The determination of internal gas flows by a transient numerical technique

1971 ◽  
Author(s):  
R. SERRA
Keyword(s):  
Numerical Technique ◽  
Gas Flows

Determination of Internal Gas Flows by a Transient Numerical Technique

AIAA Journal ◽  
1972 ◽  
Vol 10 (5) ◽  
pp. 603-611 ◽  
Author(s):  
RAYMOND A. SERRA
Keyword(s):  
Numerical Technique ◽  
Gas Flows

A NEW TECHNIQUE ESTIMATING LOCATION OF MEAN JOINT CENTERS OF ROTATION WITH ASSOCIATED DISPERSIONS AND ASSESSING TO FUNCTIONAL COORDINATE SYSTEM OF MOVING LIMB SEGMENTS

2006 ◽  
Vol 06 (04) ◽  
pp. 373-384
Author(s):  
ERIC BERTHONNAUD ◽  
JOANNÈS DIMNET
Keyword(s):  
Numerical Technique ◽  
New Technique ◽  
Helical Axis ◽  
Joint Movement ◽  
Time Step ◽  
Data Set ◽  
Minimization Procedure ◽  
A New Technique ◽  
Joint Center

Joint centers are obtained from data treatment of a set of markers placed on the skin of moving limb segments. Finite helical axis (FHA) parameters are calculated between time step increments. Artifacts associated with nonrigid body movements of markers entail ill-determination of FHA parameters. Mean centers of rotation may be calculated over the whole movement, when human articulations are likened to spherical joints. They are obtained using numerical technique, defining point with minimal amplitude, during joint movement. A new technique is presented. Hip, knee, and ankle mean centers of rotation are calculated. Their locations depend on the application of two constraints. The joint center must be located next to the estimated geometric joint center. The geometric joint center may migrate inside a cube of possible location. This cube of error is located with respect to the marker coordinate systems of the two limb segments adjacent to the joint. Its position depends on the joint and the patient height, and is obtained from a stereoradiographic study with specimen. The mean position of joint center and corresponding dispersion are obtained through a minimization procedure. The location of mean joint center is compared with the position of FHA calculated between different sequential steps: time sequential step, and rotation sequential step where a minimal rotation amplitude is imposed between two joint positions. Sticks are drawn connecting adjacent mean centers. The animation of stick diagrams allows clinical users to estimate the displacements of long bones (femur and tibia) from the whole data set.

A Solution of a Mixed Boundary Value Problem—Acoustic Pressure Fields in a Finite Container

1972 ◽  
Vol 94 (3) ◽  
pp. 643-648
Author(s):  
L. P. Solomon ◽  
N. Schryer
Keyword(s):  
Boundary Conditions ◽  
Pressure Field ◽  
Mixed Boundary ◽  
Numerical Technique ◽  
Boundary Value ◽  
Strong Function ◽  
Pressure Fields ◽  
End Conditions ◽  
Finite Domains

This paper investigates the effects of different boundary conditions in calculating pressure fields corresponding to incipient cavitation. We have utilized a technique which allows us to obtain a numerical solution of this problem for various frequencies and geometrical configurations. Our results provide evidence that determination of the pressure field is not only a function of depth but also a strong function of radius and whether or not the end conditions involve the use of a baffle. We have found that, particularly at the higher frequencies, the changing of the boundary conditions will cause large variations and differences in the pressure field. The numerical technique provides a method which allows the calculation of mixed boundary value problems associated with the reduced wave equation in finite domains. The technique specifies known error bounds. However, the distribution of errors over the domain is unknown.

An optimized protocol for high precision measurement of Hg isotopic compositions in samples with low concentrations of Hg using MC-ICP-MS

2018 ◽  
Vol 33 (11) ◽  
pp. 1932-1940 ◽  
Author(s):  
Hongyan Geng ◽  
Runsheng Yin ◽  
Xiangdong Li
Keyword(s):  
High Precision ◽  
Precision Measurement ◽  
Direct Determination ◽  
Gas Flows ◽  
High Precision Measurement ◽  
Isotopic Compositions ◽  
Low Concentrations ◽  
Optimized Protocol ◽  
Icp Ms

Optimized gas flows achieved the direct determination of Hg isotopic compositions of 0.1 ng mL−1 solutions.

scholarly journals Applications of Accurate Isentropic Exponent Determination for Fuel Gas Measurement

1995 ◽  
Author(s):  
David J. Pack ◽  
Terry J. Edwards ◽  
Derek Fawcett
Keyword(s):  
Natural Gas ◽  
Gas Flow ◽  
Precise Measurement ◽  
Gas Flows ◽  
Fuel Gas ◽  
Isentropic Exponent ◽  
Natural Gas Transmission ◽  
Gas Measurement ◽  
Cost Penalty

This paper discusses the determination and application of the isentropic exponent to the various thermodynamic processes found in a high pressure natural gas transmission system. Increasing demands for more precise measurement of natural gas, coupled with the need for greater efficiency and accountability of transportation and processing operations had led to our research and development efforts into the more precise measurement of gas flow, and the determination of gas thermodynamic properties including isentropic exponent. The isentropic exponent has many applications, some of which include: • the determination of the expansion factor ϵ, for calcuation of flow using an orifice or venturi type meter; • the volumetric efficiency in a reciprocating compressor; • the determination of the compression head for a centrigual compressor; • the engine power required for the set given conditions for gas compressor; • the calculation of discharge temperatures for compressors; and • the direct measurement of gas density. As can be appreciated, the application of an incorrect value for the isentropic exponent represents an error in the parameter determined. For large volume gas flows, this can translate into a significant cost penalty.

Determination of growth parameters for atomic layer epitaxy using reflectance difference spectroscopy

1996 ◽  
Vol 74 (S1) ◽  
pp. 85-88 ◽  
Author(s):  
R. Arès ◽  
C. A. Tran ◽  
S. P. Watkins
Keyword(s):  
Growth Rate ◽  
Growth Parameters ◽  
Atomic Layer ◽  
Atomic Layer Epitaxy ◽  
Gas Flows ◽  
Difference Spectroscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Reflectance Difference Spectroscopy

Reflectance difference spectroscopy (RDS) has been used to monitor the anisotropy of the surface of InAs and GaAs grown by atomic layer epitaxy (ALE). Saturation of the RDS signal is observed when the surface is fully covered with one monolayer of the impinging surface species. This property is used to optimize the growth interruptions for the ALE cycle. Good correlation of the RDS saturation is observed with growth-rate measurements obtained by X-ray diffraction (XRD). When exposure times are sufficiently long for saturation to be observed in the RDS signal, a growth rate of one monolayer per cycle (1 ML/cycle) is achieved. In principle all the different growth parameters such as exposure and purge times as well as gas flows can be determined in a few cycles performed on a single substrate. Without RDS the same results would require several growth runs and time consuming X-ray characterization.

scholarly journals Building Planets with Dusty Gas

2004 ◽  
Vol 213 ◽  
pp. 231-234
Author(s):  
S. T. Maddison ◽  
R. J. Humble ◽  
J. R. Murray
Keyword(s):  
Solar Nebula ◽  
Numerical Technique ◽  
Dynamical Evolution ◽  
Gas Flows ◽  
Dusty Gas ◽  
Dust Distribution ◽  
Self Gravity ◽  
Gas Medium

We have developed a new numerical technique for simulating dusty-gas flows. Our code incorporates gas hydrodynamics, self-gravity and dust drag to follow the dynamical evolution of a dusty-gas medium. We have incorporated several descriptions for the drag between gas and dust phases and can model flows with submillimetre, centimetre and metre size “dust”. We present calculations run on the APAC1 supercomputer following the evolution of the dust distribution in the pre-solar nebula.

Sign in / Sign up

Export Citation Format

Share Document