| 1. |
|
|
| 2. |
|
|
| 3. |
- Björkman, Stina, et al.
(author)
-
Microvascular dysfunction in women with a history of hypertensive disorders of pregnancy: A population-based retrospective cohort study
- 2024
-
In: British Journal of Obstetrics and Gynecology. - : WILEY. - 1470-0328 .- 1471-0528. ; 131:4, s. 433-443
-
Journal article (peer-reviewed)abstract
- ObjectiveTo evaluate microvascular function in women with previous hypertensive disorders of pregnancy (HDP).DesignRetrospective population-based cohort study.SettingLinkoping, Sweden.PopulationWomen aged 50-65 years, participating in the Swedish CArdioPulmonary bioImage Study (SCAPIS) at one site (Linkoping) 2016-18, who underwent microcirculatory assessment (N = 1222).MethodsForearm skin comprehensive microcirculatory assessment was performed with a PeriFlux PF6000 EPOS (Enhanced Perfusion and Oxygen Saturation) system measuring oxygen saturation and total speed resolved perfusion. Obstetric records were reviewed to identify women with previous HDP. Data on cardiovascular risk factors, comorbidities, medication, lifestyle, anthropometric data, and biochemical analyses were obtained from SCAPIS. The microcirculatory data were compared between women with and without previous HDP.Main outcome measuresSkin microcirculatory oxygen saturation and total speed resolved perfusion at baseline and post-ischaemic peak.ResultsWomen with previous pre-eclampsia displayed impaired post-ischaemic peak oxygen saturation compared with women with normotensive pregnancies (88%, interquartile range [IQR] 84-89% vs 91%, IQR 87-94%, p = 0.001) 6-30 years after pregnancy. The difference remained after multivariable adjustment (& beta; -2.69, 95% CI -4.93 to -0.45).ConclusionsThe findings reveal microvascular dysfunction at long-term follow up in women with previous pre-eclampsia and strengthen the possible role of endothelial dysfunction as a link to the increased risk of cardiovascular disease in women with HDP.
|
|
| 4. |
- Bladh, Gabriel, 1959-, et al.
(author)
-
Editorial Nordidactica 2023:1 Jubileum
- 2023
-
In: Nordidactica. - Karlstad : Karlstads universitet. - 2000-9879. ; :1
-
Journal article (other academic/artistic)
|
|
| 5. |
- Bladh, Henrik, et al.
(author)
-
Probing the smallest soot particles in low-sooting premixed flames using laser-induced incandescence
- 2015
-
In: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 35, s. 1843-1850
-
Journal article (peer-reviewed)abstract
- In this work we investigate nascent soot particles by analyzing laser-induced incandescence (LII) signals obtained in low-sooting premixed flames. The analysis covers two data sets obtained in separate experimental campaigns. The first data set was obtained in a previous work (Mouton et al., 2013) in methane/oxygen/nitrogen flames (equivalence ratio range 1.95 < Phi < 2.32) at 26.7 kPa, whereas the second was performed in atmospheric ethylene/air flames (1.77 < Phi < 2.00). Both studies show similar trends, i.e. a gradual change of the fluence curves (evolution of the LII signal as function of the laser fluence) from the well-known S-shaped curve for mature soot found at high heights above the burner (HAB) and high equivalence ratio, to a nearly linear behavior for nascent soot found at low HAB and reduced equivalence ratio. With this change comes a decrease in the LII decay time (and hence inferred particle size). Also, this decay time appears to be almost constant with HAB in flames having the lowest equivalence ratio at which the incandescence signal could be detected. In these flames, so-called nucleation flames, the stability of the particle size with HAB suggests that recently nucleated particles have undergone marginal surface growth and coagulation. Existence of such nucleation flames is of great interest for improving the theoretical description of the nucleation step. Experimental results are analyzed by using a theoretical model for LII to determine the particle size evolution throughout the flame at various experimental conditions. We highlight the size difference from nascent soot particles up to mature soot, giving insight into the particle nucleation and the surface growth processes as a function of reaction time and flame conditions. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
|
|
| 6. |
- Bladh, Johan
(author)
-
Hydropower generator and power system interaction
- 2012
-
Doctoral thesis (other academic/artistic)abstract
- After decades of routine operation, the hydropower industry faces new challenges. Large-scale integration of other renewable sources of generation in the power system accentuates the role of hydropower as a regulating resource. At the same time, an extensive reinvestment programme has commenced where many old components and apparatus are being refurbished or replaced. Introduction of new technical solutions in existing power plants requires good systems knowledge and careful consideration. Important tools for research, development and analysis are suitable mathematical models, numerical simulation methods and laboratory equipment. This doctoral thesis is devoted to studies of the electromechanical interaction between hydropower units and the power system. The work encompasses development of mathematical models, empirical methods for system identification, as well as numerical and experimental studies of hydropower generator and power system interaction. Two generator modelling approaches are explored: one based on electromagnetic field theory and the finite element method, and one based on equivalent electric circuits. The finite element model is adapted for single-machine infinite-bus simulations by the addition of a network equivalent, a mechanical equation and a voltage regulator. Transient simulations using both finite element and equivalent circuit models indicate that the finite element model typically overestimates the synchronising and damping properties of the machine. Identification of model parameters is performed both numerically and experimentally. A complete set of equivalent circuit parameters is identified through finite element simulation of standard empirical test methods. Another machine model is identified experimentally through frequency response analysis. An extension to the well-known standstill frequency response (SSFR) test is explored, which involves measurement and analysis of damper winding quantities. The test is found to produce models that are suitable for transient power system analysis. Both experimental and numerical studies show that low resistance of the damper winding interpole connections are vital to achieve high attenuation of rotor angle oscillations. Hydropower generator and power system interaction is also studied experimentally during a full-scale startup test of the Nordic power system, where multiple synchronised data acquisition devices are used for measurement of both electrical and mechanical quantities. Observation of a subsynchronous power oscillation leads to an investigation of the torsional stability of hydropower units. In accordance with previous studies, hydropower units are found to be mechanically resilient to subsynchronous power oscillations. However, like any other generating unit, they are dependent on sufficient electrical and mechanical damping. Two experimentally obtained hydraulic damping coefficients for a large Francis turbine runner are presented in the thesis.
|
|
| 7. |
- Bladh, Johan, et al.
(author)
-
Standstill Frequency Response Test on a Synchronous Machine Extended With Damper Bar Measurements
- 2016
-
In: IEEE transactions on energy conversion. - 0885-8969 .- 1558-0059. ; 31:1, s. 46-56
-
Journal article (peer-reviewed)abstract
- Standstill Frequency Response (SSFR) test data from a salient-pole synchronous machine with reconfigurable damper winding is presented. In addition to the regular measurements, the damper bar currents are measured and used to obtain the stator-to-damper transfer functions. The test is performed three times with physically different damper winding configurations. An extension to the standard SSFR test analysis scheme is suggested where the stator-to-damper transfer functions are included. The validity of the identified models is substantiated by comparison of the simulated and measured machine response to a drive torque step disturbance. It is found that the damper winding measurements can be incorporated in the analysis scheme to isolate the effect of the damper circuits. However, for a machine of the type studied, also the standard SSFR test produce yields models that are accurate enough for power system studies.
|
|
| 8. |
- Bladh, Johan, et al.
(author)
-
Synchronised measurements on hydropower units during power system startup
-
In: Hydro Review Worldwide. - 1072-9542.
-
Journal article (peer-reviewed)abstract
- During a recent full-scale blackstart test of the Nordic power system, measurements of electrical and mechanical quantities using both phasor measurement units (PMUs) and synchronised local acquisition devices was performed. This paper describes the measurement system and discusses a few important considerations for synchronised measurements in multiple hydropower stations. One generator's response to a \unit[100]{MW} load step is shown and an observed subsynchronous oscillation is discussed. It is shown that comprehensive measurements using multiple synchronised data acquisition devices can be performed using off-the-shelf hardware and existing infrastructure. The findings show the danger of assuming that all the interesting information is found at the fundamental frequency.
|
|
| 9. |
- Bladh, Johan, et al.
(author)
-
Torsional stability of hydropower units under influence of subsynchronous oscillations
- 2013
-
In: IEEE Transactions on Power Systems. - 0885-8950 .- 1558-0679. ; 28:4, s. 3826-3833
-
Journal article (peer-reviewed)abstract
- Hydropower units are known to be comparatively insensitive to subsynchronous power oscillations. During a startup test of an electrical island in the Nordic power system, a series capacitor tripped due to a subsynchronous oscillation within the normal frequency range of hydropower unit torsional modes. Since no thermal units were connected, it is motivated to question the traditional view. In this paper, the small-signal and transient torsional mode stability of hydropower units is assessed through time-domain simulations. The model is based on the first IEEE benchmark model for subsynchronous resonance which has been tuned to fit one of the blackstart test system units for which detailed measurements are available. The stability conditions are investigated for several load conditions and machine configurations. It is found that the damping in the startup test system is sufficient to prevent growing oscillations. A fault however could expose the machines to high transient torques.
|
|
| 10. |
- Gallo, Yann, et al.
(author)
-
A Study of In-Cylinder Soot Oxidation by Laser Extinction Measurements During an EGR-Sweep in an Optical Diesel Engine
- 2015
-
In: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
-
Journal article (peer-reviewed)abstract
- Two competing in-cylinder processes, soot formation and soot oxidation, govern soot emissions from diesel engines. Previous studies have shown a lack of correlation between the soot formation rate and soot emissions. The current experiment focuses on the correlation between soot oxidation rates and soot emissions. Laser extinction is measured using a red (690nm) laser beam, which is sent vertically through the cylinder. This wavelength is long enough to minimize absorption interference from poly-aromatic hydrocarbons, while still in the visible regime. It is modulated at 72 kHz in order to produce 10 pulses per crank angle degree at an engine speed of 1200 rpm. The intake oxygen concentration is varied between 9% and 21%. The time resolved extinction measurements are used to estimate soot oxidation rates during expansion. High-speed video imaging is used in conjunction with the laser-extinction technique to indicate the location of the sooting regions, and to assess beam steering effects. The oxidation processes are described using single exponential decay fits and an attempt to correlate them with the late cycle rate of heat release was made.
|
|
