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131.
To improve the understanding of flame propagation through a nonpremixed vortex ring, the characteristics of fuel concentration in a vortex ring have been investigated experimentally. The vortex ring was generated by the ejection of propane with a single stroke motion of a speaker. Planar laser-induced fluorescence (PLIF) technique was adopted by seeding acetone as a tracer to fuel stream, in which the PLIF signal intensity is directly proportional to the concentration of acetone. This technique provides non-intrusive and instantaneous measurement of concentration field. Results showed that fuel concentration and its gradient decreased with the evolution of a vortex ring. When a nonpremixed flame propagated through a vortex ring, the flame location coincides with the inner most spiral mixing layer of fuel and air in a vortex ring. 相似文献
132.
Balestra F Bedfer Y Bertini R Bland LC Brenschede A Brochard F Bussa MP Choi S Colantoni ML Dressler R Dzemidzic M Faivre JC Ferrero A Ferrero L Foryciarz J Fröhlich I Frolov V Garfagnini R Grasso A Heinz S Jacobs WW Kühn W Maggiora A Maggiora M Manara A Panzieri D Pfaff HW Piragino G Popov A Ritman J Salabura P Tchalyshev V Tosello F Vigdor SE Zosi G;DISTO Collaboration 《Physical review letters》2002,89(9):092001
Total and differential cross sections for the exclusive reaction pp-->pp rho observed via the pi(+)pi(-) decay channel have been measured at p(beam)=3.67 GeV/c. The observed total meson production cross section is determined to be (23.4+/-0.8+/-8) mu b and is significantly lower than typical cross sections used in model calculations for heavy-ion collisions. The differential cross sections measured indicate a strong anisotropy (approximately cos(theta(CM)(rho)) in the rho(0) meson production. 相似文献
133.
134.
Yu. G. Naidyuk I. K. Yanson L. V. Tyutrina N. L. Bobrov P. N. Chubov W. N. Kang Hyeong-Jin Kim Eun-Mi Choi Sung-Ik Lee 《JETP Letters》2002,75(5):238-241
We have analyzed about a hundred voltage-dependent differential resistance dV/dI(V) curves of metallic point contacts between c-axis-oriented MgB2 thin film and Ag, which exhibit clear Andreev reflection features connected with the superconducting gap. About one half of the curves show the presence of a second larger gap. The histogram of the double gap distribution reveals distinct maxima at 2.4 and 7 meV, while curves with single-gap features result in a more broad maximum at 3.5 meV. The double-gap distribution is in qualitative agreement with the distribution of gap values over the Fermi surface calculated by H. J. Choi et al. (cond-mat/0111183). The data unequivocally show the presence of two gaps: ΔS=2.45±0.15 meV and ΔL=7.0±0.45 meV in MgB2 with the gap ratio ΔL/ΔS=2.85±0.15. Our observations further prove a widely discussed multigap scenario for MgB2, where two distinct gaps are seen in the clean limit, while a single averaged gap is present in the dirty one. 相似文献
135.
Yang Shin Park Chang Hee Lee Baek Hui Kim Jongmee Lee Jae Woong Choi Kyeong Ah Kim Jeong Hwan Ahn Cheol Min Park 《Magnetic resonance imaging》2013
Purpose
The purpose of the study was to determine significant imaging features to differentiate between infiltrative hepatocellular carcinoma (HCC) and confluent fibrosis (CF) in liver cirrhosis using Gd-EOB-DTPA-enhanced 3-T magnetic resonance imaging.Material and methods
Nineteen infiltrative HCCs and eight CFs were included. We evaluated the difference in imaging findings and apparent diffusion coefficient (ADC) between the two entities. We compared T2-weighted image (WI) and hepatobiliary phase (HBP) in terms of the clarity of the lesion outer margin.Results
Seventeen infiltrative HCCs showed lobulated margin, while focal CFs showed either straight (n = 3) or irregular margins (n = 5) (P = .001). All infiltrative HCCs had intact or bulging contours, and all focal CFs showed capsular retraction (P = .001). Fourteen infiltrative HCCs and two focal CFs showed arterial enhancement (P = .035). The ADC of infiltrative HCCs was significantly lower than that of CFs (P = .001). Satellite nodules were noted in 10 infiltrative HCCs. In terms of outer margin clarity, infiltrative HCCs showed a more distinct margin on HBP than on T2-WI (P = .005), while these two sequences were not significantly different in focal CFs (P = 1.000).Conclusion
HBP improved the imaging characteristics of infiltrative HCC, allowing it to be distinguished from focal CF. Infiltrative HCC showed lower ADC values than focal CF. Lobular configuration, contour bulging, enhancement pattern, associated satellite nodules and portal vein thrombosis were still found to be highly suggestive MR findings for infiltrative HCC. 相似文献136.
Han Mo Jeong Ah Young Jo Mi Yeon Choi Man Jae Han Jae Young Jho 《Journal of Macromolecular Science: Physics》2013,52(5):789-799
The characteristics and performance of an ionic polymer–metal composite (IPMC), prepared with an anion‐exchange acrylic copolymer, was examined. The acrylic copolymer was synthesized by the radical copolymerization of fluoroalkyl methacrylate and 2‐(dimethyl amino)ethyl methacrylate(AMA). Effects of the AMA repeating unit's content in the copolymer and effects of the anion type present on the actuation of the IPMC were observed. The optimal content of 19.4 wt% AMA in the IPMC copolymer yielded the best actuation. The actuation also improved according to the type of anion present in the composite, in the following order: Br???4 ?. 相似文献
137.
Sang Hyop Choi Dong Hoon Kim Anjanapura V. Raghu Kakarla Raghava Reddy Hyung-Il Lee Koo Sik Yoon 《Journal of Macromolecular Science: Physics》2013,52(1):197-207
Nanocomposites of waterborne polyurethane (WPU) reinforced with functionalized graphene sheets (FGSs) were effectively prepared by casting from a colloidal dispersion of FGS and WPU, and the morphology and physical properties were examined. The finer aqueous FGS dispersions or WPU with smaller particles yielded nanocomposites with enhanced electrical conductivity and thermal resistance due to finely dispersed FGS. The FGS nucleated the crystallization of the polycaprolactone (PCL) segments in WPU and improved its modulus. However, FGS inhibited crystal growth and deteriorated the tensile properties at high deformation, i.e., tensile strength and elongation at break, because the interaction between FGS and WPU hindered the chain rearrangement of WPU in the nanocomposite. 相似文献
138.
Purpose
The purpose of the study was to validate the diagnostic performance of high-resolution isovolumetric magnetic resonance arthrography (MRA) for intrinsic ligament and triangular fibrocartilage complex (TFCC) tears of the wrist as compared to conventional MR imaging (MRI).Materials and methods
Forty-eight patients with traumatic TFCC tears at arthroscopy were enrolled. All patients had underwent proton-density- and T2-weighted MRI before arthrography and three-dimensional T1 high-resolution isovolumetric examination (3D-THRIVE) MRA on a 3-T MR. We assessed the presence of scapholunate interosseous ligament (SLIL)/lunotriquetral interosseous ligament (LTIL) or TFCC tears using the arthroscopy as a gold standard.Results
Arthroscopy revealed 37 TFCC central tears, 15 TFCC peripheral tears, 20 SLIL tears and 13 LTIL tears. Sensitivities of MRI and MRA were 70.3% and 94.6% for detection of TFCC central tears, 60.0% and 93.3% for detection of TFCC peripheral tears, 65.0% and 85.0% for SLIL tears, and 61.5% and 84.6% for LTIL tears. The specificity of the MRI was 100% for the detection of ligaments and TFCC tears. The specificities of the MRA for detection of TFCC central tears, TFCC peripheral tears, SLIL tears and LTIL tears were 100%, 97%, 96.4% and 100%, respectively.Conclusion
Isovolumetric 3D-THRIVE wrist MRA provided better results for depiction of intrinsic ligament and TFCC tears than wrist MRI. 相似文献139.
Spatiotemporal magnetization reversal dynamics in a Ni(80)Fe(20) microstructure is studied using ps time scale scanning Kerr microscopy. Time domain images reveal a striking change in the reversal associated with the reduction in switching time when a transverse bias field is applied. Magnetization oscillations subsequent to reversal are observed at two resonance frequencies, which sensitively depend on the bias field strength. The oscillation at f = 2 GHz is caused by the damped precession of M, while the lower frequency approximately 0.8 GHz mode is interpreted in terms of domain wall oscillation. 相似文献
140.
Sung Won Chae Geon Choi Hee Joon Kang Jong Ouck Choi Sung Min Jin 《Journal of voice》2001,15(2):278-283
We have evaluated the relationship between voice change and premenstrual syndrome (PMS) by comparing acoustic measurements made during the follicular phase and the premenstrual phase. Twenty-eight women were followed for 2 months for this study. Each participant was asked to produce an /a/ sound for 5 seconds at the midfollicular phase of the menstrual cycle and then 2-3 days before menstruation. Each voice sample was stored and analyzed by the Dr. Speech Science program. The voice data collected from all subjects during the two phases were compared. After that, the subjects were divided into a PMS-positive and PMS-negative group according to the criteria cited in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV); the voice data from each group were compared separately between the two phases. There was no significant difference in the acoustic parameters between the two phases in all subjects (N = 28). In the PMS-positive group (N = 16), jitter was significantly increased during the premenstrual phase compared to the follicular phase (p = 0.048). The patient's PMS score was not correlated with the severity of voice change. We conclude that the change of voice parameter was objectively identified in the PMS-positive group, therefore more careful voice habituation is required during the premenstrual phase in that group. 相似文献