Conditions Of Non-stationarity Research Articles

VARIABILIDADE DA CONCENTRAÇÃO MÉDIA DE CO2 ACIMA DA FLORESTA AMAZÔNICA DURANTE A NOITE ASSOCIADA A DISTINTOS REGIMES TURBULENTOS

We studied the Nocturnal Boundary Layer - CLN on area of primary tropical forest northeast of Amazonas State in Amazon Tall Tower Observatory - ATTO. We applied the method of Sun et al. (2012) to characterization three regimes dinamic stability in CLN: 1) a weak turbulence, with low average wind speed; 2) strong turbulence, with high avarage wind speed and 3) turbulent intermittency and nonstationarity conditions. There are seasonal variations in the values of c and from one regime to another. We investigated some of the main statistical characteristics of CO 2 concentrations - c for each one the turbulent regimes. c slightly increases with the increase of the value of a characteristic turbulence velocity scale, V TKE until a threshold value, V L , from which a sudden increase in the values of c is observed.This find is important consequences for parametrization of meteorological variables in the NBL and modelling of the atmospheric flod in the interface forest-atmosferic.

Which downscaled rainfall data for climate change impact studies in urban areas? Review of current approaches and trends

Changes in extreme precipitation should be one of the primary impacts of climate change (CC) in urban areas. To assess these impacts, rainfall data from climate models are commonly used. The main goal of this paper is to report on the state of knowledge and recent works on the study of CC impacts with a focus on urban areas, in order to produce an integrated review of various approaches to which future studies can then be compared or constructed. Model output statistics (MOS) methods are increasingly used in the literature to study the impacts of CC in urban settings. A review of previous works highlights the non-stationarity nature of future climate data, underscoring the need to revise urban drainage system design criteria. A comparison of these studies is made difficult, however, by the numerous sources of uncertainty arising from a plethora of assumptions, scenarios, and modeling options. All the methods used do, however, predict increased extreme precipitation in the future, suggesting potential risks of combined sewer overflow frequencies, flooding, and back-up in existing sewer systems in urban areas. Future studies must quantify more accurately the different sources of uncertainty by improving downscaling and correction methods. New research is necessary to improve the data validation process, an aspect that is seldom reported in the literature. Finally, the potential application of non-stationarity conditions into generalized extreme value (GEV) distribution should be assessed more closely, which will require close collaboration between engineers, hydrologists, statisticians, and climatologists, thus contributing to the ongoing reflection on this issue of social concern.

Dynamics of temperature-frequency processes in multifrequency crystal oscillators with digital compensations of resonator performance instability

Design and construction peculiarities of multifrequency crystal oscillators technically invariant to temperature effects have been considered. The analysis of thermodynamic characteristics of multifrequency temperature-compensated crystal oscillators was performed in conditions of nonstationarity of the thermal behavior of piezoelectric resonator. The volume density of heat source was determined during the excitation of quartz crystal resonator. Thermodynamic processes occurring in multifrequency crystal oscillators were investigated at the stage of settling of quartz crystal resonator oscillations. The need of taking into account the thermodynamic component during the investigation of high-speed thermal processes taking place in quartz crystal resonators was proved. The efficiency of using a multifrequency-algorithmic approach for ensuring the invariance of piezoresonance devices was estimated. It was shown that the use of this approach makes it possible to essentially reduce the temperature instability of crystal oscillators and reduce the up time of these devices due to a more exact compensation of initial frequency drifts.

Method for adaptive decoding in case of information transmission in condition of influence of deliberate noise

It is proposed a method for increase of reliability of information transmission in wireless networks, functioning in conditions of influence of deliberate noise. The method is based on additional application of uncertainty factor in case of decision making in the turbo decoder in conditions of non-stationarity of the transmission channel. In a process of adaptive regulation of turbo code decoding iterations amount is modified for each data packet basing on dynamic calculation of uncertainty factor. Simulation results show increase of signal to noise ratio results in decoding iteration decrease, and information transmission reliability increase.

The Peculiarities of Acoustical Monitoring of Moving Objects in Shallow Water Areas

The article considers peculiarities of underwater monitoring of moving objects in the shallow water areas, particularly seaports. These areas are characterized by a multitude of factors influencing the efficiency of detection. Nonstationarity conditions of sound propagation and specific interference caused by shipping are the major factors. The various algorithms for the space-time signal processing have been tested and some experimental results are presented. It has been shown that the use of clipped mode in conjunction with the correlation processing of wideband signals and subsequent speckle tracking allow realizing high efficiency of monitoring.

A Bayesian Analysis of Autoregressive Time Series Panel Data

We describe a Bayesian hierarchical model to analyze autoregressive time series panel data. We develop two algorithms using Markov-chain Monte Carlo methods, a restricted algorithm that enforces stationarity or nonstationarity conditions on the series and an unrestricted algorithm that does not. Two examples show that restricting stationary series to be stationary provides no new information, but restricting nonstationary series to be stationary leads to substantial differences from the unrestricted case. These examples and a simulation study also show that, compared with inference based on individual series, there are gains in precision for estimation and forecasting when similar series are pooled.

Testing and evaluation of thermosyphon solar water heating system by means of components testing and whole system testing and simulation in Jordan

The basic method to evaluate the solar collectors thermal behaviour is characterized by a general test method, that is testing of flat plate collectors efficiency under nearly steady state conditions while it might be impossible to guarantee steady state conditions for solar water heater systems installed in the actual applications. A test method for solar water heater system by means of a whole system testing was developed to characterize the thermal behaviour for a thermosyphon solar water heating system with flat plate collector of 3.7 m 2 and 150 liter hot water storage under non-stationarity conditions, that is unsteady state conditions. The new test method is validated through comparing its results with the results of separate tests of the collectors and storage of the SWH system. The yearly energy gain is predicted by simulating the whole system using the modular structured program TRNSYS[3]. The comparison between the results of the two test methods shows an agreement in the predicted yearly energy gain for the same data base within 4%.