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ABSTRACT: The experimentally accessible degree of undercooling of single micron-sized liquid pure tin drops has been studied via differential fast scanning calorimetry. The cooling rates employed ranged from 100 to 14 000 K∕s. The diameter of the investigated tin drops varied in the range from 7 to 40 μm. The influence of the drop shape on the solidification process could be eliminated due to the nearly spherical shape of the single drop upon heating and cooling and the resultant geometric stability. As a result it became possible to study the effect of both drop size and cooling rate in rapid solidification experimentally. A theoretical description of the experimental results is given by assuming the existence of two different heterogeneous nucleation mechanisms leading to crystal nucleation of the single tin drop. In agreement with the experiment these mechanisms yield a shelf-like dependence of crystal nucleation on undercooling. A dependence of crystal nucleation on the size of the tin drop was observed and is discussed in terms of the mentioned theoretical model, which can possibly also describe the nucleation for other related rapid solidification processes.
The Journal of chemical physics 02/2013; 138(5):054501. · 3.09 Impact Factor
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ABSTRACT: (Bi0.9Ba0.1)(Fe0.95Mn0.05)O3 films were prepared on LaNiO3-coated surface oxidized Si substrates. XRD and Raman measurements confirm that the (Bi0.9Ba0.1)(Fe0.95Mn0.05)O3 film has pure R3c structure. Clear ferromagnetism with saturated magnetization of about 25 emu/cm3 has been observed at room temperature. The ferroelectric properties of the (Bi0.9Ba0.1)(Fe0.95Mn0.05)O3 film was confirmed by the observation of the ferroelectric domains and the converse piezoelectric coefficient d
33 versus applied voltage hysteresis loops by piezoelectric force microscopy (PFM). The observation of ferromagnetism and ferroelectricity
in (Bi0.9Ba0.1)(Fe0.95Mn0.05)O3 films indicates the potential multiferroic applications.
KeywordsMultiferroic–BiFeO3
–Ferroelectricity–Ferromagnetism
Journal of Superconductivity and Novel Magnetism 05/2012; 24(5):1497-1500. · 0.65 Impact Factor
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ABSTRACT: Non-adiabatic fast scanning calorimetry has been developed to in-situ measure the response of single metallic drops to temperature
changes in a large range of cooling rate spanning four orders of magnitude. In particular, the effect of cooling rate on the
degree of undercooling of one 10μm Sn-drop is studied. The experimental results show that the undercooling could be increased
first significantly with increasing cooling rate going over to a stage of slow increase for high cooling rates, which indicates
a shelf-like dependence of undercooling level on cooling rate before and after a “crossover” at a cooling rate of about 1000
K/s where two different heterogeneous mechanisms act simultaneously. First theoretical estimates are developed on the specific
feature of the heterogeneous nucleation process of the effect analyzed and possible directions of further research are anticipated.
Applied Physics A 05/2012; 104(1):189-196. · 1.63 Impact Factor
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ABSTRACT: Bi3TiNbO9 (BTN) thin films with layered perovskite structure were fabricated on fused silica by pulsed laser deposition. The XRD pattern
revealed that the films are single-phase perovskite and highly (00l) textured. Their fundamental optical constants, such as band gap, linear refractive index, and linear absorption coefficient,
were obtained by optical transmittance measurements. The dispersion relation of the refractive index vs. wavelength follows
the single electronic oscillator model. The nonlinear optical absorption of the films was investigated by single beam Z-scan
method at a wavelength of 800nm with laser duration of 80fs. We obtained the nonlinear absorption coefficient β=1.44×10−7m/W. The results show that the BTN thin films are promising for applications in absorbing-type optical devices.
Applied Physics A 04/2012; 96(4):1017-1021. · 1.63 Impact Factor
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ABSTRACT: The traditional Sn–Pb eutectic solder alloys are being phased out from the electronics industry due to the toxicity of lead
(Pb), leading to the development and implementation of lead-free solders. Sn3.5Ag lead-free solder alloy, considered to be
one of the promising alternatives to replace the traditionally used Sn–Pb solder, however, still has some weaknesses, such
as its higher melting temperature than that of the Sn–Pb solder alloy. A possible way to decrease the melting temperature
of a solder alloy is to decrease the alloy particle size to the nanometer range. Sn3.5Ag nanoparticles with different size
distribution were synthesized using chemical reduction method by applying NaBH4 as reduction agent. The melting properties of these synthesized nanoparticles were studied by differential scanning calorimetry
(DSC), and size-dependent melting temperature depression of these nanoparticles has been observed. Gibbs–Thomson equation
was used to analyze the size-dependent melting temperature property, giving a good prediction of the melting temperature depression
for the Sn-based lead-free solder alloy nanoparticles.
Journal of Materials Science Materials in Electronics 04/2012; 21(9):868-874. · 1.08 Impact Factor
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ABSTRACT: A novel non-resonant energy harvesting mechanism with wide operation frequency band is investigated for collecting energy
from low frequency ambient vibration. A free-standing magnet is packaged inside a sealed hole which is created by stacking
five pieces of printed circuit board substrates embedded with multi-layer copper coils. This device was tested under various
acceleration conditions. Considering the air damping effect, two types of device structures with different covered plates
are investigated. For type I, one covered acrylic plate with drilled air holes and another plate with no holes are used to
package the moving magnet. For type II, the middle hole is sealed by two acrylic plates with drilled air holes. The output
voltage of type II is better than the one of type I at the same acceleration. When the energy harvester of type II is shook
at 1.9g acceleration along longitudinal direction of the hole, the 9mV output voltage with 40Hz bandwidth, i.e., from 40
to 80Hz, is generated. The maximum output power within the ranges of 40–80Hz, i.e., operation bandwidth, is measured as
0.4μW under matched loading resistance of 50Ω. Experimental results show that type I device has wider frequency bandwidth,
higher center frequency and smaller output voltage than type II device because type I device experiences severe damping influence.
Microsystem Technologies 04/2012; 16(6):961-966. · 0.93 Impact Factor
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ABSTRACT: The size-dependent solidification undercooling was investigated for single micro-sized particles of pure Sn employing differential
scanning calorimeter (DSC). The particles were obtained from a solvent-encapsulation remelting and quenching (SERQ) process.
Because of the basically unchanged spherical shape of the measured single particles during a series of continuous heating
and cooling processes, it allows studying the independent effect of particle size on undercooling. Applying classical nucleation
theory in conjunction with available thermodynamic data yields an increasing undercooling with decreasing particle size. The
theoretical description is in good agreement with the experimental data.
Keywordssingle particle measurement-undercooling-size-dependence-pure Sn
Chinese Science Bulletin 04/2012; 55(19):2063-2065. · 1.32 Impact Factor
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ABSTRACT: Layered-perovskite ferroelectric Bi2.85La0.15TiNbO9 (LBTN) optical waveguiding thin films were grown on fused silica substrates by pulsed laser deposition (PLD). X-ray diffraction
(XRD) revealed that the film is highly (00l) textured. We observed sharp and distinct transverse electric (TE) and transverse magnetic (TM) multimodes and measured the
refractive indices of LBTN thin films at 632.8nm. The ordinary and extraordinary refractive indices were calculated to be
n
TE=2.358 and n
TM=2.464, respectively. The film homogeneity and the film-substrate interface were analyzed using an improved version of the
inverse Wentzel–Kramer–Brillouin (iWKB) method. The refractive index of the film remains constant at n
0 within the waveguiding layer. The average transmittance of the film is 70% in the wavelength range of 400–1400nm and the
optical waveguiding properties were evaluated by the optical prism coupling method. Our results showed that the LBTN films
are very good electro-optical active material.
Applied Physics A 04/2012; 97(4):741-744. · 1.63 Impact Factor
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ABSTRACT: The undercooling of the single micro-sized droplet of Sn-3.0Ag-0.5Cu (wt%) alloy has been studied via the newly developed
fast calorimetric scanning technique, by which the fast heating and cooling treatment for a single droplet can be realized,
with the maximum heating or cooling rate being 1×104 K/s. Owing to the nearly spherical shape of the single droplet upon heating and cooling and the resultant geometric stability,
the influence of the droplet size on the solidification process could be eliminated. As a result, the puzzled issue on how
to separate the mutual effects of droplet size and cooling rate in the field of rapid solidification has been primarily solved,
making it possible to study separately the effect of droplet size and cooling rate. Meanwhile, the in-situ observation on deep undercooling could be actualized in this condition, differing from that obtained only by theoretical
calculation. The results showed that the undercooling was increased with the increasing cooling rate, and the maximum in-situ measured undercooling reached 116.9 K. The undercooling of the single droplet, however, was increased abruptly when cooled
at the rate of 2×103 K/s. The undercooling increased slightly as the cooling rate was increased continuously to 1×104 K/s, implying the infeasibility for gaining large undercooling only by increasing the cooling rate.
Science in China Series E Technological Sciences 04/2012; 52(6):1707-1711. · 1.02 Impact Factor
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ABSTRACT: To assess and compare the flap morphology using anterior segment optical coherence tomography (AS-OCT) in laser in situ keratomileusis (LASIK) with Femto LDV femtosecond lasers versus Hansatome mechanical Microkeratome.
AS-OCT (Visante) was used to compare 1 month postoperatively the morphology of the flaps created with Femto LDV femtosecond lasers or Hansatome Microkeratome. The intended flap thickness was 110µm and 160µm respectively. The thickness of twenty-five points across each flap, which were 0mm, 1.5mm, 2.5mm, and 3.5mm to the corneal vertex on the horizontal, vertical, 45° and 135° meridian respectively, was evaluated.
One month postoperative, the central flap thickness in the Femto LDV group was 107.43±4.70µm, while 125.90±17.50µm in the Hansatome group. The difference between the actual and the expected flap thickness was 5.61±3.84µm and 31.52±12.27µm, respectively. The Hansatome group had presented a statistically significant result (P<0.001). Flap morphology showed a more regular planar shape in the Femto LDV group and a meniscus shape in the Hansatome group.
AS-OCT is a direct and fast procedure to assess the flap morphology. The morphology by AS-OCT showed that the flaps created with Femto LDV femtosecond laser were more accurate and regular than the flaps created with Hansatome microkeratome.
International journal of ophthalmology. 01/2012; 5(1):69-73.
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Signal Processing. 01/2012; 92:54-62.
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ABSTRACT: Otitis media is a middle ear disease common in children under three years old. Otitis media can occur in normal individuals with no other symptoms or syndromes, but it is often seen in individuals clinically diagnosed with genetic diseases such as CHARGE syndrome, a complex genetic disease caused by mutation in the Chd7 gene and characterized by multiple birth defects. Although otitis media is common in human CHARGE syndrome patients, it has not been reported in mouse models of CHARGE syndrome. In this study, we report a mouse model with a spontaneous deletion mutation in the Chd7 gene and with chronic otitis media of early onset age accompanied by hearing loss. These mice also exhibit morphological alteration in the Eustachian tubes, dysregulation of epithelial proliferation, and decreased density of middle ear cilia. Gene expression profiling revealed up-regulation of Muc5ac, Muc5b and Tgf-β1 transcripts, the products of which are involved in mucin production and TGF pathway regulation. This is the first mouse model of CHARGE syndrome reported to show otitis media with effusion and it will be valuable for studying the etiology of otitis media and other symptoms in CHARGE syndrome.
PLoS ONE 01/2012; 7(4):e34944. · 4.09 Impact Factor
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ABSTRACT: A high temperature superconducting magnetic energy storage system (HT-SMES) is constructed using YBCO coated conductor and is integrated with a cryogenic system using sub-cooled LN2. A closed loop control algorithm, based on the digital signal processor (DSP) TMS320F2812, is proposed using the 2G HT-SMES to compensate dynamic voltage sag in power systems. A dynamic simulation experiment for compensation of instantaneous voltage sag is achieved. The experiment circuit is built using a signal conditioning circuit, a DSP controlling circuit, a power conversion circuit and a SMES unit. Analysis of the voltage waveforms before and after compensation validates that this SMES system is able to compensate instantaneous voltage sag.
IEEE Transactions on Appiled Superconductivity 07/2011; · 1.04 Impact Factor
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ABSTRACT: To facilitate a variety of applications, positioning systems are deployed in indoor settings. For example, Bluetooth and RFID positioning are deployed in airports to support real-time monitoring of delays as well as off-line flow and space usage analyses. Such deployments generate large collections of tracking data. Like in other data management applications, joins are indispensable in this setting. However, joins on indoor tracking data call for novel techniques that take into account the limited capabilities of the positioning systems as well as the specifics of indoor spaces. This paper proposes and studies probabilistic, spatio-temporal joins on historical indoor tracking data. Two meaningful types of join are defined. They return object pairs that satisfy spatial join predicates either at a time point or during a time interval. The predicates considered include “same X,” where X is a semantic region such as a room or hallway. Based on an analysis on the uncertainty inherent to indoor tracking data, effective join probabilities are formalized and evaluated for object pairs. Efficient two-phase hash-based algorithms are proposed for the point and interval joins. In a filter-and-refine framework, an R-tree variant is proposed that facilitates the retrieval of join candidates, and pruning rules are supplied that eliminate candidate pairs that do not qualify. An empirical study on both synthetic and real data shows that the proposed techniques are efficient and scalable.
Data Engineering (ICDE), 2011 IEEE 27th International Conference on; 05/2011
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ABSTRACT: The work reported in this paper is in support of applications of ferrites in measurement systems operating at frequencies in the range 100-600 GHz. Measurements of the magneto-optical characteristics of selected grain-oriented hexaferrite ceramics from 75 to 600 GHz are described; a quasi-optical transmissometer driven by a multiband vector-network-analyser is used to provide the required high dynamic range, spectral-resolution, and scan-speeds. The implications of the results of the measurements are examined.
IEEE Transactions on Microwave Theory and Techniques 01/2011; · 1.85 Impact Factor
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Proceedings of the 2011 IEEE International Conference on Multimedia and Expo, ICME 2011, 11-15 July, 2011, Barcelona, Catalonia, Spain; 01/2011
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Proceedings of the 2011 IEEE International Conference on Multimedia and Expo, ICME 2011, 11-15 July, 2011, Barcelona, Catalonia, Spain; 01/2011
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IEEE Transactions on Image Processing. 01/2011; 20:3524-3533.
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18th IEEE International Conference on Image Processing, ICIP 2011, Brussels, Belgium, September 11-14, 2011; 01/2011
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ABSTRACT: Compared with single-carrier DSSS, multi-tone DSSS (MT) obtains larger processing gain with equal spectrum efficiency, but it is more sensitive to imperfect carrier synchronization due to much spectral overlap on non-orthogonal subcarriers. In this paper, the carrier synchronization errors of MT system, including frequency offset and phase noise, were modeled as slowly varying Gaussian random processes with little variance. The coherent decision statistics and bit error rate (BER) were theoretically derived with imperfect carrier synchronization, which were verified by numerical simulations. The results show that, in the presence of synchronization errors, the BER performance of MT with same spreading codes on subcarriers is not determined by processing gain, while for different code case the performance could be improved since inter-subcarrier interference is suppressed by larger processing gain at the cost of bandwidth efficiency.
Communication Technology (ICCT), 2010 12th IEEE International Conference on; 12/2010
