88 research outputs found

    Modal decomposition technique for multimode fibers

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    International audienceWe propose a new solution for modal decomposition in multimode fibers, based on a spectral and spatial imaging technique. The appearance of spurious modes in the spectral and spatial processing of the images at the output of the fiber under test when it has more than two modes is demonstrated theoretically. The new method, which allows us to identify spurious modes, is more accurate, simpler, and faster than previously reported methods. For demonstration, measurements in a standard step-index multimode fiber and a small-core microstructured fiber are carried out successfully

    Calculation of Temperature-Dependent Thermal Expansion Coefficient of Metal Crystals Based on Anharmonic Correlated Debye Model

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    This study aims to calculate the anharmonic thermal expansion (TE) coefficient of metal crystals in the temperature dependence. The calculation model is derived from the anharmonic correlated Debye (ACD) model that is developed using the many-body perturbation approach and correlated Debye model based on the anharmonic effective potential. This potential has taken into account the influence on the absorbing and backscattering atoms of all their nearest neighbors in the crystal lattice. The numerical results for the crystalline zinc (Zn) and crystalline copper (Cu) are in agreement with those obtained by the other theoretical model and experiments at several temperatures. The analytical results show that the ACD model is useful and efficient in analyzing the TE of coefficient of metal crystals

    Sea-level rise and resilience in Vietnam and the Asia-Pacific: A synthesis

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    Climate change induced sea-level rise (SLR) is on its increase globally. Regionally the lowlands of China, Vietnam, Bangladesh, and islands of the Malaysian, Indonesian and Philippine archipelagos are among the world’s most threatened regions. Sea-level rise has major impacts on the ecosystems and society. It threatens coastal populations, economic activities, and fragile ecosystems as mangroves, coastal salt-marches and wetlands. This paper provides a summary of the current state of knowledge of sea level-rise and its effects on both human and natural ecosystems. The focus is on coastal urban areas and low lying deltas in South-East Asia and Vietnam, as one of the most threatened areas in the world. About 3 mm per year reflects the growing consensus on the average SLR worldwide. The trend speeds up during recent decades. The figures are subject to local, temporal and methodological variation. In Vietnam the average values of 3.3 mm per year during the 1993-2014 period are above the worldwide average. Although a basic conceptual understanding exists that the increasing global frequency of the strongest tropical cyclones is related with the increasing temperature and SLR, this relationship is insufficiently understood. Moreover the precise, complex environmental, economic, social, and health impacts are currently unclear. SLR, storms and changing precipitation patterns increase flood risks, in particular in urban areas. Part of the current scientific debate is on how urban agglomeration can be made more resilient to flood risks. Where originally mainly technical interventions dominated this discussion, it becomes increasingly clear that proactive special planning, flood defense, flood risk mitigation, flood preparation, and flood recovery are important, but costly instruments. Next to the main focus on SLR and its effects on resilience, the paper reviews main SLR associated impacts: Floods and inundation, salinization, shoreline change, and effects on mangroves and wetlands. The hazards of SLR related floods increase fastest in urban areas. This is related with both the increasing surface major cities are expected to occupy during the decades to come and the increasing coastal population. In particular Asia and its megacities in the southern part of the continent are increasingly at risk. The discussion points to complexity, inter-disciplinarity, and the related uncertainty, as core characteristics. An integrated combination of mitigation, adaptation and resilience measures is currently considered as the most indicated way to resist SLR today and in the near future.References Aerts J.C.J.H., Hassan A., Savenije H.H.G., Khan M.F., 2000. 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    Impacts of monetary policies on the real estate bubble in Hanoi, Vietnam

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    The development of the real estate market always goes hand in hand with the fluctuation of the economy. In recent years, this market has experienced many recessions and «freezes» associated with the appearance of a real estate bubble. To approach this issue, this paper studies and gives an overview of the real estate bubble and the impact of monetary policies on the real estate bubble in Vietnam. This paper’s purpose is to identify and measure the influence of monetary policies, including interest rates, credit and money supply, on the real estate bubble in Ha Noi. The vector autoregression model (VAR) is used to test the interaction of the variables in the model. Dickey-Fuller test (DF) is applied to determine the stationarity of the variables, while the Akaike information criterion (AIC), Likelihood Ratio (LR), Final prediction error (FPE), Hannan-Quinn information criterion (HQ) and Schwarz criterion (SC) are used to find optimal lag of the model; then Granger causality test is utilized to determine the two-way correlation between variables. The results showed that the real estate bubble reacted quickly to shocks from macroeconomic factors representing the monetary policy, consisting of interbank interest rates, credit growth, and money supply growth. Thus, it is concluded that monetary policy is not only the cause of formation, but also one of the effective solutions to deflate the real estate bubble. AcknowledgmentThis research is funded by Vietnam Ministry of Education and Training (MOET) under grant number [B2022-NTH-03]

    Reliability and validity of the Vietnamese version of the Hamilton D-17 scale

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    BackgroundWhile depression is a common mental disorder, the diagnosis of this condition is still challenging. Thus, there is a need to have a validated tool to help evaluate symptoms of depression. This study aimed to evaluate the reliability and validity of the Vietnamese version of the Hamilton D-17 scale.MethodsA cross-sectional, descriptive, and validation study was conducted on 183 patients including 139 depressed and 44 non-depressed patients at the University Medical Center of Medicine and Pharmacy University at Ho Chi Minh City. Internal reliability and inter-rater reliability was measured using Cronbach's alpha and intraclass correlation coefficients (ICC). Confirmatory factor analysis (CFA) was used to evaluate construct validity. The Patient Health Questionnaire (PHQ9) was used to measure concurrent validity of the Hamilton D-17. Area under the ROC curve was used to measure criterion validity.ResultsBoth Cronbach alpha coefficient and ICC were at good level at alpha = 0.83 and ICC = 0.83. CFA with a second-order model consisting of four factors fitted the data at good to excellent level. The SRMR (Standardized Root Mean Squared Residual) was 0.066, RMSEA (Root Mean Square Error of Approximation) (90% CI) was 0.053 (0.036–0.069), CFI (comparative fit index) was 0.93, TLI (Tucker Lewis index) was 0.92. The Hamilton D-17 and the PHQ-9 had a correlation coefficient of r = 0.77 (p < 0.001). The Hamilton D-17 had a very high level of criterion validity with AUC of 0.93 (0.88–0.98).ConclusionThe Vietnamese version of the Hamilton D-17 scale has a high level of validity and reliability. The scale should be used to assess symptoms of depression among Vietnamese patients

    A non-destructive method to measure coupling and propagation losses in optical guided structures

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    International audienceWe propose and demonstrate a nondestructive method for loss measurement in optical guided structures. In the proposed approach, the device under test does not require connectors at its ends, thus making this technique available for both optical fibers and integrated optical waveguides. The loss measurement is feasible over a broad range, from low (0.2 dB/km ) to high (of the order of 1 dB/mm ) loss values. This method is validated through measurements performed on a microstructured holey fiber and on a photonic-crystal waveguide. The obtained results are in good agreement with theoretical calculations and measurements obtained by other approaches

    Impacts of Economic Development on the Awareness of Cultural Preservation of Ethnic Minority People in the Border Region of Northern Vietnam

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    Purpose: The aim of this study is to examine how the Vietnamese government's economic development strategies affect ethnic minority people's knowledge of cultural preservation in the border area of Northern Vietnam.   Theoretical framework: The study focuses on three main driven factors of the awareness of cultural preservation that are economic changes, societal changes, and environmental changes from three economic fields: agriculture, industry, and trade and services.   Design/methodology/approach: The research sample was taken from ethnic minorities in Northern Vietnam's border area. For questionnaire administration, interviewees are selected at random from the population. Face-to-face, drop-off, and phone-calling approaches were used to disseminate the questionnaire. We received 544 completed returns out of 725 surveys sent out. The data was then cleaned and analyzed with SPSS 20 software using Partial Least Squares Structural Equation Modelling (PLS-SEM).   Findings: The results of a study of ethnic minority communities in seven provinces in Northern Vietnam's border region show that the development of agriculture, industry, trade and service significantly impacts ethnic minority people's awareness of cultural preservation issues due to environmental changes. In contrast, economic and sociological developments appear to have little influence on ethnic minority people's attention to cultural preservation. This phenomenon may be due to the long-term effects of economic and sociological changes, which mostly affect intangible cultural heritages. In contrast, environmental impats are felt swiftly and primarily on physical cultural heritages that can be seen.   Research, Practical & Social implications: The findings of the research provide policymakers with valuable insights on the effects of economic development on cultural preservation. The study's recommendations can inform policies that promote sustainable economic development while preserving the cultural heritage of ethnic minority communities.   Originality/value: The research focuses on the border region of Northern Vietnam, which is an area of strategic importance for economic development and cultural preservation. The study's unique focus on this region provides insights into the cultural and economic dynamics of a specific area that has not been extensively studied

    ĐẶC ĐIỂM DÒNG CHẢY VEN BỜ BẮC TRUNG BỘ (HÀ TĨNH - THỪA THIÊN-HUẾ) THỜI KỲ 4/2016

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    This paper presents the modeled results of general current pattern (daily average value) in Northern Central Vietnam Coast (Ha Tinh - Thua Thien-Hue) during April 2016. Study results show that in general, current flowed from the North to the South with small and instable velocity (V ≈ 0.1 - 0.2 m/s). From 2nd to 6th April current flowed from the South to the North. From 7th to 29th April current flowed from the North to the South. During 13rd to 16th April current velocity was weak (V ≤ 0.1 m/s). In the southern region of Thua Thien-Hue province, the direction of current was instable (from 6th to 9th and from 20th to 22nd April current flowed from the South to the North). Current distribution pattern from modeled results was in accordance with the propagation characteristics of surface water temperatures in the studied area through data analysis of satellite images.Bài báo trình bày kết quả tính toán trường dòng chảy tổng hợp trung bình ngày cho khu vực ven bờ Bắc Trung Bộ (Hà Tĩnh - Thừa Thiên-Huế) thời kỳ 4/2016. Kết quả nghiên cứu cho thấy trong thời gian nghiên cứu nhìn chung dòng chảy tổng hợp trung bình ngày có hướng từ bắc xuống nam, tốc độ tương đối nhỏ V ≈ 0,1 - 0,2 m/s và không ổn định. Từ 2-6/4/2016 dòng chảy tổng hợp trung bình ngày ven bờ có hướng từ nam lên bắc. Từ 7-29/4/2016 dòng chảy ven bờ có hướng từ bắc xuống nam. Các ngày 13-16/4/2016 dòng chảy tổng hợp trung bình ngày có tốc độ nhỏ (V ≤ 0,1 m/s). Khu vực phía nam Thừa Thiên-Huế dòng chảy tổng hợp trung bình ngày có hướng bị biến động mạnh nhất (các ngày 6-9/4 và 20-22/4 hướng dòng từ nam lên bắc). Đặc điểm phân bố dòng chảy tính toán tương đối phù hợp với đặc điểm lan truyền nhiệt độ nước tầng mặt tại khu vực nghiên cứu qua số liệu phân tích ảnh vệ tinh

    De novo copy number variations in candidate genomic regions in patients of severe autism spectrum disorder in Vietnam

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    Autism spectrum disorder (ASD) is a developmental disorder with a prevalence of around 1% children worldwide and characterized by patient behaviour (communication, social interaction, and personal development). Data on the efficacy of diagnostic tests using copy number variations (CNVs) in candidate genes in ASD is currently around 10% but it is overrepresented by patients of Caucasian background. We report here that the diagnostic success of de novo candidate CNVs in Vietnamese ASD patients is around 6%. We recruited one hundred trios (both parents and a child) where the child was clinically diagnosed with ASD while the parents were not affected. We performed genetic screening to exclude RETT syndrome and Fragile X syndrome and performed genome-wide DNA microarray (aCGH) on all probands and their parents to analyse for de novo CNVs. We detected 1708 non-redundant CNVs in 100 patients and 118 (7%) of them were de novo. Using the filter for known CNVs from the Simons Foundation Autism Research Initiative (SFARI) database, we identified six CNVs (one gain and five loss CNVs) in six patients (3 males and 3 females). Notably, 3 of our patients had a deletion involving the SHANK3 gene–which is the highest compared to previous reports. This is the first report of candidate CNVs in ASD patients from Vietnam and provides the framework for building a CNV based test as the first tier screening for clinical management
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