Organic phototransistor based on poly(3-hexylthiophene)/TiO₂ nanoparticle composite

2008-2009 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Highly photosensitive thin film transistors based on a composite of poly(3-hexylthiophene) and titania nanoparticles

2009-2010 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Thermal annealing and temperature dependences of memory effect in organic memory transistor

We investigate the annealing and thermal effects of organic non-volatile memory with floating silver nanoparticles by real-time transfer curve measurements. During annealing, the memory window shows shrinkage of 23 due to structural variation of the nanoparticles. However, by increasing the device operating temperature from 20 to 90 °C after annealing, the memory window demonstrates an enlargement up to 100. The differences in the thermal responses are explained and confirmed by the co-existence of electron and hole traps. Our findings provide a better understanding of organic memory performances under various operating temperatures and validate their applications for temperature sensing or thermal memories. © 2011 American Institute of Physics.published_or_final_versio

Evaluation of Cybersecurity Threats on Smart Metering System

Smart metering has emerged as the next-generation of energy distribution, consumption, and monitoring systems via the convergence of power engineering and information and communication technology (ICT) integration otherwise known as smart grid systems. While the innovation is advancing the future power generation, distribution, consumption monitoring and information delivery, the success of the platform is positively correlated to the thriving integration of technologies upon which the system is built. Nonetheless, the rising trend of cybersecurity attacks on cyber infrastructure and its dependent systems coupled with the system’s inherent vulnerabilities present a source of concern not only to the vendors but also the consumers. These security concerns need to be addressed in order to increase consumer confidence so as to ensure greatest adoption and success of smart metering. In this paper, we present a functional communication architecture of the smart metering system. Following that, we demonstrate and discuss the taxonomy of smart metering common vulnerabilities exposure, upon which sophisticated threats can capitalize. We then introduce countermeasure techniques, whose integration is considered pivotal for achieving security protection against existing and future sophisticated attacks on smart metering systems

Scaling behaviour of small-scale dynamos driven by Rayleigh–Bénard convection

A numerical investigation of convection-driven dynamos is carried out in the plane layer geometry. Dynamos with different magnetic Prandtl numbers Pm are simulated over a broad range of the Rayleigh number Ra. The heat transport, as characterized by the Nusselt number Nu, shows an initial departure from the heat transport scaling of non-magnetic Rayleigh–Bénard convection (RBC) as the magnetic field grows in magnitude; as Ra is increased further, the data suggest that Nu grows approximately as Ra2/7, but with a smaller prefactor in comparison with RBC. Viscous (ϵu) and ohmic (ϵB) dissipation contribute approximately equally to Nu at the highest Ra investigated; both ohmic and viscous dissipation approach a Reynolds-number-dependent scaling of the form Rea, where a≈2.8. The ratio of magnetic to kinetic energy approaches a Pm-dependent constant as Ra is increased, with the constant value increasing with Pm. The ohmic dissipation length scale depends on Ra in such a way that it is always smaller, and decreases more rapidly with increasing Ra, than the viscous dissipation length scale for all investigated values of Pm

The expression and regulation of enzymes mediating the biosynthesis of triglycerides and phospholipids in keratinocytes/epidermis

Triglycerides and phospholipids play an important role in epidermal permability barrier formation and function. They are synthesized de novo in the epidermis via the glycerol-3-phosphate pathway, catalyzed sequentially by a group of enzymes that have multiple isoforms including glycerol-3-phosphate acyltransferase (GPAT), 1-acylglycerol-3-phosphate acyltransferase (AGPAT), Lipin and diacylglycerol acyltransferase (DGAT). Here we review the current knowledge of GPAT, AGPAT, Lipin and DGAT enzymes in keratinocytes/epidermis focusing on the expression levels of the various isoforms and their localization in mouse epidermis. Additionally, the factors regulating their gene expression, including calcium induced differentiation, PPAR and LXR activators, and the effect of acute permeability barrier disruption will be discussed

Designing nano-aluminum laden fuel pump for aviation applications

In view of the fact that traditional liquid propellants cannot meet the design requirements of large-thrust flight vehicle, it has become a new trend to add nano-metal powder to liquid propellants to greatly increase density and specific impulse. In order to achieve the variable flow-rate and variable-proportion transportation of aviation fuel with nano-aluminum, a new type of solid-liquid mixing pumping system is designed, including powder conveying device, stirring device, pump and corresponding drive and transmission system. For the purpose of avoiding the frictional contact between the rotors, which will bring potential hazard to nano-aluminum powder, a non-contact twin-screw pump with synchronous gears is designed. Among them, based on the considerations of flow pulsation, volumetric efficiency and manufacturing difficulty, cycloid profile is adopted for screw rotors. After completing the functional design, geometric parameter design, structural design, 3D modeling, prototype manufacturing and preliminary performance estimation of the mixing pumping system, the performance of the screw feeder, agitator, screw pump was tested through experiments to meet the expected design requirements. The designed agitator can achieve sufficient mixing at 500 rpm in less than 10 s. Even though 50-micron clearances are designed with a relatively small rotor diameter, the volumetric efficiency of screw pump can reach above 50% when the discharge pressure is below 450 kPa and the flow rate is set as 10 L/min, the power of the screw pump is less than 700 W. This design facilitates the rapid real-time preparation of metallized propellants and provides a reference for further improving the design and control methods of nanoparticle two-phase flow pumping

Factors Governing the Chemical Stability of Shear-Exfoliated ZnSe(alkylamine) II–VI Layered Hybrids

Advances in the production of two-dimensional (2D) materials such as graphene and MoS2 during the past two decades have spurred the search for other van der Waals materials with distinct functional properties. However, reducing the dimensionality of bulk van der Waals materials can lead to structural rearrangement and chemical degradation, especially in the presence of air. These challenges have slowed the progress of the discovery and analysis of chemically diverse 2D materials. Here, we provide a case study on the shear exfoliation of a class of wide band gap van der Waals materials termed II–VI layered hybrids (II–VI LHs) and show how reducing their dimension influences their structural and chemical stabilities. ZnSe(butylamine) and ZnSe(octylamine) are exfoliated, yielding shear-thinned material whose resistance toward degradation via oxidation is studied in depth by a variety of macro- and microscopic characterization techniques. Mechanical energy input, solvent–ligand interaction, and exposure to ambient conditions all play important roles in the stability of these materials. Our findings suggest that moderately coordinating alkylamine layers stabilize 2D materials that would otherwise degrade during exfoliation and exposure to air

Strain-induced Evolution of Electronic Band Structures in a Twisted Graphene Bilayer

Here we study the evolution of local electronic properties of a twisted graphene bilayer induced by a strain and a high curvature. The strain and curvature strongly affect the local band structures of the twisted graphene bilayer; the energy difference of the two low-energy van Hove singularities decreases with increasing the lattice deformations and the states condensed into well-defined pseudo-Landau levels, which mimic the quantization of massive Dirac fermions in a magnetic field of about 100 T, along a graphene wrinkle. The joint effect of strain and out-of-plane distortion in the graphene wrinkle also results in a valley polarization with a significant gap, i.e., the eight-fold degenerate Landau level at the charge neutrality point is splitted into two four-fold degenerate quartets polarized on each layer. These results suggest that strained graphene bilayer could be an ideal platform to realize the high-temperature zero-field quantum valley Hall effect.Comment: 4 figure