HYDRODYNAMIC INTERACTION BETWEEN SHIPS AND RESTRICTED WATERWAYS

Author(s):  
E Lataire ◽  
M Vantorre

In open and unrestricted waters the water displaced by a forward sailing vessel can travel without major obstruction underneath and along the ship. In restricted and shallow sailing conditions, the displaced water is squeezed between the hull and the bottom and/or the bank. This results in higher flow velocities and as a consequence a pressure drop around the same hull. In the vicinity of a bank this pressure drop generates a combination of forces and moments on the vessel, known as bank effects. The major achievement of the presented research is the development of a realistic and robust formulation for these bank effects. This knowledge is acquired with an extensive literature study on one hand and with dedicated model tests carried out in different towing tanks on the other. The majority of the utilised model tests were carried out in the shallow water towing tank at Flanders Hydraulics Research in Antwerp, Belgium. The data set on bank effects consists of more than 8 000 unique model test setups (which is by far the most elaborate research ever carried out on this subject). These model tests provide the input for the analysis of bank effects and the creation of the mathematical model.

2017 ◽  
Vol Vol 159 (A1) ◽  
Author(s):  
E Lataire ◽  
M Vantorre

In open and unrestricted waters the water displaced by a forward sailing vessel can travel without major obstruction underneath and along the ship. In restricted and shallow sailing conditions, the displaced water is squeezed between the hull and the bottom and/or the bank. This results in higher flow velocities and as a consequence a pressure drop around the same hull. In the vicinity of a bank this pressure drop generates a combination of forces and moments on the vessel, known as bank effects. The major achievement of the presented research is the development of a realistic and robust formulation for these bank effects. This knowledge is acquired with an extensive literature study on one hand and with dedicated model tests carried out in different towing tanks on the other. The majority of the utilised model tests were carried out in the shallow water towing tank at Flanders Hydraulics Research in Antwerp, Belgium. The data set on bank effects consists of more than 8 000 unique model test setups (which is by far the most elaborate research ever carried out on this subject). These model tests provide the input for the analysis of bank effects and the creation of the mathematical model. Overall the magnitude of the bank induced forces increase with:  A higher forward speed of the ship  A higher propeller load  A lower under keel clearance  A more confined navigation area: steeper banks, smaller channel width  A smaller distance between ship and bank The mathematical model copes with a wide range of ship types and bank configurations and is suitable for implementation (and has been implemented) in full mission bridge simulators which can be used for training purposes as well as for research to support the admittance policy or exploitation of ports and waterways.


Electronics ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 996
Author(s):  
Norshakirah Aziz ◽  
Md Jan Nordin ◽  
Said Jadid Abdulkadir ◽  
Muhammad Muhaimin M. Salih

The advancement of technology has enabled powerful microprocessors to render high-quality graphics for computer gaming. Despite being intended for leisure purposes, several components of the games alongside the gamer’s environmental factors have resulted in digital addiction (DA) towards computer games such as massively multiplayer online games (MMOG). Excessive gaming among adolescents has various negative impacts on an individual. However, only a few researchers have addressed the impact of DA on physical health. Thus, the primary objective of this research is to study the impact of DA on physical health among Malaysian adolescents. This study focuses on Malaysian adolescents of ages 12–18 years old who are addicted to computer games, specifically the MMOG. The methodology used for the study involves focus group discussions (FGD) and extensive literature study. The FGD sessions have involved both medical experts and game experts. The outcome of FGD discussion is recorded and justified with the existing relevant literature from high-impact journals, theses, conferences, books, and reports. This paper provides evidence of five physical health impacts of DA associated with adolescents. The factors of DA, the addiction components existing in MMOG computer games, and the DA health risk assessment are presented in the results section. Based on the study, it is concluded that DA among Malaysian adolescents can cause various impacts on physical health such as obesity, back pain, and neck pain, orthopaedic/joint muscle, eyesight problem, hearing problem, as well as physical inactivity.


2009 ◽  
Vol 39 (1) ◽  
pp. 95-118 ◽  
Author(s):  
CHRISTINA MOKHTAR ◽  
LUCINDA PLATT

AbstractThis article investigates the ethnic patterning of exit from means-tested benefits in a UK town. Lone parents in the UK face high risks of poverty and high rates of receipt of means-tested, out-of-work benefits. There has been extensive policy concern with lone parents' poverty and with potential ‘welfare dependency’. Investigation of welfare dynamics has unpacked the notion of welfare dependency, and has stimulated policy to better understand the factors associated with longer rather than shorter durations. However, within this analysis, there has been little attention paid to ethnicity. This is despite the fact that the extensive literature on the UK's minority ethnic groups has emphasised diversity in both rates of lone parenthood and risks of poverty. To date we have little understanding of ethnic variation in lone parents' welfare dynamics. Using a data set drawn from administrative records, this article analyses the chances of leaving means-tested benefit for a set of lone mothers in a single town, exploring whether there is variation by ethnic group. We find that, controlling for basic demographic characteristics, there is little evidence to suggest that ethnicity affects the chances of benefit exit, even between groups where rates of lone parenthood are very different.


Author(s):  
A I Ryazanov

This paper describes the aerohydrodvnamics of processes in chambers of Gorlov's hydro-pneumatic power system. The mathematical model is developed to determine the main parameters of the processes: water and air velocities, air pressure in the chamber, the periods of time required to fill and empty the chambers and the output of energy during the cycle. The results obtained are in agreement with experimental data and model tests.


2021 ◽  
Vol 14 (11) ◽  
pp. 540
Author(s):  
Eyden Samunderu ◽  
Yvonne T. Murahwa

Developments in the world of finance have led the authors to assess the adequacy of using the normal distribution assumptions alone in measuring risk. Cushioning against risk has always created a plethora of complexities and challenges; hence, this paper attempts to analyse statistical properties of various risk measures in a not normal distribution and provide a financial blueprint on how to manage risk. It is assumed that using old assumptions of normality alone in a distribution is not as accurate, which has led to the use of models that do not give accurate risk measures. Our empirical design of study firstly examined an overview of the use of returns in measuring risk and an assessment of the current financial environment. As an alternative to conventional measures, our paper employs a mosaic of risk techniques in order to ascertain the fact that there is no one universal risk measure. The next step involved looking at the current risk proxy measures adopted, such as the Gaussian-based, value at risk (VaR) measure. Furthermore, the authors analysed multiple alternative approaches that do not take into account the normality assumption, such as other variations of VaR, as well as econometric models that can be used in risk measurement and forecasting. Value at risk (VaR) is a widely used measure of financial risk, which provides a way of quantifying and managing the risk of a portfolio. Arguably, VaR represents the most important tool for evaluating market risk as one of the several threats to the global financial system. Upon carrying out an extensive literature review, a data set was applied which was composed of three main asset classes: bonds, equities and hedge funds. The first part was to determine to what extent returns are not normally distributed. After testing the hypothesis, it was found that the majority of returns are not normally distributed but instead exhibit skewness and kurtosis greater or less than three. The study then applied various VaR methods to measure risk in order to determine the most efficient ones. Different timelines were used to carry out stressed value at risks, and it was seen that during periods of crisis, the volatility of asset returns was higher. The other steps that followed examined the relationship of the variables, correlation tests and time series analysis conducted and led to the forecasting of the returns. It was noted that these methods could not be used in isolation. We adopted the use of a mosaic of all the methods from the VaR measures, which included studying the behaviour and relation of assets with each other. Furthermore, we also examined the environment as a whole, then applied forecasting models to accurately value returns; this gave a much more accurate and relevant risk measure as compared to the initial assumption of normality.


2018 ◽  
Author(s):  
Muhammad Subhan

This article discussed the mathematical model of the dynamics of Minang language and Indonesialanguage to describe the language extinction. This research use literature study. Model of the dynamics ofMinang language and Indonesia language in form of non linier diferensial equation’s system. From theresults of the analysis obtained three equilibrium. The equilibrium of Minang language extinction is stable.The equilibrium of Indonesia language extinction is not stable. The equilibrium of free language extinction isstable if volatility level of both language is low. Howover, not stable if volatility level of both language ishigh. At the end, there will be done a kind of simulation is performed to illustrate the analysis resultsobtained.


India is a worldwide agriculture business powerhouse. Future of agriculture-based products depends on the crop production. A mathematical model might be characterized as a lot of equations that speak to the conduct of a framework. By using mathematical model in agriculture field, we can predict the production of crop in particular area. There are various factors affecting crops such as Rainfall, GHG Emissions, Temperature, Urbanization, climate, humidity etc. A mathematical model is a simplified representation of a real-world system. It forms the system using mathematical principles in the form of a condition or a set of conditions. Suppose we need to increase the crop production, at that time the mathematical model plays a major role and our work can be easier, more significant by using the mathematical model. Through the mathematical model we predict the crop production in upcoming years. .AI, ML, IOT play a major role to predict the future of agriculture, but without mathematical models it is not possible to predict crop production accurately. To solve the real-world agriculture problem, mathematical models play a major role for accurate results. Correlation Analysis, Multiple Regression analysis and fuzzy logic simulation standards have been utilized for building a grain production benefit depending model from crop production. Prediction of crop is beneficiary to the farmer to analyze the crop management. By using the present agriculture data set which is available on the government website, we can build a mathematical model.


Author(s):  
Sajad Badalkhani ◽  
Ramazan Havangi ◽  
Mohsen Farshad

There is an extensive literature regarding multi-robot simultaneous localization and mapping (MRSLAM). In most part of the research, the environment is assumed to be static, while the dynamic parts of the environment degrade the estimation quality of SLAM algorithms and lead to inherently fragile systems. To enhance the performance and robustness of the SLAM in dynamic environments (SLAMIDE), a novel cooperative approach named parallel-map (p-map) SLAM is introduced in this paper. The objective of the proposed method is to deal with the dynamics of the environment, by detecting dynamic parts and preventing the inclusion of them in SLAM estimations. In this approach, each robot builds a limited map in its own vicinity, while the global map is built through a hybrid centralized MRSLAM. The restricted size of the local maps, bounds computational complexity and resources needed to handle a large scale dynamic environment. Using a probabilistic index, the proposed method differentiates between stationary and moving landmarks, based on their relative positions with other parts of the environment. Stationary landmarks are then used to refine a consistent map. The proposed method is evaluated with different levels of dynamism and for each level, the performance is measured in terms of accuracy, robustness, and hardware resources needed to be implemented. The method is also evaluated with a publicly available real-world data-set. Experimental validation along with simulations indicate that the proposed method is able to perform consistent SLAM in a dynamic environment, suggesting its feasibility for MRSLAM applications.


2020 ◽  
Vol 54 (3) ◽  
pp. 651-675 ◽  
Author(s):  
W. J. A. van Heeswijk ◽  
M. R. K. Mes ◽  
J. M. J. Schutten ◽  
W. H. M. Zijm

The domain of urban freight transport is becoming increasingly complex. Many urban supply chains are composed of small and independent actors that cannot efficiently organize their highly fragmented supply chains, thereby negatively affecting the quality of life in urban areas. Both companies and local administrators try to improve transport efficiency and reduce external costs, but the effects of such interventions are difficult to predict, especially when applied in combination with each other (an urban logistics scheme). This paper presents an agent-based simulation model to quantify the effects of urban logistics schemes on multiple actors. We provide a detailed mathematical representation in the form of a Markov decision process. Based on an extensive literature study, we aggregate data to represent various actors in typical Western European cities. We perform numerical experiments to obtain insights into urban logistics schemes. The results show that most schemes yield significant environmental improvements but that achieving long-term financial viability is challenging for urban consolidation centers in particular. We also demonstrate that interventions, such as subsidies and access restrictions, do not always yield the intended effect. In a backcasting experiment, we identify conditions and schemes to achieve a financially viable urban consolidation center.


Sign in / Sign up

Export Citation Format

Share Document