On the Effect of Claw Geometry on the Vibration of Single-Phase Claw-Pole BLDC Machines

Nejat Saed,Shahin Asgari,Annette Muetze 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-

In automotive auxiliary applications, where cost is typically the primary design criterion for mass-produced fractional horsepower drives, single-phase BLDC machines are usually preferred over their three-phase counterparts. These small drives are barely audible compared to the main drive system in automotive applications. However, single-phase BLDC machines have an inherently high vibration, which may excite nearby structures or components to produce noise. This study compares the vibration performance of single-phase claw-pole BLDC machines with different claw geometries using simulations and experiments. Along with the conventional rectangular claw shape, two well-known strategies for reducing noise and vibration by modifying the stator’s claw geometry are compared. Moreover, the trapezoidal claw shape, which is more common in claw-pole stepper motors and alternators, is analyzed. Results of finite dement analysis and experimental investigations indicate that, although skewing the claws could be a practical approach to mitigate the vibration, a trapezoidal claw shape can significantly reduce the vibration of these machines.

Repair of diaphragmatic injury and placement of tube thoracostomy during right upper quadrant peritonectomy

Nejat Ozgul,Derman Basaran,Gokhan Boyraz,M. Coskun Salman 대한부인종양학회 2016 Journal of Gynecologic Oncology Vol.27 No.1

Objective: Patients with advanced or recurrent ovarian cancer often have metastatic disease in the upper abdominal region, especially to the right hemidiaphragm, which requires diaphragmatic resection in order to achieve optimal cytoreduction. The aim of this surgical video is to demonstrate repair of a diaphragmatic injury and placement of tube thoracostomy during right upper quadrant peritonectomy in a patient with recurrent ovarian cancer. Methods: This is the case of a 45-year-old woman presented with platinum sensitive recurrent ovarian cancer. Abdomen computed tomography also confirmed peritoneal carcinomatosis and pelvic recurrent mass. HIPEC was administered after complete cytoreduction including bilateral upper quadrant peritonectomy, during which diaphragmatic injury occurred near the central tendon and pleural cavity was entered. We inserted a chest tube through the 6th intercostal space in the anterior axillary line in order to prevent postoperative massive pleural effusion. Diaphragmatic defect was closed primarily after the tube placement. The chest tube was withdrawn on the third postoperative day and the patient was discharged on postoperative day 25 without any complications. Results: The central tendon of diaphragm is the most vulnerable part for lacerations. Diaphragmatic repairs could be performed by various techniques; interrupted or continuous, locking or non-locking sutures, with either permanent or absorbable materials. In our view, all of the techniques provide similar results and surgeons can choose any of them as long as they are comfortable with the procedure. Conclusion: In most cases, these lacerations can be repaired primarily without necessitating tube thoracostomy. However, performance of HIPEC can cause massive pleural effusions which can lead to significant pulmonary morbidity. Therefore, retrograde placement of the chest tube under direct vision is quite straightforward when the diaphragm is opened.

Surface defects characterization with frequency and force modulation atomic force microscopy using molecular dynamics simulations

Hossein Nejat Pishkenari,Ali Meghdari 한국물리학회 2010 Current Applied Physics Vol.10 No.2

This paper is devoted to the characterization of the surface defects using a recently developed AFM technique called frequency and force modulation AFM (FFM–AFM). The simulated system includes a recently developed gold coated AFM probe which interacts with a sample including single-atom vacancy and impurities. In order to examine the behavior of the above system on different transition metals, the molecular dynamics (MD) simulation with Sutton–Chen (SC) inter-atomic potential is used. In this study,an online imaging simulation of the probe and sample is performed, and the effects of the horizontal scan speed, the effective frequency set-point, the cantilever stiffness, the tip-sample rest position and the cantilever quality factor on the resulting images are investigated. Using a proposed optimum controlling scheme for the excitation force amplitude, the cantilever horizontal speed can be increased.

Surface elasticity and size effect on the vibrational behavior of silicon nanoresonators

Hossein Nejat Pishkenari,Bahram Afsharmanesh,Ehsan Akbari 한국물리학회 2015 Current Applied Physics Vol.15 No.11

Predominance of nano-scale effects observed in material behavior at small scales requires implementation of new simulation methods which are not merely based on classical continuum mechanic. On the other hand, although the atomistic modeling methods are capable of modeling nano-scale effects, due to the computational cost, they are not suitable for dynamic analysis of nano-structures. In this research, we aim to develop a continuum-based model for nano-beam vibrations which is capable of predicting the results of molecular dynamics (MD) simulations with considerably lower computational effort. In this classical-based modeling, the surface and core regions are taken to have different mechanical properties, where core atoms are assumed to have macroscale properties whereas surface layer is showing a different elastic modulus from the core components. By estimating physical parameters of proposed classical model using molecular dynamics results and the genetic algorithm, calibrated classical EulereBernoulli and Timoshenko beam models are developed. The results demonstrates that a Timoshenko beam model incorporating surface effects and having calibrated parameters, is able to provide almost the same results as molecular dynamics method which can be used to predict the vibrational behavior of nano-beams at different scales from nano to macro.

Vibrational analysis of the fullerene family using Tersoff potential

Hossein Nejat Pishkenari,Pooriya Ghaf Ghanbari 한국물리학회 2017 Current Applied Physics Vol.17 No.1

Using Tersoff bond order potential, a vibrational analysis of the spherical fullerene family, namely C60, C80, C180, C240, C260, C320, C500, and C720 was performed. To evaluate the validity of our results, we have compared our simulation results with available experimental data and also with DFT B3LYP/6-31G(d) calculations. In general, molecular stiffness tends to decrease with increasing size, but its variation is limited in cases where mostly the tension-compression interaction sites are active such as the breathing mode. Furthermore, the bond length of each molecule is derived and compared with experimental and theoretical values calculated for graphene. Finally, vibrational frequencies are plotted in a histogram to reveal the common frequency gap and concentration points of the frequency distribution.

Win at All Costs or Lose Gracefully in High-Stakes Competition? Gender Differences in Professional Tennis

Anbarci, Nejat,Lee, Jungmin,Ulker, Aydogan SAGE Publications 2016 JOURNAL OF SPORTS ECONOMICS Vol.17 No.4

<P>This article examines line-call challenges by male and female professional tennis players in major tournaments around the world. In terms of utilization rates, we find that the genders behave similarly. Nevertheless, we do detect some intriguing gender differences in these challenges. First, male players’ challenges are more likely to be provoked by those of their opponents. More importantly, at tiebreaks, females are more likely to reverse an umpire’s unfavorable call, while males make relatively more unsuccessful challenges. Furthermore, we find that men are a lot more likely to make “embarrassing” line-call challenges at tiebreaks and offenses (i.e., when the shot lands at the opponent’s side of the tennis court) than women. These significant gender differences suggest that women particularly diverge from men at crucial junctures of the match such as tiebreaks. Differences in factors such as risk aversion, overconfidence, pride, shame, and strategic signalling behavior might help us to explain these gender-difference findings in line call challenges.</P>

A close look at the motion of C60 on gold

Hossein Nejat Pishkenari,Alireza Nemati,Ali Meghdari,Saeed Sohrabpour 한국물리학회 2015 Current Applied Physics Vol.15 No.11

In this paper, we have studied the motion of buckminsterfullerene (C60) on a gold surface by analyzing its potential energy and using classical molecular dynamics method. The results can be employed to investigate the motion of C60-based nanocars which have been made in recent years. For this purpose, we have studied the translational and rotational motions of C60 molecule independently. First, we have calculated the potential energy of a C60 molecule on a gold surface in different orientations and positions and employed this data to predict fullerene motion by examining its potential energy. Then we have simulated the motion of C60 at different temperatures using classical molecular dynamics methods. Specifying the regime of the motion at different temperatures is one of main goals of this paper.We have found that the rotational motion of C60 molecule on the gold substrate, was easier than its sliding (translational) motion. Also, the regime of motion of fullerene depended on temperature. The results demonstrate that three different regimes of motion, dependent on temperature, could be observed: rare jumps to adjacent cells, frequent jumps, and continuous motion. Employing the results of this paper not only helps to understand the C60 motion on the gold surface but also provides an appropriate tool for realizing motion of the thermally-driven fullerene-based nanocars.

Association of the XRCC1 gene polymorphisms with cancer risk in Turkish breast cancer patients

Ugur Deligezer,Nejat Dalay 생화학분자생물학회 2004 Experimental and molecular medicine Vol.36 No.6

The X-ray repair cross-complementing group 1 (XRCC1) gene is believed to play an important role in base excision repair and displays genetic polymorphisms. Data on the role of XRCC1 polymorphisms in cancer susceptibility is inconsistent. In the present study, we investigated the effect of two XRCC1 polymorphisms, Arg194Trp and Arg399Gln, on breast cancer risk in a casecontrol study involving Turkish breast cancer patients and healthy women. Both alleles exhibited a similar distribution among cases and controls leading to lack of any significant association between the XRCC1 polymorphisms and breast cancer risk, either in homozygotes and heterozygotes or combined. The allele frequency of the codon 194 variant was very low in cases and healthy individuals (5.3 and 3.9%, respectively) compared to that of the variant 399Gln allele (39.7 and 37.4%). Our results do not support evidence for a role of the XRCC1 polymorphism in developing breast cancer.

Real-time Topography and Hamaker Constant Estimation in Atomic Force Microscopy Based on Adaptive Fading Extended Kalman Filter

Milad Seifnejad Haghighi,Hossein Nejat Pishkenari 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.7

In this study, a novel technique based on adaptive fading extended Kalman filter for atomic force microscopy is proposed to directly estimate the topography of a sample surface without needing any control system. While in conventional imaging techniques, the scanning speed or the bandwidth is limited due to a relatively large settling time, the method proposed in this research is able to address this issue and estimate the topography throughout transient oscillation of the microcantilever. With this aim, an estimation process using an adaptive fading extended Kalman filter (augmented with forgetting factor) as the system observer is designed and coupled with the system dynamics to obtain sample topography. Obtained results demonstrate that the sample height is estimated by this algorithm with high accuracy and a relatively high scanning speed. Moreover, the observer is able to identify the topography and Hamaker constant simultaneously. Therefore, the presented approach can compensate for the low scanning speed of the classical imaging method as well as eliminate the need for a closed-loop controller.

Contralateral Superior Cerebellar Artery Syndrome : A Consequence of Brain Herniation

Mohseni, Meysam,Habibi, Zohreh,Nejat, Farideh The Korean Neurosurgical Society 2017 Journal of Korean neurosurgical society Vol.60 No.3

Vascular compromise is a well-known consequence of brain herniation syndromes. Transtentorial brain herniation most often involves posterior cerebral arteries. However, isolated involvement of contralateral superior cerebellar artery (SCA) during unilateral impending brain herniation is reported only once and we present another case of this exceedingly rare entity. A 24-year-old man was referred to us with impending herniation due to a multiloculated hydrocephalus, and during the course of illness, he developed an isolated SCA ischemia in the opposite side of the most dilated entrapped horn. In the current article we discuss the probable pathophysiologic mechanisms of this phenomenon, as well as recommending more inclusive brain studies in cases suspected of Kernohan-Woltman notch phenomenon in unilateral brain herniation. The rationale for this commentary is that contralateral SCA transient ischemia or infarct might be the underdiagnosed underlying pathomechanism of ipsilateral hemiparesis occurring in many cases of this somehow vague phenomenon.