Browsing by Subject "Design"

Now showing 1 - 20 of 66

Open Access
Acoustical design and noise control in metro stations: Case studies of the Ankara metro system
(2007) Sü, Z.; Çalíşkan, M.
The aim of this research is to demonstrate the importance of initial strategies in acoustical design of underground metro stations. The paper searches for practical design solutions by evaluating different materials for providing optimum acoustical conditions in such spaces. Acoustical designs of three metro stations on a new expansion line in Ankara including Sogutozu, Bilkent and ODTU metro stations are presented through computer simulation. Predictions of room acoustical parameters are presented for both platform and ticket office floors in terms of parameters like reverberation time (RT), speech transmission index (STI) and A-weighted sound level (SPL) distribution within spaces. Simulated reverberation times are evaluated in view of legislative requirements. The study confirms the importance of using sound absorbing materials on the ceiling and sidewalls together. The nonwoven material, used behind perforated metal suspended ceilings, has proved effective in reverberation control.
Open Access
Adaptive control design for nonlinear systems via successive approximations
(ASME, 2017) Babaei, N.; Salamcı, M. U.; Karakurt, Ahmet Hakan
The paper presents an approach to the Model Reference Adaptive Control (MRAC) design for nonlinear dynamical systems. A nonlinear reference system is considered such that its response is designed to be stable via Successive Approximation Approach (SAA). Having designed the stable reference model through the SAA, MRAC is then formulated for nonlinear plant dynamics with a new adaptation rule to guarantee the convergence of the nonlinear plant response to that of the response of the nonlinear reference model. The proposed design methodology is illustrated with examples for different case studies.
Open Access
Adaptive measurement matrix design for compressed DoA estimation with sensor arrays
(IEEE, 2015) Özer, Berk; Lavrenko, A.; Gezici, Sinan; Römer, F.; Galdo, G. D.; Arıkan, Orhan
In this work we consider the problem of measurement matrix design for compressed 3-D Direction of Arrival (DoA) estimation using a sensor array with analog combiner. Since generic measurement matrix designs often do not yield optimal estimation performance, we propose a novel design technique based on the minimization of the Cramér-Rao Lower Bound (CRLB). We develop specific approaches for adaptive measurement design for two applications: detection of the newly appearing targets and tracking of the previously detected targets. Numerical results suggest that the developed designs allow to provide the near optimal performance in terms of the CRLB.
Open Access
The architectural colour design process: an evaluation of sequential media via semantic ratings
(John Wiley & Sons, 2010-01) Ural, S. E.; Yilmazer, S.
In recent studies, contextual situations of applied colours are compared to colours presented as samples or chips. Findings of such studies point out different results in terms of similarities or differences between the evaluations of isolated abstract colours and contextualized situations. Architectural and spatial contexts have their own characteristics regarding colouring criteria, so it is of great importance to examine the architectural spatial colouring process from this point of view. This study explores this process by investigating the consistency of semantic ratings of four sequential stages of the architectural colour design process, namely, colour chips samples, abstract compositions, perspective drawings and 3D models. The architectural context for the study was a simple interior space. Fifteen different colour schemes were applied on the four media representing the stages. Subjects rated the 15 sets against seven bipolar, five-step semantic differential scales. The scales consisted of harmonious-discord, pleasant-unpleasant, comfortableuncomfortable, spacious-confined, static-dynamic, exciting-calming and extroverted-introverted. Findings indicated that there are significant associations between the evaluations of the abstract compositions, the perspective drawings and the 3D models; however, the evaluations of colour chips are significantly different than the others. The medium effect observed mostly between abstract and contextualized media. Additionally, factor analysis showed that pleasantness, harmony, spaciousness and comfort are connected in the evaluations of contextual situations, while pleasantness and harmony differ from spaciousness and comfort in the evaluations of colour chips and abstract compositions. The factor of activity (arousal) (dynamism, excitement, and extroversion) stays the same for all four media. It is also found that different colour characteristics are determinative over different media. © 2010 Wiley Periodicals, Inc.
Open Access
Broadband quarter-wave plates at near-infrared using high-contrast gratings
(2013) Mutlu, M.; Akosman, A.E.; Kurt G.; Gokkavas, M.; Özbay, Ekmel
In this paper, we report the theoretical and experimental possibility of achieving a quarter-wave plate regime by using high-contrast gratings, which are binary, vertical, periodic, near-wavelength, and two-dimensional high refractive index gratings. Here, we investigate the characteristics of two distinct designs, the first one being composed of silicon-dioxide and silicon, and the second one being composed of silicon and sapphire. The suggested quarter-wave plate regime is achieved by the simultaneous optimization of the transverse electric and transverse magnetic transmission coefficients, TTE and TTM, respectively, and the phase difference between these transmission coefficients, such that |TTM| ≅ |TTE| and \TTM - \TTE ≅ -/2. As a result, a unity circular polarization conversion efficiency is achieved atλ0 = 1.55 μm for both designs. For the first design, we show the obtaining of unity conversion efficiency by using a theoretical approach, which is inspired by the periodic waveguide interpretation, and rigorous coupled-wave analysis (RCWA). For the second design, we demonstrate the unity conversion efficiency by using the results of finite-difference time-domain (FDTD) simulations. Furthermore, the FDTD simulations, where material dispersion is taken into account, suggest that an operation percent bandwidth of 51% can be achieved for the first design, where the experimental results for the second design yield a bandwidth of 33%. In this context, we define the operation regime as the wavelength band for which the circular conversion efficiency is larger than 0.9. © 2013 SPIE.
Open Access
Cache-based query processing for search engines
(Association for Computing Machinery, 2012-11-01) Cambazoglu, B. B.; Altıngovde, I. S.; Ozcan, R.; Ulusoy, Özgür
In practice, a search engine may fail to serve a query due to various reasons such as hardware/network failures, excessive query load, lack of matching documents, or service contract limitations (e.g., the query rate limits for third-party users of a search service). In this kind of scenarios, where the backend search system is unable to generate answers to queries, approximate answers can be generated by exploiting the previously computed query results available in the result cache of the search engine.In this work, we propose two alternative strategies to implement this cache-based query processing idea. The first strategy aggregates the results of similar queries that are previously cached in order to create synthetic results for new queries. The second strategy forms an inverted index over the textual information (i.e., query terms and result snippets) present in the result cache and uses this index to answer new queries. Both approaches achieve reasonable result qualities compared to processing queries with an inverted index built on the collection. © 2012 ACM.
Open Access
Collaborative digital environments to enhance the creativity of designers
(Elsevier, 2015-01) Karakaya, A. F.; Demirkan H.
This study explores the interaction of the essential components of creativity and collaboration in a digital environment in the design process. The framework is based on Amabile’s componential theory of creativity, which is composed of three intra-individual components of creativity and the social environment. The digital environment as the social component of creativity provides the technical infrastructure for the analysis of data related to creativity and collaboration. Protocol coding method is used for the analysis of the qualitative and quantitative data stored in The Modular Object Oriented Developmental Learning Environment (MOODLE) forum posts that were formed by the comments or critiques given during the collaboration process by the team members, instructors or jury members. Findings indicate that the social environment component named as the reactivity to proposals is closely related to idea generation as the creative relevant process component and group interaction as the task motivation component. Furthermore, it is found that the number of sketches and design ideas produced through critiques are the main design issues that enhance creativity in collaborative digital environments.
Open Access
Colour and design: from natural patterns to monochrome compositions
(Elsevier, 2011-03) Olguntürk, N.; Demirkan, H.
There is no doubt that nature provides endless inspiration to the world of design. In order to explore the role of colour in design, forty-two people were asked to first choose a pattern from nature, then to abstract this pattern into geometric shapes and finally to colour this pattern. All work done by the participants were statistically analysed to find out the effect of colour on design. Findings of the study suggest that colour in a pattern is the first principal component of design as a unifier whereas this is replaced with the number of shapes in one group in black and white patterns.
Open Access
Combined component swapping modularity for a VCT engine controller
(ASME, 2010) Çakmakcı, Melih; Ulsoy, A.G.
The use of bi-directional communication provides additional design freedom which can be used to maximize the swapping modularity of networked smart components. In this paper, application of a design method for combined swapping modularity of two or more system components is discussed. Development of measures for combined swapping modularity is important to be able to analyze more realistic engineering cases. The combined modularity problem is a more difficult problem compared to the individual component swapping modularity problem. First, two approaches (simultaneous and sequential) for combining component swapping modularity of two or more components are presented. Then these combined modularity approaches are used to design controllers which maximize the component-swapping modularity of the Variable Camshaft Timing (VCT) component (i.e. actuator and sensor) and the Exhaust Gas Oxygen (EGO) sensor for an internal combustion engine. Copyright © 2009 by ASME.
Open Access
Compiler directed network-on-chip reliability enhancement for chip multiprocessors
(Association for Computing Machinery, 2010-04) Ozturk, O.; Kandemir, M.; Irwin, M. J.; Narayanan, S.H. K.
Chip multiprocessors (CMPs) are expected to be the building blocks for future computer systems. While architecting these emerging CMPs is a challenging problem on its own, programming them is even more challenging. As the number of cores accommodated in chip multiprocessors increases, network-on-chip (NoC) type communication fabrics are expected to replace traditional point-to-point buses. Most of the prior software related work so far targeting CMPs focus on performance and power aspects. However, as technology scales, components of a CMP are being increasingly exposed to both transient and permanent hardware failures. This paper presents and evaluates a compiler-directed power-performance aware reliability enhancement scheme for network-on-chip (NoC) based chip multiprocessors (CMPs). The proposed scheme improves on-chip communication reliability by duplicating messages traveling across CMP nodes such that, for each original message, its duplicate uses a different set of communication links as much as possible (to satisfy performance constraint). In addition, our approach tries to reuse communication links across the different phases of the program to maximize link shutdown opportunities for the NoC (to satisfy power constraint). Our results show that the proposed approach is very effective in improving on-chip network reliability, without causing excessive power or performance degradation. In our experiments, we also evaluate the performance oriented and energy oriented versions of our compiler-directed reliability enhancement scheme, and compare it to two pure hardware based fault tolerant routing schemes. © 2010 ACM.
Open Access
Concurrent design of energy management and vehicle traction supervisory control algorithms for parallel hybrid electric vehicles
(Institute of Electrical and Electronics Engineers Inc., 2016) Dokuyucu, H. I.; Cakmakci, M.
In this paper, concurrent design of energy management (EM) and traction control algorithms for a vehicle equipped with a parallel hybrid powertrain is studied. This paper focuses on designing the two control algorithms together as one control design problem, which are traditionally considered separately. First, optimal control actions and operating points are obtained by applying dynamic programming (DP). Then, this information is used for developing a rule-based supervisory controller. Our objective is to minimize the fuel consumption and the wheel slip simultaneously. Two control problems are also solved separately and compared with the concurrent solution. Results show that promising benefits can be obtained by using the concurrent design approach rather than considering two control problems separately. Under the same conditions, the vehicle with the concurrent supervisory controller is 16% more efficient in fuel consumption and experiences 12% less wheel slip, assuming slippery road friction conditions. © 1967-2012 IEEE.
Open Access
Decentralized stabilization of interconnected systems: Structural conditions
(1992) Yu, R.; Sezer, M. E.
A unified framework is provided for the design of high-gain decentralized controllers for the stabilization of several classes of interconnected systems. These classes are characterized in terms of the structure of the interconnections among the subsystems, and include all those known in the literature to be decentrally stabilizable. The simple decentralized stabilizability tests, on which the results are based, can also be used to check the stabilizability of individual interconnected systems that do not belong to any one of the classes considered.
Open Access
Deriving feasible deployment alternatives for parallel and distributed simulation systems
(Association for Computing Machinery, 2013-07) Çelik, T.; Tekinerdogan, B.; Imre, K.
Parallel and distributed simulations (PADS) realize the distributed execution of a simulation system over multiple physical resources. To realize the execution of PADS, different simulation infrastructures such as HLA, DIS and TENA have been defined. Recently, the Distributed Simulation Engineering and Execution Process (DSEEP) that supports the mapping of the simulations on the infrastructures has been defined. An important recommended task in DSEEP is the evaluation of the performance of the simulation systems at the design phase. In general, the performance of a simulation is largely influenced by the allocation of member applications to the resources. Usually, the deployment of the applications to the resources can be done in many different ways. DSEEP does not provide a concrete approach for evaluating the deployment alternatives. Moreover, current approaches that can be used for realizing various DSEEP activities do not yet provide adequate support for this purpose. We provide a concrete approach for deriving feasible deployment alternatives based on the simulation system and the available resources. In the approach, first the simulation components and the resources are designed. The design is used to define alternative execution configurations, and based on the design and the execution configuration; a feasible deployment alternative can be algorithmically derived. Tool support is developed for the simulation design, the execution configuration definition and the automatic generation of feasible deployment alternatives. The approach has been applied within a large-scale industrial case study for simulating Electronic Warfare systems. © 2013 ACM.
Open Access
Design and analysis of slotted sectoral waveguide array antennas embedded in cylindrically stratified media
(IEEE, 2014-07) Kalfa, Mert; Ertürk Vakur B.
Slotted waveguide antennas are being widely used in military and commercial applications for many decades. Low cross-polarization, high power capacity, ease of fabrication in microwave bands, and the ability to form arrays make them excellent candidates for phased array antennas in radar applications. However, due to slots being highly resonant (narrow-band, high Q) radiators, their design parameters are very sensitive; hence, accurate design and analysis methods are required for a successful antenna design. Moreover, slotted waveguide array antennas are low-profile structures, which makes them suitable candidates for conformal and structure-integrated applications. Conformal and structure-integrated system solutions are especially required for air platforms, where aerodynamics, radar cross-section (RCS) and efficient use of real estate are of utmost importance. Although the accurate and efficient design and analysis of low-profile conformal slotted waveguide arrays are of great interest, available solution methods in the literature usually suffer in terms of efficiency and memory requirements. Among the available solution methods, one of the widely used solvers are integral equation (IE) based ones that utilize the method of moments (MoM). However, IE solvers suffer from long matrix fill times, especially for matrix entries related to the cylindrically stratified media. © 2014 IEEE.
Open Access
Design and determination of stator geometry for axial flux permanent magnet free rod rotor synchronous motor
(2011) Kalender O.; Ege, Y.; Nazlibilek, S.
During designing a new axial flux permanent magnet free rod rotor synchronous motor, it is important to know before hand in which phase the largest angular velocity can occur, what is the ways to reduce the power consumption, how to achieve to increase or decrease the rotation speed by changing the core geometry. Therefore, presenting these preliminary information that are necessary for the design of a free rod rotor synchronous motor to the researchers is the aim of this work. In this respect, this study presents the design and geometrical dimensions of the stator for a new synchronous motor which is an axial flux permanent magnet free rod machine with three, four, five and six phases. This type of motors are an innovative approach especially for the applications used in industrial stirrers. Each type of stator is designed such that it has an appropriate number of phases. The rotating magnetic field over the stator is established by a PIC based microcontroller feeding the interface circuit to the stator wounds. The maximum angular speeds of bar magnet rotors with four different lengths and masses are calculated theoretically and determined experimentally. In addition, the effects of the distance between the rotor and stator, the angular speed of the rotor within the limits of the operation, and the volume of the liquid to be stirred to the power applied are investigated. Furthermore, the effects of the lengths and angular speeds of the bar magnet rotors to the distance between the rotor and stator are determined. In the light of the information obtained and taking into account the power used, the most appropriate parameters and variables such as the stator geometry changing with the phase used, the length of rotor, the distance between the rotor and stator and the angular speeds of rotor are determined. © 2011 Elsevier Ltd. All rights reserved.
Open Access
Design and fabrication of CSWAP gate based on nano-electromechanical systems
(Springer, Cham, 2016) Yüksel, Mert; Erbil, Selçuk Oğuz; Arı, Atakan B.; Hanay, M. Selim
In order to reduce undesired heat dissipation, reversible logic offers a promising solution where the erasure of information can be avoided to overcome the Landauer limit. Among the reversible logic gates, Fredkin (CSWAP) gate can be used to compute any Boolean function in a reversible manner. To realize reversible computation gates, Nano-electromechanical Systems (NEMS) offer a viable platform, since NEMS can be produced en masse using microfabrication technology and controlled electronically at high-speeds. In this work-in-progress paper, design and fabrication of a NEMS-based implementation of a CSWAP gate is presented. In the design, the binary information is stored by the buckling direction of nanomechanical beams and CSWAP operation is accomplished through a mechanism which can selectively allow/block the forces from input stages to the output stages. The gate design is realized by fabricating NEMS devices on a Silicon-on-Insulator substrate. © Springer International Publishing Switzerland 2016.
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Design of LDPC codes for two-way relay systems with physical-layer network coding
(IEEE, 2013) Tanc, A. K.; Duman, T. M.; Tepedelenlioglu, C.
This letter presents low-density parity-check (LDPC) code design for two-way relay (TWR) systems employing physical-layer network coding (PLNC). We focus on relay decoding, and propose an empirical density evolution method for estimating the decoding threshold of the LDPC code ensemble. We utilize the proposed method in conjunction with a random walk optimization procedure to obtain good LDPC code degree distributions. Numerical results demonstrate that the specifically designed LDPC codes can attain improvements of about 0.3 dB over off-the-shelf LDPC codes (designed for point-to-point additive white Gaussian noise channels), i.e., it is new code designs are essential to optimize the performance of TWR systems.
Open Access
Design, fabrication and characterization of high-performance solarblind AlGaN photodetectors
(SPIE, 2005) Özbay, Ekmel
Design, fabrication, and characterization of high-performance AlxGal-xN-based photodetectors for solar-blind applications are reported. AlxGal-xN heterostructures were designed for Schottky, p-i-n, and metal-semiconductor-metal (MSM) photodiodes. The resulting solar-blind AlGaN detectors exhibited low dark current, high detectivity, and high bandwidth.
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Economic design of EWMA control charts based on loss function
(Elsevier, 2009) Serel, D. A.
For monitoring the stability of a process, various control charts based on exponentially weighted moving average (EWMA) statistics have been proposed in the literature. We study the economic design of EWMA-based mean and dispersion charts when a linear, quadratic, or exponential loss function is used for computing the costs arising from poor quality. The chart parameters (sample size, sampling interval, control limits and smoothing constant) minimizing the overall cost of the control scheme are determined via computational methods. Using numerical examples, we compare the performances of the EWMA charts with Shewhart over(X, -) and S charts, and investigate the sensitivity of the chart parameters to changes in process parameters and loss functions. Numerical results imply that rather than sample size or control limits, the users need to adjust the sampling interval in response to changes in the cost of poor quality.
Open Access
The effect of competition on learning in games
(Pergamon Press, 2015) Cagiltay, N. E.; Ozcelik, E.; Ozcelik, N. S.
Today serious games are having an important impact on areas other than entertainment. Studies show that serious games have a potential of creating learning environments to better reach the educational and training goals. The game design characteristics and game elements are need to be explored in detail for increasing the expected benefits of the gaming environments. In this study, the effect of competition, one of the design elements of game environments, on learning is analyzed experimentally. The study is conducted with 142 students. The results of this study show that when a competition environment is created in a serious game, motivation and post-test scores of learners improve significantly. The results of this study are expected to guide the serious game designers for improving the potential benefits of serious games. © 2015 Elsevier Ltd.