An experimental investigation into the performance of externally pressurized rectangular air bearings

An experimental programme which was designed to investigate the performance characteristics of externally pressurized rectangular air bearings considering the effects of pad geometry and inlet gas conditions is presented. Three forms of rectangular bearings were considered: one arrangement consisted of continuous plane surfaces, the second had a recessed pad and a plane bed and the third had a plane bed and a recessed pad with a step in the bearing area following the recess.

The results revealed that the recess length has a dominant effect on the pressure distribution in the air film. The effect of pressure depression is obvious at extremely small clearances and supply pressures. Such an effect is exaggerated when a step is introduced in the pad surface. The introduction of the step improves the load-carrying capacity of the bearing as long as the bearing is free from shock-wave formation.     

Live-Load Distribution Factors for Prestressed Concrete, Spread Box-Girder Bridge

This study presents an evaluation of shear and moment live-load distribution factors for a new, prestressed concrete, spread box-girder bridge. The shear and moment distribution factors were measured under a live-load test using embedded fiber-optic sensors and used to verify a finite element model. The model was then loaded with the American Association of State Highway and Transportation (AASHTO) design truck. The resulting maximum girder distribution factors were compared to those calculated from both the AASHTO standard specifications and the AASHTO LRFD bridge design specifications. The LRFD specifications predictions of girder distribution factors were accurate to conservative when compared to the finite element model for all distribution factors. The standard specifications predictions of girder distribution factors ranged from highly unconservative to highly conservative when compared to the finite element model. For the study bridge, the LRFD specifications would result in a safe design, though exterior girders would be overdesigned. The standard Specifications, however, would result in an unsafe design for interior girders and overdesigned exterior girders.     

Toxic emissions resulting from sucralose added to electronic cigarette liquids

Electronic cigarettes (ECIGs) are appealing in part because of the many flavors of the liquids used in them. Concerns have been raised that some ECIG liquid flavors, especially those that are sweet, are attracting otherwise nicotine-naïve youth to ECIGs. Sucralose is an artificial, non-caloric sweetener that is added to some ECIG liquids. In this study, we evaluated the toxicants, namely isomers of chloropropanols that can be produced when sucralose-containing ECIG liquid is aerosolized. An analytical separation method relying on solid-phase extraction (SPE) to isolate chloropropanols from the propylene glycol/glycerol matrix was developed. Chloropropanols were then derivatized by silylation before they were analyzed on GC-MS. The influence of different ECIG operating conditions on the generation of chloropropanols was studied by varying ECIG device design and power output and also the sucralose concentration of the liquid. Heated sucralose-containing ECIG liquids produce two toxic compounds that can be found in the resulting aerosols. The two chloropropanols, 3-monochloro-1,2-propanediol (3-MCPD), and 1,3-dichloropropanol (1,3-DCP) that were detected under all conditions were found to be correlated significantly with liquid sucralose content. Effective regulation of ECIGs will minimize user and bystander exposure to these and other ECIG toxicants.

Copyright © 2019 American Association for Aerosol Research     

An integrated,generic approach to pattern mining: data mining template library

Frequent pattern mining (FPM) is an important data mining paradigm to extract informative patterns like itemsets, sequences, trees, and graphs. However, no practical framework for integrating the FPM tasks has been attempted. In this paper, we describe the design and implementation of the Data Mining Template Library (DMTL) for FPM. DMTL utilizes a generic data mining approach, where all aspects of mining are controlled via a set of properties. It uses a novel pattern property hierarchy to define and mine different pattern types. This property hierarchy can be thought of as a systematic characterization of the pattern space, i.e., a meta-pattern specification that allows the analyst to specify new pattern types, by extending this hierarchy. Furthermore, in DMTL all aspects of mining are controlled by a set of different mining properties. For example, the kind of mining approach to use, the kind of data types and formats to mine over, the kind of back-end storage manager to use, are all specified as a list of properties. This provides tremendous flexibility to customize the toolkit for various applications. Flexibility of the toolkit is exemplified by the ease with which support for a new pattern can be added. Experiments on synthetic and public dataset are conducted to demonstrate the scalability provided by the persistent back-end in the library. DMTL been publicly released as open-source software (), and has been downloaded by numerous researchers from all over the world.     

Soaking–drying frequency effect on gypsum-rich roadbed sand

This article presents the California bearing ratio (CBR) and moisture content behaviour of a gypsum-rich roadbed sand with a gypsum content of about 39% subjected to cyclic soaking and drying. Frequencies of 8-, 14- and 60-day cycle lengths were adopted together with six cycles of soaking and drying for each frequency. Each cycle consisted of two equal time periods of soaking and drying. For each frequency, 13 pairs of CBR samples were prepared and subjected to cyclic soaking and drying in the laboratory under a surcharge load of 45 lb (200 N). The time variation of moisture content during cyclic soaking and drying at the top, middle and bottom of each CBR sample was studied as well. The article reveals that for each cycle, the CBR decreases during soaking and increases during drying for all frequencies.     

Synthesised magnetic nanoparticles coated zeolite (MNCZ) for the removal of arsenic (As) from aqueous solution

A novel adsorbent, magnetic nanoparticle (γ-Fe₂O₃)-coated zeolite (MNCZ), was prepared for the removal of arsenic (As) ions from aqueous solution. The influence of different sorption parameters, that is, contact time, acidic reaction (pH) and initial arsenic concentration were studied using batch equilibrium techniques. The results obtained showed that the MNCZ was effective for the removal of As from aqueous solution, and the percentage removal of As could reach over 95.6% at a pH value of 2.5 within 15?min. Moreover, the removal of As depended on the initial concentration of As. For the regeneration of MNCZ material, 0.1?M NaOH was suitable for the desorption of As (70% after 15?min), and the regenerated material showed an adsorption capacity of 93.95% within five cycles. We concluded that MNCZ presents a reusable adsorbent for a fast, convenient and highly efficient removal of As from aqueous solution.     

Inorganic chemistry of chromium and its speciation in Whetlerite

Chromium compounds are among the impregnants that enhance the ability of carbon air filters to absorb and destroy toxic agents such as CK and AC. The possibility of inhaling chromium-containing carbon dust from such filters has caused concern because, in addition to being an essential nutrient, chromium has been identified as a chemical carcinogen in humans. The essentiality or carcinogenicity of chromium depends upon its chemical speciation. Solubility and oxidation state are particularly important factors in assessing the potential hazards associated with the possible inhalation of chromium-containing dusts from these impregnated carbons or Whetlerites. The chemical speciation of the chromium in Whetlerite was found to be: from 0.6 to 1.3% insoluble trivalent chromium; from 1.0 to 1.3% insoluble hexavalent chromium; and from 0.7 to 0.9% soluble hexavalent chromium. The impregnation process, and the resulting speciation of chromium in Whetlerite, is consistent with the inorganic chemistry of chromium.