Contour Gradients Research Articles

Zahedan climate and January–March composite analysis forecasts

This study shows that the mean monthly temperature and precipitation for Zahedan from January to March are predictable. They have oscillatory behavior in relation to El Niño–Southern Oscillation (ENSO) phases. The 200hPa vector wind composite mean maps from January to March show that a jet streak oscillates between 27°N and 30°N, to the west of Iran. These oscillations result in strong contour gradients of 1000hPa geopotential height during strong La Niña events; by contrast, they result in weak contour gradients during El Niño events in the southeast of the country. The composite forecasts for Zahedan based on El Niño/La Niña seem to be skillful for the strong events and show some skill for neutral events. The applicability of the forecasts in water management, agriculture, health, and other fields is considerable.

Semantic Rule Based Image Visual Feature Ontology Creation

Multimedia is one of the important communication channels for mankind. Due to the advancement in technology and enormous growth of mankind, a vast array of multimedia data is available today. This has resulted in the obvious need for some techniques for retrieving these data. This paper will give an overview of ontology-based image retrieval system for asteroideae flower family domain. In order to reduce the semantic gap between the low-level visual features of an image and the high-level domain knowledge, we have incorporated a concept of multi-modal image ontology. So, the created asteroideae flower domain specific ontology would have the knowledge about the domain and the visual features. The visual features used to define the ontology are prevalent color, basic intrinsic pattern and contour gradient. In prevalent color extraction, the most dominant color from the images was identified and indexed. In order to determine the texture pattern for a particular flower, basic intrinsic patterns were used. The contour gradients provide the information on the image edges with respect to the image base. These feature values are embedded in the ontology at appropriate slots with respect to the domain knowledge. This paper also defines some of the query axioms which are used to retrieve appropriate information from the created ontology. This ontology can be used for image retrieval system in semantic web.

Subaortic Stenosis Revisited

Brachfeld and Gorlin's revised concept of subaortic stenosis derived from their recognition that the large magnitudes of the pressure gradients were incompatible with the relatively mild anatomic lesions found at surgery in 3 of their patients, and the rapidity of their arterial pulse upstroke. They proposed that a gradient caused by a superimposed systolic stenosis was responsible for the large pressure gradients and the overestimation of the severity of the discrete subaortic stenosis (DSAS). A fourth patient had no anatomic cause for the pressure gradient, and findings compatible with hypertrophic cardiomyopathy (HCM). All 4 patients had septal hypertrophy which they felt was instrumental in the brisk pulse contour and dynamic gradients across the outflow tract. In the ensuing decades, imaging techniques have been developed which permit detailed studies of ventricular ejection patterns in dynamic gradients associated with HCM and DSAS. These studies have been interpreted variously. The prevailing view is that there is a dynamic obstruction that increases progressively in severity during systole, as proposed by Brachfeld and Gorlin. An opposing view is that dynamic gradients can occur in the absence of any hindrance to ejection, and that these gradients instead result from rapid and complete emptying of the ventricle. Regardless of their cause, dynamic gradients are often superimposed upon gradients caused by DSAS and valvar aortic stenosis, leading to exaggerated estimates of severity. These dynamic gradients are uncovered when the anatomic cause of stenosis is removed, and seemingly increase the postoperative morbidity. A greater understanding of the significance of dynamic gradients and the mechanism(s) responsible for them should lead to more rational management of DSAS and HCM in the future.

A contribution to the upper‐air climatology of tropical south america

AbstractAn upper‐air climatology of tropical South America is presented using objectively analysed geopotential height, temperature and wind data from various radiosonde stations for the common period 1970‐1974.In the lower troposphere the South Atlantic high dominates the geopotential height patterns extending deeply into interior Brazil in Southern winter. In the upper troposphere, contour gradients are concentrated around the subtropical region in winter. Temperature analysis shows the steep meridional gradient in winter. In summer, the Peruvian‐Bolivian Altiplano heating effect is manifested in the mid‐tropospheric temperature fields and also in the thickness field.Lower‐tropospheric flow throughout the year is marked by an anticyclonic turning of easterlies over much of eastern Brazil. Easterlies originating from the South Atlantic high penetrate further inland in Southern winter. Upper‐tropospheric flow changes dramatically from mainly westerly in winter to a well‐defined anticyclone over the Altiplano and a trough downstream over northeast Brazil in summer. Thickness and temperature patterns indicate that the upper anticyclone is maintained by a warm‐core system whereas the trough is marked by a relatively cold temperature. Upper tropospheric flows are equivalent barotropic in nature over tropical South America. The map discussion of summer and winter circulation is complemented by cross‐sections of meridional wind component along approximately 60°W.

Refraction of water waves by islands and shoals with circular bottom‐contours

The bending of water waves by islands and shoals with circular bottom‐contours is Investigated from an analytical standpoint to obtain a precise determination of resulting wave‐patterns and wave‐heights. SNELL'S law of refraction is assumed, and FERMAT'S law or the principle of least time therefore applies. Application of FERMAT'S law and of the established relation between wave‐velocity and depth of water enables determinations of lines orthogonal to tho wave crests for various types of contour gradients. Five different cases are discussed. It is shown that for certain contour gradients, islands have no shore protected from high waves. A shoal is characterized by the dividing of a single crest Into two crests. Height variation along refracted crests at considerable distances beyond an island is shown to bo critically dependent upon contour gradient.