Computer program for structural analysis of layered orthotropic ring-stiffened shells of revolution (SALORS): Linear stress analysis option

Program handles segmented, laminar, orthotropic shells with discrete rings. Meridional variations are handled in material properties, temperatures, and wall thickness. Allows for linear variations of temperature through each layer of shell wall

An algorithm for determining program feasibility of a multi-mode PAM commutator telemetry system Technical report no. 10

Algorithm formulation for evaluation of strapping arrangement programs for PAM multimode commutation system of Saturn telemetry syste

Vibration and Instability of Plate-Assemblies including Shear and Anisotropy (VIPASA) user's guide, addendum

Extensions developed at Langley Research Center to the VIPASA computer program are described including a procedure for simple thermal stress analysis and options for graphical display of output. Input requirements for operation of the modified program are given in detail

The effect of ring distortions on buckling of blunt conical shells

A rigorous analytical study of cones stiffened by many thin-gage, open-section rings is presented. The results are compared with data previously obtained from uniform pressure tests of the Viking mission flight aeroshell and of the Viking structural prototype aeroshells. A conventional analysis, in which the rings are modeled as discrete rigid cross sections, is shown to lead to large, unconservative strength predictions. A more sophisticated technique of modeling the rings as shell branches leads to much more realistic strength predictions and more accurately predicts the failure modes. It is also shown that if a small initial imperfection proportional to the shape of the buckling mode is assumed, the critical buckling modes from analysis and test are in agreement. However, the reduction in buckling strength from the perfect-shell predictions is small

Flutter design of stiffened-skin panels for hypersonic aircraft

Design factors for flutter control of stiffened exterior skin panels for hypersonic aircraf

An Emerging Containment of (Legal) Concern: PFAS Legal Issues at the State and Federal Level

Per- and polyfluoroalkyl substances, or PFAS, are a class of man-made industrial chemicals that have been widely used in a variety of ways, primarily in water-resistant coatings and fire-fighting foam. Their widespread use has led to broad contamination threats to human drinking water sources, including surface and groundwater. As a result, they are an emerging contaminant of concern that are swiftly turning into a global health threat on the forefront of regulatory and policy debates. PFAS have been detected in both aquatic life and humans, and research is increasingly clear that there are concrete health risks to excessive exposure. Currently there are no binding federal restrictions of PFAS, leading some states to take the lead in developing regulations for this class of emerging contaminants. This paper will give a brief overview of what PFAS is, what the federal and state governments are doing about it, and various recommendations. This abstract has been taken from the authors\u27 introduction

Langevin Thermostat for Rigid Body Dynamics

We present a new method for isothermal rigid body simulations using the quaternion representation and Langevin dynamics. It can be combined with the traditional Langevin or gradient (Brownian) dynamics for the translational degrees of freedom to correctly sample the NVT distribution in a simulation of rigid molecules. We propose simple, quasi-symplectic second-order numerical integrators and test their performance on the TIP4P model of water. We also investigate the optimal choice of thermostat parameters.Comment: 15 pages, 13 figures, 1 tabl

Climate change impact on thermal comfort in Mexico City housing

This is the author accepted manuscript. The final version is available from WEENTECH via the DOI in this record4th International Conference on Energy, Environment and Economics (ICEEE2019), 20-22 August 2019, Edinburgh, ScotlandA two storey terraced house was modelled in ESP-r with a simple window opening control strategy to represent typical dwellings found in Mexico City and the adjoining municipalities. Future weather data was generated for years in this century based on morphing methods developed from the literature and by the authors and a TMY weather file developed from historical data between 1975 to 1989 by WhiteBox Technologies. The population in the region under consideration is a little over 20 million which represents 16% of Mexico’s population. The present day climate is such that air conditioning is rarely used in single family housing. The main cooling strategy in the hottest months (Mid February to mid June) is window opening. This was modelled considering that if the interior temperature was at or above 18°C and the exterior air temperature was below the interior air temperature then windows would be open. The air flow was modelled using the flow network model within ESP-r. It was found that in the latter part of the present century, this strategy would become increasingly ineffective. This is likely to lead to a considerable increase in installed air conditioning in single family dwellings and a consequent increase in electricity demand and consumption leading to a need for substantial investments in electricity transmission and distribution systems in the region to bring in power from distant sources.Engineering and Physical Sciences Research Council (EPSRC)CONACYT-SENER-Sustentabilidad Energética fund Mexic

New Langevin and Gradient Thermostats for Rigid Body Dynamics

We introduce two new thermostats, one of Langevin type and one of gradient (Brownian) type, for rigid body dynamics. We formulate rotation using the quaternion representation of angular coordinates; both thermostats preserve the unit length of quaternions. The Langevin thermostat also ensures that the conjugate angular momenta stay within the tangent space of the quaternion coordinates, as required by the Hamiltonian dynamics of rigid bodies. We have constructed three geometric numerical integrators for the Langevin thermostat and one for the gradient thermostat. The numerical integrators reflect key properties of the thermostats themselves. Namely, they all preserve the unit length of quaternions, automatically, without the need of a projection onto the unit sphere. The Langevin integrators also ensure that the angular momenta remain within the tangent space of the quaternion coordinates. The Langevin integrators are quasi-symplectic and of weak order two. The numerical method for the gradient thermostat is of weak order one. Its construction exploits ideas of Lie-group type integrators for differential equations on manifolds. We numerically compare the discretization errors of the Langevin integrators, as well as the efficiency of the gradient integrator compared to the Langevin ones when used in the simulation of rigid TIP4P water model with smoothly truncated electrostatic interactions. We observe that the gradient integrator is computationally less efficient than the Langevin integrators. We also compare the relative accuracy of the Langevin integrators in evaluating various static quantities and give recommendations as to the choice of an appropriate integrator.Comment: 16 pages, 4 figure