ĐẶC TRƯNG QUANG PHỔ CỦA VẬT LIỆU Ca2Al2SiO7 ĐỒNG PHA TẠP Ce3+ VÀ Sm3+

Luminescent materials Ca2Al2SiO7 co-doped with Ce3+ and Sm3+ were prepared with the solid-state reaction method. The XRD diffraction patterns show that the samples have a single tetragonal phase structure. The luminescent spectra of Ca2Al2SiO7: Ce3+,Sm3+ phosphor have a broad band with a peak at 420 nm, characterizing the transition of the electronic configuration of Ce3+ ion and narrow lines peaked at about 563, 602, 645, and 712 nm, representing the transition of the Sm3+ ion. The energy transfer from Ce3+ to Sm3+ was presented and discussed.Vật liệu phát quang Ca2Al2SiO7 đồng pha tạp Ce3+ và Sm3+ được chế tạo bằng phương pháp phản ứng pha rắn. Giản đồ nhiễu xạ tia X cho thấy vật liệu có cấu trúc pha tứ giác. Phổ bức xạ của vật liệu Ca2Al2SiO7:Ce3+,Sm3+ gồm một dải rộng có cực đại bức xạ ở bước sóng 420 nm, đặc trưng cho chuyển dời của ion Ce3+ và các vạch hẹp ở bước sóng 563, 602, 645 và 712 nm đặc trưng cho chuyển dời của ion Sm3+. Hiện tượng truyền năng lượng từ ion Ce3+ sang ion Sm3+ cũng được trình bày và thảo luận

A Tracking Bracelet Device for Kids with Detachment Warning Function

In this paper, we design a tracking bracelet device for kids with novel function that can detect in real-time whether the device is still attached or not. The novel function in combined with setting of a safe zone yields an absolute tracking of thekid safety. A prototype is implemented achieving a small size of 60 x 60 x 25 mm. The test results demonstrate that the proposed device works very well with 100 % of exact warning when the kids are assumed in danger. Moreover, thanks to alow power consumption of about 64 mW in average, the device is expected to work continuously at least 18 hours

Characterizing the spatial distribution of coral reefs in the South-Central Coast region of Viet Nam using Planetscope imagery

This study aims to understand the spatial distribution of coral reefs in the central region of Viet Nam. We classified live coral cover in Son Tra Peninsula (ST) and Cu Lao Cham Island (CLC) in the South-Central Coast Region of Viet Nam using the Maximum Likelihood Classifier on 3 m Planetscope imagery. Confusion matrices and the accuracy of the classifier were assessed using field data (1,543 and 1,560 photographs in ST and CLC, respectively). The results showed that the reef’s width ranged from 30 to 300 m across the study site, and we were able to detect live coral cover across a depth gradient of 2 to 6 m below the sea surface. The overall accuracies of the classifier (the Kappa coefficient) were 76.78% (0.76) and 78.08% (0.78) for ST and CLC, respectively. We found that 60.25% of coral reefs in ST were unhealthy and the live coral cover was less than 50%, while 25.75% and 11.46% of those in CLC were in good and excellent conditions, respectively. This study demonstrates the feasibility of utilizing Planetscope imagery to monitor shallow coral reefs of small islands at a high spatial resolution of 3 m. The results of this study provide valuable information for coral reef protection and conservation

Research on lemongrass oil extraction technology: hydrodistillation, steam istillation, and microwave-assisted hydrodistillation

Nowaday, people's health issues are of particular interest and motivate them to focus on natural products from countless herbs and plants. Essential oil is one of the most remarkable natural substances. There are hundreds of essential oils and they contain a lot of aromatic compounds [1]. These aromatic compounds are widely used in many products in food, pharmaceuticals and cosmetics. Inside, Lemongrass (Cymbopogon citratus stapf) oil with mainly citral (neral and geranial) component has been considered an important component in the antibacterial, antifungal, antioxidant, antiseptic activities [2]

Research on Lemongrass Oil Extraction Technology (Hydrodistillation, Microwave-Assisted Hydrodistillation)

Microwave-assisted hydro-distillation (MAHD) is preferred to traditional extraction methods due to shorter extraction time, the inability of volatile components to be damaged or decomposed which in turn improve the efficiency and quality of essential oils. In this research, we investigated the parameters that affect the extraction of lemongrass oil process by MAHD method and compare with those of hydro-distillation (HD) method. Four parameters were identified which are: raw material size, raw material to water ratio, extraction time and microwave power. The results show that the optimum condition for determining the lemongrass essential oil content is 20 mm in the 90 min extraction time with a microwave power of 450 W at raw material to water ratio of 1:3 (g/mL). When compared to the HD method, we found that the yield lemongrass oil of MAHD method is 0.35% on 90 min and the yield of HD method is 0.2% on 360 min. The quality of oil samples at different extraction method was evaluated by determining their chemical constituents through GC-MS. The highest identified component is Citral with 93.28% for MAHD, while the HD was 83.85%. Therefore, MAHD method is highly efficient and shorten the time needed for the extraction of essential oils

Green technology to optimize the extraction process of turmeric (Curcuma longa L.) oils

Turmeric oil has many uses in the field of medicine and food. There are many methods of extracting essential oils from plants. However, every traditional method has limitation regarding the heat transfer, time or quality of the oil obtained. In this study, the combination of microwave extraction and response surface methodology are used to extract turmeric oil and optimize the factors that influence the extraction process. The results showed that optimal influencing factors such as the ratio of water to the raw materials were 2.99:1 (mL/g), the microwave power used at 456.60 (W) for the extraction time was 102.43 (min) for the essential oil yield of 0.95 (%) with 100 % reliability

Functionalizing multifunctional Fe3O4 nanoparticle-based biocompatible, magnetic and photoluminescent nanohybrids: preparation and characterization

A combination of ring-opening polymerization (ROP) and coordination chemistry methodology has been expanded for the synthesis of a multifunctional, biocompatible, magnetic, luminescent nanohybrid complex comprising magnetite (Fe3O4) nanoparticles (MNPs), poly(ε-caprolactone) (PCL) and europium ions (Eu3+). The structural and morphological characteristic of the nanohybrid intricate were studied by appropriate spectrum and physical researches. The superparamagnetic behaviour and unique Eu3+ fluorescence properties with a high emission intensity of MNP-PCL-Eu3+ were investigated via measurements with a superconducting quantum interference equipment magnetism and fluorescence spectroscopy