Impact Strength Of Glass And Glass Ceramic

Strength of glass and glass ceramic was measured with a bar impact technique. High-speed movies show regions of tensile and compressive failure. The borosilicatc glass had a compressive strength of at least 2.2 GPa, and the glass ceramic at least 4 GPa. However, the BSG was much stronger in tension than GC. In ballistic tests, the BSG was the superior armor.Mechanical Engineerin

More Thought - More Framing Effects?

Three studies investigate the impact of the amount of elaboration on framing effects. In all three studies, participants were exposed to decision scenarios similar to the �Asian disease� problem (Tversky & Kahneman, 1981). The results replicated previous findings: Participants avoided the risky option when the scenario was framed in terms of gains, but preferred the risky option when the scenario was framed in terms of losses. Most importantly, these effects were most pronounced when participants spent more time working on the decision, because of either increased elaboration time (Study 1 and 2) or increased processing motivation (Study 3). Moreover, increased elaboration increased framing effects only when the situation required the scenario to be enriched with additional information. The discussion focuses on the possibility that increased elaboration may not necessarily result in less bias in social judgment and decision making.

Unsupervised Terminological Ontology Learning based on Hierarchical Topic Modeling

In this paper, we present hierarchical relationbased latent Dirichlet allocation (hrLDA), a data-driven hierarchical topic model for extracting terminological ontologies from a large number of heterogeneous documents. In contrast to traditional topic models, hrLDA relies on noun phrases instead of unigrams, considers syntax and document structures, and enriches topic hierarchies with topic relations. Through a series of experiments, we demonstrate the superiority of hrLDA over existing topic models, especially for building hierarchies. Furthermore, we illustrate the robustness of hrLDA in the settings of noisy data sets, which are likely to occur in many practical scenarios. Our ontology evaluation results show that ontologies extracted from hrLDA are very competitive with the ontologies created by domain experts

Sand Penetration By High-Speed Projectiles

Tungsten projectiles were shot into sand at velocities between 600 and 2200 m/s. Penetration was maximum at about 775 m/s. Below that velocity, projectiles were apparently stabilized by a fin set. Above that velocity, projectiles were broken by transverse loads. High-speed penetration resulted in comminution of sand particles, reducing their size by about 1000 times.Mechanical Engineerin

A finite element based method for solution of optimal control problems

A temporal finite element based on a mixed form of the Hamiltonian weak principle is presented for optimal control problems. The mixed form of this principle contains both states and costates as primary variables that are expanded in terms of elemental values and simple shape functions. Unlike other variational approaches to optimal control problems, however, time derivatives of the states and costates do not appear in the governing variational equation. Instead, the only quantities whose time derivatives appear therein are virtual states and virtual costates. Also noteworthy among characteristics of the finite element formulation is the fact that in the algebraic equations which contain costates, they appear linearly. Thus, the remaining equations can be solved iteratively without initial guesses for the costates; this reduces the size of the problem by about a factor of two. Numerical results are presented herein for an elementary trajectory optimization problem which show very good agreement with the exact solution along with excellent computational efficiency and self-starting capability. The goal is to evaluate the feasibility of this approach for real-time guidance applications. To this end, a simplified two-stage, four-state model for an advanced launch vehicle application is presented which is suitable for finite element solution

Biostratigraphy and ecostratigraphy of Late Cretaceous deposits in the Kunrade area (South-Limburg, SE Netherlands)

The Late Cretaceous deposits in the Kunrade area in South-Limburg (SE Netherlands) differ from the classic outcrops around Maastricht in their lithofacies and fossil content. On the basis of biostratigraphic and ecostratigraphic data from 24 sections (2 boreholes and 22 outcrops), an ecostratigraphic subdivision into five ecozones is proposed. This ecozonation is correlated with sections at Valkenburg a/d Geul (Thermae Borehole), Maastricht (Kastanjelaan Borehole), Hoepertingen and Diet-Heur

X-Ray Tomography To Measure Size Of Fragments From Penetration Of High-Velocity Tungsten Rods

Behind-armor debris that results from tungsten rods penetrating armor steel at 2 km/s was studied by analysis of recovered fragments. Fragment recovery was by means of particle board. Individual fragments were analyzed by x-ray tomography, which provides information for fragment identification, mass, shape, and penetration down to masses of a few milligrams. The experiments were complemented by AUTODYN and EPIC calculations. Fragments were steel or tungsten generated from the channel or from the breakout through the target rear surface. Channel fragment motions were well described by Tate theory. Breakout fragments had velocities from the projectile remnant to the channel velocity, apparently depending on where in the projectile a fragment originated. The fragment size distribution was extremely broad and did not correlate well with simple uniform-fragment-size models.Mechanical Engineerin

Sobre las facies de ostrácodos del Carbonífero superopr y su uso para correlaciones en las Cuencas Hulleras

Desde el año 1964 se está realizando una investigación sisteiziática sobre la presencia de ostrácodos en el nordeste de la Cuenca Hullera de Asturias. Partes de este trabajo ya se publicaron en "Leidse Geologische Meddelingten" y en "Notas y Comunicaciones del Instituto Geológico y Minero de España". Resultó posible seguir ciertos horizorites fosilíferosde una tniiia n otra y así correlacionar capas de carbón sobre distancias a veces bastante estimables. El interés económico que tiene esto último está bien claro.El motivo principal de haber escogido los ostrácodos entre otras clases de fósiles para estos fines es el siguiente: Los ostrácodos por su pequeñez (raramente más de dos milímetros), están normalmente mejor conservados que los macrofósiles, puesto que éstos con frecuencia son afectados, ya sea por la diagénesis de los sedimentos o por los movimientos tectótnicos que influyen en la roca. Además se encuentran los ostrácodos en relativa abundancia en los estratos carboníferos, bien sea en sedimentos marinos, fluviales o salobres. Otras clases de  microfósiles, como por ejemplo los foraminíferos, están limitados a los niveles marinos y únicamente en las calizas abundan

A weak Hamiltonian finite element method for optimal control problems

A temporal finite element method based on a mixed form of the Hamiltonian weak principle is developed for dynamics and optimal control problems. The mixed form of Hamilton's weak principle contains both displacements and momenta as primary variables that are expanded in terms of nodal values and simple polynomial shape functions. Unlike other forms of Hamilton's principle, however, time derivatives of the momenta and displacements do not appear therein; instead, only the virtual momenta and virtual displacements are differentiated with respect to time. Based on the duality that is observed to exist between the mixed form of Hamilton's weak principle and variational principles governing classical optimal control problems, a temporal finite element formulation of the latter can be developed in a rather straightforward manner. Several well-known problems in dynamics and optimal control are illustrated. The example dynamics problem involves a time-marching problem. As optimal control examples, elementary trajectory optimization problems are treated