4653 research outputs found
Sort by
Distributed asynchronous rendezvous planning on the line for multi-agent systems
No full textMulti-agent systems have become increasingly significant in various application areas such as search-andrescue, exploration, surveillance, and assembly. In this study, we focus on the asynchronous autonomous rendezvous planning in multi-robot (i.e. multi-agent) systems. The objective is that the robots located in linear environments to gather rapidly at a previously unknown rendezvous location. We consider that no robot knows the positions of the other robots and its own global position. Furthermore, the robot does not know its initial distance to any other robot. Our focus is on the asynchronous case where it is not required the robots to start executing the algorithm simultaneously. We propose and develop a rendezvous planning algorithm, namely MAR, that combines distributed coordination and online motion planning. We theoretically analyze the performance of our algorithm and show that it has a constant competitive ratio. Our extensive simulations demonstrate the performance and scalability through the analysis of the key performance metrics of interest including competitive ratio, distance traveled, total time, number of rounds, and number of meetings. Additionally, we demonstrate the performance and applicability of our algorithm MAR through experimental analysis in a realistic robotic simulator.Computer Science, Theory & Method
Screenscapingthe City:Reproduction of the Image of İstanbulin Online TV Series
No full textThis article explores the portrayal of Istanbul's urban image in TV series produced for online platforms, examining how these visual narratives influence public perception. By revisiting Kevin Lynch's theories on urban imagery, the study analyzes four prominent TV series set in Istanbul: Persona (& Scedil;ahsiyet), The Protector (Hakan: Muhaf & imath;z), Ethos (Bir Ba & scedil;kad & imath;r), and The Gift (Atiye). Each series utilizes Lynch's five urban elements path, edge, district, node, and landmark to craft unique visual narratives. Changing urban views and evolving tourism trends driven by digital platforms are transforming the city's image. The study aimed to explore the city image by developing a new perspective towards reading how Istanbul is screened in online TV series. Paths highlight socio-economic disparities by connecting various districts, both urban and rural, while edges, such as the Bosporus and other waterfronts, create physical and symbolic boundaries emphasizing themes of isolation and confinement. Districts portray contrasting social structures, with some series focusing on dense, bustling areas and others on rural. Nodes serve as critical locations for key events and character interactions, weaving the narrative threads together, and landmarks, particularly historical ones like Hagia Sophia Mosque and the Grand Bazaar, ground the stories in Istanbul's rich cultural heritage. The analysis reveals that these TV series not only utilize Istanbul's urban elements to enhance storytelling but also contribute to the evolving perception of the city, depicting it as a place of stark social contrasts, urban dichotomies, and mythical heritage. Through this lens, the study underscores the significant role of visual media in constructing urban narratives, showing how Istanbul's blend of historical grandeur and contemporary vibrancy is instrumentalized and reproduced in the selected TV series. These series collectively shape and reinforce Istanbul's image in the global imagination, highlighting the city's multifaceted nature and its importance as a cultural and historical hub.Ar
Data fusion integrated network forecasting scheme classifier (DFI-NFSC) via multi-layer perceptron decomposition architecture
No full textThe Massive Access Problem of the Internet of Things stands for the access problem of the wireless devices to the Gateway when the device population in the coverage area is excessive. We develop a hybrid model called Data Fusion Integrated Network Forecasting Scheme Classifier (DFI-NFSC) using a Multi-Layer Perceptron (MLP) Decomposition architecture specifically designed to address the Massive Access Problem. We utilize our custom error metric to display throughput and energy consumption results. These results are obtained by emulating the Joint Forecasting-Scheduling (JFS) system on a single IoT Gateway and distinguishing between ARIMA, LSTM, and MLP forecasters of the JFS system. The outcomes indicate that the DFI-NFCS method plays a notable role in improving performance and mitigating challenges arising from the dynamic fluctuations in the diversity of device types within an IoT gateway's coverage zone.Computer Science, Information Systems || Engineering, Electrical & Electronic || Telecommunication
Wireless transmission of vital body data and ambient magnetic field with wearable IoT device attached smart textile
No full textThe use of smart textiles is expanding. The wearer's data are transferred to the Cloud by a mobile device, and shared with authorized parties. The study aims to monitor continuously and share our wearable smart textile's heartbeat, body temperature, and the surrounding magnetic field data, providing early intervention before negative health events occur, or a high magnetic field is of concern to its wearer. A heartbeat sensor, a temperature sensor, and an ESP32 module with a built-in Hall effect sensor were integrated with a special conductive wire woven fabric. The data measured by the sensors were sent to the cloud server wirelessly by the ESP32. Our custom-made software analyzes the collected data with statistical methods, enabling the generation of predictions and early warnings. The generated reports can be sent to the smart textile user, doctors, and authorized third-party health institutions, and relevant magnetic field authorities. Our study shows that the body temperature reported by the designed smart textile has less than a 2.0% error compared with the actual value. On the other hand, the reported heartbeat has a 11.0% error, as it largely depends on sensor quality and placement location. In addition to these, continuous monitoring of the ambient magnetic field has been achieved with smart textiles. Our smart textile design sends the wearer's body temperature, heartbeat, and surrounding magnetic field information to a cloud server automatically and wirelessly. Our custom-made software and mobile application use the data to provide early warnings and live reports on users' mobile devices.Materials Science, Textile
Theoretical Exergoenvironmental Analysis of a Tunnel Furnace and Drying System in a Brick Production
No full textThe performance of a tunnel furnace and a tunnel dryer in a brick production was exergoenvironmentally assessed. The real production data of a brick factory in Turkey with a daily production capacity of 392 tons of fired bricks were used in the analysis. The exergoenvironmental factor of the control volume was calculated as 0.87. The specific exergoenvironmental cost of the control volume was determined to be 559.55 euro/h, 3.39 eurocent/ kg fired brick and 1.94 eurocent/MJ. The specific exergoeconomic cost and the environmental damage prevention cost were obtained to be 0.41 euro cent/MJ and 1.53 euro cent/MJ, respectively. Because the ratio of exergoenvironmental cost to sales price of 2.41 euro cent / kg fired brick was 1.41 (above 1), it was concluded that the brick production in Turkey was not sustainable in terms of exergoenvironmental analysis.Multidisciplinary Science
Performance Attributes of Environmental, Social, and Governance Exchange-Traded Funds
No full textRecently, interest in socially responsible investing has grown, including new investment vehicles such as environmental, social, and governance exchange-traded funds (ESG ETFs). Despite their rising popularity, few studies have attempted to examine the performance characteristics of these stylized funds. This study aimed to fill this knowledge gap by elaborating on the performance attributes of ESG ETFs and examining fund managers' security selection and market timing skills. Our results suggest that these funds generally underperform relative to conventional ETFs in many aspects. Additionally, the market timing skills of fund managers require improvement but are comparable to those of conventional ETFs. These results are robust to selecting the individual funds and alternative indices used in the sample. Furthermore, both the security selection and market timing skills of ESG ETF managers deteriorated significantly during the COVID-19 pandemic. Finally, the results indicate a slightly weaker cointegrated relationship between ESG ETFs and their benchmark indices when compared to conventional ETFs, suggesting that potential investors in ESG ETFs should carefully inspect the funds to make informed decisions.Economic
Robust, extended goal programming with uncertainty sets: an application to a multi-objective portfolio selection problem leveraging DEA
No full textThis study presents a two-phase approach of Data Envelopment Analysis (DEA) and Goal Programming (GP) for portfolio selection, representing a pioneering attempt at combining these techniques within the context of portfolio selection. The approach expands on the conventional risk and return framework by incorporating additional financial factors and addressing data uncertainty, which allows for a thorough examination of portfolio outcomes while accommodating investor preferences and conservatism levels. The initial phase employs a super-efficiency DEA model to streamline asset selection by identifying suitable investment candidates based on efficiency scores, setting the stage for subsequent portfolio optimization. The second phase leverages the Extended GP (EGP) framework, which facilitates the comprehensive incorporation of investor preferences to determine the optimal weights of the efficient assets previously identified within the portfolio. Each goal is tailored to reflect specific financial factors spanning both technical and fundamental aspects. To tackle data uncertainty, robust optimization is applied. The research contributes to the robust GP (RGP) literature by analyzing new RGP variants, overcoming limitations of traditional and other uncertain GP models by incorporating uncertainty sets. Robust counterparts of the EGP models are accordingly developed using polyhedral and combined interval and polyhedral uncertainty sets, providing a flexible representation of uncertainty in financial markets. Empirical results, based on real data from the Tehran Stock Exchange comprising 779 assets, demonstrate the superiority of the proposed approach over traditional portfolio selection methods across various uncertainty settings. Additionally, a comprehensive sensitivity analysis investigates the impact of uncertainty levels on the robust EGP models. The proposed framework offers guidance to investors and fund managers through a pragmatic approach, enabling informed and robust portfolio decisions by considering efficiency, uncertainty, and extended financial factors.Operations Research & Management Scienc
Assessment of exergy-based performance and sustainability indicators of a sewage water source heat pump system
No full textExergy analysis helps identify the amount and the positions of exergy losses in any system along with its main components. To achieve sustainability, these irreversibilities should be diminished. This study aims at presenting the exergetic-based performance of a sewage water source heat pump system based on experimental data. Initially, the exergetic performance assessments are carried out and then the exergetic performance results are evaluated using exergy-based sustainability indicators. The SWSHP system had the values for exergetic efficiency 57.77%-63.81% and overall sustainability index 2.31-2.72, respectively. Eight other exergy-based indicators are applied to determine and compare the most impacted component among the others.Thermodynamics || Energy & Fuel
Design and production of ıntegrated compact M-SIW filter-patch antenna with out-of-band suppression for 5G applications
No full textIn this article, the Integrated M-SIW (Microstrip-Substrate Integrated Waveguide) band-pass filter-patch antenna (IMBPF-PA) design with 5.90 GHz resonant frequency and the out-of-band suppression is presented, produced and measured for 5G applications using the CST (Computer Simulation Technology) Studio Suite program. The out-of- band frequencies in the 1.50-12.00 GHz wide operating frequency region are suppressed in the BPIGF-PA design. The antenna gain increase in the simulation results of the filter-antenna compared to the patch antenna is 0.32% and the in-band frequency range increase is 22%. In the measurement, the antenna gain increase was 0.78% and the in-band frequency range increase was 14.4%.Engineering, Multidisciplinar