During 1968 to 1985, 109 workers who had been engaged in the production of pentachlorophenol, using non-gamma isomers of hexachloroclohexane (BHC) as the raw material, were surveyed. Endemic chloracne among them had been noted since 1974. The prevalence of chloracne was 73.4% (80/109) in total and 95.2% (20/21) in a trichlorobenzene (TCB) tank area where dioxin and dibenzofurans levels were thousands of ppm. To our knowledge, PCDDs and PCDFs have not previously been reported from thermal decomposition of BHC. Urinary porphyrins were significantly higher among exposed workers than among the controls but there was no significant difference between the workers with chloracne and those without. The conduction velocities of the median motor nerves were much slower among the workers in the TCB tank area where the highest PCDDs contamination appeared. The mortality study cohort was relatively young. Based on the three deaths observed during the follow-up, no association could be drawn.
In order to study the forming quality of AlSi10Mg powder for SLM process without supporting structure, as well as lay the foundation of subsequence structural design of Aluminum SLM technique, a series of typical coupons have been designed and printed. Based on comprehensive consideration of layout direction, overhang angle, hole size, etc., Xline 2000R with optimized process parameter has been used as SLM equipment for AlSi10Mg powder. Through the analysis of printed coupons, the beneficial conclusion is made which can be used to guide future design, especially for the structure with complex shape.
The influence of Mo and V contents on the microstructure and secondary hardening of 6Cr6W2MoV steel was studied in this paper, and the process factors and the transformation mechanism of the influence results were discussed by phase equilibrium thermodynamic analysis. The results show that, the microstructure of 6Cr6W2MoV steel is uniform and thin, in which the undissolved carbide size after quenching is 0.23μm. In the heating and cooling process of the annealing, the dissolution and precipitation of M23C6↔M6C carbides transformation can be used to carbides distributing uniform refinement. Adding an overmany Mo content will lead to coarsening of carbide particles due to small amplitude of M23C6↔M6C transformation. Adding an overmany V content will appear a small of the bulk MC carbide on the crystallization, so the heterogeneity of carbides is increasing. The tempering hardness of 6Cr6W2MoV steel is 63.5HRC, and when adding an overmany Mo content the maximal hardness arrives to 65HRC. Adding Mo changes the carbide composing, it is conducive to the variety of carbides precipitation strengthening near intermediate temperature and the tempering hardness increasing. When adding an overmany V content the more MC carbide well occupy more amount of C, the tempering temperature dispersion increases too, so the tempering hardness debases deservedly and the highest hardness only reaches HRC60.5.
To study the mechanical evolution rule of the supporting part in the process of the reinforced concrete chimney blasting demolition, a finite element model based on a practical project is established by explicit analysis software LS-DYNA. By means of four different Angle blasting cut finite element models, the stress distribution of the supporting part and neutral axis moving rule is drawn. It will help to develop the theory of the reinforced concrete chimneys blasting demolition.
Given the issue that most of the parking lot intellectualized degree and management level is relatively low, this paper focuses on the function design based on Zigbee wireless sensor network, puts forward an intelligent parking lot management system based on Internet of things. This system mainly adopted CC2530 chip as the core of the Zigbee information processing unit to realize the short distance, low power wireless transmission. The intelligent parking lot management system this paper introduced can detect in individual's use of the parking space in the parking lot, and the number of vehicles in the parking lot.
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