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Dynamic multi-UAV path planning for multi-target search and connectivity
No full textIn this work, we propose and analyze multi-drone path planners for multi-target search and connectivity. The goal of the unmanned aerial vehicle (UAV) mission is to search an unknown area to detect, connect and monitor multiple randomly distributed targets to the ground control station (GCS) while maintaining the connectivity of the UAVs to GCS. To this end, we propose to use two types of UAVs: search and relay. The search drones scan the area via onboard sensors, whereas relay UAVs provide connectivity. We propose three different responses to target detection with increasing adaptability: (i) follow pre-planned paths and inform GCS when possible, (ii) follow pre-planned paths and inject new UAVs to monitor the detected targets, (iii) assign a search UAV to monitor target, and re-plan remaining UAV paths. Furthermore, we implement multi-objective optimization-based planners for single-type UAVs, where the paths are optimized in terms of total coverage time and percentage connectivity. Our results show that less adaptive schemes detect all targets faster; however, the connectivity of the UAVs and the targets to GCS is significantly better for the adaptive schemes. The joint-optimization methods, on the other hand, in their basic form, trade-off detection time to improve connectivity. When they are used in conjunction with relays, the connectivity performance is improved; however, the overall mission times may be up to 40% higher than our proposed methods, depending on the number of UAVs and targets.TÜBİTA
Cultural tourism and rural community resilience: A framework and its application
No full textRural heritage settlements have encountered many challenges and risks due to the rapid evolution of the cultural tourism economy, such as changing demographics, overcrowding, evolving consumer demands, and biodiversity loss. Conservation of environmental and sociocultural assets of these rural settlements and strengthening community resilience have been considered indispensable in global sustainable development. In this regard, a growing body of research has investigated the implications to wider issues of environmental sustainability through lessons learned from these rural, vernacular settlements. However, discussions on transformation driven by tourism and socio-cultural resilience in rural contexts have attracted limited attention. Contributing to this gap in the literature, based on a longitudinal survey study (spanning from 2000 to 2022) conducted in Behramkale (rural, vernacular village in Turkiye), this paper investigates rural community resilience strategies adopted by residents to cope with transformation led by cultural tourism and strict heritage conservation restrictions. The study results showed that the new development area (new settlement) of the village served as an infrastructure of the old settlement, by means of a home for the local residents, and an economic asset for the village. The establishment of the new settlement, to some extent, prevented the displacement of local residents and provided the continuation of the traditional rural economy in the village.Publisher versio
A finite element based homogenization code in python: hompy
No full textThe ability to predict the effective material property of composites with periodic micro -structures based on homogenization theory has been an effective method to analyze structures with complex heterogeneities. Homogenization codes have been made available for educational purposes including the homogenization code for the prediction of effective elasticity and thermal material properties in MATLAB. The aim of this educational paper is to present a Python version of the existing homogenization code and provide detailed diagrams of its key modules extending its ability to conduct analysis and design studies possibly via integration into commercial FEM software. Python has become a popular programming language due to its wide applicability to several disciplines, its portability, its flexibility by means of programming paradigms, its open -source nature, its well -documented libraries, and its easy -to -learn syntax. To increase the applicability and community reach of the homogenization algorithm presented, we provide a Python translation of the wellknown MATLAB implementation. By doing so, we aim to increase the integration potential and adaptability of the homogenization approach to other computing packages and target adoption by a wider audience by leveraging the advantages of basing the solution on a free and open -source platform
Simulation of migration paths using agent-based modeling: The case of Syrian refugees en route to Turkey
No full textThe decade-long Syrian civil war has triggered a significant migration wave in the Middle East, with Turkey hosting the largest number of Syrian refugees. Our study introduces an agent-based model (ABM) designed to simulate and predict migration paths in potential future refugee crises. The primary goal is to support aid organizations in planning the delivery of essential aid services during migration movements, offering insights that can be applied to various geographical areas and migration scenarios. While we use the Syrian refugee movement to Turkey as a case study, the model is intended as a flexible tool for analyzing migration patterns in future crises. The proposed ABM considers two characteristics of refugee groups: level of risk sensitivity and level of information. To enhance the model's functionality, we have extended the A* algorithm with a cost metric to calculate the weighted average of distance and risk to a destination point. Our case study examines the crisis in southern Idlib through six scenarios, offering insights into refugee numbers, migration paths, camp occupancy rates, and heat maps of densely populated regions for each scenario. Validation is performed by comparing model outcomes with situation reports and official statements from the relevant period, demonstrating the proposed ABM's potential for adaptation to other migration instances and further analysis under different parameters.TÜBİTA
Culinary sustainability as a resilience practice for Syrian refugees amidst urban precarity in Istanbul
No full textIn a context of urban precarity and food insecurity, our research examines how Syrian women in Istanbul (Turkey) (re-)create "Syrian cultural foods" as part of fulfilling gendered expectations for homemaking. Fleeing civil war since 2011, Syrians find safety in Turkey, but they struggle with a financially and politically insecure temporary protection status making the daily act of cooking a significant challenge. In contrast to research focused on sustainability primarily in terms of health and nutrition, we show the important role that culture plays in determining what food is considered sustaining. Specifically, we identify "culinary sustainability" strategies which are culturally embedded food practices that foster resilience for migrants in a new setting. Based on semi-structured interviews and participant observations in the kitchens of Syrian women in Istanbul, we identify three strategies: 1) Homemade food practices, 2) Adjustment, and 3) Recycling. Addressing a burgeoning literature that tries to integrate sustainability and resilience studies, we show how each strategy corresponds to a feature of cultural resilience (engaging forms of resistance, adaptation and innovation). Under severe socio-economic constraints, Syrian women use creative adaptations to innovate tasty new ways of showing culinary care in a new country and an unfamiliar megacity, Istanbul.TÜBİTA
Underwater visible light communication (UVLC)
No full textThe rising demand for underwater communication systems stems from the expanding range of human activities in underwater realms, including scientific data collection, environmental monitoring, military and national security uses, and oil field exploration. While wire-line systems, especially optical fibers, offer real-time communication, their inflexibility, high costs, and operational drawbacks limit their practical use, fueling the need for underwater wireless communication. Acoustic signaling is a common choice, enabling transmission over kilometers but with quite limited data rates, thus hindering high-bandwidth applications. For shorter ranges, optical communication emerges as a highcapacity alternative, utilizing the transparency of water to transmit blue or green light. Modeling the underwater optical channel is particularly important for designing effective Underwater Visible Light Communication (UVLC) systems. The traditional Beer-Lambert law faces limitations, leading to exploration of alternative models for accurate predictions. Evaluating UVLC performance reveals that the propagation distance is limited to tens of meters in non-turbid water under ideal conditions. However, this distance can decrease due to other factors, including turbulence-induced fading, which affects link fidelity. Therefore, solutions are needed to improve link fidelity and overcome the limitations
Bayesian optimization of passive RF circuits
No full textThis paper presents a study on the application of Bayesian algorithm to the optimization of passive RF circuits. We evaluate the efficiency of Bayesian Optimization in improving performance parameters and compare it to commonly used algorithms. The methodology employs Gaussian Processes as surrogate models and acquisition functions for efficient optimization. Experimental results on RF circuit parameters showcase the effectiveness of Bayesian Optimization in handling complex, nonlinear optimization problems
Perakendeciler için tersine lojistik üzerine makaleler.
No full textAs the retail industry expands and evolves, particularly with the growth of e-commerce, retailers are increasingly faced with higher levels of product returns. With this increase, it is no longer feasible to dispatch returned products to outlets or landfills; hence, retailers must re-evaluate returns in their inventories to maximize profits while minimizing the environmental impact of unsold merchandise. In the fast fashion retail sector, handling product returns has become a significant challenge due to rapidly changing consumer preferences and high product return rates. In Chapter 2, we aim to study a retailer's optimal inventory control policy under product returns to maximize expected profit. We model a period's returns to be stochastically dependent on the previous period's sales quantity. Using dynamic programming formulation, we solve for the optimal periodic review inventory policy and provide structural results on the optimal policy of the final period. Through numerical studies, we show that incorporating detailed sales-dependent returns could increase a retailer's expected profit by 23%. Ignoring this dependency in determining the optimal inventory policy results in increased order frequency, higher levels of backorders, and more leftovers, but above all could lead to a significant overestimation of the resulting profit. In managing inventories, retailers must consider product return flows arriving from various sales periods and are obligated to track detailed sales and return data meticulously. In Chapter 3 we present an optimal inventory control policy for a retailer facing stochastic product returns over multiple periods to maximize expected profit during a single selling season consisting of finite periods. The problem is formulated using dynamic programming, and due to its computational complexity, we propose an Approximate Dynamic Programming value iteration algorithm using basis functions. Our proposed algorithm reduces the solution time drastically without a significant sacrifice from optimality and generates solutions for instances that are not solvable exactly otherwise. We assess the significance of utilizing detailed return information and show that our proposed model enhances retailers' profits compared to a model aggregating return information. We also show the increase in profit improvement under conditions of mark-down pricing or order capacity constraints. Retailers often employ various sales channels, concurrently managing both brickand- mortar and online stores. Implementing an omnichannel approach aims to harmonize the customer experience across all platforms; hence, customers encounter uniform pricing, service quality, and return conditions whether they purchase in-store or online. In Chapter 4, we present the optimal solution for the finite horizon, lost sales model, considering the complex structure of the omnichannel system and the distinctive dynamics of the fast fashion retail sector. In our model, the retailer has a warehouse for online sales and a brick-and-mortar store for offline sales. Customers can purchase items online and return them to the warehouse or the brick-and-mortar store. In the case of offline sales, returns are restricted to the brick-and-mortar store, resulting in two distinct return flows with different return rates for the brick-andmortar store. We aim to determine the optimal pre-season order quantity for the warehouse, considering the sales of both channels, along with the transshipment order quantity from the warehouse to the brick-and-mortar store during the season. We formulate the problem using dynamic programming and present a sensitivity analysis that provides valuable business insights. This dissertation introduces an inventory control model where stochastic returns depend on previous sales. The model is enhanced by integrating returns from multiple periods and multiple channels with various extensions. Through an extensive computational study, we propose several managerial insights regarding optimal inventory policies.Perakende firmaları, e-ticaret satışlarının artmasıyla birlikte ürün iadelerinin artan düzeyleri ile başa çıkmak zorunda kalmışlardır. Bu artışla birlikte iade ürünleri artık outlet mağazaları veya atık sahalarına göndermek uygun olmamaktadır; bu nedenle perakendeciler, karlarını maksimize etmek ve çevresel etkileri minimize etmek için ürün iadelerini tekrar değerlendirmelidir. Bölüm 2'de, ürün iadelerinin önceki dönem satışlarına stokastik olarak bağlı olduğu orijinal ve zengin detayları olan bir stok yönetimi modeli çalışmaktayız. Optimal periyodik envanter yönetimi modelini dinamik programlama ile çözmekte, optimal kar politikasının bazı yapısal özelliklerini ve optimal envanter politikasının son periyodunu göstermekteyiz. Ürün iadelerini dikkate alan ve ürün iadelerini dikkate almadan net talep yöntemini kullanan iki firmanın karlılık karşılaştırmalarını, simülasyon kullanarak yaptığımız ön çalışmada, net talep kullanan modele göre karlılığın % 23 arttığını gözlemledik. Bu artışın özellikle sabit satın alma maliyeti, ön sipariş maliyeti ve iade oranına daha hassas olduğunu gözlemledik. Ürün iadelerini dikkate almayıp gerçek talep yerine net talep kullanıldığında iade oranları arttıkça ön siparişlerin ve buna bağlı olarak da sipariş sıklığının arttığını gözlemledik. Ürün iadelerini dikkate almamak, optimal stok politikasını belirlemede artan sipariş sıklığına, daha yüksek seviyede ön siparişlere ve daha fazla atığa neden olabilir, ancak en önemlisi, elde edilen kârın önemli bir şekilde olduğundan fazla tahmin edilmesine yol açabilir. Hızlı moda perakende sektöründe, hızla değişen tüketici tercihleri ve yüksek ürün iade oranları nedeniyle ürün iadeleri ile başa çıkmak önemli bir zorluk haline gelmiştir. Perakendeciler, envanterlerini yönetirken ürün iadelerini ve çevresel etkilerini dikkate almalıdır. Bölüm 3'te, bir perakendecinin satış sezonu boyunca beklenen kârı maksimize etmek amacı ile çok sayıda dönemden gelen stokastik ürün iadelerinin dahil edildiği optimal bir envanter kontrol politikası sunuyoruz. Detaylı iade bilgilerinin kullanımının değerini ölçümlüyor ve önerdiğimiz modelin özellikle dönem içinde fiyat indirimi uygulandığında veya sipariş kapasitesi kısıtlamaları olduğunda perakendecilerin kârını nasıl pozitif anlamda etkilediğini gösteriyoruz. Fakat bu sefer birden fazla periyoddan gelen satış ve iade bilgisinin hesaplama karmaşıklığı nedeniyle, dinamik programlamaya alternatif olarak Yaklaşık Dinamik Programlama değer iterasyonu algoritması da önermekteyiz. Önerdiğimiz algoritma, optimal çözüm sonucundan önemli bir fedakarlık yapmadan çözüm süresini büyük ölçüde azalmakta ve başka türlü kesin olarak çözülemeyen durumlar için bir alternatif üretmektedir. Perakendeciler genellikle çeşitli satış kanallarını kullanır, hem fiziksel hem de çevrimiçi (online) mağazaları aynı anda yönetirler. Bu kanallar genellikle bağımsız olarak işlev görmüş olsa da, çok kanallı (omnichannel) sistem yaklaşımıyla tüm platformlarda müşteri deneyimini birleştirmeyi amaçlarlar. Bu, müşterinin mağazada veya çevrimiçi olarak satın alma yapmasına bağlı olarak, aynı fiyat, hizmet kalitesi ve iade koşullarıyla karşılaşması anlamına gelir. Hedef, müşterilere alışveriş deneyimleri boyunca tek bir firmayla etkileşimde bulunduklarından emin olarak, onlara sorunsuz bir servis sağlamaktır. Bölüm 4'te, çok kanallı sistemin karmaşık yapısını ve hızlı moda perakende sektörünün karakteristik dinamiklerini dikkate alarak, süreli dönem, kayıp satış modeli için optimal bir çözüm sunuyoruz. Modelimizde, perakendecinin, çevrimiçi satışlar için bir deposu ve fiziki satışlar için de bir mağazası bulunmaktadır. Müşteriler, çevrimiçi satın alabilir ve ürünleri depoya veya mağazaya iade edebilirler; offline satışlar için iadeler, mağazayla sınırlıdır ve mağaza, farklı iade oranlarına sahip iki farklı iade akışıyla karşılaşır. Sezon boyunca her iki kanal için de optimal sipariş miktarını ve her dönemde deponun mağazaya sevk edilecek envanter miktarını belirlemeyi amaçlamaktayız. Bu tez, stokastik iadelerin önceki satışlara bağlı olduğu bir envanter kontrol modelini sunmaktadır. Model, birden çok dönemden ve kanaldan gelen iadelerin entegrasyonu ile geliştirilmiş olup, çeşitli uzantıları da çalışılmıştır. Kapsamlı bir hesaplama çalışması kullanarak, optimal envanter politikaları ile ilgili bir dizi yönetimsel içgörü de önermekteyiz
Building Information Modeling (BIM)-based on-site 3D printer position optimization and path planning for digital fabrication
No full textThe on-site integration of 3D printing and Building Information Modeling (BIM) has shown the potential to improve the production processes of digital fabrication with concrete. BIM can be used in the site planning and optimization of the digital fabrication process by optimally positioning the 3D printers on the construction site. In this work, a BIM-based 3D-printer position optimization and path planning tool was developed using the Dynamo plugin of the Autodesk Revit software. This tool works similarly to the BIM- based site layout optimization tools for the operation and positioning of major construction equipment (e.g., cranes). The developed tool considers the physical properties of a robotic arm 3D printer, such as its dimensions and printing range and the geometry and location of the elements to be printed on-site. It suggests the optimum path for the 3D printer to fabricate a project. The position optimization and path planning tool are validated for a case study of a real-world 3D-printed single-floor office building and successfully reduced the number of steps required for printing the walls of the case study building, enabling significant time and energy savings.TÜBİTAKPublisher versio
Role of anionic group of methylallyl ether-based PCEs on behavior of cementitious systems with various C3A contents
No full textIn this study, the performances of methylallyl ether (HPEG) type polycarboxylate ether-based water reducing admixtures (PCE) partially substituted with phosphate and sulfonate anionic groups were investigated. The effects of synthesized PCE's on the fresh, rheological, and some hardened properties of mixtures prepared with cements having different C(3)A contents were examined. Increasing the phosphate and sulfonate substitution ratio of PCE up to a certain value improved the rheological properties of the mixtures. Best flow retention and rheological properties were obtained with 9% phosphate (P9) and 7% sulfonate (S7) PCEs. Due to the high PCE dosage used in the Marsh-funnel and mini slump experiments, the nonadsorbed PCE in the pore solution blocked the adsorbed polymers on the cement particles. Also, the hydrodynamic radius of the polymer had a significant effect on the adsorption and dispersion performance of PCE. Morover, with the increase of cement C(3)A content, the fresh properties of the mixtures were adversely affected. However, the increase in C(3)A content up to a certain value improved the hardened properties of the cementitious system. (c) 2024 American Society of Civil Engineers.TÜBİTAK ; Ministry of National Education - Turke