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69th International Astronautical Congress: #InvolvingEveryone, IAC 2018

作者： Kyle, Rankin Neerav, Shah John, Krizmanic Steven, Stochaj Asal, Naseri Department of Mechanical and Aerospace Engineering New Mexico State University United States Goddard Space Flight Center NASA United States CRESST NASA GSFC University of Maryland Baltimore County United States Klipsch School of Electrical and Computer Engineering New Mexico State University United States Program Manage/Systems Engineer Space Dynamics Laboratory United States

The Virtual Telescope for X-Ray Observations (VTXO) is an Astrophysics SmallSat mission being developed to demonstrate 10-milliarcsecond X-ray imaging using a Phase Fresnel Lense (PFL)-based space telescope. PFLs promise to provide several orders of magnitude improvement in angular resolution over current state of the art X-ray optics. However, PFLs for astronomical applications requires a very long focal length, for VTXO the focal length is estimated to be in the range of 0.5 km to 4 km. Since these focal lengths are not feasible on a single spacecraft, the proposed solution is to use two separate spacecraft, one with the lense(s), and the second with an X-ray camera. These two spacecrafts will then fly in a formation approximating a single rigid telescope. In order to achieve this configuration, the two spacecraft must maintain the formation a focal length distance apart, with centimeter level control, and sub-millimeter level knowledge requirements. Additionally, for the telescope to achieve sufficient exposure time, the system must keep the telescope axis pointed at a fixed target on the celestial sphere for durations on the order of a few hours. VTXO's system architecture calls for two CubeSats to operate in a highly eccentric Earth orbit with one of the spacecraft's traveling on a natural keplarian orbit. The second spacecraft will then fly on a â€œpseudoâ€¥ orbit maintaining a fixed offset relative to the celestial sphere during observations. Observations with this system will occur near apogee where differential forces on the spacecrafts are minimal which in turn minimizes fuel consumption. The â€œpseudoâ€¥ orbit where the second spacecraft is located is not quite a stable orbit requiring small continuous propulsion to maintain formation. This paper and presentation will overview VTXO's system architecture, additionally it will look in depth at the formation flying techniques, including fuel consumption, and methods for establishing, and maintaining the form

关键词： Orbits

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Imaging real-time amorphization of hybrid perovskite solar cells under electrical biasing

arXiv

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arXiv 2020年

作者： Kim, Min-Cheol Ahn, Namyoung Cheng, Diyi Xu, Mingjie Pan, Xiaoqing Kim, Suk Jun Luo, Yanqi Fenning, David P. Tan, Darren H.S. Zhang, Minghao Ham, So-Yeon Jeong, Kiwan Choi, Mansoo Meng, Ying Shirley Department of NanoEngineering University of California San Diego 9500 Gilman Drive San diegoCA92093 United States Global Frontier Center for Multiscale Energy Systems Seoul National University Seoul08826 Korea Republic of Materials Science and Engineering Program University of California San Diego 9500 Gilman Drive San diegoCA92093 United States Irvine Materials Research Institute University of California Irvine IrvineCA92697 United States Department of Materials Science and Engineering University of California Irvine IrvineCA92697 United States Department of Physics and Astronomy University of California Irvine IrvineCA92697 United States School of Energy Materials and Chemical Engineering Korea University of Technology and Education Cheonan31253 Korea Republic of University of California San Diego San diegoCA92093 United States Department of Mechanical Engineering Seoul National University Seoul08826 Korea Republic of

Perovskite solar cells have drawn much attention in recent years, owing to its world-record setting photovoltaic performances. Despite its promising use in tandem applications and flexible devices, its practicality is still limited by its structural instability often arising from ion migration and defect formation. While it is generally understood that ion instability is a primary cause for degradation, there is still a lack of direct evidence of structural transformation at the atomistic scale. Such an understanding is crucial to evaluate and pin-point how such instabilities are induced relative to external perturbations such as illumination or electrical bias with time, allowing researchers to devise effective strategies to mitigate them. Here, we designed an in-situ TEM setup to enable real-time observation of amorphization in double cation mixed perovskite materials under electrical biasing at 1 V. It is found that amorphization occurs along the (001) and (002) planes, which represents the observation of in-situ facet-dependent amorphization of a perovskite crystal. To reverse the degradation, the samples were heated at 50 oC and was found to recrystallize, effectively regaining its performance losses. This work is vital toward understanding fundamental ion-migration phenomena and address instability challenges of perovskite optoelectronics. Copyright © 2020, The Authors. All rights reserved.

关键词： Perovskite

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Current md forcefields fail to capture key features of protein structure and fluctuations: a case study of cyclophilin a and t4 lysozyme

arXiv

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arXiv 2020年

作者： Mei, Zhe Grigas, Alex T. Treado, John D. Corres, Gabriel Melendez Vuorte, Maisa Sammalkorpi, Maria Regan, Lynne Levine, Zachary A. O’Hern, Corey S. Department of Chemistry Yale University New HavenCT06520 United States Integrated Graduate Program in Physical and Engineering Biology Yale University New HavenCT06520 United States Graduate Program in Computational Biology and Bioinformatics Yale University New HavenCT06520 United States Department of Mechanical Engineering and Materials Science Yale University New HavenCT06520 United States Department of Biology UPR Humacao Puerto RicoHumacao00792 Puerto Rico Department of Chemistry and Materials Science School of Chemical Engineering Aalto University Aalto Finland Department of Bioproducts and Biosystems School of Chemical Engineering Aalto University Aalto Finland Institute of Quantitative Biology Biochemistry and Biotechnology Center for Synthetic and Systems Biology School of Biological Sciences University of Edinburgh Edinburgh United Kingdom Department of Pathology Yale School of Medicine New HavenCT06520 United States Department of Molecular Biophysics and Biochemistry Yale University New HavenCT06520 United States Department of Physics Yale University New HavenCT06520 United States Department of Applied Physics Yale University New HavenCT06520 United States

Globular proteins undergo thermal fluctuations in solution, while maintaining an overall well-defined folded structure. In particular, studies have shown that the core structure of globular proteins differs in small, but significant ways when they are solved by x-ray crystallography versus solution-based NMR spectroscopy. Given these discrepancies, it is unclear whether molecular dynamics (MD) simulations can accurately recapitulate protein conformations. We therefore perform extensive MD simulations across multiple force fields and sampling techniques to investigate the degree to which computer simulations can capture the ensemble of conformations observed in experiments. By analyzing fluctuations in the atomic coordinates and core packing, we show that conformations sampled in MD simulations both move away from and sample a larger conformational space than the ensemble of structures observed in NMR experiments. However, we find that adding inter-residue distance restraints that match those obtained via Nuclear Overhauser Effect measurements enables the MD simulations to sample more NMR-like conformations, though significant differences between the core packing features in restrained MD and the NMR ensemble remain. Given that the protein structures obtained from the MD simulations possess smaller and less dense protein cores compared to those solved by NMR, we suggest that future improvements to MD forcefields should aim to increase the packing of hydrophobic residues in protein cores. © 2020, CC BY.

关键词： Molecular dynamics

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Linearization of two-state thruster models

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Journal of Physics: Conference Series 2020年第1期1490卷

作者： Dieky Adzkiya Hendro Nurhadi Teguh Herlambang Department of Mathematics Institut Teknologi Sepuluh Nopember Indonesia Center of Excellence for Mechatronics and Industrial Automation Research Center Institut Teknologi Sepuluh Nopember Indonesia Department of Industrial Mechanical Engineering Institut Teknologi Sepuluh Nopember Indonesia Study Program of Information Systems Universitas Nahdlatul Ulama Surabaya Indonesia

A thruster is a device used for station keeping, attitude control, in the reaction control system, or long-duration, low-thrust acceleration. Thruster is one of the main components in autonomous surface vehicle. In th...

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Performance Management systems for Project Management Offices: A Case-Based Study

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Procedia Manufacturing 2019年 39卷 923-931页

作者： Rafael Duarte Fernando Deschamps Edson Pinheiro de Lima André Pepino Rene Marcel Guzman Clavijo Universidade Positivo R. Prof. Pedro Viriato Parigot de Souza 5300 Curitiba - PR 81280-330 Brazil Industrial and Systems Engineering Graduate Program (PPGEPS) – Pontifical Catholic University of Parana (PUCPR) R. Imac. Conceição 1155 Curitiba - PR 80215-901 Brazil Department of Mechanical Engineering (DEMEC) Federal University of Parana (UFPR) Av. Cel. Francisco H. dos Santos 230 - Centro Politécnico Bloco IV Curitiba - PR 81530-000 Brazil Federal University of Technology – Parana (UTFPR)

Project Management Offices (PMOs) are organizational structures in charge of managing and coordinating several simultaneous projects within companies. Due to the complexity of different projects’ objectives, it’s usual to simplify project indicators and control them by means of the well-known triple constraint or “iron triangle”: scope, cost and time. This approach does not account for the organizational strategy, internal and external stakeholders’ interests, nor other specific indicators. The problems due to the lack of integration caused by this oversimplification are yet amplified in complex project portfolios related to technology development and deployment, since in this kind of scenario the marketing competition demands new features, at lower costs, in no time. These points could be addressed by operations management approaches, such as the Performance Management systems Design Framework (PMSDF). To identify the viability and relevance in using this method in PMOs, this work adopts a mixed methods research. Is begins with a Systematic Literature Review to better understand performance management routine and tools in PMO. It was followed by meetings with two project management consultants, to identify the best practices, habits and advises, to check the differences between practitioner and academic views. Finally, it was conducted interviews with the PMO Director of a trucks’ manufacturer and a PMO Manager in an agrarian-cattle-breeding cooperative, to verify how such companies measure their PMO’s successes. The last step was to adapt the PMSDF to the project management context, evaluating the PMO operation in a medium-sized software development company and propose the restructuration of its Performance Management System.

关键词： PMS PMO KPI Operations Strategy PMSDF

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On the comparison of three numerical methods applied to building simulation: finite-differences, RC circuit approximation and a spectral method.

arXiv

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arXiv 2019年

作者： Berger, Julien Gasparin, Suelen Dutykh, Denys Mendes, Nathan Univ. Grenoble Alpes Univ. Savoie Mont Blanc CNRS LOCIE Chambéry73000 France Univ. Grenoble Alpes Univ. Savoie Mont Blanc CNRS LAMA Chambéry73000 France Thermal Systems Laboratory Mechanical Engineering Graduate Program Pontifical Catholic University of Paraná Rua Imaculada Conceição 1155 Curitiba - ParanáCEP: 80215-901 Brazil

Predictions of physical phenomena in buildings are carried out by using physical models formulated as a mathematical problem and solved by means of numerical methods, aiming at evaluating, for instance, the building thermal or hygrothermal performance by calculating distributions and fluxes of heat and moisture transfer. Therefore, the choice of the numerical method is crucial since it is a compromise among \(i\) the solution accuracy, \(ii\) the computational cost to obtain the solution and \(iii\) the complexity of the method implementation. An efficient numerical method enables to compute an accurate solution with a minimum computational run time \(CPU\). On that account, this article brings an investigation on the performance of three numerical methods. The first one is the standard and widely used finite-difference approach, while the second one is the so-called RC approach, which is a particular method brought to the building physics area by means of an analogy of electric circuits. The third numerical method is the spectral one, which has been recently proposed to solve nonlinear diffusive problems in building physics. The three methods are evaluated in terms of accuracy on the assessment of the dependent variable \(temperature or vapor pressure\) or of density of fluxes for three different cases: i\) heat diffusion through a concrete slab, ii\) moisture diffusion through an aerated concrete slab and iii\) heat diffusion using measured temperatures as boundary conditions. Results highlight the spectral approach as the most accurate method. The RC based model with a few number of resistances does not provide accurate results for temperature and vapor pressure distributions neither to flux densities nor conduction loads. Copyright © 2019, The Authors. All rights reserved.

关键词： Numerical methods

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Design and Simulation of a Porous Rectangular Board-Foldable Trolley

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IOP Conference Series: Materials Science and engineering 2019年第1期644卷

作者： Yau-Ren Shiau Jiunn Fang Yu-Lan Chen Department of Industrial Engineering and Systems Management Feng Chia University Taichung 407 Taiwan Department of Aerospace and Systems Engineering Feng Chia University Taichung 407 Taiwan Ph.D. Program of Mechanical and Aeronautical Engineering Feng Chia University Taichung 407 Taiwan

To reduce the structural weight and volume and satisfy an optimal balance of performance constraints, a study using a porous rectangular foldable board and structurally improved trolley model was conducted, and motion simulations were performed to derive the static and transient structural properties. The simulations revealed that the fatigue lifetimes of both the main structure and the porous boards were in a high-standard-value range, whereas the transient analysis indicated that both the directional deformation and equivalent stress exhibited minimal local values. For porous boards simply supported only on two sides, the trolley had a much smaller collapsed volume than other types of trolley. The static analysis indicated that this trolley prototype had a good safety coefficient and long fatigue lifetime. The transient analysis showed that the porous area had a higher strength and bending load than the non-porous area. The overall transient response was close to that of a steady-state, showing a negligible effect on the ***.

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Author Correction: Insights from a multiscale framework on metabolic rate variation driving glioblastoma multiforme growth and invasion

Communications engineering

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Communications engineering 2025年第1期4卷 59页

作者： Meitham Amereh Shahla Shojaei Amir Seyfoori Tavia Walsh Prashant Dogra Vittorio Cristini Ben Nadler Mohsen Akbari Department of Mechanical Engineering University of Victoria 3800 Finnerty Road Victoria V8P 5C2 BC Canada. Laboratory for Innovations in MicroEngineering (LiME) University of Victoria 3800 Finnerty Road Victoria V8P 5C2 BC Canada. Centre for Advanced Materials and Related Technologies (CAMTEC) University of Victoria 3800 Finnerty Road Victoria V8P 5C2 BC Canada. Department of Anatomy and Cell Sciences University of Manitoba 66 Chancellors Cir Winnipeg R3B 2E9 MB Canada. Mathematics in Medicine Program Department of Medicine Houston Methodist Research Institute 6670 Bertner Ave. Houston 77030 TX USA. Department of Physiology and Biophysics Weill Cornell Medical College 1300 York Ave. New York 10065 NY USA. Neal Cancer Center Houston Methodist Research Institute 6670 Bertner Ave. Houston 77030 TX USA. Department of Imaging Physics University of Texas M.D. Anderson Cancer Center 1515 Holcombe Blvd Houston 77030 TX USA. Physiology Biophysics and Systems Biology Program Graduate School of Medical Sciences Weill Cornell Medicine 1300 York Ave. New York 10065 NY USA. Department of Mechanical Engineering University of Victoria 3800 Finnerty Road Victoria V8P 5C2 BC Canada. makbari@uvic.ca. Laboratory for Innovations in MicroEngineering (LiME) University of Victoria 3800 Finnerty Road Victoria V8P 5C2 BC Canada. makbari@uvic.ca. Centre for Advanced Materials and Related Technologies (CAMTEC) University of Victoria 3800 Finnerty Road Victoria V8P 5C2 BC Canada. makbari@uvic.ca. School of Biomedical Engineering University of British Columbia 2329 West Mall Vancouver V6T 1Z4 BC Canada. makbari@uvic.ca.

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Considering discrepancy when calibrating a mechanistic electrophysiology model

arXiv

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arXiv 2020年

作者： Lei, Chon Lok Ghosh, Sanmitra Whittaker, Dominic G. Aboelkassem, Yasser Beattie, Kylie A. Cantwell, Chris D. Delhaas, Tammo Houston, Charles Novaes, Gustavo Montes Panfilov, Alexander V. Pathmanathan, Pras Riabiz, Marina Weber dos Santos, Rodrigo Worden, Keith Mirams, Gary R. Wilkinson, Richard D. Computational Biology & Health Informatics Dept. of Computer Science University of Oxford United Kingdom MRC Biostatistics Unit University of Cambridge United Kingdom Centre for Mathematical Medicine & Biology School of Mathematical Sciences University of Nottingham United Kingdom Department of Bioengineering University of California San Diego United States Systems Modeling and Translational Biology GlaxoSmithKline R&D Stevenage United Kingdom ElectroCardioMaths Programme Centre for Cardiac Engineering Imperial College London United Kingdom CARIM School for Cardiovascular Diseases Maastricht University Netherlands Graduate Program in Computational Modeling Universidade Federal de Juiz de Fora Brazil Department of Physics and Astronomy Ghent University Belgium Laboratory of Computational Biology and Medicine Ural Federal University Ekaterinburg Russia U.S. Food and Drug Administration Center for Devices and Radiological Health Office of Science and Engineering Laboratories United States Department of Biomedical Engineering King’s College London Alan Turing Institute United Kingdom Dynamics Research Group Department of Mechanical Engineering University of Sheffield United Kingdom School of Mathematics and Statistics University of Sheffield United Kingdom

Uncertainty quantification (UQ) is a vital step in using mathematical models and simulations to take decisions. The field of cardiac simulation has begun to explore and adopt UQ methods to characterise uncertainty in model inputs and how that propagates through to outputs or predictions. In this perspective piece we draw attention to an important and under-addressed source of uncertainty in our predictions — that of uncertainty in the model structure or the equations themselves. The difference between imperfect models and reality is termed model discrepancy, and we are often uncertain as to the size and consequences of this discrepancy. Here we provide two examples of the consequences of discrepancy when calibrating models at the ion channel and action potential scales. Furthermore, we attempt to account for this discrepancy when calibrating and validating an ion channel model using different methods, based on modelling the discrepancy using Gaussian processes (GPs) and autoregressive-moving-average (ARMA) models, then highlight the advantages and shortcomings of each approach. Finally, suggestions and lines of enquiry for future work are provided. Copyright © 2020, The Authors. All rights reserved.

关键词： Uncertainty analysis

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A study on static structural of non-rotor unmanned aerial vehicle 5

A study on static structural of non-rotor unmanned aerial ve...

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5th International Multi-Conference on engineering and Technology Innovation, IMETI 2016

作者： Chen, Yu-Lan Fang, Jiunn Shiau, Yau-Ren Hung, Wei-Chun Ph.D. Program of Mechanical and Aeronautical Engineering Feng Chia University Taichung407 Taiwan Department of Aerospace and Systems Engineering Feng Chia University Taichung407 Taiwan Department of Industrial Engineering and Systems Management Feng Chia University Taichung407 Taiwan

Multi-rotor unmanned aerial vehicles (UAVs) have become common in recent years, but non-rotor UAVs are still relatively rare. This study used an aerodynamic model to replace the multi-rotor design concept and examine load bearing capabilities, specifically for delivery of medical goods by non-rotor UAV. We use static structural simulations for static analysis and fatigue analysis to investigate the capabilities of different structural materials. The simulation results combined fatigue strength verifications, structural safety factor calculations, and finite element analyses to calculate parameters like total deformation, stress ratios, and strain magnitudes to analyze structural fatigue life. The analyses indicated that the factors of safety and fatigue lifetimes of two structural materials far exceeded standard values. They can be used to optimize designs that prevent plastic deformation and breakage. Time and money are saved in the research and development process by carrying out these calculations and static analyses of physical properties before prototypes are actually built. © The Authors, published by EDP Sciences, 2017.

关键词： Safety factor

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