Changing test and data modeling requirements for screening latent defects as statistical outliers

The expanded role of test demands a significant change in mind-set of nearly every engineer involved in the screening of semiconductor products. The issues to consider range from DFT and ATE requirements, to the design and optimization of test patterns, to the physical and statistical relationships of different tests, and finally, to the economics of reducing test time and cost. The identification of outliers to isolate latent defects will likely increase the role of statistical testing in present and future technologies. An emerging opportunity is to use statistical analysis of parametric measurements at multiple test corners to improve the effectiveness and efficiency of testing and reliability defect stressing. In this article, we propose a "statistical testing" framework that combines testing, analysis, and optimization to identify latent-defect signatures. We discuss the required characteristics of statistical testing to isolate the embedded-outlier population; test conditions and test application support for the statistical-testing framework; and the data modeling for identifying the outliers.     

An observation of microbial cell accumulation in a finned tube

Biofouling in heat exchange equipment results in significant energy loss by increasing heat transfer resistance and fluid frictional resistance. This paper compares the deposition and distribution of attached microbial cells on a smooth tube and a tube with inner fins after 100 hours exposure. Preliminary results suggest a significantly different distribution of attached microbial cells on the finned tube.     

Postanesthetic vasoconstriction slows peripheral-to-core transfer of cutaneous heat, thereby isolating the core thermal compartment

Forced-air warming during anesthesia increases core temperature comparably with and without thermoregulatory vasoconstriction. In contrast, postoperative forced-air warming may be no more effective than passive insulation. Nonthermoregulatory anesthesia-induced vasodilation may thus influence heat transfer. We compared postanesthetic core rewarming rates in volunteers given cotton blankets or forced air. Additionally, we compared increases in peripheral and core heat contents in the postanesthetic period with data previously acquired during anesthesia to determine how much vasomotion alters intercompartmental heat transfer. Six men were anesthetized and cooled passively until their core temperatures reached 34 degrees C. Anesthesia was then discontinued, and shivering was prevented by giving meperidine. On one day, the volunteers were covered with warmed blankets for 2 h; on the other, volunteers were warmed with forced air. Peripheral tissue heat contents were determined from intramuscular and skin thermocouples. Predicted changes in core temperature were calculated assuming that increases in body heat content were evenly distributed. Predicted changes were thus those that would be expected if vasomotor activity did not impair peripheral-to-core transfer of applied heat. These results were compared with those obtained previously in a similar study of anesthetized volunteers. Body heat content increased 159 +/- 35 kcal (mean +/- SD) more during forced-air than during blanket warming (P < 0.001). Both peripheral and core temperatures increased significantly faster during active warming: 3.3 +/- 0.7 degrees C and 1.1 +/- 0.4 degrees C, respectively. Nonetheless, predicted core temperature increase during forced-air warming exceeded the actual temperature increase by 0.8 +/- 0.3 degree C (P < 0.001). Vasoconstriction thus isolated core tissues from heat applied to the periphery, with the result that core heat content increased 32 +/- 12 kcal less than expected after 2 h of forced-air warming (P < 0.001). In contrast, predicted and actual core temperatures differed only slightly in the anesthetized volunteers previously studied. In contrast to four previous studies, our results indicate that forced-air warming increases core temperature faster than warm blankets. Postanesthetic vasoconstriction nonetheless impeded peripheral-to-core heat transfer, with the result that core temperatures in the two groups differed less than might be expected based on systemic heat balance estimates. Implications: Comparing intercompartmental heat flow in our previous and current studies suggests that anesthetic-induced vasodilation influences intercompartmental heat transfer and distribution of body heat more than thermoregulatory shunt vasomotion.