1,689 research outputs found
A Flexible DSTATCOM Operating in Voltage or Current Control Mode
The topology and control are discussed of a distribution static compensator (DSTATCOM) that can be operated flexibly in the voltage or current control mode. In the voltage control mode, the DSTATCOM can force the voltage of a distribution bus to be balanced sinusoids. In the current control mode, it can cancel distortion caused by the load, such that current drawn by the compensated load is pure balanced sinusoid. Both these objectives are achieved, irrespective of unbalance and harmonic distortions in load currents or source voltages. The chosen DSTATCOM topology includes three single-phase voltage source inverters connected in parallel to a filter-capacitor, which allows the high-frequency component of the current to pass. A switching control scheme is proposed, and its suitability is proved for this problem. The proposed scheme is verified using computer simulation studie
DEM slope-failure analysis of the Minami-Aso / Tateno area during the 2016 Kumamoto earthquakes
The Kumamoto earthquakes, which occurred on April 16, 2016, included deep large-scale landslides in the Minami-Aso village / Tateno area; the Aso Bridge collapsed completely because of this slope failure. Aso Bridge is considered to have collapsed for various reasons, e.g., fault displacements, earthquake accelerations, and landslide sediment depositions on the bridge. In this study, the possibility of landslide-sediment depositions on the bridge was assessed as a reason for the bridge collapse using the discrete element method (DEM), and the landslides at Aso Bridge were reproduced. An experiment and analysis were conducted on the large deformation of aluminum-bar laminated ground with wall movement, to confirm the applicability of DEM to large ground-deformation problems. Next, the Aso Bridge slope-failure analysis was carried out, based on different analysis conditions, and the sediment distribution was compared with field observation results from qualitative and quantitative viewpoints. It was concluded that sediment deposition on the bridge was not a cause of the Aso Bridge failure
Regional ventricular wall motion abnormalities in tricuspid atresia after the fontan procedure
AbstractObjectieves. The purpose of this study was to determine whether wall motion abnormalities are present before or after the Fontan procedure in patients with a univentricular heart of the left ventricular type with an absent right atrioventricular valve connection (tricuspid atresia) and to assess the impact of such abnormalities on ventricular performance and clinical outcome.Background. Normal systolic and diastolic ventricular (unction is critical for a successful Fontan repair. However, there have been no previous studies addressing the relation between regional ventricular function and hemodynamic factors.Methods. Thirty-seven pediatric patients were studied with biplane ventricular cineangiography. There were 20 male and 17 female patients whose mean age at the time of the Fontan operation was 6.5 ± 3.5 years (range 2.5 to 15.6). Eighteen patients were studied preoperatively, 25 at >1 year postoperatively and 6 serially. Wall motion was assessed by a centerline method. Normal ranges for wall motion and other variables were established from 25 normal subjects.Results. Wall motion abnormalities were observed in 2 of 18 patients preoperatively and in 11 of 25 patients postoperatively. Age at operation and ventricular volumes did not differ between postoperative patients who had normal (group I, 14 patients) or abnormal (group II, 11 patients) wall motion. However, ventricular mass and the mass/volume ratio were significantly greater and systolic variables and cardiac index were significantly lower in group II versus group I. Two patients in group I were considered to have a clinically poor outcome (persistent heart failure), and five in group II had heart failure, including one who died late.Conclusions. These observations suggest that postoperative regional wall motion abnormalities in this setting are not rare, may be related to excessive hypertrophy and may contribute to cardiac dysfunction and a poor clinical outcome
Hydrological study of Lyngmossen bog, Sweden: Isotopic tracers (3H, ÎŽ2H and ÎŽ18O) imply three waters with different mobilities
The 3H concentration and stable isotope ratio of hydrogen and oxygen, ÎŽ2H and ÎŽ18O, of waters extracted from a Sphagnum-dominant raised bog in Lyngmossen, Sweden, were measured in order to understand where the precipitation is retained and how mobile it is. Three types of waters, which were defined by extractability, were collected from the peat. Two waters were extracted by compressing samples with different pressures (SQW1 and SQW2). The other water was obtained by distilling the compressed samples (DW). 3H was detected in all types of water from depths of 0â50âŻcm: the concentrations in SQW1, SQW2 and DW ranged 1.17â3.07 Bq/L, 0.98â2.03 Bq/L, and 1.02â1.54 Bq/L, respectively. The maximum 3H concentrations of SQW1, SQW2 and DW were all detected at a depth of around 15âŻcm, whose 14C age covers the year of the atomic bomb experiments. The 3H results of SQW1/2 indicate that SQW consists of at least two waters of different mobility, water flowing rapidly downward and immobile water. Sphagnum hyaline cells may be responsible for the immobile water.
The ÎŽ18O and ÎŽ2H relationship exhibited independent trends between SQW and DW. The distinct difference observed between the two waters at the surface (0â5âŻcm) indicates that the two waters may be supplied by precipitation at different times of the year, or alternatively that DW comprises plant water taken in from hyaline cells. The ÎŽ18O and ÎŽ2H values of both SQW and DW in the shallow layer increased with increasing depth, and in the layer around 30âŻcm depth, those of SQW showed a distinct decrease with depth. Isotope fractionation caused by evaporation and/or plant utilization of water at the surface layer are considered to be the main causes of such isotopic variation at the surface. Evaporation is likely to take place in much drier conditions for DW than for SQW, probably through stems by capillary action. In SQW freezing may be a possible cause for the decrease of ÎŽ18O and ÎŽ2H around 30âŻcm depth. DW is isotopically very well separated from two SQW1/2.
Integrating all isotopic information, we conclude the presence of three different waters: least mobile water at shallow depth perhaps in hyaline cells, which can be extracted by squeezing peat with low pressure; most mobile water in a deeper layer than 30âŻcm, extracted also by squeezing peat; mobile but least extractable water, which is likely water inside plant tissues
Rare K decays in a model of quark and lepton masses
An extension of a model of neutrino masses to the quark sector provides an
interesting link between these two sectors. A parameter which is important to
describe neutrino oscillations and masses is found to be a crucial one
appearing in various ``penguin'' operators, in particular the so-called Z
penguin. This parameter is severely constrained by the rare decay process
. This in turn has interesting implications on the
decay rates of other rare processes such as , etc..., as well
as on the masses of the neutrinos and the masses of the vector-like quarks and
leptons which appear in our model.Comment: 34 pages, 10 figures, corrected some typos in the introductio
Long Distance Contribution to
We revisit the calculation of the long distance contribution to . We discuss this process within the framework of chiral
perturbation theory, and also using simple models for the vertex. We argue that it is unlikely that this mode can be used to
extract information on short distance parameters. The process
is also long-distance dominated and we find that .Comment: References added, one typo corrected. Version to appear in Nuclear
Physics
Radiative Corrections to Double Dalitz Decays: Effects on Invariant Mass Distributions and Angular Correlations
We review the theory of meson decays to two lepton pairs, including the cases
of identical as well as non-identical leptons, as well as CP-conserving and
CP-violating couplings. A complete lowest-order calculation of QED radiative
corrections to these decays is discussed, and comparisons of predicted rates
and kinematic distributions between tree-level and one-loop-corrected
calculations are presented for both pi-zero and K-zero decays.Comment: 25 pages, 18 figures, added figures and commentar
Thermo-mechanical behaviour of a compacted swelling clay
Compacted unsaturated swelling clay is often considered as a possible buffer
material for deep nuclear waste disposal. An isotropic cell permitting
simultaneous control of suction, temperature and pressure was used to study the
thermo-mechanical behaviour of this clay. Tests were performed at total
suctions ranging from 9 to 110 MPa, temperature from 25 to 80 degrees C,
isotropic pressure from 0.1 to 60 MPa. It was observed that heating at constant
suction and pressure induces either swelling or contraction. The results from
compression tests at constant suction and temperature evidenced that at lower
suction, the yield pressure was lower, the elastic compressibility parameter
and the plastic compressibility parameter were higher. On the other hand, at a
similar suction, the yield pressure was slightly influenced by the temperature;
and the compressibility parameters were insensitive to temperature changes. The
thermal hardening phenomenon was equally evidenced by following a
thermo-mechanical path of loading-heating-cooling-reloading
Adolescent Idiopathic Scoliosis Screening for School, Community, and Clinical Health Promotion Practice Utilizing the PRECEDE-PROCEED Model
Background
Screening for adolescent idiopathic scoliosis (AIS) is a commonly performed procedure for school children during the high risk years. The PRECEDE-PROCEDE (PP) model is a health promotion planning model that has not been utilized for the clinical diagnosis of AIS. The purpose of this research is to study AIS in the school age population using the PP model and its relevance for community, school, and clinical health promotion.
Methods
MEDLINE was utilized to locate AIS data. Studies were screened for relevance and applicability under the auspices of the PP model. Where data was unavailable, expert opinion was utilized based on consensus.
Results
The social assessment of quality of life is limited with few studies approaching the long-term effects of AIS. Epidemiologically, AIS is the most common form of scoliosis and leading orthopedic problem in children. Behavioral/environmental studies focus on discovering etiologic relationships yet this data is confounded because AIS is not a behavioral. Illness and parenting health behaviors can be appreciated. The educational diagnosis is confounded because AIS is an orthopedic disorder and not behavioral. The administration/policy diagnosis is hindered in that scoliosis screening programs are not considered cost-effective. Policies are determined in some schools because 26 states mandate school scoliosis screening. There exists potential error with the Adam's test. The most widely used measure in the PP model, the Health Belief Model, has not been utilized in any AIS research.
Conclusion
The PP model is a useful tool for a comprehensive study of a particular health concern. This research showed where gaps in AIS research exist suggesting that there may be problems to the implementation of school screening. Until research disparities are filled, implementation of AIS screening by school, community, and clinical health promotion will be compromised. Lack of data and perceived importance by school/community health planners may influence clinical health promotion practices
K_L \ra \mu^\pm e^\mp \nu \overline{\nu} as background to K_L \ra \mu^\pm e^\mp
We consider the process K_L \ra \mu^\pm e^\mp \nu \overline{\nu} at next to
leading order in chiral perturbation theory. This process occurs in the
standard model at second order in the weak interaction and constitutes a
potential background in searches for new physics through the modes K_L \ra
\mu^\pm e^\mp. We find that the same cut, ~MeV, used to remove
the sequential decays K_{l3}\ra \pi_{l2} pushes the B(K_L \ra \mu^\pm e^\mp
\nu \overline{\nu}) to the level, effectively removing it as a
background.Comment: 8 pages, LaTeX, 1 figure appended as postscript file after
\end{document}. Fermilab-Pub-93/024-
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