Physical Sciences and Mathematics Commons^™

ผลของแอโรมาติกพอลิเอสเทอร์พอลิออลต่อสมบัติของโฟมพอลิไอโซไซยานูเรตแบบแข็ง, สุวมิตร เชื่อมชิต

Chulalongkorn University Theses and Dissertations (Chula ETD)

งานวิจัยนี้ศึกษาผลจากการใช้แอโรมาติกพอลิเอสเทอร์พอลิออลสองชนิด คือ พอลิออล A และพอลิออล B เป็นองค์ประกอบหลักต่อสมบัติของโฟมพอลิไอโซไซยานูเรตแบบแข็ง โดยพอลิออล A และพอลิออล B มีค่าหมู่ไฮดรอกซิลต่างกัน คือ 220 และ 350 mg.KOH/g ตามลำดับ เตรียมโฟมด้วยดัชนีไอโซไซยาเนตที่ 250, 280 และ 300 ศึกษาเวลาที่ใช้ในการเกิดปฏิกิริยา คือ เวลาที่สารผสมเป็นครีม เวลาที่สารผสมเป็นเจล เวลาที่โฟมหยุดฟู และเวลาที่ผิวหน้าของโฟมไม่เกาะติดกับผิวสัมผัสของวัสดุ สมบัติเชิงกายภาพและสมบัติเชิงกลของโฟมที่ศึกษามีดังนี้ คือ ความหนาแน่น การเปลี่ยนแปลงของหมู่ไอโซไซยาเนตและอัตราส่วนระหว่างหมู่ไอโซไซยานูเรตและหมู่ยูรีเทน ความต้านทานต่อแรงกดอัด สัณฐานวิทยา เสถียรภาพทางความร้อน ค่าการนำความร้อน และสมบัติการป้องกันการลามไฟ จากการศึกษาพบว่าโฟมพอลิไอโซไซยานูเรตที่เตรียมจากพอลิออล B สูตร F6 ที่ดัชนีไอโซไซยาเนต 280 มีสมบัติที่ใกล้เคียงกับเป้าหมายที่ต้องการ คือ ความหนาแน่น 35-40 kg/m3 ค่าการนำความร้อนที่น้อยกว่าหรือเท่ากับ 0.023 W/mK และผ่านการทดสอบมาตรฐานการลามไฟ DIN 4102-B2 ดังนั้น สูตรการผลิตโฟมจากพอลิออล B สูตร F6 ที่ดัชนี 280 มีความเป็นไปได้ที่จะนำไปใช้ในงานเชิงอุตสาหกรรม

Historical Trends In Air Temperature, Precipitation, And Runoff Of A Plateau Inland River Watershed In North China, Along Zhang, Ruizhong Gao, Xixi Wang, Tingxi Liu, Lijing Fang

Civil & Environmental Engineering Faculty Publications

Understanding historical trends in temperature, precipitation, and runoff is important but incomplete for developing adaptive measures to climate change to sustain fragile ecosystems in cold and arid regions, including the Balagaer River watershed on the Mongolian Plateau of northeast China. The objective of this study was to detect such trends in this watershed from 1959 to 2017. The detection was accomplished using a Mann-Kendall sudden change approach at annual and seasonal time scales. The results indicated that the abrupt changes in temperature preceded that in either runoff or precipitation; these abrupt changes occurred between 1970 and 2004. Significant (α = …

Computational Fluid Dynamics Study Of The Effects Of Secondary Flows In 90-Degree Pipe Elbow Erosion, O. Ayala, G. Rivera-Hernández, C. Knight

Engineering Technology Faculty Publications

Computational fluid dynamics (CFD) of particle-laden fluid flows through a 90-degree pipe elbow at Reynolds numbers 1,000 and 10,000 were completed; for different dimensionless elbow curvature ratios of 1.0, 1.5, and 2.5; and for particles with different Stokes numbers of 0.01, 0.1, 0.5, 1.0, 5.0, and 10.0. There were two scenarios in the study. For the first, the particles felt drag from the primary (or the axial) flow as well as from the secondary fluid flows in the elbow. For the second, the secondary fluid flow in the 90-degree bend was suppressed from the particle drag, thus the particles only …

Singlet Fission In A Hexacene Dimer: Energetics Dictate Dynamics, Samuel N. Sanders, Elango Kumarasamy, Kealan J. Fallon, Matthew Y. Sfeir, Luis M. Campos

Publications and Research

Singlet fission (SF) is an exciton multiplication process with the potential to raise the efficiency limit of single junction solar cells from 33% to up to 45%. Most chromophores generally undergo SF as solid-state crystals. However, when such molecules are covalently coupled, the dimers can be used as model systems to study fundamental photophysical dynamics where a singlet exciton splits into two triplet excitons within individual molecules. Here we report the synthesis and photophysical characterization of singlet fission of a hexacene dimer. Comparing the hexacene dimer to analogous tetracene and pentacene dimers reveals that excess exoergicity slows down singlet fission, …

Double Inclusive Small-X Gluon Production And Their Azimuthal Correlations In A Biased Ensemble, Gary Kapilevich

Publications and Research

We consider double gg → g production in the presence of a bias on the unintegrated gluon distribution of the colliding hadrons or nuclei. Such bias could be due to the selection of configurations with a greater number of gluons or higher mean transverse momentum squared or, more generally, due to a modified spectral shape of the gluon distribution in the hadrons. Hence, we consider reweighted functional averages over the stochastic ensemble of small-x gluons. We evaluate explicitly the double inclusive gluon transverse momentum spectrum in high-energy collisions, and their azimuthal correlations, for a few simple examples of biases.

"Lagrangian Disks" In M-Theory, Sebastián Franco, Sergei Gukov, Sangmin Lee, Rak-Kyeong Seong, James Sparks

Publications and Research

While the study of bordered (pseudo-)holomorphic curves with boundary on Lagrangian submanifolds has a long history, a similar problem that involves (special) Lagrangian submanifolds with boundary on complex surfaces appears to be largely overlooked in both physics and math literature. We relate this problem to geometry of coassociative submanifolds in G₂ holonomy spaces and to Spin(7) metrics on 8-manifolds with T² fibrations. As an application to physics, we propose a large class of brane models in type IIA string theory that generalize brane brick models on the one hand and 2d theories T[M₄] on …

Investigating The Time Scales Of Electromechanical Motion In Graphene Drumheads Using Pump-Probe Spectroscopy With Stm, Alana P. Gudinas

Honors Theses and Capstones

Scanning tunneling microscopy (STM) has transformed the field of condensed matter physics over the past few decades, allowing scientists to image materials at the atmomic scale, manipulate individual atoms, and probe electronic states on the surface of materials. In recent years, there have been numerous developments to introduce time-resolved measurements to STM in order to probe atomic-scale dynamic processes and combine spatial and temporal resolution. Advances like THz-STM setups achieve femtosecond resolution, but require complex external setups. All-electronic pump-probe spectroscopy for STM (directly analogous to optical pump-probe spectroscopy) has been pioneered by Loth et al., and newer applications (Natterer et …

Decreasing Uncertainty In Nuclear Magnetic Resonance Measurements Through The Application Of Pappus Chains, Ryan Williams

Honors Theses and Capstones

To make further advancements in nuclear polarization, the Dynamic Nuclear Polarization Group at the University of New Hampshire requires an accurate measurement of the polarization of their materials. Through a non-traditional method of data analysis, the uncertainty in this polarization measurement via Nuclear Magnetic Resonance (NMR) was reduced. To extract the polarization, we measure an NMR signal through the real impedance of our circuitry, whose area is proportional to the polarization. However, our signal size depends on how in-tune our circuitry is with a specific frequency, with the signal growing smaller the less in-tune it becomes. A new method of …

Quantifying Electron Precipitation In The Van Allen Radiation Belts, Timothy Raeder

Honors Theses and Capstones

The spatial and temporal distribution of high energy electron precipitation from the Van Allen radiation belts is not currently well-understood. The FIREBIRD-II mission (2015-present) and the Van Allen Probes (2012-2019) provide a unique opportunity to examine the behaviors and drivers of high energy electron precipitation. This study quantifies electron precipitation observed by FIREBIRD-II as a function of radial distance (L-shell), magnetic local time (MLT), hemisphere, and geomagnetic indices (Kp). Electron precipitation was observed to peak at L-shell 4.5-5. Regions of elevated electron precipitation were identified at L-shell 4-6 at dawn (MLT 6-9) and dusk (MLT 15-21). Hemisphere filtering indicated very …

A Content Analysis-Based Approach To Explore Simulation Verification And Identify Its Current Challenges, Christopher J. Lynch, Saikou Y. Diallo, Hamdi Kavak, Jose J. Padilla

VMASC Publications

Verification is a crucial process to facilitate the identification and removal of errors within simulations. This study explores semantic changes to the concept of simulation verification over the past six decades using a data-supported, automated content analysis approach. We collect and utilize a corpus of 4,047 peer-reviewed Modeling and Simulation (M&S) publications dealing with a wide range of studies of simulation verification from 1963 to 2015. We group the selected papers by decade of publication to provide insights and explore the corpus from four perspectives: (i) the positioning of prominent concepts across the corpus as a whole; (ii) a comparison …

Method Development For The Analysis Of Fatty Acids In Adipose Tissue Using Stir Bar Sorptive Extraction Coupled With Gas Chromatography-Mass Spectrometry, Angela Marisol Encerrado Manriquez

Open Access Theses & Dissertations

The project was aimed to develop an easy and sensitive analytical tool to study the role of fatty acids (FAs) profile in periprostatic adipose tissue (PPAT) and prostate cancer (PCa). PCa is the second leading cause of cancer-related death among American men. Although obesity has been mostly ruled out by many researchers as a risk factor for developing PCa, it has shown to be associated with PCa metastasis and progression. Periprostatic adipose tissue, which was present on 48% of prostatic surfaces, has been reported to act as energy sources for facilitating a positive microenvironment for PCa tumor progression. To understand …

Mathematical Modeling Of Microemulsification Processes, Numerical Simulations And Applications To Drug Delivery, Ogochukwu Nneka Ifeacho

Open Access Theses & Dissertations

Microemulsion systems are a great pharmaceutical tool for the delivery of formulations containing multiple hydrophilic and hydrophobic ingredients of varying physicochemical properties. These systems are gaining popularity because of its long shelf life, improved drug solubilisation capacity, easy preparation and improvement of bioavailability. Despite the advantages associated with the use of microemulsion systems in pharmaceutical industries, the major challenge impeding their use has been and continues to be the lack of understanding of these systems.

Microemulsions can be mathematically modeled by an initial boundary value problem involving a sixth order nonlinear time dependent equation. In this Thesis, we present a …

Reconciling Carbon Flux Discrepancies In A Desert Environment: Characterizing Influences Of Soil Processes Using Automated Co2 Flux Chambers, Alejandro Lara

Open Access Theses & Dissertations

Dryland ecosystems play a fundamental role in controlling the balance of carbon on a global scale. These ecosystems dominate the inter-annual variability of carbon uptake by terrestrial ecosystems, and this is driven by temperature and precipitation patterns. Despite this global importance, there are some important discrepancies that have been reported between CO2 fluxes measured with differing techniques, particularly between eddy covariance tower measurements of net ecosystem exchange (NEE) of carbon (C) versus on-the-ground methods such as chambers and biomass surveys. The discrepancy is a consequence of instrumentation and measurement technique differences; yet, its biological origins remain unknown. The goal of …

Using Machine Learning On An Imbalanced Cancer Dataset, James Ekow Arthur

Open Access Theses & Dissertations

With an estimated 1.4 million cancer diagnosis worldwide and the increasing death of cancer patients. It is prudent to investigate methods, approaches and smarter ways of predicting and diagnosing of cancer so that a holistic techniques can be used to curb or reduce false predictions , increase exact predictions and also meticulos prognosis information .

Can a feasible technique be developed for the general problem of prognosis and diagnosis of cancer be developed ?

We will show here that this problem of cancer prognosis and diagnosis can be efficiently tackled with the aid of machine learning techniques and the best, …

Development Of Software Tools And Experimental In Situ Electron Spin Resonance For Characterizing The Magnetic And Electrocatalytic Properties Of Transition Metal Chalcogenide Crystals, Jose Armando Delgado

Open Access Theses & Dissertations

Studying the magnetic properties and crystal defects of transition metal chalcogenide crystals is of paramount importance for utilizing them for next generation spintronics devices and hydrogen evolution reaction catalysts. Hydrothermally grown transition metal chalcogenide nanocrystals (MoS2, Ru2S3, Rh2S3, Co2S8) were chosen as catalysts for the hydrogen evolution reaction due to their low dimensionality and previous utilization as catalysts for hydrodesulfurization. The relationship between crystal defect sites and catalytic activity must be discerned to maximize the efficiency of hydrogen production during the hydrogen evolution reaction. ESR spectroscopy was utilized as a spin sensitive technique to study the defects and local changes …

Active Seismic Studies In Lemon Creek Valley Glacier, Juneau, Alaska: Characterization Of Subglacial Sediments To Understand Glacier Dynamics, Lucia Fernanda Gonzalez

Open Access Theses & Dissertations

Deformation and flow properties of subglacial sediments as well as the presence and volume of water at the ice/bed interface strongly influence glacier dynamics. Studies of Lemon Creek Glacier, a small temperate valley glacier in the Juneau Icefield, near Juneau, Alaska, have shown that the glacier is rapidly retreating, with a negative mass balance every year since 1957. However, the bed topography and properties of subglacial sediments at the base of Lemon Creek Glacier remained unknown until now. In this project, we process and interpret ~1-km-long NW-SE trending active-source seismic reflection profiles collected during June and July 2017 near the …

Development On Of An Unmanned Aerial Vehicle-Based Orangutan Population Assessment And Monitoring Method For The Multifunctional Landscape Of East Kalimantan, Indonesia, Muhammad Sugihono Hanggito

Open Access Theses & Dissertations

Deforestation, habitat degradation, and other forms of land conversion are threatening the existence of orangutans (Pongo spp.), the critically endangered great apes that only live on the two large Sunda-shelf islands of Sumatra and Borneo. Currently, orangutan populations persist not only within conservation or protected areas but also in other functional landscapes such as forest/acacia plantations, oil palm plantations, and mining concessions. The presence of orangutan populations in this recently modified multifunctional landscape has the potential to exacerbate human-orangutan conflict, which could further threaten orangutan populations. Lack of information about the distribution and size of orangutan populations hampers long term …

Benchmarking Machine Learning Methods For Molecular Property Prediction, Govinda Bahadur Kc

Open Access Theses & Dissertations

Machine learning (ML) techniques have been widely applied in a variety of areas ranging from pattern recognition, natural language processing, and computer games to self-driving cars, clinical diagnostics, and molecular structure prediction easing day to day life of human beings. Drug discovery is an expensive, complex, and time taking process. Currently, the pharma industry is hoping to leverage machine learning methods in expediting the drug discovery process. Molecular property prediction is one of the most important tasks in drug discovery. While developing a new drug relies on a proper understanding of molecular properties, there has been great interest in the …

Planar Motion Control Of A Cube Satellite Using Cold Gas Thrusters, Christian Lozoya

Open Access Theses & Dissertations

This Thesis presents a mathematical model developed for the computational simulation ofCubeSat movement using four thrusters that permit uniaxial translation and rotation. Arbitrary functions are fit to boundary conditions to simulate the force, acceleration, velocity, and displacement of the CubeSat along a plane. The model is used to derive a motion control algorithm assuming constant pressure and mass. A single model describes both translation and rotation. This Thesis also explores the relationship between propellant consumption and the time required to complete a displacement implied by the model.

Optimization Of Regional Scale Numerical Weather Prediction & Air Quality Model For The Paso Del Norte Region, Suhail Mahmud

Open Access Theses & Dissertations

Improvement of the Accuracy and Forecast capability of the Numerical Weather Prediction (NWP) models and Air Quality Models (AQM) are critical issues in today's scientific study of Meteorology and Air Pollution. The models for these predictions are dependent on topography, climate, initial and boundary conditions, domain size, and computational efficiency. Different techniques such as Data Assimilation, Ensemble Methods, Increased Computing Capacity to achieve higher model resolution, and Improved Physics Schemes can be used to address this problem. In this study, the NWP models, the Weather and Research Forecast (WRF), and the HYSPLIT models, were enhanced for the Paso Del Norte …

Towards The Development Of A Cohesive Design-Driven Code Quality Metrics, Omar Masmali

Open Access Theses & Dissertations

Software complexity is an indicator of expected future maintenance and sustainability. Excessive complexity suggests that software or a component of software has a design or implementation that is difficult to understand, modify, and maintain. Several complexity measures have been developed by researchers to identify and characterize degrees of complexity. Code smells are widely adopted as indicators for low code quality. Many studies have adopted fixed threshold values for code smells and other quality metrics. These fixed threshold values often ignore the uniqueness of each software system and the unique roles each component play. Moreover, these thresholds are largely fixed throughout …

Expression, Purification, And Characterization Of Recombinant Human Npas2, Brenda Moreno

Open Access Theses & Dissertations

Many living organisms have biological clocks known as circadian rhythms that control various physiological and behavioral processes, tailored with the day and night. At the cellular level, the circadian clock drives daily rhythms with a transcriptional-translational feedback loop (TTFL) established by multiple transcription factors and genes under their regulation. Circadian Locomotor Output Cycles Kaput (CLOCK) and Brain and Muscle ARNT-like protein 1 (BMAL1) are two of those transcription factors, initiating the TTFL by forming a heterodimeric complex that bind to DNA promoters. Neuronal PAS domain protein 2 (NPAS2) is a functional analog to CLOCK. Less knowledge about NPAS2, in contrast …

Discovery Of Glycan-Based Biomarkers For Cutaneous Leishmaniasis And Chagas Disease By Reversed Immunoglycomics, Alba Lucia Montoya

Open Access Theses & Dissertations

Protozoa are the causative agents of a number of diseases that affect humans and mammalian animals. Several forms of leishmaniasis are caused by different Leishmania species (Leishmania spp.), while Chagas disease (CD) is caused by the parasite Trypanosoma cruzi (T. cruzi). These members of the Trypanosomatidae family have characteristic glycoconjugates broadly distributed on their cell surfaces, which can be useful for diagnosis and follow-up of chemotherapy for the diseases.

Leishmania spp. expresses an “exotic” surface glycocalyx mainly composed of a number of glycosyl-phosphatidylinositol (GPI)-anchored proteins, a complex lipophosphoglycan (LPG) and a family of low-molecular mass glycoinositol-phospholipids (GIPLs), some of them …

Brian Valdez - Dynamics And Control Of A 3-Dof Manipulator With Deep Learning Feedback, Brian Orlando Valdez

Open Access Theses & Dissertations

With the ever-increasing demands in the space domain and accessibility to low-cost small satellite platforms for educational and scientific projects, efforts are being made in various technology capacities including robotics and artificial intelligence in microgravity. The MIRO Center for Space Exploration and Technology Research (cSETR) prepares the development of their second nanosatellite to launch to space and it is with that opportunity that a 3-DOF robotic arm is in development to be one of the payloads in the nanosatellite. Analyses, hardware implementation, and testing demonstrate a potential positive outcome from including the payload in the nanosatellite and a deep learning …

A Comprehensive And Modular Robotic Control Framework For Model-Less Control Law Development Using Reinforcement Learning For Soft Robotics, Charles Sullivan

Open Access Theses & Dissertations

Soft robotics is a growing field in robotics research. Heavily inspired by biological systems, these robots are made of softer, non-linear, materials such as elastomers and are actuated using several novel methods, from fluidic actuation channels to shape changing materials such as electro-active polymers. Highly non-linear materials make modeling difficult, and sensors are still an area of active research. These issues have rendered typical control and modeling techniques often inadequate for soft robotics. Reinforcement learning is a branch of machine learning that focuses on model-less control by mapping states to actions that maximize a specific reward signal. Reinforcement learning has …

Spatially Adaptive Estimation Of Spectrum, Yi None Xie

Open Access Theses & Dissertations

When analyzing a stationary time series, one of the questions we are often interested in is how to estimate its spectrum. Many approaches have been proposed to this end. Most are focused on smoothing the periodogram using a single smoothing parameter across all Fourier frequencies. In this paper, we smooth the log periodogram by placing a spatially adaptive prior called the dynamic shrinkage prior, so that varying degrees of smoothing may be applied to different intervals of Fourier frequencies, resulting in less biased estimates of the spectrum. Further research will extend this approach to spectral estimation for nonstationary time series.

Antioxidant Intervention In Radical-Induced Protein Damage, Emmanuel Zubia

Open Access Theses & Dissertations

Many environmental toxicants are known to increase free-radical production, which can create cellular havoc and lead to a myriad of ailments. Antioxidants can be used to ameliorate the prevalence of free radicals, potentially serving as prophylactics against radical-induced disorders. Many exogenous antioxidants are phytochemicals in origin, such as ascorbic acid, gallic acid, and ellagic acid. Some of these antioxidants can be found in traditional medicine, like tanshinone and brazilin, which have been studied and are known to have low cytotoxicity. Here we test the radical rescue capacity of a selected group of phytochemical antioxidants on protein rescue models. Specifically, our …

Abstraction Techniques In Security Games With Underlying Network Structure, Anjon Basak

Open Access Theses & Dissertations

In a multi-agent system, multiple intelligent agents interact with each other in an environment to achieve their objectives. They can do this because they know which actions are available to them and which actions they prefer to take in a particular situation. The job of game theory is to analyze the interactions of the intelligent agents by different solution techniques and provide analysis such as predicting outcomes or recommending courses of action to specific players. To do so game theory works with a model of real-world scenarios which helps us to make a better decision in our already complex daily …

Understanding The Digital Lives Of Transnational Students: A Case Study, Chowaing Chagra Belekeh

Open Access Theses & Dissertations

The proliferation and the fast-paced evolution of digital information communication technologies (ICTs) in contemporary times have arguably raised concern for us to comprehend what we do with these technologies and what these technologies do for us. The experience of engaging these technologies may not necessarily be the same for everyone—especially students who come from around the world to attain post-graduate degrees in the United States. This research focused on understanding the digital lives, choices, and experiences of transnational students who navigate and negotiate geopolitical borders and boundaries (physical)– in their quest for education. Using a case study analysis and collecting …

A Comparative Study Of The Impact Of Depth In Deep Learning Architectures, Kirsten Byers

Open Access Theses & Dissertations

Machine Learning continues to evolve as applications become more complex. Neural Networks, or Deep Networks, are integral to machine learning and the entire taxonomy of Artificial Intelligence [Sze17]. Intelligent structures and algorithms continue to advance, keeping pace with the complexi-ty of data. Changes in architecture, algorithms, and parameters are necessary to keep up with com-putational complexity and data available. This study focuses on how changes in depth of the archi-tecture affect performance on three distinct datasets, including one on Heart Disease. An adaptable network is created in original code, trained, and tested on these datasets. Its performance parameters are observed …