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41.
42.
Ş. Hakan Atapek Şeyda Polat Sibel Zor 《Protection of Metals and Physical Chemistry of Surfaces》2013,49(2):240-246
In this study, a tempered martensitic matrix was obtained in a low carbon steel, by applying austenization, quenching and tempering heat treatments. After austenization at 1000°C for 30 minutes, steel samples were quenched in water and then tempered at 200, 540 and 600°C for 30 minutes. Hardness measurements were done and then immersion tests were carried out in a 3.5 wt % NaCl solution for periods ranging between 1–7 days. Weight losses of the samples were determined after each immersion period and microstructural studies were performed on the corroded surfaces. Corrosion rates were calculated using weight loss data and verified by potentiodynamic tests. Results revealed that corrosion behavior of the experimental steels was directly affected by tempering temperature, hardness and microstructure. 相似文献
43.
Shahram Minaei Oguzhan ÇiÇekoglu Hakan Kuntman Sait TÜrkÖz 《International Journal of Electronics》2013,100(8):915-922
Three new current-mode second-order filter configurations which employ one or two current controlled conveyors (CCCIIs) and three passive elements are presented. Each proposed filter can realize one of the bandpass, lowpass or highpass responses all at high impedance outputs. The proposed filters offer current-control of pole angular frequency ωo without disturbing the parameter ωo /Q. No component matching is required and all the passive and active sensitivities are low. PSPICE simulation results are given to confirm the theoretical analysis. 相似文献
44.
Modifying of Cotton Fabric Surface with Nano-ZnO Multilayer Films by Layer-by-Layer Deposition Method 总被引:1,自引:0,他引:1
Şule S Uğur Merih Sarıışık A Hakan Aktaş M Çiğdem Uçar Emre Erden 《Nanoscale research letters》2010,5(7):1204-1210
ZnO nanoparticle–based multilayer nanocomposite films were fabricated on cationized woven cotton fabrics via layer-by-layer
molecular self-assembly technique. For cationic surface charge, cotton fabrics were pretreated with 2,3-epoxypropyltrimethylammonium
chloride (EP3MAC) by pad-batch method. XPS and SEM were used to examine the deposited nano-ZnO multilayer films on the cotton
fabrics. The nano-ZnO films deposited on cotton fabrics exhibited excellent antimicrobial activity against Staphylococcus aureus bacteria. The results also showed that the coated fabrics with nano-ZnO multilayer films enhanced the protection of cotton
fabrics from UV radiation. Physical tests (tensile strength of weft and warp yarns, air permeability and whiteness values)
were performed on the fabrics before and after the treatment with ZnO nanoparticles to evaluate the effect of layer-by-layer
(LbL) process on cotton fabrics properties. 相似文献
45.
Yasin Varol Hakan F. Oztop Ahmet Koca Engin Avci 《Expert systems with applications》2009,36(3):5813-5821
Forecasting of entropy generation of laminar natural convection in a partially cooled square cross-sectional room has been performed using support vector machines (SVM). The two-dimensional room was modeled as floor heating story with a window. Values of temperature and velocities were obtained by solving governing equations of natural convection with finite difference technique and using these values entropy generation was calculated with its definition. Forecasting of entropy generation due to fluid friction irreversibility (FFI) and heat transfer irreversibility (HTI) were made with known values for unknown parameters using SVM. Thus, calculation time was extremely reduced and values were obtained even for non-convergence cases. It was observed that the SVM was a strong method to predict the entropy generation without computational fluid dynamic analysis for all cases. 相似文献
46.
Havva Kazdal Zeytin Hakan Yildirim Banu Berme Selim Duduolu Gürkan Kazdal Adem Deniz 《钢铁研究学报(英文版)》2011,18(11):31-39
Heat treatment methods were applied to white cast iron for improving the impact and wear resistance. Additionally, chemical composition optimization was made. Furthermore, the effect of boron addition on such applications was investigated. Samples were investigated by using optical and electron microscope methods. Hardness, wear and impact tests were conducted. The results showed that the secondary carbides in the standard alloy were iron-enriched, needle-like carbides M3C when the boron-added alloy contained Fe23(C,B)6 type, globular secondary carbides. It was concluded that heat treatment B provided higher wear and hardness properties, compared to the standard heat treatment. Optimum mechanical properties were obtained by lower destabilisation temperatures and increasing temperature reduced the wear resistance and hardness. 相似文献
47.
Türker Tanergü?lü Hakan Mara? Cevriye Gencer Haluk Aygüne? 《Information Systems Frontiers》2012,14(2):423-444
In this study, a decision support system (DSS) based on the interactive use of location models and geographical information
systems (GIS) was developed to determine the optimal positions for air defence weapons and radars. In the location model,
the fire units are considered as the facilities to be located and the possible approach routes of air vehicles are treated
as demand points. Considering the probability that fire by the units will miss the targets, the objective of the problem is
to determine the positions that provide coverage of the approach routes of the maximum number of weapons while considering
the military principles regarding the tactical use and deployment of units. In comparison with the conventional method, the
proposed methodology presents a more reliable, faster, and more efficient solution. On the other hand, owing to the DSS, a
battery commander who is responsible for air defence becomes capable of determining the optimal weapon and radar positions,
among the alternative ones he has identified, that cover the possible approach routes maximally. Additionally, he attains
the capability of making such decisions in a very short time without going to the field over which he will perform the defence
and hence without being subject to enemy threats. In the decision support system, the digital elevation model is analysed
using Map Objects 2.0, the mathematical model is solved using LINGO 4.0 optimization software, and the user interface and
data transfer are supported by Visual Basic 6.0. 相似文献
48.
Zafer Erenel Hakan Altınçay 《Engineering Applications of Artificial Intelligence》2012,25(7):1505-1514
In automatic text categorization, the influence of features on the decision is set by the term weights which are conventionally computed as the product of term frequency and collection frequency factors. The raw form of term frequencies or their logarithmic forms are generally used as the term frequency factor whereas the leading collection frequency factors take into account the document frequency of each term. In this study, it is firstly shown that the best-fitting form of the term frequency factor depends on the distribution of term frequency values in the dataset under concern. Taking this observation into account, a novel collection frequency factor is proposed which considers term frequencies. Five datasets are firstly tested to show that the distribution of term frequency values is task dependent. The proposed method is then proven to provide better F1 scores compared to two recent approaches on majority of the datasets considered. It is confirmed that the use of term frequencies in the collection frequency factor is beneficial on tasks which does not involve highly repeated terms. It is also shown that the best F1 scores are achieved on majority of the datasets when smaller number of features are considered. 相似文献
49.
In this paper, a new joint multilevel data encryption and channel coding mechanism is proposed, which is called ??multilevel/advanced encryption standard?Csystematic distance 4?Ccontinuous phase frequency shift keying?? (ML/AES-SD4-CPFSK). In the proposed scheme, we have not only taken advantage of spatial diversity gains but also optimally allocated energy and bandwidth resources among sensor nodes as well as providing high level of security and error protection for cooperative communications in wireless sensor networks. Relay protocols of cooperative communications, such as amplify-and-forward and decode-and-forward with/without adversary nodes, have been studied for 4CPFSK, 8CPFSK, and 16CPFSK of ML/AES-SD4-CPFSK. We have evaluated the error performances of multilevel AES for data encryption, multilevel SD-4 for channel coding, and various CPFSK types for modulation utilizing cooperative communications in wireless sensor networks. According to computer simulation results, significant diversity gain and coding gain have been achieved. As an example, bit error rate (BER) performance of 10?5 value has been obtained at a signal-to-noise ratio (SNR) of ?6?dB for SD-4-CPFSK scheme in a compared related journal paper, whereas in our proposed system, we have reached the same BER value at a SNR of ?23?dB with amplify-and-forward with direct path signal protocol in 16-level AES, two-level SD-4 coded 16CPFSK, and at the same time, we have reached the same BER value at a SNR of ?22?dB with amplify-and-forward without direct path signal protocol in 16-level AES, two-level SD-4 coded 16CPFSK. 相似文献
50.
Hakan Demir Ahmet Koyun Ş. Özgür Atayılmaz Özden Ağra Ahmet Selim Dalkılıç 《Journal of Mechanical Science and Technology》2013,27(8):2497-2506
Heat transfer from finned pipes buried in the soil has been investigated using experimental, analytical and numerical techniques. The experimental setup consists of a ground source heat pump system and two separate ground heat exchangers. Constant surface temperature approach based on Carslaw and Jaeger’s theory study was used for calculating the heat transfer from the pipes analytically. The problem was modeled and solved using a CFD program numerically. Effects of the fin number, fin length and simulation time on the heat transfer rate have been investigated and compared with bare tube. A modified analytical formula was also proposed for finned pipes in this study. 相似文献