Changes In Ambient Pressure Research Articles

Ultrasensitive gas pressure sensor based on two parallel Fabry-Perot interferometers and enhanced Vernier effect

An ultra-high sensitivity optical fiber gas pressure sensor based on enhanced Vernier effect is proposed. The sensor consists of FPI1 and FPI2 in parallel. FPI1 is composed of single mode fiber, quartz capillary and polydimethylsiloxane film. FPI2 consists of single mode fiber, large inner-diameter capillary, and small inner-diameter capillary. Because FPI1 and FPI2 have different sensing mechanisms for gas pressure, the interference fringes of FPI1 and FPI2 drift in the opposite direction with the change of ambient gas pressure. When FPI1 and FPI2 with a similar free spectral range are connected in parallel, an enhanced Vernier effect is generated. Compared with the traditional Vernier effect gas pressure sensor, the enhanced Vernier effect gas pressure sensor realizes ultra-high sensitivity gas pressure measurement without increasing the difficulty of sensor manufacturing. The sensitivity of the enhanced Vernier effect gas pressure sensor is as high as 283.32 nm/MPa, which is about 1.7 times that of the traditional Vernier effect barometric sensor (170.03 nm/MPa). In addition, the sensor has the advantages of good repeatability and stability, low cost, small temperature cross-sensitivity and easy manufacture. The sensor structure designed provides a new design idea and scheme for the ultra-high sensitivity optical fiber gas pressure sensor.

Quantifying antisite defect concentrations in yttrium aluminum garnet by high-precision density analysis

Quantifying the nature and density of lattice defects in high-quality crystals is often difficult or impossible with commonly employed material characterization techniques. In many cases, even the density of intentionally doped impurities present in a grown crystal must be inferred indirectly using methods such as mapping spatial variations in crystal properties or, when the defects are optically active, interpreting optical absorption with imprecisely known oscillator strengths. In this work we explore gravimetric techniques to obtain absolute defect densities in crystals, a powerful approach often overlooked in modern materials science. A hydrostatic weighing apparatus based on Archimedes’ principle was constructed, tested, and refined to enable high-precision density measurements of small crystal samples. Application of this system is illustrated by determining the density of Yttrium Aluminum Garnet (YAG) relative to a high-purity silicon crystal density reference, minimizing traditional difficulties in correcting for the variations in surface tension and the water and air density due to small changes in ambient temperature, pressure, and solution composition. This method, using a relatively simple apparatus and small samples, is effective in measuring the intrinsic concentration of Y–Al antisite lattice defects in YAG, agreeing with results from far more elaborate high-resolution optical laser spectroscopy at cryogenic temperatures. Furthermore, we quantitatively analyze the effects of several potential sources for error, including natural variations in isotope distributions, residual surface contamination, and ambient temperature or pressure variations. Subsequently, we find that the density analysis method is a promising technique for characterizing new and modified materials being developed for applications ranging from solid-state lasers and scintillators to quantum information.

Numerical analysis of vortex and cavitation dynamics of an axial-flow pump

ABSTRACT This study focuses on the correlative mechanism of the ambient pressure and inflow uniformity on the vortex and cavitation dynamics of an axial flow pump. The shear stress transport k – ω turbulence model and Schnerr–Sauer cavitation model are applied in the unsteady detached eddy simulation. The results show that the vortex merging between the primary and secondary tip leakage vortices (TLV) happens earlier with the growth of the cavity at a lower ambient pressure. The contact position of the merged TLV to the adjacent blade moves upstream with the decrease in the cavitation number. As the uniformity of the axial inflow decreases, TLV merging and vortex shedding are also promoted. The nonlinear variation of the initial angle of attack of the impeller blade leads to the compression or expansion of sheet cavitation under non-uniform inflow conditions. The evolution process and energy transfer of the vortices are verified quantitatively using a power spectral density analysis of kinetic energy fluctuations, and the short-wave instability leads to the fast decline of spectrum peaks at a higher frequency in the cavitating flow. It is crucial to avoid severe changes of ambient pressure and inflow uniformity to ensure the design performance of pump in actual working environment.

Publisher Correction: Effect of ambient pressure change on pure tungsten laser spot welding

Publisher Correction: Effect of ambient pressure change on pure tungsten laser spot welding

Effect of ambient pressure change on pure tungsten laser spot welding

Effect of ambient pressure change on pure tungsten laser spot welding

Efficacy of Balloon Tuboplasty for Baro-Challenge-Induced Eustachian Tube Dysfunction: A Systematic Review and a Retrospective Cohort Study of 39 Patients.

Baro-challenge-induced Eustachian tube dysfunction (ETD) manifests due to inadequate Eustachian tube (ET) function during rapid ambient pressure changes, although ET function may be normal in normobaric situations. This systematic review and retrospective cohort study aimed to evaluate the effectiveness of balloon Eustachian tuboplasty (BET) for the treatment of baro-challenge-induced ETD. PubMed, the Cochrane Library, Scopus, and Helsinki University Hospital cohort. A systematic literature search was conducted in November 2020 and resulted in 174 articles. Eight articles fulfilled the inclusion criteria. Data was available altogether from 74 adult baro-challenge-induced ETD patients. In addition, we retrospectively evaluated 39 BET operations at Helsinki University Hospital from 2011 to 2020. Data from these 39 patients were collected from medical charts, and a questionnaire was sent to the patients. Meta-analysis was used to evaluate subjective symptom improvement, changes in ETD Questionnaire-7 (ETDQ-7) scores, and Valsalva maneuver performance. In the systematic review, the outcome parameters varied between studies. Improvement was reported in subjective symptoms, Valsalva maneuver, ETDQ-7, tubomanometry, and pressure chamber test. Response rate for the Helsinki University Hospital cohort study was 72% (28/39). Mean follow-up time from the BET to the questionnaire was 4 years 8 months (SD 26months). Of those patients 93% (26/28) found the operation beneficial. Meta-analysis including up to 113 patients showed improvement in Valsalva maneuver, ETDQ-7, and improvement in subjective symptoms. Overall improvement in symptoms was noted in 81% of the patients. BET seems to be effective in the majority of patients with baro-challenge-induced ETD.

Barodontalgia and Dental Barotrauma Among Scuba Divers.

INTRODUCTION: Barometric pressure variation during dives may induce barodontalgia and barotrauma. Barodontalgia refers to oral pain resulting from a change in ambient pressure. The aim of this study was to investigate the occurrence of barodontalgia and dental barotrauma among French civilian scuba divers.METHODS: A nationwide cross-sectional internet-based survey was conducted among French scuba divers over 18 yr of age registered by the French Federation of Underwater Sports (FFESSM). The online questionnaire was distributed from October to December 2020. It contained questions regarding general characteristics of participants, barodontalgia and dental barotrauma occurrences, and relationship of the diver with his/her dentist.RESULTS: There were 684 scuba divers (65.4% men; aged 48 ± 12 yr) who participated in the study. Barodontalgia was reported by 18.7%, with some respondents reporting more than one episode. Most barodontalgia affected posterior (81.2%) and upper teeth (55.2%) with dental filling (50.0%). At least one dental barotrauma was reported by 10.1% of respondents, including mainly loss or fracture of a dental filling (4.2%). The occurrence of dental barotrauma was significantly higher among men (12.3%) than women (5.9%) and increased significantly with the age, the years of diving and the diving qualification.CONCLUSION: Information should be provided to divers on the importance of routine dental checkups.Kougeon K, Yasukawa K, Baudet A. Barodontalgia and dental barotrauma among scuba divers. Aerosp Med Hum Perform. 2022; 93(5):421-425.

Numerical Simulation of Decompression Process of a Mars Rover in the Launch Phase

This paper performs numerical simulation on the decompression process of a Mars rover using FLUENT. The pressure differential between the inside and outside of the Mars rover resulting from changes in ambient pressure of the rocket fairing is investigated. In terms of numerical simulation, PROFILE outlet boundary conditions are developed and the impacts of ambient pressure settings, time steps, and mesh density are investigated to improve the accuracy of simulation results. The decompression process of the separate large module, large and small modules under two types of ambient pressures are simulated. The results show that the largest pressure differential between the inside and outside of the module body is less than 2200 Pa. Because of the small size of the small module, the results for the separate large module and the large/small modules are consistent. The pressure differential between the inside and outside of the rover is mainly influenced by the variation in ambient pressure.

In-Vivo Measurement of Ocular Deformation in Response to Ambient Pressure Modulation.

A novel approach is presented for the non-invasive quantification of axial displacement and strain in corneal and anterior crystalline lens tissue in response to a homogenous ambient pressure change. A spectral domain optical coherence tomography (OCT) system was combined with a custom-built set of swimming goggles and a pressure control unit to acquire repetitive cross-sectional scans of the anterior ocular segment before, during and after ambient pressure modulation. The potential of the technique is demonstrated in vivo in a healthy human subject. The quantification of the dynamic deformation response, consisting of axial displacement and strain, demonstrated an initial retraction of the eye globe (−0.43 to −1.22 nm) and a subsequent forward motion (1.99 nm) in response to the pressure change, which went along with a compressive strain induced in the anterior crystalline lens (−0.009) and a tensile strain induced in the cornea (0.014). These mechanical responses appear to be the result of a combination of whole eye motion and eye globe expansion. The latter simulates a close-to-physiologic variation of the intraocular pressure and makes the detected mechanical responses potentially relevant for clinical follow-up and pre-surgical screening. The presented measurements are a proof-of-concept that non-contact low-amplitude ambient pressure modulation induces tissue displacement and strain that is detectable in vivo with OCT. To take full advantage of the high spatial resolution this imaging technique could offer, further software and hardware optimization will be necessary to overcome the current limitation of involuntary eye motions.

Gas-stabilizing solid cavitation nuclei for systemic or transdermal ultrasound-enhanced drug and vaccine delivery and immunomodulation

Originally developed for diagnostic purposes and already approved for clinical use, lipid and protein-shelled microbubbles were a natural choice as initial nucleation agents for cavitation-based therapies entering the clinic. However, several emerging therapeutic ultrasound applications require nuclei that: (i) are significantly smaller in size, in order to overcome a particular biological barrier such as the leaky vasculature of tumours or the stratum corneum; (ii) offer greatly increased cavitation persistence, both during a single extended ultrasound pulse and in terms of extended circulation following intravenous administration; (iii) have better resilience to sudden ambient pressure changes in order to enable direct injection without nuclei destruction into tissue targets via a needle and syringe; and (iv) are made of materials or have an increased payload or surface area that can interact beneficially with the relevant tissue target during or following cavitation. Gas-stabilizing solid particles will be reviewed in this context, providing an overview of their known characteristics in terms of size distribution, associated acoustic emissions, cavitation thresholds, cavitation persistence and circulation. The relationship between this acoustic characterization and associated bioeffects including drug and vaccine delivery, and immunomodulation will subsequently be explored.

A Bioresorbable Dynamic Pressure Sensor for Cardiovascular Postoperative Care.

Bioresorbable electronics that can be absorbed and become part of the organism after their service life are a new trend to avoid secondary invasive surgery. However, the material limitation is a significant challenge. There are fewer biodegradable materials with pressure-sensitive properties. Here, a pressure sensor based on the triboelectric effect between bioabsorbable materials is reported. This effect is available in almost all materials. The bioresorbable triboelectric sensor (BTS) can directly convert ambient pressure changes into electrical signals. This device successfully identifies abnormal vascular occlusion events in large animals (dogs). The service life of the BTS reaches 5 days with a high service efficiency (5.95%). The BTS offers excellent sensitivity (11 mVmmHg-1 ), linearity (R2 = 0.993), and good durability (450000 cycles). The antibacterial bioresorbable materials (poly(lactic acid)-(chitosan 4%)) for the BTS can achieve 99% sterilization. Triboelectric devices are expected to be applied in postoperative care as bioresorbable electronics.

Polyisobutylene and Silicone in Warm Edge Glazing Systems—Evaluation of Long-Term Performance

This article describes the characteristics of one type of sealing system used in warm edge glazing units and analyses the possible causes of damage. Attention was focused on the performance of the dual seal, PIB/silicone system. This type of glazing is widely used for modern curtain walls and roofs of office buildings and shopping centres. Study was focused on PIB displacement defects, which affects both the appearance and thermal performance of the curtain wall system. Wide-ranging field surveys were conducted to examine the problems identified in some office buildings. The information gathered in this way was used to identify the critical areas and causes of seal displacement in the analysed insulating glass units (IGUs). Laboratory tests were conducted on PIB and silicone seals retrieved from the removed defective units. The properties of these materials were determined and used to evaluate the applied edge sealing system and build a representative numerical model. Due to the problems encountered in deriving accurate analytical formulas, finite element (FE) approximation was used as a problem solving tool. The generated FE model and strain analysis were the key parts to obtaining a true representation of the actual behaviour of IGUs subjected to various environmental loads, taking into account the influence of the air cavity. Results of computer simulations and laboratory tests were compared for model validation. The effect of changes in ambient pressure was examined, showing the development of tensile strains in the silicone and PIB, which can lead to debonding. The greatest principal strains occur at the silicone/butyl rubber interface and this location should be considered to be the most susceptible to failure. The observations are summarised in the final conclusions. Additionally, as field study showed, after ten years in service, the percentage of damaged units is considerable. More frequent IGUs inspection should cover both appearance and thermal imaging to detect unsealed panels. From the standpoint of both durability and appearance, dual silicone/PIB should be phased out in favour of modern seal systems.

On simulating the effect of gravity on concurrent flame spread over thin paper through variations in ambient pressure

The environment inside a spacecraft, or a space habitat, can greatly differ from those on earth, affecting the burning behavior of solid fuels. Because in a gravity field there is a flame-induced buoyancy, it is very difficult to reproduce on Earth the environmental conditions of a spacecraft, or a habitat in the Moon or Mars, thus making fire testing and burning predictions harder. A potential alternative approach to overcome this problem is to reduce buoyancy effects by using reduced ambient pressure in normal gravity. The objective of this work is to explore the possibility of simulating the effect of gravity, and in turn buoyancy, through changes in ambient pressure, on upward/concurrent flame spread over a thin combustible solid. Comparisons with available data at different gravity levels are used to determine the extent to which low-pressure can be used to replicate flame spread characteristics at different gravities. Experiments of the upward/concurrent flame spread over thin Kimwipe paper sheets were conducted in normal gravity inside a pressure chamber with ambient pressures ranging between 100 and 30 kPa and a forced flow velocity of 10 cm/s. Results show that reductions of pressure slow down the flame spread over the paper surface, and also reduces flame intensity. Comparison with published partial gravity data shows that as the pressure is reduced, the normal gravity flame spread rate approaches that observed at different gravity levels. The data presented is correlated in terms of a mixed convection non-dimensional number that describes the convective heat transferred from the flame to the solid, and that also describes the primary mechanism controlling the spread of the flame. The correlation provides information about the similitudes of the flame spread process in variable pressure, flow velocity and gravity environments, providing guidance for potential ground-based testing for fire safety design in spacecraft.

Performance Evaluation of Coupling Variants for an Active Middle Ear Implant Actuator: Output, Conductive Losses, and Stability of Coupling With Ambient Pressure Changes.

This study aims to investigate the performance of an active middle ear implant actuator for various coupling configurations. Actuator output and conductive losses were measured, and the stability of coupling was evaluated by challenging the link between actuator and ossicles through pressure events in magnitudes that occur in daily life. Actuator coupling efficiency and the occurrence of conductive losses were measured in 10 temporal bones through laser Doppler vibrometry on the stapes footplate for various coupling types (incus short process with and without laser hole, incus long process, stapes head). To test the stability of coupling, actuator output was measured before and after daily-life pressure events that were simulated; Valsalva maneuvers (500 cycles of -40 to +60 hPa) and jumping into a swimming pool and diving 3 m deep (a step change of 300 hPa). Actuator output was similarly high for all types of coupling to the incus (short process and long process) and most efficient for coupling to the stapes head. Conductive losses occurred in two temporal bones (TBs) for short process coupling but for seven TBs for coupling to the incus long process. All coupling types were stable and did not lose efficiency after pressure events in the low-frequency range (<1 kHz). Losses in output of 13 to 24 dB were observed in one TB at frequencies from 3 to 6 kHz. Actuator output was similarly high for all types of coupling to the incus but coupling to the incus long process led to a higher occurrence of conductive losses. All three coupling configurations connected the actuator securely to the ossicular chain, under variations of barometric pressure that can be expected in daily life.

BIOGAS AS AN ALTERNATIVE FUEL FOR AUTOMOTIVE TRANSPORT IN MOUNTAIN AREAS

The potential of low-calorie gases, in particular, biogas, which Ukrainian agriculture and industry produce in significant quantities, is almost never used here. The number of available domestic facilities for recycling such gases is scanty, although, in most developed countries, the significant number of such factories is operating. Landfill biogas is one of the promising energy sources, still, today, it is either emitted into the atmosphere, polluting it, or burned in flares. The use of biogas as fuel in automotive internal combustion engines is not sufficiently studied. However, the substitution of gasoline for biogas reduces engine power and increases fuel consumption. Especially this should be taken into account when operating vehicles in mountainous terrain under the conditions of reduced atmospheric pressure and temperature. Nevertheless, researching how mountain conditions can influence the performance of biogas-powered automobile engines is not given enough attention yet in Ukraine and in the world. Operation of cars on the mountain roads of the Carpathian region at the altitudes of 1000 ÷ 2000 m above sea level with rises and descents up to 12% and the section length up to 10 ÷ 15 km is difficult. The higher is the level of the terrain above the sea, the lower become the atmospheric pressure, air density and temperature, which deteriorates the filling of the car engine cylinders. The engine cooling rate decreases because of the air dilution and small speeds on steep slopes. Simultaneously, running engines on an excessively enriched fuel-air mixture and moving mainly in lower gears lead to engine overheating. Under the mountainous terrain conditions, Air to Boil temperature decreases. As we know the blend composition of biogas, it is possible to calculate its combustion value as well as the combustion value of the gas-air mixtures. Based on analytical research, we have plotted some graphs that reflect the dependence of the changes in the effective power and effective specific biogas consumption on the changes in ambient temperature and atmospheric pressure.

Methods for Characterizing Artificial Smoke Generators for Standardizing Inflight Smoke Detection Certification

False alarm resistant smoke detectors must pass the inflight smoke-detection certification test for implementation in aircraft. Inflight certification testing uses artificial smoke generators due to health and safety. Currently, there are no objective parameters to quantify an artificial smoke generator’s aerosol production for certification testing. Therefore, this study’s design was to create a framework for potential guidelines for standardizing an artificial smoke generator’s aerosol production. Although the aerosols created by artificial smoke generators look like real smoke, there are inconsistencies between models that could create smoke detectors not activating during certification testing. Aerosols created by artificial smoke generators must be similar to smoke for many of the false alarm resistant smoke detectors to alarm. Therefore, verifying which artificial smoke generators produce an aerosol with similar particle characteristics to smoke is essential for the implementation of false alarm resistant detectors in aircraft. Furthermore, standardizing the artificial smoke generators for the total quantity of aerosol produced, rate of aerosol production, and repeatability of aerosol production and quantifying the effects of the ambient environment is necessary to ensure the reliability and integrity of the certification test. One possible result of a non-standard aerosol production during certification testing, specifically in regards to an unexpected overabundance of aerosol production, may cause the certification of smoke detection system that would not alarm the specified threat. Conversely, insufficient aerosol production during certification testing could create the requirement of a lower smoke detection threshold than intended, creating an unfair financial burden. This study found that artificial smoke generators produce an aerosol with similar particle size distributions and light scattering characteristics to smoke created by smoldering foam, smoldering wood, and lithium-ion battery thermal runaway vent-gas. Therefore, it is reasonable to conclude that aerosols from the tested artificial smoke generators are capable of alarming most false alarm resistant smoke detectors. Furthermore, there were measurable differences in the total quantity of aerosol produced and the rate of aerosol production between smoke generators used by four major airframe manufacturers for smoke-detection certification testing. In addition, changes in ambient temperature and pressure that may occur during a typical flight profile affected an individual smoke generator’s production of aerosol. Sufficiently heating the smoke generator’s mineral oil before aerosol production can mitigate the effects of varying ambient temperatures.

Barodontalgia: Dental Implications at High Altitudes

Barodontalgia is a symptom of a pre-existing subclinical oral diseases rather than a pathological conditionitself. It was considered earlier as a “flyer’s toothache,” barodontalgia is described as pain that occurs in thetooth utilizing changes in ambient pressure usually in people who fly or dive. It is the whole responsibilityof the dental health professionals to provide the aviators with the best dental treatment as well as awarenessabout the hazards to the dental treatments at higher altitudes. This piece of writing gives sufficient informationabout the need and protocols to be followed especially for the patients commonly at higher altitudes. Thisarticle aims at providing adequate knowledge about barodontalgia and the responsibilities towards itsprevention both by the dentist and the flight crew members.

Eustachian tube function test as a predictor of middle ear barotrauma.

Most of the cases of middle ear barotrauma in divers are due to the impassability of the Eustachian tube. The aim of our study is to compare the results of tympanometry and Valsalva part of Eustachian Tube Function test (ЕТF-test) with the ability of divers to compensate for the change in ambient pressure in a hyperbaric chamber. The study included 35 professional divers undergoing annual medical examination. For all subjects is measured first intratympanal pressure at rest, then after the maneuver of Valsalva with impedancemeter. Then a barofunction test (BFT) was performed to assess the diving fitness and the passability of the Eustachian tubes. It consists of divers compressing and decompressing in a hyperbaric chamber to a pressure of 2.2 ATA for 1 minute. Based on results from previous studies we are using a 20 DaPa cutoff point on the ETF test to predict Eustachian tube passability and a successful barofunction test. In the current study 24 divers have ETF test results higher than 20 DaPa. 3 divers have ETF test values lower than 20 DaPa in both ears, but none of them displayed difficulties in the BFT. 8 divers have ETF values lower than 20 DaPa in one ear and higher than 20 DaPa in the other. 7 of the last group displayed difficulties with the BFT in the ear with poor ETF result. We consider that the ETF test can be used to assess diving fitness as a screening method before performing a BFT, as values above 20 DaPa guarantee Eustachian tube function sufficient for diving activities. Values of 20 DaPa and less are not a definite predictor of the BFT results. The results of the ETF test can also be used in the usual work of an otorhinolaryngologist to evaluate Eustachian function in cases of unilateral disease of middle ear.

Smoothed particle hydrodynamics modeling of fuel drop impact on a heated surface at atmospheric and elevated pressures.

The outcomes of fuel drop impact on heated walls will affect the fuel-air mixture distribution and the subsequent combustion and emissions in internal combustion engines. Existing numerical models for drop-wall interactions are mainly validated for conditions at atmospheric pressures. In this work, a numerical method, based on smoothed particle hydrodynamics, was developed to simulate the drop impact on a heated wall at high pressures. The effects of high temperature and high pressure on the evaporation of the drop were considered. The impact regimes under various wall temperatures and ambient pressures were identified, including deposit, contact splash, film splash, and rebound. Numerical predictions were validated by experimental observations. The present method predicted the increase in the critical temperature above which the drop would rebound as the ambient pressure increased. For example, for n-heptane drop impact on a 200 °C wall at We=50, the drop rebounds at 1 bar but deposits at 20 bars ambient pressure. The present method is able to capture the shift in the Leidenfrost point with the change in ambient pressure. The ability to predict such effects of the ambient pressure on drop-wall interactions is important in simulating spray impingement at realistic engine conditions.

압축 공기를 사용한 소형 이젝트의 진공 흡입 성능 평가 요인에 관한 연구

This study analyzed the internal flow structure of a small ejector and the major design factors that affect suction force. The ejector had a limited total length of 45 mm, and the primary nozzle had a diameter of 1 mm. This study investigated the effect of the main parameters on optimum nozzle opening ratio based on injection flow as well as the influence of the mixing chamber design on vacuum suction performance. The second nozzle had a significant effect when the diameter was 18 mm. Other parameter values were studied to identify design elements that determine the shape of the mixing chamber. The effect of the pad opening gap and the change in ambient pressure on the control state of the inflow ratio and the possibility of non-contact gripping were also examined.