53 research outputs found
SYNTHESIS OF GOLD NANOPARTICLES AND INTERACTION WITH AN ORGANIC DYE UNDER VARYING PH CONDITIONS: A UV–VISIBLE SPECTROSCOPIC STUDY
No full textGold nanoparticles or shortened as AuNPs possess unique optical and physicochemical properties, enabling them to be used in various applications such as in sensing, catalysis, photonics, and biomedical systems. In this study, gold nanoparticles were synthesized by the Turkevich citrate reduction method and their interaction with sodium fluorescein (NaFl) was investigated by UV–Visible spectroscopy under varying pH conditions. Spherical AuNPs have been seen to exhibit a surface plasmon resonance (SPR) peak in the 530–543nm region. Interaction studies revealed that sodium fluorescein demonstrated pH-dependent interaction, with clear evidence of dimer formation and enhanced adsorption onto the AuNP surface at alkaline pH (pH 9.2). This result highlights the interaction behaviour of structurally and functionally different organic dyes with gold nanoparticles, emphasizing the critical role of dye charge, structures of the molecules, and the pH of the solutions in governing nanoparticle–dye interactions
Population balance equation for collisional breakage: A new numerical solution scheme and its convergence
No full text<p><strong>Synopsis</strong></p><p>These files represent a reference implementation of the finite volume method for the solution of the discretised population balance equation for collisional breakge. Several test cases are provided. </p><p>Implementation language: Matlab (FORTRAN-derivative)</p><p>The method and its capabilities are described in<br>P. Kuswah, A. Das, J. Saha, A. Bück, "Population balance equation for collisional breakage: A new numerical solution scheme and its convergence", Communications in Nonlinear Science and Numerical Simulation, vol 121, 107244, 2023. </p><p>If the method or code is used in other work, cite<br>P. Kuswah, A. Das, J. Saha, A. Bück, "Population balance equation for collisional breakage: A new numerical solution scheme and its convergence", Communications in Nonlinear Science and Numerical Simulation, vol 121, 107244, 2023. </p><p><strong>License</strong></p><p>The implementation is distributed as-is without taking over any responsibility by the authors or their affiliated institutions for potential damages resulting from its use. </p><p>The implementation is made available under Creative Commons Attribution Non Commercial No Derivatives 4.0 International. </p><p><strong>Folder contents</strong></p><p>The reference implementations are provided for the cases discussed in the mentioned publication. The implementation of the finite volume methode is stored in the sub-folders "DPBE_Brk", calling sequence and required initialisiations are given in the files "Main_FPT.m".</p><p>In case of problems, bug reports, feel free to contact any author.</p><p>On behalf of all authors,</p><p>Andreas Bück<br>Institute of Particle Technology<br>Friedrich-Alexander-Universität Erlangen-Germany<br>[email protected]<br>www.spg.forschung.fau.de</p><p> </p><p>v1.0: 31.08.2023</p>
Data mining – project II
No full textThe purpose of this report is to document what the author had done in the project to investigate
problems in data mining and designing novel algorithms to solve it and compare against existing
approaches. The objective of the project is to determine whether the current approaches to
datamining are optimal and come up with possibly better methods to go about it. The project
requires the author to data mine from a given set of data, analyze the results and attempt to
improve upon existing methodologies.Bachelor of Engineering (Computer Engineering
Effects due to unconventional pairing in transport through a normal metal-superconductor-normal metal hybrid junction
No full textQuantum transport through a helical ring in presence of Aharonov-Bohm flux and Rashba spin-orbit interaction
No full textEffect of concentration variation in graphene oxide (GO) membranes for water flux optimization
No full textIn situ power-loss estimation of IGBT modules
No full textA fault detection and prediction method for insulated-gate bipolar transistors (IGBTs) has been improved over the past decades to reduce system downtime. In situ lifetime estimation of IGBT modules has been challenging due to a number of requirements: the necessity to operate at high voltage in the switching environment and the measurement precision of the gate-threshold voltage or collector-to-emitter voltage. This thesis presents a wear-fatigue estimation framework that consists of collector-to-emitter measurement, power loss calculation, and thermal lifetime prediction model. The measurement circuit enables the estimation of power loss across a variety of IGBT modules with minimum impact on system reliability.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2023-05-01The student, Qichen Jin, accepted the attached license on 2021-04-29 at 10:53.The student, Qichen Jin, submitted this Thesis for approval on 2021-04-29 at 10:58.This Thesis was approved for publication on 2021-04-29 at 15:19.DSpace SAF Submission Ingestion Package generated from Vireo submission #16596 on 2021-09-16 at 20:14:39Made available in DSpace on 2021-09-17T04:06:56Z (GMT). No. of bitstreams: 2
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Previous issue date: 2021-04-29Embargo set by: Seth Robbins for item 118716
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Condition monitoring of SiC MOSFETs on LLC resonant converter
No full textSilicon carbide (SiC) MOSFETs are widely acknowledged for low loss, fast switching and remarkable thermal conductivity compared to silicon (Si) counterparts. SiC-based power electronic converters, therefore, are optimal when operated at medium voltage to high voltage in high switching frequency applications, which results in a much higher power density than Si-based power converters. The reliability of SiC devices, however, remains a significant hindrance to their wide adoption in power electronics in transportation, industry and military applications. Real-time condition monitoring of SiC devices in SiC-based power converters addresses the reliability issues by providing an early sign of potential failure. Since one of the most consistent failure precursors of a degraded SiC MOSFET is an increase of gate leakage current, a circuitry is developed to track and estimate the on-state gate leakage current of the device during operation. To demonstrate the functionality of the proposed method, an LLC full-bridge resonant converter that operates at a medium voltage and high switching frequency was designed and used to obtain the experimental results. This converter will operate at various duty ratios, DC-link voltages, switching frequencies and output loads to show the consistency and accuracy of the proposed condition monitoring method. With proper calibration, this cost-effective method obtains an accurate gate leakage estimation which opens opportunities to perform prognostic and health monitoring of SiC devices.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2023-05-01The student, Patrick Wang, accepted the attached license on 2021-04-23 at 02:17.The student, Patrick Wang, submitted this Thesis for approval on 2021-04-23 at 02:49.This Thesis was approved for publication on 2021-04-26 at 14:56.DSpace SAF Submission Ingestion Package generated from Vireo submission #16521 on 2021-09-16 at 17:05:03Made available in DSpace on 2021-09-17T02:34:46Z (GMT). No. of bitstreams: 2
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Previous issue date: 2021-04-26Embargo set by: Seth Robbins for item 118577
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An online power loss calculation framework for IGBTs in a three-phase inverter
No full textLimitedMade available in DSpace on 2020-08-27T00:51:36Z (GMT). No. of bitstreams: 2
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Previous issue date: 2020-05-15Embargo set by: Seth Robbins for item 115971
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Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemAuthor requested closed access (OA after 2yrs) in Vireo ETD systemInsulated-gate bipolar transistors (IGBTs) are used in a wide range of high-power applications for their high voltage blocking and current conduction capabilities. In these applications, IGBTs are subjected to harsh operating conditions and face reliability issues. Online health monitoring has been proposed to reduce IGBT failure as it enables condition evaluation while keeping the power electronics system in operation. To perform online health monitoring, it is crucial to know the junction temperature of the IGBT. Many proposed methods of online health monitoring investigate the use of thermo-sensitive electrical parameters. These parameters are strong functions of the junction temperature of an IGBT. However, these parameters also vary with operating conditions like dc-link voltage and load current, which can affect the junction temperature calculation. This thesis introduces an IGBT power loss calculation framework for six IGBTs in a three-phase two-level inverter. Using a Foster network model of an IGBT module, the power loss information gives the difference between the junction temperature and the case temperature of the IGBT. The proposed framework has three main components: on-state voltage measurement circuits, a sensor interface circuit board, and a data storage system. In this thesis, two IGBT on-state voltage measurement topologies are examined and discussed. Software requirements for the sensor interface board are specified. Finally, the algorithm of a data storage system is proposed. The data storage system receives data from the measurement and sensor boards. It measures the output current of each inverter leg and calculates the power loss in all six IGBT modules.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2022-05-01The student, Michael Wu, accepted the attached license on 2020-05-15 at 11:34.The student, Michael Wu, submitted this Thesis for approval on 2020-05-15 at 11:42.This Thesis was approved for publication on 2020-05-15 at 11:54.DSpace SAF Submission Ingestion Package generated from Vireo submission #15410 on 2020-08-25 at 17:45:1
A distributed electromechanical spine for bio-inspired robots
No full textBiological mechanisms are embraced in mobile robots to interact with their surroundings. Although current bio-inspired robots perform well, their performance is limited due to the lack of a flexible spine. A spine provides an animal's agility, a wide range of motion, balance, and efficiency. It can be created using motors, which have been widely used for robotic joints. However, this conventional method introduces design complexity, low actuation speed, low efficiency, poor backdrivability, and backlash issue. Moreover, a vertebra in the spine does not fully rotate like a conventional motor. This thesis introduces a distributed and scalable two-dimensional electromechanical spine for bio-inspired robots. It proposes an approach that mimics an actual animal spinal structure and muscles by combining a magnetic core and two coils in a module. Six modules are connected in series to form a spine. A single module and the entire system represent a vertebra and vertebrae, respectively. The proposed actuator utilizes electromagnetic force induced by coil currents to control torque at each module. This actuator has several benefits, including modularity, scalability, distributed actuation, simple structure, and gearless design, as well as better cooling mechanism and compliance. While a motor has a trade-off between torque and speed, the proposed actuator has a trade-off between torque and angular flexibility. Furthermore, the proposed actuator uses normal stress to produce force, while a motor uses shear stress. This approach results in high torque capability without using gears. A distributed air-gap model is proposed to improve force estimation by taking non-uniform air gaps and core saturation into consideration. Core-flux density and coil-current density are considered as design constraints in the design procedure. A torsion spring mechanism is applied to each module to improve the torque capability. Finally, feasibility of the proposed actuation system is verified by both simulation and experimental results.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2021-12-01The student, Bonhyun Ku, accepted the attached license on 2019-12-12 at 11:15.The student, Bonhyun Ku, submitted this Thesis for approval on 2019-12-12 at 11:27.This Thesis was approved for publication on 2019-12-12 at 12:03.DSpace SAF Submission Ingestion Package generated from Vireo submission #14795 on 2020-02-28 at 17:24:25Made available in DSpace on 2020-03-02T22:18:19Z (GMT). No. of bitstreams: 2
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Previous issue date: 2019-12-12Embargo set by: Seth Robbins for item 113941
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