High sensitivity nanostructure incorporated interdigital silicon based capacitive accelerometer

Interdigital structures are realized on silicon substrates with high sensitivity to acceleration. The process employs a combination of anisotropic back-side micromachining with front-side vertical deep reactive ion etching of silicon. The incorporation of silicon-based nano-structures on the vertical planes of fingers leads to a significant increase in the capacitance of the device from 0.45 for simple planes to 40 pF for the nano-structured planes. Such structures show high sensitivity to inclination and accelerations, which could be due to field emission of electrons from nano-metric features. Around 8% change in the capacitance is observed upon a tilting sensor from 0° to 90° angle, which makes it proper for possible use as an earthquake sensor. A preliminary model for the capacitance and its dependence on the measurement voltage is presented.     

Shear testing of thick adhesive layers using the ENF-specimen

An existing experimental method to determine cohesive laws for adhesive layers loaded in shear is further developed. The method is based on differentiation of the energy release rate (ERR) with respect to the adhesive shear deformation at the crack tip. The test geometry used is an ENF-specimen for which the adherends are assumed to deform linearly elastic. The original method is expanded to account for situations where the thickness of the adhesive layer is not negligible as compared to the adherend thickness. To this end, a novel mathematical expression for the energy release rate (ERR) is derived. No assumptions on the form of the cohesive law are made; it is implicitly included in the derivation. The expression for the ERR contains the applied load and the shear deformation of the adhesive layer at the initial position of the crack tip, in addition to geometrical properties and the elastic modulus of the adherend material. Numerical simulations are performed to verify the accuracy of the mathematical expression for the ERR. Preliminary results from experiments performed on an epoxy adhesive are presented. The cohesive law of the adhesive layer is extracted by using a blunted crack tip. Verifying simulations confirm that the local pre-fracture behavior is accurately captured.     

Structure,spectroscopic properties and laser performance of Nd:YNbO4 at 1066 nm

We have demonstrated continuous wave (CW) laser operation of Nd:YNbO₄ crystal at 1066 nm for the first time. A maximum output power of 1.12 W with the incident power of 5.0 W is successfully achieved corresponding to an optical-to-optical conversion efficiency of 22.4% and a slope efficiency of 24.0%. The large absorption cross section (8.7 × 10⁻²⁰ cm²) and wide absorption band (6 nm) at around 808 nm indicates the good pumping efficiency by laser diodes (LD). The small emission cross section (29 × 10⁻²⁰ cm²) and relative long lifetime of the ⁴F_3/2 → ⁴I_11/2 transition indicates good energy storage capacity of Nd:YNbO₄. Moreover, the raw materials of Nd:YNbO₄ are stable, thus, it can grow high-quality and large-size by Czochralski (CZ) method. Therefore the Nd:YNbO₄ crystal is a potentially new laser material suitable for LD pumping.     

Effects of severe blockage on heat transfer from a sphere in power-law fluids

The momentum and thermal energy equations describing the forced convection heat transfer from a heated sphere settling at the axis of a long cylindrical tube filled with a power-law fluid have been solved numerically. The extensive new results reported herein encompass wide ranges of conditions as: Reynolds number, 1 ≤ Re ≤ 100; Prandtl number, 5 ≤ Pr ≤ 100, power-law index, 0.2 ≤ n ≤ 2 and blockage ratio, 0.5 ≤ λ ≤ 0.95. The range of values of the power-law index (n) used here include both the shear-thinning (n < 1) and shear-thickening (n > 1) fluid behaviours. The overall heat transfer is strongly modulated by Re, n and λ depending upon whether the recirculation region is formed in the rear of the sphere and/or on the proximity of the tube wall. Furthermore, the results reported herein elucidate the effect of the type of thermal boundary condition (isothermal or isoflux) on the surface of the sphere as well as that of the velocity profile (uniform or fully developed Poiseuille profile) in the tube. Overall, the average Nusselt number bears a positive dependence on the Reynolds and Prandtl numbers and blockage ratio. The shear-thinning behaviour (n < 1) augments heat transfer over and above the corresponding Newtonian value whereas shear-thickening behaviour (n > 1) adversely influences it. The present numerical results (~ 4000 data) have been consolidated by incorporating the blockage factor into an existing expression valid for λ = 0 for Newtonian fluids.     

Fuzzy MCDM framework for locating a nuclear power plant in Turkey

Turkey has recently initiated a project to revise its nuclear policy. The revised nuclear energy policy considers searching for possible alternative locations for future nuclear power plants in Turkey. At the most basic level, the public cannot accurately evaluate whether it is willing to support nuclear energy unless it has an idea about where the power plants are likely to be located. It is argued that the selection of a facility location is a multi-criteria decision-making problem including both quantitative and qualitative criteria. In this research, given the multi-criteria nature of the nuclear facility location selection problem, a new decision tool is proposed to rank the alternative nuclear power plant sites in Turkey. The proposed tool is based on fuzzy Entropy and t norm based fuzzy compromise programming to deal with the vagueness of human judgments. Finally, a discussion and some concluding remarks are provided.     

Graphene–Gold Nano-ring antenna for Dual-resonance optical application

To achieve dual resonance qualification, we are suggested a sub-wavelength dual-ring Nano-antenna based on combination of Graphene and gold where Nano-Antenna with dual-resonance is attractive for spectroscopy and bio-sensing applications. The result shows that with these structures, we could be achieved dual-resonance characteristic of Infra red (IR) and optical regime. In addition, by biasing of the Graphene, we are attained a reconfigurable characteristic for our second resonance. Therefore, in this current research, the extinction, reflection and absorption cross section are studied for every structure and formation. For modeling the prototype Nano-antenna, SiN Substrate is selected with refractive index of 1.98 and silver with Palik optical characteristic for metal layer is modified. Simulation has been done with FDTD method. Of course, because of symmetry of the structure, the prototype Nano-antenna has similar manner for vertical or horizontal polarization. As a result, proposed Nano-antenna is useful for THz medical spectroscopy with simple method of designing and second frequency controlling only with graphene biasing. Here, we are debated about graphene placement and biasing interaction on the bonding and anti-bonding mode where we show that the gold and graphene interaction will affect on E-field distribution by making dipole or quad resonance.     

浅谈工件的重复定位

工件定位4种方式中的重复定位,是教学难点之一。针对学生存在的问题,提出增加定位分析习题课等方法,帮助学生很好地掌握工件在夹具中定位的知识。     

Quasi-isotropic bending responses of metallic sandwich plates with bi-directionally corrugated cores

In order to reduce anisotropic behaviors of sandwich plates with open channel cores under the bending load, bi-directionally corrugated cores were introduced. Bi-directionally corrugated core has two additional design parameters related with a corrugation pass than uni-directionally corrugated core, so that its properties with respect to core orientations can be controlled. Sandwich plate with bi-directionally corrugated core is designed optimally so that beam buckling of face sheets is reduced drastically and anisotropic buckling behavior in the face sheets is minimized. The cores fabricated by a sectional forming process were bonded with face sheets by adhesive bonding. Three-point bending experiments were carried out with respect to core orientations. It has been shown from the experiments that sandwich plates with bi-directionally corrugated cores exhibit quasi-isotopic bending behaviors and structural performances in sandwich plates.