Thermodynamic efficiency of water use in a gas turbine cycle

A review of known variants of water and water steam use in the cycle of a gas-turbine plant is given. A specific feature of the approach is comparison of the efficiency of variants based on thermodynamic modeling by means of a generalized scheme.     

Factors influencing the use of infant car restraints

Over a six-week period 100 mothers in Dunedin, New Zealand obtained General Motors infant car seats from a rental scheme. In interviews conducted in the maternity hospital, before the seats had been used, the mother's perceptions of the comfort and ease of use of the seat were recorded. All mothers rated the seats as very safe. From details of 2,830 car trips undertaken by these mothers while their infants were 0-3 months old and from a further 687 journeys by 85 of those mothers when their infants were 4-6 months old we found that an infant car seat was used for only 72% of journeys with the younger infant compared to 91% of journeys with the older infant. Those mothers who had rated the seat--before ever using it--as appearing uncomfortable or difficult to use were less likely to make use of it. The seat was least likely to be used when the mother was going out for more than two hours in the evening for some purpose that involved only a short car journey.     

Factors influencing worker use of personal protective eyewear

Objective

To identify and describe the array of factors that influence a workers’ decision to wear personal protective eyewear (PPE) and the barriers that exist in preventing their use.

Design, setting and participants

A series of focus groups enrolled workers and supervisors primarily from manufacturing, construction, or service/retail industries that had potential exposure to eye injury hazards in their job tasks. Focus group sessions were facilitated to collect qualitative and quantitative data in two categories, “sought information” and “emergent themes”, related to the factors influencing use of PPE.

Results

We conducted a series of 7 groups with 51 participants, 36 (71%) males and 15 (29%) females ranging in age from 19 to 64 years old, from a variety of occupations including construction (24%), production (22%), installation, repair and maintenance (14%), and healthcare (10%). Most were highly experienced in their occupation (>10 years); males (86%) and females (53%), and had received some safety training in the past (82%). The majority of workers in this study were required to wear PPE on their worksite (78%), however only 55% had a dedicated safety officer. A conceptual model that summarizes the “sought information” and “emergent themes” is presented that depicts the decision making process for the factors influencing use of PPE and consists of three primary branches; perceptions of hazards and risks, “barriers” to PPE usage, and enforcement and reinforcement. Lack of comfort/fit, and fogging and scratching of the eyewear were suggested as the most important barriers to PPE usage. Younger age and lack of safety training were other important factors affecting use of PPE.

Conclusions

Several potentially modifiable factors identified would lead to an increase in workers’ PPE use and encourage supervisors to provide ongoing positive feedback on the continuous use of PPE by workers at risk for an eye injury.     

Factors influencing mechanical and wear performance of dental composite: A review

With environmental concerns, the development of a posterior restorative as a true alternative to dental amalgam is needed. Hence in this regard, the development of dental composites have gained more and more research interest, as they have the advantages of better aesthetic look, better physical, mechanical and tribological properties over the other available dental materials. In this study, the physical, mechanical and wear behavior of dental composite materials have been reviewed. Numerous experimental results, analytical studies and their significance were also discussed for various dental composite materials. The wear performances of dental composite materials depend up on various factors including oral environment, resin chemistry, filler technology and interfacial bonding strength etc. In oral environment, the presence of medium such as water, air, heptane, ethanol, artificial saliva etc. and durations up to which composite is kept such as seven days, one month or three months etc. affect the performance of dental composite. Abrasion and erosion are two major causes for the wear behavior of dental composite / human teeth. The major issue, most significant challenges and effect of each of those factors affecting the performance of dental composite materials were also presented along with some recommendation.     

Seat belts: Factors influencing their use a literature survey

The review is based on studies relevant to seat belt use, reported between 1960 and 1970 from England, Finland, Sweden and the U.S.A. Following a general discussion on the methodology used, the findings of the surveys are grouped according to those variables most extensively studied. Studies of seat belt promoting campaigns and experiments in natural settings or in the laboratory are also discussed in the light of the specific methodological difficulties and weaknesses. It is concluded that the output from all the research activity on this problem area must be considered meagre, the most consistent findings being the differences in use levels between highway and city driving and the relation of belt usage and educational level. Campaign effects generally seem to have been small or none at all. Possible reasons for this are discussed and tentative recommendations are made. A few problem areas in need of research are suggested.     

拉杆松弛对燃气轮机组合转子性能退化的影响

 组合转子作为燃气轮机的核心部件,其性能退化将对整个燃气轮机的性能产生重大影响,揭示组合转子性能退化机理并进行退化特征分析对燃气轮机的可靠运行具有重要意义．为揭示组合转子结构损伤导致的性能退化机理,考虑拉杆螺栓在高温下的应力松弛,得到基于时间历程的拉杆预紧力变化规律;通过拉杆预紧力定义组合转子退化量指标,评估组合转子的退化程度;计算轮盘界面接触刚度,进行考虑接触界面的组合转子动力学分析,进而得到燃气轮机组合转子不同退化量下的动力学特征．结果表明：温度是影响组合转子性能退化的敏感参数;拉杆松弛导致组合转子固有频率漂移,组合转子前3阶固有频率的降低率相差很小,并在一定范围内与退化量呈线性关系．     

Advanced gas turbine engines and corrosion problems

It is stressed that it is important to solve the problem of corrosion in engineering. Engineering methods of solving these problems are discussed on examples of increasing the strength reliability of structural elements of long-life gas turbine engines operating under corrosive effect conditions.Translated from Problemy Prochnosti, No. 8, pp. 78–86, August, 1993.     

Factors influencing premature graduation from the use of child restraints in Japan

This study examined the association of child passenger restraint use by younger and older children taking into account situational factors and driver/child passenger characteristics. The Japanese national traffic accident data pertaining to children injured in rear-end collisions where the drivers were not-at-fault was analyzed, while applying the quasi-induced exposure method. Multivariate logistic regression analyses were conducted to examine the adjusted effects of predictors for proper restraint use by 0-5, 6-9, and 10-12-year-old children. Unbelted drivers, child's seating position, the number of total occupants, and the child's age were significantly associated with restraint use by both younger and older children. Riding in the rear seats was strongly associated with older SB-age children not being properly restrained, suggesting a link between the lack of booster seat-use requirements and the generally low restraint use rate in rear seats as well as the premature graduation from CRS use in general. The results were discussed in light of other international findings in this field.     

Hot corrosion in gas turbine components

The macroscopic and microscopic characteristics as well as the proposed mechanisms of Type I (high-temperature) and Type II (low-temperature) hot corrosion are reviewed. Two case histories of gas turbine blade failures are presented. Different practical approaches to minimize hot corrosion are described.     

Specification of gas turbine disc forgings

Abstract

The cost of failures in gas turbine discs, both in human life and financial terms, is particularly high, and it has always been recognized that the component must be fully specified against the design requirement, and totally predictable in operation. This was originally achieved by making a reproducible forging consistent with the design strength assumptions and which approached the engineer's model of the material as ‘elastic, isotropic, and free from defects’. Today's improved understanding of materials behaviour in terms of the relationship between material property and microstructure, together with the designer's need for higher–strength materials, has led to an approach which now recognizes the role of both structure and ‘defects’ within the forging. This, and the need to improve the cyclic properties of components, is now imposing on the forger complex microstructural and quality requirements that can be met only by process control and by a move towards closer-to-size and more complex shape requirements. Future material needs are discussed in relation to controlling the discontinuity behaviour, together with the change in philosophy that this is bringing to the control of the manufacturing process.

MST/255     

Impingement cooling of gas turbine components

Impingement cooling heat transfer data were obtained for test geometries relevant to full coverage gas turbine combustion chamber wall cooling with the full flame tube pressure loss across the impingement plate. An impingement hole pitch to diameter ratio (X/D) of between 10 and 13 is appropriate for this application and two test geometries within this range were studied. The impingement gap to hole diameter ratio (Z/D) was the main parameter studied together with the hole Reynolds number. A significant influence of Z/D on the heat transfer was found and a general correlation equation derived. Evidence of enhanced impingement heat transfer for Z/D less than unity was found.     

Failure analysis of gas turbine buckets

The failure of a gas turbine first stage bucket was investigated by visual inspection and finite element analysis. The failure of a major bucket cooling passage was a critical cause of the separation of a bucket segment and caused microstructural deterioration of the neighboring regions by serious thermal load. Changes of microstructural morphologies of the damaged buckets under the thermal and mechanical stress were observed. After coating stripping, the bucket surface condition was evaluated through visual inspection and finite element analysis. The TMF (thermal-mechanical fatigue) cracking of surface coatings on the suction and pressure sides of the bucket was described.     

Condition assessment of gas turbine blades and coatings

This paper brings out the metallurgical investigation that was carried out on discoloured low pressure turbine rotor blade (LPTR) for its platinum modified aluminium coating integrity and overheated high pressure turbine rotor blade (HPTR) for its blade material and coating integrity. LPTR blades were investigated as they were for the requirement of reuse. Heat tinting, EDS and XRD were carried out to present the harmonized inference that the coating was in good condition. HPTR blades were sectioned to study under SEM. Regions of platinum modified aluminide coating degradation and DS CM 247 LC base material cracking were observed which make the particular lot unusable.     

Factors influencing the use of artificial intelligence in government: Evidence from China

Some studies have discussed the potential and challenges related to the use of artificial intelligence (AI) in government. However, there are few empirical studies that have examined factors that influence the use of AI in government. By collecting policy documents and empirical data from the government, IT enterprises, and the public in China, we identified the influencing factors in the three stages of government adoption, implementation, and decision-making. The research results show that the influencing factors of government application of AI are different at different stages and with different stakeholders’ backgrounds.     

Factors influencing the use of booster seats: a state-wide survey of parents

This study used telephone interview data on booster seat use from a state-wide probability sample of parents with children ages 4-8-years-old who were living in Michigan. Interviews were completed with parents of children in 350 households. Analyses examined the entire sample, and three sub-groups: always users, part-time booster seat users, and booster seat non-users. Results indicated that booster seat legislation was a key determinant of the level of use and the motivation to use booster seats. Nearly 70% of part-time users said that they used booster seats because they believed it was the law. Similarly, 60% of part-time and non-booster seat users said that they would be more likely to use booster seats if use were mandated by law, with non-users being 3.5 times more likely than part-time users to agree that a law would increase their booster seat use. Finally, over 90% of part-time and non-booster seat users said it would be easier for them to use booster seats if a law required it, and non-users were almost six times more likely than part-time users to agree that a law would make use easier. The need for booster seat laws, issues of social equity, and implications for intervention were discussed.     

Nonlinear gas turbine modeling using NARMAX structures

The estimation of a nonlinear autoregressive moving average with exogenous inputs (NARMAX) model of an aircraft gas turbine is presented. A method is proposed whereby periodic signals with certain harmonic content are used to qualify the nature of the nonlinearity of the engine in the frequency domain. The static behavior of the engine is investigated in the time domain to approximate the order of nonlinearity and this information is used a priori to restrict the search space of the potential NARMAX models. A forward-regression orthogonal estimation algorithm is then employed to select the model terms using the error reduction ratio. The performance of the estimated NARMAX model is illustrated against a range of small- and large-signal engine tests