Trichloroacetic acid‐imprinted polypyrrole film and its property in piezoelectric quartz crystal microbalance and electrochemical sensors to application for determination of haloacetic acids disinfection by‐product in drinking water

A molecularly trichloroacetic acid (TCAA) imprinted non‐crosslinked polypyrole (TCAA‐MIPpy) has been successfully prepared and evaluated in its properties for both piezoelectric quartz crystal microbalance (QCM) and electrochemical means of detection, and application of such sensors for determination of haloacetic acid concentrations in water. Haloacetic acid selectivity was demonstrated in gravimetric or in electrochemical sensors via either cyclic voltammetric or inter‐digitated conductometric (IDC) analyses studies upon comparison with nonimprinted polypyrrole and TCAA‐imprinted polypyrrole. The measurement results with all these systems revealed that the prepared molecularly imprinted polymer can recognize TCAA well from structurally similar compounds. The TCAA‐MIPpy incorporated with only the IDC transduction system produced the specific signal for TCAA detection in aqueous environment, which is useful for the quantifying TCAA disinfection by‐product in water. The analytical application for determination of TCAA in real‐life samples was readily achieved with the incorporation of TCAA‐MIPpy in the IDC analysis system, the results revealing the high sensitivity and selectivity of the method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Application of automated blind for daylighting in tropical region

This paper reports an experimental and simulation study on application of automated Venetian blind for daylighting in tropical climate. A horizontal blind system operating automatically under programmed control was constructed and integrated onto the glazed windows to form a window system with an automated blind in a room of a laboratory building. A dimming controller was also integrated to the lighting system of the room. Different operation schemes of the window system were devised and tested in the attempt to maximize energy savings while maintaining the quality of the visual environment in the room. Intensive measurement of illuminance of the interior space was undertaken during the experiments. A methodology for calculation of interior daylight illuminance and associated glare corresponding to the configurations of the experiments was adopted. The method was coded into a computer program. Results of calculation from the program agree well with those from experiments for all the schemes of operation conducted. The program was used to simulate the situation when each scheme of operation was implemented for a whole year. It was found that such window system with automated blind enabled energy savings of 80%, but a more sophisticated scheme also helped maintain the interior visual quality at high level.     

Density functional theory evidence for an electron hopping process in single-walled carbon nanotube-mediated redox reactions

The electron hopping mechanism in the single-walled carbon nanotube (SWCNT)-mediated redox reaction between anthraquinonyl (AQH₂) and 4-arylhydroxyl amine (4AHA) groups is studied by density functional theory calculations. The (8, 0) SWCNT is used to mimic the real system of interest. It is found that electrons from the oxidized AQH₂ group can be transferred to the oxidizing 4AHA group, at the other end of the nanotube, by a hopping process through the mediating SWCNT. Disparity of electron densities ascribable to non-localized electrons confirms this finding. The disparity, partial electron density difference, and Hirshfeld partial charges analyses show that the SWCNT can hold 87% of the extra electron density of the hypothetical negative intermediate produced from the oxidation of the AQH₂ process. Chemical attachments of these two redox reagents to the SWCNT also cause new impurity states within the band gap, thereby giving more metallic characteristics to the system. These findings provide a detailed understanding of the electron hopping process and agree well with a previous experimental study.     

Comparative study of sub-volt differential difference current conveyors

Enhancing the performances of analog circuits with sub-volt supplies becomes a great challenge for circuit designers. Techniques such as bulk-driven (BD) and quasi-floating gate (QFG) count among the suitable ones for ultra-low voltage (ULV) operation capability with extended input voltage range and simple CMOS circuitry. However, in comparison to the conventional gate-driven (GD) MOS transistor (MOST), these techniques suffer from several disadvantages such as low transconductance value and bandwidth that limit their applicability for some applications. Therefore, the idea of merging the BD and QFG techniques to eliminate their drawbacks appears as efficacious solution. This new merging is named bulk-driven quasi-floating gate (BD-QFG)^* technique and in order to demonstrate its advantages in compassion to BD and QFG ones, this paper presents a comparison study of three ULV differential difference current conveyor (DDCC) blocks based on BD, QFG and BD-QFG techniques. The significant increment of the transconductance and the bandwidth values of the BD-QFG are clearly observed. The proposed CMOS structures of the DDCCs work at ±300 mV supply voltage and 18.5 µW power consumption. The simulation results using 0.18 µm CMOS n-Well process from TSMC show the features of the proposed circuits.     

The fluidity of fly ash-cement paste containing naphthalene sulfonate superplasticizer

The zeta potential measurement indicated that the surface potential of fly ash was different from ordinary Portland cement (OPC) in both sign and value. Hence, the Derjaguin-Landau-Verway-Overbeek (DLVO) theory for dispersion-flocculation of heterogeneous particles with different surface potentials was applied to explain the influence of fly ash on the rheology of cement paste containing naphthalene sulfonate superplasticizer. For the fly ash-cement paste without superplasticizer, the sign of zeta potential of fly ash was different from OPC. Thus, the extent of the potential energy barrier between particles was small or even showed negative value, and the change in the rheology of the fly ash-cement paste was mainly dependent on the bulk solid volume of fly ash, which was related to available free water for fluidizing paste. For the fly ash-cement paste with naphthalene sulfonate superplasticizer, fly ash and cement had the same sign and dispersed well due to higher potential barrier. The extent of potential energy barrier depended on the absolute value of surface potential, which was represented by a function of the amount of adsorbed superplasticizer. The bulk solid volume of fly ash also affected the change in flow ability, but the effect of potential energy barrier between particles was superior to that of the bulk solid volume of fly ash.     

Theoretical study on novel double donor-based dyes used in high efficient dye-sensitized solar cells: The application of TDDFT study to the electron injection process

The geometries and electronic structures of organic dye sensitizers, CCT1A, CCT2A, CCT3A, CCT1PA, and CCT2PA comprising double-donor groups, π-spacer, and acceptor group forming D–D–π–A system, were studied using DFT and TDDFT. The calculated results have shown that TDDFT calculation using a newly-designed functional which takes into long-range interaction, CAM-B3LYP, was reasonably capable of predicting the excitation energies and the absorption spectra of the molecules. The adsorption of these dyes on the TiO₂ anatase (1 0 1) surface and the electron injection mechanism were also investigated using a dye-(TiO₂)₃₈ cluster model, employing PBE and TD-CAM-B3LYP calculations, respectively. The adsorption energy (E_ads) of CCTnA (n = 1–3) was calculated to be ?15.26, ?18.93, and ?20.12 kcal/mol respectively, indicating strong adsorption of dye to a TiO₂ surface by carboxylate groups. These calculated results suggested that the CCT3A is a promising candidate for highly efficient DSSCs. It was shown that the electron injection mechanism occurs by direct charge-transfer transition in a dye-TiO₂ interacting system, resulted in the stronger electronic coupling strengths of the anchoring group of the dyes and the TiO₂ surface which corresponded to higher observed J_sc as expected in CCT3A dye. Through a combined theoretical and experimental investigation we have shown that the trend of charge-injection efficiency in dye-sensitized solar cells constituted from dyes is determined by the adsorption energy of dye-(TiO₂)₃₈ complexes.     

Thiosalicylic acid as a devulcanizing agent for mechano-chemical devulcanization

A mechano-chemical devulcanization process for vulcanized natural rubber (NV) was investigated. Thiosalicylic acid was used as a test devulcanizing agent in comparison to diphenyl disulfide as the reference. The optimum condition for devulcanization of NR vulcanizates (NVs) was found to be grinding of the NV and subsequent mixing with a selected devulcanizing agent at 140°C for 30 min. The degree of devulcanization was indicated by using sol-gel fractions of the devulcanized rubber (DVR). Revulcanized rubber was made by using virgin natural rubber (NR) containing DVR at different ratios. The tensile strength of the DVR/NV composite, after revulcanization, decreased by 5–10%, while the elongation at brake was improved by 5–10% at a DVR content of 5–15%. Devulcanization of industrial truck tires, as a typical sample of industrial products, was also demonstrated for the practical application of this technique.     

Distributions of sky luminance and radiance of North Bangkok under standard distributions

In the tropics, the sky is luminous and variable. Distribution of luminance over the sky dome is non-uniform and varies widely and dynamically with weather condition. The high luminosity offers good potential for daylighting, but an understanding of the luminance distribution of tropical sky would help advance the movement for daylighting. This paper reports results of a characterization of sky luminance and radiance under the standard sky luminance patterns proposed by Kittler using measurements from a station located north of Bangkok. In accordance to the standard sky luminance classification, the sky patterns of north Bangkok mostly fall into clear and intermediate types. During cooler months, the sky is clear for over 60% of the time. In the midst of the rainy season, the sky falls into the intermediate category for over 40% of the time. The high incidence of clear sky on this classification differs from earlier results that use sky ratio and Perez's clearness indices in the classification of sky condition.     

Effect of fly ash on autogenous shrinkage

The correlation between autogenous shrinkage and degree of hydration of fly ash was determined with the selective dissolution method. Then, the relationship between the degree of hydration of fly ash and autogenous shrinkage was examined. The results showed that the degree of hydration of fly ash increased as its Blaine surface area increased. The degree of hydration of fly ash increased with time, and autogenous shrinkage increased corresponding to the increase in the degree of hydration of fly ash. Moreover, it was found that the total quantity of Al₂O₃ in cement-fly ash samples affected autogenous shrinkage at early ages, but the long-term influence was very small.     

CMOS WTA maximum and minimum circuits with their applications to analog switch and rectifiers

This paper presents design of a voltage-mode multiple-inputs winner-take-all (WTA) maximum (max) and minimum (min) circuits. The proposed circuits are realized in a CMOS technology with low-component counts of transistors. They display usability of the proposed building block, where the maximum bandwidth of voltage follower is around 1 GHz and low-delay time is around 1.5 ns with high-input and low-output impedances. The THD obtained is around 0.8% within the 0.6Vp−p input range. The power dissipation of the proposed circuits is obtained to be around 0.62 mW with ±1.25 V power supplies. In applications, half-wave and full-wave rectifiers and analog switch are included. Computer simulation results by using SPICE program with TSMC 0.25 μm are carried out to show the performance of the proposed WTA max and min circuits, rectifiers and analog switch. In addition, the sample layout of the max circuit occupies an area of around 798 μm² and post-layout simulation results are exhibited to concrete the pre-layout simulation results.