Performance of Concrete Exposed to Corrosive Environment

A comprehensive programme to investigate the behaviour of portland cement concrete exposed to corrosive environment was chalked out in this short duration study.The programme composed of compressive strength study, weight loss study , effect of carbonation, pH test study and study of ultrasonic pulse velocity test. Investigation to study the performance of portland cement concrete of M20 strength exposed to corrosive environment ( 5% H2SO4 Solution, 5% HC 1 Solution, 10% (NH4SO4 Solution and 10% NaOH Sol- ution ) revealed that the concrete cube deteriorated more in acidic environment than alkaline environment. The stre-ngth of PCC exposed to aggressive medium reduced signif- icantly after exposure of 28 days. This reduction in strength was mainly due to expansive salt formation . The formation of expansive salt also resulted in loss of cem-entitious properties and loss of weight. The concrete exposed to H2SO4 solution was found least durable . This study also shows that higher the ultrasonic pulse velocity lower is the corrosion . This paper presents an approach of investigation along with analysis of test results of PCC exposed to corrosive environment

Leased farming degrading the farmlands? Analysis of farmers' perceptions in Andaman and Nicobar Islands, India

Not AvailableThis study was undertaken in Andaman and Nicobar Islands by conducting primary survey of leased-in and non-leased land cultivators. Total agriculture land of the islands decreased due to massive tsunami followed by earthquake during 2004. Due to various biotic and abiotic factors, land degradation in these islands is high, and land leasing practice aggravates it. The leased rent varies from ` 17,500 ha-1 annum-1 to-1 -1 ` 26,500 ha annum , and both cash and crop sharing mechanisms are practiced. Our analysis indicated that soils of leased land are degraded, and were categorized from moderate to severe level of degradation. The main reasons observed were that leasedin farmers mostly cultivate vegetables wherein more cultural working is required, which leads to loosening of soil and permits soil erosion at higher rate. Since, these islands receive more than 2800 mm rainfall annually with high intensity, it leads to faster erosion of soils. As the conservation measures need high investment, leased-in farmers are hesitant to invest due to short time lease of agreement (1 to 2 years). Thus, the study highlights that there should be clear cut policy for leased land to protect the limited and fragile agri-ecosystem of Andaman and Nicobar Islands. The findings will provide information for future research and policy decisions on leased land practices.Not Availabl

An accurate inner diameter measurement

The inaccurate deflection behavior of the probing system degrades the performance of the diameter-measuring machines. In this experiment, the probing is improved, applying an autocollimator and an angular positioning datum. We have devised this datum using a liquid wedge. A ring gauge is chosen as a workpiece to evaluate the deflection behavior of the probing system. The improved uncertainty of the probing is found as low as 40 nm. Subsequently, the inner diameter of the ring gauge is measured on this experimental setup. By employing a simulation, we aligned the workpiece. The deflections of the stylus are optimized to achieve zero deflection error at the zenith points. Consequently, the swing of the probe at the zenith points is combined with the rectilinear displacement of the workpiece to estimate the inner diameter. The uncertainty of the measurement of the ring gauge is improved up to 140 nm

A novel method of diameter measurement of pistons used in pressure standards using scanning principle and fusion technique

The requirement of improved certainties in the measurement of the diameter and the form of cylindrical artifacts is increasing day-by-day. Such requirements become indispensable in typical applications, like the inspection of the fuel injection systems and calibration of pressure balances. A new experiment is set to measure the diameter of a cylindrical artifact, particularly the piston of a pressure-measuring device. Three displacement sensors are used to scan the cross-section of a cylinder and a reference gauge block. At the same time, the scanning process is simulated for ideal conditions. The coordinate data thus obtained in the scanning is fused on to a circle. The misalignments in the experimental setup are refined by iterative scanning the artifacts under test until the experimentally obtained surface profiles match with the simulated ones. Then, the fused circle represents the diameter of the cylindrical object. According to substitution technique, the deviation of the diameter of the artifact under test is determined from the size of the gauge block. Finally, the expanded measurement uncertainty is estimated

Effect of ultraviolet radiation exposure on optical nonlinearity and switching traits of SnO2 thin films deposited by thermal evaporation

Highly transparent amorphous SnO2 thin films were deposited using the thermal evaporation method and characterized. The influence of the UV radiation exposure (for approximately 2 h) on the morphology, linear and nonlinear optical properties of the films was evaluated for the first time. The optical switching performance of the as-deposited thin films was examined using the pump–probe technique. A continuous wave (CW) diode-pumped solid-state laser (532 nm with maximum power of 100 mW) and He-Ne laser (633 nm with maximum power of 35 mW) was used for the pump and probe beam, respectively. The band gap energies of the films were calculated using the Mott and Davis model fitting procedure. The films transmittance was increased and band gap was decreased upon the UV exposure. The signal modulations in the films were observed with the increase in the pump power. The signal intensities of both as-deposited and UV radiation exposed films were correspondingly dropped from 7.58 to 7.47 mW and from 8.16 to 8.05 mW, when the pump power was raised beyond 20 mW. The achieved SnO2 films displayed unaltered dynamic range under the UV radiation exposure. In addition, the nonlinear absorption coefficients of the UV radiation exposed films were increased from 0.10139 to 0.36435 cm W-1. This indicated the stabilization of the films upon the UV exposure and subsequent removal of the excess oxygen. The higher value of the nonlinear absorption by the films satisfied their figure of merit. The proposed SnO2 thin films may be effective for the development of the nonlinear optical devices working in the UV region