Floating zone convection

The microgravity research, as a branch of the advanced sciences and a spe- cialized field of high technology, has been made in China since the late 1980's. The research group investigating microgravity fluid physics consisted of our col- leagues and the authors in the Institute of Mechanics of the Chinese Academy of Sciences (CAS), and we pay special attention to the floating zone convection as our first research priority. Now, the research group has expanded and is a part of the National Microgravity Laboratory of the CAS, and the research fields have been extended to include more subjects related to microgravity science. Howev- er, the floating zone convection is still an important topic that greatly holds our research interests.

Three-dimensional superresolution by three-zone complex pupil filters

Complex pupil filters are introduced to improve the three-dimensional resolving power of an optical imaging system. Through the design of the essential parameters of such filters, the transmittance and radius of the first zone, three-dimensional superresolution is realized. The Strehl ratio and the transverse and axial gains of such filters are analyzed in detail. A series of simulation examples of such filters are also presented that prove that three-dimensional superresolution can be realized. The advantage of such filters is that it is easy to realize three-dimensional superresolution, and the disadvantage is that the sidelobes of the axial intensity distribution are too high. But this can be overcome by the application of a confocal system. (C) 2005 Optical Society of America.

Design and application of three-zone annular filters

We design three-zone annular filters to be applied to optical storage system. The designed filters extend the depth of focus and realize transverse superresolution simultaneously, which will improve the performance of optical storage system greatly. And we propose two feasible schemes to improve imaging resolution of three-dimensional imaging system. One scheme depends on a complex filter formed by cascading of a three-zone phase filter and a three-zone amplitude filter. The complex filter converge the optimized transverse superresolution and the optimized axial superresolution of two different filters onto a single filter. It can improve the three-dimensional imaging performances greatly. Another scheme depends on a single three-zone complex filter. We propose a three-zone complex filter with phase shift 0.8 pi, which presents bigger design margin, better imaging quality and stronger three-dimensional superresolution capability. (c) 2006 Elsevier GmbH. All rights reserved.

Superresolution by three-zone pure phase plate with 0, pi, 0 phase variation

Superresolution is very important in imaging and optical storage systems, and has attracted much attention. In this article, concentric three-zone phase plate with 0, pi, 0 phase variation has been investigated numerically to show that this kind of phase plate can be used to obtain three-dimensional superresolution. In addition, the number of intensity maximum, focal depth, focal shift, full-width half-maximum, and relative intensity of side lobe are listed for different radii of the phase zones, which paves the way for design of the phase plate. Therefore, one can choose values of radii for desired intensity distribution in focal region, such as for the purpose of radial superresolution with high focal depth in optical storage. (c) 2006 Elsevier Ltd. All rights reserved.

Single crystal beta-Ga2O3: Cr grown by floating zone technique and its optical properties

beta-Ga2O3: Cr single crystals were grown by floating zone technique. Absorption spectra and fluorescence spectra were measured at room temperature. The values of field splitting parameter Dq and Racah parameter B were obtained by the peak values of absorption spectra. The value 10Dq/B=23.14 manifests that in beta-Ga2O3 crystals Cr3+ ions are influenced by low energy crystal field. After high temperature annealing in air, the Cr3+ intrinsic emission was enhanced and the green luminescence disappeared. The strong and broad 691 nm emission was obtained at 420 nm excitation due to the electron transition occurred from T-4(2) to (4)A(2). The studies manifest that the beta-Ga2O3 crystals have the potential application for tunable laser.

Factors affecting leaf morphology: a case study of Ranunculus natans C. A. Mey. (Ranunculaceae) in the arid zone of northwest China

In order to examine the role of environmental factors affecting foliar morphology, we performed a case study of leaf morphological variation of Ranunculus natans found in the arid zone of northwest China. We found that foliar phenotypic variation differed significantly between populations. We described substantial positive correlations between altitude and leaf area (LA) as well as leaf perimeter (LP), and also between longitude and number of teeth, along with dissection index (DI). The pH, conductivity, and salinity of the environment caused a significant decrease in both LA and LP. Ranked in terms of their impacts on leaf morphology, the six selected factors were: altitude > pH > conductivity > salinity > longitude > latitude. We found that foliar morphological variations are functional responses to water-quantity factors (e.g., altitude and longitude at regional scales) and water-availability relation factors (e.g., pH, conductivity, and salinity at local scales), rather than to temperature-relation factors (latitude). Therefore, altitude and longitude, along with pH, conductivity, and salinity, are the main factors that significantly influence foliar morphology in the arid zone of China. We found that main factors played major roles in plant phenotypic plasticity in a complex ecosystem, although different combinations and interactions of environmental and geographical factors in each local environment may obscure the general trends in trait changes along environmental gradients.

Root zone microbial populations, urease activities, and purification efficiency for a constructed wetland

In order to investigate the effects of microorganisms and their urease activities in macrophytic root zones on pollutant removal, four small-scale plots (SSPs) of vertical/reverse-vertical flow wetlands were set up to determine: a) the relationship between the abundance of microorganisms in the root zones and water purification efficiency; and b) the relationship between urease activities in the root zones and pollutant removal in a constructed wetland system. Total numbers of the microbial population (bacteria, fungi, and actinomyces) along with urease activities in the macrophytic root zones were determined. In addition, the relationships between microbial populations and urease activities as well as the wastewater purification efficiencies of total phosphorus (TP), total Kjeldahl nitrogen (TKN), biochemical oxygen demand in 5 days (BOD5), and chemical oxygen demand (COD) were also analyzed. The results showed that there was a highly significant positive correlation (r = 0.9772, P < 0.01) between the number of bacteria in the root zones and BOD5 removal efficiency and a significant negative correlation (r = -0.9092, P < 0.05) between the number of fungi and the removal efficiency of TKN. Meanwhile, there was a significant positive correlation (r = 0.8830, P < 0.05) between urease activities in the root zones and the removal efficiency of TKN. Thus, during wastewater treatment in a constructed wetland system, microorganism and urease activities in the root zones were very important factors.

The methane hydrate formation and the resource estimate resulting from free gas migration in seeping seafloor hydrate stability zone

It is a typical multiphase flow process for hydrate formation in seeping seafloor sediments. Free gas can not only be present but also take part in formation of hydrate. The volume fraction of free gas in local pore of hydrate stable zone (HSZ) influences the formation of hydrate in seeping seafloor area, and methane flux determines the abundance and resource of hydrate-bearing reservoirs. In this paper, a multiphase flow model including water (dissolved methane and salt)-free gas hydrate has been established to describe this kind of flow-transfer-reaction process where there exists a large scale of free gas migration and transform in seafloor pore. In the order of three different scenarios, the conversions among permeability, capillary pressure, phase saturations and salinity along with the formation of hydrate have been deducted. Furthermore, the influence of four sorts of free gas saturations and three classes of methane fluxes on hydrate formation and the resource has also been analyzed and compared. Based on the rules drawn from the simulation, and combined information gotten from drills in field, the methane hydrate(MH) formation in Shenhu area of South China Sea has been forecasted. It has been speculated that there may breed a moderate methane flux below this seafloor HSZ. If the flux is about 0.5 kg m-2 a-1, then it will go on to evolve about 2700 ka until the hydrate saturation in pore will arrive its peak (about 75%). Approximately 1.47 109 m3 MH has been reckoned in this marine basin finally, is about 13 times over preliminary estimate.