Лесотехнически Университет

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The paper examines the specific characteristics considered when determining the amount of sheet material necessary for manufacturing machine parts with a predominant number of sheet material components. The possibility of optimising material consumption at the design stage is emphasised by incorporating the capabilities of AutoCAD software. Research conducted revealed that the quantity of material with a predominant number of sheet material components, such as a cyclone separator, is increasingly subject to the accuracy of cutting and positioning of workpiece unfolding on the sheet material, which is ultimately related to the increased process optimisation.

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This study examines some of the most common problems associated with cutting thin logs. Various authors summarise information regarding some of the characteristic features and difficulties that arise when cutting this type of timber. Several approaches are presented to processing thin logs with different types of primary woodworking machines. The dimensional and qualitative characteristics of this timber are directly related to the quantitative and assortment gains and the deficiencies and defects in the final product. The application of technologies for further processing the obtained bonded materials in producing engineered wood products (EWP) is associated with high labour costs and low quantitative and qualitative yields. Nevertheless, research in this area needs to continue due to the increasingly intensive decrease in the diameter of trees and, consequently, a decrease in the average and large construction wood.

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The present paper focuses exclusively on establishing a Centre for Precision Agriculture (CPA)– a specialised facility explicitly tailored for training, lectures, laboratory exercises and seminars. The project involves the transformation of the existing auditorium into a modern venue for applied studies and scientific research at Dobrudja College of Technology, geared towards implementing innovations in the field of precision agriculture. Examined carefully are the parameters that are likely to affect the construction and design of lecture halls and other educational spaces, as well as the selection of proper audio-visual systems. Thoroughly analysed are various factors, including the design specifications for contemporary educational technology, which are subsequently reviewed in relation to the potential design alternatives within the existing space.

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The curriculum in the "Engineering Design (Interior and Furniture Design)" Bachelor program has frequently changed over the years regarding how and what kind of study modules are taught. In the 2020-2021 academic year, the teaching staff was presented with another novelty – the transition to full-time virtual training in practical design and purely artistic disciplines.

In the context of introducing a new virtual education modality, the new teachers in the department decided to leverage the moment and test innovative ways of working that are widely applicable in their practices and were formerly introduced in their design training in foreign universities. Their approach was based on integrating design thinking with the traditional approach used in the program to bridge two separate study modules from the curriculum – "Graphic Design" and "Furniture Design for Public Spaces". In the process, the assistant professors introduced a few new tools, principles, and perspectives, all with the idea of raising the level of engagement and practical fieldwork experience among students, taking advantage of the positive aspects of working in a virtual environment.

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With the help of our own non-stationary model, the temperature field and defrosting durations of frozen beech logs with a diameter of 0.4 m, initial temperature of −10 ^oC, and moisture content of 0.4 kg∙kg^-1, 0.6 kg∙kg^-1, and 0.8 kg∙kg^-1 were determined at water temperatures in the boiling pit equal to 80 ^oC. Using the determined durations, the change in energy required for carrying out of the entire defrosting 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 maximum possible value f = 75% the total energy consumption of the pit increases from 145.1 kWh.m^-3 to 180.2 kWh∙m^-3, i.e. by 24.2% when the moisture content of the frozen logs increases from 0.4 kg∙kg^-1 to 0.8 kg∙kg^-1. With a decrease in f, the thermal efficiency of the pit decreases almost proportional to f, mainly due to the increase in the specific energy required to heat the water in the pit.

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A mathematical description of the energy Q_ice-bw required for melting the temperature dependent part of frozen bound water in wood, using a software package Table Curve 2D v.5.01 has been presented. This package allows for the selection of equations, which provide the best similarity between the calculated with them values of Q_ice-bw during thermal treatment of wood containing ice and the respective numerical data obtained with an adequate temperature-energy model of Q_ice-bw. The type and coefficient values of the Table Curve equations for Q_ice-bw in this work have been determined for the case of thermal treatment of frozen beech wood with an initial temperature of −1 ^oC, −10 ^oC, −20 ^oC, −30 ^oC, −40 ^oC and moisture content of 0.4 kg·kg^-1, 0.6 kg·kg^-1, and 0.8 kg·kg^-1. The equations obtained for Q_ice-bw can be used for development and automatic implementation of scientifically based energy-efficient regimes for steaming or boiling of frozen wood materials with different parameters.

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This paper presents the results of an experimental study conducted with a self-propelled milling unit PT-400 with a multifunctional forestry milling machine FAE 300/S-225 for complete soil preparation for reforestation of poplar clearings. Regression models were developed to determine the relative fuel consumption and time consumption for complete soil preparation of poplar clearings. Based on the obtained results, the influence of the speed parameters of the forestry cutters and the working conditions in the fellings on the size of the operating costs was determined. Of all the factors that express the conditions of work, the diameter and density of the stumps have the greatest weight and dominance on the cost indicators. The amount of shredded shoots, bushes and wood waste ranks third, and the mechanical composition of the soil has the least influence. To mitigate the impact of more severe working conditions, it is best to use the cutter's "rotational frequency" factor. Regardless of the type of technological operation performed, lower operating costs are obtained at a higher frequency of rotation of the cutter. Given that this factor can be managed within wider limits, it is recommended that forestry cutters for shredding stumps and roots and mulching wood waste, shoots and bushes, operate at a higher frequency of rotation of the rotor – over 500 min^-1.

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The paper reviews the influence of modern technology – the Internet of Things (IOT) on the public environment. Different aspects of this influence on the principals of how the spaces function, how they are designed and furnished are studied. The leading trends in these principals, initiated by the penetration of IOT technology, are shown, as human centric lighting and heating, smart furniture etc. All these are leading to energy saving, increased security, productivity and comfort enhancement.

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The features of the smart interior design are considered: area minimisation, modes of operation, used materials and environmental changes.

A completely new services, provided by the smart interior are discovered, such as prevention of wrong actions, prediction of future actions and personalised services. Based on the above the extraction of new interior design principals (focused on the kitchen design) are concluded.

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The Douglas-fir is a perspective species for Europe, introduced in Bulgaria long ago. During this time many studies have been made on the growth and productivity of forests of this tree species. Mechanical properties are an important part in the design of timber structures and the calculation of processing regimes. The values given for the properties depend on the altitude and the location of the wood under study in the stem.

The subject of the research in this study is the Douglas fir wood and the determination of some mechanical properties of the wood, which  has been done for the first time in our country. Standard methods and test bodies were used to establish the mechanical properties in this study.

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As the water content changes, the wood cells shrink or swell. These are some of the processes characterising the variability of wood. They greatly complicate processing and limit the application of wood materials. These properties depend on many factors, one of which is the scale (dimensions) of the wooden samples. Many observations show that the shrinkage and swelling processes proceed differently when the wooden samples is a few millimeters or a few centimeters. There is an even greater difference in the behavior of earlywood and latewood when they are examined separately.

The article study the processes of shrinkage and swelling during repeated wetting and drying. Samples with a constantly decreasing cross-section were investigated.

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Wood is a renewable raw material in different kinds, patterns, strengths, and varieties that nature has provided to be used in a myriad of applications since before history. With the rapid increase in population on earth, and the consequent growing need for wood, fast-growing wood species became of more importance every day though their properties of these species are considered rather poor. However, they can satisfactorily be used in wood-based composite panels, like particleboard, medium-density fiberboard (MDF), high-density fiberboard (HDF), flakeboard, plywood, oriented strand lumber (OSL), and wood-plastic composites (WPCs). Still, production and application of composite panels have some troublesome drawbacks, including vulnerability to water and high humidity, and hot-press as a bottleneck in the production process as well. Over the past two decades or so, many studies were carried out to overcome these drawbacks and to improve properties in composite panels from different aspects, using different materials at nano- and micro-scales, mostly as resin reinforcement, additives, and cross-bonding agents. The present article tries to briefly provide an outlook on the strengths and weaknesses of some of the above mentioned materials that have been used in Iran, with an aim of giving an idea to young researchers for their future studies.

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The aim of the present research is the construction of graphic surfaces defined by sections with parallel planes or by the points coordinates of the network nodes. To achieve the set goal, an algorithm for constructing 2 and 3 images of graphical surfaces, defined by curves, has been investigated. An approbation of the algorithm is also presented along with its application in an architectural environment.