406 research outputs found

    Radiation Induced Point and Cluster-Related Defects with Strong Impact to Damage Properties of Silicon Detectors

    Full text link
    This work focuses on the investigation of radiation induced defects responsible for the degradation of silicon detectors. Comparative studies of the defects induced by irradiation with 60Co- rays, 6 and 15 MeV electrons, 23 GeV protons and 1 MeV equivalent reactor neutrons revealed the existence of point defects and cluster related centers having a strong impact on damage properties of Si diodes. The detailed relation between the microscopic reasons as based on defect analysis and their macroscopic consequences for detector performance are presented. In particular, it is shown that the changes in the Si device properties after exposure to high levels of 60Co- doses can be completely understood by the formation of two point defects, both depending strongly on the Oxygen concentration in the silicon bulk. Specific for hadron irradiation are the annealing effects which decrease resp. increase the originally observed damage effects as seen by the changes of the depletion voltage. A group of three cluster related defects, revealed as deep hole traps, proved to be responsible specifically for the reverse annealing. Their formation is not affected by the Oxygen content or Si growth procedure suggesting that they are complexes of multi-vacancies located inside extended disordered regions.Comment: 14 pages, 15 figure

    Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an

    Full text link
    Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis

    Impacts of the Tropical Pacific/Indian Oceans on the Seasonal Cycle of the West African Monsoon