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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6

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Now showing 1 - 10 of 98
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    PublicationOpen Access
    Long-term cyclic use of a sample collector for toilet-based urine analysis
    (Nature Publishing Group (NPG), 2021) Temirel, Mikail; Yenilmez, Bekir; Department of Mechanical Engineering; Department of Mechanical Engineering; Taşoğlu, Savaş; Faculty Member; 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; 291971
    Urine analysis via a toilet-based device can enable continuous health monitoring, a transformation away from hospital-based care towards more proactive medicine. To enable reliable sample collection for a toilet-attached analyzer, here a novel sample collector is proposed. The applicability of the proposed sample collector is validated for long-term use. Geometric parameters of the 3D-printed sample collector are optimized. The collected and leftover volumes are quantified for a range of urination speeds and design parameters. For long-term cyclic use, the protein concentrations of samples are quantified and the effectiveness of washing the sample collector is assessed.
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    PublicationOpen Access
    Dynamic characterization and damping control of a MEMS structure - art. no. 671509
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2007) Department of Mechanical Engineering; Department of Mechanical Engineering; Alaca, Ilgım Veryeri; Başdoğan, İpek; Faculty Member; College of Engineering; 50569; 179940
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    PublicationOpen Access
    Offline force control and feedrate scheduling for complex free form surfaces in 5-Axis milling
    (Elsevier, 2012) Erdim, Hüseyin; Department of Mechanical Engineering; Department of Mechanical Engineering; Khavidaki, Sayed Ehsan Layegh; Lazoğlu, İsmail; Faculty Member; Manufacturing and Automation Research Center (MARC); College of Sciences; N/A; 179391
    An enhanced Force model based Feedrate Scheduling (FFS) technique for rough cutting of parts with complex free form surfaces in 5-axis machining is presented. In order to estimate the cutting forces in complex 5-axis machining an enhanced solid modeler kernel based model is developed to find the complicated engagement between cutter and workpiece for each cutter location. In this paper, cutter-workpiece engagement model is presented using the commercial Parasolid solid modeler kernel, and then cutting forces are estimated based on the developed model. In this approach, the resultant cutting forces are kept constant on a user defined threshold. The feedrate will be adjusted to keep the resultant cutting forces constant all along the tool path. Therefore, it is shown that this approach allows decreasing the cycling time drastically. The scheduled feedrate in each cutter location is carried out in NC blocks using an off-line postprocessor that can be used in commercial CAM software. Eventually, the proposed FFS technique is experimentally tested on rough machining of an impeller with free form surfaces and force validations are presented in this article.
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    PublicationOpen Access
    Supporting negotiation behavior with haptics-enabled human-computer interfaces
    (Institute of Electrical and Electronics Engineers (IEEE), 2012) Department of Mechanical Engineering; Department of Mechanical Engineering; Küçükyılmaz, Ayşe; Sezgin, Tevfik Metin; Başdoğan, Çağatay; PhD Student; Faculty Member; Faculty Member; College of Engineering; N/A; 18632; 125489; N/A
    An active research goal for human-computer interaction is to allow humans to communicate with computers in an intuitive and natural fashion, especially in real-life interaction scenarios. One approach that has been advocated to achieve this has been to build computer systems with human-like qualities and capabilities. In this paper, we present insight on how human-computer interaction can be enriched by employing the computers with behavioral patterns that naturally appear in human-human negotiation scenarios. For this purpose, we introduce a two-party negotiation game specifically built for studying the effectiveness of haptic and audio-visual cues in conveying negotiation related behaviors. The game is centered around a real-time continuous two-party negotiation scenario based on the existing game-theory and negotiation literature. During the game, humans are confronted with a computer opponent, which can display different behaviors, such as concession, competition, and negotiation. Through a user study, we show that the behaviors that are associated with human negotiation can be incorporated into human-computer interaction, and the addition of haptic cues provides a statistically significant increase in the human-recognition accuracy of machine-displayed behaviors. In addition to aspects of conveying these negotiation-related behaviors, we also focus on and report game-theoretical aspects of the overall interaction experience. In particular, we show that, as reported in the game-theory literature, certain negotiation strategies such as tit-for-tat may generate maximum combined utility for the negotiating parties, providing an excellent balance between the energy spent by the user and the combined utility of the negotiating parties.
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    PublicationOpen Access
    Understanding formation and structure of peptide nanofibers via steered MD simulations
    (Elsevier, 2012) Department of Mechanical Engineering; Department of Mechanical Engineering; Engin, Özge; Özgür, Beytullah; Sayar, Mehmet; PhD Student; Faculty Member; College of Engineering; N/A; N/A; 109820
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    PublicationOpen Access
    Molecular dynamics study of orientation-dependent tensile properties of Si nanowires with native oxide: surface stress and surface energy effects
    (Institute of Electrical and Electronics Engineers (IEEE), 2021) Esfahani, Mohammad Nasr; Department of Mechanical Engineering; Department of Mechanical Engineering; Alaca, Burhanettin Erdem; Zarepakzad, Sina; Faculty Member; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Engineering; Graduate School of Sciences and Engineering; 115108; N/A
    Molecular dynamics (MD) simulations are employed to investigate the influence of native oxide layer on the mechanical properties of Si nanowires (NWs) through analyzing surface stress and surface energy effect. This work studies the tensile response of Si NWs along <100> and <110> crystal orientations. MD results are compared with the traditional core-shell model on the estimation of the modulus of elasticity of Si NWs with a native oxide layer. Density functional theory (DFT) methods are used to verify MD results on the surface energy calculations. Surface stress and surface elastic constants are studied for native oxide surface using MD simulations and compared with unreconstructed surfaces. In this work, the role of native oxide is addressed to understand the difference between experimental and computational findings on the modulus of elasticity of Si NWs.
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    PublicationOpen Access
    Special issue on surface haptics
    (Institute of Electrical and Electronics Engineers (IEEE), 2020) Giraud, Frederic; Levesque, Vincent; Choi, Seungmoon; Department of Mechanical Engineering; Department of Mechanical Engineering; Başdoğan, Çağatay; Faculty Member; College of Engineering; 125489
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    PublicationOpen Access
    Buckling of stiff polymers: influence of thermal fluctuations
    (American Physical Society (APS), 2007) Emanuel, Marc; Mohrbach, Herve; Schiessel, Helmut; Kulic, Igor M.; Department of Mechanical Engineering; Department of Mechanical Engineering; Sayar, Mehmet; Faculty Member; College of Engineering; 109820
    The buckling of biopolymers is a frequently studied phenomenon The influence of thermal fluctuations on the buckling transition is, however, often ignored and not completely understood. A quantitative theory of the buckling of a wormlike chain based on a semiclassical approximation of the partition function is presented. The contribution of thermal fluctuations to the force-extension relation that allows one to go beyond the classical Euler buckling is derived in the linear and nonlinear regimes as well. It is shown that the thermal fluctuations in the nonlinear buckling regime increase the end-to-end distance of the semiflexible rod if it is confined to two dimensions as opposed to the three-dimensional case. The transition to a buckled state softens at finite temperature. We derive the scaling behavior of the transition shift with increasing ratio of contour length versus persistence length.
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    PublicationOpen Access
    Thermal effects on the crystallization kinetics, and interfacial adhesion of single-crystal phase-change gallium
    (Wiley, 2020) Yunusa, Muhammad; Lahlou, Alienor; Department of Mechanical Engineering; Department of Mechanical Engineering; Sitti, Metin; Faculty Member; School of Medicine; College of Engineering; 297104
    Although substrates play an important role upon crystallization of supercooled liquids, the influences of surface temperature and thermal property have remained elusive. Here, the crystallization of supercooled phase-change gallium (Ga) on substrates with different thermal conductivity is studied. The effect of interfacial temperature on the crystallization kinetics, which dictates thermo-mechanical stresses between the substrate and the crystallized Ga, is investigated. At an elevated surface temperature, close to the melting point of Ga, an extended single-crystal growth of Ga on dielectric substrates due to layering effect and annealing is realized without the application of external fields. Adhesive strength at the interfaces depends on the thermal conductivity and initial surface temperature of the substrates. This insight can be applicable to other liquid metals for industrial applications, and sheds more light on phase-change memory crystallization.
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    PublicationOpen Access
    High-performance magnetic FePt (L1(0)) surface microrollers towards medical imaging-guided endovascular delivery applications
    (Wiley, 2021) Bozüyük, U.; Suadiye, E.; Aghakhani, A.; Doğan, N.O.; Lazovic, J.; Tiryaki, M.E.; Schneider, M.; Karacakol, A.C.; Demir, S.O., Richter, G.; Department of Mechanical Engineering; Department of Mechanical Engineering; Sitti, Metin; Faculty Member; College of Engineering; School of Medicine; 297104
    Controlled microrobotic navigation in the vascular system can revolutionize minimally invasive medical applications, such as targeted drug and gene delivery. Magnetically controlled surface microrollers have emerged as a promising microrobotic platform for controlled navigation in the circulatory system. Locomotion of micrororollers in strong flow velocities is a highly challenging task, which requires magnetic materials having strong magnetic actuation properties while being biocompatible. The L10-FePt magnetic coating can achieve such requirements. Therefore, such coating has been integrated into 8 µm-diameter surface microrollers and investigated the medical potential of the system from magnetic locomotion performance, biocompatibility, and medical imaging perspectives. The FePt coating significantly advanced the magnetic performance and biocompatibility of the microrollers compared to a previously used magnetic material, nickel. The FePt coating also allowed multimodal imaging of microrollers in magnetic resonance and photoacoustic imaging in ex vivo settings without additional contrast agents. Finally, FePt-coated microrollers showed upstream locomotion ability against 4.5 cm s?1 average flow velocity with real-time photoacoustic imaging, demonstrating the navigation control potential of microrollers in the circulatory system for future in vivo applications. Overall, L10-FePt is conceived as the key material for image-guided propulsion in the vascular system to perform future targeted medical interventions.