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1
Hawley, Robert L. "Borehole investigations of firn processes /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/6796.
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Hashemzadeh, Majid. "Investigations into fibre laser cutting." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/14057/.
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Fibre laser cutting of mild steel using oxygen and nitrogen is widely used in industries throughout the world. An IPG YLR-2000 Ytterbium fibre machine with a maximum power of 2 kW and a wavelength of 1.06 µm is used throughout this research. The effects of oxygen and nitrogen as assist gases on the feature of laser cutting process are different in terms of kerf width, surface roughness, heat affected zone and striation pattern. The kerf width in oxygen laser cutting is wider than that for nitrogen. The striation pattern on oxygen cut edge is smoother than that for the nitrogen cut edge. When using oxygen, the cut edge is covered by a fragile oxide layer while this feature is not seen on the nitrogen cut edge. After laser cutting with oxygen, the cut edge is dross free whilst nitrogen cut edge is drossy. Laser piercing is used to generate a starting point for laser cutting. The pierced hole is normally larger than the kerf width, which means that it cannot lie on the cutline. An experimental programme investigating the piercing process as a function of laser and assist gas parameters is presented. Oxygen and nitrogen were used as assist gases, with pressures ranging from 0.3 to 12 bar. The sizes, geometries and piercing time of the holes produced have been analysed. The pierced hole size decreases with increasing gas pressure and increasing laser power. Oxygen assist gas produced larger diameter holes than nitrogen. A new technique is presented which produces pierced holes no larger than the kerf with and would allow the pierced hole to lie on the cut line of the finished product – allowing better material usage. This uses an inclined jet of nitrogen when piercing prior to oxygen assisted cutting. Specific point energy (SPE) is a concept that has been successfully used in laser welding where SPE and power density determine penetration depth. This analysis allows welding carried out by different laser systems to be directly compared. This work investigates if the SPE concept can be applied to laser cutting. Laser cutting of various thicknesses of mild steel, two different optical set ups and three different delivery fibres with a range of powers and translation speeds is done to gain results for numerous different parameter combinations. It is found that the SPE concept is applicable to laser cutting and the following effects noted: for given material thickness and any given value of SPE, cost is decreased by using a larger beam diameter; for given cut sheet thickness, cutting efficiency increases with SPE; for given value of SPE, cutting efficiency increases as material thickness decreases.
3
Pert, Alastair David. "The use of smoke residues in forensic fire investigations." Thesis, University of Lincoln, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496076.
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Bahr, Oliver [Verfasser]. "Numerical and Experimental Investigations on Unbraced Composite Frames in Fire / Oliver Bahr." Aachen : Shaker, 2011. http://d-nb.info/107259241X/34.
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Williams, Eleri. "Experimental and theoretical investigations of nanosecond fibre laser micromachining." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/72916/.
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Pulsed ytterbium-doped fibre lasers based on a master oscillator power amplifier (MOPA) architecture possess attractive characteristics over their Q-switched diode-pumped solid-state counterparts. These include a relatively low cost of ownership and a flexible operating window with respect to the pulse duration, shape and repetition rate. For micro machining applications, given this inherent large processing window available with respect to the pulse characteristics, the effect of process parameters on particular machining outcomes needs to be investigated. The literature review conducted identified four important gaps in the knowledge surrounding the nanosecond fibre laser machining of materials. These gaps included the optimisation of the nanosecond fibre laser machining during milling operations, with the aim of obtaining both high surface quality and material removal rates, as well as the need for complimentary theoretical and experimental studies on the basic nanosecond laser material interaction for a wide range of engineering materials. In addition, the characterisation of the nanosecond laser machining of bulk metallic glasses, and the investigation of processing conditions leading to crystallisation of their amorphous structure, were identified as knowledge gaps that need to be addressed. The first knowledge gap was the focus of Chapter 3. The particular parameters under investigation in this study were the pulse duration and repetition frequency, the pulse overlap, the scanning strategy and the distance between linear machined tracks when processing aluminium. The results showed that, for each of the pulse durations studied, the specific frequency at which both the highest energy and average power are delivered leads to the maximum material removal rate (MRR) achievable, and to high values of surface roughness. It was also observed that the lowest surface roughness obtained corresponds to a specific frequency range which is common for all pulse durations. Following this, a design of experiments was conducted for a given pulse duration with the aim of identifying an optimum combination of parameters with respect to the attained surface roughness while operating at the frequency resulting in the highest MRR. This optimisation study resulted in a 60% decrease in the achieved surface roughness and also showed that the distance between machined tracks had the highest influence on the surface finish among the parameters considered. In the following chapter, a theoretical model was developed to predict the topographical evolution of the single pulse craters as a result of the time-dependent temperature rise in the processed materials when the laser beam is incident on its surface. In addition to this theoretical study, in an to attempt to understand the laser material interaction on a more fundamental level, single pulse experiments were conducted at varying laser fluence values and pulse durations leading to the formation of single craters on the surface of a number of materials namely, titanium, silicon and silicon carbide. In particular, different pulse lengths were investigated at decreasing values of fluence until no visible effect on the material surface could be observed. Based on this investigation, the fluence corresponding to the ablation threshold for each material at different pulse durations could be found whilst identifying the relationship between the laser processing parameters and the dimensions of the single craters. Scanning Electron Microscopy (SEM) micrographs of the craters were also used to observe phenomena such as melt ejection as a result of varying the process parameters. The experimental results were compared with the theoretical predictions and a good agreement between both set of data was found with respect to the achieved depths and diameters of the craters. The additional knowledge gaps were the focus of Chapter 5. In particular, the characterisation of nanosecond laser machining of a zirconium-based bulk metallic glass (BMG) was conducted using the approach employed in Chapter 4. Similar conclusions were reached with regard to the single pulse material removal behaviour when varying the fluence and pulse duration. In addition, milling of the material with different parametric combinations was implemented to investigate the crystallisation behaviour of the BMG. To complement these experimental tests, the theoretical model reported in Chapter 4 was further developed to predict the heating and cooling rates of the milling process. From this study, it was found that varying the process parameters of the machining of BMG results in a variation in the critical cooling rate (from the melt temperature to the glass transition temperature) which may result in crystallisation of the material.
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Carter, Jeremy Nigel. "Investigations of rare earth doped fluorozirconate fibre lasers and amplifiers." Thesis, University of Southampton, 1992. https://eprints.soton.ac.uk/399360/.
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This thesis presents the results of a three year study into the use of thulium and praseodymium doped fluorozirconate fibres as low threshold, potentially miniature laser sources at a variety of wavelengths from the visible to the infrared. Thulium doped fluorozirconate fibre is also investigated as a high gain optical amplifier at 810nm. Pumped at the semiconductor diode compatible wavelength of 790nm, laser emission has been demonstrated at 1.9µm, 2.3µm, 1.47µm and 810nm in thulium doped fluorozirconate fibres, with diode pumped operation achieved at 1.91µm. The transition at 810nm has been operated as an optical amplifier where single pass gains in excess of 22dB have been demonstrated for less than 60mW of pump power. The gain characteristics of this transition have been modelled and show good agreement with the experimentally observed performance. Operated as a laser emitting around 810nm, this transition has demonstrated both high efficiencies (> 70%), low thresholds (< 13mW of pump power) and tunability over 30nm. A Judd-Ofelt analysis has been carried out for thulium-doped fluorozirconate fibre to extract spectroscopic data for explanation of the system performance. In praseodymium doped fluorozirconate fibre, visible laser emission has been observed at 635nm, 605nm, 520nm and 491nm both when pumped by an argon ion laser at 472.7nm and by upconversion pumping when using two Ti:sapphire pump lasers tuned to 1.01µm and 835nm. An analytical model of the performance of these upconversion pumped visible fibre laser transitions is presented and shows good agreement with experiment. Pump power requirements for laser action on the high gain 635nm transition have been shown to be as low as 20mW from each pump laser and there exists, therefore, the possibility of semiconductor laser diode pumping.
7
Wagner, Lara Suzanne. "Investigations of Upper Mantle Structure using Broadband Seismology." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1204%5F1%5Fm.pdf&type=application/pdf.
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Matei, Adriana. "Optical investigations of biological samples in far infrared." [S.l. : s.n.], 2005. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11814266.
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Wu, C. M. L. "Theoretical investigations of stress concentrations in carbon fibre reinforced plastic structures." Thesis, University of Bristol, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.232791.
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Constantinou, Marios, and Michael Gehde. "Infrared welding of continuous fibre-reinforced thermoplastics – Investigations on overlapping joints." Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-226689.
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Continuous fibre-reinforced thermoplastics often are offered as impregnated and consolidated semi-finished products which are known as organic sheets. The thermoplastic matrix leads to several advantages including the thermoformability and weldability.
Parts made of organic sheets are frequently produced by forming the semi-finished product into half-shells and stiffening those shells in the course of the process e.g. by the injection moulding of ribs. Larger and more complex parts with hollow body structures can be manufactured e.g. by forming the semi-finished products into half-shells and joining the half-shells. However, the currently available manufacturing technologies for parts made of organic sheets have cap profile shaped joints which prevent the use of the reinforcing fibres across the joint plane.
Investigations have proven that overlapping weld joints in organic sheets show much higher strengths than cap profile shaped joints which can be explained by the fibre use across the joint plane. Furthermore, the infrared welding technology was verified as an appropriate process for the welding of organic sheets since no need for additional welding material is given, short heating times can be realized and no contact of the infrared emitters to the joining parts is required. Therefore, the present study shall reveal the high potential of the overlapping welding of organic sheets. Influences on the weld strengths of infrared welded organic sheets are described and potential improvements concerning the materials to be welded as well as the welding process are shown.
11
Wölfel, Jens. "In vitro investigations on the fine-tuned interaction between neurotrypsin and agrin /." Zürich, 2008. http://opac.nebis.ch/cgi-bin/showAbstract.pl?sys=000254460.
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Berwick, M. "Investigations toward Faraday effect optical current sensors and optical fibre frequency shifters." Thesis, University of Kent, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.290423.
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Choi, Ming Fat. "Investigations into fibre optic sensing systems for gaseous oxygen and carbon dioxide." Thesis, University of the West of England, Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240829.
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Perry, Ian Richard. "Investigations into ytterbium, ytterbium-erbium and thulium-doped silica-based fibre lasers." Thesis, University of Southampton, 1991. https://eprints.soton.ac.uk/427927/.
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Martin, Haydn. "Investigations into a multiplexed fibre interferometer for on-line, nanoscale, surface metrology." Thesis, University of Huddersfield, 2010. http://eprints.hud.ac.uk/id/eprint/8797/.
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Current trends in technology are leading to a need for ever smaller and more complex featured surfaces. The techniques for manufacturing these surfaces are varied but are tied together by one limitation; the lack of useable, on-line metrology instrumentation. Current metrology methods require the removal of a workpiece for characterisation which leads to machining down-time, more intensive labour and generally presents a bottle neck for throughput. In order to establish a new method for on-line metrology at the nanoscale investigation are made into the use of optical fibre interferometry to realise a compact probe that is robust to environmental disturbance. Wavelength tuning is combined with a dispersive element to provide a moveable optical stylus that sweeps the surface. The phase variation caused by the surface topography is then analysed using phase shifting interferometry. A second interferometer is wavelength multiplexed into the optical circuit in order to track the inherent instability of the optical fibre. This is then countered using a closed loop control to servo the path lengths mechanically which additionally counters external vibration on the measurand. The overall stability is found to be limited by polarisation state evolution however. A second method is then investigated and a rapid phase shifting technique is employed in conjunction with an electro-optic phase modulator to overcome the polarisation state evolution. Closed loop servo control is realised with no mechanical movement and a step height artefact is measured. The measurement result shows good correlation with a measurement taken with a commercial white light interferometer.
16
Thompson, Aaron. "Biogeochemical Response of Multiple Iron Redox Oscillations: Laboratory and Field Investigations." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1415%5F1%5Fm.pdf&type=application/pdf.
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Park, Jinyong. "Experimental and Numerical Investigations of Fluid Flow for Natural Single Rock Fractures." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1385%5F1%5Fm.pdf&type=application/pdf.
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Bosnjak, Josipa [Verfasser], and Joško [Akademischer Betreuer] Ožbolt. "Explosive spalling and permeability of high performance concrete under fire : numerical and experimental investigations / Josipa Bosnjak. Betreuer: Josko Ozbolt." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2014. http://d-nb.info/1058362151/34.
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Bošnjak, Josipa [Verfasser], and Joško [Akademischer Betreuer] Ožbolt. "Explosive spalling and permeability of high performance concrete under fire : numerical and experimental investigations / Josipa Bosnjak. Betreuer: Josko Ozbolt." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-95122.
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Scarfuto, Rosalinda Ruiz. "Investigations into the impact of tactile perception on the artist's creative process expressed on a 3D Poetic Canvas using the methodology of a 'Forest Flaneur'." Thesis, University of Sunderland, 2018. http://sure.sunderland.ac.uk/9617/.
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This practice-led study explores the experiences of four poets in relation to specific landscapes and its inspiration on the creative practitioner. The research study focuses on tactile perception and its influence on the artistic process as both experiential and interpretative tool. It utilizes the idea of the ‘haptic intuitive’ (Di Giovine, 2015), specifically the finger pads, for a qualitative phenomenological study framed by fieldwork in nature and expressed in a 3D poetic canvas. The Flaneur methodology was applied to the approach made in the field and developed. This poetic style of walking which is historically associated with Baudelaire is chiefly applied to research in urban settings (Frisby, 1998) However, in this research study, the concept of a “Forest Flaneur” was developed as the scope of the fieldwork involved rural settings and encouraged movement (walking) in random directions primarily linked to tactile attraction in natural landscapes. The methodology developed focused on case studies of four walking poets’ inspirational landscapes (Wordsworth, Whitman, Machado and Snyder). The notion of the “Forest Flaneur” which has been developed in this study is a poetic walking style in nature, highlighting tactile memories, in rural settings. The contribution to knowledge focuses on a method of revisiting the experiences of poets in relation to their specific inspirational landscape and refining that method through exploring the tactile dimension of experience. This method of separating the tactile from the non-tactile has relevance for the creative practitioner, Furthermore, when undertaking this research I allowed a period of 15+ day’s gestation period between the haptic work in the field and the creative response to that experience on the poetic canvas in the studio. This relationship to time and what I have called ‘the looping of experience’ became a second key part of the research methodology. This methodology uses the memory of a visceral emotive ‘in situ moment’ as a stimulus - a memory formed in the somosensory cortex as a response to the 15+day gestation period. The cognitive process that is a consequence of the time lapse, or ‘time looping’ between the two events, synthesizes in the brain with the recall activity undertaken in the studio during the creative process. The research suggests that haptic experience (tactile perception) tends to enrich the creative process in both visual art and poetry.
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Mönefors, Berntell Agneta. "Children's voice and participation in social welfare investigations." Thesis, Linköpings universitet, Tema Barn, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-133710.
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There is a principal consent both in the convention on the rights of the child, the Swedish social service act and in “Barns behov i centrum” (BBiC, similar to the British “Looking after children”, LAC) that children should participate and have an impact on matters that affect them in relation to their age and maturity. This thesis focus on how children’s voices are recorded in social welfare files and how their participation in the investigation is constructed. I have read the interviews and the social reports of ten children, conducted by social workers in a municipality in the outskirts of Stockholm. The children’s voices in the files are a secondary voice, they are the social worker’s interpretation of the interviews with the children. I have used thematic analysis in order to answer my research questions. The result shows that all children had been able to talk to the social worker and nearly all of them were informed about why there was an investigation. The children’s stories were valued as true by the social workers and they were referred as information givers. Most of them were only interviewed orally, without support from child adaptive methods. They had very limited impact on how the investigation were conducted, how their information would be used and on the choice of intervention.
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Islam, Mohd Nokibul LAll Pradeep. "Investigations on damage mechanics and life prediction of fine-pitch electronics in harsh environments." Auburn, Ala., 2005. http://repo.lib.auburn.edu/2005%20Summer/doctoral/ISLAM_MOHD_11.pdf.
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Brenner, Falko [Verfasser]. "Asynchronous video interviews in selection: A systematic review and five empirical investigations / Falko Brenner." Berlin : Freie Universität Berlin, 2020. http://d-nb.info/1212031725/34.
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Panniello, Mariangela. "The lost maps : two-photon investigations of the fine scale organization of auditory cortex." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:d51b9bac-be1c-4788-bdc9-739bb90847a2.
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The spatial arrangement of neuronal responses in primary auditory cortex (A1) has so far been investigated by using microelectrode recording techniques or imaging of the intrinsic signal, which led to controversial results, at present still discussed. On the other hand, two-photon calcium imaging allows us to investigate the cortical functions at an unprecedented level of spatial detail, and has recently offered new insight into the fine-scale organization of frequency responses in A1. In this thesis, I used two-photon calcium imaging to compare, for the first time, the fine-scale cortical representation of sound frequency to that of two other sound features, crucial for survival and communication in all mammals: differences in intensity between the two ears (interaural level differences; ILDs), and frequency modulation (FM). I found that most neurons in layers II-III of the mouse A1 were tuned to ILDs favouring the contralateral ear, but midline and ipsilateral tuning were present too. Binaural preferences were heterogeneously distributed in space, both on the fine scale (within ∼ 200 μm) and on the global one (up to ∼ 1 mm). Moreover, A1 neurons were mostly tuned to slow FM sweeps within the range of those used in species-specific calls. Cells activated by similar rates tended to be spatially proximal, indicating a level of local organization similar to the one I found for frequency tuning, and higher than that of ILD responses. Finally, I set the groundwork for two-photon studies of the A1 of the ferret, by presenting the first evidence of the microscopic organization of the tonotopic map in this species. My results shed light on some long-held questions about the response properties of A1, and confirm two-photon imaging as a powerful tool for investigating the processing of sensory signals in the cortex of both small and large mammals.
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Boru, Fikre Endashaw [Verfasser]. "Numerical and experimental response and stability investigations of anisotropic rotor-bearing systems / Fikre Endashaw Boru." Kassel : Universitätsbibliothek Kassel, 2010. http://d-nb.info/1006337660/34.
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Tick, Geoffrey Ray. "Dissolution and enhanced solubilization of immiscible phase organic liquids in porous media : Theoretical, laboratory, and field investigations." Diss., The University of Arizona, 2003. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_2003_398_sip1_w.pdf&type=application/pdf.
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Brumboiu, Iulia Emilia. "The Electronic Structure of Organic Molecular Materials : Theoretical and Spectroscopic Investigations." Licentiate thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-218225.
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In the present thesis the electronic properties of two organic molecules were studied by means of density functional theory (DFT) in connection to their possible applications in organic photovoltaics and molecular spintronics respectively. The first analysed system is the C60 derivative PCBM extensively used in polymer solar cells for the charge separation process. Since fullerenes have been shown to undergo modifications as a result of light exposure, investigating their electronic structure is the first step in elucidating the photodegradation process. The electronic excitations from core levels to unoccupied molecular orbitals reveal not only the empty level structure of the molecule, but provide additional information related to the chemical bonds involving a specific atom type. In this way, they represent a means of determining the chemical changes that the molecule might withstand. The electronic transitions from carbon 1s core levels to unoccupied states are explained for the unmodified PCBM by a joint theoretical (DFT) and experimental study using the near edge x-ray absorption fine structure (NEXAFS) spectroscopy. The second investigated system is the transition metal phthalocyanine with a manganese atom as the metal center. Manganese phthalocyanine (MnPc) is a single molecular magnet in which the spin switch process can be triggered by various methods. It has been shown, for instance, that the adsorption of hydrogen to the Mn center changes the spin state of the molecule from 3/2 to 1. More interestingly, the process is reversible and can be controlled, opening up the possibility of using MnPc as a quantum bit in magnetic memory devices. Up to this date, the d orbital occupation in MnPc has been under a long debate, both theoretical and experimental studies revealing different configurations. In this thesis the electronic structure of the phthalocyanine is thoroughly analysed by means of DFT and the calculated results are compared to photoelectron spectroscopy measurements. The combination of theoretical and experimental tools reveals that in gas phase at high temepratures the molecule exhibits a mixed electronic configuration. In this light, the possible control of the specific electronic state of the central metal represents an interesting prospect for molecular spintronics.
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McCray, John Emory. "Enhanced dissolution of multiple-component nonaqueous phase organic liquids in porous media using Cyclodextrin theoretical, laboratory, and field investigations /." Diss., The University of Arizona, 1998. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1998_72_sip1_w.pdf&type=application/pdf.
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Krishnan, Venkata. "Structural investigations on organometallic complexes and nanomaterials by X-ray absorption fine structure and Raman spectroscopy." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-27631.
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Albedah, Mohammed. "Experimental and Theoretical Investigations of Magnetic, Electronic Structure, and Hyperfine Interaction Properties of New Fe-Based Superconductors and EuFeAs₂." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/41636.
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This thesis presents the experimental studies of the magnetic and hyperfine interaction
properties of four novel Fe-based superconductors (ThFeAsN, CsEuFe4As4, Rb1-δEuFe4As4, and
EuFe0.97Ni0.03As2) and one new non-superconducting compound (EuFeAs2). It is supplemented by
ab-initio calculations of the electronic structure and magnetism of the three superconductors. The
experimental studies are based on the results of x-ray diffraction, magnetic susceptibility,
magnetization, and 57Fe and 151Eu Mössbauer spectroscopy measurements.
The superconductor ThFeAsN crystallizes in the tetragonal space group P4/nmm with the
lattice parameters a = 4.0356(1) Å and c = 8.5286(1) Å. It is shown that there is no magnetic order
of the Fe magnetic moments down to 2.0 K. We suggest that nonappearance of Fe magnetism in
ThFeAsN may be because of an internal uniaxial chemical pressure whose presence is manifested
by the unusually small c/a ratio. We provide theoretical evidence for a mixture of ionic and
covalent chemical bonding and metallic characteristics. We present a detailed analysis of the
calculated energy band structure of ThFeAsN. A quadrupole doublet well describes the shape of
the Mössbauer spectra with a small quadrupole splitting that increases with lowering temperature.
Good agreement is found between the calculated and extrapolated 0 K quadrupole splitting values.
A fair agreement is noted between the experimental Debye temperature 332(2) K and 370 K of the
calculated one.
We show that the superconductor CsEuFe4As4 crystallizes in the tetragonal space group
P4/mmm with the lattice parameters a = 3.8956(1) Å and c = 13.6628(5) Å. We show that the Fe
atoms carry no magnetic moment down to 2.1 K and that the ferromagnetic order is related to the
Eu magnetic moments. We establish that the Curie temperature Tc = 15.97(8) K found from the
temperature dependence of the hyperfine magnetic field at 151Eu nuclei is well-matched with the
temperature dependence of the transferred hyperfine magnetic field at 57Fe nuclei that is produced
by the ferromagnetically ordered Eu sublattice. The magnetic moments of the Eu atoms are shown
to be perpendicular to the crystallographic c-axis. The T 3⁄2 power-law perfectly describes the
temperature dependence of the principal component of the electric field gradient tensor, both at Fe
and Eu sites. The calculated and the measured parameters of the hyperfine-interaction are in
excellent agreement with each other. We determine that the Debye temperature of CsEuFe4As4 is
295(3) K.
Ab-initio calculations suggest a mixture of ionic, covalent, and metallic bonding between
the constituent atoms in the CsEuFe4As4 superconductor. We confirm that the strongly localized
Eu f states are the origin of the magnetic moment of CsEuFe4As4, in agreement with the
experimental results. We show that an almost zero magnetic moment carried by the Fe atoms is
caused by the spin-up and spin-down states' apparent symmetry. We show that the Fermi surfaces
have hole-like and electron-like pockets located at the center and corners of the Brillouin zone,
respectively.
The superconductor Rb1-δEuFe4As4 crystallizes in the tetragonal space group P4/mmm with
the lattice parameters a = 3.8849(1) Å and c = 13.3370(3) Å. We show that the Fe atoms carry no
magnetic moment down to 2.1 K and that the ferromagnetic order is associated solely with the Eu
magnetic moments. The Curie temperature Tc = 16.54(8) K is found from the temperature
dependence of both the hyperfine magnetic field at 151Eu nuclei and the transferred hyperfine
magnetic field at 57Fe nuclei induced by the ferromagnetically ordered Eu sublattice. We find that
the Eu magnetic moments lie in the ab plane. It is observed that the temperature dependence of the
principal component of the electric field gradient tensor, at both Fe and Eu sites, is well described
by a T3⁄2 power-law relation. There is good agreement between the calculated and measured
parameters of the hyperfine-interaction. We determine that the Debye temperature of
Rb1-δEuFe4As4 is 391(8) K.
Ab-initio calculations indicate the presence of a mixture of ionic, covalent, and metallic
bonding between the constituent atoms in the RbEuFe4As4 superconductor. We show that the
magnetic moment of RbEuFe4As4 is mainly a result of the strongly localized Eu f states. It is shown
that an almost zero magnetic moment carried by the Fe atoms originates from an apparent
symmetry of the spin-up and spin-down states. We show that the electrical and chemical properties
of RbEuFe4As4 are closely associated with the presence of the Fe 3d states in the Fermi energy
region. The Fermi surfaces display hole-like and electron-like pockets, respectively, at the center
and corners of the Brillouin zone.
We find that in both the EuFeAs2 compound and 14 K superconductor EuFe0.97Ni0.03As2
the antiferromagnetic ordering of the Fe sublattice is of a spin-density-wave type with the Néel
temperatures and Fe saturation magnetic moments of 106.2(1.9) K, 0.78(1) μB and 56.6(2.2) K,
0.47(1) μB, respectively. We show that the Néel temperatures and the saturation hyperfine
magnetic fields in the two compounds with the antiferromagnetically ordered Eu sublattice are
44.4(5) K, 294.2(7) kOe and 43.5(1) K, 290.5(1) kOe respectively. The 3% substitution of Fe by
Ni in EuFeAs2, aside from producing superconductivity in EuFe0.97Ni0.03As2, radically reduces the
strength of magnetism of the Fe sublattice and has nearly no impact on the magnetism of the Eu
sublattice. The appearance of antiferromagnetically ordered Fe and Eu sublattices in
EuFe0.97Ni0.03As2 verifies that superconductivity and magnetism coexist in this compond. The
growth of the magnitude of the main component of the electric field gradient tensor, at both Fe
and Eu sites, with reducing temperature, is well described by a T3⁄2 power-law relation. We
determine the Debye temperatures of EuFeAs2, EuFe0.97Ni0.03As2, and the FeAs2 impurity phase
to be 355(18), 428(14), and 594(25) K, respectively.
In summary, for all of the studied compounds, there is no magnetic ordering associated
with iron sub-lattices in the ThFeAsN, CsEuFe4As4, and Rb1-δEuFe4As4 compounds. The iron
sublattice is magnetically ordered in the EuFeAs2 and the EuFe0.97Ni0.03As2 superconductor. There
is a coexistence of magnetism and superconductivity associated with europium in the CsEuFe4As4,
Rb1-δEuFe4As4, EuFe0.97Ni0.03As2 compounds. There is a good agreement between the calculated
and the measured hyperfine and magnetic parameters for most studied compounds.
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Herritsch, Alfred. "Investigations on Wood Stability and Related Properties of Radiata Pine." Thesis, University of Canterbury. Chemical and Process Engineering, 2007. http://hdl.handle.net/10092/1203.
Full textAbstract:
Previous studies on wood instability have identified some wood basic properties which influence the timber distortion and shape changes while the wood is losing or gaining moisture. These properties include wood anisotropic shrinkage, equilibrium moisture content (EMC) in both desorption and adsorption, fibre saturation point (FSP) and water diffusion coefficient. This study investigated the stability related wood properties and their variations within the stems of the New Zealand grown radiata pine trees. The basic density, EMC and shrinkage for the earlywood and the latewood were also experimentally determined. In taking into account these properties and their variations, an analytical model was developed to simulate the wood distortion. The equilibrium moisture content was determined at 30°C and humidity range from 27% to 90%. It was found that the EMC difference between the earlywood and the latewood was negligible. The experimental results also show that the EMC decreases from pith towards the bark over the disc cross section and the trend is most obvious at high humidities (70-90%). Along the tree height, the EMC decreases from ground towards the top of the stem. The tangential shrinkage results were highly variable but, in general, the latewood has higher values than the earlywood. The opposite trend was found for the longitudinal shrinkage, higher values for the earlywood than the latewood. In the tree height direction, the tangential shrinkage was found to decrease with the tree height. This follows the same trend as the microfibril angle which in general also decreases with the tree height. The fibre saturation point (FSP) was determined from the tangential shrinkage values at different equilibrium moisture contents. These were taken as the intersection point of the tangential shrinkage line with the moisture content axis. The experimental results have revealed a trend that the FSP decreases from the pith towards the bark and also decreases with the tree height. Similar behaviour was found for the tangential and longitudinal swelling during the adsorption. The moisture transport within radiata pine was investigated based on the diffusion theory under transient and isothermal condition of 30°C. The moisture dependant diffusion coefficient was derived from the experimental data using the inverse analysis method. The surface emission coefficient was determined by taking into account the variable surface moisture content, wood density and the ambient conditions. In the experiments, 138 samples in total (46 samples for each XIV of the longitudinal, tangential and radial directions) were used and their diffusion coefficients were determined for both the adsorption and the desorption with moisture content ranging from 6% to 22%. The derived diffusion coefficients are comparable with the reported data in the literature. Further investigation of the wood type influence on the diffusion coefficient revealed that compression wood has the lowest diffusion coefficients in the three directions (longitudinal, tangential and radial) both in the desorption and in the adsorption. In addition, the moisture content has the least influence on the diffusion coefficient in the compression wood. Investigation on the effects of the wood density has shown that in general, the diffusion coefficient decreases with increasing wood density although the correlations are only significant for the longitudinal direction in desorption. An analytical model for the simulation of the wood twist was developed which is based on the geometry and geometrical changes of the grains aligning non parallel to the pith. A board consists of numerous such grains which change the length and shape with moisture content change. The model predictions confirm that the grain angle, the tangential and longitudinal shrinkage and the conical angle all affect the development of the board twist. However, the discrepancies between the model prediction and the experimental data are significant, partly due to the experimental uncertainties and partly due to the model errors. In this study, sound velocity in the longitudinal direction was measured for the test samples used in the shrinkage experiments. The results revealed that the correlations between the sound velocity and the volumetric shrinkage at oven dry are significant. Based on this finding, the relationship between the tangential shrinkage and the radial shrinkage, the tangential shrinkage can be predicted from the sound velocity measurements. As the tangential shrinkage has significant influence on the wood distortion, this method can be used to segregate logs which may be prone to wood distortion.
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Marziale, Lodovico. "Advanced Techniques for Improving the Efficacy of Digital Forensics Investigations." ScholarWorks@UNO, 2009. http://scholarworks.uno.edu/td/1027.
Full textAbstract:
Digital forensics is the science concerned with discovering, preserving, and analyzing evidence on digital devices. The intent is to be able to determine what events have taken place, when they occurred, who performed them, and how they were performed. In order for an investigation to be effective, it must exhibit several characteristics. The results produced must be reliable, or else the theory of events based on the results will be flawed. The investigation must be comprehensive, meaning that it must analyze all targets which may contain evidence of forensic interest. Since any investigation must be performed within the constraints of available time, storage, manpower, and computation, investigative techniques must be efficient. Finally, an investigation must provide a coherent view of the events under question using the evidence gathered. Unfortunately the set of currently available tools and techniques used in digital forensic investigations does a poor job of supporting these characteristics. Many tools used contain bugs which generate inaccurate results; there are many types of devices and data for which no analysis techniques exist; most existing tools are woefully inefficient, failing to take advantage of modern hardware; and the task of aggregating data into a coherent picture of events is largely left to the investigator to perform manually. To remedy this situation, we developed a set of techniques to facilitate more effective investigations. To improve reliability, we developed the Forensic Discovery Auditing Module, a mechanism for auditing and enforcing controls on accesses to evidence. To improve comprehensiveness, we developed ramparser, a tool for deep parsing of Linux RAM images, which provides previously inaccessible data on the live state of a machine. To improve efficiency, we developed a set of performance optimizations, and applied them to the Scalpel file carver, creating order of magnitude improvements to processing speed and storage requirements. Last, to facilitate more coherent investigations, we developed the Forensic Automated Coherence Engine, which generates a high-level view of a system from the data generated by low-level forensics tools. Together, these techniques significantly improve the effectiveness of digital forensic investigations conducted using them.
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Døssland, Åse Lyslo. "Fibre Reinforcement in Load Carrying Concrete Structures : Laboratory and Field Investigations compared with Theory and Finite Element Analysis." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for konstruksjonsteknikk, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2289.
Full textAbstract:
Fibre reinforcement can provide an alternative to conventional steel bars in order to improve the efficiency and working conditions on construction sites and in the prefabrication industry. Through the fibres ability to bridge cracks they improve the structural behaviour of the concrete by increased shear, moment and punching resistance, increased dowel effect, reduced crack spacing and crack widths, increased flexural stiffness and increased ductility in compression. A main reason for limited use of FRC in load-carrying structures seems to be the lack of accepted design guidelines. The principal aim of this research project is to improve the current knowledge of the mechanical and structural behaviour of fibre reinforced concrete, focusing on practical applications. An experimental study is carried out where the following parameters are investigated: fibre volume, fibre length, steel versus synthetic fibres, size effect, influence of conventional reinforcement, self compacting versus vibrator compacted concrete, casting process and type of structural element. Most of the test series were evaluated through calculations and finite element analysis (FEA) and compared with available design rules. Generally the agreement was good, both with discrete and smeared crack approach. This shows that FEA is an appropriate tool to determine the contribution of fibres to the load bearing capacity. Moreover, the results of the test series implied that the theoretical framework that exists today describes the behaviour of fibre reinforced structures relatively well, and that the design rules which are developed is satisfactory.
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Larsson, Daniel. "Exposure to crime as a consequence of poverty : five investigations about relative deprivation, poverty and exposure to crime." Doctoral thesis, Umeå : Department of Sociology, Umeå University, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-832.
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Klein, Katharina [Verfasser], Heinrich [Akademischer Betreuer] Miller, and Peter [Akademischer Betreuer] Lemke. "Variability in dry Antarctic firn : Investigations on spatially distributed snow and firn samples from Dronning Maud Land, Antarctica / Katharina Klein. Gutachter: Heinrich Miller ; Peter Lemke. Betreuer: Heinrich Miller." Bremen : Staats- und Universitätsbibliothek Bremen, 2014. http://d-nb.info/1072226634/34.
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Mahroug, Mohamed E. M. "Behaviour of continuous concrete slabs reinforced with FRP bars. Experimental and computational investigations on the use of basalt and carbon fibre reinforced polymer bars in continuous concrete slabs." Thesis, University of Bradford, 2013. http://hdl.handle.net/10454/6332.
Full textAbstract:
An investigation on the application of basalt fibre reinforced polymer (BFRP) and carbon fibre reinforced polymer (CFRP) bars as longitudinal reinforcement for simple and continuous concrete slabs is presented. Eight continuously and four simply concrete slabs were constructed and tested to failure. Two continuously supported steel reinforced concrete slabs were also tested for comparison purposes. The slabs were classified into two groups according to the type of FRP bars. All slabs tested were 500 mm in width and 150 mm in depth. The simply supported slabs had a span of 2000 mm, whereas the continuous slabs had two equal spans, each of 2000 mm. Different combinations of under and over FRP (BFRP/CFRP) reinforcement at the top and bottom layers of slabs were investigated. The continuously supported BFRP and CFRP reinforced concrete slabs exhibited larger deflections and wider cracks than the counterpart reinforced with steel. The experimental results showed that increasing the bottom mid-span FRP reinforcement of continuous slabs is more effective than the top over middle support FRP reinforcement in improving the load capacity and reducing mid-span deflections.
Design guidelines have been validated against experimental results of FRP reinforced concrete slabs tested. ISIS¿M03¿07 and CSA S806-06 equations reasonably predicted the deflections of the slabs tested. However, ACI 440¿1R-06 underestimated the deflections, overestimated the moment capacities at mid-span and over support sections, and reasonably predicted the load capacity of the continuous slabs tested.
On the analytical side, a numerical technique consisting of sectional and longitudinal analyses has been developed to predict the moment¿curvature relationship, moment capacity and load-deflection of FRP reinforced concrete members. The numerical technique has been validated against the experimental test results obtained from the current research and those reported in the literature. A parametric study using the numerical technique developed has also been conducted to examine the influence of FRP reinforcement ratio, concrete compressive strength and type of reinforcement on the performance of continuous FRP reinforced concrete slabs. Increasing the concrete compressive strength decreased the curvature of the reinforced section with FRP bars. Moreover, in the simple and continuous FRP reinforced concrete slabs, increasing the FRP reinforcement at the bottom layer fairly reduced and controlled deflections.
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Mahroug, Mohamed Elarbi Moh. "Behaviour of continuous concrete slabs reinforced with FRP bars : experimental and computational investigations on the use of basalt and carbon fibre reinforced polymer bars in continuous concrete slabs." Thesis, University of Bradford, 2013. http://hdl.handle.net/10454/6332.
Full textAbstract:
An investigation on the application of basalt fibre reinforced polymer (BFRP) and carbon fibre reinforced polymer (CFRP) bars as longitudinal reinforcement for simple and continuous concrete slabs is presented. Eight continuously and four simply concrete slabs were constructed and tested to failure. Two continuously supported steel reinforced concrete slabs were also tested for comparison purposes. The slabs were classified into two groups according to the type of FRP bars. All slabs tested were 500 mm in width and 150 mm in depth. The simply supported slabs had a span of 2000 mm, whereas the continuous slabs had two equal spans, each of 2000 mm. Different combinations of under and over FRP (BFRP/CFRP) reinforcement at the top and bottom layers of slabs were investigated. The continuously supported BFRP and CFRP reinforced concrete slabs exhibited larger deflections and wider cracks than the counterpart reinforced with steel. The experimental results showed that increasing the bottom mid-span FRP reinforcement of continuous slabs is more effective than the top over middle support FRP reinforcement in improving the load capacity and reducing mid-span deflections. Design guidelines have been validated against experimental results of FRP reinforced concrete slabs tested. ISIS-M03-07 and CSA S806-06 equations reasonably predicted the deflections of the slabs tested. However, ACI 440-1R-06 underestimated the deflections, overestimated the moment capacities at mid-span and over support sections, and reasonably predicted the load capacity of the continuous slabs tested. On the analytical side, a numerical technique consisting of sectional and longitudinal analyses has been developed to predict the moment-curvature relationship, moment capacity and load-deflection of FRP reinforced concrete members. The numerical technique has been validated against the experimental test results obtained from the current research and those reported in the literature. A parametric study using the numerical technique developed has also been conducted to examine the influence of FRP reinforcement ratio, concrete compressive strength and type of reinforcement on the performance of continuous FRP reinforced concrete slabs. Increasing the concrete compressive strength decreased the curvature of the reinforced section with FRP bars. Moreover, in the simple and continuous FRP reinforced concrete slabs, increasing the FRP reinforcement at the bottom layer fairly reduced and controlled deflections.
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Adhiambo, Oreje Joy Susan. "Assessment of prescribing patterns and availability of anti-malarial drugs to children under five years of age in a rural district in Kenya." University of Western Cape, 2013. http://hdl.handle.net/11394/3927.
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Magister Public Health - MPHAim: The aim of this study was to assess the prescribing practices and availability of antimalarial drugs to children under five years of age in primary health care facilities in Bondo district.
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Hamilton, William David. "Investigations into metal-ligand diatomics, the fine and hyperfine spectroscopy of cobalt fluoride, and insights into computational analysis of hyperfine interactions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0018/NQ54592.pdf.
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Wegorzewski, Anna Viktoria [Verfasser]. "Geochemical and mineralogical investigations of fine growth structures of ferromanganese nodules from the Clarion and Clipperton Zone, Pacific Ocean / Anna Viktoria Wegorzewski." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2015. http://d-nb.info/1068920793/34.
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Robin, Vincent. "Reconstruction of fire and forest history on several investigation sites in Germany, based on long and short-term investigations - Multiproxy approaches contributing to naturalness assessment on a local scale." Thesis, Aix-Marseille 3, 2011. http://www.theses.fr/2011AIX30057.
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Sur la base de constats globaux concernant l’importance d’appliquer des modes de gestion durable des zones forestières et le manque d’investigation concernant l’histoire passée des feux en Europe centrale, il a été entrepris de reconstruire l’histoire des événements de feux et de la dynamique forestière pour des sites d’étude en Allemagne. L’ensemble des données obtenues et analysées ont été utilisées pour l’évaluation du niveau de naturalité des sites étudiés, cette notion étant essentielle pour la mise en place d’une gestion durable, et/ou pour des projets de conservation et / ou de restauration des systèmes perturbés. Concernant les dynamiques des écosystèmes en Europe centrale, il a été souvent mis en évidence que l’homme joue un rôle essentiel depuis des millénaires. Par conséquent, l’approche historique des événements de feux et de la dynamique forestière à été réalisée sur de longues échelles temporelles. Neuf sites d’étude ont été sélectionnés incluant une large gamme de systèmes forestiers d’Europe centrale. Les sites d’études sont répartis dans deux zones générales d’étude : le nord de l’Allemagne (Schleswig-Holstein), qui comprend quatre sites d’étude, et le centre de l’Allemagne (le Harz), qui comprend cinq sites d’étude. Quatre disciplines ont été principalement utilisées. Pour définir l’état actuel des sites d’études ceux-ci ont été caractérisés, utilisant divers indicateurs dendrométriques concernant la structure et la composition des parcelles analysées. Pour obtenir des informations à propos de la dynamique forestière des peuplements forestiers en place des analyses dendroécologiques ont été utilisées. Pour analyser la dynamique forestière sur une longue échelle temporelle, à une échelle spatiale comparable, des analyses pédoanthracologiques ont été menées, combinées à des analyses de sols. De plus, des analyses anthracologiques de séquences de tourbes ont été réalisées, fournissant, combinées avec les données pedoanthracologiques, des enseignements à propos de l’histoire des incendies. L’état actuel et la dynamique forestière récente des sites étudiés indiquent divers niveaux de complexité des peuplements forestiers, correspondant souvent à divers niveaux postulés d’impact anthropique. Il a été obtenu huit chronologies moyennes, standardisées en haute et moyenne fréquences, âgées au maximum de 1744 et au minimum de 1923 ans. A partir de ces chronologies des changements dans les conditions de croissance de peuplements forestiers ont été mises en évidence. Basées sur un ensemble de 71 charbons de bois datés par radiocarbone, il a été mis en évidence, à l’échelle locale et globale, deux principales phases présentant plus d’événements de feux datés, une durant le Pléistocène supérieur/Holocène inférieur, une autre durant l’Holocène supérieur. Pour les deux phases identifiées des forçages climatique et anthropogénique ont été respectivement postulés comme déterminisme des occurrences de feux. Finalement, les différentes données collectées ont été utilisées de façon combinée pour reconstruire l’histoire des feux et des forêts des sites étudiés, afin de contribuer à l’évaluation de leur niveau de naturalitéConsidering two global observations in Central Europe of, firstly, the need for, and development of, sustainable and biological conservation practices for forest and/or woodland areas and, secondly, the lack of long-term fire history, an attempt has been made to reconstruct the fire and the forest history at several investigation sites in Germany. The overall data set gathered and analyzed has been used for on-site naturalness assessment. This latter notion is crucial for forest system conservation/restoration planning, considering the past human impact on forest dynamics. Also, in view of this past human impact on forest systems, which is well-documented for Central Europe, as occurring on a multi-millennium scale, an historical perspective perceptive that combined a long and short temporal scale of investigation was used.Nine investigation sites were selected, in order to include various and representative types of Central European forest. Therefore, the investigation sites were located in two main investigation areas. One is in Northern Germany (Schleswig-Holstein) and includes four investigation sites. The other is in Central Germany (Harz Mountains) and includes five investigation sites. Four main approaches were used. To assess the current state of the investigated site, forest stand characterization was undertaken (i.e. based on various forest attributes that concern stand structure and composition). Tree ring series were analyzed to provide insights about short-term forest tree population dynamics. Then, charcoal records from soil (combined with soil analysis) and peat sequences were qualitatively and quantitatively analyzed. These last two approaches also provide information about the past fire history. Forest current and short-term dynamics illustrated various levels of stand complexity, often corresponding to various levels of human impact that had been postulated. Eight mean site tree-ring chronologies, standardized in high and mid-frequency signal, spanning at a maximum of up to AD 1744 and at a minimum of up to AD 1923, were obtained. The insight, about the identification of events of growing changes and the correlated temporal and, if possible, spatial patterns, was discussed. Charcoal analysis provided a long-term insight about fire history. Based on 71 charcoal radiocarbon dates, it was shown on a macro-scale that there were two phases that had a greater frequency of fire - one during the transition from the late Pleistocene to the early Holocene, and one during the mid- and late Holocene. A strong human control during the most recent fire phase has been postulated. This is supported by on-site soil and peat charcoal record analysis, allowing one to point out the event of environmental changes (disturbances), at local scales. In the end, the on-site data from the various indicators were combined to assess the fire and forest history and the naturalness level of the investigated sites, based on past insights, thereby contributing to a better understanding of the present and helping to anticipate the future
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Hartig, Jens. "Numerical investigations on the uniaxial tensile behaviour of Textile Reinforced Concrete." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-66614.
Full textAbstract:
In the present work, the load-bearing behaviour of Textile Reinforced Concrete (TRC), which is a composite of a fine-grained concrete matrix and a reinforcement of high-performance fibres processed to textiles, exposed to uniaxial tensile loading was investigated based on numerical simulations. The investigations are focussed on reinforcement of multi-filament yarns of alkali-resistant glass. When embedded in concrete, these yarns are not entirely penetrated with cementitious matrix, which leads associated with the heterogeneity of the concrete and the yarns to a complex load-bearing and failure behaviour of the composite. The main objective of the work was the theoretical investigation of effects in the load-bearing behaviour of TRC, which cannot be explained solely by available experimental results. Therefore, a model was developed, which can describe the tensile behaviour of TRC in different experimental test setups with a unified approach. Neglecting effects resulting from Poisson’s effect, a one-dimensional model implemented within the framework of the Finite Element Method was established. Nevertheless, the model takes also transverse effects into account by a subdivision of the reinforcement yarns into so-called segments. The model incorporates two types of finite elements: bar and bond elements. In longitudinal direction, the bar elements are arranged in series to represent the load-bearing behaviour of matrix or reinforcement. In transverse direction these bar element chains are connected with bond elements. The model gains most of its complexity from non-linearities arising from the constitutive relations, e. g., limited tensile strength of concrete and reinforcement, tension softening of the concrete, waviness of the reinforcement and non-linear bond laws. Besides a deterministic description of the material behaviour, also a stochastic formulation based on a random field approach was introduced in the model. The model has a number of advantageous features, which are provided in this combination only in a few of the existing models concerning TRC. It provides stress distributions in the reinforcement and the concrete as well as properties of concrete crack development like crack spacing and crack widths, which are in some of the existing models input parameters and not a result of the simulations. Moreover, the successive failure of the reinforcement can be studied with the model. The model was applied to three types of tests, the filament pull-out test, the yarn pull-out test and tensile tests with multiple concrete cracking. The results of the simulations regarding the filament pull-out tests showed good correspondence with experimental data. Parametric studies were performed to investigate the influence of geometrical properties in these tests like embedding and free lengths of the filament as well as bond properties between filament and matrix. The presented results of simulations of yarn pull-out tests demonstrated the applicability of the model to this type of test. It has been shown that a relatively fine subdivision of the reinforcement is necessary to represent the successive failure of the reinforcement yarns appropriately. The presented results showed that the model can provide the distribution of failure positions in the reinforcement and the degradation development of yarns during loading. One of the main objectives of the work was to investigate effects concerning the tensile material behaviour of TRC, which could not be explained, hitherto, based solely on experimental results. Hence, a large number of parametric studies was performed concerning tensile tests with multiple concrete cracking, which reflect the tensile behaviour of TRC as occurring in practice. The results of the simulations showed that the model is able to reproduce the typical tripartite stress-strain response of TRC consisting of the uncracked state, the state of multiple matrix cracking and the post-cracking state as known from experimental investigations. The best agreement between simulated and experimental results was achieved considering scatter in the material properties of concrete as well as concrete tension softening and reinforcement wavinessDie vorliegende Arbeit beschäftigt sich mit Untersuchungen zum einaxialen Zugtragverhalten von Textilbeton. Textilbeton ist ein Verbundwerkstoff bestehend aus einer Matrix aus Feinbeton und einer Bewehrung aus Multifilamentgarnen aus Hochleistungsfasern, welche zu textilen Strukturen verarbeitet sind. Die Untersuchungen konzentrieren sich auf Bewehrungen aus alkali-resistentem Glas. Das Tragverhalten des Verbundwerkstoffs ist komplex, was aus der Heterogenität der Matrix und der Garne sowie der unvollständigen Durchdringung der Garne mit Matrix resultiert. Das Hauptziel der Arbeit ist die theoretische Untersuchung von Effekten und Mechanismen innerhalb des Lastabtragverhaltens von Textilbeton, welche nicht vollständig anhand verfügbarer experimenteller Ergebnisse erklärt werden können. Das entsprechende Modell zur Beschreibung des Zugtragverhaltens von Textilbeton soll verschiedene experimentelle Versuchstypen mit einem einheitlichen Modell abbilden können. Unter Vernachlässigung von Querdehneffekten wurde ein eindimensionales Modell entwickelt und im Rahmen der Finite-Elemente-Methode numerisch implementiert. Es werden jedoch auch Lastabtragmechanismen in Querrichtung durch eine Unterteilung der Bewehrungsgarne in sogenannte Segmente berücksichtigt. Das Modell enthält zwei Typen von finiten Elementen: Stabelemente und Verbundelemente. In Längsrichtung werden Stabelemente kettenförmig angeordnet, um das Tragverhalten von Matrix und Bewehrung abzubilden. In Querrichtung sind die Stabelementketten mit Verbundelementen gekoppelt. Das Modell erhält seine Komplexität hauptsächlich aus Nichtlinearitäten in der Materialbeschreibung, z.B. durch begrenzte Zugfestigkeiten von Matrix und Bewehrung, Zugentfestigung der Matrix, Welligkeit der Bewehrung und nichtlineare Verbundgesetze. Neben einer deterministischen Beschreibung des Materialverhaltens beinhaltet das Modell auch eine stochastische Beschreibung auf Grundlage eines Zufallsfeldansatzes. Mit dem Modell können Spannungsverteilungen im Verbundwerkstoff und Eigenschaften der Betonrissentwicklung, z.B. in Form von Rissbreiten und Rissabständen untersucht werden, was in dieser Kombination nur mit wenigen der existierenden Modelle für Textilbeton möglich ist. In vielen der vorhandenen Modelle sind diese Eigenschaften Eingangsgrößen für die Berechnungen und keine Ergebnisse. Darüber hinaus kann anhand des Modells auch das sukzessive Versagen der Bewehrungsgarne studiert werden. Das Modell wurde auf drei verschiedene Versuchstypen angewendet: den Filamentauszugversuch, den Garnauszugversuch und Dehnkörperversuche. Die Berechnungsergebnisse zu den Filamentauszugversuchen zeigten eine gute Übereinstimmung mit experimentellen Resultaten. Zudem wurden Parameterstudien durchgeführt, um Einflüsse aus Geometrieeigenschaften wie der eingebetteten und freien Filamentlänge sowie Materialeigenschaften wie dem Verbund zwischen Matrix und Filament zu untersuchen. Die Berechnungsergebnisse zum Garnauszugversuch demonstrierten die Anwendbarkeit des Modells auf diesen Versuchstyp. Es wurde gezeigt, dass für eine realitätsnahe Abbildung des Versagensverhaltens der Bewehrungsgarne eine relativ feine Auflösung der Bewehrung notwendig ist. Die Berechnungen lieferten die Verteilung von Versagenspositionen in der Bewehrung und die Entwicklung der Degradation der Garne im Belastungsverlauf. Ein Hauptziel der Arbeit war die Untersuchung von Effekten im Zugtragverhalten von Textilbeton, die bisher nicht durch experimentelle Untersuchungen erklärt werden konnten. Daher wurde eine Vielzahl von Parameterstudien zu Dehnkörpern mit mehrfacher Matrixrissbildung, welche das Zugtragverhalten von Textilbeton ähnlich praktischen Anwendungen abbilden, durchgeführt. Die Berechnungsergebnisse zeigten, dass der experimentell beobachtete dreigeteilte Verlauf der Spannungs-Dehnungs-Beziehung von Textilbeton bestehend aus dem ungerissenen Zustand, dem Zustand der Matrixrissbildung und dem Zustand der abgeschlossenen Rissbildung vom Modell wiedergegeben wird. Die beste Übereinstimmung zwischen berechneten und experimentellen Ergebnissen ergab sich unter Einbeziehung von Streuungen in den Materialeigenschaften der Matrix, der Zugentfestigung der Matrix und der Welligkeit der Bewehrung
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Blessenohl, Michael Andreas [Verfasser], and López-Urrutia José R. [Akademischer Betreuer] Crespo. "Fine-structure investigations in highly charged ions using spectroscopy in the vacuum ultraviolet regime / Michael Andreas Blessenohl ; Betreuer: José R. Crespo López-Urrutia." Heidelberg : Universitätsbibliothek Heidelberg, 2020. http://d-nb.info/1216249369/34.
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Kraatz, Lindsey M. "Acoustic and sedimentological investigations of seabed conditions and related bio-geological parameters in a tidally energetic, fine-grained environment: York River Estuary, Virginia." W&M ScholarWorks, 2013. https://scholarworks.wm.edu/etd/1539616722.
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The transport and fate of fine-grained sediments is a critical factor affecting the physical, chemical, and biological health of estuaries, coastal embayments, riverine, lacustrine, and continental shelf environments. A geophysical and sedimentological study of the York River as a part of the NSF Multi-disciplinary Benthic Exchange Dynamics (MUDBED) project was conducted to determine: 1) the primary drivers of sediment erodibility within a fine-grained system, 2) if these drivers can be accurately measured through sedimentological and acoustic information, and 3) the spatial and seasonal variability of erosion within the estuary. Previous studies indicate that increased erodibility within the York River Estuary is mainly due to recent ephemeral deposition, whereas lower erodibility is associated with eroded or biologically reworked conditions. By studying key physical and biological parameters in the York River estuary, we can more generally apply knowledge gained on relationships among sediment facies, seabed erodibility, and the recent history of deposition, erosion, consolidation, and biological reworking. Three different experiments were conducted to look at erosion, deposition, consolidation, and biological reworking in the Clay Bank region of the York River Estuary, each highlighting varying scales of temporal change. The first experimental approach utilized an Imagenex 881A rotary sonar for one- to three-month deployments to examine surficial changes of the seabed, from hourly to monthly timescales, and allow scientists to track movement of sediment in and out of the system using sonar imagery. Optimized parameters were determined for cohesive sediment environments and a real-time observing rotary sonar was created to analyze the seabed on an hourly basis. In the second experiment, cores were collected on a weekly basis to investigate relationships between sediment properties and erodibility during the post-freshet dissipation of the mid-estuary turbidity maximum as well as over the spring-neap cycle. Grain size, water content, abundance of resilient pellets, the occurrence of 7Be, and x-radiographs were analyzed and compared to the results of Gust microcosm erosion tests to further constrain the controls on erodibility. The third experimental approach utilized seven high-resolution bathymetric surveys conducted between September 2008 and August 2009 within a 3.75 km 2 region at Clay Bank. Seabed height was shown to vary both spatially and temporally in association with the spring freshet, likely related to the presence and migration of a local secondary turbidity maximum.
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Blessenohl, Michael A. [Verfasser], and López-Urrutia José R. [Akademischer Betreuer] Crespo. "Fine-structure investigations in highly charged ions using spectroscopy in the vacuum ultraviolet regime / Michael Andreas Blessenohl ; Betreuer: José R. Crespo López-Urrutia." Heidelberg : Universitätsbibliothek Heidelberg, 2020. http://d-nb.info/1216249369/34.
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Blessenohl, Michael A. [Verfasser], and López-Urrutia José Ramon [Akademischer Betreuer] Crespo. "Fine-structure investigations in highly charged ions using spectroscopy in the vacuum ultraviolet regime / Michael Andreas Blessenohl ; Betreuer: José R. Crespo López-Urrutia." Heidelberg : Universitätsbibliothek Heidelberg, 2020. http://d-nb.info/1216249369/34.
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Robin, Vincent [Verfasser]. "Reconstruction of fire and forest history on several investigation sites in Germany, based on long and short-term investigations - Multiproxy approaches contributing to naturalness assessment on a local scale / Vincent Robin." Kiel : Universitätsbibliothek Kiel, 2011. http://d-nb.info/1045968153/34.
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Du, Plessis Minette. "The validity and reliability of the General Child Assessment model as pre-forensic screening instrument for children between three and five years old." Thesis, North-West University, 2012. http://hdl.handle.net/10394/9013.
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The forensic assessment of young children is a difficult and often daunting task for professionals working in the field of child sexual abuse. A forensic assessment with pre-school children requires that the professional have knowledge of various aspects of the children themselves and the disclosure of abuse, and remain as neutral and objective as possible while conducting the assessment. Literature indicates that the knowledge of the child’s social, behavioural and developmental level is essential in order to conduct a developmental sensitive forensic interview. Although the term “pre-forensic screening” is relatively new in the field of forensics, Hewitt (1999) and Carnes (2006) refer to “pre-screening” and “developmental, behavioural and social assessment”, respectively.
The study examined the usefulness of the General Child Assessment Model as a pre-forensic screening technique specifically for children aged 3-5 years.
The researcher adopted a qualitative approach to explore the usefulness of the General Child Assessment Model as a pre-forensic screening instrument with professionals working in the clinical as well as forensic field.
Seven semi-structured interviews were conducted with professionals trained in the general child assessment model. The interviews focused on the professionals’ use of the model in general, the value they attached to the model, its usefulness as a pre-forensic screening instrument with children aged 3-5 years, strengths and limitations of the model as a pre-forensic screening instrument, and practical recommendations for using the model in the forensic context.
The data from the semi-structured interviews was analysed and divided into themes and subthemes, which were further described and linked with relevant literature .It became clear that the use of this assessment model had value in the therapeutic as well as forensic context.
The model was described as an important and valuable part of the forensic process as it provides a holistic view of the child in context. The strengths and limitations of the model as a pre-forensic screening instrument were also explored and the participants made practical recommendations to optimise the use of the model as a pre-forensic screening instrument. In addition, a case study was used to evaluate the model as a pre-forensic screening instrument.Thesis (MSW (Forensic Practice))--North-West University, Potchefstroom Campus, 2013.
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Masiak, Christian [Verfasser], Jörn Hendrich [Akademischer Betreuer] Block, Jörn Hendrich [Gutachter] Block, and José María [Gutachter] Millán. "Financing SMEs and Entrepreneurial Opportunities: Firm- and Regional-Level Investigations from Europe / Christian Masiak ; Gutachter: Jörn Hendrich Block, José María Millán ; Betreuer: Jörn Hendrich Block." Trier : Universität Trier, 2018. http://d-nb.info/1227038453/34.
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Schumann, Achim. "Untersuchungen zur Leistungsfähigkeit der Ionenmobilitätsspektrometrie als Detektionsverfahren für flüchtige Thermolyseprodukte bei der Entstehung von Bränden - Investigations about the Performance of Ion Mobility Spectrometry as a Detection method for volatile Thermolysis Products during Fire Development." Gerhard-Mercator-Universitaet Duisburg, 2001. http://www.ub.uni-duisburg.de/ETD-db/theses/available/duett-10252001-120413/.
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The present work describes the use of Ion Mobility Spectrometry (IMS) as a detection method for specific thermolysis products with respect to the early recognition of fires. By using additional analytic methods such as simultaneous differential thermal analysis/thermogravimetry (DTA/TG), gas chromatography/mass spectrometry (GC/MS) and Infrared spectrometry (IR) the specific thermolysis products depent on the temperature of the fire load were characterized and identified. While considering possible interference like e.g. varying atmospheric humidity the limits of detection and determination of the detectable gasses by IMS were determined.