A review and comparative study of upwind biased schemes for compressible flow computation. Part I: 1—D first—order schemes

2000 ◽  
Vol 7 (1) ◽  
pp. 19-55 ◽  
Author(s):  
P. R. M. Lyra ◽  
K. Morgan
Keyword(s):  
Comparative Study ◽  
Compressible Flow ◽  
Flow Computation ◽  
First Order

scholarly journals Comparative Study of Chemical Stability of Two H1Antihistaminic Drugs, Terfenadine and ItsIn VivoMetabolite Fexofenadine, Using LC-UV Methods

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Anna Gumieniczek ◽  
Anna Berecka-Rycerz ◽  
Rafał Pietraś ◽  
Izabela Kozak ◽  
Karolina Lejwoda ◽  
...  
Keyword(s):  
Comparative Study ◽  
Chemical Stability ◽  
First Order ◽  
First Order Kinetics ◽  
Kinetics Of Degradation ◽  
Effects Of Temperature ◽  
High Doses ◽  
Antihistaminic Drugs ◽  
Kinetics Of

A comparative study of chemical stability of terfenadine (TER) and itsin vivometabolite fexofenadine (FEX) was performed. Both TER and FEX were subjected to high temperature at different pH and UV/VIS light at different pH and then quantitatively analyzed using new validated LC-UV methods. These methods were used to monitor the degradation processes and to determine the kinetics of degradation for both the compounds. As far as the effects of temperature and pH were concerned, FEX occurred more sensitive to degradation than TER. As far as the effects of UV/VIS light and pH were concerned, the both drugs were similarly sensitive to high doses of light. Using all stress conditions, the processes of degradation of TER and FEX followed the first-order kinetics. The results obtained for these two antihistaminic drugs could be helpful in developing their new derivatives with higher activity and stability at the same time.

District Technology Leadership Then and Now: A Comparative Study of District Technology Leadership From 2001 to 2014

2018 ◽  
Vol 54 (4) ◽  
pp. 589-616 ◽  
Author(s):  
Jayson W. Richardson ◽  
William L. Sterrett
Keyword(s):  
Comparative Study ◽  
Research Methods ◽  
Teaching And Learning ◽  
Digital Technologies ◽  
Leadership Preparation ◽  
Technology Leadership ◽  
District Level ◽  
First Order ◽  
District Level Leaders ◽  
Technology Initiatives

Purpose: This article focuses on district superintendents who were recognized as eSchoolNews Tech-Savvy Superintendents. Research Methods: Using interviews, this study compares data from superintendents who won this award between 2001 and 2010 in contrast to those who won the award between 2011 and 2014. The focus of the study is on understanding how discussions of challenges and successes within this population have shifted over nearly 15 years. Findings: A key finding is that these district-level leaders have shifted away from first-order changes of implementing technology initiatives and toward second-order changes of supporting teaching and learning that is supported with modern digital technologies. Implications: Recommendations are made for leadership preparation as well as lines of inquiry.

Modified Governing Equations for Unsteady Compressible Flow in Ducts

1978 ◽  
Vol 45 (4) ◽  
pp. 723-726 ◽  
Author(s):  
A. Celmin¸sˇ
Keyword(s):  
Compressible Flow ◽  
Power Law ◽  
Unsteady Flows ◽  
Tube Flow ◽  
Axially Symmetric ◽  
Governing Equations ◽  
Flow Equations ◽  
Circular Tubes ◽  
First Order ◽  
General Conservation

Conventional governing equations for unsteady compressible tube flows are reviewed and it is shown that they neglect first-order terms which can have significant magnitudes. The derivation of correct tube flow equations from general conservation laws is demonstrated for the case of axially symmetric straight tubes. The traditionally neglected terms are computed explicitly for unsteady flows with power law profiles through circular tubes.

scholarly journals The effect of core size on the speed of compressible hollow vortex streets

2017 ◽  
Vol 836 ◽  
pp. 797-827 ◽  
Author(s):  
Darren G. Crowdy ◽  
Vikas S. Krishnamurthy
Keyword(s):  
Mach Number ◽  
Compressible Flow ◽  
Vortex Core ◽  
Perturbation Expansion ◽  
Core Size ◽  
Flow Equations ◽  
Stable Case ◽  
First Order ◽  
Aspect Ratios ◽  
Vortex Streets

The effect of weak compressibility on the speed of steadily translating staggered vortex streets of hollow vortices in isentropic subsonic flow is studied. A small-Mach-number perturbation expansion about the incompressible solutions for staggered streets of hollow vortices found recently by Crowdy & Green (Phys. Fluids, 2011, vol. 23, 126602) is carried out; the latter solutions provide a desingularization of the classical point vortex streets of von Kármán. The first-order compressible flow correction is calculated. We employ a novel scheme based on a complex variable formulation of the compressible flow equations (the Imai–Lamla method) combined with conformal mapping theory to track the vortex shape in this free boundary problem. The analysis to find the perturbed streamfunction and compressible vortex shapes is greatly facilitated by exploiting a calculus based on use of the Schottky–Klein prime function of a conformally equivalent parametric annulus. It is found that, for a vortex street of specified aspect ratio comprising vortices of specified circulation, the vortex core size is a key determinant of whether compressibility increases or decreases the steady propagation speed (relative to the incompressible street with the same parameters) and that both eventualities are possible. We focus attention on streets with aspect ratios around 0.28, which is close to the neutrally stable case for incompressible flow, and find that a critical vortex core size exists at which compressibility does not affect the speed of the street at first order in the (squared) Mach number. Streets comprising vortices with core size below the critical value speed up due to compressibility; larger vortices slow down.

The Hybrid Isothermal Air Lubricated Journal Bearing

1979 ◽  
Vol 101 (4) ◽  
pp. 444-450 ◽  
Author(s):  
V. Kamala
Keyword(s):  
Comparative Study ◽  
Carrying Capacity ◽  
Journal Bearing ◽  
Order Perturbation ◽  
Load Carrying Capacity ◽  
Eccentricity Ratio ◽  
Small Eccentricity ◽  
First Order ◽  
Load Carrying ◽  
First Order Perturbation

This paper analyzes the load-carrying capacity of the hybrid air lubricated journal bearing. Assuming a small eccentricity ratio, a first order perturbation solution is obtained. The air is fed to the bearing through inherent restrictor with feeding holes distributed around the circumference in one, two, and three feeding planes (Fig. 1). The number of feeding holes in each plane is sufficiently large to permit the feeding planes being treated as the line sources. The results are given for the load-carrying capacity and the attitude angle. A comparative study is made of the three types of gas feeding arrangements.

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