Quantitative models on corrosion fatigue crack growth rates in metals: Part II. application of fatigue crack growth rate modeling for nickel-based superalloys at elevated temperatures

Approaches to predict da/dN-àK for environmental situations; including empirical interpolative equations, linear superposition of mechanical fatigue and time-based environmental cracking, and mechanism-based models; are presented. For several material-environment systems, these models were incorporated in fracture mechanics life prediction methods, and successes have been reported in evaluating the corrosion fatigue contribution. Considerable uncertainties are, however, associated with these models. The linear superposition analysis is emphasized; material-environment systems that are severely environment-sensitive should be adequately described by this method. Direct and indirect methods exist to define time-based crack growth rates for use in linear superposition predictions of da/dN. The linear superposition approach is effective, but only for those cases where K_ISCC is high relative to typical flawed component stress intensity levels. Empirical curve-fit models require an extensive environmental crack growth rate data base, which are costly to develop, and are effective for interpolations but not predictions of fatigue crack growth data. Mechanism-based models for broad predictions of cycle-time dependent da/dN versus àK, and other variables such as frequency or hold time, are in an infant state.     

Effect of Vibrational Modes on Sand Pressure and Pattern Deformation in the EPC Process

During the EPC (expendable pattern casting) process, one of the essential requirements is to prevent pattern distortion duringsand filling and compaction. A new method which vibrates the system in a two-dimensional circular mode has been appliedto the EPC process. The molding properties of unbonded sand obtained by this new vibration mode are investigated andcompared with those in the one-dimensional vertical mode. For adequate compaction of sand. the circular vibration mode ismore effective than the vertical mode. Sand became more fluidized by the circular vibration and the particle pressure coefficientwas close to unity The particle pressure coefficient, which is defined as the ratio of horizontal to vertical sand pressure, isresponsible for the effectiveness of sand filling.     

Analysis of the glow curves obtained from LiF:Mg,Cu,Na,Si TL material using the general order kinetics model

Three-dimensional thermoluminescence (TL) spectra based on temperature, wavelength and intensity for newly developed LiF:Mg,Cu,Na,Si TL material at the Korea Atomic Energy Research Institute (KAERI) were measured and analysed. The glow curves were obtained by integration of luminescence intensity over all wavelengths at each temperature, and various trapping parameters related to the traps were determined by analysing these curves. A computerised glow curve deconvolution (CGCD) method which was based on the general order kinetics (GOK) model was used for the glow curve analysis. The glow curves of LiF:Mg,Cu,Na,Si TL material were deconvoluted to six isolated glow curves which have peak temperatures at 333, 374, 426, 466, 483 and 516 K. The main glow peak of peak temperature at 466 K had activation energy of 2.06 eV and a kinetic order of 1.05. This TL material was also found to have three recombination centres, 1.80 eV, 2.88 eV and 3.27 eV by analysis of the TL spectra.     

The evolution of cluster network structure and firm growth: a study of industrial software clusters

Since the cluster began to receive attention as a critical environmental factor in geographical economics, it has provided a major research methodology across multiple disciplines from industrial organization, strategic management, regional innovation system, and Triple Helix to virtual clusters. Network structure analysis (NSA) offers a common framework to observe clusters that have been studied separately from the viewpoint of industrial organization and strategic management. Industrial structure analysis, is based on the externality of a network and the resource-based view, focused on the inherent network capacity, have been combined with the study of structural changes through cluster NSA, to create a new direction for the growth of industry and individual firms. This study aims to analyze the correlation between the networking of structural change and a firm’s performance by selecting a software industrial cluster as a representative case for the knowledge industry. We examine the network structural positions of each node during the cluster evolution process. This empirical study has significance for establishing a firm’s growth strategy as well as supporting the policy about clusters, through outlining the dynamic evolution process of the networking activities in a knowledge industry cluster.     

Volumetric real-time imaging using a CMUT ring array

A ring array provides a very suitable geometry for forward-looking volumetric intracardiac and intravascular ultrasound imaging. We fabricated an annular 64-element capacitive micromachined ultrasonic transducer (CMUT) array featuring a 10-MHz operating frequency and a 1.27-mm outer radius. A custom software suite was developed to run on a PC-based imaging system for real-time imaging using this device. This paper presents simulated and experimental imaging results for the described CMUT ring array. Three different imaging methods--flash, classic phased array (CPA), and synthetic phased array (SPA)--were used in the study. For SPA imaging, two techniques to improve the image quality--Hadamard coding and aperture weighting--were also applied. The results show that SPA with Hadamard coding and aperture weighting is a good option for ring-array imaging. Compared with CPA, it achieves better image resolution and comparable signal-to-noise ratio at a much faster image acquisition rate. Using this method, a fast frame rate of up to 463 volumes per second is achievable if limited only by the ultrasound time of flight; with the described system we reconstructed three cross-sectional images in real-time at 10 frames per second, which was limited by the computation time in synthetic beamforming.     

Electrochemical detection of peroxynitrite using a biosensor based on a conducting polymer-manganese ion complex

A peroxynitrite (ONOO(-)) biosensor has been developed through the preparation of a new manganese-[poly-2,5-di-(2-thienyl)-1H-pyrrole)-1-(p-benzoic acid)] (Mn-pDPB) complex. DPB monomer was first synthesized and polymerized for the purpose of providing a polymer backbone for complex formation with Mn(2+) ion. The Mn-pDPB complex was characterized via Magnetomotive Force (MMF) simulation, X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry. The complex selectively enhanced the reduction process of ONOO(-) which was used as the analytical signal for chronoamperometric detection. A polyethyleneimmine (PEI) layer was coated on the complex surface to increase selectivity and stability. The chronoamperometric calibration plot showed the hydrodynamic range of 2.0 × 10(-8)-5.0 × 10(-7) M. The detection limit was determined to be 1.9 (±0.2) × 10(-9) M based on S/N = 3. The microbiosensor, fabricated on a 100 μm diameter Pt tip, was applied in a real rat plasma sample for the detection of spiked concentrations of ONOO(-). The reliability and long-term stability of the microbiosensor was also examined with YPEN-1 cells in vitro, and the results shown were promising.