Thesis (M.S.)--Rochester Institute of Technology, 2005. / Typescript. Includes bibliographical references (leaves 100-104).

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Thesis advisor: Brian B. Zhou / This thesis presents work in the context of multimodal magnetometry for two-dimensional (2d) materials. Research on van der Waals materials has been rapidly emerging and several imaging techniques have been developed in the past decades. Among the modern techniques, solid-state spins feature outstanding sensitivity and nano-scale spatial resolution. Yet their full capacity in sensing still has room for improvement, as the quantum nature of their properties haven't been fully utilized. My research involves developing state-of-the-art sensing techniques to add new `function modules' to the nitrogen-vacancy (NV) centers, with the goal of uncovering dynamical magnetic and electrical phenomena of 2d materials. In the first chapter I will briefly discuss the basic opto-spin properties of the NV center. One shall see why NV is preferred as a quantum sensing probe: the opto-spin property comes handy as one simply counts photons to manipulate and read out quantum states, and the stability and long quantum coherence time makes NV adaptive with various environments and engineering. In the second chapter I will discuss the experimental setup with the focus on the home-built confocal microscope, which equips our sensing technique with the pump-probe scanning ability of sub-um 2d resolution. In the third chapter I will discuss the developments of the sensing protocols, including the ac susceptometry and the opto-magnetization mapping, based on the lock-in method using the quantum dynamical decoupling sequences. In the fourth chapter I will describe the ac susceptibility measurements on thin CrBr3 flakes. The magnetization behaviors under kHz to MHz excitations reveal the domain morphology and domain wall mobility, providing insights to the exchange interaction of the chromium trihalides in the 2d limit. In the fifth chapter I will describe the pump-probe measurements on few-layer CrCl3 flakes. The mapping result demonstrates a photo-generated enhancement of the in-plane magnetization. Along with the time-resolved photoluminescence measurement, the results are indicative of a defect-assisted Auger recombination process of excitons. To conclude, the multimodal sensing techniques with NV developed in this thesis allow for more versatile experiments with sensitivity for low-dimensional systems. The developments bring up new perspectives on fundamental physics in atomically thin materials, providing new ideas for future technological applications such as spintronics and quantum memory. / Thesis (PhD) — Boston College, 2024. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

Approved for public release; distribution is unlimited / The thesis deals with the detection and tracking of dim point targets in infrared images. Research topics include image process modeling with adaptive two-dimensional Least Mean Square (LMS) and Recursive Least Squares (RLS) prediction filters. Target detection is performed by significance testing the prediction error residual. A pulse tracker is developed which may be adjusted to discriminate target dynamics. The methods are applicable to detection and tracking in other spectral bands. / http://archive.org/details/adaptivedimpoint00dema / Major, United States Marine Corps

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Darbo esmė giliau pažvelgti į brūkšninių kodų rūšis, panaudojimo galimybes ir išsiaiškinti jų privalumus bei trūkumus. Darbo tikslas išnagrinėti QR brūkšninio kodo sandarą, kiekvienos sudedamos dalies svarbą ir savybes. Taip pat sukurti programinę įrangą QR kodo lokalizavimui vaize ir palyginti su praktikoje naudojamais produktais. / This paper investigates different barcodes, use cases, advantages and disadvantages. Aim of this paper is to analyse stucture and characteristics of QR code, develop software to locate QR code in picture, compare results with other software.

The ability to effectively analyze particulate matter (PM2.5) in air is becoming increasingly pertinent. Allen Goldstein of the University of California in Berkeley is studying the semi-volatile fraction of organic compounds in PM2.5 through the use of the thermal desorption aerosol gas chromatograph (TAG) system. However, as conventional GC does not provide adequate separation power, the development of comprehensive two-dimensional gas chromatography (GC × GC) was required. GC × GC works more effectively by utilizing a modulator that periodically traps and focuses analytes from a primary column onto a secondary column. This allows for the primary and secondary columns to separate the analytes based on two different properties. This report focuses on the continuing study and enhancement of a modulator designed by Ognjen Panić during his Masters project. Improving and testing the robustness of this dual stage modulator was originally the focus of this project. However, this study led to the development of a single stage modulator. In addition to that, the effect of modulator characteristics such as length of the restriction, total length of the modulator and wall thickness on the modulator performance were studied. A robustness test of the single stage modulator was also completed. Experiments conducted tested the characteristics of the new modulator to ensure it performed effectively and would satisfy the requirements of the TAG system. A study comparing the sensitivity of conventional gas chromatography and GC × GC was also preformed. The sensitivity of GC × GC was on average an order of magnitude better than that of 1D GC.

In this dissertation we used tunable particle-particle and particle-substrate attraction to achieve reversible two-dimensional crystallization of colloids on homogeneous and patterned substrates. Total internal reflection and video microscopy techniques were used to quantify the interparticle and particle-substrate interactions in these colloidal systems. Equilibrium and dynamic simulations were then utilized to link these colloidal interactions to the experimental colloidal phase behaviour. The importance of the nature of the attractive interaction in successfully crystallizing colloids has also been documented. The first set of experiments demonstrates the use of temperature and specific ion effects to reversibly control the net particle-substrate van der Waals (vdW) attraction. Colloidal stabilization was achieved via the use of adsorbed polymer brush layers. By using evanescent wave microscopy, we directly and precisely measured how temperature and specific ion effects control the dimensions of adsorbed polymer layers and hence the net van der Waals attraction in between the colloids and the substrate. However, the magnitude of the van der Waals attraction decays very rapidly with increasing surface separation and is therefore not conducive to the self assembly of colloidal crystals. We successfully used thermoresponsive polymer nanoparticles to control the depletion attraction between micron sized silica particles and thereby induced reversible crystallization of the micron sized silica colloids on homogeneous substrates. Video and evanescent wave microscopy techniques were used to measure the nanoparticle-induced attractive interaction as a function of temperature. The experimentally observed phase behaviour was verified via simulations that utilized knowledge of the measured colloidal depletion interactions. Finally, patterned surface topologies were used to position attractive colloidal crystals. Simulations were used to link the measured colloidal interactions to experimental phase behaviour as well as substrate topology. An extension of the concepts developed in this dissertation might suggest a general strategy to assemble colloidal particles into robust and annealable crystals contributing to the fabrication of photonic bandgap materials.