Lateral crushing in tightly packed arrays of thin-walled metal tubes

The plastic-collapse load and post-collapse behaviour of ductile, thin-walled tubes compressed between cylindrical indenters are analyzed for a complete range of indenter radii; experiments on steel, brass and aluminium alloy tubes show the usefulness of this analysis when deflections are large. The effect of shear force is considered; shear can develop when the sides of the tube are constrained against lateral expansion. While crushing by diametrically opposed indenters results in symmetrical modes of deformation, any shear in addition to the normally applied forces results in an asymmetrical mode of deformation which is more compliant than the symmetrical mode. The asymmetrical mode of deformation is initially unstable.     

Design of parts and manufacturing systems for reliability and maintainability

The design of parts and manufacturing systems can be viewed from different perspectives. This paper discusses the design of parts and manufacturing systems from reliability and maintainability perspectives. A convenient method of considering reliability and maintainability is through the use of design rules which are based on empirical and theoretical knowledge. Four design rules for improvement of reliability and maintainability of systems are presented. The design rules are proven and substantiated with numerical results. The relationship between the design for reliability and maintainability rules and design for manufacturing process rules is discussed.     

An Empirical Study Evaluating Social Networking Continuance and Success

Social networking site (SNS) use decisions have led to major economic and social transformations worldwide. While many organizations seek to use SNSs from a strategic perspective to reach their customer, it is important to understand what makes SNSs successful in order to use them for competitive purposes. The current research evaluates the influence of the social capital theory on SNS success measures. A model was developed and empirically tested using two data samples to ensure valid and reliable results for success of SNSs. The results display the importance of social capital in SNS success followed by practitioner and academic implications.     

Poly(L‐lactic acid) with added α‐tocopherol and resveratrol: optical,physical, thermal and mechanical properties

Poly(L ‐lactic acid) (PLLA) films containing various concentrations of two natural antioxidants, α‐tocopherol and resveratrol, were fabricated by a melt compounding and compression molding process. The influence of the antioxidants on the optical properties such as color and UV‐visible light transmission was analyzed. The thermal, mechanical, rheological and physical properties of PLLA films with added antioxidants were assessed. PLLA films with added α‐tocopherol and resveratrol showed a yellowish brown color and the lightness was influenced by the presence of the antioxidants. The glass transition and melting temperatures were significantly reduced with the addition of antioxidants while enhanced thermal stability was observed, which could be a benefit and important for processing and production. PLLA films with added antioxidants were slightly more hydrophobic than neat PLLA. The combination effect of plasticizing and enhancement of the elastic modulus with differing concentrations of two antioxidants played a critical role in the mechanical and thermomechanical properties of PLLA films. The melt viscosity of the PLLA films with added antioxidants was substantially higher than that of neat PLLA. The higher melt viscosity and G′(ω) could be an indication of formation of entanglement between PLLA and the two antioxidants. Copyright © 2012 Society of Chemical Industry     

Gaseous Nanocarving‐Mediated Carbon Framework with Spontaneous Metal Assembly for Structure‐Tunable Metal/Carbon Nanofibers

Vapor phase carbon (C)‐reduction‐based syntheses of C nanotubes and graphene, which are highly functional solid C nanomaterials, have received extensive attention in the field of materials science. This study suggests a revolutionary method for precisely controlling the C structures by oxidizing solid C nanomaterials into gaseous products in the opposite manner of the conventional approach. This gaseous nanocarving enables the modulation of inherent metal assembly in metal/C hybrid nanomaterials because of the promoted C oxidation at the metal/C interface, which produces inner pores inside C nanomaterials. This phenomenon is revealed by investigating the aspects of structure formation with selective C oxidation in the metal/C nanofibers, and density functional theory calculation. Interestingly, the tendency of C oxidation and calculated oxygen binding energy at the metal surface plane is coincident with the order Co > Ni > Cu > Pt. The customizable control of the structural factors of metal/C nanomaterials through thermodynamic‐calculation‐derived processing parameters is reported for the first time in this work. This approach can open a new class of gas–solid reaction‐based synthetic routes that dramatically broaden the structure‐design range of metal/C hybrid nanomaterials. It represents an advancement toward overcoming the limitations of intrinsic activities in various applications.     

The influence of altruism on influenza vaccination decisions

Game theory is based on the assumption that individuals act according to self-interest and make decisions that maximize their personal payoffs. To test this fundamental assumption, we conducted a survey study in the context of influenza vaccination decisions. Contrary to the assumption of self-interest, we found that altruism plays an important role in vaccination decisions. Nevertheless, altruistic motivation has not yet been considered in epidemiological models, in predictions of vaccination decisions or in the design of vaccination policies. To determine the impact of altruism on the adherence to optimal vaccination policies and on resulting disease burden, we incorporated altruism into a game-theoretic epidemiological model of influenza vaccination. We found that altruism significantly shifted vaccination decisions away from individual self-interest and towards the community optimum, greatly reducing the total cost, morbidity and mortality for the community. Therefore, promoting altruism could be a potential strategy to improve public health outcomes.     

Electrospray‐deposited nickel ferrite thin film electrode for hydrogen production in PV‐assisted water electrolysis system

Nanocrystalline Ni ferrite thin film was prepared by electrospray deposition technique and characterized by different analytical techniques at different annealing temperatures. All these films were studied by photovoltaic‐assisted water electrolysis system for solar to hydrogen production efficiency measurement. Highly dense and uniform surface morphology was observed in as‐deposited film, which changed into agglomerated nanocrystalline grains of irregular size and shape with change in annealing temperature. The X‐ray photoelectron spectroscopy study showed that the as‐deposited film was a mixture of an oxyhydroxide form of iron and an Ni₂O₃ form of nickel, whereas it changed into ferrite phase with change in annealing temperature. The as‐deposited film was observed to be of amorphous phase, which changed to crystalline cubic spinel structure with change in annealing temperature. The solar to hydrogen production efficiency was found to increase in a film with an increase in annealing temperature. The film annealed at 500°C showed a high solar to hydrogen production efficiency (8.29%) with constant performance of up to initial 500 h. Thereafter, the performance slowly declined by 11% when up to 1000 h. Copyright © 2011 John Wiley & Sons, Ltd.     

Near-optimal state feedback design for singularly perturbed systems by unified approach

A near optimal state feedback design for singularly perturbed systems by a unified approach using the delta operator is presented with an example of the aircraft longitudinal motion. The main contribution of this paper is to explore the use of the i -operator that has attracted a new attention in systems science. The i -operator system unifies the continuous system and the discrete system together without loosing any characteristics of both systems. The paper offers the following; Finite-word-length-characteristics are improved using the i -operator. Floating-point-operations are reduced by block diagonalization and by time-invariant optimal feedback gain from the algebraic Riccati equation. The results of adopting those approaches are illustrated in the simulation figures and compared with the earlier one.     

Protypology: A new stage in the standardization of metal products

Standardization is analyzed as a scientific discipline. The science of standardization may be referred to as protypology. On that basis, the stages in the development of standards for various types of carbon-steel products with ultrafine-grain structure are discussed.