Literatura científica selecionada sobre o tema "Altitude"
Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos
Consulte a lista de atuais artigos, livros, teses, anais de congressos e outras fontes científicas relevantes para o tema "Altitude".
Ao lado de cada fonte na lista de referências, há um botão "Adicionar à bibliografia". Clique e geraremos automaticamente a citação bibliográfica do trabalho escolhido no estilo de citação de que você precisa: APA, MLA, Harvard, Chicago, Vancouver, etc.
Você também pode baixar o texto completo da publicação científica em formato .pdf e ler o resumo do trabalho online se estiver presente nos metadados.
Artigos de revistas sobre o assunto "Altitude"
1
Tang, Yan Fei, Chao Ding, Ya Ping He, De Chuang Zhou, and Jian Wang. "Studies on the Effect of Altitude on the Flammable Liquids' Flash Point." Advanced Materials Research 908 (March 2014): 345–48. http://dx.doi.org/10.4028/www.scientific.net/amr.908.345.
Texto completo da fonteResumo:
Presented in this paper is part of an experimental series conducted at different altitudes to investigate the influence of altitude on the flammable liquids flash point. The BS-1 closed bomb apparatus is used to measure the flash points of two flammable liquids (dimethylacetylamide (DMA) and RP-5 Jet A) in a hypobaric chamber under the altitude change from 4860 km to the sea level. The experimental results show that the flash points of DMA and Jet A decrease linearly with the increase in altitude in the low altitude region below the corresponding critical altitudes but non-linearly above. The critical altitudes for DMA and RP-5 Jet A are found to be 3 km and 3.83 km respectively. When the altitude reaches or surpasses the critical altitude, the flash point decreases rapidly. In particular, the flash point of the DMA exhibits a peculiar sudden transition above the critical altitude.
2
Nazarali, Samir, Henry Liu, Maleeha Syed, Terry Wood, Samuel Asanad, Alfredo A. Sadun, and Rustum Karanjia. "Aircraft Cabin Pressurization and Concern for Non-Arteritic Anterior Ischemic Optic Neuropathy." Aerospace Medicine and Human Performance 91, no. 9 (September 1, 2020): 715–19. http://dx.doi.org/10.3357/amhp.5498.2020.
Texto completo da fonteResumo:
BACKGROUND: Cabin pressurization is the process by which aircraft maintain a comfortable and safe environment for passengers flying at high altitudes. At high altitudes, most patients can tolerate changes in pressurization; however, passengers at high risk of hypoxia may experience ischemic events. The purpose of this study was to evaluate variations in pressurization of commercial aircraft at cruising altitude and describe its relevance in relation to patients with non-arteritic anterior ischemic optic neuropathy (NAION).METHODS: Altimeters were used to measure altitude and cabin altitude at cruising altitude aboard 113 commercial flights, including 53 narrow-body and 60 wide-body aircraft.RESULTS: Cabin altitude ranged from 4232 ft to 7956 ft at cruising altitudes ranging from 30,000 ft to 41,000 ft. The mean cabin altitude for all flights was 6309 876 ft. Narrow-body aircraft had a significantly higher mean cabin altitude (6739 829 ft) compared to wide-body aircraft (5929 733 ft). For all flights, the mean cruising altitude was 35,369 2881 ft with narrow-body aircraft cruising at a lower altitude of 34,238 2389 ft compared to wide-body aircraft at 36,369 2925 ft. Newer generation aircraft had a mean cabin altitude of 6066 837 ft, which was lower than the mean cabin altitude of older aircraft (6616 835 ft).DISCUSSION: Innovation in flight design has offered the ability for aircraft to fly at greater altitudes while maintaining lower cabin altitude. Those at high risk of hypoxia-induced complications may consider aircraft type when air travel is required.Nazarali S, Liu H, Syed M, Wood T, Asanad S, Sadun AA, Karanjia R. Aircraft cabin pressurization and concern for non-arteritic anterior ischemic optic neuropathy. Aerosp Med Hum Perform. 2020; 91(9):715719.
3
PANKAJ PANWAR, SHARMISTHA PAL, NANCY LORIA, MED RAM VERMA, N.M. ALAM, V.K. BHATT, and N.K. SHARMA. "Spatio-temporal variability of climatic parameters across different altitudes of North- Western Himalaya." Journal of Agrometeorology 21, no. 3 (November 10, 2021): 297–306. http://dx.doi.org/10.54386/jam.v21i3.252.
Texto completo da fonteResumo:
Climate change impact varies across different altitudinal ranges and demands local specific management strategies for water resource and farming system management. The present study analyses spacio-temporal climate parameters across different altitudes of Himachal Pradesh a hilly state of India. Analysis shows that annually, minimum temperature has significantly decreased by -0.09°C at altitude I (350 - 400 m) while maximum temperature has significantly increased by 0.05°C at altitudes I and II (1400-1500 m) and decreased significantly by -0.08°C at altitude III (2000- 2100 m). Higher regions Altitude – IV (2900-3000 m) received lowest rainfall (746.1 mm) with 30.2 % variation. Seasonal rainfall variability was higher in post monsoon (102 - 174%) and least in monsoon (21 - 57%). Annual rainfall at altitude I is strongly irregular (PCI 20.1 to 22.3), followed by altitude – IV (PCI 15-25); altitude – II irregular (PCI 15-20) and altitude – III moderate to irregular (PCI 12 -19) rainfall. Seasonal Index values for four altitudes fall between 0.91-0.96 revealed that rainfall is irregular and markedly seasonal with longer drier season. Higher wavelet powers in altitude - I and II after 2005 suggests frequency of extreme rainfall occurrence had increased.
4
Chapman, Robert F., Trine Karlsen, Geir K. Resaland, R. L. Ge, Matthew P. Harber, Sarah Witkowski, James Stray-Gundersen, and Benjamin D. Levine. "Defining the “dose” of altitude training: how high to live for optimal sea level performance enhancement." Journal of Applied Physiology 116, no. 6 (March 15, 2014): 595–603. http://dx.doi.org/10.1152/japplphysiol.00634.2013.
Texto completo da fonteResumo:
Chronic living at altitudes of ∼2,500 m causes consistent hematological acclimatization in most, but not all, groups of athletes; however, responses of erythropoietin (EPO) and red cell mass to a given altitude show substantial individual variability. We hypothesized that athletes living at higher altitudes would experience greater improvements in sea level performance, secondary to greater hematological acclimatization, compared with athletes living at lower altitudes. After 4 wk of group sea level training and testing, 48 collegiate distance runners (32 men, 16 women) were randomly assigned to one of four living altitudes (1,780, 2,085, 2,454, or 2,800 m). All athletes trained together daily at a common altitude from 1,250–3,000 m following a modified live high-train low model. Subjects completed hematological, metabolic, and performance measures at sea level, before and after altitude training; EPO was assessed at various time points while at altitude. On return from altitude, 3,000-m time trial performance was significantly improved in groups living at the middle two altitudes (2,085 and 2,454 m), but not in groups living at 1,780 and 2,800 m. EPO was significantly higher in all groups at 24 and 48 h, but returned to sea level baseline after 72 h in the 1,780-m group. Erythrocyte volume was significantly higher within all groups after return from altitude and was not different between groups. These data suggest that, when completing a 4-wk altitude camp following the live high-train low model, there is a target altitude between 2,000 and 2,500 m that produces an optimal acclimatization response for sea level performance.
5
Zhu, Lu-lu, Zhi-jun Ma, Ming Ren, Yu-miao Wei, Yu-hua Liao, You-lu Shen, Shi-ming Fan, et al. "Distinct Features of Gut Microbiota in High-Altitude Tibetan and Middle-Altitude Han Hypertensive Patients." Cardiology Research and Practice 2020 (November 21, 2020): 1–15. http://dx.doi.org/10.1155/2020/1957843.
Texto completo da fonteResumo:
Indigenous animals show unique gut microbiota (GM) in the Tibetan plateau. However, it is unknown whether the hypertensive indigenous people in plateau also have the distinct gut bacteria, different from those living in plains. We sequenced the V3-V4 region of the gut bacteria 16S ribosomal RNA (rRNA) gene of feces samples among hypertensive patients (HPs) and healthy individuals (HIs) from 3 distinct altitudes: Tibetans from high altitude (3600–4500 m, n = 38 and 34), Hans from middle altitude (2260 m, n = 49 and 35), and Hans from low altitude (13 m, n = 34 and 35) and then analyzed the GM composition among hypertensive and healthy subgroups using the bioinformatics analysis, respectively. The GM of high-altitude Tibetan and middle-altitude Han HPs presented greater α- and β-diversities, lower ratio of Firmicutes/Bacteroidetes (F/B), and higher abundance of beneficial Verrucomicrobia and Akkermansia than the low-altitudes HPs did. The GM of high-altitude Tibetan and middle-altitude HIs showed greater α-diversity and lower ratio of F/B than the low-altitudes HIs did. But, β-diversity and abundance of Verrucomicrobia and Akkermansia among different subgroups of HIs did not show any differences. Conclusively, the high-altitude Tibetan and middle-altitude Han HPs have a distinct feature of GM, which may be important in their adaptation to hypertension in the plateau environments.
6
Wan, Yongkuan, Nana Ding, Tingting Tian, Kun Sun, and Baoli Fan. "Sex-Specific Differences in the Clonality of Hippophae tibetana at Different Altitudes in Alpine Meadows of the Eastern Qinghai–Tibet Plateau." Forests 16, no. 1 (January 9, 2025): 107. https://doi.org/10.3390/f16010107.
Texto completo da fonteResumo:
Dioecious plants have different needs for natural resources due to sex differences, which can lead to skewed sex ratios. Clonal growth facilitates and optimizes resources of clonal plants. So, dioecious plants show inter-sex differences in clonality. However, it is unclear how the clonality varies between female and male plants when they exhibit skewed sex ratios along an altitudinal gradient. Here, we investigated the sex ratio and clonality of Hippophae tibetana populations growing at three altitudes in the alpine meadow. We founded that (i) H. tibetana growing at different altitudes mainly consisted of II and III age classes, with a significantly male-biased sex ratio observed at a low altitude, a female-biased ratio at a middle altitude, and no significant sex-bias in the population at a high altitude. (ii) The population distribution was generally random at both low and high altitudes, while clustered at middle altitudes with an increasing scale. Meanwhile, the male and female populations at a low altitude showed a negative correlation, while the male and female at a middle altitude only showed a negative correlation at a 0–0.5 m scale, and spatial independence with increasing scales. (iii) Females of H. tibetana had a strong clonal capacity than male plants at a middle altitude, while the opposite was observed at a low altitude. The number of males of H. tibetana growing at a low altitude and with higher clonal diversity were higher than females at mid altitude. Our findings will contribute to the understanding of the sexual dimorphism exhibited by dioecious plants as well as the importance of a clonal adaptation in response to environmental change.
7
Bogar, K., and P. Schatz. "Altitude and Concussions in the NFL: Is There Really a “Mile-High” Effect?" Archives of Clinical Neuropsychology 34, no. 5 (July 2019): 759. http://dx.doi.org/10.1093/arclin/acz026.29.
Texto completo da fonteResumo:
Abstract Purpose The literature on altitude and concussions in football shows some evidence of protective effects of living and training and playing at high altitudes. We explored the likelihood of sustaining concussions within the AFC West division, specifically comparing games hosted at high altitude in Denver versus games hosted by at low altitudes in Los Angeles, Oakland, and Kansas City. Methods Information was recorded for all regular season AFC West division games (N= 42) occurring in the 2012–2018 seasons. Altitude for each stadium was calculated using DaftLogic’s Google Sandbox. Concussion incidence for the 2012–2018 seasons was collected from PBS Frontline’s Concussion-Watch and weekly injury reports (NFL.com). Chi-square analyses compared likelihood of: concussions occurring in High Altitude versus Low Altitude, a Broncos player sustaining a concussion in High Altitude versus Low Altitude, and a non-Broncos AFC West player sustain a concussion in High Altitude versus Low Altitude. Results Chi-square analyses revealed no greater likelihood of players sustaining concussions in High Altitude versus Low Altitude (p=.35), or of Broncos (p=1.00) or non-Broncos (p=.47) AFC West players sustaining concussions in High Altitude versus Low Altitude. Conclusion Altitude is not a significant factor for increased likelihood of concussions, and popular theories such as “the mile-high effect” are not supported by the data. We found no evidence for the proposed protective factor of living and training at high altitude for Broncos team members, as they showed an equal likelihood of sustaining a concussion at high and low altitude.
8
Tang, Weizhen, Jie Dai, and Zhousheng Huang. "Comprehensive assessment of air pollutant and noise emissions at airports across different altitudes." Metascience in Aerospace 1, no. 3 (2024): 292–308. http://dx.doi.org/10.3934/mina.2024013.
Texto completo da fonteResumo:
<p>We utilized the International Civil Aviation Organization (ICAO) standard emission model, refined with adjustments for fuel flow, LTO cycle work mode time, and emission indices, to investigate the environmental footprint of airports at different altitudes. Airports categorized as high (above 5000 $ \mathrm{f}\mathrm{t} $), medium (1500–5000 $ \mathrm{f}\mathrm{t} $), and low (below 1500 $ \mathrm{f}\mathrm{t} $) altitudes were selected to provide a comprehensive representation of the altitude spectrum. The analysis was anchored over the period spanning 2016 to 2017. Emission inventories for air pollutants and noise were computed for these airports, focusing on the LTO (Landing and Take-Off) cycle. Our findings indicated that high altitude airports exhibit the highest $ {\mathrm{N}\mathrm{O}}_{\mathrm{x}} $ emissions, reaching 406.4 $ \mathrm{t} $, whereas low altitude airports record the highest noise levels at 73.1 $ \mathrm{d}\mathrm{B} $. Significant disparities in emission profiles were observed across different phases of the LTO cycle at airports of varying altitudes. Notably, during the climb phase, the types and proportion of $ {\mathrm{N}\mathrm{O}}_{\mathrm{x}} $ emissions at high altitude airports were as high as 71.8%, contrasting with the 45.6% at low altitude airports. Additionally, emissions of gaseous pollutants from major aircrafts, exemplified by the A320 model, escalated with altitude. Specifically, $ {\mathrm{N}\mathrm{O}}_{\mathrm{x}} $ emissions increased from 10.55 $ \mathrm{k}\mathrm{g}/\mathrm{c}\mathrm{y}\mathrm{c}\mathrm{l}\mathrm{e} $ at low altitude to 20.48 $ \mathrm{k}\mathrm{g}/\mathrm{c}\mathrm{y}\mathrm{c}\mathrm{l}\mathrm{e} $ at high altitude, and $ \mathrm{C}\mathrm{O} $ emissions from 10.88 $ \mathrm{k}\mathrm{g}/\mathrm{c}\mathrm{y}\mathrm{c}\mathrm{l}\mathrm{e} $ to 22.89 $ \mathrm{k}\mathrm{g}/\mathrm{c}\mathrm{y}\mathrm{c}\mathrm{l}\mathrm{e} $. A robust correlation between $ {\mathrm{N}\mathrm{O}}_{\mathrm{x}} $ emissions and $ {L}_{den} $ was identified among airports at different altitudes, with correlation coefficients of 0.96 for low altitude, 0.97 for medium altitude, and 0.93 for high altitude airports. This study delineates the distinct characteristics of air pollutant and noise emissions from airports across altitudes, offering novel insights for the environmental assessment of airport operations.</p>
9
Luo, Chaoxin, Xin Xu, Changrong Du, and Qijun Zhi. "A Study on the Evolution of Emission Altitude with Frequency Among 104 Normal Pulsars." Universe 11, no. 1 (January 12, 2025): 17. https://doi.org/10.3390/universe11010017.
Texto completo da fonteResumo:
Utilizing the databases from the European Pulsar Network (EPN), the Australia Telescope National Facility (ATNF), and published literature data, a geometric method was used to investigate the multifrequency emission altitude of 104 pulsars. We found that the evolution of emission altitudes with frequency for the majority of pulsars can be fitted using a power-law function with a normalization constant. In this work, it is found that the frequency evolution of pulsar emission altitude can be divided into three groups according to their different frequency dependencies of emission altitude (emission altitude decreases with frequency (Group A, η≤−0.1), keeps relatively constant with frequency (Group B, −0.1<η≤0.1), and increases with frequency (Group C, η≥0.1)), where η is the emission altitude variation rate. We also computed the emission altitudes across multiple frequency bands for these pulsars, thereby estimating the approximate range of the pulsar emission regions. We found that most pulsar emissions occur at altitudes of tens to hundreds of kilometers above the polar cap, with differences in emission altitude between the three groups becoming more clear at lower frequencies.
10
Li, Jingyi, Nating Huang, Xun Zhang, Ci Sun, Jiarui Chen, and Qing Wei. "Changes of collagen content in lung tissues of plateau yak and its mechanism of adaptation to hypoxia." PeerJ 12 (October 1, 2024): e18250. http://dx.doi.org/10.7717/peerj.18250.
Texto completo da fonteResumo:
Collagen is crucial for tissue structure, functional maintenance, and cellular processes such as proliferation and differentiation. However, the specific changes in collagen expression and its associated genes in the lung tissues of yaks at high altitudes and their relationship with environmental adaptation remain poorly understood. Studying differences in the content of collagen fibers and gene expression between yaks at high (4,500 m) and low (2,600 m) altitudes, as well as between cattle at low altitudes (2,600 m). Using Masson staining, we found that the collagen fiber content in the lung tissues of yaks at low altitude was significantly higher compared to yaks at high altitude and cattle at the same altitude (P < 0.05). It was revealed through transcriptomic analyses that genes differentially expressed between high and low altitude yaks, as well as between low altitude yaks and cattle, were notably enriched in pathways related to cell adhesion, collagen synthesis, focal adhesion, and ECM-receptor interactions. Specifically, genes involved in mesenchymal collagen synthesis (e.g., COL1A1, COL1A2, COL3A1), basement membrane collagen synthesis (e.g., COL4A1, COL4A2, COL4A4, COL4A6), and peripheral collagen synthesis (e.g., COL5A1, COL6A1, COL6A2, COL6A3) were significantly upregulated in the lung tissues of yaks at low altitude compared to their high altitude counterparts and cattle (P < 0.05). In conclusion, yaks at lower altitudes exhibit increased collagen synthesis by upregulating collagen gene expression, which contributes to maintaining alveolar stability and septal flexibility. Conversely, the expression of collagen genes in yak lung tissues was down-regulated with the increase in altitude, and it was speculated that the decrease in collagen may be used to constrain the function of elastic fibers that are more abundant at high altitude, so as to enable them to adapt to the harsh environment with hypoxia and high altitude. This adaptation mechanism highlights the role of collagen in environmental acclimatization and contributes to our understanding of how altitude and species influence collagen-related physiological processes in yaks.
Teses / dissertações sobre o assunto "Altitude"
1
Chateigner, Coelsch Sophie Santoul Jérôme. "L'enfant en altitude." [S.l.] : [s.n.], 2004. http://theses.univ-nantes.fr/thesemed/chateignerMED04.pdf.
Texto completo da fonte
2
Campos, Prímula Viana. "Interação solo-altitude-vegetação em campos de altitude no sudeste do Brasil." Universidade Federal de Viçosa, 2016. http://www.locus.ufv.br/handle/123456789/10129.
Texto completo da fonteResumo:
Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-04-24T16:45:55Z
No. of bitstreams: 1
texto completo.pdf: 1544486 bytes, checksum: a0b3a96263e8f99177e2a72cba7dcc38 (MD5)<br>Made available in DSpace on 2017-04-24T16:45:55Z (GMT). No. of bitstreams: 1
texto completo.pdf: 1544486 bytes, checksum: a0b3a96263e8f99177e2a72cba7dcc38 (MD5)
Previous issue date: 2016-02-25<br>Conselho Nacional de Desenvolvimento Científico e Tecnológico<br>O estudo avaliou padrões de diversidade, estrutura e formas de vida em três comunidades vegetais associadas a afloramentos rochosos nos campos de altitude do Parque Nacional (PARNA) do Caparaó, MG/ES, Brasil, bem como a influência da altitude e solo nos mesmos parâmetros vegetacionais em três comunidades no Parque Estadual Serra do Brigadeiro (PESB), MG, Brasil. Foram alocadas 100 parcelas de 1x1 m distribuídas ao acaso em cada um dos três ambientes (300 em cada parque). Foram calculados os parâmetros quantitativos clássicos, os índices de diversidade e equabilidade, similaridade florística, curvas de rarefação e dominância-diversidade, bem como análise dos espectros biológicos e vegetacionais, usando as formas de vida de Raunkiaer. Para análise químicas e físicas coletou-se uma amostra simples de solo (0-10 cm). No PARNA Caparaó, foram amostradas 58 espécies, pertencentes a 49 gêneros e 32 famílias. As curvas de rarefação apresentaram tendência à estabilização da assíntota aproximadamente a partir das 75 unidades amostrais em todas as áreas. Entre as áreas existem diferenças significativas entre a riqueza, abundância e cobertura. O índice de diversidade de Shannon-Wiener permaneceu entre 3,00-2,76 e equabilidade de Pielou com dois valores 0,77 e 0,75. As curvas de dominância-diversidade apresentaram distribuição log-normal e geométrica. A proporção do número de espécies por forma de vida foi similar entre as áreas, ao contrário do espectro vegetacional, com destaque para as espécies hemicriptófitas. No PESB, foram amostrados 9.276 indivíduos, pertencentes a 39 famílias e 102 espécies. Entre as áreas existem diferenças significativas entre a riqueza, abundância, cobertura, bem como nos parâmetros edáficos. O índice de diversidade de Shannon-Wiener permaneceu entre 3,07-3,20 e equabilidade de Pielou (0,74-0,79). A CCA indicou dois grupos distintos formados para abundância e cobertura, indicando a concentração das espécies em habitats preferenciais, em função da altitude, bem como da fertilidade e textura do solo. A partir do GLM, a riqueza de espécies foi correlacionada com atributos químicos do solo, assim como ambos os parâmetros estruturais da vegetação, que além de apresentar relação com variáveis químicas do solo, foram influenciados pela altitude. Os resultados apontam a falta de informações em relação aos fatores abióticos que possam reger nesses ambientes.<br>This study assessedthe diversity, structure and life-form patterns in three plant communities associated with rocky outcrops in the campos de altitude of the Caparaó National Park, MG/ES states, Brazil, as well as the influence of altitude and soil on these vegetation parameters in three communities from the Serra do Brigadeiro State Park, MG state, Brazil. For that, 100 plots (1x1 m) were randomly distributedacross each of the three environments (300 in each park).Classical quantitative parameters were calculated: diversity and evenness indexes, floristic similarity, and rarefaction and dominance-diversity curves. Biological and vegetation spectra were also analyzed, by using Raunkiaer‟s life-form classification. For soil chemical and physical analyses, a simple sample (0-10 cm depth) was collected. In the PARNA Caparaó, were sampled a total of 58 species belonging to 49 genera and 32 families were sampled. The rarefaction curves showed a tendency to stabilization of the asymptote at approximately 75 of the sampled units in all areas. There are significant differences between the areas regarding species richness, abundance and coverage. Shannon-Wiener‟s diversity index ranged between 3.00 and 2.76, while Pielou‟s evenness index showed the values of 0.77 and 0.75. The dominance-diversity curves showed log-normal and geometric distributions. The proportion of the number of species per life-form was similar between the areas, with the hemicryptophytes showing the highest values. The vegetation spectrum, however, differed. In the PESB, were sampled A total of 9276 individuals belonging to 39 families and 102 species were analyzed. There are significant differences between the areas regarding richness, abundance, coverage and edaphic parameters. The areas, however, are relatively similar. Shannon-Wiener‟s diversity index ranged between 3.07 and 3.20, while Simpson‟s index ranged from 0.6 to 0.8 and Pielou‟s evenness from 0.74 to 0.79. The CCA revealed the existence of two distinct gradients formed by abundance and coverage, thus indicating the concentration of species in preferential habitats according to the altitude, as well asto soil fertility and texture. Through the GLM, the species richness was shown to be correlated with soil chemical attributes, as were both vegetation structural parameters, which besides showing a relationship with soil chemical variables were also influenced by the altitude.The results indicate the lack of a relationship with abiotic factors on these environments.
3
Suissa, Nathalie. "Bioimpedance transthoracique en altitude." Toulouse 3, 1994. http://www.theses.fr/1994TOU31068.
Texto completo da fonte
4
Bennett, April M. "Active Regulation of Speed During a Simulated Low-altitude Flight Task: Altitude Matters!" Wright State University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=wright1167238078.
Texto completo da fonte
5
Mason, Nicholas. "Mechanisms of altitude-related cough." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209711.
Texto completo da fonteResumo:
The original work presented in this thesis investigates some of the mechanisms that may be responsible for the aetiology of altitude-related cough. Particular attention is paid to its relationship to the long recognised, but poorly understood, changes in lung volumes that occur on ascent to altitude. The literature relevant to this thesis is reviewed in Chapter 1.<p><p>Widespread reports have long existed of a debilitating cough affecting visitors to high altitude that can incapacitate the sufferer and, on occasions, be severe enough to cause rib fractures (22, 34, 35). The prevalence of cough at altitude has been estimated to be between 22 and 42% at between 4200 and 4900 m in the Everest region of Nepal (10, 29). Traditionally the cough was attributed to the inspiration of the cold, dry air characteristic of the high altitude environment (37) but no attempts were made to confirm this aetiology. In the first formal study of cough at high altitude, nocturnal cough frequency was found to increase with increasing altitude during a trek to Everest Base Camp (5300 m) and massively so in 3 climbers on whom recordings were made up to 7000 m on Everest (8). After 9 days at 5300 m the citric acid cough threshold, a measure of the sensitivity of the cough reflex arc, was significantly reduced compared with both sea level and arrival at 5300 m.<p><p>During Operation Everest II, a simulated climb of Mount Everest in a hypobaric chamber, the majority of the subjects were troubled above 7000 m by pain and dryness in the throat and an irritating cough despite the chamber being maintained at a relative humidity of between 72 and 82% and a temperature of 23ºC (18). This argued against the widely held view that altitude-related cough was due to the inspiration of cold, dry air. <p><p>In the next major hypobaric chamber study, Operation Everest III, nocturnal cough frequency and citric acid cough threshold were measured on the 8 subjects in the study. The chamber temperature was maintained between 18 and 24ºC and relative humidity between 30 and 60% (24). This work is presented in Chapter 2 and, demonstrated an increase in nocturnal cough frequency with increasing altitude which immediately returned to control values on descent to sea level. Citric acid cough threshold was reduced at 8000 m compared to both sea level and 5000 m values. Changes in citric acid cough threshold at lower altitudes may not have been detected because of the constraints on subject numbers in the chamber. The study still however demonstrated an increase in clinical cough and a reduction in the citric acid cough threshold at extreme altitude, despite controlled environmental conditions, and thus refuted the long held belief that altitude-related cough is solely due to the inspiration of cold, dry air. <p><p>If altitude-related cough is not simply due to the inspiration of cold, dry air, other possible aetiologies are:<p>•\<br>Doctorat en Sciences médicales<br>info:eu-repo/semantics/nonPublished
6
Brown, K. D., and Trevor Sorensen. "HIGH ALTITUDE TRANSMITTER FLIGHT TESTING." International Foundation for Telemetering, 2004. http://hdl.handle.net/10150/605062.
Texto completo da fonteResumo:
International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California<br>This paper describes a high altitude experimental flight test platform developed by the University of Kansas (KU) and the National Nuclear Security Administration’s Kansas City Plant (NNSA’s Kansas City Plant) for high altitude payload flight testing. This platform is called the Kansas University Balloon Experiment Satellite (KUBESat). The paper describes the flight test platform and experimental flight test results captured at Fort Riley, KS from characterization of the KCP developed Distributed Transmitter (DTX).
7
Cohen, Hagit. "Hovering at a low altitude /." Online version of thesis, 1990. http://hdl.handle.net/1850/10903.
Texto completo da fonte
8
Sengul, Orhan. "Low Altitude Radar Wave Propagation Modelling." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608467/index.pdf.
Texto completo da fonteResumo:
LOW ALTITUDE RADAR WAVE PROPAGATION MODELLING
In this PhD thesis, propagation aspects of low altitude radar performance have been modeled using geometrical optics. Both the path propagation factor and the radar clutter have been modeled. Such models already exist at various complexity levels, such as round earth specular reflection combined with knife edge hill diffraction [SEKE:IEEE,Ap-
34,No:8,1980] and round earth and slant plateau reflection combined with hill diffraction [RADCAL: 1988-2000,EE,METU]. In the proposed model we have considered an extension
to RADCAL&rsquo<br>s model to include convex and concave slant plateaus between hills and depressions (troughs). This propagation model uses a reflection model based on the
Geometrical Theory of Reflection for the convex and concave surfaces. Also, back scattering from surface (clutter) is formulated for the new model of the terrain profile. The
effects of the features of the terrain profile on the path propagation factor have been investigated. A real terrain data have been smoothed on the basis of the above study. In
order to verify the formulation, the Divergence and Convergence Factors associated with the convex and concave plateaus, respectively are inserted into the RADCAL program. The chosen terrains have convex or concave plateaus in the model. The output of the RADCAL is compared with measured values and other propagation algorithms such as Forward-Backward Spectrally Accelerated (FBSA) [FBSA:IEEE Vol.53, No:9,2005] and Parabolic Equation Method [TPEM:IEEE Vol.42,No:1,1994]. Moreover, as the RADCAL Propagation model is based on the ray optics, the results are also compared with another ray optics based propagation model. For this purpose the results of SEKE [Lincoln Lab.] propagation model are used. SEKE model has been used to compute path loss for different types of terrain as a
function of receiving antenna height at a fixed distance between transmit and receive antennas. For Beiseker W35 Terrain profile, the results of RADCAL, SEKE and measurements are compared. All results are in good agreement with those of RADCAL.
9
York, Julia McRae. "Respiratory mechanics of high altitude waterfowl." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58744.
Texto completo da fonteResumo:
Birds living at high altitude (>3,000 meters) are not only able to cope with reduced oxygen availability due to hypobaria, but they are also able to achieve one of the most metabolically costly form of locomotion at these altitudes: flight. To perform such a metabolically demanding activity, in addition to energetically expensive daily tasks such as foraging, predator escape, and reproduction, all in oxygen limited (hypoxic) conditions, means that high altitude birds must enhance oxygen supply to maintain oxygen homeostasis. The primary means of increasing oxygen supply is increasing ventilation of the respiratory gas exchange surface. However, the metabolic cost of ventilation is unknown for birds at rest, as is whether this cost varies among bird species. In this thesis, the cost and work of breathing are compared in fourteen avian species to determine whether variation in the work of breathing is due to mechanical or morphological changes in the respiratory system, and if any observed changes are associated with living at high altitude. High altitude birds tended to have large and compliant respiratory systems compared with low altitude taxa, which reduces the work of breathing. However, the evidence also suggests that respiratory morphology and mechanics in birds may be more constrained by life history strategy than by evolutionary time at altitude, although species in this study that have no high altitude sister taxa (their lineages have never radiated to high altitude) struggled the most with increasing oxygen supply. Finally, birds at rest were estimated to have a lower cost of breathing than mammals, contrary to the hypothesis that cost of breathing would be high in birds due to the heavy flight muscles weighing down the sternum.<br>Science, Faculty of<br>Zoology, Department of<br>Graduate
10
Johnson, Pamela Lesley. "Sleep and Breathing at High Altitude." University of Sydney, 2008. http://hdl.handle.net/2123/3531.
Texto completo da fonteResumo:
Doctor of Philosphy (PhD)<br>This thesis describes the work carried out during four treks, each over 10-11 days, from 1400m to 5000m in the Nepal Himalaya and further work performed during several two-night sojourns at the Barcroft Laboratory at 3800m on White Mountain in California, USA. Nineteen volunteers were studied during the treks in Nepal and seven volunteers were studied at White Mountain. All subjects were normal, healthy individuals who had not travelled to altitudes higher than 1000m in the previous twelve months. The aims of this research were to examine the effects on sleep, and the ventilatory patterns during sleep, of incremental increases in altitude by employing portable polysomnography to measure and record physiological signals. A further aim of this research was to examine the relationship between the ventilatory responses to hypoxia and hypercapnia, measured at sea level, and the development of periodic breathing during sleep at high altitude. In the final part of this thesis the possibility of preventing and treating Acute Mountain Sickness with non-invasive positive pressure ventilation while sleeping at high altitude was tested. Chapter 1 describes the background information on sleep, and breathing during sleep, at high altitudes. Most of these studies were performed in hypobaric chambers to simulate various high altitudes. One study measured sleep at high altitude after trekking, but there are no studies which systematically measure sleep and breathing throughout the whole trek. Breathing during sleep at high altitude and the physiological elements of the control of breathing (under normal/sea level conditions and under the hypobaric, hypoxic conditions present at high altitude) are described in this Chapter. The occurrence of Acute Mountain Sickness (AMS) in subjects who travel form near sea level to altitudes above 3000m is common but its pathophysiology not well understood. The background research into AMS and its treatment and prevention are also covered in Chapter 1. Chapter 2 describes the equipment and methods used in this research, including the polysomnographic equipment used to record sleep and breathing at sea level and the high altitude locations, the portable blood gas analyser used in Nepal and the equipment and methodology used to measure each individual’s ventilatory response to hypoxia and hypercapnia at sea level before ascent to the high altitude locations. Chapter 3 reports the findings on the changes to sleep at high altitude, with particular focus on changes in the amounts of total sleep, the duration of each sleep stage and its percentage of total sleep, and the number and causes of arousals from sleep that occurred during sleep at increasing altitudes. The lightest stage of sleep, Stage 1 non-rapid eye movement (NREM) sleep, was increased, as expected with increases in altitude, while the deeper stages of sleep (Stages 3 and 4 NREM sleep, also called slow wave sleep), were decreased. The increase in Stage 1 NREM in this research is in agreement with all previous findings. However, slow wave sleep, although decreased, was present in most of our subjects at all altitudes in Nepal; this finding is in contrast to most previous work, which has found a very marked reduction, even absence, of slow wave sleep at high altitude. Surprisingly, unlike experimental animal studies of chronic hypoxia, REM sleep was well maintained at all altitudes. Stage 2 NREM and REM sleep, total sleep time, sleep efficiency and spontaneous arousals were maintained at near sea level values. The total arousal index was increased with increasing altitude and this was due to the increasing severity of periodic breathing as altitude increased. An interesting finding of this research was that fewer than half the periodic breathing apneas and hypopneas resulted in arousal from sleep. There was a minor degree of upper airway obstruction in some subjects at sea level but this was almost resolved by 3500m. Chapter 4 reports the findings on the effects on breathing during sleep of the progressive increase of altitude, in particular the occurrence of periodic breathing. This Chapter also reports the results of changes to arterial blood gases as subjects ascended to higher altitudes. As expected, arterial blood gases were markedly altered at even the lowest altitude in Nepal (1400m) and this change became more pronounced at each new, higher altitude. Most subjects developed periodic breathing at high altitude but there was a wide variability between subjects as well as variability in the degree of periodic breathing that individual subjects developed at different altitudes. Some subjects developed periodic breathing at even the lowest altitude and this increased with increasing altitude; other subjects developed periodic breathing at one or two altitudes, while four subjects did not develop periodic breathing at any altitude. Ventilatory responses to hypoxia and hypercapnia, measured at sea level before departure to high altitude, was not significantly related to the development of periodic breathing when the group was analysed as a whole. However, when the subjects were grouped according to the steepness of their ventilatory response slopes, there was a pattern of higher amounts of periodic breathing in subjects with steeper ventilatory responses. Chapter 5 reports the findings of an experimental study carried out in the University of California, San Diego, Barcroft Laboratory on White Mountain in California. Seven subjects drove from sea level to 3800m in one day and stayed at this altitude for two nights. On one of the nights the subjects slept using a non-invasive positive pressure device via a face mask and this was found to significantly improve the sleeping oxyhemoglobin saturation. The use of the device was also found to eliminate the symptoms of Acute Mountain Sickness, as measured by the Lake Louise scoring system. This finding appears to confirm the hypothesis that lower oxygen saturation, particularly during sleep, is strongly correlated to the development of Acute Mountain Sickness and may represent a new treatment and prevention strategy for this very common high altitude disorder.
Livros sobre o assunto "Altitude"
1
Chalayan, Hussein. Altitude. [London]: [Hussein Chalayan], 1999.
Encontre o texto completo da fonte
2
Alt, Alfons. Altitude. Marseille, France: Images en manoeuvre, 2007.
Encontre o texto completo da fonte
4
Swenson, Erik R., and Peter Bärtsch, eds. High Altitude. New York, NY: Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4614-8772-2.
Texto completo da fonte
6
Copyright Paperback Collection (Library of Congress), ed. Altitude zero. New York: Jove Books, 1993.
Encontre o texto completo da fonte
7
Angelis-Harmening, Kristina. "--Cada uno tiene en la puna su gente": Intercambio y verticalidad en el siglo XVI en los yungas de La Paz. Markt Schwaben, Germany: A. Saurwein, 2000.
Encontre o texto completo da fonte
8
Grow, Nanda B., Sharon Gursky-Doyen, and Alicia Krzton, eds. High Altitude Primates. New York, NY: Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4614-8175-1.
Texto completo da fonte
9
Júlio, Bandeira, and Jardim Botânico do Rio de Janeiro., eds. Campos de altitude. [Rio de Janeiro]: Editora Index, 1989.
Encontre o texto completo da fonte
10
Williamson, Janice. Altitude X 2. Calgary: Univesity of Calgary Students' Union Press, 1992.
Encontre o texto completo da fonteCapítulos de livros sobre o assunto "Altitude"
1
Böning, Dieter, Michael I. Lindinger, Damian M. Bailey, Istvan Berczi, Kameljit Kalsi, José González-Alonso, David J. Dyck, et al. "Altitude." In Encyclopedia of Exercise Medicine in Health and Disease, 53. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-540-29807-6_2072.
Texto completo da fonte
2
Vandermark, Lesley W., Santiago Lorenzo, and Robert F. Chapman. "Altitude." In Sport and Physical Activity in the Heat, 125–44. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-70217-9_8.
Texto completo da fonte
3
Schumacker, Paul T. "Cellular and Molecular Mechanisms of O2 Sensing." In High Altitude, 1–22. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-8772-2_1.
Texto completo da fonte
4
Bärtsch, Peter, and Jim S. Milledge. "Blood and Haemostasis." In High Altitude, 203–16. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-8772-2_10.
Texto completo da fonte
5
Swenson, Erik R., and Niels V. Olsen. "Renal Function and Fluid Homeostasis." In High Altitude, 217–36. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-8772-2_11.
Texto completo da fonte
6
Richalet, Jean-Paul. "Endocrine Function." In High Altitude, 237–52. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-8772-2_12.
Texto completo da fonte
7
Hamad, Noor, and Simon Travis. "Gastrointestinal Function." In High Altitude, 253–70. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-8772-2_13.
Texto completo da fonte
8
Mazzeo, Robert S., and Erik R. Swenson. "Immune System." In High Altitude, 271–84. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-8772-2_14.
Texto completo da fonte
9
Brooks, George A. "Nutrition and Metabolism." In High Altitude, 285–300. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-8772-2_15.
Texto completo da fonte
10
Lundby, Carsten. "Exercise." In High Altitude, 301–23. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-8772-2_16.
Texto completo da fonteTrabalhos de conferências sobre o assunto "Altitude"
1
Ockier, Carl, Christian Kolb, and Adeline Berthe. "Very High Altitude Flight Testing of the H145 Helicopter." In Vertical Flight Society 73rd Annual Forum & Technology Display, 1–11. The Vertical Flight Society, 2017. http://dx.doi.org/10.4050/f-0073-2017-12180.
Texto completo da fonteResumo:
The H145 is a multipurpose twin-engine helicopter with a maximum gross weight of 3700 kg (8160 lbs). The H145 entered service in 2014 and was originally certified for Cat B take-off and landing up to 16000 ft density altitude and Cat A operations up to 12000 ft density altitude. Because of its excellent high altitude performance, several operators requested an increase of the maximum certified altitude of the H145. Flight testing for this altitude extension was conducted in May 2015 near La Paz, Bolivia, at density altitudes between 15000 and 18200 ft. Although testing at such extremely high altitudes was very demanding, the results were as or better than expected. Analysis of the performance and controllability showed that the aircraft could comfortably and safely operate up to a maximum pressure/density altitude of 20000 ft for Cat B operations, and up to a pressure/density altitude of 15000/16000 ft for Cat A operations. EASA certification for these operations was obtained in March 2017.
2
Wei, Fu-Shang. "Servo-Flap Rotor Design for High Density Altitude Operation." In Vertical Flight Society 72nd Annual Forum & Technology Display, 1–9. The Vertical Flight Society, 2016. http://dx.doi.org/10.4050/f-0072-2016-11400.
Texto completo da fonteResumo:
It is a unique and challenging task to design a servo-flap main rotor control system that is operational at high density altitudes. At such elevated altitudes, both the main rotor blade and the servo-flap aerodynamics strongly affect helicopter operation. The changes in flap lift alter the aerodynamic pitching moment with respect to the main rotor blade, which results in an interesting blade feathering motion and its required control input. The servo-flap rotor design does not require any pitch link control spring rate. In addition, the blade torsional stiffness and tennis racket moment due to centrifugal force, are almost un-changed by the high altitude air density. The helicopter’s high altitude operation can be achieved through a unique combination of rotor design, servo-flap control, and installed engine power. The servo-flap rotor has a unique ability that allows flap adjustment every time the pilot alters the operating aircraft density altitude by 5,000 feet. This allows the aircraft to retain the same flight characteristics at any altitude that it had at sea level. This unique feature makes the servo-flap rotor one of the best candidates for high altitude flight operation. A new and improved design feature is proposed in this paper. The high altitude actuator control system provides a steady null offset that is simultaneously applied to all flaps. The new actuator signal is introduced in parallel with the basic servo-flap control system. The new hardware is designed to be used within the present control system. This design opens up the autorotation flap control range without impacting servo-flap flight control operation and safety.
3
Zheng, Jinglin, David B. Bogy, Shuyu Zhang, and Wentao Yan. "Effects of Altitude on the Thermal Flying Height Actuation." In ASME/STLE 2009 International Joint Tribology Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/ijtc2009-15118.
Texto completo da fonteResumo:
Thermal flying-height control (TFC) is now a key technology used in hard disk drives (HDD) to push the magnetic spacing to sub-5nm. The precise control of the flying height (FH) actuation is a major consideration in improving the read/write capability as well as increasing the reliability. In this paper, we investigate the response of TFC sliders to altitude change with a focus on the actuation efficiency variation with altitude. Numerical and experimental results both indicated an increase in the actuation efficiency at higher altitudes. Simulations are conducted which disclose that increased protrusion and less pushback near the transducer contribute to the efficiency increase at higher altitudes. This study is of practical importance for improving the heater and ABS designs to reduce HDD sliders’ sensitivities to altitude changes.
4
Vogt, Wilson, Chad Dunbar, and Lance Nichols. "Altitude Control System for High Altitude Helium Weather Balloons." In 2020 Academic High Altitude Conference. Iowa State University Digital Press, 2022. http://dx.doi.org/10.31274/ahac.11635.
Texto completo da fonte
5
Yu, Xinghang, Hongwei Ma, Lei Shi, and Lianpeng Zhao. "Experimental Study on Internal Flow Field of a High-Speed Centrifugal Compressor at Different Altitudes." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-15118.
Texto completo da fonteResumo:
Abstract The alteration of altitude will affect the stability of centrifugal compressors. In this paper, the pressure field on the casing wall of a high-speed centrifugal compressor at two different altitudes (h = 0m and h = 4500m) was investigated by using 15 high-response pressure sensors. The operating condition of the centrifugal compressor ranged from choke condition to developed stall condition. The results show that the interaction of the shock wave and splitter-blade tip leakage flow occurs at 70% chord region near the choke condition, and the loss is more severe at the high altitudes. At the near-stall condition, the unstable disturbance at the low altitude is caused by the collapse of the horseshoe vortex, and the unstable disturbance at the high altitude is dominated by advanced breakdown of the main-blade tip leakage vortex. At the developed-stall condition, the stall mechanisms at the two altitudes are different, both of which are closely related to the main-blade tip leakage flow. With the decrease of flow rate, the unsteady disturbance caused by the volute tongue moves upstream from the diffuser to the impeller inlet. At the same time, the unsteady disturbance propagates along the opposite direction of the rotational direction in the partial impeller passage at the low altitude case. However, the circumferential propagation characteristics at the high altitudes case are not obvious.
6
Huang, Rong, Jimin Ni, Xiuyong Shi, Qiwei Wang, and Zhenxu Cheng. "Assessing and Characterizing the Effect of Altitude on Fuel Economy, Particle Number and Gaseous Emissions Performance of Gasoline Vehicles under Real Driving." In WCX SAE World Congress Experience. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2023. http://dx.doi.org/10.4271/2023-01-0381.
Texto completo da fonteResumo:
<div class="section abstract"><div class="htmlview paragraph">High altitudes have a significant effect on the real driving emissions (RDE) of vehicles due to lower pressure and insufficient oxygen concentration. In addition, type approval tests for light-duty vehicles are usually conducted at altitudes below 1000 m. In order to investigate the influence of high altitude on vehicles fuel economy and emissions, RDE tests procedure had been introduced in the China VI emission regulations. In this study, the effect of altitude on fuel economy and real road emissions of three light-duty gasoline vehicles was investigated. The results indicated that for vehicles fuel economy, fuel consumption (L/100 km) for the tested vehicles decreased while the mean exhaust temperature increased with an increase in altitudes. Compared to near sea level, the fuel consumption (L/100 km) of the tested vehicle was reduced by up to 23.28%. For emissions, carbon monoxide (CO) and particle number (PN) emissions consistently increased and nitrogen oxide (NO<sub>X</sub>) emissions first increased and then decreased with an increase in altitude. At specific test modes, the CO emissions of tested vehicles were urban &gt; rural &gt; motorway in descending order. Compared to near sea level, NO<sub>X</sub> emissions increased slightly at an altitude of 2300 m, while PN emissions increased by up to 20 times or more. Therefore, the reasonableness of altitude expansion factor development needed to be considered when refining RDE regulations. For vehicle manufacturers, the focus should be on PN emissions at high altitude regions.</div></div>
7
Cyrus, John D., David J. Bents, and David M. Overholt. "A Supercharged Turbojet for High Altitude Atmospheric Science Investigations." In ASME 1999 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/99-gt-106.
Texto completo da fonteResumo:
A study was conducted for NASA Dryden Flight Research Center to investigate the viability of developing an externally powered zero stage booster fan to boost the altitude performance of a high altitude turbojet from 80 kft. to over 90 kft., in order to realize a very high altitude subsonic remotely piloted aircraft (RPA) capable of atmospheric science missions. A modified non-airbreathing torpedo engine powers the booster fan. The powered fan is grafted onto an airbreathing turbojet (the General Electric YJ97 jet engine) and is used to supercharge the engine (boost inlet pressure and airflow) at altitudes above its original design limits. The inlet boost keeps the engine operating and delivering thrust, at subsonic speeds, to mission altitudes over 95,000 ft. If this modified engine were grafted back into the air vehicle it was originally designed for (the Viet Nam era AQM-91A Compass Arrow) the modifications would enable the vehicle to increase its maximum altitude from 80,000 ft to over 88,000 ft for periods up to 45 min. With some additional wing area, the aircraft, which is in the 5000 lbm TOGW class, could carry a 500 lbm payload to altitudes over 92,000 kft with an operational radius over 1500 NMi. This study examined a number of candidate component arrangements to realize this fan-boosted propulsion system. Performance was estimated for the subsystem components, the resulting propulsion systems, and the associated RPA. In addition, the study estimated the time and cost to demonstrate/validate this concept in a full-scale propulsion system wind tunnel test program. This paper describes the concept, summarizes the concept selection efforts and performance analysis conducted during the study, and explains the rationale behind this unusual approach. A description of the proposed development and test program, and the cost estimate, lies beyond the scope of this paper.
8
Papadopoulos, George, Daniel Bivolaru, Andrew Murphy, and Spencer Siu. "Fluid Velocity Sensing at Extreme Altitude or Low Density Environments." In ASME 2022 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/fedsm2022-87083.
Texto completo da fonteResumo:
Abstract Methods to measure wind speed and direction range from simple hot-wire / hot-film anemometers to sophisticated sonic and laser/image-based instrumentation. While these can work well on the ground and to low altitudes, there are challenges in implementation for high altitude measurements at the 20 km and above range, where a near space environment exists. The low pressure, low density environment does not support the conditions needed for all known measurement methods to generate an engineering value for the full velocity vector at the cm/s accuracy and resolution needed to allow for high altitude balloon or platform trajectory correction. The National Oceanic and Atmospheric Administration (NOAA) regularly reports relative wind conditions to the 60 kft (18 km) level. Above this level operators are left to modeling and simulation of the stratified air to determine prevailing wind conditions that can be used to provide trajectory control via altitude changes. An in-situ, on-board sensor that can measure all three components of velocity with resolution and accuracy in the cm/s range can take out the uncertainty that is involved in the software-based approach, and together with other navigation aids, complete a trajectory solution for high altitude platforms and science balloons that will help them extend their mission envelope to greatly benefit operational effectiveness. The development of a novel wind speed sensor solution that can operate at the high altitudes of interest and meet resolution requirements is described. The sensor solution can also be applied in other low density environments to measure flow velocity, as well as, harsh environments that may be challenging for other velocity measurement methods. The paper also includes discussion on the design and fabrication of a special high altitude closed vessel with an integrated wind tunnel, capable of generating wind at altitudes more than 45 km, used in the current project for experimental validation, but could also support future sensor calibration efforts.
9
Morales, Mateo, Sergio D. Roa, Luis E. Muñoz, Diego A. Ferreira, and Omar D. Lopez Mejia. "Influence of Altitude on the Performance of a Bicycle-Cyclist Set." In ASME 2017 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/detc2017-67955.
Texto completo da fonteResumo:
There is a tradeoff between power delivery and aerodynamic drag force when cyclists ride at different altitudes. The result is particular to the characteristics of the bicycle as well as the aerobic fitness of the cyclist. This work proposes a methodology based on an integrated approach to the study of the influence of altitude on power output and aerodynamic drag over a particular bicycle-cyclist set. The methodology consists of an independent analysis for each of the effects, to conclude with an integration of results that allows estimating the overall effect of altitude on cycling performance. A case study for the application of the methodology was developed, and the obtained results apply for the specific bicycle-cyclist set under analysis. First, the relationship between power and time was analyzed for a male recreational cyclist based on all-out effort tests at two different altitudes: 237 meters and 2652 meters above sea level (m.a.s.l). Second, the effects of environmental conditions on air density and drag area coefficient due to altitude changes were analyzed based on Computational Fluid Dynamics (CFD) simulations. It was found that for the bicycle-cyclist set under study, the sustainable power output for 1-hour cycling was reduced 45W for the high-altitude condition as a consequence of the reduction in the maximum oxygen uptake capacity. In addition, the aerodynamic drag force is reduced in greater proportion due to the change in air density than due to the change in drag coefficient. Finally, the results of both effects were integrated to analyze the overall influence of altitude on cycling performance. It was found that for the analyzed case study, the aerodynamic advantage at higher altitude dominates over the disadvantage of reduction in power output: despite delivering 45W less, the subject can travel an additional distance of 900 meters during a one hour ride for the high-altitude condition compared to that in low altitude.
10
Broatch, Alberto, Vicente Bermúdez, Jose Ramón Serrano, Roberto Tabet-Aleixandre, Javier Gómez, and Stefan Bender. "Analysis of Passenger Car Turbocharged Diesel Engines Performance When Tested at Altitude and of the Altitude Simulator Device Used." In ASME 2018 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icef2018-9549.
Texto completo da fonteResumo:
According to current worldwide trends for homologation vehicles in real driving conditions, is forced to test the engines in altitude and in highly dynamic driving cycles in order to approach nowadays and next future emissions standard. Up to now, there were two main options to perform this type of tests: round-robin tests of the whole vehicle or hypobaric chambers, both with high costs and low repeatability. In this paper a new device is described, which can emulate ambient conditions at whatever altitude between sea level and 5000m high. Even it can be used to emulate ambient conditions at sea level when test bench is placed up to 2000 m high. The main advantages of the altitude simulation equipment are: dynamic emulation of all the psychrometric variables affecting the vehicles during round-robin tests; lower space usage and low energy consumption. The altitude simulator has been validated comparing with results from a hypobaric chamber at different altitudes. Previously a research about the dispersion in the measurements of both testing devices has been done for assessing the results of the comparison experiment. Final conclusion resulted in the same operating performance and emissions of the studied engine with both types of testing equipments for altitude simulation.
Relatórios de organizações sobre o assunto "Altitude"
1
Baldessari, Gianni, Oliver Bender, Domenico Branca, Luigi Crema, Anna Giorgi, Nina Janša, Janez Janša, Marie-Eve Reinert, and Jelena Vidović. Smart Altitude. Edited by Annemarie Polderman, Andreas Haller, Chiara Pellegrini, Diego Viesi, Xavier Tabin, Chiara Cervigni, Stefano Sala, et al. Verlag der Österreichischen Akademie der Wissenschaften, March 2021. http://dx.doi.org/10.1553/smart-altitude.
Texto completo da fonteResumo:
This final report summarizes the outcomes of the Smart Altitude project. The Smart Altitude project ran from June 2018 to April 2021 and was carried out by ten partners from six different countries in the Alpine Space (Austria, France, Italy, Germany, Slovenia, and Switzerland). The project was co-financed by the European Union via Interreg Alpine Space. The aim of the project was to enable and accelerate the implementation of low-carbon policies in winter tourism regions by demonstrating the efficiency of a step-by-step decision support tool for energy transition in four Living Labs. The project targeted policymakers, ski resort operators, investors, tourism, and entrepreneurship organizations. The Smart Altitude approach was designed to ensure suitability across the Alpine Space, thereby fostering its replication and uptake in other winter tourism regions and thus increasing the resilience of mountain areas.
2
Tissotvanpatot, Martha, David Irwin, Robert Gotshall, and Karyn Hamilton. Rapid Altitude Acclimatization. Fort Belvoir, VA: Defense Technical Information Center, May 2008. http://dx.doi.org/10.21236/ada500150.
Texto completo da fonte
3
Muza, Stephen R., Charles S. Fulco, and Allen Cymerman. Altitude Acclimatization Guide. Fort Belvoir, VA: Defense Technical Information Center, March 2004. http://dx.doi.org/10.21236/ada423388.
Texto completo da fonte
4
Muza, Stephen R., Paul B. Rock, Michael Zupan, James Miller, and William R. Thomas. Influence of Moderate Altitude Residence on Arterial Oxygen Saturation at Higher Altitudes. Fort Belvoir, VA: Defense Technical Information Center, May 2003. http://dx.doi.org/10.21236/ada421496.
Texto completo da fonte
5
Hein, C. A., and K. H. Bhavnani. An Expanded Altitude Algorithm for Computing Altitude-Dependent Corrected Geomagnetic Coordinates. Fort Belvoir, VA: Defense Technical Information Center, October 1996. http://dx.doi.org/10.21236/ada324654.
Texto completo da fonte
6
Peterson, Brian, J. Beeco, Sharolyn Anderson, and Damon Joyce. Exploring spatial patterns of overflights at Mount Rushmore National Memorial. National Park Service, June 2022. http://dx.doi.org/10.36967/nrr-2293663.
Texto completo da fonteResumo:
The purpose of this study was to explore the spatial patterns of overflights at Mount Rushmore National Memorial (Mount Rushmore). Overflights were analyzed from August 15th, 2020 to May 15th, 2021 using Automatic Dependent Surveillance-Broadcast (ADS-B) and radar data from L3Harris. The first phase of analysis focused on all overflights and found a high concentration of overflights fly above Mount Rushmore. The second phase of analysis focused on low-level overflights that fly below 9,000ft mean sea level (MSL), which showed that many low-level overflights fly in a ring-shaped pattern around Mount Rushmore. The third phase of analysis removed all overflights known to not be air tours. Point density analysis was conducted using waypoints segmented into 500ft above ground level (AGL) altitude intervals, which showed that the density of overflights varied by altitude interval and the 1,000-1,500ft AGL range had the highest density of overflights around and above Mount Rushmore. This altitude interval also had the highest number of waypoints. It was also determined that the aircraft owners who fly the most helicopter routes fly at mean and median altitudes less than 1,600ft AGL. This information can be used for planning and management purposes and this study serves as a resource for future research that intends to use more advanced analytics.
7
Bissett, W. P. High Altitude Hyperspectral Imaging Spectroscopy. Fort Belvoir, VA: Defense Technical Information Center, August 2005. http://dx.doi.org/10.21236/ada439987.
Texto completo da fonte
8
Day, James L. KC-135 Low Altitude Tactics. Fort Belvoir, VA: Defense Technical Information Center, April 1988. http://dx.doi.org/10.21236/ada194927.
Texto completo da fonte
9
Agrimson, Erick Paul, James Flaten, Mara Blish, Rachel Hedden, and Amanda Grove. High Altitude Thermal Wake Investigation. Ames (Iowa): Iowa State University. Library. Digital Press, January 2013. http://dx.doi.org/10.31274/ahac.8151.
Texto completo da fonte
10
Voss, Hank D., and Natalie A. Ramm. High-Altitude Balloon Atmospheric Database. Ames (Iowa): Iowa State University. Library. Digital Press, January 2012. http://dx.doi.org/10.31274/ahac.8346.
Texto completo da fonte