Standard gas and vapour mixtures for chromatography

Standard mixtures of gases and vapours are prepared gravimetrically with a high degree of accuracy and are used for the calibration of large quantities of multi-component mixtures which may serve as chromatographic standards for routine analysis of gases and vapours. A dilution method is used for the preparation of very low concentrations such as fractions of a parts/10⁶ of pentane in helium.     

Universal parameter optimisation in games based on SPSA

Most game programs have a large number of parameters that are crucial for their performance. While tuning these parameters by hand is rather difficult, efficient and easy to use generic automatic parameter optimisation algorithms are known only for special problems such as the adjustment of the parameters of an evaluation function. The SPSA algorithm (Simultaneous Perturbation Stochastic Approximation) is a generic stochastic gradient method for optimising an objective function when an analytic expression of the gradient is not available, a frequent case in game programs. Further, SPSA in its canonical form is very easy to implement. As such, it is an attractive choice for parameter optimisation in game programs, both due to its generality and simplicity. The goal of this paper is twofold: (i) to introduce SPSA for the game programming community by putting it into a game-programming perspective, and (ii) to propose and discuss several methods that can be used to enhance the performance of SPSA. These methods include using common random numbers and antithetic variables, a combination of SPSA with RPROP, and the reuse of samples of previous performance evaluations. SPSA with the proposed enhancements was tested in some large-scale experiments on tuning the parameters of an opponent model, a policy and an evaluation function in our poker program, MCRAISE. Whilst SPSA with no enhancements failed to make progress using the allocated resources, SPSA with the enhancements proved to be competitive with other methods, including TD-learning; increasing the average payoff per game by as large as 0.19 times the size of the amount of the small bet. From the experimental study, we conclude that the use of an appropriately enhanced variant of SPSA for the optimisation of game program parameters is a viable approach, especially if no good alternative exist for the types of parameters considered. Editors: Michael Bowling · Johannes Fürnkranz · Thore Graepel · Ron Musick     

Influence of Cure Regime on the Strain Development in an Epoxy Resin as Monitored by a Fiber Bragg Grating Sensor

In this paper, the effects of different cure regimes on the strain development in an anhydride‐cured epoxy resin were investigated by fiber optical measurements. The course of the strain signal was detected by an embedded fiber Bragg grating sensor in the unconstrainedly curing epoxy. The build‐up of strain was detected for various cure regimes differing in the dwelling times of the first isothermal step, heating rates to the cure temperature, and final curing temperatures, respectively. Characteristic points (gelation, vitrification) of the cure regimes were identified by conversion‐ and T_g‐determinations via DSC and assigned to changes of the FBG signal. The fiber Bragg sensing technique allowed us to find those variables of the cure regimes which mostly affect the strain development and thus, the level of the residual strain. It was established that the dwelling time and heating rate to the cure temperature influence markedly the residual strain whereas the cure temperature affects this value to a lesser extent for the selected cure regimes. So, the above parameters should be selected properly for an optimum cure regime characterized by the build‐up of a minimum residual strain.

     

Monitoring of cure‐induced strain of an epoxy resin by fiber Bragg grating sensor

In this study, we present a method to detect cure‐induced strain in an epoxy resin (EP) with a Fiber Bragg Grating (FBG) sensor. By embedding the optical fiber into the EP resin the characteristics during isothermal cure (gel point, vitrification) could be precisely detected due to changes in the fiber strain. In a follow up dynamic temperature scan the coefficient of thermal expansion and the glass transition temperature (T_g) of the fully cured EP were determined by the FBG sensor technique. All results obtained by the fiber optical method showed a very good agreement with those deduced by independent techniques, viz. rheological measurements, differential scanning calorimetry, and thermomechanical analysis. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Determination methods of the grafting yield in glycidyl methacrylate‐grafted ethylene/propylene/diene rubber (EPDM‐g‐GMA): Correlation between FTIR and 1H‐NMR analysis

A normalized and universally applicable calibration function for the Fourier‐transformed infrared (FTIR) quantification of the glycidyl methacrylate (GMA) grafting yield in polymers of known compositions having ethylene block sequences was established. The ¹H nuclear magnetic resonance (¹H‐NMR) spectroscopy results achieved on different GMA‐grafted ethylene/propylene/diene rubber (EPDM‐g‐GMA) and ethylene/GMA copolymers were correlated to their FTIR data to calibrate the relative determination of the FTIR method. Both direct and indirect standardization approaches were followed and evaluated. The calibration deduced was used to investigate the free radical grafting reaction of GMA on EPDM rubber in the melt phase. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2616–2624, 1999     

Interaction of PIB-succinimides and other engine oil additives

The paper shows the results of investigations into the interactions between different types of succinimides and zinc dialkyl dithiophosphates. Various properties of additives in oil solutions were tested and examined by various methods, in order to show the existence of interactions of various strengths between different types of succinimide and ZnDDP.     

Curing,gelling, thermomechanical,and thermal decomposition behaviors of anhydride‐cured epoxy (DGEBA)/epoxidized soybean oil compositions

This work was aimed at studying the effects of incorporation of epoxidized soybean oil (ESO) in a standard bisphenol A‐type epoxy resin (EP) cured by anhydride hardener. The EP/ESO ratio was set for 100/0, 75/25, 50/50, 25/75, and 0/100 (wt%/wt%). The investigations performed covered the curing, rheology (gelling), thermomechanical (TMA), and thermogravimetric analysis (TGA) of the EP/ESO compositions. The results showed that the dilution of EP with ESO was accompanied with marked changes in the curing, gelling behavior, and final properties. Differential scanning calorimetry revealed that the crosslinking of EP/ESO ≥ 50/50 occurred in two steps. This has been considered for the cure schedule set. The gel time of EP/ESO, determined at T = 100, 120, 140°C, respectively, increased with increasing ESO content. The activation energy of gelling increased with increasing ESO content. The glass transition temperature decreased with increasing ESO content. The samples were transparent that was traced to the presence of domains smaller in size than the wavelength of the visible light based on atomic force microscopy inspection. According to TMA, the coefficient of thermal expansion in the glassy state increased with increasing ESO content but was independent of the latter in the rubbery stage. TGA indicated that with increasing ESO content the thermal degradation started earlier and the char yield decreased. The Ozawa, Flynn, and Wall (OFW) approach was adapted to TGA tests to calculate the activation energy of thermal degradation. The activation energy depended on the ESO content of the EP/ESO blends and also on their actual decomposition stage. The latter means a limitation for the OFW approach. POLYM. ENG. SCI., 54:747–755, 2014. © 2013 Society of Plastics Engineers     

Optimization of the Tilted-Pulse-Front Terahertz Excitation Setup Containing Telescope

Optimization of the telescopic tilted-pulse-front terahertz excitation setup with respect to the imaging errors is given. A guideline is presented in the form of simple analytical formulae describing the optimal geometrical configuration of the telescopic setup. Pump pulse distortions and terahertz wave-front distortions are analyzed by ray tracing calculations supposing near-infrared pump pulses with 200 fs transform limited pulse length. The detrimental effects of imaging errors in a tilted-pulse-front terahertz source can be significantly reduced by using telescopic imaging instead of one-lens. It is also shown, that in the case of the one-lens setup significant, and in the case of the telescopic setup, less significant reduction of the imaging errors can be achieved by using achromat lens(es) instead of singlet one(s). Calculation results show that the telescopic setup consisting of two achromat lenses is the most promising choice among the practically relevant schemes.     

Designing robust network topologies for wireless sensor networks in adversarial environments

In this paper, we address the problem of deploying sink nodes in a wireless sensor network such that the resulting network topology be robust. In order to measure network robustness, we propose a new metric, called persistence, which better captures the notion of robustness than the widely known connectivity based metrics. We study two variants of the sink deployment problem: sink selection and sink placement. We prove that both problems are NP-hard, and show how the problem of sink placement can be traced back to the problem of sink selection using an optimal search space reduction technique, which may be of independent interest. To solve the problem of sink selection, we propose efficient heuristic algorithms. Finally, we provide experimental results on the performance of our proposed algorithms.