The Radon Monitoring System in Daya Bay Reactor Neutrino Experiment

We developed a highly sensitive, reliable and portable automatic system (H$^{3}$) to monitor the radon concentration of the underground experimental halls of the Daya Bay Reactor Neutrino Experiment. H$^{3}$ is able to measure radon concentration with a statistical error less than 10\% in a 1-hour measurement of dehumidified air (R.H. 5\% at 25$^{\circ}$C) with radon concentration as low as 50 Bq/m$^{3}$. This is achieved by using a large radon progeny collection chamber, semiconductor $\alpha$-particle detector with high energy resolution, improved electronics and software. The integrated radon monitoring system is highly customizable to operate in different run modes at scheduled times and can be controlled remotely to sample radon in ambient air or in water from the water pools where the antineutrino detectors are being housed. The radon monitoring system has been running in the three experimental halls of the Daya Bay Reactor Neutrino Experiment since November 2013

A study of the effect of ionization and illumination on morphologies of planetary nebulae

We carry out a modelling study of the effect of ionization and illumination on the morphologies of planetary nebulae (PNs), aiming to investigate the hypothesis of Kwok (2010) that the bipolar and multipolar lobes of PNs can be produced by leakage of UV photons into those directions. Using photoinization code, we construct a series of nebular models consisting of a dense envelope and cones of low density. The results show that the visible morphologies of PNs may be fundamentally different from their intrinsic structures. © 2012 International Astronomical Union.published_or_final_versio

HUBBLE SPACE TELESCOPE OBSERVATIONS AND GEOMETRIC MODELS OF COMPACT MULTIPOLAR PLANETARY NEBULAE

published_or_final_versio

An Infrared Imaging Study of the Bipolar Proto-Planetary Nebula IRAS 16594-4656

High-resolution mid-infrared images have been obtained in N-band and Q-band for the proto-planetary nebula IRAS 16594-4656. A bright equatorial torus and a pair of bipolar lobes can clearly be seen in the infrared images. The torus appears thinner at the center than at the edges, suggesting that it is viewed nearly edge-on. The infrared lobes correspond to the brightest lobes of the reflection nebula seen in the Hubble Space Telescope (HST) optical image, but with no sign of the point-symmetric structure seen in the visible image. The lobe structure shows a close correspondence with a molecular hydrogen map obtained with HST, suggesting that the dust emission in the lobes traces the distribution of the shocked gas. The shape of the bipolar lobes shows clearly that the fast outflow is still confined by the remnant circumstellar envelope of the progenitor asymptotic giant branch (AGB) star. However, the non-detection of the dust outside of the lobes suggests that the temperature of the dust in the AGB envelope is too low for it to be detected at 20 microns.Comment: Accepted by the Astrophysical Journa

Development of a GIS Based Water Management Tool for a Large Scale Rice Irrigation Scheme

A GIS based model was developed to integrate the vast amounts of spatially distributed information from the Kerian Irrigation Scheme comprising eight compartments which are further subdivided into 28 blocks. The model consists of three modules. The "Scheduling" program computes irrigation deliveries based on spatial and temporal demand of the paddy field by each compartment, block or secondary canal. The "Monitoring" program gives information by compartment and by block on the uniformity of water distribution and the shortfall or excess. Relative Water Supply (RWS), Water Use Efficiency (WUE), Cumulative Relative Water Supply (CRWS), and Water Productivity Index (WPI) were computed by the "Evaluation" module. The post-season analysis uses weekly information on hydro-climatic parameters, irrigation delivery and irrigation indices by block within each compartment. On a weekly basis, RWS and WUE were found to range from 1.01 to 2.24 and 45% to 99% respectively in the main season and 1.01 to 1.87 and 53.57% to 96.15% respectively in the off season. The average values of RWS and WUE were found to be 1.53 and 68.15% in the main season and 1.33 and 78.47% in the off season respectively. The average values of WPI were also found to be 0.13 and 0.22 kg/m3 in the main season and off seasons respectively. Color-eoded thematic maps were produced for the monitoring of Seasonal Yields and Cropping Intensity (CI) by block and compartment of the scheme. The results are displayed allowing the manager to view maps, tables and graphs in a comprehensible form to ease decision making as the season progresses. This study would be useful to improve the irrigation system management based on feedback of field information