15670
Display of vector fields using a reaction-diffusion model
Effective visualization of vector fields relies on the ability to control the size and density of the underlying mapping to visual cues used to represent the field. In this paper we introduce the use of a reaction-diffusion model, already well known for its ability to form irregular spatio-temporal patters, to control the size, density, and placement of the vector field representation. We demonstrate that it is possible to encode vector field information (orientation and magnitude) into the parameters governing a reaction-diffusion model to form a spot pattern with the correct orientation, size, and density, creating an effective visualization. To encode direction we texture the spots using a light to dark fading texture. We also show that it is possible to use the reaction-diffusion model to visualize an additional scalar value, such as the uncertainty in the orientation of the vector field. An additional benefit of the reaction-diffusion visualization technique arises from its automatic density distribution. This benefit suggests using the technique to augment other vector visualization techniques. We demonstrate this utility by augmenting a LIC visualization with a reaction-diffusion visualization. Finally, the reaction-diffusion visualization method provides a technique that can be used for streamline and glyph placement.
21779382
Computational Engineering and Science Program at the University of Utah
We describe a new graduate program at the Univesity of Utah that we consider a first step towards the modernization of the University's curriculum in what we call "Computational Engineering and Science" (CES). Our goal is to provide a mechanism by which a graduate student can obtain integrated expertise and skills in all areas that are required for the solution of a particular computational problem.
17446260
Genetic Programming with Fitness Based on Model Checking
Model checking is a way of analysing programs and program-like structures to decide whether they satisfy a list of temporal logic statements describing desired behaviour. In this paper we apply this to the fitness checking stage in an evolution strategy for learning finite state machines. We give experimental results consisting of learning the control program for a vending machine.
31047077
Deriving Genetic Programming Fitness Properties by Static Analysis
The aim of this paper is to introduce the idea of using static analysis of computer programs as a way of measuring fitness in genetic programming. Such techniques extract information about the programs without explicitly running them, and in particular they infer properties which hold across the whole of the input space of a program. This can be applied to measure fitness, and has a number of advantages over measuring fitness by running members of the population on test cases. The most important advantage is that if a solution is found then it is possible to formally trust that solution to be correct across all inputs. This paper introduces these ideas, discusses various ways in which they could be applied, discusses the type of problems for which they are appropriate, and ends by giving a simple test example and some questions for future research.
59685614
Supporting Error-Driven Design
This paper argues that two limitations restrict the utility of interface specification languages. Firstly, they provide no means of capturing the cognitive conditions that lead to operator ‘error’. This makes it difficult to distinguish between the normal behaviour of an expert and the mistakes that often lead to problems for novices. The second weakness is that interface notations cannot easily be used to represent and reason about asynchronous failures. This prevents designers from identifying solutions to failures that could occur at many different points during interaction. These are significant limitations because they reflect a pre-occupation with normative behaviour. Unless we have some means of analysing system failure and operator error then we will continue to have interfaces that are designed to support perfect users in perfect environments.
18085576
Semantic errors - diagnosis and repair
In compiler technology, semantic error handling has too often used ad hoc techniques and terse messages of fixed content. In contrast, we present general models of diagnosis and repair of semantic errors and illustrate their use in the York Ada Workbench Compiler. The diagnostic model focuses upon the problem of selecting suitable information from which the programmer can locate and correct an error; following a brief discussion of an approach in which <underline>filters</underline> are applied to reports, and we give a more extensive account of a new approach using an <underline>interactive diagnostic interpreter</underline>. The repair model is based upon the idea of <underline>plastic</underline> nodes which are introduced into the compiler's internal representation of a program to replace <underline>normal</underline> nodes which are missing or erroneous.
37787829
The epistemics of accidents
Human intervention has played a critical role in the causes of many major accidents. At Three Mile Island, the operators isolated a reactor from its heat sink. The pilots of the Boeing 737 at Kegworth managed to shut down their one functioning engine. Staff continued to allow trains to deposit passengers in Kings? Cross after the fire had started. In retrospect, it seems impossible to predict all of the ways that human intervention might threaten safety. It is, therefore, important that we learn as much as possible from those accidents that do occur. This task is complicated because conventional accident reports contain many hundreds of pages of prose. They present findings drawn from many different disciplines: metallurgy; systems engineering; human factors; meterology. These findings are, typically, separated into a number of distinct chapters. Each section focuses upon a different aspect of the accident. This makes it difficult for designers to recognize the ways in which operator intervention and system failure combine during major failures. The following pages use formal methods to address these concerns. It is argued that mathematical specification techniques can represent human factors and system failures. Unfortunately, formal methods have not previously been used to analyse the factors that motivate operator intervention. This paper, therefore, argues that epistemic extensions of mathematical notations must be recruited in order to support the formal analysis of major accidents.