Simulation studies to improve design for midlife 275-kV cable refurbishment

Simulation studies to reduce the number of link positions on an existing 275-kV cable route due for refurbishment are presented. This reduction in the number of link positions will effectively reduce the overall cost of maintenance and will also improve reliability. It is shown that the proposed layout and bonding arrangement can produce sheath voltages of up to 200 V during load conditions, 3 kV during external faults, and 6.4 kV during internal faults. Transient sheath to ground voltages of up to 100 kVp during lightning and up to 95 kVp during faults can be experienced. These voltages will be acceptable in normal service. The capital efficiency of the refurbishment, which reduces the number of link positions, should also reduce the risks of subsequent failure and the cost of maintenance.     

Comparative studies on the solvent extraction of transition metal cations by calixarene, phenol and ester derivatives

The ionophore solvent extraction of various alkali metal and transition metal cations from the aqueous phase to the organic phase was carried out by using diazo-coupling calix[n]arenes [p-(4-phenylazophenylazo)calix[4]arene (L1) and p-phenylazocalix[6]arene (L2)], phenol derivatives [2,6-dimethyl-3-phenylazophenol (L3), 2-(5-bromo-2-pyridylazo)-5-diethylamino phenol (L4), 2-chloro-4-nitro(phenylazo)-5-sec-butyl-2-phenol (L5) and 2-chloro-4-nitro(phenylazo)-5-tert-butyl-2-phenol (L6)], and ester derivatives [quinoline-8-benzoate (L7), phenyl-1,4-dibenzoate (L8), p-tolyltiobenzoate (L9)]. It was found that, all the compounds (L1-L9) examined showed selectivity for transition metal cations such as Ag+, Hg+ Hg2+, and poor efficiency for alkali metal cations (Na+ and K+). The best extraction efficiency was obtained with L1 and L4.     

Optimization of Residual Stresses in the Surface Regions of Injection Moldings

The present study focused on the optimization of the injection molding process parameters to minimize thermal residual stresses in the surface regions of the polystyrene and high density polyethylene parts. Process parameters such as melt temperature, mold temperature and cooling time were considered as variables and their effects on residual stresses in surface regions of the parts were investigated by utilizing design of experiment (DOE), Taguchi and analysis of variance (ANOVA) methods. As a result, the most important parameters for residual stresses in surface regions of the PS and HDPE parts were found melt temperature and mold temperature, respectively.     

Assessment of target types and layouts in 3D laser scanning for registration accuracy

3D laser scanning technology is now widely and increasingly used in several construction tasks such as indoor mapping, project control, construction metrology and automation, development of as-built models, and resource management through scanning, data processing, and modeling stages. The accuracy of these stages affects the quality of the end product and can be improved by decreasing the errors caused by manual work processes. This paper focuses specifically on data acquisition errors caused by target setup, acquisition, and reorientation. The paper explores how different target types and target layouts affect registration accuracy. A total of twelve tests were conducted with phase-based and time-of-flight scanners in both exterior and interior scan scenes in order to assess registration errors and time inefficiencies associated with current scanning practices. The paper compares different target types (paper, paddle, and sphere) and presents the lessons learned to achieve optimal target layout design.     

A multiple-step slit die rheometer for rheological characterization of extruded starch melts

Extrusion cooking is a very important process in the field of cereal and snack manufacturing. The rheological properties of the starch based matrix strongly influence this process. A newly developed online rheometer was mounted on a twin screw extruder in order to measure these properties. It was possible to obtain viscosity of wheat flour and corn grits at typical extrusion cooking conditions over a shear rate range of three decades. Flow curves for varying screw speed and water content at a constant thermomechanical history of the starch were measured. Also the temperature dependence of the apparent viscosities could be determined showing activation energies in the range found for synthetic polymers. Furthermore, additional pressure drops that occur at step changes of the slit height were detected. Thus, it was possible to evaluate visco-elastic properties of extruded starch melts at different extrusion cooking conditions.     

Optimal and suboptimal receivers for code‐multiplexed transmitted‐reference ultra‐wideband systems

In this study, optimal and suboptimal receivers are investigated for code‐multiplexed transmitted‐reference (CM‐TR) ultra‐wideband systems. First, a single‐user scenario is considered, and a CM‐TR system is modeled as a generalized noncoherent pulse‐position modulated system. Based on that model, the optimal receiver that minimizes the bit error probability is derived. Then, it is shown that the conventional CM‐TR receiver converges to the optimal receiver under certain conditions and achieves close‐to‐optimal performance in practical cases. Next, multi‐user systems are considered, and the conventional receiver, blinking receiver, and chip discriminator are investigated. Also, the linear minimum mean‐squared error (MMSE) receiver is derived for the downlink of a multi‐user CM‐TR system. In addition, the maximum likelihood receiver is obtained as a performance benchmark. The practicality and the computational complexity of the receivers are discussed, and their performance is evaluated via simulations. The linear MMSE receiver is observed to provide the best trade‐off between performance and complexity/practicality. Copyright © 2011 John Wiley & Sons, Ltd.     

Power quality improvement with an extended custom power park

This paper describes the operation principles of an extended custom power park (CPP). The proposed park is more effective when it is compared to the conventional power parks regarding the yield of improving both current and voltage quality of linear and nonlinear loads using dynamic voltage restorer (DVR), active power filter (APF), static transfer switch (STS) and diesel generator (DG). Moreover, a supervisory power quality control centre is presented to coordinate these custom power (CP) devices by providing pre-specified quality of power. A fast sag/swell detection unit is also presented to improve the system response. The ability of the extended CPP for power quality improvements is further analyzed using PSCAD/EMTDC through a set of simulation tests.     

Impact of initial conditions on the initiation of ferroresonance

The impact of initial conditions on the initiation of ferroresonance is investigated. The investigation is carried out by simulating the behaviour of the model of a 275 kV electromagnetic voltage transformer circuit for a range of practical values of other system parameters. The initial conditions are varied within a practically possible range of initial values of transformer voltage and transformer flux linkage. Additionally, the initiation of ferroresonance is investigated by varying the values of phase angle of voltage source and values of shunt capacitance for the initial values that could appear in two basic cases of ferroresonance initiation.     

Optimum insulation thickness of the piping system with combined economic and environmental method

In the present study, an alternative method combining economic and environmental costs is suggested for the pipe insulation. This method is called as combined economic and environment method (CEEM). Bilecik, which is located in the Marmara region, Turkey, is chosen. Rockwool and glass wool are chosen as insulation materials. The optimum insulation thicknesses of three different methods including CEEM, economic, and environmental approaches are calculated and compared. Optimum points are 0.46 m (CEEM), 0.39 m (economic approach), and 0.54 m (environmental approach) for rockwool; and 0.46 m (CEEM), 0.40 m (economic approach), and 0.59 m (environmental approach) for glass wool. In addition, annual cost savings and energy savings are determined.