Лесотехнически Университет

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The modern approach in design seeks to preserve traditional concepts in creativity, but through the eyes of contemporary art. A complete design of a modular composition of a carved ceiling in the tradition and artistic techniques of Renaissance art is presented. It is combined with modern LED lighting to match the shape and composition of the wood carving. This project also preserves the cultural heritage of the dying craft of woodcarvers. The project was realized using a traditional carving technique. The lighting was installed and the calculated illuminance was tested, which corresponds to the design.

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The aim of this study is to propose methods on research and analysis of interior spaces, by the means of sensor systems. The authors suggest quantitative observation of movement without other feedback from the occupant. The method is based on a system of sensors and technical solutions that was developed by the authors and is described in a patent with reg.№ 3895 U1 with authors Pavlina Vodenova, Desislava Angelova and Stela Tasheva.

The proposal is meant to look into the dissatisfied and/or unanticipated in the environment project needs of the occupants and based on the data analysis, to offer optimization models.

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The object of the present article is a summary of Students’ Work Diaries, prepared by every team participating in the Project-Based Learning Module (PBLM) called Design Project, a study module of the Engineering Design (Interior and Furniture Design) Bachelor Program.

The following questions related to the diaries are considered in the article: Are students paying enough attention to these diaries as a tool to present their work? To what extent is the submitted information sincere and complete? Are students’ work diaries an effective way of grading each students’ teamwork and the individual members?

Based on the analysis made of students’ diaries from Design Project module in four successive years, conclusions and recommendations are made. The aim is to improve the requirements for the preparation of student diaries, so that teachers can use them for grading the work done by teams and their individual members.

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This paper aims to explore the significance of visual communication in contemporary higher education and the impact it has on student engagement and learning. Visual communication is examined as a crucial element, not only by establishing an institutional identity that attracts students and partners but also in enhancing the learning experience as it facilitates the comprehension of intricate concepts, fosters creativity, and promotes innovation among students. The various forms of visual communication are classified by impact type and outcome, and suggestions are given on how they can be integrated by higher education institutions to improve their engagement with students and other stakeholders, thereby fortifying their brand identity and securing a competitive edge in the educational landscape. The paper addresses the important role of visual communication in the improvement of learning outcomes by simplifying complex ideas, accommodating diverse learning styles, transcending language barriers, and enriching online learning. Prospective trends in this field are suggested such as technological advancements, personalized approaches, increased social engagement, and a heightened emphasis on inclusivity and sustainability. The paper concludes that by actively incorporating visual communication strategies, higher education institutions can improve their engagement with students and other stakeholders, thereby strengthening their brand identity and positioning themselves effectively in the competitive education environment.

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Products made of thermally treated wood have different requirements for the quality of the created surface, depending on the area of their application. While we can make do with a milled surface for tiling and flooring, we have more sophisticated products such as garden furniture, etc. require final surface sanding. The article focuses on the effect of thermal modification on the quality of the ground surface. It compares the surface quality of the ground surface of native woods oak, spruce and meranti with their thermally treated variants at temperatures of 160°C, 180°C, 200°C and 220°C. Quality is examined on a surface sanded with a belt sander with 80-grit sandpaper.

It points to the fact that the process of thermal modification slightly impairs the quality of the ground surface. However, when evaluating a surface on a larger scale, the quality of the created surface is influenced mainly by the "natural roughness of the wood" by the opening of anatomical elements of the wood, which are the primary source of increased roughness.

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This article deals about the possibilities of obtaining information from a sawdust sample using the Matlab program. Using sawdust analyzing during chip machining, it makes it possible to determine unsuitable conditions by cutting and woodworking, such as dulling of the tool, unsuitable cutting conditions, overheating of the tool and others. Such conditions can have negative effects on the operation and economics of the company.

Commonly used sawdust sizing methods, such as sieving, obtain only partial information about a given sample. On the other hand, by means of image analysis of a sawdust sample, it is possible to find out much more, for example the largest and smallest dimension of each single particle, its circularity, area, perimeter, eccentricity, convex hull major and minor axis length, or color of the particle. For some other particle analysis methods, it is not appropriate to repeat the experiment with the same sample, because it may occur damage of the sample during the measurement. This can happen during sieving, where the sample is mechanically stressed and can crumble. In the image analysis, the sawdust is scattered on the substrate and a digital image of these sawdust is create. Therefore, there is no mechanical damage on the sample.

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With the help of our own non-stationary model, the defrosting times of frozed beech logs with a diameter of 0.4 m, initial temperature of −10^oC, −20^oC, −30^oC, and moisture content of 0.6 kg∙kg^-1 were determined at water temperatures in the boiling pit equal to 80^oC. Using the determined logs’ defrosting durations, the change in energy required for the entire plasticization process and that for each of the 5 components of the pit’s thermal balance was calculated. Computer simulations were performed for a well-insulated concrete pit with working volume of 20 m³ and degree of filling with logs f equal to 25%, 50%, and 75%. It was found that at f = 75% the total energy consumption of the pit increases from 163.6 kWh.m^-3 to 177.6 kWh∙m^-3 when the initial temperature of the logs decreases from −10^oC to −30^oC. The thermal efficiency of the studied pit decreases almost proportional to the decreasing of f, mainly due to the increase in the specific energy required to heat the water in the pit.

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The present study aims to establish the mechanical properties of three-layered particleboards with a face layer entirely from beech and oak particles. Three compositions of the panels were studied, with the corresponding content of the face layers as follows: 30%, 40% and 50%. To analyse the possibility of reducing the content of pinewood particles in the core layer, it is replaced with sunflower stalk particles with the participation of 30%, 40% and 50%. This research determined the effect of those factors on the main mechanical properties of particleboards.

As a result of the study, it was found that the increase in the percentage of the face layers leads to a significant increase in the mechanical properties of the panels. It was found that by using the hardwood in the face layers of the panels, the share of this raw material can be increased to 50%, and sunflower stalks are a suitable raw material as an alternative raw material for the core layer of the particleboards.

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Recycling Medium-Density Fiberboard panels is a significant challenge and is not a widespread industry practice. Given the reduced costs, the methods for recycling this material with hydrothermal hydrolysis of the resins are more promising than those with acid hydrolysis. Despite the considerable amount of research on the topic, the effect of the hydrolysis regime on the stiffness and deformation at the bending load of recycled MDF panels (rMDF) remains limited.

In the present work was conducted a study on the effect of hydrothermal hydrolysis regime, with a variation in temperature from 121°C (saturated steam pressure 0.2 MPa) to 134° (saturated steam pressure 0.3 MPa) and the hydrolysis time from 30 min to 60 min on the stiffness and deformation behaviour of rMDF. It was found that the stiffness of the panels was not significantly affected by the hydrolysis regime, but the rMDF had about ten per cent less stiffness than the control panel from natural fibres. It was determined that the optimal hydrolysis regime is at 121° and has a processing time of 30 minutes. Concerning the investigated rMDF characteristics, it is not recommended that the panels be composed entirely of recycled fibres.

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The current study aims to assess the level of noise emission generated by the CNC milling machine Rover A.3.30 (Biesse, Italy). The change of the А-weighted sound pressure level (L_pA) measured at the operator's position at idle mode and during milling operations was investigated in relation to cutting tool rotation speed (n) and radial depth of cut (h) when processing particle boards, medium density fiberboards (MDF) and plywood. Sound pressure levels were determined using the precision digital noise meter CEL-620B1 (CASELLA, UK), taking into account the correction coefficients, accounting for the influence of background noises and sound field characteristics. The results show that at idle mode, without movement of the units along the x and y axes, the noise emission level was L_pA = 72,6 dB(A), which is significantly below the upper safe limit of 85 dB(A) for eight hours of exposure. It was found that the A-weighted sound pressure level during cutting mode changed from 79,5 dB(A) to 85,6 dB(A), depending on the characteristics of the cutting process. The lowest level was registered when processing particle boards, followed by that of processing MDF and the highest level was measured for plywood. On the basis of the performed experiments, graphical dependencies representing the relationship between the different factors were compiled.