The effect of silicon on the glass forming ability of the Cu47Ti34Zr11Ni8 bulk metallic glass forming alloy during processing of composites

Composites of the Cu47Ti34Zr11Ni8 bulk metallic glass, reinforced with up to 30 vol % SiC particles are synthesized and characterized. Results based on x-ray diffraction, optical microscopy, scanning Auger microscopy, and differential scanning calorimetry (DSC) are presented. During processing of the composites, a TiC layer forms around the SiC particles and Si diffuses into the Cu47Ti34Zr11Ni8 matrix stabilizing the supercooled liquid against crystallization. The small Si addition between 0.5 and 1 at. % increases the attainable maximum thickness of glassy ingots from 4 mm for Cu–Ti–Zr–Ni alloys to 7 mm for Cu–Ti–Zr–Ni–Si alloys. DSC analyses show that neither the thermodynamics nor the kinetics of the alloy are affected significantly by the Si addition. This suggests that Si enhances the glass forming ability by chemically passivating impurities such as oxygen and carbon that cause heterogeneous nucleation in the melt

Microstructures and mechanical properties of tungsten wire/particle reinforced Zr57Nb5Al10Cu15.4Ni12.6 metallic glass matrix composites

Tungsten wire or particle reinforced metallic glass matrix composites are produced by infiltrating liquid Zr57Nb5Al10Cu15.4Ni12.6 (Vit106) into tungsten reinforcements at 1150 and at 1425 K. X-ray diffraction, differential scanning calorimetry, and scanning electron microscopy are carried out to characterize the composite. The matrix of the composite processed at 1150 K is mostly amorphous, with some embedded crystals. During processing, tungsten dissolves in the glass-forming melt and upon quenching precipitates over a relatively narrow zone near the interface between the tungsten and matrix. In the composites processed at 1425 K, tungsten dissolves in the melt and diffuses through the liquid medium, and then reprecipitates upon quenching. The faster kinetics at this high temperature results in a uniform distribution of the crystals throughout the matrix. Mechanical properties of the differently processed composites containing wires and particles are compared and discussed. The composites exhibit a plastic strain failure of up to 16% without sacrificing the high-failure strength, which is comparable to monolithic Vit106

Mechanical properties of Zr_(57)Nb_5Al_(10)Cu_(15.4)Ni_(12.6) metallic glass matrix particulate composites

To increase the toughness of a metallic glass with the nominal composition Zr_(57)Nb_5Al_(10)Cu_(15.4)Ni_(12.6), it was used as the matrix in particulate composites reinforced with W, WC, Ta, and SiC. The composites were tested in compression and tension experiments. Compressive strain to failure increased by more than 300% compared with the unreinforced Zr_(57)Nb_5Al_(10)Cu_(15.4)Ni_(12.6), and energy to break of the tensile samples increased by more than 50%. The increase in toughness came from the particles restricting shear band propagation, promoting the generation of multiple shear bands and additional fracture surface area. There was direct evidence of viscous flow of the metallic glass matrix within the confines of the shear bands

Processing of carbon-fiber-reinforced Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 bulk metallic glass composites

Carbon-fiber-reinforced bulk metallic glass composites are produced by infiltrating liquid Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 into carbon fiber bundles with diameter of the individual fiber of 5 mum. Reactive wetting occurs by the formation of a ZrC layer around the fibers. This results in a composite with a homogeneous fiber distribution. The volume fraction of the fibers is about 50% and the density of the composite amounts to 4.0 g/cm(^3)

Development Status of a Three-Dimensional Electron Fluid Model for Hall Thruster Plume Simulations

A 3-D electron fluid model has been developed as a stepping stone to fully describe the electron current flow across magnetic fields inside a vacuum chamber and to provide electron flux to solar arrays for spacecraft surface charging model. A detailed description of the numerical treatment of the electric potential solver, including finite-volume formulation, implementation, and the treatment of boundary conditions, are presented in this paper. Verification tests of the model are presented

An Adaptive Fault-Tolerant Event Detection Scheme for Wireless Sensor Networks

In this paper, we present an adaptive fault-tolerant event detection scheme for wireless sensor networks. Each sensor node detects an event locally in a distributed manner by using the sensor readings of its neighboring nodes. Confidence levels of sensor nodes are used to dynamically adjust the threshold for decision making, resulting in consistent performance even with increasing number of faulty nodes. In addition, the scheme employs a moving average filter to tolerate most transient faults in sensor readings, reducing the effective fault probability. Only three bits of data are exchanged to reduce the communication overhead in detecting events. Simulation results show that event detection accuracy and false alarm rate are kept very high and low, respectively, even in the case where 50% of the sensor nodes are faulty

Interfacial instability-driven amorphization/nanocrystallization in a bulk Ni45Cu5Ti33Zr16Si1 alloy during solidification

We report on experimental evidence for local amorphization/nanocrystallization at the interfaces between the B2-ordered Ni(Ti,Zr) phase and the NiTiZr phase with P63/mmc during solidification of a multicomponent Ni45Cu5Ti33Zr16Si1 alloy. So far there are several well-known mechanisms for interfacial amorphization in the solid state but no interfacial instability-driven amorphization/nanocrystallization during transition from liquid to solid state has been reported to our knowledge. The curvature of the interfacial area of the ordered Ni(Ti,Zr) phase is locally negative accompanying reverse atomic diffusion. This results in the frustration of the strong ordering tendency of the Ni(Ti,Zr) phase, and induces local amorphization/nanocrystallization

Fair Value Accounting And Financial Stability – Based On The Adoption

Fair value accounting refers to the accounting method which an asset or liability is estimated based on the current market price, so called fair value. Under the fair value accounting, it is more difficult for managers to hide bad information, because the value of an asset or liabilities is re-estimated periodically to reflect the changes in fair value in the market. In this case, firms’ financial stability will be increased. On the other hand, fair value accounting can intensity the volatility of the numbers in the financial statement, which leads to decreases the financial stability. This papers empirically examines the effect of the fair value accounting on the financial stability based on the IFRS adoption in Korea. Using the non-financial firms listed in KOSPI and KOSDAQ from 2000 to 2013, we find that the expansion of fair value accounting increases financial stability. The results support the argument that fair value accounting prohibits managers from hiding bad information, rather it enforces the disclosure of value-relevant information to the investors. The results are consistent with a battery of robustness checks. Thus, the overall results show that the expansion of fair value accounting increase financial stability.

Engineering of Corynebacterium glutamicum for the secretory production of recombinant proteins via Tat-dependent pathway

Corynebacterium glutamicum, which has been an industrial producer of various L-amino acids, nucleic acids, and vitamins, is now also regarded as a potential host for the secretory production of recombinant proteins since it exhibits numerous ideal features for protein secretion: (i) it has a single cellular membrane as a gram-positive bacterium, which allows proteins to be easily secreted into the extracellular medium. (ii) C. glutamicum secretes only a few endogenous proteins into the culture medium, which allows the simpler purification of target proteins in downstream process. (iii), secreted proteins from C. glutamicum can be kept stable because extracellular protease activity is rarely detectable. To harness its potential as an industrial platform for recombinant protein production, the development of an efficient secretion system is necessary. To achieve this goal first, we engineered several genetic parts in C. glutamicum: (i) synthetic promoters, (ii) plasmid copy number, (iii) signal peptides, (iv) co-expression of secretion machinery proteins. Using the engineered host-vector systems, gram-scale production of recombinant proteins could be achieved in fed-batch cultivation

Development Status of a 3-D Electron Fluid Model for Hall Thruster Plume Simulations

A 3-D electron fluid model has been developed as a steping stone to fully describe the electron current flow across magnetic fields inside a vacuum chamber and to provide electron flux to solar arrays for spacecraft surface charging model. A detailed description of the numerical treatment of the electric potential solver, including finite-volume formulation, implementation, and the treatment of boundary conditions, are presented in this paper. Verification tests of the model are presented