Evaluation on wear behavior of Cr-Ag-N and Cr-W-N PVD nanocomposite coatings using two different types of tribometer

Practice has proven that CrN performs better than TiN under some specific tribological applications. Nevertheless, the relatively soft nature of CrN still remains a problem. This paper reports experimental results on increases in hardness of sputtered PVD CrN coatings by means of additions of varying content of Ag or W. The resulting Cr-Ag-N and Cr-W-N coatings, grown on JIS SKH51 steel substrates, were characterized using SEM, EDS, WDS, XRD, micro-indentation hardness testing and scratch adhesion tests. Moreover, wear behavior was studied on two types of tribometer, employing different contact regimes — a ‘cylinder-on-disk’ line-contact reciprocating-sliding regime and a ‘ball-on-disk’ point-contact rotating-sliding regime.The experimental results can be summarized as follows: The hardness of Cr-W-N coatings increased with increasing W content; reversely, that of Cr-Ag-N coatings decreased with increasing Ag content. The additions of Ag and W resulted in a formation of secondary phases, elemental Ag and WN, respectively, uniformly embedded in the CrN coatings. With the two different types of tribometer, the observed trends for wear behavior, wear and friction coefficient, were nearly identical, indicating that both Ag and W additions to CrN coatings were beneficial. However, the Cr-W-N coatings were significantly more wear resistant than the Cr-Ag-N coatings. With the addition of W at 6.8 at.%, the largest wear improvement of 73%-85% was achieved.     

REACTIVE DIFFUSION BETWEEN Si AND NbC AT 1300℃

ＲＥＡＣＴＩＶＥＤＩＦＦＵＳＩＯＮＢＥＴＷＥＥＮＳｉＡＮＤＮｂＣＡＴ１３００℃Ｃ．Ｒ．Ｋａｏ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｃａｌＥｎｇｉｎｅｅｒｉｎｇＮａｔｉｏｎａｌＣｅｎｔｒａｌＵｎｉｖｅｒｓｉｔｙＣｈｕｎｇＬｉ，Ｔａｉｗａｎ）Ｊ．Ｗｏｏｄｆ...     

Phase equilibria of the cu-in system II: Thermodynamic assessment and calculation of phase diagram

The phases in the Cu-In binary were modelled thermodynamically using the Redlich-Kister expression for the Gibbs energies of the solution phases, the Wagner-Schottky model for those of the η (η)’)-Cu₂ln phase (taking η and η)’ to be a single phase), and assuming line compound behavior for the other intermetallic phases. The model parameters were obtained using primarily the thermodynamic data, as well as the phase equilibrium data. The thermodynamic values for the various phases calculated from the models are in reasonable agreement with the experimentally determined thermodynamic data that are available in the literature. The entropies of melting for the intermetallic phases obtained from the models are in accord with the values calculated from the empirical formulas suggested by Kubaschewski. The calculated phase diagram is also in reasonable agreement with the experimentally determined diagram, with the calculated temperatures for all the invariant equilibria within 1°C of the experimental values. The discrepancies between the calculated and experimental phase boundaries at the invariant temperatures are less than 1 at.% except those involving βCu₄Inn and γCu₇ln₃. These two phases were taken to be line compounds in the present study, although experimentally they exist over appreciable ranges of homogeneity. Current address: Dept. of Chemical Engineering, National Tsing Hua University, Taiwan.     

Enhancing the accuracy of WLAN-based location determination systems using predicted orientation information

Indoor location determination has emerged as a significant research topic due to the wide-spread deployment of wireless local area networks (WLANs) and the demand for context-aware services inside buildings. However, prediction accuracy remains a primary issue surrounding the practicality of WLAN-based location determination systems. This study proposes a novel scheme that utilizes mobile user orientation information to improve prediction accuracy. Theoretically, if the precise orientation of a user can be identified, then the location determination system can predict that user’s location with a high degree of accuracy by using the training data of this specific-orientation. In reality, a mobile user’s orientation can be estimated only by comparing variations in received signal strength; and nevertheless the predicted orientation may be incorrect. Incorrect orientation information causes the accuracy of the entire system to decrease. Therefore, this study presents an accumulated orientation strength algorithm which can utilize uncertain estimated orientation information to improve prediction accuracy. Implementation of this system is based on the Bayesian model, and the experimental results indeed show the effectiveness of our proposed approach.     

Elliptical trough reflector for the collection of light from linear sources

A trough reflector with a reflective, truncated elliptical surface was designed to efficiently collect freely propagating light from a linear source. The source was placed at one focus of the reflector, and light was collected through a rectangular aperture near the second focus. Collection efficiency was much greater than that of a spherical integrator and approximately 6.5x greater than that of an objective lens; as much as approximately 55% of the light could be captured from the full aperture. This reflector could be used to efficiently collect surface fluorescence excited by use of evanescent waves in fluorescence-based fiber optic or capillary waveguide sensors.     

Polarization-Dependent Periodic Pulse Oscillation in a Diode-Laser-Pumped and Intracavity Frequency-Doubled Nd:YVO 4 Laser

We demonstrate that two cross-polarized longitudinal modes can have 50% higher conversion efficiency than two parallel-polarized longitudinal modes in a diode-laser-pumped and intracavity frequency-doubled Nd:YVO(4) laser when operated under periodic pulse oscillation. Through simulations of the rate equations for primary frequency intensities and gains, we also verify that this effect can be attributed to gain competition and complementary conversion coefficient between second-harmonic and sum-frequency generations.     

Mixed films of TiO(2)-SiO(2) deposited by double electron-beam coevaporation

We used double electron-beam coevaporation to fabricate TiO(2)-SiO(2) mixed films. The deposition process included oxygen partial pressure, substrate temperature, and deposition rate, all of which were real-time computer controlled. The optical properties of the mixed films varied from pure SiO(2) to pure TiO(2) as the composition of the films varied accordingly. X-ray diffraction showed that the mixed films all have amorphous structure with a SiO(2) content of as low as 11%. Atomic force microscopy showed that the mixed film has a smoother surface than pure TiO(2) film because of its amorphous structure.

Linear and Bruggeman's effective medium approximation models fit the experimental data better than other models.

     

Global exponential robust stability of reaction–diffusion interval neural networks with continuously distributed delays

This paper considers the existence of the equilibrium point and its global exponential robust stability for reaction-diffusion interval neural networks with variable coefficients and distributed delays by means of the topological degree theory and Lyapunov-functional method. The sufficient conditions on global exponential robust stability established in this paper are easily verifiable. An example is presented to demonstrate the effectiveness and efficiency of our results.