Complete characterization of ultrashort pulse sources at 1550 nm

This paper reviews the use of frequency-resolved optical gating (FROG) to characterize mode-locked lasers producing ultrashort pulses suitable for high-capacity optical communications systems at wavelengths around 1550 nm, Second harmonic generation (SHG) FROG is used to characterize pulses from a passively mode-locked erbium-doped fiber laser, and both single-mode and dual-mode gain-switched semiconductor lasers. The compression of gain-switched pulses in dispersion compensating fiber is also studied using SHG-FROG, allowing optimal compression conditions to be determined without a priori assumptions about pulse characteristics. We also describe a fiber-based FROG geometry exploiting cross-phase modulation and show that it is ideally suited to pulse characterization at optical communications wavelengths. This technique has been used to characterize picosecond pulses with energy as low as 24 pJ, giving results in excellent agreement with SHG-FROG characterization, and without any temporal ambiguity in the retrieved puls

Gearing

Gearing technology in its modern form has a history of only 100 years. However, the earliest form of gearing can probably be traced back to fourth century B.C. Greece. Current gear practice and recent advances in the technology are drawn together. The history of gearing is reviewed briefly in the Introduction. Subsequent sections describe types of gearing and their geometry, processing, and manufacture. Both conventional and more recent methods of determining gear stress and deflections are considered. The subjects of life prediction and lubrication are additions to the literature. New and more complete methods of power loss predictions as well as an optimum design of spur gear meshes are described. Conventional and new types of power transmission systems are presented

The Sunrise Mission

The first science flight of the balloon-borne \Sunrise telescope took place in June 2009 from ESRANGE (near Kiruna/Sweden) to Somerset Island in northern Canada. We describe the scientific aims and mission concept of the project and give an overview and a description of the various hardware components: the 1-m main telescope with its postfocus science instruments (the UV filter imager SuFI and the imaging vector magnetograph IMaX) and support instruments (image stabilizing and light distribution system ISLiD and correlating wavefront sensor CWS), the optomechanical support structure and the instrument mounting concept, the gondola structure and the power, pointing, and telemetry systems, and the general electronics architecture. We also explain the optimization of the structural and thermal design of the complete payload. The preparations for the science flight are described, including AIV and ground calibration of the instruments. The course of events during the science flight is outlined, up to the recovery activities. Finally, the in-flight performance of the instrumentation is briefly summarized.Comment: 35 pages, 17 figure

The train has left the station: Do markets value intra-city access to inter-city rail connections?

This paper analyzes the impact of access to inter-city rail connections on property prices using hedonic, difference-in-difference and time-difference estimation strategies. We investigate the reorganization of the rail system in post-unification Berlin, Germany, which provides much variation in accessibility. Evidence does not support the existence of localized effects. Neither in proximity to stations nor at city-level are there significant price adjustments. No significant price effect is revealed on distance to stations, even when allowing for a complementary relationship. An increase in the attractiveness of central locations coinciding with the final announcement of the train schedule is not attributable to the intervention.Property prices; transport innovation; inter-city connection; railroad; Berlin

The Legacy of the Tevatron in the Area of Accelerator Science

For more than 25 years the Tevatron was the highest energy accelerator in the world, providing the first access to particle collisions beyond 1 TeV and achieving an ultimate performance a factor of four hundred beyond the original design goals. This article reviews the many formidable challenges that were overcome, and the knowledge gained, in building, operating, and improving the Tevatron over its lifetime. These challenges included: the first operations of an accelerator based on superconducting magnets, production of antiprotons in sufficient numbers to support a useable luminosity, management of beam-beam, intrabeam, and other collective effects, novel manipulations of the beam longitudinal phase space, and development and application of a wide variety of innovative technologies. These achievements established the legacy of the Tevatron as the progenitor of all subsequently constructed high energy hadron colliders.Comment: Submitted to Annual Reviews of Nuclear and Particle Scienc

Meta-heuristic algorithms in car engine design: a literature survey

Meta-heuristic algorithms are often inspired by natural phenomena, including the evolution of species in Darwinian natural selection theory, ant behaviors in biology, flock behaviors of some birds, and annealing in metallurgy. Due to their great potential in solving difficult optimization problems, meta-heuristic algorithms have found their way into automobile engine design. There are different optimization problems arising in different areas of car engine management including calibration, control system, fault diagnosis, and modeling. In this paper we review the state-of-the-art applications of different meta-heuristic algorithms in engine management systems. The review covers a wide range of research, including the application of meta-heuristic algorithms in engine calibration, optimizing engine control systems, engine fault diagnosis, and optimizing different parts of engines and modeling. The meta-heuristic algorithms reviewed in this paper include evolutionary algorithms, evolution strategy, evolutionary programming, genetic programming, differential evolution, estimation of distribution algorithm, ant colony optimization, particle swarm optimization, memetic algorithms, and artificial immune system

From Periphery to Core: Economic Adjustments to High Speed Rail

This paper presents evidence that high speed rail systems, by bringing economic agents closer together, sustainably promote economic activity within regions that enjoy an increase in accessibility. Our results on the one hand confirm expectations that have led to huge public investments into high speed rail all over the world. On the other hand, they confirm theoretical predictions arising from a consolidate body of (New) Economic Geography literature taking a positive, man-made and reproducible shock as a case in point. We argue that the economic geography framework can help to derive ex-ante predictions on the economic impact of transport projects. The subject case is the German high speed rail track connecting Cologne and Frankfurt, which, as we argue, provides exogenous variation in access to regions due to the construction of intermediate stations in the towns of Limburg and Montabaur.NEG; high speed rail; transport policy; market access; acces-sibility

Changing nature and sustainability of the industrial district model : the case of Technic Valley in France

This paper examines the impact of contemporary pressures on industrial districts and analyses the changes that are taking place in an industrial district confronted with disembedding and globalization. We discuss the following questions: what are the processes and consequences of disembedding for the changing shape and form of inter-firm trust, contract and network forms? Is there an evolution in subcontracting and trade interdependency? What is the role of institutional infrastructures? We performed a longitudinal qualitative study using a number of different data sources to analyse the evolution of one French industrial district, particularly how new pressures of internationalization and disembedding work to reconfigure inter-firm relations in this district. While the recent literature is dominated by notions about industrial districts that concern only the trend towards increased competition or disembeddedness, this article shows that there is no unilinear trend. In contrast with the findings of certain recent studies, we argue that economic logic does not fully account for recent developments since the adjustment that are being made by the district are characterized rather by re-embeddedness, increased cooperation and institutionalization.industrial district, globalization, economic sociology