A model has been developed using the general-purpose Navier-Stokes solver CFX4 to simulate Atmospheric Boundary Layer flow over complex terrain. This model has been validated against the measured data from the Askervein Hill experiment, and has been shown to perform well. The CFD model is also compared to the WAsP linear model of wind flow over topography, and a significant improvement is noted for flow over complex topography. Boundary conditions, gridding issues and sensitivity to other solver parameters have all been investigated. An advanced roughness model has been developed to simulate flow over forest canopies, using a resistive body force within the canopy volume. The model is validated against measured data for simple 2D cases, and for a complex 3D case over real topography. The model is shown to give a more physically realistic profile for the wind speed in and just above forest canopies than the standard roughness length model used in most CFD simulations. An automated methodology for setting up CFD simulations using the models described has been developed. A custom pre-processing package to implement this has been written, to enable the use of the CFD methodology in a commercial environment.

In 1960's Gordon Moore predicted that the increase in the number of components in integrated circuits would exponentially decrease the relative manufacturing cost per component with time. The semiconductor industry has managed to keep that pace for nearly 45 years and one of the main contributors to this phenomenal improvement in technology is advancement in the field of lithography. However, the technical challenges ahead are severe and the future roadmap laid by the International Technology Roadmap for Semiconductors looks mostly red (i.e. no solution has been found to specific problem). There are efforts in the industry and academia directed toward development of newer, alternative lithographic techniques. Step and Flash Imprint Lithography (SFIL) has recently emerged as one of the most promising alternatives, capable of producing high resolution patterns. While it has numerous advantages over conventional photolithography, several engineering challenges must be overcome to eliminate defects due to the nature of contact imprinting if SFIL is to be a viable alternative technique for manufacturing tomorrow's integrated circuits. The complete filling of template features is vital in order for the SFIL imprint process to truly replicate the template features. The feature filling phenomena for SFIL was analyzed by studying diffusion of a gas, entrapped in the features, through liquid imprint resist. A simulation of the dynamics of feature filling for different pattern configurations and process conditions during the SFIL imprint step is presented. Simulations show that initial filling is pressure-controlled and very rapid; while the rest of the feature filling is diffusion-controlled, but fast enough that diffusion of entrapped gas is not a cause for non-filling of features. A theory describing pinning of an air-liquid interface at the feature edge of a template during the SFIL imprint step was developed, which shows that pinning is the main cause of non-filling of features. Pinning occurs when the pressure at the air-liquid interface reaches the pressure of the bulk liquid. At this condition, there is no pressure gradient or driving force to move the liquid and fill the feature. The effect of several parameters on pinning was examined. A SFIL process window was established and template modifications are proposed that minimize the pinning at the feature edge while still preventing any extrusion along the mesa (pattern containing area on the template) edge. Part of semiconductor manufacturing community believes that optical lithography has the capability to drive this industry further and is committed to the continuous improvement of current optical patterning approaches. Some of the major challenges with shrinking critical dimensions (CDs) in coming years are the control of line-edge roughness (LER) and other related defects. The current CDs are such that the presence or absence of even a single polymer molecule can have a considerable impact on LER. Therefore molecular level understanding of each step in the patterning process is required. Computer simulations are a cost-effective approach to explore the huge process space. Mesoscale modeling is one promising approach to simulations because it captures the stochastic phenomena at a molecular level within reasonable computational time. The modeling and simulation of the post-exposure bake (PEB) and the photoresist dissolution steps are presented. The new simulator enables efficient exploration of the statistical excursions that lead to LER and the formation of insoluble residues during the dissolution process. The relative contributions of the PEB and the dissolution step to the LER have also been examined in the low/high frequency domain. The simulations were also used to assess the commonly proposed measures to reduce LER. The goal of the work was to achieve quantification of the effect of changes in resist composition, developer concentration, and process variables on LER and the associated defectivity. / text

Open and connected fractures, where present, control fluid flow and dominate solute transport. Flow through fractures has major implications for water resource management, underground waste repositories, contaminant remediation, and hydrocarbon exploitation. Complex fracture morphology makes it difficult to quantify and predict flow and transport accurately. The difficulty in usefully describing the complex morphology of a real fracture from a small 3-D volume or 2-D profile sample remains unresolved. Furthermore, even when complex fracture morphology is measured across three-dimensions, accurate prediction of discharge remains difficult. High resolution x-ray computed tomography (HXRCT) data collected for over 20 rock surfaces and fractures provide a useful dataset to study fracture morphology across scales of several orders of magnitude. Samples include fractured rock of varying lithology, including sandstone, volcanic tuffs and crystalline igneous and metamorphic rocks. Results suggest that the influence of grain size on surface roughness is not readily apparent due to other competing variables such as mechanics, skins and coatings, and weathering and erosion. Flow tests of HXRCT-scanned fractures provide real discharge data allowing the hydraulic aperture to be directly measured. Scale-invariant descriptions of surface roughness can produce constrained estimates of aperture variability and possibly yield better predictions of fluid flow through fractures. Often, a distinction is not made between the apparent and true fracture apertures for rough fractures measured on a 2-D topographic grid. I compare a variety of local aperture measurements, including the apparent aperture, two-dimensional circular tangential aperture, and three-dimensional spherical tangential aperture. The mechanical aperture, the arithmetic mean of the apparent local aperture, is always the largest aperture. The other aperture metrics vary in their ranking, but remain similar. Results suggest that it may not be necessary to differentiate between the apparent and true apertures. Rock fracture aperture is the predominant control on permeability, and surface roughness controls fracture aperture. A variety of surface roughness characterizations using statistical and fractal methods are compared. A combination of the root-mean-square roughness and the surface-to-footprint ratio are found to be the most useful descriptors of rock fracture roughness. Mated fracture surfaces are observed to have nearly identical characterizations of fracture surface roughness, suggesting that rock fractures can be sampled by using only one surface, resulting in a significantly easier sampling requirement. For mated fractures that have at least one point in contact, a maximum potential aperture can be constrained by reflecting and translating a single surface. The maximized aperture has a nearly perfect correlation with the RMS roughness of the surface. These results may allow better predictions of fracture permeability thereby providing a better understanding of subsurface fracture flow for applications to contaminant remediation and water and hydrocarbon management. Further research must address upscaling fracture morphology from hand samples to outcrops and characterizing entire fracture networks from samples of single fractures. / text

This research experimentally shows the effect of sediment roughness characteristics on the acoustic reflection coefficient. This information is useful when trying to classify various types of sediment over an area. This research was conducted in an indoor laboratory tank at Applied Research Laboratories (ARL) at the University of Texas at Austin. A single beam echo-sounder (SBES) system was developed to project and receive a wideband (3 kHz to 30 kHz) acoustic pulse. A method was developed using the system transfer function to create a custom pulse that would minimize the dynamic range over the wide frequency band. A matched filtering and data processing algorithm was developed to analyze data over the full frequency bandwidth and over smaller frequency bands. Analysis over the smaller frequency bands showed the effect of the roughness on the reflection coefficient with respect to frequency. It was found that the reflection coefficient is significantly lower at the higher frequencies (above 20 kHz) than at the lower frequenices [sic] due to off specular scattering. It was also found that the variability of the reflection coefficient was significantly higher for the rough sediment than for the smooth sediment. / text

Interface roughness can have a significant effect on the scattering of sound energy, and therefore an understanding of the effects of roughness is essential to making predictions of sound propagation and transmission underwater. Many models of roughness scattering currently in use are two dimensional (2D) in nature; three dimensional (3D) modeling requires significantly more time and computational resources. In this work, an effort is made to quantify the effects of 3D scattering in order to assess whether or under what conditions 3D modeling is necessary. To that end, an exact 3D roughness scattering model is developed based on a commercially available finite element package. The finite element results are compared with two approximate scattering models (the Kirchhoff approximation and first order perturbation theory) to establish the validity and regimes of applicability of each. The rough surfaces are realizations generated from power spectra measured from the sea floor. However, the surfaces are assumed to be pressure release (as on an air-water interface). Such a formulation is nonphysical, but allows the assessment of the validity of the various modeling techniques which is the focus of this work. The comparison between the models is made by calculating the ensemble average of the scattering from realizations of randomly rough surfaces. It is shown that a combination of the Kirchhoff approximation and perturbation theory models recovers the 3D finite element solution. / text

Self-compacting concrete has soon been around for a decade. Recently the prefabrication industry has started to use this fairly new concrete type in larger scales, mainly because of its distinctive properties.  There are still certain areas that need to be thoroughly examined, such as bond capacity. There have been very few studies regarding shear capacity due to the fact that the procedure is complicated. This report will highlight a method to examine the shear capacity of different surfaces that have been prewetted as well as non-prewetted surfaces. The surface areas follow BBK 04’s and Eurocode 2’s demand for surface roughness.  A smooth surface will be completed in order to confirm if the different shapes influence the bond strength by shear stress or not.                        The purpose of this essay is to measure the bond strength within the shear capacity as well as examine the impact it has on surface roughness and treatment for shear bond. The method used to identify the shear capacity is called L-shaped Push-Off Test. The dimension of the object was selected with the help of a previous research paper. The Sand-Patch method is predominantly used to measure the surface roughness.  The results showed no difference between the demands of surfaces of BBK04 and Eurocode 2 considering the shear capacity. However the non-prewetted surface was measured with the highest shear capacity value. Apart from the shear strength, deformation was measured in both vertical and horizontal direction and it was clearly shown that the vertical deformation was measured to be ten times higher than the horizontal deformation.  There was no difference between the BBK 04 and Eurocode 2 considering the vertical deformation. However the difference occurred on the horizontal direction between BBK 04 and Eurocode 2 where the specimens of Eurocode 2 received three times higher deformation compared to BBK 04. The conclusion can be drawn that the surface roughness of BBK 04 would be more suitable than eurocode2 considering deformation.      The overall result was that the surface treatment with the demands of BBK 04 and Eurocode 2 showed minor difference after being measured with the Push-Off Test method. This has been confirmed with the estimated shear capacity (1.2 MPa). The results revealed that the treatment of surface could be made in either way, brush or rake. As a conclusion the assessment of the shear strength showed that Eurocode 2's demand is too strict comparing demands of BBK 04. / Att bestämma vidhäftningen mellan prefabricerade element och senare pågjutning på arbetsplats är viktigt. Självkompakterande betong är en betongtyp som flera prefabricerade företag börjat använda på grund av dess goda egenskaper. Dock finns några oklarheter som behöver utredas vidare, exempelvis vidhäftningskapaciteten vid pågjutning. I och med införandet av Eurokod blev det större krav på skrovligheten jämfört med tidigare krav i BBK 04. För självkompakterande betong kan det vara svårt att få till en skrovlighet enligt både BBK och speciellt Eurokod. För undersökning av vidhäftningskapacitet kopplat till draghållfastheten finns beprövade metoder som följer svensk standard. Dock finns ingen svensk standard för vidhäftningsprov för skjuvhållfastheten, bland annat på grund av att för få undersökningar har utförts och att provnings-utförandet är mer komplext. Syftet med denna undersökning är att jämföra olika mätmetoder för att mäta skjuvspänningar för vidhäftningen mellan prefabelement och pågjutningsbetong samt att också undersöka olika metoder för att mäta ytjämnheten. Målet är att identifiera skjuvkapaciteten i vidhäftningen samt få reda på vilken påverkan ytjämnhet och ytbehandling har för vidhäftningen. Detta för att utvärdera om Eurokod 2:s hårdare krav på skrovlig yta är nödvändig jämfört med BBK 04 med avseende på skjuvning. Ytor som ska jämföras är avdragen yta och yta som uppfyller BBK 04:s samt Eurokod 2:s  krav på skrovlig yta. Mätmetoder för skrovlighet ska undersökas för att senare utvärderas och användas i undersökningen.  Förutom dessa ytor som normalt förvattnas ska även en yta som följer BBK 04:s krav på skrovlig yta utan förvattning undersökas om förvattning har någon positiv inverkan på vidhäftningen. Den mätmetod som valdes för att identifiera skjuvhållfastheten var L-formad Push-Off-metod, vilket dimensionerades med hjälp av en referensundersökning. Provkroppen tillverkades i Strängbetongs fabrik i Kungsör och innan pågjutningen utfördes mättes ytjämnheten på vidhäftningsytan med hjälp av Sand-Patch-metoden. För att bekräfta validiteten hos Sand-Patch-metoden användes också en annan mätmetod, så kallad Profilmall. Efter att ytorna var uppmätta och pågjutningen hårdnat skickades provkropparna till CBI Betonginstitut för skjuvhållfasthetsprovning samt tryckprovning. Resultaten från undersökningen visade att inga större skillnader i skjuvhållfasthet mättes mellan Eurokods och BBKs krav på ytjämnhet, men det visade sig att den obehandlade ytan klarade av högst skjuvhållfasthet. Alla värden var betydligt högre än vad både Eurokod och BBK 04 anger för hållfasthetsklassen C45/55. Under provningstillfället upptäcktes sprickbildning vid 85 kN både i den befintliga betongen samt vid pågjutningen på de tunnaste delarna, för samtliga provförsök. Utöver skjuvhållfastheten mättes även deformationer såväl vertikalt som horisontellt och det framgick tydligt i resultatet att vertikala deformationerna var mer än tio gånger större än de horisontella. Ingen skillnad mellan BBK och Eurokod kunde tydas vid vertikala deformationer, dock vid horisontella deformationer mättes Eurokod till tre gånger större horisontella deformationer jämfört med BBK. Detta tyder på att BBKs krav på skrovlighet är bättre än Eurokod ur deformationssynvinkel Med denna undersökning som grund kan tillverkarna välja att avstå från Eurokod 2:s hårdare krav på skrovlig yta och fortsätta att behandla ytan enligt BBK 04. I och med detta menar författarna att Eurokod 2:s hårdare krav på skrovlig yta inte är nödvändig jämfört med BBK 04 med avseende på skjuvning (vidhäftning), vilket var det primära målet för undersökningen.

This work was carried out to study the effect of shot-peening on the fatigue behaviour of carbon steels. Differently heat treated medium and high carbon steel specimens were selected. Medium carbon steels, AISI 1141 and AISI 1151, were respectively air cooled and quenched-tempered. A high carbon steel, C70S6 (AISI 1070), was air cooled. The other material was a powder metal (0.5% C) steel. Each group of steels was divided into two. One was shot-peened. The other half remained in their original conditions. All were fatigue tested under fully reversed (R=-1) tension-compression loading conditions. Microhardness tests were carried out on both the grip and gage sections of selected non shot-peened and shot-peened specimens to determine the hardness profile and effect of cycling. Shot-peening was found to be deeper on one side of each specimen. Compressive residual stress profiles and surface roughness measurements were provided. Shot-peening increased the surface roughness from 0.26±0.03µm to 3.60±0.44µm. Compressive residual stresses induced by shot-peening reached a maximum of -463.9MPa at a depth of 0.1mm.The fatigue limit (N≈106 cycles) and microhardness profiles of the non shot-peened and shot-peened specimens were compared to determine the material behaviour changes after shot-peening and cycling. Also their fatigue properties were related to the manufacturing process including heat and surface treatments. Comparing the grip and gage microhardness profiles of each steel showed that neither cyclic softening nor hardening occurred in the non shot-peened condition. Cyclic softening was apparent in the shot-peened regions of all steels except powder metal (PM) steel. The amount of softening in the shot-peened region was 55.0% on the left side and 73.0% on the right in the AISI 1141 steel , 46.0% on the left side and 55.0% on the right in the C70S6AC steel and 31.0% on the right side in AISI 1151QT steel. Softening was accompanied by a decrease in the depth of surface hardness. It is suggested that although the beneficial effects of shot peening, compressive residual stresses and work hardening, were offset by surface roughness, crack initiation was more likely to occur below the surface. Surface roughness was not a significant factor in controlling the fatigue lives of AISI 1141AC and C70S6 steels, since they were essentially the same for the non shot-peened and shot-peened conditions. Shot-peening had very little effect on the push-pull fatigue limit of C70S6 steel (-2.1%), and its effect on AISI 1141AC steel was relatively small (6.0%). However, the influence of shot-peening on the AISI 1151QT and PM steels was more apparent. The fatigue limit of the PM steel increased 14.0% whereas the fatigue limit of the AISI 1151QT steel decreased 11.0% on shot peening.

No description available.

This thesis investigated the interaction of complex vegetation with wind flow and sediment transport at a creosote shrubland located in New Mexico and formed part of a larger on-going study to improve wind erosion modeling techniques. Directionally dependent roughness densities, λ, were computed and compared to mean wind speed ratios (WSRs) derived from anemometry data. A significant relationship existed among decreasing WSRs and increasing λ, indicating that shelter to the ground changed depending on the orientation of the wind. WSRs were larger on the west, more sparsely vegetated side, than in the east, demonstrating that distribution and plant size have a significant effect on near surface winds. Comparison of these data to a similar study completed in a mesquite coppice dune field demonstrated weaknesses in the roughness density parameter. These results have application for improving the understanding of interactions between wind flow and vegetation in complex rangeland environments.

Baigiamajame magistro darbe eksperimentiškai ištirta įvairių rūšių kartono ir puskartonio savybių kaita spausdinant fleksografiniais ir ofsetiniais dažais. Ištirtos atspaudų spalvinės charakteristikos CIE L*a *b * spalvų erdvėje, išnagrinėta kartono paviršiaus šiurkštumo, mechaninio stiprumo tempiant bei atsparumo lenkiant kaita spausdinant priklausomai nuo spaudos būdo ir dažų sluoksnio storio atspaude. Taip pat ištirtos kartonų ir atspaudų trinties savybės ir nustatytos statinės (SK) ir kinetinės (KK) koeficientų vertės bei jų priklausomybė nuo prispaudimo jėgos. Šių koeficientų vertės buvo nustatytos tarp kartono ir kartono, tarp kartono ir atspaudo ir tarp atspaudo ir atspaudo bei ištirtos ST ir SK priklausomybės nuo kartono PPS šiurkštumo, dažų kiekio atspaude. Išanalizuoti darbo rezultatai ir pateiktos galimos nustatytųjų priklausomybių fizikinės priežastys. Darbą sudaro 7 dalys: įvadas, literatūros apžvalga, darbo tikslas ir uždaviniai, tyrimų metodika, tyrimų rezultatai ir jų aptarimas, išvados, literatūros sąrašas. Darbo apimtis: 63 p. be priedo, 49 iliustr., 8 lent., 22 bibliografiniai šaltiniai. / In master thesis were experimentally investigated the different types of carboard, flexographic and offset prints. The prints color characteristics of the CIE L*a*b* color space, the carboard roughness, mechanical strenght in tension and cardboard bending resistance were examined depending on the way the press and ink content on prints. Also was investigated the friction properties, static (SCOF) and kinetic (KCOF) values and of their dependence on the load. These values have been determined between the board and the board, the board and print and two prints. and the dependence of the the SCOF and KCOF values on the carboard PPS roughness, ink content on prints was investigated. The results were analyzed and presented in the fixed physical addiction causes. The Master Thesis inludes 7 parts: introductions, publications review, goal and challenges, methods, results and discussion, conclusions, bibliographical references. The Master Thesis contains: 63 pages, 49 tables, 8 figures, 22 bibliographical references.