India Meteorological Department has the responsibility of monitoring and prediction of cyclonic disturbances (CDs) including tropical cyclone (TC) and depression, collection, processing and archival ...of all data pertaining to CDs and preparation of best track data over the North Indian Ocean (NIO). The process of post-season analysis of CDs to determine the best estimate of a CD’s position and intensity along with other characteristics during its lifetime is described as ’best tracking’. The best tracking procedure has undergone several changes world-over including NIO due to change in definition and classification of TCs, monitoring and analysis tools and procedure and physical understanding of TCs. There have been a few attempts to document the temporal changes in the best track procedure including changes in observational network, monitoring technique, area of responsibility for monitoring, terminology and classification of the TCs over the NIO. Hence, a study has been undertaken to review the temporal variations in all the above aspects of best tracking procedure and its impact on quality of best track parameters over the NIO. The problems and prospective with the best track data over the (NIO) have been presented and discussed. Based on quality and availability, the whole period of best track information may be broadly classified into four phases, viz. (i) pre-1877, (ii) 1877–1890, (iii) 1891–1960 and (iv) 1961–2010. The period of 1961–2010 may be further classified into (a) 1961–1973, (b) 1974–1990 and (c) 1991–2010. As optimum observational network including satellite leading to better estimation of location and intensity without missing of CDs was available since 1961, the climatology of genesis, location, intensity, movement (track) and landfall can be best represented based on the data set of 1961–2010. The best track parameters need to be reanalysed since 1891, based on the present criteria/classification of CDs to develop a digital data set of every six hourly position, intensity and other characteristics throughout the life period of each recorded CD over the NIO to meet the world standard. At least attempt should be made from 1974 when all types of major data including satellite, radar, surface and upper air observations are available for best track analysis. The reanalysis of best track parameters can help in better understanding and prediction of CDs and address the issues related to climate change aspects over the NIO region.
A nonlinear sliding surface is proposed to improve the transient response for general discrete multiple-input-multiple-output linear systems with matched perturbations. The tracking case is analyzed, ...and it is shown that the scheme is able to achieve low overshoot and low settling time simultaneously; this is not possible with a linear sliding surface. The control law is based on the discrete-time sliding mode equivalent control and thus eliminates chattering. The control law is proposed based on two approaches: (1) reaching-law-based approach which needs only disturbance bounds and (2) disturbance-observer-based approach. Multirate output feedback is used to relax the need of the entire state vector for the implementation of the control law. A magnetic tape position control application is used to show the effectiveness of the proposed scheme.
India Meteorological Department (IMD) introduced the objective tropical cyclone (TC) intensity forecast valid for next 24 h over the north Indian Ocean (NIO) in 2003 and extended up to 72 h in 2009. ...In this study, an attempt is made to evaluate the TC intensity forecast issued by IMD during 2005–2011 (7 years) by calculating the absolute error (AE), root mean square error (RMSE) and skill in intensity forecast in terms of maximum sustained surface wind (MSW). The accuracy of TC intensity forecast has been analysed with respect to basin of formation (Bay of Bengal, Arabian Sea and NIO as whole), season of formation (pre-monsoon and post-monsoon seasons), intensity of TCs (cyclonic storm and severe cyclonic storm or higher intensities) and type of track of TCs (climatological/straight moving and recurving/looping type). The study shows that the average AE (RMSE) in intensity forecast is about 11(14), 14(19) and 20(26) knots, respectively, for 24-, 48- and 72-h forecasts over the NIO as a whole during 2009–2011. The skill of intensity forecast is about 44 %(48 %), 60 %(58 %) and 60 %(65 %) for 24-, 48- and 72-h forecasts during 2009–2011 with respect to AE (RMSE). There is no significant improvement in terms of reduction in AE and RMSE of MSW forecast over the NIO like that over the northwest Pacific and northern Atlantic Oceans during 2005–2011. However, the skill in intensity forecast compared to persistence method has significantly improved by about 6 %(10 %) and 9 %(8 %) per year, respectively, for 12- and 24-h forecasts considering the AE (RMSE) during 2005–2011. There is also significant increasing trend in percentage of 24-h intensity forecasts with error of 10 knots or less during 2005–2011.
Over the last few years, the research on discrete-time sliding mode control has received a considerable attention. Unlike its continuous-time counterpart, discrete-time sliding mode control is not ...invariant in general. In this note, an algorithm is presented for robust discrete-time sliding mode control using the concept of multirate output feedback
In this paper, the method to design the reduced-order switching function for an uncertain linear system in special coordinate basis (SCB) form is proposed. The sliding mode control with this method ...guarantees the asymptotic stability of all the states of system in presence of matched disturbance. The proposed design method is applicable to the system with unstable internal dynamics as well. This method enables the option of designing the control law with reduced-order states that are involved in the design of switching function. Also, a high performance sliding mode step-tracking control for non-minimum phase systems using reduced-order nonlinear switching function is proposed. The method is also extended to multiple-input and multiple-output (MIMO) systems. An effectiveness of sliding mode control with reduced-order switching function is shown through numerical examples.
This paper proposes the application of a new algorithm for the position control of a Stewart platform. The conventional integral sliding mode controller is a combination of nominal control and ...discontinuous feedback control hence the overall control is discontinuous in nature. The discontinuity in the feedback control is undesirable for practical applications due to chattering which causes the wear and tear of the mechanical actuators. In this paper the existing integral sliding mode control law for systems with matched disturbances is modified by replacing the discontinuous part by a continuous modified twisting control. This proposed controller is continuous in nature due to the combinations of two continuous controls. The desired position of the platform has been achieved using the proposed controller even in the presence of matched disturbances. The effectiveness of the proposed controller has been proved with the simulation results.
•Super twisting observer is used to estimate the leg velocity knowing the leg lengths.•The existing integral sliding mode control algorithm is modified using the twisting algorithm based control.•The performance of the controller is evaluated by applying the position control of a Stewart platform.
Magnetic studies have been performed to characterize Co
0.3
Cu
0.7
granular alloy synthesized by chemical reduction. The alloy consists of superparamagnetic (SPM) particles with a mean size of 14 nm ...and a blocking temperature distribution extending to ∼380 K. Even at 4 K where the alloy is largely ferromagnetic, the average magnetic moment of cobalt is smaller than its expected value indicating that not all Co atoms contribute to ferromagnetism. A significant temperature dependent exchange bias field is obtained from above 100 K down to 2 K. These observations suggest that the particles have a Co rich SPM core, surrounded by uncompensated dilute Co spin moments at the surface. Such a distribution, with lowering of temperature, leads to the co-existence of ferromagnetic (FM) and antiferromagnetic (AFM) interactions in the core and surface regions, respectively. Also, the sample exhibits a weak spin-glass like ordering occurring at ∼7 K. The overall behavior of the system is that of an assembly of almost non-interacting magnetic nanoparticles as suggested by the study of relaxation of magnetization. If during relaxation certain external conditions are temporarily disturbed,
e.g.
, by lowering the temperature or changing the magnetic field the magnetization also changes accordingly; but as the conditions are restored the magnetization returns to its previous value. Such magnetic 'memory effect' has been studied with various experimental protocols and persists strongly even at room temperature.
Non-interacting magnetic CoCu nanoparticles with a blocking temperature distribution show strong magnetic memory effect even at room temperature.
•Co rich clusters in Co-Cu nanogranular alloys yield zero-field 59Co NMR signal.•NMR signal is obtained from both fcc and hcp phases of Co.•Signals show lattice regions of Co atoms and that with NN ...atoms replaced by Cu.•The above regions constitute the core and the shell, respectively, of Co clusters.•The core having one-fifth of the volume of clusters dominates in the magnetism.
We have performed 59Co zero field nuclear magnetic resonance (NMR) experiment at 4 K on CoxCu1-x (x = 0.10, 0.32 and 0.76) nanogranular alloys. The NMR signal arises from Co rich ferromagnetic clusters formed within the Cu matrix. The analysis of NMR spectra shows that the resonance peaks arise from both fcc and hcp phases of Co. However, Co nuclei experience magnetic hyperfine field from Co only environment as well as other environments in which nearest-neighbor (NN) Co atoms are replaced by Cu. Assuming that these two environments constitute the core and the shell of the Co clusters, it is estimated using previous magnetization measurements that the contribution of core dominates in the ferromagnetism of the particles though it occupies only about 20% of the volume of Co clusters even for high Co containing alloys.
Finger millet Eleusine coracana (L.) Gaertn is mostly cultivated in the arid and semi-arid regions of India. In this study, 11 finger millet genotypes were evaluated for six traits in a randomized ...complete block design with three replications at Ranichauri (E1), Dehradun (E2) and Pantnagar (E3) of Uttarakhand during kharif 2018 and 2019. The analysis of variance revealed significant variation among genotypes due to genotypes (G), environments (E) and G×E interaction (GEI) effects. The environment contributed for 37.3%, 38.6%, 58.2%, 65.5%, 21.0% and 76.9% of the total variation for days to 50% flowering, plant height, number of tillers, number of heads, number of fingers and grain yield, respectively. Grain yield exhibited a crossover-type GEI effect with a high environmental and GEI variance proportion. The mean grain yield over the locations was ranged from 16.9 (E1) to 38.8 q/ha (E3), whereas the genotypic mean was stretched from 22.7 (PF5) to 34.3 q/ha (PF8). The GGE biplot graphical analysis identified three mega environments, and the best genotypes were PF5, PF6 and PF2 in E1; PF8 in E2; PF10 and PF11 in E3. Based on a hypothetical ideal genotype, PF8 was identified as the best genotype owing to the high mean grain yield and stability over the locations. The ranking of genotypes based on ideal genotype would be as follows: PF8>PF10>PF3>PF7>PF2>PF1>PF11>PF4>PF9>PF6>PF5. The location Dehradun had high discriminating ability and representativeness and considered as the best environment for selecting high-yielding and stable genotypes among the locations.
Hazards associated with tropical cyclones are long-duration rotatory high-velocity winds, very heavy rain and storm tide. India has a coastline of about 7,516 km of which 5,400 km is along the ...mainland. The entire coast is affected by cyclones with varying frequency and intensity. The India Meteorological Department (IMD) is the nodal government agency that provides weather services related to cyclones in India. However, IMD has not identified cyclone-prone districts following any specific definition though the districts for which cyclone warnings are issued have been identified. On the other hand, for the purpose of better cyclone disaster management in the country, it is necessary to define cyclone proneness and identify cyclone-prone coastal districts. It is also necessary to decide degree of hazard proneness of a district by considering cyclone parameters so that mitigation measures are prioritised. In this context, an attempt has been made to prepare a list of cyclone hazard prone districts by adopting hazard criteria. Out of 96 districts under consideration, 12, 45, 31 and 08 districts are in very high, high, moderate and low categories of proneness, respectively. In general, the coastal districts of West Bengal, Orissa, Andhra Pradesh and Tamil Nadu are more prone and are in the high to very high category. The cyclone hazard proneness factor is very high for the districts of Nellore, East Godawari, and Krishna in Andhra Pradesh; Yanam in Puducherry; Balasore, Bhadrak, Kendrapara and Jagatsinghpur in Orissa; and South and North 24 Parganas, Medinipur and Kolkata in West Bengal. The results give a realistic picture of degree of cyclone hazard proneness of districts, as they represent the frequency and intensity of land falling cyclones along with all other hazards like rainfall, wind and storm surge. The categorisation of districts with degree of proneness also tallies with observed pictures. Therefore, this classification of coastal districts based on hazard may be considered for all the required purposes including coastal zone management and planning. However, the vulnerability of the place has not been taken into consideration. Therefore, composite cyclone risk of a district, which is the product of hazard and vulnerability, needs to be assessed separately through detailed study.
