Studies on parametric sensitivity and safe operation criteria of batch processes

Heat accumulation in batch reactors may eventually lead to a temperature runaway. Critical values of process parameters were used to investigate process safety. Parameter sensitivity is discussed for a wide range of operating conditions. Two criteria for safe operation are presented, based on critical values of process parameters.     

A comparative study of important risk factors involved in offshore and domestic outsourcing of software development projects: A two-panel Delphi study

We investigated the risk factors of outsourced software development. Our first objective was to create empirically generated lists of risk factors for both domestically- and offshore-outsourced projects. Our second objective was to compare these two contexts: how do the risk factors change and which ones are most important in each. To address these objectives, we conducted two Delphi surveys to identify the important risk factors from a client perspective, in domestic and offshore settings. We qualitatively compared the results of the surveys to identify similarities and differences across their risk profiles. We identified three types of risks: those that appeared in both contexts; those that appeared in both but were exacerbated in the offshore context; and those that were unique to the offshore context. Our findings suggested that traditional project management risks were important in both contexts; however, the offshore context seemed to be more vulnerable to some traditional risks as well as factors that were unique to it.     

Decentralized optimality conditions of stochastic differential decision problems via Girsanov’s measure transformation

In this paper, we apply two methods to derive necessary and sufficient decentralized optimality conditions for stochastic differential decision problems with multiple Decision Makers (DMs), which aim at optimizing a common pay-off, based on the notions of decentralized global optimality and decentralized person-by-person (PbP) optimality. Method 1: We utilize the stochastic maximum principle to derive necessary and sufficient conditions which consist of forward and backward Stochastic Differential Equations (SDEs), and conditional variational Hamiltonians, conditioned on the information structures of the DMs. The sufficient conditions for decentralized PbP optimality are local conditions, closely related to the necessary conditions for decentralized PbP optimality. However, under certain convexity condition on the Hamiltonian, and a global version of the sufficient conditions for decentralized PbP optimality, we show decentralized global optimality. Method 2: We utilize the value processes of decentralized PbP optimal policies, we relate them to solutions of backward SDEs, we identify sufficient conditions for decentralized PbP optimality, and we show these are precisely those derived via the maximum principle. For both methods, as usual, we utilize Girsanov’s theorem to transform the initial decentralized stochastic optimal decision problems, to equivalent decentralized stochastic optimal decision problems on a reference probability space, in which the controlled process and the information processes which generate part of the information structures of the DMs, are independent of any of the decisions.     

Dextran-coated gold nanoparticles for the assessment of antimicrobial susceptibility

Bacteria rapidly evolve mechanisms to become resistant to antibiotics. Therefore, identifying an effective antibiotic or antibacterial agent and administering it at concentrations that will successfully prevent bacterial growth (antimicrobial susceptibility) is critical for health care decision making and vital for the battle against multi-drug-resistant bacteria. Currently, the determination of antimicrobial susceptibility requires at least 24 h. Herein, we describe a nanoparticle-based antimicrobial susceptibility assay based on the concanavalin A-induced clustering of dextran-coated gold nanoparticles, which sense the presence of available complex carbohydrates in bacterial suspension. Under conditions of bacterial growth inhibition, addition of concanavalin A results in the formation of extensive dextran gold nanoassemblies, which are facilitated by the presence of free carbohydrates in solution and result in large shifts in the surface plasmon band of the nanoparticles. Meanwhile, at conditions of increased bacterial growth, a decrease in the amount of free carbohydrates in solution will occur due to an increased carbohydrate uptake by the proliferating bacteria. This will result in a decrease in the size of the gold nanoparticle clusters and an increase in the number of nanoparticles that bind to bacterial surface carbohydrates, causing lower shifts in the plasmonic band. The gold nanoparticle-based assessment of antimicrobial susceptibility yields results within 3 h and can be used for the high-throughput screening of samples during epidemics and identification of potential antimicrobial agents to expedite clinical decision-making in point-of-care diagnostics.     

Performance Outages in CWDM Optical Networks due to the Polarization-Dependent Gain of Semiconductor Optical Amplifiers

This letter presents, for the first time, the derivation of analytical formulae for the probability density function and the cumulative density function (cdf) of the optical signal-to-noise ratio variation in optical local and metropolitan area networks employing coarse wavelength-division multiplexing due to the weak polarization-dependent gain (PDG) of cascaded semiconductor optical amplifiers (SOAs). The cdf is used to calculate the outage probability and to derive specifications for the maximum allowable value of PDG per SOA in order to achieve a given network size     

Metal ion sorption and desorption on zeolitized tuffs from the Nevada Test Site

Because of the hundreds of nuclear weapon tests conducted on the Nevada Test Site (NTS) during the Cold War, the migration of radionuclides and contaminants is a potential concern. The mobility of these compounds and our ability to remediate contaminated sites are controlled by sorption and desorption processes, which depend frequently on the nature of the contaminant, the mineralogy of the site, and the geochemical conditions. The sorption and desorption behavior of strontium (Sr) and lead (Pb), two metal cations with different chemistries, commonly found on nuclear test sites were studied. Strontium showed pH-independent and ionic-strength-dependent sorption, consistent with ion exchange processes at permanent charge sorption sites. The sorption uptake of Sr increased with decreasing ionic strength of background solution. Strontium desorption from the adsorbents was enhanced by increased background electrolyte concentration and was a function of background electrolyte composition. The fractional uptake of Pb was higher, compared to that of Sr, and was only pH dependent at the highest ionic strength used (1.0 M). This pH-dependent sorption behavior, consistent with formation of surface complexes at amphoteric surface hydroxyl sites or formation of surface precipitates, could explain the decreased Pb desorption, compared to that of Sr, especially at increased background electrolyte concentrations. Under conditions typical for the groundwater at the NTS (I = 0.003 M, pH = 8.0), both Pb and Sr are expected to bind strongly on tuffs with composition similar to the zeolitized tuffs used in this study. Any increase in the dissolved ion concentration of the groundwater, however, may result in, at least partial, release of Sr and enhanced Sr mobility.     

Equilibrium in multiphase polydisperse fuids

Based on the principle of Gibbs phase equilibrium, three different algorithms are developed for phase equilibrium calculations of polydisperse mixtures. These algorithms are based on (i) the equality of the chemical potentials of components in each phase, (ii) the minimization of the total Gibbs free energy of the system with respect to all the system variables, and (iii) the equilibrium ratios constraint between the phases. All three algorithms demonstrate applicability to mixtures with different mole fraction distribution functions and different equations of state. The results of calculations using the three phase algorithms are compared with the simulated multicomponent hydrocarbon mixture data, and the results are in good agreement.Nomenclature a, b Interaction parameter in the equation of state - CP Critical point - F(I) Density distribution function - f Fugacity - G Gibbs free energy - I Distributed variable - I ₀ Initial value of density distribution function - K(I) Equilibrium ratio of component I - P Pressure (atm) - R Gas constant - T Temperature (K) - v Molar volume - Z Compressibility factor - h Variance of density distribution function - Chemical potential - F _v Moles vapor per moles in system - Y Fugacity coefficient - i, j Component identifiers - f Feed stream - L Liquid phase - V Vapor phase