Evolving model-free scattering matrix via evolutionary algorithm: 16^{16}O-16^{16}O elastic scattering at 350 MeV

We present a new procedure which enables to extract a scattering matrix $S(l)$ as a complex function of angular momentum directly from the scattering data, without any a priori model assumptions implied. The key ingredient of the procedure is the evolutionary algorithm with diffused mutation which evolves the population of the scattering matrices, via their smooth deformations, from the primary arbitrary analytical $S(l)$ shapes to the final ones giving high quality fits to the data. Due to the automatic monitoring of the scattering matrix derivatives, the final $S(l)$ shapes are monotonic and do not have any distortions. For the $^{16}$O-$^{16}$O elastic scattering data at 350 MeV, we show the independence of the final results of the primary $S(l)$ shapes. Contrary to the other approaches, our procedure provides an excellent fit by the $S(l)$ shapes which support the ``rainbow'' interpretation of the data under analysis.Comment: 7 pages, 7 figures, to be published in Phys. Rev. C (2005

Fast gradient descent for drifting least squares regression, with application to bandits

Online learning algorithms require to often recompute least squares regression estimates of parameters. We study improving the computational complexity of such algorithms by using stochastic gradient descent (SGD) type schemes in place of classic regression solvers. We show that SGD schemes efficiently track the true solutions of the regression problems, even in the presence of a drift. This finding coupled with an $O(d)$ improvement in complexity, where $d$ is the dimension of the data, make them attractive for implementation in the big data settings. In the case when strong convexity in the regression problem is guaranteed, we provide bounds on the error both in expectation and high probability (the latter is often needed to provide theoretical guarantees for higher level algorithms), despite the drifting least squares solution. As an example of this case we prove that the regret performance of an SGD version of the PEGE linear bandit algorithm [Rusmevichientong and Tsitsiklis 2010] is worse that that of PEGE itself only by a factor of $O(\log^4 n)$. When strong convexity of the regression problem cannot be guaranteed, we investigate using an adaptive regularisation. We make an empirical study of an adaptively regularised, SGD version of LinUCB [Li et al. 2010] in a news article recommendation application, which uses the large scale news recommendation dataset from Yahoo! front page. These experiments show a large gain in computational complexity, with a consistently low tracking error and click-through-rate (CTR) performance that is $75\%$ close

Colloidal Dynamics on Disordered Substrates

Using Langevin simulations we examine driven colloids interacting with quenched disorder. For weak substrates the colloids form an ordered state and depin elastically. For increasing substrate strength we find a sharp crossover to inhomogeneous depinning and a substantial increase in the depinning force, analogous to the peak effect in superconductors. The velocity versus driving force curve shows criticality at depinning, with a change in scaling exponent occuring at the order to disorder crossover. Upon application of a sudden pulse of driving force, pronounced transients appear in the disordered regime which are due to the formation of long-lived colloidal flow channels.Comment: 4 pages, 4 postscript figure

Optically bound microscopic particles in one dimension

Counter-propagating light fields have the ability to create self-organized one-dimensional optically bound arrays of microscopic particles, where the light fields adapt to the particle locations and vice versa. We develop a theoretical model to describe this situation and show good agreement with recent experimental data (Phys. Rev. Lett. 89, 128301 (2002)) for two and three particles, if the scattering force is assumed to dominate the axial trapping of the particles. The extension of these ideas to two and three dimensional optically bound states is also discussed.Comment: 12 pages, incl. 5 figures, accepted by Phys. Rev.

Antecedent and Consequence of E-procurement Implementation on Performance of Small and Medium Enterprises: An Institutional Theory Perspective

The purpose of the study is to investigate the antecedents of e-procurement adoption and implementation and its consequence on organizational performance of small and medium enterprises in Ghana. Using the institutional theory as theoretical lens, the study examined the influence of memetic, normative and coercive force on e-procurement implementation. The findings of the study indicate memetic, normative and coercive forces have a positive impact on the adoption and implementation of e-procurement system among SMEs. Consequently, e-procurement implementation on performance of SMEs. The findings of the study have both implication for academic and practice. The findings of this study have significant implications for policy makers, SMEs, and other stakeholders in the procurement process in Ghana. Policymakers can use the study findings to develop policies and regulations that promote e-procurement adoption among SMEs. SMEs, on the other hand, can use the study findings to identify the benefits of e-procurement adoption and make informed decisions on implementing e-procurement systems. Keywords: Institutional Theory, SME performance, Ghana, PLS – SEM, Normative Forces, Memetic Forces, Coercive Forces DOI: 10.7176/EJBM/15-9-02 Publication date:May 31st 202

TEKSTUR DEFORMASI DAN REKRISTALISASI BAJA LEMBARAN CANAI DINGIN BEBAS INTERSTISI

TEKSTUR DEFORMASI DAN REKRISTALISASI BAJA LEMBARAN CANAI DINGIN BEBAS INTERSTISI. Perkembangan tekstur kristalografi dipelajari pada baja lembaran bebas interstisi canai dingin. Tekstur yang diamati adalah tekstur deformasi setelah pencanaian dingin dan tekstur rekristalisasi atau tekstur annealing setelah proses annealing. Tekstur deformasi baja lembaran bebas interstisi dipelajarimelalui variasi persen reduksi ketebalan dengan selang reduksi antara 50,5% hingga 90 %. Sementara tekstur rekristalisasi dipelajari melalui variasi laju pemanasan annealing antara 32 oC/jam hingga 128 oC/jam, variasi waktu penahanan annealing antara 5 jam hingga 20 jam dan variasi suhu annealing dari 700 oC hingga 900 oC. Perkembangan tekstur deformasi dan rekristalisasi dipelajari melalui pengujian difraksi sinar-X. Tekstur kristalografi diukur untuk tekstur yang mempengaruhi sifat mampu bentuk, yaitu tekstur [111] dan tekstur [100]. Pengujian tarik terhadap spesimen pada orientasi yang berbeda terhadap arah pencanaian kemudian dilakukan untuk memperoleh nilai r yang merupakan parameter sifat mampu bentuk baja lembaran