Browsing by Quartile "N/A"

Now showing 1 - 20 of 3406

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1.07 - Rubberlike elasticity
(Elsevier, 2012) Mark, J.E.; Department of Chemical and Biological Engineering; Erman, Burak; Faculty Member; Department of Chemical and Biological Engineering; College of Engineering; 179997
Molecular structure, molecular and phenomenological theories, and computer simulations of amorphous rubberlike polymeric networks of rubber elasticity are discussed. Behavior of responsive gels, multimodal, liquid-crystalline, and reinforced elastomers in the state of thermodynamic equilibrium are outlined. Characterization of structure and properties based on stress–strain experiments, optical and spectroscopic techniques, scanning tunneling microscopy, atomic force microscopy, nuclear magnetic resonance, small-angle and Brillouin scattering, and pulse wave propagation are outlined. © 2012 Elsevier B.V. All rights reserved.
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10-NJ multipass-cavity femtosecond CR3+: LiCAF laser pumped by low-power single-mode diodes
(Optical Society of America, 2009) Kärtner, Franz X.; Fujimoto, James G.; Demirbaş, Ümit; Department of Physics; Sennaroğlu, Alphan; Faculty Member; Department of Physics; College of Sciences; 23851
We report on the generation of 9.9-nJ, 95-fs pulses at a repetition rate of 9.58 MHz from a multipass-cavity Cr3+:LiCAF laser pumped by single-mode diodes with a total absorbed pump power of only 540 mW.
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16.4: the optics of an autostereoscopic multiview display
(SID, 2010) Baghsiahi, Hadi; Selviah, David R.; Willman, Eero; Fernández, Anibal; Day, Sally E.; Surman, Phil A.; N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Erden, Erdem; Chellappan, Kishore Velichappattu; Ürey, Hakan; Master Student; Researcher; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; 8579
An autostereoscopic head-tracked back projection display that uses an RGB laser illumination source and a fast light engine is described. Images are horizontally scanned columns controlled by a spatial light modulator that directs two or more images in the directions of the apposite viewers 'eyes.
Open Access
1899 yılı Osmanlı İmparatorluğu için jeomekansal ve çok modlu bir ulaşım ağı oluşturma denemesi
(Koç University Research Center for Anatolian Civilizations (ANAMED) / Koç Üniversitesi Anadolu Medeniyetleri Araştırma Merkezi (ANAMED), 2020) Gerrits, Piet; Department of History; Kabadayı, Mustafa Erdem; Özkan, Osman; Koçak, Turgay; Faculty Member; Teaching Faculty; Department of History; College of Social Sciences and Humanities; 33267; N/A; N/A
Open Access
2D hybrid meshes for direct simulation Monte Carlo solvers
(Institute of Physics (IOP) Publishing, 2013) Şengil, Nevsan; Department of Mathematics; Şengil, Uluç; Master Student; Department of Mathematics; College of Sciences
The efficiency of the direct simulation Monte Carlo (DSMC) method decreases considerably if gas is not rarefied. In order to extend the application range of the DSMC method towards non-rarefied gas regimes, the computational efficiency of the DSMC method should be increased further. One of the most time consuming parts of the DSMC method is to determine which DSMC molecules are in close proximity. If this information is calculated quickly, the efficiency of the DSMC method will be increased. Although some meshless methods are proposed, mostly structured or non-structured meshes are used to obtain this information. The simplest DSMC solvers are limited with the structured meshes. In these types of solvers, molecule indexing according to the positions can be handled very fast using simple arithmetic operations. But structured meshes are geometry dependent. Complicated geometries require the use of unstructured meshes. In this case, DSMC molecules are traced cell-by-cell. Different cell-by-cell tracing techniques exist. But, these techniques require complicated trigonometric operations or search algorithms. Both techniques are computationally expensive. In this study, a hybrid mesh structure is proposed. Hybrid meshes are both less dependent on the geometry like unstructured meshes and computationally efficient like structured meshes.
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2D scanning MEMS stage integrated with microlens arrays for high-resolution beam steering
(IEEE, 2009) Department of Electrical and Electronics Engineering; N/A; Department of Electrical and Electronics Engineering; N/A; N/A; N/A; Ürey, Hakan; Gökçe, Sertan Kutal; Holmstrom, Sven; Arslan, Aslıhan; Ataman, Çağlar; Seren, Hüseyin Rahmi; Faculty Member; Master Student; Researcher; Master Student; PhD Student; Master Student; Other; Department of Electrical and Electronics Engineering; College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; N/A; 8579; N/A; N/A; N/A; N/A; N/A; N/A
A novel MEMS stage using one set of comb fingers, capable of 2-axis motion is designed and developed. With an integrated 1.1mm square microlens-array it deflects 40um in-plane at 60V and 95um out-of-plane at 100V.
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3D articulated shape segmentation using motion information
(Institute of Electrical and Electronics Engineers (IEEE), 2010) Department of Computer Engineering; N/A; Yemez, Yücel; Kalafatlar, Emre; Faculty Member; Master Student; Department of Computer Engineering; College of Engineering; Graduate School of Sciences and Engineering; 107907; N/A
We present a method for segmentation of articulated 3D shapes by incorporating the motion information obtained from time-varying models. We assume that the articulated shape is given in the form of a mesh sequence with fixed connectivity so that the inter-frame vertex correspondences, hence the vertex movements, are known a priori. We use different postures of an articulated shape in multiple frames to constitute an affinity matrix which encodes both temporal and spatial similarities between surface points. The shape is then decomposed into segments in spectral domain based on the affinity matrix using a standard K-means clustering algorithm. The performance of the proposed segmentation method is demonstrated on the mesh sequence of a human actor.
Open Access
3D bioprinted organ?on?chips
(Wiley, 2022) Mustafaoğlu, Nur; Zhang, Yu Shrike; Department of Mechanical Engineering; N/A; N/A; Dabbagh, Sajjad Rahmani; Sarabi, Misagh Rezapour; Birtek, Mehmet Tuğrul; Taşoğlu, Savaş; Faculty Member; Department of Mechanical Engineering; KU Arçelik Research Center for Creative Industries (KUAR) / KU Arçelik Yaratıcı Endüstriler Uygulama ve Araştırma Merkezi (KUAR); Koç Üniversitesi İş Bankası Yapay Zeka Uygulama ve Araştırma Merkezi (KUIS AI)/ Koç University İş Bank Artificial Intelligence Center (KUIS AI); College of Engineering; Graduate School of Social Sciences and Humanities; Graduate School of Sciences and Engineering; N/A; N/A; N/A; 291971
Organ-on-a-chip (OOC) platforms recapitulate human in vivo-like conditions more realistically compared to many animal models and conventional two-dimensional cell cultures. OOC setups benefit from continuous perfusion of cell cultures through microfluidic channels, which promotes cell viability and activities. Moreover, microfluidic chips allow the integration of biosensors for real-time monitoring and analysis of cell interactions and responses to administered drugs. Three-dimensional (3D) bioprinting enables the fabrication of multicell OOC platforms with sophisticated 3D structures that more closely mimic human tissues. 3D-bioprinted OOC platforms are promising tools for understanding the functions of organs, disruptive influences of diseases on organ functionality, and screening the efficacy as well as toxicity of drugs on organs. Here, common 3D bioprinting techniques, advantages, and limitations of each method are reviewed. Additionally, recent advances, applications, and potentials of 3D-bioprinted OOC platforms for emulating various human organs are presented. Last, current challenges and future perspectives of OOC platforms are discussed.
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3D face recognition
(Institute of Electrical and Electronics Engineers (IEEE), 2006) Dutaǧaci, H.; Sankur, B.; Department of Computer Engineering; Yemez, Yücel; Faculty Member; Department of Computer Engineering; College of Engineering; 107907
In this paper, we compare face recognition performances of various features applied on registered 3D scans of faces. The features we compare are DFT or DCT- based features, ICA-based features and NNMF-based features. We apply the feature extraction techniques to three different representations of registered faces: 3D point clouds, 2D depth images and 3D voxel representations. We also consider block-based DFT or DCT-based local features on 2D depth images and their fusion schemes. Experiments using different combinations of representation types and feature vectors are conducted on the 3D-RMA dataset. / Bu bildiride, kayıtlı 3B yüz taramalarında uygulanan çeşitli özelliklerin yüz tanıma performanslarını karşılaştırıyoruz. Karşılaştırdığımız özellikler, DFT veya DCT tabanlı özellikler, ICA tabanlı özellikler ve NNMF tabanlı özelliklerdir. Öznitelik çıkarma tekniklerini kayıtlı yüzlerin üç farklı temsiline uyguluyoruz: 3B nokta bulutları, 2B derinlik görüntüleri ve 3B voksel temsilleri. Ayrıca, 2D derinlik görüntüleri ve bunların füzyon şemaları üzerindeki blok tabanlı DFT veya DCT tabanlı yerel özellikleri de dikkate alıyoruz. 3D-RMA veri seti üzerinde farklı temsil türleri ve özellik vektörleri kombinasyonları kullanılarak deneyler yapılmıştır.
Open Access
3D face recognition by projection based methods
(Society of Photo-optical Instrumentation Engineers (SPIE), 2006) Dutaǧaci, Helin; Sankur, Bülent; Department of Computer Engineering; Yemez, Yücel; Faculty Member; Department of Computer Engineering; College of Engineering
In this paper, we investigate recognition performances of various projection-based features applied on registered 3D scans of faces. Some features are data driven, such as ICA-based features or NNMF-based features. Other features are obtained using DFT or DCT-based schemes. We apply the feature extraction techniques to three different representations of registered faces, namely, 3D point clouds, 2D depth images and 3D voxel. We consider both global and local features. Global features are extracted from the whole face data, whereas local features are computed over the blocks partitioned from 2D depth images. The block-based local features are fused both at feature level and at decision level. The resulting feature vectors are matched using Linear Discriminant Analysis. Experiments using different combinations of representation types and feature vectors are conducted on the 3D-RMA dataset.
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3D isometric shape correspondence
(IEEE, 2010) Department of Computer Engineering; Yemez, Yücel; Sahillioğlu, Yusuf; Faculty Member; PhD Student; Department of Computer Engineering; College of Engineering; Graduate School of Sciences and Engineering; 107907; 215195
We address the problem of correspondence between 3D isometric shapes. We present an automatic method that finds the optimal correspondence between two given (nearly) isometric shapes by minimizing the amount of deviation from isometry. We optimize the isometry error in two steps. In the first step, the 3D points uniformly sampled from the shape surfaces are transformed into spectral domain based on geodesic affinity, where the isometry errors are minimized in polynomial time by complete bipartite graph matching. The second step of optimization, which is well-initialized by the resulting correspondence of the first step, explicitly minimizes the isometry cost via an iterative greedy algorithm in the original 3D Euclidean space. Our method is put to test using (nearly) isometric pairs of shapes and its performance is measured via ground-truth correspondence information when available.
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3D object matching via multivariate shape distributions
(Institute of Electrical and Electronics Engineers (IEEE), 2005) Akgül, C.B.; Sankur, B.; Schmitt, F.; Department of Computer Engineering; Yemez, Yücel; Faculty Member; Department of Computer Engineering; College of Engineering; 107907
3B nesne eşleştirme literatüründe, problemi şekil dağılımlarının karşılaştırılmasına indirgeyen yöntemler bulunmaktadır. Şekil dağılımı, 3B nesne yüzeyi üzerinde hesaplanan bir işlevin değerlerinin olasılık dağılımı olarak tanımlanır. Bu çalışmada varolan yöntemi, birden çok işlevin getirdiği şekil bilgisinden aynı anda yararlanacak şekilde genişletiyoruz. Çokboyutlu şekil dağılımları adını verdiğimiz bu 3B nesne betimleyicilerini, örnek bir 3B nesne veri tabanındaki nesneler için parametrik olmayan yaklaşımlarla kestiriyor, karşılaştırmaları alternatif metrikler yoluyla yapıyoruz. Elde edilen kesinlik-geri getirme eğrileri çokboyutlu şekil dağılımlarının karşılaştırılmasının yeni bir 3B nesne eşleştirme paradigması olabileceğini göstermektedir.
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3D printed biodegradable polyurethaneurea elastomer recapitulates skeletal muscle structure and function
(American Chemical Society (ACS), 2021) Gokyer, Seyda; Berber, Emine; Vrana, Engin; Orhan, Kaan; Abou Monsef, Yanad; Guvener, Orcun; Zinnuroglu, Murat; Oto, Cagdas; Huri, Pinar Yilgor; Department of Chemistry; Department of Chemistry; Yılgör, Emel; Yılgör, İskender; Researcher; Faculty Member; Department of Chemistry; College of Sciences; College of Sciences; N/A; 24181
Effective skeletal muscle tissue engineering relies on control over the scaffold architecture for providing muscle cells with the required directionality, together with a mechanical property match with the surrounding tissue. Although recent advances in 3D printing fulfill the first requirement, the available synthetic polymers either are too rigid or show unfavorable surface and degradation profiles for the latter. In addition, natural polymers that are generally used as hydrogels lack the required mechanical stability to withstand the forces exerted during muscle contraction. Therefore, one of the most important challenges in the 3D printing of soft and elastic tissues such as skeletal muscle is the limitation of the availability of elastic, durable, and biodegradable biomaterials. Herein, we have synthesized novel, biocompatible and biodegradable, elastomeric, segmented polyurethane and polyurethaneurea (TPU) copolymers which are amenable for 3D printing and show high elasticity, low modulus, controlled biodegradability, and improved wettability, compared to conventional polycaprolactone (PCL) and PCL-based TPUs. The degradation profile of the 3D printed TPU scaffold was in line with the potential tissue integration and scaffold replacement process. Even though TPU attracts macrophages in 2D configuration, its 3D printed form showed limited activated macrophage adhesion and induced muscle-like structure formation by C2C12 mouse myoblasts in vitro, while resulting in a significant increase in muscle regeneration in vivo in a tibialis anterior defect in a rat model. Effective muscle regeneration was confirmed with immunohistochemical assessment as well as evaluation of electrical activity produced by regenerated muscle by EMG analysis and its force generation via a custom-made force transducer. Micro-CT evaluation also revealed production of more muscle-like structures in the case of implantation of cell-laden 3D printed scaffolds. These results demonstrate that matching the tissue properties for a given application via use of tailor-made polymers can substantially contribute to the regenerative outcomes of 3D printed tissue engineering scaffolds.
Open Access
3D printed personalized magnetic micromachines from patient blood-derived biomaterials
(American Association for the Advancement of Science (AAAS), 2021) Ceylan, Hakan; Doğan, Nihal Olcay; Yaşa, İmmihan Ceren; Department of Mechanical Engineering; Sitti, Metin; Musaoğlu, Miraç Nur; Kulalı, Zeynep Umut; Faculty Member; Department of Mechanical Engineering; College of Engineering; School of Medicine; 297104; N/A; N/A
While recent wireless micromachines have shown increasing potential for medical use, their potential safety risks concerning biocompatibility need to be mitigated. They are typically constructed from materials that are not intrinsically compatible with physiological environments. Here, we propose a personalized approach by using patient blood-derivable biomaterials as the main construction fabric of wireless medical micromachines to alleviate safety risks from biocompatibility. We demonstrate 3D printed multiresponsive microswimmers and microrollers made from magnetic nanocomposites of blood plasma, serum albumin protein, and platelet lysate. These micro-machines respond to time-variant magnetic fields for torque-driven steerable motion and exhibit multiple cycles of pH-responsive two-way shape memory behavior for controlled cargo delivery and release applications. Their proteinaceous fabrics enable enzymatic degradability with proteinases, thereby lowering risks of long-term toxicity. The personalized micromachine fabrication strategy we conceptualize here can affect various future medical robots and devices made of autologous biomaterials to improve biocompatibility and smart functionality.
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3D shape correspondence by isometry-driven greedy optimization
(IEEE Computer Soc, 2010) N/A; Department of Computer Engineering; Sahillioğlu, Yusuf; Yemez, Yücel; PhD Student; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; 215195; 107907
We present an automatic method that establishes 3D correspondence between isometric shapes. Our goal is to find an optimal correspondence between two given (nearly) isometric shapes, that minimizes the amount of deviation from isometry. We cast the problem as a complete surface correspondence problem. Our method first divides the given shapes to be matched into surface patches of equal area and then seeks for a mapping between the patch centers which we refer to as base vertices. Hence the correspondence is established in a fast and robust manner at a relatively coarse level as imposed by the patch radius. We optimize the isometry cost in two steps. in the first step, the base vertices are transformed into spectral domain based on geodesic affinity, where the isometry errors are minimized in polynomial time by complete bipartite graph matching. the resulting correspondence serves as a good initialization for the second step of optimization in which we explicitly minimize the isometry cost via an iterative greedy algorithm in the original 3D Euclidean space. We demonstrate the performance of our method on various isometric (or nearly isometric) pairs of shapes for some of which the ground-truth correspondence is available.
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3D shape recovery and tracking from multi-camera video sequences via surface deformation
(Institute of Electrical and Electronics Engineers (IEEE), 2006) Skala, V.; N/A; Department of Computer Engineering; Sahillioğlu, Yusuf; Yemez, Yücel; PhD Student; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; 215195; 107907
This paper addresses 3D reconstruction and modeling of time-varying real objects using multicamera video. The work consists of two phases. In the first phase, the initial shape of the object is recovered from its silhouettes using a surface deformation model. The same deformation model is also employed in the second phase to track the recovered initial shape through the time-varying silhouette information by surface evolution. The surface deformation/evolution model allows us to construct a spatially and temporally smooth surface mesh representation having fixed connectivity. This eventually leads to an overall space-time representation that preserves the semantics of the underlying motion and that is much more efficient to process, to visualize, to store and to transmit. / Bu makale, çok kameralı video kullanarak zamanla değişen gerçek nesnelerin 3B yeniden yapılandırılmasını ve modellenmesini ele almaktadır. Çalışma iki aşamadan oluşmaktadır. İlk aşamada, nesnenin ilk şekli, bir yüzey deformasyon modeli kullanılarak silüetlerinden kurtarılır. Aynı deformasyon modeli, ikinci aşamada, yüzey evrimi yoluyla zamanla değişen siluet bilgisi yoluyla geri kazanılan ilk şekli izlemek için de kullanılır. Yüzey deformasyonu/evrimi modeli, sabit bağlantıya sahip uzamsal ve zamansal olarak pürüzsüz bir yüzey ağ temsili oluşturmamıza izin verir. Bu, sonunda, altta yatan hareketin anlamını koruyan ve işlemesi, görselleştirmesi, depolaması ve iletmesi çok daha verimli olan genel bir uzay-zaman temsiline yol açar.
Open Access
3D-printed contact lenses: challenges towards translation and commercialization
(Future Medicine, 2022) Yetişen, Ali K.; Department of Mechanical Engineering; Taşoğlu, Savaş; Özdalgıç, Berin; Faculty Member; PhD Student; Department of Mechanical Engineering; KU Arçelik Research Center for Creative Industries (KUAR) / KU Arçelik Yaratıcı Endüstriler Uygulama ve Araştırma Merkezi (KUAR); Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); College of Engineering; Graduate School of Sciences and Engineering; 291971; 323683
NA
Open Access
3D-printed microneedles in biomedical applications
(Elsevier, 2021) Rahbarghazi, Reza; Yetişen, Ali Kemal; N/A; Department of Mechanical Engineering; Dabbagh, Sajjad Rahmani; Sarabi, Misagh Rezapour; Sokullu, Emel; Taşoğlu, Savaş; Faculty Member; Faculty Member; Department of Mechanical Engineering; KU Arçelik Research Center for Creative Industries (KUAR) / KU Arçelik Yaratıcı Endüstriler Uygulama ve Araştırma Merkezi (KUAR); Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); Graduate School of Social Sciences and Humanities; Graduate School of Sciences and Engineering; School of Medicine; College of Engineering; N/A; N/A; 163024; 291971
Conventional needle technologies can be advanced with emerging nano- and micro-fabrication methods to fabricate microneedles. Nano-/micro-fabricated microneedles seek to mitigate penetration pain and tissue damage, as well as providing accurately controlled robust channels for administrating bioagents and collecting body fluids. Here, design and 3D printing strategies of microneedles are discussed with emerging applications in biomedical devices and healthcare technologies. 3D printing offers customization, cost-efficiency, a rapid turnaround time between design iterations, and enhanced accessibility. Increasing the printing resolution, the accuracy of the features, and the accessibility of low-cost raw printing materials have empowered 3D printing to be utilized for the fabrication of microneedle platforms. The development of 3D-printed microneedles has enabled the evolution of pain-free controlled release drug delivery systems, devices for extracting fluids from the cutaneous tissue, biosignal acquisition, and point-of-care diagnostic devices in personalized medicine.
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48.4: Beam forming for a laser based auto-stereoscopic multi-viewer display
(Blackwell Publishing Ltd, 2011) Baghsiahi, Hadi; Selviah, David R.; Willman, Eero; Fernández, Anibal; Day, Sally E.; Surman, Phil A.; N/A; Department of Electrical and Electronics Engineering; N/A; N/A; N/A; Department of Electrical and Electronics Engineering; Akşit, Kaan; Ölçer, Selim; Mostafazadeh, Aref; Erden, Erdem; Chellappan, Kishore Velichappattu; Ürey, Hakan; PhD Student; Other; N/A; Other; N/A; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; College of Engineering; N/A; N/A; N/A; N/A; N/A; 8579
An auto-stereoscopic back projection display using a RGB multiemitter laser illumination source and micro-optics to provide a wider view is described. The laser optical properties and the speckle due to the optical system configuration and its diffusers are characterised. © 2011 SID.
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80-NJ multipass-cavity chirped-pulse Cr4+: forsterite laser
(Optical Society of America, 2010) Fujimoto, James G.; Department of Physics; Sennaroğlu, Alphan; Çankaya, Hüseyin; Faculty Member; Researcher; Department of Physics; College of Sciences; Graduate School of Sciences and Engineering; 23851; N/A
By using 8.5 W of incident pump power, we obtained 80-nJ, 5.5-ps pulses at 1260 nm with a spectral width of 17 nm from a multipass-cavity, chirped-pulse Cr4+:forsterite laser operated at 4.9-MHz repetition rate. © 2010 Optical Society of America.