580 research outputs found
Codoping Zinc Oxide Nanowires
No full textabstract: The zinc oxide nanowires being grown are not developing properly and need to be fixed. In order to do this, the furnace equipment and experimental procedure must be tested until the results produced yield acceptable quality zinc oxide nanowires. After experimentation the nanowires were produced to an acceptable quality. With quality nanowires to experiment with, testing began to examine the effects of different thicknesses of aluminum dopants. Once doped and annealed, the wires were transferred to a substrate with a grid so contact points could be applied. However; the experiment was phased out once this step was half way complete due to the lab shifting to examine co-doping zinc oxide nanowires as explored in part two of this paper. The goal of co-doping zinc oxide film is to create an ideal p/n type relationship for power generation, so this project focuses on altering the electrical properties of zinc oxide through doping that will allow more energy to be generated from the solar panels than current zinc oxide solar panels. The zinc oxide film doped with manganese was sputtered onto a silicon substrate. The experiment failed to create a co-doped sample because an x-ray photoelectron spectroscopy reading of the sample proved no nitrogen existed in the zinc oxide doped with manganese film. This experiment leads into this research teams work with co-doping, so instead of viewing this project as a failure it is seen as a learning experience. The research team is examining the results and creating new experiments to run to fix the problem. I currently work with my mentor Dr. Hongbin Yu and Seung Ho Ahn while doing research
Theoretical and Finite Element Analysis of Origami and Kirigami Based Structures
No full textabstract: Origami and kirigami, the technique of generating three-dimensional (3D) structures from two-dimensional (2D) flat sheets, are now more and more involved in scientific and engineering fields. Therefore, the development of tools for their theoretical analysis becomes more and more important. Since much effort was paid on calculations based on pure mathematical consideration and only limited effort has been paid to include mechanical properties, the goal of my research is developing a method to analyze the mechanical behavior of origami and kirigami based structures. Mechanical characteristics, including nonlocal effect and fracture of the structures, as well as elasticity and plasticity of materials are studied. For calculation of relative simple structures and building of structures’ constitutive relations, analytical approaches were used. For more complex structures, finite element analysis (FEA), which is commonly applied as a numerical method for the analysis of solid structures, was utilized. The general study approach is not necessarily related to characteristic size of model. I believe the scale-independent method described here will pave a new way to understand the mechanical response of a variety of origami and kirigami based structures under given mechanical loading.Dissertation/ThesisDoctoral Dissertation Mechanical Engineering 201
The Techniques of Eye Movement Operating System Based on Human Eye Movements Characteristics
No full textQuasi-Double Diagonally Dominant H-Tensors and the Estimation Inequalities for the Spectral Radius of Nonnegative Tensors
No full textIn this paper, we study two classes of quasi-double diagonally dominant tensors and prove they are H-tensors. Numerical examples show that two classes of H-tensors are mutually exclusive. Thus, we extend the decision conditions of H-tensors. Based on these two classes of tensors, two estimation inequalities for the upper and lower bounds for the spectral radius of nonnegative tensors are obtained
Linear convergence of the NQZ algorithm for finding the H-spectral radius of nonnegative tensors.
No full textThe R-linear convergence of the NQZ algorithm for computing the H-spectral radius of a class of weakly irreducible nonnegative tensors is established by utilizing the directed graphs of tensors. Meanwhile, an upper bound for the root convergence factor R is derived and a general condition ensuring the linear convergence of the NQZ algorithm is provided
Usefulness of the CHADS2 and R2CHADS2 scores for prognostic stratification in patients with coronary artery disease
No full textYuerui Li, Juan Wang, Lyu Lv, Cui Xu, Hongbin Liu Department of Geriatric Cardiology, Chinese PLA General Hospital, National Clinical Research Center for Geriatric Diseases, Beijing, China Objective: The current risk model for long-term prediction in coronary artery disease (CAD) is complicated, while a simple useful model is still lacking. We aim to investigate if CHADS2 and R2CHADS2 scores could predict long-term outcome for patients with CAD. Patients and methods: We enrolled 3,700 patients with CAD between November 2010 and September 2014 at the Department of Cardiology from Chinese PLA General Hospital. The CHADS2 and R2CHADS2 scores were calculated. All cases were followed to track the incidence of composite end point consisting of cardiovascular (CV) death, myocardial infarction (MI), stroke, heart failure, and all-cause death. Results: During a median 2.9-year follow-up, 443 patients experienced at least one element of the composite end point of CV death (n=168 [4.6%]), MI (n=59 [1.6%]), stroke (n=96 [2.6%]), heart failure (n=101 [2.8%]), and all-cause death (n=240 [6.6%]). Multivariate Cox regression analyses showed that the CHADS2 score (hazard ratio [HR]: 2.18, 95% CI: 2.00–2.38, p<0.0001) and the R2CHADS2 score (HR: 1.93, 95% CI: 1.83–2.04, p<0.0001) were independently associated with composite outcome. Receiver-operating characteristic analysis showed that compared with the CHADS2 score, the R2CHADS2 score had better discrimination for the prediction of long-term combined outcome (0.772 vs 0.791, p=0.0013). Conclusion: CHADS2 and R2CHADS2 scores provide a quick and useful tool in predicting long-term outcome for patients with CAD. Keywords: CHADS2 score, R2CHADS2 score, coronary artery disease, prognosis, risk factors, renal functio
Cationic Effects on Photo- and X-ray Radioluminescence of K<sub>3</sub>RE(PO<sub>4</sub>)<sub>2</sub>:Ce<sup>3+</sup>/Pr<sup>3+</sup> (RE = La, Gd, and Y) Phosphors toward X-ray Detection
No full textCationic tuning for lanthanide (Ce3+/Pr3+)-activated inorganic phosphors with stable, efficient, and fast-decay 5d-4f emissions has emerged as an important strategy toward the continuing pursuit of superior scintillators. The in-depth understanding of the cationic effects on photo- and radioluminescence of lanthanides Ce3+ and Pr3+ centers is requisite for the rational cationic tuning. Here, we perform a systematic study on the structure and photo- and X-ray radioluminescence properties of K3RE(PO4)2:Ce3+/Pr3+ (RE = La, Gd, and Y) phosphors to elucidate the underlying cationic effects on their 4f-5d luminescence. By using the Rietveld refinements, low-temperature synchrotron-radiation vacuum ultraviolet-ultraviolet spectra, vibronic coupling analyses, and vacuum-referred binding energy schemes, the origins of lattice parameter evolutions, 5d excitation energies, 5d emission energies, and Stokes shifts as well as good emission thermal stabilities of K3RE(PO4)2:Ce3+ systems are revealed. In addition, the correlations of Pr3+ luminescence to Ce3+ in the same sites are also discussed. Finally, the X-ray excited luminescence manifests that the K3Gd(PO4)2:1%Ce3+ sample possesses a light yield of ∼10,217 photons/MeV, indicating its potentiality toward X-ray detection application. These results deepen the understanding of cationic effects on Ce3+ and Pr3+ 4f-5d luminescence and inspire the inorganic scintillator development.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.RST/Luminescence Material
Graphene-Supported Silver Nanoparticles for pH-Neutral Electrocatalytic Oxygen Reduction
No full textDeveloping an electrocatalyst with desired activity and affordable cost for oxygen reduction reaction (ORR) of microbial fuel cell (MFC) remains a key challenge for practical application of MFC in wastewater treatment. In order to find an economic replacement of Pt-based catalysts while maintaining comparable catalytic efficiency, an electrocatalyst of graphene-supported silver nanoparticles (AgNPs/rGO) was prepared via a facile coreduction and its activity toward ORR in pH-neutral MFC was examined. It has been demonstrated that one-pot aqueous coreduction yielded high-quality AgNPs/rGO catalyst, as revealed by X-ray diffraction and transmission electron microscope. Interestingly, the XPS profiles also indicated the presence of oxygen-containing groups on graphene surface, which provided nuclei to form AgNPs. The resultant AgNPs/rGO catalyst displayed good ORR catalytic activity under pH-neutral condition in cyclic voltammogram and its selectivity of four-electron reduction was verified by rotating disk electrode (RDE) measurement. Moreover, AgNPs/rGO could deliver power generation and sustainability comparable to those of commercial Pt/C in a double-chamber MFC. Thus, we have demonstrated, for the first time, that graphene sheets may provide an alternative way for preparation of Ag nanocomposite catalyst and AgNPs when loaded onto graphene surface can function as a promising replacement of Pt-based catalysts under pH-neutral condition. Since Ag is less expensive and more resistant to poisons than Pt, AgNPs/rGO has better potential to be applied to MFC for recovering energy during wastewater treatment.Engineering, Electrical & ElectronicNanoscience & NanotechnologyMaterials Science, MultidisciplinaryPhysics, AppliedSCI(E)[email protected]; [email protected]; [email protected]; [email protected]; [email protected]
Commutators of Marcinkiewicz integrals on Herz spaces with variable exponent
No full textsummary:Let for be a homogeneous function of degree zero and a BMO function. The commutator generated by the Marcinkiewicz integral and is defined by \begin {equation*} \displaystyle [b,\mu _\Omega ] (f)(x)=\biggl (\int ^\infty _0\biggl |\int _{|x-y|\leq t} \frac {\Omega (x-y)}{|x-y|^{n-1}}[b(x)-b(y)]f(y) {\rm d} y\bigg |^2\frac {{\rm d} t}{t^3}\bigg )^{1/2}. \end {equation*} In this paper, the author proves the -boundedness of the Marcinkiewicz integral operator and its commutator when satisfies some conditions. Moreover, the author obtains the corresponding result about and on Herz spaces with variable exponent
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