By implementing the rolled-up microfabrication method based on strain engineering, several systems are investigated within the contents of this thesis. The structural morphing of planar geometries into three-dimensional structures opens up many doors for the creation of unique material configurations and devices. An exploration into several novel microsystems, encompassing various scientific subjects, is made and methods for on-chip integration of these devices are presented. The roll-up of a metal and oxide allows for a cylindrical hollow-core structure with a cladding layer composed of a multilayer stack, plasmonic metamaterial. This structure can be used as a platform for a number of optical metamaterial devices. By guiding light radially through this structure, a theoretical investigation into the system makeup of a rolled-up hyperlens, is given. Using the same design, but rather propagating light parallel to the cylinder, a novel device known as a metamaterial optical fiber is defined. This fiber allows light to be guided classically and plasmonically within a single device. These fibers are developed experimentally and are integrated into preexisting on-chip structures and characterized. A system known as lab-in-a-tube is introduced. The idea of lab-in-a-tube combines various rolled-up components into a single all-encompassing biosensor that can be used to detect and monitor single bio-organisms. The first device specifically tailored to this system is developed, flexible split-wall microtube resonator sensors. A method for the capturing of embryonic mouse cells into on-chip optical resonators is introduced. The sensor can optically detect, via photoluminescence, living cells confined within the resonator through the compression and expansion of a nanogap built within its walls. The rolled-up fabrication method is not limited to the well-investigated systems based on the roll-up from semiconductor material or from a photoresist layer. A new approach, relying on the delamination of polymers, is presented. This offers never-before-realized microscale structures and configurations. This includes novel magnetic configurations and flexible fluidic sensors which can be designed for on-chip and roving detector applications.

Granular materials are characterized by its discrete nature which makes their behaviour very complex to understand when subjected to various loading situations. Comparing other materials, the understanding of granular materials is poor. This is because experimental analysis provides the macroscopic responses of the considered assembly whereas the discrete nature of the particles point to the fact of understanding the micro scale details and correlating it with the overall behaviour. Among the various modeling tools viz. analytical, physical or numerical, Discrete Element Method (DEM) a numerical technique, originally developed by Cundall (1971, 1974) and modified by Cundall and Strack (1979a, 1979b) is widely used for granular materials. Later a thorough description of DEM was given by Cundall (1988) and Hart et al (1988). Moreover Cundall & Hart (1992) reported discrete element code as one which allows finite displacements and rotations of discrete bodies along with recognition of new contacts as the calculation progresses which is followed in particle flow code and is used for this study. Generally the discrete particles are modeled as discs or spheres in 2-D and 3-D simulations respectively. The discs or spheres were considered as it is very easy to characterize the grain interactions and the contact detection. Even though the significance of particle shape has been reported in literature, a comprehensive 3-D study of the effect of particle shape on the various aspects of soil behaviour is lacking and is not reported. Particle shape is generally defined in terms of elongation, roundness and texture. Elongation is an indication of the particle aspect ratio whereas roundness measures the sharpness or angularity of particle’s edges and corners. Texture is related to the roughness of the surface. Particle gradation also plays a role in the mechanical behaviour. The influence of each of these factors on the mechanical behaviour of the assembly is important. Hence the major factors like elongation, texture etc which are used to define the particle shape are incorporated in this study. Evaluating the particle shape is another hurdle. In this study, the particle shape is analyzed using a 3D laser scanner which helps to identify the major and minor axis lengths of the particle. Additionally, the effective use of 3D DEM on large scale real life applications incorporating the particle shape effect is also not dealt with very extensively. Hence in this research, a comprehensive study on the calibration of DEM using glass beads, effect of particle shape on drained and undrained monotonic behaviour, liquefaction, post liquefaction and dynamic properties and the application of DEM to a grain polishing machine and an underground tunnel assembly is presented. In the present study, a set of drained triaxial tests were done on glass bead assembly using a laboratory triaxial set up. The glass beads used for the test were spherical and ellipsoidal in shape. The shape of glass beads was characterized through a sophisticated method of 3D laser scanning. In this scanning, the shape of the image of the glass bead is captured through an array of digitized points. These images obtained as unstructured 3D triangular meshes on processing will render the long and short axes of the particle which can be used for proper modeling of the particle shape. After obtaining the long and short axes for the particles, the same is used for the numerical modeling of the glass beads. The numerical simulation results have shown that the assembly modeled with clumped particles gives results qualitatively and quantitatively similar to the observed experimental macro responses. Hence this is used to demonstrate the power of DEM to realistically model the granular behaviour by incorporating the particle shape effect. In addition, undrained simulation of granular material has been numerically predicted from drained triaxial tests which are similar to the approach proposed by Norris et al (1997). An excellent correlation between undrained results predicted from drained triaxial test and undrained test (performed under constant volume conditions) has been observed. This further underlines the fact that the constant volume simulations are equivalent to undrained tests. Having validated the DEM results to the values obtained from the experiments on glass beads, a series of monotonic drained and undrained triaxial tests were performed on cylindrical assemblies of height to diameter ratio 2:1. Four different sets of assemblies were prepared which consists of particles of different aspect ratio to study the influence of particle shape. The behaviour of these assemblies under drained shearing indicates that the strength of the clumped assemblies is higher than that of the spherical assembly at all confining pressures. This has been explained from the magnitude of the anisotropic vi coefficients associated with the fabric and normal contact force tensors. It is also noted that eventhough both assemblies reach the peak strength at the same axial strain, the strain softening associated with the clumped assembly is very rapid which is due to the fact that clumps try to push each other apart as it offers more resistance to rotation resulting in dilation. Another significant observation is that a general increase in aspect ratio will not keep on increasing the strength. As the aspect ratio increases, the particles have a tendency to orient along their larger dimensions. This helps them to attain the lowest potential energy leading to a stable equilibrium and resulting in inherent fabric anisotropy. But when the particles try to align along the larger dimension, the formation of strong contact forces along the direction of loading is hindered. In addition, the lower strength associated with the higher aspect ratio particle assembly can also be attributed to the formation of unexpected void spaces when these longer particles bridge gaps over the underlying grains. The critical state studies indicate that the clumped assembly is having a higher residual strength compared to that of the spherical assembly. In the case of clumped assemblies also, irrespective of the initial loose or dense state of the assembly and the confining pressure applied, the samples reached the same critical state which underlines that the critical state is unique for a granular material. Moreover, the critical state line is non-linear for both the spherical and clumped assemblies. The studies conducted on the liquefaction behaviour indicates that at lower confining pressures the assemblies with particles consisting of lower aspect ratios loses its strength at less number of cycles which can be attributed to the interlocking of non-spherical particles resulting in higher number of contacts per particle. Moreover, during the initial cycles of loading, it is seen that the strong contacts are predominantly in the vertical direction or more precisely along the direction of maximum axial strain. But the plots extracted at higher cycles indicated that the strong contacts along the vertical direction have diminished considerably. This reduction in contact force magnitude and force chain indicates a drop in the number of contacts and is clearly visible in the gradual decrease of average coordination number. Another significant observation is that as the confining stresses increases, the rate of pore pressure generation of the assembly vii consisting of only spherical particles is less compared to the other two samples. Furthermore, at higher confining pressures, when the load direction reverses, the fabric of the clumped assemblies fails to change to a new orientation immediately. But to retain equilibrium the force anisotropy will quickly adjust itself. This mismatch results in losing the contacts and resulting in lower strength and less resistance to liquefaction at higher stresses for assemblies consisting of clumped particles. The post liquefaction study of the numerically liquefied samples shows that the assembly consisting of clumped shaped particles gained strength at a much faster rate compared to the assembly consisting of only spheres. This may be attributed to the ability of the clumps to rearrange themselves on a faster rate compared to that of the spherical particles. The rate of development of average coordination number is very significant as it explains the ability of the assembly to build up the deviatoric stress from a complete collapsed structure. As the contacts develop, the average coordination number as well as the deviatoric stress starts increasing with both the values higher for the assembly consisting of clumped particles. The evaluation of the dynamic properties viz. shear modulus and damping ratio showed a trend similar to the experimental observations on real granular materials. It is observed that the normalized shear modulus reduces with an increase in shear strain and the rate of reduction is very high at low strains for all the samples. It can be seen that as the confining pressure increases, the normalized shear modulus value also increases and the rate of increment is higher for the assemblies consisting of non-spherical particles. Furthermore, for all the samples the threshold shear strain is about 0.001 up to which the behaviour is elastic. Beyond the threshold shear strain, the variation of the normalized shear modulus ratio is non-linear. At small shear strains, the energy dissipation is low resulting in smaller values of damping. As the strains increase, the non-linearity in the constitutive behaviour results in higher material damping leading to high damping value. The simulations of the food polishing machine helps to understand the pattern of hitting of clumped grains on the wall with due importance to the velocity of hit, angle of hit, force of hit, and the number of grains hitting the wall. The modeling and subsequent extraction of the data helped to identify that the wear and tear of the machine was not uniform and was clustered to specific regions due to the non-uniform distribution of the considered parameters. This helped to design a more sophisticated system such that the parts which are subjected to more deterioration are provided with additional support. To bring out the effect of the particle shape, simulations are performed using spherical particles and the results show that the pattern of variation is same, but the magnitudes are different owing to the less surface area associated with the spherical particles. The 3-D simulations of an underground tunnel assembly in a weak weathered rock helped to understand the variation in the stability of the system with and without lining. It was observed that the introduction of lining resulted in a more stable configuration and the circumferential stresses were found to be distributed uniformly around the tunnel. FEM simulations also show a similar trend of stress and strain variations but were unable to capture the ground loosening around the tunnel and the formation of the ground arch whereas DEM could realistically capture all these phenomena. It was observed that as the shape changes from sphere to non-spherical particles, circumferential stresses around the tunnels increased. In addition, as the distance from the tunnel face increases, the strains are reduced. The maximum vertical strain near the crown of the tunnel is observed for the assembly consisting of spherical particles. In short, this research is focused on a comprehensive understanding of the particle shape effect on the mechanical behaviour of granular mass. Numerical simulations incorporating the shape effect has been done on drained and undrained monotonic shear tests, critical state, liquefaction, post liquefaction and dynamic properties. Besides, the granular dynamics simulation of the movement of long food grains in a food polishing machine and the behaviour of an underground tunnel in a granular assembly is also reported.

Jahresbericht der Universitätsbibliothek Chemnitz - Berichtsjahr 2005 / Annual report of the University Library of Chemnitz in 2005

>Magister Scientiae - MSc

>Magister Scientiae - MSc / The Kuils River Catchment is an urban river catchment that forms part of the larger Kuils-Eerste River system draining the eastern half of the Cape Metropolitan Authority area and Stellenbosch Municipality. Rapid urbanisation has resulted in the encroachment of residential and industrial areas into the river system through channelization and sewage disposal. This research project intends to assess the quality of surface runoff in the Kuils River catchment and determining non-point source pollutant loading rates in the catchment using GIS-based modelling. The study results show how modelled potential sources of surface runoff and NPS pollutants using desktop GIS analysis tools in a sequential process that involved different levels of software applications could explain the characteristics of the catchment. With the help of the Expected Mean Concentration (EMC) values associated with surface runoff from land use/covers, NPS pollutant loads were assessed downstream towards the Kuils River Catchment outlet using the Nonpoint Source Pollution and Erosion Comparison Tool (N-SPECT) based in ArcGIS. The outputs from this model consist of predicted annual pollutant loading (mg/mvyear) for each Kuils-Eerste River that occurs in the catchment. The results have shown clearly the spatial distribution of sources of particular pollutants in the catchment. Further or advanced processing knowhow with this model might provide far reaching insights into the problem and it is however recommended that these results produced using N-SPECT be compared to those of other hydrologic models using the same inputs.

Der Gasthof Lotzdorf bei Radeberg, erbaut und geführt von Wilhelm Riemer und Pauline Riemer, war eine Legende. Die Biografie beschreibt die Lebensleistung der Familie Riemer, den Aufstieg und Untergang des Gasthof Lotzdorf bzw. Riemers Gasthof mit Gasthaus, Ballsaal, Gästegarten, unzähligen großen und kleinen Veranstaltungen und der berühmten, bereits 1927 installierten '1000-Flammen-Kugel'. Einer damaligen Besonderheit.

No description available.

This work is devoted to investigate light confinement in rolled-up microtubular cavities and their optofluidic applications. The microcavities are fabricated by a roll-up mechanism based on releasing pre-strained silicon-oxide nanomembranes. By defining the shape and thickness of the nanomembranes, the geometrical tube structure is well controlled. Micro-photoluminescence spectroscopy at room temperature is employed to study the optical modes and their dependence on the structural characteristics of the microtubes. Finite-difference-time-domain simulations are performed to elucidate the experimental results. In addition, a theoretical model (based on a wave description) is applied to describe the optical modes in the tubular microcavities, supporting quantitatively and qualitatively the experimental findings. Precise spectral tuning of the optical modes is achieved by two post-fabrication methods. One method employs conformal coating of the tube wall with Al2O3 monolayers by atomic-layer-deposition, which permits a mode tuning over a wide spectral range (larger than one free-spectral-range). An average mode tuning to longer wavelengths of 0.11nm/ Al2O3-monolayer is obtained. The other method consists in asymmetric material deposition onto the tube surface. Besides the possibility of mode tuning, this method permits to detect small shape deformations (at the nanometer scale) of an optical microcavity. Controlled confinement of resonant light is demonstrated by using an asymmetric cone-like microtube, which is fabricated by unevenly rolling-up circular-shaped nanomembranes. Localized three-dimensional optical modes are obtained due to an axial confinement mechanism that is defined by the variation of the tube radius and wall windings along the tube axis. Optofluidic functions of the rolled-up microtubes are explored by immersing the tubes or filling their core with a liquid medium. Refractive index sensing of liquids is demonstrated by correlating spectral shift of the optical modes when a liquid interacts with the resonant light of the microtube. In addition, a novel sensing methodology is proposed by monitoring axial mode spacing changes. Lab-on-a-chip methods are employed to fabricate an optofluidic chip device, allowing a high degree of liquid handling. A maximum sensitivity of 880 nm/refractive-index-unit is achieved. The developed optofluidic sensors show high potential for lab-on-a-chip applications, such as real-time bio/chemical analytic systems.

<p dir="ltr">Digital soil mapping (DSM) combines field and laboratory data with environmental factors to predict soil properties. The accuracy of these predictions depends on factors such as model selection, data quality and quantity, and landscape characteristics. In our study, we investigated the impact of sample density and the use of various environmental covariates (ECs) including slope, topographic position index, topographic wetness index, multiresolution valley bottom flatness, and multiresolution ridge top flatness, as well as the spatial resolution of these ECs on the predictive accuracy of four predictive models; Cubist (CB), Random Forest (RF), Regression Kriging (RK), and Ordinary Kriging (OK). Our analysis was conducted at three sites in Indiana: the Purdue Agronomy Center for Research and Education (ACRE), Davis Purdue Agriculture Center (DPAC), and Southeast Purdue Agricultural Center (SEPAC). Each site had its unique soil data sampling designs, management practices, and topographic conditions. The primary focus of this study was to predict the spatial distribution of soil properties, including soil organic matter (SOM), cation exchange capacity (CEC), and clay content, at different depths (0-10cm, 0-15cm, and 10-30cm) by utilizing five environmental covariates and four spatial resolutions for the ECs (1-1.5 m, 5 m, 10 m, and 30 m).</p><p dir="ltr">Various evaluation metrics, including R², root mean square error (RMSE), mean square error (MSE), concordance coefficient (pc), and bias, were used to assess prediction accuracy. Notably, the accuracy of predictions was found to be significantly influenced by the site, sample density, model type, soil property, and their interactions. Sites exhibited the largest source of variation, followed by sampling density and model type for predicted SOM, CEC, and clay spatial distribution across the landscape.</p><p dir="ltr">The study revealed that the RF model consistently outperformed other models, while OK performed poorly across all sites and properties as it only relies on interpolating between the points without incorporating the landscape characteristics (ECs) in the algorithm. Increasing sample density improved predictions up to a certain threshold (e.g., 66 samples at ACRE for both SOM and CEC; 58 samples for SOM and 68 samples for CEC at SEPAC), beyond which the improvements were marginal. Additionally, the study highlighted the importance of spatial resolution, with finer resolutions resulting in better prediction accuracy, especially for SOM and clay content. Overall, comparing data from the two depths (0-10cm vs 10-30cm) for soil properties predications, deeper soil layer data (10-30cm) provided more accurate predictions for SOM and clay while shallower depth data (0-10cm) provided more accurate predictions for CEC. Finally, higher spatial resolution of ECs such as 1-1.5 m and 5 m contributed to more accurate soil properties predictions compared to the coarser data of 10 m and 30 m resolutions.</p><p dir="ltr">In summary, this research underscores the significance of informed decisions regarding sample density, model selection, and spatial resolution in digital soil mapping. It emphasizes that the choice of predictive model is critical, with RF consistently delivering superior performance. These findings have important implications for land management and sustainable land use practices, particularly in heterogeneous landscapes and areas with varying management intensities.</p>

Wappen sind nicht nur schöne Schmuckstücke, sondern mit ihrer Blasonierung (Wappenbeschreibung) wird die Deutung und Darlegung geschichtlicher Hintergrundinformationen möglich, die wie im Fall des Radeberger Stadt-Wappens eng mit der Geschichte der Mark Meißen, der Erfolgsgeschichte Sachsens unter der Herrschaft der Wettiner und der Entwicklung von Burg und Stadt Radeberg verbunden sind. Das Radeberger Stadtwappen wird in der Heraldik mit seinem in einem Schild dargestellten Bildelement „Rad“ als „sprechendes“ oder „redendes“ Wappen bezeichnet, da dieses Bildmotiv ohne weitere Umschreibung den Namen der Stadt versinnbildlicht. Durch den 1507 durch Herzog Georg dem Bärtigen (1471–1539) verliehenen Wappenbrief an die Stadt Radeberg, der mit Blasonierung und Tinktur des Wappenbildes versehen ist, wurde das Stadtwappen von diesem Zeitpunkt an durch den Herzog als festgeschriebenes, „unveränderliches Wappenbild“ gesetzt, also damals schon im bestehenden Wappenrecht „zum Gesetz“ erhoben (s. „Acta des Königl. Hauptstaatsarchiv zu Dresden, HStA 10707, Nr. 5717 v. 2. Mai 1894“, Wappenbrief S.2/3). In Sachsen wurde ab 1894 eine Revision aller Stadtwappen und Siegel durch das Königliche Ministerium des Innern durchgeführt. Weder der Stadtrat noch der Bürgermeister besaßen Wissen über den Wappenbrief und seine Inhalte. Verlorengegangen und damit unbekannt waren ebenfalls das gesetzliche Wappenbild und die Festlegungen für seine Blasonierung. Bei dieser staatlichen Revision wurde offenbar, dass selbst die zur Überprüfung angeforderten Wappensiegel und -stempel der Stadt nicht mehr den Vorgaben des Wappenbriefes von 1507 entsprachen. Auch das aufgesetzte Wappenbild im Schlussstein des 1876 fertiggestellten Rathausportals war in Unkenntnis der amtlichen Vorgaben mit einem abweichenden heraldischen Bildelement versehen worden. Als Hausmarke am Schlussstein des Rathauses „festgemauert“ angebracht, entspricht es damit bis heute nicht den herzoglichen Vorgaben von 1507 und damit auch nicht dem Wappenrecht, welches unveränderlich Gültigkeit besitzt. Durch das Königliche Hauptstaatsarchiv Dresden (HStA) erhielt die Stadtverwaltung Radeberg 1895 erneut eine Abschrift des herzoglichen Wappenbriefes und eine verbindliche Zeichnung des Wappens zugestellt. In diesem Artikel werden die historische Entwicklung der Radeberger Stadtsiegel und -wappen ab dem Jahre 1233 einschl. der Blasonierung (Wappenbeschreibung) und Tingierung (Farbgebung) mit Wappenbegründung (ab 1507 auf Basis des Original-Wappenbriefes von Herzog Georg dem Bärtigen) behandelt. Die 'historische Begründung für Stadtsiegel und Wappen' auf Grundlage der Original-Dokumente und Original-Siegel im Sächsischen Hauptstaatsarchiv Dresden wird mit korrekten Quellen-Nachweisen und neuen Fotografien bewiesen. Ausgangspunkt ist das originale Stadtsiegel des Thimo von Radeberch aus dem Jahre 1233. Entstehung und Gestaltung der Radeberger Stadt-Fahne runden den Artikel ab. Angefügt ist ein umfangreiches Quellen- und Literaturverzeichnis mit Archivalien-Nr.:Einführung 2 1. Blasonierung (Wappenbeschreibung) des Radeberger Wappens mit Wappenbegründung 5 1.1. Original Wappenbrief von Herzog Georg dem Bärtigen von 1507 / Abschrift 6 1.2. Radeberger Stadtwappen – Heraldische Darstellungsregeln seit 1507 10 1.3. Blasonierung – Beschreibung und Deutung des „gesetzlichen Kleinodes“ 10 1.4. Tingierung 12 1.4.1.Heraldische Stadtfarben für Radeberg 12 1.4.2 Heraldische Fahnen, Flaggen, Banner (Vexillologie) 12 1.5. Die Stadt Radeberg – Historische Begründung für Stadtsiegel und Wappen 12 2. Siegel und Wappen als Quelle der Geschichtsforschung 14 2.1. Erster urkundlicher Nachweis des Namens „Radeberch“ 1233 14 2.2. Die „de Radberch“ – Ritter, Castellane der Burgwarte, aber kein Adelsgeschlecht 15 2.3. Besiedlungspolitik: Zuerst kam der Krieger – danach der deutsche Bauer 17 2.4. Entstehung und Gebrauch der Wappen 19 2.4.1. Ritter führen Wappen als Erkennungszeichen in freier Annahme 19 2.4.2. Wappen werden zur „Wappenmode“ bei Bürgern und Städten 20 2.5. Thimos Wappen – Ursprung unserer Burg- und Ortsgeschichte? 21 2.5.1. Der Name „Radberch“ und drei Radteile geben immer wieder Rätsel auf 21 2.5.2. Gelehrte und ihre Wappenbilddeutungen – Widersprüche und Abweichungen 22 2.5.3. Radeberg erhielt 1412 Stadtrecht – eigenes Siegel mit Wappen gab es bereits 23 2.5.4. Radeberg 1507 mit besonderer Auszeichnung begnadet – einem Wappenbrief 24 3. 1894 – Beginn der Wappen- Revision aller sächsischer Städtewappen durch das Sächsische Ministerium des Innern 26 4. Radeberger Wappen mit „Rad, Löwe und Schwert“ – Kommunales Hoheitszeichen und Symbol für Heimatzugehörigkeit 27 5. Radeberger Stadtwappen und Radeberger Fahne – sie gehen als Botschafter der Stadt um die Welt 28 6. Quellen, Erläuterungen: 29