Applied Mechanics and Materials Vols. 110-116

Abstract: To find a kind nanoparticles can be used as additive in lubricants, oil-soluble calcium borate nanoparticles were prepared in the present of Na₂B₄O₇.10H₂O, CaCl₂, and oleic acid as modifier by in-situ method, and the effects of different reaction conditions on the coil-solubility of the nanoparticles were investigated. The results indicate that the surface of calcium borate was altered from hydrophilicity to hydrophobicity after the modification with oleic acid, and so the nanoparticles possess high solubility in mineral base oils. Moreover, TT-IR confirms that the bond of oleic acid onto the surface of calcium borate nanoparticles exists.

Abstract: This paper studies coupling between localized surface plasmons in metal nanoparticle waveguides of different materials and sizes, and then discusses another nanostructure, nanoshells, that support localized plasmons, and closes with conclusions in a variety of situations.

Abstract: FDTD method is used to simulate SPPs in the Kretschmann structure. It is observed that the surface plasmon wave propagates not only with the attenuation but also with the oscillation. This paper explains the reasons for this phenomenon: the oscillation is caused by coupling of SPPs in the metal - air interface and dielectric - metal interface.

Abstract: To obtain a understanding of the deform mechanism and ideal strength in superhard nanocomposites nc-TiN/a-BN. we studied, using the first-principles calculation method, the geometrical stucture, the electronic density and the tensile stress-strain response of a theoretical interfacial system TiN/BN/TiN, which consists of two TiN slabs and one sandwiched BN monolayer. The calculated results show that Friedel oscillations weaken the Ti-N interplanar bonds next to the interface, where decohesion happens. A comparison with the TiN/SiN/TiN interface was done, showing that the orientation has the huger influence on the tensile strength of TiN/BN/TiN interface.

Abstract: We demonstrate self-collimation phenomena based on a new type of photonic crystals made of square lattice with ring shaped holes. The plane wave expansion (PWE) method is used to get the three dimensional band diagram and equi-frequency of the second band which displays the self-collimation phenomena for the structure we proposed in this paper. The collimation angle is mainly depending on the maximum flatness half width (MFHW) of the equi-frequency. The FDTD method is employed to demonstrate the electric field amplitude distributions for the collimation phenomena. Partly, in order to achieve high efficient coupling of the input and output port, we modify both surface structures to modulate the wave-front to obtain desired effect. The parameter of the input surface is modified which will prevent the production of surface modes which takes away the EM power and enhance the transmittance. For a square lattice with the modified parameters at each side of the input surface, the surface modes are suppressed to couple with the continuum of the dielectric waveguide modes. More importantly, they might have potential application in integrated optical circuits.

Abstract: A new synthesis of Ag @ Au core-shell composite nanoparticles (NPs) was described by spontaneous deposit Au on the surface of Ag seeds which were prepared with the photochemical method in sodium citrate solution. The Ag core @ Au shell (or Ag core @ Au-Ag alloy shell) composite NPs with monodisperse and uniform shape were about 10 nm. The core/shell nanostructure was confirmed by UV-vis spectrum and TEM characterization as well as cyanide ion (CN-) dissolution experiment. The reaction mechanism of forming Ag @ Au composite NPs was briefly discussed.

Abstract: New techniques that can control Casimir forces in nanosacle structures may soon ensure the physical realization of switchable Casimir-force devices. In order to provide useful insights into the behaviour of this class of switches, the idea of Casimir-force actuation window has been proposed here to assist in the design of such switches. The influence of surface effects including residual surface stress and surface elasticity on the pull-in parameters of Casimir actuated switches has been demonstrated. These effects, together with other currently known difficulties due to uncertainties such as surface roughness and trapped electric charge may hinder the realization of this class of devices. An Euler-Bernoulli beam model has been employed to demonstrate surface effects in a nanocantilever switch, and numerical solutions employing a finite difference approach have been obtained for the static bending of this switch. The results demonstrate that surface effects play a significant role in the selection of basic design parameters of Casimir actuated switches, such as static deflection and detachment length. Threshold value of residual surface stress is also studied for these switches. The predictions reveal that exclusion of surface effects in Casimir-force actuation window may result in non-functional switch designs.

Abstract: A highly loaded high-pressure turbine with a supersonic nozzle guide vane and a transonic rotor for a Variable Cycle Engine (VCE) has been investigated. Film cooling strategies were designed for the whole stage, during which the positions, injection orientations and arrangements of cooling holes were confirmed. Three-dimensional steady numerical simulations have been performed in the two operation modes of low and high bypass ratio with different thermodynamic cycle parameters according to the VCE and the coolant injections have been simulated by means of additional source term method. The influences of coolant injections in the fully cooled turbine stage on aerodynamic performance and flow characteristics have been analyzed. The results indicate that, the supersonic nozzle guide vane, over-expansion degree of main flows, fluctuations of static pressure and intensity of corner vortex are lessened or alleviated. In the transonic rotor, expansion and doing work capabilities in the mixed fluid are strengthened. Proper coolants injections are beneficial to the flow characteristics in the blade passage.

Abstract: Exergy analysis permits meaningful efficiencies to be evaluated for a system or process, and the sources, causes and locations of thermodynamic losses to be determined. This study presents exergetic modeling of a small turbojet engine via exergetic response surfaces. Turbojet engine consists of an inlet, a centrifugal compressor, reverse flow combustion chamber, axial-flow turbine and exhaust nozzle. The flight Mach number and altitude are examined on the exergetic efficiencies of total engine performance. The results of analysis are given as three dimensional exergetic response surface plots related to these operating parameters.

Abstract: Oil analysis technique is used as predictive and proactive tools to identify the wear modes of rubbing parts and to diagnose the faults in machinery. In this paper, the wear behavior of diesel engines, especially on oil analysis, is studied based on condition data. In terms of analyzing historical data, descriptive statistics is used as data mining tools to find the relationship between condition factors of the machine and its final status. The equipments have been monitored in two different environments which are: plantation-forestry, and general construction. Based on this relationship a specific baseline is achieved for selected sets of equipment in their specific conditions. A striking result is that the new baseline for each material is different significantly in each condition, which shows that for each condition making a specific baseline is essential.