Operating envelope charts for the Langley 0.3-meter transonic cryogenic wind tunnel

To take full advantage of the unique Reynolds number capabilities of the 0.3-meter Transonic Cryogenic Tunnel (0.3-m TCT) at the NASA Langley Research Center, it was designed to accommodate test sections other than the original, octagonal, three-dimensional test section. A 20- by 60-cm two-dimensional test section was installed in 1976 and was extensively used, primarily for airfoil testing, through the fall of 1984. The tunnel was inactive during 1985 so that a new test section and improved high speed diffuser could be installed in the tunnel circuit. The new test section has solid adaptive top and bottom walls to reduce or eliminate wall interference for two-dimensional testing. The test section is 33- by 33-cm in cross section at the entrance and is 142 cm long. In the planning and running of past airfoil tests in the 0.3-m TCT, the use of operating envelope charts have proven very useful. These charts give the variation of total temperature and pressure with Mach number and Reynolds number. The operating total temperature range of the 0.3-m TCT is from about 78 K to 327 K with total pressures ranging from about 17.5 psia to 88 psia. This report presents the operating envelope charts for the 0.3-m TCT with the adaptive wall tes t section installed. They were all generated based on a 1-foot chord model. The Mach numbers vary from 0.1 to 0.95

An investigation of passive control methods for shock-induced separation at hypersonic speeds

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76765/1/AIAA-1992-2725-533.pd

Hedgerow olive orchards: reality or utopia?

Actualmente las plantaciones de olivar tienen unas densidades que no suelen superar los 330 olivos por hectárea. El mayor coste su cultivo se produce en la recolección, donde se necesita una gran cantidad de mano de obra. Recientemente ha surgido un nuevo tipo de plantaciones cuyas densidades se acercan a las 2000 plantas por hectárea y donde los olivos se disponen en setos continuos separados unos 3,5 m. La mayor ventaja de este tipo de plantaciones es su recolección totalmente mecanizada, mediante máquinas cabalgadoras que pasan por encima de los setos, en un sistema muy parecido al usado en la vid. Además, estas plantaciones son de muy temprana entrada en producción y muy productivas, al menos en los primeros años. La variedad que se utiliza, casi en exclusiva, para este tipo de plantaciones es ‘Arbequina’. En el presente trabajo se describen los resultados de un ensayo comparativo de variedades que se estableció en el año 2000 y del que se han recogido ya 4 cosechas. Este ensayo incluye las variedades ‘Arbequina’, ‘Arbequina i-18’, ‘Arbosana’, ‘Koroneiki’, ‘Fs-17’ y ‘UC 2-35’. De ellas, ‘Arbequina’ y ‘Arbosana’ han sido las más productivas y ‘UC 2-35’ la menos vigorosa de las ensayadas. También se describen los resultados de un ensayo comparativo de densidades desde 754 a 2580 plantas/ha que fue establecido en el año 1999. Hasta ahora, la densidad más productiva parece ser la de 2000 plantas/ ha. Habrá que esperar a los próximos años para tener resultados más definitivos sobre éstos ensayos ya que es de esperar que a partir de ahora es cuando aparezcan los problemas relacionados con la competencia entre árboles. En conclusion, en un escenario donde las ayudas de la Unión Europea van a ir disminuyendo progresivamente, y donde la mano de obra es cada vez más difícil de encontrar, la capacidad real de este tipo de plantaciones de ser rentables a largo plazo determinará el futuro éxito de las mismas.Nowadays, olive orchards have a densities not higher than 330 trees/ha. The major cost correspond to harvest operations, which is very labour demanding. Recently, a new type of olive plantations with densities around 2.000 tress/ha has appeared. The major advantage of this type of plantations is their totally mechanised harvest, by vineyards straddle-harvesting machines.These plantations have a very early bearing and very productive, at least in the first years. The most common cultivar used is ‘Arbequina’. In the present work, data of the first four harvest of a variety comparative trial are reported. This trial include ‘Arbequina’, ‘Arbequina i-18’, ‘Arbosana’, ‘Koroneiki’, ‘Fs- 17’ y ‘UC 2-35’ cultivars. From the ‘Arbequina’ and ‘Arbosana’ had been the most productive and ‘UC 2-35’ the less vigorous. Results of a trial testing densities between 780 and 2580 trees/ha is also described. Up to now, the higher densities have been the most productive ones. However, more definitive results can be obtained in the coming years, when problems of competence among trees started to appear. In summary, as in the near future is expected that the subsides from the EU are going to be greatly reduced and the labour for harvesting is difficult to find, the ability to this type of plantations to be profitable at long term will determine their success

Estimating biophysical and geometrical parameters of grapevine canopies ('Sangiovese') by an unmanned aerial vehicle (UAV) and VIS-NIR cameras

Three zones of different vine vigour were identified in a mature vineyard (Vitis vinifera 'Sangiovese') to test the potential of the Visible-Near Infrared (VIS-NIR) spectral information acquired from an unmanned aerial vehicles (UAV) in estimating the leaf area index (LAI), leaf chlorophyll, pruning weight, canopy height and canopy volume of grapevines. A significant linear correlation between the normalized differential vegetation index (NDVI) and LAI or between NDVI and leaf chlorophyll was found at day of the year (DOY) 162 and 190, whereas in August the relationship between NDVI and leaf chlorophyll was less evident. The canopy volume of low-vigour (LV) vines was 35 and 45 % of the high-vigour (HV) and medium-vigour (MV) ones, respectively. The pruning weight was linearly correlated with NDVI values of each vigour cohort. A good correlation between the measured canopy volume and UAV-estimated one as well as between measured and estimated canopy height was found. Our results indicated that the combined use of VIS-NIR cameras and UAV is a rapid and reliable technique to determine canopy structure and LAI of grapevine

Updated single and dual crop coefficients for tree and vine fruit crops

ReviewThe present study reviews the research on the FAO56 crop coefficients of fruit trees and vines performed over the past twenty years. The main objective was to update information and extend tabulated single (Kc) and basal (Kcb) standard crop coefficients. The selection and analysis of the literature for this review have been done to consider only studies that adhere to FAO56 method, computing the reference ET with the FAO Penman– Monteith ETo equation and field measuring crop ET with proved accuracy. The crops considered refer to vine fruit crops, berries and hops, temperate climate evergreen fruit trees, temperate climate deciduous fruit trees and, tropical and subtropical fruit crops. Papers satisfying the conditions expressed above, and that studied the crops under pristine or appropriate eustress conditions, were selected to provide for standard Kc and Kcb data. Preference was given to studies reporting on the fraction of ground cover (fc), crop height (h), planting density, crop age and adopted training systems. The Kc and Kcb values obtained from the selected literature generally show coherence relative to the crop biophysical characteristics and reflect those characteristics, mainly fc, h and training systems. The ranges of reported Kc and Kcb values were grouped according to crop density, particularly fc and h, and were compared with FAO56 (Allen et al., 1998) previously tabulated Kc and Kcb values, as well as by Allen and Pereira (2009) and Jensen and Allen (2016), which lead to define update indicative standard Kc and Kcb values. These values are aimed for use in crop water requirement computations and modeling for irrigation planning and scheduling, thus also aimed at supporting improved water use and saving in orchards and vinesinfo:eu-repo/semantics/publishedVersio

Eddy covariance and sap flow measurement of energy and mass exchanges of woody crops in a Mediterranean environment

Evapotranspiration estimation by micrometeorological techniques through the assessment of mass and energy exchanges in the soil-plant-atmosphere continuum (SPAC) is a very active research area, involving both well-known and novel measurement techniques. A crucial aspect in validating experimental results is the integration of independent measurements of mass and energy exchanges in the SPAC. To this aim, the development and validation of an integrated approach in major tree crop species, involving different independent techniques, are presented. Eddy covariance estimates of ET fluxes were compared to up-scaled sap flow measurements in olive, orange and grapevine, three important Mediterranean tree crop species with contrasting ecophysiological characteristics and responses to water deficits. These differences can affect directly the degree of coupling of the tree to the environment and, consequently, the degree of correspondence between instantaneous transpirational flux at tree level and the micrometeorological measurement of ET at orchard level. Data were analyzed to verify to what extent, in the three species, transpirational flow at orchard level is regulated by tree conductance, capacitance effects related to tree size or by environmental demand. Hourly observations were helpful in detecting physiological processes of the three species only when data were analyzed taking into consideration their diurnal changes

Risk Allocation in Toll Highway Concessions in Spain: Lessons from Economic Recession

Spain has a long tradition of encouraging toll highways by granting concessions to private companies. Concessions in Spain have been characterized by a willingness to transfer considerable risk to the private sector. Traffic demand, acquisition of the right-of-way, and financial risk have often been allocated to the private sector. From 1996 to 2011, 16 toll highway concessions, covering a total distance of 835 km, were awarded by the central government of Spain with this approach. Some of those highways started their operations just before the economic recession began. The recession had negative consequences for Spain's economy. The gross domestic product per capita plummeted, and the unemployment rate increased from 9% to 20% of the working population in just 2 years. The recession also had severe consequences for the economic performance of toll highway concessions. Traffic levels declined at a much greater rate than did the gross domestic product. In addition, the conditions imposed by the financial markets on borrowers became much stricter because of the liquidity crisis. This study analyzes the impact that the economic recession ultimately had on the performance of toll highway concessions in Spain and the actions that the government adopted to avoid the bankruptcy of the concessionaires. It was found that the economic recession helped identify some deficiencies in how risk had been allocated in Spain. The measures that both Spain and the European Union are adopting so as to improve risk allocation are discussed

Can anthocyanin presence ameliorate the photosynthetic performance of Prunus saplings subjected to polyethylene glycol-simulated water stress?

The aim was the evaluation of the biochemical and physiological responses of green- (GP) and red-leafed (RP) Prunus cerasifera mature leaves to 20 d of polyethylene glycol (PEG 6000)-induced water stress in order to elucidate a possible ameliorative role exerted by anthocyanins. At 10 d, the anthocyanin content remained unchanged in RP water-stressed leaves. Photosynthetic rate was lower in GP than that of RP (83.4 vs. 76.5%, respectively), paralleled by a higher degree of photoinhibition (Fv/Fm) in GP leaves. Leaves of GP accounted for higher content of soluble sugars at 10 d, when RP only showed a slight sucrose increase. At 20 d of stress, both morphs recovered their Fv/Fm values, suggesting the ability of both genotypes to adjust their photosynthetic metabolism under conditions of water stress. In conclusion, besides the sunscreen role served by anthocyanins, the carbon sink by these flavonoids might have further prevented sugar accumulation and the consequent sugar-promoted feedback regulation of photosynthesis in drought-stressed red leaves