Nano Temperature Sensor Using Selective Lateral Growth of Carbon Nanotube Between Electrodes

This paper presents lateral growth of carbon nanotube (CNT) between two electrodes and its use as nano temperature sensor. Fabrication of electrodes is made by MEMS techniques. The CNT is grown selectively by microwave plasma chemical vapor deposition between two electrodes. After wire bonding, the grown CNT is tested and calibrated. The growth conditions of CNT, such as the flow rate of CH₄ or N₂ gas, are varied to obtain a high-quality CNT sensor. SEM is used to observe the shape and structure of CNT, while Raman spectrum analysis is used to indicate the degree of graphitization or amorphous structure in the CNT. The I-V curve of CNT is measured at different temperature, and a linear relationship between the electric resistance of CNT and the temperature is obtained. This result indicates that CNT can be used as a temperature sensor     

CONSECUTIVE ESTERIFICATION OF 1,4-BUTANEDIOL WITH ACRYLIC ACID BY HOMOGENEOUS CATALYSIS

The esterification of 1,4-butanediol with acrylic acid catalyzed by sulfuric acid in the absence of solvent was studied in a batch stirred reactor. Experiments were carried out with different acid/ alcohol mole ratios and different amounts of sulfuric acid in the temperature range 70 to 90°C and 1 atm. It was found that the esterification of 1.4-butanediol with acrylic acid is a two-step consecutive, reversible reaction and each esterification step follows a first-order rate expression with respect to each component. A kinetic model was proposed to describe such a consecutive, reversible esterification reaction catalyzed by sulfuric acid. The equilibrium constants were determined from the equilibrium concentrations of each component while the rate constants in each reaction step were calculated by correlating the experimental data with the developed kinetic model.     

Concurrent process/inspection planning for a customized manufacturing system based on genetic algorithm

Producing products with multiple quality characteristics is always one of the concerns for an advanced manufacturing system. To assure product quality, finite manufacturing resources (i.e., process workstations and inspection stations) could be available and employed. The manufacturing resource allocation problem then occurs, therefore, process planning and inspection planning should be performed. Both of these are traditionally regarded as individual tasks and conducted separately. Actually, these two tasks are related. Greater performance of an advanced manufacturing system can be achieved if process planning and inspection planning can be performed concurrently to manage the limited manufacturing resources. Since the product variety in batch production or job-shop production will be increased for satisfying the changing requirements of various customers, the specified tolerance of each quality characteristic will vary from time to time. Except for finite manufacturing resource constraints, the manufacturing capability, inspection capability, and tolerance specified by customer requirement are also considered for a customized manufacturing system in this research. Then, the unit cost model is constructed to represent the overall performance of an advanced manufacturing system by considering both internal and external costs. Process planning and inspection planning can then be concurrently solved by practically reflecting the customer requirements. Since determining the optimal manufacturing resource allocation plan seems to be impractical as the problem size becomes quite large, in this research, genetic algorithm is successfully applied with the realistic unit cost embedded. The performance of genetic algorithm is measured in comparison with the enumeration method that generates the optimal solution. The result shows that a near-optimal manufacturing resource allocation plan can be determined efficiently for meeting the changing requirement of customers as the problem size becomes quite large.     

ELF Electric Field Coupling to Dielectric Spheroidal Models of Biological Objects

The extremely low frequency (ELF) electric field coupling to dielectric spheroidal models of biological objects is studied. Simple expressions are obtained to determine the internal electric field strength induced inside two nonspherical spheroids; a prolate dielectric spheroid and an oblate dielectric spheroid. Certain numerical results are graphically presented for various geometric shapes of the spheroid. The results show that, unlike the symmetric dielectric sphere, the relative position of the spheroid with respect to the orientation of the impressed electric field is an extremely important parameter which considerably affects the electric field coupling.     

Regionalization of natural flow regime: application to environmental flow optimization at ungauged sites

In this work we use the regionalization approach (RA) to derive the natural flow regime at an ungauged site. The derived natural flow regime, expressed by the regional cdf models of 32 indicators of hydrologic alteration (IHA) is used in the histogram matching approach (HMA) to seek the optimal environmental flows for a proposed multiobjective diversion weir in Taiwan. The results reveal that the outcomes associated with the planning constant scheme are significantly improved by the optimal time‐varying scheme. The histogram dissimilarities of 32 IHA associated with the planning scheme are consistently greater than those associated with the optimal scheme, especially for low‐flow IHA. Despite the inherent discrepancy between different approaches to generating flow data at the ungauged site, the optimal outcomes resulting from the RA‐based natural flow regime appear to be plausible and consistent with those reported in the previous work, thus validating the RA used in this work. We also explore the effect of weighting factors on the optimal outcomes. The results reveal that the weighting factor of the ecosystem needs objective dominates all optimal outcomes, while those of the agricultural demands and interbasin transfers objectives have minor effects on the optimal outcomes. The global optimal solution is obtained with a full or null weighting assigned to the ecosystem needs objective, while the least optimal solution is obtained as the interbasin transfers objective is given a null weighting and the agricultural demands objective is weighted more than the ecosystem needs objective. River managers and decision makers may select more balanced weir operation strategies based on the results presented in this work. Copyright © 2008 John Wiley & Sons, Ltd.     

Cu/SiO2 catalyst prepared by electroless method

Cu/SiO₂ catalysts prepared by an electroless deposition method were investigated and compared with those by an impregnation method. Copper contents varied from 5% to 15% and SiO₂ was used as support. All catalysts were characterized by BET, DSC, SEM and TPR and tested by an n-butanol dehydrogenation reaction for activities and stabilities. BET analysis showed that the catalysts prepared by the two methods present larger average pore size and less surface area than those of the fresh SiO₂, indicating that smaller pores may get blocked during the course of preparation. This blockage is more severe in the impregnation method. SEM photos showed that the electroless method produces smaller copper crystals than the impregnated method. The reaction activity was found to be in the order of the calcined electroless copper catalyst>the fresh electroless copper catalyst>impregnated copper catalyst. © 1998 Society of Chemical Industry     

Compression molding simulation of chopped fiber reinforced polymeric composites in plate-rib type geometry

A study on anisotropic material flow of polymeric composites in compression molding was conducted. Flow resistance and material anisotropy were measured by compression and tension tests to quantify the inhomogeneity of chopped fiber reinforced polymeric composites. The material was assumed to obey Hill's anisotropic yield criterion with its associated flow rule. An anisotropic finite element formulation was developed to simulate the material flow under various conditions. This two-dimensional model was applied to plane strain compression in a mold with plate-rib type geometry to substantiate the effect of fiber induced anisotropy. The predictions were compared with experimental results.     

Propagation of Surfactant-Dispersed Multiwalled Carbon Nanotubes in Porous Media

Understanding the transport of carbon nanotubes in porous media is essential to their applications in subsurface reservoirs, e.g., delivering catalysts or chemicals to targeted formations. In this study, a series of laboratory experiments are conducted to explore the transport of surfactant-dispersed multiwalled nanotubes (MWNT) in different porous media in flow-through columns at elevated electrolyte levels. Noncovalent bonding of ethoxylated alcohols adsorbed on the MWNT surface provides them with outstanding dispersion stability and excellent transport properties in a crushed-limestone sand pack. Superior transport performance in silica sand is obtained with binary nonionic–anionic surfactant formulations, which provide both steric repulsion and electrostatic repulsion between nanoparticle–nanoparticle and nanoparticle–sand surface. The mobility of MWNT suspensions are further investigated in the exposure to multiphase flow, e.g., with residual oil present, or coinjected with air into the sand pack. Coinjecting surfactant-dispersed MWNT suspensions with air (i.e., MWNT-stabilized foams) has hardly any impact on their propagation; retention in the sand pack remains quite low. With the presence of oil in the sand pack, the transport of MWNT suspensions is highly dependent on the type of surfactants used as the dispersant. For surfactants that achieved modest interfacial tension (IFT) reduction, the injected MWNT suspension bypasses the oil phase, and little impact on retention is observed. When the dispersant surfactant is also adjusted for an ultralow IFT condition, greater MWNT retention in the porous medium is observed because surfactants detach from the MWNT surface and aggressively partition to the oil/water interface, allowing the MWNT to flocculate and become deposited in the porous medium.