Ministry of Science and Technology, Vietnam最新文献_第10页

Advanced magnetocaloric microwires: What does the future hold? 先进的磁性微丝：未来会怎样？

Ministry of Science and Technology, Vietnam Pub Date : 2023-12-14 DOI: 10.31276/VJSTE.65(4).14-24

Hong-Xian Shen, N.T.M. Duc, H. Belliveau, Lin Luo, Yunfei Wang, Jian-Fei Sun, Faxiang Qin, M. Phan

{"title":"Advanced magnetocaloric microwires: What does the future hold?","authors":"Hong-Xian Shen, N.T.M. Duc, H. Belliveau, Lin Luo, Yunfei Wang, Jian-Fei Sun, Faxiang Qin, M. Phan","doi":"10.31276/VJSTE.65(4).14-24","DOIUrl":"https://doi.org/10.31276/VJSTE.65(4).14-24","url":null,"abstract":"Magnetic refrigeration (MR) based on the magnetocaloric effect (MCE) is a promising alternative to conventional vapor compression refrigeration techniques. The cooling efficiency of a magnetic refrigerator depends on its refrigeration capacity and operation frequency. Existing refrigerators possess limited cooling efficiency due to the low operating frequency (around tens of Hz). Theory predicts that reducing geometrical effects can increase the operation frequency by reducing the relaxation time of a magnetic material. As compared to other shapes, magnetocaloric wires transfer heat most effectively to a surrounding environment, due to their enhanced surface area. The wire shape also yields a good mechanical response, reducing the relaxation time and consequently increasing the operation frequency of the cooling device. Experiments have validated the theoretical predictions. By assembling microwires with different magnetocaloric properties and Curie temperatures into a laminate structure, a table-like magnetocaloric bed can be created and used as an active cooling device for micro-electro-mechanical system (MEMS) and nano-electro-mechanical system (NEMS). This paper assesses recent progress in the development of magnetocaloric microwires and sheds light on the important factors affecting the magnetocaloric behavior and cooling efficiency in microwire systems. Challenges, opportunities, and strategies regarding the development of advanced magnetocaloric microwires are also discussed.","PeriodicalId":18650,"journal":{"name":"Ministry of Science and Technology, Vietnam","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139001319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

One-dimensional numerical model of landslide over high-steep slopes: Theory and verification to the analytical solution 高陡边坡滑坡的一维数值模型：理论和对解析解的验证

Ministry of Science and Technology, Vietnam Pub Date : 2023-11-25 DOI: 10.31276/vjst.65(11).42-46

Van Khoi Pham, V. N. Vu

{"title":"One-dimensional numerical model of landslide over high-steep slopes: Theory and verification to the analytical solution","authors":"Van Khoi Pham, V. N. Vu","doi":"10.31276/vjst.65(11).42-46","DOIUrl":"https://doi.org/10.31276/vjst.65(11).42-46","url":null,"abstract":"At the steep slope areas, landslide events may suddenly occur due to prolonged heavy rain and seriously affect humans’ lives and their properties. Numerical models simulating landslides help us to predict the real landslide phenomenon effectively because they are not only time-saving compared to physical models but also acceptable accuracy. In this paper, the one-dimensional nonlinear shallow water equations using the global coordinate system are established as the proposed model governing equations. The hybrid finite difference-finite volume method, the implicit method and the automatical time step controlling technique are employed to stably simulate the landslide events over the high-steep slopes. To validate the proposed numerical model to the analytical solution, authors continuously derive the non-dimensional governing equations in one dimension as well as using the global coordinate system. The numerical results are in good agreement with the analytical solution. The proposed numerical model can be used to simulate the landslides and the landslide-induced tsunami events, especially for simulating the high-steep slope conditions.","PeriodicalId":18650,"journal":{"name":"Ministry of Science and Technology, Vietnam","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139238004","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Graphene thermally modified with polyvinyl alcohol applied as conductive water-based paints based on polyurethane 聚乙烯醇热修饰石墨烯用作基于聚氨酯的导电水基涂料

Ministry of Science and Technology, Vietnam Pub Date : 2023-11-25 DOI: 10.31276/vjst.65(11).37-41

Ngoc Diep Le, Thi Kim Oanh Nguyen, Ho Phuong Thao Le, Duy Linh Nguyen, M. Dang, D. Doan

{"title":"Graphene thermally modified with polyvinyl alcohol applied as conductive water-based paints based on polyurethane","authors":"Ngoc Diep Le, Thi Kim Oanh Nguyen, Ho Phuong Thao Le, Duy Linh Nguyen, M. Dang, D. Doan","doi":"10.31276/vjst.65(11).37-41","DOIUrl":"https://doi.org/10.31276/vjst.65(11).37-41","url":null,"abstract":"This paper presents the fabrication of thermally reduced graphene modified with polyvinyl alcohol (PVA), which can be used as a conductive water-based paint based on polyurethane (PU). Graphite oxide (GO) was oxidised from graphite by the Hummer method, and then graphene was formed by the thermal-reducing GO method. The graphene was modified by dispersing it into a PVA solution with various concentrations and mass ratios to optimise the modification process. The graphene modified with PVA could be easily dispersed in water. Water-borne PU film-forming polymer was prepared by polymerisation reaction between isophorone diisocyanate with poly(tetramethylene glycol) and dimethylolpropionic acid. The carboxylate functional groups on the surface of the polymer particles make the polymer particles dispersed well and stable in water, so this polymerisation process does not use any surfactants. The characterisation methods included field emission scanning electron microscope with energy-dispersive X-ray spectroscopy (FESEM-EDX), specific surface area measurement, Raman microspectroscopy, resistance measurement... The graphene-based conductive paint has good adhesion, conductivity of the dry paint film was from 0.1-4 mS/cm with graphene content in the dry paint film was about 5-10 wt%.","PeriodicalId":18650,"journal":{"name":"Ministry of Science and Technology, Vietnam","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139236740","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Characteristics of iron-manganese nodules containing nickel and cobalt in chromite deposits in Co Dinh, Thanh Hoa province 清化省高定铬铁矿床中含镍和钴的铁锰结核的特征

Ministry of Science and Technology, Vietnam Pub Date : 2023-11-25 DOI: 10.31276/vjst.65(11).23-31

Tien Dung Le, Van Duc Tran, Huu Trong Nguyen, Khac Giang Nguyen, Xuan Ban To, Thi Ly Ly Nguyen

{"title":"Characteristics of iron-manganese nodules containing nickel and cobalt in chromite deposits in Co Dinh, Thanh Hoa province","authors":"Tien Dung Le, Van Duc Tran, Huu Trong Nguyen, Khac Giang Nguyen, Xuan Ban To, Thi Ly Ly Nguyen","doi":"10.31276/vjst.65(11).23-31","DOIUrl":"https://doi.org/10.31276/vjst.65(11).23-31","url":null,"abstract":"Along with the chromite ore bodies, very early on, geologists recorded the presence of cobalt (Co) and nickel (Ni) metal. The resource of cobalt and nickel is forecasted with over 3 million tons of Ni and over 260 thousand tons of Co metals. Until now, however, knowledge about the existence form and distribution of Ni and Co in chromite ore bodies is very limited. Researching the sludge in the chromite mines and in comparison with manganese nodules found in the ocean floor helps to detect the presence of particles of iron and manganese (Fe-Mn nodules) in granular sewage sludges and in primary chromite ore bodies. Fe-Mn hydroxides, including todorokite mineral, are believed to be the adsorption medium and forming of Ni and Co in the Co Dinh placer chromite. Determining the existence form and distribution of Ni and Co in chromite placer deposits has scientific and practical significance in sampling orientation, sample processing, geological exploration, and reserve and resource estimations, sorting and recovering technology of Co and Ni metals.","PeriodicalId":18650,"journal":{"name":"Ministry of Science and Technology, Vietnam","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139237120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effect of the Ce3+ concentration on the crystallite structure and optical properties of ZnO nanomaterials synthesised by sol-gel method Ce3+ 浓度对溶胶-凝胶法合成的氧化锌纳米材料晶粒结构和光学特性的影响

Ministry of Science and Technology, Vietnam Pub Date : 2023-11-25 DOI: 10.31276/vjst.65(11).63-68

Thi Bich Hop Dang, Van Cuong Nguyen, Quoc Thuan Hoang, Tien Ha Le, Van Quang Nguyen, Thi Lan Huong Pham

{"title":"Effect of the Ce3+ concentration on the crystallite structure and optical properties of ZnO nanomaterials synthesised by sol-gel method","authors":"Thi Bich Hop Dang, Van Cuong Nguyen, Quoc Thuan Hoang, Tien Ha Le, Van Quang Nguyen, Thi Lan Huong Pham","doi":"10.31276/vjst.65(11).63-68","DOIUrl":"https://doi.org/10.31276/vjst.65(11).63-68","url":null,"abstract":"In this study, Ce3+-doped ZnO nanomaterials (Zn1-xO:xCe3+ NPs) were synthesised using the sol-gel method. X-ray diffraction (XRD) pattern and Raman spectra analysis showed that at 1% doping concentration, Zn2+ ions were replaced with Ce3+ ions in the ZnO lattice. However, at higher concentrations (3 and 5%), the CeO2 phase was formed, preventing the diffusion process of Ce3+ ions into the lattice. Field emission scanning electron microscopy (FESEM) images showed that the obtained material had a particle size of several tens of nanometers. X-ray energy dispersive (EDS) spectroscopy and EDS mapping spectra revealed that the synthesised Zn1-xO:xCe3+ NPs had high purity and the Ce element was uniformly distributed in the sample. UV-Vis spectroscopy confirmed the strong interaction between Ce3+ ions and ZnO lattice, leading to increased light absorption in the visible region. The photoluminescence (PL) spectrum of ZnO showed two emission regions peaking at 389 and 650 nm, attributed to band to band recombination and defect types of ZnO such as oxygen vacancy (Vo) and/or oxygen interstitial (Oi), respectively. In comparison with ZnO, the PL spectrum of Zn1-xOx:Ce3+ (x=1-5) samples showed that the visible region emission appeared at new peak at 580 nm originating to the 3d → 4f transition of Ce3+ ions. As the doping concentration increased gradually from 1 to 5%, the 580 nm peak intensity increased, and the 389 peak intensity decreased significantly, indicating that Ce3+ ions inhibited the NBE recombination process of ZnO. This study suggested that Ce3+ doped ZnO NPs have a great potential for application in visible-light photocatalysis.","PeriodicalId":18650,"journal":{"name":"Ministry of Science and Technology, Vietnam","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139237906","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Study on the influence of some factors on the high burning rate of energy-carrying materials based on acrylonitrile butadiene rubber with end-chain carboxyl group 研究某些因素对带有端链羧基的丙烯腈丁二烯橡胶载能材料高燃烧率的影响

Ministry of Science and Technology, Vietnam Pub Date : 2023-11-25 DOI: 10.31276/vjst.65(11).06-10

Duc-Long Nguyen, Van Hung Nguyen, Huu-Thanh Tran, Van Diep Doan, Van Hung Hoang

{"title":"Study on the influence of some factors on the high burning rate of energy-carrying materials based on acrylonitrile butadiene rubber with end-chain carboxyl group","authors":"Duc-Long Nguyen, Van Hung Nguyen, Huu-Thanh Tran, Van Diep Doan, Van Hung Hoang","doi":"10.31276/vjst.65(11).06-10","DOIUrl":"https://doi.org/10.31276/vjst.65(11).06-10","url":null,"abstract":"Heterogeneous energy-carrying materials possess outstanding advantages compared to other energy-carrying materials, therefore, research and development of this type of material to create propulsion for flying objects is an inevitable trend in the field of military science and space. This paper presents the results of research on the influence of a number of factors on the technological properties and combustion rate of heterogeneous energy-carrying materials based on acrylonitrile butadiene rubber CKH-10KTP and ammonium perchlorate (AP).The research results show that the combustion law depends on the pressure of heterogeneous energy-carrying materials based on CKH-10KTP and ultra-fine AP (specific surface area 2.61÷3.85 m2/g), using a combustion catalyst ferrocene derivative. The study also determined the optimal content of combustion catalyst - plasticiser to be 3.5÷3.8%. The research results are a solid scientific basis for optimally determining the parameters of radioactivity, energy of energy-carrying materials, supplementing the national data source in the design of aircraft engines, meeting requirements in the new context.","PeriodicalId":18650,"journal":{"name":"Ministry of Science and Technology, Vietnam","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139238241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Fabrication and properties of Fe3O4/C composite materials Fe3O4/C 复合材料的制作与性能

Ministry of Science and Technology, Vietnam Pub Date : 2023-11-25 DOI: 10.31276/vjst.65(11).52-56

T. Bui, Ha Thang Doan

引用次数: 0

Development of a tunable, narrow, and ultraviolet Ce:LiCAF crystal multipass laser amplifier for environmental application 开发用于环境应用的可调谐窄紫外 Ce:LiCAF 晶体多通道激光放大器

Ministry of Science and Technology, Vietnam Pub Date : 2023-11-25 DOI: 10.31276/vjst.65(11).01-05

Van Diep Nguyen, Xuan Tu Nguyen, Van Duong Pham, Thi Khanh Van Nguyen, Van Minh Nguyen, Van Thu Vu, Hong Minh Pham

引用次数: 0

Mathematical model for the calculation of life cycle cost of the Kamaz truck 计算卡玛兹卡车生命周期成本的数学模型

Ministry of Science and Technology, Vietnam Pub Date : 2023-11-25 DOI: 10.31276/vjst.65(11).69-72

Ngoc Tuan Vu, Trung Kien Nguyen, Dinh-Son Le, Van-An Tran, Anh-Tuan Phung, Thanh Duong Nguyen

引用次数: 0

Load-current demand forecasting in substations of urban railway lines 城市铁路变电站的负荷-电流需求预测

Ministry of Science and Technology, Vietnam Pub Date : 2023-11-25 DOI: 10.31276/vjst.65(11).47-51

Van Khoi Tran

{"title":"Load-current demand forecasting in substations of urban railway lines","authors":"Van Khoi Tran","doi":"10.31276/vjst.65(11).47-51","DOIUrl":"https://doi.org/10.31276/vjst.65(11).47-51","url":null,"abstract":"Load-current forecasting is important in the operation and energy management of urban railway lines. It helps control strategies to manage and distribute energy optimally, thereby saving energy and reducing voltage fluctuations. This paper presents a method to predict the traction current at the busbar of a substation using the supervised machine learning algorithm. Because the traction power load is supplied from both adjacent traction power stations, and the energy exchange process between trains also takes place during work, the input data are selected to combine the value history of busbar currents and feeder currents. Besides, the neural network configuration and the number of training cycles in the estimated model can be adjusted to achieve the desired accuracy. The proposed method was tested and adjusted based on the actual operation data at the Lang traction station on 24 June, 2022. The estimated results compared with measurement data from the supervisory control and data acquisition (SCADA) have proven that the largest absolute error is no more than 5 (A). The maximum relative error is not more than 0.005, and the mean squared error does not exceed 0.01 over the whole operating time of a day from 4h45 to 22h45.","PeriodicalId":18650,"journal":{"name":"Ministry of Science and Technology, Vietnam","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139236678","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0