Thermoplastic Mandrel for Manufacturing Composite Components with Complex Structure

This study was to solve the mandrel demolding problem after curing the composite component with complex structure. In this paper, a reusable thermoplastic mandrel with heating softening characteristics was developed by resin transfer molding (RTM). The glass transition temperature (Tg), surface roughness, and reusability of the mandrel, as well as the shape, surface roughness, thickness uniformity, and internal quality of the formed structure, were tested. The result showed that the Tg of the mandrel was between 80 and 90 °C and the surface roughness was less than Ra 0.5 μm. Additionally, the mandrel can be recycled and can still maintain a good shape after 20 times of deformation. By using this method, the demolding process can be realized by heating and softening the mandrel. The profile error of the formed structure was within 0.5 mm, the surface roughness was less than Ra 0.5 μm, the thickness error was within 0.2 mm, and the average porosity of the upper and lower halves of composite parts was 0.72% and 0.61%. All those data showed that the formed part was in good shape and of good quality. The thermoplastic mandrel can solve the demolding problem of composite materials with complex shapes.

The Effect of Agarose on 3D Bioprinting

In three-dimensional (3D) bioprinting, the accuracy, stability, and mechanical properties of the formed structure are very important to the overall composition and internal structure of the complex organ. In traditional 3D bioprinting, low-temperature gelatinization of gelatin is often used to construct complex tissues and organs. However, the hydrosol relies too much on the concentration of gelatin and has limited formation accuracy and stability. In this study, we take advantage of the physical crosslinking of agarose at 35–40 °C to replace the single pregelatinization effect of gelatin in 3D bioprinting, and printing composite gelatin/alginate/agarose hydrogels at two temperatures, i.e., 10 °C and 24 °C, respectively. After in-depth research, we find that the structures manufactured by the pregelatinization method of agarose are significantly more accurate, more stable, and harder than those pregelatined by gelatin. We believe that this research holds the potential to be widely used in the future organ manufacturing fields with high structural accuracy and stability.

Nanostructures for Achieving Selective Properties of a Thermophotovoltaic Emitter

This paper focuses on the research and development of a suitable method for creating a selective emitter for the visible and near-infrared region to be able to work optimally together with silicon photovoltaic cells in a thermophotovoltaic system. The aim was to develop a new method to create very fine structures beyond the conventional standard (nanostructures), which will increase the emissivity of the base material for it to match the needs of a selective emitter for the VIS and NIR region. Available methods were used to create the nanostructures, from which we eliminated all unsuitable methods; for the selected method, we established the optimal procedure and parameters for their creation. The development of the emitter nanostructures included the necessary substrate pretreatments, where great emphasis was placed on material purity and surface roughness. Tungsten was purposely chosen as the main material for the formation of the nanostructures; we verified the effect of the formed structure on the resulting emissivity. This work presents a new method for the formation of nanostructures, which are not commonly formed in such fineness; by this, it opens the way to new possibilities for achieving the desired selectivity of the thermophotovoltaic emitter.

Study of water absorption capability of swellable starch

Usually for the production of swellable starch extrusion treatment or drying on a drum roller dryer are used. The properties of swellable starch with a newly formed structure are evaluated mainly by the water absorption capacity in water under the action of temperature. The ability of swellable starch to thicken, stabilize, bind and enamel various food and non-food products depends on this indicator. The study of the index of water absorption capacity (WAC) of swellable starch obtained by our improved technology based on the use of convective dryer is an urgent and priority task. Research methodology. Control – extruded corn starch. Samples of swellable starch obtained by preparation of starch suspensions of different concentrations of 25, 30, 35 and 40 % were dried under conditions of two-stage convective drying, crushed and sieved. Research results. The obtained samples of swellable starch differ in the value of WAC. It is shown that the WAC of swellable starch affects not only the method of its production but also affects the concentration of starch suspension (SS) from which the samples of swellable starch were made. The obtained value of the approximation coefficient shows that the strongest bond (value - 1) has a sample of swellable starch obtained by convective drying from a concentration of SS 25 %. Conclusions. The WAC of extruded and swellable starch samples obtained by convective drying from different concentrations of SS from 25 to 40 % was investigated. It is shown that at a temperature of 20 °С the lowest value of WAC has swellable starch obtained from 25 % of the concentration of SS and the highest value in 35 % of the concentration of SS. Low strength of the newly formed structure is detected by samples at different temperatures, in particular, extruded starch and a sample obtained from SS 25 % at an aqueous solution temperature of 40-50 °C, a sample obtained from SS 30 % at 60 °C, a sample obtained from SS 35 % at temperature of 40 °C, the sample was obtained from SS 40 % at temperatures of 30 and 50 °C.

Nouveau short-course therapy and morphism mapping for clinical pulmonary Mycobacterium kansasii

Standard therapy [isoniazid, rifampin, ethambutol], with or without a macrolide, for pulmonary Mycobacterium kansasii lasts more than a year. Therefore, shorter treatment duration regimens are required. We used data from 32 Taiwanese patients treated with standard therapy who were followed using repetitive sampling-based sputum Mkn time-to-positivity in liquid cultures to calculate kill slopes [γ] based on ordinary differential equations and time-to-extinction of each patient’s bacterial burden. The γ was 0.18 [95% Confidence Interval (CI): 0.16-0.20] log10 CFU/mL/day on standard therapy. Next, we identified Mkn time-to-extinction in the hollow fiber system model of pulmonary M. kansasii disease [HFS-Mkn] treated with standard therapy, which was a γ of 0.60 [95% CI: 0.45-0.69) log10 CFU/mL/day. The γs and time-to-extinctions between the two datasets formed structure-preserving maps based on category theory: thus, we could map them from one to the other using morphisms. This mapping identified a multistep non-linear transformation-factor for time-to-extinction from HFS-Mkn to patients. Next, a head-to-head study in the HFS-Mkn identified median time-to-extinction for standard therapy of 38.7 [95% CI: 29.1-53.2) days, isoniazid-rifampin-ethambutol-moxifloxacin of 21.7 [95% CI: 19.1-25) days, isoniazid-rifampin-moxifloxacin of 22 [96% CI: 20.1-24.5) days, and rifampin-moxifloxacin-tedizolid of 20.7 [95% CI:18.5-29) days. Our transformation-factor based translation predicted the proportion of patients of 90.7 [88.74-92.35)% achieving cure with standard therapy at 12 months, and 6-months cure rates of 99.8 [95% CI: 99.27-99.95)% for isoniazid-rifampin-ethambutol-moxifloxacin, 92.2 [90.37-93.71)% for isoniazid-rifampin-moxifloxacin, and 99.9 [99.44-99.99)% for rifampin-moxifloxacin-tedizolid. Thus, rifampin-moxifloxacin-tedizolid and isoniazid-rifampin-ethambutol-moxifloxacin are predicted to be short-course chemotherapy regimens for pulmonary M. kansasii disease.

Formation of ferroelectric photonic crystals with a period of 1.5–10 μmusing transverse acoustic waves

It is shown that when interfering transverse acoustic waves act on a ferroelectric through a layer of a liquid electrode, it is possible to form regular domain structures with a period of 1.5–10 μm at frequencies of 400–30 MHz, respectively. Variants with liquid electrodes based on highly dissipative liquids[C4mim][PF6]andLiPF6–PCare considered. The frequency depend-ences of the spatial period of the domain structure and the angles of incidence of transverse waves on the “acoustic line-liquid” interface are obtained for frequencies limited by the New-tonian model of a liquid. Based on the simulation results, recommendations are given on the choice of the type of liquid electrodes, the values of thecarrier frequency of acoustic waves for a given period of the formed structure, as well as the angles of incidence of waves at the “paratellurite-liquid”interface at room temperature.

THE ESTIMATION OF MATURITY LEVEL OF COGNITIVE UNIVERSAL LEARNING ACTIVITIES OF THE 7-9 GRADES’ STUDENTS AT THE MATHEMATICS LESSONS IN THE CONDITIONS OF TWO-SUBJECT MONITORING

The necessity to perform diagnostic procedures within the contemporary process of teaching mathematics is caused by the importance of timely obtaining of the information on the current maturity level of the subject, meta-subject, and personal learning outcomes of students. The task is to choose an assessment technique adequate in educational trends and scientifically grounded. The authors propose to solve the issue of estimation of cognitive universal activities of the 7-9 grades’ students at the mathematics lessons in the conditions of two-subject monitoring. The paper shows that cognitive universal learning activities are a dynamic and important newly formed structure of a person depending on the age peculiarities in the formation process and should be considered in the maturity level assessment. The authors propose and substantiate the structure and step-by-step composition of the cognitive universal learning activities, which allow demonstrating them in a diagnosable view. It made it possible to identify and characterize the maturity level and criteria of the considered learning activities, assessment stages and procedures, and diagnostic tools. The paper presents the author’s conceptual model to assess cognitive universal learning activities when teaching mathematics, which demonstrates the important characteristic of the assessment process – a nonlinear nature. The research resulted in the identification of a specific principle of the assessment of cognitive universal learning activities – a two-subject principle. The implementation of this principle makes it possible to use the subject material to determine the maturity level of both the subject and meta-subject learning results. The authors describe the diagnostic tools, present the diagnostics process chart, the system of assessing certain tasks and give an example of typical assignments on the Equations topic of Algebra course for 7th grade.

Numerical study on structures formed by the deposition and solidification of a single molten droplet

The formed structure is of importance in determining the surface quality of a component made by droplet-based 3D printing. In the present work, the molten droplet solicitation process was simulated under an axisymmetric system where the smallest length scale and time scale were fully resolved. Evolutions of sharp droplet interfaces were captured through the front tracking method. Parametric studies have been carried out to explore how the dynamic metrics, which include the Ohnesorge number (Oh) and Weber number (We), can affect the structure of depositing droplet. The effect of the superheat parameter on the cooling rate was also investigated in the final section. Numerical results show that the inertial resisting force is critical dynamics in the variation of horizontal dimensionless length at the early deposition process. Three levels of Oh numbers and stages of We numbers were classified according to the deformation behavior. Flattening degree under different Oh number and We number cases were both fitted well by the exponential function. This paper also reveals that the variation law of the cooling rate and solidification time is affected by the superheat parameter, resulting in a feasible and promising method to predict droplet deformation time through the fully resolved numerical simulations during the manufacturing process.

HISTORICALLY FORMED STRUCTURE OF THE GARDENING SYSTEM INTHE CENTER OF YEREVAN AND ITS MODERN PROBLEMS

The article examines the historical, landscape and urban planning features of Yerevan, which determined the planning structure and development of the city's greening system. The analysis of the city relief in terms of heights and natural types of landscapes is given. Particular attention is paid to the description of urban planning axes and compositional nodes of the landscaping system, created during the Soviet period according to the general plan of 1937.For the first time, the structure and types of tree plantations of squares and city streets are analyzed, depending on their functional purpose and location in the city. The description of the design solution for the Children’s railway in the gorge of Hrazdan river and the station building, as well as the widespread assortment of the trees and bushes in the city in the Soviet period. The main problems of the current state of the green areas of the center are considered and the directions of reorganization of the city greening system are given. The ways of solving existing problems by the introducing regulations for the preservation of existing plantings in center of Yerevan and the prospects for their development are proposed.