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Elevated temperature mechanical characteristics and fracture behavior of a novel beta titanium alloy
No full textIn the present work, the elevated-temperature deformation characteristics and microstructural evolution of a Ti-5V-5Mo-5Cr-4Al alloy in solution-treatment conditions were studied under a tensile load at temperatures in the range of 25 to 550 °C and strain rates between 0.001 and 0.1 s−1. The results obtained indicated that, essentially, dynamic recovery (DRV) was the dominant softening mechanism in the case of the regimes considered. An analysis based on transmission electron microscopy (TEM) and the assessment of the mechanical behavior of the solution-heat-treated Ti-5V-5Mo-5Cr-4Al alloy revealed that dynamic precipitation (DPN) only took place at a strain rate of 0.001 s−1 and at temperatures of 450 °C and 500 °C. Void coalescence occurred upon an increase in the deformation temperature and a decrease in the strain rate due to a higher rate of diffusion and the provision of sufficient time for growth, respectively. The results obtained in the present study pave the way for the robust processing of this novel β titanium alloy. Depending on the deformation parameters, the deformation characteristics can be governed by either DRV (at moderate temperatures) or DPN (at moderate temperatures and at low rates of deformation).Publisher versio
Growth of NGVs and comparative study of cylinder material for CNG storage
No full textIn the present paper, the growth of Natural Gas Vehicles (NGVs) and the various pressure vessels used for storing compressed natural gas (CNG) is discussed.Also, the comparison of Von-mises stress in pressure vessels (PVs) due to internal pressure with different materials has been investigated numerically.Substantial use of natural gas is recorded as an alternative fuel, and the high-pressure storage of natural gas has resulted in using various types of cylinders in automobiles.Metal cylinders are extensively used in NGVs and are fabricated with different materials to satisfy services, safety and related factors.Metals and their alloys are often employed to make type I cylinders.It is important to calculate the failure pressure limit for a particular geometry of the tank against the yield strength of the material in case of metallic cylinders. An axisymmetric finite element model was made using the ABAQUS finite element platform to mimic the stress levels for two materials, viz steel alloy, and an aluminium alloy.The internal test pressure and geometric details of the cylinder were kept constant.The yield stress of material and numerical results have been compared.It was found that the steel alloy has outperformed the aluminium alloy for the given thickness of the cylinder.In contrast, the aluminium alloy failed to sustain the test pressure of 25 MPa.ESTCON ; Ministry of Higher Education, Malaysia ; Universiti Teknologi Petrona
Feature extraction for enhancing data-driven urban building energy models
No full textBuilding energy demand assessment plays a crucial role in designing energy-efficient building stocks. However, most studies adopting a data-driven approach feel the deficiency of datasets with building-specific information in building energy consumption estimation. Hence, the research objective of this study is to extract new features within the climate, demographic, and building use type categories and increase the accuracy of a non-parametric regression model that estimates the energy consumption of a building stock in Seattle. The results show that adding new features to the original dataset from the building use type category increased the regression results with a 6.8% less error and a 30.8% higher R2 Score. Therefore, this study shows that building energy consumption estimation can be enhanced via new feature extraction equipped with domain knowledge
Collaboration in co-located collaborative digital games - towards a quadripartite taxonomy
No full textIn this paper, we propose a taxonomy for the classification of collaborative interaction situations derived from studying a set of co-located collaborative gameplay sessions. The taxonomy builds on the MDA framework and Activity Theory (AT) as top-level attributes, and offers the analytical dimensions WHAT, WHO, WHEN and HOW, each containing a number of sub-categories, for evaluating different levels of collaborative interaction mediated by games. The work is based on a three stage process: design of game instances, data collection, and analysis of play sessions. This taxonomy is an initial step towards capturing the complexity of collaboration mediated by games, and helps in understanding and studying collaboration as a phenomena in game design. Our preliminary work provides a characterization of multiple dimensions of collaborative interaction, providing game designers a starting point for deeper understanding into collaborative interaction mediated by a collocated gameplay.European Commission ; Aarhus Universitets Forskningsfon
Noise analysis of mode matched vibratory gyroscopes
No full textMEMS (micro-electromechanical system) vibratory gyroscopes have attracted a lot of interest recently and these gyroscopes made their way through portable devices and smart phones. However, their performance is not enough to cope with the demanding requirements of applications such as dead reckoning. Mode-matched gyroscopes can be a solution for this problem. Various mode-matched gyroscope architectures have been proposed and their noise performances have been analyzed in detail. However, in most of these analyses zero-rate output was considered and the noise analysis for dynamic cases were ignored. In this paper, we demonstrate the noise analysis of mode-matched vibratory gyroscope using the power spectral density (PSD) and the Allan deviation methods while in rotation. We show that for mode-matched gyros the noise performance of a rotating gyro can be significantly different from that of a gyro that does not experience any rotation. We also show that this difference is due to the coupling between the drive and sense systems via Coriolis force. This sets a fundamental limit for the noise performance of mode-matched vibratory gyroscopes where ARW (angle random walk) increases proportionally with the rotation rate for the open loop and the force to rebalance operation modes.TÜBİTA
A new sensitivity-based mapping scheme for topology optimization of graded TPMS designs
No full textGraded TPMS topologies display excellent mechanical and thermal properties. Design schemes targeting optimal performance exist, but final reconstructed designs still suffer from performance degradation. To overcome this challenge, we propose an automated design framework based on the integration of a homogenization-based topology optimization scheme and a new mapping strategy. Optimized designs obtained using a modified SIMP technique are reconstructed as graded gyroid structures. Unlike mapping strategies using relative density values prior to TPMS infill, for the first time, we make use of readily available adjoint sensitivities for mapping optimal densities to graded gyroid structures. Results show that the proposed framework delivers performance-preserving graded designs when compared to original optimized designs obtained using OptiStruct and superior performance in comparison to standard density-based mapping methods. The resulting graded design is manufactured using additive manufacturing, and three-point bending tests are performed confirming simulation results and demonstrating the applicability of the presented design scheme.TÜBİTA
Economic lot sizing problem with tank scheduling
No full textWe introduce a multiple-item economic lot sizing problem where items are produced through the fermentation of some raw materials. Fermentation takes place in specialized tanks that have finite capacities, and duration of the fermentation process is item dependent. When fermentation starts, the tanks are not available for the duration of the fermentation process. We analyze the complexity of this problem under various assumptions on the number of items and tanks. In particular, we show that several cases of the problem are (strongly) NP-hard, and we propose polynomial time algorithms to some single item cases. In addition, we propose a quick and simple heuristic approach for one of the multiple item cases
Advancing humanoid robots for social integration: Evaluating trustworthiness through a social cognitive framework
No full textTrust is an essential concept for human-human and human-robot interactions. Yet only a few studies have addressed this concept from a robot perspective - that is, forming robot trust in interaction partners. Our previous robot trust model relies on assessing the trustworthiness of the interaction partners based on the computational cognitive load incurred during the interactive task [1]. However, this model does not take into account the social markers indicative of trustworthiness, such as the gestures displayed by a human partner. In this study, we make a step toward this point by extending the model by integrating a social cue processing module to achieve social human-robot interaction. This new model serves as a novel social cognitive trust framework to enable the Pepper robot to evaluate the trustworthiness of its interaction partners based on both cognitive load (i.e., the cost of perceptual processing) and social cues (i.e., their gestures). For evaluating the efficacy of the framework, the Pepper robot with the developed model is put to interact with human partners who may take the roles of a reliable, unreliable, deceptive, or random suggestion providing partner. Overall, the results indicate that the proposed framework allows the Pepper robot to differentiate the guiding strategies of the partners by detecting deceptive partners and thus select a trustworthy partner in case of a free choice to perform the next task.German Research Foundation (DFG) ; International Joint Research Promotion Program, Osaka University ; Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) Japan Society for the Promotion of Scienc
Aderanssız yumuşak çelik donatının aderanssız ard germeli prefabrik duvar sistemlerinin deprem davranışı üzerindeki etkileri
No full textSeismic energy dissipation of precast concrete lateral force-resisting systems constructed based on non-emulative or jointed connections is very limited since these systems experience little to no damage during seismic events. One of the additional seismic energy dissipation mechanisms for unbonded post-tensioned precast concrete shear walls, which are constructed based on jointed connections, is using unbonded mild steel reinforcement over the wall joints, where joint gap opening occurs under lateral loads. Seismic energy dissipation is achieved by cyclic yielding of unbonded mild steel reinforcement both in tension and compression. Post-tensioned steel tendons are provided to resist lateral forces and minimize permanent drifts under seismic loads. Effects of unbonded mild steel bars on the system energy dissipation capacity and permanent drifts are not documented comprehensively for non-emulative precast concrete lateral force resisting systems. The main objective of this study is to investigate the effects of the mild steel design parameters on the seismic behavior of non-emulative unbonded post-tensioned precast concrete shear wall systems. In this study, a developed numerical finite element (FE) model is verified for a jointed post-tensioned precast concrete shear wall system with experimental data. The experimentally verified modeling approach is used to develop FE models for several 5- story unbonded post-tensioned shear walls to investigate the effects of unbonded mild steel design parameters such as steel amount, location along the joint, and unbonded length on wall lateral behavior including its self-centering, energy dissipation capacity, and permanent prestress force losses for the unbonded tendons. The nonlinear structural behavior of the walls was determined by performing monotonic and cyclic pushover analyses, and nonlinear time history analysis with the OpenSees software. The finding of this study provides new and valuable contributions to the existing literature to further improve the seismic design of non-emulative precast lateral force resisting systems and provide a better understanding of the influence of unbonded mild steel on the seismic performance of jointed precast concrete walls.Prefabrik duvar panellerinin birleşim yerlerinde ıslak beton kullanılmadan oluşturulan kuru bağlantılı aderanssız ard germeli prefabrik (AAP) duvar sistemleri yanal deprem kuvvetleri etkisinde sırasında çok az veya hiç yapısal hasar görmediğinden bu sistemlerin deprem enerji sönümleme kapasitesi çok sınırlıdır ve bundan dolayı göreli kat ötelemeleri genelde büyüktür. Bu sistemlerin deprem enerjisini sönümleme kapasitesini artırmak ve kat ötelemelerini sınırlamak için ek sismik enerji sönümleme mekanizmalarından biri, deprem yükleri altında kat duvar panellerin birleşim derzlerinde oluşan açılmadan faydalanarak bu derzler üzerinde aderanssız yumuşak çelik donatı kullanılmasıdır. Sismik enerji sönümlenmesi hem çekme hem de basma kuvvetleri altında aderanssız yumuşak çelik donatının döngüsel akması ile sağlanır. Literatürdeki çalışmalarda, kuru bağlantılı prefabrik sistemlerin deprem yükleri gibi yanal kuvvetler altında aderanssız yumuşak çelik çubuklar kullanılarak sağlanabilecek enerji sönümleme kapasiteleri, bu çubukların detaylı tasarım ilkeleri ve duvarlardan oluşan taşıma sisteminin sahip olduğu kendinden merkezlenme (ihmal edilebilir kalıcı ötelenme) özelliği üzerindeki etkileri kapsamlı bir şekilde incelenmemiştir. Bu çalışmanın temel amacı, aderanssız yumuşak çelik donatının tasarım parametrelerinin belirlenmesi ve bu parametrelerin AAP duvar sistemlerinin sismik davranışı üzerindeki etkilerini araştırmaktır. Bu çalışmada, kuru bağlantılı aderanssız ard germeli prefabrik duvar sistemleri için geliştirilmiş bir sayısal sonlu eleman (FE) modeli deneysel verilerle doğrulanmıştır. Bir dizi beş katlı aderanssız ard germeli perde duvar için sonlu eleman modelleri oluşturulmuştur. Bu duvarlar sistemleri için aderanssız yumuşak çelik donatı miktarı, duvarların birleşim derzi boyunca bu donatının konumu ve donatının aderanssız bırakılan boyu gibi bu donatının tasarım parametrelerinin, duvar sisteminin kendi kendine merkezlenme, enerji sönümleme kapasitesi ve deprem sonrası aderanssız ard germe çubuklarında oluşan ard germe kuvvetinde oluşan germe kayıpları gibi duvar sisteminin deprem davranışı üzerindeki etkileri araştırılmıştır. Sismik tasarımı yapılan duvarların deprem yükleri altındaki yapısal davranışları, OpenSees analiz programı kullanılarak yapılan doğrusal olmayan itme analizleri (pushover), döngüsel (tersinir) kuvvet-yer değiştirme (cyclic) ve doğrusal olmayan zaman tanım alanında dinamik analizlerle belirlenmiştir. Bu çalışmadan elde edilen veriler, kuru bağlantılı aderanssız ard germeli prefabrik duvar sistemlerinin deprem tasarımını geliştirmek, deprem enerjisini sönümlemek için derzler boyunca duvar panelleri arasında kullanılan aderanssız yumuşak çeliğin tasarım ilkelerini ortaya koymak ve bu enerji sönümleme donatısının bu prefabrik duvar sistemlerinin sismik performansı üzerindeki etkilerinin daha iyi anlaşılmasını sağlamak için mevcut literatüre yeni ve değerli katkılar sağlamaktadır
IBAM: IPFS and blockchain based authentication for MQTT protocol in IoT
No full textDecentralized systems have proven themselves as a dominant authentication and storage paradigm for IoT systems where smartwatches are integrated with MQTT messaging framework for transmitting medical data to doctors. However, the security concerns with centralized frameworks presented vital security challenges regarding data privacy and network security for healthcare systems. This paper will present an integrated framework involving a reliable and lightweight e-health data-sharing framework that combines the decentralized interplanetary file system (IPFS) and blockchain on a smartwatch platform. Particularly, this framework helps in trustworthy control mechanisms which use smart contracts to achieve authentication and storage for both subscribers and publishers. We presented a simulation using Ethereum blockchain and IPFS in a real data-sharing scenario with the MQTT protocol. Our analysis proved that our approach satisfies lightweight access control requirements since it demonstrates the low latency of the framework and optimized energy consumption with high security and data privacy levels