5,725 research outputs found

    On certain equations of arbitrary length over torsion-free groups

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    Let GG be a non-trivial torsion free group and tt be an unknown. In this paper we consider three equations (over GG) of arbitrary length and show that they have a solution (over GG) provided two relations among their coefficients hold. Such equations appear for all lengths greater than or equal to eight and the results presented in this article can substantially simplify their solution.Comment: arXiv admin note: substantial text overlap with arXiv:1903.0650

    Crystal nucleation mechanism in melts of short polymer chains under quiescent conditions and under shear flow

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    We present a molecular dynamics simulation study of crystal nucleation from undercooled melts of n-alkanes, and we identify the molecular mechanism of homogeneous crystal nucleation under quiescent conditions and under shear flow. We compare results for n-eicosane(C20) and n-pentacontahectane(C150), i.e. one system below the entanglement length and one above. Under quiescent conditions, we observe that entanglement does not have an effect on the nucleation mechanism. For both chain lengths, the chains first align and then straighten locally. Then the local density increases and finally positional ordering sets in. At low shear rates the nucleation mechanism is the same as under quiescent conditions, while at high shear rates the chains align and straighten at the same time. We report on the effects of shear rate and temperature on the nucleation rates and estimate the critical shear rates, beyond which the nucleation rates increase with the shear rate. We show that the viscosity of the system is not affected by the crystalline nuclei.Comment: 9 page

    STR-920: STRUCTURAL BEHAVIOUR OF REINFORCED HIGH PERFORMANCE CONCRETE COLUMNS SUBJECTED TO MONOTONIC AXIAL LOADING

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    This paper presents the results of experimental and analytical investigations on the structural performance of high performance reinforced concrete (HPC) columns subjected to monotonic axial loading. Reinforced columns made of self-consolidating concrete (SCC), engineered cementitious composite (ECC) and ultra-high performance concrete (UHPC) were tested to failure under axial loading. The test variables included concrete strength and length/slenderness of columns (classified as short and long columns). The UHPC and ECC columns demonstrated excellent ductility and higher energy absorbing capacity compared to their SCC counterparts. UHPC columns also illustrated higher ultimate load capacity compared to both ECC and SCC columns. The efficiency of UHPC and ECC columns was also judged based on strength and ductility ratio compared to their SCC counterparts. Existing models and other Code based equations were used to predict the axial load capacity as a part of analytical investigation. The predictions suggested the need for the modification of existing models/Code based equations for UHPC and ECC columns

    Strategi Kolaborasi Pengembangan Wisata Berbasis Edukasi di Clungup Mangrove Conservation Desa Tambakrejo Kabupaten Malang

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    Pengembangan wisata alam berbasis edukasi memiliki tantangan yang serius di ranah mempertahankan eksistensi dan keberlanjutan lingkungan. Setiap stakeholder yang ada harus berani menjamin keterlibatan mereka dapat memberi kontribusi yang positif bagi keberlangsungan ekosistem kawasan pantai. Model Quintuple Helix memberikan posisi yang signifikan bagi lingkungan alami masyarakat untuk memperoleh perhatian yang lebih. Berangkat dari realitas, penelitian ini bertujuan untuk mencari strategi yang ideal bagi kolaborasi pengembangan wisata berbasis edukasi. Penelitian ini dilakukan dengan metode deskriptif kualitatif, pengambilan data dilakukan dengan observasi, wawancara dan studi dokumen. Adapun hasil dari penelitian ini berupa konsep strategi kolaborasi yang ideal untuk pengembangan wisata berbasis edukasi dengan model Quintuple Helix. Melalui model ini dapat memberikan modal tambahan berupa manajemen berbasis kualitas pembangunan yang efektif, keseimbangan alam yang terjamin, serta garansi terhadap generasi mendatang agar tetap dapat merasakan keberlanjutan lingkungan

    Sharing Polarization within Quantum Subspaces

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    Given an ensemble of n spins, at least some of which are partially polarized, we investigate the sharing of this polarization within a subspace of k spins. We assume that the sharing results in a pseudopure state, characterized by a single purity parameter which we call the bias. As a concrete example we consider ensembles of spin-1/2 nuclei in liquid-state nuclear magnetic resonance (NMR) systems. The shared bias levels are compared with some current entanglement bounds to determine whether the reduced subspaces can give rise to entangled states.Comment: 7 pages, 3 figure

    Anomalous transport in half-metallic ferromagnetic CrO2

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    We have investigated transport properties of CrO2 thin films deposited on TiO2 and sapphire substrates. The films are good metals down to low temperatures. The residual resistivity is of the order of 6 micro-ohhmcm for films deposited on TiO2 and two times higher for films on sapphire substrates. The sign of the magnetoresistance (MR) changes from negative to positive at a temperature around 100 K. This fact, as well as a rapid change in the ordinary and anomalous Hall coefficients suggest a change in the electronic state. At lower temperatures the MR is a linear function of the applied field. This linear dependence might be explained as intergrain tunneling MR. This interpretation is also suggested by the angular MR. The planar Hall effect measurements reveal that the CrO2 thin films are not in a single magnetic domain state even for films deposited on an isostructural TiO2 substrate

    MEASURING THE PROCESS EFFICIENCY OF CONTROLLED WELDING PROCESSES

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    This The process efficiency in Seem and Arc Welding is a crucial input to Mathematical models of the process and requires the use of an accurate welding calorimeter. In this paper we compare a liquid nitrogen calorimeter with an insulated box calorimeter for measuring the process efficiency of Fronius CMT, Lincoln STT and Rapid Arc, Kemppi FastRoot and standard pulsed GMAW. All the controlled dip transfer processes had a process efficiency of around 85% when measured with the liquid nitrogen calorimeter
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