Effects of Mg Al Alloy Powder on the Combustion and Infrared Emission Characteristics of the Mg Al PTFE Viton Composition

Metal-Fluorocarbon compositions are the pyrotechnic formulations which have been widely used in infrared decoy flares to protect aerial targets from infrared guide missile seekers. In this work, the effect of Mg-Al alloy powder (i.e. the particle size and the content) on the combustion and the infrared emission characteristics (i.e. the infrared emission distribution and the infrared radiance) of the pyrotechnic composition based on Mg-Al alloy, polytetrafluoroethylene (PTFE) and Viton rubber are described. The results show that the high burning rate (with the values of 4.0 mm.s-1 to 10.0 mm.s-1, depend on the compression density) of this composition is achieved with a high content of Mg-Al alloy or when using fine Mg-Al alloy particles as well as coarse PTFE particles. On the other hand, the infrared emission radiance (in the wavelength range of 2.5 μm to 5.0 μm) of Mg-Al/PTFE/Viton composition reaches maximum values (i.e. 17.7 W.cm-2.Sr-1 and 21.0 W.cm-2.Sr-1 with the size of Mg-Al particles are 20 μm and 120 μm, respectively) at 60 wt% Mg-Al alloy. Finally, the Mg-Al/PTFE/Viton composition has a similar combustion and emission characteristics as the Mg/PTFE/Viton composition

Obscurant and Radiation Characteristics of Infrared Screening Smoke Composition Based on Red Phosphorus

Red phosphorus-based camouflage compositions are often used on naval ships to counter anti-ship missiles. This work focused on investigating the obscurant and infrared radiation characteristics of infrared-screening smoke of pyrotechnic compositions based on red phosphorus, Mg-Al alloy, barium nitrate and Viton A rubber. The results demonstrated that the smoke clouds of the formulation based on red phosphorus and Mg-Al alloy have a high attenuation capability to 1.064 µm laser radiation. Besides, these smokescreens also have a better emission power in the wavelength range of 2.5-5 and 8-14 µm. Therefore, the smoke compositions based on red phosphorus and Mg-Al alloy can be used in camouflage devices on naval ships against infrared and laser-guided missiles

How scientific research changes the Vietnamese higher education landscape: Evidence from social sciences and humanities between 2008 and 2019

Background: In the context of globalization, Vietnamese universities, whose primary function is teaching, there is a need to improve research performance. Methods: Based on SSHPA data, an exclusive database of Vietnamese social sciences and humanities researchers’ productivity, between 2008 and 2019 period, this study analyzes the research output of Vietnamese universities in the field of social sciences and humanities. Results: Vietnamese universities have been steadily producing a high volume of publications in the 2008-2019 period, with a peak of 598 articles in 2019. Moreover, many private universities and institutions are also joining the publication race, pushing competitiveness in the country. Conclusions: Solutions to improve both quantity and quality of Vietnamese universities’ research practice in the context of the industrial revolution 4.0 could be applying international criteria in Vietnamese higher education, developing scientific and critical thinking for general and STEM education, and promoting science communication

Invited; Microfabrication of BiTeSb thermoelectric devices for applications to IoT sensors

In this study, thermoelectric power generation devices and an energy harvesting system to generate electricity from a low-quality heat source or environmental temperature fluctuation near room temperature are developed. Thermoelectric power generators (TEG) composed of Bi2Te3-Sb2Te3 with metal nanoparticles are microfabricated using electrodeposition of the thermoelectric materials and microfabrication technology (Figs 1 and 2). Using the fabricated TEG, the temperature-fluctuation thermoelectric power generation (TF-TEG) unit is developed. As shown in Fig. 3, a heat storage material (phase change material: PCM) was contacted to one side of the thermoelectric element, and the other side was made to exchange heat with the outside air. Please click Download on the upper right corner to see the full abstract

Thermoresistance of p-Type 4H–SiC Integrated MEMS Devices for High-Temperature Sensing

There is an increasing demand for the development and integration of multifunctional sensing modules into power electronic devices that can operate in high temperature environments. Here, the authors demonstrate the tunable thermoresistance of p‐type 4H–SiC for a wide temperature range from the room temperature to above 800 K with integrated flow sensing functionality into a single power electronic chip. The electrical resistance of p‐type 4H–SiC is found to exponentially decrease with increasing temperature to a threshold temperature of 536 K. The temperature coefficient of resistance (TCR) shows a large and negative value from −2100 to −7600 ppm K−1, corresponding to a thermal index of 625 K. From the threshold temperature of 536–846 K, the electrical resistance shows excellent linearity with a positive TCR value of 900 ppm K−1. The authors successfully demonstrate the integration of p–4H–SiC flow sensing functionality with a high sensitivity of 1.035 μA(m s−1)−0.5 mW−1. These insights in the electrical transport of p–4H–SiC aid to improve the performance of p–4H–SiC integrated temperature and flow sensing systems, as well as the design consideration and integration of thermal sensors into 4H–SiC power electronic systems operating at high temperatures of up to 846 K

Rice monitoring using ENVISAT-ASAR data: preliminary results of a case study in the Mekong River Delta, Vietnam

Vietnam is one of the world’s largest rice exporting countries, and the fertile Mekong River Delta at the southern tip of Vietnam accounts for more than half of the country’s rice production. Unfortunately, a large part of rice crop growing time coincides with a rainy season, resulting in a limited number of cloud-free optical remote sensing images for rice monitoring. Synthetic aperture radar (SAR) data allows for observations independent of weather conditions and solar illumination, and is potentially well suited for rice crop monitoring. The aim of the study was to apply new generation Envisat ASAR data with dual polarization (HH and VV) to rice cropping system mapping and monitoring in An Giang province, Mekong River Delta. Several sample areas were established on the ground, where selected rice parameters (e.g. rice height and biomass) are periodically being measured over a period of 12 months. A correlation analysis of rice parameters and radar imagery values is then being conducted to determine the significance and magnitude of the relationships. This paper describes a review of the previous research studies on rice monitoring using SAR data, the context of this on-going study, and some preliminary results that provide insights on how ASAR imagery could be useful for rice crop monitoring. More work is being done to develop algorithms for mapping and monitoring rice cropping systems, and to validate a rice yield prediction model for one year cycle using time-series SAR imagery

Transformer-Based Deep Learning Detector for Dual-Mode Index Modulation 3D-OFDM

In this paper, we propose a deep learning-based signal detector called TransD3D-IM, which employs the Transformer framework for signal detection in the Dual-mode index modulation-aided three-dimensional (3D) orthogonal frequency division multiplexing (DM-IM-3D-OFDM) system. In this system, the data bits are conveyed using dual-mode 3D constellation symbols and active subcarrier indices. As a result, this method exhibits significantly higher transmission reliability than current IM-based models with traditional maximum likelihood (ML) detection. Nevertheless, the ML detector suffers from high computational complexity, particularly when the parameters of the system are large. Even the complexity of the Log-Likelihood Ratio algorithm, known as a low-complexity detector for signal detection in the DM-IM-3D-OFDM system, is also not impressive enough. To overcome this limitation, our proposal applies a deep neural network at the receiver, utilizing the Transformer framework for signal detection of DM-IM-3D-OFDM system in Rayleigh fading channel. Simulation results demonstrate that our detector attains to approach performance compared to the model-based receiver. Furthermore, TransD3D-IM exhibits more robustness than the existing deep learning-based detector while considerably reducing runtime complexity in comparison with the benchmarks

Deep Neural Network-Based Detector for Single-Carrier Index Modulation NOMA

In this paper, a deep neural network (DNN)-based detector for an uplink single-carrier index modulation nonorthogonal multiple access (SC-IM-NOMA) system is proposed, where SC-IM-NOMA allows users to use the same set of subcarriers for transmitting their data modulated by the sub-carrier index modulation technique. More particularly, users of SC-IMNOMA simultaneously transmit their SC-IM data at different power levels which are then exploited by their receivers to perform successive interference cancellation (SIC) multi-user detection. The existing detectors designed for SC-IM-NOMA, such as the joint maximum-likelihood (JML) detector and the maximum likelihood SIC-based (ML-SIC) detector, suffer from high computational complexity. To address this issue, we propose a DNN-based detector whose structure relies on the model-based SIC for jointly detecting both M-ary symbols and index bits of all users after trained with sufficient simulated data. The simulation results demonstrate that the proposed DNN-based detector attains near-optimal error performance and significantly reduced runtime complexity in comparison with the existing hand-crafted detectors

Recent progress in angle-insensitive narrowband and broadband metamaterial absorbers

Recent progress in angle-insensitive narrowband and broadband metamaterial absorbers is presented herein. Initially, a few narrowband structures are described along with their absorption mechanisms. A bandwidth-enhanced absorber, conceptually derived from the existing narrowband geometry, is also discussed. Finally, several broadband absorbers having wide absorption bandwidths across different microwave frequency ranges are illustrated. The reported structures are primarily designed to exhibit high angularly stable responses suitable for practical applications. Furthermore, their geometries are fourfold symmetric, thereby displaying polarization-independent characteristics. Experimental verifications of the designed absorbers have been confirmed under normal and oblique incidences. The angle insensitivity, polarization independence, flexible absorption bandwidths (from narrowband to broadband), and commercial feasibility of the reported structures might establish them as potential candidates for manifold absorber applications

CHARACTERIZATION AND ADSORPTION CAPACITY OF AMINE-SIO2 MATERIAL FOR NITRATE AND PHOSPHATE REMOVAL

Amine-SiO2 material was synthesized and applied as a novel adsorbent for nitrate and phosphate removal from aqueous solution. The characterization of Amine-SiO2 were done by using TGA, FTIR, BET, and SEM analyses. Results showed that Amine-SiO2 had higher nitrate and phosphate adsorption capacity of 1.14 and 4.16 times, respectively, than commercial anion exchange resin (Akualite A420). In addition, Amine-SiO2 also had good durability with stable performance after at least 10 regeneration times, indicating that this material is very promising for commercialization in the future as an adsorbent for water treatment