Selective removal of CO from hydrogen-rich stream over CuO/CexSn1−xO2–Al2O3 catalysts

The solid solutions of Ce_xSn_1−xO₂ incorporated with alumina to form Ce_xSn_1−xO₂–Al₂O₃ mixed oxides, by the suspension/co-precipitation method, were used to prepare CuO/Ce_xSn_1−xO₂–Al₂O₃ catalysts for the selective oxidation of CO in excess hydrogen. Incorporating Al₂O₃ increased the dispersion of Ce_xSn_1−xO₂, but did not change their main structures and did not weaken their redox properties. Doping Sn⁴⁺ into CeO₂ increased the mobility of lattice oxygen and enhanced the activity of the 7%CuO/Ce_xSn_1−xO₂–Al₂O₃ catalyst in the selective oxidation of CO. The selective oxidation of CO was weakened as the doped fraction of Sn⁴⁺ exceeded 0.5. Incorporating appropriate amounts of Sn⁴⁺ and Al₂O₃ could obtain good candidates 7%CuO/Ce_xSn_1−xO₂–Al₂O₃(20%), 1–x=0.1–0.5, for a preferential oxidation (PROX) unit in a polymer electrolyte membrane fuel cell system for removing CO. Its activity was comparable with, and its selectivity was much larger than, that of the noble catalyst 5%Pt/Al₂O₃.     

Airside performance of herringbone wavy fin-and-tube heat exchangers – data with larger diameter tube

This study examines the airside performance of the wavy fin-and-tube heat exchangers having a larger diameter tube (D_c = 16.59 mm) with the tube row ranging from 1 to 16. It is found that the effect of tube row on the heat transfer performance is quite significant, and the heat transfer performance deteriorates with the rise of tube row. The performance drop is especially pronounced at the low Reynolds number region. Actually more than 85% drop of heat transfer performance is seen for F_p ～ 1.7 mm as the row number is increased from 1 to 16. Upon the influence of tube row on the frictional performance, an unexpected row dependence of the friction factor is encountered. The effect of fin pitch on the airside performance is comparatively small for N = 1 or N = 2. However, a notable drop of heat transfer performance is seen when the number of tube row is increased, and normally higher heat transfer and frictional performance is associated with that of the larger fin pitch.     

Evaluation of commercial lithium-ion cells based on composite positive electrode for plug-in hybrid electric vehicle applications. Part I: Initial characterizations

Evaluating commercial Li-ion batteries presents some unique benefits. One of them is to use cells made from established fabrication process and form factor, such as those offered by the 18650 cylindrical configuration, to provide a common platform to investigate and understand performance deficiency and aging mechanism of target chemistry. Such an approach shall afford us to derive relevant information without influence from processing or form factor variability that may skew our understanding on cell-level issues. A series of 1.9 Ah 18650 lithium ion cells developed by a commercial source using a composite positive electrode comprising {LiMn_1/3Ni_1/3Co_1/3O₂ + LiMn₂O₄} is being used as a platform for the investigation of certain key issues, particularly path-dependent aging and degradation in future plug-in hybrid electric vehicle (PHEV) applications, under the US Department of Energy's Applied Battery Research (ABR) program. Here we report in Part I the initial characterizations of the cell performance and Part II some aspects of cell degradation in 2C cycle aging. The initial characterizations, including cell-to-cell variability, are essential for life cycle performance characterization in the second part of the report when cell-aging phenomena are discussed. Due to the composite nature of the positive electrode, the features (or signature) derived from the incremental capacity (IC) of the cell appear rather complex. In this work, the method to index the observed IC peaks is discussed. Being able to index the IC signature in details is critical for analyzing and identifying degradation mechanism later in the cycle aging study.     

Slip-System-Related Dislocation Study from <Emphasis Type="Italic">In-Situ</Emphasis> Neutron Measurements

A combined experimental/computational approach is employed to study slip-system-related dislocation-substructure formation during uniaxial tension of a single-phase, face-centered-cubic (fcc), nickel-based alloy. In-situ neutron-diffraction measurements were conducted to monitor the peak-intensity, peak-position, and peak-broadening evolution during a displacement-controlled, monotonic-tension experiment at room temperature. The measured lattice-strain evolution and the macrostress/macrostrain curves were used to obtain the material parameters required for simulating the texture development by a visco-plastic self-consistent (VPSC) model. The simulated texture compared favorably with experimentally-determined texture results over a range of 0 to 30 pct engineering strain. The grain-orientation-dependent input into the Debye-intensity ring was considered. Grains favorably oriented relative to the two detector banks in the geometry of the neutron experiment were indicated. For the favorably oriented grains, the simulated slip-system activity was used to calculate the slip-system-dependent, dislocation-contrast factor. The combination of the calculated contrast factor with the experimentally-measured peak broadening allows the assessment of the parameters of the dislocation arrangement within the specifically oriented grains, which has a quantitative agreement with the transmission-electron-microscopy results. This article is based on a presentation given in the symposium entitled “Neutron and X-Ray Studies for Probing Materials Behavior,” which occurred during the TMS Spring Meeting in New Orleans, LA, March 9–13, 2008, under the auspices of the National Science Foundation, TMS, the TMS Structural Materials Division, and the TMS Advanced Characterization, Testing, and Simulation Committee.

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<Emphasis Type="Italic">In-Situ</Emphasis> Electrochemical Investigations of a Nickel-Based Alloy Subjected to Fatigue

The HASTELLOY C2000 superalloy is a commercially designed superalloy manufactured to function in reducing and oxidizing corrosive solutions. The industrial applications have tremendous potential in automotive, structural, aviation, and storage components. Although C2000 demonstrates good reducing and oxidizing traits in extremely aggressive media (which are attractive features of its chemistry), changes in the mechanical properties are believed to be insignificant due to its strong propensity to passivate under corrosive conditions. The ductility behavior and corrosion properties of C2000 are superior to those of stainless steels. The objective of the present study is to examine the corrosion-fatigue behavior of C2000 in a 3.5 wt pct sodium-chloride (NaCl) solution. C2000 submerged in 3.5 wt pct NaCl at room temperature is not susceptible to localized corrosion, such as pitting, during fatigue. At an accelerated potential of 350 mV, the current responses show an increase in the current due to slip steps emerging to the surface as a result of fatigue. The crack-initiation site and the examination of the fracture morphology are discussed. This article is based on a presentation given in the symposium entitled “Deformation and Fracture from Nano to Macro: A Symposium Honoring W.W. Gerberich’s 70th Birthday,” which occurred during the TMS Annual Meeting, March 12–16, 2006 in San Antonio, Texas and was sponsored by the Mechanical Behavior of Materials and Nanomechanical Behavior Committees of TMS.

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Oxidation behaviour of metallic glass foams

In this study, the effects of porosity on the oxidation behaviour of bulk-metallic glasses were investigated. Porous Pd- and Fe-based bulk-metallic glass (BMG) foams and Metglas ribbons were studied. Oxidizing experiments were conducted at 70 °C, and around 80 °C below glass-transition temperatures, (T_gs). Scanning-electron microscopy/energy-dispersive spectroscopy (SEM/EDS) studies revealed little evidence of oxidation at 70 °C. Specimens exhibited greater oxidation at T_g - 80 °C. Oxides were copper-based for Pd-based foams, Fe-, Cr-, and Mo-based for Fe-based foams, and Co-based with borosilicates likely for the Metglas. Pd-based foams demonstrated the best oxidation resistance, followed by Metglas ribbons, followed by Fe-based foams.     

A hybrid computational strategy for identification of structural parameters

By identifying parameters such as stiffness values of a structural system, the numerical model can be updated to give more accurate response prediction or to monitor the state of the structure. Considerable progress has been made in this subject area, but most research works have considered only small systems. A major challenge lies in obtaining good identification results for systems with many unknown parameters. In this study, a non-classical approach is adopted involving the use of genetic algorithms (GA). Nevertheless, direct application of GA does not necessarily work, particularly with regards to computational efficiency in fine-tuning when the solution approaches the optimal value. A hybrid computational strategy is thus proposed, combining GA with a compatible local search operator. Two hybrid methods are formulated and illustrated by numerical simulation studies to perform significantly better than the GA method without local search. A fairly large structural system with 52 unknown parameters is identified with good results, taking into consideration the effects of incomplete measurement and noisy data.     

Surveying instructor and learner attitudes toward e-learning

The trend of using e-learning as a learning and/or teaching tool is now rapidly expanding into education. Although e-learning environments are popular, there is minimal research on instructors’ and learners’ attitudes toward these kinds of learning environments. The purpose of this study is to explore instructors’ and learners’ attitudes toward e-learning usage. Accordingly, 30 instructors and 168 college students are asked to answer two different questionnaires for investigating their perceptions. After statistical analysis, the results demonstrate that instructors have very positive perceptions toward using e-learning as a teaching assisted tool. Furthermore, behavioral intention to use e-learning is influenced by perceived usefulness and self-efficacy. Regarding to learners’ attitudes, self-paced, teacher-led, and multimedia instruction are major factors to affect learners’ attitudes toward e-learning as an effective learning tool. Based on the findings, this research proposes guidelines for developing e-learning environments.