A theory of many-body wave scattering is developed under the assumption a << d << λ, where a is the characteristic size of the small body, d is the distance between neighboring bodies and λ is the wave-length in the medium in which the bodies are embedded. The multiple scattering is essential under these assumptions. The author’s theory is used for creating materials with a desired refraction coefficient. This theory can be used in practice. A recipe for creating materials with a desired refraction coefficient is formulated. Materials with a desired radiation pattern, for example, wave-focusing materials, can be created.

Heat recovery is one of the measures proposed for the appropriate use of ammonia in tropical countries. This article analyzes a heat recovery system installed in an industrial refrigeration plant. Based on comparative readings of operating parameters of the installation, determined the effectiveness of the heat exchange, the increase in the efficiency of the refrigeration system, as well as the fuel saved by heating water in the industry. The results obtained reported that the thermal design based on heat exchange in annular spaces allows a significant saving of resources and a high rate of thermal utilization.

Metamaterial perfect absorber is very important in the study of refractive index sensor. The time domain finite difference method is used to simulate the surface plasmon structure. The double nanorod periodic structure is designed, and the parameters of the top layer structure are optimized according to the impedance matching principle, and the absorption rate of the structure to the light wave reaches 99.6% when the wavelength is about 12 mm. The absorption spectroscopy of the structure is studied with the change of the refractive index of the spatial medium around the structure, and the sensitivity of the double nanorod structure is 4,008 nm/RIU, which can be used to measure the refractive index of the gas.

In the trend of the 4th Industrial Revolution and the trend of digital transformation, along with the orientation of building ecologically sustainable agriculture, modern countrysides, civilized knowledge farmers, meeting the requirements of international economic integration. More than ever, countries’ agriculture requires human resources from managers to researchers and those directly getting involved in agricultural production that meet the standards of professional qualifications, capacity and quality of work performance. In Vietnam, in terms of resources in the agricultural sector, there is a surplus of manual and simple labor but a shortage of high-skilled workers and lack of good managers and organizers. In terms of policies and laws in the field of agriculture, it is relatively complete when there are 15 laws passed in 4 production sectors: fisheries, forestry, horticulture and animal husbandry. This is an important legal basis to mobilize resources, including agricultural human resources in order to develop the country. However, the legal system on human resource development in the field of agriculture in general and on training, education, compensation and support in particular is still lacking and scattered. Thus, the article focuses on analyzing the current status of regulations and practices of implementing regulations on human resource development in the agricultural sector, thereby proposing corresponding policies and laws in Vietnam in the next time.

This study explores the early travelers to Petra, Jordan, during the 20th century. To gain insights into the evolution of early travel experiences to Petra during this specific period, the researchers utilized narrative analysis and conducted in-depth interviews with 14 elderly inhabitants of Wadi Musa who resided in the area at that time. These interviews provided valuable information and served as a basis for visually representing the primary routes that emerged from the participants’ narratives. This study delves into the accessibility of early travelers to Petra in the 20th century by creating a comprehensive map that outlines the trails, byways, and roads used by these travelers to reach Petra. The study’s findings also revolve around the identified stages derived from the data gathered through these interviews.