Vibration analysis of cryocoolers

The vibrations of Gifford-McMahon (GM) and pulse-tube (PT) cryocoolers were measured and analyzed. The vibrations of the cold-stage and cold-head were measured separately to investigate their vibration mechanisms. The measurements were performed while maintaining the thermal conditions of the cryocoolers at a steady state. We found that the vibration of the cold-head for the 4 K PT cryocooler was two orders of magnitude smaller than that of the 4 K GM cryocooler. On the other hand, the vibration of the cold-stages for both cryocoolers was of the same order of magnitude. From a spectral analysis of the vibrations and a simulation, we concluded that the vibration of the cold-stage is caused by an elastic deformation of the pulse tubes (or cylinders) due to the pressure oscillation of the working gas.     

Microstructural damage evolution and arrest in binary Fe–high-Mn alloys with different deformation temperatures

We investigated the damage evolution behaviors of binary Fe–28–40Mn alloys (mass%) from 93 to 393 K by tensile testing. The underlying mechanisms of the microstructure-dependent damage evolution behavior were uncovered by damage quantification coupled with in situ strain mapping and post-mortem microstructure characterization. The damage growth behaviors could be classified into three types. In type I, the Fe–28Mn alloy at 93 K showed premature fracture associated with ductile damage initiation and subsequent quasi-cleavage damage growth associated with the \(\upvarepsilon \)-martensitic transformation. In type II, the Fe–28Mn alloy at 293 K and the Fe–32Mn alloy at 93 K showed delayed damage growth but did not stop growing. In type III, when the stacking fault energy was \(>\,\)19 \(\hbox {mJ/m}^{2}\), the damage was strongly arrested until final ductile failure.     

A case of progressive saccular aneurysm caused by localized dissection of descending aorta

A 37-year-old man with alcoholic polyneuropathy showed involuntary movement as intermittent flexion-extension or abduction-adduction of his toes identical to "painful legs and moving toes (PLMT)" and muscle cramps. Regarding the sequential spreading of PLMT and cramps from unilateral to contralateral leg muscles and phasic discharges observed by a needle EMG in the foot muscles during PLMT, we suppose that a spinal or supraspinal mechanism was responsible for the production of those movements. This case showed novel aspects of PLMT which was induced by sensory stimulation of the left lower leg and subsequently initiated cramps. The destruction of the lumbar sympathetic ganglion remarkably ameliorated the spontaneous PLMT and cramps, whereas sensory stimulation of the left lower leg still induced those movements. Therefore, we think that sensory inputs from peripheral nerves played a critical role in the generation of PLMT and cramps, and abnormal activities of spinal sympathetic nerves exacerbated those involuntary movements. Sensory induced PLMT may be a subgroup of this movement disorder.     

PD signal propagation characteristics in GIS and its locationsystem by frequency components comparison

Propagation characteristics of partial discharge signal in GIS were investigated in a laboratory and at a 300 kV underground substation. The laboratory test indicates that signal damping can be attributed to two major mechanisms; reflection due to irregularity of characteristic impedance such as spacers, and the mode shift from TEM to TE or TM. Tests at the substation show that the signal damping phenomena are independent of propagation direction, and the mode shift gives rise to a large signal damping. The major higher mode seems to be TE₁₁ . Amplitudes of observed waveforms using narrow-band filters that agree well with the corresponding frequency components observed with a spectrum analyzer show irregular or random behavior depending upon their observation point. This indicates that narrow-band filters do not seem to be suitable for a partial discharge location system by a frequency component comparison, and the realizability of the system using broadband filters instead is discussed     

Development of a high‐speed electromagnetic repulsion mechanism for high‐voltage vacuum circuit breakers

This paper presents a design and testing of a new high‐speed electromagnetic driving mechanism for a high‐voltage vacuum circuit breaker (VCB). This mechanism is based on a high‐speed electromagnetic repulsion and a permanent magnet spring (PMS). This PMS is introduced instead of the conventional disk spring due to its low spring energy and more suitable force characteristics for VCB application. The PMS has been optimally designed by the 3D nonlinear finite‐elements magnetic field analysis and investigated its internal friction and eddy‐current effect. Furthermore, we calculated the dynamic of this mechanism coupling with the electromagnetic field and circuit analysis, in order to satisfy the operating characteristics—contact velocity, response time, and so on, required for the high‐speed VCB. A prototype VCB, which was built based on the above analysis, shows sufficient operating performance. Finally, the short circuit interruption tests were carried out with this prototype breaker, and we have been able to verify its satisfying performance. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(1): 34–40, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20398     

Development and Application of Sintering Dynamics Simulation for Automotive Catalyst

Sintering behavior of Pt/γ-Al₂O₃, Pt/ZrO₂ and Pt/CeO₂ catalyst was studied using an originally developed 3D sintering simulator. Experimental results were well reproduced. While Pt on the γ-Al₂O₃ sintered significantly, Pt on CeO₂ presented the highest stability against sintering. On the other hand, grain growth of supports was significant in the order; ZrO₂ > CeO₂ > γ-Al₂O₃.     

A molecular thermometer based on luminescence of copper(II) tetraphenylporphyrin

The photoluminescence (PL) spectra from solid samples consisting of polystyrene and 5,10,15,20-tetraphenyl-21H,23H-porphine copper(II) (CuTPP) revealed two sharp peaks at 653 and 720 nm, and indicated another broad peak at around 780 nm, which could not be observed in CuTPP solutions. The intensity ratio of the two peaks appearing at 653 nm and at around 780 nm demonstrated clear dependence on temperature. This dependence of the PL intensity ratio was observed under the atmosphere and even in water. The findings mean that we were able to utilize PL from CuTPP as a thermometer under various conditions. We measured the temperatures of an organic light-emitting diode (OLED) during operation based on its electroluminescence, where the OLED contained CuTPP as a light-emitting dopant, to demonstrate the CuTPP thermometer.     

A new method for estimating the cellular structure of plastic foams based on dielectric anisotropy

The characterization of the cellular structure of plastic foams has long been of importance to investigate their physical properties. We have been developing an instrument that measures the orientation of seat materials based on their dielectric anisotropy. It is demonstrated by electromagnetic theory that composite materials with an island-sea structure show a macroscopic anisotropy of dielectric constant because of the shape of islands, even if both the islands and sea are dielectrically isotropic themselves. The orientation based on the dielectric anisotropy caused by the shape of cells was investigated for the polystyrene by using our microwave cavity resonator method. From this data, a better manufacturing condition to minimize the thermal shrinkage was derived. The manufacturing condition was taken as extrusion rate, foaming temperature and die gap. The shape of cells of polystyrene foams was estimated using the derived equations, which express the maximum and minimum dielectric constant of whole composite materials as a function of the eccentricity of their ellipsoidal islands and the volume fraction and the dielectric constant of each materials in the islands-sea structure.