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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only Non-invasive raman classification comparison with pXRF of monochrome and related qing porcelains: lead-rich-, lead-poor-, and alkali-based glazes(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Colomban, Philippe; Gallet, Xavier; Fournery, Nicolas; Quette, Béatrice; Franci, Gülsu Şimşek; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM)Chinese porcelain with an optically clear colored glaze, imported to Europe from the Kangxi period (1662–1722, Qing Dynasty) onwards was highly collected by the French Elite of the 18th century. The bright colors with a clear, shiny glaze were unlike anything produced in Europe at that time. The colors of enamelled artifacts (on biscuits or already glazed porcelain) can be fully monochrome or consist of associations of large monochromatic areas with or without application of gilding. Non-invasive portable XRF and mobile Raman analyses have previously shown their effectiveness in the characterization of (colored) glassy silicates. In this study, we compare the Raman signatures of twenty-one Chinese artifacts fully—or with major monochrome area (sancai)—decorated with blue, turquoise (or celectian blue), honey-yellow, green, eggplant, and red color. Different types of glazes are identified and confirmed by pXRF: lead-rich, lead-poor-alkali, lead-doped alkali, and alkali-based compositions. However, an unexpected low level of lead is observed in the turquoise glazes, likely to optimize the gloss. Raman spectroscopy appears more reliable to compare the Pb content than pXRF. This work presents Raman spectral signatures of glazes that can potentially be used for non-invasive object classification and counterfeit detection.Publication Metadata only Roadmap for clinical translation of mobile microrobotics(Wiley-V C H Verlag Gmbh, 2024) Bozuyuk, Ugur; Wrede, Paul; Yildiz, Erdost; Department of Mechanical Engineering; Sitti, Metin; Department of Mechanical Engineering; College of Engineering; School of MedicineMedical microrobotics is an emerging field to revolutionize clinical applications in diagnostics and therapeutics of various diseases. On the other hand, the mobile microrobotics field has important obstacles to pass before clinical translation. This article focuses on these challenges and provides a roadmap of medical microrobots to enable their clinical use. From the concept of a "magic bullet" to the physicochemical interactions of microrobots in complex biological environments in medical applications, there are several translational steps to consider. Clinical translation of mobile microrobots is only possible with a close collaboration between clinical experts and microrobotics researchers to address the technical challenges in microfabrication, safety, and imaging. The clinical application potential can be materialized by designing microrobots that can solve the current main challenges, such as actuation limitations, material stability, and imaging constraints. The strengths and weaknesses of the current progress in the microrobotics field are discussed and a roadmap for their clinical applications in the near future is outlined. The clinical use of medical microrobots gets closer to reality with the rapidly growing biomedical research on them. However, the clinical translation of microrobots has several challenges and obstacles, including scalability, biocompatibility, and imaging. In this review article, a realistic roadmap for medical microrobots is conceptualized with the collaborative efforts of microrobot researchers and clinicians.Publication Metadata only Theoretical maximum thermoelectric performance of p-type Hf- and Zr-Doped NbFeSb Half-Heusler compounds(Wiley, 2024) Park, Hyunjin; Kim, Sang-il; Kim, Jeong-Yeon; Shin, Weon Ho; Kim, Hyun-Sik; Department of Chemistry; Aydemir, Umut; Department of Chemistry; Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); College of SciencesHalf-Heusler compounds are promising materials for thermoelectric applications due to their high zT at elevated temperatures. However, their intrinsic high thermal conductivity limits their efficiency. Doping with Hf or Zr can improve the zT of these materials. Recently, a high zT of 1.5 at 1200 K achieved in p-type Nb1-xHfxFeSb has attracted much attention. While the effect of doping Hf in thermal conductivity is studied thoroughly, the effect of Hf doping on band parameters is not fully evaluated. This study investigates the effect of Hf and Zr doping on the electronic band parameters and thermoelectric properties of NbFeSb using the Single Parabolic Band model. The results show that Hf doping increases the weighted mobility of the samples, while Zr doping has no significant effect. Hf doping with x = 0.14 is predicted to improve the zT of NbFeSb by 35% at 300 K (0.19 -> 0.26). These results show the intricate effects of Hf and Zr doping on the electronic and thermal properties of NbFeSb.Publication Metadata only End-to-end deep multi-modal physiological authentication with smartbands(IEEE-Inst Electrical Electronics Engineers Inc, 2021) Ekiz, Deniz; Dardağan, Yağmur Ceren; Aydar, Furkan; Köse, Rukiye Dilruba; Ersoy, Cem; N/A; Can, Yekta Said; Researcher; College of Social Sciences and Humanities; N/AThe number of fitness tracker users increases every day. Most of the applications require authentication to protect privacy-preserving operations. Biometrics such as face images have been used widely as login tokens, but they have privacy issues. Moreover, occlusions like face masks used for COVID may reduce their effectiveness. Smartbands can track heart rate, movements, and electrodermal activities. They have been widely used for health-related applications. The use of smartbands for authentication is in the exploratory stage. Physiological signals gathered from smartbands may be used to create a multi-modal and multi-sensor authentication system. The popularity of smartbands enables us to deploy new applications without a need to buy additional hardware. In this study, we explore the multi-modal physiological biometrics with end-to-end deep learning and feature-based traditional systems. We collected multi-modal physiological data of 80 people for five days using modern smartbands. We applied a deep learning approach to the multi-modal physiological data and used feature-based traditional machine learning classifiers. The CNN-LSTM model achieved a 9.31% equal error rate and outperformed other models in terms of authentication performance.Publication Metadata only Silk as a biodegradable resist for field-emission scanning probe lithography(Institute of Physics (IOP) Publishing, 2020) Sadeghi, Sadra; Rangelow, Ivo W.; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; N/A; N/A; Department of Electrical and Electronics Engineering; Alaca, Burhanettin Erdem; Kumar, Baskaran Ganesh; Melikov, Rustamzhon; Doğru-Yüksel, Itır Bakış; Nizamoğlu, Sedat; Faculty Member; Other; PhD Student; PhD Student; Faculty Member; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştirmalari Merkezi (KUYTAM); N/A; N/A; N/A; N/A; College of Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; 115108; N/A; N/A; N/A; 130295The patterning of silk allows for manufacturing various structures with advanced functionalities for optical and tissue engineering and drug delivery applications. Here, we propose a high-resolution nanoscale patterning method based on field-emission scanning probe lithography (FE-SPL) that crosslinks the biomaterial silk on conductive indium tin oxide (ITO) promoting the use of a biodegradable material as resist and water as a developer. During the lithographic process, Fowler-Nordheim electron emission from a sharp tip was used to manipulate the structure of silk fibroin from random coil to beta sheet and the emission formed nanoscale latent patterns with a critical dimension (CD) of similar to 50 nm. To demonstrate the versatility of the method, we patterned standard and complex shapes. This method is particularly attractive due to its ease of operation without relying on a vacuum or a special gaseous environment and without any need for complex electronics or optics. Therefore, this study paves a practical and cost-effective way toward patterning biopolymers at ultra-high level resolution.Publication Metadata only Structural changes in a Schiff base molecular assembly initiated by scanning tunneling microscopy tip(Institute of Physics (IOP) Publishing, 2016) Tomak, A.; Bacaksiz, C.; Mendirek, G.; Sahin, H.; Hur, D.; Gorgun, K.; Senger, R. T.; Peeters, F. M.; Zareie, H. M.; N/A; Birer, Özgür; Researcher; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; N/AWe report the controlled self-organization and switching of newly designed Schiff base (E)-4-((4-(phenylethynyl) benzylidene) amino) benzenethiol (EPBB) molecules on a Au (111) surface at room temperature. Scanning tunneling microscopy and spectroscopy (STM/STS) were used to image and analyze the conformational changes of the EPBB molecules. The conformational change of the molecules was induced by using the STM tip while increasing the tunneling current. The switching of a domain or island of molecules was shown to be induced by the STM tip during scanning. Unambiguous fingerprints of the switching mechanism were observed via STM/STS measurements. Surface-enhanced Raman scattering was employed, to control and identify quantitatively the switching mechanism of molecules in a monolayer. Density functional theory calculations were also performed in order to understand the microscopic details of the switching mechanism. These calculations revealed that the molecular switching behavior stemmed from the strong interaction of the EPBB molecules with the STM tip. Our approach to controlling intermolecular mechanics provides a path towards the bottom-up assembly of more sophisticated molecular machines.Publication Metadata only Modeling and characterization of comb-actuated resonant microscanners(Iop Publishing Ltd, 2006) N/A; Department of Electrical and Electronics Engineering; Ataman, Çağlar; Ürey, Hakan; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 8579The dynamics of the out-of-plane comb-drive actuator used in a torsional resonant mode microscanner is discussed. The microscanner is fabricated using the standard SOI technology by Fraunhofer, IPMS and utilized in various display, barcode scanning, spectroscopy and other imaging applications. The device is a parametrically excited system and exhibits hysteretic frequency response, nonlinear transient response, subharmonic oscillations, multiple parametric resonances, and alternating-oscillation-frequency behavior. Analytical and numerical models are developed to predict the parametric system dynamics. The analytical model is based on the solution of the linear Mathieu equation and valid for small angular displacements. The numerical model is valid for both small and large deflection angles. The analytical and numerical models are validated with the experimental results under various ambient pressures and excitation schemes and successfully predict the dynamics of the parametric nature of the microscanner. As many as four parametric resonances are observed at 30 mTorr. The models developed in this paper can be used to optimize the structure and the actuator.Publication Metadata only Comb-actuated resonant torsional microscanner with mechanical amplification(IEEE-Inst Electrical Electronics Engineers Inc, 2010) Brown, Dean; Davis, Wyatt O.; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; N/A; Department of Electrical and Electronics Engineering; Arslan, Aslıhan; Holmstrom, Sven; Gökçe, Sertan Kutal; Ürey, Hakan; Researcher; Researcher; Master Student; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; 8579A comb-actuated torsional microscanner is developed for high-resolution laser-scanning display systems. Typical torsional comb-drive scanners have fingers placed around the perimeter of the scanning mirror. In contrast, the structure in this paper uses cascaded frames, where the comb fingers are placed on an outer drive frame, and the motion is transferred to the inner mirror frame with a mechanical gain. The structure works only in resonant mode without requiring any offset in the comb fingers, keeping the silicon-on-insulator-based process quite simple. The design intent is to improve actuator efficiency by removing the high-drag fingers from the high-velocity scanning mirror. Placing them on the lower velocity drive frame reduces their contribution to the damping torque. Furthermore, placement on the drive frame allows an increase of the number of fingers and their capacity to impart torque. The microscanner exhibits a parametric response, and as such, the maximum deflection is found when actuated at twice its natural frequency. Analytical formulas are given for the coupled-mode equations and frame deflections. A simple formula is derived for the mechanical-gain factor. For a 1-mm x 1.5-mm oblong scanning mirror, a 76. total optical scan angle is achieved at 21.8 kHz with 196-V peak-to-peak excitation voltages. [2009-0304]Publication Metadata only Resonance fluorescence in a waveguide geometry(IEEE, 2012) Rephaeli, Eden; Fan, Shanhui; Department of Electrical and Electronics Engineering; Kocabaş, Şükrü Ekin; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; N/AWe show how to calculate the first-and second-order statistics of the scattered fields for an arbitrary intensity coherent-state light field interacting with a two-level system in a waveguide geometry. Specifically, we calculate the resonance fluorescence from the qubit, using input-output formalism. We derive the transmission and reflection coefficients, and illustrate the bunching and antibunching of light that is scattered in the forward and backward directions, respectively. Our results agree with previous calculations on one-and two-photon scattering as well as those that are based on the master equation approach.Publication Metadata only A diversity combination model incorporating an inward bias for interaural time-level difference cue integration in sound lateralization(MDPI, 2020) N/A; N/A; Department of Computer Engineering; N/A; Mojtahedi, Sina; Erzin, Engin; Ungan, Pekcan; PhD Student; Faculty Member; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; School of Medicine; N/A; 34503; N/AA sound source with non-zero azimuth leads to interaural time level differences (ITD and ILD). Studies on hearing system imply that these cues are encoded in different parts of the brain, but combined to produce a single lateralization percept as evidenced by experiments indicating trading between them. According to the duplex theory of sound lateralization, ITD and ILD play a more significant role in low-frequency and high-frequency stimulations, respectively. In this study, ITD and ILD, which were extracted from a generic head-related transfer functions, were imposed on a complex sound consisting of two low- and seven high-frequency tones. Two-alternative forced-choice behavioral tests were employed to assess the accuracy in identifying a change in lateralization. Based on a diversity combination model and using the error rate data obtained from the tests, the weights of the ITD and ILD cues in their integration were determined by incorporating a bias observed for inward shifts. The weights of the two cues were found to change with the azimuth of the sound source. While the ILD appears to be the optimal cue for the azimuths near the midline, the ITD and ILD weights turn to be balanced for the azimuths far from the midline.