WoS

Permanent URI for this collectionhttps://hdl.handle.net/20.500.14411/18

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4D Printing of Reusable Mechanical Metamaterial Energy Absorber, Experimental and Numerical Investigation
(Iop Publishing Ltd, 2025) Fallah, Ali; Saleem, Qandeel; Scalet, Giulia; Koc, Bahattin
This study investigates the compression behavior, energy absorption, shape memory properties, and reusability of 4D-printed smart mechanical metamaterials. Four structural configurations, i.e. honeycomb, re-entrant, and two modified re-entrant designs were developed to assess microstructure effects. Samples were fabricated using Polylactic Acid (PLA), a widely used shape memory polymer (SMP) in 4D printing, and polyethylene terephthalate glycol (PETG), an emerging SMP with demonstrated shape memory performance in recent studies. Cold-programming-induced shape recovery was evaluated at room temperature, simulating real-world conditions. Finite element simulations of compression and shape memory cycles matched experimental results well. Auxetic samples with negative Poisson's ratios showed superior energy absorption. However, only PETG demonstrated sufficient reusability, while PLA proved unsuitable for reusable designs. The PETG-3 modified re-entrant structure exhibited the best performance, with high energy absorption, delayed densification onset, and shape recovery and reusability factors of 0.95 and 0.96, respectively. Findings highlight the importance of considering both shape recovery and reusability when designing smart structures to address industrial challenges.
Afthd: Bayesian Accelerated Failure Time Model for High-Dimensional Time-To Data
(Springernature, 2025) Kumari, Pragya; Bhattacharjee, Atanu; Vishwakarma, Gajendra K.; Tank, Fatih
Analyzing high-dimensional (HD) data with time-to-event outcomes poses a formidable challenge. The accelerated failure time (AFT) model, an alternative to the Cox proportional hazard model in survival analysis, lacks sufficient R packages for HD time-to-event data under the Bayesian paradigm. To address this gap, we develop the R package afthd. This tool facilitates advanced AFT modeling, offering Bayesian analysis for univariate and multivariable scenarios. This work includes diagnostic plots and an open-source R code for working with HD data, extending the conventional AFT model to the Bayesian framework of log-normal, Weibull, and log-logistic AFT models. The methodology is rigorously validated through simulation techniques, yielding consistent results across parametric AFT models. The application part is also performed on two different real HD liver cancer datasets, which reveals the proposed method's significance by obtaining inferences for survival estimates for the disease. Our developed package afthd is competent in working with HD time-to-event data using the conventional AFT model along with the Bayesian paradigm. Other aspects, like missing values in covariates within HD data and competing risk analysis, are also covered in this article.
Citation - WoS: 3
An Agent-based Trading Infrastructure for Combinatorial Reverse Auctions
(Ieee, 2014) Bayindir, Hakan; Kilic, Hurevren; Rehan, Mohammed; Computer Engineering
A Combinatorial Reverse Auction Trading Infrastructure - CRATI is designed and implemented as an agent-based system. Two basic building blocks Java Agent Development Framework (JADE) and an Open Source Java Constraint Programming Library (Choco Solver) are used to facilitate agent interactions and an optimization task. For our purpose, it is shown that auction Winner Determination Problem (WDP) can suitably be represented as a weighted set covering problem instance whose solution gives the decided winners of the auction process. In order to realize the system, a variation of Contract Net protocol is designed and implemented to handle auctions that occur in the platform from start to finish.
The American Dream: Cultural and Social Downfall in John Steinbeck's of Mice and Men
(Literary Voice, 2022) Aras, Goksen; Takva, Serdar; Department of English Language and Literature
As known, throughout history, most societies have experienced hard times that have made life difficult to bear. Among these hard times are political, social and economic conditions which shape the ways human beings perceive the world and lead their lives. The Great Depression, that ravaged American society in the 1929s, is one of the most catastrophic economic events in the history of America and it is considered to be a calamity resulting in unemployed, desperate and even homeless people. John Steinbeck, being one of the foremost representatives of American writers, handles the devastating effects of the Great Depression and how it affected numerous people from different parts of the community. In this period, from women to the black, from the old to the disabled. most people wanted to lead a life based on humanly standards but what they expected turned into a frustration paving the way for the impossibility of the American dream and thus cultural and social downfall of such people no matter how hard they try to achieve their goals. Steinbeck's novel titled Of Mice and Men in this context is a touching representation of frustration, hopelessness, despair to have a place to live in, and a portrayal of unattainable happiness and the impossible American dream. This paper explores the futile efforts to realize the American dream and thus unhappiness and failure from Steinbeck's point of view and it presents the reflections of such a concept through the fictionalized characters in the novel.
An Application of Stochastic Maximum Principle for a Constrained System With Memory
(Ankara Univ, Fac Sci, 2025) Savku, Emel
In this research article, we study a stochastic control problem in a theoretical frame to solve a constrained task under memory impact. The nature of memory is modeled by Stochastic Differential Delay Equations and our state process evolves according to a jump-diffusion process with time-delay. We work on two specific types of constraints, which are described in the stochastic control problem as running gain components. We develop two theorems for corresponding deterministic and stochastic Lagrange multipliers. Furthermore, these theorems are applicable to a wide range of continuous-time stochastic optimal control problems in a diversified scientific area such as Operations Research, Biology, Computer Science, Engineering and Finance. Here, in this work, we apply our results to a financial application to investigate the optimal consumption process of a company via its wealth process with historical performance. We utilize the stochastic maximum principle, which is one of the main methods of continuous-time Stochastic Optimal Control theory. Moreover, we compute a real-valued Lagrange multiplier and clarify the relation between this value and the specified constraint.
Association of Abdominal Stria With Pelvic Floor Dysfunction in Primigravid Pregnant Women
(Springer London Ltd, 2023) Karakaya, G.; Sonmezer, E.; Dokmeci, F.; Seval, M. M.; Cetinkaya, S. E.; Varli, B.
ATA50 TELESCOPE: HARDWARE
(Universidad Nacional Autonoma Mexico instituto Astronomia, 2014) Yesilyaprak, C.; Yerli, S. K.; Aksaker, N.; Yildiran, Y.; Guney, Y.; Gucsav, B. B.; Yasar, E.
ATA50 Telescope is a new telescope with RC optics and 50 cm diameter. It was supported by Atatiirk University Scientific Research Project (2010) and established at about 2000 meters altitude in city of Erzurum in Turkey last year. The observations were started a few months ago under the direction and control of Atatiirk University Astrophysics Research and Application Center (ATASAM). The technical properties and infrastructures of ATA50 Telescope are presented and we have been working on the robotic automation of the telescope as hardware and software in order to be a ready-on-demand candidate for both national and international telescope networks.
Citation - WoS: 56
Best Proximity Point on Different Type Contractions
(Natural Sciences Publishing Corp-nsp, 2011) Karapinar, Erdal; Erhan, Inci M.; Mathematics
In this manuscript, some proximity points are obtained by using different types cyclic contractions. Also, generalized cyclic Meir Keeler contraction is introduced and a new fixed point theorem for this cyclic mapping is stated.
Citation - WoS: 1
BIOINSPIRED CONCEPTUAL DESIGN (BICD): CONCEPTUAL DESIGN OF A GRASSHOPPER-LIKE JUMPING MECHANISM AS A CASE STUDY
(design Soc, 2011) Eroglu, Aylin Konez; Erden, Zuhal; Erden, Abdulkadir; Department of Mechatronics Engineering; Mechatronics Engineering
The evolution process of nature creates highly effective, power efficient, and perfectly structured biological systems. These excellent systems provide an inexhaustible source for engineers and scientists who desire to inspire ideas, processes, structures, functions, and behaviors from biological domain and implement them into engineering domain. This approach is called "Bioinspired" and challenging for engineers. However, some problems of the practical approaches are observed. One of the problems is "ad hoc" nature of the process. Each bioinspired design product has resulted in a differing design process and a generalization was not possible. Another problem rises due to the terminology difference between engineers and biologists. To overcome these problems, a need for a systematic bioinspired design (BID) process was realized in early 2000s and since then, considerable research on the BID methodology has been progressed. Within the context of BID, this paper introduces a new approach on bioinspired conceptual design (BICD) procedure for hybrid bioinspired robots which can be inspired from multiple biological systems. An illustrative case study is given in the paper.
Citation - WoS: 3
Biomechanical Design and Control of Lower Limb Exoskeleton for Sit-to-Stand and Stand-to-Sit Movements
(Ieee, 2018) Qureshi, Muhammad Hamza; Masood, Zeeshan; Rehman, Linta; Owais, Muhammad; Khan, Muhammad Umer; Mechatronics Engineering
In this paper, we present design and development phase of lower limb robotic exoskeleton that can assist paralyzed individuals. Motion of the human wearing exoskeleton is introduced by actuators. Both exoskeleton legs are attached to the supporting frame by passive universal joints. The exoskeleton provides 3 DOFs per limb of which two joints are active and one passive. The control actions i.e., sit-to-stand and stand-to-sit movements are triggered using Double Pole Double Throw (DPDT) toggle switch. The control scheme is implement using Switch control method and the feedback is provided by means of current measurement. This assistive device can be utilized for the disabled persons. The simulation results are provided that evaluates the performance of the control actions on exoskeleton.
Citation - WoS: 1
Characterization of Satellite Transponder Impairments Based on Simulations with Test Data
(Ieee, 2015) Ulubey, Orhan; Gulgonul, Senol; Kara, Ali; Department of Electrical & Electronics Engineering
A satellite transponder simulator based on actual test data of TURKSAT 3A satellite has been developed to analyze degradation in multicarrier scenarios. Communication impairment sources through a transponder are explained in conjunction with a methodology defined to characterize total degradation resulting from them. Several transponder utilization scenarios are studied with respect to total degradation and optimum operation conditions are demonstrated.
COMPARISON OF COMPUTER-BASED PROPAGATION MODELS WITH EXPERIMENTAL DATA COLLECTED IN AN URBAN AREA AT 1800 MHz
(Ieee, 2015) Acar, Tarik; Caliskan, Fatma; Aydin, Elif; Department of Electrical & Electronics Engineering
Nowadays a lot of models are set for the efficient and economic usage of frequency band since the band is a limited source. Therefore, the propagation models created for this purpose were studied in the literature. These models are Free Space Path Loss (Fspl) + Reflection plus Multiple Diffraction (RMD), COST-Hata and COST-WI models. In order to compare the success of the models, electric field strength measurements were taken in a chosen district (Mustafa Kemal Mahallesi Ankara, Turkey) where an irregular structure style can be observed. First set of measurements were recorded at random coordinates and second set of measurements were collected by the following coordinates tracking on a single line. As a conclusion, measured values were compared with the results which were taken from the mentioned models with graphical presentations. The most appropriate model was tried to be found and as another aim of the study, a correction factor was generated as a modification for COST-Hata propagation model.
Comparison of Field Survey-Based Macroseismic Intensity Map and Numerical Macroseismic Intensity Maps Using Mars and Multiple Regression Methods for 6th of February 2023 Kahramanmaraş Earthquakes
(Springer Science and Business Media Deutschland GmbH, 2024) Albayrak, Kubilay; Askan, Aysegul; Yerlikaya-Ozkurt, Fatma; Industrial Engineering
Earthquakes are natural events that cause damage to built environments by the instant seismic energy release. This energy is measured by instrumental devices to obtain the peak ground motion parameters such as Peak Ground Acceleration (PGA) and Peak Ground Velocity (PGV). Additional measurements based on the questionnaires after the earthquakes are required to identify the felt or macro seismic intensity levels. These measurements are crucial to identify the total effects of earthquakes over not only an area but also for the spatial distribution of ground motion parameters. For this purpose, it is important to study the multi-variable criteria correlations between ground motion parameters and Modified Mercalli Intensity (MMI) levels based on linear relationships of predictor variable couples. In this regard, the Multivariate Adaptive Regression Splines (MARS) Method and the Multiple Linear Regression Method are used. The entire dataset is composed of 69 earthquakes between 2005 and 2022 with 2171 ground motion parameters coupled with MMI levels. For MMI-based correlations, the MARS method is used to identify the non-linearities between predictor variables by piecewise linear functions, but for the Multiple Linear Regression Method, the least correlated variables of PGA-Epicentral Distance and PGV-Epicentral Distance are used to obtain the relationship between MMI and PGM parameters. The resulting equations obtained for the entire Turkiye database are performed to identify MMI maps of the 6th of February 2023, Kahramanmaras Earthquakes, and these maps are used to check the accuracy of the results by the comparison of field survey-based MMI maps. Finally, the numerical MMI maps are found to be consistent with the field survey-based MMI maps.
A Comparison of Wavelet Family of Transforms from Image Forensics Perspective
(Turgut Ozal Univ, 2012) Ozparlak, Levent; Avcibas, Ismail
In this study, we compare wavelet based transforms for the cases of different image forensics problems. We extract wavelet based features and make experiments for different problems. The results show that a mixture of wavelet based features give the best performance in each experiment. In the absence of such a classifier with mixed features, the best performing features were obtained from contourlet transform coefficients.
A Coupled Modelling and Simulation Approach to Electromagnetic Sheet Metal Forming
(Taylor & Francis Ltd, 2025) Aslan, Ozgur; Kabakci, Gamze Cakir; Sait, Ferit; Camalan, Caner; Baranoglu, Besim; Bayraktar, Emin; Aerospace Engineering; Mechanical Engineering; Manufacturing Engineering
This study presents a coupled numerical and experimental investigation of electromagnetic forming (EMF) for aluminium sheets. A custom simulation framework is developed in ABAQUS/Standard using user-defined material (UMAT) and load (DLOAD) subroutines. The magnetic pressure exerted on the workpiece is computed through a finite difference-based solution of Maxwell's equations and applied to the mechanical solver. The mechanical response of the material is modelled using a strain-rate-sensitive plasticity law calibrated for aluminium 7075-O. Experimental forming trials are performed using a custom-built EMF setup, and the results are compared with numerical predictions to validate the model. The comparison shows strong agreement in deformation profiles, confirming the predictive capability of the proposed simulation strategy. This work offers a reliable computational tool for optimising EMF processes and provides insights into material behaviour under high strain rate electromagnetic loading.
Creative Pattern Trials for Above the Keyboard Wear With Trompe L'oeil Illusion
(Anadolu Univ, 2022) Aydeniz, Sena Surmeli; Cegindir, Nese Yasar; Textile and Fashion Design
The design scenario of this study is based on seeking answers to the question "How can we produce different, extraordinary and original shirts for working women with the Trompe l'oeil (illusion) technique?". The sample of the study, in which the user-oriented design research method was used, is women working above the keyboard. Within the scope of the study, three women's shirts were produced with creative pattern applications. The classical techniques known in garment production have been reconstructed with the Trompe l'oeil technique. The findings were discussed in two dimensions as the process carried out for these three shirts and the prototype evaluation. Osborn's checklist was used to create the design value of the shirts. For the evaluations of the marketability of the products, measurement was made in the form of voting over Google Forms. As a result of the voting, the first prototype was found to be more suitable for the target audience. Based on the individual comments received, it has been observed that originality varies when the position and needs of the target audience come into play. The importance of the user profile in creative product design has been understood.
Cultural Logics of Honor, Face, and Dignity as Moderators of the Relationship Between Group Process and Pro-Migrant Collective Action Intentions
(Elsevier, 2025) Besta, Tomasz; Thomas, Emma; Celikkol, Goksu; Olech, Michal; Jurek, Pawel; Van Zomeren, Martijn; Wlodarczyk, Anna
Although group identification, efficacy, and injustice appraisals are well-established predictors of collective action support, contextual factors are rarely examined. We address this oversight in preregistered study by testing whether country-level norms moderate the relationships identity, anger at injustice, and efficacy have with support for pro-immigrant solidarity collective action using data from 22 countries (N = 4615). Given that cultures that emphasize honor and face prioritize harmony and social cohesion over conflict, we expected that honor codes and face orientation would attenuate the links identity, injustice, and efficacy have with collective action support. Results showed that identification, efficacy, and anger at injustice were linked to collective action intentions in most countries, but honor codes attenuated the relationship between anger and collective action intentions. We further discuss the implications and limitations of these results in light of cross-cultural studies of pro-immigrant attitudes and actions. Overall, our findings complement research on predictors of collective action and the dual-chamber model of collective action by presenting potential cultural constraints.
Diagnostic Value of Thyroid Physical Examination in the Elderly and Comparison with Ultrasonography
(UK Scientific Publishing Ltd, 2025) Gulmez, Mehmet Ihsan; Aydin, Canset; Surgical Sciences
This study is part of the health project called "Health screening for the elderly in Ankara" for patients aged 65 and over, with 1200 participants. Patients with missing laboratory tests (n = 59), movement disorders and/or bedridden (n = 54) were excluded from the study. PE was performed by a geriatrician or an ear, nose, and throat surgeon, and ultrasonographic evaluation was performed by a radiologist. PE and USG findings were compared. We aimed to investigate the diagnostic accuracy of physical examination (PE) of the thyroid gland (TG) in patients over 65 years of age and to assess the reliability by comparing PE with ultrasonographic (USG) examination. The median age of the patients participating in the study was 71.17. When the differences between thyroid nodules (TN), the number of TN size, and goiter detection were compared in terms of PE and USG, all values were statistically signifi- cant, and P values were < 0.001. The sensitivity of PE of TG was calculated as 31.0%. In our study, the sensitivity of PE of TG in terms of TN and goiter was found to below. The diagnostic accuracy of PE of TG is low, and therefore, its impact on clinical decision-making is limited. Furthermore, detected nodules rarely progress to clinically relevant disease, leading to overdiagnosis and overtreatment. Especially in groups at risk for nodules and malignancy, PE must be combined with imaging methods and, if necessary, pathological examination, even if nodules or goiter are not palpable in PE.
Does the Relationship Between Sustainable Human Resource Management and Organizational Identification Vary by Culture ? Evidence From 35 Countries Based on Globe Framework
(Emerald Group Publishing Ltd, 2025) Turek, D.; Wojtczuk-Turek, A.; Edgar, F.; Podgorodnichenko, N.; Okay-Somerville, B.; Fu, N.; Zhang, G.
Purpose: The article discusses the relationships between sustainable HRM and organizational identification, conceptualized at the individual level, and the moderating role of cultural dimensions conceptualized at the country level (described in GLOBE’s framework). The study’s theoretical model based on social exchange theory proposes that sustainable HRM practice increases organizational identification. However, the strength of this identification depends on the dimensions of national culture. Thus, we assumed national culture functions as a second-level moderator in the relationship between sustainable HRM and organizational identification. Design/methodology/approach: We conducted the study with data from 10,421 employees across 35 countries. We used a multilevel modeling approach for data analysis. Findings: The study revealed the cross-level interaction effects of national culture on the relationship between sustainable HRM practice and organizational identification. Specifically, the results indicate that sustainable HRM strengthens employees’ organizational identification more in cultures with higher levels of gender egalitarianism and lower levels of humane orientation. Originality/value: This study demonstrates that the relationship between sustainable HRM practices and employees’ organizational identification is culturally sensitive. It highlights the need to consider cultural context when assessing the impact of sustainable HRM practices on employee outcomes. Furthermore, it shows that certain cultural dimensions can enhance the effect of sustainable HRM practices. © 2025, Emerald Publishing Limited.
Driving Conditions Leading To Thermal Runaway in Li-Ion Battery EV's
(IEEE, 2024) Ertan, H. Bulent; Azuaje-Berbeci, Bernardo J.; Electrical-Electronics Engineering
The adoption of high-energy-density lithium-ion batteries (LIB) as the energy source in electric vehicles (EV) introduces significant safety concerns. Thermal runaway (TR), a self-accelerating rise in battery temperature resulting in catastrophic failure, is a significant safety concern. Cooling system failure within the EV's thermal management system is one of several factors that can trigger TR. Typically, TR is initiated by exceeding a critical temperature threshold under abusive conditions. Understanding the operating conditions that lead to the path of TR is essential for ensuring EV and occupant safety. Recently, a detailed electrochemical-thermal model that incorporates the chemical reactions within the battery until TR is introduced. This paper aims to illustrate how this model can be used to identify the conditions leading to TR under realistic EV driving scenarios. For this purpose, an Advisor/Matlab-based model of a hybrid EV is developed and verified by tests, is used to estimate the current required from the vehicle's battery pack at a given driving condition. This is followed by the prediction of battery thermal response using the mentioned finite-element-analysis-based battery model. Several scenarios are tested in this paper to determine whether TR occurs and to identify the factors contributing to TR. This study aids in comprehending the factors that contribute to TR and the development of preventative measures for battery management system design.

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