04. Trường Đại học Khoa học tự nhiên (University of Science)
Tài nguyên nội sinh
Các bộ sưu tập số Luận văn Thạc sĩ, Luận án Tiến sĩ, Đề tài Báo cáo khoa học… của Thư viện Trường ĐH. Khoa học tự nhiên – ĐHQG-HCM được xây dựng nhằm hỗ trợ cho hoạt động giảng dạy và nghiên cứu của Nhà trường.
Duyệt 04. Trường Đại học Khoa học tự nhiên (University of Science) theo Nhan đề
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50 years field oriented control of three phase ac drives in the practice - The state-of-the-art
From DC motors (DCM) we know, it is possible to independently control the two currents of the flx and torque generating. Because the two DCM circuits are completely isolated, we obtain simple adjustment algorithms that require little computing time on the microprocessor. This paper aims to provide an overview of the development status of FOC in industrial practice. The content presented deals mainly with 3-phase induction motors.
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A balanced edge detector for aeromagnetic data
One of the most significant challenges in interpreting magnetic data is to mitigate the influence of the magnetization direction in the shape of the anomalies, especially when reduction to the pole fails to position them over the sources. We propose a balanced high-order filter that has low sensitivity to the direction of the resultant magnetization. We consider an edge-detector filter based on directional analytic signals of the vertically-integrated anomaly field. To ensure that anomalies from shallow and deep sources are equalized, we balance this filter with the magnitude of its two-dimensional Hilbert transform. The proposed filter is tested using aeromagnetic data from Apiai Terrane, Southern Brazil. The enhanced map is highly correlated with the study area's NE-SW trend of geological structures. Our results highlight the importance of using the directional analytical signals, which help reduce the influence of the magnetization direction, and the balancing filters, for equalizing the signal of shallow and deep causative sources.
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A closed-form solution for a queueing model of energy efficient Ethernet links
To save energy consumption of Ethernet switches, IEEE has standardized a new energyeffient operation for Ethernet links with a low-power state and transition mechanisms between the high-power state for transporting traff and the low-power state. In this paper, we propose a queueing model with the Markov Modulated Compound Poisson Process that is able to characterize backbone packet traffi We derive a closed-form solution for the stationary distribution of the proposed queueing model. We show that our model can capture an entire system where the transition times are constant.
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A colorimetric multiplex RPA approach for on-site dual monitoring of Vibrio parahaemolyticus and White Spot Syndrome Virus in Pacific Whiteleg shrimp
White spot syndrome virus (WSSV) and Vibrio parahaemolyticus represent the most prevalent and serious pathogens in Viet Nam's shrimp industry, annually inflicting major production losses. With no existing therapeutic measures, timely and accurate diagnosis is imperative for curbing outbreaks and limiting economic impacts through isolation and culling protocols. However, conventional techniques like polymerase chain reaction (PCR) and quantitative PCR require advanced laboratory infrastructure that is incompatible with rapid on-site pathogen surveillance.
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A combined approach for sustainable use of mountainous agricultural land: land suitability evaluation and ecological economic model
In the quest for poverty reduction, developing sustainable agriculture and stabilizing cultivation areas for specialty plants can be substantially improved by a new approach, which combines land suitability assessment and designs of ecological-economic models. The land suitability was assessed according to the FAO framework and the Vietnamese standard TCVN-8409:2012. The criteria were grouped in climate, topography, and soil physicochemical properties. The seven land utilization types selected for analysis included orange, banana, tea, turmeric, cinnamon, chinaberry, and chukrasia in mountainous regions of Thanh Hoa and Nghe An Provinces, Vietnam. The results showed that the most suitable lands (S1) for cultivating these crops were 169.916 ha for orange, 201.166 ha for banana, 107.636 ha for tea, 570,744 ha for turmeric, 233.987 ha for cinnamon, 633.306 ha for chinaberry, and 280.704 ha for chukrasia. Based on that foundation, the study designed three ecological models with economic efficiency and elaborated on six formations of the models. The analyses obtained from the research also allowed the proposal of six prioritized spaces for land use and environmental protection, which were illustrated on a 1:100,000 map of proposed agricultural land use. Therefore, this study provided a detailed and reliable approach for researchers and managers in agricultural land use planning. A proper procedure for the assessment of agricultural land in mountainous areas can be suggested from this research.
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A comparison of benzene-core PCF optical characteristics with hexagonal and circular lattices
This work compares the optical characteristics of benzene photonic crystal fiber with hexagonal lattice (H-PCF) and circular lattice (C-PCF). The difference in the radius between the rings is used to optimize effective area, nonlinearity, attenuation, and chromatic dispersion simultaneously. A series of numerical studies show that the effective mode area and attenuation are small for C-PCF and large for H-PCF geometries. That is the reason why the nonlinear coefficient of H-PCF is larger. Meanwhile, flat dispersion over a wide wavelength range is achieved mostly with H-PCFs in both dispersion modes. Our optimized fibers with near-zero flat dispersion, small loss, and large nonlinearity can enhance supercontinuum generation efficiency to generate a broad spectrum with high coherence.
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A COMPARISON OF THREE VARIANT CALLING PIPELINES USING SIMULATED DATA
Advances in next generation sequencing allow us to do DNA sequencing rapidly at a relatively low cost. Multiple bioinformatics methods have been developed to identify genomic variants from whole genome or whole exome sequencing data. The development of better variant calling methodologies is limited by the difficulty of assessing the accuracy and completeness of a new method. Normally, computational methods can be benchmarked using simulated data which allows us to generate as much data as desired and under controlled scenarios. In this study, They compared three variant calling pipelines: Samtools/VarScan, Samtools/Bcftools, and Picard/GATK using two simulated datasets. The result showed a significant difference between the three pipelines in two cases. In Chromosome 6 dataset, GATK and Bcftools pipelines detected more than 90% of variants. Meanwhile, only 82.19% of mutations were detected by VarScan. In NA12878 datasets, the result showed GATK pipeline was more sensitive than Bcftools and Varscan pipeline. All pipelines showed a high Positive Predictive Value. Moreover, by a measure of run time, VarScan was the highest pipeline but GATK has an option for multithreading which is a way to make a program run faster. Therefore, GATK is more effective than Bcftools and Varscan to variant calling with a lower coverage dataset.
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A comprehensive review of rock dust for soil remineralization in sustainable agriculture and preliminary assessment of nutrient values in micronized porous basalt rock from Nghe An province, Viet Nam
This review delves into the utilization of rock powder as a mineral-derived fertilizer to support soil remineralization in the context of sustainable agriculture. Soil remineralization has emerged as a key strategy for ensuring long-term soil fertility and reducing the dependency on synthetic fertilizers. This review critically assesses the methodological approaches applied in various studies, taking into account factors such as local rock mineralogy, soil conditions, crop types, and nutrient uptake by plants.
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A comprehensive review of rock dust for soil remineralization in sustainable agriculture and reliminary assessment of nutrient values in micronized porous basalt rock from Nghe An province, Viet Nam
This review examines the use of rock powder as a mineral-derived fertilizer to promote soil remineralization in sustainable agriculture. Soil remineralization has emerged as a key strategy for ensuring long-term soil fertility and reducing reliance on synthetic fertilizers. This review critically assesses the methodological approaches employed in various studies, considering factors such as local rock mineralogy, soil conditions, crop types, and plant nutrient uptake. The review encompasses methods such as nutrient value analysis, nutrient release rate assessment, and crop cultivation experiments conducted in both laboratory and field settings, as well as implications for soil remineralization. Additionally, we present findings from a preliminary study on the nutrient content of basalt rock from Nghe An Province, Vietnam. This investigation focuses on assessing the nutrient values in a specific porous basalt material processed into micro- and nanometer-sized particles using a high-energy ball mill, thereby enhancing the efficiency of nutrient release. The study employs various analytical techniques, including XRD, XRF, SEM/EDS, and ICP-MS, to quantify macro- and micro-nutrient compositions. While basalt rock samples may exhibit limitations in providing macronutrients (like K) compared to commercial azomite rock, they offer advantages in supplying secondary macronutrients (such as Ca). This analysis provides insights into the potential use of micronized basalt rock for soil remineralization.
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A CONTRIBUTION TO THE TAXONOMIC KNOWLEDGE OF THE GENUS Thrinchostoma (Thrinchostoma s. str.) Saussure (Hymenoptera: Halictidae) FROM VIETNAM, WITH NEW RECORDS OF THREE SPECIES AND A KEY TO SPECIES
Four species of the little-known bee genus Thrinchostoma Saussure, 1890 from Vietnam are presented including Thrinchostoma (Thinchostoma s. str.) tonkinense Blüthgen, 1926 and three new records: T. (T.) flaviscapus Bülthgen, 1926; T. (T.) sladeni Cockerell, 1913; and T. (T.) yunnanense Niu & Zhu, 2016. The occurrence of T. (T.) tonkinense Blüthgen, 1926 in Vietnam is confirmed. A key to species and distribution map of four species of the genus Thrinchostoma are also provided for Vietnam.
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A critical review on factors affecting the two-stage anaerobic digestion of biodegradable solid waste
Anaerobic digestion (AD) technology has attracted considerable attention from the scientific community and has become a crucial component of sustainable solid waste management systems. It is the only biotechnological process capable of converting highmoisture biomass waste into energy through a series of biochemical steps, including hydrolysis, acidogenesis, acetate production, and methane generation. Notably, the two-stage anaerobic digestion (TAD) process, which separates methanogenesis and hydrolysis into two distinct reactors, offers significant advantages over conventional methods. The performance of AD systems is influenced by various factors, including growth conditions (such as carbon-tonitrogen ratio, pH, and temperature), operational parameters (such as retention time and organic loading rate), feedstock pretreatment, and potential inhibitors. While these aspects have been widely studied in single-stage anaerobic digestion systems, research on their impact in TAD systems remains limited. This study aims to provide a comprehensive review of the factors affecting TAD systems. It synthesizes the latest research findings from recent years and discusses optimal operating conditions to enhance TAD performance.
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A data constrained approach for occupational silicosis detection on chest X-rays with few-shot learning
Occupational silicosis is a serious lung disease caused by long-term exposure to silica dust, mainly affcting workers in industries such as mining and construction. Diagnosis of silicosis is challenging due to subtle disease manifestations on chest X-rays (CXRs) and limited labeled medical data. Traditional deep learning models, such as Convolutional Neural Networks (CNNs), often require large datasets, which are often heavily expensive and time-consuming for collection and annotation, yet useful for specialized medical applications. To address these challenges, we present the use of FewShot Learning (FSL) to enable accurate detection of occupational silicosis with a minimal number of labeled examples. Our experimental results demonstrate that the FSL-based model achieves 84.4% accuracy and 46.0% mIoU in the 1-shot setting and 89.52% accuracy with 47.89% mIoU in the 4-shot setting. These fidings highlight the potential of FSL to improve diagnostic accuracy in datalimited environments, making it a viable solution for improving medical image analysis in resourceconstrained settings.
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A design of tuned mass damper with piezoelectric stack energy harvester and two-stage force amplification frame
The paper deals with a novel tuned mass damper (TMD) with an energy harvester consisting of a combination of piezo stacks and two-stage force amplification frames connected in series with TMD springs (TMD-2sPSFAFs). The governing equations of 2sPSFAF are established first, followed by those of TMD-2sPSFAF. It will be demonstrated that the reduced order model of the series combination of 2sPSFAF and TMD spring is an equivalent piezo stack energy harvester. Using the optimal results according to the fixed point theory, the conditions for selecting stiffnesses of piezo stacks and TMD spring are obtained. Next, a numerical examination of the electromechanical system reveals that the voltage amplitude curve has a fixed point independent of TMD spring stiffness. Furthermore, an effective stiffness of the TMD spring would be found to ensure that the peaks of mechanical magnification and voltage amplitude curves are of equal heights.
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A discovery of the genus Philoplitis Nixon, 1965 (Hymenoptera: Braconidae: Microgastrinae) in Vietnam, with description of two new species
The small microgastrine genus Philoplitis Nixon, 1965 from Vietnam is newly recorded. As a result, two new species are described and fully illustrated, viz. Philoplitis ipunctatus Long, sp. nov. and Philoplitis cariniferus Long, sp. nov.. Additionally, the genus Philoplitis is recorded for the first time for Vietnam, and the comparative characters of Philoplitis species summarized in a table.
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A Discussion on the Renaming of Cymodocea serrulata to Oceana serrulata: Implications for Seagrass Research and Conservation in Vietnam
The seagrass species previously classified as Cymodocea serrulata has been reclassified as Oceana serrulata. This reclassification is based on genetic analysis, which reveals a distinct separation of this species from others within the Cymodocea genus. This change will have implications for future research and taxonomy, highlighting the value of advanced genetic techniques in elucidating the relationships between seagrass species. Nevertheless, further analysis is warranted as new evidence emerges. The transition to the designation Oceana serrulata harmonizes traditional morphological descriptions with modern genetic phylogenetics, enabling a more precise classification.
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A fast overlapping community detection algorithm based on label propagation and social netwo rk graph clustering coefficient
In this paper, we present an algorithm to fid overlapping communities in very large social networks. The algorithm is based on the label propagation technique, and we fid the overlapping communities in the network by improving the clustering coeffient. Tests on a set of popular, standard social networks and certain real networks have shown the high speed and high effiency in fiding overlapping communities.