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Kinetic Hydrate Inhibitors─Which is Best, Block or Statistical Copolymers?
Get PDFKinetic hydrate inhibitors (KHIs) have been used for nearly 30 years to prevent gas hydrate formation in oil and gas production flow lines. The main component in KHI formulations is one or more water-soluble polymers. Copolymers are often used, to improve either the performance or compatibility issues such as high temperature or brine composition. Industrially, copolymers are mostly obtained by conventional radical polymerization, giving statistical copolymers. Some work has been previously reported on block copolymers as KHIs but it is still not clear if this type of polymer structure gives any significant advantages. Here we report the controlled synthesis of well-defined statistical and block copolymers containing the most commercially common vinyl amide monomers used in KHIs, that is, N-vinyl caprolactam, N-vinylpyrrolidone, and N-isopropylacrylamide. The polymerization control enabled a good structural comparison of the KHI performance of block versus statistical copolymers. KHI experiments were conducted under high pressure in steel rocking cells with a natural gas mixture. Most tests were without but sometimes with a liquid hydrocarbon phase. In summary, we did not observe a significant performance improvement for the block copolymers compared to that of the equivalent statistical copolymers.journal articl
Generating Diverse Translation with Perturbed kNN-MT
No full textGenerating multiple translation candidates would enable users to choose the one that satisfies their needs.Although there has been work on diversified generation, there exists room for improving the diversity mainly because the previous methods do not address the overcorrection problem$2014the model underestimates a prediction that is largely different from the training data, even if that prediction is likely.This paper proposes methods that generate more diverse translations by introducing perturbed k-nearest neighbor machine translation (kNN-MT).Our methods expand the search space of kNN-MT and help incorporate diverse words into candidates by addressing the overcorrection problem.Our experiments show that the proposed methods drastically improve candidate diversity and control the degree of diversity by tuning the perturbation’s magnitude.conference pape
Atomic-Scale Multimodal Characterization of Self-Assembled InAs/InGaAlAs Quantum Dots
No full textSelf-assembled quantum dots (QDs) are potential candidates for photoelectric and photovoltaic devices, because of their discrete energy levels. The characterization of QDs at the atomic level using a multimodal approach is crucial to improving device performance because QDs are nanostructures with highly correlated structural parameters. In this study, scanning transmission electron microscopy, geometric phase analysis, and atom probe tomography were employed to characterize structural parameters such as the shape, strain, and composition of self-assembled InAs-QDs with InGaAlAs spacer layers. The measurements revealed characteristic AlAs-rich regions above the QDs and InAs-rich regions surrounding the QD columns, which can be explained by the relationship between the effect of strain and surface curvature around the QD. The methodology described in this study accelerates the development of future QD devices because its multiple perspectives reveal phenomena such as atomic-scale segregations and allow for more detailed discussions of the mechanisms of these phenomena.journal articl
High-resolution electron energy analyzer with wide acceptance angle for hard X-ray photoelectron holography: integrating PESCATORA and retarding field analyzer
Get PDFPhotoelectron holography requires measuring the photoelectron angular distribution across a wide acceptance angle, typically exceeding ±45°. This necessitates an electron analyzer that offers both a large acceptance angle and high energy resolution for kinetic energies ranging from several hundred to several thousand eV. Our previously developed high-resolution retarding field analyzer (RFA) achieves excellent energy resolution. However, its close electrode spacing limits operation at high voltages (several thousand eV). To address this limitation, we propose a novel electron analyzer that combines a parallelizing electron lens (PESCATORA) with an RFA. The PESCATORA lens parallelizes the trajectories of photoelectrons. Subsequently, the RFA decelerates and analyzes their energy. This two-stage approach allows for a sufficient distance between the RFA electrodes, enabling high-voltage operation. The resulting analyzer functions as a high-pass filter with a sharp energy cut-off. By incorporating lock-in detection, this system can be further worked as a bandpass electron analyzer. Our simulation also suggests that a specially designed mesh electrode within the RFA allows bandpass operation without the need for lock-in detection.journal articl
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Get PDF奈良先端科学技術大学院大学博士(工学)doctoral thesi
Development of Implantable Multifunctional Sensing System for Fluorescence Imaging and Fast-scan Cyclic Voltammetry
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Test Case Generation for Python Libraries Using Execution Traces of Client Projects’ Test-Suites
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An Empirical Study to Understand Pythonic Lists and Dictionaries Usage in Textbooks
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