ÚADI-odbor transportních a stavebních strojů

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    Effect of the body mass index and length of work on the stress of individual body parts of chainsaw operators
    (Czech Academy of Agricultural Sciences, 2024-08-23) Staněk, Luboš; Mergl, Václav
    The subject of this study is to point out the issue of various impacts of musculoskeletal disorders in chainsaw operators and their impact on human health. The first goal was to find out whether the body mass index is responsible for excessive stress to individual parts of the body of chainsaw operators at work. The second goal was to determine whether the excessive load to the individual body parts is affected by the time of working with the chainsaw. Questionnaires created for the fulfilment of the goals were distributed to professional forest loggers working in the Czech Republic, which were filled in by 161 of them. Questions in the first part of the questionnaire were formulated in such a way that answers to them would clearly identify information on the individual respondents. The second part of the questionnaire was focused on the assessment of the load upon 12 body parts of the operators (each part being split into the right and left sides). The results of the statistical analysis showed that neither the body mass index (BMI) nor the length of time working with the chainsaw affect the load on the individual parts of the body of the chainsaw operators.
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    Advancing sustainability in forestry machinery: Electro-Hybrid drives for greenhouse gas reduction and enhanced energy efficiency
    (SCIENDO, 2024-03-01) Mergl, Václav; Zeizinger, Lukáš; Kománek, Martin
    This article deals with the possibility of reducing greenhouse gas emissions and fuel consumption in machines using cut-to-length (CTL) technology with the help of electro-hybrid systems. The text discusses the individual components of these systems. Furthermore, the article contains technical solutions for current electro-hybrid drive systems of harvesters, forwarders and forwarding trailers, including their description and available parameters. The current technical and technological development of electro-hybrid drive systems and their components leads to a significant improvement in the performance of drives of the new generation of CTL machines and to higher energy efficiency. Thanks to this, the use of electro-hybrid drive systems in these machines could significantly reduce greenhouse gas emissions as well as operating costs.
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    Verifying the Lifting and Slewing Dynamics of a Harvester Crane with Possible Levelling When Operating on Sloping Grounds
    (MDPI, 2022-02-20) Mergl, Václav; Kašpárek, Jaroslav
    This paper focuses on the force and torque load of a harvester hydraulic crane employed on sloping grounds, both levelled and not levelled. Field research was conducted for this purpose and the results were compared with a dynamic analysis of the crane in MSC Adams. It was found that levelling the slewing platform of the crane is necessary for use on sloping grounds, primar-ily because the effect on the force and lifting torques is reduced. The research showed that when the slope of the slewing gear is up to 12°, the lifting torque reaches a higher maximum lifting force than when the slewing gear is in a horizontal position (0°). As part of the theoretical veri-fication by a dynamic analysis of the crane and the AH6 machine, a different pressure was de-tected in the lifting cylinder of the crane compared to the field research. The total deviation be-tween the simulation and the field research was 9.82%. The slewing torque of the hydraulic crane without the slewing bearing being levelled can be characterized 97.38% by a parabola whose vertex is located in front of the front part of the machine and falls as the crane moves left or right. Overall, it can be determined that when the crane rotates up a slope, whether it is from left or right, the slewing torque reaches the lowest values, and its value increases as the crane gets closer to the front of the machine (along the longitudinal axis of the machine). This change in the slewing torque is then characterized by a parabola. Furthermore, an effect was observed of the slewing gear slope on the lifting torque, which reached higher values in a tilted position than on a flat surface.
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    Difference in the magnitude of power saw vibrations affecting the operator during forest felling
    (Sciendo, 2023-03-01) Staněk, Luboš; Neruda, Jindřich; Mergl, Václav
    This study deals with a question whether the magnitude of vibrations affecting the power saw operator during the tree felling is still the same or not. For this purpose, the tree felling was broken down into several partial operations (pruning of lower tree part; cutting of buttresses; felling; delimbing) at which the values of vibrations were recorded and mutually compared. The vibrations were measured during the felling of 121 trees with the activity being made by one feller with one type of power saw and one type of power saw chain, and the felled trees included both live and dead standing trees. The vibrations were measured on the front and rear handles of the power saw in compliance with standards EN ISO 22867, EN ISO 5349-1 and EN ISO 5349-2. As to the mutual comparison, research results demonstrated a difference in 69.23% of cases. A maximum increase of vibrations during the experiment (17.0 m s(-2)) was recorded on the rear handle during the partial activity of Delimbing live trees, the lowest increase of vibrations (0.320 m s(-2)) being localized in the same partial activity, only on the front handle.
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    Application of Isothermal and Isoperibolic Calorimetry to Assess the Effect of Zinc on Hydration of Cement Blended with Slag.
    (MDPI, 2019-09-10) Šiler, Pavel; Šilerová, Iva; Novotný, Radoslav; Másilko, Jiří; Bednárek, Jan; Janča, Martin; Koplík, Jan; Hajzler, Jan; Matějka, Lukáš; Marko, Michal; Pokorný, Přemysl; Opravil, Tomáš; Šoukal, František
    This work deals with the influence of zinc on cement hydration. The amount of zinc in cement has increased over recent years. This is mainly due to the utilization of solid waste and tires, which are widely used as a fuel in a rotary kiln. Zinc can also be introduced to cement through such secondary raw materials as slag, due to increased recycling of galvanized materials. The aim of this work was to determine the effect of zinc on the hydration of Portland cement, blended with ground blast furnace slag (GBFS). This effect was studied by isothermal and isoperibolic calorimetry. Both calorimetry methods are suitable for measurements during the first days of hydration. Isoperibolic calorimetry monitors the hydration process in real-life conditions, while isothermal calorimetry does so at a defined chosen temperature. Zinc was added to the cement in the form of two soluble salts, namely Zn(NO3)(2), ZnCl2, and a poorly soluble compound, ZnO. The concentration of added zinc was chosen to be 0.05, 0.1, 0.5, and 1mass percent. The amount of GBFS replacement was 15% of cement dosage. The newly formed hydration products were identified by X-ray diffraction method (XRD).