Poly(ethylene glycol)/poly(methyl methacrylate) blends as novel form‐stable phase‐change materials for thermal energy storage

In this study, we focused on the preparation and characterization of poly(ethylene glycol) (PEG)/poly(methyl methacrylate) (PMMA) blends as novel form‐stable phase‐change materials (PCMs) for latent‐heat thermal energy storage (LHTES) applications. In the blends, PEG acted as a PCM when PMMA was operated as supporting material. We subjected the prepared blends at different mass fractions of PEG (50, 60, 70, 80, and 90% w/w) to leakage tests by heating the blends over the melting temperature of the PCM to determine the maximum encapsulation ratio without leakage. The prepared 70/30 w/w % PEG/PMMA blend as a form‐stable PCM was characterized with optical microscopy and Fourier transform infrared spectroscopy. The thermal properties of the form‐stable PCM were measured with differential scanning calorimetry (DSC). DSC analysis indicated that the form‐stable PEG/PMMA blend melted at 58.07°C and crystallized at 39.28°C and that it had latent heats of 121.24 and 108.36 J/g for melting and crystallization, respectively. These thermal properties give the PCMs potential LHTES purposes, such as for solar space heating and ventilating applications in buildings. Accelerated thermal cycling tests also showed that the form‐stable PEG/PMMA blend as PCMs had good thermal reliability and chemical stability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The Production and Characterization of Ytterbium‐Stabilized Zirconia Films for SOFC Applications

(ZrO₂)_1–x(Yb₂O₃)_x binary systems were investigated in the doping range of 0.02 ≤ x ≤ 0.12. Ytterbium‐doped zirconia powders were synthesized using the Pechini method. X‐ray diffraction (XRD) measurements showed that fcc ZrO₂ was stabilized for 8–12 mol% Yb‐doping rate. The produced Yb‐stabilized Zr (YbSZ) films were characterized; their thickness and homogeneity properties depended on the nature of the YbSZ slurry. All coating parameters were optimized and determined with precoating treatments. The samples were characterized by differential thermal analysis/thermal gravimetry (DTA/TG), scanning electron microscopy (SEM) and ac impedance measurements.     

Analytical modelling and simulation of small scale,typical and highly available Beowulf clusters with breakdowns and repairs

Beowulf clusters are very popular because of the high computational power they can provide at reasonably low costs. However, the most pressing issues of today’s cluster solutions are the need for high availability and performance. Cluster systems are clearly prone to failures. Even if cover is provided with some probability c, there would be reconfiguration and/or rebooting delays to resume the operation following a failure. In this paper, the performability modelling of both typical and highly available Beowulf multiprocessor systems is presented. The models developed provide a large degree of flexibility to evaluate the performability of typical and highly available Beowulf cluster systems.     

Measurement of efffective atomic numbers of holmium doped and undoped layered semiconductors via transmission method around the absorption edge

Effective atomic numbers were measured for InSe and InSe having different Holmium concentrations measured in the energy region 15.746–40.930 keV using a Si(Li) detector. InSe:Holmium(0.0025), InSe:Holmium(0.0050), InSe:Holmium(0.025) InSe:Holmium(0.05) and InSe crystals have been grown by the Bridgman–Stocbarger method. The measured values were compared with the theoretical ones obtained using WinXCom being a Windows version of XCOM on the basis of mixture rule. The objective of this work is to show that there is a relation between effective atomic numbers and doped Ho fractions to InSe.     

Influence of hydroxypropyl beta-cyclodextrin on the corneal permeation of pilocarpine

The influence of hydroxypropyl β-cyclodextrin (HPβCD) on the corneal permeation of pilocarpine nitrate was investigated by an in vitro permeability study using isolated rabbit cornea. Pupillary-response pattern to pilocarpine nitrate with and without HPβCD was examined in rabbit eye. Corneal permeation of pilocarpine nitrate was found to be four times higher after adding HPβCD into the formulation. The reduction of pupil diameter (miosis) by pilocarpine nitrate was significantly increased as a result of HPβCD addition into the simple aqueous solution of the active substance. The highest miotic response was obtained with the formulation prepared in a vehicle of Carbopol® 940. It is suggested that ocular bioavailability of pilocarpine nitrate could be improved by the addition of HPβCD.     

Block polymers from poly(ethylene oxide) and styrene

Block copolymers containing poly(ethylene oxide) and polystyrene segments were synthesised via chemical reactions. A step-wise procedure was first employed to prepare peroxycarbamates which were later used to initiate free radical polymerization of styrene at elevated temperatures. In some runs the polymerization temperature and time were programmed. Styrene contents, molecular weights, elastic modulus—temperature relationships, impact strengths and stress—strain behaviour of the copolymers were determined.     

The behavior of organic components in copper recovery from electroless plating bath effluents using 3D electrode systems

An electrochemical method was applied for the recovery of copper both from the spent solutions and from the rinse waters of electroless copper plating baths, containing copper sulfate, formaldehyde, quadrol, and NaOH. Experiments were conducted in a rotating packed cell (Rollschichtzelle) to investigate the effects of current density, electrolyte composition, temperature, and pH on the copper recovery. All the copper (final CCu=0.1 ppm) was recovered from the waste and rinse waters of chemical copper plating plants with 70% current efficiency by the electrochemical treatment in a rotating packed cell at 130 A/m2 current density, room temperature, with 5mm diameter cathode granules, with the presence of formaldehyde, and with a specific energy consumption of 3.2-3.5 kW h/kg Cu. On the other hand, final copper concentrations of 5 ppm were reached with 62% current efficiency and 5.5-5.8 kW h/kg Cu specific energy consumption, with electrolytes containing no formaldehyde.     

Influence of different outdoor design conditions on design cooling load and design capacities of air conditioning equipments

Outdoor design conditions are important parameters for energy efficiency of buildings. The result of incorrect selection of outdoor design conditions can be dramatic in view of comfort and energy consumption. In this study, the influence of different outdoor design conditions on air conditioning systems is investigated. For this purpose, cooling loads and capacities of air conditioning equipments for a sample building located in Adana, Turkey are calculated using different outdoor design conditions recommended by ASHRAE, the current design data used in Turkey and the daily maximum dry and wet bulb temperatures of July 21st, which is generally accepted as the design day. The cooling coil capacities obtained from the different outdoor design conditions considered in this study are compared with each other. The cost analysis of air conditioning systems is also performed. It is seen that the selection of outdoor design conditions is a very critical step in calculation of the building cooling loads and design capacities of air conditioning equipments.