Browsing by Subject "Measurement"

Now showing 1 - 18 of 18

Open Access
Architectural requirements for energy efficient execution of graph analytics applications
(IEEE, 2015-11) Özdal, Muhammet Mustafa; Yeşil, Şerif; Kim, T.; Ayupov, A.; Burns, S.; Öztürk, Özcan
Intelligent data analysis has become more important in the last decade especially because of the significant increase in the size and availability of data. In this paper, we focus on the common execution models and characteristics of iterative graph analytics applications. We show that the features that improve work efficiency can lead to significant overheads on existing systems. We identify the opportunities for custom hardware implementation, and outline the desired architectural features for energy efficient computation of graph analytics applications. © 2015 IEEE.
Open Access
Autonomous multiple teams establishment for mobile sensor networks by SVMs within a potential field
(2012) Nazlibilek, S.
In this work, a new method and algorithm for autonomous teams establishment with mobile sensor network units by SVMs based on task allocations within a potential field is proposed. The sensor network deployed into the environment using the algorithm is composed of robot units with sensing capability of magnetic anomaly of the earth. A new algorithm is developed for task assignment. It is based on the optimization of weights between robots and tasks. The weights are composed of skill ratings of the robots and priorities of the tasks. Multiple teams of mobile units are established in a local area based on these mission vectors. A mission vector is the genetic and gained background information of the mobile units. The genetic background is the inherent structure of their knowledge base in a vector form but it can be dynamically updated with the information gained later on by experience. The mission is performed in a magnetic anomaly environment. The initial values of the mission vectors are loaded by the task assignment algorithm. The mission vectors are updated at the beginning of each sampling period of the motion. Then the teams of robots are created by the support vector machines. A linear optimal hyperplane is calculated by the use of SVM algorithm during training period. Then the robots are classified as teams by use of SVM mechanism embedded in the robots. The support vector machines are implemented in the robots by ordinary op-amps and basic logical gates. Team establishment is tested by simulations and a practical test-bed. Both simulations and the actual operation of the system prove that the system functions satisfactorily. © 2012 Elsevier Ltd. All rights reserved.
Open Access
Better stability with measurement errors
(Springer New York LLC, 2016-06) Argun, A.; Volpe, G.
Often it is desirable to stabilize a system around an optimal state. This can be effectively accomplished using feedback control, where the system deviation from the desired state is measured in order to determine the magnitude of the restoring force to be applied. Contrary to conventional wisdom, i.e. that a more precise measurement is expected to improve the system stability, here we demonstrate that a certain degree of measurement error can improve the system stability. We exemplify the implications of this finding with numerical examples drawn from various fields, such as the operation of a temperature controller, the confinement of a microscopic particle, the localization of a target by a microswimmer, and the control of a population.
Open Access
Data mining experiments on the Angiotensin II-Antagonist in Paroxysmal Atrial Fibrillation (ANTIPAF-AFNET 2) trial: ‘exposing the invisible’
(Oxford University Press, 2016) Okutucu, S.; Katircioglu-Öztürk, D.; Oto, E.; Güvenir, H. A.; Karaagaoglu, E.; Oto, A.; Meinertz, T.; Goette, A.
Aims: The aims of this study include (i) pursuing data-mining experiments on the Angiotensin II-Antagonist in Paroxysmal Atrial Fibrillation (ANTIPAF-AFNET 2) trial dataset containing atrial fibrillation (AF) burden scores of patients with many clinical parameters and (ii) revealing possible correlations between the estimated risk factors of AF and other clinical findings or measurements provided in the dataset. Methods: Ranking Instances by Maximizing the Area under a Receiver Operating Characteristics (ROC) Curve (RIMARC) is used to determine the predictive weights (Pw) of baseline variables on the primary endpoint. Chi-square automatic interaction detector algorithm is performed for comparing the results of RIMARC. The primary endpoint of the ANTIPAF-AFNET 2 trial was the percentage of days with documented episodes of paroxysmal AF or with suspected persistent AF. Results: By means of the RIMARC analysis algorithm, baseline SF-12 mental component score (Pw = 0.3597), age (Pw = 0.2865), blood urea nitrogen (BUN) (Pw = 0.2719), systolic blood pressure (Pw = 0.2240), and creatinine level (Pw = 0.1570) of the patients were found to be predictors of AF burden. Atrial fibrillation burden increases as baseline SF-12 mental component score gets lower; systolic blood pressure, BUN and creatinine levels become higher; and the patient gets older. The AF burden increased significantly at age >76. Conclusions: With the ANTIPAF-AFNET 2 dataset, the present data-mining analyses suggest that a baseline SF-12 mental component score, age, systolic blood pressure, BUN, and creatinine level of the patients are predictors of AF burden. Additional studies are necessary to understand the distinct kidney-specific pathophysiological pathways that contribute to AF burden. Published on behalf of the European Society of Cardiology.
Open Access
Environmental efficiency in carbon dioxide emissions in the OECD: a non-parametric approach
(Academic Press, 2000) Zaim, O.; Taskin, F.
The role of the environment is an important issue in the policy-making and hence, the accurate assessment of the environmental conditions is vital. In this paper, an environmental efficiency index is developed for the OECD countries using non-parametric techniques. The approach adopted is based on the assumption that there is just one production process behind the production of both goods and pollution emissions. The index derived in this work measures the extent of the required output sacrifice, due to the transformation of the production process, from one where all outputs are strongly disposable to the one which is characterized by weak disposability of pollutants. Using this index, we first conduct cross-section comparisons on the state of each country's production process in its treatment of pollution emissions. We then trace each country's modification of their production processes overtime. The results indicate that if the disposability for CO2 emissions were strictly restricted as the result of an environmental regulation, the total value of output loss to the OECD countries as a whole would correspond to 3.7, 4.8 and 3.5% of the total OECD GDP for 1980, 1985 and 1990, respectively. © 2000 Academic Press.
Open Access
Experimental results for 2D magnetic resonance electrical impedance tomography (MR-EIT) using magnetic flux density in one direction
(Institute of Physics Publishing, 2003) Birgül, Ö.; Eyüboğlu, B. M.; İder, Y. Z.
Magnetic resonance electrical impedance tomography (MR-EIT) is an emerging imaging technique that reconstructs conductivity images using magnetic flux density measurements acquired employing MRI together with conventional EIT measurements. In this study, experimental MR-EIT images from phantoms with conducting and insulator objects are presented. The technique is implemented using the 0.15 T Middle East Technical University MRI system. The dc current method used in magnetic resonance current density imaging is adopted. A reconstruction algorithm based on the sensitivity matrix relation between conductivity and only one component of magnetic flux distribution is used. Therefore, the requirement for object rotation is eliminated. Once the relative conductivity distribution is found, it is scaled using the peripheral voltage measurements to obtain the absolute conductivity distribution. Images of several insulator and conductor objects in saline filled phantoms are reconstructed. The L2 norm of relative error in conductivity values is found to be 13%, 17% and 14% for three different conductivity distributions.
Open Access
Fair task allocation in crowdsourced delivery
(Institute of Electrical and Electronics Engineers, 2018) Basik, F.; Gedik, B.; Ferhatosmanoglu, H.; Wu, K.
Faster and more cost-efficient, crowdsourced delivery is needed to meet the growing customer demands of many industries. In this work, we introduce a new crowdsourced delivery platform that takes fairness towards workers into consideration, while maximizing the task completion ratio. Since redundant assignments are not possible in delivery tasks, we first introduce a 2-phase assignment model that increases the reliability of a worker to complete a given task. To realize the effectiveness of our model in practice, we present both offline and online versions of our proposed algorithm called F-Aware. Given a task-to-worker bipartite graph, F-Aware assigns each task to a worker that maximizes fairness, while allocating tasks to use worker capacities as much as possible. We present an evaluation of our algorithms with respect to running time, task completion ratio, as well as fairness and assignment ratio. Experiments show that F-Aware runs around $10^7\times$ faster than the TAR-optimal solution and assigns 96.9% of the tasks that can be assigned by it. Moreover, it is shown that, F-Aware is able to provide a much fair distribution of tasks to workers than the best competitor algorithm. IEEE
Open Access
Inertial imaging with nanomechanical systems
(Nature Publishing Group, 2015) Hanay, M. S.; Kelber, S. I.; O'Connell, C. D.; Mulvaney, P.; Sader, J. E.; Roukes, M. L.
Mass sensing with nanoelectromechanical systems has advanced significantly during the last decade. With nanoelectromechanical systems sensors it is now possible to carry out ultrasensitive detection of gaseous analytes, to achieve atomic-scale mass resolution and to perform mass spectrometry on single proteins. Here, we demonstrate that the spatial distribution of mass within an individual analyte can be imaged - in real time and at the molecular scale - when it adsorbs onto a nanomechanical resonator. Each single-molecule adsorption event induces discrete, time-correlated perturbations to all modal frequencies of the device. We show that by continuously monitoring a multiplicity of vibrational modes, the spatial moments of mass distribution can be deduced for individual analytes, one-by-one, as they adsorb. We validate this method for inertial imaging, using both experimental measurements of multimode frequency shifts and numerical simulations, to analyse the inertial mass, position of adsorption and the size and shape of individual analytes. Unlike conventional imaging, the minimum analyte size detectable through nanomechanical inertial imaging is not limited by wavelength-dependent diffraction phenomena. Instead, frequency fluctuation processes determine the ultimate attainable resolution. Advanced nanoelectromechanical devices appear capable of resolving molecular-scale analytes.
Open Access
Left-and right-handed transmission peaks near the magnetic resonance frequency in composite metamaterials
(American Physical Society, 2004) Katsarakis, N.; Koschny, T.; Kafesaki, M.; Economou, E. N.; Özbay, Ekmel; Soukoulis, C. M.
We present free-space microwave measurements on composite metamaterials (CMMs) consisting of split ring resonators (SRRs) and wires either on the same dielectric board or on alternating boards. Our experimental results disprove the widely held belief that the occurrence of a CMM transmission peak within the stop bands of the SRRs alone and wires alone constitutes a clear demonstration of left-handed (LH) behavior. This belief is based on the assumption that the stop bands of SRRs alone and wires alone are not affected by the simultaneous presence of both. We show here that this assumption is wrong: The effective plasma frequency, ω′p, of the CMM is actually substantially lower than the wires-only plasma frequency, ωp; furthermore, the in-plane wires, as opposed to the off-plane case, push the magnetic resonance frequency of the SRRs, ωm, to a higher value, ω′m, for the CMM. We conclude that the criterion for deciding whether a peak in the transmission spectrum through a CMM is really left-handed is for the peak to be located above ω′m and below ω′p. Our results provide a definite way for experimentally identifying ω′p.
Open Access
Link recommendation in P2P social networks
(WOSS, 2012) Aytaş, Yusuf; Ferhatosmanoğlu, Hakan; Ulusoy, Özgür
Social networks have been mostly based on a centralized infrastructure where the owner hosts all the data and services. This model of “fat server & thin clients” results in many systems and practical problems such as privacy, censorship, scalability, and fault-tolerance. While a P2P infrastructure would be a natural alternative for implementing social networks, it has surprisingly not attracted enough attention yet. Significant research is needed to develop a P2P social network system. From an algorithmic perspective, most graph algorithms for social networks assume that the global graph is available. These need to be revisited in a P2P setting where the nodes have limited information with connectivity to only their neighbors. Following these observations, in this paper, we focus on social network link recommendation problem in a P2P setting. We investigate methods to recommend links to improve social connections as well as the efficiency of the overlay network. We evaluate our methods with respect to measures developed for P2P social networks.
Open Access
Measuring welfare states beyond the three worlds: Refining state-of-the-art tools
(Wiley-Blackwell Publishing Ltd., 2021-01-13) Bölükbaşı, Tolga; Öktem, K. G.; Savaş, Efe
The past decades saw the expansion of the geography of comparative welfare state research beyond the three worlds embracing a heterogeneous set of mainly middle-income countries. In response, two leading state-of-the-art tools for measuring welfare states through social rights, Social Citizenship Indicators Program (SCIP) and Comparative Welfare Entitlements Dataset (CWED), integrated many new countries into their datasets. Comparative welfare state research has yet to address the extent to which these measurement tools originally developed for measuring classic welfare states work equally well for measuring welfare states beyond the three worlds. In this article, we explore a number of challenges these datasets face in measuring these new cases. These challenges, we believe, stem from a set of key institutional characteristics widely prevalent in these welfare states. These characteristics are overt and hidden conditionalities, unconventional instruments, informal practices, nature of changes in statutory pension age and labour market characteristics of the representative worker. We propose a set of solutions to refine these datasets for comparing all cases, old and new. We conclude by drawing lessons for comparative research focusing not only on welfare states beyond the three worlds but also on the three worlds themselves.
Open Access
Modeling AoII in push- and pull-based sampling of continuous time Markov chains
(IEEE, 2024) Cosandal, Ismail; Akar, Nail; Ulukus, Sennur
Age of incorrect information (AoII) has recently been proposed as an alternative to existing information freshness metrics for real-time sampling and estimation problems involving information sources that are tracked by remote monitors. Different from existing metrics, AoII penalizes the incorrect information by increasing linearly with time as long as the source and the monitor are de-synchronized, and is reset when they are synchronized back. While AoII has generally been investigated for discrete time information sources, we develop a novel analytical model in this paper for push- and pull-based sampling and transmission of a continuous time Markov chain (CTMC) process. In the pull-based model, the sensor starts transmitting information on the observed CTMC only when a pull request from the monitor is received. On the other hand, in the push-based scenario, the sensor, being aware of the AoII process, samples and transmits when the AoII process exceeds a random threshold. The proposed analytical model for both scenarios is based on the construction of a discrete time MC (DTMC) making state transitions at the embedded epochs of synchronization points, using the theory of absorbing CTMCs, and in particular phase-type distributions. For a given sampling policy, analytical models to obtain the mean AoII and the average sampling rate are developed. Numerical results are presented to validate the analytical models as well as to provide insight on optimal sampling policies under sampling rate constraints.
Open Access
Monitoring progress toward fulfilling rights in early childhood under the convention on the rights of the child to improve outcomes for children and families
(Oxford University Press, 2013) Hertzman, C.; Vaghri, Z.; Arkadas-Thibert, A.
Can the United Nations Convention on the Rights of the Child (UN-CRC), to which 193 countries are signatory, be used as a tool to support developmental health in the early years? Improving early childhood development (ECD) requires finding ways for social determinants and child rights approaches to work together, which, to date, has not occurred. However, in 2005, the UN-CRC Monitoring Committee issued General Comment 7: Implementing Rights in Early Childhood (GC7) in response to the observation that children under the age of 8 were often overlooked in countries' reporting of progress toward implementing UN-CRC. This chapter shows how a commitment from the UN-CRC Monitoring Committee and key relevant international agencies (WHO, UNICEF) to a long-term program of monitoring compliance with GC7, in conjunction with monitoring of ECD developmental outcomes in all signatory countries, could help move global society toward equity in developmental health from the start of life. © Oxford University Press, 2014.
Open Access
Predicting middle school students’ mathematics achievement using decision trees
(2023-09) Yeter, Buse
In today's world, it is crucial to raise individuals who can think critically and flexibly, see things from a variety of perspectives, and develop creative solutions to common challenges in many countries including Türkiye. One of the ways to attain this purpose is to provide qualified mathematics education. During this qualified education determining the extent to which students meet the program goals is an important and fundamental part of the process of educating the individuals. Education should be provided in accordance with the requirements of the age using a curriculum with qualified measurement, assessment, and evaluation practices. This study aims to predict middle school students’ achievement at four grade levels in mathematics at the end of the semester utilized as a predictor measurement and assessment approach. Chi-squared Automatic Interaction Detection (CHAID), a decision tree analysis, was used to examine the importance of exams, quizzes, homework, and teacher observation in predicting the end-of-semester achievements. As a result of the study, when the first semester is examined in general, quizzes are mostly determined as the best predictor of student success, while exams are generally for the second semester. Implications for teachers and students are stated.
Open Access
Reliability and validity of the pain anxiety symptom scale in Persian speaking chronic low back pain patients
(Lippincott Williams and Wilkins, 2017) Shanbehzadeh, S.; Salavati, M.; Tavahomi, M.; Khatibi, A.; Talebian, S.; Kalantari K. K.
Study Design. Psychometric testing of the Persian version of Pain Anxiety Symptom Scale 20. Objective. The aim of this study was to assess the reliability and construct validity of the PASS-20 in nonspecific chronic low back pain (LBP) patients. Summary of Background Data. The PASS-20 is a self-report questionnaire that assesses pain-related anxiety. The Psychometric properties of this instrument have not been assessed in Persian-speaking chronic LBP patients. Methods. One hundred and sixty participants with chronic LBP completed the Persian version of PASS-20, Tampa Scale of Kinesiophobia (TSK), Fear-Avoidance Beliefs Questionnaire (FABQ), Pain Catastrophizing Scale (PCS), trait form of the State-Trait Anxiety (STAI-T), Oswestry Low Back Pain Disability Index (ODI), Beck Depression Inventory (BDI-II), and Visual Analogue Scale (VAS). To evaluate test-retest reliability, 60 patients filled out the PASS-20, 6 to 8 days after the first visit. Test-retest reliability (intraclass correlation coefficient [ICC], standard error of measurement [SEM], and minimal detectable change [MDC]), internal consistency, dimensionality, and construct validity were examined. Results. The ICCs of the PASS-20 subscales and total score ranged from 0.71 to 0.8. The SEMs for PASS-20 total score was 7.29 and for the subscales ranged from 2.43 to 2.98. The MDC for the total score was 20.14 and for the subscales ranged from 6.71 to 8.23. The Cronbach alpha values for the subscales and total score ranged from 0.70 to 0.91. Significant positive correlations were found between the PASS-20 total score and PCS, TSK, FABQ, ODI, BDI, STAI-T, and pain intensity. Conclusion. The Persian version of the PASS-20 showed acceptable psychometric properties for the assessment of pain-related anxiety in Persian-speaking patients with chronic LBP. © 2017 Wolters Kluwer Health, Inc. All rights reserved.
Open Access
StyleRes: transforming the residuals for real ımage editing with StyleGAN
(IEEE, 2023-07-22) Pehlivan, Hamza; Dalva, Yusuf; Dündar, Aysegül
We present a novel image inversion framework and a training pipeline to achieve high-fidelity image inversion with high-quality attribute editing. Inverting real images into StyleGAN’s latent space is an extensively studied problem, yet the trade-off between the image reconstruction fidelity and image editing quality remains an open challenge. The low-rate latent spaces are limited in their expressiveness power for high-fidelity reconstruction. On the other hand, high-rate latent spaces result in degradation in editing quality. In this work, to achieve high-fidelity inversion, we learn residual features in higher latent codes that lower latent codes were not able to encode. This enables preserving image details in reconstruction. To achieve high-quality editing, we learn how to transform the residual features for adapting to manipulations in latent codes. We train the framework to extract residual features and transform them via a novel architecture pipeline and cycle consistency losses. We run extensive experiments and compare our method with state-of-the-art inversion methods. Qualitative metrics and visual comparisons show significant improvements. Code: https://github.com/hamzapehlivan/StyleRes
Open Access
Uniqueness and reconstruction in magnetic resonance-electrical impedance tomography (MR-EIT)
(Institute of Physics Publishing, 2003) İder, Y. Z.; Onart, S.; Lionheart, W. R. B.
Magnetic resonance-electrical impedance tomography (MR-EIT) was first proposed in 1992. Since then various reconstruction algorithms have been suggested and applied. These algorithms use peripheral voltage measurements and internal current density measurements in different combinations. In this study the problem of MR-EIT is treated as a hyperbolic system of first-order partial differential equations, and three numerical methods are proposed for its solution. This approach is not utilized in any of the algorithms proposed earlier. The numerical solution methods are integration along equipotential surfaces (method of characteristics), integration on a Cartesian grid, and inversion of a system matrix derived by a finite difference formulation. It is shown that if some uniqueness conditions are satisfied, then using at least two injected current patterns, resistivity can be reconstructed apart from a multiplicative constant. This constant can then be identified using a single voltage measurement. The methods proposed are direct, non-iterative, and valid and feasible for 3D reconstructions. They can also be used to easily obtain slice and field-of-view images from a 3D object. 2D simulations are made to illustrate the performance of the algorithms.
Open Access
Working memory in unaffected relatives of patients with schizophrenia: a meta-analysis of functional magnetic resonance imaging studies
(Oxford University Press, 2016) Zhang, R.; Picchioni, M.; Allen, P.; Toulopoulou, T.
Working memory deficits, a core cognitive feature of schizophrenia may arise from dysfunction in the frontal and parietal cortices. Numerous studies have also found abnormal neural activation during working memory tasks in patients' unaffected relatives. The aim of this study was to systematically identify and anatomically localize the evidence for those activation differences across all eligible studies. Fifteen functional magnetic resonance imaging (fMRI) manuscripts, containing 16 samples of 289 unaffected relatives of patients with schizophrenia, and 358 healthy controls were identified that met our inclusion criteria: (1) used a working memory task; and (2) reported standard space coordinates. Activation likelihood estimation (ALE) identified convergence across studies. Compared to healthy controls, patients' unaffected relatives showed decreases in neural activation in the right middle frontal gyrus (BA9), as well as right inferior frontal gyrus (BA44). Increased activation was seen in relatives in the right frontopolar (BA10), left inferior parietal lobe (BA40), and thalamus bilaterally. These results suggest that the familial risk of schizophrenia is expressed in changes in neural activation in the unaffected relatives in the cortical-subcortical working memory network that includes, but is not restricted to the middle prefrontal cortex.