Ground cover and leaf area index relationship in a grass, legume and crucifer crop

Canopy characterization is essential for describing the interaction of a crop with its environment. The goal of this work was to determine the relationship between leaf area index (LAI) and ground cover (GC) in a grass, a legume and a crucifer crop, and to assess the feasibility of using these relationships as well as LAI-2000 readings to estimate LAI. Twelve plots were sown with either barley (Hordeum vulgare L.), vetch (Vicia sativa L.), or rape (Brassica napus L.). On 10 sampling dates the LAI (both direct and LAI-2000 estimations), fraction intercepted of photosynthetically active radiation (FIPAR) and GC were measured. Linear and quadratic models fitted to the relationship between the GC and LAI for all of the crops, but they reached a plateau in the grass when the LAI mayor que 4. Before reaching full cover, the slope of the linear relationship between both variables was within the range of 0.025 to 0.030. The LAI-2000 readings were linearly correlated with the LAI but they tended to overestimation. Corrections based on the clumping effect reduced the root mean square error of the estimated LAI from the LAI-2000 readings from 1.2 to less than 0.50 for the crucifer and the legume, but were not effective for barley.

Effect of Sb incorporation on the electronic structure of InAs quantum dots

On the basis of optical characterization experiments and an eight band kp model, we have studied the effect of Sb incorporation on the electronic structure of InAs quantum dots (QDs). We have found that Sb incorporation in InAs QDs shifts the hole wave function to the center of the QD from the edges of the QD where it is otherwise pinned down by the effects of shear stress. The observed changes in the ground-state energy cannot merely be explained by a composition change upon Sb exposure but can be accounted for when the change in lateral size is taken into consideration. The Sb distribution inside the QDs produces distinctive changes in the density of states, particularly, in the separation between excitation shells. We find a 50% increase in the thermal escape activation energy compared with reference InAs quantum dots as well as an increment of the fundamental transition decay time with Sb incorporation. Furthermore, we find that Sb incorporation into quantum dots is strongly nonlinear with coverage, saturating at low doses. This suggests the existence of a solubility limit of the Sb incorporation into the quantum dots during growth.

A 2D computational parametric analysis of the sheltering effect of fences on a railway vehicle standing on a bridge and experiencing crosswinds

In a crosswind scenario, the risk of high-speed trains overturning increases when they run on viaducts since the aerodynamic loads are higher than on the ground. In order to increase safety, vehicles are sheltered by fences that are installed on the viaduct to reduce the loads experienced by the train. Windbreaks can be designed to have different heights, and with or without eaves on the top. In this paper, a parametric study with a total of 12 fence designs was carried out using a two-dimensional model of a train standing on a viaduct. To asses the relative effectiveness of sheltering devices, tests were done in a wind tunnel with a scaled model at a Reynolds number of 1 × 105, and the train’s aerodynamic coefficients were measured. Experimental results were compared with those predicted by Unsteady Reynolds-averaged Navier-Stokes (URANS) simulations of flow, showing that a computational model is able to satisfactorily predict the trend of the aerodynamic coefficients. In a second set of tests, the Reynolds number was increased to 12 × 106 (at a free flow air velocity of 30 m/s) in order to simulate strong wind conditions. The aerodynamic coefficients showed a similar trend for both Reynolds numbers; however, their numerical value changed enough to indicate that simulations at the lower Reynolds number do not provide all required information. Furthermore, the variation of coefficients in the simulations allowed an explanation of how fences modified the flow around the vehicle to be proposed. This made it clear why increasing fence height reduced all the coefficients but adding an eave had an effect mainly on the lift force coefficient. Finally, by analysing the time signals it was possible to clarify the influence of the Reynolds number on the peak-to-peak amplitude, the time period and the Strouhal number.

Ice volume estimates from ground-penetrating radar surveys, Wedel Jarlsberg Land glaciers, Svalbard

One of the aims of the SvalGlac project is to obtain an improved estimate, with reliable error estimates, of the volume of Svalbard glaciers and their potential contribution to sea level rise. As part of this work, we present volume calculations, with detailed error estimates, for eight glaciers on Wedel Jarlsberg Land, southern Spitsbergen, Svalbard. The volume estimates are based upon a dense net of GPR-retrieved ice thickness data collected over several field campaigns spanning the period 2004-2011. The total area and volume of the ensemble are 502.9±18.6 km2 and 80.72±2.85 km3, respectively. Excluding Ariebreen (a tiny glacier, menor que 0.4 km2 in area), the individual areas, volumes and average ice thickness lie within 4.7-141.0 km2, 0.30-25.85 km3 and 64-183 m, respectively. The maximum recorded ice thickness, ca. 619±13 m, is found in Austre Torellbreen. To estimate the ice volume of small non-echo-sounded tributary glaciers, we used a function providing the best fit to the ice thickness along the centre line of a collection of such tributaries where echo-soundings were available, and assuming parabolic cross-sections. We did some tests on the effect on the measured ice volumes of the distinct radio-wave velocity (RWV) of firn as compared to ice, and cold versus temperate ice, concluding that the changes in volume implied by such corrections were within the error bounds of our volume estimate using a constant RWV for the entire glacier inferred from common mid-point measurements on the upper ablation area.

Discrete element analysis for the assessment of the accuracy of load cell-based dynamic weighing systems in grape harvesters under different ground conditions

Dynamic weighing systems based on load cells are commonly used to estimate crop yields in the field. There is lack of data, however, regarding the accuracy of such weighing systems mounted on harvesting machinery, especially on that used to collect high value crops such as fruits and vegetables. Certainly, dynamic weighing systems mounted on the bins of grape harvesters are affected by the displacement of the load inside the bin when moving over terrain of changing topography. In this work, the load that would be registered in a grape harvester bin by a dynamic weighing system based on the use of a load cell was inferred by using the discrete element method (DEM). DEM is a numerical technique capable of accurately describing the behaviour of granular materials under dynamic situations and it has been proven to provide successful predictions in many different scenarios. In this work, different DEM models of a grape harvester bin were developed contemplating different influencing factors. Results obtained from these models were used to infer the output given by the load cell of a real bin. The mass detected by the load cell when the bin was inclined depended strongly on the distribution of the load within the bin, but was underestimated in all scenarios. The distribution of the load was found to be dependent on the inclination of the bin caused by the topography of the terrain, but also by the history of inclination (inclination rate, presence of static periods, etc.) since the effect of the inertia of the particles (i.e., representing the grapes) was not negligible. Some recommendations are given to try to improve the accuracy of crop load measurement in the field.

New On-Line Excitation-System Ground Fault Location Method Tested in a 106 MVA Synchronous Generator

In this paper, a novel excitation-system ground-fault location method is described and tested in a 106 MVA synchronous machine. In this unit, numerous rotor ground-fault trips took place always about an hour after the synchronization to the network. However, when the field winding insulation was checked after the trips, there was no failure. The data indicated that the faults in the rotor were caused by centrifugal forces and temperature. Unexpectedly, by applying this new method, the failure was located in a cable between the excitation transformer and the automatic voltage regulator. In addition, several intentional ground faults were performed along the field winding with different fault resistance values, in order to test the accuracy of this method to locate defects in rotor windings of large generators. Therefore, this new on-line rotor ground-fault detection algorithm is tested in high-power synchronous generators with satisfactory results.

A Novel Ground Fault Identification Method for 2 x 5 kV Railway Power Supply Systems

The location of ground faults in railway electric lines in 2 × 5 kV railway power supply systems is a difficult task. In both 1 × 25 kV and transmission power systems it is common practice to use distance protection relays to clear ground faults and localize their positions. However, in the particular case of this 2 × 25 kV system, due to the widespread use of autotransformers, the relation between the distance and the impedance seen by the distance protection relays is not linear and therefore the location is not accurate enough. This paper presents a simple and economical method to identify the subsection between autotransformers and the conductor (catenary or feeder) where the ground fault is happening. This method is based on the comparison of the angle between the current and the voltage of the positive terminal in each autotransformer. Consequently, after the identification of the subsection and the conductor with the ground defect, only the subsection where the ground fault is present will be quickly removed from service, with the minimum effect on rail traffic. This method has been validated through computer simulations and laboratory tests with positive results.

Field-winding fault detection in synchronous machines with static excitation through frequency response analysis.

Frequency Response Analysis is a well-known technique for the diagnosis of power transformers. Currently, this technique is under research for its application in rotary electrical machines. This paper presents significant results on the application of Frequency Response Analysis to fault detection in field winding of synchronous machines with static excitation. First, the influence of the rotor position on the frequency response is evaluated. Secondly, some relevant test results are shown regarding ground fault and inter-turn fault detection in field windings at standstill condition. The influence of the fault resistance value is also taken into account. This paper also studies the applicability of Frequency Response Analysis in fault detection in field windings while rotating. This represents an important feature because some defects only appear with the machine rated speed. Several laboratory test results show the applicability of this fault detection technique in field windings at full speed with no excitation current.

Celebrity endorsers' performance on the “ground” and on the “floor”

This article analyzes the relationship between two types of performances, one on the ground (of a tennis court) and the other on the floor (of the stock market). The empirical application looks into the tennis player, Rafael Nadal, and his endorsing firms. The findings show a positive reaction in the market value when the tennis player wins matches in the Grand Slams, the intriguing effect being the diminishing sensitivity pattern that such reaction shows and the absence of loss aversion.

Impedance spectroscopy study of the effect of environmental conditions in the microstructure development of OPC and slag cement mortars

In this work, the microstructure of mortars made with an ordinary Portland cement and slag cement has been studied. These mortars were exposed to four different constant temperature and relative humidity environments during a 180-day period. The microstructure has been studied using impedance spectroscopy, and mercury intrusion porosimetry as a contrast technique. The impedance spectroscopy parameters make it possible to analyze the evolution of the solid fraction formation for the studied mortars and their results are confirmed with those obtained using mercury intrusion porosimetry. The development of the pore network of mortars is affected by the environment. However, slag cement mortars are more influenced by temperature while the relative humidity has a greater influence on the OPC mortars. The results show that slag cement mortars hardened under non-optimal environments have a more refined microstructure than OPC mortars for the studied environmental conditions.

The fate and effect of crude oil spilled on subarctic permafrost terrain in interior Alaska /

Mode of access: Internet.

The effect of a well on the flow of a nearby stream /

Mode of access: Internet.

Operator, organizational, direct support and general support maintenance manual : tent, frame type, universal field maintenance, expandable, cotton duck, fire, mildrew [sic], water, and weather resistant, w/o floor, floor area 27 ft w, 22 ft h, 64 ft lg, length expandable in 8-foot increments, w/covers, frames, ground anchor kit, liners, FSN 8340-935-6372.

"January 1970."

The effect of timing and severity of water deficit on growth, development, yield accumulation and nitrogen fixation of mungbean

Mungbean (Vigna radiata L.), as a dryland grain legume, is exposed to varying timing and severity of water deficit, which results in variability in grain yield, nitrogen accumulation and grain quality. In this field study, mungbean crops were exposed to varying timing and severity of water deficit in order to examine: (1) contribution of the second flush of pods to final grain yield with variable timing of relief from water deficit, (2) the sensitivity to water deficit of the accumulation of biomass and nitrogen (N) and its partitioning to grain, and (3) how the timing of water deficit affects the pattern of harvest index (HI) increase through pod filling. The results showed that the contribution of the second flush to final yield is highly variable (1-56%) and can be considerable, especially where mid-season stress is relieved at early pod filling. The capacity to produce a second flush of pods did not compensate fully for yield reduction due to water stress. Relief from mid-season stress also resulted in continued leaf production, N-2 fixation and vegetative biomass accumulation during pod filling. Despite the wide variation in the degree of change in vegetative biomass and N during pod filling, there were strong relationships between grain yield and net-above-ground biomass at maturity, and grain N and above-ground N at maturity. Only in the extreme situations were HI and nitrogen HI affected noticeably. In those treatments where there was a large second flush of pods, there was a pronounced biphasic pattern to pod number production, with HI also progressing through two distinct phases of increase separated by a plateau. The proportion of grain yield contributed to by biomass produced before pod filling varied from 0 to 61% with the contribution greatest under terminal water deficit. There was a larger effect of water deficit on N accumulation, and hence N-2 fixation, than on biomass accumulation. The study confirmed the applicability of a number of long-standing physiological concepts to the analysis of the effect of water deficit on mungbean, but also highlighted the difficulty of accounting for timing effects of water deficit where second flushes of pods alter canopy development, biomass and yield accumulation, and N dynamics. Crown Copyright (C) 2003 Published by Elsevier B.V. All rights reserved.

Effect of experimentally induced low back pain on postural sway with breathing

Although breathing perturbs balance, in healthy individuals little sway is detected in ground reaction forces because small movements of the spine and lower limbs compensate for the postural disturbance. When people have chronic low back pain (LBP), sway at the ground is increased, possibly as a result of reduced compensatory motion of the trunk. The aim of this study was to determine whether postural compensation for breathing is reduced during experimentally induced pain. Subjects stood on a force plate with eyes open, eyes closed, and while breathing with hypercapnoea before and after injection of hypertonic saline into the right lumbar longissimus muscle to induce LBP. Motion of the lumbar spine, pelvis, and lower limbs was measured with four inclinometers fixed over bony landmarks. During experimental pain, motion of the trunk in association with breathing was reduced. However, despite this reduction in motion, there was no increase in postural sway with breathing. These data suggest that increased body sway with breathing in people with chronic LBP is not simply because of reduced trunk movement, but instead, indicates changes in coordination by the central nervous system that are not replicated by experimental nociceptor stimulation.