51 research outputs found
Microscale study of frictional properties of graphene in ultra high vacuum
No full textWe report on the frictional properties of epitaxial graphene on SiC in ultra high vacuum. Measurements have been performed using a microtribometer in the load regime of 0.5 to 1 mN. We observed that a ruby sphere sliding against graphene results in very low friction coefficients ranging from 0.02 to 0.05. The friction and also the stability of the graphene layer is higher than that under similar conditions in ambient conditions. The friction shows a load dependence. Finally it was found that graphene masks the frictional anisotropy which was observed on the SiC surface
Untersuchungen zum Einlaufverhalten binärer alpha-Messinglegierungen unter Ölschmierung in Abhängigkeit des Zinkgehaltes
No full textReibsysteme müssen heutzutage immer größeren technischen, ökologischen und ökonomischen Anforderungen bei gleichzeitig abnehmender Reibung und Verschleiß gerecht werden. Eine Möglichkeit dies zu erreichen ist, das Einlaufverhalten von tribologischen Systemen zu optimieren. In der vorliegenden Arbeit wird das Einlaufverhalten von binären Messinglegierungen gegen 1.3505 unter Ölschmierung untersucht
Thermal conductance of interfaces between titanium nitride and group IV semiconductors at high temperatures
No full textThis article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Samreen Khan, Xinping Shi, Joseph Feser, Richard Wilson; Thermal conductance of interfaces between titanium nitride and group IV semiconductors at high temperatures. Appl. Phys. Lett. 22 July 2024; 125 (4): 041601. https://doi.org/10.1063/5.0220124 and may be found at https://doi.org/10.1063/5.0220124.
© 2024 Author(s). Published under an exclusive license by AIP Publishing.
This article will be embargoed until 07/22/2025.Measuring the temperature dependence of material properties is a standard method for better understanding the microscopic origins for that property. Surprisingly, only a few experimental studies of thermal boundary conductance at high temperatures exist. This lack of high temperature data makes it difficult to evaluate competing theories for how inelastic processes contribute to thermal conductance. To address this, we report time domain thermoreflectance measurements of the thermal boundary conductance for TiN on diamond, silicon-carbide, silicon, and germanium between 120 and 1000 K. In all systems, the interface conductance increases monotonically without stagnating at higher temperatures. For TiN/SiC interfaces, ranges from 330 to 1000 MW/m2-K, with a room temperature conductance of 750 MW/m2-K. The interface conductance for TiN/diamond ranges from 140 to 950 MW/m2-K. Notably, for all four interfacial systems, the conductance continues to increase with temperature even after all phonon modes in the vibrationally soft material are thermally excited. This observation suggests that inelastic processes are significant contributors to the thermal conductance in all four interfacial systems, regardless of whether the materials forming the interface are vibrationally similar or dissimilar. Our study fills a notable gap in the literature for how interfacial conductance evolves at high temperatures and tests burgeoning theories for the role of inelastic processes in interfacial thermal transport.This work was supported as part of ULTRA, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award No. DE-SC0021230
Differences in unilateral chest press muscle activation and kinematics on a stable versus unstable surface while holding one versus two dumbbells
No full textabstract: Training the bench press exercise on a traditional flat bench does not induce a level of instability as seen in sport movements and activities of daily living. Twenty participants were recruited to test two forms of instability: using one dumbbell rather than two and lifting on the COR bench compared to a flat bench. Electromyography (EMG) amplitudes of the pectoralis major, middle trapezius, external oblique, and internal oblique were recorded and compared. Differences in range of motion (ROM) were evaluated by measuring an angular representation of the shoulder complex. Four separate conditions of unilateral bench press were tested while lifting on a: flat bench with one dumbbell, flat bench with two dumbbells, COR Bench with one dumbbell, and COR Bench with two dumbbells. The results imply that there are no differences in EMG amplitude or ROM between the COR bench and traditional bench. However, greater ROM was found to be utilized in the single dumbbell condition, both in the COR bench and the flat bench.The final version of this article, as published in PeerJ, can be viewed online at: https://peerj.com/articles/1365
Development of global inter-country inter-industry system for various policy perspectives
No full textGlobalization and international economic integration are not new phenomena. However, the recent evolution of global supply and procurement networks has significantly changed foreign dependencies both for inputs (imports) and outputs (exports). These important changes in global production systems challenge conventional statistics and databases provided by national statistics offices since these are no longer sufficient to provide adequate insights into policy discussions. The notable specification features of the global interindustry model developed in this thesis are summarized as follows:
1) Covers approximately 90% to 95% of global value added, exports, imports and production are available in the system for individual countries for time series between 1995 and 2011.
2) It is harmonized with the System of National Accounts, an international comparable accounting framework of economic statistics. Therefore, GDP, trade balances and final expenditures in the model of this thesis match the numbers officially published by national statistics agencies.
3) The direct purchases by non-residents and international transportation and trade margin structures are estimated at the sectoral level. To author’s knowledge, this is a unique methodology to link the statistical sources in purchases’ and basic prices. Without this methodological specification, a large part of the trade in services particularly for wholesale, water and air transportation and tourism expenditures on hotels and restaurants industries would be misallocated as is the case in many earlier inter-country (multi-regional) models.
4) The model is specifically designed to analyze the globalization impacts for different policy areas with important extensions to account for regional dimension (Chapter 3) and the role of firm heterogeneity on trade intensity (Chapter 4).
The subsequent chapters of this dissertation detail the methodology for the compilation techniques used to develop the various types of international input-output (IIO) models to analyze the different policy areas described in Chapter 1. The second chapter describes the estimation procedure for developing a spatially extensive IIO model using to the maximum possible extent all available statistical data sources. This model is, therefore, capable of analyzing various policy areas discussed earlier. The third chapter is an extension of the model developed in the second chapter in the context of subnational regions. This extension allows regional planners to analyze the economic impact in the context of participation of regional economies in global production networks. The extension of the model in chapter 4 is particularly designed to analyze the Trade in Value Added (TiVA) indicators by introducing firm heterogeneity in the processing trade of manufacturing activities using examples from China and Mexico. This split in processing trade activities greatly enhances the understanding of the role and magnitude of empirical estimates of emerging regions where their primary tasks in production systems are assigned for the assembly of imported intermediate products. The final chapter provides a summary of this thesis and discusses the wide range of additional policy analyses directly conducted by author.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2019-12-01The student, Norihiko Yamano, accepted the attached license on 2017-11-25 at 16:54.The student, Norihiko Yamano, submitted this Dissertation for approval on 2017-11-25 at 16:57.This Dissertation was approved for publication on 2017-11-30 at 09:02.DSpace SAF Submission Ingestion Package generated from Vireo submission #11754 on 2018-03-13 at 09:55:52Made available in DSpace on 2018-03-13T15:21:09Z (GMT). No. of bitstreams: 2
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Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 105168
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Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 105168
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Effects of load on good morning kinematics and EMG activity
No full textabstract: Many strength and conditioning coaches utilize the good morning (GM) to strengthen the hamstrings and spinal erectors. However, little research exists on its electromyography (EMG) activity and kinematics, and how these variables change as a function of load. The purpose of this investigation was to examine how estimated hamstring length, integrated EMG (IEMG) activity of the hamstrings and spinal erectors, and kinematics of the lumbar spine, hip, knee, and ankle are affected by changes in load. Fifteen trained male participants (age = 24.6 ± 5.3 years; body mass = 84.7 ± 11.3 kg; height = 180.9 ± 6.8 cm) were recruited for this study. Participants performed five sets of the GM, utilizing 50, 60, 70, 80, and 90% of one-repetition maximum (1RM) in a randomized fashion. IEMG activity of hamstrings and spinal erectors tended to increase with load. Knee flexion increased with load on all trials. Estimated hamstring length decreased with load. However, lumbar flexion, hip flexion, and plantar flexion experienced no remarkable changes between trials. These data provide insight as to how changing the load of the GM affects EMG activity, kinematic variables, and estimated hamstring length. Implications for hamstring injury prevention are discussed. More research is needed for further insight as to how load affects EMG activity and kinematics of other exercises.The final version of this article, as published in PeerJ, can be viewed online at: https://peerj.com/articles/708
Skilled labor spillovers from University to High Tech Corporations: The Case of the Research Triangle Park and the University of North Carolina at Chapel Hill
No full textRobust covariance estimation for data fusion from multiple sensors
No full textThis paper addresses the robust estimation of a covariance matrix to express uncertainty when fusing information from multiple sensors. This is a problem of interest in multiple domains and applications, namely, in robotics. This paper discusses the use of estimators using explicit measurements from the sensors involved versus estimators using only covariance estimates from the sensor models and navigation systems. Covariance intersection and a class of orthogonal Gnanadesikan-Kettenring estimators are compared using the 2-norm of the estimates. A Monte Carlo simulation of a typical mapping experiment leads to conclude that covariance estimation systems with a hybrid of the two estimators may yield the best results.IEEE Transactions on Instrumentation and Measuremen
In situ observation of wear particle formation on lubricated sliding surfaces
No full textS.420-429The topography of a Cu surface was monitored in situ during a sliding experiment with lubrication. Fe and steel pins were used as counter-faces and poly alpha olefin (PAO-8) was utilized as lubricant. 3-D images of a specific area within the wear track were acquired after every cycle. These experiments were carried out with a state-of-the-art tribometer, which uses a holographic microscope in immersion to observe the Cu surface online. The results show the evolution of the wear track, with a particular focus on the generation of flake-like wear particles. For the first time, these phenomena are correlated with the dynamic behavior of the surface. It is shown that the generation of wear particles results from various processes that occur on the surface, apart from crack propagation. The areas where wear takes place spread within the wear track during the experiment. Additional investigations of the subsurface structure were performed by means of focussed ion beam cross-s ections. These revealed a gradient from nanocrystalline to ultrafine-crystalline grain structure beneath the Cu surface, as well as an orientation effect when sliding in one direction, linking the present work with the results published in the literature. Finally, X-ray photoelectron spectroscopy depth profiles were obtained from the counter-faces. These indicated material transfer from the softer to the harder surface, but no deposition from the sliding pins onto the Cu surface.60Nr.
Modelling, Simulating and Forecasting Regional Climate and Weather
No full textThis eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contac
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