A control method to suppress the rotational oscillation of a magnetic levitating system

A magnetic levitation technique has a potential to realize a non-contact object manipulation. As a result, it is expected that a lot of problems caused by contacts can be evaded. Then, the authors developed a magnetic levitation system that was able to manipulate a magnetically levitated hand by non-contact. In this system, four electromagnets are assigned on a horizontal plane for 3-D positioning of the hand. However, it had been examined only about the movement of three directions so far. In this study, a new controller was presented which was developed to suppress the rotation around z-axis, and its effectiveness was conformed through magnetic levitating experiments.     

Impact assessment of the increase in fossil fuel prices on the global energy system,with and without CO2 concentration stabilization

It is important to evaluate impacts of fossil fuel price hikes and climate stabilization that force the global energy system to adopt alternative and efficient technologies by routing future energy system dynamics into a different technology roadmap. Hence, a high-regional-resolution and technology-rich DNE21+ model is used for the simulation of some price-hike scenarios for the period from 2000 to 2030 by increasing the ordinate of cost–potential curve of crude oil, natural gas and coal by 55 US$(00)/bbl, 3.8 US$(00)/kcf and 56 US$(00)/tonne, respectively, above their reference values; and 550 ppmv stabilization is implemented by carbon limitation from 6998 to 8250 MtC/yr. This study detected that hike in fossil fuel prices acts as an anti-catalyst for human-induced anthropogenic emissions and alleviates heavy dependency upon fossil fuels. Further, it partially solves problems of climate change by reducing CO₂ emission levels (23%), reflects human behavior through energy conservation (1.4 Gtoe), calls for efficiency improvement (7%), adopts more efficient and alternative technologies, compared to reference; however, with 550 ppmv stabilization, energy conservation rises to 1.6 Gtoe, demands 16% higher efficiency improvement and reduces CO₂ emission by 36%, relative to reference.     

Thermal diffusivity measurement of papers by an ac Joule heating method

The thermal diffusivity (α) of paper, a porous and thin material, was determined by an ac Joule heating method developed in our laboratory. With this technique the thermal diffusivity of paper was obtained directly with high reproducibility without the need for special preparations, such as the black coating, required in conventional methods. The thermal diffusivity (α) of paper was obtained as a function of temperature and the apparent density (ρ). The apparent thermal conductivity (λ) of paper was calculated from α, ρ, and the heat capacity at constant pressure (C_p): α decreased with increasing apparent density, but λ did not show a density dependence. © 1998 SCI.     

Room-temperature continuous-wave operation of GaN-based laser diodes grown by raised-pressure metalorganic chemical vapor deposition

We report our new raised-pressure metalorganic chemical vapor deposition (RP-MOCVD) technique and the room-temperature continuous-wave (cw) operation of GaN-based laser diodes grown using this technique. We have found that both the defect density as measured by etch-pit density and optical pumping threshold-powder density decreases as the growth pressure is increased beyond 1 atm. We fabricated GaN-based laser diodes and achieved lasing under cw conditions at 20°C. The threshold current density was 3.5 kA/cm² and the operation voltage at threshold was 16.8 V.     

Low temperature catalytic steam gasification of HyperCoal to produce H2 and synthesis gas

HyperCoal is an ultra clean coal with ash content <0.05 wt%. Catalytic steam gasification of HyperCoal was carried out with K₂CO₃ at 775–650 °C for production of H₂ rich gas and synthesis gas. The catalytic gasification of HyperCoal showed nearly four times higher gasification rate than raw coal. The major gases evolved were H₂: 63 vol%, CO: 6 vol% and CO₂: 30 vol%. Catalyst was recycled for four times without any significant rate loss. The partial pressure of steam was varied from 0.5 atm to 0.05 atm in order to investigate the effect of steam pressure on H₂/CO ratio. The H₂/CO ratio decreased from 9.5 at 0.5 atm to 1.9 at 0.05 atm. No significant decrease in gasification rate was observed due to change in partial pressure of steam. Gasification rate decreased with decreasing temperature and become very slow at 650 °C. The preliminary results showed that HyperCoal, an ash less coal, could be a potential hydrocarbon resource for H₂ and synthesis gas production at low temperature by catalytic steam gasification process.     

Comparison of bone formation ingrafted periosteum harvested from tibia and calvaria

Periosteum covers the bone surface and displays the potential to initiate bone formation, after injury to the bone. Numerous studies have demonstrated that the periosteum plays major roles in the healing process after bone fracture. Some reports have described that in the healing of long bone fractures, the periosteum forms new bone by intramembranous and endochondral ossification. Other researchers insist that healing of defects in membrane bone shows bone formation by intramembranous ossification. However, previous studies have not been able to clarify differences in bone formation patterns. We hypothesized that differences in bone formation pattern are associated with the periosteal potential for cell differentiation. The present study grafted periosteum, harvested from the tibia and calvaria, into the suprahyoid muscle, with the aim of interrupting release of factors from bone matrix. Bone formation, after grafting periosteum, harvested from the tibia and calvaria, was examined histologically and radiographically. Grafted tibial periosteum formed a large area of new bone by intramembranous and endochondral ossification, while grafted calvarial periosteum displayed intramembranous ossification. Grafted tibial periosteum formed a larger area of bone than grafted calvarial periosteum. Patterns of cell differentiation thus differ between grafted periosteum, harvested from the tibia and calvaria.     

A simple recognition of maximal planar graphs

In this paper, we consider the problem of determining whether a given graph is a maximal planar graph or not. We show that a simple linear time algorithm can be designed based on canonical orderings. Our algorithm needs no sophisticated data structure and is significantly easy to implement compared with the existing planarity testing algorithms.     

Coherent Precipitation of Copper Metal in Low-Temperature-Fired Ni-Zn-Cu Ferrite

Coherent copper-metal precipitates at grains adjacent to the Σ= 5 coincident-site lattice (CSL) boundary in a low-temperature-fired Ni-Zn-Cu ferrite have been observed and analyzed using analytical electron microscopy. This precipitation behavior is related to the copper solubility limits in the Ni-Zn-Cu ferrite during cooling after sintering, and preferential solute segregation may be dominant at stacking faults rather than at the Sigma = 5 CSL boundary. Copper-metal precipitates have a 〈100〉 matrix ∥〈100〉 Cu coherent relationship to the ferrite matrix.     

On the Regenerative Braking of DC Motors with AC Supply

A new method is described in which the dc motor may regenerate power effectively to ac supply. The principle is similar to that with a dc chopper for regeneration of the power from dc motor to dc supply. In this new method, however, thyristor switches synchronizing to the ac supply are used instead of a dc chopper. The principle and the power calculations as well as experimental results are presented. From theoretical and experimental considerations it is clarified that there exist suitable trigger angles in the thyristor of the synchronizing switches.