System For Different Numbers Research Articles

On the Validity of Granger Causality for Ecological Count Time Series

Knowledge of causal relationships is fundamental for understanding the dynamic mechanisms of ecological systems. To detect such relationships from multivariate time series, Granger causality, an idea first developed in econometrics, has been formulated in terms of vector autoregressive (VAR) models. Granger causality for count time series, often seen in ecology, has rarely been explored, and this may be due to the difficulty in estimating autoregressive models on multivariate count time series. The present research investigates the appropriateness of VAR-based Granger causality for ecological count time series by conducting a simulation study using several systems of different numbers of variables and time series lengths. VAR-based Granger causality for count time series (DVAR) seems to be estimated efficiently even for two counts in long time series. For all the studied time series lengths, DVAR for more than eight counts matches the Granger causality effects obtained by VAR on the continuous-valued time series well. The positive results, also in two ecological time series, suggest the use of VAR-based Granger causality for assessing causal relationships in real-world count time series even with few distinct integer values or many zeros.

Detecting defect dynamics in relativistic field theories far from equilibrium using topological data analysis

We study nonequilibrium dynamics of relativistic N-component scalar field theories in Minkowski space-time in a classical statistical regime, where typical occupation numbers of modes are much larger than unity. In this strongly correlated system far from equilibrium, the role of different phenomena such as nonlinear wave propagation and defect dynamics remains to be clarified. We employ persistent homology to infer topological features of the nonequilibrium many-body system for different numbers of field components N via a hierarchy of cubical complexes. Specifically, we show that the persistent homology of local energy density fluctuations can give rise to signatures of self-similar scaling associated with topological defects, distinct from the scaling behavior of nonlinear wave modes. This contributes to the systematic understanding of the role of topological defects for far-from-equilibrium time evolutions of nonlinear many-body systems. Published by the American Physical Society 2024

Spin and exchange in mixed quantum states from first principles in Feynman path integral quantum statistical mechanics representation

The exchange and space correlations in the system of indistinguishable electrons against the background of thermal fluctuations are studied from first principles. A complete set of mutually orthogonal spin-coordinate basis functions symmetric with respect to permutations in coordinate and spin variables is constructed by the action of Young symmetry operators. As an illustration of a general approach, Path Integral Monte Carlo (PIMC) computer simulation of mixed quantum states of four electrons in a model ellipsoidal nanoscopic trap with soft walls is performed. The equilibrium value of the spin is calculated as well as the mechanism of its formation depending on the temperature and shape of the trap in connection with the evolution of the spatial organization of electrons is analyzed. The Quantum-statistical calculation, executed with a fundamentally accurate description of the permutation symmetry of electrons and the spin variable, includes in explicit form the Coulomb and exchange correlations of all orders and the energy exchange with a thermal bath. The equilibrium values ​​of the spin in dependence of the shape of the potential well and temperature as well as statistical distributions over the eigenfunctions of the spin squared operator are obtained. A general, fundamentally accurate and numerically implementable on computers available today computers approach for describing the spin states of systems of different numbers of indistinguishable fermions with spin 1/2 in the representation of path integrals is formulated.The regularities in dependence of spin on the shape of the system and on the temperature are studied. The variations in the geometry of the trap in direction of elongated shapes are accompanied by the transfer of a part of the electron cloud first from the equator to the poles of the ellipsoidal potential well, and then in the opposite direction with the subsequent collapse of the ring-shaped form into a compact clot in the center and its decomposition into two fragments localized on the axis of rotation. The spin of the mixed quantum state of four electrons at room temperature varies depending on the geometry of the system in the opposite direction, compared with the system of two and three electrons, reaching its maximum at a spherical shape. Spin states of electron ensembles several nanometers in size are unstable to thermal perturbations already in the region of room temperatures. Compression leads to a stabilization of spin states. The calculation results indicate a strong dependence of the energy of collective mixed spin states of electrons on a detailed account of exchange and Coulomb high-orders spatial correlations.

An Approach for Pose Invariant Face Recognition System Using Log-Gabor Feature

Biometrics is the process based on humans’ characters like behavioural and physical. Among the biometrics traits, face recognition has attained much importance for the authentication of individuals. Face recognition with pose variation is one of the major challenges among the illumination and expression. The system is widely used as surveillance which can withstand in places like ATMs, Airports, and Streets to track the criminals. The face recognizing mainly depends on the feature extraction from the face. Project aim is to extract those features which are invariant even though the pose changes. In the proposed work face recognition by using Log Gabor features is addressed. Firstly, colour images with variation in poses are captured followed by the extraction of facial features components like eyes, nose, mouth, and chin through Log Gabor features. The identification of the person is done using KNN classifier where the matching is carried out by calculating the Euclidean distance between the training and test pairs. Finally, experimental results show the performance of the system for different number of the users.

Capacity Analysis of Multiple-input-multiple-output System Over Rayleigh and Rician Fading Channel

This paper aims to analyze the channel capacity in terms of spectral efficiency of a multiple-input-multiple-output (MIMO) system when channel state information (CSI) is known using water-filling algorithm and unknown at the transmitter side which it has been shown that the knowledge of the CSI at the transmitter enhancing the performance, the random Rayleigh and Rician channel models are assumed. Ergodic capacity and outage probability are the most channel capacity definitions which are investigated in this study. MATLAB code is devised to simulate the capacity of MIMO system for different numbers of antenna nodes versus different signal-to-noise ratio (SNR) values. In addition, the outage capacity probabilities for vary transmission rate and SNR are discussed.

English

Application of renewable energy in Sudan is a major issue in strategic planning for alternatives fossil fuels to provide part of local energy demand. Sudan is an important case study in the context of renewable energy because Sudan possesses relatively high profusion of solar radiation, moderate wind speeds. This paper discussed the efficient system of sustainable renewable energy for domestic used and its total cost. The method of this paper was collection of the basic data of solar radiation, wind speed, others required input data, and then hybrid optimization simulation model was developed using the electric renewable energy software Hybrid Optimization Model for Electric Renewable (HOMER). The simulation model has been used to find out the best technically viable renewable based energy efficient system for different numbers of household. It finds as the result some topologies of hybrid power. The simulation results have been presented the most efficient achievement and economic way for different numbers of household. The overall cost of energy would be low if the turbine cost decreases in Khartoum. The project lifetime has been considered for 25 years and the annual real interest rate has been taken as 4%. Key words: HOMER, Khartoum- renewable energy, power system, domestic.

Investigation of four wave mixing effect with different number of input channels at various channel spacing

In this paper the design, implementation and performance analysis of four wave mixing (FWM) in optical communication system for different number of input channels is presented using various values of channel spacing. Here, all the input channels have been spaced evenly at various values like 6.25GHz, 12.5GHz, 25GHz, 40GHz, 50GHz with the different number of channels at the input i.e. with 2, 4, 6, 8, 12 input channels. The simulation results reveal that the four wave mixing is minimum when the channel spacing is maximum i.e. 50GHz with minimum number of channels i.e. 2 input channels. It is observed that on increasing the channel spacing, the interference between the input frequencies decreases and hence the four wave mixing also decreases. Also, on increasing the number of input channels/users, the interference between the input frequencies increases and thus, the four wave mixing also increases.

A Comparative Analysis of Feed-Forward and Generalized Regression Neural Networks for Face Recognition Using Principal Component Analysis

In this paper we give a comparative analysis of performance of feed forward neural network and generalized regression neural network based face recognition. We use different inner epoch for different input pattern according to their difficulty of recognition. We run our system for different number of training patterns and test the system’s performance in terms of recognition rate and training time. We run our algorithm for face recognition application using Principal Component Analysis and both neural network. PCA is used for feature extraction and the neural network is used as a classifier to identify the faces. We use the ORL database for all the experiments.

Design and performance of photovoltaic power system as a renewable energy source for residential in Khartoum

This paper discussed the efficient system of sustainable renewable energy for domestic used and its total cost. The method of this paper was the collection of the basic data of solar radiation, wind speed and other required input data, and then hybrid optimization simulation model was developed using the electric renewable energy software hybridoptimization model of renewable energy (HOMER). Simulation model has been used to find out the best technically viable renewable based energy efficient system for different numbers of household. The result of some topologies of hybrid power was found. Simulation results have been presented as the most efficient achievement and economic way for different numbers of household. The overall cost of energy would be low if the turbine cost decreases in Khartoum. The project life time has been considered for 25 years and the annual real interest rate has been taken as 4%.The coast in 25 homes was found to be 1,567,220 USA$. Key words: Khartoum, hybrid optimization model of renewable energy (Homer), renewable energy, power system, domestic.

Hybrid Options Analysis for Power Systems for Rural Electrification in Algeria

Adrar, Djelfa, Illizi and Djanet, are the most rural zones in Algeria where grid connected electric system for the inhabitants will not be possible to establish even in future. Diesel is the main fuel for fulfilling the energy demand. Solar and Wind resources are the hybrid options for these four sites. HOMER, a software for optimization of renewable based energy efficient system for different numbers of households- 1, 20. It shows that per unit (kWh) cost of energy varies from 1.49, 2.46, 1.84 and 4.1 USD to 1.19, 2.16, 1.33, and 1.52 USD respectively for: Adrar, Djelfa, Illizi and Djanet.. On the other hand it's revealed too that the energy cost depends largely on the renewable energy potential quality (Adrar: 1.19 USD and Djelfa 2.16 USD).

Stable islands in the stability chart of milling processes due to unequal tooth pitch

The use of unequal tooth pitch is a known means to influence and to prevent chatter vibrations in milling. While the process dynamics of equally pitched end mills can be modeled by non-autonomous differential equations with a single constant delay, the dynamics of unequally pitched end mills lead to differential equations with multiple constant delays. In this paper the process stability of an unequally pitched end mill is investigated experimentally and theoretically. The numerical approximation of the stability limit relies on two fundamental methods: Ackermann's method to control systems with delay and the method of the piecewise constant subsystems. On the basis of these two methods two ways for the theoretical stability analysis are derived. The first way neglects the time dependency of the system by replacing the time varying system matrices by their means. The second way accounts for the time dependency of the system by combining Ackermann's method to control systems with delay with the method of the piecewise constant subsystems, which results in the semi-discretization method. Besides the exemplary investigation of a specific end mill the two methods are compared for a simple one degree of freedom system for different number of teeth, different alternating and linear tooth pitch variations and different helix angles. It is shown, that unlike equally pitched end mills also at high radial immersions the time dependency of the system leads to significant differences between the stability limits of the unequally pitched end mills, predicted by the two methods. Depending on the time variance of the system and the unequal tooth pitch stable islands can arise, which are largely located within the stable peaks of the stability diagram of the system where the time varying system matrices are replaced by their means. The correctness of the results are backed up for several operating points by time domain simulations, taking into account the trochoidal movement of the cutting edges, the time varying character of the system and teeth jumping out of contact.

The Effect of Subcarrier-Based Channel Estimation on the BER Bound of Turbo Coded OFDM/SDMA System

In this paper, we study the performance of the channel estimation in a Turbo coded, orthogonal frequency division multiplexing (OFDM) with multiple antennas at the receiver. We survey the accuracy of the channel estimation for different number of users and different number of pilot subcarriers. Moreover, since there is not a closed form solution to the BER of the Turbo coded system for different number of constellation size. We develop an equation to obtain the BER bound of the Turbo coded OFDM/SDMA system with M-ary quadrature amplitude modulation (MQAM) in the Rayleigh flat fading channel as a function of the signal constellation and characteristic of the Turbo code with a curve fitting and then propose a method for selecting switching threshold in adaptive modulation case.

CATV Amplifiers: Figure of Merit and the Coefficient System

A coefficient system has been devised which makes use of transmission objectives and amplifier performance to provide a new method of optimizing CATV system design. Maximum system length, in number of tandem amplifiers, is given for a reference amplifier. This number is called the system coefficient. Each other amplifier, either line or distribution, is assigned an amplifier coefficient which shows the number of reference amplifiers to which it is equivalent. For all amplifiers in tandem, the sum of the amplifier coefficients must be less than or equal to the system coefficient. This allows different kinds of amplifiers to be mixed in the same system and systems of different numbers of channels or bandwidth to be mixed to form a larger system. In addition, a line amplifier figure of merit can be derived which is independent of transmission requirements.