Dynamics of circular arrangements of vorticity in two dimensions

The merger of two like-signed vortices is a well-studied problem, but in a turbulent flow, we may often have more than two like-signed vortices interacting. We study the merger of three or more identical co-rotating vortices initially arranged on the vertices of a regular polygon. At low to moderate Reynolds numbers, we find an additional stage in the merger process, absent in the merger of two vortices, where an annular vortical structure is formed and is long-lived. Vortex merger is slowed down significantly due to this. Such annular vortices are known at far higher Reynolds numbers in studies of tropical cyclones, which have been noticed to a break down into individual vortices. In the pre-annular stage, vortical structures in a viscous flow are found here to tilt and realign in a manner similar to the inviscid case, but the pronounced filaments visible in the latter are practically absent in the former. Interestingly at higher Reynolds numbers, the merger of an odd number of vortices is found to proceed very differently from that of an even number. The former process is rapid and chaotic whereas the latter proceeds more slowly via pairing events. The annular vortex takes the form of a generalised Lamb-Oseen vortex (GLO), and diffuses inwards until it forms a standard Lamb-Oseen vortex. For lower Reynolds number, the numerical (fully nonlinear) evolution of the GLO vortex follows exactly the analytical evolution until merger. At higher Reynolds numbers, the annulus goes through instabilities whose nonlinear stages show a pronounced difference between even and odd mode disturbances. It is hoped that the present findings, that multiple vortex merger is qualitatively different from the merger of two vortices, will motivate studies on how multiple vortex interactions affect the inverse cascade in two-dimensional turbulence.Comment: Abstract truncated. Paper to appear in Physical Review

A screening of the dicotyledonous weed flora for the occurrence of C<SUB>4</SUB> dicarboxylic acid pathway of photosynthesis

Using the criteria of leaf anatomy, carbon dioxide compensation point and photosynthetic rate under reduced oxygen tension, a number of the local herbaceous and dicotyledonous weeds were screened for the occurrence of the C4 pathway of photosynthesis. Of the thirty-two species, belonging to nine families seventeen species revealed the characteristics of the C4 plants. All of the plants surveyed here were hitherto not tested and therefore the present results extend the number of plants already known to possess the Hatch-Slack pathway of photosynthesis. Another noteworthy feature of the investigation was the finding of interspecific differences within the generaHeliotropium, Alternanthera, Mollugo andEuphorbia in the presence or absence of the C4 pathway

Development of a creep data base management system for engineering materials

A fully menu driven creep data base management system has been developed for various high temperature materials using the client /server (C/S) architecture with Sybase system. 10 as backend and power builder 4.0 as an inter-face. The relational data base constitutes of various classes of materials, their heat treatment, prior history and the related creep properties at different test condit-ions, in addition to the source process route and chemical composition details.Top-down approach has been adopted in designing the entity-relationship (E-R) model. The creep data is organized into the third normal form, and the entire system is divided into manageable modules. Coding for the system is done using Transact-SQL for data defin- ition, manipulation and control operations, and power script language for application development. This article briefly outlines the formulation of data base design, and the implemented E-R model, in addition , to the prese-ntation of various screen formats used for data entry and retrieval modules

Classifiers in Image processing

Image classification is a necessary step in pattern recognition, the efficiency and accuracy mainly depends on the classification .To do the successful classification pre-processing, segmentation, at last feature extraction have to do. Recognition rate depends on all the steps but classification has its own importance in pattern recognition. Some important classifier such assupport vector machine (SVM),artificial neural network(ANN), decision tree, KNN etc. All has their importance in one or the other way. In this paper there is a discussion about many classifiers

Purification of a 19-kDa pore-forming cytolysin from the sea anemone Heteractis magnifica

Pore-forming cytolysins of 19 kDa from sea anemones present a remarkable cytolytic property. In the present work, a purified 19-kDa cytolysin was obtained from the sea anemone Heteractis magnifica. The purification steps involved ammonium sulfate precipitation and subsequently desalting by dialysis against 10 mM sodium phosphate buffer (pH 7.4), followed by anion exchange chromatography in DEAE-Sepharose® column (GE Healthcare, Sweden) and gel filtration chromatography using Sephadex® G-50 matrix (GE Healthcare, Sweden). The active fractions from the gel filtration chromatography were pooled and rechromatographed in the same column. The final active fraction showed a prominent protein band of molecular mass of 19 kDa when analyzed by SDS-PAGE

A Survey on Feature Extraction Techniques for Handwritten Character Recognition

The efficiency and accuracy of the optical character recognition system is very much dependent on the appropriate choice of the feature extraction techniques used. In the field of pattern recognition hand written character recognition is an interesting field of research. If the features calculated or observed for a character are enough and complete to specify it then classification errors can be minimized. So feature extraction plays a vital role in the handwritten character recognition. This paper describes about the different techniques of feature extraction

PHARMACOKINETIC DRUG INTERACTIONS OF GLICLAZIDE AND ITOPRIDE IN NORMAL AND DIABETIC RATS

Objective: The present study was aimed to investigate the safety, reliability of Gliclazide and possible drug interaction with Itopride when they were administered as combination treatment.Methods: Studies were conducted in normal and streptozotocin induced diabetic rats with oral administration of selected doses of gliclazide, itopride and their combination. Blood samples were collected from rats by retro orbital/marginal ear vein puncture at regular intervals of time. All the blood samples were analyzed for pharmacokinetic parameters by HPLC method.Results: There was no significant difference in pharmacokinetic parameters of both Gliclazide alone and combination with itopride in healthy and diabetic rats on day 1 and day 8.Conclusion: Based on the results it can be concluded that the concurrent administration of these two drugs have potential benefit without any drug interactions in the effective management of diabetes and gastroparesis.Â

Bandwidth Recycling using Variable Bit Rate

IEEE 802.16 standard was designed to support the bandwidth demanding applications with quality of service (QoS). Bandwidth is reserved for each application to ensure the QoS. For variable bit rate (VBR) applications, however, it is difficult for the subscriber station (SS) to predict the amount of incoming data. To ensure the QoS guaranteed services, the SS may reserve more bandwidth than its demand. As a result, the reserved bandwidth may not be fully utilized all the time. In this paper, we propose a scheme, named Bandwidth Recycling, to recycle the unused bandwidth without changing the existing bandwidth reservation. The idea of the proposed scheme is to allow other SSs to utilize the unused bandwidth when it is available. Thus, the system throughput can be improved while maintaining the same QoS guaranteed services. Mathematical analysis and simulation are used to evaluate the proposed scheme. Simulation and analysis results confirm that the proposed scheme can recycle 35% of unused bandwidth on average. By analyzing factors affecting the recycling performance, three scheduling algorithms are proposed to improve the overall throughput. The simulation results show that our proposed algorithm improves the overall throughput by 40% in a steady network. Keywords: WiMAX, IEEE 802.16, Bandwidth Recyclin

Pembuatan Administrasi Users Account Shell Linux Menggunakan PHP

Dalam mengatur konfigurasi user Linux tidak terlalu mudah bagi seorang yang selalu berpergian karena untuk dapat mengaturnya harus berhadapan dengan computer dan linux tersebut. Maka dari itu dalam penelitian ini membuat sebuah fasilitas remote control berbasiskan desktop bagi pengguna yang ingin mengaksses Linux tersebut dimana saja. Untuk mengatasi hal itu buat suatu aplikasi dapat mengakses linux dan mengatur konfigurasinya melalui web browser, yang dapat diakses dimana saja dan kapanpun. Dalam penelitian ini software yang dDigunakan fungsi dalam PHP yaitu PHP Exec yang berfungsi untuk mengkonversi perintah yang diketikan pada web browser menjadi perintah yang dikenali dalam sistem operasi Linux dan dengan menggunakan pemrogramman Bash. Hasil yang akan didapatkan adalah sebuah aplikasi berbasiskan web browser yang mampu mangkonfigurasi user Linux dengan secara online, dengan beberapa fitur tambahan yang digunakan untuk melengkapi aplikasi ini