Physical Sciences and Mathematics Commons^™

Testimi I Java Dhe Node.Js Aplikacioneve, Nderim Bytyçi

Theses and Dissertations

Testimi është njëra nga fazat e ciklit të zhvillimit të një softueri. Se sa ai softuer është i besueshëm dhe konsistent ndaj përdoruesit, vlerësohet me anë të shumë testeve qofshin ato automatike apo manuale nga një tester i kualifikuar. Shpeshherë eksperienca e dobët e testerit, shkakton probleme dhe vonesa në lëshim (release) të aplikacionit dhe kjo ndikon në reputacionin e kompanisë si dhe pakënaqësinë e përdoruesit. Në mënyrë që të evitojmë raste të tilla, aplikacioni duhet testuar. Testimi i një produkti ka shumë benefite, dhe njëra nga më të rëndësishmet është efikasiteti dhe kursimi i buxhetit, sepse nëse gabimet (bugs) …

Testimi I Përformances Së Web Aplikacioneve, Nita Belegu

Theses and Dissertations

Meqenëse numri i web aplikacioneve është në rritje dhe këto web aplikacione gjithnjë e më tepër po bëhen më komplekse, atëherë edhe kërkesat për performancë të avancuar rriten njëkohësisht. Padyshim, nga çdo web aplikacion secili nga ne kërkon që të jetë mjaft i shpejtë, por në të njëjtën kohë edhe të ketë siguri. Me një klikim në një faqe në web, dëshirojmë që ajo të ngarkohet mjaftë shpejtë ashtu që të përfundojmë punët e caktuara dhe t’i dedikohemi punës tjetër. Në të kundërtën, nëse faqja ngarkohet shumë ngadalë, njeriu është i prirur që të dorëzohet për atë punë që ka …

Ndikimi I Sulmeve Kibernetike Në Sektorin Bankar Dhe Shëndetësor Gjatë Vitit 2020, Triflona Tolaj

Theses and Dissertations

- Punimi im i temës së diplomës është një hulumtim shkencor rreth sulmeve kibernetike dhe ndikimit të tyre në dy sektorët më të rrezikuar, sektorin bankar dhe atë shëndetësor. Tema është përzgjedhur e tillë pasi që çdo ditë përballemi me risi të reja në fushën e teknologjisë. Kjo gjë ka ndikuar edhe në rritjen e sulmeve kibernetike, e numri i tyre është shtuar edhe më shumë gjatë periudhës së po këtij viti, pandemisë së koronavirusit. Në kapitujt e parë të projektit është shtjelluar fillimisht koncepti i sigurisë kibernetike dhe masat që duhet të merren për mbrojtjen ndaj sulmeve të mundshme, …

Classification Of Pedagogical Content: Review And Research Challenges, Vedat Apuk

Theses and Dissertations

The advent of the Internet and a large number of digital technologies has brought with it many different challenges. A large amount of data is found on the web, which in most cases is unstructured and unorganized, and this contributes to the fact that the use and manipulation of this data is quite a difficult process. Due to this fact, the usage of different machine learning techniques for Text Classification has gained its importance, which improved this discipline and made it more interesting for scientists and researchers for further study. These techniques bring a lot of advantages, as they are …

Interneti I Gjerave Ne Shendetesi, Mihrije Morina

Theses and Dissertations

Me avancimin e teknologjive të komunikimit të informacionit, evolucioni i Internetit ka krijuar një rrjet të kudogjendur, i përbërë nga objekte (ose gjëra) të ndërlidhura, të quajtur Interneti i Gjërave (IoT). Kohët e fundit, komuniteti akademik ka bërë përparime të mëdha në kërkimin dhe zhvillimin e sigurisë për aplikacionet e bazuara në IoT, duke u përqëndruar, në veçanti, në sistemet e kujdesit shëndetësor të bazuar në rrjetet e IoT. Interneti i Gjërave (IoT) është i pajisur me çdo proces kompjuterik, mikrokontrolluesit dhe marrësit për fuqizimin e komunikimit dhe është ndërtuar me pirgje të përshtatshme protokolli që i ndihmojnë ata të …

Hardware Hacking, Purpleair – Rast Studimi, Pajtim Cakaj

Theses and Dissertations

Gajtë këtij punimi unë do të trajtoj temën Hardware Hacking, ma konkretisht hakimi i paisjes PurpleAir. Do të analizojë sistematikisht mekanizmat e përditësimit të firmware-it të pajisjeve të njohura të monitorimit të cilësisë së ajrit PurpleAir dhe paraqes sulme (fizike) harduerike dhe sulme nga distanca kundër këtyre pajisjeve, cilat janë dobësit që një haker i shfrytëzon për të hakuar këto paisje, cilat janë pasojat e hakimit të këtyre paisjeje si dhe do të tregohet projektimi dhe implementimi për një sistem të sigurt të përditësimit të firmware-it të këtyre paisjeve e që si rast studimi është marr paisja PurpleAir.

Access Control For The Internet Of Things, Yllka Bahtiri

Theses and Dissertations

Access control for the internet of things controlli i qasjes ne koncept është siguria që minimizon rrezikun për biznes apo organizata të ndryshme të qasjes së paautorizuar në sistemet fizike dhe logjike.

Ndryshe mundemi të themi se është një teknik që rregullon cilët persona çfarë munden te

shikojnë dhe çfarë munden të perdorin në një mjedis informatikë.

Interneti i gjerave mundëson shërbime që do ta përmisojnë jetën e përditshme të njerzëve, do të

krijojnë biznese të reja dhe do të bëjnë ndërtesa, qytete dhe transportin më te zgjuar. Internet of

things ka ardhur për të përshkruar një numer të teknologjive …

การปรับปรุงสมบัติของไนลอน 6 รีไซเคิลด้วยเทอร์โมพลาสติกพอลิ(อีเทอร์-เอสเตอร์)อิลาสโตเมอร์และโวลลาสโทไนต์, คุณัญญา จันทร์ฉาย

Chulalongkorn University Theses and Dissertations (Chula ETD)

งานวิจัยนี้ พอลิเมอร์ผสมของไนลอน 6 รีไซเคิล/เทอร์โมพลาสติกพอลิ (อีเทอร์-เอสเตอร์) อิลาสโตเมอร์หรือไฮทรีล ได้ถูกเตรียมด้วยกระบวนการผสมแบบหลอมเหลวโดยใช้เครื่องอัดรีดแบบสกรูคู่และขึ้นรูปชิ้นทดสอบด้วยเครื่องฉีดแบบ เพื่อศึกษาและเปรียบเทียบสมบัติเชิงกล สมบัติทางความร้อน และลักษณะสัณฐานวิทยาของชิ้นงาน ผลการศึกษาพบว่า การเติมไฮทรีลในไนลอน 6 รีไซเคิล ส่งผลให้ความทนแรงและการยืดตัว ณ จุดขาด ของไนลอน 6 รีไซเคิล ได้รับการปรับปรุงให้ดีขึ้น เนื่องมาจากไฮทรีลเป็นพอลิเมอร์ยืดหยุ่นและสามารถกระจายตัวได้อย่างสม่ำเสมอในพอลิเมอร์เมทริกซ์ของไนลอน 6 รีไซเคิล หากแต่ทำให้สมบัติเชิงกล เช่น ความทนแรงดึง, ยังส์มอดุลัส, ความทนแรงดัดโค้ง, มอดุลัสการดัดโค้ง และเสถียรภาพทางความร้อนลดต่ำลง จึงปรับปรุงสมบัติที่สูญเสียไปโดยเลือกพอลิเมอร์ผสมไนลอน 6 รีไซเคิล/ไฮทรีล ที่อัตราส่วน 70/30 ซึ่งเป็นอัตราส่วนที่มีค่าความทนแรงกระแทกสูงที่สุด ไปเตรียมเป็นพอลิเมอร์คอมพอสิตด้วยโวลลาสโทไนต์ ปริมาณ 10, 20, และ 30 ส่วนต่อเรซิน 100 ส่วน ผลการวิจัยพบว่า การเติมโวลลาสโทไนต์สามารถช่วยปรับปรุงค่าความทนแรงดึง, ยังส์มอดุลัส, ความทนแรงดัดโค้ง, มอดุลัสการดัดโค้ง, เสถียรภาพทางความร้อน, อุณหภูมิการเสียรูปด้วยความร้อน และมอดุลัสสะสมของพอลิเมอร์คอมพอสิตให้เพิ่มสูงขึ้น นอกจากนี้ยังพบว่า การเติมโวลลาสโทไนต์ในพอลิเมอร์ผสมยังสามารถช่วยลดการหลอมหยดและลดการลามไฟของพอลิเมอร์คอมพอสิตอีกด้วย หากแต่ไม่สามารถปรับปรุงความทนแรงกระแทก และการยืดตัว ณ จุดขาด ได้ เนื่องมาจากโวลลาสโทไนต์เป็นวัสดุที่มีความแข็งตึงสูง จึงส่งผลให้ไปขัดขวางการเคลื่อนไหวสายโซ่ของโมเลกุล

การเปรียบเทียบประสิทธิภาพของวิธีทดแทนค่าสูญหายในข้อมูลพหุระดับ: การประยุกต์ใช้กับการวิเคราะห์ความเหลื่อมล้ำทางการศึกษา, นวลรัตน์ ฉิมสุด

Chulalongkorn University Theses and Dissertations (Chula ETD)

การวิจัยครั้งนี้มีวัตถุประสงค์เพื่อ (1) เพื่อเปรียบเทียบประสิทธิภาพของวิธีทดแทนค่าข้อมูลสูญหาย 3 วิธี ได้แก่วิธี MI-FCS, วิธี RF และวิธี Opt.impute ซึ่งประกอบด้วย วิธี Opt.knn , Opt.tree, วิธี Opt.svm, และวิธี Opt.cv โดยใช้การจำลองข้อมูลและนำผลที่ได้มาประยุกต์ใช้กับข้อมูลจริง (2) เพื่อวิเคราะห์ความเหลื่อมล้ำทางการศึกษา ด้วยโมเดลพหุระดับโดยใช้ข้อมูลที่มีการทดแทนค่าสูญหาย และเปรียบเทียบผลที่ได้ กับการวิเคราะห์ความเหลื่อมล้ำทางการศึกษาที่ไม่ได้ทดแทนค่าสูญหาย ผลการวิจัยพบว่า (1) จากการพิจารณาผลการเปรียบเทียบประสิทธิภาพของวิธีทดแทนค่าสูญหายโดยใช้การจำลองข้อมูลในภาพรวม จะพบว่าส่วนใหญ่วิธีทดแทนค่าสูญหาย Otp.impute มีแนวโน้มให้ประสิทธิภาพสูงที่สุด รองลงมาคือ วิธีทดแทนค่าสูญหาย RF และวิธีทดแทนค่าสูญหาย MI – FCS ตามลำดับ (2) ผู้วิจัยรวบรวมข้อมูลทุติยภูมิของนักเรียนชั้นมัธยมศึกษาปีที่ 3 จากสถาบันทดสอบทางการศึกษาแห่งชาติ (สทศ.) ปีการศึกษา 2563 จำนวน 2,109 โรงเรียนที่อยู่ในสังกัดสำนักเขตพื้นที่การศึกษามัธยมศึกษา(สพม.) นำวิธีทดแทนค่าสูญหายที่ได้จากการจำลองข้อมูลมาประยุกต์ใช้กับข้อมูลทุติยภูมิดังกล่าว ผลการวิจัย จะพบว่าสัดส่วนของนักเรียนที่ครอบครัวขาดแคลนทุนทรัพย์และไม่ได้พักอาศัยอยู่กับบิดามารดาระดับโรงเรียน ส่งผลกระทบต่อผลสัมฤทธิ์ ทางการเรียนของนักเรียนระดับโรงเรียน อย่างมีนัยสำคัญทางสถิติ โดยผลกระทบที่เกิดขึ้นสะท้อนให้เห็นถึงความเหลื่อมล้ำทางการศึกษา และเมื่อเปรียบเทียบผลที่ได้กับการวิเคราะห์ความเหลื่อมล้ำทางการศึกษาที่ไม่ได้ทดแทนค่าสูญหาย แสดงให้เห็นว่าหากนำข้อมูลวิเคราะห์ผลการวิจัยโดยไม่คำนึงถึงค่าสูญหาย หรือตัดค่าสูญหายทิ้ง อาจจะส่งผลกระทบต่อการประมาณค่าพารามิเตอร์ที่แท้จริง อย่างมีนัยสำคัญทางสถิติ หรือไม่สามารถอนุมานไปสู่ประชากรได้อย่างถูกต้องและแม่นยำ

Systematic Incorporation Of Gold Nanoparticles Onto Mesoporous Titanium Oxide Particles For Green Catalysts, Jian Hou, Wongi Jang, Jaehan Yun, Franklin Obinna Egemole, Dianguo Geng, Hongsik Byun, Dong-Woo Kang, Jun-Hyun Kim

Faculty Publications – Chemistry

This report describes the systematic incorporation of gold nanoparticles (AuNPs) onto mesoporous TiO₂ (MPT) particles without strong attractive forces to efficiently serve as reactive and recyclable catalysts in the homocoupling of arylboronic acid in green reaction conditions. Unlike using nonporous TiO₂ particles and conventional SiO₂ particles as supporting materials, the employment of MPT particles significantly improves the loading efficiency of AuNPs. The incorporated AuNPs are less than 10 nm in diameter, regardless of the amount of applied gold ions, and their surfaces, free from any modifiers, act as highly reactive catalytic sites to notably improve the yields …

Determination Of Volatile Compounds In Yellow Curry Paste Using From-Two-To-One Dimensional Gas Chromatography-Mass Spectrometry, Natsuda Singtothog

Chulalongkorn University Theses and Dissertations (Chula ETD)

In this work, an approach to allow improved analysis with one-dimensional GC-MS (1D GC-MS) was established and demonstrated for analysis of a pool of yellow curry paste samples. The approach involved initial application of comprehensive heart cut two-dimensional GC-MS (CH/C 2D GC-MS) to obtain a full volatile profile by comparing the experimental mass spectrum and retention index of each compound with the mass spectra and retention indices of standard compounds from a database. The obtained volatile profile was then used to generate a selected ion monitoring (SIM) method, which was then applied with 1D GC-MS using a SIM mode. This …

Pna-Immobilized Paper For Detection Of Pcr Amplicons, Nuttapon Jirakittiwut

Chulalongkorn University Theses and Dissertations (Chula ETD)

DNA detection is very important in diverse fields leading to a continuous increase in the research and development of various DNA sensors. This study focuses on the development of a paper-based DNA sensor by using pyrrolidinyl PNA as a recognition probe. The PNA-immobilized DNA sensor was designed to contain several PNA probes in the same device as a self-check system to increase the accuracy and facilitate the data collection and interpretation. The PNA-immobilized paper was then utilized for the detection of the DNA target, followed by the visualization of the captured target DNA via an enzyme-catalyzed colorimetric reaction. In this …

Aeolian Sand Stringers In The Upper Midwest, Usa: Morphology, Stratigraphy, And Paleoenvironmental Significance, Kenzie L. Shandonay

All Graduate Theses, Dissertations, and Other Capstone Projects

Sand stringers are subtle (~1-10 m high), elongate (several km long, up to 100 m wide) aeolian landforms that lack a slip face and generally have a northwest-southeast orientation. They are ubiquitous across the Upper Midwest, including southeast Minnesota and western Wisconsin. Despite their prevalence, the timing, processes, and environmental conditions during sand stringer formation and evolution are poorly understood. This research aims to describe sand stringer morphology and stratigraphy, reconstruct regional paleoclimate, and characterize the timing and geomorphic processes of sand stringer formation and evolution in response to shifts in environmental conditions. This study investigates two sand stringers: Good-1 …

Classification Of Chess Games: An Exploration Of Classifiers For Anomaly Detection In Chess, Masudul Hoque

All Graduate Theses, Dissertations, and Other Capstone Projects

Chess is a strategy board game with its inception dating back to the 15th century. The Covid-19 pandemic has led to a chess boom online with 95,853,038 chess games being played during January, 2021 on lichess.com. Along with the chess boom, instances of cheating have also become more rampant. Classifications have been used for anomaly detection in different fields and thus it is a natural idea to develop classifiers to detect cheating in chess. However, there are no specific examples of this, and it is difficult to obtain data where cheating has occurred. So, in this paper, we develop 4 …

Proposed Data Governance Framework For Small And Medium Scale Enterprises (Smes), Rejoice Okoro

All Graduate Theses, Dissertations, and Other Capstone Projects

Data governance is not a one size fits all, instead, it should be an evolutionary process that can be started small and measurable along the way. This research aims at proposing a data governance framework by ensuring data management processes, data security and control are compliant with laws and policies. This article also presents the first results of a comparative analysis between three data privacy laws and outlines five components which together form a data governance framework for SMEs. The data governance model documents data quality roles and their type of interaction with data quality management activities exploring how data …

Xtreme-Noc: Extreme Gradient Boosting Based Latency Model For Network-On-Chip Architectures, Ilma Sheriff

All Graduate Theses, Dissertations, and Other Capstone Projects

Multiprocessor System-on-Chip (MPSoC) integrating heterogeneous processing elements (CPU, GPU, Accelerators, memory, I/O modules ,etc.) are the de-facto design choice to meet the ever-increasing performance/Watt requirements from modern computing machines. Although at consumer level the number of processing elements (PE) are limited to 8-16, for high end servers, the number of PEs can scale up to hundreds. A Network-on-Chip (NoC) is a microscale network that facilitates the packetized communication among the PEs in such complex computational systems. Due to the heterogeneous integration of the cores, execution of diverse (serial and parallel) applications on the PEs, application mapping strategies, and many other …

Examining Patterns And Drivers Of Spatial And Temporal Variability In Playa Hydroperiod In The High Plains Region Of Western Kansas, Luis Lepe

All Graduate Theses, Dissertations, and Other Capstone Projects

Playa wetlands are some of the most important natural features of the High Plains of the central United States. Playas provide a range of ecosystem services such as groundwater recharge, surface water storage, and wetland habitat. However, playa functions are declining due to land cover change, climate change, and playa and watershed modifications. There are only a few studies that have examined the variability and controls on playa water storage. This project aims to determine how playa and watershed morphology, watershed land cover, and precipitation patterns affect timing and duration of water storage in 92 playas distributed throughout a 10-county …

The Kiwanis Site: A Multi-Method Geophysical Approach To Investigating Mound Features, Luke Burds

All Graduate Theses, Dissertations, and Other Capstone Projects

Subtle mound-like landforms can be genetically ambiguous features within a landscape. A variety of geomorphological and anthropological processes can result in these equifinal forms being difficult to interpret. Being able to reliably and noninvasively differentiate them is important for legal as well as cultural and spiritual reasons. A suite of non-invasive geophysical methods were thus used on mounds at the Kiwanis site in western Wisconsin in order to determine if culturally diagnostic indicators could be recorded in geophysical data. Genesis of these mounds is ambiguous given the presence of aeolian landforms in immediate proximity. As a control, the same geophysical …

Trondhjemite Leucosomes Generated By Partial Melting Of A Hornblende-Gabbro (Alvand Plutonic Complex, Hamedan, Nw Iran), Adel Saki, Federico Lucci, Mirmohammad Miri, John C. White

EKU Faculty and Staff Scholarship

This work describes the petrogenesis of in situ and in-source trondhjemite leucosomes generated by low-degree partial melting of the Jurassic Cheshmeh-Ghasaban hornblende-gabbros in the northern Alvand batholith (Hamedan, NW Iran). These leucosomes occur in a metatexite migmatite as patches, net-structures, veinlets, and dikes at scales ranging from a few millimetres to a few metres. They have high SiO2 (mean ≈ 78 wt%) and Na2O (4–5 wt%) with low Al2O3 (wt%), K2 O (

Multiscale Modeling Of Biological Complexes: Strategy And Application, Xiaochuan Zhao

Graduate College Dissertations and Theses

Simulating protein complexes on large time and length scales is often intractable at the atomistic resolution. To address this challenge, we have developed new approaches to integrate coarse-grained (CG), mixed-resolution (referred to as AACG throughout this dissertation), and all-atom (AA) modeling for different stages in a single molecular simulation. First, we developed a top-down multiscale modeling approach — a new approach, which combines CG, AACG, and AA modeling — to simulate peptide self-assembly from monomers. We simulated the initial encounter stage with the CG model, while the further assembly and reorganization stages are simulated with the AACG and AA models. …

The Origins Of Manufactured Dissent And The Efficacy Of Climate Change Narratives, Emma Elisabeth Giering

Graduate College Dissertations and Theses

The year of 2020 revealed many things about the fragility of socially constructed institutions and the public trust which grants such entities legitimacy, which is perhaps what reinvigorated social discourse surrounding the existential threat posed by climate change. Amid a pandemic, Americans watched wildfires engulf much of the west coast, environmental regulations unravel in the hands of the Trump administration, and Wall Street begin trading futures contracts on the U.S.’s water supply. Given the ever-expanding record of environmental travesties, how are citizens to respond, and from where should they derive their inspiration for response?

This thesis answers the above question …

Upcycling Dairy Manure Fine Solids Captured By Dissolved Air Flotation As Part Of A Phosphorus Recovery And Reuse Strategy, Katherine Keith Porterfield

Graduate College Dissertations and Theses

Dissolved air flotation (DAF) has shown potential to substantially improve phosphorus (P) mass balance on dairy farms by capturing P associated with fine solids from liquid manure, enabling new management options. However, at < 25% total solids, further dewatering and other upcycling is necessary to facilitate export of recovered fine solids off farm for use in bagged or bulk products. I generated plant foods using DAF-captured dairy manure fine solids thermally dried to 45% total solids blended with other organic residuals. Dry biomass of tomato and marigold seedlings amended with 6% v/v plant food was six-times greater than the unamended control and not significantly different from a market alternative treatment. Because thermal dewatering can be prohibitively costly, I generated a second batch of plant foods using DAF-captured dairy manure fine solids conditioned with 3, 4.5 and 6% (w/w) quicklime or lime kiln dust (LKD) and dewatered using a benchtop press for comparison with thermally dried fine solids. Tomato seedling biomass was similar for thermally dried and LKD plant foods, but quicklime plant foods had no effect compared to the unamended control. Quicklime and LKD conditioned fine solids contained approximately 30 and 10 times less plant-available P than thermally dried fine solids, respectively—likely due to precipitation of Ca-P minerals. These studies indicate that DAF-captured dairy manure fine solids could be upcycled to bagged horticultural products with substantial agronomic value, however sustainable materials drying remains a key challenge to realizing this potential.

Vinyl Cations As Cyclopentenone Precursors Via C‒H Insertion Or Alkene Addition Reactions, Magenta Hensinger

Graduate College Dissertations and Theses

We report that Lewis acid mediated reactions of β-hydroxy-α-diazo carbonyls provide facile access to vinyl cation intermediates, which can form mono- and bicyclic cyclopentenone ring systems. Vinyl cations are sp hybridized cations that can be exploited as carbene surrogates or as electrophiles. The methodology reported in this dissertation is important because cyclopentenone rings are common motifs in natural products or can be used as synthetic intermediates.

The first portion of this dissertation will discuss vinyl cations we’ve used as carbene surrogates in metal free C‒H insertion reactions. Treating β-hydroxy-α-diazo carbonyls with a Lewis acid provided vinyl cation intermediates after loss …

Investigating The Phase Of Green Leaf Volatile Derived Secondary Organic Aerosol Using An Electrical Low Pressure Impactor, Kevin Fischer

Graduate College Dissertations and Theses

Airborne particulate matter consists of small particles suspended in the air and is a ubiquitous component of the Earth’s atmosphere. These particles, known as aerosols, broadly affect both human health and the global climate. Secondary organic aerosol (SOA), a subset of atmospheric aerosol, are produced by the gas phase oxidation of volatile organic compounds (VOCs) originating from anthropogenic and biogenic sources. Of particular interest are a sub class of biogenic VOCs released by stressed plants, green leaf volatiles (GLVs), which are susceptible to oxidation via ozonolysis and form SOA. While important strides have been made in better understanding SOA, many …

Characterizing Mass Loss In Central Cuba Using Long-Term Sediment Generation Rates And Rock Dissolution Rates, Mae Kate Campbell

Graduate College Dissertations and Theses

Knowledge of denudation rates over geologic timescales provides important insight into the processes that govern soil formation, the regulation of Earth’s climate, and the evolution of landscapes. Accurately establishing long-term denudation rates is also key to understanding how human actions have altered the rates and patterns of erosion over time. While cosmogenic nuclides are often used to measure long-term denudation rates at the basin scale, these rates can be unrepresentative of total landscape denudation in areas where significant mass loss occurs through rock dissolution. In tropical landscapes, mass loss by solution often represents a significant portion of total landscape mass …

Nonlinear Impedance Spectroscopy To Characterize Hole Transport And Recombination Dynamics In Organic Semiconductor Devices, Robin Rice

Graduate College Dissertations and Theses

Impedance Spectroscopy (IS) is an increasingly common technique to characterize both solid state and electrochemical systems including solar cells and light emitting diodes (LEDs). However, IS relies on a system response being linear with its input such that a time invariant impedance can be defined. This is usually achieved by a small amplitude input. However, doing so suppresses responses of the nonlinear processes which are of considerable interest to those designing and optimizing these devices, such as charge carrier recombination and space charge effects. This investigation employs the recently developed nonlinear extension to IS (NLIS) based in Fourier analysis of …

Two-Dimensional Bose–Hubbard Model For Helium On Graphene, Jiangyong Yu

Graduate College Dissertations and Theses

An exciting development in the field of correlated systems is the possibilityof realizing two-dimensional (2D) phases of quantum matter. For a systems of bosons, an example of strong correlations manifesting themselves in a 2D environment is provided by helium adsorbed on graphene. We construct the effective Bose-Hubbard model for this system which involves hard-core bosons (U ≈ ∞) and repulsive nearest-neighbor (V > 0) interactions. In this work, we focus on the calculations of single particle properties of the model such as the hopping parameter t. This is accomplished via Wannier Theory and Band structure calculations, which proves to be reliable …

Transient Effects In Solution-Processed Organic Thin Films, Jing Wan

Graduate College Dissertations and Theses

Due to the weak van der Waals forces between organic semiconductor molecules, the molecular packing depends sensitively on the processing methods and conditions. Thus, understanding the crystallization mechanisms during solution deposition are essential for fundamental studies and reproducible fabrication of electronic devices.The performance of Organic field effect transistors (OFETs) also depends heavily on extrinsic factors such as contact resistance and interfacial defects, which can produce a different kind of transient effect at the metal-semiconductor contact. We have observed structural transient effects during the crystallization process of two small molecule organic semiconductors made from solution. We report in situ X-ray scattering …

Investigating Spatial And Temporal Variability Of Environmental And Biological Controls On Riparian Soil Denitrification, Brittany Victoria Lancellotti

Graduate College Dissertations and Theses

Soil denitrification is a critical component of nitrogen (N) cycling on Earth. It is a microbially-mediated process that removes N from soils by reducing nitrate (NO3-), a highly bioavailable molecule and significant contributor to eutrophication, to gaseous forms of N (N2 or N2O). Riparian areas, which are located at the interface between terrestrial and aquatic ecosystems, are areas of elevated denitrification rates, as they frequently exhibit favorable conditions for this process. Denitrification provides a critical ecosystem service by reducing N inputs to streams and rivers. However, this process is highly variable in time and space, making it difficult to predict …

First Pan-Arctic Assessment Of Dissolved Organic Carbon In Lakes Of The Permafrost Region, Lydia Stolpmann, Caroline Coch, Anne Morgenstern, Julia Boike, Michael Fritz, Ulrike Herzschuh, Kathleen Stoof-Leichsenring, Yury Dvornikov, Birgit Heim, Josefine Lenz, Amy Larsen, Katey Walter Anthony, Benjamin Jones, Karen Frey, Guido Grosse

Geography

Lakes in permafrost regions are dynamic landscape components and play an important role for climate change feedbacks. Lake processes such as mineralization and flocculation of dissolved organic carbon (DOC), one of the main carbon fractions in lakes, contribute to the greenhouse effect and are part of the global carbon cycle. These processes are in the focus of climate research, but studies so far are limited to specific study regions. In our synthesis, we analyzed 2167 water samples from 1833 lakes across the Arctic in permafrost regions of Alaska, Canada, Greenland, and Siberia to provide first pan-Arctic insights for linkages between …