EXPERIMENTAL STUDIES OF DEPOSITION RATES IN THE PRESENCE OF ALKALI SULFATE VAPOR SCAVENGING BY SUBMICRON PARTICLES IN COMBUSTION GAS BOUNDARY LAYERS†

Particle defects play a major role in yield losses in semiconductor device fabrication. It is generally acknowledged that about 50 percent of all yield losses are due to particles. Processing of devices with 0.35 to 0.5 μm minimum feature sizes will exacerbate the effects of particles due to the large relative abundance of submicron particles. The cleanroom is no longer the major particle contributor because current state-of-the-art cleanrooms have less than 10 particles (<0.5 μm) per cubic foot. Particles in processing equipment now play the dominant role in wafer contamination. An analysis of the status and needs of particle detection techniques for semiconductor processing equipment and processes clearly shows that they are inadequate to meet the requirements of the next generation of devices. Detection limits must be improved both in terms of particle diameter and in the number of particles on a wafer. An experimental laser particle counter was fabricated and used to show that such a detector would be extremely useful for in-vacuum realtime particle detection. Experimental studies on wafer surface measurements show that current wafer surface scanning techniques cannot provide the level of detection needed for future devices. Ideas for a new generation of particle detection equipment are presented.

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Experimental Studies on Wake-Induced Transition of Turbulent Boundary Layers

Volume 7: Fluids and Heat Transfer, Parts A, B, C, and D ◽

10.1115/imece2012-86486 ◽

2012 ◽

Author(s):

Keiji Takeuchi ◽

Susumu Fujimoto ◽

Eitaro Koyabu ◽

Tetsuhiro Tsukiji

Keyword(s):

Boundary Layer ◽

Flat Plate ◽

Boundary Layers ◽

Turbulence Intensity ◽

Intensity Distribution ◽

Experimental Studies ◽

Turbulent Boundary Layers ◽

Bypass Transition ◽

Pressure Gradients ◽

Hot Wire

Wake-induced bypass transition of boundary layers on a flat plate subjected to favorable and adverse pressure gradients was investigated. Detailed boundary layer measurements were conducted using two hot-wire probes. A spoked-wheel-type wake generator was used to create periodic wakes in front of the flat plate. The main focus of this study was to reveal the effect of the Strouhal number, which changed by using different numbers of wake-generating bars, on the turbulence intensity distribution and the transition onset position of the boundary layer on the flat plate using two hot-wire probes.

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Portable HEPA Purifiers to Eliminate Airborne SARS-CoV-2: A Systematic Review

Otolaryngology ◽

10.1177/01945998211022636 ◽

2021 ◽

pp. 019459982110226

Author(s):

David T. Liu ◽

Katie M. Philips ◽

Marlene M. Speth ◽

Gerold Besser ◽

Christian A. Mueller ◽

...

Keyword(s):

English Language ◽

High Efficiency ◽

Experimental Studies ◽

Mitigation Strategies ◽

Data Sources ◽

Submicron Particles ◽

World Health ◽

Indoor Environments ◽

Or Efficiency ◽

Current State

Objective Current epidemiologic predictions of COVID-19 suggest that SARS-CoV-2 mitigation strategies must be implemented long-term. In-office aerosol-generating procedures pose a risk to staff and patients while necessitating examination room shutdown to allow aerosol decontamination by indwelling ventilation. This review summarizes the current state of knowledge on portable high-efficiency particulate air (HEPA) purifiers’ effectiveness in eliminating airborne SARS-CoV-2 from indoor environments. Data Sources Medline, Embase, Cochrane Databases, and the World Health Organization’s COVID-19 Global Literature on Coronavirus Disease. Review Methods Data sources were systematically searched for original English-language published studies indexed up to January 14, 2021 per the following search strategy: (“HEPA” OR “High-efficiency” OR “High-efficiency particulate air” OR “Efficiency particulate” OR “Purifier” OR “Filter” OR “Cleaner” OR “Filtration”) AND (“COVID” OR “COVID-19” OR “SARS-CoV-2” OR “Coronavirus”). Additional relevant studies were identified by searching the reference lists of included articles. Results Eleven published studies have evaluated the effectiveness of portable HEPA purifiers in eliminating airborne SARS-CoV-2 with relevantly sized surrogate particles. Ten studies evaluated aerosols and submicron particles similar in size to SARS-CoV-2 virions. In all studies, portable HEPA purifiers were able to significantly reduce airborne SARS-CoV-2-surrogate particles. The addition of portable HEPA purifiers augmented other decontamination strategies such as ventilation. Conclusion Experimental studies provide evidence for portable HEPA purifiers’ potential to eliminate airborne SARS-CoV-2 and augment primary decontamination strategies such as ventilation. Based on filtration rates, additional air exchanges provided by portable HEPA purifiers may be calculated and room shutdown times potentially reduced after aerosol-generating procedures.

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