Proefschrift Maastricht. / Met lit. opg. - Met samenvatting in het Engels.

Syfte: Syftet med den här studien var att se ackommodationens roll i inducerad hyperopi på stereoseende och visus både monokulärt och binokulärt på avstånd och nära. Metod: Urvalet bestod av 14 emmetroper med åldern 20-28 år med en medelålder på 24 år. Stereoseende och visus mättes upp på 6 m och 40 cm både monokulärt och binokulärt. Visus mättes med logMAR tavla och stereoseendet med Randot på 6 m med test chart 2000, Dutch organisation for Applied Scientific Research (TNO) stereotest (Lameris Ootech, Ede, Netherlands)  för stereoseende och en när logMAR tavla för 40 cm. Med inducering av minuslinserna -1D, -2D och -3D på alla tester. Resultat: Monokulär inducering på stereoseendet på avstånd gav signifikant skillnad  på alla styrkorna (p<0,05). Binokulär inducering på avstånd gav inte en signifikant skillnad på -1D (p>0,05) men signifikant skillnad på -2D och -3D (p<0,05). Monokulär inducering på nära gav en signifikant skillnad på alla styrkorna (p<0,05). Binokulär inducering på nära gav inte en signifikant skillnad på -1D och -2D (p>0,05) men en signifikant skillnad på -3D (p<0,05). Visus både avstånd och nära gav ingen signifikant skillnad på binokulärt eller monokulärt (p>0,05). Slutsats: Även om stereoseendet påverkas av både monokulär och binokulär inducering av minuslinser påverkas inte visus i denna studie. Studien visar även att monokulär inducering påverkar stereoseendet mer än vad binokulär inducering gör. / This study investigated the effect of both monocular and binocular induced visual stress with minus lenses, to see the difference of effect on visual acuity and stereopsis.   The study had 14 emmetropes with mean age of 24. Stereopsis and visual acuity was measured on both 6 m and 40 cm, using logMAR visual chart for visual acuity and Randot test for stereopsis on 6 m with test chart 2000, TNO test for stereopsis and near logMAR chart for visual acuity at 40 cm. On all the test there was induced visual stress using minus lenses of power -1D, -2D and -3D on the dominant eye for monocular and for binocular.   The monocular blur on stereopsis for distance was a significant difference on all lenses (p<0.05). Binocular blur on distance did not give a significant difference regarding -1D (p>0.05) but gave a significant difference on both -2D and -3D (p<0.05). Monocular blur on near gave a significant difference on all lenses (p<0.05). Binocular blur on near did not give a significant difference on -1D and -2D (p>0,05) but on -3D there was a significant difference (p<0.05). Visual acuity gave on both distance and near no significant difference in any of the tests (p>0.05).   The study shows that even tough stereopsis was affected on both monocular and binocular induced visual stress there was no effect on visual acuity. It also shows that monocular induced stress affects stereopsis more than that of binocular induced stress.

Following some incidents in high-rise buildings, such as Ronan Point London 1968, in which collapse of a limited number of structural elements progressed to a failure disproportionate to the initial cause, consideration of robustness was introduced in British Standard. The main method of preventing progressive collapse for providing robustness to steel framed buildings with precast concrete floor slabs focuses on the allowable tying forces that the reinforcement in between the slabs and in hollowcores should carry. However there are uncertainties about the basis of the practical rules associated with this method. This thesis presents the results of numerical and analytical studies of tie connection behaviour between precast concrete floor slabs (PCFS). It is shown that under current design regulations the tie connection is not able to resist the accidental load limit applied on the damaged floor slabs. By establishing the capability of a finite element model to depict and predict the behaviour of concrete members in situations such as arching and catenary action against several experimental tests, an extensive set of parametric studies was conducted in order to identify the effective parameters in enhancing the resistance of the tie connection between PCFSs. These parameters include: tie bar diameter, position, length, yield stress and ultimate strain; the slab’s height, length; and the compressive strength of the grouting concrete in between the slabs that encases the tie bar. Recommendations are made based on the findings of this parametric study in order to increase the resistance of the tie connection. Based on the identified effective parameters in the parametric study a predictive analytical relationship is derived which is capable of determining the maximum vertical displacement and load that the tie connection is able to undergo. This relationship can be used to enable the connection to capture the accidental limit load on a damaged slab. The identified parameters are examined in a three dimensional finite element model to assess their effect when columns of the structure are lost in different locations such as an edge, corner or internal column. Based on the findings of this study methods for improving the connections performance are presented. Also the effect of alternative transverse tying method is evaluated and it is concluded that although this kind of tie increases the load carrying capacity of the connection, its effect on the catenary action is not significant.

Syfte: Syftet med denna studie är att undersöka om stereoseendet på nära håll påverkas genom att skapa en vertikal imbalans inducerad av 1 prismadioptri och således om det kan ge information som kan ligga till grund för glasval vid exempelvis anisometropi i vertikalled. Metod: 30 deltagare mellan 20-31 år, med medelålder 22,9 + 2,12, som uppfyllde inklusionskriterierna undersöktes. Subjektiv refraktion utfördes och en korrektion togs fram för deltagarna. Därefter undersöktes stereoseendet med TNO-test, först med 1 prd inducerad framför det dominanta ögat, därefter med 1 prd inducerad framför det icke-dominanta ögat, och sist med endast full korrektion. Därefter sammanställdes och analyserades resultatet. Resultat: Det hittades inget signifikant förhållande mellan 1 prd inducerad i vertikalled och stereoseende på nära håll, oavsett framför vilket öga vertikalprisma placerades (p>0,05). När två outliers togs bort blev medianen för 1 prd framför dominant öga 90”, med 1 prd framför det icke-dominanta ögat 60” och med full korrektion 60”. Medianvärden och medelrankning visar en trend där stereopsis försämras med 1 prd inducerad i vertikalled, jämfört med full korrektion och störst försämring gavs med 1 prd inducerat framför det dominanta ögat. Slutsats: Studien visar att stereopsis på nära håll inte påverkas av att inducera 1 prd i vertikalled. Däremot kan studien påvisa en trend där stereoseendet påverkas negativt oavsett om vertikalprisma induceras framför det dominanta ögat eller icke-dominanta ögat. Störst försämring på stereopsis gavs när vertikalprisma placerades framför det dominanta ögat. / Purpose: The aim of this study was to investigate whether near-stereopsis is affected by creating a vertical imbalance induced by 1 prism dioptre and whether it can provide information considering glass selection, for example in case of anisometropia in the vertical direction. Method: 30 participants between ages of 20-31, with mean age 22,9 + 2,12, who met the inclusion criteria were examined. Subjective refraction was performed and a correction was produced for the participants. Stereovision was examined with TNO test, first with 1 prd induced in front of the dominant eye, then with 1 prd induced in front of the non-dominant eye, and lastly with only full correction. The results were compiled and analyzed. Result: No significant relationship was found between 1 prd induced in the vertical direction and near stereo vision, regardless of which eye the vertical prism was placed in front of (p>0,05). When two outliers were removed, the median stereopsis for 1 prd in front of the dominant eye was 90”, with 1 prd in front of the non-dominant eye 60” and with full correction 60”. Median values and mean ranking show a trend where stereopsis worsens with 1 prd induced in the vertical direction, compared to full correction, and the greatest deterioration was given with 1 prd induced in front of the dominant eye. Conclusion: The study shows that stereopsis at near is not statistically significantly affected by inducing 1 prd in the vertical direction. However, this study can demonstrate a trend where stereopsis is negatively affected regardless of whether vertical prism is induced in front of the dominant eye or the non-dominant eye. The greatest deterioration in stereopsis occurred when the vertical prism was placed in front of the dominant eye.

Masters Research - Master of Philospohy (MPhil) / It has been shown that masonry material properties, in particular, unit flexural bond strength (ft), vary significantly throughout masonry structures, despite the fact that often only one type of brick and mortar are used. Unit flexural bond strength was previously identified as one of the most important material parameters contributing to the strength of clay brick unreinforced masonry (URM) walls in flexure. It was the objectives of this research, in the context of clay brick URM walls subject to vertical bending, to examine how unit flexural bond strength varied spatially in a clay brick URM wall, determine a best fit probability distribution function which can describe expected variability in unit flexural bond strength and determine how this variability and other factors affect wall behaviour and failure load using 3D non-linear finite element analysis (FEA). It was hoped that modelling a full sized clay brick URM wall subject to vertical bending using a 3D non-linear FEA model would more accurately predict wall failure load (compared to current analytical methods) and allow the examination of crack pattern development as the wall progresses to failure upon being laterally loaded. The first part of the research project was to conduct an experimental program to examine unit-to-unit spatial strength correlation within six full sized clay brick URM walls and to characterise a unit flexural bond strength probability distribution. It was observed that although weak correlation in unit flexural bond strength exists in some courses and between courses, these locations were difficult to predict and didn����t follow any particular pattern relating to for example, mortar batch. Therefore, although somewhat counter-intuitive, the results indicate that statistically significant correlation between adjacent unit flexural bond strengths is not likely to be observed. It was also observed that clay brick wall unit flexural bond strengths obtained for all of the walls tested best fit a truncated Normal probability distribution. Strength of the brick/mortar interface appeared to be governed by factors relating to workmanship (and therefore mortar quality and moisture content), weather (which can affect material characteristics like brick suction rate) and inherent material variability. It would appear that brick suction rate can significantly affect the overall strength of a URM wall. v Stochastic analysis was conducted for walls with and without uncorrelated spatial variability in unit flexural bond strength and associated tensile fracture energy (GfI ). It was found that the TNO DIANA 9.2 FEA package could be used to implement spatial variability of various material parameters and reasonably accurately model failure of clay brick URM walls in vertical bending. From the non-linear FEA model development stage, it was observed that because the brick/mortar bond has significantly more strength capacity in compression, it appears that the lateral load resistance of the wall comes from a combination of the ability of the brick/mortar bond to tensile soften while providing significant compressive resistance at the compressive edge. It was found for a spatial stochastic analysis with spatial variability in bond strength (referred to from now on as a spatial stochastic analysis), with COVs of 0.1, 0.3 and 0.5, that COV of wall failure loads were relatively small, being 0.02, 0.04 and 0.06 respectively. For the non-spatially varying stochastic analysis with fully correlated bond strength (now referred to as non-spatial stochastic analysis), with COVs of 0.1, 0.3 and 0.5, COV of wall failure loads were 0.07, 0.20 and 0.32 respectively. For the spatial stochastic analysis, it was found that with a bond strength COV increase from 0.1 to 0.5 the mean wall failure load dropped from 2.25 kPa to 2.0 kPa (an 11% reduction). Despite the relatively small drop in magnitude of the mean wall failure load with increase in bond strength COV, the mean wall failure loads were statistically different to one another. For the non-spatial stochastic analysis, mean failure load stayed relatively constant at 2.24-2.25 kPa. These results could be explained by examining the 3D wall progression to failure. For walls with spatial variability in bond strength, it is expected that wall failure load COVs would be smaller because those walls would consistently be composed of smaller valued bond strengths which would consistently contribute to weakness in the wall. For the non-spatial wall simulations, this effect would not occur as failure load is determined by one uniform weak or strong bond strength. It was proposed that failure of a clay brick URM wall is not governed by one course only cracking, but rather, instability in the wall is governed by several courses in the vicinity of locations of large bending moment. It was shown that various current stochastic approximations which employ a unit failure hypotheses in combination with a linear/elastic approximation for first cracking load all underestimated wall capacity significantly. The reason for this is suggested as being vi because all hypotheses only assume failure is governed by one course and linear/elastic theory only considers the tensile capacity of a joint and neglects strength capacity available as a result of joint tension softening and the resistance to failure provided by compressive strength on the compression side of the wall. The hypotheses also don’t take into consideration factors which affect overall wall bond strength mean which result from influences such as workmanship, weather and material variability factors, such as (for example), variation in brick suction rate due to weather conditions which can make the overall strength of the wall stronger or weaker. Based upon a comparison in wall failure load COV for the spatial and non-spatial stochastic wall analysis results, a more realistic approach for future modelling attempts of spatial variability in masonry material properties is suggested. This would address the issue of external factors such as workmanship and weather on the overall strength of the wall, as well as the inherent bond strength variability due to material variability. For walls with spatial variability in bond strength, upon examination of numerous wall simulation results, several crack patterns were witnessed and are discussed.

The research work presented in this thesis reports for the first time the fabrication of Titanium Niobium complex oxide (TiNb2O7 (TNO)) thin films by employing pulsed laser deposition and their use as the anode material in Li-ion micro batteries. Chapter 1 provides a brief introduction to complex metal oxides as multifunctional materials. In the first section of this chapter, a brief introduction is given about the history of TNO complex oxide material. The complex structure and properties of TNO oxide are also discussed briefly. In the second section, the importance and need of thin film batteries in emerging applications is discussed. Finally, the specific objectives of the current research are outlined in the last section. Chapter 2 gives the details about various experimental methods and characterization tools used in this research. The first part gives a brief overview about the principles and the use of different experimental methods involved in the growth of TNO thin films using pulsed laser deposition. Details, including the laboratory setup designed for PLD growth, also described briefly. In the second part, the different state-of-the-art characterization tools used in this research are described in terms of their principles and their applications such as measuring structural, morphological, chemical and electrochemical properties. Chapter 3 describes the synthesis and characterization of TNO bulk targets prepared via solid state reaction. In the first part, the detailed descriptions of experimental conditions are given. In the second part, the study of as-prepared TNO targets by various characterization tools such as XRD, Raman, SEM and XPS for understanding its structure, morphology and chemical properties are discussed briefly. The emphasis is made on the preparation of a quality target by careful observations. Chapter 4 mainly describes the comprehensive studies carried out on the fabrication and characterization of TNO thin films using PLD. In the first part, the preliminary experimental conditions for the growth of TNO thin films on Pt (200)/TiO2/SiO2/ Si (100) substrates are explained briefly. The importance of primary understanding about target-laser interaction through the structural, morphology changes observed by various characterization tools is discussed. In the latter part of the chapter, the effects of systematic variation of deposition parameters on the properties of the grown TNO thin films are described extensively. Various advanced characterization tools are used to study the changes in as-grown TNO thin films in terms of their structural, morphological and chemical changes by various advanced characterization tools. Chapter 5 is an account of the state-of-the-art characterization tools that are used on the as-grown TNO thin films for determining structural, compositional and elemental information with nanometer spatial resolution. In the first part, the effects of various processing conditions used during FIB are discussed briefly, along with observed results. An attempt has been made to solve the experimental difficulties during FIB for cross sectional sample preparation for HRTEM analysis. Later, the imaging, diffraction and spectroscopic studies carried out on TNO thin films using HRTEM, STEM HAADF, and EDXS elemental mapping are discussed in detail. Finally, obtained results are correlated to the experimental conditions during PLD growth. Chapter 6 focuses on the usage of as-grown TNO thin films as a new anode material in rechargeable Li-ion micro batteries. The various experimental details, battery cell fabrication, etc are described in the first part of the chapter. Then the comprehensive studies are carried out for demonstrating TNO thin films as anode material in micro batteries. Besides this, the basic cyclic voltammogram and charge-discharge tests carried out on a TNO electrode are discussed in detail. The structural, morphological studies are done before and after the electrochemical cell reaction to understand the crystal stability of TNO as an anode electrode. The effects of important experimental parameters on their electrochemical properties are also described briefly. Finally, the observed results are compared with existing literature. Chapter 7 summarizes the present research reported in this thesis and discusses the future research that could give insight into the understanding and optimization of TNO thin films for better usage in battery applications.

The main purpose of this project is to investigate different tool steels in terms of their ability to withstand material transfer buildup, so-called galling, occurring in SMF (sheet metal forming) operations. The ability to withstand galling is vital to optimize cost-effectiveness and increase the work tool’s effective operational time. This investigation studies four different tool steels, including a TiN-coating, with the intention of evaluating the microstructures, chemical composition and hardness effect on galling resistance in dry conditions using a slider-on-flatsurface (SOFS) tribo-tester which measures the coefficient of friction during sliding. An OP (optical profilometer) was used to measure the size and geometry of lump growth on the tool and damage on the work sheet. A scanning electron microscope (SEM) was used to identify the interacting tribological mechanisms exhibited at different stages during the slide. The SEM figures confirmed three different types of characteristic patterns exhibited in the tracks after tribo- testing which were categorized as mild adhesive, abrasive and severe adhesive damage. A SEM figure that illustrates a ragged contact surface and an obvious change in the sheet materials plastic behavior is in this report regarded as a sign of severe adhesive contact, the characteristics could possibly be explained by local high temperature and high pressure followed by a sudden pressure drop and creation of hardened welds or solders between the two surfaces which increase the frictional input needed for further advancement. Friction coefficients observed in the initial 100% mild adhesive stage were, μ=0,22-0,26 succeeded by abrasive SEM characteristics often in association with mild adhesive contact and friction values between μ=0,25-0,4 which where sometimes followed by severe adhesive SEM characteristics in 100% of the contact zone with friction values between μ=0,34- 0,9 respectively. The tool material that performed best according to the friction detection criteria was Sv21 closely followed by Sleipner (TiN coated) and Va40 (HRC 63.3). Unfortunately was the friction criteria, a significant raise in friction for defining a sliding length to galling, not adequate for dry conditions due to immediate material transfer succeeded by cyclic changes between partial or 100% abrasive+mild adhesive and severe adhesive contact. The mechanism that change abrasive wear in association with mild adhesive contact, (moderate friction input), to sever adhesive wear, (higher friction input), is dependent on lump shape (lump geometry) and can appear at comparably low speeds 0,04-0,08 [m/s] and low friction energy input (μ=0,34), the magnitude of the change in friction is therefore not always significant and hardly detectable on the friction graph. This was quite unexpected but could be explained by concentration of friction energy rater than the absolute amount. The problem with using friction graphs for galling evaluation was increased even further when a very small lump size and low corresponding rate of material transfer to the tool surface caused a sustainable high raise in friction (μ≈0,3→0,6) on a TiN-coated tool steel called Sleipner. A hardly detectable or similar friction raise for Sv21 and Va40 showed much larger corresponding lump size and rate of material transfer. This means that friction graphs demonstrate a clear problem with quantifying lump size [m3] and rate of  material transfer [m3/s]. Another phenomenon called stick slip behavior, material transfer and lump growth followed by a sudden decrease in lump size and transfer of material back to the work sheet, is also not possible to detect on a friction graph. Because a drop in friction can easily be a change in contact temperature and lump attack angle due to a growing lump and not a decreasing lump.   The conclusion, a friction graph is not suited for galling evaluation and ranking in dry SOFS conditions. A ranking should primarily be based on dimensional OP measurements of the cross section of formed tracks and scratches or preferably by repeated OP measurements of the tool surface during a single test, the last revel the exact lump growth history and true lump growth even in the sliding direction. / civilingenjörsexamen

<p>The main purpose of this project is to investigate different tool steels in terms of their ability to withstand material transfer buildup, so-called galling, occurring in SMF (sheet metal forming) operations. The ability to withstand galling is vital to optimize cost-effectiveness and increase the work tool’s effective operational time. This investigation studies four different tool steels, including a TiN-coating, with the intention of evaluating the microstructures, chemical composition and hardness effect on galling resistance in dry conditions using a slider-on-flatsurface (SOFS) tribo-tester which measures the coefficient of friction during sliding.</p><p>An OP (optical profilometer) was used to measure the size and geometry of lump growth on the tool and damage on the work sheet. A scanning electron microscope (SEM) was used to identify the interacting tribological mechanisms exhibited at different stages during the slide. The SEM figures confirmed three different types of characteristic patterns exhibited in the tracks after tribo- testing which were categorized as mild adhesive, abrasive and severe adhesive damage.</p><p>A SEM figure that illustrates a ragged contact surface and an obvious change in the sheet materials plastic behavior is in this report regarded as a sign of severe adhesive contact, the characteristics could possibly be explained by local high temperature and high pressure followed by a sudden pressure drop and creation of hardened welds or solders between the two surfaces which increase the frictional input needed for further advancement. Friction coefficients observed in the initial 100% mild adhesive stage were, μ=0,22-0,26 succeeded by abrasive SEM characteristics often in association with mild adhesive contact and friction values between μ=0,25-0,4 which where sometimes followed by severe adhesive SEM characteristics in 100% of the contact zone with friction values between μ=0,34- 0,9 respectively. The tool material that performed best according to the friction detection criteria was Sv21 closely followed by Sleipner (TiN coated) and Va40 (HRC 63.3). Unfortunately was the friction criteria, a significant raise in friction for defining a sliding length to galling, not adequate for dry conditions due to immediate material transfer succeeded by cyclic changes between partial or 100% abrasive+mild adhesive and severe adhesive contact. The mechanism that change abrasive wear in association with mild adhesive contact, (moderate friction input), to sever adhesive wear, (higher friction input), is dependent on lump shape (lump geometry) and can appear at comparably low speeds 0,04-0,08 [m/s] and low friction energy input (μ=0,34), the magnitude of the change in friction is therefore not always significant and hardly detectable on the friction graph. This was quite unexpected but could be explained by concentration of friction energy rater than the absolute amount. The problem with using friction graphs for galling evaluation was increased even further when a very small lump size and low corresponding rate of material transfer to the tool surface caused a sustainable high raise in friction (μ≈0,3→0,6) on a TiN-coated tool steel called Sleipner.</p><p>A hardly detectable or similar friction raise for Sv21 and Va40 showed much larger corresponding lump size and rate of material transfer. This means that friction graphs demonstrate a clear problem with quantifying lump size [m3] and rate of  material transfer [m3/s]. Another phenomenon called stick slip behavior, material transfer and lump growth followed by a sudden decrease in lump size and transfer of material back to the work sheet, is also not possible to detect on a friction graph. Because a drop in friction can easily be a change in contact temperature and lump attack angle due to a growing lump and not a decreasing lump.</p><p> </p><p>The conclusion, a friction graph is not suited for galling evaluation and ranking in dry SOFS conditions. A ranking should primarily be based on dimensional OP measurements of the cross section of formed tracks and scratches or preferably by repeated OP measurements of the tool surface during a single test, the last revel the exact lump growth history and true lump growth even in the sliding direction.</p><p> </p> / civilingenjörsexamen