6,671 research outputs found
Are sutural structures in biology the optimal topological design?
No full textSutural structures are widely observed in biology and attract lots of attention. However, the majority of current research focuses on understanding the characteristics of sutural structures, with little research investigating whether sutural structures in biology are the optimal topological design. To disclose this mystery, this paper summarizes the characteristics of sutural structures found in nature and characterizes their shapes by several important geometric parameters. By establishing analytical models and finite element models of sutural structures, we investigate the stiffness, strength, and damping energy dissipation properties of sutural structures in biomaterials and optimized the sutural shapes based on genetic algorithm (GA) under static tensile and shear loading, as well as dynamic uniaxial loading. Under static loading, sutural structures with interlocking features demonstrate great stiffness and strength. Under dynamic loading, the frequency of the external excitation and the sutural shapes jointly determine the energy dissipation performance. We find that the sutural shapes in typical biomaterials evolve to optimal shapes to achieve certain optimal mechanical properties. Additionally, genetic algorithms provide a paradigm for the design of materials with multi-objectives, allowing for the design of sutural structures that balance various mechanical properties
Native p-type transparent conductive CuI via intrinsic defects
No full textThe ability of CuI to be doped p-type via the introduction of native defects has been investigated using first-principles pseudopotential calculations based on density functional theory. The Cu vacancy has a lower formation energy than any of the other native defects, which include I vacancy (V(I)), Cu interstitial (Cu(i)), I interstitial (I(i)), Cu antisite (Cu(I)), and I antisite (I(Cu)). Combined with its shallow acceptor level, it offers sufficient hole concentrations in CuI. The natural band alignments as compared to zinc-blende ZnS, ZnSe, and ZnTe have also been calculated in order to further identify the p-type dopability of CuI. It is found that CuI has a relatively high valence band maximum and conduction band minimum, which also makes it easy to dope CuI p-type in terms of the doping limit rule. In addition, the small effective mass of the light hole-about 0.303m(0)-can provide high mobility and p-type conductivity in CuI. All of these results make CuI an ideal candidate for native p-type materials (C) 2011 American Institute of Physics. [doi:10.1063/1.3633220
Atomistically-informed hardening and kinetics models of helium bubble in irradiated tungsten
No full textIn fusion reactor environment, helium bubble acts as a crucial inducement to the performance degradation of plasma facing tungsten, leading to irradiation hardening and embrittlement. The dislocation interacted with helium bubble directly controls the service reliability and safety of irradiated materials. However, the fundamental question regarding the mechanism and quanti-tative model of this interaction between dislocation and helium-bubble remains largely unex-plored. Based on systematic molecular dynamics studies, the interaction mechanism phase diagram is built as a function of helium bubble characters for different types of dislocations. The atomistically-informed mechanism-based models of irradiation hardening and dislocation-helium bubble reaction kinetics are developed, which consider the climb behavior of edge dislocation, the temperature dependent mobility of screw dislocation, as well as the effects of helium-to-vacancy ratio and size of helium bubble. These models can be directly used in micro and meso scale simulations, such as discrete dislocation dynamics and crystal plasticity models. Further-more, the models well predict the macroscopic experimental results
Youthhood
No full textTESTING-GROUND issue 03, Youthhood, examines worlds through youthful eyes, makes evident young ambitions, and questions how we can better empower young people to design cities, landscapes, and a planet that works for them. The issue includes contributions from: Carmel Keren, Jude Daniel Smith, Claire Edwards, Kazeem Kuteyi, Emmanuel Adarkwah, Reza Nik, Dan Cui, Kristofer Cullum-Fernandez, Fida Sassi, Simeon Shtebunaev, Daze Aghaji, Averill Dimabuyu, Sarri Elfaitouri, Rebecca McDonald-Balfour, and Ed Wall.
Rebecca McDonald-Balfour (Author), Jude Daniel Smith (Author), Daze Aghaji (Author), Carmel Keran (Author), Alexis Liu (Author), Dan Cui (Author), Kristofer Cullum-Fernandez (Author), Fida Sassi (Author), Averill Dimabuyu (Author), Ed
Impact damage of composite laminates with high-speed waterjet
No full textRain erosion may cause substantial damage to aircrafts during supersonic flight. Such event is investigated here via high-speed waterjet impact on composite laminates. An experimental setup is developed to produce waterjets with the speed up to 700m/s and a finite element model of the waterjet-composite impact event is established. The consistency of experiment and simulation results validates the adopted numerical methods. The distribution of the water-hammer pressure is non-uniform and the maximum pressure occurs near the contact periphery when the water is about to eject laterally. After a high-speed (300∼560m/s) waterjet impacts a composite laminate, the impacted surface depression is observed, and the typical surface damage presents a central region with no visible surface damage surrounded by a faded “failure ring” with resin removal, matrix cracking and minor fiber fracture. Delamination occurs at the interfaces of adjacent layers with unequal dimensions and longitudinal matrix cracking appears on the back surface. Both the velocity and the diameter of waterjets are crucial factors on CFRP damage extents. Water-hammer pressure, the stagnation pressure and propagation of stress waves are failure mechanisms for most matrix damage in CFRP impacted by waterjets.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Structural Integrity & Composite
Sampling and Reconstruction of Signals on Product Graphs
No full textIn this paper, we consider the problem of subsampling and reconstruction of signals that reside on the vertices of a product graph, such as sensor network time series, genomic signals, or product ratings in a social network. Specifically, we leverage the product structure of the underlying domain and sample nodes from the graph factors. The proposed scheme is particularly useful for processing signals on large-scale product graphs. The sampling sets are designed using a low-complexity greedy algorithm and can be proven to be near-optimal. To illustrate the developed theory, numerical experiments based on real datasets are provided for sampling 3D dynamic point clouds and for active learning in recommender systems.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Signal Processing System
Ban dao ti yi zhi jie gou zai guang cui hua he guang dian cui hua zhong de yan jiu
No full textLi, Qian = 半導體异质结构在光催化和光電催化中的研究 / 李乾.Thesis Ph.D. Chinese University of Hong Kong 2015.Includes bibliographical references (leaves 145-162).Abstracts also in Chinese.Title from PDF title page (viewed on 30, December, 2016).Li, Qian = Ban dao ti yi zhi jie gou zai guang cui hua he guang dian cui hua zhong de yan jiu / Li Qian
A Conversational User Interface for Instructional Maintenance Reports
No full textMaintaining a complex system, such as a modern production line, is a knowledge-intensive task. Many firms use maintenance reports as a decision support tool. However, reports are often poor quality and tedious to compile. A Conversational User Interface (CUI) could streamline the reporting process by validating the user's input, eliciting more valuable information, and reducing the time needed. In this paper, we use a Technology Probe to explore the potential of a CUI to create instructional maintenance reports. We conducted a between-groups study (N = 24) in which participants had to replace the inner tube of a bicycle tire. One group documented the procedure using a CUI while replacing the inner tube, whereas the other group compiled a paper report afterward. The CUI was enacted by a researcher according to a set of rules. Our results indicate that using a CUI for maintenance reports saves a significant amount of time, is no more cognitively demanding than writing a report, and results in maintenance reports of higher quality. Internet of ThingsHuman-Centred Artificial Intelligenc
The Logic of Knowledge-Based Cooperation in the Social Dilemma
No full textComputer Science, Artificial IntelligenceComputer Science, Theory & MethodsCPCI-S(ISTP)
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