Relationship between mirror dimensions and failure stress for optical fibers
Standard glass optical fiber was intentionally damaged and strength tested in tension for a wide range of failure stress values. The mirror/mist boundary on each specimen was measured and compared to the measured failure stress. When the size of the fracture mirror is small compared to the fiber diameter, the well-known linear square root dependence of strength on mirror size was reaffirmed. However, when the mirror size approaches the fiber diameter, this relationship does not hold. The classical relationship overestimates the failure stress for large mirrors. It was determined that the circular shape of the fiber contributes to, but can not fully account for, departure from the classical strength/mirror relationship. A new empirical relationship was developed to enable predictive determinations of failure stress to levels as low as 20 to 25 kpsi (0.14 to 0.17 GPa).
Investigation of mechanical stress applied to the optical modular cables at low temperatures
This paper presents the investigate of mechanical loadings applied to the optical cables module structure at low temperatures. Mechanical loads experienced by the optical cable in the process of construction of fiber-optic communication lines, and in the course of their operation, are major factors affecting the reliability and service life optical cable. Over the past few years, optical cable modular design greatly supplanted other modifications, so in this article addresses the evaluation of mechanical loads applied to the modular design cables at low temperatures.
Coated-wire electrodes containing polymer immobilized ionophores blended with poly(vinyl chloride).
Polymers containing covalently attached 18-crown-6 or 2.2.2 cryptand units were incorporated into plasticized PVC membranes and the composite membranes were examined as potassium ion sensor elements. Ionophores were linked to carboxy-PVC and to poly(acrylic acid) via amide linkages to an alkyl spacer unit. Coated-wire electrodes (CWEs) from the immobilized ionophores gave acceptable responses, but conventional ion-selective membrane electrodes (ISEs) prepared by solvent casting were inactive. Dip-cast membranes did give active ISEs. Potassium electrode performance was independent of the loading of the ionophore within the acrylate support polymer, but depended upon the spacer length. Ion selectivity varied with the ionophore loading within the support polymer. Selectivity is a composite of the ionophore selectivity and ion-exchange interactions with the acrylate backbone, giving selectivities akin to carboxylate substituted crown ethers, notably enhanced monovalent/divalent ion discrimination relative to the ionophore in solution. Polymer immobilization extended the lifetime of active electrodes.