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Verification of calculations carried out with the Eclipse treatment planning system

Ahmad H., Ahmad M., Ali S., Khattak M. R., Shaheen W., Gilani J. A., Ahmad K.

Polish Journal of Medical Physics and Engineering

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2018

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Vol. 24, Iss. 3

109--114

EN

The goal of radiotherapy is to deliver prescribed dose to the target volume and simultaneously minimize the dose to the healthy organs. The purpose of this work was to verify the accuracy of calculations carried out with a treatment planning system (TPS). Measurements carried out with thermoluminescence detectors (TLDs) were compared with doses calculated with TPS. Doses were measured and calculated both in the open beam’s region and under individual blocks. Measurements were performed in the Randophantom. The work was carried out for photon beams generated in the Varian CLINAC 2100C accelerator. The maximum / minimum percentage differences between measured and calculated doses were 4.9/0.6%, 2.6/0%, and 3.5%/0.5% in open, shielded and partially shielded points, respectively. Differences between the measured and calculated doses were within acceptable limits.

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The deployment of performance measurement system under the supply chain management environment: the case of Malaysian manufacturing companies

Ahmad K., Zabri S. M.

Management and Production Engineering Review

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2018

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Vol. 9, No. 1

3--12

EN

Performance measurement system in supply chain management (SCM) has been receiving increasing attention by business organizations as a way to evaluate efficiency in supply chain activities. Assessing the performance of supply chain uncovers the gap between planning and actual performance as to trace the potential problems thus ascertain necessary areas for improvement. This research aims to investigate the application of performance measurement system in SCM as well as exploring its relationship with organization’s performance among Malaysian manufacturing firms. By utilizing the questionnaire method, respondents involved were requested to indicate the extent to which they use a number of 24 selected performance measures that are related to SCM. The results show that the majority of the observed manufacturing firms utilize specific performance measurement tools in evaluating the supply chain performance. The current performance measurement techniques, the Balanced Score Card is adopted by around a quarter of the total responding firms followed by Supply Chain Operations References Model – SCOR, which attracts total users of only a fifth of the total respondents. In particular, performance measures under customer service category recorded the highest number of usage followed by cost-based performance measures and operations management. The results of this investigation also unveil few major points that are important to be highlighted. Firstly, the obtained outcomes of this study bring to light the significant relationships between the utilization of supply chain performance measures under customer service, operations management and organizational performance. In addition, this study discovered a significant correlation between the size of the organization and the extent of use of supply chain performance measures and how these two variables positively correlated. Lastly, the findings also suggested that the performance measures for SCM has been playing a crucial role in enhancing the performance of the organizations and is increasingly operated as the firms grow in size. Based on the brief highlighted points listed above, it is not an exaggeration to say that this research contributes new information to the body of knowledge in performance measurement system in SCM and its associations with organizational performance.

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Limit cycle oscillation prediction based on Finite Element-Modal approach

Ahmad K., Wu Z., Rahman H.

Archive of Mechanical Engineering

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2018

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Vol. LXV, nr 4

497--514

EN

The central theme of this work was to analyze high aspect ratio structure having structural nonlinearity in low subsonic flow and to model nonlinear stiffness by finite element-modal approach. Total stiffness of high aspect ratio wing can be decomposed to linear and nonlinear stiffnesses. Linear stiffness is modeled by its eigenvalues and eigenvectors, while nonlinear stiffness is calculated by the method of combined Finite Element-Modal approach. The nonlinear modal stiffness is calculated by defining nonlinear static load cases first. The nonlinear stiffness in the present work is modeled in two ways, i.e., based on bending modes only and based on bending and torsion modes both. Doublet lattice method (DLM) is used for dynamic analysis which accounts for the dependency of aerodynamic forces and moments on the frequency content of dynamic motion. Minimum state rational fraction approximation (RFA) of the aerodynamic influence coefficient (AIC) matrix is used to formulate full aeroelastic state-space time domain equation. Time domain dynamics analyses show that structure behavior becomes exponentially growing at speed above the flutter speed when linear stiffness is considered, however, Limit Cycle Oscillations (LCO) is observed when linear stiffness along with nonlinear stiffness, modeled by FE-Modal approach is considered. The amplitude of LCO increases with the increase in the speed. This method is based on cantilevered configuration. Nonlinear static tests are generated while wing root chord is fixed in all degrees of freedom and it needs modification if one requires considering full aircraft. It uses dedicated commercial finite element package in conjunction with commercial aeroelastic package making the method very attractive for quick nonlinear aeroelastic analysis. It is the extension of M.Y. Harmin and J.E. Cooper method in which they used the same equations of motion and modeled geometrical nonlinearity in bending modes only. In the current work, geometrical nonlinearities in bending and in torsion modes have been considered.