Wear behavior of self-lubricating Fe-Cr-C-Mn-Cu alloys: Smearing effect of second phase particles

Newly developed self-lubricating Fe-Cr-C-Mn-Cu cast composite alloys were investigated to study the role of Cu-rich second phase particles which smear on the wear surface during sliding. The wear resistance of the material was improved with an increasing copper concentration. The improved wear resistance was probably obtained by forming a protective tribofilm, which prevented metal-to-metal contact through smearing of the embedded Cu-rich second phase particles. This formation of protective oxide films during sliding is likely to improve the wear resistance of austenitic Fe-Cr-C-Mn-Cu cast composite alloys.     

Modeling of thermal creep behavior in Zr-1.1Nb-0.05Cu alloys

The power-law dependency is suitable for describing the thermal creep behavior of modern zirconium alloys. In contrast to the previous phenomenological and empirical models, mechanistic approaches with power-law relations were made to explain the creep rates of the Zr-1.1Nb-0.05Cu alloy. For the modeling, the experimental stress and temperature parameters were varied according to the operating conditions of nuclear power plants. It was observed that the creep was controlled by the dislocation glide and climb mechanism. The proposed model explained the experimental data well, and was able to estimate the creep rates for elongated times.     

Tuning the electronic band structure of PCBM by electron irradiation

Tuning the electronic band structures such as band-edge position and bandgap of organic semiconductors is crucial to maximize the performance of organic photovoltaic devices. We present a simple yet effective electron irradiation approach to tune the band structure of [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM) that is the most widely used organic acceptor material. We have found that the lowest unoccupied molecular orbital (LUMO) level of PCBM up-shifts toward the vacuum energy level, while the highest occupied molecular orbital (HOMO) level down-shifts when PCBM is electron-irradiated. The shift of the HOMO and the LUMO levels increases as the irradiated electron fluence increases. Accordingly, the band-edge position and the bandgap of PCBM can be controlled by adjusting the electron fluence. Characterization of electron-irradiated PCBM reveals that the variation of the band structure is attributed to the molecular structural change of PCBM by electron irradiation.     

Antiproliferative and antioxidant properties of anthocyanin-rich extract from açai

An anthocyanin-rich extract, generated from açai (AEA), was investigated for its antioxidant properties and antiproliferative activity against C-6 rat brain glioma cells and MDA-468 human breast cancer cells. AEA has an ORAC value of 2589 μmoles trolox equivalents (TE)/g dried powder and a DPPH radical-scavenging activity of 1208 μmoles TE/g, suggesting that AEA is an exceptional source of natural antioxidants. In addition, AEA remarkably suppresses proliferation of C-6 rat brain glioma cells, but has no effect on the growth of MDA-468 human breast cancer cells. Further experiments demonstrated that the AEA treatment dose-dependently inhibited the growth of C-6 rat glioma cells with an IC₅₀ of 121 μg/ml. The DNA ladder fragmentation results indicated that AEA induced apoptosis of C-6 rat brain glioma cells. To compare açai with other anthocyanin-rich extracts, a number of berry extracts, including blueberry, strawberry, raspberry, blackberry and wolfberry, were assessed for potential antiproliferative activity against C-6 rat brain glioma cells. However, none of them showed suppressing effect. The results suggest that the active antiproliferative constituents in AEA are unlikely to be anthocyanins normally found in common berries.     

Investigation on the valence state of Te ions in the Bi6Ti5TeO22 thin film using X-ray photoelectron spectroscopy

Bi₆Ti₅TeO₂₂ (BTT) thin films were grown on a Pt/Ti/SiO₂/Si(1 0 0) substrate under various conditions and the valence state of the Te ion was investigated. For the BTT films grown at 300 °C, most of the Te ions existed as Te⁴⁺ ions. However, for the 10 mol% Mn-added BTT films grown at 300 °C, Te⁶⁺ ions were found even in the film grown under low oxygen partial pressure (OPP) and their number increased with increasing OPP. This increase was attributed to the presence of Mn²⁺ ions, which assisted the transition of Te⁴⁺ ions to Te⁶⁺ ions in order to maintain the charge balance of the Ti⁴⁺ sites. Furthermore, in the films grown at 300 °C under a high OPP of 80.0 Pa and subsequently annealed at 600 °C under a high oxygen pressure of 101 kPa, most of the Te ions existed as Te⁶⁺ ions. However, for the film grown at 300 °C under low OPP, even though the film was annealed under a high oxygen pressure of 101 kPa, only a few of Te⁶⁺ ions were formed, whereas most of Te ions remained as the Te⁴⁺ ions.     

Experimental study of inelastic buckling strength and stiffness requirements for longitudinally stiffened panels

An experimental study was conducted in order to verify a proposed equation for the minimum required stiffness for longitudinal stiffeners attached on compression plates. Nine test specimens of stiffened plates were fabricated and tested to their ultimate strengths. Test results are compared with the maximum strengths predicted for stiffened plates by finite element analysis and by the proposed SSRC type critical stress curve. Fairly good correlations were observed, thereby confirming experimentally the adequacy of the proposed equation for the minimum required stiffness of the longitudinal stiffener attached to the compression panel and a modified SSRC type critical stress curve encompassing both the buckling ranges of plastic yield and the transition zones. A set of conclusions is drawn from the experimental studies as to the buckling behaviors of stiffened plates.     

Crystallization of amorphous silicon thin film by using a thermal plasma jet

Amorphous silicon (a-Si) films deposited on glass substrates were crystallized using a thermal plasma jet and the treated films are analyzed to find the relationship between plasma characteristics and crystallization process conditions. The crystallization process conditions were found to have different optimal operating regimes depending on the nozzle geometry. Numerical analysis of the thermal plasma jets showed that the different operating regimes for crystallization were caused by modifications of the plasma characteristics by the nozzle geometry. It is revealed that a stepped-divergent nozzle is more efficient for the thermal plasma annealing process than the conventional cylindrical one due to the broadened high-temperature region and the lowered axial velocity in the plasma jet.     

Image interpolation using MLP neural network with phase compensation of wavelet coefficients

When interpolating images in the wavelet domain, the main problem is how to estimate the finest detail coefficients. Wavelet coefficients across scales have an interscale dependency, and the dependency varies according to the local energy of the coefficients. This implies the possible existence of functional mappings from one scale to another scale. If we can estimate the mapping parameters from the observed coefficients, then it is possible to predict the finest detail coefficients. In this article, we use the multilayer perceptron (MLP) neural networks to learn a mapping from the coarser scale to the finer scale. When exploiting the MLP neural networks, phase uncertainty, a well-known drawback of wavelet transforms, makes it difficult for the networks to learn the interscale mapping. We solve this location ambiguity by using a phase-shifting filter. After the single-level phase compensation, a wavelet coefficient vector is assigned to one of the energy-dependent classes. Each class has its corresponding network. In the simulation results, we show that the proposed scheme outperforms the previous wavelet-domain interpolation method as well as the conventional spatial domain methods.