LVS EN Research Articles

Effective Mechanical Properties of a Composite Material Reinforced by Oil Shale Ash Particles

This study determined the elastic properties of composites and concretes reinforced with oil shale ash (OSA) particles, a byproduct of oil shale combustion in an electric power plant in Estonia (Auvere). Since 2018, OSA has no longer been classified as hazardous waste in the EU, enabling its reuse in sustainable materials. The present research examined the effect of OSA on the elastic properties of epoxy–OSA and concrete–OSA composites. The experimental results show that the elastic modulus of epoxy resin increases with an increase in the ash concentration, while it decreases in concrete with a higher OSA content. Theoretical models, including the rule of mixtures, finite element method (FEM), Mori–Tanaka method, and Halpin–Tsai method, were used to predict these properties numerically. The rule of mixtures and FEM generally overestimated the modulus for epoxy–OSA, whereas the Mori–Tanaka and Halpin–Tsai methods provided closer predictions. For concrete–OSA, the compressive strength tests followed the LVS EN 12390-3:2019 standards, with elastic modulus conversions being made via IS 456:2000 Clause 6.2.3.1, which showed a variable decrease across different strength classes. The findings highlight the potential of OSA as a reinforcing filler in construction materials, promoting environmental sustainability by repurposing industrial waste while offering mechanical benefits.

Evaluation of Fatty Acid Composition in Amaranth Pasta Developed for a Vegan Diet

Abstract Consumers’ growing demand for vegan products creates a need for new nutrient-dense products. Amaranth seeds are characterised as a nutritious product due to the content of proteins, fats, etc. Considering the high-quality fats and their amount in amaranth seeds, the aim of this study was to analyse the profile of fatty acids in amaranth pasta which was developed for a vegan diet. Seven samples: amaranth, amaranth-oat, and amaranth-buckwheat pasta in different ratios, were analysed in the study. The preparation of samples for analysis was carried out according to LVS EN ISO 6498:2012; fatty acid composition was determined using the GC/MS analytic method. The highest total fat content was determined in the amaranth pasta – 5453.62 mg 100 g−1 of product, followed by the amaranth-oat pasta (85%/15%) – 4988.14 mg 100 g−1 of product and amaranth-oat pasta (70%/30%) – 4772.93 mg 100 g−1 of product. In the developed pasta samples, over 70% of total fat was unsaturated fatty acids and more than one-third of total fat was PUFA. The highest PUFA/SFA ratio was determined for amaranthoat pasta (70%/30%), amaranth-buckwheat pasta (85%/15%), and amaranth-buckwheat pasta (70%/30%). Quantitatively, the essential fatty acids were oleic acid, linoleic acid, and palmitic acid. The triterpene squalene was detected with a probability of 90% in all amaranth, amaranth-oat, and amaranth-buckwheat pasta samples. The developed pasta for a vegan diet contains good-quality fat.

Formate Esters Containing Biodiesel - Diesel Mixed Fuels

The blends of varying proportions of biodiesel (FAME) containing formate esters of glycerol and 93.0 wt.% fatty acid methyl esters, obtained in an interesterification reaction with methyl formate without further purification, and winter diesel fuel, were prepared, analyzed and compared with winter diesel fuel. The obtained results showed that blends comprising up to 20 vol.% of FAME fulfill the requirements of the standard LVS EN 590 concerning such characteristics as cold flow properties, viscosity, density, and carbon residue. The increase of FAME content worsens the cold flow properties; however, the mixed fuel with 20 vol.% or lower FAME content, according to the cloud point and cold filter plugging point values, remains in the same severe climate "Class 0" group as winter fuel. The carbon residue of mixed fuels raises with increasing FAME content, but stay low and do not exceed the limits of standard for mixtures with FAME percentage up to 20 vol.%. The comparison of mixed fuels containing 20 vol.% of FAME and the same amount of neat biodiesel (99.6 wt.% of fatty acid methyl esters) shows that the difference is negligible. The obtained results have indicated a good potential of FAME obtained in the interesterification reaction with methyl formate without further purification as a diesel fuel additive for up to 20 vol.%.

Possibilities of Useful Use of Glued Wooden Construction Residues.

People have erected buildings with the use of timber structures for a long time. The uses of timber constructions are very diverse—it is used for the production of exterior wall and roof constructions, window frames and doors, and it is used for dry as well as wet premises. Scandinavian countries have extremely vast experience of using timber structures. Latvia has a rather extensive timber processing and timber structure manufacturing sector. Many companies are involved in timber processing, however, to enable even more extensive use of timber structures, environmental and technically economic requirements of contemporary building must be taken into consideration. Environmental requirements for timber structures provide certain advantages in comparison to other building materials, but technically economic requirements are very important as well. The development of manufacturing of glued constructions and research of production processes of these constructions allows one to find solutions for the reduction in the cost of timber structures, and the results of such research can ensure significant development of the use of timber structures in building, as well as reduce total construction costs. The basic objective of the study is to investigate the residual materials arising as a result of processing cross-laminated timber constructions (CLT panels), material generated as a result of high levels of construction production, and research of the opportunities to reprocess the residual materials generated as a result of laminated timber structure manufacturing into materials suitable for production of building constructions. The majority of CLT panels are manufactured using 20, 30 and 40 mm thick boards, and, during the panel manufacturing process, there are various standard thicknesses of panels, for example, 60, 80, 100, 120, 140, 160 mm, etc. Various layers are used for the creation of various thicknesses depending on the necessary technical properties. Various arrangements of the thickness of a single panel will cause different structural and physical behaviour (i.e., impact of changes in moisture, fire resistance, etc.). During the research and for the purposes of testing of CLT panels, only residues with equal types and thicknesses of lamellae were selected. Two main purposes were included in the panel testing process: (1) Comparison of technical performance of the residues of CLT panels with the classic CLT panel. Curve strength and tensile strength tests were performed in accordance with LVS EN standards (LVS EN 16351: 2016 and LVS EN 408 + A1: 2012). All the samples were prepared according to the LVS EN standards. (2) To assess the impact of two resins (melamine urea formaldehyde (MUF) and polyurethane (PU)), widely used in industry, on structural properties of recycled CLT material. Results of the research show that recycling residues of glued wooden constructions may lead to good results, and manufacturing residues of CLT panels may be successfully used in construction and for the reduction in CLT panel manufacturing costs.

Interesterification of rapeseed oil with methyl acetate in the presence of potassium tert-butoxide solution in tetrahydrofuran

Production of biodiesel (FAME) via transesterification of triglycerides with methanol in the presence of basic catalysts has largely increased over time despite the low value of the by-product glycerol. Interesterification of the same feedstock with methyl acetate allows to obtain biofuel with higher yield, as the by-product of this reaction, i.e. triacetin, can be included into the fuel composition. Investigation of interesterification with methyl acetate to oil molar ratio 18 at 55 °C during 1 h in presence of potassium tert-butoxide solution in tetrahydrofuran shows that after catalyst to oil molar ratio 0.1 slow increase of FAME and a decrease of triacertin content occur. Variation of catalyst to oil molar ratio does not allow to lower the content of intermediates below 19 wt%. An increase of methyl acetate to oil molar ratio from 18 to 65 reduces the mass fraction of intermediates to 9.5% and FAME to triacetin mass ratio to 5.2. The fuel characteristics of obtained products are close to or comply with the requirements of LVS EN 14214, excluding the requirements for FAME and intermediate content and density. The optimal region of methyl acetate to oil molar ratio as the reasonable compromise between the yield of the target products and removable excess of reactant could be from 24 to 40.

Impact of Maternal Diet on Human Milk Composition Among Lactating Women in Latvia.

Background and objectives: Many studies indicate that the maternal diet is an important factor affecting human milk composition. Human milk composition among lactating women in Latvia, as well as the maternal diet during lactation, has not been sufficiently studied. The aim of this research was to assess dietary habits and macronutrient intake among lactating women in Latvia and to examine the effect of diet on human milk composition. Materials and Methods: Research was conducted between November 2016 and December 2017. Mature human milk samples (n = 61) along with a 72h food diary, a food frequency questionnaire (FFQ), and a questionnaire about maternal and infant characteristics were obtained from voluntary women who were recruited via an invitation published in a social media member group for nursing mothers. Fat content in human milk was determined by LVS ISO 2446:2008, protein content was determined by LVS EN ISO 8968-1:2014, lactose was determined by ISO 22662:2007, and the fatty acid profile was analyzed using gas chromatography. Dietary data were evaluated using the Finnish food composition database Fineli, release 19 (3 March 2018). Results: Median values for fat, protein, and lactose in mature human milk were 4.40%, 1.08%, and 6.52%, respectively. Predominant fatty acids in human milk were oleic acid (C18:1 n9c), palmitic acid (C16:0), and linoleic acid (C18:2 n6c) at 34.60%, 24.00%, and 11.00% of total fatty acids, respectively. The trans elaidic acid (C18:1 n9t) level was <0.10% in all human milk samples. Significant, positive associations (p < 0.05) were found between maternal dietary intake of linoleic, α-linolenic, docosahexaenoic, total cis-monounsaturated, total cis-polyunsaturated, and total n-6 and n-3 polyunsaturated fatty acids, the ratio of n-6/n-3, and the level of these fatty acids in human milk. Total energy and carbohydrate intake among participants were lower, but total fat, saturated fat, and sugar intake were higher than recommended. Protein, linoleic acid, and α-linolenic acid intake were adequate, but docosahexaenoic acid intake was noticeably lower than recommended. Women should be supported with information regarding their nutritional needs during lactation and the possible impact of diet on human milk composition. Conclusion: Macronutrient (fat, protein, and lactose) content in human milk is not affected by maternal diet. Conversely, the human milk fatty acid profile is affected by the immediate diet consumed by the mother. Habitual dietary habits can also impact the fatty acid profile of human milk.

ENERGY WOOD STORES IN UNDERGROWTH OF FORESTS IN LATVIA

INTRODUCTION&#x0D; Forest resources are the most significant natural asset of the state of Latvia. According to data of the 2nd stage of forest resource monitoring for 2014, Latvia has 3575 thousand hectares of forest land comprising 55.3 percent of the total territory of Latvia, while the total timber stock is estimated at 668 million cubic meters (Bumanis et al., 2014).&#x0D; However, from the available data on forest resources it is only possible to theoretically and hypothetically state what proportion of these resources would be useful and economically justified as an energy supply. Each forest stand has a certain amount of undergrowth and understorey – small woody plants (shrubs) which have not been researched much until now. A precise determination of the amount of energy wood in Latvian forests would be of great benefit to the Latvian economy.&#x0D; MATERIAL AND METHODS&#x0D; Research data were collected in forests at the Jelgava Forest District “Forest Research Station”. The research was carried out in two forest subquarters of forest site type Myrtillosa mel. Eight circle-shaped sample plots were established. The area of each single plot was 25 m2.&#x0D; In the sample plots, the understorey and undergrowth trees were cut at the root neck. A sample was prepared from each tree harvested which was then sent for drying.&#x0D; The wood samples were transferred to "Forest and wood products research and development institute Ltd” for moisture determination. Total moisture content of the wood sample was determined according to standard LVS EN ISO 18134-2: 2016.&#x0D; RESULTS&#x0D; In the forest subquarter with a stand composition of 10Pine (66 years old) the sum biomass of undergrowth and understorey was 177.91 kg per sample plot. In the forest subquarter with a stand composition of 9Pine1Birch (88 years old) there was a total understorey tree mass of 180.9 kg but 16.17 kg of undergrowth per plot. This means there was more biomass in understorey than undergrowth in the site investigated.&#x0D; DISCUSSION&#x0D; When the tree stand was 10Pine (66 years old) the amount of dry matter to be extracted from all sample plots was 12.37 t ha-1 on average. In the forest subquarter with a stand composition of 9Pine1Birch (88 years old) the amount of dry mass is 10.24 t ha-1 on average.&#x0D; According to previous research, 7-20 t ha-1 of dry mass was obtained in Sweden, 7 to 12 t ha-1 in Poland, 6 to 14 t ha-1 in Germany and 8 to 12 t ha-1 in Latvia (Lazdina et al., 2010). There are also several researches papers which describe biomass from young hardwood stands on abandoned agricultural land in Canada: the values vary from 0,6 t ha-1 to 82,6 t ha-1 (Lupi et al., 2017). Consequently, a sufficient amount of biomass was obtained in the forest subquarters investigated in our research, which fits with the results of other studies carried out.&#x0D; CONCLUSION&#x0D; The volume of potential energy wood in undergrowth and understorey in Myrtillosa mel. forest site types is significant and it is advisable to use it as a raw material for energy production together with felling residues. However, it is necessary to evaluate the technical and technological capabilities from an economic perspective in each particular case.&#x0D;

Effect of High-Pressure Processing on Microbial Quality of Skimmed Milk

Abstract High pressure processing (HPP) is an alternative to traditional thermal treatment and can be used in the dairy industry for increasing the microbiological safety of milk and for preserving its biologically active substances. HPP effectiveness in providing microbiological quality of product is still under discussion; thus, the aim of the study was to evaluate the effect of HPP technology on microbiological quality of skimmed milk. Raw, pasteurised (78 °C, 15–20 s), HPP treated (250 MPa, 15 min; 400 MPa, 3 min; 400 MPa, 15 min; 550 MPa, 3 min) and skimmed milk, processed by combining pasteurisation and HPP were analysed and compared. The total plate count (LVS ISO 4833-1:2013) and presence of coliforms (LVS EN ISO 16654:2002) were determined in analysed skimmed milk samples. Significant decrease (p &lt; 0.05) of colony forming units (CFU) was observed in samples processed by combining two treatment types: pasteurisation and HPP. The minimum treatment parameters for shelf-life extension of skimmed milk were determined: pressure not less than 400 MPa and holding time at least 15 minutes.

Effect of various carbohydrate additives on peroxide formation in fat for confectionery production

A lot of ingredients used for food may have their own antioxidant activity. For this reason, it is necessary to explore the effect of natural antioxidants and non-specific antioxidants of some confectionery ingredients for the stabilization of food products against the formation of peroxides. The aim of the study was to verify the effect of some carbohydrates in preventing the formation of peroxides in fat for the confectionery production and to prove that the quality and shelf-life of confectionery products are affected by ingredients used in the compositions of confectionery products and by compounds that are formed in their interaction. Butter was used as the basic ingredient to study the fat stability. The effect of carbohydrates used in confectionery and their interaction with butter was examined, and the peroxides were determined. The effect of vanillin in facilitating or preventing the above-mentioned interaction was also determined. Peroxides were determined by means of the standard LVS EN ISO 3960:2010. It was established that practically all carbohydrates decreased the formation of peroxides in the samples. The quantity of peroxides in butter with 30 % of sucrose was by 10.7 % lower, with 30 % of glucose – by 41.3 % lower comparing to butter without additives after the samples had been stored for 30 days at 28 ± 2 °C. The most effective after 30 days of storage was sorbitol which decreased the formation of peroxides by 65.3 %. The same activity was also established for vanillin. Its antioxidant activity was similar to the activity of sugars, and therefore their summary activity reduces in confectionery products. It is established that the activity of sugars is quite temporary, and with increasing the quantity of peroxides in the product it decreases or completely disappears.DOI: http://dx.doi.org/10.5755/j01.ct.68.1.18879

Research of Surface Roughness Anisotropy

Abstract The authors of the paper have investigated surfaces with irregular roughness for the purpose of determination of roughness spacing parameters perpendicularly to machining traces – RSm1 and parallel to them – RSm2 , as well as checking the relationship between the surface anisotropy coefficient c and surface aspect ratio Str from the standard LVS EN ISO 25178-2. Surface roughness measurement experiments with 11 surfaces show that measuring equipment values of mean spacing of profile irregularities in the longitudinal direction are not reliable due to the divergence of surface mean plane and roughness profile mean line. After the additional calculations it was stated that parameter Str can be used for determination of parameter RSm2 and roughness anisotropy evaluation for grinded, polished, friction surfaces and other surfaces with similar characteristics.

Leachates of Thermally Modified Pine (Pinus sylvestris L.) Wood

Abstract During the last decades, thermally modified wood has become an object of interest among the wood scientists as an environmentally friendly material, because nowadays environmental aspects of materials have become more and more significant. Leaching is one of the processes that occurs in outdoor use. The aim of this study was to evaluate concentration of potentially hazardous substances in leachates of thermally modified pine wood. Scots pine (Pinus sylvestris L.) wood was thermally modified using Wood Treatment Technology (WTT) company device at 170 °C for 1 hour (TMP170/1) and at 160 °C for 3 hours (TMP160/3) and the mass loss was calculated. Material preparation and leaching procedure was made according to standard LVS EN 84:2000. In obtained leachates, the content of sugars, acetic acid, furfural and tannic acid were determined. Results showed that the total wood mass loss was 7.1 ± 1.4% (n=20) for TMP170/1 and 4.0 ± 1.6% (n=20) for TMP160/3. The initial leaching velocity differs between both modes and is higher for TMP160/3. The velocity decreases exponentially with immersion time and reaches plateau after 7th (5 days) immersion, but leaching still continues after the 9th immersion (14 days). The main components in leachates were tannic acid and pentoses. Among all studied compounds furfural is the hardest leachable one. Thermally modified wood treated at TMP170/1 is more environmentally friendly due to less water leachable substances. It is worth looking forward by investigating volatile organic compounds emissions in the air as it also could give high impact on human health.

Generation of a Test Reference Year for Alūksne, Latvia

Abstract Precise and reliable meteorological data are necessary for building performance analysis. Since meteorological conditions vary significantly from year to year, there is a need to create a test reference year (TRY), to represent the long-term weather conditions over a year. In this paper two different TRY data models were generated and compared: TRY and TRY-2. Both models where created by analysing every 3-hour weather data for a 30-year period (1984–2013) in Alūksne, Latvia, provided by the Latvian Environment Geology and Meteorology Centre (LEGMC). TRY model was generated according to standard LVS EN ISO 15927-4, but to create second model - TRY-2, 30 year average data were applied. The generated TRY contains typical months from a number of different years. The data gathered from TRY and TRY-2 models where compared with the climate data from the Latvian Cabinet of Ministers regulation No. 379, Regulations Regarding Latvian Building Code LBN 003-01. Average monthly temperature values in LBN 003-01 were lower than the TRY and TRY-2 values. The results of this study may be used in building energy simulations and heating-cooling load calculations for selected region. TRY selection process should include the most recent meteorological observations and should be periodically renewed to reflect the long-term climate change.

Impact of wood fraction, moisture and steam explosion on the development of an innovative insulation material

&lt;p class="R-AbstractKeywords"&gt;&lt;span lang="EN-GB"&gt;The study shows development of an innovative bulk heat insulation material from grey alder (&lt;em&gt;Alnus incana&lt;/em&gt; L. Moench) chips and birch (&lt;em&gt;Betula pendula, Betula verrucosa&lt;/em&gt;) flakes as residues of plywood production. The research is actual for the plywood production companies and for producers that process grey alder chips to make an innovative products with high added value. Chips and flakes eco-efficient converted to fibrous mass by steam explosion (SE) technology at temperatures (T) of 200 to 235 °C and time interval of 0 to 5 min. Application of SE technology to obtain fibrous insulating material is in the news at a global level and has not been studied previously. The bulk density of raw and SE materials determined using standardised method specified in LVS EN 15103: 2010. The bulk density of SE materials studied depending on the raw material fraction and moisture as well as depending on the SE conditions. The lowest bulk density (53 kg m&lt;sup&gt;-3&lt;/sup&gt;) achieved SE material of grey alder chips with 12% of raw moisture processed at T 235 °C for 1 min. This is the optimal result, which reveals the industrial competitiveness of bulk heat insulation materials and indicate the justification for the further examination.&lt;/span&gt;&lt;/p&gt;

Design Methods of Elements from Cross-laminated Timber Subjected to Flexure

Design methods of cross-laminated timber elements subjected to bending is considered. The methods are based on LVS EN 1995–1–1. The presented methods were checked by the experiment and analytically. Two cross-laminated timber plates with the total thickness of 95mm were tested under action of static load. The considered cross-laminated timber plates were analysed by FEM method, which is based on the using of computational program ANSYSv14. The comparison of stresses acting in the edge fibres of the plate and the maximum vertical displacements shows that the considered methods can be used for engineering calculations so as the difference between the experimentally and analytically obtained results does not exceed 20%.

Some functional properties of composite material based on scrap tires

Abstract The utilization of scrap tires still obtains a remarkable importance from the aspect of unloading the environment from non-degradable waste [1]. One of the most prospective ways for scrap tires reuse is a production of composite materials [2] This research must be considered as a continuation of previous investigations [3, 4]. It is devoted to the clarification of some functional properties, which are considered important for the view of practical applications, of the composite material. Some functional properties of the material were investigated, for instance, the compressive stress at different extent of deformation of sample (till 67% of initial thickness) (LVS EN 826) [5] and the resistance to UV radiation (modified method based on LVS EN 14836) [6]. Experiments were realized on the purposefully selected samples. The results were evaluated in the correlation with potential changes of Shore C hardness (Shore scale, ISO 7619-1, ISO 868) [7, 8]. The results showed noticeable resistance of the composite material against the mechanical influence and ultraviolet (UV) radiation. The correlation with the composition of the material, activity of binder, definite technological parameters, and the conditions supported during the production, were determined. It was estimated that selected properties and characteristics of the material are strongly dependent from the composition and technological parameters used in production of the composite material, and from the size of rubber crumb. Obtained results show possibility to attain desirable changes in the composite material properties by changing both the composition and technological parameters of examined material.

Electric Arc Hazards

This article aims to analyse the electric arc exposure hazards to human health and to develop proposals for improvement of safe operation of electric equipment in organizations. The study is carried out on the situation in the field of regulatory documents governing the safe operation of electric equipment; moreover, recommendations are also given. It is concluded that the standard IEC 61482-1-2 (LVS EN 61482- 1-2) is adapted in the Republic of Latvia, which puts forward the requirements to protective clothing against electric arc exposure, but this standard only takes into account the spectrum of partially served electric devices. It is, therefore, necessary to introduce the international standard IEC 61482-1-1, which takes into account the actual short-circuit current magnitude and environmental layout of electric devices.

Vitamin C content in Latvian cranberries dried in convective and microwave vacuum driers

Cranberries belong to a group of evergreen dwarf shrubs or trailing vines in the genus Vaccinium subgenus Oxycoccus. Traditionally they grow in acidic bogs throughout the cooler parts of the world; when cultivated are grown on low trailing vines in great sandy bogs. The research focuses on the study of vitamin C changes in Latvia grown wild (Vaccinium oxycoccus L.) and cultivated (Vaccinium macrocarpon Ait.) cranberries during convective and microwave vacuum drying. Latvian wild cranberries and cultivated cranberry varieties ‘Early Black’, ‘Ben Lear’, ‘Stevens’, ‘Bergman’ and ‘Pilgrim’ from Kurzeme region harvested in 2010 were used for experiments. Mechanical and thermal pre-treatment of fresh berries was applied for better water evaporation in drying process. During experiments the berries were dried: in a convective air dryer by controlled hot air stream circulation velocity of 1.2 m s-1 at temperature +50±2°C. The berries were placed on the perforated sieve (diameter 0.185 m, diameter of holes – 0.002 m); the moisture content of dried berries was 9.0±0.1%. Following quality parameters were analysed during experiments: moisture content (oven-drying method) and vitamin C content (LVS EN 14130:2003). Experimentally it was ascertained that drying time of berries by various drying methods mainly depends on the pre-treatment manner. During the drying process moisture content of cranberries decreased from on average 86.94% to 9.00%, about ∼10.00 times. Vitamin C is the least stable of all vitamins and it can be easily degraded during processing and storage. The most harmful factors to vitamin C content are the presence of oxygen, prolonged heating in the air ambiance and exposure to light. The initial content of vitamin C in wild and cultivated fresh cranberries was differing, which mainly depends on varieties’ individuality. Current research proved that vitamin C content loss in cranberries processed by microwave vacuum drying method comparing with drying in convective cabinet type dryer was smaller.

Thermal Bridge Impact on the Heating Demand in a Low-Energy House

Thermal Bridge Impact on the Heating Demand in a Low-Energy House Thermal bridges typically occur at the junction of different building components where it is difficult to achieve continuity in the thermal insulation layer. In this paper thermal bridges are investigated in the first one-family low-energy house in Latvia. The proportion of the overall heat loss due to thermal bridging is determined based on the results from a numerical calculation method described in the standard LVS EN ISO 10211 and from the simplified calculation method given in the standard LVS EN ISO 14683. In this paper the software tool THERM is used for two-dimensional thermal bridge model simulations. The results suggest that 7.7 % of the total heat transmission losses occur due to thermal bridges.