Segregation in a fluidized binary granular mixture: Competition between buoyancy and geometric forces

Starting from the hydrodynamic equations of binary granular mixtures, we derive an evolution equation for the relative velocity of the intruders, which is shown to be coupled to the inertia of the smaller particles. The onset of Brazil-nut segregation is explained as a competition between the buoyancy and geometric forces: the Archimedean buoyancy force, a buoyancy force due to the difference between the energies of two granular species, and two geometric forces, one compressive and the other-one tensile in nature, due to the size-difference. We show that inelastic dissipation strongly affects the phase diagram of the Brazil nut phenomenon and our model is able to explain the experimental results of Breu et al. (PRL, 2003, vol. 90, p. 01402).Comment: 5 pages, 2 figure

Application of artificial neural networks in nonlinear analysis of trusses

A method is developed to incorporate neural network model based upon the Backpropagation algorithm for material response into nonlinear elastic truss analysis using the initial stiffness method. Different network configurations are developed to assess the accuracy of neural network modeling of nonlinear material response. In addition to this, a scheme based upon linear interpolation for material data, is also implemented for comparison purposes. It is found that neural network approach can yield very accurate results if used with care. For the type of problems under consideration, it offers a viable alternative to other material modeling methods

HTTP Mailbox - Asynchronous RESTful Communication

We describe HTTP Mailbox, a mechanism to enable RESTful HTTP communication in an asynchronous mode with a full range of HTTP methods otherwise unavailable to standard clients and servers. HTTP Mailbox allows for broadcast and multicast semantics via HTTP. We evaluate a reference implementation using ApacheBench (a server stress testing tool) demonstrating high throughput (on 1,000 concurrent requests) and a systemic error rate of 0.01%. Finally, we demonstrate our HTTP Mailbox implementation in a human assisted web preservation application called "Preserve Me".Comment: 13 pages, 6 figures, 8 code blocks, 3 equations, and 3 table

Influinsasi Media Internet terhadap Proses Pemilu di Indonesia

Jaringan komputer telah berkembang begitu pesatnya, tanpa disadari jaringan komputer telah berevolusi sedemikian rupa. Pada awal pengembangannya teknologi tersebut digunakan hanya untuk kepentingan internal departemen pertahanan Amerika Serikat. Namun seiring dengan perkembangan jaman teknologi tersebut telah menyebar di berbagai belahan dunia yang bertujuan untuk mempermudah transformasi data dan informasi supaya dinikmati dengan cepat. Alhasil muncul lah teknologi masterpiece dambaan semua golongan, yaitu internet. Nama yang tidak asing lagi di telinga kebanyakan orang. Dengan internet, apapun bisa dilakukan. Sebuah teknologi yang memberikan keleluasan bagi para penggunanya, tanpa batas teritorial, dimana pun, kapan pun bisa mengakses teknologi tersebut. Kenyataanya, teknologi tersebut bisa dimanfaatkan untuk apa saja. Ada dampak positif dan negatif yang ditimbulkan dari teknologi internet. Salah satunya adalah pemanfaatan internet dalam rangka penyelenggaraan PEMILU di Indonesia. Hal tersebut bisa dilihat dari PEMILU 2009 ini, dimana penggunaan internet bisa dimanfaatkan untuk berkampanye secara online. Caleg yang mengerti IT bisa memanfaatkan internet untuk menyapa konstituen mereka serasa di dunia nyata. Barangkali itulah salah satu contoh dimana internet bisa digunakan untuk melakukan kampanye dalam proses PEMILU yang berlangsung. Barangkali itulah adanya proses pengaruh internet terhadap masyarakat yang semakin lama mulai merasakan kelebihan salah satu masterpiece teknologi informasi tersebut

Young Stars with SALT

We present a spectroscopic and kinematic analysis of 79 nearby M dwarfs in 77 systems. All are low-proper-motion southern hemisphere objects and were identified in a nearby star survey with a demonstrated sensitivity to young stars. Using low-resolution optical spectroscopy from the Red Side Spectrograph (RSS) on the South African Large Telescope (SALT), we have determined radial velocities, H-alpha, Lithium 6708\AA, and Potassium 7699\AA~equivalent widths linked to age and activity, and spectral types for all our targets. Combined with astrometric information from literature sources, we identify 44 young stars. Eighteen are previously known members of moving groups within 100 parsecs of the Sun. Twelve are new members, including one member of the TW Hydra moving group, one member of the 32 Orionis moving group, nine members of Tucana-Horologium, one member of Argus, and two new members of AB Doradus. We also find fourteen young star systems that are not members of any known groups. The remaining 33 star systems do not appear to be young. This appears to be evidence of a new population of nearby young stars not related to the known nearby young moving groups.Comment: 23 pages, 11 figures, 6 tables. Accepted to Ap