Low crosstalk 4 × 4 TiLiNbO3optical switch with permanently attached polarization maintaining fiber array

Several low crosstalk 4 × 4 crossbar optical switch arrays have been fabricated for use atlambda = 1.3 mum. Each array consists of 16 independently functioning directional coupler switches. We describe the typical device performance characteristics. The average insertion loss is 5.2 dB. Crosstalk levels routinely measured < -35 dB. The voltage required to operate the device is ≈ 13 V. The inputs to one of the device arrays were permanently attached to four laser transmitters using lensed polarization maintaining fiber at the laser end and an array of polarization maintaining fibers at the device end.     

Flexural properties of sawdust reinforced phenolic composites: Pilot study

The advantageous properties of sawdust and phenolic resins were combined by making sawdust reinforced phenolic composites with different percentages by weight of sawdust. The sawdust was divided into three grades in accordance with its particulate size. Garamite and propylene glycol were added individually and together to enhance the flexural properties of the composites obtained. Without any garamite and propylene glycol, it was discovered that the best flexural properties of the composites were obtained when the percentage by weight of sawdust (<300 μm) is up to 15%. Beyond this, the flexural properties dropped significantly; in addition, the fluidity of the composite was very low and the mixture was not suitable for casting. In general, the flexural modulus of the composites decreases with an increase in sawdust content, i.e., they are more elastic but their maximum flexural strain does not improve. Garamite was therefore added to improve the maximum flexural strains of the composites and this was successful. The addition of propylene glycol makes the composite more plastic. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Formation of interfacial brittle phases sigma phase and IMC in hybrid titanium-to-stainless steel joint

The microstructures of the brazed joints for commercially pure Ti and stainless steel were investigated by the applications of various filler alloys including Ag-, Ti-, Zr- and Ni-based alloys. Generally, the dissimilar joints between Ti and stainless steel were dominated by the Ti-based intermetallic compounds (IMCs), e.g. (Ti, Zr)2(Fe, Ni), TiFe, TiCu, and Ti2(Fe, Ni), due to a significant dissolution of Ti from the base metal. The (Fe-Cr) σ phase was also observed near the stainless steel due to a segregation of Cr into the interface region. This research demonstrates empirically that the brittleness of the Ti and stainless steel joint can not be avoided only by applying single braze alloy or single insert metal, and thus an introduction of additional suitable interlayer between the filler alloy and the base metal is necessary to prevent the brittleness of the joint.     

The Status and Trend of Water Pollution Control Technology in China

ABSTRACT

The feasibility of predicting total summer crop water use by grassland, based on early or pre-season soil moisture reserves, was investigated. Tests were based on the correlation over time between simulated soil moisture and related variables at six South African climate stations. A weather driven computer budget model was used to simulate daily soil moisture reserves. Results indicate that early prediction of seasonal crop water use is not feasible, but that deep soil moisture is stable enough over time to be a reliable monitoring variable for crop growing conditions. Moisture stored in the deep soil has good potential for monitoring more severe drought conditions.     

Effect of extrinsic impedance and parasitic capacitance on figure of merit of RF MOSFET

This paper investigates the impact of source/drain impedance, gate-to-bulk capacitance, and gate resistance on device properties from 0 to 50 GHz for 0.13-/spl mu/m MOSFETs. Better device characteristics (g/sub m/ and C/sub gg/) can be found on MOSFETs with lower metal (or source/drain) resistance. But the best frequency characteristics (f/sub T/ and f/sub max/) occurred on MOSFETs with medium metal (or source/drain) resistance due to the increased interconnection capacitances. For radio frequency MOSFETs with finger-gate structure, better high-frequency behavior occurred on devices with medium finger-gate width W/sub f/ because of the tradeoff between gate (or source/drain) resistance and parasitic capacitance.     

Spiral grain—An adaptation of trees to withstand stem breakage caused by wind-induced torsion

Expressions are derived for the internal mechanical stress components in trees when exposed to bending and torsion by wind forces. The crown is modeled as rectangular, and the stem taper so that the maximum bending stress is equal at all heights. Trees with asymmetric crowns will undergo torsion as well as bending, and the shear stresses associated with torsion are determined and compared to the bending stresses. The results show that shear failure is likely to occur relatively high up on the stem when the crown asymmetry is a few decimeters. The fact that torsion might be critical to the strength of trees towards wind forces, introduces an explanation to spiral grain growth. It is shown that spiral grain in the direction of the wind-induced torque improves the bending strength of the tree. Spiral grain is therefore beneficial for trees with a prevailing external torque.     

Untersuchungen zum Einfluß der Probendicke auf das Verformungs- und Bruchverhalten bauteilähnlicher Großzugproben

Influence of specimen thickness on the deformation and fracture behaviour of wide plates The influence of specimen thickness on the deformation behaviour and the load bearing capacity has been investigated with large scale double-edge-notched-tension-specimens (DENT). The difference of the state of stress can be modelled by simplifications (plain strain, plain stress). Equations for the calculation of plastic limit loads taking into account the defect ratio a/W have been derived based on analytical, numerical and experimental investigations. Already existing equations may lead to unsafe prediction in special situations. The difference between plastic limit and maximum load is smaller for the thicker specimens due to higher toughness requirements. The toughness requirements have been quantified for the DENT-specimens using the J-integral analysis. The requirements mainly depend on the overall dimensions (W, B), the thickness ratio (B/W) and the defect ratio (a/W).     

Mechanisms and solutions to gate oxide degradation in flash memory by tunnel-oxide nitridation engineering

Increasing attention has been paid to the peripheral gate-oxide integrity degradation of Flash memory devices that is induced by the tunnel-oxide nitridation. In this letter, the mechanisms of tunnel-oxide nitridation-induced degradation are characterized. We report that both a local oxide thinning effect and nitrogen residue will impact the integrity of gate-oxide. Minimizing the local thinning effect with an in situ steam generation (ISSG) oxidation process and removing the nitrogen residues from the silicon wafer surface by either an additional sacrificial oxide process or over-dip are proven to be useful in recovering the gate-oxide integrity. An optimum approach with the tunnel-oxide nitridation is proposed in this work that results in comparable or even better gate-oxide property than other approaches that have no tunnel-oxide nitridation process.     

The effect of different exposure conditions on the biofilm/copper interface

The effects of the different exposure conditions on the electrochemical behavior of copper were evaluated in a growth medium containing Shewanella oneidensis MR-1. Impedance spectra were recorded at the corrosion potential (E_corr) in three different cells for one week of exposure followed by cyclic voltammetry. A second time constant was observed in the impedance spectra of copper that was partially immersed in the test cell, where the electrode was in contact with an air/liquid interface (cell B). These spectra resembled those usually observed for metals covered with a polymer coating. Complete immersion of copper in the electrolyte (no air/liquid interface) or deaeration of cell B resulted in one-time-constant spectra that are typical of those found for passive metals. Excellent corrosion protection was provided by MR-1 regardless of exposure condition. E_corr increased with time for the partially immersed Cu electrode exposed to the aerated solution in cell B, while it decreased for the other two exposure conditions. Cathodic polarization curves recorded after exposure for 7 days showed two reduction peaks for copper tested in cell B, while no reduction peaks were observed for the other cases. Similar results were obtained using cyclic voltammetry.