Metalorganic Chemical Vapor Deposition of CdTe(133) Epilayers on Si(211) Substrates

Single-crystalline CdTe(133) films have been grown by metalorganic chemical vapor deposition on Si(211) substrates. We studied the effect of various growth parameters on the surface morphology and structural quality of CdTe films. Proper oxide removal from the Si substrate is considered to be the principal factor that influences both the morphology and epitaxial quality of the CdTe films. In order to obtain single-crystalline CdTe(133) films, a two-stage growth method was used, i.e., a low-temperature buffer layer step and a high- temperature growth step. Even when the low-temperature buffer layer shows polycrystalline structure, the overgrown layer shows single-crystalline structure. During the subsequent high-temperature growth, two-dimensional crystallites grow faster than other, randomly distributed crystallites in the buffer layer. This is because the capturing of adatoms by steps occurs more easily due to increased adatom mobility. From the viewpoint of crystallographic orientation, it is assumed that the surface structure of Si(211) consists of (111) terrace and (100) step planes with an interplanar angle of 54.8°. This surface structure may provide many preferable nucleation sites for adatoms compared with nominally flat Si(100) or (111) surfaces. The surface morphology of the resulting films shows macroscopic rectangular-shaped terrace—step structures that are considered to be a (111) terrace with two {112} step planes directed toward 〈110〉.     

Comparison of the antioxidant activities of roasted and explosive puffed coffees

We investigated the explosive process effect on antioxidant activities of coffee bean. The total polyphenol contents of powdered extract of explosive puffing coffee bean at 0.75 MPa (PEP 7.5) and powdered extract of explosive puffing coffee bean at 0.9 MPa (PEP 9.0) were at a significantly higher than that of the powdered extract of roasting coffee bean (PER) (P < 0.05). PEP 7.5 showed the highest levels of 3‐CQA (86.23 μg mg^?1), 4‐CQA (43.71 μg mg^?1), and 5‐CQA (31.66 μg mg^?1), and PEP 9.0 had also similar levels of chlorogenic acids, with 3‐CQA (77.99 μg mg^?1), 4‐CQA (43.71 μg mg^?1), and 5‐CQA (30.32 μg mg^?1). PEP 7.5 and PEP 9.0 showed relatively higher antioxidant capacities in DPPH, ABTS, taurine, FRAP, and β‐carotene/linoleic acid assays. PEPs partly recovered the HepG2 cell damage induced by t‐BOOH. These results suggest that puffed coffee has beneficial health effects, and could be used for the development of novel processed coffee products.     

Molecular dynamics study on the effect of solution-wall interaction potential on the properties of solution in uniformly charged hydrophobic channel

We numerically investigate the effect of the solution-wall (i.e., water-wall and ion-wall) interaction potential on the properties of confined aqueous solution by using molecular dynamics (MD) simulations. The effect is determined by comparing results obtained from the MD simulation using the Lennard-Jones (L-J) potential for the water-wall and ion-wall interactions and those using a purely repulsive potential, i.e., the Weeks-Chandler-Andersen-like potential. In the MD simulations, 680 water molecules and 20 chloride ions are included between uniformly charged plates that are separated by 2.6 nm. The results show that the properties of solution are influenced only in the region close to the wall: The water molecules are more densely packed for the case of the L-J potential. Comparison of the results of the MD simulations in the case of the L-J potential with those provided by solving the Poisson-Boltzmann equation, we found that classical continuum theory fails to predict the ion density and electrostatic potential distributions in the region near to the wall, but far way from the wall, the prediction from the continuum theory is in line with the MD simulation.     

Release behavior of active material from poly(vinyl amine)/polyelectrolyte composite hollow particles

Polyvinyl amine (PVAm) hydrogel hollow particles treated by layer-by-layer (LbL) assembly methods were fabricated. The structures of the prepared particles were confirmed through zeta-potential measurements and scanning electron microscopy (SEM). In addition, the loading amount and release rate of Chromotrope 2R (CR) from the prepared particles in each deposition step was investigated. The loading amount had an alternating tendency according to an increase in the layer number. When the outermost layer consisted of poly(sodium 4-styrenesulfonate) (PSS), CR permeation was prevented by ionic repulsion between the PSS and CR. On the other hand, CR easily permeated into the particles when the outermost layer was poly(diallyldimethyl ammonium chloride) (PDDA). The release rate was then changed by ionic interaction between the CR and the cationic polyelectrolyte and by the ionic repulsive force between the CR and the anionic polyelectrolyte. These results indicate that PVAm hydrogel hollow particles treated by the LbL method could potentially be used in the controlled release of water-soluble materials.     

Enhancement of the punch pin durability induced by the PVD coating in production process of the automotive inner pipe

This experimental studies were carried out in order to understand the effects of the PVD coating and the UNSM treatment of HSS55 (high speed steel 55) during the production of the automotive inner pipe by the plastic deformation of S45C. The field test and the SEM images revealed that the PVD coating is necessary in spite of the high compressive residual stresses which were formed at the head of a punch pin. Upon the application of the AlCrN coating with the UNSM treatment the productivity and reliability of a punch pin had improved more than about 2.6 times compared to that of the TiN coating without the UNSM treatment. It is likely that the improvement is caused by the decreased stress concentration factor by the ‘wrapped in oxides’ inside of an abrasion pit. The abrasion pits were mostly generated within range of 5% ∼ 50% of the diameter ratio from the end of a pin and reached the maximum value about 17% from the end of a pin.     

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.