Wide-band metamaterial perfect absorber through double arrow shape printed on a thin dielectric

A wide-band metamaterial perfect absorber was introduced. The dual arrow shapes and the ground plane were in between the 0.0035λ TLY-3. Lump element technique was applied to enhance the absorption bandwidth, which was connected between both of the arrow structures. The limitation during fabrication process in using lump element, had seriously restricted its practical applications for microwave absorption. Then, a very thin line was connected between both arrow structures to represent the resistance by lump element which was expected to ease the fabrication process and practical applications as well. Four cases were analyzed: double arrow, double arrow with lump connected, double arrow with lump connected and 9 mm air gap, and thin line connected with 6 mm air gap. The fourth case achieved the highest operational absorbency frequency, which developed about 7.38 GHz (3.87 GHz to 11.25 GHz) approximately to 7.38 GHz. Three resonant frequencies were achieved; 4.17 GHz, 6.09 GHz and 10.30 GHz with perfect absorbency. These properties are expected to be used in practical applications such as satellite and radar communications transmission. These properties of the metamaterial absorber could increase the functionality of the metamaterial absorber to be used in any application especially in reducing radar cross section for stealth application.

A New Type of Hierarchical Honeycomb In-Plane Impact Study

Honeycomb materials have low density, high specific strength and stiffness, impact resistance, and good sound insulation effect, and therefore are widely used in aerospace, automobile, and ship field applications. In this paper, we study the in-plane impact response of a second-order hierarchical honeycomb (SHH) material. Its main structure is a hexagonal honeycomb, and the substructure is composed of an augmented double arrow honeycomb (ADAH) negative Poisson’s ratio unit. Through a finite element simulation, the failure stress of an hierarchical honeycomb in two directions of quasi-static crushing and dynamic crushing was analyzed; the failure stress of the hierarchical honeycomb under different densities, different speeds, and different substructures was discussed; and the theoretical failure stress was verified. The numerical analysis results show that a second-order hierarchical honeycomb (SHH) has better collapse stress than a first-order regular hexagonal honeycomb (FHH) and an augmented double arrow honeycomb (ADAH).

Mechanical Properties of Corner Joints Made of Honeycomb Panels with Double Arrow-Shaped Auxetic Cores

The development of both light and strong wood-derived materials is an interesting research area, particularly in terms of usability in, e.g., furniture constructions. Honeycomb panels being current industry standard are relatively thick (32 mm and 40 mm), thus their attractiveness in designing furniture is limited. In a few studies, it has been shown that honeycomb panels with paper cores are characterized by unsatisfactory mechanical properties, especially when the composite thickness is less than 20 mm. From the literature, it is also evident that mechanical properties might be improved by introducing auxetic features into the core structure. Even though it is a concept with great potential, there are a few studies dealing with honeycomb panels with auxetic cores made of paper. Furthermore, there is no research on the corner joints made from such material. For this reason, the aim of the study was to test the bending behavior of the corner adhesive joints made of honeycomb panels with double arrow-shaped auxetic cores. Within the research, the core cell was adopted based on literature and preliminary studies, paper auxetic cores were produced by the use of the designed and 3d printed device, and joints stiffness and strength were calculated analytically based on the experiment results. Evaluated corner joints stiffness, both in compression and tension test, is greater for samples made of panels with designed auxetic cores. Surprisingly, in the analyzed range of elasticity, it was statistically proved that the values of joint stiffness coefficient K did not vary significantly between compared joints pairs.

Differentiated Developmental Assessment of Speed-Coordination Abilities of 5–11 Forms Pupils Using the Double-Arrow Test

The working out of new tests will generally change the approach to physical education of schoolchildren. If the new tests include more creative motor problem solving component, children will approach them with a completely different creative understanding and implementation. The purpose of the research is to determine the standards of differentiated developmental assessment of pupils` speed-coordination abilities using the Double -Arrow Test. Standards for the differentiated developmental assessment of senior pupils` speed-coordination abilities using the Double -Arrow Test are calculated according to a 12-point sigmoid scale. The methods of theoretical analysis and synthesis, analysis of scientific and methodological literature, methods of mathematical statistics have been used in the research paper. The reseach participants. This study was conducted at the Volodymyr the Great “Cadet Corps” Boarding Lyceum No 23, that is located in Kyiv. 406 pupils of 5-11 forms (n = 406) were involved in the research and divided into age groups, accordingly 17-16, 15-14, 13-12,10-11 years old. The children and their parents were informed about all the features of the study and agreed to participate in the experiment. The results of the research. Standards for differentiated developmental assessment of pupils` speed-coordination abilities using the Double-Arrow Test, which are calculated according to the 12-point sigmoid scale for pupils aged 17-16 within 22,73 – 17,47 sec., for pupils 15-14 within 24,17 – 17,56 sec., for pupils aged 13-12 within 18,24 – 28,2 sec. and for pupils aged 11-10 within 18,53 – 29,03 seconds. Conclusions. According to the research results, senior pupils of 17-16 years old have more developed abilities to adapt and quickly change motor actions, as well as improved spatiotemporal and dynamic characteristics of their orientation. This is due to accelerated physical developmental at this age. The assessment results of the 15-10 year old pupils` are almost at the same level.