Semi-blind sparse channel estimation with constant modulus symbols

We propose two methods for the estimation of sparse communication channels. In the first method, we consider the problem of channel estimation based on training symbols, and formulate it as an optimization problem. In this formulation, we combine the objective of fidelity to the received data with a non-quadratic constraint reflecting the prior information about the sparsity of the channel. This approach leads to accurate channel estimates with much shorter training sequences than conventional methods. The second method we propose is aimed at taking advantage of any available training-based data, as well as any "blind" data based on unknown, constant modulus symbols. We propose a semi-blind optimization framework making use of these two types of data, and enforcing the sparsity of the channel, as well as the constant modulus property of the symbols. This approach improves upon the channel estimates based only on training sequences, and also produces accurate estimates for the unknown symbols

Incremental Distance Transforms (IDT)

A new generic scheme for incremental implementations of distance transforms (DT) is presented: Incremental Distance Transforms (IDT). This scheme is applied on the cityblock, Chamfer, and three recent exact Euclidean DT (E2DT). A benchmark shows that for all five DT, the incremental implementation results in a significant speedup: 3.4×−10×. However, significant differences (i.e., up to 12.5×) among the DT remain present. The FEED transform, one of the recent E2DT, even showed to be faster than both city-block and Chamfer DT. So, through a very efficient incremental processing scheme for DT, a relief is found for E2DT’s computational burden

Türdeş yoğunlukta olmayan arkaplan ve önplana sahip nesnelerin olasılık yoğunluk fonksiyonu tabanlı veri terimi ve parametrik olmayan şekil önbilgisi kullanılarak bölütlenmesi (Segmentation of inhomogeneous foreground and background intensity objects using a probability density function based data term and nonparametric shape priors)

Bu çalısmada türdes yoğunlukta olmayan arkaplan ve önplana sahip resimlerin bölütlenmesini ele alıyoruz. Bölütlenecek olan nesnenin iç ve dıs bölgelerinin türdes olmaması bölütleme islemini zorlastırmaktadır. Türdes olmama durumunun sebepleri arasında görüntülerin düsük kalitede olması ve gürültü gösterilebilir. Ayrıca bu bölgelerin kendileri yüzey dokusuna sahip olabilirler. Zorlu bölütleme sorunlarını çözmek üzere önerilen ve sıkça kullanılan bir yaklasım sekil önbilgisini kullanmaktır. Sekil önbilgisi kullanılarak düsük kalitedeki görüntülerin bölütlenmesinde gelismeler kaydedilmistir. Ancak; mevcut sekil tabanlı yaklasımların çoğu bölütlenecek olan nesnenin iç ve dıs bölgelerini türdes olarak kabul ettikleri için yukarıda bahsi geçen özelliklere sahip görüntülerde basarılı bir sonuç vermemektedirler. Biz bir yandan türdes olmayan bölge yeğinliklerinin olasılık yoğunluk fonksiyonlarını, diğer yandan da bölütlenecek nesnelerin sekillerini öğrenip kullanan bir bölütleme yaklasımı öneriyoruz. Önerdiğimiz yöntem türdes yoğunlukta olmayan bölgelere sahip görüntülerin bölütlenmesinde basarılı sonuçlar vermektedir

Multipole analysis of spin observables in vector meson photoproduction

A multipole analysis of vector meson photoproduction is formulated as a generalization of the pseudoscalar meson case. Expansion of spin observables in the multipole basis and behavior of these observables near threshold and resonances are examined.Comment: 15 pages, latex, 2 figure

Confinement and the analytic structure of the one body propagator in Scalar QED

We investigate the behavior of the one body propagator in SQED. The self energy is calculated using three different methods: i) the simple bubble summation, ii) the Dyson-Schwinger equation, and iii) the Feynman-Schwinger represantation. The Feynman-Schwinger representation allows an {\em exact} analytical result. It is shown that, while the exact result produces a real mass pole for all couplings, the bubble sum and the Dyson-Schwinger approach in rainbow approximation leads to complex mass poles beyond a certain critical coupling. The model exhibits confinement, yet the exact solution still has one body propagators with {\it real} mass poles.Comment: 5 pages 2 figures, accepted for publication in Phys. Rev.

The quest for axions and other new light particles

Standard Model extensions often predict low-mass and very weakly interacting particles, such as the axion. A number of small-scale experiments at the intensity/precision frontier are actively searching for these elusive particles, complementing searches for physics beyond the Standard Model at colliders. Whilst a next generation of experiments will give access to a huge unexplored parameter space, a discovery would have a tremendous impact on our understanding of fundamental physics

Impact of the relatively light fourth family neutrino on the Higgs boson search

The existence of a fourth fermion generation has mostly been considered as a source of enhanced Higgs signals with respect to the 3 family Standard Model predictions. However, a fourth Standard Model family neutrino could cause the opposite situation. It is shown that relatively light fourth family neutrino (2m_(nu_(4))<m_(H)) could drastically change the interpretation of the search results for the Higgs boson, especially if m_(H)<170 GeV.Comment: 5 pages, 9 figure

The ATLAS muon micromegas R&D project: towards large-size chambers for the s-LHC

Detectors based on the bulk-Micromegas technology exhibit position resolution better than 100 m m at counting rates of up to several tens of kHz/cm(2), along with trigger capabilities. These characteristics, combined with the detector's mechanical robustness and the possibility for cost-effective industrial production, makes them a promising candidate for the ATLAS Muon Spectrometer upgrade in a future luminosity enhancement of the LHC. The R&D project status will be presented together with the obtained results in the effort to define the baseline system specifications