scholarly journals Characterization and Investigation of Nonlinear Behaviour of Radio Refractivity during the Rainy and Dry Seasons in the Coastal Region of Nigeria

2021 ◽  
Vol 25 (7) ◽  
pp. 1155-1161
Author(s):  
A.E. Adeniji ◽  
E.M. Ajeigbe ◽  
K.S. Ojo
Keyword(s):  
Meteorological Parameters ◽  
Coastal Region ◽  
Nonlinear Effects ◽  
Nonlinear Behaviour ◽  
Radio Communication ◽  
National Space ◽  
Communication Links ◽  
Radio Signals ◽  
Quantification Analysis ◽  
Dry Seasons

The transmission and receiving of good quality of signals globally has been impaired due to the internal activities of the troposphere linked to the nonlinear behaviour of the meteorological parameters. This paper focusses on characterizing and investigating the nonlinear behaviour of radio refractivity during the rainy and dry seasons in the coastal region of Nigeria using temperature, pressure and relative humidity data collected over a period of two years by the Centre for Atmospheric Research, National Space Research and Development Agency (NASRDA) from Lagos state. Data obtained were analyzed by False Nearest Neighbour (FNN) and Recurrence Quantification Analysis (RQA). The results show that recurrence techniques are able to identify the periods where there are high predictability and low predictability. The investigation of nonlinear effects of meteorological parameters and the hydrometeors on the troposphere help to avoid fading of radio signals along with the radio communication links.

Nonlinear Sloshing in Fixed and Vertically Excited Containers

2002 ◽  
Author(s):  
Jannette B. Frandsen ◽  
Alistair G. L. Borthwick
Keyword(s):  
Perturbation Theory ◽  
Free Surface ◽  
Small Perturbation ◽  
Numerical Solutions ◽  
Vertical Direction ◽  
Nonlinear Effects ◽  
Breaking Waves ◽  
Surface Flow ◽  
Nonlinear Behaviour ◽  
Computational Domain

Nonlinear effects of standing wave motions in fixed and vertically excited tanks are numerically investigated. The present fully nonlinear model analyses two-dimensional waves in stable and unstable regions of the free-surface flow. Numerical solutions of the governing nonlinear potential flow equations are obtained using a finite-difference time-stepping scheme on adaptively mapped grids. A σ-transformation in the vertical direction that stretches directly between the free-surface and bed boundary is applied to map the moving free surface physical domain onto a fixed computational domain. A horizontal linear mapping is also applied, so that the resulting computational domain is rectangular, and consists of unit square cells. The small-amplitude free-surface predictions in the fixed and vertically excited tanks compare well with 2nd order small perturbation theory. For stable steep waves in the vertically excited tank, the free-surface exhibits nonlinear behaviour. Parametric resonance is evident in the instability zones, as the amplitudes grow exponentially, even for small forcing amplitudes. For steep initial amplitudes the predictions differ considerably from the small perturbation theory solution, demonstrating the importance of nonlinear effects. The present numerical model provides a simple way of simulating steep non-breaking waves. It is computationally quick and accurate, and there is no need for free surface smoothing because of the σ-transformation.

Mobile Multimedia Streaming Using Secure Multipath in Wireless Ad Hoc Networks

2012 ◽  
pp. 141-159
Author(s):  
Lei Chen ◽  
Chung-Wei Lee
Keyword(s):  
Ad Hoc Networks ◽  
Ad Hoc ◽  
Data Distribution ◽  
Multimedia Streaming ◽  
Ad Hoc Routing ◽  
Secure Data ◽  
Communication Links ◽  
Radio Signals ◽  
Streaming Service ◽  
Hoc Networks

Supporting reliable and secure multimedia streaming service is a challenging task in the environment of wireless Mobile Ad hoc Networks (MANETs) where radio signals are prone to security attacks and the quality of media streaming is degraded by signal strength loss and interference. The mobility of mobile devices makes streaming even more difficult as communication links are often broken when the devices move out of the transmission range of their neighbors. This paper proposes a stable multipath routing algorithm and an intelligent secure data distribution scheme for multimedia streaming in MANETs. The multipath Neighbor Stability Routing is able to find more stable and long-lasting paths than traditional ad hoc routing algorithms. The secure data distribution takes historical data-path distribution into consideration and maximally disperses new multimedia data to reduce the possibility of information leakage to unauthorized parties. The authors’ simulation and analysis indicate that the combination of these two mechanisms can provide high quality paths to achieve secure multimedia streaming.

scholarly journals Ecological anatomy of Eugenia punicifolia (Kunth) DC. (MYRTACEAE) in the restinga region,state of Ceará

2019 ◽  
Vol 41 (6) ◽  
Author(s):  
Viviane de Oliveira Thomaz Lemos ◽  
Eliseu Marlônio Pereira de Lucena ◽  
Oriel Herrera Bonilla ◽  
Bruno Edson-Chaves
Keyword(s):  
Leaf Blade ◽  
Coastal Region ◽  
The State ◽  
Vascular Bundles ◽  
The Sun ◽  
Natural Conditions ◽  
Ecological Anatomy ◽  
Dry Seasons ◽  
Sun And Shade ◽  
Sclerenchyma Fibers

Abstract The species Eugenia punicifolia (Kunth) DC. (myrtle) occurs in the coastal region of the state of Ceará and has ecological and medicinal importance. This study aimed to characterize the leaf anatomy of myrtle (E. punicifolia) in the rainy and dry seasons, as well as in the sun and shade in the restinga region of the state of Ceará and to contribute to the understanding of the morphoanatomic variations in response to the natural conditions of the occurrence of this species. For this, collections of fully expanded leaves were performed at the Botanical Park of Ceará and fixed in FAA70, being replaced by 70% ethanol after 24 hours. The usual anatomical procedures were then performed in order to qualitatively and quantitatively analyze the leaf blade, petiole and epidermis structures. As a result, it was found that myrtle has xeromorphic characteristics such as thick cuticle, hypoestomatic leaf and sclerenchyma fibers in the median vein vascular bundles. It was concluded that E. punicifolia has great plasticity to adjust well under the analyzed conditions.

scholarly journals The atmospherical drought as a decisive factor of yield in the main sour cherry varieties of Hungary

2012 ◽  
Vol 18 (2) ◽  
Author(s):  
L. Lakatos ◽  
T. Szabó ◽  
M. Soltész ◽  
Z. Szabó ◽  
Z. Sun ◽  
...  
Keyword(s):  
Water Supply ◽  
Meteorological Parameters ◽  
Photosynthetic Activity ◽  
Sour Cherry ◽  
Air Humidity ◽  
Tree Crown ◽  
Fruit Species ◽  
Relative Air Humidity ◽  
Dry Seasons ◽  
Effects Of Drought

Atmospheric drought causes heavy diffi culties of water supply in most fruit species grown in Hungary, although the modern, intensive plantations are already equipped with irrigation. The use a dripping systems are widely applied, therefore nothing was done to avert the risk of atmospheric drought. In excessively dry seasons the reduction of yields is often due to atmospheric drought. Present study aims to utilise measured data of meteorological parameters (relative air humidity and temperature) to develop an index to characterise drought and measure its effect on fruit yield. Causes influencing yields are multiple. Phytosanitary problems are combined with defi cits of water supply. Water deficit of the soil is avoided by dripping irrigation, but the atmosphere is infl uenced by sprinklers only. Atmospherical drought increases the transpiration of the trees intensely and causes reduction of photosynthetic activity, consequently impairs the yield. Applying the index developed in a plantation of 6 sour cherry varieties grown in Hungary (Meteor, Nefris, Pándy, Újfehértói fürtös, Kántorjánosi, Debreceni bôtermô), we measured the specific yields (yield per volume of tree crown) during the period 1989–2011 using the meteorological database of the growing site. Additionally, other parameters characterising the drought are compared and searched for a method most reliable for judging the specific yielding capacity of sour cherry varieties. The results proved convincingly the utility of the index, especially for the varieties Pándy and Újfehértói fürtös. Comparison with other indices expressing the effects of drought revealed the superiority of our index, which will be applied in the future to express the risk of atmospheric drought.

scholarly journals Review of the Multicarrier Modulation Techniques used in Modern Wireless Communications

Telecom IT ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 55-66
Author(s):  
I. Grishin ◽  
A. Kalinkina
Keyword(s):  
Communication Networks ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Filter Bank ◽  
Multicarrier Modulation ◽  
Wireless Communication Networks ◽  
Frequency Division ◽  
Radio Communication ◽  
Modulation Techniques ◽  
Radio Signals

This article provides an overview of the technologies for generating radio signals, such as orthogonal frequency division multiplexing and its modifications: universal filtered multicarrier and filter bank multi-carrier currently used in wireless communication networks. Subject of research: methods of multicar-rier modulation. Main results: Overview of modern methods of forming multicarrier signals in radio communication systems. A number of computational experiments have been performed to compare the characteristics of signal localization, peak-to-average ratios and spurious emissions. Practical implica-tions: the results can be used in choosing the type of modulation in the case of the development of digi-tal radio communication systems.

scholarly journals Time Series and Empirical Orthogonal Transformation Using Meteorological Parameters across the Climatic Zones in Nigeria

2019 ◽  
pp. 257-272
Author(s):  
D. O. Akpootu ◽  
B. I. Tijjani ◽  
U. M. Gana
Keyword(s):  
Time Series ◽  
Relative Humidity ◽  
Solar Radiation ◽  
Meteorological Parameters ◽  
Orthogonal Transformation ◽  
Global Solar Radiation ◽  
Climatic Zones ◽  
Sunshine Hours ◽  
Dry Seasons ◽  
The Mean

Time series and empirical orthogonal transformation analysis was carried out for four (4) selected tropical sites, which are situated across the four different climatic zones, viz. Sahelian, Midland, Guinea savannah and Coastal region in Nigeria using measured monthly average daily global solar radiation, maximum and minimum temperatures, sunshine hours, rainfall, wind speed, cloud cover and relative humidity meteorological data during the period of thirty one years (1980-2010). Seasonal Auto Regressive Integrated Moving Average (ARIMA) models were developed along with their respective statistical indicators of coefficient of determination (R2), Root Mean Square Error (RMSE), Mean Absolute Percentage Error (MAPE) and Mean Absolute Error (MAE). The results indicated that the models were found suitable for one step ahead global solar radiation forecast for the studied locations. Furthermore, the results of the time series analysis revealed that the model type for all the meteorological parameters show a combination of simple seasonal with one or more of either ARIMA, winter’s additive and winter’s multiplicative with the level been more significant as compared to the trend and seasonal variations for the exponential smoothing model parameters in all the locations. The results of the correlation matrix revealed that the global solar radiation is more correlated to the mean temperature except for Akure where it is more correlated to the sunshine hours; the mean temperature is more correlated to the global solar radiation; the rainfall is more correlated to the relative humidity and the relative humidity is more correlated to the rainfall in all the locations. The results of the component matrix revealed that three seasons are identified in Nguru located in the Sahelian region namely, the rainy, the cool dry (harmattan) and the hot dry seasons while in Zaria, Makurdi and Akure located in the Midland, Guinea savannah and Coastal zones two distinct seasons are identified namely, the rainy and dry seasons.

scholarly journals Experimental Dynamic Analysis of Nonlinear Beams under Moving Loads

2012 ◽  
Vol 19 (5) ◽  
pp. 969-978 ◽  
Author(s):  
A. Bellino ◽  
S. Marchesiello ◽  
L. Garibaldi
Keyword(s):  
Natural Frequencies ◽  
Linear Time ◽  
Moving Load ◽  
Nonlinear Effects ◽  
Experimental Tests ◽  
Interesting Case ◽  
Reinforced Concrete Beams ◽  
Nonlinear Behaviour ◽  
Time Varying ◽  
Over Time

It is well known that nonlinear systems, as well as linear time-varying systems, are characterized by non-stationary response signals. In this sense, they both show natural frequencies that are not constant over time; this variation has however different origins: for a time-varying system the mass, and possibly the stiffness distributions, are changing over time, while for a nonlinear system the natural frequencies are amplitude-dependent. An interesting case of time-varying system occurs when analyzing the transit of a train over a railway bridge, easily simulated by the crossing of a moving load over a beam. In this case, the presence of a nonlinearity in the beam behaviour can cause a significant alteration of the modal parameters extracted from the linearized model, such that the contributions of the two effects are no more distinguishable.For this study, some reinforced concrete beams have been tested in the framework of a vast project: these beams show a clear softening nonlinear behaviour, well detectable when the excitation is produced by a hammer (free response). If the passage of a carriage is considered, moreover, the variation of natural frequencies is always larger than expected because of this softening nonlinearity.The article first analyzes theoretically the two effects on the natural frequencies of a simply supported beam, then a numerical and an experimental tests are presented. The identification procedure is conducted with a linear algorithm called ST-SSI, which has been demonstrated to be appropriate for the analysis of non-stationary signals, in particular in presence of moving masses. The article shows that the nonlinear contribution can be well estimated by using this linear tool but, on the contrary, when also moving masses are present, it is difficult to separate the nonlinear effects from the time varying ones.

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