Article citation info:on a continuous scale. In such situations, the lifetimes and repair times can be expressed in terms of the number of working and repairing periods (cycles), respectively. Thus, it is essential to construct discrete time reliability models for repairable multi-state systems.The discrete time reliability has drawn continuous attention in both model analysis and problem solution. Bracquemond and Gaudoin [5] presented a good overview of discrete probability distributions used in reliability for modeling discrete lifetimes of non-repairable systems. The discrete time reliability modeling for general binary systems can be found in [4,22,34]. Eryilmaz [14], Guerry [16] and Sadek and Limnios [35], presented the discrete time reliability models for Markov multi-state systems. The discrete time reliability models for semi-Markov multi-state systems were investigated in [1,4,10]. However, most of the reported works mainly focus on the issues of IntroductionThe availability, as a performance measure, is one of the most important indicators for characterizing a repairable system and its components. For repairable multi-state systems with various performance levels, the availability is more meaningful than reliability to measure the effectiveness of the system to satisfy consumer demand.In the past few years, a variety of methods are available in the literature for analyzing the availability of repairable multi-state systems. Some of them are Monte Carlo simulation [41,42], stochastic Petri nets [19,21], universal generating function [24,32], Markov models [6,37] and the combinations of the above methods [9]. However, conventional availability analysis methods for repairable multi-state systems are based on the continuous time models. In some engineering circumstances, it is sometimes impossible or inconvenient to measure the lifetimes and repair times length of some systems (components) HU L, SU P, PENG R, ZHANG Z. Fuzzy Availability Assessment for Discrete Time Multi-State System under Minor Failures and Repairs by Using Fuzzy L z -transform. Eksploatacja i Niezawodnosc - Maintenance and Reliability 2017; 19 (2): 179-190 discrete time systems with the exact reliability data. As stated in Garg [15], the complicated system has the massive fuzzy uncertainty due to which it is difficult to get the exact probability of the events. Thus, it is of large practical value to investigate the availability assessment for discrete time repairable system with fuzzy uncertainty. fuzzy discrete time Markov model with fuzzy transition probability matrix is proposed to analyze the fuzzy state probability of each component at any discrete time. The fuzzy L z -transform of the discrete-state discrete-time fuzzy Markov chain is developed to extend the L z -transform of the discrete-state continuous-time Markov model with crisp sets. Based on the α-cut approach and the fuzzy L z -transform, the dynamic fuzzy availability of the system is computed by using parametric programming technique. To illustrate the proposed method,...

A novel algae fermentation strain was obtained in our previous work. This strain can produce alginate lyase and alcohol dehydrogenase used for the ethanol fermentation from algae. This research investigated the fermentation, separation and purification of alginate lyase, and the molecular weight of alginate lyase was determined. The optimum conditions for enzyme fermentation were as follows: fermentation medium with 20 g L–1 alginate, initial pH 6.0, and temperature 35 °C. The flasks were cultured in a shaking incubator at 120 rpm for 96 h. The enzyme was purified using the method of salting out, dialysis, and gel chromatography. After purification, the SDS-PAGE method was used to determine the molecular weight of the protein. The molecular weight of alginate lyase was 30–35 KDa. This research contributes to algae biodegradation and fuels production from algae.

The effect of magnesium content on the phase structure and electrochemical properties of Ml 1)x Mg x Ni 2.78-Co 0.50 Mn 0.11 Al 0.11 (x = 0.05, 0.10, 0.20, 0.30) hydrogen storage alloys was investigated. The results of X-ray diffraction reveal that all the alloys consist of the major phase (La, Mg)Ni 3 and the secondary phase LaNi 5 . With increase in x, the relative content of the (La, Mg)Ni 3 phase increases gradually, and the maximum capacity and low temperature dischargeability of the alloy electrodes first increase and then decrease. When x is 0.20, the discharge capacity of the alloy electrode reaches 363 mAh g )1 at 293 K and 216 mAh g )1 at 233 K, respectively. The high rate dischargeability of the alloy electrodes increases with increase in x. When the discharge current density is 1200 mA g )1 , the high rate dischargeability of the alloy electrodes increases from 22.0% to 50.4% with x increasing from 0.05 to 0.30. The cycling stability of the electrodes decreases gradually with increase in magnesium content.

The production of bioethanol from algae has attracted wide attention in the field of energy. A novel algae fermentation strain, Meyerozyma guilliermondii, can produce alginate lyase and alcohol dehydrogenase (ADH) at the same time. At present, there is no research on the fermentation conditions, separation, and purification of the alcohol dehydrogenase of Meyerozyma guilliermondii. In this research, the fermentation conditions of Meyerozyma guilliermondii, the separation, and purification processes of alcohol dehydrogenase, and the performance study of alcohol dehydrogenase were studied. According to the experimental results, the optimum fermentation conditions for enzyme production were as follows: fermentation medium with alginate, initial pH 5.0, and fermentation temperature of 30 °C. The highest enzyme activity reached 69.9 U mL-1 crude enzyme. The optimal treating time of the ultrasonic separation procedure was 12 min at power of 320 W. The suitable purification method of the enzyme was salting out and dialysis method. When saturation reached 50 %, the total enzyme activity was the highest. Finally, the properties of enzyme were studied in this research. The maximum activity was reached at pH 7. The optimum temperature of ADH activity was 35 °C.