Effects of Powder Processing on the Green Compacts of High-Purity BaTiO3

Two processing methods have been used to prepare different green compacts of high-purity BaTiO₃. The substructures of agglomerates have been examined by SEM, and the strength of the agglomerates was interpreted in a plot of the logarithm of the pressure versus the relative density, which is consistent with the structures of cut surfaces of green compacts. The Hg-penetration results have been used to compare the uniformity of the powder compacts. The wer method (wet milling and subsequent wet pressing) was used to produce uniform green compacts.     

Development of a four‐cell DMFC stack with air‐breathing cathode and dendrite flow field

A four‐cell direct methanol fuel cell (DMFC) stack with an air‐breathing cathode with an active area of 0.48 cm² for each cell is designed, fabricated and tested. A pure copper sheet 300 µm thick with innovative perforated flow plates (dendrite type) is fabricated and used for the cathode. For the anode, conventional serpentine flow channels made of pure copper sheets 250 µm thick are used. An extensive parametric study is conducted to determine the optimum working conditions for the fuel flow rate (anode), methanol solution concentration, channel‐to‐land ratio and stack temperature. Comparisons are made with conventional serpentine flow channels. In addition, CO₂ (water) bubbles in the anode (cathode) channels are visualized, and the results are presented and discussed. It is found that the maximum stack power of the four‐cell μDMFC stack is up to 40 mW/cm² with a limiting current density of 335 mA/cm² at a maximum volumetric and gravimetric power density of 11.16 mW/cm³ and 3.13 W/kg, respectively. Copyright © 2014 John Wiley & Sons, Ltd.     

Phase Equilibrium in the Ni-Ti-Zr System at 800 °C

The isothermal Ni-Ti-Zr phase diagram at 800 °C was constructed by means of 50 equilibrated alloys. Electron microprobe analyses were used to determine the phase compositions and phase relationships. There is one ternary phase Ni(Ti,Zr)₂ formed in the central region. Most of the Ni-Ti and Ni-Zr binary intermetallic phases show a large Zr or Ti solubility and extend to the ternary region. According to the results of DTA measurements, there are lower liquidus regions around the ternary phase due to the ternary phase reactions with the binary intermetallic phases. There is a potential region to form the bulk metallic glass.     

The effect of tenocyte/hyaluronic acid therapy on the early recovery of healing Achilles tendon in rats

The aim of this study was to explore the potential for a better recovery outcome for the Achilles tendon at an early healing stage when a mixed biomaterial-tenocyte injection is used. The experimental animals underwent single limb Achilles tendon transection followed by suturing repair. A solution of either hyaluronic acid with or without tenocytes or normal saline was randomly chosen to be injected around the injury site after surgery. To obtain the comprehensive recovery condition of the rats on different management protocols, the animals were evaluated histologically, mechanically, and functionally. A significant difference in the recovery condition was found in the injured tendon injected with the hyaluronic acid solution with tenocytes compared with the other groups. Tendon stiffness and the locomotion abilities of the rats with healing Achilles tendons were improved in the hyaluronic acid with tenocyte transplantation group. The acceleration of the inflammatory phase in rats with the hyaluronic acid with tenocyte injections might be the major reason for the better functional outcomes.     

Characteristics of electrolyte supported micro-tubular solid oxide fuel cells with GDC-ScSZ bilayer electrolyte

In this study, a gadolinia-doped ceria (GDC)-supported micro tubular SOFC (T-SOFC) was fabricated using extrusion and dip-coating techniques (Cell A). The effects of inserting a scandium-stabilized zirconia (ScSZ) layer as an electron blocking layer between the GDC layer and the GDC-Ni anode layer were also explored (Cell B). The microstructures and electrochemical performances of Cell A and Cell B were investigated and compared. The layer thicknesses of the GDC and ScSZ bi-layer electrolytes were approximately 285 μm and 8 μm respectively. With the inserted ScSZ layer, both the ohmic resistance and the polarization resistance significantly increased at all the operating temperatures. The increase in the ohmic resistance of Cell B was predominantly due to the interfacial resistance, while the substantial escalation in the polarization resistance was mainly because of the low bulk oxygen diffusion process in the ScSZ layer and the smaller charge transfer processes occurring at the interfaces. The OCV of Cell B showed a slight decrease from 1.06 to 0.98 V and that of Cell A experienced an obvious decline from 0.92 to 0.76 V as the temperature rose from 650 to 800 °C. The ScSZ layer of Cell B successfully inhibited the OCV loss caused by the electronic conduction in GDC. The maximum power densities (MPDs) of Cell A at 650, 700, 750, and 800 °C were 0.20, 0.27, 0.33, and 0.36 Wcm⁻², and those of Cell B 0.16, 0.23, 0.32, and 0.42 Wcm⁻². The MPD of Cell B was improved at temperatures above 750 °C but remained inferior to that of Cell A below 750 °C. This is due to the fact that, as operating temperature increased above 750 °C, the benefit of the higher OCV in Cell B surpassed the deficiency of the higher cell resistance, thereby leading to a higher MPD.     

Effects of anode and cathode perforated flow field plates on proton exchange membrane fuel cell performance

The effects of both anode and cathode perforated flow field configurations on proton exchange membrane fuel cell performance are studied herein through electrochemical polarization techniques, electrochemical impedance spectroscopy, and cyclic voltammetry. The results demonstrate that serpentine flow field configuration in both anodes and cathodes is the best arrangement for cell performance (serpentine/serpentine, perforated/perforated, and serpentine/perforated). An electrochemical impedance spectroscopy examination shows that the serpentine/serpentine flow plate configuration results in a significant reduction in charge transfer resistance in a high current density (low voltage) regime. It further indicates that in a serpentine/serpentine flow pattern, a maximum electrochemical area is obtained with a higher Pt utilization of about 70% and is secured with full hydration at a cell temperature of 80°C. Finally, energy and exergy efficiencies analyses were also made. Data have been extracted and presented. Copyright © 2013 John Wiley & Sons, Ltd.     

Verification Approach of Metropolis Design Framework for Embedded Systems

In this paper, we focus on the verification approach of Metropolis, an integrated design framework for heterogeneous embedded systems. The verification approach is based on the formal properties specified in Linear Temporal Logic (LTL) or Logic of Constraints (LOC). Designs may be refined due to synthesis or be abstracted for verification. An automatic abstraction propagation algorithm is used to simplify the design for specific properties. A user-defined starting point may also be used with automatic propagation. Two main verification techniques are implemented in Metropolis the formal verification utilizing the model checker Spin and the simulation trace checking with automatic generated checkers. Translation algorithms from specification models to verification models, as well as algorithms of generated checkers are discussed. We use several case studies to demonstrate our approach for verification of system level designs at multiple levels of abstraction.     

Mountain c-regressions method

Since Quandt [The estimation of the parameters of a linear regression system obeying two separate regimes, Journal of the American Statistical Association 53 (1958) 873-880] initiated the research on 2-regressions analysis, switching regression had been widely studied and applied in psychology, economics, social science and music perception. In fuzzy clustering, the fuzzy c-means (FCM) is the most commonly used algorithm. Hathaway and Bezdek [Switching regression models and fuzzy clustering, IEEE Transactions on Fuzzy Systems 1 (1993) 195-204] embedded FCM into switching regression where it was called fuzzy c-regressions (FCR). However, the FCR always depends heavily on initial values. In this paper, we propose a mountain c-regressions (MCR) method for solving the initial-value problem. First, we perform data transformation for the switching regression data set, and then implement the modified mountain clustering on the transformed data to extract c cluster centers. These extracted c cluster centers in the transformed space will correspond to c regression models in the original data set. The proposed MCR method can form well-estimated c regression models for switching regression data sets. According to the properties of transformation, the proposed MCR is also robust to noise and outliers. Several examples show the effectiveness and superiority of our proposed method.     

Effect of Metallic-Coating Properties on the Tribology of Coated and Oil-Lubricated Ceramics

Friction and wear behavior was determined for zirconia ceramics lubricated with solid coatings (Ag, Au, and Nb) deposited by ion-beam-assisted-deposition (IBAD) techniques, and a polyol-ester-based synthetic oil. Although the use of soft Ag and Au coatings as solid lubricants in conjunction with the synthetic oil significantly reduced the fiction and wear under boundary lubrication at temperatures up to 250°C, these films had poor durability. In contrast, the Nb coating was more durable in terms of chemical reactivity and adhesion during the tribo-tests than were the Ag or Au films. However, the friction and wear behavior of the Nb-coated zirconia was poorer than that of the ceramics coated with Ag or Au.     

Cellulose nanocrystals and self-assembled nanostructures from cotton, rice straw and grape skin: a source perspective

Cellulose nanocrystals (CNCs) have been derived by sulfuric acid hydrolysis (64–65 wt% H₂SO₄, 10 mL/g cellulose, 45 °C) of pure cellulose isolated from cotton, rice straw and grape skin, producing relatively consistent products in 60, 45 and 30 min, respectively, and generally reflecting the extent of crystallinity and crystallite sizes of these cellulose sources. CNCs in nanorod forms are observed from all three cellulose sources and, in the case of cotton and grape skin, in the presence of more dominant forms of nanoparticles. Cotton CNCs are <10-nm-wide nanorods at up to 40 aspect ratios, whereas rice straw CNCs are flat ribbon cross-sectional shaped in 10:2:1–44:5:1 length/width/thickness ratios, and those from grape skin are abundant nanoparticles but fewer nanorods, all of very different nanoscale dimensions. Freezing (?196 °C) and freeze-drying (?50 °C) of dilute CNC suspensions induce self-assembling of these CNC populations into yet further distinctly different morphologies. Self-assembled cotton CNCs are loosely organized nanorods and nanospheres, whereas grape skin CNCs are mainly nanospheres of 5-nm-sized nanoparticles clusters around nanorod cores. Uniquely, rice straw CNCs assembled anisotropically into ultra-thin non-porous fibers. These source-linked unique CNC geometries and the ability of CNCs to self-assemble into different morphologies present wide ranging dimensions of these renewable cellulose nanomaterial building blocks from by-products of the world largest fiber, cereal and fruit crops.