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An extensive review is given of the results from literature on electron beam induced deposition. Electron beam induced deposition is a complex process, where many and often mutually dependent factors are involved. The process has ...
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An extensive review is given of the results from literature on electron beam induced deposition. Electron beam induced deposition is a complex process, where many and often mutually dependent factors are involved. The process has been studied by many over many years in many different experimental setups, so it is not surprising that there is a great variety of experimental results. To come to a better understanding of the process, it is important to see to which extent the experimental results are consistent with each other and with the existing model. All results from literature were categorized by sorting the data according to the specific parameter that was varied (current density, acceleration voltage, scan patterns, etc.). Each of these parameters can have an effect on the final deposit properties, such as the physical dimensions, the composition, the morphology, or the conductivity. For each parameter-property combination, the available data are discussed and (as far as possible) interpreted. By combining models for electron scattering in a solid, two different growth regimes, and electron beam induced heating, the majority of the experimental results were explained qualitatively. This indicates that the physical processes are well understood, although quantitatively speaking the models can still be improved. The review makes clear that several major issues remain. One issue encountered when interpreting results from literature is the lack of data. Often, important parameters (such as the local precursor pressure) are not reported, which can complicate interpretation of the results. Another issue is the fact that the cross section for electron induced dissociation is unknown. In a number of cases, a correlation between the vertical growth rate and the secondary electron yield was found, which suggests that the secondary electrons dominate the dissociation rather than the primary electrons. Conclusive evidence for this hypothesis has not been found. Finally, there is a limited understanding of the mechanism of electron induced precursor dissociation. In many cases, the deposit composition is not directly dependent on the stoichiometric composition of the precursor and the electron induced decomposition paths can be very different from those expected from calculations or thermal decomposition. The dissociation mechanism is one of the key factors determining the purity of the deposits and a better understanding of this process will help develop electron beam induced deposition into a viable nanofabrication technique.
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The new constructs in aspect-oriented programming bring new types of programming faults with respect to crosscutting concerns, such as incorrect pointcuts and advice. This paper presents a UML-based approach to testing whether or ...
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The new constructs in aspect-oriented programming bring new types of programming faults with respect to crosscutting concerns, such as incorrect pointcuts and advice. This paper presents a UML-based approach to testing whether or not an aspect-oriented program conforms to its expected crosscutting behavior. We explore aspect-oriented UML design models to derive tests for exercising interactions between aspects and classes. Each aspect-oriented model consists of class diagrams, aspect diagrams, and sequence diagrams. For a method under test, we weave the sequence diagrams of the advice on the method into the method's sequence diagram. Based on the woven sequence diagram and class/aspect diagrams, we then generate an AOF (Aspect-Object Flow) tree by applying coverage criteria such as condition coverage, polymorphic coverage, and loop coverage to woven sequence diagrams. In the AOF tree, each path from the root to a leaf is an abstract message sequence, indicating a template of test cases. A concrete test case is obtained by creating objects that satisfy the collective constraints in the template. Our empirical study shows that the model-based testing approach is capable of revealing several types of aspect-specific faults, including incorrect advice type, incorrect (weaker or stronger) pointcut strengths, and incorrect aspect precedence.
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It is known that elementary bosons condense in a unique state, not so much because this state has the lowest free-particle energy but because it costs a macroscopic amount of energy to put the particles into different states which...
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It is known that elementary bosons condense in a unique state, not so much because this state has the lowest free-particle energy but because it costs a macroscopic amount of energy to put the particles into different states which can then interact through quantum particle exchanges. Since individual exchanges between the two fermions of a composite boson are ignored when composite particles are replaced by elementary bosons, it is of importance to reconsider the exchange-energy argument for the stability of the Bose-Einstein condensate in the case of composite bosons. We do this here in the light of the new many-body theory which allows us to take exactly into account all possible exchanges between the fermionic components of the composite bosons. We confirm that the condensate of composite bosons occupies a single state, this state being moreover pure: a coherent superposition of states close in energy is shown to be less favorable for both elementary and composite bosons.
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The objective of this research was to develop a microwave-vapor heat treatment (MW-VHT) for mangoes (Mangifera indica L.) cv. Namdokmai Si Thong to disinfest the oriental fruit fly, Bactrocera dorsalis (Hendel). The mortality of o...
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The objective of this research was to develop a microwave-vapor heat treatment (MW-VHT) for mangoes (Mangifera indica L.) cv. Namdokmai Si Thong to disinfest the oriental fruit fly, Bactrocera dorsalis (Hendel). The mortality of oriental fruit fly eggs and quality acceptability characterized by thermal-death-time and thermal-quality-time overlay plots were initially obtained by hot-water immersion. Two treatments within a range of acceptable quality were selected for inoculation experiments to confirm MW-VHT process. The acceptable range was temperature ranging from 46 to 55C with time ranging from 2 to 20 min. The MW-VHT using microwave for preheating followed by vapor for holding processes effectively disinfested oriental fruit fly eggs. Changes in physiochemical properties of mangoes, e.g., color, titratable acid (TA), total soluble solid (TSS), TSS/TA and firmness, of MW-VHT-treated mangoes were not significantly different (P > 0.05) from physiochemical properties of the nontreated mangoes. MW-VHT resulted in less heat damage of mangoes than conventional vapor heat treatment (VHT) and shortened process time more than 90% during the preheating period. MW-VHT also retained equivalent or better lethality of oriental fruit fly eggs than did conventional VHT.
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Plasma-sprayed yttria-stabilized zirconia (YSZ) continues to play an important role in enhancing performance of both propulsion and land-based gas turbine engines. Tailoring the microstructure and properties of these thermal barri...
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Plasma-sprayed yttria-stabilized zirconia (YSZ) continues to play an important role in enhancing performance of both propulsion and land-based gas turbine engines. Tailoring the microstructure and properties of these thermal barrier coatings towards achieving both prime reliance and manufacturing reproducibil-ity is a complex task due to the multitude of interrelated parameters that influence the plasma spray process and the deposit formation dynamics.
In this article, we report on a study that connects thermal spray coatings through process science and materials science utilizing the concept of process maps. Process maps are representations of interrelationships among control parameters and measured responses. First-order process maps have been established for three YSZ powder morphologies, linking the plasma forming torch parameters to the particle state (responses) through a design of experiments approach and in-flight diagnostics. Refinements to representation of the raw particle characteristics are proposed through the use of group parameters (melting index and kinetic energy) from the experimental results. First-order process maps have been used for process parameterization and feedback control.
Correlating the first-order responses with coating properties allows representation of coating properties in the form of second-order process maps and enables identification of process windows. As will be demonstrated in this paper, these advances provide a platform with which to construct comprehensive process-microstructure-property relationships with implications for coating design, process efficiency and full-field assessment of manufacturing reliability.
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This paper investigates dynamic responses of a viscous fluid flow introduced under a time dependent pressure gradient in a rigid cylindrical tube that is lined with a deformable porous surface layer. With the Darcy's law and a lin...
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This paper investigates dynamic responses of a viscous fluid flow introduced under a time dependent pressure gradient in a rigid cylindrical tube that is lined with a deformable porous surface layer. With the Darcy's law and a linear elasticity assumption, we have solved the coupling effect of the fluid movement and the deformation of the porous medium in the Laplace transform space. Governing equations are deduced for the solid displacement and the fluid velocity in the porous layer. Analytical solutions in the transformed domain are derived and the time dependent variables are inverted numerically using Durbin's algorithm. Interaction between the solid and the fluid phases in the porous layer and its effects on fluid flow in tube are investigated under steady and unsteady flow conditions when the solid phase is either rigid or deformable. Examples are presented for flows driven by a Heaviside or a sinusoid pressure gradient. Significant effects of the porous surface layer on the flow in the tube are observed. The analytical solutions can be used to test more complicated numerical schemes.
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The paper concentrates on increasing convec-tive heat transfer due to periodically pulsating impinging air jets. A maximum enhancement rate of cooling effectiveness up to 20% could be detected at an excitation Strouhal number of S...
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The paper concentrates on increasing convec-tive heat transfer due to periodically pulsating impinging air jets. A maximum enhancement rate of cooling effectiveness up to 20% could be detected at an excitation Strouhal number of Sr = 0.82 when using a high pulsation magnitude. Reductions up to 5% occured at low Strouhal numbers with coincident high pulsation magnitudes as well. The thermal results were completed with phase-locked flow field investigations by means of PIV and surface visualizations using the oil film method.
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The Choptank River is an estuary, tributary of the Chesapeake Bay, and an ecosystem in decline due partly to excessive nutrient and sediment loads from agriculture. The Conservation "Effects Assessment Project for the Choptank Riv...
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The Choptank River is an estuary, tributary of the Chesapeake Bay, and an ecosystem in decline due partly to excessive nutrient and sediment loads from agriculture. The Conservation "Effects Assessment Project for the Choptank River watershed was established to evaluate the effectiveness of conservation practices on water quality within this watershed. Several measurement frameworks are being used to assess conservation practices. Nutrients (nitrogen and phosphorus) and herbicides (atrazine and metolachlor) are monitored within 15 small, agricultural subwatersheds and periodically in the lower portions of the river estuary. Initial results indicate that land use within these subwatersheds is a major determinant of nutrient concentration in streams. In addition, the ~(18)O isotope signature of nitrate was used to provide a landscape assessment of denitrification processes in the presence of the variable land use. Herbicide concentrations were not correlated to land use, suggesting that herbicide delivery to the streams is influenced by other factors and/or processes. Remote sensing technologies have been used to scale point measurements of best management practice effectiveness from field to subwatershed and watershed scales. Optical satellite (SPOT-5) data and ground-level measurements have been shown to be effective for monitoring nutrient uptake by winter cover crops in fields with a wide range of management practices. Synthetic Aperture Radar (RADARSAT-1) data have been shown to detect and to characterize accurately the hydrology (hydroperiod) of forested wetlands at landscape and watershed scales. These multiple approaches are providing actual data for assessment of conservation practices and to help producers, natural resource managers, and policy makers maintain agricultural production while protecting this unique estuary.
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A hierarchical multi-scale model that couples a region of material described by discrete dislocation plasticity to a surrounding region described by conventional crystal plasticity is presented. The coupled model is aimed at captu...
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A hierarchical multi-scale model that couples a region of material described by discrete dislocation plasticity to a surrounding region described by conventional crystal plasticity is presented. The coupled model is aimed at capturing non-classical plasticity effects such as the long-range stresses associated with a density of geometrically necessary dislocations and source limited plasticity, while also accounting for plastic flow and the associated energy dissipation at much larger scales where such non-classical effects are absent. The key to the model is the treatment of the interface between the discrete and continuum regions, where continuity of tractions and displacements is maintained in an average sense and the flow of net Burgers vector is managed via "passing" of discrete dislocations. The formulation is used to analyze two plane strain problems: (ⅰ) tension of a block and (ⅱ) crack growth under mode I loading with various sizes of the discrete dislocation plasticity region surrounding the crack tip. The computed crack growth resistance curves are nearly independent of the size of the discrete dislocation plasticity region for region sizes ranging from 30 μm × 30 μm to 10 μm × 5 μm. The multi-scale model can reduce the computational time for the mode I crack analysis by a factor of 14 with little or no loss of fidelity in the crack growth predictions.
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A comprehensive numerical study of the equivalent thermal conductivity of a multi-holed clay brick with the size of 240 × 115 × 90 (in mm) has been conducted, and 50 kinds of combination of holes and arrangements are examined. T...
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A comprehensive numerical study of the equivalent thermal conductivity of a multi-holed clay brick with the size of 240 × 115 × 90 (in mm) has been conducted, and 50 kinds of combination of holes and arrangements are examined. The indoor-outdoor temperature difference varies from 50 ℃ to 20 ℃. The effects of following factors are studied in details: the hole surface radiation, the width-wise and length-wise hole numbers, and the indoor-outdoor temperature difference. The major findings are as follows: (1) the radiation between hole surfaces has some effect on the equivalent thermal conductivity, thus it should be taken into account; (2) the hole number and arrangement affect the thermal conductivity in a rather complicated manner. Analysis shows that depending on the relative importance of natural convection, surface radiation and heat conduction through the clay solid, the thermal conductivity may decrease with the hole number or increase with the hole number and (3) among the 50 kinds of combination, the optimum configuration is found which has five length-wise holes, four width-wise holes and all the holes are from bottom to top in the depth direction of a brick. Its equivalent thermal conductivity is 0.419 W/(m K), which is only 53.1% of solid clay of which it is made, showing great energy-saving possibility if it is adopted in the construction of building wall.
Detailed discussion of the simulated results is conducted and flow field and temperature distributions are also provided for some typical configurations.
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