Effect of blade rotation on particle classification performance of hydro-cyclones

The effects of top blade rotation of hydro-cyclones on particle classification performance were examined experimentally and via a simulation study.It was noticed that the cut size of a hydro-cyclone decreases as the rotational speed of the top plate increases. Compared to the standard case without rotation, the accuracy of classification with top plate rotation increases under the wide range of operational conditions.Newly proposed type-D cyclones with a special blade indicated the smallest cut size with a high accuracy of classification. The increase of classification accuracy is due to the production of outward radial flow near the top plate and this result was simulated by a CFD calculation.The computer simulation also agreed qualitatively with the experimental data.     

Modeling and real‐time simulation of UPFC

We have developed a digital real‐time simulator of Power Electronics Controllers, so‐called FACTS (Flexible AC Transmission Systems) Controllers and/or Custom Power by using MATLAB^TM/SIMULINK^TM and dSPACE^TM System. This paper describes the modeling and the calculation accuracy of a UPFC (Unified Power Flow Controller) model. Hence, the developed simulator operates at a large time step, in order to improve simulation accuracy, a correction processing of the switching delay is implemented into the UPFC model. Calculation accuracy of the real‐time UPFC model is at the same level as EMTDC^TM results. We confirm stable operation of the developed UPFC model by connecting a commercial real‐time digital simulator (RTDS^TM). © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(1): 19–26, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20200     

Preparation of various DLC films by T-shaped filtered arc deposition and the effect of heat treatment on film properties

Different types of diamond-like carbon (DLC) films (ta-C, a-C, ta-C:H and a-C:H) were prepared on super hard alloy (WC-Co) substrate using a T-shape filtered arc deposition (T-FAD) system. At first, the film properties, such as structure, hydrogen content, density, hardness, elastic modulus, were measured. Ta-C prepared with a DC bias of −100 V showed the highest density (3.1 g/cm³) and hardness (70-80 GPa), and the lowest hydrogen content (less than 0.1 at. %). It was found that the hardness of the DLC film is proportional to approximately the third power of film density. The DLC films were then heated for 60 min in an electric furnace at 550 °C in N₂. Only the ta-C film hardly change its structure, although other films were graphitized. The 200-nm thick ta-C film was then heated for 60 min through the temperature range from 400 to 800 °C in N₂ with 2 vol.% of O₂ and the film structure found to be stable up to 700 °C. The substrate was oxidized at 800 °C, indicating the ta-C film had a thermal barrier function up to that temperature.     

Polyglycolide as a Biodegradable Nucleating Agent for Poly(L‐lactide)

DSC indicated that the nucleation of PLLA is enhanced in the presence of PGA even at a PGA content as low as 0.1 wt.‐%. However, the enhancing behavior of PGA was different to that of other nucleating agents for PLLA. Polarized optical microscopy revealed that the presence of PGA increased the number of PLLA spherulites per unit area. WAXD showed that in the PLLA/PGA films, PLLA and PGA crystallize separately to form their respective crystallites and PGA crystallites were formed at a PGA content at above 3 wt.‐% (at least). FTIR spectroscopy indicated that that there are significant interactions between PLLA and PGA chains in amorphous regions. Such interactions should have enhanced the growth of PLLA crystallites from the surface of PGA crystallites.

     

Atomic-scale in-situ observation of carbon nanotube growth from solid state iron carbide nanoparticles

We have first observed the nucleation and growth process of carbon nanotubes (CNTs) from iron carbide (Fe 3C) nanoparticles in chemical vapor deposition with C 2H 2 by in situ environmental transmission electron microscopy. Graphitic networks are formed on the fluctuating iron carbide nanoparticles, and subsequently CNTs are expelled from them. Our atomic scale observations suggest that carbon atoms diffuse through the bulk of iron carbide nanoparticles during the growth of CNTs.     

Crystallization behavior of linear 1-arm and 2-arm poly(l-lactide)s: Effects of coinitiators

Linear 1-arm and 2-arm poly(l-lactide) [i.e., poly(l-lactic acid) (PLLA)] polymers having relatively low number-average molecular weights (M_n) (≤5 × 10⁴ g mol⁻¹) were synthesized by ring-opening polymerization of l-lactide initiated with tin(II) 2-ethylhexanoate (i.e., stannous octoate) and coinitiators of l-lactic acid, 1-dodecanol (i.e., lauryl alcohol), and ethylene glycol (these PLLA polymers are abbreviated as LA, DN, and EG, respectively). For M_n below 1.5 × 10⁴ g mol⁻¹, non-isothermal crystallization during heating and isothermal spherulite growth were disturbed in linear 2-arm PLLA (EG) compared to those in linear 1-arm PLLA (LA and DN). This finding indicates that the chain directional change, the incorporation of the coinitiator moiety as an impurity in the middle of the molecule, and their mixed effect disturbed the crystallization of linear 2-arm PLLA compared to that of linear 1-arm PLLA, in which the chain direction is unvaried and the coinitiator moiety is incorporated in the chain terminal. Also, the finding strongly suggests that the reported low crystallizability of multi-arm PLLA (arm number ≥ 3) compared to that of linear 1-arm PLLA is caused not only by the presence of branching points but also by the chain directional change, the incorporation of the coinitiator moiety in the middle of the molecule, and their mixed effect. The effects of the chain directional change and the position of the incorporated coinitiator moiety on the crystallization and physical properties of linear 1-arm and 2-arm PLLA decreased with an increase in M_n.     

Casting of High-Aluminum-Content Mg Alloys Strip by a Horizontal Twin-Roll Caster

This study was aimed to investigate casting of high-aluminum-content Mg alloys strip by a horizontal twin-roll caster. A horizontal-type twin-roll caster was equipped with a nozzle. This nozzle was movable. The roll size was φ300 × W150, and copper rolls were used. The rolling road was very small. It was possible to cast AZ91D and AZ121 magnesium alloys continuously by a horizontal twin-roll caster. There was gloss and no crack. The thickness of as-cast strip of AZ91D was 4.5 mm and that of AZ121 was 4.6 mm, respectively. In the case that roll velocity was 48 m/min, the thickness of as-cast strip of AZ121 was 2.0 mm. A 2.0-mm-thick strip was able to coil, and the diameter was φ500 mm. The microstructures of the as-cast strip of AZ91D and AZ121 magnesium alloys were observed using light optical microscopy. Isometric dendrite crystals were observed at the as-cast strip. The as-cast strip without facing of AZ91D and AZ121 magnesium alloys were able to hot rolling of 75 pct reduction. The surface of the as-rolled sheet was flat and glossy. The tensile strength of the as rolled was 230 MPa and the elongation of as rolled was 4 pct.     

Highly Enhanced Accelerating Effect of Melt‐Recrystallized Stereocomplex Crystallites on Poly(L‐lactic acid) Crystallization, 2–Effects of Poly(D‐lactic acid) Concentration

The effects of varying concentrations of incorporated PDLA on the acceleration of PLLA homo‐crystallization due to stereocomplex (SC) crystallite formation are investigated in PLLA films doped with PDLA over the wide concentration range of 1–10 wt%. PLLA homo‐crystallization is accelerated for all the PDLA concentrations when the processing temperature T_p is just above the endset melting temperature of the SC crystallites (T_p = 226–238 °C), although the appropriate T_p range becomes narrow at low concentrations of PDLA. The accelerating effects of SC crystallites depend on the SC crystalline thickness and the interaction between the SC crystalline regions and PLLA amorphous regions for T_ps below and above the melting peak temperature of the SC crystallites, respectively.