Extreme motion response analysis of moored semi-submersibles     

O. Yilmaz  A. Incecik 《Ocean Engineering》1996,23(6):497-517

The motion response prediction of offshore structures may be carried out using time domain or frequency domain models or model tests. The frequency domain analysis uses the simplified, linearised form of the motion equations and it is very economical. The time domain analysis, unlike frequency domain models, is adequate to deal with non-linearities such as viscous damping and mooring forces, but it requires sophisticated solution techniques and it is expensive to employ. For moored semisubmersibles time domain techniques must be employed since there are strong nonlinearities in the system due to mooring line stiffness and damping and viscous drag forces. In the first part of this paper a time domain model to predict the dynamic response of a semi-submersibles are developed and the effect of thrusters and mooring line damping are incorporated into the time domain model. In the second part time domain simulations are carried out to find the total extreme motions and mooring forces.  相似文献   

Photometric Solution of the Eclipsing Binary V351 Pegasi     

B. Albayrak  G. Djurašević  S. Selam  M. Yilmaz  S. Erkapić  O. Aksu  T. Tanriverdi 《Astrophysics and Space Science》2005,296(1-4):293-296

BVR light curves of the recently discovered eclipsing binary V351 Peg were studied to derive the preliminary physical parameters of the system. The light curves were obtained at the TüBİTAK* – Turkish National Observatory (TUG) during three nights in August, 2003. The solutions were made using Djurašević’s inverse problem method. V351 Peg is a system in an overcontact configuration (f _over∼ 21 %) with a relatively small temperature difference between the components ΔT ≈ 20 K. The results suggest a significant mass and energy transfer from the more massive primary onto the less massive secondary. The hot area on the less massive star, near the neck region, can be considered as a consequence of this mass and energy exchange between the components through the connecting neck of the common envelope. TüBİTAK: The Scientific and Technical Research Council of Turkey.  相似文献   

The effect of the sampling strategies on the landslide susceptibility mapping by conditional probability and artificial neural networks   总被引：4，自引：2，他引：2  

Işık Yilmaz 《Environmental Earth Sciences》2010,60(3):505-519

This study presented herein compares the effect of the sampling strategies by means of landslide inventory on the landslide susceptibility mapping. The conditional probability (CP) and artificial neural networks (ANN) models were applied in Sebinkarahisar (Giresun–Turkey). Digital elevation model was first constructed using a geographical information system software and parameter maps affecting the slope stability such as geology, faults, drainage system, topographical elevation, slope angle, slope aspect, topographic wetness index, stream power index and normalized difference vegetation index were considered. In the last stage of the analyses, landslide susceptibility maps were produced applying different sampling strategies such as; scarp, seed cell and point. The maps elaborated were then compared by means of their validations. Scarp sampling strategy gave the best results than the point, whereas the scarp and seed cell methods can be evaluated relatively similar. Comparison of the landslide susceptibility maps with known landslide locations indicated that the higher accuracy was obtained for ANN model using the scarp sampling strategy. The results obtained in this study also showed that the CP model can be used as a simple tool in assessment of the landslide susceptibility, because input process, calculations and output process are very simple and can be readily understood.  相似文献   

Structural and Geomorphological Aspects of the Kat Landslides (Tokat—Turkey) and Susceptibility Mapping by Means of GIS     

Işik Yilmaz  Mustafa Yildirim 《Environmental Geology》2006,50(6):931-931

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Monitoring of protected bands of Terkos drinking water reservoir of metropolitan Istanbul near the Black Sea coast using satellite data     

H. Gonca Coskun  Ozlem Gulergun  Levent Yilmaz 《International Journal of Applied Earth Observation and Geoinformation》2006

In this study, remote sensing (RS) with computer-based geographic information systems (GIS) techniques are used as a tool for monitoring the water basin area and water quality in Istanbul's relatively less polluted and comparatively less destroyed catchment of the metropolis drinking water dam reservoir named Terkos. It is necessary to work with recent data to be able to identify the effects of urbanization on the water quality of the Terkos dam catchment area that supplies drinking water to the metropolis. RS is an important tool to monitor water quality and urban terrain. For this aim, a project has been initiated at the Technical University Remote Sensing Laboratory, under the Istanbul Water and Sewerage Administration (ISKI) sponsorship in Istanbul. The project uses SPOT-PAN, XS and IRS-1C/D PAN and satellite data of 1993 and 2000 for urban analysis and Landsat-TM and LISS-III satellite data of 1992 and 2000 for water quality. For calibration and validation, ground truth samples are collected from the experimental area. The RS data was converted into the UTM coordinate system and image enhancement and classification techniques are used. Raster data is converted to vector data to assess the study area for analyzing in GIS for the purpose of planning and decision-making on protected water basin zones. As a result of monitoring land use and water quality changes, recommendations are made for planning and management of the protected environment of the Terkos catchment protected area. Measuring land use change is a very important issue for controlling the future development of the basin, GIS techniques are performed and results are illustrated in established models on the four protected zones of Terkos water basin.  相似文献   

Liquefaction-induced ground deformations at Hotel Sapanca during Kocaeli (Izmit),Turkey earthquake     

K. Onder Cetin  T. Leslie Youd  Raymond B. Seed  Jonathan D. Bray  Rodolfo Sancio  W. Lettis  M. Tolga Yilmaz  H. Turan Durgunoglu 《Soil Dynamics and Earthquake Engineering》2002,22(9-12):1083-1092

This paper presents a study of liquefaction-induced ground deformations at the Hotel Sapanca site during the 1999 Kocaeli (Izmit)—Turkey earthquake. The paper discusses: (1) observed ground deformations and displacements after the earthquake, (2) the results of field investigations by means of borings and in situ index tests including standard penetration tests (SPT), static cone penetration tests (CPT) and piezocone (CPTU) tests, (3) analyses of observed ground settlements and lateral deformations by a suite of methods, and (4) comparisons of observed and calculated ground movements.  相似文献   

Geotechnical evaluation of Miocene gypsum from Sivas (Turkey)   总被引：2，自引：0，他引：2  

Ergun Karacan  Işik Yilmaz 《Geotechnical and Geological Engineering》2000,18(2):79-90

Gypsum is widely distributed in Sivas (Turkey), occurring chiefly in the formations of Miocene age. The gypsum is generally of the alabastrine type with a little of the porphiroblast type and contains traces of clay minerals, anhydrite and calcite. It is a moderately strong rock in terms of its unconfined compressive strength which is related to the crystal size. Strength increases as the crystal size decreases. The strength of gypsum was reduced by approximately 55%, when the samples were kept in the water for 20 days. Most samples exhibit plastic–elastic–plastic deformation. The gypsum has a high modulus ratio, and is a moderately deformable rock. High lateral deformations and low vertical deformations are observed under the vertical stress conditions in accordance with the relationship between modulus ratio and strain.  相似文献   

Validation of a TRMM-based global Flood Detection System in Bangladesh     

Caitlin Balthrop Moffitt  Faisal Hossain  Robert F. Adler  Koray K. Yilmaz  Harold F. Pierce 《International Journal of Applied Earth Observation and Geoinformation》2011

Although the TRMM-based Flood Detection System (FDS) has been in operation in near real-time since 2006, the flood ‘detection’ capability has been validated mostly against qualitative reports in news papers and other types of media. In this study, a more quantitative validation of the FDS over Bangladesh against in situ measurements is presented. Using measured stream flow and rainfall data, the study analyzed the flood detection capability from space for three very distinct river systems in Bangladesh: (1) Ganges– a snowmelt-fed river regulated by upstream India, (2) Brahmaputra – a snow-fed river that is braided, and (3) Meghna – a rain-fed and relatively flashier river. The quantitative assessment showed that the effectiveness of the TRMM-based FDS can vary as a function of season and drainage basin characteristics. Overall, the study showed that the TRMM-based FDS has great potential for flood prone countries like Bangladesh that are faced with tremendous hurdles in transboundary flood management. The system had a high probability of detection overall, but produced increased false alarms during the monsoon period and in regulated basins (Ganges), undermining the credibility of the FDS flood warnings for these situations. For this reason, FDS users are cautioned to verify FDS estimates during the monsoon period and for regulated rivers before implementing flood management practices. Planned improvements by FDS developers involving physically-based hydrologic modeling should transform the system into a more accurate tool for near real-time decision making on flood management for ungauged river basins of the world.  相似文献   

Numerical Modelling of Steep Slopes in Open Rock Quarries     

Murat Yilmaz  Altay Ertin  Selman Er  Atiye Tugrul 《Journal of the Geological Society of India》2018,91(2):232-238

The key question regarding steep rock slopes along rock quarries is their stability because a rock slope failure can have critical results. In this study, the aim is to investigate the areas with potential risk for jointed karstic limestones in a rock quarry. First, to determine rock mass properties, scan-line surveys were performed, and the major orientations of discontinuities were analyzed using stereographic projection. Then, the physicomechanical properties of the slope-forming rock were determined in the laboratory, and geomechanical properties of the rock mass were determined using an empirical failure criterion. Finally, the quarry slope stability was assessed in accordance with numerical modelling. According to the results obtained, the numerical modelling of steep rock slopes can be efficiently evaluated by using finite element method. Beside this, the presence of joints intersecting the main discontinuity sets, the filling materials of discontinuities resulting from weathering of limestone and surface deposits, surcharge load due to mine waste dumped on the slopes and excavation blasting during construction of quarry area play a key role when modelling the steep rock slopes by using finite element method.  相似文献   

Investigation of Soil Conditioning Tests with Three-Dimensional Numerical Modeling     

Salim Pourmand  Hamid Chakeri  Mohammad Sharghi  Yilmaz Ozcelik 《Geotechnical and Geological Engineering》2018,36(5):2869-2879

Due to the diverse and complex structure of soil and the variety of foam-modifier materials that are used, it is difficult to provide a model to predict the laboratory behavior of modified soils. For example, several studies have shown independently that the amount of the foam-modified soil depends on several factors, such as the internal friction angle and normal stiffness. Of late, modeling by numerical methods has become popular in engineering sciences and the modeling of complex material behavior is possible with the help of numerical methods. In this research, the performance and efficiency of the numerical method in the modeling of laboratory tests such as the slump test and the uniaxial compressive strength test were investigated and it was found that numerical modeling performs very well in predicting the results of these tests for foam-modified sand samples. In order to achieve this goal, the slump test and the uniaxial compressive strength test were performed in the laboratory on several modified sand samples in order to obtain the laboratory results for these samples. Then, numerical simulation of these experiments was carried out using PFC^3D software. The results of numerical modeling were compared with the experimental results, and good agreement was observed. Finally, after calibration of the numerical model using the experimental results, the effect of changes in the internal friction angle and the normal stiffness of the modified sand in the amount of the slump was investigated. According to the results of this sensitivity analysis, it was determined that by increasing both effective parameters the amount of the slump of foam-modified sand decreases and that the parameters are the most important factors in controlling the slump value.  相似文献