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Hydrothermal extraction of a-Fe2O3 nanocrystallite from hematite ore
N.M. Khalil,M.M.S. Wahsh,Elhadi E. Saad 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1
a-Fe2O3 nanocrystallite has been extracted from its ore raw material by using simple chemical method. Mineralogical and chemical compositions of the raw material were investigated using X-ray diffraction(XRD), infrared (IR) and X-ray fluorescence (XRF) techniques. Also, thermal behavior includingthermogravimetry (TG) and differential thermal analysis (DTA) of the raw material was examined. Scherrer’s equation and XRD data were used to determinate the crystallite size and phase composition ofthe extracted hematite nanocrystallite. Morphology of the extracted a-Fe2O3 particles was tested usingscanning electron microscope (SEM). About 96.80% of the total iron oxide present in the rawmaterial sample was extracted as a-Fe2O3 withthe average crystallite size less than 100 nm. The extracted a-Fe2O3 nanocrystallite is considered as apromise material for great technological applications as ceramic humidity sensors, catalysts, pigments,ferrofluid, recording systems, etc.
Dual Vector Control Strategy for a Three-Stage Hybrid Cascaded Multilevel Inverter
Mohamad N. Abdul Kadir,Saad Mekhilef,Hew Wooi Ping 전력전자학회 2010 JOURNAL OF POWER ELECTRONICS Vol.10 No.2
This paper presents a voltage control algorithm for a hybrid multilevel inverter based on a staged-perception of the inverter voltage vector diagram. The algorithm is applied to control a three-stage eighteen-level hybrid inverter, which has been designed with a maximum number of symmetrical levels. The inverter has a two-level main stage built using a conventional six-switch inverter and medium- and low- voltage three-level stages constructed using cascaded H-bridge cells. The distinctive feature of the proposed algorithm is its ability to avoid the undesirable high switching frequency for high- and medium- voltage stages despite the fact that the inverter’s dc sources voltages are selected to maximize the number of levels by state redundancy elimination. The high- and medium- voltage stages switching algorithms have been developed to assure fundamental switching frequency operation of the high voltage stage and not more than few times this frequency for the medium voltage stage. The low voltage stage is controlled using a SVPWM to achieve the reference voltage vector exactly and to set the order of the dominant harmonics. The inverter has been constructed and the control algorithm has been implemented. Test results show that the proposed algorithm achieves the desired features and all of the major hypotheses have been verified.
M. N. Abdul Kadir,Saad Mekhilef,Hew Wooi Ping 전력전자학회 2007 ICPE(ISPE)논문집 Vol.- No.-
This paper demonstrates the Direct Torque Control Permanent Magnet Synchronous Motor (DTC-PMSM) drive fed by asymmetrical multilevel inverter. The cascaded Hbridges topology with ratio-3 dc voltage sourced cells inverter has been employed. The DTC controller receives a reference torque and flux signals, the torque controller output determines the position of the desired flux vector. The amplitude of this vector is determined by the reference flux amplitude. The reference voltage vector is calculated as a continuous value using a technique developed originally for the SVM controlled drive. In this study, however, the reference voltage vector has been approximated to the nearest voltage vector achievable by one switching state of the multilevel inverter. The performance of two- and three-cells per arm inverter drives has been compared to that of the SVM-inverter drive at two values of the switching intervals. The results reflect the low switching frequency and torque ripple advantages of the proposed scheme.
Dual Vector Control Strategy for a Three-Stage Hybrid Cascaded Multilevel Inverter
Kadir, Mohamad N. Abdul,Mekhilef, Saad,Ping, Hew Wooi The Korean Institute of Power Electronics 2010 JOURNAL OF POWER ELECTRONICS Vol.10 No.2
This paper presents a voltage control algorithm for a hybrid multilevel inverter based on a staged-perception of the inverter voltage vector diagram. The algorithm is applied to control a three-stage eighteen-level hybrid inverter, which has been designed with a maximum number of symmetrical levels. The inverter has a two-level main stage built using a conventional six-switch inverter and medium- and low- voltage three-level stages constructed using cascaded H-bridge cells. The distinctive feature of the proposed algorithm is its ability to avoid the undesirable high switching frequency for high- and medium- voltage stages despite the fact that the inverter's dc sources voltages are selected to maximize the number of levels by state redundancy elimination. The high- and medium- voltage stages switching algorithms have been developed to assure fundamental switching frequency operation of the high voltage stage and not more than few times this frequency for the medium voltage stage. The low voltage stage is controlled using a SVPWM to achieve the reference voltage vector exactly and to set the order of the dominant harmonics. The inverter has been constructed and the control algorithm has been implemented. Test results show that the proposed algorithm achieves the desired features and all of the major hypotheses have been verified.
An on-line condition monitoring system for induction motors via instantaneous power analysis
M. Irfan,N. Saad,R. Ibrahim,V. S. Asirvadam 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.4
Condition monitoring is an important factor in assuring well-being of motors. Existing approaches of condition monitoring are dependenton expensive special sensors. This paper reviews various forms of existing condition monitoring methods and highlights theneed for an economical intelligent fault diagnosis system. In this study, the methodology taken in developing a condition monitoringsystem for the motor bearing faults identification, utilizing the commonly available motor stator current and voltage is demonstrated. Thisunique diagnostic condition monitoring system provides continuous real time tracking of the various bearing defects and determines theseverity which can be adopted for fast decision making. The study on different bearing faults under no-load and full-load conditions iscarried out experimentally and analyzed, and the results on the real hardware implementation confirm the effectiveness of the proposedapproach.
Prabhu, Shamit S.,Khan, Saad A.,Doudnikoff, Alexander L.,Reebye, Uday N. The Korean Dental Society of Anesthsiology 2019 Journal of Dental Anesthesia and Pain Medicine Vol.19 No.1
Myasthenia gravis (MG) is a neuromuscular autoimmune disorder which clinically presents as muscular weakness and fatigue due to autoantibody formation against acetylcholine receptors (AChR), leading to their subsequent destruction. Due to the neuromuscular implications of MG, certain considerations must be taken into account when providing anesthesia to MG patients. In the following case report, we have outlined procedural considerations for the anesthetic management of a patient with MG undergoing deep sedation for an elective oral surgery in an outpatient setting, as well as a discussion of relevant literature.
Hassan AL-Alawi,Saad Al-Nazhan,Nassr Al-Maflehi,Mazen A. Aldosimani,Mohammed Nabil Zahid,Ghadeer N. Shihabi 대한치과보존학회 2020 Restorative Dentistry & Endodontics Vol.45 No.1
Objectives: The purpose of this study was to determine the incidence of radix molaris (RM) (entomolaris and paramolaris) in the mandibular first permanent molars of a sample Saudi Arabian subpopulation using cone-beam computed tomography (CBCT). Materials and Methods: A total of 884 CBCT images of 427 male and 457 female Saudi citizens (age 16 to 70 years) were collected from the radiology department archives of 4 dental centers. A total of 450 CBCT images of 741 mature mandibular first molars that met the inclusion criteria were reviewed. The images were viewed at high resolution by 3 examiners and were analyzed with Planmeca Romexis software (version 5.2). Results: Thirty-three (4.5%) mandibular first permanent molars had RM, mostly on the distal side. The incidence of radix entomolaris (EM) was 4.3%, while that of radix paramolaris was 0.3%. The RM roots had one canal and occurred more unilaterally. No significant difference in root configuration was found between males and females (p > 0.05). Types I and III EM root canal configurations were most common, while type B was the only RP configuration observed. Conclusions: The incidence of RM in the mandibular first molars of this Saudi subpopulation was 4.5%. Identification of the supernumerary root can avoid missing the canal associated with the root during root canal treatment.