On the Conjectures Regarding the 4-Point Atiyah Determinant

For the case of 4 points in Euclidean space, we present a computer aided proof of Conjectures II and III made by Atiyah and Sutcliffe regarding Atiyah's determinant along with an elegant factorization of the square of the imaginary part of Atiyah's determinant

Impact dynamics research facility for full-scale aircraft crash testing

An impact dynamics research facility (IDRF) was developed to crash test full-scale general aviation aircraft under free-flight test conditions. The aircraft are crashed into the impact surface as free bodies; a pendulum swing method is used to obtain desired flight paths and velocities. Flight paths up to -60 deg and aircraft velocities along the flight paths up to about 27.0 m/s can be obtained with a combination of swing-cable lengths and release heights made available by a large gantry. Seven twin engine, 2721-kg aircraft were successfully crash tested at the facility, and all systems functioned properly. Acquisition of data from signals generated by accelerometers on board the aircraft and from external and onboard camera coverage was successful in spite of the amount of damage which occurred during each crash. Test parameters at the IDRF are controllable with flight path angles accurate within 8 percent, aircraft velocity accurate within 6 percent, pitch angles accurate to 4.25 deg, and roll and yaw angles acceptable under wind velocities up to 4.5 m/s

Climate, Not Conflict, Explains Extreme Middle East Dust Storm

The recent dust storm in the Middle East (September 2015) was publicized in the media as a sign of an impending ‘Dust Bowl.’ Its severity, demonstrated by extreme aerosol optical depth in the atmosphere in the 99th percentile compared to historical data, was attributed to the ongoing regional conflict. However, surface meteorological and remote sensing data, as well as regional climate model simulations, support an alternative hypothesis: the historically unprecedented aridity played a more prominent role, as evidenced by unusual climatic and meteorological conditions prior to and during the storm. Remotely sensed normalized difference vegetation index demonstrates that vegetation cover was high in 2015 relative to the prior drought and conflict periods, suggesting that agricultural activity was not diminished during that year, thus negating the media narrative. Instead, meteorological simulations using the Weather Research and Forecasting (WRF) model show that the storm was associated with a cyclone and ‘Shamal’ winds, typical for dust storm generation in this region, that were immediately followed by an unusual wind reversal at low levels that spread dust west to the Mediterranean Coast. These unusual meteorological conditions were aided by a significant reduction in the critical shear stress due to extreme dry and hot conditions, thereby enhancing dust availability for erosion during this storm. Concluding, unusual aridity, combined with unique synoptic weather patterns, enhanced dust emission and westward long-range transport across the region, thus generating the extreme storm

Impact data from a transport aircraft during a controlled impact demonstration

On December 1, 1984, the FAA and NASA conducted a remotely piloted air-to-ground crash test of a Boeing 720 transport aircraft instrumented to measure crash loads of the structure and the anthropomorphic dummy passengers. Over 330 time histories of accelerations and loads collected during the Full-Scale Transport Controlled Impact Demonstration (CID) for the 1-sec period after initial impact are presented. Although a symmetric 1 deg. nose-up attitude with a 17 ft/sec sink rate was planned, the plane was yawed and rolled 13 deg. at initial (left-wing) impact. The first fuselage impact occurred near the nose wheel well with the nose pitched down 2.5 deg. Peak normal (vertical) floor accelerations were highest in the cockpit and forward cabin near the nose wheel well and were approximately 14G. The remaining cabin floor received normal acceleration peaks of 7G or less. The peak longitudinal floor accelerations showed a similar distribution, with the highest (7G) in the cockpit and forward cabin, decreasing to 4G or less toward the rear. Peak transverse floor accelerations ranged from about 5G in the cockpit to 1G in the aft fuselage

Effects of introducing a parametric Cad in a first year course in engineering degree regarding quality of technical drawings

Comunicació presentada al ICERI 2019 12th annual International Conference of Education, Research and Innovation (Seville, Spain. 11-13 November, 2019).The evolution of teaching in technical drawing during the last years has been addressed towards new paradigms based on 3D modeling. Nevertheless, not only 3D modeling skills are important for an engineer, but the ability to generate quality technical drawings also are part of the learning objectives and should, therefore, be included in the curriculum. For several years, the core subject of technical drawing at Universitat Jaume I has been a common subject during the first course of different Engineering bachelor’s degrees (Mechanical, Industrial Technologies, Electrical, Chemical, and Agrifood/Rural). However, in the last two years, the subject in the case of Agrifood Engineering has been taught independently. This course, aiming for a more intuitive introduction to 3D modeling, the subject has experienced a general methodological change for all the degrees, except for the Agrifood Engineering one. Apart from changing the order of contents with the intention of improving spatial vision, the use of a different commercial CAD software was implemented, this being parametric. In a previous work, the effect of this general methodological change was assessed through the academic performance regarding 3D modeling by comparing the scores before and after implementing the change, as well as through specific questionnaires addressed to students and teachers, obtaining very positive results. Notwithstanding, the effects of the change performed on the obtainment of technical drawings were not analyzed. Taking advantage of having two groups (the one that has experienced the change and the one that did not), they were asked to model and generate the drawing of the same parts in their final exams, with the aim of comparing the scores obtained when assessing their skills of modeling, but also in creating technical drawings (views, sections and dimensioning) and in the quality on technical drawings presentation (title block, line thickness, etc.). Scores were collected and statistical analyses were performed, bringing to light that despite the good results that were obtained in previous studies regarding the 3D modeling, teaching efforts in how to generate technical drawings with quality should be reinforced in future

The physics of wind-blown sand and dust

The transport of sand and dust by wind is a potent erosional force, creates sand dunes and ripples, and loads the atmosphere with suspended dust aerosols. This article presents an extensive review of the physics of wind-blown sand and dust on Earth and Mars. Specifically, we review the physics of aeolian saltation, the formation and development of sand dunes and ripples, the physics of dust aerosol emission, the weather phenomena that trigger dust storms, and the lifting of dust by dust devils and other small-scale vortices. We also discuss the physics of wind-blown sand and dune formation on Venus and Titan.Comment: 72 journal pagers, 49 figure

Erosión en bancales: la trayectora de la escorrentía y su relación con el deterioro del Ribazo (Norte Comunidad Valenciana)

[Resumen] El cultivo en terrazas requiere la adecuación del terreno a las labores agrícolas: reducción de la erosión, favorecimiento de la infiltración, y hacer más cómodas las labores agrícolas. Estos objetivos se consiguen, en su mayor parte, reduciendo la pendiente de la ladera. La solución que se dé al drenaje de la escorrentía en la explotación determina, según se comenta en este artículo, la vulnerabilidad de los muros, sobre todo cuando las labores de mantenimiento se abandonan, como es el caso en extensas áreas montañosas de la península.[Abstract] The terrace cultivation needs a suitable field for farming works: to reduce the erosion, to permit infiltration and to do more comfortable farming works. You can reach most of these aims reducing the slope. The solution for the water drainage in the fields cause, as the article says, the vulnerability of the walls, especially when the maintenance works are left, as in vast mountains areas in the peninsula

Sharing of hand kinematic synergies across subjects in daily living activities

The motor system is hypothesised to use kinematic synergies to simplify hand control. Recent studies suggest that there is a large set of synergies, sparse in degrees of freedom, shared across subjects, so that each subject performs each action with a sparse combination of synergies. Identifying how synergies are shared across subjects can help in prostheses design, in clinical decision-making or in rehabilitation. Subject-specific synergies of healthy subjects performing a wide number of representative daily living activities were obtained through principal component analysis. To make synergies comparable between subjects and tasks, the hand kinematics data were scaled using normative range of motion data. To obtain synergies sparse in degrees of freedom a rotation method that maximizes the sum of the variances of the squared loadings was applied. Resulting synergies were clustered and each cluster was characterized by a core synergy and different indexes (prevalence, relevance for function and within-cluster synergy similarity), substantiating the sparsity of synergies. The first two core synergies represent finger flexion and were present in all subjects. The remaining core synergies represent coordination of the thumb joints, thumb-index joints, palmar arching or fingers adduction, and were employed by subjects in different combinations, thus revealing different subject-specific strategies