17 results
Search Results
Now showing 1 - 10 of 17
- ItemEvaluation of optical data gained by ARAMIS-measurement of abdominal wall movements for an anisotropic pattern design of stress-adapted hernia meshes produced by embroidery technology(London [u.a.] : Institute of Physics, 2017) Breier, A.; Bittrich, L.; Hahn, J.; Spickenheuer, A.For the sustainable repair of abdominal wall hernia the application of hernia meshes is required. One reason for the relapse of hernia after surgery is seen in an inadequate adaption of the mechanical properties of the mesh to the movements of the abdominal wall. Differences in the stiffness of the mesh and the abdominal tissue cause tension, friction and stress resulting in a deficient tissue response and subsequently in a recurrence of a hernia, preferentially in the marginal area of the mesh. Embroidery technology enables a targeted influence on the mechanical properties of the generated textile structure by a directed thread deposition. Textile parameters like stitch density, alignment and angle can be changed easily and locally in the embroidery pattern to generate a space-resolved mesh with mechanical properties adapted to the requirement of the surrounding tissue. To determine those requirements the movements of the abdominal wall and the resulting distortions need to be known. This study was conducted to gain optical data of the abdominal wall movements by non-invasive ARAMIS-measurement on 39 test persons to estimate direction and value of the major strains.
- ItemFabrication of a new photo-sensitized solar cell using TiO2\ZnO Nanocomposite synthesized via a modified sol-gel Technique(London [u.a.] : Institute of Physics, 2020) Mahdi Rheima, Ahmed; Hadi Hussain, Dhia; Jawad Abed, HayderThe current research synthesized was carried out using a modified solgel Technique for titanium dioxide ( TiO2) and zinc oxide (ZnO) nanocomposite. The morphology and optical properties of the synthesized nanocomposite were examined using a transmission electron microscope ( TEM) and UV-Visible spectroscopy. The structure of the synthesized nanocomposite was proved using X-ray Diffraction(XRD). The particle size of the ZnO/TiO2 nanocomposites was found to be range between 11 to 27.37 nm. The product of TEM has proof of the inclusion in the ZnO matrix of spherical TiO2particles. Also found were TiO2 sections attached to the ZnO-like rodlike particles., the ZnO/TiO2 Nanocomposites had better optical absorbing properties. The nanocomposite has been used to create a new photosensitizer solar cell with the efficiency of energy conversion of approximately 4.6%, using (E)-ethyl 4- ((4-nitrobenzylidene)) aminobenzoate as organic photo-sensitized (OPS) by (ITO/TiO2\ZnO nanocomposite/POS/iodine/silver (Ag) nanofilm/ITO).
- ItemConversion of carbon dioxide into storable solar fuels using solar energy(London [u.a.] : Institute of Physics, 2019) Ennaceri, Houda; Abel, BerndNowadays, there are two main energy and environmental concerns, the first is the risk of running out of fossil fuels in the next few decades, and the second is the alarming increase in the carbon dioxide concentrations in the atmosphere, causing global warming and rise of see levels. Therefore, solar-driven technologies represent a substantial solution to fossil fuels dependence, global warming and climate change. Unlike most scientific research, which aim to use solar energy to generate electricity, solar energy can also be harnessed by recycling the carbon dioxide in the atmosphere through high-tech artificial photosynthesis with the objective of producing storable and liquid solar fuels from CO2 and water. There are two types of solar fuels, the first being hydrogen, which can be produced by mean of water splitting processes. The combustion of hydrogen generates water, which is a completely clean option for the environment. The second type of solar fuels consists of carbon-based fuels, such as methane (CH4), carbon monoxide (CO), or alcohols such as methanol (CH3OH) and ethanol (C2H5OH). The production to liquid solar fuels liquid fuels is of great interest, since they can be used in the current industrial infrastructures such as the automobiles' sector, without substantial changes in the vehicles' internal combustion engines. Therefore, guaranteeing a smooth transition from fossil fuel energy to renewable energy without radical economic consequences. Also, and most importantly, when these solar fuels are burned, they will only release the exact amount of CO2 which was initially used, which represents an optimal process for sustainable transport.
- ItemRaman imaging to study structural and chemical features of the dentin enamel junction(London [u.a.] : Institute of Physics, 2015) Alebrahim, M.A.; Krafft, C.; Popp, J.; El-Khateeb, Mohammad Y.The structure and chemical features of the human dentin enamel junction (DEJ) were characterized using Raman spectroscopic imaging. Slices were prepared from 10 German, and 10 Turkish teeth. Raman images were collected at 785 nm excitation and the average Raman spectra were calculated for analysis. Univariate and multivariate spectral analysis were applied for investigation. Raman images were obtained based on the intensity ratios of CH at 1450 cm-1 (matrix) to phosphate at 960 cm-1 (mineral), and carbonate to phosphate (1070/960) ratios. Different algorithms (HCA, K-means cluster and VCA) also used to study the DEJ. The obtained results showed that the width of DEJ is about 5 pm related to univariate method while it varies from 6 to 12 ÎĽm based on multivariate spectral technique. Both spectral analyses showed increasing in carbonate content inside the DEJ compared to the dentin, and the amide I (collagen) peak in dentin spectra is higher than DEJ spectra peak.
- ItemBasic material and technology investigations for material bonded hybrids by continuous hybrid profile fabrication(London [u.a.] : Institute of Physics, 2021) Schubert, K.; Gedan-Smolka, M.; Marschner, A.; Rietzschel, T.; Uhlig, K.; Löpitz, D.; Wagner, D.; Knobloch, M.; Karjust, Krist; Otto, Tauno; Kübarsepp, Jakob; Hussainova, IrinaThe development of multi-material hybrids by injection molding has been studied very intensively at the IPF in the past. For that, a material bonding between the different substrates was achieved by using a newly developed two-step curing powder coating material as latent reactive adhesive. The aim of the project “Hybrid Pultrusion” was to perform a novel approach for the fabrication of material bonded metal-plastic joints (profiles) in a modified pultrusion process. Therefore, powder pre-coated steel coil is combined with a glass-fiber reinforced epoxy resin matrix. For initial basic studies, the impregnated fiber material has been applied on the pre-coated steel sheets using the Resin Transfer Molding process (RTM-process). It was proved via lap shear tests, that this procedure resulted in very high adhesive strengths up to 35 MPa resulting from the formation of a covalent matrix-steel bonding as well. In addition, the failure mechanism was subsequently studied. Furthermore, by adapting the successful material combination to the pultrusion process it was demonstrated that material bonded hybrids can be achieved even under these continuous processing conditions.
- ItemAdvances in electron channelling contrast imaging and electron backscatter diffraction for imaging and analysis of structural defects in the scanning electron microscope(London [u.a.] : Institute of Physics, 2020) Trager-Cowan, C.; Alasmari, A.; Avis, W.; Bruckbauer, J.; Edwards, P.R.; Hourahine, B.; Kraeusel, S.; Kusch, G.; Jablon, B.M.; Johnston, R.; Martin, R.W.; Mcdermott, R.; Naresh-Kumar, G.; Nouf-Allehiani, M.; Pascal, E.; Thomson, D.; Vespucci, S.; Mingard, K.; Parbrook, P.J.; Smith, M.D.; Enslin, J.; Mehnke, F.; Kneissl, M.; Kuhn, C.; Wernicke, T.; Knauer, A.; Hagedorn, S.; Walde, S.; Weyers, M.; Coulon, P.-M.; Shields, P.A.; Zhang, Y.; Jiu, L.; Gong, Y.; Smith, R.M.; Wang, T.; Winkelmann, A.In this article we describe the scanning electron microscopy (SEM) techniques of electron channelling contrast imaging and electron backscatter diffraction. These techniques provide information on crystal structure, crystal misorientation, grain boundaries, strain and structural defects on length scales from tens of nanometres to tens of micrometres. Here we report on the imaging and analysis of dislocations and sub-grains in nitride semiconductor thin films (GaN and AlN) and tungsten carbide-cobalt (WC-Co) hard metals. Our aim is to illustrate the capability of these techniques for investigating structural defects in the SEM and the benefits of combining these diffraction-based imaging techniques.
- ItemInfluence of microwave plasma treatment on the surface properties of carbon fibers and their adhesion in a polypropylene matrix(London [u.a.] : Institute of Physics, 2016) Scheffler, C.; Wölfel, E.; Förster, T.; Poitzsch, C.; Kotte, L.; Mäder, G.; Madsen, Bo; Biel, A.; Kusano, Y.; Lilholt, H.; Mikkelsen, L.P.; Mishnaevsky Jr., L.; Sørensen, B.F.A commercially available carbon fiber (CF) with an epoxy-based sizing (EP-sized CF) and an unsized CF have been plasma treated to study the effect on the fiber-matrix adhesion towards a polypropylene matrix. The EP-sized fiber was chosen because of its predictable low adhesion in a polypropylene (PP) matrix. The fibers have been modified using a microwave low-pressure O2/CO2/N2-gas plasma source (Cyrannus®) developed at IWS in a batch process. One aim of this study was the evaluation of parameters using high energies and short time periods in the plasma chamber to see the effect on mechanical performance of CF. These results will be the fundamental work for a planned continuous plasma modification line. The CF surface was characterized by determining the surface energies, single fiber tensile strength and XPS analysis. The adhesion behavior before and after plasma treatment was studied by single fiber pull-out test (SFPO) and scanning electron microscopy (SEM). It was shown that the CO2- and O2-plasma increases the number of functional groups on the fiber surface during short time plasma treatment of 30 s. Carboxylic groups on the unsized CF surface resulting from O2-plasma treatment lead to an enhanced fiber-matrix adhesion, whereas the fiber strength was merely reduced.
- ItemMagnetic field dynamos and magnetically triggered flow instabilities(London [u.a.] : Institute of Physics, 2017) Stefani, F.; Albrecht, T.; Arlt, R.; Christen, M.; Gailitis, A.; Gellert, M.; Giesecke, A.; Goepfert, O.; Herault, J.; Kirillov, O.N.; Mamatsashvili, G.; Priede, J.; RĂĽdiger, G.; Seilmayer, M.; Tilgner, A.; Vogt, T.; Gerbeth, Gunther; Stieglitz, RobertThe project A2 of the LIMTECH Alliance aimed at a better understanding of those magnetohydrodynamic instabilities that are relevant for the generation and the action of cosmic magnetic fields. These comprise the hydromagnetic dynamo effect and various magnetically triggered flow instabilities, such as the magnetorotational instability and the Tayler instability. The project was intended to support the experimental capabilities to become available in the framework of the DREsden Sodium facility for DYNamo and thermohydraulic studies (DRESDYN). An associated starting grant was focused on the dimensioning of a liquid metal experiment on the newly found magnetic destabilization of rotating flows with positive shear. In this survey paper, the main results of these two projects are summarized.
- ItemQuantifying texture evolution during hot rolling of AZ31 Twin Roll Cast strip(London [u.a.] : Institute of Physics, 2015) Gorelova, S.; Schaeben, H.; Skrotzki, Werner; Oertel, Carl-GeorgMulti-pass rolling experiments with an AZ31 Twin Roll Cast (TRC) alloy were performed on an industrial scaled four-high rolling mill. Within the rolling with an intermediate annealing the evolution of texture was investigated. To quantify the extent of preferred crystallographic orientation experimental X-ray pole figures were measured after different process steps and analyzed using the free and open Matlab® toolbox MTEX for texture analysis. The development of the fiber texture was observed and analyzed in dependence on rolling conditions. In the initial state the specimen exhibits a texture composed of a weak basal texture and a cast texture with {0001}-planes oriented across the rolling direction. During the following rolling process a fiber texture was developed. The expected strength increment of the fiber texture was quantitatively confirmed in terms of volume portions of the orientation density function around the fiber and in terms of the canonical parameters of fitted pseudo Bingham distributions. On the results of this work a model for prediction of the texture evolution during the strip rolling of magnesium in the examined parameter range was developed.
- ItemComputational Simulations of the Lateral-Photovoltage-Scanning-Method(London [u.a.] : Institute of Physics, 2018) Kayser, S.; Lüdge, A.; Böttcher, K.The major task for the Lateral-Photovoltage-Scanning-Method is to detect doping striations and the shape of the solid-liquid-interface of an indirect semiconductor crystal. This method is sensitive to the gradient of the charge carrier density. Attempting to simulate the signal generation of the LPS-Method, we are using a three dimensional Finite Volume approach for solving the van Roosbroeck equations with COMSOL Multiphysics in a silicon sample. We show that the simulated LPS-voltage is directly proportional to the gradient of a given doping distribution, which is also the case for the measured LPS-voltage.