Modification of the ELPI to measure mean particle effective density in real-time

A new modification of electrical low pressure impactor (ELPI) for the particle effective density measurement is presented. The system is capable of real-time operation and it is based on the serial measurement of mobility and aerodynamic diameter. In the studied configuration, a zeroth order mobility analyser is installed inside of the ELPI-instrument. The system is feasible for single modal distributions. For several particle materials and varying size distributions, the measured average density values were within 15% of the values obtained with a reference method.     

Parallel Interference Cancellation in Multiuser CDMA Channel Estimation

Parallel interference cancellation (PIC) based channel parameter estimators for frequency selective fading channels are proposed for the uplink in code-division multiple-access (CDMA) mobile communication systems. The performance of PIC based algorithms depends heavily on the quality of the multiple-access interference estimates, which can be improved by using adaptive channel estimation filters. The performance of two adaptive complex channel coefficient estimation filters has been verified in a fading channel by computer simulations. According to the results, the PIC based adaptive channel estimators outperform clearly conventional, successive interference cancellation, and decorrelation based adaptive channel estimators. The PIC method is also used in delay tracking. By using the principles of sample-correlate-choose-largest (SCCL) delay trackers, a robust algorithm for multiuser delay tracking in fading channels is obtained.     

Odontogenic focus as the etiology of cerebral ischemia]

Several authors have established a relationship between osteoporosis and periodontal disease. The ageing process is associated with a loss of both oral and total bone mass. It has been shown that a reduction of bone mineralization aggravates pathological periodontal changes, resulting in less support for the teeth. The present study investigates the nutritional influences that may condition the appearance of both pathological process. Insufficient dietary calcium and a reduction in the calcium: phosphorous ratio may favour the appearance of both these conditions by promoting bone reabsorption. Bone loss affects the following in descending order: jaw bones (especially alveolar bone), cranial bones, ribs, vertebrae and long bones. Alveolar bone which has the highest rate of renewal, is affected first and consequently is the most severely affected in the long term. The role of calcium in the etiology of osteoporosis is a controversial issue. Nevertheless, its implication has been proven in numerous investigations. The effect of adequate calcium intake on dental health has formed the basis of several recent studies. These investigations have demonstrated that increased calcium intake improves the suffering of inflammatory processes and tooth mobility in patients suffering from gingivitis with haemorrhaging. Based on the results of studies which link dietary calcium and phosphorous to the risk of osteoporosis and periodontal disease, and bearing in mind that in a large proportion of the Spanish population calcium intake is below that recommended, there is a need for a general improvement of the diet. It may be of special interest to increase the calcium intake of patients suffering periodontal disease. It may also help in the prevention of osteoporosis.     

Concentration quenching of Tb3+ luminescence in LaOBr and Gd2O2S phosphors

The concentration quenching of trivalent terbium ${}^5\text{D}{}_{\mathrm{3,4}}\text{→}{}^7\text{F}{}_{\mathrm{J}}$ emissions from UV-excited (La, Tb) OBr and (Gd, Tb)₂O₂S phosphors was studied. The activation concentration x was varied from 5·10^?5 to 0.2 for (La_1?xTb_x) OBr and from 10^?3 to 0.1 for (Gd_1?xTb_x)₂O₂S. ${}^5\text{D}{}_3\text{→}{}^7\text{F}{}_{\mathrm{J}}$ emissions (blue) were observed to quench first and the Tb³⁺ concentration giving rise to maximum intensity was 0.003 in (La, Tb) OBr and between 0.005 and 0.01 in (Gd, Tb)₂O₂S. The optimum concentration for ${}^5\text{D}{}_4\text{→}{}^7\text{F}{}_{\mathrm{J}}$ (green) emissions was 0.05 in (La, Tb) OBr and 0.03 in (Gd, Tb)₂O₂S. Dipole-dipole and dipole-quadrupole interactions are possible mechanisms for the quenching of emissions from the ⁵D₃ and ⁵D₄ levels.A method for determining the Tb³⁺ concentration in these phosphors, based on the intensity ratios of the ${}^5\text{D}{}_3\text{→}{}^7\text{F}{}_{\mathrm{J}}$ and ${}^5\text{D}{}_4\text{→}{}^7\text{F}{}_{\mathrm{J}}$ transitions, is also presented.     

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.     

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.