Chemically grown, porous, nickel oxide thin-film for electrochemical supercapacitors

A porous nickel oxide film is successfully synthesized by means of a chemical bath deposition technique from an aqueous nickel nitrate solution. The formation of a rock salt NiO structure is confirmed with XRD measurements. The electrochemical supercapacitor properties of the nickel oxide film are examined using cyclic voltammetery (CV), galvanostatic and impedance measurements in two different electrolytes, namely, NaOH and KOH. A specific capacitance of ∼129.5 F g⁻¹ in the NaOH electrolyte and ∼69.8 F g⁻¹ in the KOH electrolyte is obtained from a cyclic voltammetery study. The electrochemical stability of the NiO electrode is observed for 1500 charge-discharge cycles. The capacitative behaviour of the NiO electrode is confirmed from electrochemical impedance measurements.     

Fuzzy algorithm for calculating roll speed variation based on roll separating force in hot rolling

Thickness control of hot-rolled strips has become an important issue in recent years because of the need for improving the quality of the hot-rolled strip. For this purpose, various thickness control systems such as finishing mill set-up (FSU), automatic gauge control (AGC), and looper control system, have been developed at steel works. Although these systems have greatly improved the quality of the strip thickness, there still exists a small amount of thickness deviation. It is difficult to adequately control by applying conventional thickness control techniques since hot rolling process is a highly nonlinear system in which many process parameters are coupled. In this study, a fuzzy algorithm to calculate the roll speed variations was developed in order to improve the thickness uniformity of hot-rolled strips. Since the strip thickness is mostly affected by the magnitude of roll separating force depending on the roll speed, the strip thickness deviation between the desired and actual thicknesses can be reduced by controlling roll speed. In order to carry out this investigation, slab analysis was carried out to determine the relation between roll separating force and roll speed for various process parameters such as roll speed, reduction ratio, strip entry thickness, and front and back tensions. From the production data, the effective stress-strain rate relations of the materials used in slab analyses were acquired. Based on the analytical results, the relation between roll separating force and roll speed was approximated by a log function. A fuzzy algorithm was developed to determine variations in roll speed according to variations of roll separating force, depending on various ranges of rolling temperature, reduction ratio, front and back tensions, and strip thickness. In addition, simulations to predict roll speed variations for a small amount of thickness deviation were carried out at continuous finishing mills consisting of seven stands and the calculated roll speed variations were found to be reasonable. Thus, the developed fuzzy algorithm might be useful in reducing the thickness deviation in the actual hot rolling mills.     

The impact of fluorinated MWCNT additives on the enhanced dynamic mechanical properties of e-beam-cured epoxy

Multi-walled carbon nanotubes were embedded into e-beam-cured epoxy resin to improve the mechanical properties of epoxy resin. The surfaces of these carbon nanotubes were modified using a fluorination treatment to improve their dispersion and adhesion in epoxy resin. The dynamic mechanical properties of epoxy/carbon nanotube composites were investigated at various heating rates and frequencies. As an effect of fluorination treatment, the semi-ionic bond of C–F on the surface of multi-walled carbon nanotubes played an important role in the improved dispersion and adhesion of carbon nanotubes into the epoxy resin. The storage modulus and loss modulus of the composites increased with higher applied frequency. The activation energy of the composites was increased by the effects of a higher heating rate due to the slow heat transfer in the epoxy/carbon nanotube composites. Eventually, the dynamic mechanical properties of the investigated epoxy were significantly improved by the carbon nanotubes dispersed therein via the fluorination treatment.     

New high-density intensified housing developments in Asia: qualities,potential and challenges

In the context of urban development intensification, public space often faces typological and programmatic contest and negotiations among the increasing number of diverse users, resulting in the emergence of new urban space typologies. This paper highlights the key considerations and trends in the development of new urban spaces in the context of high-density, high-intensity residential urban environments in Asia. It employs a comparative analysis of critical parameters and challenges of urban space design in three exemplary case studies from Singapore, Beijing and Tokyo, assessing their capacity to become models for quality-intensified housing development in future high-density environments.     

Fabrication of a graded-index polymer optical fiber preform without a cavity by inclusion of an additional monomer under a centrifugal force field

When two or more monomers with different densities and refractive indices are polymerized under a centrifugal force field, a radially varying refractive index is generated owing to the difference in density of the monomers. After the polymerization is completed, a cavity is generated about the rotational axis as a result of inherent volume shrinkage during bulk radical polymerization. Therefore it is necessary to feed an additional monomer into the cavity to compensate for the undesirable volume shrinkage. We have successfully fabricated a preform with graded indices for polymer optical fiber without a cavity by adding another monomer during rotation of the reactor. One can control the overall refractive-index profile by changing the rotation speed. Furthermore, the refractive-index profile can be predicted as a function of rotating speed by use of a simple mathematical model.     

Dynamic mechanical behavior of continuous multilayer composites

The dispersion processes in multilayer laminate composites of styrene acrylonitrile (SAN) and polycarbonate (PC) were studied utilizing the torsion pendulum. A third damping peak with a log decrement intensity of approximately one was observed at a temperature intermediate to the damping peaks corresponding to the T_g's of the two constituent phases. Variations of numerous material and experimental parameters such as composition ratio, orientation, thermal history, thermal cycling, number of layers, and layer thickness, as well as overall changes in the composition of the phases had no effect on the observance of a third peak. Only the disruption of the continuous layer structure effectively eliminated this novel transition. The origin of this transition was explained by assuming appropriate temperature dependencies for the controlling viscoelastic parameters in such a continuous layer composite.     

Effects of CdCl2 on the electrical properties of sintered CdS films

CdS films on glass substrates with various amounts of CdCl₂ have been prepared by coating and sintering, and their microstructure, electrical resistivity, carrier concentration and mobility have been investigated. The sintering rate is strongly increased near the melting temperature of CdCl₂ and the enhancement in the sintering is via a liquid-phase sintering mechanism. Doping of chlorine also occurs during the sintering and the solubility of chlorine in CdS is of the order of 10¹⁸ cm^–3 at 650° C. The electron concentration of the sintered CdS films which contained CdCl₂ before sintering increases with increasing grain size. The electron mobility increases sharply with increasing average grain size due to a sharp decrease in the total trap density, which is proportional to the total grain-boundary area.     

Engineering thermostability in serine protease inhibitors

Unlike most globular proteins, the native form of serine protease inhibitors (serpins) is strained. Previous studies of human alpha(1)-antitrypsin, a prototype plasma serpin, revealed that various unfavorable interactions, such as overpacking of side chains, buried polar groups and cavities, are the structural basis of the strain. The local strain could be relieved by various stabilizing single amino acid substitutions, which appeared to remove these unfavorable interactions. To improve the stability of other clinically important serpin members, here we examined whether the rules found in alpha(1)-antitrypsin studies are applicable to other serpins. Amino acid substitutions were introduced at various positions in human alpha(1)-antichymotrypsin and human antithrombin III that were equivalent to the sites of stabilizing substitutions of alpha(1)-antitrypsin. Two-thirds of the substitutions increased thermostability in all serpins tested. Mutational analysis and structural examination suggest that serpins are suboptimally folded using common structural strategies at many sites, even though some structural details can vary in individual members. The results suggest that schemes discovered with alpha(1)-antitrypsin, an easily manipulative serpin, are a useful basis for engineering conformational characteristics of other clinically important serpins.     

Compressible flow analysis of filling and postfilling in injection molding with phase-change effect

In order to predict the shrinkage, warpage and mechanical properties of the injection molded parts, it is necessary to know the history of the flow field during injection-molding processes. In the present investigation a numerical simulation program was developed to predict the flow field in filling and post-filling stages of injection molding. To simulate the real molding conditions more accurately, a generalized Hele-Shaw model for a non-Newtonian fluid was assumed considering the effects of phase change and compressibility of the resin. A finite-element-finite-difference (FEM-FDM) hybrid scheme with control volume approach was employed as the solving technique. For modeling the viscosity of the resin, a modified Cross model was used with a double-domain Tait equation of state being employed in describing the compressibility of the resin during molding. The energy balance equation, including latent-heat dissipation for semicrystalline materials, was solved in order to predict the solidified layer and temperature profile in detail. For verification of the numerical results obtained from the developed program, the simulation results were compared with the experimental results obtained from the test mold set designed in the current study using commercial-grade PP and the data available in the literature. Based on a comparison between experiments and simulations, it was found that the currently developed program was useful in unified simulations of filling and post-filling in injection-molding processes when considering the phase-change effect.