A history of numerical modelling of the Wairakei geothermal field

The history of computer modelling of the Wairakei geothermal field is reviewed. It covers the development of lumped-parameter models during the 1970s and then discusses the evolution and first applications of geothermal reservoir simulation techniques. The development of reservoir models of Wairakei at the University of Auckland began in the early 1980s; current models produces good matches against field data. Many future scenarios have been run using the University's models and have been presented at various regulatory hearings. The general conclusion from these scenarios is that Wairakei can continue producing electricity at the current level for at least another 50 years, and if Wairakei is shut down after 100 years of operation it will recover to its pre-exploitation state after a further 300 years.     

Thermal diffusion in the modified Frazier schemes with column heights varied at a constant increment for improved performance

The effects of column number and column-height increment on the degree of separation in the modified Frazier scheme of thermal diffusion columns with the total sum of column heights fixed, has been investigated. The equations, which may be employed to predict the optimal column number and the optimal column-height increment for the maximum separation, have been derived. Considerable improvement in performance is obtainable if the column number and column-height increment in a modified Frazier scheme with the total sum of column heights fixed, are properly assigned under a certain flow-rate operation, instead of using the conventional Frazier scheme of constant column height with the same total sum of column heights.     

Plasma-enhanced chemical vapor deposition carbon nanotubes for ethanol gas sensors

Carbon nanotubes (CNTs) have been fabricated by microwave plasma-enhanced chemical vapor deposition for detecting the presence of ethanol vapor. The conductance of the CNTs decreases when the sensors are successively exposed to ethanol vapor at room temperature. The surface of the CNTs was modified in oxygen plasma to elevate the detection sensitivity for ethanol. Successful utilization of CNTs in gas sensors may open a new window for the development of novel nanostructure gas devices.     

Development of a Digital-Convolution-Based Process Emulator for Three-Dimensional Microstructure Fabrication Using Electron-Beam Lithography

Although electron-beam lithography has been demonstrated to be feasible in creating 3-D micropolymer structures, the proximity effect due to forward and backward scatterings usually makes it difficult to precisely determine the distribution of electron irradiation. The process design for creating the desired shape still largely depends on a trial-and-error basis. Therefore, in order to reduce the cost and to accelerate product development, it is important to utilize computer-aided design tools. A method, called as element growth method, which is based on digital convolution approach, is developed and presented under an OpenGL environment to reduce the cost and the developmental period for fabrication. By using such a convolution approach, this emulator converts the processing parameters into a final spatial-dosage distribution and subsequently into the final geometry of structures. In addition, a physically based kernel function is also proposed and used. Examples of 3-D microstructures such as the microlens are presented. By these tools, it is possible to provide guidelines for optimizing the fabrication process and to reduce the cost for the related e-beam lithography-based 3-D fabrication.     

Electronically coupled porphyrin-arene dyads for dye-sensitized solar cells

An acetylene-linked porphyrin-perylene anhydride and an acetylene-linked porphyrin-naphthalic anhydride have been synthesized; the highly conjugated acetylenic bridge in these porpyrins efficiently mediates electronic interaction between the porphyrin and perylene units to extend the π-conjugation of the porphyrin dye and to cause both broadening and red shifts of both the Soret and Q absorption bands. This condition is a useful feature for efficient dye-sensitized solar cell applications. The optical, electrochemical and photovoltaic properties of the new linked anhydrides show that the HOMO-LUMO gap decreased upon extension of π-conjugation, indicating a strong electronic coupling between the porphyrin and the perylene or naphthalene unit.     

Effect of organoclay on the mechanical / thermal properties of microcellular injection molded polystyrene–clay nanocomposites

An organically modified montmorillonite was compounded with polystyrene (PS) in a twin-screw extruder. The organoclay polystyrene nanocomposites were then injection molded by conventional and microcellular methods. Nitrogen was used as the blowing agent. The effect of organoclay content on the mechanical and thermal properties was investigated. The results showed that when the MMT content was 1 wt.%, the nanocomposites have maximum tensile strength, wear resistance, and cell density. Moreover, the addition of organoclay increases the glass transition and decomposition temperature of the nanocomposites. The XRD results showed that the layer spacing of the nanocomposites decreases by comparison with the organoclay. TEM pictures showed that MMT is well dispersed within the PS matrix.     

Gasoline permeation resistance of the as‐blow‐molded and annealed polyethylene,polyethylene/polyamide,and polyethylene/modified polyamide bottles

An investigation of the gasoline permeation resistance of the as‐blow‐molded and annealed polyethylene, polyethylene (PE)/polyamide (PA), and polyethylene/modified polyamide (MPA) bottles is reported. The gasoline permeation resistance improves dramatically after blending PA and MPA barrier resins in PE matrices during blow‐molding, and the order of barrier improvement corresponds to the order of barrier improvement of the barrier resins added in PE. Somewhat unexpectedly, the gasoline permeation rates of the annealed PE and/or PE/PA bottles annealed at 90°C or higher temperatures increase significantly with the annealing temperature and time. On the contrary, the gasoline permeation resistance of the annealed PE/MPA bottles increase significantly as the annealing temperature and/or time increase. For instance, the gasoline permeation rate of the PE/MPA bottle annealed at 120°C for 32 h is about 190 times slower than that of the as‐blow‐molded PE bottle. Further investigations found that, after blending the MPA and PA barrier resins in PE matrices, the relatively nonpolar hydrocarbon components present in the gasoline fuels were significantly blocked, without permeation during the permeation tests, in which the as‐blow‐molded PE/MPA bottle inhibited the permeation of hydrocarbon components more successfully than did the as‐blow‐molded PE/PA bottle. In contrast, the amounts of polar components that permeated through the as‐blow‐molded PE/PA and PE/MPA bottles were very small and about the same as the amount that permeated through the as‐blow‐molded PE bottle. Possible mechanisms accounting for these interesting behaviors are proposed in this study. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2827–2837, 2001     

Plasticized properties of poly (lactic acid) and triacetine blends

Systematically investigations of the plasticizing effects of triacetine (TAc) on crystallization, chain mobility, microstructure, and tensile properties of the Poly (lactic acid)/triacetine (PLA/TAc) blends are reported. A new transition hump was observed on the tan δ curve of PLA_xTAc_y specimens at temperatures ranging from ?80 to ?20°C. Thermal, wide angle X‐ray diffraction (WAXD) and dynamic mechanical analysis properties of PLA and PLA_xTAc_y series specimens suggest that PLA and PLA_xTAc_y series specimens can hardly crystallize by cooling the melt in room temperature. However, significant recrystallization of α form PLA crystals was found during the annealing processes of PLA_xTAc_y series specimens. Some “less perfect” β form PLA crystals were found as the TAc contents of PLA_xTAc_y specimens reach 30 wt %. Further morphological analysis show that the inherent brittle deformation behavior of the PLA specimen was successfully transformed into relatively ductile fracture behavior after blending sufficient but optimum amounts of TAc in PLA resins. Possible reasons accounting for this interesting recrystallization, thermal, microstructure and tensile properties of PLA_xTAc_y specimens are proposed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Novel contact hole fabrication using selective liquid-phasedeposition instead of reactive ion etching

This work forms a contact hole utilizing the selectively liquid-phase deposited (S-LPD) silicon-oxide technique instead of the conventional reactive ion etching (RIE). The n⁺/p junction diode with contact hole formed by S-LPD exhibits an order of magnitude less reverse current, larger forward current, smaller ideality factor, and better thermal stability than that formed by RIE. A Schottky junction with S-LPD contact hole also possesses several excellent characteristics, including ideality factor, reverse current and barrier height, even without sintering treatment. These characteristics confirm the effectiveness of the S-LPD technique in replacing conventional RIE to form contact holes, particularly for future ultra-shallow junctions     

An amorphous silicon random nanocone/polymer hybrid solar cell

This paper proposes and experimentally demonstrates an a-Si:H random nanocone/PEDOT:PSS/P3HT:PCBM hybrid solar cell to extend the absorption to near infrared and solve the difficulty of carrier transport through organic-inorganic interface. The internal electrical field inside a-Si:H random nanocone force holes move to the anode and electrons move to the cathode. The insertion of a layer of PEDOT:PSS conducting polymer between organic-inorganic interface could cause electrons and holes to partially recombine, thus establishing an electrically connected a-Si:H and P3HT:PCBM bulk heterojunction, which enables carriers transport through organic-inorganic interfaces efficiently. As compared to conventional polymer solar cells, the open-circuit voltage of hybrid solar cells was increased from 0.51 to 0.78 V. Additionally, the power conversion efficiency was increased from 1.73% to 2.22%, which demonstrates approximately 28% enhancement, indicating that the hybrid structure could largely increase the efficiency of polymer solar cells.