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141.
142.
This paper presents Hurst exponent footprints from pseudo-dynamic measurements of significantly varied activities on a damaged bridge structure during rehabilitation through continuous monitoring. The system is interesting due to associated uncertainty in large-scale structures and significant presence of human intervention arising from fundamentally different processes. Investigations into the variation of computed Hurst exponents on time series of limited lengths are carried out in this regard. The Hurst exponents are compared with respect to specific events during the rehabilitation, as well as with the data collection locations. The variations of local Hurst exponents about the values computed for each activity are presented. The scaling of Hurst exponents for different activities is also investigated; these are representative of the extent of multifractality for each event. The extent of multifractality is assessed along with its source and time dependency. 相似文献
143.
Mimi Miyoung Lee Jennifer B. Chauvot Julie Vowell Shea Mosley Culpepper Brian J. Plankis 《School science and mathematics》2013,113(4):159-169
This paper is based on an online graduate program for middle school science and mathematics teachers in Texas titled Integration of Science, Mathematics and Reflective Teaching (iSMART). Launching the program for its first cohort in fall 2010, the authors attempted to answer the following two questions in this paper: (a) How do the members of the iSMART design team and the first cohort of teacher participants define science and mathematics integration with similar and different emphases? and (b) How would these definitions and concerns impact the ongoing design of the program? The iSMART design team members and the participating cohort teachers had a shared view regarding the importance of integration and its possible impact on student motivation. The findings also revealed that the two groups showed some different points of emphasis in their definitions of integration. These issues will be addressed in the ongoing design of the program in the following three areas: (a) design of the second summer meeting activities, (b) greater emphasis on teacher as researcher and action research, and (c) administrative support for teacher collaboration. 相似文献
144.
In this article, we propose an algorithm, nesta-lasso, for the lasso problem, i.e., an underdetermined linear least-squares problem with a 1-norm constraint on the solution. We prove under the assumption of the restricted isometry property (rip) and a sparsity condition on the solution, that nesta-lasso is guaranteed to be almost always locally linearly convergent. As in the case of the algorithm nesta, proposed by Becker, Bobin, and Candès, we rely on Nesterov’s accelerated proximal gradient method, which takes $O(\sqrt {1/\varepsilon })$ iterations to come within $\varepsilon > 0$ of the optimal value. We introduce a modification to Nesterov’s method that regularly updates the prox-center in a provably optimal manner. The aforementioned linear convergence is in part due to this modification. In the second part of this article, we attempt to solve the basis pursuit denoising (bpdn) problem (i.e., approximating the minimum 1-norm solution to an underdetermined least squares problem) by using nesta-lasso in conjunction with the Pareto root-finding method employed by van den Berg and Friedlander in their spgl1 solver. The resulting algorithm is called parnes. We provide numerical evidence to show that it is comparable to currently available solvers. 相似文献
145.
Estrella Johnson John Caughman Julie Fredericks Lee Gibson 《The Journal of Mathematical Behavior》2013
As part of an effort to scale up an instructional innovation in abstract algebra, several mathematicians have implemented an inquiry-oriented, group theory curriculum. Three of those mathematicians (co-authors here) also participated in iterative rounds of interviews designed to document and investigate their experiences as they worked to implement this curriculum. Analyses of these interviews uncovered three themes that were important to these mathematicians: coverage, goals for student learning, and the role of the teacher. Here, by drawing on interview data, classroom data, and first person commentaries, we will present and discuss each teacher's perspective on these three themes. 相似文献
146.
Domain experts have two major advantages over novices with regard to problem solving: experts more accurately encode deep problem features (feature encoding) and demonstrate better conceptual understanding of critical problem features (feature knowledge). In the current study, we explore the relative contributions of encoding and knowledge of problem features (e.g., negative signs, the equals sign, variables) when beginning algebra students solve simple algebraic equations. Thirty-two students completed problems designed to measure feature encoding, feature knowledge and equation solving. Results indicate that though both feature encoding and feature knowledge were correlated with equation-solving success, only feature knowledge independently predicted success. These results have implications for the design of instruction in algebra, and suggest that helping students to develop feature knowledge within a meaningful conceptual context may improve both encoding and problem-solving performance. 相似文献
147.
Nicolas Dupré Julie Oliveri Jeremy Degryse Jean-Frédéric Martin Dominique Guyomard 《Ionics》2008,14(3):203-207
The growth and evolution of the interphase, due to contact with the ambient atmosphere or electrolyte, are followed using 7Li magic-angle spinning nuclear magnetic resonance (MAS NMR) in the case of two materials amongst the most promising candidates for positive electrodes for lithium batteries: LiFePO4 and LiMn0.5Ni0.5O2. The use of appropriate experimental conditions to acquire the NMR signal allows observing only the «diamagnetic» lithium species at the surface of the grains of active material. The reaction of LiMn0.5Ni0.5O2 with the ambient atmosphere or LiPF6 (1 M in Ethylene Carbonated/DiMéthyl Carbonate (EC/DMC)) electrolyte is extremely fast and leads to an important amount of lithium-containing diamagnetic species compared to what can be observed in the case of LiFePO4. The two studied materials display a completely different surface chemistry in terms of reactivity and/or kinetics of the surface towards electrolyte. Moreover, these results show that MAS NMR is a very promising tool to monitor phenomena taking place at the interface between electrode and electrolyte. 相似文献
148.
Cycloelimination of Imidazolidin‐2‐ylidene N‐Heterocyclic Carbenes: Mechanism and Insights into the Synthesis of Stable “NHC‐CDI” Amidinates
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Aleksandr V. Zhukhovitskiy Julie Geng Prof. Dr. Jeremiah A. Johnson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(15):5685-5688
We report the discovery that 1,3‐bis(aryl)imidazolidin‐2‐ylidenes, one of the most widely studied classes of N‐heterocyclic carbenes (NHCs), undergo quantitative conversion to zwitterionic “NHC‐CDI” amidinates upon heating to ≈100 °C in solution. The mechanism of this novel NHC decomposition process is studied in detail. These studies enabled the rational synthesis of a new class of bench stable amidinates from a panel of NHCs and carbodiimides. We expect these constructs to find utility in a variety of applications. 相似文献
149.
150.
Dr. Mick Hornum Julie Stendevad Dr. Pawan K. Sharma Dr. Pawan Kumar Rasmus B. Nielsen Dr. Michael Petersen Dr. Poul Nielsen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(30):7387-7395
Nucleotides that contain two nucleobases (double-headed nucleotides) have the potential to condense the information of two separate nucleotides into one. This presupposes that both bases must successfully pair with a cognate strand. Here, double-headed nucleotides that feature cytosine, guanine, thymine, adenine, hypoxanthine, and diaminopurine linked to the C2′-position of an arabinose scaffold were developed and examined in full detail. These monomeric units were efficiently prepared by convergent synthesis and incorporated into DNA oligonucleotides by means of the automated phosphoramidite method. Their pairing efficiency was assessed by UV-based melting-temperature analysis in several contexts and extensive molecular dynamics studies. Altogether, the results show that these double-headed nucleotides have a well-defined structure and invariably behave as functional dinucleotide mimics in DNA duplexes. 相似文献