Finite element of slender beams in finite transformations: a geometrically exact approach

This article is devoted to the modelling of thin beams undergoing finite deformations essentially due to bending and torsion and to their numerical resolution by the finite element method. The solution proposed here differs from the approaches usually implemented to treat thin beams, as it can be qualified as ‘geometrically exact’. Two numerical models are proposed. The first one is a non‐linear Euler–Bernoulli model while the second one is a non‐linear Rayleigh model. The finite element method is tested on several numerical examples in statics and dynamics, and validated through comparison with analytical solutions, experimental observations and the geometrically exact approach of the Reissner beam theory initiated by Simo. The numerical result shows that this approach is a good alternative to the modelling of non‐linear beams, especially in statics. Copyright © 2003 John Wiley & Sons, Ltd.     

Effect of luminaire fire-resistive shell design on lighting performance

Fire-resistive shells over luminaires are required to preserve the integrity of fire-resistive floor-ceiling assemblies. What are the effects of shell design on luminaire performance? The object of the work reported here is to initiate development of guidelines for selecting the right shell for the right application.     

Statistical analysis of achievable resolution limit in the near field source localization context

In this fast communication, we derive the statistical resolution limit (SRL), characterizing the minimal parameter separation, to resolve two closely spaced known near-field sources impinging on a linear array. Toward this goal, we conduct on the first-order Taylor expansion of the observation model a Generalized Likelihood Ratio Test (GLRT) based on a Constrained Maximum Likelihood Estimator (CMLE) of the SRL. More precisely, the minimum separation between two near-field sources, that is detectable for a given probability of false alarm and a given probability of detection, is derived herein. Finally, numerical simulations are done to quantify the impact of the array geometry of the signal sources power distribution and of the array aperture on the statistical resolution limit.     

Dynamic optical trap generation using FLC SLMs for the manipulation of cold atoms

Abstract

Trapping and manipulation of cold atoms using optical potentials require the ability to generate and control a time varying light intensity distribution. Such an application demands that fast changing intensity distributions are generated, which are however free from flickering, or noise in general. Ferroelectric spatial light modulators are good candidates to achieve this because of their high refresh rate but they suffer from noise due to changes in the state of individual pixels during an animated sequence. A direct binary search based optimization routine was developed which minimizes the noise during such sequences. Filter sequences designed using this technique have been tested experimentally and the results demonstrated that flicker noise was eliminated.     

Starch Granule-Bound Proteins and Polypeptides: The Influence of the waxy Mutations

Proteins are found as integral components of starch granule structure. The starch granule-bound proteins from the endosperm of nonmutant (normal) and waxy (glutinous) cereals were extracted and subsequently separated by electrophoresis on denaturing SDS-polyacrylamide gels. The silver stained gels revealed that for cereals the waxy protein (starch granule-bound starch synthase) was approximately 60 kD. The cereals containing the waxy mutation do not show this protein. Compared to the nonmutant genotypes of other cereals, the waxy protein of barley, Hordeum vulgare is greatly diminished. Based on this observation, there may be reason to suspect that starch synthesis in barley varies from that of other cereals. There are minor homologous proteins among the cereals studied, including, maize, teosinte, rice, millet, sorghum, and barley. Starch granules from all cereal genotypes studied exhibited a minor protein at 68 kD. Most (81%) genotypes showed a 65 kD protein, which may correspond to a minor isozyme of starch granule-bound starch synthase. Minor proteins occurred at 70 kD and 72 kD in 71% and 57% of the genotypes studied, respectively. The minor proteins could be isozymes of starch granule-bound starch synthase or the proposed granule-bound forms of branching enzyme and oligosaccharide synthase.     

A pilot-scale evaluation of magnetic ion exchange treatment for removal of natural organic material and inorganic anions

The objective of this research was to evaluate a magnetic ion exchange process (MIEX) for the removal of natural organic material (NOM) and bromide on a continuous-flow pilot-scale basis under different operating conditions and raw water characteristics. The most important operating variable was the effective resin dose (ERD), which is the product of the steady-state resin concentration in the contactor and the regeneration ratio. The raw water employed in this study had a moderate concentration of ultraviolet (UV)-absorbing substances and dissolved organic carbon (DOC), and a low turbidity, alkalinity, and concentration of competing anionic species. Experiments were conducted using the ambient raw water and raw water spiked with bromide, chloride, and sulfate. Substantial removal of UV-absorbing substances and DOC was achieved at ERDs as low as 0.16mL/L. Moderate bromide removal was achieved, depending on the ERD. Increasing the sulfate concentration resulted in decreased removal of UV-absorbing substances, DOC, and bromide. Consistent results were observed between the continuous-flow pilot plant tests and batch equilibrium studies.     

Classifying land development in high-resolution panchromatic satellite images using straight-line statistics

We introduce a set of measures based on straight lines to assess land development levels in high-resolution (1 m) panchromatic satellite images. Most urban areas locally (such as in a 400/spl times/400 m/sup 2/ area) exhibit a preponderance of straight-line features, generally appearing in fairly simple quasi-periodic organizations. Wilderness and rural areas produce line structures in more random spatial arrangements. We use this observation to perform an initial triage on the image to restrict the attention of subsequent more computationally intensive analyses. Statistical measures based on straight lines guide the analysis. We base these measures on length, contrast, orientation, periodicity, and location. On these, we trained and tested parametric and nonparametric classifiers. These tests were for a two-class problem (urban versus rural). However, because our ultimate goal is to extract residential regions, we then extended these ideas to address the detection of suburban regions. To do so, some use of spatial coherence is required; suburban regions are especially difficult to detect. Therefore, we introduce a decision system to perform suburban region classification via an overlapping voting method for consensus discovery. Our data were taken from regions all around the world, which underscores the robustness of our approach. Based on extensive testing, we can report very promising results in distinguishing developed areas.     

Attributes, characteristics, and applications of titanium and its alloys

It is well known that titanium has properties attractive to the aerospace and other industries, and that its applications are limited due to its high cost. This overview will provide those not directly involved with titanium an explanation of why titanium is an attractive material, with aerospace being a primary focus. A brief summary of titanium applications and some of its unique properties will also be discussed.     

Acoustic emissions simulation of tumbling mills using charge dynamics

Knowledge of the internal variables of a mill is of importance in design and performance optimization of the mill, notwithstanding the difficulty in measuring these variables within the harsh mill environment. To overcome this problem, the research has focused on measuring the internal parameters through non-invasive measurement methods such as the use of the vibration/acoustic signal obtained from the mill. Alternatively, virtual instruments, such as discrete element methods (DEM), are employed. Here, a methodology is developed to simulate on-the-shell acoustic signal emitted from tumbling mills using the information extracted from a DEM simulator. The transfer function which links the forces exerted on the internal surface of the mill and the acoustic signal measured on the outer surface is measured experimentally. Given this transfer function and the force distribution obtained from the DEM simulation, and assuming a linear time-invariant response, the on-the-shell acoustic of a laboratory scale ball mill has been simulated. Comparison of this simulated signal with the signal measured experimentally can be used as a criterion to judge the validity of the DEM simulations, and as a tool for enhancing our understanding of both DEM simulations and the use of acoustics within the context of mineral processing. The results derived from preliminary experiments on a laboratory scale mill shows satisfactory agreement between the actual measurement and the simulated acoustic signal.     

Gas environment effect on cavitation damage in stretched polyvinylidene fluoride

The influence of gas sorption on damage nucleation of a semicrystalline polymer during coupled diffuso‐mechanical monotonic loading in tension was investigated for the first time. Alpha‐poly(vinylidene fluoride) was mechanically strained under the presence of two chemically different gases, hydrogen and carbon dioxide, at a temperature of 30°C and a pressure up to 120 bar. The cavitation damage at the microstructure scale after gas decompression was assessed from a careful SEM and TEM micrographs analysis. Compared with SEM, TEM allowed quantifying the smallest cavities (ten‐nanometer size). If decompression in hydrogen appeared to have only a slight effect on cavitation however, carbon dioxide showed a detrimental effect on damage nucleation with the exhibition of a significant population of small cavities. On the other hand, tension under gas pressure is more sensitive to hydrogen than to carbon dioxide. Once interaction with gaseous carbon dioxide takes place the plasticizing effect is in competition with damage by cavitation. POLYM. ENG. SCI., 54:2139–2146, 2014. © 2013 Society of Plastics Engineers