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

The effects of ground vibration induced by construction activities of urban railways in Hanoi

Many construction activities such as pile driving, drilling, roadbed compaction, drilling and blasting tunnels can cause ground vibration, which affects buildings and people nearby. If the wave intensity is high while the distance to neighboring buildings is close, the presence of damage in buildings is inevitable. Determination of the vibration radius which can cause damage in surrounding structures regarding each source of vibration is a necessary requirement for planning, construction technology selection and design method. It can minimize risks to surrounding buildings. The content of this article presents the measurement method to accurately estimate the vibration level of the construction activities of Hanoi pilot urban railway line 3 passing the busy Kim Ma street, Hanoi. High sensitivity vibration accelerometers are gathered in lines from the vibration source. It is shown that predicting the radius of the impact of construction site vibrations to neighboring buildings is possible. If the level of vibration is high then measures can be taken to prevent damage caused by the construction of the Hanoi pilot urban railway line. From obtained results, some solutions are proposed to minimize and avoid possible negative impacts

Research and application of indirect monitoring methods for transport infrastructures to monitor and evaluate structural health

Currently, bridge constructions in Vietnam, as well as in the world, are regularly monitored and evaluated to ensure safety in the exploitation process and to prevent damage. The traditional method of monitoring by geodetic tools through monitoring cycles often brings results with significant errors, thus not really representing the performance of the structure and potential damages on it. Recently, to overcome the factors observed by geodetic methods, sensors are directly located on the construction to monitor the change of parameters, such as stress, deformation and vibrations. From that monitoring it is possible to assess the mining safety level of the structure through the data collected continuously from the sensors. However, the funding needs for each monitoring system and for each specific project may be very large, not to mention the need to spend a large amount of resources to maintain the monitoring system for many projects, including high prices from experts and exclusive distributors. Instead of using sensors and machines on constructions, the research and application of sensors placed on a vehicle that often passes on a traffic structure may present several benefits. In this case, the structures are indirectly monitored through equipment placed on vehicles moving along the structure. In this work, focus is given on researching and application of indirect monitoring methods by installing sensors on vehicles to identify frequency and evaluate bridge structures’ performance.The authors acknowledge the financial support of the project research “B2021-GHA04” of the Ministry of Education and Training Vietnam. This work is financed by national funds through FCT - Foundation for Science and Technology, under grant agreement [POCI-01-0247-FEDER-039555-UM.2.19] attributed to the 2nd author. This work was partly financed by FCT / MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB/04029/2020

Damage detection of structural based on indirect vibration measurement results combined with Artificial Neural Network

In Structural Health Monitoring (SHM), damage detection and maintenance are among the most critical factors. For surface damage, damage detection is simple and easy to perform. However, detecting and repairing is difficult for damage hidden deep in the structure. Using the structure's dynamic features, damage can be detected and repaired in time. With the development of sensor technology, indirect vibration measurement solutions give accurate results, minimizing errors by infinitely increasing the number of measurements. This solution offers a great opportunity to reduce the cost of structural health monitoring. Based on the large amount of data obtained from indirect monitoring, artificial intelligence technologies can be used to obtain a more comprehensive model of SHM. In this paper, the dynamic responses of the structure will be extracted and determined through a vehicle crossing the bridge. Based on the results of structural dynamic response, a finite element model is built and updated so that this model can represent the real structure. Damage cases will be analyzed and evaluated as input to train the Artificial neural network. The trained network can detect damage through regular health monitoring by indirect methods

Damage detection of structural based on indirect vibration measurement results combined with Artificial Neural Network

In Structural Health Monitoring (SHM), damage detection and maintenance are among the most critical factors. For surface damage, damage detection is simple and easy to perform. However, detecting and repairing is difficult for damage hidden deep in the structure. Using the structure's dynamic features, damage can be detected and repaired in time. With the development of sensor technology, indirect vibration measurement solutions give accurate results, minimizing errors by infinitely increasing the number of measurements. This solution offers a great opportunity to reduce the cost of structural health monitoring. Based on the large amount of data obtained from indirect monitoring, artificial intelligence technologies can be used to obtain a more comprehensive model of SHM. In this paper, the dynamic responses of the structure will be extracted and determined through a vehicle crossing the bridge. Based on the results of structural dynamic response, a finite element model is built and updated so that this model can represent the real structure. Damage cases will be analyzed and evaluated as input to train the Artificial neural network. The trained network can detect damage through regular health monitoring by indirect methods

Standardised patient study to assess tuberculosis case detection within the private pharmacy sector in Vietnam.

BACKGROUND: Of the estimated 10 million people affected by (TB) each year, one-third are never diagnosed. Delayed case detection within the private healthcare sector has been identified as a particular problem in some settings, leading to considerable morbidity, mortality and community transmission. Using unannounced standardised patient (SP) visits to the pharmacies, we aimed to evaluate the performance of private pharmacies in the detection and treatment of TB. METHODS: A cross-sectional study was undertaken at randomly selected private pharmacies within 40 districts of Vietnam. Trained actors implemented two standardised clinical scenarios of presumptive TB and presumptive multidrug-resistant TB (MDR-TB). Outcomes were the proportion of SPs referred for medical assessment and the proportion inappropriately receiving broad-spectrum antibiotics. Logistic regression evaluated predictors of SPs' referral. RESULTS: In total, 638 SP encounters were conducted, of which only 155 (24.3%) were referred for medical assessment; 511 (80·1%) were inappropriately offered antibiotics. A higher proportion of SPs were referred without having been given antibiotics if they had presumptive MDR-TB (68/320, 21.3%) versus presumptive TB (17/318, 5.3%; adjusted OR=4.8, 95% CI 2.9 to 7.8). Pharmacies offered antibiotics without a prescription to 89.9% of SPs with presumptive TB and 70.3% with presumptive MDR-TB, with no clear follow-up plan. CONCLUSIONS: Few SPs with presumptive TB were appropriately referred for medical assessment by private pharmacies. Interventions to improve appropriate TB referral within the private pharmacy sector are urgently required to reduce the number of undiagnosed TB cases in Vietnam and similar high-prevalence settings

Fabrication of TiC reinforced CoCrFeMnNi high-entropy alloy composite using high-pressure torsion

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Fabrication Route based on Powder Metallurgy to Obtain High Tensile Strength-Ductility Synergy in High-Entropy Alloy

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CÁC YẾU TỐ ẢNH HƯỞNG ĐẾN QUÁ TRÌNH CHẾ TẠO VẬT LIỆU CHITOSAN DẠNG HẠT VỚI CẤU TRÚC RỖNG

Chitosan has been widely used in biomedical fields due to its high biocompatibility. Especially, chitosan beads with hollow interior are gaining attention because they can absorb more drugs and release them in a sustained manner. Previous studies showed that the formation of chitosan hollow beads required organic solvents and toxic crosslinking reagents, which might limit their application in biological systems. Therefore, this study aims to fabricate chitosan beads with a core/shell structure by using simple ionic gelation in mild conditions. Chitosan synthesized from chitin was used in bead formation with sodium tripolyphosphate (STPP) as a crosslinking agent. Beads with the largest core diameter are obtained from a 2% (w/v) 205.6 kDa chitosan solution in 1% acetic acid at pH = 9 of the STPP solution.Chitosan được ứng dụng nhiều trong lĩnh vực y dược nhờ khả năng tương thích sinh học cao. Trong đó, vật liệu dạng hạt rỗng được quan tâm nghiên cứu nhờ hiệu suất hấp thụ thuốc cao và khả năng phóng thích thuốc ổn định trong thời gian dài. Các nghiên cứu trước đây cho thấy để tổng hợp hạt chitosan có cấu trúc rỗng người ta phải sử dụng dung môi hữu cơ và tác nhân tạo liên kết độc hại, làm ảnh hưởng đến tính an toàn sinh học của vật liệu. Vì vậy, mục tiêu của nghiên cứu này là chế tạo hạt chitosan với cấu trúc rỗng bằng phương pháp đơn giản và an toàn. Chitosan được tổng hợp từ chitin sau đó được đưa vào quá trình tạo hạt với tác nhân sodium tripolyphosphate (STPP). Kết quả cho thấy hạt với đường kính lỗ rỗng lớn nhất được tạo ra từ chitosan với khối lượng phân tử 205,6 kDa và nồng độ chitosan 2% (w/v) trong trong acetic acid 1% (v/v) tại pH = 9 của dung dịch STPP