9,309 research outputs found

    Stress-structure relation in dense colloidal melt under forward and instantaneous reversal of shear

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    Dense supercooled colloidal melt in forward shear from a quiescent state shows overshoot in shear stress at 10% strain with an unchanged fluid structure at equal stress before and after overshoot. In addition, we find overshoot in normal stress with a monotonic increase in osmotic pressure at an identical strain. The first and second normal stress become comparable in magnitude and opposite in sign. Functional dependence of the steady state stress and osmotic pressure with Peclet number demonstrate signature of crossover between Newtonian and nearly- Newtonian regime. Moreover, instantaneous shear reversal from steady state exhibit Bauschinger effect, where strong history dependence is observed depending on the time of flow reversal. The distribution of particulate stress and osmotic pressure at the point of flow reversal is shown to be a signature of the subsequent response. We link the history dependence of the stress-strain curves to changes in the fluid structure measured through the angular components of the radial distribution function. A uniform compression in transition from forward to reversed flowing state is found.Comment: 8 pages, 6 figure

    Controlling motile disclinations in a thick nematogenic material with an electric field

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    Manipulating topological disclination networks that arise in a symmetry-breaking phase transfor- mation in widely varied systems including anisotropic materials can potentially lead to the design of novel materials like conductive microwires, self-assembled resonators, and active anisotropic matter. However, progress in this direction is hindered by a lack of control of the kinetics and microstructure due to inherent complexity arising from competing energy and topology. We have studied thermal and electrokinetic effects on disclinations in a three-dimensional nonabsorbing nematic material with a positive and negative sign of the dielectric anisotropy. The electric flux lines are highly non-uniform in uniaxial media after an electric field below the Fr\'eedericksz threshold is switched on, and the kinetics of the disclination lines is slowed down. In biaxial media, depending on the sign of the dielectric anisotropy, apart from the slowing down of the disclination kinetics, a non-uniform electric field filters out disclinations of different topology by inducing a kinetic asymmetry. These results enhance the current understanding of forced disclination networks and establish the pre- sented method, which we call fluctuating electronematics, as a potentially useful tool for designing materials with novel properties in silico.Comment: 17 Pages, 14 Figure

    Online Steiner Tree with Deletions

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    In the online Steiner tree problem, the input is a set of vertices that appear one-by-one, and we have to maintain a Steiner tree on the current set of vertices. The cost of the tree is the total length of edges in the tree, and we want this cost to be close to the cost of the optimal Steiner tree at all points in time. If we are allowed to only add edges, a tight bound of Θ(logn)\Theta(\log n) on the competitiveness is known. Recently it was shown that if we can add one new edge and make one edge swap upon every vertex arrival, we can maintain a constant-competitive tree online. But what if the set of vertices sees both additions and deletions? Again, we would like to obtain a low-cost Steiner tree with as few edge changes as possible. The original paper of Imase and Waxman had also considered this model, and it gave a greedy algorithm that maintained a constant-competitive tree online, and made at most O(n3/2)O(n^{3/2}) edge changes for the first nn requests. In this paper give the following two results. Our first result is an online algorithm that maintains a Steiner tree only under deletions: we start off with a set of vertices, and at each time one of the vertices is removed from this set: our Steiner tree no longer has to span this vertex. We give an algorithm that changes only a constant number of edges upon each request, and maintains a constant-competitive tree at all times. Our algorithm uses the primal-dual framework and a global charging argument to carefully make these constant number of changes. We then study the natural greedy algorithm proposed by Imase and Waxman that maintains a constant-competitive Steiner tree in the fully-dynamic model (where each request either adds or deletes a vertex). Our second result shows that this algorithm makes only a constant number of changes per request in an amortized sense.Comment: An extended abstract appears in the SODA 2014 conferenc

    Biodiversity of the Indian Desert and it´s value

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    The state of Rajasthan is situated between 23º3’ and 30º12’ N latitude and 69º30’ and 78º17’ E longitude . The total land area of the state is about 3,24,239 km²out of which about 1,98,100 km² is arid and the rest semi arid. The physical features are characterized mainly by the Aravallis and to the some extent by the vindhyan formation, and the Deccan trap. A major portion of western Rajasthan has desert soils and sandy plains. Sand dunes occupy a greater part of western Rajasthan ( 1,20, 983 km²). The soils of the desert plains are loamy sand to loam and the eastern part has alluvial soil which supports good forests and agricultural crop. Occurrence of saline soils with pH up to 9.0 is a common feature in the sandy areas of Rajasthan. The average annual rainfall in the state is 525-675 mm, and the annual precipitation in different tracts of Rajasthan varies from 13 mm to 1766 mm. Out of the total areaforests cover only about 37,638 km² and are rich in biodiversity. Rajasthan is rich in biodiversity which has a great economic value. Characterization of different plant species of economic value was undertaken. (Table 1-6)

    An Empirical Study on Gur (Jaggery) Industry (with special reference to operational efficiency & profitability measurement)

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    Gur (Jaggery) is a natural, traditional product of sugarcane. It can define as a honey brown coloured raw lump of sugar. Kushinagar district of Uttar-Pradesh has large number of Gur manufacturing units, mostly located in the rural areas and the manufacturers are following conventional methods for producing this. In the district the major clusters which are having more numbers of manufacturing units are Sukraouli, Kasia, Hata and Padarauna. Around half of the rural population is employed in gur making industry in this region. Although, there is no R & D assistance and marketing institutions for support. It is found that the manufacturers are producing majorly for distilleries and local licker producers, not for the food-plate or common man's consumption. The paper examines the cost-return analysis, profitability and operational efficiency of Gur manufacturing units in study area. The study revealed that units of medium and large sizes were able to cover their operating expenses with significant level of profit but small size units were earning a marginal profit. The profit earned by this category was very low as compared to other two sizes. The manufacturers are not interested in any new product of Gur, they just want to earn more profit through Gur only. This research will urged the policymakers to streamline strategies that promote stabilization of sugarcane economy and make the nation credible supplier of Gur in the International market, benefiting Gur makers, sugarcane growers and related stakeholders.