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- 검색키워드
- 저자 : Arslan Ali (검색결과 38 건)
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Ali Osman Arslan,Mehmet Kurtoglu,Fatih Eroglu,Ahmet Mete Vural 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4
The arm inductance (AI) of a modular multilevel converter (MMC) affects both the fault and circulating current magnitudes. In addition, it has an impact on the inverter efficiency and harmonic content. In this study, the AI of a three-phase MMC isoptimized in a novel way in terms of DC voltage utilization, harmonics and efficiency. This MMC has 10 submodules (SM) perarm and the power circuit topology of the SM is a half-bridge. The optimum AI is adopted and verified in an MMC that has 100SMs per arm. Then the phase shift (PS) and phase disposition (PD) pulse width modulation (PWM) methods are investigated forbetter DC voltage utilization, efficiency and harmonics. It is found that similar performances are obtained for both modulationtechniques in terms of DC voltage utilization. However, the total harmonic distortion (THD) of the PS-PWM is found to be0.02%, which is slightly lower than the THD of the PD-PWM at 0.16%. In efficiency calculations, the switching and conductionlosses for all of the semiconductor are considered separately and the minimum efficiency of the 100-SM based MMC is found tobe 99.62% for the PS-PWM and 99.64% for the PD-PWM with the optimal value of the AI. Simulation results are verified withan experimental prototype of a 6-SM based MMC.
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Arslan, Ali Osman,Kurtoglu, Mehmet,Eroglu, Fatih,Vural, Ahmet Mete The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4
The arm inductance (AI) of a modular multilevel converter (MMC) affects both the fault and circulating current magnitudes. In addition, it has an impact on the inverter efficiency and harmonic content. In this study, the AI of a three-phase MMC is optimized in a novel way in terms of DC voltage utilization, harmonics and efficiency. This MMC has 10 submodules (SM) per arm and the power circuit topology of the SM is a half-bridge. The optimum AI is adopted and verified in an MMC that has 100 SMs per arm. Then the phase shift (PS) and phase disposition (PD) pulse width modulation (PWM) methods are investigated for better DC voltage utilization, efficiency and harmonics. It is found that similar performances are obtained for both modulation techniques in terms of DC voltage utilization. However, the total harmonic distortion (THD) of the PS-PWM is found to be 0.02%, which is slightly lower than the THD of the PD-PWM at 0.16%. In efficiency calculations, the switching and conduction losses for all of the semiconductor are considered separately and the minimum efficiency of the 100-SM based MMC is found to be 99.62% for the PS-PWM and 99.64% for the PD-PWM with the optimal value of the AI. Simulation results are verified with an experimental prototype of a 6-SM based MMC.
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Babar Ali,Xiaocheng Lan,Muhammad Tahir Arslan,Syed Zulfiqar Ali Gilani,Huanjun Wang,Tiefeng Wang 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.88 No.-
Glycerol dehydration to value-added acrolein over zeolite catalysts is a useful approach to offer asustainable economic route for the biodiesel industry. Glycerol dehydration over H-ZSM-5 withconventional morphology often exhibits a significant mass transfer limitation and inhibits the access toactive sites in the micropores, which causes low activity, selectivity, and severe catalyst deactivation. Inthis study, a significant impact of b-axis channel length on acrolein selectivity and catalyst activity wasrevealed by using H-ZSM-5 synthesized with varied channel length in b-axis of 60, 130, 180, and 250 nm. Complete glycerol conversion and high acrolein selectivity (88%) were observed over H-ZSM-5 with60 nm channels length in b-axis, due to high availability of active sites and enhanced diffusion throughthe shortest channels, which dramatically suppressed the coke formation. The catalysts with long b-axischannels exhibited a slow internal diffusion, leading to increased polymerization side reactions and cokeformation.
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Tatli, Ali Murat,Urakci, Zuhat,Kalender, Mehmet Emin,Arslan, Harun,Tastekin, Didem,Kaplan, Mehmet Ali Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.5
Background: Elevated serum alpha-fetoprotein (AFP) levels in adults are considered abnormal. This parameter is used mostly in the diagnosis and follow-up of hepatocellular carcinomas and yolk sac tumors. Among the other rare tumors accompanied with elevated serum AFP levels, gastric cancer is the most common. In this study, we evaluated the follow-up and comparison of the treatment and marker response of patients with metastatic gastric cancer who had elevated serum AFP levels. Materials and Methods: We performed a retrospective study, including all consecutive patients with advanced gastric cancer, who received systemic chemotherapy with elevated AFP level. Results: Seventeen metastatic gastric cancer patients with elevated AFP levels at the time of diagnosis were evaluated. Fourteen (82.4%) were males and three (17.6%) were females. The primary tumor localization was the gastric body in 8 (76.4%), cardia in 7 (41.2%), and antrum in 2 (11.8%). Hepatic metastasis was observed in 13 (76.4%) at the time of diagnosis. When the relationship of AFP levels and carcinoembryonic antigen (CEA) response of the patients with their radiologic responses was evaluated, it was found that the radiologic response was compatible with AFP response in 16 (94.1%) patients and with CEA response in 12 (70.6%); however, in 5 (29.4%) patients no accordance was observed between radiological and CEA responses. Conclusions: Follow-up of AFP levels in metastatic gastric cancer patients with elevated AFP levels may allow prediction of early treatment response and could be more useful than the CEA marker for follow-up in response evaluation.
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Istemen, Iismail,Arslan, Ali,Olgune, Semih Kivanc,Afser, Kemal Alper,Acik, Vedat,Arslan, Baris,Okten, Ali Ihsan,Gezercan, Yurdal The Korean Neurosurgical Society 2021 Journal of Korean neurosurgical society Vol.64 No.2
Objective : The subaxial cervical pedicle screwing technique shows powerful biomechanical properties for posterior cervical fusion. When applying a pedicle screw using the freehand technique, it is essential to analyse cervical computed tomography and plan the surgery accordingly. Normal cervical computed tomography is usually performed in the supine position, whereas during surgery, the patient lies in a prone position. This fact leads us to suppose that radiological evaluations may yield misleading results. Our study aimed to investigate whether there is any superiority between preoperative preparation on computed tomography performed in the prone position and that performed in the supine position. Methods : This study included 17 patients (132 pedicle screws) who were recently operated on with cervical vertebral computed tomography in the prone position and 17 patients (136 pedicle screws) who were operated on by conventional cervical vertebral computed tomography as the control group. The patients in both groups were compared in terms of age, gender, pathological diagnosis, screw malposition and complications. A screw malposition evaluation was made according to the Gertzbein-Robbins scale. Results : No statistically significant difference was observed between the two groups regarding age, gender and pathological diagnosis. The screw malposition rate (from 11.1% to 6.9%, p<0.05), mean malposition distance (from 2.18 mm to 1.86 mm, p <0.05), and complications statistically significantly decreased in the prone position computed tomography group. Conclusion : Preoperative surgical planning by performing cervical vertebral computed tomography in the prone position reduces screw malposition and complications. Our surgical success increased with a simple modification that can be applied by all clinicians without creating additional radiation exposure or additional costs.
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Ali Dogan,H. Murat Arslan 국제구조공학회 2012 Steel and Composite Structures, An International J Vol.12 No.4
This paper presents the mode-shape analysis of the cross-ply laminated composite cylindrical shallow shells. First, the kinematic relations of strains and deformation are given. Then, using Hamilton’s principle, governing differential equations are developed for a general curved shell. Finally, the stress-strain relation for the laminated, cross-ply composite shells are obtained. By using some simplifications and assuming Fourier series as a displacement field, the governed differential equations are solved by the matrix algebra for shallow shells. Employing the computer algebra system called MATHEMATICA; a computer program has been prepared for the solution. The results obtained by this solution are compared with the results obtained by (ANSYS and SAP2000) programs, in order to verify the accuracy and reliability of the solution presented.
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An Energy Efficient Charging Technique for Switched Capacitor Voltage Converters With Low-Duty Ratio
Arslan, Saad,Shah, Syed Asmat Ali,Lee, Jae-Jin,Kim, Hyungwon IEEE 2018 IEEE transactions on circuits and systems. a publi Vol.65 No.6
<P>Charging a capacitor array of a switched-capacitor (SC) dc-dc converter, supplying load circuits with a very short active period, can be pivotal to achieve high energy efficiency of its operation. This is because the capacitors may lose most of the stored energy during a long sleep period, and thus every sleep-to-active transition requires full recharging of the capacitors. In this brief, we present an energy efficient capacitor charging technique called split-capacitor charging, which charges a capacitor array in a step-wise fashion. Circuit simulations demonstrate that the proposed technique can reduce the energy wastage during sleep-to-active transition up to 66%. When tested on load circuits with a short active period, a voltage converter employing the proposed charging method shows up to 24% improvement in energy efficiency over conventional SC converters.</P>
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A study on Milne-type inequalities for a specific fractional integral operator with applications
Arslan Munir,Ather Qayyum,Laxmi Rathour,Gulnaz Atta,Siti Suzlin Supadi,Usman Ali 강원경기수학회 2024 한국수학논문집 Vol.32 No.2
Fractional integral operators have been studied extensively in the last few decades by various mathematicians, because it plays a vital role in the developments of new inequalities. The main goal of the current study is to establish some new Milne-type inequalities by using the special type of fractional integral operator i.e Caputo Fabrizio operator. Additionally, generalization of these developed Milne-type inequalities for $s$-convex function are also given. Furthermore, applications to some special means, quadrature formula, and $q$-digamma functions are presented.
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Ali Dogan,H. Murat Arslan,Huseyin R. Yerli 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.4
This paper presents effects of anisotropy and curvature on free vibration characteristics of cross-ply laminated composite cylindrical shallow shells. Shallow shells have been considered for different lamination thickness, radius of curvature and elasticity ratio. First, kinematic relations of strains and deformation have been showed. Then, using Hamilton’s principle, governing differential equations have been obtained for a general curved shell. In the next step, stress-strain relation for laminated, cross-ply composite shells has been given. By using some simplifications and assuming Fourier series as a displacement field, differential equations are solved by matrix algebra for shallow shells. The results obtained by this solution have been given tables and graphs. The comparisons made with the literature and finite element program (ANSYS).
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Arslan, Deniz,Bozcuk, Hakan,Gunduz, Seyda,Tural, Deniz,Tattli, Ali Murat,Uysal, Mukremin,Goksu, Sema Sezgin,Bassorgun, Cumhur Ibrahim,Koral, Lokman,Coskun, Hasan Senol,Ozdogan, Mustafa,Savas, Burhan Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.6
Background: The American Joint Committee on Cancer (AJCC) published a new staging system ($7^{th}$ edition) in 2009. In our study, we evaluated the survival results and prognostic factors among T4 local advanced non-small cell lung cancer (LA-NSCLC) patients in a large heterogeneous group, in accordance with this new system. Materials and Methods: We retrospectively evaluated the files of 122 T4 N0-3 M0 LA-NSCLC patients, identified according to the new staging system, treated at two centers between November 2003 and June 2012. Variables correlating with univariate survival at p<0.20 were later included in multivariate Cox regression analysis. Here, selection of relevant predictors of survival was carried out in accordance with the likelihood ratio formula with p<0.05 regarded as significant. Results: The median age was 60 and the median follow-up period was 17.4 months. Median overall survival (OS) was 18.3 months, the 1 year overall survival (OS) rate was 72%, and the 5 year OS rate was 28%. Statistically significant predictors of survival were (p<0.20) ECOG-PS (Eastern Cooperative Oncology Group Performance Status), age, T4 factor subgroup, stage and primary treatment in OS univariate analysis. On multivariate analysis for OS ECOG-PS (p=0.001), diagnostic stage (p=0.021), and primary treatment (p=0.004) were significant. In the group receiving non-curative treatment, the median OS was 11.0 months, while it was 19.0 months in the definitive RT group and 26.6 months in the curative treatment group. There was a significant difference between the non-curative group and the groups which had definitive RT and curative operations (respectively p<0.001 and p=0.001) in terms of OS, but not between the groups which had definitive RT and curative operations. The median event free survival (EFS) rate was 9.9 months, with rates of 46% and 19% at 3 and 5 years, respectively. On univariate analysis of EFS rate with ECOG-PS, weight loss and staging, statistical significance was found only for thorax computerized tomography (CT)+18F-fluorodeoxy-glucose positron emission tomography-CT (PET-CT) use, stage and primary treatment (p<0.20). In multivariate analysis with EFS, only the primary treatment was statistically significant (p=0.001). In the group receiving non-curative treatment, the median EFS was 10.5 months while in the curative operation group it was 14.7 months. When all the primary treatment groups were taken into consideration, grade III/IV side effect swas observed in 57 patients (46.6%). Esophagitis was most prominent among those that received definitive radiotherapy. Conclusions: Independent prognostic factors among these 122 heterogeneous LA-NSCLC T4 N0-3 M0 patients were age at diagnosis, ECOG-PS, stage and primary treatment, the last also being a significant prognostic indicator of EFS. Our findings point to the importance of appropriate staging and a multidisciplinary approach with modern imaging methods in this patient group. In those with T4 lesions, treatment selection and the effective use of curative potential should be the most important goal of clinical care.
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