Design and Research of GaN-Based Motor Drive System with LC Output Filter

Zekai Lyu,Ming Yang,Donglin Xu,Shuyu Shang,Dianguo Xu 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This paper presents a gallium nitride (GaN) – based servo motor drive system. Compared to actual inverters based on insulated gate bipolar transistors (IGBTs), the proposed design extends the pulse width modulation (PWM) frequency to 100 kHz. This allows motor filters with small component sizes. Based on this, an LC filter is added to the motor drive system, and an undamped resonance suppression algorithm is proposed to suppress the resonance introduced by the filter. By adding a proper time delay, system can be stable without any additional sensors or power losses. As a result, ideal sinusoidal line-line voltage at the motor terminals, high motor efficiency and low switching noise are achieved.

Current Loop Bandwidth Extension for AC Servo System Based on GaN-HEMT and FPGA

Zekai Lyu,Ming Yang,Jiang Lon g,Shuyu Shang,Dianguo Xu 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

In order to increase the productivity of the manufacturing process, a servo system with high bandwidth current loop should be realized. Switching frequency and digital delay are the main factors affecting the bandwidth of current controller. This paper focuses on the design of Gallium Nitride (GaN) semiconductors based AC servo drive system, one of its aims is to increase switching frequency. The field-programmable gate array (FPGA) is used, multiple stator current sampling and multiple PWM duty cycle update (MSMU) in a carrier period is proposed to reduce digital delay. Experiments on 100 kHz switching frequency show that the current control loop bandwidth can be extended to 6 kHz.

Forced vibrations of an elastic circular plate supported by unilateral edge lateral springs

Zekai Celep,Mustafa Gençoğlu 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.83 No.4

The present study deals with forced vibrations of an elastic circular plate supported along its circular edge by unilateral elastic springs. The plate is assumed to be subjected to a uniformly distributed and a concentrated load. Under the combination of these loads, equations of motion are explicitly derived for static and dynamic response analyses by assuming a series of the displacement functions of time and other unknown parameters which are to be determined by employing Lagrangian functional. The approximate solution is sought by applying the Lagrange equations of motions by using the potential energy of the external forces that includes the contributions of the edge forces and the external moments, i.e., those of the effects of the boundary condition to the analysis. For the numerical treatment of the problem in the time domain, the linear acceleration procedure is adopted. The tensionless character of the support is taken into account by using an iterative process and, the coordinate functions for the displacement field are selected to partially fulfill the boundary conditions so that an acceptable approximation can be achieved faster. Numerical results are presented in the figures focusing on the nonlinearity of the problem due to the plate lift-off from the unilateral springs at the edge support.

Effects of Calcium Channel Blockers On Hyaluronidaseinduced Capillary Vascular Permeability

Zekai Halici,Halis Suleyman,Elif Cadirci 대한약학회 2008 Archives of Pharmacal Research Vol.31 No.7

Inflammation and increased capillary permeability is a significant aspect of the pathogenesis of many diseases including atherosclerosis. L-type calcium channel blockers (CCB) are commonly used as cardiovascular drugs. Amlodipine, lacidipine, and nicardipine were evaluated for anti-inflammatory activity on the paw oedema produced by carrageenan. The effect of these drugs was compared with the activity of indomethacin. Their effects on vascular permeability were also tested by hyaluronidase-induced capillary permeability. In our animal experiments, amlodipine decreased the carrageenan-induced paw oedema at doses of 1, 3, and 6 mg kg-1 by 27.3%, 43.7%, and 67.3% four hour after carrageenan administration; the same doses of lacidipine and nicardipine decreased paw oedema by 37.1%, 55.6%, 76.4%, 11.2%, 31.0%, 91%; and indomethacin decreased oedema by 38.2% at a dose of 6 mg kg-1. Lacidipine significantly inhibited the hyaluronidase-induced increase in capillary permeability at doses of 1, 3, and 6 mg kg-1 compared with the control group. However, amlodipine and nicardipine significantly inhibited the hyaluronidase-induced increase in capillary permeability at 3 and 6 mg kg-1 doses. A 6 mg kg-1 dose of indomethacin significantly decreased the capillary permeability which was increased by hyaluronidase. These results suggest that CCBs can be efficient anti-inflammatories, and can also significantly decrease capillary permeability.

Assessment of swelling pressure of stabilized Bentonite

Angin, Zekai,Ikizler, Sabriye Banu Techno-Press 2018 Geomechanics & engineering Vol.15 No.6

In this study, a comprehensive laboratory experimental programme was conducted on expansive soil with a high swelling potential to study the influence of different additive materials on swelling pressure and index properties. Lime, sand, multifilament fiber and fibrillated fiber were used for stabilization of expansive soil. Lime, sand and fibers were respectively added to the expansive soil at 0-7%, 0-80%, 0-0.5%. On each mixture that was prepared by the proportions mentioned above, Atterberg limits, compaction, and swelling pressure tests were conducted. From the result of these experiments, the swelling pressure-time relation could be replaced by a rectangular hyperbola established to facilitate the prediction of ultimate percent swelling with a few initial data points. The best type of additive and its optimum ratio for engineering purposes could be estimated rapidly by this approach.

Geotechnical field investigation on giresun hazelnut licenced warehause and spot exchange

Angin, Zekai Techno-Press 2016 Geomechanics & engineering Vol.10 No.4

This paper describes a geotechnical field investigation in Giresun hazelnut licenced warehause and spot exchange during twelve months to determine the soil profile and static project applicability. It is also aimed to determine the superstructure loads and evaluate the relevance of foundation filling materials of the main, laboratory, package and admin buildings. The main building has $88.50{\times}63.20(5593.2)m^2$ site area. It has a big raft foundation. Eleven geotechnical reports were prepared between 2 December 2014 and 25 May 2015. Maximum settlements and safe bearing capacities were calculated to decide to be able to proceed to the next step. Also, the detail observations and evaluations were presented from October 2014 to December 2014. It has been seen that the foundation is designed as a single foundation one. But, in the light of observations, it has been evaluated that the foundation project for package building is not adequate, and after these excavations it must be revised as a raft foundation. The thickness of foundation and structural details should be defined/drawn after analyzing the details by using a special software. Construction joints should be designed between different buildings interfaces to avoid damages and cracks with in different settlements. The environmental drainage must be projected and applied to avoid the probable damage of surface waters on foundations.

Effects of Calcium Channel Blockers On Hyaluronidaseinduced Capillary Vascular Permeability

Halici, Zekai,Suleyman, Halis,Cadirci, Elif 대한약학회 2008 Archives of Pharmacal Research Vol.31 No.7

Inflammation and increased capillary permeability is a significant aspect of the pathogenesis of many diseases including atherosclerosis. L-type calcium channel blockers (CCB) are commonly used as cardiovascular drugs. Amlodipine, lacidipine, and nicardipine were evaluated for anti-inflammatory activity on the paw oedema produced by carrageenan. The effect of these drugs was compared with the activity of indomethacin. Their effects on vascular permeability were also tested by hyaluronidase-induced capillary permeability. In our animal experiments, amlodipine decreased the carrageenan-induced paw oedema at doses of 1, 3, and $6\;mg\;kg^{-1}$ by 27.3%, 43.7%, and 67.3% four hour after carrageenan administration; the same doses of lacidipine and nicardipine decreased paw oedema by 37.1%, 55.6%, 76.4%, 11.2%, 31.0%, 91%; and indomethacin decreased oedema by 38.2% at a dose of $6\;mg\;kg^{-1}$. Lacidipine significantly inhibited the hyaluronidase-induced increase in capillary permeability at doses of 1, 3, and $6\;mg\;kg^{-1}$ compared with the control group. However, amlodipine and nicardipine significantly inhibited the hyaluronidase-induced increase in capillary permeability at 3 and $6\;mg\;kg^{-1}$ doses. A $6\;mg\;kg^{-1}$ dose of indomethacin significantly decreased the capillary permeability which was increased by hyaluronidase. These results suggest that CCBs can be efficient anti-inflammatories, and can also significantly decrease capillary permeability.

Evaluation of Endothelial Dysfunction in Bipolar Affective Disorders: Serum Endocan and Urotensin-II Levels

Elif Oral,Zekai Halici,Irfan Cinar,Elif Ozcan,Zerrin Kutlu 대한정신약물학회 2019 CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE Vol.17 No.2

Objective: This study investigated changes in urotensin-II (U-II) and endocan levels which can be used as an early biological marker of endothelial injury in the episode and remission phases of bipolar affective disorder (BAD). Methods: We compared endocan and U-II levels, which has been shown to be closely associated with neurotransmitter systems in addition to continuity of endothelial structure and inflammatory response, in patients with BAD in remission for at least one year (n=42) and in patients still in manic or depressive episodes (n=16) with healthy controls (n=30). Results: Both endocan and U-II levels were significantly higher in the bipolar patients than in the controls. Endocan and U-II levels were also significantly correlated with one another (p =0.000, r=0.833). Both endocan (p =0.000) and U-II levels (p =0.000) were significantly higher in the bipolar attack group compared to the subjects in remission, and in the remission group compared to the controls. Conclusion: In this study we determined significantly higher endocan and U-II levels in BAD compared to the controls, while serum endocan and U-II levels of patients undergoing attacks were also significantly higher than those of the controls and also those of patients in remission.

Effects of a Glutamine Enema on Anastomotic Healing in an Animal Colon Anastomosis Model

Mani Habibi,Osman Zekai Oner,Mehmet Tahir Oruc,Nurullah Bulbuller,Sebahat Ozdem,Sukru Ozdemir,Arsenal Sezgin Alikanooglu,Rojbin Karakoyun,Ugur Dogan,Ayper Ongen,Umit Koc 대한대장항문학회 2015 Annals of Coloproctolgy Vol.31 No.6

Purpose: Anastomotic leakage in colorectal surgery is a very important issue. Although many studies have shown the positive effects of enteral glutamine (Gln) on anastomotic healing, none has assessed the effects of administering Gln via an enema for anastomotic healing. To fill this study gap, this study investigated the intraluminal effect of administration of Gln enema on the healing of colonic anastomosis in a rat model. Methods: Thirty Wistar albino rats were divided into three groups containing 10 rats each and were subjected to distal left colon transection and anastomosis. Postoperatively, group I (the control group) was administered no treatment, group II was administered daily placebo enemas containing physiological saline, and group III was administered daily 2% L-Gln enemas. After sacrifice on postoperative day 5, anastomotic healing, burst pressure, tissue hydroxyproline levels, and histological parameters were measured, and group values were compared via statistical analysis. Results: Group III was found to have the highest mean bursting pressure and tissue hydroxyproline levels and the lowest mean ischemia score. While the values of these parameters were not found to differ significantly among the groups, the lack of significance may have been due to the limited number of subjects examined. Conclusion: Administration of a Gln enema may have a positive effect on anastomosis in terms of bursting pressure and histopathological parameters. Future research should examine administration of a preoperative Gln enema as a means of decreasing the traumatic effects of the enema and identifying its applicability in surgical practice.

Numerical modelling and finite element analysis of \r\nstress wave propagation for ultrasonic pulse velocity testing of concrete

Ismail Ozgur Yaman,Zekai Akbay,Haluk Aktan 한국계산역학회 2006 Computers and Concrete, An International Journal Vol.3 No.6

Stress wave propagation through concrete is simulated by finite element analysis. The concrete medium is modeled as a homogeneous material with smeared properties to investigate and establish the suitable finite element analysis method (explicit versus implicit) and analysis parameters (element size, and solution time increment) also suitable for rigorous investigation. In the next step, finite element analysis model of the medium is developed using a digital image processing technique, which distinguishes the mortar and aggregate phases of concrete. The mortar and aggregate phase topologies are, then, directly mapped to the finite element mesh to form a heterogeneous concrete model. The heterogeneous concrete model is then used to simulate wave propagation. The veracity of the model is demonstrated by evaluating the intrinsic parameters of nondestructive ultrasonic pulse velocity testing of concrete. Quantitative relationships between aggregate size and testing frequency for nondestructive testing are presented.