Hierarchical formal verification using a hybrid tool

We describe a hybrid formal hardware verification tool that links the HOL interactive proof system and the MDG automated hardware verification tool. It supports a hierarchical verification approach that mirrors the hierarchical structure of designs. We obtain the advantages of both verification paradigms. We illustrate its use by considering a component of a communications chip. Verification with the hybrid tool is significantly faster and more tractable than using either tool alone

Integrating MDG variable ordering in a VHDL-MDG design verification system

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal

Compositional verification using interface recognizers/suppliers (IRS)

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal

Selection of systems to perform extravehicular activities, man and manipulator. Volume 2 - Final report

Technologies for EVA and remote manipulation systems - handbook for systems designer

Design and stability analysis of high performance packet switches

With the rapid development of optical interconnection technology, high-performance packet switches are required to resolve contentions in a fast manner to satisfy the demand for high throughput and high speed rates. Combined input-crosspoint buffered (CICB) switches are an alternative to input-buffered (IB) packet switches to provide high-performance switching and to relax arbitration timing for packet switches with high-speed ports. A maximum weight matching (MWM) scheme can provide 100% throughput under admissible traffic for lB switches. However, the high complexity of MWM prohibits its implementation in high-speed switches. In this dissertation, a feedback-based arbitration scheme for CICB switches is studied, where cell selection is based on the provided service to virtual output queues (VOQs). The feedback-based scheme is named round-robin with adaptable frame size (RR-AF) arbitration. The frame size in RR-AF is adaptably changed by the serviced and unserviced traffic. If a switch is stable, the switch provides 100% throughput. Here, it is proved that RR-AF can achieve 100% throughput under uniform admissible traffic. Switches with crosspoint buffers need to consider the transmission delays, or round-trip times to define the crosspoint buffer size. As the buffered crossbar switch can be physically located far from the input ports, actual round-trip times can be non-negligible. To support non-negligible round-trip times in a buffered crossbar switch, the crosspoint buffer size needs to be increased. To satisfy this demand, this dissertation investigates how to select the crosspoint buffer size under non-negligible round trip times and under uniform traffic. With the analysis of stability margin, the relationship between the crosspoint buffer size and round-trip time is derived. Considering that CICB switches deliver higher performance than lB switches and require no speedup, this dissertation investigates the maximum throughput performance that these switches can achieve. It is shown that CICB switches without speedup achieve 100% throughput under any admissible traffic through a fluid model. In addition, a new hybrid scheme, based on longest queue-first (as input arbitration) and longest column occupancy first (as output arbitration) is proposed, which achieves 100% throughput under uniform and non-uniform traffic patterns. In order to give a better insight of the feedback nature of arbitration scheme for CICB switches, a frame-based round-robin arbitration scheme with explicit feedback control (FRE) is introduced. FRE dynamically sets the frame size according to the input load and to the accumulation of cells in a VOQ. FRE is used as the input arbitration scheme and it is combined with RR, PRR, and FRE as output arbitration schemes. These combined schemes deliver high performance under uniform and nonuniform traffic models using a buffered crossbar with one-cell crosspoint buffers. The novelty of FRE lies in that each VOQ sets the frame size by an adjustable parameter, Δ(i,j) which indicates the degree of service needed by VOQ(i, j). This value is adjusted according to the input loading and the accumulation of cells experienced in previous service cycles. This dissertation also explores an analysis technique based on feedback control theory. This methodology is proposed to study the stability of arbitration and matching schemes for packet switches. A continuous system is used and a control model is used to emulate a queuing system. The technique is applied to a matching scheme. In addition, the study shows that the dwell time, which is defined as the time a queue receives service in a service opportunity, is a factor that affects the stability of a queuing system. This feedback control model is an alternative approach to evaluate the stability of arbitration and matching schemes

Lessons learned on the Skylab program

Lessons learned in the Skylab program and their application and adaptation to other space programs are summarized. Recommendations and action taken on particular problems are described. The use of Skylab recommendations to identify potential problems of future space programs is discussed

On-board B-ISDN fast packet switching architectures. Phase 1: Study

The broadband integrate services digital network (B-ISDN) is an emerging telecommunications technology that will meet most of the telecommunications networking needs in the mid-1990's to early next century. The satellite-based system is well positioned for providing B-ISDN service with its inherent capabilities of point-to-multipoint and broadcast transmission, virtually unlimited connectivity between any two points within a beam coverage, short deployment time of communications facility, flexible and dynamic reallocation of space segment capacity, and distance insensitive cost. On-board processing satellites, particularly in a multiple spot beam environment, will provide enhanced connectivity, better performance, optimized access and transmission link design, and lower user service cost. The following are described: the user and network aspects of broadband services; the current development status in broadband services; various satellite network architectures including system design issues; and various fast packet switch architectures and their detail designs

Efficient Regeneration Of Chemical Solvents For Carbon Dioxide Capture By Polymeric Membrane Contactors

Although extensive research attention has been drawn to using membranes for carbon dioxide (CO2) capture from flue gas, the use of membranes for stripping CO2 solvents has rarely been studied. The technical feasibility of using polymeric membrane based separation technology to recover CO2 from CO2 saturated chemical solvents such as monoethanolamine is investigated in the present research. A membrane system was built to study the performance of several common polymeric porous membranes for the recovery of CO2 from saturated aqueous MEA solution by the thermal swing process. The stripped CO2 gas was swept by mass flow controlled N2 reference gas and was measured by a non-dispersive infrared CO2 analyzer and gas chromatography. Substantial CO2 permeation flux through the membrane together with superior selectivity suggests the promises of membrane contactors as an alternative stripping configuration for CO2 recovery. Parametric screening design of experiments studied parameters of process temperature, retentate flow rate, and sweep gas rate. Process temperature was identified as the only significant factor, which is consistent with individual parametric study results. Heat energy efficiency characterization of this system showed that roughly half of the heat energy was used for the stripping process at 80ºC and above. The membrane material candidates screening experiment results showed that polypropylene and polytetrafluoroethylene porous membranes outperformed polyester, polyamide, polyvinylidene fluoride, polysulfone and cellulose acetate. Compositional, structural and surface morphological characterization was also utilized on the membranes before and after this process. Mass transfer mechanism study and mass transfer coefficients calculation reveals that the liquid boundary layer resistance is responsible for more than 90% of the overall mass transfer resistance, much greater than either the membrane resistance or gas layer resistance. Membrane wetting and fouling effects were found to deteriorate membrane performance. Polypropylene membranes with different pore size were studied and compared. There was no significantly change of CO2 flux for membrane pore size from 0.1micron to 2.5 micron. The membrane with pore size of 0.6 micron was found to have best selectivity. The energy utilization efficiency did not change significantly for membranes with different pore size. Membranes with pore size 2.5 micron and below were found to be not wetted during the experiments and membranes with pore size of 5 micron and 10 micron were wetted during the process

Skylab reuse study, reference data, part 1

The accommodations provided by the airlock module and the orbital workshop were completely examined with the thought of total reactivation as an enhancement to the STS long duration missions. Each subsystem is described and a summary of subsystem performance during the Skylab missions is presented. End-of-mission status and the status of today for each subsystem is shown together with refurbishment/resupply requirements and refurb kit descriptions to restore Skylab to full operational capability. An inspection/refurbishment and operations plan for Skylab is included. The initial Shuttle-tended operational activity would provide a safe, effective phase of Skylab rehabilitation while simultaneously benefitting the Orbiter crew through the addition of private accommodations, off-duty recreation area, and physical conditioning equipment. This period would also permit exercising selected onboard experiments