No abstract

No abstract

The grain boundary (GB) properties of polycrystalline Cu(In1-x ,Ga x )Se2 (CIGS) have been characterized using electron beam-induced current (EBIC) measurements, electron backscatter diffraction (EBSD) patterns, and scanning spreading resistance microscopy (SSRM) measurements. The polished cross section of CIGS solar cells was evaluated by these three methods, and the surface EBIC image was obtained by scanning electron microscopy (SEM). A combination of the EBIC and EBSD techniques makes it possible to investigate the effect of the GBs on the minority carrier collection. Furthermore, the SSRM mapping enables the analysis of grain-by-grain carrier profiling by measuring the spreading resistance of CIGS solar cells. It was found from these results that the twin boundaries of CIGS grains do not contribute to carrier recombination. Furthermore, the brighter EBIC signals were observed at the GBs of CIGS, which showed that the produced electron–hole pairs easily separate from each other and that the minority carriers are repelled from the GBs. This remarkable property of the GBs is suitable for application of CIGS to solar cells.

Indirect measurement of the flow rate of a centrifugal blood pump using the driving motor current was studied. The pump flow rate can be expressed as a function of the motor current under a given motor speed in the absence of energy loss resulting from uncertain mechanical contact friction. The magnetically suspended centrifugal blood pump (MSCP), developed by the collaboration of Kyoto University and NTN Inc., was suitable for the application of this measuring method because the impeller is suspended magnetically inside the pump housing without any mechanical contact. The effect of fluid viscosity on the pump performance was investigated in detail, and it was Centrifugal blood pumps are expected to become good left ventricular assist devices (LVADs) because of their advantages of small size, low cost, and easy handling. Currently available centrifugal blood pumps, however, have 2 crucial problems for longterm use, blood degeneration and thrombus formation around the sealing parts of the rotating shafts. We have been developing the magnetically suspended centrifugal blood pump (MSCP, Fig. 1) to eliminate the problems related to the shaft sealing (14). The complete magnetic suspension system holds the impeller without any mechanical contact between it and the pump casing wall. For long-term use of the MSCP as an LVAD, including implanted use, it is important to have a monitoring system for the pump flow rate that does not require frequent electric calibration. This study deals with our attempt to use the MSCP itself as a sensor for the possible to estimate the pump flow rate and the pressure difference through the pump (from inlet port to outlet port) accurately by monitoring the motor current and speed when the kinematic viscosity of working fluids was known. The kinematic viscosity of working fluids can also be measured with the MSCP. The motor current and motor speed were monitored in a chronic animal experiment, and the estimated flow rate and pressure difference showed good correlation with directly measured data. Key Words: Ventricular assist device-Rotary blood pump-Magnetic suspension-Indirect flow rate measurement-Viscosity.pump flow rate and the pressure difference through the pump. Because of the magnetic suspension system, the MSCP has no mechanical friction losses, no matter what the running condition of the pump is. Because all the energy losses of the MSCP are fluid dynamic losses, the relationship among pump flow rate, motor current, and motor speed is stable. The pump flow rate, therefore, can be estimated by measuring the motor current and motor speed when the effect of fluid viscosity on pump performances is known. The effect of fluid viscosity on pump characteristics, on which this method is based, was closely investigated. The pressure difference through the pump could also be estimated from the pump flow rate and the pressure and flow rate characteristics. The accuracy of this method was evaluated in a chronic animal experiment.

No abstract