Speedes: A Case Study Of Space Operations

This thesis describes the application of parallel simulation techniques to represent the structured functional parallelism present within the Space Shuttle Operations Flow using the Synchronous Parallel Environment for Emulation and Discrete-Event Simulation (SPEEDES), an object-oriented multi-computing architecture. SPEEDES is a unified parallel simulation environment, which allocates events over multiple processors to get simulation speed up. Its optimistic processing capability minimizes simulation lag time behind wall clock time, or multiples of real-time. SPEEDES accommodates an increase in process complexity with additional parallel computing nodes to allow sharing of processing loads. This thesis focuses on the process of translating a model of Space Shuttle Operations from a procedural oriented and single processor approach to one represented in a process-driven, object-oriented, and distributed processor approach. The processes are depicted by several classes created to represent the operations at the space center. The reference model used is the existing Space Shuttle Model created in ARENA by NASA and UCF in the year 2001. A systematic approach was used for this translation. A reduced version of the ARENA model was created, and then used as the SPEEDES prototype using C++. The prototype was systematically augmented to reflect the entire Space Shuttle Operations Flow. It was then verified, validated, and implemented

Addressing nodal constraints on the capacity of railways

As demand for passenger and freight transport on Britain’s railways increases, providing additional capacity and making the best use of the existing infrastructure are priorities for the industry. Since the stations and junctions forming the nodes of the railway network tend to form the constraints on route and network capacity, improved understanding of their operation and capacity characteristics is particularly important. This paper describes research undertaken to improve the understanding of nodal capacity and capacity utilisation, and to route and schedule trains more efficiently through nodes, thus improving service quality and/or releasing capacity for additional train service

Summary of the First Workshop on Sustainable Software for Science: Practice and Experiences (WSSSPE1)

Challenges related to development, deployment, and maintenance of reusable software for science are becoming a growing concern. Many scientists’ research increasingly depends on the quality and availability of software upon which their works are built. To highlight some of these issues and share experiences, the First Workshop on Sustainable Software for Science: Practice and Experiences (WSSSPE1) was held in November 2013 in conjunction with the SC13 Conference. The workshop featured keynote presentations and a large number (54) of solicited extended abstracts that were grouped into three themes and presented via panels. A set of collaborative notes of the presentations and discussion was taken during the workshop. Unique perspectives were captured about issues such as comprehensive documentation, development and deployment practices, software licenses and career paths for developers. Attribution systems that account for evidence of software contribution and impact were also discussed. These include mechanisms such as Digital Object Identifiers, publication of “software papers”, and the use of online systems, for example source code repositories like GitHub. This paper summarizes the issues and shared experiences that were discussed, including cross-cutting issues and use cases. It joins a nascent literature seeking to understand what drives software work in science, and how it is impacted by the reward systems of science. These incentives can determine the extent to which developers are motivated to build software for the long-term, for the use of others, and whether to work collaboratively or separately. It also explores community building, leadership, and dynamics in relation to successful scientific software

Interactive tailor system

Interactive Tailor System is an online system designed for tailors. A system that enables tailors to keep the data of their customers. A profile of each customer will be created by the tailor. All necessary details of the clients are stored in the system and retrieved. The measurements of customers will be recorded and found easily when needed. The tailors will use a picture see the measurements of the customers. The tailor will need to click the leg in order to see how much it measures. Before using the system users need to register then they must login with their username and password in order to enter the system. The system is constituted of different components such login function, insertion of data in the database, extraction of data from the database, search facility, mail sending. The methodology chosen to develop this system is waterfall model approach. This method is simple to implement, the amount of resources needed are minimal and after each phase the output is obtained, therefore it has clear visibility

WIP control at end of line of semiconductor industry using CONWIP

Advancement of technology and trends in globalization has resulted in higher customer demands and expectations. Manufacturers now offer mass customization to stay competitive. In the semiconductor industry, where product mix and volume are high, production is further complicated by the different process routes and processing times for different product families. Coupled with rapid changeovers of products, it is essential to keep the work in process (WIP) low in order to reduce the inventory level on the shop floor. Constant W1P (CONWIP) is a production control strategy applicable in many manufacturing environment that use cards to control W1P level. This research was conducted in a semiconductor manufacturing company facing difficulty in reducing the variation in WIP on the shopfloor. The objectives of this research are to design and develop simulation models for single loop CONWIP, multi loop CONW1P, hybrid CONW1P, single loop CONWlP and multi loop CONWIP with buffer size optimization based on the environment in the case company. With the developed models, the maximum throughput (TH) and minimum W1P were determined. Discrete event simulation models were developed using the Witness Software for processes at the End of Line (EOL) production in the company. Experiments were conducted using these models to compare the current system with the single loop, multi loop, and hybrid CONWIP control mechanisms. ln addition, buffer optimization incorporating single loop and multi loop control were also examined. Performance parameters of TH and WIP level were compared in all experiments. The results show that CONWTP production control is more effective in reducing WlP level compared to the current system. Secondly, the single loop CONWIP showed the least number of cards in the system. However, hybrid CONWIP is more robust and provides a better control mechanism compared to the single and multi loop system. Buffer optimization control can further reduce the number of cards in the single and multi loop control. The developed simulation models are useful to determine the number of cards in the system and buffer size for each process. With these models, the production personnel can monitor and control the WJP dynamically to meet current demands and utilize the shopfloor space for more productive purposes

Teaching operating system concepts using multimedia and internet

The prime objective of the thesis is to research and demonstrate the benefits and advantages of using Internet and multimedia tools for an interactive educational leaning experience. As we speak Internet is developing as a mainstream communication medium via personal computer as a tool at a breathtaking speed. The information technology field is a prime reason behind such phenomenon as it continues to mature and expand. In what is described as the information age , the students of information technology need to master and devour new complex technological concepts and ideas at faster rate than ever before. The traditional approach using the textbooks is not feasible due to their static, linear and often colorless nature. So there is a tremendous need to develop an interactive, fun and yet detailed and challenging educational experience. In next several chapters, the solution is presented as to how to tackle such a challenge or task, by using the Operating System concepts, specifically using Memory Management concepts as a case study. The concepts include topics such as logical vs. physical address space, etc

Reusable Rocket Engine Operability Modeling and Analysis

This paper describes the methodology, model, input data, and analysis results of a reusable launch vehicle engine operability study conducted with the goal of supporting design from an operations perspective. Paralleling performance analyses in schedule and method, this requires the use of metrics in a validated operations model useful for design, sensitivity, and trade studies. Operations analysis in this view is one of several design functions. An operations concept was developed given an engine concept and the predicted operations and maintenance processes incorporated into simulation models. Historical operations data at a level of detail suitable to model objectives were collected, analyzed, and formatted for use with the models, the simulations were run, and results collected and presented. The input data used included scheduled and unscheduled timeline and resource information collected into a Space Transportation System (STS) Space Shuttle Main Engine (SSME) historical launch operations database. Results reflect upon the importance not only of reliable hardware but upon operations and corrective maintenance process improvements

Performance modeling and control of web servers

This thesis deals with the task of modeling a web server and designing a mechanism that can prevent the web server from being overloaded. Four papers are presented. The first paper gives an M/G/1/K processor sharing model of a single web server. The model is validated against measurements ands imulations on the commonly usedw eb server Apache. A description is given on how to calculate the necessary parameters in the model. The second paper introduces an admission control mechanism for the Apache web server basedon a combination of queuing theory andcon trol theory. The admission control mechanism is tested in the laboratory, implemented as a stand-alone application in front of the web server. The third paper continues the work from the secondp aper by discussing stability. This time, the admission control mechanism is implemented as a module within the Apache source code. Experiments show the stability and settling time of the controller. Finally, the fourth paper investigates the concept of service level agreements for a web site. The agreements allow a maximum response time anda minimal throughput to be set. The requests are sorted into classes, where each class is assigneda weight (representing the income for the web site owner). Then an optimization algorithm is appliedso that the total profit for the web site during overload is maximized