Ergonomic posture analysis of different postures in laptop users at non-official places and related musculoskeletal disorders by rapid upper limb assessment method

Background: Laptops are not ergonomically being designed as the same as a desktop computer and are not suitable for prolonged use. The current study aimed to assess the different postures laptop users, especially in non-official places, and its effect on musculoskeletal disorders (MSDs). Study Design: This was a cross-sectional study. Methods: One hundred and fifty university students were chosen that have continuous use of laptop for 5 years. Data were gathered by questionnaire (demographic data, laptop use-related questions and visual posture questions) and posture analysis using Rapid Upper Limb Assessment method. T-test, Chi-square and Spearman correlation coefficient tests were used in data analysis. Results: The mean of body weight in males and females was 77.58 ± 13.34 kg and 62.35 ± 10.67 kg, respectively. Two postures, including E (sitting on the sofa and put the laptop on the table) and F (sitting and working on an office chair and desk), were the most current postures by the users. Postures M and K had been as the most inappropriate postures, while postures D and G were defined as postures that are more appropriate. Conclusion: Laptop is using frequently as a popular device at home, dormitory or other non-official places. Due to nature of these places and inherent characteristics of laptops, it is not possible to make it adjust for the body based on ergonomic principals. Neck, upper and lower back, shoulder and wrist are organs that influence more by laptop based on body configuration

Performance evaluation of complex electricity generation systems

To evaluate the performance of complex electricity generation systems, a new dynamic network-based data envelopment analysis (DNDEA) approach is presented. Past data envelopment analysis (DEA) studies on energy system efficiency have often ignored the dynamics of each process of the system individually. Here a network-based DEA method is built, which considers the interrelationships of the operations to determine the efficacy of the system. For assessing the performance over successive periods, with time-based dependencies between the successive periods, a dynamic DEA (DDEA) model is proposed. In DDEA, a linear combination of the efficiencies in successive periods is used as the complement of the system. The network-based and dynamic features of the created model enable measuring the performance of each sub-system process and the entire system in multi-period planning horizons simultaneously. These features make the DEA model identify changes in system efficiencies so much better than the current approaches. The created model is comprehensively implemented in the Iranian electricity sector using real data. Based on the findings, the efficiencies of power generation and transmission sectors are decreasing while the distribution performance is increasing. The proposed model could be applied to electricity generation systems in other countries as well.Peer reviewe