Engineering and reliability aspects of connectors in electronic system applications

This paper describes engineering and reliability aspects of connectors in Electronic Systems. While the physical design of connectors is relatively simple, the reliability in the field is complex as their performances are affected by a direct contact with the environment and the pollutants of the atmosphere. This complexity is further increased when lubrication is used to reduce the friction and wear on connector contact sliding surfaces.     

HBsAg, chronic lymphoproliferative disorders, and cirrhosis of liver

This study reports the incidence of HBsAg in a series of chronic lymphoproliferative disorders in which a high incidence of cirrhoses had been previously observed. Twenty-three cases were collected from the necropsy records. The type of lymphoma was reviewed in the light of the new functional classifications of non-Hodgkin malignant lymphomas introduced by Lennert and Lukes. The presence of HBsAg in the liver was investigated by the indirect immunofluorescence technique. Eleven cases showed plasmocytoid features and were considered as immunocytomas. Seven cases showed cirrhosis of the liver; six of them belonged to the immunocytoma group. Four cases were positive for HBsAg. Three of them were found among the group combining cirrhosis and immunocytoma. They presented the abundant nodular distribution of HBsAg typical of inactive cirrhosis.A parallel is drawn between the often reported association of Waldenstr?m's syndrome and cirrhosis and the association of immunocytoma and cirrhosis observed in this study. The analogy is all the more justified since most of the lymphomas associated with Waldenstr?m's syndrome happen to be immunocytomas. Therefore the association between HB virus infection and cirrhosis on the one hand and chronic lymphoproliferative disorders on the other may not be purely coincidental. A chronic antigenic stimulus such as persisting HBsAg could trigger the proliferation of a malignant lymphoid clone.     

Theoretical comparison of the band broadening in nonretained electrically and pressure-driven flows through an ordered chromatographic pillar packing

Using a well-validated computational fluid dynamics simulation method, based on a multi-ion transport model, a detailed analysis of the differences in band broadening between pressure-driven (PD) and electrically driven (ED) flows through perfectly ordered, identical chromatographic pillar packings has been made. It was found that, although the eddy-diffusion band-broadening contributions were nearly completely absent in the considered structure, the ED flow still yields much smaller plate heights than the PD flow. This difference could be fully attributed to the different ways in which the ED and PD velocity profiles reshape when passing through a tortuous pore structure with undulating cross section. Whereas in the PD case the parabolic tip of the band front is continually squeezed and extended each time it passes a pore constriction, the ED flow displays some kind of band front restoring mechanism, with which the fluid elements of the band front are (at least partly) laterally re-aligned after each pore constriction passage. This could be clearly visualized from a series of step-by-step images of the progression of a sharply "injected" species band moving through the packing under ED and PD conditions.     

A correlation for the pressure drop in monolithic silica columns

To gain insight into how the pressure drop in monolithic silica columns is determined by the microscopic details of the pore structure, a series of well-validated computational fluid dynamics simulations has been performed on a simplified model structure, the so-called tetrahedral skeleton column. From these simulations, a direct correlation between the pressure drop and two main structural properties (skeleton thickness and column porosity) of the monolithic skeleton could be established. The correlation shows good agreement with the experimental pressure-drop data available from the literature on silica monoliths, especially when a correction for the flow-through pore size heterogeneity is made. The established correlation also yields a much more accurate representation of the relation between the flow resistance and the bed porosity than does the Kozeny-Carman model, making it much better suited for porosity optimization calculations.     

Transport properties of self compacting concrete with limestone filler or fly ash

The durability of a cementitious material is greatly influenced by the permeability of the material for potentially aggressive substances. As the pore structure of self compacting concrete (SCC) might be different in comparison with traditional concrete (TC), some changes in durability behaviour may occur. At this moment however, it is unclear how significant these differences will be with regard to the concrete practice. In this paper, the gas and water transport in SCC with limestone filler or fly ash is investigated experimentally. Nine different concrete compositions are considered: one TC and eight SCC mixtures. Some important parameters like the water/cement (W/C) and cement/powder ratio (C/P), type of filler (limestone filler and fly ash), type of aggregate and type of cement are considered. The results of the gas and water transport are discussed and linked to experimental data concerning pore volume. Lower transport properties can be obtained by using fly ash instead of limestone as filler material, by lowering the W/C ratio, decreasing the C/P ratio at a constant W/C ratio or using blast furnace slag cement instead of portland cement. The effect of changing from gravel to crushed limestone is small. SCC is differing strongly of TC with respect to the apparent gas permeability. This difference is probably due to the differences in pore volume, as seen from MIP results.     

Online state and input force estimation for multibody models employing extended Kalman filtering

This paper discusses the use of Subsystem Global Modal Parameterization (SS-GMP) reduced multibody models in an augmented discrete extended Kalman filter (A-DEKF) to generate a general formalism for online coupled state/input estimation in mechanisms. The SS-GMP approach is proposed to reduce a general multibody model of a mechanical system into a real-time capable model without considerable loss in accuracy. In order to use these reduced models with an extended Kalman filter, the necessary derivatives of this model are provided. An exponential integration scheme is used to discretize the model in order to be compatible with discrete time filters. Finally, the augmented approach is used for the estimation, in which the unknown external forces are considered as additional states to be estimated. The proposed approach is validated numerically and compared to three other filtering approaches. The validation demonstrates that the proposed approach provides accurate results while still maintaining real-time performance.     

A variable column length strategy to expedite method development

A variable length method development (or VL-MD)strategy, exploiting the potential of an automatic column coupling system, is proposed and has been applied to a number of different pharmaceutical and environmental samples with a varying degree of complexity. The proposed strategy consistently produced separation methods that had at least an equally good critical pair resolution and an equally short run time to those of methods produced using commercially available MD assistance software. In some cases, the VL-MD strategy allowed the MD time to be drastically shortened from >30 h to an overnight run of only 12 h. The developed strategy has the potential to become fully automated provided that reliable chromatogram read-out software becomes available. The advantage of combining different stationary phase types to improve the available selectivity and the integration into the general VL-MD strategy was also demonstrated.     

Thermal modulation for multidimensional liquid chromatography separations using low-thermal-mass liquid chromatography (LC)

We report on a proof-of-principle experiment with a novel thermal modulation device with potential use in two-dimensional liquid chromatography (LC × LC) systems. It is based on the thermal desorption concept used in two-dimensional gas chromatography (GC × GC) systems. Preconcentration of neutral analytes eluting from the first dimension column is performed in a capillary "trap" column packed with highly retentive porous graphitic carbon particles, placed in an aluminum low-thermal-mass LC heating sleeve. Remobilization of the trapped analytes is achieved by rapidly heating the trap column, by applying temperature ramps up to +1200 °C/min. Compared to the nonmodulated signal, the presented thermal modulator yielded narrow peaks, and a concentration enhancement factor up to 18 was achieved. With a thermally modulated LC separation of an epoxy resin, it is shown that when the thermal modulation is applied periodically, the trapped and concentrated molecules can be released periodically and that the modulating interface can both serve as a preconcentration device and as an injector for the second dimension column of an LC × LC setup. Because of the thermal modulation, a high-molecular-weight epoxy resin could be adequately separated and the different fractions were identified with a GPC analysis, as well as an offline second dimension LC analysis.