Modelling the Effects of Friction on Tool-Chip Interface Temperature During Orthogonal Cutting of Al6061-T6 Aluminium Alloy

© IEOM Society International - IEOM 2019In this work, finite element simulations based on the analytical model derived with the MATLAB software were used to establish the temperature fields within the cutting tool and tool-chip interface. The average tool-chip interface temperature model was simulated and the simulation results were compared with experimental results for validation. At a maximum cutting speed of 90 m/min, the maximum temperature obtained from the experiment was 410 oC, at same rake angle of 0o. However, the developed model predicted 490 oC under the same conditions. The higher value obtained by the model can be attributed to the negligence of heat losses to the surrounding by both convection and radiation modes, as an assumption in the formulated model. A similar trend of these results was also recorded for the case of rake angle and feed rate of 30o and 0.0635 mm/rev, respectively. It was observed that the simulation results and experimental measurements for the average tool-chip interface temperature agreed significantly.Final Published versio

Coupling of Nonlocal Potentials to Electromagnetic Fields

Nonlocal Hamiltonians are used widely in first-principles quantum calculations; the nonlocality stems from eliminating undesired degrees of freedom, e.g. core electrons. To date, attempts to couple nonlocal systems to external electromagnetic (EM) fields have been heuristic or limited to weak or long wavelength fields. Using Feynman path integrals, we derive an exact, closed-form coupling of arbitrary EM fields to nonlocal systems. Our results justify and clarify the couplings used to date and are essential for systematic computation of linear and especially nonlinear response.Comment: 1 figure, 1 tabl

Health Inequities with Somali Women in Kuala Lumpur

Edited by Kirandeep Kau

EFFECT OF MIXED COUNTERIONS ON THE AGGREGATION BEHAVIOR OF CETYLPYRIDINIUM CHLORIDE

Critical micelle concentrations (cmc) of cetylpyridinium chloride (CPC) in aqueous sodium bromide and tetrabutylammonium bromide (TBAB) solutions were determined at 30 °C from surface tension and conductance methods. Bromide decreases cmc of CPC more than chloride. A modified form of Corrin-Harkins equation has been used to describe the variation of cmc with added electrolyte concentration in the presence of mixed counter ions. From the slope of this equation the lower limit to the value of total counter ion binding constant (β) can be known and binding constants of the individual counter ions (β1 and β2) can be determined provided β is known.  It is demonstrated that the mixed-electrolyte-model (MEM) of Shanks and Franses (J. Phys. Chem. 1992, 96, 1794) can be applied to analyze the conductance data of surfactant solution containing mixed counter ions.  The value of β obtained from the MEM was then used to determine β1 and β2. By this treatment we could show that (i) bromide preferentially binds to CPC micelle by replacing chloride counterion, (ii) bromide binding is more than chloride and (iii) aggregation number of CPC is higher in the presence of bromide. These observations are in accordance with the reported results of SANS and counter ion trapping studies

Pengaruh Penggunaan Internet Terhadap Hasil Belajar IPS Peserta Didik Kelas X Smk Nurul Huda Sukaraja Oku Timur

Penelitian ini bertujuan untuk mengetahui hasil belajar IPS peserta didik yang pembelajarannya menggunakan internet sebagai sumber belajar. Penelitian ini merupakan penelitian kuantitatif. Populasi dalam penelitian ini adalah seluruh peserta didik SMK Nurul Huda Sukaraja yang terdiri dari Sembilan kelas. Pengambilan sampel dalam penelitian ini dilakukan secara acak melalui pengundian, dan dan kelas yang terpilih adalah kelas X Akuntansi yang berjumlah 19 peserta didik. Teknik pengumpulan data menggunakan angket dan tes. Uji hipotesis yang digunakan dalam penelitian ini menggunakan uji t. diperoleh  sebesar 30,885 dan nilai b sebesar 0,387. Tabel distribusi t dicari pada α = 5 dengan derajad kebesaran (df) n-2 atau 19 - 2 = 17. Pengujian satu sisi (signifikansi = 0,05) hasil diperoleh untuk  sebesar 1,734. Kriteria pengujian hipotesis, yaitu H0 diterima jika < , H0 ditolak jika > . Hasil perhitungan uji t yang sudah dilakukan menunjukkan bahwa  30,885 >  1,734, artinya Ha diterima.Jadi, terdapat pengaruh penggunaan internet terhadap hasil belajar IPS peserta didik kelas X SMK Nurul Huda Sukaraja OKU Timur

Dimensionless scaling of heat-release-induced planar shock waves in near-critical CO2

We performed highly resolved one-dimensional fully compressible Navier-Stokes simulations of heat-release-induced compression waves in near-critical CO2. The computational setup, inspired by the experimental setup of Miura et al., Phys. Rev. E, 2006, is composed of a closed inviscid (one-dimensional) duct with adiabatic hard ends filled with CO2 at three supercritical pressures. The corresponding initial temperature values are taken along the pseudo-boiling line. Thermodynamic and transport properties of CO2 in near-critical conditions are modeled via the Peng-Robinson equation of state and Chung's Method. A heat source is applied at a distance from one end, with heat release intensities spanning the range 10^3-10^11 W/m^2, generating isentropic compression waves for values < 10^9 W/m^2. For higher heat-release rates such compressions are coalescent with distinct shock-like features (e.g. non-isentropicity and propagation Mach numbers measurably greater than unity) and a non-uniform post-shock state is present due to the strong thermodynamic nonlinearities. The resulting compression wave intensities have been collapsed via the thermal expansion coefficient, highly variable in near-critical fluids, used as one of the scaling parameters for the reference energy. The proposed scaling applies to isentropic thermoacoustic waves as well as shock waves up to shock strength 2. Long-term time integration reveals resonance behavior of the compression waves, raising the mean pressure and temperature at every resonance cycle. When the heat injection is halted, expansion waves are generated, which counteract the compression waves leaving conduction as the only thermal relaxation process. In the long term evolution, the decay in amplitude of the resonating waves observed in the experiments is qualitatively reproduced by using isothermal boundary conditions.Comment: As submitted to AIAA SciTech 2017, available at http://arc.aiaa.org/doi/pdf/10.2514/6.2017-008

Coating thickness and coverage effects on the forces between silica nanoparticles in water

The structure and interactions of coated silica nanoparticles have been studied in water using molecular dynamics simulations. For 5 nm diameter amorphous silica nanoparticles we studied the effects of varying the chain length and grafting density of polyethylene oxide (PEO) on the nanoparticle coating's shape and on nanoparticle-nanoparticle effective forces. For short ligands of length $n=6$ and $n=20$ repeat units, the coatings are radially symmetric while for longer chains ($n=100$) the coatings are highly anisotropic. This anisotropy appears to be governed primarily by chain length, with coverage playing a secondary role. For the largest chain lengths considered, the strongly anisotropic shape makes fitting to a simple radial force model impossible. For shorter ligands, where the coatings are isotropic, we found that the force between pairs of nanoparticles is purely repulsive and can be fit to the form $(R/2r_\text{core}-1)^{-b}$ where $R$ is the separation between the center of the nanoparticles, $r_\text{core}$ is the radius of the silica core, and $b$ is measured to be between 2.3 and 4.1.Comment: 20 pages, 6 figure