Graduate School of Engineering and Science

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  • ItemOpen Access
    Macroporous Surgical Mesh from a Natural Cocoon Composite
    (2022-04-25) Chen, Y.-M.; Zang, L.-S.; Koc-Bilican, B.; Bilican, Ismail; Holland, C.; Cansaran-Duman, D.; Karaduman, T.; Çolak, A.; Bayır, Y.; Halici, Z.; Ozmen, S.; Ali, A.; Labidi, J.; Elbuken, Caglar; Kaya, M.; Bilican, Ismail; Elbuken, Caglar
    Recently, traditional polymer-based surgical meshes have drawn unwanted attention as a result of host tissue complications arising from infection, biocompatibility, and mechanical compatibility. Seeking an alternative solution, we present a hierarchically structured nanofibrous surgical mesh derived from the naturally woven cocoon of the Japanese giant silkworm, termed MothMesh. We report that it displays nontoxicity, biocompatibility, suitable mechanical properties, and porosity while showing no adverse effect in animal trials and even appears to enhance cell proliferation. Hence, we assert that the use of this natural material may provide an effective and improved alternative to existing synthetic meshes
  • ItemOpen Access
    Visual perception of the built environment in virtual reality: a systematic characterization of human aesthetic experience in spaces with curved boundaries
    (American Psychological Association, 2022-07-04) Boz, Tuğçe Elver; Demirkan, Halime; Ürgen, Burcu Ayşe; Boz, Tuğçe Elver; Demirkan, Halime; Ürgen, Burcu Ayşe
    Visual perception of architectural spaces and human aesthetic experience in these spaces have recently received considerable interest in cognitive science. However, it has been difficult to construe a common understanding of aesthetic experience for architectural space, since different studies use different scales to measure aesthetic experiences. In this interdisciplinary study spanning cognitive science and architecture, we aim to provide an empirically driven systematic characterization of human aesthetic experience and investigate what aspects of the architectural spaces affect aesthetic experience. To this end, we manipulated various architectural variables including the shape of the curvilinear boundaries of architectural spaces as well as their size, light, texture, and color in virtual reality. We then had people evaluate these spaces by exhausting a large list of commonly used scales in the literature and applied principal component analysis to reveal the key dimensions of aesthetic experience. Our findings suggest that human aesthetic experience can be reduced to 3 key dimensions, namely familiarity, excitement, and fascination. Each of these dimensions are differentially affected by the various architectural variables revealing their differences. In sum, our study provides a comprehensive framework to characterize human aesthetic experience in virtual architectural spaces with curved boundaries.
  • ItemOpen Access
    Sheared two-dimensional radiofrequency excitation for off-resonance robustness and fat suppression in reduced field-of-view imaging
    (Wiley, 2022-09-30) Barlas, Bahadır Alp; Bahadır, Çağla Deniz; Kafalı, Sevgi Gökçe; Yılmaz, Uğur; Sarıtaş, Emine Ülkü; Barlas, Bahadır Alp; Bahadır, Çağla Deniz; Kafalı, Sevgi Gökçe; Yılmaz, Uğur; Sarıtaş, Emine Ülkü
    Purpose: Two-dimensional (2D) echo-planar radiofrequency (RF) pulses are widely used for reduced field-of-view (FOV) imaging in applications such as diffusion-weighted imaging. However, long pulse durations render the 2D RF pulses sensitive to off-resonance effects, causing local signal losses in reduced-FOV images. This work aims to achieve off-resonance robustness for 2D RF pulses via a sheared trajectory design. Theory and Methods: A sheared 2D RF pulse design is proposed to reduce pulse durations while covering identical excitation k-space extent as a standard 2D RF pulse. For a given shear angle, the number of sheared trajectory lines is minimized to obtain the shortest pulse duration, such that the excitation replicas are repositioned outside the slice stack to guarantee unlimited slice coverage. A target fat/water signal ratio of 5% is chosen to achieve robust fat suppression. Results: Simulations, imaging experiments on a custom head and neck phantom, and in vivo imaging experiments in the spinal cord at 3 T demonstrate that the sheared 2D RF design provides significant improvement in image quality while preserving profile sharpnesses. In regions with high off-resonance effects, the sheared 2D RF pulse improves the signal by more than 50% when compared to the standard 2D RF pulse. Conclusion: The proposed sheared 2D RF design successfully reduces pulse durations, exhibiting significantly improved through-plane off-resonance robustness, while providing unlimited slice coverage and high fidelity fat suppression. This method will be especially beneficial in regions suffering from a variety of off-resonance effects, such as spinal cord and breast. © 2022 International Society for Magnetic Resonance in Medicine.
  • ItemOpen Access
    Mind perception and social robots: the role of agent appearance and action types
    (Association for Computing Machinery, 2021-03-08) Saltık, İmge; Erdil, Deniz; Urgen, Burcu A.; Saltık, İmge; Erdil, Deniz; Urgen, Burcu A.
    Mind perception is considered to be the ability to attribute mental states to non-human beings. As social robots increasingly become part of our lives, one important question for HRI is to what extent we attribute mental states to these agents and the conditions under which we do so. In the present study, we investigated the effect of appearance and the type of action a robot performs on mind perception. Participants rated videos of two robots in different appearances (one metallic, the other human-like), each of which performed four different actions (manipulating an object, verbal communication, non-verbal communication, and an action that depicts a biological need) on Agency and Experience dimensions. Our results show that the type of action that the robot performs affects the Agency scores. When the robot performs human-specific actions such as communicative actions or an action that depicts a biological need, it is rated to have more agency than when it performs a manipulative action. On the other hand, the appearance of the robot did not have any effect on the Agency or the Experience scores. Overall, our study suggests that the behavioral skills we build into social robots could be quite important in the extent we attribute mental states to them.
  • ItemOpen Access
    Çoklu kontrast MRG’de çoklu görüntü geriçatımı
    (IEEE, 2021-07-19) Özbey, Muzaffer; Çukur, Tolga; Özbey, Muzaffer; Çukur, Tolga
    Çoklu kontrastlı manyetik rezonans görüntülerinin (MRG) edinimi, tanı bilgi birikimini artırarak klinik tanıda önemli bir role sahiptir. Hastanın hareketsiz kalması gereken uzun tetkik süreleri, çoklu kontrast MRG edinimini sınırlandırmaktadır. Görüntülerin alt örneklenerek toplanması ve geriçatımı ile tarama süreleri kısaltılabilmektedir. Yaygın yöntemler, tek kontrasta ait alt örneklenmiş MR görüntülerinden aynı kontrasta ait tam örneklenmiş MR görüntüsü üretmektedir. Ancak girdi verisindeki tek kontrastlı MR görüntüsüne ait sınırlı bilgiler, geriçatım performansını sınırlandırmaktadır. Bu yüzden, çoklu kontrast MRG girdi verilerinin kullanımı ile geriçatım performansı artırılabilir. Bu çalışma kapsamında, birden fazla kontrasta ait alt örneklenmiş görüntülerden, tam örneklenmiş görüntüleri eş zamanlı olarak üreten bir çoklu kontrast MRG geriçatım yöntemi önerilmiştir. Önerilen yöntem, yüksek frekans değerlerini daha iyi tahmin ederek oldukça gerçekçi görüntüler üreten çekişmeli üretici ağlar kullanılarak uygulanmıştır. Önerilen yöntem, çoklu kontrast beyin MR görüntüleri içeren verisetinde test edilmiş, sayısal ve görsel değerlendirmeler sonucunda alternatif tekli kontrast geriçatım yöntemine göre daha üstün performans sağladığı kanıtlanmıştır.