Vietnam Journal of Science and Technology

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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.
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 flavon...... 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
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)
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
Xây dựng hệ thống rút trích các nội dung chính của văn bản khoa học tiếng Việt dựa trên cấu trúc
Vietnam Journal of Science and Technology - Tập 52 Số 3 - Trang 269-280 - 2014
Tạ Nguyễn, Vũ Đức Lung
Bài báo trình bày cách thức rút trích các câu có nội dung quan trọng trong các văn bản khoa học tiếng Việt dựa trên cấu trúc. Hệ thống rút trích được xây dựng dựa trên một quy trình chặt chẽ mà bài báo đề xuất với việc áp dụng nhiều phương pháp khác nhau trong việc tính toán độ quan trọng thông tin của câu. Kết quả thử nghiệm cho thấy kết hợp phương pháp độ đo cục bộ và toàn cục (TF.IDF) với cách ...... hiện toàn bộ
Estimating thermal stability of phosphated and phosphated sulfated mesoporous zirconia
Vietnam Journal of Science and Technology - Tập 54 Số 6 - Trang 748-754 - 2016
Phong Pham Van, Khanh Dieu Hong Nguyen
Mesoporous phosphated zirconia (m-PZ) and mesoporous phosphated sulfated zirconia (m-PSZ) were synthesized through condensation methods using Zr3(PO4)4 and Zr(SO4)2 as precursors respectively. The precursors, solvents with suitable molar or mass ratios were mixed at 100oC for 48 hours to obtain the mesoporous channels. An oxophosphate process was used to synthesize the m-PSZ material for improving...... hiện toàn bộ
#mesoporous #zirconia #oxophosphate #thermal stability
Methodological aspects for the study of nucleation and growth mechanisms of metals from deep eutectic solvents based on choline chloride
Vietnam Journal of Science and Technology - Tập 60 Số 3 - Trang 424-435 - 2022
Dao Vu Phuong Thao, Pham Thi Lanh, Chu Thi Xuan, Nguyen Van Hieu, Le Manh Tu
This paper presents a methodology for studying nucleation and growth mechanisms of metals onto a glassy carbon electrode in a deep eutectic solvent (DES), a mixture of choline chloride and urea at a molar ratio of 1:2. Characteristics and composition of Co(II) complexes formed with the DES were evaluated by means of UV-vis measurements, which confirmed the good stability of these species at room t...... hiện toàn bộ
#electronucleation and growth #physical mathematical model #deep eutectic solvent.
Synthesis of two new hydroximinosteroids from cholesterol and their biological evaluation
Vietnam Journal of Science and Technology - Tập 57 Số 5 - Trang 527-538 - 2019
Dinh Thi Ha, Baskar Salvaraja, Pham Quoc Long, Ngo Dai Quang, Do Huu Nghi, Lee Jae Wook, Tran Thi Thu Thuy
A simple and efficient synthesis of two new hydroximinosteroidal derivatives (11, 13) from cholesterol was described. The cytotoxicity of these compounds, their intermediates were evaluated on human cancer cell lines including Hep-G2, HeLa and T98G. Compound 13 presented a potent antiproliferative effect to T98G cancer cell at 2.9 mM of IC50. In addition, the antimicrobial assay showed that two ne...... hiện toàn bộ
#cholesterol #hydroximinosteroid #HeLa #HepG2 #T98G
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