WoS İndeksli Yayınlar Koleksiyonu
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Conference Object Citation - WoS: 1Citation - Scopus: 52D Coverage Analysis of Sensor Networks with Random Node Deployment(IEEE, 2017) Birtane, Sibel; Kazdal, Seda; Sahingoz, Ozgur KorayIn last few decades, as a result of the advances in microelectromechanical systems, Wireless Sensor Networks (WSNs) have gained a considerable attention due to their low-cost, low-power and small-scale sensor nodes which are used to integrate sensing, processing, communicating capabilities to solve many different real world problems. The placement of sensor nodes is a very important step to cover the theater of these application areas. Increasing the coverage of WSN system is one of the important research interests to determine the quality of service of the system. The location of sensor nodes can be determined by humans to increase the coverage area. However, in the remote or hostile environments, the random deployment of sensor nodes is needed to be used. In this paper, the different random deployment techniques have been studied, and the experimental results are obtained have been shared to show the effectiveness of these techniques. Finally, the alternative approaches are mentioned to guide the researchers, as well.Conference Object 2D Vector Representation of Binomial Hierarchical Tree Items(Institute of Electrical and Electronics Engineers Inc., 2022) Dönmez, İ.; Karateke, S.; Zontul, M.Today Artificial Intelligence (AI) algorithms need to represent different kinds of input items in numeric or vector format. Some input data can easily be transformed to numeric or vector format but the structure of some special data prevents direct and easy transformation. For instance, we can represent air condition using humidity, pressure, and temperature values with a vector that has three features and we can understand the similarity of two different air measurements using cosine-similarity of two vectors. But if we are dealing with a general ontology tree, which has elements "entity"as the root element, its two children "living things"and "non-living things"as first- level elements repeatedly children of "living things"that are "Animals", "Plants"as second level elements, it is harder to represent this kind of data with numeric values. The ontology tree starts from the general items and goes to specific items. If we want to represent an element of this tree with a vector; how can it be possible? And if we want the measured similarity using some methods like cosine-similarity, which one similarity is higher, ("Animal"and "non-living thing") or ("Animal"and "Living thing")? How should we select the values of this vector for each item of the hierarchical tree? In this paper, we propose an original and basic idea to represent the hierarchical tree items with 2D vectors and in the proposed method the cosine-similarity metric works for measuring the semantic similarity of represented items at the same level as parent items. There are two important results related to our representation: (1) The "y"values of the items give the hierarchical level of the item. (2) For the same level items, the cosine similarities between the parent item and child items are higher if the child belongs to this parent compared to other childrens'. In other words, the cosine similarity between the parent item and child items is highest if the child belongs to this parent. © 2022 IEEE.Article Citation - WoS: 4Citation - Scopus: 437 Years after the Chernobyl(Akademiai Kiado Zrt., 2024) Gunay, Osman; Yalcin, Caner; Guray, R. Taygun; Karakurt, Didem Avci; Tantoglu, Ezgi; Basdemir, SafaThis study aims to assess the artificial and natural radiation dose levels in certain districts of Kocaeli province within the Marmara region, 37 years after the Chernobyl nuclear accident, and evaluate the current status prior to potential nuclear leakage events from Zaporijya or other nuclear power plants. Radioactive concentrations of Th-232, U-238, K-40 and Cs-137 were determined using HPGe gamma spectrometry in 26 soil samples collected from the region of interest. The average concentrations were found to be 22.35 Bqkg(-1) for U-238, 26.36 Bqkg(-1) for Th-232, 368.34 Bqkg(-1) for K-40, and 2.44 Bqkg(-1) for Cs-137. Furthermore, the study revealed an absorbed dose rate of 41.73 nGyh(-1), an annual effective dose equivalent of 51.18 mu Svy(-1), and an excess lifetime cancer risk of 0.00018.Article Citation - WoS: 56Citation - Scopus: 683D Bio-Printing of Levan/Polycaprolactone/Gelatin Blends for Bone Tissue Engineering: Characterization of the Cellular Behavior(Pergamon-Elsevier Science Ltd, 2019) Duymaz, B.T.; Erdiler, F.B.; Alan, T.; Aydogdu, M.O.; İnan, A.T.; Ekren, N.; Uzun, M.; Şahin, Yeşim Müge; Buluş, Erdi; Oktar, F.N.; Selvi, S.S.; Toksoy, Oner E.; Kilic, O.; Bostan, M.S.; Eroglu, M.S.; Gunduz, O.; Duymaz, Busra Tugce; Erdiler, Fatma Betul; Alan, Tugba; Aydogdu, Mehmet Onur; Inan, Ahmet Talat; Ekren, Nazmi; Gunduz, OguzhanPoly(epsilon-caprolactone) (PCL), gelatin (GT) and different concentrations of low molecular weight Halomonas levan (HLh) were combined and examined to develop physical networks serving as tissue scaffolds to promote cell adhesion for biocompatibility. Three-dimensional bioprinting technique (3D bioprinting) was employed during manufacturing the test samples and their comprehensive characterization was performed to investigate the physicochemical properties and biocompatibility. Physical properties of the printing materials such as viscosity, surface tension, and density were measured to determine optimal parameters for 3D bioprinting. The scanning electron microscope (SEM) was used to observe the morphological structure of scaffolds. Fourier-Transform Infrared Spectroscopy (FT-IR) and differential scanning calorimetry (DSC) were used to identify the interactions between the components. In-vitro cell culture assays using standard human osteoblast (Hob) cells showed increased biocompatibility of the printing materials with increasing HLh content. Thus, the formulations including the HLh are expected to be a good candidate for the production of 3D printed materials.Article Citation - WoS: 12Citation - Scopus: 143D EM Data Driven Surrogate Based Design Optimization of Traveling Wave Antennas for Beam Scanning in X-Band: An Application Example(WINEF, 2022) Belen, Aysu; Gunes, Filiz; Palandoken, Merih; Tarı, Özlem; Belen, Mehmet A.; Mahouti, PeymanIn this paper, design and optimization of a microstrip elliptic traveling wave antenna (TWA) are presented for the beam scanning in X-band as an application of 3D data driven surrogate based design optimization technique. A novel Modified Multi-Layer Perceptron (M2LP) algorithm is utilized as a fast and accurate black-box modeling and compared to the alternative Multi-Layer Perceptron (MLP), Support Vector Regression Machine (SVRM), Gradient Boosted Tree algorithms for the generation of surrogate model of the TWA design. In order to have a computationally efficient modeling, Latin-Hyper Cube Sampling LHS method is utilized to obtain the training and test data from 3D CST Microwave numerical computation tool. A novel meta-heuristic, population based optimization algorithm, Invasive Weed Optimization (IWO) is applied to build up M2LP model for the determination of the optimal geometric design parameters. The optimum TWA model has total physical size of 100 mm × 20 mm with the operation frequency band between 8.5 and 12 GHz and measured overall gain of 7.1–11.8 dBi. The steerable radiation pattern characteristic is measured to be between −70 and 25 degrees. Thus, the proposed TWA design points out superior radiation performance for X band radar applications. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Article Citation - WoS: 16Citation - Scopus: 213D Printed Styrax Liquidus (Liquidambar orientalis Miller)-Loaded Poly (L-Lactic Acid)/Chitosan Based Wound Dressing Material: Fabrication, Characterization, and Biocompatibility Results(Elsevier B.V., 2023) Cakmak, Hanife Yuksel; Ege, Hasan; Yilmaz, Senanur; Agturk, Gokhan; Yontem, Fulya Dal; Enguven, Gozde; Sarmis, Abdurrahman; Cakmak, Zeren; Gunduz, Oguzhan; Ege, Zeynep RuyaThe medicinal plant of Styrax liquidus (ST) (sweet gum balsam) which extracted from Liquidambar orientalis Mill tree, was loaded into the 3D printed polylactic acid (PLA)/chitosan (CS) based 3D printed scaffolds to investigate its wound healing and closure effect, in this study. The morphological and chemical properties of the ST loaded 3D printed scaffolds with different concentrations (1 %, 2 %, and 3 % wt) were investigated by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FT-IR), respectively. In addition, the mechanical and thermal properties of the materials were investigated by Tensile test and Differential Scanning Calorimetry (DSC), respectively. The antimicrobial activities of the ST loaded 3D printed scaffolds and their incubation media in the PBS (pH 7.4, at 37 °C for 24 h) were investigated on two Gram-positive and two Gram-negative standard pathogenic bacteria with the agar disc diffusion method. The colorimetric MTT assay was used to determine the cell viability of human fibroblast cells (CCD-1072Sk) incubated with free ST, ST loaded, and unloaded 3D printed scaffolds. The 1 % and 2 % (wt) ST loaded PLA/CS/ST 3D printed scaffolds showed an increase in the cell number. Annexin V/PI double stain assay was performed to test whether early or late apoptosis was induced in the PLA/CS/1 % ST and PLA/CS/2 % ST loaded groups and the results were consistent with the MTT assay. Furthermore, a wound healing assay was carried out to investigate the effect of ST loaded 3D printed scaffolds on wound healing in CCD-1072Sk cells. The highest wound closure compared to the control group was observed on cells treated with PLA/CS/1 % ST for 72 h. According to the results, novel biocompatible ST loaded 3D printed scaffolds with antimicrobial effect can be used as wound healing material for potential tissue engineering applications. © 2023 Elsevier B.V.Article Citation - WoS: 23Citation - Scopus: 313D Printing Artificial Blood Vessel Constructs Using PCL/Chitosan/Hydrogel Biocomposites(Wiley-VCH Verlag GmbH, 2019) Ulağ, Songül; Kalkandelen, Cevriye; Oktar, Faik Nüzhet; Uzun, Muhammet; Şahin, Yeşim Müge; Karademir, Betül; Arslan, Sema; Özbolat, İbrahim Tarık; Mahiroğulları, Mahir; Gündüz, Oğuzhan; Ulag, Songul; Kalkandelen, Cevriye; Oktar, Faik Nuzhet; Uzun, Muhammet; Sahin, Yesim Muge; Karademir, Betul; Gunduz, OguzhanThe present paper aims to overcome the problems related to previous use of autologous grafts using available synthetic grafts. To examine the optimum of the ideal vessel-like constructs parameters are produced at 230 degrees C. At this production temperature, the elastic modulus values of the constructs ranges from 56 MPa to 174 MPa. The maximum cell proliferation is obtained from PCL/7wt.%CS/5wt.%H that is tested by mitochondrial dehydrogenase activity. The structures are visualized with all constructs after cell fixation by making use of the HUVEC cell line.Article Citation - WoS: 13Citation - Scopus: 12A CAD of Fully Automated Colonic Polyp Detection for Contrasted and Non-Contrasted CT Scans(Springer Heidelberg, 2017) Tulum, Gökalp; Bolat, Bülent; Osman, Onur; Tulum, Gokalp; Bolat, Bulent; Osman, OnurComputer-aided detection (CAD) systems are developed to help radiologists detect colonic polyps over CT scans. It is possible to reduce the detection time and increase the detection accuracy rates by using CAD systems. In this paper, we aimed to develop a fully integrated CAD system for automated detection of polyps that yields a high polyp detection rate with a reasonable number of false positives. The proposed CAD system is a multistage implementation whose main components are: automatic colon segmentation, candidate detection, feature extraction and classification. The first element of the algorithm includes a discrete segmentation for both air and fluid regions. Colon-air regions were determined based on adaptive thresholding, and the volume/length measure was used to detect air regions. To extract the colon-fluid regions, a rule-based connectivity test was used to detect the regions belong to the colon. Potential polyp candidates were detected based on the 3D Laplacian of Gaussian filter. The geometrical features were used to reduce false-positive detections. A 2D projection image was generated to extract discriminative features as the inputs of an artificial neural network classifier. Our CAD system performs at 100% sensitivity for polyps larger than 9 mm, 95.83% sensitivity for polyps 6-10 mm and 85.71% sensitivity for polyps smaller than 6 mm with 5.3 false positives per dataset. Also, clinically relevant polyps (6 mm) were identified with 96.67% sensitivity at 1.12 FP/dataset. To the best of our knowledge, the novel polyp candidate detection system which determines polyp candidates with LoG filters is one of the main contributions. We also propose a new 2D projection image calculation scheme to determine the distinctive features. We believe that our CAD system is highly effective for assisting radiologist interpreting CT.Article Citation - WoS: 8Citation - Scopus: 13A Class of Second Order Nondifferentiable Symmetric Duality Relations Under Generalized Assumptions(Journal Mathematics & Computer Science-JMCS, 2020) Dubey, Ramu; Vandana; Mishra, Vishnu Narayan; Karateke, Seda; Dubey, Ramu; Vandana; Mishra, Vishnu Narayan; Karateke, SedaIn this article, a pair of second-order nondifferentiable symmetric dual model in optimization problem is formulated over arbitrary cones. For a differentiable function, we consider the definition of strongly K-pseudobonvexity convexity. Next, we derive the appropriate duality results under aforesaid assumptions.Article A Comparative Analysis of the First Cycle Degree Programmes in Business in Terms of the Number of Course Units and the Student Workloads(Univ Deusto, 2022) Sarıgül, Hasmet; Şengelen, Hakan Eren; Sarigul, Hasmet; Sengelen, Hakan ErenThis comparative study aims to determine the differences between the curricula of the first cycle degree programmes in business in Turkey in terms of the number of course units and the student workloads. In this context, (1) the courses included in the Bologna course information packages of business schools on their web sites have been examined; (2) course units have been gathered together in content-related groups, (3) the numbers of course units in each content- related group have been determined, (4) total student workload of each content- related group has been determined by means of the institutionally allocated ECTS credits, (5) the differences between public and foundation business schools have been tested for each content-related group in terms of total number of course units and total student workload, and (6) the differences between the business schools using Turkish and those using a foreign language as the medium of instruction have been tested for each content-related group in terms of total number of courses and total student workload. The methods used in the research are document review and multivariate analysis. The data of 147 business schools has been used in the study and the outputs of the research reveal that there are significant differences in most of the content-related groups between both the business school groupings described above at points (5) and (6) in terms of the number of course units and student workload.Article Citation - WoS: 43Citation - Scopus: 50A Comparative Study on the Electrical and Dielectric Properties of Al/Cd-Doped ZnO/p-Si Structures(Springer, 2019) Büyükbaş-Ulusan, A.; Taşcıoğlu, İlke; Tataroğlu, A.; Yakuphanoğlu, F.; Altındal, S.; Buyukbas-Ulusan, A.; Tascioglu, I.; Tataroglu, A.; Yakuphanoglu, F.; Altindal, S.We have reported on the electrical and dielectric properties of Al/CdxZn1-xO/p-Si structures. The cadmium-doped zinc oxide (CdxZn1-xO) thin films with various Cd dopants (x=0.10, 0.20 and 0.30) were deposited on p-Si wafers via sol-gel spin coating method. The admittance (Y=G(m)+i omega C-m) measurements were performed at 1MHz. The C-2-V plots were used to extract the main electrical parameters such as the diffusion potential (V-D), the concentration of acceptor atoms (N-A), depletion region width (W-D) and barrier height (Phi(B)). The experimental results reveal that the capacitance increases with higher Cd dopant concentration due to the presence of interfacial charges while an opposite behaviour is observed in conductance. The lower values of conductance in the sample with high Cd content can be attributed to increase in series resistance. The dielectric measurements also confirm the effect of Cd substitution in ZnO on the device performance.Article A Comparison of Automated Segmentation and Manual Tracing of Magnetic Resonance Imaging To Quantify Lateral Ventricle Volumes(Kare Yayıncılık, 2022) ACER, Niyazi; KAMAŞAK, Burcu; KARAPINAR, Burak Oğuzhan; AKKUŞ YETKİN, Esra; İPEKTEN, FundaObjective: Ventricular volume measurements have been proposed as a useful biomarker for several neurological diseases. The goal of this study was to compare the performance of 3 fully-automated tools, volBrain (http://volbrain.upv.es), ALVIN (Automatic Lateral Ventricle Delineation) (https://sites.google.com/site/mrilateralventricle/), and MRICloud (http://mricloud.org), with expert hand tracing to quantify lateral ventricle (LV) volume using magnetic resonance images. Materials and Methods: The sample comprised 24 healthy subjects (age: 25.1±5.7 years, all male). Volumes derived from each automated measurement were compared to hand tracing results performed by 2 specialists to assess the percent volume difference using the intraclass correlation coefficient (ICC), concordance correlation coefficient (CCC), Dice index value, and Bland-Altman analysis. Results: The ICC agreement of the Manual_1 and Manual_2 was very good (0.979), and there was no statistically significant difference (p>0.001). The volume difference of all methods was similar. The CCC with MRICloud and ALVIN was higher than that of volBrain. Bland-Altman plots indicated that the 3 automated methods demonstrated acceptable agreement. Conclusion: Compared with hand tracing, the LV volumes generated by MRICloud were more accurate than those of volBrain and ALVIN. LV volume values can provide valuable data related to the volumetric dependencies of the anatomical structures in various clinical conditions that can now be easily obtained using automated tools.Conference Object A Comparison Study on Personality Traits Based on the Attitudes of University Students toward Entrepreneurship(Elsevier, 2016) Çolakoğlu, Nurdan; Gözükara Yıldız, İzlemParticular personality traits motivate individuals to act entrepreneurially and to exercise entrepreneurial activities, which include but not limited to high need for achievement, innovativeness, propensity to risk-taking, tolerance to ambiguity and internal locus of control (Thomas & Mueller, 2000; Utsch & Rauch, 2000). Therefore, the present study aimed to compare personality traits based on the attitudes of university students toward entrepreneurship. This study was conducted in a foundation university in Turkey. The study data was collected using questionnaires. According to the study results, students with entrepreneurial intention are more innovative, have higher need for achievement and greater internal locus of control than those who do not have such intention.Other A Correlation Between the Genotype and Clinical Course in Hemophilia B Patients(Wiley, 2018) Koç, B.; Çolakoğlu, S.; Berber, Ergül; Zülfikar, B.…Article A Critical Discussion on Turkish Students' Thoughts About Syrians Over Nation-State Teachings(Istanbul Univ, 2020) Civelek, Hatice YaprakThis study is mainly based on chats with secondary and high school students. The implicit points in their daily complaints about their Syrian peers in neighborhoods were turned into a problematic for a qualitative survey. The students living in the regions in which generally Syrian immigrants are located account for the research group. The results were based on the analysis of the students' letters they wrote to their Syrian peers in the spring of 2018: 150 letters saluting the young Syrians with "Dear my Syrian Friend" are exposed to a discourse analysis. The theoretical structure drawing classical and contemporary Marxist approaches together argues that the relationship between nation-state ideology and education creates a kind of political socialization in response to the ideal value of "fully-democratic education". The salutations and nationalist statements that the students wrote reveal that not any mechanism of acceptance works. The students accuse the Syrians, particularly young men, of being unfaithful to their own country foremost, and of weakening the economy of the country where they took refuge by being a cheap labor force, behaving inappropriately towards the traditional and moral values, becoming a threat to Turkish language, having high fertility, taking over common spaces and behaving loosely.Article Citation - WoS: 14Citation - Scopus: 14A Cross-Cultural Investigation Into the Relationships Among Parental Support for Basic Psychological Needs, Sense of Uniqueness and Happiness(Routledge Journals, Taylor & Francis Ltd, 2014) Şimşek, Ömer Faruk; Demir, Melikşah; Simsek, Omer Faruk; Demir, MeliksahA significant number of empirical studies have reported that parental support for basic psychological needs is a robust correlate of adolescent happiness. Yet, less is known about the mechanisms responsible for this link. The present study proposed a model suggesting that personal sense of uniqueness explains why satisfaction of basic psychological needs in parent-child relationships is related to happiness. This mediational model was tested among late adolescents in Turkey and the United States. Analyses relying on structural equation modeling and bootstrapping supported the model in both cultures. Implications of the findings for theory and cross-cultural research are discussed. Directions for future research that could improve our understanding of the dynamic interplay between basic needs, sense of uniqueness and well-being are provided.Article A Documentation and Conservation Method for Water Mills(Yildiz Technical Univ, Fac Architecture, 2017) Örs Çorapçıoğlu, Gülferah; Ulusoy Binan, Demet; Ors Corapcioglu, Gulferah; Ulusoy Binan, DemetWatermills are examples of industrial heritage carrying traces of improvement in hydraulic power technology and reveal societies' cultural structure and lifestyle since the ancient times. They are "historical documents" in terms of structure type, assembly, and production techniques. A research conducted on the water mills of Anatolia known to be used for grinding in three different water basins revealed that watermills surviving to the present day are not considered cultural heritage and are unregistered; hence, a study for the conservation of these structures was decided to be started. To effectively conserve them, creating inventories for the identified watermills was undertaken. Accordingly, a "watermill inventory" model was developed by creating two different forms about settlement and structure details, using the TUBA-TUKSEK Turkish Cultural Inventory Project principles as guidelines. These forms were used for documenting 25 watermills identified in "Eastern Black Sea Basin" and "aglayan, Sulak, Arili" subbasins. The watermills were examined according to criteria based on their originality and integrity of their structure and technology. The original structural sustainability of the watermills was determined to be under threat, and the determined deteriorations were numerically evaluated according to their form, location, and significance. Based on results of the evaluation, a conservation approach was designed and used to identify watermills having priority for conservation according to the structures ranked according to their deterioration status.Article Citation - WoS: 2Citation - Scopus: 2A Dynamic Inverse Distance Weighting-Based Local Face Descriptor(Springer, 2020) Çevik, Nazife; Cevik, NazifeThis paper proposes a novel high-performance dynamic inverse distance weighting based local descriptor (DIDWLD) for facial recognition. Studies proposed thus far have focused on finding local descriptors that can represent the texture of the face best. However, the robustness of the descriptors against rotational variances and noise affects have been largely omitted. Thus, this study does not only concern with proposing a high-discriminative descriptor, but also a robust one against rotational changes and noise affects. DIDWLD mainly basis on Inverse Distance Weighting (IDW). That is, for each pixel in the image, a new descriptive value is calculated, taking into account the intensity values of the neighboring pixels and their distance to the reference pixels. A dynamic distance-decay parameter is applied throughout the image rather than keeping it uniform as done in ordinary IDW. The calculated descriptor is independent of the changes in the rotation. Because, when calculating the descriptor, the intensity values of the surrounding pixels with their distances to the reference pixel are taken into consideration, yet their directional relation to the reference pixel is ignored. Furthermore, when a pixel is suffered to noise, inherently, its neighboring pixels are also affected. Hence, by taking into account the effect of the surrounding pixels and also the original intensity value of the pixel, the degrading impact of noise on recognition performance is mitigated. The results of extensive simulations show the remarkable and competitive performance of the proposed method regarding recognition accuracy, and robustness against rotational variances and, noise effects.Article Citation - WoS: 3Citation - Scopus: 4A Finite Element Model of the Deltoid Muscle and Biomechanical Analysis of the Standing Dumbbell Fly for Shoulder Exercises(Springer Heidelberg, 2022) Asadi Dereshgi, Hamid; Serbest, Kasim; Dereshgi, Hamid Asadi; Serbest, KasimThe shoulder joint participates in different resistance training due to its high mobility. In previous studies, deltoid muscle force was investigated by the electromyography method. However, the effects of increasing exercise weight on deltoid biomechanics have not been adequately studied. In this study, shoulder biomechanics in dumbbell fly movements performed with different dumbbell weights were investigated. Accordingly, the biomechanical model of the upper extremity was prepared and the motion analysis of the dumbbell fly exercise was performed. Then, the exercise was simulated with MATLAB Simscape tools. As a result of the simulation, shoulder joint moment and deltoid muscle force were calculated. Thus, the finite element model was performed to examine the mechanical behavior of the deltoid muscle during exercises. In dumbbell fly exercises performed with different weights, the maximum joint moment was 42.82 Nm, 54.32 Nm and 65.83 Nm, respectively. Additionally, the highest muscle force was calculated as 1378 N, 1750 N, and 2121 N, respectively. When the weight of the dumbbell increased by 33.33%, maximum joint moment increased by 26.85% and 21.18%, and maximum muscle force increased by 26.99% and 21.20%, respectively. However, although the dumbbell weight increased by 25%, the maximum stress in the deltoid muscle increased strikingly by 33.33%. Consequently, it was observed that increasing the weight of the dumbbell did not cause the same increase in shoulder joint moment and deltoid muscle force. Moreover, it was found that increasing the weight of the dumbbell increases the stress in the deltoid muscle to a higher extent.Conference Object A Joint Design of User Modeling and Resource Management in Cognitive Radio Networks(IEEE, 2019) Sadreddini, Zhaleh; Guler, ErkanThe limited available spectrum and inefficient spectrum utilization make it necessary to employ dynamic spectrum access techniques. The key enabling technology for dynamic spectrum access is cognitive radio (CR), which exploits the existing wireless spectrum opportunistically and utilizes the licensed spectrum when primary users are passive. Thus, the activities of primary radio (PR) and cognitive radio (CR) users play a major role in the performance of cognitive radio networks. In this paper, a joint solution for user modeling and spectrum management is offered. The activities of PR and CR users are modeled through three-state Markov chain as the spectrum resource blocks are utilized with help of service-level overbooking strategy. Simulation results show the performance of the booking limit with respect to the channel release ratio of CR users and consequently the improved revenue of the network.
