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  • Viet Nam National University Ho Chi Minh City  (7)
  • 1
    Online Resource
    Online Resource
    Analysis and simulation of a single buoy mooring system based on sea environment
    Viet Nam National University Ho Chi Minh City ; 2014
    In:  Science and Technology Development Journal Vol. 17, No. 3 ( 2014-09-30), p. 146-155
    Details
    In: Science and Technology Development Journal, Viet Nam National University Ho Chi Minh City, Vol. 17, No. 3 ( 2014-09-30), p. 146-155
    Abstract: Single Point Mooring (SPM) is of great use to offshore floating structures which are currently in use in Vietnam’s coastal waters. However, this country is facing the lack of the related guidelines and standards for analysis, simulation and design of SPM system. This fact is the rationale for this paper which is aimed to propose a procedure for computation of the effects of sea environment on a SPM system. Specifically, the procedure enables the identification of maximum load exerting on the mooring buoy. Then, such identification together with the water depth parameter enables the determination of the optimal length and diameter of the desired chain. Finally, this paper presents a primary simulation of the mooring chain system according to various water depth conditions.
    Type of Medium: Online Resource
    ISSN: 1859-0128 , 1859-0128
    URL: Article
    DOI: 10.32508/stdj.v17i3.1496
    Language: Unknown
    Publisher: Viet Nam National University Ho Chi Minh City
    Publication Date: 2014
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  • 2
    Online Resource
    Online Resource
    Study on the effect of HMTA and ZnO seed layer on the morphology of ZnO nanorods synthesized by electrochemical method
    Viet Nam National University Ho Chi Minh City ; 2013
    In:  Science and Technology Development Journal Vol. 16, No. 4 ( 2013-12-31), p. 13-21
    Details
    In: Science and Technology Development Journal, Viet Nam National University Ho Chi Minh City, Vol. 16, No. 4 ( 2013-12-31), p. 13-21
    Abstract: In this paper we investigated the effect of Hexamethylenetetramine (HMTA, C6H12N4) concentration on the growth of ZnO nanorods on ITO substrates and the influence of the ZnO seed layer on its orientation growth. ZnO nanorods were synthesized by the two-step method of stable flow electrochemical method of saline solution Zn(NO3)2 at 90oC. As result, the high hexagonal crystalline ZnO nanorods were well oriented according to the (002) lattice network. The change of amperage and electrolysis time have show the effetive control of morphology and size of ZnO nanorods which has been studied by XRD and SEM images
    Type of Medium: Online Resource
    ISSN: 1859-0128 , 1859-0128
    URL: Article
    DOI: 10.32508/stdj.v16i4.1599
    Language: Unknown
    Publisher: Viet Nam National University Ho Chi Minh City
    Publication Date: 2013
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  • 3
    Online Resource
    Online Resource
    Identify soil acidification due to reclamation of coastal potential acid sulfate soils from shrimp farming activities in Can Gio, Ho Chi Minh City
    Viet Nam National University Ho Chi Minh City ; 2018
    In:  Science & Technology Development Journal - Science of The Earth & Environment Vol. 2, No. 1 ( 2018-12-30), p. 49-56
    Details
    In: Science & Technology Development Journal - Science of The Earth & Environment, Viet Nam National University Ho Chi Minh City, Vol. 2, No. 1 ( 2018-12-30), p. 49-56
    Abstract: Soil acidification is one of the top concerns of the coastal wetland areas. In recent decades, by reclamation of coastal potential acid sulfate soils for agricultural activities (rice field, shrimp farming,...), humans have caused soil acidification. pH and the presence of secondary iron minerals (hematite, goethite) and ferric iron minerals (jarosite, schwertmannite, copiapite) are considered as the indicators of acidic soil. This study is to rapidly detect acidic status of soil through identifying secondary iron minerals by characterized band ratios. Sentinel-2A data with B4/B2 and B11/B8 can determine iron oxides and ferric iron minerals. The identified spectral result of fallowed ponds on ratio images shows the correlation with measured pH and mineral composition data (XRD). This research promises applicability of used band rationing method as well as potential of Sentinel-2A data in monitoring soil acidification in coastal wetland areas.  
    Type of Medium: Online Resource
    ISSN: 2588-1078 , 2588-1078
    URL: Article
    DOI: 10.32508/stdjsee.v2i1.472
    Language: Unknown
    Publisher: Viet Nam National University Ho Chi Minh City
    Publication Date: 2018
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  • 4
    Online Resource
    Online Resource
    Synthesis of ZnO nanorods on ZnO/ITO seed layer by electrochemical method and its application in solar cell device
    Viet Nam National University Ho Chi Minh City ; 2013
    In:  Science and Technology Development Journal Vol. 16, No. 4 ( 2013-12-31), p. 5-12
    Details
    In: Science and Technology Development Journal, Viet Nam National University Ho Chi Minh City, Vol. 16, No. 4 ( 2013-12-31), p. 5-12
    Abstract: In this paper, we study on the effects of ZnO nanorods /seed ZnO on properties of hybrid solar cells. ZnO nanorods fabricated by electrochemical method of two-step stable flow of liquid Zn(NO3)2. 6H2O (0.005 M) and C6H12N4 (0.005 M). Morphology and optoelectronic properties of ZnO nanorods were studied by SEM images, UV-VIS transmission spectra, X-ray diffraction and photoluminescence spectrum. Elaboration of hybrid solar cells by inserting ZnO nanorods on organic photoactive layer of P3HT:PCBM and ITO, as result the solar cell conductivity performance is significantly improved. Experimental results show that ~ 1,392 mA/cm2 Jsc, Voc ~ 0.49 V, FF = 0.32, and PCE = 0.23%.
    Type of Medium: Online Resource
    ISSN: 1859-0128 , 1859-0128
    URL: Article
    DOI: 10.32508/stdj.v16i4.1598
    Language: Unknown
    Publisher: Viet Nam National University Ho Chi Minh City
    Publication Date: 2013
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  • 5
    Online Resource
    Online Resource
    Elaboration of Conductive Polymer thin films (P3HT/PCBM) by spin coating method – Application for hybrid organic solar cell
    Viet Nam National University Ho Chi Minh City ; 2014
    In:  Science and Technology Development Journal Vol. 17, No. 3 ( 2014-09-30), p. 30-40
    Details
    In: Science and Technology Development Journal, Viet Nam National University Ho Chi Minh City, Vol. 17, No. 3 ( 2014-09-30), p. 30-40
    Abstract: The nanostructured polymer-fullerene thin film is one of the most prominent materials to make the hybrid bulk heterojunction solar cell (BHJ) with high conversion efficiency. Especially when the blend of P3HT and PCBM was used as the donor and acceptor materials. The properties of P3HT and PCBM layer in solar cell has been much studied and considered as high performance systems. One of the important factors for the high performance device is the fabrication  of photo active layer with the appropriate thickness and morphology. In the ideal case, the intermolecular distance between the polymer and fullerene should be approximately 10-20 nm (the exciton diffusion distance) giving an area of extensive contact between the two phases. After the dissociation of carriers, the two polymer phases should create the path way for carriers to reach electrodes. But so far, this ideal configuration has not been published. In this work, we’ve elaborated the P3HT and PCBM photo active layers by spin coating methodon glass substrates covered ITO electrode. The rotational velocity was determined to get the necessary effective thickness of the polymer film. The annealing effect on structure, optical and electrical properties of the polymer thin film with different content of PCBM were also investigated. The experiments show the best device on electrode ITO has I-V characteristic as a photodiode and short circuit current (Isc) aboutmili-Ampere. These results demonstrate convincingly that polymer layers elaborated by spin coating method can result a good performance of the device.
    Type of Medium: Online Resource
    ISSN: 1859-0128 , 1859-0128
    URL: Article
    DOI: 10.32508/stdj.v17i3.1368
    Language: Unknown
    Publisher: Viet Nam National University Ho Chi Minh City
    Publication Date: 2014
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  • 6
    Online Resource
    Online Resource
    Investigation of methylene blue adsorption capacity of porous chitosan particles
    Viet Nam National University Ho Chi Minh City ; 2020
    In:  Science & Technology Development Journal - Engineering and Technology Vol. 2, No. SI2 ( 2020-07-06), p. First-
    Details
    In: Science & Technology Development Journal - Engineering and Technology, Viet Nam National University Ho Chi Minh City, Vol. 2, No. SI2 ( 2020-07-06), p. First-
    Abstract: Chitosan obtained from shrimp shells and SiO2 nanoparticles obtained from rice husk ash were used to synthesize chitosan - SiO2 composite materials. In order to obtain a porous chitosan adsorbent, the SiO2 particles in the chitosan - SiO2 composite material were removed with NaOH solution. With the orientation of applying adsorbent in wastewater treatment of textile industry, the ability of methylene blue adsorption of chitosan with porous structure has been investigated. Survey results show that chitosan has porous structure with good adsorption capacity of methylene blue. The adsorption capacity of materials depends on many factors such as: structure of particles; pH of adsorption medium and temperature. Adsorbent material is made of composite chitosan - SiO2 with the ratio of chitosan/SiO2 equal to 1/1 (w/w) with the best adsorption capacity. Materials with good adsorption capacity at pH = 6, at low pH, the adsorption capacity of the material is significantly reduced. Temperature has a great influence on the adsorption capacity of the material. The suitable temperature for adsorption of materials is 40 oC. With a higher temperature, the desorption process will be accelerated. This makes the adsorption capacity of the material decrease. The maximum methylene blue adsorption capacity of the material is determined about 7.25 mg/g after 40 minutes of adsorption time.
    Type of Medium: Online Resource
    ISSN: 2615-9872 , 2615-9872
    URL: Article
    DOI: 10.32508/stdjet.v2iSI2.467
    Language: Unknown
    Publisher: Viet Nam National University Ho Chi Minh City
    Publication Date: 2020
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  • 7
    Online Resource
    Online Resource
    Effect of hydrothermal treatment temperature on morphology of obtained calcium silicate from rice husk ash
    Viet Nam National University Ho Chi Minh City ; 2016
    In:  Science and Technology Development Journal Vol. 19, No. 3 ( 2016-09-30), p. 69-75
    Details
    In: Science and Technology Development Journal, Viet Nam National University Ho Chi Minh City, Vol. 19, No. 3 ( 2016-09-30), p. 69-75
    Abstract: This research report on the effect of hydrothermal treatment temperature on morphology of obtained calcium silicate from Vietnam Rice Husk Ash (VRHA). VRHA is collected at the Mekong Delta River, burn to obtain the active silica which can be used for further step. The obtained silica is hydrothermal treated in the present of Ca-source so that the Ca/Si molar ratio of 1.0 for different treatment temperature such as 110, 130, 150 and 180oC. XRD and SEM of samples before and after hydrothermal treatment confirm the present of nano-Calcium Silicate Hydrate (CSH) such as Tobermorite and Xonotlite. These CSH can be used as inorganic light weight thermal insulator application. The obtained calcium silicate after hydrothermal treatment at high temperature have leave-like crystal, and these crystal interlock together.
    Type of Medium: Online Resource
    ISSN: 1859-0128 , 1859-0128
    URL: Article
    DOI: 10.32508/stdj.v19i3.575
    Language: Unknown
    Publisher: Viet Nam National University Ho Chi Minh City
    Publication Date: 2016
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