scholarly journals Air pressure propagation through Wind Cave and Jewel Cave: How do pressure waves travel through barometric caves?

2021 ◽  
Vol 50 (3) ◽  
pp. 263-273
Author(s):  
Annika Gomell ◽  
Daniel Austin ◽  
Marc Ohms ◽  
Andreas Pflitsch
Keyword(s):  
Response Times ◽  
External Pressure ◽  
Black Hills ◽  
Air Pressure ◽  
Pressure Waves ◽  
Pressure Gradients ◽  
Pressure Data ◽  
Almost All ◽  
Pressure Changes ◽  
Pressure Propagation

In barometric caves, air pressure gradients between the outside atmosphere and the cave induce strong bidirectional compensating currents, which control almost all elements of speleoclimatology, including air temperature, humidity, and CO2 dynamics. Therefore, this study set out to investigate air pressure propagation through Wind Cave and Jewel Cave – two major barometric cave systems in the Black Hills of South Dakota, USA. Based on high-resolution air pressure data from both the surface and several measurement sites inside the caves, four systematic changes of pressure waves during their journey through the caves and their related speleoclimatological processes were identified and discussed: Compared to the outside atmosphere, the pressure signals within Wind Cave and Jewel Cave showed (1) an absolute displacement due to different altitudes of the measuring sites, (2) a delay related to the travel times of the pressure wave to the measuring sites, (3) a smoothing effect, and (4) a damping effect due to long response times of the caves to external pressure changes. The spatial distribution of the changes observed in this study shows that for Wind Cave, the cave opening and the narrow entrance area represent the main obstacle for pressure propagation, while for Jewel Cave, the deep areas have the greatest influence on the development of air pressure gradients. Our analyses provide completely new insights into the processes and mechanisms inside barometric caves, which will significantly contribute to the understanding of pressure-related airflow dynamics and all related elements of speleoclimatology.

Pressure Gradients Affecting the Labyrinth during Hypobaric Pressure

1997 ◽  
Vol 106 (6) ◽  
pp. 495-502 ◽  
Author(s):  
Konrád S. Konrádsson ◽  
Björn I. R. Carlborg ◽  
Joseph C. Farmer
Keyword(s):  
Cerebrospinal Fluid ◽  
Eustachian Tube ◽  
Ambient Pressure ◽  
Pressure Gradients ◽  
Cochlear Aqueduct ◽  
Fluid Compartment ◽  
Large Pressure ◽  
Fluid Compartments ◽  
Pressure Changes ◽  
Considerable Pressure

Hypobaric effects on the perilymph pressure were investigated in 18 cats. The perilymph, tympanic cavity, cerebrospinal fluid, and systemic and ambient pressure changes were continuously recorded relative to the atmospheric pressure. The pressure equilibration of the eustachian tube and the cochlear aqueduct was studied, as well as the effects of blocking these channels. During ascent, the physiologic opening of the eustachian tube reduced the pressure gradients across the tympanic membrane. The patent cochlear aqueduct equilibrated perilymph pressure to cerebrospinal fluid compartment levels with a considerable pressure gradient across the oval and round windows. With the aqueduct blocked, the pressure decrease within the labyrinth and tympanic cavities was limited, resulting in large pressure gradients toward the chamber and the cerebrospinal fluid compartments, respectively. We conclude that closed cavities with limited pressure release capacities are the cause of the pressure gradients. The strain exerted by these pressure gradients is potentially harmful to the ear.

scholarly journals Research on HAR-Based Floor Positioning

2021 ◽  
Vol 10 (7) ◽  
pp. 437
Author(s):  
Hongxia Qi ◽  
Yunjia Wang ◽  
Jingxue Bi ◽  
Hongji Cao ◽  
Shenglei Xu
Keyword(s):  
Barometric Pressure ◽  
Air Pressure ◽  
Location Based Services ◽  
Sensor Data ◽  
Reference Station ◽  
Position Change ◽  
Radio Signals ◽  
Positioning Method ◽  
Pressure Changes

Floor positioning is an important aspect of indoor positioning technology, which is closely related to location-based services (LBSs). Currently, floor positioning technologies are mainly based on radio signals and barometric pressure. The former are impacted by the multipath effect, rely on infrastructure support, and are limited by different spatial structures. For the latter, the air pressure changes with the temperature and humidity, the deployment cost of the reference station is high, and different terminal models need to be calibrated in advance. In view of these issues, here, we propose a novel floor positioning method based on human activity recognition (HAR), using smartphone built-in sensor data to classify pedestrian activities. We obtain the degree of the floor change according to the activity category of every step and determine whether the pedestrian completes floor switching through condition and threshold analysis. Then, we combine the previous floor or the high-precision initial floor with the floor change degree to calculate the pedestrians’ real-time floor position. A multi-floor office building was chosen as the experimental site and verified through the process of alternating multiple types of activities. The results show that the pedestrian floor position change recognition and location accuracy of this method were as high as 100%, and that this method has good robustness and high universality. It is more stable than methods based on wireless signals. Compared with one existing HAR-based method and air pressure, the method in this paper allows pedestrians to undertake long-term static or round-trip activities during the process of going up and down the stairs. In addition, the proposed method has good fault tolerance for the misjudgment of pedestrian actions.

Total Pressure Correction of a Sub-Miniature Five-Hole Probe in Areas of Pressure Gradients

2012 ◽  
Author(s):  
J. Town ◽  
A. Akturk ◽  
C. Camcı
Keyword(s):  
Pressure Measurement ◽  
Measurement Errors ◽  
Total Pressure ◽  
Pressure Gradients ◽  
Pressure Data ◽  
Flow Conditions ◽  
Complex Flow ◽  
Ducted Fan ◽  
The Difference ◽  
Best Fit

Five-hole probes, being a dependable and accurate aerodynamic tools, are excellent choices for measuring complex flow fields. However, total pressure gradients can induce measurement errors. The combined effect of the different flow conditions on the ports causes the measured total pressure to be prone to a greater error. This paper proposes a way to correct the total pressure measurement. The correction is based on the difference between the measured total pressure data of a Kiel probe and a sub-miniature prism-type five-hole probe. By comparing them in a ducted fan related flow field, a line of best fit was constructed. The line of best fit is dependent on the slope of the line in a total pressure versus span and difference in total pressure between the probes at the same location. A computer program, performs the comparison and creates the correction equation. The equation is subsequently applied to the five-hole probe total pressure measurement, and the other dependent values are adjusted. The validity of the correction is then tested by placing the Kiel probe and the five-hole probe in ducted fans with a variety of different tip clearances.

Abstract TMP89: Collaterals and Reperfusion Mediate Blood Pressure Changes in Acute Ischemic Stroke

Stroke ◽  
2017 ◽  
Vol 48 (suppl_1) ◽  
Author(s):  
David S Liebeskind ◽  
Graham W Woolf ◽  
Nerses Sanossian ◽  
Jason D Hinman ◽  
Radoslav Raychev ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Ischemic Stroke ◽  
Acute Ischemic Stroke ◽  
Endovascular Therapy ◽  
Arterial Occlusion ◽  
Patient Specific ◽  
Pressure Data ◽  
Blood Pressure Data ◽  
Pressure Changes ◽  
Continuous Blood Pressure

Background: The pathophysiology and optimal management of blood pressure changes in acute ischemic stroke remain unknown. Blood pressure guidelines do not consider patient-specific or serial data on dynamic blood pressure readings. We investigated continuous blood pressure data during endovascular therapy for acute stroke to discern changes associated with collaterals, recanalization and reperfusion. Methods: Continuous monitoring blood pressure data was collected in consecutive cases of endovascular therapy for acute ischemic stroke due to ICA or proximal MCA occlusion. Angiography details were independently analyzed to document site of arterial occlusion, baseline collateral grade, time of device deployments, time of recanalization, time of final reperfusion, final AOL recanalization and final TICI reperfusion. Statistical analyses correlated instantaneous and serial blood pressure changes with these angiographic parameters. Results: 80 patients (median age 73 years; 33 women) were studied. Arterial lesions included 37 ICA and 41 proximal M1 MCA occlusions. Collateral grade prior to intervention included 2 ASITN grade 4, 26 grade 3, 23 grade 2, 6 grade 1 and 0 grade 0. oTICI2C reperfusion scores after thrombectomy included 2 TICI 3 (100%), 22 TICI 2C (90-99%), 25 TICI o2B (67-89%), 9 TICI m2B (50-66%), 19 TICI 2A (<50%) and 3 TICI 0/1. More robust collateral grade was associated with greater reperfusion scores (r=0.32, p=0.028). The change in blood pressure (ΔBP) from earliest BP to time of recanalization was mean 59% of ΔBP during the entire procedure. Better collaterals were associated with lower BP prior to recanalization (r=-0.377, p=0.012). Lower BP prior to recanalization was linked with greater TICI reperfusion (r=-0.242, p=0.050). Higher TICI reperfusion scores were also associated with a greater drop or ΔBP at the time of recanalization (r=0.269, p=0.031). AOL recanalization was not related to ΔBP. Conclusions: Collaterals and reperfusion, but not recanalization, mediate blood pressure changes in acute ischemic stroke. Prospective, precision medicine stroke studies should leverage patient-specific, real-time data on continuous blood pressure with imaging correlates to define BP goals of future in-hospital management.

Effects of Slow-Acting Brakes Application Time Regulated Limits on Freight In-Train Forces

2015 ◽  
Vol 809-810 ◽  
pp. 1133-1138
Author(s):  
Cătălin Cruceanu ◽  
Camil Ion Crăciun
Keyword(s):  
Numerical Simulations ◽  
Air Pressure ◽  
Application Time ◽  
Pressure Data ◽  
Longitudinal Dynamics ◽  
Filling Time ◽  
Tensile Forces ◽  
Filling Characteristics ◽  
Brake Cylinder

The paper originally investigates the influence of the admitted ranges of slow-acting filling time of brake cylinder on longitudinal dynamics of freight trains, using experimental air pressure data obtained in tests on filling characteristics. Mechanical and pneumatic models are summarized and numerical simulations were performed for a train composed of six wagon train, in different filling characteristics configurations. The results reflect significant effects on in-train forces values, while evolution and disposition of compression and tensile forces between neighbored vehicles in the long of the train are also affected.

scholarly journals Delayed Presentation of Traumatic Right-Sided Diaphragmatic Hernia after Abdominoplasty

2014 ◽  
Vol 2014 ◽  
pp. 1-4 ◽  
Author(s):  
Caroline C. Jadlowiec ◽  
Lois U. Sakorafas
Keyword(s):  
Diaphragmatic Hernia ◽  
Normal Pressure ◽  
Positive Pressure ◽  
Delayed Presentation ◽  
Pressure Gradients ◽  
Abrupt Changes ◽  
Thoracic And Abdominal ◽  
Pressure Changes ◽  
Surgical Manipulation ◽  
Diaphragmatic Hernias

Traumatic diaphragmatic hernias are rare and challenging to diagnose. Following trauma, diagnosis may occur immediately or in a delayed fashion. It is believed that left traumatic diaphragmatic hernias are more common as a result of the protective right-sided anatomic lie of the liver. If unrecognized, traumatic diaphragmatic injuries are subject to enlarge over time as a result of the normal pressure changes observed between the thoracic and abdominal cavities. Additionally, abrupt changes to the pressure gradients, such as those which occur with positive pressure ventilation or surgical manipulation of the abdominal wall, can act as a nidus for making an asymptomatic hernia symptomatic. We report our experience with a delayed traumatic right-sided diaphragmatic hernia presenting with large bowel incarceration two months after abdominoplasty. In our review of the literature, we were unable to find any reports of delayed presentation of a traumatic right-sided diaphragmatic hernia occurring acutely following abdominoplasty.

The Effects of Small Changes of Prandtl Number and the Viscosity-Temperature Index on Skin Friction

1964 ◽  
Vol 15 (4) ◽  
pp. 392-406 ◽  
Author(s):  
A. D. Young
Keyword(s):  
Boundary Layer ◽  
Prandtl Number ◽  
Pressure Gradient ◽  
Skin Friction ◽  
Laminar Boundary Layer ◽  
Wall Temperature ◽  
External Pressure ◽  
Main Stream ◽  
Pressure Gradients ◽  
Temperature Index

SummaryThe analytic simplifications in boundary-layer analysis that result from the assumptions that the Prandtl number σ and the viscosity-temperature index ω are unity make it desirable to be able to assess the effects of the departures of the actual values of these parameters from unity. In this paper only the effects on skin friction are considered. Formulae of acceptable validity and wide application are first used to produce generalised curves for these effects for given main-stream Mach numbers and wall temperature conditions for the case of zero external pressure gradient for both laminar and turbulent boundary layers (Figs. 1 and 2).A number of calculated results for the laminar boundary layer with favourable and adverse pressure gradients is then analysed (Figs. 3, 4 and 5) and it is shown that these results are consistent with the assumption that, for a given wall temperature, the effects of small changes of σ and ω on skin friction are independent of the external gradient, so that the appropriate curves of Figs. 1 and 2 apply. Where the change of a- is associated with a change of wall temperature (e.g. if the heat transfer is specified as zero) then the interaction between pressure gradient and this temperature change can be significant in its effects on skin friction for the laminar boundary layer and can only be assessed if the effects of changes of wall temperature with constant σ and ω have been separately determined for the pressure distribution considered. It is inferred that in all cases, except with large adverse pressure gradients and imminent separation, the effects of changes of ω and σ for the turbulent boundary layer are reliably predicted by the zero pressure gradient curves of Figs. 1 and 2 and the effect of any associated change of wall temperature can then be reliably inferred from the zero pressure gradient formula (equation (15)) in the absence of more specific calculations covering a range of wall temperatures.

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