Groundwater simulation models have been incorporated into a genetic algorithm to solve three groundwater management problems: maximum pumping from an aquifer; minimum cost water supply development; and minimum cost aquifer remediation. The results show that genetic algorithms can effectively and efficiently be used to obtain globally (or, at least near globally) optimal solutions to these groundwater management problems. The formulation of the method is straightforward and provides solutions which are as good as or better than those obtained by linear and nonlinear programming. Constraints can be incorporated into the formulation and do not require derivatives with respect to decision variables as in nonlinear programming. More complicated problems, such as transient pumping and multiphase remediation, can be formulated and solved using this method. The computational time required for the solution of genetic algorithm groundwater management models increases with the complexity of the problem. The speedup attainable by solving genetic algorithm problems on massively parallel computers is significant for problems where the simulation time required to complete each generation is high. have included linear programming [Aguado et al., 1974; Molz and Bell, 1977; Willis, 1979], nonlinear programming Paper number 94WR00554. ß 0043-1397/94/94 WR-00554505.00 [Gorelick et al., 1979, 1984; Wanakule et al., 1986; Ahlfeld et al., 1988; McKinney and Lin, 1992b], dynamic programming [Andricevic, 1990; Lee and Kitanidis, 1991; Culver and Shoemaker, 1992], and optimal control [Willis and Newman, 1977; Jones et al., 1987]. Extensive literature reviews on this topic can be found in the works by Gorelick [ 1983], Ahlfeld [1986], and Willis and Yeh [1987].Nonlinear programming techniques have been used to solve groundwater management problems for the past decade. These methods employ gradient-based algorithms to adjust decision variables so as to optimize the objective function of a management model. These algorithms require the computation of sensitivities of state variables, e.g., head or concentration, at certain locations to decision variables, e.g., pumping rates, at other locations. Sensitivities can be obtained by either the adjoint sensitivity or perturbation methods [Yeh, 1986]. These sensitivities are difficult to program, in the case of the adjoint sensitivity method, or computationally expensive to generate, in the case of perturbation methods, and in general, are not robust. Furthermore, the cost functions of typical groundwater system components may be either discontinuous, e.g., well field capital costs, or highly complicated, e.g., treatment process costs, making it difficult to calculate or estimate the derivatives of these functions with respect to the decision variables. Groundwater management problems tend to be highly nonlinear and nonconvex mathematical programming problems, especially in the case of aquifer remediation design with mass transport constraints. As such, there is no guarantee that a global optimum o...

The term nanoimprint lithography (NIL) describes a number of processes used to form nanoscale structures by molding or embossing. Step and flash imprint lithography (S-FIL, a trademark of Molecular Imprints, Inc.) is a variant of NIL that can be performed at room temperature and low pressure. In S-FIL, a low-viscosity liquid imprint material is hardened in a patterned template by exposure to UV light. S-FIL is ideally suited to integrated-circuit device fabrication. Materials development for S-FIL has progressed significantly since its introduction in 1999. We discuss the status of materials development, with specific emphasis on the imprint material and functional materials, template fabrication and release layers, and S-FIL process variations.

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This paper presents the first micrometeorological-based measurements of methane (CH4) emissions from Asian rice paddies of which we are aware. The research features the tunable diode laser trace gas analyzer system (TGAS) recently developed at the University of Guelph. CH 4 fluxes were measured between March 9 and 24, 1992, from an irrigated rice paddy field at the International Rice Research Institute (IRRI), the Philippines. The daytime CH 4 flux averaged 6.0/xg m -2 s -1 . The CH 4 fluxes displayed a diurnal trend similar to daily soil temperature curves, with peak emissions of about 8/xg m -2 s -1 in the early afternoon. A tenfold increase in CH 4 emissions (to about 70/xg m -2 s -1) during a brief weeding experiment resulted from soil disturbance. Up to 25/xg m -2 s -1 of CH 4 were released during a drying of the field, after which unsuitable soil redox potentials apparently suppressed methanogenesis. The CH 4 flux was also arrested when the field was flooded with oxygen-rich water during a heavy rainstorm. where Fme flux of CH 4 (/xg m -2 s-l); K eddy diffusivity (m2 s -•); ACme change in CH 4 concentration (/xg m-3); Az (m) vertical height difference. TGAS measurements were used to determine a finite CH 4 concentration difference ACme. Three estimates of the eddy diffusivity K were inferred using micrometeorological tech-SIMPSON ET AL.' TUNABLE DIODE LASER MEASUREMENT OF METHANE FLUXES 7285 OF METHANE FLUXES 7289

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An epitaxial layer of an InGaN light-emitting diode (LED) structure was separated from a truncated-triangle-striped patterned-sapphire substrate through a chemical lift-off (CLO) process. A crystallographic stable and terminated V-shaped GaN grooved pattern was observed on the lift-off GaN surface. A peak wavelength blueshift phenomenon of the micro-photoluminescence spectrum was observed on the lift-off LED epitaxial layer (440.7 nm) compared with the LED/sapphire structure (445.8 nm). The free-standing LED epitaxial layer with a 453 nm electroluminescence emission spectrum was realized through a CLO process with the potential to replace the traditional laser lift-off process for vertical LED applications. (c) 2010 The Japan Society of Applied Physic

InGaN-based light-emitting diodes (LEDs) grown on triangle-shaped patterned sapphire substrates were separated through a chemical lift-off process by laterally etching an AlN sacrificial layer at the GaN/sapphire substrate interface. After the epitaxial growth, an air-void structure was observed at the patterned region on the sapphire substrate that provided an empty space to increase the lateral etching rate of the AlN buffer layer. The lateral etching rate of the AlN buffer layer was calculated at 10 mu m/min for the 100-mu m-width LED chip that was lifted off from the sapphire substrate. A triangular-shaped hole structure and a hexagonal-shaped air-void structure were observed on the lift-off GaN surface that was transferred from the patterned sapphire substrate. Comparing to the LED/sapphire structure, a peak wavelength blueshift phenomenon of the micro-photoluminescence spectra was observed on the lifted off LED chip caused by the release of a compressive strain at the GaN/sapphire substrate interface. The chemical lift-off process was achieved by using an AlN buffer layer as a sacrificial layer in a hot potassium hydroxide solution. (C) 2010 The Japan Society of Applied Physic