Science and Technology Development Journal 2020-04-03T13:40:20+00:00 Phuc Van Pham Open Journal Systems A preliminary study on gas metal arc welding-based additive manufacturing of metal parts 2020-04-03T13:40:20+00:00 Van Thao LE <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> 2020-02-16T00:00:00+00:00 ##submission.copyrightStatement## A computational study of cysteine and glutathione binding to small gold cluster Au8 2020-04-03T13:40:19+00:00 Si Thanh Nguyen Pham Nhat Vu <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> 2020-02-17T00:00:00+00:00 ##submission.copyrightStatement## Using edge elements for modeling of 3-D magnetodynamic problem via a subproblem method 2020-04-03T13:40:17+00:00 Vuong Quoc Dang Christophe Geuzaine <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> 2020-02-20T00:00:00+00:00 ##submission.copyrightStatement## Xao tam phan (Paramignya trimera) methanol extract induced apoptosis in hepatocellular carcinoma HepG2 cell line in vitro 2020-04-03T13:40:01+00:00 Sinh Truong Nguyen Nghia Minh Do Phuc Hong Vo Trinh Thi – Tu Nguyen Kiet Dinh Truong Phuc Van Pham <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> 2020-03-31T01:41:42+00:00 ##submission.copyrightStatement## Establishing murine models of hepatocellular carcinoma using NOD/SCID, nude and Balb/c mice: An initial comparative study 2020-04-03T13:40:07+00:00 Nghia Minh Do Sinh Truong Nguyen Phuc Hong Vo Trinh Thi-Phuong Ngo Kiet Dinh Truong Phuc Van Pham <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> 2020-03-19T00:00:00+00:00 ##submission.copyrightStatement## On the cominimaxness of generalized local cohomology modules 2020-04-03T13:40:04+00:00 Cam Thi Hong Bui Tri Minh Nguyen <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> 2020-03-24T23:03:28+00:00 ##submission.copyrightStatement## A review of the genus Sphenomorphus Fitzinger, 1843 (Squamata: Scincidae) in southern Vietnam, with additional data on S. sheai and S. tridigitus 2020-04-03T13:40:06+00:00 Manh Van Le Luan Thanh Nguyen Ba Dinh Vo Robert W. Murphy Vu Dang Hoang Nguyen Sang Ngoc Nguyen <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> 2020-03-24T00:00:00+00:00 ##submission.copyrightStatement## Forecasting of saline intrusion in Ham Luong river, Ben Tre province (Southern Vietnam) using Box-Jenkins ARIMA models 2020-04-03T13:40:10+00:00 Thai Thanh Tran Luong Duc Thien Ngo Xuan Quang Lam Van Tan <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> 2020-03-02T00:00:00+00:00 ##submission.copyrightStatement## Bio-Electro-Fenton: a novel method for treating leachate in Da Phuoc Landfill, Vietnam 2020-04-03T13:40:09+00:00 Ho Nhut Linh Hai Truong Nam Ho <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> 2020-03-19T00:00:00+00:00 ##submission.copyrightStatement##