Browsing by Subject "Threshold"

Now showing 1 - 6 of 6

Open Access
Alternative futures for the European Union-Turkey accession negotiations
(Metropolitni Univerzita Praha, 2013) Güner, S. Ş.
This work proposes a simple two-period interaction model to study EU-Turkey accession negotiations. Turkey perceives the EU as composed of two distinct groups with respect to its accession: traditional supporters and objectors. Supporters opt for either cooperation or defection in period one while objectors consistently oppose Turkish accession. Turkey reacts to cooperation and defection in the second period under its perceptions of EU support. Future uncertainties concerning Turkey's accession do not prevent supporters' cooperation provided that Turkey becomes successful in economics, political reforms, and foreign policy. Turkey continues to negotiate not because it appreciates supporters' cooperation but because no supporter defects. Supporters become concerned about the future interacting with a failing Turkey. Unlike impatient supporters that are less concerned about the future, patient supporters oppose a failing Turkey's accession. Turkey then extremely appreciates supporters' cooperation but quits accession process that becomes highly costly.
Open Access
Boundaries of gendered space : traditional Turkish house
(2001) Dengiz, Esma Burçin
This work looks at the traditional Turkish house and its two boundaries from the point of gender-space relationship. Acknowledging that gender and space mutually construct each other, this thesis explains both the manifestation of gender difference in the built environment in general, and how the domestic environment in Ottoman architecture and gender mutually construct each other. The two boundaries of the hayat house are analyzed, as regards the body and the gaze of the woman. These are the house-street boundary (street façade and its components, also living areas which are adjacent to the street façade’s interior and exterior) and the house-garden boundary (garden façade and its components, also living areas which are adjacent to the garden façade’s interior and exterior). In this respect, the boundaries of the house are thresholds between the public and the private, the exterior and the interior, therefore they express the binaries that these bring within. By looking at the body and gaze of the woman at these thresholds, the oppositions of these thresholds are illustrated.
Open Access
Characteristic equations for the lasing Modes of infinite periodic chain of quantum wires
(IEEE, 2008-06) Byelobrov, V. O.; Benson, T. M.; Altıntaş, Ayhan; Nosich, A.I.
In this paper, we study the lasing modes of a periodic open optical resonator. The resonator is an infinite chain of active circular cylindrical quantum wires standing in tree space. Characteristic equations for the frequencies and associated linear thresholds of lasing are derived. These quantities are considered as eigenvalues of specific electromagnetic-field problem with "active" imaginary part of the cylinder material's refractive index - Lasing Eigenvalue Problem (LEP). ©2008 IEEE.
Open Access
The effect of context-dependent lightness on contrast detection and identification, and its neural correlates
(2017-10) Karatok, Zahide Pamir
Perceived contrast of a grating varies with its background (or mean) luminance: of the two gratings with the same photometric contrast the one on higher luminance background appears to have higher contrast. On the other hand, context often causes a large perceived difference between equiluminant regions (e.g., simultaneous brightness contrast). Does perceived contrast also vary with contextdependent background lightness even when the luminance remains constant? In this study, the effect of context-dependent lightness on contrast perception was investigated using psychophysical and functional magnetic resonance imaging (fMRI) methods. First, we measured appearance judgments of participants and demonstrated that context-dependent lightness of background in uences the perceived contrast of rectified gratings. Perceived contrast of gratings superimposed on equiluminant but perceptually lighter background is higher compared to ones on perceptually darker backgrounds. However, this pattern is valid only for incremental, not for decremental contrast. Literature indicates a significant difference between visual processing near and above threshold. Also, behaviorally it has been shown that appearance and threshold tasks are mediated by different mechanisms. Therefore, here, we also measured the effect of context-dependent lightness on contrast detection and discrimination thresholds using a 2-IFC procedure. Results indicate that both detection and discrimination thresholds are lower for the gratings superimposed on perceptually lighter backgrounds. Differently from the appearance results, the effect was observed both for incremental and decremental contrast. In an fMRI study, we investigated whether activity in any brain region correlates with background-lightness-dependent contrast perception. Although our stimulus was physically identical, we observed difference in BOLD response within pre-defined region of interests (ROIs) in different visual areas. Both for incremental and decremental contrast, activation, especially in V1, was greater when the grating was superimposed on lighter background for all the contrast levels tested. Variation in V1 activity with varying contrast links better with the detection and discrimination thresholds than the appearance results. Therefore, this study might offer a neural evidence for dissociation between the mechanisms underlying detection (threshold) and identification (appearance) measures. However, the relationship between the threshold and fMRI data does not really agree with the previous findings in literature. These results indicate that the neural activation caused by the detection mechanism may change depending on the absolute or perceived value of the contrast.
Open Access
Lasing modes of infinite periodic chain of quantum wires
(IEEE, 2009-06-07) Byelobrov, V. O.; Benson, T. M.; Sewell, P.; Altıntaş, Ayhan; Nosich, A. I.
In this paper, we study the scattering and eigenvalue problems for a periodic open optical resonator that is an infinite chain of active circular cylindrical quantum wires standing in free space. The scattering problem is solved by the method of partial separation of variables. The eigenvalue problem differs from the first one by the absence of the incident field and presence of "active properties" of cylinders and yields the frequencies and thresholds of lasing. ©2009 IEEE.
Open Access
Microcavity lasers on polymer materials: Boundary integral equation modeling and experiments
(IEEE, 2015-04) Nosich, A.I.; Smotrova, E.I.; Lebental, M.; Sukharevsky Ilya O.; Altıntaş, Ayhan
We consider the modeling and experiments with polymer dye-doped lasers shaped as thin flat cavities, allowing one to consider them as two-dimensional (2-D) active cavities. We focus our modeling on the H-polarized electromagnetic field in a kite-shaped laser. Assuming that the lasing-mode frequency is real-valued, we look for it together with the corresponding threshold value of material gain. Such electromagnetic-field problem is reduced to the Muller set of the boundary integral equations (MBIE), discretization of which yields determinantal equation. Numerical results reveal various types of modes existing in the kite including the perturbed whispering gallery (WG) modes that have the lowest thresholds. Their far-field emission patterns show good agreement with the measurements. © 2015 IEEE.