Thermal equilibration of samples for neutron scattering

2013 ◽  
Vol 46 (1) ◽  
pp. 279-285 ◽  
Author(s):  
Tobias K. Herman ◽  
Sarah C. Parks ◽  
Julia Scherschligt
Keyword(s):  
Relaxation Time ◽  
Neutron Scattering ◽  
Material Properties ◽  
Thermal Relaxation ◽  
Sample Cell ◽  
Time Constants ◽  
Thermal Equilibration ◽  
Temperature Relaxation ◽  
Relaxation Time Constants ◽  
Selection Of

Temperature relaxation and equilibration of samples for neutron scattering was investigated in a selection of samples and sample cells within the range of 5–300 K. A simple model was developed that relates thermal relaxation time constants to material properties of the sample and sample cell. This model should facilitate extension of this study to prediction of thermal behavior in other systems.

scholarly journals Virtual Breast Quasi-static Elastography (VBQE)

2016 ◽  
Vol 39 (2) ◽  
pp. 108-125 ◽  
Author(s):  
David Rosen ◽  
Yu Wang ◽  
Jingfeng Jiang
Keyword(s):  
Relaxation Time ◽  
Three Dimensional ◽  
Primary Objective ◽  
Transfer Efficiency ◽  
External Compression ◽  
Time Resolved ◽  
Time Constants ◽  
Strain Measurements ◽  
Relaxation Time Constants

Viscoelasticity Imaging (VEI) has been proposed to measure relaxation time constants for characterization of in vivo breast lesions. In this technique, an external compression force on the tissue being imaged is maintained for a fixed period of time to induce strain creep. A sequence of ultrasound echo signals is then utilized to generate time-resolved strain measurements. Relaxation time constants can be obtained by fitting local time-resolved strain measurements to a viscoelastic tissue model (e.g., a modified Kevin-Voigt model). In this study, our primary objective is to quantitatively evaluate the contrast transfer efficiency (CTE) of VEI, which contains useful information regarding image interpretations. Using an open-source simulator for virtual breast quasi-static elastography (VBQE), we conducted a case study of contrast transfer efficiency of VEI. In multiple three-dimensional (3D) numerical breast phantoms containing various degrees of heterogeneity, finite element (FE) simulations in conjunction with quasi-linear viscoelastic constitutive tissue models were performed to mimic data acquisition of VEI under freehand scanning. Our results suggested that there were losses in CTE, and the losses could be as high as −18 dB. FE results also qualitatively corroborated clinical observations, for example, artifacts around tissue interfaces.

Interpretation of relaxation time constants for amorphous pharmaceutical systems

2000 ◽  
Vol 89 (3) ◽  
pp. 417 ◽  
Author(s):  
Sheri L. Shamblin ◽  
Bruno C. Hancock ◽  
Yves Dupuis ◽  
Michael J. Pikal
Keyword(s):  
Relaxation Time ◽  
Time Constants ◽  
Relaxation Time Constants

Effects of Thermomechanical Coupling and Relaxation Times on Wave Spectrum in Dynamic Theory of Generalized Thermoelasticity

1998 ◽  
Vol 65 (3) ◽  
pp. 605-613 ◽  
Author(s):  
C. S. Suh ◽  
C. P. Burger
Keyword(s):  
Relaxation Time ◽  
Wave Spectrum ◽  
Relaxation Times ◽  
Thermal Relaxation ◽  
Generalized Thermoelasticity ◽  
Thermomechanical Coupling ◽  
Order Of Magnitude ◽  
Relaxation Time Constants ◽  
Thermoelastic Waves ◽  
Insight Into

A spectral study is performed to gain insight into the effects of relaxation times and thermomechanical coupling on dynamic thermoe Iastic responses in generalized thermoelasticity. The hyperbolic thermoelastic theories of Lord and Schulman (LS) and Green and Lindsay (GL) are selected for the study. A generalized characteristic equation is derived to investigate dispersion behavior of thermoelastic waves as functions of thermomechanical coupling and relaxation time constants. Thermomechanical coupling is found to impose a significant influence on phase velocities. The GL model implicitly indicates that the order of magnitude of the thermomechanical relaxation time can never be greater than that of thermal relaxation time.

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