Faculty of Engineering

Permanent URI for this communityhttps://hdl.handle.net/10679/10

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Contributions to humanitarian and non-profit operations: Equity impacts on modeling and solution approaches
(Springer, 2019-09-14) Koyuncu, Burcu Balçık; Smilowitz, K.; Industrial Engineering; KOYUNCU, Burcu Balçık
Equity has been acknowledged as an important concern in designing and managing humanitarian and non-profit operations over the past decade. Given the significant demands for relief supplies created by a disaster and the scarcity of resources (such as supplies, vehicles, equipment), it is inevitable that some needs will be satisfied later than others, and effective prioritization is crucial. Relief organizations are faced with the challenge of finding ways to deliver resources in an equitable way to increase the chances of survival of people. These issues also emerge in the operations of non-profit organizations that allocate distribute scarce resources. Important contributions have been made by women in studying equity in humanitarian and non-profit operations, both in terms of practical insights and methodological advances. In this chapter, we review key papers written by women, which have advanced the literature in characterizing equity in humanitarian and non-profit operations and exploring the methodological implications of equity.
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Design and implementation of VLC-based smart barrier gate systems
(Elsevier, 2021-07) Rasti-Meymandi, A.; Madahian, A.; Abouei, J.; Mirvakili, A.; HajiAkhondi-Meybodi, Z.; Mohammadi, A.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, an innovative and smart Visible Light Communication (VLC)-based Intelligent Transportation System (ITS) is designed. The proposed system uses vehicle LED headlamps as a remote controller. Differential Pulse Position Modulation (DPPM) is utilized for the sake of its asynchronicity. The system features an innovative optical interference cancellation mechanism to address the unwanted variable DC component and AC line noise in the received signal. The feasibility of the proposed system is demonstrated experimentally in day and night conditions using an off-the-shelf LED headlights. The Bit Error Rate (BER) performance of the system in terms of angular position of the vehicle with respect to the VLC receiver at different link ranges is evaluated. The prototype successfully demonstrates the smart control over the barrier gate using the ATmega microcontrollers family for the outdoor environment. BER of lower than 10(-3) is achieved for a maximum link range of 4.4 meters.
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Handbook of thermal science and engineering
(Springer Nature, 2018-07-05) Kulacki, F. A.; Acharya, S.; Chudnovsky, Y.; Cotta, R. M.; Devireddy, R.; Dhir, V. K.; Mengüç, Mustafa Pınar; Mostaghimi, J.; Vafai, K.; Mechanical Engineering; Kulacki, F. A.; MENGÜÇ, Mustafa Pınar
This Handbook provides researchers, faculty, design engineers in industrial R&D, and practicing engineers in the field concise treatments of advanced and more-recently established topics in thermal science and engineering, with an important emphasis on micro- and nanosystems, not covered in earlier references on applied thermal science, heat transfer or relevant aspects of mechanical/chemical engineering. Major sections address new developments in heat transfer, transport phenomena, single- and multiphase flows with energy transfer, thermal-bioengineering, thermal radiation, combined mode heat transfer, coupled heat and mass transfer, and energy systems. Energy transport at the macro-scale and micro/nano-scales is also included. The internationally recognized team of authors adopt a consistent and systematic approach and writing style, including ample cross reference among topics, offering readers a user-friendly knowledgebase greater than the sum of its parts, perfect for frequent consultation. The Handbook of Thermal Science and Engineering is ideal for academic and professional readers in the traditional and emerging areas of mechanical engineering, chemical engineering, aerospace engineering, bioengineering, electronics fabrication, energy, and manufacturing concerned with the influence thermal phenomena.
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Hierarchical mixtures of generators for adversarial learning
(IEEE, 2019) Ahmetoğlu, A.; Alpaydın, Ahmet İbrahim Ethem; Computer Science; ALPAYDIN, Ahmet Ibrahim Ethem
Generative adversarial networks (GANs) are deep neural networks that allow us to sample from an arbitrary probability distribution without explicitly estimating the distribution. There is a generator that takes a latent vector as input and transforms it into a valid sample from the distribution. There is also a discriminator that is trained to discriminate such fake samples from true samples of the distribution; at the same time, the generator is trained to generate fakes that the discriminator cannot tell apart from the true samples. Instead of learning a global generator, a recent approach involves training multiple generators each responsible from one part of the distribution. In this work, we review such approaches and propose the hierarchical mixture of generators, inspired from the hierarchical mixture of experts model, that learns a tree structure implementing a hierarchical clustering with soft splits in the decision nodes and local generators in the leaves. Since the generators are combined softly, the whole model is continuous and can be trained using gradient-based optimization, just like the original GAN model. Our experiments on five image data sets, namely, MNIST, FashionMNIST, UTZap50K, Oxford Flowers, and CelebA, show that our proposed model generates samples of high quality and diversity in terms of popular GAN evaluation metrics. The learned hierarchical structure also leads to knowledge extraction.
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An investigation into the optothermal behavior of a high power red light emitting diode: impact of an optical path
(ASME, 2021-03) Muslu, Ahmet Mete; Özlük, Burak; Arık, Mehmet; Mechanical Engineering; ARIK, Mehmet; Muslu, Ahmet Mete; Özlük, Burak
Monochromatic light emitting diodes (LEDs) are getting more attention day by day for a very wide range of applications such as general lighting, signage, automotive lighting, display, water purification, and skin imaging. While they are taking place in a large number of applications, thermal challenges associated with the operation of LEDs have become a significant issue to address since their performance is greatly affected by thermal conditions. Thus, this study focuses on identifying thermal, optical, and electrical characteristics of an AlGaInP-based red LED considering the impact of the LED dome on the chip performance. The junction temperature measurement results obtained with forward voltage change method were validated with thermal imaging method (TIM) and computational models. It was observed that the LED dome may critically affect the thermal, optical, and electrical behaviors of the LED chip. In fact, a 3.7% increase in junction temperature and a 6.1% drop in optical conversion efficiency were found at the normal operation of the red LED after the LED dome was removed. The results were also compared with a blue LED, and lower junction temperatures were measured for the red LED at each driving current. The difference in junction temperature became even more noticeable at higher driving currents. Results have shown a good agreement between three different methods with a maximum variation of 6.9%.
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Molecular modeling of MOF membranes for gas separations
(World Scientific Publishing Co., 2017-01-01) Fındıkçı, İlknur Eruçar; Keskin, S.; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar
Metal organic frameworks (MOFs) have received significant attention as membrane materials in the last decade. MOFs typically have high porosities, tunable pore sizes, large surface areas, reasonable thermal and mechanical stabilities. These properties make them ideal membrane materials for gas separations. Considering the very large number of available MOF structures, it is not practically possible to test membranebased gas-separation performance of MOFs using purely experimental means. Molecular modeling methods are highly useful to complement experimental studies by providing insights into the gas-separation mechanisms of MOFs. Molecular simulation studies have been recently used to screen large numbers of MOFs for gas separation applications to identify the most promising MOF membranes. In this way, experimental efforts, time, and resources can be directed to the materials with the highest separation performance. The aim of this chapter is to review the recent advances in molecular modeling of MOF membranes for gas-separations and address the current opportunities and challenges in using molecular simulations for MOF membranes.
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Transdisciplinarity as a learning challenge: Student experiences and outcomes in an innovative course on wearable and collaborative robotics
(IEEE, 2023-06) Kılıç-Bebek, Ebru; Nizamis, K.; Vlutters, M.; Bebek, Özkan; Karapars, Gülhis Zeynep; Ünal, Ramazan; Yılmaz, Deniz; Uğurlu, Regaip Barkan; Industrial Design; Sectoral Education and Professional Development; Mechanical Engineering; Mitchell, J.; BEBEK, Ebru Kılıç; KARAPARS, Gülhis Zeynep; BEBEK, Özkan; ÜNAL, Ramazan; UĞURLU, Regaip Barkan; Yılmaz, Deniz
Contribution: This study provides evidence for the benefit of short online courses for transdisciplinary competence development of graduate students. It shows the significant challenges students face while learning, and provides instructional recommendations to improve students’ learning quality and professionalism. Background: Developing wearable and collaborative robots requires industry collaboration and transdisciplinary competence. Industry’s involvement in long-term programs is becoming infeasible, and the nature of transdisciplinary learning has not been explored to inform instructional practices. Intended Outcomes: This study aimed to provide instructional recommendations based on an in-depth examination of a diverse group of graduate students’ learning and teamwork experiences as well as outcomes in a 5-day online transdisciplinary course. Application Design: 31 graduate students of engineering, industrial design, and health fields from 4 countries participated in online mixed-discipline instructional sessions and teams to address a real industry challenge. A mixed-methods approach was used to examine students’ experiences and learning outcomes based on a competence measure, session participation data, student journal entries, team progress reports, team elaboration visuals, and final team presentations. Findings: Students’ knowledge of industrial design, medical considerations, ethics and standards, effective teamwork, and self-regulated learning were increased. Students’ high motivation helped them deal with the challenges involved. Daily student journals, team reports, and visual elaboration tools were found to be beneficial for determining the challenges and learning quality. The observed student progress within 5 days is promising, making it worthwhile to further explore the benefits of short online courses for increasing graduates’ readiness and establishing university-industry collaborations in education.

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