Ph.D.
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Item Development of Sustainable Cement Mortar Incorporating Rice Husk Ash(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2011-12) Rashid, Muhammad Harunur; Molla, Prof. Dr. Md. Keramat AliThe study for the development of sustainable cement mortar incorporating rice husk ash was conducted by several approaches. Several researchers have been conducting research to replace the ordinary Portland cement by new materials with pozzolanic and cementitious properties. The aim of this study was to investigate the performance of cement mortar with rice husk ash for its sustainable development. A detail investigation was conducted to produce the rice husk ash with appropriate properties by effective incineration process. The fineness of rice husk ash based on different incineration systems, retention time and grinding time was determined. Characterization of rice husk ash was performed with XRD, SEM and chemical composition analysis. The effect of rice husk ash on heat of hydration was examined. Eventually, the performance of cement mortar with different proportions of rice husk ash was evaluated based on strength, permeability, sorptivity, salt crystallization, resistance to sulphate attack and effect of elevated temperature ranging from 200 to 700°C. The result shows that the highest fineness of 6894 cm2/gm was obtained for rice husk ash produced in laboratory burning system with 60 hours retention and 180 minutes grinding. The result of XRD confirmed the amorphous state of rice husk ash produced in laboratory burning system at 663.6°C. The maximum compressive strength of 33.09 MPa at 28 days was found for control sample. The highest compressive strengths at later age of 90, 350, 600 and 900 days were found to be 38.08, 38.80, 39.09 and 39.23 MPa respectively for 20% replacement with rice husk ash. The highest permeability of 4905 columbs was found in case of control sample at 28 days age. The result indicates that the permeability is inversely proportional to rice husk ash and curing age of sample. The trend of sorptivity was found similar to permeability and the highest value of control sample was found to be 0.214 kg/m2-min0.5. It was found that the mortar samples with 15% and 20% rice husk ash sustained up to standard 20 cycles in salt crystallization. No crack or spalling was observed due to sulphate attack on the mortar samples with 15 and 20% replacement of OPC with rice husk ash. The control sample exhibits the highest strength of 44.47 and 23.85 MPa at 200 and 700°C respectively. The sample having 15% rice husk ash shows maximum strength of 48.26 and 43.52 MPa at 300°C and 400°C respectively while the highest strength was obtained at 500°C for sample with 20% rice husk ash. The findings of the present study would contribute to the sustainable development of cement mortar incorporating rice husk ash.Item Evaluation of Contamination Potential and Treatment Techniques of Leachate Generated from Landfill Lysimeter(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2014-08) Islam, Md. Rafizul; Alamgir, Prof. Dr. MuhammedIn this study one open dump lysimeter with leachate detection and collection system as well as two sanitary lysimeter having two different types of cap liner were simulated. After designing a reference cell, construction of landfill lysimeter was started in January 2008 and completed in July 2008. In all construction process locally available civil construction materials were used. The municipal solid waste (MSW) of 2800 to 2985 Kg having the total volume of 2.60 m3 (diameter 1.48 m; height 1 .6m) as well as moisture and organic content of 65, 52 %, respectively, was deposited in each lysimeter by applying required compaction energy. This study endeavors to characterize leachate and investigate the tropical climatic influence on leachate characteristics under different seasonal variation. The leachate characteristics, leachate generation and climatic influence parameter had been monitored since June 2008 to Dec. 2010. These periods covered both the dry and rainy season. The leachate generation followed the rainfall pattern and open dump lysimeter-A without top cover demonstrated more leachate generation due to percolation of rainfall than that of sanitary lysimeter-B and C. Open dump lysimeter-A showed lower concentration of TKN and NH4-N as well as TKN load, while both the concentration and load of COD higher in compared to sanitary lysimeter-B and C. Sanitary lysimeter-B, not only revealed lower leachate generation, but also produced reasonable lower concentration and load of COD in compared with open dump lysimeter-A. Result depicted that lysimeter operational mode had direct effect on leachate quality. In contrary, sanitary lysimeter-C showed higher composition of LFG in compared to sanitary lysimeter-B due to the providing of lower compaction of cap liner in sanitary lysimeter-C. in absence of compacted clay liner (CCL) and hence percolation of rainwater that facilitated rapid degradation of MSW in open dump lysimeter-A and resulted in higher settlement than that of sanitary lysimeter-B and C. In sanitary lysimeter-B and C, leachate generation showed lesser amount than that of open dump lysimeter-A due to the providing of cap liner in lysimeter-B and C, played an important role to reduce the percolation of rainwater. Study revealed leachate pollution index (LPI) and sub-pollution indices (sub-LPI) for lysimeter significantly higher and proper treatment to be necessary before discharging the leachate into the water bodies. To meet the standard discharge condition lysimeter leachate was treated in the laboratory through the phytoremediation treatment process by using aquatic reactors of duckweed, snail, helencha and topapana, but the removal efficiency was not satisfactory. Then the leachate was treated through the chemical coagulation process by using FeCl3, PAC, FeSO4 and Al2(SO4)3 in various dosages and pH. Result revealed that FeCl3 more effective for removing pollutant. In the laboratory, leachate was further treated by using FeCl3 at optimum dosage and the concentration and consequently the values of LPI of treated leachate were found within the limit of maximum discharge standards. Finally, it can be concluded that leachate generated from lysimeter may be discharge after required level of chemical treatment into the natural streams to maintain the limit of maximum discharge standards.Item Efficient Mode Selection Scheme for Video Coding(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh., 2016-11) Yusuf, Md. Salah Uddin; Ahmad, Professor Dr. MohiuddinVideo coding plays vital role in communications and multimedia applications. The appearance and development of various new multimedia services have need for higher coding efficiency. H.264/AVC is the latest international video coding standard that can achieve considerably highest coding efficiency than previous standards and uses rate-distortion optimized (RDO) mode selection technique. This means that the encoder has to code the video by exhaustively trying all the mode combinations including the different intra and inter prediction modes. However, this mode selection process also makes the encoding process extremely complex, especially in the computation of the rate-distortion cost function, which includes the computations of the sum of squared difference (SSD) between the original and reconstructed image blocks and context-based entropy coding of the block. So, the highly complex mode selection process limits the practical implementation of codec’s. This dissertation proposes six different fast and efficient schemes to reduce the computational complexity of mode (Intra and Inter) selection process. It also can effectively reduce the spatial and temporal redundancy. In H.264/AVC intra coding, DC mode is used to predict regions with no unified direction and the predicted pixel values are same and thus smooth the varying regions which are not well de-correlated. A modified DC prediction (MDCP) mode is suggested to replace the existing DC mode based on the distance between the predicted and reference pixels. By analyzing the impact of scanning, a new Z-scan scheme is proposed which can remarkably reduce bit rates compared with AVS codec using conventional zigzag scan, while the PSNR of video sequences are maintained. The entire macroblock is divided into simple motion or complex motion contents and their cost functions are calculated by using the developed rate-based fast and efficient mode selection scheme, which plays a vital role as no additional operation module is required. To avoid the entropy coding method during intra and inter mode decision, a rate estimation method proposed and readjusted to fit the characteristic of low complexity distortion functions of SATD and SAITD that use more accurate estimation while achieving higher prediction performance with low computational requirement of feature. In addition, a relative sum of absolute difference (RSAD) based inter mode decision algorithm is proposed to determine the best inter mode without calculating xiv rate-distortion costs. To further speedup SKIP mode early termination algorithm is adopted. Based on the probability characteristics, a fast inter mode decision algorithm is suggested which can determine the best inter mode only by calculating the Hadamard Transform (H-SAD) cost instead of rate distortion cost and avoid most of the complex computation processes like quantization, variable length coding, pixel reconstruction etc. To make the motion estimation process fast, a search point reduction scheme is introduced. Then the ranking and performance of the commonly used scheme are analyzed for different kinds of video. Experimental results indicate that the proposed efficient mode selection schemes reduce the computational complexity of H.264/AVC codec without sacrificing the quality of video which can be applied in implementing real time encoder for low-power mobile devices and general purpose computers.