Experimental and theoretical study of steam condensation induced water hammer phenomena

We investigate the steam condensation induced water hammer (CIWH) phenomena and present experimental and theoretical results. The experiments were performed in the PMK-2 facility, which is a full-pressure thermo-hydraulic model of the primary loop of the VVER-440/312 type nuclear power plant and located in the Atomic Energy Research Institute Budapest, Hungary.The present experimental setup is capable to measure CIWH phenomena in a wide range of steam pressure, cold water temperature and mass flow rate at a high level of accuracy. On the theoretical side CIWH is studied and analyzed with the WAHA3 model based on two-phase flow six first-order partial differential equations that present one-dimensional, surface averaged mass, momentum and energy balances. A second order accurate high-resolution shock-capturing numerical scheme was applied with different kind of limiters in the numerical calculations. Our study clearly shows that Relap5 and Cathare which are used in the nuclear industry to simulate nuclear power plant accidents cannot resolve the narrow pressure peaks created during a CIWH event. Only WAHA3 can model CIWH properly. Experimentally measured and theoretically calculated pressure peaks are in good agreement, however simulations always show additional pressure peaks. As a new feature in this study we present calculations without additional unphysical reflections caused by boundary conditions.     

Influence of Al2O3 on the performance of CeO2 used as catalyst in the direct carboxylation of methanol to dimethylcarbonate and the elucidation of the reaction mechanism

In this paper we show that modification of ceria by loading alumina strongly reduces the oxidation of methanol and the consequent reduction of Ce(IV) to Ce(III) with increase of both the life of the catalysts and their selectivity. The combination of surface techniques (XPS and BET) with structural techniques (XRD) has allowed a good characterisation of the working catalysts. Spectroscopic analyses (DRIFT and multinuclear solid state and solution NMR) have permitted the monitoring of the species formed on the surface of the catalyst and released from it. The formation of DMC takes place in successive steps such as (i) interaction of methanol with the catalyst surface with the formation of the surface-bound OCH₃; (ii) building on the catalyst surface of the hemicarbonate moiety [–OCH₃ → –OC(O)OCH₃]; and (iii) reaction of the latter with the gas-phase methanol to afford the organic carbonate.     

Modeling and Analysis of Broadband Cellular Networks with Multimedia Connections

As mobile networking is moving towards the direction of providing high-speed multimedia services, the presence of connections that do not generate traffic at constant rate is becoming reality in wireless environment. For preliminary network design purposes analytical models are necessary that examine the performance or wireless networks with such connections. In this paper an analytical method is presented to calculate call-level system parameters of cellular networks with multimedia connections. The method is based on an approximate recursive calculation. The accuracy of the approximation is verified by computer simulations. The derivation of the distributions of user describing time variables and two simple admission control policies are also presented and investigated.     

Quality‐based charging solutions for wireless multimedia services

The evolution of mobile telecommunication networks and access bandwidth has enabled operators to deliver IPTV services for mobile customers; however, the existing mobile charging solutions are not effectively addressing the billing requirements of multimedia streams. This paper develops a quality‐based charging solution for 3GPP wireless networks with the aim of providing a fair pricing solution for multimedia services. An appropriate business model is selected and a streaming proxy‐based charging architecture is developed based on the quality of the multimedia service. The proposed algorithms are theoretically evaluated by the derivation of the formulas of the distribution and the expected value of the price discount. A testbed is built and the findings are evaluated and compared with traditional charging functions. Copyright © 2014 John Wiley & Sons, Ltd.     

Effects of different inorganic salts and organic nutrient components on the growth of Lentinula edodes (Shiitake) mycelium on solid medium

The influence of 11 inorganic salts and various organic nutrients on the mycelial growth of Lentinula edodes (Berk) Pegler (Shiitake) on solid medium was studied. All of these inorganic salts exerted concentration‐dependent inhibitory effects. Nitrite caused the strongest inhibition: 8 mM nitrite inhibited the growth completely. The inhibitory effect of nitrite could be reduced by the addition of ascorbic acid or a black tea extract. The effects of the addition of the different organic nutrients were investigated in order to optimize the composition of the culture medium. The medium containing malt extract (15 g l^?1), starch (3 g l^?1) and oak wood chips (20 g l^?1) proved best for mycelial growth. Growth was not promoted by components with a high organic nitrogen content. Copyright © 2003 Society of Chemical Industry     

Photostructural transformations in amorphous chalkogenide nanolayered films produced by thermal vapour deposition

Photo- and thermoinduced changes of As₂S₃ \Se_xTe_1−x (0.1 < x < 0.5) multilayer structures were investigated by optical and electrical methods as well as by low angle X-ray diffraction (LAXD). It was shown that samples with total thicknesses up to 0.7–0.8 μm of 4–20 nm thick alternating layers with good periodicity, may be prepared by cyclic thermal vapour deposition. The structure of this multilayer may be changed by thermal treatment or illumination with focused laser beam due to the interdiffusion. The corresponding photoinduced changes of optical parameters (absorption, refraction) are useful for optical reading.     

LC-MS method development to evaluate major triterpenes in skins and cuticular waxes of grape berries

Predominant triterpenes (free oleanolic acid, β-sitosterol and β-sitosterol-3-O-β- d -glucoside) in skin and cuticular wax of grape berries have been analysed by liquid chromatography–mass spectrometry (LC-APCI-MS). The validity of the developed method was established by determining linearity, recovery, precision, accuracy, limit of detection and quantification. Detection limits were in the range of 0.12–0.25 mg L⁻¹, and linearity values ranged up to 105 mg L⁻¹. The repeatability of the method was good. High variability was found among the measured grape varieties based on triterpene content, quantitites of oleanolic acid of cuticular wax ranged from 31.53 mg kg⁻¹ to 162.01 mg kg⁻¹ of the twelve analysed samples. The highest sitosterol content was measured in the sample 'Othello' (73.12 mg kg⁻¹), while maximum sitosterol glucoside content was also found in 'Othello' variety (13.68 mg kg⁻¹). The results showed that the study on triterpenes could be an informative tool to characterise grape varieties.