SmOOD: Smoothness-based Out-of-Distribution Detection Approach for Surrogate Neural Networks in Aircraft Design

Aircraft industry is constantly striving for more efficient design optimization methods in terms of human efforts, computation time, and resource consumption. Hybrid surrogate optimization maintains high results quality while providing rapid design assessments when both the surrogate model and the switch mechanism for eventually transitioning to the HF model are calibrated properly. Feedforward neural networks (FNNs) can capture highly nonlinear input-output mappings, yielding efficient surrogates for aircraft performance factors. However, FNNs often fail to generalize over the out-of-distribution (OOD) samples, which hinders their adoption in critical aircraft design optimization. Through SmOOD, our smoothness-based out-of-distribution detection approach, we propose to codesign a model-dependent OOD indicator with the optimized FNN surrogate, to produce a trustworthy surrogate model with selective but credible predictions. Unlike conventional uncertainty-grounded methods, SmOOD exploits inherent smoothness properties of the HF simulations to effectively expose OODs through revealing their suspicious sensitivities, thereby avoiding over-confident uncertainty estimates on OOD samples. By using SmOOD, only high-risk OOD inputs are forwarded to the HF model for re-evaluation, leading to more accurate results at a low overhead cost. Three aircraft performance models are investigated. Results show that FNN-based surrogates outperform their Gaussian Process counterparts in terms of predictive performance. Moreover, SmOOD does cover averagely 85% of actual OODs on all the study cases. When SmOOD plus FNN surrogates are deployed in hybrid surrogate optimization settings, they result in a decrease error rate of 34.65% and a computational speed up rate of 58.36 times, respectively

Integrating air systems in aircraft multidisciplinary design optimization

The strong interactions between aircraft and air systems necessitate the integration of the latter to multidisciplinary design optimization (MDO) considerations of the former. This research presents such a methodology considering environmental control and ice protection systems. These systems consume pressurized bleed air from the aircraft's engines to perform their respective functions. We first describe the models used to predict the behavior of these systems and then propose different approaches to their integration into an existing aircraft MDO environment. A business jet test case was studied using the developed methodology. The comparison of MDO results obtained with and without the considered air systems demonstrate the impact on optimal aircraft design and confirm the importance of integrating air systems in the aircraft MDO environment in early design stages.Les forces d'interaction entre avions et systèmes d'air nécessitent l'intégration de ces dernières par l'intermédiaire d'optimisations multidisciplinaires (MDO). Cette recherche présente une telle méthodologie considérant le contrôle de l'environnement et les systèmes de protection contre la glace. Ces systèmes consomment de l'air prélevé sous pression provenant des moteurs de l'avion afin de remplir leurs fonctions respectives. Nous décrivons d'abord les modèles utilisés afin de prédire le comportement de ces systèmes, puis nous proposons diverses approches d'intégration dans un environnement MDO existant. Une étude de cas d'un avion d'affaire a été étudiée en utilisant la méthodologie développée. La comparaison des résultats MDO obtenus, avec et sans les systèmes d'air considérés, démontrent l'impact sur la conception optimale de l'avion et confirme l'importance de l'intégration des systèmes d'air dans l'environnement MDO tôt dans les premières étapes de conception

Identifying parameters of a discrete numerical model of soil from a geotechnical field test

International audienc

miRNA expression in advanced Algerian breast cancer tissues.

Breast cancer is one of the commonest cancers among Algerian females. Compared to Western populations, the median age of diagnosis of breast cancer is much lower in Algeria. The objective of this study is to explore the expression of several miRNAs reported to be deregulated in breast cancer. The miRNAs miR-21, miR-125b, miR-100, miR-425-5p, miR-200c, miR-183 and miR-182 were studied on tumor and normal adjacent Algerian breast tissues using quantitative reverse transcription real time PCR, and the results were analyzed according to clinical characteristics. Compared to the normal adjacent tissues, miR-21, miR-183, miR-182, miR-425-5p and miR-200c were found to be upregulated while miR-100 and miR-125b were insignificantly deregulated. A positive correlation was noted among miR-183, miR-182 and miR-200c and among miR-425-5p, miR-183, miR-200c and miR-21. Further global miRNA microarray profiling studies can aid in finding ethnic specific miRNA biomarkers in the Algerian breast cancer population

Western and ketogenic diets in neurological disorders: can you tell the difference?

The prevalence of obesity tripled worldwide between 1975 and 2016, and it is projected that half of the US population will be overweight by 2030. The obesity pandemic is attributed, in part, to the increasing consumption of the high-fat, high-carbohydrate Western diet, which predisposes to the development of the metabolic syndrome and correlates with decreased cognitive performance. In contrast, the high-fat, low-carbohydrate ketogenic diet has potential therapeutic roles and has been used to manage intractable seizures since the early 1920s. The brain accounts for 25% of total body glucose metabolism and, as a result, is especially susceptible to changes in the types of nutrients consumed. Here, we discuss the principles of brain metabolism with a focus on the distinct effects of the Western and ketogenic diets on the progression of neurological diseases such as epilepsy, Parkinson's disease, Alzheimer's disease, and traumatic brain injury, highlighting the need to further explore the potential therapeutic effects of the ketogenic diet and the importance of standardizing dietary formulations to assure the reproducibility of clinical trials.Funding. This work has been funded by an American University of Beirut Faculty of Medicine grant to F.H.K. via the Medical Practice Plan (MPP), titled “Impact of metabolic stress-induced neuroinflammation on molecular and behavioral outcomes post-traumatic brain injury.” The funding agency had no role in the writing of the manuscript or the decision to submit it for publicatio