Search results for "Variable"
showing 10 items of 1674 documents
Setpoints compensation in industrial processes via multirate output feedback control
2013
This paper investigates the setpoints compensation for a class of complex industrial processes. Plants at the device layer are controlled by the local regulation controllers, and a multirate output feedback control approach for setpoint compensation is proposed such that the subsystems can reach the dynamically changed setpoints and the given economic objective can also be tracked via certain economic performance index (EPI). First, a sampled-data multivariable direct output feedback proportional integral (PI) controller is designed to regulate the performance of the subsystems. Second, the outputs and control inputs of the plants at the device layer are sampled at operation layer sampling …
Genetic and morphologic diversity of European fan palm (Chamaerops humilisL.) populations from different environments from Sicily
2014
Chamaerops humilis is decreasing in abundance in Mediterranean Europe, which has induced the European community to call for its protection in Special Areas of Conservation. However, information about its genetic and morphological variability, which is crucial to the development of any conservation strategies, is insufficient. The present study aimed to investigate the genetic and morphological variability of C. humilis in Sicily, which was selected as a model because of the high number of dense populations. The relationships between morphological traits and climatic variables were studied to highlight patterns of adaptation to the environment, along with the genetic similarity among the pop…
First tests of spatially variable rate herbicide application on Durum wheat in Sicily
2002
Using the conventional farming system, durum wheat requires the spraying of high herbicide rates. Herbicide residues can cause pollution of soil and ground water. This paper refers to first tests of spatially variable rate herbicide application on durum wheat. The tests showed the effectiveness of the variable rate herbicide application, which allowed an almost even grain yield over the entire field and a saving of 27% of herbicide mixture.
Adjustment time and offset of a system for spatially variable rate fertilisation
2005
The aim of this research is to measure the adjustment time and offset of a cheap system for spatially variable rate fertilisation, designed, developed and set up by the Mechanics Section of I.T.A.F. Department. In order to test the system, a centrifugal fertiliser spreader, working by gravity, was modified connecting an actuator with the two hopper shutter slides. Two different actuator types were tested, in order to measure the accordingly variable adjustment time and offset. The adjustment offset of the centrifugal spreader increases with increasing machine average forward speed and decreases with increasing fertiliser rate, considering the same rate variation. The main components of the …
Genetic diversity of Mediterranean cattle breeds related to geography and climate
2015
In recent decades, changes in climate have caused impacts on natural and human systems. Mediterranean countries will be particularly affected by this phenomenon, with growing temperatures and reduced rainfall. Understanding how species and ecosystems respond to climate change has become a crucial focus in biodiversity conservation and management. The genome-wide SNP panels allows providing background information on genome structure in domestic animals, opening new perspectives to livestock genetics. The International Project GALIMED "Genetic Adaptation of Bovine Livestock and production systems in MEDiterranean region", develops an integrated approach that combines the analysis of SNP marke…
Aquaculture effects on some physical and chemical properties of the water column: A meta-analysis
2007
More than 30 peer-reviewed articles (1980–2005) were analysed using meta-analytical reviewing techniques, and about 340 study cases were used to test whether aquaculture facilities had any effects on physical and chemical variables. The analysis tested differences between experimental conditions vs. chosen-by-author controls. Across all study cases, cultivated organisms (fish, shrimps and bivalves) did not have any clear effects on the water temperature and salinity. Dissolved oxygen also was found to be unaffected by aquaculture practices. On the other hand, crowding led to significant pH variations, which was more accentuated in shrimp (d+ = 0.66;P 0.05).Water transparency and turbidity w…
Time Resolved X-Ray Spectral Analysis of Class II YSOs in NGC 2264 During Optical Dips and Bursts
2016
Pre-Main Sequence stars are variable sources. The main mechanisms responsible for their variability are variable extinction, unsteady accretion, and rotational modulation of both hot and dark photospheric spots and X-ray active regions. In stars with disks this variability is thus related to the morphology of the inner circumstellar region (<0.1 AU) and that of photosphere and corona, all impossible to be spatially resolved with present day techniques. This has been the main motivations of the Coordinated Synoptic Investigation of NGC2264, a set of simultaneous observations of NGC2264 with 15 different telescopes. We analyze the X-ray spectral properties of stars with disks extracted du…
Accretion in young stars: measure of the stream velocity of TW Hya from the X-ray Doppler shift
2015
High-resolution X-ray spectra are a unique tool to investigate the accretion process in young stars. In fact X-rays allow to investigate the accretion-shock region, where the infalling material is heated by strong shocks due to the impact with the denser stellar atmosphere. Here we show for the first time that it is possible to constrain the velocity of the accretion stream by measuring the Doppler shift of the emitted X-rays. To this aim we analyzed the deep Chandra/HETGS observation of the accreting young star TW Hya. We selected a sample of emission lines free from significant blends, fitted them with gaussian profiles, computed the radial velocity corresponding to each line, and average…
Effects of radiation in accretion regions of classical T Tauri stars
2019
Context. Models and observations indicate that the impact of matter accreting onto the surface of young stars produces regions at the base of accretion columns where optically thin and thick plasma components coexist. Thus, an accurate description of these impacts is necessary to account for the effects of absorption and emission of radiation. Aims. We study the effects of radiation emerging from shock-heated plasma in impact regions on the structure of the pre-shock down-falling material. We investigate whether a significant absorption of radiation occurs and if it leads to a pre-shock heating of the accreting gas. Methods. We developed a radiation hydrodynamics model describing an accreti…
RC beams retrofitted by FRP oriented in any direction: Influence of the effectiveness factors
2022
Shear strength of FRP-retrofitted RC beams is usually influenced by different brittle failure modes characterizing the collapse of the FRP reinforcement. The most significant analytical models for assessing the shear strength of FRP-retrofitted RC beams reflect the effect of brittle failure through an effectiveness factor “R”, which reduces the ultimate tensile strength of FRP. The brittle collapse of FRP reinforcement often leads to a lower shear contribution by steel stirrups due to hindering of the yielding of all stirrups involved by critical cracking. Some analytical models consider this phenomenon introducing a further effectiveness factor “r”, which reduces the yielding strength of s…