Long term absolute sea level changes by tide gauge and continuous GPS data

Norveç kıyılarındaki ANDENES ve TREGDE mareograf istasyonlarındaki uzun dönemli mutlak deniz seviyesi değişimleri mareograf ve Sabit GPS zaman serilerinin analizi ile araştırılmıştır. Aylık ortalama deniz seviyesi ile Sabit GPS yükseklik zaman serilerindeki periyodik sinyallerin konumsal ve zamansal karakteri Deneysel Ortogonal Fonksiyon ve spektral analiz yöntemleri kullanılarak belirlenmiştir. Hem mareograf hem de Sabit GPS yükseklik zaman serisi doğrusal trendleri En Küçük Karelerle harmonik analiz yöntemiyle hesaplanmıştır. TREGDE’de anlamlı bir deniz seviyesi trendi bulunmazken, ANDENES mareograf istasyonunda uzun dönemli mutlak deniz seviyesinin 2.44 ± 0.21 mm/yıl hızla yükseldiği belirlenmiştir. Bu değer literatürdeki 1-3 mm/yıl düzeyindeki global deniz seviyesi değişimleri ile uyumludur.Anahtar Kelimeler: Mutlak deniz seviyesi, Sabit GPS, Deneysel Ortogonal Fonksiyon analizi, Spektral analiz. Long term absolute sea level changes at ANDENES and TREGDE tide gauges at Norwegian coasts are investigated by the analysis of the tide gauge and Continuous GPS time series. The spatial and temporal character of interannual to interdecadal sea level varitaions in tide gauge monthly mean sea level data and periodic signals in Continuous GPS height time series are determined by using Emprical Ortogonal Function and spectral analysis methods. The linear trends of both tide gauge and Continuous GPS height time series are calculated by harmonic analysis method with Least Squares Estimation. While no significant relative sea level trend is found at TREGDE, 2.04 ± 0.19 mm/year is found at ANDENES. While no significant absolute vertical movement is determined at TGDE and ANDE, the absolute vertical velocity of ANDO Continuous GPS station is 0.40 ± 0.10 mm/year and generally agrees with 0.89 mm/year land uplift determined by a Post Glacial Rebound model. The absolute sea level at ANDENES tide gauge is determined to be rising with a rate of 2.44 ± 0.21 mm/year by combining the vertical velocity of ANDE Continuous GPS station with the relative sea level trend. This value is consistent with the global sea level rise estimates which is in the order of 1-3 mm/year.Keywords: Absolute sea level, Continuous GPS, Emprical Orthogonal Function analysis, Spectral analysis.    

Improving TNFGN velocities via utilizing time series analysis of continuous GPS stations

Kampanya tipi GPS gözlemleri kullanıcıya elindeki alıcı sayısından daha fazla sayıda noktada gözlem yapma imkânı vererek ölçü bölgesinin daha yüksek konumsal çözünürlükle izlenmesine olanak sağlamaktadır. Diğer taraftan, kampanya tipi veriler zamansal olarak seyrektirler ve küçük sıçramaları tespit edemeyecek kadar yetersizdirler. Sabit GPS noktasında toplanan sürekli GPS verileri ile yer kabuğu hareketlerine yönelik kinematik modelleme çalışmalarını gerçekleştirmek mümkün olabilmektedir. Bu çalışmada; sabit GPS istasyonları zaman serileri analizi ile hesaplanan periyodik etkilerin TUTGA hızlarına düzeltme olarak getirilerek daha gerçekçi hıza ulaşılması için bir yaklaşım önerilmiştir. Verileri herkese açık 6 sabit GPS istasyonundan elde edilen veriler GAMIT-GLOBK yazılımı ile değerlendirilerek zaman serileri analizine hazır hale getirilmiştir. EBOK analizi ile seçilen istasyonlara ait en uygun modelin Beyaz Gürültü ve Kırpışma Gürültüsünün birleşimi olduğu görülmüştür. Zaman serileri içindeki anlamlı sinyallerin frekanslarını ve genliklerini istasyon bazında hesaplamak amacıyla GPS zaman serilerine, boşluklu veriler için oldukça uygun bir yöntem olan Lomb-Scargle algoritması uygulanmıştır. Tüm istasyonlarda ortak olarak senelik ve altı aylık etkilerin baskın olduğu tespit edilmiştir. Böylece, TUTGA hızlarına düzeltme olarak getirilecek periyodik etkilerin hangilerinin modelleneceğine karar verilmiştir. Senelik ve altı aylık etkilerin, TUTGA hızlarına nasıl ilave edilebileceğine dair bir algoritma geliştirilerek, hız alanının iyileştirilmesi için bir yöntem önerilmiştir. Çalışmadan elde edilen sonuçlara ilişkin bir değerlendirme yapılarak, Türkiye genelinde ve bölgesel olarak nasıl uygulanabileceğine ilişkin yatay ve düşey hızlar için bir değerlendirme yapılmıştır. Anahtar Kelimeler: Sabit GPS, zaman serileri analizi, spektral analiz, TUTGA.Campaign type GPS measurements provide higher resolution spatial monitoring of region by supplying to the observer more station than of his receiver number. On the other hand, campaign type measurements return baseline measurements with very coarse temporal sampling. This may not be a major problem for studying only slow, steady interseismic deformations, but changes in this behavior which occur over timescales less than the separation in observations will be missed by field campaigns. It is possible to make geodetic and geodynamic calculations, carry out kinematic modeling of crustal movements via using continuous GPS measurements obtained from CGPS stations. In this study, an algorithm is investigated to receive more accurate velocity field and improve velocity obtained from campaign type GPS measurements by adding corrections to the velocities via utilizing time series analysis of continuous GPS stations. Another important usage of velocities is the densification of geodetic networks. According to the Big Scale Mapping Guide, velocities of C1 and C2 points are produced using TNFGN velocities via interpolating at related sites. Thus, obtaining accurate and reliable velocities at networks like TNFGN becomes essential. In the event that TNFGN velocities are evaluated from campaign type measurements, it is more than normal to encounter errors at densification networks due to error propagation rule. Public data of Ankara, İstanbul, Trabzon, Mersin, Gebze and Antalya stations is used as test measurements.13 ITRF stations are included to the processes for realization of datum in ITRF2000.  GPS processes were done by GAMIT-GLOBK software and time series are created in ITRF2000. Also, outliers were removed at this stage. Pope test was applied to the time series and they became ready to time series analysis. Time series of related stations are prepared by completing the GPS process until the beginning of the year 2006 that constitutes the scope of this study. As with many other geophysical phenomena, noise in GPS position time series can be described as a power law process. Maximum Likelihood Estimation (MLE) was applied to investigate stochastic noise properties of GPS time series. Time series were tested by different noise models and a combination of white noise+flicker noise was found best describing model. In case only white noise model used, in other words using solely Least Squares Adjustment, uncertainties would be underestimated 7 times at north and east component and 8 times at up component. Missing values cause gaps in what otherwise would be evenly sampled data, and an even sampling may sometimes be impossible in the first place, for technical reasons. When Fourier analysis is used, and some data points are missing, they have to be provided in a more or less arbitrary way. The Lomb-Scargle algorithm has several computational advantages over more common approaches, such as Fourier analysis, including direct treatment of missing values and an estimate of a false discovery rate. Lomb-Scargle algorithm which is suitable for unequally spaced time series was applied to investigate the amplitudes and frequencies of dominant signals on a station by station basis. Seasonal signals are a potentially important part of the error budget for continuous GPS sites. Annual and semi-annual signals were determined dominant common to all sites. Thus, these periodical signals were chosen to be brought as corrections to TNFGN velocity field. An algorithm is suggested on how to apply annual and semi-annual effects in order to improve both deformation measurements and TNFGN velocities. Firstly, annual and semi-annual quantities derived from spectral analysis of all three components of continuous GPS stations, are interpolated at selected grid points. Periodic effects related to north and east component found inadequate for modeling throughout Turkey. Instead, it is proposed to use the horizontal periodic effects in an area of 10-20 km around the CGPS station. Annual and semi-annual periodics of vertical component are found convenient for interpolating at grid points. After obtaining the measurement epochs of TNFGN sites, corrections are computed at those related epochs. Finally, after adding corrections to coordinates, new velocities are obtained. New velocities are found consistent with the velocities that are derived from a complete time series analysis. An assessment is given to evaluate the results obtained from this study on how to apply both locally and in the vicinity of Turkey for horizontal and vertical velocity fields. Keywords: Continuous GPS, time series analysis, spectral anaysis, TNFGN

Jeodezik dönüşümlerde sürekliliğin irdelenmesi

In this study, the models based on the finite elements approach rather than the geometric transformation methods that are insufficient especially in the applications on larger areas and continuity problem are investigated. In the first step of the study, the project area is divided into solution regions and piecewise defined trial functions are determined for each region. These functions are continuous throughout the project area and yield much better solutions than defining the whole area with a single function. Continuity are defined between the solution regions and the continuities, C0, C1, and C2, are evaluated in the model and reflected in the solution. Furthermore, the continuity can also be provided for the studies performed in the neighboring areas. In the second phase, the common points in the solution regions are transformed into triangular elements by triangulation. Triangular elements are formed up with respect to the principles of continuity, and a separate triangular coordinate system is defined for each triangle. A function to be used for an inner-triangle interpolation in the triangular coordinate system is obtained by using the values of functions and derivations of trial function on the edge points of the triangles. By this function, the transformation value of a point is calculated without any residuals for the common points.Keywords: Geodetic transformations, finite elements, continuity, piecewise defined trial functions, triangular elements.Bu çalışmada, jeodezik dönüşümlerde özellikle büyük alanları kapsayan uygulamalarda yetersiz kalan geometrik dönüşüm yöntemleri yerine sonlu elemanlar yaklaşımını temel alan modeller ve dönüşümlerdeki süreklilik problemi irdelenmektedir. İlk olarak, proje alanları çözüm bölgelerine ayrılmış ve her çözüm bölgesi için parça parça tanımlı deneme fonksiyonları belirlenmiştir. Bu fonksiyonlar tüm proje alanı boyunca süreklidirler ve tüm alanın tek bir fonksiyonla ifade edilmesine göre çok daha iyi sonuçlar verirler. Süreklilik, çözüm bölgeleri arasında tanımlanır ve C0,, C1,, C2 süreklilikleri matematik modelin içinde değerlendirilerek çözüme yansıtılır. Ayrıca, süreklilik komşu alanlarda devam edecek çalışmalar içinde sağlanabilir. İkinci aşamada, çözüm bölgelerindeki dayanak noktaları üçgen elemanlar biçimine dönüştürülür. Üçgen elemanlar süreklilik ilkelerine göre oluşturulur ve her üçgen içinde ayrı bir üçgen koordinat sistemi tanımlanır. Üçgenin köşe noktalarındaki fonksiyon ve türev değerleri kullanılarak, dayanak noktalarına düzeltme getirilmeden bir noktanın dönüşüm değeri hesaplanır.Anahtar Kelimeler: Jeodezik dönüşümler, sonlu elemanlar, süreklilik, parça parça tanımlı deneme fonksiyonları, üçgen elemanlar

The accuracy assessment of InSAR measurements and reducing data points

Yapay Açıklıklı Radar İnterferometrisi (InSAR), yeryüzü topografyasının ve  deformasyonun belirlenmesi için yeni bir jeodezik tekniktir ve yersel ölçümlere ihtiyaç duymaz. InSAR ölçü sadece uydu bakış doğrultusunda bilgi verir. Bu ölçüler yörünge, topografya veya atmosfer kaynaklı hataları içerisinde barındırabilir. Bu ölçülerin doğruluğu İzmit Depremi örnek verisi üzerinde test edilmiştir. İzmit depremiyle ilgili olarak bu bölgedeki GPS noktalarındaki ölçümlerle aynı noktalardaki InSAR ölçüleri karşılaştırılmış, aradaki fark yaklaşık ±4 cm bulunmuştur. InSAR ölçülerinin çözülmesi sırasında başlangıç noktası kaynaklı hatalardan kurtulabilmek amacıyla aynı noktalar arasındaki göreli farklar incelenmiştir. Bu durumda farkların ortalaması ±2 cm’dir. Aradaki farkın nedeninin hem GPS hem de InSAR’ın kendi içerisinde barındırdığı hata kaynakları hem de GPS ölçülerinin deprem sonrası hareketleri içermemesine rağmen, InSAR ölçülerinin elde edildiği deprem sonrasına ait görüntünün depremden 1 ay sonrasına ait olması nedeniyle deprem sonrası hızlı hareketleri içermesi olduğu değerlendirilmiştir. InSAR ölçüleri çok yoğun olması nedeniyle, hesaplama yükü çok ağırdır. Ayrıca bu ölçülerin GPS ve nivelman gibi başka jeodezik yöntemlere ait ölçü gruplarıyla kullanılmaları durumunda çok baskın olmaktadırlar. Bu nedenle seyrekleştirilmelerine ihtiyaç vardır. InSAR ölçülerinin seyrekleştirilmesi üzerine yeni bir algoritma geliştirilmiş, bu algoritmanın sık kullanılan quadtree algoritması ile karşılaştırması yapılmıştır. Yeni algoritmanın quadtree algoritmasına göre InSAR veri kümesini 2/3 oranında daha az noktayla daha doğru bir şekilde temsil ettiği hesaplanmıştır. Bu seyrekleştirme algoritmasının yapılacak çalışmalarda kullanılabileceği değerlendirilmiştir. Anahtar Kelimeler: GPS, InSAR, doğruluk, nokta seyrekleştirme. Interferometric Synthetic Aperture Radar (InSAR) is a new geodetic technique for determining earth topography and deformation and it does not need any land survey. InSAR uses Synthetic Aperture Radar (SAR ) images which are in the region of microwave of electromagnetic spectrum It is a method in which phase component of SAR images are differenced and effects other than the deformation are removed to determine deformation. These phase difference images are called interferograms. In interferograms every 2π cycle of phase corresponds to one wavelength deformation in line of sight (LOS). To determine absolute deformation these cycles have to be unwrap namely added over each other. InSAR measurements can include many types of errors. These errors can be caused by orbit, digital elevation model or atmosphere. Not  many  studies has been interested on the accuracy of these measurements. In this study the accuracy of InSAR measurements are tested for İzmit Earthquake by GPS measurements Firstly, The interferogram was constructed by ERS-1 SAR images. Because of the inadequacy of the phase unwrapping algorithm, every cycle of the interferogram was digitized. The measurements at GPS points were compared with the InSAR measurements at the same points for İzmit Earthquake. 11 GPS points lay over the interferogram. The comparison was made for north and south of North Anatolian Fault (NAF) separately, 8 of the GPS points stay north of the NAF, 3 of them south. For the aim of comparison, the deformation of GPS in 3 dimensions was projected on LOS of InSAR measurements. For the North of the NAF, the average of the differences is 38 mm and all the differences are in the same direction. The reason for this difference is thought to be the postseismic deformation which was included by InSAR measurements but not by GPS measurements. For South of the NAF the average of the difference is 94 mm and al the differences are in the same direction. The main reason for this differences is the beginning point that is chosen to unwrap phase. It can be seen that the GPS point which is near the beginning point but out of the InSAR measurements coverage area has a 91mm displacement in LOS. This means that the beginning point has a 91 mm shift. In this case the difference for the South of the NAF is only 3 mm. Another test was held to check the accuracy. It was taking in to account the double differences between GPS points. By this namely, differencing displacement between two GPS points and checking InSAR measurements at those point, we can get rid of unwrapping beginning point error. The average of differences is 20 mm and Standard deviation is ±7mm. InSAR measurements are highly dense compared with other geodetic observations. For calculation convenience, this huge number of data points is reduced by different approaches. One of the most used is quadtree algorithm. Quadtree algorithm, divides the data in quadrants and checks the rms value for each quadrant. If the rms value of a quadrant bigger than a threshold value determined at the beginning, algorithm goes on dividing that quadrant to another quadrants. If the rms value is smaller than the threshold value, the algorithm stops for that quadrant. This algorithm generally gives good results but it does not take in to account the natural patterns that exist in data. In this study a new algorithm is investigated which takes into account the patterns in a data set and can represent the data by smaller number than quadtree. In this new developed algorithm contour lines are created for the data with the selected interval taking into account the slope of the data. Then, these contour lines are simplified by the commonly used Douglas-Poiker algorithm. And all the vertices of the simplified contour lines are converted to data points. And for other purposes such as weighting all of these data points are associated with the points in the original dataset that each of them represents.  To test the results this new algoritm was compared with quadtree algorithm for İzmit earthquake interferogram. The data set was sampled by quadtree and newly developed algorithm. And by these sampled points, the original data set was tried to be constructed again. Differences are taken with the reconstructed dataset and original dataset for two algorithms. It was observed that the new algorithm represents the original data more accurately with 2/3 less points if  compared  with the quadtree. Keywords: GPS, InSAR, accuracy, data reduction

THE USE OF THE AUTOMATED DIGITAL ZENITH CAMERA SYSTEM IN ISTANBUL FOR THE DETERMINATION OF ASTROGEODETIC VERTICAL DEFLECTION

The Digital Zenith Camera Systems (DZCSs) are dedicated astrogeodetic instruments used to obtain highly accurate astrogeodetic vertical deflection (VD) data. The first Turkish DZCS, the Astrogeodetic Camera System (ACSYS), was developed in Istanbul, Turkey in 2015. The ACSYS was capable of determining astrogeodetic VDs with an accuracy of ~0.3 arcseconds. However, it had some limitations in observation duration: because of the semi-automated mechanical design, levelling the system towards zenith was a time-consuming process. Since 2016, the ACSYS has been modernized through system upgrades and new technological components. In this paper, we describe the instrument design of the new DZCS—ACSYS2—observation procedures, evaluation of the test data and calculations of these data. The preliminary ACSYS2 astrogeodetic test observations were conducted at Istanbul Technical University (ITU) test station. The standard deviation results of the repeated observations reveal a VD measurement precision of ~0.3 arcseconds for both the North-South and East-West components. To investigate the accuracy of the system, a lightweight total station based-geodetic system—QDaedalus—was also used at the ITU test station. The comparison of the VDs data between ACSYS2 and QDaedalus system shows that the ACSYS2 can produce reliable VDs data

Kısa boyların elektro-optik uzaklık ölçerlerle ölçülmesinde presizyon araştırması

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1981Thesis (Ph.D.) -- İstanbul Technical University, Institute of Science and Technology, 1981Bu çalışmada; kısa boyların elektro-optik uzaklık öl çerlerle ölçülmesinde ölçme, hesaplama, kalibrasyon yöntem leri ile ölçmelerin presizyonlarının hesaplanması araştırıl maktadır. Çalışmanın I. bölümünde; elektro-optik uzaklık ölçerle rin çalışma ve ölçme ilkeleri incelenmekte ve bu tip alet lerle ölçülen kısa boyların hesap yüzeyine indirgenmesinin matematik modeli çıkarılmaktadır. II. Bölümde, elektro-optik uzaklık ölçmelerinde oluşan hatalar incelenmiş ve bu hatalara bağlı olarak bir ölçmenin karesel ortalama hata eşitliği verilmiştir. Ayrıca kırılma indisi eşitliği irdelenerek, en uygun atmosferik koşullarda kırılma indisi karesel ortalama hatasının ± 1.10 oranında olabileceği gösterilmiştir. III. Bölümde, elektro-optik uzaklık ölçerlerin kalib rasyon yöntemleri araştırılmaktadır.Şimdiye kadar uygulanan laboratuar ölçemeleriyle kalibrasyon ve arazi ölçmeleriyle II kalibrasyon yöntemlerinin matematik modelleri verilmektedir. IV. Bölümde, DI3 (Wild),AutoRanger (Keuffel and Esser) elektro-optik uzaklık ölçerleriyle: Laboratuarda oluşturulan kısa bazda ve arazide ise Schwendener tipi [ö] kontrol ke narında ve ayrıca B.Witte,H.Fröhlich tipi [lO] kontrol kena rında kalibrasyon ölçmeleri yapılıp değerlendirilmekte ve yön temler karşılaştırılmaktadır. Ölçmelerin okuma ve yöneltme ka- resel ortalama hatalarının hesaplanmasının matematik modeli ve r i lmek t ed ir. V.Bölüm ise,elde edilen sonuçları ve önerileri içermekte dir.In this research measurement, computation and calibra tion methods of measuring short ranges by electro-optical distance measurement instruments are investigated. Besides the computation precision of measurements are searched throughly. In the first part the functioning and measurement principles of electro-optical distance measurement instru ments are given. Besides these the properties of the carrier waves and modulation waves, their derivation, methods of measuring phase difference of the electro -optical distance measurement istruments are given. Starting from these the mathematical relationship to derive a distance is stipulated, Following these instrumental phenomena for short ranges measured by this brand of instruments the mathematical model of reducing them to the reference surface is derived. In the second part the error that occured during measu rement by electro-optical distance measurement instruments II have been investigated. The mean error of a measurement is given as the sum of two components one of which is inde pendent of the measured range while the other is dependent of the measured ange. Besides these geometrical correction error, centering error, additive constant error, phase me asuring error, pointing error, the error of velocity of lights in vacuo, refractive index error and modulation frequency error were investigated seperately and their formation, characteristics, their effects were discussed. Under various atmospheric conditions for various carrier waves it was shown as a result of the errors of measuring temperature and atmospherical pressure the mean square error of the refrac tive index would be of the order 1.10 under typical conditions. In the third part of this work the methods of calibrati on of these brand of instruments are investigated. Calibra tion methods may be grouped under two headings: 1- Calibration in the laboratory 2- Calibration in the field Modulation frequencies may be found by frequency coun ters in the laboratory end the calibration of the additive constant end phase difference measurement may be done in Ill short bases in the laboratory. The formation of such bases and the mathematical model of evaluation of these measurements are given. In the field calibration may be done by section and intersection methods. For the formation of calibration Lines where the measurement of additive constant and measurement of phase difference may be done jointly for undertaking ca libration measurements, along calibration lines and for eva luation of measurements the most appropriate mathematical model is given. It was shown that this was the best method of determining the mean square error of range measurements. In the fourth part, starting from the measurement done on the short base formed in the Laboratory calibration mea surements were done and evaluated; methods of calibration were compared. In the field the same deeds were carried on calibration lines of the type H.R. Schwendener,B.Witte and H.Fröhlich. Measurements in the laboratory and in the field were carried by DI3 (Wild) and AutoRanger (Kueffel and Esser) electro-optical distance measurement instrument. From the measurement done on the short base formed in the laboratory it was found that the function of phase IV difference measurement is given by the following trigonomet rical functions for the two instruments used throughout this study: For DI3 -2.15[mm].sin(A^+23?13)± 0.22[mm] For AutoRanger 2.13[mm].sin (A^-43?42)±0.35[mm] For the mean square error of a single reading the follo wing values were found for the two instruments: For DI3 ±0.90 [mm] For AutoRanger ±0.53 [mm] From the measurements done on the calibration lines for med in the field it was not possible to determine the func tion of phase difference measurement in a reliable way. I t was found that DI3 did not have an additive constant and for the additive constant of the AutoRanger the following walue was found: K =4. 2 [mm] ±1.3 [mm] It was determined that the additive constants of the two instruments did not depend on the range in a significant way. From field measurements it was found that the reading and pointing mean square error has the following walues for the two instruments: V For DI3 ±1.6 [mm] For AutoRanger ±2.1 [mm] By comparing the results thus obtained it was found that the additive constant and the function of phase diffe rence measurement may be taken following two trigonometri cal functions for the two instruments: For DI3 F [nım]=-2.05.sin(Aı|;+23fl3)±0.4 [nmi] For AutoRanger F [rnm]=4. 2+2.13.sin(Ai];-43?42)±1.3[mm] Z r Z It was demonstrated that to correct the measurements by using the abowe stated trigonometric functions bettered the results. In the fifth part results are given and propositions are explained as for as the subject matter of this thesis is concerned. The random component of the mean square error of a measu rement is composed of reading mean square error, pointing mean square error, centering mean square error, geometrical reduction mean square error and refractive index mean square error. These mean square errors may be controlled by the num ber of measurements. To this end the number of measurements made in one setting of the instrument by independend pointings, and in a range the number of setting the instrument under VI different atmospheric conditions should be determined. The systematic component of the mean square error of a measurement should be determined by calibration. The function of phase difference measurement should be determined at the short bases formed in the laboratory. In calibration lines of the type B.Witte and H.Fröhlich the determination of the additive constant is depended on the closeness of the phase of the function of phase diffe rence measurement to zero. If the function of phase diffe rence measurements has forward and backward phases, then the measurement of calibration lines should be corrected accor ding to this. The reliability and the precision of the additive cons tant computed from the corrected measurements in line with the function of phase difference measurement determined at the calibration line of the type B.Witte, H.Fröhlich type are close to the one computed at the calibration line of the type H.C.Schwendener.DoktoraPh.D

Okuma Kazanımları Açısından Ortaokul Türkçe Ders Kitapları

Okuma, Türkçe Dersi Öğretim Programı (2018)’nda en çok kazanım sayısının görüldüğü dil becerisi olması bakımından önemlidir. 2018-2019 eğitim-öğretim yılı ortaokul Türkçe ders kitapları, belirtilen programa göre hazırlanmıştır. Bu araştırmanın amacı, Türkçe Dersi Öğretim Programı (2018)’na göre Millî Eğitim Bakanlığınca hazırlanan 5, 6, 7 ve 8. sınıf Türkçe ders kitaplarını okuma kazanımları açısından incelemektir. Nitel bir durum çalışması olan araştırmada içerik analizi tekniğinden yararlanılmıştır. Kitapların hem kendi içinde hem de kitaplar arasında okuma kazanımlarının düzenli bir biçimde kullanılmaması, araştırmanın dikkat çeken sonucudur. Kitap yazarları, kazanımları 1 kere kullandıktan sonra kazanımların dağılımına dikkat etmemektedir. Bu durum, öğrencilerin bazı okuma becerilerini edinmesinde risk oluşturmaktadır. Araştırmanın bulgu ve sonuçlarından hareketle ders kitabı ve program yazarlarına yönelik birtakım önerilere yer verilmiştir

Characterisation of magnesium matrix composite reinforced with SiC particulates manufactured by powder metallurgy method

WOS: 000304193000015Particle reinforced magnesium metal matrix composites (MMCs) and related manufacturing methods are among important research topics because of their low density, high specific stiffness, strength and wear resistance. SiCp/Mg composites are commonly used materials for fabrication of light-weight functional components. Magnesium powders with mean size of 69 mu m were used as raw material while reinforcement material was selected as SiCp with the average particle size of 84 mu m. Different amounts of SiCp (3, 6, and 9 wt. %) were added to the magnesium matrix and the composite materials were sintered in a vacuum furnace at 590 degrees C. Structural characterisation of the produced composites was performed using several techniques such as scanning electron microscopy (SEM) and X-ray diffraction. The green density of the composite materials increased with SiCp addition. The hardness of the composites was found to be higher than the pure Mg. Reinforcement with 9 wt. % SiCp showed significant increase in the compressive strength of magnesium matrix composites