Theory revision with queries: Horn, read-once, and parity formulas

A theory, in this context, is a Boolean formula; it is used to classify instances, or truth assignments. Theories can model real-world phenomena, and can do so more or less correctly. The theory revision, or concept revision, problem is to correct a given, roughly correct concept. This problem is considered here in the model of learning with equivalence and membership queries. A revision algorithm is considered efficient if the number of queries it makes is polynomial in the revision distance between the initial theory and the target theory, and polylogarithmic in the number of variables and the size of the initial theory. The revision distance is the minimal number of syntactic revision operations, such as the deletion or addition of literals, needed to obtain the target theory from the initial theory. Efficient revision algorithms are given for Horn formulas and read-once formulas, where revision operators are restricted to deletions of variables or clauses, and for parity formulas, where revision operators include both deletions and additions of variables. We also show that the query complexity of the read-once revision algorithm is near-optimal.     

Welding of Very Dissimilar Materials (Fe-Al)

Designers of transportation vehicles (air, land, or sea) continually seek ways to reduce vehicle weight in response to increasing fuel economy mandates, mission requirements, or other competitive pressures. One way to do this is by the selection of material types and their properties based on functional and structural requirements. While these material changes can help meet performance mandates, their implementation in a production environment relies on retaining economic competitiveness. This article traces the history of the various joining processes relevant to the current challenge in joining the very dissimilar families of steel (Fe) and aluminum (Al) alloys.     

Surface ionization properties of alkali metal oxide bronze

The process of selective ionization of a nitro compound (trinitrotoluene) on the surface of poly- and single-crystalline samples of sodium-vanadium oxide bronze has been studied in air at atmospheric pressure.     

The oxidative stability of omega-3 oil-in-water nanoemulsion systems suitable for functional food enrichment: A systematic review of the literature

There is growing demand for functional food products enriched with long chain omega-3 polyunsaturated fatty acids (LCω3PUFA). Nanoemulsions, systems with extremely small droplet sizes have been shown to increase LCω3PUFA bioavailability. However, nanoemulsion creation and processing methods may impact on the oxidative stability of these systems. The present systematic review collates information from studies that evaluated the oxidative stability of LCω3PUFA nanoemulsions suitable for use in functional foods. The systematic search identified seventeen articles published during the last 10 years. Researchers used a range of surfactants and antioxidants to create systems which were evaluated from 7 to 100 days of storage.

Nanoemulsions were created using synthetic and natural emulsifiers, with natural sources offering equivalent or increased oxidative stability compared to synthetic sources, which is useful as consumers are demanding natural, cleaner label food products. Equivalent vegetarian sources of LCω3PUFA found in fish oils such as algal oils are promising as they provide direct sources without the need for conversion in the human metabolic pathway. Quillaja saponin is a promising natural emulsifier that can produce nanoemulsion systems with equivalent/increased oxidative stability in comparison to other emulsifiers. Further studies to evaluate the oxidative stability of quillaja saponin nanoemulsions combined with algal sources of LCω3PUFA are warranted.     

Choosing Confrontation or Consensus in the Inner City: Lessons from a Community-University Partnership

This article describes the experiences of a Los Angeles inner-city neighbourhood in its attempt for revitalization. The authors headed a Community-University Partnership and worked with graduate students to offer technical support to a neighbourhood-based coalition. The students, local residents, merchants and neighbourhood institutions attempted to follow an asset-based consensus building approach to community development. The article describes the different components of their strategy for physical, economic, cultural and social revitalization, and analyzes the lessons learned from the successes and setbacks of this effort. Finally, the authors discuss some apparent limitations of the asset-based consensus approach.     

Trees and wood: working with natural river processes

A history of land clearance and riparian tree and wood management has resulted in limited riparian woodland and wood along British rivers. However, river management approaches are now being promoted that ‘work with natural processes’ to reduce flood risk through measures intended to restore, protect and emulate the natural function of catchments, rivers, estuaries and coasts. Wood has started to be reintroduced into river channels during river restoration and natural flood management activities, but this needs to be undertaken using appropriate quantities, locations and designs that mimic natural tree‐wood features. This paper reviews the knowledge that is needed to support wood reintroduction activities including (i) the characteristics of the riparian tree species and wood that are present; (ii) the importance of river size relative to that of trees and wood pieces; and (iii) the way trees, wood and geomorphic processes interact across rivers and floodplains of different energy and style.     

Rapid Quantitative Measurement of Extrusion-Induced Starch Fragmentation by Automated Gel Permeation Chromatography

Gel permeation chromatography with application of the universal calibration concept was found to be a rapid and effective method for quantification of extrusion-induced starch fragmentation. This method (Timpa. J.D., J. Agr. Food Chem. 39 (1991), 270–275) employs dimethyl acetamide (DMAC) with lithium chloride to solubilize samples and automated gel permeation chromatography for fractionation. Instrumentation was equipped with a viscometer and refractometer, data was interpreted by application of the universal calibration concept. These results confirm that the largest starch molecules in corn meal (107 to 108 Daltons) were slightly prone to fragmentation. Fragments produced were primarily in the weight range of 104–107 Daltons. In addition, some smaller fragments (ranging between 5,000 and 7.500) were also generated by extrusion.     

Development and hot-melt impregnation of a model controlled flow prepreg system

A controlled-flow epoxy-based model prepreg resin system was developed. The formulation of the model controlled-flow resin was designed from performance information obtained from a commercially available controlled-flow resin, presently used in the aircraft industry. Thermoanalytical techniques including rheometry were used to provide the necessary information to develop the model system along with a formulation methodology developed by Seferis and co-workers. The model resin formulation, which was a combination of tetraglycidyl ether of methylenedianiline (TGMDA), diglycidyl ether of bisphenol-A (DGEBA), carboxyl-modified butadiene/acrylonitrile rubber (CMBN), carboxyl-terminated butadiene/acrylonitrile rubber (CTBN), bisphenol-A (BPA), diaminodiphenyl sulfone (DDS), and dicyandiamide (DICY), was hot-melt impregnated into unidirectional carbon fibers on a laboratory scale hot-melt prepreg machine. A two-parameter, three-level design of experiments was performed on the prepreg processing parameters in which impregnation temperature and pressure were varied. Thus, a total of nine different experimental prepregs were produced and characterized by resin content, extent of impregnation, and tack. The results from the characterization of the nine experimental prepregs are compared with the effects of the prepreg processing conditions. These results are also compared with the results generated for the commercial controlled-flow resin. Collectively, this work provides a fundamental basis by which the analysis and rational utilization of controlled-flow matrix prepregs can be effected.     

Developments in the continuous galvanizing of steel

The performance history of galvanized steels, particularly in the automotive industry, has heightened demand for both hot-dip galvanized and electrogalvanized products. Such marketability has led to the commissioning of several new galvanizing lines in recent years. Still, for this timehonored coating process to remain competitive, researchers are investigating methods to improve surface appearance, coating uniformity, corrosion resistance and cost effectiveness.     

Characteristics of Bi-metallic Interfaces Formed During Direct Energy Deposition Additive Manufacturing Processing

Metallurgical and Materials Transactions B - Various additive manufacturing processes are being evaluated to reduce the time and cost for fabrication of low volume, complex, and multifunctional...