Efficient Generation of Coherent Stokes Field in Hydrogen Gas-Filled Hollow Core Photonic Crystal Fibres

In this paper, we study of the coherent Stokes generation in a transient Raman regime by Hydrogen gas-filled hollow-core photonic crystal fibres (HC-PCFs) configuration. The temporal and spatial evolution of the pump and Stokes field envelopes as well as the coherence and population inversion is numerically observed. The influence of the pump pulse width and gas pressure on the energy exchange along fiber and Stokes generation efficiency is investigated

SEASONAL VARIATION OF PHYTOPLANKTON FUNCTIONAL GROUPS IN TUYEN LAM RESERVOIR, CENTRAL HIGHLANDS, VIETNAM

Seasonal changes in freshwater phytoplankton assemblages at Tuyen Lam Reservoir in the Central Highlands of Vietnam were classified into 23 functional groups based on physiological, morphological, and ecological characteristics. A total of 168 species were recorded during 10 surveys from 2015 to 2019 at 7 sampling sites, with Chlorophyta dominating in number of species. Phytoplankton abundance varied from 0.18×105 to 21.2×105 cells/L during the study period, mainly due to cyanobacteria. Seven of the 23 functional groups were considered to be dominant (relative density > 5%).  The dominant functional groups were groups M and G in the dry season and groups M, G, P, and E in the rainy season. Group M (Microcystis aeruginosa) was the most common in both seasons, while group P (Closterium, Staurastrum, Aulacoseira), group E (Dinobryon, Synura), and group G (Sphaerocystis, Eudorina) were more common in the rainy season. The Shannon diversity index (H¢) showed that phytoplankton communities were relatively diverse and that most of the study sites were lightly polluted. However, the ecological status has deteriorated at some locations due to the overgrowth of group M, leading to eutrophication in this reservoir. This study highlights the usefulness of functional groups in the study of seasonal changes in phytoplankton dynamics. Functional groups are applied for the first time at Tuyen Lam Reservoir and can be used to predict early-stage cyanobacterial blooms in future studies

LBMT team at VLSP2022-Abmusu: Hybrid method with text correlation and generative models for Vietnamese multi-document summarization

Multi-document summarization is challenging because the summaries should not only describe the most important information from all documents but also provide a coherent interpretation of the documents. This paper proposes a method for multi-document summarization based on cluster similarity. In the extractive method we use hybrid model based on a modified version of the PageRank algorithm and a text correlation considerations mechanism. After generating summaries by selecting the most important sentences from each cluster, we apply BARTpho and ViT5 to construct the abstractive models. Both extractive and abstractive approaches were considered in this study. The proposed method achieves competitive results in VLSP 2022 competition.Comment: In Proceedings of the 9th International Workshop on Vietnamese Language and Speech Processing (VLSP 2022

Optical pulse Self-compressor combined the Nonlinear coupler with Backward Raman fiber amplifier

Based on the nonlinearity of the nonlinear optical coupler (NOC) and the amplifying capacity of the backward Raman fiber amplifier (PBRFA), a new optical system to compress the optical pulse (optical pulse self-compressor: OPSC) is proposed. Using the expressions describing relationship between output intensities from both output ports and input one of NOC and the expression describing the amplification of the PBRFA, the compressing process of the optical pulse propagating through OPSC is simulated. The results show that the peak of optical pulse will be enhanced and the duration of optical pulse will be reduced significantly, and the shape of input pulse is completely compressed with certain efficiency. It means the optical pulse is self-compressed without the pump pulse

OPTICAL BISTABILITY IN A DEGENERATE TWO-LEVEL EIT MEDIUM UNDER THE INFLUENCE OF AN EXTERNAL MAGNETIC FIELD: AN ANALYTICAL APPROACH

We investigate the behavior of optical bistability in a degenerate two-level atomic medium using an external magnetic field to separate the lower level into two distinct levels that both connect to an upper level by the probe and coupling laser fields. Based on analytical solutions, the absorption spectrum and behavior of optical bistability in an electromagnetically induced transparency regime under an external magnetic field are investigated. By controlling the external magnetic field, we find that the appearance and disappearance of the optical bistability can be easily controlled according to the strength of the magnetic field in the transparent window domain. Furthermore, the effects of the intensity of the coupling laser field and the parameters of the system on the behavior of optical bistability are also considered. The proposed model is useful for applications in all-optical switches and magneto-optic storage devices.We investigate the behavior of optical bistability in a degenerate two-level atomic medium using an external magnetic field to separate the lower level into two distinct levels that both connect to an upper level by the probe and coupling laser fields. Based on analytical solutions, the absorption spectrum and behavior of optical bistability in an electromagnetically induced transparency regime under an external magnetic field are investigated. By controlling the external magnetic field, we find that the appearance and disappearance of the optical bistability can be easily controlled according to the strength of the magnetic field in the transparent window domain. Furthermore, the effects of the intensity of the coupling laser field and the parameters of the system on the behavior of optical bistability are also considered. The proposed model is useful for applications in all-optical switches and magneto-optic storage devices

Radicular cyst in a primary molar following pulp therapy with gutta percha : a case report and literature review

A radicular cyst (RC) in deciduous dentition is relatively rare. This clinical report presents a case of RC that condition derived from a primary molar undergone an endodontic treatment with gutta-percha approximately one year ago. In addition, we also considered whether intracanal medicaments and gutta-percha filling material related to the formation and development of the cyst or not

Antibacterial Nanocomposites Based on Fe 3

For the vulcanized natural rubber (NR), incorporation of silver nanoparticles (AgNPs) into the NR matrix did not exhibit the bactericidal property against Escherichia coli (E. coli). However, incorporation of AgNPs into polyethylene (PE) matrix showed good antibacterial activities to both Gram-negative and Gram-positive bacteria. In the present work, NR/PE (85/15) blends have been prepared by melt blending with presence of compatibilizer in an internal mixer. To possess antibacterial property, AgNPs (5–10 nm) or Fe3O4–Ag hybrid nanoparticles (FAgNPs, 8 nm/16 nm) were added into PE matrix before its blending with NR component. The tensile test indicated that the presence of compatibilizer in NR/PE blend significantly enhanced the tensile strength and elongation at break (up to 35% and 38% increases, resp.). The antibacterial activity test was performed by monitoring of the bacterial lag-log growth phases with the presence of nanocomposites in the E. coli cell culture reactor. The antibacterial test showed that the presence of FAgNPs in NR/PE blend had a better antibacterial activity than that obtained with the lone AgNPs. Two similar reasons were proposed: (i) the faster Ag+ release rate from the Fe3O4–Ag hybrid nanoparticles due to the electron transfer from AgNP to Fe3O4 nanoparticle and (ii) the fact that the ionization of AgNPs in hybrid nanostructure might be accelerated by Fe3+ ions

Integrating of PLS-SEM and the Importance Performance Matrix Analysis to Exploring the Role of Provincial Competitiveness Index to Growth

Provincial competitiveness was one of the engines of growth under the institutional theory. The Vietnam Provincial Competitiveness Index (PCI) has been surveyed since 2005 to reflect the perceptions of local business environments, categorized into 10 sub-indices with 128 indicators. The current PCI has challenged the governance due to its broad construction. This study aimed to reconstruct the indicators in each PCI sub-index to be more specific for improving governance. The paper further explored the importance-of performance of both the PCI sub-index and its indicators to the provincial growth in Vietnam. Secondary data of 63 provinces during the period of 2017-2020 have been used with the employment of Exploratory Factor Analysis (EFA), Partial Least Square Structural Equation Model (PLS-SEM), and the extension of the importance-performance matrix analysis (IPMA). Our results showed the reliability and validity of 21 measured items under 5 PCI sub-indices. The findings confirmed the positive impact of the PCI index on growth. Moreover, the highest importance but lowest performance of SLO (law and order) was implied. SLA (land access and security of tenure), on the contrary, peaked the performance with the lowest importance. The importance of STC (time costs and regulatory compliance), SPA (proactive provincial leadership), and SLP (labor quality) has been ranked with the former sharing the highest priority while similar performance of the four sub-indices has been found. The results implied that the provincial authorities should prioritize their efforts to improve governance based on the importance-performance analysis of PCI sub-indices. Moreover, the importance and performance of each sub-index indicator reflected the great governance improvement with an average performance of 50%. However, special attention should be focused on vocational training, effective state officials, and legal support to the business due to their high importance but low performance

Exercise Motivation among Fitness Center Members: A Combined Qualitative and Q-Sorting Approach

This study aimed to explore the components of Exercise Maintenance Motivation (EMM) and identify its consensus and distinguishing aspects among members of fitness centers (FCs) in Vietnam. The study incorporated both qualitative and Q-sorting methodologies across two stages. The first stage involved conducting ten in-depth and four focus-group interviews with 39 members of six different FCs in Vietnam, resulting in the generation of 40 EMM statements. In the second stage, these statements were subjected to Q-sorting by 39 participants. The KADE application for the Q method was used for data analysis, and Principal Component Analysis was employed to determine the optimal number of factors. The analysis yielded four factors, encompassing 34 statements and accounting for 86% of the variance in EMM components among participants. These components, labeled “F1. Exercise achievements”, “F2. Exercise environments”, “F3. Exercise enjoyment”, and “F4. Workout-aholic”, achieved consensus among 17 (37%), 14 (30%), 5 (12%), and 3 (7%) participants, respectively. The leading motivational expressions were “get to be healthier”, “a better-looking appearance”, and “get a fit body appearance”. These were followed by FC-based supportive exercise conditions, positive feelings, and exercise addiction. There were five consensus statements that spanned all four factors. The numbers of distinguishing statements varied across factors, with F1, F3, and F4 each contributing 11 (28.2%) and F2 contributing 15 (38.5%). This study contributed to the four central drivers of EMM. To facilitate the development of a comprehensive EMM scale, future research should incorporate larger samples, allowing for a dissection of motivational paradigms.   Doi: 10.28991/HEF-2023-04-03-07 Full Text: PD