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This paper presents the application of the MCNP5 code to conduct a modification design and simulation of a thermal neutron beam for neutron capture studies at the Dalat Nuclear Research Reactor (DNRR). The designed configuration of the horizontal neutron channel No.2 at the DNRR, which contains a conical collimator of 240.3 cm in length, and neutron filters of crystal Al2O3 and Bi with alternative thickness, were simulated. A pure thermal neutron beam can be obtained at the irradiation position when a composition of crystal filter of 20 cm Al2O3 and 6 cm Bi is employed. The thermal and epithermal neutron fluxes are 1.02´108 n/cm2/s (account for 97.92% of total neutron flux) and 0.22´107 n/cm2/s (account for 2.08% of total neutron flux), respectively.

The Natural Science Educational Program is implemented from 2021 - 2022, the secondary schools where are allowed to use one of the textbook sets for this program. The assessment is aimed at evaluating the capacity and capacity development of students, in which natural science competence is a specific ability of the subject. However, the teachers still have many difficulties in assessing students' abilities. In this study, we have proposed and described in detail the levels of assessment of natural science competence through a specific topic. At the same time, we have suggested a competency assessment process for teachers to implement. The results of this study aim to help secondary school teachers do this work effectively, meeting the requirements of the General Education Program 2018.

This paper investigates a cognitive radio network where a secondary sender assists a primarytransmitter in relaying primary information to a primary receiver and also transmits its own information toa secondary recipient. This sender is capable of jamming to protect secondary and/or primary informationagainst an eavesdropper and self-powering by harvesting radio frequency energy of primary signals.Security capability of both secondary and primary networks are analyzed in terms of secrecy outageprobability. Numerous results corroborate the proposed analysis which serves as a design guidelineto quickly assess and optimize security performance. More importantly, security capability trade-offbetween secondary and primary networks can be totally controlled with appropriate selection of systemparameters.

Breeding turtles in farms for offering them in the food market is a profitable market in Vietnam. Here we study, through structured questionnaires with 73 owners of turtle farms, the social and economic contexts of this business activity. We also collected ecological data for the most intensely bred species, the Wattle-necked softshell turtle, Palea steindachneri. Palea farms were typically small family-owned companies, with just 1 to 4 employees working just 1 – 2 h per day but almost every day in the week, and with 1 to 4 ponds available in the facilities. Sex ratio of farmed turtles was heavily skewed to females in both P. steindachneri and Amyda cartilaginea (the secondly most frequently bred species), and their clutch size was very similar. Inside farms, mating of P. steindachneri occurred in February, egg deposition in March – July with a peak in May, and egg hatching in May – October, with a peak in July. In Vietnam, the typical owner of P. steindachneri farms is a self-made man who had enjoyed very little management and support from government for his/her business.

We investigate cognitive radio networks where the unlicensed sender operates in the overlay mode to relay the information of the licensed transmitter as well as send its individual information. To secure information broadcasted by the unlicensed sender against the wire-tapper, we invoke jammers to limit eavesdropping. Also, to exploit efficiently radio frequency energy in licensed signals, we propose the unlicensed sender and all jammers to scavenge this energy source. To assess the security measures of both licensed and unlicensed networks, we first derive rigorous closed-form formulas of licensed/unlicensed secrecy outage probabilities. Next, we validate these formulas with Monte-Carlo simulations before using them to achieve insights into the security capability of the proposed jamming-aided energy harvesting cognitive radio networks in crucial system parameters.

Energy scavenging overlay networks with artificial noise (ESONwAN) integrate three emerging (energy harvesting, cognitive radio, physical layer security) technologies to boost spectrum utilization efficiency, energy efficiency, and message security, which sufficiently provide secured communication demands of an immense number of users in modern wireless systems. This paper analyzes secrecy throughput of these networks over Nakagami-m fading channels. Numerous results corroborate the theoretical analysis and demonstrate that the secrecy throughput of both secondary and primary networks increases significantly with better fading conditions and is adjusted, traded-off and maximized by various options.