A robust model-free controller for a three-phase grid-connected photovoltaic system based on ultra-local model

In this paper, a robust model-free controller for a grid-connected photovoltaic (PV) system is designed. The system consists of a PV generator connected to a three-phase grid by a DC/AC converter. The control objectives of the overall system are to extract maximum power from the PV source, to control reactive power exchange and to improve the quality of the current injected into the grid. The model-free control technique is based on the use of an ultra-local model instead of the dynamic model of the overall system. The local model is continuously updated based on a numerical differentiator using only the input–output behavior of the controlled system. The model-free controller consists of a classical feedback controller and a compensator for the effects of internal parameter changes and external disturbances. Simulation results illustrate the efficiency of the controller for grid-connected PV systems.     

An investigation of the drivers,barriers, and incentives for environmental management systems in the Malaysian food and beverage industry

Clean Technologies and Environmental Policy - Food production and consumption is one of the major causes of global environmental degradation. One way to address environmental impacts in the food...     

Hybrid intelligent framework for one-day ahead wind speed forecasting

Neural Computing and Applications - Nowadays wind power is considered as one of the fastest growing alternative energies, that is expected to continue to grow rapidly in the upcoming...     

A Distributed Routing Method for Dynamic Multicasting

Single point, sender based control does not scale well for multicast delivery. For applications, such as group video or teleconferencing a low total cost multicast tree is required. In this article we present a destination driven algorithm to minimize the total tree cost of multicast tree in a dynamic situation for the whole session duration. In this heuristic approach we considered the staying duration of participants are available at the time of joining. The performance of our algorithm is analyzed through extensive simulation and evaluated against several other existing dynamic multicast routing and also against one well known near optimum heuristic algorithm used for solving Steiner tree problem. We have further tested our algorithm using erroneous information given by the joining participants. Simulation results show that its performance does not degrade that much even when the range of error is considerably high, which proves the robustness of our algorithm.     

Model Validation for Bridge-Road-Vehicle Dynamic Interaction System

The dynamic response of highway bridges subjected to moving truckloads has been observed to be dependent on (1) dynamic characteristics of the bridge; (2) truck configuration, speed, and lane position on the bridge; and (3) road surface roughness profile of the bridge and its approach. Historically, truckloads were measured to determine the load spectra for girder bridges. However, truckload measurements are either made for a short period of time [for example, weigh-in-motion (WIM) data] or are statistically biased (for example, weigh stations) and cost prohibitive. The objective of this paper is to present results of a 3D computer-based model for the simulation of multiple trucks on girder bridges. The model is based on the grillage approach and is applied to four steel girder bridges tested under normal truck traffic. Actual truckload data collected using a discrete bridge WIM system are used in the model. The data include axle loads, truck gross weight, axle configuration, and statistical data on multiple presence (side by side or following). The results are presented as a function of the static and dynamic stresses in each girder and compared with code provisions for dynamic load factor. The study provides an alternate method for the development of live-load models for bridge design and evaluation.     

Entrepreneurship in an Unstable Environment: The Experience of the Occupied Territories

The research aims at exploring the relationship between small business enterprises and their environments through an empirical investigation of the methods and strategies adopted by a number of industrial firms operating in the West Bank and the Gaza Strip in response to the exigencies and challenges of the uprising in the occupied territories in order to survive. Though the problems faced by the industrial sector as a result of the unique situation in the areas are almost unparalleled in other parts of the world, it has been possible to gain fresh insight into the dynamics of the environmental factors and their impact on organizational structure and function. Despite innumerable obstacles, the industrial sector has achieved a reasonable degree of growth.     

An assessment of the θ-projection method for the representation and extrapolation of creep data for a 1%Cr, 12%Mo, 14%V steel tested at 565°C

Constant stress creep data for a wrought 1%Cr, $\text{1}\text{2}\text{\%}\text{Mo}$, $\text{1}\text{4}\text{\%}\text{V}$ steel obtained from six tests carried out at 565°C have been fitted and extrapolated using the θ-projection method. Creep curves for high stresses were fitted well, but curves extrapolated to stress levels below those used in the θ-projection did not represent well the available data for primary-secondary creep. To enable a satisfactory extrapolation of results, it was found necessary to redefine the failure condition to be less sensitive to the shape of the latter sections of the tertiary creep curve. This was achieved by defining lifetime as the point on the curve at which the strain rate reached a fixed multiple of the creep rate at half the rupture time. The extrapolated data compare well with the results of tests carried out independently on a cast 1%Cr, $\text{1}\text{2}\text{\%}\text{Mo}$, $\text{1}\text{4}\text{\%}\text{V}$ steel. The extrapolation procedure not only predicts the ‘knee’ in the log stress-log lifetime curve but allows extrapolation of lifetimes by over a factor of thirty. In addition, acceptable predictions have been made of constant load experimental data.     

Chromosome comparison between populations of the collared peccary, Tayassu tajacu, raised in captivity

The collared peccary (Tayassu tajacu) is widely distributed over the American continent, being found from the south of the USA to the north of Argentina. In Brazil, it is spread all over the country, being one of the potential species to be raised in captivity. Therefore, the cytogenetic techniques could be a potential tool for reproductive monitoring of animals raised in captivity, mainly when destined for commercial purposes. This study had the objective of determining the chromosome number of two populations raised in captivity and characterizing them by GTG banding. For this purpose, an analysis was made of mitotic metaphases obtained from lymphocyte cultures made from blood samples of 11 animals, six of which from the Northeast and five from the North of Brazil. The results of this analysis showed the same karyotype pattern for the species (2n=30 chromosomes and NF=48), besides corresponding to the South American pattern of the species, i.e., without a translocation between autosomes 1 and 8, chromosome X acrocentric, and no differences were found between the two populations studied. However, chromosomal polymorphisms were observed compared to data from the literature on populations from North and South America.     

Charge density dependence of elastic modulus of strong polyelectrolyte hydrogels

The mechanical behavior of a series of strong polyelectrolyte hydrogels based on acrylamide and 2-acrylamido-2-methylpropane sulfonic acid sodium salt (AMPS) was investigated. The hydrogels were prepared at a fixed crosslinker ratio and monomer concentration, but at various charge densities, i.e. AMPS contents between 0 and 100 mol%. The elastic modulus of the hydrogels after their preparation first increases with increasing charge density but then decreases continuously. Investigation of the swollen state properties of the hydrogels shows existence of a large number of ionic groups inside the gel that are ineffective in gel swelling. The results indicate two opposite effects of charged groups on the elastic modulus of the hydrogels: formation of multiplets acting as additional crosslinks in the gel increases the elastic modulus of ionic hydrogels, whereas the effect of the electrostatic interaction of charged groups on elastic free energy decreases the modulus.