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61.
We consider a standby-redundant model of two units, where we assume that one unit is operative and the other unit is in standby at time t = 0. If the operative unit fails, a unit in standby is put into preventive maintenance policy of the operative unit to maintain our the preventive maintenance policy of the operative unit to maintain our system with high reliability. Our concern for the system is the time to the first system-down. The Laplace-Stieltjes transform of the time distribution to the first system-down and the mean time to the first system-down are derived by applying the relationship between Markov renewal processes and signal flow graph. Further, the behavior after the system-down is investigated by using the results of Markov renewal processes. Finally, numerical examples are presented for the k-Erlang failure time distributions. The optimal preventive maintenance time is discussed. 相似文献
62.
An ordering policy allows a spare, delivered after a constant lead time, to be put into inventory. Under certain conditions there exists a finite and unique ordering policy maximizing the cost effectiveness, which balances the system effectiveness and the cost and is defined as [s-availability]/[s-expected cost rate]. 相似文献
63.
A failure model with degradation and catastrophic modes is briefly discussed and some general equations are shown. 相似文献
64.
A standby-redundant repairable system having only two units and an imperfect switchover is considered. The Lapace-Stieltjes transform of the distribution of the time to first system faflure (TFSF) and the mean TFSF are derived. Numerical comparisons of the mean TFSF with both perfect and imperfect switching are made. All time distributions, except repair of the main units, are exponential. 相似文献
65.
Shunji Nomura Hisashi Yoshino Ken Ando 《Journal of the American Ceramic Society》1993,76(10):2687-2690
The role of oxygen for the hole doping has been investigated for single-phased (Bi,Pb)2 Sr2 Ca2 Cu3 O. z Defects introduced by oxygen have been clarified to be interstitial atoms by pycnometric density measurements. The c axis decreases and the modulation periods along the b axis also decrease with increasing oxygen content in the crystal. It is likely that extra oxygen ions exist between the BiO double layers and those oxygen ions are responsible for the modulation. Samples with oxygen content ranging from 9.99 to 10.18 showed superconductivity. The critical temperature T c , exhibited a maximum value (109 K) at 10.07 oxygen atoms in the formula unit, which coincided with the average Cu valence of 2.13. The data indicated that hole formation was governed by oxygenation reaction in this system. 相似文献
66.
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68.
Hayato Osaki Takefumi Kanda Shoki Ofuji Norihisa Seno Koichi Suzumori Takahiro Ukida 《Advanced Robotics》2018,32(9):500-510
AbstractRobots composed of hydraulic actuators have been utilized in various fields and at disaster sites. However, the hydraulic control system for multiple-degree-of-freedom mechanisms is large because such systems require many control components. The purpose of this research was to develop a small hydraulic flow control valve. This paper describes the fabrication and evaluation of a small three-way valve by particle excitation using a piezoelectric transducer. This valve consists of two transducers and can switch the inlet and outlet ports by applying an AC voltage of different driving frequencies to each transducer because each transducer has different resonant frequencies. The flow rate was controlled by applying a voltage to the piezoelectric transducer. We evaluated the vibration characteristics of the fabricated three-way valve. The vibration velocity exhibited peaks at 120 and 155 kHz for the inlet and outlet port, respectively, and that of each transducer increased with the applied voltage. Therefore, this three-way valve can switch the opening port by changing the driving frequencies and continuously controlling the flow rate. As a result, we have succeeded in driving the novel small three-way valve. 相似文献
69.
By using pulse surface reaction rate analysis (PSRA), the detailed structure of the intermediate hydrocarbon species was revealed by measuring the dynamic behavior of both CO and H2 produced from the CO2-CH4 reaction on supported Ni catalysts. It was found that the number of hydrogen atoms involved in the intermediate was different from one catalyst support to another: 2.7 for MgO, 2.5 for ZnO, 2.4 for Al2O3,1.9 for TiO2, and 1.0 for SiO2. 相似文献
70.
The cryogel catalyst of platinum on alumina was prepared from aluminum sec-butoxide and H2PtCl6 through the sol-gel technique and subsequent freeze drying. The cryogel catalyst showed higher thermal stability of platinum
than the corresponding xerogel or impregnation catalysts, which was ascribed to the more intimately developed platinum-alumina
interaction accompanied by the encapsulation of the metal into the alumina cryogel. It was also shown that platinum accessibility
was higher on the cryogel than on the xerogel despite the higher thermal stability of the metal on the formed than on the
latter. For the VOC combustion, the cryogel exhibited higher activity than the xerogel and impregnation catalysts. Also for
the methane combustion the cryogel showed higher activity, although it showed lower activity than the impregnation catalysts
above 600 °C. By the addition of ceria as an additive to the cryogel catalyst, the CH4 combustion activity was improved especially in the temperature region above 600 °C. 相似文献