230 research outputs found
Design and experimental verification of an improved magnetostrictive energy harvester
This paper summarizes and extends the modeling state of the art of magnetostrictive energy harvesters with a focus on the pick-up coil design. The harvester is a one-sided clamped galfenol unimorph loaded with two brass pieces each containing a permanent magnet to create a biased magnetic field. Measurements on different pick-up coils were conducted and compared with results from an analytic model. Resistance, mass and inductance were formulated and proved by measurements. Both the length for a constant number of turns and the number of turns for a constant coil length were also modeled and varied. The results confirm that the output voltage depends on the coil length for a constant number of turns and is higher for smaller coils. In contrast to a uniform magnetic field, the maximal output voltage is gained if the coil is placed not directly at but near the fixation. Two effects explain this behavior: Due to the permanent magnet next to the fixation, the magnetic force is higher and orientates the magnetic domains stronger. The clamping locally increases the stress and forces the magnetic domains to orientate, too. For that reason the material is stiffer and therefore the strain smaller. The tradeoff between a higher induced voltage in the coil and an increasing inductance and resistance for every additional turn are presented together with an experimental validation of the models. Based on the results guidelines are given to design an optimal coil which maximizes the output power for a given unimorph
Mechanical properties of magnetostrictive iron-gallium alloys
Single crystal specimens of Fe-17 at. % Ga were tested in tension at room temperature. Specimens with a tensile axis orientation of [110] displayed slip lines on the specimen faces corresponding to slip on the {110}with a critical resolved shear stress of 220 MPa. Yielding began at 0.3% elongation and 450 MPa. An ultimate tensile strength of 580 MPa was observed with no fracture occurring through 1.6% elongation. The Young s modulus was 160 GPa in the loading direction with a Poisson s ratio of -0.37 on the (100) major face. A specimen with a tensile axis orientation of [100] showed slip lines corresponding to slip on the {211}with critical resolved shear stress of 240 MPa. Discontinuous yielding began at 0.8% elongation, which was thought to result from twinning, kink band formation, or stress-induced transformation. The Young\u27s modulus was 65 GPa in the loading direction with a Poisson s ratio of 0.45 on the (001) major face. A maximum tensile strength of 515 MPa was observed with fracture occurring after 2% elongation. A sizeable elastic anisotropy of 19.9 was identified for Fe-27.2 at. % Ga accompanied by a Poisson\u27s ratio of -0.75 to produce a large in-plane auxetic behavior
ACE-ASIA - Regional climatic and atmospheric chemical effects of Asian dust and pollution
Although continental-scale plumes of Asian dust and pollution reduce the amount of solar radiation reaching the earth's surface and perturb the chemistry of the atmosphere, our ability to quantify these effects has been limited by a lack of critical observations, particularly of layers above the surface. Comprehensive surface, airborne, shipboard, and satellite measurements of Asian aerosol chemical composition, size, optical properties, and radiative impacts were performed during the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) study. Measurements within a massive Chinese dust storm at numerous widely spaced sampling locations revealed the highly complex structure of the atmosphere, in which layers of dust, urban pollution, and biomass-burning smoke may be transported long distances as distinct entities or mixed together. The data allow a first-time assessment of the regional climatic and atmospheric chemical effects of a continental-scale mixture of dust and pollution. Our results show that radiative flux reductions during such episodes are sufficient to cause regional climate change
Overview of ACE-Asia spring 2001 investigations on aerosol-radiation interactions
In spring 2001 the Asian Pacific Regional Aerosol
Characterization Experiment (ACE-Asia) made
extensive measurements from land, ocean, air and
space platforms. A primary objective was to
quantify the interactions between aerosols and
radiation. This talk presents illustrative results from
each type of platform, with initial assessments of
regional aerosol radiative forcing obtained by
combining satellite and suborbital results
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Indian summer monsoon onset forecast skill in the UK Met Office initialized coupled seasonal forecasting system (GloSea5-GC2)
Accurate and precise forecasting of the Indian monsoon is important for the socio-economic security of India, with improvements in agriculture and associated sectors from prediction of the monsoon onset. In this study we establish the skill of the UK Met Office coupled initialized global seasonal forecasting system, GloSea5-GC2, in forecasting Indian monsoon onset. We build on previous work that has demonstrated the good skill of GloSea5 at forecasting interannual variations of the seasonal mean Indian monsoon using measures of large-scale circulation and local precipitation. We analyze the summer hindcasts from a set of three springtime start-dates in late April/early May for the 20-year hindcast period (1992-2011). The hindcast set features at least fifteen ensemble members for each year and is analyzed using five different objective monsoon indices. These indices are designed to examine large and local-scale measures of the monsoon circulation, hydrological changes, tropospheric temperature gradient, or rainfall for single value (area-averaged) or grid-point measures of the Indian monsoon onset. There is significant correlation between onset dates in the model and those found in reanalysis. Indices based on large-scale dynamic and thermodynamic indices are better at estimating monsoon onset in the model rather than local-scale dynamical and hydrological indices. This can be attributed to the model's better representation of large-scale dynamics compared to local-scale features. GloSea5 may not be able to predict the exact date of monsoon onset over India, but this study shows that the model has a good ability at predicting category-wise monsoon onset, using early, normal or late tercile categories. Using a grid-point local rainfall onset index, we note that the forecast skill is highest over parts of central India, the Gangetic plains, and parts of coastal India - all zones of extensive agriculture in India. El Niño Southern Oscillation (ENSO) forcing in the model improves the forecast skill of monsoon onset when using a large-scale circulation index, with late monsoon onset coinciding with El Niño conditions and early monsoon onset more common in La Niña years. The results of this study suggest that GloSea5's ensemble-mean forecast may be used for reliable Indian monsoon onset prediction a month in advance despite systematic model errors
Predictability and prediction skill of the boreal summer intraseasonal oscillation in the Intraseasonal Variability Hindcast Experiment
The role of salinity in the decadal variability of the North Atlantic meridional overturning circulation
Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Climate Dynamics 33 (2009): 777-793, doi:10.1007/s00382-008-0523-2.An OGCM hindcast is used to investigate the linkages between North Atlantic Ocean
salinity and circulation changes during 1963–2003. The focus is on the eastern subpolar
region consisting of the Irminger Sea and the eastern North Atlantic where a careful
assessment shows that the simulated interannual to decadal salinity changes in the upper
1500 m reproduce well those derived from the available record of hydrographic
measurements. In the model, the variability of the Atlantic meridional overturning
circulation (MOC) is primarily driven by changes in deep water formation taking place in
the Irminger Sea and, to a lesser extent, the Labrador Sea. Both are strongly influenced by
the North Atlantic Oscillation (NAO). The modeled interannual to decadal salinity changes
in the subpolar basins are mostly controlled by circulation-driven anomalies of freshwater
flux convergence, although surface salinity restoring to climatology and other boundary
fluxes each account for approximately 25% of the variance. The NAO plays an important
role: a positive NAO phase is associated with increased precipitation, reduced northward
salt transport by the wind-driven intergyre gyre, and increased southward flows of
freshwater across the Greenland-Scotland ridge. Since the NAO largely controlled deep
convection in the subpolar gyre, fresher waters are found near the sinking region during
convective events. This markedly differs from the active influence on the MOC that salinity
exerts at decadal and longer timescales in most coupled models. The intensification of the
MOC that follows a positive NAO phase by about 2 years does not lead to an increase in
the northward salt transport into the subpolar domain at low frequencies because it is
cancelled by the concomitant intensification of the subpolar gyre which shifts the subpolar
front eastward and reduces the northward salt transport by the North Atlantic Current
waters. This differs again from most coupled models, where the gyre intensification
precedes that of the MOC by several years.Support from NSF Grant
82677800 with the Woods Hole Oceanographic Institution, and (to CF) from the Institut
universitaire de France and European FP6 project DYNAMITE (contract 003903-GOCE)
and (to JD) from the NOAA Office of Hydrologic Development through a scientific
appointment administered by UCAR is gratefully acknowledged
Mutation Analysis of NR5A1 Encoding Steroidogenic Factor 1 in 77 Patients with 46, XY Disorders of Sex Development (DSD) Including Hypospadias
BACKGROUND: Mutations of the NR5A1 gene encoding steroidogenic factor-1 have been reported in association with a wide spectrum of 46,XY DSD (Disorder of Sex Development) phenotypes including severe forms of hypospadias. METHODOLOGY/PRINCIPAL FINDINGS: We evaluated the frequency of NR5A1 gene mutations in a large series of patients presenting with 46,XY DSD and hypospadias. Based on their clinical presentation 77 patients were classified either as complete or partial gonadal dysgenesis (uterus seen at genitography and/or surgery, n = 11), ambiguous external genitalia without uterus (n = 33) or hypospadias (n = 33). We identified heterozygous NR5A1 mutations in 4 cases of ambiguous external genitalia without uterus (12.1%; p.Trp279Arg, pArg39Pro, c.390delG, c140_141insCACG) and a de novo missense mutation in one case with distal hypospadias (3%; p.Arg313Cys). Mutant proteins showed reduced transactivation activity and mutants p.Arg39Pro and p.Arg313Cys did not synergize with the GATA4 cofactor to stimulate reporter gene activity, although they retained their ability to physically interact with the GATA4 protein. CONCLUSIONS/SIGNIFICANCE: Mutations in NR5A1 were observed in 5/77 (6.5%) cases of 46,XY DSD including hypospadias. Excluding the cases of 46,XY gonadal dysgenesis the incidence of NR5A1 mutations was 5/66 (7.6%). An individual with isolated distal hypopadias carried a de novo heterozygous missense mutation, thus extending the range of phenotypes associated with NR5A1 mutations and suggesting that this group of patients should be screened for NR5A1 mutations
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