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Observed Impacts of Climate Variability on LULC in the Mesopotamia Region

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Computers, Materials & Continua 2021年第5期67卷 2255-2269页

作者： Muntaha Alzubade Orkan Ozcan Nebiye Musaoglu Murat Türke¸s Istanbul Technical university Istanbul3400Turkey bogazici university Istanbul3400Turkey

Remote sensing analysis techniques have been investigated extensively,represented by a critical vision,and are used to advance our understanding of the impacts of climate change and variability on the environment.This study aims to find a means of analysis that relies on remote sensing techniques to demonstrate the effects of observed climate variability on Land Use and Land Cover(LULC)of the Mesopotamia region,defined as a historical region located in the Middle East.This study employed the combined analysis of the Normalized Difference Vegetation Index(NDVI),Land Surface Temperature(LST),and two statistical analysis methods(Pearson Correlation Analysis,r;Coefficient of Determination,R^(2)),which were applied using the Moderate Resolution Imaging Spectroradiometer data and observed surface meteorological data from 2000 to 2018.The resulting NDVI images show five LULC classes with NDVI values varying between−0.3 and 0.9.Furthermore,changes in the classified LULC area were compared statistically to those in NDVI values,where a positive relationship was found.Also,when the LST values and temperature are more extreme,the NDVI values were found to be smaller,suggesting a decrease in the density of vegetation cover.A negative correlation was found through Pearson correlation analysis(r=∼−0.64),indicating a direct effect of increased temperatures on LULC.Indeed,this negative relationship between NDVI and LST was proven using R^(2) values,where a two-dimensional scatter plot analysis showed that R^(2) ranges from 0.54 to 0.9.Ultimately,the results obtained from this study reveal changes that may have many prominent effects in the field of LULC classification,accelerating the implications of climate change and variability factors.

关键词： NDVI LST MODIS data meteorological data Mesopotamia

Production of "Tricalcium Phosphate/Titanium Dioxide" Coating Surface on Titanium Substrates

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Journal of Materials Science & Technology 2010年第11期26卷 1006-1010页

作者： Onder Albayrak Sabri Altintas Department of Mechanical Engineering Mersin University Department of Mechanical Engineering Bogazici University

A new method for the production of the coating surface consisting of tricalcium phosphate （TCP） and titanium dioxide （TiO2） on titanium （Ti） substrates by using electrophoretic deposition （EPD） method has been developed.Crack occurrence on coating surface and hydroxyapatite （HA） decomposition into TCP,which are commonly encountered in EPD method,were used as an advantage in this study.HA nano-powders synthesized by acid-base method were used as the coating material.They were deposited on Ti substrates with different voltages and durations.Cracks on the deposited surface were observed by scanning electron microscopy （SEM）.Samples were sintered in air atmosphere to allow TiO2 growth from the Ti substrate to fill the cracks.SEM observation and X-ray diffraction （XRD） analysis proved the occurrence of complete decomposition of HA into TCP,TiO2 growth between cracks,and coalescence of TCP/TiO2 on coating surface.This type of coating surface is expected to increase the coating strength because of TiO2 growth in the cracks and its coalescence with TCP.

关键词： Electrophoretic deposition Hydroxyapatite Bioceramics Microstructure

Amniotic membrane welded to contact lens by 1470-nm diode laser:a novel method for sutureless amniotic membrane transplantation

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International Journal of Ophthalmology(English edition) 2014年第6期7卷 996-1000页

作者： Rifat Rasier Murat Gulsoy Department of Ophthalmology Istanbul Bilim University School of Medicine Instute of Biomedical Engineering Bogazici University

AIM: To avoid the side effects of the suture usage by welding amniotic membrane(AM) to contact lens(CL)with laser.METHODS: AM was taken from pregnant women and cleaned from blood clots with sterile phosphate-buffered physiological saline solution which included antibiotics.Stromal side of the AM was spread inside of the CL and it was welded to CL by 1470 nm diode laser. And 600 μm diameter fiber tip of the laser was contacted with the epithelial side of the AM from 4 separate points. After welding excess amniotic membrane around the CL was cut with a scalpel.RESULTS: Stromal side of the AM was spread inside of the CL and then with laser fiber, different power levels and exposure times were applied on the epithelium of AM and 340 m W for seven seconds was found optimal.CL and AM attached with the spot welding effect in 4points by touching fiber tip. CL-AM welded complex did not separated from each other while holding AM that extend beyond the CL with the help of two forceps.CONCLUSION: As a conclusion, it was aimed in this study to achieve the success of the conventional amniotic membrane transplantation(AMT) with the easiness of applying a CL and to avoid risks and side effects of corneal or conjunctival suturing. The results showed that the application of the CL-AM complex will be as easy as the application of a CL and lasts shortly.

关键词： amniotic membrane contact lens laser welding

Performance analysis of a distributed power control algorithm for shared and split spectrum femtocell networks

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Control Theory and Technology 2016年第4期14卷 314-322页

作者： Kamil SENEL Mehmet AKAR Department of Electrical and Electronics Engineering Bogazici University Istanbul 34342 Turkey

In this paper, we study the performance of a distributed power adjustment algorithm for shared and split spectrum allocation setups. The theoretical analysis reveals that the convergence of the power control algorithm is guaranteed under different spectrum allocation schemes and the convergence rate is exponential. The performance analysis is also carried out via simulations which demonstrate the algorithm fairness under Jain＇s and Atkinkons＇ fairness indices.

关键词： Femtocell networks power control consensus

Intraocular pressure elevation after intravitreal triamcinolone acetonide injection: a Meta-analysis

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International Journal of Ophthalmology(English edition) 2016年第1期9卷 139-144页

作者： Cansu Yuksel-Elgin Ceyhun Elgin Department of Ophthalmology Sariyer Ismail Akgun Public Hospital Department of Economics Bogazici University

AIM：To report on intraocular pressure（IOP）after intravitreal injections of triamcinolone acetonide.·M ETHODS：Systematic literature review of studies that investigated the effects of an injection of triamcinolone Intravitreal triamcinolone acetonide on IOP was conducted according to the Cochrane Collaboration methodology and the reported effects have been analyzed with Meta-analysis.·RESULTS：We found that the IOP follows an inverted-U shape pattern over time starting with an average value of14.81±1.22 mm Hg before the injection,rising to a maximum of 19.48±2.15 mm Hg after one month of injection and falling down to 16.16±1.92 mm Hg after6mo.Moreover,country of study,age,previous history of glaucoma and gender compositions matter for crossstudy were different in reported IOP changes.·CONCLUSION：Our findings may be helpful in determining pressure elevation risk of intravitreal triamcinolone acetonide therapy as well as comparing it with those of more recent therapies such as the antivascular endothelial growth factor agents.

关键词： intravitreal injections intraocular pressure Meta-analysis

Use of fly ash with no water consumption for cold regions transportation infrastructure

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Research in Cold and Arid Regions 2015年第5期7卷 619-625页

作者： Gokhan Baykal Department of Civil Engineering Bogazici University

The construction period in cold regions is very short due to problems related to excavation and use of frozen soils in embankment construction, which leads to excessive deformations upon thawing. Also, handling of compaction water is critical due to freezing temperatures. Coalburning thermal power plants are very common in cold regions to supply electricity. The inorganic part of the pulverized coal after burning produces fly ash, which is available in large volumes. Due to excavation difficulties and the poor engineering behavior of frozen soils in cold regions, the utilization of fly ash when it is readily available must be promoted. Any construction technique which utilizes alternative materials like fly ash and minimizes water consumption has a potential to extend the short construction season and even allow service and maintenance during extreme weather conditions. This paper presents two potential techniques to solve the moisture affinity of silt-sized materials like fly ash. One technique involves in-plant production of fly ash pellets using cold-bonding pelletization to manufacture aggregates of up to 40,000-~tm diameter from 15- to 60-~tm-diameter fly ash grains. Large disc pelletizers have annual production capacities of up to one million ton at a reasonable cost. The product has adequate strength for embankment construction even when no water is used and no compaction is applied. The second technique is an in situ mixing technique which uses snow instead of compaction water for fly ash. The snow is the main element in this technique to compact the embankment. Water is needed for the hydration reactions to form cementitious minerals in fly ash. The slower the hydration reaction, the greater the crystal growth of cementitious minerals. In the proposed technique, in situ snow is mixed with fly ash and is compacted on-site. The temperature increase due to the hydration reaction of fly ash upon contact with snow crystals provides water for continued long-term hydration, which results in high strength, a hig

关键词： cold regions embankment construction frozen soil compaction water fly ash pellets snow-compacted fly ash

SPT based determination of undrained shear strength:Regression models and machine learning

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Frontiers of Structural and Civil Engineering 2020年第1期14卷 185-198页

作者： Walid Khalid MBARAK Esma Nur CINICIOGLU Ozer CINICIOGLU Department of Civil Engigeering Bogazici UniversityIstanbul 34342Turkey School of Business Quantitative Methods DivisionIstanbul UniversityIstanbul 34320Turkey

The purpose of this study is the accurate prediction of undrained shear strength using Standard Penetration Test results and soil consistency indices,such as water content and Atterberg limits.With this study,along with the conventional methods of simple and multiple linear regression models,three machine learning algorithms,random forest,gradient boosting and stacked models,are developed for prediction of undrained shear strength.These models are employed on a relatively large data set from different projects around Turkey covering 230 observations.As an improvement over the available studies in literature,this study utilizes correct statistical analyses techniques on a relatively large database,such as using a train/test split on the data set to avoid overfitting of the developed models.Furthermore,the validity and consistency of the prediction results are ensured with the correct use of statistical measures like p-value and cross-validation which were missing in previous studies.To compare the performances of the models developed in this study with the prior ones existing in literature,all models were applied on the test data set and their performances are evaluated in terms of the resulting root mean squared error(RMSE)values and coefficient of determination(R^2).Accordingly,the models developed in this study demonstrate superior prediction capabilities compared to all of the prior studies.Moreover,to facilitate the use of machine learning algorithms for prediction purposes,entire source code prepared for this study and the collected data set are provided as supplements of this study.

关键词： undrained shear strength linear regression random forest gradient boosting machine learning standard penetration test

Intensity measures for seismic liquefaction hazard evaluation of sloping site

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Journal of Central South university 2015年第10期22卷 3999-4018页

作者：陈志雄程印肖杨卢谅阳洋 Key Laboratory of New Technology for Construction of Cities in Mountain Area of Ministry of Education(Chongqing university) School of Civil Engineering Chongqing University Kandilli Observatory and Earthquake Research Institute Bogazici University

This work investigates the correlation between a large number of widely used ground motion intensity measures(IMs) and the corresponding liquefaction potential of a soil deposit during earthquake loading. In order to accomplish this purpose the seismic responses of 32 sloping liquefiable site models consisting of layered cohesionless soil were subjected to 139 earthquake ground motions. Two sets of ground motions, consisting of 80 ordinary records and 59 pulse-like near-fault records are used in the dynamic analyses. The liquefaction potential of the site is expressed in terms of the the mean pore pressure ratio, the maximum ground settlement, the maximum ground horizontal displacement and the maximum ground horizontal acceleration. For each individual accelerogram, the values of the aforementioned liquefaction potential measures are determined. Then, the correlation between the liquefaction potential measures and the IMs is evaluated. The results reveal that the velocity spectrum intensity(VSI) shows the strongest correlation with the liquefaction potential of sloping site. VSI is also proven to be a sufficient intensity measure with respect to earthquake magnitude and source-to-site distance, and has a good predictability, thus making it a prime candidate for the seismic liquefaction hazard evaluation.

关键词：地震液化危险性评价强度指标液化场地地震地面运动场地液化势加速度表地震荷载

Digital astro-geodetic camera system for the measurement of the deflections of the vertical:tests and results

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International Journal of Digital Earth 2016年第9期9卷 914-923页

作者： K.Halicioglu R.Deniz H.Ozener Geodesy Department Kandilli Observatory and Earthquake Research InstituteBogazici UniversityIstanbulTurkey Geomatics Engineering Department Istanbul Technical UniversityIstanbulTurkey

This study introduces the new results of a novel low-cost digital zenith camera system operated in Turkey that uses astronomical and geodetic instrumentation.Currently,it is possible to determine deflections of the vertical(DoV)components by using a vast amount of information gathered from geo-referenced star images,tilt measurements,and Global Navigation Satellite System technology.This new design of an astro-geodetic camera system is used for calculating DoV components with 12 independent solutions on a test station in Istanbul,and additional observations were performed to investigate the external accuracy of the system on a test network.A specific leveling method is developed to align system toward the zenithal direction.The final results of the observations on a test station located in Istanbul indicate that the accuracy of the system is about±0.19 arc-seconds in latitude and±0.28 arc-seconds in longitude determination.The system has been further tested on a network with 4 control points that have averagely 20 km baselines.At the test network,the root mean square of the average value of the vertical deflections is calculated as±0.36 arc-seconds.Furthermore,DoV components are compared with the values that are calculated using global geopotential models.

关键词： Geodetic astronomy geoid digital zenith camera system