scholarly journals Visual illusion of the change of the size of architectural and urban objects observed upon a change of the observer's distance: Parameters that influence it phenomenologically

Spatium ◽  
2010 ◽  
pp. 38-46
Author(s):  
Djordje Djordjevic ◽  
Gordana Vujic
Keyword(s):  
Angular Size ◽  
Target Volume ◽  
Target Object ◽  
Linear Perspective ◽  
Dynamic Relationship ◽  
Visual Phenomenon ◽  
Visual Phenomena ◽  
Perceptual Aspect ◽  
Perceptual Sense ◽  
Expected Increase

This paper explores the visual phenomena of a seeming change of the target-object's size (as a focus of concrete visual perception) in the function of an observer's motion so that it 'seems' contrary to the law of linear perspective (in the sense of an expected increase of the target volume/monumentality - by getting closer or a decrease - by getting farther away). This phenomenon is described in a geometrical and perceptual aspect; the result of this comprehensive approach led to identify parameters that determine it phenomenologically. It was established that the explored visual phenomenon is a specific 'size illusion', i.e. an 'angular size illusion' that occurs when influenced by factors of the perceptual kind - activated by a specific dynamic relationship (on a visual plan) between the target object and its surrounding competitive objects, as an observer moves. By understanding the character of this phenomenon (both in a geometrical and perceptual sense), it is possible to apply the acquired knowledge in practice - in programming the visual effects to be obtained (such as to visually optimize or minimize the monumentality of targeted objects) in all architectural and urban fields (planning, designing and reconstruction).

The Cone Model: Recognizing gaze uncertainty in virtual environments

2020 ◽  
Vol 2020 (9) ◽  
pp. 288-1-288-8 ◽  
Author(s):  
Anjali K. Jogeshwar ◽  
Gabriel J. Diaz ◽  
Susan P. Farnand ◽  
Jeff B. Pelz
Keyword(s):  
Virtual Environment ◽  
Angular Size ◽  
Target Object ◽  
Angular Distance ◽  
Gaze Direction ◽  
Calibration Error ◽  
Gaze Behavior ◽  
The Gaze ◽  
Head Mounted Display ◽  
Cone Model

Eye tracking is used by psychologists, neurologists, vision researchers, and many others to understand the nuances of the human visual system, and to provide insight into a person’s allocation of attention across the visual environment. When tracking the gaze behavior of an observer immersed in a virtual environment displayed on a head-mounted display, estimated gaze direction is encoded as a three-dimensional vector extending from the estimated location of the eyes into the 3D virtual environment. Additional computation is required to detect the target object at which gaze was directed. These methods must be robust to calibration error or eye tracker noise, which may cause the gaze vector to miss the target object and hit an incorrect object at a different distance. Thus, the straightforward solution involving a single vector-to-object collision could be inaccurate in indicating object gaze. More involved metrics that rely upon an estimation of the angular distance from the ray to the center of the object must account for an object’s angular size based on distance, or irregularly shaped edges - information that is not made readily available by popular game engines (e.g. Unity© /Unreal© ) or rendering pipelines (OpenGL). The approach presented here avoids this limitation by projecting many rays distributed across an angular space that is centered upon the estimated gaze direction.

Angular size of OH emission regions

1967 ◽  
Vol 31 ◽  
pp. 71-72
Author(s):  
B. F. Burke ◽  
P. P. Crowther ◽  
J. M. Moran ◽  
A. E. E. Rogers ◽  
J. A. Ball ◽  
...  
Keyword(s):  
Angular Size ◽  
Emission Sources ◽  
Ngc 6334

Interferometry gives effective diameters less than 20″ for the OH emission sources in W3and Sgr B2. The sources in W49and NGC 6334 contain two or more components, some of which are smaller than 25″.

Distance to SN 1987A and the LMC

1999 ◽  
Vol 190 ◽  
pp. 549-554
Author(s):  
Nino Panagia
Keyword(s):  
Angular Size ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Distance Modulus ◽  
Absolute Size ◽  
Sn 1987A

Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ringRabs= (6.23 ± 0.08) x 1017cm and an angular sizeR″ = 808 ± 17 mas, which give a distance to the supernovad(SN1987A) = 51.4 ± 1.2 kpc and a distance modulusm–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to bed(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus ofm–M(LMC) = 18.58±0.05.

Detection and Characterization of earth-like Planets

1997 ◽  
Vol 161 ◽  
pp. 299-311 ◽  
Author(s):  
Jean Marie Mariotti ◽  
Alain Léger ◽  
Bertrand Mennesson ◽  
Marc Ollivier
Keyword(s):  
Direct Detection ◽  
Contrast Ratio ◽  
Angular Size ◽  
Physical Nature ◽  
Major Axis ◽  
Infrared Emission ◽  
Space Technology ◽  
Semi Major Axis ◽  
Earth Like Planets ◽  
Visible Wavelengths

AbstractIndirect methods of detection of exo-planets (by radial velocity, astrometry, occultations,...) have revealed recently the first cases of exo-planets, and will in the near future expand our knowledge of these systems. They will provide statistical informations on the dynamical parameters: semi-major axis, eccentricities, inclinations,... But the physical nature of these planets will remain mostly unknown. Only for the larger ones (exo-Jupiters), an estimate of the mass will be accessible. To characterize in more details Earth-like exo-planets, direct detection (i.e., direct observation of photons from the planet) is required. This is a much more challenging observational program. The exo-planets are extremely faint with respect to their star: the contrast ratio is about 10−10at visible wavelengths. Also the angular size of the apparent orbit is small, typically 0.1 second of arc. While the first point calls for observations in the infrared (where the contrast goes up to 10−7) and with a coronograph, the latter implies using an interferometer. Several space projects combining these techniques have been recently proposed. They aim at surveying a few hundreds of nearby single solar-like stars in search for Earth-like planets, and at performing a low resolution spectroscopic analysis of their infrared emission in order to reveal the presence in the atmosphere of the planet of CO H2O and O3. The latter is a good tracer of the presence of oxygen which could be, like on our Earth, released by biological activity. Although extremely ambitious, these projects could be realized using space technology either already available or in development for others missions. They could be built and launched during the first decades on the next century.

Radiation oncology and functional imaging

2005 ◽  
Vol 44 (S 01) ◽  
pp. S38-S40
Author(s):  
Th. Herrmann
Keyword(s):  
Functional Imaging ◽  
Radiation Oncology ◽  
Bronchogenic Carcinoma ◽  
Brain Tumours ◽  
Tumour Volume ◽  
Target Volume ◽  
Head And Neck Tumours ◽  
Pet Ct ◽  
Surrounding Healthy Tissue ◽  
Prostate Carcinomas

Summary:PET/CT imaging is most likely to be of use in radiation oncology with patients who have poorly defined target volume areas, e.g. brain tumours, bronchogenic carcinoma, and cases of miscellaneous geographical miss. Other tumours that call for dose escalated radiotherapy, such as head and neck tumours, bronchogenic carcinoma, and prostate carcinomas may further benefit from an accurate delineation of the metabolically active tumour volume and its differentiation from surrounding healthy tissue, or tumour atelectasis.

Influence of Radioiodine Therapy on Urinary Iodine Excretion

1998 ◽  
Vol 37 (03) ◽  
pp. 107-112 ◽  
Author(s):  
I. Lauer ◽  
M. Bähre ◽  
E. Richter ◽  
B. Melier
Keyword(s):  
Time Course ◽  
Radioiodine Therapy ◽  
Urinary Iodine ◽  
Target Volume ◽  
Urinary Iodine Excretion ◽  
Urinary Creatinine ◽  
Iodine Excretion ◽  
Kinetics Of ◽  
Persistent Elevation ◽  
Benign Thyroid

Summary Aim: In 214 patients with benign thyroid diseases the time-course of urinary iodine excretion (UIE) was investigated in order to identify changes after radioiodine therapy (RITh). Method: UIE was measured photometrically (cerium-arsenite method) and related to urinary creatinine on the first and last day of the radioiodine test and then three days, seven days, four weeks, and six months after 1311 administration. Results: As compared with the level found immediately before radioiodine therapy, median UIE had almost doubled four weeks after therapy and was still significantly elevated six months after therapy. This increase correlated significantly with the target volume as measured by scintigraphy and sonography. Conclusions: The persistent elevation of UIE for months after RITh is a measure of treatment-induced damage to thyrocytes. Therefore, in view of the unfavourable kinetics of iodine that follow it, RITh should if possible be given via a single-dose regime.

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