Khalid I. Alzebdeh

An Eigenvalue Based Approach for Assessing the Decomposability of Interdependent Design Project Tasks

The Concurrent engineering process is characterized by executing a large number of interdependent project tasks. One effective way of managing such tasks is to decompose them into groups. However, not all tasks are decomposable. Without the need to apply a decomposition method, this paper describes a simple, quantitative approach to test whether an underlying pattern of relationships exists between interdependent project tasks, such that they may be rearranged into groups. In addition, a grouping efficiency index is introduced to predict how good the best possible decomposition is. The proposed approach and the grouping index are applied to simple hypothetical projects and a sample project adapted from the literature. Both the approach and the grouping index are proved to be powerful yet very easy to use.

Factor Analysis of Obstacles Restraining Productivity Improvement Programs in Manufacturing Enterprises in Oman

Manufacturing enterprises can face obstacles that make productivity improvement efforts ineffective or even prevent improvement operations. This paper reports on an investigation of the internal obstacles restraining productivity improvement programs in the manufacturing enterprises of developing countries, using Oman as a case study. Data required for this study were collected through a questionnaire given to production and operations managers at 51 manufacturing enterprises in Oman. The results of applying factor analysis to a dataset of 15 obstacles showed that these obstacles can be reduced to three major factors. Ranked according to their importance, these factors are poor management practices, employee job dissatisfaction, and poor human resource management. The findings of this research are of value to production and operations managers of manufacturing enterprises who are interested in conducting productivity improvement programs not only in Oman but also in developing countries with environments similar to that of Oman, such as the Gulf Cooperation Council (GCC) countries.

Investigation of frictional effects on buckling behavior of drill string

The in-house developed experimental setup that imitates the wellbore being drilled in presence of surrounding drilling fluid is utilized to investigate the buckling phenomena of drill string. The paper also presents experimental investigations on the effect of changing the friction coefficient on the buckling lock-up situations of drill string. Results reveal that axial transferred loads decrease with the increase of friction coefficient. The results, highlights the significance of changing the drilling fluid rheology, mainly the friction factor, to reduce the friction between the wellbore and the tubing, and thus improve axial force transfer which is mainly responsible for initiation of buckling and limited reach of drilling operation. Drilling fluid with lower friction factor significantly reduces the friction between the tubing and the wellbore. The tube takes the same shape with the change of COF at the same load.Copyright

Evaluation of Effective Elastic Mechanical Properties of Graphene Sheets

The mechanical behaviour of a single-layer nanostructured graphene sheet is investigated using an atomistic-based continuum model. This is achieved by equating the stored energy in a representative unit cell for a graphene sheet at atomistic scale to the strain energy of an equivalent continuum medium under prescribed boundary conditions. Proper displacement-controlled (essential) boundary conditions which generate a uniform strain field in the unit cell model are applied to calculate one elastic modulus at a time. Three atomistic finite element models are adopted with an assumption that force interactions among carbon atoms can be modeled by either spring-like or beam elements. Thus, elastic moduli for graphene structure are determined based on the proposed modeling approach. Then, effective Young’s modulus and Poisson’s ratio are extracted from the set of calculated elastic moduli.Results of Young’s modulus obtained by employing the different atomistic models show a good agreement with the published theoretical and numerical predictions. However, Poisson’s ratio exhibits sensitivity to the considered atomistic model. This observation is supported by a significant variation in estimates as can be found in the literature. Furthermore, isotropic behaviour of in-plane graphene sheets was validated based on current modeling.Copyright

An approach for testing the feasibility of decomposing interdependent design tasks for concurrent engineering

Concurrent engineering process is characterized by executing a large number of interdependent project tasks. One effective way of managing such tasks is to decompose them into groups. However, not all tasks are decomposable. Without the need to apply a decomposition method, this paper describes a simple quantitative approach to test whether an underlying pattern of relationships exists between interdependent design tasks, such that they may be rearranged into groups. In addition, a grouping efficiency index for predicting the goodness of the best possible obtainable decomposition is introduced. The proposed approach and the grouping index were applied to simple hypothetical projects and a sample project adapted from the literature. Both the approach and the grouping index are proved to be powerful yet very easy to use.