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University of Minnesota

1. Suri, Pranav Kumar. Static and Dynamic Electron Microscopy Investigations at the Atomic and Ultrafast Scales.

Degree: PhD, Material Science and Engineering, 2016, University of Minnesota

Advancements in the electron microscopy capabilities – aberration-corrected imaging, monochromatic spectroscopy, direct-electron detectors – have enabled routine visualization of atomic-scale processes with millisecond temporal resolutions in this decade. This, combined with progress in the transmission electron microscopy (TEM) specimen holder technology and nanofabrication techniques, allows comprehensive experiments on a wide range of materials in various phases via in situ methods. The development of ultrafast (sub-nanosecond) time-resolved TEM with ultrafast electron microscopy (UEM) has further pushed the envelope of in situ TEM to sub-nanosecond temporal resolution while maintaining sub-nanometer spatial resolution. A plethora of materials phenomena – including electron-phonon coupling, phonon transport, first-order phase transitions, bond rotation, plasmon dynamics, melting, and dopant atoms arrangement – are not yet clearly understood and could be benefitted with the current in situ TEM capabilities having atomic-level and ultrafast precision. Better understanding of these phenomena and intrinsic material dynamics (e.g. how phonons propagate in a material, what time-scales are involved in a first-order phase transition, how fast a material melts, where dopant atoms sit in a crystal) in new-generation and technologically important materials (e.g. two-dimensional layered materials, semiconductor and magnetic devices, rare-earth-element-free permanent magnets, unconventional superconductors) could bring a paradigm shift in their electronic, structural, magnetic, thermal and optical applications. Present research efforts, employing cutting-edge static and dynamic in situ electron microscopy resources at the University of Minnesota, are directed towards understanding the atomic-scale crystallographic structural transition and phonon transport in an iron-pnictide parent compound LaFeAsO, studying the mechanical stability of fast moving hard-drive heads in heat-assisted magnetic recording (HAMR) technology, exploring the possibility of ductile ceramics in magnesium oxide (MgO) nanomaterials, and revealing the atomic-structure of newly discovered rare-earth-element-free iron nitride (FeN) magnetic materials. Via atomic-resolution imaging and electron diffraction coupled with in situ TEM cooling on LaFeAsO, it was found that additional effects not related to the structural transition, namely dynamical scattering and electron channeling, can give signatures reminiscent of those typically associated with the symmetry change. UEM studies on LaFeAsO revealed direct, real-space imaging of the emergence and evolution of acoustic phonons and resolved dispersion behavior during propagation and scattering. Via UEM bright-field imaging, megahertz vibrational frequencies were observed upon laser-illumination in TEM specimens made out of HAMR devices which could be detrimental to their long-term thermal and structural reliability. Compression testing of 100-350 nm single-crystal MgO nanocubes…

Subjects/Keywords: dynamic TEM; high-resolution TEM; iron pnictides; static TEM; ultrafast electron microscopy; ultrafast TEM

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Suri, P. K. (2016). Static and Dynamic Electron Microscopy Investigations at the Atomic and Ultrafast Scales. (Doctoral Dissertation). University of Minnesota. Retrieved from http://hdl.handle.net/11299/182214

Chicago Manual of Style (16th Edition):

Suri, Pranav Kumar. “Static and Dynamic Electron Microscopy Investigations at the Atomic and Ultrafast Scales.” 2016. Doctoral Dissertation, University of Minnesota. Accessed August 25, 2019. http://hdl.handle.net/11299/182214.

MLA Handbook (7th Edition):

Suri, Pranav Kumar. “Static and Dynamic Electron Microscopy Investigations at the Atomic and Ultrafast Scales.” 2016. Web. 25 Aug 2019.

Vancouver:

Suri PK. Static and Dynamic Electron Microscopy Investigations at the Atomic and Ultrafast Scales. [Internet] [Doctoral dissertation]. University of Minnesota; 2016. [cited 2019 Aug 25]. Available from: http://hdl.handle.net/11299/182214.

Council of Science Editors:

Suri PK. Static and Dynamic Electron Microscopy Investigations at the Atomic and Ultrafast Scales. [Doctoral Dissertation]. University of Minnesota; 2016. Available from: http://hdl.handle.net/11299/182214


KTH

2. Leifsdotter, Josefine. Investigation of the micelle-to-vesicle transition in mixtures of an anionic and a cationic surfactant: the effect of adding salt.

Degree: Chemical Science and Engineering (CHE), 2012, KTH

Catanoinic systems spontaneously form micelles and vesicles, which are self-assembled spherical structures made up by surfactants. In the core of the micelle a drug, or other organic substance, can be kept to stabilize it when placed in an aqueous environment. The micelle-to-vesicle transition corresponds to the moment when the drug is releases, and understanding which factors that trigger this transition is thus of great interest for the pharmaceutical industry. In this study the micelle-to-vesicle transition in water and the effect of salt were studied for the systems 95 mol% SDS/DDAB and 95 mol% SDeS/DDAB with different total concentrations. The static light scattering measurements showed that the micelle-to-vesicle transition for the system 95 mol% SDS/DDAB was shifted to lower total concentrations both when 50 mM NaBr and 100 mM NaBr were added, and that the transition was unaffected by changing the anionic surfactant from SDS to SDeS when no salt had been added. A phase separation was observed when 50 mM NaBr was added to 95 mol% SDeS/DDAB (the Krafft point was probably reached), and when 100 mM NaBr was added to the same system the sample remained opaque one week after mixing the sample and also after heating it to 40°C in a water bath. The curve for sample 95 mol% SDS/DDAB 1/8192 mM + 100 mM NaBr was oscillating implying possible defects in the vesicle membrane. The cryo-TEM images confirmed the light scattering results and additionally showed that at higher total concentrations agglomeration occurred, while whenever salt was added less vesicles seemed to appear, while both discs and broken vesicles were present suggesting that the disc structure is preferred over the spherical structure when salt is present. Also a vesicle inside another vesicle was discovered for the sample 0.95 SDS/DDAB 3.75 mM + 50 mM NaBr. The mole fraction of anionic surfactant in the aggregates (x) was calculated using a MATLAB code based on the Poisson-Boltzmann theory. The results from the calculations showed that a higher amount of SOS was needed for the system 0.95 SOS/CTAB than the amount of SDS and SDeS needed for the systems 0.95 SDS/DDAB and 0.95 SDeS/DDAB when forming aggregates, indicating that a shorter chain of the anion and the higher spontaneous curvature of the cation leads to a higher curvature. Also a larger amount of cation was needed when the tail was single than when it was double in order to form stable spherical structures. Finally, as the total concentration decreased the x value also decreased in all cases, thus the spontaneous curvature was decreased.

Subjects/Keywords: SDS; DDAB; NaBr; Static light scattering; cryo-TEM; drug delivery; perforated vesicles; Krafft point

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Leifsdotter, J. (2012). Investigation of the micelle-to-vesicle transition in mixtures of an anionic and a cationic surfactant: the effect of adding salt. (Thesis). KTH. Retrieved from http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-158474

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Leifsdotter, Josefine. “Investigation of the micelle-to-vesicle transition in mixtures of an anionic and a cationic surfactant: the effect of adding salt.” 2012. Thesis, KTH. Accessed August 25, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-158474.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Leifsdotter, Josefine. “Investigation of the micelle-to-vesicle transition in mixtures of an anionic and a cationic surfactant: the effect of adding salt.” 2012. Web. 25 Aug 2019.

Vancouver:

Leifsdotter J. Investigation of the micelle-to-vesicle transition in mixtures of an anionic and a cationic surfactant: the effect of adding salt. [Internet] [Thesis]. KTH; 2012. [cited 2019 Aug 25]. Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-158474.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Leifsdotter J. Investigation of the micelle-to-vesicle transition in mixtures of an anionic and a cationic surfactant: the effect of adding salt. [Thesis]. KTH; 2012. Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-158474

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


University of Illinois – Urbana-Champaign

3. Lee, Shih-hao. Efficient Finite Element Electromagnetic Analysis for High-Frequency/High-Speed Circuits And Multiconductor Transmission Lines.

Degree: PhD, Electrical and Computer Engineering, 2009, University of Illinois – Urbana-Champaign

This dissertation comprises the following four components. (1) Development of a robust and efficient 3-D finite element electromagnetic field solver with high-order vector elements for high-frequency and high-speed circuit simulations. The solver supports wave port and lumped port excitations as well as the incorporation of lumped networks and circuit models in a distributed finite element model. An adaptive multipoint model order reduction method is developed for fast broadband analysis. (2) Development of a fast and accurate multiconductor transmission line simulator and parameter extractor with improved model order reduction techniques. A methodology is further proposed for a combined quasi-TEM and full-wave transmission line analysis, which possesses their respective advantages and ensures full-wave accuracy from DC to very high frequencies. The transmission line analysis also takes into account the frequency dependence of dielectric materials. (3) Study of the low-frequency instability problem in the 3-D full-wave finite element simulation. The tree-cotree splitting is combined with several other techniques to improve the matrix conditioning and extend full-wave solutions down to very low frequencies for a more robust broadband characterization of high-speed digital circuits. (4) A combined domain decomposition–model order reduction (DD–MOR) method for efficient full-wave analysis of interconnections in multilayer printed circuit boards. The method not only brings a significant enhancement to computational efficiency while maintaining full-wave accuracy, but also provides great flexibility in the finite element mesh generation. Advisors/Committee Members: Jin, Jianming (advisor), Jin, Jianming (Committee Chair), Cangellaris, Andreas C. (committee member), Schutt-Ainé, José E. (committee member), Feng, Milton (committee member).

Subjects/Keywords: electromagnetics; microwave; finite element method (FEM); nodal elements; vector elements; edge elements; higher-order elements; triangular elements; tetrahedral elements; finite element analysis; full-wave analysis; impedance boundary condition; port boundary condition; wave port; lumped port; deembedding; thin-wire approximation; thin wire modeling; internal impedance; lumped elements; lumped circuits; field-circuit simulation; EM-circuit simulation; stamping; reduced-order modeling; model order reduction (MOR); fast frequency sweep; solution space projection (SSP); quasi-static analysis; quasi-TEM analysis; generalized eigenproblem; Lanczos algorithm; modal analysis; eigenanalysis; frequency-dependent media; anisotropic media; Debye model; multiconductor transmission lines; transmission line parameters; frequency-dependent losses; conductor loss; dielectric loss; substrate loss; characteristic impedance; skin effect; proximity effect; parameter extraction; resistance; inductance; capacitance; conductance; per-unit-length; composite conductors; waveguide; filter; coplanar waveguide (CPW); striplines; microstrip lines; high-frequency circuits; RF circuits; high-speed circuits; tree-cotree splitting; low-frequency breakdown; low-frequency instability; preconditioning; bonding wire; printed circuit board; multilayer printed circuit board (PCB); via-holes; signal integrity; electromagnetic coupling; interconnects; domain decomposition; Approximate Modal Interface (AMI); Approximate Modal Interface–Solution Space Projection (AMI–SSP); domain decomposition–model order reduction (DD–MOR); computer-aided design (CAD)

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Lee, S. (2009). Efficient Finite Element Electromagnetic Analysis for High-Frequency/High-Speed Circuits And Multiconductor Transmission Lines. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/11987

Chicago Manual of Style (16th Edition):

Lee, Shih-hao. “Efficient Finite Element Electromagnetic Analysis for High-Frequency/High-Speed Circuits And Multiconductor Transmission Lines.” 2009. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed August 25, 2019. http://hdl.handle.net/2142/11987.

MLA Handbook (7th Edition):

Lee, Shih-hao. “Efficient Finite Element Electromagnetic Analysis for High-Frequency/High-Speed Circuits And Multiconductor Transmission Lines.” 2009. Web. 25 Aug 2019.

Vancouver:

Lee S. Efficient Finite Element Electromagnetic Analysis for High-Frequency/High-Speed Circuits And Multiconductor Transmission Lines. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2009. [cited 2019 Aug 25]. Available from: http://hdl.handle.net/2142/11987.

Council of Science Editors:

Lee S. Efficient Finite Element Electromagnetic Analysis for High-Frequency/High-Speed Circuits And Multiconductor Transmission Lines. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2009. Available from: http://hdl.handle.net/2142/11987

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