Science and Technology Development Journal http://stdj.scienceandtechnology.com.vn/index.php/stdj <p><span id="result_box" class="" lang="en"><span title="Tạp chí Phát triển Khoa học và Công nghệ (PTKH&amp;CN) của Đại học Quốc gia thành phố Hồ Chí Minh (ĐHQG-HCM) được thành lập từ năm 1997, ra số đầu tiên vào tháng 1 năm 1998. Từ năm 2006 Tạp chí đã"><strong>Science and Technology Development Journal</strong> (STDJ), Vietnam National University - Ho Chi Minh City (VNU-HCM) was established in 1997. And the first issue was published in January 1998 with </span><span title="đăng ký mã số chuẩn quốc tế ISSN 1859-0128.">ISSN 1859-0128. </span><span title="Từ đó cho đến nay, Tạp chí PTKH&amp;CN đã trở thành diễn đàn khoa học quan trọng nhất của đội ngũ cán bộ nghiên cứu, giảng viên, nghiên cứu sinh của ĐHQG-HCM và cũng là diễn đàn khoa học công nghệ đáng tin cậy của">Since then, STDJ has become the most important scientific forum of scientists from VNU-HCM as well as</span><span title="nhiều nhà nghiên cứu, giảng viên các trường đại học khác tại Việt Nam."> other universities. </span><span title="Tạp chí đã trải qua 20 năm phát triển và đã trở thành nhịp cầu giao lưu khoa học, cũng như làm phong phú tài liệu tham khảo cho đội ngũ giảng viên, nghiên cứu sinh, sinh viên ĐHQG-HCM nói riêng và các Trường đại">The magazine has undergone 20 years of development and has become a bridge for scientific exchanges, as well as enriching reference materials for the faculty, doctoral students, students of VNU-HCM in particular and other universities, institutes... </span></span></p> <p><span id="result_box" class="" lang="en"><span title="học phía Nam nói chung. "><br></span><span title="Tính đến hết năm 2016 Tạp chí đã xuất bản được 276 số với 2714 bài nghiên cứu của các nhà khoa học, cán bộ trong và ngoài ĐHQG-HCM trong 5 lĩnh vực nghiên cứu: Kỹ thuật và Công nghệ, Khoa học Tự nhiên,">By the end of 2016, the journal has published 276 issues with 2714 research articles in five areas of research: Engineering and Technology, Natural Sciences, </span><span title="Khoa học Xã hội và Nhân văn, Kinh tế luật và Khoa học Quản lý, Khoa học Trái đất và Môi trường tương ứng với 5 chuyên san chuyên ngành của Tạp chí.">Social Sciences and Humanities, Economics of Law and Management Sciences, Earth Sciences and Environment corresponding to 5 specialized journals of the Journal. </span></span></p> <p><span id="result_box" class="" lang="en"><span title="Tạp chí đã được phát hành tại các thư viện của các đơn vị thành viên của ĐHQG-HCM, các Sở Khoa học Công nghệ của các tỉnh thành trên cả nước và được Hội đồng học hàm Giáo sư Nhà nước đánh giá cao.">The magazine has been widely indexed in the various libraries at Vietnam. </span></span></p> <p><span id="result_box" class="" lang="en"><span title="Từ tháng 12/2006 Tạp chí đã nhận được sự giúp đỡ của tổ chức mạng quốc tế về các xuất bản phẩm khoa học thuộc Hội đồng khoa học quốc tế để tham gia vào mạng lưới các Tạp chí Khoa học quốc tế. "><br></span><span title="Hiện nay tạp chí bao gồm 5 chuyên san sau đây: ">The journal currently consists of the following five sections:<br></span><span title="• Kỹ thuật và Công nghệ, ">• Engineering and Technology</span></span></p> <p><span id="result_box" class="" lang="en"><span title="• Khoa học Tự nhiên, ">• Natural Sciences</span></span></p> <p><span id="result_box" class="" lang="en"><span title="• Khoa học Xã hội và Nhân văn, ">• Social Sciences and Humanities</span></span></p> <p><span id="result_box" class="" lang="en"><span title="• Kinh tế luật và Khoa học Quản lý, ">• Economics, Law and Management</span></span></p> <p><span id="result_box" class="" lang="en"><span title="• Khoa học Trái đất và Môi trường">• Sciences of Earth and Environment</span></span></p> <p><span class="" lang="en"><span title="• Khoa học Trái đất và Môi trường"><span id="result_box" class="" lang="en">• Health Sciences : It includes work from basic science, clinical science, dental, nursing and other related medical fields. <br></span></span></span></p> Viet Nam National University Ho Chi Minh City en-US Science and Technology Development Journal 1859-0128 <p>Copyright The Author(s) 2018. This article is published with open access by Vietnam National University, Ho Chi Minh city, Vietnam. This article is distributed under the terms of the&nbsp;<a href="https://creativecommons.org/licenses/by/4.0/" target="_blank" rel="noopener">Creative Commons Attribution License (CC-BY 4.0)</a> which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.&nbsp;</p> Enthusiastic discussions on solid physic and material science at SPMS2019 http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/1768 <p>At 11<sup>th</sup> National Conference of Solid Physics and Material Science (SPMS2019), to which eminent scientists (5 plenary speakers and 16 invited speakers) were invited, most of the discussion focused on solid physic and material science. Around 300 researchers interested in the subject attended the conference and actively participate in the discussion. There were more than 200 reports with five specialized subcommittees: (A) Physics and magnetic materials, (B) Semiconductor and dielectric physics, (C) Materials - semiconductor components - dielectric, (D) Biomedical materials - agriculture, energy - environment, (E) Composite materials - metals - ceramics. Besides, numerous reports submitted to the Journal of Science and Technology (Vietnam Academy of Science and Technology), full-text reports sent to the Organizing Committee, after a critical review process, had been summarized and published in the Collection of conference reports.</p> <p>&nbsp;</p> Van-Duong Dao Duc Chien Nguyen Wiesław Stręk ##submission.copyrightStatement## http://creativecommons.org/licenses/by/4.0 2020-04-09 2020-04-09 23 2 490 498 10.32508/stdj.v23i2.1768 title description none g Improved error of electromagnetic shielding problems by a two-process coupling subproblem technique http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/2054 <p>Introduction: The direct application of the classcial finite element method for dealing with magnetodynamic problems consisting of thin regions is extremely difficult or even not possible.&nbsp; Many authors have been recently developed a thin shell model in order to overcome this drawback. However, this development generally neglects inaccuracies around edges and corners of thin shell, that lead to inaccuracies of the magnetic fields, eddy currents and joule power losses, specially increasing with the thickness.</p> <p>Methods: In this article, we propose a two-process coupling subproblem technique for improving the errors that overcome thin shell assumptions. This technique is&nbsp; based on the subproblem method to couple SPs in two-processes. The first scenario is an initial problem solved with coils/stranded inductors together with thin region models. The obtained solutions are then considered as volume sources for the second scenario including actual volume improvements that scope with the thin shell assumptions. The final solution is sum up of the subproblem solutions achieved from both the scenarios. The extended method is approached for the <em>h</em>-conformal magnetic formulation.</p> <p><strong>Results:</strong> The obtained results of the method are checked/compared to be close to the reference solutions computed from the classcial finite element method and the measured results. This can be pointed out a very good agreement.</p> <p><strong>Conclusion: </strong>The extended method has been also successfully applied to the practical problem (TEAM workshop problem 21, model B).</p> Vuong Quoc Dang ##submission.copyrightStatement## http://creativecommons.org/licenses/by/4.0 2020-05-18 2020-05-18 23 2 524 527 10.32508/stdj.v23i2.2054 title description none g An explicit topology optimization method using moving polygonal morphable voids (MPMVs) http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/2067 <p><strong>Introduction</strong>: Conventional topology optimization approaches are implemented in an implicit manner with a very large number of design variables, requiring large storage and computation costs. In this study, an explicit topology optimization approach is proposed by movonal morphable voids whose geometry parameters are considered as design variables.</p> <p><strong>Methods</strong>: Each polygonal void plays as an empty-material zone that can move, change its shapes, and overlap with its neighbors in a design space. The geometry eters of MPMVs consisting of the coordinates of polygonal vertices are utilized to render the structure in the design domain in an element density field. The density function of the elements located inside polygonal voids is described by a smooth exponential function that allows utilizing gradient-based optimization solvers.</p> <p><strong>Results &amp; Conclusion</strong>: Compared with conventional topology optimization approaches, the MPMV approach uses fewer design variables, ensure mesh-independence solution without filtering techniques or perimeter constraints. Several numerical examples are solved to validate the efficiency of the MPMV approach.</p> Hoang Van-Nam ##submission.copyrightStatement## http://creativecommons.org/licenses/by/4.0 2020-06-27 2020-06-27 23 2 536 540 10.32508/stdj.v23i2.2067 title description none g Factors affecting acrylamide mitigation in fried potatoes http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/1906 <p><strong>Introduction</strong>: Recent findings of acrylamide, a carcinogenic agent to humans, in foods have led to great efforts to elucidate the mechanisms of acrylamide formation and its mitigation. The acrylamide was generated during the browning process by the Maillard reaction of amino acid asparagine and reducing sugars at temperatures above 120 °C. Asparagine was determined to be a precursor of acrylamide formation. Therefore, asparagine reduction in raw materials can be taken into account to limit the acrylamide level in prepared foods. L-asparaginase has been used to consume acrylamide precursor by catalyzing the conversion of asparagine into aspartic acid and ammonia. Several factors including enzyme concentration, pH, temperature and frying time can influence the efficiency of acrylamide mitigation by enzyme. In the present work, we selected potatoes as raw materials to investigate the effects of factors on the acrylamide mitigation in fried potatoes.</p> <p><strong>Methods</strong>: By pre-treating potato strips in different conditions of enzyme concentrations, pH, temperature and frying time, the effects of these parameters on acrylamide levels in fried products were evaluated by measuring UV-Vis spectra of sample solutions containing acrylamide. The maximum absorbance values at 224 nm were used to determine the acrylamide concentrations by calculation from a calibration curve. Experimental data were statistically analyzed by one-way ANOVA. Colorspace measurements were performed to describe the differences in colors of the fried products after various frying times.</p> <p><strong>Results</strong>: A calibration curve was established to determine the acrylamide content of sample solutions via their maximum absorbance values. Pre-treatment of potato strips with a solution of 1.0 IU/mL asparaginase at 37 °C, pH 7.3, for 30 min led to a 45.6% reduction of acrylamide in French fries compared to a solution without enzyme. The optimum pH value for the most efficient enzyme activity was 7.3. Frying time ranging from 1.0 to 6.0 min increased acrylamide content and induced a darker appearance product.</p> <p><strong>Conclusions</strong>: By using UV-Vis measurements, we demonstrated the effects of factors on L-asparaginase based acrylamide mitigation in fried potatoes. The conditions which gave the lowest acrylamide concentrations were assessed. The results could be applicable for commercial processes to minimize acrylamide content in prepared potatoes.</p> Hoan Thi Pham Hao Minh Hoang ##submission.copyrightStatement## http://creativecommons.org/licenses/by/4.0 2020-06-30 2020-06-30 23 2 548 554 10.32508/stdj.v23i2.1906 title description none g Evaluation of low energy X-ray depth dose distribution by gafchromic film for dosimetry in food irradiation http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/1739 <p><strong>Introduction:</strong> Dosimetry is of crucial importance in radiation processing of food. Among others, plastic film has been widely used for dosimetry in radiation therapy since its density is quite similar to the equivalent biological materials. In this study, the depth dose distribution was estimated by using gafchromic film for the purpose of dosimetry in food irradiation.</p> <p><strong>Experimental</strong>: The HD-V2 gafchromic dosimetry film was employed to measure the interested dose instead of ion chamber. A stack of 19 PMMA (polymethyl methacrylate) sheets interleaved with 20 pieces of gafchromic film was made. The phantom was applied in the low energy X-ray beams (maximum 100 keV) to obtain the depth dose profile.</p> <p><strong>Results</strong>: A significant correlation between absorbed doses (D) and color level or optical density (O.D.) of irradiated dosimetry films was observed. The fitting function has the form of , where a, b, c are the parameters to be fitted. The depth dose distribution in the 30 mm thickness phantom was inferred from the calibration.</p> <p><strong>Conclusion:</strong> The present method and the depth dose profile to be obtained are very meaningful in the processing of foodstuffs by radiation.</p> Ngoc Hoang Van Huy Viet Le Son An Nguyen Kume Tamikazu ##submission.copyrightStatement## http://creativecommons.org/licenses/by/4.0 2020-05-09 2020-05-09 23 2 517 523 10.32508/stdj.v23i2.1739 title description none g Secretory expression of the recombinant FGF-2 protein in Pichia pastoris carrying multiple copies of target gene http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/1746 <p><strong>Introduction:</strong> Fibroblast growth factor-2 (FGF-2) is a multifunctional protein that plays an important role in the regulation of proliferation, differentiation and migration of a variety of cells. The recombinant human FGF-2 (rhFGF-2) is currently used in stem cell culture, medicine and cosmetic products. In this study, we aim to produce secreted rhFGF-2 protein from a <em>Pichia pastoris </em>strain containing multiple copies of the <em>fgf-2</em> gene to eliminate the disadvantages of intracellular expression systems.</p> <p><strong>Methods:</strong> The recombinant <em>Pichia pastoris</em> carrying the <em>fgf-2</em> gene was cloned by using homologous cloning method. The recombinant strains were screened by PCR reactions using specific primers for the target gene and the AOX1 promoter sequence. Moreover, the copy number of the <em>fgf-2 </em>gene inserted into the <em>P. pastoris</em> genome was identified by semi-quantitative PCR method. The secreted rhFGF-2 protein was collected in the induced BMMY medium at a final methanol concentration of 0.5%, and purified by one-step heparin affinity chromatography. The quantity and biological activity of the purified protein were determined by competitive ELISA method and MTT assay on NIH-3T3 cell line, respectively.</p> <p><strong>Results: </strong>Various recombinant <em>P. pastoris </em>clones carrying different copy numbers of the <em>fgf-2 </em>gene were obtained and categorized into 3 groups: the low copy strains (4-5 copies), medium copy strains (8-11 copies), and high copy strains (more than 20 copies). Among those strains, the 4-copy one produced the rhFGF-2 protein at the highest expression level. After purification, the purity of rhFGF-2 protein reached 98.8%, and the recovery yield was 179.2 µg of protein from 200 mL of flask culture (equivalent to 850 µg/L). The purified rhFGF-2 protein showed similar biological activity on NIH-3T3 cell line with the commercial FGF-2 protein.</p> <p><strong>Conclusion: </strong>The recombinant FGF-2 protein was successfully secretory expressed from <em>Pichia pastoris</em>, and successfully purified by only one-step chromatography.</p> Hân Khả Lê Nghĩa Hiếu Nguyễn Oanh Cao Kiều Nguyễn Nhân Trí Nguyễn ##submission.copyrightStatement## http://creativecommons.org/licenses/by/4.0 2020-04-14 2020-04-14 23 2 499 507 10.32508/stdj.v23i2.1746 title description none g Fusion-fission in the reactions of the 58Ni + 251Cf and 64Zn + 248Cm combinations http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/2056 <p><strong>Introduction</strong>: In the present study, we evaluate the nucleon evaporation, alpha decay, and fission widths in the fusion-fission of the <sup data-id="s-98c180d643e5">58</sup>Ni+<sup data-id="s-855dc9789ae7">251</sup>Cf and <sup data-id="s-1a0519a15e1f">64</sup>Zn + <sup data-id="s-515c9f12011f">248</sup>Cm reactions for the synthesis of the super-heavy <sup data-id="superscript-6">309, 312</sup>126 nuclei.</p> <p><strong>Methods</strong>: The feasibility of the synthesis of the <sup data-id="superscript-7">309, 312</sup>126 isotopes via the mentioned systems is investigated based on the widths. The widths in the excitation energy range of E<sup data-id="superscript-8">*</sup> = 10 – 100 MeV are calculated in the scope of the statistical model, in which the level density is calculated by using the Fermi-gas model. By employing the LISE++ code, the level densities the compound nuclei, <sup data-id="superscript-9">309, 312</sup>126 nuclei, are calculated to be about 10<sup data-id="superscript-10">5</sup> – 10<sup data-id="superscript-11">50</sup> (MeV<sup data-id="superscript-12">-1</sup>) in the energy range of interest.</p> <p><strong>Results</strong>: The lifetime of the compound nuclei, <sup data-id="superscript-13">309, 312</sup>126 nuclei, which are estimated based on the total width, is about 10<sup data-id="superscript-14">-22</sup>-10<sup data-id="superscript-15">-20</sup> s. The fission has the largest width compared to those of the alpha decay and nucleon evaporations. Hence, the <sup data-id="superscript-16">58</sup>Ni+<sup data-id="superscript-17">251</sup>Cf and <sup data-id="superscript-18">64</sup>Zn + <sup data-id="superscript-19">248</sup>Cm combinations are appropriate to the study of the mass distribution. In addition, the large alpha decay widths suggest the <sup data-id="superscript-21">309, 312</sup>126 isotopes be the alpha-decay nuclei.</p> <p><strong>Conclusion</strong>: The results are expected to be useful for considering measurements at facilities in the near future.</p> Duy Ngoc Nguyen ##submission.copyrightStatement## http://creativecommons.org/licenses/by/4.0 2020-05-24 2020-05-24 23 2 528 535 10.32508/stdj.v23i2.2056 title description none g Relationship between water temperature and phytoplankton communities in Ba Lai river, Viet Nam http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/1755 <p><strong>Introduction</strong>: Phytoplankton which can affect higher trophic levels play a pivotal role as primary producers. Phytoplankton structure and diversity may, besides other factors, be controlled by the changing of water temperatures. Hence, the present study aimed to determine some relationship between phytoplankton assemblage and water temperature in Ba Lai River, Vietnam.</p> <p><strong>Methods</strong>: In this research, sample data along the Ba Lai Estuary during two surveys were carried out in rainy season (September, 2017) and in dry season (March, 2018), and analyzed by Spearman's correlation and Linear regression analysis to find the correlations.</p> <p><strong>Results</strong>: The results showed that the temperature of surface water in Ba Lai River was quite stable spatially. A total of 128 species belonging to 5 groups- namely cyanobacteria, diatoms, green algae, euglenids and dinoflagellates- were recorded in which diatoms were clearly dominant. Additionally, multiple stepwise linear regression revealed that phytoplankton assemblage correlated significantly with the temperature of surface water. The water temperature had a significant positive correlation with chlorophyll-a concentration but was negatively correlated with Margalef’s diversity index in the rainy season. Moreover, the significant negative association of water temperature with biomass of phytoplankton and biomass of diatoms, which was principal in species number, were determined in the dry season.</p> <p><strong>Conclusion</strong>: This study investigated the phytoplankton communities and found their correlation with environment in the area, and demonstrated advantages of phytoplankton which warrant their further research.</p> Yen Thi Hoang Tran Luu Thanh Pham ##submission.copyrightStatement## http://creativecommons.org/licenses/by/4.0 2020-07-03 2020-07-03 23 2 536 547 10.32508/stdj.v23i2.1755 title description none g Removal of methyl orange by heterogeneous fenton process using iron dispersed on alumina pillared bentonite pellet http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/2139 <div data-id="paragraph-d80270c3f224"><strong>Introduction</strong>: Heterogeneous Fenton is one of the Advanced Oxidation Processes (AOPs) and has been proven to be effective on azo dye degradation. However, a low-cost catalyst and factors affecting the processes of this system were further investigated.</div> <div data-id="paragraph-d80270c3f224"><strong>Methods</strong>: In this study, pellets of iron alumina pillared bentonite (PFeAPB) were prepared by dispersing iron ions on alumina pillared bentonite pellet. Catalyst activity and lifetime were investigated via efficiencies of Methyl Orange (MO) decolorization and Chemical Oxygen Demand (COD) removal, a typical dye type of textile wastewater. Characteristics of the PFeAPB catalyst were examined by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area, and X-ray fluorescence (XRF).</div> <div data-id="paragraph-d80270c3f224"><strong>Results</strong>: Results of batch experiments showed that specific surface area of the PFeAPB catalyst was 111.22 m<sup data-id="superscript-1">2</sup>/g higher than its precursor by 2 times (57.79 m<sup data-id="superscript-2">2</sup>/g). Goethite, Hematite and Maghemite phases with approximately 11.5% of iron elements containing in the catalyst were detected via XRD and XRF. Experimental conditions of pH, initial MO solution, Hydrogen Peroxide concentration, reaction time and catalyst loading were 2.0 ± 0.1, 12.7 mmol/L, 150 min and 20 g/L, respectively, to achieve 88.68 ± 5.69% of MO decolorization and 50.27 ± 6.05% of COD removal while dissolved iron in this heterogeneous Fenton process was below standard limit (2 ppm). Catalyst activity decreased by 5.22% in decolorization efficiency after the two first reusages.</div> <div data-id="paragraph-d80270c3f224"><strong>Conclusion</strong>: These primary results showed the potential of applying PFeAPB catalyst in heterogeneous Fenton process with low iron leaching into water.</div> <div data-id="p-2d92943bdead">&nbsp;</div> Ngo Thi Thuan Tran Tien Khoi Nguyen Thi My Chi Nguyen Ngoc Vinh ##submission.copyrightStatement## http://creativecommons.org/licenses/by/4.0 2020-06-30 2020-06-30 23 2 555 563 10.32508/stdj.v23i2.2139 title description none g Textiles from orange peel waste http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/1730 <p>The global textile business is now gearing towards greener alternatives to combat pollution and avoid synthetics in production. Ironically, there is an increased awareness among consumers on the quality of the product and choices they make in their shopping. The natural and synthetic fibres have set limitations, which has made manufacturers look out for other alternative fibres. Bamboo, banana, milk, and corn are experimented for its commercial capabilities to perform as a textile material. To add on to the list, orange, the popular, and the most preferred fruit are known for its refreshing flavour. The peels after consumption/ processing of the fruit are discarded in the landfill, which is an organic waste with immense potential.&nbsp; This paper details the successful brand ‘Orange fibre’, its journey from scratch, and the properties of textiles made from processing orange peel waste. The current areas of research have also been covered in a brief way, to invite more scholars to create solutions for the hitherto pollution orange peel waste.&nbsp;</p> <p>&nbsp;</p> Aishwariya Sachidhanandham ##submission.copyrightStatement## http://creativecommons.org/licenses/by/4.0 2020-06-01 2020-06-01 23 2 508 516 10.32508/stdj.v23i2.1730 title description none g