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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only Optimizing photonic devices under fabrication variations with deep photonic networks(SPIE-Int Soc Optical Engineering, 2024) Department of Electrical and Electronics Engineering; Görgülü, Kazım; Vit, Aycan Deniz; Amiri, Ali Najjar; Mağden, Emir Salih; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of EngineeringWe propose a deep photonic interferometer network architecture for designing fabrication-tolerant photonic devices. Our framework incorporates layers of variation-aware, custom-designed Mach-Zehnder interferometers and virtual wafer maps to optimize broadband power splitters under fabrication variations. Specifically, we demonstrate 50/50 splitters with below 1% deviation from the desired 50/50 ratio, even with up to 15 nm over-etch and under-etch variations. The significantly improved device performance under fabrication-induced changes demonstrates the effectiveness of the deep photonic network architecture in designing fabrication-tolerant photonic devices and showcases the potential for improving circuit performance by optimizing for expected variations in waveguide width.Publication Metadata only Single-atom SN-loaded exfoliated layered titanate shows photocatalytic activity in hydrogen generation(NLM (Medline), 2023) Ide, Yusuke; Matsumoto, Hiroaki; Igarashi, Keisuke; Department of Chemistry; Üstünel, Tuğçe; Doustkhah, Esmail; Kaya, Sarp; Department of Chemistry; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Graduate School of Sciences and Engineering; College of SciencesN/APublication Metadata only Numerical simulation of milling operations on flexible composite parts(MATERIALS RESEARCH FORUM LLC, 2024) Nutte, Matthias; Riviere-Lorphevre, Edouard; Dambly, Valentin; Arrazola, Pedro-Jose; Ducobu, Francois; Department of Mechanical Engineering; Lazoğlu, İsmail; Department of Mechanical Engineering; Manufacturing and Automation Research Center (MARC); College of EngineeringFiber-reinforced polymers (FRPs) are a widely used and growing material in industry, thanks to their excellent mechanical properties. Manufactured FRPs parts usually have thin walls. These parts also require finishing operations such as edge trimming. Problems like those encountered when machining thin metal parts are also encountered with FRPs: form error, chatter vibrations and poor surface finish. However, the study and numerical modelling of thin FRP parts are not well developed up to now. The aim of this paper is to demonstrate the feasibility of adapting a numerical model for metals to FRPs. The modelling of the shape error during the thinning of a CFRP (Carbon Fiber Reinforced Polymers) part is studied in this paper using a quasi-static analysis. Compared to metals, two adaptations are introduced here for the FRPs. First, the material properties are adapted from isotropic to orthotropic. Secondly, a mechanical model was applied to calculate cutting forces for FRPs. The results of the study show the feasibility of this adaptation and examination of form error in the case of FRPs.Publication Metadata only A novel magnetomechanical pump to actuate ferrofluids in minichannels(Begell House, Inc, 2011) Bilgin, Alp; Kurtoglu, Evrim; Erk, Hadi Cagdas; Sesen, Muhsincan; Kosar, Ali; Department of Chemistry; Acar, Havva Funda Yağcı; Faculty Member; Department of Chemistry; College of Sciences; 178902An improvement in the current methods of ferrofluid actuation was presented in this paper. A novel magnetomechanical microfluidic pump design was implemented with a ferrofluid as the active working fluid. Obtained flow rates were comparable to previous results in this research line. It was also seen that the basic pump architecture, which the subject pump is based on, enables much more room for further development.Publication Metadata only Impregnation of Ru(cod)(tmhd)(2) into PDMS film in supercritical carbon dioxide(Trans Tech Publications Ltd, 2012) Ge, Minglan; Ding, Fuchen; Department of Chemical and Biological Engineering; Erkey, Can; Faculty Member; Department of Chemical and Biological Engineering; College of Engineering; 29633Metallopolymer nanocomposites has attracted much attention recently. The impregnation of organometallic compound from the supercritical solution into the polymer matrix has several advantages. The impregnation process isotherm of bis(2,2,6,6-tetramethy1-3,5-heptanedionato) (1,5-cyclooctadiene) ruthenium (II) (Ru(cod)(tmhd)(2)) into polydimethylsiloxane (PDMS) film in supercritical carbon dioxide (scCO(2)) was investigated. The experiments for determining the isotherm were carried out at 40 degrees C and 10.34 MPa. It was found that the impregnation isotherm is linear up to the saturation concentration of the precursor in scCO(2) fluid phase. The slope of the linear curve defined equilibrium partition coefficient K provides a measure of the partitioning of Ru(cod)(tmhd)(2) between the PDMS film and scCO(2) fluid phase and it is constant under the same conditions. It showed that K is mainly govered by the density of scCO(2) and does not change much with temperature at a constant density of scCO(2).Publication Metadata only Development of highly stable and luminescent aqueous CdS quantum dots with the poly(acrylic acid)/mercaptoacetic acid binary coating system(Amer Scientific Publishers, 2009) Lieberwirth, I.; Department of Chemistry; N/A; Department of Chemical and Biological Engineering; Acar, Havva Funda Yağcı; Çelebi, Serdar; Serttunalı, Nazlı İpek; Faculty Member; Master Student; Undergraduate Student; Department of Chemistry; Department of Chemical and Biological Engineering; College of Sciences; Graduate School of Sciences and Engineering; College of Engineering; 178902; N/A; N/AHighly stable and luminescent CdS quantum dots (QD) were prepared in aqueous solutions via in situ capping of the crystals with the poly(acrylic acid) (PAA) and mercaptoacetic acid (MAA) binary mixtures. The effect of reaction temperature and coating composition on the particle size, colloidal stability and luminescence were investigated and discussed in detail. CdS QDs coated with either PAA or MAA were also prepared and compared in terms of properties. CdS-MAA QDs were highly luminescent but increasing reaction temperature caused an increase in the crystal size and a significant decrease in the quantum yield (QY). Although less luminescent and bigger than CdS-MAA, CdS-PAA QDs maintained the room temperature size and QY at higher reaction temperatures. CdS-MAA QDs lacked long term colloidal stability whereas CdS-PAA QDs showed excellent stability over a year. Use of PAA/MAA mixture as a coating for CdS nanoparticles during the synthesis provided excellent stability, high QY and ability to tune the size and the color of the emission. Combination of all of these properties can be achieved only with the mixed coating. CdS coated with PAA/MAA at 40/60 ratio displayed the highest QY (50% of Rhodamine B) among the other compositions.Publication Metadata only Hybrid cufe-cofe Prussian blue catalysts on BIVO4 for enhanced charge separation and injection for photoelectrochemical water oxidation(American Chemical Society (ACS), 2022) Vishlaghi, Mahsa Barzgar; Akbari, Sina Sadigh; Karadas, Ferdi; Department of Chemistry; N/A; N/A; Kaya, Sarp; Usman, Emre; Barzgarvishlaghi, Mahsa; Faculty Member; Master Student; PhD Student; Department of Chemistry; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); College of Sciences; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; 116541; N/A; N/AThe utilization of cocatalysts on the photoelectrode surface is a feasible strategy to achieve a high photocurrent density in the photoelectrochemical water oxidation process. The catalysts can enhance the activity by improving the reaction kinetics, retarding charge carrier recombination, or accumulating charge carriers. In this work, we have utilized a CuFe-CoFe Prussian blue (PB) catalyst layer on the BiVO4 photoanode surface to enhance its water oxidation activity. The hybrid catalyst, in which the semiprecious cobalt ions are partially substituted with earth-abundant copper ions, exhibits 56% higher photocurrent density than the CoFe PB-modified BiVO4. We show that photogenerated hole accumulation is present in the CuFe PB layer, which results in higher charge extraction from the BiVO4 surface. The CoFe PB layer on top of the CuFe one facilitates the charge transfer due to its catalytic activity toward the oxygen evolution reaction (OER).Publication Metadata only Recent technological developments in the diagnosis and treatment of cerebral edema(Wiley-V C H Verlag Gmbh, 2021) Deshmukh, Karthikeya P.; Jiang, Nan; Yetişen, Ali K.; N/A; Department of Mechanical Engineering; Dabbagh, Sajjad Rahmani; Taşoğlu, Savaş; N/A; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 291971Latest technological advancements in neurocritical care have translated to improved clinical outcomes and have paved the way for the effective diagnosis and treatment of cerebral edema. Effective management of cerebral edema has the potential to provide a personalized treatment by obtaining the complete pathophysiological information of the patient. The aims of this review are to inform the reader about the research and development in this field in the past decade as well as the materialization of scientific literature through patents. There is a growing interest in multimodal monitoring of the diseased brain as it provides a necessary means to implement effective intervention strategies. Although there is a gradual shift toward the adoption of noninvasive devices for research purposes, their clinical applications are hindered by their inaccuracies. However, the inherent risk of complication and high costs of implementation challenge the status quo. The role of neuroprotectants is explored and the combination of neurodiagnostic and neuroprotective approaches is proposed. Finally, the impacts of the current state of global affairs are discussed and it is predicted that the rising number of traumatic brain injury patents will inevitably translate to improvements in technologies to effectively address cerebral edema.Publication Metadata only An easily available lysosomal-targeted ratiometric fluorescent probe with aggregation induced emission characteristics for hydrogen polysulfide visualization in acute ulcerative colitis(Royal Society of Chemistry (RSC), 2021) Xiang, Chunbai; Li, Chunbin; Xiang, Jingjing; Luo, Yuan; Peng, Jiaofeng; Deng, Guanjun; Wang, Jianguo; Li, Hongchun; Zhang, Pengfei; Gong, Ping; Cai, Lintao; Department of Chemistry; Kölemen, Safacan; Faculty Member; Department of Chemistry; College of Sciences; 272051Hydrogen polysulfide (H2Sn, n >1), as a direct oxidizing form of hydrogen sulfide, is closely associated with intestinal diseases such as ulcerative colitis (UC). A probe that can selectively detect H2Sn in the pathological environment of UC is in urgent demand. Ratiometric probes are powerful in the quantitative detection of H2Sn in living organisms. Herein, we developed a ratiometric fluorescent probe TCFPB-H2Sn for selective detection of H(2)S(n)in vitro and in vivo. Significantly, TCFPB-H2Sn demonstrated a fast, sensitive and specific detection performance for H2Sn, and has excellent lysosomal targeting ability and aggregation-induced emission (AIE) characteristics. More importantly, TCFPB-H2Sn was the first probe to achieve endogenous H2Sn imaging in acute ulcerative colitis successfully.Publication Metadata only Elastic constants of a Laves phase compound: C15 NbCr2(Materials Research Society, 1997) Chu, Fredy; Wills, Josephine M.; Chen, S. P.; Albers, Robert C; Thoma, Dan J.; Mitchell, Thomas Elliot; Department of Physics; Örmeci, Alim; Researcher; Department of Physics; College of Sciences; N/AThe single-crystal elastic constants of C15 NbCr2 have been computed by using a first-principles, self-consistent, full-potential total energy method. From these single-crystal elastic constants the isotropic elastic moduli are calculated using the Voigt and Reuss averages. The calculated values are in fair agreement with the experimental values. The implications of the results are discussed with regards to Poisson's ratio and the direction dependence of Young's modulus.