Sökning: "Discrete Fourier Transform DFT"

Visar resultat 1 - 5 av 16 uppsatser innehållade orden Discrete Fourier Transform DFT.

1. 1. Approach for frequency response-calibration for microphone arrays

   M1-uppsats, KTH/Hälsoinformatik och logistik

   Författare :Jacob Drotz; [2023]
   Nyckelord :microphone array; frequency response; calibration; sine sweep; inverse filter; digital signal processing DSP ; convolution; Fast Fourier Transform FFT ; Discrete Fourier Transform DFT ; acoustic measurements; audio engineering; mikrofonarray; frekvenssvar; kalibrering; sinussvep; inverterat filter; digital signalbehandling; faltning; Fast Fourier Transform FFT ; Discrete Fourier Transform DFT ; akustiska mätningar; ljudteknik;

   Sammanfattning : Matched frequency responses are a fundamental starting point for a variety ofimplementations for microphone arrays. In this report, two methods for frequencyresponse-calibration of a pre-assembled microphone array are presented andevaluated. LÄS MER

3. 2. Deep Learning Based Out-of-focus Detection on Surveillance Footage

   Master-uppsats, Lunds universitet/Matematik LTH

   Författare :Hanna Bengtsson; Teodora Kerac; [2023]
   Nyckelord :Deep Learning; CNN; Out-of-focus detection; Mathematics and Statistics;

   Sammanfattning : Loss of focus in surveillance cameras can occur due to factors such as environmental aspects, sabotage or system errors. The focus loss leads to degraded footage that is of no use for either post-investigation or automatic video analysis. LÄS MER

4. 3. Automatic classification of cardiovascular age of healthy people by dynamical patterns of the heart rhythm

   Master-uppsats, Linköpings universitet/Statistik och maskininlärning

   Författare :priya kurian pullolickal; [2022]
   Nyckelord :Electrocardiogram ECG measures the electrical impulses of the heart. The time inter- val between two successive R peaks measured in millisecond using an ECG is called as an RR-interval. The distribution of the RR-intervals as well as classification of cardiovascu- lar age of healthy people from RR-interval was done in this thesis. For that; the data was preprocessed and time series plots were analyzed from sample dataset. The RR-intervals were then aligned to have the same start time using functions written and then an aver- age RR-interval series for each decade was created. The coefficient of variation was very less for this averaged dataset which concluded that averaging the RR-interval was a good approach. The averaged dataset per age decade as well agreed to the conclusion of the sample data set that the heart rate variability decreases with increasing age. Three clusters of age decade were also visible in the averaged dataset. The kurtosis; skew; mean; me- dian; histograms and Q-Q Plot were calculated for the sample as well as averaged dataset to find the distribution. The values all concluded that the RR-intervals follow Gaussian distribution or mixture of Gaussian distribution. The Poincaré plots showed that the dis- tribution of RR-interval is comet shaped for healthy individuals. The features were ex- tracted from the distribution as well as from the distribution of Discrete Fourier Transform DFT for classifying the age group from RR-intervals. Svitzky-Golay filtering was done to smooth the signal before taking the features from DFT. Random Forest and Support Vector Machine was the machine learning algorithms used to classify the age decade. Later the results were compared using a dataset from physionet that had RR-intervals of individuals suffering from myocardial infraction. The age classification using Random Forest and Sup- port Vector Machine concluded that the Gdańsk dataset using Random Forest Algorithm and three classes gave the highest test accuracy of 59% for the dataset.;

   Sammanfattning : .... LÄS MER

5. 4. Sparse Approximation of Spatial Channel Model with Dictionary Learning

   Master-uppsats, KTH/Skolan för elektroteknik och datavetenskap (EECS)

   Författare :Matilda Zhou; [2022]
   Nyckelord :Spatial channel model SCM ; dictionary learning; compressive sensing CS ; discrete Fourier transform DFT ; overcomplete discrete Fourier transform ODFT ; Rumslig kanalmodell; ordbokslärning; kompressionsavkänning; diskret Fourier-transform; överkomplett diskret Fourier-transform;

   Sammanfattning : In large antenna systems, traditional channel estimation is costly and infeasible in some situations. Compressive sensing was proposed to estimate the channel with fewer measurements. Most of the previous work uses a predefined discrete Fourier transform matrix or overcomplete Fourier transform matrix to approximate the channel. LÄS MER

7. 5. Numeriska fouriertransformen och dess användning : En introduktion

   Kandidat-uppsats, Linköpings universitet/Tillämpad matematik; Linköpings universitet/Tekniska fakulteten

   Författare :Kristoffer Tondel; [2022]
   Nyckelord :Fast Fourier Transform; FFT; Discrete Fourier transform; DFT; Scientific Computing; Partial differential equation; PDE; Williamsons Runga-Kutta; Fast Fourier Transform; FFT; Diskreta fouriertransformen; DFT; Beräkningsmatematik; Partiella differential ekvation; PDE; Williamsons Runga-Kutta;

   Sammanfattning : The aim of this bachelor's thesis is to use three variants of the discrete Fourier transform (DFT) and compare their computational cost. The transformation will be used to numerically solve partial differential equations (PDE). In its simplest form, the DFT can be regarded as a matrix multiplication. LÄS MER