Apparent activation volume for creep of copper and alpha brass at intermediate temperatures

Experimental measurements of the apparent activation volume for creep,V ^*, of Cu and Cu-30% Zn conducted at intermediate temperatures showed two types of strain dependencies. At the lower temperatures and higher stresses,V ^* decreased with increasing creep strain, ε, while at higher temperatures and lower stresses,V ^* was essentially independent of strain. The low temperature-high stress behaviour for Cu and Cu-30% Zn was found to be consistent with the dominance of a dislocation intersection mechanism. The high temperature-low stress data for the pure metals suggest that the rate-controlling process involves the nonconservative motion of jogs on screw dislocations. For the latter conditions, an additional contribution from solute drag-limited dislocation glide also appears to be important in governing the creep behaviour of the alloy.     

Studies on structural aspects of cellulose acetate

In the present investigation an attempt has been made to throw light on the structure of stiff chain amorphous polymers. For this purpose cellulose acetates (CA) having different degrees of substitution (DS) were prepared. The samples were characterised by IR-spectroscopy, Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). Scanning electron micrographs of the cryogenically fractured surfaces of these polymers showed that along with lamellar structures, nodular structures were also observable.     

A production demonstration of wafer-to-wafer plasma gate etchcontrol by adaptive real-time computation of the over-etch time from insitu process signals

An adaptive nonlinear controller for wafer-to-wafer plasma etch control is described. It uses real-time process signatures and historical data from a relational database for a computation of the over-etch time for the current wafer etching within the reactor. For an MOS gate etch the standard deviation of the oxide thickness between the gate and the source (or drain) is in the range of 10 Å. This is comparable to open-loop control or timed etch where the operator selects the ideal over-etch time. The controller has thus achieved a minimum of human equivalence and often performs better by 40%     

Delivering services by building and running virtual organisations

Customers in the future are likely to obtain their services from coalitions of service providers. These coalitions can be described as virtual organisations (VOs); they are groups of service providers that form relationships to service customers’ demands on an ad-hoc basis. For a VO to be effective, it must be reliable and scalable, and, realistically, it must be created and maintained in a dynamic, open and competitive environment. The CONOISE-G project has focused on resolving the technology challenges that emerged from these requirements. Specifically, CONOISE-G provides mechanisms to assure effective operation of VOs in the face of failure, unexpected events and changing requirements in a dynamic, open and competitive environment. In this paper, we describe the CONOISE-G system, motivated by a scenario based on mobile service provision, outline its use in the context of VO formation and perturbation, and review current efforts to progress the work to deal with unreliable information sources.     

THE SELF-HEATING AND IGNITION OF HOPS

Hops obtained from a brewery in Australia were examined for propensity to spontaneous combustion. The method used was basket heating and monitoring of the central temperature, so that supercritical behaviour could be clearly distinguished from subcritical. Frank Kamenetskii ignition theory was applied to the results and an extrapolation performed to gain insight into safe stockpiling heights.     

A theory for vortex shedding from the keels of marine vehicles

Summary This paper presents a discrete vortex-shedding method for predicting the damping forces experienced by a floating marine vehicle responding at and around roll resonance. The method utilizes a Schwartz-Christoffel transformation, the temporal flow development being calculated to yield vortex positions, pressures and overall forces on the vessel hull. The effect of the velocity term in Bernoulli's equation on hull forces is calculated by integrating pressure and confirmed using the Blasius formula. A functional form of the vortex-induced moment amplitude is deduced from the theory and applied to a frequency-domain equation of roll motion for the vessel. Comparison of theory with test data indicates that the vortex-shedding theory does predict the effects of this phenomenon on the roll motions of a specific hull shape. An extensive review of previous work in this area is also presented.     

Polymerization of methyl methacrylate in micellar phase: A kinetic study

Polymerization of methyl methacrylate (MMA) using Ce(IV) as initiator in aqueous nitric acid solution in the presence of sodium lauryl sulphate (NaLS) has been studied kinetically at a temperature range of 25–35°C. The rate of polymerization (R_p) increases with increasing concentration of NaLS, and it was also proportional to [MMA]²; but, in the presence of NaLS, the change of R_p with respect to [Ce(IV)] and [H⁺] were not linear and similarly the rate of Ce(IV) disappearance was not proportional to its original concentration. The overall activation energy of the polymerization process in presence of 0.01M NaLS was found to decrease by ～ 7.0 kcal mol^?1. The monomer–micelle association constant has been calculated to be 5.135 × 10⁴ mol^?1 L. The polymer obtained in surfactant medium is sparingly soluble in benzene and DMSO. From infrared spectra clear evidence of vinyl polymerization was obtained.     

Measurement of kinetic perfusion parameters of gadoteridol in intact myocardium: effects of ischemia/reperfusion and coronary vasodilation

Quantitation of myocardial perfusion is feasible using contrast enhanced magnetic resonance imaging. A method to quantitate myocardial blood flow is provided by the Kety model modified to account for a diffusable tracer such as gadoteridol. In the present study, perfusion parameters of the modified Kety model (partition coefficient and extraction efficiency) were determined for gadoteridol in intact myocardium using a constant flow, isolated, perfused heart model. Perfusion conditions included hearts with normal perfusion, hearts made globally ischemic for 20 min then perfused normally, and hearts whose coronary flow was more than doubled with 9 microM adenosine. T1 relaxation times were rapidly measured at 0.5 T following step increases in perfusate gadoteridol concentration and at steady state. Both the partition coefficient and extraction efficiency were found to be significantly increased in ischemic/reperfused hearts compared to normal. While flow rates in adenosine hearts were too high for accurate extraction efficiency determination using this technique, the partition coefficient was no different between adenosine and normally perfused hearts. The method described in this article allowed the kinetic parameters of the modified Kety model to be determined in intact heart using NMR relaxation time measurements as the basis of the calculation.