The Effect of Star Formation on Observed Properties of High Redshift Absorption Systems

Damped Lyman-alpha absorber systems (DLAs) are thought to be one of the best probes to understand structure formation in the early universe. DLAs are defined as such systems with neutral hydrogen column density N(HI) \u3e 2x1020 cm-2. They have also been considered to be the most important neutral-gas reservoir for star formation at high redshift, and the key to uncovering the mystery of the progenitors of present-day galaxies. For many years, there has been a debate on the nature of the galaxies causing these absorptions at high redshift. One idea is that DLAs are small proto-galaxy clumps formed in the process of hierarchical structure formation. Another idea is that DLAs can be best explained with rapidly rotating, large, cold disks of galaxies. It is believed that through full understanding of the mechanism that control the processes, we are able to construct the history of galaxy evolution. In order to test on these ideas, we used high-resolution AMR (adaptive mesh refinement) hydrodynamics simulations to study kinematics properties and abundances of DLAs at redshift z = 3. Our simulations are based on standard cold dark matter cosmology (ΛCDM), and include full radiative transfer and star formation/feedback recipes, which are considered to be the two key ingredients to solve the low velocity-widths problem found in previous numerical simulations. Our results show that although we are able to reproduce the observed column density distribution, our velocity widths are still much lower than the observations. Further more, we plot line profiles through the points with highest radial velocities, which we believe are in the violent star or galaxy forming regions. From the single line profile, we can see some star formation/feedback effects by comparing the simulation runs with and without star formation/feedback. However, in a larger picture, these effects are not very obvious. This is probably due to the small volume size and insufficient grid-resolution. We conclude that it is essential to include full radiative transfer in order to reproduce reasonable HI column density distribution, and for further simulations, we should have larger volume size, and much higher resolution in order to resolve substructures such as star forming regions or supernova explosions

Quiescent X-Ray/Optical Counterparts of the Black Hole Transient H 1705-250

We report the result of a new Chandra observation of the black hole X-ray transient H 1705-250 in quiescence. H 1705-250 was barely detected in the new 50 ks Chandra observation. With 5 detected counts, we estimate the source quiescent luminosity to be Lx~9.1e30 erg/s in the 0.5-10 keV band (adopting a distance of 8.6 kpc). This value is in line with the quiescent luminosities found among other black hole X-ray binaries with similar orbital periods. By using images taken with the Faulkes Telescope North, we derive a refined position of H 1705-250. We also present the long-term lightcurve of the optical counterpart from 2006 to 2012, and show evidence for variability in quiescence.Comment: 5 pages, 2 figures; Accepted for publication in MNRA

The Conditional Mode in Parametric Frontier Models

We survey formulations of the conditional mode estimator for technical inefficiency in parametric stochastic frontier models with normal errors and introduce new formulations for models with Laplace errors. We prove the conditional mode estimator converges pointwise to the true inefficiency value as the noise variance goes to zero. We also prove that the conditional mode estimator in the normal-exponential model achieves near-minimax optimality. Our minimax theorem implies that the worst-case risk occurs when many firms are nearly efficient, and the conditional mode estimator minimizes estimation risk in this case by estimating these small inefficiency firms as efficient. Unlike the conditional expectation estimator, the conditional mode estimator produces multiple firms with inefficiency estimates exactly equal to zero, suggesting a rule for selecting a subset of maximally efficient firms. Our simulation results show that this “zero-mode subset” has reasonably high probability of containing the most efficient firm, particularly when inefficiency is exponentially distributed. The rule is easy to apply and interpret for practitioners. We include an empirical example demonstrating the merits of the conditional mode estimator

Research on the Motivation and Attitude of College students' Physical Education in Taiwan

College students' physical education plays an important role in physical activity and cultivates the concept of independent health management. At present, what kind of learning attitude do Taiwan college students face in physical education? What motivation does the student influence the attitude of the physical education? What is the relevance? All of the above are the purpose of this study. The research method adopts the questionnaire survey method, and the survey data adopts descriptive statistical analysis, independent sample t test, single factor variance analysis, LSD post hoc comparison method, and typical correlation analysis. Research results: 1. The different background variables of Taiwanese college students are that the main motivation factor of physical education is to obtain good health fitness for "physical health". 2. Taiwanese college students have different background variables. They all think that the "cognitive learning" of physical education is the main factor of attitude, that is, the knowledge about health care and sports skills. 3. There is a positive correlation between learning motivation and learning attitude (ρ=.90). Learning motivation is one of the important factors affecting learning attitude. Research conclusions: 1. The factors of Taiwanese male and female college students' motivation for learning in physical education are mainly based on "physical health". 2. Freshmen have higher motivations and learning attitudes in physical education than second-grade to fourth-grade. 3. Taiwan female college students average 1 or 2 times per week, male college students have the most athletes 2 to 3 times per week, more than 90% of college students like sports. 4. There is a positive correlation between learning motivation and learning attitude, indicating that the stronger the attribute of learning motivation "physical health", the higher the student's learning attitude. 5. Satisfying students' motivation for learning helps students to learn positively. 6. Another important task of the college physical education class is to prepare students for future lifelong sports

Can gravitational infall energy lead to the observed velocity dispersion in DLAs?

The median observed velocity width v_90 of low-ionization species in damped Ly-alpha systems is close to 90 km/s, with approximately 10% of all systems showing v_90 > 210 km/s at z=3. We show that a relative shortage of such high-velocity neutral gas absorbers in state-of-the-art galaxy formation models is a fundamental problem, present both in grid-based and particle-based numerical simulations. Using a series of numerical simulations of varying resolution and box size to cover a wide range of halo masses, we demonstrate that energy from gravitational infall alone is insufficient to produce the velocity dispersion observed in damped Ly-alpha systems, nor does this dispersion arise from an implementation of star formation and feedback in our highest resolution (~ 45 pc) models, if we do not put any galactic winds into our models by hand. We argue that these numerical experiments highlight the need to separate dynamics of different components of the multiphase interstellar medium at z=3.Comment: 12 Pages, 9 Figures, accepted to ApJ, printing in colour recommende

The Conditional Mode in Parametric Frontier Models

We survey formulations of the conditional mode estimator for technical inefficiency in parametric stochastic frontier models with normal errors and introduce new formulations for models with Laplace errors. We prove the conditional mode estimator converges pointwise to the true inefficiency value as the noise variance goes to zero. We also prove that the conditional mode estimator in the normal-exponential model achieves near-minimax optimality. Our minimax theorem implies that the worst-case risk occurs when many firms are nearly efficient, and the conditional mode estimator minimizes estimation risk in this case by estimating these small inefficiency firms as efficient. Unlike the conditional expectation estimator, the conditional mode estimator produces multiple firms with inefficiency estimates exactly equal to zero, suggesting a rule for selecting a subset of maximally efficient firms. Our simulation results show that this “zero-mode subset” has reasonably high probability of containing the most efficient firm, particularly when inefficiency is exponentially distributed. The rule is easy to apply and interpret for practitioners. We include an empirical example demonstrating the merits of the conditional mode estimator

Automating the audit of electronic invoices with a soft robot

Taiwan's Chi Mei Medical Center has completed four challenges mentioned in published robotic process automation (RPA) studies including automating a dynamic process, designing feasible human-robot collaboration, incorporating other emerging technologies, and bringing positive business impacts. Its executives called a committee to implement the electronic invoicing. This implementation includes the creation of a software robot to download automatically cloud electronic invoice (E-invoice) data from Taiwan's E-invoice platform and detect the inconsistency between them and on-premise data. This bot operates when internal auditors are off their office. They satisfied this software robot since the remaining work is only verifying the resulting inconsistency. The Chi Mei Medical Center measured the time and costs before and after adopting software robots to audit E-invoice; consequently, it welcomed more bots automating other business processes. In conclusion, integrating a software robot with other emerging technologies mitigates the possible errors provided by this bot. A good human-robot collaboration relies on the consideration of human perspective in choosing RPA tasks. Free bot creators are sufficient to verify that automating a business process using a bot is a reasonable investment.Comment: 11 pages, 6 figures, 1 tabl

Fermion Absorption Cross Section and Topology of Spherically Symmetric Black Holes

In 1997, Liberati and Pollifrone in Phys. Rev. D56 (1997) 6458 (hep-th/9708014) achieved a new formulation of the Bekenstein-Hawking formula, where the entropy and the Euler characteristic are related by $S=\chi A/8$. In this work we present a relation between the low-energy absorption cross section for minimally coupled fermions and the Euler characteristic of (3+1)-dimensional spherically symmetric black holes, i.e. $\sigma =\chi g_h^{-1}A$. Based on the relation, using the Gauss--Bonnet--Chern theorem and the $\phi$-mapping method, an absorption cross section density is introduced to describe the topology of the absorption cross section. It is shown that the absorption cross section and its density are determined by the singularities of the timelike Killing vector field of the spacetime and these singularities carry the topological numbers, Hopf indices and Brouwer degrees, naturally.Comment: 16 pages, no figures, accepted by Phys. Lett.