Temperatures during the dry cutting of titanium alloy using diamond composites with ceramic bonding phases

In this paper the thermal properties of diamond composites with ceramic bonding phases, such as the Ti–Si–C system with nanometric Ti(CN) and TiB₂ are presented. The thermal conductivities of the materials were analyzed by the laser pulse method. In addition, computational simulations of the temperature dependence on the distance from the cutting edge were performed according to the finite element method for the investigated composites, commercial PCD, and hypothetical diamond monocrystal.Досліджено теплові властивості алмазних композитів з керамічними зв’язуючими фазами, таких як системи Ti–Si–C з нанометровим Ti(CN) і TiB₂. Теплопровідності матеріалів проаналізовано за допомогою методу лазерного імпульсу. Крім того, методом скінченних елементів виконано числове моделювання залежності температури від відстані до ріжучої кромки для досліджених композитів, комерційного PCD і гіпотетичного монокристалу алмазу. Розглянуто дві швидкості різання в ході числового обчислення: 100 і 200 м/хв.Исследованы тепловые свойства алмазных композитов с керамическими связующими фазами, таких как системы Ti–Si–C с нанометровым Ti(CN) и TiB₂. Теплопроводности материалов проанализированы с помощью метода лазерного импульса. Кроме того, методом конечных элементов выполнено числовое моделирование зависимости температуры от расстояния до режущей кромки для исследованных композитов, коммерческого PCD и гипотетического монокристалла алмаза. Рассматривали две скорости резки в ходе числового вычисления: 100 и 200 м/мин

Constraining stellar assembly and AGN feedback at the peak epoch of star formation

We study stellar assembly and feedback from active galactic nuclei (AGN) around the epoch of peak star formation (1<z<2), by comparing hydrodynamic simulations to rest-frame UV-optical galaxy colours from the Wide Field Camera 3 (WFC3) Early-Release Science (ERS) Programme. Our Adaptive Mesh Refinement simulations include metal-dependent radiative cooling, star formation, kinetic outflows due to supernova explosions, and feedback from supermassive black holes. Our model assumes that when gas accretes onto black holes, a fraction of the energy is used to form either thermal winds or sub-relativistic momentum-imparting collimated jets, depending on the accretion rate. We find that the predicted rest-frame UV-optical colours of galaxies in the model that includes AGN feedback is in broad agreement with the observed colours of the WFC3 ERS sample at 1<z<2. The predicted number of massive galaxies also matches well with observations in this redshift range. However, the massive galaxies are predicted to show higher levels of residual star formation activity than the observational estimates, suggesting the need for further suppression of star formation without significantly altering the stellar mass function. We discuss possible improvements, involving faster stellar assembly through enhanced star formation during galaxy mergers while star formation at the peak epoch is still modulated by the AGN feedback.Comment: 6 pages, 4 figures, accepted for publication in MNRAS Letter

A fixed point theorem for multifunctions and an application

The main result is a fixed point theorem for compositions of chain faithful multifunctions (Corollary 2.3). The theorem is then applied to get sufficient conditions for the fixed point property of the product of two partially ordered sets.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45583/1/12_2005_Article_BF01195267.pd

Inequality, Fiscal Capacity and the Political Regime: Lessons from the Post-Communist Transition

Using panel data for twenty-seven post-communist economies between 1987-2003, we examine the nexus of relationships between inequality, fiscal capacity (defined as the ability to raise taxes efficiently) and the political regime. Investigating the impact of political reform we find that full political freedom is associated with lower levels of income inequality. Under more oligarchic (authoritarian) regimes, the level of inequality is conditioned by the state’s fiscal capacity. Specifically, oligarchic regimes with more developed fiscal systems are able to defend the prevailing vested interests at a lower cost in terms of social injustice. This empirical finding is consistent with the model developed by Acemoglu (2006). We also find that transition countries undertaking early macroeconomic stabilisation now enjoy lower levels of inequality; we confirm that education fosters equality and the suggestion of Commander et al (1999) that larger countries are prone to higher levels of inequality.http://deepblue.lib.umich.edu/bitstream/2027.42/57211/1/wp831 .pd

SDSS J162520.29+120308.7 – a new SU Ursae Majoris star in the period gap

We report results of an extensive world-wide observing campaign devoted to the recently discovered dwarf nova SDSS J162520.29+120308.7 (SDSS J1625). The data were obtained during the July 2010 eruption of the star and in August and September 2010 when the object was in quiescence. During the July 2010 superoutburst, SDSS J1625 clearly displayed superhumps with a mean period of Psh = 0.095942(17) days (138.16 ± 0.02 min) and a maximum amplitude reaching almost 0.4 mag. The superhump period was not stable, decreasing very rapidly at a rate of ˙P = −1.63(14) × 10−3 at the beginning of the superoutburst and increasing at a rate of ˙P = 2.81(20) × 10−4 in the middle phase. At the end of the superoutburst, it stabilized around the value of Psh = 0.09531(5) day. During the first twelve hours of the superoutburst, a low-amplitude double wave modulation was observed whose properties are almost identical to early superhumps observed in WZ Sge stars. The period of early superhumps, the period of modulations observed temporarily in quiescence, and the period derived from radial velocity variations are the same within measurement errors, allowing us to estimate the most probable orbital period of the binary to be Porb = 0.09111(15) days (131.20 ± 0.22 min). This value clearly indicates that SDSS J1625 is another dwarf nova in the period gap. Knowledge of the orbital and superhump periods allows us to estimate the mass ratio of the system to be q ≈ 0.25. This high value poses serious problems for both the thermal and tidal instability (TTI) model describing the behaviour of dwarf novae and for some models explaining the origin of early superhumps

UV-dropout Galaxies in the GOODS-South Field from WFC3 Early Release Science Observations

We combine new high sensitivity ultraviolet (UV) imaging from the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) with existing deep HST/Advanced Camera for Surveys (ACS) optical images from the Great Observatories Origins Deep Survey (GOODS) program to identify UV-dropouts, which are Lyman break galaxy (LBG) candidates at z~1-3. These new HST/WFC3 observations were taken over 50 sq.arcmin in the GOODS-South field as a part of the Early Release Science program. The uniqueness of these new UV data is that they are observed in 3 UV/optical (WFC3 UVIS) channel filters (F225W, F275W and F336W), which allows us to identify three different sets of UV-dropout samples. We apply Lyman break dropout selection criteria to identify F225W-, F275W- and F336W-dropouts, which are z~1.7, 2.1 and 2.7 LBG candidates, respectively. Our results are as follows: (1) these WFC3 UVIS filters are very reliable in selecting LBGs with z~2.0, which helps to reduce the gap between the well studied z~>3 and z~0 regimes, (2) the combined number counts agrees very well with the observed change in the surface densities as a function of redshift when compared with the higher redshift LBG samples; and (3) the best-fit Schechter function parameters from the rest-frame UV luminosity functions at three different redshifts fit very well with the evolutionary trend of the characteristic absolute magnitude, and the faint-end slope, as a function of redshift. This is the first study to illustrate the usefulness of the WFC3 UVIS channel observations to select z<3 LBGs. The addition of the new WFC3 on the HST has made it possible to uniformly select LBGs from z~1 to z~9, and significantly enhance our understanding of these galaxies using HST sensitivity and resolution.Comment: Accepted for publication in ApJ (24 pages, 7 figures