1,768 research outputs found
Automated design analysis, assembly planning and motion study analysis using immersive virtual reality
Previous research work at Heriot-Watt University using immersive virtual reality (VR) for cable harness design showed that VR provided substantial productivity gains over traditional computer-aided design (CAD) systems. This follow-on work was aimed at understanding the degree to which aspects of this technology were contributed to these benefits and to determine if engineering design and planning processes could be analysed in detail by nonintrusively monitoring and logging engineering tasks. This involved using a CAD-equivalent VR system for cable harness routing design, harness assembly and installation planning that can be functionally evaluated using a set of creative design-tasks to measure the system and users' performance. A novel design task categorisation scheme was created and formalised which broke down the cable harness design process and associated activities. The system was also used to demonstrate the automatic generation of usable bulkhead connector, cable harness assembly and cable harness installation plans from non-intrusive user logging. Finally, the data generated from the user-logging allowed the automated activity categorisation of the user actions, automated generation of process flow diagrams and chronocyclegraphs
Access to liquidity and corporate investment in Europe during the financial crisis
We use a unique data set to show how firms in Europe used credit lines during the financial crisis. We find that firms with restricted access to credit (small, private, non-investment-grade, and unprofitable) draw more funds from their credit lines during the crisis than their large, public, investment-grade, profitable counterparts. Interest spreads increased (especially in "market-based economies"), but commitment fees remained unchanged. Our findings suggest that credit lines did not dry up during the crisis and provided the liquidity that firms used to cope with this exceptional contraction. In particular, credit lines provided the liquidity companies needed to invest during the crisis
Computing optimal strategies for a cooperative hat game
We consider a `hat problem' in which each player has a randomly placed stack
of black and white hats on their heads, visible to the other player, but not
the wearer. Each player must guess a hat position on their head with the goal
of both players guessing a white hat. We address the question of finding the
optimal strategy, i.e., the one with the highest probability of winning, for
this game. We provide an overview of prior work on this question, and describe
several strategies that give the best known lower bound on the probability of
winning. Upper bounds are also considered here
Electronic damping of molecular motion at metal surfaces
A method for the calculation of the damping rate due to electron-hole pair
excitation for atomic and molecular motion at metal surfaces is presented. The
theoretical basis is provided by Time Dependent Density Functional Theory
(TDDFT) in the quasi-static limit and calculations are performed within a
standard plane-wave, pseudopotential framework. The artificial periodicity
introduced by using a super-cell geometry is removed to derive results for the
motion of an isolated atom or molecule, rather than for the coherent motion of
an ordered over-layer. The algorithm is implemented in parallel, distributed
across both and space, and in a form compatible with the
CASTEP code. Test results for the damping of the motion of hydrogen atoms above
the Cu(111) surface are presented.Comment: 10 pages, 3 figure
A Comparison of Exergaming Interfaces for Use in Rehabilitation Programs and Research
Exergames or active video games are video games with interfaces that require active involvement and the exertion of physical force by participants. These exergames are designed to track body motion and provide both fun and exercise for game players. Numerous video game console companies have designed exergaming interfaces that are becoming very popular. This paper examines the nature of the interfaces and explores the possibility of using these interfaces for rehabilitation programs and research. While many systems exist, this paper will focus on three major players: Sony PlayStation Move, Nintendo Wii, and Microsoft Xbox 360 Kinect. Comparisons include the technical specifications, the motion sensed by each interface, and the motion required in each therapeutic activity type. Discussion addresses the research implications of using these tools
Dielectronic Recombination in Li+ Ions
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Dielectronic Recombination in Li+ Ions
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Approximate Deadline-Scheduling with Precedence Constraints
We consider the classic problem of scheduling a set of n jobs
non-preemptively on a single machine. Each job j has non-negative processing
time, weight, and deadline, and a feasible schedule needs to be consistent with
chain-like precedence constraints. The goal is to compute a feasible schedule
that minimizes the sum of penalties of late jobs. Lenstra and Rinnoy Kan
[Annals of Disc. Math., 1977] in their seminal work introduced this problem and
showed that it is strongly NP-hard, even when all processing times and weights
are 1. We study the approximability of the problem and our main result is an
O(log k)-approximation algorithm for instances with k distinct job deadlines
The Asymptotic distribution of circles in the orbits of Kleinian groups
Let P be a locally finite circle packing in the plane invariant under a
non-elementary Kleinian group Gamma and with finitely many Gamma-orbits. When
Gamma is geometrically finite, we construct an explicit Borel measure on the
plane which describes the asymptotic distribution of small circles in P,
assuming that either the critical exponent of Gamma is strictly bigger than 1
or P does not contain an infinite bouquet of tangent circles glued at a
parabolic fixed point of Gamma. Our construction also works for P invariant
under a geometrically infinite group Gamma, provided Gamma admits a finite
Bowen-Margulis-Sullivan measure and the Gamma-skinning size of P is finite.
Some concrete circle packings to which our result applies include Apollonian
circle packings, Sierpinski curves,
Schottky dances, etc.Comment: 31 pages, 8 figures. Final version. To appear in Inventiones Mat
- âŠ