Static and quasielastic light-scattering measurements were utilized to investigate the shape, size, and polydispersity of mixed micelles composed of the nonionic surfactants dodecyl hexaoxyethylene glycol monoether (C12E6) and dodecyl octaoxyethylene glycol monoether (C12E8) in aqueous solutions. We determined the molecular weight and diffusion coefficient of these micelles and showed that they are rodlike. The average diffusion coefficient of the mixed micelles was measured at various total surfactant concentrations in the range between approximately 30 and 1000 times the critical micellar concentration of the surfactant mixture. Pure C12E6, pure C12E8, and three different mixtures of C12E6 and C12E8 were studied in the temperature range 10 °C ≤ T ≤ 55 °C. We found that the mixed micelles could be satisfactorally described as prolate ellipsoids with an average long axis which grows in size as the total surfactant concentration increases. The extent of this growth is more pronounced when the relative proportion of C12E6 in solution is increased or as the temperature approaches the boundary of phase transition into coexisting micelle-rich and micelle-poor phases. We propose a phenomenological model to quantitatively describe the linear growth of rodlike mixed micelles. Two parameters of this model which control the observed linear growth of the mixed C12E6 and C12E8 micelles were deduced from the experimental data and compared with the values predicted by a recently developed molecular−thermodynamic theory of mixed micellization.

Abstract-We discuss the challenge of managing the Multifunction Phased Array Radar (MPAR) timeline to satisfy the requirements of its multiple missions, with particular focus on weather surveillance. This command and control (C2) function partitions the available scan time amongst these missions, exploits opportunities to service multiple missions simultaneously and utilizes techniques for increasing scan rate where feasible. After reviewing candidate MPAR architectures and relevant previous research, we describe a specific C2 framework that is consistent with a demonstrated active array architecture using overlapped sub-arrays to realize multiple, concurrent receive beams. Analysis of recently articulated requirements for nearairport and national scale aircraft surveillance indicate that, with this architecture, 40-60% of the MPAR scan timeline would be available for the high-fidelity weather observations currently provided by the Weather Service Radar (WSR-88D) network. We show that appropriate use of sub-array generated concurrent receive beams, in concert with previously documented, complementary techniques to increase the weather scan rate, could enable MPAR to perform full weather volume scans at a rate of 1 per minute. Published observing system simulation experiments, human-in-the-loop studies and radar-data assimilation experiments indicate that 2 high-quality weather radar observations at this rate may significantly improve the lead time and reliability of severe weather warnings relative to current observation capabilities.

This article summarizes research and risk reduction that will inform acquisition decisions regarding NOAA’s future national operational weather radar network. A key alternative being evaluated is polarimetric phased-array radar (PAR). Research indicates PAR can plausibly achieve fast, adaptive volumetric scanning, with associated benefits for severe-weather warning performance. We assess these benefits using storm observations and analyses, observing system simulation experiments, and real radar-data assimilation studies. Changes in the number and/or locations of radars in the future network could improve coverage at low altitude. Analysis of benefits that might be so realized indicates the possibility for additional improvement in severe-weather and flash-flood warning performance, with associated reduction in casualties. Simulations are used to evaluate techniques for rapid volumetric scanning and assess data quality characteristics of PAR. Finally, we describe progress in developing methods to compensate for polarimetric variable estimate biases introduced by electronic beam-steering. A research-to-operations (R2O) strategy for the PAR alternative for the WSR-88D replacement network is presented.

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