Mastitis prevalence, associated microorganisms and related risk factors were determined in dairy operations from municipalities belonging to the province of Pamplona (Norte de Santander). California Mastitis Test (CMT) was performed in 1208 quarters from 302 animals located in 108 rural properties. Milk samples from positive quarters (trace up to 3+) were obtained and submitted for microbiological isolation. Analysis of a 64 variables survey related to the milking practices in the rural properties under study and its link with the presence of the disease was performed using contingency charts and chi-square test (χ2). Determined prevalence per individual was 54,6% (165/302) (95% CI 48.8 to 60.3) CMT positive animals. In 67,6% (73/108) (95% CI 58.3 to 75.7) of the rural properties the presence of at least one animal testing positive was detected, whereas a total of 21,6% quarters (260/1208) (95% CI 19.3 to 23.9) showed CMT reactivity. From the samples subjected to isolation and microbiological characterization, a total of 74.4% were compatible with Staphylococcus aureus, 12.3% with Streptococcus agalactiae and 13.3% with coliforms. A total of 17 characteristics were associated with the presence of mastitis, all of which were related to poor milking practices. The presence of contagious mastitis associated microorganisms, shows the need for training and orientation to implement proper milking practices and enhance the competitiveness of this sector in the region, which will result in an increase in production.
This paper presents a study conducted to estimate the remaining theoretical life of one type of 400 kV latticed steel towers installed on a power transmission line in Venezuela. The study focused on determining the structural behavior and vibration characteristics of suspension towers on the fore mentioned line, considering material loss of their structural members due to atmospheric corrosion, in different design conditions. For this purpose, a commercially available FEM code was used to build models to perform structural and modal analysis of the chosen type of tower, in order to determine load effects in the structure (stress and deformation), natural frequencies and mode shapes in each of the different design states. Then, a simple methodology engineered as part of this study leads to prediction of the tower’s service life based on an allowable state of stress and deformation in the tower (direct and vibration-induced) affected by different reliability factors and taking into account corrosion effects and corrosion rates in a particular environment along the transmission line.
Among other types of wagons, CVG Ferrominera Orinoco (FMO) uses 350 hopper type wagons for ore transportation. Each of these wagons has a mechanical linkage system, made up of nine mobile elements plus a frame to open and close two rotary doors located at the bottom of the wagons. This paper presents development of a mathematical model to find out how the calibrating lengths of the operating mechanism’s four adjustable members allow variations of the angular position of the doors from its fully closed position. The mathematical model is obtained from the total differentials of the kinematics constraints equations and is used to find the relative influence coefficients of each adjustable member on the kinematic accuracy of the doors motion. The results show that the maximum error depends mainly upon the correct positioning of the primary element. It is also proved that two of the adjustable members in the original design do not play an important role in the tight closing.
Among other types of wagons, Ferrominera Orinoco Company uses 350 hopper type wagons for ore transportation. Each of these wagons has a mechanical linkage system, made up of nine mobile elements plus a frame to open and close two rotary discharge doors located at the bottom of the wagons. This paper presents the influence of clearances in the kinematic pairs of the operating mechanism for a tight sealing of the doors. For this purpose, a new mathematical model is developed to show how the positioning error of the doors — from its theoretical fully closed position — may be controlled via an adequate assignment of the clearances in the kinematic pairs. The results show that the positioning errors of each door due to clearances are independent from one another and may be obtained by modelling the kinematic cycle comprising each door as an equivalent five degree of freedom linkage as to obtain the maximum possible error of each door according to the combination of clearances in the kinematic pairs. This way, the most appropriate normalized fit may be assigned in order to limit a maximum positioning output error of each door.
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