Evaluating Pore Space in Macroporous Ceramics with Water‐Based Porosimetry

We show that water‐based porosimetry (WBP), a facile, simple, and nondestructive porosimetry technique, accurately evaluates both the pore size distribution and throat size distribution of sacrificially templated macroporous alumina. The pore size distribution and throat size distribution derived from the WBP evaluation in uptake (imbibition) and release (drainage) mode, respectively, were corroborated by mercury porosimetry and X‐ray micro‐computed tomography (μ‐CT). In contrast with mercury porosimetry, the WBP also provided information on the presence of “dead‐end pores” in the macroporous alumina.     

Structural characterization of vacuum evaporated ZnSe thin films

Thermally evaporated ZnSe thin films deposited on glass substrates within substrate temperatures (T _s)at 303 K-623 K are of polycrystalline nature having f.c.c. zincblende structure. The most preferential orientation is along [111] direction for all deposited films together with other abundant planes [220] and [311]. The lattice parameter, grain size, average internal stress, microstrain, dislocation density and degree of preferred orientation in the film are calculated and correlated with T _s.     

Experimental difficulties associated with permeability measurements in aluminum alloys

The general principles and experimental difficulties associated with the measurement of permeability in aluminum alloys have been discussed, in order to ease the further development of experimental methods suitable for such measurements. In order to avoid the surface-tension effects associated with liquid/gas interfaces in the narrow channels of the mushy zone, a flux melt can be used at the inlet of the permeameter. Electron-beam (EB) welding has been shown to be a suitable method for ensuring a complete wetting between the sample and flux after remelting to the test temperature. Moreover, the influence of the permeameter design and the experimental procedure on grain detachment, preferred-flow channel formation, and coarsening have been revealed through microstructural images.     

Intermediate Air Filters for General Ventilation Applications: An Experimental Evaluation of Various Filtration Efficiency Expressions

Neither the European standard nor the US standard for classification of intermediate class filters comprises testing of filter performance with respect to ultrafine particles (UFPs) or particles of the most penetrating size (MPPS). This could turn out to be a major lack in classification standards since UFPs have been pointed out as a serious health hazard. In this study, fractional efficiencies of eight new full-scale bag filters and twenty-three new filter medium samples were determined. The influence of air velocity and aerosol type was investigated, and correlations between efficiencies for UFPs (EF_UFPs), MPPS-sized particles (EF_MPPS) and 0.4 μm-sized particles (EF_0.4μm) were established. The tested bag filters were challenged by four aerosol types: a neutralized atomized oil aerosol, the same oil aerosol but non-neutralized, a non-neutralized thermally generated oil smoke, and a “natural” indoor aerosol. The tests were carried out at different air velocities through the filter medium, ranging between 0.08 m/s and 0.22 m/s. The relationships that were observed between EF_UFPs, EF_MPPS, and EF_0.4μm appeared to be linear within the observed filtration efficiency ranges. These relationships were similar regardless of the test aerosol type used, but somewhat different for glass fiber filters than for charged synthetic filters. Generally, EF_MPPS was 10–20% lower than EF_0.4μm. The influence of air velocity variations on the size resolved efficiency was determined. The glass fiber filters showed practically the same fractional efficiencies regardless of whether the test aerosol was neutralized or not. However, the charged synthetic filters showed substantially lower efficiencies when tested with the non-neutralized aerosol compared to the case when the aerosol was neutralized.

Copyright 2013 American Association for Aerosol Research     

The Morphology Control of BaTiO3 Particles Synthesized in Water and a Water/Ethanol Solvent

The experimental conditions for the growth of shape‐controlled BaTiO₃ particles in NaOH and Ba(NO₃)₂ aqueous and water/ethanol solutions using various TiO₂‐containing precursors were studied at 80°C–100°C. The different chemistries and physical characteristics of the precursors resulted in different BaTiO₃ formation rates and morphologies_. Nanocrystalline anatase led to irregularly shaped BaTiO₃ particles, whereas star‐like, single‐crystalline BaTiO₃ particles grew from aerogel TiO₂ and sodium titanate (NT) belts in alkaline aqueous solutions. With the addition of ethanol, the star‐like BaTiO₃ particles changed to square‐like, the size of which decreased with an increase in the ethanol content. The electron microscopy observations supported a dissolution–precipitation mechanism as the primary reaction mechanism for the formation of BaTiO₃ nanocrystals, which further aggregated into single‐crystalline star‐ or square‐like particles by oriented attachment. The modification in the water solution with ethanol is believed to influence both the nucleation and aggregation process and consequently influence the particle shape and size.     

Electrical Control of the Reflectance of Porous Silicon Layers

In this paper we demonstrate the filling of porous silicon (PS) layers with liquid crystals (LC's) in order to control the reflectance electrically. The preparation of PS and the choice of the right group of LC's will be presented. Especially an oxidation of PS is necessary so that the methods and parameters of oxidation will also be discussed. As a first result the increasing and decreasing of the thickness oscillations in the reflectance as a function of the applied voltage can be observed.     

Modeling and validation of a boost pressure actuation system,for a series sequentially turbocharged SI engine

An actuation system for flexible control of an advanced turbocharging system is studied. It incorporates a vacuum pump and tank that are connected to pulse width modulation controlled vacuum valves. A methodology for modeling the entire boost pressure actuation system is developed. Emphasis is placed on developing component models that are easily identified from measured data, without the need for expensive measurements.The models have physical interpretations that enable handling of varying surrounding conditions.The component models and integrated system are evaluated on a two stage series sequential turbo system with three actuators having different characteristics.Several applications of the developed system model are presented, including a nonlinear compensator for voltage disturbance rejection where the performance of the compensator is demonstrated on an engine in a test cell. The applicability of the complete system model for control and diagnosis of the vacuum system is also discussed.     

Efficient false positive free set synchronization using an extended bloom filter approach

Synchronization between two sets is an important requirement for many distributed applications. A basic prerequisite is to find out which elements of set A are not in set B and vice versa. A very space efficient data structure for such membership queries that has been used a lot in networking applications is the Bloom filter. Unfortunately, the Bloom filter owes its high efficiency to the fact that there is a chance of false positives when querying the filter. This precludes the adoption of Bloom filters in applications that cannot tolerate such errors. In this paper we present an approach that augments Bloom filters with a trie-based mechanism that deterministically and efficiently finds the false positives after using the Bloom filter to synchronize two sets. We show that the added communication overhead for our approach is negligible compared to the overhead of a plain Bloom filter.