Sistem Mühendisliği Anabilim Dalı

Stochastic modeling of post-earthquake road clearance for maximizing accessibility and metaheuristic solution approaches

Disasters have had a great impact on human life throughout the 21st century in terms of loss of life, property, and economic growth. Post-disaster debris clearance is of utmost importance in disaster response and recovery. The goal in planning debris clearance operations in emergency response is to maximize road network accessibility and enable casualty transport to medical facilities, primary relief distribution to survivors, and evacuation of survivors from the affected region. An optimal debris clearance plan leads to fast access to warehouses, temporary survivor camps and medic tents/hospitals. Debris clearance is also important in the affected region's post-disaster recovery because it impacts the speed of business re-openings. Here, we develop a novel scenario-based mathematical model to represent the road network debris clearance scheduling problem with multiple cleaning crews. The goal is to maximize network accessibility throughout the clearance process of a given road network with blockages. The model's output schedule is consistent in the sense that it takes all clearing time scenarios into consideration. We ensure the reliability of any given solution by determining the required number of different clearance time estimate scenarios using the Sample Average Approximation Method (SAA). The proposed mathematical model can create schedules for small-scale networks due to the curse of dimensionality. Therefore, to deal with larger-scale networks, the designed metaheuristics include combinations or stand-alone versions of Biased Random Sampling (BRS), Tabu Search (TS), Simulated Annealing (SA), and Variable Neighborhood Search algorithms (VNS). To enable the usage of the model in practice, we also propose a rolling horizon approach to revise the initial schedule based on updated clearance time estimates received from the field.

Proje risklerinin sistem dinamik modellemesi

ABSTRACT Risk, defined as exposure to the possibility of economic or financial loss or gains, physical damage, or injury, or delay as a consequence of the uncertainty associated with pursuing a cause of action, is by nature subjective. The fast changing environmental conditions, information technology, and the complexity of the projects increase risk threat and make project management more susceptible to risks. This sensitiveness is also at its highest level in telecommunication projects, because there are various technologies and scientific techniques used in telecommunication projects increasing the uncertainty and complexity. Project risk dynamics are difficult to understand and control. Therefore managing project risks requires an approach supported by special tools and techniques. System dynamic (SD) modeling is a tool that covers a wide range of project management needs, by addressing the system issues that influence and often dominate the project outcome. With SD modeling approach we will be able to see all things as a whole. SD modeling also will enable us to build formal computer simulation of complex project risk dynamics, so we can identify and analyze probable risks within the project and respond to them. In the thesis project, we attempt to classify all project risks within the framework of PSO (People-System-Organization) concept. Five risk sectors are defined. 1. Social Risk 2. Economic Risk 3. Technical Risk 4. Political Risk 5. Ecological Risk Political and Ecological risk sectors are excluded and the first three sectors are defined as endogenous in the model. In Stock and Flow Map these three sectors are determined as main stocks. Modeling these three risk sectors stock and flow diagrams 46 risk variables are used. There are three main stocks and seven sub-stocks in the model. Moving from causal map to computer simulation we used the approach called NUMBER (Normalized Unit Modeling by Elementary Relationships), which enable us to limit the variable's values between 0 and 1. We needed to use this approach because we did not have the real data. After forming the equations we simulated the model with time bound which is assumed to be 60 months. Simulation results show that all main risk sectors increase in the initial times of the project. Then if all thins go well the risk levels begin to decrease but never zero. Economic Risk shows the highest level about 0.6 at the time 18 in the base model The highest levels of the other two main risk factors are about 0.3 at a determined time. Near the base model we defined an alternative model to which a new variable called Hiring New Staff is added. After simulating the alternative model it was observed that to introduce new personnel to an ongoing project increases risks levels and project cost, decreases productivity, quality and leads to a poor team relationship. The model can be simulated with different policies and designs. It enables us to see various situations of risk factors and other variables affecting risks. In this way, irrelevant risks can be eliminated, preventing unnecessary mitigating efforts. At the end of this study we are able to have a complete picture of telecommunication project risk dynamics with the help of an SD model computer simulation. This may help us in seeing risk behaviors during project time and formulating responses to risks for mitigating their impacts on telecommunication projects. XIV

Aggregate production planning by linear programming with an application

Information security management system and information security risk management methodology development

Information security is the protection of information from threats in order to ensure business continuity by reducing business risks, and maximizing return on investments and business opportunities. In strategic terms, the confidentiality, integrity and availability of crucial information must be provided via an effective information security management system to ensure business continuity. In today's world, information is exposed to a growing number of threats. Thus, ensuring the information security is vital for today's interconnected business environment. Information security policies are the basis for a reliable information security system and are critical to protect the organisation's Information System (IS) resources and data. ISO 27001:2005 provides a widely-accepted information security management guideline for establishing, implementing, operating, monitoring, maintaining and improving an information security management system (ISMS). Although it is suitable for all kinds of organizations there is a lack of a comprehensive framework, supporting process model, and methodology that can enable an enterprise to implement and effectively manage information security. Thus, the purpose of this study is to examine a pharmaceutical firm's information security management system, and to develop an appropriate framework and methodology to ensure integration of information security management with other enterprise business processes.

An online algorithm for the glass cutting problem with defects of multiple grades and products with quality classes

In this thesis, we focus on the problem of placing cutting patterns on a sheet of flat glass that contains various types of defects. In flat glass production, a continuous glass sheet is cut into glass products of different sizes and different quality classes. Each quality class indicates the maximum number of defects of each type that can be tolerated on a glass product. Products that do not meet the quality requirements defined by their quality classes are considered scrap and sent back to the furnace to be recycled. In a continuous glass production line, patterns to be cut from the glass sheet have to be determined in real time, which limits the time available for decision making. The main goal of the glass cutting problem is to determine the cutting patterns in a limited time so as to minimize the total area of scrap glass. In selecting the products to be cut, daily production targets of each product type are also considered to ensure timely delivery of orders. To solve this real time glass cutting problem, we propose an online algorithm that solves a series of static cutting problems over a rolling horizon using various approaches and implements the first few cuts from each static solution to avoid a myopic decision. In this study, we develop genetic algorithm (GA), dynamic programming (DP) and Mixed Integer Programming (MIP) based methods for solving the static cutting problem on a glass sheet of fixed size that contains defects. These methods are integrated into the online algorithm and tested using realistic instances with different defect densities. In the initial versions of the algorithm, production targets are used as constraints. Later, production targets are integrated into the objective function in order to the improve solution quality by balancing the production of different products during the production run. Moreover, an adaptive version of the algorithm, which is capable of adjusting itself based on the current status of the production run, is also provided in this study. This thesis is one of the first studies in the literature that solves a real time cutting problem with defects of multiple grades and products with quality classes.