Optimal density for balancing the thermal conductivity and compressive strength of foamed ceramic

Foamed ceramic becomes increasingly popular in building engineering due to its thermal, acoustic and other advantages. However, conflicts often exist between its different properties. In this paper, we seek a balance between the thermal conductivity and the compressive strength of foamed ceramic. Experiments are performed on foamed ceramic with different densities. Nonlinear regression is then adopted to quantify the relationship between the thermal conductivity/compressive strength and the bulk density. The results indicate that both the thermal conductivity and the compressive strength increase with the rising density. Based on the requirements in the Chinese national standard, the optimum density range of foamed ceramic is proposed, satisfying a balance between the thermal and mechanical performance.

Management of productivity of sunflower plants depending on terms of sowing and density of standing in arid conditions of the Right-bank Steppe of Ukraine

The article presents the results of scientific research conducted in 2016–2018, in order to determine the impact of sowing dates and standing density on the growth, development and productivity of sunflower hybrids. The field experiment was performed by the method of splitting plots in three replications in the experimental field of the Institute of Agriculture of the Steppe of NAAS in arid conditions of the Right Bank Steppe of Ukraine. The material for the study were sunflower hybrids of the middle-early maturity group – Forward, LG 56.32, LG 54.85, LG 5582 (Factor A); terms of sowing – the first when warming up the soil at a depth of seed wrapping to 5–6°C, the second when warming up the soil at a depth of seed wrapping to 7–8°C, the third when warming up the soil at a depth of seed wrapping to 9–10°C (Factor B); density of standing plants – 50, 60, 70 thousand per hectare (Factor C).Research found that the productivity of sunflower plants directly depends on the temperature of the soil (sowing dates), optimal water regime, density of standing plants, genetic and morphological characteristics of hybrids. It is also established that by regulating timing of sowing and selecting the optimal density of standing plants can affect the growth and development of sunflower plants, bypassing critical periods during cultivation. The optimal time for sowing sunflower for hybrids LG 55.82 and LG 54.85 is warming the soil at depth of seed wrapping up to 5–6°C, for hybrids Forward and LG 56.32 is warming the soil at a depth of seed wrapping up to 9–10°C. On average, according to the years of research, the highest seed yield of 3.85 t ha–1 was formed by the hybrid LG 55.82, which is higher than that of the hybrids Forward, LG 54.85 and LG 56.32 by 19.8%; 5.5% and 6.0%, respectively. It is established that the optimal density of sunflower is 60 thousand plants per hectare. Thus, sunflower productivity varied significantly under the influence of the morphobiological features of the hybrid – factor A (the proportion of impact was 47.5%), density of standing plants (factor C) – 5.4%, sowing time (factor B) – 3.4%.

Data-driven sequential three-way decisions for unlabeled information system

Based on the granular computing and three-way decisions theory, the sequential three-way decisions (S3WD) model implements the idea of progressive computing. However, almost S3WD models are established based on labeled information system, and there is still a lack of S3WD model for processing unlabeled information system (UIS). In this paper, to solve the issue of given accepted number for UIS, a data-driven sequential three-way decisions (DDS3WD) model is proposed. Firstly, from the perspective of similarity computed by TOPSIS, a general three-way decisions model for UIS based on decision risk is presented and its shortcomings are analyzed. Then, a concept of optimal density difference is defined to establish the DDS3WD model for UIS by updating attributes. Finally, the related experiments show that DDS3WD is feasible and effective for dealing with UIS under the condition of given accepted number of objects.

Substantiation of the method of manufacturing gauze swabs depending on the purpose of use

Annotation. Gauze remains the main dressing. It is used to make swabs for drying wounds and dissecting tissues. The purpose of the work is to establish the optimal density of the swab for drainage of the wound and preparation of tissues. Swabs made of 10x12 cm gauze fragments were investigated. The gauze fragments were weighed before and after immersion in water and the absorption capacity per unit dry weight was calculated. The dissecting properties of the swabs were investigated on plasticine blocks, the surface of which was pressed with a force of 12 N. The formed depressions were filled with gypsum. The volume and weight of the casts were determined. To determine the reliability of the difference between the two mean values used the reliability criterion t (Student’s test). It was found that loose swabs absorbed 913.5±43.9% of water, medium density – 766.3±55.2%, dense – 682.9±70.1 (p˂0.05). This is due to the fact that loose swabs have the largest in radius and length of the capillaries. When studying the recesses formed by embossing the swab on the surface of the block, it was found that when using loose swabs formed a deep conical recess, which indicated the risk of injury. When embossed with dry swabs of medium density received molds weighing 0.034±0.0000011 g, wet – 0.033±0.0000011 g (p>0.05). When using dense swabs – 0.037±0.0000011 g and 0.034±0.0000011 g, respectively (p˂0.05). Dense swabs showed the best dissecting properties. When wet, they are slightly but significantly reduced. Medium density swabs have slightly worse dissecting properties. When wet, they did not change significantly. We attribute the decrease in dissecting properties to the displacement of water from the gauze when pressed. Thus, loose swabs (∆M=913.5%±43.9%) absorb fluid best, which determines their predominant use for wound drying. Dense swabs are characterized by the lowest absorption capacity (682.9±70.1%), the best dissecting properties.

Identification of the optimal density of the cucumber plants of different varieties in the Left Bank Forst Stepp of Ukraine

The results of the research of the cucumber plants desity of Konkurent, Beregvoy, Feniks – 640, Dzherelo varieties are represented in the article. The plants wore graun in open sail conditions of the Left-Band Forest – Steppe of Ukraine with the intertihlage width of 1,4 m. The researches were conducted in 1997-2015 at the Fruit and vegetable grawing and Storage Chair of Kharkiv National Agrarian University named affer V. V. Dokuchayiv. The results of the research witness that the optimal plant density for the cucumber of Konkurent and Beregvoy varieties is 90 -100 pieces per hectar. For Feniks – 640 variety the lensity is 80 – 90 thausands pieces per hectar. It is necessary to treat the plants of Dzherelo varieties with density of 100 – 110 thausands pieces per hectar. Key words : cucumber, variety, density, Konkurent, Beregvoy, Feniks – 640, Dzherelo, crop productivity, phenological obserwation

INFLUENCE OF FINE-DISPERSED ADDITIVE FROM CONCRETE SCRAP ON STRUCTURE FORMATION OF PORTLANDCEMENT

The object of the study is the effect of the introduction of a mineral additive (Ssp = 900 m2/kg) of the fraction (0.315–5 m) of the screening out of crushing concrete scrap into Portland cement for the production of various building products and structures. A fraction of concrete scrap of 0.315–5 mm is used in the work, since the X-ray phase analysis of various fractions of concrete scrap shows that these fractions have a rational content of non-hydrated particles of C3S and C2S. It is proved that the use of finely ground concrete scrap (Ssp = 900 m2/kg) as a mineral additive in Portland cement increaseINFLUENCE OF FINE-DISPERSED ADDITIVE FROM CONCRETE SCRAP ON STRUCTURE FORMATION OF PORTLANDCEMENT s the physical and mechanical properties of concrete. Comparative physical and mechanical indicators of the hardening of composite binders indicate that the most stable results with a uniform increase in strength is a composition with 5 % mineral additive, with an increase in strength from 2 to 7 days by 36 % and from 7 to 28 days by 46 %. It is found that the most rational are the compositions with 5 % and 10 % mineral additives providing an increase in the strength of the samples by 16% compared to the control composition. Due to the high dispersion, the mineral additive from concrete scrap acts as additional crystallization centers during the hydration of Portland cement, which leads to the creation of a skeleton coral-like structure, which additionally overgrows with submicroscopic crystals. With a specific surface area of 900 m2/kg, the best conditions are created for the formation of the primary frame and its further overgrowth with various crystalline calcium hydrates, which provide optimal density and strength.

The Effect of Print Speed on Surface Roughness and Density Uniformity of Parts Produced Using Binder Jet 3D Printing

One of the main benefits of binder jetting is the ability to print quickly compared to other metal additive manufacturing methods. Demand for higher throughput continues to increase, but the effects of faster print speeds on part outcomes are not yet clearly understood. MIM powders are used to achieve optimal density and surface finish. Printing at slower speeds results in densities near 98% and average surface roughness values as low as 4 μm (Ra), in the as-sintered condition. In this study, spread speeds were varied in order to understand the effect of print speed on surface roughness. 316L D90 -22 μm powder was used to print with 3 different spread speeds, 2 different layer thicknesses, and 2 different printhead droplet sizes. The surface finish and density were quantified for the sintered parts that were oriented at 0, 22.5, and 45 degrees with respect to the Z- direction.