On using degenerated solid shell elements in adaptive refinement analysis

Three different degenerated shell elements are studied in an adaptive refinement procedure for the solution of shell problems. The stress recovery procedure expressed in a convective patch co‐ordinate system is used for the construction of continuous smoothed stress fields for the a posteriori error estimation. The performance of the stress recovery procedure, the error estimator and the adaptive refinement strategy are tested by solving three benchmark shell problems. It is found that when adaptive refinement is used, the adverse effects of boundary layers and stress singularities are eliminated and all the elements tested are able to achieve their optimal convergence rates. It is also found that the accuracy of the shell elements increases with the number of polynomial terms included in the stress and strain approximations. In addition, if complete Lagrangian polynomial terms are used, the element will be less sensitive to shape distortion than the one in which only complete polynomial terms are employed. Copyright © 1999 John Wiley & Sons, Ltd.     

Timing constraint specification and analysis

Real‐time programmers have to deal with the problem of relating timing constraints associated with source code to sequences of machine instructions. This paper describes an environment to assist users in the specification and analysis of timing constraints. A timing analyzer predicts the best and worst case bounds for these constrained portions of code. A user interface for this timing analyzer was developed to depict whether these constraints were violated or met. A user is allowed to specify timing constraints within the source code of a C program. The user interface also provides three different methods for interactively selecting portions of programs. After each selection the corresponding bounded times, source code lines, and machine instructions are automatically displayed. Users are prevented from only selecting portions of the program for which timing bounds cannot be obtained. In addition, a technique is presented that allows the timing analysis to scale efficiently with complex functions and loops. The result is a user‐friendly environment that supports the user specification and analysis of timing constraints at a high (source code) level and retains the accuracy of low (machine code) level analysis. Copyright © 1999 John Wiley & Sons, Ltd.     

Application of factorial experimental design to demonstrate the influence of processing conditions on the fusion of poly(vinyl chloride)/chlorinated polyethylene/oxidized polyethylene blends

Poly(vinyl chloride) (PVC)/chlorinated polyethylene (CPE)/oxidized polyethylene (OPE) blends were prepared in a Haake torque rheometer at various temperatures, rotor speeds, and totalized torques. A 2³ factorial experimental design was applied to study the main two-factor interaction, and three-factor interaction effects of temperature, rotor speed, and totalized torque on the heat of fusion of PVC/CPE/OPE blends, which were examined using differential scanning calorimetry. The sequence of the main effects on the heat of fusion of PVC/CPE/OPE blends, in ascending order, is temperature < rotor speed < totalized torque. The sequence of the two-factor interaction effects on the heat of fusion of PVC/CPE/OPE blends, in ascending order, is temperature vs rotor speed < temperature vs totalized torque < rotor speed vs totalized torque. The three-factor interaction effect is not significantly related to the heat of fusion of PVC/CPE/OPE blends. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2755–2761, 1999     

Newtonian power curve and drop size distributions for vibromixers

Power input data are presented for a twin flat disk up-and-down moving (vibromixer) impeller operating in a small vessel with a range of Newtonian liquids. Vibromixer power number and Reynolds number are defined and are used to establish the Newtonian power curve for this type of mixer. Drop size distributions are presented for xylene-in-water dispersions under turbulent flow conditions in the vibromixer and are shown to vary with the maximum velocity of the disk (2πAf). The Sauter mean drop diameter of the distribution is related to the vibromixer Weber number, (We =ρ(2πAf)²D/σ), by an equation of the type d₃₂/D = C (We)^?3/5 with the coefficient C = 0.37.     

Investigation of the Burning Behavior of Cryogenic Solid Propellants

Cryogenic Solid Propellant (CSP)‐technology is a new approach to develop more powerful rocket motors. CSPs include the advantages of classical solid propellants to save weight as well as those of a high energy content and safety of modern liquid propellants. The charges consist of liquid and/or gaseous fuels and oxidizers, both frozen. Two main versions of CSP‐technology can be realised: 1. Mono‐CSPs show the burning behavior of solid propellants. Experiments with mono‐CSPs have been carried out under inert pressure conditions in a window bomb. Mono‐CSPs have a stable burning behavior with a constant regression rate which follows the Vieille's law under varying pressure conditions. 2. The advantage of high safety is obtained by assembling oxidizer and fuel in sandwich configurations. The grain geometry governs the burning behavior. Such systems can be externally controlled, e.g. by the heat from a gas generator or they can work self‐sustained. A Rod‐in‐Matrix burner shows self‐sustained combustion in an inert pressure atmosphere with overall burning rates in a similar range as solid rocket propellants which obey also a Vieille‐like pressure law. Disc stack burners have also been investigated, the combustion of which is strongly dependent on the disc thickness. For a short time Mach's nodes have been observed in the exhaust plume of a disc stack burner. Currently, the temperature ranges are limited to the boiling temperature of liquid nitrogen. Therefore, liquid oxidizers like H₂O₂ have been used. However, for the first time a propellant strand of polymer rods embedded in solid oxygen was prepared and burnt. The experiments with CSPs end in the combustion of a small rocket motor showing no serious technical obstacles. Simplified models based on the heat flow equation can simulate the burning characteristics of the frozen energetic materials including phase transitions.     

SOME THERMODYNAMIC PROPERTIES OF Pd-In ALLOYS

1.IntroductionPdalloysareausefulsubjectforrelatingthermodynamicpropertieswithelectronicandelasticquantitiesofthecomponents.ThethermodynamicfunctionsofanumberofinterstitialandsubstitutionalPdalloysexhibitanalogouscharacteristicsandmaybeinterpretedinthesamemanner-Twoeffectswerediscussedtoaccountforthenon-idealproperties.An"elastic"effectisassociatedwiththelatticedistortionbroughtaboutbythedissolvedparticles.Theenergyofelasticstrainfieldsoftwoseparatesoluteatomsischangediftheparticlesenteradjace…     

Synthesis and thermally stimulated current study of molecular relaxations of the grafted polymethylphenylsiloxane segment in thiodiphenol-modified epoxy resin

A series of grafted polymethylphenylsiloxane (PMPS) segments in thiodiphenyl-containing epoxy resin (ESTP) was prepared. The structure was evaluated by IR, ¹H-NMR, and ¹³C-NMR measurements. DSC measurements on the grafted ESTP epoxy resins showed a decreasing trend for T_g with increasing content of PMPS siloxane. The TSC measurements further confirmed this trend. This result suggests that the matrix of ESTP copolymer was less rigid with grafting of PMPS oligomer, due to the Si—O—C linkage at the opened glycidyl ether chain located approximately between the BPA and 4,4′-thiodiphenoxyl chains in the epoxy backbone. A new and broad sub-T_g transition appeared at −60°C in the TSC spectrum was observed for the cooperative motion of this siloxane moiety. All copolymers showed sub-T_g relaxations of γ- and δ-modes, observed at −100 and −130°C, respectively. These two relaxations may be attributed to the motions of BPA and the terminal groups in the epoxy matrix. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1523–1530, 1998     

Replacement of carcinogenic alkylating agent ethylene oxide in the synthesis of (Z)-3-dodecen-1-YL (E)-2-butenoate,sex pheromone of sweet-potato weevil,Cylas formicarius elegantulus (summers) andCylas formicarius formicarius (F.)

An alternative synthesis of (Z)-3-dodecen-1-y1 (E)-2-butenoate without use of carcinogenic ethylene oxide and HMPA is described. By coupling of the tetrahydropyranyl (THP) ether of 3-butyn-1-ol with 1-bromooctane with sodamide in liquid ammonia, 12-(2-tetrahydropyranyloxy)-9-dodecyne was obtained; subsequent hydrolysis and semihydrogenation afforded (Z)-3-dodecen-1-ol. The alcohol was then reacted with crotonyl chloride to give the desired crotonate with a total yield of 29.8%. Males of sweet-potato weevil,Cylas formicarius were strongly attracted to the synthetic sex pheromone. The attraction from the dispenser of polyethylene tube was better than the attraction from the dispenser of rubber septum in the field.     

Preparation of epoxy resin/silica hybrid composites for epoxy molding compounds

Phenolic novolac/silica and cresol novolac epoxy/silica hybrids were prepared through in situ sol‐gel reaction of tetraethoxysilane (TEOS). The formed hybrids were utilized as a curing agent and an epoxy resin in epoxy curing compositions, respectively. Via the two‐step preparation route, the resulting epoxy resin/silica hybrid nanocomposites exhibited good thermal stability, high glass transition temperatures, and low coefficients of thermal expansion. High condensation degree of the condensed silica was observed with a high content of siloxane bridges, p > 85%, measured by ²⁹Si NMR. The two‐step route also provides feasibility of preparation of epoxy resin/silica hybrid nanocomposites compatible with the current processes of manufacturing of epoxy molding compounds. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 4047–4053, 2003     

Current‐input OTRA Schmitt trigger with dual hysteresis modes

A simple current‐input Schmitt trigger is presented and implemented. It consists of one operational transresistance amplifier and a resistor. In addition, the circuit offers dual hysteresis mode operations within the same topology. The circuit operations are described. Experimental and simulation results are given to verify the theoretical analysis. Copyright © 2009 John Wiley & Sons, Ltd.