Pulak M Pandey and Gurminder Singh
The effect of unit cell shape and strut size variation was studied on the flexural properties of the ordered copper foam in the present study. The developed rapid manufacturing method using 3D printing and ultrasonic vibration- assisted pressureless sintering was employed to fabricate samples. Two different shapes such as simple cubic (SC) and body-centred cubic (BCC) were used as the unit cells for the samples with three different strut sizes 1, 1.3 and 1.6 mm. Three-point bend test was performed to obtain the flexural properties such as flexural modulus and ultimate flexural strength. Different shapes of failure curves were noticed during the test, which was owing to the different unit cell shapes. The fracture was obtained to be brittle in nature due to the micro-pores of the struts. The fractured surfaces of the two different unit cells were also studied. The samples with the simple cubic unit cell shapes possessed better flexural properties as compared to the body-centred cubic unit cell samples.
Seydou Sinde
In this paper, the emphasis is put on the effect of the surface back pressure on selected foam rheological properties. A hydraulic model for foam drilling in vertical well has been developed using Visual Basic program to thoroughly analyze foam hydrodynamics and to study the effect of the back pressure on these selected rheological properties such annular pressure, foam quality, density, effective viscosity, power and consistency indices and cuttings concentration along the entire annular section. The model intends to simulate and predict foam rheology and characteristic parameters for foam drilling in vertical wells. The model was evaluated and validated by running its program on two foam-drilled wells in the Middle East. The developed model was also compared with two other models: Valco-Economides’ model; and Sporker’s model. The average errors of the developed model accuracy were 2.59% and 10.85% for the first and second wells, respectively. The model accuracy was slightly better than that of Valco-Economides’ one, but less than that of the Sporker’s one.
Pramod Ram Wadate and H.M. Dharmadhikari
Abundant solar energy is freely available almost round the year in India. As per the current scenario of global warming and climatic change, solar energy is the cleanest source in nature. Concentrated solar power (CSP)has hardly contributed to the overall installed solar power capacity in the country. CSP technologies are Parabolic Trough Collector (PTC), Linear Fresnel Reflector (LFR), Paraboloid Dish and Solar Power Tower. This paper presents a review of CSP in solar parabolic dish concentrator to understand thermal aspect like thermal efficiency, optical efficiency, useful heat gain, heat losses, solar irradiation, etc. for various applications and current development. The current scenario of global CSP is discussed to meet the future challenges and need of the society.
Ali Koçak, Burak Toydemir, Melih Bulgur
Commonly, material and vibration characteristics of masonry structures remain uncertain in the evaluation of existing structures under external loads such as earthquake, heat, wind, etc. In addition, determination of compressive and tensile strength of a masonry walls is not straightforward. However, it is very important to know the characteristic parameters such as eigen values, periods and mode shapes of a structure beforehand in order to create accurate and reliable physical models. Since each historical structure has its own unique wall and bearing characteristics, it is not possible to accept random initial values for the bearing capacity and other parameters of the structure. Besides, conducting vertical and lateral loading experiments is costly and time consuming. An alternative way to determine these parameters that govern the structural behavior is to carry out experimental vibration tests using accelerometers. This method, which is also called as Operational Modal Analysis (OMA), is used to obtain the free and forced vibration response of structures by experimental means and to determine the modal parameters of the structure. OMA is very important for the appropriate use of an analysis method and the model parameters used in the analysis. In this study, two masonry buildings, one of which is historical, are discussed and the modal parameters of buildings are determined experimentally with OMA. Characteristic values obtained from OMA were compared with the three dimensional finite element method by adjusting characteristic model parameters.
G. M. Jahid Hasan and Naila Matin
The present study focuses on the entire coastline of Bangladesh, which was analyzed for the last thirty years, with a five years’ interval in between, to identify the changes in the shoreline position due to erosion or accretion. Shoreline positions for the time period 1989-2019, were manually digitized using multi-temporal Landsat satellite images of 30m resolution and comparable tidal conditions. A polygon-based approach was then employed in Arc GIS to determine the areal changes in the three different exposed coastal zones. The central zone was found to be the most dynamic in terms of both erosion and accretion. The western zone was mostly characterized by erosion, whereas only the eastern zone experienced a net land gain in this time span. Periodic reversal fromerosion or accretion was also noted in several locations. The outcome of this study regarding the general trend (erosional or depositional) along the coastline, is expected to aid the proper planning and land management of the coastal zones in Bangladesh.
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