245 results
Search Results
Now showing 1 - 10 of 245
Conference Object Citation - Scopus: 2Design and Fabrication of Ka Band Circular Horn Antenna;(2012) Danaci,S.; Gürtekin,E.; Özyurt,E.; Kara,A.In this paper, design and fabrication of a circular horn antenna is presented. The antenna is designed for experimental use at Ka band. The design process includes feeding structure for coaxial line and geometrical parameters of the antenna. The bandwidth of the antenna is measured as 2.25GHz, (S 11 ≤-10dB) which satisfies the requirements of targeted experimental study. A reference monopole is also designed for the measurements of antenna parameters. Antenna radiation pattern is measured with the reference monopole antenna using a VNA (S12) instead of typical signal generator/spectrum analyzer pair. Accuracy of antenna parameters along with the errors made in fabrication process is also discussed in the paper. © 2012 IEEE.Conference Object Citation - WoS: 8Citation - Scopus: 7UTILIZATION OF REACTOR GRADE PLUTONIUM AS ENERGY MULTIPLIER IN THE LIFE ENGINE(Amer Nuclear Soc, 2012) Sahin, Sumer; Sahin, Haci Mehmet; Acir, AdemThe accumulated reactor grade (RG)-plutonium as nuclear waste of conventional reactors is estimated to exceed 1700 tonnes. Laser Inertial Confinement Fusion Fission Energy (LIFE) engine is considered to incinerate RG-plutonium in stockpiles. Calculations have been conducted for a constant fusion driver power of 500 MWth in S-8-P-3 approximation using 238-neutron groups. RG-plutonium out of the nuclear waste of LWRs is used in form of fissile carbide fuel in TRISO particles with volume fractions of 2, 3, 4, 5 and 6 %, homogenously dispersed in the Flibe coolant. Respective tritium breeding ratio (TBR) values per incident fits ion neutron are calculated as TBR = 1.35, 1.52, 1.73, 2.02 and 2.47 at start-up. With the burn up of fissionable RG-Pu isotopes in the coolant, TBR decreases gradually. Similarly, blanket energy multiplications are calculated as M-0 = 3.8, 5.5, 7.7, 10.8 and 15.4 at start-up, respectively. Calculations have indicated prospects of achievability of very high burn up values (> 400 000 MD.D/MT).Conference Object Renewability and Sustainability Aspects of Nuclear Energy(Amer inst Physics, 2014) Sahin, SumerRenewability and sustainability aspects of nuclear energy have been presented on the basis of two different technologies: (1) Conventional nuclear technology; CANDU reactors. (2) Emerging nuclear technology; fusion/fission (hybrid) reactors. Reactor grade (RG) plutonium, U-233 fuels and heavy water moderator have given a good combination with respect to neutron economy so that mixed fuel made of (ThO2/RG-PuO2) or (ThC/RG-PuC) has lead to very high burn up grades. Five different mixed fuel have been selected for CANDU reactors composed of 4 % RG-PuO2 + 96 % ThO2; 6 % RG-PuO2 + 94 % ThO2; 10 % RG-PuO2 + 90 % ThO2; 20 % RG-PuO2 + 80 % ThO2; 30 % RG-PuO2 + 70 % ThO2, uniformly taken in each fuel rod in a fuel channel. Corresponding operation lifetimes have been found as similar to 0.65, 1.1, 1.9, 3.5, and 4.8 years and with burn ups of similar to 30 000, 60 000, 100 000, 200 000 and 290 000 MW.d/ton, respectively. Increase of RG-PuO2 fraction in radial direction for the purpose of power flattening in the CANDU fuel bundle has driven the burn up grade to 580 000 MW. d/ton level. A laser fusion driver power of 500 MWth has been investigated to burn the minor actinides (MA) out of the nuclear waste of LWRs. MA have been homogenously dispersed as carbide fuel in form of TRISO particles with volume fractions of 0, 2, 3, 4 and 5 % in the Flibe coolant zone in the blanket surrounding the fusion chamber. Tritium breeding for a continuous operation of the fusion reactor is calculated as TBR = 1.134, 1.286, 1.387, 1.52 and 1.67, respectively. Fission reactions in the MA fuel under high energetic fusion neutrons have lead to the multiplication of the fusion energy by a factor of M = 3.3, 4.6, 6.15 and 8.1 with 2, 3, 4 and 5 % TRISO volume fraction at start up, respectively. Alternatively with thorium, the same fusion driver would produce similar to 160 kg U-233 per year in addition to fission energy production in situ, multiplying the fusion energy by a factor of similar to 1.3.Conference Object A Linear Time Algorithm for the Prediction of Compression During Multimedia Transmission(2009) Çevik,A.In this paper, alternative approaches and solutions are introduced to improve the quality of multimedia transmissions on various services. Regarding the improvement, several approaches are proposed incluing an automated network feedback approach based on a two-way language protocol. Secondly, and independent from automated feedback, measure-once and linear-time measure-many tracking algorithms are proposed in order to make an approximation about the quality/compression ratio of the transmission of a multimedia object.Conference Object Citation - WoS: 1Sustainable Software Engineering: a Move Towards Future(Ieee, 2017) Mishra, Alok[No Abstract Available]Conference Object Citation - Scopus: 20Design and Development of a Remote and Virtual Environment for Experimental Training in Electrical and Electronics Engineering(2010) Kara,A.; Aydin,E.; Ozbek,M.E.; Cagiltay,N.European Remote Radio Laboratory (ERRL) has been developed by the support of European Commission. It intends to provide remote access to high cost devices remotely, and perform experiments in radio frequency (RF), communications and microwave domains of Electrical ad Electronics Engineering. The system has been operational for two years, and been integrated into curriculum of some courses. In this work, the hardware and software structures of the system are presented. Then, experimental content and the motivations in the design of the system are discussed. ©2010 IEEE.Conference Object Citation - Scopus: 2Effect of Discontinuity Orientation and Spacing on the Blasting Performance in Some Open Cast Mines of Tki-Turkey(International Society for Rock Mechanics, 2003) Kaçar,G.; Özgenoglu,A.; Bilgin,H.A.In this study, the influences of rock mass properties on the blasting performance in open cast mines are investigated. To this end, discontinuity spacings and discontinuity orientations are measured and full scale blasts with various designs are observed in open cast mines of Aegean Lignite (ELI) and Bursa Lignite (BLI) Establishments belonging to Turkish Coal Enterprises (TKI). For each blast, blasting cost is calculated, and particle size distribution representing the fragmentation of muckpile is determined by means of Split-Desktop software using image processing. 50%(K50), 80%(K80) passing sizes and topsize values are used in the determination of blasting performance according to rock mass properties. The relationships between orientation angle, which is the acute angle between the strikes of slope face and major discontinuity, and 50%(K50) and 80%(K80) passing sizes and topsize values and also blasting cost are investigated in order to analyse the influences of major discontinuity orientation on fragmentation and blasting cost. Furthermore, the relationships between discontinuity modal spacing (or block size index) and 50%(K50) and 80%(K80) passing sizes and topsize values and also blasting cost are investigated in order to analyse the influences of discontinuity spacing on fragmentation and blasting cost. In this paper, the trends observed in these relationships are discussed and the importance of it in mining is commented. © 2003 10th ISRM Congress. All rights reserved.Conference Object Aldose Reductase Natural Inhibitors From Ethyl Acetate Extracts From Southern Turkey(Taylor & Francis inc, 2010) Onay, Melih; Coruh, Nursen; Isgor, Belgin[No Abstract Available]Conference Object Nested multipartite secret sharing(2011) Kaskaloglu,K.; Özbudak,F.Quite recently, Tassa introduced an ideal and perfect secret sharing scheme realizing conjunctive hierarchical threshold access structures motivated by the problem of sharing a private key among three employees of a bank, at least one of whom must be a department manager, for the purpose of signing an electronic funds transfer. We ask the natural question concerning What if there are two branches of banks that are needed to be involved in the signing process? In such a case, one might encounter the presence of two distinct hierarchies involved in the same access structure. In this paper, being motivated by such a sample scenario, we describe a new generalization, what we name nested multipartite access structures, which may involve the well-known compartmented or hierarchical access structures as substructures. The corresponding generic scheme we describe employs multivariate interpolation and is ideal, linear and perfect with probability 1 O(q1) on a finite field Fq. We describe the scheme in particular for the trivariate case as an example. Such an approach is hopefully useful not only for the initial motivating example, but also for a variety of interesting scenarios. In particular, we propose a non-nested generalization for the conventional compartmented access structures, which depicts a stronger way of controlling the additional t (t1 + + t m) participants. © 2011 IEEE.Conference Object Citation - WoS: 13Search-Based Parallel Refactoring Using Population-Based Direct Approaches(Springer-verlag Berlin, 2011) Kilic, Hurevren; Koc, Ekin; Cereci, IbrahimAutomated software refactoring is known to be one of the "hard" combinatorial optimization problems of the search-based software engineering field. The difficulty is mainly due to candidate solution representation, objective function description and necessity of functional behavior preservation of software. The problem is formulated as a combinatorial optimization problem whose objective function is characterized by an aggregate of object-oriented metrics or pareto-front solution description. In our recent empirical study, we have reported the results of a comparison among alternative search algorithms applied for the same problem: pure random, steepest descent, multiple first descent, simulated annealing, multiple steepest descent and artificial bee colony searches. The main goal of the study was to investigate potential of alternative multiple and population-based search techniques. The results showed that multiple steepest descent and artificial bee colony algorithms were most suitable two approaches for an efficient solution of the problem. An important observation was either with depth-oriented multiple steepest descent or breadth-oriented population-based artficial bee colony searches, better results could be obtained through higher number of executions supported by a lightweight solution representation. On the other hand different from multiple steepest descent search, population-based, scalable and being suitable for parallel execution characteristics of artificial bee colony search made the population-based choices to be the topic of this empirical study. I In this study, we report the search-based parallel refactoring results of an empirical comparative study among three population-based search techniques namely, artificial bee colony search, local beam search and stochastic beam search and a non-populated technique multiple steepest descent as the baseline. For our purpose, we used parallel features of our prototype automated refactoring tool A-CMA written in Java language. A-CMA accepts bytecode compiled Java codes as its input. It supports 20 different refactoring actions that realize searches on design landscape defined by an adhoc quality model being an aggregation of 24 object-oriented software metrics. We experimented 6 input programs written in Java where 5 of them being open source codes and one student project code. The empirical results showed that for almost all of the considered input programs with different run parameter settings, local beam search is the most suitable population-based search technique for the efficient solution of the search-based parallel refactoring problem in terms of mean and maximum normalized quality gain. However, we observed that the computational time requirement for local beam search becomes rather high when the beam size exceeds 60. On the other hand, even though it is not able to identify high quality designs for less populated search setups, time-efficiency and scalability properties of artificial bee colony search makes it a good choice for population sizes >= 200.
