Corrosion and creep resistance of some dental amalgam alloys

Corrosion behaviour, creep values and phase transformation of conventional, admixed, unicompositional and two palladium-enriched amalgam alloys were investigated. Weight-loss method and solution analysis for dissolved metal ions were used. Creep values were determined after different immersion periods. X-ray diffraction was carried out to follow up phase transformation after different immersion periods and/or aging in dry air at 37 degrees up to one year. The results have shown that addition of palladium has improved corrosion and creep resistance and reduced gamma 1 to beta 1 phase transformation, and that gamma 2 did not appear again in high copper or palladium-enriched amalgam up to one year.     

Preparation and application of some new disperse anthraquinone dyes

(Hydroxymethyl)anthraquinones behave as primary alcohols and were used as alkylating agents for different aromatic compounds in the presence of Friedel-Crafts catalysts. The mechanism of the reaction was studied and the position of coupling was elucidated using the mass spectrometric technique. The resulting products are free from water-solubilising groups and were found to be valuable for dyeing synthetic fibres with different degrees of fastness properties.     

Magnetic fields and loop Voltages inside reduced- and full-scale structures produced by direct lightning strikes

This paper presents a numerical electromagnetic analysis of magnetic fields and loop voltages inside reduced- and full-scale lightning protection systems (LPSs) "structures" resulting from direct lightning strikes. The method of moments is employed to model the whole structure in three dimensions except the lightning channel. The lightning channel is simulated by the well-known transmission-line model (TL model), where the influence of the lightning-channel generated electric and magnetic fields are taken into account. Three distinct LPSs were modeled, namely, reduced-scale model with return conductors (RSRC), reduced-scale model with lightning channel (RSLC), and full-scale model with lightning channel (FS). The computed results of magnetic fields and magnetic-field derivatives were verified versus some experimental results for the RSRC model. In addition, the scale factor for all the measured quantities were also checked as functions of the geometrical scale factor for the positive and the negative first stroke currents. The lightning shielding performance with and without bonding was investigated for three distinct lightning stroke types, namely, the negative first, the negative subsequent, and the positive strokes. The voltages and currents generated in loops located inside the struck FS LPS were computed with and without bonding and grounding resistance and for different lightning current waveforms, locations and inclination of the lightning channel, and return stroke velocity.     

Finance-Based Scheduling: Tool to Maximize Project Profit Using Improved Genetic Algorithms

Contractor’s ability to procure cash to carry out construction operations represents a crucial factor to run profitable business. Bank overdrafts have always been the major source to finance construction projects. However, it is not uncommon that bankers set a limit on the credit allocated to an established overdraft. Bankers’ interest rates and consequently contractors’ financing costs are basically determined based on the allocated credit limits. Furthermore, project indirect costs are directly proportional to the project duration which is affected by the allocated credit limit. Thus, the credit limit affects project financing costs and indirect costs which in turn affect project profit. However, finance-based scheduling produces financially executable schedules at specified credit limits while maintaining the demand of time minimization. Thus, finance-based scheduling provides a tool to control the credit requirements. This control enables contractors to negotiate lower interest rates which reduce financing costs. Thus, finance-based scheduling enables contractors to reduce project indirect costs and financing costs. This paper utilizes genetic algorithm’s technique to devise finance-based schedules that maximize project profit through minimizing financing costs and indirect costs.     

Synthesis and studies of egyptian bagasse pith phenol formaldehyde cationic exchangers

The article is concerned with a simple method for preparing cationic resins from polycondensation of Egyptian bagasse pith (as a source of cheap and renewable material) with phenol and paraformaldehyde as a cross-linking agent. Optimum principal reaction conditions of the preparation and properties are determined and compared with resin without bagasse pith content. The Synthesized resins are stable in water, organic solvents, thermal treatment, and mineral acids (1M). The sample having a cation exchange capacity up to 3.92 meq g^?1 of dry resins are being introduced as new cationic exchangers. The synthesized resins are used in the study of the possible separation of univalent cations. The rational thermodynamic equilibrium constants (In K) are calculated for Li⁺ ?Na⁺ exchanges on the resins having a various amount of bagasse pith. The thermodynamic parameters are computed and suitable explanations are described. © 1994 John Wiley & Sons, Inc.     

Reliability of the jeddah seawater RO desalination plant based upon operations experience

Demand on commercial RO seawater desalination plants can be assured with increase in reliability and with high levels of performance. Such improvements can best be achieved through “lessons learned” from experience gained in available RO systems such as the large Jeddah RO plant.In this study, critical components which affect plant performance have been identified and methods of improving the design have been recommended. Failure data has been extracted from operation and maintenance reports.An assessment is made of the impact of failures and outages on the availability of the RO desalination plant. The single largest influence on the effective capacity of a water supply system based on RO desalination of seawater is found to be plant availability and maintainability. The design configuration of the plant is also found to have an impact on the acceptability of water supply system performance.     

High-voltage power cables plug into the future

The four dominant types of high-voltage transmission cable -paper insulated oil filled (OF), cross-linked polyethylene insulated, oil filled, gas insulated, and high-temperature superconducting - offer a variety of advantages, disadvantages, and potential for future development. So does an emerging technology, high-temperature superconducting cable. This article examines them all and assesses their position in the new world of high-voltage underground transmission.     

Shot-Peening Effect on High Cycling Fatigue of Al-Cu Alloy

The present work was aimed at evaluating the effects of shot-peening on the high cycle fatigue performance of the age-hardening aircraft alloy Al 2024 at different almen intensities. Shot-peening to full coverage (100 pct) was performed using spherically conditioned cut wire (SCCW 14) with an average shot size of 0.36 mm and at almen intensities of 0.1, 0.2, and 0.3 mmA. After applying the various mechanical surface treatments, the changes in the surface and near-surface layer properties such as microhardness, residual stress-depth profiles, and surface roughness were determined. The microhardness, surface roughness, and the residual stresses increased proportionally with the almen intensity. Electropolitically polished conditions were used as reference in the mechanically surface treated specimens. A significant improvement was seen in the fatigue performance of the 0.1 mmA.     

D-SUB: Decision Support System for Subcontracting Construction Works

Letting work to subcontractors is a very common practice in construction industry. Subcontractors help contractors overcome problems including the need of special expertise, shortage in resources, and limitation in finances. The decision to subcontract involves designating work items to be subcontracted and making assignments to subcontractors. Generally, work assignments to subcontractors can be for the total quantity of a work item or a proportion thereof. This paper presents a decision support system that makes assignments to subcontractors of the work items designated for subcontracting. Moreover, the system calculates and plots the overdraft profile based on the financial terms of the contract and project schedule. The ultimate goal of the system is to make work assignments to subcontractors under constraints economical and predict the expected profit at the end of the project. The system encompasses four basic components including project data, linear programming module, sensitivity analysis module, and financial analysis module. The sensitivity analysis adds strength and flexibility to the system by allowing the user to experiment with different scenarios. Finally, the developed system that represents a structured method for making subcontracting decisions is demonstrated through an illustrative example project.