Pochai, Nopparat

Preferred name

Pochai, Nopparat

Alternative Name

Pochai, N.

Main Affiliation

School of Science

nopparat.po@kmitl.ac.th

Now showing 1 - 10 of 92

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A simple mathematical model of water quality control for recirculating pond on a shrimp farm
(2021-01-01)
Kraychang, Witsarut
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Meechowna, Sompoom
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Welamas, Weerapol
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Pochai, Nopparat
— In many countries, shrimp is one of the most valuable export commodities. Shrimp farming raises a number of issues, including shrimp waste contamination, shrimp feed residues, and biochemical reactions in the shrimp pond. In this research, mathematical models were utilized to analyze the water quality in shrimp ponds and wastewater treatment ponds for circulation systems, with BOD serving as a significant indication of water quality. In the circulation system, two separate ponds were investigated: the shrimp pond and the wastewater treatment pond. The shrimp pond was tested for pollutant levels generated by shrimp excretion, shrimp feed residues, and biochemical reactions. A Chaipattana low-speed surface aerator was used to treat the shrimp pond pollutants, and some of the waste was drained to the next pond. The pollutant levels in the treatment pond were investigated. This pond is polluted by sewage from the shrimp pond as well as biological reactions. Lower-efficiency aerators treat the contaminants in the treatment pond, and part of the waste is transferred to the next pond. The advection equation is being used to describe the pollutant concentration in two ponds, and Runge-Kutta order 4 is also being used to determine the approximated solution to the problem. The results of the mathematical model are presented in graphs and tables comparing the pollutant concentrations in many cases. The last section shows an example of wastewater treatment by aerator in a shrimp pond. It was found to reduce the number of days needed for wastewater treatment. The water quality could generate shrimp in this condition, but the water quality could not grow shrimp if the aerator was not turned on the first day of shrimp farming and then turned on the next day. On the first day of shrimp farming, the aerator should not be turned off since the pollutant concentration would be high, making wastewater treatment difficult the next day. In addition, the research showed a maximum five-day reduction in wastewater treatment time (last days of the month). When wastewater is treated every other day, every three days, or every five days, the pollutant concentration must be lower than the minimum necessary for shrimp farming. It can also be used to reduce the cost of water treatment by saving energy.
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A One-dimensional Salinity Measurement Model in the Chao Phraya River with the Chao Phraya Barrage Dam Using a Shooting Method
(2023-03-01)
Vanishkorn, Buddhaporn
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Pochai, Nopparat
Sea water receding from the Gulf of Thailand causes salinity diffusion in the Chao Phraya River, Thailand, and the amount of northern water is reduced in the dry season. It has an impact on people, particularly the generation of tap water. The Samlae raw water pumping station is the major pumping station. The Ban Krachaeng subdistrict is located in Mueang district, Pathum Thani province, and is affected by saltwater intrusion, which causes the salinity level to exceed the recommended threshold. In order for the Metropolitan Waterworks Authority (MWA)'s water supply system to achieve the standard, the salinity index at the Samlae raw water pumping station is controlled to not exceed the surveillance threshold of 0.25 g/l in this research. A barrage dam consists of a number of large gates that can be opened or closed to control the amount of fresh water passing through. There is a Chao Phraya barrage dam which is across the Chao Phraya River at Chai Nat, the northern part of the focused area. The objective of this research is to demonstrate a onedimensional steady-state salinity measurement model in a river with a barrage dam. Irrigation is done in rivers with dams using the shooting method to estimate the solution. The results obtained from simulating simulated salinity measurements from Phra-Nakhon Tai Power Plant Station to Samlae Station demonstrated that the shooting method can be used to accurately estimate the solution. Freshwater flow velocity and salinity dissolving efficiency were discovered to be the most important elements controlling salinity levels. The suggested salinity control approach may help to regulate the salinity level until it reaches a normal level.
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A Simulation of Shoreline Evolution with a Groin Structure Using an Alternative Machine Learning Algorithm
(2025-07-01)
Manilam, Surasak
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Pochai, Nopparat
Uneven sediment transport is a major cause of coastal erosion. Using groin structures is one method to help slow the outflow of sediment from the shoreline. Studying coastal behavior and forecasting future shoreline changes are crucial for managing and assessing the viability of remediation strategies. This research presents simulations of shoreline evolution with a single groin structure using two different methods, such as mathematical modeling and an alternative machine learning. A mathematical model is a representation of a real-world shoreline evolution phenomenon using partial differential equations. A machine learning algorithm is designed to learn patterns and relationships directly from real data. In this research, an alternative machine learning algorithm is designed to learn patterns and relationships directly from mathematical simulation data and let the machine make a decision in a situation that it has never learned before. For mathematical modeling, we introduced a one-dimensional model to predict the shoreline evolution. The initial and the boundary conditions with related parameter settings are introduced. The Saulyev finite difference method is used to obtain the approximated solution. An alternative machine learning algorithm for unexpected shoreline evolution prediction is also proposed. For alternative machine learning simulations, we identified six suitable features for the training dataset and developed an alternative K-nearest neighbor algorithm. It provides a way of predicting the evolution of the shoreline with a single groin structure. Additionally, an exact solution in an ideal scenario is used to test the precision of the simulation as well. The results show that the Saulyev technique outperforms an alternative K-nearest neighbor algorithm due to the lower root mean square error value. Both results of them are closed together. According to the research, mathematical modeling outperforms the KNN regression technique in terms of computational effectiveness during time periods of 0.5, 1, 5, 10, 15, and 20 years. Based on the modeling configuration and parameter simplicity, the KNN algorithm is still a good option for non-expert users.
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Numerical simulations for reactive nitrogen compounds pollution measurements in a stream using Saulyev method
(2020-01-01)
Vongkok, Areerat
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Pochai, Nopparat
Nutrient pollution is one of most harmful environmental problems, and is caused by surplus nitrogen in water. This nitrogen concentration occurring in water can take several forms, such as organic nitrogen, ammonia, nitrite, nitrate, and dissolved nitrogen gas. Pollution levels can be measured via data collection; however, this is a rather difficult and complex process, and the results obtained widely deviate in term of measurement. A mathematical model can be used in complicated water-quality measurement. The advection-dispersion-reaction model provides a pollutant concentration field. In this research, there are five numerical models for nitrogen pollutant concentration measurement in a stream proposed: a total nitrogen dispersion model, an organic nitrogen dispersion model, an ammonia dispersion model, a nitrite dispersion model, and a nitrate dispersion model. The traditional Forward Time Central Space finite difference technique and the unconditionally explicit Saulyev technique are employed to obtain five approximated types of organic and inorganic nitrogen pollutant concentrations in each time and place. This paper proposes five forms of nitrogen pollutant measurement model for the unconditionally stable Saulyev method, so as to make it more accurate without incurring any significant loss of computational efficiency. The five approximated forms of pollutant concentrations obtained indicate that all models improve the nutrient pollution measurement process.
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Numerical models of nitrogen compound measurements in a stream with removal mechanism using Saulyev technique with cubic spline interpolation
(2019-11-17)
Vongkok, Areerat
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Pochai, Nopparat
Nutrient pollution negatively affects ecology, environment and human health, due to excess contaminated nitrogen in aquatic ecosystems. Nitrogen has various forms, such as organic nitrogen, ammonia, nitrite, and nitrate. Nitrogen removal mechanisms are important for nitrogen compound pollutant control. Microbial agents provide an alternative for nitrogen removal and are implemented by natural removal mechanisms. For pollution level measurements, data collection from actual measurement processes can be only limitedly collected in some situations. The mathematical models play a role in data approximation that can describe relations of processes and reactions. Six numerical models in one-dimensional nitrogen pollutant and nitrogen remover measurement in a stream are proposed. The proposed models are combined with total nitrogen with a removal mechanism, organic nitrogen, ammonia, nitrite, nitrate, and nitrogen remover dispersion models. These models are implemented through use of an efficient numerical technique, which is the unconditionally explicit Saulyev finite difference technique, associated with the cubic spline interpolation to initial and left boundary conditions through practical simulations. All six models related to nitrogen compound measurements in a stream with removal mechanism models give accurately approximated solutions. The proposed numerical models can be applied to other realistic problems.
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A numerical computation of the non-dimensional form of a non-linear hydrodynamic model in a uniform reservoir
(2009-11-01)
Pochai, Nopparat
A mathematical model is used to simulate the water current and the elevation in a uniform reservoir. A non-linear hydrodynamic model that provides the velocity field and elevation of the water flow is considered. In the simulating process, the Lax-Wendroff technique is used to approximate the solutions. The numerical solution can be the input data for a water-quality model that is applicable for the optimal control of water treatment in the system to achieve minimum cost. © 2009 Elsevier Ltd. All rights reserved.
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A mathematical model for the risk analysis of airborne infectious disease in an outpatient room with personal classification factor
(2020-12-01)
Suebyat, Kewalee
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Oyjinda, Pravitra
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Konglok, Sureerat A.
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Pochai, Nopparat
Every day, a large number of people will use a hospital, creating a main air quality problem which may mean the risk of airborne infectious disease contamination in outpatient rooms, and affects human health. TB, COVID-19, MERS, and SARS are a hazardous communicable disease which are spread from person to person through the air or the aerosol in different ways, such as through coughing, spitting, sneezing, speaking, or through wounds. US scientists in the laboratory have shown that the virus can live in an aerosol and remain infectious for at least 3 hours. A new human coronavirus now known as the serious acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (formerly known as HCoV-19) emerged in late 2019 in Wuhan, China, and is now triggering a pandemic. COVID-19, TB, MERS and SARS-threats and opportunities progress against deadly infection make more people sick in the hospital. Therefore, we should be aware of the care and control of these diseases. Consequently, good air quality management is required to control and reduce possible infected air, such as carbon dioxide (CO2) concentration. In this research, a mathematical model for the risk analysis of airborne infectious disease in an outpatient room is proposed. Not only considering one type of person but also in this research, people are considered according to personal classifications. There are 4 types-patient, relative, worker, and outsider, staying in an outpatient room, which is in accordance with the real world. Air quality control manipulations are simulated using the inlet and outlet ventilation rates adjustment under the condition of a number of surrounding people with a personal classified factor. The fourth-order Runge-Kutta (RK4) is used to approximate the model solution. The proposed numerical model can be used to describe the dynamical dispersion of airborne infectious disease in an outpatient room. The results of the model are satisfactory, and it will be able to control airborne disease in more complicated structures.
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Health Behavior and Emotional Responses of Thai National Team Athletes during the COVID-19 Pandemic: A Comparative Study of Individual and Team Sports
(2025-08-01)
Pluemsamran, Theeratheeta
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Pariyavuth, Pariya
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Pochai, Nopparat
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Panurushthanon, Phichayavee
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Punthipayanon, Sirichet
Objectives: COVID-19 significantly impacted athletes’ health behavior and emotional well-being. Disruptions to training routines, competition schedules, and social structures raised concerns about psychological resilience, especially for elite athletes. In this study, we (1) adapted and validated the Emotional State Questionnaire (EST-Q-2) for Thai athletes, (2) examined the emotional responses and associated health behavior patterns of Thai national team athletes during the COVID-19 pandemic, and (3) compared emotional states between individual and team sport athletes. Methods: We surveyed 280 Thai national team athletes (146 male, 134 female) preparing for the 19th Asian Games. Participants completed the culturally adapted EST-Q-2, measuring 5 dimensions: depression, general anxiety, panic disorder, fatigue, and insomnia. We compared emotional responses by sport type. Results: The most prominent symptoms reported were fatigue and insomnia (M = 3.26), general anxiety (M = 2.84), depression (M = 2.35), and panic disorder (M = 2.17). We found no statistically significant differences between individual and team sport athletes across emotional dimensions. The adapted EST-Q-2 demonstrated strong reliability (Cronbach’s α = 0.80). Conclusion: The COVID-19 pandemic adversely affected the emotional states and health behavior of Thai national athletes, with high levels of fatigue and sleep disturbances. The lack of significant differences between sport types indicates a universal psychological impact, underscoring the need for targeted mental health interventions regardless of sport category.
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A numerical treatment of nondimensional form of water quality model in a nonuniform flow stream using Saulyev scheme
(2011-11-24)
Pochai, Nopparat
The stream water quality model of water quality assessment problems often involves numerical methods to solve the equations. The governing equation of the uniform flow model is one-dimensional advection-dispersion-reaction equations (ADREs). In this paper, a better finite difference scheme for solving ADRE is focused, and the effect of nonuniform water flows in a stream is considered. Two mathematical models are used to simulate pollution due to sewage effluent. The first is a hydrodynamic model that provides the velocity field and elevation of the water flow. The second is a advection-dispersion-reaction model that gives the pollutant concentration fields after input of the velocity data from the hydrodynamic model. For numerical techniques, we used the Crank-Nicolson method for system of a hydrodynamic model and the explicit schemes to the dispersion model. The revised explicit schemes are modified from two computation techniques of uniform flow stream problems: forward time central space (FTCS) and Saulyev schemes for dispersion model. A comparison of both schemes regarding stability aspect is provided so as to illustrate their applicability to the real-world problem. © 2011 Nopparat Pochai.
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Numerical treatment of a two-dimensional vertically-averaged groundwater flow model using alternating direction explicit methods
(2020-01-01)
Yena, Supawan
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Pochai, Nopparat
Leachate from a landfill can flow down and contaminate groundwater. Mathematical models are often used to describe groundwater flow, which can help designers to identify an appropriate location for a landfill area. We focused on simulation of hydraulic head of groundwater under landfill construction in a rural area. We used a partial differential equation model called two-dimensional vertically-averaged groundwater flow model to explain groundwater volume, in particular, to explain the hydraulic head of the groundwater which strongly affected the groundwater quality. We applied two alternating direction explicit methods to the groundwater flow model under general boundary conditions and rates of change of boundary conditions to obtain an approximate hydraulic head of groundwater. An alternating direction explicit method for all types of boundaries is used to find approximate solutions. The traditional alternative direction explicit method was modified to form our modified alternative direction explicit method. The results of all method are closed. The traditional alternative direction explicit method and the modified alternative direction explicit method led to more accurate solutions than forward time centered space in heterogeneous aquifer, two methods ensured that a stable solution of all interior points can be obtained by using a fine grid spacing.

Pochai, Nopparat

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