Search results for "volumetric"
showing 10 items of 175 documents
Study of the column efficiency using gradient elution based on Van Deemter plots.
2018
Performance of chromatographic columns is of major importance in the development of more efficient separation methods. So far, a common practice is to study the column behavior in isocratic elution by modifying the flow rate and fitting the theoretical plate height values versus the mobile phase linear velocity, according to the Van Deemter equation. In this work, an approach is presented to extend the measurement of efficiency to linear gradient elution, where the mean retention factor is kept constant at each assayed flow. This avoids a possible source of uncertainty due to the change in the distribution equilibria profile, and makes the mean interactions with the stationary phase in grad…
Prediction of Peak Shape and Characterization of Column Performance in Liquid Chromatography as a Function of Flow Rate
2015
Traditionally, column performance in liquid chromatography has been studied using information from the elution of probe compounds at different flow rates through van Deemter plots, which relate the column plate height to the linear mobile phase velocity. A more recent approach to characterize columns is the representation of the peak widths (or the right and left peak half-widths) for a set of compounds versus their retention times, which, for isocratic elution, give rise to almost linear plots. In previous work, these plots have been shown to facilitate the prediction of peak profiles (width and asymmetry) with optimization purposes. In this work, a detailed study on the dependence of the …
A discrete-element model for viscoelastic deformation and fracture of glacial ice
2015
a b s t r a c t A discrete-element model was developed to study the behavior of viscoelastic materials that are allowed to fracture. Applicable to many materials, the main objective of this analysis was to develop a model specifically for ice dynamics. A realistic model of glacial ice must include elasticity, brittle fracture and slow viscous deformations. Here the model is described in detail and tested with several benchmark simulations. The model was used to simulate various ice-specific applications with resulting flow rates that were compatible with Glen's law, and produced under fragmentation fragment-size distributions that agreed with the known analytical and experimental results.
Apparent and Real Distribution in GPC (Experiments with PMMA Samples)
1971
Abstract Molecular weight distribution curves obtained by GPC are broadened if concentration and flow rate are fixed in the usual range. Therefore, the apparent nonuniformity U app of the samples is larger than the real non-uniformity U = (Mw/Mn) −1. For a number of fractionated and unfractionated samples of polymethyl methacrylate we determined M n and M w by osmotic, light-scattering, and viscosity measurements. Thus, the real value of U can be compared to U app obtained by GPC at different concentrations and flow rates, υ. The excess nonuniformity U exc is evaluated as function of concentration c, polydispersity, molecular weight, and flow rate. For c = 0 and υ = 0, U exc is not far from…
Assessment of spatial perception for a multi-layer volumetric display: the effect of exocentric and egocentric distance on relative depth judgements
2020
Three-dimensional images on multiple depth layers of the volumetric display provide the physiological depth cues which ensure the high precision of depth judgements at close viewing distances and enhance the user experience. However, the contribution of physiological cues declines with an increase of viewing distance (egocentric distance), and the human spatial perception varies depending on the inter-stimuli distance (exocentric distance). We conducted a psychophysical experiment to test the perception of three-dimensional images rendered on the volumetric display depending on exocentric and egocentric stimuli distance. The constant angular size visual stimuli were displayed on different d…
Looking in Depth: Visual Distance Perception of Stimuli on Volumetric Multi-Planar Display
2018
Ability to distinguish relative location of visual stimuli on a multi-planar display was evaluated within psychophysical experiment in order to figure out the impact of physical distance between stimuli across depth of volumetric data.
Visual Search Performance Depending on Target-Distractor Difference on Volumetric Display and Flat Panel Display
2019
The search items were demonstrated on the volumetric display and flat panel display. In contrast to the correct response rate, the search time and number of interactions were considerably affected by the type of visualization.
Visual search in three-dimensional non-medical images: visual-motor performance of radiologists
2019
The visual search abilities of radiologists are systematically trained due to the specifics of their professional tasks. We investigated whether the visual-motor performance of radiologists, residents and students varied when searching non-medical targets on the volumetric display. As a result, no significant differences were found in the correct response rate among three groups. However, the total number of interactions was considerably higher for the resident radiologists and medical students comparing to the experienced radiologists. Our results suggest that the radiological experience does not interfere with the outcome in the developed visual search task, but may be reflected in motor …
EEG smadzeņu aktivitātes novērtējums trīs-dimensiju attēlu uztverē
2021
Darbs ir uzrakstīts angļu valodā uz 30 lapaspusēm. Tas satur 9 attēlus, 1 tabula un 26 atsauces uz literatūras avotiem. Tā kā trīsdimensiju tehnoloģijas strauji attīstās, pētījumos nepieciešams izvērtēt iekārtas un to mijiedarbību ar cilvēku. Pētījuma mērķis ir novērtēt uzvedības un neirofizioloģiskās iezīmes cilvēkiem, kuri veic uzdevumu izmantojot divas dažādas vizualizācijas: volumetrisko un stereoskopisko. Izmantojot elektroencefalogrāfiju tika reģistrēta smadzeņu aktivitāte un analizēti iegūtie potenciāli un neirālās svārstības. Spēcīgu dziļuma uztveres ietekmi ar abām vizualizācijas tehnoloģijām novēroja tikai vēlīnos uztveres procesos paura garozas reģionā. Turklāt ātrāks reakcijas l…
Numerical and experimental study of hydrostatic displacement machine
2012
This paper presents a simulation tool to determine the structural deflections and corresponding leakage flow in a hydrostatic displacement motor. The simulation tool is applied to a new motor principle that is categorized as an extreme low-speed high-torque motor with dimensions that calls for attention to the volumetric efficiency. To counteract structural deflections the motor is equipped with compensation pressure volumes that may be used to limit the leakage flow across the end faces of the circular rotor. This leakage flow is investigated by solving Reynolds equation for the pressure distribution across both end faces. The fluid pressure is combined with structural calculations in a fl…