Analysis of RTN signals in Resistive-Switching RAM device and its correlation with device operations

Filament rupture/restoration induced by movement of defects, e.g. oxygen ions/vacancies, is considered as the switching mechanism in HfO2 RRAM. However, details of filament alteration during switching are still speculative, due to the limitations of existing experiment-based probing techniques, impeding its understanding. In this work, for the first time, an RTN-based defect tracking technique is developed for RRAM devices, which can monitor the movements of defects and statistically provide their spatial and energy profiles. The critical filament region is experimentally identified and its alteration is observed and correlated with switching operations under various operation conditions. This provides a useful tool for further development of RRAM technology

Effect of using agro-fertilizers and N-fixing Azotobacter enhanced biofertilizers on the growth and yield of corn

Corn is an important crop and is grown widely around the world. Corn is a food source for human as well as animal and processed into industrial product such as ethanol. Corn is one of the important productions of Malaysia as the climate is suitable for corn growth. In this study, organic fertilizers such as biofertilizer, N-fixing Azotobacter enhanced biofertilizers and compost were added to the soil to determine best practice in using organic fertilizers for higher corn yield and growth. The study was conducted in plot experiment with five replications based on randomized block design in the summer of 2012. All plots were manually harvested and yield was adjusted to 15% moisture. Grain yield (total corn harvested) at maturity was determined by harvesting the two central rows of each plot. Statistical analysis was performed on the effect of fertilizer treatments on plant growth, corn yield and nitrogen, phosphorous and potassium contents of plant materials. The means were compared according to Duncan multiple range test. The results showed that organic fertilizers in the form of N-fixing Azotobacter enhanced biofertilizer increased yield with positive effects on measured plant height, weight and leaf index. Given the significant enhancement in growth and yield of corn taking place mainly with N-fixing Azotobacter fertilizers under organic condition, the mechanism for this beneficial effect could be due to the more balanced nutrition and improved absorption of nitrogen and other mineral nutrients by the corn

Topological superfluid of spinless Fermi gases in p-band honeycomb optical lattices with on-site rotation

In this paper, we put forward to another route realizing topological superfluid (TS). In contrast to conventional method, spin-orbit coupling and external magnetic field are not requisite. Introducing an experimentally feasible technique called on-site rotation (OSR) into p-band honeycomb optical lattices for spinless Fermi gases and considering CDW and pairing on the same footing, we investigate the effects of OSR on superfluidity. The results suggest that when OSR is beyond a critical value, where CDW vanishes, the system transits from a normal superfluid (NS) with zero TKNN number to TS labeled by a non-zero TKNN number. In addition, phase transitions between different TS are also possible

Performance characteristics and estimation of measurement uncertainty of two plating procedures for Listeria monocytogenes enumeration in chicken meat

The objectives highlighted in the present study were to determine the estimates of measurement uncertainty associated with PALCAM and CHROMagar TM Listeria media, to compare the efficacy between both media in relation to their measurement uncertainties. In addition, this study was carried out to assess the performance characteristics of spread and spiral plating procedures based on the comparison of Listeria monocytogenes enumeration between PALCAM and CHROMagar TM Listeria media. This work involved pure culture experiment, artificially contaminated samples experiment and naturally contaminated samples experiment. In pure culture experiment, PALCAM performance was relatively inferior to CHROMagar TM Listeria medium for both plating procedures. From the artificially contaminated samples, the results revealed that the values of repeatability, reproducibility, and measurement uncertainty at 95% confidence interval were comparable between both media under evaluation. However, at the level of naturally contaminated samples, the performance of CHROMagar TM Listeria medium was refutable as the presence of high number of competitive microorganisms reduced the clarity of the medium. The current emphasis in ensuring microbiological safety which requires use of accredited laboratories has led to measurable need for measurement uncertainty to ensure reliability of test results for global acceptance

Pore-scale direct numerical simulation of particle transport in porous media

A computational platform for direct numerical simulation of fluid-particle two-phase flow in porous media is presented in this study. In the proposed platform, the Navier-Stokes equations are used to describe the motion of the continuous phase, while the discrete element method (DEM) is employed to evaluate particle-particle and particle-wall interactions, with a fictitious domain method being adopted to evaluate particle-fluid interactions. Particle-wall contact states are detected by the ERIGID scheme. Moreover, a new scheme, namely, base point-increment method is developed to improve the accuracy of particle tracking in porous media. In order to improve computationally efficiency, a time splitting strategy is applied to couple the fluid and DEM solvers, allowing different time steps to be used which are adaptively determined according to the stability conditions of each solver. The proposed platform is applied to particle transport in a porous medium with its pore structure being reconstructed from micro-CT scans from a real rock. By incorporating the effect of pore structure which has a comparable size to the particles, numerical results reveal a number of distinct microscopic flow mechanisms and the corresponding macroscopic characteristics. The time evolution of the inlet to outlet pressure-difference consists of large-scale spikes and small-scale fluctuations. Apart from the influence through direct contacts between particles, the motion of a particle can also be affected by particles without contact through blocking a nearby passage for fluid flow. Particle size has a profound influence on the macroscopic motion behavior of particles. Small particles are easier to move along the main stream and less dispersive in the direction perpendicular to the flow than large particles

Strong Southward Transport Events Due to Typhoons in the Taiwan Strait

Transport through the Taiwan Strait under the influence of five typhoons was investigated using both buoy observations and numerical model simulations during the period of 27 August to 5 October 2005. The results show that the effects of typhoons on the Taiwan Strait and its adjacent sea area caused strong southward transport events in the Taiwan Strait, which changed the direction of the Taiwan Strait northward transport temporarily. Typhoon-generated local wind stress and/or along-strait water level gradient were the direct driving factors in these southward transport events. The numerical results show that the Coriolis force made a negative contribution to these events and the contribution of the along-strait momentum gradient was insignificant

Algorithms for Fault-Tolerant Placement of Stateful Virtualized Network Functions

Traditional network functions (NFs) such as firewalls are implemented in costly dedicated hardware. By decoupling NFs from physical devices, network function virtualization enables virtual network functions (VNF) to run in virtual machines (VMs). However, VNFs are vulnerable to various faults such as software and hardware failures. To enhance VNF fault tolerance, the deployment of backup VNFs in stand-by VM instances is necessary. In case of stateful VNFs, stand-by instances require constant state updates from active instances during its operation. This will guarantee a correct and seamless handover from failed instances to stand-by instances after failures. Nevertheless, such state updates to stand-by instances could consume significant network bandwidth resources and lead to potential admission failures for VNF requests. In this paper, we study the fault-tolerant VNF placement problem with the optimization objective of admitting as many requests as possible. In particular, the VNF placement of active/stand-by instances, the request routing paths to active instances, and state transfer paths to stand-by instances are jointly considered. We devise an efficient heuristic algorithm to solve this problem, and propose a bi-criteria approximation algorithm with performance guarantees for a special case of the problem. Simulations with realistic settings show that our algorithms can significantly improve the request admission rate compared to conventional approaches

Stochastic Computing Based on Volatile Ovonic Threshold Switching Devices

Ovonic Threshold Switching (OTS) selector is essential in the 1S (selector) -1R (resistive switching device) crossbar memory array to suppress the sneak current paths. OTS exhibits inherent stochastic characteristics in its switching process and can be used for implementing true random number generators (TRNGs). Stochastic computing (SC) can be further designed and realized by exploiting the probabilistic switching behavior in the OTS. The stochastic bit streams generated by OTS are demonstrated with good computation accuracy in both multiplication operation and edge detection circuit for image processing. Moreover, the distribution of random bit in the stochastic streams generated by OTS has been statistically studied and linked to the defect de/localization behavior in the chalcogenide material. Weibull distribution of the delay time supports the origin of such probabilistic switching, facilitates further optimization of the operation condition, and lays the foundation for device modelling and circuit design. Considering its other advantages such as simple structure, fast speed, and volatile nature, OTS is a promising material for implementing SC in a wide range of novel applications, such as image processors, neural networks, control systems and reliability analysis

Analysis of mercury-containing protein fractions in brain cytosol of the maternal and infant rats after exposure to a low-dose of methylmercury by SEC coupled to isotope dilution ICP-MS

The mercury-containing protein fractions in the brain cytosol of the maternal and infant rats after exposure to low-dose of methylmercury chloride (0.3 mg Hg kg1 day1) were analyzed by a SEC-ICPMS method with the postcolumn isotope dilution analysis. The enriched spiking including 34S, 65Cu, 67Zn and 198Hg was continuously added into the eluate from the HPLC column and then the isotopediluted fractions were on-line measured by ICP-MS. Therefore, the absolute amounts of sulfur, mercury, zinc and copper in the eluted protein fractions could be attained after calculation of the corresponding peak areas in the mass flow chromatogram. Five mercury-containing protein fractions were monitored in the maternal sample, whereas only one was in the infant sample. The mercury content in the infant sample was about 10 times lower than the one in the maternal sample. In the meantime, two copper- and four zinc-containing fractions were found in both maternal and infant samples. The detection limit for S, Cu, Zn and Hg are 11, 0.1, 1.5 and 0.2 ng, respectively. The results demonstrate that different mercury-containing protein fractions may exist in brain cytosol between maternal and infant rats and the quantitative calculation may be helpful for the toxicological study