On metricity of two heterogeneous measures in the presence of missing values

Heterogeneous Euclidean-overlap metric and heterogeneous value difference metric given in machine learning literature are useful for the consideration of mixed-type data for machine learning, pattern recognition and data mining tasks. Mixed-type variables are quite common in practical problems, but this property has been taken into account only seldom in pattern recognition, data mining and decision making algorithms. We observed that these two distance measures are not actually metrics after having found a special situation when they are not metric, but pseudometric, a feature to be noted while using them. Nevertheless, by changing their definitions somewhat, it is possible to meet the metricity. Especially in medical applications, the redefinition of the two measures might be important, since otherwise it is possible in theory that, for example, two identical cases would be classified differently. Nearest neighbor searching tests with medical data were run to illustrate the behavior of these measures. Notwithstanding the violation of the metricity their original forms yielded slightly better classification results. The reason was that in real data sets tested there were very few almost similar cases according to these distance measures, and the original forms based on more separating distances than the redefinitions were slightly better in the classification.     

Hydrocarbon condensation in heavy-duty diesel exhaust

The semivolatile mass fraction of diesel exhaust particles was studied using size-resolved on-line techniques (DMA-ELPI; TDMA-ELPI). The average density of the semivolatile liquid on the particles was measured to be approximately 0.8 g/cm3. The measured size resolved values of mass transfer imply that condensation, or diffusion-limited mass transfer, plays a major role in driving the volatile matter to the diesel exhaust particles. The measured mass change values correspond to highly size dependent mass fractions for the semivolatile component, ranging from approximately 20-80%. Integrated over particle size distribution, the volatile mass fractions were 25 and 45% for the two load points studied. Calculation, based on the measured particle properties, indicates that only 10% volatile mass fraction could be explained by monolayer adsorption. The size resolved changes in particle effective density, fractal dimension, volatile mass fractions and mass are all in agreement with theoretical considerations of condensation.     

The status of trace elements in staple foods

The effects of food processing on some cereal and potato products are discussed with respect to the status of 11 trace elements. The influences of milling, bread making and cooking of potatoes on the contents of trace elements are demonstrated. It is shown that these recently obtained results are quite representative for the former federal Republic of Germany (FRG) as compared with results published previously. Average intake levels of undesired elements such as cadmium and lead, as well as of essential elements such as calcium, copper, iron, magnesium, manganese, molybdenum, nickel, selenium and zinc via consumption of cereal and potato products are calculated.     

Particulate emissions from large-scale medium-speed diesel engines: 2. Chemical composition

The effect of diesel fuel and operation mode on diesel particulate matter (PM) emissions was studied using a combination of a gravimetric impactor (DGI) and SEM/EDX analysis of PM particles from 0.005 to 2.5 μm aerodynamic size. Tests were made with heavy fuel oil (HFO) and light fuel oil (LFO) with medium speed (500 rpm), turbo-charged, power per cylinder ~1 MW, multivariable large-scale diesel engines. Diesel PM was sampled from diluted and cooled exhaust gases. The sampled PM was found to be primarily made of carbon and sulphur derived from the fuel and lube oil but contain several other chemical species as well. In this paper the submicron particle size range (0.2-0.5 μm and 0.5-1.0 μm) is discussed. The EDX analysis gave reasonably accurate quantitative results featuring the important elements present in the samples, namely, C, O, Mg, Si, S, Cl, Ca, V, Fe, Ni, Zn (and Al). The results indicate that the finest particles originate primarily from the fuel while the somewhat larger particles contain also significant amounts of elements derived from the lubrication oil. As expected, the concentrations of sulphur and certain metallic elements such as V, Ni, Ca, Zn, Fe, Mg are significantly higher in diesel PM from HFO firing than for LFO firing.     

Mass Measurement of Non-Spherical Particles: TDMA-ELPI Setup and Performance Tests

An ELPI was introduced to the TDMA setup for measurement of effective density and particle mass. This allows measurement of particle mass change also in cases when the particles are non-spherical or have voids. In addition to mass change of a particle, the density of transferred matter can be calculated if either unconditioned or conditioned particles are spherical and the bulk (material) density of the core particle is known. The performance of the system was tested by numerical simulations and laboratory experiments. According to the results, the smallest detectable particle mass change is approximately ± 17%. The measured density for the condensing species was within 15% of the bulk density value. Particle mass change caused by condensation of semi-volatile components of exhaust gas on diesel soot particles was also demonstrated.     

Electrical Agglomeration of Aerosol Particles in an Alternating Electric Field

A laboratory scale test system has been designed and constructed to study the electrical agglomeration of charged aerosol particles as a method to increase the fine particle collection efficiency of electrostatic precipitators. The system consists of test aerosol generator, aerosol charger, agglomerator chambers, and aerosol measurement equipment. Air atomizing nozzles and the TSI six-jet atomizer have been used as the test particle generators. The test particles have been charged by a corona discharge. Two types of agglomerator chambers have been investigated. In one agglomerator the gas flows between two parallel plates, across which the alternating high voltage is applied. The other agglomerator is a quadrupole structure with cylindrical electrodes positioned between the grounded plates. Particle concentration and size distribution measurements have been carried out downstream of the agglomerator with agglomerator voltage on and off. Particle concentrations and size distributions have been measured with differential mobility analyzer (DMA) and a Berner low pressure impactor. These measurements show that agglomeration causes about a 4%-8% decrease in the fine particle concentration when the total mass concentration is between 1 and 2 g/m³. There was no difference between the results measured with the parallel plate and the quadrupole agglomerator.     

Efficient cross-validation for kernelized least-squares regression with sparse basis expansions

We propose an efficient algorithm for calculating hold-out and cross-validation (CV) type of estimates for sparse regularized least-squares predictors. Holding out H data points with our method requires O(min(H ² n,Hn ²)) time provided that a predictor with n basis vectors is already trained. In addition to holding out training examples, also some of the basis vectors used to train the sparse regularized least-squares predictor with the whole training set can be removed from the basis vector set used in the hold-out computation. In our experiments, we demonstrate the speed improvements provided by our algorithm in practice, and we empirically show the benefits of removing some of the basis vectors during the CV rounds.     

A review of revaporisation behaviour of radioactive Cs deposits and its impact on the source term in severe nuclear accidents from Phébus FP results and single effect testing

ABSTRACT

Revaporisation of the fission products deposited in the primary circuit of a reactor was identified as a possible late source of fission product release during a severe accident: e.g. loss of coolant accident (LOCA). Subsequent testing has shown that revaporisation is very likely to occur given a breach of the reactor and is an important contributor for the source term release to the containment and biosphere. The first part reviews the revaporisation mechanisms of Cs and other volatile or semi-volatile fission products transported in the primary circuit that were derived from the Phebus FP and associated programmes. The second part examines the separate effects testing to determine the high temperature chemistry of volatile and semi-volatile fission products (I, Mo, Ru) and structural materials (Ag, B), as well as atmospheric effects that substantially affect the source term. Finally, it examines Cs data from reactor accident sites that is providing additional knowledge of longer-term fission product chemistry. The results have been summarised in the form of a table and schematic diagram. This accumulated knowledge and experience has important applications in minimising contamination during decommissioning and site remediation techniques, as well as improving SA simulation codes and raising nuclear safety.