Air Pressure Variations Research Articles

Current concepts for quality assured long-distance transport of temperature-sensitive red blood cell concentrates

The German Armed Forces Blood Service in Koblenz supplies red blood cell concentrates (RBCs) to military and civilian institutions at home and to field hospitals during peacekeeping operations abroad. During long-distance transport, blood products can be exposed to extreme environmental conditions or inappropriate handling, which may compromise product quality. Different active and passive cooling systems, cooling elements, packaging material and data loggers were examined in a climate chamber. A number of techniques for measuring temperature were investigated in order to preserve the blood products' quality during transport, including some field tests with multiparametric data recording. Any kind of active cooling systems, conventional cooling elements and customary packaging material, as well as temperature-sensitive labels, minimum-maximum thermometers and intra-product measurement were found to be unsuitable for military requirement. The best results were obtained when the passively cooling RCB 25 transport box (Dometic) was used together with latent heat/cold storage elements (deltaT) and Junior data loggers (Escort). The elaborated protocol allows temperatures to be maintained between 2 and 6 degrees C as required by European guidelines for at least 36 h each and between 1 and 10 degrees C as required by German guidelines for at least 48 or 64 h at ambient temperatures between -10 and 40 degrees C. Preliminary results indicate that care must be taken concerning additional factors such as air pressure variation or vibration.

Predictive Modeling and Investigation on the Formation of Stiff Air-Layer around the Grinding Wheel

In grinding process, a stiff air layer is generated around the wheel periphery due to high surface speed of the porous grinding wheel. This stiff air layer restricts grinding fluid to reach deep inside the grinding zone. The formation of stiff air layer has been studied experimentally by obtaining the variation of air pressure around the wheel periphery under different wheel speeds. With the help of the experimental data, a mathematical model has been developed to predict the pressure of the stiff layer of air under different wheel speed. From the model it is found that at close proximity to the wheel, air pressure obtained is very high, and this establishes quantitatively the formation of stiff air layer around the grinding wheel.

Reply to the discussion by Leong et al. on “Assessment of the use of the vapour equilibrium technique in controlled-suction tests”Appears in Canadian Geotechnical Journal, 46(12): 1482–1484.

The authors would like to thank the discussers for their interest in our paper and their valuable comments. The discussers have highlighted our conclusion by providing experimental data related to the difficulty in controlling total suction when hastening the equilibrium condition of vapour transfer by using a magnetic stirrer in their reference salt solution reservoir. Their data complement the approach followed by the authors using numerical results, even though they apply a different experimental procedure — the authors use a forced convection system to facilitate vapour transfer. Nevertheless, the authors agree with the discussers that these hastening procedures could possibly result in air pressure and temperature differences created along the constant mass circuit that would induce variations in the relative humidity, which is supposedly controlled by the reference salt solution reservoir. With this being stated, the authors would also like to present some experimental results to provide further evidence of what they concluded using numerical simulations. Dueck (2004) studied the influence of air pressure changes in a forced convection circuit of vapour — driven by an air pump — and their consequences on the applied relative humidity. Figure R1 shows a scheme of the experimental setup and the evolution of differential air pressures between two points of the circuit (upstream and downstream of the filter stones that transfer vapour to or from the soil). The point upstream of the filter is near the reference reservoir (‘‘ref’’ in the figure), while the point downstream of the filter is close to the aspiration branch of the air pump (‘‘p’’ in the figure) and is subjected to a pressure drop. After vapour equalization, the pump is turned on and air is forced through the circuit. At 67 min, the speed of the pump is rapidly increased and is then reduced from 78 min on. The consequences on the evolution of the relative humidity at the same two points of the circuit are shown in Fig. R2. As observed, downstream point ‘‘p’’ near the pump undergoes important relative humidity changes due to air pressure drop, while upstream point ‘‘ref’’ is buffered by the reference salt solution reservoir. The mass rate transfer under isothermal conditions of vapour by convection with a known air flow rate has been expressed in terms of the differences in mixing ratio (mass of vapour per unit mass of dry air) between the reference salt solution reservoir and the soil (see for example, Jotisankasa et al. 2007). As a consequence, an expression to account for the effects of air pressure variations on the relative humidity can be proposed based on the assumption under vapour equilibrium and isothermal conditions that the mixing ratio, x, set by the reference salt solution is also set at another point of the constant mass circuit. Assuming vapour and dry air as ideal gases and at the same temperature, the following expression is obtained for the mixing ratio: x = Mmwuv/ (Mmdauda) = 0.622 uv/uda, where Mmw and Mmda are the molecular masses of water and the dry air mixture, respectively; uda is the dry absolute air pressure; and uv is the vapour pressure. The following expressions are obtained between the relative humidity reference reservoir, hr ref, set by the salt solution, and another point of the circuit, hr p,

Modelling atmospheric and induced non-tidal oceanic loading contributions to surface gravity and tilt measurements

We investigate the contribution of atmospheric and its induced non-tidal oceanic loading effects on surface time-varying gravity and tilt measurements for several stations in Western Europe. The ocean response to pressure forcing can be modelled accordingly to the inverted barometer, i.e. assuming that air pressure variations are fully compensated by static sea height changes, or using ocean general circulation models.Wevalidate two runs of theHUGO-mbarotropic ocean model by comparing predicted sea surface height variations with hundred tide-gauge measurements along the European coasts. We then show that global surface pressure field, as well as a barotropic high-resolution ocean model forced by air pressure and winds allow in most cases a significant reduction of the variance of gravity residuals and, to a smaller extends tilt residuals. Wefinally show that precise gravity measurements with superconducting gravimeters allow the observation of large storm surges, occurring in the North Sea, even for inland stations. However, we also confirm that the continental hydrology contribution cannot be neglected. Thanks to their specific sensitivity feature, only tiltmeters closest to the coast can clearly detect the loading due to these storm surges.

Mermin habitually answers opinions, real and abstract

David Mermin criticizes the “reification” of magnetic fields, but he allows that spark chamber trajectories and atomic spectra are real, so why not also accept magnetic fields, ionic lattices, the cosmic microwave background, and so on? And is reification such a bad habit? Intuitive flashes of insight come as much from immersing yourself in the reality of the physics as from holding your nose and manipulating formal symbols. Often, reification leads us in the right direction: I assume Mermin has no plans to revive Mach’s crusade against the reality of the atom.I sympathize with Mermin’s desire to distinguish between mathematical abstractions like quantum field operators and solid realities like metals, but by any reasonable standard, magnetic fields are just as real as equally invisible variations in air pressure. Mermin worries that quantum mechanics describes fields—and atoms and everything else—in weird abstract terms, but allowing the weirdness of quantum mechanics to undermine the normal concept of what is real seems like a case of taking a successful theory too seriously, which is just what he was warning us not to do.© 2009 American Institute of Physics.

Frequency stability measurement of a transfer-cavity-stabilized diode laser by using an optical frequency comb

We report results of frequency stability measurements of an extended cavity diode laser (ECDL) whose frequency is stabilized by a non-evacuated scanning transfer cavity. The transfer cavity is locked to a commercial frequency stabilized helium–neon laser. Frequency stability is measured by use of an optical frequency comb. The environmental perturbations (variations of temperature, air pressure, and humidity) are also simultaneously measured. The observed frequency drift of the ECDL is well explained by environmental perturbations. An atmospheric pressure variation, which is difficult to control with a non-evacuated cavity, is mainly affected to the frequency stability. Thus we put the cavity into a simple O-ring sealed (non-evacuated) tube. With this simple O-ring sealed tube, the frequency drift is reduced by a factor of 3, and the Allan variance reaches a value of 2.4×10−10, corresponds to the frequency stability of 83 kHz, at the average time of 3000 s. Since the actual frequency drift is well estimated by simultaneous measurement of the ambient temperature, pressure, and humidity, a feed-forward compensation of frequency drifts is also feasible in order to achieve a higher frequency stability with a simple non-evacuated transfer cavity.

The influence of topographic and lithologic features on horizontal deformations

SUMMARY A number of studies have been carried out in order to determine the magnitude of effects originating from the surroundings of an observation site which influence seismometer records or deformation observations with tilt- or strainmeters. The investigations generally comprise thermal, atmospheric, topographic, and cavity effects, as well as ocean loading. Recently, these studies have been continued and extended using Finite Element (FE) modeling. The effects are investigated exemplarily using air pressure variations as loading signal. The observatory sites differ in their local surroundings. Based on this the influence on topographic and lithologic features is investigated with respect to air pressure changes. The models developed reflect different topographies around stations: wide and narrow valleys, hill flanks, and flat areas. At the foot of the hill flank, galleries are integrated into the models. The topographic and the gallery geometry influence are systematically investigated with regard to e.g. rock coverage above an observation site, changes in the hill slope, width of a valley, and lithology. The deformations are only caused by air pressure changes and not associated with gravity changes due to an advancing pressure front. For loading different air pressure scenarios are simulated with an uniform load and a pressure front which moves over the model in different directions. As an elastic rheology is considered, the effects can be scaled to actual occurring air pressure variations. Initial studies focus on the cavity effect to estimate the order of magnitude to separate the pure cavity effect from other influences. Studies of topographic effects, e.g. an increasing slope angle, yield a non-linear increase in the strain component with amplitudes up to 2 nstrain and tilt changes up to 2 nrad for a uniform air pressure load of 1 hPa for PREM parameterized models. Different lithologies can result in five times larger deformations. For moving high pressure areas, changes emerge in strain of up to 2 nstrain and in tilt of up to 4.2 nrad. The results obtained improve the interpretation of deformations observed with regard to fundamental geodynamic processes, and contribute to the selection of future observation sites.

Accuracy analysis and stabilization design of the Fabry–Perot frequency discriminator in double-edge wind lidars

The measurement error of a double-edge wind lidar caused by a disturbed Fabry–Perot interferometer (FPI) is analyzed. Several error sources such as air pressure variations, temperature changes, and mechanical vibrations are considered in the measurement-error model. The simulation results show that a double-edge wind lidar is so sensitive to environmental variations that the measurement error reaches ±60 m/s if the FPI is not stabilized. In order to compensate the external disturbance acting on the FPI, a nonlinear proportional–integral–derivative (PID) control scheme is designed based on the transmission measurement of the calibration channel. An arc tangent function is used to improve the feedback gain of the usual PID control design. The results show that with the new controller the measurement accuracy of the wind lidar can be improved 4–5 times in comparison with the usual control design, and the range of the measurement error is only ±3 m/s.

Air pressure variations at drainage stacks of high‐rise residential buildings

PurposeThe purpose of this paper is to examine the air pressure variations in an in‐use drainage stack of high‐rise residential buildings with the probable influence of occupant loads.Design/methodology/approachThe air pressure variations in a drainage stack of a typical in‐use high‐rise residential building in Hong Kong were correlated to the number of water closet (WC) flushes of the building. In particular, measured diurnal WC flushing patterns of the residential buildings were used to correlate the diurnal pressure variations measured at 16 m above the stack base in a 115 m high, 150 mm diameter fully vented drainage stack of a typical high‐rise residential building of Hong Kong.FindingsThe occurrence of the maximum air pressure in the stack could be correlated with the expected hourly WC flushes of the high‐rise residential buildings with mathematical demonstrations.Research limitations/implicationsThere may be high speed transients in the stack (>1 hertz) which was not measured.Originality/valueThe result would be a useful source of reference for the development of control strategies against probable appliance seal loss in high‐rise residential buildings.

Ionization-overheating instability threshold in the electrodeless microwave discharge plasma

Experiments with a pulsed freely localized electrodeless microwave discharge in air under a pressure corresponding to the ascending branch of the pressure dependence of the breakdown field are described. The discharge is initiated in a focused quasi-optical electromagnetic beam. The minimal threshold values of the electromagnetic field (for which a brighter plasma channel extended along the field is formed in the initially spatially homogeneous diffuse discharge plasma) are determined by varying air pressure for several fixed values of this field in the focal region of the beam. In accordance with the prevailing theory, this phenomenon is interpreted as the result of evolution of ionization-overheating instability in the microwave discharge plasma.

Evaluation Method for Air Pressure Variation and Station Facility Member Deterioration Caused by High-Speed Train Passage in Stations

When trains pass through stations at high speeds, large variations in air pressure occur. As the structural members that make up station facilities are susceptible to these repeated variations, it can be assumed that the likelihood of member deterioration is high. Since future train speed increases will result in larger air pressure variations, it is essential to make efforts to ensure the structural safety of stations. To this end, we developed calculation equations for air pressure variations based on the results of field measurements and model tests, and also proposed prediction methods for response deformation and an evaluation method for the fatigue strength of members exposed to air pressure variations.

On the effects of air pressure variations on radon exhalation into the atmosphere

A model is studied which claims to describe the effects of air pressure variations on the outflow of radon into the atmosphere from loose deposits that are treated as a porous medium having the gas dynamic properties described by Darcy’s law. It is shown that the model results are in satisfactory agreement with the experimental data acquired from a network for monitoring subsoil radon in the Petropavlovsk-Kamchatskii Geodynamic Site in 1997–2006. A technique has been developed for estimating the Darcy coefficient based on radon concentration data in loose deposits at various depths.

The solar cycle and two regimes of long-term variations of surface air pressure in high and middle latitudes of the Northern Hemisphere in the winter period

The solar cycle and two regimes of long-term variations of surface air pressure in high and middle latitudes of the Northern Hemisphere in the winter period

Vibration damping engine mount for internal combustion engine

In a method applicable to a vibration damping engine mount for an internal combustion engine and the vibration damping engine mount therefor, a varying air pressure is supplied to a vibration controllable support mechanism (3), and one of (i) a negative pressure developed in a negative pressure pump (30) and (ii) the atmospheric pressure to the vibration controllable support mechanism is supplied to the vibration controllable support mechanism, constituting the vibration damping engine mount, in accordance with the vibration of the internal combustion engine (2).

Low Temperature Membrane Properties

Nafion properties at low and subzero temperatures were experimentally measured. Membrane water content was measured by setting water activity = 1 and varying air pressure from 0 and 0.96 atm at 30{degree sign}C. Water content in mol SO3-/mol H2O =14 and 22 was found when air pressure = 0 and 0.94 atm, respectively. Schroeder's paradox did not exist in the absence of air. The state of water was shown to depend on the cooling rate, where melting and freezing peaks were lower for a 10{degree sign}C/min cooling rate than for a 1{degree sign}C/min cooling rate. The freezing peaks were -27 and -16{degree sign}C for 10 and 1{degree sign}C/min cooling scan rates. Membrane conductivity was measured from 0 to 80{degree sign}C for 100% RH vapor-equilibrated and 0 and 95{degree sign}C for liquid-equilibrated Nafion. The liquid-equilibrated conductivity had an activation energy of 10.2 kJ/mol.

Investigation of meteorological effects on strain measurements at two stations in Hungary

Analysis of extensometric and meteorological data from two observatories (Sopron and Pécs) in Hungary were carried out in order to investigate and to compare the stability of a deep and a surface observatory against the influences of temperature and air pressure variations. Long-term periodical variations of extensometric data, tidal analysis of the extensometric data and calculation of coherence between extensometric and air pressure data were applied as tools of comparison. Investigational results support the assumption that a deep observational site is less sensitive to the variations of the meteorological parameters than a surface one. The coherence calculations show unambiguously that the deformation measurements are less disturbed by air pressure variations especially of some days periods due to the weather system and the average noise level at tidal and higher frequencies is lower at the deep registration site than in the case of the near surface observatory.

Results of tidal research

At the Geodetic and Geophysical Research Institute of the Hungarian Academy of Sciences the tidal research was started in the mid-sixties of the last century. At first, measurements by horizontal pendulums (Tomaschek-Ellenberger, Melchior) were carried out. At the beginning of the 70's a new horizontal pendulum with capacitive transducer was developed. By means of this pendulum tidal measurements were carried out at the Geodynamical Observatory in Sopronbánfalva and local geodynamical movements were monitored in a coal mine in Pécs and at our nuclear power plant in Paks. At the beginning of the 90's a quartz tube extensometer with capacitive transducer was installed at the Geodynamical Observatory in Sopron and in the uranium mine in Pécs. The extensometers in Budapest installed in the early 80's, the extensometer in Výhne (Slovakia) were mounted with capacitive transducers. New, in-situ calibration method was developed at our institute and all of these extensometers were recalibrated by the new calibration device. A microbarograph of high resolution was also developed for the study of atmospheric tide in 1991. The investigation of the connection between air pressure variations and geodynamical phenomena has been carried out since 1992. This paper presents the developed instruments and the results obtained by these instruments.

Meteorologically Induced Modulation in Sea Level off Tikkavanipalem Coast—Central East Coast of India

Abstract This article examines the seasonal variability of nontidal contributions of the sea level oscillations off Tikkavanipalem coast in Andhra Pradesh (India), which is located on the western boundary of the Bay of Bengal. The analysis is based on simultaneous observations of tidal and surface meteorological parameters in four temporal segments of 1-month duration each during a 1-year period in 1997–98. Sea level oscillations along the Tikkavanipalem segment of the central east coast of India contain contributions from tidal and set-up/set-down motions. Local wind pattern, coastal current, and air pressure variations particularly influence the residual sea level elevation (difference of the measured and astronomically induced daily mean sea level) in this region. Observed response of the sea level elevation to the barometric pressure represents an amplified/delayed inverted barometer effect. The relative importance of tidal and nontidal contributions to the sea level is found to be seasonal, as the co...

Observation of number concentrations of atmospheric aerosols and analysis of nanoparticle behavior at an urban background area in Japan

To clarify nanoparticle behavior, observations of atmospheric aerosols, weather, and trace gases were carried out for about 1 month in summer and in winter at a region apart from major emission sources in Nagakute, Japan. The relation of nanoparticles with pollutants was clarified, and the potential of photochemical nucleation was pointed out based on the relation with meteorology and trace gas concentrations. The variation in particle size depends on the concentration of materials to be used in coagulation, condensation, and evaporation processes, except for photochemical nucleation. In winter, a minimum peak diameter of particle size distribution of about 40 nm was observed during the morning rush, and the growth rate of particle size during the morning was 7.6 nm h−1. On the other hand, the minimum size was recorded in the daytime in summer, and a large growth rate of 14.7 nm h−1 was obtained in the evening. The particle growth due to coagulation and condensation was thought to start with the morning rush and to continue until the next early morning in winter. The coagulation and condensation materials promoting particle growth were produced during the daytime, and a decrease in ambient temperature might contribute to particle growth during the night. In addition, a continuous particle growth was seen under a stable high atmospheric pressure for a few days. The average cyclic period of the particle growth and shrinkage of 81.9 h, which was calculated as a result of a Fourier analysis, was observed, and good correspondence was shown with the variation in atmospheric air pressure. The average growth rate during the time periods was 59.5 nm day−1 in winter and 103.3 nm day−1 in summer. The reason for the high value of the average growth in summer was thought to be the large amount of the materials produced which were used for particle growth through coagulation and condensation processes.

Modeling of Air Venting in Pressure Die Casting Process

In this study an analytical model has been developed to describe air pressure and residual air mass variations in pressure die casting for atmospheric venting. During injection of molten metal into a die cavity, air is evacuated from the cavity through vents. In this study, the influences of air velocity and friction factor due to temperature dependent viscosity and vent roughness change have been investigated. The results of the model show that there is a critical area ratio over which a quasi steady state is reached, therefore, the air pressure in the cavity remains constant. In addition, for each area ratio there is a critical/minimum time ratio below which outlet Mach number is not large enough to create choked flow. In this case, the rate of outflow air mass is not maximum. Finally, the results of the model addresses that the friction factor depends on hydraulic diameter of the vent and assuming a constant value for it is not valid.