Deposition of Ti/TiC Composite Coatings on Implant Structures Using Laser Engineered Net Shaping

A new method of depositing hard and wear resistant composite coatings on metal-onmetal bearing surfaces of titanium implant structures is proposed and demonstrated. The method consists of depositing a Ti/TiC composite coating (~ 2.5 mm thick) on titanium implant bearing surfaces using Laser Engineered Net Shaping (LENS®). Defect-free composite coatings were successfully produced at various amounts of the reinforcing TiC phase with excellent interfacial characteristics using a mixture of commercially pure Ti and TiC powders. The coatings consisted of a mixture of coarser unmelted/partially melted (UMC) TiC particles and finer, discreet resolidified (RSC) TiC particles uniformly distributed in the titanium matrix. The amounts of UMC and RSC were found to increase with increasing TiC content of the original powder mixture. The coatings exhibited a high level of hardness, which increased with increasing TiC content of the original powder mixture. Fractographic studies indicated that the coatings, even at 60 vol.% TiC, do not fail in a brittle manner. Various aspects of LENS® deposition of Ti/TiC composite coatings are addressed and a preliminary understanding of structure-property-fracture correlations is presented. The current work shows that the proposed approach to deposit composite coatings using laser-based metal deposition processes is highly-effective, which can be readily utilized on a commercial basis for manufacture of high-performance implants.Mechanical Engineerin

Entanglement Induced Fluctuations of Cold Bosons

We show that due to entanglement, quantum fluctuations may differ significantly from statistical fluctuations. We calculate quantum fluctuations of the particle number and of the energy in a sub-volume of a system of bosons in a pure state, and briefly discuss the possibility of measuring them. We find that energy fluctuations have a non-extensive nature.Comment: Replaced with published version. Added calculations, explanations and clarifications, results unchange

Process Parameters Optimization for Ultrasonically Consolidated Fiber-Reinforced Metal Matrix Composites

As an emerging rapid prototyping technology, Ultrasonic Consolidation (UC) has been used to successfully fabricate metal matrix composites (MMC). The intent of this study is to identify the optimum combination of processing parameters, including oscillation amplitude, welding speed, normal force, operating temperature and fiber orientation, for manufacture of long fiber-reinforced MMCs. The experiments were designed using the Taguchi method, and an L25 orthogonal array was utilized to determine the influences of each parameter. SiC fibers of 0.1mm diameter were successfully embedded into an Al 3003 metal matrix. Two methods were employed to characterize the bonding between the fiber and matrix material: optical/electron microscopy and push-out tests monitored by an acoustic emission (AE) sensor. SEM images and data from push-out tests were analyzed and optimum combinations of parameters were achieved.Mechanical Engineerin

Spitzer Constraints on the z=6.56 Galaxy Lensed by Abell 370

We report on Spitzer IRAC observations of the spectroscopically confirmed z=6.56 lensed Ly-alpha emitting source HCM 6A which was found behind the cluster Abell 370. Detection of the source at 3.6 and 4.5 microns, corresponding to rest-frame optical emission, allows us to study the stellar population of this primeval galaxy. The broadband flux density at 4.5 microns is enhanced compared to the continuum at other wavelengths, likely due to the presence of strong H-alpha in emission. The derived H-alpha line flux corresponds to a star-formation rate of around 140 M_{sun}/yr, more than an order of magnitude larger than estimates from the ultraviolet continuum and Ly-alpha emission line. The dust extinction required to explain the discrepancy is A_V of about 1 mag. The inference of dust at such high redshifts is surprising and implies that the first epoch of star-formation in this galaxy occurred at z~20.Comment: 11 pages, 3 figures, ApJ Letters in pres

Molecular theory of elastic constants of liquid crystals. III. Application to smectic phases with tilted orientational order

Using the density functional formalism we derive expression for the distortion free energy for systems with continuous broken symmetry and use it to derive expression for the elastic constants of smectic phases in which director is tilted with respect to the smectic layer normal. As in the previous papers of the series (Phys. Rev. A {\bf 45}, 974 (1992), E {\bf 49}, 501, (1994)) the expressions for the elastic constants are written in terms of order and structural parameters. The structural parameters involve the generalised spherical harmonic coefficients of the direct pair correlation function of an effective isotropic liquid. The density of this effective isotropic liquid depends on the nature and amount of ordering present in the system and is evaluated self- consistently. We estimate the value of elastic constants using reasonable guess for the order and structural- parameters.Comment: 31 pages; 1 Fig. in GIF format, To be appear in Phys. Rev.

Authenticity and place attachment of major visitor attractions

This paper aims to explore the relationships between place attachment and perceived authenticity of major visitor attractions. The empirical study was conducted with a sample of international tourists to major visitor attractions in two capital cities, Helsinki, Finland and Jerusalem, Israel. The results indicate a positive correlation between place attachment and authenticity. Major visitor attractions located in places with considerable heritage experience value are considered more authentic, and that authenticity of visitor attractions is influenced by place attachment moderated by iconicity and heritage value of the destination region. These findings provide insight to the ways tourists perceive authenticity of visitor attractions and highlight the importance of the heritage value of tourism destinations for strategic planning and marketing purposes

A passion for plant life

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Improving Linear Weld Density in Ultrasonically Consolidated Parts

Ultrasonic consolidation is a novel additive manufacturing process with immense potential for fabrication of complex shaped three-dimensional metallic objects from metal foils. The proportion of bonded area to unbonded area along the layer interface, termed linear weld density (LWD), is perhaps the most important quality attribute of ultrasonically consolidated parts. Part mechanical properties largely depend on LWD and a high level of LWD must be ensured in parts intended for load-bearing structural applications. It is therefore necessary to understand what factors influence LWD or defect formation and devise methods to enhance bond formation during ultrasonic consolidation. The current work examines these issues and proposes strategies to ensure near 100% LWD in ultrasonically consolidated aluminum alloy 3003 parts. The work elucidates the effects of various process parameters on LWD and a qualitative understanding of the effects of process parameters on bond formation during ultrasonic consolidation is presented. The beneficial effects of using elevated substrate temperatures and its implications on overall manufacturing flexibility are discussed. A preliminary understanding of defect morphologies and defect formation is presented, based on which a method (involving surface machining) for minimizing defect incidence during ultrasonic consolidation is proposed and demonstrated. Finally, trade-offs between part quality and build time are discussed.Mechanical Engineerin

Growth and development of the banana plant3. A. The origin of the inflorescence and the development of the flowers: B. The structure and development of the fruit

In this paper, which is presented in two parts, the growth and development of the banana plant have been examined from the standpoint of the origin of the inflorescence and the development of the flowers (Part A) and the structure and development of the fruit (Part B). First the main centres of growth in these structures are located and the manner of their development is presented. Thereafter, attention is focused upon the salient events which determine the alternative courses of development with a view to designating the chemical and physiological stimuli that may be required

Sexual harassment: Overlooked and under-researched

Purpose This paper aims to focus on the gap between the very high prevalence of sexual harassment in the tourism and hospitality industry (the phenomenon) and the limited academic discussion about it (academic knowledge), and suggests ways to bridge this gap. Design/methodology/approach The gap between phenomenon and knowledge is identified by comparing official data regarding sexual harassment in the tourism and hospitality industry with a content analysis of the academic literature. Tribe’s (2006) knowledge force-field model is used to analyze this gap. Findings The five truth barriers identified by Tribe (2006), namely, person, rules, position, ends and ideology, are confirmed by the data. Five counter-forces – triangulation, interdisciplinary, collaboration, humanism and critical praxis – are developed to counter these truth barriers. Practical implications The five counter-forces offer practical solutions for research, higher education programs and the tourism industry. They demonstrate ways to reduce the high prevalence of sexual harassment in the industry and improve the working conditions of employees. Originality/value Underpinned by Tribe’s conceptual model, the paper identifies and analyzes a relative silence regarding sexual harassment in the tourism and hospitality academy in contrast to its prevalence in the industry. Additionally, it advances Tribe’s model by identifying five truth-facilitating forces. Further, it offers a research agenda for revealing hidden topics and/or biased knowledge by understanding the relationship between tourism and hospitality phenomena and academic knowledge