A fabrication history based strain-fatigue model for prediction of crack initiation in a radial loading wheel

A strain-based fatigue model concerning fabrication history is applied to predict the fatigue life of a commercial car wheel under radial loads. As the prior conditions, the strain fatigue testing is performed on standard specimen of DP590 and FB540 steels at various fabrication states, including raw materials, pre-strain and pre-strain + bake. Furthermore, the strain distribution of car wheel during its rotation under radial loads is simulated via ANSYS. The fatigue properties mainly determined by crack initiation of car wheels at various fabrication states are predicted via local stress–strain method, in which the scale and surface factors are also taken into account. The radial fatigue testing is carried out, and the results are used to validate the present model. The fracture mechanism is analysed using FEI Nova 400 field emission gun scanning electron microscope

Uptake of iron and its effect on grain refinement of pure magnesium by zirconium

The uptake of iron by molten magnesium from uncoated new mild steel crucibles at temperatures 680°C, 730°C, and 780°C has been investigated. It was shown that the uptake of iron was sluggish at 680°C and the use of 0.05% zirconium addition could effectively suppress the increase in iron content within the first 2 h of holding at temperature. Rapid and severe uptake of iron was observed at 780°C. As a consequence, it was found that the grain refinement of pure magnesium achieved by 1% zirconium addition nearly vanished after 60 min hold at 780°C due to the depletion of soluble zirconium. The uptake of iron at 730°C was conspicuous but it was still controllable by use of 0.05% zirconium addition within the first 60 min of holding at temperature. The work conducted using an aluminium titanite crucible and a boron nitride coated mild steel crucible at 730°C further confirmed the highly detrimental influence of the uptake of iron on the grain refinement of pure magnesium by zirconium. The characteristic zirconium rich coring structures developed from circular to rosette like when the melt was held at 730°C in an uncoated mild steel crucible, while no such evolution was observed when held in an aluminium titanite crucible at the same temperature. Recommendations to minimise the consumption of zirconium by the uptake of iron were made based on the results obtained from this investigation. The mechanism of grain refinement of magnesium by a low concentration of zirconium is discussed

Studi Cara Kerja Komponen Sistem Hidrolik Excavator

One of the heavy equipment in the industrial world is an excavator. This heavy equipment, better known as the backhoe, is used to dredge mining materials, such as coal. The main components of the Excavator are Attachments (Boom, Arm and Bucket). To keep the Excavator functioning properly during the operation process, Preventive Maintenance is needed. Hydraulic Cylinder functions as a system for moving work equipment. This analysis aims to determine the types of maintenance in Hydraulic Excavators. The inspection procedure is carried out by performing a performance test consisting of a pressure test on the hydroulic system. Visual inspection was also carried out on hydraulic hose, control valve, hydraulic filter, hydraulic pump, hydraulic cylinder. Next is Preventive Maintenance, which is the implementation of daily, weekly, monthly and annual maintenance work. In daily maintenance, inspection will be carried out, check all lubrication and perform service. Weekly maintenance is carried out every 60 working hours. Monthly maintenance is carried out every 250 working hours, while annual maintenance is carried out every 2500 working hours. The operation of the Excavator unit must be in accordance with the Manual Book. So that the service life of the unit along with the excavator components is in accordance with its life time

ANALISIS BIAYA SATUAN PROGRAM STUDI UNTUK DASAR KEBIJAKAN ANGGARAN DI UNY

Latar Belakang : dengan meningkatnya keinginan untuk melanjutkan kuliah ke Perguruan Tinggi bagi lulusan sekolah menengah di Indonesia dan semakin tingginya biaya yang ditanggung oleh calon mahasiswa maka pemerintah dihadapkan pada kondisi untuk mendorong universitas agar dapat beroperasi dengan lebih efisien dan lebih produktif. Tujuan: Tujuan penelitian ini adalah mengembangkan metode baru penilaian efisiensi dan produktivitas universitas Lembaga Pendidikan Tenaga Keguruan (LPTK) di Indonesia dengan mempergunakan Data Envelopment Analysis dan pendekatan Malmquist yang secara teknis efektif untuk menghitung efisiensi dan produktivitas dari sebuah Universitas. Target Khusus : Target khusus yang ingin dicapai dalam penelitian ini adalah terciptanya suatu model penilaian efisiensi dan produktivitas Lembaga Pendidikan Tenaga Keguruan dengan menggunakan pendekatan penilaian Data Envelopment Analysis dan metode Malmquist yang bermanfaat untuk peningkatan dan penguatan institusi pendidikan di Indonesia. Metode Penelitian : Penelitian ini merupakan penelitian research and development yang dilaksanakan dalam dua tahap. Kegiatan penelitian tahun I meliputi (1) analisis kebutuhan yaitu pengkajian variabel yang akan menjadi faktor penilaian efisiensi dan produktivitas beserta mekanisme pengumpulan datanya (2) disain model perhitungan efisiensi dan produktivitas dari Lembaga Pendidikan Teknologi dan Kejuruan (3) implementasi perhitungan efisiensi dan produktivitas dari 12 Universitas LPTK negeri di Indonesia dengan Data Envelopment Analysis dan metode Malmquist. Penelitian tahun II dan III ditargetkan untuk melakukan perhitungan perbandingan efisiensi dan produktivitas Universitas di Indonesia dengan menambah jumlah sampel Universitas yang dianalisis beserta pembuatan sistem informasi kinerja Universitas di Indonesia dengan Basis data yang memuat variable-variabel yang menjadi data penilaian kinerja. Luaran yang diharapkan dari penelitian ini adalah terciptanya model penilaian efisiensi dan produktivitas universitas LPTK menggunakan metode DEA dan Malmquist serta sistem informasi kinerja Universitas di Indonesia dan mampu menghasilkan publikasi pada jurnal ilmiah nasional atau internasional yang terakreditasi

Primordial nucleosynthesis with a varying fine structure constant: An improved estimate

We compute primordial light-element abundances for cases with fine structure constant alpha different from the present value, including many sources of alpha dependence neglected in previous calculations. Specifically, we consider contributions arising from Coulomb barrier penetration, photon coupling to nuclear currents, and the electromagnetic components of nuclear masses. We find the primordial abundances to depend more weakly on alpha than previously estimated, by up to a factor of 2 in the case of ^7Li. We discuss the constraints on variations in alpha from the individual abundance measurements and the uncertainties affecting these constraints. While the present best measurements of primordial D/H, ^4He/H, and ^7Li/H may be reconciled pairwise by adjusting alpha and the universal baryon density, no value of alpha allows all three to be accommodated simultaneously without consideration of systematic error. The combination of measured abundances with observations of acoustic peaks in the cosmic microwave background favors no change in alpha within the uncertainties.Comment: Phys. Rev. D accepted version; minor changes in response to refere

Phase transition from a dx2−y2d_{x^2-y^2} to dx2−y2+dxyd_{x^2-y^2}+d_{xy} superconductor

We study the phase transition from a $d_{x^2-y^2}$ to $d_{x^2-y^2}+d_{xy}$ superconductor using the tight-binding model of two-dimensional cuprates. As the temperature is lowered past the critical temperature $T_c$, first a $d_{x^2-y^2}$ superconducting phase is created. With further reduction of temperature, the $d_{x^2-y^2}+d_{xy}$ phase is created at temperature $T=T_{c1}$. We study the temperature dependencies of the order parameter, specific heat and spin susceptibility in these mixed-angular-momentum states on square lattice and on a lattice with orthorhombic distortion. The above-mentioned phase transitions are identified by two jumps in specific heat at $T_c$ and $T_{c1}$.Comment: Latex file, 5 pages, 6 postscript figures, Accepted in Physical Review

Long-term perturbations due to a disturbing body in elliptic inclined orbit

In the current study, a double-averaged analytical model including the action of the perturbing body's inclination is developed to study third-body perturbations. The disturbing function is expanded in the form of Legendre polynomials truncated up to the second-order term, and then is averaged over the periods of the spacecraft and the perturbing body. The efficiency of the double-averaged algorithm is verified with the full elliptic restricted three-body model. Comparisons with the previous study for a lunar satellite perturbed by Earth are presented to measure the effect of the perturbing body's inclination, and illustrate that the lunar obliquity with the value 6.68\degree is important for the mean motion of a lunar satellite. The application to the Mars-Sun system is shown to prove the validity of the double-averaged model. It can be seen that the algorithm is effective to predict the long-term behavior of a high-altitude Martian spacecraft perturbed by Sun. The double-averaged model presented in this paper is also applicable to other celestial systems.Comment: 28 pages, 6 figure

The Ricci flow on noncommutative two-tori

In this paper we construct a version of Ricci flow for noncommutative 2-tori, based on a spectral formulation in terms of the eigenvalues and eigenfunction of the Laplacian and recent results on the Gauss-Bonnet theorem for noncommutative tori.Comment: 18 pages, LaTe

Origin of Life

The evolution of life has been a big enigma despite rapid advancements in the fields of biochemistry, astrobiology, and astrophysics in recent years. The answer to this puzzle has been as mind-boggling as the riddle relating to evolution of Universe itself. Despite the fact that panspermia has gained considerable support as a viable explanation for origin of life on the Earth and elsewhere in the Universe, the issue remains far from a tangible solution. This paper examines the various prevailing hypotheses regarding origin of life like abiogenesis, RNA World, Iron-sulphur World, and panspermia; and concludes that delivery of life-bearing organic molecules by the comets in the early epoch of the Earth alone possibly was not responsible for kick-starting the process of evolution of life on our planet.Comment: 32 pages, 8 figures,invited review article, minor additio