Optical communication and fiber design

Optical fiber has evolved from a not-so-transparent glass tube to an extraordinarily efficient transmission medium. It is now acknowledged as a central element of modern telecommunication being part of the whole optimization process to further improve transmission system performance and cost. In this paper, we briefly introduce transmission system optimization problematics as well as key fiber characteristics. We then review the elements of fiber design for optimized optical communication networks, including metropolitan, long and ultra-long haul applications and show how fibers have evolved over the last ten years to keep pace with more and more demanding requirement of transmission system.     

Articulated hybrid mobile robot mechanism with compounded mobility and manipulation and on-board wireless sensor/actuator control interfaces

This paper presents the development of a remotely operated mobile robot system with a hybrid mechanism whereby the locomotion platform and manipulator arm are designed as one entity to support both locomotion and manipulation interchangeably. The mechanical design is briefly described as well as the dynamic simulations used to analyze the robot mobility and functionality. As part of the development, this paper mainly focuses on a new generalized control hardware architecture based on embedded on-board wireless communication network between the robot’s subsystems. This approach results in a modular control hardware architecture since no wire connections are used between the actuators and sensors in each of the mobile robot subsystems and also provides operational fault-tolerance. The effectiveness of this approach is experimentally demonstrated and validated by implementing it in the hybrid mobile robot system. The new control hardware architecture and mechanical design demonstrate the qualitative and quantitative performance improvements of the mobile robot in terms of the new locomotion and manipulation capabilities it provides. Experimental results are presented to demonstrate new operative tasks that the robot was able to accomplish, such as traversing challenging obstacles, and manipulating objects of various capacities; functions often required in various challenging applications, such as search and rescue missions, hazardous site inspections, and planetary explorations.     

Ultrathin PECVD epitaxial Si solar cells on glass via low‐temperature transfer process

Fabrication of high‐quality ultrathin monocrystalline silicon layers and their transfer to low‐cost substrates are key steps for flexible electronics and photovoltaics. In this work, we demonstrate a low‐temperature and low‐cost process for ultrathin silicon solar cells. By using standard plasma‐enhanced chemical vapor deposition (PECVD), we grow high‐quality epitaxial silicon layers (epi‐PECVD) from SiH₄/H₂ gas mixtures at 175 °C. Using secondary ion mass spectrometry and transmission electron microscopy, we show that the porosity of the epi‐PECVD/crystalline silicon interface can be tuned by controlling the hydrogen accumulation there. Moreover, we demonstrate that 13–14% porosity is a threshold above which the interface becomes fragile and can easily be cleaved. Taking advantage of the H‐rich interface fragility, we demonstrate the transfer of large areas (∽10 cm²) ultrathin epi‐PECVD layers (0.5–5.5 µm) onto glass substrates by anodic bonding and moderate annealing (275–350 °C). The structural properties of transferred layers are assessed, and the first PECVD epitaxial silicon solar cells transferred on glass are characterized. Copyright © 2016 John Wiley & Sons, Ltd.     

Nanoparticle probes and mid-infrared chemical imaging for DNA microarray detection

To date most mid-infrared spectroscopic studies have been limited, due to lack of sensitivity, to the structural characterization of a single oligonucleotide probe immobilized over the entire surface of a gold-coated slide or other infrared substrate. By contrast, widely used and commercially available glass slides and a microarray spotter that prints approximately 120-μm-diameter DNA spots were employed in the present work. To our knowledge, mid-infrared chemical imaging (IRCI) in the external reflection mode has been applied in the present study for the first time to the detection of nanostructure-based DNA microarrays spotted on glass slides. Alkyl amine-modified oligonucleotide probes were immobilized on glass slides that had been prefunctionalized with succinimidyl ester groups. This molecular fluorophore-free method entailed the binding of gold-nanoparticle-streptavidin conjugates to biotinylated DNA targets. Hybridization was visualized by the silver enhancement of gold nanoparticles. The adlayer of silver, selectively bound only to hybridized spots in a microarray, formed the external reflective infrared substrate that was necessary for the detection of DNA hybridization by IRCI in the present proof-of-concept study. IRCI made it possible to discriminate between diffuse and specular external reflection modes. The promising qualitative results are presented herein, and the implications for quantitative determination of DNA microarrays are discussed.     

Cinemetrics: Embodying architectural representation in the digital age

How can architecture emerge from the prison of its current forms of representation? Grahame Shane1 1 D.G. Shane, “Balkanization and the Postmodern City,” in Peter Lang (ed.), Mortal City, New York: Princeton Architectural Press, 1995, pp. 55-69. interprets the concluding diagram of Robin Evans' Projective Cast: Architecture and its Three Geometries2 2 Robin Evans, The Projective Cast: Architecture and Its Three Geometries, Cambridge, MA: MIT Press, 1995. as a critique of postmodern architecture's self-reflection and lack of engagement with the world. Shane argues that Evan's diagram depicts architectural representation as a self-reinforcing, closed, conceptual triangle of mirrored reflections between the human observer, the scopic regime of perspective, orthographic architectural drawing conventions, and designed objects. Shane draws his interpretation from Evans's early work on Victorian prison architecture as well as one of Evan's last public lectures. Shane characterized Evans' critical view of postmodern architectural practice and representation as a “self-correcting means of stabilization and pacification of the physical, built environment.”3 3 Shane, “Balkanization and the Postmodern City,” p. 68 This essay develops a theory of Cinemetrics that demonstrates how contemporary architectural production, with the aid of digital tools, has the capacity to break this closed system with open-ended, embodied cybernetic feed-back loops within a wider public culture engaged in the making and imagining of architecture.4 4 Brian McGrath and Jean Gardner, Cinemetrics: Architectural Drawing Today, London: Wiley-Academy, 2007. This essay argues that this break can only be accomplished by embodying architectural representation through a careful engagement with Gilles Deleuze's philosophy of movement and time images derived from cinema,5 5 Gilles Deleuze, Cinema 1: the movement image, Hugh Tomlinson and Habberjam (trans.), Minneapolis, MN: University of Minnesota, 1986; Cinema 2: the time-image, Hugh Tomlinson and Robert Galeta (trans.), Minneapolis, MN: University of Minnesota, 1989. Henri Bergson's theories of memory, attention and duration,6 6 Henri Bergson, Creative Evolution, Arthur Mitchell (trans.), Lanham, MD: University Press of America, 1991; Henri Bergson, Matter and Memory, M.N. Paul and W.S. Palmer (trans.), New York: Zone Books, 1991. and from Charles Sanders Peirce's pragmatic semiosis.7 7 Charles Sanders Peirce, The Essential Peirce: Selected Philosophical Writings, Vol. 2 (1893-1913), Peirce Edition Project, Bloomington, IN: Indiana University Press, 1998.      

Microstructure-Based Estimation of Strength and Ductility Distributions for $$\alpha +\beta $$ Titanium Alloys

Titanium alloys are processed to develop a wide range of microstructure configurations and therefore material properties. While these properties are typically measured experimentally, a framework for property prediction could greatly enhance alloy design and manufacturing. Here a microstructure-sensitive framework is presented for the prediction of strength and ductility as well as estimates of the bounds in variability for these properties. The framework explicitly considers distributions of microstructure via new approaches for instantiation of structure in synthetic samples. The parametric evaluation strategy, including the finite element simulation package FEpX, is used to create and test virtual polycrystalline samples to evaluate the variability bounds of mechanical properties in Ti-6Al-4V. Critical parameters for the property evaluation framework are provided by measurements of single crystal properties and advanced characterization of microstructure and slip system strengths in 2D and 3D. Property distributions for yield strength and ductility are presented, along with the validation and verification steps undertaken. Comparisons between strain localization and slip activity in virtual samples and in experimental grain-scale strain measurements are also discussed.

     

Impact of oxygen concentration during the deposition of window layers on lowering the metastability effects in Cu(In,Ga)Se2/CBD Zn(S,O) based solar cell

The purpose of the present paper is to focus on the impact of oxygen gas partial pressure during the sputtering of i‐ZnO and ZnMgO on the transient behavior of Cu(In,Ga)Se₂ (CIGSe) based solar cells parameters when a CBD‐Zn(S,O) buffer layer is used. Based on electrical characterization of cells, it is observed that the effect of light soaking is different on J–V characteristics depending on whether oxygen is or is not present during the first deposition time of the i‐ZnO or ZnMgO layers. In fact, when cells are prepared with standard i‐ZnO, the efficiencies are very low and a pronounced transient behavior is observed. However, when the first 10 nm of i‐ZnO or ZnMgO is formed by sputtered layer without adding oxygen during the process, depending on the thickness of the buffer layer, the transient effects strongly decreases. It is then possible to get stable cells reaching efficiencies quite similar to the CdS reference cells, especially with ZnMgO, without any post‐treatments. Copyright © 2015 John Wiley & Sons, Ltd.