Biomechanical analysis of loading/unloading a ladder on a truck

Loading/unloading a ladder on vehicles are frequent tasks and involve overhead handling that may expose workers to risk factors of shoulder musculoskeletal disorders. The objective of the present study was to evaluate posture, forces required and perceived exertion when loading and unloading the ladder on a utility truck. Thirteen male overhead line workers from an electric utility in Brazil participated in this study. Shoulder elevation angle was measured using inclinometers. The required force to load/unload the ladder was measured by dynamometer. Subjective assessment of the perceived exertion was recorded to compare the exertion reported during the test conditions to the field conditions. The task of loading/unloading the ladder presented risks of shoulder musculoskeletal disorders (MSDs) to workers because it requires high levels of force (approximately 60% of the maximal force) combined with overhead posture of the shoulders (more than 100° from the neutral posture). Age and height presented to interfere in biomechanical risks presented in load/unload task. There was no significant difference between the subjective exertion during the test conditions and handling the ladder in the field. Ergonomic intervention is recommended to reduce these risks for shoulder MSDs.     

Low back pain disability and stay at work: contradiction or necessity?

The incidence of occupational diseases in the population is high and factors such as long working hours, poor posture, psychological and physical stress can contribute to its development. Among work-related musculoskeletal disorders, back pain has a high prevalence. The aim of the present study was to quantify and characterize pain complaints and to identify individuals with low back pain, in order to assess the degree of disability. Participated 226 employees of an institution of higher education. They answered a general questionnaire about location and quantification of pain complaints visual analog scale for pain and the Quebec Disability Questionnaire. Of all the workers, 69.60% had some type of musculoskeletal complaint; of those, 15.41% had low back pain. Considering workers who had back pain, 54.9% were female, 52.94% are under 30 years old and 43.14% between 1 and 5 years of work. As for the final score for the degree of disability, 41.17% had minimal disability and 37.25% moderate disability. The present study found large number of pain complaints and high prevalence of low back pain, resulting in individual's inability and difficulties in performing work activities.     

Kinematic analysis of post office employees' workstations

This study analyzed a post office clerk's tasks, comparing two workstation models. The clerk was facing the client in one, and seated at 45 degrees to the counter in the other. We analyzed the most frequent tasks and those presenting the most critical points: 1) payment of a postal order; 2) accepting a registered letter, breaking them down into subtasks. We used an optoelectronic system for kinematic analysis, and calculated the range of motion of the trunk and arms in the three spatial planes. The 45( position required less torsion of the trunk and head when using the printer, placed to the left of the employee. A larger worktop improved the workstation, leaving more room for equipment and allowing the worker to sit frontally to the monitor. However, this solution involved a shorter distance between the worker and the client with longer extension of the shoulder and elbow and less trunk flexion. These findings suggested a modification in the layout that shortens the distance between the worker and client.     

Robust bootstrap densities for dynamic conditional correlations: implications for portfolio selection and Value-at-Risk

ABSTRACT

Many financial decisions such as portfolio allocation, risk management, option pricing and hedge strategies are based on the forecast of the conditional variances, covariances and correlations of financial returns. Although the decisions depend on the forecasts covariance matrix little is known about effects of outliers on the uncertainty associated with these forecasts. In this paper we analyse these effects on the context of dynamic conditional correlation models when the uncertainty is measured using bootstrap methods. We also propose a bootstrap procedure to obtain forecast densities for return, volatilities, conditional correlation and Value-at-Risk that is robust to outliers. The results are illustrated with simulated and real data.     

Column generation approach for the point-feature cartographic label placement problem

This paper proposes a column generation approach for the Point-Feature Cartographic Label Placement problem (PFCLP). The column generation is based on a Lagrangean relaxation with clusters proposed for problems modeled by conflict graphs. The PFCLP can be represented by a conflict graph where vertices are positions for each label and edges are potential overlaps between labels (vertices). The conflict graph is decomposed into clusters forming a block diagonal matrix with coupling constraints that is known as a restricted master problem (RMP) in a Dantzig-Wolfe decomposition context. The clusters’ sub-problems are similar to the PFCLP and are used to generate new improved columns to RMP. This approach was tested on PFCLP instances presented in the literature providing in reasonable times better solutions than all those known and determining optimal solutions for some difficult large-scale instances.     

Emergy Measures of Carrying Capacity to Evaluate Economic Investments

This paper outlines a method for determining carrying capacity for economic investments based on an emergy evaluation of the environmental resources of a region. Using data from tourism development in Mexico and Papua New Guinea, the concept of carrying capacity is related to intensity of development, environmental support area, and the fit of economic development in local environments and economies.Emergy, a unit of resource use and work potential, is used to quantitatively evaluate intensity of development. Emergy evaluation is briefly described and the evaluations of tourism used to further explain the methodology. The total annual resource use for the tourist resorts and the economies in which they are embedded (including inputs of renewable and nonrenewable resources and purchased goods and services) was calculated and converted to emergy units. The renewable resource base and an Environmental Loading Ratio (ELR), are proposed as a means for determining both long term and short term carrying capacity respectively. The concept of sustainable development is related to the net emergy benefits that result from development. Expressed as a ratio of the amount of emergy received by the local economy to the amount that is exported (embodied in tourists), sustainability is suggested to result from a positive emergy trade balance.     

Quasi-maximum likelihood estimation of GARCH models in the presence of missing values

This work presents a new method to deal with missing values in financial time series. Previous works are generally based in state-space models and Kalman filter and few consider ARCH family models. The traditional approach is to bound the data together and perform the estimation without considering the presence of missing values. The existing methods generally consider missing values in the returns. The proposed method considers the presence of missing values in the price of the assets instead of in the returns. The performance of the method in estimating the parameters and the volatilities is evaluated through a Monte Carlo simulation. Value at risk is also considered in the simulation. An empirical application to NASDAQ 100 Index series is presented.     

A new continuous distribution on the unit interval applied to modelling the points ratio of football teams

We introduce a new flexible distribution to deal with variables on the unit interval based on a transformation of the sinh–arcsinh distribution, which accommodates different degrees of skewness and kurtosis and becomes an interesting alternative to model this type of data. We also include this new distribution into the generalised additive models for location, scale and shape (GAMLSS) framework in order to develop and fit its regression model. For different parameter settings, some simulations are performed to investigate the behaviour of the estimators. The potentiality of the new regression model is illustrated by means of a real dataset related to the points rate of football teams at the end of a championship from the four most important leagues in the world: Barclays Premier League (England), Bundesliga (Germany), Serie A (Italy) and BBVA league (Spain) during three seasons (2011–2012, 2012–2013 and 2013–2014).