Search results for: optical study

Authors: Mohamedou El Boukhary, Farba Bouyagui Tamboura, A. Hamady Barry, T. Moussa Seck, Mohamed L. Gaye

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Nowadays, low-schiff acyl-hydrazone ligands are highly sought after due to their wide applications in various fields of biology, coordination chemistry, and catalysis. They are studied for their antioxidant, antibacterial and antiviral properties. The complexes of transition metals and the lanthanide they derive are well known for their magnetic, optical, and catalytic properties. In this work, we present the synthesis of an acyl-hydrazone (H2L) schiff base and their 3d transition complexes. The ligand (H2L) is characterized by IR, NMR (1H; 13C) spectroscopy. The complexes are characterized by different physic-chemical techniques such as IR, UV-visible, conductivity, measurement of magnetic susceptibility. The study of XRD allowed us to elucidate the crystalline structure of the manganese (Mn) complex. The asymmetric unit of the complex is composed of two molecules of the ligand, one manganese (II) ion, and two coordinate chloride ions; the environment around Mn is described as a pentagonal base bipyramid. In the crystal lattice, the asymmetric unit is bound by hydrogen bonds.

Keywords: synthene, acyl-hydrazone, 3D transition metal complex, application

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Authors: Reza Eslami-Farsani, Mohammad Alipour

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The effect of deformation on the semisolid microstructure and degree of globularity of Al–15%Mg₂Si composite produced by the strain induced melt activation (SIMA) process was studied. Deformation of 25% was used. After deformation, the samples were heated to a temperature above the solidus and below the liquidus point and maintained in the isothermal conditions at three different temperatures (560, 580 and 595 °C) for varying time (5, 10, 20 and 40 min). The microstructural study was carried out on the alloy by the use of optical microscopy. It was observed that strain induced deformation and subsequently melt activation has caused the globular morphology of Mg₂Si particles. The results showed that for the desired microstructures of the alloy during SIMA process, the optimum temperature and time are 595 °C and 40 min respectively.

Keywords: deformation, semisolid, SIMA, Mg₂Si phase, modification

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Authors: H. Zengin, M. E. Turan, Y. Turen, H. Ahlatci, Y. Sun

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This study aimed for improving wear resistance of AM60 magnesium alloy by Ti addition (0, 0.2, 0.5, 1wt%Ti). An electric resistance furnace was used to produce alloys. Pure Mg together with Al, Al-Ti and Al-Mn were melted at 750 ⁰C in a stainless steel crucible under controlled Ar gas atmosphere and then poured into a metal mould preheated at 250 ⁰C. Microstructure characterizations were performed by light optical (LOM) and scanning electron microscope (SEM) after the wear test. Wear rates and friction coefficients were measured with a pin-on-disk type UTS-10 Tribometer test device under a load of 20N. The results showed that Ti addition altered the morphology and the amount of b-Mg₁₇Al₁₂ phase in the microstructure of AM60 alloy. b-Mg₁₇Al₁₂ phases on the grain boundaries were refined with increasing amount of Ti. An improvement in wear resistance of AM60 alloy was observed due to the alteration in the microstructure by Ti addition.

Keywords: magnesium alloy, titanium, SEM, wear

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Authors: M. Ravindiran, P. Shankar

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This paper deals with the comparison of two synthesis methods, namely, sol-gel, and combustion to prepare Fe doped ZnO nano material. Characterization results for structural, optical and magnetic properties were analyzed for the sol gel and combustion synthesis derived materials. Magnetic studies of the prepared compounds reveal that the combustion synthesis derived material has good magnetization of 50 emu/gm with a better hysteresis loop curve.

Keywords: DMS, combustion, ferromagnetic, synthesis methods

Procedia PDF Downloads 422

Authors: T. P. Yu, J. J. Liu, X. L. Zhu, Y. Yin, W. Q. Wang, J. M. Ouyang, F. Q. Shao

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A strong electromagnetic field with E>1015V/m can be supplied by an intense laser such as ELI and HiPER in the near future. Exposing in such a strong laser field, laser-matter interaction enters into the near quantum electrodynamics (QED) regime and highly non-linear physics may occur during the laser-matter interaction. Recently, the multi-photon Breit-Wheeler (BW) process attracts increasing attention because it is capable to produce abundant positrons and it enhances the positron generation efficiency significantly. Here, we propose an all-optical scheme for bright gamma rays and dense positrons generation by irradiating a 1022 W/cm2 laser pulse onto an Al cone filled with near-critical-density plasmas. Two-dimensional (2D) QED particle-in-cell (PIC) simulations show that, the radiation damping force becomes large enough to compensate for the Lorentz force in the cone, causing radiation-reaction trapping of a dense electron bunch in the laser field. The trapped electrons oscillate in the laser electric field and emits high-energy gamma photons in two ways: (1) nonlinear Compton scattering due to the oscillation of electrons in the laser fields, and (2) Compton backwardscattering resulting from the bunch colliding with the reflected laser by the cone tip. The multi-photon Breit-Wheeler process is thus initiated and abundant electron-positron pairs are generated with a positron density ~1027m-3. The scheme is finally demonstrated by full 3D PIC simulations, which indicate the positron flux is up to 109. This compact gamma ray and positron source may have promising applications in future.

Keywords: BW process, electron-positron pairs, gamma rays emission, ultra-intense laser

Procedia PDF Downloads 255

Authors: Diana Rymuszka, Konrad Terpiłowski, Lucyna Hołysz, Elena Goncharuk, Iryna Sulym

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Superhydrophobic surfaces exhibit extremely high water repellency. The commonly accepted basic criterion for such surfaces is a water contact angle larger than 150°, low contact angle hysteresis and low sliding angle. These surfaces are of special interest, because properties such as anti-sticking, anti-contamination and self-cleaning are expected. These properties are attractive for many applications such as anti-sticking of snow for antennas and windows, anti-biofouling paints for boats, waterproof clothing, self-cleaning windshields for automobiles, dust-free coatings or metal refining. The various methods for the preparation of superhydrophobic surfaces since last two decades have been reported, such as phase separation, electrochemical deposition, template method, plasma method, chemical vapor deposition, wet chemical reaction, sol-gel processing, lithography and so on. The aim of the study was to investigate the influence of modified colloidal silica, used as a filler, on the hydrophobicity of the polymer film deposited on the glass support activated with plasma. On prepared surfaces water advancing (ӨA) and receding (ӨR) contact angles were measured and then their total apparent surface free energy was determined using the contact angle hysteresis approach (CAH). The structures of deposited films were observed with the help of an optical microscope. Topographies of selected films were also determined using an optical profilometer. It was found that plasma treatment influence glass surface wetting and energetic properties that is observed in higher adhesion between polymer/filler film and glass support. Using the colloidal silica particles as a filler for the polymer thin film deposited on the glass support, it is possible to produce strongly adhering layers of superhydrophobic properties. The best superhydrophobic properties were obtained for surfaces of the film glass/polimer + modified silica covered in 89 and 100%. The advancing contact angle measured on these surfaces amounts above 150° that leads to under 2 mJ/m2 value of the apparent surface free energy. Such films may have many practical applications, among others, as dust-free coatings or anticorrosion protection.

Keywords: contact angle, plasma, superhydrophobic, surface free energy

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Authors: Marivane Turim Koschevic, Maycon dos Santos, Marcello Lima Bertuci, Farayde Matta Fakhouri, Silvia Maria Martelli

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Natural fibers are rich raw materials in cellulose and abundant in the world, its use for the cellulose nanocrystals extraction is promising as an example cited is the cattail, macrophyte native weed in South America. This study deals with the pre-treatment cattail of crushed fibers, at six different methods of mercerization, followed by the use of bleaching. As a result, have found The positive effects of treating fibers by means of optical microscopy and spectroscopy, Fourier transform (FTIR). The sample selected for future testing of cellulose nanocrystals extraction was treated in 2.5% NaOH for 2 h, 60 °C in the first stage and 30vol H2O2, NaOH 5% in the proportion 30/70% (v/v) for 1 hour 60 °C, followed by treatment at 50/50% (v/v) 15 minutes, 50°C, with the same constituents of the solution.

Keywords: cellulose nanocrystal, chemical treatment, mercerization, natural fibers

Procedia PDF Downloads 285

Authors: J. Alvarez, J. Pimienta, R. Sarmiento

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Diode lasers working in free mode present different shifting and broadening determined by external factors such as temperature, current or mechanical vibrations, and they are not more useful in applications such as spectroscopy, metrology, and cooling of atoms, among others. Different configurations can reduce the spectral width of a laser; one of the most effective is to extend the optical resonator of the laser diode and use optical feedback either with the help of a partially reflective mirror or with a diffraction grating; this latter configuration is not only allowed to reduce the spectral width of the laser line but also to coarsely adjust its working wavelength, within a wide range typically ~ 10nm by slightly varying the angle of the diffraction grating. Two settings are commonly used for this purpose, the Littrow configuration and the Littmann Metcalf. In this paper, we present the design, construction, and characterization of a compact extended laser cavity in Littrow configuration. The designed cavity is compact and was machined on an aluminum block using computer numerical control (CNC); it has a mass of only 380 g. The design was tested on laser diodes with different wavelengths, 650nm, 780nm, and 795 nm, but can be equally efficient at other wavelengths. This report details the results obtained from the extended cavity working at a wavelength of 780 nm, with an output power of around 35mW and a line width of less than 1Mhz. The cavity was used to observe the spectrum of the corresponding Rubidium D2 line. By modulating the current and with the help of phase detection techniques, a dispersion signal with an excellent signal-to-noise ratio was generated that allowed the stabilization of the laser to a transition of the hyperfine structure of Rubidium with an integral proportional controller (PI) circuit made with precision operational amplifiers.

Keywords: Littrow, Littman-Metcalf, line width, laser stabilization, hyperfine structure

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Authors: Jorge Prada, Christina Cordes, Carsten Harms, Walter Lang

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The development of microfluidic-based biosensors over the last years has shown an increasing employ of thermoplastic polymers as constitutive material. Their low-cost production, high replication fidelity, biocompatibility and optical-mechanical properties are sought after for the implementation of disposable albeit functional lab-on-chip solutions. Among the range of thermoplastic materials on use, the Cyclo-Olefin Copolymer (COC) stands out due to its optical transparency, which makes it a frequent choice as manufacturing material for fluorescence-based biosensors. Moreover, several processing techniques to complete a closed COC microfluidic biosensor have been discussed in the literature. The reported techniques differ however in their implementation, and therefore potentially add more or less complexity when using it in a mass production process. This work introduces and reports results on the application of a purely thermal bonding process between COC substrates, which were produced by the hot-embossing process, and COC foils containing screen-printed circuits. The proposed procedure takes advantage of the transition temperature difference between two COC grades foils to accomplish the sealing of the microfluidic channels. Patterned heat injection to the COC foil through the COC substrate is applied, resulting in consistent channel geometry uniformity. Measurements on bond strength and bursting pressure are shown, suggesting that this purely thermal bonding process potentially renders a technique which can be easily adapted into the thermoplastic microfluidic chip production workflow, while enables a low-cost as well as high-quality COC biosensor manufacturing process.

Keywords: biosensor, cyclo-olefin copolymer, hot embossing, thermal bonding, thermoplastics

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Authors: Matthew Ferguson, Tatyana Konkova, Ioannis Violatos

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Microstructure analysis of additively manufactured (AM) materials is an important step in understanding the interrelationship between mechanical properties and materials performance. Literature on the effect of laser-based AM process parameters on the microstructure in the substrate-deposit interface is limited. The interface region, the adjoining area of substrate and deposit, is characterized by the presence of the fusion zone (FZ) and heat-affected zone (HAZ), experiencing rapid thermal gyrations resulting in thermal-induced transformations. Inconel 718 was utilized as work material for both the substrate and deposit. Three blocks of Inconel 718 material were deposited by Direct Energy Deposition (DED) using three different laser powers, 550W, 750W and 950W, respectively. A coupled thermo-mechanical transient approach was utilized to correlate temperature history to the evolution of microstructure. The thermal history of the deposition process was monitored with the thermocouples installed inside the substrate material. The interface region of the blocks was analyzed with Optical Microscopy (OM) and Scanning Electron Microscopy (SEM), including the electron back-scattered diffraction (EBSD) technique. Laser power was found to influence the dissolution of intermetallic precipitated phases in the substrate and grain growth in the interface region. Microstructure and thermal history data were utilized to draw conclusive comparisons between the investigated process parameters.

Keywords: additive manufacturing, direct energy deposition, electron back-scattered diffraction, finite element analysis, inconel 718, microstructure, optical microscopy, scanning electron microscopy, substrate-deposit interface region

Procedia PDF Downloads 196

Authors: T. D. Ibragimov, A. R. Imamaliyev, G. M. Bayramov

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The polymer network liquid crystals based on the liquid crystals Н37 and 5CB with polymethylvinilpirydine (PMVP) and polyethylene glycol (PEG) have been developed. Mesogene substance 4-n-heptyoxibenzoic acid (HOBA) is served for stabilization of obtaining composites. Kinetics of network formation is investigated by methods of polarization microscopy and integrated small-angle scattering. It is shown that gel-like states of the composite H-37 + PMVP + HOBA and 5CB+PEG+HOBA are formed at polymer concentration above 7 % and 9 %, correspondingly. At slow cooling, the system separates into a liquid crystal –rich phase and a liquid crystal-poor phase. At this case, transition of these phases in the H-37 + PMVP + HOBA (87 % + 12 % + 1 %) composite to an anisotropic state occurs at 49 оС and и 41 оС, accordingly, while the composite 5CB+PEG+HOBA (85% +13 % +2%) passes to anisotropic state at 36 оС corresponding to the isotropic-nematic transition of pure 5CB. The basic electro-optic parameters of the obtained composites are determined at room temperature. It is shown that the threshold voltage of the composite H-37 + PMVP + HOBA increase in comparison with pure H-37 and, accordingly, there is a shift of voltage dependence of rise times to the high voltage region. The contrast ratio worsens while decay time improves in comparison with the pure liquid crystal at all applied voltage. The switching times of the composite 5CB + PEG + HOBA (85% +13 % +2%) show anomalous behavior connected with incompleteness of the transition to an anisotropic state. Experimental results are explained by phase separation of the system, diminution of a working area of electro-optical effects and influence of areas with the high polymer concentration on areas with their low concentration.

Keywords: liquid crystals, polymers, small-angle scattering, optical properties

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Authors: Ivayla Trifonova, Naoum Jamous, Holger Schrödl

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A good web design is a prerequisite for a successful business nowadays, especially since the internet is the most common way for people to inform themselves. Web design includes the optical composition, the structure, and the user guidance of websites. The importance of each website leads to the question if there is a way to measure its usefulness. The aim of this paper is to suggest a methodology for the evaluation of web design. The desired outcome is to have an evaluation that is concentrated on a specific website and its target group.

Keywords: evaluation methodology, factor analysis, target group, web design

Procedia PDF Downloads 622

Authors: Hyeong-Jin Kim, Jong Kook Lee

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Zirconia has biological, mechanical and optical properties, so, it used as a dental implant material in human body. But, it is difficult to form directly bonding with living tissues after the procedure and induces the falling away from implanted parts of the body. To improve this phenomenon, it is essential to increase the surface roughness of zirconia implants and induce a forming-ability of strong bonds. In this study, we performed a room temperature spray coating on zirconia specimen to obtain a highly roughened zirconia surface. To get optimal surface roughness, we controlled the distance between the nozzle and the substrate, coating times and powder condition. Bonding microstructure, surface roughness, and chemical composition of the coating layer were observed by SEM, XRD and roughness tester.

Keywords: implant, aerosoldeposition, zirconia, dental

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Authors: Samvel H. Sargsyan

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Together with the study of electron-optical properties of nanostructures and proceeding from experiment-based data, the study of the mechanical properties of nanostructures has become quite actual. For the study of the mechanical properties of fullerene, carbon nanotubes, graphene and other nanostructures one of the crucial issues is the construction of their adequate mathematical models. Among all mathematical models of graphene or carbon nano-tubes, this so-called discrete-continuous model is specifically important. It substitutes the interactions between atoms by elastic beams or springs. The present paper demonstrates the construction of the discrete-continual beam model for carbon nanotubes or graphene, where the micropolar beam model based on the theory of moment elasticity is accepted. With the account of the energy balance principle, the elastic moment constants for the beam model, expressed by the physical and geometrical parameters of carbon nanotube or graphene, are determined. By switching from discrete-continual beam model to the continual, the models of micropolar elastic cylindrical shell and micropolar elastic plate are confirmed as continual models for carbon nanotube and graphene respectively.

Keywords: carbon nanotube, discrete-continual, elastic, graphene, micropolar, plate, shell

Procedia PDF Downloads 148

Authors: Taurino S. R. Neto, Epitácio D. S. Neto, Flávio Signorelli, Gustavo G. M. Balbi, Alex H. Higashi, Mário Luiz R. Monteiro, Eloisa Bonfá, Danieli C. O. Andrade, Leandro C. Zacharias

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Purpose: To perform a multimodal evaluation, including the use of Optical Coherence Angiotomography (OCTA), in patients with primary antiphospholipid syndrome (PAPS) without ocular complaints and to compare them with healthy individuals. Methods: A complete structural and functional ophthalmological evaluation using OCTA and microperimetry (MP) exam in patients with PAPS, followed at a tertiary rheumatology outpatient clinic, was performed. All ophthalmologic manifestations were recorded and then statistical analysis was performed for comparative purposes; p <0.05 was considered statistically significant. Results: 104 eyes of 52 subjects (26 patients with PAPS without ocular complaints and 26 healthy individuals) were included. Among PAPS patients, 21 were female (80.8%) and 21 (80.8%) were Caucasians. Thrombotic PAPS was the main clinical criteria manifestation (100%); 65.4% had venous and 34.6% had arterial thrombosis. Obstetrical criteria were present in 34.6% of all thrombotic PAPS patients. Lupus anticoagulant was present in all patients. 19.2% of PAPS patients presented ophthalmologic findings against none of the healthy individuals. The most common retinal change was paracentral acute middle maculopathy (PAMM) (3 patients, 5 eyes), followed by drusen-like deposits (1 patient, 2 eyes) and pachychoroid pigment epitheliopathy (1 patient, 1 eye). Systemic hypertension and hyperlipidaemia were present in 100% of the PAPS patients with PAMM, while only six patients (26.1%) with PAPS without PAMM presented these two risk factors together. In the quantitative OCTA evaluation, we found significant differences between PAPS patients and controls in both the superficial vascular complex (SVC) and deep vascular complex (DVC) in the high-speed protocol, as well as in the SVC in the high-resolution protocol. In the analysis of the foveal avascular zone (FAZ) parameters, the PAPS group had a larger area of FAZ in the DVC using the high-speed method compared to the control group (p=0.047). In the quantitative analysis of the MP, the PAPS group had lower central (p=0.041) and global (p<0.001) retinal sensitivity compared to the control group, as well as in the sector analysis, with the exception of the inferior sector. In the quantitative evaluation of fixation stability, there was a trend towards worse stability in the PAPS subgroup with PAMM in both studied methods. Conclusions: PAMM was observed in 11.5% of PAPS patients with no previous ocular complaints. Systemic hypertension concomitant with hyperlipidemia was the most commonly associated risk factor for PAMM in patients with PAPS. PAPS patients present lower vascular density and retinal sensitivity compared to the control group, even in patients without PAMM.

Keywords: antiphospholipid syndrome, optical coherence angio tomography, optical coherence tomography, retina

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Authors: Daira Radouane, Naim Boudmagh, Hamada Adel

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The but of this handling is to use the technique of the shearing with a mechanism lapping machine of image: a prism of Wollaston. We want to characterize this prism in order to be able to employ it later on in an analysis by shearing. A prism of Wollaston is a prism produced in a birefringent material i.e. having two indexes of refraction. This prism is cleaved so as to present the directions associated with these indices in its face with entry. It should be noted that these directions are perpendicular between them.

Keywords: non destructive control, aluminium, interferometry, treatment of image

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Authors: Muhammad Safi, Abdul Manan

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In recent years, research in aircraft avionics systems (i.e., radars and antennas) has grown revolutionary. Aircraft technology is experiencing an increasing inclination from all mechanical to all electrical aircraft, with the introduction of inhabitant air vehicles and drone taxis over the last few years. This develops an overriding need to summarize the history, latest trends, and future development in aircraft avionics research for a better understanding and development of new technologies in the domain of avionics systems. This paper focuses on the future trends in antennas and phased arrays for avionics systems. Along with the general overview of the future avionics trend, this work describes the review of around 50 high-quality research papers on aircraft communication systems. Electric-powered aircraft have been a hot topic in the modern aircraft world. Electric aircraft have supremacy over their conventional counterparts. Due to increased drone taxi and urban air mobility, fast and reliable communication is very important, so concepts of Broadband Integrated Digital Avionics Information Exchange Networks (B-IDAIENs) and Modular Avionics are being researched for better communication of future aircraft. A Ku-band phased array antenna based on a modular design can be used in a modular avionics system. Furthermore, integrated avionics is also emerging research in future avionics. The main focus of work in future avionics will be using integrated modular avionics and infra-red phased array antennas, which are discussed in detail in this paper. Other work such as reconfigurable antennas and optical communication, are also discussed in this paper. The future of modern aircraft avionics would be based on integrated modulated avionics and small artificial intelligence-based antennas. Optical and infrared communication will also replace microwave frequencies.

Keywords: AI, avionics systems, communication, electric aircrafts, infra-red, integrated avionics, modular avionics, phased array, reconfigurable antenna, UAVs

Procedia PDF Downloads 67

Authors: Lina F. Ballesteros, Hafsae Lamsaf, Miguel A. Cerqueira, Lorenzo M. Pastrana, Sandra Carvalho, Jose A. Teixeira, S. Calderon V.

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The use of bio-based packaging materials containing metallic and bimetallic nanostructures is relatively modern technology. In this sense, the food packaging industry has been investigating biological and renewable resources that can replace petroleum-based materials to reduce the environmental impact and, at the same time, including new functionalities using nanotechnology. Therefore, the main objective of the present work consisted of developing bio-based poly-lactic acid (PLA) films with Zinc (Zn) and Zinc-Iron (Zn-Fe) nanostructures deposited by magnetron sputtering. The structural, antimicrobial, and optical properties of the films were evaluated when exposed at 60% and 96% relative humidity (RH). The morphology and elemental analysis of the samples were determined by scanning (transmission) electron microscopy (SEM and STEM), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The structure of the PLA was monitored before and after deposition by Fourier transform infrared spectroscopy (FTIR) analysis, and the antimicrobial and color assays were performed by using the zone of inhibition (ZOI) test and a Minolta colorimeter, respectively. Finally, the films were correlated in terms of the deposit conditions, Zn or Zn-Fe concentrations, and thickness. The results revealed PLA films with different morphologies, compositions, and thicknesses of Zn or Zn-Fe nanostructures. The samples showed a significant antibacterial and antifungal activity against E. coli, P. aeruginosa, P. fluorescens, S. aureus, and A. niger, and considerable changes of color and opacity at 96% RH, especially for the thinner nanostructures (150-250 nm). On the other hand, when the Fe fraction was increased, the lightness of samples increased, as well as their antimicrobial activity when compared to the films with pure Zn. Hence, these findings are relevant to the food packaging field since intelligent and active films with multiple properties can be developed.

Keywords: biopolymers, functional properties, magnetron sputtering, Zn and Zn-Fe nanostructures

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Authors: D. Heinemann, S. Schramm, S. Knabner, D. Baumgarten

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Purpose: Applying solder paste to printed circuit boards (PCB) with stencils has been the method of choice over the past years. A new method uses a jet printer to deposit tiny droplets of solder paste through an ejector mechanism onto the board. This allows for more flexible PCB layouts with smaller components. Due to the viscosity of the solder paste, air blisters can be trapped in the cartridge. This can lead to missing solder joints or deviations in the applied solder volume. Therefore, a built-in and real-time inspection of the printing process is needed to minimize uncertainties and increase the efficiency of the process by immediate correction. The objective of the current study is the design of an optimal imaging system and the development of an automatic algorithm for the detection of applied solder joints from optical from the captured images. Methods: In a first approach, a camera module connected to a microcomputer and LED strips are employed to capture images of the printed circuit board under four different illuminations (white, red, green and blue). Subsequently, an improved system including a ring light, an objective lens, and a monochromatic camera was set up to acquire higher quality images. The obtained images can be divided into three main components: the PCB itself (i.e., the background), the reflections induced by unsoldered positions or screw holes and the solder joints. Non-uniform illumination is corrected by estimating the background using a morphological opening and subtraction from the input image. Image sharpening is applied in order to prevent error pixels in the subsequent segmentation. The intensity thresholds which divide the main components are obtained from the multimodal histogram using three probability density functions. Determining the intersections delivers proper thresholds for the segmentation. Remaining edge gradients produces small error areas which are removed by another morphological opening. For quantitative analysis of the segmentation results, the dice coefficient is used. Results: The obtained PCB images show a significant gradient in all RGB channels, resulting from ambient light. Using different lightings and color channels 12 images of a single PCB are available. A visual inspection and the investigation of 27 specific points show the best differentiation between those points using a red lighting and a green color channel. Estimating two thresholds from analyzing the multimodal histogram of the corrected images and using them for segmentation precisely extracts the solder joints. The comparison of the results to manually segmented images yield high sensitivity and specificity values. Analyzing the overall result delivers a Dice coefficient of 0.89 which varies for single object segmentations between 0.96 for a good segmented solder joints and 0.25 for single negative outliers. Conclusion: Our results demonstrate that the presented optical imaging system and the developed algorithm can robustly detect solder joints on printed circuit boards. Future work will comprise a modified lighting system which allows for more precise segmentation results using structure analysis.

Keywords: printed circuit board jet-printing, inspection, segmentation, solder paste detection

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Authors: Mohammad Karimi, Magnus Heurlin, Lars Samuelson, Magnus Borgstrom, Hakan Pettersson

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Nanowire semiconductors are promising candidates for optoelectronic applications such as solar cells, photodetectors and lasers due to their quasi-1D geometry and large surface to volume ratio. The functional wavelength range of NW-based detectors is typically limited to the visible/near-infrared region. In this work, we present electrical and optical properties of IR photodetectors based on large square millimeter ensembles (>1million) of vertically processed semiconductor heterostructure nanowires (NWs) grown on InP substrates which operate in longer wavelengths. InP NWs comprising single or multiple (20) InAs/InAsP QDics axially embedded in an n-i-n geometry, have been grown on InP substrates using metal organic vapor phase epitaxy (MOVPE). The NWs are contacted in vertical direction by atomic layer deposition (ALD) deposition of 50 nm SiO2 as an insulating layer followed by sputtering of indium tin oxide (ITO) and evaporation of Ti and Au as top contact layer. In order to extend the sensitivity range to the mid-wavelength and long-wavelength regions, the intersubband transition within conduction band of InAsP QDisc is suggested. We present first experimental indications of intersubband photocurrent in NW geometry and discuss important design parameters for realization of intersubband detectors. Key advantages with the proposed design include large degree of freedom in choice of materials compositions, possible enhanced optical resonance effects due to periodically ordered NW arrays and the compatibility with silicon substrates. We believe that the proposed detector design offers the route towards monolithic integration of compact and sensitive III-V NW long wavelength detectors with Si technology.

Keywords: intersubband photodetector, infrared, nanowire, quantum disc

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Authors: Saheli Mitra, Ramesh Karri, Praveen K. Mylapalli, Arka. B. Dey, Gourav Bhattacharya, Gouriprasanna Roy, Syed M. Kamil, Surajit Dhara, Sunil K. Sinha, Sajal K. Ghosh

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The most well-known structures of lyotropic liquid crystalline systems are the two dimensional hexagonal phase of cylindrical micelles with a positive interfacial curvature and the lamellar phase of flat bilayers with zero interfacial curvature. In aqueous solution of surfactants, the concentration dependent phase transitions have been investigated extensively. However, instead of changing the surfactant concentrations, the local curvature of an aggregate can be altered by tuning the electrostatic interactions among the constituent molecules. Intermediate phases with non-uniform interfacial curvature are still unexplored steps to understand the route of phase transition from hexagonal to lamellar. Understanding such structural evolution in lyotropic liquid crystalline systems is important as it decides the complex rheological behavior of the system, which is one of the main interests of the soft matter industry. Sodium dodecyl sulfate (SDS) is an anionic surfactant and can be considered as a unique system to tune the electrostatics by cationic additives. In present study, imidazolium-based ionic liquids (ILs) with different number of carbon atoms in their single hydrocarbon chain were used as the additive in the aqueous solution of SDS. At a fixed concentration of total non-aqueous components (SDS and IL), the molar ratio of these components was changed, which effectively altered the electrostatic interactions between the SDS molecules. As a result, the local curvature is observed to modify, and correspondingly, the structure of the hexagonal liquid crystalline phases are transformed into other phases. Polarizing optical microscopy of SDS and imidazole-based-IL systems have exhibited different textures of the liquid crystalline phases as a function of increasing concentration of the ILs. The small angle synchrotron x-ray diffraction (SAXD) study has indicated the hexagonal phase of direct cylindrical micelles to transform to a rectangular phase at the presence of short (two hydrocarbons) chain IL. However, the hexagonal phase is transformed to a lamellar phase at the presence of long (ten hydrocarbons) chain IL. Interestingly, at the presence of a medium (four hydrocarbons) chain IL, the hexagonal phase is transformed to another hexagonal phase of direct cylindrical micelles through the lamellar phase. To the best of our knowledge, such a phase sequence has not been reported earlier. Even though the small angle x-ray diffraction study has revealed the lattice parameters of these phases to be similar to each other, their rheological behavior has been distinctly different. These rheological studies have shed lights on how these phases differ in their viscoelastic behavior. Finally, the packing parameters, calculated for these phases based on the geometry of the aggregates, have explained the formation of the self-assembled aggregates.

Keywords: lyotropic liquid crystals, polarizing optical microscopy, rheology, surfactants, small angle x-ray diffraction

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Authors: F. Z. Benabid, S. Kridi, F. Zouai, D. Benachour

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The aim of present work is to characterize the PVDF/TiO2 blends as nanocomposites, and study the effect of TiO2 on properties of different compositions and the evaluation of the effectiveness of the method used for filler treatment. Nanocomposite samples were synthesized by molten route in an internal mixer. The TiO2 nanoparticles were treated with stearic acid in order to obtain a good dispersion, and the demonstration of the effectiveness of the treatment on the morphology and roughness of the nanofiller was established by microstructural analysis by FTIR and AFM. The various developed nanocomposite compositions were characterized by different methods; i.e. FTIR, XRD, SEM and optical microscopy. Rheological, dielectric and mechanical studies were also performed. The results showed a remarkable increase in the crystallinity of the PVDF/neat TiO2 nanocomposite containing 1 wt% loading of filler, due to the nucleation effect of TiO2 nanoparticles. A good dispersion was obtained in PVDF/treated TiO2 nanocomposites. The rheological study showed an increase in the fluidity in all developed nanocomposite compositions, involved by the orientation of TiO2 nanoparticles in the flow direction. The dielectric study revealed an increase in electrical conductivity in PVDF/neat TiO2 nanocomposites. However, in PVDF/ treated TiO2 nanocomposites, the electrical conductivity was decreased by the addition of 0.5 and 2 wt% loading of filler.

Keywords: nanocomposites, PVDF, TiO2, comixing, mechanical treatment

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Authors: Chien-Liang Chao, Yun-Sheng Lin

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Secondary metabolites are applied in the human life of the Chinese herbal medicine. Many drugs are originally extracted from natural products with combination of pharmaceutical and chemical studies. Crude extract of the leaves from Zamia furfureace L. has been shown to exhibit anticancer activities. The first chemical investigation of this plant was carried out by our group. In this study, four known compounds were isolated from Zamia furfureace L. with three lignins (Sesamin (1), Wodeshiol (2) and Paulownin (3)), and one dipeptide (Aurantiamide acetate (4)). The structures of these compounds were analyzed through the 1D-NMR(1H-NMR,13C-NMR)、2D-NMR(COSY、HMQC、HMBC、NOESY) spectroscopic analysis, and by comparison of variety of physical data (IR, mass spectrometry, ultraviolet, optical rotation). Among them, Aurantiamide acetate (4) exhibited weak cytotoxic activity against human gastric cancer cells.

Keywords: Zamia furfureace L., AGS, sesamin, Aurantiamide acetate, secondary metabolites

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Authors: F. Demir, A. S. Kipcak, O. Dere Ozdemir, E. M. Derun, S. Piskin

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Fruit juices play important roles in human health as being a key part of nutrition.Juice and nectar are two categories of drinks with so many variations for consumers, regardless of age, lifestyle and taste preferences, which they can find their favorites. Juices contain 100% pulp when pulp content of ‘nectar’ changes between 25%-50%. In this study, potassium (K), magnesium (Mg), and phosphorus (P) contents in orange juice and nectar is determined for conscious consumption. For this purpose inductively coupled plasma optical emission spectrometry (ICP-OES) is used to find out potassium (K), magnesium (Mg), and phosphorus (P) contents in orange juices and nectar. Furthermore, the daily intake of elements from orange juice and nectar that affects human health is also investigated. From the results of experiments K, Mg and P contents are found in orange juice as 1351; 73,25; 89,27 ppm and in orange nectar as 986; 33,76; 51,30 respectively.

Keywords: element, health, ICP-OES, orange juice

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Authors: Ssu-Han Chen, Der-Baau Perng

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Molding process in IC manufacturing secures chips against the harms done by hot, moisture or other external forces. While a chip was being molded, defects like cracks, dilapidation, or voids may be embedding on the molding surface. The molding surfaces the study poises to treat and the ones on the market, though, differ in the surface where texture similar to defects is everywhere. Manual inspection usually passes over low-contrast cracks or voids; hence an automatic optical inspection system for molding surface is necessary. The proposed system is consisted of a CCD, a coaxial light, a back light as well as a motion control unit. Based on the property of statistical textures of the molding surface, a series of digital image processing and classification procedure is carried out. After training of the parameter associated with above algorithm, result of the experiment suggests that the accuracy rate is up to 93.75%, contributing to the inspection quality of IC molding surface.

Keywords: molding surface, machine vision, statistical texture, discrete Fourier transformation

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Authors: Tariq Ahamad, Mohammed S. Al-Kahtani, Taisir Eldos

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Optical communications technology has made enormous and steady progress for several decades, providing the key resource in our increasingly information-driven society and economy. Much of this progress has been in finding innovative ways to increase the data carrying capacity of a single optical fiber. In this research article we have explored basic issues in terms of security and reliability for secure and reliable information transfer through the fiber infrastructure. Conspicuously, one potentially enormous source of improvement has however been left untapped in these systems: fibers can easily support hundreds of spatial modes, but today’s commercial systems (single-mode or multi-mode) make no attempt to use these as parallel channels for independent signals. Bandwidth, performance, reliability, cost efficiency, resiliency, redundancy, and security are some of the demands placed on telecommunications today. Since its initial development, fiber optic systems have had the advantage of most of these requirements over copper-based and wireless telecommunications solutions. The largest obstacle preventing most businesses from implementing fiber optic systems was cost. With the recent advancements in fiber optic technology and the ever-growing demand for more bandwidth, the cost of installing and maintaining fiber optic systems has been reduced dramatically. With so many advantages, including cost efficiency, there will continue to be an increase of fiber optic systems replacing copper-based communications. This will also lead to an increase in the expertise and the technology needed to tap into fiber optic networks by intruders. As ever before, all technologies have been subject to hacking and criminal manipulation, fiber optics is no exception. Researching fiber optic security vulnerabilities suggests that not everyone who is responsible for their networks security is aware of the different methods that intruders use to hack virtually undetected into fiber optic cables. With millions of miles of fiber optic cables stretching across the globe and carrying information including but certainly not limited to government, military, and personal information, such as, medical records, banking information, driving records, and credit card information; being aware of fiber optic security vulnerabilities is essential and critical. Many articles and research still suggest that fiber optics is expensive, impractical and hard to tap. Others argue that it is not only easily done, but also inexpensive. This paper will briefly discuss the history of fiber optics, explain the basics of fiber optic technologies and then discuss the vulnerabilities in fiber optic systems and how they can be better protected. Knowing the security risks and knowing the options available may save a company a lot embarrassment, time, and most importantly money.

Keywords: in-house networks, fiber optics, security risk, money

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Authors: Junze Li, M. Li

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Laser diodes fabricated from the III-nitride material system are emerging solutions for the next generation telecommunication systems and optical clocks based on Ca at 397nm, Rb at 420.2nm and Yb at 398.9nm combined 556 nm. Most of the applications require single longitudinal optical mode lasers, with very narrow linewidth and compact size, such as communication systems and laser cooling. In this case, the GaN based distributed feedback (DFB) laser diode is one of the most effective candidates with gratings are known to operate with narrow spectra as well as high power and efficiency. Given the wavelength range, the period of the first-order diffraction grating is under 100 nm, and the realization of such gratings is technically difficult due to the narrow line width and the high quality nitride overgrowth based on the Bragg grating. Some groups have reported GaN DFB lasers with high order distributed feedback surface gratings, which avoids the overgrowth. However, generally the strength of coupling is lower than that with Bragg grating embedded into the waveguide within the GaN laser structure by two-step-epitaxy. Therefore, the overgrowth on the grating technology need to be studied and optimized. Here we propose to fabricate the fine step shape structure of first-order grating by the nanoimprint combined inductively coupled plasma (ICP) dry etching, then carry out overgrowth high quality AlGaN film by metalorganic chemical vapor deposition (MOCVD). Then a series of gratings with different period, depths and duty ratios are designed and fabricated to study the influence of grating structure to the nano-heteroepitaxy. Moreover, we observe the nucleation and growth process by step-by-step growth to study the growth mode for nitride overgrowth on grating, under the condition that the grating period is larger than the mental migration length on the surface. The AFM images demonstrate that a smooth surface of AlGaN film is achieved with an average roughness of 0.20 nm over 3 × 3 μm2. The full width at half maximums (FWHMs) of the (002) reflections in the XRD rocking curves are 278 arcsec for the AlGaN film, and the component of the Al within the film is 8% according to the XRD mapping measurement, which is in accordance with design values. By observing the samples with growth time changing from 200s, 400s to 600s, the growth model is summarized as the follow steps: initially, the nucleation is evenly distributed on the grating structure, as the migration length of Al atoms is low; then, AlGaN growth alone with the grating top surface; finally, the AlGaN film formed by lateral growth. This work contributed to carrying out GaN DFB laser by fabricating grating and overgrowth on the nano-grating patterned substrate by wafer scale, moreover, growth dynamics had been analyzed as well.

Keywords: DFB laser, MOCVD, nanoepitaxy, III-niitride

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Authors: Mireille Vonlanthen, Pasquale Porcu, Ernesto Rivera

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Dendritic macromolecules are presenting unique physical and chemical properties. One of them is the faculty of transferring energy from a donor moiety introduced at the periphery to an acceptor moiety at the core, mimicking the antenna effect of the process of photosynthesis. The mechanism of energy transfer is based on the Förster resonance energy exchange and requires some overlap between the emission spectrum of the donor and the absorption spectrum of the acceptor. Since it requires a coupling of transition dipole but no overlap of the physical wavefunctions, the energy transfer by Förster mechanism can occur over quite long distances from 1 to a maximum of 10 nm. However, the efficiency of the transfer depends strongly on distance. The Förster radius is the distance at which 50% of the donor’s emission is deactivated by FRET. In this work, we synthesized and characterized a novel series of dendrimers bearing pyrene moieties at the periphery and a Ru (II) complex at the core. The optical and photophysical properties of these compounds were studied by absorption and fluorescence spectroscopy. Pyrene is a well-studied chromophore that has the particularity to present monomer as well as excimer fluorescence emission. The coordination compounds of Ru (II) are red emitters with low quantum yield and long excited lifetime. We observed an efficient singulet to singulet energy transfer in such constructs. Moreover, it is known that the energy of the MLCT emitting state of Ru (II) can be tuned to become almost isoenegetic with respect to the triplet state of pyrene, leading to an extended phosphorescence lifetime. Using dendrimers bearing pyrene moieties as ligands for Ru (II), we could combine the antenna effect of dendrimers as well as its protection effect to the quenching by dioxygen with lifetime increase due to triplet-triplet equilibrium.

Keywords: dendritic molecules, energy transfer, pyrene, ru-trisbipyridine complex

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Authors: Rui He, Seung-Eun Baik, Min-Jae Lee, Myong-Hoon Lee

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The polarizer is one of the most essential optical elements in LCDs. Currently, the most widely used polarizers for LCD is the derivatives of the H-sheet polarizer. There is a need for coatable polarizers which are much thinner and more stable than H-sheet polarizers. One possible approach to obtain thin, stable, and coatable polarizers is based on the use of highly ordered guest-host system. In our research, we aimed to fabricate coatable polarizer based on highly ordered liquid crystalline monomer and dichroic dye ‘guest-host’ system, in which the anisotropic absorption of light could be achieved by aligning a dichroic dye (guest) in the cooperative motion of the ordered liquid crystal (host) molecules. Firstly, we designed and synthesized a new reactive liquid crystalline monomer containing polymerizable acrylate groups as the ‘host’ material. The structure was confirmed by 1H-NMR and IR spectroscopy. The liquid crystalline behavior was studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). It was confirmed that the monomers possess highly ordered smectic phase at relatively low temperature. Then, the photocurable ‘guest-host’ system was prepared by mixing the liquid crystalline monomer, dichroic dye and photoinitiator. Coatable polarizers were fabricated by spin-coating above mixture on a substrate with alignment layer. The in-situ photopolymerization was carried out at room temperature by irradiating UV light, resulting in the formation of crosslinked structure that stabilized the aligned dichroic dye molecules. Finally, the dichroic ratio (DR), order parameter (S) and polarization efficiency (PE) were determined by polarized UV/Vis spectroscopy. We prepared the coatable polarizers by using different type of dichroic dyes to meet the requirement of display application. The results reveal that the coatable polarizers at a thickness of 8μm exhibited DR=12~17 and relatively high PE (>96%) with the highest PE=99.3%, which possess potential for the LCD or flexible display applications.

Keywords: coatable polarizer, display, guest-host, liquid crystal

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Authors: Atilla Evcin, Bahri Ersoy, Süleyman Akpınar, I. Sinan Atlı

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Ceramic, polymer and composite nanofibers are nowadays begun to be utilized in many fields of nanotechnology. By the means of dimensions, these fibers are as small as nano scale but because of having large surface area and microstructural characteristics, they provide unique mechanic, optical, magnetic, electronic and chemical properties. In terms of nanofiber production, electrospinning has been the most widely used technique in recent years. In this study, carbon nanofibers have been synthesized from solutions of Polyacrylonitrile (PAN)/ N,N-dimethylformamide (DMF) by electrospinning method. The carbon nanofibers have been stabilized by oxidation at 250 °C for 2 h in air and carbonized at 750 °C for 1 h in H2/N2. Images of carbon nanofibers have been taken with scanning electron microscopy (SEM). The images have been analyzed to study the fiber morphology and to determine the distribution of the fiber diameter using FibraQuant 1.3 software. Then polymer composites have been produced from mixture of carbon nanofibers and silicone polymer. The final polymer composites have been characterized by X-ray diffraction method and scanning electron microscopy (SEM) energy dispersive X-ray (EDX) measurements. These results have been reported and discussed. At result, homogeneous carbon nanofibers with 100-167 nm of diameter were obtained with optimized electrospinning conditions.

Keywords: electrospinning, characterization, composites, nanofiber

Procedia PDF Downloads 388