http://stdj.scienceandtechnology.com.vn/index.php/stdj/issue/feed Science and Technology Development Journal 2019-09-23T12:22:22+00:00 Phuc Van Pham pvphuc@vnuhcm.edu.vn Open Journal Systems http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/871 A high dynamic range imaging algorithm: implementation and evaluation 2019-09-23T12:22:21+00:00 http://stdj.scienceandtechnology.com.vn/public/journals/2/article_871_cover_en_US.png Vu Hong Son hongson.ute@gmail.com <p>Camera specifications have become smaller and smaller, accompanied with great strides in technology and thinner product demands, which have led to some challenges and problems. One of those problems is that the image quality is reduced at the same time. The decrement of radius lens is also a cause leading to the sensor not absorbing a sufficient amount of light, resulting in captured images which include more noise. Moreover, current image sensors cannot preserve whole dynamic range in the real world. This paper proposes a Histogram Based Exposure Time Selection (HBETS) method to automatically adjust the proper exposure time of each lens for different scenes. In order to guarantee at least two valid reference values for High Dynamic Range (HDR) image processing, we adopt the proposed weighting function that restrains random distributed noise caused by micro-lens and produces a high quality HDR image. In addition, an integrated tone mapping methodology, which keeps all details in bright and dark parts when compressing the HDR image to Low Dynamic Range (LDR) image for display on monitors, is also proposed. Eventually, we implement the entire system on Adlink MXC-6300 platform that can reach 10 fps to demonstrate the feasibility of the proposed technology.</p> <p>&nbsp;</p> 2019-08-07T00:00:00+00:00 ##submission.copyrightStatement## http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/1704 Frequency distribution of dental caries disease among the local community of Harichand 2019-09-23T12:22:19+00:00 http://stdj.scienceandtechnology.com.vn/public/journals/2/article_1704_cover_en_US.png Haroon Haroon phamvanphuc2308@gmail.com Tauseef Ahmad ahmad@seu.edu.cn Muhammad Khan phamvanphuc2308@gmail.com Inamullah Inamullah phamvanphuc2308@gmail.com Arif Jan phamvanphuc2308@gmail.com Hui Jin phamvanphuc2308@gmail.com <p>A cross-sectional study was designed to determine the dental caries disease and associated risk factors among the study subjects in Harichand, Pakistan. A total of 150 patients were investigated, of which male to female percentage was (77%) and (23%) respectively. The maximum tooth decay (33%) was found in the age (years) of 21-30. The results showed that decayed and missing teeth (DMT) were (57%), followed by decayed, missing and filled teeth (DMFT) (27%) and filled teeth (FT) (16%). Most of the patients were suffering from score 6, (30%). The DMT and score 6 was recorded high among the study subjects in Harichand. This study will update the epidemiology of dental caries diseases, increase awareness, and provide the base line information for future research and intervention. Further studies are recommended on large scale.</p> 2019-08-20T00:00:00+00:00 ##submission.copyrightStatement## http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/1225 Homology of Borel Subgroup of SL(2,\mathbb{F}_p) 2019-09-23T12:22:20+00:00 http://stdj.scienceandtechnology.com.vn/public/journals/2/article_1225_cover_en_US.png Bui Anh Tuan phamvanphuc2308@gmail.com Bao Quoc Vo voquocbao0603@gmail.com <p>In this paper we compute the integral homology of the Borel subgroup $B$ of the special linear group $SL(2,\mathbb{F}_p), p$ is a prime number. Arcoding to Adem \cite{AJM} these are periodic groups. In order to compute the integral homology of $B,$ we decompose it into $\ell-$ primary parts. We compute the first summand based on Invariant Theory and compute the rest summand based on Lyndon-Hochschild-Serre spectral sequence. We assume that $p$ is an odd prime and larger than $3.$</p> 2019-08-18T22:18:56+00:00 ##submission.copyrightStatement## http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/1236 The influence of thickness on ammonia gas sensitivity of reduced graphene oxide films 2019-09-23T12:22:22+00:00 http://stdj.scienceandtechnology.com.vn/public/journals/2/article_1236_cover_en_US.png Tran Quang Nguyen tranquangnguyen27071986@gmail.com Huynh Tran My Hoa phamvanphuc2308@gmail.com Tran Quang Trung rungvlcr@yahoo.com.sg <p>Graphene is a single carbon layer in a two-dimensional (2D) lattice. Its delocalized π bonds give rise to unique electronic properties, but these π bonds are easily influenced by the environment. Meanwhile, many publications present that the sensitivity of graphene is not only necessarily intrinsic to this material but also by external defect. In this study, we produced reduced Graphene Oxide (rGO) sensors based on random rGO plates. We analyzed the ammonia (NH3 ) sensitivity of such sensors as a function of thickness of rGO films (in terms of change in transparence) at room temperature. When the thickness of rGO films decreased, a maximum response was observed for the thinnest rGO film (the transparence was 84 %), with a sensitivity up to 38 %. Our results suggest that the dependence of NH3 sensitivity on rGO films thickness is dictated by the fully exposed surface area for thinnest films and by 2D charge carrier hopping through edge defects.</p> <p>&nbsp;</p> 2019-08-03T00:00:00+00:00 ##submission.copyrightStatement## http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/1289 The research determines appropriate parameters in the synthesis process of syringic acid grafted chitooligosaccharides 2019-09-23T12:22:17+00:00 http://stdj.scienceandtechnology.com.vn/public/journals/2/article_1289_cover_en_US.png Hoai Van Bui hoai.hufi@gmail.com Dai-Nghiep Ngo ndnghiep@hcmus.edu.vn <p><strong>Introduction</strong>: The aim of this study is to determine appropriate parameters in the synthesis of syringic acid onto chitooligosaccharides (COSs) with an ascorbic acid/hydrogen peroxide redox pair in order to obtain the derivative with the highest grafting degree.</p> <p><strong>Methods</strong>: In this study, syringic acid grafted COSs, catalysed by an ascorbic acid/hydrogen peroxide redox pair were investigated. The synthesis conditions were investigated, including the mass ratio between syringic acid and COSs, pH, temperature and synthesis time. Characteristics of the derivative were evaluated by Thin Layer Chromatography (TLC), Ultraviolet-Visible (UV-vis) and Fourier Transform Infrared (FT-IR) spectroscopy. The activities of COSs and derivative were evaluated by antimicrobial ability.</p> <p><strong>Results</strong>: The results showed, that the best conditions for the synthesis were the mass ratio between syringic acid and COSs at 0.5:1, pH 5, temperature 27<sup>o</sup>C, for 6 hours with grafting degree at 32%. The TLC assay showed, that free ascorbic acid and syringic acid are not present in the product. The UV-vis and FT-IR data confirmed, that syringic acid was successfully conjugated onto COSs. Furthermore, the antibacterial assay showed that syringic acid grafted onto COSs had minimum inhibitory concentration against foodborne pathogenic bacteria at 1%.</p> <p><strong>Conclusion</strong>: The syringic acid onto chitooligosaccharides were successfully synthesized by free radical mediated grafting method with an ascorbic acid/hydrogen peroxide redox pair. The grafting degree of syringic acid onto COSs was greatly affected by many factors, including COSs, syringic acid, pH, as well as temperature and time of reaction. Moreover, the new derivative showed enhanced antibacterial capabilities, as compare to free COSs.</p> <p>&nbsp;</p> 2019-08-22T00:00:00+00:00 ##submission.copyrightStatement## http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/1660 Triterpenoid Glycosides from Olax imbricata 2019-09-23T12:22:16+00:00 http://stdj.scienceandtechnology.com.vn/public/journals/2/article_1660_cover_en_US.png Nga Thi Vo ngavt@hcmute.edu.vn Suong Thi Minh Huynh suonghuynh2405@yahoo.com.vn Huong Thi My Nguyen huongmanro@gmail.com Huy Thuc Duong thuchuy84@yahoo.com Phung Kim Phi Nguyen kimphiphung@yahoo.fr <p><strong>Introduction</strong>:<em> Olax imbricata</em>, owning antibacterial, antioxidant, and anti-inflammatory activities, has been investigated as one of traditional diabetic plants in Vietnam. In our previous publications on <em>Olax imbricata</em>, the structure analysis of the isolated compounds were reported, including two phenolic compounds, three phenolic glycosidic compounds, a sesquiterpenoid tropolone and 1,2,3,4-tetrahydronaphthalene derivatives. This article described the isolation and structure elucidation of three triterpenoid glycosides isolated from the methanol extract of Olax imbricata growing in Phu Yen province. Additionally, the evaluation of inhibitory activity for a-glucosidase was performed on a pure compound.</p> <p><strong>Method</strong>: The methanol extract of this plant applied the chromatographic techniques, including thin-layer chromatography and silica gel column chromatography, led to the isolation of three pure compounds. The structures of three isolated compounds were elucidated by the spectroscopic data, including 1D and 2D NMR spectra in a combination of HRESIMS, and the sugar moieties were elucidated by acid hydrolysis. The a-glucosidase inhibitory assay was applied to a pure compound by the colorimetric method.</p> <p><strong>Results</strong>: Three triterpenoid glycosides, namely 3-O-a-L-rhamnopyranosyl-(1-&gt;4)-b -D-glucopyranosyl-(1-&gt;3)-6′- O-ethyl-b -Dglucuronyl oleanolic acid (<strong>1</strong>), oleanolic acid 28-O-b -D-glucopyranoside (<strong>2</strong>) and spergulacin (<strong>3</strong>) were isolated and elucidated. The compound <strong>2</strong> showed its strong potentiala-glucosidase inhibitory activity with the IC<sub>50</sub> value of 56.15+/-1.31 mM.</p> <p><strong>Conclusion</strong>: Among them, compound 1 is a new one, the compounds <strong>2</strong> and <strong>3</strong> were isolated for the first time from the genus Olax. The compound 2 exhibited the potential a-glucosidase inhibition activity, contributing to demonstrating the diabetes treatment ability of <em>Olax imbricata</em> in the folklore.</p> <p>&nbsp;</p> 2019-09-02T00:00:00+00:00 ##submission.copyrightStatement##