Air Density Correction Research Articles

YÜKSEK GERİLİM LABORATUVARLARI İÇİN IoT TABANLI HAVA İSTASYONU TASARIMI VE UYGULAMASI

This study presents the design and implementation of an internet of things (IoT) based weather station for high voltage laboratories using the Raspberry Pi 4 Model B and two BME680 sensors. The weather station calculates the relative air density and humidity correction coefficients using the temperature, pressure, and relative humidity data obtained from the sensors. The study investigates the effect of the constant and real-time calculation of these coefficients on the measurement of AC, DC and lightning breakdown voltage using spherical electrodes. Measurements were performed within a laboratory setting for a period of 12 hours, and the obtained results were subsequently compared. The findings reveal that the real time calculation of the correction coefficients leads to a reduction in measurement errors. The study also includes the development of a web-based user interface using HTML and CSS, which is hosted on the Raspberry Pi 4 using the Flask web framework. This interface allows users to access the weather station data from any device with a web browser and provides real-time monitoring of the current coefficients, as well as the capability to calculate actual parameters online.

Evaluation of influential correction factors applicable for absolute beta dosimetry of 85Kr, 90Sr–90Y and 106Ru–106Rh beta emitters

Extrapolation ionization chamber is normally used for absolute measurement of absorbed dose to tissue and in standardization of beta particle emitting sources in particular. However, in this technique, several correction factors are applied to the measured ionization current to evaluate the true value of the dose to the tissue from beta radiation. These correction factors are described in ISO 6980–2:2004. Out of these, ion recombination correction factor (ksat) and ambient air density correction factor (kad) are evaluated experimentally during measurement of ionization current. Other significant correction factors are backscatter correction factor (kba), correction factor for perturbation in electron spectrum due to ionization chamber side wall scatter (kpe), correction factor for difference in attenuation of beta spectrum due to change in ambience condition (kabs) and correction factor for radial non-uniformity of dose inside detector volume (kra). Experimental evaluation of correction factors kba, kpe and kabs are not easily achievable. In the present work four significant correction factors kba, kpe, kabs and kra are derived theoretically by Monte Carlo particle transport simulation. These correction factors are evaluated for beta emission spectrum of 85Kr, 90Sr–90Y and 106Ru–106Rh radioactive sources.

TDC-based horizontal leakage area estimation in multiunit residential buildings: Three correction factors

Infiltration and interzonal airflow driven by wind and stack interactions in a multi-unit residential building (MURB) are crucial factors affecting indoor air and environmental qualities. To analyze the weather-driven airflow in MURBs, it is essential to define accurately the horizontal leakage areas for serial airflow paths on typical and basement floors in the multizone airflow modeling. Considering the challenges in measuring numerous leakage areas, a horizontal leakage estimation method based on the thermal draft coefficient (TDC) is proposed, in which the leakage areas are calculated by the stack-driven pressure differences relatively easy to measure. Moreover, three correction coefficients are theoretically suggested to minimize the TDC uncertainties from (1) different household envelope areas, (2) horizontal temperature distributions on each floor, and (3) multiple shafts in real MURBs. Two validation studies were conducted in a real MURB. First, the TDC-based models were validated by CONTAMW, and the effectiveness of the three correction factors was shown in the simulation-based case. The envelope area ratio correction factor was most effective for leakage areas in dwelling units. The shaft ratio correction factor was necessary for elevator doors on typical floors and all leakage areas on basement floors. The air density correction factor could improve all leakage areas under the horizontal temperature distributions on each floor. Then, based on field measurements, the proposed method was applied to leakage estimation in the building. Compared with the existing method, the field-measurement-based validation case demonstrated a significant improvement in the leakage estimation under measurement uncertainties.

Partial differentiation of air density in mass metrology

There are four major uncertainty components to be considered when performing mass comparisons. They are uncertainties of weighing process, reference weight used, air buoyancy, and mass comparator. The systematic effect of air buoyancy can be greatly reduced if the air density and the densities of the test and reference weights are known. This paper will emphasis on the uncertainty due to air buoyancy correction only. To calculate the uncertainty of air density correction, partial derivatives of temperature, barometric pressure and humidity must be performed. In this paper, two methods for partial differentiation of air density components are discussed.

Using atmospheric inputs for Artificial Neural Networks to improve wind turbine power prediction

A robust machine learning methodology is used to generate a site-specific power-curve of a full-scale isolated wind turbine operating in an atmospheric boundary layer to drastically improve the power predictions, and, thus, the forecasting of the monthly energy production estimates. The study has important implication in measuring the financial feasibility of wind farms by improving the accuracy of monthly energy estimates. The significance of the study is that atmospheric stability and air-density are accounted in the power predictions of the wind turbine. Artificial Neural Networks (ANN) machine learning approach is used to generate multi-parameter input models to estimate the power produced by the wind turbine. The ANN model in this study uses Feed Forward Back Propagation (FFBP) algorithm. The power- and wind-data is obtained from a 2.5 MW wind turbine that has a Meteorological tower located 900 m Southwest of the wind turbine in Kirkwood, Iowa, USA. The study investigates the role of atmospheric boundary-layer metrics – Wind Speed, Density (a measure of stratification), Richardson Number, turbulence intensity, and wind shear as input parameters into the ANN model. The study investigates the influence of FFBP ANN hyper-parameters on the power prediction accuracy. Comparison of the FFBP ANN model to other power curve correction techniques demonstrated an improvement in the Mean Absolute Error (MAE) of 40% when compared to the density correction (the next closest). The five-parameter 4-layer FFBP ANN has an average energy production error of 0.4% for the nine months while the IEC this error is −3.7% and for the air density correction the error is −1.9%, respectively. Finally, the study determines the performance of the FFBP ANN model for different atmospheric stability regimes (Unstable, Stable, Strongly Stable, Strongly Unstable and Neutral) classified using two criterions - Richardson number and Turbulence intensity. The largest MAE occurs during the strongly stable regime of the atmospheric boundary layer for both criteria.

Development Testing Method and Analysis Static Thrust for Propeller Based Propulsion

Propulsion system development involved aircraft manufacturer and engine or propeller manufacturer to perform test and evaluation. The main of this research was propulsion testing for unmanned aerial vehicle by evaluating thrust in static condition. Static thrust testing was conducted by force measurement using load cell and data acquisition systems. Thrust measurement result was compared with analytical method and computer fluid dynamic simulation. Analytical method in this paper used vortex blade element theory to calculated static thrust meanwhile Computational fluid dynamic was running both 2 dimension and 3 dimension simulation. Vortex blade element theory analysis combined with computational flight dynamic simulation for propeller aerofoil at 70% location. Test result compared with analytical and CFD calculation using non dimensional parameter. Analytical calculation deviated 5.08% from experiment meanwhile CFD calculation give 13.56% but still in error tolerances. Error tolerances considered from friction force, sensor accuracy and air density correction with total 6.33 kgf.

Seasonal Correction of Offshore Wind Energy Potential due to Air Density: Case of the Iberian Peninsula

A constant value of air density based on its annual average value at a given location is commonly used for the computation of the annual energy production in wind industry. Thus, the correction required in the estimation of daily, monthly or seasonal wind energy production, due to the use of air density, is ordinarily omitted in existing literature. The general method, based on the implementation of the wind speed’s Weibull distribution over the power curve of the turbine, omits it if the power curve is not corrected according to the air density of the site. In this study, the seasonal variation of air density was shown to be highly relevant for the computation of offshore wind energy potential around the Iberian Peninsula. If the temperature, pressure, and moisture are taken into account, the wind power density and turbine capacity factor corrections derived from these variations are also significant. In order to demonstrate this, the advanced Weather Research and Forecasting mesoscale Model (WRF) using data assimilation was executed in the study area to obtain a spatial representation of these corrections. According to the results, the wind power density, estimated by taking into account the air density correction, exhibits a difference of 8% between summer and winter, compared with that estimated without the density correction. This implies that seasonal capacity factor estimation corrections of up to 1% in percentage points are necessary for wind turbines mainly for summer and winter, due to air density changes.

Incorporating air density into a Gaussian process wind turbine power curve model for improving fitting accuracy

AbstractA power curve conventionally represents the relationship between hub height wind speed and wind turbine power output. Power curves facilitate the prediction of power production at a site and are also useful in identifying the significant changes in turbine performance which can be vital for condition monitoring. However, their accuracy is significantly influenced by changes in air density, mainly when the turbine is operating below rated power. A Gaussian process (GP) is a nonparametric machine learning approach useful for power curve fitting. Critical analysis of temperature correction is essential for improving the accuracy of wind turbine power curves. The conventional approach is to correct the data for air density before it is binned to provide a power curve, as described in the IEC standard. In this paper, four different possible approaches of air density correction and its effect on GP power curve fitting model accuracy are explored to identify whether the traditional IEC approach used for air density correction is most effective when estimating power curves using a GP. Finding the most accurate air density compensation approach is necessary to minimize GP model uncertainty.

개회로 파장 변조 분광법과 에디 공분산 방법으로 논에서 관측된 CH<sub>4</sub> 플럭스 자료의 보정

CH4 is a trace gas and one of the key greenhouse gases, which requires continuous and systematic monitoring. The application of eddy covariance technique for CH4 flux measurement requires a fastresponse, laser-based spectroscopy. The eddy covariance measurements have been used to monitor CO2 fluxes and their data processing procedures have been standardized and well documented. However, such processes for CH4 fluxes are still lacking. In this note, we report the first measurement of CH4 flux in a rice paddy by employing the eddy covariance technique with a recently commercialized wavelength modulation spectroscopy. CH4 fluxes were measured for five consecutive days before and after the rice transplanting at the Gimje flux monitoring site in 2012. The commercially available EddyPro TM program was used to process these data, following the KoFlux protocol for data-processing. In this process, we quantified and documented the effects of three key corrections: (1) frequency response correction, (2) air density correction, and (3) spectroscopic correction. The effects of these corrections were different between daytime and nighttime, and their magnitudes were greater with larger CH4 fluxes. Overall, the magnitude of CH4 flux increased on average by 20-25% after the corrections. The National Center for AgroMeteorology (www.ncam.kr) will soon release an updated KoFlux program to public users, which includes the spectroscopic correction and the gap-filling of CH4 flux.

Improved correlation between CT emphysema quantification and pulmonary function test by density correction of volumetric CT data based on air and aortic density

ObjectivesTo determine the improvement of emphysema quantification with density correction and to determine the optimal site to use for air density correction on volumetric computed tomography (CT). MethodsSeventy-eight CT scans of COPD patients (GOLD II–IV, smoking history 39.2±25.3 pack-years) were obtained from several single-vendor 16-MDCT scanners. After density measurement of aorta, tracheal- and external air, volumetric CT density correction was conducted (two reference values: air, −1000HU/blood, +50HU). Using in-house software, emphysema index (EI) and mean lung density (MLD) were calculated. Differences in air densities, MLD and EI prior to and after density correction were evaluated (paired t-test). Correlation between those parameters and FEV1 and FEV1/FVC were compared (age- and sex adjusted partial correlation analysis). ResultsMeasured densities (HU) of tracheal- and external air differed significantly (−990±14, −1016±9, P<0.001). MLD and EI on original CT data, after density correction using tracheal- and external air also differed significantly (MLD: −874.9±27.6 vs. −882.3±24.9 vs. −860.5±26.6; EI: 16.8±13.4 vs. 21.1±14.5 vs. 9.7±10.5, respectively, P<0.001). The correlation coefficients between CT quantification indices and FEV1, and FEV1/FVC increased after density correction. The tracheal air correction showed better results than the external air correction. ConclusionDensity correction of volumetric CT data can improve correlations of emphysema quantification and PFT.

Evaluation of Temperature Effects for Onboard Sound Intensity Measurements

As a portion of the overall research work for NCHRP Project 1–44, an examination of temperature effects on the onboard sound intensity method of measuring tire–pavement noise at the source was conducted. The study focused on whether a single, average normalization would be beneficial when applied to a full range of pavement types. Testing was conducted over 10 months, over a temperature range of more than 60°F (16°C), and on 10 pavements representing a variety of both asphalt and portland cement concrete design categories and covering a range in noise level of about 10 dB. On the basis of a statistical approach, temperature normalization was found to reduce uncertainty of the data and is recommended to be included in the method of test. Linear air temperature normalization is recommended, since a logarithmic regression did not further improve the fit of the data. Less scatter and improvements in the data were seen with the correlation to air temperature as opposed to pavement temperature. Theoretical and empirical assessments of the air density correction found the air density correction did not reduce uncertainty in the data and was not needed.

Impulse breakdown voltages of air gaps: a new approach to atmospheric correction factors applicable to international standards

In the design of high-altitude high-voltage transmission systems and in the optimization of the reliability of power sources in aeronautical environments, it is important to have reliable data concerning the effect of air density and humidity on reducing air insulation performance under local conditions. This is helpful also in the modeling of discharges and lightning in mountainous regions. This paper describes a systematic laboratory investigation of the combined effects of humidity and gas density on the breakdown strength of a 0.2 m rod/plane air gap that is subjected to positive-polarity lightning impulses, using a test chamber to reproduce the conditions commonly found in such regions. The results show that there are appreciable deviations between the measured humidity and air density correction factors and those of the 1973 and 1989 IEC Standards when extended to low air density. The paper proposes the adoption of a radically different correction procedure, based upon the influence of density and humidity on streamer propagation field, and including the effect of the high gradient in the anode region.

Acclimatization to High Altitude in the Tien Shan: A Comparative Study of Indians and Kyrgyzis

To study the changes in pulmonary function of human male volunteers from 2 different populations: Indians and Kyrgyzis before and after ascent to 3,200 m and during a 4-week stay at that altitude. Ten healthy soldiers of the Indian army (22-25 years of age) and 10 Kyrgyzis recruits (19-20 years of age), height and weight matched, were volunteers in this study. Their pulmonary functions were evaluated at baseline (Bishkek, 760 m); on days 2, 13, and 25 at a mountain clinic at Tuya Ashuu pass (3,200 m) in the northern Tien Shan Range; and on return to Bishkek. A dry spirometer was used to measure lung function at each location. Results indicated that Kyrgyzis had significantly larger forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV(1)) than those of the Indians, but their peak expiratory flow rate (PEF), forced expiratory flow rate at 25% to 75% of FVC (FEF(25-75%)), and maximal voluntary ventilation (MVV) measures were comparable. At high altitude (HA), FVC showed significant reduction on day 2, with subsequent recovery in the Kyrgyzis; but in the Indians, FVC showed gradual reduction, and on day 25, it was significantly reduced compared with the baseline value. FEV(1) did not show any change with altitude in either group. Expiratory flow rates and MVV showed significantly higher values at HA in both groups. However, after air density correction for the 2 altitudes, PEF and MVV showed no changes from their baseline values, and the mid-expiratory flow rate (FEF(25-75%)) was actually reduced in both groups: on day 2 in the Kyrgyzis and on day 25 in the Indians. On day 2 of return from a 4-week stay at HA, all test measures were back to their baseline values. The major difference between the 2 populations was larger lung volumes in the Kyrgyzis compared with the Indians, with no differences seen in their flow rate measures. Also, there was a different time schedule of altitude-induced reductions in FVC and FEF(25-75%).

The effect of ambient pressure on well chamber response: Experimental results with empirical correction factors

For some air-communicating well-type chambers used for low-energy brachytherapy source assay, deviations from expected values of measured air kerma strength were observed at low pressures associated with high altitudes. This effect is consistent with an overcompensation by the air density correction to standard atmospheric temperature and pressure (P(TP)). This work demonstrates that the P(TP) correction does not fully compensate for the high altitude pressure effects that are seen with air-communicating chambers at low photon energies in the range of 20-100 keV. Deviations of up to 18% at a pressure corresponding to an approximate elevation of 8500 ft for photon energies of 20 keV are possible. For high-energy photons and for high-energy beta emitters in air-communicating chambers the P(TP) factor is applicable. As expected, the ambient pressure does not significantly affect the response of pressurized well chambers (within 1%) to either low- or high-energy photons. However, when used with beta emitters, pressurized chambers appear to exhibit a slight dependence on the ambient pressure. Using measured data, the response and correction factors were determined for three models of air-communicating well chambers for low-energy photon sources at various pressures corresponding to elevations above sea level. Monte Carlo calculations were also performed which were correlated with the experimental findings. A more complete study of the Monte Carlo calculations is presented in the accompanying paper, "The effect of ambient pressure on well chamber response: Monte Carlo calculated results for the HDR1000 Plus."

Mass comparisons using air buoyancy artefacts

This work is a follow-up to a previous study that was aimed at reducing the uncertainty of the air density correction used to correct mass comparisons for the effects of air buoyancy. To clarify the difference observed previously in moist air between two absolute methods (CIPM-81/91 formula and air buoyancy artefacts determination), additional measurements were carried out in moist air, dry nitrogen and vacuum. The results obtained by the two methods for nitrogen density were in good agreement while the discrepancy was confirmed for the moist air density. A comparison of a 1 kg stainless steel mass against a 1 kg Pt/Ir mass standard was carried out to compare the accuracy of these two methods. The results of this comparison made in moist air, dry nitrogen and vacuum by using buoyancy artefacts gave an agreement within 1 µg. Our particular results confirmed the good accuracy of the air buoyancy artefacts method and reinforced the hypotheses that the accuracy of the air density using the CIPM formula is limited by the estimation of its composition.

Air density correction in ionization dosimetry

Air density must be taken into account when ionization dosimetry is performed with unsealed ionization chambers. The German dosimetry protocol DIN 6800-2 states an air density correction factor for which current barometric pressure and temperature and their reference values must be known. It also states that differences between air density and the attendant reference value, as well as changes in ionization chamber sensitivity, can be determined using a radioactive check source. Both methods have advantages and drawbacks which the paper discusses in detail. Barometric pressure at a given height above sea level can be determined by using a suitable barometer, or data downloaded from airport or weather service internet sites. The main focus of the paper is to show how barometric data from measurement or from the internet are correctly processed. Therefore the paper also provides all the requisite equations and terminological explanations. Computed and measured barometric pressure readings are compared, and long-term experience with air density correction factors obtained using both methods is described.

Critical switching impulse strength of long air gaps: modelling of air density effects

A physical modeling approach to investigate the effect of reduced air density on leader inception and sparkover of long air gaps under positive switching impulses with critical front time is presented. The model accounts for the effect of air density on continuous leader inception voltage, leader length, and sparkover voltage. The results of the model provides critical positive switching impulse air density correction factors for rod-plane, rod-rod, conductor-plane, conductor-rod, and conductor-tower window gaps over a wide range of gap distances and relative air densities. The model findings were extensively checked against previous experimental results with quite satisfactory agreement.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The air density correction to eddy flux measurements

Under the usual assumptions for the atmospheric surface layer, we show that air density fluctuations, particularly those due to temperature fluctuations associated with a heat flux, result in a small mean vertical wind velocity. Because of this, there can be a significant correction to eddy flux measurements of passive scalars, for example CO2, whose average concentration is very large compared to concentration fluctuations associated with the eddy flux.

Malfunction of linear accelerator dose monitoring systems.

Malfunctions of the dose monitoring systems of two linear accelerators were studied. A variation of plus or minus 2.5% over an air density correction factor range from 1.02 to 1.07 was measured, suggesting that the ionization-type monitor chambers were open to the atmosphere. An average variation of minus 2.0% was present between early morning calibrations and those performed later in the day. Any variation caused by changes in control console temperature was within experimental error. This type of malfunction can lead to errors in delivered doses of 5%.

Simplified Air Density Correction of Vacuum Cleaner Performance Data

This paper presents a simplified method for absolute determination of the perfornance correction for air density variations in a convenient ready to use form. It was developed through the use of computer analysis of data for 14 widely differing vacuum cleaner motors. By acknowledging that a 1-percent error in the vacuum correction factor was acceptable, a single curve was developed. A wattage correction factor curve was also developed. Because of the variance in efficiencies between motors, however, this curve has an error range of 4 5 percent. The curves were then verified experimentally by more than 1000 tests taken in environmental and altitude chambers in the ambient range from 50 to 100°F and 24 to 30 inches of mercury barometric pressure.