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Nguyen Thi Duyen,Nguyen Minh Khoi,Phan Nguyen Truong Thang,Duong Minh Tan,Tran Viet Hung,Do Thi Ha 한국생약학회 2020 Natural Product Sciences Vol.26 No.4
A new compound, 3β-acetoxylanosta-7,9(11),24-triene-26-al (3), and seven known compounds (1 – 2 and 4 – 8) were isolated from Ganoderma tropicum (Jung.) Bres. collected in Tay Nguyen, Vietnam. The structures of these compounds were determined by one- and two-dimensional nuclear magnetic resonance spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and high-resolution ESI-MS, and by comparison with literature data. All of the isolated compounds were tested for nitroblue tetrazolium (NBT) reduction activity in Saccharomyces cerevisiae-stimulated RAW 246.7 cells. Among them, compounds 2 – 4 and 6 – 8 enhanced the NBT reduction in a dose-dependent manner.
Structural reliability analysis using temporal deep learning-based model and importance sampling
Truong-Thang Nguyen,Viet-Hung Dang 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.3
The main idea of the framework is to seamlessly combine a reasonably accurate and fast surrogate model with the importance sampling strategy. Developing a surrogate model for predicting structures’ dynamic responses is challenging because it involves high-dimensional inputs and outputs. For this purpose, a novel surrogate model based on cutting-edge deep learning architectures specialized for capturing temporal relationships within time-series data, namely Long-Short term memory layer and Transformer layer, is designed. After being properly trained, the surrogate model could be utilized in place of the finite element method to evaluate structures’ responses without requiring any specialized software. On the other hand, the importance sampling is adopted to reduce the number of calculations required when computing the failure probability by drawing more relevant samples near critical areas. Thanks to the portability of the trained surrogate model, one can integrate the latter with the Importance sampling in a straightforward fashion, forming an efficient framework called TTIS, which represents double advantages: less number of calculations is needed, and the computational time of each calculation is significantly reduced. The proposed approach’s applicability and efficiency are demonstrated through three examples with increasing complexity, involving a 1D beam, a 2D frame, and a 3D building structure. The results show that compared to the conventional Monte Carlo simulation, the proposed method can provide highly similar reliability results with a reduction of up to four orders of magnitudes in time complexity.
High-Resolution Simulations for Vietnam - Methodology and Evaluation of Current Climate
Jack Katzfey,Kim Nguyen,John McGregor,Peter Hoffmann,Suppiah Ramasamy,Hiep Van Nguyen,Mai Van Khiem,Thang Van Nguyen,Kien Ba Truong,Thang Van Vu,Hien Thuan Nguyen,Tran Thuc,Doan Ha Phong,Bang Thanh Ng 한국기상학회 2016 Asia-Pacific Journal of Atmospheric Sciences Vol.52 No.2
To assist the government of Vietnam in its efforts to better understand the impacts of climate change and prioritise its adaptation measures, dynamically downscaled climate change projections were produced across Vietnam. Two Regional Climate Models (RCMs) were used: CSIRO’s variable-resolution Conformal-Cubic Atmospheric Model (CCAM) and the limited-area model Regional Climate Model system version 4.2 (RegCM4.2). First, global CCAM simulations were completed using bias- and variance-corrected sea surface temperatures as well as sea ice concentrations from six Coupled Model Intercomparison Project Phase 5 (CMIP5) global climate models. This approach is different from other downscaling approaches as it does not use any atmospheric fields from the GCMs. The global CCAM simulations were then further downscaled to 10 km using CCAM and to 20 km using RegCM4.2. Evaluations of temperature and precipitation for the current climate (1980-2000) were completed using station data as well as various gridded observational datasets. The RCMs were able to reproduce reasonably well most of the important characteristics of observed spatial patterns and annual cycles of temperature. Average and minimum temperatures were well simulated (biases generally less than 1oC), while maximum temperatures had biases of around 1oC. For precipitation, although the RCMs captured the annual cycle, RegCM4.2 was too dry in Oct.-Nov. (−60% bias), while CCAM was too wet in Dec.- Mar. (130% bias). Both models were too dry in summer and too wet in winter (especially in northern Vietnam). The ability of the ensemble simulations to capture current climate increases confidence in the simulations of future climate.
Hoan Minh Tran,Lan Ngoc Tan Phan,Thang Van Le,Thuy Thuy Truong,Tam Huu Nguyen,Khuong Tung Truong,Le-Thu T. Nguyen,Mai Thanh Phong,Ha Tran Nguyen 한국고분자학회 2019 폴리머 Vol.43 No.4
A novel organic photocatalyst, 4-(10H-phenothiazin-10-yl)-N,N-diphenylaniline (PDPA) has been successfully synthesized from triphenylamine and phenothiazine moiety via Buchwald-Hartwig C-N coupling. The chemical structure of catalyst was characterized via proton nuclear magnetic resonance (1H NMR) and the optical properties were investigated via UV-vis spectroscopy. The PDPA has been applied as an organic photocatalyst for metal free atom transfer radical polymerization (O-ATRP). The well-controlled molecular weights of polymethacrylates have been obtained with high yield of 95% and narrow polydispersity index (Đ).
A Metadata-enabled Approach for Scalable Video Streaming in Heterogeneous Networks
Thang, Truong Cong,Le, Hung T.,Nguyen, Duc V.,Pham, Anh T. Korea Multimedia Society 2015 The journal of multimedia information system Vol.2 No.1
In today's pervasive computing environments, multimedia content should be adapted to meet various conditions of network connections, terminals, and user characteristics. Scalable Video Coding (SVC) is a key solution for video communication over heterogeneous networks, where user terminals have different capabilities. This paper presents a standard-compliant approach that adapts an SVC bitstream to support multiple users. The adaptation problem is formulated as an optimization problem, focusing on the tradeoff between qualities of different spatial layers of an SVC video. Then the adaptation process is represented by standard metadata of MPEG-21, which can be solved by universal processing to enable interoperable and automatic operation. Our approach provides the users with optimal quality, a wide flexibility, and seamless adaptation. To the best of our knowledge, this is the first study that shows the adaptation tradeoff between spatial layers of a conforming SVC bitstream.
Adaptive Video Streaming over HTTP with Dynamic Resource Estimation
Truong Cong Thang,Hung T. Le,Hoc X. Nguyen,Anh T. Pham,강정원,노용만 한국통신학회 2013 Journal of communications and networks Vol.15 No.6
Adaptive hypertext transfer protocol (HTTP) streaminghas become a new trend to support adaptivity in video delivery. AnHTTP streaming client needs to estimate exactly resource availabilityand resource demand. In this paper, we focus on themost importantresource which is bandwidth. A new and general formulationfor throughput estimation is presented taking into account previousvalues of instant throughput and round trip time. Besides, weintroduce for the first time the use of bitrate estimation in HTTPstreaming. The experiments show that our approach can effectivelycope with drastic changes in connection throughput and video bitrate.
Adaptive Video Streaming over HTTP with Dynamic Resource Estimation
Thang, Truong Cong,Le, Hung T.,Nguyen, Hoc X.,Pham, Anh T.,Kang, Jung Won,Ro, Yong Man The Korea Institute of Information and Commucation 2013 Journal of communications and networks Vol.15 No.6
Adaptive hypertext transfer protocol (HTTP) streaming has become a new trend to support adaptivity in video delivery. An HTTP streaming client needs to estimate exactly resource availability and resource demand. In this paper, we focus on the most important resource which is bandwidth. A new and general formulation for throughput estimation is presented taking into account previous values of instant throughput and round trip time. Besides, we introduce for the first time the use of bitrate estimation in HTTP streaming. The experiments show that our approach can effectively cope with drastic changes in connection throughput and video bitrate.
Huong, Truong Thu,Bac, Ta Phuong,Thang, Bui Doan,Long, Dao Minh,Quang, Le Anh,Dan, Nguyen Minh,Hoang, Nguyen Viet International Journal of Computer ScienceNetwork S 2021 International journal of computer science and netw Vol.21 No.6
Since machine learning was invented, there have been many different machine learning-based algorithms, from shallow learning to deep learning models, that provide solutions to the classification tasks. But then it poses a problem in choosing a suitable classification algorithm that can improve the classification/detection efficiency for a certain network context. With that comes whether an algorithm provides good performance, why it works in some problems and not in others. In this paper, we present a data-centric analysis to provide a way for selecting a suitable classification algorithm. This data-centric approach is a new viewpoint in exploring relationships between classification performance and facts and figures of data sets.
Nga Thi Hang PHAN,Thang Quyet Nguyen,Dung TRUONG,Nguyen The HUYNH 한국유통과학회 2019 The Journal of Asian Finance, Economics and Busine Vol.6 No.2
The paper aims to investigate the factors of brand equity affecting the purchase intention of car buyers in Ho Chi Minh City. The authors use qualitative method and quantitative research to study the matters, specifically using scales and data collected for Cronbach alpha reliability testing, analysizing the discovery factor of EFA, CFA and verifying the regression models through AMOS software with SEM linear modeling. The study proposes four factors: (1) brand awareness, (2) self-expression value, (3) perceived quality, (4) brand psychology impacting on the brand loyalty and intention to buy cars of customers. The results show that all four factors are statistically significant for positive brand loyalty and purchase willing. The results showed that brand loyalty positively affects consumers' intention to buy cars. Among the factors included in the study, the brand psychology is a new factor which developed by experts in the context of Vietnam. This is the first study in Vietnam to quantify clearly the element of "crowd psychology" affecting the interests and habits of Vietnamese consumers. This explains why Vietnamese consumers prefer brands that are familiar in the market and some new cars with nice models and colors suitable for Vietnamese psychology.