Hybrid fiber amplifiers consisting of cascaded TDFA and EDFA for WDM signals

The detailed gain characteristics of hybrid fiber amplifiers that consist of cascaded thulium-doped fiber amplifiers (TDFAs) and erbium-doped fiber amplifiers (EDFAs) are reported. The experimental results showed that the hybrid amplifiers have gains of over 20 dB with the bandwidth of more than 80 nm in the wavelength range between 1460 and 1560 nm. The low noise figure (NF) below 7 dB was obtained in 1460-1540 nm when placing a TDFA in the first stage followed by an EDFA and in 1480-1560 nm when placing amplifiers in a reversed order. The gain of TDFA and EDFA was optimized for minimizing the gain variation ratio (GVR=(maximumgain-minimumgain)/minimumgain: in the unit of decibels) of the hybrid amplifiers, and it could be minimized to less than 0.4 for the amplifiers that have gain in the wavelength region from 1460 to 1537 nm. The gain-equalization technique was applied, and the hybrid amplifier that had an average gain of 20 dB, a gain excursion of less than 2 dB, an output power of 14.5 dBm, and an NF of less than 7 dB in the 77-nm gain band was achieved.     

A new installation for treatment of road runoff: up-flow filtration by porous polypropylene media.

We installed a new device on a paved road to treat runoff from a roadway surface. All the stormwater runoff was transferred into the device and the runoff equivalent to 10 mm/hr or less was treated. The treatment method consists of sedimentation and up-flow filtration with porous polypropylene (PPL) processes. The treated runoff was discharged into the existing storm drainage pipe. The average removal efficiency of the initial runoff at the beginning of rainfall which has high pollution intensity was about 90% for SS, about 70% for COD, about 40% for total phosphorus (T-P), about 80% for Pb and Cd, about 70% for Zn, Cu, Mn and Cr, and about 60% for polycyclic aromatic hydrocarbons (PAHs). The overall removal efficiencies of the experiment that ran for four months remained > 60% of SS, > 40% of COD, > 60% of heavy metals, and > 40% of PAHs. The PPL is excellent for removing smaller size particulates of suspended solids, which originate basically from diesel exhaust, as well as larger size particulates from automobile tires, asphalt roads, and other accumulated source(s) of clay and sand, etc.     

Detection of moving object by mobile stereo omnidirectional system (SOS)

Moving object detection with a mobile image sensor is an important task in robotics and computer vision, when considering the practical use of robotics in human environments. In this paper, we propose a robust method that detects moving objects in the environment using the omnidirectional depth information obtained by a mobile Stereo Omnidirectional System (SOS). In order to detect only the moving objects within the depth image that are obtained by a sensor in motion, we first estimate the ego‐motion of the sensor, and generate a predicted depth image for the current time from the depth obtained at the previous time by only considering the ego‐motion of the sensor. Then the predicted depth image is compared with the actual one obtained at the current time, and the inconsistent regions are detected as moving objects. When the sensor moves, occlusions will occur in the scene and they will cause false detections. However, these false detections can be suppressed by estimating the occlusion regions using the ego‐motion parameters of the sensor and the jump edges in the depth image. The effectiveness of the method is shown with experimental results for a real environment. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(3): 29–38, 2005; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20155     

Development of extruded ethylene propylene rubber insulated superconducting cable

A superconducting power cable is one of the promising ways of underground transmission of huge electric power in the future. The authors have long proposed the idea of the extruded polymer insulation for superconducting cables. The prominent features of the design are to exploit the excellent electrical properties of polymer in the cryogenic temperatures and to separate the helium coolant from the electrical insulation. Although the extruded cross-linked polyethylene cable has proved ability at the liquid nitrogen temperature, the cable insulation cracked due to mechanical stress during cooling to the liquid helium temperature. To overcome this problem, ethylene propylene rubber (EPR) was selected as a new insulating material considering the good results of mechanical and electrical tests of EPR samples at cryogenic temperatures. An extruded EPR insulated superconducting cable 15 m in length was fabricated and a cooling test down to the liquid helium temperature and a voltage test at the liquid helium temperature were carried out with fair success. This is a breakthrough in terms of the electrical insulation design of cryogenic cables.     

The apparent induction period for γ-Al2O3 development in thermal oxide films on aluminium

A novel technique has been employed to allow ready detection of fine crystallites, probably of -Al₂O₃, of sizes generally less than 10 nm in thermal oxide films on aluminium. Using this approach, the relationship between the average population density of -Al₂O₃ crystals and oxidation time has been obtained for the first time. Importantly, it has been found that oxidation at temperatures of 515 or 490°C results in fine crystal development almost from the onset of thermal oxidation. Thus, the so-called induction period for the growth of the -Al₂O₃ crystals, determined previously from weight gain data, should now be regarded as the oxidation time required for both the population density and sizes of the crystals to become sufficiently large to cause significant deviation in the weight gain data from the initial inverse logarithmic law describing the growth of the amorphous oxide.     

Synthesis and conformational studies of polymers and copolymers of O,O′-dimethyl-l-β-3,4-dihydroxyphenyl-α-alanine with γ-benzyl-l-glutamate

Eight different copolymers of $\text{O,O′-}\text{dimethyl-}\text{l}\text{-β-3,4-}\text{dihydroxyphenyl}\text{-α-}\text{alanine}$ ($\text{O,O′-}\text{dimethyl-}\text{l}\text{-}\text{Dopa}$) and γ-benzyl-l-glutamate with degrees of polymerization of 320-80 have been synthesized by the N-carboxyanhydride method. From the results obtained by a study of the optical rotatory dispersion and circular dichroism for the copolymer series, the conformation of $\text{poly}\text{(O,O′-}\text{dimethyl-}\text{l}\text{-Dopa}\text{)}$ is a right-handed helix in helicogenic solvents such as chloroform, dioxane or 2-chloroethanol. Copolymers containing less than 50 mol % glutamate show a circular dichroism peak at 285 nm suggesting stacking of aromatic groups in the side chain. $\text{Poly}\text{(O,O′-}\text{dimethyl-}\text{l}\text{-Dopa}\text{)}$ is in the random coil structure in trifluoroacetic acid or hexafluoroacetone. The results were compared with those of $\text{poly}\text{(O,O′-}\text{dicarbobenzoxy-}\text{l}\text{-Dopa}\text{)}$ and poly(l-Dopa).     

Improved synthetic method and conformation studies of polymers and copolymers of l-β-3,4-dihydroxyphenyl-α-alanine with l-glutamic acid

Eight different copolymers of l-β-3,4-dihydroxyphenyl-α-alanine (l-Dopa) and l-glutamic acid with high degrees of polymerization have been synthesized by the treatment of a series of $\text{copoly}\text{(O,O′-}\text{dimethyl-}\text{l}\text{-Dopa}$, γ-benzyl-l-glutamate) with boron tribromide in chloroform. The conformation of poly(l-Dopa) has been established to be a right-handed helix in trimethyl phosphate on the basis of the following observations. The [θ]₂₂₂ and b₀ values of the copolymers were almost linear with composition in trimethyl phosphate. The linear relationship between the rotation properties and composition indicates that poly(l-Dopa) has the same helical sense as that of poly(l-glutamic acid) which is a right-handed α-helix.     

Influence of silicon on the growth of barrier-type anodic films on titanium

Amorphous anodic titania, stabilised by incorporation of silicon species, is shown to grow to high voltages on sputter-deposited, single-phase Ti-Si alloys during anodizing at a constant current density in ammonium pentaborate electrolyte. The films comprise two main layers, with silicon species confined to the inner layers. An amorphous-to-crystalline transition occurs at ∼60 V on the Ti-6 at.% Si alloy, while the transition is suppressed to voltages above 140 V on alloys with 12 and 26 at.% silicon. The crystalline oxide, nucleated at a depth of ∼40% of the film thickness, is associated with the presence of a precursor of crystalline oxide in the pre-existing air-formed oxide. The modified structure of the air-formed oxide due to increased incorporation of silicon species suppresses the amorphous-to-crystalline transition until the onset of dielectric breakdown. The transport numbers of cations and anions during growth of the anodic oxides are independent of the concentration of silicon species in the inner layer, despite the marked change in the field strength.