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排序方式: 共有103条查询结果,搜索用时 15 毫秒
1.
B. Hijazi F. Cointault J. Dubois S. Coudert J. Vangeyte J. Pieters M. Paindavoine 《Precision Agriculture》2010,11(6):684-702
Excessive fertiliser use has been a main contributor to the increasing environmental imbalance observed in the past 20 years.
Better accuracy in spreading would limit excess fertiliser loss into the environment. Increased accuracy begins by understanding
the fertiliser spreading process from the vane to the soil. Our work concentrates on the use of centrifugal spreaders, as
these are most commonly used in Europe. Progress in imaging devices and image processing has resulted in the availability
of new technologies to use when describing the behaviour of fertiliser granules during ejection from centrifugal spreaders.
Fertiliser deposition on the soil can be predicted using a ballistic flight model, but this requires determination of the
velocities and the directions of the granules when they leave the spinning disc. This paper presents improvements to the high
speed imaging system that we had previously developed, i.e. enhancements to the illumination and the image processing. The
illumination of the previous system, which used many separate flashes, did not give consistent illumination. We have improved
it by using a stroboscope with power-LEDs, located at 1 m height around the digital camera and controlled by a Field-programmable
gate array (FPGA) card. The image processing has been improved by development of a multi-phase method based on a cross-correlation
algorithm. We have compared the cross-correlation method to the Markov Random Fields (MRF) method previously implemented.
These tests, based on multi-exposure images, revealed that cross-correlation method gives more accurate results than the MRF
technique, with guaranteed sub-pixel accuracy. Knowing that an error of one pixel can lead to a prediction error between 200
and 500 mm on the ground, the latter method gives an accuracy range between 0.1 and 0.4 pixels, whereas the MRFs technique
is limited to 3 and 9 pixels for the vertical and horizontal components of the velocities, respectively. The sub-pixel accuracy
of the new method was proven by applying it on simulated images with known displacements between the grains. By using a realistic
spreading model, the simulated images are similar to those obtained with a high speed imaging system. This sub-pixel accuracy
now makes it possible to decrease the resolution of the camera to that of a classical high-speed camera. These improvements
have created an affordable and durable system appropriate for installation on a spreader. Farmers could use this system to
both calibrate the spreader and verify the fertiliser distribution on the ground. 相似文献
2.
Zientara S Sailleau C Dauphin G Roquier C Rémond EM Lebreton F Hammoumi S Dubois E Agier C Merle G Bréard E 《The Veterinary record》2002,150(19):598-601
In October 2000, bluetongue virus was detected on the French island of Corsica. The disease was also reported in Sardinia, Calabria, Sicily and on the Spanish islands of Majorca and Minorca. This paper describes the use of molecular techniques for a rapid identification and serotype determination of serotype 2 of the virus. The nucleotide sequences of segments 2 and 7 of the genome of the Corsican strain were determined and its phylogenetic relationships are described. 相似文献
3.
Empirical relationships between land use/cover and estuarine condition in the Northeastern United States 总被引:1,自引:0,他引:1
Wilfrid Rodriguez Peter V. August Yeqiao Wang John F. Paul Arthur Gold Norman Rubinstein 《Landscape Ecology》2007,22(3):403-417
Land–water interactions were examined in three regions in the Virginian Biogeographic Province; the southern shore of Cape
Cod, Massachusetts; the Hudson/Raritan region of New York; and the eastern shore of the Delmarva (Delaware/Maryland/Virginia)
Peninsula. Cumulative distribution functions were used to evaluate similarity in environmental condition among estuaries.
Spatial-setting variables (location in a river, coastal lagoon, or in open waters) were associated with variation for some
measures of estuarine condition. Patterns of coastal urban and agriculture gradients were measured and their relationship
with indicators of estuarine condition was modeled statistically. When estuaries were pooled, the highest variation explained
by spatial-setting variables was found for dissolved oxygen (DO, R
2 = 0.44) and salinity (R
2 = 0.58), with DO decreasing in river locations and salinity decreasing with rainfall and sampling locations near rivers.
The explanatory power for the other indicator variables was low and varied from 6% to 27%. Rainfall explained some of the
variation (R
2 = 0.23) in total suspended solids. Moderate (0.4 < | r | < 0.7) to strong (| r | ≥ 0.7) linear associations were found between total urban area and measures of estuarine condition. Within regions, total
urban area was positively associated with Silver (r = 0.59), Cadmium (r = 0.65), and Mercury (r = 0.47) in Cape Cod, and inversely related to DO (r = −0.65) in the Hudson/Raritan region. No associations were found in the Delmarva Peninsula study area. Total area of agriculture
showed a moderate association with Arsenic in Cape Cod, but no other associations were found in the other two regions. Our
analyses show a measurable impact of urban land use on coastal ecosystem condition over large areas of the northeastern United
States. This pattern was most evident when many different landscapes were considered simultaneously. The relationship between
urban development and estuarine condition were weaker within the individual regions studied. The use of land use/cover models
for predicting estuarine condition is a challenging task that warrants enhancements in the type, quantity, and quality of
data to improve our ability to discern relationships between anthropogenic activities on land and the condition of coastal
environments. 相似文献
4.
5.
Dubois D 《Science (New York, N.Y.)》1932,76(1976):441-443
6.
Helga Guderley Brigitte A. Lavoie Nicole Dubois 《Fish physiology and biochemistry》1994,13(5):419-431
Thermal acclimation may directly modify muscle metabolic capacities, or may modify them indirectly via effects upon physiological processes such as growth, reproduction or senescence. To evaluate these interacting effects, we
examined the influence of thermal acclimation and acclimatization upon muscle metabolic capacities and tissue masses in 1
+ stickleback, Gasterosteus aculeatus, in which confounding interactions between temperature and senescense should be absent. Furthermore, we examined the influence
of thermal acclimation upon individual growth rate, muscle enzyme levels and tissue masses in 2 + stickleback sampled at the
beginning of their final reproductive season. For 1 + stickleback, cold acclimation more than doubles mitochondrial enzyme
levels in the axial muscle. Thermal acclimation did not change the condition of 1 + stickleback at feeding levels which could
not maintain the condition of 2+ stickleback. Compensatory metabolic responses to temperature were not apparent in field acclimatized
1 + stickleback. The growth rate of 2 + stickleback was markedly affected by temperature: warm-acclimated fish generally lost
mass even at very high levels of feeding (up to 78 enchytraid worms per day) while cold-acclimated fish gained mass. This
suggests that warm temperatures accelerate the senescence of 2 + stickleback. Generally, muscle enzyme activities increased
with growth rate. In axial muscle, the relationships between CS activity and growth rate differed with acclimation temperature.
Independent of the influence of growth rate, CS activities were consistently higher in cold- than warm-acclimated 2 + stickleback,
suggesting compensatory increases of CS activity with cold acclimation.
Corresponding author; This paper is dedicated to the memory of Gerry J. FitzGerald who passed away on March 14, 1994. 相似文献
7.
8.
9.
Summary Thirty, one-season-old Rosa canina Inermis seedlings (8–12 mm in diameter) were grown in the greenhouse. After 5 months, single-node softwood cuttings were made of each plant. Analysis of variance demonstrated marked differences between the internode length, number of leaflets per leaf and the leaf area of the original seedling, and between the time of axillary bud-break, axillary sprout length and weight of adventitious roots of their 23-day-old cuttings. Clonal root weight of cuttings was highly significantly correlated with: number of leaflets per leaf (r=–0.65), leaf area (r=+0.65), and days to axillary bud-break (r=+0.62). The origin of heterogeneity among Inermis seedling rootstocks, its probable effect on the flower production of cut roses and its possible use in the selection for clonal rootstocks are discussed. 相似文献
10.
Identification on commercialized products of AFLP markers able to discriminate slow- from fast-growing chicken strains 总被引:2,自引:0,他引:2
Fumière O Dubois M Grégoire D Théwis A Berben G 《Journal of agricultural and food chemistry》2003,51(5):1115-1119
The European chicken meat market is characterized by numerous quality marks: "Label de Qualité Wallon" in Belgium, "Label Rouge" in France, denominations of geographical origin, organic agriculture, etc. Most of those certified productions have specifications requiring the use of slow-growing chicken strains. The amplified fragment length polymorphism (AFLP) technique has been used to search molecular markers able to discriminate slow-growing chicken strains from fast-growing ones and to authenticate certified products. Two pairs of restriction enzymes (EcoRI/MseI and EcoRI/TaqI) and 121 selective primer combinations were tested on individual DNA samples from chicken products essentially in carcass form that were ascribed as belonging to either slow- or fast-growing strains. Within the resulting fingerprints, two fragments were identified as type-strains specific markers. One primer combination gives a band (333 bp) that is specific for slow-growing chickens, and another primer pair generates a band (372 bp) that was found to be characteristic of fast-growing chickens. The two markers were isolated, cloned, and sequenced. The effectiveness and the specificity of the two interesting determinants were assessed on individuals of two well-known strains (ISA 657 and Cobb 500) and on commercialized products coming from various origins. 相似文献