Browsing by Subject "Experiments"
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Item Open Access Adaptive OFDM modulation for underwater acoustic communications: Design considerations and experimental results(Institute of Electrical and Electronics Engineers Inc., 2014) Radosevic, A.; Ahmed, R.; Duman, T. M.; Proakis, J. G.; Stojanovic, M.In this paper, we explore design aspects of adaptive modulation based on orthogonal frequency-division multiplexing (OFDM) for underwater acoustic (UWA) communications, and study its performance using real-time at-sea experiments. Our design criterion is to maximize the system throughput under a target average bit error rate (BER). We consider two different schemes based on the level of adaptivity: in the first scheme, only the modulation levels are adjusted while the power is allocated uniformly across the subcarriers, whereas in the second scheme, both the modulation levels and the power are adjusted adaptively. For both schemes we linearly predict the channel one travel time ahead so as to improve the performance in the presence of a long propagation delay. The system design assumes a feedback link from the receiver that is exploited in two forms: one that conveys the modulation alphabet and quantized power levels to be used for each subcarrier, and the other that conveys a quantized estimate of the sparse channel impulse response. The second approach is shown to be advantageous, as it requires significantly fewer feedback bits for the same system throughput. The effectiveness of the proposed adaptive schemes is demonstrated using computer simulations, real channel measurements recorded in shallow water off the western coast of Kauai, HI, USA, in June 2008, and real-time at-sea experiments conducted at the same location in July 2011. We note that this is the first paper that presents adaptive modulation results for UWA links with real-time at-sea experiments.Item Open Access Artificial neural network modeling and simulation of in-vitro nanoparticle-cell interactions(American Scientific Publishers, 2014) Cenk, N.; Budak, G.; Dayanik, S.; Sabuncuoglu, I.In this research a prediction model for the cellular uptake efficiency of nanoparticles (NPs), which is the rate that NPs adhere to a cell surface or enter a cell, is investigated via an artificial neural network (ANN) method. An appropriate mathematical model for the prediction of the cellular uptake rate of NPs will significantly reduce the number of time-consuming experiments to determine which of the thousands of possible variables have an impact on NP uptake rate. Moreover, this study constitutes a basis for targeted drug delivery and cell-level detection, treatment and diagnosis of existing pathologies through simulating NP-cell interactions. Accordingly, this study will accelerate nanomedicine research. Our research focuses on building a proper ANN model based on a multilayered feed-forward back-propagation algorithm that depends on NP type, size, surface charge, concentration and time for prediction of cellular uptake efficiency. The NP types for in-vitro NP-healthy cell interaction analysis are polymethyl methacrylate (PMMA), silica and polylactic acid (PLA), all of whose shapes are spheres. The proposed ANN model has been developed on MATLAB Programming Language by optimizing a number of hidden layers (HLs), node numbers and training functions. The datasets are obtained from in-vitro NP-cell interaction experiments conducted by Nanomedicine and Advanced Technology Research Center. The dispersion characteristics and cell interactions with different NPs in organisms are explored using an optimal ANN prediction model. Simulating the possible interactions of targeted NPs with cells via an ANN model will be faster and cheaper compared to the excessive experimentation currently necessary.Item Open Access Authorship attribution: performance of various features and classification methods(IEEE, 2007-11) Bozkurt, İlker Nadi; Bağlıoğlu, Özgür; Uyar, ErkanAuthorship attribution is the process of determining the writer of a document. In literature, there are lots of classification techniques conducted in this process. In this paper we explore information retrieval methods such as tf-idf structure with support vector machines, parametric and nonparametric methods with supervised and unsupervised (clustering) classification techniques in authorship attribution. We performed various experiments with articles gathered from Turkish newspaper Milliyet. We performed experiments on different features extracted from these texts with different classifiers, and combined these results to improve our success rates. We identified which classifiers give satisfactory results on which feature sets. According to experiments, the success rates dramatically changes with different combinations, however the best among them are support vector classifier with bag of words, and Gaussian with function words. ©2007 IEEE.Item Open Access Automatic rule learning exploiting morphological features for named entity recognition in Turkish(2011) Tatar, S.; Cicekli I.Named entity recognition (NER) is one of the basic tasks in automatic extraction of information from natural language texts. In this paper, we describe an automatic rule learning method that exploits different features of the input text to identify the named entities located in the natural language texts. Moreover, we explore the use of morphological features for extracting named entities from Turkish texts. We believe that the developed system can also be used for other agglutinative languages. The paper also provides a comprehensive overview of the field by reviewing the NER research literature. We conducted our experiments on the TurkIE dataset, a corpus of articles collected from different Turkish newspapers. Our method achieved an average F-score of 91.08% on the dataset. The results of the comparative experiments demonstrate that the developed technique is successfully applicable to the task of automatic NER and exploiting morphological features can significantly improve the NER from Turkish, an agglutinative language. © The Author(s) 2011.Item Open Access Compiler-directed energy reduction using dynamic voltage scaling and voltage islands for embedded systems(Institute of Electrical and Electronics Engineers, 2013) Ozturk, O.; Kandemir, M.; Chen G.Addressing power and energy consumption related issues early in the system design flow ensures good design and minimizes iterations for faster turnaround time. In particular, optimizations at software level, e.g., those supported by compilers, are very important for minimizing energy consumption of embedded applications. Recent research demonstrates that voltage islands provide the flexibility to reduce power by selectively shutting down the different regions of the chip and/or running the select parts of the chip at different voltage/frequency levels. As against most of the prior work on voltage islands that mainly focused on the architecture design and IP placement related issues, this paper studies the necessary software compiler support for voltage islands. Specifically, we focus on an embedded multiprocessor architecture that supports both voltage islands and control domains within these islands, and determine how an optimizing compiler can automatically map an embedded application onto this architecture. Such an automated support is critical since it is unrealistic to expect an application programmer to reach a good mapping correlating multiple factors such as performance and energy at the same time. Our experiments with the proposed compiler support show that our approach is very effective in reducing energy consumption. The experiments also show that the energy savings we achieve are consistent across a wide range of values of our major simulation parameters. © 1968-2012 IEEE.Item Open Access An experiment to observe the impact of UML diagrams on the effectiveness of software requirements inspections(IEEE, 2009) Albayrak, ÖzlemSoftware inspections aim to find defects early in the development process and studies have found them to be effective. However, there is almost no data available regarding the impact of UML diagram utilization in software requirements specification documents on inspection effectiveness. This paper addresses this issue by investigating whether inclusion of UML diagrams impacts the effectiveness of requirements inspection. We conducted an experiment in an academic environment with 35 subjects to empirically investigate the impact of UML diagram inclusion on requirements inspections' effectiveness and the number of reported defects. The results show that including UML diagrams in requirements specification document significantly impacts the number of reported defects, and there is no significant impact on the effectiveness of individual i nspections. © 2009 IEEE.Item Open Access Experimental characterization of capacitive micromachined ultrasonic transducers(IEEE, 2007) Ölçüm, Selim; Atalar, Abdullah; Köymen, Hayrettin; Oğuz, Kağan; Şenlik, Muhammed N.In this paper, capacitive micromachined ultrasonic transducers are fabricated using a sacrificial surface micromachining process. A testing procedure has been established in order to measure the absolute transmit and receive sensitivity spectra of the fabricated devices. The experiments are performed in oil. Pulse-echo experiments are performed and the results are compared to the pitch-catch measurements using calibrated transducers.Item Restricted Experimental science and the rational artist in early modern europe(1986) Crombie, Alistair C.Item Open Access Fe promoted NOx storage materials: structural properties and NOx uptake(American Chemical Society, 2010) Kayhan, E.; Andonova, S. M.; Şentürk, G. S.; Chusuei, C. C.; Ozensoy, E.Fe promoted NOx storage materials were synthesized in the form of FeOx/BaO/Al2O3 ternary oxides with varying BaO (8 and 20 wt %) and Fe (5 and 10 wt %) contents. Synthesized NOx storage materials were investigated via TEM, EELS, BET, FTIR, TPD, XRD, XPS, and Raman spectroscopy, and the results were compared with the conventional BaO/Al2O3 NOx storage system. Our results suggest that the introduction of Fe in the BaO/Al2O3 system leads to the formation of additional NOx storage sites which store NOx mostly in the form of bidentate nitrates. NO2 adsorption experiments at 323 K via FTIR indicate that, particularly in the early stages of the NOx uptake, the NOx storage mechanism is significantly altered in the presence of Fe sites where a set of new surface nitrosyl and nitrite groups were detected on the Fe sites and the surface oxidation of nitrites to nitrates is significantly hindered with respect to the BaO/Al2O3 system. Evidence for the existence of both Fe3+ as well as reduced Fe2+/(3-x)+ sites on the freshly pretreated materials was detected via EELS, FTIR, Raman, and XRD experiments. The influence of the Fe sites on the structural properties of the synthesized materials was also studied by performing ex situ annealing protocols within 323-1273 K followed by XRD and Raman experiments where the temperature dependent changes in the morphology and the composition of the surface domains were analyzed in detail. On the basis of the TPD data, it was found that the relative stability of the stored NOx species is influenced by the morphology of the Ba and Fe containing NOx-storage domains. The relative stabilities of the investigated NOx species were found to increase in the following order: N2O3/NO+ < nitrates on γ-Al2O3 < surface nitrates on BaO < bidentate nitrates on FeOx sites < bulk nitrates on BaO.Item Open Access Integrated segmentation and recognition of connected Ottoman script(S P I E - International Society for Optical Engineering, 2009-11) Yalniz, I. Z.; Altingovde, I. S.; Güdükbay, Uğur; Ulusoy, ÖzgürWe propose a novel context-sensitive segmentation and recognition method for connected letters in Ottoman script. This method first extracts a set of segments from a connected script and determines the candidate letters to which extracted segments are most similar. Next, a function is defined for scoring each different syntactically correct sequence of these candidate letters. To find the candidate letter sequence that maximizes the score function, a directed acyclic graph is constructed. The letters are finally recognized by computing the longest path in this graph. Experiments using a collection of printed Ottoman documents reveal that the proposed method provides >90% precision and recall figures in terms of character recognition. In a further set of experiments, we also demonstrate that the framework can be used as a building block for an information retrieval system for digital Ottoman archives. © 2009 Society of Photo-Optical Instrumentation Engineers.Item Open Access A measurable force driven by an excitonic condensate(American Institute of Physics Inc., 2014) Hakioǧlu, T.; Özgün, E.; Günay, M.Free energy signatures related to the measurement of an emergent force (≈10-9N) due to the exciton condensate (EC) in Double Quantum Wells are predicted and experiments are proposed to measure the effects. The EC-force is attractive and reminiscent of the Casimir force between two perfect metallic plates, but also distinctively different from it by its driving mechanism and dependence on the parameters of the condensate. The proposed experiments are based on a recent experimental work on a driven micromechanical oscillator. Conclusive observations of EC in recent experiments also provide a strong promise for the observation of the EC-force. © 2014 AIP Publishing LLC.Item Open Access Mitigating the gender gap in the willingness to compete: evidence from a randomized field experiment(Oxford University Press, 2019-08) Alan, Şule; Ertaç, SedaWe evaluate the impact on competitiveness of a randomized educational intervention that aims to foster grit, a skill that is highly predictive of achievement. The intervention is implemented in elementary schools, and we measure its impact using a dynamic competition task with interim performance feedback. We find that when children are exposed to a worldview that emphasizes the role of effort in achievement and encourages perseverance, the gender gap in the willingness to compete disappears. We show that the elimination of this gap implies significant efficiency gains. We also provide suggestive evidence on a plausible causal mechanism that runs through the positive impact of enhanced grit on girls' optimism about their future performance.Item Open Access Multiple-resampling receiver design for OFDM over Doppler-distorted underwater acoustic channels(2013) Tu, K.; Duman, T. M.; Stojanovic, M.; Proakis J. G.In this paper, we focus on orthogonal frequency-division multiplexing (OFDM) receiver designs for underwater acoustic (UWA) channels with user-and/or path-specific Doppler scaling distortions. The scenario is motivated by the cooperative communications framework, where distributed transmitter/receiver pairs may experience significantly different Doppler distortions, as well as by the single-user scenarios, where distinct Doppler scaling factors may exist among different propagation paths. The conventional approach of front-end resampling that corrects for common Doppler scaling may not be appropriate in such scenarios, rendering a post-fast-Fourier-transform (FFT) signal that is contaminated by user-and/or path-specific intercarrier interference. To counteract this problem, we propose a family of front-end receiver structures that utilize multiple-resampling (MR) branches, each matched to the Doppler scaling factor of a particular user and/or path. Following resampling, FFT modules transform the Doppler-compensated signals into the frequency domain for further processing through linear or nonlinear detection schemes. As part of the overall receiver structure, a gradient-descent approach is also proposed to refine the channel estimates obtained by standard sparse channel estimators. The effectiveness and robustness of the proposed receivers are demonstrated via simulations, as well as emulations based on real data collected during the 2010 Mobile Acoustic Communications Experiment (MACE10, Martha's Vineyard, MA) and the 2008 Kauai Acomms MURI (KAM08, Kauai, HI) experiment.Item Open Access On the influence of hard leverage in a soft leverage bargaining game: the importance of credible claims(Academic Press, 2016) Bolton, G. E.; Karagözoğlu, E.What makes a bargaining proposal credible? We study how hard leverage (binding commitment) influences soft leverage (appealing to a focal point) in a rich-context bargaining game known to exhibit competing claims to focality. In three treatments, our experiment varies one bargainer's ability to commit, holding the soft leverage condition fixed. As in previous studies, we observe that opening offers are consistent with the available soft leverage. The influence of hard leverage is most evident in the concessionary stage. Hard and soft leverage interact to influence outcomes: Hard leverage advantages its holder, yet settlements largely stay between the two focal points. We posit that focal points induce mutual expectations of bargainer social preferences that, when combined with the Nash bargaining solution, imply the comparative statics concerning the settlements observed. A similarly modified version of the Zeuthen–Harsanyi model of the bargaining process, agrees with the comparative statics on opening offers and concessions. © 2016 Elsevier Inc.Item Open Access Optimizing shared cache behavior of chip multiprocessors(ACM, 2009-12) Kandemir, M.; Muralidhara, S. P.; Narayanan, S. H. K.; Zhang, Y.; Öztürk, ÖzcanOne of the critical problems associated with emerging chip multiprocessors (CMPs) is the management of on-chip shared cache space. Unfortunately, single processor centric data locality optimization schemes may not work well in the CMP case as data accesses from multiple cores can create conflicts in the shared cache space. The main contribution of this paper is a compiler directed code restructuring scheme for enhancing locality of shared data in CMPs. The proposed scheme targets the last level shared cache that exist in many commercial CMPs and has two components, namely, allocation, which determines the set of loop iterations assigned to each core, and scheduling, which determines the order in which the iterations assigned to a core are executed. Our scheme restructures the application code such that the different cores operate on shared data blocks at the same time, to the extent allowed by data dependencies. This helps to reduce reuse distances for the shared data and improves on-chip cache performance. We evaluated our approach using the Splash-2 and Parsec applications through both simulations and experiments on two commercial multi-core machines. Our experimental evaluation indicates that the proposed data locality optimization scheme improves inter-core conflict misses in the shared cache by 67% on average when both allocation and scheduling are used. Also, the execution time improvements we achieve (29% on average) are very close to the optimal savings that could be achieved using a hypothetical scheme. Copyright 2009 ACM.Item Open Access Pedestrian dead reckoning employing simultaneous activity recognition cues(Institute of Physics Publishing, 2012-01-11) Altun, K.; Barshan, B.We consider the human localization problem using body-worn inertial/magnetic sensor units. Inertial sensors are characterized by a drift error caused by the integration of their rate output to obtain position information. Because of this drift, the position and orientation data obtained from inertial sensors are reliable over only short periods of time. Therefore, position updates from externally referenced sensors are essential. However, if the map of the environment is known, the activity context of the user can provide information about his position. In particular, the switches in the activity context correspond to discrete locations on the map. By performing localization simultaneously with activity recognition, we detect the activity context switches and use the corresponding position information as position updates in a localization filter. The localization filter also involves a smoother that combines the two estimates obtained by running the zero-velocity update algorithm both forward and backward in time. We performed experiments with eight subjects in indoor and outdoor environments involving walking, turning and standing activities. Using a spatial error criterion, we show that the position errors can be decreased by about 85% on the average. We also present the results of two 3D experiments performed in realistic indoor environments and demonstrate that it is possible to achieve over 90% error reduction in position by performing localization simultaneously with activity recognition.Item Open Access Performance information, production uncertainty, and subjective entitlements in bargaining(INFORMS, 2015) Karagözoğlu, E.; Riedl, A.We experimentally explore the effect of performance information and production uncertainties on (i) subjective entitlements derived from the production process and (ii) bargaining over the jointly produced surplus. We hypothesize that performance information and details of the production process affect entitlements, which in turn influence bargaining behavior. We find that, without performance information, subjective entitlements are mostly mutually consistent, and bargaining mainly ends with an equal split. In stark contrast, negotiators derive strong, mutually inconsistent, subjective entitlements when there is performance information. These subjective entitlements affect opening proposals, concessions, and bargaining duration and lead to asymmetric agreements. Moreover, given performance information, endogenous variations in entitlements influence bargaining, suggesting an independent role of subjective entitlements. Production uncertainties influence bargaining, especially when performance information is present, but do not substantially mitigate the effect of entitlements. Theoretical bargaining models allowing for reference points or fairness principles can partly account for the empirical results. Yet, important aspects are left unexplained and our results suggest ways for extending these models. © 2015 INFORMS.Item Open Access Two learning approaches for protein name extraction(Academic Press, 2009) Tatar, S.; Cicekli, I.Protein name extraction, one of the basic tasks in automatic extraction of information from biological texts, remains challenging. In this paper, we explore the use of two different machine learning techniques and present the results of the conducted experiments. In the first method, Bigram language model is used to extract protein names. In the latter, we use an automatic rule learning method that can identify protein names located in the biological texts. In both cases, we generalize protein names by using hierarchically categorized syntactic token types. We conducted our experiments on two different datasets. Our first method based on Bigram language model achieved an F-score of 67.7% on the YAPEX dataset and 66.8% on the GENIA corpus. The developed rule learning method obtained 61.8% F-score value on the YAPEX dataset and 61.0% on the GENIA corpus. The results of the comparative experiments demonstrate that both techniques are applicable to the task of automatic protein name extraction, a prerequisite for the large-scale processing of biomedical literature. © 2009 Elsevier Inc. All rights reserved.Item Open Access Understanding the plasmonic properties of dewetting formed Ag nanoparticles for large area solar cell applications(Optical Society of American (OSA), 2013) Günendi, M.C.; Tanyeli I.; Akgüç G.B.; Bek, A.; Turan, R.; Gülseren O.The effects of substrates with technological interest for solar cell industry are examined on the plasmonic properties of Ag nanoparticles fabricated by dewetting technique. Both surface matching (boundary element) and propagator (finite difference time domain) methods are used in numerical simulations to describe plasmonic properties and to interpret experimental data. The uncertainty on the locations of nanoparticles by the substrate in experiment is explained by the simulations of various Ag nanoparticle configurations. The change in plasmon resonance due to the location of nanoparticles with respect to the substrate, interactions among them, their shapes, and sizes as well as dielectric properties of substrate are discussed theoretically and implications of these for the experiment are deliberated. ©2013 Optical Society of America.Item Open Access A Wi-Fi cluster based wireless sensor network application and deployment for wildfire detection(Hindawi Publishing Corporation, 2014) Ulucinar, A.R.; Korpeoglu I.; Cetin, A.E.We introduce the wireless sensor network (WSN) data harvesting application we developed for wildfire detection and the experiments we have performed. The sensor nodes are equipped with temperature and relative humidity sensors. They are organized into clusters and they communicate with the cluster heads using 802.15.4/ZigBee wireless links. The cluster heads report the harvested data to the control center using 802.11/Wi-Fi links. We introduce the hardware and the software architecture of our deployment near Rhodiapolis, an ancient city raising on the outskirts of Kumluca county of Antalya, Turkey. We detail our technical insights into the deployment based on the real-world data collected from the site. We also propose a temperature-based fire detection algorithm and we evaluate its performance by performing experiments in our deployment site and also in our university. We observed that our WSN application can reliably report temperature data to the center quickly and our algorithms can detect fire events in an acceptable time frame with no or very few false positives. © 2014 Alper Rifat Ulucinar et al.