Investigation on the Effect of Pre-heating with Butane Gas Torch in Formability of High Tension Steel (HTS) by Using Taguchi Experimental Method in Roll Forming Process

This study was carried out to evaluate a new roll forming process involving pre-heating using a gas torch. The temperature distribution for the formed sheet was observed using a 3D-IR graph generated from a thermal imaging camera. The appropriate distance between the formed sheet and the butane gas torch was also determined based on the results of the flame characteristics. The thermal effects of the formed sheet were confirmed by the temperature distribution. Spring-back analysis was applied to the Nominal the Best characteristic of Taguchi’s experimental method. In spring-back analysis, the forming speed is an influential variable. Bow analysis was applied to the Smaller the best characteristic of Taguchi’s experimental method. Lastly, at room temperature, the roll forming process was performed with pre-heating and formability was analyzed with respect to spring-back, bow and variance of bending angle (buckling). Spring-back, bow and buckling with the roll forming process involving pre-heating got improved by 0.97°, 0.17 mm and 0.20, respectively, compared to the same processes at room temperature. Forming speed appeared to have the most influence on the formability and pre-heating was found to improve the formability in the roll forming process.     

Modeling buffer utilization in cell-based networks

Variable bit rate traffic is characteristically bursty and the arrivals are highly correlated. New network technology carries such traffic in cell-based networks where the service is a discrete time, deterministic process with the service rate determined by bandwidth negotiated by the user. Managing such networks is hard, and predicting cell loss at a station with limited buffer capacity K is essential to enable the user to negotiate his quality of service requirements. We present an analysis to determine the queue length distribution and the loss probability in such circumstances. For our analysis, we use an m-phase Markov Modulated Bernoulli Process with binomial distributed batch arrivals and deterministic service and limited capacity K, i.e. a MMBP^[X]_(m)/D/1 − K queuing system. We show that the system can be analyzed using the so-called unfinished work approach. The validity of our evaluation technique is illustrated by comparing our analytical results against those obtained from an event-driven siimulation of the same system.     

Relative primary adhesion of Pseudomonas aeruginosa, Serratia marcescens and Staphylococcus aureus to HEMA-type contact lenses and an extended wear silicone hydrogel contact lens of high oxygen permeability.

PURPOSE: To compare multiple strains of Pseudomonas aeruginosa and representative isolates of Staphylococcus aureus and Serratia marcescens for their relative primary adhesion to a high Dk silicone hydrogel lens (36% H2O) with that of a HEMA-type lens (58% H2O). METHODS: A radiolabeled cell procedure with a 2-h cell exposure was employed for enumerating bacteria on unworn and worn silicone hydrogel (balafilcon A) and HEMA-type (etafilcon A) hydrogel lenses. RESULTS: The degree of primary adhesion of P. aeruginosa to 7-day worn balafilcon A lens was similar to the degree of adhesion to unworn balafilcon A lenses. The degree of primary adhesion by clinical strains to unworn balafilcon A lenses and etafilcon lenses was strain variable, but did not differ markedly for the two lenses with a given strain of P. aeruginosa. Relative to most of the pseudomonad strains, adhesion to the hydrogel lenses by S. aureus and S. marcescens was non-significant. CONCLUSION: Adhesion of strains of P. aeruginosa to a hydrogel contact lens does not appear to differ appreciably between the HEMA-type etafilcon A and the high Dk silicone hydrogel balafilcon A lens.     

An Applicable Strategy for Improvement Recovery in Simultaneous Analysis of 20 Pesticides Residue in Tea

It is important to have a reliable method to analyze pesticides in tea, a beverage commonly consumed in Iran. A validated method was developed for the determination of 20 pesticides in tea based on QuEChERS sample preparation and capillary gas chromatography‐quadrupole mass spectrometry in selective ion monitoring mode (GC‐MS/SIM) using triphenyl methane (TPM) solution as an internal standard. We used fortified, extracted, and cleaned‐up tea samples instead of calibration standards for quantitation, which substantially reduced adverse matrix‐related effects and negative recovery affected by graphite carbon black (GCB) on pesticide analysis. The recovery of pesticides at 3 concentration (40, 60, and 240 ng/g) ranged from 79.5% to 111.4% (n = 3). The method had acceptable repeatability with RSDr < 20%. The limits of quantification (LOQ) for all pesticides were ≤20 ng/g. The analytical results of the proposed method were in good agreement with proficiency test results (FAPAS, 19116). The recoveries and repeatabilities were in accordance with the criteria set by SANCO Guideline. The validated method was suitable for the analysis of pesticides in tea.     

Hopf bifurcation index for large scale power systems

In this paper, we propose a novel index for the prediction of the Hopf bifurcation (HB) in power systems. The proposed index has strictly less processing load and less computation time in comparison to former HB indices. It also uses modern control properties of the power system such as system matrix and critical eigenvalue. Therefore, stochastic subspace system identification (SSSI) is used as a tool for estimation and prediction of the proposed HB index. Combining beneficial properties of SSSI methods and the processing advantages of the proposed index, we project a new algorithm for power system monitoring. The algorithm is easy and straight-forward. We conduct several test conditions for the proposed materials using 2-area 4-machine system, New England 10-Machine and IEEE 50-machine system. Simulation outcome expresses good performance of proposed index in comparison to former HB indices. The proposed index has fairly linear behavior, without discontinuities with respect to increases of system load. It also has less computation load.     

Particle phase acidity and oligomer formation in secondary organic aerosol

A series of controlled laboratory experiments are carried out in dual Teflon chambers to examine the presence of oligomers in secondary organic aerosols (SOA) from hydrocarbon ozonolysis as well as to explore the effect of particle phase acidity on SOA formation. In all seven hydrocarbon systems studied (i.e., alpha-pinene, cyclohexene, 1-methyl cyclopentene, cycloheptene, 1-methyl cyclohexene, cyclooctene, and terpinolene), oligomers with MW from 250 to 1600 are present in the SOA formed, both in the absence and presence of seed particles and regardless of the seed particle acidity. These oligomers are comparable to, and in some cases, exceed the low molecular weight species (MW < 250) in ion intensities in the ion trap mass spectra, suggesting they may comprise a substantial fraction of the total aerosol mass. It is possible that oligomers are widely present in atmospheric organic aerosols, formed through acid- or base-catalyzed heterogeneous reactions. In addition, as the seed particle acidity increases, larger oligomers are formed more abundantly in the SOA; consequently, the overall SOA yield also increases. This explicit effect of particle phase acidity on the composition and yield of SOA may have important climatic consequences and need to be considered in relevant models.