6.1 First step of SEM:
The main idea of this chapter is to understand the results which were obtained using AMOS 21. The current study collected the data from 424 survey questionnaires from Jordanian people who using smart phone in three cities; Amman, Irbid and Aqaba.
As mentioned in chapter 5, the confirmatory factor analysis (CFA) was applied to evaluate model fitness, reliability and validity construct.
The model adequately fit the observed data as the values of fit indices are all within their recommended level where; ?2 (CMIN/ DF: 3.014), goodness of fit index (GFI: 0.908), adjusted goodness of fit index (AGFI: 0.812), root mean square error of approximation (RMSEA: ?0.059), normed of fit index (NFI: 0.941), and comparative of fit index (CFI: 0.951) (Hair et al., 2010).
In the reliability matter; there were three main tests; internal consistency (Cronbach’s alpha) which was calculated using SPSS. AMOS 21 used to calculate composite reliability (CR), and average variance extracted (AVE). As mentioned in chapter 5 the result came higher than the threshold for each latent construct (Cronbach’s alpha ?0.70, CR >0.70, AVE >0.50) (Hair et al, 2010; Nunnally, 1978).
In the last step of SEM first stage; validity was tested. As seen in chapter 5 the standardized factor load for each item was higher than the cut-off point of 0.50, with the p value less than 0.0001 (Hair et al., 2010). Also all inter-correlation estimates were found to be ? 0.85(Kline, 2005) and the squared root of AVE for each construct was higher than the inter-correlation estimates with other corresponding constructs (Fornell and Larcker, 1981). Therefore validity is satisfied in this study.
6.2 Second step of SEM (Hypothesis Tests):
This study adopted UTAUT2 model along with privacy, technology anxiety and awareness. The structural model accomplishes an accepted level within the terms of predictive power in the dependent factor (behavioral intention) with R² 60%. R² value explains how much a group of independent factors is able to explain the statistical variance in one single dependent factor (Kline, 2011).
In the details; there are 8 paths between the independent factors (exogenous factors) which are (Performance Expectancy, Effort Expectancy, Price value, Technology anxiety, Privacy, Hedonic Motivation, Awareness, and Facilitating Conditions), and the dependent factor (endogenous factor) which is (Behavioral Intentions). Using AMOS 21 for the second stage of SEM; the structural model was examined to test the research hypotheses (Hair et al., 2010).
For the first path which is PE? BI (?=0.21 p
An aircraft powerplant, or piston engine, produces thrust to propel an aircraft. Internal combustion engines are most commonly used in light aircraft. These engines convert fuel into heat energy and then into mechanical energy through a four stroke cycle. This mechanical energy moves the propeller to produces thrust.
Design Types & Principles
Most small aircraft are designed with reciprocating engines. The name is derived from the back-and-forth, or reciprocating, motion of the pistons that produces the mechanical energy necessary to accomplish work. Engines are classified according to the arrangement of the cylinders.
IN LINE: These cylinders are arranged in a single row along the crankcase. Usually just six to allow for cooling. They take up little space in the cowl and are fairly low powered engines. Commonly used in light aircraft such as the Tiger Moth and Chipmunk.
V-TYPE: The cylinders are arranged in two rows and an angle of 90, 60 or 45 degrees in V form along the crankcase. Connecting rods of opposing cylinders are connected to the same crankpins. There therefore always an even number of cylinders. This reduces the weight/horsepower ratio.
FLAT/ HORIZONTALLY OPPOSED: This is probably the most commonly used design amongst modern light aircraft. Directly opposing cylinders operate off a centrally located crankshaft resulting in a good weigh/horsepower ratio. These engines are air cooled.
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RADIAL: A bank of cylinders are arranged radially about the crankshaft resulting in large, round cowls which are difficult to streamline. However this arrangement leads to a low weigh/horsepower ratio. Due to the firing order there is always an uneven number of cylinders. Usually 3, 6 or 9.
110301149531100In a four-stroke engine, the conversion of chemical energy into mechanical energy occurs over a four-stroke operating cycle. The four separate strokes of the piston occur in the following order:
The induction stroke begins as the piston starts its downward travel from the top dead centre. When this happens, the exhaust valve closes and the intake valve opens drawing the fuel-air mixture into the cylinder.
The compression stroke begins when the intake valve closes, and the piston starts moving back to the top of the cylinder. The inlet valve is timed to close shortly after bottom dead centre (B.D.C) and the exhaust valve remains closed. The fuel/air mixture is then compressed, increasing both temperature and pressure.
The power stroke begins just before top dead centre (T.D.C) when the compressed fuel-air mixture is ignited by the spark plug. This forces the piston downward away from the cylinder head, creating the power that turns the crankshaft through its first full rotation. During the down stroke, temperature and pressure decrease and the exhaust valve opens.
The exhaust stroke is used to purge the cylinder of burned gases as the piston is pushed on its second up stroke. Just before top dead centre, the inlet valve opens to take advantage of the low pressure within the cylinder and the process starts all over again.
41422546800Basic Construction & Components
Cylinders: This is the part of the engine in which power is produce through the four stroke cycle. The cylinder consists of the head which holds the inlet/ exhaust valves and the barrel manufactured from aluminium alloy and high grade steel with cooling fins on the outside.
Pistons: Are simply cast aluminium plungers that move back and forth inside the cylinders. To reduce friction between the moving piston and the cylinder wall, piston compression rings, oil control rings and oil scraper rings are mounted in groves cut into the piston.
Connecting Rods: form the link between the crankshaft and the pistons. Strength is required to withstand the force of the power stroke, while weight must be kept to a minimum to allow for the constant change in direction of the pistons.
Crankshaft: is the backbone of any piston engine. It converts the reciprocal (back and forth) motion of the pistons into rotary motion which helps turn the propeller. Much like the pedals of a bicycle. They are designed with strength and durability in mind since maximum force and wear apply to the crankshaft during operation.
Crankcase: is the housing that contains the crankshaft and serves the purpose of;
Mounting the cylinders
Support the crankshaft
Oil-tight internal lubrication
Support for attachment of accessories
Valves: A fuel/air mixture enters the cylinders through the inlet valve port and, once burned, the exhaust gas exits the cylinder through the exhaust valve port. Timing gears allow for the correct valve timing which is essential for the to the success of the stroke cycle.
Combustion of our fuel/air mixture does not occur instantaneously, it takes some time. The ignition of our spark plugs are therefore timed to occur just before T.D.C. This is known as advanced ignition. In our piston engines, since the RPM is relatively low (maximum 2700 RPM), the ignition timing is fixed. Because of this at lower RPM settings, such as start-up, the ignition needs to be delayed. One of the methods used to solve this problem is the impulse magneto. Firing off the spark plugs at the appropriate time according to the relevant RPM setting.
Detonation occurs when the temperature and pressure of the compressed fuel/air mixture within the cylinders, or combustion chamber reaches excessive levels to cause instantaneous combustion or an explosion within the cylinder. This results in a ‘hammer-like’ blow instead of a rapid, powerful push.
High manifold pressure (excessive temperatures)
High air intake temperature
Low octane rated fuel (High octane fuel resists greater temperatures and pressures)
Incorrect use of mixture control (Mixture too lean)
Excessive cylinder temperature and pressure
Rough running engine (self-destruction through vibration)
Burnt valves (loss of power)
SYMPTOMS & PREVENTION:
Rough running engine and high cylinder temperatures may indicate detonation. The following action should be taken;
Mixture — Rich (assists in engine cooling)
Speed —– Increase (forward speed helps engine cooling)*Pitch nose down
Power —– Decrease (reduce cylinder pressures)
Hot spots within the cylinder cause the mixture to ignite prematurely before the spark plug fires. Hot spots can include red hot spark plug electrodes, glowing pieces of carbon or red-hot exhaust valves. Unlike detonation, pre-ignition generally occurs in only one cylinder.
Fuel octane too low
Mixture too lean
Incorrect ignition timing
Pre-ignition can lead to detonation, and significant engine damage. Prevention of both pre-ignition and detonation requires the engine to be operated within the correct manifold pressure settings, cylinder head temperatures and mixture settings.
Mixture settings should be slightly rich rather than too lean, as this leads to high temperatures. Ensure correct fuel rating and when in doubt, always use a higher octane rating.
6.2 Descriptive Data Analysis
This section discusses the general demographic descriptions, demographic features of the respondents, on the basis of the implementation of the four building block shop floor management tools, the two improvement practices and the improvement outcomes.
6.2.1 Demographic description
Table 6.8 shows the sample distribution of survey participants’ qualifications. 77.2%, of the participants reported that they did not attend university; followed by 21.4 % who held a bachelor degree; and a small 1.4% had a masters degree or above. All employees, irrespective of their qualifications were encouraged to contribute in individual improvement suggestions scheme and also to participate in group improvement activities.
Qualification Frequency Percentage (%)
Secondary/college or below 407 77
Bachelor Degree 113 38.3
Masters Degree or above 7 1.3
Total 527 100
Table 6.8 Sample distribution on participants’ qualification
In the context of the position held in the company, Table 6.9 indicates that the line supervisor to shop floor worker was 1:10.2 (54 line supervisors to 446 shop floor operators). Thus, there was no considerable difference between the proportions of respondents in the ratio of line supervisors to shop floor operators and the data obtained from the joint ventures official documents for all employees (about 1:8). Additionally, Table 6.9 also exhibits that majority of the respondents (77%) were shop floor operatives, 12.9% were line supervisors and 3.2% managers. It obviously marks that Improvement activities were not dominated by the top and middle management. This is in consonancet with the ideas of Caffyn (1999), Bodek (2002), Bessant and Caffyn (1997) who opined that the employees’ total involvement was one of the critical enablers for implementing continuous improvement.
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