Fleet management in free-floating bike sharing systems using predictive modelling and explorative tools

For redistribution and operating bikes in a free-floating systems, two measures are of highest priority. First, the information about the expected number of rentals on a day is an important measure for service providers for management and service of their fleet. The estimation of the expected number of bookings is carried out with a simple model and a more complex model based on meterological information, as the number of loans depends strongly on the current and forecasted weather. Secondly, the knowledge of a service level violation in future on a fine spatial resolution is important for redistribution of bikes. With this information, the service provider can set reward zones where service level violations will occur in the near future. To forecast a service level violation on a fine geographical resolution the current distribution of bikes as well as the time and space information of past rentals has to be taken into account. A Markov Chain Model is formulated to integrate this information. We develop a management tool that describes in an explorative way important information about past, present and predicted future counts on rentals in time and space. It integrates all estimation procedures. The management tool is running in the browser and continuously updates the information and predictions since the bike distribution over the observed area is in continous flow as well as new data are generated continuously

Reputation in multi agent systems and the incentives to provide feedback

The emergence of the Internet leads to a vast increase in the number of interactions between parties that are completely alien to each other. In general, such transactions are likely to be subject to fraud and cheating. If such systems use computerized rational agents to negotiate and execute transactions, mechanisms that lead to favorable outcomes for all parties instead of giving rise to defective behavior are necessary to make the system work: trust and reputation mechanisms. This paper examines different incentive mechanisms helping these trust and reputation mechanisms in eliciting users to report own experiences honestly. --Trust,Reputation

Burying the palaces? Ideologies in the Shaft Grave period

The ‘Shaft Grave Phenomenon’ is often seen as a straightforward development caused by increased access to precious (‘prestige’) items. It shall be argued here that it rather mirrors a gradual transformation of the self-identity of the mainland élites. The Shaft Grave chiefs strongly took over symbols from Crete, where the palatial élite had a strong religious connotation. This points to the conclusion that the mainland élite tried to establish a more sophisticated system of religious control, unlike the individual and personal cult visible in the MH burials. They realized the potential institutionalized religious authority had as a means of domination, connected with complex and standardised systems of representation, centralization and administration of cult, and tried to introduce this idea to the mainland. However, the symbols had to be modified and translated into a language mainland people would understand, and placed in contexts traditionally used as arenas of social display. These contexts were different from the ones the symbols originally were associated with, since on the MH mainland the grave (as opposed to the Minoan palace) was the place where transcendental ideas were articulated through material actions and expressions

Modélisation du prétraitement des textes

Dans cet article, nous définissons un modèle pour l'étape de prétraitement des textes dans le cadre de la fouille de textes et plus généralement de l'extraction d'informations à partir de textes. Cet article ne contient pas les détails de l'implémentation. L'objectif est d'obtenir un modèle générique de normalisation des textes bruts. La motivation de cet article est de généraliser les travaux assez confidentiels et spécialisés qui existent pour cette étape de prétraitement. Cette étape est pourtant incontournable et d'elle dépend grandement la qualité des analyses obtenues à toutes les étapes ultérieures

Non-collinear interaction of photons with orbital angular momentum

We elucidate the consequences of a phase-matching theory that describes second-harmonic generation of two non-collinear incident light beams that carry orbital angular momentum (OAM). More specifically, the two incident beams generate a third that, depending on the incident OAM, may experience a significantly smaller conversion efficiency in comparison to that based on the conventional phase-matching theory. This is the case even for incident angles substantially less than those required for non-conservation of OAM in the nonlinear interaction. Experiments are performed under different conditions and are in excellent agreement with the theory. Our results have implications beyond the specific case studied here of second-harmonic generation, in particular for parametric down-conversion of photons.Comment: 6 pages, 4 figure

Cracking the Network Code: Four Principles for Grantmakers

As grantmakers and nonprofits are looking for ways to collaborate more effectively, many are experimenting working with and through networks to achieve greater impact. Because networks are by definition loosely controlled and emergent, understanding how to effectively support them feels like a mystery to many grantmakers.GEO's newest publication sets out to crack the code behind the network mystique. In fact, there is a method to working more efficiently and effectively through networks, and a critical first step for grantmakers is adopting a network mindset, which may require dramatic shifts in attitude and behavior for some. "Cracking the Network Code" outlines four principles that comprise the network mindset, illustrates the principles with a range of examples of networks that have achieved real results, and offers practical questions and recommendations to help grantmakers achieve the benefits and avoid common pitfalls of working through networks

Flow-time estimation in dynamic job shops with priority scheduling using a hybrid modelling approach

A new approach for due date assignment in dynamic job shops with priority scheduling is presented. The future temporal development of the production system, eventually determining the flow-time of a job, is governed by both the processing of the jobs already present in the system as well as the processing of future arriving jobs. We combine a simulation-like approach for the already known jobs with a stochastic model describing the influence of future arriving jobs. The resulting model is a hybrid system dynamics model that can be solved numerically, leading to estimates for the flow-time of all available jobs. In a simulation study, we compare the new approach with other popular methods known in literature. Our results indicate that the new method significantly outperforms all other studied methods in terms of accuracy of the estimates, in most cases by at least a factor of two. Furthermore, the effect of priority scheduling can be modelled correctly, yielding good estimates for jobs of different priorities

Coherent control of light interaction with graphene

We report the experimental observation of all-optical modulation of light in a graphene film. The graphene film is scanned across a standing wave formed by two counter-propagating laser beams in a Sagnac interferometer. Through a coherent absorption process the on-axis transmission is modulated with close to 80% efficiency. Furthermore we observe modulation of the scattered energy by mapping the off-axis scattered optical signal: scattering is minimized at a node of the standing wave pattern and maximized at an antinode. The results highlight the possibility to switch and modulate any given optical interaction with deeply sub-wavelength films.Comment: 4 pages, 4 figure

Process performance analysis and layout optimization for a medium-sized manufacturing enterprise

For estimating the potential for process improvement for a medium-sized mechanical manufacturing enterprise, a study was performed. The goal was to identify potential for throughput time reduction and for improvement of the material handling by layout optimization of the factory. The study is based on statistical data analysis of historical order processing data.From these data, the flow of the orders through the production system as well as dynamical properties of the order flow like, e.g., waiting times at the working stations, was derived. The results show that there is a large potential for reduction of throughput time. The ratio of waiting times to processing times is quite large compared with reference values from analytical queuing systems and benchmarks. Based on the quantitative data of the order flow, both a manual and a numerical layout optimization was performed. With both methods, a significant reduction of the total transport way compared with the actual situation could be achieved. However, the numerical approach was significantly better than the manual approach