Laws Governing Free and Actual Drying Shrinkage of 50 mm Thick Mongolian Scotch Pine Timber

The relationships between free shrinkage and actual shrinkage of different layers in Mongolian Scotch pine (Pinus sylvestris var. mongolica Litv.) were explored to provide basic data for the further study of drying shrinkage properties. The free shrinkage coefficients at different temperatures and the actual shrinkage strain of each layer were examined under conventional drying. The results showed high precision of free drying shrinkage of corresponding layers of thin small test strips in each layer of sawn timber. The free shrinkage increased linearly as moisture content declined. At the same temperature, the free shrinkage coefficient reached the largest values for the first layer (above 0.267), while the smallest values were recorded for the ninth layer (below 0.249). Except for the ninth layer, the free shrinkage coefficients in width directions of other representative layers decreased as temperature increased. At constant temperature, the difference in free shrinkage coefficient of test materials in the length direction of sawn timber was small for the first layer, but slightly larger and changed irregularly in the fifth and ninth layer direction. At the end of conventional drying, the plastic deformation of each layer in the early stage of drying showed a reducing trend or even reversal due to the effects of reverse stress and later damp heat. In sum, these findings look promising for future optimization of wood drying process.

Experimental Investigation of the Technical Performances of SRX-Stabilized Graded Macadam

The technical performances of Solution Road RomixSoilfix- (SRX-) stabilized graded macadam (SSGM) are investigated to promote its application. The specimen curing conditions were proposed to improve the test efficiency by analyzing the influence of curing temperature on the unconfined compressive strength and moisture content variation. Moreover, the mechanical properties (e.g., CBR, strength, and resilient modulus) and pavement performances (e.g., temperature shrinkage, water stability, and freezing stability) of SSGM were evaluated through laboratory tests. The results show that the recommended curing temperature in the drying oven should be 100°C ± 2°C and the recommended curing time should not be less than 16 h. Furthermore, the CBR, unconfined compressive and splitting strengths, and resilient modulus of SSGM increase with the content of SRX stabilizer. The temperature shrinkage coefficient is approximately 15% of the cement-stabilized grading crushed stone. The dry-wet recovery strength ratio is approximately 96% after four dry-wet cycles. The freeze-thaw recovery strength ratio is approximately 58% after five freeze-thaw cycles. The freezing stability of SSGM can be improved by increasing the content of SRX stabilizer. The technical performances of SSGM should fulfill the technical requirements.

Analysis of Shrinkage Phenomena in the Process of Cheese Vacuum Drying

The work is devoted to the study of the shrinkage phenomena during the vacuum dehydration of the cheese varieties “Sovetskiy” and “Gollandskiy”. During the research, the dependences of the cheese shrinkage coefficient on the initial mass fraction of moisture were obtained. It was found that when the mass fraction of the cheese moisture increases, an increase in the shrinkage coefficient of the product occurs. The greatest increase in the cheese shrinkage coefficient is observed when the mass fraction of moisture is more than 50%. It was established that with increasing temperature and heat load, the moisture content on the cheese surface rapidly decreases, while in the central layers it changes more slowly. Shrinkage at elevated temperatures is less; however, dry cheese has a large mass fraction of moisture. It was found that an increase in the difference in the mass fraction of moisture between the inner and surface layers is accompanied by an increase in the difference between the actual shrinkage and possible shrinkage corresponding to the amount of liquid removed. The coefficients of shrinkage in the volume of the “Sovetskiy” and “Gollandskiy” cheese varieties were calculated: they lie in the range of 0.017–0.004 and 0.006–0.003, respectively. The dependences of the cheese shrinkage coefficients on the drying layer thickness, shape and size of grinding were obtained. Keywords: cheeses, vacuum drying, shrinkage

Solutal Convection in Layered Sorbing Porous Media

<p>We study convective instability in the vertically layered porous media saturated with mixture. The mixture consists of a carrier fluid and solid nanoparticles. The nanoparticles are considered as solute within the continuous approach. The porous media are two horizontal sublayers with different permeabilities. The solute concentration is maximal near the upper boundary and is zero near the lower boundary of the superposed sublayers. Thus, one has suitable conditions for the onset of solutal convection in the gravitational field.</p><p>The porous sublayers are reactive media, which can absorb nanoparticles. The mixture transport here is accompanied by immobilization. It is described by the mobile/immobile media model. The mobile phase is carried by fluid flow, while the immobile phase is absorbed by porous matrix. The linear kinetic equation for the mixture redistribution between the phases is applied. The Boussinesq approximation is used in the equations for convection in each of the sublayers. Numerical simulation is performed by the shooting method.</p><p>We apply a linear stability theory to find the threshold Rayleigh-Darcy number for the onset of solutal convection. This similarity criterion is determined through the average permeability and porosity of uncontaminated porous sublayers. For the first time, we introduce a solutal pore shrinkage coefficient, which is analogous to the thermal expansion coefficient for thermal natural convection. This coefficient shows that porosity decreases as the concentration of immobile phase grows in the presence of sorption. Particles in this case join the surface of pores and shrink the void space.</p><p>Firstly, we find the permeability ratios for bimodal marginal stability curves in the uncontaminated sublayers. Here, the sublayer permeabilities differ by approximately 100 times. The bimodal curves demonstrate the competition between two convective instabilities. One of them is for the local convective rolls that generate within the more permeable layer and the other is for the large-scale rolls penetrating both layers. The rolls are similar to thermal natural convection in the multi-layered porous media studied by McKibbin and O'Sullivan (1980). For sorbing porous media, the type of convective rolls strongly depends on the solutal pore shrinkage coefficient. Even a small change in its value can produce a large variation of flow streamlines from the convective rolls localized within the upper highly permeable sublayer to the rolls covering both the upper and lower sublayers. The observed sorption effect on the transition from local to large-scale convection is due to the fact that the permeability ratio depends on the solutal pore shrinkage coefficient. It is also found that sorption effect delays the onset of solutal convection.</p><p>The work was supported by the Russian Science Foundation (Grant No. 20-11-20125).</p>

Features of Use of Rapid Prototyping Technology in the Manufacture of Wax Models of GTE Turbine Blades

The paper presents the main results related to the peculiarities of using 3D printing technology and methods of rapid prototyping in the manufacture of wax models of blades of a GTE turbine. The main design solutions that must be used in the design of a blade blank are presented in detail: the total shrinkage coefficient, equidistant rolling of the airfoil profile, allowance along tract surfaces, radial fillets, and a number of others. The results of control of geometric dimensions of the turbine blade blanks at the corresponding stages of the technological process showed deviations from the nominal value within the tolerance range for the executable dimensions, and the statistical information from the measurement of an experimental batch of wax models of blade blanks showed stability of the silicone tooling and ability to manufacture a series of wax models of the blades in the amount of 100 pieces when using one mold.

CHIP FORMATION DURING THERMAL FRICTION TURN-MILLING

This paper presents the results of chip formation studies in the processing of 30KhGSA steel by thermofriction turn-milling. When studying the process in this work there are presented the results of studying chip formation when the processing of chip formation there is used the metallographic method. Chip root area investigated. The dependence of the chip shrinkage coefficient on the cutting speed and feed was also investigated. It is established that with increasing supply S the value of the chip shrinkage coefficient K decreases. The higher the chip shrinkage factor, the more work will be required to cut the chips and the more complex the processing process.

Physical properties of sessile oak (quercus petraea l) used by the wood industry in Kosovo

The paper shows some physical properties of sessile oak obtained in Kosovo regions. In the study are shown: wood shrinkage, specific gravity, shrinkage coefficient for 1% change of moisture content, ratio of shrinkage in tangential and radial direction etc. The amount of volumetric shrinkage of sessile oak is 15.95%, heartwood part has an average shrinkage 15.41% in The shrinkage of sapwood part is 17.56%. Specific gravity at: wet condition: (1.013gr/cm3); 12% (0.853gr/cm3) and 0% (0.826gr/cm3) of moisture content. Specific gravity of heartwood at: wet condition (1.05gr/cm3); 12% (0.88gr/cm3); 0% (0.85gr/cm3). The specific gravity of sapwood at: wet condition (0.91gr/cm3); 12% (0.77gr/cm3); 0% (0.748gr/cm3). The ratio of average shrinkage between tangential and radial cutting direction is 1.71%. This ratio was significantly higher in sapwood than heartwood. Coefficient of shrinkage (changing 1% of moisture content) in the radial direction is 0.00196, and 0.00323 in tangential direction.

Generalized Linear Mixed Model Analysis of Acute Respiratory Infection Data on Children

Statistical modeling often involves data which has a distribution of the exponential family. Generalized Linear Model (GLM) was developed to model these data by using a link function between the mean of the response variable and the linear form of the predictor variable. If the data of the response variable comes from several census blocks that are taken randomly, then the diversity between census blocks should not be ignored because it can increase bias. The Generalized Linear Mixed Model (GLMM) is a method that can capture a variety of random effects. However, it does not rule out if there are many predictor variables involved in the model and we use GLMMLasso as a combination method of GLMM and Lasso to shrink the parameter coefficients to zero, it is used to reduce the variance. In this study, a simulation was conducted to GLMMLasso use different numbers of predictor variables and different values of shrinkage coefficients to determine which shrinkage coefficient values have a minimum bias on parameter prediction. Acute Respiratory Infection (API) data on children in Jakarta is used to know the factors that could cause increased cases. The simulation result is the shrinkage coefficient which produces a minimum bias is 30, and the R2 value of data analysis on the model is 99.24%

Research on Shrinkage Chemical Properties of Cement Stabilized Macadam Material Based on a Multi-dimensional Expansion and Shrinkage Tester

In order to find out the shrinkage law of cement stabilized macadam material under specific conditions, this paper studied the expansion and shrinkage properties of cement stabilized macadam material under two environmental conditions, five kinds of cement dosage conditions, suspended compacted type and skeleton compaced type based on the multi-dimensional expansion and shrinkage tester. Through the test comparison, it is confirmed that the water loss rate of cement stabilized macadam material increases with the increase of cement dosage, showing a general change rule of rising first and then stabilizing. The average increase of the total water loss rate of suspended compacted cement stabilized macadam at room temperature was greater than that of the skeleton compacted cement stabilized macadam. The dry shrinkage strain also follows the above trend. Either at room temperature or under the conditions of dry shrinkage box, the water loss rate of suspended compacted cemeny stabilized macadam is higher than that of skeleton compacted cement stabilized macadam , which can be up to 3.23% higher. By comparing the temperature shrinkage coefficient under the high and low temperature environment, the temperature coefficient of the skeleton compacted cement stabilized macadam is smaller than that of the suspended compacted cement stabilized macadam. The temperature shrinkage coefficient of the suspended compacted cement stabilized macadam increases by 5.56% on average for each 0.5% increase of the cement dosage, and the temperature shrinkage coefficient of the skeleton compacted cement stabilized macadam increases by 6.33% on average. Through the comparative analysis of tests, it can be found that the anti-reflection crack ability of the skeleton compacted cement stabilized macadam material is better, and the fine aggregate content should be strictly controlled in the construction.

Deformability of Bisphenol A-Type Epoxy Resin-Based Polymer Concrete with Different Hardeners and Fillers

This study experimentally investigated the deformability characteristics of bisphenol A-type epoxy resin-based polymer concrete produced using two types of hardener and four types of filler. In particular, the basic properties of epoxy resin polymer concrete, including the modulus of elasticity, setting shrinkage, and thermal expansion, were experimentally investigated to obtain basic data for evaluating compatibility and dimensional stability. The properties of the epoxy resin polymer concrete were determined when different types of hardener and filler were employed. Differences in deformability can be identified based on these properties. In the present study, the setting shrinkage, coefficient of thermal expansion, and modulus of elasticity were lowest when fly ash was employed as one of the four fillers. Hence, it is advantageous to use fly ash as a repair material for ordinary Portland cement concrete structures. Therefore, the results of this study will be helpful when selecting the types of hardener and filler needed to tailor the epoxy resin polymer concrete produced to be suitable for a particular application.