Synthesis of a new polyarylenvinylene derivative based on a terstyryl group linked by a maleimide group

Summary The new polyarylenevinylene, structurally based on a terstyryl group linked by a maleimide group, was prepared from a new dibrominated diphenylmaleimide monomer and p-divinylbenzene by Heck-type Pd catalyzed polycondensation. The polymer was soluble in common organic solvents and had M _w and the polydispersity index of 73,600 g/mol and 5.0, respectively. Analysis with IR and NMR indicated that the polymer had a stereoregular vinylene sequence in the backbone of Z, E, E-configurations in series. The polymer showed optical absorption maximums at 353 nm and 444 nm and the bright orange red-colored photoluminescence at 570 nm in a solution and 590 nm in a film. Received: 19 September 2000/Revised version: 4 December 2000/Accepted: 11 December 2000     

An AGV routing policy reflecting the current and future state of semiconductor and LCD production lines

This paper presents an efficient policy for AGV and part routing in semiconductor and LCD production bays using information on the future state of systems where AGVs play a central role in material handling. These highly informative systems maintain a great deal of information on current and near-future status, such as the arrival and operation completion times of parts, thereby enabling a new approach for production shop control. Efficient control of AGVs is vital in semiconductor and LCD plants because AGV systems often limit the total production capacity of these very expensive plants. With the proposed procedure, the cell controller records the future events chronologically and uses this information to determine the destination and source of parts between the parts' operation machine and temporary storage. It is shown by simulation that the new control policy reduces AGV requirements and flow time of parts.     

Polyester polyol synthesis by alternating copolymerization of propylene oxide with cyclic acid anhydrides by using double metal cyanide catalyst

Ring-opening copolymerizations of propylene oxide (PO) with cyclic acid anhydrides, succinic anhydride (SA), maleic anhydride (MA) and phthalic anhydride (PA) were carried out in the presence of a double metal cyanide (DMC) catalyst of molecular formula Zn_2.3Cl_1.0[Co(CN)₆]_1.0?2.0^tBuOH?1.0H₂O as a means of developing functional polyols bearing ester backbones. Uniform alternating copolymers are produced when [PO]/[anhydride] in the copolymer approaches unity. All resulting copolymers have moderate molecular weights (M_n = 2300–10,600) and a narrow polydispersity index (1.02–1.49). The apparent reactivity ratio of PO is 0.34, 0.28, and 0.26 for PO/SA, PO/MA, and PO/PA copolymerizations, respectively, assuming that the reactivity ratio of the anhydrides is zero. The DMC-catalyzed PO copolymerizations with anhydrides are an efficient way to produce polyester polyols, expanding the versatility of conventional polyols.     

Decision on the memory size of embedded information systems in an ubiquitous maintenance environment

Over the last decade, emerging information communication technologies have changed our stereotype of manufacturing and service companies. Now products equipped with embedded systems can be wirelessly networked, which leads to gathering and analyzing product status, and taking appropriate actions for maintenance operations during product lifecycle in an ubiquitous way. In this environment, it is necessary to determine the appropriate memory size of embedded systems for minimizing total maintenance system costs because the memory cost is a main cost factor for implementing the ubiquitous maintenance environment. We call it memory size decision problem in this study. We have formulated this problem with a non-linear model having constraints. The decision variable is the memory size of each embedded system. To solve this problem, we have proposed a meta heuristic search method based on genetic algorithms. To show the usefulness of the proposed heuristic, we have carried out computational experiments.     

Charge distributions in PC/SAN/PCL polymer blends

The formation of space charge in polycarbonate (PC)/poly (styrene-co-acrylonitrile) (SAN) blends containing poly (ϵ-caprolactone) (PCL) as a compatibilizer for improving the miscibility, has been studied by measuring spatial charge distributions. It is found that the miscibility of PC/SAN blends is improved as the PCL content increases. The amount of charge accumulated in the blends decreases when the PCL content increases to 15% by weight and then increases when the PCL content is >15% wt. The decrease of charge at the PCL content <15% wt was attributed to the combined effects of changes in conductivities and the molecular interactions at the domain interfaces. The increase of charge at the PCL content >15% wt was attributed to the trapping of charge at the amorphous and crystalline phases of PC and PCL     

Effect of H2O evolving from TEOS based SiO2 film on the EEPROM cell characteristic

In this paper, we investigate the effect of water (H₂O) molecules evolving from silicon dioxide (SiO₂) film deposited by low pressure chemical vapor deposition (LPCVD) at 670 °C on the transistor characteristic of an electrically erasable programmable read only memory (EEPROM) cell. Fourier Transform Infra red (FT-IR) analysis reveals that H₂O is captured during film deposition and diffused to silicon surface during high thermal processing. The diffused H₂O molecules lower threshold voltage (V_t) of cell transistor and, thus, leakage current of the cell transistor is increased. In erased cell, V_t lowering is 0.25 V in which it increases leakage current of cell transistor from 1 to 100 pA. This results in the lowering of high voltage margin of a 512 Kb EEPROM from 2.8 to 2.6 V at 85 °C.     

Ultrasonic inspection of studs (bolts) using dynamic predictive deconvolution and wave shaping

Bolt degradation has become a major issue in the nuclear industry since the 1980's. If small cracks in stud bolts are not detected early enough, they grow rapidly and cause catastrophic disasters. Their detection, despite its importance, is known to be a very difficult problem due to the complicated structures of the stud bolts. This paper presents a method of detecting and sizing a small crack in the root between two adjacent crests in threads. The key idea is from the fact that the mode-converted Rayleigh wave travels slowly down the face of the crack and turns from the intersection of the crack and the root of thread to the transducer. Thus, when a crack exists, a small delayed pulse due to the Rayleigh wave is detected between large regularly spaced pulses from the thread. The delay time is the same as the propagation delay time of the slow Rayleigh wave and is proportional to the site of the crack. To efficiently detect the slow Rayleigh wave, three methods based on digital signal processing are proposed: wave shaping, dynamic predictive deconvolution, and dynamic predictive deconvolution combined with wave shaping.     

Sol-Gel-Derived Soda Lime-High Silica Glass

Sols containing well-mixed tetraethyl orthosilicate, sodium methylate (CH₃ONa), and Ca metal dissolved in HCIO₄ were hydrolyzed at low pH. After gelation, controlled drying, and subsequent firing at 600°C, the mixture yielded clear glass chunks. Glasses containing 85% to <100% SiO₂, which otherwise are difficult to make by conventional melting techniques, could be made using this technique.