Identification of the Saline Zone in a Coastal Aquifer Using Electrical Tomography Data and Simulation

A novel approach that borrows methods commonly used in environmental geophysics was developed for obtaining the estimates of the aquifer parameters. Specifically, estimates of hydraulic conductivity were obtained from field measurements of the electrical resistivity while accounting for the karsticity of the geological formations in the area of study. Geophysically determined hydraulic conductivity estimates were introduced to a 3-D groundwater numerical simulator (Princeton Transport Code – PTC) to compute the hydraulic heads distribution of the area of interest. The calibration of the numerical model was obtained matching the hydraulic-heads predicted by the simulator with the hydraulic-heads measured at specific well locations. Simulated hydraulic-heads were used with the Chyben-Herzberg equation to approximate the position of the sharp freshwater/saltwater interface of the base of the water supply aquifer. The existence of the faults impacts the groundwater flow and the distribution of the freshwater/saltwater interface.     

Modification of the preparation procedure for increasing the hydrodesulfurisation activity of the CoMo/γ-alumina catalysts

In this work we have examined whether the re-impregnation of CoMo/γ-alumina catalysts or the replacement of the conventional non-dry impregnation step by “equilibrium deposition filtration” (EDF) may be used for improving their surface characteristics and thus their catalytic activity.

Two samples were prepared. In the first sample (EDF) the molybdenum species were mounted by “equilibrium deposition filtration” whereas in the second sample these species were mounted by non-dry impregnation (NDI). In both cases the Co was deposited on the calcined Mo/γ-Al₂O₃ precursor solid by simple dry impregnation. An aliquot of each sample was impregnated again with an amount of pure water equal to its pore volume and then it underwent drying and calcination.

The catalysts prepared were characterized using N₂ adsorption measurements (BET), UV–vis diffuse reflectance spectroscopy (DRS), laser Raman spectroscopy (LRS) and NO chemisorption. The hydrodesulfurization (HDS) activities over the catalysts studied were determined using a continuous-flow tubular fixed-bed microreactor operating in a differential mode at atmospheric pressure.

It was confirmed that the replacement of the conventional impregnation by equilibrium deposition filtration results to catalysts with relatively high active surface and high portion of the well-dispersed octahedral cobalt and thus, to catalysts with 30% higher HDS activity. The re-impregnation resulted to partial dissolution and re-dispersion of the Mo and Co supported oxidic phases. Concerning the NDI catalyst re-impregnation resulted to an increase of the active surface and of the portion of the well-dispersed octahedral cobalt and thus to 25% higher catalytic activity. The opposite effects were observed for the EDF catalyst which exhibited almost 7% lower activity after re-impregnation.     

Enabling trust formation within agent-mediated virtual environments

In e-commerce, the role of trust becomes vital for establishing and maintaining customer relationships. Drawing from established theoretical work on trust and relationship marketing, this paper synthesises a series of trust constructs, determinant variables and trust building processes, and proposes a framework for the formation of trust in customer-business relationships. The framework is conceptualised in the context of an electronic servicescape, where trust is formed through iterative interactions with promises being made, enabled and fulfilled. Based on this framework, the paper illustrates how the application of agent and virtual reality technologies can provide the environment and facilitate the expressiveness demanded by such a servicescape.     

Sensory and microbiological quality assessment of beef fillets using a portable electronic nose in tandem with support vector machine analysis

The performance of a portable quartz microbalance based electronic nose has been evaluated in monitoring aerobically packaged beef fillet spoilage at different storage temperatures (0, 4, 8, 12, and 16 °C). Electronic nose data were collected from the headspace of meat samples in parallel with data from microbiological analysis for the enumeration of the population dynamics of total viable counts, Pseudomonas spp., Brochothrix thermosphacta, lactic acid bacteria and Enterobacteriaceae. Qualitative interpretation of electronic nose data was based on sensory evaluation discriminating samples in three quality classes (fresh, semi-fresh, and spoiled). Support Vector Machine (SVM) classification and regression models using radial basis kernel function were developed to classify beef fillet samples in the respective quality class, and correlate the population dynamics of the microbial association with electronic nose sensor responses. The obtained results demonstrated good performance in discriminating meat samples in one of the three pre-defined quality classes. Overall classification accuracies of prediction above 89% were obtained for the three sensory classes regardless of storage temperature. For SVM regression model development, correlations above 0.96 and 0.86 were obtained between observed and predicted microbial counts for the training and test data sets, respectively.     

Cooperative user–network interactions in next generation communication networks

Next Generation Communication Networks employ the idea of convergence, where heterogeneous access technologies may coexist, and a user may be served by anyone of the participating access networks, motivating the emergence of a Network Selection mechanism. The triggering and execution of the Network Selection mechanism becomes a challenging task due to the heterogeneity of the entities involved, i.e., the users and the access networks. This heterogeneity results in different and often conflicting interests for these entities, motivating the question of how they should behave in order to remain satisfied from their interactions. This paper studies cooperative user–network interactions and seeks appropriate modes of behaviour for these entities such that they achieve own satisfaction overcoming their conflicting interests.     

Service configuration and traffic distribution in composite radio environments

This paper adopts the assumption that cellular, broadband fixed wireless access (BFWA), wireless local area networks (WLAN), and digital video broadcasting (DVB) systems can be co-operating components of a composite-radio infrastructure. It is believed that through the composite radio concept, operators will be enabled to offer efficient, in terms of cost and QoS, wireless access to broadband IP-based services. The exploitation of this infrastructure calls for the application of computational intelligence (CI) technologies for the development of appropriate, sophisticated service and network resource management functionality. In this context, this paper identifies and addresses the important problem of service configuration and distribution in a composite radio environment (SCD-CRE). The problem's objective is to determine the best way to accommodate a demand volume, with which the composite radio infrastructure is faced. The pro finds the QoS levels that can be offered, and the networks that can support the demand at the selected QoS levels. The paper includes a first approach to the definition, mathematical formulation, and solution of a version of the SCD-CRE problem. Results indicating some of the capabilities of the SCD-CRE are also presented. Further application fields for CI technologies are indicated, in the area of the necessary reconfiguration of the managed, radio and fixed, network segments.     

Inhibition of the decrease of volatile esters and terpenes during storage of a white wine and a model wine medium by glutathione and N-acetylcysteine

Glutathione and N‐acetylcysteine, each at 20 mg L^?1, were tested as inhibitors of the decrease of volatile esters and terpenes during storage of Debina white wine. Moreover, the inhibition of the decrease of isoamyl acetate, ethyl hexanoate and linalool in a model wine medium by glutathione and N‐acetylcysteine, each at 0–20 mg L^?1, was also tested. Several volatiles, such as isoamyl acetate, ethyl hexanoate, ethyl octanoate, ethyl decanoate and linalool, decreased during wine storage. Glutathione or N‐acetylcysteine significantly restricted the decrease of these volatiles. In the model medium, each thiol inhibited the decrease of the three volatiles in a dose‐dependent manner. N‐acetylcysteine inhibited the decrease of all three volatiles at 2.5 mg L^?1 while glutathione at 2.5 or 5.0 mg L^?1. The present results indicate that glutathione and N‐acetylcysteine may be taken into account as potent inhibitors of the disappearance of aromatic esters and terpenes in wines.     

The clinical value of solid marker transit studies in childhood constipation and soiling

Assessment of constipation in childhood is difficult, particularly when the presenting symptom is spurious diarrhoea or faecal incontinence. We have therefore assessed the clinical usefulness, reliability and acceptability of a solid marker transit technique in 52 patients with constipation (median age 8.0 years; range 2-13.5 years) at two referral centres. Median duration of symptoms was 60 months. Soiling was a prominent feature in 43 children (83%). Ten, 3 mm pieces of 6FG radio-opaque Silastic tubing were given orally at 9am on days 1, 2 and 3 and a plain abdominal film taken on day 5. Laxative treatment was not interrupted. Each film was divided into right colon, left colon and rectosigmoid areas, using bony landmarks, and the marker content of each area counted. The coefficient of variation of intra and inter-observer errors was 3.1% and 2.1% respectively. By day 5, 7% (group median) of markers were still in the right colon, 17% in the left colon and 42% in the rectosigmoid. Twenty-one patients (40%) had normal transit, 4 (8%) mild delay, 9 (17%) moderate and 18 (35%) severe transit delay. Marker distribution indicated slow pan-colonic transit in 29% and slow segmental transit in 10%. In 21%, clustering of markers in the rectosigmoid suggested outlet obstruction. A significant correlation was found between both transit delay and marker distribution and the severity of clinical symptoms of constipation and soiling. Repeat studies in six children following colonic evacuation revealed significant improvement (P < 0.05) in marker transit.(ABSTRACT TRUNCATED AT 250 WORDS)     

Symposium on Operations Research 1995 Jahrestagung der DGOR, GM?OR und ?GOR (SOR '95) Universit?t Passau, 13. September –15. September, 1995

Jahrestagung der DGOR, GMÖOR und ÖGOR (SOR '95) Universität Passau, 13. September –15. September, 1995