The VATLY Radio Telescope

A small radio telescope (SRT) has been installed on the roof of the Hanoi astrophysics laboratory VATLY. It is equipped with a 2.6 m diameter mobile parabolic dish remotely controlled in elevation and azimuth and with super-heterodyne detection around the 21 cm hydrogen line. First results of observations of the Sun and of the centre of the Milky Way are presented. They demonstrate the high quality of the telescope performance and are used to evaluate lobe size, signal to noise ratios, anthropogenic interferences and measurement accuracies. Particular attention is given to the measurement of the pointing accuracy. The rich measurement programme that is now at hand is briefly sketched

Simulation of proton-induced and iron-induced extensive air showers at extreme energies

The development of extensive air showers at extreme energies is studied using a simulation model much simpler and cruder, but also more transparent and flexible, than existing sophisticated codes. Evidence for its satisfactory performance is presented. As an illustration, shower elongation rates are evaluated in the $10^{18}$ to $10^{20}$ eV region and compared with recently published data. Lateral distribution functions of both muons and electrons/photons are also briefly discussed. Reliable results are obtained in the comparison between proton-induced and iron-induced showers.Comment: 22 pages, Preprint submitted to Astroparticle Physic

Response of Water Cherenkov Detectors to Small Signals: a Case Study

Detailed studies of the response of the VATLY water Cherenkovdetector, a replica of those used in the ground array of the PierreAuger Observatory, are presented with emphasis on the response to lowamplitude signals. The method used is to detect decay electrons frommuons stopping in the water volume. Results include properties of the detection process as well as of the atmospheric cosmic ray flux

Extensive Air Showers and the LPM Effect

A very simple model of thelongitudinal development of electromagnetic showers is presented,allowing for easy calculations at the highest energies where usualsimulation codes become impracticable because of the enormousmultiplicity of secondary shower particles. Shower profiles aredescribed in terms of a few parameters having Gaussianfluctuations. The model is applied to the impact of theLandau-Pomeranchuk-Migdal effect on the shower development, whichis found negligible in practical cases

Investigation on Air Pollution in Vietnam : Concentration of Water-soluble Ions in Suspended Particulate Matters

Joint Research on Environmental Science and Technology for the Eart

The Vatly Radio Telescope: Performance Study

A detailed account of the performance of the VATLY radio telescope, operated in HaNoi on and near the 21 cm HI line, is given. Drift scans across the Sun are used to measure the dependence of the gain on frequency and power, revealing small nonlinearities at or below the percent level. Interferences associated with the electromagnetic pollution in the Ha Noi environment are described. The sensitivity of the instrument is discussed and demonstrated with the detection of the Crab. The reliability of the measurement of the spectral flux density is illustrated by comparing solar flux data measured in Ha Noi and at the Australian observatory of Learmonth

Effects of different fibre sources in pig diets on growth performance, gas emissions and slurry characteristics

The effects of different fibre sources in pig diets on growth performance, ammonia (NH3), hydrogen sulphide (H2S), greenhouse gas (GHG) emissions and slurry characteristics was studied on 20 crossbred pigs [Duroc x F1 (Landrace x Yorkshire)]. The experimental diets included one low-fibre (LF) diet without maize distiller’s dried grains with solubles (DDGS), brewer’s grain (BG) and coconut cake (CC) and 3 high-fibre (HF) diets with maize DDGS or BG or CC. The experiment was conducted according to a completely randomized design with 5 replications and lasted 62 days. In the growing period and the overall, pigs fed diets LF and HF-DDGS had higher average daily gain (ADG) compared to pigs fed diets HF-BG and HF-CC (P 0.05), while N and P excretions (g/head/day) were greater for diet HF-CC than for diet LF (P < 0.05). The CO2 emission was greater for diets HF-BG and HF-CC than for diets LF and HF-DDGS (P 0.05). In both periods, CH4 emission was lower in diet LF than in diet HF-BG and HF-CC (P < 0.05), while NH3 emission was higher for pigs fed diet LF than pigs fed HF-BG and HF-CC (P < 0.05). The H2 S emission was not affected by diets in both periods. In conclusion, different fibre sources in pig diets may be a practical method to alter growth performance, slurry characteristics and NH3, GHG emissions

Mapping Atomic Hydrogen in the Disk of the Milky Way

The VATLY radio telescope has been used to draw the map of atomic hydrogen gas in the disk of the Milky Way. Evidence has been obtained for its differential rotation, its cloud and arm structure and the presence of a dark matter halo

DRY DEPOSITION MONITORING IN VIETNAM AND REMOVAL OF AIR POLLUTANTS BY USING BIODIESEL FUEL

Joint Research on Environmental Science and Technology for the Eart