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Effects of magnet shapes on total harmonic distortion and cogging torque in a permanent magnet synchronous generator for wind turbines

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Clean Energy 2023年第5期7卷 1058-1068页

作者： Erol Kurt Adem Dalcalı Gazi university Department of Electrical and Electronics EngineeringTechnology FacultyAnkaraTurkey bandırma onyedi eylul university Department of Electrical and Electronics EngineeringFaculty of Engineering and Natural SciencesBandırmaBalıkesirTurkey National Research university TIIAME100000TashkentUzbekistan

This paper explores and theoretically reports the effects of different magnet structures on the cogging torque and the total harmonic distortion of the output waveforms from a permanent magnet *** generator is a radial flux machine and four different structures are considered for the magnet arrangement in the rotor component and modelled in the Ansys/Maxwell electromagnetic simulation *** three-phase machine exhibits different behaviours towards various magnet structures,***,inclined slotted rectangular,skewed double rectangular and inclined slotted skewed double rectangular,*** has been proven by finite element analysis and Fourier analysis that both the cogging and total harmonic distortion values vary significantly for all *** cogging torque values change in the range of 89.95 to 436.75 mNm and the lowest cogging torque is measured for the inclined slotted skewed double rectangular magnet geometry,while the conventional rectangular magnet geometry yields the worst value with 436.75 ***,the total harmonic distortion values varies between 1.63 and 3.55 for different magnetic *** the worst total harmonic distortion value is obtained from the inclined slotted rectangular magnet,the best total harmonic distortion is acquired from the skewed double rectangular *** these results will provide scientists and engineers with important information in order to obtain more efficient machines.

关键词： renewable energy wind power finite element method synchronous generator wind turbines

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Chronic otitis media and middle ear variants:Is there relation?

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World Journal of Clinical Cases 2023年第15期11卷 3481-3490页

作者： Fatma Dilek Gokharman Düzgün Can Senbil Sonay Aydin Erdal Karavas Ozge Ozdemir Arzu Gülsah Yalcin Pınar Nercis Kosar Department of Radiology Ankara Training and Research HospitalAnkara 06230Turkey Department of Radiology Erzincan Binali Yildirim UniversityErzincan 24100Turkey Department of Radiology Bandırma 17 Eylül UniversityBalıkesir 10200Turkey

BACKGROUND Chronic otitis media(COM)is an inflammatory disease that lasts for a long *** is common in developing *** loss can result from *** relationship between variations in middle ear anatomy and COM was investigated in our *** To compare the prevalence of middle ear anatomic variations between the cases with COM and healthy *** This retrospective study included 500 patients with COM and 500 healthy *** presence of those variants was determined:Koerner’s septum,facial canal dehiscence,high jugular bulb,jugular bulb dehiscence,jugular bulb diverticulum,sigmoid sinus anterior location and deep tympanic *** A total of 1000 temporal bones were *** incidences of these variants were respectively(15.4%-18.6%),(38.6%-41.2%),(18.2%-4.6%),(2.6%-1.2%),(1.2%-0%),(8.6%-0%),(0%-0%).It was observed that only high jugular bulb(Ply located sigmoid sinus frequencies(P=0.002)in the case group were statistically significantly higher than the control *** COM is a multifactorial disease and variants of middle ear have always been important in terms of potential risk for complication during surgery but rarely associated with COM as an etiology or as a consequence of the *** didn't find a positive correlation between COM and Koerner’s septum and facial canal *** ended up with a significant conclusion with the variants of dural venous sinuses-high jugular bulb,dehiscence of jugular bulb,diverticulum of jugular bulb and anteriorly located sigmoid sinus-that have been studied less and frequently associated with inner ear illnesses.

关键词： Chronic otitis media Radiology Inflammation Hearing loss Mastoid cells Head and neck

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Numerical Study on the Hydrodynamic Performance of Antifouling Paints

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Journal of Marine Science and Application 2020年第1期19卷 41-52页

作者： Utku Cem Karabulut Yavuz HakanÖzdemir BarışBarlas Department of Naval Architecture and Marine Engineering Bandırma Onyedi Eylül University10200 BalıkesirTurkey Department of Motor Vehicles and Transportation Technologies Çanakkale 18 Mart University17020ÇanakkaleTurkey Department of Naval Architecture and Marine Engineering İstanbul Technical University34469İstanbulTurkey

This study presents a simple numerical method that can be used to evaluate the hydrodynamic performances of antifouling *** Reynolds-averaged Navier-Stokes equations were solved through a finite volume technique,whereas roughness was modeled with experimentally determined roughness ***,the methodology was validated with previous experimental studies with a flat ***,flow around the Kriso Container Ship was ***,full-scale results were predicted using Granville’s similarity *** indicated that roughness has a similar effect on the viscous pressure resistance and frictional resistance around a Reynolds number of 10^***,the increase in frictional resistance due to roughness was calculated to be approximately 3%-5%at the ship scale depending on the paint.

关键词： Antifouling paint Surface roughness Frictional resistance Ship resistance Computational fluid dynamics RANS

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Numerical Investigation of the Effect of Surface Roughness on the Viscous Resistance Components of Surface Ships

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Journal of Marine Science and Application 2022年第3期21卷 71-82页

作者： Utku Cem Karabulut Yavuz HakanÖzdemir BarışBarlas bandırma onyedi eylül university Department of Naval Architecture and Marine Engineering10200 BalıkesirTurkey Çanakkale 18 Mart university Department of Motor Vehicles and Transportation Technologies17020ÇanakkaleTurkey Istanbul Technical university Department of Naval Architecture and Marine Engineering34469İstanbulTurkey

Recently,computational fluid dynamics(CFD)approaches have been effectively used by researchers to calculate the resistance characteristics of ships that have rough outer *** approaches are mainly based on modifying wall functions using experimentally pre-determined roughness *** several recent studies have shown that CFD can be an effective tool to calculate resistance components of ships for different roughness conditions,most of these studies were performed using the same ship geometry(KRISO Container Ship).Thus,the effect of ship geometry on the resistance characteristics of rough hull surfaces is worth *** this study,viscous resistance components of four different ships are calculated for different roughness ***,flat plate simulations are performed using a previous experimental study for comparison ***,the viscous resistance components of three-dimensional hulls are *** simulations are performed using two different turbulence models to investigate the effect of the turbulence model on the *** examination of the distributions of the local skin friction coefficients of the DTMB 5415 and Series 60 showed that the plumpness of the bow form has a significant effect on the increase in frictional resistance with increasing *** significant finding of the study is that viscous pressure resistance is directly affected by the surface *** all geometries,viscous pressure resistances showed a significant increase for highly rough surfaces.

关键词： surface roughness frictional resistance ship resistance computational fluid dynamics RANS

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Defects‑Rich Heterostructures Trigger Strong Polarization Coupling in Sulfides/Carbon Composites with Robust Electromagnetic Wave Absorption

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Nano-Micro letters 2025年第1期17卷 528-547页

作者： Jiaolong liu Siyu Zhang Dan Qu Xuejiao Zhou Moxuan Yin Chenxuan Wang Xuelin Zhang Sichen li Peijun Zhang Yuqi Zhou Kai Tao Mengyang li Bing Wei Hongjing Wu Mengyang li Bing Wei Hongjing Wu School of Physics Xidian UniversityXi’an 710071People’s Republic of China School of Advanced Materials and Nanotechnology State Key Discipline Laboratory of Wide Band Gap Semiconductor TechnologyXidian UniversityXi’an 710071People’s Republic of China School of Microelectronics Xidian UniversityXi’an 710071People’s Republic of China School of Telecommunication Engineering Xidian UniversityXi’an 710071People’s Republic of China MOE Key laboratory of Material Physics and Chemistry Under Extraordinary School of Physical Science and TechnologyNorthwestern Polytechnical UniversityXi’an 710072People’s Republic of China The Ministry of Education Key laboratory of Micro and Nano Systems forAerospace School of Mechanical EngineeringNorthwestern PolytechnicalUniversityXi’an 710072People’s Republic of China

Defects-rich heterointerfaces integrated with adjustable crystalline phases and atom vacancies,as well as veiled dielectric-responsive character,are instrumental in electromagnetic *** methods,however,constrain their delicate ***,an innovative alternative is proposed:carrageenan-assistant cations-regulated(CACR)strategy,which induces a series of sulfides nanoparticles rooted in situ on the surface of carbon *** unique configuration originates from strategic vacancy formation energy of sulfides and strong sulfides-carbon support interaction,benefiting the delicate construction of defects-rich heterostructures in M_(x)S_(y)/carbon composites(M-CAs).Impressively,these generated sulfur vacancies are firstly found to strengthen electron accumulation/consumption ability at heterointerfaces and,simultaneously,induct local asymmetry of electronic structure to evoke large dipole moment,ultimately leading to polarization coupling,i.e.,defect-type interfacial ***“Janus effect”(Janus effect means versatility,as in the Greek two-headed Janus)of interfacial sulfur vacancies is intuitively confirmed by both theoretical and experimental investigations for the first ***,the sulfur vacancies-rich heterostructured Co/Ni-CAs displays broad absorption bandwidth of 6.76 GHz at only 1.8 mm,compared to sulfur vacancies-free CAs without any dielectric *** defects-rich heterostructures,this one-pot CACR strategy may steer the design and development of advanced nanomaterials,boosting functionality across diverse application domains beyond electromagnetic response.

关键词： Defects-rich heterointerfaces Sulfides Polarization coupling Electromagnetic wave absorption

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A study on Al_2O_3 passivation in GaN MOS-HEMT by pulsed stress

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Chinese Physics B 2008年第4期17卷 1405-1409页

作者：岳远征郝跃张进城冯倩倪金玉马晓华 Key laboratory of Wide band-Gap Semiconductor Materials and Devices Xidian University

This paper studies systematically the drain current collapse in AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors （MOS-HEMTs） by applying pulsed stress to the device. low-temperature layer of Al2O3 ultrathin film used as both gate dielectric and surface passivation layer was deposited by atomic layer deposition （AlD）. For HEMT, gate turn-on pulses induced large current collapse. However, for MOS-HEMT, no significant current collapse was found in the gate turn-on pulsing mode with different pulse widths, indicating the good passivation effect of AlD Al2O3. A small increase in Id in the drain pulsing mode is due to the relieving of self-heating effect. The comparison of synchronously dynamic pulsed Id - Vds characteristics of HEMT and MOS-HEMT further demonstrated the good passivation effect of AlD Al2O3.

关键词： AlGaN/GaN MOS-HEMT Al2O3 passivation

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A k·p analytical model for valence band of biaxial strained Ge on(001) Si_(1-x)Ge_x

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Chinese Physics B 2012年第5期21卷 501-507页

作者：王冠宇张鹤鸣高翔王斌周春宇 Key laboratory of Wide band-Gap Semiconductor Materials and Devices School of MicroelectronicsXidian University

In this paper,the dispersion relationship is derived by using the k·p method with the help of the perturbation theory,and we obtain the analytical expression in connection with the deformation *** calculation of the valence band of the biaxial strained Ge/（001）Si1-xGex is then *** results show that the first valence band edge moves up as Ge fraction x decreases,while the second valence band edge moves *** band structures in the strained Ge/（001）Si 0.4 Ge 0.6 exhibit significant changes with x decreasing in the relaxed Ge along the [0,0,k] and the [k,0,0] ***,we employ a pseudo-potential total energy package（CASTEP） approach to calculate the band structure with the Ge fraction ranging from x = 0.6 to *** analytical results of the splitting energy accord with the CASTEP-extracted *** quantitative results obtained in this work can provide some theoretical references to the understanding of the strained Ge materials and the conduction channel design related to stress and orientation in the strained Ge pMOSFET.

关键词： strained Ge valence band k·p method dispersion relationship

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Groove-type channel enhancement-mode Al GaN/GaN MIS HEMT with combined polar and nonpolar AlGaN/GaN heterostructures

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Chinese Physics B 2016年第8期25卷 340-346页

作者：段小玲张进成肖明赵一宁静郝跃 Key laboratory of Wide band-Gap Semiconductor Technology School of Microelectronics Xidian University

A novel groove-type channel enhancement-mode AlGaN/GaN MIS high electron mobility transistor（GTCE-HEMT）with a combined polar and nonpolar AlGaN/GaN heterostucture is presented. The device simulation shows a threshold voltage of 1.24 V, peak transconductance of 182 m S/mm, and subthreshold slope of 85 m V/dec, which are obtained by adjusting the device parameters. Interestingly, it is possible to control the threshold voltage accurately without precisely controlling the etching depth in fabrication by adopting this structure. Besides, the breakdown voltage（VB） is significantly increased by 78% in comparison with the value of the conventional MIS-HEMT. Moreover, the fabrication process of the novel device is entirely compatible with that of the conventional depletion-mode（D-mode） polar AlGaN/GaN HEMT. It presents a promising way to realize the switch application and the E/D-mode logic circuits.

关键词： AlGaN/GaN HEMT enhancement-mode operation groove-type channel nonpolar

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Effect of Si doping in wells of AlGaN/GaN superlattice on the characteristics of epitaxial layer

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Chinese Physics B 2012年第7期21卷 455-459页

作者：张伟薛军帅周晓伟张月刘子阳张进成郝跃 Key laboratory of Wide band-Gap Semiconductor Materials and Devices Xidian University

An A1GaN/GaN superlattice grown on the top of a GaN buffer induces the broadening of the full width at half maximum of （102） and （002） X-ray diffraction rocking curves. With an increase in the Si-doped concentration in the GaN wells, the full width at half maximum of the （102） rocking curves decreases, while that of the （002） rocking curves increases. A significant increase of the full width at the half maximum of the （002） rocking curves when the doping concentration reaches 2.5 × 10^19 cm-3 indicates the substantial increase of the inclined threading dislocation. High level doping in the A1GaN/GaN superlattice can greatly reduce the biaxial stress and optimize the surface roughness of the structures grown on the top of it.

关键词： A1GaN/GaN superlattice Si doping

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Influences of different structures on the characteristics of H_2O-based and O_3-based la_xAl_yO films deposited by atomic layer deposition

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Chinese Physics B 2016年第5期25卷 434-440页

作者：费晨曦刘红侠汪星赵冬冬王树龙陈树鹏 Key laboratory for Wide-band Gap Semiconductor Materials and Devices of Education School of Microelectronics Xidian University

H_2O-based and O_3-based la_xAl_yO nanolaminate films were deposited on Si substrates by atomic layer deposition（AlD）. Structures and performances of the films were changed by different barrier layers. The effects of different structures on the electrical characteristics and physical properties of the la_xAl_yO films were studied. Chemical bonds in the la_xAl_yO films grown with different structures and different oxidants were also investigated with x-ray photoelectron spectroscopy（XPS）. The preliminary testing results indicate that the la_xAl_yO films with different structures and different oxidants show different characteristics, including dielectric constant, equivalent oxide thickness（EOT）, electrical properties, and stability.

关键词： atomic layer deposition oxidant dielectric constant equivalent oxide thickness

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