Liquid-core low-refractive-index-contrast Bragg fiber sensor

We propose and experimentally demonstrate a low-refractive-index-contrast hollow-core Bragg fiber sensor for liquid analyte refractive index detection. The sensor operates using a resonant sensing principle- when the refractive index of a liquid analyte in the fiber core changes, the resonant confinement of the fiber guided mode will also change, leading to both the spectral shifts and intensity changes in fiber transmission. As a demonstration, we characterize the Bragg fiber sensor using a set of NaCl solutions with different concentrations. Strong spectral shifts are obtained with the sensor experimental sensitivity found to be ~1400nm/RIU (refractive index unit). Besides, using theoretical modeling we show that low-refractive-index-contrast Bragg fibers are more suitable for liquid-analyte sensing applications than their high-refractive-index-contrast counterparts.Comment: 3 pages, 4 figure

Does participatory water management contribute to smallholder incomes? Evidence from Minle County, Gansu Province, P.R. China

Since the early 1990s, the Chinese water sector has undergone an important institutional reform that has shifted major responsibilities in irrigation management from the government toward water users, organized in so-called Water User Associations (WUAs). Such participatory water management is not only assumed to increase water use efficiency, but also to stimulate the incomes of member households. This study aims to provide empirical evidence of the impact of participatory water management on WUA performance and farmer incomes, using data collected for the year 2007 among 317 households and 35 WUAs in Minle County, Gansu Province. We find that having democratically elected leaders has a positive effect on WUA performance, by increasing investment levels and improving canal quality. Participation in decision making, however, has a significant negative impact on canal quality and does not affect other WUA performance indicators. Two aspects of WUA performance, investment levels and financial health, are found to have a positive impact on the farm income of member households, while water use per mu has a significant negative impact on farm incomes. We find evidence that households belonging to better performing WUAs increase their farm incomes at the expense of non-farm income. The resulting net impact of participatory water management on total household income is not significant for the households in our sample

Earthquake source parameters of the 2009 Mw 7.8 Fiordland (New Zealand) earthquake from L-band InSAR observations

The 2009 MW7.8 Fiordland (New Zealand) earthquake is the largest to have occurred in New Zealand since the 1931 Mw 7.8 Hawke’s Bay earthquake, 1 000 km to the northwest. In this paper two tracks of ALOS PALSAR interferograms (one ascending and one descending) are used to determine fault geometry and slip distribution of this large earthquake. Modeling the event as dislocation in an elastic half-space suggests that the earthquake resulted from slip on a SSW-NNE orientated thrust fault that is associated with the subduction between the Pacific and Australian Plates, with oblique displacement of up to 6.3 m. This finding is consistent with the preliminary studies undertaken by the USGS using seismic data

Thermophysical and thermochemical properties of new thermal barrier materials based on Dy2O3–Y2O3 co-doped zirconia

Dy2O3-Y2O3 co-doped ZrO2 would potentially give lower thermal conductivity and higher coefficient of thermal expansion, which is a promising ceramic thermal barrier coating material for aero gas turbines and high temperature applications in metallurgical and chemical industry. In this study, Dy2O3-Y2O3 co-doped ZrO2 ceramics were prepared using solid state reaction methods. Dy0.5Zr0.5O1.75 and Dy0.25Y0.25Zr0.5O1.75 consist of pure cubic fluorite phase, whereas both Dy0.06Y0.072Zr0.868O1.934 and Dy0.02Y0.075Zr0.905O1.953 have tetragonal and cubic composite phases. The influence of the chemical composition on coefficient of thermal expansion (CTE) and the thermal conductivity was investigated by varying the content of rare earth dopant. Dy0.06Y0.072Zr0.868O1.934 exhibited a lower thermal conductivity and higher coefficient of thermal expansion as compared with standard 8 wt.% Y2O3 stabilized ZrO2 which is used in conventional thermal barrier coatings. The compatibility between the thermally grown oxide that consists of Al2O3 and the new compositions is critical to ensure the durability of thermal barrier coatings. Hence, the compatibility between Al2O3 and Dy2O3-Y2O3 codoped YSZ was investigated by mixing two types of powders and eventually sintered at 1300˚C. Dy0.06Y0.072Zr0.868O1.934 is compatible with Al2O3, whereas YAlO3 and Dy3Al2(AlO4)3 were formed when Dy0.25Y0.25Zr0.5O1.75 and Al2O3 were mixed and sintered

On the Integrability, B\"Acklund Transformation and Symmetry Aspects of a Generalized Fisher Type Nonlinear Reaction-Diffusion Equation

The dynamics of nonlinear reaction-diffusion systems is dominated by the onset of patterns and Fisher equation is considered to be a prototype of such diffusive equations. Here we investigate the integrability properties of a generalized Fisher equation in both (1+1) and (2+1) dimensions. A Painlev\'e singularity structure analysis singles out a special case ($m=2$) as integrable. More interestingly, a B\"acklund transformation is shown to give rise to a linearizing transformation for the integrable case. A Lie symmetry analysis again separates out the same $m=2$ case as the integrable one and hence we report several physically interesting solutions via similarity reductions. Thus we give a group theoretical interpretation for the system under study. Explicit and numerical solutions for specific cases of nonintegrable systems are also given. In particular, the system is found to exhibit different types of travelling wave solutions and patterns, static structures and localized structures. Besides the Lie symmetry analysis, nonclassical and generalized conditional symmetry analysis are also carried out.Comment: 30 pages, 10 figures, to appear in Int. J. Bifur. Chaos (2004