Validation of CFD Codes for the Helicopter Wake in Ground Effect

When a helicopter takes off, lands, or makes hovering or taxiing flights in ground effect, its downwash interferes with the ground. Encounters with such highly turbulent helicopter wakes have been blamed for two fixed-wing aircraft crashes in the United Kingdom. Additional incidents including tents blown away are reported in Japan. Due to these accidents, the Japan Aerospace Exploration Agency (JAXA) and the University of Glasgow (UoG) are investigating the helicopter wake structure in ground effect, especially during taxiing, by means of computational fluid dynamics (CFD). In this study, CFD codes of UoG and JAXA are validated through comparing numerical results of each party and flight experiment data. As a result, it is found that the CFD codes show qualitatively the same results each other and they are also close to the experiment

The absence of finite-temperature phase transitions in low-dimensional many-body models: a survey and new results

After a brief discussion of the Bogoliubov inequality and possible generalizations thereof, we present a complete review of results concerning the Mermin-Wagner theorem for various many-body systems, geometries and order parameters. We extend the method to cover magnetic phase transitions in the periodic Anderson Model as well as certain superconducting pairing mechanisms for Hubbard films. The relevance of the Mermin-Wagner theorem to approximations in many-body physics is discussed on a conceptual level.Comment: 33 pages; accepted for publication as a Topical Review in Journal of Physics: Condensed Matte

MiR-133a in Human Circulating Monocytes: A Potential Biomarker Associated with Postmenopausal Osteoporosis

Background: Osteoporosis mainly occurs in postmenopausal women, which is characterized by low bone mineral density (BMD) due to unbalanced bone resorption by osteoclasts and formation by osteoblasts. Circulating monocytes play important roles in osteoclastogenesis by acting as osteoclast precursors and secreting osteoclastogenic factors, such as IL-1, IL-6 and TNF-a. MicroRNAs (miRNAs) have been implicated as important biomarkers in various diseases. The present study aimed to find significant miRNA biomarkers in human circulating monocytes underlying postmenopausal osteoporosis. Methodology/Principal Findings: We used ABI TaqManH miRNA array followed by qRT-PCR validation in circulating monocytes to identify miRNA biomarkers in 10 high and 10 low BMD postmenopausal Caucasian women. MiR-133a was upregulated (P = 0.007) in the low compared with the high BMD groups in the array analyses, which was also validated by qRT-PCR (P = 0.044). We performed bioinformatic target gene analysis and found three potential osteoclast-related target genes, CXCL11, CXCR3 and SLC39A1. In addition, we performed Pearson correlation analyses between the expression levels of miR-133a and the three potential target genes in the 20 postmenopausal women. We did find negative correlations between miR-133a and all the three genes though not significant. Conclusions/Significance: This is the first in vivo miRNA expression analysis in human circulating monocytes to identif

Relationship between pilot workload and turbulence intensity for helicopter operations in harsh environments

This paper proposes a method for predicting the workload experienced by a pilot when flying a helicopter in highly turbulent wakes where the spatial scales of the eddies are comparable with the size of the aircraft. In this method, the temporal and spatial wind variations over the helicopter are quantified using wavelet decomposition. The extracted wind variation parameters are then correlated with pilot workload using a neural network trained by appropriate turbulence-workload datasets. The proposed method has been used to predict pilot workload for helicopter deck landings in ship airwakes that were produced using unsteady CFD. The prediction performance was seen to be comparable to that of a previous method based on the standard deviations of 4-axis pilot control activities. The proposed method has also been shown to be capable of predicting pilot workload for a different type of ship airwake to the one used to train the neural network. Further improvements in the method are planned to reflect the different dynamic characteristics exhibited by different helicopter types, and the effects of these on pilot workload.Copyright © 2009 by the American Helicopter Society International, Inc. All rights reserved