نتایج جستجو برای: scatter

تعداد نتایج: 12375  

2011
Fredrik Kjolstad Torsten Hoefler Marc Snir

Many high performance applications spend considerable timepacking data into contiguous communication buffers. Datatypesprovide an alternative by describing the layout of the communi-cated data. This empowers the runtime system to retrieve non-contiguous elements directly from application data structures.However, programmers find complex datatypes hard to use andare reluc...

Journal: :European Journal of Operational Research 2006
Francisco Herrera Manuel Lozano Daniel Molina

Scatter search is an evolutionary method that shares with genetic algorithms, a well-known evolutionary approach, the employment of a combination method that combines the features of two parent vectors to form several offspring. Furthermore, it uses improvement strategies to efficiently produce the local tuning of the solutions. An important aspect concerning scatter search is the trade-off bet...

Journal: :Annals of nuclear medicine 2005
Jingming Bai Jun Hashimoto Koichi Ogawa Atsushi Kubo Atsushi Fukunaga Satoshi Onozuka Koichi Uchida

OBJECTIVE The aim of this study was to evaluate the effect of scatter and attenuation correction in region of interest (ROI) analysis in brain perfusion single-photon emission tomography (SPECT) and to assess the influence of selecting the reference area on semi-quantification. METHODS Ten normal subjects were enrolled and injected with 123I-iodoamphetamine to undergo simultaneous emission an...

2016
Dongcai Hu Hao Chen Yuan Wang Yunbin Chen Zhou Xu

In the flat panel detector-based cone beam CT system, the scatter photons which reach the flat panel detector increase the detected signal, produce the image cupping artifact and reduce the image contrast. To conquer the X-Ray scatter problem, this study proposes the beam attenuation grid -based scatter correction algorithm that needs to add a beam attenuation grid (BAG) between the X-Ray sourc...

2012
Yuantao CHEN Weihong XU Jiaying WU Guiping ZHANG

In this paper, a reformative scatter difference discriminant criterion (SDDC) with fuzzy set theory is studied. The scatter difference between between-class and within-class as discriminant criterion is effective to overcome the singularity problem of the within-class scatter matrix due to small sample size problem occurred in classical Fisher discriminant analysis. However, the conventional SD...

Journal: :The Journal of animal ecology 2016
Zhishu Xiao Zhibin Zhang

It is well known that direct effects of seed predators or dispersers can have strong effects on seedling establishment. However, we have limited knowledge about the indirect species interactions between seeds of different species that are mediated by shared seed predators and/or dispersers and their consequences for plant demography and diversity. Because scatter-hoarding rodents as seed disper...

2015
Peter G.F. Watson Ernesto Mainegra‐Hing Nada Tomic Jan Seuntjens

Cone-beam computed tomography (CBCT) images suffer from poor image quality, in a large part due to contamination from scattered X-rays. In this work, a Monte Carlo (MC)-based iterative scatter correction algorithm was implemented on measured phantom data acquired from a clinical on-board CBCT scanner. An efficient EGSnrc user code (egs_cbct) was used to transport photons through an uncorrected ...

2017
Mohammad Javad Tahmasebi Birgani Nahid Chegeni Mohammad Ali Behrooz Marziyeh Bagheri Amir Danyaei Azin Shamsi

INTRODUCTION One of the important input factors in the commissioning of the radiotherapy treatment planning systems is the phantom scatter factor (Sp) which requires the same collimator opening for all radiation fields. In this study, we have proposed an analytical method to overcome this issue. METHODS The measurements were performed using Siemens Primus Plus with photon energy 6 MV for fiel...

2004
Songcan Chen Xubing Yang

Fisher linear discriminant analysis (FLDA) $nds a set of optimal discriminating vectors by maximizing Fisher criterion, i.e., the ratio of the between scatter to the within scatter. One of its major disadvantages is that the number of its discriminating vectors capable to be found is bounded from above by C-1 for C-class problem. In this paper for binary-class problem, we propose alternative FL...

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