The Resource constrained shortest path problem implemented in a lazy functional language

The resource constrained shortest path problem is an NP-hard problem for which many ingenious algorithms have been developed. These algorithms are usually implemented in FORTRAN or another imperative programming language. We have implemented some of the simpler algorithms in a lazy functional language. Benefits accrue in the software engineering of the implementations. Our implementations have been applied to a standard benchmark of data files, which is available from the Operational Research Library of Imperial College, London. The performance of the lazy functional implementations, even with the comparatively simple algorithms that we have used, is competitive with a reference FORTRAN implementation

Changing regional images; are regional marketing campaigns successful?

An important element in the urban and regional development strategy of many local and regional governments is geographical marketing. The process of geographical marketing combines promotional, spatial and organisational activities, and can be aimed at various groups. In 1989 a marketing campaign was started by the province of Groningen, in the northern part of the Netherlands. This campaign, which is still being carried on, has used various means of communication: advertisements in newspapers and magazines, and radio and television commercials. It has been aimed at entrepreneurs and at the general public as well. An ex ante study of the public image of Groningen was carried out before the start of the campaign. For this purpose a random sample of the Dutch population was inquired by telephone. Since then similar inquiries were carried out every two years, in order to measure the effects of the campaign. In these inquiries the image of the provinces of Friesland and Noord-Brabant was measured along with that of Groningen, and used for reference. The availability of this kind of data for a period of twelve years, measured at regular intervals, provides an opportunity to study the development of regional images through time. In this paper the data of the inquiries will be analysed. One of the main questions to be answered in the paper relates to the pace and the nature of the changes in image, observed in all three provinces. The second question specifically deals with the influence of the marketing campaign on the image of Groningen.

The mental map of Dutch entrepreneurs. Changes in the subjective rating of locations in the Netherlands, 1983-1993-2003

Empirical studies on firm location and migration show that actual location decisions are often based on incomplete and inaccurate information about potential locations. Decision makers seem to be guided by their subjective interpretation of reality, not so much by reality itself. Twenty years ago this fundamental idea was the starting point for a research program of the Faculty of Spatial Sciences of the University of Groningen that focussed on the subjective rating of locations by Dutch entrepreneurs. The first picture of this subjective valuation, based on an extensive postal enquiry, was taken in 1983 (Pellenbarg 1985) and repeated by an identical project in 1993 (Meester 1999). A third enquiry, again identical to the first and second, was held in 2003. On the basis of the three projects a true comparison can now be made of the mental maps of Dutch entrepreneurs in the years 1983, 1993, and 2003. This paper describes and analyses the three mental maps. Moreover, the data are used in a factor analysis, to try to establish the basic influences that form the entrepreneurial mental maps. It shows that the basic shape of the mental maps (a dome with centrally located Utrecht as a summit) did not change much in twenty years. A closer look however, reveals that the dome is flattening. In the first period (1983-1993) we witness a decrease of appreciation of the locations on its West flank (the ‘old’ Randstad) while in the second period (1993-2003) this decrease extends to the Eastern parts of the Randstad. The factor analysis suggests that three fundamental dimensions determine the entrepreneurs’ judgments: potency, activity, and evaluation. Potency may be understood as centrality of location. Activity is correlated to agglomeration. It is hypothesized that landscape and culture determine the evaluative dimension.

Energy-Efficient Streaming Using Non-volatile Memory

The disk and the DRAM in a typical mobile system consume a significant fraction (up to 30%) of the total system energy. To save on storage energy, the DRAM should be small and the disk should be spun down for long periods of time. We show that this can be achieved for predominantly streaming workloads by connecting the disk to the DRAM via a large non-volatile memory (NVM). We refer to this as the NVM-based architecture (NVMBA); the conventional architecture with only a DRAM and a disk is referred to as DRAMBA. The NVM in the NVMBA acts as a traffic reshaper from the disk to the DRAM. The total system costs are balanced, since the cost increase due to adding the NVM is compensated by the decrease in DRAM cost. We analyze the energy saving of NVMBA, with NAND flash memory serving as NVM, relative to DRAMBA with respect to (1) the streaming demand, (2) the disk form factor, (3) the best-effort provision, and (4) the stream location on the disk. We present a worst-case analysis of the reliability of the disk drive and the flash memory, and show that a small flash capacity is sufficient to operate the system over a year at negligible cost. Disk lifetime is superior to flash, so that is of no concern

Enabling Robots to Communicate their Objectives

The overarching goal of this work is to efficiently enable end-users to correctly anticipate a robot's behavior in novel situations. Since a robot's behavior is often a direct result of its underlying objective function, our insight is that end-users need to have an accurate mental model of this objective function in order to understand and predict what the robot will do. While people naturally develop such a mental model over time through observing the robot act, this familiarization process may be lengthy. Our approach reduces this time by having the robot model how people infer objectives from observed behavior, and then it selects those behaviors that are maximally informative. The problem of computing a posterior over objectives from observed behavior is known as Inverse Reinforcement Learning (IRL), and has been applied to robots learning human objectives. We consider the problem where the roles of human and robot are swapped. Our main contribution is to recognize that unlike robots, humans will not be exact in their IRL inference. We thus introduce two factors to define candidate approximate-inference models for human learning in this setting, and analyze them in a user study in the autonomous driving domain. We show that certain approximate-inference models lead to the robot generating example behaviors that better enable users to anticipate what it will do in novel situations. Our results also suggest, however, that additional research is needed in modeling how humans extrapolate from examples of robot behavior.Comment: RSS 201

Time-domain ptychography

Through dedicated measurements in the optical regime we demonstrate that ptychography can be applied to reconstruct complex-valued object functions that vary with time from a sequence of spectral measurements. A probe pulse of approximately 1 ps duration, time delayed in increments of 0.25 ps is shown to recover dynamics on a ten times faster time scale with an experimental limit of approximately 5 fs.Comment: 5 pages, 4 figures, new title and minor text change

How migrating 0.0001% of address space saves 12% of energy in hybrid storage

We present a simple, operating-\ud system independent method to reduce the num-\ud ber of seek operations and consequently reduce\ud the energy consumption of a hybrid storage\ud device consisting of a hard disk and a flash\ud memory. Trace-driven simulations show that\ud migrating a tiny amount of the address space\ud (0.0001%) from disk to flash already results\ud in a significant storage energy reduction (12%)\ud at virtually no extra cost. We show that the\ud amount of energy saving depends on which part\ud of the address space is migrated, and we present\ud two indicators for this, namely sequentiality and\ud request frequency. Our simulations show that\ud both are suitable as criterion for energy-saving\ud file placement methods in hybrid storage. We\ud address potential wear problems in the flash\ud subsystem by presenting a simple way to pro-\ud long its expected lifetime.\u

Architecture-based Qualitative Risk Analysis for Availability of IT Infrastructures

An IT risk assessment must deliver the best possible quality of results in a time-effective way. Organisations are used to customise the general-purpose standard risk assessment methods in a way that can satisfy their requirements. In this paper we present the QualTD Model and method, which is meant to be employed together with standard risk assessment methods for the qualitative assessment of availability risks of IT architectures, or parts of them. The QualTD Model is based on our previous quantitative model, but geared to industrial practice since it does not require quantitative data which is often too costly to acquire. We validate the model and method in a real-world case by performing a risk assessment on the authentication and authorisation system of a large multinational company and by evaluating the results w.r.t. the goals of the stakeholders of the system. We also perform a review of the most popular standard risk assessment methods and an analysis of which one can be actually integrated with our QualTD Model