Atomic fountain of laser-cooled Yb atoms for precision measurements

We demonstrate launching of laser-cooled Yb atoms in a cold atomic fountain. Atoms in a collimated thermal beam are first cooled and captured in a magneto-optic trap (MOT) operating on the strongly-allowed ${^1S}_0 \rightarrow {^1P}_1$ transition at 399~nm (blue line). They are then transferred to a MOT on the weakly-allowed ${^1S}_0 \rightarrow {^3P}_1$ transition at 556~nm (green line). Cold atoms from the green MOT are launched against gravity at a velocity of around 2.5~m/s using a pair of green beams. We trap more than $10^7$ atoms in the blue MOT and transfer up to 70\% into the green MOT. The temperature for the odd isotope, $^{171}$Yb, is $\sim$1~mK in the blue MOT, and reduces by a factor of 40 in the green MOT.Comment: 6 pages, 7 figure

An Explicit Finite Element Integration Scheme for Linear Eight Node Convex Quadrilaterals Using Automatic Mesh Generation Technique over Plane Regions

This paper presents an explicit integration scheme to compute the stiffness matrix of an eight node linear convex quadrilateral element for plane problems using symbolic mathematics and an automatic generation of all quadrilateral mesh technique , In finite element analysis, the boundary problems governed by second order linear partial differential equations,the element stiffness matrices are expressed as integrals of the product of global derivatives over the linear convex quadrilateral region. These matrices can be shown to depend on the material properties and the matrix of integrals with integrands as rational functions with polynomial numerator and the linear denominator (4+ ) in bivariates over an eight node 2-square (-1 ).In this paper,we have computed these integrals in exact and digital forms using the symbolic mathematics capabilities of MATLAB. The proposed explicit finite element integration scheme is illustrated by computing the Prandtl stress function values and the torisonal constant for the square cross section by using the eight node linear convex quadrilateral finite elements.An automatic all quadrilateral mesh generation techniques for the eight node linear convex quadrilaterals is also developed for this purpose.We have presented a complete program which automatically discritises the arbitrary triangular domain into all eight node linear convex quadrilaterals and applies the so generated nodal coordinate and element connection data to the above mentioned torsion problem. Key words: Explicit Integration, Gauss Legendre Quadrature, Quadrilateral Element, Prandtl’s Stress Function for torsion, Symbolic mathematics,all quadrilateral mesh generation technique

Thermal Stability of Phase Change Material

Along with the heat transfer mechanism for the development of a latent heat storage unit (LHSU), the choice of the phase change material (PCM) plays an important role. The enviable thermo-physical, kinetic, and chemical properties of PCM with the economy is an essential criterion for efficient thermo-economical LHSU. The most important criteria that have limited widespread use of LHSU are the useful life of phase change materials. For long term performance of LHSU, the PCM used in the system should be thermally stable and reliable. It does not deteriorate its own properties, especially latent heat and melting point after a repeated number of thermal cycles. Thus an exhaustive literature survey is carried out for different types of PCMs used. The primary objective of this chapter is to carry out a critical review of thermal stability of different group of PCM especially for low temperature applications. Further, an extensive list of different PCMs which are undergone thermal cyclic tests by different researchers is prepared. This information is towards the selection of reliable PCM for latent heat storage unit

A New Approach to Automatic Generation of an all Pentagonal Finite Element Mesh for Numerical Computations over Convex Polygonal Domains

A new method is presented for subdividing a large class of solid objects into topologically simple subregionssuitablefor automatic finite element meshing withpentagonalelements. It is known that one can improve the accuracy of the finite element solutionby uniformly refining a triangulation or uniformly refining a quadrangulation.Recently a refinement scheme of pentagonal partition was introduced in [31,32,33]. It is demonstrated that the numerical solutionbased on the pentagonal refinement scheme outperforms the solutions based on the traditional triangulation refinement scheme as well as quadrangulation refinement scheme. It is natural to ask if one can create a hexagonal refinement or general polygonal refinement schemes with a hope to offer even further improvement. It is shown in literature that one cannot refine a hexagon using hexagons of smaller size. In general, one can only refine an n-gon by n-gons of smaller size if n = 5. Furthermore, we introduce a refinement scheme of a generalpolygon based on the pentagon scheme. This paper first presents a pentagonalization (or pentagonal conversion) scheme that can create a pentagonal mesh from any arbitrary mesh structure. We also introduce a pentagonal preservation scheme that can create a pentagonal mesh from any pentagonal mesh

Autonomous underground water detection Robot

India is one of the most water challenged countries in the world. Water demand is continuously increasing day by day, as people’s demand of water for different household and industrial purpose is increasing. Due to this, surface water is not able to meet the demands of water supply. Due to this need of underground water has increased. This work is focused to meet the challenge of finding out underground water in a simple way with the help of robot. This Arduino based robot would analyze the surface using Wenner method to find the presence of water body under the earth surface. Global Positioning System (GPS) attached to robot will send location of underground water to operator who is taking note of readings of water level. The data received during analysis will be fed through a program which will follow logic and store the amount of water present at that particular depth. This data will help to plot the map of where underground water is available in sufficient quantity

Equilibrium and thermodynamic parameters for heterogeneous esterification of butyric acid with methanol under microwave irradiation

Synthesis of methyl butyrate was investigated in a microwave irradiated batch reactor in presence of acid ion-exchange resin catalyst, amberlyst-15. Methyl ester was heterogeneously produced by the reaction between butyric acid and methanol. Effect of reaction parameters of temperature (323-343 K), catalyst loading (0-10.5% w/w), alcohol to acid ratio, M (1-5), and amount of molecular sieves added (0-13.5% w/w) on conversion were studied. Equilibrium conversion of 92.6% was achieved in 60 minutes under microwave irradiation. Equilibrium constants at varied temperatures and dependency of equilibrium constant on temperature were studied. Equilibrium constant and equilibrium conversion showed increase with the increase in temperature as expected as per le-Chatelier principle. Van't Hoff plot for esterification of butyric acid was linear with negative slope indicating that reaction was endothermic. Comparative study showed that microwave irradiated method for methyl butyrate synthesis to be very efficient and fast compared with conventional and ultrasound assisted routes under optimized reaction conditions

A New Approach to an all Quadrilateral Mesh Generation over Arbitrary Linear Polygonal Domains for Finite Element Analysis

This paper describes a scheme for finite element mesh generation of a convex, non-convex polygon and multiply connected linear polygon. We first decompose the arbitrary linear polygon into simple sub regions in the shape of polygons.These subregions may be simple convex polygons or cracked polygons.We can divide a nonconvex polygon into convex polygons and cracked polygons We then decompose these polygons into simple sub regions in the shape of triangles. These simple regions are then triangulated to generate a fine mesh of triangular elements. We propose then an automatic triangular to quadrilateral conversion scheme. Each isolated triangle is split into three quadrilaterals according to the usual scheme, adding three vertices in the middle of the edges and a vertex at the barrycentre of the element. To preserve the mesh conformity a similar procedure is also applied to every triangle o f the domain to fully discretize the given convex polygonal domain into all quadrilaterals, thus propagating uniform refinement. This simple method generates a high quality mesh whose elements confirm well to the requested shape by refining the problem domain. The proposed scheme has been realized as computer programs and a number of examples have been included to demonstrate the technique. Although the paper describes the scheme as applied to planar domains, it could be extended to three dimensions as well