Jussi Lahtinen

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We propose a data reduction method based on a probabilistic similarity framework where tw ovectors are considered similar if they lead to similar predictions. We show how this type of a probabilistic similarity metric can be de ned both in a supervised and unsupervised manner. As a concrete application of the suggested multidimensional scaling scheme, we(More)
Information and knowledge are critical resources in operating and maintaining industrial process plants. The basis for the required knowledge repository is created at the design stage and extended after the hand-over of design data with modifications, maintenance histories and operational experiences. It is in the common interest of plant owners,(More)
Many nuclear instrumentation and control (I&C) systems are designed using a function block diagram description of the system. Strict requirements pertain to the verification of these systems. Different verification techniques, including structure-based testing, are demanded by standards and the regulators. Unfortunately, the traditional structure-based(More)
When high-dimensional data vectors are visualized on a twoor three-dimensional display, the goal is that two vectors close to each other in the multi-dimensional space should also be close to each other in the low-dimensional space. Traditionally, closeness is defined in terms of some standard geometric distance measure, such as the Euclidean distance,(More)
Instrumentation and control (I&C) systems play a vital role in the operation of safety-critical processes. Digital programmable logic controllers (PLC) enable sophisticated control tasks which sets high requirements for system validation and verification methods. Testing and simulation have an important role in the overall verification of a system but are(More)
In this paper we address the problem of analyzing web log data collected at a typical online newspaper site. We propose a two-way clustering technique based on probability theory. On one hand the suggested method clusters the readers of the online newspaper into user groups of similar browsing behaviour, where the clusters are determined solely based on the(More)
Model checking is a powerful formal verification method that can also be used to evaluate PLC software. A lot of manual work and some expertise are still needed. Proposed methods for automating the process rely on standardised specification languages, but PLC software is often vendor-specific, and the source code for function blocks may not even be(More)
Defects in safety-critical software systems can cause large economical and other losses. Often these systems are far too complex to be tested extensively. In this work a formal verification technique called model checking is utilized. In the technique, a mathematical model is created that captures the essential behaviour of the system. The specifications of(More)
Digital instrumentation and control (I&C) systems containing programmable logic controllers are challenging to verify. They enable complicated control functions and the state spaces (number of distinct values of inputs, outputs and internal memory) of the designs easily become too large for comprehensive manual inspection. Model checking is a formal method(More)
In nuclear power plants, novel digitalized I&C systems have brought out new needs for safety evaluation. The programmable digital logic controllers enable complicated control functionalities and, thus, their comprehensive verification is a difficult task. Model checking is a promising method that enables complete verification of the logic design when a(More)