Predictable migration and communication in the Quest-V multikernal

Quest-V is a system we have been developing from the ground up, with objectives focusing on safety, predictability and efficiency. It is designed to work on emerging multicore processors with hardware virtualization support. Quest-V is implemented as a ``distributed system on a chip'' and comprises multiple sandbox kernels. Sandbox kernels are isolated from one another in separate regions of physical memory, having access to a subset of processing cores and I/O devices. This partitioning prevents system failures in one sandbox affecting the operation of other sandboxes. Shared memory channels managed by system monitors enable inter-sandbox communication. The distributed nature of Quest-V means each sandbox has a separate physical clock, with all event timings being managed by per-core local timers. Each sandbox is responsible for its own scheduling and I/O management, without requiring intervention of a hypervisor. In this paper, we formulate bounds on inter-sandbox communication in the absence of a global scheduler or global system clock. We also describe how address space migration between sandboxes can be guaranteed without violating service constraints. Experimental results on a working system show the conditions under which Quest-V performs real-time communication and migration.National Science Foundation (1117025

Mixed-Criticality Scheduling with I/O

This paper addresses the problem of scheduling tasks with different criticality levels in the presence of I/O requests. In mixed-criticality scheduling, higher criticality tasks are given precedence over those of lower criticality when it is impossible to guarantee the schedulability of all tasks. While mixed-criticality scheduling has gained attention in recent years, most approaches typically assume a periodic task model. This assumption does not always hold in practice, especially for real-time and embedded systems that perform I/O. For example, many tasks block on I/O requests until devices signal their completion via interrupts; both the arrival of interrupts and the waking of blocked tasks can be aperiodic. In our prior work, we developed a scheduling technique in the Quest real-time operating system, which integrates the time-budgeted management of I/O operations with Sporadic Server scheduling of tasks. This paper extends our previous scheduling approach with support for mixed-criticality tasks and I/O requests on the same processing core. Results show the effective schedulability of different task sets in the presence of I/O requests is superior in our approach compared to traditional methods that manage I/O using techniques such as Sporadic Servers.Comment: Second version has replaced simulation experiments with real machine experiments, third version fixed minor error in Equation 5 (missing a plus sign

Water resources assessment and management in drylands

Drylands regions of the world face difficult issues in maintaining water resources to meet current demands which will intensify in the future with population increases, infrastructure development, increased agricultural water demands, and climate change impacts on the hydrologic system. New water resources evaluation and management methods will be needed to assure that water resources in drylands are optimally managed in a sustainable manner. Development of water management and conservation methods is a multi-disciplinary endeavor. Scientists and engineers must collaborate and cooperate with water managers, planners, and politicians to successfully adopt new strategies to manage water not only for humans, but to maintain all aspects of the environment. This particularly applies to drylands regions where resources are already limited and conflicts over water are occurring. Every aspect of the hydrologic cycle needs to be assessed to be able to quantify the available water resources, to monitor natural and anthropogenic changes, and to develop flexible policies and management strategies that can change as conditions dictate. Optimal, sustainable water management is achieved by cooperation and not conflict, thereby necessitating the need for high quality scientific research and input into the processhttp://www.mdpi.com/2073-4441/8/6/239Published versio

Do the Fallacies you Favour Retard the Growth of Knowledge?

A simple way to approach fallacies is to ask, Has reasoning-strategy X retarded or halted the growth of knowledge? and seek uncontroversial historical events as empirical support for the fallacy moniker. Historical support also offers a means of retiring reasoning strategies heretofore thought fallacious—they are wrongly accused if they helped drive knowledge. Finally, this approach allows us to be more critical of our argumentative practices. Evidence is offered for an Intuitive Fallacy: In its extreme form it rules out the possibility of (contradicting) evidence; in its weaker form, it is a non-response to evidence that appears to be a response

Geothermal electricity generation and desalination: an integrated process design to conserve latent heat with operational improvements

A new process combination is proposed to link geothermal electricity generation with desalination. The concept involves maximizing the utilization of harvested latent heat by passing the turbine exhaust steam into a multiple effect distillation system and then into an adsorption desalination system. Processes are fully integrated to produce electricity, desalted water for consumer consumption, and make-up water for the geothermal extraction system. Further improvements in operational efficiency are achieved by adding a seawater reverse osmosis system to the site to utilize some of the generated electricity and using on-site aquifer storage and recovery to maximize water production with tailoring of seasonal capacity requirements and to meet facility maintenance requirements. The concept proposed conserves geothermally harvested latent heat and maximizes the economics of geothermal energy development. Development of a fully renewable energy electric generation-desalination-aquifer storage campus is introduced within the framework of geothermal energy development

Bounds on effective Majorana neutrino masses at HERA

The lepton-number violating process e p \to nu_e l l' X mediated by Majorana neutrinos is studied for the HERA collider for (l l') = (e tau), (mu tau), (mu mu) and (tau tau). Only the muonic decay of the tau is considered. The direct limit on the effective muon Majorana mass, is improved significantly to 4.0 times 10^3 GeV and for the first time direct limits on the analogous effective masses connected with the tau sector are given, namely 4.2 times 10^3 GeV for , 4.4 times 10^3 GeV for and 2.0 times 10^4 GeV for . We find that a more general analysis for an upgraded HERA could improve this values by a factor of up to 40, yet still being orders of magnitude worse than indirect limits.Comment: 9 pages, 4 figures, revised versio

Students on the fly: Preliminary data from a year‐long

As part of an ongoing, year‐long ethnographic study on laptop adoption and usage, selected families, young professionals, and students in Tempe Arizona and the Puget Sound area in Washington State have been given some form of laptop computer, based on activity maps participants furnished to researchers. These 32 participants, 12 of them students, are being followed for one year as they report on their experiences. Preliminary data after one month reveal some surprises: A quarter of the students expressed desire/need for larger font sizes on their laptops; all students receiving a laptop without a CD/DVD drive complained that it depressed some of their mobile desires; and stylishness, even in a larger device, played a prominent role for some students. After initial excitement over Tablet functionality (rotating screen, pen), usage at this stage for the most part entails using the pen to navigate.Mobile and Tailored Platforms, Microsoft Corporatio

Methods of NMR structure refinement: molecular dynamics simulations improve the agreement with measured NMR data of a C-terminal peptide of GCN4-p1

The C-terminal trigger sequence is essential in the coiled-coil formation of GCN4-p1; its conformational properties are thus of importance for understanding this process at the atomic level. A solution NMR model structure of a peptide, GCN4p16-31, encompassing the GCN4-p1 trigger sequence was proposed a few years ago. Derived using a standard single-structure refinement protocol based on 172 nuclear Overhauser effect (NOE) distance restraints, 14 hydrogen-bond and 11 ϕ torsional-angle restraints, the resulting set of 20 NMR model structures exhibits regular α-helical structure. However, the set slightly violates some measured NOE bounds and does not reproduce all 15 measured 3J(HN-HCα)-coupling constants, indicating that different conformers of GCN4p16-31 might be present in solution. With the aim to resolve structures compatible with all NOE upper distance bounds and 3J-coupling constants, we executed several structure refinement protocols employing unrestrained and restrained molecular dynamics (MD) simulations with two force fields. We find that only configurational ensembles obtained by applying simultaneously time-averaged NOE distance and 3J-coupling constant restraining with either force field reproduce all the experimental data. Additionally, analyses of the simulated ensembles show that the conformational variability of GCN4p16-31 in solution admitted by the available set of 187 measured NMR data is larger than represented by the set of the NMR model structures. The conformations of GCN4p16-31 in solution differ in the orientation not only of the side-chains but also of the backbone. The inconsistencies between the NMR model structures and the measured NMR data are due to the neglect of averaging effects and the inclusion of hydrogen-bond and torsional-angle restraints that have little basis in the primary, i.e. measured NMR dat

Distributed real-time fault tolerance in a virtualized separation kernel

Computers are increasingly being placed in scenarios where a computer error could result in the loss of human life or significant financial loss. Fault tolerant techniques must be employed to prevent an error from resulting in a fault causing such losses. Two types of errors that are common in real-time and embedded system are soft errors, i.e. data bit corruption, and timing errors, such as missed deadlines. Purely software based techniques to address these types of errors have the advantage of not requiring specialized hardware and are able to use more readily available commercial off-the-shelf hardware. Timing errors are addressed using Adaptive Mixed-Criticality, a scheduling technique where higher criticality tasks are given precedence over those of lower criticality when it is impossible to guarantee the schedulability of all tasks. While mixed-criticality scheduling has gained attention in recent years, most approaches assume a periodic task model and that the system has a single criticality level which dictates the available budget to all tasks. In practice these assumptions do not hold: different types of tasks are better served by different scheduling approaches and only a subset of high critical tasks might require additional capacity to meet deadlines. In the latter case, this occurs when a process has experienced a fault and requires additional capacity to perform the recovery. In this thesis, soft errors are addressed using a novel real-time fault tolerance method based on a virtualized separation kernel. Instead of executing redundant copies of an application on separate machines, the applications are consolidated onto one multi-core processor and use hardware virtualization extensions to partition the applications. This allows new recovery schemes to be explored. In addition, the maximum recovery time is sufficiently bounded to ensure recovery occurs in a timely manner without affecting the normal execution of the application. A virtualized separation kernel in combination with Adaptive Mixed-Criticality techniques creates a fault tolerant system that predictably detects and recovers from timing and soft errors