A study of the local site effects on the ground response for the city of Eskişehir,Turkey

Bulletin of Engineering Geology and the Environment - Local soil characteristics play a key role in determining soil-structure interaction and reliability of the superstructure behavior under...     

Swenson's operation for neonatal Hirschsprung's disease

OBJECTIVE: To describe our experience with Swenson's operation for Hirschsprung's disease done during the neonatal period. DESIGN: Retrospective study. SETTING: University department of paediatric surgery. SUBJECTS: 10 Neonates with Hirschsprung's disease. INTERVENTIONS: Rectosigmoidectomy and pull through (Swenson's operation), with covering transverse colostomy. MAIN OUTCOME MEASURES: Mortality, morbidity, and continence. RESULTS: The median age at definitive operation was 25 days (range 15-35). There was one late death three weeks after discharge from hospital of respiratory and cardiac failure. Two patients presented with caecal perforation and two with intestinal obstruction; in all four Hirschsprung's disease was diagnosed on frozen section, a transverse colostomy was done, and the Swenson's operation was done electively. The other six were diagnosed by barium enema examination and biopsy, and underwent total bowel irrigation followed by Swenson's operation and transverse colostomy. The colostomies were closed three to four weeks later. There were no postoperative complications. All nine surviving patients were continent (3-4 stools/day), at a mean (SD) follow up of 21 (5) months. CONCLUSION: With the current high standards of anaesthesia and neonatal intensive care, and an experienced surgeon, Swenson's operation for neonatal Hirschsprung's disease is safe and the procedure of choice for this condition.     

Trans FA and solid fat contents of margarines marketed in Turkey

Trans FA (TFA), solid fat contents (SFC), and slip melting points of 12 different tub and stick margarines marketed in Turkey were examined in this study. No trans isomers were found in four margarines, which suggests they were formulated from interesterified or blended fats and oils. The products with no TFA generally had more short-chain saturated FA, which suggests coconut oil-based oil components. TFA content of the other 10 products varied from 7.7 to 37.8%. Compared to the products formulated in North America, Turkish margarines contain more TFA and have higher SFC.     

An investigation on wear behavior of UHMWPE/carbide composites at elevated temperatures

Ultra-high molecular weight polyethylene (UHMWPE) is extensively used in frictional applications due to its advanced wear resistance. This advanced polymer is reinforced with hard particulate fillers for further developments against wear conditions. Since elevated temperatures prevail in the service conditions, wear behavior of UHMWPE composites is an important issue for the engineering applications. In the present work, UHMWPE-based composites including silicon carbide (SiC) fillers were fabricated in a compression molding chamber. In the specimen preparation stage, molding pressure, filler amount, and filler particle size were varied to investigate the influence of these variables. Upon deciding the optimum parameters from the wear tests conducted at room temperature, the wear experiments were repeated for the optimum specimen at elevated temperatures, such as 40 and 60°C. According to the results, the wear behavior of the SiC/UHMWPE composites is heavily changed by the effect of elevated temperature. Adhesive effect is pronounced at elevated temperatures while the wear characteristics possess the abrasive effect in the sliding path. In addition, the composites exhibit an accelerated material loss as temperature increases during the frictional system.     

Optimization of clamped circular piezoelectric composite actuators

This paper addresses the design of clamped circular piezoceramic composite unimorph and bimorph configurations, specifically the conflicting requirements of maximum volume displacement for a prescribed bandwidth. An optimization problem is formulated that implements analytical solutions for unimorph and bimorph configurations using laminated plate theory, including the use of oppositely polarized piezoceramic patches. A range of actuator geometric parameters are studied, and bounds for volume displacement and natural frequency of optimal designs are determined and presented via design curves. In the selected design space, Pareto optimization results for unimorph and bimorph configurations show that optimal volume displacement is related to the bandwidth by a universal power law such that the product of the square of the natural frequency and the displaced volume, a “gain-bandwidth” product, is a constant. Characteristic trends are also described that are independent of the actuator radius for the Pareto optimal piezoceramic patch thickness and radius versus normalized bandwidth. The results are relevant, for example, in the design of zero-net mass-flux or synthetic jet actuators used in flow control applications.     

An assessment of total RMR classification system using unified simulation model based on artificial neural networks

Engineering design has great importance in the cost and safety of engineering structures. Rock mass rating (RMR) system has become a reliable and widespread pre-design system for its ease of use and variety in engineering applications such as tunnels, foundations, and slopes. In RMR system, six parameters are employed in classifying a rock mass: uniaxial compressive strength of intact rock material (UCS), rock quality designation (RQD), spacing of discontinuities (SD), condition of discontinuities (CD), condition of groundwater (CG), and orientation of discontinuities (OD). The ratings of the first three parameters UCS, RQD, and SD are determined via graphic readings where the last three parameters CD, CG, and OD are estimated by the tables that are composed of interval valued linguistic expressions. Because of these linguistic expresions, the estimated rating values of the last three become fuzzy especially when the related conditions are close to border of any two classes. In such cases, these fuzzy situations could lead up incorrect rock class estimations. In this study, an empirical database based on the linguistic expressions for CD, CG, and OD is developed for training Artificial Neural Network (ANN) classifiers. The results obtained from graphical readings and ANN classifiers are unified in a simulation model (USM). The data obtained from five different tunnels, which were excavated for derivation purpose, are used to evaluate classification results of conventional method and proposed model. Finally, it is noted that more accurate and realistic ratings are reached by means of proposed model.     

Foresight analysis of wind power in Turkey

The Turkish wind energy industry is one of the most competitive and fastest growing industries in the energy sector. Industrial energy demands, Kyoto agreement and carbon trade are shown as probable causes. Currently, Turkey has a total installed capacity of about 48.5 GW for electricity from all energy sources. High energy prices and unstable suppliers have stimulated Turkey's growing interest in wind business and wind power. This paper analyzes Turkey's wind energy future perspective and power generation strategy with a view to explaining Delphi approach to wind energy development. In this study, the two‐round Delphi survey was conducted by experts to determine and measure the expectations of the sector representatives through online surveys where a total of 70 experts responded from 24 different locations. The majority of the Delphi survey respondents were from 23 different universities (60%), electricity generation industries (21%), two different governmental organizations (11%), nongovernmental organizations (6%) and other institutions (2%). The article discusses not only the expert sights on wind energy technology but also all bibliometrical approaches. The results showed that Turkey's wind power installed capacity is expected to exceed 40 GW by the end of the 2020 s and in the middle of the 2030 s, and Turkey would be the European leading country in the field of electricity generation from the wind. Copyright © 2011 John Wiley & Sons, Ltd.     

Microstructural features and electrical properties of copper oxide added potassium sodium niobate ceramics

In this study, effects of 0.5, 1.0 and 1.5 mole% CuO addition on the properties of potassium sodium niobate (K_0.5Na_0.5)NbO₃-KNN ceramics were investigated. Pure KNN and CuO-added KNN pellet samples were sintered at 1100 and 1090 °C for 4 h, respectively. Phase analysis showed that all samples crystallized in pure orthorhombic perovskite phase. Addition of 1.0 and 1.5 mole% CuO caused grain growth, densification and formation of a liquid phase at the grain boundaries. Curie temperature has shifted from 480 to 435 °C with increasing CuO ratio. The most remarkable characteristic of the hysteresis loops were the constricted nature of the 0.5 mole% CuO-added KNN's curve and the antiferroelectric-like appearance of the 1.5 mole% CuO-added KNN's curve. Piezeoelectric properties of d₃₃ = 120 pC/N, k_p = 0.27 and Q_m = 772 were obtained from the 1.5 mole% CuO-added KNN.     

Stabilized electrospinning of heat stimuli/in situ crosslinkable nanofibers and their self‐same nanocomposites

We present a strategy for stabilizing the morphological integrity of electrospun polymeric nanofibers by heat stimuli in situ crosslinking. Amorphous polymer nanofibers, such as polystyrene (PS) and its co‐polymers tend to lose their fiber morphology during processing at temperatures above their glass transition temperature (T_g) typically bound to happen in nanocomposite/structural composite applications. As an answer to this problem, incorporation of the crosslinking agents, phthalic anhydride (PA) and tributylamine (TBA), into the electrospinning polymer solution functionalized by glycidylmethacrylate (GMA) copolymerization, namely P(St‐co‐GMA), is demonstrated. Despite the presence of the crosslinker molecules, the electrospinning polymer solution is stable and its viscosity remains unaffected below 60 °C. Crosslinking reaction stands‐by and can be thermally stimulated during post‐processing of the electrospun P(St‐co‐GMA)/PA‐TBA fiber mat at intermediate temperatures (below the T_g). This strategy enables the preservation of the nanofiber morphology during subsequent high temperature processing. The crosslinking event leads to an increase in T_g of the base polymer by 30 °C depending on degree of crosslinking. Crosslinked nanofibers are able to maintain their nanofibrous morphology above the T_g and upon exposure to organic solvents. In situ crosslinking in epoxy matrix is also reported as an example of high temperature demanding application/processing. Finally, a self‐same fibrous nanocomposite is demonstrated by dual electrospinning of P(St‐co‐GMA) and stabilized P(St‐co‐GMA)/PA‐TBA, forming an intermingled nanofibrous mat, followed by a heating cycle. The product is a composite of crosslinked P(St‐co‐GMA)/PA‐TBA fibers fused by P(St‐co‐GMA) matrix. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44090.     

High-mobility pentacene phototransistor with nanostructured SiO2 gate dielectric synthesized by sol-gel method

We have fabricated a pentacene based phototransistor by employing a modified nanostructured SiO₂ gate dielectric. The photosensing properties of the pentacene thin film transistor fabricated on n-Si substrate with nanostructured SiO₂ as gate dielectric have been investigated. The photocurrent of the transistor increases with an increase in illumination intensity. This suggests that the pentacene thin film transistor behaves as a phototransistor with p-channel characteristics. The photosensitivity and responsivity values of the transistor are 630.4 and 0.10 A/W, respectively at the off state under AM 1.5 light illumination. The field effect mobility of the pentacene phototransistor was also found to be 2.96 cm²/Vs. The nanostructured surface of the gate possibly is the cause of the high-mobility value of the phototransistor due to light scattering from the increased surface area.