162 research outputs found
Jun yan.
No full text羅靄伊著 ; 楊潤餘, 索以同譯.Translation of: Le visage émerveillé.Fiction.Luoaiyi zhu ; Yang Runyu, Suoyi tong yi
Leveraging free carriers effects for infrared photonic structures and devices
No full textIn this work, three types of novel photonic devices/structures were developed. The first one is a metal grating structure that combines the characters of ‘moth-eye’ structure and an extraordinary optical transmission grating. Therefore it has the capability to provide a uniform electrical distribution while simultaneously reducing the optical reflection loss. It can be applied to the active optoelectronic devices which require both optical and electrical access.
The second device is a slot waveguide made with a hybrid doped semi-conductor/metal architecture. Our waveguide takes advantage of the doped semiconductor, which has highly controllable optical response as a designer plasmonic material in the mid-infrared. The local wavelength of the mode that propagates in the waveguide can be expanded at a selected frequency. Therefore the waveguide can function as a photonic wire, which potentially enables the design and fabrication of an integrated metatronic circuit.
The third device is a room-temperature photodetector based on a resonant RF circuit. It consists a microstrip busline and a split-ring resonator that is capacitively coupled to the busline; the RF circuit is built on a semiconductor substrate, with the great flexibility of changing the underlying material system by epitaxial growth. We experimentally investigated the responsivity of this type of detector and concluded that both the material and the geometry will have great impact on the detector response. This detector architecture offers the potential for multiplexing arrays of detectors on a single read-out line; it also can allow us to perform carrier dynamics characterization of semiconductor materials.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2018-12-01The student, Runyu Liu, accepted the attached license on 2016-11-23 at 13:28.The student, Runyu Liu, submitted this Dissertation for approval on 2016-11-23 at 14:14.This Dissertation was approved for publication on 2016-11-28 at 13:35.DSpace SAF Submission Ingestion Package generated from Vireo submission #10310 on 2017-02-28 at 14:36:43Made available in DSpace on 2017-03-01T16:36:54Z (GMT). No. of bitstreams: 3
LIU-DISSERTATION-2016.pdf: 10986617 bytes, checksum: 60aff26f05a5b09ba07cd89009e045b6 (MD5)
LICENSE.txt: 4206 bytes, checksum: d6d4b8b9e5787f053c8e5fcaebb1d73e (MD5)
PROQUEST_LICENSE.txt: 4552 bytes, checksum: 173fed2c7c737d0398c0702512ac239e (MD5)
Previous issue date: 2016-11-28Embargo set by: Seth Robbins for item 98598
Lift date: 2019-03-01T16:37:19Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 98598 on 2019-03-02T10:15:18Z
Design of multidimensional nanophotonic materials with improved performance and functionalities
No full textMulti-dimensional (2D and 3D) architectures with characteristic feature sizes on the order of a micrometer and below can exhibit extraordinary properties that are not present in their non-structured counterparts. Of particular interest are 3D microstructures, which have been found promising due to their unique photonic, electronic, thermal, and mechanical properties. Due to their unique potential to control the propagation of light in all directions, it is the photonic properties of three-dimensionally microstructure materials, so-called 3D photonic crystals (3D PhCs), that have attracted the greatest amount of attention. Although 3D PhCs have been suggested to have great promise, in practice they have been limited by both the properties of the available constituent materials and difficulties in processing materials with feature sizes small enough to impact visible and near IR wavelengths.
This thesis will thus focus on developing novel techniques to overcome some long-lasting processing challenges in the 3D PhCs community and provide 3D structures that may also be of interest for their electronic, thermal, and mechanical properties. As an overview, in Chapter One we will first introduce the background of PhCs as well as the current achievements and challenges. In Chapters Two to Chapter Four, we will show 1) how a newly developed transfer printing method can be used to enrich the functionalities of 3D PhCs made by holographic lithography (Chapter Two) and 2) how metallic alloy systems may be more interesting than pure metals for 3D metallic PhCs under elevated temperature (Chapter Three & Four). Based on the learnings in these two chapters, we will then continue our discussions in Chapter Five to Chapter Seven on how electrochemical approaches can become powerful in creating novel structures with superior electronic and photonic properties that can potentially lead to a significant improvement in the technology field. Finally, additional to the design of static photonic devices made with solid materials, in Chapter Eight, the design of a new dynamic controllable 3D PhC based on reconfigurable microplasma arrays is simulated and experimentally presented. The unifying theme of this thesis is therefore to build a better understanding of how light and materials with complex structures will interact and make an impact on the development of 3D PhCs as well as other nanophotonic technologies.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2020-05-01The student, Runyu Zhang, accepted the attached license on 2018-04-16 at 13:19.The student, Runyu Zhang, submitted this Dissertation for approval on 2018-04-16 at 13:36.This Dissertation was approved for publication on 2018-04-17 at 17:03.DSpace SAF Submission Ingestion Package generated from Vireo submission #12275 on 2018-08-31 at 17:19:05Made available in DSpace on 2018-09-04T20:36:35Z (GMT). No. of bitstreams: 4
ZHANG-DISSERTATION-2018.pdf: 5964979 bytes, checksum: f1be1642150d81e48b037baeb0a34fb0 (MD5)
LICENSE.txt: 4208 bytes, checksum: ce9b49b1a09fb8ea793cabc755e87c86 (MD5)
RightsLink Printable License.pdf: 102378 bytes, checksum: d95587ccdc6f2fc477215b8c463b069b (MD5)
Rightslink? by Copyright Clearance Center.pdf: 138178 bytes, checksum: c622ec93464c1962bf7f2df7dd9dc23f (MD5)
Previous issue date: 2018-04-17Embargo set by: Seth Robbins for item 107256
Lift date: 2020-09-04T20:37:00Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 107256
Lift date: 2020-09-04T20:42:08Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 107256 on 2020-09-05T09:15:23Z
Effect of friction and cohesion on anisotropy in quasi-static granular materials under shear
No full textWe study the effect of particle friction and cohesion on the steady-state shear stress and the contact anisotropy of a granular assembly sheared in a split-bottom ring shear cell. For non-cohesive frictional materials, the critical state shear stress first increases and then saturates with friction. The contact number density is found to decrease monotonically, while the anisotropy of the contact network saturates after an initial increase. For cohesive powders, the relation between shear stress and confining pressure becomes non-linear. Interestingly the contact number density stays almost unaffected, while the structural anisotropy decreases with increasing cohesion, hinting at a redistribution of the network with almost constant contact number density
On the use of Graphics Processing Units (GPUs) for molecular dynamics simulation of spherical particles
No full textGeneral-purpose computation on Graphics Processing Units (GPU) on personal computers has recently become
an attractive alternative to parallel computing on clusters and supercomputers. We present the GPU-implementation of an
accurate molecular dynamics algorithm for a system of spheres. The new hybrid CPU-GPU implementation takes into
account all the degrees of freedom, including the quaternion representation of 3D rotations. For additional versatility, the
contact interaction between particles is defined using a force law of enhanced generality, which accounts for the elastic and
dissipative interactions, and the hard-sphere interaction parameters are translated to the soft-sphere parameter set. We prove
that the algorithm complies with the statistical mechanical laws by examining the homogeneous cooling of a granular gas with
rotation. The results are in excellent agreement with well established mean-field theories for low-density hard sphere systems.
This GPU technique dramatically reduces user waiting time, compared with a traditional CPU implementation
FEM-DEM simulation of two-way fluid-solid interaction in fibrous porous media
No full textFluid flow through particulate media is pivotal in many industrial processes, e.g. in fluidized beds, granular storage, industrial filtration and medical aerosols. Flow in these types of media is inherently complex and challenging to simulate, especially when the particulate phase is mobile. The goals of this paper are twofold: (i) the derivation of accurate correlations for the drag force, taking into account the effect of microstructure, to improve the higher scale macro-models and (ii) incorporating such closures into a “compatible” monolithic multi-phase/scale model that uses a (particle-based) Delaunay triangulation (DT) of space as basis – in future, possibly, involving also multiple fields
Hydraulic and acoustic investigation of sintered glass beads
No full textIn the present contribution, we are focussing on the hydraulical and acoustical charcterization of sintered glass beads. For the experiments sintered mono-and weakly polydisperse glass bead samples were applied. Depending on the particle size, degree of particle dispersion and sample treatment during the sintering process, the produced cylindircal samples exhibit different hydraulic and acoustic properties. The more general focus of our research lies on the physical behaviour of oil-water emulsions in porous media by means of combined electromagnetic and acoustic wave propagation. For this purpose, a hydraulic multi-task measuring cell was developed. This cell allows carrying out simple hydraulic permeability and challenging ultrasound experiments in porous materials saturated with Pickering emulsions. In the first phase of our experiments, hydraulical and acoustical measurements of cylindrical sintered glass bead samples were performed in order to determine their intrinsic permeabilities and effective ultrasound velocities. The intrinsic permeability ks , a coupling parameter between the solid matrix and the pore fluid, has a huge influence on wave propagation in fluid-saturated porous media. For the assessment of permeabilities, particle size distributions and porosities of the investigated glass beads were determined
Evolution of the effective moduli for anisotropic granular materials during pure shear
No full textWe analyze the behavior of a frictionless dense granular packing sheared at constant volume. Goal is to predict the evolution of the effective moduli along the loading path. Because of the structural anisotropy that develops in the system, volumetric and deviatoric stresses and strains are cross coupled via four distinct quantities, the classical bulk and shear moduli and two anisotropy moduli. Here, by means of numerical simulation, we apply small perturbations to various equilibrium states that previously experienced different pure shear strains and investigate the effect of the microstructure (2 nd rank fabric tensor) on the elastic bulk response. Besides the expected dependence of the bulk modulus on the isotropic fabric, we find that both the isotropic density of contacts and the (deviatoric) orientational anisotropy affect the anisotropy moduli. Interestingly, the shear modulus of the material depends also on the actual stress state, along with the (isotropic and anisotropic) contact configuration
Fibrous random materials: From microstructure to macroscopic properties
No full textFibrous porous materials are involved in a wide range of applications including composite materials, fuel cells, heat exchangers and (biological)filters. Fluid flow through these materials plays an important role in many engineering applications and processes, such as textiles and paper manufacturing or transport of (under)ground water and pollutants. While most porous materials have complex geometry, some can be seen as two-dimensional particulate/fibrous systems, in which we introduce several microscopic quantities, based on Voronoi and Delaunay tessellations, to characterize their microstructure. In particular, by analyzing the topological properties of Voronoi polygons, we observe a smooth transition from disorder to order, for increasing packing fraction. Using fully resolved finite element (FE) simulations of Newtonian, incompressible fluid flow perpendicular to the fibres, the macroscopic permeability is calculated in creeping flow regimes. The effect of fibre arrangement and local crystalline regions on the macroscopic permeability is discussed and the macroscopic property is linked to the microscopic structural quantities
- …
