High-Dimensional Bayesian Optimisation with Large-Scale Constraints -- An Application to Aeroelastic Tailoring

Design optimisation potentially leads to lightweight aircraft structures with lower environmental impact. Due to the high number of design variables and constraints, these problems are ordinarily solved using gradient-based optimisation methods, leading to a local solution in the design space while the global space is neglected. Bayesian Optimisation is a promising path towards sample-efficient, global optimisation based on probabilistic surrogate models. While Bayesian optimisation methods have demonstrated their strength for problems with a low number of design variables, the scalability to high-dimensional problems while incorporating large-scale constraints is still lacking. Especially in aeroelastic tailoring where directional stiffness properties are embodied into the structural design of aircraft, to control aeroelastic deformations and to increase the aerodynamic and structural performance, the safe operation of the system needs to be ensured by involving constraints resulting from different analysis disciplines. Hence, a global design space search becomes even more challenging. The present study attempts to tackle the problem by using high-dimensional Bayesian Optimisation in combination with a dimensionality reduction approach to solve the optimisation problem occurring in aeroelastic tailoring, presenting a novel approach for high-dimensional problems with large-scale constraints. Experiments on well-known benchmark cases with black-box constraints show that the proposed approach can incorporate large-scale constraints.Comment: Conference paper submitted to AIAA Scitech 2024 Foru

Managing data sharing in OpenStack Swift with Over-Encryption

The sharing of large amounts of data is greatly facilitated by the adoption of cloud storage solutions. In many scenarios, this adoption could be hampered by possible concerns about data confidentiality, as cloud providers are not trusted to know the content of the data they store. Especially when the data are organized in objects, the application of an encryption layer is an interesting solution to this problem, because it offers strong confidentiality guarantees with a limited performance overhead. In a data sharing scenario, the management of access privileges then requires an adequate support for key derivation and for managing policy evolution. We present a solution that provides transparent support for the encryption of objects stored on Swift. Our system offers an efficient management of the updates to the access control policy, including revocation of authorizations from some of the sharing users. We explore several alternatives for the architecture, associated with distinct levels of transparency for the applications, and integrate different options for the management of policy updates. Our implementation and experiments demonstrate the easy integration of the approach with existing cloud storage solutions

Evaluation of a large set of patients with Autoimmune Polyglandular Syndrome from a single reference centre in context of different classifications

Purpose: To characterize patients with APS and to propose a new approach for their follow-up. Query ID="Q1" Text="Please check the given names and familynames." Methods: Monocentric observational retrospective study enrolling patients referred to the Outpatients clinic of the Units of Endocrinology, Diabetology, Gastroenterology, Rheumatology and Clinical Immunology of our Hospital for Autoimmune diseases. Results: Among 9852 patients, 1174 (11.9%) [869 (73.9%) female] were diagnosed with APS. In 254 subjects, the diagnosis was made at first clinical evaluation (Group 1), all the other patients were diagnosed with a mean latency of 11.3 ± 10.6 years (Group 2). Group 1 and 2 were comparable for age at diagnosis (35.7 ± 16.3 vs. 40.4 ± 16.6 yrs, p =.698), but different in male/female ratio (81/173 vs 226/696, p =.019). In Group 2, 50% of patients developed the syndrome within 8 years of follow-up. A significant difference was found after subdividing the first clinical manifestation into the different outpatient clinic to which they referred (8.7 ± 8.0 vs. 13.4 ± 11.6 vs. 19.8 ± 8.7 vs. 7.4 ± 8.1 for endocrine, diabetic, rheumatologic, and gastroenterological diseases, respectively, p <.001). Conclusions: We described a large series of patients affected by APS according to splitters and lumpers. We propose a flowchart tailored for each specialist outpatient clinic taking care of the patients. Finally, we recommend regular reproductive system assessment due to the non-negligible risk of developing premature ovarian failure

General-purpose finite element solver based on Python and Cython

The `pyfe3d` module is a general-purpose finite element solver for structural analysis and optimization based on Python and Cython. The main principles guiding the development of `pyfe3d` are: simplicity, efficiency and compatibility. The aimed level of compatibility allows one to run this solver in any platform, including the Google Colab environment.Please, cite this software using: Saullo G. P. Castro. (2023). General-purpose finite element solver based on Python and Cython (Version 0.4.1). Zenodo. DOI: https://doi.org/10.5281/zenodo.6573489

Nucleophilic displacement reactions in ionic liquids: Substrate and solvent effect in the reaction of NaN3 and KCN with alkyl halides and tosylates

Room-temperature ionic liquids have been used as environmentally benign solvents for the preparation of primary and secondary alkyl azides and nitriles under solid-RTIL phase-transfer conditions. The reaction of primary, secondary, and tertiary halides or tosylates with KCN and NaN3 has been investigated in three ionic liquids ([bmim] [PF6], [bmim] [N(Tf)(2)], and [hpyr] [N(Tf)(2)]). The observed nucleofugacity scales for the reaction of NaN3 are similar to those reported for the same process in cyclohexane, indicating that in these solvents it is possible to evidence the intrinsic ability to depart of leaving groups. Changes in the nature of the IL cation or anion determine significant modifications in reactivity of the investigated substrates. Reactivity has been interpreted considering a gradual shift of the mechanism from concerted S(N)2 (primary substrates) to stepwise S(N)1 (tertiary substrate, 3), through the nucleophilically assisted formation of an ion pair intermediate, in the case of 2d

Data set for bionic simulation of double clap-and-fling wing mechanism with SPH FSI method

&lt;p&gt;Data set containing the rigid-body based flapping wing models coupled with smoothed particle hydrodynamics (SPH), by means of &lt;a href="https://github.com/DualSPHysics/DualSPHysics/wiki/9.-New-in-DualSPHysics#new-in-dualsphysics-v50"&gt;DualSPHysics version 5.0 &lt;/a&gt;and &lt;a href="https://projectchrono.org/download/"&gt;Project Chrono&lt;/a&gt;.&lt;/p&gt;&lt;p&gt;These models are part of the paper:&lt;/p&gt;&lt;blockquote&gt;&lt;p&gt;Yanwei Zhang, Zhonglai Wang, Saullo G. P. Castro. Bionic simulation of double clap-and-fling wing mechanism with SPH FSI method. EngXriv Preprint, 2022. &lt;a href="https://doi.org/10.31224/2652"&gt;DOI: 10.31224/2652&lt;/a&gt;&lt;/p&gt;&lt;/blockquote&gt;&lt;p&gt;File "simulations.zip" contains the simulation files.&lt;/p&gt;&lt;p&gt;File "DualSPHysics_v5.0.zip" contains the compiled DualSPHysics software.&lt;/p&gt;&lt;p&gt;Procedure to run the simulations on a Windows machine:&lt;/p&gt;&lt;ul&gt;&lt;li&gt;Working directory: .\simulations\flappingwing\case01&lt;/li&gt;&lt;li&gt;Step 1: Obtain rigid bodies by modeling of SOLIDWORKS and Macro command of FreeCAD (e.g. external_wing111.stl)&lt;/li&gt;&lt;li&gt;Step 2: Run ".bat" file (e.g. flapping01.bat) to start simulation and force acquisition&lt;/li&gt;&lt;li&gt;Step 3: Revise ".bat" and ".xml" (e.g. flapping01.bat and flapping01_Def.xml)to adapt to the next case. If required, change the model and Macro command of step 1. Common modification items:&lt;/li&gt;&lt;/ul&gt;&lt;p&gt;&lt;geometry&gt;-&lt;definition&gt; &lt;floatings&gt;- &lt;floating&gt;&lt;angularvel&gt; &lt;floatings&gt;- &lt;floating&gt;&lt;property&gt; &lt;properties&gt;-&lt;propertyfile&gt; &lt;initials&gt; &lt;execution&gt;-&lt;special&gt;-&lt;chrono&gt; &lt;execution&gt;-&lt;special&gt;-&lt;inout&gt; &lt;parameters&gt;&nbsp;&lt;/p&gt;&lt;ul&gt;&lt;li&gt;Step 4: Run "Filter.m" to handle force data by filters. Step 5: Compare forces of all cases. PS: Other files are revised function files derived from DualSPHysics 5.0.&lt;/li&gt;&lt;/ul&gt;&lt;p&gt;&nbsp;&lt;/p&gt;&lt;p&gt;Abstract: Three-dimensional numerical simulations of flexible flapping wings based&lt;br&gt;on the fluid-structure interaction in biological and bioinspired flow have become a&lt;br&gt;vibrant and challenging research topic. The present paper focuses on a parametric&lt;br&gt;study of the aerodynamic performance of a bionic flexible clapping wing. The proposed&lt;br&gt;model deforms the wing in spanwise and chordwise directions based on the six rigid&lt;br&gt;bodies connected along the wing veins using ball links and springs. Unsteady effects of&lt;br&gt;flapping wing micro air vehicles with a double clap-fling configuration are investigated&lt;br&gt;using an air-solid interaction model based on smoothed particle hydrodynamics and&lt;br&gt;rigid multi-body dynamics. A validation experiment determined the convergence&lt;br&gt;conditions and computational model accuracy. The proposed numerical model is&lt;br&gt;evaluated in terms of flexible variation law and aerodynamic performance. The results&lt;br&gt;indicate that the flapping frequency, angle of attack, and wind velocity significantly&lt;br&gt;influence the lift. Furthermore, increasing the frequency will monotonically expand&lt;br&gt;the maximum and time-averaged lift curve values. When the angle of attack is less&lt;br&gt;than 30 ◦, the influence on the time-averaged and maximum lift is proportional to the&lt;br&gt;angle of attack. When the angle of attack is larger than 45 ◦, a stall-like condition&lt;br&gt;is detected. To broaden the applicability of the present findings, a dimensionless&lt;br&gt;parameter, reduced frequency, is defined, and its influence on the maximum and time-&lt;br&gt;averaged lift is investigated. This parametric study shows that as the reduced frequency&lt;br&gt;increases, the maximum and time-averaged lift increases and then decreases. The&lt;br&gt;present study could reach a modeling framework that better explains the clapping&lt;br&gt;wing aerodynamics.&lt;br&gt;&nbsp;&lt;/p&gt

Development priorities and private investment in developing countries: Clean development mechanism projects in the electricity sector [Le mécanisme de développement propre dans le secteur électrique: Partage de la rente carbone entre développement et rémunération de l'investisseur]

International audienceGiven the relative weight of future greenhouse gases emissions of the Developing Countries (DCs) in the next decades, offering them the opportunity to participate to climate policies is a condition for achieving the goal of the Climate Convention. Thus, the Clean Development Mechanism (CDM) defined in art. 12 of the Kyoto Protocol, aims at reducing the cost of Annex 1 countries commitment in term of reduction of emissions, but also at limiting the risk that the DCs' unquestionable right to develop will offset the Annex 1 countries efforts: in order to be a win-win mechanism, the CDM should help to progress faster on a less polluting development path. Beyond political principles, there is the necessity to incorporate the decision making process of future CDM real actors. Regarding host country authorities, what is at stake is to bring in missing investment capacity to satisfy internal needs of goods and services, taking advantage of the additional incentive created by CDM certificates. For private investors, the objective is to maximise the global sum of commercial revenues plus CDM carbon income. The present paper examines potential CDM projects opportunities in the electric sector. Quantified pre-simulations for the Tahumanu project, which consists in building a 3 x 2 200 kVA hydropower plant instead of subsidized diesel plants in the Bolivian Pando Province, and which is co-financed by E7 as a CDM learning opportunity for seven large Annex 1 countries electricity companies, offer a realistic illustration of possible CDM projects set up and arrangements with the host country

Measuring geometric imperfections of variable–angle filament–wound cylinders with a simple digital image correlation setup

Measuring the geometric imperfections in cylindrical shells is a critical step necessary to create accurate numerical models that can capture the imperfection-sensitive behavior of these structures. Modern composite structures, such as variable–angle filament–wound (VAFW) cylinders, have a unique imperfection signature that is still unknown to the scientific community. This new class of variable–stiffness structures developed by our research group combines wide tailoring capabilities with the efficient manufacturability enabled by filament winding process. The present study proposes a novel imperfection measurement method that is simple and applicable to both small and large structures. The topographic data is measured with only a pair of cameras. Practical aspects of using digital image correlation (DIC) are described and discussed in detail, such as lighting, focus adjustment, and calibration. State–of–the–art best–fit routines, based on least–squares optimization, are used to transform raw data into a common coordinate system. Finally, the transformed data is stitched to build a full 3D imperfection pattern that can be readily used in a nonlinear finite element analysis. The developed method is used to measure the imperfections of 12 VAFW cylinders. The mass of the cylinders is used to validate the geometric imperfections and evaluate the variability of the proposed methodology.Peer reviewe