Single-machine scheduling with stepwise tardiness costs and release times

We study a scheduling problem that belongs to the yard operations component of the railroad planning problems, namely the hump sequencing problem. The scheduling problem is characterized as a single-machine problem with stepwise tardiness cost objectives. This is a new scheduling criterion which is also relevant in the context of traditional machine scheduling problems. We produce complexity results that characterize some cases of the problem as pseudo-polynomially solvable. For the difficult-to-solve cases of the problem, we develop mathematical programming formulations, and propose heuristic algorithms. We test the formulations and heuristic algorithms on randomly generated single-machine scheduling problems and real-life datasets for the hump sequencing problem. Our experiments show promising results for both sets of problems

AlGaAs/GaAs transverse junction stripe lasers with distributed feedback

Transverse junction stripe (TJS) lasers with periodic feedback were fabricated in two geometries. An interferometric and wet chemical etching technique was used to create a feedback grating across the entire pumping region for the distributed feedback (DFB) TJS laser and to create the separate distributed Bragg reflectors/DBR) for the TJS/DBR laser. The TJS/DFB laser was a double heterostructure device grown by liquid phase epitaxy (LPE) and had a third order grating etched in the top ALO.2GaO.8As layer. The grating was buried by growing an ALO.35GaO.65As layer on the grating by metal organic chemical vapor deposition (MO-CVD). The TJS/DBR laser was also fabricated in an LPE double heterostructure. The top AlGaAs layer was thinned to 0.1 micron over more than half of the laser so that the grating would be close to the GaAs active layer and optical field. Single mode operation in both configurations was obtained. The thermal shift of the laser wavelength in both cases was less than 1 Angstrom/deg K, compared to the 3 Angstrom/deg K shift of the spontaneous emission peak

Market dynamics immediately before and after financial shocks: quantifying the Omori, productivity and Bath laws

We study the cascading dynamics immediately before and immediately after 219 market shocks. We define the time of a market shock T_{c} to be the time for which the market volatility V(T_{c}) has a peak that exceeds a predetermined threshold. The cascade of high volatility "aftershocks" triggered by the "main shock" is quantitatively similar to earthquakes and solar flares, which have been described by three empirical laws --- the Omori law, the productivity law, and the Bath law. We analyze the most traded 531 stocks in U.S. markets during the two-year period 2001-2002 at the 1-minute time resolution. We find quantitative relations between (i) the "main shock" magnitude M \equiv \log V(T_{c}) occurring at the time T_{c} of each of the 219 "volatility quakes" analyzed, and (ii) the parameters quantifying the decay of volatility aftershocks as well as the volatility preshocks. We also find that stocks with larger trading activity react more strongly and more quickly to market shocks than stocks with smaller trading activity. Our findings characterize the typical volatility response conditional on M, both at the market and the individual stock scale. We argue that there is potential utility in these three statistical quantitative relations with applications in option pricing and volatility trading.Comment: 16 pages, double column, 13 figures, 1 Table; Changes made in Version 2 in response to referee comment

Anti-de Sitter boundary in Poincare coordinates

We study the space-time boundary of a Poincare patch of Anti-de Sitter (AdS) space. We map the Poincare AdS boundary to the global coordinate chart and show why this boundary is not equivalent to the global AdS boundary. The Poincare AdS boundary is shown to contain points of the bulk of the entire AdS space. The Euclidean AdS space is also discussed. In this case one can define a semi-global chart that divides the AdS space in the same way as the corresponding Euclidean Poincare chart.Comment: In this revised version we add a discussion of the physical consequences of the choice of a coordinate system for AdS space. We changed figure 1 and added more references. Version to be published in Gen. Relat. Grav

The limit space of a Cauchy sequence of globally hyperbolic spacetimes

In this second paper, I construct a limit space of a Cauchy sequence of globally hyperbolic spacetimes. In the second section, I work gradually towards a construction of the limit space. I prove the limit space is unique up to isometry. I als show that, in general, the limit space has quite complicated causal behaviour. This work prepares the final paper in which I shall study in more detail properties of the limit space and the moduli space of (compact) globally hyperbolic spacetimes (cobordisms). As a fait divers, I give in this paper a suitable definition of dimension of a Lorentz space in agreement with the one given by Gromov in the Riemannian case.Comment: 31 pages, 5 figures, submitted to Classical and Quantum gravity, seriously improved presentatio

LpL^p-Spectral theory of locally symmetric spaces with QQ-rank one

We study the $L^p$-spectrum of the Laplace-Beltrami operator on certain complete locally symmetric spaces $M=\Gamma\backslash X$ with finite volume and arithmetic fundamental group $\Gamma$ whose universal covering $X$ is a symmetric space of non-compact type. We also show, how the obtained results for locally symmetric spaces can be generalized to manifolds with cusps of rank one

Four New Delta Scuti Pulsators from a Variability Survey of 131 Stars

In a photometric variability survey of 131 stars with B < 14 mag, we have found four new Delta Scuti stars. We were sensitive to oscillation amplitudes as low as a few mmag. The detection rate of short-period (P < 0.1 d) pulsating variable stars, which may be relevant for planned large variability surveys such as GAIA, POI, and even the LSST, was therefore 3%. All four new variable stars have low pulsation amplitude (tens of mmag), and one has a very short period (0.0198 d). This star is one of the fastest known Delta Scuti pulsators. The short period of this variable star makes it observationally tractable, and it may therefore be a particularly good candidate for asteroseismological studies. All four new variable stars will add to the cadre of low-amplitude and relatively short-period Delta Scuti stars that are potentially useful for learning about the structure of stars on or near the main sequence, slightly more massive than the Sun.Comment: To appear in the June 2002 issue of PASP, 9 pages, 6 figure

Who is the best player ever? A complex network analysis of the history of professional tennis

We consider all matches played by professional tennis players between 1968 and 2010, and, on the basis of this data set, construct a directed and weighted network of contacts. The resulting graph shows complex features, typical of many real networked systems studied in literature. We develop a diffusion algorithm and apply it to the tennis contact network in order to rank professional players. Jimmy Connors is identified as the best player of the history of tennis according to our ranking procedure. We perform a complete analysis by determining the best players on specific playing surfaces as well as the best ones in each of the years covered by the data set. The results of our technique are compared to those of two other well established methods. In general, we observe that our ranking method performs better: it has a higher predictive power and does not require the arbitrary introduction of external criteria for the correct assessment of the quality of players. The present work provides a novel evidence of the utility of tools and methods of network theory in real applications.Comment: 10 pages, 4 figures, 4 table

Experimental and kinetic study on ignition delay times of methane/hydrogen/oxygen/nitrogen mixtures by shock tube

This study aims (1) to analyze the performances among regencies/ cities in Jambi Province, and (2) to categorize the regencies/ cities in Jambi Province based on economic, human resources, and infrastructure development performances. Datas used in this study are secondary data of 2009-2012 from Statistics Indonesia, consists of eight component indicators to assess the performance of economic development, the five component indicators to assess the performance of the components of human resources development, and eight component indicators to assess the performance of infrastructure development. The analytical method used to achieve the objectives of the first research purposes is principal component analysis (PCA) which followed by factor analysis and to achieve the third purpose is cluster analysis. The results showed that (1) Jambi City is ranked first in the overall development performance, followed by of Tanjab Barat and Batang Hari Regencies, (2) four clusters of regencies/ cities in Jambi Province are formed based on the performance of development, namely: cluster I (Kerinci, Merangin, and Tebo Regencies) have lower performance of regional development, cluster II (Tanjab Timur Regency) has average to high performance of regional development, cluster III (Sarolangun, Batang Hari, Muaro Jambi, Tanjab Barat, Bungo Regencies, and Sungai Penuh City) have average performance of regional development, and cluster IV (Jambi City) has high performance of regional development