Strong Influences of Melting Time and Tm3+ Concentration on Blue Up-Conversion Photoluminescence for Tm3+/Yb3+ Co-Doped TeO2–TlO0.5–ZnO Glass

In this study, by a conventional melt quenching method, we synthesized novel up-conversion phosphors of 60TeO₂–30TlO_0.5–(9−x)ZnO–xTm₂O₃–1Yb₂O₃ (x = 0.1–0.5) glasses, whose system was recently developed in our collaborative group, and their blue up-conversion photoluminescence (UCPL) of Tm³⁺ ions via three-step energy transfer from near-infrared (NIR) sensitizer of Yb³⁺ ions was observed. In particular, the substantial rate of the energy transfer <γ_d5> in the third step from Yb³⁺ to Tm³⁺ under excitation at 975 nm, which determined the final blue UCPL intensity, was estimated as a function of the rare-earth concentration. With an aid of analytical methods of PL lifetime and Judd–Ofelt theory, it was revealed that the highest energy transfer rate <γ_d5> was achieved to be 2.07 × 10⁻¹⁷ cm³/s for x = 0.2, and further increasing Tm₂O₃ content x in the fixed Yb₂O₃ resulted in the decrease in the energy transfer rate <γ_d5>. One of the plausible causes was concentration quenching of Yb³⁺ ions. The other was back-transfer from Tm³⁺ to Yb³⁺ ions. The influence of the condition of glass synthesis and the melting time on <γ_d5> was also discussed.     

Photoluminescence spectra of Si1-xGex/Si quantum well structures grown by three different techniques

Photoluminescence (PL) spectra of Si_1-xGe_x/Si multiple quantum wells have been measured at 4.2 K for the samples grown by three different techniques; conventional molecular beam epitaxy (MBE), gas-source MBE, and ultra high vacuum chemical vapor deposition (UHV-CVD). Only in the case of conventional MBE, strong emission bands appear about 80 meV below the band gap of Si_1-xGe_x. These strong emission bands disappear after the annealing at 800° C. From the dependence of the PL intensity on the excitation power, strong emission is considered to be due to some recombination center. On the other hand, in the case of gas-source MBE and UHV-CVD, the strong emission bands are undetectable, although the band-edge PL lines of Si_1-xGe_x are clearly observed. There is no significant change in the PL spectra after the annealing. The origin of the strong emission band is considered to be defects which are characteristic of conventional MBE.     

Normalizing the influence of flaw length on failure pressure of straight pipe with wall-thinning

Burst tests using wall-thinned pipe of carbon steel for high-temperature use were conducted in order to examine the influence of length of wall-thinning on burst pressure. Then, three-dimensional elastic-plastic large deformation finite element analyses (EP-FEA) were performed to accurately predict the burst pressure obtained by the tests. The failure pressure corresponding to the burst pressure in tests was defined as the maximum pressure during the analysis including the instability condition after the peak of pressure. The results showed that the failure pressure obtained by EP-FEA agreed well with the experimental results. Finally, failure pressures of wall-thinned pipes with various sizes, thicknesses, flaw lengths and depths were examined by EP-FEA with the same procedure of analysis as validated in this paper. The results showed that, from the standpoint of influence of flaw length on failure pressure, it is preferable to normalize flaw length by pipe mean radius of the unflawed section R rather than by shell parameter (Rt)^0.5, where t is the thickness of the unflawed section.     

Golden Mean analysis of bulk metallic glasses with critical diameter over half-inch for their mole fractions of compositions

Eighteen bulk metallic glasses (BMGs) with critical diameters over ～15 mm in Pd-, Zr-, Mg-, Y-, La-, Pt- and Ca-based multicomponent alloys were analyzed for their mole fractions of compositions with Golden Mean (? ～ 1.618). The results proved that the 18 BMG compositions are describable with m?^?n or mΦ^?n where Φ^?n is ?^?(n+1) plus ?^?(n?1) and m and n are positive integers. The maximum difference in fractions between the analyzed and experimental compositions was 0.038. The irrational nature of ? makes the compositions of the 18 BMGs different from those of the stoichiometric intermetallic compounds and near eutectic compositions, leading to the high glass-forming ability. The possible prototypes of the 18 BMGs have the ability to form critically-percolated local atomic arrangements for both Metal–Metal and Metal–Metalloid types of BMGs. Golden Mean analysis provides a new alloy design for fractions of alloying elements owing to its irrationality.     

Virtual fully connected WDM network: A high-performance single-hop architecture for metropolitan area networks

With the widespread use of broadband access technologies and the development of high-speed Internet backbones, the requirement for high-performance metropolitan area networks (MANs) is increasing. Traditional ring- or star-based metro networks are costly to scale up to high speed and cannot recover from multiple failures, while backbone solutions are too expensive to fit into the cost-sensitive metro market. This paper proposes a virtual fully connected (VFC) architecture for metro networks to provide high-performance node-to-node all-optical transportation. The architecture emulates a fully connected network by providing optical channels between node pairs without intermediate buffering, and thus realizes single-hop transportation and avoids expensive packet routers. In addition, a scheduling algorithm is developed for medium access control and dynamic bandwidth allocation, which achieves 100% throughput and provides a fairness guarantee. Simulations show that the VFC network achieves good performance under both uniform and non-uniform loads.     

Present status of development of high chromium steel for Japanese FBR components

This paper presents the establishment of the provisional specifications and material strength standard of the high chromium (Cr) steels for fast breeder reactor (FBR) components. For the improvement of toughness and ductility of the steels, a series of mechanical tests and metallurgical examinations are performed for several kinds of high Cr steels with the controlled balance of tungsten (W) and molybdenum (Mo). In addition, the effect of heat treatment condition on material properties is also investigated. Based on these results, it is revealed that W should be diminished to achieve better ductility and toughness and that it is difficult to improve the long-term properties by changing heat treatment condition. Then the provisional specifications of the high Cr steel for FBR components are given and the provisional material strength standard is proposed for the specifications of the steel. The standard obtained in this study is utilized for the FBR plant design.     

Amphiphilic Counterion Activators for DNA: Stimuli‐Responsive Cation Transporters and Biosensors in Bulk and Lipid Bilayer Membranes

We report that amphiphilic counterions can enable DNA to act as cation carrier, enzyme detector and biosensor. Calf thymus DNA is used as example throughout the study. Evaluation of a series of counterion activators suggests that strong amphiphilicity, alkyl or calix[4]arene tails and guanidinium cations give best results, whereas weak amphiphilicity, bola‐amphiphilicity, planar aryl tails and ammonium cations are less satisfactory for various reasons. In the U‐tube, DNA–counterion complexes can carry cations such as safranin O or p‐xylene‐bis‐pyridinium bromide (DPX) across bulk chloroform membranes, whereas anions such as carboxyfluorescein (CF) and (8‐Hydroxy‐1,3,6‐pyrenetrisulfonate (HPTS) are not transported. Uptake of DNA–counterion complexes into intact vesicles is demonstrated by DNA trapping experiments with internal polylysine. Comparison of results from different assays suggests that DNA–counterion complexes act as cation carriers under mild conditions, whereas pore formation and lysis dominate at higher concentrations. Applicability of DNA–counterion transporters for the detection of enzyme activity is demonstrated with phytate as an inactivating substrate and phytase as a reactivating enzyme. Compatibility with biosensing is exemplified with the fluorometric monitoring of phytate levels in almond extracts. The conceptual significance of these findings is briefly discussed, as are promising perspectives such as the application of DNA chemistry to multianalyte sensing in fluorogenic vesicles.     

Installation of 66 kV XLPE power-optical fiber composite submarinecable and water pipe for the Trans-Tokyo Bay Highway

The manufacturing and the installation of the optical fiber composite submarine cable and water pipe for the Trans-Tokyo Bay Highway were completed in 1993. It was the longest Japanese 66 kV XLPE power-optical fiber composite submarine cable and the first application of optical fiber composite submarine water pipe composed of two hollow galvanized steel armour wires inserted with optical fiber to monitor and control construction sites. This paper describes the application and development of the hollow steel armour wire with optical fiber ribbon and the features of construction and installation of the optical fiber composite submarine cable and water pipe