Drive systems for high-speed gearless elevators

The authors present a new standardized type of gearless traction machine drive system with a PM motor for high-speed elevators. Some control functions which are indispensable for improving the performance of elevator systems have been addressed. Stringent evaluation, environment and life tests ensure that the presented system is not only high-performance but long-lasting and more reliable     

Microstructural Evolution of Transparent PLZT Ceramics Sintered in Air and Oxygen Atmospheres

Transparent lanthanum-doped lead zirconate titanate (PLZT) ceramics were fabricated by air-pressure sintering. When the PLZT (9/65/35) specimens were sintered in air, the microstructure was not uniform throughout the body; the outer region near the surface was completely dense, while the inner region of the body was porous. The thickness of the outer dense layer increased parabolically with sintering time. When the specimen was sintered in air at 1200°C for 8 h, the thickness of the dense layer was ∼0.25 mm. Therefore, when the specimen had a thickness of <0.5 mm, it was dense and transparent. This difference in microstructure was attributed to the formation of lattice vacancies as a result of PbO evaporation from the surface. The sintering atmosphere also was important in determining the thickness of the dense layer. The thickness was strongly dependent on the oxygen partial pressure of the atmosphere. The oxygen-gas trapped in pores was deemed to migrate easily through the lattice vacancies. By sintering in an oxygen-gas atmosphere at 1200°C for 8 h, a transparent PLZT with thickness up to 2 mm was fabricated.     

Oxidation and reduction characteristics of oxygen carrier particles and reaction kinetics by unreacted core model

The reaction kinetics of the oxygen carrier particles, which are used as bed material for a fluidized bed chemical looping combustor (CLC), has been studied experimentally by a conventional thermal gravimetrical analysis technique. The weight percent of nickel and nickel oxide in oxygen carrier particles and reaction temperature were considered as experimental variables. After oxidation reaction, the pure nickel particle was sintered and unsuitable to use as fluidizing particles. The oxidation reaction rate increased with increasing weight percent of nickel in oxygen carrier particles and reaction temperature. The rate of reduction shows maximum point with weight percent of nickel oxide (57.8%) and reaction temperature (750 or 800 °C) increased. In this work, the reaction between air and Ni/ bentonite particle was described by a special case of unreacted core model in which the global reaction rate is controlled by product layer diffusion resistance. However, the reaction between CH₄ and NiO/bentonite particle was described by unreacted core model in which the global reaction rate is controlled by chemical reaction resistance. The temperature dependence of the effective diffusivity of oxidation reaction and reaction rate constant of reduction reaction could be calculated from experimental data and fitted to the Arrhenius equation. Presented at the Int’l Symp. on Chem. Eng. (Cheju, Feb. 8-10, 2001), dedicated to Prof. H. S. Chun on the occasion of his retirement from Korea University.     

Developing a heuristics for glass cutting process optimization: A case of two-dimensional two-stage guillotine cutting with multiple stock sizes

This paper presents a heuristic algorithm for a two-dimensional two-stage guillotine cutting problem with multiple stock sizes by allowing the rotation of items by 90°. The proposed algorithm generates levels or strips where the first item or base item is selected according to the length of the strip and packs the next items beside the base item in the strip. For each type of item, strips are generated for packing each type of item in a base item. The best n orders in a yield of strips or the best n strips are selected for each type of item. The selected best n strips are packed in one type of bin. For the other types of bins, another best n strips are selected and packed in each type of bin. The best yield in all types of bins is then selected. This iteration is executed until the number of item demands in the overall demands is less than the number of item demands in the bin. Four numerical examples generated from actual industries are illustrated to highlight the applicability of the proposed algorithm with some comments.     

Characterization of growth and protein contents from microalgae Navicula incerta with the investigation of antioxidant activity of enzymatic hydrolysates

Microalgae are major primary producers of organic matters in aquatic environments through their photosynthetic activities. Benthic diatom Navicula incerta is the major component of phytoplankton and also relatively easy to cultivate, used as live food source in aquaculture. The growth characteristics of N. incerta were estimated under combinations of temperature, salinity, and light; and also its composition and antioxidant activities were determined. The maximum cell density of 87×10⁵cells/mL, was reached at 20°C, 250 μmol/m²·sec, 33‰ salinity, pH 8.3, 12:12 light:dark, and F/2 medium on 2 weeks of the culture period. The antioxidant enzymatic hydrolysates efficiently quenched different free radicals: 1,1-diphenyl-2-pycryl-hydrazyl (DPPH) (pepsin IC₅₀=196.0 μg/mL), hydroxyl (α-chymotrypsin IC₅₀=102.0 μg/mL), and superoxide (neutrase IC₅₀=169.0 μg/mL). These results suggest that the enzymatic hydrolysate from N. incerta acts as a candidate against antioxidant and could be used as a potential functional food ingredient.     

Effects of different storage conditions on the metabolite and microbial profiles of white rice (Oryza sativa L.)

Food Science and Biotechnology - Microbial populations in white rice (Oryza sativa L.) samples stored for 6&nbsp;months in open or closed conditions were studied and their metabolite profiles...     

Agent-based fractal architecture and modelling for developing distributed manufacturing systems

For their timely response to the rapidly changing manufacturing environment and markets, future manufacturing systems must be flexible, adaptable, and reusable. Recently, bionic (or biological), holonic, and fractal manufacturing systems (FrMS) have been discussed as potential candidates for the next generation of manufacturing systems. This study focuses on the FrMS, which is based on the concept of autonomous cooperating agents referred to as fractals. The major component of the FrMS is a basic fractal unit (BFU). It consists of five functional modules: observing module (observer), analysing module (analyser), resolving and executing module (resolver), organizing module (organizer), and reporting module (reporter). Although the FrMS has many conceptual advantages, the implementation of the system has been known to be difficult. This paper is a preliminary study of the basic components and the architecture with an eye toward the future implementation of FrMS. In order to describe the characteristics of a fractal, this paper presents several models including function models using IDEF0, working models using Petri-net, and static/dynamic models using the unified modelling language (UML).     

Characterization of complex die-pressed Al2O3 green compact using liquid immersion,X-ray tomography,and numerical simulations

This study examined the compaction behavior of a green ceramic component with a complex shape formed by die pressing at 50 MPa using spray-dried alumina. Compared to a simple cylindrical sample, the sample with a complex shape revealed a higher degree of microstructural inhomogeneity and crack formation. Granule deformation and pore distribution at different sample locations were observed by optical microscopy after infiltrating liquid into the voids of a green compact. The refractive index of the immersion liquid should be different slightly from that of alumina for better observations. X-ray micro-computed tomography was also used to visualize the pore distribution and crack shape. Numerical simulations based on the Drucker-Prager/Cap model were performed to distinguish the stress and displacement distribution within the compact. The significant stress gradient at the crack initiation point could explain crack formation, whereas the application of a higher pressure resulted in a further increase in stress gradient.