Permanent Regime Research Articles

Individual differences in beat perception affect gait responses to low- and high-groove music.

Slowed gait in patients with Parkinson’s disease (PD) can be improved when patients synchronize footsteps to isochronous metronome cues, but limited retention of such improvements suggest that permanent cueing regimes are needed for long-term improvements. If so, music might make permanent cueing regimes more pleasant, improving adherence; however, music cueing requires patients to synchronize movements to the “beat,” which might be difficult for patients with PD who tend to show weak beat perception. One solution may be to use high-groove music, which has high beat salience that may facilitate synchronization, and affective properties, which may improve motivation to move. As a first step to understanding how beat perception affects gait in complex neurological disorders, we examined how beat perception ability affected gait in neurotypical adults. Synchronization performance and gait parameters were assessed as healthy young adults with strong or weak beat perception synchronized to low-groove music, high-groove music, and metronome cues. High-groove music was predicted to elicit better synchronization than low-groove music, due to its higher beat salience. Two musical tempi, or rates, were used: (1) preferred tempo: beat rate matched to preferred step rate and (2) faster tempo: beat rate adjusted to 22.5% faster than preferred step rate. For both strong and weak beat-perceivers, synchronization performance was best with metronome cues, followed by high-groove music, and worst with low-groove music. In addition, high-groove music elicited longer and faster steps than low-groove music, both at preferred tempo and at faster tempo. Low-groove music was particularly detrimental to gait in weak beat-perceivers, who showed slower and shorter steps compared to uncued walking. The findings show that individual differences in beat perception affect gait when synchronizing footsteps to music, and have implications for using music in gait rehabilitation.

Celebrity Humanitarianism: The Ideology of Global Charity

Celebrity Humanitarianism: The Ideology of Global Charity

Diagnostic Fault of the Induction Machine with Application of the Neural Network

Although the asynchronous machine is known by its qualities of robustness and low cost of construction, however, it happen that it has an electrical or mechanical fault. This article presented rotoric faults which are treated as part of the detection of broken bars, and the inverter faults (switch fault). This detection technique is based on neural network. The simulation was elaborated on Matlab/Simulink that show results used to assess the performance of the technique presented. Keyword: asynchronous machine, diagnostic, rotoric faults, broken bar, five Levels inverter, neural network. 1. I NTRODUCTION The induction machine is largely used in industry, mainly due to its reliability and relatively low cost. The control of the induction machine must take into account machine specificities: the high order of the model, the nonlinear functioning as well as the coupling between the different variables of control. The new industrial applications necessitate speed variations having high dynamic performances, a good precision in permanent regime, and high capacity of overload on all rang of speed and robustness to the different perturbation. The voltage source inverters construct a non controllable function in the power electronic; it is used in the variable application domains. The strategy obtaining by this technique is based on the study of variation speed in induction machine. The strong functional evolution was based, on one hand, the development of components for semi-conductor entirely commendable, ability, and robustness, the other hand, on the quasi generalized used of the technique pulse width modulation (PWM) (1) (2).The five levels inverter structural is more adapted in the ground power application, because the output voltage and current presented a reduction of the harmonic distortion.

A Wind Turbine System Model using a Doubly-Fed Induction Generator (DFIG)

The ever growing interest in developing green energy worldwide has led to the development of hybrid energy system. Many hybrid energy systems do involve wind systems due to the availability and easy access of wind resource. This paper works on the development and the simulation of a wind farm adaptable to high voltage transmission network. It also implements a control of pitch angle using a PID controller, in order to stabilize rotor speed. Firstly a comprehensive analytical model of wind turbine has been presented and this was followed by the modeling of the wind farm under SimPowerSystem of Simulink. The simulated wind turbine system uses a Doubly Fed Induction Generator (DFIG) having a capacity of six (6) MW that supplies a distribution system at 33 KV. A load is connected at the end of the distribution network through a 20 km, 33 KV feeder. PID control system has been implemented to regulate the speed of the rotor vis-avis the wind speed variations. Results show that the speed regulation was very good. In permanent regime, the variation of rotor speed was almost insignificant despite the continuous variation of the wind speed within the interval of 12 to 15 m/s. At the same time, the active and reactive power obtained were in agreement with the simulation pre-set values. General Terms Modeling, Simulation, Wind Turbine, Wind Farm, Speed Control, pitch angle

Mexico and the United States Assume a Legal Duty to Provide Colorado River Delta Restoration Flows: An Important International Environmental and Water Law Precedent

In 2012, Mexico and the United States interpreted a treaty allocating the use of the Colorado River to protect a stressed delta in Mexico by establishing a pilot programme delivering a base flow to the Delta. Minute 319 is a possible first step toward a permanent adaptive management regime for the Delta because it sets three important international water and environmental law precedents. First, it is a de facto implementation of the ecosystem conservation mandates of the United Nations Convention on the Law of the Non‐navigational Uses of International Watercourses. Second, Minute 319 is equally recognition of the emerging duty of riparian States to cooperate in the long‐term management of shared rivers. Third, although Minute 319 was the product of sovereign‐to‐sovereign negotiations, it was made possible by nongovernmental organizations (NGOs). It thus illustrates the important role that NGOs can play in the implementation of international environmental and water law.

Longitudinal dynamic fracture of polymer pipes

To study the rapid crack propagation (RCP) resistance of polymer pipes, an experimental set-up and a numerical model are proposed. The way to solicit polymer pipes, imposed displacements or pressure, is discussed. Indeed, it has been demonstrated that it is necessary to load polymer pipe with imposed displacements and not internal gas pressure. For a pressurised pipe, a relevant estimation of the energy released rate is difficult because of the work of external forces which can not be precisely determined during crack propagation and of course during gas leak. An experimental set-up, with imposed displacements, has been machined to ensure an approximately L = 13R permanent RCP regime with L and R which are, respectively, the length and the radius of the pipe. The energy release rate is then calculated with the help of a finite element procedure knowing the crack tip location.

Laminar motion of the incompressible fluids in self-acting thrust bearings with spiral grooves.

We analyze the laminar motion of incompressible fluids in self-acting thrust bearings with spiral grooves with inner or external pumping. The purpose of the study is to find some mathematical relations useful to approach the theoretical functionality of these bearings having magnetic controllable fluids as incompressible fluids, in the presence of a controllable magnetic field. This theoretical study approaches the permanent motion regime. To validate the theoretical results, we compare them to some experimental results presented in previous papers. The laminar motion of incompressible fluids in bearings is described by the fundamental equations of fluid dynamics. We developed and particularized these equations by taking into consideration the geometrical and functional characteristics of these hydrodynamic bearings. Through the integration of the differential equation, we determined the pressure and speed distributions in bearings with length in the “pumping” direction. These pressure and speed distributions offer important information, both quantitative (concerning the bearing performances) and qualitative (evidence of the viscous-inertial effects, the fluid compressibility, etc.), for the laminar and permanent motion regime.

Generic stochastic Monte Carlo model of the photoinduced mass transport in azo-polymers and fine structure of Surface Relief Gratings

We study theoretically the possible origin of a double-peak fine structure of Surface Relief Gratings in azo-functionalized poly(etherimide) reported recently in experiments. To improve the statistics of experimental data additional measurements were done. For the theoretical analysis we develop a stochastic Monte Carlo model for photoinduced mass transport in azobenzene-functionalized polymer matrix. The long sought-after transport of polymer chains from bright to dark places of the illumination pattern is demonstrated and characterized, various scenarios for the intertwined processes of build-up of density and SRG gratings are examined. Model predicts that for some azo-functionalized materials double-peak SRG maxima can develop in the permanent, quasi-permanent or transient regimes. Available experimental data are interpreted in terms of model's predictions.

Accelerated Aging of a Solar Absorber Material Subjected to Highly Concentrated Solar Flux

To support the fast growth of Concentrating Solar Power (CSP) technologies, R&D efforts need to be continued to minimize costs. Reducing manufacturing, processing and maintenance costs is key to reach a competitive low production price for electricity.From this perspective, one issue that becomes increasingly significant is the service lifetime of solar absorber materials. In solar tower receivers, absorber materials are subjected to very intense solar flux and cyclic thermal stresses. The chemical and physical aging mechanisms such as corrosion and oxidation, or the possible apparition of cracks or delamination are responsible for the change of the material's surface and bulk properties over time. This causes the thermal performance of the material to decline more or less rapidly.Taking a two-layer solar absorber material (metal + coating) that is commonly used in power tower receivers (SOLAR TWO, GEMASOLAR, SOLHYCO), we have designed several accelerated aging tests by analyzing the thermal behavior of the material in permanent and variable regimes. The experimental tests consist in subjecting the material to cyclic irradiance of variable intensity, amplitude and period to determine the fastest and most realistic tests. A Solar Accelerated Aging Facility (SAAF) was built for this purpose. It is made of a 2-meter diameter parabola concentrating the solar radiation (up to 16,000 times) onto a material sample that is cooled by air or water in direct contact with its rear face. A flux sensor coupled to a shutter allows us to apply the desired solar irradiance while an infrared pyrometer monitors surface temperature of the sample.Following different constant-irradiance solar aging treatments, the properties that are characteristic of the aging are estimated. The normal solar absorptance of each sample is evaluated by a solar optical fiber reflectometer. The thermophysical properties of the paint such as the thermal diffusivity, effusivity, conductivity and the thermal contact resistance between the paint layer and the metal substrate are estimated by inverse method using the measurements of an impulse photothermal experiment. In addition, untreated samples are characterized in order to provide rare data on the ‘not aged’ material.Careful attention should be paid to the preliminary vitrification heat treatment carried out to give the black paint its optimal absorption properties before being used. The results of the aging tests show a slight deterioration of the properties corresponding to the first aging signs of the material. The solar absorptance and the thermal effusivity of the paint coating are the most affected properties during the tests.

Mechanical and Geometrical Characterization of the Conveyors Belts from Mineral Resources Exploitation

Conveyor belt is one of the most common types of continuous handling equipment used for moving rocks of various sizes horizontally or inclined. From researches done in the exploitation of mineral resources and rocks and from the Strength of Materials calculations in this paper is observed above the conveyor sizing and other elements of the transporter requires knowing how belt traction forces (tensions thereof) varies on the conveyor length. In all cases the operation of the conveyor belt must be provided without engaging the slip phenomenon and limiting its displacement (between sets of rollers) so conveyor can operating at optimum parameters. The materials that make up a conveyor belt can be divided into two categories: materials for coating plates or outer shell and a resistance part, areas with inserts that can be textile and steel cables. Because the bands are subjected to tensile efforts and wear phenomena we determine the maximum strength they can operate without going into permanent deformation regime. Conveyor belt dimensioning calculations and other elements of a conveyor varies depending on its length and the carrier operating situations. We can see, also, that sizing conveyor belt and other conveyor components require knowledge of how belt traction forces (tensions thereof) varies along the length of the conveyor. The tensions from the conveyor belt will be study for the climb section and for the descend section. It mentions that the specific resistance to motion of the belt on full branch, consisting of resistances due: current material deformation, rotation rollers camps because pressing rubber layer and roll belt and belt bending. Since current material strength due to deformation and bending belt represents a large percentage of total specific resistance to motion, it follows that resistance decreases with decreasing displacement belt between rollers and increase with the effort in belt, respectively. This explains that resistance decreases with increasing length of conveyor (especially when its initial stretch is great), and with increasing conveyor tilt too. Also, we observe, from the values of forces calculated in the paper, that the resistance to rotation of the roller bearings decreases with increasing load on the roll, hence the values adopted for specific resistance to movement can be more larger on the empty branch than on the full. Knowing how to calculate resistances to motion of the belt, you can fix that occur belt efforts through the points made on the contour method, starting point of the drum motor development and ending point of winding it. These movement resistances calculated for empty and full branches are needed to precisely determine the installed power of the conveyor belt.

Tribo-electrochemical impedance: A new technique for mechanistic study in tribocorrosion

On the basis of a classical model of triboelectrochemistry, a new approach is proposed based on an impedance ratio of a mechanical perturbation and an electrochemical response. Theoretical derivation, experimental setup and application to a passive stainless steel in a borate solution are presented. Transient characteristics yielded by the technique, associated to a permanent tribological regime, are found to obey a two-time-constant law. They are discussed and compared to the global repassivation transients of the material after switching off the abrasive friction.

FAO-56 methodology for determining water requirement of irrigated crops: critical examination of the concepts, alternative proposals and validation in Mediterranean region

The present study evaluates firstly the ability of the FAO-56 methodology, based on the two-step approach “reference evapotranspiration (ET0)—crop coefficient (K c),” to accurately determine the actual evapotranspiration (ET) of irrigated crops and proposes, secondly, the alternative approaches for improving this determination. The FAO-56 methodology is supported by two hypotheses: (1) ET0 represents all effects of weather and (2) K c varies predominately with specific crop characteristics and only marginally with climate, which enables the transfer of K c standard values among locations and climates. On the base of the theoretical analysis and experimental observations, a critical examination of the previous hypotheses demonstrates that they are not verified by reality. The first hypothesis is not verified for two reasons: (a) The formulation adapted by the Penman–Monteith equation and proposed in FAO-56 methodology for calculating ET0 uses climatic variables determined at a 24-h average scale. However, in principle it is only valid in permanent regime, in other words at least on an hourly scale. (b) The FAO-56-proposed formulation attributes a constant value to the canopy resistance of the reference surface; but in reality, this resistance is variable in relation to the climatic variables. The second hypothesis, concerning the two-step approach, is also not verified because the values of K c largely vary in relation to climatic variables (radiation, air vapour pressure deficit and wind speed). This fact does not support the possibility of the transferability of K c values into locations where the local conditions deviate from the conditions where the adjusted values of K c were determined. The weakness of the ET estimation, observed on several crops cultivated in the Mediterranean region, through the application of the FAO-56 methodology, is the result of errors accumulation, associated with that affects the determination of either ET0 or K c. The present study underlines the advantage of using a one-step approach in the calculation of ET, since it is based on fewer computation steps and, consequently, on fewer error sources than the two-step model. Two models adopting this approach are proposed and validated, one of which can be considered as operational, i.e. it only needs standard meteorological data as input. The use of these models enables an improvement of the ET estimation. This objective is a key component of any strategy to improve agricultural water management in Mediterranean region.

Economic Barriers to Democratization in MENA

The literature on regime change in the MENA region had claimed the occurrence of political liberalization and democratization during the 1990s, foreseeing a transition from the dominant authoritarianism in the region to politically more liberal regimes. These analyses neglect the state of permanent authoritarian political regimes with the centralized economic power and their role as periphery states in the world system. In this paper, we have reassessed the existing literature on regime change in the MENA region taking into account the economic and political impacts of rentier economies, with a close look at the countries in the region where popular uprisings took place to overthrow authoritarian leaders during the first half of 2011. We have followed Schlumberger's (2002) method of classification and comparative approach in order to pinpoint a correlation between the authoritarian regime's economic power based on resource allocation, its political dominance and the leaders' role in neo-liberal global political economy.

On the multiple ecological roles of water in river networks

The distribution and movement of water can influence the state and dynamics of terrestrial and aquatic ecosystems through a diversity of mechanisms. These mechanisms can be organized into three general categories wherein water acts as (1) a resource or habitat for biota, (2) a vector for connectivity and exchange of energy, materials, and organisms, and (3) as an agent of geomorphic change and disturbance. These latter two roles are highlighted in current models, which emphasize hydrologic connectivity and geomorphic change as determinants of the spatial and temporal distributions of species and processes in river systems. Water availability, on the other hand, has received less attention as a driver of ecological pattern, despite the prevalence of intermittent streams, and strong potential for environmental change to alter the spatial extent of drying in many regions. Here we summarize long‐term research from a Sonoran Desert watershed to illustrate how spatial patterns of ecosystem structure and functioning reflect shifts in the relative importance of different ‘roles of water' across scales of drainage size. These roles are distributed and interact hierarchically in the landscape, and for the bulk of the drainage network it is the duration of water availability that represents the primary determinant of ecological processes. Only for the largest catchments, with the most permanent flow regimes, do flood‐associated disturbances and hydrologic exchange emerge as important drivers of local dynamics. While desert basins represent an extreme case, the diversity of mechanisms by which the availability and flow of water influence ecosystem structure and functioning are general. Predicting how river ecosystems may respond to future environmental pressures will require clear understanding of how changes in the spatial extent and relative overlap of these different roles of water shape ecological patterns.

Flow Model of Pure Water in a Pipeline

Potable water in Tunisia has well defined characteristics. Thus, the Water researches and Technologies Centre-Borj Cedria mainly processing Natural Waters Laboratory, has worked on the physic-chemical quality of the water. As the Higher Institute of Agronomy-chott mariem have studied the phenomena associated with flows. For this work shows that natural water flows that can be generated in a pipeline. During operation of agricultural pumps (centrifugal pumps), the speed of the electric motor increases from zero to the permanent regime speed. This change in regime influences the flow of the hydraulic installation and forced it to follow the starting dynamic law of the motor. Under the effect of the friction force, due to the fluid viscosity, the transient regime is dumped until reaching the normal operating conditions. In this work, we study this phenomenon and see the influence of the pump startup on the hydraulic behaviour of one dimensional flow throw a cylindrical pipe of linear elastic behaviour. The pipe is connected to constant level reservoir at the downstream end. The problem is governed by a two coupled linear hyperbolic partial differential equations which are the equations of continuity and motion. The mathematical model is solved by the method of characteristics where at the upstream end, that is, at the pump station, the boundary condition is given by the differential equation for speed change of the pump motor. A theoretical relationship is introduced to express the motor torque in terms of the time. At the downstream end the discharging reservoir is assumed to be at a constant level. The computed head and discharge time curves, caused by the starting of the pump, are plotted at some cross sections of the pipe. The results show that the evolution of the hydraulic variables is well influenced by the applied motor torque.

On the Optimal Control of the Vintage Capital Growth Model with Endogenous Labour Supply

We prove that the introduction of endogenous indivisible labor supply into the vintage capital growth model does not rule out the turnpike and optimal permanent regime properties, notably the non-monotonicity properties of optimal paths, inherent in this model.

Study of Flow Problems and Those of Soil Compaction in an Agricultural Farm

In agricultural land can be observed problems regarding water and soil. The problems of water flow can cause breaks in pipes, and the problems associated with soil because of the passage of vehicles and lead to compaction, engender changes in soil parameter directly affects the infiltration water and fruit yield regression plants. In this paper, we will study numerically the flow in pipes and soil compaction. So, a first part examines the phenomena of demurrage pumps; when starting a pump, the speed of the electric motor rises from zero up to the permanent regime speed. This change in regime influences the flow of the hydraulic installation and forced it to follow the starting dynamic law of the motor. Under the effect of the friction force, due to the fluid viscosity, the transient regime is dumped until reaching the normal operating conditions. In this work, we study this phenomenon and see the influence of the pump startup on the hydraulic behaviour of one dimensional flow throw a cylindrical pipe of linear elastic behaviour. The pipe is connected to constant level reservoir at the downstream end. The problem is governed by a two coupled linear hyperbolic partial differential equations which are the equations of continuity and motion. The mathematical model is solved by the method of characteristics where at the upstream end, that is, at the pump station, the boundary condition is given by the differential equation for speed change of the pump motor. A theoretical relationship is introduced to express the motor torque in terms of the time. At the downstream end the discharging reservoir is assumed to be at a constant level. The computed head and discharge time curves, caused by the starting of the pump, are plotted at some cross sections of the pipe. The results show that the evolution of the hydraulic variables is well influenced by the applied motor torque. In a second part of the numerical study of soil compaction is developed.

Penstock failure detection system at the "Valsan" hydro power plant

"Valsan" is a small Hydro Power Plant, 5 MW, situated at about 160 km north of Bucharest, Romania, on the small "Valsan" river in a remote mountainous area. It is equipped with a single Francis turbine. The penstock is located in the access shaft of the HPP. "Hidroelectrica", the Romanian company that operates the HPP, was trying to implement a remote penstock failure detection system. Starting from a classic hydraulic problem, the authors of the paper derived a method for failure detection and localization on the pipe. The method assumes the existence of 2 flow meters and 2 pressure transducers at the inlet and outlet of the pressurized pipe. Calculations have to be based on experimental values measured in a permanent regime for different values of the flow rate. The method was at first tested on a pipe, in the Hydraulic Laboratory of the Technical University of Civil Engineering Bucharest. Pipe failure was modelled by opening of a valve on a tee branch of the analyzed pipe. Experimental results were found to be in good agreement with theoretical ones. The penstock of the "Valsan" HPP, was modelled in EPANET, in order to: i) test the method at a larger scale; ii) get the right flow and pressure transducers that are needed to implement it. At the request of "Hidroelectrica" a routine that computes the efficiency of the turbine was added to the monitoring software. After the system was implemented, another series of measurements were performed at the site in order to validate it. Failure was modelled by opening an existing valve on a branch of the penstock. Detection of the failure was correct and almost instantaneous, while failure location was accurate within 5% of the total penstock length.

Discrete simulation of dense flows of polyhedral grains down a rough inclined plane

The influence of grain angularity on the properties of dense flows down a rough inclined plane are investigated. Three-dimensional numerical simulations using the nonsmooth contact dynamics method are carried out with both spherical (rounded) and polyhedral (angular) grain assemblies. Both sphere and polyhedra assemblies abide by the flow start and stop laws, although much higher tilt angle values are required to trigger polyhedral grain flow. In the dense permanent flow regime, both systems show similarities in the bulk of the material (away from the top free surface and the substrate), such as uniform values of the solid fraction, inertial number and coordination number, or linear dependency of the solid fraction and effective friction coefficient with the inertial number. However, discrepancies are also observed between spherical and polyhedral particle flows. A dead (or nearly arrested) zone appears in polyhedral grain flows close to the rough bottom surface, reflected by locally concave velocity profiles, locally larger coordination number and solid fraction values, smaller inertial number values. This dead zone disappears for smooth bottom surfaces. In addition, unlike sphere assemblies, polyhedral grain assemblies exhibit significant normal stress differences, which increase close to the substrate.

A numerical thermal approach to study the accelerated aging of a solar absorber material

Solar power tower receivers are exposed to highly-concentrated solar flux. The strong flux variations that they are exposed to during their service life enhance the physical–chemical aging mechanisms and cause the decrease of the material’s thermal performance. A material that is commonly used for these applications was selected for our study. It is used for the absorber tubes of a solar power tower receiver. This material is made of an alloy (Inconel 625) that is coated with a silicone-based paint coating (Pyromark 2500 black) to increase the solar radiation absorption capacity.With the aim of determining the optimal conditions to accelerate the aging of this two-layer material (metal+paint coating), an axisymmetric 2-D model reproducing its thermal behavior was developed. Several thermal indicators (temperature, thermal gradients, temporal gradient), which are representative of the thermal aging factors and the material’s thermal performance, are analyzed in different configurations of boundary conditions. One configuration was defined according to the normal working conditions of a particular solar power plant application; the others are associated with various boundary conditions with the potential to increase or modify the thermal stress factors to accelerate the aging mechanisms. Other aging factors such as humidity, pollutants, and dust are not investigated in this paper. Several simulations were run in permanent and variable regimes. The most influencing boundary conditions and material properties were highlighted by a sensitivity study. To design relevant aging tests, particular attention should be paid to the incident solar power and the cooling characteristics of the material. The surface total absorptance, the thermal conductivities and the thermal contact resistance between the paint and the metal layers are the parameters that most affect the material’s thermal behavior. The evolution of those material properties characterizes the aging and should be monitored. Irradiance cycles were simulated for their potential to increase the thermal fatigue. Depending on the average, the amplitude and the period of the cycle, the evolution of the thermal indicators were analyzed. They were compared to select the most appropriate aging tests that are to be performed. From there, two aging strategies were determined. To put them in practice, an experimental Solar Accelerated Aging Facility (SAAF) was built and is described in this paper. It enables to perform accelerated aging experiments with a 2-m-diameter parabola concentrating the sun radiation up to 16,000 times. A preliminary experiment to validate the model confirmed that the simulation results are in good agreement with the experimental.