Journal of Water resources & Environmental engineering
Tạp chí của Trường Đại học Thủy lợi
Thực nghiệm trên mô hình vật lý hoàn thiện phương pháp xác định “thoát không” dưới tấm bê tông bản mặt
CFRD là đập đá đổ được chống thấm bằng các tấm bê tông bản mặt. Các đập CFRD khi đưa vào sử dụng thường có biến dạng lớn của thân đập dẫn đến hiện tượng mất tiếp xúc giữa tấm bê tông bản mặt và phần còn lại của thân đập. Kết quả tạo ra khoảng trống giữa tấm bê tông bản mặt và lớp đệm, hiện tượng này được các nhà nghiên cứu gọi là hiện tượng “thoát không”. Hiện tượng “thoát không” thay đổi cơ chế làm việc của tấm bê tông bản mặt, có thể dẫn đến sự cố sập gẫy ảnh hưởng đến an toàn của công trình. Tính khả thi của phương pháp phân tích dao động xác định “thoát không” tại hiện trường đã được chứng minh bằng mô hình số. Trong khuôn khổ bài báo này nhóm nghiên cứu sẽ trình bày kết quả thực nghiệm trên mô hình vật lý nhằm khẳng định các kết quả thu được từ các nghiên cứu trên mô hình số đồng thời xây dựng quy trình thực nghiệm trước khi đưa vào áp dụng thực tế tại hiện trường.
Reliability of benefits steel strong steel frame resistance to windload using finite element method
The article studies the Stochastic Finite Element Method (SFEM) to analyze bevel frames with semi-rigid connections subjected to wind loads when the connection and load parameters are the same quantities. random. Algorithm to analyze the structure's behavior is a combination of the method of mathematical modeling and the Monte-Carlo simulation. The calculation program is then used to evaluate the reliability of a semi-rigid beveled steel frame subjected to wind loads
Research on optimal operation method of multi- reservoir cascade hydropower using genetic algorithm
Optimizing the operation of hydropower plants (HPPs) is of great significance for the Vietnamese power system in the context of an increasing trend of renewable energy sources in power generation. HPPs with regulated reservoirs can be an effective solution to ensure balance and stability for the power system. To optimize the operation of reservoirs for power generation, classical mathematical optimization algorithms such as linear programming, nonlinear programming, and dynamic programming are commonly used. Currently, genetic algorithm (GA) is the most widely applied algorithm in the field of artificial neural networks (ANN) to find optimal weights. Applying the GA algorithm to the optimization of the operation of cascade hydropower reservoirs is a good solution for making operational decisions for the reservoir system. This article provides a basis for applying the GA algorithm to calculate optimal power generation operation for the Lai Chau, Ban Chat, Son La, Hoa Binh cascade hydropower reservoir system.
Policies and institutions in mangrove forest governance in Vietnam
Mangroves are important ecosystems that need to be well managed to preserve and promote their values. The research focused on the current status of policies and institutions for mangrove management. The results show that most of the mangrove areas in Vietnam (except special-use forests) are managed by the Commune People's Committee under the direct guidance of the Department of Natural Resurces and Environment (DONRE) at districts and provinces. Forest owner groups: Management Boards, Commune People's Committees cooperate with local communities and social organizations. There is an overlap between forest owner groups as well as management forms. The right to decide on the how to use mangroves, manage the forest area belongs to the goverment (through apropriate authorities). In general, mangrove management policy currently not yet encourage the participation of stakeholders. This result shows that it is necessary to continue to develop institutional and policy systems to better support mangrove governance
Experimental investigation of heat transfer for a free jet impinging on a flat surface
This paper reports the study of heat transfer of a free jet impinging on the heated flat surface. The horizontal free jet of water was impinged on the vertical surface, which was the heated copper metal plate. The images of temperature field on the copper plate were taken with an infrared thermal camera. Thus, the thermal images were used to discuss the heat transfer of the impinging jet.
Technology for controlling the flow fluctuation during operation of sluice in flood season, applied to sluice in Phuc Tho commune
The flow fluctuation has been studied in quite extensively for large-scale flood control works, however, this issue has been less addressed for culverts through levee. The operational experience has shown that there are many negative impacts of flow dynamics on the culvert structure and levee system such as the uplift instability, the local surface erosion of the stilling basin or the downstream channel, collapsing of part of the levee system, etc. According to the requirement of sluice and levee safety during flood season, the task of reducing fluctuation needs to be performed. The article not only pointed out the types of fluctuation that need to pay attention behind the operation gate, but also specified the locations where the sluice and levee could be destructively affected by the fluctuation. In addition, structural and non-structural countermeasures reducing negative impacts of fluctuation are also mentioned. Research has proposed measures to reduce flow dynamics for operating culverts without interfering with their structure.
Solutions to integrated water resources management on Phu Quoc island
Phu Quoc is the largest and beautiful island in Vientam. The unique environmental features of this island contribute to tourism appeal. The economic development focusing on tourism and urban expansion has been putting great pressure on water resources in this area. Although surface water is relatively abundant, Phu Quoc is facing many challenges in the development due to the temporal uneven distribution of surface water, along with increasing water demand. These are water scarcity in the dry season, partial flooding in the rainy season and water pollution, especially in the context of climate change. To ensure the sustainable development of Phu Quoc island, the application of integrated water resource management is necessary in this area. On the basis of assessing the existing legal framework and institutional settings for water resource management in Vietnam, as well as analyzing the current problems of water resources, this article has proposed several solutions to intergrated water resources management on Phu Quoc island as required by the existing legal framework.
Determination of load-bearing capacity of bored piles based on axial static compression test results in field conditions
Determining the load-bearing capacity of bored piles from axial static compression tests is a reliable method that allows testing of the calculated load-bearing capacity according to theory, thereby selecting the most accurate load-bearing capacity value for the pile. The principle of the experimental method is to load the pile in axial compression gradually, and measure the corresponding settlement of the pile until the ultimate load value of that load level is reached. This method is suitable for the practical working model of the pile and soil, thus providing highly reliable results in evaluating the load-bearing capacity of the pile. However, quantifying the displacement of the pile head corresponding to the ultimate load, which is only a convention; or the axial compression load, Pthu, is specified to be taken as two hundred percent of the design loadbearing capacity, Ptk, while this value depends on the theoretical calculation method of the pile load-bearing capacity, geotechnical conditions, and depth of the pile, resulting in different errors in the obtained results. This article is based on the results of axial static compression tests on bored piles at some construction sites in weak soil areas in Ho Chi Minh City, comparing and evaluating them with load-bearing capacity values calculated from different theoretical methods in TCVN 10304: 2014
Methods for determining the pricing of undergraduate training services in hydraulic structures engineering at Thuyloi university
Education and training are the basis for creating a quality labour force, discovering talents, and creating conditions for them to develop their full potential. In order to have a foundation and conditions for implementing regulations on assigning tasks, ordering, or bidding for the provision of undergraduate training services with the use of state budget funds for branches in the fields of agriculture and rural development, the Ministry of Agriculture and Rural Development has implemented the determination of the list of training disciplines, the development of economic and technical norms for undergraduate training, the criteria for selecting the training providers providing training services, etc. To have sufficient grounds for providing training services at the university level, it is necessary to calculate the training service price. The article researches the price of training services in the field of Hydraulic Structures Engineering at Thuyloi University to serve as a basis for future application
Stakeholder engagement in mangrove governance: Case study in the north and north central coastal Vietnam
Mangroves are known as an ecosystem with important environmental and economic roles. Implementing good mangrove governance is a necessary condition to ensure the conservation and promotion of these important ecosystem functions and services. Participation is at the core of resource management in general and mangroves in particular. Therefore, the objective of the study is to assess the status of stakeholder participation in mangrove governance. The results show that the group performing the state management function is assessed as having a high influence and this group is also said to be highly interested in the management of mangroves in the localities. The local mangrove development support group is assessed as having a low to high level of interest. The group directly involved in the protection and use of mangroves is said to have a high degree of influence and interest in mangrove management and development in the localities.
Sedimentation transportation model in Soc Trang coastal area by grain size trend analysis method
The distribution of sediments in the coastal and estuary region is quite complicated. The sediments in these areas are influenced by many natural factors such as tidal regimes, inshore currents as well as pathways of sediment transport from the rivers. Spatial variation of particle size parameters may reflect sediment transport patterns and sedimentation dynamics environments. In this study, 169 samples of coastal surface sediments in Soc Trang province were collected using a specialized sediment grab and analyzed to evaluate the sediment distribution in this area. These samples were analyzed by the Laser diffraction analysis on Horiba LA-960V2. The proportion of sand and alluvium in the samples is 43.98% and 56.02%, respectively. In the sand composition, small sand accounted for 52% (0.125 - 0.25 nm), very small sand accounted for 48% (0.063 - 0.125 nm), and the average grain grade of the whole sample is 4.61(Φ). The fine-grained components are mainly concentrated along the coast and gradually coarser towards the sea. It shows that the coastal currents dominate and affect the coastal sediments in the study area
Research on the sliding mode control algorithm for an automotive active suspension system
The suspension system is used to control the vibrations of the vehicle while traveling on the road. In this paper, the sliding mode control (SMC) algorithm is designed to control the active suspension (active suspension). This is a complex algorithm, and it is suitable for nonlinear oscillation systems with the input excitation being of predetermined form, such as automobile suspension systems. The simulation process is done by MATLAB-Simulink software with two specific cases. According to the calculation results, the displacement and acceleration of the vehicle body are reduced sharply when using the sliding control algorithm for the suspension system. In addition, the car's stability is also better guaranteed when equipped with an active suspension system (as evidenced by the change in wheel dynamics load). The chattering phenomenon still occurs when the oscillation changes phase; this is the nature of the sliding mode control algorithm. However, its influence is not great. In the following studies, the sliding mode control algorithm can be combined with other intelligent algorithms to solve this problem.
Method for building universal levels of training: Case studies for majors hydraulic construction technology in Thuyloi university
Building economic - technical norms on training as a basis for determining training costs is really necessary, an important basis for implementing the policy of innovation. The full calculation of training costs to implement the mechanism of assigning tasks, ordering or bidding for public service provision with the use of state budget funds. University-level training for majors in the fields of agriculture and rural development in our country shows that most industries have a low level of socialization, especially for training industries. Such as Soil Science, Engineering construction of water works... The job demand for university-educated human resources of the This discipline is huge. The article researches on training norms of hydraulic engineering at the Thuyloi University as a basis for calculation for lecturers.
The study on calculation methods to determinate basic parameters of photovoltaic pumping sytem (PVPS) supplying water for remote areas
The life of ethnic minority communities in remote areas is still difficult. Water and power supply for domestic use is still inadequate, especially the water source for daily use. When the infrastructure has not been invested, grid electricity has not reached these areas, Photovoltaic Pumping System (PVPS) is an effective solution. Currently, in Vietnam, the PVPS system is almost not applied because there is no scientific basis for calculation and design of this system. This paper provides a scientific basis for calculating the capacity as well as the flow rate of the solar pumping system. The study was applied to calculate the PVPS system supplying domestic water for Lung Lu villages in Ha Giang provice.
Design optimization of the condenser of loop heat pipe using a 1-dimensional numerical model
This paper reports the optimal calculation of loop heat pipe condensers length based on the maximum length of the condenser, the maximum heater temperature, and the condensation condition. A 1-dimensional numerical model, which assumes heat is transferred through 1 direction, was used for the calculation. A new solution algorithm was proposed using 3 additional conditions of condensers length, the pore diameter of the wick, and temperature limitation of the heat source besides the other 2 conditions of thermal energy balance and capillary/loss pressure. The calculation converged and the results were suitable qualitatively, for example, the condensers length was smaller in case of worsening condensation condition (natural convection) than in case of better condensation condition (forced convection) or to obtain shorter condensers length smaller pore diameter was required. However, experimental researches have to be carried out in the next step to confirm these results quantitatively
Study of irrigation water pricing method based on service approach
Irrigation service pricing has been receiving much attention from state management agencies and researchers, especially in the context of implementing the Law on Hydraulic Works. Although irrigation water pricing method has been regulated by the State, its implementation and efficiency for different types of irrigation systems are themes of discussion. This paper presents method for determining irrigation water prices based on a service approach and uses two-component water pricing to calculate irrigation water prices for the study case of pump irrigation system of Thanh Nghia cooperative. The research results indicated that irrigation service prices depend remarkly on the level of service provided. An adjustment of pump head and selection of pumping time are two key factors affecting the cost of irrigation system, and therefore, the irrigation service prices. The results showed that the variable cost of the irrigaiton system would decrease about 75% in a possible case for choosing by the farmers. The application of service-based approach and twocomponent water pricing is able to change the behavior of supplier and water users towards achieving efficiency in irrigated agricultural production. This study provides lessons learnt for implementation and replication of the new irrigation water pricing method for various irrigation systems nationwide in the future
Modern experiment methods to verify the efficiency of using mineral admixtures in cementitious material of hardened cement applied for concrete of marine structures
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.
Applying supervised learning to find out water user’s behavior through ability to pay for irrigation water fee
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.
Review methods on predicting sediment scour at downstream of hydraulic works
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.
Water tenure analysis in Nui Coc Irrigation System in the Red River Basin, Vietnam
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.
Y3Al3B2O12:RE3+ (RE = Tb, Eu): A promising material for the application of light emitting diode (LED)
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.
Effects of riplox_based chemical complex on the control of urban lake water quality
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
A model for permeability estimation in porous media using a capillary bundle model with the similarly skewed pore size distribution
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
Influence of different sand types on the properties of self-compacting concrete used for the Dong Nang Ren irrigation project-Bac Lieu province
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.
An effective approach for low-light image enhancement
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.
Calculating design flood under the context of climate change - a case study in the south central and central highlands area
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
On finite-time attractivity for semilinear generalized rayleigh-stokes equation involving delays
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.
An integrated method for multi-objective optimal design of a piped irrigation network
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.
Comparative study on the surface treatment for marine structure rehabilitation with glass Fiber-Reinforced high strength Self-Compacting mortar
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.
Research on the effects of reinforced concrete piles on the seepage characteristics in sand foundation of under-dike culverts by physical model
The under-dike culverts is one of the important items constituting a dike system. Many culverts are built on permeation sensitive sand foundation. The solution for seepage modifications is driving impermeability sheet pile and driving reinforced concrete piles to increase the bearing capacity of the foundation, keep the settlement within allowable range. There have been many incidents of under-dike culverts on sand foundation due to seepage during the last time. As recorded, most of the incidents occurred adjacent to the culverts with the foundation supported by reinforced concrete piles. The problem is that reinforced concrete piles can change the characteristics of seepage flow, thereby increasing seepage deformation and leading to instability of the structure. In this study, a mathematical relation between the hydraulics, works, soil factors has established based on the dimensional analysis method. On this basis, a new experimental model was designed to perform test series with different conditions. This paper presents the results of an experimental study to determine the change of seepage characteristics in the sand foundation of the under-dike culverts due to the influence of reinforced concrete piles