Reverse reachability analysis: A new technique for deadlock detection on communicating finite state machines

The communicating finite state machines can exchange messages over bounded FIFO channels. In this paper, a new technique, called reverse reachability analysis, is proposed to detect deadlocks on the communication between the communicating finite state machines. The technique is based on finding reverse reachable paths starting from possible deadlock states. If a reverse reachable path can reach the initial global state, then deadlock occurs. Otherwise the communication is deadlock-free. The effectiveness of the technique has been verified by some real protocols such as a specification of X.25 call establishment/clear protocol and Bartlet's alternating bit protocol.     

Solution and applications of the Lyapunov equation for controlsystems

Recent advances in control systems analysis and design have implied new uses for the Lyapunov equation of the form AX+XA^T+Q=0. Implementation requirements for the incorporation of the use of Lyapunov equations in practical design, however, point out the need for a set of specialized numerical procedures. This special set of numerical procedures must efficiently solve large, sparse Lyapunov equations, solve sets of Lyapunov equations that differ only in the coefficient matrix Q, and provide good low rank estimates of the Lyapunov equation solution X in the case where low rank approximations are applicable. Discussions of the motivations for the solution of these problems and of candidate solution approaches are provided     

Formal Analysis of Streaming Downloading Protocol for System Upgrading

For a PC-mobile download system which is embedded with streaming download protocol, there are problems that the data cannot be transmitted correctly from the PC to the mobile, or the transmission is unacceptably slow. To solve these problems, we carry out a formal analysis for the protocol with some timing parameters and a given probability of message loss and unordered data using a probabilistic model checking tool PRISM. We introduce a technique to reduce the state space of the system modeling the protocol which is a network of probabilistic timed automata. The experimental results in PRISM give us a clear explanation to the problems, and are helpful in identifying the optimal parameter settings to meet industrial requirements.     

Microwave plasma enhanced chemical vapor deposition diamond synthesis from high carbon content source

To synthesize diamond films by microwave plasma enhanced chemical vapor deposition (MPECVD), the methane concentration (CH₄/H₂)plays a crucial role. It is well-known that there always exists a critical methane concentration (≤0.6%) only below which a good quality diamond film can be obtained. In this study, however, the phenomena of diamond synthesis resulting from high carbon concentration conditions were observed. The molten metals, e.g., Ag, Cu, were used as the deposition substrates on which crystalline diamonds can be achieved from a methane content of CH₄/H₂≥6% or even from solid carbon sources. These results suggest that there may exist a low methane content boundary layer (<0.6%) in the proximity of molten metal surface on which suitable species, CH, CH⁺, H_α and H_β are composed for the diamond nucleation and growth similar to the condition as in the conventional low methane contents. The molten metal inclines to dissolve other forms of carbonaceous materials other than diamond, and thus keeps a much higher steady supply of carbon atoms that enhances the quality as well as the growth rate of the forming diamonds. Received: 23 June 2001 / Accepted: 23 July 2001     

Direct Vapor Pressure Measurement of Heatset Inks

Several types of ink are used in web offset printing. However, heatset inks predominate in general commercial work. In these inks, the vehicle consists of resin dissolved in a solvent, and drying takes place mainly by evaporation. In heatset web offset printing, the printed web is passed through dryers, which raise the temperature of the web enough to cause evaporation of the solvent. leaving only the resin to bind the pigment into a film and to the paper.

Since the solvents used in the heatset inks vary in boiling range from approximately 232° C to 316° C, and the solvent selected depends on the printing conditions, it is necessary to determine the vapor pressure values of heatset inks versus web temperatures for drying calculations. The isoteniscope method is limited to only the vapor pressure measurement of liquids. It cannot be used for materials such as heatset inks. To overcome this difficulty, an apparatus was designed and con- structed by TEC Systems for directly measuring the vapor pressure versus temperature of heatset inks from approximately 21°C to 316°C. In this paper, TEC's apparatus, test procedure developed, and typical test results for pure solvents and heatset inks will be described.     

Precision winding of fiber optic filament. II. Winding control

For pt.I see ibid., vol.39, no.3, p.258-67 (1992). The winding of fiber optic filament in the hoop, or precision, pattern is considered. Various automatic control options that have been designed and tested are described. The controllers are designed to regulate the fiber lag angle, which is the angle at which the feed filament approaches the take-up spool. Successful, flawless winding is directly related to accurate lag regulation. The contributions are distinguished by the fact that the automatic winding rate is 10 to 30 times greater than that achieved before by operator-assisted winding     

Clinical trial of a new lightwand device (Trachlight) to intubate the trachea

BACKGROUND: Transillumination of the soft tissue of the neck using a lighted stylet (lightwand) is an effective and safe intubating technique. A newly designed lightwand (Trachlight) incorporates modifications to improve the brightness of the light source as well as flexibility. The goal of this study was to determine the effectiveness and safety of this device in intubating the trachea of elective surgical patients. METHODS: Healthy surgical patients were studied. Patients with known or potential problems with intubation were excluded. During general anesthesia, the tracheas were intubated randomly using either the Trachlight or the laryngoscope. Failure to intubate was defined as lack of successful intubation after three attempts. The duration of each attempt was recorded as the time from insertion of the device into the oropharynx to the time of its removal. The total time to intubation (TTI), an overall measure of the ease of intubation, was defined as the sum of the durations of all (as many as three) intubation attempts. Complications, such as mucosal bleeding, lacerations, dental injury, and sore throat, were recorded. RESULTS: Nine hundred fifty patients (479 in the Trachlight group and 471 in the laryngoscope group) were studied. There was a 1% failure rate with the Trachlight, and 92% of intubations were successful on the first attempt, compared with a 3% failure rate and an 89% success rate on the first attempt with the laryngoscope (P not significant). All failures were followed by successful intubation using the alternate device. The TTI was significantly less with the Trachlight compared with the laryngoscope (15.7 +/- 10.8 vs. 19.6 +/- 23.7 s). For laryngoscopic intubation, the TTI was longer for patients with limited mandibular protrusion and mentohyoid distance, with a larger circumference of the neck, and with a high classification according to Mallampatti et al. However, there was no relation between the TTI and any of the airway parameters for Trachlight. There were significantly fewer traumatic events in the Trachlight group than in the laryngoscope group (10 vs. 37). More patients complained of sore throat in the laryngoscope group than in the Trachlight group (25.3% vs. 17.1%). CONCLUSIONS: In contrast to laryngoscopy, the ease of intubation using the Trachlight does not appear to be influenced by anatomic variations of the upper airway. Intubation occasionally failed with the Trachlight but in all cases was resolved with direct laryngoscopy. The failures of direct laryngoscopy were resolved with Trachlight. Thus the combined technique was 100% successful in intubating the tracheas of all patients.     

Photodegradation mechanism and stabilization of polyphenylene oxide and rigid‐rod polymers

Poly(2,4‐dimethyl‐1,4‐phenylene oxide) (PPO), poly(benzo[1,2‐d:5,4‐d′]bisoxazole‐2,6‐diyl‐1,4‐phenylene) (PBO) and poly(benzo[1,2‐d:4,5‐d′]bisthiazole‐2,6‐diyl‐1,4‐phenylene) (PBZT), which are polymers with extended conjugated structures, undergo a self‐sensitized photo‐induced electron‐transfer reaction. A second component is not required. This article presents many similar observations on these polymers when they are exposed to light and evidence to support the proposed photo‐induced electron‐transfer mechanism. Methods to stabilize these polymers against photo‐oxidation are also described. Workers investigating other conjugated polymeric systems may find the experimental methods, observations and polymer stabilization approaches discussed in this review useful. Copyright © 2005 Society of Chemical Industry     

Synthesis and characterization of a novel proton‐exchange membrane for fuel cells operating at high temperatures and low humidities

The synthesis of a p‐toluidine/formaldehyde (PTF) resin was performed, and the effects of the molar ratio of the individual monomers and the polymerization conditions on the structure of the PTF resin were studied. Fourier transform infrared and ¹³C‐NMR spectra were used to characterize the PTF. Wide‐angle X‐ray diffraction patterns revealed the crystalline structures of various PTFs. Polarized optical microscopy revealed that the molar ratio of the monomers had a strong effect on the crystalline morphologies. A longer polymerization time turned out a polymer with a higher intrinsic viscosity and molecular weight, which led to differences in the proton conductivity. All of the PTFs showed a higher proton conductivity than a commercial Nafion membrane at 90–100°C and 0% relative humidity. The proton conductivity of the PTF series could be improved by sulfonation with sulfuric acid and could be maintained after blending with polyurethane. Pure methanol could be used as a fuel source because of the insolubility and nonwetting properties of PTF in methanol to increase the output current density for a PTF membrane electrode assembly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008