George Eckel

Bio: George Eckel is an academic researcher. The author has contributed to research in topics: Combustion & Microsoft Windows. The author has an hindex of 3, co-authored 3 publications receiving 170 citations.

INSIDE Windows NT

Abstract: This tutorial and reference sets out to instruct users in organizing and managing multiple tasks, and multiple programs, in Windows. It focuses on sharing and transferring data and graphics between Windows applications, either using a single computer, or by sharing across a network.

Building a UNIX Internet server

Abstract: This instructional guide aims to educate the reader in all relevant issues to consider when building a UNIX Internet Server.

Inside Windows NT workstation

Abstract: This valuable handbook provides a source of reference for those who want to get the most out of Windows NT Workstation.

Numerical Prediction of a Lean Blow-Out Event of a Lab-Scale, Swirl-Stabilized Spray Flame

Abstract: Alternative jet fuels have a high potential to reduce emissions in aviation and to increase the independence from mineral oil. However, as a safe operation must be guaranteed, new fuels have to pass elaborate and expensive tests to be finally certified. To reduce the costs and time of the certification process, numerical simulations can be used to assess the impact of a new fuel on combustion. Further, the detailed simulations provide an insight into the fuel sensitive sub-processes. The lean blowout (LBO), i.e. the lower stability limit of a gas turbine combustor, is of primary concern for safe operation and the approval of alternative jet fuels. The paper at hand focuses on the formulation of a calculation protocol for the numerical representation of a lab-scale LBO experiment. The test case is a swirl-stabilized spray flame, which mimics several key features of aero-engine combustors. The LBO-limits are determined by a stepwise reduction of the fuel mass flow starting from a stable operation point above the measured blowout limit. Towards extinction, the heat release rate in the combustor drops. Furthermore, fuel is still evaporating, but less fuel is burned, leading to an accumulation of fuel in the combustion chamber. The blow-out is defined by a steep drop in heat release combined with a large increase of the gaseous fuel mass fraction in the computational domain. The semi-automated calculation protocol is able to successfully capture a blowout event at an equivalence ratio of ϕ = 0.32 and can thus be applied to evaluate alternative jet fuels in the future. In addition, a reignition event is observed for equivalence ratios slightly above ϕLBO.

Probabilistic Modeling and Uncertainty Quantification of Detailed Combustion Simulation for a Swirl Stabilized Spray Burner

Abstract: Abstract To enable risk informed decisions in the simulation-based design and development of novel combustors, uncertainties in the simulation results must be considered. However, due to the high computational costs for their quantification, these uncertainties are commonly not taken into account. Therefore, this work aims at applying an efficient methodology for uncertainty quantification based on Polynomial Chaos Expansion to a semi-technical spray burner reflecting characteristics typically found in modern aeroengine combustors. This requires accurate treatment of the multicomponent liquid fuel, a combustion model relying on finite rate chemistry and a scale resolving hybrid turbulence model to account for highly unsteady flow features and combustion. To overcome the need for costly experimental data for the spray boundary conditions, an algebraic primary breakup model is utilized. The resulting reduction in a priori information is compensated through probabilistic modeling and uncertainty quantification. Due to their importance in the design process, temperature distribution in the gas phase as well as the flame position are considered as the primary quantities of interest. For these quantities of interest, moderate uncertainties are found in the probabilistic simulation results. Further, the predictive capability of the simulation model under uncertainties is quantitively assessed by defining accurary metrics for the gas phase temperature prediction. The study further reveals that the imposed input uncertainties affect quantities of interest in both the dispersed and the gas phase through phase coupling effects.

Improving the reliability of commodity operating systems

Abstract: Despite decades of research in extensible operating system technology, extensions such as device drivers remain a significant cause of system failures. In Windows XP, for example, drivers account for 85% of recently reported failures.This article describes Nooks, a reliability subsystem that seeks to greatly enhance operating system (OS) reliability by isolating the OS from driver failures. The Nooks approach is practical: rather than guaranteeing complete fault tolerance through a new (and incompatible) OS or driver architecture, our goal is to prevent the vast majority of driver-caused crashes with little or no change to the existing driver and system code. Nooks isolates drivers within lightweight protection domains inside the kernel address space, where hardware and software prevent them from corrupting the kernel. Nooks also tracks a driver's use of kernel resources to facilitate automatic cleanup during recovery.To prove the viability of our approach, we implemented Nooks in the Linux operating system and used it to fault-isolate several device drivers. Our results show that Nooks offers a substantial increase in the reliability of operating systems, catching and quickly recovering from many faults that would otherwise crash the system. Under a wide range and number of fault conditions, we show that Nooks recovers automatically from 99% of the faults that otherwise cause Linux to crash.While Nooks was designed for drivers, our techniques generalize to other kernel extensions. We demonstrate this by isolating a kernel-mode file system and an in-kernel Internet service. Overall, because Nooks supports existing C-language extensions, runs on a commodity operating system and hardware, and enables automated recovery, it represents a substantial step beyond the specialized architectures and type-safe languages required by previous efforts directed at safe extensibility.

Disco: running commodity operating systems on scalable multiprocessors

Abstract: In this article we examine the problem of extending modern operating systems to run efficiently on large-scale shared-memory multiprocessors without a large implementation effort. Our approach brings back an idea popular in the 1970s: virtual machine monitors. We use virtual machines to run multiple commodity operating systems on a scalable multiprocessor. This solution addresses many of the challenges facing the system software for these machines. We demonstrate our approach with a prototype called Disco that runs multiple copies of Silicon Graphics' IRIX operating system on a multiprocessor. Our experience shows that the overheads of the monitor are small and that the approach provides scalability as well as the ability to deal with the nonuniform memory access time of these systems. To reduce the memory overheads associated with running multiple operating systems, virtual machines transparently share major data structures such as the program code and the file system buffer cache. We use the distributed-system support of modern operating systems to export a partial single system image to the users. The overall solution achieves most of the benefits of operating systems customized for scalable multiprocessors, yet it can be achieved with a significantly smaller implementation effort.

A five-year study of file-system metadata

Abstract: For five years, we collected annual snapshots of file-system metadata from over 60,000 Windows PC file systems in a large corporation. In this article, we use these snapshots to study temporal changes in file size, file age, file-type frequency, directory size, namespace structure, file-system population, storage capacity and consumption, and degree of file modification. We present a generative model that explains the namespace structure and the distribution of directory sizes. We find significant temporal trends relating to the popularity of certain file types, the origin of file content, the way the namespace is used, and the degree of variation among file systems, as well as more pedestrian changes in size and capacities. We give examples of consequent lessons for designers of file systems and related software.

Using Secure Coprocessors

Abstract: : How do we build distributed systems that are secure? Cryptographic techniques can be used to secure the communications between physically separated systems, but this is not enough: we must be able to guarantee the privacy of the cryptographic keys and the integrity of the cryptographic functions, in addition to the integrity of the security kernel and access control databases we have on the machines. Physical security is a central assumption upon which secure distributed systems are built; without this foundation even the best cryptosystem or the most secure kernel will crumble. In this thesis, I address the distributed security problem by proposing the addition of a small, physically secure hardware module, a secure coprocessor, to standard workstations and PCs. My central axiom is that secure coprocessors are able to maintain the privacy of the data they process. This thesis attacks the distributed security problem from multiple sides. First, I analyze the security properties of existing system components, both at the hardware and software level. Second, I demonstrate how physical security requirements may be isolated to the secure coprocessor, and showed how security properties may be bootstrapped using cryptographic techniques from this central nucleus of security within a combined hardware/software architecture.

World Wide Web registration information processing system

Abstract: A World Wide Web registration processing system is disclosed for assisting World Wide Web users in registering at World Wide Web web sites. For each such user, the registration processing system includes a long term repository for the user's web site registration information so that this information can be automatically transferred to a plurality of web sites to which the user may at time to time request to be registered. Further, the registration processing system provides the user with the capability to have a common user identification that may be used for accessing services at a plurality of web sites.