Rolling element bearings localized fault diagnosis using signal differencing and median filtration

With the increase complexity of bearings’ processing algorithms and the growing trend of using computationally demanding algorithms, it is advantageous to provide analysts with a simple to use and implement algorithm. In this spirit, this paper combines simple functions to provide machine condition analysts with the capacity to diagnose bearing faults without all the complexity and jargon that comes with existing methods. The paper proposes a simplified surveillance and diagnostic algorithm for diagnosing localized faults in rolling element bearings using measured raw vibration signals. The proposed algorithm is based on analyzing the frequency content obtained from applying a median filter on the squared derivative signal (first or higher derivatives) of the vibration signal. The combination of signal differencing and median filters provides a squared envelope signal, which can be used directly to diagnose faults. Signal differencing gives a measure of jerk forces and lifts the high frequency content of the signal. To select the optimum order of differentiation, Kurtosis and maximum correlated kurtosis (MCK) are proposed. Median filter usage represents a better alternative of normal low pass filtration. This completely suppresses impulses with large magnitudes, which may interfere with the diagnosis. The length of the median filter (odd number 3, 5, 7 etc.) is selected as such to include the first 10 harmonics of the defect frequency. Simulated signals are used to demonstrate the efficiency of the proposed algorithm and give insights into the choices of the differentiation and smoothening orders. The proposed processing algorithm gives a first measure (surveillance) for detecting localized faults in rolling element bearings in a very simple way and can be employed in online learning and diagnosis systems. Results obtained from applying the algorithm on complex vibration signals from two types of gearboxes are compared with a well-established semi-automated technique with good correspondence

Teacher leadership in government schools in Qatar: opportunities and challenges

The current study is an attempt to understand how teachers working in Qatari government schools understand the concept of teacher leadership. This topic has received little attention in the educational leadership literature in this context. Teachers came to Qatar during and after its massive educational reform (2003-2017), mainly from countries in the Middle East and North Africa (MENA) region and are employed in an advanced educational system equipped with the most recent educational technologies and resources. The Ministry of Education (MoE) offers comprehensive professional development programmes, and a licencing system guarantees uniformity in teachers’ qualifications to ensure quality education. These opportunities have made it imperative to investigate how teachers perceive the concept of teacher leadership, examine the factors that influence these perceptions and provide suggestions to foster teacher leadership in schools. Adopting the teacher leadership definition of York-Barr and Duke (2004), this mixed methods study used a questionnaire based on the Teacher Leadership Inventory (TLI) tool developed by Angelle and DeHart (2011) and semi-structured interviews to collect data regarding teacher leadership perceptions. 2,969 people responded to the questionnaire and 96 teacher leaders were interviewed. The results of the study showed that teachers define teacher leadership in terms of formal leadership roles, e.g. subject coordinators. However, teachers in Qatar practise many informal leadership roles to support other teachers socially and professionally. Contrary to previous research, school level (preschool, primary, preparatory, secondary or complex) was not a significant variable in the quantitative phase although interviewees stated that school level affected teacher leadership practices. The qualitative phase results revealed many factors that support teacher leadership (including support from other staff including the principal, and from family members) as well as factors that inhibit it (dealing with difficult people, lack of team support, language and cultural differences, continuous changes from the MoE)

Causes of Construction delay in UNRWA projects in the Gaza Strip

Construction delay causes time and cost overruns for both owners and contractors. Claims and disputes may also be created due to construction delay. This paper investigated the causes and levels of delay on 90 completed projects in the Gaza Strip. The investigated projects are public nonresidential projects (mainly schools and medical centers). The result of this research reveal that the main causes of construction delay are unavailability of materials, political instability, bad weather, design changes, additional works, owners delay, and site conditions. The improvement of materials supply to Gaza Strip by establishing an independent materials resource and improving the owner’s contract document preparation will mitigate the delay of construction projects

Support vector machine cost estimation model for road projects

A cost estimate is one of the most important steps in road project management. There are ranges of factors that mostly affect the final project cost. Many approaches were used to estimate project cost, which took into consideration probable project performance and risks. The aim is to improve the ability of construction managers to predict a parametric cost estimate for road projects using SVM (support vector machine). The work is based on collecting historical road executed cases. The 12 factors were identified to be the most important factors affecting the cost-estimating model. A total of 70 case studies from historical data were divided randomly into three sets: training set includes 60 cases, cross validation set includes three cases and testing set includes seven cases. The built model was successfully able to predict project cost to the AP (accuracy performance) of 95%

Modelling the parametric construction project cost estimate using fuzzy logic

The research aims to model to predict the parametric cost estimation in construction building projects in Gaza Strip using Fuzzy logic. The building factors which effect the parametric cost estimation were surveyed. A questionnaire survey and relative index ranking technique were used to indicate the most five important factors from the view points of contractors, clients and consultants. 106 Case studies from real executed construction project in Gaza Strip were collected for the most important five factors to build up Fuzzy logic Model. The results revealed the ability of Fuzzy Model to predict cost estimate to an acceptable degree of accuracy

Student teachers' perspectives towards teacher leadership

This qualitative study aimed to explore six student teachers' changing perceptions and understandings of teacher leadership during their participation in a practicum experience in Qatar. The practicum experience particularly targeted developing student teachers understanding of teacher leadership through discussions, coaching, and mentoring. Data collection was carried out through a quantitative survey, and qualitative semi-structured interviews and weekly reflective journals in order to document not only changing perceptions, but also the factors influencing such changes. Findings revealed some improvement in student teachers' definitions, awareness, and practises of teacher leadership. However, they did not fully associate their practises as being completely leadership-oriented. Implications of the study pertain to providing suitable opportunities for leadership development within teacher preparation programs to help student teachers acknowledge their contributions and practises as pertaining to teacher leadership.Scopu

Simulation of vibrations produced by localized faults in rolling elements of bearings in gearboxes

A combined gear/bearing model has been made to study the interaction between gears and bearings in the presence of faults. The thirty-four degree-of-freedom model of the University of New South Wales (UNSW) gearbox test rig is a lumped mass parameter model, which has the capacity to model different fault types (localized inner/outer race faults and extended faults). This is in addition to its original capacity for modelling spalls and cracks in the gears. The gear/bearing model takes into consideration the slippage in the bearings, the Hertzian contact and the nonlinearity of the bearing stiffness (time variant). Results have earlier been published for simulated local faults in the inner and outer races of the bearings as well as for an extended inner race fault. For a complete modelling of localized faults, the simulation model has now been updated to enable simulating faults in the rolling elements. The modeling of the faults in the rolling elements takes into consideration the difference in race curvature and represents a new contribution to the development of the model. The agreement between the processed simulated and measured signals shows the robustness of the developed model and its suitability for testing new diagnostic and prognostic algorithms

Application of Project Time Management Tools and Techniques to the Construction Industry in the Gaza Strip

The objective of this paper is to investigate the level of applying theproject time management tools and techniques by public ownersand construction contractors in the Gaza Strip. This study hasbeen conducted by means of a survey questionnaire. Seventythreequestionnaires were distributed to target constructioncontractors and twenty-five questionnaires to public owners. Sixtycompleted questionnaires from contractors and twenty-threequestionnaires from public owners were received and analysed.The survey results indicated that contemporary project timemanagement tools and techniques are not widely used amonglocal contractors and owners. Lack of subcontractor’s knowledgeand awareness of the importance of project time managementtools and techniques are still major obstacles toward the efficientutilisation of such tools. This study recommended that there is anurgent need to establish a professional industry body such as anInstitute of Building to review and evaluate existing local projectmanagement practices. This professional body may be establishedby the government through the Ministry of Housing and PublicWorks or by the local university in cooperation with a similarinternational professional industry body. Current training effortshould be tailored to encourage owners and contractors to usework breakdown structures, resource optimisation, and networkscheduling

Factors affecting stakeholder management in construction projects in the Gaza Strip

One of the major emerging concerns in the management of construction projects is the recognition and management of project stakeholders, since the stakeholders are a major source of uncertainty in construction projects. The construction industry in the Gaza Strip has involved a diverse range of stakeholders. This research aims to evaluate the most common factors affecting the stakeholder management process in construction projects. A literature review was conducted on topics related to stakeholder management. A questionnaire survey was carried out among professionals in the construction industry. Ninety-eight questionnaires were distributed to experts from government, municipality, and non-government organizations. Sixty-seven questionnaires were received, with a 68% response rate. The mean and relative importance index were used to analyse the questionnaire results. The main factors affecting the