Internal oxidation in gold alloys containing small amounts of Fe and Sn

Internal oxidation was observed in gold-rich alloys as substrates for porcelain veneers in dental restorations, which contain small amounts of Fe and Sn. The internal oxidation proceeded with oxygen ions diffusing to the inner part of the alloy through Fe₂O₃ formed at the grain boundaries of the alloy matrix. SnO₂ was formed internally together with the Fe₂O₃. The external oxidation zone was composed of only Fe₂O₃ in a wide range of Fe and Sn concentrations. Fe₃O₄ was formed with Fe₂O₃ in the Sn-rich composition range by reduction of Fe₂O₃ in the presence of Sn. A band mainly composed of SnO₂ was formed at the inside of the internal oxidation zone in the composition range where Fe₃O₄ formed. In the Sn-rich alloys this internal oxidation band of SnO₂ moved to the external oxidation zone.     

Calculated effect of radially asymmetric heat generation on temperature and heat flux distribution in a fuel rod

The effect of radially asymmetric heat generation on the temperature and heat flux distribution in a fuel rod is evaluated. Based on practical assumptions, the temperature distribution in power reactor fuel can be obtained between reasonable limits by solving the steady-state heat conduction equation with asymmetric heat generation.     

Characterization of polymer films using a slow positron beam

Polymer structures have been investigated using positron annihilation lifetime spectroscopy (PALS) with a slow positron beam as well as a conventional radioactive source (²²Na). The properties of the free volume holes near the polymer surface were studied as a function of the positron implantation energy. The longest lifetime was associated with ortho-positronium (o-Ps) annihilation in the free volume holes. In polytetrafluoroethylene film, the lifetime of o-Ps was observed to decrease with increasing positron implantation depth, and a significant change in the o-Ps lifetime was found at a short distance (about 10 nm) from the surface, while its intensity increased. This result implies that near the polymer surface the free volume holes become larger that in the bulk. The effect of temperature on the polymer sub-surface layers was also studied. For high molecular weight polystyrene, the glass transition temperature for the sub-surface was lower than that for the bulk and thermal expansion coefficient of the sub-surface layers was found to be larger than the bulk value. Electronic Publication     

An Improvement Method of Matrix Converter Drives Under Input Voltage Disturbances

While the matrix converter has many advantages that include bidirectional power flow, a size reduction, a long lifetime, and sinusoidal input currents, it is vulnerable to the input voltage disturbances, because it directly exchanges the input voltage to the output voltage. The instantaneous effective power control (IEPC) method has been proposed to compensate the input voltage disturbances, in which the instantaneous effective power is kept constant by controlling input current. However, to date, no method has been proposed to maintain the stability of the system with the IEPC. The purpose of this paper is to propose a method to control the stability of the system with IEPC. First, this paper explains the IEPC theoretically. Next, a model of the system with the IEPC is developed, and stability analyses are conducted. Then, based on the results of the analyses, a stability control method for the system with the IEPC is proposed. Furthermore, the validities of the proposed method are demonstrated by simulation and experiments. Finally, a restart performance of the system after momentary power interruption is discussed. Because the IEPC does not need phase-locked-loop to detect the phase angle of the input voltage, fast restart is expected     

Trunk motion control during the flight phase while hopping considering angular momentum of a humanoid

In previous studies, various stabilizing control methods for humanoids during the stance phase while hopping and running were proposed. Although these methods contribute to stability while hopping and running, it is possibility that the control during the flight phase could also affect the stability. In this study, we investigated whether the control during the flight phase can affect the stability of a humanoid while running. To achieve stable hopping, we developed a control system that accounts for the angular momentum of the whole body during the flight phase. In this system, the angular momentum generated by the motion of the lower body in each time interval is calculated during the flight phase, and the trunk joints are controlled to generate the angular momentum necessary to compensate for the deviation of the waist posture, which is used as the reference point for the motion coordinate system of the robot. Once the proposed control system was developed and simulated, we found that the hopping duration in the unconstrained state was extended.     

Risk assessment of airborne fine particles and nanoparticles

Pulmonary health effects of fine particles and nanoparticles are overviewed in this paper, mainly based on the researches conducting in our laboratory. For the hazard assessment, we exposed rats to aerosolized asbestos-substitutes or nanoparticles aerosols (nickel oxide and titanium dioxide), and examined the biological and pathological effects of the particle on lung, a major target organ for the particles, and cytokines which are related to inflammation, fibrosis and carcinogenesis in the lung. It is essential to perform comprehensive evaluation of the toxicity of poorly soluble powder samples using the precise characterization data and exposure methods, such as single instillation or aerosol inhalation.     

Fluctuations in Tracer Amounts in a Compartmental System with a Markovian Transition Process

This communication considers a method for evaluating fluctuations in the integral type output of a linear time-invariant compartmental system with a Markovian transition process. First, we derived a mathematical formula to calculate variances and covariances of integral type. outputs, as with radioisotope data, when transition rates are known. Then, an estimate for the upper limits of variances and covariances, i.e., 1/2?initial dose, when the transition rates are not given beforehand, was introduced.     

完善中铜一期选厂工艺流程实现达产达标

1　小组概况建组时间:1981年7月小组性质:现场管理、攻关型小组活动情况:每月活动一次以上,有记录,有报表循环次数:已完成15个ＰＤＣＡ循环本次循环时间:1997年4月～12月注册编号:1997-05小组成员:见表1表1　铜选厂选矿ＱＣ小组情况一览表姓　名文化程度职务、职称组内职务姓　名文化程度职务、职称组内职务钟国健本　科副厂长、工程师组　长庞烈新高　中维修班班长组　员王团生本　科厂长、工程师副组长方长宽高　中维　修　工组　员李辉跃本　科助理工程师副组长张保国高　中值班长、技师组　员龙赞林高　中副厂长、技师组　员吕新才高　…