Tạp chí và Tuyển tập Hội nghị

Rehabilitation method plays an important role in maintenance process of the structure in general and the marine structure in particular. This paper aims to present a comparative study on the surface treatment for marine structure rehabilitation with glass fiber-reinforced high strength self-compacting mortar or SCM. Three types of rehabilitation methods in terms of surface treatment are as-cast surface, surface prepared with steel brush and surface with hole-connector. The experimental results showed that flexural strength of rehabilitated beam with as-cast surface, surface prepared with steel brush, and surface with hole-connector has improved 22%, 31% and 4% respectively higher than that of non-rehabilitated one. The precracked rehabilitated beams had load-carry capacity, for the case of as-cast surface, surface prepared with steel brush, and surface with hole-connector, their flexural strength were 41%, 37% and 31% respectively that of the corresponding non-precracked beams. Visual observation of the non-rehabilitated and rehabilitated beam cross-section after the third-point bending test revealed that their failure mode was similar. Besides, regarding the rehabilitated beams, there is no crack between conventional concrete and SCM.
Keywords: Rehabilitation, surface treatment, marine structure, high strength self-compacting mortar

An integrated method for multi-objective optimal design of a piped irrigation network
Số 82 - Số Tiếng Anh (12/2022) > trang 09-16 | Tải về (441.60 KB)
Dang Minh Hai

Tóm tắt

Recently, piped irrigation systems have been getting more and more widely utilized. This paper aims to propose an integrated Non-domimated Sorting Genetic Algorithm II (NSGA II) and Multiply Criteria Decision Making (MCDM) method for finding the ultimately optimal design of piped irrigation networks when simultaneously considering minimum cost of pipes and maximum life span of pipes. The coupled method was applied on a real piped irrigation system consisting of 30 pipe segments. First, 11 Pareto optimal solutions were found by using NSGA II. Then, the optimal solution with the pipe cost of 11.5 ×109 VND and the life span of 43.6 years was ultimately selected based on Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) selection methods. The proposed coupled method could be applied to find optimal design for other piped irrigation systems.
Keywords: Pipe networks, optimal design, NSGA II, selection methods

On finite-time attractivity for semilinear generalized rayleigh-stokes equation involving delays
Số 82 - Số Tiếng Anh (12/2022) > trang 17-24 | Tải về (224.11 KB)
Do Lan*, Nguyen Thi Ly, Pham Nam Giang, Vu Nam Phong

Tóm tắt

In this article, a functional semilinear Rayleigh-Stokes equation involving a fractional derivative with delay is investigated. The paper employs the time-fractional derivative which is Riemann-Liouville type. By using the fixed point argument and some useful estimates, the writers derive some global existence results. Also, the finite-time attractivity of all solutions are proved thanks to a Halanay- type inequality.
Keyword: Rayleigh-Stokes equation, finite-delay, finite-time stability

Calculating design flood under the context of climate change - a case study in the south central and central highlands area
Số 82 - Số Tiếng Anh (12/2022) > trang 25-31 | Tải về (563.31 KB)
Ngo Le Long*, Le Thi Hai Yen, Ngo Le An

Tóm tắt

Currently, under the impact of climate change (CC), the phenomenon of extreme and against-the-order-of-nature weather appears more and more. Floods often occur suddenly, causing a great deal of damage to people and property. The South Central and Central Highlands have short and steep terrain and are also home to many small and medium reservoirs subjected to direct changes from the flow variation. There have been many studies and reports on the impacts of climate change on heavy rainfall in the area. However, there is some uncertainty between the results due to differences in input models, scenarios and destabilization methods. The paper focuses on assessing and analyzing the change of maximum rainfall in the South Central and Central Highlands under the average climate change scenarios (RCP4.5) and high climate change scenarios (RCP8.5) using different global climate models (GCM). The variation among the models (in percentile 25 to 75 percent) varied from 10 percent to 50 percent, indicating the uncertainty in the rainfall simulation of each GCM. As a result, flood simulation from the rainfall will be different according to the different climate models. The proposed report on the creation of zoning maps of design flood variation under the impact of climate change is based on the "consensus" of trends among GCM models. Based on that, the design floods in the basins in each region will be adjusted accordingly to ensure the safety and economics of the works
Keywords: Design flood, climate change, global climate model, statistical details

An effective approach for low-light image enhancement
Số 82 - Số Tiếng Anh (12/2022) > trang 32-37 | Tải về (671.23 KB)
Phu-Hung Dinh

Tóm tắt

Low-light image enhancement plays an essential role in many applications of image processing. According to our observations, although many methods have been proposed to solve this problem, the obtained enhanced image may be lost in detail. This paper presents a new approach to solve the above problem. First, we introduce a method of decomposing an image into two components based on a Gaussian filter. Then, this image decomposition method is applied to decompose the input image into two components, the base layer ( ) and detail layer ( ). Local Brightening ( ) method is applied to the component, obtaining the component. The Laplacian edge detection (LED) operator is applied to the detail component ( ), yielding the feature component ( ). The Marine predators algorithm (MPA) is applied to find the suitable parameters ( , and ) for the , , and components. Finally, the enhanced image is calculated as the sum of the components ( , , and ) multiplied by the corresponding adaptation coefficients. Four evaluation indexes, three image enhancement algorithms, three other optimization algorithms, and 95 low-light images were used and evaluated. The experimental results show that the proposed method effectively enhances image quality and ensures sharp images.
Keywords: Low-light image enhancement, Gaussian filter, MPA.

Influence of different sand types on the properties of self-compacting concrete used for the Dong Nang Ren irrigation project-Bac Lieu province
Số 82 - Số Tiếng Anh (12/2022) > trang 38-44 | Tải về (744.62 KB)
Nguyen Viet Duc*, Vu Quoc Vuong

Tóm tắt

The scarcity of natural sand for construction in the current circumstance has made researchers and engineers search for another resource to replace it. This paper presents a study on the influence of crushed sand and natural sand on the properties of self-compacting concrete (SCC) implemented for the Dong Nan Ren irrigation project-Bac Lieu province. The experiment pointed out that at fresh state the SCC mixture with natural sand had shown better performance than that with crushed sand. In the meantime, both mixtures with crushed and natural sand have yielded the self-compacting properties (slump flow value and T500) in accordance with the requirement of the concerned project. Compressive and flexural strength at 28 days of the SCC with crushed sand are 10.1% and 21.9% respectively higher than that of the one with natural sand. Besides, both of them achieved the waterproof grade W6, which is suitable for construction of hydraulic structures. This outcome verifies that in case there is a lack of natural sand, the crushed sand can substantially replace it for the SCC production.
Keywords: Self-compacting concrete, crushed sand, natural sand, fresh and hardened concrete properties

A model for permeability estimation in porous media using a capillary bundle model with the similarly skewed pore size distribution
Số 82 - Số Tiếng Anh (12/2022) > trang 45-51 | Tải về (245.39 KB)
Nguyen Van Nghia, Dao Tan Quy and Luong Duy Thanh*

Tóm tắt

Permeability estimation has a wide range of applications in different areas such as water resources, oil and gas production or contaminant transfer predictions. Few models have been proposed in the literature using different techniques to estimate the permeability from properties of the porous media, such as porosity, grain size or pore size. In this study, we develop a model for permeability for porous media using an upscaling technique. For this, we conceptualize a porous medium as a bundle of capillary tubes with the similarly skewed pore size distribution. The proposed model is related to microstructural properties such as maximum radius, porosity, tortuosity and a characteristic constant of porous media. The model is successfully compared to published experimental data as well as to an existing model in the literature.
Keywords: Permeability, porous media, capillaries, pore size distribution

Applying supervised learning to find out water user’s behavior through ability to pay for irrigation water fee
Số 82 - Số Tiếng Anh (12/2022) > trang 52-60 | Tải về (281.19 KB)
Hoa-Thi-Thu Bui

Tóm tắt

Supervised machine learning is considered as one of the methods to find out variable relationships more informative compared to traditional statistical methods. In this article, both traditional statistical analysis and supervised machine learning approaches are used to study consumer behavior through their willingness to pay for irrigation services. 222 households in Nam Dinh, Thai Nguyen, and Phu Tho province were investigated. By the regression model, the results show that the variable area (DT) and yield of winter-spring crop (NS_DX) directly affect the household’s willingness to pay. The result shows that the majority willing to pay of households for irrigation water are higher than the current level. However, by the supervised machine learning approach, the errors of the model, predictions of the household’s payment level, and solutions to avoid overfitting are also shown, which could not be implemented if using traditional statistical analysis.
Keywords: Supervised learning, water user behavior, wilingness to pay

Y3Al3B2O12:RE3+ (RE = Tb, Eu): A promising material for the application of light emitting diode (LED)
Số 82 - Số Tiếng Anh (12/2022) > trang 61-67 | Tải về (420.92 KB)
Phan Van Do

Tóm tắt

Y3Al3B2O12 polycrystalline singly doped and co-doped with RE3+ ions (RE = Tb or/and Eu) have been synthesized by the solid-state interaction method at a temperature of 1250oC. The measurements of the luminescence excitation and luminescence spectra have been carried out at room temperature. The emission-color feature of materials was analyzed by CIE chromatic coordinates diagram and the correlated color temperature. The optimal concentration of RE3+ ions for emission of materials was found by studying the luminescence spectra. The rate and efficiency of the energy transfer process from Tb3+ to Eu3+ in Y3Al3B2O12:Tb3+,Eu3+ polycrystalline have also been calculated based on the lifetime of the 5D4 level of the Tb3+ ion.
Keywords: YAB polycrystalline, CIE diagram, energy transfer

Effects of riplox_based chemical complex on the control of urban lake water quality
Số 82 - Số Tiếng Anh (12/2022) > trang 68-75 | Tải về (298.66 KB)
Thi Thuy Bui*, Nguyet Anh Pham, Thuy Anh Tran, Duc Ha Tran

Tóm tắt

The objectives of this study were to prove the control of the lake water quality in terms of turbidity, total suspended solid (TSS), chemical oxygen demand (COD), and number of the algal cells by using the Riplox-based chemical complex (including (Ca(NO3)2) and (FeCl3) at concentrations ranging from 5 mM to 50 mM, with the presence of CuSO4 4 mg/L), considering the effects of the chemical fraction, the chemical concentration, and the treatment time. Raw water was sampled from Trieu Khuc Lake and treatment process was carried out in the lab scale. Overall, the great treatment results were achieved from the application of Ca(NO3)2/FeCl3 ratio of 1:1 (v/v) at a concentration of 0.5 M and the treatment time of 3 hours. The presence of CuSO4 4 mg/L in the Riplox-based chemical complex showed a good performance in reduction of number of the algal cells. The flocs formation when dissolving Ca(NO3)2 and FeCl3 in the water and denitrification were found to be major mechanisms for enhancing treatment performance. The findings demonstrate that the application of Riplox-based chemical complex with the presence of CuSO4 4 mg/L would control the urban lake water quality and can be widely applied for the case of Vietnam
Keyword: Algal reduction, denitrification, flocculation, urban lake, water quality

Water tenure analysis in Nui Coc Irrigation System in the Red River Basin, Vietnam
Số 82 - Số Tiếng Anh (12/2022) > trang 76-86 | Tải về (312.73 KB)
Le Van Chinh

Tóm tắt

Vietnam is considered to have a sound legal systems for water resources management but the enforcement of these systems remains limitations. This weakness and its causes were reported in various studies on institutional arrangements. However, the clear relations among stakeholders with respect to water resources, or water tenure, and level of implementation of water tenure governance which are related to these limitations remain undocumented. Using the new approach on water tenure analysis to identify issues and conflicts related to water tenure arrangements in a pilot area in Vietnam is the aim of this study. Most of the types of possible formal (8) and informal (7) water tenure arrangements were identified in the pilot area. The analysis of the water tenure governance in terms of 14 aspects and assessment of water tenure security were conducted in the study area. The study results illustrate the needs to improve the implementation of law enforcement and to strengthen the process of water tenure governance. Based on the analysis results, several relevant solutions are recommended including review and update of current legal framework and strengthening the enforcement of current legal regulations in Vietnam.
Keywords: Water tenure, institutional arrangements, governance

Review methods on predicting sediment scour at downstream of hydraulic works
Số 82 - Số Tiếng Anh (12/2022) > trang 87-95 | Tải về (339.92 KB)
Le Thi Thu Hien

Tóm tắt

The phenomenon of scouring at downstream of sluice or culvert has engrossed the attention of many researchers due to its importance in ensuring the safety of hydraulic structures. Persistent scouring may lead to exposure of the foundations of these structures, thereby causing a threat to their stability. In this study, three methods, namely: physical model, numerical model, artificial inteligent (AI) approach used to predict scour hole geometry are reviewed. Understanding their limitations, strengths and their basic scope of applicability can help researchers select a sufficient tool in predicting scouring problem.
Keyword: Sediment scour, physical model, numerical model, AI approach

Modern experiment methods to verify the efficiency of using mineral admixtures in cementitious material of hardened cement applied for concrete of marine structures
Số 82 - Số Tiếng Anh (12/2022) > trang 96-103 | Tải về (928.13 KB)
Nguyen Thi Thu Huong

Tóm tắt

An experimental study using modern experiment methods for the cement specimens incorporating 0% fly ash+0% silica fume-F0S0, 30% fly ash+0% silica fume-F30S0, 25% fly ash+5% silica fume-F25S5, 20% ash fly+10% silica fume-F20S10, 15% fly ash+15% silica fume-F15S15 was reported. Results confirmed that the specimens with the replacement fly ash and silica fume showed the helpful transformation of hydration products and a good improvement of microstructure on hardened cement. This is due to the reduction of calcium hydroxide and the increase of secondary CSH in the cement matrix from the pozzolanic reaction of a mineral admixture. The result of the study with modern experiment methods confirmed the improvement of strength and durability for hardened cement using mineral admixture, thereby ensuring the good applicability of the additional admixtures used in concrete of marine structures.
Keywords: Modern experiment method, cementitious material, admixture, hardened cement, hydration products, CaO.SiO2.H2O-CSH, concrete of marine structures