iki Elastik Çeyrek Düzleme Oturan ve Dairesel Rijit Bir Panç ile Bastırılan Elastik Tabaka Problemi

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2011Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2011Bu çalışmada, iki elastik çeyrek düzleme oturan ve bastırılan sürtünmesiz elastik tabaka problemi incelenmiştir. A ğ ın npriımP ifadeleri elde elastisite teorisi ve integral dönüşüm tekniği kullanılarak yer d^ ' f 1 f .. ..vnıılanmıstır edilmiştir. Tabaka için Fourier dönüşümü, çeyrek düzlem için Metlin ? hilinmeven olduöu iki Tabaka ve çeyrek düzleme ait sınır şartları sağlatılarak temas geri m rauss-Jacobi singüler integral denklem elde edilmiştir. Integra! denklemlerin sayıs Ç /arıcaDina cevrek integrasyon formülasyonu ile yapılmıştır. Problemde dış yuke rıjı aı P JLaierek savisal düzlemler arası açıklık mesafesine ve malzeme özelliklerine degışı ğ incelenmiş ve uygulamalar yapılmıştır. Bu değerlere ilişkin temas mesafeleri ve tem g bunlara ait sonuçlar grafikler ile gösterilmiştirİn this study, a frictionless contact problem for an elastic laye g v means o f a is considered. The concentrated force in the vertical dırectıon ıs app nfelasticitv and rigid cylindrical stamp. The gravity force is neglected and by usın9 obtained Fourier integral transform technique, the expressions of displacements an m,arter Dİanes Usinq transform is applied to the elastic layer and Metlin transform 'sapp lıed to the the boundary conditions, two singular integral eguatıonsare ° b * n e d ” h™ ' ^ and contact stresses are unknovvns. The numerical Solutions o e ı g , orobiem out by the method o f Gauss-Jacobi integration formula. The numerıca PP rv ijndrical stamp are performed for different numerical values ofexternal load, the distance between two quarter planes and material properties. demonstrated bv contact stresses are examined associated with those values. T e s graphic

iki Elastik Çeyrek Düzleme Oturan ve Dairesel Rijit Bir Panç ile Bastırılan Elastik Tabaka Probleminde Temas Mesafelerinin Yapay Sinir Ağı ile Hesabı

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2011Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2011Bu çalışmada, iki elastik çeyrek düzleme oturan ve tekil yükü ileten dairesel rijit bir panç ile bastırılan sürtünmesiz ve ağırlıkları ihmal edilmiş elastik tabaka probleminde, temas mesafelerinin Yapay Sinir Ağı (YSA) yöntemi ile hesabı incelenmiştir. Temas mesafelerinin hesaplanması için uç katmanlı geriye yayılma öğrenme algoritması olan bir ağ yapısı kullanılmıştır. Problem integral dönüşüm tekniği ve elastisite teorisi kullanılarak teorik olarak çözülmüştür. YSA’nın eğitim ve test aşamalarında ise; dış yüke, rijit dairesel panç yarıçapına, çeyrek düzlemler arası açıklık mesafesine ve malzeme özelliklerine değişik değerler verilerek oluşturulmuş örnekler kullanı mıştır. Bütün örnekler normalize edilmiş ve YSA yeterli hassasiyete kadar eğitilmiştir. Teorik sonuçlar ile YSA sonuçları karşılaştırılmış ve YSA hesaplarının teorik sonuçlara oldukça yakın çıktığı görülmüştür. YSA yönteminin doğru olarak kullanılması halinde, özellikle zaman gerektiren çalışmalarda, alternatif sayısal bir yöntem olabileceği belirtilmiştir.İn this study, the contact lengths calculation by Artificial Neural Netvvorks (ANNs) in the case o f frictionless and neglected gravity force contact problem for an elastic layer resting on two quarter planes is considered. The concentrated force in the vertical direction is applied to the layer by means o f a rigid cylindrical stamp. A three layered ANNs with backpropagation learning algorithm is utilized for calculation o f the contact lengths. The problem is solved theoretıcally by using the theory ofelasticity and integral transform technique. The patterns used in traınıng and testing stages o f ANN are formed by different numerical values o f external load, radıus o f the rıgıd cylindrical stamp, the distance betvveen two quarter planes and material properties. Ali o f the patterns are normalized and ANN is trained to acceptable tolerance. Theoretical and ANN Solutions are compared and it is seen that ANN Solutions are quite close to theoretical Solutions. İt is demonstrated that ifproperly used, ANN can be a suitable numerical tool, especially ın time consuming problems

Modeling Future Ecosystem Services of Lake Beyşehir

Freshwater ecosystems serve various ecosystem services such as supplying water for different purposes and food as provisioning services, nitrogen retention, flood protection as regulating services and recreation as cultural services. Lake Beyşehir is the largest freshwater lake in Turkey and it is critically important in terms of supplying ecosystem services for the area including irrigation, drinking water to a certain extent, fisheries and recreation. In this study, we applied the eco-hydrological model SWAT (Soil and Water Assessment Tool), to evaluate the effects of potential land use changes and the projected future climate on water and nutrient runoff of Lake Beyşehir catchment. Climate change scenarios were based on IPCC 5th main scenarios (RCP 4.5 and RCP 8.5) derived from 2 regional climate models (GFDLESM2M and IPSL-CMA-LR) for 2 different time periods (2030s and 2060s). Outputs of eco-hydrological model and the climate models were subsequently used as input to two individual lake ecosystem models (PCLake, General Lake Model). Chlorophyll a, water level and cyanobacteria biomass was used as a proxy to determine whether Lake Beyşehir will continue to supply its ecosystem services in the future as well. Our preliminary results showed that climate change scenarios demonstrate great variability in terms of precipitation which caused higher uncertainty in predicting future water levels. In addition, increased temperature had strong effect on chlorophyll a and cyanobacteria biomass which deteriorate the water quality and may result in loss of drinking water value of Lake Beyşehir

Inferring past environmental changes in three Turkish lakes from sub-fossil Cladocera

Cladocerans are increasingly used in palaeolimnological studies as their community composition is sensitive to both anthropogenic and natural forces in lakes. We present the results of a palaeolimnological investigation of three Turkish shallow lakes located in cold dry steppe and semi-dry Mediterranean climatic regions. The aim was to elucidate historical changes in environmental conditions by analysing sub-fossil cladocerans in Pb-210-dated sediment cores. Sub-fossil cladoceran remains from the surface sediment of 40 Turkish lakes were analysed to examine the environmental factors that most correlated with variation in the cladoceran assemblage. Redundancy analysis showed that salinity, macrophyte abundance, fish density, depth and total phosphorus were the most correlated with change in cladoceran assemblage composition with eigenvalues for the first and the second axes being lambda (1) = 0.312 and lambda (2) = 0.061, respectively. Sedimentary cladoceran assemblages from three cores were placed passively within the framework of the surface sediment ordination. The results reveal a prevalent impact of salinity, fish abundance and water level changes from the past to present. Thus, using cladoceran-based inferences, we traced key environmental changes related to variation in climate change, restoration and water level regulation over the last century

Restoration of Eutrophic Lakes with FluctuatingWater Levels: A 20-Year Monitoring Study of TwoInter-Connected Lakes

Eutrophication continues to be the most important problem preventing a favorable environmental state and detrimentally impacting the ecosystem services of lakes. The current study describes the results of analyses of 20 year monitoring data from two interconnected Anatolian lakes, Lakes Mogan and Eymir, receiving sewage effluents and undergoing restoration. The first step of restoration in both lakes was sewage effluent diversion. Additionally, in hypertrophic Lake Eymir, biomanipulation was conducted, involving removal of benthi-planktivorous fish and prohibition of pike fishing. The monitoring period included high (H) and low (L) water levels (WL) enabling elucidation of the effects of hydrological changes on lake restoration. In shallower Lake Mogan, macrophyte abundance increased after the sewage effluent diversion in periods with low water levels even at turbid water. In comparatively deeper Lake Eymir, the first biomanipulation led to a clear water state with abundant macrophyte coverage. However, shortly after biomanipulation, the water clarity declined, coinciding with low water level (LWL) periods during which nutrient concentrations increased. A second biomanipulation was conducted, mostly during high water level (HWL) period, resulting in a major decrease in nutrient concentrations and clearer water, but without an expansion of macrophytes. We conclude that repetitive fish removal may induce recovery but its success may be confounded by high availability of nutrients and adverse hydrological conditions

Modeling the effects of climatic and land use changes on phytoplankton and water quality of the largest Turkish freshwater lake: Lake Beyşehir

Climate change and intense land use practices are the main threats to ecosystem structure and services of Mediterranean lakes. Therefore, it is essential to predict the future changes and develop mitigation measures to combat such pressures. In this study, Lake Beysehir, the largest freshwater lake in the Mediterranean basin, was selected to study the impacts of climate change and various land use scenarios on the ecosystem dynamics of Mediterranean freshwater ecosystems and the services that they provide. For this purpose, we linked catchment model outputs to the two different processed-based lake models: PCLake and GLM-AED, and tested the scenarios of five General Circulation Models, two Representation Concentration Pathways and three different land use scenarios, which enable us to consider the various sources of uncertainty. Climate change and land use scenarios generally predicted strong future decreases in hydraulic and nutrient loads from the catchment to the lake. These changes in loads translated into alterations in water level as well as minor changes in chlorophyll a (Chl-a) concentrations. We also observed an increased abundance of cyanobacteria in both lake models. Total phosphorus, temperature and hydraulic loading were found to be the most important variables determining cyanobacteria biomass. As the future scenarios revealed only minor changes in Chl-a due to the significant decrease in nutrient loads, our results highlight that reduced nutrient loading in a warming world may play a crucial role in offsetting the effects of temperature on phytoplankton growth. However, our results also showed increased abundance of cyanobacteria in the future may threaten ecosystem integrity and may limit drinking water ecosystem services. In addition, extended periods of decreased hydraulic loads from the catchment and increased evaporation may lead to water level reductions and may diminish the ecosystem services of the lake as a water supply for irrigation and drinking water