| 1 | Modified constrained adaptive formation control scheme for autonomous underwater vehicles under communication delays显示文摘The performance of a formation control algorithm for a group of autonomous underwater vehicles(AUVs)may be degraded due to communication constraints between the leader and the follower AUVs.Moreover,as the distance between the AUVs change due to ocean waves,the delay in communication also varies.In this study,a modified constrained adaptive controller(CAC)is proposed to resolve the issue of variable-delay as well as actuator saturation.Due to the on-line reduction of the cost function,the gains of the CAC are updated at each sampling time taking into account the effects of communication delay.This improves the path-following accuracy of the leader AUV as well as follower AUVs.The effectiveness of the proposed control algorithm is demonstrated by implementing it on a prototype AUV(ODRA-I)model.The obtained simulation and experimental results show that the follower AUVs maintain a desired distance from the leader AUV to avoid a collision.For the proposed algorithm,the desired path-following performance of the follower AUV is maintained even when the delay is changed from 0 to 5 s.Moreover,the proposed control algorithm is efficient in avoiding actuator saturation. | Chhavi Suryendu Bidyadhar Subudhi | 2020 | IET Cyber-Systems and Robotics2020，2，1： | 3 |
| 2 | Foraminiferal biostratigraphy of lignite mines of Kutch,India:Age of lignite and fossil vertebrates显示文摘The lignite deposits of Kutch, India are stratigraphically referred to the Naredi Formation and considered to be Early Eocene in age. The biostratigraphy of the older mine at Panandhro and a newly opened mine at Matanomadh has constrained the upper age limit of lignite to the early Bartonian. Its lower age may extend to the late Lutetian. Temporally the formation of lignite corresponds to the warming event of the Middle Eocene and suggests a humid climate at the onset of the warming. The previous palynological studies have already suggested dominance of tropical angiospermic pollen. A diverse assemblage of fossil whales and other vertebrates, many of them supposedly the oldest representatives, were reported from Panandhro mine. These were initially assigned to the Early Eocene and later to the Lute? tian age. The present biostratigraphic study revises their age to the Early Bartonian. | Pratul Kumar Saraswati Sonal Khanolkar Dalta Surya Narayana Raju Suryendu Dutta Santanu Banerjee | 2014 | Journal of Palaeogeography2014，3，1： | 2 |
| 4 | Organo-petrographic and geochemical characteristics of Gurha lignite deposits,Rajasthan,India:Insights into the palaeovegetation,palaeoenvironment and hydrocarbon source rock potential显示文摘The sedimentary sequence containing lignite deposits in Gurha quarry of the Bikaner-Nagaur Basin(Rajasthan)has been investigated.The samples from lignite and allied shale horizons were evaluated for petrographical,palynological,palynofacies and organic geochemical inferences,to depict the source flora and to reconstruct the palaeodepositional conditions prevailed during the sedimentation.An assessment for the hydrocarbon generation potential of these deposits has also been made.The results revealed the dominance of huminite macerals and phytoclasts organic matter(OM) indicating the existence of forested vegetation in the vicinity of the depositional site.A relatively high terrigenous/aquatic ratio(TAR) and the carbon preference index(CPI) are also suggesting the contribution of higher plants in the peat formation.However,the n-alkane distributions,maximizing at n-C17 and n-C29,showed inputs from the algal communities along with the higher plant derived organic matters.Recovered palynomorphs of the families Onagraceae,Meliaceae,Arecaceae,Rhizophoraceae,Rubiaceae,Ctenolophonaceae, etc.together with oleanene and ursane types of triterpenoids suggest the contribution from angiosperms source vegetation.Interestingly,the presence of Araucareaceae and Podocarpaceae pollen grains shows the existence of gymnosperms vegetation.Further,the presence of tetracyclic diterpanes;demethylated entbeyerane,sandaracopimarane,pimarane,and Kaurane type of compounds confirms the contribution of conifers.The variation in the values of the coefficient of non-equality(H:0.68%-7.56%),the standard deviation(8:0.04%-0.16%) and the coefficient of variability(V:16.10%-46.47%),also shows the heterogeneity in the source organic matter.The various petrographical indices,palynological entities,and geochemical parameters indicate that the peatforming vegetation was accumulated under a mixed environment and fluctuating hydrological settings.The interpretation of palynofacies data on APP(Amorphous organic matter-Phytoclast-Palynomorphs) diagram suggests that the accumulation of organic matter occurred in a dysoxic-suboxic condition in a proximal(to land)setting with the shift to an anoxic condition in distal setting towards the termination of sedimentation.The huminite(ulminite) reflectance(R_r) values(av.0.28%) showed a good relationship with average T_(max) value(414℃),suggesting the immaturity.The TOC content ranges of 13-59 wt.%,and HI values vary between 101 and 546 mg HC/g TOC in the studied samples.Collectively,the studied lignite and shale samples have the admixed kerogens(Type Ⅲ-Ⅱ) and exhibit the ability to generate the gaseous to oil hydrocarbons upon maturation. | Runcie Paul Mathews Bhagwan DSingh Vikram Partap Singh Alpana Singh Hukam Singh Mahesh Shivanna Suryendu Dutta Vinod A.Mendhe Rimpy Chetia | 2020 | Geoscience Frontiers2020，11，3： | 0 |
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