Sivil Havacılık Uçak Yaklaşma ve İnişinde GPS ve GLONASS Kullanılarak Bulunan GBAS Düşey Koruma Seviyelerinin Performans Analizi

In this paper, an analysis has been performed to quantify and compare the Vertical Protection Levels (VPLs) performances using GPS (Global Positioning System) and GLONASS (GLObal NAvigation Satellite System - GLObalnaya NAvigatsionnaya Sputnikovaya Sistema) satellite navigation systems for the largest Turkish Airport (Istanbul Ataturk Airport – IST). The VPLs are position error bounds computed at aircraft with ensured high navigation performances for initiation of intendent precision aircraft approach and landing in the Ground Based Augmentation System (GBAS). The GBAS, therefore, is an advanced navigation system and designed to provide civil aircraft user with high navigation performances. All defined algorithms in GBAS are built entirely on the GPS positioning solutions. In this study, an alternative constellation of global satellite navigation system GLONASS is considered and its performances are quantified for potential usability in future. In this respect, IST is selected as an implementation site in analysis. Two approaches have been proposed in the quantification of system availability for the given site; a) full constellation with increased elevation mask, b) two satellite outages as a worst-case scenario in the quantification of system availability. Investigations have shown that the GPS could provide superior performance over GLONASS in compliance with the GBAS availability requirements (i.e., exhibits high performance). However, the outcomes are also promising for the prescribed GBAS VPL performance using an alternative constellation (GLONASS) for supporting a precision approach and landing of an aircraft at the IST.Bu çalışmada, Turkiye’nin en büyük havaalanı (İstanbul Atatürk Havaalanı – IST) için GPS (Global Positioning System) ve GLONASS (GLObal NAvigation Satellite System - GLObalnaya NAvigatsionnaya Sputnikovaya Sistema) uydu navigasyon sistemleri kullanılarak düşey koruma seviyeleri’nin (VPL) performansları hesaplanmış ve karşılaştırılmıştır. VPL’ler, konum sınırlama değerleri olup yüksek güvenilirlikle uçak’ta hesaplanır ve GBAS’in (Yer Temelli Genişleme Sistemi) uçak hassas yaklaşma ve inişinde kullanılır. Bundan dolayı, GBAS sivil uçaklara yüksek navigasyon performansı sunan ileri bir navigasyon sistemi olarak tasarlanmıştır. GBAS’in bütün algoritmaları GPS konum belirleme çözümlerine dayanmaktadır. Bu çalışmada, alternatif bir uydu navigasyon sistemi olan GLONASS’ın gelecekte kullanılabilirliği dikkate alınmış olup performansı hesaplanmıştır. Bu anlamda, IST bir uygulama sahası olarak seçilmiştir. Seçilen uygulama alanı için performans hesaplamada iki yaklaşım kullanılmıştır; a) tam uydu sistemleri ile artan yükselti açısı değişimi, b) kötü senaryo olarak iki uydunun devre dışı bırakılması olarak hesaplamalarda kullanılmıştır. Bulgular GPS’in GLONASS’tan daha iyi GBAS şartlarını sağlayan yüksek bir performans sergilediğini göstermiştir. Öteyandan, alternatif bir uydu sistemi olan GLONASS’ın da belirlenen GBAS VPL değerlerine uyumlu olabileceği ve uçak hassas yaklaşma ve inişte IST için kullanılabileceği kanıtlanmıştır

Policy transfer from advanced to less-advanced institutional environments: labour market orientations of US MNEs in Turkey

Cataloged from PDF version of article.The extant research on policy transfer insufficiently addresses two issues. First, transfer to less-advanced countries. Second, micro-institutional pressures on subsidiaries, particularly the role of local partners in joint ventures (JVs). This study investigates the transfer of labour market orientations by American multinational enterprises to their Turkish subsidiaries by focusing on the influences of macro- and micro-institutional factors when the ‘transferor’ is an advanced and ‘transferee’ is a less-advanced economy, ‘dominance effects’, and the role of local JV partners. Case study findings provide evidence for ‘smooth’ transfer of the policy. This uncommon finding is discussed as a result of ‘ideal combination’ of ‘encouraging pressures’ at the macro- and micro-institutional levels, including role of local JV partners and the nature of the policy transferred

Letters lost:capturing appearance in crowded peripheral vision reveals a new kind of masking

Peripheral vision is strongly limited by crowding, the deleterious influence of flanking items on target perception. Distinguishing what is seen from what is merely inferred in crowding is difficult because task demands and prior knowledge may influence observers' reports. Here, we used a standard identification task in which participants were susceptible to these influences, and to minimize them, we used a free-report-and-drawing paradigm. Three letters were presented in the periphery. In Experiment 1, 10 participants were asked to identify the central target letter. In Experiment 2, 25 participants freely named and drew what they saw. When three identical letters were presented, performance was almost perfect in Experiment 1, but it was very poor in Experiment 2, in which most participants reported only two letters. Our study reveals limitations of standard crowding paradigms and uncovers a hitherto unrecognized effect that we call redundancy masking

MEMAHAMI PELAYANAN PERPOSAN NASIONAL BERBASIS TEKNOLOGI INFORMASI (TI)

Tulisan ini ingin memasyarakatkan ilmu pengetahuan dan teknologi (iptek) tentang pelayanan perposan nasional berbasis teknologi informasi (TI). Dengan dikembangkannya peranan TI setidaknya dapat meningkatkan mutu dan kapasitas pelayanan yang selama ini dilakukan secara manual. Penerapannya sudah dilakukan secara bertahap di sejumlah wilayah Indonesia, tentunya berdasarkan kemampuan dan dukungan pemerintah daerah dalam memfasilitasi infrastrukturnya. Penerapan TI tersebut, diharapkan dapat meningkatkan pengetahuan masyarakat terhadap kepentingan berinteraksi dengan atau melalui media pendukung komunikasi, terutama dalam menjalankan roda bisnis ataupun korespondensi antar individu. Selain itu, ketepatan-kecepatan waktu penyampaian sural maupun dokumen lain dalam bentuk elektronik melalui pemanfaatan TI, terutama bagi jangkauan layanan di daerah. Berbagai layanan berbasis TI telah ditampilkan, misalnya sural elektronik, transfer keuangan elektronik dan seterusnya. Oleh karenanya, dengan membaca dan memahami pelayanan perposan berbasis TI akan membuka cakrawala dalam duniaperposan di Indonesia

Multidimensional feature interactions in visual crowding: When configural cues eliminate the polarity advantage.

Crowding occurs when surrounding objects (flankers) impair target perception. A key property of crowding is the weaker interference when target and flankers strongly differ on a given dimension. For instance, identification of a target letter is usually superior with flankers of opposite versus the same contrast polarity as the target (the "polarity advantage"). High performance when target-flanker similarity is low has been attributed to the ungrouping of target and flankers. Here, we show that configural cues can override the usual advantage of low target-flanker similarity, and strong target-flanker grouping can reduce - instead of exacerbate - crowding. In Experiment 1, observers were presented with line triplets in the periphery and reported the tilt (left or right) of the central line. Target and flankers had the same (uniform condition) or opposite contrast polarity (alternating condition). Flanker configurations were either upright (||), unidirectionally tilted (\\ or //), or bidirectionally tilted (\/ or /\). Upright flankers yielded stronger crowding than unidirectional flankers, and weaker crowding than bidirectional flankers. Importantly, our results revealed a clear interaction between contrast polarity and flanker configuration. Triplets with upright and bidirectional flankers, but not unidirectional flankers, showed the polarity advantage. In Experiments 2 and 3, we showed that emergent features and redundancy masking (i.e. the reduction of the number of perceived items in repeating configurations) made it easier to discriminate between uniform triplets when flanker tilts were unidirectional (but not when bidirectional). We propose that the spatial configurations of uniform triplets with unidirectional flankers provided sufficient task-relevant information to enable a similar performance as with alternating triplets: strong-target flanker grouping alleviated crowding. We suggest that features which modulate crowding strength can interact non-additively, limiting the validity of typical crowding rules to contexts where only single, independent dimensions determine the effects of target-flanker similarity

What Line Drawings Reveal About the Visual Brain

Scenes in the real world carry large amounts of information about color, texture, shading, illumination, and occlusion giving rise to our perception of a rich and detailed environment. In contrast, line drawings have only a sparse subset of scene contours. Nevertheless, they also trigger vivid three-dimensional impressions despite having no equivalent in the natural world. Here, we ask why line drawings work. We see that they exploit the underlying neural codes of vision and they also show that artists’ intuitions go well beyond the understanding of vision found in current neurosciences and computer vision

High confidence and low accuracy in redundancy masking.

Visual scenes typically contain redundant information. One mechanism by which the visual system compresses such redundancies is 'redundancy masking' - the reduction of the perceived number of items in repeating patterns. For example, when presented with three lines in the periphery, observers frequently report only two lines. Redundancy masking is strong in radial arrangements and absent in tangential arrangements. Previous studies suggested that redundancy-masked percepts predominate in stimuli susceptible to redundancy masking. Here, we investigated whether strong redundancy masking is associated with high confidence in perceptual judgements. Observers viewed three to seven radially or tangentially arranged lines at 10° eccentricity. They first indicated the number of lines, and then rated their confidence in their responses. As expected, redundancy masking was strong in radial arrangements and weak in tangential arrangements. Importantly, with radial arrangements, observers were more confident in their responses when redundancy masking occurred (i.e., lower number of lines reported) than when it did not occur (i.e., correct number of lines reported). Hence, observers reported higher confidence for erroneous than for correct judgments. In contrast, with tangential arrangements, observers were similarly confident in their responses whether redundancy masking occurred or not. The inversion of confidence in the radial condition (higher confidence when accuracy was low and lower confidence when accuracy was high) suggests that redundancy-masked appearance trumps 'veridical' perception. The often-reported richness of visual consciousness may partly be due to overconfidence in erroneous judgments in visual scenes that are subject to redundancy masking

Foveal target repetitions reduce crowding

Crowding is the limitation of peripheral vision by clutter. Objects that are easily identified when presented in isolation are hard to identify when presented flanked by similar close-by objects. It is often assumed that the signal of a crowded target is irretrievably lost because it is combined with the signals of the flankers. Here, we asked whether a target signal can be enhanced (or retrieved) by items presented far outside the crowding region. We investigated whether remote items matching a peripheral, crowded target enhanced discrimination compared to remote items not matching the target. In Experiment 1, we presented the remote item at different locations in the visual field and found that, when presented in the fovea, a matching remote item improved target discrimination compared to a nonmatching remote item. In Experiment 2, we varied stimulus onset asynchronies between target and remote items and found a strong effect when the remote item was presented simultaneously with the target. The effect diminished (or was absent) with increasing temporal separation. In Experiment 3, we asked whether semantic knowledge of a target was sufficient to improve target discrimination and found that this was not the case. We conclude that crowded target signals are not irretrievably lost. Rather, their accurate recognition is facilitated in the presence of remote items that match the target. We suggest that long-range grouping mechanisms underlie this "uncrowding" effect