Volume 27 (2019): Issue 44 (June 2019)

The paper is focused on additive manufacturing (AM) which is the process of producing objects from a three-dimensional (3D) model by joining materials layer by layer, as opposed to the subtractive manufacturing methodologies [1], directly from raw material in powder, liquid, sheet, or a filament form without the need for moulds, tools, or dies. The article demonstrates potential environmental implications of additive manufacturing related to the key issues including energy use, occupational health, waste and lifecycle impact. AM provides a cost-effective and time-efficient way to fabricating products with complicated geometries, advanced material properties and functionality. Based on this review, we identified that additive manufacturing will have a significant societal impact in the near future. A critical technical review of the promises and potential issues of AM is beneficial for advancing its further development.

The paper is focused on the experiment where the effects of the cutting environment and feed of drilling on the bores roughness and cylindricity were evaluated. Dry drilling of aluminium alloys (without using cutting fluids) is an environmentally friendly machining process but also an extremely difficult task, which is due to the tendency of aluminium to adhere to the drills made of conventional materials such as high-speed steel; and therefore three cutting environments (namely two different emulsions and compressed air) were used in the experiment. The article demonstrates multicriterial optimization of input factors (cutting environment, feed) for two defined target functions: roughness and cylindricity). The measured values were subjected to mathematico–statistical Analysis of Variance (ANOVA). ANOVA was used for examining the effects of machining parameters and their contribution to the surface roughness and bores cylindricity. The optimal cutting parameters were evaluated for “Smaller-the-Better” quality characteristics of both output responses, as can be seen in our article published previously. Based on the ANOVA, we determined that cutting environment exhibited higher percentage of contribution on bores quality than feed of machining. The results show 77.37 % impact of cutting environment and 8.13 % impact of feed on quality of machined bores.

This scientific study deals with investigation of the heat of combustion and effective heat of combustion of selected electrical cables. Two different electrical cables for rated voltage of 0.6/1 kV were investigated. Both cables were power three-core with cross-section area of each core of 1.5 mm². The cores of both cables were made of a bar cooper wire. Insulations of conductors of both cables were made of silane cross-linked polyethylene without any inorganic filler, while the bedding and outer sheath were made of polyethylene-based copolymer (the beddings were filled with two fillers - aluminium hydroxide and calcium carbonate, while the outer sheath were filled only with aluminium hydroxide). Reaction to fire class of both cables was B2_ca, s1, d0, a1. The main difference in the investigated cables was that the core of one of them was wrapped in a glass mica tape (this cable showed circuit integrity maintenance under fire conditions during 180 minutes). The heat of combustion and effective heat of combustion were determined by the oxygen bomb calorimeter according to the ISO 1716:2018 standard. The highest effective heat of combustion showed the insulation of wires (for both cables 42.47 ± 0.03 MJ/kg), lower value showed outer sheath (interval form13.61 to 15.26 MJ/kg) and the lowest value was determined for bedding (interval from 4.69 to 6.39 MJ/kg). The effective heath of combustion per unit of length of both investigated cables lies in the interval from 1.37 to 1.38 MJ/m. Therefore, there is no significant difference in effective heats of combustion of the electrical cables investigated.

The aim of the research described in this paper was to study the impact of the electrical cables slope on the flame out time and the flame spread rate. Measured cables were thermally loaded by methanol flame (diameter of the container was 106 mm) at seven different slopes with respect to the horizontal plane (the slopes were 0° – horizontal orientation, 15°, 30°, 45°, 60°, 75° and 90° - vertical orientation). The first tested electrical cable was a copper three-core power one resistant to the flame spread with circuit integrity of the cable system during 30 minutes under fire (cross-section of each core was 1.5 mm²). The second tested electrical cable was a copper two-core signal one resistant to the flame spread with circuit integrity of the cable system during 30 minutes under fire (cross-section of each core was 0.5 mm²). The first electrical cable did not show reaction to fire class. The reaction to fire class of the second tested cable was B2_ca, s1, d1, a1. The obtained results proved that slope had virtually no impact on the flame out time and the flame spread over the tested cable surface (tested cables of all slopes stopped burning after 1 to 5 seconds after methanol flame burned out). Likewise, the flame spread was only negligibly beyond the border of flame action for each cable slope.

The article deals with the determination of fire characteristics of industrial dust samples. Particle size granulometry and determination of explosion parameters according to EN 14034 (Lower Explosion Limit LEL, P_max, K_st) are presented. The minimum ignition temperatures of the dust layer and dispersed dust from the hot surface according to EN ISO / IEC 80079-20-2: 2016 were measured. It was found that LEL is 60 g.m⁻³, P_max is 8.61 bar, and K_st is 89 bar.s⁻¹.m. The minimum ignition temperature (MIT) of dust layer is 280 ° C and the minimum ignition temperature of dispersed dust is 400 ° C.

Floating coal dusts are always produced during coal mining process in the underground mines. In a coal mine and other coal processing or utilizing industries, there are always some potential safety problems, such as coal dust explosion accidents.[1,2] During lignite mining and processing, flammable coal dust is produced. Fire properties of coal dust depend on the particle size. The article deals with the measurement of explosion characteristics of lignite in dependence of particle size at three various concentrations. The measurements were carried out according to EN 14034-1+A1:2011 Determination of explosion characteristics of dust clouds. Part 1: Determination of the maximum explosion pressure p_max of dust clouds. Tests of the lignite dust clouds explosions showed that the maximum value of the pressure was reached at the concentrations of 500 g.m⁻³ and the particle size between 0 – 56 µm. At this concentration, the highest explosion pressure of 8.25 bar was reached.

Fire protection is an important part of the industry where flammable and explosive dusts are found. Production, storage and transport of food powders such as flour can be very dangerous in terms of explosiveness. The article deals with the measurement of explosion characteristics of wheat flour dust. The measurements were carried out according to EN 14034-1+A1:2011 Determination of explosion characteristics of dust clouds. Part 1: Determination of the maximum explosion pressure p_max of dust clouds and the maximum rate of explosion pressure rise according to EN 14034-2+A1:2012 Determination of explosion characteristics of dust clouds - Part 2: Determination of the maximum rate of explosion pressure rise (dp/dt)_max of dust clouds. A sample of wheat flour with a median particle size 84 μm exhibits the maximum explosion pressure 7.00 bar at the concentration of 600 g.m⁻³ and then explosion constant is 16.9 bar.s⁻¹.m. A sample of wheat flour with a median particle size 50 μm exhibits the maximum explosion pressure 7.97 bar at the concentration of 1000 g.m⁻³ and the explosion constant 54.9 bar.s⁻¹.m.Based on the results of the measurements, we found that the particle size distribution has a significant influence on the explosion parameters of the wheat flour samples.

The presence of dyes in effluents is a major concern due to their adverse effects to many forms of life. Dyes are generally removed by conventional sorbents. This article discusses the use of adsorbents from the waste metal production (low-cost sorbents), red mud (RM) and black nickel mud (BNM), to remove methylene blue solution (MB) under different test conditions, such as time and temperature of sorption and weight of sorbent samples. From the obtained data, we can claim that the highest achieved sorption efficiency was achieved by a RM sorbent at 60 °C after 48 hours of sorption with all three weights of samples (83.01 – 83.72%).

The aim of the research was to determine the fire risk of selected flammable liquids (alcohols). Four alcohols, methanol, ethanol, propanol, and butanol, were chosen for the research. Flammable liquids were examined in a cone calorimeter at 0 and 5 kW.m⁻² heat fluxes. Both, the cone calorimeter and test procedure, were in accordance with ISO 5660-1:2015. The fire risk was evaluated mainly on the basis of heat release rate, effective heat of combustion and carbon monoxide yield. Comparison of the achieved parameters of selected alcohols shows that the fire risk of the investigated alcohols increases with increasing the molar mass of alcohol and applied heat flow.

In order to manage the Construction Safety in a professional and due manner, it is of the key importance to have in place an Occupational Health and Safety Management System, consisting, similarly as a house project, of correct foundations as preparation, planning, procurement, properly set up rules and contractual relations, especially if a site of approx. 5,000 daily manpower is of a concern. Pillars of safe construction follow, i.e. education and training, inspections, communication and, last but not least, human behaviour. The purpose of the following article is to introduce the Human Behaviour Improvement Tools applied in the NPP Mochovce, completion process of Units 3&4, focusing on the implementation and the observance of the OH&S rules.

Chemical igniters are used in the study of dispersed dusts. Energy released during their use is defined by EN 14034 at 2 x 5 kJ. The Standard does not define the exact composition of the pyrotechnic mixture. The condition of using the igniter is to release energy according to the Standard. This article is focused on pyrotechnic composition with magnesium powder. It deals with various ways of activating, preparing and sealing the pyrotechnic mixture in the igniter. These values are important for setting up a device for studying the explosive properties of dispersed dusts.

Formaldehyde is a toxic chemical commonly found in the environment. Owing to its increased usage, its incidence has also increased, and there is a need to determine the concentration of formaldehyde for the pollution control purposes. In general, spectrophotometric methods are easy to perform, low-cost, selective and sensitive, but every spectrophotometric method has its advantages and disadvantages, which are an important factor when selecting the method for determination of formaldehyde. Therefore, the aim of the research described in this paper was to compare the current spectrophotometric methods and to summarize their advantages and disadvantages.

Nanomaterials are sure to take an important part in shaping the 21st century. Nevertheless, their increasing application in many fields of the industry also turns attention to the impact on health and environment. To achieve this goal, it is necessary to fully understand the influence of nanoparticles on the environment and the relevant safety issues.

The aim of the present review is to characterise the current state of regulation and legislation of nanomaterials, as well as the factors of safety assessment and their toxicity.

Microalgae are photosynthetic autotrophic microscopic organisms growing in a range of aquatic and terrestrial habitats. They produce a huge complex of compounds in their surroundings which are of important use to humans. Their commercial use lies in human nutrition, animal and aquatic feed, in cosmetics products, natural pigments, pharmaceutical industry, bio-fertilizer for extracting high-value molecules, stable isotope biochemicals, and for the synthesis of antimicrobial, antiviral, antibacterial and anticancer drugs. Therefore, it is necessary to develop a simple, effective and economically advantageous method for harvesting the algal products. Magnetic separation is a simple separation process. Different synthesis methods have been used by researchers to obtain magnetic particles of varying size and shapes according to the algae to be studied. Chemical co-precipitation method has been the most commonly used method, which helps in synthesizing magnetic particles of the micro to nano range. Naked, coated and surface modified are the general types of magnetic particles used for algal harvesting with its own advantages and disadvantages.

Water is one of the most important substances on earth; nowadays, its pollution is one of the main environmental problems. Textile industries pose a significant environmental problem for earth. Firstly, it is due to their huge water consumption, and secondly, they produce a lot of wastewater contaminated with dyes, chemicals, suspended solids, etc. These contaminants can make water unsuitable for the desired purposes (e.g., drinking, watering, washing and showering). The one of the promising methods for the removal of dyes from the contaminated wastewater is adsorption. In this process, we can use low cost waste materials as an adsorbent. This paper presents an overview of utilization of the spent coffee grounds for the removal of dyes from wastewater.

The aim of the research described in this article was to optimize the basic sulphur process of lignin removal from the raw radially cut basswood (Tilia Cordata) pieces of various thicknesses. Lignin removal took place chemically in several consecutive steps in which the influence of individual parameters was investigated (solutions of NaOH + Na₂SO₃, KOH + Na₂SO₃, its concentrations, time of leaching, efficacy of whitening agents, effect of sample washing between individual baths, etc.). Through experiments, it was found that the change of fresh NaOH + Na₂SO₃ solution during the experiment had no significant effect. In contrast, skipping the washing of the samples with boiling distilled water after the hydroxide bath had a significant effect on the rate and efficiency of lignin removal with H₂O₂ in the following step. When comparing the lignin removal efficiency of NaOH + Na₂SO₃ and KOH + Na₂SO₃, the delignification process was clearly demonstrated to be more effective using the KOH + Na₂SO₃ solution. Application of the above-mentioned procedures has helped to streamline the lignin removal process from solid basswood.

In general, the probability of an undesirable event occurring and its consequence is the gist of the risk characteristics. Thus, risk is part of all the activities that a person performs. The use of weapons and possession of weapons is a great risk. It makes difference who owns them, where they are used and under what circumstances. At present, the great risk is also associated with the possession and use of expansion weapons, also called acoustic weapons. This issue is still very sensitive; the aim of this article is to highlight the risks of reverse modification of such weapons. Publication of this contribution does not support or otherwise supports the use and sale of any type of weapons.

Open-plan office is a distraction to employee performance. According to a study by Cornell University, Ithaca, NY, working in a noisy office with ringtones, business conversations and office equipment sounds can lead to heart disease, because workplace noise causes stress. The paper focuses on noise analysis in an open-office work environment, the effect of noise on the selected operational position, as determined by standardized noise exposure LEX, 8h. Based on the results obtained, appropriate measures were proposed.