Evaluation and Optimization of Power Electronic Converters using Advanced Computer Aided Engineering Techniques

Oza, Ritesh,Emadi, Ali The Korean Institute of Power Electronics 2003 JOURNAL OF POWER ELECTRONICS Vol.3 No.2

Computer aided engineering (CAE) is a systematic approach to develop a better product/application with maximum possible options and minimum transition time. This paper presents a comprehensive feasibility analysis of various CAE techniques for evaluation and optimization of power electronic converters and systems. Different CAE methods for analysis, design, and performance improvement are classified. In addition, their advantages compared to the conventional workbench experimental methods are explained in detail and through examples.

Evaluation and Optimization of Power Electronic Converters using Advanced Computer Aided Engineering Techniques

Ritesh Oza,Ali Emadi 전력전자학회 2003 JOURNAL OF POWER ELECTRONICS Vol.3 No.2

Computer aided engineering (CAE) is a systematic approach to develop a better product/application with maximum possible options and minimum transition time. This paper presents a comprehensive feasibility analysis of various CAE techniques for evaluation and optimization of power electronic converters and systems Different CAE methods for analysis, design, and performance improvement are classified In addition, their advantages compared to the conventional workbench experimental methods are explained m detail and through examples

Morphological and morphometric study of pulmonary vein anatomy in relation to cardiac invasive and electrophysiological procedures

Harshal Oza,Bhavik Doshi 대한해부학회 2023 Anatomy & Cell Biology Vol.56 No.4

Pulmonary veins (PVs) and their myocardial sleeves play an important role in the development of atrial fibrillation. Hence, detailed knowledge of PV anatomy is required to improve the procedural success rate and prevent complicationsduring cardiac procedures. The aim of this study was to evaluate the PV anatomy along with anatomical variations inthe Indian population. Total 100 formalin fixed cadaveric hearts were examined. The number and pattern of the PVswere observed along with the measurement of their horizontal and vertical diameters. The ovality index for each PV wascalculated. Classical PV pattern was observed in 62% cases. Variant pattern like additional right middle PV pattern and leftcommon PV pattern were found in 20% and 10% cases respectively. A separate pattern with presence of both right middlePV and left common PV was observed in 6% cases. In the classical pattern right superior PV was the largest followed by rightinferior, left superior and left inferior PV. The additional right middle PV had the smallest diameter whereas the left commonPV had the largest diameter. Almost all the veins had greater vertical diameters in comparison to horizontal diameters. Thevariant PVs were oval and had greater ovality index compared to the normal PVs. In classical pattern 54.8% hearts whereas invariant pattern 79% hearts had one or more oval PV. The given data can help clinicians for planning and execution of variousinterventional and electrophysiological procedures involving PVs.

MESSAGE

B. M. Oza 한인문화연구원 1994 한인문화논총 Vol.11 No.-

One-dimensional ordered growth of magneto-crystalline and biocompatible cobalt ferrite nano-needles

Ravichandran, M.,Oza, G.,Velumani, S.,Ramirez, J.T.,Garcia-Sierra, F.,Andrade, N.B.,Garza-Navarro, M.A.,Garcia-Gutierrez, D.I.,Asomoza, R. North-Holland 2014 Materials letters Vol.135 No.-

<P>In this letter, we have reported a novel synthesis of CoFe2O4 nano-needles by a co-precipitation method using precursors of ferric chloride and cobalt nitrate at 80 degrees C. The structural and magnetic properties of as-grown needle-like CoFe2O4 nanostructures exhibit cubic spinel structure. CoFe2O4 nano-needles have an average diameter of 15 nm with an aspect ratio of 30:50, which was depicted by High-resolution transmission electron microscopy (HRTEM). Superconducting Quantum Interference Device (SQUID) confirmed the property of superparamagnetism. The magnetic measurement illustrated that the coercivity (Hc) of CoFe2O4 nano-needles increased from -145.84 Oe at 5 K to -25.38 Oe at 312 K. The cell viability studies of CoFe2O4 nano-needles were performed in the concentration range of 5-1000 mu g/ml on L6 (Skeletal muscle cell lines) and Hep-2 (Larynx carcinoma) cells using 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. There was more than 50% cell viability for both the cell lines, but Hep-2 cells were more prone to killing as compared to L6 cells. Such biocompatible nanostructures can be used as drug-delivery systems for cancer therapeutics. (C) 2014 Elsevier B.V. All rights reserved.</P>

Effectiveness of medical coating materials in decreasing friction between orthodontic brackets and archwires

Nursel Aricia,Berat S. Akdenizb,Abdullah A. Oza,Yucel Gencerc,Mehmet Tarakcic,Selim Arici 대한치과교정학회 2021 대한치과교정학회지 Vol.51 No.4

Objective: The aim of this in vitro study was to evaluate the changes in friction between orthodontic brackets and archwires coated with aluminum oxide (Al2O3), titanium nitride (TiN), or chromium nitride (CrN). In addition, the resistance of the coatings to intraoral conditions was evaluated. Methods: Stainless steel canine brackets, 0.016-inch round nickel-titanium archwires, and 0.019 × 0.025-inch stainless steel archwires were coated with Al2O3, TiN, and CrN using radio frequency magnetron sputtering. The coated materials were examined using scanning electron microscopy, an X-ray diffractometer, atomic force microscopy, and surface profilometry. In addition, the samples were subjected to thermal cycling and in vitro brushing tests, and the effects of the simulated intraoral conditions on the coating structure were evaluated. Results: Coating of the metal bracket as well as nickel-titanium archwire with Al2O3 reduced the coefficients of friction (CoFs) for the bracket-archwire combination (p < 0.01). When the bracket and stainless steel archwire were coated with Al2O3 and TiN, the CoFs were significantly lower (0.207 and 0.372, respectively) than that recorded when this bracket-archwire combination was left uncoated (0.552; p < 0.01). The friction, thermal, and brushing tests did not deteriorate the overall quality of the Al2O3 coatings; however, some small areas of peeling were evident for the TiN coatings, whereas comparatively larger areas of peeling were observed for the CrN coatings. Conclusions: Our findings suggest that the CoFs for metal bracket-archwire combinations used in orthodontic treatment can be decreased by coating with Al2O3 and TiN thin films. [Korean J Orthod 2021;51(4):270-281]

Osteosarcoma of the mandible: A case report with an early radiographic manifestation

Lavanya Samraj,Sriram Kaliamoorthy,Ramesh Venkatapathy,Nirima Oza 대한영상치의학회 2014 Imaging Science in Dentistry Vol.44 No.1

Osteosarcoma is a classical malignant bone-forming neoplasm which usually presents with an aggressive clinical course. The current case is presented with the radiographic feature of widening of the periodontal ligament space of the involved teeth, which is considered to be the earliest radiographic manifestation of osteosarcoma involving the jaw bone. The main aim of this case report was to focus on the importance of early diagnosis of this tumor based on clinical and radiographic examinations, and confirmation by histopathology. Considering the rarity of the disease type and particularly taking into account the fast progression and aggressiveness of this neoplasm, it is clear that the presentation of a clinical case represents a major contribution to better understanding of osteosarcomas involving the jaw bone.

Synthesis of CuIn_1-xGa_xSe₂ Nanoparticles by Thermal Decomposition Method with Tunable Ga Content

Latha, M.,Devi, R. Aruna,Velumani, S.,Oza, Goldie,Reyes-Figueroa, P.,Rohini, M.,Becerril-Juarez, I. G.,Yi, Junsin American Scientific Publishers 2015 Journal of Nanoscience and Nanotechnology Vol.15 No.11

<P>Chalcopyrite CuIn1-xGaxSe2 (CIGS) nanoparticles were synthesized by mixing copper (I) chloride (CuCl), Indium (III) chloride (InCl3), gallium (III) chloride (GaCl3) and selenium (Se) in oleylamine (OLA) at 260 degrees C for 4 h under nitrogen atmosphere. The Ga/(In + Ga) ratio was tuned across the entire stoichiometric range from 0 to 1. X-ray diffraction analysis (XRD) revealed chalcopyrite crystal structure for samples prepared with x = 0, 0.3, 0.5, 0.7 and 1. The lattice parameters a and c decreased linearly with increasing Ga concentration which is consistent with Vegard's law. Raman spectra exhibited A(1) optical phonon vibrational mode for synthesized nanoparticles which gradually shifted to higher wavenumber with increasing Ga content. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) images showed irregular as well as hexagonal plate like morphologies in the size range of 100 to 400 nm. High-resolution transmission electron microscopy (HR-TEM) images showed well-defined lattice fringes and d-spacing correspond to (112) plane which gradually decreases with increasing Ga content. The material compositions of synthesized CIGS nanoparticles with x = 0, 0.3, 0.5, 0.7 and 1 were very close to the desired stoichiometry which was confirmed by energy dispersive X-ray analysis (EDAX). Ultra-violet visible near infrared (UV-VIS-NIR) absorption spectra of the synthesized CIGS nanoparticles revealed that the bandgap could be tuned over the range 1 to 1.7 eV by varying the Ga/(In+Ga) ratio.</P>

Osteosarcoma of the mandible: A case report with an early radiographic manifestation

Samraj, Lavanya,Kaliamoorthy, Sriram,Venkatapathy, Ramesh,Oza, Nirima Korean Academy of Oral and Maxillofacial Radiology 2014 Imaging Science in Dentistry Vol.44 No.1

Osteosarcoma is a classical malignant bone-forming neoplasm which usually presents with an aggressive clinical course. The current case is presented with the radiographic feature of widening of the periodontal ligament space of the involved teeth, which is considered to be the earliest radiographic manifestation of osteosarcoma involving the jaw bone. The main aim of this case report was to focus on the importance of early diagnosis of this tumor based on clinical and radiographic examinations, and confirmation by histopathology. Considering the rarity of the disease type and particularly taking into account the fast progression and aggressiveness of this neoplasm, it is clear that the presentation of a clinical case represents a major contribution to better understanding of osteosarcomas involving the jaw bone.

Multi-Secondary Transformer: A Modeling Technique for Simulation - II

Patel, A.,Singh, N.P.,Gupta, L.N.,Raval, B.,Oza, K.,Thakar, A.,Parmar, D.,Dhola, H.,Dave, R.,Gupta, V.,Gajjar, S.,Patel, P.J.,Baruah, U.K. Journal of International Conference on Electrical 2014 Journal of international Conference on Electrical Vol.3 No.1

Power Transformers with more than one secondary winding are not uncommon in industrial applications. But new classes of applications where very large number of independent secondaries are used are becoming popular in controlled converters for medium and high voltage applications. Cascade H-bridge medium voltage drives and Pulse Step Modulation (PSM) based high voltage power supplies are such applications. Regulated high voltage power supplies (Fig. 1) with 35-100 kV, 5-10 MW output range with very fast dynamics (${\mu}S$ order) uses such transformers. Such power supplies are widely used in fusion research. Here series connection of isolated voltage sources with conventional switching semiconductor devices is achieved by large number of separate transformers or by single unit of multi-secondary transformer. Naturally, a transformer having numbers of secondary windings (~40) on single core is the preferred solution due to space and cost considerations. For design and simulation analysis of such a power supply, the model of a multi-secondary transformer poses special problem to any circuit analysis software as many simulation softwares provide transformer models with limited number (3-6) of secondary windings. Multi-Secondary transformer models with 3 different schemes are available. A comparison of test results from a practical Multi-secondary transformer with a simulation model using magnetic component is found to describe the behavior closer to observed test results. Earlier models assumed magnetising inductance in a linear loss less core model although in actual it is saturable core made-up of CRGO steel laminations. This article discusses a more detailed representation of flux coupled magnetic model with saturable core properties to simulate actual transformers very close to its observed parameters in test and actual usage.