Abstract: In a network topology design apparatus for designing a network topology connecting a plurality of points by communication lines so that a predetermined traffic volume is transmitted between the plurality of points, chromosomes wherein the network topology is represented in a matrix are created, and a genetic algorithm is applied to evolve the chromosomes in order to improve cost performance. Then by applying a local search method to the chromosomes which have been evolved by the genetic algorithm, to search the chromosomes in the neighborhood of the evolved chromosomes, a chromosome with a better cost performance is determined. In this way, genetic algorithms and local search methods are applied to design a network topology with excellent cost performance.

Abstract: A polycarbonate composition comprising 100 parts by weight of an aromatic polycarbonate, 0.005 to 0.2 part by weight of an ester of an aliphatic monocarboxylic acid having 10 to 25 carbon atoms and an aliphatic polyhydric alcohol having 2 to 10 carbon atoms, and 0.015 to 0.3 part by weight of a first aromatic compound which is an aromatic ether, ester or carbonate compound having at least four benzene rings in the molecule, wherein the above ester is contained in the above range to ensure that the first aromatic compound is contained in a deposit on the polymer contacting surface of a metal mold in an amount of 0.5 to 3 parts by weight based on 1 part by weight of the ester when a 120 mm x 50 mm board having a thickness of 2 mm is injection molded at a cylinder temperature of 380° C., a mold temperature of 80° C., an injection speed of 200 mm/sec and a holding pressure of 3,432 kPa (35 kgf/cm2).

Abstract: An aromatic polycarbonate composition which is suitable for use in the production of an optical molded article such as an optical disk or lens and has excellent heat stability and releasability at the time of molding. This composition comprises 100 parts by weight of an aromatic polycarbonate obtained by reacting an aromatic dihydroxy compound with a carbonic acid diester in the presence of at least one ester exchange catalyst selected from the group consisting of an alkali metal compound and an alkali earth metal compound, 0.0001 to 0.3 part by weight of an epoxy compound and 0.015 to 0.3 part by weight of an aromatic compound having at least four benzene rings in the molecule.

Abstract: An aromatic polycarbonate which has a low radical concentration and retains a good color, transparency, durability and stability even after it is kept under high temperature and high humidity for a long time and a composition thereof. The polycarbonate and composition are advantageously used in an optical disk substrate.

Abstract: A polycarbonate having excellent color and stability and a production process therefor. In the production of a polycarbonate by melt polycondensing a dihydroxy compound and a carbonic acid diester in the presence of an ester exchange catalyst, the each content of an aldehyde group in the dihydroxy compound and the carbonic acid diester is reduced to 3×10−6 equivalent/mol or less.

Abstract: In a network topology design apparatus for designing a network topology connecting a plurality of points by communication lines so that a predetermined traffic volume is transmitted between the plurality of points, chromosomes wherein the network topology is represented in a matrix are created, and a genetic algorithm is applied to evolve the chromosomes in order to improve cost performance. Then by applying a local search method to the chromosomes which have been evolved by the genetic algorithm, to search the chromosomes in the neighborhood of the evolved chromosomes, a chromosome with a better cost performance is determined. In this way, genetic algorithms and local search methods are applied to design a network topology with excellent cost performance.

Abstract: A method of producing a polycarbonate or the like which is excellent in hydrolysis and heat stability such as a reduction in molecular weight at the time of molding and color retention and moldability such as releasability and transferability, rarely experiences residence deterioration such as coloring, crosslinking and gel formation and has an extremely small content of foreign matter by employing a special structure for an opening in the side surface of a horizontal cylindrical vacuum resin treating apparatus, supplying a molten polycarbonate into a unidirectional rotary intermeshing double-screw extruder under specific conditions, adding a specific agent under specific conditions and cleaning the inner surface of a production apparatus by a specific method.

Abstract: A polycarbonate having excellent color and stability and a production process therefor.

Abstract: A polycarbonate which is stable against thermal decomposition at a temperature range for melt molding without adding a heat resistant stabilizer and suitable for the melt molding of a thin product, production method and molded products thereof. The polycarbonate is comprising mainly a recurring unit represented by the following formula (1), and has a percentage of the total of integrated intensities of all signals detected at four ranges, &dgr;=2.14 to 2.17 ppm, &dgr;=3.46 to 3.49 ppm, &dgr;=3.62 to 3.69 ppm and &dgr;=5.42 to 5.46 ppm to the integrated intensity of a signal derived from a methyl group detected at a range of &dgr;=1.50 to 2.00 ppm of 0.01 to 2.0% in its 1H-NMR spectrum in heavy chloroform and a viscosity average molecular weight of 10,000 to 100,000.

Abstract: A method for maintaining polycarbonate pellets by maintaining the potential of electrostatic charge of polycarbonate pellets (A) having adhering foreign matter having a particle diameter of 0.5 to 10 &mgr;m in an amount of 10,000 pieces/g or less in a range of ±10 kV in steps up to the step of melting the polycarbonate pellets (A) for producing a polycarbonate molded article.

Abstract: A new gamma-ray stabilizer comprising a combination of 100 parts by weight of a benzyl compound (A) having a specific chemical structure and 0.01 to 10 parts by weight of a pentaerythritol phosphorous ester (B) having a spirocyclic structure. Said stabilizer is preferably blended in such a manner that said (A) is contained in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of a thermoplastic polymer (polycarbonate or the like), and said (B) is contained in an amount of 0.01 to 1 part by weight based on 100 parts by weight of said (A).

Abstract: An aromatic polycarbonate composition which contains 0.05 to 65 ppm of bonded phosphorus atoms to polycarbonate chains and free phosphorus compounds consisting of a tervalent phosphorus compound and a pentavalent phosphorus compound in a specific ratio. It is excellent in transparency, color stability and residence stability at the time of molding and is suitably used in disk substrates.

Abstract: An aromatic polycarbonate composition comprising at least one quaternary onium salt selected from the group consisting of a phosphoric acid phosphonium salt, phosphonic acid phosphonium salt, condensed phosphoric acid phosphonium salt, phosphorous acid phosphonium salt, phosphonous acid phosphonium salt, boric acid phosphonium salt, sulfuric acid phosphonium salt, phosphoric acid ammonium salt, phosphonic acid ammonium salt, condensed phosphoric acid ammonium salt, phosphorous acid ammonium salt, phosphonous acid ammonium salt, boric acid ammonium salt and sulfuric acid ammonium salt,and has a viscosity average molecular weight of 10,000 to 100,000 and a melt viscosity stability of 0.5% or less. The aromatic polycarbonate composition has excellent transparency, heat resistance and color stability. A process for producing the above aromatic polycarbonate composition is also disclosed.

Abstract: A method for producing a high-quality thermoplastic branched polycarbonate which is used in blow-molding, extrusion or vacuum molding from a linear aromatic polycarbonate efficiently. The thermoplastic branched polycarbonate is produced by melt-mixing and reacting a substantially linear aromatic polycarbonate with an acid anhydride having at least two cyclic acid anhydride groups in a molecule in the presence of a basic catalyst.

Abstract: In a process for producing a polyarylate through the polycondensation of an aromatic dihydroxy compound and an aromatic ester bond forming precursor, a salicylic acid ester compound having a specific structure is used as a terminal modifying agent. In a process for producing a polyarylate through the polycondensation of an aromatic dihydroxy compound and an ester bond forming aromatic dicarboxylic acid derivative, a polyarylate of high-molecular weight having excellent color tone and hue stability is obtained.

Abstract: An aromatic polycarbonate which has high durability and is excellent in color tone, transparency and mechanical strength, especially an aromatic polycarbonate which has high durability and stability when it is used under high temperature and high humidity conditions for a long time, and production method and use thereof. In the aromatic polycarbonate which has a sodium element content of 100 ppb or less and a content of each of Ni, Pb, Cr, Mn and Fe of 70 ppb or less and the method of producing a polycarbonate by polycondensing an aromatic dihydroxy compound and a carbonic acid diester, the above aromatic polycarbonate is produced by controlling 1) the content of sodium element contained in each of the above raw materials to 52 ppb or less, 2) the content of each of Fe, Cr, Mn, Ni and Pb to 40 ppb or less and 3) the amount of a specific catalyst to a specific value based on the content of Fe contained in the raw materials.

Abstract: The present invention provides a salicylic acid ester derivative having an impurity content lower than a specific level and expressed by the following formula (1) (in the formula, R1 is methyl group or ethyl group, R2, which may be substituted optionally, is an alkyl group having a carbon number of from 1 to 30, alkoxy group having a carbon number of from 1 to 30, aryl group having a carbon number of from 6 to 30, aryloxy group having a carbon number of from 6 to 30, aralkyl group having a carbon number of from 6 to 30 or aralkyloxy group having a carbon number of from 6 to 30). The salicylic acid ester derivative is effective as a terminal blocking agent or a polymerization. promoting agent for a polycarbonate, and gives a polycarbonate having good color tone and suitable for optical material use.

Abstract: A polycarbonate resin composition which is excellent in thermal stability such as color retention at the time of melt molding, for example, the prevention of yellowing, and moldability such as releasability and transferability and therefore particularly suitable for the production of precision optical moldings such as optical disk substrates and lenses. The polycarbonate resin composition comprises (A) an aromatic polycarbonate, and (B) a cyclic carbonate compound, a monoester compound of a divalent aliphatic alcohol having 3 to 14 carbon.

Abstract: Aromatic polycarbonate having a reduced discoloration and improved heat stability, hue, etc. is provided by keeping a pressure in a raw material melting vessel and the linear velocity of a gas in a transporting piping in a specific range, keeping the concentration of a nitrogen-containing basic compound in a specific range, recycling a byproduct containing specific amounts of impurities, suppressing the amounts of a nitrogen-containing basic compound, metallic elements and a silicic acid derivative in the carbonic acid diester at specific values or less, prescribing the material quality of the reaction facilities, and/or forming an oxide layer at the inner wall surfaces of the reaction facilities.

Abstract: The relative intensity of fluorescent light of a melt-polycondensed aromatic polycarbonate produced by the transesterification process (melt polymerization process) of an aromatic dihydroxy compound and a carbonic acid diester in the presence of a catalyst comprising a basic nitrogen compound and/or a basic phosphorus compound in combination with an alkali metal compound is suppressed to 4.0×10−3 or below at a wavelength of 465 nm based on a standard substance in a fluorescent light spectrum obtained by the excitation wavelength of 320 nm. An aromatic polycarbonate having good color stability, especially good stability to the deterioration of the chip color during storage of the chip in air at room temperature can be produced by the present invention.