EXTRACTION OF GOLD AND SILVER FROM TURKISH GOLD ORE BY AMMONIACAL THIOSULPHATE LEACHING

Although cyanide is a widespread leaching reagent for the recovery of precious metals, there still are continuing investigations on alternative processes due to the related environmental problems concerned. Thiosulphate leaching of precious metals is one of the processes that were developed as an alternative and nontoxic technique to conventional cyanidation. The aim of this experimental study was to investigate the possibilities of leaching gold and silver in ammoniacal thiosulphate solutions on a laboratory scale. Samples used in the experiments were taken from Ovac?k Gold Mine, located in the Bergama region of Turkey. The influence of temperature, copper sulphate concentration, ammonia concentration, thiosulphate concentration, sodium sulfite concentration, and solid–liquid ratio on gold and silver leaching recoveries was investigated and optimum leaching conditions were determined. At these conditions, 99.57% Au and 95.87% Ag leaching recoveries were achieved.     

Web-Vacuum: Web-Based Environment for Automated Assessment of Civil Infrastructure Data

Data quality is extremely important where information dramatically influences the decisions being made. In the context of civil infrastructure systems, planning and management activities are critically dependent on data to support the efficient allocation of resources, detailed cost-benefit analysis, and informed decision-making. A Web-based tool, called Web-Vacuum, which employs data-mining (DM) techniques and partially implements a two-level data-quality assessment procedure, was developed to support the general purpose of data-quality assessment. The algorithms, workflow, and interfaces used in Web-Vacuum are presented. A data-quality assessment case study using a bridge management system data set is used to demonstrate that the application of Web-Vacuum can be used to assist in determining the quality of a data set.     

Stability of C60 chains: molecular dynamics simulations

A linearly aligned structure of three C60 fullerene, interconnected by two benzorods of same size, have been investigated under heat treatment. The overall structure resembles a section of a beaded string. Nine different lengths of benzorods have been considered, and the effect on the thermal stability have been investigated by means of molecular dynamics method. It has been found that the structure is thermally stable up to elevated temperatures, and the linear alignment of the structure is persistent, up to the temperature of decomposition.     

No-but-semantic-match: computing semantically matched xml keyword search results

Users are rarely familiar with the content of a data source they are querying, and therefore cannot avoid using keywords that do not exist in the data source. Traditional systems may respond with an empty result, causing dissatisfaction, while the data source in effect holds semantically related content. In this paper we study this no-but-semantic-match problem on XML keyword search and propose a solution which enables us to present the top-k semantically related results to the user. Our solution involves two steps: (a) extracting semantically related candidate queries from the original query and (b) processing candidate queries and retrieving the top-k semantically related results. Candidate queries are generated by replacement of non-mapped keywords with candidate keywords obtained from an ontological knowledge base. Candidate results are scored using their cohesiveness and their similarity to the original query. Since the number of queries to process can be large, with each result having to be analyzed, we propose pruning techniques to retrieve the top-k results efficiently. We develop two query processing algorithms based on our pruning techniques. Further, we exploit a property of the candidate queries to propose a technique for processing multiple queries in batch, which improves the performance substantially. Extensive experiments on two real datasets verify the effectiveness and efficiency of the proposed approaches.     

Improvement of BIB packaging product filling valve CIP performance and efficiency

This paper presents the work carried out to improve the clean-in-place (CIP) performance of a product fill valve used extensively for the bag in box (BIB) packaging of wine. Computational fluid dynamics (CFD) models were developed in an attempt to improve the CIP, remove areas of cavitation and increase the flow through the valve. Food processing industries rely on high product throughput as well as excellent CIP ability of equipment used to package foods and beverages. Detailed investigations were undertaken on velocity, pressure distribution, wall shear stress and turbulence intensity with a view to increase the valve performance. The original valve is of cylindrical type and therefore, initial attempts were considered keeping the cylindrical shape but raising the valve stem by 10 mm, changing the angle of the inlet tube from 30° to 37° and lengthening the outlet tube by 7 mm. All showed improved mass flow, reduction of cavitation but failed to increase the CIP performance. Then, attempts were made using semi-spherical configuration. Computer simulation has shown that the cleanability by CIP of the redesigned fill valve has been significantly improved which could not be achieved by cylindrical shape. The redesigned fill valve also has an improved flow capability of 47% over the original design when operated at the same pressure, and approaching 60% when operated at equivalent internal pressure drops.     

Optimal placement and routing strategies for resilient two‐tiered sensor networks

In hierarchical sensor networks using relay nodes, sensor nodes are arranged in clusters and higher powered relay nodes can be used as cluster heads. The lifetime of such a network is determined primarily by the lifetime of the relay nodes. In this paper, we propose two new integer linear programs (ILPs) formulations for optimal data gathering, which maximize the lifetime of the upper tier relay node network. Unlike most previous approaches considered in the literature, our formulations can generate optimal solutions under the non‐flow‐splitting model. Experimental results demonstrate that our approach can significantly extend network lifetime, compared to traditional routing schemes, for the non‐flow‐splitting model. The lifetime can be further enhanced by periodic updates of the routing strategy based on the residual energy at each relay node. The proposed rescheduling scheme can be used to handle single or multiple relay node failures. We have also presented a very simple and straightforward algorithm for the placement of relay nodes. The placement algorithm guarantees that all the sensor nodes can communicate with at least one relay node and that the relay node network is at least 2‐connected. This means that failure of a single relay node will not disconnect the network, and data may be routed around the failed node. The worst case performance of the placement algorithm is bounded by a constant with respect to any optimum placement algorithm. Copyright © 2008 John Wiley & Sons, Ltd.     

Low loss and low dispersion hybrid core photonic crystal fiber for terahertz propagation

In this paper, a hybrid-core circular cladded photonic crystal fiber is designed and analyzed for application in the terahertz frequency range. We introduce a rectangular structure in addition to a conventional hexagonal structure in the core to reduce the material absorption loss. The modal characteristics of the fiber have been investigated using full vector finite element method. Simulated results exhibit an ultra-low effective material loss of 0.035 cm\(^{-1}\) and ultra-flattened dispersion of 0.07 ps/THz/cm. Some other important fiber characteristics suitable for terahertz signal transmission including confinement loss, core power fraction, effective area and single-mode conditions of the fiber have also been investigated. In order to simplify design and facilitate fabrication, only circular shaped air holes have been employed. Due to its promising characteristics, the proposed waveguide may provide efficient transmission of broadband terahertz signals.     

Optimal regenerator assignment and resource allocation strategies for translucent optical networks

Physical layer impairments in wavelength-routed networks limit the maximum distance, a signal can travel in the optical domain, without significant distortion. Therefore, signal regeneration is required at some intermediate nodes for long-haul lightpaths. In translucent WDM networks, sparsely located regenerators at certain nodes can be used to offset the impact of physical layer impairments. The routing and wavelength assignment (RWA) techniques in such translucent networks need to take into consideration the availability of regenerators and the maximum optical reach of the transparent lightpaths (without any regeneration). Although there has been significant research interest in RWA algorithms for translucent networks, much of the research has focused on dynamic RWA techniques. Only a handful of recent papers have considered the static (offline) case, and they typically propose heuristic algorithms to solve this complex design problem for practical networks. In this paper, we propose a generalized integer linear program (ILP) based formulation for static regenerator assignment and RWA in translucent WDM optical networks, with sparse regenerator placement. To the best of our knowledge, such a formulation that optimally allocates resources for a set of lightpaths for translucent networks, given the physical network, the locations of the regenerators, and the maximum optical reach has not been considered before. The proposed formulation is important for two reasons. First, it can serve as a benchmark for evaluating different heuristic approaches that may be developedin the future. Second, we show that using a novel node representation technique, it is possible to drastically reduce the number of integer variables. This means that unlike existing ILP formulations, our approach can actually be used to generate optimal solutions for practical networks, with hundreds of lightpath demands.     

Securing Wireless Sensor Networks Against Denial‐of‐Sleep Attacks Using RSA Cryptography Algorithm and Interlock Protocol

Wireless sensor networks (WSNs) have been vastly employed in the collection and transmission of data via wireless networks. This type of network is nowadays used in many applications for surveillance activities in various environments due to its low cost and easy communications. In these networks, the sensors use a limited power source which after its depletion, since it is non‐renewable, network lifetime ends. Due to the weaknesses in sensor nodes, they are vulnerable to many threats. One notable attack threating WSN is Denial of Sleep (DoS). DoS attacks denotes the loss of energy in these sensors by keeping the nodes from going into sleep and energy‐saving mode. In this paper, the Abnormal Sensor Detection Accuracy (ASDA‐RSA) method is utilized to counteract DoS attacks to reducing the amount of energy consumed. The ASDA‐RSA schema in this paper consists of two phases to enhancement security in the WSNs. In the first phase, a clustering approach based on energy and distance is used to select the proper cluster head and in the second phase, the RSA cryptography algorithm and interlock protocol are used here along with an authentication method, to prevent DoS attacks. Moreover, ASDA‐RSA method is evaluated here via extensive simulations carried out in NS‐2. The simulation results indicate that the WSN network performance metrics are improved in terms of average throughput, Packet Delivery Ratio (PDR), network lifetime, detection ratio, and average residual energy.