The effects of selected aldehydes, ketones and carboxylic acids on off-flavours in water

The effects of selected aldehydes, ketones and carboxylic acids on the development of off‐flavours in water were studied. Combinations of hexanal, octanal, 2‐octanone, 5‐nonanone, hexanoic acid and nonanoic acid were rated by the off‐flavour intensities they created in water at concentrations just at or below the threshold value of each analyte. Two different sensory panels evaluated the off‐flavours induced by different combinations of the analytes. The observations of the two panels agreed well. From these studies, it could be concluded that aldehydes play an important role in the development of off‐flavours intensities in water. There were synergistic effects between aldehydes and ketones, as well as between aldehydes and carboxylic acids. Small amounts of aldehydes and carboxylic acids – well below their respective threshold values – caused an increase in the off‐flavour intensity. No synergism between ketones and carboxylic acids could be observed.     

Short resolution proofs for a sequence of tricky formulas

 A class of propositional formulas, encoding the property that every finite, transitive digraph with no two-cycles must have a source, has been investigated by Krishnamurty and conjectured as hard for resolution. In this note we prove, opposed to that conjecture, that there are proofs of polynomial lengths (or even linear in the lengths of the formulas) of those formulas. Received March 15, 1994/November 28, 1994     

Objectives of Modelling Evacuation from Buildings during Accidents: Some Path-model Scenarios

The basic objective of developing an evacuation model is to supply the user with valid and valuable information on which conclusions concerning the safe evacuation from a building can be drawn. Several evacuation models have been developed over the last 15 years. In our opinion, many of these models are too narrowly focused, perhaps not meeting the needs of the decision maker. This paper discusses the objectives of evacuation studies and the selection of a suitable modelling technique relative to these objectives. We show that many different approaches to evacuation modelling are appropriate for different types of studies. In the discussion about different existing models and solution techniques, we present some of the basic philosophy lying behind the simulation model EVACSIM. EVACSIM has been developed to meet the need for an evacuation model that can combine knowledge about human behaviour with the ability to perform large-scale simulations of network processes. EVACSIM treats people as individuals and it has the capacity to collect any information of interest (in principle) regarding their movements, their exposure to potential accident effects and their time to exit the different parts of the structure. The role of an evacuation model in an evacuation analysis is also discussed.     

Scientific and structural base of manufacturing

Science comes from Latin scientia meaning knowledge. Science is difficult to define, but we can obtain an understanding of what we mean. Knowledge, however, is wider in scope than what we generally define as science. Engineering, of which manufacturing is a part, requires creativity, fantasy, scope, and imagination as well as scientific knowledge. These elements are also needed in the scientific work itself. Scientific quality and language to tell the result must be considered separately from each other. Scientific quality means true and accurate knowledge, and the language must be adapted to the problem and to the receiver of the scientific result. Axiomatic decision-rules are being proposed as a scientific method to help in sorting out good solutions in engineering. The manufacturing system can be described and analysed as three main production systems: the manufacturing production system (MPS), the data production system (DPS), and the innovation production system (IPS).     

Exposure to Volatile Organic Compounds of Microbial Origin (MVOC) during Indoor Application of Water-based Paints

The market for water-based paints (WBP) is growing, and these paints are favoured due to their low emission of volatile organic compounds (VOC). Because of the risk for microbial growth, biocides are usually added to WBP. Our study aimed to measure exposure to VOCs potentially of microbial origin (MVOC), during indoor application of typical Scandinavian WBP. Low concentrations of three MVOCs, 3-methyl-furan, 1-octen-3-ol, and 2-octen-1-ol, were detected during 5 out of 20 painting operations (25%). Mean exposures to MVOC and TVOC were 0.15 and 5000 μg/m³, respectively. No relation between MVOC and TVOC was observed. The highest exposure to MVOC was measured from an ecological paint, claimed to be low in VOCs and chemical additives. The results suggest that microbial growth in WBP may occur, and that measurements of MVOCs could be used as a means of quality control for WBP. The use of biocides in paint should be guided by the principle of a balance between the risk of contact allergies or other possible health hazards from the biocides, and the risk of microbial growth. If microbial growth occurs in paint, it may cause both unpleasant odor and potential health hazards for house painters and dwellers.     

Virtual origins of fire plumes

A model is proposed for correlating measurements of virtual origins of fire plumes, made possible in conjunction with a relation established recently for predicting mean flame heights. The model is consistent with plume theory and is shown to correlate available determinations of virtual origins quite well. However, precise experiments are needed to fully test the model and to investigate anticipated effects of fuel identity. It is shown that the results of this work lead to a rationale for the success of previously proposed temperature correlations which appear to be valid even into the flaming regions of plumes.     

Antiplasticization and transition to marked nonlinear viscoelasticity in poly(vinyl chloride)/acrylonitrile–butadiene copolymer blends

A series of PVC/NBR blends with varying acrylonitrile (AN) content in the NBR has been studied in uniaxial tension creep tests. The tests have been carried out at 21.5 ± 0.5°C covering creep times from 10 to 1000 sec. NBR with low AN content, having poor compatibility with PVC, gives the blends with higher compliance and increased time dependence of the compliance. A higher AN content in the NBR gives the blends with the opposite properties when the NBR is added in small amounts. NBR with 40 wt-% AN is found to act as an antiplasticizer giving minimal creep compliance when 7 wt-% NBR is added. The antiplasticization reveals a considerably increased stress level at which the transition from approximatively linear to marked nonlinear viscoelasticity occurs and a decreased stress dependence of the creep compliance in the nonlinear viscoelastic range. Since the antiplasticization is also associated with a suppression of the β-transition mechanism, the results provide a demonstration of the importance of β-mechanism in the stress activated processes responsible for the appearance of nonlinear viscoelasticity in solid polymers.