Colloidal silica removal in coagulation processes for wastewater reuse in a high-tech industrial park.

Four experiments of coagulation and flocculation were conducted to investigate the characteristics of colloidal silica removal in a high-tech industrial wastewater treatment plant for reclamation and reuse of the effluent. Experimental results illustrated that poly-aluminium chloride (PACl) showed higher performances on colloidal silica removal than alum. Interestingly, the two coagulants demonstrated the same capacity on silica removal. The specific silica removal capacity was approximately 0.135 mg SiO2/mg Al2O3 when the dosage of coagulants was in the range 30-150 mg/L Al2O3. In addition, the silica was reduced significantly at the condition of pH above 8. Experimental data implied that precipitation of aluminium flocs was the major mechanism for colloid silica removal in PACl and alum coagulation, besides, charge adsorption was also important for improving removal efficiency. Moreover, the addition of polyacrylic acid (PAA) as a flocculant could slightly advance silica removal in the PACl coagulation. The combined PACl/PAA/flocs coagulation was effective for the removal of colloidal silica, soluble COD, and turbidity and also suitable as a pretreatment unit in wastewater reclamation and reuse processes.     

Public grid computing participation: An exploratory study of determinants

Using the Internet, “public” computing grids can be assembled using “volunteered” PCs. To achieve this, volunteers download and install a software application capable of sensing periods of low local processor activity. During such times, this program on the local PC downloads and processes a subset of the project's data. At the completion of processing, the results are uploaded to the project and the cycle repeats.     

A systematic approach for product families formation in Reconfigurable Manufacturing Systems

The aim of this work is to establish a methodology for an effective working of Reconfigurable Manufacturing Systems (RMSs). These systems are the next step in manufacturing, allowing the production of any quantity of highly customised and complex products together with the benefits of mass production. In RMSs, products are grouped into families, each of which requires a system configuration. The system is configured to produce the first family of products. Once it is finished, the system is reconfigured in order to produce the second family, and so forth. Therefore, the effectiveness of a RMS depends on the formation of the best set of product families. Therefore, a methodology for grouping products into families, which takes into account the requirements of products in RMSs, is an issue of core importance. These requirements are modularity, commonality, compatibility, reusability, and product demand. The methodology starts by calculating, for each product requirement, a matrix that summarises the similarity between pairs of products. Then, through the use of the AHP methodology, a unique matrix that comprises the similarity values between products is obtained. The Average Linkage Clustering algorithm is applied to this matrix in order to obtain a dendogram that shows the diverse sets of product families that may be formed.     

Gigabit pulse position bistability in semiconductor lasers

The paper briefly reviews the major forms of optical bistability in active optical devices compatible for use in gigabit optical communication systems, and reports an entirely new optical bistability for the first time. Unlike previous devices, the two bistable states of the optical device are each a series of picosecond optical pulses at 1 GHz or greater repetition rates, and are distinguished by a half period temporal shift between their temporal positions in relation to a clock pulse. The bistable device is based on a gain switched semiconductor laser. Theoretical studies suggest 100-ps switching speeds might be achieved, and experimental results are reported indicating optically triggered switching times of 500 ps.     

A design model for surface-termination optimization of off-statesemiconductor devices

An optimization design model for surface termination of off-state semiconductor devices under reverse-bias conditions is presented. The multivariable design model is used to optimize the surface profile shapes for nonplanar devices and the doping profiles of material regions along the surface for planar devices. The effectiveness of the design model in reducing the peak surface electric field to below 50% of the bulk value is demonstrated for two examples of each type of device     

Geothermal reservoir simulation

This paper is intended to be a state of the art review of geothermal reservoir simulation. Its recent application to the modelling of real geothermal reservoirs is described and put in the context of an emerging general approach to reservoir modelling. The use of computer simulation for geothermal well test analysis is described. One of the main recent uses of reservoir simulators has been for conducting numerical experiments aimed at improving the understanding of geothermal reservoir physics. Such studies on fractured reservoirs, the thermal structure of reservoirs and the effects of non-condensable gases and dissolved salts are outlined.     

Investigation of the geothermal anomaly of Travale (Tuscany) by telluric, magnetotelluric and geomagnetic deep sounding measurements

As part of the European Community research programme telluric, magnetotelluric and geomagnetic deep sounding measurements were undertaken at 40 sites within the geothermal area of Travale. In the period range of 6–10,000 s the telluric field inside the Travale graben is strongly polarized and directed, independent of the period, about parallel to the graben strike. The lateral variation of the telluric field amplitude is determined mainly by the distribution of the rocks (e.g. the central part of the geothermal anomaly inside the graben is correlated with a horst structure of resistive rocks) and an influence of the geothermal anomaly on the telluric field distribution cannot be observed. The apparent resistivity, as well as the phase curves, are rather similar at all sites within the graben, exhibiting 4–40 ohm · m for periods of 10 s and 50–500 ohm · m for periods of 10,000 s in E-polarization. In the period range of 10–100 s the E- and B-polarization of magnetotelluric measurements can be interpreted by the 2-D effect of the Travale graben, while with increasing period the induced current system becomes more and more 3-D below all sites. This limits the determination of the sedimentary cover thickness (max. 2500 m) by 1-D and 2-D model calculations to periods of less than 100 s.     

WHIM, the Window Handler and Input Manager

This article describes WHIM, the Window Handler and Input Manager, a window management system being developed as part of the QuickSilver operating system project at IBM's Almaden Research Center. Another version of WHIM runs under AIX on the IBM PC RT. This article contrasts and compares the overlapped window scheme used in WHIM with the tiled window scheme used in other systems. The advantages of the window management scheme used in WHIM are detailed, and the effect of display interfaces on the window manager is described.     

Evaluation of NDT methods for detection of prestressing steel damage at post-tensioned concrete structures

For an assessment of the risk potential of existing structures, where in the case of prestressing steel damage the load-bearing capacity could be significantly affected, non-destructive testing techniques which enable reliable evaluation of the condition of the prestressing steels are of utmost importance. During the demolition of a post-tensioned concrete bridge in Berlin where damage of prestressing wires due to hydrogen-induced stress corrosion cracking were found in former investigations, parts of the girders of the bridge superstructure could be taken out. After non-destructive investigations by means of two testing techniques based on magnetic leakage flux measurement and one technique based on electromagnetic resonance measurement, subsequent removal of the concrete cover up to the ducts, opening the ducts and evaluation of the prestressing steels allowed a verification of the results obtained by the NDT methods. From the results it can be concluded that areas with fractures of several wires can be detected by the two techniques based on magnetic leakage flux measurement.