Determination of mode power distribution in a parabolic-index optical fibers: Theory and application

A novel measurement method for determining mode power distribution in a multimode parabolic-index fiber is developed. Using this method, the mode power distributions are obtained in terms of the principal mode number by numerically processing the measured Fraunhofer diffraction patterns of the near-field patterns on an output fiber endface. As an example, differential mode attenuation of a multimode parabolic-index fiber is measured. It is confirmed experimentally that the method is practically applicable to the mode power distribution measurements in a parabolic-index fiber.     

Reaction mechanism for the hydrogenolysis of coal-derived preasphaltene

Preasphaltene, prepared in advance from hydrogenation of Akabira coal, was further hydrogenated at 385 °C with a hydrogen initial pressure of 9.8 MPa for various reaction times. According to the structural analysis and the variation of the inert oxygen content of the remaining preasphaltene and the benzenesoluble product, it is concluded that the conversion of preasphaltene to asphaltene plus oil is principally the reaction of the splitting of ether linkages which reduces the polymerization degree and the saturation of the aromatic rings with hydrogen which increases the solubility in benzene.     

Photoinduced optical anisotropy and reorientation in copolymers containing 4-methoxyazobenzene side groups and methyl methacrylate units using linearly polarized 633 nm light

Liquid crystalline (LC) and non-LC copolymers that contain 4-methoxyazobenzene side groups and methyl methacrylate units were synthesized to compare the photoinduced reorientation behavior using the polarization absorption spectra of thin films. Irradiating with non-polarized 365 nm light saturated the Z-isomer in the copolymer films and subsequent exposure to a linearly polarized (LP) 633 nm light generated a photoinduced optical anisotropy (ΔA) for all Z-isomer films based on an axis-selective Z-to-E photoisomerization. When a copolymer did not exhibit a LC nature, ΔA gradually increased until 60-80 mol% of the Z-isomers isomerized to the E-isomers, but decreased upon further photoisomerization reaction. On the other hand, the magnitude of the photoinduced ΔA of a film continuously increased for LC copolymers until E-isomer formation was saturated. Thermal amplification of the photoinduced ΔA was observed for LC copolymers, but the thermal treatment resulted in the disappearance of the photoinduced ΔA for the non-LC copolymers. The axis-selective Z-to-E photoisomerization that preserves the direction of the transition moment of both isomers caused the photoinduced ΔA and increased the liquid crystalline nature of the film during the Z-to-E photoisomerization to induce the self-organization of the mesogenic groups.     

Highly enantioselective hydrogenation of α-Alkyl-β-arylpropenoic acids over cinchonidine-modified palladium catalyst

Enantioselective hydrogenation of (E)- α-alkyl-β-arylpropenoic acids was studied over the cinchonidine-modified Pd/C under the conditions optimized for (E)-α,β-diarylpropenoic acids. Enantiomeric excess (ee) of the product was increased by adjusting the α-alkyl group as a properly bulky isopropyl. The ee was as high as 80% when the β-group is phenyl, and reached 86% with p-anisyl group. Stereoselection of those substrates is similar to that of (E)-α,β-diarylpropenoic acids.     

A preliminary study for fiber spinning of mixed solutions of polyrotaxane and cellulose in a dimethylacetamide/lithium chloride (DMAc/LiCl) solvent system

Polyrotaxane fiber and polyrotaxane/cellulose blend fibers were prepared by wet-spinning of the polyrotaxane or polyrotaxane/cellulose blend solution dissolved in the new solvent system, i.e. dimethylacetamide/lithium chloride (DMAc/LiCl), into methanol and a subsequent annealing. In the resultant polyrotaxane/cellulose fiber, some undissolved rodlike cellulose microcrystals were oriented along with the fiber axis, resulting in formation of nanocomposite-like structure. From tensile measurements, it was found that the Young's modulus and tensile strength of the fibers with polyrotaxane/cellulose ratio of 1:1 and 2:1 were higher than those of the pure cellulose fiber. Although the mechanical properties of the fiber with polyrotaxane/cellulose ratio of 4:1 and the pure polyrotaxane fiber were lower than those of the pure cellulose fiber, these fibers showed significantly large strain at break (up to 90% strain), presumably due to the sliding of the cyclodextrin rings of the polyrotaxane in the fibers.     

Phase-modulated optical signal detection by retardation method

A noise-free signal detection technique, based on the retardation method, is described. In this method, a phase-modulated light, after being transmitted through an optical transmission line, is divided into two beams in an interferometer, and temporal correlation is made on optical phase for these light beams. The original signal is regenerated by detecting light intensity variation caused by the interference phenomenon. The light detection part structure and its optimum parameters are described. The basic retardation detection system behavior was successfully confirmed experimentally. Characteristics of the retardation method are clarified, compared to those for the heterodyne detection method.     

Coal hydrogenolysis in the presence of NaOH

High pressure hydrogenolysis of coal was carried out in the presence of sodium hydroxide at 350–500 °C and initial pressures of 3, 10 and 13 MPa for 15–60 min. Similar experiments were carried out under nitrogen. The yield of solid product decreased with increased reaction temperature because of the increased production of gases which are mainly hydrocarbons. Extraction of the solid products, formed under hydrogen, with pyridine and benzene shows higher yields than when nitrogen is used. This indicates that depolymerization and hydrogenation reactions were accelerated in the presence of sodium hydroxide under hydrogen.     

Phase equilibria of the VS-V5S8 system from 923 to 1323 K

Sulfur partial pressure-isotherms at temperatures from 923 to 1323 K were obtained over a wide range of compositions of VS-V₅S₈ by combining results from the phase equilibria of the VS-V₃S₄ system in the present study and those from previously reported ones for the V₃S₄-V₅S₈ system at temperatures from 923 to 1173 K. The phase equilibria of VS-V₃S₄ were determined for the composition range from VS_1.08 to VS_1.333 by the quenching method under controlled partial pressure of sulfur in the range from 10¹⁴ to 10 ⁻³ atm (1 atm = 101.3 kPa) at temperatures from 1023 to 1323 K. Three vanadium sulfides were observed for this composition range in agreement with results reported in the literature,i.e. orthorhombic VS, hexagonal VS, and V₃S₄. The quenched V₃S₄ phase with nonstoichiometric composition extended over both metal-rich and sulfur-rich regions of the plateau, supposedly representing a two phase region, observed on each Ps₂-composition isotherm. This anomalous phase relation was discussed along with the profiles of the isotherms. The partial molar enthalpies of sulfur in the nonstoichiometric hexagonal VS and V₃S₄ regions were calculated from the isotherms. Their values ranged from −46 to −56 kcal/g-at. (from −190 to −240 kJ/g-at.) and decreased with increasing deviation from stoichiometry.