Pub Date : 2023-12-14DOI: 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
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.
{"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":"13 17","pages":""},"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}
Pub Date : 2023-11-25DOI: 10.31276/vjst.65(11).42-46
Van Khoi Pham, V. N. Vu
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.
{"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":"42 5","pages":""},"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}
Pub Date : 2023-11-25DOI: 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
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%.
本文介绍了用聚乙烯醇（PVA）修饰的热还原石墨烯的制备方法，这种石墨烯可用作基于聚氨酯（PU）的导电水性涂料。采用 Hummer 法从石墨中氧化出氧化石墨（GO），然后用热还原 GO 法形成石墨烯。将石墨烯分散到不同浓度和质量比的 PVA 溶液中对其进行改性，以优化改性过程。用 PVA 修饰的石墨烯很容易分散在水中。异佛尔酮二异氰酸酯与聚（四甘醇）和二羟甲基丙酸发生聚合反应，制备出水性聚氨酯成膜聚合物。聚合物颗粒表面的羧酸官能团使聚合物颗粒在水中分散良好且稳定，因此这种聚合工艺不使用任何表面活性剂。表征方法包括场发射扫描电子显微镜与能量色散 X 射线光谱（FESEM-EDX）、比表面积测量、拉曼微光谱、电阻测量...石墨烯基导电涂料具有良好的附着力，干漆膜的导电率为 0.1-4 mS/cm，干漆膜中的石墨烯含量约为 5-10 wt%。
{"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":"394 1","pages":""},"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}
Pub Date : 2023-11-25DOI: 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
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.
除了铬铁矿体，地质学家很早就发现了钴（Co）和镍（Ni）金属。据预测，钴和镍的资源量分别为 300 多万吨镍金属和 26 万多吨钴金属。然而，迄今为止，有关铬铁矿体中镍和钴的存在形式和分布的知识非常有限。对铬铁矿矿井中的污泥进行研究，并与海底发现的锰结核进行比较，有助于发现颗粒状污水污泥和原生铬铁矿矿体中存在铁和锰颗粒（铁锰结核）。铁锰氢氧化物，包括沱沱矿，被认为是科定块状铬铁矿中镍（Ni）和钴（Co）的吸附介质和形成物。确定铬铁矿块矿床中 Ni 和 Co 的存在形式和分布，对取样定位、样品处理、地质勘探、储量和资源估算、Co 和 Ni 金属的分选和回收技术具有科学和现实意义。
{"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":"34 38","pages":""},"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}
Pub Date : 2023-11-25DOI: 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
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.
{"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":"23 10","pages":""},"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}
Pub Date : 2023-11-25DOI: 10.31276/vjst.65(11).06-10
Duc-Long Nguyen, Van Hung Nguyen, Huu-Thanh Tran, Van Diep Doan, Van Hung Hoang
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.
{"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":"21 1","pages":""},"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}
Pub Date : 2023-11-25DOI: 10.31276/vjst.65(11).52-56
T. Bui, Ha Thang Doan
Climate change is currently one of the most serious problems facing the world. In this study, Fe3O4 powder was used as electrode active material, nanocarbon was used as an additive to fabricate Fe3O4/C composites applying for energy storage systems. The size and morphology of iron oxide and nanocarbon were investigated by scanning electron microscopy. The effects of the additive, the content of the electrode components on the electrochemical properties of the Fe3O4/C composite electrode have been studied by cyclic voltammetry. The results showed that the content of the electrode components strongly affects the electrochemical characteristics of the electrode. The important role of the carbon additive in the Fe3O4/C composite electrode was confirmed: Nanocarbon increases the electrical conductivity of the electrode thereby enhancing the redox reaction rate of iron. The positive effect of the K2S additive in electrolyte was demonstrated by increased redox reaction rate of iron, improved cyclability of Fe3O4, reduced hydrogen evolution, and thus increased the discharge capacity of Fe3O4/C.
{"title":"Fabrication and properties of Fe3O4/C composite materials","authors":"T. Bui, Ha Thang Doan","doi":"10.31276/vjst.65(11).52-56","DOIUrl":"https://doi.org/10.31276/vjst.65(11).52-56","url":null,"abstract":"Climate change is currently one of the most serious problems facing the world. In this study, Fe3O4 powder was used as electrode active material, nanocarbon was used as an additive to fabricate Fe3O4/C composites applying for energy storage systems. The size and morphology of iron oxide and nanocarbon were investigated by scanning electron microscopy. The effects of the additive, the content of the electrode components on the electrochemical properties of the Fe3O4/C composite electrode have been studied by cyclic voltammetry. The results showed that the content of the electrode components strongly affects the electrochemical characteristics of the electrode. The important role of the carbon additive in the Fe3O4/C composite electrode was confirmed: Nanocarbon increases the electrical conductivity of the electrode thereby enhancing the redox reaction rate of iron. The positive effect of the K2S additive in electrolyte was demonstrated by increased redox reaction rate of iron, improved cyclability of Fe3O4, reduced hydrogen evolution, and thus increased the discharge capacity of Fe3O4/C.","PeriodicalId":18650,"journal":{"name":"Ministry of Science and Technology, Vietnam","volume":"34 40","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139237119","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}
Pub Date : 2023-11-25DOI: 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
In this paper, the authors present results on the development of both an oscillator and a 4-pass amplifier of ultraviolet and narrow linewidth pulses using a Ce:LiCAF crystal. By using a grating at one end of the laser cavity, the output laser wavelength of the laser can be tuned from 285 nm to 296 nm with a maximum output power of 8 mW at 288.5 nm. Moreover, amplification in a 4-pass amplifier of the Ce:LiCAF laser was investigated theoretically and experimentally. From the results, 49.0 mW amplified pulses can be obtained using a 4-pass amplifier with 7.0 mW power and 3.6 ns pulse duration at 288.5 nm injection, corresponding to an amplifier gain of 7. Furthermore, the angular scattering intensity of some common single-particle aerosols such as black carbon, brown carbon, and polluted water has been studied using the Ce:LiCAF laser. This result can serve as the basis for the multipass laser amplifier’s environmental application, particularly in identifying atmospheric particles.
{"title":"Development of a tunable, narrow, and ultraviolet Ce:LiCAF crystal multipass laser amplifier for environmental application","authors":"Van Diep Nguyen, Xuan Tu Nguyen, Van Duong Pham, Thi Khanh Van Nguyen, Van Minh Nguyen, Van Thu Vu, Hong Minh Pham","doi":"10.31276/vjst.65(11).01-05","DOIUrl":"https://doi.org/10.31276/vjst.65(11).01-05","url":null,"abstract":"In this paper, the authors present results on the development of both an oscillator and a 4-pass amplifier of ultraviolet and narrow linewidth pulses using a Ce:LiCAF crystal. By using a grating at one end of the laser cavity, the output laser wavelength of the laser can be tuned from 285 nm to 296 nm with a maximum output power of 8 mW at 288.5 nm. Moreover, amplification in a 4-pass amplifier of the Ce:LiCAF laser was investigated theoretically and experimentally. From the results, 49.0 mW amplified pulses can be obtained using a 4-pass amplifier with 7.0 mW power and 3.6 ns pulse duration at 288.5 nm injection, corresponding to an amplifier gain of 7. Furthermore, the angular scattering intensity of some common single-particle aerosols such as black carbon, brown carbon, and polluted water has been studied using the Ce:LiCAF laser. This result can serve as the basis for the multipass laser amplifier’s environmental application, particularly in identifying atmospheric particles.","PeriodicalId":18650,"journal":{"name":"Ministry of Science and Technology, Vietnam","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139236687","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}
Pub Date : 2023-11-25DOI: 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
Currently, research on life cycle and product life cycle management is of interest in many countries, especially for products of high complexity and long service life. One of the issues of product life cycle management is the calculation and determination of product life cycle costs. Calculating the product life cycle costs will allow managers and users to know the cost that needs to be spent on acquiring the product (purchase cost), as well as corrective maintenance cost, preventive maintenance cost, operation cost, disposal cost, and also indicates the economic efficiency of purchasing, operating and using this product.This paper presents the mathematical model allowing a truck’s life cycle cost calculation and performs calculations for a specific Kamaz 43119/43118 truck. The calculation results allow evaluation of the contribution level of the cost components in the product life cycle, thus allowing managers to build financial estimates for the life cycle stages and compare the calculated product life cycle costs with the types of products in suitable circulation.
{"title":"Mathematical model for the calculation of life cycle cost of the Kamaz truck","authors":"Ngoc Tuan Vu, Trung Kien Nguyen, Dinh-Son Le, Van-An Tran, Anh-Tuan Phung, Thanh Duong Nguyen","doi":"10.31276/vjst.65(11).69-72","DOIUrl":"https://doi.org/10.31276/vjst.65(11).69-72","url":null,"abstract":"Currently, research on life cycle and product life cycle management is of interest in many countries, especially for products of high complexity and long service life. One of the issues of product life cycle management is the calculation and determination of product life cycle costs. Calculating the product life cycle costs will allow managers and users to know the cost that needs to be spent on acquiring the product (purchase cost), as well as corrective maintenance cost, preventive maintenance cost, operation cost, disposal cost, and also indicates the economic efficiency of purchasing, operating and using this product.This paper presents the mathematical model allowing a truck’s life cycle cost calculation and performs calculations for a specific Kamaz 43119/43118 truck. The calculation results allow evaluation of the contribution level of the cost components in the product life cycle, thus allowing managers to build financial estimates for the life cycle stages and compare the calculated product life cycle costs with the types of products in suitable circulation.","PeriodicalId":18650,"journal":{"name":"Ministry of Science and Technology, Vietnam","volume":"30 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139237988","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}
Pub Date : 2023-11-25DOI: 10.31276/vjst.65(11).47-51
Van Khoi Tran
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.
{"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":"37 1","pages":""},"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}
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