Effect of airflow direction on human perception of draught
Forty subjects, 20 women and 20 men, were exposed to airflows from five different directions: horizontally towards the front, the back, and the left side and vertically upwards and downwards. The subjects were exposed to stepwise increased air velocities ranging from less than 0.10 m/s to 0.40 m/s at three temperature levels 20, 23 and 26 o C. The results showed that airflow direction has an impact on perceived discomfort due to draught. At 20 o C and 23 o C, airflow from below was perceived as most uncomfortable followed by airflows towards the back and front. At 26 o C airflow from above and towards the back caused most dissatisfaction due to draught, but generally only a few of the subjects perceived discomfort at this temperature. Discomfort due to draught was most often felt at the body regions directly exposed to the airflow. These were the legs, the feet, and the lower back at airflow from below; the neck, the shoulders and the hands at airflow from above; the neck, the back, the shoulders and the legs at airflow from behind; the knee and the arm facing the windbox when exposed to air movements directed towards the side; and the hands and the knees when exposed to air movements towards the front.
Perception and sensitivity to horizontal turbulent air flows at the head region.
This work deals with experimental investigations on human reaction to local air movements of people in global thermal comfort, performing light activity. An analysis on draught risk was developed comparing the results with previous research findings on human response to draught. The intensity of air velocity, in terms of mean value and relative turbulence, was referred to the level at which normally clothed people could perceive and feel air movements behind the neck, in global neutral thermal condition. This work provides evidence of how the exposure duration to air movements plays a fundamental role on air flow sensitivity. The human reaction to an air flow was observed to vary with exposure duration: the feeling changes in intensity while the air flow persists blowing constantly. Moreover, different reactions have been observed between female and male test persons. Although these results were observed in the typical situation of horizontal air jet flows blowing from behind, they could apply in climatically controlled environments, where air flow is supplied horizontally at low speed, and the occupants are sitting far from the inlet section.
Multilayer high density flex technology
The industrial trend of shrinking microelectronic devices while increasing the density of interconnections places great demands on the substrates upon which these devices are packaged. Multilayer flex circuits will provide the interconnection densities needed to meet these demands in a wide range of packaging and interconnection technologies. This paper discusses the development of ultra-high density flexible circuits. Processes and materials to fabricate fine line pitches from 12.5 /spl mu/m to 40 /spl mu/m are examined. Various microvia structures, through hole and blind via, are demonstrated. A test vehicle was designed and built for BGA packages to illustrate the density capability. A four-layer structure is demonstrated by using Z-connection to connect two layer pairs. Electrical, mechanical, and reliability test results are presented to show the selection of flex substrate material, Z-connection methodology and fabrication processes. A cost comparison of high-density flex to alternative substrates is discussed to identify potential.