Fully Symbolic TCTL Model Checking for Incomplete Timed Systems

In this paper we present a fully symbolic TCTL model checking algorithm for incomplete timed systems. Our algorithm is able to prove that a TCTL property is violated or satisfied regardless of the implementation of unknown timed components in the system. For that purpose the algorithm computes over- approximations of sets of states fulfilling a TCTL property φ for at least one implementation of the unknown components and under-approximations of sets of states fulfilling φ for all possible implementations of the unknown components. The algorithm works on a symbolic model for timed systems, called a finite state machine with time (FSMT), and makes use of fully symbolic state set representations containing both the clock values and the state variables. In order to handle incomplete timed systems our model checking algorithm deals with different communication methods between the system and its unknown components, e.g. shared integer variables and urgent and non-urgent synchronization. Our experimental results demonstrate that it is possible to prove interesting properties at early stages of the design when parts of the overall system may not yet be finished. Additionally, fading out components of a large system may dramatically reduce the complexity of the system and thus the effort for verification

Automated Procedures in Iso17025 Routine Dioxin Laboratory:Impact on the Throughput

peer reviewe

On-line PLE-LC sample preparation for the measurement of dioxins and WHO-PCBs in food and feed

peer reviewe

Hazard Ratio and Hazard Index as Preliminary Estimators Associated to the Presence of Furans and Alkylfurans in Belgian Foodstuffs.

peer reviewedThis paper provides an estimation of the hazard related to the presence of furan and five alkyl furans (2- and 3-methylfuran, 2-ethylfuran, 2,5- and 2,3-dimethylfuran) in foodstuffs available in the Belgian market. To achieve this objective, a specific sampling plan was designed to ensure that the samples collected (n = 1003) represent the diversity of the Belgian food chain. Herein, the concepts of the Hazard Ratio of a sample (HRs) and the Hazard Index of a sample (HIs) were introduced to primarily characterize the hazard related to the co-occurrence of these compounds. The HRs was measured as the ratio of the potential daily exposure to a substance (expressed in mg/Kg of food) to both the 10% reference dose level for chronic effects (expressed in mg/(kg b.w*day)) and the human standard weight (expressed in kg). Whereas the HIs is the sum of the HRs of compounds that affect the same target organ/system, a hazard index greater than one indicates a highly contaminated matrix that could induce a hazard. It is an alarm indicating that additional attention should be given to this matrix. This may involve additional analyses to confirm the high level, to identify sources, etc. It is also an alarm for the risk assessor to be very careful with flagged matrices and to avoid combination with other matrices. The HIs highlight a relatively low concern for all foods analyzed (HI median < 1.0) with a relatively higher suspected hazard for coffee drinks (HI median = 0.068, HI max = 0.57). This preliminary estimation of the potential hazard suggests that coffee beverages should be examined in more detail in a full risk assessment and that coffee consumption should be taken with caution given the levels of furan and alkylfurans reported in this study