crystal ball simulation in water conservancy

2010 3rd International Conference on Power Electronics and Intelligent Transportation System
The Application of Crystal Ball Simulation Software in the Schedule Risk Analysis of Water Conservancy and Hydropower Project
I.
INTRODUCTION
From the 60's of the 20th century, scholars has began to study MonieCarlo Method to calculate and analyze PERT network.The main idea of this method is to use sampling techniques to calculate the duration of each random process, and then calculate the completion time of the project.After Simulating for many times, and then statistical analysis, we can get the expectation value and variance of project duration, and then get the probability of project completion time.However,the fatal flaw in the Monte Carlo Method is that it ignores the interaction between risk factors and regards the various risk factors as independent variables.Secondly, during the progress of simulation, considering the fact that the random selection can not fully reflect the random function of the duration of the process actual, there are inevitably some analog distortion.Furthermore, what we can get finally is only the macro statistical parameters such as project duration, variance, the probability of the completion, but little information on the parameters of unit processes, which makes its effect on project schedule control significantly decreased.A final note to use Monte Carlo is that its accuracy and simulation times N are related. The calculation error ε = Χασ / N. If the confidence factor Χα and standard deviation σ is constant, then to improve the accuracy of the calculation is to increase the times of simulation, and when the precision is increased by one order of magnitude, the calculation of the number must be increased by two orders of magnitude.
Wang Zhonghui
Department of Project Management University of Hohai Nanjing, Jiangsu Province, China wzh860114@163.com With the development of the technology of risk analysis and computer technology, these defects are to find a viable solution. For example, the hotter study in recent years, that is ,the combination of PERT and Monte Carlo Method,which solves the problem of interaction between risk factors to a certain extent .When we design the program, the process information can be added into statistical design modules to provide more details for decision-making. Also ,we should choose models which are more in line with the law of random occurrence to analyze and simulate, reduce the interference of non-actual simulation and increase the speed and accuracy of simulation.At the same time ,we ought to strengthen the statistical processing function of simulation parameters so that MonieCarlo can guide practice and serve production better. In summary, MonieCarlo Method is a better network schedule risk analysis method. Furthermore, with the fast development of computer technology, the application of MonieCarlo will have good prospects. II. THE MEANING AND CAUSES OF PROGRESS RISK A. The Meaning of Progress Risk Progress risk means the probability that the calculated completion date exceeds the provided or planned completion date. Construction progress risk can be expressed as Pr: Pr= P(TC> TP) Where: TC-calculated completion date; TP-provided or planned completion date. TC is uncertain, it is mainly influenced by the uncertainty that the time required to complete a job and the estimated number of days available in a month. TP is often determined by hydrological factors, which is also uncertain. B. The Causes of Progress Risk The uncertainty or randomness in water conservancy and hydropower construction can be summarized as the subjective aspects and objective aspects. Subjective aspects include the uncertainty of calculated completion date. The objective aspects are mainly determined by hydrological, meteorological and other factors, including the uncertainty of days available for construction and provided or planned completion date. 1). The Uncertainty of Calculated Lasting Time
Yang Gaosheng
Department of Project Management University of Hohai Nanjing, Jiangsu Province, China ygshh@hhu.edu.cn
Abstract - One of the keys to the construction progress construction is the control and management of the construction progress . This paper analyzes the construction schedule risk as well as its causes of water conservancy and hydropower project,and then use Crystal Ball simulation software to quantitatively analyze the schedule and obtain a more accurate analysis results. This makes decision makers understand the possible changes in the future and also provides the scientific basis of risk for them to take appropriate measures. Index Terms water conservancy and hydropower project;schedule risk analysis; Monte Carlo simulation; Crystal Ball simulation software
978-1-4244-9162-9/10/$26.00 ©2010 IEEE
311
Biblioteka Baidu
PEITS2010
In the water conservancy and hydropower project, the time required to complete a sub-part of the project is called the lasting time. It is estimated by engineering quantity, materials supply plan and construction project quota, or estimated directly by related indexes or experiences. So these estimations are uncertain with different degrees. Besides, the degrees are also different with the change of construction content. 2). The Number of Effective Days per Month for Construction In the construction of water conservancy and hydropower project, in general, the use of holiday approaches does not need us to consider the suspension of statutory holidays, but we should take into account the hydrological and meteorological (such as rain) factors. For example, the filling of dam construction, in particular the construction of impervious clay, which is greatly influenced by rainfall. That is to say, rainy days per month directly affect the amount of days which can be used for effective construction. The number of days per month for effective construction can be calculated by: the number of effective days for construction =the number of days on the calendar - the suspension days caused by hydro-meteorological factors. Where, the suspension days caused by hydrometeorological factors each month is uncertain, the distribution of this uncertainty can be simulated on the basis of a lot of information derived from each month. B. The Uncertainty of Provided or Planned Completion Date In water conservancy and hydropower project, some control points, such as closure, flood detention and power generation phased schedule, their specific completion dates are uncertain. The uncertainty is greatly influenced by hydrological factors. Given a lot of information ,we can analyze the distribution law, if not, we can assume that they obey the triangle distribution. III . The OVERVIEW ON MONTE CARLO WITH CRYSTAL BALL SIMULATION SOFTWARE With the development of project risk management, risk prediction research and the application of the software has reached a certain level. Based on the Monte Carlo simulation method, Crystal Ball engineering simulation software is an important tool for risk assessment. Crystal Ball simulation software is developed by the United States Decisioneering, which is hanging in the Excel add-ins, and it provides a powerful add-in for the Excel spreadsheet. Monte Carlo simulation is used in risk analysis, time series analysis forecasting,option analysis and so on, and it also wins a wide range of users and a high reputation. Crystal Ball simulation software has been recognized as the world's most widely used and most reliable simulation software. It is also very easy to use data modeling and analysis package. More than 85% of the fortune 500 companies in the world use the products and services of Crystal Ball. 75% of the