1,862 research outputs found

    The rotational velocity of the sdOB primary of the eclipsing binary system LB 3459 (AA Dor)

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    We present an analysis of the rotational velocity of the primary of LB 3459 based on 107 new high-resolution and high-S/N ESO VLT UVES spectra. 105 of them cover a complete orbital period (0.26 d) of this binary system. We have determined an orbital period of P = 22600.702 +/- 0.005 sec, a radial velocity amplitude of A_1 = 39.19 +/- 0.05 km/sec, and T_0 = 2451917.152690 +/- 0.000005. From simulations of the He II 4686A line profile (based on NLTE model atmosphere calculations), we derive v_rot = 47 +/- 5 km/sec. We present an animation which shows the orbital movement of the binary system, its synthetic lightcurve, and compares the phase-dependent variation of the predicted with the observed He II 4686A line profile. The radius of the cool component is almost the same size like Jupiter but its mass is about 70 times higher than Jupiter's mass. Thus, from its present mass (M_2 = 0.066 M_sun), the secondary of LB 3459 lies formally within the brown-dwarf mass range (0.013 - 0.08 M_sun). It might be a former planet which has survived the previous common-envelope phase and even has gained mass.Comment: 7 pages, 11 Postscript figures, to appear in A&

    Pole-placement Predictive Functional Control for over-damped systems with real poles

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    This paper gives new insight and design proposals for Predictive Functional Control (PFC) algorithms. Common practice and indeed a requirement of PFC is to select a coincidence horizon greater than one for high-order systems and for the link between the design parameters and the desired dynamic to be weak. Here the proposal is to use parallel first-order models to form an independent prediction model and show that with these it is possible both to use a coincidence horizon of one and moreover to obtain precisely the desired closed-loop dynamics. It is shown through analysis that the use of a coincidence horizon of one greatly simplifies coding, tuning, constraint handling and implementation. The paper derives the key results for high-order and non-minimum phase processes and also demonstrates the flexibility and potential industrial utility of the proposal

    Temperature dependence of the resistance of metallic nanowires (diameter ≥\geq 15 nm): Applicability of Bloch-Gr\"{u}neisen theorem

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    We have measured the resistances (and resistivities) of Ag and Cu nanowires of diameters ranging from 15nm to 200nm in the temperature range 4.2K-300K with the specific aim to assess the applicability of the Bloch-Gr\"{u}neisen formula for electron phonon resistivity in these nanowires. The wires were grown within polymeric templates by electrodeposition. We find that in all the samples the resistance reaches a residual value at T=4.2K and the temperature dependence of resistance can be fitted to the Bloch-Gr\"{u}neisen formula in the entire temperature range with a well defined transport Debye temperature (ΘR\Theta_{R}). The value of Debye temperature obtained from the fits lie within 8% of the bulk value for Ag wires of diameter 15nm while for Cu nanowires of the same diameter the Debye temperature is significantly lesser than the bulk value. The electron-phonon coupling constants (measured by αel−ph\alpha_{el-ph} or αR\alpha_{R}) in the nanowires were found to have the same value as that of the bulk. The resistivities of the wires were seen to increase as the wire diameter was decreased. This increase in the resistivity of the wires may be attributed to surface scattering of conduction electrons. The specularity p was estimated to be about 0.5. The observed results allow us to obtain the resistivities exactly from the resistance and gives us a method of obtaining the exact numbers of wires within the measured array (grown within the template).Comment: 9 pages, 10 figure

    Reflexivity in correctional research: Researcher perspectives on parenthood in a study with incarcerated parents

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    © The Author(s) 2018. As incarceration rates rise worldwide, increasing numbers of parents are separated from their children. Researchers have studied the psychosocial impact on inmates and their families extensively. However, few researchers have examined how their own perspectives affect the collection and interpretation of data, specifically about parenting in correctional settings. This paper consider methodological implications of conducting research with incarcerated mothers and fathers, employing critical reflexivity to explore researchers’ individual and collective experiences in a study in Australian correctional facilities. Using ourselves as informants, we examine how the context and life experiences of ‘researcher’ and ‘researched’ interact during interviews in a unique and emotionally charged environment. Correctional research requires careful adaptations to collect meaningful data from inmates and recognise their vulnerability as parents. The emotional content of interviews also has implications for analysing and interpreting research data. Our focus on interviewees as mothers and fathers, rather than as offenders, generated greater understanding of the needs of parents in custody. Recognising researchers’ feelings, experiences and perspectives on parenthood can enrich research with families affected by the criminal justice and child protection systems. These insights can also inform the understanding and practice of social workers, health practitioners, educators and students who work with marginalised parents and children

    A first course in feedback, dynamics and control: findings from an online pilot survey for the IFAC community

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    Undergraduate students in many engineering programs around the world take only one control course. The IFAC Educational Committee has developed and piloted to a limited audience a comprehensive survey for the topics to be included in such course. This issue is relevant to both academia and industry. The paper discusses the initial findings related to the design of the survey as well as the responses of the participants. The findings will be used to refine the survey and distribute it in the near future to the global control community

    The ResQu Index: A new instrument to appraise the quality of research on birth place

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    © 2017 Vedam et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Objective: Place of birth is a known determinant of health care outcomes, interventions and costs. Many studies have examined the maternal and perinatal outcomes when women plan to give birth in hospitals compared with births in birth centres or at home. However, these studies vary substantially in rigour; assessing their quality is challenging. Existing research appraisal tools do not always capture important elements of study design that are critical when comparing outcomes by planned place of birth. To address this deficiency, we aimed to develop a reliable instrument to rate the quality of primary research on maternal and newborn outcomes by place of birth. Study design: The instrument development process involved five phases: 1) generation of items and a weighted scoring system; 2) content validation via a quantitative survey and a modified Delphi process with an international, multi-disciplinary panel of experts; 3) inter-rater consistency; 4) alignment with established research appraisal tools; and 5) pilot-testing of instrument usability. Results: A Birth Place Research Quality Index (ResQu Index) was developed comprising 27 scored items that are summed to generate a weighted composite score out of 100 for studies comparing planned place of birth. Scale content validation indices were .89 for clarity, .94 for relevance and .90 for importance. The Index demonstrated substantial inter-rater consistency; pilot-testing confirmed feasibility and user-friendliness. Conclusion: The ResQu Index is a reliable instrument to evaluate the quality of design, methods and interpretation of reported outcomes from research about place of birth. Higher-scoring studies have greater potential to inform evidence-based selection of birth place by clinicians, policy makers, and women and their families. The Index can also guide the design of future research on place of birth

    Fuel Optimization in Multiple Diesel Driven Generator Power Plants

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    This paper presents two fuel optimization approaches for independent power producer (IPP) power plants consisting of multiple diesel driven generator sets (DGs). The optimization approaches utilize assumed information about the fuel consumption characteristics of each DG in an effort to demonstrate the potential benefits of acquiring such information. Reasonable variations in fuel consumption characteristics are based on measurements of a DG during restricted air filter flow operation. The two approaches are: (i) a gradient search approach capable of finding the optimal power generation for each DG in a fixed selection of DGs accommodating a given plant power reference and (ii) a genetic algorithm approach further capable of determining the optimal selection of DGs to operate in an IPP power plant. Both approaches show notable potential benefits, in terms of fuel savings, compared to current market-leading solutions
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