Meslek Yüksekokulları
https://hdl.handle.net/11494/1005
Vocational Schools2024-03-28T14:14:12ZImproving the Spatial Accuracy of UAV Platforms Using Direct Georeferencing Methods: An Application for Steep Slopes
https://hdl.handle.net/11494/4895
Improving the Spatial Accuracy of UAV Platforms Using Direct Georeferencing Methods: An Application for Steep Slopes
Zeybek, Mustafa; Taşkaya, Selim; Elkhrachy, Ismail; Tarolli, Paolo
The spatial accuracy of unmanned aerial vehicles (UAVs) and the images they capture
play a crucial role in the mapping process. Researchers are exploring solutions that use image-based
techniques such as structure from motion (SfM) to produce topographic maps using UAVs while
accessing locations with extremely high accuracy and minimal surface measurements. Advancements
in technology have enabled real-time kinematic (RTK) to increase positional accuracy to 1–3 times the
ground sampling distance (GSD). This paper focuses on post-processing kinematic (PPK) of positional
accuracy to achieve a GSD or better. To achieve this, precise satellite orbits, clock information, and
UAV global navigation satellite system observation files are utilized to calculate the camera positions
with the highest positional accuracy. RTK/PPK analysis is conducted to improve the positional
accuracies obtained from different flight patterns and altitudes. Data are collected at altitudes
of 80 and 120 meters, resulting in GSD values of 1.87 cm/px and 3.12 cm/px, respectively. The
evaluation of ground checkpoints using the proposed PPK methodology with one ground control
point demonstrated root mean square error values of 2.3 cm (horizontal, nadiral) and 2.4 cm (vertical,
nadiral) at an altitude of 80 m, and 1.4 cm (horizontal, oblique) and 3.2 cm (vertical, terrain-following)
at an altitude of 120 m. These results suggest that the proposed methodology can achieve high
positional accuracy for UAV image georeferencing. The main contribution of this paper is to evaluate
the PPK approach to achieve high positional accuracy with unmanned aerial vehicles and assess the
effect of different flight patterns and altitudes on the accuracy of the resulting topographic maps.
2023-01-01T00:00:00ZIdentifying the effects of corruption perception on the relationship between international trade and logistics performance in developing countries
https://hdl.handle.net/11494/4894
Identifying the effects of corruption perception on the relationship between international trade and logistics performance in developing countries
Acar, Avni Zafer; Kara, Karahan
Abstract. Purpose – logistics creates a strategic effect by playing a facilitating role in international trade, which has a significant impact on the economic performance of countries. Logistics performance and corruption play an influential role in determining the trade efficiency
levels of developing countries. There are two purposes in this research. First purpose is to
determine the international trade efficiency level of developing countries based on logistics
performance. The second purpose is to determine the efficiency level of trade based on both
logistics performance and corruption levels.
Research methodology – output-oriented data envelopment analysis (DEA) has been applied
in the research. The research covers the years 2012–2020. The sample area is developing
countries.
Findings – countries with full efficiency levels in 2012–2020 have been determined according
to both logistics performance and corruption scores.
Research limitations – the research covers the years 2012–2020. The sample area is developing countries.
Practical implications – the reduction of corruption levels in some developing countries is an
important factor in increasing the level of international trade efficiency.
Originality/Value – this research highlights the role of corruption in the relationship between
trade and logistics performance
2023-01-01T00:00:00ZCharacterization study of geopolymer concretes fabricated with clinker aggregates
https://hdl.handle.net/11494/4893
Characterization study of geopolymer concretes fabricated with clinker aggregates
Öz, Ali; Bekem Kara, İlknur; Bayrak, Barış; Kavaz, Esra; Kaplan, Gökhan; Aydın, Abdulkadir Cüneyt
Geopolymers are a new generation of building material that has recently been popular in reducing carbon
emissions. As a result of its amorphous alumina-silicate-based reaction product, it has many superior properties.
This study investigated the mechanical and physical properties and high-temperature resistance of groundgranulated blast furnace slag and metakaolin-based geopolymer concrete fabricated with clinker aggregates
produced in a short curing time (8 h). In alkali activators, the sodium silicate to sodium hydroxide (SS/SH) mass
ratios were 2, 2.25, 2.5 and 2.75. Two curing methods were used, namely ambient (25 ◦C) and oven curing (80 ◦C). The observed unit weights vary between 2275–2392 kg/m3 for the samples of the geopolymeric composites.
Porosity and water absorption vary between 4.92 and 8.84% and 3.58–7.26%, respectively. The heat curing
application decreased the mixtures’ water absorption, unit weight, and porosity values. The compressive strength
of the samples subject to ambient curing varied between 39.2 and 59.8 MPa. Withal, the samples cured at 80 ◦C
for 8 h were between 66.9 and 112.4 MPa. The increased SS/SH ratio also increased the observed strength values.
Capillary water absorption of all samples is below 0.6 kg/m2
. Heat-cured geopolymers decreased capillary water
absorption to 0.1 kg/m2
. The weight loss after high temperature decreased as the SS/SH ratio increased. The N-AS-H gel in the zeolitic structure was observed in SEM analysis. The FT-IR analysis visualized the carbonation in
the heat-cured mixtures. As a result, over 100 MPa compressive strength values were observed with the clinker
aggregates at 80 ◦C after 8 h of curing time. Withal, a high-temperature refractory composite was developed with
the clinker aggregates. Moreover, the nuclear radiation shielding abilities of geopolymer concretes were investigated experimentally. The gamma shielding parameters of the samples were evaluated by transmission measurements in the range of 0.081–0.661 keV. Also, neutron dose measurements were performed, and the samples
produced as neutron attenuator capacity was evaluated. The radiation shielding capabilities were improved
slightly with increasing sodium silicate solution content.
2023-01-01T00:00:00ZError estimations of a weak Galerkin finite element method for a linear system of coupled singularly perturbed reaction-diffusion equations in the energy and balanced norms
https://hdl.handle.net/11494/4890
Error estimations of a weak Galerkin finite element method for a linear system of coupled singularly perturbed reaction-diffusion equations in the energy and balanced norms
Toprakseven, Şuayip; Dinibutun, Seza
This paper introduces a weak Galerkin finite element method for a system of
coupled singularly perturbed reaction-diffusion problems. The proposed method is independent of parameter and uses piecewise discontinuous polynomials on interior of each element and constant on the boundary of each element. By the Schur complement technique, the interior unknowns can be locally efficiently eliminated from the resulting linear system, and the degrees of freedom of the proposed method are comparable with the classical FEM. It has been reported that the energy norm is not adequate for singularly perturbed reaction-diffusion problems since it can not efficiently reflect the behaviour of the boundary layer parts when the diffusion coefficient is very small. For the first time, the error estimates in the balanced norm has been presented for a system of coupled singularly perturbed problems when each equation has different parameter. Optimal and uniform error estimates have been established in the energy and balanced norm on an uniform Shishkin mesh. Finally, we carry out various numerical experiments to verify the theoretical findings.
2023-01-01T00:00:00Z