Some aspects of the thermal stability of poly(alkyl itaconic acid esters)

The thermal stability of members of several series of polyitaconates has been assessed using thermogravimetric and thermal volatilisation techniques. From these data general degradation patterns have been established. The poly (di-n-alkyl itaconates) are stable up to 570K before chain breakdown occurs. The poly(mono-n-alkyl itaconates) are less stable and undergo a dehydration/de-esterification reaction at 430K which results in the formation of anhydride structures. This reaction can be suppressed by the formation of the salts. In the copolymers, salt formation also leads to increased stability but the range of copolymers studied was too restricted to draw general conclusions about their thermal behaviour.     

Linear Programming Analysis of a Water Supply System with Multiple Supply Points

An optimum water distribution system is designed using linear programming. The proposed algorithm, developed by applying an analogy of electrical network theory, discusses a distribution system with multiple supply points in comparison to an earlier paper by Gupta where the distribution system was restricted to only one source. The electrical network analogy is fully explained and a case example with two sources of supply is solved.     

Computational analysis of two-phase flow in horizontal bundles

Phase distribution during boiling flow in horizontal channels and fuel bundles tends to be asymmetric, particularly at low flows, due to gravity induced separation of the phases. Standard models and computational techniques developed for flow on vertical rod bundles cannot adequately simulate this tendency in horizontal flows, so more advanced techniques involving thermal and mechanical disequilibrium between phases are required.The paper describes the development and application of a drift flux code ASSERT (Advanced Solution of Subchannel Equations in Reactor Thermalhydraulics) which models departure from mechanical and thermal equilibrium between phases. Details of the model and computational technique are given, and parametric studies are shown to illustrate the capability of the code to simulate two-phase flow in horizontal bundles.Fundamental to the successful application of such a code are phenomenological studies aimed at the quantification of the empirical relationships selected for use. The paper concludes with a detailed study of mechanisms governing two-phase flow between neighbouring horizontal channels, isolating the driving effects of pressure gradient, gravity head and turbulent interchange by means of comparison with available experimental data.     

Heavy ion beam driven inertial confinement fusion target studies and reactor chamber neutronic analysis

A review of heavy ion beam driven target studies and reactor chamber neutronic analysis at the Institute for Neutron Physics and Reactor Technology of the Nuclear Research Center Karlsruhe is presented. Based on a single shell, multi-layered 4 mg deuterium-tritium (DT) target design, key issues of the inertial confinement fusion target behavior are discussed. These issues are: ion beam energy deposition within the target; equations of state for the different target materials under the extreme conditions encountered; numerical simulation of target compression, ignition and burn including possible instabilities; transport processes of photons, neutrons, gammas, and alphas; and reactor chamber neutronics including target spectra, blanket and first wall analysis. For most of these issues the present physics understanding is briefly reviewed, the available calculational tools are mentioned, and key problems, which need further research and development efforts, are identified. One important feature of this paper is a consistent treatment of the 4 mg DT target behavior and of the corresponding reactor chamber neutronic analysis.     

Deformation behavior of isotactic polypropylene crystallized via a mesophase

The mechanical behavior of semicrystalline isotactic polypropylene (iPP) of different crystallinity, crystal morphology and superstructure was investigated by standard tensile stress–strain analysis, dynamic-mechanical analysis, and in situ observation of the deformation by atomic force microscopy (AFM). Emphasis is put on the comparison of the mechanical characteristics of specimens containing either non-isometric lamellae, being arranged in spherulites, or nodular isometric domains, which are not organized in a superstructure. The formation of lamellae/spherulites and of nodules was controlled by the conditions of crystallization. The replacement of cross-hatched monoclinic lamellae and a spherulitic superstructure by randomly arranged isometric nodules leads to a distinct increase of the ductility and toughness, even if the crystallinity is identical. The modulus of elasticity and the yield stress increase as expected with increasing crystallinity. Slightly lower values of Young’s modulus and yield strength are detected if samples contained non-lamellar crystals in a non-spherulitic superstructure, proving an effect of the crystal shape on the deformation behavior. For the first time, tensile deformation of semicrystalline iPP which contains nodular ordered domains instead of lamellae has been followed by in situ AFM.     

Master–Slave Current-Sharing Control of a Parallel DC–DC Converter System Over an RF Communication Interface

Using analog wireless communication, we demonstrate a master-slave load-sharing control of a parallel dc-dc buck converter system, thereby eliminating the need for physical connection to distribute the control signal among the converter modules. The current reference for the slave modules is provided by the master module using radio-frequency (RF) transmission, thereby ensuring even sharing of the load current. The effect of delay due to RF transmission on system stability and performance is analyzed, and regions of operation for a stable as well as satisfactory performance are determined. We experimentally demonstrate a satisfactory performance of the master-slave converter at 20-kHz switching frequency under steady state as well as transient conditions in the presence of a transmission delay. The proposed control concept, which can potentially attain redundancy that is achievable using a droop method, may lead to more robust and reconfigurable control implementation of distributed converters and power systems. It may also be used as a (fault-tolerant) backup for wire-based control of parallel/distributed converters.     

Adaptive multichannel decision feedback equalization for volterra type nonlinear communication channels

A model-based approach for the decision feedback equalization of Volterra type nonlinear communication channels is proposed such that the linear model-based decision feedback equalization can be considered as a special case of the proposed approach. In designing the decision feedback equalizer, the nonlinear decision feedback equalization problem is visualized as a linear, multichannel equalization problem. A complete modified Gram–Schmidt orthogonalization of the input vector is achieved by using modified sequential processing multichannel lattice stages. The elements of the multichannel desired signal vector are then estimated from the new orthogonal set by using only scalar operations. The probability of error performance of the proposed equalizer is improved by the estimation of the elements of the desired signal vector through a sigmoid activation function so that a polynomial perceptron equalizer is realized. The comparative computational complexity calculations and performance results of the proposed decision feedback equalizer are also provided.     

Optimized structure and electrochemical properties of sulfonated carbon nanotubes/Co–Ni bimetallic layered hydroxide composites for high-performance supercapacitors

Technical development in electronic devices is frequently stifled by their insufficient capacity and cyclic stability of energy-storage devices. The nano-structured materials have sensational importance for providing novel and optimized combination to overcome exiting boundaries and provide efficient energy storage systems. Metal hydroxide materials with high capacity for pseudo-capacitance properties have grabbed special attention. Lately, the blend of nickel and cobalt hydroxides has been considered as a favorable class of metallic hydroxide materials owing to their comparatively high capacitance and exceptional redox reversibility. The sulfonated carbon nanotube fluid (SCNTF) was prepared by the ion exchange method to be utilized as the exceptional templates due to astonishing specific surface area, ensuring the maximum utilization of the active material. The CoNi-layered double hydroxides (LDHs)/SCNTF core-shell nanocomposite was prepared by the simple solvothermal method. Structural analysis showed that the composite material had the high conductance of carbon materials, the pseudo-capacitance characteristics of metal hydroxides, and porous structure, which facilitates the ion shuttle when the electrolyte reacts with the active material. Electrochemical analysis results showed that CoNi-LDHs/SCNTF had excellent rate performance, reversible charge-discharge properties and cycle stability. It exhibited an extreme specific capacity of 1190.5 F g^?1 at a current density of 1 A g^?1; whereas specific capacity remained 953.7 F g^?1 at the current density was 10 A g^?1. In addition, the capacity retention rate after 5000 charge-discharge cycles at a current density of 20 A g^?1 was 81.0%. The results indicated that the CoNi-LDHs/SCNTF core-shell nanocomposite material is cost efficient and an effective substitute in energy storage applications.     

Quality assurance and quality control of subgrade compaction using the dynamic cone penetrometer

The Dynamic Cone Penetrometer (DCP) is a device that is used in the construction industry for the assessment of in situ soil compaction quality. Over the past few decades, numerous correlations have been developed between the DCP test results and soil strength and stiffness parameters. This paper proposes a comprehensive set of criteria and recommendations for quality control (QC) of compacted subgrade that take into account the inherent statistical variability of DCP test results. For the development of the QC criteria, a new statistical methodology is used to extract representative test values from the raw field DCP test data. In order to use the proposed QC criteria, soils are first classified into two broad categories (fine-grained and coarse-grained) depending on their fabric and response to compaction efforts. Test results indicate that (i) for fine-grained soils, the DCP test values have good correlation with the plasticity index (PI), which is indicative of the type and amount of clay content of the soil and (ii) for coarse-grained soils, the DCP test values have good correlation with the optimum water content of the soil, which is directly related to its in situ density. DCP blow count correlation equations are presented for both soil categories. Recommendations for field DCP testing and data analysis are also provided to highlight the significance of the statistical distribution of the DCP test results in QC testing of compacted subgrade.