Master of Science (MS), Ohio University, 1982, Electrical Engineering & Computer Science (Engineering and Technology)

Guided waves propagating in isotropic and uniaxial anisotropic slab waveguides

Committee: Hollis Chen (Advisor) Subjects:

Master of Science, Miami University, 2024, Mechanical and Manufacturing Engineering

Lattice structures are celebrated for their lightweight characteristics and superior mechanical performance. In this research, a strut reinforcement technique was employed to enhance the energy absorption capacities of 3D re-entrant auxetic (Aux), hexagonal (Hex), and hybrid Auxetic-Hexagonal (AuxHex) lattice structures. The investigation involved finite element analysis to delve into the mechanical and energy absorption properties of these novel designs during quasi-static compression testing. The results from the uniaxial compression tests of the reinforced designs were then compared with those from traditional 3D hexagonal and re-entrant auxetic lattice structures. To accurately simulate the mechanical behavior of the 3D printed lattice structures, the mechanical properties of the PA2200 matrix material—manufactured via additive manufacturing—were utilized. The outcomes indicated by the stress-strain and energy absorption curves suggest that these newly proposed designs are optimal for applications requiring high energy absorption at large strains. Thus, these findings pave the way for developing novel designs in 3D hexagonal and re-entrant auxetic lattice structures, which are poised to offer enhanced mechanical strength and exceptional specific energy absorption properties. Expanding on these insights, future research could explore further variations in lattice geometry and reinforcement methods to optimize the performance of these structures under different loading conditions.

Committee: Muhammad Jahan (Advisor); Carter Hamilton (Committee Member); Jinjuan She (Committee Member); Jeff Ma (Advisor) Subjects: Biomechanics; Experiments; Materials Science; Mechanical Engineering; Mechanics

Doctor of Philosophy, University of Toledo, 2017, Biomedical Engineering

Rotator cuff injuries are very common among people over the age of 60, with more than 600,000 surgeries performed annually in the United States for rotator cuff repairs. However, in 20-80% of the cases, the repair fails due to re-rupture of the tendon at the tendon-bone insertion site. The complexity of the tendon tissue in terms of their structure, composition, and function at the tendon-to-bone interface demands for a combinatorial tissue-engineering approach in which cell maturation and function can be directed using bioactive proteins encapsulated within a biomaterial with appropriate material stiffness. Further, since tendons experience routine mechanical strains in their native environment, providing suitable mechanical cues to the engineered scaffold was considered important for the success of rotator cuff repair strategies. The objective of this dissertation was to synthesize and characterize a mechanically-conditioned biphasic composite collagen scaffold to enhance rotator cuff regeneration with (1) controlled delivery of adipose-derived stem cells (ASCs) and platelet-derived growth factor (PDGF) to augment and accelerate tendon healing, and (2) spatial material stiffness to promote gradient mineralization and matrix directionality at the tendon-bone interface. To this end, a mechanical loading bioreactor consisting of unique silicone loading chambers was designed that was capable of applying homogenous uniaxial tensile strains over 60% of the length of cell-encapsulated 3D collagen scaffolds. Uniaxial tensile mechanical loading at 2% strain with 0.1 Hz frequency was identified to be the appropriate loading modality to induce pure ASC tenogenic differentiation, along with enhanced matrix directionality and ECM gene expression within ASC-encapsulated 3D collagen scaffolds. Next, the poor protein retention and matrix stiffness properties of collagen were improved by synthesizing a composite collagen scaffold (PNCOL) interspersed with functionalized polycapr (open full item for complete abstract)

Committee: Eda Yildirim-Ayan (Advisor) Subjects: Biomedical Engineering; Biomedical Research

Master of Science in Engineering, University of Akron, 2016, Biomedical Engineering

The field of mechanobiology is aimed at understanding the role the mechanical environment plays in directing cell and tissue development, function, and disease. Mechanosensitive cells, such as osteocytes in bone, are capable of translating mechanical stimuli into cellular responses. This phenomenon can be widely found in many cells throughout the body, and yet little is known about the mechanisms and pathways by which this occurs. In order to investigate these mechanisms, researchers focus on developing in vitro models aimed at accurately simulating biologic samples with loads similar to those displayed in the in vivo environment. By designing their own systems, researchers can create specialized systems that meet their specific testing needs while saving money in comparison to purchasing expensive commercially available systems. Utilizing systems such as these, researchers can start to unravel the science behind mechanobiology and related diseases, and begin to improve and generate new treatments and cures. In this study, a model for mechanically stimulating osteocyte-like MLO-Y4 cells (known for relating to mechanosensitive bone diseases) and observing cellular response was designed, fabricated, and characterized. This model consisted of an elastic substrate for cell culture and a pure uniaxial loading device designed to apply precise loads to a biologic sample. The substrate and loading device were designed, fabricated, and characterized utilizing a series of physical and simulated tests. Once the model was completely characterized, MLO-Y4 cells were grown in the system and a series of loads were applied to correlate mechanical substrate strain to cellular metabolic and soluble activity. The resulting cellular data followed general trends found in other research verifying the effectiveness of the model for in vitro cellular experimentation.

Committee: Marnie Saunders PhD (Advisor); Ge Zhang M.D., PhD (Committee Member); Hossein Tavana PhD (Committee Member) Subjects: Biomechanics; Biomedical Engineering; Biomedical Research; Cellular Biology; Mechanical Engineering

PHD, Kent State University, 2015, College of Arts and Sciences / Chemical Physics

Topological defects plays an important role in many physical processes ranging from morphogenesis of phase transitions in condensed matter system to the response to surface confinement and application of external fields. In this dissertation, we investigate the topological defects both in lyotropic and thermotropic nematics in order to characterize the studied materials.

Committee: Oleg Lavrentovich (Advisor); Hiroshi Yokoyama (Committee Member); Liang-Chy Chien (Committee Member); Samuel Sprunt (Committee Member); Elizabeth Mann (Committee Member) Subjects: Engineering; Experiments; Materials Science; Optics; Physical Chemistry; Physics

Master of Science, The Ohio State University, 2014, Mechanical Engineering

The ability to accurately computationally predict the end properties of Poly(Ethylene Terephthalate) (PET) based components is of immense use to the packaging industry to reduce product development and lifecycle costs. One activity being undertaken prominently by the industry is the development of PET bottles to maximize the shelf life of beverage-filled bottles. This thesis deals with the development of a material model of PET for use in finite element simulation of blow molding. The mechanical behavior of PET is highly non-linear with temperature dependence, strain-rate dependence, molecular weight (Inherent Viscosity – IV) dependence, strain-state dependence and the tendency when induced by strain to crystallize. Uniaxial compression experiments were conducted on PET samples to characterize the temperature, strain-rate and IV dependence of stress-strain characteristics. The temperature range for the tests was 363K to 383K, the (true) strain rates used were 0.1/s and 1/s and the IVs of samples used were 0.80, 0.86, 0.92 and 0.98. The Dupaix-Boyce (DB) model (Dupaix, 2003) is a complex physically-based material model which can capture the viscoelastic, hyperelastic and plastic aspects of polymer mechanical behavior. This model was fit to the compression test results. Furthermore, uniaxial tension tests were conducted to check the predictive capability of the compression fit DB model in tension. The model under-predicted stress in tension and a different set of constants had to be used to fit the initial portion of the DB model stress strain results to the experimental curves. The temperature range for the tension tests was the same as for the compression tests while the strain rates used were 0.05/s, 0.1/s and 0.425/s engineering strain rate. The IVs used were 0.80, 0.92 and 0.98. A major observation from the uniaxial tension tests was the inability of the DB model to capture drastic strain hardening associated with strain-induced crystallization. Th (open full item for complete abstract)

Committee: Rebecca Dupaix (Advisor); Brain Harper (Committee Member) Subjects: Mechanical Engineering; Polymers

PHD, Kent State University, 2014, College of Arts and Sciences / Chemical Physics

In this Dissertation, we study a nanosecond electro-optic response of a nematic liquid crystal in a geometry where an applied electric field E modifies the tensor order parameter but does not change the orientation of the optic axis (director N). We use nematics with negative dielectric anisotropy with the electric field applied perpendicularly to N. The field changes the dielectric tensor at optical frequencies (optic tensor), due to the following mechanisms: (a) nanosecond creation of biaxial orientational order; (b) uniaxial modification of the orientational order that occurs over the timescales of tens of nanoseconds, and (c) quenching of director fluctuations with a wide range of characteristic times up to milliseconds. We develop a model to describe the dynamics of all three mechanisms. We design the experimental conditions to selectively suppress the contributions from the quenching of director fluctuations (c) and from the biaxial order effect (a) and thus, separate the contributions of the three mechanisms in the electro-optic response. As a result, the experimental data can be well fitted with the model parameters. The analysis provides a rather detailed physical picture of how the liquid crystal responds to a strong electric field, E ~ 108 V/m, on a timescale of nanoseconds. This work provides a useful guide in the current search of the biaxial nematic phase. Namely, the temperature dependence of the biaxial susceptibility allows one to estimate the temperature of the potential uniaxial-to-biaxial phase transition. An analysis of the quenching of director fluctuations indicates that on a timescale of nanoseconds, the classic model with constant viscoelastic material parameters might reach its limit of validity. The effect of nanosecond electric modification of the order parameter (NEMOP) can be used in applications in which one needs to achieve ultrafast (nanosecond) changes of optical characteristics, such as birefringence.

Committee: Oleg Lavrentovich DSc (Advisor); Sergij Shiyanovskii DSc (Advisor) Subjects: Condensed Matter Physics; Experiments; Materials Science; Optics; Physics

Doctor of Philosophy, University of Akron, 2013, Civil Engineering

With major breakthroughs in material science in recent years, civil engineering construction technology has simultaneously gone through major paradigm shifts. From the conventional reinforcing material like steel, we witnessed the introduction of fiber reinforced polymer bars (FRP), fiber reinforced polymer wraps and multitudes of chopped reinforcing fiber materials, metallic and synthetic in recent times. This dissertation covers a comprehensive research program that was undertaken at the University of Akron for the mechanical and structural characterization of concrete reinforced with new type of reinforcing fiber material, called as Basalt minibar. Basalt minibar is a non-corrosive structural macro fiber made from basalt fiber reinforced polymer (BFRP) bars. It is manufactured using a simplified automated method called wet-ley up process. Basalt mini-bar possesses higher tensile strength and stiffness compared to other standard synthetic fibers and at the meantime it is non-corrosive. Fibers act as the proactive reinforcement that provides the immediate tensile load carrying capacity as soon as micro cracks develop in concrete. Fiber reinforcement can be used as the proactive load carrying element and can also be used as supportive reinforcement to control issues like shrinkage in concrete. This demands for a type of a material which is durable, has adequate strength and stiffness to impart sufficient toughness to the structure and can mix well with concrete, developing good bond strength. The primary motivation behind the research is to characterize Basalt mini-bar as a new hybrid-material which possesses the beneficial features of both metallic and synthetic fiber. The overall goal of the project was achieved through tensile strength characterization of Basalt fiber reinforced polymer (BFRP) bars, followed by mechanical and toughness characterization of minibar and minibar reinforced concrete (MRC), leading to strength characterization of minibar reinfor (open full item for complete abstract)

Committee: Anil Patnaik Dr. (Advisor); William Schneider Dr. (Committee Member); Craig Menzemer Dr. (Committee Member); Joe Payer Dr. (Committee Member); Robert Schwartz Dr. (Committee Member) Subjects: Civil Engineering

PhD, University of Cincinnati, 2009, Engineering : Materials Science

Controlling the extent of nano-lamellar crystalline orientation is of great interest in polymer processes because an inexpensive plastic film can be converted into a higher valued film of dramatically improved properties. Where high degrees of uniaxial orientation are required, the polymer is typically oriented in a solid state drawing post-processing operation, where the polymer is stretched in a single direction at temperatures just below the melting point. One commercial example, currently drawing wide interest in the polymer processing field, is known as machine direction orientation (MDO). During this process, pre-existing nano-crystallites are transformed into rigid, anisotropic structures. The presence of these rigid structures significantly enhances the moduli and break strength of the polymer film. A direct connection can be formed between the polymer's analytic characteristics, MDO processing conditions and the final engineering properties of the film. Within this dissertation are: Structure-property model applicable to a wide variety of polymers that predicts critical properties of the oriented film. Process model that estimates the film temperature throughout the orientation process, a necessity for relating the effects of processing conditions to the properties of the film. Experimental examples of the use of the structure-property model, which provides a detailed description of the structural changes that are occurring during orientation. This dissertation provides several comprehensive tools for the understanding and the modeling the process-structure-property relationship of oriented polymer films. A universal structure-property model has been developed that predicts the critical properties of a wide range of oriented polymer films. A heat transfer model has also been developed that estimates the film temperature throughout the orientation process. This model can be used in conjunction with the fiber/non-fibrous gel model to understand the eff (open full item for complete abstract)

Committee: Gregory Beaucage PhD (Committee Chair); Jude Iroh PhD (Committee Member); Stephen Clarson PhD (Committee Member); Vassilios Galiatsatos PhD (Committee Member) Subjects: Materials Science; Polymers

MS, University of Cincinnati, 2005, Engineering : Materials Science

Polyethylene films are a major component in today's flexible packaging and are made with the most widely used polymer in the world. The selection of polyethylene films is the direct result of their balance of cost, processing, and physical properties. To take full advantage of this balance, the effects of the operating parameters of the film fabrication process must be understood in an effort to optimize the relationship between processing and physical properties. Of particular interest to the design of most packages is controlling the degree of molecular orientation in a film. This characteristic is generally determined by selecting the proper polymer, film fabrication process (e.g. cast vs. blown), and the ideal operating conditions (cast quench rate, blown high stalk, blown in-the-pocket, etc.) to produce a film with the desired degree of orientation. For the case where extremely high degrees of uniaxial orientation are required, the fabricated film is typically oriented in a “solid state” drawing process, where the quenched film is stretched in a given direction at temperatures below that of the melting point of the polymer. During this process, the stacked lamellae that form during the film fabrication process are transformed into rigid, long fiber-like structures. The presence of these rigid structures produce films with significantly enhanced moduli, break strengths, and optical properties. The goal of this program is to characterize the films with the intent of modeling the transformation of lamellae into fibers and predicting the previously mentioned physical properties. By doing so, a connection can be formed between the polymer's characteristics and the final film properties, resulting in the fabrication of films that are unique to the industry.

Committee: Dr. Gregory Beaucage (Advisor) Subjects:

Master of Science, The Ohio State University, 2009, Industrial and Systems Engineering

The increase in using Advanced High Strength Steel (AHSS) and aluminum sheet materials is accompanied by many challenges in forming these alloys due to their unique mechanical properties and/or low formability. Therefore, developing a fundamental understanding of the mechanical properties of AHSS, as compared to conventional Draw Quality Steel (DQS), is critical to successful process/ tools design. Also, alternative forming operations, such as warm forming or sheet hydroforming, are potential solutions for the low formability problem of aluminum alloys. In this study, room temperature uniaxial tensile and biaxial Viscous Pressure Bulge (VPB) tests were conducted for five AHSS sheet materials; DP 600, DP 780, DP 780-CR, DP 780-HY, and TRIP 780, and the resulting flow stress curves were compared. Strain ratios (R-values) were also determined in the tensile test and used to correct the biaxial flow stress curves for anisotropy. The pressure vs. dome height raw data in the VPB test was extrapolated to the burst pressure to obtain the flow stress curve up to fracture. Results of this work show that flow stress data can be obtained to higher strain values under biaxial state of stress. Moreover, it was observed that some materials behave differently if subjected to different state of stress. These two conclusions, and the fact that the state of stress in actual stamping processes is almost always biaxial, suggest that the bulge test is a more suitable test for obtaining the flow stress of AHSS sheet materials to be used as an input to FE models. An alternative methodology for obtaining the flow stress from the bulge test data, based on FE-optimization, was also applied and shown to work well for the AHSS sheet materials tested. Elevated temperature bulge tests were made for three aluminum alloys; AA5754-O, AA5182-O, and AA3003-O, using a special machine where the tools and specimen are submerged in a fluid heated to the required temperature. Several challenges were faced (open full item for complete abstract)

Committee: Taylan Altan (Advisor); Jerald Brevick (Committee Member) Subjects: Automotive Materials; Engineering; Industrial Engineering; Materials Science; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2008, Electrical and Computer Engineering

Extraordinary properties found in engineered metamaterials have drawn great interest as they can address industry demands for small, light-weight, and multifunctional devices. It is not therefore surprising that a variety of artificial materials are being widely considered for various radio frequency (RF) applications. Among these metamaterials, a recently introduced class of anisotropic photonic crystals, namely magnetic photonic (MPC) and degenerate band edge (DBE) crystals, has been shown to exhibit unique propagation modes as compared to regular periodic assemblies. For the first time, this dissertation carries out computational and experimental analysis of these new crystals for specific RF applications. Our ultimate goal is to develop high gain antenna apertures and miniature footprint antennas. In this context, this dissertation begins by establishing an understanding of the fundamental electromagnetic properties of 1D DBE and MPC crystals using the transfer matrix and spectral domain method of moments (MoM) computations. This is followed by numerical characterization of 3D DBE crystals via surface integral equations. Upon successful demonstration of the DBE mode for improved antenna performance, a measurement setup is presented to characterize low loss uniaxial materials. Subsequently, Specifically, a finite DBE assembly is built and shown to exhibit large aperture efficiency for conformal high gain antenna applications. The second half of the dissertation introduces a novel coupled transmission line concept capable of emulating DBE mode on otherwise uniform microwave substrates. Using this novel dual transmission line concept, we present examples of several small antennas on low and high contrast substrates, and fabricate a prototype to experimentally verify the printed slow wave concepts. The measured DBE antenna is shown to perform better than other recently published metamaterial antennas. It is therefore very attractive for several RF applications requi (open full item for complete abstract)

Committee: John Volakis L (Advisor); Jin-Fa Lee (Committee Member); Roberto Rojas G (Committee Member); Kubilay Sertel (Committee Member) Subjects: Electrical Engineering; Electromagnetism

Doctor of Philosophy, The Ohio State University, 2007, Mechanical Engineering

An accelerated method for determining the fatigue stress versus cycle life (S-N) behavior of isotropic materials is developed for prediction of axial (tension-compression), bending, shear, and multi-axial fatigue life at various stress ratios. The framework for this accelerated method was developed in accordance with a previous understanding of a strain energy and fatigue life correlation, which states: the total strain energy dissipated during a monotonic fracture and a cyclic process is the same material property, where each can be determined by measuring the area underneath the monotonic true stress-strain curve and the area within a hysteresis loop, respectively. The developed framework consists of the following six elements: (1) New experimental procedures used to acquire more sufficient uniaxial and multi-axial test results than conventional methods, (2) an analytical representation for the effect of the stress gradient through the fatigue zone, thus providing capability for bending fatigue prediction, (3) the effect of mean stress on fatigue life for tension/compression and bending, (4) development of an improved energy-based prediction criterion for shear loading at various stress ratios, (5) fatigue life prediction for materials experiencing the endurance limit phenomenon, and (6) the development of a multi-axial fatigue life prediction method. Validation of this accelerated fatigue life determination framework is achieved based on comparison with numerous experimental results acquired from Aluminum 6061-T6 and Titanium 6Al-4V. The results of the comparison are extremely encouraging, thus providing justification that the future direction for the strain-energy based fatigue life prediction method is very promising.

Committee: Mo-How Shen (Advisor) Subjects: Engineering, Mechanical

Master of Science (MS), Ohio University, 1988, Electrical Engineering & Computer Science (Engineering and Technology)

Anisotropic materials are widely used in optical fiber and integrated optics, raises a need for more theoretical research Previous work carried out on these materials which are either electrically or magnetically anisotropic; used one or more coordinate Systems [48], [49], proving it to be more than cumbersome, especially with coordinate transformation alone. This thesis used the famous coordinate-free approach in frequency domain invented by Chen [1] to study electromagnetic wave propagation from isotropic medium into magnetically uniaxial medium. By this method the tedious and difficult coordinate transformation is grealty reduced. Magnetically uniaxial medium is a special case of the magnetically anisotropic. It has a scalar permittivity, ε and a tensor permeability, [µ]; which is a three-by-three matrix with all off-diagonal elements being zeros, and two of the three on-diagonal elements equal. First the dispersion equation for the magnetically uniaxial material is derived and solved, followed by an introduction of its wave matrix to determine the directions of electric and magnetic fields. Then wave vectors, Brewster's angle, critical angle, energy relation, and total reflection are considered. Transmission and reflection coefficients are algebrically evaluated for certain orientation of the optic axis. To study the effect of anisotropy, the transmitted and reflected power and transmission and reflection coefficient are numerically evaluated and plotted versus the angle of incidence of the incident wave.

Committee: Hollis Chen (Advisor) Subjects:

Master of Science (MS), Ohio University, 1989, Electrical Engineering & Computer Science (Engineering and Technology)

Electromagnetic wave propagation in anisotropic uniaxial slab waveguide

Committee: Hollis Chen (Advisor) Subjects:

Master of Science (MS), Ohio University, 1981, Chemical Engineering (Engineering)

Mathematical modeling of converging fluid flow in the uniaxial die of the fixed boundary extrusion-orientation-crystallization process

Committee: John Collier (Advisor) Subjects: Engineering, Chemical

Master of Science (MS), Ohio University, 1995, Electrical Engineering & Computer Science (Engineering and Technology)

Wave reflection from a lossy uniaxial media

Committee: Hollis Chen (Advisor) Subjects:

Master of Science (MS), Ohio University, 1995, Electrical Engineering & Computer Science (Engineering and Technology)

Radiation from a small current loop in a magnetically uniaxial medium

Committee: Hollis Chen (Advisor) Subjects:

PHD, Kent State University, 2011, College of Arts and Sciences / Department of Physics

In addition to the simple calamitic mesogens, having cylindrically symmetric shape, there are more complex molecular associations formed by bridging of two molecules, e.g., via hydrogen bonding, that exhibit liquid crystal phases. In this dissertation research mesomorphic properties of two compounds namely, 4-[2, 3, 4-tri(octyloxy)phenylazo] benzoic acid (TOPAB) and 4-[2, 3, 4-tri(heptyloxy)phenylazo] benzoic acid (THPAB) and their mixtures with two simpler hydrogen bonding mesogens, 4-(4-octyloxy)benzoic acid (OOBA) and 4-(4-decyloxybenzoyloxy)benzoic acid (DBBA), were investigated using differential scanning calorimetry, polarizing optical microscopy, capacitance measurements, conoscopy, polarized Raman spectroscopy, and synchrotron x-ray scattering. Unusual x-ray scattering results, which prompted this investigation, are very different from other calamitic nematic phases. The small and large angle x-ray peaks are in the same direction while they are normally orthogonal to each other. Furthermore, similar materials have previously been considered as good candidates to exhibit the biaxial nematic phase. Contrary to normal expectations, x-ray results are not consistent with simple linear H-bonded dimer formation, as one normally would expect. In order to adequately explain the x-ray results, it is necessary to assume that oblique molecular associations in which the mesogens H-bond at approximately 67o and take on an average shape resembling a bent-core mesogen. Other techniques were employed to test if this was indeed the case and to determine if the system possessed biaxial order fluctuations or formed the biaxial nematic phase. Nematic uniaxial orientational order parameters P200 and P400 determined from x-ray diffraction and Raman measurements for TOPAB are in very good agreement: P200 = 0.52 – 0.68 and P400 = 0.12 – 0.30 from X-ray scattering; and P200 = 0.48 – 0.75 and P400 = 0.25 – 0.48 from Raman scattering. Capacitance and electro-optical measurements suppo (open full item for complete abstract)

Committee: Satyendra Kumar (Advisor) Subjects: Condensed Matter Physics

PHD, Kent State University, 2010, College of Arts and Sciences / Chemical Physics

The various homogeneous and inhomogeneous structures in liquid crystals (LCs) are often behind the interesting physical phenomena and practically useful properties. The ability to induce or control them with relatively weak electric fields makes LCs a desirable material for displays, optics, photonics and microfluidics applications. In the Dissertation, we studied the spontaneous, confinement or electric-field induced LC structures and their response to an applied electric field in nematic, cholesteric and smectic phases formed by rod-like (either achiral or chiral) and bent-core molecules. The main conclusions from this work are the following: First, we studied experimentally surface alignment, dielectric and optical properties and topological defects in thermotropic bent-core materials A131, C7 and C12, and found that observed features of these materials, such as anchoring transitions, dependence of splitting of isogyres in conoscopic images on applied electric fields or design of samples, stable isolated point defects (hedgehogs and boojums), are consistent with those of a uniaxial nematic in the entire temperature range of nematic phase. Secondly, using the fluorescence confocal polarizing microscopy for imaging the director field, we performed the first experimental studies of the scenario of layer undulations in a full three-dimensional lamellar system, represented by a short pitch cholesteric LC. We demonstrated that both qualitative and quantitative features of undulations strongly depend on the surface anchoring at the cell boundaries. We showed that the shape of undulating layers changes from sinusoidal at the onset of instabilities to zig-zag at moderate field and to the lattice of parabolic walls at high electric fields. Additionally, we demonstrated that the spatial modulation of an average refractive index resulted from layer undulations in cholesterics can be used for electric field controlled two-dimensional diffraction gratings. Finally, we describe (open full item for complete abstract)

Committee: Oleg Lavrentovich DSc (Advisor); Oleg Lavrentovich DSc (Committee Chair); Antal Jakli PhD (Committee Member); Deng-Ke Yang PhD (Committee Member); Samuel Sprunt PhD (Committee Member); David Allender PhD (Committee Member); Liang-Chy Chien PhD (Other); John Stalvey PhD (Other) Subjects: Optics; Physics