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Detection Of Nitrite By Thread-Based And Paper-Based Devices By Modified Griess Reagent, Pitcha Singhaphan
Detection Of Nitrite By Thread-Based And Paper-Based Devices By Modified Griess Reagent, Pitcha Singhaphan
Chulalongkorn University Theses and Dissertations (Chula ETD)
New thread-based and paper-based devices for the determination of nitrite ions based on modified Griess reagent were developed. The surface of the materials was chemically modified with p-aminobenzoyl moiety and chromotropic acid was used as a coupling reagent. The functionalization of the materials was confirmed by Raman spectroscopy. By using the thread-based device, the detection of nitrite was achieved by measuring the color band length. The optimum concentration of chromotropic acid was 5 mM in 0.10 M sulfuric acid mixed with 0.2 M citric acid. The working range was from 50 to 1,000 µM with a sample volume of 15 …
Detection Of Cyanide Ions Using Chemosensing Ensembles Under Indicator Displacement Assays, Ratanakorn Teerasarunyanon
Detection Of Cyanide Ions Using Chemosensing Ensembles Under Indicator Displacement Assays, Ratanakorn Teerasarunyanon
Chulalongkorn University Theses and Dissertations (Chula ETD)
Anion recognition is an attractive area of research in recent decades as anions play an important role in a wide range of chemical, biological, and environmental processes. This dissertation reports three projects dedicated to anion recognition with applications in fluoride and cyanide sensing. The first project of the dissertation describes the chemistry of two novel anthracene derivatives bearing one and two dimesitylboryl substituents (compounds 1 and 2, respectively) for the complexation of anions. All investigations provide insights into the electronic structure and effect of fluoride and cyanide binding. The results demonstrate that these boranes have a high affinity for fluoride …
Development Of Paper-Based Colorimetric Sensor For Determination Of Human Papillomavirus Dna, Sarida Naorungroj
Development Of Paper-Based Colorimetric Sensor For Determination Of Human Papillomavirus Dna, Sarida Naorungroj
Chulalongkorn University Theses and Dissertations (Chula ETD)
In this work, a paper-based analytical device (PAD) based on colorimetric assay using pyrrolidinyl peptide nucleic acid (acpcPNA) probe was developed as a sensor for the detection of Human papillomavirus (HPV) DNA. Dextrin-stabilized gold nanoparticles (d-AuNPs) was employed as a colorimetric reagent. The aggregation of d-AuNPs can be induced by positively charged acpcPNA generating a distinctive color change. After the hybridization of acpcPNA and DNA target, the residual acpcPNA probe can cause different degrees of the d-AuNPs aggregation, resulting in the detectable color change. The different color change before and after the introduction of the DNA target as a function …
Determination Of Perchlorate And Thiocyanate Ions By Ion-Selective Membrane And Bulk Optode Techniques Using Experimental Design Approach, Supacha Wirojsaengthong
Determination Of Perchlorate And Thiocyanate Ions By Ion-Selective Membrane And Bulk Optode Techniques Using Experimental Design Approach, Supacha Wirojsaengthong
Chulalongkorn University Theses and Dissertations (Chula ETD)
This research aimed to develop the detection method for perchlorate and thiocyanate in aqueous solutions using potentiometric and colorimetric techniques. The optimum conditions were designed by the central composite design (CCD) with response surface methodology (RSM). The potentiometric response of perchlorate‒selective electrode using di‒tripodal amine calix[4]arene copper(II) complex (L1-Cu) in PVC membrane was studied. The optimized pH, ion exchanger and ionophore concentrations were found at pH 8.0, 3.25 mmol/kg and 13.25 mmol/kg, respectively. The optimized condition performed a Nernstian slope of –58.02 mV/decade with R2=0.9994 in a working concentration range of 1.00×10‒6 – 1.00×10‒2 M, and the detection limit was …
Optimization Of Enantiomeric Separation By Gas Chromatography Using Beta-Cyclodextrin Derivatives As Stationary Phases, Suchada Muangsri
Optimization Of Enantiomeric Separation By Gas Chromatography Using Beta-Cyclodextrin Derivatives As Stationary Phases, Suchada Muangsri
Chulalongkorn University Theses and Dissertations (Chula ETD)
Enantiomeric separations of seventy-two underivatized chiral alcohols and forty-three trifluoroacetyl derivatives of chiral amines of various structures were investigated by gas chromatography using two types of cyclodextrin-based chiral stationary phases: heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-beta-CD (or BSiAc) and heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-beta-CD (or BSiMe). Each compound was analyzed by temperature program and the optimum isothermal condition for each compound was also determined. It was found that resolution and elution temperature obtained from a temperature program run could be used as a guideline for quickly determining the optimum isothermal condition for enantiomeric separation. For a 15-meter long capillary column, if a resolution less than 1.0 was obtained, a …
Development Of Green Methods For Synthesis Of 2-Aminobenzoxazoles From Organosulfurs, Theeranon Tankam
Development Of Green Methods For Synthesis Of 2-Aminobenzoxazoles From Organosulfurs, Theeranon Tankam
Chulalongkorn University Theses and Dissertations (Chula ETD)
2-aminobenzoxazoles are an important motif in pharmaceutical and chemical industries, however, their preparations involve the use of toxic reagents and organic solvents. Therefore, greener methods for preparation of 2-aminobenzoxazoles are highly desired. In this work, we demonstrate two novel methodologies for synthesis of 2-aminobenzoxazoles in aqueous media. The first method involves the use of "on water" microwave reaction to perform the amination of 2-mercaptobenzoxazoles into 2-aminobenzoxazoles. Various 2-aminobenzoxazoles are synthesized under additive-free condition accelerating by microwave irradiation at 100 oC for 1 hour in moderate to good yields. This synthesis can be applied to prepare 2-aminobenzoxazole in gram scale quantity. …
Development Of Fluorinated Rhodacyanine Analogues For Anti-Leishmaniasis, Thitiya Lasing
Development Of Fluorinated Rhodacyanine Analogues For Anti-Leishmaniasis, Thitiya Lasing
Chulalongkorn University Theses and Dissertations (Chula ETD)
Recently, fluorinated rhodacyanine has been disclosed as a highly effective agent against Leishmania donovani; it was shown that replacement of hydrogen with a fluorine atom on a benzothiazole unit significantly enhanced the anti-leishmanial activity. However, the role of the fluorine substituent in this analogue has not yet been clarified and mechanism of actions remains unclear. In this research, fifteen novel and three known fluorine-containing rhodacyanine analogues (10c, and 11a-11q) were synthesized and tested the anti-leishmanial activity against promastigote and axenic amastigote stages of L. martiniquensis and L. orientalis, the indigenous Leishmania species of Thailand. The SAR knowledge of this series …
Synthesis Of Coumarins As Carbonic Anhydrase Ii And Α-Glucosidase Inhibitors, Truc Phan Thi Hong
Synthesis Of Coumarins As Carbonic Anhydrase Ii And Α-Glucosidase Inhibitors, Truc Phan Thi Hong
Chulalongkorn University Theses and Dissertations (Chula ETD)
Coumarins have been occupied an important position in medicinal chemistry. In this research, umbelliferone derivatives were evaluated for inhibitory activity of two enzymes, namely carbonic anhydrase II (CA II) and α-glucosidase. First, ether, brominated ether and ester derivatives of umbelliferone were synthesized, characterized and tested for CA II inhibitory activity. However, the inhibition data could not be used to make the exact conclusion about structure-activity relationship owing to their unrepeatable results. For the second part, thirty-four derivatives of umbelliferone (ether, brominated ether, ester, sulfonamide and sulfonate derivatives) were synthesized and explored for anti-α-glucosidase activity. It was disclosed that anti-α-glucosidase activity …
Wind Load Analysis Of A High-Rise Building By Computational Fluid Dynamics, Canh Thiet Phung
Wind Load Analysis Of A High-Rise Building By Computational Fluid Dynamics, Canh Thiet Phung
Chulalongkorn University Theses and Dissertations (Chula ETD)
As new buildings become taller due to limited land area, often irregular in shapes for esthetics and some design constraints, wind load formula provided in design codes/standards cannot be applied because of the limitations. Wind tunnel test (WTT) is thus the suggested approach to obtain appropriate wind load for the design of such buildings. However, WTT is costly and time-consuming as it often requires much preparation of the small-scale model of the target building, instrumentation, and numerous realistic blocks of surrounding buildings (SBs). In this study, the CFD's accuracy will be evaluated by comparing its results to WTT by a …
Bioactive Compounds From Lichen Usnea Aciculifera Vain And Usnic Acid Conjugates, Truong Tuong Lam
Bioactive Compounds From Lichen Usnea Aciculifera Vain And Usnic Acid Conjugates, Truong Tuong Lam
Chulalongkorn University Theses and Dissertations (Chula ETD)
Phytochemical investigation of lichen Usnea aciculifera Vain led to the isolation of nine new dimeric xanthones, usneaxanthones A-I (36–44), along with 36 known compounds (1–35, 45). The chemical structures of the isolated compounds were elucidated by a combination spectroscopic data (1D, 2D NMR, HRESIMS), ECD experiments, and single-crystal X-ray as well as comparison of their NMR data with those in the literature. The biological activities of isolated compounds were evaluated for antibacterial, anti-dengue and cytotoxic activites. The results revealed that depsides may have potential as lead compounds for the development of new antibacterial and anti-dengue agents. Futhermore, dimeric xanthones exhibited …
Seismic Enhancement Of Reinforced Concrete Columns With Lap Splices Using External Steel Collars, Pochara Kruavit
Seismic Enhancement Of Reinforced Concrete Columns With Lap Splices Using External Steel Collars, Pochara Kruavit
Chulalongkorn University Theses and Dissertations (Chula ETD)
This research investigated the behavior of reinforced concrete (RC) columns with lap splices and mechanical splices. The study conducted the full-scale test and predicted a lateral load capacity using the proposed numerical model. The test configuration was a cantilever column subjected to a cyclic lateral loading and a constant gravity load. The tested specimens consisted of the RC column without lap splices, RC columns with spliced reinforcement including lap splices and mechanical splices, and RC column with lap splices strengthened by external steel collars. The experimental result indicated that the lateral load capacity of the RC column with mechanical splices …
Modified Response Spectrum Analysis For Computing Seismic Demands Of Multi-Tower Building Sharing A Common Podium, Tarek Youssef
Modified Response Spectrum Analysis For Computing Seismic Demands Of Multi-Tower Building Sharing A Common Podium, Tarek Youssef
Chulalongkorn University Theses and Dissertations (Chula ETD)
To design irregular tall buildings, performance-based design (PBD) approach, which requires nonlinear response history analysis (NLRHA), is the most accurate method. However, PBD approach is not always used in the current design practice because of its complexity, and as allowed in ASCE 7-16, design engineer can use code-based approach such as response spectrum analysis (RSA) procedure. This paper aims to investigate the accuracy of RSA procedure when applied to irregular tall buildings, and in particular for multi-tower buildings sharing a common podium. Also, a modified response spectrum analysis (MRSA) procedure previously proposed for computing shear demand in regular tall buildings, …
A Study On Intermediate Debonding For Steel Beams Strengthened With Fiber Reinforced Polymer Plates, Tosporn Prasertsri
A Study On Intermediate Debonding For Steel Beams Strengthened With Fiber Reinforced Polymer Plates, Tosporn Prasertsri
Chulalongkorn University Theses and Dissertations (Chula ETD)
There are limited previous works focusing on the occurrence of intermediate debonding in steel beams strengthened with fiber reinforced polymer (FRP) plates. Tested beams in the past experiments invoked an intermediate debonding by creating notch in steel beams. An anchorage system at FRP termination points was installed on some tested beams in literature. This research uses an initial bond defect to induce an intermediate debonding at the FRP-steel interface. The bond behavior of FRP-steel interface was investigated through the FRP-steel joints under the single lap shear testing. A four-point bending test was conducted to examine the flexural properties of FRP-strengthened …
An Application Of Line Of Balance And Building Information Modeling For Optimal Resource And Schedule: A Case Study Of An Elevated Highway Construction, Thanakon Uthai
Chulalongkorn University Theses and Dissertations (Chula ETD)
Project scheduling is an essential tool to support construction operations completing the project under limited time and cost. The linear infrastructure project such as elevated highway construction involves a large scale of working area and complexity of management. Recently, schedules are planned manually based on planners’ experience and intuition which may consume time and lead to human-errors. Moreover, the presentations of schedule by using the existing methods dose not cover the overview of projects in various aspects. The objective of this research is to establish an application of Line of Balance (LOB) and Building Information Modeling (BIM) for optimal resource …
Fundamental Solutions Of Multi-Layer Elastic Media With Couple Stress Theory, Wipavee Wongviboonsin
Fundamental Solutions Of Multi-Layer Elastic Media With Couple Stress Theory, Wipavee Wongviboonsin
Chulalongkorn University Theses and Dissertations (Chula ETD)
This thesis presents fundamental solutions of a two-dimensional, elastic, multi-layered medium under surface loadings by taking the influence of material micro-structure into account. An underlying mathematical model for simulating such small-scale influence is established within the continuum-based framework via the well-known couple stress theory. For each material layer, the generalized Navier’s equation governing the displacement field is established and the method of Fourier integral transform is applied to derive its general solution in a transformed space. A set of boundary conditions and the continuity of fields along the material interfaces are enforced to obtain a system of linear algebraic equations …
The Performance Of Automatic Adaptive Edge-Based Smoothed Finite Element Method In Engineering Mechanics Applications, Vu Hoang Le
The Performance Of Automatic Adaptive Edge-Based Smoothed Finite Element Method In Engineering Mechanics Applications, Vu Hoang Le
Chulalongkorn University Theses and Dissertations (Chula ETD)
The thesis investigates the performance of an edge-based smoothed finite element method (ES-FEM) combined with an automatic mesh refinement (AMR) algorithm to provide the solutions of in-plane elastic engineering mechanics applications. The ES-FEM adopts a strain smoothing technique over the edges adjoining the two adjacent triangular-shape meshes, whilst a layer of singular yet compatible five-node elements in addition to standard three-node ES-FEs can be employed to overcome the problems associated with stress singularity. The proposed framework enables the effective model construction of realistic engineering structures with complex geometry at modest computational resources. The AMR algorithm adopts the newest node bisection …
Thai Spelling Correction And Word Normalization On Social Text Using A Two-Stage Pipeline With Neural Contextual Attention, Anuruth Lertpiya
Thai Spelling Correction And Word Normalization On Social Text Using A Two-Stage Pipeline With Neural Contextual Attention, Anuruth Lertpiya
Chulalongkorn University Theses and Dissertations (Chula ETD)
Text correction systems (e.g., spell checkers) have been used to improve the quality of computerized text by detecting and correcting errors. However, the task of performing spelling correction and word normalization (text correction) for Thai social media text has remained largely unexplored. In this thesis, we investigated how current text correction systems perform on correcting errors and word variances in Thai social texts and propose a method designed for this task. We have found that currently available Thai text correction systems are insufficiently robust for correcting spelling errors and word variances, while the text correctors designed for English grammatical error …
Quantum Comparator Circuit On Superconducting Quantum Computer, Naphan Benchasattabuse
Quantum Comparator Circuit On Superconducting Quantum Computer, Naphan Benchasattabuse
Chulalongkorn University Theses and Dissertations (Chula ETD)
In this thesis, we present an optimised quantum comparator circuit based on Cuccaro's ripple-carry quantum adder using relative phase techniques from Maslov's multiple control Toffoli optimisation. We extend the cost function from simply counting C-Not and Toffoli gate to Qiskit cost which defines arbitrary single qubit gate cost as unity and C-Not as the only two qubit gate cost as ten. We report the comparison result between our comparator circuit with previous comparator circuits from literature using optimal Toffoli implementation with Qiskit cost, C-Not count, and circuit depth. We also report our experiment of implementing a two-bit comparator on IBM …
A Peer-To-Peer Protocol For Prioritized Software Updates On Wireless Sensor Networks, Natchanon Nuntanirund
A Peer-To-Peer Protocol For Prioritized Software Updates On Wireless Sensor Networks, Natchanon Nuntanirund
Chulalongkorn University Theses and Dissertations (Chula ETD)
Software updating is essential for devices in wireless sensor networks for adding new features, improving performance, or patching vulnerabilities. But since some deployed devices are unable to be accessed directly, data dissemination protocol is used for distributing the update to those devices. However, each software updating may have different priority, for instance, an update that adds an optional feature does not have to be applied as fast as an update that patches severe vulnerabilities. This research presents a reliable data dissemination protocol which is configurable for energy-speed trade-off deriving some concepts from BitTorrent such as Handshaking, Segmented File Transfer, and …
Semantic Segmentation On Remotely Sensed Images Using Deep Convolutional Encoder-Decoder Neural Network, Teerapong Panboonyuen
Semantic Segmentation On Remotely Sensed Images Using Deep Convolutional Encoder-Decoder Neural Network, Teerapong Panboonyuen
Chulalongkorn University Theses and Dissertations (Chula ETD)
One of the fundamental tasks in remote sensing is the semantic segmentation of the aerial and satellite images. It plays a vital role in applications, such as agriculture planning, map updates, route optimization, and navigation. The state-of-the-art model is the Deep Convolutional Encoder-Decoder (DCED). However, the accuracy is still limited since the architecture is not designed for recovering low-level features, e.g., river, low vegetation on remotely sensed images, and the training data in this domain are deficient. In this dissertation, we aim to propose the semantic segmentation architecture in five aspects, designed explicitly for the remotely sensed field. First, we …
Semi-Supervised Deep Learning With Malignet For Bone Lesion Instance Segmentation Using Bone Scintigraphy, Terapap Apiparakoon
Semi-Supervised Deep Learning With Malignet For Bone Lesion Instance Segmentation Using Bone Scintigraphy, Terapap Apiparakoon
Chulalongkorn University Theses and Dissertations (Chula ETD)
One challenge in applying deep learning to medical imaging is the lack of labeled data. Although large amounts of clinical data are available, acquiring labeled image data is difficult, especially for bone scintigraphy (i.e., 2D bone imaging) images. Bone scintigraphy images are generally noisy, and ground-truth or gold standard information from surgical or pathological reports may not be available. We propose a novel neural network model that can segment abnormal hotspots and classify bone cancer metastases in the chest area in a semi-supervised manner. Our proposed model, called MaligNet, is an instance segmentation model that incorporates ladder networks to harness …
Gui Test Case Prioritization Using Social Network Analysis, Chawannut Maitrikul
Gui Test Case Prioritization Using Social Network Analysis, Chawannut Maitrikul
Chulalongkorn University Theses and Dissertations (Chula ETD)
Graphical User Interfaces (GUIs) has become popular in today software products due to its user-friendly merit. However, GUI tests are costly and suffer explosive test cases. Moreover, software evolution causes the GUIs inevitably changed resulting in harder testing. Regression test has been widely used for GUIs software testing when software changes. It is considered to be the most expensive phase in the software testing process, though. Among several alternatives, the technique of test case prioritization would help identify the reduced set of test cases in the regression testing suite, still maintain the same criteria as the original number of test …
Ocean Current Prediction In The Gulf Of Thailand Using Spatio-Temporal Deep Learning On High-Frequency Radar, Nathachai Thongniran
Ocean Current Prediction In The Gulf Of Thailand Using Spatio-Temporal Deep Learning On High-Frequency Radar, Nathachai Thongniran
Chulalongkorn University Theses and Dissertations (Chula ETD)
Ocean surface current prediction is a crucial task for a variety of marine activities, such as disaster monitoring, search and rescue operations, power forecasting, and etc. There are three traditional forecasting approaches: (i) numerical based approach, (ii) time series based approach and (iii) machine learning based approach. However, their prediction accuracy was limited as they did not cooperate with spatial and temporal effects together, including oceanic knowledge is also not considered. This paper introduces the ocean surface prediction model that accounts for spatial and temporal characteristics by a combination between CNN and GRU and also the incorporation of oceanic inputs …
A Generative Adversarial Network For Generating Realistic Users Using Embedding From Recommendation Systems, Parichat Chonwiharnphan
A Generative Adversarial Network For Generating Realistic Users Using Embedding From Recommendation Systems, Parichat Chonwiharnphan
Chulalongkorn University Theses and Dissertations (Chula ETD)
User data has been used by many companies to understand user behaviors and find new business strategies. However, common techniques could not be used when it comes to new products that have not yet been released due to the fact that there are no prior data available. In this work, we propose a framework for generating realistic user data on new products which can then be analyzed for insights. Our model uses Conditional Generative Adversarial Network (CGAN) with the Straight-Through Gumbel estimator which can also handle discrete-valued outputs. The CGAN is conditioned on product features learned using a recommendation system …
Adaptive Matrix Multiplication For Various Degree Of Sparsity Using Tensorflow, Siraphob Theeracheep
Adaptive Matrix Multiplication For Various Degree Of Sparsity Using Tensorflow, Siraphob Theeracheep
Chulalongkorn University Theses and Dissertations (Chula ETD)
Matrix multiplication is a fundamental operation used in many problems, and many matrix multiplication algorithms are proposed for many computing environments. TensorFlow is a machine learning platform with many mathematic library functions including matrix multiplication. TensorFlow provides two methods, tf.matmul and tf.sparse_matmul, for matrix multiplication. It is suggested that tf.matmul should be used for dense matrices, and tf.sparse_matmul should be used for sparse matrices. In this work, an approach is proposed to improve the efficiency of matrix multiplication in TensorFlow. The proposed approach divides each matrix into four submatrices, and chooses either tf.matmul or tf.sparse_matmul for the multiplication of each …
Thai Stock Return Prediction Using Deep Learning Models With Stock Indicators And Textual Features, Tanawat Chiewhawan
Thai Stock Return Prediction Using Deep Learning Models With Stock Indicators And Textual Features, Tanawat Chiewhawan
Chulalongkorn University Theses and Dissertations (Chula ETD)
Stock prediction task is notoriously challenging due to the uncertainty and dynamic external factor which influence the stock behavior. Recently, Deep learning research is gaining popularity on this task but often focuses on only a particular type of data; numeric indicators or textual information. Moreover, most researches focus on only a single stock or a market index. In this paper, we aim to predict multiple stock returns using both types of data. The model consists of dual-stage attention recurrent neural network, our proposed stock relation inference framework, and textual features integration. The proposed stock relation inference help tackles multiple time-series …
Machine Reading Comprehension For Multiclass Questions On Thai Corpus, Theerit Lapchaicharoenkit
Machine Reading Comprehension For Multiclass Questions On Thai Corpus, Theerit Lapchaicharoenkit
Chulalongkorn University Theses and Dissertations (Chula ETD)
Previous Thai question answering and machine reading comprehension researches focus on small scale dataset and do not utilize the deep learning approach to build the models. In this research, we develop a Thai machine reading comprehension (MRC) model on Thai MRC dataset provided by NECTEC. This dataset consists of 17,000 question-answer pairs and has two classes of questions, which are factoid and yes-no questions. We use BIDAF as the based MRC architecture. We have performed experiments with 3 different multiclass model designs, which includes special tokens, joint, and cascade model. We also utilize contextual embeddings for Thai language to enhance …
Determining The Effective Authentication Factors Using Touchscreen Phones' Random Numeric Keypad, Nareerat Benjapatanamongkol
Determining The Effective Authentication Factors Using Touchscreen Phones' Random Numeric Keypad, Nareerat Benjapatanamongkol
Chulalongkorn University Theses and Dissertations (Chula ETD)
For the past decade, the increased usage of touchscreen phone devices has driven the mobile application market that prompted the financial institutes to release their own mobile banking applications to better serve their customers. To date, there are two ways a Thai bank customer can access his/her account(s) via the mobile banking application i) using a 6-digit Personal Identification Number (PIN) or ii) using fingerprint. To help to strengthen the current PIN-only authentication which may be exposed to smudge and shoulder-surfing attacks, the research studied and determined the effective authentication factors using a random numeric keypad. The results from the …
Projection And Determinants Of Cognitive Ability Among Older Persons In Thailand : Role Of Education, Paolo Miguel Vicerra
Projection And Determinants Of Cognitive Ability Among Older Persons In Thailand : Role Of Education, Paolo Miguel Vicerra
Chulalongkorn University Theses and Dissertations (Chula ETD)
This thesis examines the role of education on cognitive ability among the older population of Thailand. The nationally-representative data primarily utilised in this thesis is 2016 Population Change and Well-being in the Context of Aging Society. Other datasets had been used in selected themes within this thesis. Multiple analytic approaches had been applied to this study to show various effects of education gradients on cognitive functioning. In the first study, education and other covariates including income, health status, living arrangement, and social participation among others had been analysed by gender to test if the significant factors would be similar. It …
Oxidation States Of Trace Elements In Synthetic Corundum, Ontima Yamchuti
Oxidation States Of Trace Elements In Synthetic Corundum, Ontima Yamchuti
Chulalongkorn University Theses and Dissertations (Chula ETD)
Natural and synthetic corundums have various colors due to trace elements in their structures. Despite the abundance of research on impurities in natural corundum, little is known about trace elements in synthetic corundum. This project is aimed to quantify trace elements and identify their oxidation states related to coloration in red, blue, and yellow synthetic corundums. A total of 15 corundums, synthesized by melt growth process, were investigated by advanced analytical techniques. X-ray diffraction results indicate that all synthetic corundums contain crystalline Al2O3. Measurements from Electron Probe Micro-Analyzer, UV-Vis-NIR, and X-ray Absorption Near Edge Structure spectrometry suggest that Cr3+ is …