Search

• A detail study of rain fade at Ka band over tropical region has been done. • Performance comparison of experimental link at 20/30 GHz with ITU-R model done. • "s" parameter relating fade slope to filter characteristics is calculated. Dynamic characteristics of Ka band rain fade (or rain attenuation) over tropical region are relatively less studied, though they are essential for implementation of suitable fade mitigation techniques. In this paper, dynamic characteristics of rain fade at 20 GHz and 30 GHz from GSAT-14 satellite are reported with experimental measurements at Ahmedabad, India. ITU-R model for fade slope probability distribution has been analyzed in this paper and Ka band rain fade has been investigated based on this fade-slope analysis. The ITU-R model is found to closely match 20 GHz measurements, though differences increase at 30 GHz. Fade slopes are found to be within ±0.5 dB/s at both 20 and 30 GHz. Both positive and negative slopes of the fade slope distributions are quasi-similar. ITU-R model's s parameter, relating fade slope to filter characteristics, is found to be very close to the measured value for this region. Distributions of fade slopes are also found to be dependent on the standard deviation values similar to ITU-R recommendation at 20 GHz, but significant deviation is observed at 30 GHz. This observed frequency dependency might be due to increase in cloud attenuation at high frequencies or may be due to limited data set. Results indicate needs of further experimental data at high frequencies from other tropical regions to gain further insight into the fade slope characteristics. This will ultimately help in designing a better prediction model in future. [ABSTRACT FROM AUTHOR]

Abstract: Although reinforced concrete structures are designed as per codes/standards but enough care is not always taken during construction process. As a result, the structures start showing signs of distress, some times less than 10 years of service life, requiring early repair and rehabilitation work. In this paper, a case study of 3 no. (G+8) multi-storeyed buildings badly damaged due to corrosion and Bhuj (India) earthquake of 2001, rehabilitated in 2003 has been presented. Repair strategy involved removal of delaminated carbonated concrete cover, application of rust remover, anti-corrosion coating, polymer bond coat, polymer modified mortar, injection of low viscosity epoxy grout to beam-column junctions and cracks, repair of masonry cracks with polymer modified mortar & grouting with SBR modified cement grout and jacketing of columns at the ground floor. Extensive material testing was carried out and specifications for acrylic and SBR polymer modified mortar were selected for durable repairs. Strict quality control and assurance both in material and workmanship was adopted. After nine years of successful rehabilitation and functioning, some signs of distress in the form of cracks and spalls due to rebar corrosion have been noted at some locations, requiring rehabilitation again. Some recommendations/conclusions have been given for durable concrete constructions and rehabilitation work. [Copyright &y& Elsevier]

The current study presents the oxidative potential (OP) along with a wide range of chemical speciation of particulate matter with an aerodynamic diameter less than 10 μm (PM 10) at five sites representing different environments in Ahmedabad, a big city in western India. On an average, PM 10 concentrations were 116 ± 36, 228 ± 43, 133 ± 29, 101 ± 21, and 70 ± 20 μg m−3; volume-normalized OP (OP V) were 2.51 ± 0.71, 5.62 ± 0.68, 2.69 ± 0.76, 2.14 ± 0.41, and 1.55 ± 0.51 nmol DTT min−1 m−3; and mass-normalized OP (OP M) were 22 ± 3, 25 ± 5, 21 ± 6, 21 ± 2, and 22 ± 3 pmol DTT min−1 μg−1 over Bapunagar (backward residential area), Narol (industrial), Paldi (bus transport hub), Income Tax (huge running traffic) and Science City (posh residential area), respectively. Overall, OP V showed a significant linear correlation with PM 10 , whereas OP M showed near uniformity with increasing PM 10. Although the OP M values were similar, the site-to-site variability in PM 10 concentration reflects the corresponding health risks associated with PM 10 exposure for the people living in these areas. Further, a noticeable temporal variation in OP M at Narol and Paldi suggests that species with diverse OP M contributed to PM 10 on different days. A strong linear relationship between the ratio of OP V to the mass concentration of organic carbon (OP OC) and the ratio of m/z 43 signal to total water-soluble organic aerosols (WSOA) signals (f43) suggests that the fossil-fuel combustion derived WSOA have higher OP. Furthermore, the relationships of OP with water-soluble trace metals and brown carbon are also investigated and discussed in this paper. Nitrogenous organic compounds particularly emitted from the traffic-related sources in Paldi and Income Tax have higher OP OC than those emitted from other sources over Bapunagar, Narol, and Science City. Image 1 • Oxidative potential (OP) cannot be determined by PM 10 mass alone. • Volume-normalized OP shows a significant spatial variability over Ahmedabad. • Nitrogenous organics from the traffic-related sources have higher OP. [ABSTRACT FROM AUTHOR]