نتایج جستجو برای: محاسبه های dft

تعداد نتایج: 513852  

2004

The standard method for spectrum analysis in digital signal processing (DSP) is the discrete Fourier transform (DFT), typically implemented using a fast Fourier transform (FFT) algorithm. However, there are applications that require spectrum analysis only over a subset of the N center frequencies of an N-point DFT. A popular, as well as efficient, technique for computing sparse DFT results is t...

مقدمه: گیاه نیشکر و شکر حاصل از آن حاوی انواع ترکیبات فنولی است که خواص آنتی اکسیدانی مطلوبی نیز دارند. از این رو پژوهش حاضر به بررسی امکان اندازه گیری این ترکیبات فنولی در شکر قهوه ای با استفاده از روش DFT می­پردازد. مواد و روش‌ها: در این پژوهش از دو نوع شکر پخت (II) و پخت (III) در فرایند تولید شکر نمونه­گیری شد و در ابتدا با استفاده از دستگاه کروماتوگرافی ما...

2012
Krzysztof Duda

Discrete Fourier Transform (DFT) is probably the most popular signal processing tool. Wide DFT use is partly dedicated to fast Fourier Transform (FFT) algorithms (Cooley & Tukey, 1965, Oppenheim et al., 1999, Lyons, 2004). DFT may also be efficiently computed by recursive algorithms in the window sliding by one sample (Jacobsen & Lyons, 2003, Duda, 2010). Unfortunately, DFT has two main drawbac...

2017
Kimihiko Hirao Jong-Won Song

Electronic structure calculations are now indispensible for understanding chemical phenomena. Density functional theory (DFT), which is simple, conceptual, and applicable to large systems, has emerged as a powerful computational tool to tackle molecular electronic structures. DFT efficiently calculates electronic structure with high accuracy, and its algorithm is suitable for parallel computing...

Journal: :Kardiologia polska 2007
Agnieszka Zienciuk Andrzej Lubiński Tomasz Królak Ewa Lewicka-Nowak Maciej Kempa Anna Pazdyga Grzegorz Raczak

BACKGROUND An increased defibrillation threshold (DFT) may limit the efficacy of an implantable cardioverter-defibrillator (ICD) in termination of life-threatening ventricular arrhythmias. A search for methods of decreasing DFT has been ongoing since the introduction of ICD into clinical practice. AIM To assess the effects of various shock polarities on DFT. METHODS The study group consiste...

Journal: :Physical chemistry chemical physics : PCCP 2014
Scott Sneddon Daniel M Dawson Chris J Pickard Sharon E Ashbrook

Periodic density functional theory (DFT) calculations have recently emerged as a popular tool for assigning solid-state nuclear magnetic resonance (NMR) spectra. However, in order for the calculations to yield accurate results, accurate structural models are also required. In many cases the structural model (often derived from crystallographic diffraction) must be optimised (i.e., to an energy ...

1998
James L. Massey

| Some applications of the Discrete Fourier Transform (DFT) in coding and in cryptography are described. The DFT over general commutative rings is introduced and the condition for its existence given. Blahut's Theorem, which relates the DFT to linear complexity, is shown to hold unchanged in general commutative rings. I. The (Usual) Discrete Fourier Transform Let be a primitive N th root of uni...

2015
Jason Yust

Music theorists have only recently, following groundbreaking work by Quinn, recognized the potential for the DFT on pcsets, initially proposed by Lewin, to serve as the foundation of a theory of harmony for the twentieth century. This paper investigates pcset “arithmetic” – subset structure, transpositional combination, and interval content – through the lens of the DFT. It discusses relationsh...

2010
G. STEIDL

The discrete Fourier-cosine transform (cos-DFT), the discrete Fourier-sine transform (sin-DFT) and the discrete cosine transform (DCT) are closely related to the discrete Fourier transform (DFT) of real-valued sequences. This paper describes a general method for constructing fast algorithms for the cos-DFT, the sin-DFT and the DCT, which is based on polynomial arithmetic with Chebyshev polynomi...

اعلایی, مجتبی, خراسانی, الهام, دیلی‌نظر, نجمه, شهبازی, فرهاد,

The geometrical frustration in the magnetic pyrochlore oxides causes interesting properties at low temperatures in these materials. Therefore, we studied two challenging materials, Er2Ti2O7 and Tb2Ti2O7, using an ab intio method, based on Density Functional Theory (DFT). To take into account the f electrons coulomb interactions correctly, we employed DFT+U, a Hubbard method correction. As spin-...

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