Science and Technology Development Journal <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="" 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> A preliminary study on gas metal arc welding-based additive manufacturing of metal parts <p><strong>Introduction</strong>: In the past three decades, additive manufacturing (AM), also known as 3D printing, has emerged as a promising technology, which allows the manufacture of complex parts by adding material layer upon layer. In comparison, with other metal-based AM technologies, gas metal arc welding-based additive manufacturing (GMAW-based AM) presents a high deposition rate and has the potential for producing medium and large metal components. To validate the technological performance of such a manufacturing process, the internal quality of manufactured parts needs to be analyzed, particularly in the cases of manufacturing the parts working in a critical load-bearing condition. Therefore, this paper aims at investigating the internal quality (i.e., and mechanical properties) of components manufactured by the GMAW-based AM technology.</p> <p><strong>Method</strong>: A gas metal arc welding robot was used to build a thin-walled component made of mild steel on a low-carbon substrate according to the AM principle. Thereafter, the specimens for observing and mechanical properties were extracted from the built thin-walled component. The of the specimen were observed by an optical microscope; the hardness was measured by a digital tester, and the tensile tests were carried out on a tensile test machine.</p> <p><strong>Results</strong>: The results show that the GMAW-based AM-built thin-walled components possess an adequate that varies from the top to the bottom of the built component: structures with primary dendrites in the upper zone; granular structure of with small regions of at grain boundaries in the middle zone, and grains of in the lower zone. The hardness (ranged between 164±3.46 HV to 192±3.81 HV), yield strength (YS <sub data-id="subscript-2f3c4a9ad20f48338fc20fac7d764663">offset of 0.2%</sub> ranged from 340±2 to 349.67±1.53 ), and ultimate tensile strength (UTS ranged from 429±1 to 477±2 ) of the GMAW-based AM-built components were comparable to those of wrought mild steel.</p> <p><strong>Conclusions</strong>: The results obtained in this study demonstrate that the GMAW-based AM-built components possess adequate and good mechanical properties for real applications. This allows us to confirm the feasibility of using a conventional gas metal arc welding robot for additive manufacturing or repairing/re-manufacturing of metal components.</p> Van Thao LE ##submission.copyrightStatement## 2020-02-16 2020-02-16 23 1 422 429 10.32508/stdj.v23i1.1714 title description none g A computational study of cysteine and glutathione binding to small gold cluster Au8 <p><strong>Introduction</strong>: Understanding the binding mechanism between gold and is a fundamental step for numerous applications in biosensors and targeted drug delivery. This study aims to clarify the adsorption behaviors of CYS and GSH on the gold surface using a small gold Au<sub data-id="s-679f22a93baa">8</sub> cluster as a model reactant.</p> <p><strong>Methods</strong>: Here, we examine in details the molecular interaction between Au<sub data-id="subscript-2">8</sub> cluster with (CYS) and (GSH) by means of density functional theory (DFT). The PBE functional is employed in combination with the basis set for non-metal atoms and the basis set for gold. Harmonic frequencies are also computed to confirm optimized geometries as local minima or transition states on the potential energy surfaces.</p> <p><strong>Results</strong>: The calculated results show that these molecules prefer to anchor on the gold cluster via the sulfur atom with the adsorption energies of 20.3 and 30.8 / for CYS and GSH, respectively, in gas phase. In water, such values are considerably reduced, namely 19.0 / for CYS and 26.4 / for GSH. If a visible light with a frequency of v = 6x10<sup data-id="superscript-1">14</sup> Hz (500 nm) is applied, the time for the recovery of CYS and GSH from the most stable complexes will be about 1.24 and 6.03x10<sup data-id="superscript-2">7</sup> seconds at 298 K in gas phase.</p> <p><strong>Conclusion</strong>: The Au<sub data-id="subscript-3">8 </sub>cluster could be a promising material for designing sensor in CYS and GSH selective detection.</p> Si Thanh Nguyen Pham Nhat Vu ##submission.copyrightStatement## 2020-02-17 2020-02-17 23 1 430 438 10.32508/stdj.v23i1.1715 title description none g Using edge elements for modeling of 3-D magnetodynamic problem via a subproblem method <p><strong>Introduction</strong>: The mathematical modeling of electromagnetic problems in electrical devices are often presented by Maxwell’s equations and constitutive material laws. These equations are partial differential equations linked to fields and their sources. In order to solve these equations and simulate the distribution of magnetic fields and eddy current losses of electromagnetic problems, a subproblem method for modeling a 3-D magnetodymic problem with the b-conformal formulation is proposed.</p> <p><strong>Methods</strong>: In this paper, the subproblem method with using edge finite elements is proposed for coupling subproblems via several steps to treat and deal with some troubles regarding to electromagnetic problems that gets quite difficulties when directly applying a finite element method. In the strategy subproblem method, it allows a complete problem to define into several subproblems with adapted dimensions. Each subproblem can be solved on its independent domain and mesh without performing in whole domain or mesh. This easily supports meshing and decreases computing time.</p> <p><strong>Results</strong>: The obtained results, the subproblem method with edge elements indicates magnetic flux densities and the eddy current losses in the conducting region. The computed results is also compared with the measured results done by other authors. This can be shown that there is a very good agreement.</p> <p><strong>Conclusion</strong>: The validated method has been successfully applied to a practical test problem (TEAM Problem 7).</p> Vuong Quoc Dang Christophe Geuzaine ##submission.copyrightStatement## 2020-02-20 2020-02-20 23 1 439 445 10.32508/stdj.v23i1.1718 title description none g Xao tam phan (Paramignya trimera) methanol extract induced apoptosis in hepatocellular carcinoma HepG2 cell line in vitro <p><strong>Introduction</strong>: Xao Tam Phan (Paramignya trimera) has long been used in Viet Nam as an herbal medicine for the treatment of Hepatitis, hepatocellular carcinoma, and diabetes. This study aimed to determine the anti-proliferation effect of Paramignya trimera extract (<em>P. trimera</em> extract) on HepG2 hepatocellular carcinoma cells.</p> <p><strong>Methods</strong>: AlamarBlue assay was used to determine the IC<sub>50</sub> values of <em>P. trimera</em> extract on HepG2 cells. Adipose-derived stem cells (ADSCs) was used as normal cell control. For apoptosis examination, <em>P. trimera</em> extract-treated HepG2 cells were incubated with Annexin V/Propidium iodide (PI). Then they have been analyzed their expression of Annexin-V and PI by flow cytometry. The cell nuclear degradation also was evaluated by PI/Hoechst 33342 staining assay.</p> <p><strong>Results</strong>: Doxorubicin and <em>P. trimera</em> extract IC<sub>50</sub> values on HepG2 cells were 55.13 +/- 2.028 ng/ml and 582.533 +/- 16.521 mg/ml, respectively. Those on ADSCs were 5.96 +/- 0.56 ng/ml and 268.976 +/- 19.325 mg/ml, respectively. Side effect index value (SEI) of <em>P. trimera</em> extract was 2.175 +/- 0.12, and the SEI of doxorubicin was 8.71 +/- 0.36. Flow cytometry analysis indicated significant apoptosis on <em>P. trimera</em> extract-treated HepG2 cells at a dose of 500 mg/ml (32.39 +/- 2.28% apoptotic cells, and 14.63 +/- 1.59% necrotic cells). Nuclear aggregation and degradation was seen on 500 mg/ml <em>P. trimera</em> treated HepG2 cells.</p> <p><strong>Conclusion</strong>: <em>P. trimera</em> extract could inhibit HepG2 hepatocellular carcinoma cell proliferation by inducing apoptosis.</p> <p>&nbsp;</p> Sinh Truong Nguyen Nghia Minh Do Phuc Hong Vo Trinh Thi – Tu Nguyen Kiet Dinh Truong Phuc Van Pham ##submission.copyrightStatement## 2020-03-31 2020-03-31 23 1 484 489 10.32508/stdj.v23i1.2013 title description none g Establishing murine models of hepatocellular carcinoma using NOD/SCID, nude and Balb/c mice: An initial comparative study <p><strong>Introduction</strong>: Hepatocellular carcinoma (HCC) is one of the leading causes of cancer mortality in the world. Therefore, more and more studies are developing novel therapies to treat this disease. The pre-clinical trials on animals are a vital step to evaluate the efficacy as well as side effects of these novel therapies. Hence, this study aimed to develop the murine model of HCC using 3 kinds of mice: NOD/SCID, nude and <em>Balb/c</em> mice.</p> <p><strong>Methods</strong>: HCC cell line HepG2 was used in this study. They were injected into 3 kinds of mice: NOD/SCID, nude and <em>Balb/c</em> mice at three doses: 5 x 10<sup>6</sup>, 2.5 x 10<sup>6</sup>, and 1.25 x 10<sup>6</sup> cells. Tumor size and body weight of the mice were recorded daily. To confirm these tumors in mice as malignant tumors, they were removed and analyzed by histopathology.</p> <p><strong>Results</strong>: The results showed that in nude mice, the tumors appeared after 1 day of injection and could be detected by the naked eye; they continuously developed until the end of the study. In NOD/SCID mice, the tumors could be detected by the naked eye after 3 days of injection; their sizes also increased until the end of the experimental study. Meanwhile, in <em>Balb/c</em> mice, although the tumors could be observed by the naked eye on the 3<sup>rd</sup> day after cell injection, they regressed and markedly disappeared after 30 days. The dose of 5 x 10<sup>6</sup> cells per mouse induced the largest tumors (1.2 cm in diameter) in NOD/SCID mice. The histopathological analysis showed that the tumors collected from nude and NOD/SCID mice also displayed the poorly differentiated malignant carcinoma with muscle tissue invasion.</p> <p><strong>Conclusion</strong>: Both nude and NOD/SCID mice are appropriate for future studies to establish HCC murine models using HepG2 injection.</p> Nghia Minh Do Sinh Truong Nguyen Phuc Hong Vo Trinh Thi-Phuong Ngo Kiet Dinh Truong Phuc Van Pham ##submission.copyrightStatement## 2020-03-19 2020-03-19 23 1 454 460 10.32508/stdj.v23i1.1767 title description none g On the cominimaxness of generalized local cohomology modules <p>The local cohomology theory plays an important role in commutative algebra and algebraic geometry. The I-cofiniteness of local cohomology modules is one of interesting properties which has been studied by many mathematicians. The <em>I</em>-cominimax modules is an extension of <em>I</em>-cofinite modules which was introduced by Hartshorne. An <em>R</em>-module <em>M</em> is <em>I</em>-cominimax if Supp_R(M)\subseteq V(I) and Ext^i_R(R/I,M) is minimax for all&nbsp; i\ge 0. In this paper, we show some conditions such that the generalized local cohomology module H^i_I(M,N) is <em>I</em>-cominimax for all i\ge 0. We show that if H^i_I(M,K) is <em>I</em>-cofinite for all i&lt;t and all finitely generated <em>R</em>-module <em>K</em>, then&nbsp; H^i_I(M,N) is <em>I</em>-cominimax for all i&lt;t&nbsp; and all minimax <em>R</em>-module <em>N.</em>&nbsp; If <em>M</em> is a finitely generated <em>R</em>-module, <em>N</em> is a minimax <em>R</em>-module and <em>t</em> is a non-negative integer such that&nbsp; dim Supp_R(H^i_I(M,N))\le 1 for all i&lt;t then H^i_I(M,N) is <em>I</em>-cominimax for all&nbsp; i&lt;t. When&nbsp; dim R/I\le 1 and H^i_I(N) is <em>I</em>-cominimax for all&nbsp; i\ge 0 then H^i_I(M,N) is <em>I</em>-cominimax for all i\ge 0.</p> Cam Thi Hong Bui Tri Minh Nguyen ##submission.copyrightStatement## 2020-03-24 2020-03-24 23 1 479 483 10.32508/stdj.v23i1.1696 title description none g A review of the genus Sphenomorphus Fitzinger, 1843 (Squamata: Scincidae) in southern Vietnam, with additional data on S. sheai and S. tridigitus <p><strong>Introduction</strong>: Among 14 species of forest skinks (genus Sphenomorphus) in Vietnam, seven were recorded from southern part of the country. Shea’s forest skink, <em>S. sheai</em>, was described from Kon Tum Plateau based on a single female. Similarly, the tridigital forest skink, <em>S. tridigitus</em>, was also described based on a single putrid and desiccated specimen found dead on a road in Bach Ma; specimens collected recently in Laos did not fully agree with the original description. Hence, additional specimens from type localities of both poorly known species are necessary to discern their morphological variation. In addition, little is known about hemipenis and distribution of the other forest skinks in southern Vietnam. Our study seeks to (1) confirm the occurrence of all known species in the area and access their distributions, (2) provide additional morphological data on poorly known <em>S. sheai</em> and <em>S. tridigitus</em>, and (3) describe hemipenial structure of known species.</p> <p><strong>Methods</strong>: We analyzed the morphology of 47 specimens of forest skink collected from southern Vietnam to identify species. Scales were observed and counted under a zoom stereo microscope and measurements were taken with a digital caliper.</p> <p><strong>Results</strong>: Analyses confirmed the occurrence of seven species of Sphenomorphus in southern Vietnam, including <em>S. annamiticus, S. buenloicus, S. indicus, S. maculatus, S. sheai, S. tridigitus,</em> and <em>S. yersini</em>. New specimens of <em>S. sheai</em> had one enlarged anterior temporal and eight or nine lamellae under fourth toe, which differed from the original description. Additional specimens of <em>S. tridigitus</em> from the type locality verified that the holotype has 20 mid-body scale rows and first supralabial and nasal fused, but they differed from the holotype in having upper temporal overlapped or overlapping the lower one. Fieldwork discovered 20 new localities for all seven species. The hemipenes of four species involved those with symmetric and asymmetric lobes.</p> <p><strong>Conclusion</strong>: We confirm the occurrence of seven species of<em> Sphenomorphus</em> in southern Vietnam with 20 additional distribution records. Hemipenial structures of known species form two groups. New specimens of <em>S. sheai</em> and <em>S. tridigitus</em> differ slightly from the holotypes.</p> Manh Van Le Luan Thanh Nguyen Ba Dinh Vo Robert W. Murphy Vu Dang Hoang Nguyen Sang Ngoc Nguyen ##submission.copyrightStatement## 2020-03-24 2020-03-24 23 1 470 478 10.32508/stdj.v23i1.1733 title description none g Forecasting of saline intrusion in Ham Luong river, Ben Tre province (Southern Vietnam) using Box-Jenkins ARIMA models <p><strong>Introduction</strong>: Ham Luong River is a branch of Mekong River located in Ben Tre Province, which has played a crucial role in supporting livelihoods of local residents and the province's economic development. However, the saline intrusion has been expanding in Ham Luong River, which seriously affects the productive agriculture, aquaculture, and further causes tremendous difficulties for local people's lives. Thus, it is crucial to have research for forecast the saline intrusion in Ham Luong River. Our aim was to develop mathematical models in order to forecast the saline intrusion in Ham Luong River, Ben Tre Province.</p> <p><strong>Methods</strong>: The Auto regressive integrated moving average (ARIMA) model was built to forecast the weekly saline intrusion in Ham Luong River, which has been obtained from Ben Tre Province's Hydro-Meteorological Forecasting Center over eight years (from 2012 to 2019).</p> <p><strong>Results</strong>: The saline concentration increased from January to March and then decreased from April to June. The highest salinity occurred in February and March while the lowest salinity was observed in early June. Moreover, the ARIMA technique provided an adequate predictive model for a forecast of the saline intrusion in An Thuan, Son Doc, and An Hiep station. However, the ARIMA model in My Hoa and Vam Mon might be improved upon by other forecasting methods.</p> <p><strong>Conclusion</strong>: Our study suggested that the nonseasonal/seasonal ARIMA is an easy-to-use modeling tool for a quick forecast of the saline intrusion.</p> Thai Thanh Tran Luong Duc Thien Ngo Xuan Quang Lam Van Tan ##submission.copyrightStatement## 2020-03-02 2020-03-02 23 1 446 453 10.32508/stdj.v23i1.1747 title description none g Bio-Electro-Fenton: a novel method for treating leachate in Da Phuoc Landfill, Vietnam <p><strong>Introduction:</strong> Leachate is a noticeable pollution problem because it contains a considerable amount of persistent organic&nbsp;pollutants (POPs). If leachate isn’t treated thoroughly, its leak will negatively affect the environment. Therefore, appropriate treatment technologies are required to remove them. Bio-Electro-Fenton (BEF) is a new method using microorganisms such as electrolytes to convert chemical energy into electricity to help create H<sub>2</sub>O<sub>2</sub> support advanced oxidation process (AOPs). The potentiality of the applicability of BEF technology as a pretreatment step for leachate from Da Phuoc landfill (operation time &gt; 12 years), Ho Chi Minh City. <strong>Methods:</strong> The BEF pilot scale model (30 x 10 x 10 cm) is divided by a proton exchange membrane (PEM) (Nafion®112) into two chambers (anode and cathode). Cathode chamber used a graphite electrode, the anode chamber used a carbon fabric electrode. The experiments aimed to determine the optimal conditions of parameters affecting the BEF system by determining the efficiency of COD removal and BOD<sub>5</sub>/COD ratio in leachate. <strong>Results:</strong> At optimal conditions of the model including pH 3, [Fe<sup>2+</sup>] = 4g/L, current intensity = 1A, reaction time &nbsp;60 minutes and airflow = 12 L/min, as a result COD was reduced by 68.2% from 4950 mgO<sub>2</sub>/L to 1574.1 mgO<sub>2</sub>/L, the ratio of BOD<sub>5</sub>/COD = 0.1. <strong>Conclusion:</strong> The study result showed that Bio-electro-Fenton process is effective for wastewater with high concentrations of pollutant and difficult to treat as leachate<strong><em>,</em></strong> suggesting that the appropriate method for pre-treatment processes support the thorough elimination of pollutants.</p> Ho Nhut Linh Hai Truong Nam Ho ##submission.copyrightStatement## 2020-03-19 2020-03-19 23 1 461 469 10.32508/stdj.v23i1.1736 title description none g