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Search Results: 1 - 10 of 2590 matches for " propagation "
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Neutrino Oscillations and Superluminal Propagation, in OPERA or Otherwise  [PDF]
Jo?o Magueijo
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.41013
Abstract:

We digress on the implications of recent claims of superluminal neutrino propagation. No matter how we turn it around such behaviour is very odd and sits uncomfortably even within far-fetched theories. In the context of non-linear realizations of the Lorentz group (where superluminal misbehaviour is run of the mill) one has to accept rather contrived constructions to predict superluminal properties for the neutrino. The simplest explanation is to require that at least one of the mass states be tachyonic. We show that due to neutrino mixing, the flavor energy does not suffer from the usual runaway pathologies of tachyons. For non-tachyonic mass states the theories become more speculative. A neutrino specific dispersion relation is exhibited, rendering the amplitude of the effect reasonable for a standard Planck energy. This uses the fact that the beam energy is close to the geometrical average of the neutrino and Planck mass; or, seen in another way, the beam energy is unexceptional but its gamma factor is very large. A dispersion relation crossing over from a low energy bradyonic branch to a high energy tachyonic one is also considered. We comment on consistency with SN 1987Awithin these models.

Research of Social Network Information Propagation Model Based on Public Interest and Opinion  [PDF]
Juntao Li, Tingting Dong, Meng Li
Social Networking (SN) , 2016, DOI: 10.4236/sn.2016.52008
Abstract: During the diffusion of information on the network, the users generally have such an experience that at the beginning they get aware of the news they never know and may be willing to inform others, then their interests fade away, finally the information stops flowing. Meantime, their points of view are changing as the networks’ structure changes. Therefore, this article brings in the interest attenuation mechanism and the social networks consensus evolution mechanism on the basic of the improved SEIR model. So to begin with, we establish a model to analyze how users’ interests change during the diffusion of information on the network. Second we establish another model to analyze the evolution of the opinion during the diffusion of information on the network. At last, we establish a final model by using dynamic equations adding the results of the two models above.
Study of Propagation of Ion Acoustic Waves in Argon Plasma  [PDF]
N. S. Suryanarayana, Jagjeet Kaur, Vikas Dubey
Journal of Modern Physics (JMP) , 2010, DOI: 10.4236/jmp.2010.14039
Abstract: The properties of small amplitude acoustic waves (IAW) in unmagnetised plasma have been discussed in detail. An experimental set up to study the propagation of IAW in argon plasma has been descried. The speed of IAW under different conditions of discharge current and pressure has been measured from the time-of flight technique. From these measurements, electron temperatures have been calculated. The results have been compared with those obtained by single probe method, and were found to be in good agreement with each other so IAW speeds can be used to calculate plasma parameters.
Synthesis of Chained Achromatic Layer Systems Forming Controlled Low Transmittance Bands  [PDF]
Mohamed Medhat, Samy S. Farag
Optics and Photonics Journal (OPJ) , 2011, DOI: 10.4236/opj.2011.13021
Abstract: The approach utilized in the design of achromatic periods formed of two layers a high-index and a low-index is developed by combining the first two periods together. These two periods are therefore reduced to three layers a central one, an upper layer and a lower layer. Both the upper and lower layers are matched to the central at two different wavelengths. This forms the so called a combined achromatic period or the basic unit. Multilayers showing low transmittance bands are then synthesized of this basic unit. Parameters used in the synthesis of such multilayers are pointed out and their control role is investigated.
The Prediction of Propagation Loss of FM Radio Station Using Artificial Neural Network  [PDF]
Ali Riza Ozdemir, Mustafa Alkan, Mehmet Kabak, Mehmet Gulsen, Murat Hüsnü Sazli
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2014, DOI: 10.4236/jemaa.2014.611036
Abstract: In order to calculate the propagation loss of electromagnetic waves produced by a transmitter, a variety of models based on empirical and deterministic formulas are used. In this study, one of the artificial neural networks models, Levenberg-Marquardt algorithm, which is quite effective for predicting the propagation is used and the results obtained by this algorithm are compared with the simulation results based on ITU-R 1546 and Epstein-Peterson models. In this paper, the propagation loss of FM radio station using artificial neural networks models is studied depending on the Levenberg-Marquardt algorithm. For training the artificial neural network, as the input data; range (r), effective antenna height (h) and terrain irregularity (H) parameters are involved and measured values are treated as the output data. The good results obtained in the city area reveal that the artificial neural network is a very efficient method to compute models which integrate theoretical and experimental data. Meanwhile, the results show that an ANN model performs very well compared with theoretical and empiric propagation models with regard to prediction accuracy, complexity, and prediction time. By comparing the results, the RMSE for Neural Network Model using Levenberg-Marquardt is 9.57, and it is lower than that of classical propagation model using Epstein-Peterson for which RMSE is 10.26.
Link Quality Prediction for 802.11 MANETs in Urban Microcells  [PDF]
Gregor Gaertner, Eamonn O. Nuallain
Journal of Computer and Communications (JCC) , 2016, DOI: 10.4236/jcc.2016.413005
Abstract: In this paper we derive the optimal link quality predictor (LQPR) whose parameters are estimated from signal power and node speed samples. We propose a fast estimator for these parameters whose computational complexity is three orders lower than that of the optimal estimator with only a slight loss in accuracy thus enabling real- time execution. We show that using the most recent local mean of the signal as a predictor of future signal strength is also a very close approximation to the optimal predictor. This is the central result of this paper. It obviates the need for complex and/or computationally intensive link quality predictors for 802.11 in urban microcells and has the advantage of not requiring node speed information. The LQPRs are evaluated against the lower error bound. We show that the LQPR based on the most recent local mean of the signal predicts the packet reception probability for pedestrians in urban microcells on average with a mean absolute error of 13.47%, 16.54%, 18.21% and 19.38% for 1 s, 2 s, 3 s and 4 s into the future respectively. This LQP accuracy resembles closely the lower error bound with, for example, a difference of only 2.47% at 2 s into the future.
Effect of Growth Regulators in Production and Rooting of Coffea arabica L. Minicuttings  [PDF]
Paulo Fernando Marques Cavalcanti Filho, Diego Corona Baitelle, Sílvio de Jesus Freitas, Waldinei Souza da Silva, Paulo Cesar dos Santos, Weverton Pereira Rodrigues, Silvério de Paiva Freitas, Ismael Louren?o de Jesus Freitas, Tamara Locatelli, Abra?o Carlos Verdin Filho, Guilherme Bessa Miranda
American Journal of Plant Sciences (AJPS) , 2018, DOI: 10.4236/ajps.2018.94049
Abstract:

The plants of C. arabica do not naturally produce a large number of orthotropic sprouts, hindering clonal multiplication by cutting, which would be the simplest technique with a lower cost of production compared to other methods of vegetative propagation. An alternative form, used successfully in the propagation of eucalyptus, is propagation by minicutting, which consists of pruning the shoot apex of the plant, forming the ministumps, which in variable time interval emits the shoots that will be used to make minicutting. In C. arabica plants the number of shoots can be increased with the application of growth regulators and fertilizers. So, the purpose of this work was to verify the effect of growth regulators and foliar fertilizers on the emission and development of orthotropic shoots of C. arabica. The experiment was installed in a randomized complete block design, with ten treatments composed by growth regulators and fertilizers: T1 (Control); T2 (Stimulate + Sturdy + Enervig); T3 (Stimulate + Vitakelp + Biozyme); T4 (Tiba + Sturdy + Enervig); T5 (Tiba + Vitakelp + Biozyme); T6 (Brs + Sturdy + Enervig) T7 (Brs + Vitakelp + Biozyme); T8 (Stimulate); T9 (TIBA); T10 (Brs-Brassinoesteroid), each plot consisting of two plants. Biometric and physiological parameters were evaluated for the ministumps, as well as the biometric parameters of the shoots and plant survival. The results showed that there was no influence of the treatments on the biometric parameters of the ministumps. A greater number of orthotopic sprouts were obtained in treatments with the TIBA growth regulator, as well as a greater plant survival of the minicuttings, after 25 days of transplanting in a greenhouse. It was concluded that TIBA treatments influenced the production and quality of clonal minicuttings of C. arabica.

INFLUêNCIA DE DIVERSOS SUBSTRATOS NO DESENVOLVIMENTO DE MUDAS DE MARACUJAZEIRO AZEDO (Passiflora edulis Sims f. flavicarpa DEG)
SILVA, ROGéRIO PEREIRA DA;PEIXOTO, JOSé RICARDO;JUNQUEIRA, NILTON TADEU VILELA;
Revista Brasileira de Fruticultura , 2001, DOI: 10.1590/S0100-29452001000200036
Abstract: with the purpose of evaluating the influence of substrate on the development of yellow passion fruit, an experiment in a greenhouse at embrapa cerrados station has been conducted. the experimental design was a randomized block in a factorial scheme 2 x 4 x 3 x 2, totalizing 48 treatments, 18 useful plants by plot and four replications. the treatments had consisted of combinations of: two commercial substrate (plantmaxr ? to the base of vermiculiter plus pines bark and vermiculiter ? to the base of vermiculiter); three organic sources ? f.o. (humus, cows manure and nutriplantar (product base of bacteria) and absence of f.o., in the ratio of 3:1 of the basic substrate for f.o.; two formulated fertilizers [osmocoter as 14-14-14 (product of slow release of nutrients) and 4-14-8, of normal release], besides the absence of fertilizer and, absence and presence of glomus etunicatum. the artificial substrate plantmaxr was upper than the vermiculiter in all the analyzed features. among the f.o., the nutriplantar with cows manure had provided the best performance. the osmocoter promoted the biggest development of seedlings, followed by 4-14-8. the presence of absence of f.o. matched with plantmaxr practically did not influence the analyzed features. it must not use glomus etunicatum associated the plantmaxr, due to the high phosphorus content in this substrate.
Características físicas e químicas de substratos para produ??o de mudas de Ilex paraguariensis St. Hil.
Wendling, Ivar;Guastala, Daniel;Dedecek, Renato;
Revista árvore , 2007, DOI: 10.1590/S0100-67622007000200003
Abstract: this work aimed to evaluate the physical and chemical properties of different materials and their compositions, as well as their efficiency in the production of ilex paraguariensis seedlings in plastic tubes. the work was conducted at the baldo s.a. company nursery in s?o mateus do sul, pr, brazil. six materials were used to formulate 14 treatments: cattle manure, semi-decomposed sawdust, ilex paraguariensis chopped stems, underground earth, commercial substrate based on pinus bark and earthworm humus. the results indicated that the treatments containing sawdust, ilex paraguariensis stems and mainly cattle manure, besides being more economical, produced good quality seedlings. the treatments consisting of 40% cattle manure and 60% sawdust stood out because of the good cost-benefit ratio and the easiness of preparation. substrate chemical characteristics did not affect the physical characteristics, as well the influence of physical characteristics on ilex paraguariensis seedling production depends on the analyzed variable.
Propagation Modelling Using Integral Equation Methods to Enable Co-existence and Address Physical Layer Security Issues in Cognitive Radio  [PDF]
Eamonn O. Nuallain
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2011, DOI: 10.4236/ijcns.2011.43017
Abstract: In this paper it is envisaged that cognitive radios (CRs) consult a supporting network infrastructure for per-mission to transmit. The network server either grants or rejects these requests by estimating, from the CR’s geo-location and antenna features, the likely impact its transmission would have on incumbents and other CR devices. This decision would be based on a real-time radio environment map [1] which would be kept up to date with readings from CRs, sensors and dynamic radio propagation prediction. By this means coexistence with incumbents and other CRs can be satisfied. It is maintained here that integral-equation (IE) - based al-gorithms are suitable candidates for the propagation engine given their ‘automatic’ nature and that they can be implemented to give results arbitrarily close to the exact numerical solution. IE methods based on the Fast Multipole Method are examined as a likely route to achieve the accuracy and speed necessary for real-time propagation mapping. It is concluded that the results obtained using one of the most recent of these, the Field Extrapolation Method (FEXM) [2], are promising for rural/suburban profiles and could serve to enable co-existence, for example, in IEEE802.22 networks. It is also explained how dynamic propagation prediction can address some fundamental security threats to CR networks.
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