Rajshahi University Journal of Science and Engineering

Study of the Influence of Temperature on the Deposition of SiO₂ Films from Reaction of Silicone Oil Vapor and Ozone Gas

Arifuzzaman Rajib — 2016-11-19

This work reports the influence of deposition temperature on the deposition of SiO₂ films on silicon substrate by using chemical reaction of silicone oil vapor andozone gas at low temperature. An organic solution as a catalyst at atmospheric pressure has been used to enhance the deposition rate of SiO₂. The deposition rate of SiO₂ films was found to vary with the variation of the concentration of the catalyst and deposition temperature (160°C ~ 260°C). The deposited SiO₂ films were confirmed by Fourier transform infrared (FTIR) spectroscopy. The thickness and refractive index of the as-deposited films were measured by the laser ellipsometry. FT-IR spectra of the as-deposited films were very much similar to those of SiO2 films found in literature. The deposition temperature was found to influence the deposition rate of SiO₂ strongly. The maximum deposition rate was found to 17.2 nm per minute for the case of 220°C. The deposition temperature also influenced the refractive index of the films. Experimental results showed that the deposition temperature could be a major parameter for the enhancement of the deposition rate.

Fabrication and Characterization of Aluminium-Rice Husk Ash Composite Prepared by Stir Casting Method

Adnan Adib Ahamed — 2016-11-19

Metal Matrix Composites (MMCs) constitute an important category of design and weight-efficient materials. This article highlights on the work where an attempt is taken to fabricate aluminium matrix composite reinforced with rice husk ash (RHA) particles, an agricultural byproduct with high amount of silica. RHA particles, upon analysis, are incorporated into the Al matrix melt by stir casting. Magnesium (~1%) is used as a wetting agent between matrix and reinforcement. 3, 6 and 9% wt. of RHA are added into the matrix. The microstructure analysis reveals the reinforcing particle distribution inside the matrix which indicates successful fabrication of the composites. The density and mechanical properties such as strength and hardness are measured for both unreinforced metal and composites. The results found in the tests show a decrease in density with increasing reinforcement while increasing yield strength, ultimate strength and hardness of the composites with increasing reinforcement from the unreinforced condition.

Study on Wear and Morphological Behavior of Electron Beam Dose Irradiated Polyoxymethylene Copolymer (POM-C)

Md. Shahinur Rahman — 2016-11-19

Polyoxymethylene copolymer (POM-C) is the most prominent engineering thermoplastic consisting of repeating carbon-oxygen bonds in the form of oxymethylene groups (OCH2). It is widely used to make small gear wheels, ball bearings, precision parts, automotive and consumer electronics. In this study, the POM-C round blocks were irradiated with 165 KeV electron beam energy in five doses (100, 200, 300, 500 and 700 kGy) in vacuum condition at room temperature. The wear rate, surface hardness and morphological properties of electron beam dose irradiated POM-C blocks surfaces have been analyzed using pin on disk tribometer, optical microscopy, nano-indenter, Raman spectroscopy, 3D nano surface profiler and scanning electron microscopy (SEM). The electron beam irradiation transferred the wear phenomena of unirradiated POM-C sample from the abrasive wear (plough and cracks), adhesive wear (grooving/striation, micropitting) and scraping to mild scraping and striation for the 100 kGy dose irradiated POM-C sample due to cross-linking (macroscopic networks), chemical free radicals formations and partial physical modification (smoothness), which can be concluded from tribometer, optical microscopic, SEM and Raman spectroscopic observations. It also reduced the surface wear rate and average surface roughness with increasing microsurface hardness at threshold value of cross-linking among all unirradiated and others doses irradiated POM-C blocks. The level of tribological (wear and morphology) attribute improvement relies on the electron beam irradiation condition (energy and dose rate) depending on chemical and physical factors of polymeric materials.

Effect of Cu content on the Electrochemical Corrosion Behavior of Peak-aged Al-6Si-0.5Mg Alloys in Sodium Chloride Solution

Abul Hossain — 2016-11-19

The purpose of this study is to understand the electrochemical corrosion behavior of 1wt% Cu content Al-6Si-0.5Mg alloy in 0.1M NaCl solution. The potentiodynamic polarization curves reveal that 1wt% Cu content alloy is less prone to corrosion than the Cu free alloy. The EIS test results show that corrosion resistance or polarization resistance (R_ct) increases with the addition of 1wt% Cu to Al-6Si-0.5Mg alloy. Higher polarization resistance (R_p) has been obtained with the addition of 1wt% Cu to the Al-6Si-0.5Mg alloy. Due to addition of Cu and thermal modification, the magnitude of open circuit potential (OCP), corrosion potential (E_corr) and pitting corrosion potential (E_pit) of Al-6Si-0.5Mg alloy in NaCl solution were shifted to the more noble direction.

Friction and Structural Responses of Ion Implanted Polyoxymethylene Copolymer (POM-C)

Md. Shahinur Rahman — 2016-11-19

Polyoxymethylene copolymer (POM-C) round block was implanted with 120 KeV ions of He to doses of 5 x 10¹⁶ and 1 x 10¹⁶ ions cm^-2. It was also implanted with 120 KeV ions of Ar + He and He + Ne to dose of 1 x 10¹⁶ ions cm^-2, respectively. The friction coefficient behavior of both implanted and unimplanted POM-C blocks was investigated using a ball on disk tribometer mechanism. The friction coefficient of He ion implanted POM-C block at a dose of 5 x 10¹⁶ ions cm^-2 is lowest compared to all unimplanted and others ions doses implanted POM-C blocks. It also shows the moderate surface texturing (atomic rearrangement), lower surface micro-hardness and average surface roughness compared to both unimplanted and other ions doses implanted POM-C blocks due to well adjusted carbonization, cross-linking and ions-target atoms collisions, which is ascertained from SEM-EDS, Raman spectroscopic and surface profiling observations. The other ions doses implanted POM-C blocks demonstrate the higher friction coefficient and surface roughness with polymer surface deformation (crazing, cracking, pitting and gas evolution, bond breaking) due to severe chain scission, surface dose delivered atomic displacements and chemical structural degradation. It is concluded that the variation in friction coefficient behavior of POM-C block resulted from its structural response for ion beam implantation on the top surface.

Synthesis and Characterization of Cellulose-based Eco-Friendly Hydrogels

Md. Obaidul Haque — 2016-11-19

Biodegradable nature of hydrogels is highly appreciable and core expectation at present time. Cellulose and cellulose derivatives can be copolymerized in producing green hydrogels for improving the absorption performance of many adsorbent products. Hydrogels are polymeric substances and due to hydrophilic functional groups in their structure capable of holding large amount of water compared to its body mass. Crosslinking is one of the simplest reactions used to improve the physico-chemical properties of cellulose and cellulose derivatives. In the present paper an innovative cellulose based environment friendly hydrogel was experimentally synthesized as an alternative to acrylate-based synthetic hydrogels for personal care product and other absorption purposes. The cellulose based hydrogels were prepared by free radical graft copolymerization reaction of cotton with acrylic acid (AA) and acrylamide (AM) using N,N-methylne-bis-acrylamide (MBA) as a crosslinker in the presence of initiator potassium persulphate (K₂S₂O₈) system. The maximum water absorption capacity of the prepared hydrogels were 50 g/g in deionized water. Optimized preparation condition was invstigated depending on monomer concentration, initiator concentration, crosslinker concentration,pH, time and temperaturefor equilibrium water absorption which were 120%, 10%, 5%, 7, 2h and 50°C respectively.For structural characterization FTIR spectroscopy, SEM analysis, TGA and XRD technique were performed. The result ensuresthat the characteristic of prepared hydrogel can be effectively used in personal absorbent products, tissue engineering, biomedical application etc. and as adsorbent material in polluted water treatment.

Preparation of Hydrophobic Poly (lauryl methacrylate-divinyl benzene) Coated Magnetic Nano-composite Particles and Their Application as Adsorbents for Organic Pollutants

Rukhsana Shabnam — 2016-11-19

This work introduces a method for the preparation of magnetic nano-composite particles coated with highly crosslinked poly (lauryl methacrylate) (PLMA), a hydrophobic polymer containing long chain alkyl groups for application in waste water treatment. The produced magnetic composite particles named Fe₃O₄/SiO₂/P(LMA-DVB) were characterized by Fourier Transform IR (FTIR), Transmission electron microscopy (TEM) and X-ray diffractometer (XRD) analyses. Then the prepared composite particles were used for the removal of organic pollutants from water. The adsorption behavior was dependent on the nature of the pollutants with congo red showed highest adsorption efficiency.

Experimental Study on Silicon Nanocrystals Rich Lanthanum Fluoride Films for Future Electronic Devices

Md. Ferdous Rahman — 2016-11-19

Feasibility for the future electronic devices a thorough investigation on Silicon nanocrystals (Si-NCs) rich Lanthanum Fluoride (LaF₃) film fabricated using a novel onestep chemical method has been reported here. Colloidal solution of Si-NCs in hydrofluoric acid (HF) was prepared from meso-porous silicon by ultrasonic vibration (sonication). On a silicon (Si) substrate LaCl₃ solution in HCL is allowed to react with the colloidal solution of prepared Si-NCs. LaCl₃ reacts with HF of Si-NCs solution and produces LaF₃ crystals that deposits on the silicon substrate as a film embedding Si-NCs. This is a novel single step chemical way of depositing LaF₃ insulating layer embedding Si-NCs (LaF₃:Si-NCs). The XRD and EDX analysis of the deposited film show a polycrystalline and non-stoichiometric nature of LaF₃. The presence of Si-NCs was confirmed by SEM. Application of this material has been tested for low-voltage operating non-volatile memory (NVM) and Schottky junction solar cells. The Al/LaF₃:Si-NCs/Al structure as NVM offered a memory window of 525 mV at a programming and erasing bias of 2V. LaF₃:Si-NCs films showed strong light absorption. Current-Voltage (I-V) characteristics of the Schottky device in ITO/LaF₃:Si-NCs/Al structure showed a dependency on the incident light intensity where current was varied in the range of 5 mA to 40 mA and under various light illumination i.e., 400 lux to 1200 lux. Experimental results show a lot of promise of Si-NCs-rich LaF₃ film to be used as an insulating film in non-volatile memory as well as a photoactive material in Schottkey junction solar cell.

Preparation of Highly Cross-linked Magnetic Polymer Composite Particles and Application in the Separation of Arsenic from Water

M. K. Sharafat — 2016-11-19

Iron oxide magnetic particles have become a promising research field in separation technology because of their easy separation by external magnetic field and can be applied for the removal of toxic metals from waste water. Highly cross-linked Fe₃O₄/P(S-DVB) particles were prepared in this research by suspension polymerization of styrene (S) and divinylbenzene (DVB) in presence of nanosized Fe₃O₄ particles. At first Fe₃O₄ nanoparticles were prepared by co-precipitation of Fe²⁺ and Fe³⁺ from their alkaline aqueous solution. To stabilize the magnetic particles, the surface of the particles was modified with oleic acid. The morphology and surface structure were characterized by Fourier Transform IR(FTIR), Transmission Electron Microscope (TEM), Scanning Electron Microscope(SEM), and light microscope.The adsorption behavior of As(III) on composite polymer particles was evaluated and a comparative study with reference copolymer particles revealed that composite polymer particles possessed better adsorption capacity.

Hydrodynamics of Microalgae and CO₂ flow in a Tubular Photobioreactor and consequent effects on Microalgae growth

Saumen Barua — 2016-11-19

In biofuel technology from microalgae, the main optimal factors for microalgae cultivations are light, CO₂ and temperature. As microalgae are photosynthetic microorganisms thus they convert sunlight, water and CO₂ to algal biomass. We consider a two phase flow for CO₂ and Microalgae suspension to understand fluid dynamics phenomena after injecting CO₂ gas inside a tubular Photobioreactor (PBR).The growth rate of the microalgae cell is taken as a function of available sun light at Chittagong University of Engineering & Technology (CUET) in our study. A 20.94m long and 0.025m tubular PBR is considered for the simulation. To observe the microalgae cell growth, we selected the 21st June for a bright sunny and the longest day of a year. From the simulation after day seven we observed a very slow growth for the microalgae culture. It is noted that the growth related to concentration of microalgae is increased by day length with respect to continuous sunlight. A small fluctuation of shear rate around Uloop area is also found in our simulation which may be caused to reduce the volumetric production due to cell fragility. From the velocity profile we found that, the velocity is generally higher in the middle of the tube gives a parabolic shape of the suspension flow.

Molecular Evolutionary Analysis of a-Defensin Peptides in Vertebrates

Arafat Rahman — 2016-11-19

?-Defensin is a group of polypeptides with antimicrobial activity found in the host defense system and it is widely distributed in, but not limited to mammalian epithelial cells and phagocytes. These molecules protect the organism from a diverse spectrum of bacteria, viruses, fungi, and protozoan parasites. Different studies have revealed widesequence variation within ?-defensin sequences, but the underlying evolutionary cause is not well-studied. In this study, the ?-defensin gene from 25 vertebrate species has been comprehensively collected and computationally analyzed. NCBI gene and nucleotide databases were accessed to extract meta-information about ?-defensin gene's defensin domain and leader propeptide sequences. Full coding sequences downloaded from nucleotide database by splitting out intron sequence. MEGA software used to construct phylogenetic tree using Neighbor-Joining method, which indicates that ?-defensin gene evolution does not matches with species evolution. Selection analysis was carried out using Data Monkey web-server's FEL, SLAC, IFEL, MEME, TOGGLE and REL program on both propeptide and defensin super-family codon-aligned sequences to test different hypothesises. Positively selected sites were found on both propeptide and defensin domain, but the effect of negative selection pressure was higher on leader sequences. It was found that mutations in the positively selected sites of defensin domain had stabilizing effect on protein. Phyre2 web-server was used for homology modeling of selected ?-defensin genes. Structural variation is observed on ?-defensinproteins which may indicate heterogeneous structure-function relationship between species that reflects its interaction with diverse pathogens. This study provides a new perspective on the relationships among ?-defensin gene repertoires which will help to infer its evolution.

Regression Based Robust QTL Analysis for F₂ Population

Md. Jahangir Alam — 2016-11-19

This Quantitative trait locus (QTL) analysis is a widely used statistical approach for the detection of important genes in the chromosomes. Maximum likelihood (ML) based interval mapping (IM) is one of the most popular approaches for QTL analysis. However, it is relatively complex and computationally slower than regression based IM. Haley-Knott (HK) and extended Haley-Knott (eHK) regression based IM save computation time and produce similar results as ML-IM. However, these approaches are not robust against phenotypic outliers. In this research, we have developed a robust regression based IM approach by maximizing beta-likelihood function for intercross (F₂) population. The proposed method reduces to the HK-IM method when beta ? 0. The tuning parameter beta controls the performance of the proposed method. The simulation results show that the proposed method improves performance over the existing IM approaches in the case of data contaminations; otherwise, it shows almost the same results as the classical IM approaches.

Analyzing Wavelet and Bidimensional Empirical Mode Decomposition of MRI Segmentation using Fuzzy C-Means Clustering

Gulam Sarwar Chuwdhury — 2016-11-19

Image segmentation is a vital step in medical image processing. Magnetic resonance imaging (MRI) is used for brain tissues extraction in white and gray matter. These tissues extraction help in image segmentation applications such as radiotherapy planning, clinical diagnosis, treatment planning. This paper presents utilization of fuzzy C-means (FCM) clustering by using wavelet and bidimensional empirical mode decomposition (BEMD) to improve the quality of noisy MR images. The signal to noise ratio (SNR) value is calculated from FCM clustering data to examine the best segmentation technique. The experiment with synthetic Brain Web images has demonstrated the efficiency and robustness of the appropriate approach in segmenting medical MRI.

Multidimensional Markov Stationary Feature for Image Retrival Systems

Md. Saiful Islam — 2016-11-19

Markov Stationary Features (MSF) not only considers the distribution of colors like histogram method does, also characterizes the spatial co-occurrence of histogram patterns. However, handling large scale database of images, simple MSF method is not sufficient to discriminate the images. In this paper, we have proposed a robust content based image retrieval algorithm that enhances the discriminating capability of the original MSF. The proposed Multidimensional MSF (MMSF) algorithm extends the MSF by generating multiple co-occurrence matrices with different quantization levels of an image. Publicly available WANG1000 and Corel10800 databases are used to evaluate the performance of the proposed algorithm. The experimental result justifies the effectiveness of the proposed method.

Simulation of Normal Incidence Sound Absorption Coefficients of Perforated Panels With/Without Glass Wool by Transmission Line Parameters in a Two-Port Network

Takayoshi Nakai — 2016-11-19

This paper describes simulation of normal incidence sound absorption coefficients of perforated panels by transmission line parameters in a two-port network. Maa and Sakagami have investigated micro perforated panels, MPP. But their theories can treat only near 1 % perforation rates of perforated panels with back cavities. If sound propagates as a plane wave, sound propagation can be represented as transmission line parameters in a two-port network. Perforated panels, back cavities, and glass wool absorption materials are represented as matrix of transmission line parameters, respectively. Transmission line parameters of a perforated panel with a back cavity are calculated as multiplication of their matrices. An input impedance can be calculated from the transmission line parameters. A normal incident absorption coefficient is calculated from the input impedance. Holes of the perforated panels have losses of viscous friction and thermal conduction at their walls. Simulations are done in the condition of 0.25 mm to 5 mm diameters of holes, 0.25 % to 25 % perforation rates, 0.5 mm to 5 mm thickness of the perforated panels with back cavities in which there are or are not glass wool absorption materials. The results of these simulations are good agreements with the results of our measurements by transfer function method except in the condition of more than 1 mm diameter of holes.

Comparison of Encryption Algorithms for Multimedia

Md. Martuza Ahamad — 2016-11-19

Cryptographic techniques play crucial role when users exchange information. Multimedia plays an important role in learning and sharing experiences. When multimedia contents are shared among the users, it faces security threats. Usually multimedia contents takes much space. Encryption technique should be time efficient. In this work we consider four encryption techniques: Blowfish, AES, XOR and RSA and four types of media content: text, image, audio and video. Simulation shows that AES is time efficient than others. Comparing between symmetric and asymmetric cryptography, symmetric cryptographic techniques take less time than asymmetric technique.

An Improvement in Representation of Audio Signal in Time-Frequency Plane using EMD-2TEMD Based Approach

Kazi Mahmudul Hassan — 2016-11-19

This study proposed an enhanced time-frequency representation of audio signal using EMD-2TEMD based approach. To analyze non-stationary signal like audio, timefrequency representation is an important aspect. In case of representing or analyzing such kind of signal in time-frequency-energy distribution, hilbert spectrum is a recent approach and popular way which has several advantages over other methods like STFT, WT etc. Hilbert-Huang Transform (HHT) is a prominent method consists of Empirical Mode Decomposition (EMD) and Hilbert Spectral Analysis (HSA). An enhanced method called Turning Tangent empirical mode decomposition (2T-EMD) has recently developed to overcome some limitations of classical EMD like cubic spline problems, sifting stopping condition etc. 2T-EMD based hilbert spectrum of audio signal encountered some issues due to the generation of too many IMFs in the process where EMD produces less. To mitigate those problems, a mutual implementation of 2T-EMD & classical EMD is proposed in this paper which enhances the representation of hilbert spectrum along with significant improvements in source separation result using Independent Subspace Analysis (ISA) based clustering in case of audio signals. This refinement of hilbert spectrum not only contributes to the future work of source separation problem but also many other applications in audio signal processing.

A Practical Approach to Spectrum Analyzing Unit Using RTL-SDR

Md. Habibur Rahman — 2016-11-19

In the present scenario, there has been an immense advancement in the field of wireless communication in this modern engineering world. Now-a-days Software Defined Radio (SDR) technology is an indisputable emerging technology and presents new challenges for communications engineers. The advancement of SDR system has made significant progress in recent years which makes it as a serious substitute of traditional hardware radio architectures where the mathematical procedures are obligatory to decode and process radio signals using analogue circuitry. Recently, computers have turned out to be powerful enough to do the required mathematical calculations using software. So aim of this paper is to demonstrate a RTL-SDR based spectrum analyzer which can be used proficiently as an alternative of existing hardware spectrum analyzer. This approach will lessen the complexity of analogue hardware system with the higher tractability of software based filtering and demodulation techniques. As RTL-SDR devices are quite cheap (Approximately 20$) and small sized, this system also offers cost effectiveness with provision of portability. An experimental study was conducted with suitable conditions to examine the feasibility and efficiency of the proposed system. The outcome of experimental result is thoroughly examined in this paper.