Sürdürülebilir Kalkınma Amaçları
Yazarlar
- Dertli, Enes(24)
- Cuce, Erdem(18)
- İspirli, Hümeyra(14)
- Cuce, Pinar Mert(13)
- Alım, Bünyamin(12)
- Mercan, Emin(12)
- Sert, Durmuş(12)
- Şenay, Volkan(12)
- Tozlu, Alperen(11)
- Artar, Musa(10)
- Korkmaz, Şadan(10)
- Pat, Suat(10)
- Yilmaz, Mustafa Tahsin(10)
- Özen, Soner(10)
- Gökçe, H.S.(9)
- Sagdic, Osman(9)
- Şakar, Erdem(9)
- Bayram, Ozkan(8)
- Demirtas, M.(8)
- Purcek, G.(8)
- Ergün, Mustafa(7)
- Yanar, H.(7)
- Demir, Lütfü(6)
- Taylan, Osman(6)
- Abdioglu, M.(5)
- Abdioglu, Murat(5)
- Alim, Bünyamin(5)
- Carbas, Serdar(5)
- Guclu, Tamer(5)
- Gökçe, H. Süleyman(5)
- Sayyed, M.I.(5)
- Han, İbrahim(4)
- Ozturk, K.(4)
- Zhang, Z.F.(4)
- Zhang, Z.J.(4)
- Özahi, Emrah(4)
- Şahin, Engin(4)
- Abusoglu, Aysegul(3)
- Andiç-Çakır, Özge(3)
- Baltakesmez, Ali(3)
Yayınlar
- MakaleAçık Erişim2017Scopus SJRQ1Concretes with synthetic aggregates for sustainability
Tekin, Ilker; Yasin Durgun, Muhammed; Gencel, Osman; Bilir, Turhan; Brostow, Witold; Hagg Lobland, Haley E.
We have used waste marble aggregates, marble dust and fly ash from thermic power plants as fillers in concretes for replacing natural aggregates. We have used two different kinds of cements. After curing, we have determined the workability (by slump tests), air content, unit weight, Schmidt hardness, ultrasound pulse velocity, compressive strength and carbonation depth. The concretes containing waste marble at least match or exceed the workability and strength of the control concrete type. Fly ash significantly improves the workability. Utilizing waste marble aggregate at the replacement ratio of 100% along with waste marble dust, fly ash and pozzolanic cements in concrete leads to lower cost – achieving at the same time environmentally friendly production process with decreased consumption of natural resources and energy. Our work also contributes to enhancement of sustainability by finding a use for marble waste and fly ash.
AtıfScopus28WoS24OpenAlex33
İncele - MakaleYalnız künye2017Scopus SJRQ1Toward cost-effective and energy-efficient heat recovery systems in buildings: Thermal performance monitoring
Cuce, Pinar Mert; Cuce, Erdem
Recent studies show that it is possible to reduce heating or cooling demand of a building as using heat recovery systems. Heat recovery technology is basically utilised to mitigate the heat loss, and hence energy consumption due to HVAC. Within the scope of this study, thermal comfort analyses of a test house integrated with a novel polycarbonate heat exchanger are conducted. At pre and post-retrofit case, temperature, relative humidity and CO2 measurements are carried out for a test period of one week. The results indicate that the internal CO2 concentration is not at desirable range due to lack of ventilation in the test house at the pre-retrofit case. However, following the integration of the novel ventilation system into the test house, CO2 concentration is found to be varying notably from 350 to 400 ppm which corresponds to the actual comfort conditions for indoor environments. It is also concluded from the results that the average relative humidity inside the test house at the post-retrofit case is found to be 57%, which is in the desired range whereas it is considerably high before retrofitting.
AtıfScopus26WoS25OpenAlex33İncele - MakaleAçık Erişim2017Scopus SJRQ1Thermal regulation impact of green walls: An experimental and numerical investigation
Cuce, Erdem
Green walls can be basically defined as climbing plants grown either directly against, or on support structures integrated to external building walls. Similar to other types of green infrastructure, they are in the centre of interest owing to their remarkable benefits such as reducing internal building temperatures, mitigating building energy consumption and facilitating urban adaptation to a warming climate. In this research, thermal regulation feature of green wall systems is experimentally and numerically investigated through a case study conducted in the Jubilee Campus of University of Nottingham. Internal wall temperatures are measured time-dependently for different cases and the results are compared with those of ordinary walls for a reliable and realistic approach. Different sky conditions are also considered within the scope of this research as an independent variable. Experimental results are verified by numerical models carried out in Ecotect. The results reveal that an average of 2.5 °C reduction in internal wall temperature can be achieved via green walls with about 10 cm thick climbing vegetation of Hedera helix, which is very promising.
AtıfScopus168WoS138OpenAlex178İncele - MakaleAçık Erişim2017Scopus SJRQ1Thermal performance assessment of a novel liquid desiccant-based evaporative cooling system: An experimental investigation
Cuce, Pinar Mert
Energy consumption in buildings due to heating, cooling and air conditioning (HVAC) systems has a steadily growing trend as a consequence of enhanced indoor thermal comfort conditions. The role of cooling in HVAC oriented energy consumption is remarkable especially in regions with extreme climatic conditions such as Africa and Middle East. In hot and arid climates, cooling demand is usually met by cost-effective evaporative cooling solutions. However, in hot and humid climates, evaporative cooling systems are not capable of providing cooling as the outdoor air is already almost saturated in most cases. Therefore in this research, a novel desiccant-based evaporative cooling system is presented. For different values of inlet supply air temperature and relative humidity provided by a standard environmental chamber, temperature and relative humidity values are measured experimentally at the inlet and outlet of dehumidification and humidification unit, respectively. Since the main purpose of the system developed is to provide cost-effective thermal comfort conditions especially in humid climates, dehumidification effectiveness is calculated for each case tested. The results indicate that the system provides attractive findings for temperate and humid climatic conditions, where stand-alone evaporative cooling systems are inconclusive. For a case of average inlet relative humidity of 94.7% and average inlet air temperature of 38.6 °C, the average outlet relative humidity and air temperature are determined to be 65.5% and 33.3 °C, respectively. An average of 5.3 °C reduction is achieved in supply air temperature as well as an average of 63.7% dehumidification effectiveness which is attractive and promising.
AtıfScopus35WoS32OpenAlex37İncele - MakaleAçık Erişim2017Scopus SJRQ1Delocalization and charge transfer studies of PERMENDUR49, KOVAR and Ti50Co50 alloys from relative K X-ray intensity ratios
Uğurlu, Mine; Alım, Bünyamin; Han, İbrahim; Demir, Lütfü
Kβ-to-Kα X-ray intensity ratios of Fe, Ni, Co, Ti, V in pure form and PERMENDUR49 (Fe49Co49V2), KOVAR (Fe54Ni29Co17) and Ti50Co50 alloys were calculated in order to determine valence-electron structure of the samples. The obtained experimental Kβ-to-Kα X-ray intensity ratios were found to be 0.1252 ± 0.0025, 0.1256 ± 0.0027, 0.1298 ± 0.0026, 0.1327 ± 0.0028, 0.1346 ± 0.0027 for pure Ti, V, Fe, Co and Ni, respectively. These values of present pure metals have increased with the increment in atomic number of these pure metals. Also, although the obtained these values for metal atoms in PERMENDUR49, Ti50Co50 and for Fe, Ni metal atoms in KOVAR approximately compatible with respect to results same pure metals, the obtained experimental Kβ-to-Kα X-ray intensity ratios for Co in KOVAR are significantly different from the appropriate values for pure Co metal. Then, the valence-electron populations of these alloys were calculated in order to answer as to why the characteristic properties of the studied alloys are distinct from each other. The valence-electron structures of these metals in pure form and alloys were determined by comparison of the calculated Kβ-to-Kα X-ray intensity ratios with the results of multi-configurations Dirac-Fock (MCDF) calculations to understand the charge-transfer and/or delocalization phenomena of these alloys. The experimental n3d values were found to be 3.2694, 4.7905, 7.7941, 7.9618, 8.500 for pure Ti, V, Fe, Co and Ni, respectively. The calculated 3d and 4s, 4p electron population values for Ti, V and Co in pure form have shown very little deviation from the appropriate values of Ti in Ti50Co50 and Co, V in PERMENDUR49. Also, the deviation for these values is greater for Fe, Ni, in KOVAR, Co in Ti50Co50, Fe in PERMENDUR49 with respect to the corresponding values of pure metals and the largest deviation for these values is observed for Co metal atoms in KOVAR alloy. We have also calculated the weighted average numbers of 3d and 4s, 4p electrons per one atom as well as the superposition of 3d and 4s, 4p electrons, as obtained from pure metal values. While the obtained superposition 3d electron numbers of present alloys exhibit a decreasing tendency as S3d(Ti50Co50) < S3d(PERMENDUR49) < S3d(KOVAR), the obtained weighted average 3d electron numbers of present alloys has opposite tendency (A3d(KOVAR) < A3d(PERMENDUR49) < A3d(Ti50Co50)). The analysis show that valance-electron population of elements in these alloys indicated differences with respect to the pure metal and each other. These differences can be related to type of alloy elements, concentration of alloy elements, charge transfer and/or delocalization phenomena between of individual metal atoms in alloys. Also, the obtained results show that there are alloying effect on valence-electron population due to charge transfer and/or delocalization phenomena.
AtıfScopus15WoS15OpenAlex16İncele - MakaleYalnız künye2017Scopus SJRQ1Role of airtightness in energy loss from windows: Experimental results from in-situ tests
Cuce, Erdem
The rate of air leakage related energy loss from glazed areas is unequivocal especially in older and poorly installed windows. Therefore, in this research, a comprehensive experimental investigation is done to analyse the importance of air leakage on overall heat transfer coefficient (U-value) of conventional air filled double glazed windows. The tests are conducted in a typical UK dwelling of Nottingham fitted with traditional air filled double glazed windows. One sash of the test window is sealed internally with a special transparent cover to provide excellent airtightness whereas the second window sash is left as it is to represent the ordinary case. The experiments are conducted in April 2016, and dynamic co-heating test methodology is applied to evaluate the rate of enhancement in the U-value of airtight window sash. The results indicate that the airtight window sash has a notably lower U-value compared to the ordinary window sash due to the impact of airtightness and reverse heat flux during noon time owing to the greenhouse effect between transparent cover and internal glazing. The overall U-value of ordinary window sash is found to be 2.67 W/m2K, whereas it is 1.79 W/m2K for airtight window sash. It is observed that about 33% of reduction in heat losses can be achieved via airtight windows.
AtıfScopus60WoS59OpenAlex75İncele - BildiriYayıncıda açık erişim2017Thermal and Acoustic Properties of Aerogels: Preliminary Investigation of the Influence of Granule Size
Moretti, Elisa; Merli, Francesca; Cuce, Erdem; Buratti, Cinzia; Capozzoli, A.; Serra, V.; Howlett, R.
The influence of granules size in silica aerogels is experimentally investigated in terms of thermal and acoustic performance characteristics. The transmission loss (TL) is measured at normal incidence in a traditional impedance tube, whereas the thermal conductivity (λ) is evaluated using a Hot Plate apparatus, setting up an appropriate methodology, due to the nature of the sample. The results reveal that the small granules (granules size in the 0.01-1.2 mm range), which have the highest density, have the best performance both in terms of thermal and acoustic properties. Depending on the granules size, λ varies in 19-22 mW/mK range at 10°C, whereas a TL equal to 13 dB at about 6400 Hz for 20 mm thickness is obtained for small granules.
AtıfScopus58WoS46OpenAlex63İncele - MakaleYalnız künye2017Scopus SJRQ1An accurate model for photovoltaic (PV) modules to determine electrical characteristics and thermodynamic performance parameters
Cuce, Erdem; Cuce, Pinar Mert; Karakas, Ibrahim Hakki; Bali, Tulin
Accurate and reliable modelling of photovoltaic (PV) modules is necessary for design and performance estimation of PV systems. Manufacturers of PV modules usually provide some basic electrical parameters specified at only one single operating condition, which is commonly known as standard test conditions (STCs). However, PV systems operate over a wide range of outdoor conditions, and the manufacturers’ reports do not cover sufficient information about how the PV modules react with respect to changes in the two most important environment-oriented conditions, which are solar intensity and operating cell temperature. In this respect, an accurate and reliable tool is required by designers to predict electrical characteristics and thermodynamic performance parameters of PV modules. Therefore in this research, a novel mathematical model is developed to determine solar intensity and cell temperature dependency of PV module parameters and thermodynamic efficiency figures. A simple one-diode model is proposed considering series resistance and shunt conductance. Mitsubishi PV-UJ225GA6 225 W polycrystalline silicon PV module and Kyocera KD205GH-2P 205 W multicrystal PV module are utilised for model assessment. Model results are compared with environmental chamber tests and manufacturers’ performance reports, and a very good agreement is achieved.
AtıfScopus97WoS85OpenAlex110İncele - MakaleAçık Erişim2017Scopus SJRQ1Improvement in levitation force performance of bulk MgB2 superconductors through coronene powder adding
Erdem, O.; Abdioglu, M.; Guner, S.B.; Celik, S.; Kucukomeroglu, T.
The effect of coronene (C24H12) addition on the levitation force properties of MgB2 superconductor has been investigated for the first time in this study. The polycrystalline disk-shaped MgB2 + y wt % C24H12 samples (y = 0, 2, 4, 6, 8, 10), were synthesized by a pellet/closed tube method at 850 °C under Ar atmosphere, after hot pressing at 200 °C. XRD analysis indicates a decrease in lattice parameters of coronene added samples and confirms substitution of carbon in boron sites. An increase in lattice strain and a decrease in grain size are observed due to the carbon substitution effect. Vertical and lateral levitation force measurements under zero-field-cooled and field-cooled regimes were carried out at different temperatures of 20, 25 and 30 K. It was found that the coronene addition significantly increases the high-field critical current density of MgB2. The Jc values were obtained as 4.6 × 103 Acm−2 and 1.3 × 104 Acm−2 for pure and 4 wt % coronene added samples at 20 K and 4 T. In addition, the levitation force measurements show that 4 wt % coronene adding is very effective in increasing both the vertical and lateral levitation force performances at 20 K. The maximum levitation force for 4 wt % coronene added sample corresponds to 7.58 N/g whereas the reference sample shows 6.73 N/g at 20 K in ZFC regime. The results point out that the hydrocarbon of C24H12 is an effective carbon-containing additive for MgB2 and can be useful for optimizing the levitation performance of MgB2 superconductors for potential applications.
AtıfScopus25WoS21OpenAlex27İncele - MakaleYalnız künye2017Scopus SJRQ1A study on some physical properties of a Pb-doped GaAs thin film produced by thermionic vacuum arc
Şenay, Volkan; Özen, Soner; Pat, Suat; Korkmaz, Şadan
A 155 nm Pb-doped GaAs thin film was deposited on a glass substrate by means of the thermionic vacuum arc technique in 30 s using GaAs and Pb pellets as source materials. Tools and techniques such as an optical reflectometer, UV-VIS-NIR spectrophotometer, FESEM, EDX, AFM and optical tensiometer were employed to investigate the physical properties of the produced film. From the optical investigations, the refractive index at the wavelength of 632.8 nm and optical band gap of the film were found to be 4.03 and 1.13 eV respectively. It was observed that Pb doping increased the value of refractive index and decreased the band gap value. A uniform surface morphology with fine grain covering the entire surface was observed through the FESEM and AFM studies while 50–80 nm grain size and 2.22 nm root mean square roughness values were obtained. The EDX analysis confirmed the presence of Ga, As and Pb elements in the film. The wetting experiments revealed that the contact angle value was dependent on the liquid used. The surface free energy calculated with OWRK/Fowkes and Equation of State approaches were about 26 mN/m.
AtıfScopus6WoS6OpenAlex5İncele - MakaleYalnız künye2017Scopus SJRQ2The surface morphology research of the BGaN thin films deposited by thermionic vacuum arc
Özen, Soner; Pat, Suat; Şenay, Volkan; Korkmaz, Şadan
In this paper, BGaN thin films with two different thicknesses were deposited on two different substrates and their surface morphologies were investigated. The amorphous glass and semi-crystalline polyethylene terephthalate substrates were selected. At the same time, two different deposition angles are selected with a view to the effect of deposition angle on surface morphology. The surface and optical properties were determined by using X-ray diffractometer (XRD), atomic force microscope (AFM), spectroscopic ellipsometry (SE) and optical interferometer. The thicknesses of thin films on substrates are about 30 nm and 40 nm. According to the atomic force microscope images, small-dimensional grains observed on relatively large grains. The roughness values of the thin films on the polyethylene terephthalate substrate are lower than on the glass substrate.
AtıfScopus10WoS9OpenAlex10İncele - MakaleAçık Erişim2017Scopus SJRQ1An energy prediction algorithm for wind-powered wireless sensor networks with energy harvesting
Kosunalp, Selahattin
Energy harvesting (EH) from environmental energy sources has the potential to ensure unlimited, uncontrollable and unreliable energy for wireless sensor networks (WSNs), bringing a need to predict future energy availability for the effective utilization of the harvested energy. The majority of previous prediction approaches have exploited the diurnal cycle dividing the whole day into equal-length time slots in which predictions were carried out in each slot independently. This is not, however, efficient for wind energy as it exhibits non-controllable behaviour in that the amount of energy to be harvested varies over time. This paper proposes a novel approach to predict the wind energy for EH-WSNs depending on the energy generation profile of latest condition. The distinctive feature of the proposed approach is to consider the recent conditions in current-day, instead of past-day's energy generation profiles. The performance of the proposed algorithm is evaluated using real measurements in comparison with state-of-art approaches. Results show that the proposed strategy significantly outperforms the two popular energy predictors, EWMA and Pro-Energy.
AtıfScopus48WoS36OpenAlex51İncele - MakaleYalnız künye2017Scopus SJRQ2The Al doping effect on the surface, optical, electrical and nanomechanical properties of the ZnO and AZO thin films prepared by RF sputtering technique
Pat, Suat; Mohammadigharehbagh, Reza; Özen, Soner; Şenay, Volkan; Yudar, H. Hakan; Korkmaz, Şadan
In this study, ZnO and aluminum doped ZnO (AZO) thin films were deposited at constant RF power of 100 W for the determine of the structural, surface, optical, electrical and nanomechanical properties. X–Ray diffraction (XRD), atomic force microscopy (AFM), nanoindentation technique and UV–Vis spectrophotometer were used. ZnO (100) and ZnO (004) orientations were detected in the ZnO and AZO films. The crystallite size values for the films were calculated as to be as 35 nm and 20 nm for ZnO and AZO thin films, respectively. It was found that the roughness values decreased to 3.15 nm from 5.15 nm for AZO and ZnO films, respectively. The hardness values of the ZnO and AZO thin films are measured as 7 GPa and 11 GPa. Young's modulus values were determined as 155 GPa and 95 GPa for ZnO and AZO films, respectively. The ZnO and AZO thin films have high transparency.
AtıfScopus50WoS50OpenAlex57İncele - MakaleAçık Erişim2017Scopus SJRQ1Effect of high pressure homogenization (HPH) on microstructure and rheological properties of hazelnut milk
Gul, Osman; Saricaoglu, Furkan Turker; Mortas, Mustafa; Atalar, Ilyas; Yazici, Fehmi
The effect of high pressure homogenization (HPH) on microstructure and rheological properties of hazelnut milks was investigated. Hazelnut milk samples were produced from cold pressed hazelnut cake and homogenized up to 150 MPa pressure. Microstructural and rheological properties of products, except temperature sweep, were greatly affected by HPH treatments. Homogenized samples showed significant reduction in particle size, which turned from bimodal and poly-disperse to monodisperse distributions. HPH decreased the consistency of products from 91.82 to 0.51 Pa.sn and increased flow behavior index from 0.15 to 0.36. All samples showed higher values G′ than G″, which indicates that samples could be classified as soft-gel network, and hazelnut milk samples did not obey the Cox-Merz rule without multiplying angular frequency with shift factor. In conclusion, HPH can be used to reduce the consistency of samples and the friction loss, thus minimizing the amount of energy required to flow during processing and distribution. Industrial relevance. Vegetable based beverages are available at any supermarket as an alternative to dairy products with an increasing consumer acceptance. Between these beverages hazelnut milk samples are the most noteworthy products due to important role in human nutrition and health, and moreover due to well accepted and widely consumed product. Due to its composition, hazelnut milks have very high consistency, and therefore, the energy consumption for processing and handling is too high. In this research, the high pressure homogenization (HPH) technology was successfully proposed to be used for improving microstructural properties, and hence reducing its consistency. The energy consumption during processing and distribution can be minimized by reducing the consistency and friction losses of product.
AtıfScopus97WoS80OpenAlex100İncele - MakaleAçık Erişim2017Scopus SJRQ1Potential application of high pressure homogenization (HPH) for improving functional and rheological properties of mechanically deboned chicken meat (MDCM) proteins
Saricaoglu, Furkan Turker; Gul, Osman; Tural, Serpil; Turhan, Sadettin
The potential application of high pressure homogenization (HPH) for modifying the solubility, emulsifying and foaming properties, particle size distributions, zeta potential and rheological properties of mechanically deboned chicken meat (MDCM) proteins was evaluated. HPH decreased particle size, produced higher zeta potential and stronger electrostatic repulsion, and hence, improved water solubility, as well as emulsifying, foaming properties, flow ability and dynamic shear properties of protein suspensions. Steady and dynamic shear results indicated that samples had shear-thinning and soft-gel network behavior due to higher G′ than G″. Creep and recovery tests were explained with Burgers and exponential decay models, respectively, and led to a better understanding the internal structure, as well as elastic and viscous behavior. The final percentage recovery increased as homogenization pressure increased due to strengthened solid-like structure of protein suspensions. These results revealed that HPH can be a valuable process to improve functional and rheological properties of MDCM proteins.
AtıfScopus53WoS51OpenAlex56İncele - MakaleAçık Erişim2016Scopus SJRQ1Experimental determination of Drucker-Prager yield criterion parameters for normal and high strength concretes under triaxial compression
Öztekin, Ertekin; Pul, Selim; Hüsem, Metin
In this study, parameters which define Drucker-Prager yield criterion were investigated experimentally for both normal strength concrete (NSC) and high strength concrete (HSC) by triaxial compression tests. Total 16 concrete series with different concrete strength were produced. While 8 concrete series were produced as NSC (20 MPa < fcm < 55 MPa), other 8 series were produced as HSC (55 MPa < fcm < 85 MPa). Each series contains 16 specimens. Triaxial compression tests were performed on these concrete specimens. Concrete compressive strength of the specimens were measured under 4 different lateral compression level (0, 1, 2 and 4 MPa). After Mohr circles were drawn by using the data obtained from triaxial compression tests, the values of cohesion were determined between 5 MPa and 13 MPa for NSC and 13 MPa and 19 MPa for HSC. The values of internal friction angle were also obtained between 27° and 34° for NSC, 34° and 39° for HSC from the Mohr circles. The parameters defining the Drucker-Prager yield criterion were determined by using the values of cohesion and internal friction angle. Finally, after some equations were proposed to calculate the parameters by using concrete compressive strength, the validation of these equations were also proved in this study.
AtıfScopus83WoS74İncele - MakaleAçık Erişim2016Scopus SJRQ1Improvement in performance properties of asphalt using a novel boron-containing additive
Oruç, Şeref; Yılmaz, Bahadır
In current times, many additives are used to improve the performance characteristics of asphalt. In this study, a new additive that contains boron, given the short name of cyclic borate ester (CBE), was chemically synthesised in laboratory conditions. It was added to the asphalt binder as 1%, 2%, 4% and 6% ratios of asphalt by weight, and modified asphalt samples were produced. The effects of CBE on the conventional properties of asphalt binder (penetration, softening point, ductility, flash point, Fraass breaking point) were examined using a dynamic shear rheometer, rotational viscosity, a rolling thin film oven, a pressure aging vessel and bending beam rheometer test methods. Results showed that the use of CBE additive increased the hardness, softening point, viscosity, flash-point value and rutting resistance of asphalt binder and decreased temperature sensitivity. CBE also enhanced elastic responses (increased complex shear modulus and decreased phase angle), aging resistance and low-temperature cracking resistance and did not change the cohesion property.
AtıfScopus25WoS24OpenAlex28İncele - MakaleAçık Erişim2016Scopus SJRQ1Use of Q-learning approaches for practical medium access control in wireless sensor networks
Kosunalp, Selahattin; Chu, Yi; Mitchell, Paul D.; Grace, David; Clarke, Tim
This paper studies the potential of a novel approach to ensure more efficient and intelligent assignment of capacity through medium access control (MAC) in practical wireless sensor networks. Q-Learning is employed as an intelligent transmission strategy. We review the existing MAC protocols in the context of Q-learning. A recently-proposed, ALOHA and Q-Learning based MAC scheme, ALOHA-Q, is considered which improves the channel performance significantly with a key benefit of simplicity. Practical implementation issues of ALOHA-Q are studied. We demonstrate the performance of the ALOHA-Q through extensive simulations and evaluations in various testbeds. A new exploration/exploitation method is proposed to strengthen the merits of the ALOHA-Q against dynamic the channel and environment conditions.
AtıfScopus41WoS29OpenAlex37İncele - MakaleYalnız künye2016Scopus SJRQ1Optical, structural, morphological and compositional characterization of a Co-doped GaAs semiconducting thin film produced by thermionic vacuum arc
Şenay, Volkan; Özen, Soner; Pat, Suat; Korkmaz, Şadan
A 80 nm 2 at% Co-doped GaAs thin film was deposited on a glass substrate under a high vacuum condition by means of the thermionic vacuum arc technique using GaAs and Co pellets as source materials. Tools and techniques such as an optical reflectometer, XRD, UV-VIS-NIR spectrophotometer, FESEM, EDX, and AFM were employed to investigate some of the physical properties of the produced film. From the optical investigations, the refractive index at 632.8 nm and optical band gap of the film were determined to be 3.60 and 1.42 eV respectively. XRD characterization indicated that the film contained GaAs and Co phases. A uniform surface morphology with fine grain covering the entire surface was observed through the FESEM and AFM studies, while 30 nm grain size and 2.72 nm root mean square roughness were obtained. The EDX analysis also confirmed the presence of Ga, As and Co in the film.
AtıfScopus19WoS17OpenAlex18İncele - MakaleYalnız künye2016Scopus SJRQ1Optimization of strength, ductility and electrical conductivity of Cu-Cr-Zr alloy by combining multi-route ECAP and aging
Purcek, G.; Yanar, H.; Demirtas, M.; Alemdag, Y.; Shangina, D.V.; Dobatkin, S.V.
Properties of Cu-Cr-Zr alloy with ultrafine-grained (UFG) structure produced by equal-channel angular pressing (ECAP) via different routes have been investigated. Special attention was paid to the optimization of multi-functional structural, thermal, electrical and mechanical properties of the alloy by aging of UFG one. Multi-pass ECAP via different routes gives rise to the formation of a deformation-induced submicrocrystalline structure with the grain (subgrain) sizes in the range of 200-300. nm depending on applied routes which leads to high hardness and strength in the Cu-Cr-Zr alloy with reduced ductility. Amongst the applied routes, route-Bc was found to be the best processing path for achieving the lowest grain size, the highest hardness and strength. Aging of 8Bc-processed UFG samples increases the hardness and strength of Cu-Cr-Zr alloy while retaining an electrical conductivity comparable to that of aged coarse-grained (CG) one. A satisfactory electrical conductivity of 71%IACS without considerable loss of peak hardness was achieved after aging of 8Bc-processed UFG alloy at 425. °C for 240. min. The precipitation strengthened UFG alloy remains its stable behavior at elevated temperatures up to 450. °C.
AtıfScopus164WoS147OpenAlex151İncele