174 research outputs found
Tensile properties of CFRP manufactured by resin transfer molding considering stacking sequences at various strain rates
No full textThis paper is concerned with the improvement of a tensile test method and the material properties of carbon fiber reinforced polymer manufactured by resin transfer molding considering stacking sequences at various strain rates for auto-body. Auto-body structure experiences the strain rates up to several hundreds per second during car crash. In order to apply the carbon fiber reinforced polymer panel into auto-body structures, it is critical to acquire the material properties of carbon fiber reinforced polymer at various strain rates considering stacking sequences. The tensile test method is improved for acceptable test results. Test specimens are modified for high-speed tensile tests of carbon fiber reinforced polymer in order to achieve designated strain rates and eliminate the effect from unfavorable conditions of inhomogeneity of deformation. Various types of grip tab materials are employed for acceptable failure modes. Tensile tests have been carried out with non-crimp fabric made by 50K high strength carbon fiber (NCF) and woven fabric made by a 2/2 twill pattern of 3K high strength carbon fiber (TWILL) with different stacking sequences of 0 degrees and 90 degrees unidirectional cases as well as [0 degrees/90 degrees] and [45 degrees/-45 degrees] symmetric cases. Digital image correlation method and force equilibrium grid method are adopted for strain and stress measurement of a carbon fiber reinforced polymer specimen during a tensile test. The material properties acquired indicate that the carbon fiber has little rate dependency, while the epoxy matrix has remarkable rate hardening at strain rates from 0.001 s(-1) to 100 s(-1).
Variational approach to bifurcation from infinity for nonlinear elliptic problems
No full textFor any N >= 1 and sufficiently small epsilon > 0, we find a positive solution of a nonlinear elliptic equation Delta u = epsilon(2)(V(x)u - f(u)), x is an element of R-N, when lim(vertical bar x vertical bar ->infinity) V(x) = m > 0 and some optimal conditions on f are satisfied. Furthermore, we investigate the asymptotic behaviour of the solution as epsilon -> 0
Semi-classical standing waves for nonlinear Schrodinger equations at structurally stable critical points of the potential
No full textWe consider a singularly perturbed elliptic equation epsilon(2)Delta u - V(x)u + f(u) = 0, u(x) > 0 on R-N, lim(vertical bar x vertical bar ->infinity) u(x) = 0, where V(x) > 0 for any x is an element of R-N. The singularly perturbed problem has corresponding limiting problems Delta U - cU + f(U) = 0, U(x) > 0 on R-N, lim(vertical bar x vertical bar ->infinity) u(x) = 0, c > 0. Berestycki-Lions [3] found almost necessary and sufficient conditions on the nonlinearity f for existence of a solution of the limiting problem. There have been endeavors to construct solutions of the singularly perturbed problem concentrating around structurally stable critical points of the potential V under possibly general conditions on f. In this paper, we prove that under the optimal conditions of Berestycki-Lions on f is an element of C-1, there exists a solution concentrating around topologically stable positive critical points of V, whose critical values are characterized by minimax methods
A 7.8Gb/s/pin 1.96pJ/b Compact Single-Ended TRX and CDR with Phase-Difference Modulation for Highly Reflective Memory Interfaces
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STRUCTURAL CHARACTERIZATION AND SUBUNIT COMMUNICATION OF ESCHERICHIA COLI PYRUVATE DEHYDROGENASE MULTIENZYME COMPLEX By
No full textand approved b
mavros_controllers - Aggressive trajectory tracking using mavros for PX4 enabled vehicles
No full text<p>Aggressive trajectory tracking using mavros offboard commands for PX4 enabled vehicles</p>
B-TMS: Bayesian Traversable Terrain Modeling and Segmentation Across 3D LiDAR Scans and Maps for Enhanced Off-Road Navigation
No full textRecognizing traversable terrain from 3D point cloud data is critical, as it directly impacts the performance of autonomous navigation in off-road environments. However, existing segmentation algorithms often struggle with challenges related to changes in data distribution, environmental speci- ficity, and sensor variations. Moreover, when encountering sunken areas, their performance is frequently compromised, and they may even fail to recognize them. To address these challenges, we introduce B-TMS, a novel approach that per- forms map-wise terrain modeling and segmentation by utilizing Bayesian generalized kernel (BGK) within the graph structure known as the tri-grid field (TGF). Our experiments encompass various data distributions, ranging from single scans to partial maps, utilizing both public datasets representing urban scenes and off-road environments, and our own dataset acquired from extremely bumpy terrains. Our results demonstrate notable contributions, particularly in terms of robustness to data distribution variations, adaptability to diverse environmental conditions, and resilience against the challenges associated with parameter changes
Novel phase and phase transition behavior of a superionic conductor observed on the nanoscale
Get PDFThis dissertation documents the work performed in the pursuit of a PhD degree in the research group of Prof. Prashant K. Jain at the University of Illinois at Urbana-Champaign. I employed in-situ transmission electron microscopy (TEM) for understanding the ionic structure, vacancy ordering, phase transitions, and ion transport in a prototypical fast-ion conductor, copper selenide. Major objectives of my work were to elucidate i) the nature of the structural phase transition by which copper selenide becomes a superionic phase and ii) the microscopic mechanisms of ionic motion in this material. My studies were performed on nanostructures of copper selenide. Chapter 1 introduces the concept of a superionic conductor and describes one particular example, copper selenide, which is the model system studied in my work. Also, I briefly discuss in-situ high-resolution TEM the primary technique I used, and the advantages and capabilities this method offered for my studies of copper selenide. Chapter 2 presents an interesting finding made in the course of my TEM studies: the observation of a novel phase of cuprous selenide in nanocrystals. This novel phase exhibits an unusually longer-range of Cu-vacancy ordering and is found from density functional theory (DFT) calculations to be a metastable phase. After thorough characterization of the different phases of copper selenide in nanocrystals under TEM, I investigated, using in-situ TEM, the phase transition behavior of copper selenide nanocrystals from their ordered state to their superionic phase, the results of which are described in Chapter 3. From the spatiotemporal kinetics interrogated by in-situ TEM, we determined the precise nucleation sites of the phase transition and establish a correlation between the dynamics of the cations and anions in the transition. Next, we studied using in-situ TEM the ionic structure and dynamics in copper selenide nanowires, which are one-dimensional structures with anisotropy unlike zero-dimensional nanocrystals. As described in Chapter 4, I observed anti-phase boundaries, a type of planar defect, in the nanowires. Investigation of the phase transition behavior near anti-phase boundaries led us to conclude that this planar defect impedes the growth of the superionic phase. Also, I observed the motion of this defect under electron beam irradiation. From the characteristics of the motion, we infer how copper ions migrate in the copper selenide lattice. Taken together, my work leveraged well-defined nanostructures and in-situ TEM to shed broadly applicable insights into the atomistic dynamics involved in a phase transition, vacancies and defects in ionic compounds, and the nature of cation transport in superionic materials.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2022-12-01The student, Jaeyoung Heo, accepted the attached license on 2020-11-30 at 18:02.The student, Jaeyoung Heo, submitted this Dissertation for approval on 2020-11-30 at 21:46.This Dissertation was approved for publication on 2020-12-03 at 08:07.DSpace SAF Submission Ingestion Package generated from Vireo submission #15999 on 2021-03-04 at 16:20:01Made available in DSpace on 2021-03-05T21:42:45Z (GMT). No. of bitstreams: 12
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Previous issue date: 2020-12-03Embargo set by: Seth Robbins for item 117219
Lift date: 2023-03-05T21:43:00Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Onl
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