Using multivariate statistical methods to detect fires

Fire detectors must accurately detect fires, but they should not respond to false alarms. Contemporary smoke detectors sometimes cannot discriminate between smoke and odor sources. These detectors can also be slow in responding to smoldering fire sources. In this paper, a statistical approach for detecting fires based on fusing sensor signals from multiple sensors is presented. The multivariate statistical approach, called principal component analysis, is used to compress the sensor information down to a small number of variables that can be interpreted more easily than the raw sensor signals themselves. Experimental results presented here show that the proposed approach is more accurate than a conventional smoke alarm, particularly for early detection of smoldering fires. However, this new approach does not overcome the problem of false alarms. In spite of this current limitation, the method discussed holds great promise for future fire detection applications.     

采用冷却倾斜板铸造方法生产悬架零部件用EN Aw 6082铝合金锻坯(英文)

对采用冷却倾斜板铸造方法生产EN AW 6082铝合金锻坯用于制备悬架零部件的可行性进行研究。采用冷却倾斜板铸造方法生产的EN AW 6082铝合金坯料具有细小的均匀组织,可直接用于锻造生产而不需要另外的均匀化处理。这可能是因为铸造开始时采用较小的过热和冷却倾斜板上发生较多的凝固所致。对采用冷却倾斜板铸造和均匀化处理的含或者不含Cr的EN AW 6082铝合金坯料,通过锻造生产的悬架零部件均具有均匀的组织,经过标准的人工时效处理后硬度可达到HV110。     

Effect of Cr and Zr on the grain structure of extruded EN AW 6082 alloy

The effects of Cr and Zr addition on the coarse grain surface layer in EN AW 6082 tube extrusions were investigated. The decoration of the tube surfaces and the weld seams with coarse recrystallized grains reflects the strain as well as the temperature gradients that predominate across the section of the tubes during extrusion. The recrystallization resistance provided by Mn does not suffice to avoid the coarse surface grains. With structural features that are almost identical to those of the base 6082 alloy, the 6082 alloy with 0.06 wt% Zr also fails to offer any improvement. The coarse grain surface layer is much thinner and recrystallization is entirely avoided across the weld seams upon the addition of 0.15 wt% Cr. The superior recrystallization resistance of the revised alloy is attributed to the increase in the population of the Cr-rich Al(Cr,Mn,Fe)Si as well as (Al, Si)₃Zr dispersoid particles. It is reasonable to conclude that the coaddition of Zr and Cr has a favourable impact on the resistance to recrystallization of EN AW 6082 alloy.     

Ultrasonic characterization of lactose dissolution

The ultrasonic properties (at 2.25 MHz) of lactose solutions and suspension of lactose crystals (d ∼ 50 μm) were measured as a function of concentration (0–40 wt.%). Ultrasonic velocity increased linearly with concentration regardless of the state of dissolution of the lactose crystals while ultrasonic attenuation was low and concentration-independent when the lactose was dissolved and increased approximately linearly with the concentration of suspended crystals. Therefore the amount of lactose present and the state of dissolution can be determined simultaneously with single ultrasonic sensor. A sensor based on this principle was applied to a stirred tank and used to measure the time taken to mix powdered lactose into a solution and the time for the added lactose to dissolve.