633 research outputs found

    Direct numerical simulation of turbulent Couette-Poiseuille flow with zero skin friction

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    The near-wall scaling of mean velocity U(y) is addressed for the case of zero skin friction on one wall of a fully turbulent channel flow. The present DNS results can be added to the evidence in support of the conjecture that U is proportional to √yw in the region just above the wall at which the mean shear dU/dy = 0

    Combination Of Cfd And Csd Packages For Fluid-Structure Interaction

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    In this article the UDF script file in the Fluent software was rewritten as the "connecting file" for the Fluent and the ANSYS/ABAQUS in order that the joined file can be used to do aero-elastic computations. In this way the fluid field is computed by solving the Navier-Stokes equations and the structure movement is integrated by the dynamics directly. An analysis of the computed results shows that this coupled method designed for simulating aero-elastic systems is workable and can be used for the other fluid-structure interaction problems

    Characterization, sub-cellular localization and expression profiling of the isoprenylcysteine methylesterase gene family in Arabidopsis thaliana

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    Background: Isoprenylcysteine methylesterases (ICME) demethylate prenylated protein in eukaryotic cell. Until now, knowledge about their molecular information, localization and expression pattern is largely unavailable in plant species. One ICME in Arabidopsis, encoded by At5g15860, has been identified recently. Over-expression of At5g15860 caused an ABA hypersensitive phenotype in transgenic Arabidopsis plants, indicating that it functions as a positive regulator of ABA signaling. Moreover, ABA induced the expression of this gene in Arabidopsis seedlings. The current study extends these findings by examining the sub-cellular localization, expression profiling, and physiological functions of ICME and two other ICME-like proteins, ICME-LIKE1 and ICME-LIKE2, which were encoded by two related genes At1g26120 and At3g02410, respectively. Results: Bioinformatics investigations showed that the ICME and other two ICME-like homologs comprise a small subfamily of carboxylesterase (EC 3.1.1.1) in Arabidopsis. Sub-cellular localization of GFP tagged ICME and its homologs showed that the ICME and ICME-like proteins are intramembrane proteins predominantly localizing in the endoplasmic reticulum (ER) and Golgi apparatus. Semi-quantitative and real-time quantitative PCR revealed that the ICME and ICME-like genes are expressed in all examined tissues, including roots, rosette leaves, cauline leaves, stems, flowers, and siliques, with differential expression levels. Within the gene family, the base transcript abundance of ICME-LIKE2 gene is very low with higher expression in reproductive organs (flowers and siliques). Time-course analysis uncovered that both ICME and ICME-like genes are up-regulated by mannitol, NaCl and ABA treatment, with ICME showing the highest level of up-regulation by these treatments. Heat stress resulted in up-regulation of the ICME gene significantly but down-regulation of the ICME-LIKE1 and ICME-LIKE2 genes. Cold and dehydration stimuli led to no significant change of both ICME and ICME-like gene expression. Mutant icme-like2-1 showed increased sensitivity to ABA but slightly decreased sensitivity to salt and osmotic stresses during seed germination. Conclusions: It is concluded that the ICME family is involved in stress and ABA signaling in Arabidopsis, probably through mediating the process of demethylating prenylated proteins. Identification of these prenylated proteins will help to better understand the significance of protein prenylation in Planta

    or2yw: Modeling and Visualizing OpenRefine Histories as YesWorkflow Diagrams

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    OpenRefine is a popular open-source data cleaning tool. It allows users to export a previously executed data cleaning workflow in a JSON format for possible reuse on other datasets. We have developed ortoyw, a novel tool that maps a JSON-formatted OpenRefine operation history to a YesWorkflow (YW) model, which then can be visualized and queried using the YW tool. The latter was originally developed to allow researchers a simple way to annotate their program scripts in order to reveal the workflow steps and dataflow dependencies implicit in those scripts. With ortoyw the user can automatically generate YW models from OpenRefine operation histories, thus providing a ``workflow view'' on a previously executed sequence of data cleaning operations. The ortoyw tool can generate different types of YesWorkflow models, e.g., a linear model which mirrors the sequential execution order of operations in OpenRefine, and a parallel model which reveals independent workflow branches, based on a simple analysis of dependencies between steps: if two operations are independent of each other (e.g., when the columns they read and write do not overlap) then these can be viewed as parallel steps in the data cleaning workflow.The resulting YW models can be understood as a form of prospective provenance, i.e., knowledge artifacts that can be queried and visualized (i) to help authors document their own data cleaning workflows, thereby increasing transparency, and (ii)~to help other users, who might want to reuse such workflows, to understand them better.Made available in DSpace on 2021-03-19T01:44:27Z (GMT). No. of bitstreams: 2 Parulian-or2yw Modeling and Visualizing OpenRefineOperation Histories as YesWorkflow Diagrams-522.zip: 12681794 bytes, checksum: 66787888e41c418dfebf9fcf0def8fe7 (MD5) license.txt: 4802 bytes, checksum: 58353f9dd6876860dd5221f3d7872a95 (MD5) Previous issue date: 2021-03-1

    Finite-Sample Bias Propagation in Autoregressive Estimation With the Yule–Walker Method

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    The Yule-Walker (YW) method for autoregressive (AR) estimation uses lagged-product (LP) autocorrelation estimates to compute an AR parametric spectral model. The LP estimates only have a small triangular bias in the estimated autocorrelation function and are asymptotically unbiased. However, using them in finite samples with the YW method for AR estimation can give a strong distortion in the weak parts of the power spectral density. The distortion is shown to be influential in an example without strong spectral peaks. The true biased AR model, which is computed by applying the triangular bias to the true autocorrelation function, has an infinite order. A new objective measure is introduced to determine the smallest sample size for which the unbiased asymptotic theory can be considered as a fair approximation.Multi-Scale PhysicsApplied Science

    Photo-assisted synthesis of highly fluorescent ZnSe(S) quantum dots in aqueous solution

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    [[abstract]]©2007 RSC - This paper describes the synthesis of highly water-soluble and fluorescent ZnSe(S)-alloyed quantum dots (QDs). We used zinc perchlorate hexahydrate, sodium hydrogen selenide as precursors and mercaptopropionic acid as stabilizer to synthesize ZnSe QDs in aqueous solution at 160 degrees C for 9 h. The as-prepared ZnSe QDs possess a quantum yield (QY) of 8.1% and high trapped emission. After UV irradiation using a 100 W Hg-Xe lamp for 0.5 h, ZnSe(S) QDs having a QY of 19.0% are formed from ZnSe QDs. However, aggregation of ZnSe(S) QDs under longer UV irradiation (> 0.5 h) takes place, leading to instability and irreproducibility. To overcome this, additional thiol compounds (mercaptopropionic acid, mercaptosuccinic acid, 11-mercaptoundecanoic acid, and thioglycolic acid) were separately added to ZnSe QD solutions during UV irradiation. UV irradiation and oxygen accelerate the release of S 22 from the thiol compounds, leading to the formation of ZnSe(S) QDs. Among the thiol compounds, mercaptosuccinic acid is the most suitable in terms of stability and photoluminescence intensity. We suggest that the size and functional group of the thiol compounds play an important role in determining the optical properties and stability of ZnSe(S) QDs. The as-prepared ZnSe(S) QDs fluoresce strongly (QY up to 44.0%) at 407 nm with a narrow bandwidth (W-1/2 < 25 nm) when excited at 325 nm.[[department]]生醫工程與環境科學
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