Experimental investigation of pressure distribution on a cylinder due to the wave diffraction in a finite water depth     

Hakan Akyildiz 《Ocean Engineering》2002,29(9):1119-1132

The experimental investigations on the pressure distribution around a large vertical cylinder fixed on a wave channel, piercing the free surface and subjected to regular waves have been carried out. Recently, considerable advances have been made in the development of analytical techniques for studying non-linear wave loading phenomena on large structures. However, there is a lack of high quality experimental data that may be used for validating the analytical and numerical solutions obtained. This paper describes the design and execution of an experiment conducted at the Hydraulics Laboratory in the Civil Engineering Department of the Istanbul Technical University. Experimental measurements of pressures at different locations are presented including comparisons with the computational results. This study showed that the experimental and computational results generally exhibited better correlation, however, the measured pressure values diverged from the computational results while approaching the free surface.  相似文献   

Regional Variation of the ω - Upper Bound Magnitude of GIII Distribution in and Around Turkey: Tectonic Implications for Earthquake Hazards     

Yusuf Bayrak  Serkan Öztürk  Hakan Çınar  G. Ch. Koravos  T. M. Tsapanos 《Pure and Applied Geophysics》2008,165(7):1367-1390

Complete data set of earthquakes in Turkey and the adjacent areas has been used in order to compute the ω values in 24 seismic regions of Turkey. The parameter is obtained through Gumbel’s third asymptotic distribution of extreme values and is well known as upper bound magnitude. This is an interpretation that no earthquake magnitude greater than ω can occur in a region. The results also estimate the most probable magnitude for a time period of 100 years. The estimates of ω exceed the value of 7.00 in 20 of the 24 seismic regions. An effort is also made to find a relation between the magnitude and the length of a fault in the complicated tectonics of Turkey and the surrounding area. Earthquake hazard revealed as tables and maps are also considered for Turkey and the surrounding area.  相似文献   

Development of an Analytical Method for the Determination of Trace Lead in Lake Water Samples by Flame Atomic Absorption Spectrophotometry after Vortex Assisted-Stearic Acid Coated Magnetic Nanoparticle Based Extraction     

Hakan Serbest 《洁净——土壤、空气、水》2023,51(2):2200229

In the present study, a method is proposed for the determination of lead at trace levels by slotted quartz tube-flame atomic absorption spectrophotometry (SQT-FAAS) after preconcentration with stearic acid coated magnetic nanoparticle-based dispersive solid phase extraction (SA-MNP-DSPE). The slotted quartz tube (SQT) is used to enhance the analyte atom residence time in the light path. Stearic acid coated magnetic iron oxide (Fe₃O₄) nanoparticles, which can be easily collected with an external magnet, are used as adsorbent in the extraction process. The limit of detection (LOD) and the limit of quantitation (LOQ) values of the proposed method are obtained as 0.90 and 2.9 µg L⁻¹, respectively. The method allows high repeatability in a wide linear range between 5.0 and 250 µg L⁻¹, and the relative standard deviation for six replicates is 5.8%. The detection power is enhanced by about 77-fold compared to the regular flame atomic absorption spectrophotometry (FAAS) system. The method is validated by recovery experiments to four different lake water samples. After the spiking tests, good recovery results are calculated between 97% and 106%. These results show that lead can be detected at low levels in lake water samples with high sensitivity, accuracy, and precision.  相似文献   

Selection of the data time interval for the prediction of maximum ozone concentrations     

Ju??KocijanEmail authorView author&#;s OrcID profile  Dejan?Gradi?ar  Martin?Stepan?i?  Marija?Zlata?Bo?nar  Bo?tjan?Gra?i?  Primo??Mlakar 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(6):1759-1770

This paper highlights the problem of step-length selection for the one-step-ahead prediction of ozone called the data time interval. This is done using a case study-based comparison of two approaches for predicting the maximum daily values of tropospheric ozone. The first approach is the 1-day-ahead prediction and the second is the prediction of the maximum values based on a multi-step-ahead iteration of 1-h predictions. Gaussian process modelling is utilised for this comparison. In particular, evolving Gaussian-process models are used that update on-line with the incoming measurement data. These sorts of models have been successfully used in the past for the prediction of ozone pollution. This paper contributes an assessment of the way that the maximum ozone values are predicted. A comparison of the daily maximum ozone values forecasted by a model based on 1-day-ahead predictions with those obtained by iterated 1-h-ahead predictions of the ozone with predictions at predetermined hours of the day is given. The forecast results are in favour of the on-line model based on hourly predictions when approaching closer to the real maximum values of ozone, and in favour of the daily predictions when they are made on a daily basis.  相似文献   

Is there more to eels than slime? An introduction to papers presented at the ICES Theme Session in September 2006     

Dekker  Willem; Pawson  Mike; Wickstrom  Hakan 《ICES Journal of Marine Science》2007,64(7):1366-1367

The following 15 papers in this issue of the ICES Journal ofMarine Science are based on presentations given at a Theme Session—"Isthere more to Eels than Slime?"—at the ICES Annual ScienceConference held in Maastricht, the Netherlands, during September2006. International involvement in research on the Europeaneel (Anguilla anguilla) started in 1968, when a draft synopsisof eel biology, fisheries, and aquaculture was prepared at theEuropean Inland Fisheries Advisory Commission (EIFAC) sessionin Rome. By 1975, an ICES Eel Working Group had been set up(WGEEL), and it met in Copenhagen to document information oneel populations and fisheries and, for the first time, to notedeclining trends in catches. These were the subjects of a jointEIFAC/ICES symposium in Helsinki in 1976, where mitigation byrestocking was first proposed,  相似文献   

Sensitivity of the active fracture model parameter to fracture network orientation and injection scenarios   总被引：1，自引：1，他引：0  

Hakan Başağaoğlu  Sauro Succi  Chandrika Manepally  Randall Fedors  Danielle Y. Wyrick 《Hydrogeology Journal》2009,17(6):1347-1358

Active fractures refer to the portions of unsaturated, connected fractures that actively conduct water. The active fracture model parameter accounts for the reduction in the number of fractures carrying water and in the fracture–matrix interface area in field-scale simulations of flow and transport in unsaturated fractured rocks. One example includes the numerical analyses of the fault test results at the Yucca Mountain site, Nevada (USA). In such applications, the active fracture model parameter is commonly used as a calibration parameter without relating it to fracture network orientations and infiltration rates. A two-dimensional, multiphase lattice-Boltzmann model was used in this study to investigate the sensitivity of the active fracture model parameter to fracture network orientation and injection scenarios for an unsaturated, variable dipping, and geometrically simple fracture network. The active fracture model parameter differed by as much as 0.11–0.44 when the effects of fracture network orientation, injection rate, and injection mode were included in the simulations. Hence, the numerical results suggest that the sensitivity of the active fracture model parameter to fracture network orientation, injection rates, and injection modes should be explored at the field-scale to strengthen the technical basis and range of applicability of the active fracture model.  相似文献   

An alternative approach for the Istanbul earthquake early warning system     

Hakan Alcik  Oguz Ozel  Yih-Min Wu  Nurcan M. Ozel  Mustafa Erdik 《Soil Dynamics and Earthquake Engineering》2011

Two recent catastrophic earthquakes that struck the Marmara Region on 17 August 1999 (M_w=7.4) and 12 November 1999 (M_w=7.2) caused major concern about future earthquake occurrences in Istanbul and the Marmara Region. As a result of the preparations for an expected earthquake may occur around Istanbul region, an earthquake early warning system has been established in 2002 with a simple and robust algorithm, based on the exceedance of specified thresholds of time domain amplitudes and the cumulative absolute velocity (CAV) levels (Erdik et al., 2003 [1]). In order to improve the capability of Istanbul earthquake early warning system (IEEWS) for giving early warning of a damaging earthquake in the Marmara Region, we explored an alternative approach with the use of a period parameter (τ_c) and a high-pass filtered vertical displacement amplitude parameter (Pd) from the initial 3 s of the P waveforms as proposed by Kanamori (2005) [2] and Wu and Kanamori (2005) 3 and 4. The empirical relationships both between τ_c and moment magnitude (M_w), and between Pd and peak ground velocity (PGV) for the Marmara Region are presented. These relationships can be used to detect a damaging earthquake within seconds after the arrival of P waves, and can provide on-site warning in the Marmara Region.  相似文献   

Palaeomagnetic study of the Kepezdağ and Yamadağ volcanic complexes, central Turkey: Neogene tectonic escape and block definition in the central-east Anatolides     

H. Gürsoy  O. Tatar  J.D.A. Piper  F. Kobulut  Zafer Akp&#x;nar  Baochun Huang  A.P. Roberts  B.L. Mesci 《Journal of Geodynamics》2011,51(5):308-326

The Anatolian accretionary collage between Afro-Arabia and Eurasia is currently subject to two tectonic regimes. Ongoing slip of Arabia relative to Africa along the Dead Sea Fault Zone in the east is extruding crustal blocks away from the indenter by a combination of strike-slip and rotation. This zone of compression gives way to an extensional province in western Turkey, which also includes the eastern sector of Aegean Province. Although it is now well established that rotational deformation throughout Anatolia is distributed and differential, the sizes of the blocks involved are poorly understood. As a contribution towards evaluating this issue in central-east Turkey, we report palaeomagnetic study of the mid-Miocene Kepezda? and Yamada? volcanic complexes in central-south Anatolia (38–39.5°N, 37.5–39°E). A distributed sample through the Yamada? complex identifies eruption during an interval of multiple geomagnetic field reversals (40 normal, 36 reversed, 8 intermediate sites) with a selected mean defined by 63 sites of D/I = 335.4/51.1° (α₉₅ = 4.4°). The smaller Kepezda? complex (8 reversed, 4 normal and 1 intermediate site) yields a comparable mean direction from 12 sites of 338.7/49.8° (α₉₅ = 14.1°). In the context of a range of radiometric age evidence, two thick normal polarity zones within the Yamada? succession probably correlate with zones C5ACn and C5ADn of the Geomagnetic Polarity Time Scale and imply that the bulk of the volcanic activity took place between ∼15 and 13.5 Ma. Comparison of the palaeomagnetic results with the adjoining major plate indenters shows that the Yamada? complex has rotated CCW by 29.3 ± 5.2° relative to Eurasia; the much smaller dataset from the Kepezda? complex indicates a comparable CCW rotation of 26.0 ± 11.8° with respect to Eurasia. The Arabian Indenter has also been rotating CCW since mid Miocene times, and the block incorporating these two volcanic complexes north of the East Anatolian Fault Zone (EAFZ) is determined to have rotated 18.2 ± 6.0° CCW relative to the northern perimeter of Arabia. Comparison with data to the north identifies quasi-uniform rotation across a ∼200 km wide block extending from the Central Anatolian Fault Zone in the northwest to close to the East Anatolian transform fault zone in the south east. Although absence of suitable younger rocks does not permit the timing of this rotation to be determined in the study area, analogies with results from the Sivas Basin suggest that it is young, and followed establishment of the major transform faults. Rotation has evidently taken place around bounding arcuate faults and accompanied westward expulsion as the accretionary collage north of Arabia has been subject to ongoing post-collisional indentation.  相似文献   

A view of tectonic structure and gravity anomalies of Hatay Region Southern Turkey using wavelet analysis     

Hakan Alp  A. Muhittin Albora Huseyin Tur 《Journal of Applied Geophysics》2011,75(3):498-505

In this study, we demonstrate wavelet analysis as a method of delineating the boundaries of subsurface geological structures. We applied wavelet transform to Bouguer anomaly data of the Cilicia Region and adjacent areas. The residual anomalies are the results of various depth and other properties of buried structures on the gravity anomaly map. The superposition of anomaly of the underground structures with different properties such as depth, density and size, increases the complexity of the overall system. Thus the extraction of the desired properties from the anomaly map becomes difficult. Different separation techniques are used to solve this problem. Wavelet transform is one of these modern approaches. Here, we tested various types of wavelet transform modeling on synthetic examples and then applied them to the gravity anomaly map of the Cilicia Region in Turkey. We have detected the borders of the Hatay Region in southern Turkey and proposed the tectonic model of this real complex structure using the wavelet transformation. The most important result we have found is the presence of a triple junction near the Hatay region.  相似文献   

Medium-scale hazard mapping for shallow landslide initiation: the Buyukkoy catchment area (Cayeli, Rize, Turkey)   总被引：2，自引：0，他引：2  

Hakan A. Nefeslioglu  Candan Gokceoglu  Harun Sonmez  Tolga Gorum 《Landslides》2011,8(4):459-483

The main purpose of this study is to develop a new hazard evaluation technique considering the current limitations, particularly for shallow landslides. For this purpose, the Buyukkoy catchment area, located in the East Black Sea Region in the east of Rize province and the south of Cayeli district, was selected as the study area. The investigations were executed in four different stages. These were (1) preparation of a temporal shallow landslide inventory of the study area, (2) assessment of conditioning factors in the catchment, (3) susceptibility analyses and (4) hazard evaluations and mapping. A total of 251 shallow landslides in the period of 1955–2007 were recognised using different data sources. A ‘Sampling Circle’ approach was proposed to define shallow landslide initiation in the mapping units in susceptibility evaluations. To accomplish the susceptibility analyses, the method of artificial neural networks was implemented. According to the performance analyses conducted using the training and testing datasets, the prediction and generalisation capacities of the models were found to be very high. To transform the susceptibility values into hazard rates, a new approach with a new equation was developed, taking into account the behaviour of the responsible triggering factor over time in the study area. In the proposed equation, the threshold value of the triggering factor and the recurrence interval are the independent variables. This unique property of the suggested equation allows the execution of more flexible and more dynamic hazard assessments. Finally, using the proposed technique, shallow landslide initiation hazard maps of the Buyukkoy catchment area for the return periods of 1, 2, 5, 10, 50 and 100 years were produced.  相似文献