NATO STO/AVT-251: A Joint Exercise in Collaborative Combat Aircraft Design

This article provides an overview about the activities performed within the NATO STO Research Task Group AVT-251 on "Multi-Disciplinary design and performance assessment of effective, agile NATO Air Vehicles". After a brief introduction to the preceding task groups and the research questions that led to the formation of AVT-251, the selection of design requirements is discussed and the approach for developing the MULDICON UCAV configuration out of its predecessor, the SACCON concept, is described. A short summary presents the work performed by the four design teams, each of which was responsible for one of the major topics on which the design task had been focused (aerodynamic shaping, control concept, engine integration, and structural concept). The task of a fifth team was two-fold: initially, it was responsible for the specification of the design requirements; later in the process, it had to join together the results of the other four teams into an overall aircraft concept and to assess this concept with respect to the initially specified set of requirements. Finally, a concluding summary of the MULDICON concept, as well as of the research questions of the AVT-251 task group are presented

Phase behavior of a system of particles with core collapse

The pressure-temperature phase diagram of a one-component system, with particles interacting through a spherically symmetric pair potential in two dimensions is studied. The interaction consists of a hard core plus an additional repulsion at low energies. It is shown that at zero temperature, instead of the expected isostructural transition due to core collapse occurring when increasing pressure, the system passes through a series of ground states that are not triangular lattices. In particular, and depending on parameters, structures with squares, chains, hexagons and even quasicrystalline ground states are found. At finite temperatures the solid-fluid coexistence line presents a zone with negative slope (which implies melting with decreasing in volume) and the fluid phase has a temperature of maximum density, similar to that in water.Comment: 11 pages, 15 figures included. To appear in PRE. Some figures in low quality format. Better ones available upon request from [email protected]

Investigation of the Enteric Pathogenic Potential of Oral Campylobacter concisus Strains Isolated from Patients with Inflammatory Bowel Disease

BACKGROUND: Campylobacter concisus, a bacterium colonizing the human oral cavity, has been shown to be associated with inflammatory bowel disease (IBD). This study investigated if patients with IBD are colonized with specific oral C. concisus strains that have potential to cause enteric diseases. METHODOLOGY: Seventy oral and enteric C. concisus isolates obtained from eight patients with IBD and six controls were examined for housekeeping genes by multilocus sequence typing (MLST), Caco2 cell invasion by gentamicin-protection-assay, protein analysis by mass spectrometry and SDS-PAGE, and morphology by scanning electron microscopy. The whole genome sequenced C. concisus strain 13826 which was isolated from an individual with bloody diarrhea was included in MLST analysis. PRINCIPAL FINDINGS: MLST analysis showed that 87.5% of individuals whose C. concisus belonged to Cluster I had inflammatory enteric diseases (six IBD and one with bloody diarrhea), which was significantly higher than that in the remaining individuals (28.6%) (P<0.05). Enteric invasive C. concisus (EICC) oral strain was detected in 50% of patients with IBD and none of the controls. All EICC strains were in Cluster 1. The C. concisus strain colonizing intestinal tissues of patient No. 1 was closely related to the oral C. concisus strain from patient No. 6 and had gene recombination with the patient's own oral C. concisus. The oral and intestinal C. concisus strains of patient No. 3 were the same strain. Some individuals were colonized with multiple oral C. concisus strains that have undergone natural recombination. CONCLUSIONS: This study provides the first evidence that patients with IBD are colonized with specific oral C. concisus strains, with some being EICC strains. C. concisus colonizing intestinal tissues of patients with IBD at least in some instances results from an endogenous colonization of the patient's oral C. concisus and that C. concisus strains undergo natural recombination

Longitudinal Associations Between Perceived Parent-Child Relationship Quality and Depressive Symptoms in Adolescence

This longitudinal study examined bidirectional paths between perceived parent-adolescent relationship quality and depressive symptoms, as well as the moderating role of sex, age, and personality type. 1313 Dutch adolescents (51% girls) from two cohorts (923 12-year olds and 390 16-year olds at Wave 1) reported on their personality, depressive symptoms, and perceived relationship quality to parents in four waves. Consistent with a relationship erosion perspective, depressive symptoms negatively predicted perceived relationship quality with parents. Relationship quality to mothers predicted depressive symptoms for boys and girls, but relationship quality to fathers predicted depressive symptoms only for boys. Personality type only moderated initial associations between relationship quality with mothers and depressive symptoms, which were stronger for Overcontrollers and Undercontrollers than for Resilients. Results thus reveal a pattern of mutual influence between perceived relationship quality and depressive symptoms that is moderated by the interplay among parent and adolescent sex and adolescent personality type

THE NATO STO TASK GROUP AVT-201

The ability to accurately predict both static and dynamic stability characteristics of air vehicles using Computational Fluid Dynamics (CFD) methods could revolutionize the air vehicle design process, especially for military air vehicles. A validated CFD capability would significantly reduce the number of ground tests required to verify vehicle concepts and, in general, could eliminate costly vehicle ‘repair’ campaigns required to fix performance anomalies that were not adequately predicted prior to full-scale vehicle development. This chapter outlines the extended integrated experimental and numerical approach to assess the of stability and control prediction method capabilities as well as the design and estimation the control device effectiveness for highly swept low observable UCAV configurations. The aim of the AVT-201 Task Group is to provide an assessment of the CFD capabilities using model-scale experiments and transferring this knowledge to real-scale application

INTRODUCTION TO THE AVT-161 AIR FACET: AN INTEGRATED COMPUTATIONAL/EXPERIMENTAL APPROACH TO UCAV STABILITY AND CONTROL ESTIMATION

Within the AVT-161 Task Group a comprehensive research program designed to investigate the ability of computational methods to predict stability and control characteristics of a generic unmanned combat air vehicle and the X-31 experimental aircraft has been undertaken. The integrated approach to simulating static and dynamic stability characteristics was performed by the NATO RTO Task Group AVT-161. The UCAV, named SACCON (Stability and Control Configuration), and the X-31 configuration was the subject of an intensive computational and experimental study. The stability characteristics of the vehicles were evaluated via a highly integrated approach, where CFD and experimental results were used in a parallel and collaborative fashion. The results show that computational methods have made great strides in predicting static and dynamic stability characteristics, but several key issues need to be resolved before efficient, affordable, and reliable predictions are available

Integrated Computational/Experimental Approach to Unmanned Combat Air Vehicle Stability and Control Estimation

A comprehensive research program designed to investigate the ability of computational methods to predict stability and control characteristics of a generic unmanned combat air vehicle has been undertaken. The integrated approach to simulating static and dynamic stability characteristics was performed by the NATO Research and Technology Organization Task Group AVT-161. The vehicle named Stability and Control CONfiguration (SACCON) was the subject of an intensive computational and experimental study. The stability characteristics of the vehicle were evaluated via a highly integrated approach, where computational fluid dynamics and experimental results were used in a parallel and collaborative fashion. The results show that computational methods have made great strides in predicting static and dynamic stability characteristics, but several key issues need to be resolved before efficient, affordable, and reliable predictions are available

Detached-Eddy Simulation of the vortical flow field about the VFE-2 delta wing

The numerical simulation of the flow for the VFE-2 delta wing configuration with rounded leading edges is presented using the Cobalt Navier–Stokes solver. Cobalt uses a cell-centered unstructured hybrid mesh approach, and several numerical results are presented for the steady RANS equations as well as for the unsteady DES and DDES hybrid approaches. Within this paper the focus is related to the dual primary vortex flow topology, especially the sensitivity of the flow to angle of attack and Reynolds number effects. Reasonable results are obtained with both steady RANS and SA-DDES simulations. The results are compared and verified by experimental data, including surface pressure and pressure sensitive paint results, and recommendations for improving future simulations are made

Multi-Disciplinary Design and Performance Assessment of Effective, Agile NATO Air Vehicles

NATO STO Task Group AVT-25 has been working for three years on re-designing an effective, agile UCAV to meet a specific set of mission requirements. The task group is a follow-on to previous groups that analyzed the SACCON UCAV geometry with wind tunnel and CFD simulations, as well as control surface effectiveness estimations. AVT-215 started with the SACCON geometry and then re-designed the configuration to meet specific Mission requirements. The re-design resulted in a new geometry called MULDICON. Details of the design process and multi-disciplinary analysis that took place in the group will be presented, and will serve to introduce the other related papers

NATO STO/AVT-251: A Joint Exercise in Collaborative Combat Aircraft Design

This article provides an overview about the activities performed within the NATO STO Research Task Group AVT-251 on "Multi-Disciplinary design and performance assessment of effective, agile NATO Air Vehicles". After a brief introduction to the preceding task groups and the research questions that led to the formation of AVT-251, the selection of design requirements is discussed and the approach for developing the MULDICON UCAV configuration out of its predecessor, the SACCON concept, is described. A short summary presents the work performed by the four design teams, each of which was responsible for one of the major topics on which the design task had been focused (aerodynamic shaping, control concept, engine integration, and structural concept). The task of a fifth team was two-fold: initially, it was responsible for the specification of the design requirements; later in the process, it had to join together the results of the other four teams into an overall aircraft concept and to assess this concept with respect to the initially specified set of requirements. Finally, a concluding summary of the MULDICON concept, as well as of the research questions of the AVT-251 task group are presented