High temperature oxidation behavior of ferritic steel in supercritical water at 550–700°C

Oxidation tests were conducted on ferritic steel T22 exposed to deaerated supercritical water at 550–700°C and 25 MPa. Oxide films formed on T22 had a double-layered structure with the outer layer consisting of iron oxide and the inner layer consisting of spinel oxide. Pores formed on the surface of samples initially but healed at longer exposure time and higher temperature. Cracks occurred along the grain boundaries in the oxide scale at 600–700°C for 200 and 400 h. The oxidation kinetics obeyed a near-parabolic law in all cases. The data of activation energy of T22 indicated that the likely oxidation rate-controlling step may be the outward diffusion of iron along the magnetite bulk.     

Dynamic compressive response and failure behavior of fiber polymer composites embedded with tetra-needle-like ZnO nanowhiskers

Glass fiber polymer composites embedded with tetra-needle-like zinc oxide (ZnO) nanowhiskers were prepared. The prepared composites exhibited excellent mechanical properties after the effective dispersion of ZnO nanowhiskers in the resin. The static and dynamic compressive properties of the composites were tested in the thickness and in-plane directions. The macro- and microfracture morphologies of the damaged specimens were obtained by using a scanning electron microscope. The results show that the compressive properties of the composites could be significantly affected by strain rates. As the strain rate increases, the composites have a higher strength. The compressive properties of the composites are affected by the content of ZnO nanowhiskers in the resin. The high strength of the composites can be attributed to the three-dimensional structures of ZnO nanowhiskers and the corresponding stress transfer.     

A new approach to dynamic fuzzy modeling of genetic regulatory networks

In this paper, the dynamic fuzzy modeling approach is applied for modeling genetic regulatory networks from gene expression data. The parameters of the dynamic fuzzy model and the optimal number of fuzzy rules for the fuzzy gene network can be obtained via the proposed modeling approach from the measured gene expression data. One of the main features of the proposed approach is that the prior qualitative knowledge on the network structure can be easily incorporated in the proposed identification algorithm, so that the faster learning convergence of the algorithm can be achieved. Two sets of data, one the synthetic data, and the other the experimental SOS DNA repair network data with structural knowledge, have been used to validate the proposed modeling approach. It is shown that the proposed approach is effective in modeling genetic regulatory networks.     

Carbon nanotubes/polydimethylsiloxanes systems for thermal management of miniaturized electronic components

The thermal performances of nanocomposite layers formed by Single-walled Carbon Nanotubes (SWCNT) dispersed in 2 different kind of polydimethyl-siloxane (PDMSO) matrices has been investigated by measuring the thermal resistance under conditions similar to the ones used for thermal management in microelectronics. A series of nanocomposite samples with thickness in the range 25 microm(-1) cm have been tested. The nanocomposites were prepared varying the amounts of nanotubes embedded in the matrix (from 0.1 to 5%w). In some cases also microsized graphites were mixed to the nanotube's fillers. For 25 micron thick layers, the thermal resistance of the neat silicone specimen can be reduced of 54% with the addition of 2%w carbon nanotubes. The variation of thermal conductivity as a function of the SWCNT's loading is reported and discussed. Furthermore the dispersion's effects of the nanotubes in the layers and the effects on the realization of a net-like system have been investigated.     

White up-conversion luminescent property in Re3+:Gd3Ga5O12 nanocrystals

Rare-earth ions doped Gd3Ga5O12 nanocrystals have been prepared by a propellant combustion synthesis method and their up-conversion properties were systematically investigated in this paper. XRD, SEM, TEM, and up-conversion emission spectra were used to characterize the synthesized nanocrystals. Energy transfer from Yb3+ to Er3+ and Tm3+ can occur simultaneously in the as-synthesized Gd3Ga5O12 nanocrystals. The up-conversion mechanisms and relevant energy transfer processes are discussed. A white light generation was observed when the Yb3+, Er3+ and Tm3+ were directly incorporated in the Gd3Ga5O12 lattice. And its calculated color coordinates is (0.35, 0.41) under the excitation at 974.5 nm. The bright white luminescent nanocrystals may have potential application in the field of lighting, displays and photonics.     

A visualization of shear strain in processing by high-pressure torsion

Optical microscopy was used to examine the shear strain imposed in duplex stainless steel disks during processing by high-pressure torsion (HPT). The results show a double-swirl pattern emerges in the early stages of HPT and the two centres of the swirl move towards the centre of the disk with increasing revolutions. Local shear vortices also develop with increasing numbers of revolutions. At 20 revolutions, there is a uniform shear strain pattern throughout the disk and no local shear vortices.     

Development of pseudo-ductile permanent formwork for durable concrete structures

The present investigation focuses on a new approach for the construction of durable concrete structures. Using Pseudo-ductile Cementitious Composites (PDCC) of relatively low water/binder ratio, permanent formworks are first fabricated. Normal concrete is then cast to make structural components. With low permeability and high crack resistance, the permanent formwork acts as effective surface cover to prevent the corrosion of steel reinforcements. The formwork can be made with PDCC alone, or with the incorporation of Glass Fiber Reinforced Plastics (GFRP) rods. In some structural components, the GFRP reinforcements will be sufficient to provide the necessary load-carrying capacity. When higher loads are to be carried, steel reinforcements can be added to produce a component with very high durability (due to the thick cover to steel) as well as ductile behavior. This paper focuses on mechanical aspects of this construction concept. The development of PDCC for formwork fabrication is first described. The bond between PDCC and concrete, in relation to various surface treatment methods, will be investigated with beam specimens. Test results on concrete beams made with GFRP reinforced PDCC formwork are then presented and compared to theoretical predictions. A design example is performed to demonstrate the use of GFRP/PDCC permanent formwork for constructing the deck of a footbridge. The results of this investigation show promise of the technology for practical applications.     

蓄能运行有利于风电等新能源的可持续发展

蓄能运行即通过不同蓄能设施利用电网低谷剩余电能储存转换,变成和再生能源一样,可周而复始更新使用,形成可持续发展的循环机制。蓄能设施涵盖抽水蓄能和其他蓄电、蓄能装置。当今水电发展受限于水能资源,在原电力开发基础上再考虑蓄能运行后可使之步入新的境界,有利于风电等新能源和整个电网的可持续发展。     

Large‐Stroke Electrochemical Carbon Nanotube/Graphene Hybrid Yarn Muscles

Artificial muscles are reported in which reduced graphene oxide (rGO) is trapped in the helical corridors of a carbon nanotube (CNT) yarn. When electrochemically driven in aqueous electrolytes, these coiled CNT/rGO yarn muscles can contract by 8.1%, which is over six times that of the previous results for CNT yarn muscles driven in an inorganic electrolyte (1.3%). They can contract to provide a final stress of over 14 MPa, which is about 40 times that of natural muscles. The hybrid yarn muscle shows a unique catch state, in which 95% of the contraction is retained for 1000 s following charging and subsequent disconnection from the power supply. Hence, they are unlike thermal muscles and natural muscles, which need to consume energy to maintain contraction. Additionally, these muscles can be reversibly cycled while lifting heavy loads.