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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Item Metadata only RIS-enhanced resilience in cell-free MIMO(VDE Verlag GmbH, 2023) 0000-0001-5566-2392; Weinberger, Kevin; Reifert, Robert-Jeron; Sezgin, Aydin; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Faculty Member; College of Engineering; 149116More and more applications that require high reliability and fault tolerance are realized with wireless network architectures and thus ultimately rely on the wireless channels, which can be subject to impairments and blockages. Hence, these architectures require a backup plan in the physical layer in order to guarantee functionality, especially when safetyrelevant aspects are involved. To this end, this work proposes to utilize the reconfigurable intelligent surface (RIS) as a resilience mechanism to counteract outages. The advantages of RISs for such a purpose derive from their inherent addition of alternative channel links in combination with their reconfigurability. The major benefits are investigated in a cell-free multiple-input and multiple-output (MIMO) setting, in which the direct channel paths are subject to blockages. An optimization problem is formulated that includes rate allocation with beamforming and phase shift configuration and is solved with a resilience-aware alternating optimization approach. Numerical results show that deploying even a randomly-configured RIS to a network reduces the performance degradation caused by blockages. This becomes even more pronounced in the optimized case, in which the RIS is able to potentially counteract the performance degradation entirely. Interestingly, adding more reflecting elements to the system brings an overall benefit for the resilience, even for timesensitive systems, due to the contribution of the RIS reflections, even when unoptimized.Publication Metadata only Magnetically steerable bacterial microrobots moving in 3D biological matrices for stimuli-responsive cargo delivery(American Association for the Advancement of Science (AAAS), 2022) Akolpoglu, Mukrime Birgul; Alapan, Yunus; Dogan, Nihal Olcay; Baltaci, Saadet Fatma; Yasa, Oncay; Tural, Gulsen Aybar; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Sitti, Metin; Faculty Member; School of Medicine; College of Engineering; 297104Bacterial biohybrids, composed of self-propelling bacteria carrying micro/nanoscale materials, can deliver their payload to specific regions under magnetic control, enabling additional frontiers in minimally invasive medicine. However, current bacterial biohybrid designs lack high-throughput and facile construction with favorable cargoes, thus underperforming in terms of propulsion, payload efficiency, tissue penetration, and spatiotemporal operation. Here, we report magnetically controlled bacterial biohybrids for targeted localization and multistimuliresponsive drug release in three-dimensional (3D) biological matrices. Magnetic nanoparticles and nanoliposomes loaded with photothermal agents and chemotherapeutic molecules were integrated onto Escherichia coil with similar to 90% efficiency. Bacterial biohybrids, outperforming previously reported E. coli-based microrobots, retained their original motility and were able to navigate through biological matrices and colonize tumor spheroids under magnetic fields for on-demand release of the drug molecules by near-infrared stimulus. Our work thus provides a multifunctional microrobotic platform for guided locomotion in 3D biological networks and stimuli-responsive delivery of therapeutics for diverse medical applications.Publication Metadata only Programmable aniso-electrodeposited modular hydrogel microrobots(American Association for the Advancement of Science (AAAS), 2022) Zheng, Zhiqiang; Wang, Huaping; Demir, Sinan Ozgun; Huang, Qiang; Fukuda, Toshio; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Sitti, Metin; Faculty Member; School of Medicine; College of Engineering; 297104Systems with programmable and complex shape morphing are highly desired in many fields wherein sensing, actuation, and manipulation must be performed. Living organisms use nonuniform distributions of their body structural composition to achieve diverse shape morphing, motion, and functionality. However, for the micro -robot fabrication, these designs often involve complicated robotic architectures requiring time-consuming and arduous fabrication processes. This paper proposes a single-step aniso-electrodeposition method for fabricat-ing modular microrobots (MMRs) with distinct functions in each modular segment. By programming the electric field, the microscale stripe-shaped structure can be endowed with diverse shape-morphing capabilities, such as spiraling, twisting, bending, and coiling. The proposed fabrication method can develop MMRs with multiple independent modules onto which cells, drugs, and magnetic nanoparticles can be loaded to achieve multifunc-tionality. Thus, MMRs can perform multiple tasks, such as propulsion, grasping, and object delivery, simultane-under control and ionic and stimuli.Publication Metadata only A new crossover operator for single machine total weighted tardiness problem with sequence dependent setup times(Gazi Üniversitesi, 2012) Kartal, Zuhal; Hasgül, Servet; N/A; Kirlik, Gökhan; PhD Student; Graduate School of Sciences and Engineering; N/AThe single machine total weighted tardiness problem with sequence dependent setup times is a challenging and heavily studied problem. This problem is NP-hard, so several heuristics have been proposed in the literature so far. One of them is the genetic algorithm. The genetic algorithm is both powerful solution technique and applicable to wide range of different problem types, although its performance is heavily parameter and operator dependent. It is seen in literature that the well-conducted and adapted genetic algorithm operators and parameters increase the solution quality. In this study, a new crossover operator is proposed for the single machine with sequence dependent setup times problem to minimize the total weighted tardiness. The proposed crossover operator improves the relative positions by using apparent tardiness cost with setups (ATCS) heuristic while preserving the absolute positions. These are the two main aspects of the permutation type crossover operators for scheduling problems. The performance of the proposed crossover operator is tested by comparing it with partially mapped crossover (PMX) in different test cases using benchmark instances from literature. It is shown that the proposed ATCS based crossover operator gives better results than PMX in all test problems.