We report recent results on the performance of FLASH (Free Electron Laser in Hamburg) operating at a wavelength of 13.7 nm where unprecedented peak and average powers for a coherent EUV radiation source have been measured. In the saturation regime the peak energy approached 170 µJ for individual pulses while the average energy per pulse reached 70 µJ. The pulse duration was in the region of 10 femtoseconds and peak
The empirical relation between density and velocity of pedestrian movement is not completely analyzed, particularly with regard to the 'microscopic' causes which determine the relation at medium and high densities. The simplest system for the investigation of this dependency is the normal movement of pedestrians along a line (single-file movement). This article presents experimental results for this system under laboratory conditions and discusses the following observations: The data show a linear relation between the velocity and the inverse of the density, which can be regarded as the required length of one pedestrian to move. Furthermore we compare the results for the single-file movement with literature data for the movement in a plane. This comparison shows an unexpected conformance between the fundamental diagrams, indicating that lateral interference has negligible influence on the velocity-density relation at the density domain 1 m −2 < ρ < 5 m −2 . In addition we test a procedure for automatic recording of pedestrian flow characteristics. We present preliminary results on measurement range and accuracy of this method.
Capacity estimation is an important tool for the design and dimensioning of pedestrian facilities. The literature contains different procedures and specifications which show considerable differences with respect to the estimated flow values. Moreover do new experimental data indicate a stepwise growing of the capacity with the width and thus challenge the validity of the specific flow concept. To resolve these differences we have studied experimentally the unidirectional pedestrian flow through bottlenecks under laboratory conditions. The time development of quantities like individual velocities, density and individual time gaps in bottlenecks of different width is presented. The data show a linear growth of the flow with the width. The comparison of the results with experimental data of other authors indicates that the basic assumption of the capacity estimation for bottlenecks has to be revised. In contradiction with most planning guidelines our main result is, that a jam occurs even if the incoming flow does not overstep the capacity defined by the maximum of the flow according to the fundamental diagram.
The progress of image processing during recent years allows the measurement of pedestrian characteristics on a "microscopic" scale with low costs. However, density and flow are concepts of fluid mechanics defined for the limit of infinitely many particles. Standard methods of measuring these quantities locally (e.g. counting heads within a rectangle) suffer from large data scatter. The remedy of averaging over large spaces or long times reduces the possible resolution and inhibits the gain obtained by the new technologies.In this contribution we introduce a concept for measuring microscopic characteristics on the basis of pedestrian trajectories. Assigning a personal space to every pedestrian via a Voronoi diagram reduces the density scatter. Similarly, calculating direction and speed from position differences between times with identical phases of movement gives low-scatter sequences for speed and direction. Closing we discuss the methods to obtain reliable values for derived quantities and new possibilities of in depth analysis of experiments. The resolution obtained indicates the limits of stationary state theory.
Introducti onIn the reactive model [Pnu85) of classical concurrency theory, a process reacts to stimuli presented by its environment. A mechanistic view of the reactive model has been given by Milner [Mil80) in terms of button pushing ezperiments. The environment or observer experiments on a process by attempting to depress one of several buttons that the process possesses as its interface to the outside world. The experiment succeeds if the button is unlocked and therefore goes down; otherwise the experiment fails. In response to a successful experiment, the process makes an internal state transition and is then ready for further experimentation.The reactive model has been adopted by Larsen and Skou [LS89) for probabilistic processes: a buttonpressing experiment succeeds, with probability 1, or else fails. If successful, the process makes an internal state transition according to a probability distribution associated with the depressed button.In the probabilistic case, it is interesting to consider a more "probabilistic" form of experimentation we call the generative model. In this setting, an observer may attempt to depress more than one button at a time.•Research supported by NSF Grant CCR-8704309.
ed.a c. ukNow the process is more or less on equal footing with its environment, and will decide, according to a prescribed probability distribution, which button if any will go down. In :response to a successful outcome, this same probability distribution, conditioned by the process's choice of button, will govern the internal state transition made by the process. Figure 1. For P, an a-or b-experiment will succeed with probability 1, whereas a c-expe:riment will fail. In the case of an aexperiment, P will branch left with probability t and right with probability i· Note that no information is given about the relative probability of performing an a-action versus a b-action in P's initial state.For the generative process Q, if the observer simultaneously attempts to depress the a and b buttons, Q will unlock its a-button with probability i and its b-button with probability l-In the former case, Q will branch left with probability t and right with probability ~,
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