Enhanced control strategy of full-bridge modular multilevel converter

This paper describes a control approach that allows the cell capacitor voltages of the full-bridge modular multilevel converter (FB-MMC) to be controlled independent of the input dc link voltage. Moreover, this control approach offers the possibility of operating FB-MMC from bi-polar dc link voltages; thus, creating new possibilities for building generic hybrid dc grids with reversible dc link voltage, where the conventional line commutated current source converters can operate alongside voltage source converters. Furthermore, the presented control approach improves the dc fault ride-through of the FB-MMC compared to existing approaches. This could be achieved by an active control of the arm currents and cell capacitor voltages, and full exploitation of the FB-MMC redundant switch states. Operation of the FB-MMC with reversible DC link voltage and decoupled control of the cell capacitor voltages from the dc link voltage are demonstrated using simulations. The major findings and implications of this work are highlighted

SBML models and MathSBML

MathSBML is an open-source, freely-downloadable Mathematica package that facilitates working with Systems Biology Markup Language (SBML) models. SBML is a toolneutral,computer-readable format for representing models of biochemical reaction networks, applicable to metabolic networks, cell-signaling pathways, genomic regulatory networks, and other modeling problems in systems biology that is widely supported by the systems biology community. SBML is based on XML, a standard medium for representing and transporting data that is widely supported on the internet as well as in computational biology and bioinformatics. Because SBML is tool-independent, it enables model transportability, reuse, publication and survival. In addition to MathSBML, a number of other tools that support SBML model examination and manipulation are provided on the sbml.org website, including libSBML, a C/C++ library for reading SBML models; an SBML Toolbox for MatLab; file conversion programs; an SBML model validator and visualizer; and SBML specifications and schemas. MathSBML enables SBML file import to and export from Mathematica as well as providing an API for model manipulation and simulation

Millisecond accuracy video display using OpenGL under Linux

To measure people’s reaction times to the nearest millisecond, it is necessary to know exactly when a stimulus is displayed. This article describes how to display stimuli with millisecond accuracy on a normal CRT monitor, using a PC running Linux. A simple C program is presented to illustrate how this may be done within X Windows using the OpenGL rendering system. A test of this system is reported that demonstrates that stimuli may be consistently displayed with millisecond accuracy. An algorithm is presented that allows the exact time of stimulus presentation to be deduced, even if there are relatively large errors in measuring the display time

The Sensitivity of Auditory-Motor Representations to Subtle Changes in Auditory Feedback While Singing

Singing requires accurate control of the fundamental frequency (F0) of the voice. This study examined trained singers’ and untrained singers’ (nonsingers’) sensitivity to subtle manipulations in auditory feedback and the subsequent effect on the mapping between F0 feedback and vocal control. Participants produced the consonant-vowel /ta/ while receiving auditory feedback that was shifted up and down in frequency. Results showed that singers and nonsingers compensated to a similar degree when presented with frequency-altered feedback (FAF); however, singers’ F0 values were consistently closer to the intended pitch target. Moreover, singers initiated their compensatory responses when auditory feedback was shifted up or down 6 cents or more, compared to nonsingers who began compensating when feedback was shifted up 26 cents and down 22 cents. Additionally, examination of the first 50 ms of vocalization indicated that participants commenced subsequent vocal utterances, during FAF, near the F0 value on previous shift trials. Interestingly, nonsingers commenced F0 productions below the pitch target and increased their F0 until they matched the note. Thus, singers and nonsingers rely on an internal model to regulate voice F0, but singers’ models appear to be more sensitive in response to subtle discrepancies in auditory feedback

A PC parallel port button box provides millisecond response time accuracy under Linux

For psychologists, it is sometimes necessary to measure people's reaction times to the nearest millisecond. This article describes how to use the PC parallel port to receive signals from a button box to achieve millisecond response time accuracy. The workings of the parallel port, the corresponding port addresses, and a simple Linux program for controlling the port are described. A test of the speed and reliability of button box signal detection is reported. If the reader is moderately familiar with Linux, this article should provide sufficient instruction for him or her to build and test his or her own parallel port button box. This article also describes how the parallel port could be used to control an external apparatus

You Can't Get There From Here: Hubble Relaxation in the Local Volume

A beginning end-point for galaxy motions within the 10-Mpc Local Volume is constructed by requiring a smooth distribution of (luminous) mass at the time of recombination, which is shown to be equivalent to a smooth Hubble flow at early times. It is found, by this purely kinematical method, that present peculiar motions are too small by a factor of at least several (and largely in the wrong direction) to have produced the observed structures within the age of the universe. Known dynamical effects are inadequate to remove the discrepancy. This result is different in origin from previously known ``cold flow'' problems. The simple dynamical picture often used within the Local Volume (for instance, in deriving masses through calculation of a zero-velocity surface) is thus called into question. The most straightforward explanation (though not the only possible) is that there exists a large quantity of baryonic matter in this region so far undetected, and unassociated with galaxies or groups.Comment: 23 pages, accepted by the Astronomical Journa

New mobilities across the lifecourse: A framework for analysing demographically-linked drivers of migration

Date of acceptance: 17/02/2015Taking the life course as the central concern, the authors set out a conceptual framework and define some key research questions for a programme of research that explores how the linked lives of mobile people are situated in time–space within the economic, social, and cultural structures of contemporary society. Drawing on methodologically innovative techniques, these perspectives can offer new insights into the changing nature and meanings of migration across the life course.Publisher PDFPeer reviewe

THE HELIUM PURIFICATION SYSTEM FOR THE PROPOSED PEBBLE BED REACTOR EXPERIMENT

A helium coolant side-stream purification system consisting of parallel sections for radioactive and nonradioactive decontamination was designed for the proposed Pebble Bed Reactor Experiment. Primary equipment components are two gas coolers, gas heater, charcoal delay trap, CuO oxidizer, molecular sieve adsorber, and full flow filter. The charcoal delay trap is sized to provide a hold-up of 30 min for Kr isotopes. 6 hr hold-up for Xe isotopes, and 99.9% retention of iodine isotopes resulting in "decontamination factors" varying from 1 for Kr/sup 85/ to 556 for I/sup 131/. Nonradioactive decontamination will result in a steady state concentration of CO/sub 2/ in the coolant of 20.8 ppm or less. Total cost of the system excluding auxiliary equipment and containment is estimated to be .690. (auth

Process simulation and thermodynamic analysis of a micro turbine with post-combustion CO2 capture and exhaust gas recirculation

With the effects of the emissions from power plants causing global climate change, the trend towards lower emission systems such as natural gas power plant is increasing. In this paper a Turbec T100 micro gas turbine is studied. The system is assessed thermodynamically using a steady-state model; model results of its alteration with exhaust gas recirculation (EGR) are presented in this paper. The process simulation with EGR offers a useful assessment when integrated with post-combustion CO2 capture. The EGR model results in the enrichment of the CO2 which decrease the energy demand of the CO2 capture system

Patient perceptions of electronic medical records use and ratings of care quality

Purpose: Despite considerable potential for improving health care quality, adoption of new technologies, such as electronic medical records (EMRs), requires prudence, to ensure that such tools are designed, implemented, and used meaningfully to facilitate patient-centered communication and care processes, and better health outcomes. The association between patients’ perceptions of health care provider use of EMRs and health care quality ratings was assessed.\ud Method: Data from two iterations of the Health Information National Trends Survey, fielded in 2011 and 2012, were pooled for these analyses. The data were collected via mailed questionnaire, using a nationally representative listing of home addresses as the sampling frame (n=7,390). All data were weighted to provide representative estimates of quality of care ratings and physician use of EMR, in the adult US population. Descriptive statistics, t-tests, and multivariable linear regression analyses were conducted.\ud Results: EMR use was reported significantly more frequently by females, younger age groups, non-Hispanic whites, and those with higher education, higher incomes, health insurance, and a usual source of health care. Respondents who reported physician use of EMRs had significantly higher ratings of care quality (Beta=4.83, standard error [SE]=1.7, P<0.01), controlling for sociodemographic characteristics, usual source of health care, and health insurance status.\ud Conclusion: Nationally representative data suggest that patients’ perceptions of EMR use are associated with their perceptions of the quality of the health care they receive