2957 research outputs found
Sort by
Designing Multi-Functional Magnetic Storage Cubes for Use in Modern Homes and Schools
Full text linkUsing modern methodologies in the sectors and subareas of industrial design, where they currently find only marginal application, brings a potential for interrelating technology, the arts, and fine arts. To illustrate this, we present model procedures and options for designing a versatile storage cube that integrates magnetic structural components facilitating easy and quick assembly. In addition to being an item of real furniture, portable and readily convertible into a table or soft stool, the cube supports children's creative games and helps to develop their overall skills in the present-day household and in pre-primary and primary education. The basic material rests in birch plywood, and the joint edges between the individual walls are covered with smooth plastic guards manufactured via additive 3D printing from corn fodder-based filament. Thus, an interesting structural detail, namely, plastic edges, is generated, reinforcing the entire product. The walls comprise decorative, multicolor, polyurethane foam-based elements that can be removed and reinserted. Regarding the manufacturing technology, CNC machining and laser shaping are widely employed on the main parts, and the plastic edges are 3D-printed. In terms of the original idea, the product responds to customer requirements within a specific design project. The robustness and stability tests have proved that the cubes fully satisfy the relevant standards.O
Heart Rate Index as a Measure of Physical Workload in Chainsaw Operations
Full text linkTimber harvesting operations, including manual and motor-manual activities, require workers who are in good health to be able to work effectively. The aim of our paper was to introduce a simplified index methodology for workload assessment. Generally available wearable technology, namely Garmin, Biostrap, and Whoop devices, were used. The dependence of the heart rate (HR) on physical workload was examined to calculate the Heart Rate Index. The case study was performed with several variations of chainsaw devices cutting the poplar wood. It was proved that the use of a heavier work tool, MS 500i/90 cm 9.3 kg, contributes both to the creation of a non-ergonomic working position and to an increase in the energy required to perform work, which was represented by an increase in heart rate. With a lighter work tool and a shorter cutting blade, both a decrease in heart rate and a reduction in the working time performed in a non-ergonomic position were achieved. The results can be used in common practice for workers' self-assessment to increase safety and health protection at work or work productivity, not only in forestry-related professions.O
Plastic deformation assessment of sawdust-rPET composites under bending load
Full text linkDue to the scarcity of raw wood materials and the current state of the market's economic growth, the development of novel composite materials utilizing alternate raw material sources is crucial. Sawdust and waste polymers, such as empty bottles, are excellent sources of low-cost materials for making useful and cost-effective wood-plastic composites. This article's main goal is to ascertain how different filler contents and percentages, as well as two different types of polymer matrices, affect the mechanical properties of sawdust-reinforced composite in the plastic range of force-deflection diagram of bending test. Sawdust-plastic composites based on waste polyethylene terephthalate (PET) and biodegradable polymers were produced by the flat press method and prepared for mechanical testing. This study examined comprehensively the plastic range of the three-point bending test. The limit of proportionality (LOP), bending strength or modulus of rupture (MOR), plastic potential "PP", four tangent moduli as well as approximated plastic work "AW", total plastic work "BW" and the values of approximation error "ΔW" were measured using three-point bending test. The finite element method (FEM) analysis was also conducted to prepare a numerical model and compare its results with experimental results. According to the study's findings, the bending features of rPET-reinforced composites declined as the filler percentage increased. Among all the rPET-reinforced composites, the 40% sawdust filled composite had the best mechanical performance. When compared to the rPET matrix, the biodegradable polymer demonstrated superior mechanical performance in the plastic zone of the bending test. However, both the 40% sawdust-filled rPET composite and the biodegradable composites filled with 50% sawdust fulfilled the ANSI standard as an appropriate replacement for medium-density fiberboard (MDF) for interior applications.O
Utility of cytochrome c oxidase I for the deciphering of unstable phylogeny and taxonomy of gorals, genus Nemorhaedus Hamilton Smith, 1827 (Bovidae, Ovibovina)
Full text linkGorals represent ungulate mammals of the Palearctic and Indo-Malayan realms that face habitat destruction and intense hunting pressure. Their classification has been the subject of various (mainly genetic) assessments in the last decade, but some results are conflicting, hampering some conservation-based decisions. Genetic sampling of gorals has increased considerably in recent years, at least for mitochondrial (mt) DNA. Results based on two mt genes (cytochrome b and the D-loop) are currently available. Still, the utility of cytochrome oxidase subunit I remains unanalysed, even though it belongs among the gene markers that enable a correct species identification in mammals. This study examines phylogenetic relationships and species delimitation in gorals using all currently available cytochrome oxidase subunit I sequences, including the not yet analysed goral population from Pakistan. Our results of various phylogenetic approaches, such as maximum parsimony, likelihood and Bayesian inference, and exploration of species boundaries via species delimitation support the validity of six species of goral, namely N. baileyi, N. caudatus, N. cranbrooki, N. evansi, N. goral, and N. griseus. This result accords well with results based on other mt genes, especially the cytochrome b from the highly exhaustive data sampling. Our study also summarises common sources of errors in the assessment of goral phylogeny and taxonomy and highlights future priorities in understanding goral diversification.O
Two new species of Hemidactylus Goldfuss, 1820 (Squamata: Gekkonidae) from the coastal areas of northern Somaliland
Full text linkThe taxonomy of many Hemidactylus geckos from the Horn of Africa has recently been evaluated. However, the lack of fresh material for some species and also regions has led to the misidentification of some taxa and an underestimation of the true diversity in others. In this study we analyse new material of Hemidactylus collected from poorly known coastal areas of northern Somaliland. Our results support the existence of two yet undescribed species within the arid clade. One of the new species is small-sized and closely related to H. afarensis from the Afar Triangle in Ethiopia, and together with two other species (H. foudaii, H. sinaitus) forms the monophyletic group for which we propose here the name sinaitus species group. The other new species is medium to large-sized, known from only one locality, and belongs to the macropholis species group, where it is a sister species of H. macropholis. Both new endemic species from the northern coastal hyper-arid plains highlight the role of northern Somaliland as an important biodiversity hotspot. Furthermore, our results show pronounced genetic diversity within H. macropholis, and imply possible existence of cryptic taxa within the species. Hemidactylus arnoldi and H. tropidolepis have, for the first time, been sequenced and placed in a phylogenetic context in this study. Our results confirm that H. tropidolepis is nested within the African radiation and is most closely related to H. funaiolii. Hemidactylus arnoldi clustered within the Arabian radiation of Hemidactylus and it was recovered as a sister lineage to all other species of the radiation.O
Development of Douglas fir merchantable stem volume model in the conditions of the Czech Republic
Full text linkA precise merchantable stem volume model of Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] is missing in the Czech Republic. The aim of this study was to fit a new model through the reparametrization of volume equations (used in the Czech Republic or in other countries). We tested four volume equations (two from the Czech Republic, one from France and one from British Columbia) in the form of a nonlinear least squares model (NLS), weighted least squares model (WLS), and nonlinear mixed effects model (NLME). In all the tested models, the diameter at breast height of a tree and the total height of a tree were used as independent variables. Models were fitted on a dataset of 185 felled sample trees from eleven research areas with ages between 19–113 years. We have found that the model according to Omule et al. (1987) fits the merchantable stem volume as the best in the version of WLS model. Median value of the relative error of the final model was only –0.53%, which is less than the errors of models which are still used in the Czech Republic today.O
Harvesting and processing of self-seeded trees along power lines
Full text linkPředmětem monografie je technologický postup údržby dřevinných porostů v ochranných pásmech podél elektrovodů. Následný transport a úprava vytěžené dendromasy bude předána odběratelům pro lesní hospodářství. Konečným produktem technologického postupu bude energetická štěpka a v některých případech i výřezy pilařské, agregátové a vlákninové. Navrženým technologickým postupem bude zvýšena bezpečnost pracovníků pro zadané práce. Vytěžené sortimenty dříví budou zpeněženy se současným úklidem pracovišť a zajištěním ekologické čistoty prací. Cílem monografie je prostudovat stávající systém údržby a nastínit další možný rozvoj. Současná praxe subjektů pracujících v oblasti lesnictví, arboristiky, údržby veřejné zeleně a dalších ukazuje na nedodržování technologických postupů, nestandardní nabídky v rámci veřejných zakázek a nedodržování bezpečnostních předpisů. Je nutné, aby byly maximálně odstraněny regionální rozdíly v přístupu prací. Rozdílné jsou přírodní podmínky, ale přístup k řešení musí být jednotný - standardizovaný. Pro zdárné zvládnutí široké problematiky by bylo velmi vhodné najít formu vnitřní specializace (zaměstnanec, oddělení pro problematiku údržby a biomasy, či externí odborná firma), aby byla zajištěna profesionalizace zvládání celé problematiky údržeb. Toto rozhodnutí je zejména vázáno na procesy předávání - kontrolu prací a jejich následné převzetí. Je velmi důležité rozdělovat přístupy k technice, která je nasazovaná v lesích hospodářských a v lesích pod zájmem ochrany přírody. Přístup i možnosti nasazování techniky jsou zcela jiné. Orgány ochrany přírody ve svých chráněných územích budou vylučovat nasazování půdních mulčovacích fréz. Nebudou tolerovat zapracovávání dendromasy do půdy, či rozmístění po ploše. Tyto činnosti se ale budou moci vykonávat právě na pozemcích lesů hospodářských. Efekt dlouhodobé rentability bude spočívat v tom, že vyvětvováním stromů bude splněna podmínka pravidelné údržby elektrovodů, ale bude možné podstatně snížit jejich sukovitost a vyprodukovat dříví mnohem vyšší jakosti a vyšší výtěžnosti cenných sortimentů, zejména výřezů zvláštní jakosti - L, D, R. Dosavadní zkušenosti ze zahraničí ukazují, že vyvětvováním lesních jehličnatých porostů je možno dosáhnout zvýšení podílu cenných sortimentů až o 20 %. Dodavatelům prací se nabízí zajistit si finančně dostupný mechanizační prostředek, který v současné době není na trhu k dostání - lehký přenosný lesnický víceúčelový vyvětvovací stroj s využitelností především na svažitých terénech, kam se těžko dostávají běžné mechanizační prostředky. Rovněž tak najde své uplatnění v městské zástavbě s ohledem na jeho příznivou hmotnost a rozměry pro rychlost přejezdů na různá pracoviště.The subject of the monograph is the technological procedure for the maintenance of tree stands in protective zones along electrical lines. Subsequent transport and treatment of extracted dendromass will be handed over to forestry customers. The final product of the technological process will be energy chip and in some cases saw-cuts, aggregates and fibers. The proposed technological procedure will increase the safety of workers for the assigned work. Extracted assortments of wood will be monetized with simultaneous cleaning of workplaces and ensuring ecological cleanliness of work. The aim of the monograph is to study the existing system of maintenance and outline further possible development. Current practice of entities working in forestry, arboristics, maintenance of public greenery and others shows non-compliance with technological procedures, non-standard tenders in public procurement and non-compliance with safety regulations. Regional disparities in access to work must be eliminated as far as possible. Natural conditions are different, but the approach to the solution must be uniform - standardized. For successful management of a wide range of issues, it would be very suitable to find a form of internal specialization (employee, maintenance and biomass department, or an external professional company) to ensure professional management of the entire maintenance issue. In particular, this decision is linked to the handover processes - inspection of works and their subsequent takeover. It is very important to divide the approaches to the technique that is used in agricultural forests and in the interests of nature conservation. The approach and possibilities of deploying techniques are completely different. The nature conservation authorities in their protected areas will exclude the use of mulch cutters. They will not tolerate the incorporation of dendromass into the soil or their distribution over the area. However, these activities will be able to be carried out on agricultural land. The effect of long-term profitability will be that the branching of trees will meet the condition of regular maintenance of electric lines, but it will be possible to significantly reduce their knotiness and produce much higher quality wood and higher yield of valuable assortments, especially logs of special quality - L, D, R. from abroad show that by branching of coniferous forest stands it is possible to achieve a share of valuable assortments by up to 20%. Work contractors are offered to secure an affordable machinery, which is currently not available on the market - a lightweight portable forestry multipurpose branching machine that can be used primarily on sloping terrain where conventional machinery is difficult to reach. It will also find its application in urban areas with regard to its favorable weight and dimensions for the speed of crossings to various workplaces.Published Versio
The educator's role in the autonomy journey for adult students with mental disorders
No full textThe vision of people with mental disorders has a historical and social nature. In the last decades, important steps have been taken toward guaranteeing dignity for these vulnerable people across the globe. This paper focuses on educators that deal with students with mental disorders in Young and Adult Education. The study is aimed to clarify a commitment to the social inclusion of people with mental disorders, which was allowed thanks to the critical education. The link between communication and education is analyzed in the paper, showing the potential of language to consolidate effective educational practices. Furthermore, the relationship between mental health, critical education, and empowerment of students is explored in this paper. Finally, examples of Brazilian initiatives that contribute to the development in this field are included here.Published Versio
Optimization of the Plate Heat Exchanger Used for Milk Precooling
Full text linkThe article deals with the adjustment of the flow rate of milk and water by a plate heat exchanger, which is used for precooling milk. First, measurements of the parameters of the device in the stable were carried out. Subsequently, the plate heat exchanger was measured in the laboratory. Water at 35 oC was used instead of milk. Different flow ratios of cooling water and cooled water (instead of milk) were set. From the measured values, changes in the temperature of cooled water were calculated depending on its flow rate at a constant ratio of cooling water and cooled water. It was found that in the measured range, there are flow values at which temperature change is maximal. This dependence applies to all selected cooling water and cooled water flow ratios: (0.8, 0.9, 1.0, 1.1, 1.2.). The results show that with the same amount of cooling water, it is possible to achieve greater cooling of milk by 0.7 to 1.6 oC, or to achieve a reduction in water consumption. The device on the farm was modified to allow the flow of milk and cooling water to be changed. The optimal values found were set, and verification measurements were performed. The saving of 4.8% of cooling water was confirmed.O
Effect of Mycotoxins in Silage on Biogas Production
Full text linkMycotoxins can pose a threat to biogas production as they can contaminate the feedstock used in biogas production, such as agricultural crops and other organic materials. This research study evaluated the contents of deoxynivalenol (DON), zearalenone (ZEA), fumonisin (FUM), and aflatoxin (AFL) mycotoxins in maize silage prior to it being processed in a biogas plant and in digestate produced at the end of the anaerobic digestion (AD) process. In the experiment, three samples of silage were collected from one silage warehouse: Variant 1 = low contamination, Variant 2 = medium contamination, and Variant 3 = heavy contamination, which were subjected to investigation. A significantly reduced biogas production was recorded that was proportional to the increasing contamination with molds, which was primarily due to the AD of silage caused by technologically erroneous silage treatment. The AD was connected with changes in silage composition expressed by the values of VS content, sugar content, lactic acid content, acetic acid content, and the ratio of lactic acid content to acetic acid content. The production of biogas and methane decreased with the increasing contents of NDF, ADF, CF, and lignin. The only exception was Variant 2, in which the content of ADF, CF, and lignin was lower (by 8-11%) than that in Variant 1, and only the content of NDF was higher (by 9%) than that in Variant 1. A secondary factor that also correlated with changes in the composition of the substrate was the development of undesirable organisms, which further contributed to its degradation and to the production of mycotoxins. It was also demonstrated in this study that during the AD process, the tested mycotoxins were degraded, and their content was reduced by 27-100%. Only the variant with low mold contamination showed a DON concentration increase of 27.8%.O