scholarly journals The reflection of a blast wave by a very intense explosion

2021 ◽  
Vol 477 (2250) ◽  
pp. 20210154
Author(s):  
Andrew W. Cook ◽  
Joseph D. Bauer ◽  
Gregory D. Spriggs
Keyword(s):  
Blast Wave ◽  
Arrival Time ◽  
Analytic Solution ◽  
Ambient Air ◽  
Spatial Dimension ◽  
Cylindrical Symmetry ◽  
Geometric Similarity ◽  
Air Density ◽  
Before And After ◽  
Planar Symmetry

We demonstrate that the geometric similarity of Taylor’s blast wave persists beyond reflection from an ideal surface. Upon impacting the surface, the spherical symmetry of the blast wave is lost but its cylindrical symmetry endures. As the flow acquires dependence on a second spatial dimension, an analytic solution of the Euler equations becomes elusive. However, the preservation of axisymmetry, geometric similarity and planar symmetry in the presence of a mirror-like surface causes all flow solutions to collapse when scaled by the height of burst (HOB) and the shock arrival time at the surface. The scaled blast volume for any yield, HOB and ambient air density follows a single universal trajectory for all scaled time, both before and after reflection.

Hearing Aids Performance in Hypobaric Environments

2021 ◽  
Vol 92 (9) ◽  
pp. 738-743
Author(s):  
Marco Lucertini ◽  
Filippo Sanjust ◽  
Roberto Manca ◽  
Luigi Cerini ◽  
Lorenzo Lucertini ◽  
...  
Keyword(s):  
High Altitude ◽  
Hearing Aids ◽  
Ambient Air ◽  
Recording System ◽  
Simulated Altitude ◽  
Acoustic Transducers ◽  
Before And After ◽  
Rapid Decompression ◽  
Pressure Changes ◽  
First Session

OBJECTIVE: High altitudes imply exposure to a decreased ambient air pressure. Such a situation may also alter the performance of acoustic transducers using vibrating diaphragms due to air rarefaction. This study aimed at analyzing the performance at high altitude of hearing aids (HAs) where mechano-electric and electro-mechanic transducers are used. METHODS: A hypobaric chamber was used to perform two separated experimental sessions. In the first one two commercial models of HAs were exposed to a simulated altitude of 25,000 ft (7620 m) and to a subsequent rapid decompression profile, with a rapid climb (< 3 s) from 8000 (2438 m) to 25,000 ft. The second session separately analyzed the performance of microphone and receiver at an altitude of 9000 and 15,000 ft (2743 and 4572 m). Before and after the first session, the HAs were tested with an electronic ear while a dedicated recording system was used in the second session. RESULTS: No HA damage or dysfunction was detected during the first session. In the second one, the microphone showed a mild decrease of its output, while the receiver exhibited a much higher reduction of its output. CONCLUSION: Our findings highlight the safe use of HAs even under extreme environmental pressure changes. For altitudes exceeding 10,000 ft (3048 m), a recalibration of the HAs output via a dedicated program may be suggested. Lucertini M, Sanjust F, Manca R, Cerini L, Lucertini L, Sisto R. Hearing aids performance in hypobaric environments. Aerosp Med Hum Perform. 2021; 92(9):738743.

scholarly journals Guidelines for depth data collection in rivers when applying interpolation techniques (kriging) for river restoration

2007 ◽  
Vol 4 (3) ◽  
pp. 1069-1094
Author(s):  
M. Rivas-Casado ◽  
S. White ◽  
P. Bellamy
Keyword(s):  
River Restoration ◽  
Sampling Strategy ◽  
Spatial Dimension ◽  
Sampling Strategies ◽  
Depth Data ◽  
Cyclic Patterns ◽  
Efficient Sampling ◽  
Before And After ◽  
Geostatistical Techniques ◽  
River Site

Abstract. River restoration appraisal requires the implementation of monitoring programmes that assess the river site before and after the restoration project. However, little work has yet been developed to design effective and efficient sampling strategies. Three main variables need to be considered when designing monitoring programmes: space, time and scale. The aim of this paper is to describe the methodology applied to analyse the variation of depth in space, scale and time so more comprehensive monitoring programmes can be developed. Geostatistical techniques were applied to study the spatial dimension (sampling strategy and density), spectral analysis was used to study the scale at which depth shows cyclic patterns, whilst descriptive statistics were used to assess the temporal variation. A brief set of guidelines have been summarised in the conclusion.

scholarly journals Seasonal and Spatial Variation of Volatile Organic Compounds in Ambient Air of Almaty City, Kazakhstan

Atmosphere ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1592
Author(s):  
Olga P. Ibragimova ◽  
Anara Omarova ◽  
Bauyrzhan Bukenov ◽  
Aray Zhakupbekova ◽  
Nassiba Baimatova
Keyword(s):  
Air Pollution ◽  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Power Plants ◽  
Ambient Air ◽  
Spatial Variations ◽  
Primary Sources ◽  
Volatile Organic ◽  
Seasonal And Spatial Variations ◽  
Before And After

Air pollution is one of the primary sources of risk to human health in the world. In this study, seasonal and spatial variations of multiple volatile organic compounds (VOCs) were measured at six sampling sites in Almaty, Kazakhstan. The seasonal and spatial variations of 19 VOCs were evaluated in 2020, including the periods before and after COVID-19 lockdown. The concentrations of 9 out of 19 VOCs had been changed significantly (p < 0.01) during 2020. The maximum concentrations of total VOCs (TVOCs) were observed on 15, 17, and 19 January and ranged from 233 to 420 µg m−3. The spatial distribution of TVOCs concentrations in the air during sampling seasons correlated with the elevation and increased from southern to northern part of Almaty, where Combined Heat and Power Plants are located. The sources of air pollution by VOCs were studied by correlations analysis and BTEX ratios. The ranges of toluene to benzene ratio and benzene, toluene, and ethylbenzene demonstrated two primary sources of BTEX in 2020: traffic emissions and biomass/biofuel/coal burning. Most of m-, p-xylenes to ethylbenzene ratios in this study were lower than 3 in all sampling periods, evidencing the presence of aged air masses at studied sampling sites from remote sources.

scholarly journals A New Geo-Propagation Model of Event Evolution Chain Based on Public Opinion and Epidemic Coupling

2020 ◽  
Vol 17 (24) ◽  
pp. 9235
Author(s):  
Yan Zhang ◽  
Nengcheng Chen ◽  
Wenying Du ◽  
Shuang Yao ◽  
Xiang Zheng
Keyword(s):  
Public Health ◽  
Public Opinion ◽  
Spatial Dimension ◽  
Real Space ◽  
Propagation Model ◽  
Health Events ◽  
Model Complex ◽  
Epidemic Area ◽  
Before And After ◽  
The Impact

The online public opinion is the sum of public views, attitudes and emotions spread on major public health emergencies through the Internet, which maps out the scope of influence and the disaster situation of public health events in real space. Based on the multi-source data of COVID-19 in the context of a global pandemic, this paper analyzes the propagation rules of disasters in the coupling of the spatial dimension of geographic reality and the dimension of network public opinion, and constructs a new gravity model-complex network-based geographic propagation model of the evolution chain of typical public health events. The strength of the model is that it quantifies the extent of the impact of the epidemic area on the surrounding area and the spread of the epidemic, constructing an interaction between the geographical reality dimension and online public opinion dimension. The results show that: The heterogeneity in the direction of social media discussions before and after the “closure” of Wuhan is evident, with the center of gravity clearly shifting across the Yangtze River and the cyclical changing in public sentiment; the network model based on the evolutionary chain has a significant community structure in geographic space, divided into seven regions with a modularity of 0.793; there are multiple key infection trigger nodes in the network, with a spatially polycentric infection distribution.

scholarly journals Interrelationships between pulse arrival time and arterial blood pressure during postural transitions before and after spaceflight

2019 ◽  
Vol 127 (4) ◽  
pp. 1050-1057
Author(s):  
Katelyn N. Wood ◽  
Danielle K. Greaves ◽  
Richard L. Hughson
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Arrival Time ◽  
Standing Posture ◽  
Pulse Arrival Time ◽  
Arterial Blood ◽  
Increased Risk ◽  
Before And After ◽  
Acute Changes ◽  
Pulse Arrival

We tested the hypothesis that acute changes in arterial blood pressure (BP) when astronauts moved between supine and standing posture before and after spaceflight can be tracked by beat-to-beat changes in pulse arrival time (PAT). Nine male crewmembers (45 ± 7 yr of age; mean mission length: 165 ± 13 days) participated in a standardized supine-to-sit-to-stand test (5 min-30 s-3 min) before flight and 1 day following return to Earth with continuous monitoring of ECG and finger arterial BP. PAT was determined from the R-wave of the ECG to the foot of the BP waveform. On average, modest cardiovascular deconditioning was detected by ~10 beats/min increase in heart rate in supine and standing posture after spaceflight ( P < 0.05). When looking across the full data collection period, the r2 values between inverse of PAT (1/PAT) and systolic (SBP) and diastolic BP (DBP) varied considerably between individuals (SBP preflight 0.142 ± 0.186, postflight 0.262 ± 0.243). Individual variability was consistent during periods of transition (SBP preflight 0.284 ± 0.324, postflight 0.297 ± 0.269); however, when SBP dropped >20 mmHg, r2 was significant in 5 of 5 preflight tests and 5 of 7 postflight tests. The standard error of the estimate based on a simple linear model during both pre- and postflight testing was 9–11 mmHg for SBP and 6–7 mmHg for DBP. Overall, the results support the hypothesis that PAT tracked dynamic changes in BP. PAT as a noninvasive, nonintrusive surrogate for changes in BP could be developed as an indicator of risk for syncope on return from spaceflight or other Earth-based applications. NEW & NOTEWORTHY Astronauts returning to Earth’s gravity are at increased risk of low blood pressure on standing. Arterial pulse arrival time tracked the decrease in arterial blood pressure on moving from supine to upright posture. Nonintrusive technology providing indicators sensitive to acute changes in blood pressure could act as an early warning system to identify risk for hypotension that place astronauts, or people on Earth, at risk of impaired cognitive performance, fainting, and falls.

Effects of atropine on potentiation of exercise-induced bronchospasm by cold air

1978 ◽  
Vol 45 (2) ◽  
pp. 238-243 ◽  
Author(s):  
E. C. Deal ◽  
E. R. McFadden ◽  
R. H. Ingram ◽  
J. J. Jaeger
Keyword(s):  
Ambient Air ◽  
Small Airways ◽  
Flow Limitation ◽  
Ambient Conditions ◽  
Cold Air ◽  
Relative Contribution ◽  
Maximal Expiratory Flow ◽  
Before And After ◽  
Expiratory Flow ◽  
Exercise Induced

The role of vagal efferent activity in the cold air potentiation of exercise-induced asthma was assessed by exercising nine subjects who breathed air at ambient and subfreezing temperatures before and after cholinergic blockade. Lung volumes and maximal expiratory flow volume curves with air and with 80% helium-20% oxygen were obtained before and 5--10 min after each challenge. Isovolume comparisons of maximal expiratory flow rates with the two gases were used to assess relative contributions of large and small airways to flow limitation. Exercise under ambient conditions resulted in the expected airway obstruction and cold air exaggerated the response. Atropine pretreatment had no effect on the cold air potentiation. After atropine with ambient air exercise, there was an increase in the relative contribution of large airways to flow limitation, whereas exercise with cold air resulted in an increase in the contribution of small airways. We concluded that the potentiating effects of cold air are local and suggest that the immediate stimulus is related to cooling of intrathoracic airways.

scholarly journals A Study on Determining Time-Of-Flight Difference of Overlapping Ultrasonic Signal: Wave-Transform Network

Sensors ◽  
2020 ◽  
Vol 20 (18) ◽  
pp. 5140
Author(s):  
Zhipeng Li ◽  
Tong Wu ◽  
Wei Zhang ◽  
Xuyang Gao ◽  
Zhenqiu Yao ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Arrival Time ◽  
Oil And Gas ◽  
Time Of Flight ◽  
Ultrasonic Signal ◽  
Signal Wave ◽  
Buried Pipelines ◽  
Ultrasonic Echo ◽  
Before And After ◽  
Novel Method

An ultrasonic sensors system is commonly used to measure the wall thickness of buried pipelines in the transportation of oil and gas. The key of the system is to precisely measure time-of-flight difference (TOFD) produced by the reflection of ultrasonic on the inner and outer surfaces of the pipelines. In this paper, based on deep learning, a novel method termed Wave-Transform Network is proposed to tackle the issues. The network consists of two parts: part 1 is designed to separate the potential overlapping ultrasonic echo signals generated from two surfaces, and part 2 is utilized to divide the sample points of each signal into two types corresponding to before and after the arrival time of ultrasonic echo, which can determine the time-of-flight (TOF) of each signal and calculate the thickness of pipelines. Numerical simulation and actual experiments are carried out, and the results show satisfactory performances.

scholarly journals Eliminate the Queuing Time in the New Suez Canal: Predicting Adjustment on Ships’ Arrival Time under Optimal Non-Queuing Toll Scheme

2021 ◽  
Vol 9 (1) ◽  
pp. 70
Author(s):  
Pey-Yuan Sun ◽  
Chen-Hsiu Laih
Keyword(s):  
Arrival Time ◽  
Suez Canal ◽  
Management Decision ◽  
Large Size ◽  
Ship Owner ◽  
Entry Time ◽  
Before And After ◽  
Pass Through ◽  
New Suez Canal ◽  
Scheduled Time

In 2016, the construction of the New Suez Canal was completed, enabling most large-size vessels to pass through and causing more ships to queue into the canal. As the queueing problem at the entrance of the canal was anticipated to be serious, an optimal non-queueing toll scheme was previously established to eliminate the queueing phenomenon at the anchorage of the canal. However, no information about each ship’s arrival time adjustment under the optimal non-queueing toll scheme is available from the previous literature. To solve this problem, we derive a series of mathematical formulae for each ship’s arrival time, length of queuing time and entry time before, and after, implementing the optimal non-queueing toll scheme. The arrival time adjustments, which enable ships to enter the canal without queueing, could then be obtained. These results enable the Suez Canal authorities to draw up the ship’s arrival timetable under the optimal non-queueing toll scheme, so that the captain could follow to enter the canal. The above information that we provide would be conducive to the management decision for the canal authorities to implement such a toll scheme. Once a tolled ship could enter the canal at the scheduled time without queueing, the ship owner could accurately control the sailing schedule, and the use of the ship could be more efficient.

ASSESSMENT OF THREE SURFACE COLLECTING AGENTS DURING TEMPERATE AND ARCTIC CONDITIONS

1985 ◽  
Vol 1985 (1) ◽  
pp. 199-201 ◽  
Author(s):  
Pamela Pope ◽  
Al Allen ◽  
William G. Nelson
Keyword(s):  
Oil Recovery ◽  
Sea Water ◽  
Field Tests ◽  
Ambient Air ◽  
Cold Weather ◽  
Test Tank ◽  
Air Temperatures ◽  
Collecting Agents ◽  
Before And After ◽  
Prudhoe Bay

ABSTRACT Laboratory and field tests were conducted to evaluate the effectiveness of using surface collecting agents in cold weather oil recovery and in situ burning operations. In a small laboratory test tank, the surface areas and equilibrium thicknesses of three Alaskan North Slope crude oils were observed before and after the application of three different surface collecting agents to each oil. Numerous small bench-top tests also were conducted to further support the observations made in the test tank. Ambient air temperatures were varied from 23° C to −17° C, while the temperatures of fresh water and laboratory-prepared sea water were varied from 15° C to 0° C. The three surface collecting agents used (Corexit OC-5, Nalco 3WP-086, Shell Oil Herder) were equally effective in concentrating the areas of thin films by as much as 95 percent within a minute or less. The efficiencies of the surface collecting agents were observed to decrease only slightly with air temperatures below 0° C. Equilibrium thicknesses and areas before and after collectant application were determined using standard photometric techniques. In addition, two field tests were conducted to evaluate the effectiveness of collecting agents on large experimental oil slicks in an onshore pit at Prudhoe Bay. In each test, approximately 1 m3 of fresh Prudhoe Bay crude oil was released and allowed to come to an equilibrium thickness. In each test, the oil was concentrated with Corexit OC-5 and Shell Oil Herder and then ignited. Winds of 4-to-6 knots (2-to-3 m/s) herded the slicks into one corner of the pit and produced an average slick thickness of 9.5 mm. The use of collectants resulted in a 5 percent reduction of the wind-herded slick areas, thus increasing the thicknesses to approximately 10 mm.

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