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Using acoustic emission to characterize friction and wear in dry sliding steel contacts
Acoustic emission (AE) was recorded during tribological tests on 52,100 steel specimens under different loads. AE signals were transformed to the frequency domain using a Fast Fourier Transform and parameters such as power, RMS amplitude, mean frequency, and energy were analyzed and compared with friction coefficient and wear volume measurements. Results show that certain acoustic frequencies reflect friction while others reflect wear. If frequencies are chosen optimally, AE and friction signals are highly correlated (Pearson coefficients >0.8). SEM and Raman analysis reveal how plastic deformation and oxide formation affect friction, wear and AE simultaneously. AE recordings contains more information than conventional friction and wear volume measurements and are more sensitive to changes in mechanism. This all demonstrates AE's potential as a tool to monitor tribological behavior.This work was supported by the Overseas Study Program of Jiangsu Higher Education Institutions; the Natural Science Foundation of Jiangsu Province, China (Grant no. BK20160353); the Natural Science Foundation of Jiangsu Higher Education Institutions (Grant no. 16KJB460032); the Key Laboratory of Suzhou (SZS201815); the Top-notch Academic Programs Project of Jiangsu Higher Education Institutions (TAPP) (Grant no. PPZY2015B186) and the Scientific Research Foundation of SIIT (Grant no. 2017kyqd015)
Multivariate Topology Simplification
Topological simplification of scalar and vector fields is well-established as an effective method for analysing and visualising complex data sets. For multivariate (alternatively, multi-field) data, topological analysis requires simultaneous advances both mathematically and computationally. We propose a robust multivariate topology simplification method based on “lip”-pruning from the Reeb space. Mathematically, we show that the projection of the Jacobi set of multivariate data into the Reeb space produces a Jacobi structure that separates the Reeb space into simple components. We also show that the dual graph of these components gives rise to a Reeb skeleton that has properties similar to the scalar contour tree and Reeb graph, for topologically simple domains. We then introduce a range measure to give a scaling-invariant total ordering of the components or features that can be used for simplification. Computationally, we show how to compute Jacobi structure, Reeb skeleton, range and geometric measures in the Joint Contour Net (an approximation of the Reeb space) and that these can be used for visualisation similar to the contour tree or Reeb graph
Genetic differentiation in Japanese flounder in the Yellow Sea and East China Sea by amplified fragment length polymorphism (AFLP) and mitochondrial DNA markers
The population structure of Japanese flounder (Paralichthys olivaceus) in the Yellow and East China Seas were analyzed using amplified fragment length polymorphism (AFLP) and cytochrome c oxidase subunit I (COI) gene sequencing. A total of 390 reproducible bands were generated by 10 AFLP primer combinations in two populations collected from the coasts of Qingdao (located at the Yellow Sea) and Zhoushan (located at the East China Sea). The percentage of polymorphic loci (P), Nei’s genetic diversity (H) and Shannon’s information index (I) values were higher in the Qingdao population (P = 72.85%, H = 0.243 and I = 0.364) than those in the Zhoushan population (P = 56.35%, H = 0.189 and I = 0.284). The genetic diversity reduction in the Zhoushan population may be attributed to fishing pressure and habitat loss in this area. Based on the COI sequencing analysis, a total of 25 polymorphic sites were examined, and 15 haplotypes were identified in the two populations. The haplotype diversity (h) and nucleotide diversity (π) values in the Qingdao population were 0.746 ± 0.0728 and 0.00334 ± 0.00103, respectively. The corresponding values in the Zhoushan population were 0.712 ± 0.0470 and 0.00318 ± 0.00049. Both the AFLP and mtDNA data revealed significant genetic differentiation between the two populations. The present study discussed the factors that may result in genetic differentiation between the populations in the Yellow and East China Seas.Keywords: Japanese flounder, amplified fragment length polymorphism (AFLP), cytochrome c oxidase subunit I (COI) gene, genetic diversity, population structur
Evaluation of SMAP, SMOS-IC, FY3B, JAXA, and LPRM Soil Moisture Products over the Qinghai-Tibet Plateau and Its Surrounding Areas
© 2019 by the authors. High-quality and long time-series soil moisture (SM) data are increasingly required for the Qinghai-Tibet Plateau (QTP) to more accurately and effectively assess climate change. In this study, to evaluate the accuracy and effectiveness of SM data, five passive microwave remotely sensed SM products are collected over the QTP, including those from the soil moisture active passive (SMAP), soil moisture and ocean salinity INRA-CESBIO (SMOS-IC), Fengyun-3B microwave radiation image (FY3B), and two SM products derived from the advanced microwave scanning radiometer 2 (AMSR2). The two AMSR2 products are generated by the land parameter retrieval model (LPRM) and the Japan Aerospace Exploration Agency (JAXA) algorithm, respectively. The SM products are evaluated through a two-stage data comparison method. The first stage is direct validation at the grid scale. Five SM products are compared with corresponding in situ measurements at five in situ networks, including Heihe, Naqu, Pali, Maqu, and Ngari. Another stage is indirect validation at the regional scale, where the uncertainties of the data are quantified by using a three-cornered hat (TCH) method. The results at the regional scale indicate that soil moisture is underestimated by JAXA and overestimated by LPRM, some noise is contained in temporal variations in SMOS-IC, and FY3B has relatively low absolute accuracy. The uncertainty of SMAP is the lowest among the five products over the entire QTP. In the SM map composed by five SM products with the lowest pixel-level uncertainty, 66.64% of the area is covered by SMAP (JAXA: 19.39%, FY3B: 10.83%, LPRM: 2.11%, and SMOS-IC: 1.03%). This study reveals some of the reasons for the different performances of these five SM products, mainly from the perspective of the parameterization schemes of their corresponding retrieval algorithms. Specifically, the parameterization configurations and corresponding input datasets, including the land-surface temperature, the vegetation optical depth, and the soil dielectric mixing model are analyzed and discussed. This study provides quantitative evidence to better understand the uncertainties of SM products and explain errors that originate from the retrieval algorithms
Quasienergy spectra of a charged particle in planar honeycomb lattices
The low energy spectrum of a particle in planar honeycomb lattices is
conical, which leads to the unusual electronic properties of graphene. In this
letter we calculate the quasienergy spectra of a charged particle in honeycomb
lattices driven by a strong AC field, which is of fundamental importance for
its time-dependent dynamics. We find that depending on the amplitude, direction
and frequency of external field, many interesting phenomena may occur,
including band collapse, renormalization of velocity of ``light'', gap opening
etc.. Under suitable conditions, with increasing the magnitude of the AC field,
a series of phase transitions from gapless phases to gapped phases appear
alternatively. At the same time, the Dirac points may disappear or change to a
line. We suggest possible realization of the system in Honeycomb optical
lattices.Comment: 4+ pages, 5 figure
Skeletons for Distributed Topological Computation
Parallel implementation of topological algorithms is highly desirable, but the challenges, from reconstructing algorithms around independent threads through to runtime load balancing, have proven to be formidable. This problem, made all the more acute by the diversity of hardware platforms, has led to new kinds of implementation platform for computational science, with sophisticated runtime systems managing and coordinating large threadcounts to keep processing elements heavily utilized. While simpler and more portable than direct management of threads, these approaches still entangle program logic with resource management. Similar kinds of highly parallel runtime system have also been developed for functional languages. Here, however, language support for higher-order functions allows a cleaner separation between the algorithm and `skeletons' that express generic patterns of parallel computation. We report results on using this technique to develop a distributed version of the Joint Contour Net, a generalization of the Contour Tree to multifields. We present performance comparisons against a recent Haskell implementation using shared-memory parallelism, and initial work on a skeleton for distributed memory implementation that utilizes an innovative strategy to reduce inter-process communication overheads
Reversible Metal-Semiconductor Transition of ssDNA-Decorated Single-Walled Carbon Nanotubes
A field effect transistor (FET) measurement of a SWNT shows a transition from
a metallic one to a p-type semiconductor after helical wrapping of DNA. Water
is found to be critical to activate this metal-semiconductor transition in the
SWNT-ssDNA hybrid. Raman spectroscopy confirms the same change in electrical
behavior. According to our ab initio calculations, a band gap can open up in a
metallic SWNT with wrapped ssDNA in the presence of water molecules due to
charge transfer.Comment: 13 pages, 6 figure
Unified dark energy thermodynamics: varying w and the -1-crossing
We investigate, in a unified and general way, the thermodynamic properties of
dark energy with an arbitrary, varying equation-of-state parameter w(a). We
find that all quantities are well defined and regular for every w(a), including
at the -1-crossing, with the temperature being negative in the phantom regime
(w(a)-1). The density and
entropy are always positive while the chemical potential can be arbitrary. At
the -1-crossing, both temperature and chemical potential are zero. The
temperature negativity can only be interpreted in the quantum framework. The
regular behavior of all quantities at the -1-crossing, leads to the conclusion
that such a crossing does not correspond to a phase transition, but rather to a
smooth cross-over.Comment: 5 pages, version published in Class. Quant. Gra
Excited Heavy Baryons and Their Symmetries III: Phenomenology
Phenomenological applications of an effective theory of low-lying excited
states of charm and bottom isoscalar baryons are discussed at leading and
next-to-leading order in the combined heavy quark and large expansion.
The combined expansion is formulated in terms of the counting parameter
; the combined expansion is in powers of
. We work up to next-to-leading order. We obtain
model-independent predictions for the excitation energies, the semileptonic
form factors and electromagnetic decay rates. The spin-averaged mass of the
doublet of the first orbitally excited sate of is predicted to be
approximately . It is shown that in the combined limit at leading and
next-to-leading order there is only one independent form factor describing
; similarly, and
decays are described by a single independent form factor. These form factors
are calculated at leading and next-to-leading order in the combined expansion.
The electromagnetic decay rates of the first excited states of and
are determined at leading and next-to leading order. The ratio of
radiative decay rates is predicted to be approximately
0.2, greatly different from the heavy quark effective theory value of unity.Comment: 21 pages, 2 figure
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