DC motor proportional control system for orthotic devices

Multi-channel proportional control system for operation of dc motors for use with externally-powered orthotic arm braces is described. Components of circuitry and principles of operation are described. Schematic diagram of control circuit is provided

Simulating Brownian suspensions with fluctuating hydrodynamics

Fluctuating hydrodynamics has been successfully combined with several computational methods to rapidly compute the correlated random velocities of Brownian particles. In the overdamped limit where both particle and fluid inertia are ignored, one must also account for a Brownian drift term in order to successfully update the particle positions. In this paper, we present an efficient computational method for the dynamic simulation of Brownian suspensions with fluctuating hydrodynamics that handles both computations and provides a similar approximation as Stokesian Dynamics for dilute and semidilute suspensions. This advancement relies on combining the fluctuating force-coupling method (FCM) with a new midpoint time-integration scheme we refer to as the drifter-corrector (DC). The DC resolves the drift term for fluctuating hydrodynamics-based methods at a minimal computational cost when constraints are imposed on the fluid flow to obtain the stresslet corrections to the particle hydrodynamic interactions. With the DC, this constraint need only be imposed once per time step, reducing the simulation cost to nearly that of a completely deterministic simulation. By performing a series of simulations, we show that the DC with fluctuating FCM is an effective and versatile approach as it reproduces both the equilibrium distribution and the evolution of particulate suspensions in periodic as well as bounded domains. In addition, we demonstrate that fluctuating FCM coupled with the DC provides an efficient and accurate method for large-scale dynamic simulation of colloidal dispersions and the study of processes such as colloidal gelation

Highly charged ions with E1, M1, and E2 transitions within laser range

Level crossings in the ground state of ions occur when the nuclear charge Z and ion charge Z_ion are varied along an isoelectronic sequence until the two outermost shells are nearly degenerate. We examine all available level crossings in the periodic table for both near neutral ions and highly charged ions (HCIs). Normal E1 transitions in HCIs are in X-ray range, however level crossings allow for optical electromagnetic transitions that could form the reference transition for high accuracy atomic clocks. Optical E1 (due to configuration mixing), M1 and E2 transitions are available in HCIs near level crossings. We present scaling laws for energies and amplitudes that allow us to make simple estimates of systematic effects of relevance to atomic clocks. HCI clocks could have some advantages over existing optical clocks because certain systematic effects are reduced, for example they can have much smaller thermal shifts. Other effects such as fine-structure and hyperfine splitting are much larger in HCIs, which can allow for richer spectra. HCIs are excellent candidates for probing variations in the fine-structure constant, alpha, in atomic systems as there are transitions with the highest sensitivity to alpha-variation

Integrating interaction through CMC for French as a second language in the Anglophone context in Cameroon: the Melff project at the University of Buea

English and French are both official languages of Cameroon. After independence, a series of events occurred that caused the Anglophone community, a minority, to consider that French was becoming the dominant language. Part of the elite continued to galvanize "Anglophone nationalism" (Dobegang, 2009). The University of Buea is situated in one of the two Anglophone regions. It is one of the few Universities where students and lecturers are obliged to work in English. In the framework of the promotion of bilingualism and national integration, English and French are taught in all state universities. It is within this context that Functional French, a level A2 (CEFR) course is offered at the University of Buea. The course is compulsory for the validation of Bachelor degrees in order to enable the students to communicate in a French-speaking environment, i.e. the majority of regions in Cameroon. These goals are never met because of many problems related to student attitudes and motivation, and the conditions in which the course is taught: time allocated to the course is limited (40 hours over two semesters), mixed-level groups, and large groups up to 80 students. With respect to the total number of students registered, many retake the course. Language competences almost exclusively focus upon reading and listening comprehension with little or no interaction. The Melff project aims to improve this situation by introducing blended learning using two online platforms: Moodle and VoiceForum (Fynn, 2010); a forum for posting text and audio with a space for teacher feedback. Melff coordinates the contents of face-to-face classes with weekly sessions in the computer resource centre (plus extra private home access). With this design we aim, while keeping constant the amount of mandatory teacher and students workloads, to offer students the first occasion for real interaction in the second language. Tests will be made in order to compare achievement in the former learning context and the new blended context. By increasing students' levels we expect to reduce the number of students who fail the course and, thus, reduce the number of years they have to wait before validating their Bachelor's. In turn, we hope to reduce the class sizes (because of exam success). We are now in the pilot phase which will finish in June 2012. This phase involves two classes - a sample of thirty students. In our communication, we will report on this pilot phase based on the oral and written forums and questionnaires concerning participation, motivation and learning benefit. Our challenge, similar to that of many other language teachers in developing countries, will be to introduce real oral and written communicative situations using CALL, despite time and resources being limited

Kinetics of chlorine depletion and microbial growth in household plumbing systems

To date, the microbial ecology of water treatment and distribution systems has never been systematically explored. Despite chronic problems with microbial growths in water distribution systems, the waterworks literature would indicate that the fundamentals, techniques and applications of microbial ecology are virtually unknown to the waterworks profession. Microbial ecology is the science that explores the relationships between microorganisms and their environment. A study of microbial ecology involves an assessment of the changes in the total and individual members of the microbial community. In distribution systems, the microbial ecology would be influenced by the influx of organisms, the surface colonization of distribution mains, the invasion of distribution systems by organisms from external sources, variations in flow, the chemical composition of the distributed water and the effective concentration of residual disinfectant. In addition, seasonal water temperature changes would be expected to affect total microbial populations. An assessment of microbial ecology requires the determination of, at least, four basic parameters.Project # G-1235-02 Agreement # 14-08-0001-G-1235-0

Development of new methodology for the assessment of water treatment plant performance with respect to the removal of cyst-sized particles

"This is the fourth in a four-part series of year-long studies conducted at the Capital City Water Treatment Plant, Jefferson City, Missouri, over the period of 1985 to 1989, to evaluate the effect of temperature on water treatment plant performance and to observe the subsequent changes in water quality during distribution."--IntroductionProject # G-1572-06 Agreement # 14-08-0001-G-157

Candidate molecular ions for an electron electric dipole moment experiment

This paper is a theoretical work in support of a newly proposed experiment (R. Stutz and E. Cornell, Bull. Am. Soc. Phys. 89, 76 2004) that promises greater sensitivity to measurements of the electron's electric dipole moment (EDM) based on the trapping of molecular ions. Such an experiment requires the choice of a suitable molecule that is both experimentally feasible and possesses an expectation of a reasonable EDM signal. We find that the molecular ions PtH+, HfH+, and HfF+ are suitable candidates in their low-lying triplet Delta states. In particular, we anticipate that the effective electric fields generated inside these molecules are approximately of 73 GV/cm, -17 GV/cm, and -18 GV/cm respectively. As a byproduct of this discussion, we also explain how to make estimates of the size of the effective electric field acting in a molecule, using commercially available, nonrelativistic molecular structure software.Comment: 25 pages, 3 figures, submitted to Physical Review

Seasonal effects on total bacterial removals in a rapid sand filtration plant

The present study is the first comprehensive study of the removal of total bacterial cells from a drinking water supply. Using the direct microscopic count to enumerate the total bacterial population present in raw, settled and filtered water, it was possible to determine bacterial removals by physical processes, such as coagulation, sedimentation and filtration. The 15-month longitudinal study was performed at the Capital City Water Company treatment plant serving Jefferson City, Missouri. The results confirmed earlier survey results indicating that bacterial cell removals by conventional water treatment processes are far lower than turbidity reductions would indicate. Moreover, bacterial removals are significantly impaired when water temperatures are low. Most bacterial removal is accomplished by pretreatment (coagulation and sedimentation). Filtration, as a single unit operation, was found to be ineffective in achieving significant bacterial removals throughout the entire study period. Based on the results, it is evident that the enumeration of the total bacterial population is the most fundamental and basic microbiological measurement that can be made to evaluate water treatment plant performance.Project # G-1027-04 Agreement # 14-08-0001-G-1027-0