient conditions for obtaining homomorphic UC commitments. Moreover, our techniques yield public coin protocols, which are compatible with the Fiat-Shamir heuristic. These results come at the cost of realizing a restricted version of the homomorphic commitment functionality where the sender is allowed to perform any number of commitments and operations on committed messages but is only allowed to perform a single batch opening of a number of commitments. Although this functionality seems restrictive, we show that it can be used as a building block for more efficient instantiations of recent protocols for secure multiparty computation and zero knowledge non-interactive arguments of knowledge

Pose, posture, formation and contortion in kinematic systems

The concepts of pose, posture, formation and contortion are defined for serial, parallel and hybrid kinematic systems. Workspace and jointspace structure is examined in terms of these concepts. The inter-relationships of pose, posture, formation and contortion are explored for a range of robot workspace and jointspace types

Thermodynamics of phase transition in higher dimensional AdS black holes

We investigate the thermodynamics of phase transition for $(n+1)$ dimensional Reissner Nordstrom (RN)-AdS black holes using a grand canonical ensemble. This phase transition is characterized by a discontinuity in specific heat. The phase transition occurs from a lower mass black hole with negative specific heat to a higher mass black hole with positive specific heat. By exploring Ehrenfest's scheme we show that this is a second order phase transition. Explicit expressions for the critical temperature and critical mass are derived. In appropriate limits the results for $(n+1)$ dimensional Schwarzschild AdS black holes are obtained.Comment: LaTex, 11 pages, 5 figures, To appear in JHE

Anti-oxidative activities of sorghum, foxtail millet and proso millet extracts

In this study, sorghum, foxtail millet and proso millet extracts were evaluated by various in vitro antioxidant assays, including 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging activity, reducing power by Fe3+- Fe2+ transformation, and anti-lipid peroxidative activity by ferric thiocyanate. The sorghum extract contained high amount of phenolic compounds as well as a high level of antioxidant activity compared with foxtail millet and proso millet extracts. In addition, among the sorghum cultivar, me-susu (Sorghum dochna var. technicum, Snowden) extracts exhibited high levels of free radical scavenging activity, anti-oxidant capacity and anti-lipid peroxidative activity compared with - tocopherol. Taken together, these findings suggest that me-susu extracts can be considered good sources of natural anti-oxidants

Gross motor function classification system family questionnaire: validating Yoruba-Nigerian version

Background Assessment of the functional abilities of children with cerebral palsy would be more reliable if care givers are included. An instrument commonly used for assessing functional abilities in CP by their caregivers is the Gross Motor Function Classification System Family Questionnaire. No Nigerian Version of this instrument is currently available; hence this study was designed to evaluate the criterion- related validity of the Yoruba (Nigerian) version of the GMFCSFQ among care givers of children with cerebral palsy.Method Fifteen primary caregivers of children with CP, who are fluent in speaking, reading, and writing both English and Yoruba Languages, were purposively sampled from among those bringing their children or wards for physiotherapy at the University College Hospital Nigeria and involved in this study. The participants completed within one week interval, the English and Yoruba versions of the GMFCSFQ by choosing one of the five ordinal levels corresponding to the gross motor function of their children. Spearman’s correlation coefficient was used to examine the relationship between the scores from the English and the Yoruba versions of the instrument. Significant level was set at ά=0.05.Results A strong positive and significant correlation was obtained between the English and Yoruba Versions of the GFMCSFQ (ρ=0.89, p=0.00).Conclusion This suggests that the Yoruba version of the GMFCSFQ is a valid version of the original (English) version. It could therefore be used to gather information about the gross motor function of children with cerebral palsy from their family members or caregivers among Yoruba speaking people of West Africa and in Diaspora.Key words: Cerebral Palsy, Gross Motor Function, Yoruba

Speed control of synchronous machine by changing duty cycle of DC/DC buck converter

Global Conference on Energy and Sustainable Development, 2015-02-24, 2015-04-26, Coventry, UKRenewable energies such as wind or solar energy are naturally intermittent and can create technical challenges to interconnected grid in particular with high integration amounts. In addition, if wind or solar is used to supply power to a stand-alone system, continuous power supply will be met only if sufficient energy storage system is available. The global penetration of renewable energy in power systems is increasing rapidly especially wind and solar photovoltaic (PV) systems. Hybrid wind and solar PV generation system becomes very attractive solution in particular for stand-alone applications. It can provide better reliability since the weakness of one system could be complemented by the strength of the other one. When wind energy is integrated into grid, maximum power point tracking control could be used to optimize the output of wind turbine. In variable speed wind turbine, the turbine speed is varied according to the wind speed. This paper presents a comparison between two methods of controlling the speed of a wind turbine in a microgrid namely; Proportional-Integral (PI) control of the tip speed ratio and stored power curve. The PI method provides more controllability, but it requires an anemometer to measure the wind speed. The stored power curve method, however, is easier to implement, but the amount of energy extracted can be less. The system has been modelled using Matlab/Simulink.The work is financially supported by the Government of Oman, which provides a PhD grant for Rashid Al Badwawi. Also, financial support from EPSRC-DST funded RESCUES project (EP/K03619X/1)