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NVIS HF signal propagation in ionosphere using calculus of variations

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Geodesy and Geodynamics 2019年第1期10卷 72-76页

作者： Umut Sezen Feza arikan orhan arikan Department of Electrical and Electronics Engineering Hacettepe University Department of Electrical and Electronics Engineering Bilkent University

Modeling Near Vertical Incidence Sounding(NVIS) High Frequency(HF) signal propagation in the ionosphere is important. Because, ionosondes which are special types of radars probing the ionosphere with certain HF frequencies(between 2 and 30 MHz), work mostly in NVIS mode(where elevation angle is between 89 and 90°). In this work, we are going to propose a new method for NVIS wave propagation in the ionosphere by discretizing the NVIS wave propagation path into mediums in which the refractive index changes linearly, where we solve the ray propagation in each medium analytically using calculus of variations and use Snell's Law at medium changes. The main advantage of the proposed solution is the reduced computational complexity and time. This algorithm can be used to simulate and compare the behavior of vertical ionosondes together with other ray tracing algorithms.

关键词： Ionosphere HF propagation Calculus of variations

Performance of GPS slant total electron content and IRI-Plas-STEC for days with ionospheric disturbance

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Geodesy and Geodynamics 2016年第1期7卷 1-10页

作者： Feza arikan Seymur Shukurov Hakan Tuna orhan arikan T.L. Gulyaeva Department of Electrical and Electronics Engineering Hacettepe University Beytepe Ankara 06800 Turkey Department of Electrical and Electronics Engineering Bilkent Uniuersity Bilkent Ankara 06800 Turkey IZMIRAN Moscow 142190 Troitsk Russian Federation

Total Electron Content （TEC） is an important observable parameter of the ionosphere which forms the main source of error for space based navigation and positioning systems. Since the deployment of Global Navigation Satellite Systems （GNSS）, cost-effective esti- mation of TEC between the earth based receiver and Global Positioning System （GPS） sat- ellites became the major means of investigation of local and regional disturbance for earthquake precursor and augmentation system studies. International Reference Iono- sphere （IRI） extended to plasmasphere （IRI-Plas） is the most developed ionospheric and plasmaspheric climatic model that provides hourly, monthly median of electron density distribution globally. Recently, IONOLAB group {***） has presented a new online space weather service that can compute slant TEC （STEC） on a desired ray path for a given date and time using IRI-Plas model （IRI-Plas-STEC）. In this study, the performance of the model based STEC is compared with GPS-STEC computed according to the estimation method developed by the IONOLAB group and includes the receiver bias as IONOLAB-BIAS （IONOLAB-STEC）. Using Symmetric Kullback-Leibler Distance （SKLD）, Cross Correlation （CC） coefficient and the metric norm （L2N） to compare IRI-Plas-STEC and IONOLAB-STEC for the month of October 2011 over the Turkish National Permanent GPS Network （TNPGN- Active）, it has been observed that SKLD provides a good indicator of disturbance for both earthquakes and geomagnetic storms.

关键词： IonosphereTotal Electron Content (TEC)GPSIRI-Plas

Spectral investigation of traveling ionospheric disturbances:IONOLAB-FFT

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Geodesy and Geodynamics 2017年第5期8卷 297-304页

作者： Feza arikan Aysenur Yarici Hacettepe University Department of Electrical and Electronics Engineering

Ionosphere is an important layer of atmosphere which is under constant forcing from both below due to gravitational, geomagnetic and seismic activities, and above due to solar wind and galactic radiation. Spatio-temporal variability of ionosphere is made up of two major components that can be listed as spatio-temporal trends and secondary variabilities that are due to disturbances in the geomagnetic field, gravitational waves and coupling of seismic activities into the upper atmosphere and ionosphere. Some of these second order variabilities generate wave-like oscillations in the ionosphere which propagate at a certain frequency, duration and velocity. These oscillations cause major problems for navigation and guidance systems that utilize GNSS （Global Navigation Satellite Systems）. In this study, the frequency and duration of wave-like oscillations are determined using a DFT （Discrete Fourier Transform） based algo- rithm over the STEC （slant total electron content） values estimated from single GPS （Global Positioning System） station. The performance of the developed method, namely IONOLAB-FFT, is first determined using synthetic oscillations with known frequencies and durations. Then, IONOLAB-FFr is applied to STEC data from various midlatitude GPS stations for detection of frequency and duration of both medium and large scale TIDs （traveling ionospheric disturbances）. It is observed that IONOLAB-FFr can estimate TIDs with more than 80% accuracy for the following cases： frequencies from 0.6 mHz to 2.4 mHz and durations longer than 10 min; frequencies from 0.15 mHz to 0.6 mHz and durations longer than 50 min; fre- quencies higher than 0.29 mHz and durations longer than 50 rain.

关键词： IonosphereTID (traveling ionospheric disturbances)GPS (Global Positioning System)TEC (total electron content)IONOLAB-FFF

Inhomogeneous Quantum Invariance Group of Multi-Dimensional Multi-parameter Deformed Boson Algebra

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Chinese Physics Letters 2012年第1期29卷 8-10页

作者： Azmi Ali Altintas Metin Arik Ali Serdar arikan Emre Dil Faculty of Engineering Okan UniversityTuzlaIstanbulTurkey Department of Physics Boğazici UniversityBebekIstanbulTurkey Department of Physics Sakarya UniversityEsentepeSakaryaTurkey

We investigate the inhomogeneous invariance quantum group of the d-dimensional d-parameter deformed boson *** is found that the homogeneous part of this quantum group is given by the𝑑-parameter deformed general linear *** construct the d-matrix which collects all information about the non-commuting structure of the quantum group for the two-dimensional case.

关键词： group. algebra. parameter

Giant myxoinflammatory fibroblastic sarcoma with bone invasion:a very rare clinical entity and literature review

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Chinese Journal of Cancer 2014年第8期33卷 406-410页

作者： Guray Togral Murat arikan Elif Aktas Safak Gungor Department of Orthopaedics and Traumatology Oncology Training and Research HospitalVatan caddesi 06200DemetevlerAnkaraTurkey Department of Radiology Oncology Training and Research HospitalVatan caddesi 06200DemetevlerAnkaraTurkey

Myxoinflammatory fibroblastic sarcoma(MIFS) is a rare low-grade, malignant soft tissue tumor that is usually observed in the extremities of adult patients. Magnetic resonance imaging findings for this tumor type have rarely been reported. We report a case involving the distal left femur of a middle-aged man and tumoral invasion of the bone, which, to our knowledge, has been previously described only once. He was treated with distal femoral tumor resection and reconstruction with a modular prosthesis. Histopathologic diagnosis confirmed MIFS. We reviewed literature of the diagnostic imaging and bone invasion findings associated with this tumor type.

关键词：纤维母细胞文献综述浸润肉瘤肿瘤侵袭实体临床巨人

Immediate intraocular pressure rise after intravitreal injection of ranibizumab and two doses of triamcinolone acetonide

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International Journal of Ophthalmology(English edition) 2011年第4期4卷 402-405页

作者： Gul arikan Ali Osman Saatci Ferit Hakan Oner Department of Ophthalmology School of Medicine Dokuz Eylul University

AIM: To evaluate prospectively immediate intraocular pressure (IOP) changes after the intravitreal injection of ranibizumab, 2 and 4mg triamcinolone acetonide. METHODS: Patients who underwent intravitreal injection of 0.1mL (4mg) triamcinolone acetonide (TA, Group T4), 0.05mL (2mg) TA (Group T2) and 0.05mL (0.5mg) ranibizumab (Group R) comprised the study population. Overall, 229 eyes of 205 patients were injected. Fifty-four eyes (23.6%) were in Group T4, 69 eyes (30.1%) in Group T2 and 106 eyes (46.3%) in Group R. If IOP was less than 26mmHg immediately after the injection no further measurement was performed. If IOP was ≥26mmHg, IOP was remeasured till the reading was below 26mmHg at 5, 15 and 30 minutes. RESULTS: Immediately after the injection, the IOP of 28 eyes (51.9%) in Group T4, 22 eyes (31.9%) in Group T2 and 51 eyes (48.1%) in Group R were over 25mmHg. At 30 minutes, IOP of one eye (1.9%) in group T4, two eyes (2.9%) in group T2 and two eyes (1.9 %) in Group R were over 25mmHg. Immediate post-injection IOP was significantly higher in Group T4 and Group R when compared to Group T2 (P <0.001 and P <0.001, respectively). IOP was significantly higher in eyes without vitreous reflux when compared to those with vitreous reflux in all groups (P <0.001). CONCLUSION: IOP may remarkably increase immediately after the intravitreal injection of 2 or 4mg triamcinolone acetonide, and 0.5mg ranibizumab. Absence of vitreous reflux is the most important predicting factor for immediate IOP rise after the injection.

关键词： anti-VEGF agents glaucoma intraocular pressure intravitreal injection steroids

Long-term results of viscocanalostomy and phacoviscocanalostomy: a twelve-year follow-up study

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International Journal of Ophthalmology(English edition) 2015年第6期8卷 1162-1167页

作者： Uzeyir Gunenc Taylan Ozturk Gul arikan Nilufer Kocak Department of Ophthalmology Dokuz Eylul University School of Medicine

AIMTo evaluate the long-term efficacy and safety results of viscocanalostomy and *** charts of 49 glaucoma patients who underwent viscocanalostomy or phacoviscocanalostomy surgery between February 1999 and August 2004 were reviewed retrospectively. Thirty-one eyes of 21 glaucoma patients who underwent filtering procedure with a postoperative follow-up of at least 5y were included in the study. Results of complete ophthalmologic examinations were recorded and statistically analyzed. Long-term surgical outcome was defined as an overall success when intraocular pressure (IOP) was found as ≤20 mm Hg with or without antiglaucomatous medication at the last follow-up visit, while it was defined as a complete success when IOP was measured ≤20 mm Hg without antiglaucomatous *** age was 68.1±9.6y (range: 32-81y). Mean follow-up time was 101.5±27.3mo (range: 60-144mo). Viscocanalostomy was performed in 8 eyes (25.8%) and phacoviscocanalostomy was performed in 23 eyes (74.2%). The mean preoperative IOP was 23.1±7.6 mm Hg with 2.1±1.0 medications, while mean IOP was 16.8±3.8 mm Hg with 0.9±1.1 medication at the last follow-up visit. Both the IOP decrease and the reduction in the antiglaucomatous medication were statistically significant (P<0.001 and P<0.001). No case required further glaucoma surgery. Overall success and complete success were found as 87.1% and 51.6%, respectively. Complete success rate was statistically higher in phacoviscocanalostomy group compared with the viscocanalostomy group (P=0.031), however there was no significant difference in overall success rate between two groups (P=0.072).CONCLUSIONBoth viscocanalostomy and phacoviscocanalostomy provide good IOP reduction in the long-term period.

关键词： glaucoma non-penetrating glaucoma surgery phacoviscocanalostomy viscocanalostomy

Clinical outcomes of 25-gauge vitrectomy surgery for vitreoretinal diseases: comparison of vitrectomy alone and phaco-vitrectomy

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International Journal of Ophthalmology(English edition) 2016年第8期9卷 1163-1169页

作者： Mucella arikan Yorgun Yasin Toklu Melek Mutlu Umut Ozen Department of Ophthalmology Ankara Ataturk Education and Research Hospital Yildirim Beyazit University

AIMTo compare the clinical outcomes of combined 25-gauge pars plana vitrectomy (PPV) and phacoemulsification/posterior chamber intraocular lens (PC-IOL) implantation with vitrectomy alone surgery in patients with various vitreoretinal *** total of 306 eyes (145 with PPV alone and 161 with phaco-vitrectomy) were enrolled in this retrospective analysis. The surgical approach was 25-gauge PPV combined with phacoemulsification and PC-IOL implantation at the same time in eyes in phaco-vitrectomy group and only PPV in eyes in vitrectomy alone surgery group. The main outcome measures were postoperative clinical outcomes included anterior chamber inflammation, changes in intraocular pressure (IOP) and best corrected visual acuity (BCVA).RESULTSThe most common postoperative complication was anterior chamber reaction which has higher incidence in phaco-vitrectomy group (Pst day IOP of vitrectomy alone group was significantly lower than that of phaco-vitrectomy group (16.3±5.8 mm Hg vs 17.8±8.1 mm Hg, respectively, P=0.02). Hypotony (IOP≤8 mm Hg) was not different between groups in the postoperative 1st day (P>0.05). The mean preoperative visual acuity was not different between groups (1.6±0.9 logMAR vs 1.8±0.9 logMAR, respectively, P>0.05). However, the mean visual acuity was decreased in vitrectomy alone group at the final visit compared to phaco-vitrectomy group (1.2±0.8 logMAR, 0.9±0.7 logMAR, respectively P<0.05).CONCLUSIONTwenty-five gauge PPV combined with phacoemulsification surgery is a safe and efficient procedure, which can be preferred in phacic patients with a variety of vitreoretinal diseases compared to vitrectomy alone. Despite improved outcomes, this approach is not free of limitations as anterior chamber complications especially with combined surgery.

关键词： pars plana vitrectomy phacoemulsification small gauge vitrectomy

Determination of characteristics for mechanically separated organic fraction of MsW at a full-scale anaerobic digestion plant

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Waste Disposal and Sustainable Energy 2024年第2期6卷 233-241页

作者： Yagmur Kabakci Sadiye Kosar Ozgur Dogan Fehmi Gorkem Uctug Osman Atilla arikan Department of Environmental Engineering Istanbul Technical University34469 AyazagaIstanbulTurkiye TUBITAK Marmara Research Center 41400 GebzeKocaeliTirkiye Centre for Water Technology(WATEC)and Department of Biological and Chemical Engineering Aarhus UniversityOle Worms Allé38000 Aarhus CDenmark Faculty of Engineering Izmir University of Economics35330BalcovaIzmirTurkiye

Anaerobic digestion(AD)as a waste management method has the potential to reduce greenhouse gas emissions while pro-ducing renewable energy,making it a viable option for managing the organic fraction of municipal solid waste(OFMSW).OFMSW characteristics can vary depending on factors such as waste source,composition and separation *** charac-teristics of OFMSW are critical for analyzing and monitoring the AD process to optimize biogas *** this study,the waste composition and physicochemical characteristics of the mechanically separated OFMSW(ms-OFMSW)were determined at a full-scale AD plant in *** ms-OFMSW samples were collected monthly after mechanical separation and were subsequently sent to the anaerobic *** composition and physicochemical characteristics of the samples were determined by manual *** results showed that the majority of the ms-OFMSW(76.45%±1.71%)was organic,while 8.99%±1.56%was recyclable and 14.56%±1.69%was *** of environmental benefits for the recyclable materials was determined using a free online tool provided by Environmental Protection ***(399.7 GJ)and plas-tics(403.7 GJ)both saved nearly the same amount of energy while metals saved the most water(421.8 m3),with the greatest positive *** benefits ranged from 3 tons to 40 tons of carbon dioxide equivalent for each waste *** findings suggest that efficient pre-separation units can improve the anaerobic digestibility of OFMSW,while also providing greater environmental benefits by preventing recyclable waste from the anaerobic *** addition to encouraging source separation applications,this study demonstrates the need for improved technologies to separate OFMSW from mixed MSW.

关键词： Anaerobic digestion Composition Mechanical separation Organic fraction of municipal solid waste Ms-OFMSW