Pitting corrosion in pipeline steel weld zones

Steel pipelines externally exposed to seawater pit more severely in heat-affected weld zones but longer-term quantitative data are scarce. Maximum pit depths and variability are reported for the longitudinal weld in API X56 Spec 5 L grade steel pipeline samples exposed continuously to natural Pacific Ocean seawater for 3.5 years. For the first year maximum pit depths and pit depth variability for the different weld zones were very similar. Both became much greater subsequently, with the greatest increases for the heat affected zone. This is compared with steel composition and grain size and potential reasons for the observations discussed.     

Rapid prototyping system with sub-micrometer resolution for microfluidic applications

We report on a maskless lithography rapid prototyping system for fabrication of microfluidic circuits with sub-micrometer resolution in standard i-line photoresists. The micropatterning system uses the laser direct imaging technique with a focused ultraviolet laser beam and an acousto-optic deflector to steer the beam in two dimensions. The use of an acousto-optic deflector results in high patterning speeds due to absence of moving parts and achieves sub-micrometer beam positioning precision on the photoresist surface. Patterns up to 100 cm² with well defined edges and wall smoothness on the nanometer scale can be obtained. Direct illumination of the photoresist omits high-resolution masks and alignment with the photoresist sample, in turn making the lithography process more time- and cost-effective as well as flexible, with user control throughout the process. The system provides an efficient alternative to existing photolithography techniques and is especially suitable for rapid prototyping and laboratory use.     

Significant Nusselt number increase in microchannels with a segmented flow of two immiscible liquids: An experimental study

Increasingly smaller electronics requires improvement in performance of cooling systems to keep it operating reliably. We present herein a novel experimental study of convective heat transfer in serpentine microchannels with segmented liquid–liquid emulsions. It is demonstrated that this concept yields significant Nusselt number enhancement in microchannel heat sinks compared to that obtained using single phase liquid cooling. Laser Induced Fluorescence (LIF) is employed to measure temperature of the coolant with and without droplets, and micro-PIV is used to determine velocity field. For the segmented flow, up to four-fold increase of the Nusselt number was observed compared to pure water flow.     

Evaluating probability of default: Intelligent agents in managing a multi-model system

For the successful probability of default (PD) evaluation with the application of multiple prediction models two issues should be addressed: the accuracy of the analytic models which decreases over time and the evaluation of results which must be presented in a uniform shape. To deal with these two issues, a multi-agent system (MAS) and knowledge management systems (KMS) based process management system is proposed. The proposed system has two goals: to prevent the PD information quality deterioration by active management of analytical processes and to provide a universal access point allowing the simultaneous use of multiple prediction models.     

RhII-Catalyzed De-symmetrization of Ethane-1,2-dithiol and Propane-1,3-dithiol Yields Metallo-β-lactamase Inhibitors

Diversity-oriented synthesis (DOS) is a rich source for novel lead structures in Medicinal Chemistry. In this study, we present a DOS-compatible method for synthesis of compounds bearing a free thiol moiety. The procedure relies on Rh(II)-catalyzed coupling of dithiols to diazo building blocks. The synthetized library was probed against metallo-β-lactamases (MBLs) NDM-1 and VIM-1. Biochemical and biological evaluation led to identification of novel potent MBL inhibitors with antibiotic adjuvant activity.     

Synthesis,Structure and Magnetic Properties of Mn2Tb2 Tetranuclear Complex with p-tert-Butylthiacalix[4]arene

A new tert-buthylthiacalix[4]arene-based tetranuclear 3d-4f metal complex with the Mn₂Tb₂ core has been synthesized and its molecular and crystal structures have been studied by X-ray diffraction. The complex geometry is similar to that of the earlier synthesized tert-buthylthiacalix[4]arene-based M₂Ln₂ complexes with M=Mn(II), Co(II), and Ln=Gd, Pr, Eu, but unlike those systems, it exhibits intricated cooperative low-temperature magnetic properties arising from the presence of intercluster interactions. At T<8.5 K the complex shows weak spin-canted ferromagnetism and field induced metamagnetic phase transition. The paramagnetic behavior observed at temperatures higher than 8.5 K is similar to that previously reported for the Mn₂Gd₂ complex, this being indicative of the existence of competitive ferro- and antiferromagnetic intracluster interactions.     

Numerical calculation with experimental validation of pressure drop in a fixed-bed reactor filled with the porous elements

To study flow dynamics in a fixed-bed reactor, experiment and numerical simulation are used. In this work, the flow dynamics in a fixed-bed reactor filled with porous particles was simulated. For verification, experimental data were used. Porous particles were prepared from grains with sizes from 0.2 to 2.0 mm. Porous particles made by sintering grains in a muffle furnace. The study of pressure drop was performed in the velocity range up to 3 m/s. Numerical calculation was performed for a realistic computational domain obtained by RBD-algorithm (rigid body dynamics). It was found that if the pore size is less than 0.5 mm, then the flow through the porous medium of particles is minimal; if the pore size is larger than 0.5 mm, then there is a flow through the porous elements of the fixed-bed reactor. To take into account the porosity of the particles, γ correlation coefficient was proposed for the Ergun equation.     

Harmonic solutions of a mixed boundary problem arising in the modeling of macromolecular transport into vessel walls

The earliest events leading to atherosclerosis involve the transport of lpw density lipooprotein (LDL) cholesterol from the blood across endothelial cells that line the artery wall. Laplace’s equation describes the steady state diffusion profile of a tracer through the vessel wall. This gives rise to a boundary value problem with mixed Dirichlet and Robin conditions. We construct a linear system of integral equations that approximate the coefficients of the series expansion of the solution. We prove the existence of the solution to this problem analytically by using Gershgorin’s theorem on the location of the eigenvalues of the corresponding matrix. We give a uniqueness proof using Miranda’s theorem [C. Miranda, P.D.E. of Elliptic Type, Springer-Verlag, Berlin, 1970]. The analytical construction method forms the basis for a numerical calculation algorithm. We apply our results to the transport problem above, and use them to interpret experimental observations of the growth of localized tracer leakage spots with tracer circulation time.     

Input Disturbance Estimation For Linear Systems in The Bounded Noise Context

A method is presented for constructing input disturbance estimates for a linear system using noisy observations. The input disturbance of the dynamic system and the observation noise are assumed to be unknown but bounded. In addition, the structural characteristics of the input disturbance are given in the form of the maximum possible change of its magnitude per sampling time. The input disturbance represents a wide category of system uncertainties. A recursive procedure for obtaining disturbance set estimates is derived. The procedure is easy to implement and is a competitive technique comparative to the classical estimation schemes. Simulation results demonstrate the performance of the given techniques.