Pseudo-prototyping of aerospace mechanical dynamic systems with a generalized computer program

The ADAMS computer program for automated analysis of mechanisms and machines is described. The program automatically formulates mathematical models for prototype or existing mechanisms with the minimum necessary physical and geometric data. The model can then be analyzed in various modes of analysis. The outputs (displacements, velocities, acceleration and forces) can be produced in tabular and graphical (plots, wire frame graphics) form. The application of this computer program to simulating satellite docking maneuvers is illustrated

Topology Driven Improvement of FDC Build Parameters

The likeliest failure origin for advanced ceramics parts, prepared by fused deposition, is a void from improper fill. Adequate filling of each cross-section is dependent upon the deposition toolpath. Cross-sectional spaces are conventionally filled with pre-defined parameters. We propose that adaptive build parameters will control variations in geometry and property of a part. Voids, overfilling, incomplete bonding and excess traversing can be suppressed by adjusting the fill parameters for cross-sectional areas. Improved build parameters and toolpath allows for faster build time and components ofj full density. Some implementations are discussed and presented.Mechanical Engineerin

Why do British Indian children have an apparent mental health advantage?

BACKGROUND: Previous studies document a mental health advantage in British Indian children, particularly for externalising problems. The causes of this advantage are unknown. METHODS: Subjects were 13,836 White children and 361 Indian children aged 5-16 years from the English subsample of the British Child and Adolescent Mental Health Surveys. The primary mental health outcome was the parent Strengths and Difficulties Questionnaire (SDQ). Mental health was also assessed using the teacher and child SDQs; diagnostic interviews with parents, teachers and children; and multi-informant clinician-rated diagnoses. Multiple child, family, school and area factors were examined as possible mediators or confounders in explaining observed ethnic differences. RESULTS: Indian children had a large advantage for externalising problems and disorders, and little or no difference for internalising problems and disorders. This was observed across all mental health outcomes, including teacher-reported and diagnostic interview measures. Detailed psychometric analyses provided no suggestion of information bias. The Indian advantage for externalising problems was partly mediated by Indian children being more likely to live in two-parent families and less likely to have academic difficulties. Yet after adjusting for these and all other covariates, the unexplained Indian advantage only reduced by about a quarter (from 1.08 to .71 parent SDQ points) and remained highly significant (p < .001). This Indian advantage was largely confined to families of low socio-economic position. CONCLUSION: The Indian mental health advantage is real and is specific to externalising problems. Family type and academic abilities mediate part of the advantage, but most is not explained by major risk factors. Likewise unexplained is the absence in Indian children of a socio-economic gradient in mental health. Further investigation of the Indian advantage may yield insights into novel ways to promote child mental health and child mental health equity in all ethnic groups

Collapse of Double-Walled Carbon Nanotube Bundles under Hydrostatic Pressure

We use classical molecular dynamics simulations to study the collapse of single (SWNT) and double-walled (DWNT) carbon nanotube bundles under hydrostatic pressure. The collapse pressure (pc) varies as 1/R^3, where R is the SWNT radius or the DWNT effective radius. The bundles show ~ 30% hysteresis and the hexagonally close packed lattice is completely restored on decompression. The pc of DWNT is found to be close to the sum of its values for the inner and the outer tubes considered separately as SWNT, demonstrating that the inner tube supports the outer tube and that the effective bending stiffness of DWNT, D(DWNT) ~ 2D(SWNT) . We use an elastica formulation to derive the scaling and the collapse behavior of DWNT and multi-walled carbon nanotubes.Comment: This paper has been accepted for publication in Physical Review B. After publication, it will be available at http://prb.aps.org

Entanglement transitions in random definite particle states

Entanglement within qubits are studied for the subspace of definite particle states or definite number of up spins. A transition from an algebraic decay of entanglement within two qubits with the total number $N$ of qubits, to an exponential one when the number of particles is increased from two to three is studied in detail. In particular the probability that the concurrence is non-zero is calculated using statistical methods and shown to agree with numerical simulations. Further entanglement within a block of $m$ qubits is studied using the log-negativity measure which indicates that a transition from algebraic to exponential decay occurs when the number of particles exceeds $m$. Several algebraic exponents for the decay of the log-negativity are analytically calculated. The transition is shown to be possibly connected with the changes in the density of states of the reduced density matrix, which has a divergence at the zero eigenvalue when the entanglement decays algebraically.Comment: Substantially added content (now 24 pages, 5 figures) with a discussion of the possible mechanism for the transition. One additional author in this version that is accepted for publication in Phys. Rev.