Investigation, Development, and Evaluation of Performance Proving for Fault-tolerant Computers

A number of methodologies for verifying systems and computer based tools that assist users in verifying their systems were developed. These tools were applied to verify in part the SIFT ultrareliable aircraft computer. Topics covered included: STP theorem prover; design verification of SIFT; high level language code verification; assembly language level verification; numerical algorithm verification; verification of flight control programs; and verification of hardware logic

Time, Schedules, and the College Student with ADHD

Attention Deficit Hyperactivity Disorder (ADHD) is a complex, heterogeneous condition associated with organizational and time management challenges that can impact academic performance. Using information gathered through texts and 28 semi structured, in-depth interviews, I explored the everyday lived experiences of college students diagnosed with ADHD as they worked to adhere to the schedule and time expectations of their college coursework. I also the explored institutional policies and processes of the community college they attended to determine if, and how, these impacted the work of adherence. Using institutional ethnography and Liza McCoy’s three-way alignment model as frameworks, this qualitative, ethnographic study examined the responses and data from 14 community college students diagnosed with ADHD and two staff members in the Office of Disability Services. Student participants were enrolled in college credit courses and had registered for accommodations with the Office of Disability Services. The findings suggest that adhering to the expectations of college course work involved a three-way alignment between the schedule, the student’s inner experience of time, and clock time. Every student experienced some degree of disconnect between their inner experience of time and awareness of clock time, causing them distress and leading to problems adhering to the schedule. The components of the three-way alignment interacted with and influenced the executive functions of attention, focus, and memory in complex ways. The work of maintaining the alignment was unrelenting, and the students were not always successful. They had to perform additional work above and beyond that expected of their coursework just to maintain the alignment and adhere to the schedule. The students used various accommodations, strategies, and tools to maintain the alignment. None proved consistently useful over time and all added another layer of burdensome work. Only half the students used accommodations provided through the Office of Disability Services. For those who used them, the accommodations were not always helpful. Time management and organizational strategies designed to decrease effort and increase productivity often caused more work for the students and were rarely effective. Deadlines, stress, procrastination, volition, and resistance influenced adherence to the schedule. Some behaviors commonly associated with non-adherence were instead purposeful self-protective strategies the students enlisted when forced to call up abilities they did not have or could not consistently sustain. Some students developed their own organizational strategies. Traditionally, professional “experts” have driven the historic and contemporary narratives of people with ADHD. I contend that, as researchers, we have not often consulted the real experts who live these experiences every day. I offer that a true interdisciplinary effort must include people with ADHD in order to develop strategies better suited to their needs

Embracing Safe Ground Test Facility Operations and Maintenance

Conducting integrated operations and maintenance in wind tunnel ground test facilities requires a balance of meeting due dates, efficient operation, responsiveness to the test customer, data quality, effective maintenance (relating to readiness and reliability), and personnel and facility safety. Safety is non-negotiable, so the balance must be an "and" with other requirements and needs. Pressure to deliver services faster at increasing levels of quality in under-maintained facilities is typical. A challenge for management is to balance the "need for speed" with safety and quality. It s especially important to communicate this balance across the organization - workers, with a desire to perform, can be tempted to cut corners on defined processes to increase speed. Having a lean staff can extend the time required for pre-test preparations, so providing a safe work environment for facility personnel and providing good stewardship for expensive National capabilities can be put at risk by one well-intending person using at-risk behavior. This paper documents a specific, though typical, operational environment and cites management and worker safety initiatives and tools used to provide a safe work environment. Results are presented and clearly show that the work environment is a relatively safe one, though still not good enough to keep from preventing injury. So, the journey to a zero injury work environment - both in measured reality and in the minds of each employee - continues. The intent of this paper is to provide a benchmark for others with operational environments and stimulate additional sharing and discussion on having and keeping a safe work environment

Fast jitter tolerance testing for high-speed serial links in post-silicon validation

Post-silicon electrical validation of high-speed input/output (HSIO) links is a critical process for product qualification schedules of high-performance computer platforms under current aggressive time-to-market (TTM) commitments. Improvements in signaling methods, circuits, and process technologies have allowed HSIO data rates to scale well beyond 10 Gb/s. Noise and EM effects can create multiple signal integrity problems, which are aggravated by continuously faster bus technologies. The goal of post-silicon validation for HSIO links is to ensure design robustness of both receiver (Rx) and transmitter (Tx) circuitry in real system environments. One of the most common ways to evaluate the performance of a HSIO link is to characterize the Rx jitter tolerance (JTOL) performance by measuring the bit error rate (BER) of the link under worst stressing conditions. However, JTOL testing is extremely time-consuming when executed at specification BER considering manufacturing process, voltage, and temperature (PVT) test coverage. In order to significantly accelerate this process, we propose a novel approach for JTOL testing based on an efficient direct search optimization methodology. Our approach exploits the fast execution of a modified golden section search with a high BER, while overcoming the lack of correlation between different BERs by performing a downward linear search at the actual target BER until no errors are found. Our proposed methodology is validated in a realistic industrial server post-silicon validation platform for three different computer HSIO links: SATA, USB3, and PCIe3.ITESO, A.C

I\u27d just be wantin\u27 to go on\u27: gifted students talk about waiting in the regular classroom

Gifted and talented students ask, Why do we have to sit and wait in the regular classroom for other kids to learn stuff? This study uses grounded theory techniques to examine the meaning of sitting and waiting in the regular classroom from the perspective of able learners Sixteen intellectually gifted students, one boy and one girl in grades 1-8 participated in the study. The students attended schools in a suburban community in the Southeast. Semi-structured interviews, field notes of classroom observations and conversations with teachers and school administrators, and student maps of a typical school day were the data sources for the study. Data analysis involved open, axial and selective coding to produce a grounded theory. The core category for the gifted students was, Waiting is boring; sometimes, waiting is fair. A set of prepositional statements provides elaboration of the theory. The significance of this research is that it uses the voices of students to reveal the meaning of sitting and waiting that is at variance with conventional discourse on the phenomenon. The study also suggests a new avenue of inquiry for providing informed research about life in classrooms

Energy-efficient MAC protocol for wireless sensor networks

A Wireless Sensor Network (WSN) is a collection of tiny devices called sensor nodes which are deployed in an area to be monitored. Each node has one or more sensors with which they can measure the characteristics of their surroundings. In a typical WSN, the data gathered by each node is sent wirelessly through the network from one node to the next towards a central base station. Each node typically has a very limited energy supply. Therefore, in order for WSNs to have acceptable lifetimes, energy efficiency is a design goal that is of utmost importance and must be kept in mind at all levels of a WSN system. The main consumer of energy on a node is the wireless transceiver and therefore, the communications that occur between nodes should be carefully controlled so as not to waste energy. The Medium Access Control (MAC) protocol is directly in charge of managing the transceiver of a node. It determines when the transceiver is on/off and synchronizes the data exchanges among neighbouring nodes so as to prevent collisions etc., enabling useful communications to occur. The MAC protocol thus has a big impact on the overall energy efficiency of a node. Many WSN MAC protocols have been proposed in the literature but it was found that most were not optimized for the group of WSNs displaying very low volumes of traffic in the network. In low traffic WSNs, a major problem faced in the communications process is clock drift, which causes nodes to become unsynchronized. The MAC protocol must overcome this and other problems while expending as little energy as possible. Many useful WSN applications show low traffic characteristics and thus a new MAC protocol was developed which is aimed at this category of WSNs. The new protocol, Dynamic Preamble Sampling MAC (DPS-MAC) builds on the family of preamble sampling protocols which were found to be most suitable for low traffic WSNs. In contrast to the most energy efficient existing preamble sampling protocols, DPS-MAC does not cater for the worst case clock drift that can occur between two nodes. Rather, it dynamically learns the actual clock drift experienced between any two nodes and then adjusts its operation accordingly. By simulation it was shown that DPS-MAC requires less protocol overhead during the communication process and thus performs more energy efficiently than its predecessors under various network operating conditions. Furthermore, DPS-MAC is less prone to become overloaded or unstable in conditions of high traffic load and high contention levels respectively. These improvements cause the use of DPS-MAC to lead to longer node and network lifetimes, thus making low traffic WSNs more feasible.Dissertation (MEng)--University of Pretoria, 2008.Electrical, Electronic and Computer EngineeringMEngUnrestricte

NASA Formal Methods Workshop, 1990

The workshop brought together researchers involved in the NASA formal methods research effort for detailed technical interchange and provided a mechanism for interaction with representatives from the FAA and the aerospace industry. The workshop also included speakers from industry to debrief the formal methods researchers on the current state of practice in flight critical system design, verification, and certification. The goals were: define and characterize the verification problem for ultra-reliable life critical flight control systems and the current state of practice in industry today; determine the proper role of formal methods in addressing these problems, and assess the state of the art and recent progress toward applying formal methods to this area

Realizing the Nishimori transition across the error threshold for constant-depth quantum circuits

Preparing quantum states across many qubits is necessary to unlock the full potential of quantum computers. However, a key challenge is to realize efficient preparation protocols which are stable to noise and gate imperfections. Here, using a measurement-based protocol on a 127 superconducting qubit device, we study the generation of the simplest long-range order -- Ising order, familiar from Greenberger-Horne-Zeilinger (GHZ) states and the repetition code -- on 54 system qubits. Our efficient implementation of the constant-depth protocol and classical decoder shows higher fidelities for GHZ states compared to size-dependent, unitary protocols. By experimentally tuning coherent and incoherent error rates, we demonstrate stability of this decoded long-range order in two spatial dimensions, up to a critical point which corresponds to a transition belonging to the unusual Nishimori universality class. Although in classical systems Nishimori physics requires fine-tuning multiple parameters, here it arises as a direct result of the Born rule for measurement probabilities -- locking the effective temperature and disorder driving this transition. Our study exemplifies how measurement-based state preparation can be meaningfully explored on quantum processors beyond a hundred qubits.Comment: 16 pages, 18 figure