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Articles 22351 - 22380 of 302435

Full-Text Articles in Physical Sciences and Mathematics

Hybrid Feature Selection Based On Principal Component Analysis And Grey Wolf Optimizer Algorithm For Arabic News Article Classification, Osama Ahmad Alomari, Ashraf Elnagar, Imad Afyouni, Ismail Shahin, Ali Bou Nassif, Ibrahim Abaker Hashem, Mohammad Tubishat Nov 2022

Hybrid Feature Selection Based On Principal Component Analysis And Grey Wolf Optimizer Algorithm For Arabic News Article Classification, Osama Ahmad Alomari, Ashraf Elnagar, Imad Afyouni, Ismail Shahin, Ali Bou Nassif, Ibrahim Abaker Hashem, Mohammad Tubishat

All Works

The rapid growth of electronic documents has resulted from the expansion and development of internet technologies. Text-documents classification is a key task in natural language processing that converts unstructured data into structured form and then extract knowledge from it. This conversion generates a high dimensional data that needs further analusis using data mining techniques like feature extraction, feature selection, and classification to derive meaningful insights from the data. Feature selection is a technique used for reducing dimensionality in order to prune the feature space and, as a result, lowering the computational cost and enhancing classification accuracy. This work presents a …

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Helium Nanodroplets As An Efficient Tool To Investigate Hydrogen Attachment To Alkali Cations, Siegfried Kollotzek, José Campos-Martínez, Massimiliano Bartolomei, Fernando Pirani, Lukas Tiefenthaler, Marta I. Hernández, Teresa Lázaro, Eva Zunzunegui-Bru, Tomás González-Lezana, José Bretón, Javier Hernández-Rojas, Olof E. Echt, Paul Scheier Nov 2022

Helium Nanodroplets As An Efficient Tool To Investigate Hydrogen Attachment To Alkali Cations, Siegfried Kollotzek, José Campos-Martínez, Massimiliano Bartolomei, Fernando Pirani, Lukas Tiefenthaler, Marta I. Hernández, Teresa Lázaro, Eva Zunzunegui-Bru, Tomás González-Lezana, José Bretón, Javier Hernández-Rojas, Olof E. Echt, Paul Scheier

Faculty Publications

We report a novel method to reversibly attach and detach hydrogen molecules to positively charged sodium clusters formed inside a helium nanodroplet host matrix. It is based on the controlled production of multiply charged helium droplets which, after picking up sodium atoms and exposure to H2 vapor, lead to the formation of Nam+(H2)n clusters, whose population was accurately measured using a time-of-flight mass spectrometer. The mass spectra reveal particularly favorable Na+(H2)n and Na2+(H2)n clusters for specific “magic” numbers of attached hydrogen molecules. …

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Electromagnetism In Quark Matter At Intermediate Densities, Efrain J. Ferrer Nov 2022

Electromagnetism In Quark Matter At Intermediate Densities, Efrain J. Ferrer

Physics and Astronomy Faculty Publications and Presentations

Several anomalous electromagnetic effects that can take place in quark matter at low temperatures and intermediate densities will be discussed. The anomalous transport properties of the spatially inhomogeneous phase of quark matter known as the Magnetic Dual Chiral Density Wave (MDCDW) phase will be reviewed. Going beyond mean-field approximation, it will be shown how linearly polarized electromagnetic waves that penetrate the MDCDW medium mix with the phonon fluctuations to give rise to two hybridized modes of propagation called axion polaritons. Finally, some possible implications of these results for the astrophysics of neutron stars will be indicated.

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Technical Note: On Uncertainties In Plant Water Isotopic Composition Following Extraction By Cryogenic Vacuum Distillation, Haoyu Diao, Philipp Schuler, Gregory R. Goldsmith, Rolf T. W. Siegwolf, Matthias Saurer, Marco M. Lehmann Nov 2022

Technical Note: On Uncertainties In Plant Water Isotopic Composition Following Extraction By Cryogenic Vacuum Distillation, Haoyu Diao, Philipp Schuler, Gregory R. Goldsmith, Rolf T. W. Siegwolf, Matthias Saurer, Marco M. Lehmann

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Recent studies have challenged the interpretation of plant water isotopes obtained through cryogenic vacuum distillation (CVD) based on observations of a large 2H fractionation. These studies have hypothesized the existence of an H-atom exchange between water and organic tissue during CVD extraction with the magnitude of H exchange related to relative water content of the sample; however, clear evidence is lacking. Here, we systematically tested the uncertainties in the isotopic composition of CVD-extracted water by conducting a series of incubation and rehydration experiments using isotopically depleted water, water at natural isotope abundance, woody materials with exchangeable H, and organic materials …

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Quantifying The Influence Of Variations In Rock Mass Properties On Stope Stability, Shahé Shnorhokian, Hani Mitri Nov 2022

Quantifying The Influence Of Variations In Rock Mass Properties On Stope Stability, Shahé Shnorhokian, Hani Mitri

Journal of Sustainable Mining

Variations in rock mass properties are well-established in rock mechanics and underground mining. The literature is replete with methods of assessing them and determining values that are used in design or numerical analysis. In this paper, a simplified 3D model is constructed for a tabular orebody in the Canadian Shield and instability is quantified using the ”brittle shear ratio” criterion to calculate the volume at risk. A 1-4-7 stope pillar sequence is implemented on four active levels, and three variations in the properties of the host formation are assessed. It is observed that the locations of ore at risk follow …

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Prospects For Thiourea As A Leaching Agent In Colombian Gold Small-Scale Mining: A Comprehensive Review, Johana Borda, Robinson Torres Nov 2022

Prospects For Thiourea As A Leaching Agent In Colombian Gold Small-Scale Mining: A Comprehensive Review, Johana Borda, Robinson Torres

Journal of Sustainable Mining

Thiourea, as an alternative medium, is one of the most promising leaching agents for gold recovery by its commercial benefits and research challenges associated with performance and environmental impacts. This review article describes the operational conditions for the use of Thiourea vs cyanide, its chemistry, limitations, toxicity factors, environment, and recovery processes. Although thiourea gold extraction processes have not been applied on a large scale due to the instability of the reagent, its potential to overcome the limitations of cyanide is attractive to the process; with pH, potential, oxidant dosage, and temperature control, solubilized gold thiourea species are achieved. These …

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The Synthesis, Lewis Acidity And Catalytic Activity Of Bis(Catecholato)Germanes, Andrew T. Henry Nov 2022

The Synthesis, Lewis Acidity And Catalytic Activity Of Bis(Catecholato)Germanes, Andrew T. Henry

Electronic Thesis and Dissertation Repository

Main group Lewis acids have been shown to be viable alternatives to state-of-theart transition metal catalysts. While extensive research into a variety of p-block Lewis acids have been reported, the field of germanium Lewis acid chemistry has been described as “almost non-existent”. A variety of bis(catecholato)germane derivatives have been synthesized. The Lewis acidity of these compounds was analyzed by the Gutmann-Beckett and fluoride ion affinity methods demonstrating the high Lewis acidity of these complexes. The bis(catecholato)germanes were utilized as Lewis acid catalysts for the hydrosilylation of aldehydes, the hydroboration of alkynes, Friedel-Crafts alkylation of alkenes, and the oligomerization of styrene …

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Panel Destressing Strategies For Remnant Pillar Extraction, Isaac Vennes, Hani Mitri Nov 2022

Panel Destressing Strategies For Remnant Pillar Extraction, Isaac Vennes, Hani Mitri

Journal of Sustainable Mining

Large-scale panel destressing is a rockburst mitigation technique employed in deep hard rock mines during remnant pillar extraction. Panels are choke blasted in the pillar footwall to cutoff the far-field major stress in the mining area and deviate them around the pillar. In this study, the effects of panel geometry and far-field stress magnitude are investigated. Destress blast performance is assessed by measuring change to the energy release rate (ERR) of all mining steps during the extraction of a simplified remnant pillar due to destressing. It is demonstrated that the energy release rate (ERR) of critical stopes is reduced by …

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Design And Fabrication Of A Low-Cost Dip Coating System For Depositing Homogeneous And Transparent Zno Thin Films, Asaad S. Yasir, Basheer M. Hussein, Ammar S. Hameed, Noor J. Ridha, Firas K. Mohamad Alosfur, Khawla J. Tahir, Rajaa A. Madlol Nov 2022

Design And Fabrication Of A Low-Cost Dip Coating System For Depositing Homogeneous And Transparent Zno Thin Films, Asaad S. Yasir, Basheer M. Hussein, Ammar S. Hameed, Noor J. Ridha, Firas K. Mohamad Alosfur, Khawla J. Tahir, Rajaa A. Madlol

Al-Bahir Journal for Engineering and Pure Sciences

ZnO has a resistivity of up to 104 Ω cm-1 in most cases. Nevertheless, by increasing the layer thickness, the resistivity decreases as well, resulting in greater current transport. The dip coating system was developed to prepare the ultra-thin film, it relied on a controller, stepper motor and some low-cost recycled materials. Thin films of ZnO were successfully deposited on indium tin oxide substrates. The effects of the dipping cycles were investigated. Dipping processes were applied several times (1, 2, and 3) for the same concentrations (0.1) M to obtain homogeneous thin films. X-ray diffraction showed that the structure of …

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Mgrre_Thinsections_05_A_88, Mgrre Nov 2022

Mgrre_Thinsections_05_A_88, Mgrre

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Mgrre_Thinsections_Mgrre-89_4, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-89_4, Mgrre

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Mgrre_Thinsections_Mgrre-89_5, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-89_5, Mgrre

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Mgrre_Thinsections_Mgrre-89_6, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-89_6, Mgrre

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Mgrre_Thinsections_Mgrre-89_8, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-89_8, Mgrre

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Mgrre_Thinsections_Mgrre-89_9, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-89_9, Mgrre

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Mgrre_Thinsections_Mgrre-89_14, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-89_14, Mgrre

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Mgrre_Thinsections_Mgrre-89_15, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-89_15, Mgrre

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Mgrre_Thinsections_Mgrre-89_18, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-89_18, Mgrre

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Mgrre_Thinsections_Mgrre-89_20, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-89_20, Mgrre

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Mgrre_Thinsections_Mgrre-89_90, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-89_90, Mgrre

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Mgrre_Thinsections_Mgrre-93_1, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-93_1, Mgrre

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Mgrre_Thinsections_Mgrre-93_3, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-93_3, Mgrre

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Mgrre_Thinsections_Mgrre-93_7, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-93_7, Mgrre

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Mgrre_Thinsections_Mgrre-93_2, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-93_2, Mgrre

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Mgrre_Thinsections_Mgrre-93_8, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-93_8, Mgrre

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Mgrre_Thinsections_Mgrre-93_5, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-93_5, Mgrre

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Mgrre_Thinsections_Mgrre-93_6, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-93_6, Mgrre

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Mgrre_Thinsections_Mgrre-94_1, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-94_1, Mgrre

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Mgrre_Thinsections_Mgrre-94_5, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-94_5, Mgrre

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Mgrre_Thinsections_Mgrre-94_4, Mgrre Nov 2022

Mgrre_Thinsections_Mgrre-94_4, Mgrre

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