Bui, Tuan AnhNguyen, Thi Anh
Science and Technology Development Journal; Vol 22 No 2 (2019): Under publishing; 235-238 (14 June 2019)
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Introduction: In 1971, Quillen stated a conjecture that on cohomology of arithmetic groups, a certain module structure over the Chern classes of the containing general linear group is free. Over time, many efforts has been dedicated into this conjecture. Some verified its correctness, some disproved it. So, the original Quillens conjecture is not correct. However, this conjecture still has great impacts on the field cohomology of group, especially on cohomology of arithmetic groups. This paper is meant to give a brief survey on Quillen conjecture and finally present a recent result that this conjecture has been verified by the authors. Method: In this work, we investigate the key reasons that makes Quillen conjecture fails. We review two of the reasons: 1) the injectivity of the restriction map; 2) the non-free of the image of the Quillen homomorphism. Those two reasons play important roles in the study of the correctness of Quillen conjecture. Results: In section 4, we present the cohomology of ring ​ which is isomorphic to the free module ​ over ​. This confirms the Quillen conjecture. Conclusion: The scope of the conjecture is not correct in Quillens original statement. It has been disproved in many examples and also been proved in many cases. Then determining the conjectures correct range of validity still in need. The result in section 4 is one of the confirmation of the validity of the conjecture.  
THACH, Ut DongDo, Thi Lan NhiDo, Ngoc Lan AnhDo, Minh Huy
Science and Technology Development Journal; Vol 22 No 2 (2019): Under publishing; 228-234 (13 June 2019)
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Introduction: Ionic liquids (ILs) have attached many attentions due to their interesting physicochemical properties. However, ionic liquids have several disadvantages including high viscosity, difficult to purify, separate and recycle, and expensive. Therefore, supported ionic liquids (SIL) have been developed to overcome these problems. SIL based on cellulose material was conventionally synthesized by silanization reaction between ionic liquid trialkoxyl silane and hydroxyl groups on the surface of cellulose. However, low reactivity of cellulose hydroxyl groups causes the low efficiency of silanization reaction. With the aim to resolve these problems and improve the reactivity of cellulose silanization reaction, cellulose graft ionic liquid was synthesized and characterized. Methods: Cellulose graft ionic liquid (CL-IL) material was synthesized by silanization reaction. The influence of reaction condition such as IL/CL (w/w) ratio, base catalyst (NH3) and agent coupling tetraethyl orthosilicate (TEOS) on silanization reaction was investigated. The modified CL-IL materials were characterized using FT-IR, TGA, SEM. The ion exchange properties were evaluated via batch adsorption studies to evidence the efficiency of silanization reaction of cellulose. Results: The study indicated that adding TEOS with NH3 catalyst could significantly increase the number of imidazolium groups grafted on cellulose about 75% compared to the conventional approach. CL-IL material is an efficient anion exchange materials displaying fast kinetic adsorption and high capacity adsorption of MO up to 1.4 mmol g-1. Conclusion: High-efficiency of cellulose silanization was obtained by using coupling agent TEOS and base catalyst. Therefore, the silanization reaction can be used for synthesis divers of functional cellulose materials. This approach can be aimed for the design of cheaper and high-performance materials for catalysis, polymer composite and adsorption in water treatment and depollution of industrial wastewater.  
Nguyen, Hai HongDang, Liet VanVo, Vuong Van
Science and Technology Development Journal; Vol 22 No 2 (2019): Under publishing; 219-227 (07 June 2019)
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Introduction: The purpose of this paper is to determinate the position, depth, dip direction and dip angle the faults in the South region of Vietnam from the total magnetic intensity anomalies, that reduced to the magnetic pole (RTP). Methods: Based on the Oasis Montaj software, we proposed a new way to compute the positions and the depth to the top of the faults by combining the Tilt angle and the Euler deconvolution methods. In addition, the angle and direction of the dip of theses faults were also determined by considering maximum of the total horizontal derivative of the RTP upward continuation at the different height levels. Results: The results show that there are 12 faults along the longitudinal direction, latitudinal direction, Northwest — Southeast direction and Northeast — Southwest direction with the mazimum depth is about 3100 m and the dip angle changes in the range of 65-82â—¦. Results: These indicate that these methods are valuable tools for specifying the characteristics of geology, contribute to give and confirm the useful information on geological structure in the South region of Vietnam.  
Nguyen, Ngoc DuyVo, Thi To VyNguyen, Kim Uyen
Science and Technology Development Journal; Vol 22 No 2 (2019): Under publishing; 213-218 (07 June 2019)
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The critical concentration plays an important role in the consideration of the analysts, such as gamma or alpha analyzers, for the isotopic analysis. Since the 232Th isotope and its a-decay daughters are abundant in the environments of soils, rocks and water, it is necessary to investigate the content of these isotopes to reduce the risks of health. In this work, the critical concentrations of the mentioned radioactive nuclei were estimated based on their radioactivities for the alpha analysts. The a-decay half-lives of the nuclei in the decay chain of the 232Th isotope were re-examined for the radioactivities. The semi-empirical formulae proposed by Viola-Seaberg, Royer and Poenaru were applied to the estimation. The predicted half-lives were normalized by their average values and compared to the data (NuDat) of the National Nuclear Data Center, Brookhaven National Laboratory. The results show that there exist a large uncertainty, 15% - 95% dispersed from the average values (in decimal logarithmic scale), of the half-lives evaluated by each models. Most of average half-lives are close to the NuDat data except the multi-decay-mode isotopes. The relationships between the estimated half-lives and the NuDat data are deduced as linear functions. The decay-constant deviations due to the half-life uncertainty are in the range of 1% - 120% from the average values. The large radioactivity uncertainty due to the half-lives estimated by the three models should be paid an attention for considering the environmental samples for the analysis of the natural exotic isotopes using alpha spectrometers. By assuming an efficiency of 100%, the critical concentration for the alpha analyst of the 232Th nucleus is found to be in the range 1.5 – 2.5 microgram/(l or kg).
Vu, Binh ThanhTran, Nguyet Thi-AnhNguyen, Tuyet ThiDuong, Quyen Thanh-NgocLe, Phong MinhLe, Hanh ThiPham, Phuc Van
Science and Technology Development Journal; Vol 22 No 2 (2019): Under publishing; 196-212 (27 May 2019)
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Introduction: In vitro cultivation of DCs and cytokine-induced killer cells (CIK cells) - a special phenotype of T lymphocyte populations — for cancer treatment has gained significant research interest. The goal of this study is to understand whether the priming from DCs helps CIK cells to exert their toxic function and kill the cancer cells. Methods: In this research, DCs were differentiated from mononuclear cells in culture medium supplemented with Granulocyte-macrophage colony-stimulating factor (GM-CSF), and Interleukin-4 (IL-4), and were induced to mature with cancer cell antigens. Umbilical cord blood mononuclear cells were induced into CIK cells by Interferon-γ (IFN-γ), anti-CD3 antibody and IL-2. After 4-day exposure (with DC:CIK = 1:10), DCs and CIK cells interacted with each other. Results: Indeed, DCs interacted with and secreted cytokines that stimulated CIK cells to proliferate up to 133.7%. In addition, DC-CIK co-culture also stimulated strong expression of IFN-γ. The analysis of flow cytometry data indicated that DC-CIK co-culture highly expressed Granzyme B (70.47% ± 1.53, 4 times higher than MNCs, twice higher than CIK cells) and CD3+CD56+ markers (13.27% ± 2.73, 13 times higher than MNCs, twice higher than CIK cells). Particularly, DC-CIK co-culture had the most specific lethal effects on cancer cells after 72 hours. Conclusion: In conclusion, co-culture of DCs and CIK cells is capable of increasing the expression of CIK-specific characteristics and CIK toxicity on cancer cells.    
Ngoc Minh, NguyenThanh Nha, NguyenTich Thien, TruongQuoc Tinh, Bui
Science and Technology Development Journal; Vol 20 No K9 (2017); 5-14 (15 April 2019)
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The consecutive-interpolation technique has been introduced as a tool enhanced into traditional finite element procedure to provide higher accurate solution. Furthermore, the gradient fields obtained by the proposed approach, namely consecutive-interpolation finite element method (CFEM), are smooth, instead of being discontinuous across nodes as in FEM. In this paper, the technique is applied to analyze transient heat transfer problems. In order increase time efficiency, a model- reduction technique, namely the proper orthogonal decomposition (POD), is employed. The idea is that a given large-size problem is projected into a small-size one which can be solved faster but still maintain the required accuracy. The optimal POD basis for projection is determined by mathematical operations. With the combination of the two novel techniques, i.e. consecutive-interpolation and proper orthogonal decomposition, the advantages of numerical solution obtained by CFEM are expected to be maintained, while computational time can be significantly saved.
Hoang Bao Huy, TruongNgoc Dieu, Vo
Science and Technology Development Journal; Vol 20 No K9 (2017); 15-22 (15 April 2019)
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Economic operation of the electric energy generating system is one of the common problems in power system. This paper presents a new metaheuristic optimization method, the Search Group Algorithm (SGA) for solving optimal power flow (OPF) problem. The proposed method is tested for 11 different cases on the IEEE 30-bus and IEEE-118 bus systems, in which the IEEE 30-bus system is tested with different objective functions including quadratic function, valve point effects and multiple fuels. The obtained results are compared with some well-known optimization algorithms to emphasize the effectiveness of the SGA method for solving different OPF problems with complicated functions.
Thi Thuy, LeThi Tuoi, PhanThanh Tho, Quan
Science and Technology Development Journal; Vol 20 No K9 (2017); 23-30 (15 April 2019)
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Entity co-reference resolution and sentiment analysis are independent problems and popular research topics in the community of natural language processing. However, the combination of those two problems has not been getting much attention. Thus, this paper susgests to apply knowledge base to solve co- reference between object and aspect with sentiment. In addition, the paper also proposes the model of Ontology-based co-reference resolution in sentiment analysis for English text. Finally, we also discuss evaluation methods applied for our model and the results obtained.
Le Thuy Chung, KieuThi San Ha, PhanMinh Son, Le
Science and Technology Development Journal; Vol 20 No K9 (2017); 31-37 (15 April 2019)
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Located in a flat plain with an extensive covering of very soft clay, Ho Chi Minh city is still in its urbanization and urban expansion with an inevitable development in construction at rapid pace. SHANSEP parameters for soft clay in HCM City will be helpful for geotechnical engineers in quantifying the behavior of soft clay and proposing suitable solutions for soft ground improvement. This paper presents the results of 100 CIUC triaxial tests on 20 clay samples belonging to two different groups of soft clay (taken in Binh Thanh and Nha Be districts) tested with 5 different modes of OCRs, i.e. 1, 1.5, 2, 4, and 6. The test results are analyzed to obtain SHANSEP models with really high coefficient of determination (R2 ≈ 1).
Vo, Tam Dinh-LeBao Vo, ChiThi Thuy Nguyen, HuynhTruc Le, LinhThong Trong Vi, DoThi Huong Thao, Nguyen
Science and Technology Development Journal; Vol 20 No K9 (2017); 38-44 (15 April 2019)
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In this study, salmon by-products were utilised to produce high ash content (AC) salmon bone powder (SBP) using hydrolytic enzyme and apply in the production of Tra catfish cake. The by- products included 61.9% of moisture, 43.1% of protein, 45.4% of lipid, 10.2% of ash, 3.7% of calcium and 2.3% of phosphorus (on dry weight basis). The AC of SBP achieved the maximal value of 46.9% when hydrolytic enzyme of Alcalase, pH value of 6.5, temperature of 60oC, the Enzyme/Substrate (E/S) ratio of 60 U/g protein and time of 4 hours. The obtained SBP contained 23.1% of calcium, 11.7% of phosphorus and without heavy metals such as cadmium, mercury and lead. The fish cake added with 2% of SBP owned the highest gel strength, folding score and whiteness of 287.4, AA and 65.3, respectively and it was accepted by the test panel. Hence, SBP could be used in the production of Tra catfish cake as a mineral supplement.