Home About us Contact
|
Home About us Contact | ||
|
|
||
Technological Interest (technological + interest)
Selected AbstractsProcessing of Bulk Metallic GlassADVANCED MATERIALS, Issue 14 2010Jan Schroers Abstract Bulk metallic glass (BMG) formers are multicomponent alloys that vitrify with remarkable ease during solidification. Technological interest in these materials has been generated by their unique properties, which often surpass those of conventional structural materials. The metastable nature of BMGs, however, has imposed a barrier to broad commercial adoption, particularly where the processing requirements of these alloys conflict with conventional metal processing methods. Research on the crystallization of BMG formers has uncovered novel thermoplastic forming (TPF)-based processing opportunities. Unique among metal processing methods, TPF utilizes the dramatic softening exhibited by a BMG as it approaches its glass-transition temperature and decouples the rapid cooling required to form a glass from the forming step. This article reviews crystallization processes in BMG former and summarizes and compares TPF-based processing methods. Finally, an assessment of scientific and technological advancements required for broader commercial utilization of BMGs will be made. [source] Molecules on Si: Electronics with ChemistryADVANCED MATERIALS, Issue 2 2010Ayelet Vilan Abstract Basic scientific interest in using a semiconducting electrode in molecule-based electronics arises from the rich electrostatic landscape presented by semiconductor interfaces. Technological interest rests on the promise that combining existing semiconductor (primarily Si) electronics with (mostly organic) molecules will result in a whole that is larger than the sum of its parts. Such a hybrid approach appears presently particularly relevant for sensors and photovoltaics. Semiconductors, especially Si, present an important experimental test-bed for assessing electronic transport behavior of molecules, because they allow varying the critical interface energetics without, to a first approximation, altering the interfacial chemistry. To investigate semiconductor-molecule electronics we need reproducible, high-yield preparations of samples that allow reliable and reproducible data collection. Only in that way can we explore how the molecule/electrode interfaces affect or even dictate charge transport, which may then provide a basis for models with predictive power. To consider these issues and questions we will, in this Progress Report, review junctions based on direct bonding of molecules to oxide-free Si. describe the possible charge transport mechanisms across such interfaces and evaluate in how far they can be quantified. investigate to what extent imperfections in the monolayer are important for transport across the monolayer. revisit the concept of energy levels in such hybrid systems. [source] The Precipitation Behavior of Superalloy ATI Allvac 718PlusADVANCED ENGINEERING MATERIALS, Issue 3 2010Gerald A. Zickler Abstract ATI Allvac 718Plus is a novel nickel-based superalloy, which was designed for heavy-duty applications in aerospace gas turbines. The precipitation kinetics of the intermetallic , (Ni3Nb) and ,, (Ni3(Al,Ti)) phases in this alloy are of scientific as well as technological interest because of their significant influence on the mechanical properties. Important parameters like grain size are controlled by coarse , precipitates located at grain boundaries, whereas small ,, precipitates are responsible for strengthening by precipitation hardening. In the present study, the microstructure is investigated by three-dimensional atom probe tomography and simulated by computer modeling using the thermo-kinetic software MatCalc. The results of numerical simulations and experimental data are compared and critically discussed. It is shown that the chemical compositions of the phases change during isothermal aging, and the precipitation kinetics of , and ,, phases interact with each other as shown in a time temperature precipitation (TTP) plot. The TTP plot shows C-shaped curves with characteristic discontinuities in the temperature range, where simultaneous and concurrent precipitation of the , and ,, phases occurs. This leads to a competition in the diffusion of Nb and Al, which are partly present in both phases. Thus, the present study gives important information on heat treatments for ATI Allvac 718Plus in order to achieve the desired microstructure and mechanical properties. [source] Asymptotic Back Strain Approach for Estimation of Effective Properties of Multiphase MaterialsADVANCED ENGINEERING MATERIALS, Issue 1-2 2007A. Gusev Estimation of the effective properties of composite materials from those of the constituents and the material's morphology is a classical problem of both theoretical and technological interest. In this work, the authors have introduced an asymptotic back strain finite element approach for numerical estimation of effective properties of multiphase materials. The proposed approach should open an appealing pathway to rational and effective computer aided design of random microstructure composite materials. [source] Unusual Lattice-Magnetism Connections in MnBi NanorodsADVANCED FUNCTIONAL MATERIALS, Issue 7 2009Kyongha Kang Abstract Lattice parameter, particle size, and thermal expansion results obtained from high-temperature synchrotron transmission X-ray diffraction are reported for magnetostructual NiAs-type MnBi nanorods embedded in a Bi matrix. The structural data are consistent with elevated-temperature magnetic measurements that indicate a first-order nanorod Curie transition at 520,K, significantly depressed from the bulk MnBi Curie temperature of 633,K. The data suggest that the unit cell volume dependence of the magnetic behavior,also known as the volume exchange striction,of the MnBi compound is the determining factor underlying this phenomenon. The results imply that materials with magnetostructural transitions of technological interest may be altered by strain effects to tailor the interatomic distances towards the critical transition values. [source] Influence of Engineered Peptides Cadmium Sulfide Nanocrystals,ADVANCED FUNCTIONAL MATERIALS, Issue 13 2007D. Spoerke Abstract Cadmium sulfide (CdS) nanocrystals continue to generate scientific and technological interest, owing to their valuable optical, electronic, and chemical properties. Aqueous nanocrystal syntheses rely on functional capping agents to control nanocrystal form and function. We present a series of linear and dendritic engineered peptides, rich in cysteines and aspartic acids, as CdS capping agents. The chemical composition and peptide geometry were found to significantly influence CdS nanocrystal size, optical properties, and aggregation behavior. [source] Investigation of the temperature oscillations in the cylinder walls of a diesel engine with special reference to the limited cooled caseINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 11 2004C. D. Rakopoulos Abstract This work investigates the interesting phenomenon of the temperature (cyclic) oscillations in the combustion chamber walls of a diesel engine. For this purpose, a comprehensive simulation code of the thermodynamic cycle of the engine is developed taking into account both the closed and the open parts of it. The energy and state equations are applied, with appropriate combustion, gas heat transfer, and mass exchange with the atmosphere sub-models, to yield cylinder pressure, local temperatures and heat release histories as well as various performance parameters of the engine. The model is appropriately coupled to a wall periodic conduction model, which uses the gas temperature variation as boundary condition throughout the engine cycle after being treated by Fourier analysis techniques. It is calibrated against measurements, at various load and speed conditions, from an experimental work carried out on a direct injection (DI), naturally aspirated, four-stroke, diesel engine located at the authors' laboratory, which has been reported in detail previously. After gaining confidence into the predictive capabilities of the model, it is used to investigate the phenomenon further, thus providing insight into many interesting aspects of transient engine heat transfer, as far as the influence that engine wall material properties have on the values of cyclic temperature swings. These swings can take prohibitive values causing high wall thermal fatigue, when materials of specific technological interest such as thermal insulators (ceramics) are used, and may lead to deterioration in engine performance. Copyright © 2004 John Wiley & Sons, Ltd. [source] Autolytic phenotype of Lactococcus lactis strains isolated from traditional Tunisian dairy productsJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2002H. Ouzari Aims:,To evaluate the autolytic properties of Lactococcus lactis strains isolated from artisan Tunisian dairy products, their peptidoglycan hydrolase content and their activity spectrum. Methods and Results:,The autolytic phenotype of Lactococcus strains was evaluated under starvation conditions in potassium phosphate buffer. The results obtained highlighted a high degree of diversity among the strains analysed, allowing the identification of high and low autolytic Lactococcus lactis strains. Peptidoglycan hydrolase content was evaluated by renaturing SDS-PAGE using cells of Micrococcus lysodeikticus as a target for the enzymatic activity. A major activity band migrating at about 45 kDa was observed. The lytic activity, evaluated in the presence of different chemicals, was retained in 8% NaCl, 15 mmol l,1 CaCl2, and in a pH range between 5 and 9·5. The substrate specificity of peptidoglycan hydrolase from Lactococcus strains was evaluated in renaturing SDS-PAGE incorporating cells of different bacterial species. The major autolysin of Lactococcus lactis was active against cells of Lactococcus lactis subsp. lactis, Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus helveticus and Listeria monocytogenes. Conclusions:,Autolytic activity is widely distributed in Lactococcus lactis and the rate of autolysis is strain-dependent. The major peptidoglycan hydrolase showed a wide spectrum of activity against several lactic acid bacteria and bacterial species involved in food-related infection. Significance and Impact of the Study:,The autolytic phenotype of Lactococcus lactis strains isolated from Tunisian artisan dairy products has been determined, and the data obtained should allow the selection of strains of technological interest in the cheese-ripening process. [source] DEHYDRATION CHARACTERISTICS OF PAPAYA (CARICA PUBENSCENS): DETERMINATION OF EQUILIBRIUM MOISTURE CONTENT AND DIFFUSION COEFFICIENTJOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2009R. LEMUS-MONDACA ABSTRACT This study determined the drying kinetics behavior of papaya at different temperatures (40, 50, 60, 70 and 80C). Desorption isotherms were determined at 5, 20 and 50C over a relative humidity range of 10,95%. The Guggenheim, Anderson and de Boer models were found to be suitable for description of the sorption data. The samples reached equilibrium moisture of 0.10 ± 0.01 g water/g dry matter. Fick's second law model was used to calculate the effective diffusivity (6.25,24.32 × 10 - 10 m2/s). In addition, experimental data were fitted by means of seven mathematical models. The kinetic parameters and the diffusion coefficient were temperature-dependent and were evaluated by an Arrhenius-type equation. The modified Page model obtained the best-fit quality on experimental data according to statistical tests applied. PRACTICAL APPLICATIONS The main utility of this study is the application of both different empirical models and the diffusional model in tropical fruits' dehydration, which can be considered a basis for a very accurate estimation of drying time and the optimization of the same process. Two newly mathematical models are proposed in this study, through which a good fit on the data of experimental moisture content was achieved. The study of drying of papaya cultivated in Chile engages a great technological interest, because this product is widely used in the development of different products such as candying, canning, juice, syrup and marmalade. In addition, papayas cultivated in Chile, along with other tropical fruits cultivated in Brazil, Colombia and the Caribbean, have become especially important in the exportations of these countries. The major markets for these products include the U.S.A., the European Community and Asia. [source] Disorderly reasoning in information designJOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 9 2009Peter Hall The importance of information visualization as a means of transforming data into visual, understandable form is now embraced across university campuses and research institutes world-wide. Yet, the role of designers in this field of activity is often overlooked by the dominant scientific and technological interests in data visualization, and a corporate culture reliant on off-the-shelf visualization tools. This article is an attempt to describe the value of design thinking in information visualization with reference to Horst Rittel's (1988) definition of "disorderly reasoning," and to frame design as a critical act of translating between scientific, technical, and aesthetic interests. [source] | ||||||||||