Isothermal crystallization kinetics and mechanical properties of polycaprolactone composites with zinc oxide,oleic acid,and glycerol monooleate

The isothermal crystallization and mechanical behavior of polycaprolactone (PCL) with zinc oxide (ZnO) with oleic acid and glycerol monooleate (GMO) were studied. Theoretical melting points calculated by the Flory–Huggins and Thompson–Gibbs models were thoroughly compared with differential scanning calorimetry experimental observations. The isothermal crystallization kinetic parameters by Avrami analysis showed that crystallization was controlled by nucleation, crystal growth was spherical, and the nucleation type changed between thermal and athermal nucleation. X‐ray diffraction showed that when the additives were used together both the crystal thickness and the degree of crystallinity increased. A multiple‐response regression analysis was made with the ZnO, oleic acid, and GMO concentrations as variables and the crystallinity as output. Interaction parameters by the Pukanzky model were calculated from the tensile strength at the yield point and indicated that the addition of oleic acid or GMO improved the interface between the ZnO particles and PCL. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1259‐1275, 2013     

Optimization of Single Flux Quantum Circuit Based Comparators Using PSO

In the recent years, a number of groups have shown that 1-bit comparators are suitable candidates for a number of circuits such as front-end of the low temperature detector readout circuits and analog to digital converters. Even though a number of tools exist for the development of digital logic gates, we are not aware of any optimizer for analog circuits that takes into account the stochastic effects in the Josephson junctions. Comparator circuits contain just a few parameters and have been analyzed extensively by a number of groups for over a decade. However, designing the comparator cells by hand is tedious work since it is based on the statistical analysis of the input–output relations of the cell. For the result to be reliable enough, statistically meaningful number of input SFQ pulses should be generated and corresponding output pulses should be analyzed. In addition, the design parameters should be suitable for fabrication and compatible for the rest of the cell library. In this work, we report an optimization tool to find the possible minimum gray-zone width, limited by the process design rules, for single flux quantum circuit based comparators. We used Particle Swarm Optimization (PSO) algorithm to determine the minimum possible gray zone width of a 1-bit comparator. To test the reliability of the PSO algorithm, we made a brute force sweep for a quasi-one-junction SQUID (QOS) with five parameters of the comparator, namely, three junction critical currents, one inductance value, and bias current. We find that the PSO gray zone results closely matches, even exceeds, the brute force design values and takes at least two orders of magnitude less computation time.     

Tribological Properties of TiO<Subscript>2</Subscript> Reinforced Nickel Based MMCs Produced by Pulse Electrodeposition Technique

Nickel–TiO₂ composite coatings were prepared under pulse current conditions by co-deposition of TiO₂ particles and nickel from a Watts type bath. The effect of TiO₂ particle concentration was studied on microhardness, friction coefficient and wear resistance. The morphological features and the structures were studied by scanning electron microscope, X-ray diffraction analysis and 3D profilometry facilities. A wide particle size range (between 95 and 140 nm) was chosen to provide a high dispersion and load bearing ability for the co-deposited layers. It was determined that increasing the particle concentration in the electrolyte dramatically increased the co-deposited TiO₂ particles in the coating. The results showed that the high concentration of TiO₂ particles in the electrolyte yielded the highest amount of particles co-deposited in the plating layer. The influence of the co-deposited TiO₂ volume on microstructure and tribological properties in the coating were investigated. The wear tests were carried out using a constant load by a reciprocating ball-on disk configuration. Wear loss and friction coefficients of Ni/TiO₂ composites were decreased by increasing TiO₂ content in the electrolyte because of the increasing content of TiO₂ in the deposited layer. The change in wear mechanisms by changing TiO₂ content was also determined.     

Characterization of the High‐Temperature Ferroelectric (100−x−y)BiScO3–(x)Bi(Zr0.5Zn0.5)O3–(y)PbTiO3 Perovskite Ternary Solid Solution

Ternary compositions based on Bi(B′B″)O₃–PbTiO₃‐type compounds have been investigated for high‐temperature piezoelectric applications. Compositions in the ternary were chosen to be near the binary morphotropic phase boundary (MPB) composition of BiScO₃–PbTiO₃ (BS–PT). Ternary compositions in (100?x?y)BiScO₃–(x)Bi(Zr_0.5Zn_0.5)O₃–(y)PbTiO₃ [(100?x?y)BS–xBZZ–yPT] have been investigated with x ≤ 7.5. For compositions with x > 10, the Curie temperature (T_C) decreased below 400°C. Dielectric, piezoelectric, and electromechanical properties were characterized as a function of temperature, frequency, and electric field. Small additions of BZZ were shown to increase the electromechanical properties with only a small loss in T_C. The electromechanical properties were temperature stable up to the depoling temperature. The most promising composition exhibited a T_C of 430°C, piezoelectric coefficient (d₃₃) of 520 pC/N, and a planar coupling factor (k_p) of 0.45 that remained unchanged up to depoling temperature at 385°C.     

RELATIONSHIP BETWEEN ORGANIC MATTER,SULPHUR AND PHOSPHATE CONTENTS IN UPPER CRETACEOUS MARINE CARBONATES (KARABOGAZ FORMATION,SE TURKEY): IMPLICATIONS FOR EARLY OIL GENERATION

In this paper, we discuss the relationship between the organic matter, sulphur and phosphate contents of Upper Cretaceous marine carbonates (Karabogaz Formation) in the Adiyaman Petroleum Province of SE Turkey. The results of organic geochemical analyses of core samples obtained from the Karabogaz Formation suggest that phosphate deposition occurred in settings where the water column was oxic to sub-oxic. However, the preservation of organic matter was favoured in anoxic environments. Moreover, the presence of sulphur (especially sulphur incorporated into kerogen) in organic matter-rich layers led to early oil generation. The results of stepwise py-gc analyses are consistent with a model in which, with increasing maturity, S-S and C-S bonds are the first to be eliminated from the macromolecular kerogen structure. Study of the maturity evolution of S-rich kerogen by laboratory pyrolysis implies that marginally mature and/or mature kerogen in the Karabogaz Formation, which may be classified as classic “Type II” kerogen, was most probably Type II/S at lower maturity stages. This enabled oil generation to occur at relatively shallow burial depths and relatively early stages of maturation. It is reasonable to conclude that Type II/S kerogen, overlooked in previous studies, was abundant in TOC-rich intervals in the Karabogaz Formation. Early generation (and expulsion) from Type II/S kerogen may have sourced the sulphur-rich oils in the Adiyaman area oilfields.     

Experimental studies on mechanical properties of cellular structures using Nomex® honeycomb cores

An experimental method is presented to obtain the effective in-plane compliance matrices of cellular structures using Nomex® honeycomb cores without a priori assumptions such as orthotropy. In this method, firstly, uni-axial tension tests are carried out for different material orientations. The independent variables in these experiments are the material orientation and displacement of the actuator, while the main dependent variables are positions of the marker points and the force acting on the specimens. Marker tracking technique is used to determine the marker positions which are processed to get strain of the measuring domain, while the stress is estimated through external loading and core geometry. The analysis is confined to the measuring domain under near homogeneous stress and strain fields. The experiment results are processed with transformation and least squares functions to obtain all effective in-plane elastic parameters, which are compared with analytical solution based on deformation of idealized cell structure. Through this comparison, the effects of geometrical parameters of cell structure are discussed in detail. By means of the introduced method, the problem of lack of experimental studies on the effective in-plane compliances of cellular structures in the literature is expected to be solved.     

A pre-feasibility case study on integrated resource planning including renewables

In recent years, economical and environmental constraints force governments and energy policy decision-makers to change the prominent characteristics of the electricity markets. Accordingly, depending on local conditions on the demand side, usage of integrated resource planning approaches in conjunction with renewable technologies has gained more importance. In this respect, an integrated resource planning option, which includes the design and optimization of grid-connected renewable energy plants, should be evaluated to facilitate a cost-effective and green solution to a sustainable future.     

Mesoporous nanocrystalline ZnO microspheres by ethylene glycol mediated thermal decomposition

Zinc oxide (ZnO) nanostructures with various morphologies have been fabricated in literature owing to their potential applications in various emerging fields. In this study, we report a facile, one-step gram-scale synthesis of nanocrystalline mesoporous ZnO microspheres by thermal decomposition of zinc acetate dihydrate in ethylene glycol at 250?°C for 12?h. The average size of the hollow microspheres is found to be 3.01?±?0.52?µm, which are formed by loosely bonded nanocrystallites with average sizes of 17?±?4?nm. We propose a formation mechanism for the mesoporous microspheres, Ostwald ripening of spherical-like nanocrystallites, on the basis of the results obtained by different synthesis durations. We also report the possibility of tuning the morphologies of the obtained ZnO by simply modifying the thermal decomposition solution, where porous ZnO nanoplates are obtained when a mixture of ethylene glycol and water is used and ZnO nanorods with aspect ratios of ～3 are synthesized by using diethylene glycol. ZnO nanowires with lengths up to several microns are fabricated when no solvent is used, i.e. thermal decomposition in air atmosphere. Microstructural and phase characterizations of the samples are conducted by using a field-emission gun scanning electron microscope and X-ray diffractometer. Performances of the obtained nanocrystalline mesoporous ZnO microspheres in photocatalytic degradation of Rhodamine B and as active anode materials in lithium-ion batteries are also presented.     

Analyzing the solutions of DEA through information visualization and data mining techniques: SmartDEA framework

Data envelopment analysis (DEA) has proven to be a useful tool for assessing efficiency or productivity of organizations, which is of vital practical importance in managerial decision making. DEA provides a significant amount of information from which analysts and managers derive insights and guidelines to promote their existing performances. Regarding to this fact, effective and methodologic analysis and interpretation of DEA results are very critical. The main objective of this study is then to develop a general decision support system (DSS) framework to analyze the results of basic DEA models. The paper formally shows how the results of DEA models should be structured so that these solutions can be examined and interpreted by analysts through information visualization and data mining techniques effectively. An innovative and convenient DEA solver, SmartDEA, is designed and developed in accordance with the proposed analysis framework. The developed software provides DEA results which are consistent with the framework and are ready-to-analyze with data mining tools, thanks to their specially designed table-based structures. The developed framework is tested and applied in a real world project for benchmarking the vendors of a leading Turkish automotive company. The results show the effectiveness and the efficacy of the proposed framework.     

Ferrofluid actuation with varying magnetic fields for micropumping applications

Magnetic nanoparticle suspensions and their manipulation are becoming an alternative research line. They have vital applications in the field of microfluidics such as microscale flow control in microfluidic circuits, actuation of fluids in microscale, and drug delivery mechanisms. In microscale, it is possible and beneficial to use magnetic fields as actuators of such ferrofluids, where these fluids could move along a dynamic gradient of magnetic field so that a micropump could be generated with this technique. Thus, magnetically actuated ferrofluids could have the potential to be used as an alternative micro pumping system. Magnetic actuation of nanofluids is becoming an emergent field that will open up new possibilities in various fields of engineering. Different families of devices actuating ferrofluids were designed and developed in this study to reveal this potential. A family of these devices actuates discrete plugs, whereas a second family of devices generates continuous flows in tubes of inner diameters ranging from 254?μm to 1.56?mm. The devices were first tested with minitubes to prove the effectiveness of the proposed actuation method. The setups were then adjusted to conduct experiments on microtubes. Promising results were obtained from the experiments. Flow rates up to 120 and 0.135?μl/s were achieved in minitubes and microtubes with modest maximum magnetic field magnitudes of 300?mT for discontinuous and continuous actuation, respectively. The proposed magnetic actuation method was proven to work as intended and is expected to be a strong alternative to the existing micropumping methods such as electromechanical, electrokinetic, and piezoelectric actuation. The results suggest that ferrofluids with magnetic nanoparticles merit more research efforts in micro pumping.