The major topic of this book: Congruence lattices of finite lattices. It covers over 70 years of research and almost 200 papers.
... prolonged stationary kneeling on one or both knees on flat or inclined surfaces (see Fig. 1). Roofers, HVAC mechanics, and concrete workers perform more than 66% of their working time in kneeling, crouching, stooping, crawling postures or gaits . Occupational activities such as kneeling and squatting are associated with increase in knee pain, knee injuries, and knee osteoarthritis (KOA) . ...
Construction workers regularly perform tasks that require kneeling, crawling, and squatting. Working in awkward kneeling postures for prolonged time periods can lead to knee pain, injuries, and osteoarthritis. In this article, we present lightweight, wearable sensing, and knee assistive devices for construction workers during kneeling and squatting tasks. Analysis of kneeling on level and sloped surfaces (0 $^\circ$ , 10 $^\circ$ , and 20 $^\circ$ ) is performed for single- and double-leg kneeling tasks. Measurements from the integrated inertial measurement units are used for real-time gait detection and lower limb pose estimation. Detected gait events and pose estimation are used to control the assistive knee joint torque provided by lightweight exoskeletons with powerful quasi-direct drive actuation. Human subject experiments are conducted to validate the effectiveness of the proposed analysis and control design. The results show reduction in knee extension/flexion muscle activation (up to 39%) during stand-to-kneel and kneel-to-stand tasks. Knee-ground contact forces/pressures are also reduced (up to 15%) under robotic assistance during single-leg kneeling. Increasing assistive knee torque shows redistribution of the subject's weight from the knee in contact with the ground to both supporting feet. The proposed system provides an enabling intervention to potentially reduce musculoskeletal injury risks of construction workers.
Over the past fifty years, the United States has seen a tremendous decline in the amount of union members in the workforce. The trade unions in the construction industry have been no exception. Recently, the percentage of union members compared to the amount of employees have reached an all-time low. There has been a slight boost in members with the current climate of increased construction projects underway. But, unions still need to once again grow in strength to stay viable within the industry. Construction trade unions, especially the United Brotherhood of Carpenters, International Brotherhood of Electrical Workers, and Iron Workers, have strived to recruit more members through a variety of means. Additionally, unions have set goals to control enough market share to compete against the growing number of nonunion construction workers. Research and interviews among a variety of sources and various union members in California has shown a strong belief in strengthening unions because of their desirable benefits, training programs, higher pay and collective strength. Each individual local union strives to increase membership and market share within their given jurisdictions and have been increasingly doing so with support of their greater organizations. However, it remains questionable if they will achieve these presented goals due to an increasingly growing number of government policies targeting their growth. These policies include right-to-work laws and in some states, lack of prevailing wage laws. These policies do not directly destroy unions. They do greatly deteriorate their bargaining power when negotiating contracts. This in turn, leads to less union jobs. In California, construction unions have been able to maintain a decent amount of the project market share, largely variant on each district. However, the question remains how the construction industry would change if the union presence shrinks compared to the nonunion workforce. The shrinking amount of construction workforce would continue and labor would shift farther from the desirable blue collar career it once was.
Lower back pain (LBP), prevalence is high among the heavy equipment operators leading to high compensation cost in the construction industry. It is found that proper training program assists in reducing chances of having LBP. This study, therefore aims to examine different safety related budget available to support LBP related training program for different age group workers, utilizing system dynamics modeling approach. The simulation results show that at least 2.5% of the total budget must be allocated in the safety and health budget to reduce the chances of having LBP cases.