2018 technical reports

Research Report on Infra Sound

Richard Mann

We have successfully produced infrasound, as a mirror of that produced by Industrial Wind Turbines, in a chamber capable of accommodating a human test subject. This will permit others, with appropriate medical training and ethical oversight, to research the effects of infrasound on humans.

Optimal Matching of Stochastic Solar Generators to Stochastic Loads

Sun Sun, Srinivasan Keshav, Catherine Rosenberg, Matthew Peloso

To meet the demand for locally-produced and sustainable power, community microgrids distribute power generated by roof-mounted solar PV systems to ‘green’ consumers. In this context, we consider the problem of matching one or more inherently intermittent solar energy producers with each green consumer so that, with a high probability, a certain component of their load is met from solar generation. We formulate this optimal matching as a stochastic optimization problem which incorporates the uncertainty of both solar and loads. To solve the problem, we propose four algorithms which make different assumptions on the distributions of solar generation and loads. We compare the performance of these algorithms using real data, and find that, for our dataset, an approach that assumes Gaussian mixture models for solar and loads best fits our design requirements. We also investigate admission control algorithms to admit customers based on our matching algorithms so that the solar allocation is feasible. 

An Experimental Investigation on Understanding the Difficulties and Challenges of Software Modellers When Using Modelling Tools

Parsa Pourali, Joanne M. Atlee

Software modelling is a challenging, error-prone and tedious task. Existing Model-Driven Engineering (MDE) tools provide modellers with little aid, partly because tool providers have not investigated users’ difficulties through empirical investigations such as field studies. This report presents the results of a two-phase user study to identify the most prominent difficulties that users might face when using UML modelling tools. In the first phase, we identified the preliminary modelling challenges by analysing 30 models that were previously developed by students as a course assignment. The result of the first phase helped us to design the second phase of our user study where we empirically investigated different aspects of using modelling tools: the tools’ effectiveness, users’ efficiency, users’ satisfaction, the gap between users’ expectation and experience, and users’ cognitive difficulties. Our results suggest that users’ greatest difficulties are in (1) remembering contextual information and (2) identifying and fixing errors and inconsistencies.

DASH: Declarative Modelling with Control State Hierarchy 

Jose Serna, Nancy A. Day, Shahram Esmaeilsabzali 

We present a new language, called DASH, for describing formal behavioural models. DASH combines common modelling constructs to describe abstractly both data and control in an integrated manner. DASH uses the Alloy language for describing data and its operations declaratively, and adds syntax for labelled control state hierarchy common in Statecharts descriptions of transition systems. In addition, DASH accommodates multiple factoring paradigms for modelling (control states, events, and conditions) and includes syntactic sugar (e.g., transition comprehension, transition templates) to write models that are concise and easy to understand. We describe the formal semantics of DASH, which carefully mix the usual semantic understanding of control state hierarchy with the declarative perspective, for creating abstract models early in system development. We implement these semantics in a translator from DASH to Alloy taking advantage of Alloy language features. We demonstrate DASH, our tool, and model checking analysis in the Alloy Analyzer using several case studies. The key novel insight of our work is in combining seamlessly common data and control modelling paradigms in a way that will be intuitive for those used to either paradigm, and enabling automatic analysis of the integrated model. 

Modeling Affine and Projective Transformations in 3-Dimensions by Linear Transformations in 4-Dimensions

Juan Du, Ron Goldman, Stephen Mann 

We provide a tutorial on how to use shears and rotations in 4-dimensions to model translations and perspective projections in 3-dimensions. We also explain how to uniformly scale points about the origin and mirror points in the origin in 3-dimensions using non-uniform scaling and reflection in 4-dimensions.