Macroscopic model for multispecies ion-exchange kinetics

A model for multispecies ion-exchange kinetics based on the Nernst-Planck equation is suggested. It is analyzed in comparison with the “locally-determinate” model described by Hwang and Helfferich [1]. The model makes possible simple computation. The conditions for the occurrence of unusual kinetic curves with a maximum are clarified. The proposed model is developed for different types of kinetic problems and verified by the experimental investigation of a kinetics in ternary systems.     

Determination of porous glass surface free energy components from contact angles

The contact angles of water drops and diiodomethane drops on pellets made of controlled porosity glasses have been measured. The surface of the glasses was modified by thermal treatment at 873 K which led to an increase in the surface concentration of boron atoms. Glass modified with Carbowax 20M (polyethylene glycol) and fully hydroxylated glass have also been studied. Using the measured contact angles and modified Young equation, the dispersion and nondispersion components of the glass surface free energy have been calculated. The values show that with increasing heating time (increasing surface density of boron atoms) an increase in the surface polarity takes place. However, the polarity of the same samples decreases after treatment with Carbowax, increasingly so with higher boron atom concentrations.     

Solid state reactions in the Fe2O3-CaCO3-In2O3 system

The kinetics of solid-state reactions of powdered reactants were investigated by X-ray and by differential thermogravimetry in a magnetic field. Measurements revealed mutual diffusion of the Fe³⁺ and In³⁺ ions in the Fe₂O₃-In₂O₃ system heat treated for 3 h at 700 to 1400° C. Diffusion of indium into the Fe₂O₃ lattice caused a shift of the Curie temperature of the antiferromagnetic iron oxide towards lower temperatures. Only Caln₂O₄ was found between CaCO₃ and In₂O₃ up to 1400° C. Also, in the Fe₂O₃-CaCO₃-In₂O₃in system, the reaction started with the mutual diffusion of iron and indium and the forming of CaFe₂O₄. End-products were the magnetic -Ca₄Fe₁₄O₂₅ and CaFe₄O₇, and the non-magnetic CaFe₅O₇, depending on the In³⁺ concentration. Indium stabilized the magnetic calcium-iron oxide structures, shifting their Curie temperatures towards lower values.     

Usable optimistic fair exchange

Fairly exchanging digital content is an everyday problem. It has been shown that fair exchange cannot be achieved without a trusted third party (called the Arbiter). Yet, even with a trusted party, it is still non-trivial to come up with an efficient solution, especially one that can be used in a p2p file sharing system with a high volume of data exchanged.We provide an efficient optimistic fair exchange mechanism for bartering digital files, where receiving a payment in return for a file (buying) is also considered fair. The exchange is optimistic, removing the need for the Arbiter’s involvement unless a dispute occurs. While the previous solutions employ costly cryptographic primitives for every file or block exchanged, our protocol employs them only once per peer, therefore achieving an O(n) efficiency improvement when n blocks are exchanged between two peers. Our protocol uses very efficient cryptography, making it perfectly suitable for a p-2-p file sharing system where tens of peers exchange thousands of blocks and they do not know beforehand which ones they will end up exchanging. Therefore, our system yields up to one-to-two orders of magnitude improvement in terms of both computation and communication (40 s vs. 42 min, 1.6 MB vs. 200 MB). Thus, for the first time, a provably secure (and privacy-respecting when payments are made using e-cash) fair exchange protocol can be used in real bartering applications (e.g., BitTorrent) [14] without sacrificing performance.     

Mining non-derivable hypercliques

A hyperclique (Xiong et al. in Proceedings of the IEEE international conference on data mining, pp 387–394, 2003) is an itemset containing items that are strongly correlated with each other, based on a user-specified threshold. Hypercliques (HCs) have been successfully used in a number of applications, for example, clustering (Xiong et al. in Proceedings of the 4th SIAM international conference on data mining, pp 279–290, 2004) and noise removal (Xiong et al. in IEEE Trans Knowl Data Eng 18(3):304–319, 2006). Even though HC has been shown to respond well to datasets with skewed support distribution and low support threshold, it may still grow very large for dense datasets and lower h-confidence threshold. In this paper, we propose a new pruning method based on combining HCs and non-derivable itemsets (NDIs) (Calders and Goethals in Proceedings of the PKDD international conference on principles of data mining and knowledge discovery, pp 74–85, 2002) in order to substantially reduce the amount of generated HCs. Specifically, we propose a new collection of HCs, called non-derivable hypercliques (NDHCs). The NDHC collection is a lossless representation of HCs, that is, given the itemsets in NDHCs, we can generate the complete HC collection and their support, without additional scanning of the dataset. We present an efficient algorithm to mine all NDHC sets, NDHCMiner, and an algorithm to derive all HC sets and their support from NDHCs, NDHCDeriveAll. We experimentally compare our collection, NDHC with HC, with respect to runtime performance as well as total number of generated sets, using real and artificial data. We also show comparisons with another condensed representation of HCs, maximal hyperclique patterns (MHPs). Our experiments show that the NDHC collection offers substantial advantages over HCs, and even MHPs, especially for dense datasets and lower h-confidence values.     

The content and composition of sterols and sterol esters in low erucic acid rapeseed (Brassica napus)

The low temperature crystallization technique for the enrichment of “minor” components, such as sterols and sterol esters, from vegetable oils was applied to low erucic acid rapeseed oils. The recovery of free sterols and sterol esters was estimated by use of¹⁴C-cholesterol and¹⁴C-cholesterol oleate. 80% of the free sterols and 45% of the sterol esters were recovered in the liquid fraction, while in two studies total recoveries were 95% and 99%, respectively. This technique showed some selectivity toward the sterol bound fatty acids when compared to direct preparative thin layer chromatography (TLC) of the crude oil. Gas liquid chromatography (GLC) analysis of the free and esterified sterols as TMS-derivatives showed very little selectivity in the enrichment procedure. The fatty acid patterns of the sterol esters demonstrated, however, a preference in the liquid fraction for those sterol esters which have a high linoleic and linolenic acid content. The content of free sterols was 0.3–0.4% and that of sterol esters 0.7–1.2% of the rapeseed oils in both winter and summer types of low erucic acid rapeseed (Brassica napus) when the lipid classes were isolated by direct preparative TLC of the oils. The free sterols in the seven cultivars or breeding lines analyzed were composed of 44–55% sitosterol, 27–36% campesterol, 17–21% brassicasterol, and a trace of cholesterol. The esterified sterols were 47–57% sitosterol, 36–44% campesterol, 6–9% brassicasterol, and traces of cholesterol and Δ5-avenasterol. The fatty acid patterns of these esters were characterized by ca. 30% oleic acid and ca. 50% linoleic acid, whereas these acids constitute 60% and 20%, respectively, of the total fatty acids in the oil. Little or no variation in sterol and sterol ester patterns with locality within Sweden was observed for the one cultivar of summer rapeseed investigated by the low temperature crystallization technique.     

A comparative study of two wayfinding aids for simulated driving tasks – single-scale and dual-scale GPS aids

Global Positioning System (GPS) is currently the most frequently used wayfinding aid for driving. Yet, GPS is designed to act as a driving guide rather than to help users gain spatial knowledge. Accordingly, GPS might be less usable in situations where such knowledge is required or highly desirable. In this study, we experimentally study the influence of GPS display scales (single-scale vs. dual-scale) using simulated driving tasks in a virtual environment. The single-scale GPS is similar to the regular GPS view. The dual-scale GPS aid is a dual-scale navigation tool that provides two levels of detail, including both detailed and contextual information. The results demonstrate that the dual-scale GPS was more efficient in leading the participants to the destination during the simulated driving and was more useful for the participants to establish spatial awareness and a cognitive map; the dual-scale GPS participants also reported higher subjective evaluations. The proposed dual-scale GPS design and experimental results show some indications for designing new wayfinding aids aimed at increasing wayfinding performance while simultaneously helping users construct a cognitive map.     

梯级水电站施工导流风险效益补偿机制研究

汛期通过上游已建水电站调蓄可保障下游施工电站的度汛安全。为有效均衡上下游风险,合理分摊合作利益,对梯级水电站施工导流风险效益进行了补偿机制的设计。以总效益可量化为前提,提出补偿是落实风险效益分摊的一种支付行为,分别从补偿主客体的界定、责权利的划分、风险效益计量、补偿实施方式、补偿管理流程设计等方面,构建了梯级水电开发条件下施工导流风险效益补偿框架和程序。针对补偿制度实施存在的难点,提出了相应的对策和建议,可为流域梯级水电站风险效益补偿管理模式和制度的构建提供参考。     

The removal of dichloromethane from atmospheric pressure air streams using plasma-assisted catalysis

Plasma-assisted catalysis was used for the destruction of 500 ppm of dichloromethane, CH₂Cl₂ (DCM), in gas streams of air using a non-thermal, atmospheric pressure plasma utilising a dielectric packed bed. The combination of plasma and catalyst gave improved destruction of DCM. Eight catalysts which including alumina, TiO₂ and various zeolites were investigated with the finding that alumina in a one-stage reactor configuration and TiO₂ and HZSM-5 in two-stage configurations gave the best DCM destructions. The sodium zeolites are capable of reducing by 50% the unwanted NO_x by-products, formed by plasma processing in air. The nature of the catalyst is important in terms of the destruction efficiency, end-product selectivity and NO_x reduction.