Operating penalties in single-fiber operation 10-Gb/s, 1024-way split, 110-km long-reach optical access networks

We report for the first time optical signal-to-noise penalties which lead to performance degradations in single-fiber long-reach optical access networks when compared to identical dual-fiber systems. A simplified architecture, with reduced optical amplifier count compared to previous work, for single-fiber operation of a symmetrical 10-Gb/s, 1024-way split, 110-km long-reach optical access network is presented and demonstrated. In addition, a possible solution to remove the optical signal-to-noise penalty is suggested

Architecture to integrate multiple PONs with long reach DWDM backhaul

This paper demonstrates the feasibility of an architecture that consolidates a number of deployed Passive Optical Network (PON) infrastructures into a long-reach, high-split ratio system which further increases equipment sharing between users. The demonstrated system allows the use of uncooled lasers with possible wavelength drift across a CWDM band (20 nm) with optical amplification and narrow optical filtering with no performance degradation. A complete study of potential implementations was performed with experimental results showing that a target performance of 10-10 could be achieved over 120 km of standard fiber with transmitter wavelengths from 1542 to 1558 nm and DWDM backhaul wavelengths from 1520 to 1535 nm. This gives the potential to support up to 2560 users

Mobile phone games: understanding the user experience

Mobile gaming is viewed by the mobile communication industry as one of the ‘killer applications’ for future mobile services. Fuelled by the success of games such as Nokia’s Snake and the continuing popularity of online and console gaming, the drive is to develop ever more sophisticated and engaging gaming experiences for mobile users. However the current mobile gaming experience in terms of graphics, interaction mode and content more closely resembles that presented by personal computer games of 20 years ago than anything evoked by today’s console based offerings. Despite such limitations the appeal of mobile games continues to grow. Market research conducted by Nokia estimates that 85% of people with the game ‘Space Impact’ on their phones have tried it out and 45% play it everyday (Robens, 2001). Mobile gaming research has predominantly focused on the “mobility of gaming” (Kuivakari 2001). Such research seeks to exploit the entertainment potential of ubiquitous technologies and augmented reality, making both the proximity of others and the mobile environment itself part of the gaming experience. (See for example Bjork et al (2001), Brunnberg (2002). The research reported here aims to provide insight into what motivates people to play existing mobile phone games, despite their limitations, and seeks to identify elements of the current mobile gaming experience that should be preserved within future games. The continuing convergence of computer, consumer and communications technologies within mobile devices is raising many unknowns about how users will perceive these devices and therefore how best to design appropriate form structures and user interfaces (Sacher and Loudon 2002). This research examines the existing convergence of game playing and telephony within the mobile phone and provides early indications of how people may approach future converged devices

Mobile phone games: understanding the user experience

Mobile gaming is viewed by the mobile communication industry as one of the ‘killer applications’ for future mobile services. Fuelled by the success of games such as Nokia’s Snake and the continuing popularity of online and console gaming, the drive is to develop ever more sophisticated and engaging gaming experiences for mobile users. However the current mobile gaming experience in terms of graphics, interaction mode and content more closely resembles that presented by personal computer games of 20 years ago than anything evoked by today’s console based offerings. Despite such limitations the appeal of mobile games continues to grow. Market research conducted by Nokia estimates that 85% of people with the game ‘Space Impact’ on their phones have tried it out and 45% play it everyday (Robens, 2001). Mobile gaming research has predominantly focused on the “mobility of gaming” (Kuivakari 2001). Such research seeks to exploit the entertainment potential of ubiquitous technologies and augmented reality, making both the proximity of others and the mobile environment itself part of the gaming experience. (See for example Bjork et al (2001), Brunnberg (2002). The research reported here aims to provide insight into what motivates people to play existing mobile phone games, despite their limitations, and seeks to identify elements of the current mobile gaming experience that should be preserved within future games. The continuing convergence of computer, consumer and communications technologies within mobile devices is raising many unknowns about how users will perceive these devices and therefore how best to design appropriate form structures and user interfaces (Sacher and Loudon 2002). This research examines the existing convergence of game playing and telephony within the mobile phone and provides early indications of how people may approach future converged devices

Continuous-wave and passively Q -switched cladding-pumped planar waveguide lasers

Greater than 12W of average output power has been generated from a diode-pumped YbYAG cladding-pumped planar waveguide laser. The laser radiation developed is linearly polarized and diffraction limited in the guiding dimension. A slope efficiency of 0.5WW with a peak optical optical conversion efficiency of 0.31WW is achieved. In a related structure, greater than 8W of Q -switched average output power has been generated from a NdYAG cladding-pumped planar waveguide laser by incorporation of a Cr 4+ YAG passive Q switch monolithically into the waveguide structure. Pulse widths of 3ns and pulse-repetition frequencies as high as 80kHz have been demonstrated. A slope efficiency of 0.28WW with a peak optical optical conversion efficiency of 0.21WW is achieved

The effect of gas accretion on the radial gas metallicity profile of simulated galaxies

We study the effect of the gas accretion rate (M˙ accr) on the radial gas metallicity profile (RMP) of galaxies using the EAGLE cosmological hydrodynamic simulations, focusing on central galaxies of stellar mass M 109 M at z ≤ 1. We find clear relations between M˙ accr and the slope of the RMP (measured within an effective radius), where higher M˙ accr are associated with more negative slopes. The slope of the RMPs depends more strongly on M˙ accr than on stellar mass, star formation rate (SFR), or gas fraction, suggesting M˙ accr to be a more fundamental driver of the RMP slope of galaxies. We find that eliminating the dependence on stellar mass is essential for pinning down the properties that shape the slope of the RMP. Although M˙ accr is the main property modulating the slope of the RMP, we find that it causes other correlations that are more easily testable observationally: At fixed stellar mass, galaxies with more negative RMP slopes tend to have higher gas fractions and SFRs, while galaxies with lower gas fractions and SFRs tend to have flatter metallicity profiles within an effective radius.Fil: Collacchioni, Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Lagos, Claudia D.P.. University of Western Australia; Australia. Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions; Australia. Universidad de Copenhagen; DinamarcaFil: Mitchell, Peter D.. Leiden University; Países Bajos. Université Claude Bernard Lyon 1; FranciaFil: Schaye, Joop. Leiden University; Países BajosFil: Wisnioski, Emily. Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions; Australia. Australian National University. Research School of Astronomy and Astrophysics; AustraliaFil: Cora, Sofia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Correa, Camila A.. Leiden University; Países Bajo

Worst case and probabilistic analysis of the 2-Opt algorithm for the TSP

2-Opt is probably the most basic local search heuristic for the TSP. This heuristic achieves amazingly good results on “real world” Euclidean instances both with respect to running time and approximation ratio. There are numerous experimental studies on the performance of 2-Opt. However, the theoretical knowledge about this heuristic is still very limited. Not even its worst case running time on 2-dimensional Euclidean instances was known so far. We clarify this issue by presenting, for every p∈N , a family of L p instances on which 2-Opt can take an exponential number of steps. Previous probabilistic analyses were restricted to instances in which n points are placed uniformly at random in the unit square [0,1]2, where it was shown that the expected number of steps is bounded by O~(n10) for Euclidean instances. We consider a more advanced model of probabilistic instances in which the points can be placed independently according to general distributions on [0,1] d , for an arbitrary d≥2. In particular, we allow different distributions for different points. We study the expected number of local improvements in terms of the number n of points and the maximal density ϕ of the probability distributions. We show an upper bound on the expected length of any 2-Opt improvement path of O~(n4+1/3⋅ϕ8/3) . When starting with an initial tour computed by an insertion heuristic, the upper bound on the expected number of steps improves even to O~(n4+1/3−1/d⋅ϕ8/3) . If the distances are measured according to the Manhattan metric, then the expected number of steps is bounded by O~(n4−1/d⋅ϕ) . In addition, we prove an upper bound of O(ϕ√d) on the expected approximation factor with respect to all L p metrics. Let us remark that our probabilistic analysis covers as special cases the uniform input model with ϕ=1 and a smoothed analysis with Gaussian perturbations of standard deviation σ with ϕ∼1/σ d

CW and passively Q-switched double-clad planar waveguide lasers

Greater than 12 W of average output power have been generated from a diode pumped Yb:YAG cladding-pumped planar waveguide laser. The developed laser radiation is linearly polarized and diffraction limited in the guiding dimension. A slope efficiency of 0.5 W/W with a peak optical-optical conversion efficiency of 0.31 W/W is achieved. In a related structure, greater than 8 W of Q-switched average output power has been generated from a Nd:YAG cladding-pumped planar waveguide incorporating Cr:YAG passive Q-switch monolithically into the waveguide structure. Pulse widths of 3 nsec and PRFs as high as 80 kHz have been demonstrated. A slope efficiency of 0.28 W/W with a peak optical-optical conversion efficiency of 0.21 W/W is achieved

Young people, crime and school exclusion: a case of some surprises

During the 1990s the number of young people being permanently excluded from schools in England and Wales increased dramatically from 2,910 (1990/91) to a peak of 12,700 (1996/97). Coinciding with this rise was a resurgence of the debate centring on lawless and delinquent youth. With the publication of Young People and Crime (Graham and Bowling 1995) and Misspent Youth (Audit Commission 1996) the 'common sense assumption' that exclusion from school inexorably promoted crime received wide support, with the school excludee portrayed as another latter day 'folk devil'. This article explores the link between school exclusion and juvenile crime, and offers some key findings from a research study undertaken with 56 young people who had experience of being excluded from school. Self-report interview questions reveal that whilst 40 of the young people had offended, 90% (36) reported that the onset of their offending commenced prior to their first exclusion. Moreover, 50 (89.2% of the total number of young people in the sample), stated that they were no more likely to offend subsequent to being excluded and 31 (55.4%) stated that they were less likely to offend during their exclusion period. Often, this was because on being excluded, they were 'grounded' by their parents