Fracture surface topography analysis (FRASTA)—Development, accomplishments, and future applications

In the late 1970s, Dr. George Irwin suggested to his colleagues at the University of Maryland that valuable information about a fracture event was recorded in fracture surface topography. Under his urging, Takao Kobayashi, an associate professor at the time, began quantifying and interpreting topographical features. Over the subsequent 30 years the procedures for quantifying and interpreting fracture surface topography grew continuously into an established technology that allows a fracture event to be reconstructed in microscopic detail. FRASTA (fracture surface topography analysis) has now been applied to achieve solutions to a wide variety of failure problems. This paper chronicles the historical development of FRASTA, recounts several notable achievements, and presents the plan for further development and future applications.     

Preparation of diamondlike carbon films using nanopulse generator employing SI thyristor

Diamondlike carbon (DLC) films show high hardness, high electric resistivity, and the self‐lubricant characteristic, and many applications and synthesis methods have been reported. Pulse plasma chemical vapor deposition (CVD) is one of the synthesis methods suitable for DLC films on complicated form work, such as molding and extruding die. Ordinary, microsecond‐order pulse is used in this method. This paper describes the development of the synthesis method using nanosecond‐order pulse plasma CVD for DLC films. To realize this process, a static induction (SI) thyristor with an inductive energy storage (IES) circuit was used. Compared with microsecond, nanosecond‐order pulse plasma CVD method shows the characteristics of high electron temperature and exponential relationship between pulse frequency and growth rate. The characteristics of the thus‐obtained DLC films show two broad peaks of the disordered band at 1360 cm^?1 and the graphitic band at 1580 cm^?1 by Raman spectroscopy and hardness of 16.0 GPa and elastic modulus of 170 GPa. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(4): 1–7, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20341     

Numerical simulation on the behavior of a liquid jet into an air flow

A numerical simulation has been performed to clarify the effects of turbulence in a liquid on the deformation of the liquid jet surface into an air flow. The turbulences in the liquid jet were simulated by the Rankin vortices, and the liquid jet surface was tracked numerically by the volume of fluid method. By numerical simulations, the onset of the protrusions on the liquid jet surface is caused by the vortices in the liquid, and the surrounding air flow plays an important role in the amplification of the protrusions. The amplification rate of the trough displacement is proportional to the air‐to‐liquid velocity ratio. At large imposed vortex intensities, the trough displacement increases with the vortex intensity. On the other hand, at small imposed vortex intensities, the amplification of the trough displacement is also affected by factors other than vortex intensity. © 2001 Scripta Technica, Heat Trans Asian Res, 30(6): 473–484, 2001     

Periodical shedding of cloud cavitation from a single hydrofoil in high-speed cryogenic channel flow

In order to explain criteria for periodical shedding of the cloud cavitation, flow patterns of cavitation around a plano-convex hydrofoil were observed using a cryogenic cavitation tunnel of a blowdown type. Two hydrofoils of similarity of 20 and 60 mm in chord length with two test sections of 20 and 60 mm in width were prepared. Working fluids were water at ambient temperature, hot water and liquid nitrogen. The parameter range was varied between 0.3 and 1.4 for cavitation number, 9 and 17 m/sec for inlet flow velocity, and −8° and 8° for the flow incidence angle, respectively. At incidence angle 8°, that is, the convex surface being suction surface, periodical shedding of the whole cloud cavitation was observed on the convex surface under the specific condition with cavitation number and inlet flow velocity, respectively, 0.5, 9 m/sec for liquid nitrogen at 192°C and 1.4, 11 m/sec for water at 88°C, whereas under the supercavitation condition, it was not observable. Periodical shedding of cloud cavitation occurs only in the case that there are both the adverse pressure gradient and the slow flow region on the hydrofoil.     

Electron-beam doping-electron radiation effects in impurity overlayers and semiconductor substrates

3-9 MeV electrons were used to introduce impurity Ge atoms into Si wafers from Ge sheets, which are in contact with a Si surface at 20-60‡C in water bath. Concentration-dependent diffusivities of ∼10-18-10^-14 cm²sec^-1 for Ge in Si were measured. Activation energies of sputtering yield for Ge and of the diffusivity of Ge in Si are estimated to be ∼0.3 eV and ∼0.58 eV, respectively. In a case of hot (∼250‡C) irradiation in ∼1x10^-3 Torr vacuum, also the similar concentration profiles of impurity atoms in the substrates were observed.     

Solid-state characterization of polyethylene reactor powders and their structural changes upon annealing

Polyethylene reactor powders prepared under different conditions were characterized using transmission electron microscopy, ¹H nuclear magnetic resonance and X-ray diffraction techniques. The molecular weight of the polyethylene reactor powders was around 1 × 10⁵. A unique domain morphology, quite different from the usual melt- or solution-crystallized lamellar structure, was observed, independent of polymerization temperature (T_poly). Annealing of reactor powders caused the aggregation of these crystalline domains, due to the significant molecular motion of the amorphous chains, before melting. The critical temperature was 20 °C higher than each T_poly, and corresponded to the temperature at the active catalyst site producing the chain growth. The morphologies of powders prepared at the lower T_poly contained smaller crystals that exhibited a constrained monoclinic form. In contrast, only usual orthorhombic crystals of larger size were found within the powder prepared at the higher T_poly. These results suggest that the competitive processes of chain propagation and crystal growth upon polymerization may lead to unique variations of the crystalline and amorphous phases, but with similar intermediate components in the phase that connects them.     

Sintering Kinetics at Isothermal Shrinkage: Effect of Specific Surface Area on the Initial Sintering Stage of Fine Zirconia Powder

The isothermal shrinkage behaviors of fine zirconia powders (containing 2.8–2.9 mol% Y₂O₃) with specific surface areas of about 6 and 16 m²/g were investigated to clarify the effect of specific surface area on the initial sintering stage. The shrinkage of powder compact was measured under constant temperatures in the range of 1000°–1100°C. The increase in specific surface area enhanced the densification rate with increasing temperature. The values of activation energy ( Q ) and frequency-factor term (β₀) of diffusion at initial sintering were estimated by applying the sintering-rate equation to the isothermal shrinkage data. The Q of diffusion changes little but the β₀ increases with the increase in specific surface area. It is therefore concluded that the increase in the specific surface area of fine zirconia powder enhances the shrinkage rate because of an increase in the β₀ at the initial stage of sintering.     

A Spatial-Domain Technique for the Design of 3-D Separable-Denominator State-Space Digital Filters

In this paper,a technique for designing 3-D separable-denominator state-spacedigital filters is developed. The design process is divided intotwo phases. First, the coefficient matrices related to stabilityare constructed for the filter to be stable by using alternatingvariable method. Next, the other matrices are obtained by solvinglinear equations. These phases are repeated until there is nosignificant change in the squared error function.     

High-power 0.98 mu m GaInAs strained quantum well lasers for Er/sup 3+/-doped fibre amplifier

High-power GaInAs strained quantum well lasers with an emission wavelength of 0.98 mu m, suitable for Er/sup 3+/-doped fibre amplifier pumping, have been fabricated. A threshold current of 15 mA and a peak output power as high as 85 mW have been obtained for the ridge waveguide structure with AR/HR facet coating. Highly efficient pumping for the 1.536 mu m signals has been confirmed.<>