Output power control of wind turbine generator by pitch angle control using minimum variance control

Effective utilization of renewable energies such as wind energy as a replacement for fossil fuels is highly desirable. Wind energy is not constant and wind generator output is proportional to the cube of the wind speed, which causes the power output of wind turbine generators (WTGs) to fluctuate. In order to reduce output power fluctuations of wind farms, this paper presents an output power leveling control strategy for wind farms based on both the mean and the standard deviation of wind farm output power, a cooperative control strategy for WTGs, and a pitch angle control method using a generalized predictive controller (GPC) intended for all operating regions of WTGs. Simulation results using an actual detailed model for wind farm systems show the effectiveness of the proposed method. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 154(2): 10–18, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20247     

High‐mobility self‐aligned top‐gate oxide TFT for high‐resolution AM‐OLED

High‐mobility and highly reliable self‐aligned top‐gate oxide thin‐film transistor (TFTs) were developed using the aluminum reaction method. Al diffusion to the oxide semiconductor and homogenization of the oxygen concentration in the depth direction after annealing were confirmed by laser‐assisted atom probe tomography. The high mobility of the top‐gate TFT with amorphous indium tin zinc oxide channel was demonstrated to be 32 cm²/V s. A 9.9‐in. diagonal qHD active‐matrix organic light‐emitting diode (AM‐OLED) display was fabricated using a five‐mask backplane process to demonstrate an applicable solution for large‐sized and high‐resolution AM‐OLEDs.     

Micromirror arrays to assess luminescent nano-objects

We propose an array of submicrometer mirrors to assess luminescent nano-objects. Micromirror arrays (MMAs) are fabricated on Si (001) wafers via selectively doping Ga using the focused ion beam technique to form p-type etch stop regions, subsequent anisotropic chemical etching, and Al deposition. MMAs provide two benefits: reflection of luminescence from nano-objects within MMAs toward the Si (001) surface normal and nano-object labeling. The former increases the probability of optics collecting luminescence and is demonstrated by simulations based on the ray-tracing and finite-difference time-domain methods as well as by experiments. The latter enables different measurements to be repeatedly performed on a single nano-object located at a certain micromirror. For example, a single InGaN∕GaN nanocolumn is assessed by scanning electron microscopy and microphotoluminescence spectroscopy.     

Histological evaluation on bone regeneration of dental implant placement sites grafted with a self-setting alpha-tricalcium phosphate cement

This study aimed to evaluate the histological characteristics of the new bone formed at dental implant placement sites concomitantly grafted with a self-setting tricalcium phosphate cement (BIOPEX-R). Standardized defects were created adjacent to the implants in maxillae of 4-week-old male Wistar rats, and were concomitantly filled with BIOPEX-R. Osteogenesis was examined in two sites of extreme clinical relevance: (1) the BIOPEX-R-grafted surface corresponding to the previous alveolar ridge (alveolar ridge area), and (2) the interface between the grafting material and implants (interface area). At the alveolar ridge area, many tartrate-resistant acid phosphatase (TRAPase)-reactive osteoclasts had accumulated on the BIOPEX-R surface and were shown to migrate toward the implant. After that, alkaline phosphatase (ALPase)-positive osteoblasts deposited new bone matrix, demonstrating their coupling with osteoclasts. On the other hand, the interface area showed several osteoclasts initially invading the narrow gap between the implant and graft material. Again, ALPase-positive osteoblasts were shown to couple with osteoclasts, having deposited new bone matrix after bone resorption. Transmission electron microscopic observations revealed direct contact between the implant and the new bone at the interface area, although few thin cells could still be identified. At both the alveolar ridge and the interface areas, newly formed bone resembled compact bone histologically. Also, concentrations of Ca, P, and Mg were much alike with those of the preexistent cortical bone. In summary, when dental implant placement and grafting with BIOPEX-R are done concomitantly, the result is a new bone that resembles compact bone, an ideal achievement in reconstructive procedures for dental implantology.     

Pipe inspection robot using a wireless communication system

Pipe lines of any material need to be inspected after a certain number of years. Therefore, it is necessary to develop a flexible pipe inspection robot using a wireless communication system. In this research, a wireless communication system is tested, and it is verified that the system can transmit image information steadily at a high speed. On the basis of this wireless communication system, a new pipe inspection robot for drain pipes is developed. With this new system, the movement of the robot can be controlled, defects or other problems inside a pipe can be inspected, and an image of the inside of the pipe can also be transmitted in real time.     

Micro injection molding for mass production using LIGA mold inserts

Micro molding is one of key technologies for mass production of polymer micro parts and structures with high aspect ratios. The authors developed a commercially available micro injection molding technology for high aspect ratio microstructures (HARMs) with LIGA-made mold inserts and pressurized CO₂ gasses. The test inserts made of nickel with the smallest surface details of 5 μm with structural height of 15 μm were fabricated by using LIGA technology. High surface quality in terms of low surface roughness of the mold inserts allowed using for injection molding. Compared to standard inserts no draft, which is required to provide a proper demolding, was formed in the inserts. To meet higher economic efficiency and cost reduction, a fully electrical injection molding machine of higher accuracy has been applied with dissolving CO₂ gasses into molten resin. The gasses acts as plasticizer and improves the flowability of the resin. Simultaneously, pressurizing the cavity with the gasses allows high replication to be obtained. Micro injection molding, using polycarbonate as polymer resins, with the aspect ratio of two was achieved in the area of 28 × 55 mm² at the cycle time of 40 s with CO₂ gasses, in contrast to the case of the aspect ratio of 0.1 without the gasses.     

Angular variation of coercivity of interacting fine acicular skeleton particles

For fine, acicular skeleton particles of -Fe prepared from -FeOOH, the effect of interparticle interaction on the angular variation ofH _c was numerically investigated using a direct expansion scheme of the chain-of-spheres fanning model to an interacting chain system forming an orthorhombic type of regular space lattice. The model theory reveals that only magnetostatic lateral interchain interaction can affect the angular variation ofH _c. The results have been used to explain the experimentally observed effects of particle morphology and packing fraction on the angular variation ofH _c in systems made from fine acicular particles prepared for audio/video magnetic recording media. It is suggested that a local aggregate of the so-called multiple type, is unavoidably generated in the system.     

Alternating copolymerization of methyl α-phenylacrylate and methyl methacrylate by n-BuLi

The copolymerization of methyl α-phenylacrylate (MPhA) and methyl methacrylate by n-BuLi was carried out in toluene at various temperatures with an initial monomer ratio of 1:1. At ?78°C the product was a homopolymer of MPhA. The copolymer obtained at ?40°C was a mixture of poly(methyl α-phenylacrylate) and poly(methyl methacrylate) containing a small amount of alternating copolymer of both monomers. With further increase in the polymerization temperature the fraction of alternating copolymer increased and above 30°C all the copolymers obtained were alternate. With varying composition of feed monomers the copolymerization was carried out at 30°C and the alternating copolymer was obtained over a wide range of monomer feed ratios. In tetrahydrofuran the alternate sequence began to form at a lower temperature than in toluene, and all the copolymers obtained above 0°C were alternating ones. The mechanism of the copolymerization is discussed in some detail.     

Density measurement of polymer/CO2 single‐phase solution at high temperature and pressure using a gravimetric method

The densities of two polymer/CO₂ single‐phase solutions, poly(ethylene glycol) (PEG)/CO₂ and polyethylene (PE)/CO₂, were measured at temperatures higher than melting temperature of the polymer under CO₂ pressures in the range 0–15 MPa using a newly‐proposed gravimetric method. A magnetic suspension balance (MSB) was used for the density measurement under the high pressure CO₂: A thin disc‐shaped platinum plate was submerged in the considered polymer/CO₂ single‐phase solution in the MSB high‐pressure cell. The weight of the plate was measured while keeping CO₂ pressure and temperature in the sorption cell at a specified level. Since the buoyancy force exerted on the plate by the polymer/CO₂ solution reduced the apparent weight of the plate, the density of the polymer/CO₂ solution could be calculated by subtracting the true weight of the plate from its measured weight. Experimental results showed that the density of PE/CO₂ solution increased with the increase of CO₂ pressure and the density of PEG/CO₂ solution decreased with the increase of CO₂ pressure. To differentiate the effect of CO₂ dissolution in polymer from that of mechanical pressure, the density of polymer/CO₂ solution was compared with the density of neat polymer under the given mechanical pressure, which was calculated using the Sanchez–Lacombe equation of state and Pressure–Volume–Temperature data of the polymer. The comparison could elucidate that the dissolution of CO₂ in polymer reduced density of both PEG/CO₂ and PE/CO₂ systems but the degree of CO₂ induced‐density reduction was different between two polymer/CO₂ systems. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007