Papers by Keyword: Statistical Analysis

Abstract: Analysis of histograms of grain size distribution of materials nanostructured by severe plastic deformation has been carried out using statistical analysis methods. It has been established that in materials with quite homogeneous nanostructure, the fitting of histograms of grain size distribution by using a logarithmic standard distribution is not accurate enough. It is proposed to compensate for the observed imprecision by including into the model the additional component – normal distribution. It is shown that this approach is applicable to nanostructured materials with both the deformation-origin nanostructure and the grain structure formed during annealing.

Abstract: The statistical analysis method of the grain structure in bulk single-phase metal materials subjected to high-pressure torsion is proposed. The possibility of methods division of mathematical statistics observed in the grain structure materials by their sizes with the several groups identification, having various behavior at further heating is presented. The example of the grain structure analysis on the nanostructured tin bronze is given. The agreement of the received analysis results with experimental data is offered.

Abstract: This paper addresses the problem of fault detection and isolation (FDI) in wind turbine benchmark model using data driven and multi-class support vector machine (SVM) approach. Since, the fault detection is fundamental for any active system, isolation is similarly vital, and identification is decisive for fault reconfiguration as well as maintenance addition to monitoring purposes. The need for man-made dynamic system to work automatically when sensor, actuator, or system faults occur was constantly developed in order to increase reliability and decrease unavailability and maintenance costs. The key step of our approach based on extraction of mean features from sensors measurements by applying the statistical methods such as moving standard deviation and the exponential weighted moving average (EWMA). The fault detection step is invoked later based on the multi-class SVM classifier that decides the presence or not of the fault. Another important contribution of this paper is the simulation of combined sensor and actuator faults simultaneously for the first time in wind turbine benchmark model. The FDI performances are illustrated through simulation study for seven different scenario tests. The results demonstrate clearly the effectiveness of statistical and SVM approach to detect and isolate single, multiple sensor and actuator faults and outperforms many results reported in the literature for solving this problem.

Abstract: Edge trimming process is needed for finishing CFRP components to the required accuracy and surface quality. The bouncing–back effect of CFRP components is very challenging owing to spring back of trimmed edge after cutting tool pass. Ultrasonic assisted machining (UAM) is an efficient method used to enhance the quality of CFRP parts due to the reduced contact time between the tool and workpiece. This paper experimentally investigates the effect of edge trimming variables on the cutting forces and the magnitude of the bouncing back. Diamond abrasive end mills were utilized during ultrasonic assisted edge trimming of CFRP. The processes variables include spindle speed, feed rate, radial depth of cut, fiber orientations, and up/down strategy. Statistical analysis was conducted to determine the most significant factor on performance characteristics. Regression equation was also developed to predict the value of bouncing back. The results showed that depth of cut and feed rate have a significant effect on bouncing back among the process variables.

Abstract: In this studies, melt-derived route was employed to fabricate new composition of bioactive glass (BG) from SiO₂-CaO-Na₂O-P₂O₅ system. Amorphous glass structure is confirmed through X-ray diffraction (XRD). Fourier transform infrared spectroscope (FTIR) confirmed the formation of silica network with the existence of functional groups Si-O-Si (bend), Si-O-Si (tetrahedral) and Si-O-Si (stretch) for all glass composition. The bioactivity of all BG is verified by incubation in Hank’s Balanced Salt Solution (HBSS) for 1h and 24h. Based on XRD pattern, it is confirmed that all glass composition remained in amorphous structure even after 24h of immersion with weak characteristic of carbonate group (C-O) and P-O band detected in FTIR analysis on carbonated hyrdoxyapatite (CHA) formation. Therefore, the objective to develop new composition of BG is achiveable despite the lack of CHA formation.

Abstract: The paper presents an extensive theoretical background related to the travel time and the studies that were conducted during the recent years on the subject. As a concept, travel time is related to the period of time spent in travelling between two different points in space. The analysis focuses on several aspects related to the travel time concept such as its usefulness, its influencing factors, and data collection methods for its determination. In order to also provide a practical outcome, the main interurban road connection between Cluj-Napoca and Tîrgu-Mureş was studied. The road trespasses both urban and rural localities in the North-Western of Romania. For the data collection process, a GPS-based equipment was placed on a test vehicle to run the route for multiple times, at different days and hours. The collected data were studied by means of statistical analysis in order to establish the most relevant aspects of the travel time. The research goal of the paper was to evaluate the influence exerted by demographics and type of locality on travel time by means of eventual delays. The main findings were employed to analyze the traffic conditions as well as the parameters that have a major impact on them. According to the results of the analysis, the traffic flow on the interurban route is best described by the travel time and consequently the delays registered due to multiple obstructive elements such as railway level crossings, pedestrian crossings within the localities, and level intersections between different roads category. However, according to the study, it can also be concluded that travel time and therefore the eventual delays are not influenced to a great extent by neither the type of transited localities - urban or rural, nor the demographics.

Abstract: The main causes for deterioration of carbon blocks are due to the penetration and dissolution of hot metal against pores and surfaces. The active national standard GB/T 24201-2009 can only judge the hot metal dissolution, but the penetration of hot metal during test has been neglected. On the basis of national standard, a new measurement and characterization method is proposed. The study shows that with the help of back-scattered electron detect technology combined with statistical analysis, the penetration depth of hot metal could be quantitative evaluated, which could provide a reference for optimize the production of blast furnace refractories.

Abstract: In this paper, statistical data regarding off-grid inverter faults are presented, derived from the maintenance records of a major service center in Greece. Several commercial types of inverters for autonomous photovoltaic (PV) systems have been examined, presenting different types of faults and malfunctions. The service procedures recorded encompass fault diagnosis, specific failed parts, symptoms indicating malfunction and estimated cause of failure for each case. The statistical analysis undertaken leads to useful conclusions about the robustness and weak points for off-grid equipment, as well as the common failure causes and malfunction indications.

Abstract: The aim of this work is to propose the application of statistical methods (linear regression and statistical hypothesis test) to analyze the effect of parameters used in powder injection molding including sintering temperature and the feedstock composition on the flexural strength, the porosity and the density of the sintered specimens of mullite prepared by powder injection molding (PIM) and using the composite binder consisting of 80 wt% polyethylene glycol (PEG) and 20 wt% polyvinyl butyral (PVB) for molding. The lab-scale plunger type PIM machine was used to prepare the specimens. The feedstock compositions were 50 to 54 vol% mullite, and the sintering temperatures were 1300 and 1400 °C. At level of significance 0.05 for statistical analysis, feedstock composition did not affect flexural strength, porosity, and density of the sintered specimens. For sintering temperature, the specimens sintered at 1400 °C have the greater density and the lower porosity. However, the flexural strength of the specimens sintered at 1300 °C and 1400 °C are statistically similar.

Abstract: The purpose of this work is to use the statistical methods including linear regression and statistical hypothesis test to study the dissolution behavior of polyethylene glycol (PEG), a water-soluble binder, during debinding step of the green specimens of mullite formed by powder injection molding (PIM). Two systems of composite binders were investigated including (A) 80 wt% polyethylene glycol (PEG) and 20 wt% polyvinyl butyral (PVB) and (B) 78 wt% PEG, 20 wt% PVB, and 2 wt% steric acid (SA)The lab-scale plunger type PIM machine was used to prepare the green specimens consisting of mullite powder and the composite binder. The possible solid loadings of the green specimens that could be prepared by this machine were 50, 52, and 54 vol% mullite (50, 48, and 46 vol% binder). The debinding was done by soaking the green specimens in the warm water at 40 or 60 oC to remove PEG. At level of significance 0.05 for statistical analysis, the dissolution behavior of PEG can be fitted with Avarami equation. In addition, from the Avarami equation obtained from each experimental condition, the dissolution rate of PEG was independent of the parameters used in this study including solid loading in the green specimens, water temperatures for debinding, and composite binder systems.