Many engineering optimization tasks involve finding more than one optimum solution. The present study provides a comprehensive review of the existing work done in the field of multi-modal function optimization and provides a critical analysis of the existing methods. Existing niching methods are analyzed and an improved niching method is proposed. To achieve this purpose, we first give an introduction to niching and diversity preservation, followed by discussion of a number of algorithms. Thereafter, a comparison of clearing, clustering, deterministic crowding, probabilistic crowding, restricted tournament selection, sharing, species conserving genetic algorithms is made. A modified niching-based technique -modified clearing approach -is introduced and also compared with existing methods. For comparison, a versatile hump test function is also proposed and used together with two other functions. The ability of the algorithms in finding, locating, and maintaining multiple optima is judged using two performance measures: (i) number of peaks maintained, and (ii) computational time. Based on the results, we conclude that the restricted tournament selection and the proposed modified clearing approaches are better in terms of finding and maintaining the multiple optima.
Background:Work-related rotator cuff injuries are a common cause of disability and employee time loss.Purpose:To examine the effectiveness of expedited rotator cuff surgery in injured workers who underwent rotator cuff decompression or repair and to explore the impact of demographic, clinical, and psychosocial factors in predicting the outcome of surgery.Study Design:Case series; Level of evidence, 4.Methods:Injured workers who were seen at a shoulder specialty program and who underwent expedited arthroscopic rotator cuff decompression or repair were observed for a period of 6 to 12 months based on their type of surgery and recovery trajectory. The primary outcome measure was the American Shoulder and Elbow Surgeons (ASES) Standardized Shoulder Assessment Form. The impact of surgery was assessed by whether the change in the ASES score exceeded the minimal clinically important difference (MCID) of 17 points. Secondary outcomes were range of motion (ROM), medication consumption, and work status.Results:One hundred forty-six patients (43 women [29%], 103 men [71%]; mean age, 52 years; SD, 8 years) completed the study. Sixty-seven (46%) patients underwent rotator cuff repair. The mean time between the date the patient consented to have surgery and the date of surgery was 82 (SD, 44) days. There was a statistically significant improvement in ASES score and ROM and work status (52 returned to regular duties and 59 to modified duties) (P < .0001). Eighty-four percent (n = 122) of patients exceeded the MCID of 17 points. Individual factors that affected patient overall disability were preoperative ASES, work status prior to surgery, access to care, and autonomy at work. Achieving a minimal clinically meaningful change was influenced by perceived access to care, autonomy and stress at work, and overall satisfaction with the job.Conclusion:Expedited rotator cuff surgery improved disability, ROM, and work status in injured workers. Successful recovery after work-related shoulder injuries may further be facilitated by improving the psychosocial work environment and increasing access to care.
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