Papers by Keyword: Statistical Analysis

Abstract: In this paper we analyze the influence of cutting parameters on the surface quality, surface roughness respectively, processed by turning when heat treated bearing steel, also called hard turning, and processing by turning of bearing steel without heat treatment. We set parameters of the cutting regime influencing the achievement of roughness surfaces which must be within the predetermined requirements if bearing rings exceeding 500 mm in diameter. This analysis will be done by statistical methods using the software Minitab 14.

Abstract: Refueling aircraft in-flight is a complex procedure at any time and has its concerns that have not fully been addressed, these are compounded if we consider remote piloting. Long term the need will exist to refuel unmanned vehicles if they are to carry out extensive applications; these complexities of in-flight refueling increases due to time delays and visual challenges between the actual remote aircraft and operators. This paper addresses the reliability of a drogue used in refueling and what can be learnt for future designs and usage. In particular what we can interpret from remote pilots and in-situ pilots.

Abstract: This paper aimed to investigate the machining factors influencing surface roughness and to obtain the appropriate turning operation of aluminum. The Shainin design of experiment method was used to investigate the effect of the four turning factors on surface roughness. Moreover, analysis of variance and multiple comparisons were used to obtain the appropriate turning operation of the significant factors. The results showed that spindle speed was the only significant factor affecting the average surface roughness with the appropriate turning operation of 1000 rpm used for reducing surface roughness of the machined part and tool wear.

Abstract: Structural Health Monitoring (SHM) techniques have gained an increased interest to be utilised alongside NDI techniques for aircraft maintenance. However, to take the SHM methodologies from the laboratory conditions to actual structures under real load conditions requires them to be assessed in terms of reliability and robustness. In this work, a statistical analysis is carried out for an SHM system for damage detection and characterisation in composite structures. The sensitivity of the platform to parameters such as noise, sensor failure, placement tolerances and bonding has been investigated and reported.

Abstract: Structural Health Monitoring (SHM) techniques have gained an increased interest to be utilised alongside NDI techniques for aircraft maintenance. However, to take the SHM methodologies from the laboratory conditions to actual structures under real load conditions requires them to be assessed in terms of reliability and robustness. In this work, a statistical analysis is carried out for a passive SHM system capable of impact detection and identification. The sensitivity of the platform to parameters such as noise, sensor failure and in-service load conditions has been investigated and reported.

Abstract: The aim of this work is to analyze the error of the calculated integrated intensity of the x-ray peaks of a-iron (BCC-Fe) powder from x-ray diffraction (XRD) pattern by using the numerical method and the statistical analysis. The a-Fe powder was characterized by the x-ray diffractometer using step scan mode, step sizes 0.03^o 2q and 0.05^o 2q, and preset times from 0.1 to 3.5 s. The integrated intensity () of an x-ray peak and its error () were calculated using numerical method. The correlation between the relative error () and the preset time or step size were analyzed by the statistical analysis methods which are linear regression and statistical hypothesis testing. The results from the statistical analysis at significance level of 0.05 show that the relative error () correlate with x = preset time or integrated intensity by when a₁ and a₂ are the positive constants. From the mathematical model, for this work, the step size does not affect the relative error. However, the increasing of preset time reduces relative error on integrated intensity calculation. To minimize the error on XRD analysis, the preset time should be greater than one second. Moreover, on a XRD pattern, the lower integrated intensity peak has the higher relative error.

Abstract: In this work, the statistical analysis methods, including least square method and statistical hypothesis testing, were used to study the flexural strength and density of the specimens formed from mullite powder by powder injection molding (PIM). The feedstock for PIM consist of mullite powder and the composite binder consisting of 78 wt% polyethylene glycol (PEG), 20 wt% polyvinyl butyral (PVB), and 2 wt% stearic acid (SA). The PIM machine used in this work was the lab-scale plunger type. The compositions of the feedstock that could be injection molded by this machine were 50, 52, and 54vol% mullite. After molding, PEG in the green specimens was removed prior to sintering by soaking the specimens in the water at 60 °C for 24 hours while PVB and SA were removed during sintering. The sintering temperatures were 1300 to 1450°C. At significance level of 0.05, the least square method and the statistical hypothesis test showed that both feedstock compositions and sintering temperatures used in this work affected the densities of sintered specimens. However, the increasing of the flexural strength of sintered specimens was mainly by the increasing of the sintering temperature.

Abstract: At present, both at home and abroad of tunnel surrounding rock classification methods and standards are all aimed at tunnel survey and design phase. It is the cause of that surrounding rock classification are very different between design phase and tunnel construction because of the limits of investigation techniques and geological data. It is the key to the real-time construction design problem that Sentenced to a stable state of surrounding rock based on the monitoring data. This paper determines the influence factors of tunnel convergence value clearance and obtained the tunnel convergence value clearance of principal component factor and power based on the statistical analysis of a lot of tunnel monitoring measurement data. It is put forward correction formula of dynamic classification of surrounding rock according to the theory of probability and statistics. The results show that based on the real-time monitoring of tunnel surrounding rock classification method is quite coincident with the actual situation of tunnel excavation in engineering applications.

Abstract: To achieve sustainability in the composite industry, natural fibers must be able to replace synthetic fibers .In this work the tensile properties of sisal fibers were determined. The relationships between tensile strength, young modulus, failure to strain and gage length was studied. Also variation in tensile strength was quantified using statistical analysis. The relationship between Weibull statistics and gage length were also investigated. The strength of the sisal fiber obtained in this work was between 255-377 MPA and decreased with an increase in gage length. The Weibull modulus obtained was similar for all gage lengths and was around 2.5.

Abstract: During the monsoon season, certain areas in Malaysia are experiencing a flood. While during the transition period Malaysia is experiencing a drought. This phenomenon could lead to severe disaster and precaution monitoring is needed to avoid this occurrences. Low flow during the dry season could lead to several negative effects on the river ecosystem. Thus, this study was conducted to determine the low flow frequency and intensity for the Segamat city. The duration for 2 years to 100 years based on the previous 20 years of stream flow data were used to calculated. Stream flow data were obtained from the Department of Irrigation and Drainage (DID). Two prominent distribution analyses methods known as Gumbel Distribution and Log pearson Type III Distribution were applied. The distribution results were validated using Root Mean Square Error (RMSE) and California method and Weibull method are selected. Based on the analyses results, it clearly shows that the distibution of low flow are between 1 m³/s to 10 m³/s. The flow are significantly correlate with the rainfall intensity. RMSE was selected based on the lowest value of 0.721 for the Gumble Distribution and 1.831 for Log Pearson Type III Distribution. Chi-square test shows a good agreement for Gumble Distribution (7.615<12.59) and Log Pearson Type III(5.201<11.07) using 5% significant level. The confident level form both tests are valid (p>0.05), thus, this results could be used for further analyses to alleviate the low flow in the study area.