Biomechanical Effects on Lower Extremities in Human-Robot Collaborative Agricultural Tasks

The present study pertains to a key aspect of human-robot collaborative systems which is usually underestimated, namely occupational health prolepsis. The aim of this investigation was to assess the biomechanical effects of manual symmetric load lifting related to a synergistic agricultural task that utilizes an unmanned ground vehicle to undertake the carriage of loads. Towards that goal, kinetic and kinematic data were collected from the lower extremities of thirteen experienced workers, by testing three different deposit heights (70, 80, 90 cm) corresponding to possible adjustments of the available agricultural robot. Moreover, the muscle activation levels of three lower extremity muscles and one trunk muscle were evaluated via a wireless electromyography system. Overall, the experimental findings revealed that the lower examined load height was associated with larger knee flexion moments and hip extension moments. Nevertheless, this height was related to lower activation mainly of the erectus spinae muscles. Finally, insignificant alterations were observed for the ankle joint as well as the activation levels of the other muscles. Consequently, a height equal to 90 cm is suggested, however, by avoiding extreme lumbar postures. The current results can be exploited for possible ergonomic interventions concerning the optimal deposit height of a robotic platform when a similar case is designed.

Biochar Effects on Soil Compaction in Two Contrasting Soils

<p>Although research on biochar use in soils has increased, its influence on soil compaction has been reported relatively little.<strong> </strong>The primary objective of this study was to measure the effects of biochar amendment on soil compaction, including infiltration capacity and aggregation, of two contrasting soils: a low soil organic carbon and hydrophilic degraded vineyard soil and a wildfire-degraded high soil organic carbon and hydrophobic forest soil.</p><p>We conducted a controlled laboratory soil column study (6 replicates), with PVC tubes filled with control soils and soil-biochar mixtures at a range of moisture contents. The mixtures were compacted under a falling load height that mimicked the standard proctor test. After the compaction procedure, infiltration capacity was determined with a mini disk infiltrometer, and bulk density and mean weight diameter were determined for the upper and lower halves of the soil column.</p>

2D Photogrammetry as a Forwarder Load Measurement Technique

Research Highlights: In this study, we present the use of time-lapse photos as a way to estimate the height of the load on the forwarders. This approach, using nonprofessional outdoor cameras, is a cheap and time-effective solution for continuous load height measurements, and it offers at least the same accuracy as a gauge measurement. This method represents another approach to the automation of time studies in forestry. Background and Objectives: Time studies require information about the load on the forwarders. Until now, this information was obtained either by using a gauge measure, sampling of the load, or averaging the load from large area datasets. More accurate methods like laser scanning are costly and fragile. During time study preparations, we suggested a robust system of measuring the load height and tested it against the commonly used gauge measuring technique. Materials and Methods: Two cameras took pictures of the load; these photos were processed for camera lens distortion and rectified into the cartesian coordinate system, and the height of the load was calculated. These values were then tested against gauge measured values using paired t-test. Results: Straight line distance calculated from the images and the gauge-measured distance did not show a significant difference (p-value 0.9354). Calculated vertical distance was, however, significantly different from the calculated straight-line distance (p-value of 0.0015), suggesting possible bias of the gauge measured distance. The root mean square error (RMSE) of the rectification process was, on average, 0.42 cm. Conclusions: The proposed method was verified to correspond with the gauge measure method; however, our research raised the question of the gauge method reliability, as the taken measurements are not perfectly vertical, and for the correct load estimation, the vertical distance is needed. We, therefore, conclude that for this photogrammetry method, the vertical, rather than straight-line, distance should be used. The presented solution can be used for long-term data collection without interrupting the whole forwarding process for taking the load measurement. The longer data processing in office enables researchers to spend less time in the field taking hand measurements.

An Analysis on the Relationship between the Number of Particles and the Volume by Using the Gas Kinetic Theory Model

This study aims at finding out the relationship between the number of particles and the volume by using the gas kinetic theory model. In this study, the data collection was conducted three times employing different particle numbers, namely 10 particles, 20 particles and 30 particles group. During the data collection process, the scale reading of the load height was done when the load collision has been going on for 20 seconds. Based on the observations, it can be obtained that the more the number of particles, the greater the volume. The graph analysis also reveals that the slope of the three graphs varies. Graph 4.1 and graph 4.2 share the same slope that is 0.1, while the slope of graph 4.3 is 0.095. The slope of the graph illustrates that once the number of particle increases, the position of the piston will also go up. In other words, it can be said that the changes in the position of the piston (v) is directly proportional to the number of particles (n).Keywords: Kinetic Theory Of Gases, Volume, Piston Position, ParticlePenelitian ini bertujuan untuk mengetahui hubungan jumlah partikel dengan volume menggunakan model teori kinetic gas. Pada penelitian ini, pengambilan data dilakukan sebanyak tiga kali dengan jumlah partikel yang berbeda-beda yaitu 10 partikel, 20 partikel dan 30 partikel. Pada proses pengambilan data yang dilakukan, pembacaan skala ketinggian beban dilakukan ketika penumbukan beban telah berlangsung selama 20 detik. Berdasarkan hasil pengamatan diperoleh bahwa semakin banyak jumlah partikel maka volumenya akan semakin besar pula. Dari hasil analisis grafik diperoleh kemiringan pada grafik 4.1 yaitu 0,1, grafik 4.2 diperoleh kemiringan 0,1 dan grafik 4.3 diperoleh kemiringan 0,095. Kemiringan grafik menggambarkan bahwa setiap pertambahan partikel bertambah pula kedudukan piston atau dapat dikatakan hubungan antara perubahan kedudukan piston (v) berbanding lurus dengan jumlah partikel (n).Kata kunci: Teori Kinetik Gas, Volume, Kedudukan Piston, Partikel

Computational Fluid Dynamic Analyses of Flow and Combustion in a Domestic Liquefied Petroleum Gas Cookstove Burner—Part II: Burning Characteristics and Overall Performance

Liquefied petroleum gas (LPG) is widely used in domestic cookstoves as it is a clean and high energy content fuel in comparison with other traditional cooking fuels. With the increasing demand of LPG, study and improvement of cookstove performance have become an important subject. In the present work, a numerical study of the flow and thermal fields for a domestic cookstove burner has been investigated and the performance of the stove is analyzed at different parametric conditions, like the equivalence ratio of the primary fuel–air mixture, fuel flow rate, thermal load height, and loading vessel size. The maximum thermal efficiency has been found for an equivalence ratio of 1.4 for the LPG–air mixture and at load height of 20 mm. The heat flux distribution at the bottom of the vessel is found to be bimodal with the higher peak occurring closer to the center of the vessel. The thermal efficiency of the stove increases with the rise in the fuel flow rate, and it decreases with reducing cooking vessel diameter. As the vessel diameter increases, the fraction of the total heat supplied through the vessel bottom increases. The radiative component of the heat flux is found to be much smaller compared to the convective component.

Effect of Eccentric Lateral Bracing Stiffness on Lateral Torsional Buckling Resistance of Wooden Beams

An energy-based solution is developed for the lateral torsional buckling (LTB) analysis of wooden beams with flexible mid-span lateral bracing offset from section mid-height and subjected to uniformly distributed or mid-span point load. The study shows that such beams are prone to two potential buckling modes; symmetric or anti-symmetric. The symmetric mode is shown to govern the capacity of the beam for low bracing stiffness while the anti-symmetric mode governs the capacity when the bracing stiffness exceeds a threshold value. Using the present formulation, the threshold bracing stiffness required to suppress the symmetric mode and maximize the critical moments is directly obtained by solving a special eigenvalue problem in the unknown bracing stiffness. The technique thus eliminates the need for trial and error in standard solutions. A parametric study is conducted to investigate the effect of bracing height, load height, and bracing stiffness on the critical moments. A large database of runs is generated and used to develop simple expressions for determining the threshold bracing stiffness required to maximize the elastic LTB resistance.