Search

We present a rich, multiwavelength, multiscale database built around the PHANGS-ALMA CO$\,$(2-1) survey and ancillary data. We use this database to present the distributions of molecular cloud populations and sub-galactic environments in 80 PHANGS galaxies, to characterize the relationship between population-averaged cloud properties and host galaxy properties, and to assess key timescales relevant to molecular cloud evolution and star formation. We show that PHANGS probes a wide range of kpc-scale gas, stellar, and star formation rate (SFR) surface densities, as well as orbital velocities and shear. The population-averaged cloud properties in each aperture correlate strongly with both local environmental properties and host galaxy global properties. Leveraging a variable selection analysis, we find that the kpc-scale surface densities of molecular gas and SFR tend to possess the most predictive power for the population-averaged cloud properties. Once their variations are controlled for, galaxy global properties contain little additional information, which implies that the apparent galaxy-to-galaxy variations in cloud populations are likely mediated by kpc-scale environmental conditions. We further estimate a suite of important timescales from our multiwavelength measurements. The cloud-scale free-fall time and turbulence crossing time are ${\sim}5{-}20$ Myr, comparable to previous cloud lifetime estimates. The timescales for orbital motion, shearing, and cloud-cloud collisions are longer, ${\sim}100$ Myr. The molecular gas depletion time is $1{-}3$ Gyr and shows weak to no correlations with the other timescales in our data. We publish our measurements online and expect them to have broad utility to future studies of molecular clouds and star formation., 32 pages + 6 appendices. AJ in press. Data products available at https://www.canfar.net/storage/list/phangs/RELEASES/Sun_etal_2022 . Associated software package available at https://doi.org/10.5281/zenodo.6584842 . Slides summarizing the key results can be found at https://www.dropbox.com/s/7llnrob9wi0isfk/Sun_et_PHANGS_2022.pptx?dl=0

Kroz ovaj rad smo se osvrnuli na upotrebu alternativnih izolacijskih plinova obzirom da se sve više koriste zbog utjecaja stakleničkih plinova te su rješenje koje znanstvenici primjenjuju kako bi došlo do njihovog što manjeg ispuštanja. Koriste se u raznim industrijama poput elektroenergetske, kemijske, električne, a njihovu uporabu potiču razne udruge za zaštitu okoliša te vlade, a sve to u svrhu očuvanja okoliša i našeg planeta. Zbog svoje cjenovne pristupačnosti i činjenice da se crpe iz prirodnih resursa jedno su od najboljih rješenja u suvremenom svijetu. Najzastupljeniji i najkorišteniji plin je sumporov heksafluorid (SF6). Međutim, zbog štetnosti koje stvara ozonskom omotaču znanstvenici traže alternativna rješenja s boljim performansama i manjom štetnosti. Zamjene koje se koriste za SF6 su perfluorometan, perfluoroetan, perfluoropropan, perfluorociklobutan, trifluoridometan, perfluoropentan i fluoronitril. Sva istraživanja se provode u svrhu zaštite naše planete., Through this paper, we explained the use of alternative insulating gases as they are increasingly used due to the impact of greenhouse gases and are a solution that scientists apply to minimize their release. They are used in various industries such as power, chemical, electrical, and their use is encouraged by various environmental associations and the government, all for the purpose of preserving the environment and our planet. Due to their affordability and the fact that they are extracted from natural resources, they are one of the best solutions in the modern world. The most common and used gas is sulfur hexafluoride (SF6). However, because of the harmfulness it creates to the ozone layer, scientists are looking for alternative solutions with better performance and less harmfulness. Substitutes used for SF6 are perfluoromethane, perfluoroethane, perfluoropropane, perfluorocyclobutane, trifluorodomethane, perfluoropentane and fluoronitrile. All research is being conducted to protect our planet.

We present improved methods for segmenting CO emission from galaxies into individual molecular clouds, providing an update to the CPROPS algorithms presented by Rosolowsky & Leroy (2006; arXiv:astro-ph/0601706 ). The new code enables both homogenization of the noise and spatial resolution among data, which allows for rigorous comparative analysis. The code also models the completeness of the data via false source injection and includes an updated segmentation approach to better deal with blended emission. These improved algorithms are implemented in a publicly available python package, PYCPROPS. We apply these methods to ten of the nearest galaxies in the PHANGS-ALMA survey, cataloguing CO emission at a common 90 pc resolution and a matched noise level. We measure the properties of 4986 individual clouds identified in these targets. We investigate the scaling relations among cloud properties and the cloud mass distributions in each galaxy. The physical properties of clouds vary among galaxies, both as a function of galactocentric radius and as a function of dynamical environment. Overall, the clouds in our target galaxies are well-described by approximate energy equipartition, although clouds in stellar bars and galaxy centres show elevated line widths and virial parameters. The mass distribution of clouds in spiral arms has a typical mass scale that is 2.5x larger than interarm clouds and spiral arms clouds show slightly lower median virial parameters compared to interarm clouds (1.2 versus 1.4)., Accepted to MNRAS. Catalogues, code, and atlas available at http://phangs.org/data

Master's thesis in Petroleum Engineering The impact of the permeability on ultra-tight porous media influences flow behaviour inside the media. The unconventional reservoir gas permeability significantly impacts rock property estimation crucial to unconventional resource development. The rock permeability describes how unconventional reservoir gas flows into the pores, which affects reservoir development. The pressure decay approach estimates the permeability of unconventional rocks by evaluating the pressure difference in reservoirs. Due to the pulsed pressure decay method's effectiveness over the laboratory run time, the analytical solutions determine the permeability. The analytical method to determine the permeability relied on the simulated pressure results, which have limitations in estimating permeability based on constant gas properties. There will be changes between the experimental pressure and the simulated pressure results because these curves have similar late slopes for the estimated permeability. This study aims to eliminate the large differences with inconsistent results between the experimental pressure results' historical matching and those of the simulated pressure results. A representation of a mathematical model containing gas characteristics related to pressure was developed. When the minimum difference between the experimental pressure and the simulated pressure results stabilizes, the permeability estimation occurs. This study's approach estimated permeability from pulse pressure decay, using laboratory data by testing three gases that include Methane, Helium, and carbon dioxide. This new approach measures the slightest variation in the pressure decay response evaluation based on history matching. This method estimated permeability more accurately when compared with the Cui et al. (2009) analytical solution. The improved estimation of gas permeability in this study was due to the applicability of pressure-dependent gas properties and the entire pressure outcome's implementation to represent pressure decay dynamics. The sensitivity analysis shows that implementing the entire pressure outcome to represent the dynamics of pressure decay is significant in estimating permeability. In contrast, variation in porosity, Langmuir pressure, and Langmuir volume are less significant in the permeability estimation, making the pulse pressure decay approach for estimating permeability to be valid.

Modern gas detectors for detection of particles require F-based gases for optimal performance. Recent regulations demand the use of environmentally unfriendly F-based gases to be limited or banned. This review studies properties of potential eco-friendly gas candidate replacements., Four pages, four figures, presented by Giovanna Saviano at MPGD2015, Trieste, Italy

Micro-scale cooling is an efficient and effective cooling technique to achieve the goal of higher heat removal capabilities. The present research focuses to find the physical effects of fluid property variations on flow and thermal development in micro-channel. The effects of temperature-dependent density, viscosity, and thermal conductivity variations on single-phase laminar forced convection are numerically investigated. The problem is especially simulated for hydrodynamically and thermally developing water flow in micro-channel with no-slip, no-temperature jump, and constant wall heat flux boundary conditions. It is observed that the density variation induces radially inward flow due to continuity, which sharpens the axial velocity profile and decreases Nusselt number compared to constant property solution. The axial velocity profile significantly alters due to viscosity variation. This alteration varies along the micro-flow and it induces radially flow due to flow continuity. The reducing rate of Nusselt number for viscosity variation is substantially lower than constant property solution due to a significant flattening effect of the axial velocity profile, which augments the Nusselt number. Thermal-conductivity variation across the flow induces radial conduction, which enhances convection compared to constant property solution. Additionally, the effects of thermophysical fluid property variations on static gauge pressure drop are also investigated.

This is the second part of a study conducted to model the aerothermodynamic impact of suction parameters and gas properties on a multi-stage centrifugal compressor’s performance. A new iterative method has been developed in the first part to derive the equivalent performance at various operating conditions. This approach has been validated to predict the compressor map at different suction pressures and temperatures using the design characteristics as reference values. A further case is included in this paper in order to emphasize the validity of the developed approach to obtain the performance characteristics at various gas compositions. The provided example shows that the performance parameters at different gas mixtures can be predicted to within ±1.34%. Furthermore, the conducted optimization in this paper reveals that the proposed method can be applied for the compressor design evaluation corresponding to the expected variation in suction conditions. Moreover, the examined case study demonstrates the effect of gas properties’ variation on the operating point and aerodynamic stability of the entire compression system. In order to achieve that, a simple approach has been established to assess the contribution of gas properties’ variation to the inefficient and unstable compressor performance based on the available operational data.

[EN] Ideal models provide the simplest way to reproduce internal combustion engine (ICE) cycles, but they usually do not represent with sufficient accuracy the actual behaviour of an ICE. A suitable alternative for research and development applications is provided by zero-dimensional (0D) thermodynamic models. Such models are very useful for predicting the instantaneous pressure and temperature in the combustion chamber, which in turn allows the prediction of engine operation characteristics. However, they use simplifying hypotheses which lead, in some cases, to a lack of accuracy or a limited predictive capability.This paper describes a 0D single-zone thermodynamic model that takes into account the heat transfer to the chamber walls, the blow-by leakage, the fuel injection and engine deformations, along with the instantaneous change in gas properties. Special attention has been paid to the description of the specific sub-models that have been used for the calculation of the energy and mass equations terms. The procedures followed for the estimation of some mechanical and heat transfer parameters and the combustion model fitting are also detailed. After the fitting, the model was validated in different operation points in a 4-cylinder 2-l DI diesel engine, showing a good capability for accurate predictions of engine performance and the gas state in the closed cycle. © 2011 Elsevier Ltd., The authors thank the Universitat Politecnica de Valencia (PAID-06-09) and Generalitat Valenciana (GV/2010/045) for their valuable support to this work and the referees for their worthy comments.

The effects of property variations in single-phase laminar forced micro-convection with constant wall heat flux boundary condition are investigated in this work. The fully-developed flow through micro-sized circular (axisymmetric) geometry is numerically studied using two-dimensional continuum-based conservation equations. The non-dimensional governing equations show significance of momentum transport in radial direction due to mu(T) variation and energy transport by fluid conduction due to k(T) variation. For the case of heated air, variation in C(p)(T) and k(T) causes increase in Nu. This is owing to: (i) reduction in T(w) (T(w)-T(m)), and (delta T/delta r)(w) and (ii) change in delta T(m)/delta z results in axial conduction along the flow. The effects of rho(p,T) and mu(T) variation on convective-flow are indirect and lead to: (i) induce radial velocity which alters u(r) profile significantly and (ii) change in (delta u/delta r)(w) along the flow. It is proposed that the deviation in convection with C(p)(T), k(T) variation is significant through temperature field than rho(p,T), mu(T) variation on velocity field. It is noted that Nu due to variation in properties differ from invariant properties (Nu = 48/11) for low subsonic flow. (C) 2009 Elsevier Masson SAS. .

В статті представлено результати дослідження методів визначення властивостей природного газу, необхідних для побудови систем вимірювання його витрати та кількості. Визначено необхідність розробки методики розрахунку показника адіабати природного газу для тиску газу до 25 МПа на основі спрощеного набору параметрів складу газу. Представлено нову методику визначення показника адіабати, розроблену авторами на основі отриманих аналітичних залежностей для розрахунку псевдокритичної густини природного газу та регресійного рівняння показника адіабати. Виконано перевірку адекватності методики відносно масивів розрахункових значень показника адіабати, отриманих на основі високоточних рівнянь стану газу, а також відносно експериментальних даних швидкості звуку у природному газу. За результатами перевірки встановлено, що методика може бути застосована у мікропроцесорних обчислювачах витрати та кількості природного газу систем обліку. The results of investigation of methods for defining the properties of natural gas in gas flow rate and volume measurement systems are presented in the paper. It is defined that there is a need for development of the technique for calculation of natural gas isentropic exponent at the gas pressure up to 25 MPa based on the simplified set of input data on gas composition. The new technique for defining the isentropic exponent is presented. This technique was developed by the authors based on the derived analytical formulae for calculation of the pseudocritical density of natural gas and based on the derived regression equation for isentropic exponent. The adequacy of the technique is verified based on the arrays of calculated values of isentropic exponent using the high accuracy equations of state for gas as well as based on the experimental values of speed of sound in natural gas. Based on the verification results it was defined that the maximum value of relative error of the technique is not more than ±3.0 % for natural gases with the density at standard conditions of 0.6682 – 0.725 kg/m³ in the range of gas pressure from 0.1 up to 25.0 MPa and gas temperature from 250 up to 320 K. The technique can be applied in the microprocessor calculators of flow rate and volume in natural gas metering systems. В статье представлены результаты исследования методов определения свойств природного газа, необходимых для построения систем измерения его расхода и количества. Выявлена необходимость разработки методики расчета показателя адиабаты газа для давления газа до 25 МПа на основе упрощенного набора параметров состава газа. Представлена новая методика определения показателя адиабаты, разработанная авторами на основе полученных аналитических зависимостей для расчета псевдокритической плотности природного газа и регрессионного уравнения показателя адиабаты. Выполнена проверка адекватности методики относительно массивов расчетных значений показателя адиабаты, полученных на основе высокоточных уравнений состояния газа, а также относительно экспериментальных данных скорости звука в природном газе. По результатам проверки установлено, что предельное значение относительной погрешности методики не превышает 3,0% для природных газов с плотностью при стандартных условиях 0,6682 – 0,725 кг/м³ в диапазоне изменения давления от 0,1 до 25,0 МПа и температуры от 250 до 320 К. Методика может быть применена в микропроцессорных вычислителях расхода и количества природного газа систем учета.

A numerical program is developed to solve two-dimensional continnum-based governing differential equations for liquid flow in axisymmetric circular microchannel geometry. The effects of variable thermal properties in single-phase laminar forced convection with constant wall heat flux boundary conditions are studied. The numerical analysis of fully developed flow behavior investigates the effect of rho(T), mu(T), and k(T) on convection and friction characteristics in isolation and in combination. For the case of heated water, mu(T) variation and k(T) variation increases the Nusselt number due to the following effects: (1) nonnegligible radial convection causes flattening of the axial velocity profile, (2) reduction in wall temperature and axial bulk mean fluid temperature causes significant axial conduction along the flow. The effect of.(T) and mu(T) variation on friction is indirect as follows: the viscosity gradient and shear stress at the wall reduce along the flow; therefore, the Poiseuille number deviates from constant properties solution (Po = 64). The investigations also showed that pressure drop significantly differs at the microscale compared to the macroscale.

International audience; Type Ia supernovae are key tools to study accelerating expansion of the Universe. However despite active research, physics of such objects remain uncertain. To better understand potential systematics we investigate on local host galaxy properties. In this preliminary analysis, we find gas derived quantities such as metallicity and star formation rate compatible to those present in literature. Finally we show a relationship between SALT2 color and x_1 with star formation activity.