Vietnam Journal of Science and Technology

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Chemical constituents and anti-inflammatory effects of some stilbenoids from Dipterocarpus retusus fruits of Vietnam
Vietnam Journal of Science and Technology - Tập 59 Số 6 - Trang 724-733 - 2021
Ho Dac Hung, Doan Duy Tien, Nguyen Thi Ngoan, Ba Thi Duong, Do Quoc Viet, Pham Gia Dien, Bui Kim Anh, Do Huu Nghi
In this work, the crude MeOH extract of fruits of Dipterocarpus retusus Blume (Dipterocarpaceae) growing in Vietnam was prepared and studied. Five compounds: ε-viniferin, paucifloroside, ursolic acid, quercetin, and (+)-catechin, was isolated. The structures of these compounds were elucidated by spectroscopic methods. The extracts from fruits of D. retusus Blume by metanol and its some isolated st... hiện toàn bộ
#Dipterocarpus retusus Blume #fruit #ε-viniferin #paucifloroside #anti-inflammatory activity
Fully transparent metamaterial AMC backed CPW fed monopole antenna for IoT applications
Vietnam Journal of Science and Technology - Tập 59 Số 5 - Trang 623-633 - 2021
Cong Danh Bui, Arpan Desai, Thi Thanh Kieu Nguyen, Truong Khang Nguyen
In this paper, a fully transparent antenna comprising of an Artificial Magnetic Conductor (AMC) backed Co-planar Waveguide (CPW) fed dual-ring monopole is presented. The monopole antenna and AMC structure achieve transparency due to the use of AgHT-8 conductive oxide and Plexiglas substrate. Measured antenna performance shows an impedance bandwidth of 5.3 – 6 GHz (12.4%) in the U-NII-1 to U-NII-4 ... hiện toàn bộ
#Transparent antenna #monopole #AgHT #AMC #Plexiglas
Multi-band perfect absorption induced by breaking the symmetry of metamaterial structure
Vietnam Journal of Science and Technology - Tập 57 Số 4 - Trang 477-483 - 2019
Dinh Hong Tiep, Bui Son Tung, Bui Xuan Khuyen, Vu Dinh Lam
In this work, a multi-band metamaterial perfect absorber is demonstrated numerically and experimentally in the microwave region based on the breaking symmetry of geometrical structure. Initially, when the structure, which is designed in the X shape, is in the symmetric geometry, only one absorption peak is observed. By breaking the symmetry of structure, new absorption peaks emerge, leading to the... hiện toàn bộ
#metamaterial #perfect absorption #multi-band
On models with wobbling disk for brake squeal
Vietnam Journal of Science and Technology - Tập 59 Số 3 - Trang 357-367 - 2021
Tuan Nguyen Thai Minh, Nils Gräbner
Among many mathematical models of disk brakes for the explanation of brake squeal, models with wobbling disk have their own advantage over planar models. Applying a recently developed matrix form of Euler equations in rigid body dynamics, the equations establishment process can now be performed with almost all popular computing software. Furthermore, the presented models are more generalized in te... hiện toàn bộ
#5.4.1. #5.4.2.
Application of botanical pesticides in organic agriculture production: Potential and challenges
Vietnam Journal of Science and Technology - Tập 59 Số 6 - Trang 679-701 - 2021
Dao Huy Toan, Dao Van Hoang, Vu Dinh Hoang, Le Dang Quang, Tran Dai Lam
In the context of agricultural pest management, botanical pesticides are best suited for use in organic food (agricultural) production, due to their safety to humans and the environment compared to conventional pesticides. Compounds of plant origin can be highly effective, with diverse and multiple mechanisms of action, while having low toxicity towards non-target organisms. However, the large-sca... hiện toàn bộ
#botanical pesticides #plant disease #insects #weeds #phytopathogens
A critical review on wireless power transfer systems using metamaterials
Vietnam Journal of Science and Technology - Tập 60 Số 4 - Trang 587-613 - 2022
Pham Thanh Son, Bui Xuan Khuyen, Bui Son Tung, Le Thi Hong Hiep, Vu Dinh Lam
Recently, wireless power transfer (WPT) has been a topic of interest due to its attractive applications in modern life. Starting from Tesla’s idea about a century ago, WPT has developed tremendously and appeared in many of the most modern electronic devices. However, some WPT systems still have limitations such as short transmission distance, low transfer efficiency, and electromagnetic leakage. M... hiện toàn bộ
#Wireless power transfers #metamaterials #negative permeability #evanescent wave
A new flavanone glycoside with antimicrobial and cytotoxic activities from Camellia hakodae Ninh leaves
Vietnam Journal of Science and Technology - Tập 62 Số 4 - Trang 686-696 - 2024
Thi Thu Thuy Tran, Thanh Tuyen Nguyen, Gia Dien Pham, The Hung Nguyen, Thi Hanh Nguyen, Minh Tin Vu, Hong Ngoc Tran, Duc Tuan Cao, Quang Duong Pham
ABSTRACT – HCTN8: Camellia hakodae Ninh, belonging to the golden subgroup of Camellia (Theaceae), is a Camellia species native to Vietnam and primarily found in Tam Dao, Vinh Phuc province. This study aimed to isolate and identify the flavonoids from the leaves of Camellia hakodae Ninh. As a results, a new flavanone glycoside, named camehakonin A (1), was discovered alongside six known flavonoids ... hiện toàn bộ
Fuzzy sliding mode control of a structure based on hedge algebras containing input time delay
Vietnam Journal of Science and Technology - Tập 57 Số 4 - Trang 513-523 - 2019
Bui Hai Le, Le Tung Anh, Bui Van Binh, Nguyen Thai Tat Hoan
In this paper, the authors present the sliding mode control problem of a structure using hedge-algebras-based fuzzy controller considering the impact of time delay (de-sHAC). Controlled model is a structure subjected to earthquake excitations. Numerical simulations are implemented in order to show advantages of the proposed controller. Obtained results include: variation of maximum displacement an... hiện toàn bộ
#fuzzy control #sliding mode control #hedge algebras #input time delay
NGHIÊN CỨU TÍNH CHẤT ĐIỆN-TỪ CỦA HỆ VẬT LIỆU TỔ HỢP (1-x)La0,7Ca0,3MnO3 + xLa1,5Sr0,5NiO4
Vietnam Journal of Science and Technology - Tập 50 Số 4 - Trang 529 - 2017
Trần Đăng Thành, Nguyễn Thị Hà, Đỗ Hùng Mạnh, Phạm Thanh Phong, Vũ Đình Lãm, Lê Văn Hồng
Hệ vật  liệu  tổ hợp (1-x)La0,7Ca0,3MnO3 + xLa1,5Sr0,5NiO4  (0  x  0,4) được chế  tạo bằng phương pháp nghiền phản ứng kết hợp với ủ nhiệt. Khi tăng nồng độ pha điện môi La1,5Sr0,5NiO4 trong mẫu, nhiệt độ chuyển pha sắt từ - thuận từ hầu như không đổi (TC ~ 252 K) trong khi đó nhiệt độ chuyển pha kim loại - điện môi giảm từ 251 K với x = 0,0 xuống 65 K với x = 0,2. Khi  x ≥ 0,25, tính chất dẫn đ... hiện toàn bộ
Analyzing movement behavior of zebrafish in different sized confined areas
Vietnam Journal of Science and Technology - Tập 61 Số 6 - Trang 1080-1088 - 2023
Quach Kha Quang, Nguyen Quoc Anh
Movement behavior of zebrafish (Danio rerio) was analysed according to different sizes of observation arena (four sizes:and ). The observation arena was separated into corner, boundary and central areas based on experimental data. The results showed that the shapes of the corner, boundary and central areas were accordingly different in different sizes of the arena. Individuals stayed in the bounda... hiện toàn bộ
#Confined areas #Monitoring #Movement behavior #Zebrafish (Danio rerio)
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