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

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.

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

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.

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

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.

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

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.

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

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.

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

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.

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

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.

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

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.

Molecular Evolutionary Analysis of a-Defensin Peptides in Vertebrates

?-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.

Synthesis and Characterization of Cellulose-based Eco-Friendly Hydrogels

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.