PROSES PERMESINAN BUBUT PADA KACA

Kaca termasuk jenis material yang getas. Sebagai material yang getas, sifat ketermesinan (machinability) kaca sangat rendah karena nilai fracture toughness-nya yang rendah. Kekuatan fracture (fracture strength) kaca lebih rendah dari kekuatan luluhnya (yield strength). Ketika kaca diberi beban tarik atau tekuk pada suhu kamar, maka kaca akan hancur sebelum terjadi deformasi plastis. Itu sebabnya maka proses pemesinan jarang diterapkan pada kaca. Permasalahan utama proses pemesinan material getas seperti kaca adalah proses pembentukan geram dapat menimbulkan kerusakan yang cukup parah di permukaan dan di bawah permukaan (subsurface). Kerusakan seperti ini jelas menurunkan kualitas hasil proses pemesinan. Untuk menghasilkan permukaan yang halus pada material getas, adalah sangat penting jika material getas dilakukan proses pemesinan dalam kondisi ulet (ductile cutting mode). Untuk itu maka serangkaian eksperimen proses pemesinan bubut pada kaca telah dilakukan untuk mencari parameter optimum dari proses pemesinan kaca. Selain itu juga diteliti umur  pahat yang digunakan dan proses pendinginan apa yang mampu untuk memperpanjang umur pahat. Sehingga nantinya akan berdampak pada nilai ekonomi proses pemesinan kaca jika nanti dapat diterapkan di masyarakat. Dari hasil yang didapatkan ternyata proses bubut pada kaca dapat dilakukan. Kondisi permukaan paling baik didapatkan ketika proses bubut dilakukan pada  radius nose 5 mm, depth of cut 0,5 mm, feed rate 0,045 mm/rev, kecepatan spindel 30 rpm dan kondisi permesinan menggunakan  cairan pendingin dromus. Dari hasil ini juga terlihat bahwa Laju keausan tepi pahat HSS pada proses permesinan kaca sangat tinggi, sehingga dengan pertimbangan ekonomis pahat HSS tidak dapat digunakan Kata Kunci  : Permesinan, Kaca, High hydrostatic pressure, Ductile cutting mode, Laju Keausan Paha

Vitamin D metabolites affect serum calcium and phosphate in freshwater catfish, Heteropneustes fossilis

金沢大学環日本海域環境研究センター生物多様性研究部門The effects of vitamin D3, 24,25(OH)2 vitamin D3, 25(OH) vitamin D3 and 1,25(OH)2 vitamin D3 were investigated on the serum calcium and phosphate levels of freshwater catfish, Heteropneustes fossilis. The fish were injected daily intraperitoneally with these secosteroids for 10 days. Blood samples were collected at day 1, 3, 5 and 10. Serum calcium and inorganic phosphate levels were elevated by all of the treatments except for 24,25(OH)2 vitamin D3

Modeling the strangeness content of hadronic matter

The strangeness content of hadronic matter is studied in a string-flip model that reproduces various aspects of the QCD-inspired phenomenology, such as quark clustering at low density and color deconfinement at high density, while avoiding long range van der Waals forces. Hadronic matter is modeled in terms of its quark constituents by taking into account its internal flavor (u,d,s) and color (red, blue, green) degrees of freedom. Variational Monte-Carlo simulations in three spatial dimensions are performed for the ground-state energy of the system. The onset of the transition to strange matter is found to be influenced by weak, yet not negligible, clustering correlations. The phase diagram of the system displays an interesting structure containing both continuous and discontinuous phase transitions. Strange matter is found to be absolutely stable in the model.Comment: 14 pages, 1 table, 8 eps figures, revtex. Submitted to Phys. Rev. C, Presented at INPC2001 Berkeley, Ca. july 29-Aug

Upper critical field for underdoped high-T_c superconductors. Pseudogap and stripe--phase

We investigate the upper critical field in a stripe--phase and in the presence of a phenomenological pseudogap. Our results indicate that the formation of stripes affects the Landau orbits and results in an enhancement of $H_{c2}$. On the other hand, phenomenologically introduced pseudogap leads to a reduction of the upper critical field. This effect is of particular importance when the magnitude of the gap is of the order of the superconducting transition temperature. We have found that a suppression of the upper critical field takes place also for the gap that originates from the charge--density waves.Comment: 7 pages, 5 figure

Stochastic Approximation to Understand Simple Simulation Models

This paper illustrates how a deterministic approximation of a stochastic process can be usefully applied to analyse the dynamics of many simple simulation models. To demonstrate the type of results that can be obtained using this approximation, we present two illustrative examples which are meant to serve as methodological references for researchers exploring this area. Finally, we prove some convergence results for simulations of a family of evolutionary games, namely, intra-population imitation models in n-player games with arbitrary payoffs.Ministerio de Educación (JC2009- 00263), Ministerio de Ciencia e Innovación (CONSOLIDER-INGENIO 2010: CSD2010-00034, DPI2010-16920

THE EFFECT OF SWEET POTATO (IPOMOEA BATATAS L.) TUBER AND LEAVES BRANGKASAN SUBSTITUTION IN THE GROWTH PHASE LANDRACE BALI PIG (3-6 MONTHS AGE) RATION

The high price of feed/ration is the biggest problem for farmers, so it requires a way to find quality but cheap feed ingredients, for example using brangkasan/stucker, which are sweet potato leaves and twigs and tubers as feed ingredients substitution for pigs, the protein and energy content is still quite high, but the economic value has not been realized by the farmers. This study aims to determine the effect of some percentage tubers and sweet potato brangkasan/stucker to substitute the concentrate, on the performance of landrace Bali pigs. The study used a Completely Randomized Design method (CRD) with 4 treatments consisting of : T-1 30% concentrate + 60% pollard + 10% sweet potato brangkasan/stucker as control, T-2: 10% concentrate + 60% pollard + 20% sweet potato tuber + 10% sweet potato leaves brangkasan/stucker, T-3:10% concentrate + 50% pollard + 30% sweet potato tuber + 10% sweet potato leaves brangkasan/stucker and T-4:10% concentrate + 40% pollard + 40% tuber +10% sweet potato leaves brangkasan/stucker, which are repeated 5 times. Based on the results of the study, T-2 (giving 10% concentrate + 60% pollard + 20% sweet potato tuber + 10% sweet potato leaves brangkasan/stucker) causing an increase in body weight gain, final body weight and feed consumption, but decrease the feed conversion. Thus, it can be concluded that the substitution of sweet potato tubers and leaves brangkasan/stucker can be used as feed for growth phase landrace Bali pig

Self-induced and induced transparencies of two-dimensional and three- dimensional superlattices

The phenomenon of transparency in two-dimensional and three-dimensional superlattices is analyzed on the basis of the Boltzmann equation with a collision term encompassing three distinct scattering mechanisms (elastic, inelastic and electron-electron) in terms of three corresponding distinct relaxation times. On this basis, we show that electron heating in the plane perpendicular to the current direction drastically changes the conditions for the occurrence of self-induced transparency in the superlattice. In particular, it leads to an additional modulation of the current amplitudes excited by an applied biharmonic electric field with harmonic components polarized in orthogonal directions. Furthermore, we show that self-induced transparency and dynamic localization are different phenomena with different physical origins, displaced in time from each other, and, in general, they arise at different electric fields.Comment: to appear in Physical Review

Influence of incommensurate dynamic charge-density wave scattering on the line shape of high-Tc_c cuprates

We show that the spectral lineshape of superconducting La$_{2-x}$Sr$_x$CuO$_4$ (LSCO) and Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212) can be well described by the coupling of the charge carriers to collective incommensurate charge-density wave (CDW) excitations. Our results imply that besides antiferromagnetic (AF) fluctuations also low-energy CDW modes can contribute to the observed dip-hump structure in the Bi2212 photoemission spectra. In case of underdoped LSCO we propose a possible interpretation of ARPES data in terms of a grid pattern of fluctuating stripes where the charge and spin scattering directions deviate by $\alpha=\pi/4$. Within this scenario we find that the spectral intensity along $(0,0) \to (\pi,\pi)$ is strongly suppressed consistent with recent photoemission experiments. In addition the incommensurate charge-density wave scattering leads to a significant broadening of the quasiparticle-peak around $(\pi,0)$.Comment: 5 pages, 4 figure

Dispersion of Ordered Stripe Phases in the Cuprates

A phase separation model is presented for the stripe phase of the cuprates, which allows the doping dependence of the photoemission spectra to be calculated. The idealized limit of a well-ordered array of magnetic and charged stripes is analyzed, including effects of long-range Coulomb repulsion. Remarkably, down to the limit of two-cell wide stripes, the dispersion can be interpreted as essentially a superposition of the two end-phase dispersions, with superposed minigaps associated with the lattice periodicity. The largest minigap falls near the Fermi level; it can be enhanced by proximity to a (bulk) Van Hove singularity. The calculated spectra are dominated by two features -- this charge stripe minigap plus the magnetic stripe Hubbard gap. There is a strong correlation between these two features and the experimental photoemission results of a two-peak dispersion in La$_{2-x}$Sr$_x$CuO$_4$, and the peak-dip-hump spectra in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$. The differences are suggestive of the role of increasing stripe fluctuations. The 1/8 anomaly is associated with a quantum critical point, here expressed as a percolation-like crossover. A model is proposed for the limiting minority magnetic phase as an isolated two-leg ladder.Comment: 24 pages, 26 PS figure