1,720,964 research outputs found
Operator protection in rollover events of articulated narrow track tractors
No full textArticulated steering arrangements, wheeled or tracked, are commonly used on agricultural tractors and earth moving machines. In Continental Europe and Italy in particular, this configuration is typical of narrow track tractors. Despite their widespread use, there is little research that specifically investigates articulated tractor rollover protective structure (ROPS) in-field performance with respect to the ROPS test procedures. The aim was to investigate the relevance of the standardised ROPS test procedures regarding articulation joint mobility. The shortcomings of the procedures concerning the Clearance Zone and ROPS testing are evidenced and discussed. It is a recommendation of this work that an update of the international testing procedure be developed for articulated tractor types. The paper indicates how this may be accomplished and presents remedial measures that can be implemented in the interim until this latter goal is achieved
Evaluation of the Stability Behavior of an Agricultural Unmanned Ground Vehicle
Full text linkPrecision farming is the newest agricultural approach in countries with highly mechanized field operations, and the role of unmanned ground vehicles (UGVs) in smart farming is becoming increasingly prominent. This work aimed to evaluate the stability of the DEDALO UGV developed by the University of BOLOGNA for precision orchard and vineyard management. The driving part of the machine is somewhat peculiar; it moves autonomously in the field combined with a tank to store water and pesticide mixture for crop protection, with an additional structure to carry agricultural implements. The study aimed to evaluate the stability of the agricultural unladen UGV, and mulcher and sprayer mounted configurations. In the case of the sprayer, the stability behavior was evaluated with an empty and full tank. The machine, in terms of stability, was studied both laterally and longitudinally. A theoretical model was developed based on the upstream side forces measured during experimental tipping tests. The results of the experimental data were compared with the theoretical predicted results to validate the model. In the lateral test, the average value of the limit stability angle was 48 degrees, while in the longitudinal test, it was 49 degrees. The results of the model were statistically correlative (R2 > 95) and denoted that the most stable condition occurred in the case of the UGV fitted with the mulcher in the longitudinal tipping position (56 degrees), while the most unstable condition was the case of the unladen UGV in the longitudinal tipping position (40 degrees). Although the stability problem is not directly connected with the operator, as these machines do not require a driver, the lack of stability can lead to the UGV overturning with consequent risks for the surrounding environment and damage to the UGV body
The Stability of Self-Propelled Sprayers According to the ISO 16231 Standardized Procedure
No full textTractor rollover and agricultural machinery stability are subjects of interest both to manufacturers and researchers. Agricultural machines often work on rough terrain and sloping ground so instability and rollover events can easily occur. For agricultural tractors the solution adopted at international level was to provide them with Roll-Over Protective Structures (ROPS) to minimize risks for the driver in a rollover event. ROPSs are designed to absorb and sustain values of energy and forces established by the normalized OECD procedure. In the standardized test
s it is necessary to evaluate the deformation of the ROPS because a clearance zone has to be maintained for the driver. Self-propelled sprayers currently have to comply with the EC 2006/42 Directive requirements and if recognized as being at risk of potential rollover a protective measure for the driver has to be defined by the manufacturer. The object of this evaluation was to assess the stability of self-propelled sprayers designed for arable crops according to the procedure in the ISO 16231-1/2 standard and evidence critical points in the provisions of the standard procedure. The standard defines a method to measure the Static Overturning Angle (SOA) of agricultural machines to be compared to a Required Static Stability Angle (RSSA) representing
the limit for evaluating ROPS fitment on the machine. The measured angles allow it to be understood if such machines require ROPS installation. The stability angles measured were much higher than the required static stability angles so the rollover risk assessment produced a low risk for the sprayers and a ROPS protection was not needed
A numerical model for the design of a climatic chamber for simulating moderate temperature and high humidity
No full textA numerical model for the design of a climatic chamber
No full textIn the present paper, we develop a numerical analysis supporting the design of a climatic chamber suitable for tracked and wheeled tractors, i.e. having measures 5x8x4 m3 (length x width x height)..
The numerical analysis is performed by employing Matlab-Simulink, to simulate the behavior of transient systems. First, the balance equations are written with reference to the 5 blocks that can describe the climatic chamber. Then two different regimes are investigated. First, a period of 10 hours is considered in order to reach the prescribed conditions for the climatic chamber. Then, after this preparation period, the tractor’s engine is supposed to work. The performed analysis has shown that higher values of the adduction coefficient are preferable. Moreover, the dynamical analysis turned out to be a very useful instrument to drive the design
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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