Additional guarantees (AGs) for Salmonella in imported defined animal-derived foods were agreed on for Finland when it was admitted to the European Community. The aim of this project was to evaluate the impact of these AGs on the prevalence of Salmonella in the Finnish beef supply and the adequacy of their scope. According to the quantitative Bayesian model, the efficacy of AGs was mainly dependent on the proportions of different beef categories imported and the true prevalence in the countries of origin. According to the model, AGs were able to reach their target in the referred year 1999 and kept the true Salmonella prevalence of beef imports below 1% with quantified uncertainty. The extension of AGs to all imported fresh beef would have reduced the Salmonella prevalence of beef imports from three- to fourfold, whereas expanding the implementation of AGs to all imports of fresh beef, beef preparations, and beef products would have resulted in a sixfold decrease. If current AGs targeting fresh beef intended to be sold as fresh or to be processed by the Finnish industry with processes not achieving 70 degrees C were not implemented, the 95% credible interval of Salmonella prevalence in the Finnish beef supply would be 0.2 to 1.3% (mean, 0.6%) instead of 0.1 to 1.2% (mean, 0.5%). However, if the prevalence in the exporting countries were to rise or the main import countries and/or magnitudes were to change, AGs would be of greater importance. 相似文献
A lumped circuit model for calculating voltages and currents on all-dielectric self-supporting (ADSS) fiber optic cable near high voltage transmission lines has been developed. The model has been used to show that contamination levels, tower attachment points, relative ADSS and conductor sag and electrical phasing of the conductors are important parameters and must be considered in calculations, especially when determining the possibility of dry band arcs which could lead to cable damage 相似文献
Zirconia-based 8Y2O3-ZrO2 and 22MgO-ZrO2 thick thermal barrier coatings (TTBC, 1000 μm), were studied with different sealing methods for diesel engine applications.
The aim of the sealing procedure was to improve hot corrosion resistance and mechanical properties of porous TBC coatings.
The surface of TTBCs was sealed with three different methods: (1) impregnation with phosphate-based sealant, (2) surface melting
by laser glazing, and (3) spraying of dense top coating with a detonation gun. The thicknesses of the densified top layers
were 50–400 μm, depending on the sealing procedure. X-ray diffraction (XRD) analysis showed some minor phase changes and reaction
products caused by phosphate-based sealing treatment and some crystal orientation changes and phase changes in laser-glazed
coatings. The porosity of the outer layer of the sealed coating decreased in all cases, which led to increased microhardness
values. The hot corrosion resistance of TTBCs against 60Na2SO4-40V2O5 deposit was determined in isothermal exposure at 650 °C for 200 h. Corrosion products and phase changes were studied with
XRD after the test. A short-term engine test was performed for the reference coatings (8Y2O3-ZrO2 and 22MgO-ZrO2) and for the phosphate-sealed coatings. Engine tests, duration of 3 h, were performed at the maximum load of the engine and
were intended to evaluate the thermal cycling resistance of the sealed coatings. All of the coatings passed the engine test,
but some vertical cracks were detected in the phosphate-sealed coatings. 相似文献
Thermal spray processes are widely used to deposit high-chromium, nickel-chromium coatings to improve high temperature oxidation
and corrosion behavior. However, despite the efforts made to improve the present spraying techniques, such as high-velocity
oxyfuel (HVOF) and plasma spraying, these coatings may still exhibit certain defects, such as unmelted particles, oxide layers
at splat boundaries, porosity, and cracks, which are detrimental to corrosion performance in severe operating conditions.
Because of the process temperature, only mechanical bonding is obtained between the coating and substrate. Laser remelting
of the sprayed coatings was studied in order to overcome the drawbacks of sprayed structures and to markedly improve the coating
properties. The coating material was high-chromium, nickel-chromium alloy, which contains small amounts of molybdenum and
boron (53.3% Cr, 42.5% Ni, 2.5% Mo, 0.5% B). The coatings were prepared by HVOF spraying onto mild steel substrates. A high-power,
fiber-coupled, continuous-wave Nd:YAG laser equipped with large beam optics was used to remelt the HVOF-sprayed coating using
different levels of scanning speed and beam width (10 or 20 mm). Coating that was remelted with the highest traverse speed
suffered from cracking because of the rapid solidification inherent to laser processing. However, after the appropriate laser
parameters were chosen, nonporous, crack-free coatings with minimal dilution between coating and substrate were produced.
Laser remelting resulted in the formation of a dense oxide layer on top of the coatings and full homogenization of the sprayed
structure. The coatings as sprayed and after laser remelting were characterized by optical and electron microscopy (OM, SEM,
respectively). Dilution between coating and substrate was studied with energy dispersive spectrometry (EDS). The properties
of the laser-remelted coatings were directly compared with properties of as-sprayed HVOF coatings. 相似文献
In the present study, surface engineering research related to thermally sprayed wear and corrosion resistant coatings modified by in-situ and post-treatment by novel high power lasers (Nd:YAG and diode lasers) has been carried out. The main aim of the study was to create experimental based information and knowledge on simultaneous remelting of thermally sprayed (plasma, HVOF, flame) single layers for production of metallurgically bonded, dense corrosion and wear resistant coatings on surfaces of steels. The main focus of research was to estimate the needed processing parameters, which enable simultaneous laser-assisted thermal spraying. The microstructures and hardness-profiles for the coatings prepared by laser-assisted thermal spraying are also introduced. 相似文献
Expressions for the major variables in the general rate equation for solid-solid nucleation were developed on the basis of various models of the critical nucleus shape during homogeneous and heterogeneous nucleation. These models are based upon spheres, but in some a facet was incorporated at one boundary orientation to represent the presence of a partially or fully coherent structure. Gibbs’ relationship for the critical radius is applicable to all of the models. The other variables in the nucleation rate equation are affected by the model and by faceting. Reduction of AG* by faceting is concluded to be the primary cause for the presence of reproducible lattice orientation relationships and for the existence of transition phases during precipitation from solid solutions. 相似文献
Precipitation hardened single crystals of a beta (bcc) Ti-40 at. pct V + 1.0 at. pct Si alloy have been deformed in compression at 77 K and 298 K. The dependence of the yield stress upon aging time at 843 K for solution treated crystals shows two maxima which are caused by silicide precipitates. The orientation dependence of the yield stress and of the active macroscopic slip plane have been determined as a function of aging time. The solution treated as well as aged crystals exhibit an asymmetry of both the yield stress and the plane of slip, the degree of asymmetry being larger at 77 K than at 298 K. The asymmetry of slip and yielding is not affected by the presence of precipitation hardening. The results indicate that the effect of the dislocation core structure on dislocation motion is independent of the presence of precipitates.
Visually impaired children have a great disadvantage in the modern society since their ability to use modern computer technology is limited due to inappropriate user interfaces. The aim of the work presented in this paper was to develop a multimodal software architecture and applications to support learning of visually impaired children. The software architecture is based on software agents, and has specific support for visual, auditory and haptic interaction. It has been used successfully with different groups of 7-8 year-old and 12 year-old visually impaired children. In this paper we discuss the enabling software technology and interaction techniques aimed to realize our goal and our experiences in the actual use of the system. 相似文献